JP2901352B2 - Pigment dispersant and offset printing ink composition using the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pigment dispersant for stably dispersing an inorganic or organic pigment in a non-aqueous organic medium at a high concentration, and particularly to a pigment dispersant used in an offset printing ink. An object of the present invention is to provide a pigment dispersant capable of exhibiting excellent printability.

[0002]

2. Description of the Related Art Generally, coating agents such as printing inks and paints are
It is prepared by finely dispersing a pigment as a colorant in a vehicle mainly composed of a binder resin and a solvent. The obtained pigment dispersion is stable without causing re-aggregation of the pigment even when stored for a long period of time, and the coating film is required to have good gloss and to have excellent coloring properties. You. On the other hand, it is difficult to obtain a fine dispersion of such a pigment, and in order to increase the pigment concentration from the viewpoint of working efficiency, the pigment often exhibits a high viscosity, or is taken out of the disperser, mixed, and stirred. In addition, handling may be difficult in operations such as transfer and the like, and there is also a restriction that the pigment concentration in the dispersion cannot be increased. Therefore, there has been a demand for a method capable of stably dispersing a pigment at a high concentration in a vehicle and reducing the viscosity of the dispersion. For this purpose, it is necessary to increase the pigment dispersibility of the vehicle, and many studies have been conducted on the improvement of the binder resin constituting the vehicle. However, since the binder resin must have various functions as a coating forming agent, it is often difficult to significantly improve the pigment dispersibility. In practice, the pigment dispersing agent is contained in these resins. Is commonly used.

Conventionally, pigment dispersants such as USP
3996059, JP-A-61-163977, and the like have proposed compounds having a free amino group at a terminal, which are synthesized by reacting a polyester obtained by dehydrating and condensing a hydroxycarboxylic acid with a specific amine.

Further, US Pat. No. 4,224,212, US Pat.
No. 15,705, US Pat. No. 3,882,888 describe a product obtained by directly or indirectly reacting a polyalkyleneimine having a molecular weight of tens of thousands, at least exceeding 500, with the above-mentioned polyester. Further, Japanese Patent Application Laid-Open
-79279 and JP-A-2-99132 disclose the reaction products of polyamines with fatty acids and acid anhydrides.
378 and the like each propose a compound obtained by modifying a polyamine with a polyisocyanate.

[0005]

Although these various attempts have a tentative effect in terms of increasing the concentration of the pigment and stabilizing the dispersion in the non-aqueous dispersion system, they are still insufficient. In addition, when used as a dispersant in offset printing inks, the emulsifying properties of the inks have a considerable adverse effect, and a satisfactory printed matter cannot be obtained. In other words, in the offset printing method in which an image is formed by using the surface chemical repulsion of a water component called a fountain solution and the oil-based ink, the emulsifying characteristics of the ink with respect to the fountain solution must be maintained in an appropriate balance. is important. The use of a pigment dispersant that adversely affects the emulsifying properties of the ink in fountain solution causes various problems related to printability, such as transfer of the ink to non-image areas, so-called "smearing". Become. As described above, the pigment dispersant is required to maintain good printability such as emulsification suitability of the ink, in addition to the basic performance of enabling high concentration dispersion of the pigment.

In order to solve this problem, the present applicant has already proposed a dispersant using an amine such as methyliminobispropylamine in JP-A-1-31177. This is because the pigment dispersibility is improved by enhancing the three-dimensional effect,
Another object of the present invention is to improve the above-described printability by lowering the concentration of free amino groups. However, even the above-mentioned pigment dispersants cannot be said to have sufficient printing characteristics, and it is necessary to develop a pigment dispersant having higher pigment dispersion and maintaining sufficient printability.

[0007]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies in view of the above-mentioned problems, and as a result, have been able to disperse pigments in a non-aqueous dispersion system in a high concentration and stably, and to apply them to offset printing inks. Even so, a useful new dispersant has been found which does not impair its printability. That is, the present invention provides a compound having a free carboxyl group and an acid value of 1
The polyester in the range of 0 to 60 and the polyalkyleneimine containing 3 to 6 nitrogen atoms are used in an amount of 0.8 to 1.0 as an equivalent of an amino group having active hydrogen to one equivalent of a carboxyl group. The present invention provides a pigment dispersant which is a reaction product (claim 1) obtained by the reaction described in (1). Further, the present invention provides a method wherein the carboxyl group-containing polyester is 12
-A pigment dispersant obtained by dehydration polycondensation of hydroxystearic acid (Claim 2). Further, the present invention provides an offset printing ink composition containing a pigment, a resin, and an organic solvent as main components, wherein the pigment dispersant according to any one of claims 1 and 2 is used in an amount of 0.1 to
An object of the present invention is to provide an offset printing ink composition contained in a range of 100% by weight (claim 3).

Next, a concrete comparison between the dispersant according to the present invention and that of the prior art is as follows.

The above-mentioned US Pat.
In a reaction product of a polyester derived from a hydroxycarboxylic acid and an amine described in the specification such as 163977, a free amino group is introduced at a terminal in order to have an adsorption active site for a pigment. And a structure having one polyester chain in one molecule. Therefore,
With this dispersant, a so-called steric effect was small, and a sufficient dispersing effect was not obtained. In addition, as a result of increasing the concentration of amino groups having high hydrophilicity, there is a problem that printability such as emulsifying properties of ink is adversely affected. To solve this problem, Japanese Patent Application Laid-Open No.
The dispersant described in 11177 can improve pigment dispersibility by increasing the steric effect, and can improve printability by reducing the concentration of free amino groups. However, in order to further improve printability, it was necessary to further reduce the free amino group concentration. The dispersant of the present invention has been further improved in this regard. First, the dispersant of the present invention usually has three or more polyester chains reacting with the polyalkyleneimine, has a larger steric effect than those of the preceding examples, and exhibits an excellent dispersion stabilizing effect. In the prior art, the concentration of free amino groups, which was intentionally introduced to impart dispersibility and had an adverse effect on the emulsifying properties and the like of the ink, was kept very low, and printability was improved. I have. That is, the point that adsorption activity could be imparted not only by a free amino group but also by a polyamide structure is significantly different from the preceding example. Thus, it can be said that the printability was improved while maintaining the pigment dispersibility.

[0010] USP 4,224,212, USP 44
15705, US Pat. No. 3,882,888, etc., the product of directly or indirectly reacting a polyalkyleneimine with a polyester of a hydroxycarboxylic acid has a molecular weight of tens of thousands, at least 500, and Relatively highly polar sites derived from alkylene imines play a major role in one molecule.
Therefore, when used in a non-aqueous system, the compatibility is reduced and the pigment dispersion is not sufficiently achieved, or even if dissolved, it has an unfavorable effect on the emulsifying properties in the ink. On the other hand, since the dispersant of the present invention uses a polyalkylenimine containing 3 to 6 nitrogen atoms as a raw material, the dispersant does not have the above-described problems and exhibits the intended dispersion performance and printability. is there.

Further, a reaction product of a polyamine and a fatty acid or an acid anhydride described in JP-A-64-79279 or JP-A-2-99132 is useful for dispersing a pigment at a high concentration. While there is no polymer chain having an effect, the present invention has three or more polyester chains, so that sufficient pigment dispersibility can be obtained.

Further, in a compound obtained by modifying a polyamine with a polyisocyanate as disclosed in Japanese Patent Publication No. 1-54378,
The urethane bond formed by the reaction is generally difficult to dissolve in an organic solvent, and there are restrictions on the selection of the solvent for use in a non-aqueous system, but this is not the case with the present dispersant.

[0013]

The constitution of the dispersant according to the present invention will be described below after concrete comparison with the conventional dispersant.

The polyester used in the present invention includes:
Polyester synthesized by polycondensation of a compound having a carboxyl group and a compound having a hydroxyl group, which has a free carboxyl group at a terminal can be used.

The dicarboxylic acid which is one of the materials for obtaining the desired polyester having a free carboxyl group includes succinic acid, adipic acid, azelaic acid, sebacic acid, 1,12-dodecanedicarboxylic acid, 1,2 Examples of-, or 1,4-cyclohexanedicarboxylic acid, terephthalic acid and the like, and diols as other materials include diols such as ethylene glycol, diethylene glycol and propylene glycol. The desired polyester can be obtained by carrying out an esterification reaction in consideration of the number of moles using these materials.

In obtaining the dispersant of the present invention, a polyester obtained by polypolymerization of a fatty acid having a hydroxyl group is particularly preferred. Examples of the fatty acid having a hydroxyl group include ricinoleic acid, 12-hydroxystearic acid, or a commercially available castor oil fatty acid which is a mixture with a small amount of a saturated or unsaturated fatty acid, and a water additive thereof.

In order to obtain a desired polyester using these materials, a desired acid value is obtained while removing water generated by heating to 160 to 220 ° C. in the presence or absence of an esterification catalyst. What is necessary is just to react until it becomes. The acid value of the polyester is 10 to 60, preferably 20 to 50.
Is desirable. If the acid value exceeds 60, the polyester chain is not long enough, so that the dispersion stabilization due to the molecular weight effect becomes insufficient, and the concentration of polar groups such as hydroxyl groups becomes too high, thereby impairing the suitability for offset printing. Becomes Conversely, when the acid value is less than 10, the concentration of the adsorption active site becomes low, the adsorption power to the pigment surface becomes weak, and it becomes difficult to obtain a sufficient effect as a dispersant.

Specific examples of polyalkylenimines having 3 to 6 nitrogen atoms which can be used in the present invention include diethylenetriamine, triethylenetetramine, tetraethylenepentamine, pentaethylenehexamine, dipropylenetriamine. , Tripropylenetetramine, tetrapropylenepentamine, pentapropylenehexane and the like. In the reaction between these amine compounds and the polyester, the equivalent ratio of the amino group having active hydrogen of the amine to the free carboxyl group of the polyester is optimally in the range of 0.8 to 1.0.
After the above-mentioned polyesterification reaction is completed, the contents are cooled to about 100 ° C, a predetermined amount of amine is added, and the mixture is reheated to 160 to 180 ° C, and water generated by amidation is added. It can be done by recovering.

In using the dispersant of the present invention, suitable solvents include aromatic hydrocarbons such as toluene and xylene; ketones such as methyl ethyl ketone and methyl isobutyl ketone; esters such as butyl acetate and cellosolve acetate; Further, mineral oils containing aliphatic hydrocarbons as a main component and the like can be mentioned.

When the dispersant of the present invention is used for offset printing ink, which is a main use, a common solvent used for offset printing ink such as mineral oil is a desirable solvent.

Examples of the pigment used in the ink include generally used colorless or colored pigments.
Specific examples include inorganic pigments such as titanium dioxide, barium sulfate, calcium carbonate, and magnetic iron oxide, and organic pigments such as azo pigments, lake pigments, phthalocyanine pigments, isoindoline pigments, quinacridone pigments, and carbon black. .

In the field of offset printing ink,
It is common practice to prepare a base ink by replacing the water in a pigmented hydrated cake with an oily vehicle using a flushing technique. Conventionally, there has been no suitable dispersant for obtaining a yellow azo pigment base, but the dispersant of the present invention exhibits excellent effects even in such a case.

The amount of the dispersant used is 0.1 to 100% by weight, preferably 1.0 to 100% by weight, based on the above various pigments.
-20% by weight. However, this varies depending on the properties of each pigment, particularly its surface area and surface functional group concentration, and it is necessary to determine an appropriate value in each case.

In producing an offset printing ink using the dispersant according to the present invention, known binder resins, that is, various alkyd resins, various phenol resins, petroleum resins, rosin ester resins, polyester resins, and the like can be used. Other additives can be used as needed.

When the dispersant according to the present invention is used as a dispersant for inks or paints other than offset printing, it should be prepared using various resins and various organic solvents conventionally used in those fields. Can be done.

[0026]

EXAMPLES The present invention will be described below with reference to examples, but it should not be construed that the invention is limited thereto without departing from the spirit and scope of the present invention. In the description, "part"
Indicates parts by weight. Production Example 1 of Polyester Commercially available 12-hydroxystearic acid (hydroxyl value = 160 mg KOH /
g, acid value = 180 mg KOH / g)
The mixture was heated to about 0 ° C. and melted. To this, 70 parts of xylene and 1.0 part of tetra-n-butyl titanate as a catalyst were added, and water produced at 180 to 200 ° C. under a nitrogen stream was separated and collected for 12 hours. Stirred. The obtained polymer is light brown and viscous, has a nonvolatile content of 90% and an acid value of solid of 35%.
mgKOH / g (referred to as polyester a). Polyester Production Example 2 Commercial castor oil fatty acid (hydroxyl value = 160 mg KOH /
g, acid value = 180 mg KOH / g), except that the esterification reaction was carried out for 10 hours in the same procedure as in the case of polyester a.
g of a polymer was obtained (referred to as polyester b).

Example 1 In a reaction vessel similar to the above, 150 parts of polyester a and diethylenetriamine (commercially available, concentration of amino group having active hydrogen of 27 mmol / g)
(Corresponding to 0.90 equivalents of the amino group having active hydrogen of diethylenetriamine with respect to the free carboxyl group of the polyester), and formed at 160 to 180 ° C under a nitrogen stream. The mixture was stirred for 3 hours while separating and recovering water, and then xylene was distilled off under reduced pressure to obtain a dispersant a. This is a light brown viscous substance, the weight average molecular weight by GPC is 7,500, and the amine value is 5.0 mgK
The OH / g and the acid value were 8.0 mgKOH / g.

Example 2 150 parts of polyester b and 4.1 parts of triethylenetetramine (commercially available, the concentration of amino groups having active hydrogen is 23 mmol / g) (having active hydrogen with respect to free carboxyl groups) 0.90 amino group
And the same operation as in Example 1 to obtain a dispersant b. This is a light brown viscous substance, with a weight average molecular weight of 7,300 and an amine value of 5.6 mg.
The KOH / g and the acid value were 8.4 mgKOH / g.

Example 3 150 parts of polyester a and 4.0 parts of tetraethylenepentamine (commercially available, the concentration of amino groups having active hydrogen of 19 mmol / g) (active hydrogen was added to free carboxyl groups) 0.9 amino groups
And the dispersant c was obtained by the same operation as described above. This is a light brown viscous substance, having a weight average molecular weight of 9,500 and an amine value of 8.0 mgK.
The OH / g and the acid value were 7.9 mgKOH / g.

Example 4 150 parts of polyester b and 6.4 parts of pentaethylenehexamine (commercially available, the concentration of amino groups having active hydrogen is 15 mmol / g) (having active hydrogen with respect to free carboxyl groups) 0.9 amino groups
(Equivalent to 0 equivalent), and the same operation was carried out to obtain a dispersant d. This is a light brown viscous substance, the weight average molecular weight is 9100, and the amine value is 10.0 mg KOH.
/ G, acid value was 8.2 mg KOH / g.

[Comparative Example 1] 150 parts of polyester a and 3,3'-methyliminobispropylamine (a commercial product,
5.5 parts of a primary amino group having a concentration of 13.7 mmol / g (corresponding to 0.90 equivalent of the primary amino group of methyliminobispropylamine to the free carboxyl group of the polyester) Was mixed, and a dispersant e as a light brown viscous substance was obtained by the same operation as in Example 1 described above. Weight average molecular weight is 5300, amine value is 15 mg KO
H / g and the acid value were 7.7 mgKOH / g.

Comparative Example 2 150 parts of polyester a and 7.7 parts of N, N'-dimethylamino-1,3-propanediamine (commercially available, primary amino group concentration: 9.79 mmol / g) The primary amino group was equivalent to 0.90 equivalent to the free carboxyl group), and a light brown wax-like dispersant f was obtained by the same operation. The weight average molecular weight was 2,200, the amine value was 27 mg KOH / g, and the acid value was 8.4 mg KOH / g.

Comparative Example 3 A 30% aqueous solution of polyethyleneimine (commercially available, having a molecular weight of about 30) was placed in the same reactor as above.
The concentration of the amino group having an active hydrogen is 2.53 mmol / g in the form of an aqueous solution (30.0 parts) and toluene.
0 parts, stirred at 100 to 120 ° C. under a nitrogen stream,
About 20 parts of water were separated and collected. Here, polyester a
Was added (corresponding to 0.90 equivalent of the active amino group with respect to the free carboxyl group), and further stirred for 3 hours while collecting water produced at 160 to 180 ° C. under a nitrogen stream. . Then, xylene was distilled off under reduced pressure to obtain a highly viscous light brown dispersant g. The amine value was 28 mg KOH / g and the acid value was 9.0 mg KOH / g.

Comparative Example 4 In a similar reactor, 8.9 parts of polyethyleneimine having a molecular weight of about 600 (commercially available, the concentration of amino groups having active hydrogen is 8.50 mmol / g) and 150 parts of polyester a were added. Then, the mixture was stirred for 3 hours while separating and collecting water generated at 160 to 180 ° C. under a nitrogen stream under a nitrogen stream. Then, xylene was distilled off under reduced pressure to obtain a viscous light brown dispersant h. Amine value is 25 mg KOH / g, acid value is 8.7 mg KO
H / g.

Performance Evaluation Test Using the dispersants obtained in Examples 1 to 4 and Comparative Examples 1 to 4, a master base for offset printing ink and an offset ink were prepared according to the following formulation, and their properties and The performance was compared. The results are shown in Tables 1 and 2.

Indigo-based master base: phthalocyanine blue 50 parts Dispersant 5 parts Alkyd resin 10 parts Rosin-modified phenolic resin varnish 10 parts No. 5 solvent (Nippon Oil) 25 parts Black-based master base: carbon black 50 parts dispersant 5 parts Alkyd resin 10 parts Rosin-modified phenolic resin varnish 10 parts No. 5 solvent 25 parts The above-mentioned texture was sufficiently mixed, and the mixture was ground using a three-roll mill to prepare a base ink. Further, an offset ink was obtained by the following composition.

Master base 35 parts Rosin-modified phenolic resin varnish 50 parts Fluoro wax 2 parts Cobalt naphthenate (Co: 6%) 1 part 5 No. 5 solvent 12 parts 27A) 40 parts, linseed oil 25 parts,
And 35 parts of No. 5 solvent were uniformly heated and dissolved at 220 ° C.

[0038]

[Table 1]

Evaluation result of indigo ink Dispersant Base ink Ink Viscosity Coloring power Storage stability Higasawa Printability 1 a 245 115 Excellent Excellent Excellent 2 b 255 116 Excellent Excellent Excellent 3 c 230 114 114 Excellent Excellent Excellent Example 4 d 265 116 Excellent Excellent 1e 250 115 Excellent Excellent ratio 2f 680 105 Good Good Comparative 3g 720 103 Good Good Example 4h 750 103 Good Good Not possible Reference example None No meat impossible 100 Not good Good Good

[0040]

[Table 2]

Evaluation Results for Black Ink Dispersant Base Ink Viscosity Coloring Power Storage Stability Mitsuzawa Printing Suitability 1 a 155 109 Excellent Excellent Excellent 2 b 145 108 Excellent Excellent Excellent 3 c 140 108 108 Excellent Excellent Excellent 4 d 150 107 Excellent Excellent 1e 170 108 Excellent Excellent ratio 2f 375 103 Good Good Comparative 3g 660 101 Good Good Example 4h 690 102 Good Good Not possible Reference example None Not possible 100 Not possible Good Good Dispersant In the case of Reference Example where no alkyd resin was used, a considerable amount was replaced with an alkyd resin, but a master base was not formed. Therefore, a pigment concentration of 25
% To prepare a base ink to make it into an ink.

Each evaluation item was evaluated by the following method.
Viscosity The viscosity (poise) at 25 ° C. was measured using a Raleigh viscometer. Coloring Power The white base ink was colored with each base ink, and the coloring power of the base ink not using a pigment dispersant was set at 100 and expressed in%. Storage stability The base ink was stored in a thermostat at 25 ° C. for one month, and was judged by the difference in viscosity from the time of preparation (excellent,
Good is good, good is not enough, and bad is not stable). Gloss The gloss of the printed matter was visually judged. Printing stability The actual printing was performed using an offset sheet-fed printing machine manufactured by Mitsubishi Heavy Industries, and the suitability for water width, ink transferability, stains, etc. were comprehensively evaluated (excellent, excellent: good, Yes is not enough, and No is not suitable.) As can be seen from the table, high pigment dispersibility and printability were obtained only when the dispersants a to d of the present invention were used, and the printability was improved even when compared with the dispersant e of JP-A-1-31177. Have been. On the other hand, the dispersants f to h listed in Comparative Examples are not sufficient in both dispersibility and printability.

[0043]

By using the dispersant of the present invention in a non-aqueous paint or printing ink, it becomes possible to disperse the pigment in the vehicle at a higher concentration than in the past, and the resulting dispersion has a high coloration. As a result of the strength and storage stability, a significant increase in work efficiency and a reduction in inventory and transportation costs can be achieved. In addition, conventional dispersants have a problem in use in offset printing inks because they have an adverse effect on printability.However, the dispersant of the present invention has a high concentration while maintaining high printability without such a concern. The preparation of the base ink becomes possible.

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Claims (3)

(57) [Claims] 1. A free carboxyl group-containing polyester having an acid value in the range of 10 to 60 and a polyalkyleneimine having 3 to 6 nitrogen atoms are mixed with one equivalent of the carboxyl group of the polyester. 0.8 as an equivalent of the amino group having active hydrogen of the polyalkyleneimino.
A pigment dispersant characterized by reacting in the range of from 1.0 to 1.0. 2. The pigment dispersant according to claim 1, wherein the polyester is obtained by dehydration polycondensation of 12-hydroxystearic acid. 3. An offset printing ink composition comprising a pigment, a resin and an organic solvent as main components.
The pigment dispersant according to any one of the above pigments,
An offset printing ink composition containing 0.1 to 100% by weight.