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“Before joint adhesive we used translucent white silicone,” recalls DuPont’s Tony Basilio. “We would squirt it in and slide the sheets together. But, we knew that wasn’t good enough. We wanted something to replace the silicone that would have a nicer look, be longer lasting and more sanitary. Joint adhesive was the answer. I don’t think anyone had any idea how it would revolutionize the industry.”
But revolutionize the industry it did. Introduced by DuPont in 1982, joint adhesive helped propel solid surface into the spotlight as a “space-age” material. Suddenly consumers could order a countertop with a monolithic appearance that was repairable, renewable and featured “inconspicuous” seams.
“It started with the idea to use joint adhesive on the deck, but where it really blossomed was on the edges,” explains Basilio. “At the time we used 3/4-in. material and the closest thing we had to a drop edge was a piece of Corian glued back under the edge with silicone. Suddenly we had all these designs that people could come up with and make it look like a very massive countertop. It changed the look of the whole countertop.”
You already know most of the other details: Corian’s 3-oz. two-part kit was the first adhesive package on the market, but was quickly matched by a generic bi-pack system offered by the other major manufacturers. Both types of systems required the fabricators to combine the resin and activator and knead the contents vigorously by hand for five minutes. Later, an “automated” mixing technique was introduced whereby up to four kits at a time might be clamped onto a vibrating sander and vibrated for a maximum of 45 seconds.
Having the ability to mix several kits at a time helped speed up the process, but fabricators began asking for a more efficient and economical method to dispense joint adhesive. Whether it was plastic tubes or baggies, the existing containers often leaked, were messy to use and wasted a lot of material. Again taking the initiative, DuPont introduced its pneumatic bulk adhesive cartridge toward the end of the decade. The system, which contained 380 ml. of material — the equivalent of about nine 3 oz. kits — offered a continuous supply of joint adhesive that was catalyzed at the point of delivery in a mixing nozzle. The great advantage to the cartridge idea was that any unused material remained in the tube to be used at a later date. But this new system was not without its own share of problems.
“We had some growing pains with the original cartridge,” says Basilio. “The adhesive manufacturer filled the cartridge through a valve, which was also used for dispensing the resin. Often, when filling the tube, resin would dribble into the valve and harden. Fabricators had to use a screw starter to get the hardened resin out before they could use the cartridge. The other thing was the packaging company switched the plastic used to make the cartridge after we had done our initial testing of the cartridge. The problem was the new plastic swelled up after our adhesive was put in it. Guys were having trouble getting it out of the guns.”
Progress On Another Front
While DuPont was struggling with its bulk adhesive cartridge, Nevamar (Fountainhead) began work with the folks at ConProTec, a company specializing in two-part dispensing systems, to adapt the MIXPAC 250 ml. cartridge system for use with solid surface joint adhesive.
“In working with Nevamar there were some chemistry challenges,” says David Kirsch, sales and marketing manager of ConProTec, a division of MIXPAC Systems AG. “Most of the formulations at that point were 20 to one, measured by weight. But they had to get the ratio to ten to one by volume so they could use the packaging that was most user-friendly. The sheet manufacturers were looking for a way to minimize their exposure from a warranty point of view. By putting the glue in our cartridge with a specially designed static mixer and our dispensing tool, it became mistake proof, and it took away the variability of the mix.”
The MIXPAC system consists of three tightly integrated components: a static mixer tip, a two-component cartridge and the dispensing gun. The ten to one ratio of resin to activator (catalyst) is controlled by the size of the cylinders into which each material is packaged, and is dispensed into the mixer tip by dual plungers.
