JP5403219B2 - Active energy ray curable wet offset printing ink - Google Patents

Description

The present invention relates to a resin for offset printing ink and an offset printing ink using the same.

In recent offset printing technology, active energy ray curing that can be cured instantaneously by irradiating active energy rays such as ultraviolet rays from the expectation for low productivity and high productivity of ink to cope with environmental problems. The use of mold printing ink compositions is underway. For example, as the active energy ray curable resin, for example, a printing ink composition containing unsaturated polyester, epoxy acrylate, urethane acrylate, a reactive diluent, and a photoinitiator, and a resin that is cured by irradiation with ultraviolet rays are used. Are known.
For example, as suitable for offset printing, Patent Document 1 discloses that an ink composition containing a specific reactive resin containing styrene or the like as a copolymerization component, a reactive diluent, and a photoinitiator is reacted and cured with ultraviolet rays. Thus, an invention of a printing ink excellent in adhesion to a substrate, high hardness, wear resistance, and the like is described.
However, as the printing machine speeds up, misting (a large amount of ink mist is scattered, the working environment during printing deteriorates, and production efficiency is reduced) and blocking occur while having various performances of printing ink. No printing ink has been obtained.

Japanese Patent Laid-Open No. 10-17812

The present invention maintains various performances of the printing ink (adhesiveness, coating film hardness, emulsifying property, image reproducibility, glossiness, blocking resistance, etc.) by blending with the active energy ray-curable offset printing ink. An object of the present invention is to provide a resin for offset printing ink that can reduce the mist amount of the printing ink and an active energy ray-curable offset printing ink using the resin.

The present inventor is a copolymer resin obtained by polymerizing styrenes, (meth) acrylic acid alkyl ester and a hydrophilic group-containing vinyl monomer, and has a weight average molecular weight (Mw) and a glass transition temperature (Tg). It was found that the above-mentioned problems can be achieved by mixing a resin adjusted to a predetermined range with a composition of an active energy ray-curable printing ink for offset printing, and the present invention has been completed.
That is, in the present invention, the weight average molecular weight (Mw) obtained by copolymerizing a monomer component containing styrenes, alkyl (meth) acrylate and a hydrophilic group-containing vinyl monomer is 5,000 to 13,000. An active energy ray-curable wet offset printing ink comprising an active energy ray-curable wet offset printing ink resin (A) having a glass transition temperature (Tg) of 70 to 100 ° C. and a reactive diluent (B) The active energy ray curing wherein the monomer component in (A) is used in an amount of 60 to 90 parts by weight of styrene, 5 to 39 parts by weight of (meth) acrylic acid alkyl ester, and 1 to 25 parts by weight of a hydrophilic group-containing vinyl monomer; type wet offset printing ink; hydrophilic group of the hydrophilic group-containing vinyl monomer in (a) is, mosquitoes Bokishiru group, related to the active energy ray-curable wet offset printing ink is a type one selected from the group consisting of hydroxyl groups and amide groups.

Using the active energy ray-curable offset printing ink resin of the present invention, the active energy can reduce the mist amount of printing ink even in high-speed printing while having high ink performance and high adhesion to the substrate. A linear curable offset printing ink can be obtained.

The resin for offset printing ink (A) of the present invention is obtained by copolymerizing a monomer component containing styrenes, (meth) acrylic acid alkyl ester and a hydrophilic group-containing vinyl monomer.
Styrenes used in the present invention are not particularly limited, and specifically, styrene, α-methylstyrene, and the like, styrene compounds having at least one alkyl group having 1 to 4 carbon atoms in the aromatic ring, and the like. Can be mentioned. Moreover, only 1 type of these may be used independently, and 2 or more types may be used together.

As the (meth) acrylic acid alkyl ester used in the present invention, any (meth) acryloyl group having no reactive functional group can be used without any particular limitation. Specifically, Examples include methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, cyclohexyl (meth) acrylate, and the like. One of these can be used alone, or two or more can be used. . Among these, from the viewpoint of solubility with the reactive diluent (B) and blocking resistance, the (meth) acrylic acid alkyl ester is preferably one having an alkyl group having 1 to 20 carbon atoms.

The hydrophilic group-containing vinyl monomer used in the present invention is a polymerizable vinyl monomer having a hydrophilic group as a functional group. Examples of the hydrophilic group include a sulfonyl group, a carboxyl group, a hydroxyl group, a phosphoric acid group, and an amide group. Among these, a vinyl monomer containing any one kind of hydrophilic group selected from the group consisting of a carboxyl group, a hydroxyl group, and an amide group is preferable from the viewpoint of storage stability after inking. Specific examples of vinyl monomers having a carboxyl group as a functional group include (meth) acrylic acid, (meth) acrylic acid dimer, (meth) acrylic acid oligomer, hydroxy (meth) acrylate and anhydride adduct, such as Examples include 2- (meth) acryloylethylsuccinic acid, 2- (meth) acryloylethylphthalic acid, and 2- (meth) acryloylethylhexahydrophthalic acid. Specific examples of the vinyl monomer having a hydroxyl group as a hydrophilic group include 2-hydroxyethyl (meth) acrylate and 4-hydroxybutyl (meth) acrylate. Specific examples of the vinyl monomer having an amide group as a hydrophilic group include acrylamide, 2-hydroxyethylacrylamide, N, N-dimethylacrylamide, and acryloylmorpholine. Among these, it is particularly preferable to use a carboxyl group or an amide group because offset printing suitability such as emulsification suitability is improved.
These hydrophilic vinyl monomers may be used alone or in combination of two or more.

The amount of the monomer component used may be appropriately determined depending on the intended use, but is usually about 60 to 90 parts by weight of styrenes, about 5 to 39 parts by weight of alkyl methacrylate (meth) acrylate, and a hydrophilic group-containing vinyl monomer. The amount is preferably about 1 to 25 parts by weight, more preferably 70 to 85 parts by weight of styrenes, 10 to 28.5 parts by weight of alkyl methacrylate (meth) acrylate, and 1.5 to 20 parts by weight of a hydrophilic group-containing vinyl monomer. Part. By making the usage-amount of a monomer component in the said range, the balance of various characteristics as printing ink, such as misting resistance, adhesiveness, blocking resistance, ink flow property, and emulsification ability, can be kept moderate.

The polymerization method of the resin for offset printing ink (A) of the present invention is not particularly limited, and a known radical polymerization method can be employed. Radical polymerization is obtained by heating in the presence of a radical polymerization initiator. It does not specifically limit as a radical polymerization initiator, A well-known thing can be used. Specifically, for example, inorganic peroxides such as hydrogen peroxide, ammonium persulfate and potassium persulfate, organic peroxides such as benzoyl peroxide, dicumyl peroxide and lauryl peroxide, 2,2′-azobis And azo compounds such as isobutyronitrile and dimethyl-2,2′-azobisisobutyrate. Moreover, these 1 type may be used independently and may be used in combination of 2 or more types. In addition, it is preferable that the usage-amount of a radical polymerization initiator shall be about 3-10 weight part with respect to 100 weight part of all the monomer components. In addition, you may use a chain transfer agent etc. as needed. Examples of the chain transfer agent include lauryl mercaptan, dodecyl mercaptan, 2-mercaptobenzothiazole, bromotrichloromethane, and the like. These may be used alone or in combination of two or more. The amount of the chain transfer agent used is preferably about 0.01 to 5 parts by weight with respect to 100 parts by weight of all monomer components.

The resin for offset printing ink (A) thus obtained needs to adjust the weight average molecular weight (Mw) to about 5,000 to 13,000 and the glass transition temperature (Tg) to about 70 to 100 ° C. . When the weight average molecular weight (Mw) is less than 5,000, the blocking resistance is deteriorated, and when it exceeds 13,000, the misting resistance is deteriorated. Further, when the glass transition temperature (Tg) is less than 70 ° C., the misting resistance and blocking resistance are deteriorated. When the glass transition temperature (Tg) exceeds 100, the viscosity of the printing ink resin (A) becomes too high, and it is sufficient as an ink component. The amount cannot be blended.
In addition, a weight average molecular weight (Mw) is a polystyrene conversion value by a gel permeation chromatography method.

By mixing the resin component for offset printing ink of the present invention (A) with an ink component such as a reactive diluent (B), a photoinitiator, and an ink pigment that are monomer components that are cured by active energy rays such as ultraviolet rays. And an active energy ray-curable offset printing ink.

Examples of the reactive diluent (B) used in the active energy ray-curable offset printing ink of the present invention include ethylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, triethylene glycol di (meth) acrylate, Polyethylene glycol di (meth) acrylate, polyethylene glycol di (meth) acrylate, tripropylene glycol di (meth) acrylate, 1,3 butylene glycol di (meth) acrylate, 1,6 hexanediol di (meth) acrylate, 1,9 Nonanediol di (meth) acrylate, neopentyl glycol di (meth) acrylate, 2,2bis [4-{(meth) acryloxy-diethoxy} phenyl] propane, 2,2bis [4-{(meth) acryloxyate Si} phenyl] propane, 2,2bis [4-{(meth) acryloxy polyethoxy} phenyl] propane, 2,2 bis [4-{(meth) acryloxy dipropoxy} phenyl] propane, 2,2 bis [4 And bifunctional (meth) acrylic monomers such as-{(meth) acryloxypropoxy} phenyl] propane and 2,2bis [4-{(meth) acryloxy-polypropoxy} phenyl] propane.

Also, trimethylolpropane tri (meth) acrylate, tetramethylolmethane tri (meth) acrylate, tetramethylolethane tri (meth) acrylate, tetramethylolmethane tetra (meth) acrylate, ethylene oxide (EO) modified trimethylolpropane tri (meth) Examples thereof include tri- or higher functional (meth) acrylic monomers such as acrylate and dipentaerythritol hexa (meth) acrylate.

As a use ratio of the resin for offset printing ink (A) and the reactive diluent (B) of the present invention, the polymerizable monomer is usually 25 to 400 weights per 100 parts by weight of the resin for offset printing ink (A). Part by weight, preferably 60 to 230 parts by weight. When the amount of the reactive diluent (B) used is less than 25 parts by weight, the blocking resistance and curability tend to deteriorate, and when it exceeds 400 parts by weight, the adhesiveness and misting resistance tend to decrease. It is in. The viscosity of the composition obtained in the present invention is preferably 0.1 to 500 Pa · s (25 ° C.). In order to obtain a composition having a viscosity lower than this, it is necessary to add more (meth) acrylic monomers, which is not preferable. Further, a composition having a higher viscosity is not preferred because it has poor processability (workability during ink production).

It does not specifically limit as a photoinitiator, Various well-known things can be used. Specific examples include benzophenone, o-benzoylbenzoic acid methyl ester, p-dimethylaminobenzoic acid ester, p-dimethylacetophenone, thioxanthone, alkylthioxanthone, and amines. Commercially available products such as Darocur 1173, Irgacure 651, Irgacure 184, Irgacure 907 (all manufactured by Ciba Japan) may be used as they are. As a usage-amount of a photoinitiator, it is preferable to use about 0.1-10 weight part normally with respect to 100 weight part of offset printing ink and reactive diluent (B).

The pigment used in the offset printing ink of the present invention is not particularly limited, and a commonly used inorganic or organic pigment can be blended. Specific examples include white pigments such as titanium oxide, zinc white, lead white, lithobon, and antimony oxide, black pigments such as aniline black, iron black, and carbon black, yellow lead, yellow iron oxide, titanium yellow, and Hansa Yellow (10G 5G, 3G, etc.), yellow pigments such as disazo yellow, benzine yellow, and permanent yellow, orange pigments such as chrome vermilion, permanent orange, balkan first orange, indanthrene brilliant orange, iron oxide, permanent brown, para brown Brown pigments such as Bengala, Cadmium Red, Antimony Zhu, Permanent Red, Rhodamine Lake, Alizarin Lake, Thioindigo Red, PV Carmine, Monolite First Red, Quinacdrine Red Pigment, Cobalt Purple Purple pigments such as manganese purple, first violet, methyl violet lake, indanthrene brilliant violet, dioxazine violet, ultramarine, bitumen, cobalt blue, alkali blue lake, peacock blue lake, Victoria blue lake, metal free phthalocyanine blue, copper phthalocyanine Blue pigments such as blue, indanthrene blue, indigo, chrome green, chromium oxide, emerald green, naphthol green, green gold, acid green lake, malachite green lake, phthalocyanine green, polychlorobrom copper phthalocyanine, etc. Examples include various fluorescent pigments and metal powder pigments. These pigments are preferably blended in the range of about 1 to 50 parts by weight, more preferably 5 to 30 parts by weight, with respect to 100 parts by weight of offset printing ink.

The active energy ray-curable offset printing ink of the present invention contains, as essential components, the resin for printing ink of the present invention, a polymerizable monomer and a pigment, and further includes a surface conditioner, an antifoaming agent and a photosensitizer. Sensitizers, antioxidants, light stabilizers, and leveling agents can also be used. These optional components are preferably blended in an amount such that the total amount thereof is in the range of about 100 parts by weight or less with respect to 100 parts by weight of the offset printing ink. Furthermore, polymerization inhibitors such as hydroquinone, hydroquinone monomethyl ether, phenothiazine, and N-nitrosophenylhydroxylamine aluminum salt can be blended. When blending a polymerization inhibitor, it is preferably used in an amount of about 0.01 to 2% by weight relative to the offset printing ink.

Hereinafter, the present invention will be described more specifically with reference to production examples and examples, but the present invention is not limited thereto. Hereinafter, “parts” means parts by weight.
In addition, the glass transition point and the weight average molecular weight were calculated | required with the following method as a characteristic value of resin.

<Glass transition point (Tg)>
Tg (° C.) was calculated by the following formula.
(Form of FOX)
1 / Tg (K) = W1 / Tg1 + W2 / Tg2 + W3 / Tg3 + ... + Wn / Tgn
W1 + W2 + W3 + ... + Wn = 1
[Wn represents the weight fraction of each monomer, and Tgn represents the glass transition point (absolute temperature K) of each homopolymer. However, n is an integer. ]
Conversion to Celsius temperature (° C) Tg (° C) = Tg (K)-273

<Weight average molecular weight>
The weight average molecular weight was calculated | required as a polystyrene conversion value measured in the THF solvent by the gel permeation chromatography (GPC). As the GPC apparatus, HLC-8020 (manufactured by Tosoh Corporation) was used, and as the column, TSKgel superHZM (manufactured by Tosoh Corporation) was used.

Example 1 (Production of resin for offset printing ink)
A reaction vessel equipped with a stirrer, a reflux condenser with a water separator and a thermometer was charged with 77.5 parts of styrene, 20 parts of butyl methacrylate and a 98% acrylic acid solution, and 2,2′-azobis (2-methylbutyro Nitrile) (ABN-E) (7 parts) was added as a polymerization initiator, and a drop polymerization reaction was performed at 140 ° C. under reflux and stirring for 1.5 hours, and the temperature was kept for 1 hour. Thereafter, the temperature was raised to 160 ° C., the solvent was distilled off while stirring at normal pressure, the pressure was further reduced to 50 mHg or less at the same temperature, the solvent was completely distilled off, and 100 g of resin (A) for offset printing ink was obtained. Obtained. The glass transition point (Tg) and weight average molecular weight (Mw) of the obtained resin were measured by the following methods. As a result, the glass transition point was 80.8 ° C., the weight average molecular weight was 7,100, and the softening point was 105 ° C. The results are shown in Table 1.

Examples 2 to 5 and Comparative Examples 1 to 5 (Production of resin for offset printing ink)
The resin was produced in the same manner as in Example 1 except that the types and amounts of the constituent monomers of the resin were changed to those shown in Table 1, respectively. The results are shown in Table 1.

Table 1 shows the resin compositions of Examples and Comparative Examples and the physical properties of the obtained resins.

Abbreviations in Table 1 have the following meanings.
BMA; butyl methacrylate BA; butyl acrylate SMA; stearyl methacrylate ACMO; acryloylmorpholine HEMA; 2-hydroxyethyl methacrylate AA; acrylic acid ABN-E; 2,2'-azobis (2-methylbutyronitrile)

(Preparation of clear varnish)
For 50 parts of the resin for offset printing inks of Examples 1 to 5 and Comparative Examples 1 to 5 obtained, 50 parts of trimethylolpropane tri (meth) acrylate as a reactive diluent (B), under air bubbling, 130 The solution was stirred and dissolved at 1 ° C. for 1 hour. After cooling to 60 ° C., 5 parts of Irgacure 184 (registered trademark by Ciba Japan) as a photopolymerization initiator was mixed and dissolved in the resin solution to obtain a clear varnish.

(Evaluation of clear varnish)
The performance of the clear varnish obtained in the above Examples and Comparative Examples was evaluated using the following method.

<Varnish viscosity (Pa · s / 25 ° C)>
The viscosity of the clear varnish at 25 ° C. was measured with an E-type viscometer. The evaluation results are shown in Table 2.

<Emulsification suitability test>
A mixture of clear varnish and xylene in a weight ratio of 1: 2 in a glass test tube (inner diameter 18 mm × height 180 mm × thickness 1.2 mm, trade name PYREX (registered trademark) TEST18, manufactured by Iwaki Glass Co., Ltd.) 7.5 g of distilled water and 7.5 g of distilled water were collected, put a rubber stopper at the opening of the test tube, emulsified by shaking up and down 30 times, allowed to stand, and then the varnish layer and the aqueous layer were completely separated. The time until was measured.
<Emulsification suitability test>
A mixture of clear varnish and xylene in a weight ratio of 1: 2 in a glass test tube (inner diameter 18 mm × height 180 mm × thickness 1.2 mm, trade name PYREX (registered trademark) TEST18, manufactured by Iwaki Glass Co., Ltd.) 7.5 g of distilled water and 7.5 g of distilled water were collected, put a rubber stopper at the opening of the test tube, emulsified by shaking up and down 30 times, allowed to stand, and then the varnish layer and the aqueous layer were completely separated. The time until was measured. The separation time suitable for offset printing is 1 minute 30 seconds to 6 minutes.

<Blocking resistance test>
The resulting clear varnish was applied to art paper with a bar coater # 3 with a film thickness of about 5 μm, and then irradiated with a high pressure mercury air cooling lamp (120 W / cm) at an irradiation distance of 10 cm, a belt speed of 10 m / min. The cured film was formed by irradiating with ultraviolet rays under the condition of a dose of about 140 mJ / cm 2. Next, two test pieces obtained by cutting the obtained cured film into 5 cm squares were prepared, the coating surfaces were overlapped, and 1375 g of weight was placed thereon, and placed in a thermostatic chamber (23 ° C., humidity 50%) for 20 hours. After standing, blocking resistance was evaluated based on the following evaluation criteria. The adhesion evaluation results are shown in Table 2.
○: The cured film does not block.
Δ: The cured film is slightly blocked.
X: The cured film blocks.

<Adhesion test>
According to JIS K 5400, a grid was made on polyethylene terephthalate and polypropylene film, and then a cellophane tape peel test was performed and evaluated based on the following evaluation criteria. Table 2 shows the results of evaluation of adhesion.
○: 70% or more of the cured film does not peel off.
Δ: Less than 70% to about 50% of the cured film peels off.
X: The cured film is completely peeled off.

(Preparation of printing ink)
50 parts of disazo yellow (Seika Fast Yellow 2300: C.I-Pigment Yellow 12 manufactured by Dainichi Seika Kogyo Co., Ltd.) is mixed with 100 parts of the resin clear varnish of the examples and comparative examples, and the mixture is mixed with a three-roll mill and printed. An ink was prepared. Based on the above formulation, the tack value at 38 ° C. and 1200 rpm was appropriately adjusted to be 25 ± 5.

(Evaluation of printing ink)
About the printing ink obtained by the said Example and comparative example, performance was evaluated using the following method about misting resistance.
1.30 g of ink is developed on an incometer (manufactured by Toyo Seiki Co., Ltd.), rotated at a roll temperature of 38 ° C. and 1200 rpm for 1 minute, and the degree of ink scattering on white paper placed directly under the roll is measured with a Gretag color difference meter ( Using Gretag Macbeth), an average value measured arbitrarily at five locations is obtained, and evaluation is obtained by obtaining a value (ΔY) obtained by subtracting a blank value (a measured value of white paper measured in advance by the same method). did. “Unmeasurable” in Table 2 indicates a very poor misting property where the ink is scattered in a lump.
The results are shown in Table 2.

The abbreviations in Table 2 mean the following contents.
TMPTA; trimethylolpropane tri (meth) acrylate PET; polyethylene terephthalate PP; polypropylene

Claims (3)

Weight average molecular weight (Mw) obtained by copolymerizing a monomer component containing styrenes, (meth) acrylic acid alkyl ester and hydrophilic group-containing vinyl monomer is 5,000 to 13,000, and glass transition. An active energy ray-curable wet offset printing ink containing an active energy ray-curable wet offset printing ink resin (A) having a temperature (Tg) of 70 to 100 ° C. and a reactive diluent (B). The amount of the monomer component in the active energy ray-curable wet offset printing ink resin (A) is 60 to 90 parts by weight of styrene, 5 to 39 parts by weight of a (meth) acrylic acid alkyl ester, and a hydrophilic group-containing vinyl monomer 1 The active energy ray-curable wet offset printing ink according to claim 1, which is ˜25 parts by weight . 2. The hydrophilic group of the hydrophilic group-containing vinyl monomer in the active energy ray-curable wet offset printing ink resin (A) is any one selected from the group consisting of a carboxyl group, a hydroxyl group, and an amide group. Or active energy ray hardening type wet offset printing ink of 2