A polyol blend for preparing a water-blown polyurethane foam, and a method of preparing a water-blown polyurethane foam

Abstract

The invention relates to a polyol blend for preparing a water-blown polyurethane foam, the blend comprising: at least 35.0 mass-% and at most 50.0 mass-% of a polyol component, said polyol component consisting of one or more carbohydrates each having a hydroxyl functionality of equal to or more than 4; and at least 30.0 mass-% of water as a blowing agent, wherein all mass concentrations are based on the total mass of the polyol blend. The invention further relates to a method of preparing a water-blown polyurethane foam.

Description

[0001] Applicant :

[0002] Storopack Hans Reichenecker GmbH

[0003] Untere RietstraBe 30

[0004] 72555 Metzingen

[0005] 35020904WO 07 . 01.2026

[0006] KNA / KUN

[0007] Title : A polyol blend for preparing a water-blown polyurethane foam, and a method of preparing a water-blown polyurethane foam

[0008] Specification

[0009] The present invention relates to the technical field of polyurethane (PU) foams . Particularly, the present

[0010] invention relates to a polyol blend for preparing a water-blown polyurethane foam, and to a method of preparing a water-blown polyurethane foam.

[0011] Polyurethane foams are prepared by reacting one or more polyisocyanates, i . e . compounds containing at least two isocyanate functionalities, with one or more polyols, i . e . compounds containing at least two hydroxyl functionalities .In the production of polyurethanes, the polyol or polyols are typically provided as part of a liquid composition that is referred to as the "polyol blend" . Upon mixing of the polyol blend with a polyisocyanate, an exothermic reaction between the polyol or polyols and the polyisocyanate takes place . The isocyanate groups react with the hydroxyl groups, thereby forming urethane linkages which constitute the polyurethane foam' s polymer backbone .

[0012] In order to obtain the resulting polyurethane as a polyurethane foam, the polyol blend may be supplemented with a blowing agent . The presence of a blowing agent promotes the development of bubbles during the reaction and, thus, the formation of a foam structure . The phase of polyurethane formation in which the foam structure is formed by the blowing agent is referred to as the expansion phase . The expansion phase is followed by a curing phase in which the remaining chemical reactions complete and the foam solidifies into its final form. The curing phase can take varying amounts of time depending on the formulation and on the process conditions .

[0013] Blowing agents can be classified into physical blowing agents and chemical blowing agents . A physical blowing agent is normally a low boiling point liquid. Particularly, halogenated compounds such as hydrofluoroolefins (HFOs) may be used as physical blowing agent . A chemical blowing agent reacts with isocyanate groups and / or with hydroxyl groups, thereby forming a gas . Water is a preferred choice as a chemical blowing agent . Water may react with isocyanategroups under the formation of chemically unstable carbamic acid groups . The carbamic acid groups decompose, releasing carbon dioxide (CO2) and leaving behind an amine group .

[0014] Remaining water that does not react with isocyanate groups may turn into steam due to the exothermic nature of the polyurethane-forming reaction, thus additionally acting as a physical blowing agent contributing to the opening of the foam cells . The use of water as a blowing agent avoids the release of environmentally hazardous volatile substances, offering a sustainable alternative . The density of the resulting foam generally corresponds to the concentration of blowing agent, e . g. water, in the polyol blend. Thus, a higher concentration of blowing agent may result in a foam having a decreased density, and vice versa .

[0015] Polyurethane foams, particularly semi-rigid variants, have gained significant traction in industrial packaging applications due to their highly versatile protective properties . One of the key advantages of polyurethane foams lies in their ability to restrict the physical displacement of packaged items, offering excellent stability during transport . Due to the possibility of producing polyurethane foams in situ by mixing liquids, i . e . the isocyanate component and the polyol blend, voids of any geometry between an obj ect and a primary packaging material can be supplied with the mixed liquids and thus filled with polyurethane foam. During formation, the polyurethane foam may expand to fill even irregular cavities . This feature eliminates the need for custom molds or cutting pre-formed foams, providing a more efficient and flexible solution fora wide variety of packaging requirements . This adaptability simplifies the process, making it ideal for protecting items with complex shapes or sizes .

[0016] The production of rigid or semi-rigid polyurethane foams is a carefully controlled process that relies on the chemical reaction between a polyisocyanate or polyisocyanates and a polyol or polyols in the presence of one or more blowing agents . The polyol blend often comprises a polyether polyol, a polyester polyol, or a mixture of both, with polyether polyols being mostly chosen.

[0017] Polyether polyols may be synthesized via a polymerization reaction called alkoxylation . In this process, an initiator molecule containing active hydrogen atoms reacts with alkylene oxides .

[0018] In the synthesis of polyether polyols, the choice of initiators is determined by their hydroxyl functionality, which refers to the number of hydroxyl groups per molecule that is available for reaction. Common initiators such as diethylene glycol and glycerol have, respectively, a functionality of 2 and 3. However, it is also possible to use initiators with higher hydroxyl functionalities, ranging from 4 to 8 hydrogen atoms per molecule . This increased hydroxyl functionality promotes greater branching within the polyol, resulting in a higher crosslink density and a more intricate polymer network within the resulting polyurethane foam.The chosen initiator is subsequently reacted with alkylene oxides, typically in the presence of a catalyst . The most commonly used alkylene oxides in this process are propylene oxide (PO) and ethylene oxide (EO) . The reaction proceeds in a stepwise manner, where the alkylene oxide molecules sequentially attach to the hydroxyl groups of the initiator, thereby forming ether bonds . The sequence and proportion of PO and EO can be adjusted to tailor the properties of the resulting polyether polyol .

[0019] Propylene oxide typically produces hydrophobic polyether chains that are more flexible and exhibit lower viscosity. In contrast, ethylene oxide increases hydrophilicity and reactivity and is often used as a capping agent at the end of the reaction to enhance the polyol ' s compatibility with other components in the polyurethane system.

[0020] The molecular weight of the polyether polyol is regulated by the quantity of alkylene oxide introduced during the reaction. The polymer chain length, determined by the number of repeating ether units, dictates the polyol ' s molecular weight . Higher molecular weights lead to softer, more flexible foams, whereas lower molecular weights are typically employed in formulations designed for more rigid foams .

[0021] The properties of polyurethanes are significantly influenced by the polyols ' molecular structures, specifically their chain lengths and levels of hydroxyl functionality, as well as by the presence and distributionof alkylene oxides within the polyol chain. Longer and more functionalized polyols contribute to increased flexibility, softness, or rigidity in the final material, depending on the degree of branching and reactivity. These factors play a crucial role in determining the flexibility, rigidity, and overall performance characteristics of the final polyurethane material . The balance between these components allows for fine-tuning of mechanical, thermal, and chemical properties to meet specific application requirements .

[0022] Semi-rigid foams suitable for packaging applications are typically produced by reacting a polyisocyanate with a polyol blend in which the polyol component consists of a mixture of low-hydroxyl functionality, high molecular weight polyether polyols, and high-hydroxyl functionality, low molecular weight polyether polyols .

[0023] Although their peculiar properties make the polyurethane foams one of the best performing packaging materials, nowadays new challenges must be faced. In particular, the market is asking for lower environmental impact solutions and H&S (health and safety) friendly materials . The dependency from fossil-based raw materials, particularly with respect to the polyols, manufactured in only few complex plants is also a concern for end users .

[0024] The disclosure of WO 2012 021 675 A2 is directed towards avoiding the use of nonylphenol ethoxylates (NPEs) in polyol blends . WO 2012 021 675 A2 vaguely mentions the use of polyols from natural sources . However, the specificpolyol blends disclosed consistently use a polyether polyol . Further, the mass concentration of water is rather low in those polyol blends .

[0025] It is therefore an obj ect of the invention to suggest a polyol blend which employs environmentally friendly components, particularly non-fossil, renewable source based, not hazardous, not harmful, low cost and widely available components . The polyol blend should further enable the preparation of a polyurethane foam having a low density such that the polyurethane foam is suitable for packaging applications, e . g. a density ranging from 4 kg / m3to 15 kg / m3.

[0026] In accordance with a first aspect of the disclosure, a polyol blend for preparing a water-blown polyurethane foam is described.

[0027] The polyol blend comprises, based on the total mass of the polyol blend, at least 35.0 mass-% and at most 50.0 mass-% of a polyol component . Said polyol component consists of one or more carbohydrates each having a hydroxyl functionality of equal to or more than 4. Thus, the polyol component may consist of one carbohydrate having a hydroxyl functionality of equal to or more than 4, or of several carbohydrates each having a hydroxyl functionality of equal to or more than 4. The mass concentration of carbohydrates having a hydroxyl functionality of equal to or more than 4 is between 35.0 mass-% and 50.0 mass-% . The carbohydrate or carbohydrates constitute the polyol or polyols of thepolyol blend. Preferably, the polyol component is the sole polyol source in the polyol blend. However, alternatively, the polyol blend may additionally comprise one or more polyols that do not fall within the limitations of the carbohydrate or carbohydrates of the polyol component .

[0028] The polyol blend further comprises, based on the total mass of the polyol blend, at least 30.0 mass-% of water . During formation of the polyurethane foam, the water acts as a blowing agent . Preferably, water is the sole blowing agent in the polyol blend. This further reduces the environmental impact of the polyol blend. However, alternatively, an additional blowing agent may be present in the polyol blend, in addition to water .

[0029] The inventors found that the underlying obj ective can be solved by a polyol blend with the above-described composition. The combination of the claimed mass concentrations of polyol component and water gave access to semi-rigid polyurethane foams having a low density between 4 kg / m3and 15 kg / m3. The polyurethane foams thus obtained provided an optimal balance between flexibility and impact resistance . Upon impact, these polyurethane foams compress, absorbing and dissipating mechanical energy, thereby minimizing the transmission of shock and vibration forces to a packaged item. This deformation and recovery capability makes the foams particularly effective in protecting fragile or delicate items, as the foam acts as a cushion that reduces the risk of damage during transportation or handling. Furthermore, the low density ofthese foams not only contributes to material efficiency, reducing overall weight and cost, but also maintains sufficient structural integrity to safeguard sensitive items . In view of the compounds used in the polyol blend, the environmental impact of the polyol blend is low. Due to the comparatively high concentrations of polyol in the blend, the volume of the blend that is required for the production of a given amount of polyurethane foam is comparatively low. In consequence, the costs for storage and shipping of the polyol blend can be reduced.

[0030] As used herein, the term "hydroxyl functionality" refers to the number of free hydroxyl groups per molecule . Thus, a carbohydrate having a hydroxyl functionality of equal to or more than 4 comprises at least 4 free hydroxyl groups .

[0031] As used herein, the term "carbohydrate" includes monosaccharides, polysaccharides, i . e . saccharides comprising at least two monosaccharide units joined together by a glycosidic linkage, and sugar alcohols .

[0032] Preferably, the mass concentration of the polyol component in the polyol blend is at least 37.5 mass-%, most preferably at least 40.0 mass-% .

[0033] Preferably, the mass concentration of the polyol component in the polyol blend is at most 47.5 mass-%, most preferably at most 45.0 mass-% .Preferably, the mass concentration of the polyol component in the polyol blend is at least 37.5 mass-% and at most 47.5 mass-%, most preferably at least 40.0 mass-% and at most 45.0 mass-% .

[0034] Preferably, the mass concentration of water in the polyol blend is at least 32.5 mass-%, most preferably at least 35.0 mass-% .

[0035] Preferably, the mass concentration of water in the polyol blend is at least 30.0 mass-% and at most 40.0 mass-%, more preferably at least 32.5 mass-% and at most 40.0 mass-%, most preferably at least 35.0 mass-% and at most 40.0 mass-

[0036] Preferably, the carbohydrate or carbohydrates of the polyol component are chemically unmodified.

[0037] In some preferred embodiments, the polyol blend further comprises, based on the total mass of the polyol blend, at least 12.0 mass-% and at most 25.0 mass-% of a non-ionic surfactant component, said non-ionic surfactant component consisting of one or more non-ionic surfactants .

[0038] Preferably, the non-ionic surfactant or non-ionic surfactants constituting the non-ionic surfactant component are silicon-free non-ionic surfactants . The inventors found that this mass concentration of non-ionic surfactants reliably stabilized the polyol blend, regardless of the high concentrations of water and polyol present therein.Preferably, the mass concentration of the non-ionic surfactant component in the polyol blend is at least 13.0 mass-%, most preferably at least 14.0 mass-% .

[0039] Preferably, the mass concentration of the non-ionic surfactant component in the polyol blend is at most 22 mass-%, most preferably at most 20.0 mass-% .

[0040] Preferably, the mass concentration of the non-ionic surfactant component in the polyol blend is at least 13.0 mass-% and at most 22.0 mass-%, most preferably at least 14.0 mass-% and at most 20.0 mass-% .

[0041] In some preferred embodiments, the carbohydrate of the polyol component or at least one carbohydrate of the polyol component is selected from the group consisting of sucrose, fructose, glucose, galactose, xylose, lactose, maltose and dextrose . The above carbohydrates are preferred, particularly because of their high availability. Among the above-mentioned carbohydrates, the disaccharides, i . e . sucrose, lactose and maltose, are particularly preferred, because of the physical properties of the resulting polyurethane foams . Most preferably, the polyol component comprises sucrose as the carbohydrate or as one the carbohydrates . Sucrose has the advantage that highly sustainable sources can be used.

[0042] In some embodiments, the carbohydrate or carbohydrates of the polyol component are present in the polyol blend aspure substances . For example, the polyol blend may comprise sucrose as a pure substance .

[0043] In some preferred embodiments, the polyol component is provided by hydrolyzed starch, preferably hydrolyzed cornstarch, or by molasses .

[0044] Preferably, the non-ionic surfactant component is at least substantially free of nonylphenol ethoxylates (NPEs) .

[0045] In some preferred embodiments, the non-ionic surfactant component comprises an alcohol ethoxylate surfactant as a non-ionic surfactant . Preferably, the non-ionic surfactant component consists of one or more alcohol ethoxylate surfactants . Alcohol ethoxylate surfactants have a comparatively low environmental impact and prove very effective in stabilizing the polyol blend. The non-ionic surfactant component may also comprise more than one alcohol ethoxylate surfactant, i . e . a mixture of several alcohol ethoxylate surfactants .

[0046] In some preferred embodiments, the alcohol ethoxylate surfactant conforms to the structural formula RO(CH2CH2(T)XH . In these embodiments, x may have a value of at least 10 and at most 15. Thus, the average number of ethoxylate units may be at least 10 and at most 15. R may correspond to iso — CyH2y+1, wherein y has a value of at least 11 and at most 14. Thus, the alcohol of the alcohol ethoxylate surfactant may be a non-branched, saturatedalcohol . Alternatively, the alcohol may also be branched and / or saturated. Particularly preferred alcohol ethoxylate surfactants include alcohol C13-iso ethoxylated (i . e . ethoxylated isotridecanol) .

[0047] In some preferred embodiments, the non-ionic surfactant or at least one of the non-ionic surfactants has a hydrophilic-lipophilic balance (HLB) of 12-15. Such non-ionic surfactants prove particularly effective in stabilizing the polyol blend. Preferably, the non-ionic surfactant or at least one of the non-ionic surfactants has a hydrophilic-lipophilic balance (HLB) of 14-15. As used herein, the term "hydrophilic-lipophilic balance" refers to a hydrophilic-lipophilic balance calculated according to Griffin' s method.

[0048] In some preferred embodiments, the polyol blend further comprises, preferably in addition to the non-ionic surfactant component, a silicone surfactant component . The silicone surfactant component may increase the stability of the foam during the expansion phase . Specifically, the silicone surfactant component may help to maintain uniform bubble formation and prevent the foam cells from collapsing. Preferably, the silicone surfactant component is selected from the group of Polyether-Polydimethylsiloxane-Copolymers . Preferably, the mass concentration of the silicone surfactant component, based on the total mass of the polyol blend, is at least 0.5 mass-% and at most 2.0 mass-% .In some preferred embodiments, the polyol blend further comprises a cell-opening component . The cell-opening component functions to create a foam structure with open cells, thus ensuring excellent dimensional stability in low-density foams . Preferably, the cell-opening component is selected from the group consisting of Polyether-Polydimethylsiloxane-Copolymer and silicone free organic polymers . Preferably, the mass concentration of cellopening component, based on the total mass of the polyol blend, is at least 0.5 mass-% and at most 2.0 mass-% . Where the cell-opening component comprises a Polyether-Polydimethylsiloxane-Copolymer , the cell-opening component performs the dual function of stabilizing and opening cells, depending on the phase of polyurethane foam formation. Where the cell-opening component comprises a silicone free organic polymer, the effect of the cellopening component with regard to opening cells is especially pronounced. In some embodiments, the polyol blend comprises a Polyether-Polydimethylsiloxane-Copolymer (also acting as a silicone surfactant) and a silicone free organic polymer . This combination may be advantageous in case that the Polyether-Polydimethylsiloxane-Copolymer alone is not sufficient to achieve the desired extent of cell opening.

[0049] In some preferred embodiments, the polyol blend further comprises a polyurethane-forming catalyst component .

[0050] Preferably, the mass concentration of the polyurethane-forming catalyst component, based on the total mass of the polyol blend, is at least 1.0 mass-% and at most 3.0 mass-% . As used herein, the term "polyurethane-forming catalyst component" refers to a compound or a mixture of compounds that catalyzes the reaction between an isocyanate group and a hydroxyl group and the reaction between an isocyanate group and water .

[0051] Preferably, the polyurethane-forming catalyst component comprises a blowing catalyst . A blowing catalyst preferentially catalyzes the reaction between an isocyanate group and water . Preferably, the blowing catalyst is chosen from the group consisting of pentamethyldiethylenetriamine, bis -dimethyl aminoethyl ether, N, N, N ' , N ' -tetramethylethylenediamine, N, N, N' , N' -tetramethylbutylenediamine, tetramet hylhexamethylenediamine and any mixtures thereof .

[0052] Preferably, the polyurethane-forming catalyst component comprises a gelation catalyst . A gelation catalyst preferentially catalyzes the reaction between an isocyanate group and a hydroxyl group . Preferably, the gelation catalyst is selected from the group consisting of dimethylcyclohexylamine, dimethylbenzylamine and any mixtures of these .

[0053] Preferably, the polyurethane-forming catalyst component comprises a blowing catalyst and a gelation catalyst .

[0054] In accordance with a second aspect of the disclosure, a method of preparing a water-blown polyurethane foam is described .The method comprises providing an isocyanate component, the isocyanate component consisting of one or more polyisocyanates . The isocyanate component may be provided as such, i . e . without other compounds mixed with the isocyanate component . Alternatively, the isocyanate component may be provided as part of an isocyanate blend comprising one or more different compounds, such as silicones and / or physical blowing agents, that are mixed with the isocyanate component .

[0055] The method further comprises providing a polyol blend as described above .

[0056] The method further comprises mixing the isocyanate component with the polyol blend to form a, preferably homogenous, reaction mixture . Preferably, the isocyanate component and the polyol blend are mixed using a high-speed mixer or through a continuous foaming machine to achieve a homogenous reaction mixture . Preferably, the isocyanate component and the polyol blend are mixed at a mass ratio of 1.3-1. 7. Thus, the mass of the isocyanate component is 1.3 times to 1.7 times higher than the mass of the polyol blend .

[0057] The method further comprises allowing the reaction mixture to react to form a polyurethane foam. Preferably, the reaction mixture reacts to form a polyurethane foam having a density of at least 4 kg / m3and at most 15 kg / m3,particularly a free rise density of at least 4 kg / m3and at most 15 kg / m3.

[0058] In some embodiments, the polyol blend further comprises, based on the total mass of the polyol blend, at least 12.0 mass-% and at most 25.0 mass-% of a non-ionic surfactant component, said non-ionic surfactant component consisting of one or more non-ionic surfactants . Preferably, the non-ionic surfactant or non-ionic surfactants constituting the non-ionic surfactant component are silicon-free non-ionic surfactants .

[0059] In some embodiments of the method, the polyisocyanate or at least one of the polyisocyanates is selected from the group consisting of organic polyisocyanates, modified polyisocyanates and isocyanate-based prepolymers .

[0060] In some embodiments of the method, the polyisocyanate or at least one of the polyisocyanates is selected from the group consisting of aliphatic polyisocyanates, cycloaliphatic polyisocyanates, polyphenyl polymethylene polyisocyanates (PMDI ) , 4, 4 ' -, 2, 4 ' - and 2 , 2 ' -diphenyl-methanediisocyanate and the corresponding isomeric mixtures, mixtures of 4, 4 ' -, 2, 4 ' - and 2 , 2 ' -diphenyl-methanediisocyanates and polyphenyl polymethylene polyisocyanates (PMDI ) . Chemically modified multifunctional polyisocyanates, which are products resulting from the chemical reactions of the aforementioned polyisocyanates, may also advantageously be used in the isocyanate component . Examples of chemically modified multifunctional polyisocyanates include polyisocyanatescontaining biurets, ureas, esters, allophanates , and preferably carbodiimides and / or uretonimines , as well as polyisocyanates containing isocyanurate and / or urethane groups .

[0061] Most preferably, the isocyanate component comprises a polyphenyl polymethylene polyisocyanate (PMDI ) having a isocyanate functionality of at least 2.5 and at most 3.5, preferably at least 2.7 and at most 2.9. As used herein, the term "isocyanate functionality" refers to the average number of isocyanate groups of each polyphenyl polymethylene polyisocyanate (PMDI ) unit .

[0062] Preferably, the isocyanate component comprises a polyphenyl polymethylene polyisocyanate (PMDI ) having an equivalent weight of 125-175 g / mole, more preferably an equivalent weight of 130-140 g / mole . In this regard, the term "equivalent weight" refers to the mass of polyphenyl polymethylene polyisocyanate in grams that comprises one mole of isocyanate groups .

[0063] Preferably, the isocyanate component comprises a polyphenyl polymethylene polyisocyanate (PMDI ) having a viscosity of 180-700 mPa*s at 25 °C .

[0064] In some embodiments, the isocyanate composition and the polyol blend are mixed at a mass ratio of 1.0 to 2.0, more preferably at a mass ratio of 1.25 to 1.75.In some preferred embodiments of the method, the isocyanate component and / or the polyol blend are heated to an elevated temperature of at least 40 °C and at most 70 °C prior to mixing. Mixing of the isocyanate component and the polyol blend then occurs while the isocyanate component and / or the polyol blend are at the elevated temperature . This procedure facilitates mixing, particularly because the viscosity is reduced at the elevated temperature and the solubility of components, particularly in the polyol blend, is increased. Furthermore, the above-mentioned elevated temperature has a beneficial effect on the reaction kinetics .

[0065] In some preferred embodiments of the method, providing the polyol blend comprises dissolving the polyol component in at least a first portion of the water, thus obtaining a first liquid composition. Preferably, the first portion of the water constitutes the major portion of water of the final polyol blend. Subsequently, at least the non-ionic surfactant component is added to the first liquid composition. This is followed by mixing such that the polyol blend is obtained as a homogenous liquid composition. Preferably, the non-ionic surfactant component is provided as part of a second liquid composition comprising at least the non-ionic surfactant component and a second portion of the water . Providing the non-ionic surfactant component as part of the second liquid composition may facilitate handling and particularly precise dosing of the non-ionic surfactant component . The second portion of the water may constitute a minor portionof water of the final polyol blend. Specifically, the mass concentration of water in the second liquid composition, based on the total mass of the second liquid composition, may be between 10.0 mass-% and 25.0 mass-% .

[0066] Where the polyol blend comprises additional components, i . e . in addition to the polyol component, the non-ionic surfactant component and water, those additional components are preferably added to the first liquid composition along with the second liquid composition.

[0067] In some preferred embodiments of the method, a packaging material is provided. The packaging material may be a packaging bag or a packaging box . The reaction mixture is then provided in a void of the packaging material, such that the reaction mixture reacts in the void of the packaging material and the polyurethane foam is formed in the void of the packaging material . This has the advantage that the polyurethane foam may be formed to align its shape to the void of the packaging material and preferably to fill the void. The reaction mixture may be formed outside of the void and provided to the void as such.

[0068] Alternatively, the reaction mixture may be formed directly in the void of the packaging material . Thus, mixing of the polyol blend and the isocyanate component may occur in the void of the packaging material .

[0069] Examples :

[0070] Example 1 : Polyol blend and method of preparationA representative example of a polyol blend comprises (all mass concentrations are based on the total mass of the polyol blend) : 42 mass-% of a polyol component, namely sucrose; 15. 6 mass-% of a non-ionic surfactant component, namely alcohol C13-iso ethoxylated; 1.7 mass-% of a polyurethane-forming catalyst component, namely 2- (2-dimethylaminoethoxy) ethanol ; 1.0 mass-% of a silicone surfactant component, namely Polyether-Polydimethylsiloxane-Copolymer ; 1.0 mass-% of a cellopening component, namely non-siloxane copolymers; and 38.7 mass-% of water .

[0071] The polyol blend was prepared as follows : The polyol component was dissolved in a first portion of the water, thereby obtaining a first liquid composition. Said first portion constituted the major portion of water of the final polyol blend.

[0072] The non-ionic surfactant component was provided as part of a second liquid composition. The second liquid composition consisted of the non-ionic surfactant component and a second portion of the water . Specifically, the second liquid composition was 85 mass-% non-ionic surfactant component and 15 mass-% water .

[0073] The second liquid composition and the remaining components of the polyol blend, i . e . the polyurethane-forming catalyst component, the silicone surfactant component and the cellopening component, were added to the first liquidcomposition. The resulting composition was mixed, thereby obtaining the polyol blend as a homogenous liquid composition .

[0074] Example 2 : Preparation of a low-density polyurethane foam

[0075] In a representative example, a low-density polyurethane foam was prepared as follows :

[0076] A polyol blend was provided as described above in connection with example 1 .

[0077] Additionally, an isocyanate composition was provided. In this example, the isocyanate composition consisted of a polymeric diphenylmethane diisocyanate (PMDI ) having an isocyanate functionality of 2. 7-2. 9.

[0078] The polyol blend and the isocyanate composition were both heated to an elevated temperature of 40 °C to 70 °C, in this example to an elevated temperature of 55 °C .

[0079] Subsequently, the polyol blend and the isocyanate composition were mixed while at the elevated temperature, thereby obtaining a liquid reaction mixture . In this example, the isocyanate composition and the polyol blend were mixed at a mass ratio of 1.5. Thus, the mass of the isocyanate composition was one and a half times higher than the mass of the polyol mixture .The reaction mixture was allowed to react, resulting in the formation of a polyurethane foam. The final polyurethane foam had a density of 8, 0 kg / m3, an open-cell structure and was semi-rigid.

Claims

Claims1 . A polyol blend for preparing a water-blown polyurethane foam, the polyol blend comprising at least the following:- based on the total mass of the polyol blend, at least 35.0 mass-% and at most 50.0 mass-% of a polyol component, said polyol component consisting of one or more carbohydrates each having a hydroxyl functionality of equal to or more than 4 ; and- based on the total mass of the polyol blend, at least 30.0 mass-% of water as a blowing agent .

2. The polyol blend according to claim 1, wherein the polyol blend further comprises, based on the total mass of the polyol blend, at least 12.0 mass-% and at most 25.0 mass-% of a non-ionic surfactant component, said non-ionic surfactant component consisting of one or more non-ionic surfactants .

3. The polyol blend according to any one of the preceding claims, wherein the carbohydrate or at least one of the carbohydrates is selected from the group consisting of sucrose, fructose, glucose, galactose, xylose, lactose, maltose and dextrose .

4. The polyol blend according to any one of the preceding claims, wherein the polyol component is provided byhydrolyzed starch, preferably hydrolyzed cornstarch, or by molasses .

5. The polyol blend according to any one of claims 2 to 4, wherein the non-ionic surfactant component comprises an alcohol ethoxylate surfactant as a nonionic surfactant .

6. The polyol blend according to the preceding claim, wherein the alcohol ethoxylate surfactant conforms to the structural formula RO(CH2CH2(T)XH, wherein x has a value between 10 and 15, and R = iso — CyH2y+1where y has a value between 11 and 14.

7. The polyol blend according to any one of claims 2 to 6, wherein the non-ionic surfactant or at least one of the non-ionic surfactants has a hydrophilic-lipophilic balance of 12-15, preferably a hydrophilic-lipophilic balance of 14-15.

8. The polyol blend according to any one of the preceding claims, wherein the polyol blend further comprises a silicone surfactant component, particularly wherein the mass concentration of the silicon surfactant component, based on the total mass of the polyol blend, is at least 0.5 mass-% and at most 2.0 mass-% .

9. The polyol blend according to any one of the preceding claims, wherein the polyol blend further comprises a cell-opening component, particularly wherein the mass concentration of the cell-opening component, based onthe total mass of the polyol blend, is at least 0.5 mass-% and at most 2.0 mass-% .

10. The polyol blend according to any one of the preceding claims, wherein the polyol blend further comprises a polyurethane-forming catalyst component, particularly wherein the mass concentration of the polyurethane- forming catalyst component, based on the total mass of the polyol blend, is at least 1.0 mass-% and at most 3 . 0 mass-% .

11. A method of preparing a water-blown polyurethane foam, the method comprising:a . providing an isocyanate component, the isocyanate component comprising at least one polyisocyanate; b . providing a polyol blend, particularly according to any one of the preceding claims, the polyol blend at least comprising:- based on the total mass of the polyol blend, 35.0 mass-% to 50.0 mass-% of a polyol component, said polyol component consisting of one or more carbohydrates each having a hydroxyl functionality of equal to or more than 4 ; and- based on the total mass of the polyol blend, at least 30.0 mass-% of water as a blowing agent ;c . mixing the isocyanate component with the polyol blend to form a reaction mixture; andd. allowing the reaction mixture to react to form a polyurethane foam.

12. The method according to claim 11, wherein the reaction mixture is allowed to react to form a polyurethane foam having a density of at least 4 kg / m3and at most 15 kg / m3.

13. The method according to any one of claims 11 and 12, wherein the isocyanate component is heated to an elevated temperature of at least 40 °C and at most 70 °C prior to mixing with the polyol blend, and / or wherein the polyol blend is heated to an elevated temperature of at least 40 °C and at most 70 °C prior to mixing with the isocyanate component .

14. The method according to any one of claims 11 to 13, wherein providing the polyol blend comprises :- dissolving the polyol component in at least a first portion of the water, thus obtaining a first liquid composition;- adding at least a non-ionic surfactant component to the first liquid composition; and- mixing the first liquid composition and the non-ionic surfactant component such that the polyol blend is obtained as a homogenous liquid composition.

15. The method according to any one of claims 11 to 14, wherein a packaging material, particularly a packagingbag or a packaging box, is provided, and wherein the reaction mixture is provided in a void of the packaging material, such that the reaction mixture reacts in the void of the packaging material and the polyurethane foam is formed in the void of the packaging material .