Лако-красочные материалы — производство

Charles E. Frazier

Virginia Polytechnic Institute and State University, Blacksburg, Virginia, U. S.A.

I. INTRODUCTION

Over the last thirty years, the forest products industry has increasingly embraced isocyanate wood binders. This trend is partly due to the tremendous growth of the world­wide polyurethane industry. Central to this growth has been the demand for the aromatic monomer diphenylmethane diisocyanate (MDI), and the associated methylene bridged polyphenyl polyisocyanates known as polymeric MDI (pMDI). Both products are valued for the manufacture of many polyurethane and urethane/urea polymeric products. MDI and pMDI cater to different markets because of differences in functionality, reactiv­ity, and structure. These differences will become evident later. The vast majority of the polyisocyanates are used for the production of rigid foams. However, when polymeric MDI was proven effective for particleboard manufacture (in the late 1960s and early 1970s [1]), a relatively small, but significant, market was born. As the polyurethane indus­try grew, the forest products industry was developing new composite technologies. In particular, oriented strandboard (OSB) improved wood utilization efficiency because lower quality logs and alternative woods could be used to manufacture panels that were competitive in plywood markets. OSB production grew and stimulated additional tech­nologies, such as laminated strand lumber, and I-beams made with OSB webs. The rapid expansion of strand based composites was an opportunity that the polyurethane industry captured; MDI based polyisocyanates afforded many advantages for strand based wood composites. However, the isocyanate binders have not secured the entire market for reasons that we shall discuss. Currently, isocyanate wood binders are primarily used for the production of OSB and related strand products; however, they may also be used for other materials such as particleboard and medium density fiberboard. The following is an overview of the use of isocyanate wood binders in the forest products industry.