In situ foams based on polylysine

Abstract

The present invention relates to a system for producing an in-situ foam 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 amphoteric polymers (C) wherein component (B) is selected from the group consisting of reducing sugars, 1, 2, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, and 2, 3-dihydroxyacetone, glycolaldehyde, glyceraldehyde, or any mixture thereof.

Description

[0001] The present invention relates to a system for producing an in-situ foam and a method for producing the in-situ foam, the system comprising one or more poly(amino acids) (A), one or more components (B) capable of reacting with the poly(amino acids) (A) and one or more amphoteric polymers (C), wherein component (B) is selected from reducing sugars, 1,3-dihydroxyacetone, glycolaldehyde, glyceraldehyde or any mixture thereof.

[0002] Related prior art

[0003] Reactive non-thermoplastic (thermosetting) polymer foams are used in many applications, such as heat insulation, sound absorption, cushioning, cleaning, packaging and many other applications. In most cases, these reactive non-thermoplastic foams are produced by using suitable blowing agents (such as hexane, pentane, butane or its isomers or fluorocarbon hydrates or other). For the situation where the polymer reaction is not exothermic, the foam must be exposed to heat so that the blowing agent can evaporate. This is achieved by hot molds, hot air or using microwave technology. In most cases, due to the heat insulation effect during foam expansion, a large amount of heat must be applied. In addition, for the safe transportation, storage, processing and disposal of flammable blowing agents, it is necessary to ensure high safety input. An example is EP 0031 513 A2, which describes the preparation of an elastic open-cell foam based on urea-formaldehyde with a blowing agent pentane.

[0004] Another possibility is to use gases (e.g. CO2) to enable the foaming of reactive non-thermoplastic polymer foams. In this case, a high pressure drop is necessary to enable the foam to form. This can only be achieved by cost-intensive pressure-resistant equipment in the foam production.

[0005] Flexible polyurethane foams can be foamed by using water. Water reacts with the isocyanate groups of the corresponding isocyanates (e.g. TDI or MDI) to generate disubstituted ureas and CO2. CO2 acts as an inherent blowing agent in the foam formation. The final foam shows high flexibility and good sound absorption. However, the use of isocyanates leads to high safety costs in terms of safe transportation, storage, processing and disposal.

[0006] To overcome the mentioned disadvantages, open-cell, water-based, air-blown foams can be used.

[0007] An example of air-blown foam is described in WO 2017 / 067792. A mixture of >50% inorganic filler, cationic or amphoteric polymer, crosslinker, surfactant and other additives is mixed with air and cured to produce a density of 10 to 50 kg / m 3Air-blown foams. The resulting foams show good thermal insulation values ​​(about 35 mW / m*K) and a low calorific value of less than 3.0 MJ / kg. The most important application of these foams is the thermal insulation of cavities in buildings. On the other hand, these rigid foams are highly brittle and show a certain degree of shrinkage (>5%) (free-standing foams - without molds).

[0008] Another example is a foam based on urea-formaldehyde condensates as described in US Pat. No. 2,789,095. A mixture of urea-formaldehyde condensates with a suitable curing agent, surfactant and other additives is mixed with air and cured to produce a foam having a density of 12 to 15 kg / m 3 The obtained foams show good thermal insulation values ​​(about 35 mW / m*K) and good flame retardant properties [building class B2 (DIN 4102)]. On the other hand, these rigid foams are brittle and may show significant formaldehyde emissions.

[0009] WO 2016 / 009062 and WO 2011 / 138458 disclose a binder comprising a reaction product of a carbohydrate reactant and a polyamine, which can be used to consolidate loosely assembled materials such as fibers. No foam using the binder is disclosed.

[0010] WO 2022 / 136613 discloses a binder composition and its use for producing a lignocellulose composite product, the binder composition comprising polylysine having a total weight average molecular weight Mw of at least 800 g / mol as component A and 1,3-dihydroxyacetone, glycoaldehyde, glyceraldehyde or a mixture thereof as component B. A foam using the binder is not disclosed.

[0011] WO 2022 / 136614 relates to a binder composition comprising polyamine and hydroxyacetone for composite articles. A foam using the binder composition is not disclosed.

[0012] US 2011 / 0257284 A1 describes a process for producing flame-retardant polyurethane foams, which uses hyperbranched nitrogen-containing polymers, in particular hyperbranched polylysines, hyperbranched polyisocyanurates and hyperbranched polyesteramides, for providing flame retardancy to polyurethane foams. Summary of the invention

[0013] The present invention has been made in view of the above prior art and has as its object to provide an open-celled, formaldehyde- and isocyanate-free flexible foam with good sound absorption, which can be obtained from bio-based and water-based raw materials and processed in situ into air-blown foam.

[0014] Resolved technical issues

[0015] This object is solved by a foam and a system for producing an in situ foam, which system comprises one or more poly(amino acids) (A), one or more components (B) capable of reacting with the poly(amino acids) (A) and one or more amphoteric polymers (C), wherein component (B) is selected from reducing sugars, 1,3-dihydroxyacetone, glycolaldehyde, glyceraldehyde or any mixture thereof.

[0016] Preferably, the foam is not a polyurethane foam. Preferably, the foaming mixture is free of 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 solids of the sum of reactive components (A) and (B).

[0017] Preferably, the method comprises frothing a mixture comprising

[0018] 1 to 40 wt.-% of one or more poly(amino acids) (A)

[0019] 1 to 15 wt.-% of one or more components (B) capable of reacting with the poly(amino acid) (A)

[0020] 1 to 10 wt.-% of one or more amphoteric polymers (C),

[0021] 1 to 15 wt.-% of one or more surfactants (D),

[0022] 1 to 90 wt.-% of water (E),

[0023] 0 to 90 wt.-% of one or more additional additives (F),

[0024] The sum of the weight percentages of the components (A) to (F) is 100 wt.-%.

[0025] More preferably, the method comprises foaming a mixture comprising

[0026] 10 to 20 wt.-% of one or more poly(amino acids) (A)

[0027] 2 to 8 wt.-% of one or more components (B) capable of reacting with the poly(amino acid) (A)

[0028] 1 to 3 wt.-% of one or more amphoteric polymers (C),

[0029] 3 to 12 wt.-% of one or more surfactants (D),

[0030] 50 to 80 wt.-% water (E),

[0031] 0 to 34 wt.-% of one or more additional additives (F),

[0032] The sum of the weight percentages of the components A) to F) is 100 wt.-%.

[0033] More preferably, the process comprises foaming a mixture consisting essentially of components (A) to (E) in the above amounts.

[0034] Most preferably, the method comprises frothing a mixture consisting of

[0035] 10 to 20 wt.-% of one or more poly(amino acids) (A)

[0036] 2 to 8 wt.-% of one or more components (B) capable of reacting with the poly(amino acid) (A)

[0037] 1 to 3 wt.-% of one or more amphoteric polymers (C),

[0038] 3 to 12 wt.-% of one or more surfactants (D),

[0039] 57 to 80 wt.-% water (E),

[0040] The sum of the weight percentages of the components A) to E) is 100 wt.-%.

[0041] Component (A)

[0042] As component (A), poly(amino acid) (e.g., synthetic poly(amino acid), natural poly(amino acid), polypeptide, protein or a mixture thereof) is used. Poly(amino acid) is produced by polymerization of amino acids. Poly(amino acid) can be obtained by chemical synthesis or by biosynthesis in living organisms. In particular, protein can be obtained by biosynthesis in living organisms. Polypeptides can be obtained by hydrolysis of proteins.

[0043] According to the present invention, the term poly(amino acid) may also include poly(amino acid) derivatives which may be obtained by modifying the poly(amino acid) after the synthesis of the polymer.

[0044] The preferred amino acid for the polymerization reaction is a diamino acid comprising two amine groups (-NH2) 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 named as 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-NH2) rather than an amine (-NH2).

[0045] Preferably, polylysine is used as poly(amino acid). Polylysine can be produced by polymerization of lysine. Lysine itself is produced by fermenting corn starch in the presence of suitable bacteria. The production of polylysine is generally known and can be carried out as described in, for example, WO 2016062578 or from lysine salts as described in WO 2007060119. A preferred method for producing polylysine is described in WO 2022 / 136613.

[0046] Preferably, component (A) comprises at least one polylysine or consists of one or more polylysines which are the polymerization product of monomeric lysine, preferably L-lysine, and optionally other monomers selected from the group consisting of

[0047] a) an amino acid, which preferably comprises at least two amino groups,

[0048] b) an amine comprising at least two amino groups, wherein the amines are not amino acids, and

[0049] c) dicarboxylic acids and / or tricarboxylic acids, which are preferably not amino acids,

[0050] Therein at least 50 wt.-%, preferably at least 75 wt.-%, most preferably 100 wt.-% of lysine, based on the total amount of monomers, is used as monomer for the polymerization.

[0051] Preferably the poly(amino acid) (A) has a weight average molecular weight Mw in the range of 800 to 20,000 g / mol, more preferably in the range of 1,500 to 8,000 g / mol. The weight average molecular weight of the hydroxylated polymethacrylate is determined by size exclusion chromatography (SEC) with 0.1% (w / w) trifluoroacetate as solvent and 0.1 M NaCl in distilled water as eluent and calibration with poly(2-vinylpyridine) standards. Most preferably, polylysine with a molecular weight of 800 to 8,000 g / mol in an aqueous formulation is used as component (A).

[0052] Component (B)

[0053] 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 are used in the foaming mixture. Preferably, hydroxyacetone or 1,3-dihydroxyacetone is used as component (B).

[0054] Preferably, the weight ratio of poly(amino acid) (A) to component (B) is in the range of 2:1 to 5:1.

[0055] Poly(amino acids) and reducing sugars from natural sources can be used as raw materials to produce substantially bio-based foams.

[0056] It is assumed that components A and B undergo a Maillard reaction. The first step is the addition of the free amine group of the (poly)amino acid (component (A)) to the carbonyl group of a reducing sugar (ketose / aldose) (component (B)). The glycosylamine formed is unstable and undergoes a Heyns / Amadori rearrangement to form a Heyns / Amadori compound (aldehydeamine / ketoamine) with the loss of a water molecule.

[0057] In the case of the reaction of polylysine with (di)hydroxyacetone, a cross-linked thermosetting brown solid material is formed.

[0058] Component (C)

[0059] Amphoteric polymers suitable as component (C) are described, for example, in WO 2004 / 087818 and WO 2005 / 012637. Preference is given to copolymers comprising units derived from vinylamine and vinylformamide or from vinylamine and unsaturated carboxylic acids / carboxylates, and to terpolymers comprising units derived from vinylamine, vinylformamide and unsaturated carboxylic acids / carboxylates. Particular preference is given to copolymers formed from vinylamine and sodium acrylate and to terpolymers formed from vinylamine, vinylformamide and sodium acrylate. By way of example, mention may be made of F 3000.

[0060] Component (D)

[0061] Component (D) of the system comprises one or more surfactants for forming and stabilizing the foam. Anionic, cationic, nonionic or amphoteric surfactants are useful.

[0062] Suitable anionic surfactants are diphenyl oxide sulfonates, alkane sulfonates and alkylbenzene sulfonates, alkylnaphthalene sulfonates, olefin sulfonates, alkyl ether sulfonates, alkyl sulfates, alkyl ether sulfates, α-sulfofatty acid esters, amidoalkane sulfonates, acyl isethionates, alkyl ether carboxylates, N-acyl sarcosinates, alkyl phosphates and alkyl ether phosphates.

[0063] Useful nonionic surfactants include alkylphenol polyglycol ethers, fatty alcohol polyglycol ethers, fatty acid polyglycol ethers, fatty acid alkanolamides, EO-PO block copolymers, amine oxides, glycerol fatty acid esters, sorbitan esters and alkyl polyglucosides. Useful cationic surfactants include alkyl triammonium salts, alkyl benzyl dimethyl ammonium salts and alkyl pyridinium salts.

[0064] Particular preference is given to using mixtures of anionic and nonionic surfactants.

[0065] Preferably, a mixture of anionic surfactants and nonionic surfactants is used as surfactant (D). More preferably, a mixture of sodium salts of (C12-C14) fatty alcohol ether sulfates, (C12-C14) alkyl polyglycosides or mixtures thereof is used as surfactant (D).

[0066] Preferably, the weight ratio of the anionic surfactant to the nonionic surfactant is in the range of 50:50 to 90:10.

[0067] Component (E)

[0068] Water is used as component (E). Preferably, components (A), (B), (C) and (D) are used in the form of an aqueous solution or dispersion. Additional water may be added to achieve the above-mentioned composition of the mixture and to adjust the viscosity.

[0069] Component (F)

[0070] Flame retardants, fillers and salts (such as sodium formate, sodium acetate, sodium citrate, sodium chloride) can be used as further components (F). Preferably, flame retardants are used as additives (F).

[0071] The invention also provides a process for producing in situ foams by preparing an aqueous solution or dispersion of components (A) to (F) of the above-described system and foaming the aqueous solution or dispersion with a gas or a gas mixture.

[0072] In-situ foam can be obtained by mixing an aqueous composition comprising components (A) to (F) with a gas or a gas mixture under (super) atmospheric pressure and frothing it and applying mechanical force (such as stirring or shearing by a static mixer). The aqueous composition can also be frothed by dispersing an inert gas in the form of small bubbles of gas. The introduction of bubbles into the aqueous composition will be achieved by beating, shaking, stirring, whipping a stator or rotor device. It is preferred to use a mixer with a stator and / or rotor element.

[0073] The gas or gas mixture used preferably contains an inert gas such as nitrogen, argon, carbon dioxide or oxygen. Particular preference is given to using air.

[0074] A preferred method comprises the following steps:

[0075] (a) preparing an aqueous solution or dispersion comprising components (A) to (F),

[0076] (b) foaming the aqueous solution or dispersion by introducing a gas or a gas mixture into the aqueous solution or dispersion via one or more mixing elements,

[0077] (c) transferring the foam obtained in step (b) into a mold, and

[0078] (d) curing and drying the foam at 50°C to 160°C.

[0079] A subject of the present invention is also a foam obtainable by the above-described process.The dried foam preferably comprises more than 50 wt.-%, more preferably more than 65 wt.-%, of components (A) and (B) incorporated as a network matrix of the foam.

[0080] Preferably, the foam has a density determined according to DIN 53420 of between 10 and 60 kg / m 3 The density can be adjusted by the amount of the amphoteric polymer (component (C)) and the surfactant (component (D)). The density can be increased by using more reactive components (A) and (B) in the system for producing the in-situ foam.

[0081] Preferably, the foam has a Shore 000 hardness determined according to ASTM D 2240 in the range of 20 to 80.

[0082] The resulting air-blown foam exhibits high flexibility (Shore hardness) and good sound absorption properties.

[0083] The foam according to the invention

[0084] - can be obtained by air blowing foaming method

[0085] -Free of formaldehyde and isocyanate

[0086] - is open-celled, wherein the open-cell content determined by optical microscopy is greater than 95%

[0087] -It is water-based

[0088] - Not brittle and exhibits high flexibility as evidenced by low Shore hardness values

[0089] -Good sound absorption properties over a wide frequency range and low air flow

[0090] resistance.

[0091] Examples

[0092] Hereinafter, the present invention is described in more detail and specifically with reference to Examples, however, these Examples are not intended to limit the present invention.

[0093] Raw materials used:

[0094] Surfactant 1: Anionic surfactant FES 32 (31 wt.-% in water, fatty alcohol (C12-C14) ether (ca. 4EO) sulfate sodium salt, BASF SE);

[0095] Surfactant 2: nonionic surfactant, GD 70 (68 wt.-% in water, C10-C12 alkyl polyglucoside);

[0096] Water: deionized water;

[0097] Polylysine-1: has a weight average molecular weight Mw of about 2,000 g / mol (50 wt.-% in water).

[0098] Polylysine-5: having a weight average molecular weight Mw of about 5,500 g / mol (50 wt.-% in water);

[0099] Preparation of polylysine-1 and polylysine-5 by heat treatment of L-lysine according to Example 1 of WO 2022 / 136613

[0100] Amphoteric Polyethylene Amine

[0101] F3000 (11 wt.-% in water, NVF / VA / AA copolymer (35 / 35 / 30 mol%)), Solenis-BASF;

[0102] Cross-linker: 1,3-dihydroxyacetone (70 wt.-% in water, Sigma-Aldrich).

[0103] Determine the weight average molecular weight M of polylysine w

[0104] M w Determined by size exclusion chromatography under the following conditions:

[0105] Solvent and eluent: 0.1% (w / w) trifluoroacetate, 0.1 M NaCl in distilled water

[0106] ●Flow rate: 0.8ml / min

[0107] ●Injection volume: 100μl

[0108] ●The sample was filtered using a Sartorius Minisart RC 25 (0.2 μm) filter.

[0109] Column material: Hydroxylated polymethacrylate (TSKgel G3000PWXL)

[0110] ●Column size: inner diameter 7.8mm, length 30cm

[0111] ●Column temperature: 35℃

[0112] ●Detector: DRI Agilent 1100UVGAT-LCD 503 [232nm]

[0113] Calibration with poly(2-vinylpyridine) standards (from Polymer Standards Service (PSS), Mainz, Germany) with molar masses ranging from 620 to 2,890,000 g / mol and pyridine (79 g / mol)

[0114] ●The upper limit of the integral is set to 29.01 mL

[0115] ●M w The calculations include lysine oligomers and polymers as well as monomeric lysine.

[0116] Foam characterization

[0117] The foam density is determined according to DIN 53420.

[0118] Shore hardness is measured according to ASTM D 2240. For the measurement of low density foams, a scale of 000 is used (sphere diameter 2.4 mm, spring force 1.111 N).

[0119] The sound absorption was determined by impedance tube measurement according to ISO 10534-2 with a sample thickness of 30 mm and a diameter of 100 mm.

[0120] The compressive stress value (deflection under compression load) CV 40 is measured in accordance with DIN EN ISO 3386-1.

[0121] Examples 1-12: Preparation of air-blown polylysine-based foams

[0122] To the mixture of surfactant 1 and surfactant 2 in water, an aqueous dispersion of polylysine and an aqueous dispersion of the final amphoteric polyvinylamine were added and mixed by gently shaking by hand for a few seconds. Then, a crosslinker in water was added and the entire mixture was treated at high speed for 1 min with a high shear mixer (Krups Handmixer 3Mix7000). Thus, a fine-cell air-blown foam with an open cell content of greater than 95% determined by optical microscopy was produced, which was poured into a suitable mold (e.g., a box of 10×10×5 cm). The liquid foam was cured and dried at 100° C. for 24 h. After cooling, the now solid foam was demoulded.

[0123] The composition (in parts by weight) and Shore hardness 000 (23° C., 50% relative humidity) of the obtained foams are shown in Table 1. After conditioning at 50% relative humidity for 24 h, the foam density of the samples of Examples 1 to 9 was determined to be between 24 and 28 kg / m 3 within the range.

[0124] The obtained foam has an open cell structure (open cell content > 95% as determined by optical microscopy) and exhibits good sound absorption in the frequency range of 100-5.000 Hz, with the maximum sound absorption being about 2.000 Hz, similar to common open cell PUR soft foams. The sound absorption of the foam obtained from Example 1 is shown in Table 2.

[0125] The mechanical properties after conditioning temperature and moisture at 23°C, 50% relative humidity are shown in Table 3. At higher tempering temperatures, the foams show higher Shore hardness and compressive load. Conditioning at higher relative humidity produces softer foams.

[0126] In the absence of a crosslinker (Example 11), with a low molecular weight polylysine (Example 12) or without the stabilizing prepolymer polyvinylamine (Example 10), a less uniform foam may be obtained after curing.

[0127] Table 1: Composition and Shore hardness of the obtained foams

[0128]

[0129]

[0130] Table 2: Sound absorption of the foam of Example 1:

[0131] Frequency [Hz] Absorption rate 160 0.067 200 0.089 250 0.116 315 0.133 400 0.177 500 0.221 630 0.256 800 0.376 1000 0.536 1250 0.655 1600 0.779 2000 0.968 2500 0.960 3150 0.857

[0132] Table 3: Mechanical properties of Example 1 after temperature and moisture conditioning

[0133] Tempering (24h) Conditioning (72h) Compression load deflection (CV 40) / kPa Shore hardness (000) 100℃ 23℃, 50% RH 15.3 40 120℃ 23℃, 50% RH 15.8 41 140℃ 23℃, 50% RH 24.1 55 160℃ 23℃, 50% RH 34.4 72 100℃ 23℃, 80% RH 1.9 <5 120℃ 23℃, 80% RH 2.7 <5 140℃ 23℃, 80% RH 2.9 <10 160℃ 23℃, 80% RH 3.2 <10

[0134] Comparative Example C1:

[0135] Surfactant 1 FES 32 (2.4 g, 31%) and surfactant 2 To a mixture of GD 70 (0.5 g, 68%) in water (22.1 g) was added the crosslinking agent glyoxal (1 g, 2%) in water and mixed by gently shaking for a few seconds. The mixture was processed with a high shear mixer at high speed for 1 min. Thus, a fine-pore air-blown foam was produced. The amphoteric polyvinylamine The aqueous dispersion of F3000 (25 g, 11%) was carefully added to the foam and quickly homogenized. The mixture was poured into a mold of a 10×10×5 cm box. The liquid foam was cured and dried at 50°C for 24 h. A 32 kg / m 3 After cooling, the now solid foam is demoulded.

[0136] The demoulded, free-standing soft foam of Example C1 collapsed at 23°C / 50% relative humidity, with a volume shrinkage of 0% after 30 min, 10% after 120 min, 18% after 210 min, 24% after 330 min, and 47% after 3 days. The demoulded, free-standing flexible foam of Example 1 was stable under these conditions with no dimensional changes.

[0137] Comparative Example C2:

[0138] Air-blown foam made from urea-formaldehyde resin

[0139] Component A consists of 25 g of a water-soluble urea-formaldehyde precondensate ( 293 powder). When dissolved, add 3 g of urea and stir for at least 1 h. After standing for 12 hours, mix in 15 g of water. Component B consists of 4.7 mL of blowing agent ( A mixture of 514 liquid) (an aqueous solution containing 25% H3PO4 (85%), 4% resorcinol, 20% sodium bis(dimethylethyl)naphthalenesulfonate with a pH of 1-2) and 100 mL of water was produced by stirring for 30 min. 25 g of component B was treated with a high shear mixer at high speed for 1 min. Thus, a fine-pore air-blown foam was produced. 47 g of component A was carefully added to the foam and quickly homogenized. The mixture was poured into a mold of a 10×10×5 cm box. The liquid foam was cured at 50° C. and dried for 24 h. A foam weight of 18.5 kg / m 3 After cooling, the now solid foam is demoulded.

[0140] Note: The final density of air-blown foams cannot be adjusted over a wider range than solvent-blown foams. The foam density is given by the settings of the specific blowing agent and the foaming technology. Since the same foaming technology using a high shear mixer was applied within the examples and comparative examples shown, the resulting foam densities made from polylysine / dihydroxyacetone, polyvinylamine / glyoxal, and urea / formaldehyde may vary depending on the chemical composition, solid content, viscosity, optimized blowing agent.

[0141] Table 4: Mechanical properties of Example 1 and Comparative Example 2

[0142]

[0143] This indicates that polylysine / dihydroxyacetone is a flexible, non-brittle foam. Another air-blown foam based on urea-formaldehyde resin is not flexible.

Claims

1. A system for producing an in-situ foam, the system comprising one or more poly(amino acids) (A), one or more components (B) capable of reacting with the poly(amino acids) (A) and one or more amphoteric polymers (C), wherein component (B) is selected from reducing sugars, 1,3-dihydroxyacetone, glycolaldehyde, glyceraldehyde or any mixture thereof.

2. The system according to claim 1, comprising 1 to 40 wt.-% of one or more poly(amino acids) (A) 1 to 15 wt.-% of one or more components (B) capable of reacting with the poly(amino acid) (A) 1 to 10 wt.-% of one or more amphoteric polymers (C), 1 to 15 wt.-% of one or more surfactants (D), 1 to 90 wt.-% of water (E), 0 to 90 wt.-% of one or more additional additives (F), The sum of the weight percentages of the components (A) to (F) is 100 wt.-%.

3. The system according to claim 1 or 2, 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 determined by size exclusion chromatography (SEC).

4. The system according to any one of claims 1 to 3, wherein 1,3-Dihydroxyacetone was used as component (B).

5. The system according to any one of claims 1 to 4, wherein As amphoteric polymer (C) a terpolymer comprising vinylamine, vinylformamide and sodium acrylate units was used.

6. The system according to any one of claims 1 to 5, wherein As surfactant (D), sodium salt of (C12-C14) fatty alcohol ether sulfate, (C12-C14) alkyl polyglycoside or a mixture thereof is used.

7. The system according to any one of claims 1 to 6, wherein As additive (F) a flame retardant is used.

8. The system according to any one of claims 1 to 7, wherein The weight ratio of poly(amino acid) (A) to component (B) is in the range of 2.5:1 to 5:

1.

9. The system according to any one of claims 1 to 8, wherein The mixture of anionic surfactant and nonionic surfactant is used in a weight ratio of anionic surfactant to nonionic surfactant in the range of 50:50 to 90:

10.

10. A process for producing an in-situ foam by preparing an aqueous solution or dispersion of components (A) to (F) of the system according to any one of claims 1 to 9 and foaming the aqueous solution or dispersion with a gas or a gas mixture.

11. The method according to claim 10, comprising the following steps (a) preparing an aqueous solution or suspension comprising components (A) to (F), (b) foaming the aqueous solution or suspension by introducing a gas or a gas mixture into the aqueous solution or suspension via one or more mixing elements, (c) transferring the foam obtained in step (b) into a mold, and (d) curing and drying the foam at 50°C to 160°C.

12. An in-situ foam obtainable by the process according to claim 10 or 11.

13. The in-situ foam according to claim 12, having a relative humidity determined according to DIN 53420 of 10 to 60 kg / m 3 density within the range of .

14. The in-situ foam according to claim 12 or 13, having a Shore hardness in the range of 20 to 80 determined according to ASTM D 2240.

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