Polyurethane rigid foam board has the excellent performance of light weight and thermal insulation, and is widely used in the wall decoration industry of buildings and houses. In the production of Pu Faux Stone panels, the discontinuous foaming production process has the advantages of flexibility and simple process, and occupies a very important position in the market.
In cold regions, the thermal insulation performance of faux stone wall panels has always been concerned. How to improve the thermal insulation performance of products is also an important index we pursue.
The existing polyurethane composites prepared by discontinuous process are prepared by discontinuous process, that is, the prefabricated shell is placed in the mould, then the mould is injected with polyurethane resin, the mould is closed, the polyurethane resin is foamed to form polyurethane foam, and then moulded, so as to obtain polyurethane composites. Polyurethane resin is usually composed of component and poly component. How to produce Faux Stone panels with superior thermal insulation performance under the premise of energy conservation, economy and environmental protection has been a difficult problem to be solved in the industry.
In the production process, if the reaction raw materials with different density requirements are injected twice to prepare soft foam products, the requirements for larger foaming angle and degree and the impact on the system are very complex. At the same time, this is a soft foam preparation process, which does not involve the heat preservation and bubble of foam.
We are studying a process method for preparing large bubbles in faux stone panels producing process. First, raise the end of the mould close to the injection port to form a certain angle, then clean and assemble the mould, then form a second preset angle between the injection pipe and the injection port, inject foam reaction raw materials, and finally form the product. This process can improve the product quality, but the specific value of each angle and the improvement of product quality are not mentioned. In addition, the injection port of the process is set at the highest position of the die.
Through repeated experiments, we found that by improving the process, such as adjusting the angle of the mould relative to the horizontal plane when foaming in the polyurethane reaction system, the specific position of the pouring port, and the corresponding method for preparing rigid polyurethane foam in the polyurethane reaction system, the thermal insulation performance of faux stone panels can be simply and efficiently improved, and other physical properties can also be well maintained.
On the other hand, if the foaming angle of the mould is too low, the injected polyurethane reaction system raw materials will gather near the injection port, which is not conducive to the distribution of foaming reaction raw materials in the mould, resulting in poor density distribution of foam, bubbles or poor density distribution at the flow end of foam. At the same time, the flow of this part of raw materials inside the mould before inspiration will reduce the thermal insulation performance of foam. Therefore, when the pouring port is set at 1/2 of the mould height, the distribution of reaction raw materials in the mould can be improved, and the thermal insulation performance of foam can be improved, so as to improve the performance of the overall Faux Stone panels.
At present, the discontinuous process often adopts to set the injection port at the highest position of the mould, and inject a and B (including premixed physical foaming agent) into the mould cavity after being mixed by the foaming gun head. In this process, when the reaction raw materials are injected into the cavity from the highest position of the mould, a part of the raw materials will be attached to the upper end of the mould, and most of the raw materials will be injected into the bottom of the mould. When foam starts to expand, these two parts of raw materials meet, which will affect the thermal insulation performance of foam. If the injection port is changed from the top of the mould to the middle, the raw materials attached to the mould during injection will be reduced. When the injection position is set at the bottom of the mould, the reaction raw materials are injected at the bottom of the mould. When the foam starts to expand, there is no influence of multiple reaction raw materials, and the heat preservation and other physical properties of the foam can be better guaranteed.
The pouring port of polyurethane reaction system is usually set at the top of the mould. If the mould is tilted at a certain angle during foaming, the polyurethane reaction system is poured from the top, and the liquid of the polyurethane reaction system often splashes to the inner wall of the mould, resulting in uneven foaming. We tried to set the pouring port at the lower position of the mould near the horizontal plane, which solved this problem. Moreover, more unexpectedly, when the pouring port is set below 1/2, preferably less than 1/3, more preferably less than 1/4 of the height direction of the mould of the faux stone panels near the horizontal plane, we found that the u distribution of reaction raw materials in the mould can also be improved, thereby improving the thermal insulation performance of the rigid polyurethane foam. On the contrary, if the raw materials of the reaction system are not injected from the lowest part of the mould, the raw materials first flow to the bottom of the mould from a certain height, and then fill the mould. The flow of raw materials has an impact on the formation of foam bubbles, resulting in poor thermal insulation performance of faux stone wall panels.
Therefore, when the discontinuous production process is adopted, faux stone panels usually include a cavity and polyurethane foam filled in the cavity, and the cavity materials are metal, plastic, composite plate, etc. The hollow shell part can be prefabricated first, then the joint part of the hollow shell part is sealed, and the glue injection hole and exhaust hole are reserved. Finally, the hollow shell part is placed in the foam forming mould, and the polyurethane composition is applied to the cavity of the hollow shell part through the mould and the glue injection hole of the hollow shell part. After the foaming reaction of the polyurethane composition is completed, a perfect Faux Stone panels can be obtained after the foamed parts are removed from the mould.
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