High stiffness polyurethane foam composition

Abstract

A foam-forming composition may include (a) at least one isocyanate component; and (b) at least one isocyanate-reactive composition comprising: (i) at least one low molecular weight polyether polyol having an average functionality in the range of from 2 to 8 and a hydroxyl equivalent weight in the range of from 30 Da to 450 Da; (ii) at least one EO-terminated high molecular weight polyether polyol, the at least one EO-terminated high molecular weight polyether polyol having an average functionality in the range of from 2 to 8 and a hydroxyl equivalent weight in the range of from 1500 Da to 10,000 Da; and (iii) optionally, at least one high molecular weight polyether polyol having an average functionality in the range of from 1 to 8 and a hydroxyl equivalent weight in the range of from 800 Da to 10,000 Da wherein (ii) is present at a weight percent (wt%) of the sum of the polyols in the isocyanate reactive composition in the range of from 25 wt% to 75 wt%; (c) a catalyst package comprising at least one latent gelling catalyst; and (d) at least one blowing agent; wherein the foam-forming composition has an isocyanate index of from 60 to 300, and the foam has a molded foam density of from 250 kg / m3 to 750 kg / m3 according to ASTM D1622-20.

Description

Technical Field

[0001] The embodiments relate to foam-forming compositions and methods for producing polyurethane foam articles, and high-density foam articles having high modulus, elongation, and tensile strength. Background Art

[0002] Polyurethane foams are known in the art and are used in a variety of end-use applications, including cushions, support articles, encapsulants / potting compounds, and insulation materials. Polyurethane foams can be formed from a variety of chemical compositions and can utilize physical and / or chemical blowing agents. For example, polyurethane foams are typically formed by the reaction of isocyanates and polyols in the presence of a blowing agent. The performance characteristics of the foam (including hardness, density, flexibility, etc.) vary with the components used in its preparation. High-density polyurethane foams having high modulus, elongation, and tensile strength can be used in many applications, such as electric vehicle battery packs, while maintaining adhesion and thermal insulation applied in low-thickness regions (1 mm - 6 mm). Currently, it has been found that rigid and high-density foams (≥250 kg / m 3 ) cured at low temperatures (25 °C - 45 °C) are very brittle and tend to fracture at low elongation values. Additionally, in most rigid foam formulations, exothermic conditions are required for curing and developing properties, but this is often difficult to achieve in EV applications due to the presence of metal substrates and heat sinks that draw heat away from the foam-forming composition and / or potential damage to lithium-ion batteries at higher temperatures. Summary of the Invention

[0003] In one aspect, the foam-forming composition can comprise (a) at least one isocyanate component; and (b) at least one isocyanate-reactive composition comprising: (i) at least one low molecular weight polyether polyol having an average functionality in the range of 2 to 8 and a hydroxyl equivalent weight in the range of 30 Da to 450 Da; (ii) at least one EO-capped high molecular weight polyether polyol having an average functionality in the range of 2 to 8 and a hydroxyl equivalent weight in the range of 1500 Da to 10,000 Da; and (iii) optionally, at least one high molecular weight polyether polyol having an average functionality in the range of 1 to 8 and a hydroxyl equivalent weight in the range of 800 Da to 10,000 Da, wherein (ii) is present in a weight percentage (wt%) in the range of 25 wt% to 75 wt% of the sum of these polyols in the isocyanate-reactive composition; (c) a catalyst package comprising at least one latent gelling catalyst; and (d) at least one blowing agent; wherein the isocyanate index of the foam-forming composition is 60 to 300, and according to ASTM D1622-20, the foam has 250 kg / m3 to 750 kg / m 3 of molded foam density. Detailed Description

[0004] Embodiments relate to polyurethane foams and compositions having high density and stiffness, particularly at low thicknesses such as from 1 mm to 8 mm. On the other hand, the polyurethane foams are produced by reacting an isocyanate component with an isocyanate-reactive component that is a mixture of high and low molecular weight (MW) polyether polyols, and the catalyst package may have a delayed foam formation and remain a processable liquid at temperatures up to 50 °C to enhance in-mold properties. The high MW polyether polyols may also include at least one high MW polyether polyol capped with ethylene oxide. The polyurethane foams produced from the compositions disclosed herein may form closed-cell foams and may be thermally insulating.

[0005] As used herein, a "high density" foamed polyurethane composition may have a density in the range of from 200 kg / m 3 to 700 kg / m 3 or from 250 kg / m 3 to 700 kg / m 3 .

[0006] Unless otherwise indicated, all molecular weights in this specification are listed as number average molecular weights.

[0007] Polyurethane (PU) foams and methods of making the foams include the combination of reactive chemical components such as an isocyanate component with an isocyanate-reactive component to produce a foam-forming composition. The isocyanate component contains a di- or polyisocyanate that contains reactive isocyanate (N=C=O) functional groups. The isocyanate-reactive component contains two or more functional groups that react with the isocyanate functional groups such as hydroxyl or amine. The foam-forming composition may also contain other additives such as suitable catalysts, surfactants, flame retardants, viscosity modifiers, fillers, and blowing agents that may be added to one or both of the isocyanate and isocyanate-reactive components.

[0008] The isocyanate and isocyanate-reactive components may be combined in various stoichiometric ratios described by an isocyanate index. The isocyanate index is equal to the ratio of isocyanate groups to isocyanate-reactive groups such as OH groups multiplied by 100. The foam-forming PU compositions disclosed herein may have an isocyanate index in the range of 60 to 300, which is used to produce foam articles having a relatively high density while reducing excessive brittleness.

[0009] Increasing amounts of isocyanate are typically used to increase stiffness. However, the foamed PU compositions disclosed herein can exhibit a relative increase in stiffness and flexural modulus at lower relative isocyanate indices. The foamed polyurethane compositions can also exhibit good properties at relatively low thicknesses in the range of 1 mm to 10 mm or 1 mm to 5 mm. The foamed PU compositions can have a torsion (i.e., shear) modulus greater than 150 MPa or greater than 175 MPa, as determined by ASTM D5279-21. In some cases, the foamed PU compositions can have a torsion (i.e., shear) modulus of 150 MPa to 800 MPa. When tested on a microtensile tester according to the ASTM D1708-18 standard, the foamed articles can also exhibit reduced elongation at break values (e.g., equal to or greater than 6% elongation).

[0010] Compared to standard foamed compositions, the foam-forming PU compositions disclosed herein can have a delayed foam rise (stratification) after dispensing (or spraying), which can increase flowability and coverage in mold applications, particularly for molds with large surface areas and / or complex geometries. In some cases, the foam-forming PU compositions can comprise isocyanates and isocyanate-reactive components that remain liquid for 30 seconds or longer after mixing or remain liquid for 60 seconds or longer after mixing at ambient temperature. The ambient temperature can be in the range of 15 °C to 35 °C, where room temperature is typically about 23 °C. In some cases, the isocyanates and isocyanate-reactive components remain liquid for 30 seconds or longer at up to the mold temperature (such as up to 50 °C).

[0011] The foam-forming PU compositions disclosed herein comprise a two-part composition that includes an isocyanate component and an isocyanate-reactive component, as well as various additives such as a blowing agent and a catalyst combination. The isocyanate-reactive component can include a combination of polyether polyols, particularly (1) a low molecular weight (MW) polyether polyol having an average hydroxyl equivalent of 450 Da or less, and (2) a high MW polyether polyol having an average hydroxyl equivalent of 800 Da to 10,000 Da. In some cases, the high MW polyether polyol can be ethylene oxide (EO) capped at a weight percentage (wt%) of 3 wt% to 80 wt% of the polyol.

[0012] The polyether polyols disclosed herein can include products obtained by polymerizing cyclic oxides (e.g., ethylene oxide (“EO”), propylene oxide (“PO”), butylene oxide (“BO”), tetrahydrofuran, or epichlorohydrin) in the presence of a polyol initiator having a functionality in the range of 2 to 8 or 2 to 5. As understood in the art, the initiator compound or combination thereof is typically selected based on the desired functionality of the resulting polyether polyol. The polyether polyol can be formed with one or more polyol initiators, such as neopentyl glycol; 1,2-propanediol; trimethylolpropane; pentaerythritol; sorbitol; sucrose; glycerol; alkane diols, such as 1,6-hexanediol, 1,4-butanediol, 1,3-butanediol, 2,3-butanediol, 1,3-propanediol, 1,2-propanediol, 1,5-pentanediol, 2-methylpropane-1,3-diol, 1,4-cyclohexanediol, 1,3-cyclohexanedimethanol, 1,4-cyclohexanedimethanol, 2,5-hexanediol; ethylene glycol; diethylene glycol; triethylene glycol; 9(1)-hydroxymethyloctadecanol, 1,4-bis(hydroxymethyl)cyclohexane; hydrogenated bisphenol; 9,9(10,10)-bis(hydroxymethyl)octadecanol; 1,2,6-hexanetriol; and combinations thereof.

[0013] The isocyanate-reactive component can include one or more low MW polyether polyols having an average hydroxyl equivalent weight in the range of 30 Da to 400 Da as determined according to ASTM D4274D. In some cases, the low MW polyether polyol can have a number average molecular weight of 450 Da or less, or 200 Da or less. In some cases, the low MW polyether polyol includes propoxylated derivatives of polyol initiators, such as glycerol, sorbitol, butanediol, etc.

[0014] The isocyanate-reactive component can include, by weight percentage (wt%), from 25 wt% to 75 wt% or from 30 wt% to 70 wt% of the low MW polyether polyol.

[0015] In some cases, instead of or in addition to the low MW polyether polyol, the isocyanate-reactive component can include a low MW polyol, such as the polyol initiators disclosed above. In some cases, the isocyanate component can include a low MW polyol that ranges from 1 wt% to 10 wt% or from 1 wt% to 5 wt% of the weight percentage (wt%) of the isocyanate-reactive component.

[0016] The isocyanate-reactive component may include one or more high-MW polyether polyols having an average functionality in the range of 1 to 8 and an average hydroxyl equivalent weight (OHW) of 800 Da to 10,000 Da, 800 Da to 8,500 Da, or 1,000 Da to 8,000 Da. The high-MW polyether polyols can be prepared using the chemicals and polyol initiators as discussed above with respect to polyether polyols. The high-MW polyether polyols can have a functionality of 1 to 8, where the primary hydroxyl content is >60%, >40%, or >20%.

[0017] In addition, the high-MW polyether polyols can be end-capped with oligomers or polymers of ethylene oxide (EO-capped), which alters the elongation properties and toughness when compared to rigid foams of similar density. The EO-capped high-MW polyether polyols can have an ethylene oxide (EO) content of 3 wt% to 80 wt% by weight percentage (wt%). In some cases, the high-MW polyether polyols can include EO-capped high-MW polyether polyols having an EO content in the range of 3 wt% to 80 wt%, an average functionality in the range of 1 to 8, and an average molecular weight in the range of 800 Da to 10,000 Da, where the primary hydroxyls are >40%. In some cases, the range of the EO content can be 3 wt% to 50 wt%. In some cases, the range of the EO content can be 3 wt% to 28 wt%, where the functionality is 1 to 8 and the molecular weight range is 800 Da to 10,000 Da, where the primary hydroxyls are >60%.

[0018] The isocyanate-reactive component can include high-MW polyether polyols, which range from 25 wt% to 75 wt%, 30 wt% to 70 wt%, or 35 wt% to 65 wt% by weight percentage (wt%) of the total sum of all polyols in the isocyanate-reactive component.

[0019] The foam-forming composition can comprise an isocyanate component containing one or more isocyanates, such as polymeric isocyanates, aromatic isocyanates, carbodiimide-modified isocyanates. The isocyanate substances can be monomers, oligomers, prepolymers, etc. The isocyanate component can include, for example, one or more isocyanates and / or polyisocyanate compounds.

[0020] The isocyanate component can include polyisocyanates having a nominal functionality >1.5 or >2.0. In some cases, the isocyanate component can include polyisocyanates having an isocyanate (NCO) content of 10 wt% or more, 20 wt% or more, or 30 wt% or more.

[0021] The isocyanate compound can be an aliphatic polyisocyanate, cycloaliphatic polyisocyanate, araliphatic polyisocyanate, aromatic polyisocyanate, or a combination thereof. Examples of isocyanates include, but are not limited to, polymethylene polyphenyl isocyanate; toluene 2,4- / 2,6-diisocyanate (TDI); methylene diphenyl diisocyanate (MDI, including its isomers); polymeric and prepolymeric MDI; triisocyanatononane (TIN); naphthyl diisocyanate (NDI); 4,4'-diisocyanatodicyclohexyl-methane; 3-isocyanatomethyl-3,3,5-trimethylcyclohexyl isocyanate (isophorone diisocyanate, IPDI); tetramethylene diisocyanate; hexamethylene diisocyanate (HDI); 2-methyl-pentamethylene diisocyanate; 2,2,4-trimethylhexamethylene diisocyanate (THDI); dodecamethylene diisocyanate; 1,4-diisocyanatocyclohexane; 4,4'-diisocyanato-3,3'-dimethyl-dicyclohexylmethane; 4,4'-diisocyanato-2,2-dicyclohexylpropane; 3-isocyanatomethyl-1-methyl-1-isocyanatocyclohexane (MCI); 1,3-diisocyanato-2-methylcyclohexane; and combinations thereof. In addition to the isocyanates mentioned above, partially modified polyisocyanates can be utilized, including uretdione, isocyanurate, carbodiimide, uretonimine, urethane, or biuret structures and combinations thereof.

[0022] The average isocyanate equivalent weight of the isocyanate can be from 80 g / eq to 400 g / eq, such as a lower limit of 80 g / eq, 90 g / eq, or 100 g / eq to an upper limit of 400 g / eq, 390 g / eq, or 380 g / eq.

[0023] The isocyanate component can also include isocyanate prepolymers obtained by reacting an isocyanate-reactive compound with a molar excess of a polyisocyanate compound or polymeric isocyanate compound under conditions that do not result in gelling or curing. These isocyanate prepolymers can have a relatively high average isocyanate equivalent weight of >400 g / eq. The formation of isocyanate prepolymers is known in the art and can include reacting (1) at least one isocyanate compound and (2) at least one polyol compound. Isocyanate prepolymers can be described by an isocyanate index, which is defined as the ratio of isocyanate groups to isocyanate-reactive groups (such as OH groups) multiplied by 100. The isocyanate prepolymers disclosed herein can have an isocyanate index in the range of 60 to 300, 75 to 300, or 100 to 200.

[0024] Examples of commercial isocyanates include, but are not limited to, those sold under the trade name VORANATE, all of which are available from The Dow Chemical CompanyTM , PAPI TM and ISONATE TM (such as VORANATE TM M 220 and PAPI TM 27) polyisocyanates.

[0025] The isocyanate component may include isocyanate compounds having a number-average molecular weight in the range of 150 g / mol to 750 g / mol. In some cases, the number-average molecular weight of the isocyanate compound may be a low value such as 150 g / mol, 200 g / mol, 250 g / mol or 300 g / mol to a high value such as 350 g / mol, 400 g / mol, 450 g / mol, 500 g / mol or 750 g / mol. The number-average molecular weight values reported herein are determined by end-group analysis, gel permeation chromatography and other methods known in the art. The isocyanate compound can be monomeric and / or polymeric, as known in the art.

[0026] The foam-forming composition may comprise an isocyanate component in a weight percentage (wt%) in the range of 30 wt% to 80 wt%, 35 wt% to 75 wt%, 40 wt% to 70 wt%, or 45 wt% to 65 wt%.

[0027] The foam-forming PU composition may comprise one or more blowing agents, including water and aqueous fluids; chemical blowing agents such as hydrocarbons, acids, volatile organic compounds, etc.; and physical blowing agents, including gases such as nitrogen, air, carbon dioxide, etc. During mixing, the blowing agent may be added to the foam-forming composition in a weight percentage (wt%) in the range of 0.05 wt% to 10 wt% or 0.1 wt% to 5 wt%. In some cases, one or more blowing agents may be present in a weight percentage (wt%) less than or equal to 0.45 wt% or less than or equal to 0.4 wt% of the total polyols in the isocyanate-reactive composition. The blowing agent may be added to the isocyanate component and / or the isocyanate-reactive component in an amount sufficient to provide a mixture having the corresponding weight percentage described above.

[0028] The foam-forming PU composition may comprise a catalyst package containing one or more catalysts, which may include one or more of a blowing catalyst, a gelling catalyst, and a trimerization catalyst. The catalyst package may be present in the isocyanate-reactive composition. As used herein, the blowing catalyst and the gelling catalyst may be distinguished by their tendency to favor the urea (blowing) reaction in the case of the blowing catalyst or the urethane (gelling) reaction in the case of the gelling catalyst. The trimerization catalyst may be used to promote the isocyanate-forming reaction in the composition. The catalyst package may also be added as a separate stream to the reaction mixture of the isocyanate and the isocyanate-reactive composition. The catalyst package may be present in the foam-forming composition in a weight percentage (wt%) ranging from 0.1 wt% to 5 wt%, or 1 wt% to 5 wt%.

[0029] The blowing catalyst may include bis-(2-dimethylaminoethyl) ether, pentamethyldiethylenetriamine, triethylamine, tributylamine, N,N-dimethylaminopropylamine, dimethylethanolamine, N,N,N',N'-tetramethylethylenediamine, and combinations thereof, etc. Examples of commercially available blowing catalysts are those available from Evonik 5, and other commercially available blowing catalysts.

[0030] The gelling catalyst includes organometallic compounds, cyclic tertiary amines, and / or long-chain amines (e.g., containing several nitrogen atoms) and combinations thereof. Organometallic compounds include organotin compounds, such as tin(II) salts of organic carboxylic acids, e.g., tin(II) diacetate, tin(II) dioctanoate, tin(II) diethylhexanoate, and tin(II) dilaurate, and dialkyltin(IV) salts of organic carboxylic acids, e.g., dibutyltin diacetate, dibutyltin dilaurate, dibutyltin maleate, and dioctyltin diacetate. Bismuth salts of organic carboxylic acids can also be used as gelling catalysts, e.g., bismuth octanoate. Cyclic tertiary amines and / or long-chain amines include dimethylbenzylamine, triethylenediamine, and combinations thereof. Examples of commercially available gelling catalysts are those from Evonik 8, 33-LV, and T-12, and other commercially available gelling catalysts.

[0031] The trimerization catalyst can include any such catalysts known in the art. Examples of trimerization catalysts include N,N',N”-tris(3-dimethylaminopropyl)hexahydro-S-triazine; N,N-dimethylcyclohexylamine; 1,3,5-tris(N,N-dimethylaminopropyl)-s-hexahydrotriazine; [2,4,6-tris(dimethylaminomethyl)phenol]; potassium acetate, potassium octanoate; tetraalkylammonium hydroxides such as tetramethylammonium hydroxide; alkali metal hydroxides such as sodium hydroxide; alkali metal alkoxides such as sodium methoxide and potassium isopropoxide; and alkali metal salts of long-chain fatty acids having 10 to 20 carbon atoms, and combinations thereof, and so on. Some commercially available trimerization catalysts include, for example, each from Evonik Corporation of TMR-2, TMR-20, TMR-30, TMR-7, K 2097; K15, 41 and 46, and other commercially available trimerization catalysts.

[0032] The catalyst package can include a "latent catalyst" or "delay catalyst", which is defined as a catalyst compound having low catalytic activity or being relatively inactive at ambient temperature, and which becomes more catalytically active upon heating, for example, by dissociation, decomplexation, ring-opening, ionization, or tautomerization, to effect catalysis of at least one of the chemical reactions involved in the preparation of PU foams. The ambient temperature can be in the range of 15 °C to 32 °C, where room temperature is typically about 23 °C.

[0033] In terms of its function in the foaming process, the latent / delay-acting catalyst can be a gelling, foaming, and / or trimerization type of catalyst. Latent catalysts are generally a subgroup of tertiary amine gelling catalysts, which include the acid salts, phenol salts, or complexes of tertiary amine catalysts, where the acid or phenol is typically a carboxylic acid or phenolic substance, but not limited to, such as formic acid, acetic acid, propionic acid, 2-ethylhexanoic acid, phenoxyacetic acid, gluconic acid, tartaric acid, citric acid, phenol, nonylphenol, diisopropylphenol, etc.; and esters of mixtures thereof. Some available commercially available latent catalysts include, for example TMR-30, SA2LE, SA-1 / 10, 8154, NIAX TM A-107, NIAX TM C-31, NIAX TM C-225, JEFFCAT TM ZF-54, JEFFCAT TMLED-204; and mixtures thereof.

[0034] The catalyst package may include a mixture of one or more of the above catalysts and / or latent catalysts, and the range of its weight percentage (wt%) in the foam-forming composition is 0.1 wt% to 5 wt%. In some cases, the catalyst package may be added to the isocyanate component and / or the isocyanate-reactive component in an amount sufficient to provide a mixture having the corresponding weight percentage as described above.

[0035] The foam-forming composition may contain one or more fillers, including glass fiber, fiber, silica, CaCO3, kaolin, talc, alumina, aluminum trihydroxide (ATH), etc. One or more fillers may be added to the isocyanate component and / or the isocyanate-reactive component in a weight percentage (wt%) ranging from 0 wt% to 15 wt% or 1 wt% to 10 wt% of the foam-forming composition. In some cases, the filler may be added to the isocyanate component and / or the isocyanate-reactive component in an amount sufficient to provide a mixture having the corresponding weight percentage as described above.

[0036] The foam-forming composition may include a surfactant, which is present in the isocyanate and / or the isocyanate-reactive component in an amount of surfactant sufficient to provide 0.1 wt% to 5 wt% of the foam-forming mixture. The surfactant may include silicone-based surfactants, polyether-modified silicone surfactants, and organic-based surfactants. Some representative surfactants include polyorganosiloxane polyoxyalkylene block copolymers, such as those disclosed in U.S. Patent Nos. 2,834,748, 2,917,480, and 2,846,458; organic surfactants containing polyoxyethylene-polyoxypropylene block copolymers, as described in U.S. Patent No. 5,600,019, etc. Other surfactants include polyethylene glycol ethers of long-chain alcohols, tertiary amines or alkanolamine salts of long-chain allyl sulfates, alkyl sulfonates, alkyl aryl sulfonic acids, and combinations thereof. Some commercially available surfactants that can be used in the isocyanate-reactive composition include VORASURF TM DC 193, VORASURF TM 504, B8418 and mixtures thereof.

[0037] The composition may also contain one or more functional additives, such as chain extenders, expandable graphite, additional physical or chemical blowing agents, flame retardants, thixotropic agents (such as poloxamer), viscosity modifiers, cell-opening agents, emulsifiers, adhesion modifiers, antioxidants, surfactants, colorants, UV stabilizers, antistatic agents, antibacterial agents, and mixtures thereof.

[0038] The foam-forming compositions, foamed polyurethane articles, and methods of the present disclosure can be used in a variety of end applications, such as space-filling applications, automotive applications (e.g., for control modules), and the like. The foamed polyurethane articles can be used to at least partially cover or encapsulate articles, such as batteries and other electronic components. The foamed polyurethane articles can also be used for thermal insulation. In addition, the foamed polyurethane articles can be used as fire blocks. Generally, the foamed polyurethane articles of the present disclosure provide a combination of desired physical properties relative to conventional foams, including one or more of the following: reduced weight, decreased density, increased heat resistance, increased stability, and the like. The foamed polyurethane articles can be formed in an environment where hydrogen formation is a concern. Additionally, the foamed polyurethane articles can be foamed at room temperature or about room temperature, which is suitable for temperature-sensitive applications.

[0039] Foam production can include the following steps: (1) balancing the isocyanate component and the isocyanate-reactive composition for mixing; (2) preheating the mold surface to a molding temperature (generally, for example, between 25°C and 60°C), wherein optionally woven and non-woven glass or carbon fibers (e.g., fiber mats, grids, or preforms) are placed in the mold; (4) determining the loading amount of the foam-forming reaction mixture to achieve a desired overfill rate (generally, for example, 150% to 400%); (5) thoroughly and rapidly mixing the isocyanate component and the isocyanate-reactive composition within 10 seconds; (6) starting a timer at the beginning of mixing step (5); (7) immediately transferring the foam-forming reaction mixture to the mold or directly injecting the foam-forming reaction mixture into the mold; (8) closing the mold (if it is not a closed mold), and allowing the resulting foam-forming reaction mixture to react to form a PU foam article in the mold (i.e., the molded foam article); (9) opening the mold after reaching a preset demolding time; (10) demolding the foam article; and (11) after completely demolding the foam article, inspecting the foam article for defects, such as swelling, shrinkage, bulging, and cracking (if any), by visual observation.

[0040] The method for preparing the PU foam article can be achieved by any known method technology in the art. Generally, the PU foam articles of the present disclosure can be produced by continuous or discontinuous methods, including methods commonly referred to as reaction injection molding (RIM) methods or casting molding methods, wherein the foaming reaction and subsequent curing are carried out in a mold.

[0041] Mixing of the components of the foam-forming composition can be carried out at a temperature of 5°C to 80°C, 10°C to 60°C, or 15°C to 50°C. Molding of the PU foam article can be carried out within a mold temperature range of 20°C to 80°C, 30°C to 70°C, or 40°C to 60°C.

[0042] Example

[0043] The following examples are provided to illustrate embodiments of the present invention and are not intended to limit the scope of the present invention. Unless otherwise specified, all parts and percentages are by weight.

[0044]

[0045] Procedure for analyzing foaming and molding

[0046] The isocyanate-reactive component reagents were weighed on an analytical balance and combined using a DAC 600.1FVZ-K high-speed mixer. The batch was used within two hours after mixing. The water content was measured according to ASTM E203-16, and an appropriate amount of water was added to the blend to achieve the desired target. Then the isocyanate component was added to the isocyanate-reactive components at the selected ratio (isocyanate index), and the mass of the mixture was recorded. Then samples of the foam-forming composition were analyzed as a liquid mixture or poured into a mold. Samples were also prepared by mixing using a high-pressure spray system. The isocyanate and isocyanate-reactive components were combined by high-pressure spraying at 1000 psi - 3000 psi in a GRACO sprayer.

[0047] After mixing, the foam-forming composition was sprayed (for the examples of the present invention) and / or poured (examples and comparative examples of the present invention) into a container (such as an open cup or mold), and the reaction kinetics were analyzed. The samples were allowed to react, and the cream time, rise time, and green strength were recorded. Timing started when the two components were mixed. The cream time was defined as the time between the start of mixing and the rise of the liquid level (the start of the foam rising). The rise time was defined as the time between the start of mixing and the time when the foam rose smoothly to a certain height (including the cream time). The gel time was defined as the time between the start of mixing and the point at which the material formed a continuous string when probed. The tack-free time was defined as the time between the start of mixing and the time when no strings detached from the surface when pasted with a tongue depressor stick (including the cream and rise times). The handling time was defined as the time between the start of mixing and the time when the foam had sufficient rigidity not to be compressed when pushed with a finger (with a considerable amount of force).

[0048] The mold tests included parallel and vertical molds. For the parallel rise test in mold A (19 cm × 12.5 cm × 0.2 cm, where 19 cm was the rise direction), the mold was preheated in an oven at 40 °C, and the mixed resin sample was transferred to the mold while timing for approximately 32 seconds - 34 seconds. Then the mold was placed in an oven at 40 °C for 20 minutes. Then the contained mixed resin sample was measured, and the amount of material remaining in the cup after pouring was calculated.

[0049] Then the sample is demolded and the dimensions, weight of the foam are recorded, and the density is calculated. If the sample foam breaks or shatters or fractures during demolding, it is considered too brittle to be further tested. A "testable" foam does not break during demolding or during cutting the sample shape for property testing. The remaining testable foam samples are left overnight to cure, and then samples are cut out for property testing.

[0050] For the vertical rise test in mold B (20 cm × 15 cm × 0.5 cm, where 0.5 cm is the upward direction), the mold is preheated in an oven at 40 °C, and the mixed resin sample is transferred to the mold while timing about 32 seconds - 34 seconds. Then the mold is placed in an oven at 40 °C for 20 minutes. Then the contained mixed resin sample is measured, and the amount of material remaining in the cup after pouring is calculated.

[0051] Then the sample is demolded and the dimensions, weight of the foam are recorded, and the density is calculated. After demolding (10 minutes - 12 minutes), the hardness of the foam sample surface is measured with a durometer (Shore A scale), and then after 30 minutes, it is measured with a durometer (Shore D scale). If the sample foam breaks or shatters or fractures during demolding, it is considered too brittle to be further tested. A "testable" foam does not break during demolding or during cutting the sample shape for property testing. The remaining testable foam samples are left overnight to cure, and then samples are cut out for property testing.

[0052] A series of properties (I - XI) of the samples were tested as follows:

[0053] The property of sample (I) is a qualitative description of the brittleness of the sample based on whether it can be demolded after foaming for further testing of its mechanical properties.

[0054] Density (II) is a quantitative measurement of the density of the foam sample (i.e., weight / volume), conducted according to ASTM D3574 Test A.

[0055] The elastic modulus, E' (III), elongation at break (IV), and ultimate tensile strength (V) were all obtained on a micro - tensile testing machine using ASTM D1708 - 18 standard, where a PU foam sheet with a thickness of 0.2 mm was obtained after molding, aged at room temperature (23 °C) for 2 days, and stamped into a dog - bone shape.

[0056] On an Advanced Rheometric Expansion System (ARES-G2) from TA Instruments equipped with liquid nitrogen environmental control and a torsion rectangular fixture, the shear modulus (VI to VIII) and glass transition temperature (IX) in torsion mode were obtained by dynamic mechanical analysis (DMA) using ASTM D5279-21. A 2-mm thick rectangular sample of the foam prepared in metal molds (A and B) was punched (45 mm long and 12.8 mm wide). The sample length was axially aligned to the torsion axis, and the DMA was performed in torsion mode. The temperature was increased from -70 °C to 200 °C at a ramp rate of 3 °C / min. The test frequency was 1 Hz at 0.05% torsional strain, where an axial tension of 0.098 N was applied to keep the sample taut, and the data collection interval was 30 s / point. The main outputs from the identified characterization were the storage modulus, loss modulus (G”), and Tanδ in terms of shear modulus (G’).

[0057] The cream time (X) is a quantification of the foam generation time (processing time) measured after combining the isocyanate and isocyanate-reactive components by high-pressure mixing and dispensing into a cup (cream) or mold B. For the cream time, the time of foam bubble generation and the rise time were visually judged and the time was recorded. The processing time was defined as the time between the start of mixing and the foam developing sufficient rigidity to resist compression by a tongue depressor. The hardness was measured after demolding, and the processing time was recorded as Shore D > 20.

[0058] The lap shear bond strength test (XI) was determined according to ASTM D-1002-10 to quantify the apparent shear strength of a single lap joint bonding metal specimens by a tensile load. A 1-mm thick polypropylene spacer was placed between the metal substrates, with an overlap of 0.5 inches. 1-inch wide panels were assembled with removable tape at the bottom. The resin was filled into the cavity from the top, percolated by gravity, and sealed. Then the specimens were placed in an oven at 40 °C for 3 hours to cure. The foam density between the plates was determined by gravimetry. The substrates included commercially sourced E-coated cold-rolled steel (1 inch × 4 inches × 0.032 inches), i.e., ACT panels. Failures during the lap shear test were classified as adhesive failure (foam remaining only on one side of the substrate due to adhesive failure), cohesive failure (foam remaining on both sides of the substrate due to foam failure), or substrate failure (e-coating peeling off the foam or substrate fracture).

[0059] The viscosity measurement of the isocyanate-reactive component was performed on a TA Instruments AR 2000 rheometer with a 54-mm cone-plate geometry and a 450-μm gap. At a temperature of 25 °C at 100 seconds -1 to 0.01 second -1Collect data by shear rate scanning. For the isocyanate component and the individual polyol components, measure the viscosity at 25 °C using ASTM D4889.

[0060] Determine the hydroxyl number (OH#) of each polyether polyol in the formulation according to ASTM D4274, and the OH# is used to determine the hydroxyl equivalent.

[0061] Determine the water content using volumetric Karl Fischer titration according to ASTM E203-16, the standard test method for water.

[0062] Example 1: Preparation and characterization of PU foam

[0063] In this example, prepare comparative (C) and inventive (I) samples of water-blown foam as shown in Tables 2 to 7.

[0064]

[0065]

[0066]

[0067]

[0068]

[0069]

[0070]

[0071]

[0072]

[0073]

[0074] The properties of comparative samples C1 to C8 and inventive samples I1 to I13 are shown in Tables 8 - 13. Property I (nature of the foam) indicates whether the formulation foams or breaks / crumbles during the process of preparing the samples for testing Properties III - IX.

[0075]

[0076]

[0077]

[0078]

[0079]

[0080]

[0081]

[0082]

[0083] The results show that the comparative examples are brittle relative to the comparative examples. For example, the comparative samples C1 - C3 break or do not foam (Characteristic I), while C5 exhibits an elongation at break lower than the required value (i.e., Characteristic IV < 6%). In other cases, the comparative samples C4 and C7 - 8 have a tensile strength at break lower than the required value (Characteristic V < 10 MPa). Finally, for C6, the mechanical properties are satisfactory except that the density is higher than the required density (Characteristic II > 700 kg / m 3 )

[0084] In contrast, the inventive samples I1 - I13 containing a polyether polyol with an average hydroxyl equivalent weight ≥ 800 Da at a concentration of ≥ 25 wt% in the isocyanate - reactive component exhibit an elongation at break value (Characteristic IV) of ≥ 6%. For all inventive samples, the tensile strength at break (Characteristic V) remains above 10 MPa. The foam density (Characteristic II) of the inventive samples remains between 400 kg / m 3 - 700 kg / m 3 For I2, the adhesiveness (Characteristic XI) of the foam using the lap - shear adhesiveness test is 8 MPa.

[0085] In addition, for the inventive samples I1 - I13, incorporation of an ethylene oxide (EO) - capped polyether polyol with OHW > 1900 Da at an isocyanate index of 115 and a foam density (Characteristic II) in the range of 250 kg / m 3 - 700 kg / m 3 increases the modulus of the foam (Characteristic III). In addition, the elongation at break (Characteristic IV) of the inventive foam samples remains and / or increases. Thus, not only is the stiffness increased, but also the elongation at break and thus the tensile strength at break (Characteristic V) are increased.

[0086] While the foregoing relates to exemplary embodiments, other and additional embodiments can be designed without departing from the basic scope of the invention, and the scope of the invention is determined by the appended claims.

Claims

1. A foam-forming composition, the foam-forming composition comprising: (a) at least one isocyanate component; and (b) at least one isocyanate-reactive composition, the at least one isocyanate-reactive composition comprising: (i) at least one low molecular weight polyether polyol having an average functionality in the range of 2 to 8 and a hydroxyl equivalent weight in the range of 30 Da to 450 Da; (ii) At least one EO-capped high molecular weight polyether polyol, said at least one EO-capped high molecular weight polyether polyol having an average functionality in the range of 2 to 8 and a hydroxyl equivalent weight in the range of 1500 Da to 10,000 Da; and (iii) optionally, at least one high molecular weight polyether polyol having an average functionality in the range of 1 to 8 and a hydroxyl equivalent weight in the range of 800 Da to 10,000 Da, wherein (ii) is present in a weight percentage (wt%) in the range of 25 wt% to 75 wt% based on the total of the polyols in the isocyanate-reactive composition; (c) a catalyst package comprising at least one latent gelling catalyst; and (d) at least one blowing agent; wherein the isocyanate index of the foam-forming composition is from 60 to 300, and according to ASTM D1622-20, the foam has a molded foam density of 250 kg / m 3 to 750 kg / m 3 3.

2. The composition according to claim 1, wherein the at least one low molecular weight polyether polyol is present in an amount of 25 wt% to 75 wt% based on the total weight of the isocyanate-reactive components.

3. The composition according to claim 1, wherein the at least one blowing agent is water.

4. The composition according to claim 3, wherein the at least one blowing agent is present in an amount less than or equal to 0.45 wt% based on the total of the polyols in the isocyanate-reactive composition.

5. The composition according to claim 1, wherein the at least one EO-capped high molecular weight polyether polyol comprises 3 wt% to 80 wt% ethylene oxide.

6. The composition according to claim 1, wherein the polyols (b)(ii) and (b)(iii) are present in a total weight percentage in the range of 25 wt% to 75 wt% of the isocyanate-reactive components.

7. The composition according to claim 1, wherein the catalyst package comprises a blocked tertiary amine.

8. The composition according to claim 1, wherein the foam-forming composition comprises isocyanate in a weight percentage (wt%) in the range of 30 wt% to 80 wt% of the total composition.

9. A foamed article prepared from the composition according to claim 1.

10. The foamed article according to claim 9, wherein the elongation at break according to ASTM D1708-18 is greater than 6%.

11. A method for manufacturing a rigid polyurethane molded foam, the method comprising: Provided is a foam-forming composition according to any one of claims 1 to 8; and reacting the foam-forming composition to produce a foamed article.

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