Polylysine-based foams

Abstract

The present invention relates to a method for producing a foam, which comprises foaming a mixture comprising one or more poly(amino acids) (A), one or more components (B) capable of reacting with said poly(amino acids) (A), and one or more blowing agents (F), wherein component (B) is selected from a reducing sugar, 1,3-dihydroxyacetone, glycolaldehyde, glyceraldehyde, or any mixture thereof, as well as to a foam obtainable by this method.

Description

[Technical Field]

[0001] The present invention relates to a method for producing a foam, which comprises foaming a mixture comprising one or more poly(amino acids) (A), one or more components (B) capable of reacting with said poly(amino acids) (A), and one or more blowing agents (F), wherein component (B) is selected from a reducing sugar, 1,3-dihydroxyacetone, glycolaldehyde, glyceraldehyde, or any mixture thereof, as well as to a foam obtainable by this method. [Background technology]

[0002] Reactive non-thermoplastic (thermosetting) polymer foams are used in many applications. In the case of flexible non-thermoplastic polymer foams, products are used in a variety of applications, including sound absorption, cushioning, cleaning, and packaging.

[0003] Three techniques are known for producing these foams. Flexible polyurethane foams can be foamed using water. Water reacts exothermically with the isocyanate groups of the respective isocyanates (e.g., TDI or MDI) to produce disubstituted urea and CO₂. CO₂ acts as an intrinsic blowing agent in the foam formation. The final foam exhibits high flexibility and excellent sound absorption. Sometimes, the foaming reaction is supported by a physical blowing agent, such as pentane. However, the use of isocyanates requires high safety efforts for safe transportation, storage, handling, and disposal. Flexible polyurethane foams are widely described, for example in DE-A-10226414.

[0004] Another example of a flexible non-thermoplastic foam is the melamine resin foam described in German Patent Application Publication No. 09929. This foam is produced by combining a melamine-formaldehyde condensate, surfactants, salts, a curing agent, and a physical blowing agent, such as pentane or hydrofluoroolefins. Due to the low exothermic rate, the foaming process must be supported by hot air, microwaves, and / or steam. The resulting foam is lightweight and exhibits very good sound absorption, thermal insulation, and cleaning properties. However, the applications of these foams are limited by the potential release of formaldehyde during production and application.

[0005] Another example of receiving flexible foams is described in DE 2950289. These foams are based on urea-formaldehyde condensates and can be produced at 8 to 40 kg / m using pentane as blowing agent in an oven process. 3 It produces a flexible foam with a density of 1000 psi. Even in this case, its applications are limited by the possible release of formaldehyde during manufacture and application.

[0006] WO 2016 / 009062 and WO 2011 / 138458 disclose binders useful for consolidating loosely assembled materials such as fibers, comprising the reaction product of a carbohydrate reactant and a polyamine. Foams using the binders are not disclosed.

[0007] WO 2022 / 136613 discloses a binder composition comprising, as component A, polylysine having a total weight-average molecular weight Mw of at least 800 g / mol, and, as component B, 1,3-dihydroxyacetone, glycolaldehyde, glyceraldehyde, or a mixture thereof, and its use for producing a lignocellulosic composite product. Foams using the binder composition are not disclosed.

[0008] WO 2022 / 136614 relates to a binder composition containing a polyamine and hydroxyacetone for composite articles. Foams using the binder composition are not disclosed.

[0009] U.S. Patent Application Publication No. 2011 / 0257284 describes a method for making flame-retardant polyurethane foams using hyperbranched nitrogen-containing polymers, particularly hyperbranched polylysine, hyperbranched polyisocyanurate, and hyperbranched polyesteramide, to impart flame retardancy to the polyurethane foam. [Prior art documents] [Patent documents]

[0010] [Patent Document 1] DE 10226414 A1 [Patent Document 2] DE 09929 A1 [Patent Document 3] DE 2950289 A1 [Patent Document 4] International Publication No. 2016 / 009062 [Patent Document 5] International Publication No. 2011 / 138458 [Patent Document 6] International Publication No. 2022 / 136613 [Patent Document 7] International Publication No. 2022 / 136614 [Patent Document 8] US Patent Application Publication No. 2011 / 0257284 Summary of the Invention [Problem to be solved by the invention]

[0011] The present invention has been made in view of the above-mentioned prior art, and an object of the present invention is to provide a flexible foam that is formaldehyde- and isocyanate-free and has good mechanical properties, which can be obtained from bio-based raw materials and aqueous raw materials. [Means for solving the problem]

[0012] This object has been solved by a foam and a method for producing a foam, comprising foaming a mixture comprising one or more poly(amino acids) (A), one or more components (B) capable of reacting with said poly(amino acids) (A), and one or more blowing agents (F), wherein component (B) is selected from a reducing sugar, 1,3-dihydroxyacetone, glycolaldehyde, glyceraldehyde, or any mixture thereof.

[0013] Foaming of the mixture can be achieved by using an external heat source, such as a hot mold or hot air, and / or by using microwaves.

[0014] Preferably, the foam is not a polyurethane foam. Preferably, the foaming mixture does not contain isocyanates and / or polyols. Preferably, the foaming mixture comprises more than 50 wt. %, more preferably more than 70 wt. % of poly(amino acid) (A), based on the total solids content of reactive components (A) and (B).

[0015] Preferably, the method includes foaming the mixture, the mixture comprising: 10 to 60% by weight of one or more poly(amino acids) (A) 3 to 30% by weight of one or more components (B) capable of reacting with the poly(amino acid) (A). 0.5 to 5% by weight of one or more salts of inorganic acids or organic carboxylic acids (C), 3 to 10 wt. % of one or more surfactants (D); 10 to 60% by weight of water (E), 1 to 20 wt. % of one or more physical blowing agents (F); 0 to 82.5 wt. % of one or more additional additives (G), Including, The total weight percentage of the components A) to G) is 100% by weight.

[0016] More preferably, the method includes a foaming mixture consisting essentially of components A) through (F) in the amounts described above.

[0017] Most preferably, the method includes foaming the mixture, the mixture comprising: 20 to 60% by weight of one or more poly(amino acids) (A) 3 to 30% by weight of one or more components (B) capable of reacting with the poly(amino acid) (A). 0.5 to 5% by weight of one or more salts of inorganic acids or organic carboxylic acids (C), 3 to 10 wt. % of one or more surfactants (D); 10 to 60% by weight of water (E), 1 to 20 wt. % of one or more physical blowing agents (F); It consists of The total weight percentage of the components A) to F) is 100% by weight. DETAILED DESCRIPTION OF THE INVENTION

[0018] Component (A) As component (A), poly(amino acids), such as synthetic poly(amino acids), natural poly(amino acids), polypeptides, proteins, or mixtures thereof, are used. Poly(amino acids) are produced by polymerization of amino acids. Poly(amino acids) can be obtained by chemical synthesis or biosynthesis in living organisms. In particular, proteins can be obtained by biosynthesis in living organisms. Polypeptides can be obtained by protein hydrolysis.

[0019] According to the present invention, the term poly(amino acid) may also include poly(amino acid) derivatives which may be obtained by modification of the poly(amino acid) after polymer synthesis.

[0020] Preferred amino acids used in the polymerization reaction are diamino acids containing two amine (-NH) groups and at least one carboxyl (-COOH) functional group. Such diamino acids can be ornithine, diaminopimelic acid, 2,3-diaminopropionic acid, 2,4-diaminobutyric acid, and / or lysine, preferably lysine, more preferably L-lysine. Although they are sometimes called diamino acids, according to the present invention, asparagine and glutamine are not included in the group of diamino acids because the second functional group is an amide (CO-NH) and not an amine (-NH).

[0021] Preferably, polylysine is used as the poly(amino acid). Polylysine can be produced by polymerization of lysine. Lysine itself can be produced by fermenting corn starch, sugar or other carbohydrates in the presence of suitable bacteria. The production of polylysine is generally known and can be carried out, for example, as described in WO 2016 / 062578 or from lysine salts as described in WO 2007 / 060119. A preferred method for producing polylysine is described in WO 2022 / 136613.

[0022] Preferably, component (A) comprises at least one polylysine or consists of one or more polylysines, which polylysines are monomeric lysines, preferably L-lysine, and optionally: a) an amino acid (preferably containing at least two amino groups); b) an amine containing at least two amino groups (wherein the amine is not an amino acid), and c) dicarboxylic and / or tricarboxylic acids (preferably not amino acids); and the polymerization product of another monomer selected from the group consisting of: Here, at least 50% by weight, preferably at least 75% by weight, most preferably 100% by weight of lysine, based on the total amount of monomers, is used as a monomer for the polymerization reaction.

[0023] The weight-average molecular weight Mw of the poly(amino acid) (A) affects the mechanical properties of the foam. Preferably, the poly(amino acid) (A) has a weight-average molecular weight Mw in the range of 500 to 20,000 g / mol, more preferably in the range of 800 to 3,500 g / mol. The weight-average molecular weight is determined by size-exclusion chromatography (SEC) of the hydroxylated polymethacrylate using 0.1% (w / w) trifluoroacetate as the solvent and 0.1 M NaCl in distilled water as the eluent, calibrated with poly(2-vinylpyridine) standards. Most preferably, polylysine in an aqueous formulation having a molecular weight of 800 to 3,500 g / mol is used as component (A) to produce foams with appropriate Shore hardness and compressive load.

[0024] Ingredient (B) The foaming mixture contains one or more components (B) capable of reacting with the poly(amino acid) (A), selected from reducing sugars, 1,3-dihydroxyacetone, glycolaldehyde, glyceraldehyde, or any mixture thereof. Preferably, hydroxyacetone or 1,3-dihydroxyacetone is used as component (B).

[0025] Preferably, the weight ratio of poly(amino acid) (A) to component (B) is in the range of 2:1 to 5:1.

[0026] Poly(amino acids) and reducing sugars derived from natural sources can be used as raw materials to produce essentially bio-based foams.

[0027] Assume that components A and B undergo a Maillard reaction. In the first step, the free amine group of a (poly)amino acid (component (A)) adds to the carbonyl group of a reducing sugar (ketose / aldose) (component (B)). The glycosylamine formed is unstable and loses one water molecule, undergoing a Heyns / Amadori rearrangement to form a Heyns / Amadori compound (aldosamine / ketosamine).

[0028] In the case of the reaction of polylysine with (di)hydroxyacetone, a crosslinked, thermosetting, light brown solid material is formed.

[0029] Ingredients (C) As component (C), one or more salts of inorganic acids and / or one or more salts of organic carboxylic acids are added to stabilize the foam. Particularly suitable are one or more salts of oxygen or sulfur, such as formic acid, acetic acid, and citric acid, especially the sodium and / or potassium salts. Also particularly suitable are chlorides, bromides, nitrates, and dihydrogen phosphates, especially in the form of sodium and / or potassium salts. Preferably, in the form of salts of inorganic acids and / or organic carboxylic acids, sodium and potassium formate are particularly suitable, or one or more compounds selected from acetates, citrates, chlorides, bromides, sulfates, sulfites, nitrates, and dihydrogen phosphates. Particularly suitable salts of inorganic acids and / or salts of organic carboxylic acids are formates, citrates, and mixtures thereof.

[0030] To obtain a halogen-free foam, a preferred halogen-free salt is used.

[0031] Ingredients (D) Component D) of the system comprises one or more surfactants used in foam formation and stabilization. Anionic, cationic, nonionic or amphoteric surfactants can be used.

[0032] Suitable anionic surfactants are diphenylene oxide sulfonates, alkane- and alkylbenzenesulfonates, alkylnaphthalenesulfonates, olefinsulfonates, alkyl ether sulfonates, alkyl sulfates, alkyl ether sulfates, α-sulfofatty acid esters, acylaminoalkanesulfonates, acyl isethionates, alkyl ether carboxylates, N-acylsarcosinates, alkyl and alkyl ether phosphates.

[0033] Useful nonionic surfactants include alkylphenol polyglycol ethers, fatty alcohol polyglycol ethers, fatty acid polyglycol ethers, fatty acid alkanolamides, EO-PO block copolymers, amine oxides, glyceryl fatty acid esters, sorbitan esters, and alkyl polyglucosides. Useful cationic surfactants include alkyltriammonium salts, alkylbenzyldimethylammonium salts, and alkylpyridinium salts.

[0034] Mixtures of anionic and nonionic surfactants are particularly preferably used.

[0035] Preferably, a mixture of an anionic surfactant and a nonionic surfactant is used as surfactant (D), and more preferably, a sodium salt of a (C12-C14) fatty alcohol ether sulfate, a (C12-C14) alkyl polyglycoside, or a mixture thereof is used as surfactant (D).

[0036] Preferably, the weight ratio of the anionic surfactant to the nonionic surfactant is in the range of 50:50 to 90:10.

[0037] Ingredient (E) Water is used as component (E). Preferably, components (A), (B), and (D) are used as an aqueous solution or dispersion. Additional water may be added to achieve the above composition of the mixture and adjust the viscosity.

[0038] Ingredient (F) In principle, the method of the present invention can use both physical and chemical blowing agents. Either "physical" or "chemical" blowing agents are suitable (Encyclopedia of Polymer Science and Technology, Vol. I, 3rd ed., Additives, pages 203 to 218, 2003).

[0039] Physical blowing agents useful as component (F) include, for example, hydrocarbons such as butane, n-, iso-, or cyclopentane, hexane, halogenated, more specifically chlorinated and / or fluorinated hydrocarbons such as methylene chloride, chloroform, trichloroethane, chlorofluorocarbons, hydrochlorofluorocarbons (HCFCs), hydrofluorocarbons (HCFs) such as methyl nonafluorobutyl ether, hydrofluoroolefins (HFOs) such as ethyl nonofluorobutyl ether and hexafluorobutene, alcohols such as methanol, ethanol, n-propanol, or isopropanol, ethers, ketones, and esters, or methyl formate, ethyl formate, methyl acetate, or ethyl acetate. Preferred physical blowing agents have a boiling point of 0 to 80°C.

[0040] Useful chemical blowing agents include, for example, isocyanates mixed with water, which release carbon dioxide as the active blowing agent. Additionally, carbonates and bicarbonates can be used in combination with acids, which also produce carbon dioxide. Azo compounds, such as azodicarbonamide, are also suitable.

[0041] Preferably, the physical blowing agent (F) is a C4 to C8 hydrocarbon, more preferably n-, iso- or cyclo-pentane, most preferably an 80:20 mixture of n-pentane and isopentane.

[0042] 10~250 kg / m 3 To obtain a foam with a density in the range of 1 to 20 wt. %, it is preferred to use 1 to 20 wt. % of one or more physical blowing agents.

[0043] Ingredients (G) Flame retardants, fillers may be used as further components (G). Preferably, flame retardants are used as additives (G).

[0044] The subject of the present invention is also a method for producing a foam by preparing an aqueous solution or dispersion of components (A) to (G) of the system described above and foaming the aqueous solution or dispersion by heating, i.e., with hot air or microwaves.

[0045] The introduction of energy is preferably achieved via electromagnetic radiation, for example via high frequency radiation of 5 to 400 kW, preferably 5 to 200 kW, more preferably 9 to 120 kW per kilogram of mixture used in the frequency range of 0.2 to 100 GHz, preferably 0.5 to 10 GHz. Magnetrons are useful sources of dielectric radiation, and one magnetron or two or more magnetrons can be used simultaneously.

[0046] The production of polylysine foam is preferably carried out using a one-shot process, for example, using high or low pressure techniques. The foam can be produced discontinuously in an open or closed mold, or by continuously applying the reaction mixture to a conveyor belt to produce foam blocks.

[0047] As mentioned above, when preparing and foaming the polylysine component and the reducing sugar component, it is particularly advantageous to operate according to the so-called two-component method. The components are preferably mixed at a temperature in the range of 15°C to 120°C, preferably 20°C to 80°C, and introduced into a mold or applied to a conveyor belt. The temperature in the mold is usually in the range of 15 to 120°C, preferably 30 to 80°C.

[0048] The preferred method is (a) preparing an aqueous solution or suspension containing components (A) to (F); (b) transferring the aqueous solution or suspension obtained in step (a) into a mold; and (c) foaming the aqueous solution or suspension by heating to a temperature in the range of 35 to 100°C or by exposing to microwaves. Includes.

[0049] The subject of the present invention is also a foam obtainable by the process described above.

[0050] Preferably, the foam has a compressibility of 10 to 250 kg / m, determined according to DIN 53420. 3 The preferred density depends on the application. The density can be adjusted by the amount of foaming agent (F). As the density increases, the Shore hardness and compressive load can be increased. To obtain a highly flexible foam, a lower density is preferred.

[0051] Compared to melamine-formaldehyde foams, the foams according to the invention have a lower Shore hardness and are more flexible at comparable densities.

[0052] Preferably, the foam has a Shore hardness in the range of 20-100, 000, determined according to ASTM D 2240.

[0053] Preferably, the foam has a compressive stress value (compressive load deflection) according to DIN EN ISO 3386 in the range of 0.3 to 90 kPa.

[0054] The foams according to the present invention are water-based, solvent-free, formaldehyde- and isocyanate-free, can be derived from bio-based raw materials such as reducing sugars, can be produced over a wide density range, exhibit high flexibility as evidenced by low Shore hardness, have good cleaning properties, high water absorption, moderate thermal insulation, good sound absorption over a wide frequency range, and low airflow resistance.

[0055] Preferably, the open cell content is greater than 95% as measured by optical microscopy.

[0056] The foams of the present invention can be used in architecture and construction, i.e., cushioning and furniture such as seats, sofas, and mattresses in leisure or office environments, or seats, headrests, and armrests in trains, aircraft, and automobile transport. Further applications include packaging, i.e., packaging materials for protecting deliveries; cleaning applications, such as cleaning sponges, floor pads, and hand pads; filtration; acoustic applications in architecture and construction, such as sound absorption in offices, schools, restaurants, noise chambers, furniture, and separation walls, acoustic elements in walls and ceilings, and sound absorption in air conditioning; and transportation applications, such as automobile sound absorbers, under-hood motors for noise reduction, or indoor applications as headliners, sun visors, and hat racks. Further applications include industrial insulation, such as pipe insulation or air conditioning unit insulation, or wall and roof insulation in architecture and construction. Agricultural applications include growing substrates and floral foams.

[0057] Example The present invention will be described in more detail and specifically below with reference to examples, but the present invention is not limited to these examples.

[0058] Raw materials used: Surfactant 1: Anionic surfactant Hostapur® SAS 93 (C14-C17 sec. alkyl sulfonic acid sodium salt), WeylChem Surfactant 2: Nonionic surfactant Lutensol® AT80 (C16-C18 fatty alcohol ethoxylate (approximately 80 units), BASF SE) Surfactant 3: Hostapur SAS93 / Lutensol AT80 surfactant mixture in a weight ratio of 6:4 Water: deionized water; Polylysine-1: weight average molecular weight Mw approx. 1,200 g / mol (50 wt % in water); Polylysine-2: weight average molecular weight Mw about 2,000 g / mol (50% by weight in water). Polylysine-3: weight average molecular weight Mw approx. 3,000 g / mol (50% by weight in water); Polylysine-4: weight average molecular weight Mw approx. 4,000 g / mol (50% by weight in water); Polylysines-1 to -4 were prepared by heat treating L-lysine according to Example 1 of WO 2022 / 136612.

[0059] Crosslinker: 1,3-dihydroxyacetone (80% by weight in aqueous solution). Physical blowing agent: n-pentane / isopentane 80 / 20 wt% mixture. Salts: Sodium formate, sodium acetate, sodium citrate, sodium chloride MF melamine-formaldehyde precondensate having an average molecular weight (number average) Mn of 350 g / mol and a melamine:formaldehyde molar ratio of 1:3

[0060] Weight average molecular weight M of polylysine w Decision M w under the following conditions: Solvent and eluent: 0.1% (w / w) trifluoroacetate, 0.1 M NaCl in distilled water ·Flow rate: 0.8 ml / min ·Injection volume: 100μl Filter the sample through a Sartorius Minisart RC25 (0.2 μm) filter. Column material: Hydroxylated polymethacrylate (TSKgel G3000PWXL) Column size: 7.8 mm inner diameter, 30 cm length Column temperature: 35℃ Detector: DRI Agilent 1100 UV GAT-LCD503 [232 nm] Calibration using poly(2-vinylpyridine) standards (PSS, Mainz, Germany) in the molar mass range of 620–2,890,000 g / mol and pyridine (79 g / mol) The maximum cumulative volume was set to 29.01 mL. M wThe calculation of lysine includes lysine oligomers and polymers as well as monomeric lysine. was determined by size exclusion chromatography.

[0061] Foam characterization The foam density was determined according to DIN 53420.

[0062] Shore hardness was measured according to ASTM D 2240. For measurements on low density foams, a scale of 000 was used (sphere diameter 2.4 mm, spring force 1.111 N). Sample conditioning: 23°C, 50% relative humidity, 24 hours.

[0063] Air flow resistance was measured according to ASTM C-522.

[0064] The compressive stress values ​​(compressive load deflection) CV 40 were determined in accordance with DIN EN ISO 3386-1.

[0065] Examples 1-45: Preparation of foams based on pentane-bromopolylysine Polylysine, (di)hydroxyacetone, surfactant, and optional salt were dissolved in water, and the mixture was processed at high speed using a high-shear mixer for 1 minute. Next, a physical foaming agent, such as pentane, was added and stirred again for 10 seconds. Finally, the entire mixture was transferred to a heated mold or a mold (e.g., a 25 x 25 x 25 cm cardboard box) that was exposed to hot air (oven) or microwaves.

[0066] Procedure A: Microwave: 4 x 2.45 GHz, 60 seconds; then oven: 50 °C, 24 hours. Procedure B: Oven: 80 and 100°C for 24 hours.

[0067] After cooling, a new solid foam with a fine and uniform cell structure was removed from the mold.

[0068] The compositions and mechanical properties of the resulting foams are shown in Tables 1-7.

[0069] From Table 1, it can be seen that the Shore hardness and compressive load can be increased by using polylysine having a weight-average molecular weight in the range of 1,000 to 3,000 g / mol.

[0070] Tables 5 and 6 show the effect of density on mechanical properties such as Shore hardness and compressive load.

[0071] [Table 1]

[0072] [Table 2]

[0073] [Table 3]

[0074] [Table 4]

[0075] [Table 5]

[0076] [Table 6]

[0077] [Table 7]

[0078] Comparative examples C1~C15 Preparation of melamine resin foam 100 parts by weight of melamine formaldehyde precondensate MF, 38 parts by weight of water, 1.2 parts by weight of anionic surfactant T1, 0.3 parts by weight of nonionic surfactant T2, 2.5 parts by weight of sodium formate, 3.0 parts by weight of formic acid, and 19.5 parts by weight of pentane were mixed together at a temperature of 20-35°C. The mixture was introduced into a polypropylene foam mold and microwaved in a microwave oven. The resulting foam was annealed in a circulating air oven at 200°C for 20 minutes. The blowing agent content, density, and Shore hardness are summarized in Table 8.

[0079] [Table 8]

Claims

1. 1. A method for producing a foam, comprising foaming a mixture comprising one or more poly(amino acids) (A), one or more components (B) capable of reacting with said poly(amino acids) (A), and one or more foaming agents (F), wherein component (B) is selected from a reducing sugar, 1,3-dihydroxyacetone, glycolaldehyde, glyceraldehyde, or any mixture thereof.

2. The mixture 10 to 60% by weight of one or more poly(amino acids) (A) 3 to 30% by weight of one or more components (B) capable of reacting with the poly(amino acid) (A). 0.5 to 5% by weight of one or more salts of inorganic or organic carboxylic acids (C), 3 to 10 wt. % of one or more surfactants (D), 10 to 60% by weight of water (E), 1 to 20 wt. % of one or more physical blowing agents (F), 0 to 982.5 wt. % of one or more additional additives (G), Including, 10. The method of claim 1, wherein the sum of the weight percentages of components A) through G) is 100% by weight.

3. 3. The method of claim 1, wherein the poly(amino acid) (A) is polylysine having a weight average molecular weight Mw in the range of 800 to 20,000 g / mol as measured by size exclusion chromatography (SEC).

4. 4. The method according to claim 1, wherein 1,3-dihyroxyacetone is used as component (B).

5. 5. The method according to claim 1, wherein the salt of an inorganic or organic carboxylic acid (C) is Na-formate, Na-acetate or Na-citrate.

6. 6. The method according to any one of claims 1 to 5, wherein the physical blowing agent (F) is a C4 to C8 hydrocarbon.

7. 7. The method according to claim 1, wherein a mixture of anionic and nonionic surfactants is used as surfactant (D).

8. 8. The method according to claim 1, wherein a flame retardant is used as additive (F).

9. 9. The method according to any one of claims 1 to 8, wherein the weight ratio of poly(amino acid) (A) to component (B) is in the range of 2:1 to 5:

1.

10. 10. The method according to any one of claims 6 to 9, wherein the weight ratio of anionic surfactant to nonionic surfactant is in the range of 50:50 to 90:

10.

11. 11. The method according to any one of claims 1 to 10, wherein the method comprises: (a) preparing an aqueous solution or suspension containing components (A) to (G); (b) transferring the aqueous solution or suspension obtained in step (a) into a mold; and (c) foaming the aqueous solution or suspension by heating to a temperature in the range of 35-100°C or by exposing to microwaves. A method comprising:

12. A foam obtainable by the method according to any one of claims 1 to 11.

13. 10 to 250 kg / m, determined according to DIN 53420 3 13. The foam of claim 12 having a density in the range of

14. 14. The foam of claim 12 or 13, having a Shore hardness 000 in the range of 20 to 100, determined according to ASTM D 2240.

15. 15. The foam according to any one of claims 12 to 14, having a compressive stress value according to DIN EN ISO 3386-1 in the range of 0.3 to 90 kPa.

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