Study on the thickening effect of water-based polyester dispersion (2)

. Acrysol RM-8W is a low-odor, solvent-free, hydro-ionized fluid-modifier (hydrophobic modified polyurethane) with a conventional addition of 0.2% to 1.0% of the total amount of paint or varnish. Excellent low shearing and high thickening efficiency are available. The mechanism of connecting thickeners of polyurethane thickeners can be explained as: thickener molecules form bridges between particles, connect with polymer particles of emulsions and pigment particles that have been adsorbed with dispersants to form a network structure, and entangle each other to increase the viscosity of the system. As can be seen from Figure 1, even though the added amount of Acrysol RM-8W thickener reached 1.0%, the viscosity of polyester water dispersion increased by only 4% to 7%, indicating that the thickening efficiency of this type of thickener on water-based polyester dispersant was not significant. The main reason is that PnB is a good solvent of polyurethane-to-thickener, and the high content of PnB makes polyurethane thickener in the water-based polyester dispersion in a single molecule form, and can not be combined with each other to form an effective ring-like beam, thus losing the effectiveness of thickening. Rheolate150 thickener is an economical, versatile and efficient hydrophobic modified alkali-soluble acrylic thickener. In the low shear rate range to provide high efficiency thickening effect and anti-sinking, anti-flow hanging, the recommended amount of addition is generally 0.2% to 2.0% of the total amount of paint or varnish.the combined thickening of
alkali-soluble polyacrylic thickeners can be interpreted as: hydration of polyacrylate molecules under alkaline conditions, and expansion of dissolutionate root ions through the action of the same electrostatic refractive rebuke, resulting in an increase in the physical size of polymer fluids, thereby improving the viscosity of the water phase. Polypropylene esters, which have been modified by dredging, can further improve the efficiency of thickening by forming a mesh structure by bridging the bridge between latex grains and pigments. As can be found from Figure 2, when the Rheolate 150 thickener reached 1%, the viscosity of the water-based polyester dispersion increased by only 8% to 10%, which also showed poor thickening efficiency. The main reasons for the analysis are: a small amount of hydrophobic modified alkali-soluble acrylic thickeners in a large number of PnB of water-based polyester dispersion also exists in the form of a single molecule, can not form a ring structure of each other

the thickening effect of hydroxypropyl acrylic first-stage water dispersion . 2.2.1 Thickening EffectThe effect of different hydroxypropyl acrylic first-stage water dispersion on the efficiency of water-based polyester dispersion thickening was studied, the results of which are shown in Figure 3. As can be seen from Figure 3, when 5% of hydroxypropyl acrylic water dispersion is added, the viscosity of water-based polyester dispersion is increased by 10% to 25%, and when 10% hydroxypropyl acrylic water dispersion is added, water The viscosity of the hydroester dispersion increased by 30% to 35%, and when the amount of hydroxypropyl acrylic first-stage water dispersion was further increased to 20%, the viscosity of the water-based polyester dispersion was increased by 70% to 120%. The results show that the introduction of hydroxypropyl acrylic first-stage water dispersion can significantly improve the viscosity of water-based polyester dispersion, with extremely efficient thickening effect.. 2.2.2 Compatibity with water-based polyester dispersionsTo introduce hydroxypropyl acrylic first-stage water dispersions into water-based polyester dispersions, it is necessary to examine the compatibleness between the two. Table 2 describes the appearance of hydroxypropyl acrylic first-stage water dispersants mixed with water-based polyester dispersions, and when 5% of hydroxypropyl acrylic first-stage water dispersions are added, the mixed water dispersions are translucent and slightly creamy. With the increase of the addition of hydroxypropyl acrylic first-stage water dispersion, the mixed water dispersion gradually changed to a translucent emulsion state. In the storage of 30 d at 40 degrees C, adding 20% content of hydroxypropyl acrylic first-stage water dispersion is still translucent, there is no layering or precipitation phenomenon, indicating that the water dispersion compatibility and stability of the two mixed.. In order to further investigate the compatible between hydroxypropyl acrylic first-stage water dispersion and water-based polyester dispersion, the mixed water dispersion is dried after dripping on a transparent glass substrate, and the state of the dry film is shown in Figure 4. As can be seen from Figure 4, the dry film of the mixture remains transparent even with the addition of a hydroxyacrylic acid first-stage water dispersion of 10%. However, when the addition of hydroxypropyl acrylic first-stage water dispersion was increased to 20%, the dry film of the mixture showed a very slight milky light, but the transparency was still high. It is further shown that the selected hydroxypropyl acrylic first-stage water dispersion has excellent compatible with the water-based polyester dispersion.. 2.3 Thickening effect of hydroxypropyl acrylic secondary water dispersion 2.3.1 thickening effect Hydroxypropyl acrylic secondary water dispersion contains a certain amount of solvent assistance, generally translucent thin liquid. Compared with the first-level water dispersion, the secondary water dispersion does not contain emulsifying agents, the molecular weight is low, the viscosity is higher, belongs to the self-emulsified type of anionic water dispersion. Figure 5 shows the thickening results of water-based polyester dispersions by different hydroxypropyl acrylic secondary water dispersions. Like hydroxypropyl acrylic first-stage water dispersions, hydroxypropyl acrylic secondary water dispersions have a very significant thickening efficiency for water-based polyester dispersions. When 5% of hydroxypropyl acrylic secondary water dispersion is added, the viscosity of the system is increased by about 20%, when the added amount is increased to 10%, the viscosity of the system is increased by about 35%, and when the use of hydroxypropyl acrylic secondary water dispersion is further increased by 20%, the viscosity of the system is increased by 70% to 120%.2.3.2 compatible with water-based polyester dispersionshydroxypropyl acrylic secondary water dispersions and water-based polyester dispersions are found in Table 3. As can be seen from Table 3, when the amount of hydroxypropyl acrylic secondary dispersion is 5%, the mixed water dispersion is still transparent and clarified, when the added amount is increased to 10%, the water dispersion mixture changes from a clarified state to translucent, and when the amount of hydroxypropyl acrylic secondary water dispersion is further increased to 20%, the mixed water dispersion becomes a distinct translucent state of milk. After the storage of 30 d in the oven at 40 degrees C, the state of all mixed water dispersions did not change significantly, showing good storage stability.. The dry film state of the mixed water dispersion of hydroxypropyl acrylic secondary water dispersion and water-based polyester dispersion is shown in Figure 6. As can be seen from Figure 6, when hydroxypropyl acrylic secondary water dispersion is added by 5%, the dry film is still transparent. When hydroxypropyl acrylic secondary water dispersion was added by 10%, a slight fog shadow appeared in the dry film. When the addition of hydroxypropyl acrylic secondary water dispersion was increased by 20%, the dry film fog shadow was severe, but the transparency was still high. The results show that the hydroxypropyl acrylic secondary water dispersion is still showing good compatible with the water-based polyester dispersion when the amount added is 10%, and if the amount continues to increase, the coating gloss may be reduced.. 2.4 Hydroxypropyl acrylic water dispersion thickening agenthydroxypropyl acrylic water dispersion is a glial structure of the particle state, itself has the thickening effect of alkali-soluble thickening agent, that is, under alkaline conditions, its molecular structure characteristics from the curly winding state extended to a rod, thus playing a role in the thickening of the water phase. At the same time, under the action of a large number of solvent-assisted BCS, acrylic water dispersion with a glial structure will produce rapid swelling, so that its structure volume is multiplied several times, and from molecular structure analysis, the process of dissolution also exists the molecular chain from the initial tangle state to stretch the transformation, which leads to the rapid increase in the fluid and physical size of the polymer, so that the viscosity of the water polyester dispersion rises rapidly, showing significant viscosity in the experimental process. When the higher the content of hydroxypropyl acrylic water dispersion, the greater the degree of swelling and release of the molecular chain, which will also show a higher thickening efficiency.3 conclusionthe thickening efficiency of the water-based polyester dispersant by conventional connective thickeners is not obvious. However, hydroxypropyl acrylic water dispersion, whether a first-stage water dispersion or a secondary water dispersion, has a significant thickening effect on water-based polyester dispersion.when hydroxypropyl acrylic water dispersion amount reaches 10%, the viscosity of water-based polyester dispersion can be increased by 30% to 35%, at this time the two still have good compatible. When hydroxypropyl acrylic water dispersion reached 20%, the viscosity of water-based polyester dispersion increased by 70% to 120%, at this time the compatible between the two is still good.When formulating water-based polyester dispersions, especially ammonia paint systems, consideration can be given to introducing 10% to 20% hydroxypropyl acrylic water dispersions to improve the storage stability and anti-flow limit of the coating system.
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