Polylysine foam with high flexibility

Abstract

The present invention relates to a process for producing a foam, which comprises foaming a mixture, comprising one or more poly(amino acid) (A), one or more components (B1) selected from alpha-hydroxy ketones or alpha-hydroxy aldehydes or any mixture thereof, one or more components (B2) selected from polyols, and one or more blowing agents (F) and the foam obtainable by this process.

Description

[0001] Polylysine foam with high flexibility

[0002] Description

[0003] The present invention relates to a process for producing a foam, which comprises foaming a mixture, comprising one or more poly(amino acid) (A), one or more reactive components (B1) selected from alpha-hydroxy ketones and alpha-hydroxy aldehydes or any mixture thereof, one or more reactive components (B2) selected from polyols and one or more blowing agents (F) and the foam obtainable by this method.

[0004] Relevant Prior Art

[0005] Reactive, non-thermoplastic (thermoset) polymer foams are used for many applications. In the case of flexible non-thermoplastic polymer foams, the products are applied in acoustic absorption, cushioning, cleaning, packaging, and many more.

[0006] WO 2022 / 136613 A1 discloses a binder composition comprising polylysine having a total weight average molecular weight Mwof at least 800 g / mol as component (A) and 1 ,3-dihydroxyacetone, glycolaldehyde, glyceraldehyde or mixtures thereof as component (B) and the use thereof for manufacturing lignocellulosic composite articles. Foams using the binder composition are not disclosed.

[0007] WO 2022 / 136614 A1 relates to a binder composition comprising polyamines and hydroxyacetone for composite articles. Foams using the binder composition are not disclosed.

[0008] US 2011 / 0257284 A1 describes a process for producing flame-retardant polyurethane foams, using hyperbranched, nitrogen-containing polymers, in particular hyperbranched polylysines, hyperbranched polyisocyanurates, and hyperbranched polyesteramides for providing flame retardancy to polyurethane foams.

[0009] WO 2024 / 074399 A1 relates to a system for producing an in-situ foam, comprising one or more poly(amino acid) (A), one or more components (B) capable of reacting with said poly(amino acid) (A) and one or more amphoteric polymer(s) (C), wherein component (B) is selected from reducing sugars, 1 ,3-dihydroxyacetone, glycolaldehyde, glyceraldehyde or any mixture thereof and a process for producing the in-situ foam. It would be desirable to further flexibilize the crosslinked polylysine foam.

[0010] WO 2024 / 074400 A1 relates to a process for producing a foam by foaming a mixture, comprising one or more poly(amino acid) (A), one or more components (B) capable of reacting with said poly(amino acid) (A) and one or more blowing agents (F), wherein component (B) is selected from reducing sugars, 1 ,3-dihydroxyacetone, glycolaldehyde, glyceraldehyde or any mixture thereof and the foam obtainable by this method. Summary of the Invention

[0011] The present invention was made in view of the prior art described above, and the object of the present invention is to provide a flexible foam with good mechanical properties, which can be obtained from formaldehyde- and isocyanate-free, bio- and water-based raw materials.

[0012] Technical problem solved

[0013] This object was solved by a foam and a process for producing the foam, which comprises foaming a mixture, comprising one or more poly(amino acid) (A), one or more reactive components (B1) selected from alpha-hydroxy ketones and alpha-hydroxy aldehydes or any mixture thereof, one or more reactive components (B2) selected from polyols and one or more blowing agents (F).

[0014] Foaming of the mixture can be achieved by using an external heat source, such as hot molds or hot air and / or the use of microwave.

[0015] Preferably, the foam is not a polyurethane foam. Preferably, the foaming mixture does not contain isocyanates. Preferably, the foaming mixture comprises more than 50 wt.-%, more preferably more than 70 wt.-% of the poly(amino acid) (A) based on the solids of the sum of the reactive components (A) and (B).

[0016] Preferably, the process comprises foaming a mixture, which comprises

[0017] 10 to 60 wt.-% of one or more poly(amino acid) (A),

[0018] 2 to 30 wt.-%, especially 2 to 20 wt.-%, of one or more reactive components (B1) capable of reacting with said poly(amino acid) (A),

[0019] 1 to 20 wt.-% of one or more reactive components (B2),

[0020] 0 to 5 wt.-% of one or more salts of an inorganic acid or organic carboxylic acid (C),

[0021] 3 to 10 wt.-% of one or more surfactants (D),

[0022] 10 to 60 wt.-% of water (E),

[0023] 1 to 20 wt.-% of one or more physical blowing agents (F), and

[0024] 0 to 71.5 wt.-% of one or more additional additives (G), wherein the sum of the weight percentages of said components (A) to (G) is 100 wt.-%.

[0025] More preferably, the process comprises a foaming mixture which essentially consists of the components (A) to (F) in the above-mentioned amounts.

[0026] Most preferably, the process comprises foaming a mixture, which consists of

[0027] 20 to 60 wt.-% of one or more poly(amino acid) (A), 3 to 30 wt.-% of one or more components (B1) capable of reacting with said poly(amino acid) (A),

[0028] 1 to 20 wt.-% of one or mor reactive components (B2),

[0029] 0 to 5 wt.-% of one or more salts of an inorganic acid or organic carboxylic acid (C),

[0030] 3 to 10 wt.-% of one or more surfactants (D),

[0031] 10 to 60 wt.-% of water (E), and

[0032] 1 to 20 wt.-% of one or more physical blowing agents (F), wherein the sum of the weight percentages of said components (A) to (F) is 100 wt.-%.

[0033] Component (A)

[0034] As component (A) poly(amino acid)s, e.g. synthetic poly(amino acid)s, natural poly(amino acid)s, polypeptides, proteins or mixtures thereof are used. Poly(amino acid)s are produced by polymerization of amino acids. Poly(amino acid)s can be obtained by chemical synthesis or by biosynthesis in living organisms. In particular, proteins may be obtained by biosynthesis in living organisms. Polypeptides may be obtained by hydrolysis of proteins.

[0035] According to this invention, the term poly(amino acid)s may also include poly(amino acid) derivatives, which may be obtained by modification of the poly(amino acid) after polymer synthesis.

[0036] Preferred amino acids which are used for the polymerization reaction are diamino acids comprising two amine groups (-NH2) and at least one carboxyl (-COOH) functional group. Such diamino acids may be ornithine, diaminopimelic acid, 2,3-diaminopropionic acid, 2,4-diamino- butyric acid, and / or lysine, preferably lysine, more preferably L-lysine. Although they are sometimes named as diamino acids, according to this invention asparagine and glutamine are not included in the group of diamino acids, since the second functional group is an amide (CO- NH2) and not an amine (-NH2).

[0037] Preferably, polylysine is used as a poly(amino acid). Polylysine may be produced by the polymerization of lysine. Lysine itself may be produced by the fermentation of corn starch, sugar or other carbon hydrates in presence of suited bacteria. The production of polylysine is generally known and may be performed, as, e.g., described in WO 2016 / 062578 A1 or from lysine salts as described in WO 2007 / 060119 A1. A preferred process for producing polylysine is described in WO 2022 / 136613 A1.

[0038] Preferably, component (A) comprise(s) at least one polylysine or consist(s) of one or more polylysine(s), which is (are) a polymerization product of the monomer lysine, preferably L-lysine, and optionally other monomers selected from the group consisting of a) amino acids, preferably comprising at least two amino groups, b) amines comprising at least two amino groups, wherein the amines are no amino acids, and c) di- and / or tricarboxylic acids, which are preferably no amino acids, wherein at least 50 wt.-%, preferably at least 75 wt.-%, most preferably 100 wt.-% lysine, is used as monomer for the polymerization reaction based on the total amount of monomers.

[0039] Weight-average molecular weight Mwof the poly(amino acid) (A) has an influence on mechanical properties of the foam. Preferably, the poly(amino acid) (A) has a weight-average molecular weight Mwin the range from 500 to 20,000 g / mol, more preferably in the range from 800 to 20,000 g / mol, especially in the range from 800 to 5,000 g / mol. Weight-average molecular weights are determined by size exclusion chromatography (SEC) on hydroxylated polymethacrylate with 0.1% (w / w) trifluoroacetate as solvent and 0.1 M NaCI in distilled water as eluent and calibration with poly(2-vinylpyridine) standards. Most preferably, polylysine in aqueous formulation with a molecular weight from 800 to 5,000 g / mol is used as component (A) for producing foams with a suitable Shore hardness and compression load.

[0040] Components (B1) and (B2)

[0041] Components (B1) and (B2) are capable of reacting with the poly(amino acid) (A).

[0042] One or more components (B1) capable of reacting with said poly(amino acid) (A) selected from alpha-hydroxy ketones or alpha-hydroxy aldehydes such as reducing sugars, 1 ,3- dihydroxyacetone, glycolaldehyde, glyceraldehyde or any mixture thereof are used in the foaming mixture. Preferably, hydroxyacetone, 1 ,3-dihydroxyacetone, glycolaldehyde, glyceraldehyde or any mixture thereof is used. More preferably, 1 ,3-dihydroxyacetone, glycolaldehyde, glyceraldehyde or any mixture thereof is used. Alternatively preferred, hydroxyacetone or 1 ,3-dihydroxyacetone is used as component (B1).

[0043] Preferably, the weight ratio of poly(amino acid) (A) to component (B1) is in the range from 2 : 1 to 5 : 1.

[0044] Poly(amino acid)s and reducing sugars from natural sources can be used as raw materials to produce essentially bio-based foams.

[0045] It is assumed that component (A) and (B1) undergoes Maillard reaction. In the first step, the free amine group of a (poly)amino acid (component (A)) is added to the carbonyl group of the alphahydroxy ketone or alpha-hydroxy aldehyde such as reducing sugar (ketose / aldose) (component (B1)). The formed glycosylamine is unstable and undergoes a Heyns / Amadori rearrangement to the Heyns / Amadori compound (aldosamine / ketosamine) with loss of one water molecule.

[0046] The process of the invention usually provides a thermoset polymer foam.

[0047] In the case of the reaction of polylysine with (di)hydroxyacetone, a crosslinked thermoset lightbrown solid material is formed. With the addition of component (B2), the polylysine foam is getting softer. Diols based on glycol exhibit this flexibilization effect on the foam, namely EG, DEG, TEG, PEG 400, and PEG 600. Also, polyvinyl alcohol has the same effect depending on the amount added. Other polyols, partially with higher functionality, perform similar leading to softer foams with lower compression strength under dry and under humid conditions in comparison to the polylysine foam without polyol addition. The molecular weight of component (B2) may be selected according to process conditions such as viscosity.

[0048] Via comparison of thermal gravimetric analysis (TGA) on the foam, it can be verified that the polyol is at least partially incorporated presumably via chemical bonding into the reacted network from polylysine and component (B1), such as dihydroxyacetone.

[0049] One or more reactive components (B2) are selected from polyols. Polyols are organic compounds containing multiple hydroxyl groups (-OH), preferably diols, triols, and tetrols. The polyols may have a linear or branched structure. Preferred polyols are propylene glycol, ethylene glycol, glycerol, sugars alcohols, such as sorbitol, xylitol, mannitol, erythritol, and polymeric polyols, such as polyether polyols, polyester polyols, polycarbonate polyols, acrylic polyols or polycaprolactone polyols as well as polyvinyl alcohols.

[0050] Preferably, ethylene glycol (EG), diethylene glycol (DEG), triethylene glycol (TEG), polyethylene glycol (PEG), polyvinyl alcohol (PVA), 1,4-butanediol (BD), glycerol, trimethylolpropane (TMP), pentaerythritol, sorbitol or mixtures thereof are used as component (B2).

[0051] Most preferably, 1,3-dihyroxyacetone is used as component (B1) and ethylene glycol (EG), diethylene glycol (DEG), triethylene glycol (TEG), polyethylene glycol (PEG), polyvinyl alcohol (PVA), 1 ,4-butanediol (BD), glycerol, trimethylolpropane (TMP), pentaerythritol, sorbitol or mixtures thereof are used as component (B2).

[0052] Preferably, the weight ratio of reactive component (B1) to component (B2) is in the range from 60 : 1 to 2 : 1.

[0053] Component (C)

[0054] As component (C) one or more salts of an inorganic acid and / or one or more salts of an organic carboxylic acid added for stabilization of the foam. Particularly suitable are one or more salts, particularly sodium - and / or potassium salts, of the oxygen or sulfur, as the formic acid, the acetic acid, and the citric acid. Also especially suitable are chlorides, bromides, nitrates, and dihydrogen phosphates, in particular in the form of the sodium - and / or potassium salts. Preferably in the form of salts of an inorganic acid and / or salts of an organic carboxylic acid are in particular a sodium - and potassium formates or more compounds selected from, - acetates, - citrates, - chlorides, - bromides, - sulfates, - sulfites, - nitrates and - dihydrogen phosphates. Very particularly suitable salts of an inorganic acid and / or salts of an organic carboxylic acid are formates, citrates, and mixtures thereof. Preferable halogen-free salts are used to obtain halogen-free foams.

[0055] Preferably, the salts of an inorganic acid or an organic carboxylic acid (C) is Na-formate, Na- acetate or Na-citrate.

[0056] Component (D)

[0057] Component (D) of the system comprises one or more surfactants used to form and stabilize the foam. Anionic, cationic, non-ionic, or amphoteric surfactants are usable.

[0058] Suitable anionic surfactants are diphenylene oxide sulfonates, alkane- and alkylbenzenesulfonates, alkylnaphthalenesulfonates, olefinsulfonates, alkyl ether sulfonates, alkyl sulfates, alkyl ether sulfates, alpha-sulfofatty acid esters, acylaminoalkanesulfonates, acylisethionates, alkyl ether carboxylates, N-acylsarcosinates, alkyl and alkyl ether phosphates.

[0059] Useful non-ionic 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 alkylpolyglucosides. Useful cationic surfactants include alkyltriammonium salts, alkylbenzyldimethylammonium salts and alkylpyridinium salts.

[0060] Mixtures of anionic and non-ionic surfactants are employed with particular preference.

[0061] Preferably, a mixture of an anionic and a non-ionic surfactant is used as surfactant (D). More preferably, a mixture of the sodium salt of a (C12-14)-fatty alcohol ether sulfate, a (C12-C14)- alkyl polyglycoside or mixture therefrom are used as surfactants (D).

[0062] Preferably, the weight ratio of anionic surfactant to non-ionic surfactant is in the range from 50 : 50 to 90 : 10.

[0063] Component (E)

[0064] Water is used as component (E). Preferably, components (A), (B), and (D) are used as aqueous solutions or dispersions. Further water may be added to achieve the above-described composition of the mixture and to adjust viscosity.

[0065] Component (F)

[0066] In principle, the process of the present invention can use both physical and chemical blowing agents. "Physical" or "chemical" blowing agents are suitable (Encyclopedia of Polymer Science and Technology, Vol. I, 3rd ed., Additives, pages 203 to 218, 2003). Useful physical blowing agents as component (F) include for example, hydrocarbons, such as butane, n-, iso- or cyclo-pentane, hexane, halogenated, more particularly chlorinated and / or fluorinated, hydrocarbons, for example, methylene chloride, chloroform, trichloroethane, chlorofluorocarbons, hydrochlorofluorocarbons (HCFCs), hydrofluorocarbons (HCFs) like methylnonafluorbutylether, ethylnonafluorbutylether, hydrofluoroolefins (HFOs) like hexafluorobutene, alcohols, for example, methanol, ethanol, n-propanol or isopropanol, ethers, ketones and esters, for example, methyl formate, ethyl formate, methyl acetate or ethyl acetate. Preferred physical blowing agents are those having a boiling point of between 0 °C and 80 °C.

[0067] Useful chemical blowing agents include for example, isocyanates mixed with water, releasing carbon dioxide as active blowing agent. It is further possible to use carbonates and bicarbonates mixed with acids, in which case carbon dioxide is again produced. Also suitable are azo compounds, for example, azodicarbonamide.

[0068] Preferably, the blowing agent (F), preferably the physical blowing agent (F), is a C4-C8- hydrocarbon, more preferably n-, iso- or cyclo-pentane, most preferably a mixture of n-pentane and isopentane 80 : 20.

[0069] Preferably 1 to 20 wt.-% of one or more physical blowing agents are used to obtain foams with densities in the range from 10 to 250 kg / m3.

[0070] Component (G)

[0071] Flame-retardants, fillers, heat stabilizers, UV stabilizers, hydrophobization agents, antioxidants, non-reactive plasticizers, dyes, pigments, or biocides may be used as further components (G). Preferably, a flame retardant is used as additive for component (G).

[0072] Subject of the invention is also a process for producing a foam by preparing an aqueous solution or dispersion of the components (A) to (G) of the system described above and foaming the aqueous solution or dispersion by heating, i.e. , with hot air or microwave.

[0073] The introduction of energy may preferably be effectuated via electromagnetic radiation, for example, via high-frequency radiation at 5 to 400 kW, preferably 5 to 200 kW and more preferably 9 to 120 kW per kilogram of the mixture used in a frequency range from 0.2 to 100 GHz, preferably 0.5 to 10 GHz. Magnetrons are a useful source of dielectric radiation, and one magnetron can be used or two or more magnetrons at the same time.

[0074] The production of the polylysine foams is preferably carried out after the one-shot method, for example, with the aid of the high-pressure or low-pressure technique. The foams can be discontinuously produced in open or closed molds or by continuous application of the reaction mixture to conveyor belts to produce foam blocks can be created. It is particularly advantageous, according to the so-called two-component method to operate, in the case of, as stated above, a polylysine component and a reducing sugar component are prepared and foamed. The components are preferably in the range between 15 to 120 °C at a temperature, preferably 20 to 80 °C mixed and introduced into the mold or applied to the conveyor belt. The temperature in the mold is usually in the range between 15 and 120 °C, preferably between 30 and 80 °C.

[0075] A preferred process comprises the following steps:

[0076] (a) preparing an aqueous solution or suspension comprising components (A) to (G),

[0077] (b) transferring the aqueous solution or suspension obtained in step (a) into a mold, and

[0078] (c) foaming the aqueous solution or suspension by warming to a temperature in the range from 35 to 100 °C or by exposure to microwave.

[0079] Subject to the invention is also a foam obtainable by the process described above.

[0080] Preferably, the foam has a density in the range from 1 kg / m3to 250 kg / m3, more preferably in the range from 10 kg / m3to 100 kg / m3, determined according to DIN 53420:1978-12. The preferred density depends on the application. The density can be adjusted by the amount of blowing agent (F). With higher density, the Shore hardness and compression load can be increased. Lower densities are preferred for a foam with higher flexibility.

[0081] Preferably, the foam has a compression stress value CV 40 at a compression of 40% (compression load deflection) in the range from 0.3 to 90 kPa according to DIN EN ISO 3386: 2015-10.

[0082] The foam according to the invention is processed water-based, solvent-free and free of formaldehyde and isocyanate, can be obtained from biobased raw materials, such as natural amino acids and reducing sugars and can be produced over a wide density range.

[0083] The open-cell content is preferably more than 95%, determined by light microscopy.

[0084] The foam according to the invention may be used in building and construction, consumer applications, i.e. , for cushioning and furniture in leisure or office environments like seats, sofas, mattresses, or in transportation in train, aircraft and automotive in seats, headrests, armrests. Further applications are in packaging, i.e. packaging material to protect delivering good, cleaning applications, such as cleaning sponges, floor pads, hand pads, as filter medium, or in acoustic applications in building & construction, such as sound absorber in room acoustics for offices, schools, restaurants, noise chambers, furniture, separation walls, acoustic elements in walls and ceilings as well as silencer in air conditioning or transportation applications, such as sound absorber in automotive, under the hood motor for noise reduction or indoor as headliner, sun visor, hat rack. Further applications include thermal insulation in industrial applications, such as pipe insulation or insulation of air conditioning devices or for wall and roof insulation in building and construction. Applications in agriculture include growing substrate and floral foams Hereinafter, the present invention is described in more detail and specifically with reference to the examples, which however are not intended to limit the present invention.

[0085] Examples

[0086] Raw materials used:

[0087] Surfactant 1 : anionic surfactant Hostapur® SAS 93 (C14-C17 sec. alkyl sulfonate sodium salt), WeylChem;

[0088] Surfactant 2: non-ionic surfactant Lutensol® AT80 (C16-C18 fatty alcohol ethoxylate (~80 units)), BASF SE;

[0089] Water: de-ionized water;

[0090] Polylysine-1 : having a weight-average molecular weight Mwof about 2,000 g / mol (50 wt.-% in water), prepared according to Example 1 of WO 2022 / 136613 A1 by thermal treatment of L-lysine;

[0091] Crosslinker: 1 ,3-dihydroxyacetone (80 wt.-% in water), Sigma-Aldrich;

[0092] Physical blowing agent: mixture n-pentane / / so-pentane 80 / 20 wt.-%, AnalytiChem;

[0093] Salt: Na-formate, Acros Organics;

[0094] Polyol: ethylene glycol (EG), diethylene glycol (DEG), triethylene glycol (TEG), polyethylene glycol PEG 400, polyethylene glycol PEG 600, polyvinyl alcohol Mowiol® 4-88 (20 wt.-% aqueous solution) (PVA), 1,4-butanediol (BD), glycerol, trimethylolpropane (TMP), pentaerythritol, sorbitol (Sigma-Aldrich).

[0095] Determination of the weight-average molecular weight Mwof polylysine

[0096] Mwwas determined by size exclusion chromatography under the following conditions:

[0097] • Solvent and eluent: 0.1% (w / w) trifluoroacetate, 0.1 M NaCI in distilled water

[0098] • Flow: 0.8 mL / min

[0099] • Injection volume: 100 pL

[0100] • Samples are filtrated with a Sartorius Minisart RC 25 (0.2 pm) filter

[0101] • Column material: hydroxylated polymethacrylate (TSKgel G3000PWXL)

[0102] • Column size: inside diameter 7.8 mm, length 30 cm

[0103] • Column temperature: 35 °C

[0104] • Detector: DRI Agilent 1100 UV GAT-LCD 503 [232 nm]

[0105] • Calibration with poly(2-vinylpyridine) standards in the molar mass range from 620 to 2,890,000 g / mol (from PSS, Mainz, Germany) and pyridine (79 g / mol)

[0106] • The upper integration limit was set to 29.01 mL

[0107] • The calculation of Mwincludes the lysine oligomers and polymers as well as the monomer lysine.

[0108] Characterization of the foams The sample conditioning was at 23 °C, 50% rel. humidity, 24 hours and 23 °C, 80% rel. humidity, 24 hours, respectively.

[0109] The foam density is determined according to DIN EN ISO 845:2009-10 after sample conditioning at 23 °C, 50% rel. humidity, 24 hours.

[0110] Compression strength at 10% strain was measured according to DIN EN ISO 29469:2023-02 on samples after conditioning at 23 °C, 50% rel. humidity, 24 hours.

[0111] Compression stress value CV 40 at a compression of 40% was measured according to DIN EN ISO 3386-1: 2015-10 on samples after conditioning at 50% and 80% rel. humidity, 23 °C, 24 hours, respectively.

[0112] Examples 1 - 18 and Comparative Example C1

[0113] 117 g Polylysine-1 (Mw2.000 g / mol, 50 wt.-% aqueous solution), 22.7 g 1,3-dihydroxyacetone (80 wt.-% aqueous solution), 5.4 g of a surfactant mixture (6 parts per weight Hostapur® SAS93 and 4 parts per weight Lutensol® AT80), 2.0 g sodium formate and the type and amount of polyol listed in Table 1 were dissolved, and the mixture was treated with a high-shear mixer at high velocity for 1 min. Next, 8.0 g of a mixture of n-pentane / / so-pentane 80 / 20 wt.-% was added as physical blowing agent and stirred again for 10 sec. Finally, the whole mixture was transferred to a mold (e.g., cardboard box of 25 x 25 x 25 cm) and exposed to microwave. Procedure: Microwave: 4 x 2.45 GHz, 60 s; afterwards oven: 50 °C, 24 hours. After cooling, the now solid foam with fine and homogeneous cell structure was demolded.

[0114] Composition and mechanical properties of the foams obtained are shown in Table 1. With increasing amount of added TEG, the polylysine foam is getting softer. Other diols based on glycol have the same flexibilization effect like TEG, namely EG, DEG, PEG 400, and PEG 600.

[0115] Also, polyvinyl alcohol has the same effect shown by the concentration series in Table 1. Other polyols, partially with higher functionality, perform similar leading to softer foams with lower compression strength under dry and under humid conditions in comparison to the polylysine foam without polyol addition.

[0116] In the foam, the polyol is at least partially incorporated presumably via chemical bonding into the reacted network from polylysine and dihydroxyacetone. After incorporation, no peak for free, volatile polyol, which is not bonded to the polylysine network, is found in thermal gravimetric analysis (TGA). Table 1 : Composition and mechanical properties of the foams of Examples 1 to 18 and Comparative Example C1

[0117] Comparative Example 2

[0118] The procedure of Example 6 was repeated without adding 1 ,3-dihydroxyacetone. No foam was obtained.

Claims

Claims1. A process for producing a foam, which comprises foaming a mixture, comprising one or more poly(amino acid) (A), one or more components (B1) selected from alpha-hydroxy ketones and alpha-hydroxy aldehydes or any mixture thereof, one or more components (B2) selected from polyols and one or more blowing agents (F).

2. A process according to claim 1 , wherein the mixture comprises10 to 60 wt.-% of one or more poly (amino acid) (A),2 to 30 wt.-% of one or more components (B1),1 to 20 wt.-% of one or more components (B2),0 to 5 wt.-% of one or more salts of an inorganic acid or organic carboxylic acid (C),3 to 10 wt.-% of one or more surfactants (D),10 to 60 wt.-% of water (E),1 to 20 wt.-% of one or more physical blowing agents (F), and0 to 71.5 wt.-% of one or more additional additives (G), wherein the sum of the weight percentages of said components (A) to (G) is 100 wt.-%.

3. The process according to claim 1 or 2, wherein the poly(amino acid) (A) is polylysine with a weight-average molecular weight Mwin the range from 800 to 20,000 g / mol, determined by size exclusion chromatography (SEC).

4. The process according to any one of claims 1 to 3, wherein hydroxyacetone, 1 ,3- dihyroxyacetone, glycolaldehyde, glyceraldehyde or any mixture thereof is used as component (B1).

5. The process according to any one of claims 1 to 4, wherein ethylene glycol (EG), diethylene glycol (DEG), triethylene glycol (TEG), polyethylene glycol (PEG) 600, polyvinyl alcohol (PVA), 1 ,4-butanediol (BD), glycerol, trimethylolpropane (TMP), pentaerythritol, sorbitol or mixtures thereof is used as component (B2).

6. The process according to any one of claims 1 to 5, wherein salts of an inorganic acid or organic carboxylic acid (C) is Na-formate, Na-acetate or Na-citrate.

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

8. The process according to any one of claims 1 to 7, wherein a mixture of an anionic and a non-ionic surfactant is used as surfactant (D).

9. The process according to any one of claims 1 to 8, wherein a flame retardant is used as additional additive (G).

10. The process according to any one of claims 1 to 9, wherein the weight ratio of poly(amino acid) (A) to reactive component (B1) is in the range from 2 : 1 to 5 : 1.

11. The process according to any one of claims 1 to 9, wherein the weight ratio of reactive component (B1) to component (B2) is in the range from 60 : 1 to 2 : 1.

12. The process according to any one of claims 6 to 11, wherein the weight ratio of anionic surfactant to non-ionic surfactant is in the range from 50 : 50 to 90 : 10.

13. The process according to any one of claims 1 to 12, wherein the process comprises the following steps:(a) preparing an aqueous solution or suspension comprising 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 warming to a temperature in the range from 35 to 100 °C or by exposure to microwave.

14. A foam obtainable by the process according to any one of claims 1 to 13.

15. The foam according to claim 14 having a density in the range from 10 to 250 kg / m3, determined according to DIN EN ISO 845:2009-1016. The foam according to claim 14 or 15 having a compression stress value CV 40 at a compression of 40% in the range from 0.3 to 90 kPa according to DIN EN ISO 3386- 1:2015-10.

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