Rubber Granulators – Case Study: VULCANATOR® Reduces Rubber Bales and Processing Time

Problem: A manufacturer of surgical gloves had a problem in establishing a new production line to meet their capacity requirements and quality standards. The major raw ingredient in surgical gloves, natural rubber, was received in the form of full 75 lb. bales of raw rubber. The first step in the process was to reduce the bales to a small size, since dissolving of the full rubber bales would take an unacceptably long amount of time and be very costly.

A granulator was required that had to meet a number of requirements. It had to be able to reduce the tough rubber and be built to medical standards for cleanability and corrosion resistance. It also could not employ talc in the process because of the concern about allergic reactions.

It turned out finding a unit to meet these requirements wasn’t going to be easy.

A number of approaches were studied and ruled out including guillotine cutters, hammer mills and extruders. The problem is this rubber material, like most rubber, is a sticky, cold flowing product that can easily gum up in equipment. The cut pieces are sticky to the touch and can quickly re-agglomerate. The handling of this material is amongst the toughest of size reduction applications which has vexed many manufacturers for years.

The granulator manufacturers they approached either didn’t have a unit that could handle the tough rubber bales, had equipment that required expensive cooling equipment, or couldn’t supply a unit that could meet the sanitary requirements demanded by this application. In fact, several standard granulators they considered failed completely in performance tests. The key to the project’s success was finding a solution and time was quickly running out. That’s when the company’s project engineer contacted Franklin Miller.

Solution: FMI’s application engineers, working closely with the customer, performed some preliminary tests on the rubber bales. Through this evaluation process, it was determined that their 100 HP VULCANATOR® could handle the application and with some special modifications, an order was placed. To meet the tight delivery schedule the machine had to be built on an accelerated time table.

The VULCANATOR is a special granulator designed specifically for the rubber industry. It is typically used in these types of applications to promote the dissolving of rubber into solution in the molding of rubber products, adhesives and synthetic fuel oils. The units are typically sold for use before a mixing tank or sold as part of a complete mixing system for accelerated dissolving. The unit can handle various types of natural and synthetic rubber such as Butyl, Viton, EDPM, Solprene, Hypalon, Hycar and more. The VULCANATOR can handle all types and shapes including full bales, sheets and chips. Additionally, the VULCANATOR can be used for foam rubber recycling applications of such items as mattresses, car seat cushions and covers. It can even cut the metal springs trapped in these items.

The VULCANATOR employs a unique cutting design that reduces the rubber bales into progressively smaller pieces with rotating knives while minimizing heat rise. With this design, the need for expensive auxiliary cooling equipment is eliminated. A variety of screens are provided to optimize output for each application requirement. To keep the material from re-agglomerating, a partitioning agent is typically used such as talc, or limestone or surfactants.

A number of VULCANATOR models are available for handling from 500 lbs to 5000 lbs per hour of rubber. These units use from 60 HP to 250 HP motors.

For this application, the VULCANATOR was designed with all contact parts constructed of stainless steel and with a special seal system to operate in a wet environment. Access doors were provided for easy maintenance of all major cutting elements as well as convenient cleaning and sanitizing. The unit is built with a rugged welded frame construction for rigidity.

A special hopper was designed to meter the bales into the chamber and insure that the material is effectively processed by the cutting knives.

The VULCANATOR can be mounted directly above a dissolving tank or used in conjunction with a discharge conveyor such as a belt conveyor or pneumatic system. Feeding is either manual or automated with conveying equipment.

After completion of construction, the machine was put through a final shop performance test with the actual material. The powerful VULCANATOR dependably reduced a number of the full bales and met the required output size.

The unit was then installed at the plant site. After installation, the unit was started up and the results were impressive. Not only is the new process with the VULCANATOR meeting production goals, but a higher quality product is being produced. The VULCANATOR has shaved a great deal of time off the dissolving process and in so doing has made the operation more profitable. In fact, according to the plant engineer the dissolving time has been reduced by 93%. “Without the VULCANATOR, the project would not have been a success,” he said.