Description Background

This invention relates to a process for producing a polyether polyol with a desired broad equivalent weight distribution out of the reactor that is useful for low ball rebound polyurethane foams which are otherwise known as viscoelastic polyurethane foams. The term "low ball rebound" refers to a test method that is employed to quantify the resilience of a foam. ASTM D 3574 Part H details such a test. A "low ball rebound" foam or viscoelastic foam is one with a ball rebound of less than 25%.

Low ball rebound foams are useful as energy absorbing material, sound absorbing material, vibration damping and in cushioning applications such as mattresses, chairs, medical applications and other upholstered furniture. Low ball rebound foams are commonly prepared by the reaction of a polyol component with a polyisocyanate in the presence of a blowing agent. The blowing agent is usually carbon dioxide which is released when the isocyanate reacts with water present in the foam formulation. At molar equivalent polyisocyanate to isocyanate reactive materials, the amount of water that is added to the formulation influences the amount of carbon dioxide released which in turn impacts the attainable foam density and to an extent foam hardness. Foam densities are typically in the range of 35-100 kg/m3.

Likewise the polyol component selection has a significant impact on foam properties. Usually a polyol functionality of around three hydroxyl groups/molecule is employed with an average molecular weight from 400-1500. The polyol equivalent weight is the most significant factor in influencing the glass transition temperature of the foam which subsequently significantly influences foam hardness. Some foam formulators use one main polyol of a molecular weight chosen to impart a viscoelastic nature to the foam at the use temperature. Such an example can be seen in WO 2008/021034 A2, example 17. However such an approach provides a foam that tends to have a fairly narrow tan δ peak especially when employing toluene diisocyanate as the isocyanate hence more often a mixture of polyols of differing equivalent weight is used in order to broaden the tan δ peak of the foam glass transition temperature. Such examples are shown in Table 1 of WO 2009/029626 A1 , Table 1 of WO 2006/125740 A2 and Table 1 of US 2007/290594 A1 . When foamers prefer a solution based on more than one polyol, they purchase the individual polyols and can blend them at the mixhead. This requires that the polyol producer and foamer have storage tanks for each individual polyol and that the foamer has a foam mixhead that can handle these multiple streams. Alternatively the foamer can request a blend of polyols from the polyol supplier and inject this at the mixhead, hence requiring the extra blendingprocess for the polyol supplier. This results in lower storage requirements for the foamer which can be particularly useful for small foaming sites.

US 5,847,014 teaches a process for making a foam with from a polyol blend comprising a standard polyol, a non-tertiary amine polyol and amine/alcohol. US 5919395 discloses a polyol combination comprising two polyols with differing molecular weights. W09816567 discloses a foam obtained from a mixture comprising 30-70% of a polyol having a high primary hydroxyl content and 70-30% of a rigid polyol having a molecular weight in the range of 300-1000. US 2003/0105177 demonstrates the use of a polyol composition with 4 polyols differing in molecular weights, oxide composition and functionality. All these patents relate the blending of polyols after their production to provide specific characteristics. The use of numerous polyols requires storage facilities for each product hence it would be highly desirable to reduce this to a minimum. US 6,491 ,846 teaches a process for the insitu production of a blend of a polyether monol and a polyether polyol for viscoelastic foam using DMC catalysis. The process requires that a mono-functional initiator be charged into the reactor at the beginning of the production process. The patent also claims that epoxides preferentially react with the low equivalent molecules which is a characteristic of DMC catalysis as known to those skilled in the art.

The prior art does not suitably provide the capability of providing low storage requirements at foamer and polyol supplier with a high quality and desirable low ball rebound foam.

Summary of the Invention The present invention is a process to produce a polyether polyol for low ball rebound foam with a broad equivalent weight distribution via the addition of epoxide to a combination of initiators in the presence of an alkoxylation catalyst where there is a difference in the average equivalent weights of the initiators. This process can take place in a batch or continuous reactor and more than one initiator (Si) may be present in the reactor prior to the start of the epoxide feed. In a continuous reactor, an initiator or more may be fed at a later position in the reactor. An initiator or initiators (S _a ) and optionally a portion of the alkoxylation catalyst may also be added to the reactor as a steady stream during the production process or added in one or multiple loads after the start of the epoxide feed such that one initiator is a transient insitu initiator represented by the alkoxylated initiator or initiators in the reactor. The initiator (S _a ) added during the epoxide feed may be the same that was present in the reactor prior to the addition of epoxide.

Initiators suitable as (S,) in the polyol production process can have 2 to 6 epoxide reactive groups per molecule but are preferably from 2 to 4 and most preferably from 2 to 3. Preferred initiators are water, ethylene glycol, 1 ,2-propylene glycol, 1 ,3-propylene glycol, the various isomers of butylene glycol, pentalene glycol, hexylene glycol, glycerine, trimethylolpropane, castor oil, pentarythritol, sorbitol, ethylene diamine, N,N'-bis(3-aminopropyl)ethylenediamine, tripropylenetetramine, tetrapropylenepentamine and their polyoxyalkylene adducts and mixtures thereof. More preferred iniators are water, ethylene glycol, 1 ,2-propylene glycol, 1 ,3-propylene glycol, the various isomers of butylene glycol, pentalene glycol, hexylene glycol, glycerine, trimethylolpropane, castor oil, pentarythritol, ethylene diamine, N,N'-bis(3- aminopropyl)ethylenediamine and their polyoxyalkylene adducts and mixtures thereof. Most preferred initiators are water, glycerine and their polyoxyalkylene adducts and mixtures thereof.

Initiators suitable as (S _a ) in the polyol production process can have 1 to 6 epoxide reactive groups per molecule but are preferably from 2 to 4 and most preferably from 2 to 3. Preferred initiators are water, ethylene glycol, 1 ,2-propylene glycol, 1 ,3-propylene glycol, the various isomers of butylene glycol, pentalene glycol, hexylene glycol, glycerine, trimethylolpropane, castor oil, pentarythritol, sorbitol, ethylene diamine, N,N'-bis(3-aminopropyl)ethylenediamine, tripropylenetetramine, tetrapropylenepentamine, ethanol, methanol, allyl alcohol, longer chain alcohols and their polyoxyalkylene adducts and mixtures thereof. More preferred iniators are water, ethylene glycol, 1 ,2-propylene glycol, 1 ,3-propylene glycol, the various isomers of butylene glycol, pentalene glycol, hexylene glycol, glycerine, trimethylolpropane, castor oil, pentarythritol, ethylene diamine, N,N'-bis(3-aminopropyl)ethylenediamine and their polyoxyalkylene adducts and mixtures thereof. Most preferred initiators are water, glycerine and their polyoxyalkylene adducts and mixtures thereof. Polyols according to the invention that are of particular interest are those with an average equivalent weight between the initiators at least 100, preferably at least 120 and most preferably at least 140 daltons. Inventive polyols have a final equivalent weight between 135 and 800, more preferably between 160 and 500 and most preferably between 200 and 400 daltons. Molecular weights referred to in this invention are number average molecular weights.

Suitable epoxides can include, for example, ethylene oxide, propylene oxide, butylene oxide, styrene oxide, etc and mixtures thereof. The epoxides can be polymerised using well known techniques and a variety of alkoxylation catalysts such as alkali metals, alkali metal hydroxides and alkoxides as well as double metal cyanide (DMC) complex catalysts.

What is typically done by formulators who want to broaden the tan δ peak when using one main polyol in a low ball rebound foam is that they blend together polyols of differing equivalent weights to obtain a similar equivalent weight as the replaced single polyol. In order to do this, each component polyol uses a storage tank and the blending is either performed in a tank, in-line or at the mixhead. If the formulating is performed at a polyol supplier, they may use either inline blending or a blending tank to prepare the polyol and then store in a separate storage tank. The polyol blend is then supplied to foam production locations that have a limited number of storage tanks and hence they have formulations based on the lowest quantity of components, especially those components that require large storage tanks such as polyols. The resultant low ball rebound foams that they produce can tend to have a sharp tan δ peak unless they use such polyol blends. The inventive polyol described here would enable those foamers to produce a foam with a broad tan δ peak as expected from a polyol blend whilst the polyol supplier will have substantially lower storage requirements and no need to blend. If the formulating is being done at a slabstock foamer, the components can be fed directly to the mixhead. The inventive polyol could allow these foamers to free storage tanks that they may need for other foam types. The economic advantages of the inventive polyol are thus the reduced number of storage tanks required at the polyol supplier and also at self-formulating foamers along with the capability to produce low ball rebound foams with wider tan δ peaks for foamers having limited storage space.

Detailed description of the invention

The present invention is a process to produce a polyether polyol for low ball rebound foam with a broad equivalent weight distribution via the addition of epoxide to a combination of initiators in the presence of an alkoxylation catalyst where there is a difference in the average equivalent weights of the initiators. This process can take place in a batch or continuous reactor and more than one initiator (S,) may be present in the reactor prior to the start of the epoxide feed. In a continuous reactor, an initiator or more may be fed at a later position in the reactor. An initiator or initiators (S _a ) and optionally a portion of the alkoxylation catalyst may also be added to the reactor as a steady stream during the production process or added in one or multiple loads after the start of the epoxide feed such that one initiator is a transient insitu initiator represented by the alkoxylated initiator or initiators in the reactor. The initiator (S _a ) added during the epoxide feed may be the same that was present in the reactor prior to the addition of epoxide.

Initiators suitable as (S,) in the polyol production process can have 2 to 6 epoxide reactive groups per molecule but are preferably from 2 to 4 and most preferably from 2 to 3. Preferred initiators are water, ethylene glycol, 1 ,2-propylene glycol, 1 ,3-propylene glycol, the various isomers of butylene glycol, pentalene glycol, hexylene glycol, glycerine, trimethylolpropane, castor oil, pentarythritol, sorbitol, ethylene diamine, N,N'-bis(3-aminopropyl)ethylenediamine, tripropylenetetramine, tetrapropylenepentamine and their polyoxyalkylene adducts and mixtures thereof. More preferred iniators are water, ethylene glycol, 1 ,2-propylene glycol, 1 ,3-propylene glycol, the various isomers of butylene glycol, pentalene glycol, hexylene glycol, glycerine, trimethylolpropane, castor oil, pentarythritol, ethylene diamine, N,N'-bis(3- aminopropyl)ethylenediamine and their polyoxyalkylene adducts and mixtures thereof. Most preferred initiators are water, glycerine and their polyoxyalkylene adducts and mixtures thereof. Initiators suitable as (S _a ) in the polyol production process can have 1 to 6 epoxide reactive groups per molecule but are preferably from 2 to 4 and most preferably from 2 to 3. Preferred initiators are water, ethylene glycol, 1 ,2-propylene glycol, 1 ,3-propylene glycol, the various isomers of butylene glycol, pentalene glycol, hexylene glycol, glycerine, trimethylolpropane, castor oil, pentarythritol, sorbitol, ethylene diamine, N,N'-bis(3-aminopropyl)ethylenediamine, tripropylenetetramine, tetrapropylenepentamine, ethanol, methanol, allyl alcohol, longer chain alcohols and their polyoxyalkylene adducts and mixtures thereof. More preferred iniators are water, ethylene glycol, 1 ,2-propylene glycol, 1 ,3-propylene glycol, the various isomers of butylene glycol, pentalene glycol, hexylene glycol, glycerine, trimethylolpropane, castor oil, pentarythritol, ethylene diamine, N,N'-bis(3-aminopropyl)ethylenediamine and their polyoxyalkylene adducts and mixtures thereof. Most preferred initiators are water, glycerine and their polyoxyalkylene adducts and mixtures thereof.

Polyols according to the invention that are of particular interest are those with an average equivalent weight between the initiators at least 100, preferably at least 120 and most preferably at least 140 daltons. Inventive polyols have a final equivalent weight between 135 and 800, more preferably between 160 and 500 and most preferably between 200 and 400 daltons. Molecular weights referred to in this invention are number average molecular weights.

Suitable epoxides can include, for example, ethylene oxide, propylene oxide, butylene oxide, styrene oxide, etc and mixtures thereof. The epoxides can be polymerised using well known techniques and a variety of alkoxylation catalysts such as alkali metals, alkali metal hydroxides and alkoxides as well as double metal cyanide (DMC) complex catalysts.

What is typically done by formulators who want to broaden the tan δ peak when using one main polyol in a low ball rebound foam is that they blend together polyols of differing equivalent weights to obtain a similar equivalent weight as the replaced single polyol. In order to do this, each component polyol uses a storage tank and the blending is either performed in a tank, in-line or at the mixhead. If the formulating is performed at a polyol supplier, they may use either inline blending or a blending tank to prepare the polyol and then store in a separate storage tank. The polyol blend is then supplied to foam production locations that have a limited number of storage tanks and hence they have formulations based on the lowest quantity of components, especially those components that require large storage tanks such as polyols. The resultant low ball rebound foams that they produce can tend to have a sharp tan δ peak unless they use such polyol blends. The inventive polyol described here would enable those foamers to produce a foam with a broad tan δ peak as expected from a polyol blend whilst the polyol supplier will have substantially lower storage requirements and no need to blend. If the formulating is being done at a slabstock foamer, the components can be fed directly to the mixhead. The inventive polyol could allow these foamers to free storage tanks that they may need for other foam types. The economic advantages of the inventive polyol are thus the reduced number of storage tanks required at the polyol supplier and also at self-formulating foamers along with the capability to produce low ball rebound foams with wider tan δ peaks for foamers having limited storage space. Foam types useful for this invention, would be those types used in the industry for low ball rebound foam and contain:

(a) the inventive polyol claimed in this patent or a blend of two or more such polyols

(b) optionally an additional polyol or additional polyols or mixture of polyols

(c) at least water as blowing agent

(d) a surfactant or mixture of surfactants

(e) one or more catalysts

(f) one or more di-isocyanates

(g) optionally chain extenders and/or crosslinkers

(h) optional additives such as fillers, anti-static agents, colorants, preservatives, odor masks, flame retardants, biocides, antioxidants, UV stabilizers, thixotropic agents and cell openers may be used.

The inventive polyol is described in the invention description is employed in the formulation and along with other components described here. The inventive polyol is preferably present at a level of at least 10% of the polyol component of the foam and more preferably at least 30% of the polyol component.

The additional polyol or polyols may be a polyether or polyester type. The additional polyol(s) may be a mixture of one or more additional monoalcohols or polyols. The additional monoalcohol(s) or polyol(s) may be used to perform various functions such as cell-opening, providing additional higher or lower temperature glass transitions to the polyurethane, modifying the reaction profile of the system and modifying polymer physical properties, or to perform other functions.

Polyether types would be based on an initiator with functionality of 1 to 8 and one or more alkylene oxides, such as ethylene oxide, propylene oxide or 1 ,2 butylene oxide. The oxides could be randomly or block fed or a combination of these.

The additional polyol may be a polymer polyol containing a monoalcohol or polyol having an equivalent weight of 500 or greater and a disperse polymer phase.

The disperse polymer phase may be particles of an ethylenically unsaturated monomer (of which styrene, acrylonitrile and styrene-acrylonitrile copolymers are of particular interest), polyurea particles, or polyurethane particles. The disperse phase may constitute from 5 to 60% by weight of the polymer polyol.

The additional polyol may also be a polyester polyol including reaction products of polyols, preferably diols, with polycarboxylic acids or their anhydrides, preferably dicarboxylic acids or dicarboxylic acid anhydrides. The polycarboxylic acids or anhydrides may be aliphatic, cycloaliphatic, aromatic and/or heterocyclic and may be substituted, such as with halogen atoms. The polycarboxylic acids may be unsaturated. Examples of these polycarboxylic acids include succinic acid, adipic acid, terephthalic acid, isophthalic acid, trimellitic anhydride, phthalic anhydride, maleic acid, maleic acid anhydride and fumaric acid. The polyols used in making the polyester polyols preferably have an equivalent weight of 150 or less and include ethylene glycol, 1 ,2- and 1 ,3-propylene glycol, 1 ,4- and 2,3-butane diol, 1 ,6-hexane diol, 1 ,8-octane diol, neopentyl glycol, cyclohexane dimethanol, 2-methyl-1 ,3-propane diol, glycerine, trimethylol propane, 1 ,2,6-hexane triol, 1 ,2,4-butane triol, trimethylolethane, pentaerythritol, quinitol, mannitol, sorbitol, methyl glycoside, diethylene glycol, triethylene glycol, tetraethylene glycol, dipropylene glycol, dibutylene glycol and the like.

The additional polyol may also be a polyol that has been derived from vegetable oils or it may be hydroxyl-functional polybutadiene polymers are also useful additional monoalcohols and polyols.

The foam formulation includes at least one blowing agent (component (c)), water, in an amount from about 0.8 to about 3 parts per 100 parts by weight of the polyol or polyol mixture. Although it is preferred that no additional blowing agent (other than the water) be included in the foamable polyurethane composition, it is within the scope of the invention to include an additional physical or chemical blowing agent. Among the physical blowing agents are supercritical C0 ₂ and various hydrocarbons, fluorocarbons, hydrofluorocarbons, chlorocarbons (such as methylene chloride), chlorofluorocarbons and hydrochlorofluorocarbons. Chemical blowing agents are materials that decompose or react (other than with isocyanate groups) at elevated temperatures to produce carbon dioxide and/or nitrogen.

A surfactant (component (d)) is preferably included in the VE foam formulation to help stabilize the foam as it expands and cures. Examples of surfactants include nonionic surfactants and wetting agents such as those prepared by the sequential addition of propylene oxide and then ethylene oxide to propylene glycol, solid or liquid organosilicones, and polyethylene glycol ethers of long chain alcohols. Ionic surfactants such as tertiary amine or alkanolamine salts of long chain alkyl acid sulfate esters, alkyl sulfonic esters and alkyl arylsulfonic acids can also be used. The surfactants prepared by the sequential addition of propylene oxide and then ethylene oxide to propylene glycol are preferred, as are the solid or liquid organosilicones. Low odour and low volatile organic compound emission surfactants are preferred. Examples of useful organosilicone surfactants include commercially available polysiloxane/polyether copolymers such as Tegostab™ B-8228 from Evonik, and Dow Corning SZ-1180, and Niax™ 627 surfactant from Momentive Performance Materials Inc..

Non-hydrolyzable liquid organosilicones are more preferred. When a surfactant is used, it is typically present in an amount of 0.0015 to 2 parts by weight per 100 parts by weight polyol or polyol mixture. One or more surfactants may be used in the foam formulation.

One preferred catalyst type for component (e) are tertiary amine catalysts. The tertiary amine catalyst may be any compound possessing catalytic activity for the reaction between a polyol or water and a polyisocyanate and contains at least one tertiary amine group. Representative tertiary amine catalysts include trimethylamine, triethylamine, N-methylmorpholine, N-ethylmorpholine, Ν,Ν-dimethylbenzylamine, N,N- dimethylethanolamine, N,N,N',N'-tetramethyl-1 ,4-butanediamine, N,N- dimethylpiperazine, 1 ,4-diazobicyclo-2,2,2-octane, bis(dimethylaminoethyl)ether, bis(2- dimethylaminoethyl) ether, morpholine,4,4'-(oxydi-2,1-ethanediyl)bis, triethylenediamine, pentamethyl diethylene triamine, dimethyl cyclohexyl amine, N- cetyl Ν,Ν-dimethyl amine, N-coco-morpholine, Ν,Ν-dimethyl aminomethyl N-methyl ethanol amine, N, N, N'-trimethyl-N'-hydroxyethyl bis(aminoethyl) ether, N,N-bis(3- dimethylaminopropyl)N-isopropanolamine, (Ν,Ν-dimethyl) amino-ethoxy ethanol, N, N, N', N'-tetramethyl hexane diamine, 1 ,8-diazabicyclo-5,4,0-undecene-7, N,N- dimorpholinodiethyl ether, N-methyl imidazole, dimethyl aminopropyl dipropanolamine, bis(dimethylaminopropyl)amino-2-propanol, tetramethylamino bis (propylamine), (dimethyl(aminoethoxyethyl))((dimethyl amine)ethyl)ether, tris(dimethylamino propyl) amine, dicyclohexyl methyl amine, bis(N,N-dimethyl-3-aminopropyl) amine, 1 ,2- ethylene piperidine and methyl-hydroxyethyl piperazine. The foam may contain one or more of these catalysts.

Another preferred group of catalysts are those which catalyse the reaction of a polyol or water and a polyisocyanate and also enable the resultant foam to have low emissions. Such catalysts may react with isocyanate to become bonded into the urethane matrix to avoid emissions. Alternatively, the catalyst could be of a sufficiently high molecular weight such that it would not provide emissions during the industry emission tests. Representative catalysts in this group are Dimethylaminopropyl urea, 3-, Momentive Performance Material's Niax EF series and catalytically active polyols such as Voranol Voractiv series from The Dow Chemical Company. The foam formulation may contain one or more of these catalysts.

The foam formulation may also contain other catalysts. The other catalyst is a compound (or mixture thereof) having catalytic activity for the reaction of an isocyanate group with a polyol or water. Suitable such additional catalysts include, for example: d1) tertiary phosphines such as trialkylphosphines and dialkylbenzylphosphines; d2) chelates of various metals, such as those which can be obtained from acetylacetone, benzoylacetone, trifluoroacetyl acetone, 3,3,5,5-tetramethylhexanoate, ethyl acetoacetate and the like, with metals such as Be, Mg, Zn, Cd, Pd, Ti, Zr, Sn, As, Bi, Cr, Mo, n, Fe, Co and Ni;

d3) acidic metal salts of strong acids, such as ferric chloride, stannic chloride, stannous chloride, antimony trichloride, bismuth nitrate and bismuth chloride; d4) strong bases, such as alkali and alkaline earth metal hydroxides, alkoxides and phenoxides;

d5) alcoholates and phenolates of various metals, such as Ti(OR)4, Sn(OR)4 and AI(OR)3, wherein R is alkyl or aryl, and the reaction products of the alcoholates with carboxylic acids, beta-diketones and 2-(N,N-dialkylamino)alcohols; d6) alkaline and alkaline earth metal, Li, Na, Bi, Pb, Sn or Al carboxylate salts; and d7) tetravalent tin compounds, and tri- or pentavalent bismuth, antimony or arsenic compounds.

Of particular interest are tin carboxylates and tetravalent tin compounds as well as the Bismuth carboxylates. Examples of these tin based catalysts include stannous octoate, dibutyl tin diacetate, dibutyl tin dilaurate, dioctyl tin dilaurate, dimethyl tin dilaurate, dimethyltinneodecanoate, dibutyl tin dimercaptide, dialkyl tin dialkylmercapto acids, dibutyl tin oxide, dimethyl tin dimercaptide, dimethyl tin diisooctylmercaptoacetate, and the like.

Catalysts are typically used in small amounts. For example, the total amount of catalyst used may be 0.0015 to 8, preferably from 0.01 to 1 part by weight per 100 parts by weight of polyol or polyol mixture. Organometallic catalysts are typically used in amounts towards the low end of these ranges.

Component (f) is an organic polyisocyanate having an average of 1.8 or more isocyanate groups per molecule. The isocyanate functionality is preferably from about 1.9 to 4, and more preferably from 1.9 to 3.5 and especially from 1 .9 to 2.5. Suitable polyisocyanates include aromatic, aliphatic and cycloaliphatic polyisocyanates. Aromatic polyisocyanates are generally preferred based on cost, availability and properties imparted to the product polyurethane. Exemplary polyisocyanates include, for example, m-phenylene diisocyanate, 2,4- and/or 2,6-toluene diisocyanate (TDI), the various isomers of diphenylmethanediisocyanate (MDI), hexamethylene-1 ,6- diisocyanate, tetramethylene-1 ,4-diisocyanate, cyclohexane-1 ,4-diisocyanate, hexahydrotoluene diisocyanate, hydrogenated MDI (H12 MDI), naphthylene-1 ,5- diisocyanate, methoxyphenyl-2,4-diisocyanate, 4,4'-biphenylene diisocyanate, 3,3'- dimethoxy-4,4'-biphenyl diisocyanate, 3,3'-dimethyldiphenylmethane-4,4'-diisocyanate, 4,4',4"-triphenylmethane tri-isocyanate, polymethylene polyphenylisocyanates, hydrogenated polymethylene polyphenylisocyanates, toluene-2,4,6-triisocyanate, and 4,4'-dimethyl diphenylmethane-2,2',5,5'-tetraisocyanate.

Also included as suitable isocyanates would be isocyanate terminated prepolymers of previously mentioned organic polyisocyanates. Prepolymers are extensively documented and are well known to those skilled in the art. Suitable reactants to produce the prepolymers would be polyether polyols, glycols, the inventive polyol described here, polyester polyols and mixtures thereof.

Preferred polyisocyanates include MDI and derivatives of MDI such as biuret- modified "liquid" MDI products and polymeric MDI, as well as mixtures of the 2,4- and 2,6- isomers of TDI and isocyanate prepolymers based on these materials.

The foamable composition may contain a chain extender or crosslinker (component (g)), but their use is generally not preferred, and these materials are typically used in small quantities (such as up to 10 parts, especially up to 2 parts, by weight per 100 parts by weight polyol or polyol mixture) when present at all. A chain extender is a material having exactly two isocyanate-reactive groups/molecule, whereas a crosslinker contains on average greater than two isocyanate-reactive groups/molecule. In either case, the equivalent weight per isocyanate-reactive group can range from about 30 to about 125, but is preferably from 30 to 75. The isocyanate-reactive groups are preferably aliphatic alcohol, primary amine or secondary amine groups, with aliphatic alcohol groups being particularly preferred. Examples of chain extenders and crosslinkers include alkylene glycols such as ethylene glycol, 1 ,2- or 1 ,3-propylene glycol, 1 ,4-butanediol, 1 ,6-hexanediol, and the like; glycol ethers such as diethylene glycol, triethylene glycol, dipropylene glycol, tripropylene glycol and the like; cyclohexane dimethanol; glycerine; trimethylolpropane; triethanolamine; diethanolamine and the like.

Of the additives (component (h)), one or more fillers may also be present in the VE foam formulation. A filler may help modify the composition's rheological properties in a beneficial way, reduce cost and impart beneficial physical properties to the foam. Suitable fillers include particulate inorganic and organic materials that are stable and do not melt at the temperatures encountered during the polyurethane-forming reaction. Examples of suitable fillers include kaolin, montmorillonite, calcium carbonate, mica, wollastonite, talc, high-melting thermoplastics, glass, fly ash, carbon black, titanium dioxide, iron oxide, chromium oxide, azo/diazo dyes, phthalocyanines, dioxazines and the like. The filler may impart thixotropic properties to the foamable polyurethane composition. Fumed silica is an example of such a filler. When used, fillers advantageously constitute from about 0.5 to about 30%, especially about 0.5 to about 10%, by weight of the composition.

Other additives as (component (h)) can also be flame retardants to improve the fire resistance of the foam, pigment dispersions or dyes to colour the foam, re- oderants to impart a desirable odour to the foam, UV stabilisers, preservatives and anti-oxidants to improve foam ageing, anti-static agents and biocides.

The low ball rebound foam can be prepared in a so-called slabstock process, or by various molding processes. Slabstock processes are of most interest. In a slabstock process, the components are mixed and poured into a trough, container or on an interlayer on a moving conveyor belt where the formulation reacts, expands freely in at least one direction, and cures. Slabstock processes are generally operated continuously at a commercial scale.

In a slabstock process, the various components are introduced individually or in various subcombinations into a mixing head, where they are mixed and dispensed. Component temperatures are generally in the range of from 15 to 35°C prior to mixing. The dispensed mixture typically expands and cures without applied heat. In the slabstock process, the reacting mixture expands freely or under minimal restraint such as may be applied due to the weight of a cover sheet or film.

In a slabstock process, the polyols are most often delivered to the mixing head as a separate stream. Where multiple polyols are needed, this results in multiple streams and multiple storage facilities.

It is also possible to produce the low ball rebound foam in a molding process, by introducing the reaction mixture into a closed mold where it expands and cures. In a molding process, it is typical to mix the the polyol(s), water and other components (except the polyisocyanate) to form a formulated polyol stream which is mixed with the polyisocyanate immediately before filling the mold. A prepolymer can be formed from the isocyanate and isocyanate reactive species such that there is an excess of isocyanate groups.

The amount of polyisocyanate that is required to produce a low ball rebound foam is sufficient to provide an isocyanate index of from 70 to 120. A preferred range is from 75 to 1 10 and a more preferred range is from 80 to 105. Good processing is indicated by the ability to produce stable, consistent quality foam over an extended period of operation in a continuous process.

The cured foam is characterized in having very low ball rebound values otherwise known as low resiliency. Resiliency is conveniently determined using a ball rebound test, such as AST D-3574-H, which measures the height a dropped ball rebounds from the surface of the foam when dropped under specified conditions. Under the ASTM test, the cured VE foam exhibits a resiliency of no greater than 25%, especially no greater than 15%. Especially preferred low ball rebound foams exhibit a resiliency according to ASTM D-3574-H test of no greater than 15%, especially no greater than 12%.

Another test which is an indicator of a desirable low ball rebound foam is the time required for the foam to recover after being compressed. A useful test for evaluating this is the so-called compression recovery test of ASTM D-3574M, which measures the time required for the foam to recover from an applied force. According to the ASTM method, the foam sample is compressed to a certain proportion of its initial thickness, held at the compressed thickness for a specified period, and then the compression foot is released to approximately the initial height of the foam sample. The foam re-expands and at approximately full re-expansion applies a force against the withdrawn foot. The time required until this applied force reaches 4.5 Newtons is the compressive recovery time. This time is desirably at least 2 seconds, more preferably at least 5 seconds, even more preferably at least 7 seconds, but less than 30 seconds and preferably less than 20 seconds.

The cured low balkl rebound foam advantageously has a density in the range of 30-120 kg/m3, preferably from 35-100 kg/m3) and more preferably from 40-85 kg/m3). Density is conveniently measured according to ASTM D 3574-01 Test A.

A particularly desirable low ball rebound foam for many applications has a density of from 40-85 kg/m3 and a resiliency of less than 15% on the ASTM ball rebound test. A more desirable low ball rebound foam for many applications further exhibits a recovery time of at least 3 seconds but not more than 30 seconds on the ASTM compression recovery test.

Low ball rebound foam made in accordance with the invention are useful in a variety of packaging and cushioning applications, such as mattresses, seating, packaging, bumper pads, sport and medical equipment, helmet liners, pilot seats, earplugs, and various noise and vibration dampening applications.

The following examples are provided to illustrate the invention, but are not intended to limit the scope thereof. All parts and percentages are by weight unless otherwise indicated.

Illustrative Example Polyol 1

276 grams of glycerine are added to a reactor with 8 grams of KOH. The mixture is dried. 825 grams of propylene oxide is gradually added to the mixture and allowed to react fully. The KOH is removed by filtering through a cake of magnesium silicate. This polyol is not part of the invention and is provided as a control example. Illustrative Example Polvol 2

184 grams of glycerine are added to a reactor with 8 grams of KOH. The mixture is dried. 1810 grams of propylene oxide is gradually added to the mixture and allowed to react fully. The KOH is removed by filtering through a cake of magnesium silicate. This polyol is not part of the invention and is provided as a control example.

Illustrative Example Polyol 3

884 grams of a 700 molecular weight triol produced via the addition of propylene oxide on glycerine is added to a reactor together with 116 grams of glycerine and 10 grams of KOH. This is represented as S1 in the invention description. After drying, 609 grams of propylene oxide is added to this mixture at standard reaction temperatures in the absence of oxygen as known by those skilled in the art until the propylene oxide has been consumed. The KOH is removed by filtering through a cake of magnesium silicate.

Illustrative Example Polyol 4

792 grams of a 700 molecular weight triol produced via the addition of propylene oxide on glycerine is added to a reactor together with 208 grams of glycerine and 10 grams of KOH. This is represented as S1 in the invention description. After drying, 609 grams of propylene oxide is added to this mixture at standard reaction temperatures in the absence of oxygen as known by those skilled in the art until the propylene oxide has been consumed. The KOH is removed by filtering through a cake of magnesium silicate. The resulting polyol would a broad molecular weight weight distribution with an average equivalent weight of around 235, also ideal for the use in low ball rebound foams.

Illustrative Example Polyol 5

278 grams of a 550 .wt propylene oxide extended, glycerine initiated polyol is added to a N ₂ blanketed empty reactor with 46 grams of glycerine and 13 grams of KOH. The reaction mixture is dried and 232 grams of propylene oxide is added and allowed to fully react. A further 46 grams of glycerine is added to the reactor followed by the controlled addition of 232 grams of propylene oxide. After reaction a further 46 grams of glycerine is added followed by 1100 grams of propylene oxide. The mixture is allowed to react to completion. The KOH is removed by filtering through a cake of magnesium silicate.

Illustrative Example Polvol 6

254 grams of a 500 MWt ethylene oxide extended glycerine initiated polyol is added to a N ₂ blanketed empty reactor with 46 grams of glycerine along with 13 grams of KOH. After drying, 1330 grams of propylene oxide is added slowly to the reactor along with a further 92 grams of glycerine over a 2 hour period. At the end of the 2 hours, the glycerine feed is stopped and a further 200 grams of propylene oxide is fed and allowed to fully react. The KOH is removed by filtering through a cake of magnesium silicate.

Comparative example polvol 1 and inventive polyols 3 & 4

The average molecular weights of comparative example polyol 1 and the inventive polyols 3 and 4 would be expected to be within 50 grams of each other at around 700g but the distribution of molecular weights would be quite different due to the delayed addition of initiator. Inventive polyols 3 &4 would have broader molecular weight peaks with an average equivalent weight of around 235. When employed in typical low ball rebound foam formulations as per the example foam formulation, the inventive polyols would be able to impart a broader glass transition temperature in the foam. Comparative example polvol 2 and inventive polyols 5 & 6

Likewise, the average molecular weight of comparative example polyol 2 and inventive polyols 5 and 6 would be expected to be within 100g of each other but because of the delayed initiator addition, the distribution of molecular weights would be different. The inventive polyols 5 and 6 would have a broader molecular weight distribution than current state of the art reactor polyol (comparative example polyol 2) used in low ball rebound foams.