Process of Polyurethane Foam

Polyurethane foam(PU for short) is a polymer made from polyisocyanate and polyether polyols or polyester polyols or/and small molecule polyols, polyamines or water, such as chain extenders or crosslinking agents. By changing the type and composition of raw materials, can greatly change the shape of the product and its performance, from soft to hard final products. Polyurethane products are soft, semi-rigid and rigid foam plastics, elastomers (polyurethane elastomers referred to as TPU), paint coatings, adhesives, sealants, synthetic leather coating resins, elastic fibers, etc. Widely used in automobile manufacturing, refrigerator manufacturing, transportation, civil construction, footwear, synthetic leather, fabric, mechanical and electrical, petrochemical, mining machinery, medical, agriculture and many other fields.

In 1937, German Professor Otto Bayer first discovered that polyisocyanate and polyol compounds can be polymerized to produce polyurethane, and on this basis into the industrial application, Britain and the United States in 1945 ~ 1947 from Germany to obtain polyurethane resin manufacturing technology in 1950 began to industrialized. Japan introduced polyurethane industrial production technology from German Bayer and American DuPont in 1955. In the late 1950s, China's polyurethane industry began to develop rapidly in recent decades.

So far, the foaming process of polyurethane in China is divided into three kinds as follows:

I. Prepolymer method

Prepolymer foaming process is to make (white material) and (black material) prepolymer, and then add water, catalyst, surfactant, other additives in the prepolymer mixed under high speed stirring for foaming, curing at a certain temperature can be ripe.

2. Semi-prepolymer method

Semi-prepolymer method of foaming process is to make part of polyether polyol (white material) and diisocyanate (black material) prepolymer, and then the other part of polyether or polyester polyol and diisocyanate, water, catalyst, surfactant, other additives, etc., in high speed mixing mixing for foaming.

Three, one step foaming process

Add polyether or polyester polyol (white material) and polyisocyanate (black material), water, catalyst, surfactant, foaming agent, other additives and other raw materials in one step, and foam after mixing at high speed.

One - step foaming process is widely used at present. There is also the manual foam method, which is the simplest method, all the ingredients are accurately weighed, placed in a container, and then immediately mix the ingredients evenly, into the mold or foam filling space. Note: when weighing, be sure to weigh the polyisocyanate (black material) into the last.

Polyurethane hard foam is generally room temperature foaming, molding process is relatively simple. According to the degree of construction mechanization can be divided into manual foaming and mechanical foaming; According to the pressure of foaming can be divided into high pressure foaming and low pressure foaming; According to the forming way can be divided into pouring foam and spraying foam.