Research on the coating of The Water-free High Temperature Original Coating smudgy of B1B2-free medium-painting process

With the rapid development of China's national economy, the rapid development of the automobile industry, in 2015 China's total automobile production of more than 24.5 million vehicles, a record high, for seven consecutive years in the world's firstThe development of the automobile industry directly pulls the market demand of automotive coatings, automotive coatings are currently the fastest growing coatings, the use of the second largest after architectural coatingsAutomotive coatings include original paints, auxiliary coatings and automotive repair paintsAutomotive coatings are also the most demanding paint varieties, so automotive coatings often represent the highest level of contemporary coating industry developmentTraditional automotive coatings mainly solvent-based coatings, VOC emissions in 120g/
m
3
, of which, due to the low metal flash paint solid content, its VOC emissions accounted for 66% of the total amount of paint, reached 230g/
m
300
, which not only waste resources and pollution of the environment, while there are fire safety hazardsthe wet GB24409-2009 "The Limit of Harmful Substances in Automotive Coatings" on June 1, 2010 accelerated the hydraization process of automotive coatingswater-based coatings have become the mainstream direction of modern coating industry because of their low VOC content and its energy savingsin the past two years, the state environmental protection department and local governments have issued a number of relevant laws and regulations on environmental protection strictly require the use of oil-based paint, promote water-based paintAnd the vehicle coating plant is also facing the dilemma of oil-to-water, especially in the current domestic new automotive coating plant must require water-based coating line, so the domestic car water-based coating line has accounted for 40%, is expected to soon surpass the oil-based coating line, become the main coating process of the original automobile factoryAnd domestic water-based automotive coating enterprises without confusion in the paint development and coating technology and foreign paint factories such as BASF, PPG, DuPont, Libang, Hunan Kansai, etcthere is still a certain gap, the vast majority of water-based original high-temperature coatings are monopolized by foreign-funded enterprises automotive original coating from the beginning of the oily 3C2B process, oily 3C1B process, water-based 3C2B (water-based coating and water-based primer paint) , B1B2-free medium coating process evolution, automotive original coating in China has been rapid development, this paper is mainly for B1B2 free coating process coating in-depth research and analysis, and put forward scientific effective solutions and solutions 1 test part
1.1 Main raw materials
water-based acrylic resin A (Covestro); water-based acrylic resin B (DIC); polyurethane dispersion (Coestin); water-based polyester A (co-production); water-based polyester B (DIC); Dow); thickener B (Hemmings); thickener C (BASF); solvent-assisted A, solvent-assisted B, solvent-assisted C; amino A (BASF); amino B (Inrex); amino C (Zhanxin); white pulp (self-contained); substrate wetting agent (BYK), etc 1.2 Main Test Instruments
Stirring Sand Disperser, Oven, Paint Diapanel, BYK Glosser, BYK Orange Peel Instrument, Bole Fly number Adhesive Viscometer, METTLER PRECISION ELECTRONICS, SATA JET 5000HVLP GUN, ETC 1.3 the main frame of the construction because it is a new water-based project, although our company in the water-based car repair paint has mature products and technical reserves, but for B1B2 exemption process water-based high temperature original paint is still relatively unfamiliar, so the main frame is constructed first First screening the main resin, the preparation of water-based high temperature white paint, formula such as table 1 table 1 main resin screening process requirements: according to the above formula, in the case of stirring in turn to add resin, white pulp, amine and blend, substrate wetting agent, solvent, thickener, ammonia resin, and finally with water to adjust viscosity 1.3.1 B1B2 free of medium-painting construction process B1B2 non-medium coating construction parameters: spray viscosity control in 30 to 50s, film thickness control in BC1 film thickness 15 to 25 m, BC2 film thickness 8 to 20 m, spray room temperature control at 23 to 2 degrees C, relative humidity control at 50% to 80%, Flash dry 3min between BC1 and BC2, wet and wet spray, BC2 spray after flash drying 5min, into 80 c x 5min for pre-baking, then spray edifiers, baking conditions: 140 degrees C x 25min, film thickness 35-40 m 1.3.2 Appearance Test Table 2 Appearance Test Results
From Table 2 data, the higher the CF value, the best overall appearance, the best formula (3), the higher the DOI value, the best plumpness, the best formula (3), so the polyurethane system is wet Weting process is more suitable, and the formula (4), formula (5) are serious bite phenomenon, indicating that the polyester system in the wet wet wet inge process is poor, the formula (1), formula (2) appearance effect is moderate, after adjusting the formula can also be used for wet wetting process From the dryness point of view, the fast-drying formula, in the appearance of the final varnish will appear pinhole phenomenon, and slow drying formula does not wear in the phenomenon, indicating that drying too fast will cause the B1B2 layer of moisture can not be completely run off under pre-baked, so the reforest fast-drying and slow-drying resin with the use The particle problem still needs to continue to find the cause 1.4 amino resin screening 1.4.1 amino resin comparison
due to impact resistance and small particles on the screening comparison, the first consideration from the filtering comparison, formula such as table 3 table 3 amino resin comparison paint process: according to the above formula, in the case of stirring in turn added resin, white pulp, amine and agent, substrate moisturizer, solvent, thickening water, ammonia, ammonia, finally 1.4.2 appearance performance detection table 4 ammonia contrast appearance performance test
from table 4 data can be seen, after mixing resin, the appearance effect has improved, impact, adhesion can to meet the performance requirements, and from the paint film appearance and fault, the formula (7) than the formula (6), (8) have a greater improvement, But still did not achieve the best desired results, through observation found that after B1B2 pre-baking primer paint has appeared a slight contraction and small particles, so the root of the problem lies in the primer paint table dry too fast, after pre-baking there is a contraction and tweezer phenomenon, the next step plan from the solvent to adjust the amino resin selected amino resin B 1.5 solvent adjustment
1.5.1 solvent adjustment selected three different boiling point sashimi, help solvent A boiling point at 80 degrees C-100 degrees C, solvent B boiling point at 110 degrees C-130 degrees C, help solvent C boiling point at 170 degrees C-19 0 degrees C, testing the effect of solvent-assisted solvent on B1B2, the formula as shown in Table 5
Table 5 solvent formula adjustment paint process: according to the above formula, in the case of stirring in turn added resin, white pulp, amine and agent, substrate moisturizer, solvent-assisted solvent, thickener, ammonia resin, and finally with water to adjust viscosity 1.5.2 appearance performance detection Table 6 helps solvent situ compared to appearance performance detection can be obtained from Table 6 data, by adjusting the volatilization speed of the auxiliary solvent, the solvent boiling point at 110 Degrees C-130 degrees C can improve the B1B2 process of tweezers (e.g formula (10)), when assisted in the performance of the solvent Solvent volatilization speed in 170 degrees C-190 degrees C, because the pre-baking conditions are only 80 degrees C x 5min, time and temperature is not enough to make B1B2 moisture and solvent-assisted volatilization, so resulting in a decrease in gloss, so the rate of solvent volatilization should be controlled in a range similar to the pre-baking temperature 2 Results and Discussion 1) From the main resin, polyurethane performance is obviously better than acrylic and polyester system, but single-component polyurethane due to its self-drying, need to be combined with acrylic system to adjust the overall resin performance 2) in the selection of amino resin, there are methyl etherization, hexameadeation, high aureus and other resin types, relatively high ether compatibility is better, there will be no shrinkage and other problems, but amino under pre-baking and the main resin and solvent volatility has a certain impact, need to comprehensively balance the selection of suitable amino resin 3) in the choice of solvent, volatile solvent will affect the appearance of the paint film, resulting in the paint film due to the table dry too fast and block the system of solvent and moisture volatilization resulting in the appearance of small tweezer particles, adjust ingress stoic ratio and type is the key factor to solve the paint film particles 3 conclusion the use of polyurethane and acrylic system development of the B1B2 process water-based high temperature original paint, can achieve the appearance of oily 3C2B effect, its luster, plumpness, orange peel, impact resistance, adhesion, appearance, etc have met the customer's use requirements, and meet customer construction process requirements, to meet the use of on-line spray requirements Source of this article: "The 17th Annual Conference on Environmental Protection Automotive Coatings and Coatings" paper collection
author: Li Bowen (Yatu Gao New Materials Co., Ltd.)