Application of coating equipment to improve the drying bottleneck of water-based wood coatings

0 Foreword
the drying of water-based coatings and water has a close relationship, if "water" can not be rapidly volatile or "water" not volatile completely on the water-based paint, in addition to affecting the materiality of the film, its production line must be extended, resulting in an increase in non-performing products, how to make water rapid volatile will be the key to promote water-based coatings. The drying of water-based wood coating is greatly affected by temperature, humidity (especially humidity), if the temperature and humidity of the coating environment change too much and the long-term unstable environment, its drying into a film is also unstable, production efficiency can not be controlled, the planned production of furniture factory is a major bottleneck. Water-based wood coating can be sprayed with natural drying, hot air or infrared drying, microwave drying, dehumidification drying, etc. , take representative drying methods (natural drying, hot air drying, microwave drying) to make a comparison .
1 The original
(1) conventional drying (natural drying and hot air drying) is the air as a drying medium, in a reflow mode (heating can increase the speed of the flow) to make the moisture volatile and dry.
(2) microwave is a kind of high-frequency electromagnetic wave, in the spectrum of electromagnetic wave it is between ultra-short wave and infrared, microwave penetration is very large, because of the microwave exposure makes the water molecules inside the coating film high-speed motion, generating energy to accelerate the evaporation of water.
(3) natural drying and hot air drying due to air conflow, so the coating surface first dry, the internal water is more difficult to wave out, and microwave penetration force can make the internal rapid drying.
2 Test Part
The purpose of the test is to compare the differences between natural drying, traditional hot air drying and microwave drying, and to test them at different temperatures, humidity, viscosity and solid content.
2.1 Test with different pre-time (time after spraying to time to enter the oven)
conditions: temperature 30 degrees C, humidity 60%, coating volume 80 g/m2, test results see Table 1.
: 1) Hot air drying time is the pre-time, the baking time, the cooling time after baking. 2) Microwave time is the pre-time, microwave time, and post-microwave cooling time. 3) Microwave time is microwave 1 min , stop 1 min , microwave 1 min , stop min , microwave 1 min, total 5 min.
visible by Table 1, the pre-time has little effect on drying (the subsequent tests all use a 15 min pre-time).
2.2 Tested in 4 environments of high temperature and humidity, high temperature and low humidity, low temperature and humidity (see Table 2)
Table 2 Test results in 4 environments of high temperature and humidity, high temperature, low humidity, low temperature and humidity
Note: 1) Hot air drying time (15 min) and 50 degrees C×30 min roasting and 5 min cooling, a total of 50 min. 2) Microwave drying time is pre-time (15min) plus microwave 1 min, stop 1 min, microwave 1 min, stop 1 min, microwave 1 min (total 5 min) plus cooldown time 5 min, total 25 min. 3) The natural drying time is sprayed to the polishable time. 4) Coating conditions are: viscosity Iwata 2 cup 20 s, coating volume 80 g/m2.
can be seen from Table 2:
(1) natural drying is greatly affected by ambient temperature and humidity.
(2) baking as a fixed temperature, microwave is also a fixed time, affected by external temperature and humidity is very small.
(3) due to hot air drying and microwave drying time is more fixed, furniture factory can effectively control production and stable quality.
(4) microwave drying is more effective than hot air drying and natural drying.
2.3 Microwave drying with the same solid content (M-30%), different viscosity (different additions of thickeners) (see Table 3)
Note: 1) spraying volume 80 g/m2, temperature 30 degrees C, humidity 76%. 2) Drying conditions: 15 min in the pre-time and 5 min in the post-microwave cooling time. 3) Microwave interval is 1 min per microwave stop 1 min microwave. A total of 5 min.
is visible from Table 3, microwave drying is not affected by viscosity.
2.4 Microwave drying with different solid contents (different water content) of the same viscosity (Iwata 2 s) (see Table 4)
Note: 1) Spraying capacity of 80 g/m2, temperature of 31 degrees C, humidity 58%. 2) The front is 15 min. 3) Microwave 3 min first, dry model and then add microwave time.
can be seen by Table 4, microwave time is related to the moisture content of water-based coatings, the more moisture requires microwave time.
2.5 microwave drying with different viscosity and different solid content

visible by Table 6, the speed of wood dewatering to judge, microwave is 3min, hot air is 1 h×50 degrees C, the efficiency varies a lot.
2.7 Physical performance comparison
same primer, same spray amount, same coating process (same as 2 primers 2 finishes), the same coating (with Cherry sheet plank) only drying method is different, coating conditions temperature of 29 degrees C, humidity 68%, primer spray volume 80 g/m2, paint spray volume 60 g/m2. The physical comparison of the different drying methods can be found in Table 7.
by table 7 comparison, microwave drying is slightly better.
3 Analysis and discussion
(1) based on the internal space of 1 m3 (length and width of 1 m each), hot air oven power of 7kVA (12.124 kW), while microwave oven for 1 kW lamp 5 tubes a total of 5 kW, and then calculate the baking time, microwave power consumption than traditional oven much less.
(2) in the drying time and production variables control, the use of baking and microwave have a positive effect, especially microwave drying can shorten the waiting time and reduce space.
(3) the effects of microwaves on human health need to be assessed.
(4) above the test only explores the drying of water-based wood coatings, and whether microwave drying has side effects on coatings or homes requires further testing.
4 Conclusion
Comprehensive test, microwave drying has the latest, energy-saving function, can reduce costs and personnel, but also can reduce plant space, water-based wood and coating has a very high practicality, worthy of joint efforts to promote, to promote water-based wood coating can make progress in the market as soon as possible.