Flexible slabstock foams

The steric effects in isocyanates are best demonstrated by the formation of flexible foams from TDI. In the 2,4-isomer (4), the initial reaction occurs at the nonhindered isocyanate group in the 4-position. The unsymmetrically substituted ureas formed in the subsequent reaction with water are more soluble in the developing polymer matrix. Low density flexible foams are not readily produced from MDI or PMDI enrichment of PMDI with the 2,4 -isomer of MDI (5) affords a steric environment similar to the one in TDI, which allows the production of low density flexible foams that have good physical properties. The use of high performance polyols based on a copolymer polyol allows production of high resiHency (HR) slabstock foam from either TDI or MDI (2). 

The resulting slate of polyols has been demonstrated in conventional flexible slabstock foam [143], viscoelastic foam [144], and high resiliency slabstock and molded foams [145],... 

This type of alkoxylation chemistry cannot be performed with conventional alkali metal hydroxide catalysts because the hydroxide will saponify the triglyceride ester groups under typical alkoxylation reaction conditions. Similar competitive hydrolysis occurs with alternative catalysts such as triflic acid or other Brpnsted acid/base catalysis. Efficient alkoxylation in the absence of significant side reactions requires a coordination catalyst such as the DMC catalyst zinc hexacyano-cobaltate. DMC catalysts have been under development for years [147-150], but have recently begun to gain more commercial implementation. The use of the DMC catalyst in combination with castor oil as an initiator has led to at least two lines of commercial products for the flexible foam market. Lupranol Balance 50 (BASF) and Multranol R-3524 and R-3525 (Bayer) are used for flexible slabstock foams and are produced by the direct alkoxylation of castor oil. 

Authors carefully investigated the potential causes of an increase in compressive modulus, which had been previously reported for flexible slabstock foams prepared from the polyols of the study [166]. Flexible foams prepared from a standard formulation containing two different levels of the epoxidized/hydroxylated soybean... 

Flame retardants are incorporated into the formulations in amounts necessary to satisfy existing requirements. There are four main types of flexible slabstock foam conventional, high resiliency, filled, and high load-bearing foam. 

The one-shot process is used for flexible and rigid foams. In the case of slabstock foams, the ingredients are separately supplied to the mixing head. In order to adjust viscosity and mixing accuracy, some of the ingredients, such as polyol and tin catalyst, water and amine catalyst, are pre-mixed. 

Flexible urethane foams include slabstock foam, molded foam, and pour-in-place foam. In some cases, the latter two foams can be called flexible RIM foams (RIM is an abbreviation for reaction injection molding). 

The main field of polyurethane application is the furniture industry, around 30% of the total polyurethanes produced worldwide is used for the production of mattresses from flexible slabstock foams. Automotive manufacture is the second important application for flexible and semiflexible polyurethanes (seat cushioning, bumpers, sound insulation, and so forth). Rigid polyurethane foams are used in thermal insulation of buildings and refrigerators, cold stores, pipe insulation, refrigerated transport, thermal insulation in chemical and food industries. The polyurethane elastomers are used for shoe soles,... 

The random copolyether triols PO-EO, usually called heteropolyether polyols, with a MW of 3000-3600 daltons, are the most important polyether polyols for flexible PU slabstock foams, generally used in furniture industry. The worldwide consumption of flexible PU foams is presented in Figure 4.16. 

In this section the most important random copolyether PO-EO structures were presented. Considering the highest production volume, the random copolyethers PO-EO with a MW of 3000-3600 daltons are the most important polyether type produced worldwide, used in continuous flexible slabstock foams, with the highest volume of consumption (of around 78% from the total flexible foams). 

The polyether polyols for flexible PU foams frequently have a distinct, unpleasant smell. In case of flexible slabstock foams where, in the centre of the PU bun, there are high temperatures (150-170 °C), an unpleasant odour appears during the foaming process which remains for a long time in the resulting PU foams. 

Aminoplast dispersions, in spite of the accessibility and low cost of raw materials, are not produced industrially, due to the risk of toxic formaldehyde elimination, especially when the resulting aminoplast polymer polyol is used for slabstock foams and, of course, for moulded flexible foams used for seating or interior automotive parts. 

Chem. Descrip. 2,2 -Dimorpholinodiethyl ether Uses Blowing catalyst tor PU flexible and rigid team, one-component foam, slabstock foams, coatings, adhesives Properties Sp.gr. 1.1 (20/20 C) t.p. -28 C b.p. 309 C flash pt. (TCC) 295 F... 

Methyl isocyanate Toluene-2,4-diisocyanate PU foam, flexible slabstock Dimethicone copolyol PU foundry resin additive 3-Glycidyloxypropyltriethoxysilane PU mfg. 

Dabco NE500 Newly developed non-fugitive gelling catalyst for flexible slabstock foam from APCI. APCI... 

Handmix rate of rise comparison tests were performed using the same equipment and process as described for TDI and MDI hand mix foam. The formulations used are listed in Table 1.42 and the rate of rise data reported in Table 1.43. Dabco BLV with Dabco T-9 was used as the industry standard catalyst control for the water blown flexible slabstock foam formulations. The silicone surfactant used in the reported flexible slabstock formulations was DC5160. All water blown formulations were made at densities of 23 kg/m. ... 

Dabco NE600 in combination with Dabco NE500 or Dabco NE600 as a sole amine catalyst used with increased levels of T-9 provides for equal or improved performance compared to Dabco BLV in all water-blown flexible slabstock foam. In all cases, these catalyst combinations can completely replace Dabco BLV and eliminate amine emissions from the flexible slabstock foam. 

Table 1.44 Physical properties for flexible slabstock foam ...

Details on the development and use of foam model systems for flexible moulded foam have been published [14]. In this section the features characteristic of slabstock foams will be highlighted. Table 1.47 illustrates the conversion of the formulations from Table 1.42 into a model system. 

The chemical flexible slabstock foam model provides a detailed look at the performance of the industry standard catalyst Dabco BLV compared to the non-fugitive catalysts Dabco NE500 and the Dabco NE500/Dabco NE600 package, keeping the Dabco T-9 level constant. Selectivity and conversion can be calculated as described previously. Note that... 

A comparison of the foaming profile found in a standard flexible slabstock foam production with the one seen during liquid carbon dioxide foaming clearly shows a large difference in the rise profiles, especially at the lay down (Figure 2.3). 

Additional Tasks of Silicone Surfactants in Flexible Slabstock Foam Production... 

Not taking cyclic molecules into account, the general structures of industrial silicone surfactants for flexible slabstock foam production can be seen in Figure 2.13. The main building blocks of these materials are a PDMS backbone and attached polyethers based on ethylene oxide and propylene oxide addition products. The siloxane backbones can either be linear or branched and can have their polyether substituents attached in an either pendant or terminal location. These four general structures are outlined in Figure 2.13). 

---