TWI881777B - Low conductive carbon black composite and a manufacturing method thereof - Google Patents

Abstract

A low conductive carbon black composite made from a recycled plastic, which contains a carbon black, a silicon element and a titanium element, wherein the weight percent concentration (wt%) of the silicon element is between 0.4% and 4%, and the weight percent concentration (wt%) of the titanium element is between 0.2% and 2%. ​

Description

Low conductivity carbon black composite and preparation method thereof

A carbon black, especially a low conductive carbon black composite and a method for preparing the same.

Carbon black is a light and fine black powder mainly composed of carbon materials. Primary carbon black is mainly extracted from petroleum. Its molecular structure is composed of multiple primary carbon black particles adsorbed and stacked by Van der Waals force. With the smaller particle size of the primary carbon black particles and the higher the overall cleanliness of the carbon black, the carbon black can achieve a higher specific surface area, which in turn affects the blackness of the carbon black. Through the blackness and molecular structure characteristics of carbon black, the carbon black is widely used in related technology industries such as coatings, plastic reinforcing agents, and light-shielding and conductive technologies.

With the improvement of environmental awareness, the development of recycling materials has gradually become popular, and the recycling of waste plastics has also become a trend. In the current industry, the technology of recycling waste plastics into liquid oil has become mature, but the recycled carbon black made from waste plastics rarely returns to the market for recycling. The reason is that the recycled carbon black often contains a high proportion of ash of more than 30%, resulting in insufficient cleanliness, so that the blackness and specific surface area characteristics of the recycled carbon black cannot meet the industry requirements, thereby affecting the application value of the material. In view of this, the development of recycled carbon black recycling is a goal that the current related industries are eager to develop.

In order to develop a regenerated carbon black having blackness and specific surface area characteristics that can meet the industry's requirements, the present invention provides a low-conductivity carbon black composite, which comprises a carbon black and an inorganic oxide, wherein a weight percent concentration (wt%) of the inorganic oxide is between 0.5% and 6%, wherein at least a portion of the inorganic oxide is combined with the carbon black; and the inorganic oxide comprises a silicon element and a titanium element, wherein the weight percent concentration (wt%) of the silicon element is between 0.4% and 4%, and the weight percent concentration (wt%) of the titanium element is between 0.2% and 2%.

The method for preparing the low-conductivity carbon black composite comprises the following steps: thermally cracking a recycled plastic to form a carbon residue, wherein the recycled plastic comprises a plastic added and/or modified with an inorganic oxide, and the inorganic oxide comprises a silicon element and a titanium element; and acid-alkali washing the carbon residue to remove ash and form a carbon black composite.

The step of pickling and alkali washing the carbon residue comprises: continuously stirring the carbon residue in an acid washing solution and reacting it in the deashing environment, filtering and washing it with a cleaning solution to obtain an intermediate product, wherein the acid washing solution comprises a chelating agent and an acidic solution; and stirring the intermediate product in an alkaline washing solution and reacting it in the deashing environment, filtering and washing it with a cleaning solution and drying it to obtain the carbon black composite.

Furthermore, the inorganic oxide includes silicon dioxide (SiO ₂ ) and titanium dioxide (TiO ₂ ).

Furthermore, the recycled plastic is a polypropylene plastic added and/or modified with an inorganic oxide or a polyethylene plastic added and/or modified with an inorganic oxide.

Further, the weight percentage concentration (wt%) of the carbon residue in the acid washing liquid mixture is preferably between 0.5% and 3.5%; the chelating agent is an ammonium chloride solution (NH ₄ Cl) with a molar concentration (M) between 0.5 and 1.5; the acidic solution is hydrochloric acid, perchloric acid, formic acid, acetic acid, lactic acid or oxalic acid; the alkaline washing solution can be a chloride salt, a bromide salt, an iodide salt, sodium hydroxide or ammonia water; and the ratio of the chelating agent to the acidic solution is between 0.5:1 and 1:1.

Furthermore, the acidic solution and the alkaline solution have the same molar concentration and amount.

Furthermore, the deashing environment comprises a deashing temperature between 50 and 70 degrees Celsius (° C.), and a deashing time between 30 minutes and 120 minutes.

Furthermore, before the carbon slag is pickled and alkaline washed, magnetic separation is performed to remove a metal component; and physical screening is performed to select a particle size.

The steps provided by the present invention form the carbon black composite after thermal cracking the recycled plastic and deashing. By adjusting the reaction ratio of the carbon residue, the acid wash solution and the alkaline wash solution, the deashing effect and the effect of regulating the expression amount of the inorganic oxide are achieved simultaneously, so that the carbon black composite can achieve the same high cleanliness, high blackness and low conductivity characteristics as commercially available virgin carbon black.

The carbon black compound is made by regenerating the recycled plastic. The overall production process is simple. No additional processing or modification is required to make the carbon black compound meet the blackness, specific surface area and low conductivity required by the industry. It is suitable for industrial applications such as electronics or confidential instruments that often require shading and impedance, and has the characteristics of recycling and high economic value.

Please refer to FIG. 1 , which is a block diagram of a production process of a carbon black composite provided by a preferred embodiment of the present invention through the regeneration of a recycled plastic, wherein the steps include:

S1, thermally cracking a recycled plastic to form a carbon slag: the recycled plastic comprises a plastic that has been added and/or modified with an inorganic oxide, preferably, the recycled plastic is a polypropylene plastic that has been added and/or modified with an inorganic oxide, or a polyethylene plastic that has been added and/or modified with an inorganic oxide, or a polystyrene plastic that has been added and/or modified with an inorganic oxide.

The inorganic oxide includes a silicon element and a titanium element; more preferably, the inorganic oxide includes silicon dioxide (SiO ₂ ) and titanium dioxide (TiO ₂ ).

The carbon residue formed by thermal cracking of the recycled plastic contains carbon black, the inorganic oxide and ash, and the weight percentage concentration (wt%) of the ash is between 30% and 40%.

At least a portion of the inorganic oxide is combined with the carbon black.

Wherein, at least a portion of the inorganic oxide and the carbon black may be bonded to each other via chemical bonds such as ionic bonds, covalent bonds or metal bonds.

S2 (optional), physical screening to remove impurities: Since the recycled plastic may also contain other impurities such as metals, physical screening methods such as magnetic separation or screening can be used to remove impurities with a particle size exceeding 4.75 mm or having metal components, while reducing the ash content.

S3, chemical deashing to form a carbon black composite: using acid washing and alkali washing of the carbon residue in a deashing environment to remove the ash, wherein the chemical deashing step comprises:

S3-1, pickling: the carbon slag is continuously stirred in a pickling liquid and reacted in the deashing environment, and then filtered and rinsed with a cleaning liquid to obtain an intermediate product.

The pickling solution comprises a chelating agent and an acidic solution, wherein the chelating agent can be ammonium chloride, ammonium nitrate or ethylenediaminetetraacetic acid, and the acidic solution can be hydrochloric acid, perchloric acid, formic acid, acetic acid, lactic acid or oxalic acid. Further, the chelating agent is an ammonium chloride solution (NH ₄ Cl) with a molar concentration (M) between 0.5 and 1.5; the acidic solution is a hydrochloric acid (HCl) with a molar concentration (M) between 1 and 3. The ratio of the chelating agent to the acidic solution is preferably between 0.5:1 and 1:1.

S3-2, alkali washing: the intermediate product is stirred in an alkaline washing liquid and reacted in the deashing environment, filtered, rinsed with a cleaning liquid and dried to obtain the carbon black composite. The alkaline washing liquid can be an alkaline solution prepared by chlorine salt, bromine salt, iodine salt, sodium hydroxide or ammonia water. Preferably, the alkaline washing liquid is a sodium hydroxide solution (NaOH) with a molar concentration (M) between 1 and 3.

The deashing environment includes a deashing temperature between 50 and 70 degrees Celsius (° C.), and a deashing time between 30 minutes and 120 minutes.

Wherein, in step S3, the weight percent concentration (wt%) of the carbon residue in the pickling solution is preferably between 0.5% and 3.5%.

Among them, one of the purposes of the alkaline solution is to neutralize the acid solution. Therefore, it is preferred that the concentration and amount of the alkaline solution are the same as those of the acid solution to avoid adding too little alkaline solution to completely neutralize the acid solution, or adding too much alkaline solution to cause the final surface pH value of the carbon black to be alkaline, which is not conducive to subsequent applications.

It is worth noting that the content of the inorganic oxide in the carbon black will affect the conductivity and specific surface area of the final carbon black. If the inorganic oxide is too much, the conductivity and specific surface area of the carbon black will be lower. Therefore, in step S3, by adjusting the concentration and addition amount of the acid wash solution and the alkaline wash solution, the carbon residue can not only produce a deashing effect, but also the inorganic oxide that is not combined with the carbon black or the inorganic oxide with a low binding relationship with the carbon black can also produce a deashing effect. The pickling solution can also dissolve at least a portion of the inorganic oxide at the same time, so that at least a portion of the inorganic oxide is separated from the carbon residue, and the final carbon black composite retains a weight percentage concentration (wt%) of the inorganic oxide between 0.5% and 6%, so that the carbon black composite can achieve high cleanliness and high blackness, and can also have low conductivity properties.

Preferably, at least a portion of the inorganic oxide separated from the carbon residue in step 3 is not combined with the carbon black.

Furthermore, the inorganic oxide contains a silicon element with a weight percentage concentration (wt%) between 0.4% and 4% and a titanium element with a weight percentage concentration (wt%) between 0.2% and 2%.

Please refer to Tables 1 and 2. The present invention further compares and analyzes the material properties of Examples 1 to 4 and Comparative Examples 1 to 4 of the carbon black composite prepared through the above steps.

As shown in Table 1, Examples 1 to 3 respectively take 10 grams, 20 grams and 5 grams of carbon residue of different weights and mix them with the pickling solution; Example 4 prepares the pickling solution under the condition that the ratio of the chelating agent to the acidic solution is 0.5:1. Comparative Example 1 uses a large amount of the pickling solution and the alkaline solution to react with the carbon residue; Comparative Example 2 only uses the acidic solution to carry out the pickling process of step S3-1; Comparative Example 3 carries out the step S3 process at a temperature of 15 degrees Celsius (℃); Comparative Example 4 is the carbon black composite that is only washed with the cleaning solution. After the above Examples 1 to 4 and Comparative Examples 1 to 4 are prepared, the ash content ratio is tested according to the CNS5581 activated carbon ash content determination method.

Table 1 Embodiment Comparison Example 1 2 3 4 1 2 3 4 Carbon residue (g) 10 20 5 10 10 10 10 10 2M hydrochloric acid (ml) 300 300 300 300 1000 300 300 0 1M Ammonium Chloride Solution (mL) 300 300 300 150 1000 0 300 0 2M sodium hydroxide solution (ml) 300 300 300 300 1000 300 300 0 Deashing temperature(℃) 60 60 60 60 60 60 15 - Deashing time (minutes) 120 120 120 120 120 120 120 - Ash content(%) 5.6 9.3 2.2 6.1 5.3 twenty two 28 37

From the results, it can be found that the ash content of the carbon slag in Examples 1 to 4 and Comparative Example 1 after reacting with the acid wash solution and the alkaline wash solution is significantly reduced compared with Comparative Example 4 (less than 10% is the ideal standard). However, Comparative Example 2 and Comparative Example 3 still have a considerable amount of ash present therein due to the lack of the addition of the chelating agent and the reaction at the low deashing temperature.

Please refer to Table 2, and the inorganic oxide content and the conductive effect of the carbon black composite are further measured by SEM-EDS and surface impedance electrical properties test for each of the embodiments and the comparative examples.

The surface impedance electrical test is conducted by referring to the method provided in patents TWI519608B and TWI565655B. The carbon black compound, a dispersant (BYK191) and an organic solvent (PGMEA) are placed in a ball mill for mixing and dispersion to obtain a carbon black dispersion. Then, according to the method of patents TWI519608B and TWI565655B, the carbon black dispersion is mixed with a photoresist liquid to prepare a black photoresist liquid for testing. The black photoresist liquid is coated on a glass substrate, and a black coating layer with a thickness of about 0.90 to 1 μm is formed after soft baking, exposure and hard baking. Finally, the black coating layer is subjected to surface impedance measurement (resistance meter Keithley6517A) to obtain a surface impedance value.

Table 2 Embodiment Comparison Example 1 2 3 4 1 2 3 4 Silicon element(%) 1.1 3.6 0.42 1.3 0.11 9.3 9.7 2.57 Titanium(%) 0.55 1.8 0.21 0.62 0.05 4.7 5.2 0.61 Surface impedance Ω/ □ 2.3 x10 ¹⁵ 5.2 x10 ¹⁵ 1.6 x10 ¹⁵ 7.3 x10 ¹⁵ 4.3 x10 ⁷ 7.2 x10 ¹⁶ 5.6 x10 ¹⁶ 6.6 x10 ¹⁶

After elemental analysis by SEM-EDS, it can be found that after the carbon slag in Examples 1 to 4 and Comparative Example 1 reacts with the acid wash solution and the alkaline wash solution, the expression ratio of silicon and titanium is significantly lower than that of Comparative Examples 2 to 4 with poor deashing effect. It is worth noting that although the deashing effect of Comparative Example 1 is better than that of Examples 1 to 4 through the reaction of a large amount of the acid wash solution and the alkaline wash solution with the carbon slag, the performance of the inorganic oxide (ratio of silicon and titanium) is also significantly lower than that of Examples 1 to 4. Since the performance of the inorganic oxide in Comparative Example 1 is too low, the surface impedance of Comparative Example 1 is too low (the standard is to be greater than 1x10 ¹⁰ ).

The results show that the amount of the acid wash solution and/or the alkaline wash solution added in step S3 has a great influence on the performance of the inorganic oxide of the carbon black composite. When the acid wash solution and/or the alkaline wash solution is added too much, the inorganic oxide is too little, which further reduces the electrical impedance characteristics of the carbon black composite.

Please refer to Table 3. To prove that the carbon black composite prepared by the steps provided by the present invention has the blackness and specific surface area characteristics that meet the industry requirements, the present invention further compares and analyzes the material properties of Example 1, Comparative Example 4 and a commercially available native carbon black. This includes: testing a specific surface area by BET detection method.

Table 3 Virgin Carbon Black Embodiment 1 Comparison Example 4 Ash content(%) 6.95 5.6 37 Surface impedance (Ω/□) 5.2x10 ¹⁴ 2.3x10 ¹⁵ 6.6x10 ¹⁶ Specific surface area (m ² /g) 106 106 twenty one

It can be seen from the results that the carbon black composite formed by thermal cracking and deashing the recycled plastic through the steps provided by the present invention can achieve the deashing effect and the effect of regulating the expression amount of the inorganic oxide by adjusting the reaction ratio of the carbon residue, the acid washing solution and the alkaline washing solution. In addition, the carbon black composite can achieve the same high cleanliness, high blackness and low conductivity characteristics as commercially available original carbon black.

The carbon black compound is made by regenerating the recycled plastic. The overall production process is simple. No additional processing or modification is required to make the carbon black compound meet the blackness, specific surface area and low conductivity required by the industry. It is suitable for industrial applications such as electronics or confidential instruments that often require shading and impedance, and has the characteristics of recycling and high economic value.

S1~S3-2: Steps

FIG. 1 is a block diagram of a preferred embodiment of the present invention.

S1~S3-2: Steps

Claims (11)

A low-conductivity carbon black composite comprises a carbon black and an inorganic oxide, wherein the weight percentage concentration (wt%) of the inorganic oxide is between 0.5% and 6%, wherein at least a portion of the inorganic oxide is combined with the carbon black; and the inorganic oxide comprises a silicon element and a titanium element, wherein the low-conductivity carbon black composite is obtained from a recycled plastic through a thermal cracking and acid-alkali washing process, and the low-conductivity carbon black composite also has an ash content, and the ash content is not higher than 9.3%. The low-conductivity carbon black composite as described in claim 1, wherein the weight percent concentration (wt%) of the silicon element is between 0.4% and 4%; and the weight percent concentration (wt%) of the titanium element is between 0.2% and 2%. A method for preparing a low-conductivity carbon black composite provided by claim 1 or 2, the steps of which include: thermally cracking a recycled plastic to form a carbon slag, wherein the components of the carbon slag include carbon black, an inorganic oxide and an ash; and using acid washing and alkali washing of the carbon slag to remove the ash and at least a portion of the inorganic oxide and form a carbon black composite, the steps of which include: continuously stirring the carbon slag in an acid washing solution and in a deashing environment The intermediate product is reacted in an acidic washing liquid, filtered and rinsed with a cleaning liquid to obtain an intermediate product, the acidic washing liquid contains a chelating agent and an acidic solution; the intermediate product is stirred in an alkaline washing liquid and reacted in the deashing environment, filtered and rinsed with a cleaning liquid and then dried to obtain the carbon black composite, wherein the ash content of the carbon black composite is not higher than 9.3%, and the deashing environment contains a deashing temperature between 50 and 70 degrees Celsius (℃). In the production method provided in claim 3, the recycled plastic comprises a plastic that has been added and/or modified with an inorganic oxide, and the inorganic oxide comprises silicon dioxide (SiO ₂ ) and titanium dioxide (TiO ₂ ). In the manufacturing method provided in claim 4, the plastic comprises polypropylene, polyethylene or polystyrene. The preparation method provided in claim 5, wherein: the weight percentage concentration (wt%) of the carbon residue in the acid washing solution mixture is between 0.5% and 3.5%; the chelating agent is an ammonium chloride solution (NH ₄ Cl) with a molar concentration (M) between 0.5 and 1.5; the acidic solution is hydrochloric acid, perchloric acid, formic acid, acetic acid, lactic acid or oxalic acid; the alkaline washing solution can be a chloride salt, a bromide salt, an iodide salt, sodium hydroxide or ammonia water; and the ratio of the chelating agent to the acidic solution is between 0.5:1 and 1:1. The preparation method provided in claim 6, wherein the acidic solution and the alkaline washing solution have the same molar concentration and dosage. In the manufacturing method provided in claim 7, the deashing environment includes a deashing time ranging from 30 minutes to 120 minutes. As in the manufacturing method provided in claim 8, magnetic separation is performed to remove a metal component before pickling and alkali washing the carbon slag. In the production method provided in claim 8, physical screening of a particle size is performed before acid-washing and alkali-washing the carbon slag. In the production method provided in claim 9, physical screening of a particle size is performed before acid washing and alkali washing of the carbon slag.

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