In the production process of making Faux Stone panels, we have adopted a unique foaming process, which is one of our know-how. That is, in the field of polyurethane hard foam materials, we have adopted a new kind of polyurethane hard foam material and its preparation method and application. Specifically, we have used low activity polyether polyols as reactants, added inorganic powders, and reduced the reaction temperature, The heat preservation performance of the material is improved.
Polyurethane (PU) is a polymer containing urethane group (-nh-coo) in its molecular structure. Urethane is generally obtained by the reaction of isocyanate and polyol. Polyurethane material is one of the six important synthetic materials. It is a multi-purpose synthetic resin with various product forms. It is widely used in various fields of social production activities in the form of foamed plastics, coatings, adhesives and other products. Faux Stone panels is the most important form of polyurethane products. It has excellent mechanical properties and chemical resistance. It can be directly processed into Faux Stone panels from monomer raw materials at one time. In addition, it can adjust the formula combination by changing the chemical structure, specification and variety of raw materials to produce terminal products with various properties and uses. Therefore, it is widely used. Polyurethane foams are divided into three categories: soft, hard and semi-hard. Hard foams have the advantages of light weight, high specific strength, good dimensional stability, superior thermal insulation performance, strong adhesion and good aging performance. They are widely used in Faux Stone panels, building energy and temperature conservation, pipeline insulation, cold chain transportation, transportation, logistics transportation, mine filling and plugging, etc. Polyurethane rigid foam material has the advantages of fast reaction speed, high foaming ratio, strong compression resistance, strong adhesion and fast construction.
The Pu Faux Stone panels will involve the consumption of materials and energy and have an impact on the environment in the life cycle process from raw material extraction and processing to production, use, recycling and final waste treatment.
Firstly, at present, the main isocyanate used to prepare polyurethane rigid foam is polymethylene polyphenyl isocyanate (hereinafter referred to as polymeric MDI). The amount accounts for more than 50% of the total amount of polyurethane raw materials, and the more the amount, the more conducive to the increase of rigid foam strength. However, polymerized MDI is a petroleum based raw material, which means that a large amount of petrochemical materials need to be consumed in the preparation of polyurethane rigid foam, which is not conducive to energy and resource conservation. Generally, in order to reduce the consumption of petroleum raw materials, bio based materials can be used, but bio based materials will reduce the performance of foam.
Secondly, faux stone panels, as a kind of thermal insulation material with excellent performance, is a key link in energy saving and consumption reduction. Whether in wall decoration, external wall insulation or in buildings, it will have a direct impact on energy consumption. The lower the thermal conductivity of polyurethane rigid foam, the better the thermal insulation effect, and the more conducive to reducing the energy consumption of products. At the same time, in the final application, the thermal insulation performance of the faux stone panels is also related to the filling effect of polyurethane materials. If the polyurethane foam can not completely fill the cavity of the mold, a thermal bridge will be formed at the cavity, which will deteriorate the thermal insulation effect of the product. In addition, with the annual improvement of thermal insulation decorative wall panels in various countries and the rapid upgrading of market product structure, the use of PU foaming panels is becoming more and more common. The thinner the channel inside the polyurethane foam mold, the more likely it is to produce many voids, incomplete filling, uneven density distribution and other phenomena, which will ultimately affect the improvement of insulation energy efficiency of PU foam panels.
Third, with the wide application of faux stone panels, a large amount of waste will inevitably be generated. The existing treatment methods of polyurethane waste are mainly landfill or incineration. Obviously, incineration will bring secondary environmental pollution, while landfill will occupy a lot of space, and most of the waste foam is difficult to degrade. Therefore, the pressure of waste polyurethane materials on the ecological environment can not be ignored, and the growth of waste polyurethane foam and the degradation of foam need to be solved from the source.
To sum up, under the development concept of green, recycling and low carbon, it is urgent to develop relevant technologies to reduce the negative impact on the environment during the life cycle of polyurethane rigid foam from production to waste treatment.
Through cooperative research, we found that when a certain amount of isocyanate A is combined with sucrose based polyether polyol, the filling performance of polyurethane foam can be significantly improved, especially the ability to flow through narrow channels can be greatly enhanced, the generation of cavities and surface pores can be reduced, and the filling effect of complex cavity structures is good. In addition, due to the high active components in toluene diisocyanate, its usage is lower than that of polymerized MDI, which can relatively increase the proportion of bio based materials in polyurethane foam, so as to improve the biodegradability of polyurethane foam. At the same time, the combination of isocyanate A and sucrose based polyether polyol can also maintain the crosslinking degree of polyurethane rigid foam at the required level, so as to achieve better dimensional stability of Faux Stone products and take into account the performance of foam. And the polymer polyol is prepared by ring opening polymerization with epoxy compound using sucrose as the sole initiator or sucrose as one of the mixed initiators. When the mixed initiator is used, the mass proportion of sucrose in the mixed initiator is ≥ 60wt%, so as to give consideration to the performance of PU foaming.
When phase change occurs, phase change materials can absorb or release more heat from the environment and have the function of temperature regulation. Therefore, phase change materials are widely used in many fields. It is very common to report that phase change materials are applied to Pu Faux Stone panels foaming, that is, the production of temperature adjustable foaming is realized by directly adding microencapsulated phase change materials into polyurethane raw materials and then foaming. This method of directly adding phase change materials to polyurethane raw materials is easy to cause rough and disordered bubbles or even collapse of foam. In addition, after the foam is made, the phase change materials are mainly dispersed in the foam. During the use, the heat absorbed or released by the phase change materials can only be reflected through the conduction of the foam, with a certain time lag.
If the phase change material is mixed with the resin, then coated on the foam by scraping, and then cured to form polyurethane foam containing phase change material. This method is only suitable for Faux Stone panels with flat surface, but not for Faux Stone panels with complex surface shape. Add phase change materials and glass fiber powder into the exterior paint, grind and mix them evenly by ball mill, and then spray the mixture on the surface of faux stone panels with spray gun. After the paint film is dried, the temperature adjustable polyurethane foam is obtained. The thickness of sprayed material on the surface of foam is generally 0.2 ~ 1mm.
Add the phase change material to the exterior paint of the mold, stir it for 20-30min, then add the glass fiber powder, grind it for 20-30min, fully mix it, put the prepared exterior paint into the spray gun, spray it evenly on the surface of the polyurethane foam, and get the temperature adjustable polyurethane foam after the paint film is dried. The phase change material and glass fiber powder are added to the exterior paint of the mold and sprayed on the surface of the polyurethane foam. The foam can be made by molding or cutting through the block foam, which solves the problem that the mold must be made for the production of small batch or special-shaped adjustable temperature foam, and saves the time and cost of making the mold. At the same time, it solves the problem that the sprayed mold exterior paint can not form a film when penetrating into the foam. This method is suitable for the molded foam with faux stone panels and the cut foam without skin. The temperature regulating polyurethane foam mold outer paint has the advantages of uniform spraying, good film forming property, smooth surface and good temperature regulating effect.
As a producer of the PU foam Faux Stone panel, we should reduce the negative impact of the PU foam on the environment during the life cycle, improve the filling performance of the PU foam, improve the biodegradability of the PU material, and reduce the relative amount of waste foam generated after the product is scrapped.
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