JPS629267B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a water-based printing ink that has excellent printability, printing effect, and processing suitability for use in flexible packaging materials such as composite plastic films. Conventionally, plastic film composite packaging has been used in large quantities as a transparent flexible packaging material for potato chips, ramen noodles, confectionery, etc., and has shown great growth. Examples of the composition of these packaging materials include polypropylene film (OPP)/printing ink/
Adhesive / Polypropylene film (CPP) or polyethylene film, polyester film (PET) / Printing ink / Adhesive / Polypropylene film (CPP) or polyethylene, polypropylene film (OPP) / Printing ink / Isocyanate primer / Polyethylene melt coating It is a packaging material made of polyester, etc., whose edges are pasted together by heat sealing or dielectric heating, and the bags are made and filled with the contents. The printing ink used here must have sufficient adhesion and adhesion to plastic films such as OPP films, and should preferably have no residual solvent and no odor. Furthermore, it must maintain appropriate printability and printing effects. Usually, these flexible packaging materials are printed with solvent-based gravure inks that use organic solvents such as toluene, ethyl acetate, and methyl ethyl ketone. There are concerns about the problem of residual solvents migrating into containers, and despite great efforts being made to reduce residual solvents, no fundamental solution has been reached. Furthermore, solvent vapor also exists in the printing work environment, which is unfavorable from a sanitary control point of view. Therefore, the practical application of water-based printing inks that do not contain harmful organic solvents and has great future potential from the perspective of resource conservation has been considered. Acrylic acid resin, acrylic ester
Water-based printing inks that use resins as vehicles such as acrylic acid copolymer resins, styrene-maleic acid copolymer resins, hydroxyethyl cellulose, hydroxypropyl cellulose, etc., or mixtures thereof, essentially use polyester, polyethylene, or polypropylene, which have low hydrophilicity. It has poor adhesion with other films and cannot maintain sufficient adhesive strength, resulting in abnormalities such as lamination lifting and cannot be put to practical use. The present invention eliminates the drawbacks of conventional inks, and provides a water-based printing ink that is hygienic and has good adhesion to plastic film, and is fully functional as a plastic film composite flexible packaging material. This is what we provide. That is, as a result of intensive research to satisfy the above points, the present inventors have developed a water-based film that has excellent adhesion to various plastic films, is extremely low odor, and has excellent printability such as plate fogging and lamination processing suitability. We discovered a water-based printing ink using an acrylic resin as a vehicle and completed the present invention. The present invention includes the following (A) to (D) which are suitably used when producing flexible packaging materials by printing on plastic film and laminating polyolefin.
An aqueous resin dispersion obtained by emulsion polymerization using a vinyl monomer and, if necessary, a chain transfer agent, to which a basic substance and an alcohol having 1 to 3 carbon atoms are added and dissolved. The present invention relates to an aqueous printing ink using an acrylic resin solution as a vehicle component. (A) At least one selected from acrylic ester monomers and methacrylic ester monomers having an alkyl group having 1 to 3 carbon atoms.
40 to 90 parts by weight (B) α/β-ethylenically unsaturated carboxylic acid monomer 5 to 30 parts by weight (C) Hydroxyl group-containing vinyl monomer 5 to 30 parts by weight (D) Other radically polymerizable vinyl monomers 0 ~50 parts by weight The features of the present invention are that it greatly improves the adhesion strength of water-based printing ink to plastic film, which was unsatisfactory with conventional water-based resin vehicles, and that it has a higher residual strength compared to general water-based acrylic resins. The main points are that the amount of monomer is greatly reduced, making it odorless, and that the weaknesses in printing suitability such as plate fog have been greatly improved. To explain the aqueous acrylic resin according to the present invention in more detail, (A) acrylic ester monomers or methacrylic ester monomers having an alkyl group having 1 to 3 carbon atoms include methyl acrylate, ethyl acrylate, isopropyl acrylate, etc. acrylic esters,
Methyl methacrylate, ethyl methacrylate,
Methacrylic acid esters such as propyl methacrylate are used. If the amount is less than 40 parts by weight based on the total vinyl monomer, it will not be possible to obtain a resin with a transparent appearance, and problems such as ink suitability or plate clogging during printing will occur. Adhesion to the film is significantly reduced and abnormalities such as lamination lifting occur. Next, (B) α/β-ethylenically unsaturated carboxylic acid monomers include monobasic acids such as acrylic acid, methacrylic acid, and crotonic acid, and dibasic acids such as fumaric acid, itaconic acid, and maleic acid. If the amount is less than 5 parts by weight, a resin with a transparent appearance cannot be obtained. In addition, the adhesion to the film is impaired, causing the same troubles as mentioned above. If the amount exceeds 30 parts by weight, many aggregates are generated during emulsion polymerization, making it impossible to obtain a stable resin. Next, (C) hydroxyl group-containing vinyl monomers include hydroxyethyl acrylate, hydroxypropyl acrylate, hydroxyethyl methacrylate, and hydroxypropyl methacrylate. Sexuality is significantly reduced. If the amount exceeds 30 parts by weight, as with the α/β-ethylenically unsaturated carboxylic acid monomer, many aggregates will be generated during emulsion polymerization, making it impossible to obtain a stable resin. Furthermore, (D) other radically polymerizable vinyl monomers include:
n-butyl acrylate, isobutyl acrylate, 2-ethylhexyl acrylate, n-butyl methacrylate, isobutyl methacrylate,
Acrylic acid esters and methacrylic acid esters having an alkyl group of 4 or more carbon atoms such as 2-ethylhexyl methacrylate, styrene monomers such as styrene, vinyltoluene, 2-methylstyrene, t-butylstyrene, N-methylol (meth) ) acrylamide, N-substituted (meth) such as N-butoxymethyl (meth)acrylamide
Acrylic monomer, glycidyl acrylate,
Epoxy group-containing monomers such as glycidyl methacrylate, acrylonitrile, and the like can be used as appropriate. Emulsion polymerization from monomers (A) to (D) above uses an anionic or nonionic surfactant and a hydrophilic initiator alone or a redox initiator such as ammonium persulfate, potassium persulfate, or hydrogen peroxide. This can be carried out by a conventional emulsion polymerization method in the temperature range of 40°C to 90°C using water alone or in combination with a chain transfer medium. The term chain transfer agent used herein refers to a lower alcohol with a large chain transfer coefficient such as methyl alcohol, ethyl alcohol, or isopropyl alcohol, or a polymer chain transfer agent such as alkyl mercaptan, carbon tetrachloride, or carbon tetrabromide. There is no problem as long as the amount used is appropriately controlled within a range that does not adversely affect the odor of printed matter during the emulsion polymerization reaction.The purpose of its use is to lower the molecular weight of the resulting aqueous resin dispersion, This is to improve the solubility and dilutability of the acrylic resin when lower alcohol is added. Next, the basic substances used for neutralization are not particularly limited, but include ammonia, sodium hydroxide,
Potassium hydroxide or various amines such as trimethylamine, triethylamine, dimethylethanolamine, and diethylethanolamine can be used. Considering the solubility of the emulsion polymer, the amount used is preferably set to a pH of 7.0 or higher. Furthermore, alcohols having 1 to 3 carbon atoms include methyl alcohol, ethyl alcohol, n-
Lower alcohols such as propyl alcohol and isopropyl alcohol can be used. The main point of the water-based acrylic resin according to the present invention is that by post-dissolving the water-based resin dispersion obtained by emulsion polymerization, it eliminates the odor that is a problem with water-based acrylic resins obtained by conventional solution polymerization. In addition, the problems of aqueous resin dispersions obtained by emulsion polymerization, such as ink suitability and plate clogging during printing, are solved by dissolving the resin in the aqueous resin dispersion. . The water-based acrylic resin according to the present invention can be used in the same way as general water-based resins, such as ball mills, attritors,
Using a grinding machine such as a sand mill, as a coloring agent,
General inorganic pigments and organic pigments are blended, and water and/or alcohols are used as a solvent, preferably ethyl alcohol, isopropyl alcohol, n-
The desired water-based printing ink is produced by blending a lower alcohol such as propyl alcohol, blending wax as an anti-wear agent, leveling agent and other additives as necessary, and kneading. The water-based printing ink is diluted with a mixed solvent of water and/or an alcohol, preferably ethyl alcohol, isopropyl alcohol, n-propyl alcohol, etc., until it reaches a suitable viscosity during printing, and then applied to a plastic film using a gravure method or a flexo method. The structure of the plastic film composite flexible packaging material is then completed by applying a primer treatment to the printed image and then melt-coating it with polyolefin or dry lamination using a urethane-based connecting agent. Plastic films printed with the water-based printing ink of the present invention include surface-treated polypropylene films, modified polypropylene films, anchor-coated polypropylene films, polyvinylidene chloride-coated polypropylene films, which are used for flexible packaging materials of ordinary composite plastic films, etc. Various polyolefin films such as treated polyethylene film, modified polyethylene film, anchor coated polyethylene film, polyvinylidene chloride coated polyethylene film, so-called easily adhesive polyolefin film with hydrophilicity introduced to the surface and a wet tension of 40 dynes/cm or more,
Modified polyester film, surface treated polyester film, anchor coated polyester film, polyvinylidene chloride coated polyester film, wetting tension with hydrophilic groups introduced on the film surface
It is also possible to print on so-called easily adhesive polyester films of 40 dynes/cm or more, other hydrophilic films such as nylon and cellophane, and it is also possible to print on various papers, treated aluminum foils, etc. In addition, these printed plastic films can be laminated by the conventional method of applying a primer treatment to the printed surface and melt-coating polyolefin, or by dry lamination using a urethane adhesive. Furthermore, it enables a dry lamination processing method using a water-based adhesive or a solvent-free adhesive. The water-based printing ink of the present invention has excellent adhesion to various plastic films, has extremely low odor, and has excellent printing suitability for plate fogging, etc., compared to conventional water-based printing inks that use silica resin, acrylic resin, etc. as vehicles. , and has excellent lamination processing suitability, so it can be applied to various plastic film composite flexible packaging materials. The present invention will be explained below with reference to Reference Examples, Examples, and Comparative Examples, but the present invention is not limited to these Examples. Note that all parts and percentages in Reference Examples, Examples, and Comparative Examples indicate parts by weight and percentages by weight. Reference example

【table】

[Table] Charge the above substances in the above proportions into a reactor and a dropping tank that have been saturated with nitrogen gas in advance. The polymerization reaction starts at 60-63°C, and the dropwise addition starts when the temperature of the reactor reaches 65°C. The dropping time is 2 hours. The polymerization temperature is within the range of 66°C to 70°C, and the reaction is completed in about 4 hours. Then lower the temperature to around 40°C and add aqueous ammonia (25%) and isopropyl alcohol. Solid content 20%, viscosity 90cps/
A stable aqueous resin with a transparent appearance and a pH of 8.0 was obtained at 25°C. Reference example ~ The vinyl monomer components of the reference example were changed as shown below, and the other conditions were the same as in the reference example. As a result, all of the polymerization reactions were transparent in appearance and stable aqueous with a solid content of 20%. A resin was obtained.

【table】

[Table] Comparative Examples 1 to 3 Only the vinyl monomer component of the reference example was changed as shown below, and the other conditions were the same as in the reference example to conduct a polymerization reaction.

【table】

[Table] (All numbers in the table are the number of copies)
As a result, in Comparative Example 1, many aggregates were generated during polymerization, and a stable aqueous resin could not be obtained. In Comparative Examples 2 and 3, there were no particular problems in the polymerization reaction, but the final product did not have a transparent appearance, a milky white aqueous dispersion was obtained, and the suitability for ink formation was poor, making it impossible to form a stable ink. Comparative Example 4 Using the same monomer composition as in the reference example, a polymerization reaction was carried out by a conventional solution polymerization method as described below.

[Table] In the reaction vessel and dropping tank saturated with nitrogen gas (1)
Prepare 1/2 amount of (2) and 1/4 amount of (2), respectively.
After raising the internal temperature to 80°C to 85°C, the mixture is added dropwise over 2 hours. After the completion of the dropwise addition, 1/4 amount of (2) was added every hour, and the reaction was completed in about 5 hours. After lowering the temperature to around 40℃ and adding (3) and stirring, adding (4), a stable aqueous resin with a solid content of 30%, a viscosity of 250ops/25℃, and a pH of 7.8 was obtained. It had a strong residual monomer odor, making it unsuitable as a water-based printing ink. Example 1 A water-based printing ink was produced using the water-based acrylic resin obtained in Reference Example as a vehicle (referred to as vehicle A).

[Table] (1) was put into a pebble mill and kneaded for 16 hours to ensure uniform dispersion, then blended with (2) to adjust the viscosity to 30
A water-based printing ink with good stability was obtained. This ink has a viscosity of 17
Dilute with a 1:1 mixed solvent of water and isopropyl alcohol and use a gravure printing machine until 25 seconds.
Easy adhesive polypropylene film (YS-
41 (manufactured by Toray Industries, Inc.), both in the case of single-color printing and in the case of four-color overprinting, the printability and printing effect were good, and the adhesion was also good. Furthermore, the printed surface was primed (polyethyleneimine, manufactured by Nissho Chemical Co., Ltd.), and polyethylene (Mirason #14, manufactured by Mitsui Polychemical Co., Ltd.) was heated at 300°C.
As a result of melt coating, the coating suitability and lamination strength were extremely good, bag making and filling with an automatic bag making machine were normal, and the product effect was good. In addition, the results of acid distillation solvent measurement were 30 PPM of isopropyl alcohol, 55 PPM of n-propyl alcohol, and 55 PPM of ethyl alcohol per 0.2 m ² of printed matter.
20PPM, bonding, laminate with isopropyl alcohol 20PPM, n-propyl alcohol
The amount was 60 PPM and ethyl alcohol 15 PPM, which was a small amount, and no other organic solvents were detected, which was extremely better than packaging materials using conventional solvent-based inks. Detailed results are shown in Table-1. Example 2 A water-based printing ink was produced using the water-based acrylic resin obtained in Reference Example as a vehicle (referred to as vehicle B).

[Table] By the same operation as in Example 1, a water-based printing ink with good stability and a viscosity of 30 seconds was obtained by grinding and adjusting. This 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 polyester film (Q-27, manufactured by Toray Industries, Ltd.) using a gravure printing machine with a 25μ plate. As a result, both in the case of monochrome printing and in the case of four-color printing, the printability and printing effect were good, and the adhesion was also good. Furthermore, urethane adhesive (Toyo Morton Adcoat 305/Adcoat 335 = 1/1, solid content 30%, diluted with ethyl acetate) was applied to the printing surface using a gravure 40μ plate, and a polyethylene film (60μ) was applied using the dry lamination method. pasted together. As a result, the lamination suitability and lamination strength were fairly good, the bag making and filling similar to those in Example 1 were normal, and the product effect was good. In addition, the results of residual solvent measurement were 30 PPM of isopropyl alcohol, 50 PPM of n-propyl alcohol, and 50 PPM of ethyl alcohol per 0.2 m ² of printed matter.
22PPM, laminate with isopropyl alcohol
20 PPM, n-propyl alcohol 45 PPM, ethyl acetate 50 PPM, and ethyl alcohol 15 PPM, and no other organic agents were detected, indicating good results. Detailed results are shown in Table-1. Example 3 A water-based printing ink was produced using the water-based acrylic resin obtained in Reference Example as a vehicle (referred to as Vehicle C). In the same manner as in Example 1, vehicle C was used instead of vehicle A, and the mixture was ground and adjusted to obtain a highly stable water-based printing ink with a viscosity of 30 seconds. 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. A water-based ethylene-vinyl acetate copolymer adhesive Denka EVA Tex #H201 (manufactured by Denki Kagaku Kogyo Co., Ltd.) was applied to the printed surface using a 40μ gravure plate, and a polyethylene film (60μ thick) was laminated using a dry lamination method. As a result, the lamination suitability and lamination strength were extremely good, bag making and filling similar to those in Example 1 were performed without any abnormality, and the product effect was also good. In addition, the results of residual solvent measurement were 40 PPM of isopropyl and 55 PPM of n-propyl alcohol per 0.2 m ² of printed materials, and isopropyl alcohol of laminates.
30 PPM, n-propyl alcohol 50 PPM, and no other organic solvents were detected, which was good. Detailed results are shown in Table-1. Example 4 Using the aqueous acrylic resin obtained in the reference example as a vehicle (referred to as vehicle D), kneaded meat was prepared in the same manner as in Example 1 using vehicle D instead of vehicle A.
After adjustment, a stable printing ink with a viscosity of 35 seconds was obtained. Further, when Example 1 was printed on a polyvinylidene chloride coated OPP film (manufactured by KOP/OL Tohcello Co., Ltd.) under the same conditions, the printability and printing effect were good, and the adhesion was also good. Furthermore, when laminated in the same manner as in Example 2, the lamination suitability and lamination strength were also good. Detailed results are shown in Table-1. Example 5 Using the aqueous acrylic resin obtained in Reference Example as a vehicle (vehicle E), kneaded meat was prepared in the same manner as in Example 1 using vehicle E instead of vehicle A.
A highly stable printing ink with a viscosity of 32 seconds was obtained. Furthermore, as a result of printing on a polyvinylidene chloride coated polyester film (T-8000, manufactured by Toyobo Co., Ltd.) under the same conditions as in Example 1, the printability and printing effect were good, and the adhesion was also good. Furthermore, when laminated in the same manner as in Example 2, the lamination suitability and lamination strength were also good. Detailed results are shown in Table-1. Comparative example 5

[Table] (2)〓

Claims (1)

[Scope of Claims] 1. Using the following vinyl monomers (A) to (D), a basic substance and A water-based printing ink for plastics, characterized in that an aqueous acrylic resin solution in which an alcohol having 1 to 3 carbon atoms is added and dissolved is used as a vehicle component. (A) At least one selected from acrylic ester monomers and methacrylic ester monomers having an alkyl group having 1 to 3 carbon atoms.
40 to 90 parts by weight (B) α/β-ethylenically unsaturated carboxylic acid monomer 5 to 30 parts by weight (C) Hydroxyl group-containing vinyl monomer 5 to 30 parts by weight (D) Other radically polymerizable vinyl monomers 0 ~50 parts by weight