JPS6228829B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a water-based printing ink for plastics that is excellent in printability, printing effect, and processing suitability for use in plastic film bags, flexible packaging materials, and the like. In recent years, the demand for plastic films made of polyethylene, polypropylene, etc. has shown a significant increase as shopping bags made of reinforced polyethylene films and flexible packaging materials for sweets, breads, and the like. The printing ink used here needs to have sufficient adhesion density to a plastic film such as polyethylene film, and preferably has no residual solvent and no odor. Furthermore, in addition to appropriate printability and printing effect, it must also maintain various physical properties such as abrasion resistance, water resistance, scratch resistance, and kneading resistance. Usually, these printing inks for flexible packaging materials are organic inks using a vehicle in which nitrified cotton (NC) and polyamide resin or NC and maleic acid resin are dissolved in an organic solvent such as toluene, ethyl acetate, methyl ethyl ketone, or isopropyl alcohol. Previously, printing was done with solvent-based gravure printing ink, but with organic solvent-based printing ink, organic solvents remain in the packaging material, and in food packaging, there is a concern that it may migrate into food, so it takes a lot of effort to reduce residual organic solvents. Despite numerous efforts, no fundamental solution has been reached. In addition, organic solvent vapors were present in the printing work environment, which was not desirable in terms of hygiene control and posed a risk of flammability. Therefore, consideration has been given to the practical application of water-based printing inks that do not contain harmful organic solvents, are not flammable, and have great potential from a resource-saving perspective.
Consists of conventional Sierra Tsuk, Sierra Tsuk modified styrene resin, rosin modified maleic acid resin, styrene-acrylic acid resin, acrylic ester-acrylic acid resin, styrene-maleic acid resin, hydroxyethyl cellulose, hydroxypropyl cellulose, etc., or a mixture thereof. Water-based printing inks that use resin as a vehicle inherently have poor adhesion to films such as polyethylene, polypropylene, and polyester, which have low hydrophilic properties, and cannot maintain sufficient adhesive strength, so the ink easily peels off, making it impractical for practical use. I couldn't offer it. The present invention eliminates the drawbacks of such conventional methods and provides a water-based printing ink with good adhesion to plastic films, etc., which is hygienic, safe to handle, and fully functional as a flexible packaging material. It is something to do. That is, as a result of intensive research to satisfy the various points mentioned above, the inventors of the present invention have found a material that has excellent adhesion to plastics such as plastic film, printability such as plate fog, and abrasion resistance and water resistance of the printing surface. They discovered a water-based printing ink using as a vehicle an odorless water-based resin dispersion that has significantly reduced residual monomer content compared to general water-based resins, and completed the present invention. A vinyl monomer (B) that can be radically polymerized in the presence of a polymeric dispersant (A) having surfactant ability or in the presence of the polymeric dispersant (A) and a low molecular surfactant used in ordinary emulsion polymerization. ) is a water-based printing ink for plastics that uses as a vehicle component an aqueous resin dispersion in which (B) is polymerized in a ratio of 50 to 800 parts by weight to 100 parts by weight of (A). The features of the present invention are that it greatly improves the adhesion of water-based printing inks to plastics, which was unsatisfactory with conventional water-based resin vehicles, and that it greatly reduces residual monomer compared to general water-based resins. It has been reduced and odorless, has greatly improved printability such as plate fog, which is a weak point of general water-based resins, and has also greatly improved various physical properties such as abrasion resistance and water resistance. be. Examples of plastics to which the water-based printing ink of the present invention can be applied include reinforced polyethylene films used for making bags such as ordinary shopping bags, surface-treated polypropylene films used as flexible packaging materials, modified polypropylene films, and anchors. Coated polypropylene film, polyvinylidene chloride coated polypropylene film, surface-treated polyester film, modified polyester film, anchor coated polyester film, polyvinylidene chloride coated polyester film, so-called so-called films with a wet tension of 45 dynes/cm or more that have hydrophilic groups introduced into the film surface. Can be printed on easily adhesive films, etc. It is also possible to print on other hydrophilic films such as nylon and cellophane, or plastic molded products. Printing on various types of paper and treated aluminum foil is also possible. To explain in more detail about the aqueous resin dispersion according to the present invention, the polymer dispersant (A) having surface-active ability includes 5 to 50 parts by weight of an ethylenically unsaturated carboxylic acid monomer and 50 to 95 parts by weight of other polymerizable monomers. A copolymer with an average molecular weight of 3,000 to 50,000 obtained by radical polymerizing a polymerizable monomer mixture consisting of Neutralize the combination to a pH range of 6 to 11 with basic substances such as ammonia or alkali metal salts such as sodium hydroxide and potassium hydroxide, and various amines such as trimethylamine, triethylamine, dimethylethanolamine, and diethylethanolamine. This is a solution resin from which most or all of the organic solvent has been removed. As the organic solvent used during the polymerization reaction, various solvents such as alcohol, ester, ketone, and aromatic solvents can be used.
Considering the stability, odor, and drying properties of water-based printing inks, organic solvents that adversely affect them are distilled out of the system by stripping after the reaction is completed, and water alone or in combination with water and 1 to 3 carbon atoms is removed. It is desirable to substitute a mixture with a lower alcohol. Furthermore, it is also an effective method to use a polymerization chain transfer agent such as alkyl mercaptan, carbon tetrachloride, carbon tetrabromide, etc. during the polymerization reaction. Ethylenically unsaturated carboxylic acid monomers used in the polymeric dispersant (A) include monobasic acids such as acrylic acid, methacrylic acid, and crotonic acid, dibasic acids such as fumaric acid, itaconic acid, and maleic acid, or their anhydrides. If the amount is less than 5 parts by weight, it is a basic substance and cannot be sufficiently water-solubilized during neutralization, and even if it is possible, it will not be possible to polymerize it in a suspended state with the radically polymerizable vinyl monomer. In this case, a stable aqueous dispersion cannot be obtained, and if the amount exceeds 50 parts by weight, the water resistance of the obtained aqueous dispersion will be adversely affected, which is not preferable. The amount of the ethylenically unsaturated carboxylic acid exceeds 30 parts by weight, and a larger amount is preferable in terms of adhesion to plastics, stability in polymerization to obtain an aqueous resin dispersion, and the like. Other polymerizable monomers for the polymeric dispersant (A) include methyl acrylate, ethyl acrylate, isopropyl acrylate, n-butyl acrylate, isobutyl acrylate, 2-ethylhexyl acrylate, methyl methacrylate, ethyl methacrylate, propyl methacrylate, and n-butyl methacrylate. , isobutyl methacrylate, 2-
Acrylic acid or methacrylic acid alkyl esters such as ethylhexyl methacrylate, styrene, vinyltoluene, 2-methylstyrene, t
Particularly preferred are one or a combination of two or more styrenic monomers such as -butylstyrene; Substituted (meth)acrylic monomer,
Hydroxyl group-containing monomers such as hydroxyethyl acrylate, hydroxypropyl acrylate, hydroxyethyl methacrylate, hydroxypropyl methacrylate, glycidyl acrylate,
Epoxy group-containing monomers such as glycidyl methacrylate and acrylonitrile can also be used as appropriate. As the polymer dispersant (A) according to the present invention, the above-mentioned polymer dispersants are preferably used, but other polymer dispersants can also be used in combination. The polymeric dispersant (A) according to the present invention must have surface-active ability, and can produce a stable aqueous resin dispersion by polymerizing the radically polymerizable vinyl monomer (B). It has to be something. Examples of the radically polymerizable vinyl monomer (B) according to the present invention include ethylenically unsaturated carboxylic acid monomers, acrylic acid alkyl esters, methacrylic acid alkyl esters, styrene monomers, acrylonitrile, nitrogen-containing monomers such as acrylamide, glycidyl methacrylate, etc. Epoxy group-containing monomers, lower carboxylic acid vinyl esters such as vinyl acetate and vinyl propionate, etc.
Although used by species or a combination of two or more species,
In particular, it is preferable to use a styrene monomer, an acrylic acid alkyl ester, and/or a methacrylic acid alkyl ester as a main component, and the amount used is based on 100 parts by weight of the resin content of the polymer dispersant (A).
It is used in a range of 50 to 800 parts by weight, preferably 200 parts by weight.
~700 parts by weight. In this range, stable aqueous resin dispersion and adhesion to plastics,
A water-based printing ink with good printability, abrasion resistance, and other resistance properties can be obtained. If the amount is less than 50 parts by weight, there will be a problem in water resistance, and if it is more than 800 parts by weight, there will be a problem in stability during polymerization in suspension. In addition, during suspension polymerization, in order to minimize the generation of aggregates during polymerization and increase the dispersion stability of the resulting resin, alkylbenzene sulfonate, which is used in ordinary emulsion polymerization, It is also possible to use small amounts of anionic or nonionic low-molecular surfactants such as alkyl sulfates and polyoxyethylene alkyl phenol ethers as long as the water resistance does not deteriorate. Hydrophilic initiators such as ammonium persulfate, potassium persulfate, and hydrogen peroxide are most suitable as polymerization initiators because they shorten polymerization time and provide stable dispersion resins without aggregates. . The main points of the resin dispersion according to the present invention are:
The purpose of this method is to copolymerize radically polymerizable vinyl monomers in a suspended state in the presence of a solution-like polymeric dispersant having surfactant properties, and the dispersion thus obtained has a high molecular weight. In addition, since a large amount of lipophilic polymer can be introduced, abrasion resistance and water resistance are significantly improved. In addition, residual monomers remaining in the polymer dispersant solution at the end of the reaction can be greatly reduced, and odor is improved. Furthermore, the finally obtained resin dispersion has improved adhesion to plastics and printability such as plate fogging compared to a homogeneous copolymer due to the stable interposition of the solution polymer and the dispersed polymer. This is because the problems of conventional water-soluble resins such as water resistance, abrasion resistance, and odor, and the adhesion of emulsion resins to plastics, printability, and water resistance have been overcome. The water-based resin dispersion according to the present invention is prepared by mixing general inorganic pigments and/or organic pigments as colorants using a kneading machine such as a ball mill, attritor, or sand mill, in the same way as general water-based resins.
As a solvent, water and/or alcohols,
Preferably, a lower alcohol such as ethyl alcohol, isopropyl alcohol, or n-propyl alcohol is blended, wax as an anti-wear agent and other additives are blended as necessary, and the mixture is kneaded to produce the desired water-based plastic material. Printing ink is produced. The water-based printing ink is diluted with water and/or an alcohol, preferably a mixed solvent with water such as ethyl alcohol, isopropyl alcohol, n-propyl alcohol, etc., until it reaches a suitable viscosity for printing, and then applied to plastics using a gravure method or a flexo method. printed on. The water-based printing ink of the present invention has excellent adhesion to various plastics, has extremely low odor, and has excellent printing suitability such as plate fogging, compared to conventional water-based printing inks using a vehicle such as silica resin or acrylic resin. Since it has excellent physical properties such as surface abrasion resistance, water resistance, scratch resistance, and bending resistance, it can be suitably used as a surface printing ink for various plastic film flexible packaging materials. The present invention will be described below with reference to Examples and Reference Examples, but the present invention is not limited to these Examples. In addition, all parts and % in Examples and Reference Examples indicate parts by weight and % by weight. Reference example 1

[Table] (1) was charged into a reaction vessel saturated with nitrogen gas, and after raising the temperature to 80°C to 82°C, it was charged into a dropping tank (2)
The entire amount of (3) and 2 parts of (4) were added dropwise over 2 hours, and 0.5 parts of (4) were added immediately after the completion of the dropwise addition and 1 hour later, and after stirring for another 2 hours, the reaction was completed. Lower the temperature to around 40°C, add (5), stir well, and then add (6). After that, further increase the temperature to 80℃~
After raising the temperature to 82°C, perform a stripping operation while blowing nitrogen gas to distill out about 60 parts of isopropyl alcohol, and add the same amount of ion-exchanged water as the distilled amount. Lower the temperature to around 40℃ again and adjust the pH to 8.0-9.0 with ammonia water (25%). Solid content 30%, viscosity 1200cps/25℃, PH8.5
A water-soluble polymer dispersant with a transparent appearance was obtained.

[Table] After charging the polymer dispersant obtained in (1) and (2) into a reaction vessel and raising the temperature to 80℃~82℃,
1 part, and the entire amount of (3) was added dropwise over 2 hours.
After the dropwise addition is complete, the remaining 0.2 part of (4) is added and the reaction is terminated after stirring for about 2 hours. Solids content 43%, viscosity
A milky white stable aqueous resin dispersion with a temperature of 150 cps/25°C and a pH of 8.0 was obtained. Reference example 2

[Table] (1) was charged into a reaction vessel saturated with nitrogen gas, and after raising the temperature to 98°C to 100°C, it was charged into a dropping tank.
The entire amount of (2) and 3 parts of (3) were added dropwise over 2 hours, and 1 part of (3) was added immediately after and 1 hour after the completion of the dropwise addition, and after stirring for an additional 2 hours, the reaction was completed. Lower the temperature to around 40°C, add (4), stir well, and then add (5). Thereafter, the temperature is further raised to 98°C to 100°C, and then a stripping operation is performed under reduced pressure to distill out the entire amount of dioxane used as the reaction solvent. Add the same amount of ion-exchanged water as the distilled amount. Lower the temperature to around 40℃ again and adjust the pH to 8.0-9.0 with ammonia water (25%). Solid content 30
%, a viscosity of 450 cps/25°C, and a transparent appearance of a water-soluble polymer dispersant having a pH of 8.4.

[Table] Charge the polymer dispersant obtained in (1) and the entire amounts of (2) and (3) into a reaction vessel, raise the temperature to 80°C to 82°C, and then add 1.6 parts of (5). Then, add the entire amount of (4) dropwise over 2 hours. After the dropwise addition was completed, the remaining 0.4 part of (5) was added, and after stirring for about 2 hours, the reaction was terminated. Solid content 35
%, a viscosity of 250 cps/25°C, and a slightly yellow stable aqueous resin dispersion with a pH of 8.1. Reference Example 3 Production of polymeric dispersant Polymerization was carried out in the same manner as in Reference Example 1 except that acrylic acid was used as the monomer component in producing the polymeric dispersant in Reference Example 1.
A water-soluble polymer dispersant with a transparent appearance and a viscosity of 1400 cps/25°C and a pH of 8.7 was obtained. Production of water-based resin dispersion

[Table] Charge (1) and (2) into a reaction vessel and adjust the temperature to 80℃~
After raising the temperature to 82°C, add 0.8 parts of (4) and dropwise add the entire amount of (3) over 1.5 hours. After the dropwise addition was completed, the remaining 0.2 part of (4) was added, and after stirring for about 2 hours, the reaction was terminated. Solid content 40%, viscosity 350cps/25℃,
A milky white stable aqueous resin dispersion with pH 8.5 was obtained. Reference Example 4 Manufacture of polymer dispersant Same as Reference Example 1- Manufacture of aqueous resin dispersion Refer to Reference Example 2- except that the monomer components were changed to ethyl methacrylate/n-butyl methacrylate/acrylonitrile = 120/60/20 Polymerized in the same manner as Example 2-, solid content 35
%, a viscosity of 400 cps/25°C, and a slightly yellow stable aqueous resin dispersion with a pH of 8.0. Comparative Example 1 Production of polymeric dispersant Polymerization was performed in the same manner as in Reference Example 1- except that the monomer components were changed to ethyl acrylate/methacrylic acid = 97/3, and the solid content was 30% and the viscosity was
A polymer dispersant with a translucent appearance and a temperature of 1500 cps/25°C and a pH of 8.3 was obtained. Synthesis of water-based resin dispersion Reference example 1-
Polymerization was carried out in the same manner as in . A large number of aggregates were generated during the dropwise addition, and a stable aqueous resin dispersion could not be obtained. Comparative Example 2 Production of Polymer Dispersant The monomer components in Reference Example 2- were changed to methyl acrylate/2-ethylhexyl acrylate/itaconic acid = 20/20/60. Other polymerization was carried out in the same manner as in Reference Example 2. Solid content 30
%, a viscosity of 600 cps/25°C, and a transparent appearance of a water-soluble polymer dispersant having a pH of 8.5. Synthesis of aqueous resin dispersion Reference example 3-
Polymerization was carried out in the same manner as in . Solid content 40
%, a viscosity of 350 cps/25°C, and a pH of 8.5, an aqueous resin dispersion in which some aggregates were observed was obtained. Water-based printing inks using this dispersion as a vehicle had poor water abrasion resistance, resulting in damage to the printed surface and a significant decrease in commercial value. Comparative Example 3 Production of polymeric dispersant Same as Reference Example 2- Production of water-based resin dispersion The amount of polymeric dispersant used in Reference Example 2-
Reference example 2- except that it was reduced from 100 copies to 70 copies.
Polymerization was carried out in the same manner as. As a result, many aggregates were generated at the final stage of polymerization, and the resulting aqueous resin dispersion separated and coagulated and precipitated in about 1 day after being left at room temperature. Comparative Example 4 Manufacture of polymer dispersant Same as Reference Example 3- Manufacture of water-based resin dispersion The amount of polymer dispersant used in Reference Example 3-
Polymerization was carried out in the same manner as in Reference Example 3, except that the amount was changed from 200 parts to 800 parts. Solids content 34%, viscosity
A stable aqueous resin dispersion with an emulsion color of 500 cps/25°C and pH 8.5 was obtained. Water-based printing inks using this dispersion as a vehicle had poor abrasion resistance, water abrasion resistance, and adhesion, resulting in damage to the printed surface and a significant decrease in commercial value. Example 1 A water-based printing ink was produced using the water-based resin dispersion obtained in Reference Example 1 as a vehicle (referred to as vehicle A).

【table】

[Table] (1) was placed in a pepple ball mill, kneaded for 16 hours, and after uniformly dispersing, blended (2) and adjusted.
A highly stable water-based printing ink with a viscosity of 40 seconds (Zahnkup φ3 mm, manufactured by Rigosha, hereinafter the same) was obtained. This printing ink was diluted with a mixed solvent of 4:6 of water and isopropyl alcohol to a viscosity of 30 seconds, and blown into reinforced polyethylene with a surface tension of 47 dyne/cm and a thickness of 25 μm using a gravure printing machine directly connected to the inflation. As a result of printing on a film (colored with Mitsui Petrochemical Co., Ltd.'s Processing Hi-Zex 700 and Toyo Ink Manufacturing Co., Ltd.'s Masterbatch 10020 White 3%) using a gravure plate with a plate depth of 28μ, the printing effect, adhesion, abrasion resistance, water abrasion resistance, A printed product was obtained that had good scratch resistance and kneading resistance, and maintained resistance as a shopping bag. Detailed results are shown in Table 1. Example 2 A water-based printing ink was produced using the water-based resin dispersion obtained in Reference Example 2 as a vehicle (referred to as vehicle B).

[Table] In exactly the same manner as in Example 1, the pastes (1) and (2) were adjusted to obtain a highly stable water-based printing ink with a viscosity of 30 seconds. This printing ink was diluted with a 1:1 mixed solvent of water and isopropyl alcohol to a viscosity of 17 seconds, and printed on easily adhesive polypropylene film (YS42, manufactured by Toray Industries, Inc.) using a gravure printing machine with a 25μ plate. Printed matter with good effects, adhesion, abrasion resistance, water abrasion resistance, scratch resistance, and kneading resistance was obtained. In addition, the results of residual solvent measurement were good, with 30 ppm of isopropyl alcohol and 22 ppm of ethyl alcohol per 0.2 m ² of the printed matter, with no other organic solvents detected at all. Detailed results are shown in Table 1. Example 3 A water-based printing ink was produced using the water-based resin dispersion obtained in Reference Example 3 as a vehicle (referred to as vehicle C).

[Table] A highly stable water-based printing ink with a viscosity of 45 seconds was obtained by grinding and adjusting in the same manner as in Example 1. This ink was diluted with a 6:4 mixed solvent of isopropyl alcohol and water to a viscosity of 35 seconds and printed on treated polyethylene coated paper (for milk cartons, manufactured by Wehauser) using a flexo printing machine. A printed matter with good adhesion, abrasion resistance, water abrasion resistance, bending resistance, and heat resistance was obtained. Detailed results are shown in Table 1. Example 4 Using the aqueous resin dispersion obtained in Reference Example 4 as a vehicle, it was ground and adjusted in the same manner as in Example 1 to obtain a highly stable printing ink with a viscosity of 34 seconds. Furthermore, under the same conditions as in Example 2, a K-coated OPP film (Daicel
5000, manufactured by Daicel Corporation), printed matter with good printing effect, adhesion, abrasion resistance, water abrasion resistance, scratch resistance, and kneading resistance was obtained. Also,
Residual solvent measurement results are 45 ppm of isopropyl alcohol and ethyl alcohol per 0.2 ^m2 of printed matter.
The concentration was 30 ppm, and no other organic solvents were detected, which was good. Detailed results are shown in Table 1. Comparative example 5

[Table] The above formulation was ground and adjusted in exactly the same manner as in Example 1 to obtain a water-based printing ink with a viscosity of 30 seconds. Further, printing was carried out in the same manner as in Example 1, but the adhesion and abrasion resistance were poor, and the printed surface was significantly damaged, reducing the commercial value. Detailed results are shown in Table 1. Comparative example 6

[Table] (2)〓

Claims (1)

[Claims] 1 A vinyl monomer (vinyl monomer) that can be radically polymerized in the presence of a polymer dispersant (A) having surfactant ability or in the presence of the polymer dispersant (A) and a low molecular surfactant used in ordinary emulsion polymerization. A water-based printing ink for plastics, characterized in that a water-based resin dispersion in which B) is polymerized in a ratio of 50 to 800 parts by weight to 100 parts by weight of (A) is used as a vehicle component. Then, a polymerizable monomer mixture in which the polymeric dispersant (A) consists of 5 to 50 parts by weight of an ethylenically unsaturated carboxylic acid and 50 to 95 parts by weight of other polymerizable monomers is subjected to radical polymerization by a solution polymerization method in an organic solvent. A water-based printing ink for plastics, which is a water-soluble resin obtained by neutralizing the resulting copolymer with an average molecular weight of 3,000 to 50,000 with a basic substance, and then removing most or all of the organic solvent.