JPS64218B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing a laminated film with excellent gas barrier properties, including a plastic film coated with a polyvinylidene chloride resin (hereinafter referred to as a "k-coated film"). Conventionally, k-coated films have been widely used as packaging films for protecting contents and preserving them for long periods of time due to their excellent moisture-proofing and gas-barrier properties. Rather than being used alone, this k-coat film has generally been used as a laminated film in which heat-sealable films such as polyethylene film and polypropylene film are laminated. In order to manufacture laminated films, dry lamination methods and extrusion lamination methods are generally used. The dry lamination method is an adhesive method in which, for example, high molecular weight polyurethane having a urethane group at the end is dissolved in ethyl acetate, toluene, Kent, or a mixed organic solvent thereof, and a curing agent is added to the base material, K-coat film. This is a method in which a heat-sealable film is laminated after the agent is applied and dried. When applying this adhesive, the K-coat layer of the K-coat film, which is the base material, was dissolved by the organic solvent of the adhesive, resulting in a decrease in gas barrier properties, which were originally an advantage. In addition, in the extrusion method, which is another method, when forming a heat-sealing layer, the resin melted at a high temperature of 300°C or higher is applied directly onto the K-coat film, which disrupts the crystalline form of the K-coat layer and causes it to cool. At times, recrystallization occurs under poor conditions, resulting in a decrease in gas barrier properties. When laminated films are manufactured using the conventional lamination method, the above-mentioned phenomenon occurs.
A major problem was that the gas barrier property, which is a feature of k-coated film, was lost. In view of these conventional drawbacks, it is an object of the present invention to provide a method for manufacturing a laminated film in which heat-sealable films are laminated without losing the original properties of the k-coated film. The present invention will be explained in detail below. After heating the k-coat film to 80 to 120°C, 0.5 to 2 g/g of an adhesive made of a polyether resin or polyester resin having a molecular weight of several thousand to several tens of thousands and an isocyanate group at the end is applied onto the film.
This is a method for producing a laminated film in which a heat-sealable film is laminated with an adhesive having a viscosity of ^1,000 to 10,000 centipoise. Plastic films to be k-coated include films of cellophane, polyethylene terephthalate, stretched polypropylene, nylon, and the like. Examples of heat-sealable films include films made of polyethylene, polypropylene, ethylene-vinyl acetate copolymer, and Surlyn resin. The molecular weight of the resin used in the adhesive used in the present invention is from several thousand to several tens of thousands.If it is less than this, the viscosity will decrease significantly due to heat, resulting in insufficient adhesive strength, and if it is more than tens of thousands, the resin will soften unless the temperature becomes high. It cannot be used as an adhesive. If the molecular weight is within the above range, it will soften at a relatively low temperature of 80 to 120°C, and the viscosity will not drop significantly, making it suitable as an adhesive. Next, a table comparing the amount of oxygen permeation between the laminated film manufactured by the method of the present invention and the laminated film manufactured by the conventional method is shown. The laminated film consists of a k-coated stretched polypropylene film (20μ) (#6000 manufactured by Daicel Chemical) and polyethylene (50μ). The manufacturing method of the present invention involves coating a polyether resin (AD-76F-287 manufactured by Toyo Morton Co., Ltd.) at a rate of 1.5 g/ ^m2 on a k-coat stretched polypropylene film.
After softening the resin at ℃, a polyethylene film is attached.

【table】

[Table] The laminated film produced by the method of the present invention has original gas barrier properties because the K-coat layer is not dissolved by solvent and the K-coat layer is not changed by heat. Since it is possible to provide a heat-sealable film without losing the heat-sealable film, it can be widely used as a bag-making film, and is a laminated film suitable for storing contents for a long period of time. On the other hand, laminated films manufactured by conventional methods can be used in a wide range of applications by providing a heat-sealable film, but their gas barrier properties have deteriorated.

Claims (1)

[Claims] 1. After heating a plastic film coated with a polyvinylidene chloride resin to 80 to 120°C, an adhesive made of a polyether resin or a polyester resin having a molecular weight of several thousand to several tens of thousands and an isocyanate group at the end is applied onto the film. A method for producing a laminated film, which is applied by applying 0.5 to 2 g/m ² and laminating a heat-sealable film with the adhesive softened.