General knowledge of coating: development of new environmental protection coating with ultra-low VOC

Core tip: at present, China's VOC limit standard for interior wall coating is less than or equal to 200g / L, while there is no standard for exterior wall coating Currently, the coating products on the market only meet the national standard in VOC content, while the ultra-low VOC content products have not been achieved under the premise of ensuring the excellent coating performance In this paper, the hard monomer or multi-component monomer is used as the core polymer (high Tg) and the soft monomer as the shell (low Tg) The semi continuous seed polymerization is used to increase the amount of initiator, create / starve 0 reaction conditions and control the core / shell morphology Use two Application scope and advantages of roller ceramic coating Recommended introduction: the surface of ceramic rubber plate used for roller ceramic coating is cast into durable rubber plate by hundreds of independent small ceramic pieces Each ceramic piece has raised characteristics Under general conveyor belt pressure, thousands of unique cast bumps can produce positive traction, prevent slipping and extend the service life of conveyor belt roller At the same time, the bottom layer adopts high-quality rubber, which has strong elasticity and can play a good impact resistance role The scope of application of roller ceramic coating is one three six 83857180 (the same as V) 1 Roller coating in extremely harsh working environment 2 The belt joint is not suitable for fixing with iron buckle; 3 It is suitable for leather Home of coatings: at present, the VOC limit standard for interior wall coating in China is less than or equal to 200g / L, while there is no standard for exterior wall coating Currently, the coating products on the market only meet the national standard in VOC content, and the ultra-low VOC content products are not available under the premise of ensuring the overall excellent coating performance In this paper, the hard monomer or multi-component monomer is used as the core polymer (high Tg) and the soft monomer as the shell (low Tg) The semi continuous seed polymerization is used to increase the amount of initiator, create / starve 0 reaction conditions and control the core / shell morphology The semi continuous polymerization of (half) buoyancy is carried out by the two stage method by power feeding and multiple feeding methods The polymerization rate and the coagulation effect are increased The ultra-low VOC waterborne emulsion with excellent performance is synthesized by strictly controlling the polymerization sites The new type of environmental protection coatings with various targets reaching the national standard and ultra-low VOC are prepared by this emulsion Experimental study Put the mixed monomer into the constant pressure funnel according to the quantity for standby; add sodium dodecyl sulfate, OP-10 and sodium bicarbonate into the three port flask and stir for 5-10min, then add 1 / 3 monomer in the constant pressure funnel while stirring, stir for 5-10min to make the monomer fully emulsified, at this time, it can be seen that the small and medium-sized droplets in the three port flask start to increase without color change; then start to add sulfur under constant temperature Ammonium sulfate and the remaining monomer, the emulsion gradually turned into milky white; the remaining raw materials were added at about 1.5h After dropping, the temperature is raised to about 75 ℃ for 4-5h, the temperature is raised rapidly to 80 ℃ for decompression flash, then the temperature is cooled to room temperature, the pH value is adjusted to 8-10, the monomer is extracted under pressure again, and then the product is obtained The solid content of the performance test is called a certain quality emulsion In the oven, it is dried at 120 degrees Celsius until constant weight, solid content = (dry weight / wet weight) x 100% [D] the water dilution stability will weigh the emulsion to be tested in a 20mL test tube and separate the deionized water from the volume of 1:4, 1:6 and 1:8 according to the volume ratio If there is no stratification, the emulsion is stable If there is a stratified phenomenon, the higher the height of the cleaning solution is, the worse the dilution stability will be The 10g polymer emulsion samples were placed in 15mL plastic bottles for freeze-thaw stability It was frozen in a refrigerator of - 20 ± 1 ℃ for 16 hours, then melted naturally at room temperature After repeated freezing and thawing, the freeze-thaw index increased by 1 without any demulsification and the consistency of the emulsion did not change The greater the freeze-thaw index, the higher the freeze-thaw stability of the emulsion If the freeze-thaw index is zero, the emulsion does not freeze, so the freeze-thaw index must be stored at more than 5 The stability of calcium ion stability is used to characterize the ability of polymer emulsions to withstand electrolytes The method of determination is as follows: in the 20mL calibration test tube, 16mL polymer emulsion sample is added, in addition to 4mL0.5% CaCl2 solution, shake well and 48h is placed If there is no gel and stratification, the calcium ion stability of the sample is qualified If there is stratification, measure the height of the upper (or lower) clear liquid The higher the height of the clear liquid is, the worse the calcium ion stability is 3.5 mechanical Before the stability test, the polymer emulsion is filtered, then placed in the beaker of 50mL and placed on the magnetic stirrer The stirrer is opened to the maximum stirring speed and stirred 30min If there is no gel, the mechanical stability of the emulsion is good; the more the dry aggregate is, the worse the mechanical stability is Centrifuge stability, take the emulsion 5mL after filtration, add it to centrifuge tube, centrifuge 10min at the speed of 4000r/min, if it is not stratified, the stability is qualified; if stratified, the height of the supernatant liquid is measured, the higher the height is, the worse the stability is The pH value stability takes two identical test tubes to be loaded into the 5mL test emulsion sample separately, adding 1% hydrochloric acid solution and 1% sodium hydroxide solution to the two test tube respectively, so that the pH value of the emulsion in the two test tube decreases or rises Observe the change of emulsion and find the range of pH that can stabilize emulsion All other parameters were measured by transmittance 752N UV visible spectrophotometer was used to measure distilled water as reference solution at 660nm wavelength Viscosity was measured by NDJ-9S type digital viscometer Because of the low viscosity of the tested emulsion, the speed of 1# rotor and 30r/min was selected The test emulsion was put into the beaker with an inner diameter of 70mm, and the relative viscosity of the volume 90mL was measured under the condition of small emulsion volume The surface tension was measured by HAWKE-DWK surface tension tester The surface tension was measured by the William hanging plate method The particle size distribution was measured by the MicrotracVSR laser particle analyzer, and the full-scale automatic operation was carried out in the determination For rsz thermal analysis, wct-2crsz was used for differential thermal analysis; for the determination of functional groups, FTIR spectrogram was used for the analysis of functional groups The influence of emulsifier was analyzed 1 Sodium dodecyl sulfate and OP-10 were used as composite emulsifier The advantages of nonionic surfactant and ionic surfactant were well integrated In addition, the emulsifier also determines the particle size of the emulsion If only twelve alkyl sulphate is used, the latex particle size is small, the emulsion mechanical stability is good, the aggregation is less during polymerization, the polymerization process is stable, but it is more sensitive to electrolyte Adding non-ionic emulsifier OP-10 is beneficial to improving the electrolyte resistance and chemical stability of emulsion Under other conditions, the effect of emulsifier dosage on the properties of emulsion is shown in Table 1 The particle size determination curve of polymer emulsion is shown in page 1 and 2 Table 1 the influence of emulsifier on the properties of emulsion 1 Particle size determination curve 2 particle size measurement curve shows that the particle size is mainly distributed at 0.630Lm, 100Lm and 600Lm, and the particle diameter curve at Figure 2 is at 220Lm The curve analysis shows that the peak value of the particle size curve at 100Lm may be due to the excessive amount of emulsifier added, and the peak value of the curve may be caused by 600Lm or gel formation The addition of emulsifier will reduce the interfacial tension When emulsifier is added, the lipophilic group must extend to the oil phase, and the hydrophilic end is in the water phase Because the oil side of the oil-water interface is attached with the lipophilic end of a layer of emulsifier molecules, part or all of the oil-water interface is changed into the lipophilic group) oil interface, which reduces the surface tension 2 the effect of temperature on the reaction is the highest reaction temperature at 75~80 C in the reaction process The high temperature will accelerate the decomposition rate of initiator and accelerate the reaction The formation of branched chain will form other polymers In addition, the high temperature will make the emulsifier molecules adsorbed on the surface of polymer colloid rapidly and desorb to form aggregates, and the emulsion is unstable In addition, the reactive and cross-linked monomers will have cross-linking reaction at high temperature And the polymerization is exothermic reaction If the temperature is not well controlled, agglomeration will occur and particles will be produced When the temperature is high, the polymer particles are large, the residual monomers are few and the viscosity is large; otherwise, the particles are small, the residual monomers are many and the viscosity is low Table 2 shows the effect of reaction temperature on the viscosity and the state of the emulsion Table 2 Effect of polymerization temperature on polymerization reaction 3 Effect of feeding speed on polymerization effect and product performance If feeding speed is too fast, temperature changes greatly, reaction temperature is not easy to control, polymerization is not stable, and there are many agglomerates The feeding speed is too slow and the reaction time is prolonged Not only the operation cycle is long, but also the blue light of the emulsion decreases It is known from experiments that the dripping speed is 12~15 drops of /min Under these conditions, the reaction is easy to control and the emulsion is of excellent performance The spectrum measured by FTIR is shown in Figure 3 Fig 3 FTIR spectrum from the infrared spectrum: the moisture in the tested sample is completely dried, the peak at 2950cm-1 is caused by the stretching vibration of C) h, 1740cm-1 is the characteristic absorption peak of ester group, and the combination of 1250cm-1 and 1166cm-1 is a pair of double peaks of methyl methacrylate on the polymer The results show that all the three monomers participate in the copolymerization, and the structure of the synthesized terpolymer is consistent with the design structure It was found that the emulsion was stable when the pH value was 8~12 Solid content, particle size and distribution will affect the viscosity of the emulsion Emulsifier can reduce the interfacial tension of emulsion Compared with pure water, emulsifier solution is easier to expand the surface area, so it is easy to blister and will affect the distribution of particle size curve in the performance test The optimum reaction temperature is 75 ~ 80 ℃ Home of coatings is specialized in coatings, diatom mud, paint coating, coating technology, fire retardant coating news and coating, diatom mud, paint coating, coating technology, fire retardant coating decoration knowledge and decoration renderings,