Polyurethane foam formulation and sound insulation with foam-based components (engine capsule)

Description

[0001] The invention relates to a polyurethane foam formulation based on conventional polyether and novolac polyols, in particular with MDI, for the production of soft-elastic PUR molded foams with viscoelastic properties, especially for sound insulation with foams based thereon.

[0002] Soft-elastic and viscoelastic polyurethane molded foams are widely used in vehicle acoustics. Conventional soft-elastic foams are generally classified as "high resilience" and exhibit a pronounced spring characteristic with spontaneous and rapid recovery. In contrast, viscoelastic foam types are distinguished from soft-elastic foams by their delayed recovery after compression. Viscoelastic foams typically achieve significantly better damping properties compared to high-resilience foams.

[0003] Viscoelastic polyurethane (PUR) foams are typically based on MDI and a mixture of polyether polyols, usually glycerin-based. While polyols with high molecular weight and low functionality tend to be used for soft-elastic foam types, low molecular weight, especially in combination with high functionalities, leads to preferred rigid foams. For specific applications in viscoelastic formulations, the desired degree of viscoelastic properties is balanced by the ratio of soft to rigid segments within the polymer.

[0004] Unlike soft-elastic or viscoelastic foams typically produced using block foam manufacturing processes and used in the mattress or upholstery industry, acoustically effective components in the field of vehicle acoustics are preferably manufactured directly as molded parts with the desired component geometry. Two-component systems are generally used for this purpose, with one component of the reactive system consisting of various (poly)isocyanates, and the second component comprising a complex mixture of mostly different polyols, blowing agents, catalysts, stabilizers, and possibly other additives.

[0005] The typical material properties of these foams are primarily determined by the types of polyols used, their proportions, the degree of crosslinking, and the chosen density. Given their intended use in acoustically effective spring-mass encapsulations for electric motors in motor vehicles, and considering high temperatures combined with humidity conditions that often lead to premature aging or even hydrolytic degradation, either polyester or polyether polyols are used. For current applications, standard foams (HR foams) are predominantly used. Furthermore, these standard foams (based on conventional polyethers) are less susceptible to hydrolytic degradation than polyester-based types, but not sufficiently stable to withstand the aforementioned highly modified aging conditions.In general, high temperatures lead to premature material aging, while dry conditions lead to brittleness and hydrolytic conditions (resulting from high temperatures in combination with moisture) lead to softening effects, loss of mechanical and acoustic properties, or even complete material decomposition.

[0006] The various polyols differ primarily in terms of functionality, reactivity, and molecular mass, with the functionality and basic structure being directly determined by the starter molecule used. Water is usually added to the polyol component as a chemical blowing agent, reacting with the (poly)isocyanate to release carbon dioxide, which then acts as the actual blowing agent.

[0007] Soft-elastic foams are used in various forms for a wide range of acoustic applications. These applications range from simple absorbers to spring-mass structures. The sound-absorbing effect increases depending on the density or the combined mass layer. Compared to soft-elastic "high resilience" types, viscoelastic molded foams are generally characterized by better damping properties and are therefore preferred, especially in the premium sector. This specific viscoelastic material behavior can be divided into pneumatic effects and structural properties, but usually represents a combination of both. The so-called pneumatic ("asthma") effect is based on very small pore size, often in combination with a not completely open cell structure, which slows down air exchange during compression and recovery.The structural properties result from the combination of soft and hard segments within the polymer matrix and can be controlled accordingly via the quantitative distribution of differently functional polyols as well as the aforementioned primary parameters.

[0008] US 2012 / 0009407 A1 discloses a rigid polyurethane foam comprising the reaction product of an isocyanate composition and a resin composition containing a novolac polyol with an average hydroxyl functionality of 2 to 30, calculated by dividing the weight mean of the molecular weight of the novolac polyol by the equivalent weight of the novolac polyol.

[0009] The novolac polyol is present in an amount of 3 to 65 parts by weight per 100 parts by weight of the resin composition.

[0010] US 2015 / 0099851 A1 describes resins derived from cashew nut shell liquid and vinyl hydrocarbons that can be used as precursors for the production of epoxy resins and polyols for coatings, adhesives and composite formulations, exhibiting improved performance in water repellency, corrosion protection and rapid hardening during curing.

[0011] From US patent 2008 / 0015275 A1, it is known that a subgroup of phenolic resins is particularly well suited to imparting load-bearing properties to an isocyanate-based foam. It has been shown that it is possible to use these phenolic resins to partially or completely replace copolymer polyols. Furthermore, it has been described that these phenolic resins are particularly well suited to imparting energy absorption properties to an isocyanate-based foam.

[0012] WO 00 / 733 68 A1 describes a formulation of water-foamed flexible polyurethane foam in which a plasticizer containing a crosslinking / chain extender is incorporated, thereby achieving the desired softness, openness, and tensile strength. Preferred crosslinking / extenders may be polyoxyalkylene polyols having a hydroxyl number of less than 200 and an average number of 3 to 8 hydroxyl groups.

[0013] US 2017 / 0260319 A1 describes a hybrid polyurethane / polyurea polymer suitable for forming a coating on a structure in contact with water, comprising the reaction product of a polyol component consisting of one or more polyols, a polyamine, and a curing agent, such as a polyisocyanate. The polyol component includes a novolac-type polyether polyol.

[0014] Numerous different combinations of polyether polyols are known for producing soft-elastic or viscoelastic molded foams. The transition from soft-elastic to viscoelastic is gradual. This means that foams that appear clearly resilient can already exhibit measurably viscoelastic material properties. The loss factor, measured using the vibrometer method, has become established as a measurable parameter. As a rule of thumb, the higher the loss factor, the more readily the typical viscoelastic material behavior is also perceptible to the touch. For sound insulation applications, a higher loss factor usually also means better damping properties.

[0015] Besides the loss factor, the corresponding modulus of elasticity (E-modulus) plays a crucial role. Thus, comparably harder foams can exhibit significantly worse acoustic insulation properties despite a high loss factor compared to those with a low loss factor but considerably lower hardness. The known material compositions of various polyether polyols, often marketed specifically for use in viscoelastic foams, show an expected dependence on the modulus of elasticity, loss factor, and MDI index. To obtain a sufficient number of hard segments in viscoelastic foams, a correspondingly high degree of crosslinking, i.e., a high MDI index, is necessary. However, this also tends to result in higher strength or an increased modulus of elasticity.

[0016] The efficiency of foamed, acoustically effective automotive trim components is determined by the overall component design, and in particular by the specific properties of the foam systems used. Acoustic effectiveness is fundamentally divided into two categories: absorption and insulation. The absorption coefficient of a molded foam component depends primarily on the porosity and size of the surface exposed to sound and the internal cell morphology (cell size and distribution, number and ratio of open to closed cells), which in turn significantly influence the performance-determining properties of flow resistance and tortuosity.

[0017] In contrast, the insulating properties of molded foams are determined by their density and elastic spring properties. Besides the hardness, or more accurately, the softness of the foam, its elastic behavior plays a crucial role. Both rebound-elastic and viscoelastic foam types are known, with viscoelastic versions, especially in their softer settings, achieving significantly better insulation performance than rebound-elastic foams with comparable hardness and molded density due to their higher damping capacity (expressed as a loss factor). To enhance the (sheet metal) damping properties of such foams, corresponding layers of material are typically used, similar to highly elastic foams, and combined to form so-called spring-mass elements, which are then back-foamed.The acoustic effectiveness of the overall assembly is further determined by the aforementioned properties of the spring (molded foam), but additionally by the properties of the mass layer (area weight, flexural flexibility). In this combination, a higher area weight with the same amount of back-foam generally leads to improved damping of vibrating elements, which in the automotive sector are usually sheet metal parts.

[0018] In the past, little attention was paid to hydrolysis resistance in known encapsulations for electric motors in motor vehicles. During the development of new molded foams, the aging weakness of existing foams was discovered. Known viscoelastic molded foams exhibit a typical weakness with respect to compression set. Furthermore, compression set is frequently used as an indicator of material aging, particularly caused by hydrolytic processes. In addition, hydrolytic conditions lead to general degradation, which is reflected in significantly reduced mechanical properties such as tensile strength, elongation at break, and compressive strength.

[0019] The object of the present invention is therefore to increase the hydrolysis resistance of a polyurethane foam formulation.

[0020] The aforementioned problem is solved in a first embodiment of the invention by the subject matter of claim 1. This relates to a polyurethane foam formulation for the production of viscoelastic PUR molded foams, comprising: a) a novolac polyol with a hydroxyl functionality of 3, a hydroxyl number in the range of 160 to 240 mgKOH / gb) a polyether polyol with a hydroxyl functionality of 3, a hydroxyl number in the range of 20 to 40 mgKOH / gc) a block / copolymer with a hydroxyl number in the range of 25 to 45 mgKOH / g and e) a combination of catalytically active and stabilizing additives.

[0021] The polyurethane foam formulation according to the invention is based on a special material composition that meets the fundamental viscoelastic acoustic requirements and enables a molded foam that also complies with the newly defined standards regarding hydrolytic aging. The polyether-based polyol—similar to conventional foam compositions—allows for a fundamentally soft and flexible foam product. The required combination of viscoelastic properties and significantly improved temperature and hydrolysis resistance is achieved through the use of a highly aromatic polyol of the novolac type, whose molecular structure provides suitable building blocks for rigid segments while also strongly supporting thermal and hydrolytic stability. The incorporation of the novolac polyols is essential to the invention, as their primary application is in rigid polyurethanes.

[0022] The formulation according to the invention enables the production of molded foam in accordance with the above-mentioned, fundamentally modified technical requirements, which meet both the mechanical requirements and the acoustic aspects after advanced moisture aging.

[0023] The polyols used differ in the starter molecule employed, the resulting functionality, the molecular mass, and the reactivity. Furthermore, targeted modifications of the material behavior via the isocyanate component are also possible, e.g., using prepolymers.

[0024] In order to specify the above-mentioned polyols, the aforementioned various parameters have emerged in the prior art: i.) The hydroxyl functionality, which depends on the starter molecule on which the polyether polyol is synthesized; ii.) the hydroxyl or OH number, which is a measure of the hydroxyl group content and is expressed in mg KOH / g. It is determined according to DIN 53240; iii.) the molecular mass (Mw), which is a measure of the length of the polyoxyalkylene chains of the polyether polyols.

[0025] The above-mentioned quantities can be related to each other using the following equation: 56100 = OH - Zahl · Mw / Hydroxyl - Funktionalität .

[0026] The polyol component (a) consists of one or more polyols, including a first polyether polyol, namely a (Novolac) phenol-based polyether polyol having a phenol-based backbone.

[0027] Novolac-type polyether polyols can, for example, be the alkoxylation products of a phenol-aldehyde resin, which is formed by an elimination reaction of phenol with an aldehyde such as formaldehyde in the presence of an acid catalyst. Usually, a small amount of the acid catalyst or catalysts is added to a miscible phenol, followed by an aldehyde, such as formaldehyde.

[0028] The formaldehyde reacts between two phenols to form a methylene bridge, whereby electrophilic aromatic substitution occurs between the ortho and para positions of the phenol and the protonated phenol. With increasing concentration of dimers, trimers, tetramers and higher oligomers can also form.

[0029] The degree of polymerization can be controlled by adjusting the molar ratio of formaldehyde to phenol to slightly less than 1.

[0030] The novolac resin can then be alkoxylated to reduce the molecular weight to a desired level.

[0031] Phenols that can be used to manufacture Novolac resin include: o-, m- or p-cresols, ethylphenol, nonylphenol, p-phenylphenol, 2,2-bis(4-hydroxyphenol)propane, beta-naphthol, beta-hydroxyanthracene, p-chlorophenol, o-bromophenol, 2,6-dichlorophenol, p-nitrophenol, 4-nitro-6-phenylphenol, 2-nitro-4-methylphenol, 3,5-dimethylphenol, p-isopropylphenol, 2-bromo-4-cyclohexylphenol, 4-t-butylphenol, 2-methyl-4-bromophenol, 2-(2-hydroxypropyl)phenol, 2-(4-hydroxyphenol)ethanol, 2-carbethoxyphenol and 4-chloromethylphenol.

[0032] The phenols used to produce novolac-type polyether polyols can be substituted or unsubstituted.

[0033] Suitable polyether polyols of the novolac type can be obtained, for example, by reacting a condensate adduct of phenol and formaldehyde with one or more alkylene oxides, including ethylene oxide and propylene oxide.

[0034] Methods for producing such polyether polyols are described, for example, in US patents 2,838,473, 2,938,884, 3,470,118, 3,686,101 and 4,046,721.

[0035] Novolac-type polyols can also be derived from the reaction of aldehydes with phenolic lipids, such as alkylbenzoic acids (salicylic acid with an unsubstituted or substituted alkyl chain, for example having 10 to 20 carbon atoms, e.g., an acardic acid) and alkylresorcinols with an unsubstituted or substituted alkyl chain, for example having 10 to 20 carbon atoms, such as cardol, and mixtures thereof.

[0036] The polyol may preferably have a hydroxyl number of at least 160 or up to 240.

[0037] The hydroxyl number is defined as the number of milligrams of potassium hydroxide required to neutralize the acetic acid absorbed during the acetylation of one gram of polyol.

[0038] In one embodiment, the novolac-type polyol (and / or another polyether polyol) can be used to produce a polyurethane (e.g., using a novolac-type polyol to polyisocyanate ratio of about 1:3 by volume).

[0039] The polyurethane foam formulation according to the invention for the production of viscoelastic PUR molded foams further includes a second polyether polyol (b) which is different from the polyol of the novolac type.

[0040] The second polyether polyol may be derived from Cashew Nut Shell Liquid.

[0041] The second polyether polyol may contain a high molecular weight polyol with a molecular weight of 2000 to 10,000 or at least 3000 or at least 4000 or up to 7000 or up to 6000.

[0042] The second polyether polyol can be selected from a polyether triol based on glycerol and propylene oxide, a polyether triol, and mixtures thereof.

[0043] The polyol component may also include a low molecular weight polyether polyol with a MW of less than 2000, less than 1000, or less than 500.

[0044] The polyether polyols b) and c) used according to the invention are preferably produced by polymerization of epoxides such as ethylene oxide, propylene oxide, butylene oxide, tetrahydrofuran, styrene oxide or epichlorohydrin with themselves or by addition of these epoxides, optionally in mixture or successively, to starting components with reactive hydrogen atoms such as water, alcohols, ammonia or amines.

[0045] Particularly preferred among the epoxides mentioned above are ethylene oxide and propylene oxide. Most preferred are the polyether polyols used, which consist solely of propylene oxide as the epoxide component.

[0046] If several epoxides are used to synthesize the polyether polyols, the latter can exhibit any desired arrangement of the oxyalkylene units. Thus, they can be homopolymers (when using only one epoxide), copolymers (c), "random" copolymers, "capped" polymers, or polymers that are "tipped" with a mixture of different epoxides to achieve a desired primary hydroxyl group content.

[0047] According to the invention, the proportion of component (a) is 5 to 35 wt.%, based on the polyol component.

[0048] Preferably, the proportion of component (b) is 30 to 65 wt.%, based on the polyol component, and independently of this, the proportion of component (c) is 5 to 15 wt.%, based on the polyol component.

[0049] Preferably, the mass fractions of components (a) to (c) (optionally independently of one another) are in the following amounts: (a) 10 to 20 wt.%, (b) 40 to 55 wt.%, and (c) 8 to 13 wt.%. The values ​​in wt.% refer in each case to the total mass of the polyol composition. These weight fractions are preferred insofar as they result in particularly high aging resistance and hydrolysis resistance in the polyurethane foam according to the invention.

[0050] Particularly preferably in accordance with the invention, the formulation comprises catalytically active additives having at least one reactive (hydrogen-acidic) group.

[0051] In the preferred formulation, the stoichiometric ratio of the polyol components to (poly)-isocyanate can be 1:100 to 100:1 or 1:10 to 10:1 or 1:5 to 5:1 or 3:1 to 1:3.

[0052] A monofunctional alcohol, amine, or isocyanate molecule can be used in combination with the diisocyanate to control the final molecular weight.

[0053] The formulation may contain additional additives, as is known in the field.

[0054] Examples include thickeners, organic and inorganic fillers, emulsifiers, surfactants, stabilizers, pigments, dyes, UV light stabilizers, flow modifiers, antioxidants, fibers or other reinforcing materials, antistatic agents, plasticizers, thinners, humectants, antifoaming agents, mold release agents, deaerating additives, thixotropic agents, leveling agents, flame retardants, dispersants, biocides, fungicides, corrosion inhibitors, wetting and dispersing agents, colorants or other visual enhancement additives and the like.

[0055] These additives can be present, for example, in a quantity of 0.1 to 40% by weight of the formulation.

[0056] Examples of adhesion promoters include epoxy-functional silanes, such as those available under the SILQUEST® brand from Momentive Performance Materials Inc., such as Silquest® A-187 (gamma-glycidoxypropyltrimethoxysilane) and Silquest® A-186 (beta-(3,4)-epoxycyclohexyl)ethyltrimethoxysilane).

[0057] Examples of corrosion inhibitors are those that are free of heavy metals, such as calcium phosphate-based inhibitors, available under the trade name HALOX® < 430 JM, from ICL Performance.

[0058] Examples of moisture scavengers include those containing a zeolite, such as VORATRON® < EG 711, a 50% L-powder paste in castor oil available from Dow Chemical Company, and Baylith L-paste. UV light stabilizers and antioxidants can be incorporated into the coating formulation to inhibit oxidation and light degradation. UV light stabilizers, for example, can be used in amounts ranging from 0.05% to approximately 5% by weight, based on the formulation.

[0059] Light stabilizers can be used, for example, in an amount of 0.05 to 5 wt. %, based on the formulation.

[0060] Examples of light stabilizers include those sold under the trade names TINUVIN ®< and CHIMASSORB ®<, available from Ciba (BASF Corporation, Florham Park, NJ).

[0061] Examples of antioxidants include those sold under the trade names IRGANOX® and BHT, available from Ciba (BASF Corporation).

[0062] Wetting and dispersing additives for dispersing pigments, such as inorganic pigments, organic pigments and titanium dioxide, include solutions of a salt of unsaturated polyamine amides and low molecular weight acid polymers, such as ANTI-TERRA® < -U 80, a solution of a low molecular weight unsaturated polycarboxylic acid polymer and a polysiloxane copolymer, such as BYK® < -P 104 and polyether-modified polydimethylsiloxanes, such as BYK® < 307 from Byk Adhesives & Instruments.

[0063] Examples of inert diluents that can be used include aliphatic linear, branched, or cyclic ethers with 4 to 20 carbon atoms and mixed aliphatic-aromatic ethers with 7 to 20 carbon atoms, such as dibenzyl ether, tetrahydrofuran, 1,2-dimethoxyethane, or methoxybenzene; aliphatic linear, branched, or cyclic or mixed aliphatic-aromatic ketones with 4 to 20 carbon atoms, such as butanone, cyclohexanone, methyl isobutyl ketone, or acetophenone; aliphatic linear, branched, or cyclic or mixed aromatic-aliphatic alcohols with 4 to 20 carbon atoms, such as methanol, ethanol, butanol, 2-propanol, isobutanol, isopropanol, benzyl alcohol, methoxypropanol, or furfuryl alcohol; aliphatic linear, branched or cyclic or mixed aromatic-aliphatic esters such as methoxypropyl acetate;Aliphatic linear, branched or cyclic or mixed aromatic-aliphatic hydrocarbons such as toluene, xylene, heptane and mixtures of aliphatic and aromatic hydrocarbons with a boiling range above 100 °C under normal pressure, as well as low-viscosity coumaron-indene resins or xylene-formaldehyde resins.;

[0064] Aliphatic alcohols with a phenyl group, such as benzyl alcohol, 1-phenoxypro-pan-2,3-diol, 3-phenyl-1-propanol, 2-phenoxy-1-ethanol, 1-phenoxy-2-propanol, 2-phenoxy-1-propanol, 2-phenylethanol, 1-phenyl-1-ethanol or 2-phenyl-1-propanol can be used.

[0065] The diluents can be used individually or as a mixture, e.g. from 0.1 to 20 wt.% or up to 10 wt.% or up to 5 wt.% or up to 1 wt.% or formulation.

[0066] Examples of deaerators (and defoamers) include organomodified polysiloxane containing quartz dust, such as TEGO® AIREX 900, available from Evonik Industries.

[0067] Suitable filler materials include those in fibrous, particulate or other form, made from inorganic materials, ceramics, composites, metallic filler, organic polymer, glass, thermoplastics, silica beads and the like.

[0068] Examples of fillers include silicon dioxide fillers such as IMSIL®< A-8, a fiber material available from Unimin Corp., which is produced from an inert, naturally occurring alpha quartz with a unique grape-like morphology, and mica fillers such as CD-3200 available from Mica Georgia Industrial Minerals.

[0069] The filler material may be surface-treated so that it can react with at least one other compound in the mixture.

[0070] Another essential aspect of the invention is the method according to claim 7. It relates to a method for producing soft elastic molded foams with viscoelastic properties, characterized in that one A) a (poly)isocyanate component, B) a polyol formulation as defined above, C) water, D) one or more catalysts, and E) optionally further excipients, fillers, stabilizers, and / or blowing agents elicits a reaction.

[0071] The above polymer reaction can be carried out at a temperature of at least 100 °C, in particular by using MDI or a prepolymer based on MDI with an NCO content of 22 to 33%, preferably in a range of 26 to 30%.

[0072] The process may include mixing the first and second components at a temperature sufficient for the reaction to occur, wherein the first component includes the polyisocyanate and the second component includes the polyol and the polyamine.

[0073] In particular, it is preferred that the MDI index be in a range of 50 to 100, especially 65 to 85.

[0074] The polyisocyanate may include a polymeric methylenediphenyl diisocyanate.

[0075] The polyisocyanate can be in a first component, and the polyol and the polyamine can be a second component.

[0076] The formulation may further contain at least one additive selected from thickeners, organic and inorganic fillers, emulsifiers, surfactants, stabilizers, pigments, dyes, UV light stabilizers, flow modifiers, antioxidants, fibers or other reinforcing materials, antistatic agents, plasticizers, humectants, antifoaming agents, demolding agents, deaerating additives, thixotropic agents, leveling agents, flame retardants, dispersants, biocides, fungicides, corrosion inhibitors, wetting and dispersing agents, dyes or other visibility-enhancing additives and mixtures thereof.

[0077] These additives can be present, for example, in amounts ranging from 0.1 to 40% by weight, based on the formulation.

[0078] Therefore, with the aid of the present invention, a soft elastic foam with viscoelastic properties can be obtained by reaction injection molding, casting process or as a block foam with a formulation as defined above.

[0079] Another embodiment of the present invention consists of using a molded part as defined above for sound insulation, in particular for encapsulating an electric motor of a motor vehicle. Such foams are also used for encapsulating compressors. Example of implementation Engine capsule:

[0080] An acoustically effective motor encapsulation for electric motors, such as those found in Tesla Model S vehicles, is known to exist, consisting of a PUR soft foam and a heavy foil. To achieve the required effectiveness of the spring-mass structure, a high basis weight of the heavy foil is necessary. Primarily due to the comparatively high adjustable loss factor of the hydride formulation used, a significant improvement in acoustic performance is achieved. Simultaneously, the weight of the heavy foil can be reduced, which is an important requirement not only for electric vehicles.

[0081] The formulations according to the invention met the current requirements of automotive manufacturers, particularly with regard to the hydrolysis resistance of an exterior component according to DIN EN ISO 2440, even at a continuous temperature of 100°C and a short-term temperature of 120°C. In deviation from DIN EN ISO 2440, three 15-hour cycles at 120°C were measured.

Claims

1. A polyurethane foam formulation for the production of soft resilient PUR moulded foams having viscoelastic properties comprising : a) a novolac polyol having a hydroxyl functionality of 3, a hydroxyl value in the range of 160 to 240 mgKOH / gb b) a polyether polyol having a hydroxyl functionality of 3, a hydroxyl value in the range of 20 to 40 mgKOH / gc c) a block / copolymer having a hydroxyl value in the range of 25 to 45 mgKOH / g and e) a combination of catalytically active as well as stabilizing additives, characterized in that the proportion of component (a) is 5 to 35% per weight, based on the polyol component.

2. The formulation according to claim 1, characterized in that the proportion of component (b) is 30 to 65% by weight, based on the polyol component.

3. The formulation according to any one of claims 1 to 2, characterized in that the proportion of component (c) is 5 to 15% by weight, based on the polyol component.

4. The formulation according to any one of claims 1 to 3, characterized in that the novolac polyol of component (a) is based on phenol / formaldehyde polymer and is tipped with ethylene oxide and / or propylene oxide.

5. The formulation according to any one of claims 1 to 4, characterized in that the polyether polyol of component (b) and / or component (c) is derived from glycerol.

6. The formulation according to any one of claims 1 to 5, characterized in that the catalytically active additives comprise at least one reactive (hydrogen azide) group.

7. A method for the production of soft-elastic moulded foams having viscoelastic properties, characterized in that A) a (poly)isocyanate component, B) a formulation according to one of the claims from 1 to 56, C) water and D) one or more catalysts and E) optionally further auxiliaries, fillers, stabilizers and / or blowing agents are brought to reaction.

8. Method according to claim 7, characterized in that the MDI or a prepolymer based on MDI with an NCO content of 22 to 33%, preferably in a range of 26 to 30%, is used.

9. Method according to claim 7 or 8, characterized in that the MDI index is in a range from 50 to 100, in particular 65 to 85.

10. A soft elastic foam having viscoelastic properties obtainable by reaction injection moulding, casting method or as a block foam comprising a formulation according to any one of claims 1 to 6.

11. Use of a moulding part according to claim 10 as sound insulation.