KR20100056221A - Pigment dispersing agent and aqueous dispersed pigments - Google Patents

Abstract

PURPOSE: A pigment dispersing agent is provided to be more economical than the dispersion of surface-processing pigment, to obtain excellent dispersion stability, and to improve printability and the storage stability of aqueous dispersed pigments. CONSTITUTION: A pigment dispersing agent is a compound which is marked by chemical formula 1. The chemical formula 1 is Ar-X-(CH2CH2)n-OH. In chemical formula 1, Ar shows an aromatic group of C6 ~ C20, X indicates a bond, O, CH2COO, N(CH2CH2)NOH, or NH, and n indicates an integer of 5~30. Ar is an aromatic group which is selected from a phenyl group, biphenyl group, 2,2- diphenylpropane group, naphthalene group, carbazole group, and fluoren group.

Description

Pigment Dispersing Agent and Aqueous Dispersion Containing the Same {Pigment Dispersing Agent and Aqueous Dispersed Pigments}

The present invention relates to a pigment dispersant used to disperse a pigment in water and an aqueous dispersion comprising the same.

In general, many pigments with high coloration and transparent color tones have fine primary particles. In general, however, since most pigments aggregate primary particles, it is required to disperse them so that their aggregated state is converted to a finer state in order to express the properties of the pigment itself. However, as the pigment particles become finer, it is difficult to uniformly disperse the pigment particles. In particular, dispersions in poor dispersion have high viscosities, and sometimes the dispersions become gelled, making them impossible to use. Moreover, when such dispersions are mixed with other kinds of pigments, the coloration of the coated material becomes uneven or the coloring power degrades due to segregation or settling due to the aggregation of the pigments.

Moreover, some organic pigments in some cases change the pigment crystal state in the dispersion medium. In other words, when the energy of the pigment particles is unstable, their size or shape is changed to change their crystal state to a safer state. As a result, the commercial value is markedly reduced due to a significant reduction in coloration power, tonal change or generation of coarse particles.

There are various ways to disperse a pigment in water. Method of self-dispersion by modifying the surface of the pigment [US 5,851,280], dispersion of carbon black by surface oxidation in the pigment [US 5,609,671], dispersion using various dispersants [US 6,685,796, US 6,848,777, US 2006 / 0272543, and the like. The method of surface modification of pigments via Diazo coupling reaction at Cabot is also known. However, in the case of dispersion by surface modification of the pigment, there is a disadvantage that the surface modification process is complicated and the manufacturing cost increases. In addition, when the polymer dispersant is used, thermal stability of the dispersion is a problem, and when the ink is used for inkjet, there is a problem that clogging of the nozzle occurs.

In the case of carbon black, the surface oxidation method using ozone or NaOCl is also known, but it is known to use NaOCl as a peroxidation method in order to make the dispersion easier. The dispersion method using resin is also well known.

It is also known to use various derivatives having structures similar to pigments. Various structures are disclosed, such as pigment derivatives obtained by incorporating a pigment structure into a part of a pigment derivative or resin obtained by introducing a functional group such as an acidic group, a basic group or a phthalimide methyl group into the pigment structure. These structures have long been used for applications such as dispersants, particle growth inhibitors or crystal transfer inhibitors.

JP-A-2003-167112, JP-A-2002-179979, JP-2002-121418, JP-A-2002-121457 and JP-A-2001-335711 have a quinophthalone structure as a pigment dispersant. Compounds are disclosed. Each of these compounds has the effect of improving the dispersion state, but they do not have sufficient properties to produce pigment dispersions having excellent flowability and storage stability over time as the pigment particles are finely dispersed.

Therefore, there is a continuing need for research on dispersants having excellent performance.

Accordingly, the present inventors have studied and tried to disperse a pigment in water and found that a compound having a structure represented by the following formula (1) in which a hydrophilic functional group was introduced into an aromatic compound has an excellent effect as a water dispersant of the pigment. The invention was completed.

The present invention

It is characterized by a pigment dispersant represented by the following formula (1).

[Formula 1]

Ar-X- (CH ₂ CH ₂ ) _n -OH

In Formula 1, Ar represents an aromatic group of C ₆ ~ C ₂₀ ; X represents a bond, O, CH ₂ COO, N (CH ₂ CH ₂ ) _n OH or NH; n represents the integer of 5-30.

In another aspect, the present invention is characterized by a pigment and an aqueous dispersion containing 5 to 100 parts by weight of the pigment dispersant with respect to 100 parts by weight of the pigment.

In the case of using the compound of the present invention, it is more economically advantageous than dispersing the pigment by surface treatment, and excellent dispersion stability can be obtained. Therefore, it can be expected to use the aqueous dispersion obtained using the compound as an ink excellent in printability and shelf life.

The present invention

It is characterized by a pigment dispersant represented by the following formula (1).

[Formula 1]

Ar-X- (CH ₂ CH ₂ ) _n -OH

In Formula 1, Ar represents an aromatic group of C ₆ ~ C ₂₀ ; X represents a bond, O, CH ₂ COO, N (CH ₂ CH ₂ ) _n OH or NH; n represents the integer of 5-30.

Most pigments have a complex structure including a benzene ring and thus have excellent affinity with aromatic compounds. The attraction force is due to weak van der Waals forces between the aromatic compound and the pigment, but since the pigment is a particle of several tens to hundreds of nanometers, the surface area is large and the overall force is very strong. Therefore, it may be considered to use an aromatic compound as a dispersant of the pigment, in the compound 1 Ar represents an aromatic group of C ₆ ~ C ₂₀ . Preferably, Ar is selected from phenyl group, biphenyl group, 2,2-diphenylpropane group, naphthalene group, carbazole group and fluorene group. The aromatic compound is a material contained in coal tar (Coal tar) as a feature that can be easily separated through distillation.

The aromatic compounds are excellent in affinity with the pigment, but since the hydrophilicity is very insufficient, the hydrophilic compound should be modified by introducing a compound having excellent hydrophilicity. Representative examples of hydrophilic compounds introduced to improve hydrophilicity are copolymers of ethylene glycol. Therefore, in the present invention, a copolymer of ethylene glycol was introduced into the aromatic compound, but O, CH ₂ COO, and N were used as the linking agent. However, when Ar is a carbazole group, since ethylene glycol copolymer may be directly connected to N of the carbazole group, X means a bond, and when Ar is a biphenyl group or a 2,2-diphenylpropane group, It is preferable to be connected to the p (para) position of the benzene ring, and it is preferable to be connected to position 2 when Ar is a naphthalene group and to position 9 when a fluorene group. In addition, when the linker is N, two functional groups may be linked, and X represents N (CH ₂ CH ₂ ) _n OH or NH.

The degree of polymerization n of the ethylene glycol copolymer is to be in the range of 5 to 30, preferably in the range of 8 to 25. If n is less than 5, the hydrophilicity is not sufficient, so that it is insoluble in water. If it is more than 30, the viscosity becomes high, making it unsuitable for use as an ink.

In another aspect, the present invention is characterized by a pigment and an aqueous dispersion containing 5 to 100 parts by weight of the pigment dispersant with respect to 100 parts by weight of the pigment.

If the compound is used in less than 5 parts by weight, there is a problem in that the dispersion degree of the pigment is significantly lowered. When the compound is used in excess of 100 parts by weight, the viscosity is increased, and there is a disadvantage in that economic efficiency is low. The aqueous dispersion is excellent in dispersibility and printability and suitable for use as an ink of an ink jet recording apparatus.

The present invention as described above will be described in more detail with reference to the following examples, but the following examples are provided to aid the understanding of the present invention, and the scope of the present invention is not limited thereto.

Example

As shown in Table 1 below, the compound and the pigment of Chemical Formula 1 were added, pH was adjusted to between 7.5 and 8 with NaOH, and distilled water was added thereto. After dispersing at 10000rpm for 1 hour with a homogenizer, a high-pressure disperser (Microfluidizer process M103-EH, 25000psi, 1 pass) was completed to the aqueous dispersion.

The aqueous dispersion was measured D50 and D90 through a particle size meter (Otsuka, ELS-Z) and are shown in Table 1 below.

Example Formula 1 Pigment Distilled water D50
(Μm) D90
(Μm) Ar X n usage
(Parts by weight) Pigment Name usage
(Parts by weight) usage
(Parts by weight) One 2,2-diphenylpropane O 15 2 R2000 ^{1 )} 15 83 90 229 2 2,2-diphenylpropane O 20 4.5 R3500 ^{2 )} 15 80.5 95 225 3 2,2-diphenylpropane O 25 4.5 R3500 15 80.5 95 231 4 naphthalene O 15 3 R2000 15 82 90 228 5 naphthalene O 15 4.5 R3500 15 80.5 95 209 6 naphthalene NH 20 4.5 R3500 15 80.5 90 210 7 Carbazole - 15 4.5 R3500 15 80.5 85 188 8 naphthalene CH ₂ COO 20 4.5 R3500 15 80.5 95 230 9 naphthalene O 15 5 Yellow ^{3 )} 10 85 130 219 10 2,2-diphenylpropane O 20 5 yellow 10 85 130 244 11 naphthalene NH 20 5 yellow 10 85 130 217 12 Carbazole - 15 5 yellow 10 85 130 202 13 naphthalene NH 20 5 Magenta ^{4 )} 10 85 120 205 14 Carbazole - 15 5 Cyan ^{5 )} 10 85 125 214

1) Carbon black (supplied by Columbia Chemical)

2) Carbon black (supplied by Columbia Chemical)

3) C.I. Pigment Yellow 74 (supplied by Hoibasa)

4) C.I.Pigment Magenta 122 (supplied by Hoiba)

5) C.I.Pigment Cyan 15: 3 (supplied by Hoibasa)

In this example, X is linked to positions 4 and 4 'of the benzene ring for 2,2-diphenylpropane groups and to position 2 for naphthalene.

Through the above results, the aqueous dispersion according to the present invention confirmed that the particle size (D50) of the pigment is in the range of 90 ~ 130㎛, it was found that the dispersion degree of the aqueous dispersion is excellent.

Claims (5)

Pigment dispersant, characterized in that the compound represented by the formula (1): [Formula 1] Ar-X- (CH ₂ CH ₂ ) _n -OH Ar in the above formula represents an aromatic group of C ₆ ~ C ₂₀ ; X represents a bond, O, CH ₂ COO, N (CH ₂ CH ₂ ) _n OH or NH; n represents the integer of 5-30. The pigment dispersant according to claim 1, wherein Ar is an aromatic group selected from a phenyl group, a biphenyl group, a 2,2-diphenylpropane group, a naphthalene group, a carbazole group and a fluorene group. The pigment dispersant according to claim 1, wherein n represents an integer of 15 to 25. An aqueous dispersion comprising a pigment and 5 to 100 parts by weight of the pigment dispersant of any one of claims 1 to 3 with respect to 100 parts by weight of the pigment. An aqueous dispersion according to claim 4, which is used as an ink of an ink jet recording apparatus.