CN120303316A - High stiffness polyurethane foam composition - Google Patents

Abstract

The foam-forming composition may 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 30Da to 450Da, (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 1500Da to 10,000Da, 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 800Da to 10,000Da, wherein (ii) is present as a weight percent (wt%) of the sum of the polyols in the isocyanate-reactive composition, (c) the catalyst comprises at least one catalyst having an average functionality in the range of 2 to 8 and a hydroxyl equivalent weight in the range of 1500Da to 10,000Da, and (iii) optionally, the at least one high molecular weight polyether polyol having an average functionality in the range of 800Da to 8 and a hydroxyl equivalent weight in the range of 10,000Da, wherein the foam has a foam density of 53 m to 250kg is formed, and the foam density of at least one of 53 m is formed according to 37 kg/39-20.

Description

High stiffness polyurethane foam composition

Technical Field

Embodiments relate to foam-forming compositions and methods for producing polyurethane foam articles, as well as high density foam articles having high modulus, elongation, and tensile strength.

Background

Polyurethane foams are known in the art and are used in a variety of end use applications, including mats, support articles, encapsulants/potting agents, and insulation materials. Polyurethane foams may be formed from a variety of chemical compositions, and may utilize physical and/or chemical blowing agents. For example, polyurethane foams are typically formed from the reaction of an isocyanate and a polyol 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 are useful in many applications, such as electric vehicle batteries, while maintaining adhesion and thermal insulation applied in low thickness areas (1 mm-6 mm). At present, rigid and high density foams (250 kg/m ³) cured at low temperatures (25 ℃ C. To 45 ℃ C.) were found to be very brittle and prone to fracture at low elongation values. In addition, in most rigid foam formulations, exothermic conditions are required to cure and develop properties, but are 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 the lithium ion battery at higher temperatures.

Disclosure of Invention

In one aspect, the foam-forming composition may 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 30Da to 450Da, (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 1500Da to 10,000Da, 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 800Da to 10,000Da, wherein (ii) the catalyst is present in a weight percent (wt%) of the sum of the polyols in the isocyanate-reactive composition, (c) the catalyst is present in a weight percent (wt%) of 25 to 75 wt%) and (D) the foam has a foam-forming density of at least one of 53-250 kg/39 m, and wherein the foam has a foam density of at least one of 53-forming composition of from 53 to 250 kg/39 m.

Detailed Description

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

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

All molecular weights in this specification are listed as number average molecular weights unless otherwise indicated.

Polyurethane (PU) foams and methods of making foams include a combination of reactive chemical components, such as isocyanate components, and isocyanate reactive components to produce foam-forming compositions. The isocyanate component contains di-or polyisocyanates containing reactive isocyanate (n=c=o) functional groups. The isocyanate-reactive component contains two or more functional groups that react with isocyanate functional groups, such as hydroxyl groups or amines. The foam-forming composition may also contain other additives such as suitable catalysts, surfactants, flame retardants, viscosity modifiers, fillers and blowing agents, which may be added to one or both of the isocyanate and isocyanate-reactive components.

The isocyanate and the isocyanate-reactive component may be combined in various stoichiometric ratios described by the 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 ranging from 60 to 300, which is used to produce foam articles having relatively high densities while reducing excessive friability.

The increased relative amount of isocyanate is typically used to increase stiffness, however, the foamed PU compositions disclosed herein may exhibit a relative increase in stiffness and flexural modulus at lower relative isocyanate indexes. The foamed polyurethane composition may also exhibit good properties at relatively low thicknesses in the range of 1mm to 10mm or 1mm to 5mm. The foamed PU composition may have a torsional (i.e., shear) modulus of greater than 150MPa or greater than 175MPa, as determined by ASTM D5279-21. In some cases, the foamed PU composition may have a torsional (i.e., shear) modulus of 150MPa to 800 MPa. The foamed articles may also exhibit reduced elongation at break values (e.g., equal to or greater than 6% elongation) when tested on a micro tensile tester according to ASTM D1708-18.

The foam-forming PU compositions disclosed herein may have delayed foam rise (delamination) after dispensing (or spraying) compared to standard foaming compositions, which may increase flowability and coverage in mold applications, particularly for molds having large surface areas and/or complex geometries. In some cases, the foam-forming PU composition may include isocyanate and isocyanate-reactive components that remain liquid for 30 seconds or more after mixing or 60 seconds or more after mixing at ambient temperature. The ambient temperature may be in the range of 15 ℃ to 35 ℃, with room temperature typically being about 23 ℃. In some cases, the isocyanate and isocyanate-reactive components remain in the liquid state for 30 seconds or more at temperatures up to the mold (such as up to 50 ℃).

The foam-forming PU compositions disclosed herein include two-part compositions that include an isocyanate component and an isocyanate-reactive component, as well as various additives, such as blowing agents and catalyst combinations. The isocyanate-reactive component may include a combination of polyether polyols, particularly (1) a low Molecular Weight (MW) polyether polyol having an average hydroxyl equivalent weight of 450Da or less, and (2) a high MW polyether polyol having an average hydroxyl equivalent weight of 800Da to 10,000 Da. In some cases, the high MW polyether polyol may be Ethylene Oxide (EO) capped at a weight percent (wt%) of 3wt% to 80wt% of the polyol.

The polyether polyols disclosed herein may 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 polyol initiators having a functionality ranging from 2 to 8 or from 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 may be formed using one or more polyol initiators such as neopentyl glycol, 1, 2-propanediol, trimethylol propane, pentaerythritol, sorbitol, sucrose, glycerol, alkane diols such as1, 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) -methylol octadecanol, 1, 4-dimethylol cyclohexane, hydrogenated bisphenol, 9 (10, 10) -dimethylol octadecanol, 1,2, 6-hexanetriol, and combinations thereof.

The isocyanate-reactive component may include one or more low MW polyether polyols having an average hydroxyl equivalent weight in the range of 30Da to 400Da as determined according to ASTM D4274D. In some cases, the low MW polyether polyol may have a number average molecular weight of 450Da or less, or 200Da or less. In some cases, the low MW polyether polyol includes a propoxylated derivative of a polyol initiator such as glycerin, sorbitol, butylene glycol, and the like.

The isocyanate-reactive component may include a low MW polyether polyol in the range of 25wt% to 75wt% or 30wt% to 70wt% in weight percent (wt%).

In some cases, the isocyanate-reactive component may include a low MW polyol, such as the polyol initiator disclosed above, in place of or in addition to the low MW polyether polyol. In some cases, the isocyanate component may include a low MW polyol in a range of 1wt% to 10wt% or 1wt% to 5wt% of the weight percent (wt%) of the isocyanate reactive component.

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 800Da to 10,000Da, 800Da to 8,500Da, or 1,000Da to 8,000 Da. The high MW polyether polyol may be prepared using the chemicals and polyol initiators as discussed above with respect to the polyether polyol. The high MW polyether polyol may have a functionality of 1 to 8 with a primary hydroxyl content >60%, >40%, or >20%.

In addition, high MW polyether polyols can be capped with oligomers or polymers of ethylene oxide (EO caps), which change elongation characteristics and toughness when compared to rigid foams of similar density. The EO-capped high MW polyether polyol may have an Ethylene Oxide (EO) content of from 3wt% to 80wt% in weight percent (wt%). In some cases, the high MW polyether polyol may include an EO-capped high MW polyether polyol having an EO content ranging from 3wt% to 80wt%, an average functionality ranging from 1 to 8, and an average molecular weight ranging from 800Da to 10,000Da, with primary hydroxyl groups >40%. In some cases, the EO content may range from 3wt% to 50wt%. In some cases, the EO content may range from 3wt% to 28wt%, with a functionality of 1 to 8 and a molecular weight ranging from 800Da to 10,000Da, with primary hydroxyl groups >60%.

The isocyanate-reactive component may include a high MW polyether polyol in a range of 25wt% to 75wt%, 30wt% to 70wt%, or 35wt% to 65wt% of the weight percent (wt%) of the sum of all polyols in the isocyanate-reactive component.

The foam-forming composition may comprise an isocyanate component comprising one or more isocyanates, such as polymeric isocyanates, aromatic isocyanates, carbodiimide modified isocyanates. The isocyanate species may be monomers, oligomers, prepolymers, and the like. The isocyanate component may include, for example, one or more isocyanates and/or polyisocyanate compounds.

The isocyanate component may include polyisocyanates having nominal functionalities >1.5 or > 2.0. In some cases, the isocyanate component may include a polyisocyanate having an isocyanate (NCO) content of 10% by weight or more, 20% by weight or more, or 30% by weight or more.

The isocyanate compound may be an aliphatic polyisocyanate, a cycloaliphatic polyisocyanate, an araliphatic polyisocyanate, an 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 isomers thereof), polymeric and pre-polymeric MDI, triisocyanato nonane (TIN), naphthyl Diisocyanate (NDI), 4 '-diisocyanate dicyclohexyl-methane, 3-isocyanatomethyl-3, 5-trimethylcyclohexyl isocyanate (isophorone diisocyanate, IPDI), tetramethylene diisocyanate, hexamethylene Diisocyanate (HDI), 2-methyl-pentamethylene diisocyanate, 2, 4-trimethylhexamethylene diisocyanate (THDI), dodecamethylene diisocyanate, 1, 4-diisocyanatocyclohexane, 4' -diisocyanato-3, 3 '-dimethyl-dicyclohexylmethane, 4' -diisocyanato-2, 2-dicyclohexylpropane, 3-isocyanatomethyl-1-methyl-1-isocyanatocyclohexane (MCI), 1, 3-diisocyanato-4-dimethylcyclohexane, 1-isocyanatocyclohexane, and the like. In addition to the isocyanates mentioned above, partially modified polyisocyanates can be utilized including uretdione, isocyanurate, carbodiimide, uretonimine, allophanate or biuret structures, combinations thereof, and the like.

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

The isocyanate component may also include isocyanate prepolymers obtained from reacting an isocyanate reactive compound with a molar excess of a polyisocyanate compound or polymeric isocyanate compound under conditions that do not result in gelation or curing, these isocyanate prepolymers may have a higher average isocyanate equivalent weight of >400 g/eq. The formation of isocyanate prepolymers is known in the art and may 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 may have an isocyanate index in the range of 60 to 300, 75 to 300, or 100 to 200.

Examples of commercial isocyanates include, but are not limited to, polyisocyanates available entirely from the Dow chemical company (Dow Chemical Company) under the trade names VORANATE ^TM、PAPI^TM and ISONATE ^TM (such as VORANATE ^TM M220 and PAPI ^TM).

The isocyanate component may include an isocyanate compound having a number average molecular weight of 150g/mol to 750 g/mol. In some cases, the isocyanate compound may have a number average molecular weight ranging from a low value of 150g/mol, 200g/mol, 250g/mol, or 300g/mol to a high value of 350g/mol, 400g/mol, 450g/mol, 500g/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 may be monomeric and/or polymeric, as known in the art.

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

The foam-forming PU composition may include one or more blowing agents, including water and aqueous fluids, chemical blowing agents, such as hydrocarbons, acids, volatile organics, and the like, and physical blowing agents, including gases, such as nitrogen, air, carbon dioxide, and the like. During mixing, the foaming agent may be added to the foam-forming composition in a weight percent (wt%) ranging from 0.05wt% to 10wt% or from 0.1wt% to 5 wt%. In some cases, the one or more blowing agents may be present in a weight percent (wt%) of less than or equal to 0.45wt%, or less than or equal to 0.4wt% of the sum of 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 percentages described above.

The foam-forming PU composition may include 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, a blowing catalyst and a gelling catalyst can be distinguished by a propensity to favor urea (blowing) reactions in the case of a blowing catalyst or urethane (gelling) reactions in the case of a gelling catalyst. Trimerization catalysts may be used to promote isocyanate-forming reactions in the composition. The catalyst package may also be added as a separate stream to the reaction mixture of isocyanate and isocyanate-reactive composition. The catalyst package may be present in the foam-forming composition in a weight percent (wt%) ranging from 0.1wt% to 5wt%, or from 1wt% to 5 wt%.

The blowing catalyst may include bis- (2-dimethylaminoethyl) ether, pentamethyldiethylenetriamine, triethylamine, tributylamine, N, N-dimethylaminopropylamine, dimethylethanolamine, N, N, N ', N' -tetramethyl ethylenediamine, combinations thereof, and the like. An example of a commercially available blowing catalyst is that available from Evonik, inc. (Evonik)5, And other commercially available blowing catalysts.

Gelling catalysts include organometallic compounds, cyclic tertiary amines and/or long chain amines (e.g., containing several nitrogen atoms), and combinations thereof. The organometallic compounds include organotin compounds such as tin (II) salts of organic carboxylic acids, for example, tin (II) diacetate, tin (II) dioctanoate, tin (II) diethylhexanoate, and tin (II) dilaurate, and dialkyltin (IV) salts of organic carboxylic acids, for example, dibutyltin diacetate, dibutyltin dilaurate, dibutyltin maleate, and dioctyltin diacetate. Bismuth salts of organic carboxylic acids may also be used as gelling catalysts, for example bismuth octoate. The cyclic tertiary and/or long chain amines include dimethylbenzylamine, triethylenediamine, and combinations thereof. Examples of commercially available gelling catalysts are those from winning companies8、33-LV andT-12, and other commercially available gelling catalysts.

The trimerization catalyst may comprise any such catalyst known in the art. Examples of trimerization catalysts include N, N' -tris (3-dimethylaminopropyl) hexahydro-S-triazine, N-dimethylcyclohexylamine, 1,3, 5-tris (N, N-dimethylaminopropyl) -S-hexahydrotriazine, [2,4, 6-tris (dimethylaminomethyl) phenol ], potassium acetate, potassium octoate, 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 from 10 carbon atoms to 20 carbon atoms, combinations thereof, and the like. Some commercially available trimerization catalysts include, for example, those each from a winning companyTMR-2、TMR-20、TMR-30、TMR-7、K 2097;K15、41 And46, And other commercially available trimerization catalysts.

The catalyst package may include a "latent catalyst" or "delayed catalyst" which is defined as a catalyst compound that has low catalytic activity or is relatively inactive at ambient temperature and which becomes more catalytically active upon heating, for example by dissociation, decoordination, ring opening, ionization or tautomerization, to effect catalysis of at least one of the chemical reactions involved in preparing the PU foam. The ambient temperature may be in the range of 15 ℃ to 32 ℃, with room temperature typically being about 23 ℃.

The latent/delayed action catalyst may be of the gelling, foaming and/or trimerisation type with respect to its function in the foaming process. The latent catalyst is typically a subset of tertiary amine gelling catalysts, including acid salts, phenoxide salts or complexes of tertiary amine catalysts, wherein the acid or phenol is typically a carboxylic acid or phenolic material, but is not limited to esters such as formic acid, acetic acid, propionic acid, 2-ethylhexanoic acid, phenoxyacetic acid, gluconic acid, tartaric acid, citric acid, phenol, nonylphenol, diisopropylphenol, and the like, and mixtures thereof. Some commercially available latent catalysts that may be used include, for exampleTMR-30、SA2LE、SA-1/10、8154、NIAX^TMA-107、NIAX^TMC-31、NIAX^TMC-225、JEFFCAT^TMZF-54、JEFFCAT^TMLED-204; And mixtures thereof.

The catalyst package may comprise a mixture of one or more of the above catalysts and/or latent catalysts in the range of 0.1 to 5 weight percent (wt%) of the foam-forming composition. 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 percentages described above.

The foam-forming composition may comprise one or more fillers including glass fibers, silica, caCO ₃, kaolin, talc, alumina Trihydrate (ATH), and the like. The filler or fillers may be added in a weight percent (wt%) ranging from 0wt% to 15wt%, or 1wt% to 10wt% 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 percentages described above.

The foam-forming composition may include a surfactant present in the isocyanate and/or isocyanate-reactive component in an amount sufficient to provide a weight percent of the surfactant of from 0.1wt% to 5wt% of the foam-forming mixture. Surfactants may include silicone-based surfactants, polyether-modified silicone surfactants, and organic-based surfactants. Some representative surfactants include polysiloxane polyoxyalkylene block copolymers such as those disclosed in U.S. Pat. Nos. 2,834,748, 2,917,480 and 2,846,458, organic surfactants containing polyoxyethylene-polyoxypropylene block copolymers, as described in U.S. Pat. No. 5,600,019, and the like. Other surfactants include polyethylene glycol ethers of long chain alcohols, tertiary or alkanolamine salts of long chain allylic acid sulfate esters, alkyl sulfonates, alkylaryl sulfonates, and combinations thereof. Some commercially available surfactants useful in the isocyanate-reactive composition include VORASURF ^TMDC 193、VORASURF^TM 504,504,B8418 and mixtures thereof.

The composition may further comprise one or more functional additives such as chain extenders, expandable graphite, additional physical or chemical blowing agents, flame retardants, thixotropic agents (such as poloxamers), viscosity modifiers, cell openers, emulsifiers, adhesion modifiers, antioxidants, surfactants, colorants, UV stabilizers, antistatic agents, bacteriostats, and mixtures thereof.

The foam-forming compositions, foamed polyurethane articles, and methods of the present disclosure are useful 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 may be used to at least partially cover or encapsulate articles such as batteries and other electronic components. The foamed polyurethane articles may also be used for thermal insulation. In addition, the foamed polyurethane article can be used as a fire block. Generally, the foamed polyurethane articles of the present disclosure provide a combination of desirable physical properties relative to conventional foams, including one or more of reduced weight, reduced density, increased heat resistance, increased stability, and the like. The foamed polyurethane article may be formed in an environment where hydrogen formation is of concern. In addition, the foamed polyurethane article may be foamed at or about room temperature, which is suitable for temperature sensitive applications.

Foam production may include the steps of (1) equilibrating the isocyanate component and the isocyanate-reactive composition to mix, (2) pre-heating the mold surface to a molding temperature (typically, e.g., between 25 ℃ and 60 ℃) where 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 of the foam-forming reaction mixture to achieve a desired overfill rate (typically, e.g., 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 the mixing step (5), (7) immediately transferring the foam-forming reaction mixture into the mold, or directly injecting the foam-forming reaction mixture into the mold, (8) closing the mold (if not closed) and allowing the resulting foam-forming reaction mixture to react to form a PU foam article (i.e., molded foam article) in the mold, (9) opening the mold after reaching a pre-set demolding time, (10) demolding the foam article, and (11) completely inspecting the foam article for defects such as, swelling, if any, and shrinkage, of the foam article after the foam article is completely inspected.

The process for preparing the PU foam article may be accomplished by any process technique known in the art. In general, PU foam articles of the present disclosure may be produced by continuous or discontinuous processes, including processes commonly referred to as Reaction Injection Molding (RIM) processes or cast molding processes, wherein the foaming reaction and subsequent curing are performed in a mold.

The mixing of the components of the foam-forming composition may be carried out at a temperature of from 5 ℃ to 80 ℃, from 10 ℃ to 60 ℃, or from 15 ℃ to 50 ℃. The molding of the PU foam article may be performed in a mold temperature range of 20 ℃ to 80 ℃, 30 ℃ to 70 ℃, or 40 ℃ to 60 ℃.

Examples

The following examples are provided to illustrate embodiments of the invention and are not intended to limit the scope of the invention. All parts and percentages are by weight unless otherwise indicated.

Procedure for analysis of foaming and moulding

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 objective. The isocyanate component is then added to the isocyanate-reactive component in the selected ratio (isocyanate index) and the mass of the mixture is recorded. A sample of the foam-forming composition is then analyzed or decanted into a mold as a liquid mixture. 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 1000psi-3000psi in GRACO sprayer.

After mixing, the foam-forming composition was sprayed (for the inventive examples) and/or poured (inventive examples and comparative examples) into a container (e.g., open cup or mold) and the reaction kinetics were analyzed. The samples were reacted and the cream time, rise time and green strength were recorded. Timing was started when the two components were mixed. Cream time is defined as the time between the start of mixing and the rise of the liquid level (foam start rising). Rise time is defined as the time between the onset of mixing and the foam rising to a certain level (including cream time). Gel time is defined as the time between the start of mixing and the point at which the material forms a continuous string at the time of detection. Tack free time is defined as the time between the onset of mixing and the absence of wire falling off the surface when the stick is applied with a spatula (including cream and rise times). The processing time is defined as the time between the onset of mixing and the foam being sufficiently rigid to not be compressed when pushed by the finger (with considerable force).

The mold test included parallel and vertical molds. For the parallel rise test in mold a (19 cm x 12.5cm x 0.2cm, where 19cm is the direction of rise), the mold was preheated in an oven at 40 ℃ and the mixed resin sample was transferred into the mold while timing for about 32 seconds to 34 seconds. The mold was then placed in an oven at 40 ℃ for 20 minutes. The mixed resin sample contained was then measured and the amount of material remaining in the cup after pouring was calculated.

The samples were then demolded and the foam size, weight were recorded and the density calculated. Sample foam is considered too brittle to be further tested if it breaks or breaks during demolding. The "testable" foam did not break during demolding or during cutting of the sample shape for property testing. The remaining testable foam sample was left overnight to cure, and the sample was then cut out for characterization testing.

For the vertical rise test in mold B (20 cm x 15cm x 0.5cm, where 0.5cm is the rise direction), the mold was preheated in an oven at 40 ℃ and the mixed resin sample was transferred into the mold while timing for about 32 seconds to 34 seconds. The mold was then placed in an oven at 40 ℃ for 20 minutes. The mixed resin sample contained was then measured and the amount of material remaining in the cup after pouring was calculated.

The samples were then demolded and the foam size, weight were recorded and the density calculated. After demolding (10 min-12 min), the hardness of the foam sample surface was measured with a durometer (shore a scale) and then after 30 min with a durometer (shore D scale). Sample foam is considered too brittle to be further tested if it breaks or breaks during demolding. The "testable" foam did not break during demolding or during cutting of the sample shape for property testing. The remaining testable foam sample was left overnight to cure, and the sample was then cut out for characterization testing.

Samples were tested for a range of properties (I-XI) as follows:

The properties of sample (I) are a qualitative description of the brittleness of the sample according to whether it can be demolded after foaming to further test its mechanical properties.

Density (II) is a quantitative measurement of the density (i.e., weight/volume) of a foam sample, made according to ASTM D3574 test a.

The modulus of elasticity, E' (III), elongation at break (IV) and ultimate tensile strength (V) were all obtained on a micro-tensile tester using ASTM D1708-18, wherein after molding a PU foam sheet of 0.2mm thickness was obtained, aged at room temperature (23 ℃) for 2 days, and punched into a dog bone shape.

Shear modulus (VI to VIII) and glass transition temperature (IX) in torsional mode were obtained by Dynamic Mechanical Analysis (DMA) using ASTM D5279-21 on an advanced rheology expansion system (ARES-G2) from TA Instruments, equipped with liquid nitrogen environmental control and torsional rectangular clamps. Rectangular samples of the foam prepared in metal molds (a and B) were punched (45 mm long and 12.8mm wide) to a thickness of 2 mm. The sample length is axially aligned to the torsion axis and DMA is performed in torsion mode. The temperature was increased from-70 ℃ to 200 ℃ at a ramp rate of 3 ℃ per minute. The test frequency was 1Hz at 0.05% torsional strain with an axial tension of 0.098N applied to hold the sample taut and a data collection interval of 30 seconds/point. The main outputs from the identified characterization are storage modulus in terms of shear modulus (G'), loss modulus (G "), and Tan δ.

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 cream time, the time for foam bubble generation and rise time were visually judged, and the time was recorded. The treatment time is defined as the time between the onset of mixing and the foam developing sufficient rigidity to resist compression as detected by the tongue depressor. Hardness was measured after demolding and the treatment time was recorded as shore D >20.

Lap shear bond strength test (XI) was determined according to ASTM D-1002-10 test to quantify the apparent shear strength of a single lap joint bonded metal specimen by tensile load. A 1mm thick polypropylene spacer was placed between the metal substrates with an overlap of 0.5 inches. The 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. The samples were then placed in an oven at 40 ℃ for 3 hours to cure. The foam density between the plates was determined gravimetrically. The substrate comprised E-coated cold rolled steel (1 inch by 4 inches by 0.032 inches) of commercial origin, i.e., ACT panels. Failure during lap shear testing was classified as adhesive failure (foam residue on only one side of the substrate due to adhesive failure), cohesive failure (foam residue on both sides of the substrate due to foam failure) or substrate failure (e-coat peeling or substrate breakage on the foam).

The viscosity measurements of the isocyanate-reactive components were performed on a TA Instruments AR 2000 rheometer with 54mm cone-plate geometry and 450 micron gap. Data was collected at a shear rate scan of 100 seconds ^-1 to 0.01 seconds ^-1 at a temperature of 25 ℃. For the isocyanate component and the polyol component alone, the viscosity was measured at 25 ℃ using ASTM D4889.

The hydroxyl number (OH#) of each polyether polyol in the formulation was determined according to ASTM D4274, and OH# was used to determine hydroxyl equivalent weight.

The water content was determined using the volume karl fischer titration method (KARL FISCHER titration) according to ASTM E203-16 for the standard test method for water.

EXAMPLE 1 preparation and characterization of PU foam

In this example, comparative (C) and inventive (I) samples of water-blown foam were prepared as shown in tables 2 to 7.

The characteristics of the comparative samples C1 to C8 and the inventive samples I1 to I13 are shown in tables 8 to 13. Property I (nature of foam) indicates whether the formulation is foaming or breaking/crushing during the process of preparing the samples for testing properties III-IX.

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

In contrast, inventive samples I1-I13, which contain polyether polyols having an average hydroxyl equivalent weight of 800Da at a concentration of 25 wt.% or more in the isocyanate-reactive component, exhibit elongation at break values of 6% or more (characteristic IV). The ultimate tensile strength (characteristic V) was maintained above 10MPa for all inventive samples. The foam density (characteristic II) of the inventive samples was kept between 400kg/m ³-700kg/m³. For I2, the adhesion (property XI) of the foam using the lap shear adhesion test was 8MPa.

In addition, for inventive samples I1-I13, the incorporation of OHW >1900Da Ethylene Oxide (EO) -capped polyether polyol increased the modulus of the foam (property III) at an isocyanate index of 115 and a foam density in the range of 250kg/m ³-700kg/m³ (property II). In addition, the elongation at break (characteristic IV) of the inventive foam samples remains and/or increases. Therefore, not only the rigidity but also the elongation at break and further the ultimate tensile strength (characteristic V) are improved.

While the foregoing is directed to the exemplary embodiments, other and further embodiments of the invention may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow.

Claims (11)

1. A foam-forming composition, the foam-forming composition comprising:

(a) At least one isocyanate component, and

(B) At least one of the isocyanate-reactive compositions, the at least one isocyanate-reactive composition comprises:

(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 30Da 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 to 10,000Da, 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 800Da to 10,000Da,

Wherein (ii) is present in a weight percent (wt%) ranging from 25wt% to 75wt% of the sum 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 foam-forming composition has an isocyanate index of 60 to 300 and the foam has a molded foam density of 250kg/m ³ to 750kg/m ³ according to ASTM D1622-20.

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

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

4. A composition according to claim 3, wherein the at least one blowing agent is present at less than or equal to 0.45wt% of the sum of the polyols in the isocyanate-reactive composition.

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

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

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

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

9. A foamed article prepared from the composition of claim 1.

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

11. A process for producing a polyurethane rigid molded foam, the process comprising providing a foam-forming composition according to any one of claims 1 to 8, and reacting the foam-forming composition to produce a foam article.