WO2017074050A1 - Method for modifying surface of carbon black - Google Patents

Abstract

The present invention relates to a method for modifying a surface of carbon black and, more specifically, to a method for modifying a surface of carbon black, wherein the amount of sulfur-containing functional groups introduced is improved through the pretreatment of the surface of carbon black.

Description

Surface Modification Method of Carbon Black

The present invention relates to a method for surface modification of carbon black, and more particularly to a method for surface modification of carbon black to improve the amount of sulfur-containing functional groups introduced through the pretreatment of the surface of the carbon black.

Carbon black is widely used in various fields as fillers and reinforcing pigments in blending and preparing rubber compositions and plastic compositions as pigments for ink compositions, paints and the like.

When carbon black is used as a pigment for ink compositions, paints, etc., it is required to have excellent properties such as blackness, gloss, coloring power, and dispersibility, while when used as a reinforcing agent of a tire, it is excellent in wear resistance and has low hysteresis loss ratio. Is required.

In particular, in relation to the rubber composition for producing a tire, the elasticity of the rubber is due to the energy absorbing ability of the crosslinked rubber skeleton, and if the crosslinking density of the rubber is high, the tensile strength is high and the elongation is low. The crosslinking density must be carefully controlled.

On the other hand, since there is a limit in increasing the crosslinking density, a reinforcing agent such as carbon black is added to the rubber in order to increase the tensile strength while not increasing the modulus.

The properties of the fillers that directly affect the reinforcing effect of the rubber include the size, surface area and particle structure of the carbon black particles, but these properties are all related to the physical bonding between the carbon black and the rubber.

In other words, the carbon black is only physically dispersed on the rubber matrix in the composition containing the carbon black and the rubber.

Therefore, when stress is applied to a tire made of a rubber composition and the strain is continuously generated, the carbon black particles physically dispersed to maintain the elasticity of the rubber may agglomerate or leave the original position, resulting in deterioration of the tire properties. Cause.

In order to solve this problem, a technique of adding sulfur (sulfur) which can form a crosslink with rubber to the rubber composition has been introduced, but sulfur only forms a crosslink (chemical bond) between adjacent rubber molecules, There is a limit in solving the above-described problems because it does not form a chemical bond with the carbon black.

As an alternative, a method of replacing carbon black with silica or introducing a silane group on the surface of the carbon black has been introduced, but an expensive coupling agent is required for the crosslinking reaction through silica or silane groups, and alcohol byproducts are generated as a result of the crosslinking reaction. There is a problem.

Disclosure of Invention The present invention has been made to solve the above problems, and an object of the present invention is to provide a method for introducing a functional group for mediating a chemical bond as well as a physical bond between a rubber molecule and carbon black in a rubber composition on the surface of the carbon black. do.

It is also an object of the present invention to provide a reforming method for introducing a functional group capable of mediating a crosslinking reaction between rubber molecules on the surface of carbon black.

In addition, an object of the present invention is to provide a pretreatment method for introducing a functional group capable of mediating the crosslinking reaction between rubber molecules on the surface of the carbon black.

In addition, the present invention provides a surface modification method that can be applied to the carbon black manufacturing process by providing a method that can reduce the surface difficulty of the carbon black without any additional process, the manufacturing process difficulty and cost The purpose.

According to an aspect of the present invention for solving the above technical problem, a method of introducing a functional group capable of mediating chemical bonds with rubber molecules into the surface of the carbon black by performing a surface modification immediately with the production of carbon black Can be provided.

Specifically, the surface modification method of carbon black according to an embodiment of the present invention may include the following steps.

(a) pretreating the finely divided carbon black in an oxidizing gas atmosphere;

(b) mixing the pretreated carbon black with water to prepare a mixture;

(c) pelletizing carbon black in the mixture; And

(d) heat treating the pelletized carbon black while supplying a mixed gas comprising a sulfur compound in gas phase to obtain carbon black into which sulfur-containing functional groups are introduced on the surface.

According to one embodiment of the present invention, carbon black (fine powder) is synthesized from a hydrocarbon-based raw material and then started by pretreatment.

The pretreatment in step (a) may be carried out at room temperature, for example at a temperature of 20 to 35 ° C., through which the primary modification takes place on the surface of the carbon black.

Step (a) may be carried out under at least one oxidizing gas atmosphere selected from oxygen, ozone, air and NO ₂ , and pretreatment may increase the proportion of oxygen-containing functional groups on the surface of the carbon black.

In one embodiment, the pretreatment is preferably performed such that the content of oxygen-containing functional groups in the surface of the carbon black is 0.1 to 1.0 meq / g.

The content of the oxygen-containing functional groups introduced to the carbon black surface through the pretreatment of step (a) can be confirmed through the weight ratio of gases generated from the functional groups on the carbon black surface measured by thermal desorption analysis.

The weight ratio of gas CO / CO ₂ / H ₂ generated by thermal desorption analysis of the pretreated carbon black according to step (a) may be in the range of 5/1/1 to 20/10/1.

Subsequently, step (b) is a step of mixing the pretreated carbon black in the finely divided state according to step (a) with water before wet pelletization, and step (c) wet pelletizes the mixture of the finely divided carbon black and water. It's a step.

Finally, the heat treatment of step (d) can be carried out at a temperature of 160 to 500 ℃, the second modification occurs on the surface of the carbon black at the same time the moisture is completely removed from the carbon black through the heat treatment.

The heat treatment of step (d) is carried out in an atmosphere in which there is at least one sulfur compound selected from H ₂ S, SO ₂ and elemental sulfur.

At this time, the mixed gas in contact with the pretreated carbon black is preferably supplied at a gas hourly space velocity of 600 to 3,000 hr ⁻¹ , and the concentration of the sulfur compound in the gas in the mixed gas is 500 to 1,000 mg. / Nm ³ is preferred.

At least one sulfur-containing functional group selected from the monosulfide group, the disulfide group and the polysulfide group including three or more sulfur may be present on the surface of the carbon black completed by the heat treatment in step (d), and preferably Monosulfide groups and / or disulfide groups may mainly be present.

In addition, the content of sulfur in the carbon black completed until the heat treatment according to an embodiment of the present invention may be 3 wt% or more.

According to the present invention, after the surface of the surface-modified carbon black is first pretreated, a functional group capable of mediating the crosslinking reaction between the rubber molecules is introduced, thereby introducing a more uniform and higher content of the crosslinking reaction mediating functional group on the surface of the carbon black. There is an advantage that this is possible.

In addition, according to the present invention, a functional group capable of mediating the crosslinking reaction between the rubber molecules is uniformly introduced to the surface of the carbon black surface modified, and thus the carbon black in the rubber matrix through the uniform crosslinking reaction between the rubber molecule and the carbon black. It is possible to improve the dispersibility of, and to increase the crosslinking density between the rubber molecules mediated by carbon black to increase the tensile strength of the tire produced therefrom.

In addition, the chemical bond between the carbon black and the rubber molecule may be mediated through a functional group present on the surface of the surface-modified carbon black according to the present invention, and thus the bonding force between the rubber molecule and the carbon black may be further improved. Accordingly, the resistance to stress that is continuously applied to the tire, that is, wear resistance may be improved.

Certain terms are defined herein for convenience of understanding the invention. Unless defined otherwise herein, scientific and technical terms used herein may have the meanings that are commonly understood by one of ordinary skill in the art.

In addition, the singular forms also include the plural forms thereof, and the plural forms terms may also include the singular forms thereof, unless the context clearly indicates otherwise.

Hereinafter, the carbon black surface modification method according to an embodiment of the present invention will be described in detail.

According to one aspect of the present invention, a method for introducing a functional group capable of mediating chemical bonds with rubber molecules into the surface of the carbon black by performing surface modification immediately with the preparation of carbon black can be provided.

Specifically, the surface modification method of carbon black according to an embodiment of the present invention may include the following steps.

(a) pretreating the finely divided carbon black in an oxidizing gas atmosphere;

(b) mixing the pretreated carbon black with water to prepare a mixture;

(c) wet pelletizing carbon black in the mixture; And

(d) heat treating the pelletized carbon black while supplying a mixed gas containing a sulfur compound in gas phase to obtain carbon black into which sulfur-containing functional groups are introduced on the surface.

According to one embodiment of the present invention, carbon black (fine powder) is synthesized from a hydrocarbon-based raw material and then started by pretreatment.

The pretreatment in step (a) may be carried out at room temperature, for example at a temperature of 20 to 35 ° C., through which the primary modification takes place on the surface of the carbon black.

Step (a) may be carried out under an oxidizing gas atmosphere, and the pretreatment of step (a) may increase the proportion of oxygen-containing functional groups on the surface of the carbon black.

Here, the oxidizing gas is a gas containing an oxidizing material, and may be at least one selected from oxygen, ozone, air, and NO ₂ . It is also possible to use the above-mentioned oxidizing gas and at least one mixed gas selected from hydrogen, nitrogen and argon.

Primary reforming refers to oxidation reforming that occurs on the surface of the carbon black, and the proportion of oxygen-containing functional groups on the surface of the carbon black may be increased by the oxidation reforming. For example, oxidation reforming may occur in such a way that hydrogen is replaced by oxygen or oxygen-containing functional groups are introduced instead of hydrogen from the C—H bonds present in the surface of the carbon black.

Oxygen-containing functional groups include aldehyde groups, ketone groups, carboxyl groups and hydroxyl groups, and the like, and may further include other polar oxygen-containing functional groups that can be introduced through oxidation reforming occurring under an oxidizing gas atmosphere.

When the pretreatment temperature is less than 20 ° C., the rate of oxidation reforming on the surface of the carbon black is not only slow but also cannot sufficiently increase the proportion of oxygen-containing functional groups on the surface of the carbon black.

Oxygen-containing functional groups introduced into the surface of the carbon black through oxidation reforming according to the pretreatment may be replaced with sulfur-containing functional groups through reforming after heat treatment. Therefore, when oxygen-containing functional groups are not sufficiently introduced into the surface of the carbon black through oxidation reforming according to the pretreatment, it may be difficult to introduce sufficient sulfur-containing functional groups to the surface of the carbon black even after the heat treatment.

On the other hand, when the pretreatment temperature exceeds 35 ℃, the rate of oxidation reforming of the surface of the carbon black increases as the temperature is increased, but the degree is not large compared with the room temperature. As a result, the oxidation reforming effect is small compared to the energy input to increase the temperature, so the economic rise is unnecessary.

Therefore, it is preferable that the pretreatment is carried out in the above-described temperature range in order to increase the proportion of oxygen-containing functional groups in the surface of the carbon black while maintaining the surface stability of the carbon black.

In addition, in one embodiment, the pretreatment is preferably performed so that the content of oxygen-containing functional groups in the surface of the carbon black is 0.1 to 1.0 meq / g. The method of measuring the content of oxygen-containing functional groups in the surface of the carbon black may be performed by a method commonly used to quantitatively analyze functional groups containing specific elements.

When the content of the oxygen-containing functional groups introduced into the surface of the carbon black through the first pretreatment is less than 0.1 meq / g, it may be difficult to introduce sufficient sulfur-containing functional groups on the surface of the carbon black even after the heat treatment.

On the other hand, when the content of oxygen-containing functional groups introduced into the surface of the carbon black through the first pretreatment is greater than 1.0 meq / g, the content of sulfur-containing functional groups in the carbon black is too high, and using such carbon black In the compound manufacturing process, there is a problem that the vulcanization time becomes too fast and difficult to control.

The content of the oxygen-containing functional groups introduced to the carbon black surface through the pretreatment of step (a) can be indirectly confirmed by the weight ratio of gases generated from the functional groups on the carbon black surface measured by thermal desorption analysis.

The weight ratio of the gaseous CO / CO ₂ / H ₂ generated by the thermal desorption spectrometry of a carbon black treated in accordance with step (a) can range from 5/1/1 to 20/10/1.

The above-described content ratio of gas, in turn, indicates the degree of primary modification by step (a), that is, the degree of introduction of oxygen-containing functional groups, and the relatively high ratio of CO and / or CO ₂ is higher than that of H ₂ . This means that the proportion of oxygen-containing functional groups in the surface of the carbon black has increased.

In addition, the carbon black of the surface of the oxygen-in as fast than the substitution rate of a containing functional groups gaseous CO and / or CO ₂ - sulfur-containing functional group substituted speed of the contained functional group is the carbon black surface in CH H of sulfur in combination It can be understood that the similar ratio of H ₂ means that the introduction of oxygen-containing functional groups in the surface of the carbon black is not sufficient.

If the proportion of the gaseous CO and / or CO ₂ ratio of H ₂ exceeds a 20/10/1, carbon black in an oxygen-containing functional groups because of the large content of the content of sulfur is introduced into the carbon black according to the heat treatment so much When manufacturing a compound using the lower carbon black, there is a problem that the vulcanization time is too fast and difficult to control.

The wet pelletized carbon black through step (c) is present with water, and the water is removed by performing a heat treatment (drying) process (step (d)) in a separate dryer to remove carbon black as a final product. Will be obtained. At this time, the surface modification process for the carbon black may be performed simultaneously with the drying process.

The heat treatment of step (d) may be carried out at a temperature of 160 to 500 ℃, preferably 250 to 400 ℃, the second modification occurs on the surface of the carbon black at the same time the moisture is completely removed from the carbon black through the heat treatment.

The heat treatment is carried out in an atmosphere in which there is at least one sulfur compound selected from a sulfur source, such as H ₂ S, SO _2, and elemental sulfur, which can be supplied to the gas phase, and in the surface of the carbon black via secondary modification. The oxygen-containing functional groups present can be substituted with sulfur-containing functional groups.

As the sulfur-containing functional group, there may be at least one sulfur-containing functional group selected from monosulfide groups, disulfide groups and polysulfide groups comprising at least three sulfur, preferably monosulfide groups and / or disulfides Groups may be present primarily.

For example, oxygen-containing functional groups such as aldehyde groups, ketone groups, carboxyl groups and hydroxyl groups may be substituted with sulfur-containing functional groups such as monosulfide groups and disulfide groups, where aldehyde, ketone groups and hydroxyl groups are present. The actual group is released in the form of carbon monoxide (CO) gas from carbon black as it is substituted with a sulfur-containing functional group, and in the case of the carboxyl group, in the form of carbon dioxide (CO ₂ ) gas.

In addition, hydrogen may be replaced by sulfur or sulfur-containing functional groups may be introduced instead of hydrogen from CH bonds present on the surface of the carbon black through secondary modification. At this time, hydrogen is released from the carbon black in the form of hydrogen (H ₂ ) gas as it is substituted with a sulfur-containing functional group.

At this time, the mixed gas in contact with the pretreated carbon black is preferably supplied at a gas hourly space velocity of 600 to 3,000 hr ⁻¹ , and the concentration of the sulfur compound in the gas in the mixed gas is 500 to 1,000 mg. / Nm ³ is preferred.

If the gas hourly space velocity of the mixed gas is less than 600 hr ^{- 1} , the secondary reforming may not be sufficiently performed. That is, the rate at which the gaseous sulfur compound is supplied may be slow, so that the oxygen-containing functional group or hydrogen of the CH bond in the surface of the carbon black is substituted with the sulfur-containing functional group.

On the other hand, if the gas hourly space velocity (Gas Hourly Space Velocity) of the mixed gas exceeds 3,000hr ^{- 1} , there is a possibility that the reaction efficiency of the sulfur-containing gas and carbon black is lowered.

The sulfur content in the carbon black having undergone the surface modification through the above-described steps may be 3 wt% or more.

As described above, the step (d) in which the heat treatment is performed is a step of removing moisture from the carbon black containing water after wet pelletization and simultaneously modifying the surface of the carbon black. Simultaneously, the difficulty and cost of the manufacturing process can be reduced.

The following presents specific embodiments of the present invention. However, the embodiments described below are merely for illustrating or explaining the present invention in detail, and thus the present invention is not limited thereto.

Surface Modification Method of Carbon Black

Example 1

Step (a): Pretreated carbon black (grade N234) was pretreated into an oxidizing gas treatment reactor in front of the pelletizer. The oxidizing gas treatment reactor was a rotary kiln type reactor. The reaction temperature was fixed at room temperature, the reactor rotation speed was 20 rpm, and the concentration of ozone in oxygen was 90 mg / Nm ³ (4.2 vol%). The total amount of ozone supplied was 9.072 mg / CBg and pretreated with finely ground carbon black for 2 hours.

Steps (b) and (c): The carbon black in the oxidation-modified pulverized state was mixed with water of the same weight and then poured into a wet pellet maker for pelleting for 1 hour.

Step (d): The ground (pellet) carbon black was put into a dryer for drying the moisture and surface modification. The temperature in the dryer was 250 ° C. and the residence time was 2 hours. Part of the exhaust gas separated from the bag filter was used as a mixed gas, and elemental sulfur vapor was used as the gaseous sulfur compound. At this time, the mixed gas in contact with the pretreated carbon black was supplied at a gas hourly space velocity of 2,000 hr ⁻¹ , and the concentration of the sulfur compound in the gas phase in the mixed gas was 700 mg / Nm ³ .

Example 2

The surface of the carbon black was modified under the same conditions as in Example 1, but pretreatment with ozone was performed for 1 hour.

Example 3

The surface of the carbon black was modified in the same manner as in Example 1, but the total amount of ozone supplied to the pretreatment was set to 18.144 mg / CBg.

Example 4

The surface of the carbon black was modified in the same manner as in Example 1, but the gas hourly space velocity of the mixed gas of step (d) was set to 4,000 hr ⁻¹ .

Comparative Example 1

The surface of the carbon black was modified in the same manner as in Example 1, but step (d) was not performed.

Comparative Example 2

The surface of the carbon black was modified in the same manner as in Example 1, but step (a) was not performed.

Comparative Example 3

The surface of the carbon black was modified in the same manner as in Example 1, but the gas hourly space velocity of the mixed gas of step (d) was set to 500 hr ⁻¹ .

Component analysis of surface modified carbon black

division C (wt%) H (wt%) N (wt%) S (wt%) O (wt%) Example 1 95.41 0.11 0.19 3.45 0.21 Example 2 95.89 0.12 0.19 3.03 0.23 Example 3 94.25 0.10 0.17 4.59 0.12 Example 4 94.71 0.11 0.16 4.55 0.19 Comparative Example 1 97.13 0.23 0.21 0.45 1.34 Comparative Example 2 96.6 0.25 0.22 1.05 0.6 Comparative Example 3 96.09 0.17 0.18 1.50 0.42

As a result of component analysis of the surface-modified carbon black according to Examples 1 to 3 and Comparative Examples 1 to 4 (the content of elements contained in the surface-modified carbon black in terms of weight ratio), Examples 1 to In the case of Example 3, it was confirmed that the content of sulfur was 3 wt% or more.

On the other hand, in Comparative Example 1 and Comparative Example 2 that did not undergo pretreatment in the presence of oxidizing gas or heat treatment in the presence of sulfur compounds in the gas, it was confirmed that the sulfur content in the carbon black was only about 1 wt%.

In addition, even if surface modification in the same manner as in Example 1, it was confirmed that the surface modification of the carbon black is insufficiently performed if the gas space velocity of the mixed gas is too slow.

In addition, in Example 4, where the gas space velocity is too high, the surface modification of the carbon black occurs sufficiently, but there is no significant difference between the sulfur content of Example 3 and the gas gas velocity of the mixed gas in excess of 2000h ^−1. It was confirmed that there is no need to supply.

Comparison of Properties of Rubber Compositions Containing Surface-Modified Carbon Black

Rubber compositions including surface modified carbon black according to Examples 1 to 3 and Comparative Examples 1 to 4 were prepared in the following compositions.

ingredient Addition amount per 100 parts by weight (pph) caoutchouc 100 Surface modified carbon black 50 Zinc oxide 5 Stearic acid 3 sulfur 2.5 Accelerator (CBS) 0.6

Rubber specimens were prepared using the rubber composition prepared according to Table 2, and the physical properties of the rubber specimens were measured based on the following evaluation criteria according to ASTM regulations.

As an evaluation item,

Abrasion resistance (measured by actual vehicle evaluation on dry road surface for tires of 320 / 710R18 F200 standard),

Dynamic viscoelasticity (0 ° C tanδ, 60 ° C tanδ) (G ', G "tanδ is measured from -60 ° C to 80 ° C at 10Hz frequency with 0.5% strain using RDS meter)

300% elastic modulus as measured by tensile properties (measured according to ISO 37 standard),

Was selected.

division Wear resistance 0 ℃ tanδ 60 ℃ tanδ Elastic Modulus (M300) Example 1 115 110 93 100 Example 2 110 105 97 101 Example 3 125 115 85 103 Comparative Example 1 100 100 100 100 Comparative Example 2 105 100 105 90 Comparative Example 3 107 103 98 94

Abrasion resistance is a physical property associated with the life of the tire, and the measured value for Comparative Example 1, which is not pretreated, is 100, and the measured values of Examples and Comparative Examples are indexed based on the values, and are shown in Table 3 below. Abrasion resistance is better when it is larger than the reference value.

Dynamic viscoelasticity represents the changing ratio of the viscosity / elasticity of the compound with temperature changes.

0 ° C tan δ is an index showing wet anti-slip behavior called Wet Grip. It can be said that the higher the tan δ at 0 ° C., the better the wet slip behavior.

In addition, 60 ° C tan δ is an index indicating rolling resistance, and the larger the rolling resistance, the lower the fuel efficiency. Therefore, the lower tan δ at 60 ° C. results in less rolling resistance and improved fuel efficiency.

Elastic modulus is a physical property of the rubber composition that affects wear resistance and dynamic viscoelasticity, but high elastic modulus tends to increase wear resistance, but it is important to maintain a certain level of elastic modulus because it is not necessarily proportional.

Referring to Examples 1 to 3, it was confirmed that the braking performance is excellent on the dry road surface without deterioration of wear and grip performance while maintaining a certain level of elastic modulus compared to the comparative examples.

As mentioned above, although an embodiment of the present invention has been described, those of ordinary skill in the art may add, change, delete or add components within the scope not departing from the spirit of the present invention described in the claims. The present invention may be modified and changed in various ways, etc., which will also be included within the scope of the present invention.

Claims (12)

(a) pretreating the finely divided carbon black in an oxidizing gas atmosphere; (b) mixing the pretreated carbon black with water to prepare a mixture; (c) pulverizing carbon black in the mixture; And (d) heat treating the pulverized carbon black while supplying a mixed gas containing a sulfur compound in a gas phase to obtain carbon black into which sulfur-containing functional groups are introduced on the surface; Surface modification method of carbon black comprising a. The method of claim 1, The pretreatment of step (a) is carried out at a temperature of 20 to 35 ℃, Surface modification method of carbon black. The method of claim 1, The oxidizing gas is at least one selected from oxygen, ozone, air and NO ₂ , Surface modification method of carbon black. The method of claim 1, Through the pretreatment, the proportion of oxygen-containing functional groups in the surface of the carbon black increases, Surface modification method of carbon black. The method of claim 4, wherein Wherein the oxygen-containing functional group is at least one selected from an aldehyde group, a ketone group, a carboxyl group and a hydroxyl group, Surface modification method of carbon black. The method of claim 4, wherein The content of the oxygen-containing functional group on the surface of the pretreated carbon black is 0.1 to 1.0 meq / g, Surface modification method of carbon black. The method of claim 1, The heat treatment of step (d) is carried out at a temperature of 160 to 500 ℃, Surface modification method of carbon black. The method of claim 1, The sulfur compound is at least one selected from H ₂ S, SO ₂ and elemental sulfur, Surface modification method of carbon black. The method of claim 1, The mixed gas in contact with the pretreated carbon black is supplied at a gas hourly space velocity of 600 to 3,000 hr ⁻¹ , Surface modification method of carbon black. The method of claim 1, The concentration of sulfur compound in the mixed gas is 500 to 1,000 mg / Nm ³ , Surface modification method of carbon black. The method of claim 1, On the surface of the heat treated carbon black there is at least one sulfur-containing functional group selected from a monosulfide group, a disulfide group and a polysulfide group comprising at least three sulfur, Surface modification method of carbon black. The method of claim 1, The sulfur content in the heat-treated carbon black is 3 wt% or more, Surface modification method of carbon black.