METHOD FOR SYNTHESIZING POLYMER/PIGMENT HYBRID LATEX THROUGH SULFUR-FREE AND SOAP-FREE IN-SITU REVERSIBLE ADDITION-FRAGMENTATION CHAIN TRANSFER (RAFT) EMULSION COPOLYMERIZATION

Abstract

A method for synthesizing a polymer/pigment hybrid latex through sulfur-free and soap-free in-situ reversible addition-fragmentation chain transfer (RAFT) emulsion copolymerization includes the following: dispersing a pigment with a reactive emulsifier to prepare a pigment dispersion; synthesizing an amphiphilic sulfur-free ω-vinyl-terminated polymethyl methacrylate (PMMA) macromolecular RAFT agent in-situ on a surface of pigment particles through catalytic chain transfer polymerization (CCTP); and adding an acrylate monomer dropwise, allowing in-situ sulfur-free RAFT polymerization on a surface of pigment particles through the RAFT agent, and adjusting a structure and a composition of an encapsulated polymer layer to obtain a series of uniformly encapsulated and stably dispersed polymer/organic pigment hybrid latexes. The new hybrid latex prepared through sulfur-free and soap-free in-situ RAFT emulsion copolymerization has the characteristics of high dispersion stability, high pigment encapsulation efficiency, clear encapsulated polymer layer sequence, controllable structure, etc., which is suitable for surface encapsulation modification of various pigments.

Claims

1. A method for synthesizing a polymer/pigment hybrid latex through a sulfur-free and soap-free in-situ reversible addition-fragmentation chain transfer (RAFT) emulsion copolymerization, comprising the following steps: (1) dispersing a pigment with a reactive emulsifier to prepare a pigment dispersion; (2) adding a methacrylate comonomer, a cobalt complex as a catalyst, water as a solvent, and a water-soluble initiator to the pigment dispersion to form a first reaction system, and allowing the reaction system to undergo a catalytic chain transfer polymerization (CCTP) to obtain a second reaction system, wherein an RAFT agent is synthesized in-situ on surfaces of pigment particles in the second reaction system; (3) adding an acrylate monomer to the second reaction system with the RAFT agent obtained in step (2), allowing a in-situ sulfur-free RAFT polymerization through the RAFT agent, and adjusting a structure and a composition of an encapsulated polymer layer to obtain a series of uniformly encapsulated and stably dispersed polymer/organic pigment hybrid latexes.

2. The method for synthesizing the polymer/pigment hybrid latex through the sulfur-free and soap-free in-situ RAFT emulsion copolymerization according to claim 1, wherein in step (1), the reactive emulsifier is one or more from the group consisting of sodium hydroxypropane sulfonate (HPMAS), allyloxy polyoxyethylene nonyl ammonium sulfate, and nonyl phenol polyoxyethylene ether ammonium sulfate; and the reactive emulsifier is added at an amount 5% to 10% of a mass of the methacrylate comonomer.

3. The method for synthesizing the polymer/pigment hybrid latex through the sulfur-free and soap-free in-situ RAFT emulsion copolymerization according to claim 1, wherein in step (1), the pigment is titanium dioxide, phthalocyanine blue, or benzidine yellow.

4. The method for synthesizing the polymer/pigment hybrid latex through the sulfur-free and soap-free in-situ RAFT emulsion copolymerization according to claim 1, wherein in step (2), the cobalt complex is bis[(difluoroboryl)dimethylglyoximato] cobalt(II); and the cobalt complex is added at an amount 80 ppm to 120 ppm of a mass of the methacrylate comonomer.

5. The method for synthesizing the polymer/pigment hybrid latex through the sulfur-free and soap-free in-situ RAFT emulsion copolymerization according to claim 1, wherein in step (2), the methacrylate comonomer is one or two from the group consisting of methyl methacrylate (MMA) and n-butyl methacrylate (n-BMA).

6. The method for synthesizing the polymer/pigment hybrid latex through the sulfur-free and soap-free in-situ RAFT emulsion copolymerization according to claim 1, wherein in step (2), the water-soluble initiator is one or more from the group consisting of azodicyanovaleric acid (ACVA), potassium persulfate (KPS), and ammonium persulfate (APS); and the water-soluble initiator is added at an amount 1% to 5% of a mass of the methacrylate comonomer.

7. The method for synthesizing the polymer/pigment hybrid latex through the sulfur-free and soap-free in-situ RAFT emulsion copolymerization according to claim 1, wherein in step (2), the cobalt complex is dissolved in the methacrylate comonomer, and then a resulting mixture is added to the first reaction system by an injection.

8. The method for synthesizing the polymer/pigment hybrid latex through the sulfur-free and soap-free in-situ RAFT emulsion copolymerization according to claim 1, wherein in step (3), the acrylate monomer is a combination of a hard monomer and a soft monomer; the hard monomer is MMA, i-butyl methacrylate (i-BMA), or benzyl methacrylate (BzMA); and the soft monomer is butyl methacrylate (BMA) or butyl acrylate (BA).

9. The method for synthesizing the polymer/pigment hybrid latex through the sulfur-free and soap-free in-situ RAFT emulsion copolymerization according to claim 8, wherein in step (3), a mass ratio of the hard monomer to the soft monomer is 1:9 to 9:1.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0039] FIG. 1 is a schematic diagram of the process for synthesizing a polymer/organic pigment hybrid latex through sulfur-free and soap-free in-situ RAFT emulsion copolymerization. (CCTP represents catalytic chain transfer polymerization and RAFT represents reversible addition-fragmentation chain transfer polymerization)

[0040] FIG. 2 shows an emulsion particle size growth process in the sulfur-free and soap-free in-situ RAFT emulsion copolymerization process of Example 9 in Table 2. (size represents a particle size)

[0041] FIG. 3A and FIG. 3B show transmission electron microscopy (TEM) images of an unmodified pigment and a prepared polymer/organic pigment hybrid latex, where FIG. 3A is a TEM image of the unmodified pigment and FIG. 3B is a TEM image of the polymer/organic pigment hybrid latex prepared in Example 9 in Table 2.

[0042] FIG. 4 shows a .sup.1 HNMR spectrum of the RAFT agent of amphiphilic sulfur-free PMMA macromonomers bearing a vinyl group at the ω-terminus synthesized in Example 8.

DETAILED DESCRIPTION OF THE EMBODIMENTS

[0043] The above are only preferred examples of the present disclosure and are not intended to limit the present disclosure. Although the present disclosure is described in detail with reference to the foregoing examples, a person skilled in the art can still make modifications to the technical solutions described in the foregoing examples, or make equivalent replacement to some technical features. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and scope of the present disclosure should be included within the protection scope of the present disclosure.

EXAMPLES

[0044] According to the feeding ratios and conditions shown in Tables 1 and 2, a polymer/organic pigment hybrid latex was prepared, including the following steps:

[0045] 1. A reactive emulsifier was dissolved in water, a pigment was added, and a resulting mixture was subjected to ultrasonic homogenization to obtain a pigment dispersion. The reactive emulsifier was used at an amount 5% to 10% of an amount of a monomer.

[0046] 2. The CCTP method was used to synthesize an RAFT agent of amphiphilic sulfur-free PMMA macromonomers bearing a vinyl group at the ω-terminus in-situ on a surface of pigment particles. Specific experimental steps were as follows: a catalytic chain transfer agent and a methacrylate monomer were added to a 100 mL round-bottom flask with a stir bar, and nitrogen was purged for at least 1 h, such that the mixture was stirred in a nitrogen atmosphere until the solid was completely dissolved; at the same time, the pigment dispersion, an initiator (ACVA, which had a mass 2.5% of a mass of methacrylate monomer), and deionized water were added to a four-necked flask equipped with a mechanical stirrer, a reflux condenser, and a nitrogen inlet, and a resulting mixture was introduced with nitrogen and stirred at 300 rpm for at least 30 min; then a mixed solution of the methacrylate monomer and the catalyst (the feed rate is 0.6 mL/min) that had undergone oxygen-exhausting treatment in advance was injected into the four-necked flask to allow polymerization in a 70° C. constant-temperature water bath at a stirring speed of 300 rpm; and after the injection was completed, a resulting mixture was further stirred for 2 h to 3 h at the same temperature.

[0047] 3. In-situ sulfur-free RAFT polymerization was allowed through the RAFT agent of amphiphilic sulfur-free PMMA macromonomers bearing a vinyl group at the ω-terminus, and a structure and a composition of an encapsulated polymer layer were adjusted to obtain a series of polymer/organic pigment hybrid latexes with uniform encapsulation and stable dispersion. Specific experimental steps were as follows: the RAFT agent of amphiphilic sulfur-free PMMA macromonomers bearing a vinyl group at the ω-terminus was diluted with an appropriate amount of water to achieve a solid content of 20 wt %; a resulting latex was added to a four-necked flask and purged with nitrogen for 30 min under stirring at 250 rpm; then an acrylate monomer that had undergone oxygen-exhausting treatment in advance and an initiator aqueous solution were injected into the four-necked flask at an injection rate of 0.3 mL/min, where for each addition, a volume of the initiator aqueous solution was equal to a volume of the monomer; and after the addition was completed, the reaction was further conducted for 2 h to 3 h under the same conditions; where during the polymerization process, a nitrogen environment was maintained and a polymerization temperature was maintained at 80° C.

Comparative Example 1

[0048] An emulsifier SDS was dissolved in water, phthalocyanine blue and a methacrylate monomer were added, and a resulting mixture was subjected to ultrasonic homogenization to obtain a pigment dispersion; water (as a solvent) and a water-soluble initiator were added to the pigment dispersion, and a resulting mixture was introduced with nitrogen for 0.5 h under stirring, and then heated in an inert atmosphere to allow a reaction for 2 h to 3 h; and then an acrylate monomer that had undergone oxygen-exhausting treatment in advance and an initiator aqueous solution were directly added to allow polymerization to obtain a polymer/organic pigment hybrid latex.

TABLE-US-00001 TABLE 1 Meth- Mo- acrylate Emulsifier/ lecular mono- monomer weight Example Pigment type Emulsifier mer/g (%) (Mn) Compar- Phthalocyanine SDS MMA/ 9 1665 ative blue 10 g Example 1 Examples Phthalocyanine HPMAS MMA/ 3 1923 1 to 6 blue 10 g 9 1800 12 2034 BMA/ 3 1986 10 g 9 1834 12 2154 Examples DNS-86 MMA/ 3 2876 7 to 12 10 g 9 2453 12 3167 BMA/ 3 2908 10 g 9 2534 12 3245

[0049] According to the feeding ratios and conditions shown in Table 1, an RAFT agent of amphiphilic sulfur-free PMMA macromonomers bearing a vinyl group at the ω-terminus was synthesized in-situ on a surface of pigment particles through CCTP. Different emulsifiers and different methacrylate monomers could be added to obtain RAFT agents of amphiphilic sulfur-free PMMA macromonomers bearing a vinyl group at the ω-terminus with different structures. With Examples 2, 5, 8, and 11 as examples, the RAFT agent of amphiphilic sulfur-free PMMA macromonomers bearing a vinyl group at the ω-terminus had the following molecular structural formula:

##STR00003##

[0050] FIG. 4 shows a .sup.1 HNMR spectrum of the RAFT agent of amphiphilic sulfur-free PMMA macromonomers bearing a vinyl group at the ω-terminus synthesized in Example 8. The .sup.1 HNMR spectrum confirmed the presence of the ω-terminal unsaturated group in the macromolecular RAFT agent (macromonomer vinyl peaks appeared at 6.20 ppm and 5.47 ppm), indicating the success of CCTP, namely, the successful synthesis of the RAFT agent of amphiphilic sulfur-free PMMA macromonomers bearing a vinyl group at the ω-terminus. It can be seen from Examples 1 to 12 that, when a mass of the emulsifier accounts for 9% of a mass of the monomer, the macromolecular RAFT reagent has the smallest molecular weight and also has a high terminal ω-vinyl content, which is beneficial to the subsequent sulfur-free RAFT polymerization adjustment test. Therefore, an emulsifier-monomer ratio of 9% was adopted in the subsequent examples.

TABLE-US-00002 TABLE 2 Ratio of acrylate soft monomer to Methacrylate Acrylate acrylate hard Example Pigment type Emulsifier monomer monomer monomer Comparative Phthalocyanine SDS MMA BMA/BzMA 1:9 Example 1 blue Examples Phthalocyanine HPMAS MMA BMA/BzMA 1:9 1 to 8 blue BMA/BzMA 1:5 BMA/BzMA 5:1 BMA/BzMA 9:1 BMA BA/BzMA 1:9 BA/BzMA 1:5 BA/BzMA 5:1 BA/BzMA 9:1 Examples DNS-86 MMA BMA/BzMA 1:5  9 to 12 BMA/BzMA 5:1 BMA BA/BzMA 1:5 BA/BzMA 5:1 Examples Titanium DNS-86 MMA BMA/BzMA 1:5 13 to 16 dioxide BMA/BzMA 5:1 BMA BA/BzMA 1:5 BA/BzMA 5:1 Examples Benzidine DNS-86 MMA BMA/BzMA 1:5 17 to 20 yellow BMA/BzMA 5:1 BMA BA/BzMA 1:5 BA/BzMA 5:1

[0051] The obtained polymer/organic pigment hybrid latexes were used as ink for ink-jet printing of cotton fabrics, obtained printed fabrics were tested for the rubbing fastness, hand feel, air permeability, and other properties, and results were shown in Table 3.

[0052] Determination methods for the data were as follows:

[0053] 1. A particle size of the polymer/organic pigment hybrid latex was determined by a nano-laser particle size analyzer (Nano-90 nano-laser particle size analyzer (Malvern Panalytical, UK), and an average particle size was calculated for the hybrid latex.

[0054] 2. The dry and wet rubbing fastness test was conducted with reference to GB/T3920-2008 “Color Fastness to Rubbing, Textile Color Fastness Test”, where two samples were used in each of the warp and weft directions, with a size of 50 mm×200 mm; and a standard rubbing cotton cloth was used, with a size of 50 mm×50 mm.

[0055] 3. Hand feel test: Finished fabrics were touched with eyes closed (with one person in each group), and the printed fabrics were evaluated according to different hand feels. Specifically, hand feel grading was conducted from the two aspects of softness and smoothness, and a total of 5 grades were classified. Grade 1 indicates the worst hand feel, in which case a fabric feels hard and unsmooth; and grade 5 indicates the best hand feel, in which case the fabric feels soft and smooth.

TABLE-US-00003 TABLE 3 Average particle Rubbing fastness of printed fabric Hand size of emulsion Dry rubbing Wet rubbing feel/ Example (nm) fastness/grade fastness/grade grade Comparative 293 3 2-3 3 Example Example 1  235 4-5 4 4 Example 2  228 4 4 4 Example 3  239 4-5 4-5 5 Example 4  225 4 4 5 Example 5  238 4 4 4 Example 6  235 4 4 4 Example 7  237 4 4 5 Example 8  244 4-5 4-5 5 Example 9  240 4-5 4 4 Example 10 252 4-5 4 5 Example 11 248 4-5 4 4 Example 12 256 5 4-5 5 Example 13 282 4 4 4 Example 14 293 5 4-5 5 Example 15 288 4 4 4 Example 16 296 4 4 5 Example 17 267 4-5 4 4 Example 18 258 5 4-5 5 Example 19 254 5 4 4 Example 20 261 4-5 4 5

[0056] FIG. 1 is a schematic diagram of the process for synthesizing a polymer/organic pigment hybrid latex through sulfur-free and soap-free in-situ RAFT emulsion copolymerization in the above examples. The growth of emulsion particle size during the sulfur-free and soap-free in-situ RAFT emulsion copolymerization process in Example 9 was tracked, and the particle size growth was shown in FIG. 2. It can be seen that, with the gradual addition of the monomer, the emulsion particle size continuously increased, which indirectly proved that a shell was formed on a surface of the pigment during the polymerization process. The polymer encapsulation was further verified by TEME. FIG. 3A and FIG. 3B are TEM images of the original phthalocyanine blue and the polymer/organic pigment hybrid latex, respectively. It can be seen from the TEM images that the surface of the polymer/organic pigment hybrid latex prepared through sulfur-free and soap-free in-situ RAFT emulsion polymerization was covered with a thick shell.

[0057] It can be seen from Table 3 that the use of the polymer/organic pigment hybrid latex synthesized through sulfur-free and soap-free in-situ RAFT emulsion copolymerization in the present disclosure can effectively improve the existing pigment printing technology, such that printed fabrics obtained thereby have a fastness of 4 to 5 to dry and wet rubbing and feel soft. The hybrid latex has a particle size of 200 nm to 300 nm, so when the hybrid latex is used as an ink for ink-jet printing, the nozzle clogging can be reduced.