JPS6154830B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention provides coatings or printing inks, particularly water-based inks useful for gravure or flexographic printing.
More specifically, the present invention relates to a water-based coating agent that can be coated on aluminum foil, polyolefin film, etc., which are difficult to adhere to with water-based inks or paints. Conventionally, vehicles for water-based printing inks or paints for gravure or flexographic printing have been used as shellac, alkaline aqueous solutions of maleated rosins, and recently, styrene/maleic acid resins, carboxyl group-containing acrylic resins, and styrene/acrylic acid resins have been used. Synthetic resins such as alkaline aqueous solutions or these water-soluble resins and various emulsions, such as styrene-based, acrylic-based, vinyl chloride-based, vinyl acetate-based, ethylene-vinyl acetate-based, SBR (styrene-butadiene rubber)-based emulsions, etc. Mixtures, etc. are used, but all must be satisfied in printability such as leveling properties, plate jam resistance, plate fogging resistance, drying properties, and ink coating performance such as water resistance and abrasion resistance. However, it has the disadvantage of not adhering to aluminum or plastic films, especially treated polyolefin films, which limits its use.
This is the actual situation. When considering the types of aqueous vehicles based on acrylic, they are broadly classified into aqueous solution types and emulsion types, each of which has its own unique characteristics. Usually, an aqueous solution type vehicle is an ammonium salt or amine salt of a resin obtained by copolymerizing a polymerizable monomer containing an unsaturated carboxylic acid group with another polymerizable monomer in an organic solvent that is the true solvent of the polymer. It is made water soluble and has been put into practical use in some cases. This type of vehicle has relatively Newtonian fluidity, so it generally has good printability and can be used for paper printing without any problems, but because the resin has strong polarity due to its functional groups, it is highly hydrophilic and hydrophobic The adhesion to substrates such as polyolefins such as treated polyethylene, treated polypropylene, treated aluminum foil, etc. was poor, and it could not be put to practical use. On the other hand, emulsion type vehicles are usually redox polymerized using anionic or nonionic emulsifiers, but these have a high weight average molecular weight of several million, good solvent release, gloss,
Although it has relatively good water resistance and abrasion resistance, and also has relatively good adhesion to the above-mentioned hydrophobic substrate, it has strong thixotropy, so-called poor fluidity, so it has poor leveling properties. There are disadvantages such as the dry coating film cannot be redissolved, plate clogging is likely to occur, and film forming properties are poor. For this reason, many attempts have been made to improve printability, printing effect, adhesion, etc. by using the water-soluble vehicles mentioned above to cover their respective drawbacks, but still no fully satisfactory water-based coating has been obtained. Not yet. The present invention uses a vehicle useful for aqueous coatings that combines the advantages of the water-soluble type and emulsion type vehicles described above, and which has conventionally been considered difficult to adhere to. The present invention provides an aqueous coating agent that can be coated with aluminum foil and polyolefin. As a result of research to satisfy the above points, the present inventors have developed a monovalent monovalent monomer mixture having 1 to 3 carbon atoms containing 5 to 20% by weight of unsaturated carboxylic acid monomers and dissolving in the alcohol described below. The copolymer is polymerized in suspension in the presence of one or more alcohols, the resulting copolymer is neutralized with amine or ammonia, and an aqueous dispersion in water is used as a vehicle, and aluminum or polyolefin is used as a vehicle. We have now discovered a water-based coating useful for printing or painting on. The characteristic feature of the present invention is that, as mentioned above, the conventional acrylic type water-soluble vehicle for coating materials undergoes radical polymerization of the resulting copolymer in an organic solvent, which is a true solvent, and then In contrast, in the present invention, the monomer is dissolved but the copolymer of the monomer is not dissolved, after polymerization in a suspended state in a predetermined solvent, the amine is Alternatively, by partially or equivalently neutralizing the carboxyl groups in the copolymer with ammonia, it is solvated in a predetermined mixed solvent of alcohol and water, dispersed in an emulsion, and stabilized as a so-called colloidal dispersion. The vehicle is an aqueous dispersion. This dispersion has better drying properties than general water-soluble vehicles, exhibits more Newtonian fluidity than emulsions, and has good film-forming properties similar to those of water-soluble vehicles. In addition, this dispersion composition has the advantage that the resulting polymer does not dissolve in the specified hydrophilic alcohol and can be stably dispersed in the specified alcohol and water mixed solvent by neutralizing with amine or ammonia.
Compared to normal alkali-neutralized water-soluble vehicles, it is easier to balance hydrophobicity and hydrophilicity, and it is possible to create relatively strong dispersion compositions with lower polarity than normal water-soluble vehicles. Therefore, it can adhere not only to paper but also to low polarity aluminum foil, polyolefin, etc. Furthermore, when it is made into printing ink or paint, it has good adsorption with organic pigments, which is a factor that brings about good printability. It is presumed that it is getting older. As a result of measuring the adsorption ability of the resin to the pigment surface in a dilute solution of the aqueous dispersion according to the present invention, it was found that the adsorption ability of a general acrylic water-soluble vehicle was higher than that of organic compounds such as benzidine yellow, phthalocyanine blue, and watching red Ca salt. Regarding pigments, it was observed that 10 to 22 milligrams (mg) of resin was adsorbed per gram (g) of pigment.
In the aqueous dispersion of the present invention, 25
Adsorption of ~50 mg of resin was observed. In addition, as a result of measuring rutile type titanium white, a typical inorganic pigment, it was found that 12
Adsorption of ~18 mg of resin was observed, whereas adsorption of 35 to 55 mg of resin was observed with the dispersion composition of the present invention, which is 2 to 3 times more pigment than a typical acrylic water-soluble vehicle. It was recognized that the adsorption capacity of This property not only improves the storage stability of the colorant composition, improves printability such as plate fogging and plate jamming in gravure printing or flexographic printing, but also improves printing effects such as leveling property and trapping property. However, this seems to be a factor in giving a satisfactory result. To explain the present invention in more detail, the unsaturated carboxylic acid monomers used include acrylic acid, methacrylic acid, itaconic acid, fumaric acid, maleic acid, and anhydrides thereof.
If the amount is 5% by weight or less in the polymerizable monomer mixture, after neutralizing the amine or ammonia, a predetermined mixed solvent of alcohol and water (preferably, the ratio of alcohol to water is 3 to 1 to 1 in parts by weight) is used. If a stable dispersion cannot be obtained with a concentration of 20% or more (within the range of At the same time, the adhesion to aluminum foil, polyolefin film, etc. decreases. Monomers other than unsaturated carboxylic acid monomers used in the present invention include methyl acrylate, ethyl acrylate, isopropyl acrylate, n-butyl acrylate, isobutyl acrylate, n-amyl acrylate, isoamyl acrylate, Acrylic acid esters such as n-hexyl acrylate, 2-ethylhexyl acrylate, n-octyl acrylate, decyl acrylate, dodecyl acrylate, methyl methacrylate, ethyl methacrylate,
Propyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, n-methacrylate
Methacrylic acid esters such as amyl, n-hexyl methacrylate, n-octyl methacrylate, 2-ethylhexyl methacrylate, decyl methacrylate, dodecyl methacrylate, styrene, vinyltoluene, 2-methylstyrene, t-butylstyrene, chloro Styrenic monomers such as styrene, hydroxy group-containing monomers such as hydroxylethyl acrylate, hydroxypropyl acrylate, hydroxyethyl methacrylate, hydroxypropyl methacrylate, N-methylol (meth)
It can be selected from one or more of N-substituted (meth)acrylic monomers such as acrylamide and N-butoxy(meth)acrylamide, epoxy group-containing monomers such as glycidyl acrylate and grindyl methacrylate, and acrylonitrile. I can do it. In the present invention, a polymerizable monomer containing 5 to 20% by weight of an unsaturated carboxylic acid monomer having a carbon number of 1
In the presence of one or more of ~3 monohydric alcohols, i.e. methyl alcohol, ethyl alcohol, n-propyl alcohol, isopropyl alcohol, hydrophobic compared to monomers that are common water-soluble vehicle components. When polymerizing with a composition containing a considerable amount of a monomer, the polymer is obtained in a suspended state, and the desired dispersion is achieved by neutralizing it with amine or ammonia and dispersing it in water. You can get a body. Examples of hydrophobic monomers include esters of alcohols with 4 or more carbon atoms, preferably 8 or more carbon atoms, and acrylic acid or methacrylic acid, and these are preferably used in an amount of 25 to 60% by weight of the total copolymerized components. . As the radical initiator for the polymerization of the present invention, organic peroxide initiators such as benzoyl peroxide, lauroyl peroxide, cumene hydroperoxide, di-tert-butyl peroxide, and acetyl peroxide are used. The obtained copolymer is neutralized by at least 50% equivalent of the carboxyl groups contained therein and an amine such as aqueous ammonia, aminoethyl alcohol, dimethylamino alcohol, morpholin, or diethylaminoethyl alcohol, and further water is added. Thus, the desired stable dispersion can be obtained. In particular, as a neutralizing agent, aliphatic tertiary amino alcohol is most suitable for printability. The aqueous dispersion of the present invention is prepared by blending general inorganic pigments and organic pigments as colorants by using a kneading machine such as a ball mill, attritor, or sand mill in the same way as general water-soluble vehicles, and using water as a solvent. Alternatively, the desired water-based coating can be obtained by blending an alcohol, preferably a lower alcohol such as ethyl alcohol or isopropyl alcohol, and blending finely powdered wax as an anti-friction agent and other additives and kneading. Manufactured. At the time of printing or painting, the water-based coating material is diluted with water or alcohol, preferably a mixed solvent of lower alcohol such as ethyl alcohol, isopropyl alcohol, n-propyl alcohol, and water, until it reaches an appropriate viscosity, and then applied by gravure printing or flexography. It can be printed on a substrate using a method, or it can be applied to a substrate using a roll coater, air knife coater, spray, or the like. The present invention will be explained below with reference to Examples, but the present invention is not limited to these Examples in any way. In addition, the number of parts in the examples indicates parts by weight. Example 1

【table】

[Table] Charge (2) into a flask saturated with nitrogen gas, raise the temperature to 70-74℃, and then add (1) using a dropping funnel.
The entire amount of (3) and 1/2 amount of (3) were dropped almost uniformly over 2 hours. After the dropwise addition was completed, 1/4 amount of (3) was added every hour, and the reaction was completed in about 5 hours. temperature 40
After lowering the temperature to ℃, adding (4) and stirring and dispersing well,
When (5) was added, a stable milky white dispersion with a solids content of 25% was obtained. A water-based printing ink was produced using the dispersion as a vehicle (referred to as Vehicle A).

[Table] (1) was placed in a pebble mill, kneaded for 16 hours to ensure uniform dispersion, and then blended with (2) to adjust the viscosity to 18.
A water-based printing ink with good stability was obtained. This ink was diluted with a 1:1 mixed solvent of water and IPA until the viscosity reached 25 seconds (Zahn cup 3 mm), and treated with a 25μ plate using a gravure printing machine. When applied to stretched polypropylene (Torefane #2535, manufactured by Toray Industries) and treated polyethylene (Sumikasen, manufactured by Sumitomo Chemical), both showed good printability, good printing effect, and good adhesion. Detailed results are shown in Table 1.

[Table] The paste was prepared and adjusted in the same manner as in Example 1 to obtain a highly stable water-based printing ink with a viscosity of 20 seconds (Zahnkap 4 mm). This ink was diluted with a 1:2 mixed solvent of water and IPA until the viscosity reached 25 seconds (Zahnkap 3 mm), and then used on a flexographic printing machine to process treated aluminum cartons (vinyl treated, manufactured by Honshu Paper Industries) and treated polyethylene cartons (made by Jujo Paper Industries). As a result of printing on
Both had good printability, good effects, and good adhesion. Detailed results are shown in Table 1. Example 3

[Table] The following was produced in the same manner as in Example 1 to obtain a stable milky white dispersion with a solid content of 25%. A water-based printing ink was prepared as the dispersion vehicle (referred to as Vehicle B). The mixture was ground and adjusted in the same manner as in Example 1 to obtain a stable water-based printing ink with a viscosity of 22 seconds (Zahnkup: 4 mm). Furthermore, as a result of printing in the same manner as in Example 1, the printability and printing effect were good, and the adhesion was also good. Detailed results are shown in Table 1. Example 4

[Table] Example 1 was produced in the same manner as in Example 1, except for (1), to obtain a stable milky white dispersion with a solid content of 25%. A water-based printing ink was produced using the dispersion as a vehicle (referred to as vehicle C). The paste was ground and adjusted in the same manner as in Example 2, to obtain a highly stable water-based printing ink with a viscosity of 18 seconds (Zahn cup: 4 mm). Furthermore, as a result of printing in the same manner as in Example 2, the printability and printing results were good, and the adhesion was also good. Detailed results are shown in Table 1. Example 5 Vehicle A 70 parts Rioconquiero-R-1 (yellow aqueous dispersed pigment,
Toyo Ink Manufacturing Co., Ltd.) 10 Polywax 2000 Micronized (fine powder wax, manufactured by Baliko Wax, USA) 2 Water 10 IPA 7.5 Antifoaming agent (silicone emulsion) 0.5 Stir the above composition with a high-speed mixer for 1 hour A highly stable water-based printing ink with a viscosity of 25 seconds (Zahn cup 4 mm) was obtained. This printing ink was diluted 15% with water, applied to the entire surface of a treated aluminum carton using a roll coater, and dried with hot air at 120°C. It had good coating suitability, good coating effect, and good adhesion. Detailed results are shown in Table 1. Comparative example 1 Styrene 20 parts Ethyl acrylate 45〃 Methyl methacrylate 20〃 Acrylic acid 15〃 Ethyl alcohol 100〃 Isopropyl alcohol 50〃 Azobisisobutyronitrile 3〃 Dimethylaminoethyl alcohol 19〃 Water 228〃 Same as Example 1 A transparent water-soluble vehicle was obtained using the manufacturing method described above. Comparative Example 2 Styrene 12 parts Butyl acrylate 18.5〃 2-ethylhexyl acrylate 8〃 Acrylic acid 1〃 Ethylene oxide adduct of alkyl phenol ether (25%) 8 parts Sulfate of ethylene oxide adduct of alkyl phenol ether (30%) ) 1.5〃 Ion-exchanged water 50.5〃 Ammonium persulfate 0.2〃 Sodium bisulfite 0.1〃 An emulsion type vehicle was obtained from the above composition by a conventional emulsion polymerization method.

【table】

[Table] Test method Adhesion: The printed (coated) surface was peeled off with cellophane tape and the adhesion of the coating film was evaluated. Massage: Performed only on polyolefin film. The ink releasability was evaluated by vigorously rubbing the printed (coated) surface with a fingertip. Scratching: The printed (coated) surface was strongly scratched with the tip of a fingernail to evaluate the occurrence of scratches. Blocking resistance: When the printed (coated) surfaces are aligned,
A pressure bonding test was conducted under the conditions of 40° C., 80% humidity, 500 g/cm ² and 24 hours. Friction resistance: A friction test was conducted using a Sutherland type laboratory tester under the conditions of 4 pounds and 50 times, by combining the printed (coated) surface and the high quality paper surface. Water resistance: Align the printed (coated) side and the water-containing paper side,
A pressure bonding test was conducted under the conditions of 100 g/cm ² and 24 hours.

Claims (1)

[Claims] 1 A polymerizable monomer mixture containing 5 to 20% by weight of an unsaturated carboxylic acid monomer and dissolved in the alcohol described below is suspended in the presence of one or more monohydric alcohols having 1 to 3 carbon atoms. An aqueous coating agent for aluminum or polyolefin, which uses as a vehicle an aqueous dispersion in which the resulting copolymer is neutralized with amine or ammonia and dispersed in water.