聚氨酯缔合型增稠剂分水现象的理论

聚氨酯缔合型增稠剂是乳胶涂料的重要流变学助剂,本文主要介绍了聚氨酯缔合型增稠剂在乳胶体系中造成分水的机理,并在分水机理理论分析的基础上,探讨了解决涂料分水现象的方法。     

Preparation and rheological properties of SEM-25 containing associative thickener latexes and their mechanisms of thickening

Hydrophobically modified alkali-soluble acrylic latexes were prepared using varying level of SEM-25, triphenylethyl phenoxy polyoxyethylene ether methacrylate, a functional monomer bearing a long segment of ethylene oxide and a hydrophobic tetraphenyl group. Sharp increases in viscosity and light transmittance of the diluted associative thickener latexes were observed with ascendant pH starting from 7. And with further increase in the pH, viscosity of the thickener latexes rapidly fell down, while the light transmittance was kept relatively constant. It was revealed that a critical content of SEM-25 in the thickener copolymer, 5% in the present case, was required in order for the associative thickener to outperform the SEM-25 free counterpart. When used in thickening a latex of P(St–BA) (Poly(styrene–Butyl acrylate)) copolymer using a thickener copolymer with 12 wt% of SEM-25, addition of 0.34 wt% of the thickener polymer relative to P(St–BA) was necessary to have a higher viscosity than the same latex thickened using the thickener free of SEM-25. It seemed that incorporation of 0.275 mol% of SEM-25 was indispensable for the associative thickener to exceed the performance of conventional thickener.     

Improvements in the application properties of water-based low VOC coatings

Conclusions  This paper discusses a new class of acrylic latex (NeoCryl TX200) in which the colloid stabiliser is designed to interact with titanium chelates such as Tilcom AT23, thereby building up a weak gel structure which can be broken down by shear. This class of latex can be formulated with associative thickener (and their blends) in conjunction with titanium chelates, thus providing considerable formulation flexibility which cannot be achieved with conventional surfactant stabilised acrylic latex. A key feature of this new class of latex is that the colloid stabilisation system does not introduce water sensitivity, and indeed wet adhesion characteristics are fully comparable to those of state of the art adhesion promoted latexes. A further benefit of this class of latex is that of increased open-time, arising in part from its intrinsic rheological characteristics, and in part from the high film build achievable with thixotropic formulations. Rheological measurements show that introduction of titanium chelates greatly increases the low shear-rate viscosity of the system, and vane rotor measurements show that there is a near linear dependence of gel strength with titanate concentration. This gel, which is responsible for preventing in-can settlement of pigments and good brush pick-up, is partially broken down by the action of brush dripping, and is completely broken down during application (eg by brush or spray). The structure subsequently builds up with time, with gelation occurring in as little as 5–10 minutes, but with full recovery of gel strength taking in the region of 10–12 hours. The titanate chelating agent, even at high concentrations, does not contribute to the high shear-rate viscosity of the system, this being controlled by the addition of associative tickeners, either alone or in combination. The associative thickener(s) also control the low shear-rate viscosity during the period in which the gel structure has been sheared out, and thus good flow and levelling properties can be obtained through the optimisation of associative thickener type(s) and concentration(s). Although, as might be expected, cosolvents affect the rheological properties of formulations containing both associative thickener and titanium chelate, this effect is not a large one, and can be readily taken into account during formulation design.     

Interactions in associative thickener/220 nm methyl methacrylate latex dispersions

The rheology of commercial associative thickener dispersions containing 220 nm ‘model’ methyl methacrylate (MMA) latices have been examined. These high T_g MMA latices were synthesized by a semicontinuous process with variable percentages of methacrylic acid (MAA). The latex surface without monomer acid segments was only 70% saturated. The latices stabilized with neutralized methacrylic acid segments provided surfactant-saturated surfaces and uniform dispersions when thickened. With the acid-monomer-free latex, the addition of surfactant to saturate the surface of the latex and to increase the free surfactant concentration in the aqueous phase to the level needed to optimize viscosity by intermicellar participation did not effect viscosities equivalent to those noted in associative thickener dispersions containing acid-stabilized latices. These observations support the ion—dipole associative thickener mechanism previously proposed.

The viscoelastic behavior of associative thickener dispersions containing stabilized MMA/MAA latices neutralized with ammonium and alkali metal hydroxides has also been examined. The viscosities of all dispersions containing associative thickeners were highest with NH₄OH-neutralized latices. These results are interpreted in terms of the greater solubilizing power and lower pK_a value of the ammonium salt. The viscosity of hydroxy-ethylcellulose (HEC) thickened dispersions was found to be insensitive to the free surfactant concentration and the nature of the base cation, with only minimal changes in low shear rate viscosities (LSVs) being observed with increasing latex surface acids. These variables notably influence the LSV of the associative thickeners (AT), the magnitude of the latter variations being specific to the AT employed.

In oscillatory experiments, dispersions containing commercial associative thickeners, used predominately with acrylic latices in the U.S. and Australian markets, were observed to exhibit large viscous components. A large elastic component, reflecting thickening via network formation, was noted with commercial associative thickener used largely with commercial vinyl/acrylic latices.     

Waterborne latex coatings of color: I. Component influences on viscosity decreases

For almost two decades, it has been known that the addition of colorants to a waterborne latex coating thicknened with an associative thickener will result in a viscosity loss. The influence of surfactants on viscosity variations in waterborne latex coatings, as discussed in our most recent JCTCoatingsTech article,¹ is the source of the viscosity decreases. To evaluate this problem, aqueous solutions containing large quantities of five different surfactants, and the smallest particle size of the colorants, carbon black (CB), were prepared. Large quantities of surfactant were used to allow for adsorption on, and stabilization of, CB. When traditional associative polymers (HMHEC, HASE, and a telechelic HEUR) were used to thicken carbon black dispersions, viscosity decreases were not observed, for most of the surfactnat is adsorbed on the CB’s surface. There is enough surfactant, however, to promote viscosity decreases in comb-HEUR thickened CB dispersions. Moving beyond the colorant dispersions, the CB, yellow, or red colorants were then added to a commercial latex paint that contains many surfactants, glycol ether, and coalescing aids, and significant viscosity decreases were observed. The decreases were very dramatic as the colorant concentration was increased to obtain deeper color tones, due to the additional excess surfactant added to the coating. Reduction in total surfactant levels in the colorant was an obvious solution, but this led to rub-up incompatibility. The conflict between viscosity retention and rub-up incompatibility was resolved when the surfactant concentration was reduced by adding to the colorant formulation compositionally different hydrophobically-modified poly(oxyethylenes) and hydrophobe-modified maleic acid co-oligomers. Presented in part at the 81st Annual Meeting of the Federation of Societies for Coatings Technology, November 13–14, 2003 in Philadelphia, PA     

Associative polymer/particle dispersion phase diagrams III: Pigments

The colloidal interactions of both HEUR and HASE associative polymers with pigments in the presence of dispersant are complicated and subject to a number of variables. The objective of this work was to clarify the conditions needed to achieve good pigment dispersion in associative thickener systems by characterizing particle dispersion behavior. This had previously been done for latex particles, but not for pigments such as TiO₂. Good dispersion leads to optical properties, such as gloss and hiding, that are superior to nonassociative thicknener systems. Pigment dispersion phase diagrams represent a good way to visualize the complex interactions among pigments, dispersant, and thickener. The two most important variables were found to be pigment type (i.e., surface composition) and dispersant composition. Associative thickners can yield good pigment dispersion or flocculation, depending on the correct matching of dispersants and pigment type. Because of the hydrophobic functional groups governing associative thickner behavior, dispersants having some hydrophobic character yielded the best pigment dipersions and optical properties because they could couple the pigment particles with the associative thickener network. Interior-grade TiO₂ tended to yield better dispersions and optical properties than exterior-grade TiO₂. Optimized associative thickner systems generally had improved optical properties over comparable nonassociative systems. Optical properties correlated well with particle dispersion behavior as displayed by the dispersion phase diagrams. Presented at the Tess Symposium of the 230th American Chemical Society National Meeting, Aug. 28–Sept. 1, 2005, in Washington, D.C.     

乳液聚合法聚丙烯酸树脂的制备研究

介绍了以丙烯酸、苯乙烯、丙烯酸丁酯、丙烯酸羟丙酯为单体,采用过硫酸铵作为引发剂,以非离子乳化剂聚氧乙烯醚(OP-10)和阴离子乳化剂十二烷基硫酸钠(SDS)作为复合乳化剂,经过乳液聚合,制得了一种水性涂料用缔合型增稠剂.考察了丙烯酸单体含量、乳化剂用量对乳液性能和增稠剂黏度的影响.优化了反应条件,反应过程和最终乳液都很...     

聚氨酯缔合型增稠剂的研制及应用

利用聚乙二醇和二异氰酸酯聚合,并以酚类物质为链封端剂合成了缔合型增稠剂,检测和对比该产品与一支国外同类产品在乳液及乳胶涂料中的一些相关应用性能,结果显示,该产品与同类产品性能接近,具有一定的市场前景。     

Control of rheology of water-borne paints using associative thickeners

Water-borne decorative topcoats generally show inferior leveling and open time compared to solvent-based paints. Basically, this behavior is caused by the divergent viscosity–solid content relationship for dispersions and emulsions and by the relatively high evaporation rate of water. Employment of associative thickeners may improve leveling and open time of latex paints only if they introduce a substantial amount of ‘network viscosity,' characterized by a short relaxation time and little dependence on solid content. This network viscosity enables one to formulate a paint with sufficient high-shear viscosity at a particle-packing density far below the value where low-shear viscosity starts to diverge. Addition of an associative thickener not only affects rheology, but also the interaction between latex particles: Associative HEUR thickeners may induce undesired phase separation by strong bridging between the latex particles. The influence of HEUR thickeners on latex particle interaction has been studied by turbidity measurements. The experimental results could qualitatively be interpreted very well by two-particle interaction potentials computed using the Self-Consistent-Field theory of Scheutjens and Fleer. It is demonstrated how viscosity, created by the addition of an associative thickener to a highly concentrated latex, can be split up into a polymer network viscosity and a contribution to (relative) dispersion viscosity. According to these analyses, reduction of the molecular weight of tri-block HEUR thickeners yields an increase of the favorable network viscosity and a reduction of the unfavorable dispersion viscosity. However, reduction of the molecular weight of the HEUR thickener is limited by the introduction of undesired phase separation (bridging flocculation) below a certain molecular weight.     

乳胶漆中缔合型增稠剂与分散剂的合理搭配

论述了乳胶漆中缔合型增稠剂与分散剂的相互作用,分析了不同组合对乳胶漆性能的影响,确定了合理的搭配方案。     

缔合型丙烯酸酯类增稠剂的研究

以丙烯酸乙酯、甲基丙烯酸、甲基丙烯酸甲酯为主要单体,采用反应型表面活性剂.经过乳液聚合,制得了一种缔合型增稠剂.考察了反应型表面活性剂用量对增稠剂性能的影响,并与其他同类产品作了对比.实验结果表明:反应型表面活性剂的引入使增稠剂分子在水中由于缔结作用形成了网状结构,该结构使增稠剂的增稠能力和耐电解质能力明显提高.且增稠...     

乳液增稠技术的研究进展

增稠剂可以提高物系黏度,使物系保持均匀稳定的悬浮状态或乳浊状态,或形成凝胶。目前常用的增稠剂有纤维素及其衍生物类、聚丙烯酸及其共聚物类、非离子缔合型聚氨酯类等,对不同增稠剂特性的了解对于根据需要选择合适的增稠剂非常重要。主要以纤维素及其衍生物类、聚丙烯酸及其共聚物类、非离子缔合型聚氨酯类这三类主要的增稠剂为主,综述了乳液增稠的相关增稠机理以及研究应用技术。     

Vegetable oil based fatty amide as hydrophobes in associative thickener

A vegetable oil based high performance associative thickener has been designed and synthesized from a hydroxyl functional soybean oil derivative (hydroxyl value 159 mg KOH/g). An isocyanate‐terminated prepolymer was synthesized from polyethylene glycol (PEG) and isophorone diisocyanate (IPDI), and end‐capped with the hydroxyl functional soybean oil derivative to prepare a hydrophobically modified ethoxylated polyurethane (HEUR) thickener. The synthesis was monitored by infrared spectroscopy via the isocyanate peak at 2258–2270 cm^?1. Thickener efficiency was tested with a commercial styrene–acrylic latex UCAR? 443, an acrylic latex Acronal^® Optive 130 and an alkyd emulsion WorléeSol^® E 150W. High thickening efficiency was noted in the low shear region, e.g., 0.5 wt % HEUR loading with UCAR 443 increased viscosity from 0.66 P to 3.06 P at a shear rate of 1333 s^?1. The effect of soybean oil fatty amide based rheology modifier as additive in coating was evaluated in terms of gloss, viscosity, sag resistance, and flow and leveling properties. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 1530–1538, 2013     

Syneresis and rheology mechanisms of a latex-HEUR associative thickener system

This study focuses on the phase behavior, rheology, and interactions of polymer latex particles and a hydrophobically modified ethoxylated urethane (HEUR) associative thickener in water. At constant 0.25 latex particle volume fraction, increasing HEUR caused stable, followed by phase separated (syneresis), and stable mixtures as HEUR concentration increased from 0% to 2.0% (by weight) in the latex-thickener aqueous mixture. The mixtures that underwent syneresis were flocculated. The relationship between the flocculation behavior and the composition of the latex-HEUR mixtures is consistent with previous work reported by other investigators. However, detailed rheological data on systems like these that have undergone syneresis have not been reported. This paper presents detailed viscosity vs shear rate data and correlates viscosity trends with the both flocculation and syneresis behavior. The stable latex-HEUR mixtures at low HEUR levels show Newtonian or shear-thinning viscosity with well-defined low-shear Newtonian plateaus. As HEUR level is increased to levels at which syneresis is observed, erratic rheological profiles with shear thinning as well as thickening are observed. This type of shear thickening has been attributed to bridging flocculation by other investigators. When HEUR level is further increased to levels at which no syneresis is observed, low-shear Newtonian plateaus re-appeared, albeit at higher viscosities. Detailed analysis of syneresis and shear-thickening behavior of a latex-HEUR mixture containing 0.5% (by weight) HEUR showed two shear-thickening regions, one between 0.1 and 0.5 s^?1 shear rate range and another between 30 and 100 s^?1 shear rate range. Molecular weight distribution (MWD) of the HEUR thickener indicates that the two shear-thickening regions are related to the bi-modal nature of the thickener’s MWD.     

用于电脑调色的基础乳胶漆配方设计

分析了乳液体系、增稠体系对调色基础漆展色性的影响,并且探讨了调色基础乳胶漆中PVC与钛白含量的设计。     

Surfactants in water-borne paints

The main uses of surfactants in water-borne coatings are discussed. Special attention is put on the use of surfactants in latex polymerization and in post-emulsification of binders, such as alkyd resins. The advantage of polymerizable surfactants as emulsifier is pointed out and the use of atomic force microscopy (AFM) to observe differences in film properties between formulations based on polymerizable surfactants and on conventional surfactants is illustrated. The paper further discusses the problem of competitive adsorption between surfactants and between surfactant and associative thickener in paint formulations.     

高耐候性外墙乳胶涂料的研制

选用优质的丙烯酸酯乳液,颜填料,成膜助剂,分散剂,增稠剂以及其他助剂制得了高耐候性外墙乳胶涂料。介绍了该涂料的配方和生产工艺设计。讨论了丙烯酸酯乳液,颜填料及助剂对涂料的影响。     

Associative polymer/latex dispersion phase diagrams II: HASE thickeners

The colloidal interactions of HASE associative polymers and latexes in the presence of surfactant are complicated and subject to a number of variables. Both bridging and depletion flocculation can occur, in addition to good particle dispersion. Dispersion phase diagrams have been developed to help visualize these interactions. The various dispersion states can have a significant effect on coating formulations and film properties. Examples of dispersion phase diagrams are presented for a model HASE anionic associative thickener and various model latexes in the presence of sodium dodecyl-sulfate and nonionic surfactants. The major variables affecting dispersion behavior are associative polymer concentration, latex particle size, latex surface hydrophobicity, electrolyte concentration, and surfactant concentration. The dispersion phase behavior of the HASE systems is compared to that of HEUR thickened systems reported previously. A significant difference is that much less bridging flocculation is observed in the HASE systems. In addition, nonionic surfactants induced depletion flocculation in the HASE systems but not in the HEUR systems.     

Interaction between styrene/butylacrylate latex and water soluble associative thickener for coalescent free wall paints

The effect of water soluble hydrophobically modified ethylene oxide urethane (HEUR) thickener on coalescent free wall paints was studied. Three systems were looked at: latex/thickener blends, model paints (containing no fillers that could have an effect on paint rheology) and satin paints (PVC 30%). The latexes used were a styrene/butylacrylate copolymer, designed for coalescent free wall paints. A full factorial statistical experimental design was employed to study the effect of latex and formulation variables on the viscosity response for the full range of shear rates encountered in paint application. The factors considered in the design were total latex surface area, polymerization surfactant level, thickener type and thickener concentration. The surfactant level was varied between 0.85 and 1.71 parts. The two HEUR thickeners were selected based on the manufacturer's claim that they exhibited good performance at different shear rates. The thickener levels were the extremes recommended by the manufacturer. Measurements were done on Haake, Rheometrics, Brookfield and ICI Cone & Plate rheometers. Total latex surface area and the thickener level are the two significant parameters for latex thickener blends and for model paints at the same significance level, this indicates good correlation between the two systems. The introduction of clay as a filler decreases the effect of all parameters studied.