| Polyester/alkyd resin is the most important type of polymeric film-forming material in the production process of coating.Pigment carbon black is one of the most desirable pigments in coating,but how to effectively disperse pigment carbon black in coating with polyester/alkyd is an unresolved problem;this has become a technical bottleneck that restricts the advancement of such coating to higher quality.The key to solving this problem is to design and develop a carbon black hyperdispersant that is infinitely compatible with polyester/alkyd resin systems.A class of hyperdispersants with the solvation chain of polyester were designed in this dissertation.Three polyester solvation chains of the poly(phthaloyl-ethylene glycol)ester with terminal hydroxyl group(PAEG),poly(adipyl-phthaloyl-hexanediol)ester with terminal hydroxyl group(PAHP)and poly(adipyl-butenediyl-hexanediol)ester with terminal hydroxyl group(PAHM)were synthesized respectively,which were characterized by gel chromatography(GPC).After that,solvation chains were chemically modified with toluene diisocyanate(TDI)and combined with organic amines as anchoring group to prepare different hyperdispersants.The structure of hyperdispersants were analyzed by infared(IR)spectyum to confirm the degree of reaction.The prepared hyperdispersants were added to the polyester/alkyd resin coating together with the pigment carbon black to evaluate the performance of the dispersion system.The main research contents and results are as follows:(1)The optimal synthesis conditions of the solvation chains were as follows:In nitrogen atmosphere,the temperature of polymerization was 180~190°C,the catalyst was tetrabutyl titanate,the dosage was 0.15%(accounting for the total mass ratio of raw materials),the time of polymerization was 14~15 hrs.Under these conditions,the molecular weights of solvated chains PAEG,PAHP and PAHM were in the range of 1000~4 000,which reached the molecular weight of the polymer oligomer and had narrow molecular weight distribution(the distribution index was between 1.1~1.3).(2)The effect of hyperdispersant on the fineness and viscosity of the coating was was evaluated according to GB/T 1724-1979 and viscometer.The results had shown that the fineness of the coating could be reduced to 15?m,and the viscosity of the coating could be reduced to 1.82~2.52 Pa·s by selecting the appropriate solvation chain and anchoring group.(3)The effect of the hyperdispersant on the hue and gloss of the coating film was evaluated in accordance with test methods of GB/T 11186.2-1989 and GB/T9754-2007.The results had shown that for the PAEG series of hyperdispersant,when N,N-dimethyl-ethanol amine was selected as the anchoring group,the blackness(L~*=24.43)and hue of the paint film(a~*=-0.43,b~*=0.08)were consistent with those of the paint film of foreign similar products B 163(L~*=24.02,a~*=-0.44,b~*=0.06).The gloss of the paint film(77.4)was also close to that of the paint film corresponding to B 163(gloss was 80.3).For PAHP series of hyperdispersant,when polyethylene polyamine was selected as the anchoring group,the blackness(L~*=23.75)and hue(a~*=-0.27,b~*=0.05)of the paint film were consistent with the indicators of the paint film of S 325(L~*=23.63,a~*=-0.24,b~*=0.06),and the gloss of the paint film could be raised to 81 that was equivalent to the gloss of the paint film made by S 325 was81.5.As for the PAHM series of hyperdispersant,when polyethene polyamine was selected as the anchoring group,the blackness and hue of the paint film(L~*=24.21,a~*=-0.33,b~*=0.13)can reach the standrad of the paint film of S 325,and the gloss of the paint film reached 76.(4)The parallel storage experiment at 50°C was found that the dispersion with the prolongation of storage time,the disperation performance indexes of hyperdispersants decreased to varying degrees,but still could reach the level of similar foreign products B 163(or S 325). |
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