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[Chemical Knowledge]：Manufacturing method and process of polyurethane resin

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The manufacturing method
of polyurethane resin
polyurethane resin is a high-performance, multi-functional polymer material, widely used in the field of chemical production raw materials. This paper will introduce the manufacturing method of polyurethane resin, including raw material selection, preparation process, reaction mechanism and influencing factors.

1. raw material selection

1. polyol
polyol is one of the main raw materials of polyurethane resin, commonly used polyols, polyester polyols and polyether polyols. When selecting polyols, it is necessary to consider its molecular weight, functionality, hydroxyl value and other factors to meet the performance requirements of different products.
2. diisocyanate
diisocyanate is another main raw material of polyurethane resin, commonly used are diphenylmethane diisocyanate (MDI), toluene diisocyanate (TDI) and so on. The activity, toxicity, stability and other factors should be considered when selecting diisocyanate.
3. chain extender
chain extender is used to adjust the molecular weight of polyurethane material, commonly used are small molecule diol, diamine, etc. Factors such as compatibility with polyols and diisocyanates and chain extension efficiency need to be considered when selecting chain extenders.

2. preparation process

polyurethane resin preparation process mainly includes prepolymer method and one-step method.

1. Prepolymer method
prepolymer method is to react polyol and diisocyanate under certain conditions to generate prepolymer, and then add chain extender for chain extension reaction to generate polyurethane resin. The polyurethane resin prepared by this method has high molecular weight and stable performance, but the process is more complicated.
2. One-step
One-step method is to add polyol, diisocyanate and chain extender together into the reactor, and react under certain conditions to produce polyurethane resin. The polyurethane resin produced by this method has a low molecular weight, but the process is simple and the production efficiency is high.

3. Reaction Mechanism The reaction mechanism of

polyurethane resin mainly includes two steps: prepolymer generation and chain extension reaction.

1. Prepolymer generation
Polyol and diisocyanate react to generate prepolymer under certain conditions. During the reaction, factors such as temperature and pH value need to be controlled to ensure the smooth progress of the reaction.
2. Chain Extension Reaction After adding a chain extender to the
prepolymer, the chain extender reacts with the isocyanate groups in the prepolymer to generate a polyurethane resin. The chain extension reaction needs to control factors such as reaction time and temperature to ensure the molecular weight and performance of the product.

4. Influencing Factors

The factors that affect the performance of polyurethane resin mainly include the following aspects:

1. Types and ratios of raw materials
Different types and ratios of raw materials will affect the performance of polyurethane resin, so it is necessary to select appropriate raw materials according to specific application requirements.
2. Reaction temperature and time
Reaction temperature and time will affect the degree of prepolymer and chain extension reaction, thereby affecting the performance and molecular weight of polyurethane resin.
3. pH value
pH value will affect the reactivity of diisocyanate in the process of prepolymer formation, so it is necessary to control the pH value to ensure the smooth progress of the reaction.
4. types and dosage of chain extender
different types and dosage of chain extender will affect the molecular weight and performance of polyurethane resin, so it is necessary to select the appropriate chain extender and dosage according to the specific application requirements.

In short, the manufacturing method of polyurethane resin needs to consider the comprehensive effect of multiple factors to ensure the performance and quality of the product. At the same time, with the continuous progress of science and technology and the continuous improvement of application demand, the manufacturing method of polyurethane resin is also constantly improved and optimized.

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