JPH0224212B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to coated films such as coated polyolefin films, polyester films, and regenerated cellulose films. Specifically, it relates to a coated film that has excellent adhesion to printing ink and adhesion when laminated with polyethylene film, polypropylene film, etc., as well as excellent barrier properties against oxygen gas, water vapor, etc., and transparency. It is. Films such as polyolefin film, polyester film, and regenerated cellulose film are used to package food and other various items, but in order to improve their oxygen gas and water vapor barrier properties, they are coated with vinylidene chloride copolymer resin, etc. A method has been proposed. However, when printing on a surface coated with a solution or emulsion of a resin such as vinylidene chloride copolymer, the adhesion of the printing ink to the coated surface is poor and the printing ink peels off, or the polyethylene film does not stick to the coated surface. , or when a polypropylene film or the like is laminated, there are problems such as the laminated strength becoming weaker over time. The above problem is that as the vinylidene chloride content of the vinylidene chloride copolymer resin increases, the crystallinity of the vinylidene chloride copolymer improves and the oxygen gas and water vapor barrier properties improve, but on the other hand, the penetration of printing ink solvents, etc. This is thought to be because it is difficult. This trend shows that the vinylidene chloride content is 85
It was particularly noticeable at mole % or higher. The present inventors have previously developed a solution or emulsion of vinylidene chloride copolymer resin 99 as a top coating agent.
It was proposed to apply a liquid mainly consisting of ~80 parts by weight and 1 to 20 parts by weight of an acrylic copolymer resin or emulsion (Japanese Patent Laid-Open No. 53-141381). Although this method improves the adhesion of the printing ink, the water vapor and oxygen gas barrier properties are somewhat inferior. Therefore, as a result of various studies, we found that by coating the surface coated with a vinylidene chloride copolymer resin solution or emulsion with a liquid mainly consisting of an acrylic copolymer resin solution or emulsion, we were able to improve the adhesion of printing ink and improve the lamination properties. The inventors have discovered that the problem of strength can be solved and that oxygen gas and water vapor barrier properties can be maintained, leading to the present invention. That is, the present invention provides a polyolefin film,
After coating a film base material such as polyethylene film or regenerated cellulose film with an undercoating liquid mainly consisting of a solution or emulsion of a vinylidene chloride resin containing 85 mol% or more of vinylidene chloride, the coated surface is coated with a specific acrylic polymer. The present invention relates to a coated film characterized in that it is sequentially coated with a top coating liquid mainly consisting of a resin solution or emulsion. Particularly preferred materials for the film used in the present invention include biaxially oriented crystalline polypropylene film, biaxially oriented polyester film, and regenerated cellulose film in terms of high transparency and high mechanical properties. Various types of known vinylidene chloride copolymer resins can be used as the undercoat in the present invention. That is, vinylidene chloride-acrylonitrile copolymer, vinylidene chloride-vinyl chloride copolymer, vinylidene chloride-vinyl acetate copolymer, vinylidene chloride-acrylate copolymer, vinylidene chloride-acrylic acid copolymer, and copolymers thereof. In addition, as a third component, acrylic acid, methacrylic acid, etc. are copolymerized. The content of vinylidene chloride in the vinylidene chloride resin is suitably 85 mol% or more, but from the viewpoint of oxygen gas barrier properties, it is particularly preferably 88 mol% or more. Vinylidene chloride homopolymer is unsuitable in terms of heat stability, light stability, and film flexibility. When coating a biaxially oriented polypropylene film, polyester film, etc. with a vinylidene chloride copolymer resin, methods are known in which various treatments are applied to the surface of the film in order to improve adhesion. The present invention also uses these methods, namely corona discharge, high frequency,
Flame, chromium mixed liquid treatment, etc. are possible. The acrylic copolymer resin used in the top coat of the present invention includes (a) 0.1 to 10% by weight of one or more α,β-unsaturated carboxylic acids having one or more carboxyl groups; % (copolymer weight%) and (b) acrylic acid alkyl ester and/or methacrylic acid alkyl ester (each alkyl group has 1 to 12 carbon atoms), and If necessary, (c) a copolymer formed by adding one or more copolymerizable vinyl monomers in an amount of 0 to 80% by weight (copolymer weight%) may be mentioned. Examples of α,β-unsaturated carboxylic acids include acrylic acid, methacrylic acid, maleic acid,
Examples include itaconic acid, citraconic acid, crotonic acid, maleic anhydride, etc., and two or more of these α,β-unsaturated carboxylic acids may be used in combination. 2
When using an α,β-unsaturated carboxylic acid having more than one carboxyl group, a half ester thereof may be used. Examples of acrylic acid alkyl esters and methacrylic acid alkyl esters include methyl acrylate, ethyl acrylate, isopropyl acrylate, n-butyl acrylate, isobutyl acrylate, amyl acrylate, and n-acrylate.
-hexyl, 2-ethylhexyl acrylate, lauryl acrylate, methyl methacrylate, ethyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, isobutyl methacrylate,
Examples include alkyl esters of acrylic acid and methacrylic acid having 1 to 12 carbon atoms, such as amyl methacrylate, n-hexyl methacrylate, 2-ethylhexyl methacrylate, and lauryl methacrylate. The following combinations are also possible. (a) One or more acrylic acid alkyl esters, (b) One or two methacrylic acid alkyl esters.
(c) One or more types of acrylic acid alkyl esters and one or more types of methacrylic acid alkyl esters The usage ratio of these acrylic acid alkyl esters and/or methacrylic acid alkyl esters is as follows:
Together with the copolymerizable vinyl monomer, it is desirable to use an amount such that a desired second-order transition point can be obtained. Next, copolymerizable vinyl monomers are considered to be components of the acrylic copolymer mainly related to coating hardness, and include (1) vinyl-substituted aromatic hydrocarbons such as styrene and α-methylstyrene, (2) ) α,β-unsaturated aliphatic nitriles such as acrylonitrile and methacrylonitrile, (3) organic acid vinyl esters such as vinyl acetate and vinyl propionate, (4) vinyl halides such as vinyl chloride and vinylidene chloride, (5) α,β-unsaturated carboxylic acid amides such as acrylamide, methacrylamide, and N-methoxyacrylamide; (6) α,β- such as 2-hydroxyethyl (meth)acrylate and 2-hydroxypropyl (meth)acrylate; Hydroxyalkyl esters of unsaturated carboxylic acids, (7) α,β-unsaturated carboxylic acid esters with epoxy groups such as glycidyl (meth)acrylate. Of course, one type or two or more types of these copolymerizable vinyl monomers may be used as required. The polymerization reaction of the acrylic copolymer is carried out, for example, in an aqueous medium, and the method may be carried out by a method known per se (for example, Japanese Patent Publication No. 49-36942). These acrylic copolymers preferably have an average molecular weight of about 5,000 to about 15,000 and a secondary transition temperature (Tg, glass transition temperature) of about 20 to about 100°C, preferably 30 to 70°C. In addition, acrylic copolymer resin can be prepared as a solvent solution.
Alternatively, it can be used as an emulsion in which at least 90% of the particles are between 0.01 and 0.5μ, preferably between 0.01 and 0.5μ.
It is desirable to have a particle size of 0.3μ. Of course, from the spirit of the present invention, it is sufficient to coat only the surface to be printed or laminated with the topcoat. The coating amount of the top coat may be 0.005 g/m ² or more, but preferably 0.01 to 0.5 g/m ² . If it is less than 0.005g/ ^m2 , the coating will have no effect;
If it exceeds g/m ² , it is not only economically disadvantageous but also undesirable in terms of residual solvent in the coating film. In addition, the top coating methods include dip method, air knife method, gravure roll method,
A coating device such as a spray method can be used. Antioxidants, antiblocking agents, and
Additives such as inorganic or organic fine powder, antistatic agents, and ultraviolet stabilizers can be added. The coated film of the present invention can be used as it is or after being printed for use as an outer packaging. Also,
After printing on the coated surface or the coated surface, a polyethylene film, unstretched polypropylene film, etc. is laminated on that surface and used as a packaging material. Next, examples of the present invention will be shown, but these are for illustrating the present invention, and it goes without saying that the present invention is not limited thereto. The properties of the coated films in Examples were tested in the following manner. Cellophane adhesive tape test on printed surface: Printing was performed using cellophane ink based on nitrocellulose. Using a method similar to the test method commonly referred to as the Scotch tape test, pressure-sensitive cellophane adhesive tape measuring 24 mm x 200 mm is repeatedly pressed from end to end on the printed surface to firmly adhere it. The adhesive tape was suddenly peeled off at an angle of approximately 90°, and the peeling state of the printed film was observed and graded as follows. No peeling of the printing film at all ... Peeling area of 10% or less of good printing film ... Peeling area of good printing film 10 to 20% ... Peeling area of printable film of 20% or more ... Not possible Blocking property: 100mm x 100mm Several sheets of film were sandwiched between two glass plates in an atmosphere of 40℃ and 90%RH.
After being left for 24 hours under a load of 0.75 Kg/cm ² , it was allowed to cool to room temperature. The degree of blocking of the film was ranked as follows. The film separates into individual sheets without applying any force. ...If you apply a little force, it will separate into sheets. ...When force is applied, it separates into sheets, but the coating layer partially peels off. ...It cannot be divided into sheets without destroying the film. ...Not possible Water vapor permeability: Using a cup specified in JISZ-0208,
Measured under conditions of 40°C and 90%RH. Oxygen gas permeability: Gas chromatography method (measuring instrument Lyssy gas
Permeability Testing Apparatus L-66) was used for measurement at 20°C using oxygen gas with a humidity of 0% and helium gas as a compensation gas. Examples 1 to 3, Comparative Example 1 The acrylic copolymer emulsion used in this example was produced as follows. stirrer, cooler,
Pour 530 g of water containing 17.1 g of sodium lauryl sulfate as an emulsifier and 1.4 g of potassium persulfate as a polymerization catalyst into a polymerization vessel equipped with a thermometer, and heat the reaction vessel to approximately 80 g.
The mixture was warmed to ℃ while stirring. Next, a mixture of a total of 285 g of the monomers shown in Table 1 and mercaptan as a molecular weight regulator was dropped into the reactor little by little over a period of 3 hours. After the dropwise addition was completed, the temperature was maintained at 80°C for another 30 minutes, and the inside of the reactor system was neutralized with aqueous ammonia.
The mixture was kept at 60°C for 1 hour and then cooled. The resulting aqueous dispersion was adjusted to an appropriate concentration with water and isopropyl alcohol. Using the topcoat liquid (formulation A) mainly consisting of the acrylic copolymer emulsion obtained by the above method,
Apply primer liquid (formulation B) to a coating amount of 3.8 in advance.
The coated surface of a biaxially oriented polypropylene film (thickness: 20 μm) was coated using a Mayer bar so that the film had a coating weight of 20 μg/m ² (after drying). The coated film was dried in an oven at 105°C for 30 seconds. The performance of the topcoat coated film is shown in Table 2. Printing was performed using CC-ST manufactured by Toyo Ink Co., Ltd.

[Table] Topcoat (formulation A) (a) Methyl methacrylate-ethyl acrylate-methacrylic acid (55/36.6/8.4) copolymer emulsion 100 parts by weight (solid content) (b) Wax emulsion (melting point 78℃)
1.5 (c) Inorganic thread lubricant (particle size 3μ) 0.2 Undercoat (formulation B) (a) Vinylidene chloride-vinyl chloride (molar ratio 91/
9) Copolymer resin 100 parts by weight (b) Wax (melting point 65℃) 1.5 (c) Inorganic thread lubricant (particle size 3μ) 0.2 (d) Tetrahydrofuran 200 (e) Toluene 200

[Table] Example 4, Comparative Example 2 CC- for the films of Example 1 and Comparative Example 1
After printing with ST ink (manufactured by Toyo Ink Co., Ltd.), it was laminated with 40μ thick low-density polyethylene. The laminating adhesive is Harvard EP Conc (Dainippon Inc.
Co., Ltd.) at a lamination speed of 50 to 60 m/min. The strength of the obtained laminate film was as shown in Table 3.

[Table] Example 5, Comparative Example 3 The acrylic copolymer resin emulsion used in this example was produced as follows. That is, it was produced by the method shown in Example 1 with the monomer composition shown in Table 4. Topcoat liquid (formulation C) mainly consisting of the acrylic copolymer resin emulsion obtained by the above method
was coated using a Meyer bar on one side of a regenerated cellulose film whose both sides had been coated with the undercoat liquid (formulation B) shown in Example 1. The coated film was dried in an oven at 105°C for 30 seconds.

[Table] Topcoat liquid (formulation C) Styrene, butyl acrylate, 2-hydroxyethyl methacrylate, acrylic acid (52.9/31.6/15.0/0.5) copolymer emulsion 100 parts by weight (solid content) Wax Emulsion (melting point 78°C) 1.5 Inorganic lubricant (particle size 3μ) 0.2 The performance of the surface coated with the topcoat is shown in Table 5.

[Table] Examples 6 to 7, Comparative Examples 4 to 5 A biaxially oriented polypropylene film (thickness: The coated surface of 20μ) was coated by gravure roll method. The performance of the coated film coated with the topcoat is shown in Table 6. Undercoat liquid (formulation D) Vinylidene chloride-acrylic ester (molar ratio
90/10) Copolymer emulsion 100 parts by weight (solid content) Wax emulsion (melting point 78℃)
1.0 Inorganic lubricant (particle size 3μ) 0.2

[Table] Example 8 The acrylic copolymer resin used in this example was produced as follows. That is, the acrylic copolymer emulsion used in Examples 6 to 7 was salted out, dried, and powdered. A printing machine applies the topcoat liquid (formulation E) using the acrylic copolymer resin obtained by the above method to the coated surface of a polyester film (thickness: 12μ) that has been previously coated with the undercoat liquid (formulation F). The first color (first) print was coated with a first color (first) print. The printing speed of the printing machine was 80 m/min, and the drying temperature was 110°C. Topcoat liquid (formulation E) Styrene, butyl acrylate, 2-hydroxyethyl methacrylate, acrylic acid (52.9/31.6/15.0/0.5) copolymer
100 parts by weight wax (melting point 78℃) 1.5 Inorganic lubricant (particle size 3μ) 0.2 Methyl ethyl ketone 500 Toluene 500 Undercoat liquid (formulation F) Vinylidene chloride-acrylonitrile (mole ratio
92/8) Copolymer resin 100 Wax (melting point 65°C) 1.5 Inorganic lubricant (particle size 3.0μ) 0.2 Tetrahydrofuran 200 Toluene 200 The performance of the coated film after printing was as shown in Table 7.

【table】

Claims (1)

[Claims] 1. 85 mol% vinylidene chloride in the film base material
After coating an undercoat coating solution mainly consisting of a solution or emulsion of a vinylidene chloride resin containing the above, the coated surface is coated with (a) an α,β-unsaturated carboxylic acid having one or more carboxyl groups; 1 type or 2 or more types
0.1 to 10% by weight (copolymer weight%) (b) One or two of acrylic acid alkyl esters and/or methacrylic acid alkyl esters (each alkyl group has 1 to 12 carbon atoms)
and (c) a solution or emulsion of an acrylic copolymer resin obtained by copolymerizing 0 to 80% by weight (copolymer weight%) of one or more copolymerizable vinyl monomers. A coated film with excellent printability characterized by being sequentially coated with a top coating liquid. 2. The coated film according to claim 1, wherein the film base material is a polyolefin in film, a polyester film, or a regenerated cellulose film.