JP2001192584A - Carbon black for printing ink md printing ink composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide carbon black for printing ink exhibiting excellent pitch- blackness and gloss without requiring surface oxidation treatment, improved in dryness known as the shortcoming of surface oxidation treated carbon black, and having no yield value. SOLUTION: The carbon black is characterized in that (1) sol-gel transition point Wgel [wt.%]>=63/(0.28+effective volume ratio α), that (2) pH>4, and that (3) agglomerate diameter Dmod[nm]<140.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to carbon black for printing ink and a printing ink composition containing the carbon black. Here, the printing ink refers to lithographic printing ink, gravure printing ink, letterpress printing ink, screen printing ink, flexographic printing ink, intaglio printing ink, special printing ink, and the like.

[0002]

2. Description of the Related Art In general, a printing ink composition containing carbon black (hereinafter, may be simply referred to as an ink) generally has a sufficient tackiness and glossiness, a moderate tack (viscosity), and a yield value. Is required not to have
In addition, it is also required to have a drying property in which the printed surface dries quickly. For such an ink, carbon black whose surface has been appropriately oxidized is used.

[0003] As a surface oxidation treatment method for carbon black, a method using a liquid oxidizing agent such as nitric acid, hydrogen peroxide, hypochlorite, a method using a free oxygen-containing gas at a high temperature, and a method using ozone are known. Yes
No. 29754, Japanese Patent Publication No. 46-18368,
Japanese Patent Publication No. 52-13808, etc.). However,
An ink using carbon black having an acidic functional group introduced into the surface by a surface oxidation treatment has an excellent jet-blackness and glossiness, but has a problem of poor drying property. That is, the dryer added to promote drying is adsorbed on the surface of the carbon black, and the effect of the dryer is impaired. Therefore, it is necessary to reduce the number of acidic functional groups on the surface of carbon black in order to improve the drying property.

On the other hand, as a carbon black for an ink which has not been subjected to a surface oxidation treatment, has an appropriate tack and has no yield value, Japanese Patent Application Laid-Open No.
No. 200 carbon black (specific coloring power: 8
0 to 115%, nitrogen adsorption specific surface area: 50 to 100 m2 /
g, DBP absorption amount: 60 to 100 ml / 100 g, aggregate diameter D _mod 140 to 230 nm by centrifugation). However, this carbon black has insufficient jetness and gloss.

[0005] As described above, it is more difficult than before to satisfy both the gloss and the fluidity of an ink with carbon black that has not been subjected to a surface oxidation treatment. In general, when the nitrogen adsorption specific surface area of carbon black is reduced, fluidity is improved, but jetness and gloss are deteriorated. Conversely, when the nitrogen adsorption specific surface area is increased, jet blackness and glossiness are improved, but fluidity is reduced.

[0006]

DISCLOSURE OF THE INVENTION The present invention has been made in view of the above-mentioned circumstances, and has as its object to provide a carbon black which has excellent jet-blackness and glossiness without being subjected to a surface oxidizing treatment, and has excellent blackness and glossiness. The drying property which is a disadvantage is improved,
Another object of the present invention is to provide a carbon black for a printing ink having no yield value and a printing ink composition using the carbon black.

[0007]

Means for Solving the Problems As a result of intensive studies, the present inventors have obtained an ink which does not have a yield value and is excellent in dryness, jet-blackness and glossiness by using a specific carbon black. Thus, the present invention was completed.

[0008]

That is, the first aspect of the present invention is as follows.
The gist of the present invention resides in carbon black for printing inks having the following characteristics (1) to (3).

(1) Sol-gel transition point W _gel [% by weight] ≧ 6
3 / (0.28 + effective volume ratio α) (2) pH> 4 (3) Aggregate diameter D _mod [nm] <140

[0009] In the above preferred embodiment, aggregate diameter D _mod [nm] satisfies the conditions of the following (4), DBP absorption [cm ³ / 100g] satisfies the conditions of the following (5) .

Equation 5] _{(4) 140> D mod>} -0.56 × ( nitrogen adsorption specific surface area ^{[m 2 / g]) +} 155 (5) DBP absorption amount ≦ 80 cm ^3/100 g

[0010] A second aspect of the present invention resides in a printing ink composition containing the above-described carbon black.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS First, the carbon black for printing ink (hereinafter simply referred to as carbon black) according to the present invention will be described. The carbon black of the present invention has a specific range of sol-gel transition point W _gel [% by weight], p
H, the aggregate diameter D _mod [nm], and in a further preferred embodiment, the aggregate diameter D _mod [n] in a range different from the above.
m] and the DBP absorption amount in a specific range. Hereinafter, the above physical property values will be sequentially described.

[0012] (1) sol - gel transition point W _gel [wt%]: carbon black of the present invention, the sol - gel transition point W _gel [wt%] ≧ 63 / (0.28+ effective volume ratio alpha)
Condition must be satisfied.

The sol-gel transition point is the critical weight fraction of percolation determined by rheological techniques. According to the percolation theory, when a dispersoid is weakly aggregated in a dispersion system, the dispersoid is solidified to form a cluster. At this time, the maximum size of the cluster increases as the amount ratio of the dispersoid increases. When the quantitative ratio of the dispersoid reaches the sol-gel transition point, the cluster of the dispersoid becomes large enough to connect the end of the system, that is, percolate. Further, when the amount ratio of the dispersoid becomes larger than the sol-gel transition point, a network structure of the dispersoid is formed. A case where the ratio of the dispersoid is smaller than the sol-gel transition point is called a sol, and a case where the ratio is larger is called a gel.

When the dynamic elastic modulus is measured at the sol-gel transition point, both the storage elastic modulus G ′ and the loss elastic modulus G ″ are proportional to the power of the angular frequency ω. Therefore, the storage elastic modulus G ′ and the loss elastic modulus Loss tangent tan δ (=
G ″ / G ′) is a constant value n over a wide range of angular frequencies ω.
Becomes When the amount ratio of the dispersoid is smaller than the sol-gel transition point, tan δ ≧ n, and tan δ depends on the angular frequency ω. When the quantity ratio of the dispersoid is larger than the sol-gel transition point, tan δ ≦ n, where tan δ is also the angular frequency ω
Depends on. That is, the sol-gel transition point can be determined by determining the concentration of the dispersoid whose loss tangent tan δ does not depend on the angular frequency ω in rheology. As a result of the study by the present inventors, the following findings were obtained.

(I) The above-described percolation also occurs in carbon black dispersed in a varnish (also referred to as a vehicle) of an ink, and the sol-gel transition point, which is a critical weight fraction of percolation, can be measured by rheology. The sol-gel transition point differs depending on the type of carbon black.

(Ii) When the amount ratio of carbon black in the ink is larger than the sol-gel transition point, the ink does not flow unless the network structure of the carbon black is cut, so that the ink has a yield value. When the amount ratio is equal to or less than the sol-gel transition point, the ink does not have a yield value because the carbon black does not have a network structure,
Good as ink.

The effective volume ratio α is defined as follows. That is, in the case of a coagulated dispersion system, the shear rate s
There are various expressions for the shear stress σ (Pa) with respect to (s ⁻¹ ), and one of them is Casson's expression. This is represented by _{^{σ 0.5 = σ 0 0.5 + η}} ∞ 0.5 × s 0.5. Here, sigma ₀ is the extrapolated value at a shear rate of 0s ^-1, η _∞ denotes the viscosity as an extrapolated value at infinite shear rate. In the case of a spherical particle dispersion system that does not aggregate, several relational expressions have been proposed for the viscosity η (Pa · s) in the Newton region at a high shear rate and the volume fraction φ (volume%) of the dispersoid. One form is η = η _s × (1-φ / 71)
^{Expressed as -2} . Here, η _s (Pa · s) indicates that the volume fraction φ of the dispersoid is 0% by volume, that is, the viscosity of the dispersion medium. As a result of the study by the present inventors, the following findings were obtained.

(Iii) In the carbon black dispersed in the varnish, the shear stress σ (Pa) and the shear rate s (s
^-1 ) is expressed by Casson's formula.

(Iv) The density of carbon black is 1.8 g
/ Cm ³ , and the density of the varnish is 1 g / cm ³ , and the volume fraction of carbon black is calculated by the following formula (1) (where W is
When _CB is expressed by showing the weight percent of carbon black dispersed in a varnish), the eta _∞ determined by equation Casson eta
_∞ = η _s × (1−α × φ _CB / 71) ⁻²

(6) φ _CB (= 100 × (W _CB /1.8)/((W _CB /1.8)+((100−W _CB ) / 1)): volume%) 1)

In short, the effective volume ratio α is a quantity that indicates how much the contribution of carbon black to the viscosity is increased as compared to a non-agglomerated spherical particle dispersion, although the details are not clear. The effective volume ratio α differs depending on the type of carbon black.

The ink adjusts its tack when used for printing. At this time, since the varnish or carbon black is added, the weight fraction of carbon black in the ink after the tack preparation differs depending on the type of carbon black. As a result of the study by the present inventors, the following findings were obtained.

(V) Effective volume ratio α obtained by the above method
The larger the value is, the smaller the weight fraction of carbon black in the ink after tack preparation is. If the weight fraction of carbon black in the ink after the preparation of the tack is larger than the sol-gel transition point determined by the above method, the ink has a yield value due to the network structure of carbon black and is not suitable as an ink. When the weight fraction of carbon black in the ink after the preparation of the tack is equal to or smaller than the sol-gel transition point obtained by the above method, the ink has no yield value and has good fluidity. (Vi) As a result, the carbon black of the present invention has a sol-gel transition point W
_gel [% by weight] ≧ 63 / (0.28 + effective volume ratio α) must be satisfied. That is, when the relationship between the sol-gel transition point W _gel and the effective volume ratio α is out of the above range, the ink has a yield value and poor fluidity.

(2) pH: The carbon black of the present invention must satisfy the condition of pH> 4. pH is JISK
Measured according to 5101. If the surface of the carbon black has many acidic functional groups, the pH will decrease. The pH of the surface-oxidized carbon black is less than 4 (pH <
4). When carbon black whose surface has been oxidized is added to the ink, a dryer added to promote the oxidative polymerization of the varnish in the ink is adsorbed on the surface of the carbon black and reduces its effectiveness. Therefore, when the pH of the carbon black is higher than 4, the ink has good drying properties.

(3) Aggregate diameter D_mod[Nm]: of the present invention
Carbon black has an aggregate diameter D_mod[Nm] <140
It is necessary to satisfy the conditions. Aggregate diameter D_modIs carbon
Measure the size of black aggregate as Stokes diameter
Value. Stokes diameter using surfactant
Measure carbon black dispersed in water by centrifugal sedimentation.
Set. Generally, the aggregate diameter D _modThe smaller is the jet blackness
And glossiness are improved.

(4) Preferred aggregate diameter D _mod : The preferred carbon black of the present invention satisfies the following formula (II).

140> D _mod > −0.56 × (nitrogen adsorption specific surface area [m ² / g]) + 155 (II)

Carbon black satisfying the above formula (II) has no yield value even if the pH is higher than 4, and
Excellent jet-blackness and glossiness. The reason is unknown.
The nitrogen adsorption specific surface area is measured according to JIS K6217.

[0027] (5) DBP absorption amount [cm ^3/100
g]: preferred carbon blacks of the present invention satisfies the DBP absorption ≦ 80cm ³ / 100g. The DBP absorption is measured according to JIS K6217. Generally, DB
When the amount of P absorbed increases, fluidity, jetness and gloss tend to be impaired.

Next, a method for producing carbon black according to the present invention will be described. FIG. 1 and FIG. 2 are schematic diagrams showing main parts of an example of a known vertical furnace and a horizontal furnace, respectively. In each of the drawings, reference numeral (1) denotes a base oil, (1 ′) denotes a fuel, (2) to (4) denotes combustion air, (L) denotes a base oil burner position, and (θ) denotes a base oil spray angle. . The vertical furnace shown in FIG. 1 has a cylindrical reaction furnace, and the feed oil burner position (L) is defined as the length from the hearth of the reaction furnace.
Represented with a + sign. In the horizontal furnace shown in FIG. 2, a contraction portion is formed between the combustion furnace and the reaction furnace, and the position (L) of the feed oil burner is defined by the distance from the contraction portion, and is usually indicated with a minus sign. Is done.

In the method for producing carbon black according to the present invention, the vertical furnace shown in FIG. 1 is preferably used. In the vertical furnace shown in FIG. 1, the feed oil (1) entrained in the atomized air is introduced from the lower center of the cylindrical reactor by a two-fluid burner, and the combustion air (2) is used as the inner combustion air. The fuel (1 ′) which is divided into two parts (3) and the outer combustion air (4) and is introduced from below the cylindrical reactor, and the fuel (1 ′) entrained in the atomized air (or steam) is the outer combustion air. It is introduced from the vicinity of (4). The position (L) of the feed oil burner is usually selected from a range of 0 to +300 mm, and the feed oil spray angle (θ) is usually selected from a range of 20 to 120 °.

As the raw material oil, for example, C / H is 10 to 10.
16, creosote oil having a BMCI value of 110 to 170,
FCC oil, ethylene bottom oil and the like are used. Also,
The feedstock typically contains 1100-1200p per feedstock
pm of an alkali metal compound such as potassium carbonate is added. Heavy oil and natural gas are used as fuel.

The amount of the feed oil atomized air and the amount of the fuel atomized air (or steam) are usually 30 to 250 Nm.
³ / H, the amount of feed oil is usually 800-1300 Kg / H,
The amount of combustion air is usually 3500 to 5500 Nm ³ / H,
The ratio of the amount of liquid or gaseous fuel to the amount of combustion air is usually selected from the range of 10-20. The spray pressure of the feedstock oil is usually 1.96 × 10 ^{5 to} 9.8 ×.
It is selected from the range of 10 ⁵ PaG.

For the production of carbon black according to the present invention, it is important that the raw material oil is sprayed and vaporized at the highest temperature in the furnace. That is, in the conventional method, the ratio (distribution ratio) of the inner combustion air (3) / the outer combustion air (4) is set to about 1, but when producing the carbon black according to the present invention, it is usually used. It is selected from the range of 1.5-4, preferably 2-3. By adopting such conditions, that is, by changing the distribution ratio of the inner combustion air (3) and the outer combustion air (4), the inner combustion air (3) is changed.
By increasing the ratio, the temperature of the portion where the feed oil introduced from the feed oil burner (1) is vaporized can be made closer to the theoretical combustion air ratio to generate a high-temperature combustion gas atmosphere. Furthermore, it is preferable to increase the amount of atomized raw material oil air, increase the spraying speed, and reduce the diameter of oil droplets, because vaporization is improved and contact efficiency in a high temperature part in the furnace is improved.

Next, the printing ink composition according to the present invention will be described. The printing ink composition contains carbon black, varnish and auxiliaries. Varnishes are natural resins, synthetic resins, drying oils or petroleum solvents. As the auxiliary agent, a wetting agent, a fungicide, and the like in addition to a drying control agent, a viscosity controlling agent, a color adjusting agent, and the like are added as required.

[0034] Natural resins include rosin, shellac, and Gilsonite. Synthetic resins include phenolic resins, alkyd resins, petroleum resins, vinyl resins, polyamide resins, rosin-modified phenolic resins, and rosin-modified polyamide resins. No. Examples of the drying oil include linseed oil and low polymers thereof. Examples of the petroleum-based solvent include spindle oil, machine oil, and mobile oil.

The amount of carbon black in the ink may be appropriately selected according to the application, but is preferably in the range of 5 to 50% by weight, more preferably 10 to 30% by weight, and particularly preferably 10 to 20% by weight. It is. In particular, in such a range, an ink having no yield value and excellent in jet-blackness, glossiness and drying property can be obtained.

[0036]

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to the following examples unless it exceeds the gist. In addition, the test method of the carbon black used in the following examples, the preparation method of an ink, and the test method are as follows.

<Test Method> (1) Sol-gel transition point W _gel [% by weight]: “MS-8”
00 "varnish (manufactured by Showa Varnish) 100 parts by weight," F-1
A mixture of 5.3 parts by weight of “04” varnish (manufactured by Showa Varnish) and 15 parts by weight of solvent (“AF-5” manufactured by Nippon Oil) was used as a dispersion medium for measurement. After an amount of carbon black described below was premixed in this dispersion medium, the mixture was subjected to 5 passes using a three-roll mill disperser to obtain a measurement sample. The weight fraction of each carbon black is W (= 0, 10, 20, 3)
(0% by weight) was measured as follows.

A strain control type rheometer (Rheometrics
"ARES" manufactured by Scientific FE) and cones
A plate (diameter 50 mm, cone angle 0.04 rad) is used. After applying shear at a shear rate of 20 s ^-1 until the viscosity no longer changes with time, ¹ rad /
s, the loss tangent tan δ is measured at an angular frequency of 100 rad / s.

The abscissa plots the weight fraction W [% by weight] of the carbon black, and the ordinate plots the loss tangent tan δ. For Comparative Examples 1 and 5 described below, the difference between the values of tan δ measured at the two angular frequencies at W = 20% by weight was equal to or less than 0.2, and the value of W was used as the sol-gel transition point W
_gel [% by weight]. In other carbon blacks, the difference between the values of tan δ measured at two angular frequencies at W = 0, 10, 20, and 30% by weight was not equal to or less than 0.2, so that the sol-gel transition point was as follows. W _gel [wt%] was determined by interpolation. Example 1 and Comparative Example 2 described below,
3, the points of tan δ of the same angular frequency are connected by a straight line with respect to tan δ of W = 10 and 20% by weight, and in Comparative Example 4, W = 20 and 30% by weight. Was taken as the sol-gel transition point W _gel [% by weight].

(2) Carbon black effective volume ratio α:
For the measurement sample prepared in the same manner as in the above (1), the shear stress (Pa) in a state where the viscosity does not change with time at a shear rate (1 s ⁻¹ , 10 s ⁻¹ , 100 s ⁻¹ ) is similarly measured. Measured by the method. Plot the square root of the shear rate on the horizontal axis and the square root of the shear stress on the vertical axis.
The following function was fitted by the least squares method. The square of the slope was defined as the shear rate infinite viscosity η _{∞, W} at the weight fraction W (% by weight). The vertical axis is (W / 1.8) /
((W / 1.8) + ((100−W) / 1)) was plotted on the horizontal axis at 0.71 × (1− (η∞ _{, W} / η∞ _{, 0} ) ^−0.5 ). A linear function passing through 0 was fitted by the least squares method, and the slope was defined as the effective volume ratio α of the carbon black.

(3) pH of carbon black: JIS
Conforms to K5101.

(4) Aggregate diameter D _mod [nm] of carbon black by centrifugal sedimentation: 5 mg of a dry sample is mixed with a small amount of an activator, and 50 cc of a 20% by weight aqueous ethanol solution is added.
added. And it disperse | distributed for 6 minutes with the ultrasonic disperser, and it was set as the measurement sample. The aggregate diameter measuring device (manufactured by Joyes Loebl, UK) was set to 6000 rpm by centrifugal sedimentation. After adding 10 ml of spin solution (ion-exchanged water), 1 ml of buffer solution (20% by weight aqueous ethanol solution) was injected. Next, 0.5 ml of the measurement sample solution was added with a syringe to start the measurement. The maximum frequency diameter D _mod [nm] in the obtained aggregate distribution curve was determined.

(5) Nitrogen adsorption specific surface area of carbon black: based on JIS K6217.

[0044] (6) DBP absorption amount of carbon black [cm ³ / 100g]: conforms to the JISK6217.

<Ink suitability> (1) Preparation of ink: An ink was prepared using an offset rotary ink material. 100 parts by weight of "MS-800" varnish (manufactured by Showa Varnish), 5.3 parts by weight of "F-104" varnish (manufactured by Showa Varnish), solvent ("A" manufactured by Nippon Oil
F-5 ") 15 parts by weight of carbon black and 30 parts by weight of carbon black were premixed, and the mixture was subjected to 5 passes using a three-roll mill disperser to prepare a dispersion ink.

(2) Adjustment of tack: The tack value of the above-mentioned dispersed ink was adjusted according to JIS K5701 using an incometer. The target tack value was 10 ± 0.5 at 1 minute at 1200 rpm.

(3) Optical suitability (blackness): M manufactured by Toyo Seiki
An S-colored machine was used to obtain a colored paper for measurement. Collect 0.4 cc of tack adjustment ink with an ink pipette and use Toyo Seiki M
It was supplied to the roll of the S-color machine. After spreading this evenly,
Medium quality coated paper (made by Oji Paper Co., Ltd., trade name: Medium quality OK coated 6
3 kg ”). The Macbeth density of the above colored paper was measured with a reflection densitometer (“RD914” manufactured by Gretag Macbeth, USA). The Macbeth density indicates that the larger the number, the higher the jet-blackness.

(4) Optical aptitude (glossiness): Using a gloss meter (Haze-Gloss, manufactured by Big-Gardner, Germany), using a 60 ° -degree colored paper prepared in the same manner as in (3) above.
The 60 ° gloss was measured. The higher the number, the better the gloss.

(5) Flowability (yield value): JIS K57
01 and a cone-plate (diameter 25) with a stress-controlled rheometer (“DSR” manufactured by Rheometrics Scientific FE)
mm, cone angle 0.1 rad), and the yield value was measured. The shear rate with respect to the stress when the stress is gradually increased starting from the stress 0 Pa is measured, and the stress when the fluid starts to flow is defined as the yield value. If the yield value is 0, the fluidity is good.

(6) Drying property: A dryer was added to the ink after tack preparation arbitrarily set according to JIS K5701, and the drying property was evaluated by a method using a glass plate in accordance with JIS K5701. The measurement time interval was changed to an interval of 15 minutes. For 100 parts by weight of ink, dryer (6
(Weight% cobalt naphthenate: manufactured by Showa Varnish) was added in an amount of 5 parts by weight. Evaluation of drying was performed under the conditions of 25 ° C. and 70% RH.

Production Example 1 Creosote oil containing 1125 ppm of alkali (potassium carbonate) as a raw material oil (C / H ratio 14.7, BMC
I value 158) was used. Then, a vertical furnace having a cylindrical reaction furnace as shown in FIG.
0 kg / H, fuel atomized air 150 Nm ³ / H, combustion air 4500 Nm ³ / H (outside distribution amount 1200 Nm ³
/ H and an inner distribution amount of 3300 Nm ³ / H) are introduced from the lower part of the furnace and burned, and the feed oil 1130 kg / H and the feed oil atomized air 140 Nm ^{3 are} fed from the lower center part of the furnace using a two-fluid burner. By introducing / H,
Production of carbon black was performed. At this time, the spray pressure of the stock oil was 5.9 × 10 ⁵ PaG, and the stock oil spray angle (θ) and the stock oil burner position (L) were as shown in Table 1. The characteristic values of the obtained carbon black are shown in Table 2 as Example 1.

Production Examples 2 and 3 Using a horizontal furnace as shown in FIG. 2, carbon black was produced under the conditions shown in Table 1. The characteristic values of the carbon black obtained by this method are shown in Table 2 as Comparative Examples 2 and 3. However, natural gas was used as fuel.

Production Example 4 As in Production Example 1, a vertical furnace having a cylindrical reactor was used to produce carbon black under the conditions shown in Table 1. The characteristic values of the carbon black obtained by this method are shown in Table 2 as Comparative Example 4.

[0054]

[Table 1]

Example 1 Table 2 shows the characteristic values of the carbon black obtained in Production Example 1 as Example 1. An ink was prepared using this carbon black and tested for ink suitability. Table 2 shows the results.

Comparative Example 1 Table 2 shows the characteristic values of "Mitsubishi Carbon Black MA7" (manufactured by Mitsubishi Chemical Corporation) as a carbon black subjected to a surface oxidation treatment. An ink was prepared using this carbon black and tested for ink suitability. Table 2 shows the results.

Comparative Examples 2 to 4 The physical properties of the carbon blacks obtained in Production Examples 2 to 4 are shown in Table 2 as Comparative Examples 2 to 4. Inks were prepared using these carbon blacks and tested for ink suitability. Table 2 shows the results.

Comparative Example 5 Table 2 shows the characteristic values of "Raven780U" manufactured by COLUMBIAN as Comparative Example 5. An ink was prepared using this carbon black and tested for ink suitability.
Table 2 shows the results.

[0059]

[Table 2]

As is clear from Table 2, Example 1, Comparative Examples 1 and 4, in which the range of W _gel and α is in the range of W _gel ≧ 63 / (0.28 + α), have no yield value. In contrast,
Surprisingly, Comparative Examples 3 and 5 having a smaller nitrogen adsorption specific surface area than Example 1 have a large yield value. Further, in Example 1, the D _mod was smaller than that in Comparative Example 4, so that
Jet blackness and glossiness are better. Further, Example 1
Since the pH is higher than that of Comparative Example 1, that is, the surface has less acidic functional groups, the drying property is better than that of Comparative Example 1. That is, in Example 1, since the range of W _gel and α is appropriate and the D _mod and pH are appropriate, it has no yield value and is excellent in jet-blackness, gloss, and drying property.

[0061]

According to the present invention described above, the range of the sol-gel transition point W _gel to the effective volume ratio α and the aggregate diameter D
By containing a carbon black whose _mod and pH are adjusted to an appropriate range, a carbon black for printing ink which has no yield value and is excellent in jet-blackness, glossiness and drying property is provided.

[Brief description of the drawings]

FIG. 1 is a schematic view showing a main part of an example of a vertical furnace.

FIG. 2 is a schematic view showing a main part of an example of a horizontal furnace.

[Explanation of symbols]

 1: feed oil 1 ': fuel 2: combustion air 3: inside combustion air 4: outside combustion air L: feed oil burner position θ: feed oil spray angle

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 4J037 AA02 DD05 DD17 EE46 FF05 FF09 4J039 AB04 AB08 AD02 AD04 AD18 AE02 AE06 AE08 BA04 EA19 GA01 GA02 GA03 GA09 GA10

Claims (4)

[Claims] 1. A carbon black for printing ink, having the following characteristics (1) to (3): (1) Sol-gel transition point W _gel [% by weight] ≧ 6
3 / (0.28 + effective volume ratio α) (2) pH> 4 (3) Aggregate diameter D _mod [nm] <140 2. The carbon black for printing ink according to claim 1, wherein the aggregate diameter D _mod [nm] satisfies the following condition (4). (4) 140> D _mod > −0.56 × (nitrogen adsorption specific surface area [m ² / g]) + 155 3. A DBP absorption [cm ^3/100 g] is printing ink of carbon black according to claim 1 or 2 satisfies the conditions of the following (5). [Number 3] (5) DBP absorption amount ≦ 80cm ³ / 100g 4. A printing ink composition comprising the carbon black according to claim 1.