Knowledge of industrial cleaning agents

Knowledge of industrial cleaning agents

一、Current situation of domestic industrial cleaning industry：

　　The current cleaning methods in China are as follows: mechanical descaling, high-pressure water cleaning and chemical cleaning< br /> Chemical cleaning of general industrial equipment: for example, boilers, pipelines, petrochemical equipment, etc., acid, alkali and some active substances are usually used as cleaning agents. In this case, the judgment standard is usually based on the fact that people can't see dirt with the naked eye. In addition, such as the cleaning of surfaces of automobiles, trains, aircraft, ships, oil pipelines, oil transportation, oil storage tanks, equipment pipelines, boilers The same is true for the cleaning of central air conditioning, building walls, doors, windows and glass. For the maintenance and cleaning of such equipment, the general feature is that although the appearance is significantly improved and the basic performance of the equipment is improved and restored after cleaning, the long-term acid-base cleaning causes the metal loss of the equipment, shortens the service life of the equipment and affects the accuracy of the equipment or instruments; Acid base corrosion sealing system makes the equipment easy to leak; The discharge of waste liquid pollutes the environment; Construction personnel are easy to burn during construction; The operation procedure is complex. After pickling, it needs to be washed, neutralized and passivated, which makes the equipment cleaning time very long and affects the industrial safety production. The physical cleaning of industrial equipment usually uses physical methods such as ordinary water, high-pressure water, high-pressure air, brush, sand blasting and friction to complete the cleaning process. Many of these situations belong to manual operation, with high labor intensity, high risk and low technical content. It is basically a rough and low value-added labor. For cleaning with high requirements on cleaning speed, environmental protection, safety, efficiency and economy, we must comprehensively consider its feasibility from various factors. At present, there are no relevant technical products in China.
　　The cleaning equipment used in general industrial cleaning mainly include high-pressure water jet device, automatic car washing device, high-rise building exterior wall cleaning device, etc., and these cleaning have their own limitations in one way or another, and the effect is not very ideal. Precision industrial cleaning is directly related to product quality and performance. If the residual dirt is greater than the requirements, there will be bubbles, peeling, defects and other problems.
　　The cleaning of ultra-precision industrial equipment must be carried out in a super purified environment, requiring the use of ultra-high purity cleaning agent, DI water (deionized water) and advanced cleaning devices. Except for some simple equipment, at present, no enterprise in China can provide such technology and equipment, which basically depends on import, with great limitations, which greatly increases the investment.
　　At present, China's cleaning industry has a large number of enterprises and wide geographical distribution. In view of the requirements in the field of environmental protection, in 1997, there were more than 3200 enterprises consuming controlled substances and cleaning agents in China. In 1997, the consumption of ODS in this industry was 11504 tons, accounting for 16.4% of the country. As of August 1998, 23 projects in the cleaning industry had been approved by the multilateral fund, with a funding amount of US $8.5 million. Among them, 19 investment projects have a funding amount of US $7.8 million, which can eliminate 855 tons of cfcs-113 consumption (i.e. 685 tons of ODP). Elimination target: CTC will be completely eliminated in 2004, cfcs-113 will be completely eliminated in 2006 and TCA will be completely eliminated in 2010. With the further improvement of the requirements of the whole society for factors such as safety, environmental protection and efficiency, the demand for advanced cleaning methods and cleaning products such as safety, environmental protection, efficiency and convenience will be greatly increased.

二、Problems and contradictions faced by domestic industrial cleaning industry：

　　At present, there are many problems that need to be solved in China's cleaning industry. These problems focus on some contradictions and problems that can not be taken into account in the cleaning process. To solve these problems, we must analyze and study these problems and find better and comprehensive solutions. The following is an exploratory analysis of the problems existing in the cleaning industry in recent years: 1 The contradiction between the improvement of cleaning efficiency and the selection of cleaning methods< br /> At present, the cleaning efficiency of China's cleaning industry is generally not high compared with developed countries. To choose a method with high efficiency and simple and feasible method, we are faced with the problem of what method to clean and what cleaning agent to use. The cleaning with high efficiency and simple and feasible cleaning process has always been a problem we face. For example, chemical cleaning, which is widely used at present, has a fast cleaning speed, but its efficiency is not high. One is the treatment after cleaning, the second is the safety protection of personnel in the cleaning process, and the increasingly strict environmental protection requirements, the treatment and discharge of waste liquid after chemical cleaning. Environmental protection has become an important factor restricting cleaning behavior, which poses a severe challenge to our cleaning technology and process in the formulation of our cleaning scheme and the choice of cleaning agent.
　　At present, there is still no biodegradable high-performance biological cleaning agent in China. The general biological cleaning agent has low cleaning performance, high storage requirements, short storage time, difficult to survive in acidic environment, and low cleaning ability for stubborn dirt such as scale and rust. Although the environmental protection requirements of cleaning agents have been fully considered, the cleaning capacity is limited.
3、The cleaning speed of the cleaning agent conflicts with the urgency of starting the equipment.
　　General cleaning agents have limited cleaning speed and capacity, and their cleaning time is longer, which invisibly delays the normal start-up process of the equipment and affects production. Although intuitively, the cleaning cost is low, but in fact, the time is Extending, resulting in labor costs, post-cleaning processing costs, and production delay costs are greatly increased, and the price paid is far higher than the cost of using high-performance environmentally friendly cleaning agents. For example, the cleaning procedures of large-scale ethylene equipment are complicated, which is a large-scale system project. The slow speed of any link will affect the progress of the entire cleaning project.
4、The contradiction between chemical cleaning and biological cleaning.
　　At present, most of the domestic cleaning projects are concentrated in the petroleum, chemical, and electric power industries, and most of the cleaning in these industries uses chemical cleaning methods, because chemical cleaning has high cleaning efficiency and speed, but it cannot take into account post-cleaning treatment and environmental protection issues. , And biodegradable cleaning is a perfect consideration of such problems. In this way, a contradiction arises, that is, the advantages of chemical cleaning and biological cleaning cannot coexist. Moreover, we found that some of the top brands of cleaning agents also inevitably contain a certain amount of organic solvents ——Coal Tea, which is a strong carcinogen, and we must strictly avoid such substances. Environmental and personal injury. 5. The contradiction between the simplicity of the cleaning process and the safety of cleaning.
　　The cleaning process is a relatively complicated process. Different cleaning processes and different cleaning agents must be formulated for different types of equipment. In this process, the safety of the operator must be considered inevitably. For example, the pickling process must Considering that the operator is not burned by the acid liquid, and the high-pressure water jet cleaning should prevent the operator from being injured by the water jet, this requires complicated and strict cleaning protection, which brings a lot of trouble to the cleaning process. How to find a safe cleaning agent is our dream goal. In view of the above problems and contradictions, we must find a cleaning agent that is both high-speed, efficient, environmentally friendly, and safe, economical, and convenient to use. It has become an urgent requirement to solve these problems. With such a cleaning agent, we can even more High-speed, efficient, safe and environmentally friendly cleaning of our equipment can greatly improve the quality of our cleaning process. At present, such high-performance cleaning agents that can take into account all kinds of high requirements are still rare in the world, and developed countries such as Europe and the United States are also undergoing continuous development and updating.

三、 Selection of reference parameters for solvent cleaning agents
1、Good dissolving power and clearing ability.
2、It has a low surface tension and is easy to wet and penetrate the gaps on the surface of the workpiece.
3、The density is relatively large, it is easy to separate from the pollutants, and the solubility to water is low, there is a certain density difference with water, and it is easy to separate from water.
4、Compatibility is better.
5、Security is better. Not easy to burn, non-toxic, etc.
6、Environmental protection is better, and it is best to be easily biodegradable and free of animal accumulation.
7、The chemical stability is better.
8、The solvent used for gas phase cleaning has a relatively high vapor density and is easy to form a vapor layer between the condensation zone and the air. The boiling point is moderate, the latent heat of evaporation is relatively low, and it is easy to dry.
9、The cost performance is better, and the operation is simple and convenient.

四、Several key quality points of solvent-based cleaning agents
　　At present, there are many kinds of cleaning agents produced in China, but there is no uniform standard, only the relevant standards and test reports of various enterprises. The technical indicators of the cleaning agent include acidity, moisture content, toxicity, residual amount after volatilization, insulation, swelling to the material, corrosiveness to the material, flammability, and KB value. And so on, are different due to different objects of cleaning. But I think there are common important indicators, such as those introduced and discussed below.
1、 acidity
　　Any type of cleaning agent is a technical indicator that must be strictly controlled for pH. Especially for solvent-based cleaning agents, the acidity index is more important, because the workpieces to be cleaned are all finished products, and most of them are not treated. The quality of the cleaning agent directly affects the quality of the cleaned workpieces. Therefore, the acidity index represents the stability of the cleaning agent and the quality assurance of the cleaned workpiece. For example, cleaning agents such as fluorocarbons, chlorocarbons, brominated hydrocarbons, hydrocarbons and alcohols currently used in the market must strictly control acidity during the production process. At the same time, in order to prevent changes during storage and use, they must be delivered before leaving the factory. Various stabilizers and antioxidants are added to stabilize it to prevent decomposition during use and heating. Because the acidic substances such as HF, HCL and HBr decomposed by the above substances, they become acid when they encounter a small amount of water. After the acidity rises, it will not only affect the cleaned workpiece, cause the metal surface to lose luster and damage the components; and Under the long-term action of acidic medium, stainless steel equipment will also be rusted. Therefore, stabilizers must be added to the above cleaning agents. If the choice of stabilizer is not good or the amount added is not enough, the acidity of the cleaning agent will rise or produce oxidative decomposition during repeated heating and contact with the atmosphere, which will deteriorate the quality of the cleaning agent and cause corrosion of the workpiece. Usually the stabilizers or antioxidants added at the factory include the following types: phenols, alcohols and epoxy compounds, etc. The addition amount is generally within 0.05% to 5%. The acidity at the factory is controlled within 10ppm (0.001%). The acidity test is carried out in accordance with the provisions of GB4120.3, which is equivalent to the international standard ISO-1393, and adopts the acid-base titration method. Since many cleaning agents are not soluble in water, they cannot be titrated with lye. Instead, the water washing method is used to titrate the aqueous solution washed from the solvent cleaning agent. This method is more cumbersome. You can also use anhydrous ethanol lye method to directly titrate, because many cleaning agents are dissolved or partially dissolved in ethanol. This method is simple and reliable, and is convenient for workshop detection.
2、the remains
　　The non-volatile content in the cleaning agent directly affects the cleanliness of the cleaned workpiece. Since the workpiece to be cleaned is soaked in the cleaning solution and then allowed to dry naturally, the non-volatile matter in the cleaning solution may directly adhere to the workpiece. If it is an electronic component, it will affect its electrical performance, especially for microcircuit devices such as PCB boards. The number of ions attached to the board is measured in μg (NaCl μg/cm2) per square centimeter. The lower the better, it is generally controlled below 10ppm when leaving the factory. This is in accordance with the corporate standards for the production of single-solvent cleaning agents at home and abroad. The detection method is carried out in accordance with the regulations of GB6324.2—86. Similar to the method of ISO759—1981. A simple detection method is to drop a few drops of cleaning agent on the glass lens and let it evaporate naturally. By observing the residual traces on the lens, the non-volatile content of the cleaning agent can be roughly judged. Of course this is only a qualitative test
3、Moisture
　　 The water content of solvent cleaning agents is also a very important indicator. In principle, the less water the better, but mass production and use cannot be completely anhydrous, and each solvent has a certain water content. Some are completely miscible with water, such as lower alcohols, ketones and some ethers; some have a certain degree of saturated solubility at a certain temperature, such as hydrocarbons, fluorocarbons, chlorocarbons and bromine hydrocarbons, etc., when the water exceeds the saturated solubility, Delamination occurs, and the stabilizer in the solvent is pumped into the water layer, making the stability of the solvent (cleaning agent) worse. At the same time, there is water, free Fˉ, Clˉ and Brˉ ions in the cleaning agent and water generate acid, which forms a vicious circle during heating and use, and the acidity becomes higher and higher. Therefore, the acidity and moisture in the cleaning agent are two interdependent indicators that directly affect the quality of the cleaned workpiece. If some workpieces lose their luster or leave water lines on the workpiece after cleaning, it is related to acidity and moisture. At present, the water content of solvent-based cleaning agents produced at home and abroad is controlled within 100ppm (0.01%). The determination of trace moisture is carried out in accordance with the regulations of GB6283— 86. This is the Karl Fischer method. A simple cloud point method can also be used, that is, according to the provisions of GB4120. It can also be analyzed by gas chromatography.
4、Harmfulness or toxicity
　　Toxicity is an important indicator of whether the cleaning agent can be used. Although it has no direct impact on the cleaned workpieces, it has a profound impact on humans and the environment, and it is also a major factor in whether we choose it today. The toxicity of the cleaning agent is determined on the basis of animal experiments and physiological experiments on humans. Strictly speaking, any chemical solvent is toxic, just a difference in size. The level of toxicity, the safety range for humans and the precautions to be taken can only be obtained through rigorous animal experiments. That is, the measure that an animal can bear per kilogram of body weight. Although many chemical predecessors have done relevant toxicity experiments and are well documented, the current cleaning agents are not pure products, and the data on the materials can be used for reference. The mixture can only pass real animal experiments to determine the safe concentration range and establish safe protection measures and precautions for producers and users. Toxicology experiments are mainly conducted by oral and inhalation experiments. The amount of LD50 in the acute oral toxicity test for rats, that is, the greater the semi-lethal dose, the lower the toxicity; the same for the acute inhalation LD50 of rats, that is, the greater the semi-lethal dose, the greater the allowable concentration of the work environment The higher it is. Based on these measured data, the safety standards and protective measures for the cleaning agent's work site can be formulated. Toxicological experiments should be carried out by the health prevention and prevention department. According to the provisions of GB1560—1995 or GB5044—85, the price shall be calculated.