JPS623188B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a printing ink composition, and more particularly, to a printing ink composition that has excellent printability on plastics, particularly polyester films, nylon films, polyvinyl chloride coated films, etc., and has the ability to withstand heat sterilization treatment. . Gravure printing, flexo printing, silk screen printing, etc. are used to print on plastic film, but in the case of plastic film used as a packaging material, including food packaging, most of these printing methods are the winding method. In order to improve the performance of packaging materials, dry lamination or extrusion lamination is often performed after printing. In particular, polyester films and nylon films are stronger than other films and have excellent airtightness, so they can be dry-laminated with polypropylene films, etc., or they can be processed by retort processing by interposing aluminum foil in between. It can be used as a packaging material. Therefore, the printing inks used for these films are quick-drying, contain little residual land solvent, and
Lamination suitability adapted to high performance films,
There is an increasing demand for durable printing inks. Particularly in recent years, the trend toward instantization in the food industry has been very noticeable, with the packaging of ready-to-eat foods such as curries and stews being used.
After packaging, these products are heat sterilized at a temperature of 80 to 140°C for 5 to 90 minutes to ensure long-term storage. Regarding packaging materials that undergo retort sterilization, which requires the most severe sterilization conditions, there are compositions such as polyester film/polypropylene film, nylon film/polypropylene film/polypropylene film, or nylon film/aluminum foil/polypropylene film, and isocyanate-based material is used between each film. Alternatively, they are bonded using an isocyanate-epoxy adhesive or the like. 120 for retort sterilization conditions
~140℃, 30-90 minutes is normal. Most of these packaging materials are printed, printed on the inside of polyester or nylon film,
In many cases, the printing ink is sandwiched between aluminum foil or polypropylene film. This printing ink is required to have properties that do not change in quality during heat sterilization and do not cause peeling of the laminate around the printing ink portion. Conventionally, printing inks for retort packaging materials using thermoplastic polyester resins for polyester films have been known. However, this material was difficult to dry, so accidents such as blocking were likely to occur, and the printing speed could not be achieved. Furthermore, although the strength of the laminate before retort sterilization is very high, the strength of the laminate decreases when sterilized by retort, and the form of packaging is restricted, which is not always satisfactory. Furthermore, as a printing ink that can be used for both polyester film and nylon film, there is known a printing ink that uses a reaction product of a vinyl chloride-vinyl acetate copolymer resin, a polyester resin having a hydroxyl group, and an isocyanate compound as a binder component. This ink has better drying properties than the above-mentioned printing ink using thermoplastic polyester resin, can increase printing speed, and does not reduce the strength of the laminate due to retort sterilization, but because it is a reactive type, it has a pot life. , there are various restrictions on printing operations.
Furthermore, depending on the quantity of printing and the design, the amount of ink disposed of is greater than the amount of ink consumed, making it uneconomical. Furthermore, as seen in JP-A-51-94307, a printing ink using a thermoplastic polyurethane resin as a vehicle has excellent drying properties and adhesive strength to nylon film and polyester film, compared to the above two inks. However, compared to general resins used in gravure and flexographic inks, such as rosin modified resins, polyamide resins, vinyl chloride-vinyl acetate copolymer resins, polymethyl methacrylate resins, polystyrene resins, chlorinated rubber, and cyclized rubber, etc. This produces a highly viscous solution, and because of its drawability, it has poor printing properties, is prone to one-sided fogging, and has problems with printing effectiveness and printing work. In addition, many of these inks do not leak sufficiently with pigments, resulting in poor color development and poor stability over time, making it difficult to obtain inks with sufficient performance. The present invention is a printing ink composition for plastics that can address the above-mentioned problems, and is suitable for one-component printing, which is suitable for ink formation, printability, contains less acid distilling solvent, and is suitable for heat sterilization treatment such as retort printing. It provides ink. That is, a printing ink composition with satisfactory performance was obtained by using a thermoplastic polyurethane resin, a vinyl chloride-vinyl acetate copolymer resin, and a thermoplastic polyester resin as main components of the vehicle. To explain each component, thermoplastic polyurethane resin mainly plays a role in adhesion of various plastic films including polyester and nylon, and provides resistance to heat sterilization treatment such as retort, and has a terminal hydroxyl group. It is synthesized from polyester or polyether, a diisocyanate compound, and, if necessary, a chain extender. What is polyester with terminal hydroxyl groups?
Polybasic acids such as adipic acid, sebacic acid, maleic acid, maleic anhydride, phthalic acid, isophthalic acid, terephthalic acid, etc. alone or a mixture of two or more thereof, ethylene glycol, propylene glycol, butylene glycol, trimethylolpropane, It is obtained by a condensation reaction with polyhydric alcohols such as glycerin or a mixture of two or more in an excess alcohol component. Polyethers with terminal hydroxyl groups include ethylene glycol, propylene glycol, butylene glycol, hexamethylene. It is a polyether obtained by a condensation reaction of polyhydric alcohols such as glycol, trimethylolpropane, and glycerin, either singly or by mixing two or more components. In addition, diisocyanate compounds include tolylene diisocyanate, diphenylmethane diisocyanate, methylene diisocyanate, hexamethylene diisocyanate,
It refers to a diisocyanate compound such as isophorodiisocyanate and 4,4'-dicyclohexylmethane diisocyanate, or a mixture of two or more of these components, and the chain extender refers to hydrazine, hydrazidoamine, oxyamine, water, etc. Among the thermoplastic polyurethane resins synthesized from the above components, those used in the present invention have a molecular weight of
It is preferable to use a polyester or polyether having 500 to 3000 terminal hydroxyl groups and an isocyanate compound with a nitrogen content of 2 to 8% by weight. If the nitrogen content is less than 2% by weight, the adhesiveness etc. will be poor, and if it exceeds 8% by weight, the flexibility etc. will be poor. Furthermore, in terms of adhesion to polyester films and resistance to contents such as oil, those using polyester as the polyol component are better than those using polyether. As mentioned above, when a thermoplastic polyurethane resin is used alone, the suitability for forming ink and printing is poor, but these problems can be overcome by using a vinyl chloride-vinyl acetate copolymer resin and a thermoplastic polyester resin together. The vinyl chloride-vinyl acetate copolymer resin is mainly blended to impart suitability for ink formation and printability, and also serves to improve blocking properties. In vinyl chloride-vinyl acetate copolymer resin,
Weight ratio of vinyl chloride and vinyl acetate is 70~97/3~
30 and a degree of polymerization of 250 to 800. Alternatively, a partially saponified vinyl chloride-vinyl acetate copolymer resin containing 1 to 6% vinyl alcohol, or a resin containing 1 to 5% by weight of maleic acid or the like may also be used. Note that if the vinyl acetate content is too high, the adhesiveness will increase and the drying performance will deteriorate.
Furthermore, if the vinyl acetate content is too low, the solubility and compatibility with the thermoplastic polyurethane resin will be insufficient. In particular, partially saponified vinyl chloride-vinyl acetate copolymer resin has excellent compatibility and is suitable for ink formation.
Printability is also good. The weight ratio of thermoplastic polyester resin and vinyl chloride-vinyl acetate copolymer resin is thermoplastic polyurethane resin/vinyl chloride-vinyl acetate copolymer resin =
A ratio of 3/7 to 9/1 is appropriate, and those containing too much thermoplastic polyurethane resin are excellent in adhesive strength, retort suitability, and amount of residual solvent, but poor ink suitability and printing suitability. On the other hand, those containing a large amount of vinyl chloride-acetic acid copolymer resin have excellent suitability for ink formation, but have poor adhesive strength, and particularly tend to have a lower lamination strength after retorting. Therefore, the thermoplastic polyurethane resin/vinyl chloride-vinyl acetate copolymer resin ratio (weight) is 5/5 to 6/6.
is a blending ratio that provides a well-balanced combination of lamination strength, ink suitability, and printability. Thermoplastic polyurethane resin is used as an adhesive component to provide adhesion to various films.
Dibasic acids such as phthalic acid, phthalic anhydride, adipic acid, sebacic acid, maleic acid, ethylene glycol, propylene glycol, trimethylolpropane, glycerin, 1,4-butanediol, 1,3-butanediol, hexanetriol, etc. A polyester resin synthesized by condensation with a polyhydric alcohol, desmophenes from Bayer AG are commercially available. Especially phthalic acid,
Preferred is a resin obtained by reacting a dibasic acid selected from adipic acid with a polyhydric alcohol selected from ethylene glycol, propylene glycol, and trimethylolpropane. In particular, when thermoplastic polyester resin with hydroxyl groups is used, it is also possible to improve various resistances such as stronger adhesion to the film and oil resistance by mixing an isocyanate compound during printing. can. However, as the amount of thermoplastic polyester resin added to the printing ink increases, blocking tends to occur, so it is preferable to limit the amount to 30% by weight based on the total amount of the thermoplastic polyurethane resin and vinyl chloride-vinyl acetate copolymer resin. . The printing ink composition of the present invention may contain colorants such as pigments, solvents, surfactants for improving ink fluidity and modifying surface films, waxes, and other additives as appropriate. Further, resins other than the vehicle according to the present invention can also be added within a range that does not have an adverse effect. Ester-based and ketone-based solvents have excellent solubility as solvents used in the production of varnishes and printing inks for each resin related to the present invention. Considering blocking properties due to residual solvent, it is most desirable to use methyl ethyl ketone, acetone, and ethyl acetate. However, in order to improve workability, it is permissible to use a slow-drying solvent such as suitable toluene. For ink production, ordinary dispersers, ball mills, attritors, sand mills, etc. can be used. The printing ink according to the present invention is particularly suitable for polyester films and nylon films, and has properties that can withstand severe heat sterilization processes such as retorting. Furthermore, it has excellent adhesion to polyvinylidene chloride-coated films such as polyvinylidene chloride-coated moisture-proof cellophane and polyvinylidene chloride-coated polypropylene, as well as polypropylene films and vinylon films, and can be used. In addition to dry lamination using an isocyanate adhesive, extrusion lamination of polyethylene with isocyanate anchor coating or polyethyleneimine anchor coating is also possible as a laminating process. The present invention will be explained below with reference to Examples.
"Parts" and "%" indicate parts by weight and weight %. Example Formulation Example A Titanium oxide (Ishihara Sangyo Co., Ltd., Taipeiku R-820)
25 parts thermoplastic polyurethane resin (thermoplastic polyurethane resin with a nitrogen content of 4% obtained by reacting a polyester polyol with a molecular weight of 200 obtained from propylene glycol and adipic acid with tolylene diisocyanate) 6 parts vinyl chloride/vinyl acetate Polymer resin (Denki Hokkaido Co., Ltd., Electrified Vinyl 1000LT3 - Vinyl chloride/
Vinyl acetate 75/25 average degree of polymerization 380) 6 parts thermoplastic polyester resin (Bayer, Desmohen 1700) 3 parts methyl ethyl ketone 60 parts Blending example B Titanium oxide (Ishihara Sangyo Co., Ltd. - Typeke R-
820) 25 parts thermoplastic polyurethane resin (same resin as formulation example A) 7 parts vinyl chloride/vinyl acetate copolymer resin (Electrified Vinyl 1000LT3) 5 parts thermoplastic polyester resin (Desmohen 1700)
2 parts Methyl ethyl ketone 61 parts Blend example C Titanium oxide (Tiepeque R-820) 25 parts Thermoplastic polyurethane resin (Thermoplastic polyurethane resin with a nitrogen content of 5% obtained by reacting polypropylene glycol molecular weight 2000 with tolylene diisocyanate) 7 Partially saponified vinyl chloride/vinyl acetate copolymer resin (Union Carbide Co., Vinyrite)
VAGH) 3 parts thermoplastic polyester resin (Bayer, Desmohen 800) 1 part methyl ethyl ketone 64 parts Comparative example 1 Titanium oxide (Tiepeke R-820) 25 parts thermoplastic polyester resin (Toyobo Co., Ltd., Byron #200) 13 parts Nitrocellulose (Asahi Kasei Industries, L1/4)
2 parts methyl ethyl ketone 60 parts Comparative example 2 Titanium oxide (Tiepeque R-820) 25 parts Partially saponified vinyl chloride/vinyl acetate copolymer resin (Vinyrite VAGH) 8 parts Polyester resin (Desmohen 1700) 4 parts Diothyl adipate 2 parts Methyl ethyl ketone 61 parts In addition, to the compounded ink of the comparative example, 6 parts of Coronate L-75 (Japan Polyurethane Industries Co., Ltd., isocyanate compound) is added immediately before printing. After kneading each of the above formulations in a ball mill, the mixture was adjusted to Zahn Cup No. 3 (manufactured by Rigosha) for 20 seconds with a solvent, and a polyester film (Toray Industries, Lumirror 12μ), nylon film was coated with a 35μ solid plate. (Unitika Co., Ltd., Emblem 15μ), polyvinylidene chloride coated OPP film (Tokyo Cellophane Paper Co., Ltd.,
OBD), OPP film (Toray Industries, Toray Fan)
BO2535, 20μ). Next, apply isocyanate adhesive (Toyo Morton Co., Ltd.,
AD506:ADF=100:6) was adjusted to 30% solid content with ethyl acetate and applied with a 150 line 60μ solid plate.
CPP film (Toray Industries, Torayuan No. 3701, 60
μ) to produce a laminated film. In addition,
For polyester films and nylon films, laminated films were also produced in which soft aluminum foil, 9μ, was further laminated between the film and CPP. Next, the periphery of this laminated film is heat-sealed to create a bag. The bag is filled with a 1/1 mixture of salad oil and water, and heat sterilized. Observations were made regarding seal strength, etc. The results are shown in Table-Table.

【table】

【table】

【table】

[Table] As shown in the table, Examples A, B,
Printing ink C had sufficient lamination strength and heat seal strength in all configurations, and remained unchanged even after retorting and boiling treatments.

Claims (1)

[Scope of Claims] 1. A printing ink composition for plastics, characterized in that the main components of the vehicle are a thermoplastic polyurethane resin, a vinyl chloride-vinyl acetate copolymer resin, and a thermoplastic polyester resin. 2 As a thermoplastic polyurethane resin, the molecular weight
Printing for plastics according to claim 1, which uses a thermoplastic polyurethane resin having a nitrogen content of 2 to 8% by weight, obtained from a polyester or polyether having 500 to 3000 terminal hydroxyl groups and a diisocyanate compound. Ink composition. 3 As a vinyl chloride-vinyl acetate copolymer resin,
Weight ratio of vinyl chloride and vinyl acetate is 70~97/3~
30 and a polymerization degree of 250 to 800.