JPH0216925B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a printing ink composition for plastics, and more particularly, it is an object of the present invention to provide a printing ink suitable for printing various plastic films and sheets. In recent years, with the diversification of packaging containers and the increasing functionality of synthetic resin products such as synthetic leather, advanced performance and quality are also required for printing inks and various coating agents used to decorate or protect the surface of plastic films. This is becoming more and more common. In particular, with regard to printing inks, it has become necessary to address issues such as cosmetic decoration and high-grade packaging containers, adhesion to various composite films, and suitability for various post-processing. These various suitability are mainly determined by the binder resin used for printing ink, etc., and polyurethane resins have conventionally been used as binder resins for such applications. Conventional polyurethane resins are made by reacting polyols, organic polyisocyanates, and optionally chain extenders such as polyamines, but printing inks using these polyurethane resin solutions as binders can be used to coat nylon, polyester films, etc. Although it has sufficient adhesion to polyethylene and polypropylene films, which are general-purpose films, it does not have sufficient adhesion to polyethylene and polypropylene films, and also does not have sufficient suitability for lamination. Furthermore, the pigment dispersibility was insufficient, and there were problems in various printing suitability or coating suitability. Conventionally, methods of adding surfactants or other additives have been used to solve problems such as pigment dispersibility, but these additions degrade the physical properties of the film, and are used in food containers, etc. This deteriorated boiling suitability, retort suitability, etc. The present invention was made to solve the above-mentioned problems with polyurethane resins, and it was discovered that printing inks using polyurethane resins having specific functional groups have excellent pigment dispersibility and various printing suitability. It is a completed invention. That is, the present invention provides a printing ink composition for plastics mainly composed of a pigment, a polyurethane resin, and an organic medium, wherein all or a part of the polyurethane resin is a polyurethane resin having a free thiol group. The present invention aims to provide a printing ink composition for use in printing. The present invention will be explained in more detail below. Regarding the manufacturing method of the polyurethane resin having free thiol groups used in the present invention, a urethane prepolymer having free isocyanate groups is synthesized from a high molecular weight diol component and an organic diisocyanate component, and then a chain extender having a thiol group is added at a stoichiometric ratio. Alternatively, an elastomer-type polyurethane resin having terminal isocyanate groups is synthesized from a high molecular weight diol component, an organic diisocyanate component and a chain extender, and a compound such as thioglycol or aminothiol is added. It can be obtained by reaction. Further, a high molecular weight diol component, an organic diisocyanate component, a general chain extender, and the above-mentioned compound having a thiol group may be reacted simultaneously, and any production method is possible. As the reaction method, conventionally known methods can be applied. Conventionally known components can be used as the components of the polyurethane resin according to the present invention. Among the high molecular weight diol components, polyether type diols include polyalkylene glycols such as polyethylene glycol and polypropylene glycol, polyoxyethylene glycol, Polyoxyalkylene glycols such as oxypropylene glycol, polyoxyethylene propylene glycol, polyoxytetramethylene glycol, or
Examples include alkylene oxide adducts of bisphenol A such as ethylene oxide, propylene oxide, and ethylene propylene oxide, polycaprolactone diol, and polycarbonate diol groups. Polyester diols include adipic acid, phthalic anhydride, and isophthalic acid. acids, maleic acid, fumaric acid,
Dibasic acids such as succinic acid and ethylene glycol,
diethylene glycol, propylene glycol,
1.4 butadiol, neopentyl glycol, 1.6
It is obtained through a condensation reaction with glycols such as hexanediol. However, the molecular weight of these polyether-type diols and polyester-type diols must be in the range of 700 to 2,500, preferably 1,000 to 2,000, and if the molecular weight is less than 700, the polyurethane resin synthesized from them will have a high cohesive force between the resins. However, there are disadvantages in that the adhesiveness and lamination properties become excessive, and a large amount of solvent remains on the printed matter. On the other hand, if the molecular weight is 2,500 or more, the cohesive force between the resins will be insufficient and blocking will easily occur. In addition, as the organic diisocyanate component, tolylene diisocyanate, diphenylmethane diisocyanate, xylidine diisocyanate, methylene diisocyanate, isopropylene diisocyanate, hexamethylene diisocyanate,
2.2.4-or 2.4.4-trimethylhexamethylene diisocyanate, lysine diisocyanate, 1.4
-Cyclohexane diisocyanate, isophorone diisocyanate, 4,4-dicyclohexylmethane diisocyanate, etc. Note that from the viewpoint of obtaining a resin with excellent solubility, alicyclic diisocyanates such as isophorone diisocyanate and 4,4-dicyclohexylmethane diisocyanate are preferred. Examples of diamines used as chain extenders include ethylene diamine, propylene diamine, hexamethylene diamine, isophorone diamine, and dicyclohexylmethane diamine. In addition, as the thiol compound for introducing a free thiol group specified in the present invention, lower alkylene dithioglycol such as ethylene dithioglycol and propylene dithioglycol, or lower aminoalkyl thiol such as aminoethanethiol and aminopropylenethiol are used. Can be mentioned. The amount of thiol groups present in the polyurethane resin is adjusted by the ratio of -SH groups/-NCO groups, and the amount of -SH groups in the polyurethane resin thus obtained achieves the object of the present invention. This is extremely important. The amount of thiol groups in the total urethane resin used as a binder component is
A range of 0.033 to 3.3% is preferred. When the thiol group content in the total urethane resin is below this range,
Pigment dispersibility and lamination suitability deteriorate, and if it exceeds this range, the water resistance of the urethane resin film tends to deteriorate, which is not preferable. As a method for producing the polyurethane resin having free thiol groups according to the present invention, each of the above-mentioned methods can be used, and it is necessary to adjust the content of thiol groups. Solvents used at this time include aromatic solvents such as benzene, toluene, and xylene, which are commonly used as solvents for printing inks; ester solvents such as ethyl acetate, n-propyl acetate, and butyl acetate;
methanol, ethanol, isopropanol, n
-Alcoholic solvents such as butanol, acetone,
Examples include single or mixed ketone solvents such as methyl ether ketone and methyl isobutyl ketone, but from the viewpoint of the working environment, ester solvents,
Alcohol-based solvents alone or in combination are most suitable. When manufacturing printing ink using a polyurethane resin solution containing free thiol groups synthesized using each of the above components, various pigments are added to the polyurethane resin, mixed, dispersed, and mixed as necessary. , antiblocking agents, plasticizers and other additives, or compatible resins such as nitrified cotton, maleic acid resins, and salt-vinyl acetate copolymers. The printing ink thus obtained has excellent pigment dispersibility, satisfies coating performance and printing suitability, and is also excellent in adhesive properties and suitability for various processing. Hereinafter, the present invention will be specifically explained using Examples, but the present invention is not limited thereto. Synthesis Example 1 _Adipic acid and 1.4-
200 parts of polyester diol with an average molecular weight of 2000 obtained from butanediol and 44.4 parts of isophorone diisocyanate were charged, reacted for several hours while introducing N ₂ gas, and after cooling, 235 parts of ethyl acetate was added and dissolved uniformly. Isopropyl alcohol
156 parts and 13.6 parts of isophoronediamine were added, followed by 3 parts of 2-aminoethanethiol to stop the reaction, thereby obtaining the desired urethane resin having thiol groups at both terminals. The obtained urethane resin has a thiol group content
The solution was 0.49% by weight, solids content 40%, and viscosity 30 poise/25°C. (Resin binder A) Synthesis example 2 The following materials were prepared in the same manner as in synthesis example 1, and the thiol content was 0.49% by weight, the solid content was 40%, and the viscosity was 25%.
A poise/25°C solution (resin binder B) was obtained. Polyoxytetramethylene glycol (molecular weight
2000) 2000 parts Isophorone diisocyanate 44.0 parts Isophorone diamine 13.6 parts Isopropyl alcohol 156.0 parts Ethyl acetate 235.0 parts Aminoethanethiol 3.0 parts Synthesis example 3 Using the same procedure as in Example-1, combine with adipic acid.
Average molecular weight obtained from 1.4-butazinol
2000 polyester diol and 44.4 parts of isophorone diisocyanate were charged and reacted for several hours while introducing N ₃ gas.Furthermore, 13.8 parts of ethanethioglycol was charged and reacted for a further several hours to obtain a polyurethane having thiol groups at both ends.Ethyl acetate. 383 parts were added and uniformly dissolved to obtain the desired urethane resin. The obtained urethane resin has a thiol group content
1.2%, solid content 40%, viscosity 10 poise/25°C (Resin Binder C) Synthesis Example 4 Using the same procedure as Synthesis Example 3, the following materials were used to obtain a solution with a thiol content of 0.44% by weight and a solid content of 1.2%. Mold content 40%, viscosity 10
A poise/25°C solution (resin binder D) was obtained. Polyoxytetramethylene glycol (molecular weight
2000) 200.0 parts Isophorone diisocyanate 44.0 parts Ethanethioglycol 11.0 parts Ethyl acetate 383.0 parts Synthesis Example 5 Same procedure as Synthesis Example 1, except using monobutylamine instead of 2-aminoethanethiol, using the same materials and amounts. Resin binder E having no thiol groups at all and having a solid content of 40% and a viscosity of 25 poise/25°C was obtained. Synthesis Example 6 Using the same procedure as Synthesis Example 1, replacing 3 parts of 2-aminoethanethiol with isopropyl alcohol, solids content with an alkoxyl group at the end was 40%, and the viscosity was
A resin binder F of 25 poise/25° C. was obtained. Examples 1-4, Comparative Examples 1-2 Each resin binder obtained in Synthesis Examples 1-6
30 parts of isopropyl alcohol is added to 25 parts of isopropyl alcohol, 30 parts of titanium oxide and 20 parts of ethyl acetate are added for white ink, and 10 parts of shiny blue pigment and 35 parts of ethyl acetate are added for blue ink, and mixed to produce each printing ink. do. Examples 1 to 4 used resin binders A to D, and comparative examples 1 and 2 used resin binders E and F. Evaluation Test Using each printing ink obtained in Examples 1 to 4 and Comparative Examples 1 to 2, the adhesion to various films, various printing suitability, lamination suitability, boiling and retort suitability were evaluated, and the results are shown. Shown in 1. In addition, each evaluation method is based on the method described below. 1 Adhesion Each test ink was printed on a specified film using a gravure proofing machine, left for one day, and cellophane tape was applied to the printed surface, and when this was rapidly peeled off, the printed film did not come off at all. (◎)
80% or more remains on the film (〇), 50-80
The percentage remaining is indicated as (△), and the percentage remaining less than 20% is indicated as (x). 2. Suitability for printing Color development... Compare the transparency and density of printed matter to evaluate pigment dispersibility. Tone reproducibility: Compare the readjustment reproducibility by printing on a gravure plate with continuous gradation. Plate bleed property: Compare the degree of transfer of blue ink to the white plate. The above evaluation of each printing aptitude is ◎ for the most excellent, 〇 for each aptitude that does not hinder printing.
Those with insufficient aptitude are evaluated as △, and those with no aptitude are evaluated as ×. 3 Extrusion lamination strength For OPP, imine type, PET,
An isocyanate-based AC agent was used for NY, and molten polyethylene was laminated using an extrusion laminating machine. After 3 days, the sample was cut into 15 mm width and the T-type peel strength was measured using a Yasuda Seiki peel tester. did. 4 Dry lamination strength Layer CPP film on each printed matter using a dry lamination machine using urethane adhesive.3
Peeling strength was measured in the same manner as the strength of the laminate exposed after sun exposure. 5 Boiling suitability and retort suitability After laminating, the printed matter is made into a bag, a water/oil mixture is put inside, and the bag is sealed. After heating, the presence or absence of laminate lifting was determined from the appearance. The evaluation was rated as ◯ if there was no eyelids or lamination lifting, △ if pinhole-like lamination lifting was observed, and × if delamination occurred on the entire surface. 【table】

Claims (1)

[Scope of Claims] 1. A printing ink composition for plastics mainly consisting of a pigment, a polyurethane resin, and an organic medium, characterized in that all or part of the polyurethane resin is a polyurethane resin having a free thiol group. Printing ink composition for plastics. 2. The printing ink composition for plastics according to claim 1, wherein the free thiol group is contained in the total polyurethane resin in an amount of 0.033 to 3.3% by weight.