An automobile typically requires four types of filters: engine air filter, oil filter, fuel filter, and air conditioning filter, commonly referred to as the "four filters". They are responsible for filtering media in the engine intake system, lubrication system, fuel system, and air conditioning system, respectively. The components of filters need to be bonded with adhesive to ensure complete isolation between the intake and exhaust passages by the filter paper, achieving the purpose of filtering impurities in the filtering media and protecting the engine intake system, lubrication system, fuel system, and air conditioning system. With the development of the automotive market, the variety of filter types has become increasingly diverse, including barrel-shaped, plate-shaped, irregular-shaped, etc. Generally, large trucks use barrel-shaped filters, while sedans and SUVs typically use plate-shaped ones. The bonding of automotive filters mainly includes folding of filter paper, bonding of ridge glue lines (fixing teeth-shaped glue), bonding of end caps, seaming of filter paper, bonding of sealing rings, bonding of frames, etc.

Adhesives used in automotive filters can be classified according to whether they contain solvents, such as solvent-based adhesives, solvent-free adhesives, hot melt adhesives, etc. They can also be classified according to their main components, such as PU adhesives, PVC adhesives, EVA adhesives, PO adhesives, PA adhesives, epoxy adhesives, etc. According to their uses, they can be classified as end cap adhesives, filter core adhesives, seam adhesives, thread adhesives, pouring adhesives, etc. In the past, commonly used adhesives for automotive filters included single-component filter core adhesives mainly based on PVC and two-component filter core adhesives mainly based on polyurethane. Hot melt adhesives are widely used in bonding various components of filters due to their characteristics of 100% solid content, no solvents, environmental protection, non-toxicity, low odor, strong bonding strength, good weather resistance, high cohesive strength, rapid curing, and suitability for automation. Two-component PU adhesive is widely used in bonding various components of filters due to its convenient pouring, simple process, non-toxic environmental protection, and the ability to replace metal end caps, making filters more aesthetically pleasing and lightweight.