Processing Method For Making Film Have Heat Sealability
DATE：2019/9/15 9:06:44 / READ： / SOURCE：This station
Processing method for making film have heat sealability
In order to provide a heat sealability to a film which does not have heat sealability, there are mainly four methods for processing a film.
(1) Polyethylene coated type
A method of obtaining a heat sealability by extrusion coating of polyethylene, represented by a so-called polyethylene (polyethylene coated cellophane), for biaxially oriented polypropylene film, biaxially oriented polyester film, polyamide film paper , metal foil, etc. The heat sealability of such films is governed by the grade of extrusion coated polyethylene. In addition, for biaxially oriented films, heat shrinkage can degrade the appearance of the heat seal, which is the upper limit of its heat seal temperature.
Fig. 8-3-14 shows a relationship between a polyethylene grade and a heat sealability by taking a biaxially oriented polypropylene film as an example. As in the case of a single layer film, the film having a high melt flow rate has a low heat sealing initiation temperature. Of course, as the thickness of the polyethylene increases, the heat seal strength also increases.
(2) Heat-sealable resin coated type
As a representative of moisture-proof cellophane, double-sided or single-sided film coated with heat-sealable resin. In addition to cellophane, biaxially oriented polypropylene, paper, and aluminum-coated wax are also a kind of processing method. .
The double-coated film of the easy-to-seal resin is used for wrapping (wrapping) in addition to being used as a bag. Therefore, the heat-sealing strength is usually not very large, and the heat-sealing strength varies depending on the kind of the resin and the coating thickness, and cannot be generalized.
The one-sided coated film has a high heat-sealing strength for the purpose of bag making.
(3) Partial coating
This is a type of heat-sealable resin coating, that is, a processing method of coating and heat-sealing only at a heat-sealed portion, and is widely applied to a biaxially stretched film.
(4) Composite film
Including paper, aluminum foil and the like in combination with cellophane and various plastic films, most of which are heat-sealed by extrusion coating with wax or polyethylene. Therefore, they have no difference in heat sealability compared to wax coating or extrusion coating of a polyethylene film on a single layer film. When there is paper in the composite layer, the thermal conductivity is lowered, and as a result, the heat sealability is deteriorated, so care should be taken.
As a heat-sealing medium other than polyethylene, the composite with an unstretched polypropylene film is used as a means for obtaining heat-sealing properties of paper, aluminum foil, cellophane, and biaxially oriented polypropylene film. The heat sealability of the cellophane/unstretched polypropylene film and the biaxially oriented polypropylene film/unstretched polypropylene film is shown in Fig. 8-3-18. Compared with the polyethylene-coated film, the heat-sealing initiation temperature is high, and the heat-sealing range is narrow, but as a composite film, it has good transparency and good moisture resistance.
In order to provide a heat sealability to a film which does not have heat sealability, there are mainly four methods for processing a film.
(1) Polyethylene coated type
A method of obtaining a heat sealability by extrusion coating of polyethylene, represented by a so-called polyethylene (polyethylene coated cellophane), for biaxially oriented polypropylene film, biaxially oriented polyester film, polyamide film paper , metal foil, etc. The heat sealability of such films is governed by the grade of extrusion coated polyethylene. In addition, for biaxially oriented films, heat shrinkage can degrade the appearance of the heat seal, which is the upper limit of its heat seal temperature.
Fig. 8-3-14 shows a relationship between a polyethylene grade and a heat sealability by taking a biaxially oriented polypropylene film as an example. As in the case of a single layer film, the film having a high melt flow rate has a low heat sealing initiation temperature. Of course, as the thickness of the polyethylene increases, the heat seal strength also increases.
(2) Heat-sealable resin coated type
As a representative of moisture-proof cellophane, double-sided or single-sided film coated with heat-sealable resin. In addition to cellophane, biaxially oriented polypropylene, paper, and aluminum-coated wax are also a kind of processing method. .
The double-coated film of the easy-to-seal resin is used for wrapping (wrapping) in addition to being used as a bag. Therefore, the heat-sealing strength is usually not very large, and the heat-sealing strength varies depending on the kind of the resin and the coating thickness, and cannot be generalized.
The one-sided coated film has a high heat-sealing strength for the purpose of bag making.
(3) Partial coating
This is a type of heat-sealable resin coating, that is, a processing method of coating and heat-sealing only at a heat-sealed portion, and is widely applied to a biaxially stretched film.
(4) Composite film
Including paper, aluminum foil and the like in combination with cellophane and various plastic films, most of which are heat-sealed by extrusion coating with wax or polyethylene. Therefore, they have no difference in heat sealability compared to wax coating or extrusion coating of a polyethylene film on a single layer film. When there is paper in the composite layer, the thermal conductivity is lowered, and as a result, the heat sealability is deteriorated, so care should be taken.
As a heat-sealing medium other than polyethylene, the composite with an unstretched polypropylene film is used as a means for obtaining heat-sealing properties of paper, aluminum foil, cellophane, and biaxially oriented polypropylene film. The heat sealability of the cellophane/unstretched polypropylene film and the biaxially oriented polypropylene film/unstretched polypropylene film is shown in Fig. 8-3-18. Compared with the polyethylene-coated film, the heat-sealing initiation temperature is high, and the heat-sealing range is narrow, but as a composite film, it has good transparency and good moisture resistance.
Author：admin