The application and research progress of desiccant in water-based coatings.

application and research progress of desodulation agent in water-based
in Guoling1, Wang Xueke 2
(1. Nanyang Agricultural Vocational College, Nanyang, Henan 473000; 2. Nanyang Wolong Paint Co., Ltd., Henan Nanyang 473000) 0 Foreword
coating production often need to add a variety of additives to improve the dispersion of pigments, product storage stability, coating appearance, construction performance and so on. These surfactants change the surface strength of the coating so that it is easy to produce foam during the construction process, especially water-based coatings. Hazards of foams: (1) limited production capacity, (2) affect product quality, (3) cause waste, (4) pollute the environment, and (5) may cause accidents. To eliminate these adverse effects, desiccants are an indispensable additive in water-based coatings.1 deboulant composition, characteristics and action of the
1.1 desiccant composition, characteristics
the composition and effect of desiccant is seen in Table 1.1.2 The agent's functioning factor
1.2.1 Causes of bubbles in water-based coatings
The causes of bubbles in water-based coatings include:
(1) stirring dispersion during production and air during construction, which is caused by changes in the free energy of the system.
(2) wetting dispersants, emulsifiers and other additives to reduce surface stress, help foam production and stability.
(3) thickener makes the bubble wall thicken and the bubble is not easy to eliminate.
1.2.2 Factors affecting foam stability
Factors affecting foam stability are: (1) the viscosity of the solution, (2) the surface viscosity of the solution, (3) the surface viscosity of the foam, (4) the structure of the surfactant, (5) the Marangoni effect, (6) the elasticity of the foam, and (7) other factors.
other factors include: temperature, solvent volatilization speed, acidity, surfactant adsorption, foam size, foam impact degree, the interaction of various components in the system. The main factors affecting the stability of bubbles in different systems are different, and many factors exist at the same time and work together. The elasticity of the bubble is the main factor affecting the stability of the bubble.
1.2.3 Defrosting
foam is an unstable system that spontaneously changes from a state with a higher free energy to a state with a lower free energy and obeys the laws of thermodynamics.
Defrosting process: (1) damage the elasticity of the membrane; (2) promote liquid film discharge; (3) the addition of defrosting agent reduces the surface pressure of the foam local causes the bubble to break; (4) the addition of low-molecular defrosting agent ethanol, propylene alcohol, etc. reduces the concentration of surfactants in the surface layer, and dissolves into the surface active agent adsorption layer to destroy foam stability.
the action of anti-foaming agent: de-foaming agent first spontaneously into the liquid membrane, in the interface quickly spread, dispersed. Changes the interface performance of the liquid film, causing the membrane to break. There are also differences in the way different types of defrosting agents destroy foams, for example: triglycerides phosphate is to reduce the surface viscosity of the liquid film, so that the discharge speed of the liquid film increases to achieve defrosting effect;evaluation of
2 desulbant can be evaluated from the aspects of compatible, anti-foaming, de-air-degassing, brushing and so on.
common methods for evaluating de-foaming and anti-foaming performance are: bottle-shaking method, high-speed dispersion method, gas foaming method, Ross-Myers method, West German industrial standard method, concussion method and circulating foam method. These methods are used to evaluate the performance of deboulants by the change of foam volume. There is no fixed standard for the evaluation of deboulants, which are used to judge the performance of deboulation by comparing them with each other. Test methods, test conditions, desiccant concentration, stirring time and strength, and the size of desiccant droplets all had an effect on the test results. Which method is chosen for evaluation is determined by the actual application.3 Application of desobbists
3.1 Types and scope of application of desticants
The characteristics and scope of application of desticants for water-based coatings are set out in Table 2.the principles of the desiccant selection are: (1) strong de-foaming ability, (2) good stability, (3) no re-painting obstacles, (4) does not affect other performance. Finally, according to the resin type, formulation system, construction method, production process and other additives, through experiments to determine.
3.2 Dosage of desiccants
dosage of desiccants can be found in Table 3.usually added when the viscosity is high, grinding dispersion phase plus 1/3 to 1/2, deployment phase plus 1/2 to 2/3.
3.3 The problem to be paid attention to in the application
(1) In different production processes, the use of desiccant is also different, construction methods are different, dosage is not the same. Roll coating to bring into the air, bubbles increase, should be appropriate to add more desiccant.
(2) compatible issues. If the deboulant and the system of poor compatibness, there will be turbidity, floating, and even color changes, inter-layer adhesion will also be affected.
(3) stir well before use. Because deboulants are several mixtures of different properties and effects, they are easy to stratide.
(4) temperature. In the synthetic stage of resin, high temperature debobbling agent should be used, otherwise there will be de-foaming agent milk breaking, loss of de-foaming effect.
of the (5) pH. In a strong acid and alkali system, if silicone desiccant is used, severe milk breakage is produced.
(6) try to choose the products of large factories, large factories have their own production centers and technical support, batch stability is guaranteed.
(7) consider the negative effects. 4 Advances in the study of defoulants
4.1 Development of defoiling agents
the first generation of domestic products are high-level fatty alcohols, animal and vegetable oils, mineral oils, etc.; The fourth generation of products developed in recent years are mineral oils and silicones, esters, alamides, alcohols, polyethers and other organic matter and inorganic compounds.
4.2 Advances in the study of defystants
4.2.1 Mineral Oils
Are the main studies of mineral oils and hydrophobic particles at high temperatures, so that hydrophobic particles are dispersed, through "secondary aggregation" and "one aggregation", and then add emulsified agents at lower temperatures. Ichi Yueqin and other raw materials such as mineral oil, fatty acidamide, fatty acid metal soap, de-foaming aids, white carbon black and emulsifying agent to prepare a mineral oil de-foaming agent. Among them, fatty acid acetamide, fatty acid metal soap and white carbon black as debobbling substances, by changing the mineral oil in a variety of de-foaming substances mixing methods, so that the de-foaming properties and stability of deboist can be improved. This mineral oil desostage agent in coatings, paper and other industries have a good application prospects.
, etc. to add mineral oil, vegetable oil to silicon dioxide, alkyl silicon oil mixture to prepare a mineral oil defoiling agent. In order to increase the solubility with mineral oil, the length of the carbon chain of alkyl silicone oil needs to be controlled. The research shows that m (vegetable oil and its derivatives) m (mineral oil) is (7:4) to (6:1), the deflegation properties and stability of defystant are better, and the defects such as coating depression, shrink hole and edge shrink can be improved. Levig and so on will be stingrate or modified statrate, emulsifying agent white carbon black added to mineral oil, heating and stirring heating to the system is basically transparent, insulation of about 1.5 h; In order to ensure that mineral oil desablants have good dispersion and deboisting effect, it is necessary to select suitable stingrate and modified stingrate varieties through experiments, this new water-based mineral oil desolation agent has excellent performance, and is safe, environment-friendly and simple manufacturing process. Deblistering performance in a variety of water-based coatings have a very good performance, but also large-scale production. At present, the market share of mineral oil deblisters is larger, the highest cost-effective, but mainly in high PVC primers, flat light and semi-light systems, and deboping and breaking effect is not as good as polyether and silicone desulbants. Adding alkyl silicone oil or silica to make changes to improve its defocage performance and enhance stability, and improving the effect on film gloss is the research direction of such defoiling agents.
4.2.2 Polyether
polyether is used as a desmotic agent is the use of its solubility and temperature relationship characteristics, but in practice, the debobbling temperature change range is large, showing insufficient debogation capacity, so it should be modified. It was modified by hydroxyl reaction on the structure of the active group and polyether. Modified substances are stingric acid, laurel acid, fatty acids, coupled agents and so on. Zhang Xuezhen and other polyether-modified polysilioxane compound defoules made from emulsifying agents and polyether-modified polysilicae compounding in a specific proportion. Compared with domestic silicone emulsion deblister deblistering time shortened by nearly 10 s, can be widely used in biomedicine, food fermentation, coatings, industrial cleaning, petrochemical and other aspects, the application prospects are broad. Jiang Xiaoqing and others first synthesized hydrogen-containing silicone oil through molecular design in the presence of the catalyst, m (hydrophobic polyether): m (hydrophobic polyether) s 1:2.5 when the synthesis of ole propyl polyether, and finally emulsified polyether modified silicone with emulsifying agent, when the HLB value is 11.5, emulsifying agent dosage of 15% when the stable emulsion-type de-foaming agent. Zhao Jie and others first used ole propyl polyether and hydrogen-containing end polysilicaene in the platinum complex catalytic effect of the addition of polyether modified polysilioxane, and then by mechanical emulsification of polyether modified polysilicae, Span-Twen composite emulsion agent and homemade silicone cream mixed emulsification to prepare a polyether modified silicone defogant. The results show that when the mass score of silica and polyether-modified polysilicon is 6% and the mass score of Span-Tween composite emulsizer is 3%, the defog inhibition, centrifugal stability, water dispersion, and heat resistance stability of polyether-modified silicone defoiling agent are better. In different temperature systems have a better application effect.
Hu Wei at a temperature of 60 degrees C, when m (high content hydrogen silica oil) m (octetyl cyclosiloxane) - 6:94; Then, at 110 degrees C, the acid is used as a catalyst and an end hydroxyl polyether to synthesize a Si-O-C type desmoulizer. The results show that when the catalyst dosage is 0.4%; m (polyether) m (hydrogen-containing silicone oil) is 1.5:1, the polyether is successfully connected to the silicone chain segment, and the resulting desiccant is well dispersed in the water phase system, and the desumbant emulsion has stable performance, the water dispersion performance is good, and the desulbation performance is good.
first synthesized hydrogen-containing silicone oil of a specific molecular structure. Then, at a temperature of 130 degrees C, a polyether-modified silicone de-foaming agent is prepared by the addition of silicone hydrogen with homemade hydrosilicon oil and acrylic polyether. By the structural standard of desiccant, it is shown that when the reaction n (C) : n (Si-H) is 1:1, and the mass score of the catalyst is 0.002%, the resulting polyether-modified silicone desulbant has a very prominent de-foaming performance in the water-based emulsion-type coating.
, polyether desosterizers are mainly used in systems with higher compatible requirements, with weak debug capacity and less market share. The re-allocation of polyether chain segment, the re-allocation of silicon desmoulizer to improve debogation ability, broaden its application range, oil-soluble or water-soluble polyether and silicone-containing polyether compounding technology is the research direction of this type of desmotication agent.
4.2.3 Silicone class
Due to the strong surface activity of silicone-type desiccants, good thermal stability, strong de-foaming capacity, Si-C chain and Si-O chain binding stability, chemical stability, silicone-type desmoticants at home and abroad more research. Huang Cheng and other silicone paste and polyether modified silicone oil made of hydrophobic gas phase silica and dimethyl silicone oil as the main components, Span-60, Twen-60 as emulsion agent, the preparation of high-efficiency emulsion-type silicone desiccant. The anti-foaming and deblication properties and stability of the prepared silicone desiccant are good, and the application range is wide.
Denkov N. D. and so on added small white carbon black particles to the dmethyl silicone oil, chemically treated silicone-type de-foaming agent de-foaming, foam suppression effect is obvious. Goldschm. ift. AG has developed a variety of polyether modified silicone deblisters for water-based systems with good compatible and excellent de-foaming performance. The polyether-modified silicone oil (PMS) is synthesized from hydrogen-containing silicone oil and end-ene propylene polyether F6 as the catalyst. It is compounded with methyl silicone oil, white carbon black, etc., and is made with a narrow distribution range, small particle size, and spout particle desculator. The emulsion in different pH (2 to 13), high temperature conditions do not drift oil, do not layer, but also to maintain a strong foaming activity, fast de-foaming characteristics.
Sunjiang and other catalysts such as chloropropione with acrylic polyether and hydrosilicon oil (PHMS), the reaction obtained polyether modified silicone oil (PMS), and then with emulsified dimethyl silicone oil (PDMS) to prepare silicone desolation agent emulsion. The results show that the amount of emulsifying agent is 5% oil, HLB value is 8, m (polyether): m (PHMS) - 0.56, the silicone desulbant can still maintain excellent de-foaming performance under harsh conditions such as strong alkali and high temperature. Yellow, etc. with gas phase white carbon black and with 580 mPa . sdimethyl silicone oil (mass ratio of 1:12.5) is made into silicone paste at a temperature of 150 degrees C, and a new type of silicone desolant is produced by adding Tween 80-Span 80 composite emulsizer, viscosity methyl silicone oil, polyethylene alcohol and water (m (water) m (polyethylene alcohol) The drop-plus temperature is controlled at 45 degrees C, the HLB value of the compound emulsizer is 10, the reaction time is about 1 h, the de-foaming effect of the silicone desiccant is significant, the blistering time is 253 to 312 s, and the de-bubble time is 26 to 30 s.
Silicone-type desiccant surface pressure is very low, de-foaming and anti-foaming ability is excellent, the gloss of the coating film has a small impact, but when used at the wrong time, will produce poor re-coatability, coating film shrink holes and other ills. Adjusting the silicone composition to ensure deblistering performance while reducing film defects and re-painting obstacles, improving compatible and expanding the application performance in different systems, and re-matching with other types of desiccants are the development directions of this type of deblister. 5 Conclusions
pairs.