Flexible and semi-rigid polyimide-containing foams having excellent heat resistance

Abstract

The present invention relates to a reactive mixture and a process for forming isocyanate-based flexible and semi-rigid polyimide-containing foams, which foams combine high temperature resistance with good acoustic properties.

Description

Technical Field

[0001] The present invention relates to a process for forming a flexible / semi-rigid polyimide (PI)-containing foam made from a polyisocyanate, an acid anhydride, and a polyamine, which has superior temperature resistance compared to conventional flexible / semi-rigid polyurethane (PU)-containing foams made from polyisocyanates and polyols.

[0002] The present invention further relates to a reactive mixture for making a flexible / semi-rigid polyimide-containing foam according to the present invention.

[0003] The flexible / semi-rigid polyimide-containing foam according to the present invention mainly has open cells and low air flow resistance, and thus is ideal for sound insulation or sound absorption.

[0004] Furthermore, the present invention relates to the use of a flexible / semi-rigid polyimide-containing foam according to the present invention for sound absorption and / or sound insulation, and more particularly for such purposes in automotive applications.

Background Art

[0005] Conventional flexible / semi-rigid polyurethane foams have limited temperature resistance, and thus their available application ranges are greatly restricted and excluded from, for example, special / high-performance market segments. Such foams are typically not suitable for long-term exposure to temperatures exceeding 150 - 200 °C, which causes significant deterioration and degradation of their properties (such as mechanical properties).

[0006] Further advantages of high temperature-resistant foams include a reduced risk of scorch during manufacturing and improved combustion properties.

[0007] There are already numerous solutions for improving the form temperature resistance, but none of them are always practical depending on the intended use and form characteristics, and / or are too expensive to implement in highly cost - competitive industries such as the automotive industry.

[0008] One of the prior - art solutions involves significant modification of the reactive mixture used in the creation of flexible polyurethane foam, for example, incorporating more thermally stable raw materials such as replacing polyether polyol with polyester polyol. Still, the improvement in form temperature resistance is somewhat limited.

[0009] Another possibility is the use of isocyanate - based resins containing polycarboxylic acids or polyanhydrides that result in imide bonds. Such resins are known to be useful in the preparation of foam resins for insulation applications and for lightweight flame - retardant structural foams used in automobiles, aircraft, packaging, etc. Such resins can be prepared by the reaction of polyisocyanates with polycarboxylic acids or polyanhydrides. See, for example, Patent Document 1, Patent Document 2, Patent Document 3, and Patent Document 4.

[0010] Patent Document 5 discloses aromatic acid dianhydride - containing isocyanate - based resins that result in polyimide foams made by reaction with polyisocyanates. The claims and examples are limited to the use of acid dianhydrides to obtain stable foams. However, acid dianhydrides are very expensive and are only available in niche industries such as aerospace use.

[0011] To solve the above problems, it is required to create a cost - effective high - temperature - resistant flexible / semi - rigid foam. A specific example is its use in automotive engine compartment sound insulation.

[0012] Therefore, a low - density (100 kg / m3 There is a need to produce a flexible or semi-rigid form that is less than

Prior Art Documents

Patent Documents

[0013]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Patent Document 5

Summary of the Invention

[0014] The ultimate goal appears to be to obtain a flexible or semi-rigid form that is mainly composed of low-density, continuous bubbles, and this form: · Has a mostly continuous bubble structure (with a continuous bubble content of at least 50%), and · The apparent density measured according to ISO 845 is less than 100 kg / m 3 Preferably less than 50 kg / m 3 More preferably less than 20 kg / m 3 And · Has high heat resistance (against exposure to temperatures exceeding 150 - 200 °C), and · Is produced using a highly cost-competitive reactive mixture and foam-forming process.

[0015] Furthermore, the foam according to the present invention must have an appropriate level of air flow and bubble continuity (measured according to ASTM D6226-10 and calculated based on the total volume of the foam, with the continuous bubble content preferably being at least 80% by volume, more preferably at least 90% by volume, even more preferably at least 95% by volume, and most preferably at least 98% by volume), which makes the foam according to the present invention suitable for use in applications where good sound absorption and / or sound insulation are required.

[0016] It was also a further object to use polyisocyanate as a starting material and to improve prior art polyurethane (PU)-containing flexible and semi-rigid foams. This object is achieved by making a polyimide-containing foam in which the conventionally used isocyanate-reactive polyol compound is replaced with an acid anhydride and a polyamine.

[0017] Accordingly, an object of the present invention is to develop a reactive mixture and a method for making a flexible or semi-rigid polyimide-containing foam having the above characteristics.

Embodiments for Carrying Out the Invention

[0018] Definitions and Terms In the context of the present invention, the following terms have the following meanings: 1) The "NCO value" or "isocyanate value", as referred to herein, is the weight percentage of reactive isocyanate (NCO) groups in an isocyanate, modified isocyanate, or isocyanate prepolymer compound. 2) The term "average nominal functionality" (or abbreviated as "functionality") is used herein to indicate the number average of functional groups per molecule in a composition. 3) The term "average", unless otherwise specified, refers to the number average. 4) As used herein, the term "flexible form" in its broad sense refers to a low-density cellular material (apparent density < 100 kg / m 3 ) that enables a certain degree of compression resilience to provide a cushioning effect. Semi-rigid and semi-flexible forms are also part of the present invention. 5) The terms "polyurethane" and "urethane-containing material" as used and referred to herein are not limited to polymers having only urethane or polyurethane bonds. It is natural for those skilled in the art of polyurethane production that polyurethane polymers have, in addition to urethane bonds, allophanate bonds, carbodiimide bonds, urethidine dione bonds, isocyanurate bonds, and other bonds. 6) The terms "polyimide-containing material" and "polyimide-containing form" as used herein are not limited to polymers having only (poly)imide bonds. In the present invention, for the purpose of creating a stable polyimide-containing form as the final material, it is necessary to use polyamines and water as starting materials in addition to polyisocyanates and acid anhydrides, and optionally, a small amount of other chemical substances such as polyols, etc. are used in combination. It is natural for those skilled in the art of polymer production that the following bonds may also be present in small amounts: amide bonds, allophanate bonds, carbodiimide bonds, urethidine dione bonds, urethane bonds, isocyanurate bonds, and other bonds. However, the flexible and semi-rigid polyimide-containing forms according to the present invention are polyimide-containing forms having a significant amount of imide bonds. Typically, at least 20%, preferably 30%, more preferably 40% of the isocyanate groups initially present in the reactive mixture are converted to imide bonds in the final form product according to the present invention. 7) The expressions "reaction system", "reactive form formulation", and "reactive mixture" as used herein refer to the combination of reactive compounds used to create the polyimide-containing form of the present invention, in which case the polyisocyanate compound is usually maintained in one or more containers separately from the remainder of the formulation components (e.g., anhydrides, polyamines, surfactants, solvents, etc.). 8) Unless otherwise specified, the “weight percentage” (%wt or wt%) of a component in a composition refers to the weight of that component in the total weight of the composition in which the component is present, and is expressed as a percentage. 9) Unless otherwise specified, “parts by weight” of a component in a composition refers to the weight of the component used and is represented by “pbw”. 10) The “density” of a foam, when measured with a foam sample, refers to the apparent density by cutting the foam into a parallelepiped, measuring its weight, and measuring its dimensions. The apparent density is the weight-to-volume ratio when measured in accordance with ISO 845 and is expressed in kg / m 3 as. 11) The term “open-cell foam” refers to a foam having bubbles that are not completely enclosed by a cell wall membrane and are open to the foam surface either directly or by interconnecting with other bubbles so that liquid and air can move easily through the foam. As used herein, the term open-cell foam is measured in accordance with ASTM D6226-10 (continuous cell content by pycnometer) and calculated with respect to the total volume of the foam, and refers to a foam having a continuous cell content of at least 50% by volume, for example, 60 - 99.9% by volume or 75 - 99.5% by volume. 12) A “physical blowing agent” herein refers to a volatile compound (low-boiling inert liquid) such as a permanent gas like CO2, N2, and air, and a volatile compound that expands the polymer by volatilization during polymer formation but is not formed by any chemical reaction during foam formation. Examples of suitable volatile compounds include, but are not limited to, chlorofluorocarbons (CFCs), hydrofluorocarbons (HFCs), hydrochlorofluorocarbons (HCFCs), hydrofluoroolefins (HFOs), hydrochlorofluoroolefins (HCFOs), and hydrocarbons such as pentane, isopentane, and cyclopentane. The foam / foam creation process is irreversible and endothermic, i.e., it requires heat (e.g., from the exotherm of a chemical reaction) to volatilize the (low-boiling) liquid blowing agent. 13) "Chemical blowing agent" includes compounds that decompose under process conditions and expand the polymer with the gas generated as a by-product. Examples include water (which forms CO2 by reaction with isocyanate), or isocyanate further in the presence of a suitable catalyst (such as a carbodiimide catalyst, where CO2 is released by carbodiimide formation). 14) "Sound absorption" or "sound insulation" is measured in this specification according to ASTM E1050-98. 15) "Exothermic reaction" in this specification refers to the temperature that occurs during polymer formation, more specifically, the highest temperature achieved during the foam-forming step of the process for making a polyimide-containing polymer, and thus starts from the reactive (liquid) mixture according to the present invention.

[0019] Detailed Description The present invention discloses a low-density (<100 kg / m 3 ) flexible and semi-rigid polyimide-containing foam that mostly has a closed-cell structure (measured according to ASTM D6226-10 and calculated based on the total volume of the foam, with a closed-cell content of at least 50% by volume, preferably at least 80% by volume, more preferably at least 90% by volume, even more preferably at least 95% by volume, and most preferably at least 98% by volume), has high temperature resistance, and more specifically, has high temperature resistance to long-term exposure to temperatures exceeding 150 - 200 °C.

[0020] Therefore, the present invention discloses a reactive mixture for making a low-density flexible and semi-rigid polyimide-containing foam that has a closed-cell structure, has a closed-cell content of at least 50% by volume as measured according to ASTM D6226-10, and has an apparent density of less than 100 kg / m 3 The reactive mixture includes the following components to form the reactive mixture: a) a polyisocyanate composition, which includes at least one polyisocyanate compound, and b) at least one acid anhydride compound, and c) at least one aprotic polar solvent, which has a boiling point above 100 °C at atmospheric pressure, and d) at least one polyamine compound, and e) a blowing agent composition, which contains at least 50 mol% of water, calculated based on the total molar amount of the blowing agent composition, and optionally contains a physical blowing agent and / or a non-reactive chemical blowing agent having no isocyanate-reactive groups, and f) optionally, a catalyst composition, which contains at least one catalyst compound selected from urethane-forming catalyst compounds, urea-forming catalyst compounds, imide-forming catalyst compounds, amide-forming catalyst compounds, carbodiimide-forming catalyst compounds, and / or trimer-forming catalyst compounds, and g) optionally, further additives, such as surfactants, flame retardants, extenders, pigments, and / or stabilizers, etc.

[0021] According to an embodiment, the at least one aprotic polar solvent has a boiling point above 140 °C, preferably above 170 °C, more preferably higher than the exothermic heat of reaction of the reactive mixture, at atmospheric pressure.

[0022] According to an embodiment, components b) to g) are first mixed and then reacted with the polyisocyanate composition.

[0023] According to an embodiment, the foam can be created by a free-rise process, a molding process, a slabstock process, a lamination process, or a spray process.

[0024] The components can be independently supplied to the mixing head of a foam-forming machine. Preferably, the acid anhydride compound(s), polyamine(s), water, solvent(s), and optional components are premixed and then mixed with the polyisocyanate composition.

[0025] According to an embodiment, the low-density polyimide-containing foam according to the present invention has a density of < 40 kg / m 3 , preferably < 15 kg / m 3, more preferably in the range of 4 to 10 kg / m 3 is a free-rise flexible / semi-rigid form.

[0026] According to an embodiment, the low-density polyimide-containing foam according to the present invention is a foam sprayed using a spray technique for forming prior art polyurethane foams.

[0027] According to an embodiment, it has an open-cell structure and, when measured according to ASTM D6226-10 and calculated with respect to the total volume of the foam, the open-cell content is at least 50% by volume, preferably at least 80% by volume, more preferably at least 90% by volume, even more preferably at least 95% by volume, and most preferably at least 98% by volume, and when measured according to ISO 845, the apparent density is less than 100 kg / m 3 A method for producing an isocyanate-based flexible or semi-rigid polyimide-containing foam, which is less than, includes the following: i. forming a reactive mixture by mixing a polyisocyanate composition, at least one acid anhydride compound, at least one aprotic polar solvent, at least one polyamine compound, a blowing agent composition, and optionally, a catalyst composition and / or further additives; ii. foaming the reactive mixture to form a polyurea-containing foam ("polyurea pre-foam"); and iii. post-curing the polyurea pre-foam to obtain the final polyimide-containing foam.

[0028] According to an embodiment, the process for producing the low-density flexible and semi-rigid polyimide-containing foam according to the present invention includes at least the following steps: i. a step of mixing the components of the reactive mixture (polyisocyanate, acid anhydride, polyamine, solvent, water, optional additives); and then ii. a step of foaming the reactive mixture obtained in step i to form a polyurea-containing foam ("polyurea pre-foam"); and then iii. A step of post-curing the polyurea preform obtained in step ii to obtain a final polyimide-containing form.

[0029] According to an embodiment, the mixing step i can include a premixing step, in which case a blowing agent composition containing an acid anhydride compound(s), a polyamine, a solvent(s), a catalyst compound(s), and optionally further additives is first mixed and then mixed with a polyisocyanate compound to form a reactive mixture.

[0030] According to an embodiment, the step of mixing the components of the reactive mixture is carried out using a high-pressure mixing system.

[0031] According to an embodiment, the step of mixing the components of the reactive mixture is carried out using a dynamic mixing system.

[0032] According to an embodiment, no external heat is applied to the reactive mixture, and the heat generated by the reaction is sufficient to obtain a low-density foam-forming structure.

[0033] According to an embodiment, the post-curing step iii can be carried out in various ways, such as applying heat (preferably up to several hours in the range of 150 to 300 °C), microwave irradiation, IR irradiation, etc. This step can be carried out before commercialization, but if the foam is exposed to high temperatures during use, it can also be carried out in-situ during the product life of the foam.

[0034] According to an embodiment, the low-density polyimide-containing foam according to the present invention has a closed-cell content of ≧ 50% by volume, preferably at least 80% by volume, more preferably at least 90% by volume, even more preferably at least 95% by volume, and most preferably at least 98% by volume, calculated with respect to the total volume of the foam as measured according to ASTM D6226-10.

[0035] Acid anhydride compound According to the embodiment, the acid anhydride compound(s) is selected from maleic anhydride (I), phthalic anhydride (II), succinic anhydride (III), trimellitic anhydride (IV), and / or itaconic anhydride (V).

[0036]

Chemical formula

[0037]

Chemical formula

[0038]

Chemical formula

[0039]

Chemical formula

[0040]

Chemical formula

[0041] According to the embodiment, the amount of the acid anhydride(s) in the reactive mixture, calculated based on the total weight of the reactive mixture, is in the range of 10 to 60% by weight, preferably in the range of 15 to 50% by weight, more preferably in the range of 20 to 40% by weight, and even more preferably in the range of 20 to 30% by weight.

[0042] According to the embodiment, the acid anhydride(s) can be pre-dissolved in a solvent / diluent before being further mixed with the isocyanate in any case. If the polyamine(s) (primary or secondary, aliphatic or aromatic) can also be dissolved in the solution of this solvent, it can also be added separately (i.e., as a separate component / stream) to the reactive mixture.

[0043] According to an embodiment, the acid anhydride(s) can be present in the reactive mixture in their polymer and / or copolymer form, for example, as a copolymer of maleic anhydride and ethylene, propylene, isobutylene, or styrene (e.g., a copolymer of maleic anhydride and styrene, which is commercially available from Cray Valley as SMA® 1000). The acid anhydride(s) can also be present in the reactive mixture when graft-bonded as pendant groups to a polymer backbone, such as polyethylene or polyisoprene.

[0044] Polyamine compound The presence of polyamine(s) in the reactive mixture is essential to obtain a high-quality (i.e., forming fine bubbles, stable, non-collapsing, defect-free) foam. In other words, the polyamine can be regarded as a process aid, and its presence makes it possible to achieve excellent foam quality.

[0045] According to an embodiment, the polyamine compound(s) is selected from polyamine compounds having an amine functionality of 1 or more and selected from primary or secondary amines.

[0046] Suitable examples of polyamines include DETDA (diethyltoluenediamine), MDA (diphenylmethanediamine in monomeric or polymeric form), polyvinylamine, amine-modified PDMS (or other temperature-resistant polymers), and the like.

[0047] According to an embodiment, the amount of polyamine(s) in the reactive mixture, calculated relative to the total weight of the reactive mixture, is less than 30 wt%, preferably less than 20 wt%, more preferably less than 10 wt%.

[0048] Catalyst composition According to an embodiment, the catalyst compound (when used) is used in a catalytic amount sufficient to form urea and ultimately facilitate the formation of imide bonds in the polymer.

[0049] According to an embodiment, the total amount of the catalyst compound in the reactive composition is in the range of up to 5 wt%, preferably up to 4 wt%, more preferably up to 3 wt% based on the total weight of the reactive mixture. Advantageously, the amount of the catalyst compound is in the range of 0.5 wt% to up to 3 wt%, preferably in the range of 1 wt% to 2.5 wt% based on the total weight of the reactive mixture.

[0050] According to an embodiment, the catalyst composition contains at least a urea-forming catalyst compound in an amount of at least 50 wt%, preferably at least 75 wt%, more preferably at least 90 wt% based on the total weight of all the catalyst compounds in the catalyst composition.

[0051] According to an embodiment, at least one urea-forming catalyst is preferably selected from metal salt catalysts such as organotin, and amine compounds such as triethylenediamine (TEDA), N-methylimidazole, 1,2-dimethylimidazole, N-methylmorpholine, N-ethylmorpholine, triethylamine, N,N'-dimethylpiperazine, 1,3,5-tris(dimethylaminopropyl)hexahydrotriazine, 2,4,6-tris(dimethylaminomethyl)phenol, N-methyldicyclohexylamine, pentamethyldipropylenetriamine, N-methyl-N'-(2-dimethylamino)-ethyl-piperazine, tributylamine, pentamethyldiethylenetriamine, hexamethyltriethylenetetramine, heptamethyltetraethylenepentamine, dimethylaminocyclohexylamine, pentamethyldipropylenetriamine, triethanolamine, dimethylethanolamine, bis(dimethylaminoethyl)ether, tris(3-dimethylamino)propylamine, etc., and any mixture thereof. Suitable commercially available catalysts include Jeffcat® DPA, Jeffcat® ZF10, Jeffcat® Z130, Dabco® NE300, Dabco® NE1091, and Dabco® NE1550.

[0052] Blowing agent composition According to an embodiment, the reactive mixture contains at least water as a blowing agent (in addition to any other possible blowing agents), and the amount of water, calculated based on the total weight of the reactive mixture, is in the range of more than 0 wt% to a maximum of 5 wt%, preferably in the range of 0.5 to 4 wt%, more preferably in the range of 1 to 3.5 wt%, and even more preferably in the range of 1.5 to 3 wt%. According to an embodiment, a physical blowing agent other than water and / or an additional chemical blowing agent is not added to the reactive mixture.

[0053] According to an embodiment, the blowing agent composition can include a physical blowing agent and / or a non-isocyanate reactive chemical blowing agent (in addition to water) to further reduce the density of the foam. Suitable physical blowing agents can be selected from isobutene, methyl formate, dimethyl ether, methylene chloride, acetone, t-butanol, argon, krypton, xenon, chlorofluorocarbon (CFC), hydrofluorocarbon (HFC), hydrochlorofluorocarbon (HCFC), hydrofluoroolefin (HFO), hydrochlorofluoroolefin (HCFO), and hydrocarbons such as pentane, isopentane, and cyclopentane, etc., and mixtures thereof.

[0054] According to a preferred embodiment, the blowing agent composition contains at least 50 mol% water, preferably at least 65 mol% water, more preferably at least 70 mol% water, even more preferably 90 mol% water, and most preferably at least 95 mol% water, calculated based on the total molar amount of all blowing agents in the blowing agent composition.

[0055] According to an embodiment, the amount of water and / or other blowing agents (optionally) added to the reactive mixture can be varied, for example, based on the intended use and application of the foam product and the desired rigidity and density of the foam.

[0056] Solvent According to an embodiment, at least one aprotic polar solvent is present in the reactive mixture, and the solvent has a boiling point above 100°C, preferably above 140°C, more preferably above 170°C, even more preferably higher than the exotherm of the reaction of the reactive mixture, and is in an amount sufficient to at least partially dissolve / solubilize the acid anhydride under atmospheric pressure. Suitable solvents are dimethyl sulfoxide (DMSO), dimethylformamide (DMF), and triethyl phosphate (TEP). The solvent is used in the range of 5 to 40% by weight, preferably in the range of 5 to 30% by weight, more preferably in the range of 7 to 20% by weight, even more preferably in the range of 7 to 15% by weight, calculated based on the total weight of the reactive mixture.

[0057] During the post-curing process of the polyurea preform, the solvent used will be removed together with other unreacted volatile species.

[0058] Polyisocyanate composition According to an embodiment, the polyisocyanate composition is used in the range of 20 to 90% by weight, preferably in the range of 30 to 80% by weight, more preferably in the range of 40 to 70% by weight, even more preferably in the range of 45 to 65% by weight, calculated based on the total weight of the reactive mixture.

[0059] According to an embodiment, the polyisocyanate compound in the reactive mixture is selected from isocyanate compounds having a functionality > 2, such as polymeric MDI compounds or modified MDI compounds, etc., such as uretonimine, biuret, allophanate, isocyanate trimer (polyisocyanurate), etc. Commercially available examples of isocyanate compounds having a functionality > 2 include Suprasec® 5025, Suprasec® 2020, and Suprasec® 2185 manufactured by Huntsman.

[0060] According to an embodiment, polyisocyanate compounds with a high functionality such as polymeric MDI are suitable for improving the foam stability during foam formation and the like.

[0061] According to an embodiment, the polyisocyanate composition can further include a polyisocyanate compound selected from bifunctional isocyanates (diisocyanates), preferably an aliphatic diisocyanate selected from hexamethylene diisocyanate, isophorone diisocyanate, methylene dicyclohexyl diisocyanate, and cyclohexane diisocyanate, and / or an aromatic diisocyanate selected from toluene diisocyanate (TDI), naphthalene diisocyanate, tetramethylxylene diisocyanate, phenylene diisocyanate, toluidine diisocyanate, and in particular diphenylmethane diisocyanate (MDI).

[0062] According to an embodiment, the polyisocyanate compound of the polyisocyanate composition can also be an isocyanate-terminated prepolymer, which is prepared by reacting an excess amount of polyisocyanate with a suitable polyol for the purpose of obtaining a prepolymer having the indicated NCO value. The method for preparing the prepolymer is described in the art. The relative amounts of polyisocyanate and polyol depend on their equivalents and the desired NCO value and can be readily determined by those skilled in the art. The NCO value of the isocyanate-terminated prepolymer is preferably more than 5% by weight, more preferably more than 10%, and most preferably more than 15% by weight.

[0063] Isocyanate-reactive compound having an OH group According to an embodiment, the reactive mixture may further comprise an (optional) isocyanate-reactive compound (polyol) having a hydroxyl functionality in the range of 1 to 8, which isocyanate-reactive compound is selected from polyether polyols, polyester polyols, and / or polyether-polyester polyols. Preferably, the polyol is a high molecular weight polyol having a molecular weight in the range of 500 to 20,000 g / mol, more preferably in the range of 500 g / mol to a maximum of 10,000 g / mol, more preferably in the range of 500 g / mol to a maximum of 5,000 g / mol, and most preferably in the range of 650 g / mol to a maximum of 4,000 g / mol. Suitable high molecular weight polyols have molecular weights of 650 g / mol, 1,000 g / mol, and 2,000 g / mol. Suitable high molecular weight polyols include hydroxyl-terminated reaction products of dihydric alcohols such as ethylene glycol, propylene glycol, diethylene glycol, 1,4-butanediol, neopentyl glycol, 2-methyl-1,3-propanediol, 1,6-hexanediol, or cyclohexanedimethanol, or mixtures of such dihydric alcohols, and dicarboxylic acids or their ester-forming derivatives such as succinic acid, glutaric acid, and adipic acid, or their dimethyl esters, sebacic acid, phthalic anhydride, tetrachlorophthalic anhydride, or dimethyl terephthalate, or mixtures thereof. Polycaprolactone and unsaturated polyester polyols should also be considered. Polyester amides can be obtained by including an amino alcohol such as ethanolamine in the esterification mixture.

[0064] According to an embodiment, the reactive mixture can further comprise an (optional) low molecular weight polyol having a hydroxyl functionality in the range of 1 to 8, the low molecular weight polyol having a molecular weight of <500 g / mol, preferably in the range of 45 to a maximum of 500 g / mol, more preferably in the range of 50 to a maximum of 250 g / mol. Suitable examples include diols such as aliphatic diols, for example, ethylene glycol, 1,3-propanediol, 2-methyl-1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,8-octanediol, 1,9-nonanediol, 1,10-decanediol, 1,12-dodecanediol, 1,2-propanediol, 1,3-butanediol, 2,3-butanediol, 1,3-pentanediol, 2-ethyl-butanediol, 1,2-hexanediol, 1,2-octanediol, 1,2-decanediol, 3-methylpentane-1,5-diol, 2-methyl-2,4-pentanediol, 3-methyl-1,5-pentanediol, 2,5-dimethyl-2,5-hexanediol, 3-chloro-propanediol, 1,4-cyclohexanediol, 2-ethyl-2-butyl-1,3-propanediol, diethylene glycol, dipropylene glycol, and tripropylene glycol, and 1,4'-butylene diol and cyclohexanedimethanol, etc. Further suitable examples include amino alcohols such as ethanolamine, triethanolamine, diethanolamine, N-methyldiethanolamine, etc. Glycerol is an example of a suitable triol.

[0065] In order to obtain the best possible form temperature resistance, the amount of temperature-sensitive chemicals in the reactive mixture must be minimized, so the amount of polyol is preferably avoided or minimized to a concentration of less than 20% by weight, preferably less than 10% by weight, more preferably less than 5% by weight, based on the total weight of the reactive mixture.

[0066] Additive According to an embodiment, conventional components (additives and / or auxiliaries) can be used in the preparation of the polyimide-containing foam according to the invention. Such components include surfactants, flame retardants, extenders, pigments, stabilizers, etc. Suitable surfactants can be selected from silicone surfactants such as commercially available Dabco® DC 193, Tegostab® B8494, Tegostab® B8466, and Tegostab® B8416.

[0067] According to an embodiment, a radical initiator can be added to the reactive mixture for the purpose of accelerating the acid-anhydride compound (radical) polymerization during foam formation and / or post-curing. Examples include dicumyl peroxide, AIBN, or dibenzoyl peroxide.

[0068] According to an embodiment, the reactive mixture may further contain solid polymer particles, such as styrene-based polymer particles and the like. Examples of styrene polymer particles include so-called "SAN" particles of styrene acrylonitrile. An example of a commercially available polymer polyol is HYPERLITE® polyol 1639, which is a polyether polyol modified with styrene acrylonitrile polymer (SAN) and has a solids content of about 41% by weight (also referred to as polymer polyol).

[0069] According to an embodiment, the reactive mixture can include a bulking agent, and examples of the bulking agent include wood chips, wood dust, wood flakes, wood plates; paper and cardboard, both shredded or laminated; sand, vermiculite, clay, cement, and other silicate compounds; ground rubber, ground thermoplastic plastics, ground thermosetting materials; honeycombs made of any material such as cardboard, aluminum, wood, and plastics; metal particles and plates; granular or laminated cork; natural fibers such as flax fibers, hemp fibers, and sisal fibers; synthetic fibers such as polyamide fibers, polyolefin fibers, polyaramid fibers, polyester fibers, and carbon fibers; mineral fibers such as glass fibers and rock wool fibers; inorganic bulking agents such as BaSO4 and CaCO3; nanoparticles such as clay, inorganic oxides, and carbon; glass beads, ground glass, hollow glass beads; expanded or expandable beads; untreated or treated waste such as shredded, chopped, crushed, or broken waste, and especially fly ash; woven and non-woven fabrics; and combinations of two or more of these materials.

[0070] If all reactants can be reacted at once, it is also possible to react them sequentially by first mixing all or part of the components. The various components used in the production of the foam according to the present invention can actually be added in any order. The process can be selected from any of continuous processes including bulk processes, batch processes or cast processes.

[0071] According to an embodiment, the low-density polyimide-containing foam according to the present invention has a mostly closed-cell structure, and when measured according to ASTM D6226-10 and calculated with respect to the total volume of the foam, the closed-cell content is at least 50% by volume, preferably at least 80% by volume, more preferably at least 90% by volume, even more preferably at least 95% by volume, and most preferably at least 98% by volume, and is a low-density foam.

[0072] The polyimide-containing flexible and semi-rigid forms according to the present invention have high temperature resistance, which means that the forms can be used in applications where they are exposed to temperatures above 150°C, preferably above 175°C, more preferably above 200°C, with or without oxidative conditions, without significantly accompanying the deterioration of the properties over time of the relevant applications (e.g., mechanical properties, structural integrity, acoustic properties, etc.).

[0073] The polyimide-containing flexible and semi-rigid forms according to the present invention have high temperature resistance and are therefore ideally suitable as lightweight sound insulation materials in very demanding automotive / transportation and aircraft / aerospace applications, or as sound absorption materials in automotive / transportation and aircraft / aerospace.

Brief Description of the Drawings

[0074]

Figure 1

Figure 2

Examples

[0075] Chemicals used: · Maleic anhydride: acid monoanhydride, manufactured by Huntsman · Diethyltoluenediamine (DETDA): aromatic diamine, manufactured by Lonza (NH2 value: 630 mg KOH / g) · Daltocel® F435: polyether polyol, manufactured by Huntsman (OH value: 35 mg KOH / g) · PPG425: polyether polyol, manufactured by Covestro (OH value: 264 mg KOH / g) · Daltocel® F526: polyether polyol, manufactured by Huntsman (OH value: 140 mg KOH / g) ·Lipoxol® 200: Polyether polyol, manufactured by Sasol (OH value: 561 mg KOH / g) ·DMSO: Dimethyl sulfoxide. Solvent / diluent, manufactured by Acros Organics ·Tegostab® B8017: Silicon surfactant, manufactured by Evonik (OH value: 67 mg KOH / g) ·Dabco® DC193: Silicon surfactant, manufactured by Evonik (OH value: 75 mg KOH / g) ·Kosmos® 29: Tin octylate catalyst, manufactured by Evonik ·Black Repitan® 99430: Carbon black polyether polyol dispersion, manufactured by Repi (OH value: 21 mg KOH / g) ·Phosflex® 71B: Phosphate flame retardant, manufactured by ICL Industrial Products ·Irganox® 5057: Antioxidant, manufactured by BASF ·Irganox® 1135: Antioxidant, manufactured by BASF ·Ortegol® 501: Bubble continuous agent, manufactured by PU Performance Additives (OH value: 2 mg KOH / g) ·Water: Foaming agent (OH value: 6230 mg KOH / g) ·Suprasec® 6057: Polymer MDI, manufactured by Huntsman (NCO value: 31.40%) ·Suprasec® 2085: Polymer MDI, manufactured by Huntsman (NCO value: 30.50%) Test method ·Density: The foam density was measured according to the ISO 845 standard using a sample (4×4×2.5 cm 3 ), and calculated by dividing the mass by the volume. Expressed in kg / m 3 . ·Thermogravimetric analysis (TGA): Under air or nitrogen environment, a heating ramp of 20 °C / min was applied, and a thermogram was recorded using a TA Instruments Q5000 analyzer.

[0076] Example Example 1: A maleic anhydride-based polyimide foam according to the present invention, containing diamine (DETDA) in the reactive mixture

[0077] Example 1: Under free-rise conditions, in a 400 mL cup, using a Heidolph Mixer at high shear (about 3000 rpm), the isocyanate was mixed with the rest of the formulation (maleic anhydride and DETDA were previously dissolved separately in DMSO solvent) for 7 seconds to produce Foam 1 (Table 1). The polyurea preform was stored overnight in a fume hood and post-cured at 200 °C in an oven for 2 hours (to promote imide formation and remove residual trace solvents and any unreacted volatile species) to finally obtain a continuous-cell flexible polyimide-containing foam. This was then cut for subsequent property analysis.

[0078] [Table 1]

[0079] Comparative Example 1: Conventional polyurethane flexible foam Comparative Example 1: Under free-rise conditions, using a Heidolph Mixer at high shear (about 2000 rpm), the isocyanate was mixed with the polyol blend (prepared beforehand) for 10 seconds, followed by mixing with the catalyst blend (prepared beforehand) for 10 seconds, and then the resulting mixture was poured into the remaining reactive foam-forming mixture in a 20×20×20 cm 3 wooden frame. The foam was stored overnight in a fume hood, then cut and analyzed for properties.

[0080] [Table 2]

[0081] Comparative Example 2: A maleic anhydride-based polyimide foam containing no polyamine in the formulation. Example 1 was repeated, but DETDA was not used in the reactive mixture. The resulting foam was of very low quality, being partially crushed, full of internal defects, and having a rather coarse cell structure. No further analysis / characterization was performed.

[0082] The excellent temperature resistance of the polyimide-containing foam of Example 1 compared to the polyurethane foam of Comparative Example 1 was confirmed by TGA analysis (Table 3) both under air (Figure 1) and under nitrogen (Figure 2).

[0083] [Table 3]

Claims

1. The open-cell content, as measured according to ASTM D6226-10, is at least 50% by volume, and the apparent density, as measured according to ISO 845, is 100 kg / m³. 3 A reactive mixture for creating low-density isocyanate-based flexible or semi-rigid polyimide-containing foams having a density of less than the following components: a) A polyisocyanate composition comprising at least one polyisocyanate compound, and b) at least one acid monoanhydride compound, and c) At least one aprotic polar solvent having a boiling point greater than 100°C under atmospheric pressure, and d) Polyamine compounds (multiple may be included) having an amine functional value of 1 or more and being selected from primary amines or secondary amines, and e) A blowing agent composition that contains at least 50 mol% water, calculated relative to the total molar amount of all blowing agents in the blowing agent composition, and optionally contains a physical blowing agent and / or a non-reactive chemical blowing agent that does not have an isocyanate reactive group, and f) A catalyst composition comprising at least one catalyst compound, optionally selected from urethane-forming catalyst compounds, urea-forming catalyst compounds, imide-forming catalyst compounds, amide-forming catalyst compounds, carbodiimide-forming catalyst compounds, and / or trimer-forming catalyst compounds, and g) Optionally, further additives such as surfactants, flame retardants, fillers, pigments, and / or stabilizers, The reactive mixture containing the above.

2. The reactive mixture according to claim 1, wherein the acid monoanhydride compound (or more) is selected from maleic anhydride (I), phthalic anhydride (II), succinic anhydride (III), trimellitic anhydride (IV), and / or itaconic anhydride (V). 【Chemistry 1】 【Chemistry 2】 【Transformation 3】 【Chemistry 4】 【Transformation 5】

3. The reactive mixture according to claim 1 or 2, wherein the acid monoanhydride compound(s) is present in an amount of 10 to 60% by weight, preferably 15 to 50% by weight, more preferably 20 to 40% by weight, and even more preferably 20 to 30% by weight, calculated based on the total weight of the reactive mixture. 。

4. The reactive mixture according to claim 1 or 2, wherein the total amount of catalyst compounds (or more) in the reactive composition is in the range of 0.5% to a maximum of 3% by weight, preferably 1% to 2.5% by weight, based on the total weight of the reactive mixture.

5. The reactive mixture according to claim 1 or 2, wherein the amount of water is calculated relative to the total weight of the reactive mixture and is in the range of more than 0% by weight to a maximum of 5% by weight, preferably in the range of 0.5 to 4% by weight, more preferably in the range of 1 to 3.5% by weight, and even more preferably in the range of 1.5 to 3% by weight.

6. The reactive mixture according to claim 1 or 2, further comprising at least one polyol selected from polyether polyols, polyester polyols, and / or polyether-polyester polyols, having a molecular weight in the range of 500 to 20,000 g / mol, more preferably in the range of 500 g / mol to a maximum of 10,000 g / mol, more preferably in the range of 500 g / mol to a maximum of 5,000 g / mol, and most preferably in the range of 650 g / mol to a maximum of 4,000 g / mol.

7. The foam has an open-cell structure, and the open-cell content, calculated relative to the total volume of the foam as measured according to ASTM D6226-10, is at least 50 vol%, preferably at least 80 vol%, more preferably at least 90 vol%, even more preferably at least 95 vol%, and most preferably at least 98 vol%, and the apparent density, as measured according to ISO 845, is 100 kg / m³. 3 A method for producing an isocyanate-based flexible or semi-rigid polyimide-containing foam that is less than: i. To form the reactive mixture according to claim 1 or 2 by mixing the polyisocyanate composition, the at least one acid monoanhydride compound, the at least one aprotic polar solvent, the at least one polyamine compound, the blowing agent composition, and optionally the catalyst composition and / or the further additives, ii. To foam the reactive mixture and form a polyurea-containing foam ("polyurea preform"), and iii. The polyurea preform is cured to obtain the final polyimide-containing foam, The method, including the method described above.

8. The method according to claim 7, wherein, prior to the forming step i, a premixing step is performed, in which the at least one acid monoanhydride compound, the at least one polyamine compound, the aprotic polar solvent(s), the blowing agent composition, and optionally the catalyst compound(s), and / or further additives are first mixed, and then mixed with the polyisocyanate composition to form the reactive mixture.

9. The method according to claim 7, wherein the post-curing step is carried out by applying microwave irradiation or IR irradiation to apply heat in the range of 150 to 300°C for a maximum of several hours.

10. The density of the polyimide-containing foam is 4 to 40 kg / m³. 3 In the range of 4 to 15 kg / m², more preferably 4 to 15 kg / m². 3 More preferably 4 to 10 kg / m 3 The method according to claim 1 or 2, which is within the range of the present invention.

11. The open-cell content of the polyimide-containing foam is measured according to ASTM D6226-10 and calculated relative to the total volume of the foam, preferably at least 80% by volume, more preferably at least 90% by volume, even more preferably at least 95% by volume, and most preferably at least 95% by volume. The method according to claim 1 or 2, wherein the amount is at least 98% by volume.

12. An isocyanate-based flexible or semi-rigid polyimide-containing foam obtained by the method described in Claim 1 or 2, the following: ・Measured in accordance with ISO 845, the apparent density is less than 100 kg / m 3 , preferably in the range of 4 to 40 kg / m 3 , more preferably in the range of 4 to 15 kg / m 3 , even more preferably in the range of 4 to 10 kg / m 3 , and - Measured according to ASTM D6226-10 and calculated relative to the total volume of the foam, the open-cell content is at least 50 vol%, preferably at least 80 vol%, more preferably at least 90 vol%, even more preferably at least 95 vol%, and most preferably at least 98 vol%. The aforementioned form.

13. Use of the foam according to claim 12 for sound insulation or sound absorption in automotive / transportation and / or aircraft / aerospace applications.

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