Polyurethanes are formed by stepwise polymerisation of isocyanates with alcohols. The exceptional ability to formulate with polyurethanes and thereby obtain vastly different properties, from thermoplastic grades to thermoset rigid foams, has made this class of polymers the largest commercial addition type of polymer known to industry today.

The largest application area for polyurethanes is the polyurethane foam area. From the early work by Otto Bayer in 1947,"Polyurethanes", Mod. Plast., 24, 149-152, 250-262 (1947), a tremendous development has taken place and with the introduction of new types of polyols, such as the polyether polyols in the late 1950's, which along with new catalysts and silicone additives made it feasible to produce foams in a commercial and cost efficient way, polyurethane foams have rapidly grown, leading to a global annual consumption of 3,435, 000 metric tonnes by 1998.

Polyurethane foams can be divided into the subclasses flexible foams, semi-flexible foams and rigid foams. The flexible foam market is by far the largest and the typical uses of flexible foams are in furniture, bedding, carpet underlay and automotive applications. The semi-flexible grades are also to a large extent used in furniture and for automotive applications. Rigid foams are to a large extent used as insulating materials, such as insulation of refrigerators and in district heating pipes. Another well known output for rigid foams are as components in cars to provide rigidity, yet low weight, in dash boards and other structural components. Energy management is another area where semi-flexible and rigid foams are used within the automotive industry.

The basic difference in the properties of flexible, semi-flexible and rigid foams are related to the glasstransition temperature (Tg), the flexibility of the reactants as such, the cellular structure, and to a large extent the crosslink density of the formed cellular network. The crosslink density is mainly controlled by the functionality of the polyol component of a polyurethane foam, but can also be controlled by the isocyanate functionality. However, since there is a wider range of polyols available with hydroxyl functionalities ranging typically from 1 to 6, the polyol choice or mixtures of different polyol grades are the normal way to adjust the crosslink density and hence the hardness, or rigidity, of a polyurethane foam.

A key aspect in formulating polyurethane foams is to control the hardness or firmness in relation to the flexibility or elasticity of the foam. Another key aspect is to control the final density of the foam. There is always a compromise in property profile between the hardness/rigidity of a foam on the one hand and on the other hand its elastic properties.

Normally, the higher the hardness or rigidity of the foam, the higher the crosslink density and the lower the flexibility of the foam.

The balance between firmness and flexibility is especially important in flexible foams, wherein the elastic properties are of utter importance to give the feeling of softness. There is a strong need for firmness in a foam, for instance to be able to carry a person's weight and to prevent the person from sinking too low into a furniture or automotive seat. It is, from a cost efficiency point of view, of interest to the manufacturer to use as little material as possible to produce a certain foamed product that can provide the right comfort level at as low a cost as possible. It is always, for this reason, desired to work at as low density as possible. A lower density, however, increases the need for firmness in a foam while retaining the flexible properties. A lower density has a mechanical effect on the load bearing capability of a foam.

The current state of the art for controlling the firmness in flexible foams is to add polymer polyols and/or small amounts of high functionality polyols as load builders. The current polymer polyols are normally thermoplastic and supplied as particle dispersions in a polyether polyol carrier. The polymer polyols are normally of polyurea, polyurethane or polyolefinic type. The latter types are typically produced by polymerisation of styrene or copolymerisation of styrene and acrylonitrile in the presence of a polyether polyol carrier.

The polymer polyols have the advantage of conferring good load bearing capability to a flexible foam, without deteriorating the flexible properties. The disadvantages of polymer polyols are that they increase the resin viscosity at higher addition levels and also normally destabilise the foam at high addition levels as well as at lower densities and will at a certain critical density, depending on type, cause foam collapse.

High functionality polyols, such as hexitol or glycerine based low molecular weight polyols, are very efficient in building compressive loads and stabilising the foam, but will deteriorate the flexible properties even at low addition levels.

It has now quite surprisingly been found that a novel polyether polyol, a chain extended dendritic polyether, combines the positive aspects of high functionality polyols with the positive aspects of thermoplastic polymer polyols, without or with negligible negative effects associated with these types of products typically used to obtain firmness in a flexible foam.

The chain extended dendritic polyether provides, due to the dendritic globular backbone structure with a substantially linear chain extension, exceptionally high molecular weight and hydroxyl functionality, yet very low resin viscosity. The dendritic polyether of the present invention is liquid at room temperature as 100% product and does hence not require that the active load bearing component, as is the case with polymer polyols, is dispersed in a base polyol carrier in order to obtain suitable resin viscosity.

The inherently flexible backbone and the high molecular weight furthermore provides flexibility to a thermosetting matrix. The high functionality will locally significantly increase the crosslink density and hence in an effective way confer good load building properties to a flexible foam. The chain extended dendritic polyether will, due to its cross linking ability and the non-particulate nature, confer improved foam stability at low density.

The present invention accordingly refers to a polyurethane foam composition comprising at least one diisocyanate, at least one polyether alcohol having at least two primary or secondary hydroxyl group, at least one blowing agent, at least one gelling and/or blowing catalyst and at least one chain extended and optionally at least partially chain stopped dendritic polyether.

The chain extended dendritic polyether comprises in preferred embodiments a dendritic core polymer and a substantially linear chain extension bonded to said core polymer and optionally at least one chain termination bonded to said chain extension and/or said core polymer. The core polymer is preferably a polyhydric dendritic polyether obtained by ring opening addition of at least one oxetane to a di, tri or polyhydric core molecule at a molar ratio yielding a polyhydric dendritic polyether comprising a core molecule and at least one branching generation bonded to at least one hydroxyl group in said di, tri or polyhydric core molecule.

The chain extension is likewise preferably obtained by a subsequent addition of at least one allcylene oxide, such as ethylene oxide, propylene oxide, 1,3-butylene oxide, 2,4-butylene oxide, cyclohexene oxide, butadiene monoxide and/or phenylethylene oxide, to at least one hydroxyl group in said core polymer at a molar ratio said core polymer to said alkylene oxide of between 1: 1 and 1: 100, preferably between 1: 2 and 1: 50. The thus obtained chain extended dendritic polyether is in certain embodiments at least partially chain terminated by addition of at least one monomeric or polymeric compound, preferably at least one monofunctional aliphatic or aromatic isocyanate or carboxylic acid.

The di, tri or polyhydric core molecule is in embodiments of the dendritic core polymer advantegously a l,-diol, a 5-hydroxy-1, 3-dioxane, a 5-hydroxyallcyl-1, 3-dioxane, a 5-alkyl-5-hydroxyalkyl-1, 3-dioxane, a 5,5-di (hydroxyallcyl)-1, 3-dioxane, a 2-alkyl-1, 3- - propanediol, a 2, 2-dialkyl-1, 3-propanediol, a 2-hydroxy-1, 3-propanediol, a 2-hydroxy-2- - alkyl-1, 3-propanediol, a 2-hydroxyalkyl-2-alkyl-1, 3-propanediol, a 2,2-di (hydroxyalkyl) - - 1, 3-propanediol or a dimer, trimer or polymer of a said di, tri or polyhydric alcohol. Further embodiments of the di, tri or polyhydric core molecule include reaction products between at least one alkylene oxide, such as ethylene oxide, propylene oxide, 1,3-butylene oxide, 2,4-butylene oxide, cyclohexene oxide, butadiene monoxide and/or phenylethylene oxide, and a l, co-diol, a 5-hydroxy-1, 3-dioxane, a 5-hydroxyalkyl-1, 3-dioxane, a 5-alkyl-5-hydroxy- alkyl-1, 3-dioxane, a 5,5-di (hydroxyalkyl)-1, 3-dioxane, a 2-alkyl-1, 3-propanediol, a 2, 2-diallcyl-1, 3-propanediol, a 2-hydroxy-1, 3-propanediol, a 2-hydroxy-2-alkyl-1, 3- - propanediol, a 2-hydroxyalkyl-2-alkyl-1,3-propanediol, a 2,2-di (hydroxyalkyl)-1, 3- - propanediol or a dimer, trimer or polymer of a said di, tri or polyhydric alcohol.

Embodiments of the di, tri or polyhydric core molecule furthermore include and is suitably exemplified by compounds such as 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,6-cyclohexanedimethanol, 5, 5-dihydroxymethyl-1, 3-dioxan, 2-methyl-1, 3-propanediol, 2-methyl-2-ethyl-1, 3-propanediol, 2-ethyl-2-butyl-1, 3-propanediol, neopentyl glycol, dimethylolpropane, 1, 1-dimethylolcyclohexane, glycerol, trimethylolethane, trimethylolpropane, diglycerol, ditrimethylolethane, ditrimethylolpropane, pentaerythritol, dipentaerythritol, anhydroenneaheptitol, sorbitol or mannitol as well as by reaction products between at least one alkylene oxide as previously disclosed and a herein said alcohol.

The oxetane, added to said core molecule by ring opening addition, is preferably and advantageously a 3-alkyl-3- (hydroxyalkyl) oxetane, a 3,3-di (hydroxyalkyl) oxetane, a 3-allcyl-3-(hydroxyalkoxy) oxetane, a 3-allcyl-3-(hydroxyalkoxyallcyl) oxetane or a dimer, trimer or polymer of a 3-alkyl-3- (hydroxyalkyl) oxetane, a 3,3-di (hydroxyalkyl) oxetane, a 3-alkyl-3- (hydroxyallcoxy) oxetane or a 3-alkyl-3- (hydroxyallcoxyalkyl) oxetane, such as 3-methyl-3- (hydroxymethyl) oxetane, 3-ethyl-3- (hydroxymethyl) oxetane and/or 3,3-di (hydroxymethyl) oxetane. The most preferred oxetane is an oxetane of trimethylolethane, trimethylolpropane, pentaerythritol, ditrimethylolethane, ditrimethylolpropane or dipentaerythritol.

The chain extended and optionally at least partially chain terminated dendritic polyether, included in the polyurethane foam composition of the present invention, has in preferred embodiments a hydroxyl functionality of nominally less than 18 hydroxyl groups/molecule, such as less than 16 or less than 14.

The diisocyanate, included in the polyurethane foam composition of the present invention, is preferably 2, 4-toluenediisocyanate, 2, 6-toluenediisocyanate, diphenyhnethane diisocyanate or mixtures and/or polymeric derivatives of one or more of said diisocyanates.

The polyether polyol, having said at least two primary or secondary hydroxyl groups, included in the polyurethane composition of the present invention has preferably a molecular weight of at least 100 g/mole, the blowing agent is likewise preferably water, a fluorocarbons of the CFC type, methylene chloride, pentane or carbon dioxide. The gelling and/or blowing catalyst is preferably at least one organometallic or amine compound.

Embodiments of the polyurethane foam composition of the present invention can additionally comprises at least one polyester polyol having at least two primary or secondary hydroxyl groups and a molecular weight of at least 100 g/mole and/or at least one polymer polyol of polyurea, polyurethane, styrene or styrene acrylonitrile type.

In a further aspect, the present invention refers to the use of the polyurethane foam composition herein disclosed as component in production of polyurethane based domestic, industrial and vehicular goods and articles, such as domestic mattresses and other bedding, domestic and vehicular cushions, arm rests and head rests, which goods and articles in preferred embodiments are made from moulded or slabstock foam.

Without further elaboration, it is believed that one skilled in the art can, using the preceding description, utilise the present invention to its fullest extent. The following preferred specific embodiments are, therefore, to be construed as merely illustrative and not limitative of the remainder of the disclosure in any way whatsoever. These and other objects and the attendant advantages will be more fully understood from the following detailed description, taken in conjunction with appended embodiment Examples 1-4, wherein Example 1 shows preparation of second generation dendritic polyether used in Examples 2 as core polymer, Example 2 and 3 shows preparation of chain extended dendritic polyethers wherein the product of Example 1 is used as core polymer and ethylene oxide as chain extension monomer, and Example 4 show preparation and evaluation of polyurethane foam compositions, according to embodiments of the present invention, in comparison with a reference.

Example 1 7.28 kg of ethoxylated pentaerythritol (Polyol PP50TM, Perstorp Specialty Chemicals AB) and 71.7 g of BF3 ethyl etherate were charged to a steel reactor equipped with stirrer, oil heating, water cooling, nitrogen inlet and cooler. The mixture was heated to 110°C. Forced cooling was imposed to the reactor and addition of 28.55 kg of a 3-ethyl-3- (hydroxymethyl) oxetane (TMPO) commenced at a feeding rate of 0.82 kg-1. The reaction was exothermic and the exotherm continued for a further 20 minutes after completed feeding of TMPO and excessive cooling was required. The reaction was then allowed to continue at 110°C for a further 4 hours, after which 125 g of aqueous NaOH (41%) was added to stop the living character of the polymer. The reaction mixture was stirred for 20 minutes at 110°C and full vacuum was then applied to remove any residual monomer and water originating from the aqueous base.

Obtained polyhydric dendritic polyether of two generations exhibited following properties: Hydroxyl value, mg KOH/g: 518 Molecular weight, (GPC) g/mole: 1450 Nominal molecular weight, (GPC) g/mole: 1088 Polydispersity: 1.33 Example 2 35.8 kg of a polyhydric dendritic polyether obtained in Example 1 was heated to 80°C and an aqueous solution of KOH was charged in an amount corresponding to 357 g of neat KOH. The reaction mixture was stirred at said temperature for 1 hour, after which the alcoholate of the product obtained in Example 1 was considered to have formed. Full vacuum was then applied and the temperature was gradually increased to 110°C to remove any water present in the alcoholate mixture. 28.8 kg of ethylene oxide was now under pressure and nitrogen atmosphere charged to the reaction mixture during 1.5 hour and the temperature was kept at 110-120°C. The reaction was allowed to continue at 110°C for a further 3 hours after completed feeding of ethylene oxide. The reaction product was then cooled to 80°C and sulphuric acid was added in stoichiometric amounts to previously charged KOH. K2SO4 precipitated from the solution and was removed by filtration, after which the final product was recovered.

Obtained chain extended dendritic polyether exhibited following properties: Hydroxyl value, mg KOH/g: 291 Average hydroxyl functionality, eq: 14.1 Peak molecular weight (GPC), g/mole: 2723 Molecular weight (GPC), g/mole: 2575 Nominal molecular weight (GPC), g/mole: 2033 Polydispersity index: 1.27 Viscosity (25°C, Brookfield), mPas : 9200 Non-volatile content, % by weight: 99.5 Example 3 Example 2 was repeated with the difference that 86.5 kg of ethylene oxide was charged instead of 28.8 kg and that the feeding time was 3 hours instead of 1.5 hour.

Obtained chain extended dendritic polyether exhibited following properties: Hydroxyl value, mg KOH/g : 150 Average hydroxyl functionality, eq: 10.8 Peak molecular weight (GPC), g/mole: 4052 Molecular weight (GPC), g/mole: 4181 Nominal molecular weight (GPC), g/mole: 3153 Polydispersity index: 1.33 Viscosity (25°C, Brookfield), mPas : 2200 Non-volatile content, % by weight: 99.5 Example 4 Flexible polyurethane foam compositions, suitable for applications such as furniture and automotive seating, were prepared from the products obtained in Examples 2 and 3, respectively, toluene diisocyanate (TDI) (Lupranat T80, BASF AG), a base polyol with a hydoxyl value of 30 mg KOH/g (Hyperlite 1656, Bayer-Lyondell AG), water as blowing agent, a diethanolamine crosslinking/curing agent (DEOA-LF), a blowing catalyst (Niax A-l, Witco Corp. ), a surfactant (Niax'2'RS171, Witco Corp. ) and a triethylene diamine/dipropylene glycol gelatiori catalyst (DABCTM 33LV, Air Products). A reference sample was also prepared without the products of Examples 2 and 3.

All foams were made using a hand mix moulding technique carried out using a mechanically driven mixer, equipped with a 2"CONN blade, at 2500 rpm. The base polyol, the chain extended dendritic polyether, the surfactant, the crosslinker, the catalyst and the water were premixed for 30 seconds in a plastic cup, followed by the immediate addition of corresponding amount of TDI, which mixture was then stirred for 5 seconds. The polyurethane foam mixture was thereafter poured into plastic moulds with the dimension 10 x 10 cm and allowed to foam according to a free rise.

After demoulding, the obtained foams were post-cured at room temperature for a further 48 hours prior to machining to the specimen shape required for mechanical evaluation.

Subsequently, the foam specimen were conditioned for at least 16 hours at 23 2°C and 50 5% relative humidity prior to testing. The tests, density, compression force deflection (CFD) at 50% deformation and tensile properties, were carried out according to ASTM D3574.

The formulations are given in Table 1 and obtained physical and mechanical properties in Table 2 and Graph 1 below.

Table 1 Formulation Reference Sample 1 Sample 2 Sample 3 Hyperlitee 1656, g 100 95 90 95 Product acc. to Example 2, g -- 5 10 -- Product ace. to Example 3, g------5 Water, g 4 4 4 4 DEOA-LF, g 1.5 1.5 1.5 1.5 DABCOTM 33 LV, g 0.2 0.2 0.2 0.2 NiaxA-l, g 0.03 0.03 0.03 0.03 Niax RS 1715 g 0.75 0.75 0.75 0. 75 Index 105 105 105 105 Toluene diisocyanate, g 48.79 50.47 51.94 49.38 Table 2 Formulation Reference Sample 1 Sample 2 Sample 3 Density, kg/m3 33 33 34 36 CFD at 50%, N 73 98 105 84 Tensile strength, kPa 58 50--44 Elongationultimate,% 225 150 -- 155 Graph 1 Compressive force deflections (CFD) of polyurethane foams modified with chain extended dendritic polyether according to Sample 2 and 3 of Example 4.

CFD of Polyuretane Foams Modified with Chain Extended Dendritic Polyethers Chain Extended Dendritic Pblyether Content [pph]