Method for preparing self-dispersing nano carbon black based on a thiol-ene click reaction

Abstract

Disclosed is a method for preparing self-dispersing nano carbon black based on a thiol-ene click reaction. A sol-gel technique is used to graft a coupling agent containing a carbon-carbon double bond onto the surface of the carbon black, and a functional molecular chain is grafted onto the surface of the carbon black by a thiol-ene click reaction with a mercapto compound. The self-dispersing nano carbon black is obtained after centrifugation, washing and drying. The method is simple and easy to operate, has a high grafting rate, and can prepare self-dispersing nano carbon black adaptable to different systems by selecting mercapto compounds with different functional groups.

Claims

1. A method for preparing a self-dispersing nano carbon black, comprising: 1) oxidatively modifying carbon black using a liquid phase oxidant to obtain an oxidized carbon black; 2) using a coupling reaction to obtain a modified carbon black containing a double bond on the surface, wherein the oxidized carbon black is dispersed into a coupling agent alcohol solution to a nanometer scale and react at 20-80° C., pH 8.5-9.0 adjusted by an alkaline agent, for 0.5-30 hr; 3) adding a functional group to the modified carbon black containing a double bond by a thiol-ene click reaction, wherein a mercapto compound is added to the modified carbon black containing a double bond, and an initiator is stepwisely added to initiate the thiol-ene click reaction; and 4) obtaining the self-dispersing nano carbon black after centrifugation, washing and drying.

2. The method of claim 1, wherein the thiol-ene click reaction is performed at 50˜90° C. for 0.5 to 20 hours.

3. The method of claim 1, wherein the oxidized carbon black is added in an amount of 0.1%-40% by mass of the coupling agent alcohol solution.

4. The method of claim 1, wherein the alkaline agent is added in an amount of 0.1-10% by volume of the coupling agent alcohol solution.

5. The method of claim 1, wherein the initiator is selected from the group consisting of potassium persulfate, ammonium persulfate, sodium persulfate, azobisisobutyronitrile, 2,2′-azobis(isobutyramidine) dihydrochloride, 2,2′-azobis[2-(2-imidazolin-2-yl)propane] dihydrochloride and benzoyl peroxide; and wherein the initiator is added in an amount of 0.5-15% by mass of the mercapto compound.

6. The method of claim 1, wherein the coupling agent is selected from the group consisting of a silane coupling agent, a titanate coupling agent, an organic complexing coupling agent and an aluminate compound.

7. The method of claim 1, wherein the liquid phase oxidant is a nitric acid solution, a hydrogen peroxide solution, a saturated ammonium persulfate solution, perchloric acid, a sodium hypochlorite aqueous solution, an isocyanate solution or a potassium permanganate solution.

Description

BRIEF DESCRIPTION OF THE FIGURES

(1) FIG. 1 Effects of the amount of MEMO (a), the amount of ammonium hydroxide (b) or the ratio of alcohol/water (c) on the contact angle of CB/MEMO.

(2) FIG. 2 Effects of amount of MPS (a), reaction temperature (b) or the reaction time (c) on Zeta potentials and particle size of CB/MPS-g-MEMO.

(3) FIG. 3 SEM (a) and TEM (b) images of CB/MPS-g-MEMO.

(4) FIG. 4 SEM photograph of Lyocell fiber with 0% carbon black (a), 2% (w/w) carbon black (b), or 4% (w/w) carbon black (c).

DETAILED DESCRIPTION

(5) The technical details of some embodiments of the present invention are further described and illustrated below with reference to the accompanying drawings in the following examples. The examples are described only for illustration purpose, not to limit the scope of the present invention which is defined by the claims hereafter.

Example 1

(6) 0.6 g of carbon black was treated with 60 g of a nitric acid solution (concentration of 30%) at 20° C. for 0.5 hr to obtain oxidatively modified carbon black. 1 g of silane coupling agent KH570 (MEMO) was weighed and dissolved in 90 g of ethanol solution, and 1 g of the oxidatively modified carbon black was added. The carbon black was dispersed into nanoparticles by an ultrasonic cell pulverizer, 10 g of deionized water was then added, and the pH value of the system was adjusted to 8.5 with ammonium hydroxide. The reaction system was transferred to a reaction vessel and reacted at 60° C. for 12 hr. After that, 0.5 g of sodium mercapto sulfonate (MPS) was added and the temperature was raised to 60° C. An initiator azodiisobutyronitrile accounting for 1% by weight of the monomer was added dropwisely and reacted for 3 hr. High-speed centrifugation, washing and drying were then performed. The dried carbon black powder was ground and pulverized by a pulverizer and filtered through a 200-mesh sieve to obtain a water-soluble self-dispersing nano carbon black pigment.

(7) 10 g of the water-soluble self-dispersing nano carbon black pigment was ultrasonically dispersed in 90 g of mixed solvent of NMMO (N-methylmorpholine-N-oxide) and water (the mass ratio of NMMO to water wss 87:13) to obtain a carbon black dispersion. 5 g of the carbon black dispersion was added to 95 g of Lyocell fiber spinning solution, stirred uniformly, and spun by a spinning machine to obtain black Lyocell fibers.

Example 2

(8) 4 g of carbon black was treated with 40 g of a hydrogen peroxide solution (concentration of 30%) at 60° C. for 2 hr to obtain oxidatively modified carbon black. 1.3 g of silane coupling agent KH570 was weighed and dissolved in 60 g of ethanol solution, and 8 g of the oxidatively modified carbon black was added. The carbon black was dispersed into nanoparticles by an ultrasonic cell pulverizer, and 30 g of deionized water was then added, and the pH value of the system was adjusted to 9 with sodium hydroxide. The reaction system was transferred to a reaction vessel and reacted at 40° C. for 24 hr. After that, 6 g of mercaptovinyl ester was added, and the temperature was raised to 75° C. An initiator azobisiso heptonitrile accounting for 5% by weight of the monomer was added dropwisely and reacted for 6 hr. High-speed centrifugation, washing and drying were then performed. The dried carbon black powder was ground and pulverized by a pulverizer and filtered through a 200-mesh sieve to obtain an oily self-dispersing nano carbon black pigment.

(9) 10 g of the oily self-dispersing nano carbon black pigment was ultrasonically dispersed in 90 g of dichloromethane to obtain a carbon black dispersion, and 3 g of the carbon black dispersion was added to 95 g of polylactic acid fiber spinning solution, stirred uniformly, and spun by a spinning machine to obtain black polylactic acid fibers.

Example 3

(10) 4 g of carbon black was treated with 40 g of perchloric acid solution at 50° C. for 2 hr to obtain oxidatively modified carbon black. 2.5 g of silane coupling agent A151 was weighed and dissolved in 50 g of ethanol solution, 5 g of the oxidatively modified carbon black was added, the carbon black was dispersed into nanoparticles by an ultrasonic cell pulverizer, then 25 g of deionized water was added, and the pH value of the system was adjusted to 8.5 with ammonium hydroxide. The reaction system was transferred to a reaction vessel and reacted at 40° C. for 24 hr. After that, 1.5 g of mercaptopropionic acid was added, and the temperature was raised to 75° C. An initiator azodiisobutyronitrile accounting for 2% by weight of the monomer was added dropwisely and reacted for 10 hr. High-speed centrifugation, washing and drying were then performed, and the dried carbon black powder was ground and pulverized by a pulverizer and filtered through a 200-mesh sieve to obtain an water-soluble self-dispersing nano carbon black pigment.

(11) 10 g of the water-soluble self-dispersing nano carbon black pigment was ultrasonically dispersed in 90 g of mixed solvent of sodium hydroxide, urea and water (the mass ratio of sodium hydroxide to urea to water is 7:12:81) to obtain a carbon black dispersion, and 2 g of the carbon black dispersion was added to 95 g of viscose fiber spinning solution, stirred uniformly, and spun by a spinning machine to obtain black viscose fibers.

Example 4

(12) 8 g of carbon black was treated with 40 g of a saturated ammonium persulfate solution at 100° C. for 10 hr to obtain oxidatively modified carbon black. 20 g of silane coupling agent KH-A172 was weighed and dissolved in 100 g of ethanol solution, 40 g of the oxidatively modified carbon black was added. The carbon black was dispersed into nanoparticles by an ultrasonic cell pulverizer, then 90 g of deionized water was added, and the pH value of the system was adjusted to 8.5 with triethanolamine. The reaction system was transferred to a reaction vessel and reacted at 80° C. for 30 hr. After that, 20 g of mercapto propanol was added, the temperature was raised to 90° C. An initiator azobisisoheptonitrile accounting for 4% by weight of the monomer was added dropwisely and reacted for 20 hr. High-speed centrifugation, washing and drying were then performed, and the dried carbon black powder was ground and pulverized by a pulverizer and filtered through a 200-mesh sieve to obtain an oily self-dispersing nano carbon black pigment.

(13) 10 g of the oily self-dispersing nano carbon black pigment was ultrasonically dispersed in 90 g of dichloromethane to obtain a carbon black dispersion, and 5 g of the carbon black dispersion was added to 95 g of polylactic acid fiber spinning solution, stirred uniformly, and spun by a spinning machine to obtain black polylactic acid fibers.

(14) TABLE-US-00001 TABLE 1 Dispersion stability of self-dispersing nano carbon black samples prepared in Examples 1-4 and color properties of corresponding applied fibers Particle Particle Size S.sub.S Example Size (nm) Distribution (days) S.sub.T S.sub.C K/S 1 170.1 0.195 60 98 96 34.5 2 220.5 0.122 30 85 90 23.3 3 240.9 0.104 51 95 95 31.3 4 190.0 0.136 42 87 93 25.3

(15) Preparation of Carbon Black Dispersion:

(16) 10 g of raw carbon black and 10 g of self-dispersing nano carbon black pigment prepared in each Example were respectively dispersed into 90 g of the corresponding solvent, and subjected to ultrasonic treatment by ultrasonic cell pulverizer for 30 min (power: 400W) to respectively obtain carbon black dispersions before and after modification.

(17) Note: S.sub.S (storage stability): the dispersions of the carbon black pigment with and without modification were placed in a transparent sample bottle. The occurrence time of precipitation at the bottom of the bottle was recorded as the S.sub.S time.

(18) S.sub.T (heat stability): 2 mL of the carbon black dispersion was taken and placed at 60° C. for 2 hr, 1 mL of the upper dispersion was taken and diluted to a certain multiple. The particle sizes of the carbon black dispersions before and after the placement treatment were tested, and the heat stability was calculated according to Equation 1.

(19) S.sub.C (centrifugal stability): 2 mL of carbon black dispersion was taken, placed in a Centrifuge 5415D high-speed centrifuge and centrifuged at 3000 r/min for 30 min. After the centrifugation was finished, 1 mL of the upper dispersion was taken and diluted to a certain multiple. The particle sizes of the carbon black dispersions before and after centrifugation was tested respectively. The centrifugal stability was calculated according to Equation 2.

(20) $\begin{array}{cc}{S}_T=\left(1-\frac{.Math.d_0-d_T.Math.}{d_0}\right)\times 100\%& \mathrm{Eq}.\left(1\right)\\ S_C=\left(1-\frac{.Math.d_0-d_C.Math.}{d_0}\right)\times 100\%& \mathrm{Eq}.\left(2\right)\end{array}$
wherein d.sub.0 represents the particle size of the untreated carbon black dispersion (unheated or uncentrifuged), d.sub.T represents the particle size of the carbon black dispersion after being placed at different temperatures, and d.sub.C represents the particle size of the carbon black dispersion after being centrifuged at different centrifugal speeds.

(21) K/S (the color yield of the dope-dyed fiber) was measured by an X-RITE 8400 computer color measuring and matching instrument using a D65 light source at an observation angle of 10°. Different points were taken on the dyed cotton fabric and tested for three times, the average was used to calculate the K/S value according to Equation 3:

(22) $\begin{array}{cc}\frac{K}{S}=\frac{{\left(1-R\right)}^2}{2R}-\frac{1-R_0}{2R_0}& \mathrm{Eq}.\left(3\right)\end{array}$
wherein R.sub.0 and R are the reflectivities of un-dyed cotton fabric and dyed cotton fabric, respectively.
Optimized Experimental Process and Results of Water-Soluble Self-Dispersing Nano Carbon Black CB/MPS-g-MEMO in Example 1:

(23) γ-methacryloxypropyltrimethoxysilane (MEMO) was grafted onto the surface of carbon black by a sol-gel technique, and connected with sodium 3-mercapto-1-propane sulfonate (MPS) by a thiol-ene click reaction to prepare the water-soluble self-dispersing carbon black particles CB/MPS-g-MEMO. The effects of the amount of MEMO, the amount of ammonium hydroxide and the ratio of alcohol/water in the system on the contact angle of MEMO modified carbon black were investigated. The effects of the amount of MPS, reaction time and reaction temperature on the properties of CB/MPS-g-MEMO particles were investigated.

(24) Contact angle test: the contact angle of the sample to water was tested by using a Krüss DSA100 contact angle plotter, and the sample was tableted before the test.

(25) As shown in FIGS. 1 and 2, a preferred preparation process of MEMO-modified carbon black is as follows: the mass ratio of MEMO to oxidized carbon black is 125%, the mass ratio of ammonium hydroxide to the system is 0.34%, and the ratio of alcohol/water in the system is 4:1. The system herein refers to a reaction system, including a solvent, the carbon black and other reactants. A preferred preparation process of CB/MPS-g-MEMO is as follows: the mass ratio of MPS to CB/MEMO is 30%, the reaction temperature is 75° C., and the reaction time is 4 hr.

(26) As shown in FIG. 3, the particle size of CB/MPS-g-MEMO in the solvent is small, and the dispersion effect was remarkably improved. TEM photographs show that CB/MPS-g-MEMO has a core-shell structure.

(27) The results in FIGS. 1-3 have shown that surface modification of carbon black by thiol-ene click method is an effective way to improve the dispersion stability in dispersion media. After modification, the surface of the carbon black is grafted with sulfonated polysiloxane, and the extending of the hydrophilic segment in the solvent increases the electrostatic repulsion between the carbon black particles, thereby preventing the mutual aggregation of the carbon black particles.

(28) The Lyocell fiber was subjected to dope dying with a CB/MPS-g-MEMO dispersion by the method described in Example 1, and the results are shown in Table 1 below:

(29) TABLE-US-00002 TABLE 2 Effects of CB/MPS-g-MEMO content on color properties of Lyocell fiber Carbon Black % (w/w, Rubbing Carbon Black/ Fastness/Grade Washing Fastness/Grade Lyocell Fiber) K/S Dry Wet Discoloration Staining 1 25.09 4-5 4 5 4-5 1.5 30.04 4-5 4 5 4-5 1.8 32.63 4-5 4 5 4-5 2 34.23 4-5 4 5 4-5 3 34.56 4 3-4 5 4-5

(30) The results in Table 2 indicate that the K/S value of the dyed Lyocell fiber increases as the carbon black content increases. When the mass fraction of carbon black content to fiber is 2%, the K/S value of the dyed Lyocell fiber approaches the maximum, and does not increase to much with the further increase of the carbon black content. In addition, when the mass fraction of carbon black in the Lyocell fiber is less than 2%, the dope-dyed Lyocell fiber has high rubbing fastness and washing fastness. This is because the carbon black is endowed with a large surface adsorption energy due to abundant unsaturated carbon atoms on the surface. Since the nano carbon black has a small particle size and a large specific surface area, the contact area between the carbon black and the fiber molecules is large, and the acting force is strong, thereby preventing the carbon black from falling off the fiber surface. However, when the carbon black content is high, there are many carbon black particles on the surface of the dyed Lyocell fiber, so the rubbing fastness is lowered (see FIG. 4). When the carbon black mass fraction is 2%, the carbon black is filled between the Lyocell fibers to reduce the “gutters” of the fiber surface, and when the carbon black content is high, the amount of carbon black deposited on the surface of the fiber is increased.

(31) In summary, the self-dispersing CB/MPS-g-MEMO prepared by the present invention has good self-dispersibility in the NMMO system, and can be applied to the stock coloring of the Lyocell fiber that has excellent color performance.