Rigid polyurethane foam formulations and methods of making fiber reinforced polyurethane foams suitable for low temperature applications

Abstract

A polyol composition suitable for making rigid polyurethane foams includes a combination of five polyols, a surfactant, and a polyurethane gelling catalyst. The polyol composition contains up to a very small amount of foaming catalyst. When reacted with a polyisocyanate in the presence of a physical blowing agent, the polyol composition surprisingly produces a polyurethane foam that exhibits little or no loss of compressive strength when overfilled. The polyol composition is particularly useful in the manufacture of fiber-reinforced rigid foams that can be used in low temperature applications.

Description

[0001] The present invention relates to polyol formulations useful for making rigid polyurethane foams and methods for making fiber-reinforced polyurethane foams, particularly those suitable for cryogenic applications such as liquefied natural gas (LNG) tanks.

[0002] As an alternative to pipelines, the use of which may be restricted by geography, political circumstances or other reasons, very large quantities of LNG are transported by sea. Natural gas is usually liquefied on shore and then fed into large tanks on board ships. Liquefaction requires temperatures of about -150°C or lower. Storage and transportation must also be carried out at these temperatures to prevent evaporation and large pressure increases in storage and handling equipment. This requires cryogenic equipment and robust thermal insulation.

[0003] Rigidity and structural integrity are important because of the weight involved and because the tank is subject to pressure generated by the momentum of the waves transferred to the tank, which creates undulations within the tank.

[0004] Rigid polyurethane foams are the material of choice for thermal insulation. These foams are also required to contribute to the rigidity and structural integrity of the tank. Therefore, the mechanical properties of the foam are very important; therefore, the foam is often fiber reinforced to further enhance the mechanical properties.

[0005] These fiber-reinforced rigid polyurethane foams are conveniently prepared in a continuous process in which a fiber mat is laid out on a moving platform and a foam precursor fluid is applied to the fiber mat. The foam precursor fluid must penetrate through the fiber mat as it expands and solidifies to form the foam. Viscosity is important because if the foam precursor fluid is too viscous, it cannot adequately penetrate through the fibers. Poor penetration results in poor distribution of the fibers throughout the resulting foam, which adversely affects its physical and thermal properties.

[0006] The need to maximize mechanical properties such as compressive strength constrains the production process. Certain mechanical properties of the foam, such as compressive strength, tend to be maximized when the foam is produced under "free rise" conditions, i.e., the foam is allowed to expand without restriction in the vertical direction. The foam produced in this way does not have a sharp rectangular cross-section, because the top surface of the foam is curved. The foam thickness therefore varies from its edges to the middle. For this reason, the foam is subjected to a subsequent trimming step to produce a clean rectangular cross-section and a board with uniform dimensions. Trimming increases costs and also generates a large amount of waste, because oversized foam is produced and then cut to size.

[0007] Trimming can be avoided by limiting the vertical rise of the foam and "overpacking", that is, using a slight excess of foam precursor over the minimum amount required to produce a specific volume of foam. Unfortunately, when the foam itself is overpacked, the compressive strength of the foam is generally reduced. This phenomenon is generally attributed to foam cell anisotropy; the loss of compressive strength due to overpacking generally outweighs the advantages of eliminating the trimming step.

[0008] There is a need for a polyurethane foam formulation that, when overfilled, produces a foam without a significant loss in compressive strength compared to an otherwise similar foam that is not overfilled. There is also a need for a method for producing a fiber reinforced foam board that has good thermal insulation and good compressive strength properties and reduces or eliminates the need for trimming.

[0009] In a first aspect, the present invention is a polyol composition comprising:

[0010] a) a polyol comprising

[0011] P1: 15 to 30 wt. % of one or more non-amine initiated polyether polyols having a nominal functionality of 4 to 8 and a hydroxyl number of 300 to 600 mg KOH / g, based on the weight of all polyols;

[0012] P2: 18 to 35 wt. % of one or more non-amine initiated polyether polyols having a nominal functionality of 3 and a hydroxyl number of 150 to 700 mg KOH / g, based on the weight of all polyols;

[0013] P3: 15 to 35 wt. % of one or more polyester polyols having a nominal functionality of 1.5 to 2.5 and a hydroxyl number of 150 to 300 mg KOH / g, based on the weight of all polyols;

[0014] P4: 2 to 8 wt. % of one or more amine-initiated polyether polyols having a nominal functionality of 3 to 8 and a hydroxyl number of 300 to 600 mg KOH / g, based on the weight of all polyols; and

[0015] P5: 10 to 25 wt. %, based on the weight of all polyols, of one or more diols having a nominal functionality of 2 and a hydroxyl number of at least 550 mg KOH / g;

[0016] wherein polyols P1 to P5 together account for at least 95% of the total weight of all polyols;

[0017] b) 0% to 0.2% by weight, based on the weight of the polyol composition, of water;

[0018] c) 0.1 to 2.5 wt % of a surfactant, based on the weight of the polyol composition

[0019] dose; and

[0020] d) a catalytically effective amount of a polyurethane gelling catalyst.

[0021] The polyol composition is particularly suitable for making fiber-reinforced polyurethane foam by reacting with polyisocyanates in the presence of physical blowing agents and reinforcing fibers. It has an ideal low viscosity and slow initial solidification. These attributes are conducive to good penetration of the foam precursor fluid into the fibers, which leads to good product uniformity and consistent properties. The foam produced in this way has good thermal insulation and compressive strength properties. It is very surprising that the formulation of the present invention produces a fiber-reinforced foam that retains its compressive strength even when overfilled. This behavior is unusual and unexpected. The ability to overfill allows the manufacture of fiber-reinforced polyurethanes of precise sizes with little or no need for trimming. This reduces waste and eliminates or reduces the cost of trimming.

[0022] The present invention is therefore also a polyurethane foam prepared in the presence of a physical blowing agent in the reaction of a polyol composition according to the first aspect of the invention with at least one polyisocyanate, wherein the reaction is carried out in the presence of not more than 0.2% by weight of water, based on the weight of the polyol composition, and not more than 0.1% by weight of a blowing catalyst, based on the weight of the polyol composition.

[0023] The present invention is also a method for producing polyurethane foam, which comprises reacting the polyol composition of the first aspect of the present invention with at least one polyisocyanate in the presence of a physical blowing agent, wherein the reaction is carried out in the presence of not more than 0.2 wt % of water based on the weight of the polyol composition and not more than 0.1 wt % of a blowing catalyst based on the weight of the polyol composition.

[0024] In yet another aspect, the present invention is a method for producing a fiber-reinforced polyurethane foam, the method comprising the steps of:

[0025] A) Distributing the Foam Precursor Fluid onto the Reinforcement Fiber Bed

[0026] as well as

[0027] B) curing the foam precursor fluid in the presence of reinforcing fibers to produce a fiber-reinforced polyurethane foam,

[0028] wherein the foam precursor fluid comprises at least one polyisocyanate, at least one physical blowing agent and a polyol composition, the polyol composition comprising

[0029] A polyol comprising

[0030] Polyol P1: 15 to 30 wt. % of one or more non-amine initiated polyether polyols having a nominal functionality of 4 to 8 and a hydroxyl number of 300 to 600 mg KOH / g, based on the weight of all polyols;

[0031] Polyol P2: 18 to 35 wt. % of one or more non-amine initiated polyether polyols having a nominal functionality of 3 and a hydroxyl number of 150 to 700 mg KOH / g, based on the weight of all polyols;

[0032] Polyol P3: 15 to 35 wt. % of one or more polyester polyols having a nominal functionality of 1.5 to 2.5 and a hydroxyl number of 150 to 300 mg KOH / g, based on the weight of all polyols;

[0033] Polyol P4: 2 to 8 wt % of one or more amine initiated polyether polyols having a nominal functionality of 4 to 8 and a hydroxyl number of 300 to 600 mg KOH / g, based on the weight of all polyols; and

[0034] Polyol P5: 10 to 25 wt. %, based on the weight of all polyols, of one or more diols having a nominal functionality of 2 and a hydroxyl number of at least 550 mg KOH / g;

[0035] wherein polyols P1 to P5 together account for at least 95% of the total weight of all polyols;

[0036] wherein the foam precursor fluid further comprises i) 0.1 wt % to 2.5 wt % of a surfactant based on the weight of the polyol composition, ii) a catalytically effective amount of a polyurethane gelling catalyst, and iii) 0 wt % to no more than 0.2 wt % of water based on the weight of the polyol composition.

[0037] The P1 polyol is one or more non-amine initiated polyether polyols having a nominal functionality of 4 to 8 and a hydroxyl value of 300 mgKOH / g to 600 mgKOH / g. The nominal functionality may be at least 5 or at least 6, and may be, for example, up to 8. In some embodiments, the hydroxyl value is up to 350 mgKOH / g, and in some embodiments up to 500 mgKOH / g. In some embodiments, the P1 polyol is an alkoxylate of an initiator compound having 4 to 8 hydroxyl groups. Examples of such initiator compounds include pentaerythritol, erythritol, and sugars such as sorbitol and sucrose having 4 to 8 hydroxyl groups. The initiator is alkoxylated by reaction with one or more alkylene oxides, preferably 1,2-propylene oxide, ethylene oxide, or a mixture of propylene oxide and ethylene oxide. Particularly preferred P1 polyols are propoxylates of sucrose, propoxylates of sorbitol, or mixtures thereof. The P1 polyols comprise at least 15% by weight of all polyols in the polyol mixture and comprise at most 30% by weight of all polyols. In a specific embodiment, the P1 polyols comprise at least 18% by weight of all polyols and may comprise at most 25% or at most 22% by weight of all polyols.

[0038] The P2 polyol is one or more non-amine initiated polyether polyols having a nominal functionality of 3 and a hydroxyl value of 150 mgKOH / g to 700 mgKOH / g. In some embodiments, the hydroxyl value is at least 225 mgKOH / g or at least 350 mgKOH / g. In some embodiments, the P2 polyol is an alkoxylate of an initiator compound having 3 hydroxyl groups. Examples of such initiator compounds include glycerol, trimethylolpropane, and trimethylolethane. The initiator is alkoxylated by reaction with one or more alkylene oxides, of which 1,2-propylene oxide, ethylene oxide, or a mixture of propylene oxide and ethylene oxide are preferred. Propoxylates of glycerol or trimethylolpropane are particularly preferred. The P2 polyol accounts for at least 18% by weight of all polyols in the polyol mixture, and accounts for up to 35% by weight of all polyols. In specific embodiments, the P2 polyols comprise at least 20 weight percent, at least 22 weight percent, or at least 25 weight percent of all polyols, and may comprise up to 32 weight percent or up to 30 weight percent of all polyols.

[0039] P3 polyols are one or more polyester polyols with a nominal functionality of 1.5 to 2.5 and a hydroxyl value of 150 mgKOH / g to 300 mgKOH / g. The nominal functionality is preferably 1.5 to 2.2. Polyester is preferably an aromatic polyester, such as can be produced in the reaction of an aromatic dicarboxylic acid (or their derivatives, such as corresponding anhydrides or alkyl diesters) with a diol or a diol / triol mixture. Examples of such diols and triols include ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, dipropylene glycol, glycerol, etc. P3 polyols account for at least 15% by weight of all polyols in a polyol mixture, and account for up to 35% by weight of all polyols. In a specific embodiment, P3 polyols account for at least 20% by weight, at least 22% by weight, or at least 25% by weight of all polyols, and can account for up to 32% by weight or up to 30% by weight of all polyols.

[0040] P4 polyols are amine-initiated polyols having a nominal functionality of 4 to 8 and a hydroxyl value of 300 mg KOH / g to 600 mg KOH / g. P4 polyols are alkoxylates of one or more amine compounds having at least 4 amine hydrogens. The amine compound is preferably aromatic, most preferably o-toluenediamine, p-toluenediamine, or a mixture of o-toluenediamine and p-toluenediamine. The amine compound is alkoxylated by reaction with one or more alkylene oxides, preferably 1,2-propylene oxide, ethylene oxide, or a mixture of propylene oxide and ethylene oxide. Toluenediamine, in particular propoxylates of o-toluenediamine, are particularly preferred. P4 polyols account for at least 2% by weight of all polyols in the polyol mixture, and account for up to 8% by weight of all polyols. In a specific embodiment, P4 polyols account for at least 4% by weight, at least 5% by weight, or at least 6% by weight of all polyols, and may account for up to 7.5% by weight or up to 7% by weight of all polyols.

[0041] P5 polyols are one or more diols with a nominal functionality of 2 and a hydroxyl value of at least 550 mgKOH / g. Examples of these diols include ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, dipropylene glycol and tripropylene glycol. Diethylene glycol or a mixture of diethylene glycol and tripropylene glycol is preferred. P5 polyols account for at least 10% by weight of all polyols in the polyol mixture, and account for up to 25% by weight of all polyols. In a specific embodiment, P5 polyols account for at least 12% by weight or at least 15% by weight of all polyols, and can account for up to 22% by weight or up to 20% by weight of all polyols.

[0042] The P1-P5 polyols together account for at least 95% of the total weight of all polyols. They may together account for at least 96%, at least 97% or at least 98% of the total weight of all polyols, and may account for up to 100% of the total weight of all polyols.

[0043] Water, if present, is present in an amount not exceeding 0.2% by weight of the total polyol composition.Preferred amounts are not exceeding 0.15% or not exceeding 0.125% by weight of the total polyol composition.

[0044] The surfactant may be, for example, a siloxane surfactant, such as a polyether-modified polydimethylsiloxane surfactant. The surfactant may be hydrolyzable or non-hydrolyzable. Useful siloxane surfactants are available under the trade name (Evonik), VORASURF TM (Dow, Inc.) or (Siltech Corporation). The surfactant is not included in the weight of the polyol. The polyol composition comprises 0.1 wt % to 2.5 wt % of the surfactant; preferably, the amount is 0.5 wt % to 2.0 wt % or 0.75 wt % to 1.5 wt %.

[0045] The polyol composition further comprises at least one gelling catalyst. For purposes of the present invention, a "gelling" catalyst is a catalyst that promotes the reaction of isocyanate groups to alcohol groups more strongly than it promotes the reaction of isocyanate groups to water molecules. The relative catalytic activity of a catalyst for isocyanate-alcohol reactions and isocyanate-water reactions can be determined using titration methods, such as van Maris et al., "Polyurethane Catalysis by Tertiary Amines", J. Cellular Plastics 41 (July 2005), pp. 305-322. The catalytic activity for isocyanate-alcohol reactions was evaluated at 30° C. by reacting 50 mL of a 0.1533 mol / L solution of 2,4-toluene diisocyanate in benzene with 50 mL of a 0.1533 mol / L solution of diethylene glycol in benzene in the presence of 5 ML of a 0.0735 mol / L solution of the catalyst in benzene. Samples were taken at different times and unreacted isocyanate was quenched with a solution of n-butylamine in benzene. The residual isocyanate content in each sample was determined by back titration with a standardized HCl solution. The NCO content of the sample was then used to calculate the isocyanate content in L 2 The catalytic activity for the isocyanate-alcohol reaction was evaluated in the same manner using a 0.0752 mol / L solution of water in benzene instead of the diethylene glycol solution. A "gelling" catalyst is one in which the ratio of foaming:gelling catalytic activity is <0.5. Preferred gelling catalysts are those in which the ratio is <0.2, and more preferred gelling catalysts are those in which the ratio is <0.1 or <0.05.

[0046] Examples of gelling catalysts include fully methylated alkylenediamines, diethylenetriamine, imidazoles, metal-containing catalysts such as tin carboxylates, zinc carboxylates and bismuth carboxylates, particularly tin (IV) catalysts such as dimethyltin dilaurate, dibutyltin dilaurate, dimethyltin dioctoate, dibutyltin dioctoate, and tin (IV) thioglycolate having the structure R2Sn(Tg)2, wherein each R is independently a C1-10 alkyl group and each Tg is independently a thioglycolate group of the form R'OOC-CH2-S-, wherein R' is a C1-10 alkyl group.

[0047] Specific examples of gelling catalysts include:

[0048] catalyst Foaming: gelling catalytic activity ratio Tetramethylhexamethylenediamine 0.285 Tetramethylethylenediamine 0.227 Triethylenediamine; 0.134 Dimethylaminoethanol 0.123 1,2-Dimethylimidazole 0.077 Tosoh F22 Catalyst 0.032 Dibutyltin dilaurate 0.030

[0049] The polyol composition preferably contains at most 0.1 wt % of a blowing catalyst, based on the total weight of the polyol composition. A "blowing" catalyst for the purposes of the present invention is a catalyst that exhibits a ratio of foaming: gelling catalytic activity of 0.5 or greater, as measured by the titration method described above. The polyol composition preferably contains at most 0.05 wt % of a blowing catalyst, more preferably at most 0.025 wt % of a blowing catalyst. The polyol composition may be completely free of a blowing catalyst.

[0050] For the purposes of this invention, the P4 polyol is not considered to be a blowing or gelling catalyst, although it may exhibit catalytic activity due to the presence of tertiary amino groups.

[0051] In preferred embodiments, the gelling catalyst exhibits a blowing:gelling catalytic activity ratio of less than 0.2 and the polyol composition comprises no more than 0.1 wt%, no more than 0.05 wt%, or no more than 0.025 wt% of a catalyst exhibiting a blowing:gelling catalytic activity ratio of 0.2 or greater.

[0052] The polyol composition is generally useful for preparing rigid polyurethane foams by reaction with a polyisocyanate in the presence of a physical (endothermic) blowing agent. Methods for making such rigid polyurethane foams are well known in the art.

[0053] Physical blowing agents are one or more compounds having a boiling point (at 1 atmosphere) of 10°C to 80°C, preferably 10°C to 50°C, and containing no hydroxyl groups, primary and / or secondary amines, thiols, carboxyl groups or other groups other than halogen groups reactive with isocyanate groups under the curing reaction conditions. Useful physical blowing agents include hydrocarbons, hydrofluorocarbons, hydrochlorocarbons, hydrofluorochlorocarbons, ethers, etc. having the above-mentioned boiling points. Also useful are hydrofluoroolefins and hydrofluorochloroolefins, such as described, for example, in US 2007 / 0100010. Specific examples are trifluoropropylene, 1,3,3,3-tetrafluoropropylene (1234ze), 1,1,3,3-tetrafluoropropylene, 2,2,3,3-tetrafluoropropylene (1234yf), 1,2,3,3,3-pentafluoropropylene (1225ye), 1,1,1-trifluoropropylene, 1,1,1,3,3-pentafluoropropylene (1225zc), 1,1,2,3,3-pentafluoropropylene (1225yc), (Z)-1,1,1,2,3-pentafluoropropylene (1225yez), 1-chloro-3,3,3-trifluoropropylene (1233zd) and 1,1,1,4,4,4-hexafluorobut-2-ene (1336mzzm). Any mixture of two or more physical blowing agents may be used.

[0054] The physical blowing agent may be present, for example, in an amount of at least 12 parts by weight per 100 parts by weight of the polyol. The amount of the physical blowing agent may be, for example, at least 12, at least 14, or at least 15 parts by weight, and again, may be, for example, up to 25 parts, up to 22 parts, up to 20 parts, or up to 18 parts by weight.

[0055] Suitable organic polyisocyanates for use in the present invention include aliphatic, cycloaliphatic, araliphatic or aromatic polyisocyanates, or combinations of any two or more thereof. Aromatic polyisocyanates are generally preferred. Preferred aromatic diisocyanates and polyisocyanates are 2,4-toluene diisocyanate and 2,6-toluene diisocyanate and the corresponding isomer mixtures, 4,4'-diphenylmethane diisocyanate, 2,4'-diphenylmethane diisocyanate and 2,2'-diphenylmethane diisocyanate and the corresponding isomer mixtures, mixtures of 4,4'-diphenylmethane diisocyanate and 2,4'-diphenylmethane diisocyanate, polyphenyl polymethylene polyisocyanates, mixtures of 4,4'-diphenylmethane diisocyanate, 2,4'-diphenylmethane diisocyanate and / or 2,2'-diphenylmethane diisocyanate with polyphenyl polymethylene polyisocyanates (commonly referred to in the art as "polymeric MDI"), and mixtures of polymeric MDI and toluene diisocyanate. Modified polyisocyanates, i.e., products obtained by chemical reaction of organic diisocyanates and / or polyisocyanates, can also be used. Specific examples are diisocyanates and / or polyisocyanates containing esters, ureas, biuret, allophanates, uretonimines, carbodiimides, isocyanurates, uretdiones and / or carbamates, which contain 33.6 wt % to 15 wt %, preferably 31 wt % to 21 wt % isocyanate groups by the gross weight of modified polyisocyanates. Organic polyisocyanates can be used alone or in combination. Particularly preferred isocyanate functionality is 2.2 to 3.3, particularly 2.5 to 3.0, and isocyanate equivalent is 130 to 140 polymerized MDI.

[0056] The polyol composition is particularly useful for making fiber-reinforced polyurethane foams. Such fiber-reinforced foams are conveniently prepared in a method comprising the following steps:

[0057] A) dispensing a foam precursor fluid onto a bed of reinforcing fibers, and B) curing the foam precursor fluid in the presence of the reinforcing fibers to produce a fiber reinforced polyurethane foam, wherein the foam precursor fluid comprises at least one polyisocyanate, at least one physical blowing agent and a polyol composition of the present invention.

[0058] The reinforcing fibers are conveniently provided in the form of a continuous or discontinuous fiber mat, which is held together mechanically (e.g., by needling, entanglement or other means) or by a small amount of adhesive. Particularly preferred mats include randomly oriented continuous filaments and do not contain adhesive. The fibers are preferably glass fibers, but may also be other fibers, such as mineral wool, carbon fibers, synthetic organic polymer fibers, natural fibers (such as cotton, wool, silk, etc.), metal fibers, etc.

[0059] The fiber mat may have a 225 g / m 2 Up to 900g / m2 weight.

[0060] The fibers are deposited on a support. In a preferred continuous process, the support is moving and the fibers are continuously deposited on the moving support. The preferred fiber mat is conveniently fed from a roll onto the moving support. In a particularly preferred embodiment, the moving support is the lower belt of a double belt laminator.

[0061] Sufficient fibers are deposited to provide a fiber content of preferably 5 to 25 wt % or 5 to 15 wt % in the resulting fiber reinforced polyurethane foam.Multiple fiber mat layers may be stacked if necessary to provide the desired fiber content.

[0062] The facing layer may be laid on the support before depositing the fibers.

[0063] The foam precursor fluid is then distributed to the fiber bed via a distribution device. Spraying and pouring methods are generally suitable. The foam precursor fluid can be distributed to the fiber bed via a distributor device, which applies the foam precursor fluid in the form of multiple streams across the lateral width of the fiber bed. Examples of such distributor devices are described in, for example, EP2125323A, EP2234732A, WO 2021 / 045888, WO 2021 / 046019, WO 2021 / 046020, WO 2021 / 046021, and WO2012 / 046022. As the foam precursor fluid solidifies, the multiple streams expand and merge. In a preferred embodiment, the fixed distribution device continuously distributes the foam precursor fluid to the fiber bed as the fiber bed is transported through the distribution device on a moving platform.

[0064] The foam precursor fluid penetrates through the fiber bed and expands and cures to produce a polyurethane foam having reinforcing fibers embedded therein. An advantage of the polyol composition of the present invention is that it reacts somewhat slowly, at least in the early stages of curing, so it does not build up viscosity quickly and therefore has time to penetrate between the fibers of the fiber bed. This results in a more even distribution of the fibers in the product and reduces defects such as dry spots and areas without fibers.

[0065] The curing conditions are selected so that the blowing agent volatilizes and the reactive components of the foam precursor fluid react to produce a polymer foam. The conditions typically include a temperature above the boiling point of the physical blowing agent at the pressure employed. The curing reaction is exothermic, and the heat of reaction released is typically sufficient in itself to volatilize the physical blowing agent to produce a gas that expands the foam. Therefore, no special conditions are required to promote curing. The foam precursor fluid can be prepared by combining the ingredients at about room temperature (e.g., 15° C. to 30° C.), applying the foam precursor fluid to a fiber bed so that it penetrates through the fiber bed, and then allowing the foam precursor to react spontaneously without additional application of heat. Sometimes it is advantageous to accelerate curing by applying heat to the foam precursor fluid before and / or after dispensing the foam precursor fluid onto the fiber bed. This can be done, for example, by heating one or more components of the foam precursor fluid before combining them; or by heating the fiber bed after the foam precursor fluid has been dispensed onto the fiber bed. In some embodiments, the moving platform carrying the fiber bed is heated; alternatively or additionally, the upper surface of the vertical rise that limits the curing step of the foam curing can be heated to provide heat to accelerate the curing. If heated, it can be heated to a temperature of, for example, 35°C to 100°C, especially 35°C to 50°C.

[0066] In some embodiments, the foam precursor fluid is allowed to expand vertically without restriction. However, the advantages of the present invention can be seen when the vertical rise is restricted, especially when the vertical rise is restricted to a height less than the height that the foam precursor fluid would rise without restriction. This results in overfilling. Unlike other foam systems, it has been found that when the foam is overfilled, for example, from 1 wt % to 15 wt % or from 3 wt % to 10 wt %, no loss in compressive strength or a decrease in loss in compressive strength is observed. The amount of overfill is calculated as follows:

[0067]

[0068] The density 泡沫 is the density of the polyurethane foam (excluding the weight of the reinforcing fibers), and the minimum fill density is the density of the foam (again, excluding the weight of the reinforcing fibers) that rises to the same height in the same process, except under free rise conditions, i.e., without vertical restraint. Equivalently, the % overfill can be calculated as 100% multiplied by the ratio of the weight of foam per unit area at a particular vertical height to the weight per unit area of ​​foam that rises to the same height in the same process (except under free rise conditions). Foam density is conventionally measured according to ASTM D 1622.

[0069] Conveniently mechanically, i.e. by placing a physical barrier that limits further vertical rise, the vertical rise of the foam is limited. In some embodiments, the vertical expansion of the foam precursor fluid is limited by the upper belt of the double belt laminator. In this embodiment, the upper and lower belts of the double belt laminator are adjusted to provide a gap between them. The gap defines the thickness of the product. The gap is selected so that the foam is overfilled, i.e., the gap is less than the height that the foam will rise if it is not restricted. The foam precursor fluid expands and rises as it solidifies, and is limited by the belt of the double belt laminator in its vertical rise, preferably over its entire width, resulting in overfilling, a flat top surface and a rectangular cross-section. The lateral expansion of the foam precursor fluid can also be limited, for example, by enclosing the fiber bed and the foam precursor fluid in the side walls.

[0070] Suitable methods for preparing foams are described in WO 2020 / 193874. The method of WO 2020 / 193874 also includes the use of lateral side walls to limit the lateral expansion of the foam precursor fluid.

[0071] When the vertical rise of the foam is restrained, the restraint should remain in place until the foam has cured sufficiently to have a stable vertical dimension.

[0072] If desired, an upper facing layer may be placed on top of the fiber bed with the dispensed foam precursor fluid to produce a top facing layer adhered to the top surface of the fiber reinforced polyurethane foam.

[0073] Examples of facing layers include paper, plywood, decorative films, metal foils and sheets, especially aluminum foils and steel sheets, etc. In a preferred embodiment, the facing layer is paper.

[0074] The invention is particularly suitable for making thermal insulation panels for cryogenic applications, and more particularly for making thermal insulation panels for liquefied natural gas or other liquefied gas storage tanks. These foams may have a thickness of, for example, 200 mm to 500 mm, which tends to distinguish them from more general laminates. Fiber reinforced polyurethane foams useful in these applications may have a density of 80 kg / m 3 Up to 150kg / m 3 The foam density is preferably 100 to 200 mm. Such a density provides a good balance of thermal insulation and mechanical strength (particularly compressive strength). Such foams can be produced in widths of 100 mm to 5 meters, particularly 300 mm to 2.5 meters or 500 mm to 2 meters. In a preferred embodiment, the width is 800 mm to 1200 mm.

[0075] The method of the present invention can, and preferably does, include one or more downstream steps, such as cutting the fiber reinforced polyurethane foam into desired lengths, cooling the foam from the curing temperature, stacking the foam, and wrapping the foam or otherwise preparing them for shipping or storage.

[0076] The following examples are provided to illustrate the present invention but are not intended to limit the scope of the present invention. Unless otherwise indicated, all parts and percentages are by weight.

[0077] Polyol A is a propoxylate of sorbitol having a functionality of 6 and a hydroxyl number of 477 mg KOH / g (118 Da equivalent). This is the P1 polyol.

[0078] Polyol B is a propoxylated mixture of sucrose and glycerol. Its hydroxyl number is 360 mg KOH / g (156 Da equivalent). Polyol 2 contains about 58% by weight of octafunctional substances (P1 polyol) and 42% by weight of trifunctional substances (P2 polyol).

[0079] Polyol C is propoxylated glycerol. Its hydroxyl number is 665 mg KOH / g (83 Da equivalent) and its functionality is 3. This is a P2 polyol.

[0080] Polyol D is propoxylated glycerol. Its hydroxyl number is 378 mg KOH / g (156 Da equivalent) and its functionality is 3. This is a P2 polyol.

[0081] Polyol E is propoxylated glycerol. Its hydroxyl number is 239 mg KOH / g (235 Da equivalent) and its functionality is 3. This is a P2 polyol.

[0082] Polyol F is an aromatic polyester polyol having a hydroxyl number of 240 mg KOH / g (234 Da equivalent) and a functionality of 2. Its viscosity is 2000 to 4500 cP at 25° C. as reported by the manufacturer. Polyol F is a P3 polyol.

[0083] AEP is a propoxylated o-toluenediamine having a hydroxyl number of 440 mg KOH / g (127.5 Da equivalent) and a functionality of 4. AEP is a P4 polyol.

[0084] DPG is dipropylene glycol, hydroxyl number 834 mg KOH / g (67 Da equivalent), functionality 2.0. It is a P5 polyol.

[0085] TPG is tripropylene glycol, hydroxyl number 584 mg KOH / g (96 Da equivalent), functionality 2.0. It is a P5 polyol.

[0086] DBTDL is dibutyltin dilaurate.

[0087] The polyisocyanate was polymeric MDI having an isocyanate functionality = 2.7, an isocyanate equivalent weight of 136 Da and containing 40% MDI monomer.

[0088] Example 1 and Comparative Samples A to C

[0089] The polyol system was prepared by mixing the ingredients listed in Table 1.

[0090] Table 1

[0091]

[0092]

[0093] *Not an embodiment of the present invention. 1 Combined weight of the sucrose initiated portion of Polyol A and Polyol B. 2 The combined weight of the glycerol initiated portion of Polyol B and Polyols C, D and E. 3 Combined weight of DPG and TPG.

[0094] Non-reinforced foam Example 1 and comparative samples A to C are prepared from a polyol system and A to C, respectively, as follows: a catalyst is mixed with TPG. The remaining ingredients of the polyol system are mixed separately to form a polyol composition. The two mixtures are combined with 7.2 parts by weight of 1,1,1,3,3-pentafluoropropane per 100 parts of the polyol composition to form a blend, and the blend is mixed with a polyisocyanate by a high pressure press at an index of 116.1 (iso / OH). The resulting reaction mixture is distributed on a 30cm×30cm×10cm parallelepiped mold, which is initiated and cured in the mold to produce a foam with a density of 125g / L. The results are represented in Table 2 as the case of "no fiber". The sample names correspond to those of the polyol system.

[0095] Fiber reinforced panels were produced from polyol systems 1 and A to B. Because the compressive strength of the non-reinforced foam prepared from polyol system C was so low, this formulation was not used to prepare fiber reinforced panels. The fiber reinforced panels were made in a double belt lamination process using paper as face stock on the bottom and top sides of the foam. The foam thickness was set to 300 mm and the nominal width was 1050 mm.

[0096] The bottom material is fed into the laminator. 6 continuous strand glass fiber mats (Unifilo U809, from Owens Corning) are stacked on the bottom material to provide a fiber concentration of about 10% by weight in the resulting composite board. The catalyst / TPG mixture, the remainder of the polyol system, a blowing agent (1,1,1,3,3-pentafluoropropane) and polyisocyanates (116.1 (iso / OH) index) are processed by a high pressure foam machine and cast on the stacked glass fiber mat and the bottom material in a continuous manner. The amount of the reaction mixture is selected so that it is free to rise when solidified to produce a thickness of 300mm and a density of about 125g / L of enhanced foam. The top material is continuously applied to the foaming reaction mixture. The assembly is passed between the heating belts of the double belt laminator, during which time the foaming reaction mixture expands and solidifies to form a laminate with a top material layer and a bottom material layer and an enhanced foam layer. This represents a "0% overfill" ("0% OP") condition because the vertical rise of the foam is not limited by the belts of the double belt laminator. The board has a curved top surface because it has not fully expanded to meet the surface of the top belt across the entire width of the board. Therefore, the board will require subsequent trimming to produce a uniform rectangular cross-section.

[0097] Additional reinforced foams were prepared in the same general manner, but with a reduced line speed. Reducing the line speed had the effect of increasing the amount of reactive mixture applied per unit area, which resulted in overfilling and slightly reducing the weight of the glass fiber mat per unit area. These two effects resulted in reinforced foams with overfilling ratios as high as 6%. The overfilled foam expanded completely to contact the upper belt across its entire width, resulting in a uniform rectangular cross-section that required no trimming.

[0098] The compressive strength of "no fiber" foam and 0% and 6% overfilled reinforced foam was measured according to EN 826. A total of 27 test samples were cut from the left, right and center portions of the foam reinforced board and along its length (i.e., in the machine direction). The average compressive strength values ​​of these 27 samples are recorded in Table 2. In addition, the number of individual samples with a compressive strength less than 1200 kPa is reported in Table 2. 1200 kPa is considered to be the minimum acceptable compressive strength of a glass reinforced foam board with a density of 125 g / L.

[0099] Thermal conductivity is also measured according to ISO 8301:1991.

[0100] Table 2

[0101]

[0102] *Not an embodiment of the present invention. 1 The compressive strength of the fiber-free foam was too low to be determined.

[0103] As shown in the "No Fiber" data, non-reinforced foams made from Polyol Systems A and B have higher compressive strengths than foams made from Polyol System 1. However, this advantage of Polyol Systems A and B is not repeated when those polyol systems are used to make reinforced foams. In this case, Foam Example 1 made with Polyol System 1 exhibits significantly better compressive strength than those foams made with Polyol Systems A and B. At 0% overfilling, the compressive strength of Comparative A and Comparative B is actually reduced by 5% to 10% compared to the no fiber case, despite the presence of glass fiber reinforcement. This is attributed to incomplete and uneven penetration of the reaction mixture into the fiber mat in those cases.

[0104] In contrast, the compressive strength of the 0% overfilled fiber reinforced Example 1 foam is significantly higher than the corresponding fiber-free case.

[0105] The 6% overfill data demonstrates another important and unexpected advantage of the present invention. In the case of Comparative A and Comparative B, overfilling results in a further decrease in compressive strength, about 3% in the case of Comparative A and about 9% in the case of Comparative B. In contrast to those results, Example 1 unexpectedly shows a small increase in compressive strength when overfilled. This is a significant practical advantage because overfilling allows the foam to be made with uniform cross-sectional dimensions and flat top and bottom surfaces. This reduces or even eliminates the need for subsequent trimming steps and the associated waste.

Claims

1. A polyol composition, comprising: a) a polyol, the polyol comprising P1: 15 to 30 wt. % of one or more non-amine initiated polyether polyols having a nominal functionality of 4 to 8 and a hydroxyl number of 300 to 600 mg KOH / g, based on the weight of all polyols; P2: 18 to 35 wt. % of one or more non-amine initiated polyether polyols having a nominal functionality of 3 and a hydroxyl number of 150 to 700 mg KOH / g, based on the weight of all polyols; P3: 15 to 35 wt. % of one or more polyester polyols having a nominal functionality of 2 to 2.5 and a hydroxyl number of 150 to 300 mg KOH / g, based on the weight of all polyols; P4: 2 to 8 wt. % of one or more amine-initiated polyether polyols having a nominal functionality of 4 to 8 and a hydroxyl number of 150 to 300 mg KOH / g, based on the weight of all polyols; and P5: 10 to 25 wt. %, based on the weight of all polyols, of one or more diols having a nominal functionality of 2 and a hydroxyl number of at least 550 mg KOH / g; wherein polyols P1 to P5 together account for at least 95% of the total weight of all polyols; b) 0% to 0.2% by weight of water, based on the weight of the polyol composition; c) 0.1 wt % to 2.5 wt % of a surfactant, based on the weight of the polyol composition; and d) a catalytically effective amount of a polyurethane gelling catalyst.

2. The polyol composition according to claim 1, wherein the polyol composition contains no more than 0.1 wt% of a blowing catalyst.

3. The polyol composition according to claim 1 or 2, wherein the polyurethane gelling catalyst is one or more of a permethylated alkylenediamine, diethylenetriamine, imidazole and a metal-containing catalyst.

4. The polyol composition according to claim 1 or 2, wherein the polyurethane gelling catalyst is dimethyltin dilaurate, dibutyltin dilaurate, dimethyltin dioctoate, dibutyltin dilaurate, dibutyltin dioctoate ... One or more of dibutyltin octoate and tin(IV) thioglycolate having the structure R2Sn(Tg)2, wherein each R is independently C 1-10 alkyl and each Tg is independently a thioglycolate group of the form R'OOC-CH2-S-, wherein R' is C 1-10 alkyl.

5. The polyol composition of claim 1, wherein the P1 polyol is a propoxylate of sucrose, a propoxylate of sorbitol, or a mixture thereof; the P2 polyol is a propoxylate of glycerol or trimethylolpropane; the P4 polyol is a propoxylate of o-toluenediamine, the P5 polyol is diethylene glycol or a mixture of diethylene glycol and tripropylene glycol, and the polyol composition comprises no more than 0.125 wt. % water.

6. A polyurethane foam prepared in the presence of a physical blowing agent in the reaction of a polyol composition according to any one of claims 1 to 5 with at least one polyisocyanate, wherein the reaction is carried out in the presence of not more than 0.2% by weight of water, based on the weight of the polyol composition, and not more than 0.1% by weight of a blowing catalyst, based on the weight of the polyol composition.

7. A method for producing a fiber-reinforced polyurethane foam, the method comprising the steps of: A) Distributing the Foam Precursor Fluid onto the Reinforcement Fiber Bed as well as B) curing the foam precursor fluid in the presence of the reinforcing fibers to produce the fiber-reinforced polyurethane foam, wherein the foam precursor fluid comprises at least one polyisocyanate, at least one physical blowing agent and a polyol composition, wherein the polyol composition comprises a polyol, wherein the polyol comprises Polyol P1: 15 to 30 wt. % of one or more non-amine initiated polyether polyols having a nominal functionality of 4 to 8 and a hydroxyl number of 300 to 600 mg KOH / g, based on the weight of all polyols; Polyol P2: 18 to 35 wt. % of one or more non-amine initiated polyether polyols having a nominal functionality of 3 and a hydroxyl number of 150 to 700 mg KOH / g, based on the weight of all polyols; Polyol P3: 15 to 35 wt. % of one or more polyester polyols having a nominal functionality of 2 to 2.5 and a hydroxyl number of 150 to 300 mg KOH / g, based on the weight of all polyols; Polyol P4: 2 to 8 wt. % of one or more amine-initiated polyether polyols having a nominal functionality of 4 to 8 and a hydroxyl number of 150 to 300 mg KOH / g, based on the weight of all polyols; and Polyol P5: 10 to 25 wt. %, based on the weight of all polyols, of one or more diols having a nominal functionality of 2 and a hydroxyl number of at least 550 mg KOH / g; wherein polyols P1 to P5 together constitute at least 95% of the total weight of all polyols; wherein the foam precursor fluid further comprises i) 0.1 wt % to 2.5 wt % of a surfactant, based on the weight of the polyol composition, ii) a catalytically effective amount of a polyurethane gelling catalyst, and iii) 0 wt % to no more than 0.2 wt % of water, based on the weight of the polyol composition.

8. The method of claim 7, wherein the foam precursor fluid comprises from 0 wt% to no more than 0.1 wt% of a blowing catalyst based on the weight of the polyol composition.

9. The method according to claim 7 or 8, wherein in step A, the reinforcing fiber bed is laid on a moving support and the foam precursor fluid is dispensed onto the reinforcing fibers on the moving support.

10. The method according to any one of claims 7 to 10, wherein in step B, the foam precursor fluid expands in a vertical direction, and the vertical expansion of the foam precursor fluid is restricted to produce overfilling.

11. The method according to claim 9, characterized in that The overfilling is 3 to 10 wt %.

12. A method according to any one of claims 9 to 11, wherein the moving support is a lower belt of a double belt laminator and the vertical expansion of the foam precursor fluid is limited by an upper belt of the double belt laminator.

13. The method according to any one of claims 7 to 12, wherein the fiber-reinforced polyurethane foam has a thickness of 200 mm to 500 mm, a pressure of 80 kg / m 3 Up to 150kg / m 3 The foam has a density of and a reinforcing fiber content of 5 to 25 weight percent.

14. The method according to any one of claims 7 to 13, wherein the reinforcing fibers are glass fibers.

15. The method according to any one of claims 7 to 14, wherein the polyurethane gelling catalyst is one or more of dimethyltin dilaurate, dibutyltin dilaurate, dimethyltin dioctoate, dibutyltin dioctoate and tin(IV) thioglycolate having the structure R2Sn(Tg)2, wherein each R is independently a C1-10 alkyl group and each Tg is independently a thioglycolate group of the form R'OOC-CH2-S-, wherein R' is a C1-10 alkyl group; the P1 polyol is a propoxylate of sucrose, a propoxylate of sorbitol, or a mixture thereof; the P2 polyol is a propoxylate of glycerol or trimethylolpropane; the P4 polyol is a propoxylate of o-toluenediamine; the P5 polyol is diethylene glycol or a mixture of diethylene glycol and tripropylene glycol, and the polyol composition comprises no more than 0.125 wt% water.

Images