Optimization of Production Process of Polyester for Powder Coatings

Abstract:
Through the study of polyester feeding process, analysis in the polyester feeding process, the operation of the site will have a significant impact on the possible pollution of polyester, through the optimization of the operation steps in the polyester feeding process, not only to ensure that the resin feeding line is cleaned, there can be a reduction in the operation process cleaning pipeline time loss.
powder coating is a 100% solid coating in powder form, which is the biggest difference between general solvent-based and water-based coatings is that it does not use solvents or water as a dispersion medium. Therefore, powder coatings spilled in the coating process can also be recycled, and in the coating process without solvent evaporation, production and construction safety, can achieve coating automation, improve production efficiency, and facilitate transportation, storage, in line with the internationally recognized "4E" law: economical, environmental, efficient (Effectiveness) and performance excellence (Excellence), thus becoming a rapid development of coating varieties
China
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01
Problem Statement
Powder coating is composed of film resin, additives, pigments, fillers and other mixtures, crushing, screening, wherein film resin is the main component of the coating, determines the basic properties of the coating, so the performance of the resin is particularly critical. It is important to ensure consistency in the resin composition during the resin production process so that powder coatings manufactured in accordance with the powder coating formulation can have the desired performance. Due to the different resin formulation design, some raw materials of resin will be another brand of resin normal use of serious interference, easy to lead to the preparation of powder coatings will appear orange peel, pinholes and other adverse effects. This is what we usually call product pollution.
in the resin production process, product pollution mainly occurs in the later stage of the process, that is, the product production stage. After the previous batch of resin materialization, a small amount of resin left in the production line will be cured in the production line with the decrease in temperature, after melting by the resin of the current batch, mixed in the batch of products and product contamination problems occur.
In order to eliminate this impact, the factory in the product before the material, the lowering system will be cleaned operation, due to the cleaning of the pipeline operation method is not uniform, there will be different operators in the operation, cleaning standards are different, resulting in the cleaning time is not First, there is a time loss caused by cleaning, for this reason, it is necessary to develop a set of practical under-cleaning operation process, in order to unify the operation of the operator on the bottom cleaning, not only to ensure that the product is not contaminated by the previous batch of risk, but also to reduce the time loss caused by cleaning.
02
Resin outing process analysis
as shown in Figure 1, high-temperature molten resin flow through the pipeline to the resin dispenser, through the resin dispenser slowly flow to the cooling steel belt, with the rotation of the steel belt, the resin in the steel belt presented as a certain thickness of the resin thin layer, in the cooling effect of cooling water, when the resin to the crusher, the resin has become a glass-like substance, crushed by the crusher into particles.
when the product is contaminated, the most obvious manifestation is that the gel time will be very different.
is also the main reason for the appearance of orange peel, pinhole, leveling is not good. Therefore, when cleaning rules are made, the gel time of resin is an important test indicator, the test method is as follows.
1) sieve a certain amount of resin powder;
2) claim 180 mg of resin powder (deviation ±1 mg) on the weighing plate;
3) after the resin weight is stabilized, weighing a certain amount of curing agent (deviation±1 mg) on the same weighing plate to make the total weight of the resin and curing agent 200 mg;
4) Carefully pour the mixture into the measuring disc set at a temperature of 200 degrees C and start to time it with a stopwatch;
5) after melting the resin, mix the mixture evenly with a mixing rod in a circle, paying attention to the contact between the mixing rod and the measuring disc;
6) At this temperature, the mixture of resin and curing agent begins to react to form a polymer with a higher molecular weight, its viscosity begins to rise, stirring in the center of the measuring disc when the mixture is attached upward along the mixing rod
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03
Determine the resin cleaning volume scheme
to simplify the operating requirements, and ensure that the risk of product contamination is minimized, choose the resin additives the two products with the greatest difference for testing, that is, the previous batch of products glued for a short time, the longer time for the adhesion of the 31st batch of products. Before the discharge, start the discharge equipment, respectively, so that the resin fills the resin dispenser, stop the resin transfer pump at the front of the resin dispenser, and then drain the resin from the dispenser to the cooling steel belt, which is broken into a package. Repeat this operation twice, and the cleaning resin sampling, test the gel time of the resin, taking into account the cleaning resin broken first into the silo storage, and the broken resin particles in the transport process due to the collision between each other will produce fine powder, the front cleaning part of the resin particles and fine powder may stick to the silo wall, in the packaging process mixed with the current packaging batch of products after packaging, may continue to affect the performance of the product, so the results of the sample test.
From table 1 collation time data can be seen, cleaning a resin dispenser, its cleaning resin gel time is close to the factory shipment inspection of the 10t product gel time, that is, with the batch of resin filled with a resin dispenser can ensure that the previous batch of residual resin was cleaned, so the second and third cleaning time is the loss of process time. In order to reduce such unnecessary time loss, a resin cleaning method is defined.the
is filled once, i.e. the resin is filled with a resin dispenser once with the batch of material, and the
is all wrapped out, i.e. the resin filled with the resin dispenser is cooled by the steel strip and passed through the storage silo, all of which are packed out and effectively isolated from the resin behind it.
Leave 10 packs, leave the first 10 packs of normal feeding product packaging as a re-product, and the cleaning requirements into the factory operating instructions "resin out of the operating instructions", and communicate to all operators, so that they fully understand and implement this cleaning requirements. Through the implementation of this method, pollution between products has been effectively prevented.
/Cao Yinbo 1,2
1. Shanghai University School of Environmental and Chemical Engineering
2. Dixing Resin (Kunshan) Co., Ltd.