Tag rigid polyurethane foam

Cyclopentane is used as a new blowing agent for rigid polyurethane foam. Now it has been widely used in fluorine-free refrigerator, freezer industry, cold storage, pipeline insulation and other fields. In the future, cyclopentane will become the leading role in the field of polyurethane blowing agent. Dongying Liangxin Petrochemical Technology Development Limited Company will tell you about the control points of cyclopentane in the foaming process.

1. Strictly control the physical and chemical properties of stock solution
   The chemical properties of polyisocyanate, combined polyether, foaming agent, catalyst and foam stabilizer in black and white materials directly determine the chemical reaction of polyurethane synthesis and the physical properties of foam. It is the basic condition for producing qualified polyurethane foam.
   Black and white monomers shall be transparent viscous liquid without flocculent insoluble impurities. If there are insoluble impurities, the filter screen of the foaming machine will be blocked, resulting in unstable raw material flow, the ratio of black and white materials does not meet the requirements, and the mixture is uneven. Even the pipeline of the foaming machine is blocked.
   It is recommended to thoroughly clean the black and white material filter screens and needle valves of the foaming machine (and premixer) at least once a week.
2. Strictly control the proportion and injection volume of stock solution
   The proportion of black material, combined polyether and cyclopentane must be strictly controlled. When the total injection volume remains the same, if the proportion of black material is too large, bubbles will appear, if the proportion of white material is too large, soft bubbles will appear, if the proportion of cyclopentane is too large, bubbles will appear, and if the proportion is too small, bubbles will appear. If the proportion of black and white materials is out of balance, the mixture will be uneven and the foam will shrink.
   The injection volume shall be subject to the process requirements. When the injection volume is lower than the process requirement, the foam molding density and strength will be low, and even the filling will not be dense. When the injection volume is higher than the process requirements, bubble expansion and bubble leakage will occur, and the box (door) will be deformed.
3. Strictly control the process temperature and curing time
   Polyurethane foaming is a complex physical and chemical reaction process. The fluctuation of raw material, mold, preheating temperature and curing time will directly affect the foaming quality.
   A. Black material is a kind of active chemical substance, which is easy to react with water. During storage, the container shall be dry and sealed and filled with dry nitrogen for protection. It shall not be in direct contact with water during use. If the storage temperature is lower than 5 ℃, crystallization will occur, so attention must be paid to antifreeze. Once crystallization occurs, it shall be heated and melted at 70~80 ℃ before use, and fully stirred. When the storage temperature is higher than 50 ℃, an insoluble solid will be produced, the viscosity will increase and the chemical properties will change. White materials have the same properties.
   Therefore, black and white materials shall be stored in a ventilated, cool and dry place at room temperature (20~25 ℃) to avoid sun and rain.
   B. The black and white materials shall be subject to constant temperature treatment before foaming, and the foaming temperature shall be controlled at 18~25 ℃.
   When the temperature is too low, the black and white materials have high viscosity, unstable flow, poor fluidity and uneven mixing. When the temperature is too low, the reaction speed of forming foam is slow and the curing time is long. When the curing time is not enough, the box and door are still foaming after demoulding, resulting in appearance deformation.
   When the temperature is too high, the reaction is violent and difficult to control. It is easy to see that the performance of the foam injected into a large box is uneven. The foam injected at the beginning has undergone a chemical reaction, and the viscosity increases rapidly. The foam injected later has not yet reacted. As a result, the foam liquid injected later cannot push the foam liquid injected first to the front of the foaming process of the box, resulting in local cavitation in the box.
   C. The preheating furnace temperature shall be controlled at 30~50 ℃, the foaming furnace temperature shall be controlled at 35~50 ℃, and the foaming mold temperature shall be controlled at 35~45 ℃.
   The temperature of the box and door to be foamed in winter is low, so it must be preheated in the preheating furnace. Otherwise, when the hot polyurethane liquid contacts the box or door body, the chemical reaction will be seriously affected, and the foam liquid will not stick to the shell.
   When the temperature of the foaming mold is too low, the fluidity of the foaming solution system is poor, the curing time is long, the reaction is not complete, and cavitation occurs; When the temperature of the foaming mold is too high, the plastic liner is deformed by heating, and the foam system reacts violently. Therefore, the temperature of the foaming mold and the ambient temperature of the foaming furnace must be strictly controlled.
   Especially in winter, the foaming mold, preheating furnace, foaming furnace, box and door must be preheated for more than 30 minutes every morning when the line is opened. After a period of foaming in summer, the foaming system must be cooled.
   D. The foaming and curing time of black and white materials used by our company must be more than 6 minutes. The curing time is too short, and the box and door are still foaming after demoulding, resulting in appearance deformation. In particular, after the door body is deformed, the door seal gap is large when it is assembled with the box, the cold leakage occurs, the box is not insulated, and the compressor is frequently started.
4. Strictly control the injection pressure of foaming machine at 13~16mpa
   When the injection pressure is unstable, the proportion of black and white materials is unstable and the mixing is insufficient. The injection pressure difference between black and white materials shall be controlled within 5bar, otherwise the foaming machine will be damaged due to material mixing.
   During the foaming process, the injection pressure of the foaming machine shall be checked frequently, and the injection system of the foaming machine shall be cleaned to avoid blocking.
   Black, white and cyclopentane are mixed unevenly, which is manifested by uneven density of polyurethane foam, local large bubbles, cracking of foam and local softening of foam: white, yellow or black stripes appear on foam, and foam shrinks.
5. Preparation before foaming:
   A. Clean and inspect the mold. Before foaming, clean up the missing foam and other debris attached to the foaming mold, and check the mold fitting accuracy. Otherwise, serious quality problems such as damage to the box and bubble leakage will occur during foaming. Before foaming, check whether the exhaust and suction pipes of the box are well arranged as required and whether there are bends. Whether the outgoing line is complete and whether the drainage pipe has been installed. Whether the foaming process board is properly pasted according to the process requirements.
   B. Before door foaming, check whether the handle of the door body is installed correctly and whether it is inclined. Whether the wiring assembly dimension meets the process requirements. Whether the door lock is assembled as required. Whether the masking paper is pasted according to the process requirements and whether there is possibility of bubble leakage.
6. Requirements for taking and placing box (door) body:
   The (door) body shall be handled vertically and gently, and no damage to the inner and outer boxes is allowed; The foamed box (door) shall be placed on the assembly line at uniform intervals. Then check whether the foaming quality meets the requirements. The leaking bubble shall be cleaned with tools, and the box (door) shall not be scratched.
7. Foaming process control method
   1) Before each shift of production, it is necessary to check whether the parameters meet the process requirements. Check again every 3 hours and record the inspection results.
   2) Before each shift of production, the mixing condition and density of free foam must be tested. The mixing condition and density of the molded foam of the box body and the door body shall be tested once a shift. Then the free foam and molded foam were frozen at -20 ℃ for 24h, and their shrinkage was observed. The foam body shall have no obvious shrinkage. And record the inspection results.
   The above are the control points of cyclopentane in the foaming process. I hope it will help you. Please consult us for more questions about cyclopentane!

Cyclopentane used as in the production of polyurethane insulating foam

Synonyms: Pentamethylene , ciclopentano, cyclopentan, zyklopentan, unii-t86pb90rnu, hsdb 62, t86pb90rnu, cyclopentanes, cyclopentyl group, hydrocarbons, cyclic c5 and c6