I've since established Teckrez Inc. as a specialty marketer of a range of pine chemical resins with a focus on the adhesives market. There aren't many rosin or terpene tackifier producers left in the U.S. Crude Tall Oil (CTO), a Kraft paper-making byproduct, has been the major source of rosin for adhesive use in the U.S. and Europe, but there are limitations in supply. Dramatically increased energy value has diverted some CTO to fuel use (burning). With continued growth in rosin ester use in adhesives, combined with domestic supply limitations, there is a need for additional supply of a broad range of pine chemical-based tackifiers backed by expertise on producers, products, applications and market/customer needs.
Wherry: It started in 1972 when the company founder, Walter (Bud) Cleaver Sr., was sent to China as an employee of Hercules to obtain gum rosin for Hercules' rosin operations. Cleaver was very successful at that and created a wonderful relationship with certain brokers and traders. About five years later, he retired from Hercules and decided to use his contacts in China to try importing rosin and selling it to smaller companies in North America. Using the contacts that he had, Cleaver and his wife started the business, and that parlayed into a substantially large business that has branched out since then into the area of terpene resins, which also come from pine trees. The business has gone farther than China now, too; we're now active with Mexico, Brazil, Portugal and Canada. But the basic intent is still the same: we bring in pine tree raw materials - or naval stores, as they used to be called - and warehouse them here and then distribute them to North America.
Wherry: The biggest advantage to formulating with pine chemicals, or rosin derivatives, is that they're compatible with a very broad range of polymers. They're compatible with SBR, natural rubber, acrylics and a number of other things, whereas with hydrocarbons you've got to design and tailor the resin specifically for the compatibility that you want with a specific polymer. With rosin you get that because it's a very soluble and compatible compound. So, you get esters or derivatives that are in the 3000 molecular-weight range, which is fairly low when compared to the polymers they're being put together with, like natural rubber, etc., which can get up to a couple hundred thousand in molecular weight. When you add rosin esters to these things, what you get is stickiness, the ability for the adhesive to "wet" a certain substrate, and good flowability.
Wherry: Pressure sensitives, chewing-gum base, construction adhesives and labels are some of the major end uses for pine-chemical-containing adhesives and sealants. Also, hot-melts based on rosin tackifiers are used for food packaging because rosin derivatives have a very broad sanction in FDA regulations.
Furthermore, rosins are growing faster than other tackifier technologies in PSAs for two reasons: 1) Waterborne PSAs are growing somewhat faster than overall PSAs due to environmental and performance factors. Rosin tackifers dominate due to performance and compatibility advantages with the major polymers used (acrylics and SB). 2) In hot-melt PSAs, where SBCs (styrene block copolymers) are the base polymers, increased use of SBCs favoring rosins (SBS) is taking place due to shortages of isoprene containing SBCs (SIS).
Wherry: Pressure-sensitives have become a really significant market. People usually think of tapes and labels as a scotch tape type of thing, but now pressure-sensitives are being used for transdermal patches that dispense drugs through the skin, bar coding on just about every part you can think of, tags for luggage, and plastic sheets that go over the hoods of cars to prevent in-transit damage, among other things.
Wherry: I think this is definitely still true. If you think about the things adhesives are used for - labels, tapes, construction - all you have to do is look at China and see all the construction going on over there. Eventually, China will get into the construction of what they call ‘product assembly,' where you start putting your own things together with adhesives more and more rather than importing them.
The second dynamic, limited piperylene supply, is causing availability issues with C5 hydrocarbon resin tackifiers. This further favors use of rosin-containing adhesive formulations.
Wherry: It has to have an effect because SIS is one of the primary raw materials for pressure-sensitives, which I've already mentioned as one of the fastest-growing markets, and it's also a critical raw material in a number of other uses, primarily diapers, or disposable-article adhesives. So I would imagine the tightness of the SIS supply is bound to have an effect, but the hydrocarbon producers - notably Exxon and Eastman - have been able to develop petroleum-based tackifiers that will function with SIS, and, in fact, do a pretty good job. The problem with most of those, though, is that SIS requires a whole lot more tackifier than it does polymer. You might have a system where you're using twice as much resin as you do polymer, so if something happens with the supply of that polymer, it has a much bigger impact on the resin because there's a lot more resin used to get the properties you need. And I don't think there's any relief when you go looking for other tackifiers for SIS when you get to the hydrocarbon side because they've got the same supply problems.
It's hard to say if the SIS situation will mean new opportunities for pine chemicals because, as I said, rosin derivatives are very widely compatible. In an SIS, you've got a styrene endblock, which is a rigid-type plastic endblock that gives the adhesive strength. But then in the middle you've got an isoprene midblock, which is very sticky and tacky. The problem with rosin esters is that they go to both of those domains; they'll affect the properties of the midblock and the endblock. On the other hand, you can pick a hydrocarbon and design it so that it only affects one of those blocks. So I would say that I can't see the SIS shortage creating any mass opportunities for pine chemical products because SIS polymers and pine chemicals are just too compatible.