Rigid polyurethane foam

Abstract

Embodiments of the present disclosure relate to a composition for making rigid polyurethane foams for use, for example, with water heaters.

Description

Technical Field

[0001] Embodiments of the present disclosure are directed to a composition for preparing a rigid polyurethane foam. Background Art

[0002] Water heaters are usually insulated with rigid polyurethane (PU) foam using various foaming technologies. The foaming technology depends on the final market and product requirements, technical and safety characteristics, cost and performance requirements of the water heater. To this end, different production processes for applying rigid PU foam can be used. For example, under free rise conditions, just enough PU foam can be applied using "instant" technology to fill the cavity of the water heater. Alternatively, the PU molding process can include overpacking PU foam to maximize the mechanical strength properties of the rigid PU foam around the water heater. For example, in the molding process, the rigid PU foam is injected for the external liner (usually a metal or plastic external liner), or for the stripper when no external finish is used. In the latter case, a water heater insulated with bare PU foam is initially obtained, and then the water heater is covered with a removable external sheath. Therefore, the produced PU foam must have excellent aesthetics, with very few or no surface bubbles or defects, in addition to good foam flowability and fast curing characteristics. Visible bubbles or defects on the surface of the PU foam can cause unsightly surface defects in the finally assembled water heater. Therefore, there is a need in the art for a PU foam system that can produce a water heater with acceptable product quality. Summary of the invention

[0003] The present disclosure provides a fully formulated, non-flammable, zero ozone depletion (ODP) / low global warming potential (GWP) composition for preparing rigid polyurethane (PU) foam suitable for bare foam molding processes, especially those involving water heater applications. The disclosed composition allows the production of PU foams characterized by enhanced flow coupled with excellent surface aesthetics and improved thermal insulation for long-term use.

[0004] For various embodiments, the composition for producing a rigid PU foam comprises an isocyanate component, the isocyanate component comprising at least one polyisocyanate; and an isocyanate reactive system, the isocyanate reactive system comprising: 5 to 30 weight percent (wt.%) of a first polyether polyol having an average hydroxyl number of 100 to 600 mg KOH / g and an average hydroxyl functionality of 5.5 to 8; 45 to 75 wt.% of a first polyether polyol having an average hydroxyl functionality of 75 to 800 mg KOH / g; % to 3.2; 1 wt.% to 20 wt.% of a hydrofluoroolefin physical blowing agent; 1 wt.% to 5 wt.% of a chemical blowing agent comprising water; 0.5 wt.% to 5 wt.% of at least one surfactant; and 0.5 wt.% to 6 wt.% of at least one catalyst, wherein the wt.% are based on the total weight of the isocyanate-reactive system, wherein the wt.% of the first polyether polyol, the at least one second polyether polyol, the hydrofluoroolefin physical blowing agent, the chemical blowing agent, the at least one surfactant, and the at least one catalyst total 100 wt.%, and wherein the isocyanate-reactive system has an average hydroxyl functionality of 3.3 to 3.7, an average hydroxyl number of 300 mg KOH / g to 400 mg KOH / g, and is free of formic acid.

[0005] The above summary of the invention of the present disclosure is not intended to describe each disclosed embodiment or each embodiment of the present disclosure. The following description more specifically illustrates exemplary embodiments. In several places throughout this application, guidance is provided by example lists, which can be used in various combinations. In each case, the enumerated lists serve only as representative groups and should not be interpreted as exclusive lists. DETAILED DESCRIPTION

[0006] The present disclosure provides a fully formulated, non-flammable, zero ozone depletion (ODP) / low global warming potential (GWP) composition for preparing rigid polyurethane (PU) foam suitable for bare foam molding processes, especially those involving water heater applications. The disclosed composition allows the production of PU foams characterized by enhanced flowability coupled with excellent surface aesthetics and improved thermal insulation for long-term use. Such compositions are particularly useful in the production of water heaters, where the number of defects produced by the PU foams of the present disclosure is significantly less than conventional solutions even at low mold temperatures that better match typical production conditions.

[0007] For various embodiments, the composition for producing rigid PU foam of the present disclosure comprises an isocyanate component, the isocyanate component comprising at least one polyisocyanate, and an isocyanate reactive system, the isocyanate reactive system comprising: (a) a first polyether polyol, (b) at least one of a second polyether polyol, as provided herein, (c) a hydrofluoroolefin physical blowing agent, (d) a chemical blowing agent comprising water, (e) at least one surfactant; and (f) at least one catalyst. The isocyanate reactive system may also include a third polyether polyol (g) discussed herein. As used herein, "polyol" refers to a compound having an average hydroxyl functionality of 2.0 or greater, such as a diol, a triol, a tetraol, and the like. Many different polyols can be used in the isocyanate reactive system of the present disclosure, such as those discussed herein, and other polyols known to those skilled in the art.

[0008] The composition for producing rigid PU foam comprises an isocyanate reactive system having a first polyether polyol. For various embodiments, the first polyether polyol has an average hydroxyl functionality of 5.5 to 8.0. For example, the first polyether polyol may have an average hydroxyl functionality of a lower limit of 5.5, 5.7, 5.9 or 6.0 to an upper limit of 8.0, 7.8, 7.5 or 7.0. For various embodiments, the first polyether polyol has an average hydroxyl number of 100 mg KOH / g to 600 mg KOH / g. For example, the first polyether polyol can have an average hydroxyl number of 100 mg KOH / g, 110 mg KOH / g, 200 mg KOH / g, 250 mg KOH / g, 375 mg KOH / g, 400 mg KOH / g, 425 mg KOH / g, or 450 mg KOH / g to an upper limit of 600 mg KOH / g, 575 mg KOH / g, 550 mg KOH / g, 525 mg KOH / g, or 500 mg KOH / g. The hydroxyl number can be measured, for example, using ASTM E222-10.

[0009] The first polyether polyol can be an alcohol-initiated polyether polyol, such as an alcohol-initiated aliphatic or alicyclic polyether polyol. The alcohol initiator can have a hydroxyl functionality greater than 5.5 and / or a hydroxyl equivalent molecular weight less than 75g / mol, such as 15g / mol to 60g / mol, 20g / mol to 50g / mol, etc. Exemplary alcohol initiators that can be used are sorbitol and / or sucrose (alone or in combination with other initiators having a hydroxyl functionality equal to or less than 5.5), etc. Other initiators suitable for preparing the first polyether polyol can include mannitol, maltitol, trehalose, xylitol and / or mixtures of these, as long as the average hydroxyl functionality is 5.5 to 8.0. For various embodiments, the first polyether polyol is not prepared by a polyol initiator comprising any aromatic unit or amine moiety.

[0010] The first polyether polyol may have a hydroxyl equivalent weight of 75 g / mol to 550 g / mol. As used herein, the hydroxyl equivalent weight is the weight of the compound per reactive site and is calculated according to the following equation: Equivalent Weight = (56.1 x 1000) / OH Number. All individual values ​​and subranges from 75 g / mol to 550 g / mol are included; for example, the first polyether polyol may have a hydroxyl equivalent weight of 75 g / mol, 80 g / mol, 85 g / mol, 90 g / mol, 95 g / mol, or 100 g / mol to an upper limit of 550 g / mol, 500 g / mol, 400 g / mol, 300 g / mol, 250 g / mol, 200 g / mol, 175 g / mol, 150 g / mol, 145 g / mol, or 140 g / mol.

[0011] The first polyether polyol can be prepared using known equipment and reaction conditions. The first polyether polyol can be commercially available. Examples of commercially available first polyether polyols include, but are not limited to, all available from The Dow Chemical Company. VORANOL TM , such as VORANOL TM RN 482, VORANOL TM 280.VORANOL TM 370 polyols for sale and more.

[0012] The first polyether polyol can be 5 weight percent to 30 weight percent (wt.%) of the total weight of the isocyanate reactive system (components (a) to (f) or (a) to (g) provided herein), wherein the wt.% of the first polyether polyol, at least one second polyether polyol, an optional third polyether polyol, a hydrofluoroolefin physical blowing agent, a chemical blowing agent, a surfactant, and a catalyst total 100 wt.%. All individual values ​​and subranges from 5 wt.% to 30 wt.% are included; for example, the first polyether polyol can be 5 wt.%, 7 wt.%, 9 wt.%, or 11 wt.% of the total weight of the isocyanate reactive system to an upper limit of 30 wt.%, 25 wt.%, 20 wt.%, 15 wt.%, or 12 wt.%. For example, the first polyether polyol can be 9 wt.% to 25 wt.% of the total weight of the isocyanate reactive system.

[0013] The isocyanate reactive system of the composition for producing rigid PU foam also includes at least one second polyether polyol. For various embodiments, each of the at least one second polyether polyol has an average hydroxyl functionality of 2 to 3.2. For example, each of the second polyether polyols may have an average hydroxyl functionality of a lower limit of 2, 2.2, 2.4 or 2.6 to an upper limit of 3.2, 3.15 or 3.1. For various embodiments, each of the second polyether polyols has an average hydroxyl number of 75 mg KOH / g to 800 mg KOH / g. For example, each of the second polyether polyols can have an average hydroxyl number of 75 mg KOH / g, 80 mg KOH / g, 90 mg KOH / g, 100 mg KOH / g, 110 mg KOH / g, 120 mg KOH / g, 140 mg KOH / g, or 150 mg KOH / g to an upper limit of 800 mg KOH / g, 750 mg KOH / g, 725 mg KOH / g, 700 mg KOH / g, or 670 mg KOH / g. By way of example, each of the second polyether polyols can have an average hydroxyl number of 100 mg KOH / g to 750 mg KOH / g; 120 mg KOH / g to 700 mg KOH / g, or 150 mg KOH / g to 700 mg KOH / g, as well as other ranges. Each of the second polyether polyols can independently have a number average molecular weight in the range of 150 g / mol to 1500 g / mol; in the range of 800 g / mol to 1200 g / mol; in the range of greater than 350 g / mol to 650 g / mol; or in the range of 150 g / mol to 350 g / mol.

[0014] The second polyether polyol can be 45 wt.% to 75 wt.% of the total weight of the isocyanate reactive system (components (a) to (f) or (a) to (g) provided herein), wherein the wt.% of the first polyether polyol, at least one second polyether polyol, the optional third polyether polyol, the hydrofluoroolefin physical blowing agent, the chemical blowing agent, at least one surfactant, and at least one catalyst total 100 wt.%. All individual values ​​and subranges from 45 weight percent to 75 weight percent are included; for example, the second polyether polyol can be 45 wt.%, 50 wt.%, 55 wt.%, or 60 wt.% of the total weight of the isocyanate reactive system to an upper limit of 75 wt.%, 72 wt.%, or 65 wt.%. For example, at least one second polyether polyol can be 55 wt.% to 72 wt.% of the total weight of the isocyanate reactive system. For various embodiments, the isocyanate reactive system may include 5 wt.% to 30 wt.% of the first polyether polyol and 45 wt.% to 75 wt.% of at least one second polyether polyol, wherein the wt.% of the first polyether polyol, at least one second polyether polyol, optional third polyether polyol, hydrofluoroolefin physical blowing agent, chemical blowing agent, surfactant and catalyst total 100 wt.%. In other embodiments, the isocyanate reactive system may include 7 wt.% to 25 wt.% of the first polyether polyol and 50 wt.% to 72 wt.% of at least one second polyether polyol, wherein the wt.% of the first polyether polyol, at least one second polyether polyol, optional third polyether polyol, hydrofluoroolefin physical blowing agent, chemical blowing agent, surfactant and catalyst total 100 wt.%. For embodiments of the present invention, the first polyether polyol may be a sorbitol-initiated polyether polyol, and the at least one second polyether polyol may be at least one of a glycerol-initiated polyether polyol, each as provided herein.

[0015] Each of the second polyether polyols can be an alcohol-initiated polyether polyol, such as an alcohol-initiated aliphatic or alicyclic polyether polyol. For example, each of the second polyether polyols can be conventionally obtained by reacting an alkylene oxide (such as ethylene oxide, propylene oxide or butylene oxide) with a polyol or polyhydroxy alcohol initiator. Examples of suitable initiators include ethylene glycol; diethylene glycol; propylene glycol; dipropylene glycol; tripropylene glycol; 1,4-butanediol; 1,6-hexanediol; cycloaliphatic diols such as 1,4-cyclohexanediol, glycerol, triformyloxypropane and triethanolamine. The catalyst used for polymerization can be an anionic catalyst or a cationic catalyst, wherein exemplary catalysts such as potassium hydroxide (KOH), boron trifluoride, or a dicyanide complex catalyst such as zinc hexacyanocobaltate. In some embodiments, each of the second polyether polyols is obtained using propylene oxide. For the various embodiments, the at least one second polyether polyol includes at least one glycerin-initiated polyether polyol having a number average molecular weight in a range of 150 g / mol to 1500 g / mol.

[0016] Each of the second polyether polyols can be a glycerol-initiated polyether polyol prepared using known equipment and reaction conditions. Each of the second polyether polyols can be commercially available. Suitable commercially available polyether polyols include those available from VORANOL TM 220-110, VORATEC TM SD301, VORANOL TM CP 260, VORANOL TM CP450、VORANOL TM CP 755, VORANOL TM CP 1000, VORANOL TM CP 1050 and VORANOL TM CP 1055.

[0017] Each of the second polyether polyols may be present in the isocyanate-reactive system in various weight percentages, with the second polyether polyols as discussed herein constituting 45 to 75 wt. % of the isocyanate-reactive system, more preferably 50 to 75 wt. % of the isocyanate-reactive system. For example, the at least one second polyether polyol may include 5 wt.% to 20 wt.% of a first glycerol-initiated polyether polyol having a number average molecular weight of 800 g / mol to 1200 g / mol; 30 wt.% to 45 wt.% of a second glycerol-initiated polyether polyol having a number average molecular weight of greater than 350 g / mol to 650 g / mol; and 10 wt.% to 25 wt.% of a third glycerol-initiated polyether polyol having a number average molecular weight of 150 g / mol to 350 g / mol, wherein the wt.% values ​​of the first glycerol-initiated polyether polyol, the second glycerol-initiated polyether polyol, and the third glycerol-initiated polyether polyol provide 45 wt.% to 75 wt.% of the at least one second polyether polyol. In an alternative embodiment, the at least one second polyether polyol may include 7 wt.% to 17 wt.% of a first glycerol-initiated polyether polyol having a number average molecular weight of 800 g / mol to 1200 g / mol; 30 wt.% to 40 wt.% of a second glycerol-initiated polyether polyol having a number average molecular weight of greater than 350 g / mol to 650 g / mol; and 14 wt.% to 20 wt.% of a third glycerol-initiated polyether polyol having a number average molecular weight of 150 g / mol to 350 g / mol, wherein the combined wt.% value of the first glycerol-initiated polyether polyol, the second glycerol-initiated polyether polyol, and the third glycerol-initiated polyether polyol provides 45 wt.% to 75 wt.% of the at least one second polyether polyol.

[0018] The isocyanate reactive system for producing the composition of rigid PU foam may also optionally include a third polyether polyol. For various embodiments, each of the third polyether polyols has an average hydroxyl functionality greater than 3.2 to 5. For example, the third polyether polyol may have an average hydroxyl functionality greater than 3.2, 3.3, 3.4, 3.5, 3.6, 3.7, 3.8, 3.9, 4.0, 4.1 or 4.2 lower limits to 5, 4.9, 4.8, 4.7, 4.6, 4.5 or 4.4 upper limits. For various embodiments, the third polyether polyol has an average hydroxyl number of 100 mg KOH / g to 750 mg KOH / g. For example, the third polyether polyol compound can have an average hydroxyl functionality ranging from a lower limit of 100 mg KOH / g, 150 mg KOH / g, 200 mg KOH / g, 250 mg KOH / g, 275 mg KOH / g, 300 mg KOH / g, or 325 mg KOH / g to an upper limit of 750 mg KOH / g, 650 mg KOH / g, 600 mg KOH / g, 550 mg KOH / g, 500 mg KOH / g, 450 mg KOH / g, 425 mg KOH / g, 400 mg KOH / g, or 375 mg KOH / g. By way of example, the third polyether polyol can have an average hydroxyl number of 200 mg KOH / g to 600 mg KOH / g; 300 mg KOH / g to 550 mg KOH / g, or 350 mg KOH / g to 450 mg KOH / g, as well as other ranges. The third polyether polyol can have a number average molecular weight in the range of 250 g / mol to 3000 g / mol; in the range of 350 g / mol to 2500 g / mol; in the range of 400 g / mol to 2000 g / mol; in the range of 500 g / mol to 1500 g / mol; in the range of 600 g / mol to 1000 g / mol; in the range of 600 g / mol to 800 g / mol; or in the range of 650 g / mol to 750 g / mol.

[0019] The third polyether polyol can be 5 wt.% to 15 wt.% of the total weight of the isocyanate reactive system (components (a) to (g) provided herein), wherein the wt.% of the first polyether polyol, at least one second polyether polyol, the third polyether polyol, the hydrofluoroolefin physical blowing agent, the chemical blowing agent, the surfactant, and the catalyst total 100 wt.%. All individual values ​​and subranges from 5 weight percent to 15 weight percent are included; for example, the third polyether polyol can be 5 wt.%, 5.5 wt.%, or 6.5 wt.% of the total weight of the isocyanate reactive system from a lower limit to 15 wt.%, 12.5 wt.%, 11 wt.%, 10 wt.%, 9.5 wt.%, or 8.5 wt.%. For example, the third polyether polyol can be 6.5 wt.% to 8.5 wt.% of the total weight of the isocyanate reactive system. For various embodiments, the isocyanate reactive system may then comprise 5 wt.% to 30 wt.% of the first polyether polyol; 45 wt.% to 75 wt.% of at least one second polyether polyol and optionally 5 wt.% to 15 wt.% of the optional third polyether polyol, wherein the wt.% of the first polyether polyol, at least one second polyether polyol, the optional third polyether polyol, the hydrofluoroolefin physical blowing agent, the chemical blowing agent, the surfactant and the catalyst total 100 wt.%. In other embodiments, the isocyanate reactive system may comprise 9 wt.% to 25 wt.% of the first polyether polyol, 50 wt.% to 72 wt.% of at least one second polyether polyol and 5 wt.% to 10 wt.% of the optional third polyether polyol, wherein the wt.% of the first polyether polyol, at least one second polyether polyol, the optional third polyether polyol, the hydrofluoroolefin physical blowing agent, the chemical blowing agent, the surfactant and the catalyst total 100 wt.%.

[0020] The third polyether polyol can be an alcohol-initiated polyether polyol, such as an alcohol-initiated aliphatic or alicyclic polyether polyol. For example, the third polyether polyol can be conventionally obtained by reacting an alkylene oxide (such as ethylene oxide, propylene oxide or butylene oxide) with a polyol or a polyhydroxy alcohol initiator. Examples of suitable initiators include pentaerythritol; xylitol; sugar alcohols such as sucrose and another alcohol with two or three hydroxyl groups such as ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, tripropylene glycol, 1,4-butanediol, 1,6-hexanediol, a blend of cycloaliphatic diols such as 1,4-cyclohexanediol, glycerol, triformyloxypropane and triethanolamine. The catalyst for polymerization can be an anionic catalyst or a cationic catalyst, wherein exemplary catalysts such as potassium hydroxide (KOH), boron trifluoride, or a dicyanide complex catalyst such as zinc hexacyanocobaltate. In some embodiments, the third polyether polyol is obtained using propylene oxide. For the various embodiments, the third polyether polyol includes at least one sucrose / glycerol initiated polyether polyol having a number average molecular weight in a range from 500 g / mol to 900 g / mol.

[0021] The third polyether polyol may be a sucrose / glycerol initiated polyoxypropylene polyol prepared using known equipment and reaction conditions. The third polyether polyol may be commercially available. Suitable commercially available polyether polyols include all available from VORANOL 520, VORANOL TM RN 490, VORANOL TM 466、VORANOL TM 446. VORANOL TM RH 360.

[0022] For the various embodiments, neither the first polyether polyol, the at least one second polyether polyol, nor the optional third polyether polyol is prepared from a polyol initiator comprising any aromatic units or amine moieties.

[0023] Embodiments of the present disclosure provide that the isocyanate reactive system further comprises 1 wt.% to 20 wt.% of a hydrofluoroolefin physical blowing agent, wherein the wt.% is based on the total weight of the isocyanate reactive system. All individual values ​​and subranges from 1 wt.% to 20 wt.% of the hydrofluoroolefin physical blowing agent are included; for example, the hydrofluoroolefin physical blowing agent can be a lower limit of 1 wt.%, 2 wt.%, 5 wt.%, or 8 wt.% to an upper limit of 20 wt.%, 18 wt.%, 14 wt.%, or 12 wt.% of the total weight of the isocyanate reactive system.

[0024] Examples of hydrofluoroolefin physical blowing agents suitable for use in the present invention include both unsaturated hydrofluoroolefins (HFOs) and unsaturated hydrochlorofluoroolefins (HCFOs). They have negligible (low or zero) ozone depletion and low global warming potential. Suitable HFO and HCFO blowing agents include, but are not limited to, cis-1,1,1,4,4,4-hexafluoro-2-butene (HFO-1336mzz(Z)), trans-1,1,1,4,4,4-hexafluoro-2-butene (HFO-1336mzz(E)), 1,1,1,4,4,5,5,5-octafluoro-2-pentene (HFO-1438mzz), 2,3,3,3-tetrafluoropropylene (HFO-1234yf), trans-1,3,3,3-tetrafluoroprop-1-ene (HFO-1336mzz(E)), 1234ze), heptafluorobutene isomers (HFO1327), heptafluoropentene isomers (HFO1447), octafluoropentene isomers (HFO1438), nonafluoropentene (HFO1429), dichlorotrifluoropropylene (HCFO-1223), 1-chloro-3,3,3-trifluoropropylene (HCFO-1233zd), 2-chloro-3,3,3-trifluoropropylene (HCFO-1233xf) and mixtures thereof. Some of these blowing agents are called LBA, GBA, Opteon TM 1100,Opteon TM Commercially available materials are 1150, etc. Hydrofluoroolefin physical blowing agents not containing any chlorine atoms are more preferably used in the present invention.

[0025] Embodiments of the present disclosure provide that the isocyanate reactive system further comprises 1 wt.% to 5 wt.% of a chemical blowing agent comprising water, wherein the wt.% is based on the total weight of the isocyanate reactive system. All individual values ​​and subranges from 1 wt.% to 5 wt.% of the chemical blowing agent comprising water are included; for example, the chemical blowing agent can be a lower limit of 1 wt.%, 1.5 wt.%, 2 wt.%, or 2.5 wt.% to an upper limit of 5 wt.%, 4 wt.%, or 3.5 wt.% of the total weight of the isocyanate reactive system. Additional chemical blowing agents that can be used are those CO2-generating materials that are not based on organic acids.

[0026] Preferably, the chemical blowing agent is water.For the various embodiments, the chemical blowing agent does not contain any formic acid.

[0027] Embodiments of the present disclosure provide that the isocyanate reactive system further comprises 0.5 wt.% to 6 wt.% of at least one catalyst, wherein wt.% is based on the total weight of the isocyanate reactive system. All individual values ​​and subranges from 0.5 wt.% to 6 wt.% of at least one catalyst are included; for example, at least one catalyst can be a lower limit of 0.5 wt.%, 1 wt.%, 2 wt.%, or 3 wt.% to an upper limit of 6 wt.%, 5 wt.%, or 4 wt.% of the total weight of the isocyanate reactive system.

[0028] For the various embodiments, at least one catalyst may be a blowing catalyst, a gelling catalyst, a trimerization catalyst, or a combination thereof. As used herein, blowing catalysts and gelling catalysts may be distinguished by their tendency to favor urea (foaming) reactions in the case of blowing catalysts or urethane (gelling) reactions in the case of gelling catalysts. Trimerization catalysts may be used to promote the reactivity of the foam formulation. For the various embodiments, the amount of any one of the at least one or more catalysts alone may be as low as 0.1 wt.% to 0.2 wt.% or less.

[0029] Examples of blowing catalysts (e.g., catalysts that may tend to favor the blowing reaction) include, but are not limited to, short-chain tertiary amines or oxygen-containing tertiary amines. For example, blowing catalysts include bis-(2-dimethylaminoethyl) ether; pentamethyldiethylenetriamine, triethylamine, tributylamine, N,N-dimethylaminopropylamine, dimethylethanolamine, N,N,N',N'-tetramethylethylenediamine, combinations thereof, and the like.

[0030] Examples of gelling catalysts (e.g., catalysts that may tend to favor the gelling reaction) include, but are not limited to, 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, such as tin (II) diacetate, tin (II) dioctoate, tin (II) diethylhexanoate, and tin (II) dilaurate, and dialkyltin (IV) salts of organic carboxylic acids, such as dibutyltin diacetate, dibutyltin dilaurate, dibutyltin maleate, and dioctyltin diacetate. Bismuth salts of organic carboxylic acids may also be used as gelling catalysts, such as bismuth octoate. Cyclic tertiary amines and / or long chain amines include dimethylbenzylamine, N,N,N',N'-tetramethylbutylene diamine, dimethylcyclohexylamine, triethylenediamine, and combinations thereof.

[0031] Examples of trimerization catalysts include tris(dialkylaminoalkyl)-s-hexahydrotriazines, such as 1,3,5-tris(N,N-dimethylaminopropyl)-s-hexahydrotriazine; [2,4,6-tris(dimethylaminomethyl)phenol]; N-(2-hydroxypropyl)-N-tri-methylammonium formate, 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 10 to 20 carbon atoms, and combinations thereof. Some commercially available trimerization catalysts include TMR, TMR-2 TMR-30, K 2097; K15, 41. 43 and 46, etc.

[0032] Embodiments of the present disclosure provide that the isocyanate reactive system further comprises 0.5 wt.% to 5 wt.% of at least one surfactant, wherein wt.% is based on the total weight of the isocyanate reactive system. All individual values ​​and subranges from 0.5 wt.% to 5 wt.% of at least one surfactant are included; for example, at least one surfactant can be a lower limit of 0.5 wt.%, 1 wt.%, 2 wt.%, or 2.5 wt.% to an upper limit of 5 wt.%, 4 wt.%, or 3.5 wt.% of the total weight of the isocyanate reactive system.

[0033] For various embodiments, examples of at least one surfactant include silicon-based compounds, organosiloxane-polyether copolymers, such as polydimethylsiloxane and polydimethylsiloxane-polyoxyalkylene block copolymers, such as polyether-modified polydimethylsiloxane, and combinations thereof. Examples of surfactants also include non-silicone-based organic surfactants, such as nonylphenol ethoxylates, VORASURF available from The Dow Chemical Company, TM 504. Silicone surfactants are commercially available and include those sold under trade names such as NIAX TM , such as NIAX TM L 6900 and NIAX TM L6988; DABCO TM ; and TEGOSTAB TM , such as TEGOSTAB TM B 8427 and TEGOSTAB TM B 8491 and so on.

[0034] One or more embodiments of the present disclosure provide that the composition for producing rigid PU foam may include one or more additional components. Different additional components and / or different amounts of additional components may be used for various applications. Examples of additional components include pigments, colorants, flame retardants, crosslinking agents, chain extenders, antioxidants, bioretardants, and combinations thereof.

[0035] For various embodiments, the isocyanate reactive systems disclosed herein have an average hydroxyl functionality of 3.3 to 3.7 and an average hydroxyl number of 300 mg KOH / g to 400 mg KOH / g. The average hydroxyl number can be determined as the number of milligrams of potassium hydroxide equivalent to the hydroxyl content in one gram of polyol or other hydroxyl compound according to a wet analysis method for the hydroxyl content of the polyol. The hydroxyl number can be represented by the following formula:

[0036]

[0037] Where 56.1 is the atomic weight of potassium hydroxide and 1000 is the number of milligrams in one gram of sample. The hydroxyl number of the isocyanate reactive system disclosed herein can be determined as the weighted sum of the corresponding hydroxyl numbers of the first polyether polyol, at least one second polyether polyol, the optional third polyether polyol, and all potential additives (including catalysts and surfactants) that exhibit hydroxyl numbers. All individual values ​​and subranges of average hydroxyl functionality from 3.3 to 3.7 and average hydroxyl numbers from 300 mg KOH / g to 400 mg KOH / g are included. For example, the average hydroxyl functionality can be a lower limit of 3.3, 3.35, or 3.4 to an upper limit of 3.7, 3.65, or 3.6; and the average hydroxyl number can be a lower limit of 300 mg KOH / g, 320 mg KOH / g, or 330 mg KOH / g to an upper limit of 400 mg KOH / g, 380 mg KOH / g, 370 mg KOH / g, or 360 mg KOH / g. In all cases, the isocyanate-reactive systems contained no formic acid.

[0038] For the various embodiments, ASTM D 1957 and ASTM E222-10 also describe methods for determining hydroxyl number as provided herein.

[0039] The composition for producing rigid PU foam also comprises an isocyanate component including at least one polyisocyanate. As used herein, "polyisocyanate" refers to molecules having an average of greater than 1.0 isocyanate groups per molecule, such as an average functionality greater than 1.0.

[0040] For example, the isocyanate component can be an aliphatic polyisocyanate, a cycloaliphatic polyisocyanate, an aromatic aliphatic polyisocyanate, an aromatic polyisocyanate, or a combination thereof. Examples of isocyanates include, but are not limited to, toluene 2,4- / 2,6-diisocyanate (TDI), methylene diphenyl diisocyanate (MDI), polymeric MDI, triisocyanato nonane (TIN), naphthyl diisocyanate (NDI), 4,4'-diisocyanato dicyclohexylmethane, 3-isocyanatomethyl-3,3,5-trimethylcyclohexyl isocyanate (isophorone diisocyanate IIPDI), tetramethylene diisocyanate, hexamethylene diisocyanate (HDI), 2-methylpent ... Isocyanate, 2,2,4-trimethylhexamethylene diisocyanate (THDI), dodecanedimethylene diisocyanate, 1,4-diisocyanatocyclohexane, 4,4'-diisocyanato-3,3'-dimethyldicyclohexylmethane, 4,4'-diisocyanato-2,2-dicyclohexylpropane, 3-isocyanatomethyl-1-methyl-1-isocyanatocyclohexane (MCI), 1,3-diisooctylcyanato-4-methylcyclohexane, 1,3-diisocyanato-2-methylcyclohexane and combinations thereof, etc. In addition to the isocyanates mentioned above, partially modified polyisocyanates including uretdione, isocyanurate, carbodiimide, uretonimine, allophanate or biuret structure and combinations thereof, etc. can be used.

[0041] The isocyanate component may be polymeric. As used herein, when describing an isocyanate component, "polymeric" refers to homologues and / or isomers having higher molecular weights. For example, polymeric methylene diphenyl isocyanate refers to higher molecular weight homologues and / or isomers of methylene diphenyl isocyanate.

[0042] As mentioned, the isocyanate component can have an average functionality of greater than 1.0 isocyanate group / molecule. For example, the isocyanate component can have an average functionality of 1.75 to 3.50. All individual values ​​and subranges from 1.75 to 3.50 are included; for example, the isocyanate component can have an average functionality from a lower limit of 1.75, 1.85, or 1.95 to an upper limit of 3.50, 3.40, or 3.30.

[0043] The isocyanate component may have an isocyanate equivalent weight of 80 g / eq to 300 g / eq. All individual values ​​and subranges from 80 g / eq to 300 g / eq are included; for example, the isocyanate component may have an isocyanate equivalent weight of 80 g / eq, 90 g / eq, 100 g / eq, 125 g / eq, 135 g / eq, or 145 g / eq to an upper limit of 300 g / eq, 290 g / eq, or 280 g / eq.

[0044] The isocyanate component can be prepared by known methods. For example, the polyisocyanate can be prepared by phosgenating the corresponding polyamine and forming a polycarbamoyl chloride and thermally decomposing it to provide a polyisocyanate and hydrogen chloride or by a phosgene-free method, such as by reacting the corresponding polyamine with urea and an alcohol to obtain a polycarbamate and thermally decomposing it to obtain a polyisocyanate and an alcohol.

[0045] Isocyanate components are commercially available. Examples of commercial isocyanates include, but are not limited to, The product name is VORANATE TM , such as VORANATE TM M 220 and PAPI TM , such as PAPI TM 27 polyisocyanates, and other commercial isocyanates.

[0046] The isocyanate component may be utilized such that the isocyanate index used to produce the rigid PU foam composition is in the range of 100 to 150. The isocyanate index may be determined as the quotient of the actual amount of isocyanate utilized and the theoretical amount of isocyanate required to completely react all active hydrogen groups present in the isocyanate-reactive system, multiplied by one hundred. All individual values ​​and subranges from 100 to 150 are included; for example, the foam formulation may have an isocyanate index of a lower limit of 100, 110, or 120 to an upper limit of 150, 140, or 130.

[0047] The composition for producing the rigid PU foam disclosed herein can be cured to form a PU foam having a viscosity greater than 30 kg / m 3 As used herein, the core density of the PU foam is determined by the middle inner portion of the molded foam as its mass per unit volume. The foam core density is generally lower than the apparent density calculated by dividing the foam mass by its total volume due to the density variation from the epidermis to the core in the molded foam. Rigid PU foam can be prepared using known methods and conditions, which can vary for different applications. One or more embodiments of the present disclosure provide a method for forming a foam product. For various embodiments, a composition for producing a rigid PU foam is applied to a water heater. The method includes curing the foam formulation disclosed herein. The method can utilize known equipment and conditions, such as a one shot process, etc.

[0048] The foam products disclosed herein may be closed-cell foams. As used herein, "closed-cell foam" refers to foams having an open cell volume percentage of less than or equal to 10%. The foam product may have an open cell volume percentage of 1 volume percent to 10 volume percent. All individual values ​​and subranges from 1 volume percent to 10 volume percent are included; for example, the foam product may have an open cell volume percentage of 1 volume percent, 2 volume percent, 3 volume percent, 4 volume percent, or 5 volume percent to an upper limit of 10 volume percent, 9 volume percent, or 8 volume percent. The open cell content is measured according to ASTM D-6226 using a pycnometer such as the AccuPyc 1330 from Micromeretics (Norcross, Georgia), which is equipped with a FoamPyc option for calculating the open cell content.

[0049] For various embodiments, the isocyanate component and the isocyanate reactive system are reacted to produce a rigid PU foam having an average crosslink molecular weight in the range of 420 g / mole to 500 g / mole. The average crosslink molecular weight can be determined as further discussed herein. All individual values ​​and subranges from 420 to 500 are included; for example, the rigid PU foam can have an average crosslink molecular weight of 420, 430, 435, or 440 at a lower limit to 500, 490, 480, 470, or 460 at an upper limit.

[0050] The average crosslink molecular weight is the number average molecular weight per crosslink and is determined using the following formula:

[0051]

[0052] Where Mc is the average cross-link molecular weight; W POL W is the combined weight of the polyols used to form the foam; ISO,STOICH is the weight of the stoichiometric amount of isocyanate in grams; W ISO,EXC is the weight of isocyanate in excess of the stoichiometric amount of isocyanate; F ISO is the number average functionality of isocyanate; F POL is the number average functionality of the polyol used; E ISO is the equivalent weight of isocyanate; and E POL is the equivalent weight of the polyol used. The value of the average cross-link molecular weight provides an idea of ​​the degree of branching of the polymer. The higher the average cross-link molecular weight, the lower the cross-link density.

[0053] As mentioned, the rigid PU foams disclosed herein may have one or more advantageous properties compared to foams prepared from other formulations. For example, the rigid PU foams disclosed herein may have advantageously improved, i.e., reduced surface defects, good foam handling compared to foams formed from other less preferred formulations. Reduced surface defects may be desirable for many applications. As will be apparent to one skilled in the art, one example of such an application is a water heater foamed using a molding process, wherein the PU reaction mixture is injected directly against the stripper. The produced bare PU foam must have excellent aesthetics with very few or no surface bubbles or defects, in addition to having good foam flow and fast curing characteristics.

[0054] The rigid PU foam disclosed herein also exhibits advantageously improved thermal insulation properties, especially in long-term use. After aging for 50 days at room temperature, the thermal conductivity of the rigid PU foam disclosed herein is not higher than 25 mW / mK, preferably not higher than 24 mW / mK, and even more preferably not higher than 23.5 mW / mK.

[0055] Example

[0056] In the Examples (Ex) and Comparative Examples (CE), various material terms and names are used, including, for example, the following: VORANOL TM RN 482 (sorbitol-initiated propoxylated polyol; average functionality 6.0; equivalent weight 117 g / mol; hydroxyl number 477 mg KOH / g; obtained from The Dow Chemical Company); VORANOL TM CP 1055 (aliphatic polyether polyol; average functionality 3.0; equivalent weight 360 g / mol; hydroxyl number 156 mg KOH / g; obtained from The Dow Chemical Company); VORANOL TM P1010 (diol; aliphatic polyether diol; average functionality of 2.0; equivalent weight of 510 g / mol; hydroxyl number of 110 mg KOH / g; obtained from The Dow Chemical Company); VORANOL TM CP 450 (aliphatic polyether polyol; average functionality 3.0; equivalent weight 148 g / mol; hydroxyl number 383 mg KOH / g; obtained from The Dow Chemical Company); VORANOL TM CP 260 (aliphatic polyether polyol; average functionality 3.0; equivalent weight 85 g / mol; hydroxyl number 662 mg KOH / g; obtained from The Dow Chemical Company); VORANOL TMRH 360 (aliphatic polyether polyol; average functionality 4.6; equivalent weight 156 g / mol; hydroxyl number 360 mg KOH / g; obtained from The Dow Chemical Company); dimethylcyclohexylamine [DMCHA] (gelling catalyst; obtained from BordsoChem); pentamethyldiethylenetriamine [PMDETA] (blowing catalyst; obtained from Evonik); dimethylbenzylamine [DMBA] (gelling catalyst; obtained from Evonik TM get); TMR-2 (trimerization catalyst, from EVONIK TM Acquired); NIAX TM L-6988 (silicone surfactant; obtained from Momentive Performance Materials); TEGOSTAB TM B 8491 (Silicon surfactant; from EVONIK TM Acquired); NIAX TM L 6900 (surfactant; from MOMENTIVE TM obtained); deionized (DI) water (chemical blowing agent); formic acid (chemical blowing agent, obtained from get); LBA (trans-1-chloro-3,3,3-trifluoropropene; physical blowing agent; obtained from Honeywell International Inc.); 1100 (1,1,1,4,4,4-hexafluoro-2-butene); physical blowing agent; obtained from Chemours Company FC, LLC); VORANATE TM M 220 (isocyanate; polymeric MDI; wt.% of NCO = 31.4%, average functionality of NCO groups 2.7, obtained from The Dow Chemical Company).

[0057] Experimental Procedure

[0058] Ex and CE foam samples and molded panels were prepared using an A40 high pressure (HP) injection machine and a dispensing device from Cannon Afros (Cannon SpA, Italy) equipped with a FPL-14 L-shaped mixing head (Cannon SpA, Italy). The molded panels were prepared using a Brett mold with dimensions of 200 cm×20 cm×5 cm, a Super Brett mold with dimensions of 200 cm×20 cm×10 cm, or a Jumbo mold with dimensions of 70 cm×40 cm×10 cm. For all foam sample preparations, the process conditions remained the same as follows, polyol and isocyanate mixing pressure: 150 bar; temperature: 20°C to 22°C; output rate: 200 g / sec. Physical property tests were performed on foams prepared with a standard Brett mold at a mold temperature of 40°C and overfilling of 10% and 15% over the minimum packing density (MFD) of the Brett mold. De-mold swell measurements were made from panels produced with the Jumbo mold at a mold temperature of 40°C and an overfill of 10% above Brett's MFD.

[0059] Cream time was observed visually. Gel time was assessed by periodically touching the surface of the curing reaction mixture with a wooden tongue depressor. Gel time is the time after the polyisocyanate and formulated polyol composition are mixed when a string begins to form when the wooden tongue depressor is pulled apart. Tack-free time is the time when the surface of the foam is no longer tacky to the touch. Free rise density (FRD) was measured according to ASTM D 6226.

[0060] Samples of molded foam removed from the Brett mold are used to measure various foam properties: minimum fill density (MFD), average density distribution (ADD), compressive strength (CS), dimensional stability (DS), and thermal conductivity (also called lambda or k-factor). MFD is the density determined by the minimum weight required to completely fill the mold cavity and the volume of that cavity. MFD is expressed in kg / m 3 The average density deviation (ADD) is calculated as follows:

[0061]

[0062] Where: 17 is the number of samples taken from the entire length of the Brett panel, d is the average density, and di is the density of the i-th sample. The compressive strength is measured according to EN 826. The test is carried out on 10cm×10cm×5cm specimens, which are cut from the Brett panel in the direction perpendicular to the rise along the thickness direction of the foam. The thermal conductivity is measured according to EN 12667 using a Lasercomp Fox 200 equipment. The test is carried out on 20cm×20cm×2.5cm specimens, which are cut from the same position from all Ex and CE Brett molded panels. Dimensional stability (DS) tests are carried out according to EN 1604 standard. Specimens with dimensions of 9cm×9cm×3.5cm are tested under dry heat aging conditions: 80°C for 1 day. The results are reported as % linear change in three spatial directions: width, length and thickness.

[0063] Aesthetic / defect evaluations were performed at room temperature on foam panels prepared from Super Brett molds. This condition was chosen to more closely simulate actual foam making conditions used by water heater manufacturers. Polyurethane foams up to 75 mm thick are sometimes molded for use in water heaters, and more defects tend to be evident at thicker molded foams. All bubbles visually identified on the surface were marked on the foam 30 minutes after demolding. Quantitative analysis of defect formation was performed by manually counting the number of bubbles greater than 3 mm in diameter. The average value for the front and back of each panel was recorded.

[0064] The thermal conductivity of molded PU foams aged for a long time at room temperature was also measured. A smaller decrease in thermal conductivity over time is highly desirable for better energy efficiency during long-term use.

[0065] Ex and CE are described in Table 1. Details of the foam processing and resulting foam properties of Ex and CE are summarized in Tables 2 and 3.

[0066] Ex 1 presents The foam formulation of the invention with 1100 as a physical blowing agent. This formulation shows excellent shelf stability even in the absence of formic acid. The average hydroxyl functionality of the polyol used in Ex 1 is 3.6, the average hydroxyl number is 356, and the average molecular weight per crosslink is 439 g / mol.

[0067] Ex 2 shows a foam formulation with an even lower amount of high functionality polyether polyol and an increased amount of low functionality polyether polyol than Ex 1. The polyols in Ex 2 have an average hydroxyl functionality of 3.4, an average hydroxyl number of 356, and an average molecular weight per crosslink of 468 g / mol.

[0068] Ex 3 shows another foam formulation of the present invention including a third polyether polyol with a relatively high functionality of 4.6. The average hydroxyl functionality of the polyol used in Ex 3 is 3.5, and the average molecular weight per crosslink is 450 g / mol. Both values ​​are between Ex 1 and Ex 2.

[0069] Ex 4 shows a foam formulation according to the invention having an average hydroxyl functionality of 3.4 and a molecular weight per crosslink of 489 g / mol.

[0070] CE A shows the Comparative foam formulation with LBA as physical blowing agent. Compared with Ex1, this formulation contains a large amount of high functionality polyether polyols and a relatively small amount of low functionality polyether polyols (diols and triols). The average hydroxyl functionality of the polyols used in CE A is 4.2, and the average molecular weight per crosslink is 403 g / mol. In addition, formic acid is used even in relatively low amounts to provide shelf stability of the fully formulated polyol blend.

[0071] CE B shows a comparative foam formulation similar to that of CE A, but using 1100 as a physical foaming agent. 1100 and The higher molecular weight of LBA therefore requires slightly more water to maintain a comparable free rise density.

[0072] CE C shows a comparative foam formulation similar to that of CE B, but without the use of formic acid. A slightly larger amount of water is used to maintain a comparable free rise density. The amount of catalyst is also adjusted to maintain a similar reactivity profile.

[0073] CE D shows a comparative foam formulation similar to that of Ex 1, but using LBA was used as a physical blowing agent. No formic acid was used. CE D showed poor shelf stability, which is not commercially useful.

[0074] Table 1 - Ex and CE preparations .

[0075]

[0076]

[0077] Table 2: High pressure foam evaluation results

[0078]

[0079]

[0080] +Improved; ++Much improved; +++Very much improved; = / +Equals slightly improved

[0081] Table 3: Thermal conductivity of foam after aging for different times at room temperature: measured at 24°C (mW / mK)

[0082] sky CE A Ex 1 1 21.4 21.4 22 24 22.1 50 25.5 22.9 78 26.0 24.1 106 27.0 25.3 134 27.3 25.5 162 27.6 26.1 190 28.2 26.5

[0083] The results in Tables 2 and 3, as well as the aesthetic analysis, show that the fully formulated formulations of the present disclosure are significantly superior to existing foam systems for making rigid polyurethane foams. Excellent foam properties are achieved in terms of improved insulation in long-term use, good mechanical properties at lower foam densities, and significantly reduced foam surface defects.

Claims

1. A composition for producing a rigid polyurethane foam, the composition comprising: an isocyanate component comprising at least one polyisocyanate; and An isocyanate-reactive system, the isocyanate-reactive system comprising: 5 to 30 weight percent (wt.%) of a first polyether polyol having an average hydroxyl number of 100 to 600 mg KOH / g and an average hydroxyl functionality of 5.5 to 8; 45 wt.% to 75 wt.% of at least one second polyether polyol having an average hydroxyl number of 75 mg KOH / g to 800 mg KOH / g and an average hydroxyl functionality of 2 to 3.2; 1 wt.% to 20 wt.% of a hydrofluoroolefin physical blowing agent; 1 wt.% to 5 wt.% of a chemical blowing agent comprising water; 0.5 wt.% to 5 wt.% of at least one surfactant; and 0.5 wt.% to 6 wt.% of at least one catalyst, wherein the wt. % is based on the total weight of the isocyanate-reactive system, wherein the wt. % of the first polyether polyol, the at least one second polyether polyol, the hydrofluoroolefin physical blowing agent, the chemical blowing agent, the at least one surfactant, and the at least one catalyst total 100 wt. %, and wherein the isocyanate-reactive system has an average hydroxyl functionality of 3.3 to 3.7, an average hydroxyl number of 300 to 400 mg KOH / g, and is free of formic acid.

2. The composition of claim 1, wherein the isocyanate-reactive system comprises 5 to 15 wt.% of a third polyether polyol having an average hydroxyl number of 100 to 750 mg KOH / g and an average hydroxyl functionality of greater than 3.2 to 5; wherein the wt.% of the first polyether polyol, the at least one second polyether polyol, the third polyether polyol, the hydrofluoroolefin physical blowing agent, the chemical blowing agent, the at least one surfactant and the at least one catalyst total 100 wt.%.

3. The composition of any one of claims 1 or 2, wherein the first polyether polyol is 5 wt.% to 25 wt.% of the isocyanate reactive system and the at least one second polyether polyol is 50 wt.% to 72 wt.% of the isocyanate reactive system.

4. The composition of any one of claims 1, 2 or 3, wherein the at least one second polyether polyol comprises at least one glycerol initiated polyether polyol having a number average molecular weight in the range of 150 g / mol to 1500 g / mol.

5. The composition of any one of claims 1 to 3 or 4, wherein the at least one second polyether polyol comprises 5 wt.% to 20 wt.% of a first glycerol initiated polyether polyol having a number average molecular weight of 800 g / mol to 1200 g / mol; 30 wt.% to 45 wt.% of a second glycerol initiated polyether polyol having a number average molecular weight of greater than 350 g / mol to 650 g / mol; and 10 wt.% to 25 wt.% of a third glycerol initiated polyether polyol having a number average molecular weight of 150 g / mol to 350 g / mol, wherein the wt.% values ​​of the first glycerol initiated polyether polyol, the second glycerol initiated polyether polyol, and the third glycerol initiated polyether polyol provide 45 wt.% to 75 wt.% of the at least one second polyether polyol.

6. The composition according to any one of claims 1 to 5, wherein the hydrofluoroolefin physical blowing agent is 1,1,1,4,4,4-hexafluoro-2-butene.

7. The composition of any one of claims 1 to 6, wherein the isocyanate component and the isocyanate-reactive system react to produce a rigid polyurethane foam having an average crosslink molecular weight of 420 to 500 g / mole.

8. The composition according to any one of claims 1 to 7, wherein the composition has an isocyanate index of 100 to 150.

9. A rigid polyurethane foam prepared from the composition according to any one of claims 1 to 8, wherein the foam has a carbon content greater than 30 kg / m 3 core density.

10. The rigid polyurethane foam according to claim 9, wherein the foam is applied to a water heater.

Images