Analysis: Paint production film blurs the issue
- Time of issue:2015-05-01
Analysis: Paint production film blurs the issue
- Time of issue:2015-05-01
From: China Net new paint
With economic development, people's living standards improved. For the needs of the people of the house it is not just a place to shelter, but also home to comfort, appearance, performance, compatibility residence multi-faceted. Interior paint is an indispensable part of the overall housing, people of color and properties of the coating also gradually increase. Paint color is very complex modulation in paint production and construction process is often met blurs problem occurs when the coating film blurs, color standard plate produce color, toner becomes difficult, not only a waste of paint and color accurate, while the effect of open cans of paint is poor, and after drying paint coating construction and difficult to deviate from the color painted uniform.
One of flooding metallic pigments dynamic separation: the separation barrier pigment occurs in the horizontal direction so that the coating color appears uneven flooding. Floating color is the color change occurs in the vertical direction, coating one or more pigment separation occurs in the film forming and drying process, a pigment float to the surface, another pigment in situ does not move or sink in the end portion.
How to observe and judge the laboratory blurs phenomenon? Can in two ways: static tank floating color: paint evenly dispersed after standing for some time in the tank, the tank of one or more pigments appear isolated phenomenon surfaced in the surface, such as after a period of storage after seeing the tank open tank surface surfaced black, phthalocyanine blue or white and so on. Dynamic floating color coating: coating pigment particles during the drying process occurs isolated phenomenon called dynamic floating color, pigment floating dynamic separation of two cases: one is flooding and surface coating color unevenness, the other is best film floating surface color uniform, but there are differences between the surface and the underlying color. Rub with your fingers to identify the floating exhibition, first pouring paint or coating on a glass plate or black and white card paper, when leveling state, finger rub grind until the beginning of the film becomes thick, the pigment particles migrate no longer isolated, If the presence of the floating paint color, not rub rubbing surfaces grinding mill after the differences in hue, knead the pigment grinding process occurs readily separated filamentous stripes, after drying the coating surface will rub grinding angular vortex pattern, means a change in the degree of discoloration with finger rubbing research conditions, the length of time rubbing grinding mill or kneading action film and the severity of drying speed has a great influence on the degree of color change.
Flooding and Floating factors paint a lot of difference, the difference between the surface tension of the system substance pigment particle size, and a hydrophilic-lipophilic balance value for each substance (HLB), emulsion and paste compatibility for latex paint blurs greater impact, the following specific discussion.
1, the impact of particle size on pigment particle coating flooding and floating
Coating during the drying process, with the evaporation of volatiles in the coating, a portion of these volatiles will be entrained pigments, fillers coating bring them up, and these pigments, filler particles, when delivered to the surface, have a higher surface area the finer particles easy to transport, and relatively low surface area than coarse particles impede the movement, in the dried paint film, the more hydrophilic substances tend to evaporate quickly, if white pulp is relatively hydrophilic paste Some strong, that is a hydrophilic white pigment particles are more hydrophilic than the colorant pigment particles, which are more susceptible to strong polar volatiles to the surface. Plus pigment particle size difference is too large, making the face, the padding between the miscibility becomes poor due to the above reasons, this pigment obtained paint poor construction, the construction process, the phenomenon of floating white paint serious, and the film takes place floating color. Floating white hard to tune in dark colors and wasteful pigment. The solution is carefully chosen pigments, fillers, pigments and fillers to make the choice of particle size to match; in order to avoid flooding and floating phenomenon.
2, the effect of surface tension difference of flooding and floating paint
When ordinary toner, often found that some paste on white base paint is difficult to disperse uniformly dispersed after a good paint still some time soon, separation or floating color phenomenon or effect paint cans not good. In the process, paints, white pulp production and paste production process different formulations, production of white pulp is often used anionic or nonionic dispersant polyelectrolyte dispersants, and paste is to use more non-ionic dispersants, or with some anionic dispersing agent and therefore was a white pigment and colored pigment particles due to the adsorption of the different layer of wetting and dispersing agents have different surface properties, the hydrophilic-lipophilic value is not the same, the surface tension is not the same. Ionic surfactants generally larger than the surface tension of the non-ionic surfactant. Are non-ionic surfactants, because the molecular structure of a hydrophobic end is not the same, the surface tension is not the same, and the molecular structure of a hydrophobic end outermost link the largest contribution to the surface tension. Low surface energy forces between the small molecules mean molecules, low surface tension. From thermodynamic considerations, low surface tension of the material is easily adsorbed to the transfer interface, leaving the system is stable, due to surface tension reducing shrinkage weakens the liquid surface and the droplet coalescence trend curved surface of the additional pressure difference decreases, hence conducive to the level and dispersion stability. So, if the difference between the surface tension and the surface tension of the system of white slurry or paste between big difference when using this configuration slurry coating more prone to floating color.
3, compatibility between the system
Good compatibility with emulsion paste it blurs the case of paints and coating will be much better, good wetting emulsion paste for the paint color development is also very good. Often used in aqueous coatings anionic and non-ionic surfactants as wetting and dispersing agents, inorganic pigments having polar and ionic surfactants in the water system, the ability to add ionic surfactant polar groups or ions , the formation of two-story adsorption layer. In the aqueous pigment paste pigment particle surface adsorption of the surfactant to form a protective layer, a protective layer between the force but there are intermolecular forces, static electricity points, so the strength of the force between them is not the same, when the above paste mixed with all kinds of emulsion or latex, the dispersion stability of the colorant is not the same performance as surfactants and surfactant emulsion particle surface of the pigment particle surface adsorption of water that is emulsifying agents or affinity between the large, surfactant adsorbed pigment particles are stripped, so that the protective layer is thinner pigment particle surface, resulting in flocculation of the pigment, causing the paint coating film blurs. Of course, when external emulsifiers and emulsion particles in the pigment paste, surfactant compatibility filler particles outside the good, the emulsion of these pigments, wetting particles like filling the entire paint color development is good, colorful, not floating color.
4, the impact of hydrophilic-lipophilic balance value of flooding and floating
Hydrophilic-lipophilic balance (HLB) is a very sensitive issue, often using a variety of materials in the production of coatings: latex, pigments, fillers, solvents, co-solvents and various additives. These materials have their own hydrophilic-lipophilic balance (HLB value), the hydrophilic-lipophilic balance of the coating material and match the performance of the entire system is very good, floating color, blur, and so will be the watershed get over. Of course, we use the emulsion after the selected pigments and fillers, hydrophilic-lipophilic balance HLB value is a value that is not change, but by careful selection of additives, namely wetting and dispersing agents, thickeners, etc. to adjust the HLB of the entire system value, so that the HLB value of the balance of the entire system. We know that the parental substance lipophilic surface tension of a small oil terminal, paint stored in the container tank, these lipophilic substances easily float up to the surface, from the thermodynamic point of view, the whole system energy decreases, the system is stable. When the production of latex paint that is in a container in the static on the floating color, is not only ineffective cans, construction performance is not good, not good coating state. If the floating white paint, understand that the slurry HLB value is relatively small, white pulp relatively lipophilic, therefore, when the production of white pulp to make white pulp made hydrophilic point; if the paint is floating paste colors, say so pulp HLB value is relatively large, relatively hydrophilic, at the time of production of white pulp to make white pulp made lipophilic some paint to prevent floating color.
Match hydrophilic-lipophilic balance (HLB value) can be obtained by careful selection of wetting, dispersing agents to complete. Ammonium salt dispersant anionic dispersing agent with a hydrophobic group than the sodium salt of a carboxylic acid type dispersing agent to be lipophilic, HLB value is small, and with a hydrophobic group of ammonium dispersant paint coating floating color is also greatly improved. Because when the pigment particles wrapped up this type of dispersant, the pigment particles are surrounded not only static resistance, but also the presence of steric hindrance, and the coating during drying, evaporation of water, ammonia is also volatile ammonium salt , so that some of the more hydrophobic such dispersants, the pigment so as to wrap the filler particles such dispersants was more compatible with the film-forming, together with steric hindrance so that the structure becomes bulky, so that the coating film during drying, the film floating color, the dynamic process of floating color is also suppressed.
5, the impact on the paint thickener flooding and floating
Some strong pseudoplastic associative thickener with HLB value greater surfactant has a great affinity to the desorption on the surface of the pigment, causing the pigment aggregation and flocculation, and then the system was lowered and coloring power generating film blurs. Organic and inorganic pigments mixed in the system, especially when titanium dioxide and ultramarine blue, green and carbon black paste shared use weak pseudoplastic associative thickener obtain satisfactory color paint and a good leveling sex. Thickeners or dispersants certain groups such as hydrophobic end group, pigment particles have a strong affinity adsorption flocculation of pigment particles form a bridge leading to the floating paint color, highly hydrophobic associative thickeners, as a result of the hydrophobic group adsorption paste particles, causing poor bridge flocculation coloring, alkali swellable thickeners vary the amount of charge carried by ions, salt thickened result in a different number of the deposition was charged in the coating film drying, resistant to extreme different affinity of pigment particles, floating severity of different systems also differ in terms of color development.
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