WO2025195769A1

WO2025195769A1 - Polylysine foam with high flexibility

Info

Publication number: WO2025195769A1
Application number: PCT/EP2025/055917
Authority: WO
Inventors: Alexander Koenig; Johannes Ahrens; Gereon Antonius SOMMER
Original assignee: BASF SE
Current assignee: BASF SE
Priority date: 2024-03-19
Filing date: 2025-03-05
Publication date: 2025-09-25
Anticipated expiration: 2026-09-19

Abstract

The present invention relates to a process for producing a foam, which comprises foaming a mixture, comprising one or more amino acid copolymers (A), one or more components (B) capable of reacting with said amino acid copolymers (A) and one or more blowing agents (F), wherein component (B) is selected from alpha-hydroxy ketones and alpha-aldehydes such as reducing sugars, 1,3-dihydroxyacetone, glycolaldehyde, glyceraldehyde or any mixture thereof and the foam obtainable by this process.

Description

Polylysine foam with high flexibility

Description

The present invention relates to a process for producing a foam, comprising one or more amino acid copolymers (A), one or more components (B) capable of reacting with said amino acid copolymers (A) and one or more blowing agents (F), wherein component (B) is selected from alpha-hydroxy ketones and alpha-hydroxy aldehydes or any mixture thereof and the foam obtainable by this method.

Relevant Prior Art

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.

WO 2022/136613 A1 discloses a binder composition comprising polylysine having a total weight average molecular weight M_w of 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.

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

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.

CN 111763431 A discloses a method for preparing foamed plastic comprising foaming a mixture comprising collagen, derived from leather scraps, a macromolecular dialdehyde and baking soda.

US 9,156,950 B2 discloses a dry collagen powder as a precursor suitable for the preparation of a homogeneous thermoplastic collagen-based composition, further comprising a blowing agent to form a low ratio expanded foam article.

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.

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

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 and low moisture uptake, which can be obtained from formaldehyde- and isocyanate-free, bio- and water-based raw materials.

Technical problem solved

This object was solved by a foam and a process for producing the foam, which comprises foaming a mixture, comprising one or more amino acid copolymers (A), one or more components (B) capable of reacting with said amino acid copolymer (A) and one or more blowing agents (F), wherein component (B) is selected from alpha-hydroxy ketones or alphahydroxy aldehydes or any mixture thereof.

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.

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 the amino acid copolymer (A) based on the solids of the sum of the reactive components (A) and (B).

Preferably the process comprises foaming a mixture, which comprises

10 to 60 wt.-% of one or more amino acid copolymers (A),

2 to 30 wt.-% of one or more components (B) capable of reacting with said amino acid copolymers (A),

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), and 0 to 72.5 wt.-% of one or more additional additives (G), wherein the sum of the weight percentages of said components (A) to (G) is 100 wt.-%.

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

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

20 to 60 wt.-% of one or more amino acid copolymers (A),

3 to 30 wt.-% of one or more components (B) capable of reacting with said amino acid copolymers (A),

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

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

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.-%.

Component (A)

As component (A) amino acid copolymers, e.g. synthetic poly(amino acid)s, natural poly(amino acid)s, polypeptides, proteins or mixtures thereof are used. Amino acid copolymers are produced by copolymerization of at least two different amino acids or lactams. Amino acid copolymers 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.

According to this invention, the term “amino acid copolymers” may also include amino acid copolymer derivatives, which may be obtained by modification of the amino acid copolymers after polymer synthesis.

Preferred amino acids (a1) which are used for the copolymerization 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).

Preferably, lysine is used as main amino acid (a1). Lysine may be produced by the fermentation of corn starch, sugar or other carbon hydrates in presence of suited bacteria.

As comonomer (a2) preferred amino acids and derivatives thereof which are used for the copolymerization reaction with lysine are amino acids comprising one amine group (-NH2) and at least one carboxyl (-COOH) functional group or are lactams (= cyclic amides with one amide group (CO-NH)). Such amino acids or lactams may be e-amino acids with C3 to C12 or lactams with 4 to 13 ring atoms, more preferably e-aminocaproic acid (e-Ahx) and e-caprolactam (CPL), respectively.

Preferably, component (A) comprise(s) at least one amino acid copolymer or consist(s) of one or more amino acid copolymers, which is (are) a copolymerization product of monomer (a1) lysine, preferably L-lysine, and other monomers (a2) selected from the group consisting of a) amino acids, preferably e-aminocaproic acid, and/or b) lactams, preferably caprolactam, and optionally other monomers selected from the group consisting of c) amines comprising at least two amino groups, wherein the amines are no amino acids, and d) di- and/or tricarboxylic acids, which are preferably no amino acids, wherein at least 50 wt.-%, preferably 60 to 95 wt.-% lysine is used as monomer for the polymerization reaction, based on the total amount of monomers.

More preferably, the amino acid copolymer (A) is a polylysine copolymer. Most preferably, the amino acid copolymers (A) are copolymers of lysine and caprolactam or lysine and E- aminocaproic acid.

Preferably, the molar ratio of monomer (a1) to monomer (a2) is 1 :1 to 25:1 , more preferably 2:1 to 10:1.

Weight-average molecular weight M_w of the amino acid copolymer (A) has an influence on mechanical properties of the foam. Preferably, the amino acid copolymer (A) has a weightaverage molecular weight M_w in the range from 500 to 20,000 g/mol, more preferably 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 copolymer 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.

Most preferably, the amino acid copolymers (A) are copolymers of lysine and s-aminocaproic acid or lysine and caprolactam with a weight-average molecular weight M_w in the range from 800 to 20,000 g/mol, determined by size exclusion chromatography (SEC).

Component (B)

One or more components (B) capable of reacting with said amino acid copolymer (A) selected from alpha-hydroxy ketones and 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 (B).

Preferably, the weight ratio of amino acid copolymer (A) to component (B) is in the range from 2 : 1 to 5 : 1.

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

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

Reactive polylysine foams crosslinked with an alpha-hydroxy ketone or aldehyde via the Maillard reaction can be flexibilized by using copolymers of L-lysine and a less functional monomer. As the amount of free amine groups in the reacted foams is now reduced compared to foams using pure homopolymer polylysine also the moisture uptake is reduced.

In the case of the reaction of polylysine with (di)hydroxyacetone, a crosslinked thermoset lightbrown solid material is formed.

Component (C)

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 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.

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

Preferable halogen-free salts are used to obtain halogen-free foams. Component (D)

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.

Suitable anionic surfactants are diphenylene oxide sulfonates, alkane- and alkylbenzenesulfonates, alkylnaphthalenesulfonates, olefinsulfonates, alkyl ether sulfonates, alkyl sulfates, alkyl ether sulfates, alpha-sulfofatty acid esters, acyl-aminoalkanesulfonates, acyl-isethionates, alkyl ether carboxylates, N-acylsarcosinates, alkyl and alkyl ether phosphates.

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.

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

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 (C 12- 14) -fatty alcohol ether sulfate, a (C12-C14)- alkyl polyglycoside or mixture therefrom are used as surfactants (D).

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

Component (E)

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.

Component (F)

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, 3^rd 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 and 80 °C.

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.

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.

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.

Component (G)

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).

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.

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.

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. A preferred 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.

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

Preferably, the foam has a density in the range from 1 kg/m³ to 250 kg/m³, more preferably in the range from 10 kg/m³ to 100 kg/m³, determined according to DIN 53420. 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.

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.

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 reducing sugars and can be produced over a wide density range.

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

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 and 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.

Examples Raw materials used:

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

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

Water: de-ionized water;

Polylysine-1 : having a weight-average molecular weight M_w of about 2,000 - 3,000 g/mol

(50 wt.-% in water), was prepared according to Example 1 of WO 2022/136613 A1 by thermal treatment of L-lysine;

Lysine 50 wt.-% solution in water (liquid L-lysine, ADM Specialty Ingredients, USA, fermentation product from sugar waste)

£-caprolactam (CPL), Sigma-Aldrich;

£-aminocaproic acid (£-Ahx), Sigma-Aldrich;

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

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

Determination of the weight-average molecular weight M_w of polylysine and polylysine copolymers

M_w was determined by size exclusion chromatography under the following conditions:

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

• Flow: 0.8 mL/min

• Injection volume: 100 pL

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

• Column material: hydroxylated polymethacrylate (TSKgel G3000PWXL)

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

• Column temperature: 35 °C

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

• 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)

• The upper integration limit was set to 29.01 mL.

• The calculation of M_w includes the lysine oligomers and polymers as well as the monomer lysine.

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.

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

Moisture uptake was determined by the difference of climate conditioning at 80% relative humidity and 50% relative humidity.

Synthesis of Copolymers CP 1 - CP 6

2200 g of L-lysine solution (50% in water) and 122 g, 275 g, or 471 g e-caprolactam (CPL) or E- aminocaproic acid (s-Ahx), respectively, were heated under stirring in an oil bath (external temperature 140 °C). Water was distilled off and the oil bath temperature was increased by 10 °C per hour until a temperature of 180 °C is reached. The reaction mixture was stirred for an additional hour at 180 °C (oil bath temperature) and then pressure was slowly reduced to 200 mbar. After reaching the target pressure, distillation was continued for another period of time of 150 min. The product was hotly poured out of the reaction vessel, crushed after cooling and dissolved in water to give a 50 wt.-% solution.

M_w was determined from this solution without any further purification.

Table 1: Composition and molecular weight of poylysine-1 and copolymers CP1 to CP6.

Examples 1 - 6 and Comparative Example C1 :

117 g Polylysine-1 (M_w 2.426 g/mol, 50 wt.-% aqueous solution) or copolymer CP1 - CP6, 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), dissolved and the mixture was treated with a high-shear mixer at high velocity for 1 min. Next, 10.0 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.

Composition and mechanical properties of the foams obtained are shown in Table 2.

Table 2: Composition and mechanical properties of the foams of Examples 1 to 6 and Comparative Example C1 The mechanical flexibility of the foams CP1 - CP6 increases with the content of the comonomer £-caprolactam (CPL) and e-aminocaproic acid (e-Ahx), respectively, in comparison to the foam C1 from pure polylysine (no copolymer). The foam made from the copolymers is softer under dry as well under humid conditions explained by the lower crosslinking density. Also, the moisture uptake is reduced as the content of free amino groups in the foam is reduced.

Claims

1. A process for producing a foam, which comprises foaming a mixture, comprising one or more amino acid copolymers (A), one or more components (B) capable of reacting with said amino acid copolymers (A) and one or more blowing agents (F), wherein component (B) is selected from alpha-hydroxy ketones and alpha-hydroxy aldehydes or any mixture thereof.

2. A process according to claim 1 , wherein the mixture comprises

10 to 60 wt.-% of one or more amino acid copolymers (A),

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

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

3. The process according to claim 1 or 2, wherein the amino acid copolymer (A) comprises at least one copolymer, which is a copolymerization product of monomer (a1) lysine and other monomers (a2) selected from the group consisting of amino acids and/or lactams, wherein at least 50 wt.-% of lysine is used as monomer for the polymerization reaction, based on the total amount of monomers.

4. The process according to claim 1, 2 or 3, wherein the amino acid copolymer (A) is a copolymer of lysine and e-aminocaproic acid or lysine and caprolactam with a weightaverage molecular weight M_w in the range from 800 to 20,000 g/mol, determined by size exclusion chromatography (SEC).

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

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 amino acid copolymers (A) to component (B) is in the range from 2 : 1 to 5 : 1.

11. The process according to any one of claims 7 to 10, wherein the weight ratio of anionic surfactant to non-ionic surfactant is in the range from 50 : 50 to 90 : 10.

12. The process according to any one of claims 1 to 11, wherein the process comprises the following steps:

13. A foam obtainable by the process according to any one of claims 1 to 12.

14. The foam according to claim 13 having a density in the range from 1 to 250 kg/m³, determined according to DIN EN ISO 845:2009-10.

15. The foam according to claim 13 or 14 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.