Alternatives to Chlorinated Solvent Adhesives in the Mattress Manufacturing Industry

The Institute for Research and Technical Assistance (IRTA), a nonprofit organization located in Santa Monica, California, analyzed the cost and performance of alternative adhesive technologies used by the furniture and sleep products industries. This project was sponsored by the U.S. EPA with a grant from the Design for the Environment (DfE) Program. The Cleaner Technologies Substitutes Assessment (CTSA) is a partnership with industry including the International Sleep Products Association (ISPA), Southern California Edison (SCE) and the Association of Woodworking & Furnishings Suppliers® (AWFS®).

Industry Description

Flexible slabstock polyurethane foam is produced by 23 companies in about 75 pouring plants in the United States. In 1997, approximately 830 million pounds of slabstock foam were produced. By 1998, slabstock foam production doubled to about 1.6 billion pounds. Flexible slabstock foam is fabricated (cut and shaped) into pieces to be used in carpet underlay, furniture, bedding, packaging, transportation June 2000 Cleaner Technologies Substitutes Assessment Case Studies: Mattress Manufacturing ® EPA 744-R-00-006 2 CTSA: Mattress Manufacturing seating, and other products where a durable and resilient cushioning material is required.

Mattress manufacturers purchase foam from foam manufacturers or from foam fabricators and they use the foam to manufacture their bedding. There are an estimated 1,270 mattress manufacturers in the United States. Ninety percent of the mattresses are manufactured by 260 plants. Most manufacturers have between one and 50 employees. Perhaps 200 mattress manufacturers make pillow top mattresses which are generally considered a high-end bedding item. These mattresses are manufactured by using adhesive to bond the mattress itself to the pillow top. 

Adhesive Alternatives

In the 1980s and early 1990s, most of the adhesive used by mattress manufacturers was based on 1,1,1-trichloroethane (TCA), a chlorinated solvent. TCA was an effective carrier for the adhesive because it evaporates rapidly leaving an instant bond, it is fairly low in toxicity, it does not have a flash point and it is not classified as a Volatile Organic Compound (VOC) that contributes to photochemical smog. 

In the 1990s, TCA was designated as a class one ozone depleting substance and, in 1996, its production was banned for that reason. Although TCA inventory was still available, the chemical had become very expensive because of a Federal tax on ozone depleting substances. Virtually all adhesive formulators stopped making TCA adhesives and began offering adhesives based on methylene chloride (METH), also a chlorinated solvent. Like TCA, METH evaporates quickly, does not have a flash point and is not classified as a VOC. However, METH is a suspected carcinogen. In 1997, the Occupational Safety and Health Administration (OSHA) issued a regulation on METH that lowered the worker exposure level from 500 ppm to 25 ppm measured as an 8-hour time weighted average. The regulation also set an action level at 12.5 ppm. Companies with worker exposure above that level are required to institute monitoring and medical surveillance.

Alternatives to TCA and METH for bonding pillow top mattresses include hot melt adhesives, sewing and aerosol adhesives. Hot melt adhesives are 100 percent solids. They are applied with special sprayguns that heat the resins in the hot melt adhesives to 300 degrees F or higher so they can flow. In some non-mattress applications where there can be no bond line, hot melt adhesives are not a suitable alternative. In this application, however, hot melt adhesives are especially suited because workers are bonding two large thick items together. 

Some mattress manufacturers join the mattress to the pillow top by simply sewing them together. Special equipment is required for the sewing. Although the equipment is expensive, it does not require spray equipment or the use of adhesives.

Many smaller manufacturers use aerosol adhesives for bonding the pillow tops to the mattresses. These aerosol adhesives are often based on acetone, a non-chlorinated solvent. Acetone is low in toxicity and like TCA and METH, readily evaporates leaving a quick bond. It does have a very low flash point, however, and measures must be taken to minimize the chance of fire or explosion. The National Fire Protection Association (NFPA) has rated acetone as an NFPA 704 level 3 flammability hazard. State building codes and fire codes are based on NFPA guidelines. These codes vary according to location and local fire departments have regulations that affect the amount of the flammable adhesive that can be stored and require explosion proof motors and high air flow ventilation systems. Most, if not all, of the aerosol adhesives based on acetone also contain other chemicals like heptane, hexane and mineral spirits. The other chemicals in these formulations are classified as VOCs and some are toxic. 

Mattress manufacturers that wish to continue using METH adhesives have to purchase and install effective ventilation systems that reduce the worker exposure to the legal OSHA limit. In some cases, if the use of the acetone aerosols is very high, manufacturers might also have to install ventilation systems to keep the concentration of the acetone below the lower explosion limit.