In the production of car air filters, various raw materials are needed, including polyurethane materials, filter paper, filter glue, metal mesh, etc. Polyurethane foam is one of the primary materials in the production of car air filters, which is produced from the chemical reaction of two liquids, polyol and isocyanate.
Polyol or so-called poly is a polymer resin that is colorless or milky depending on the production conditions. Polyol resin contains a base polyol to which additives, catalysts, dyes, fillers, etc. are added to achieve the desired quality. Isocyanate is a brown or colorless liquid that is used as a hardener in the production of polyurethane foam.
How to combine raw materials in the production of air filters
In the above section, we got acquainted with the raw materials for filter production and found that we need raw materials such as polyurethane, air filter paper, filter glue, metal mesh, etc. to produce air filters. In this section, we will learn how to combine raw materials in the production of air filters. In the production of standard air filter foam, it is necessary to mix polyol and isocyanate well and with a specific composition ratio to form polyurethane polymer chains well.
The composition and mixing of polyurethane materials is mainly done by the injection machine. This device consists of two tanks for storing poly and iso liquid, a head for injecting materials into the filter mold, a hose or pipe for transferring materials from the tank to the head, a pump for transferring poly and iso liquid from the tank to the head. The necessary pressure to mix and combine poly and iso liquids is provided by the head of the device. Polyurethane injection machines are divided into two types, low pressure and high pressure, based on the pressure of the combination and mixing of two liquids in the head.
The high pressure foam injection device, as its name suggests, combines and mixes two liquids, poly and ISO, with high pressure, and as a result, the polyurethane foam reaction is completely completed, and the product is of high quality compared to Low pressure injection machine can be produced.
What is the advantage of the high pressure injection machine in the production of air filters?
One of the other advantages of the high pressure injection device in the production of air filter is its cleanliness because no polyurethane material remains inside the head of the device, but in the low pressure injection device, due to the remaining reactive polyurethane material in the Inside the head of the device, it is necessary to wash and clean the remaining polyurethane foam with a solvent such as methylene chloride. Due to the fact that methylene chloride is spread by wind pressure, it also pollutes the ambient air.
Why is a low pressure injection injection machine in the production of air filters?
How to combine bridge to ISO in the production of air filters
In the production of standard and quality air filter, in addition to the proper mix of poly and ISO, the ratio of the reaction composition must also be carefully observed. In the reaction of polyurethane, the OH functional group of polyol is combined with the NCO group of isocyanate and polyurethane foam is formed. Depending on the amount of hydroxyl number of polyol resin and NCO number of isocyanate, the reaction composition ratio is determined by the manufacturer of polyurethane materials.
The lower the number of active branches of the polyol resin, the less isocyanate the foam needs to form the reaction. For example, in the production of air filters, the ratio of poly to iso is 3 to 1, while in the production of cold polyurethane foam (seat foam), due to the fact that the active branches of the polyol resin are more, more isocyanate is needed to form the reaction, and the ratio of poly to iso It is 2 to 1. In hard polyurethane foam, where polyol resin has the most active branches, the ratio of poly to iso is 1 to 1.
It should be noted that adding any impurities and fillers and fillers such as calcium carbonate or PVC powder to polyol resin due to the fact that they are not active materials and do not participate in the chemical reaction causes a lower need for isocyanate. ISO changes from 3 to 1 to 4 to 1 or 5 to 1.
Of course, it should be noted that the difference in the composition ratio of the two polyurethane material manufacturers does not necessarily mean having filler in the poly, and sometimes depending on the chemical formula of the polyurethane material manufacturer, the composition ratio of the materials may be different.