In recent years, due to environmental reasons, the countries of the world have enacted corresponding laws strictly limit the emissions of VOC, water-based ultra-fine organic pigments to become a focus for researchers. Water-based ultra-fine organic pigment color bright, high tinting strength, can be prepared by high tinting strength, high transparency of the product to meet the high-end paint and ink requirements. Pigments, pigment particle size decreases, the pigment particle surface free energy increase the crushing process, the pigment particles prone to aggregation, dispersion system becomes unstable, micronization and dispersion stability of pigment still widely used for restricting water-based pigment The main obstacle. Research, development and stability of water-based ultra-fine organic pigment will bring huge economic benefits for the community. Styrene - maleic anhydride copolymer in recent years to study more polymers can be used for automobile, crude oil, leather, paper, plastic, because it contains benzene to form strong π-π bond with the paint molecules plane after the formation of solvated chain and steric maleic anhydride ring, and hydrolysis, it can be used for the dispersion of water-based paint system, but there is little research, the application is also less than ideal. In this paper, the synthesis solution polymerization styrene - maleic anhydride copolymer dispersant, the synthetic process, the use of the FI-IR spectra of GPC and its structure was characterized, and polymeric dispersant application.
1 Experimental section
1.1 Experimental apparatus and materials
Gel permeation chromatography waters1525/2414 Waters; IR200/IR100 Fourier transform infrared spectrometer, the U.S. ThermoNicolet; Nano-ZS90 particle size and zeta potential analyzer, the United Kingdom MalvernInstrumentsLtd; the IKAT18 high-speed emulsion Germany IKA Laboratory Technology company; electronic analytical balance AB204-N, Switzerland Mettler - Toledo Instruments; 80-1 centrifuge, Shanghai Guoyunlou Medical Instrument Factory;-750 EDW, sand mill, Shanghai Yi Le Electrical and Mechanical Equipment Co., Ltd.. Organic pigments (CI Pigment Yellow 14), Hangzhou color Chemical Co., Ltd.; styrene, maleic anhydride, AR, Sinopharm Chemical Reagent Co., Ltd.; dispersant (BYK-163), BYK-Chemie, Germany; peroxide benzoyl acid, analytical grade, Shanghai Ling Feng Chemical Reagent Co., Ltd.; ethyl acetate was purchased from Sinopharm Chemical Reagent Co., Ltd.; isopropyl alcohol, analytical grade, Shanghai Ling Feng Chemical Reagent Co., Ltd.; deionized water, homemade.
1.2 styrene - maleic anhydride copolymer
0.1mol styrene, the 0.14mol maleic anhydride and 100 g ethyl acetate and placed in the flask with a stirring rod, thermometer, heating to 70 ° C, insulation 30min; take 50g of ethyl acetate and the initiator benzoyl peroxide Mix the initiator solution was added to the flask with a dropping funnel, dropping time of 2h after dropping heated 5h, the polymer solution; adding a certain amount of formaldehyde, the polymer precipitated out, 50 ° C dried for 24h, the white solid dispersant.
1.3 dispersion process
Pigment Yellow 14 cake with isopropyl alcohol soaked overnight to remove organic impurities, and washed repeatedly with deionized water to remove the inorganic salts present in Pigment Yellow 14. Take the cake the quantitative treated pigment, isopropyl alcohol, polymer dispersant, deionized water is fully mixed with IKAT18 high-speed emulsifying machine emulsifying pre-dispersion, the pre-dispersion in the EDW, 750 sand mill grinding 4h, ie, The obtained water-based ultra-fine organic pigment dispersion system.
1.4 The test methods and characterization tools
Infrared spectroscopy: a synthesis of the polymer dispersant was prepared by the KBr solid tablet, IR200/IR100 Fourier transform infrared spectroscopy for the determination of the product of the infrared absorption spectrum. Molecular weight and its distribution: polystyrene standards in N, N-dimethylformamide as solvent, Determination of polymer dispersant relative molecular mass and its distribution Waters1525/2414 gel permeation chromatography. The injection volume was 0.6mL/min. The pigment particle size and zeta potential determination: a small amount of dispersed pigment diluted 2000 times, using a Nano-ZS90 particle size and zeta potential analyzer pigment particle size and Zeta potential. Centrifugal stability: 80-1 centrifuge speed 4000r/min centrifuge for some time, the first observation of the bottom of the centrifuge tube with or without precipitation, and then take the upper liquid 1mL, diluted 2000 times with 722 spectrophotometer measured absorbance , calculated absorbance r60:
Where: A0 is the absorbance of sample before centrifugation, A60 absorbance after centrifugation 60min. r60 more close to 1, that the centrifugal stability of the dispersion system, the better. Dilution stability: take 10g superfine pigment dilution of different multiples, placed in the centrifuge, centrifuge 60min at 4000r/min conditions measured absorbance before and after centrifugation, the calculation of the dispersion system than the absorbance.
2 Results and discussion
2.1 Synthesis Process
2.1.1 The effects of monomer ratio
Polymeric dispersant on the pigment dispersion depends on the interaction between the polymer and the pigment, as well as between the polymer and solvent Long hydrophilic chain of the dispersant, solvent, and the force of the polymer chains increases, resulting in polymer solution adsorption capacity, the dispersion efficiency; too short hydrophilic polymer in the surface of the pigment can not form a long enough chain solvation. repulsion between the pigment particles weaken, prone to aggregation and instability. Therefore, we must match the proportion of hydrophilic monomers and hydrophobic monomers. Table 1 for maleic anhydride and styrene molar ratio of yield and pigment dispersion stability.
Seen from Table 1: maleic anhydride with styrene molar ratio, yield up to 90% in the range of 1.2 to 1.4 changes, the higher Zeta potential, indicating that the surface of the pigment with a more negative charge, hydrophobic dispersant groups adsorbed on the surface of the pigment, the charged hydrophilic groups toward the water, the formation of electric double layer, when the pigment particles are close to each other, will be a charge on the electric double layer repulsion, thus ensuring the stability of the dispersion system.
2.1.2 the impact caused by dosage
The amount of initiator determines the concentration of free radicals in the polymerization system, resulting in the rate of polymerization conversion rate within a certain time difference, but also affect the relative molecular mass of dispersant. In this study, using benzoyl peroxide as initiator, to examine the amount of relative molecular mass of the dispersant and pigment dispersion properties, the results are shown in Table 2.
In the process of dispersion, the dispersant adsorbed on the surface of the pigment dispersant relative molecular mass is smaller, shorter polymer chains, resulting in the anchoring groups of the polymer chain combination with the pigment is not tight enough, prone to desorption phenomena, so that dispersion efficiency; the other hand, the relative molecular mass of dispersant is greater the longer the polymer chain, prone bridge phenomenon between the polymer chains make the pigment particles along with the coated polymer flocculation phenomenon occurs, it will also lead to reduce the dispersion efficiency. Seen from Table 2: When the initiator dosage of 2%, income dispersion agent is relatively moderate molecular weight, the pigment particle size is smaller, better system stability.
2.1.3 The influence of polymerization temperature
In the radical polymerization, the polymerization temperature is an important parameter, which determines the rate of polymerization and relative molecular mass of the polymer.
Can be seen from Table 3: This is the temperature, the activity of the reactants, thereby increasing the rate of initiator decomposition, and makes the active center increased the polymerization rate increased with the polymerization temperature increased, the relative molecular mass of the polymer decreased, large, in the case of constant monomer concentration, the number of monomers with each activity center to reduce the degree of polymerization decreased, resulting in lower relative molecular mass. Consider the product of molecular weight and the control of the reaction, the choice of the polymerization temperature is 70 ℃.
2.2 polymer dispersant characterization
2.2.1 Infrared Spectroscopy
Infrared spectrum of the polymer dispersant shown in Figure 1.
Can be seen from Figure 1: 1455cm-1, 1495cm-1 at the absorption peak of absorption peaks of stretching vibration in the plane of the benzene ring-C = C-chain, 704cm-1 is monosubstituted benzene ring peaks, which can be proved contains a benzene ring in the polymer; 1709cm-1, 1734cm-1, 1855cm-1 at the absorption peak of the anhydride C = O bond symmetric and asymmetric stretching vibration absorption peak, the high wave number 1855cm-1 at peak intensity than the low wave number of 1734cm-1 peak intensity, which is five-membered cyclic anhydride with one of the salient features of the 1225cm-1 at the absorption peak of the cyclic anhydride C-O stretching vibration absorption peak, which can prove that the polymer containing cyclic anhydride; 2934cm-1 and 3031cm-1 at the peak of the characteristic peaks of methylene and tert-methyl, respectively, to sum up, the polymer is a copolymer of maleic anhydride and styrene.
2.2.2GPC spectrum analysis
Styrene - maleic anhydride copolymer, GPC spectra shown in Figure 2. Figure 2 shows that: the copolymer molecular weight distribution is narrow, and in the follow-up application process, there is no negative impact of relatively wide molecular mass distribution.
2.3 polymer dispersant application
2.3.1 centrifugal stability
Pigment particles in the dispersion system will occur under the action of the centrifugal force or gravity field settlement, the use of polymeric dispersant dispersed ultrafine pigment to 4000r/min centrifuge centrifugal 1h, 2h, 3h, 4h, 5h after The determination of the absorbance of the pigment dispersion system, the results shown in Figure 3.
Figure 3 curve can be seen: After 5h centrifugation, absorbance decreased very small, according to the Lambert - Beer law, with the extension of the centrifugation time, ultra-fine pigment particles of very small part of the settlement, with the high centrifugal stability sex.
2.3.2 The dilution stability
Ultrafine pigment dispersion system were diluted in multiples, placed in a centrifuge to 4000r/min centrifuge 60min, the absorbance of the solution by centrifugation before and after dispersion to calculate the dispersion system than the absorbance.
Ultrafine pigment dispersion system was diluted 32 times, the absorbance is still as high as 97.56%, indicating that the deposition of particles in the ultrafine pigment dispersion system rarely has a good dilution stability.
2.3.3 Particle Size Analysis
Polymer dispersant dispersed pigment particle size analyzer to measure the particle size distribution, the results shown in Figure 4. It can be seen from the figure: the decentralized system of pigment particle size distribution between 100 ~ 150nm, a narrow distribution, indicating that the dispersing agent dispersion effect is more ideal.
(1) changes in the range of 1.2 to 1.4, the molar ratio of maleic anhydride with styrene, yield higher than 90%; the initiator dosage of 2% from the dispersant relative molecular mass of moderate, get pigment particle size is smaller, better system stability; consider the product of relative molecular mass and response control, choice of polymerization temperature of 70 ℃. (2) by infrared spectroscopy can be verified: the polymer is a copolymer of maleic anhydride and styrene. (3) of maleic anhydride and styrene copolymer molecular weight distribution of narrow molecular weight distribution of a wide brought in the follow-up application process, there is no negative impact. (4) the use of polymer dispersant to disperse the pigment, the pigment particle size distribution in the 100 ~ 150nm, a narrow distribution, with a good centrifugal stability, dilution stability of the dispersion effect is more ideal.