Today - Polyurethane Association of India

More documents

Recommendations

Info

PU Today Technical Article Cannon V.A.I.: Vacuum-Assisted Injection Technology for Refrigerators Production, Providing Cost-Effective Eco-design and Superior Energy Savings PIERO CORRADI Cannon Group Via Resistenza, 12 Peschiera Borromeo (Milano) Italy Abstract Cannon announces the first industrial mass production of domestic refrigerators manufactured with the new Cannon V.A.I. technology, a vacuum-assisted injection method specifically developed for the production of white cold appliances. An injection method introduced in 1998 - applying vacuum into the mold cavity where insulated sandwich panels are manufactured with the discontinuous production process - the vacuum-assisted injection has now successfully been applied to the geometrically complex design of domestic refrigerators. Prior to the foaming operation, a controlled degree of vacuum is applied into the jig where the empty refrigerator cabinet is positioned.. The reduced pressure applied into the cavity during the injection and the expansion of the foam facilitates the filling of the cabinet, providing substantial benefits: l optimized distribution of foam density throughout the entire cabinet. l the polymerization time per foaming station has been cut nearly in half due to the possibility of using high reactivity formulations providing 24 p o l y u r e t h a n e s t o d a y MAX TAVERNA Cannon Group Via Resistenza, 12 Peschiera Borromeo (Milano) Italy a significantly higher productivity. l reduced plant’s floor space in half when using the new “twin” foaming fixture - the RotoJig – specifically conceived for this technology. A partnership with Dow allowed for the development of PASCAL , an innovative technological solution that draws new frontiers in the production of refrigerators. The new Polyurethane chemistry, specifically developed for this application, reduces the foam thermal conductivity to a new reference level, while maintaining the density at least within the industry state-of-the-art levels and allowing for a shorter polymerization time. Several patents have been applied by the two companies in their respective fields of activity. In order to produce a refrigerator characterized by the same thermal conductivity in all its components, the vacuum-assisted injection technology has been extended to the door’s production method: the well known “Drum” Unit – a rotating multiple-mold manufacturing tool originally patented by Cannon in the early 1980’s – has been redesigned applying the vacuum capability, obtaining the same advantages described for the cabinets. The presentation of this Paper will be illustrated by a video, featuring the vacuum-assisted injection system during the validation phase, and by the updated results of the first industrial plant in operation at HAIER, the major global appliances producer based in P.R. of China. Initial Developments An innovative method for foaming sandwich insulation panels using vacuum during the injection phase was jointly developed – back in 1998 – by MISA (an Italian panel manufacturer), Manni (a polymerization press manufacturer), Cannon (the foaming machine producer) and Dow Italia (the supplier of the Polyurethane chemicals). Its functioning concept relied on the controlled application of vacuum into the polymerization cavity of the press, maintaining a constant level of negative pressure within the polymerization cavity during the entire injection and foam expansion’s time (Picture 1). High productivity (more than 300 large Picture 1 – Manufacture of sandwich panels with V.A.I. (Vacuum Assisted Injection) technology d e c e m b e r 2 0 1 1
panels per shift), enhanced panel quality, savings in raw materials and labor cost, and a very clean workplace characterized this new process (Picture 2). Blowing agents with a wider range of boiling points could be used and, very remarkable, Picture 2 – Demolding time greatly reduced due to the effect of vacuum during foam injection polyisocyanurate foam could be easily processed with the new injection technique. The resulting panels were filled with a foam characterized by an almost perfect distribution of density across the entire length (thus avoiding overweight, a widely used practice to guarantee a minimum safe density in the most remote corners of the panel) and by very high values of adhesion between foam and metal facings (deriving from the very low level of water required in the formulation to provide expansion, a practice which avoids the production in the foam of undesired Urea crystals that spoil adhesion properties). The Vacuum Effect As shown in Picture 3, the Pressure vs. Time graph shows the build-up of pressure in the polymerization cavity. The practice shows that safe demolding (when a panel can be demolded without the risk of swelling) can be performed at a residual pressure of approx. 200 mbar. The upper curve refers to a conventional d e c e m b e r 2 0 1 1 Picture 3 – Demolding time shortens because of reduced pressure build-up in the mold Picture PUR formulation, and the demolding time can be reached after 1800 s for a given thickness. The lower curve, referring to a vacuum-assisted injection system, shows that the application of 500 mBar of vacuum in the polymerization cavity allows to fill it faster and with a lower residual pressure. This means that the moment for safe demolding can be reached earlier, approximately at 360 s. A faster demolding that occurs without any loss of mechanical properties: in fact the structure of the foam results much finer (due to the fast-reacting formulation that can be employed) and more homogeneous in density across the entire panel due to the lower effort that the expanding mass must spend to reach the remote corners of the cavity (Picture 4). Picture 4 – Initial development with vacuum assisted molding gave promising results The minimum density at which the cavity is fully filled with foam decreases as the pressure is reduced. Working at 0.7 bar in the mold, the minimum filling density lowers by Technical Article 25%. (It has to be said that this huge savings cannot be fully exploited in practical terms of thermal insulation, since the mechanical properties of foam are also directly linked with its final molded density.) What can be concluded at this respect is that the applied vacuum helps the foam flowproperties, and the minimum filling density is significantly reduced. New Ideas Are Born It goes without saying that the successful use of vacuum-assisted injection immediately stimulated the idea to extend this technology to other application fields, beginning with the production of refrigerators and freezers. The technical problems – and the deriving advantages – were common among the two industries, but basic differences were to be found in the geometry of their respective final products. While it proved sufficiently easy to apply vacuum in the regular polymerization cavity of a sandwich panel and to obtain a perfect result, the complex geometry of a refrigerator’s cabinet immediately showed that much more engineering work was demanded to guarantee the same performance in a fridge: a 3D part with a complex inner core, “the plug” (Picture 5). Several metal parts must be moved hundreds of times per shift, in order to lock the refrigerator cabinet into its foaming position. Various sizes of cabinets must be feasible in the same Picture 5 – A combi refrigerator shows the difficult geometry, difficult to be filled with conventional foam and vacuum p o l y u r e t h a n e s t o d a y 25 PU Today
Page 1 and 2: d e c e m b e r 2 0 1 1 p o l y u r
Page 3 and 4: Dear Readers, It has been almost 75
Page 5 and 6: PUBLISHED BY THE INDIAN POLYURETHAN
Page 7 and 8: in Mumbai in the presence of many I
Page 9 and 10: solsticeLBA.com. *Source: U.S. Envi
Page 11 and 12: upgrade them for achieving superior
Page 13 and 14: inders. VORANOL VORACTIV polyols ex
Page 15 and 16: of the efforts in the collaboration
Page 17 and 18: d e c e m b e r 2 0 1 1 Product New
Page 19 and 20: gel-infused memory foam provides th
Page 21 and 22: lowing agents in flammability chara
Page 23: RAMPF at PlastIndia 2012 “Materia
Page 29 and 30: polymerization jig, by designing a
Page 31 and 32: from the RotoJig and goes to the ne
Page 33 and 34: ensure uninterrupted service to the
Page 35 and 36: to feature some sort of green or so
Page 37 and 38: Report: IPUA & Honeywell’s Semina
Page 39 and 40: eceived an excellent participation
Page 41 and 42: In this illustration the material f
Page 43 and 44: Rokopol iPol typical properties App
Page 45 and 46: d e c e m b e r 2 0 1 1 Environment
Page 47 and 48: two key messages, which are both pa
Page 49 and 50: Book Description Publication Date:

Today - Polyurethane Association of India

Create successful ePaper yourself

Delete template?

Save as template?