Rosehill revolutionise pur production with semi-continuous process
November 2006
A unique, semi-continuous reaction process for manufacturing polyurethane hot melt reactive adhesives (PURs) is set to replace outdated and inadequate techniques which have so far limited growth in the sector, according to the British company which has developed it.
Rosehill Polymers of Sowerby Bridge, West Yorkshire, have introduced a semi-continuous process to manufacture their Fleximelt range of PURs for use in a wide range of industrial applications.
Rosehill have been at the forefront of continuous reactor technology for several years and the latest version of their reactor for liquid products can produce prepolymers at a rate of 1,000 kg. in 13 minutes. It requires only one operator and has quickly brought significant environmental benefits while also improving manufacturing flexibility and efficiency and product quality and consistency. They are now applying this same production technology to the production of PUR adhesives.
Continuous manufacturing is also bringing Rosehill more export opportunities as an increasing number of European countries, notably Holland, Belgium and Germany, are anxious to replace solvent-based adhesives with PURs. The flexibility of the process means that the company can meet customer requirements more quickly, even where a large number of small batches are needed.
A PUR hot melt adhesive is a moisture curing material which is thermoplastic in its uncured state. It is melted to be applied and forms a bond when it solidifies. It can be re-melted to break the bond or reposition joints as necesssary. However, it differs from conventional thermoplastic hot melt adhesive in that after undergoing a reaction with atmospheric moisture it becomes a thermoset material that cannot be re-melted.
Dr. Colin Reed of Rosehill Polymers said: ÒPUR hot melt adhesives have been developed through much formulating expertise and the use of high quality raw materials, but manufacturing methods have hindered their exploitation. We believe that a semi-continuous reaction process is the best way to drive developments within this exciting and growing area.Ó Not only does continuous manufacturing provide a better product, it does so in an environmentally friendly way. The process generates less waste than other PUR manufacturing systems, while cleaning requirements Ð and the use of the necessary solvents Ð is much reduced.
ÒIn all aspects of our business we are looking to adopt a Ôlean manufacturingÕ approach and this continuous manufacturing process is making a substantial contribution, Ò said Dr.Reed. ÒThere is a tremendous space-saving compared with batch reactors, production speed is much higher, there are no limits on batch size and we can switch between products very easily.Ó
Rosehill are leaders in technology for the manufacture of continuously manufactured urethane polymers and their highly efficient flow reactor takes products straight from bulk storage and mixes them under intense conditions. This ensures that the reaction runs with the correct excess of isocyanate groups. This in turn provides better ÒcappingÓ of the polyols, tighter molecular weight distribution, lower melt viscosity and better crystallisation rates. As a result, Rosehill are able to easily produce specialist products containing small amounts of highly crystalline polyesters such as dodecanediol adipate. The process also yields real benefits in the packaging procedure.
Rosehill currently offer three products in their Fleximelt range of PURs:
Fleximelt 7100: fast-setting with high bond strength and most suited to automated factory processes such as profile wrapping and edge banding.
Fleximelt 7200: a range of multi-purpose reactive hot melt adhesives. They are medium to high viscosity with long open times and high uncured strength. Suitable for semi-manual assembly processes with excellent adhesion to plastics, metals, wood and MDF.
Fleximelt 7300: for flexible laminating applications, for example with fabrics, membranes and foams. Flexible, heat and chemical resistant.
The versatility of the Fleximelt range is opening up new markets for Rosehill and the company has just taken its first orders from the bookbinding industry.