This raw material report defines hydrocarbon resins as glass-like oligomers produced by polymerization of by-product streams resulting mostly from the cracking of petroleum hydrocarbons for ethylene production. The technology has its roots in resins made from coal tar byproducts of steel production, such as coumarone and indene. However, only a very small proportion of the production of hydrocarbon resins is from this source today. The three principal raw material streams are now linear C5s, such as piperylene and amylene, cyclic C5s such as cyclopentadiene and aromatic C9 and C10 fractions, heavy in reactive monomers such as styrene.

There are three basic processes for resin production, in order of volume significance:

· Polymerization with aluminum chloride catalyst

· Thermal polymerization

· Polymerization with boron trifluoride catalyst

Aluminum chloride catalysis is used for the production of the most broadly used, so-called C5 aliphatic petroleum resin and mixed C5/C9 aliphatic/aromatic hydrocarbon resins.

Thermal polymerization is used primarily with cyclopentadienic streams, with and without aromatic impurities to make so-called Cyclic resins. Unless modified with subsequent processing, principally hydrogenation, Cyclic resins tend to be low value products with a strong odor and prone to oxidative decay. The low cost of their raw materials, coupled with a low process cost, makes them attractive to produce and market.

Boron trifluoride catalysis is used to achieve properties differentiated from those that can be achieved with aluminum chloride for a given feedstock. They are most often used with lower cost aromatic feedstocks to make so-called C9 hydrocarbon resins, where aluminum chloride catalysis has limited application. As a result, boron trifluoride has a somewhat undeserved reputation for products with a strong odor.

All hydrocarbon resins can be hydrogenated to improve color, odor and stability as well as modifying compatibility. Thermally polymerized polymers are usually the focus of this upgrade for two reasons, they tend to be unstable and malodorous and they are the least expensive in terms of hydrogenation process cost. Boron trifluoride catalyzed products are the next most frequently hydrogenated products, with stability being less of a problem and hydrogenation process cost, while higher than for thermal resins, is generally lower than aluminum chloride catalyzed products. This last category is rarely hydrogenated because of the adverse process economics. For the purposes of this study, no distinction is made between types of hydrogenated hydrocarbon (H2) tackifier.

Hydrocarbon resins, as is the case for all tackifiers, are mostly used in adhesives as modifiers for polymers that have been selected for the specific end-use purpose. In a phrase, they are used to add character, or to differentiate the polymer and control cost, since in most cases, they are less costly than the base polymer.

Technically, their principal purpose is to promote adhesion in a polymer, usually at ambient temperature.

An important secondary role capitalizes on the glass-like nature of the resin in hot melt applications. In this case, the resin acts to plasticize the polymer at elevated temperature. However, while doing this, it usually has to be accomplished without significant negative effect on the cohesive strength of the polymer at ambient temperatures. Equally important for hot melts is the requirement that the thermal stability of the mixture is not impaired. Thus, in this respect, unhydrogenated Cyclics are unsuitable for hot melts, and hydrogenated resins are the most suitable.

As might be deduced from this, the role of a tackifier and plasticizer can become a little confused and to some extent, the functions overlap in many cases.

In addition to the function of tackification, a small group of specialized aromatic resins are used to offset one disadvantage of Block Copolymers – the tendency for the styrenic end blocks to soften at elevated temperatures. These are the so-called end block reinforcers. They are used because they associate with the end block and raise the temperature at which that end block starts its transition from solid to liquid. The effect is usually small, but significant in terms of finished product performance in use.

The use of hydrocarbon resins has historically developed in substitution for natural product sourced resins such as rosin derivatives or polyterpenes during times of short supply. With the development of hydrocarbon resins with lighter colors, better compatibility, enhanced tack with specific elastomers, improved specific adhesion to various substrates, and a broader range of melt points, hydrocarbon resins have now established their own presence. In many cases, they have become established in end uses where natural product based resins do not fit. High-speed automated production techniques require the higher performance adhesives made possible through the attributes only available from some of these tackifying resins.

Further, some of the traditional markets for tackifying resins, such as the construction market, have based resin selection on achieving the lowest cost at minimum performance levels, and this will probably continue. However, there is a gradual change toward the use of higher quality adhesives in response to a thrust for higher productivity. This is matched by an increasing trend toward the use of hydrogenated products, especially in hot melts, as the production cost of these resins falls with increasing volume. This resin classification report on hydrocarbon resins estimates 2003 demand with a historical perspective back to 2000 as well as forecasts through 2005 and 2010 within the U.S. Adhesives Industry.