JPH0543755B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to an aqueous printing ink composition for water-repellent paper containing a specific aqueous resin binder,
More specifically, the present invention aims to provide an aqueous printing ink composition for water-repellent paper, which is characterized by containing an alkaline aqueous solution of a specific acrylic copolymer as an aqueous resin binder. In recent years, various packaging materials, such as cardboard, heavy bags, and other types of wrapping paper, have been subjected to various types of packaging materials, such as cardboard, heavy bags, and other types of wrapping paper, in order to maintain the quality of the contents during transportation, to ensure safe transportation, and to prevent the strength of the packaging materials from deteriorating. Processing is being carried out to add various functions. In particular, water-repellent paper is widely used in cardboard boxes used for packaging fruits, vegetables, marine products, etc., in order to maintain freshness and prevent the strength of the packaging material from deteriorating due to moisture. Here, water-repellent paper is paper that has a water-repellent agent such as petroleum-based wax emulsion or silicone-based emulsion applied to the surface of cardboard liner or kraft paper, and usually has a repellency rating of R ⁶ to ^{R 10} . Water quality (according to JIS P-8137 standard). Further, the above-mentioned packaging materials are printed with high quality for the purpose of displaying various contents related to the contents and promoting sales as a product. These printings are generally performed using a flexo or gravure printing method using an aqueous printing ink composition. Conventional aqueous binders used in these water-based printing ink compositions have traditionally been alkaline aqueous solutions of silica and rosin maleic acid resins, but more recently alkaline aqueous solutions of styrene maleic acid copolymers and acrylic copolymers. Alternatively, acrylic and styrene resin emulsions are widely used. However, the above-mentioned water-based binders used in water-based printing ink compositions do not provide sufficient adhesion and transferability to water-repellent treated paper, making it impossible to obtain high-quality printed matter. It is desired to develop a water-based binder suitable for water-processed paper. For example, in Japanese Patent Publication No. 51-29041,
A water-based printing ink composition for water-repellent paper containing a specific vinyl-based copolymer consisting of styrene, (meth)acrylic acid ester, and maleic acid half ester is disclosed. However, in the case of the above water-based printing ink composition, since the structure based on the maleic acid half ester possessed by the above specific vinyl copolymer is not necessarily stable, the viscosity may change or odor may occur over time. It had drawbacks in terms of workability and printing effect during printing. The present inventor has conducted intensive research on conventional water-based printing ink compositions, especially water-based resin binders that have excellent adhesion and transfer properties to water-repellent treated paper and are capable of producing high-quality printed matter.As a result, An aqueous printing ink composition containing, as an aqueous resin binder, an acrylic copolymer having a specific monomer composition consisting of a styrene analogue, a specific (meth)acrylic acid ester, and (meth)acrylic acid,
The present invention was completed based on the discovery that it has excellent adhesion and transferability to water-repellent paper, as well as excellent gloss, printability, printing workability, and printing effect. That is, the present invention provides an aqueous printing ink composition mainly composed of a pigment, an aqueous resin binder, and an aqueous medium, in which (a)
12 to 40% by weight of styrene homologs, (b) 25 to 60% by weight of alkyl esters of acrylic acid and/or methacrylic acid whose alkyl group has 3 or less carbon atoms, (c) 25 to 40% by weight of acrylic acid and/or methacrylic acid. 40% by weight, (d)
0 to 20% by weight of other copolymerizable vinyl monomers,
[Here, the total of (a), (b), (c) and (d) above is 100% by weight]
An aqueous printing ink composition for water-repellent paper, characterized in that it contains an alkaline aqueous solution of a copolymer having a monomer composition satisfying a weight ratio of (a)/(b) of 0.25 to 1. The contents shall be as follows. Among the monomer components of the acrylic copolymer in the aqueous printing ink composition of the present invention, aromatic monovinyl compounds such as styrene, α-methylstyrene, and vinyltoluene can be used as the (a) styrene analogue. However, in industrial implementation,
From the point of view of economy and ease of polymerization, it is most preferable to use styrene or a mixture of aromatic monovinyl compounds mainly containing styrene. (b) Examples of the acrylic acid alkyl ester and/or methacrylic acid alkyl ester in which the alkyl group has 3 or less carbon atoms include methyl, ethyl, propyl, and isopropyl acrylates and methacrylates. Particularly preferred are ethyl acrylate and ethyl methacrylate. The monocar composition of the monomers (a) and (b) above is:
If it is outside the above range, the adhesion to water-repellent paper will be poor in any case, and (a)/(b) <
If it is 0.25, the dryness of the ink and the gloss of the printed matter will decrease, and blocking will occur easily, (a) / (b)
If >1, the abrasion resistance of the printed surface decreases. and (c) acrylic acid and/or methacrylic acid.
If it is less than 40% by weight, adhesion and transferability will be significantly reduced, and if it is 40% by weight or more, gloss and water resistance will be insufficient. In addition to the above three monomer components, a small amount of (d) another copolymerizable vinyl monomer can also be copolymerized, but in this case, the amount of the other copolymerizable monomer relative to the total weight of all monomer components is The percentage
If it exceeds 20% by weight, it will be difficult to achieve the object of the present invention. Specific examples of the copolymerizable vinyl monomers include acrylic acid alkyl esters having an alkyl group having 4 to 18 carbon atoms, methacrylic acid alkyl esters having an alkyl group having 4 to 18 carbon atoms, and other unsaturated carbon atoms. Acid esters and the like can be mentioned. In general, it is desirable that the resulting acrylic copolymer has a softening point of 80° C. or higher and an acid value of 130 or higher. When polymerizing the monomer mixture having the above monomer composition to produce an acrylic copolymer useful as the aqueous resin binder of the aqueous printing ink composition of the present invention, various conventionally known polymerization methods can be applied. However, from the viewpoint of ink suitability and ink fluidity, it is desirable that the molecular weight of the copolymer is in the range of 5,000 to 25,000 as measured by gel permeation chromatography (GPC). For this purpose, it is convenient to perform solution polymerization using an organic solvent having a boiling point of 80 to 150° C. that dissolves the copolymer. Of course, it is optional to use a known molecular weight regulator to keep the molecular weight of the copolymer within the above range. When the molecular weight of the copolymer is within the above range, the viscosity of the ammonia aqueous solution is usually 20% at a solid content of 20%.
~15 poise. In the present invention, in order to make the acrylic copolymer into an aqueous binder, it is necessary to use ammonia and/or volatile organic amines, which volatilize after printing and become waterproof. Specific examples of volatile organic amines include methylamine, dimethylamine, trimethylamine,
Alkylamines such as ethylamine, diethylamine, triethylamine, propylamine, and butylamine; alkanolamines such as ethanolamine, diethanolamine, triethanolamine, and propanolamine; amino alcohols such as dimethylaminoethanol and diethylaminoethanol; and morpholine. I can do it. The volatility of ammonia and organic amines affects the drying properties and fluidity of the ink, as well as the stability on the printing press (plate jams, etc.), so it is desirable to use them in an appropriate selection and combination. . The aqueous printing ink composition of the present invention uses the above-mentioned acrylic copolymer with ammonia and/or volatile organic amines selected from water or a mixture of water and a water-miscible organic solvent, preferably alcohols. It is prepared by adding pigments and other optional additives to an aqueous resin binder dissolved in an aqueous solvent, and kneading the mixture. In the present invention, various known pigments or mixtures thereof can be used, regardless of whether they are inorganic or organic. The water-based printing ink composition of the present invention can also contain other water-soluble resins or resin emulsions within a range that does not interfere with the purpose of the present invention. The aqueous printing ink composition of the present invention thus obtained has an extremely beautiful appearance on water-repellent paper, based on the adhesion and transferability to water-repellent paper of the specific acrylic copolymer that is the main component. In addition to being able to carry out printing, it has good stability over time due to its excellent pigment dispersibility, has excellent printing workability, and can produce excellent printing effects. Such excellent effects of the present invention can only be achieved by a specific monomer composition based on a combination of specific monomers and their use in specific proportions in the aforementioned acrylic copolymer, and this will be described below. This is clearly shown based on a specific example. Synthesis Example 1 Charge 600 steps of cellosolve acetate into a 2 four-necked flask, and attach a stirring device, nitrogen introduction tube, separating funnel, and reflux condenser tube. In a separate container, 192 parts of methacrylic acid, 168 parts of styrene, and ethyl acrylate.
240 parts, ditertiary butyl peroxide 9
Take a portion and mix uniformly to prepare a monomer mixture. Nitrogen gas is introduced into the flask, the flask is placed under a nitrogen stream, and the temperature is raised to the reflux temperature of cellosolve acetate in an oil bath. After raising the temperature, a separately prepared monomer mixture is added through a separating funnel over a period of about 2 hours. After the addition was completed, the polymerization reaction was continued for an additional 3 hours. During this time, the inside of the flask is kept under reflux of the solvent. After the polymerization reaction is completed, the solvent is removed by vacuum distillation and the resin is taken out. The resulting resin [A] had an acetic acid value of 203, a softening point of 115°C, and a weight average molecular weight (measured with GPC-LC-5A manufactured by Shimadzu Corporation) of 10,500. Synthesis Examples 2 to 9 Resins [B] to [I] were prepared in the same manner as in Synthesis Example 1, using each of the monomer mixtures listed in Table 1 below in place of the monomer mixture in Synthesis Example 1. Prepared. The properties of each resin are also listed in Table 1.

[Table] Comparative Synthesis Examples 1 to 10 Instead of the monomer mixture in Synthesis Example 1, each of the monomer mixtures shown in Table 2 below was used, and the same procedure as in Synthesis Example 1 was performed to prepare resins [J] to [S] was prepared. The properties of each resin are also listed in Table 2.

【table】

[Metastatic]

Water-repellent paper (liner paper for cardboard, water-repellent)
Each ink was applied onto R ⁸ ) using a hand printer, and the transferability was visually determined. [Gloss] Each ink was spread on the water-repellent paper using a bar coater (No. 8), and the gloss was visually evaluated. [Fluidity] Ink viscosity was measured using a B-type viscometer at 30 rpm and
Measurement was performed at 60 rpm, and judgment was made based on the ratio of viscosity at 30 rpm/viscosity at 60 rpm. [Stability] It was determined by the ratio of the viscosity one week after ink preparation to the viscosity immediately after ink preparation. Comparative Examples 1 to 10 Resins [J] obtained in Comparative Synthesis Examples 1 to 10
Using each of [S], a water-based binder was prepared in the same manner as in the examples, and a similar water-based ink composition was also prepared for comparison. The obtained ink compositions were tested in the same manner as in the examples, and the results are shown in Table 3. Comparative Example 11 174 g of styrene, 321 g of isopropyl alcohol half ester of maleic acid, methyl methacrylate
A styrene/maleic acid copolymer obtained by solution polymerizing 105 g of monomer is made into an aqueous solution using ammonia to obtain an aqueous binder. Using this aqueous binder, an ink was prepared in the same manner as in the examples, and the same tests were conducted, and the results are shown in Table 3.

【table】

【table】

Claims (1)

[Scope of Claims] 1. In an aqueous printing ink composition mainly composed of a pigment, an aqueous resin binder, and an aqueous medium, the aqueous resin binder includes: (a) 12 to 40% by weight of a styrene homolog; (b) an alkyl group; Alkyl ester of acrylic acid and/or methacrylic acid having 3 or less carbon atoms
25-60% by weight (c) Acrylic acid and/or methacrylic acid
25 to 40% by weight (d) A copolymerizable vinyl monomer selected from acrylic acid alkyl esters, methacrylic acid alkyl esters, and other unsaturated carboxylic acid esters having an alkyl group having 4 to 18 carbon atoms.
0 to 20% by weight (here, the total of (a), (b), (c), and (d) is 100% by weight), and a monomer whose weight ratio of (a)/(b) satisfies 0.25 to 1. 1. An aqueous printing ink composition for water-repellent paper, comprising an alkaline aqueous solution of a copolymer having the following composition: 2. The aqueous printing ink composition for water-repellent paper according to claim 1, wherein (b) is ethyl acrylate or ethyl methacrylate.