High-solid and low-viscosity coating process research and application implementation

Abstract
: At present, in general engineering machinery coatings, epoxy resin coatings supporting polyurethane coatings are mainstream products, mostly solvent-based coatings, construction VOC is mostly in 500 to 600 g/L, serious environmental pollution, reducing VOC emissions has become an urgent need for market and environmental governance. Compared with powder coatings, high solids and other low VOC environmental protection coatings, high-solid and low-stick coating processes are easier to implement. High-solid low-stick coating construction VOC is generally in 300 to 400 g/L

. In this paper, the performance quality of high-solid and low-stick coatings, site process feasibility, construction costs and environmental protection are verified and analyzed, compared with the use of ordinary solvent-based coatings. The results show that the comprehensive performance of high-solid and low-stick coating is excellent, which can meet the current green coating requirements of the construction machinery industry, and can be applied in the construction machinery industry.
keywords
: high-solid low-stick coatings, chemical and chemical properties, process verification, construction VOC
foreword
an important way to reduce the voC emissions of coatings is to develop environmentally friendly coatings, such as powder coatings, water-based coatings, high solids coatings. Powder coating VOC emissions are basically zero, but the pre-treatment requirements are high, drying energy consumption is high, water-based paint VOC emissions are greatly reduced, but the construction environment is demanding, coating costs are high, coating line transformation costs are high, high solid sub-coats belong to solvent-based coatings, can reduce the construction VOC, but its construction viscosity is high, high-pressure mixture or high-pressure airless equipment spraying.
The high-solid low-adhesive coating investigated in this paper is still solvent-based paint, paint construction solids significantly increased but its construction viscosity did not increase, the proportion of thinner addition decreased, from the source to reduce the VOC content of the coating, equipment and construction environment and solvent-based coatings consistent, compared to water-based coatings and high solid coatings, high-solid and low-adhesive coating process is easier to implement, coating line does not need to be modified, coating equipment does not need to be updated.
1 Introduction to high-solid low-adhesive coatings
Traditional solvent-based coatings contain more than 50% organic solvents, which are released into the air during use to pollute the environment and endanger human health. High-solid low-adhesive coatings by reducing the relative molecular quality of the main film-forming substances, selecting low oil-absorbing pigments, supplemented by appropriate active thinners, improve the construction solid content of coating products, greatly reduce the content of organic volatiles in the coating system, save curing energy consumption, while two components Epoxy high-solidity low-stick coatings with excellent anti-corrosion performance, two-group polyurethane high-solidified low-stick coatings with good appearance fullness, good light preservation, color preservation and weather resistance, and 2 kinds of coatings supporting excellent construction characteristics, has become an important variety of high-grade coatings.
hydroxy resin is the main component and performance of the two-component polyurethane coating, in order to prepare high-solid acrylic-type coating with excellent performance, we must first strictly control the relative molecular quality and relative molecular mass distribution of acrylic film. The hydroxyl resin selected for polyurethane coating in this paper is a chain transfer agent with peroxide butyl as free radical trigger and -based ethanol as a chain transfer agent, and the synthetic high solid score and low viscosity hydroxypropyl acrylic resin have a viscosity of less than 1,000mPa.s and a solid score of up to 65% to 70%. The resin has a low relative molecular mass and a very narrow relative molecular mass distribution. When the relative molecular mass is small, there must be a narrow distribution of relative molecular mass and sufficient hydroxylate monosomes to participate in polymerization, in order to ensure that each resin molecule has more than 2 hydroxyl, so as not to affect the quality of the coating film.
epoxy resin is an organic polymer compound containing 2 or more epoxy groups in a molecule and is the main component of two-component epoxy primer. Epoxy molecular structure contains benzene ring, ether bond, hydroxyl, epoxy group and other function groups, with good heat resistance, weather resistance, corrosion resistance and other properties. The epoxy resin selected in this paper reduces its solubility in solvents by introducing the structure of polycarbonate phenol, increasing its solubility in solvents, thus avoiding the heavy use of strong solvents. The relative molecular mass and viscosity of the resin are controlled by controlling the production process, the ratio of biphenol A to epoxy propane, the type and dosing of the catalyst, the dosing and form of alkali, the reaction temperature, time, feeding method, the reaction solvent, the water content in the reaction system and pH.
2 High-solid low-adhesive coating application research
and physical and chemical performance testing
This paper investigates the industry's high-solid low-adhesive coating application status, the brand of high-solid content coatings for physical and chemical performance testing, and with ordinary solvent-based coatings for comparison.
2.1
Basic parameters of high-solid low-adhesive coatings
compared with high-solid low-adhesive coatings and solvent-based coatings in use in terms of parameters such as coating viscosity, thinner addition during construction, solid content, VOC content during construction, etc., the results are shown in Table 1.
1 Basic performance of high-solid low-adhesive coatings
2.2
performance test
2.2.1
physical performance test
physical performance test plate selection thickness 0.2 to 0 .3 mm, 50 mm ×120 mm horse port iron plate, in accordance with GB/T 9271-2008 "color paint and varnish standard test plate" provisions for grinding, and inspection and cleaning. Then according to GB/T 1727-1992 "paint film general preparation method" to prepare a variety of coatings.
color of the paint film is determined visually. Paint film gloss according to GB /T9754-2007 "color paint and varnish without metallic pigments color paint film 20, 60 and 85 degrees mirror gloss determination" using gloss measurement, paint 60 degrees gloss less than 90, 20 degrees gloss less than 80 was judged to be unqualified, 3 test sample board with 2 test results consistent as the final basis.
paint film hardness according to GB /T 6739-2006 "color paint and varnish pencil method to determine the hardness of paint film" using Chinese brand drawing pencil measurement, primer paint film hardness is less than HB, paint film hardness is less than H, then determined to be unqualified, 3 test samples with 2 test results consistent as the final basis for the final decision.
paint film flexibility according to GB /T 1731-1993 "paint film flexibility determination method" using flexibility meter determination, the bottom, paint film flexibility greater than 1 mm is determined to be unqualified, 3 test samples with 2 pieces of consistent test results as the final basis for the final determination.
lacquer film adhesion according to GB /T 1720-1979 "paint film adhesion determination method" using adhesion measuring instrument determination, the base, paint film adhesion greater than 1 level is determined to be unqualified, 3 test samples with 2 pieces of consistent test results as the final basis for the final determination.
paint film impact resistance according to GB /T 1732-1993 "paint film impact resistance determination method" using impact tester determination, the bottom, paint film impact resistance of less than 50 cm was determined to be unqualified, 3 test samples with 2 pieces of consistent test results as the final basis for the final determination.
paint gloss item is the detection of composite coating, primer (50±5) sm plus finish (50±5) sm, each other type of paint to be tested single coating Membrane thickness (23±3) sm, each performance test produced 4 test plates, of which 3 were put into testing, 1 piece was used as a sample, the post-test results were used as a comparative test when the dispute adversity, and were numbered and marked separately.
2.2.2
Chemical Performance Test
Chemical Performance Test Plate uses a low carbon thin steel plate blast standard plate with a thickness of 2 to 4 mm and a size of 70 mm×150 mm.
primer salt mist resistance test method according to GB/T 1771-2007 "color paint and varnish resistance to neutral salt spray performance determination" to test, according to ISO 4628-1-5:2003 to judge, to observe the damage to the surface of the test plate, such as foaming, rust and the spread of rust from the line. According to GB/T1771-2007 neutral salt spray test method for testing, 2 mm outside the dash, if there is one of the phenomena of paint film foaming, rust or rust spread, then the test is not qualified, 3 test samples with 2 pieces of consistent test results as the final basis for the final determination. Each manufacturer to be tested primer single coating to make 4 test plates, film thickness (50±5) sm, of which 3 pieces into the test, 1 piece as a sample, the results of the later test when disputed as a comparative test, and respectively numbered mark.
paint resistance artificial aging detection method according to GB /T 1865-1997 "paint film resistance artificial aging measurement method" for testing, according to GB/T 1766-2008 "color paint and varnish coating aging rating method" to judge, check the color plate loss, color change, powdering, cracking and other phenomena. After the experiment, the paint film showed a chromic difference of >3. 0, loss of light >10%, or paint film powder cracking phenomenon is determined to be unqualified, 3 test samples with 2 pieces of consistent test results as the final basis for the final determination.
paint moisture-resistant heat performance according to GB/T 1740-2007 "paint film moisture-resistant heat measurement method" for testing, test continuous operation, the test plate vertical hanging on the shelf, the front of the test plate does not allow contact with each other Put the shelf into a pre-adjusted temperature, a certain humidity temperature control box, continuous test 48 h check once, 2 checks, every 72 h check once, after each inspection, the test board should change position. After the experiment, the paint film foaming, rusting, shedding, wrinkle phenomenon was judged to be unqualified, 3 test samples with 2 pieces of consistent test results as the final basis for the final determination.
paint resistance to artificial aging and moisture-resistant thermal performance testing, each manufacturer has its own matching primer (50±5) sm plus paint (50±5) m composite coating model, respectively, to make 4 test plates, of which 3 input testing, 1 piece as a sample, the results of the post-test as a comparative inspection, and respectively numbered mark.
2.3
Test Results
Physical performance of high-solid and low-stick coatings, salt spray resistance, aging resistance and heat resistance test results are shown in Tables 2 to 5. Based on the results of this comparative test, we can see: Table
2 Physical performance of high-solid low-stick coatings compared to test results Table 3 high-solid low-stick coating salt spray resistance test results
Table 4 high-solidity low-stick coatings Anti-aging performance comparison test results
Table 5 high-solid low-stick paint moisture-resistant heat performance comparison test results
(1) high-solid low-stick coating solid content (primer ≥75%, finish ≥ 6 5%) is higher than the solvent-based paint used (73% primer, 61% paint), viscosity (25 degrees C, ≤45 s) is also greatly reduced, especially the construction VOC content (primer≤380 g/L, finish ≤400 g/L) compared to solvent-based paint (primer≥587.2 g/L, finish ≥562. 3 g/L) by 30% to 45%.
(2) high-solidity low-stick coatings are basically equivalent to the physical properties of common solvent-based coatings in use.
(3) neutral salt spray resistance: in addition to D company products, other high-solid and low-stick primers can meet the current solvent-based primer salt spray resistance performance requirements (480 h, 2 mm outside the line of paint film without foaming, rust, shedding, wrinkle, rust spread).
(4) anti-aging performance: high-solid low-adhesive paint resistance to artificial accelerated aging performance can reach 1,200 h, color difference E≤3 (0 level no color change or 1 level very slight color change), loss of light ≤10% (0 level no loss of light or 1 level of very slight loss of light), and the present solvent-based paint aging performance is basically equivalent.
(5) moisture-resistant heat performance: high-solid and low-stick paint moisture-resistant heat performance can reach 800 h, paint film no foaming, rust, shedding, wrinkle phenomenon, and the existing solvent-based paint moisture-resistant heat performance is basically equivalent.
3 High-solid low-stick coating field process verification
3.1
experimental process
according to the parts coating process (throwing - cleaning - spray primer - leveling - primer drying - cooling - spray paint - leveling - paint drying - strong Cold) on-line spraying high-solid low-stick coating, large structural parts (Figure 1, Figure 2) offline, detection of the appearance of the paint film is not obvious hanging or orange peel phenomenon, in the premise of no obvious paint film defects under the premise of 24 h after detection of paint film gloss, film thickness, adhesion, hardness and so on. Among them, the thickness of the paint film, gloss inspection site is not less than 3. Paint film gloss measurement should be selected in a plane greater than 100 mm ×40 mm, so as to avoid uneven surface caused by leakage of light caused by measurement errors.
3.2
test results
en ambient temperature>10 degrees C, in accordance with the coating process, the workbench offline drying 1 h, observe the appearance of the paint film quality and drying conditions, after hanging 24 h to check the paint film gloss, average film thickness, adhesion, hardness, etc., the test results as shown in Table 6. Table
6 High-solid low-stick coating test work parts appearance quality test results
3.3
high-solid low-stick coating production trial operation analysis
ambient temperature≤10 degrees C, after 1 month of high-solid low-stick coating field test operation, found that high-solid low-stick coating drying temperature of the work parts below 60 degrees C, drying performance is worse than in the use of solvent-based coatings. Due to the high solidification and low viscosity coating construction quality content of up to 75%, its curing cross-link reaction requirements compared to conventional solvent-based epoxy primer, polyurethane finish is higher. Therefore, it is necessary to increase the drying temperature or extend the drying time to ensure the normal operation of the site.
high-solid low-stick paint dry slow, after spraying construction in the paint room, the paint attached to the ground grille stick, affecting the normal spraying of workers mobile construction work, grille cleaning workload labor intensity increased.
3.4
Process Verification Conclusion
In accordance with the parts coating process construction, spraying high-solid and low-stick coating, structural parts under the paint film drying situation is slightly worse, but paint film adhesion, gloss, hardness, appearance and other indicators and the current solvent-based paint equivalent.
because of the high construction solid content, according to the same construction method and beat, the average coating film thickness than the existing paint thickness of 10 to 15 m.
4 high-solid low-stick coating cost analysis
according to the paint construction quality solid content, construction density, comparative analysis of coating theory coating rate. According to the coating unit price and coating theory coating rate, the construction cost of coating unit area theory is calculated and analyzed. The comparative analysis of the theoretical cost of high-solid and low-stick coatings is shown in Table 7.
can be compared through cost analysis: compared to the company in the use of solvent-based coatings, water-based primers and high-solid low-stick primer unit area theory.