JPS6312792B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a print lamination film that can be laminated with printing paper or the like by only thermocompression bonding without using adhesives or solvents. As is well known, paper products such as paper cartons, publications, cards, posters, and other printed matter are coated with plastic film for the purpose of protecting the printed surface, imparting water resistance, oil resistance, and beautification. Many are laminated. Such processing is generally referred to as "print lamination" in the art. Conventionally, this print lamination involves applying an adhesive dissolved in an organic solvent to a plastic film in the coating section of a laminator.
After the organic solvent is scattered in a drying section, the adhesive-coated surface of the plastic film and the printing paper are bonded under heat and pressure. However, in the method using the above organic solvent,
There are problems in terms of work safety such as the risk of fire, as well as environmental protection such as the generation of odors and air pollution, and it is also undesirable from the perspective of resource conservation. There is a strong demand for its appearance. In view of these technical issues, the inventor of the present invention has conducted extensive research and has developed a new printed laminate that can be laminated with printing paper, etc. by only thermocompression bonding without the need to use adhesives or solvents. This led to the production of a film for use in photography. That is, the gist of the present invention relates to the provision of a novel film for print lamination, which comprises a biaxially oriented polypropylene film, having a thickness of 1 to 5 μm, and having a wetting tension of at least 36 dyn/cm by surface treatment. A composite biaxially oriented polypropylene film that can be thermocompression bonded to a printing paper or the like, consisting of a two-layer heat-sensitive adhesive resin layer, the heat-sensitive adhesive resin layer being polyethylene or a copolymer containing at least 80% by weight of ethylene; or total ethylene content of 80% by weight
It consists of a mixture of the above-mentioned polymers. Embodiments of the present invention will be described in detail below. The biaxially oriented polypropylene film in the present invention is a propylene homopolymer with a boiling n-heptane extraction residue of 90% or more, a propylene-α-olefin copolymer with an α-olefin content of 5 mol% or less, or a total Propylene content of 95
A biaxially stretched film made of the above-mentioned polypropylene resin, which is mixed with a mixture of a propylene homopolymer and a propylene-α-olefin copolymer in a proportion of mol % or more, and scraps of the film for print lamination according to the present invention. A film with a thickness of 15 to 20 μm is usually used. In addition,
It goes without saying that biaxially oriented polypropylene films subjected to coloring or surface matte treatment can also be used in the present invention. The heat-sensitive adhesive resin layer laminated on the biaxially oriented polypropylene film is polyethylene or a copolymer containing at least 80% by weight (preferably 85% or more) of ethylene, or a total ethylene content of 80% by weight or more. % by weight (preferably 85
% by weight) or more, and the heat-sensitive adhesive resin layer can be surface-treated to have a wet tension of at least 36 dyn/
It is necessary that it is maintained at a height of cm or more. There are no particular restrictions on the monomer to be copolymerized with ethylene, and any monomer that can be copolymerized with ethylene may be used. Examples include propylene, butene-1, vinyl acetate, ethyl acrylate, and acrylic acid. In addition, products modified by copolymerization such as hydrolysis or crosslinking with metal ions, or products modified by graft polymerization with maleic anhydride, etc., can also be used in the present invention if their total ethylene content is 80% by weight or more. It can be used for However, if the total ethylene content is less than 80% by weight, film waste generated in the film manufacturing process or slitting process cannot be returned to the polypropylene layer and reused, which is undesirable from the viewpoint of resource conservation. This is because, if these are intentionally returned, the transparency, slipperiness, dimensional stability, etc. will be greatly deteriorated, resulting in a biaxially oriented polypropylene film that cannot be put to practical use. Any known method may be used to laminate the heat-sensitive adhesive resin layer on the biaxially stretched polypropylene film. The thickness of the heat-sensitive adhesive resin layer may be appropriately selected depending on the smoothness of the surface of the printing paper, the required adhesive strength, etc., and is usually preferably 1 to 5 μm. At this time, if it is less than 1μ, the adhesive strength will be insufficient,
If it exceeds 5μ, transparency may be impaired, which is not preferable. The heat-sensitive adhesive resin layer has a wetting tension of at least 36 dyn/cm, preferably 38 dyn/cm due to surface treatment.
It is necessary to maintain the above value. That is, if the wet tension is less than 36 dyn/cm, the adhesive strength with printing paper etc. will be insufficient and it will not be practical. The surface treatment method may be any known means such as flame treatment or chemical treatment, but corona discharge treatment is the simplest. Note that the wetting tension herein refers to a value based on a measurement method specified in JIS K 6768 using a mixed solution of formamide and ethylene glycol monoethyl ether. Various methods can be considered for thermocompression laminating the thus obtained composite biaxially oriented polypropylene film (i.e., film for print lamination) and printing paper, etc., and any known method may be used. A pinch roll is sufficient. For example, one side of the pinch roll is 60
Using a metal roll heated to 130°C to 130°C, preferably 80 to 120°C, and a rubber roll on the other hand, a linear pressure of 5
Kg/cm or more, preferably 20 Kg/cm or more, so that the heat-sensitive adhesive resin layer of the composite biaxially oriented polypropylene film and the printing surface of the printing paper are brought together,
The purpose is achieved by passing a composite biaxially oriented polypropylene film through a metal roll and a printing paper or the like through a rubber roll so that they are in contact with each other. Next, specific examples of the present invention will be described together with comparative examples. However, it goes without saying that the present invention is not limited only to these examples. <Example 1> A melt-extruded crystalline polypropylene film (thickness 750μ) was stretched 5 times in the longitudinal direction using a roll stretching machine at 130°C, and then a vinyl acetate content of 10% by weight was applied onto the longitudinally uniaxially stretched film. , M, I6 ethylene-vinyl acetate copolymer was melt-extruded and laminated to a thickness of 30 μm, and then stretched 10 times in the transverse direction at 160°C, and the ethylene-vinyl acetate copolymer layer surface was processed to give a strength A corona discharge treatment was performed at 40 W.min/m ² to obtain the desired composite biaxially stretched polypropylene film. The thickness of this film is 18μ, of which the thickness of the ethylene-vinyl acetate copolymer layer is 3μ.
The wetting tension of the ethylene-vinyl acetate copolymer layer was 42 dyn/cm. Next, the ethylene-vinyl acetate copolymer layer maintained at the wet tension of 42 dyn/cm of this composite biaxially oriented polypropylene film and the printing surface of printing paper etc. are heated to a metal roll heated to 100°C and a linear pressure of 50 kg is applied. /cm
They were then heat-pressed and laminated between silicone rubber pinch rolls under the predetermined alignment conditions. When the laminate thus obtained is peeled off,
The printed paper was torn and it was confirmed that it had sufficient adhesiveness. <Comparative Example 1> A composite biaxially oriented polypropylene film was produced in the same manner as in Example 1 above, except that the corona discharge treatment was not performed. The wetting tension of the ethylene-vinyl acetate copolymer layer surface of this composite film is
It was less than 33 dyn/cm. Then, as in Example 1, the temperature was 100°C.
As a result of thermocompression bonding with printing paper at a linear pressure of 50 kg/cm, the two did not adhere at all. <Example 2> Composite biaxial stretching was carried out in exactly the same manner as in Example 1, except that an ethylene-ethyl acrylate copolymer of M and I4 with an ethyl acrylate content of 7% by weight was used as the heat-sensitive adhesive resin. A polypropylene film was produced. The wetting tension of the ethylene-ethyl acrylate copolymer layer surface of this film was 41 dyn/cm. Then, using the same apparatus as in Example 1, the temperature was set to 110
It was thermocompression bonded to printing paper at ℃ and linear pressure of 50 kg/cm. When the laminate thus obtained is peeled off,
The printed paper was torn and it was confirmed that it had sufficient adhesiveness. <Comparative Example 2> A composite biaxially stretched polypropylene film was produced in the same manner as in Example 2 above, except that the corona discharge treatment was not performed. The wetting tension of the ethylene-ethyl acrylate copolymer layer surface of this composite film was 33 dyn/cm or less. Then, as in Example 2, the temperature was 110°C.
As a result of thermocompression bonding with printing paper at a linear pressure of 50 kg/cm, the two did not adhere at all. <Example 3> A mixture of 10 parts by weight of the end pieces generated in the slitting process of the composite biaxially oriented polypropylene film produced in Example 1 and 100 parts by weight of the crystalline polypropylene resin used in Example 1 was prepared. The film was melt extruded (thickness: 750 μm), stretched 5 times in the machine direction at 130° C. using a roll stretching machine, and then stretched 10 times in the cross direction at 160° C. to obtain a film with a thickness of 15 μm. The physical properties of this film are shown in the table below. <Comparative Example 3> A film with a thickness of 15 μm was obtained in exactly the same manner as in Example 3 above, except that only the crystalline polypropylene resin used in Example 1 was used. The physical properties of this film are shown in the table below.

[Table] According to the results of the above Examples and Comparative Examples, first, from Examples 1 and 2 and Comparative Examples 1 and 2, effective adhesiveness is realized only by applying a surface treatment to the heat-sensitive adhesive resin layer. can be confirmed, and Example 3
From Comparative Example 3, it can be confirmed that the film used in the present invention allows for the return of its waste, and is extremely advantageous from the viewpoint of resource saving. The present invention is as described above, and if the film for print lamination according to the present invention is used, when laminating it onto printing paper, etc., it is sufficient to bond it with heat and pressure, thereby making it possible to bond the film to printing paper, etc. This ensures sufficient adhesion. Therefore,
According to the present invention, all of the problems associated with conventional laminating methods that use organic solvents are eliminated, and furthermore, it is possible to return the film waste, etc., and it can also meet the purpose of resource saving.

Claims (1)

[Claims] 1 A printing paper, etc. consisting of two layers, a biaxially oriented polypropylene film and a heat-sensitive adhesive resin layer having a thickness of 1 to 5 μm and having a wetting tension of at least 36 dyn/cm by surface treatment, is heated. It is a composite biaxially oriented polypropylene film that can be pressure-bonded, and the heat-sensitive adhesive resin layer is made of polyethylene or a copolymer containing at least 80% by weight of ethylene, or the total ethylene content is 80% by weight.
A film for print lamination comprising a mixture of the above polymers.