The Research And Development Of Process Control System For Formaldehyde Adhesive

Nowadays, the extent of process control for adhesive industry is very small in our country, most of the adhesive producing is controlled by hand going with much disturbed factors, which is very difficult to control and keep the quality of the adhesive, such as especially the content of dissociative formaldehyde in adhesive. With the increasing demands of environmental protective adhesive by society, it is very urgent for us to develop the process control system for UF resin producing. There are some difficulties to realize this kind of process control system. First, different formulation needs different producing technology, and there is no universal process control software; second, there isn't on-line apparatus used to determine the reaction end of adhesive; third, the pHmeter made in China isn't equipped with the output standard signal for industry measure; four, the traditional PI control method doesn't meet the change of temperature during producing adhesive. The process automatic control for adhesive industry is extremely restrained by all of the factors. In order to realize the process control, we must solve the following the issues: First, design the universal configuration process control software for different formulation requiring different producing technology, the user can change the adhesive formulation and its producing technology by filling the parameters to the interface blank for man and computer, once the configuration parameters have been confirmed, the computer automatically assigns the material and control to produce adhesive. Second, presently the popular way of determining the reaction end of adhesive is to time the viscosity time with the tu-cpu4 at certain temperature degree. Another way is to observe the turbid extent of adhesive dropped into certain temperature degree water. In this process control system, an on-line electronic viscosimeter has been developed to determine the reaction end of adhesive using the technology of photoelectricity and microcomputer, at the same time to measure the temperature of adhesive in the electronic viscosimeter . In terms of the two parameters of electronic viscosity time and adhesive temperature, to change the electronic viscosity time into viscosity time familiar to people tested by the tu-cpu4 at certain temperature (such as at 30℃), and to determine the reaction end of adhesive by it. Third, it is an important key to test and control the pH value to produce UF resin. In order to meet the computer to test and control the pH value in real time, whereas the pHmeter made in China can't meet the requirement, a new pHmeter applying the technology of microcomputer and software has been redesigned by the theory of pH value test, which is provided with the output standard signal forindustry measure (4~20mA or RS232). Four, there is a big lag element that absorbs heat energy first and releases that of it late during the process of producing adhesive. The traditional PI control method can't meet its demands of temperature. It is necessary to design the self-adjusting software by the characteristic of producing adhesive to control its temperature.The development of this system will be of good help to the process control of producing adhesive.