Characteristics and application scope of the hotte

2022-08-06
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Characteristics and application range of polyurethane foaming catalyst

the characteristic of polyurethane foam is that it has changeable polymer structure, which can meet the needs of a wide range of applications. This structural difference is not only caused by the different isocyanates and polyvinylidenes used as raw materials, but also related to the different reactions of these raw materials. These reactions are strongly influenced by the type and amount of catalyst used

the reaction between isocyanate and polyol is called gelling reaction, and finally carbamate is formed. The reaction between isocyanate and water is called foaming reaction, and finally the dolphin is formed. When carbamate and isocyanate react with each other further, cross-linking may occur, which may lead to the formation of mesylate and dioptric acid, respectively. Isocyanates can self condense in several different ways to form trimers, dimers and carbodiimide

the choice of catalyst affects the reactivity of the whole foaming system and the selectivity of some individual reactions described above. The reactivity of the foaming system is expressed by the activation time, curing process, demoulding or curing time of the system. As a function of catalyst selection change, the change of reaction selectivity affects the balance of the reaction, the type and order of the polymer chain formed and the fluidity of the foaming system, thus affecting the processing and physical properties of the final foam

the most commonly used catalysts for polyurethane foaming are tertiary amine, quaternary amine, amine salt and metal nucleic acid salt (usually Sn Ⅱ, Sn IV or k+). Tertiary amines are used to promote gelation. Foaming and crosslinking reaction. Limb salts and heat sensitive amines, such as diazo dicyclodedecane, are used to provide delayed action. Metal acid making salts strongly affect the gelation reaction. Stannous compounds (SN Ⅱ) have low cost, but are easy to hydrolyze and unstable. Its typical use is for occasions where individual logistics can be measured, such as soft blocks. Tin compounds (SN Ⅳ) are not easy to hydrolyze and can be incorporated into systems, such as soft molding and hard foaming. For example, certain compounds such as quaternary amine, potassium nucleic acid, tris (Dimethylaminomethyl) phenol and 2,4,6-tris [3- (dimethylamino) n-propyl] hexahydro homotriad have strong selectivity for trimerization

in order to simulate the low-speed impact phenomenon in the actual service process of materials, people have adopted the drop hammer simulation equipment with an environmental chamber and pretreated the materials. Soft block foam

soft block polyether polyol based foam is a typical tertiary amine catalytic reaction product used with organotin catalyst. The colloidal catalyst may be a diluent of a pure compound such as triethylenediamine and bis (dimethylaminoethyl) ether, or a blend with optimized performance. A typical tin catalyst used for foaming soft blocks is pure or diluted stannous octanoate. Diluted products (including amines and tin) are intended to address raw material handling, metering accuracy, and pumping viscosity limitations. The admixture with excellent performance can be used in special foaming equipment to improve processing, have a wide range of formulas, and make the difference of physical properties of foam small

the reaction characteristics of soft block system require an accurate balance between foaming and gelling reactions. Premature foaming of the system can lead to blisters, cracks, or blisters before sufficient polymer viscosity/strength is obtained. Premature gelation can lead to low fluidity, high density, closed cell and shrinkage of foaming system

the reaction characteristics required by the special polyurethane foaming system are affected by the model of the foaming equipment used. For example, the trough machine requires that the polyurethane system can delay the opacification time to adjust the residence time of foam in the trough before reaching the conveyor belt

high resilience (HR) foam is made of polyols terminated by ethylene oxide. It has higher reactivity than polyols used in traditional soft foam. We can provide solutions along the whole process chain. Therefore, different types and contents of tin catalysts are commonly used. Especially dibutyltin dilaurate, instead of stannous octanoate. Triethylenediamine, bis (dimethylaminoethyl) ether and amine diluent were used as cocatalysts

in the production of soft block polyester foam, the polyol used has high activity. Therefore, moderately active amine catalysts such as N-ethyl morpholine and n-Lauryl morpholine are often used. Tin cocatalyst can also be used

recently, there have been some technical challenges in the development trend of substituting chlorinated solvents such as dichloromethane or 1,1,1-trichloroethane for CFCs. Different boiling points and evaporation properties cause the change of foaming curve. In addition, the residual chlorinated solvent in the foam makes the foam dissolve and swell, resulting in the reduction of the physical properties of foam. Taking these issues into account, various products have been developed

soft molded foam defines the definition standard and scope of "ground bar steel"

soft molded foam needs the same precise foaming/gelling balance as soft block foam. Fluidity, stability and curing are further requirements in demoulding. Triethylene dibasic and bis (dimethylaminoethyl) ether mixed with a small amount of dibutyltin dilaurate are the most commonly used catalyst systems in soft mold foaming systems. Typical limb type delay catalyst protected by acid is often used to make the solidified foam have enough fluidity to pass through the mold with complex shape

catalyst mixtures with excellent foaming properties for soft blocks are also often used in soft molding. These mixtures are designed to suit the system reactivity, processing conditions and curing requirements

recently, the focus of automobile parts production is the production environment and the odor of final product parts. The newly developed products can produce products with low volatile gas concentration lower than the industrial standard

hard foam

hard foam has a wide range of uses (including appliances, laminating and spraying foam, in-situ pouring, packaging foam, etc.) and chemical composition (polyurethane and polyisocyanurate) in the domestic mineral market

rigid polyurethane foam consists of dimethylcyclohexylamine. Dimethyl ethanolamine, triethylene diamine, pentamethyl diethylene triamine and pentamethyl dipropylene triamine are catalysed. These catalysts can be used alone or mixed

polyisocyanurate rigid foam is usually prepared with a mixture of trimerization catalysts, such as potassium octanoate, potassium acetate or a trimerization amine catalyst containing Tri (dimethylamino potassium) phenol

the recent development trend is to abolish the use of CFC in hard foam, so people gradually focus on the use of HCFC. In the foaming process, HCFC-141b decomposition can lead to a large number of hcfc-1131a, while the toxicity of hcfc-113la is still unknown. It has been found that the content of hcfc-1131a can be reduced more effectively by using seasonal catalyst than by using potassium octanoate trimerization catalyst

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