Hard polyurethane foam formulation and method for producing fiber-reinforced polyurethane foam suitable for low-temperature applications

Abstract

The polyol composition suitable for producing rigid polyurethane foam comprises a combination of five polyols, a surfactant, and a polyurethane gelation catalyst. The polyol composition contains at most a very small amount of a blowing catalyst. The polyol composition surprisingly produces a polyurethane foam that shows little or no loss of compressive strength when overfilled when reacted with a polyisocyanate in the presence of a physical blowing agent. The polyol composition is particularly useful for producing fiber-reinforced rigid foams useful for low-temperature applications.

Description

Technical Field

[0001] The present invention relates to a polyol formulation useful for producing rigid polyurethane foam, and a method for producing a fiber-reinforced polyurethane foam, particularly suitable for cryogenic applications such as liquified natural gas (LNG) storage tanks.

[0002] As an alternative to pipelines, which may be restricted in their use due to geographical, political situations, or other reasons, very large quantities of LNG are being transported by sea. Natural gas is typically liquified on land and then supplied to large tanks on board ships. Liquefaction requires a temperature of approximately -150°C or lower. Storage and transportation must also be carried out at that temperature in order to prevent evaporation and large pressure increases in the storage and handling equipment. This requires cryogenic equipment and strong insulation.

[0003] Rigidity and structural integrity are important because of the weight involved and because the tank is subject to pressures resulting from the momentum of ocean waves transmitted to the tank, which generates wave motion within the tank.

[0004] Rigid polyurethane foam is a material selected for insulation. This foam is also required to contribute to the rigidity and structural integrity of the storage tank. Therefore, the mechanical properties of the foam are very important, and as a result, the foam is generally fiber-reinforced to further improve its mechanical properties.

[0005] These fiber-reinforced rigid polyurethane foams are conveniently produced by a continuous process in which a fiber mat is placed on a moving platform and a foam precursor fluid is applied onto the fiber mat. The foam precursor fluid must penetrate the fiber mat when expanding and curing to form the foam. Viscosity is important because if it is too high, the foam precursor fluid will not penetrate the fibers sufficiently. Insufficient penetration results in an insufficient distribution of fibers throughout the resulting foam, which adversely affects both its physical and thermal properties.

[0006] The production process is limited because it is necessary to maximize mechanical properties such as compressive strength. 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., when the foam can expand without being constrained vertically. The foam produced in this way has a curved upper surface and thus does not have a sharp rectangular cross-section. Therefore, the thickness of the foam varies from the edge to the center. For this reason, the foam is subsequently subjected to a trimming process in order to produce panels having a clean rectangular cross-section and uniform dimensions. Trimming increases costs and also generates a large amount of waste because an excessive amount of foam is produced and then cut to a predetermined size.

[0007] Trimming can be avoided by restraining the vertical rise of the foam and by "overfilling", i.e., using a slightly excessive amount of foam precursor than the minimum amount necessary to produce a specific volume of foam. Unfortunately, when the foam itself is overfilled, the compressive strength of the foam often decreases. This phenomenon is generally due to the anisotropy of the foam cells, and the loss of compressive strength due to overfilling often outweighs the advantage of eliminating the trimming process.

[0008] There is a desire for a polyurethane foam formulation that produces a foam with significantly less loss of compressive strength compared to a similar foam that is not overfilled when overfilled. There is also a desire for a method of producing a fiber-reinforced foam panel that has good thermal insulation properties and good compressive strength properties and that reduces or eliminates the need for trimming.

[0009] In a first aspect, the present invention is a polyol composition, a) P1: one or more non-amine starting polyether polyols having a nominal functionality of 4 to 8 and a hydroxyl value of 300 to 600 mg KOH / g, in an amount of 15 to 30 weight percent based on the weight of the total polyol, P2: 18 to 35 weight percent, based on the weight of the total polyol, of one or more non-amine initiated polyether polyols having a nominal functionality of 3 and a hydroxyl value of 150 to 700 mg KOH / g, P3: 15 to 35 weight percent, based on the weight of the total polyol, of one or more polyester polyols having a nominal functionality of 1.5 to 2.5 and a hydroxyl value of 150 to 300 mg KOH / g, P4: 2 to 8 weight percent, based on the weight of the total polyol, of one or more amine initiated polyether polyols having a nominal functionality of 3 to 8 and a hydroxyl value of 300 to 600 mg KOH / g, and P5: 10 to 25 weight percent, based on the weight of the total polyol, of one or more diols having a nominal functionality of 2 and a hydroxyl value of at least 550 mg KOH / g, A polyol composition comprising: The polyols P1 to P5 together constitute at least 95% of the total weight of the total polyol, b) 0 to 0.2 weight percent water, based on the weight of the polyol composition, and c) 0.1 to 2.5 weight percent surfactant, based on the weight of the polyol composition, and d) A catalytically effective amount of a polyurethane gelling catalyst, A polyol composition.

[0010] This polyol composition is particularly well - suited for use in the production of fiber - reinforced polyurethane foams by reacting with a polyisocyanate in the presence of a physical blowing agent and reinforcing fibers. The polyol composition has a desirable low viscosity and slow initial cure. These attributes are advantageous for good penetration of the foam precursor fluid into the fibers, which results in good product uniformity and consistent properties. The foam produced in this way has good thermal insulation and compression strength properties. Very surprisingly, this innovative formulation results in a fiber - reinforced foam that retains its compression strength even when over - filled. This behavior is not ordinary and is unexpected. The ability to over - fill allows for the production of fiber - reinforced polyurethanes with precise dimensions with little or no need for trimming. This reduces waste and eliminates or reduces the cost of trimming.

[0011] Accordingly, the present invention also provides a polyurethane foam produced in the reaction of a 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 water at 0.2 weight percent or less based on the weight of the polyol composition and a foaming catalyst at 0.1 weight percent or less based on the weight of the polyol composition.

[0012] The present invention also provides a method for producing a polyurethane foam comprising reacting a 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 water at 0.2 weight percent or less based on the weight of the polyol composition and a foaming catalyst at 0.1 weight percent or less based on the weight of the polyol composition.

[0013] In yet another aspect, the present invention provides a method for producing a fiber - reinforced polyurethane foam, A) distributing a foam precursor fluid onto a bed of reinforcing fibers; B) Curing the foam precursor fluid in the presence of the reinforcing fibers to produce a fiber-reinforced polyurethane foam; comprising wherein the foam precursor fluid comprises at least one polyisocyanate, at least one physical blowing agent, and a polyol composition, and the polyol composition comprises a polyol, Polyol P1: 15 to 30 weight percent, based on the weight of the total polyol, of one or more non-amine-initiated polyether polyols having a nominal functionality of 4 to 8 and a hydroxyl value of 300 to 600 mg KOH / g; Polyol P2: 18 to 35 weight percent, based on the weight of the total polyol, of one or more non-amine-initiated polyether polyols having a nominal functionality of 3 and a hydroxyl value of 150 to 700 mg KOH / g; Polyol P3: 15 to 35 weight percent, based on the weight of the total polyol, of one or more polyester polyols having a nominal functionality of 1.5 to 2.5 and a hydroxyl value of 150 to 300 mg KOH / g; Polyol P4: 2 to 8 weight percent, based on the weight of the total polyol, of one or more amine-initiated polyether polyols having a nominal functionality of 4 to 8 and a hydroxyl value of 300 to 600 mg KOH / g, and Polyol P5: 10 to 25 weight percent, based on the weight of the total polyol, of one or more diols having a nominal functionality of 2 and a hydroxyl value of at least 550 mg KOH / g; comprising wherein Polyols P1 to P5 together constitute at least 95% of the total weight of the total polyol; wherein the foam precursor fluid further comprises i) 0.1 to 2.5 weight percent, based on the weight of the polyol composition, of a surfactant, ii) a catalytically effective amount of a polyurethane gelation catalyst, and iii) 0 to 0.2 weight percent or less, based on the weight of the polyol composition, of water.

[0014] 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 to 600 mg KOH / g. The nominal functionality may be, for example, at least 5 or at least 6 and may be up to 8. The hydroxyl value is up to 350 mg KOH / g in some embodiments and up to 500 mg KOH / g in some embodiments. The P1 polyol is, in some embodiments, an alkoxylate of an initiator compound having 4 to 8 hydroxyl groups. Examples of such initiator compounds include pentaerythritol, erythritol, and sugars having 4 to 8 hydroxyl groups such as sorbitol and sucrose. 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 is preferred. Particularly preferred P1 polyols are propoxylates of sucrose, propoxylates of sorbitol, or mixtures thereof. The P1 polyol constitutes at least 15 weight percent and up to 30 weight percent of the total polyol in the polyol mixture. In certain embodiments, the P1 polyol constitutes at least 18 weight percent of the total polyol and may constitute up to 25 weight percent or up to 22 weight percent of the total polyol.

[0015] The P2 polyol is one or more non-amine initiated polyether polyols having a nominal functionality of 3 and a hydroxyl value of 150 to 700 mg KOH / g. The hydroxyl value is, in some embodiments, at least 225 mg KOH / g or at least 350 mg KOH / g. The P2 polyol is, in some embodiments, an alkoxylate of an initiator compound having 3 hydroxyl groups. Examples of such initiator compounds include glycerin, trimethylolpropane, and trimethylolethane. The initiator is alkoxylated by reaction with one or more alkylene oxides, among which 1,2-propylene oxide, ethylene oxide, or a mixture of propylene oxide and ethylene oxide is preferred. Propoxylates of glycerin or trimethylolpropane are particularly preferred. The P2 polyol constitutes at least 18 weight percent and at most 35 weight percent of the total polyols in the polyol mixture. In certain embodiments, the P2 polyol constitutes at least 20 weight percent, at least 22 weight percent, or at least 25 weight percent of the total polyols, and may also constitute at most 32 weight percent or at most 30 weight percent of the total polyols.

[0016] The P3 polyol is one or more polyester polyols having a nominal functionality of 1.5 to 2.5 and a hydroxyl value of 150 to 300 mg KOH / g. The nominal functionality is preferably from 1.5 to 2.2. The polyester is preferably an aromatic polyester such as can be produced in the reaction of an aromatic dicarboxylic acid (or its corresponding anhydride or derivative such as an alkyl diester) 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, glycerin, and the like. The P3 polyol constitutes at least 15 weight percent and up to 35 weight percent of the total polyols in the polyol mixture. In certain embodiments, the P3 polyol constitutes at least 20 weight percent, at least 22 weight percent, or at least 25 weight percent of the total polyols and can constitute up to 32 weight percent or up to 30 weight percent of the total polyols.

[0017] The P4 polyol is an amine-initiated polyol having a nominal functionality of 4 to 8 and a hydroxyl value of 300 to 600 mg KOH / g. The P4 polyol is an alkoxylate 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, among which 1,2-propylene oxide, ethylene oxide, or a mixture of propylene oxide and ethylene oxide is preferred. The propoxylate of toluenediamine, especially o-toluenediamine, is particularly preferred. The P4 polyol constitutes at least 2 weight percent and up to 8 weight percent of the total polyols in the polyol mixture. In certain embodiments, the P4 polyol constitutes at least 4 weight percent, at least 5 weight percent, or at least 6 weight percent of the total polyols, and may constitute up to 7.5 or up to 7 weight percent of the total polyols.

[0018] The P5 polyol is one or more diols having a nominal functionality of 2 and a hydroxyl value of at least 550 mg KOH / g. Examples of these 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. The P5 polyol constitutes at least 10 weight percent and up to 25 weight percent of the total polyols in the polyol mixture. In certain embodiments, the P5 polyol constitutes at least 12 weight percent or at least 15 weight percent of the total polyols, and may constitute up to 22 weight percent or up to 20 weight percent of the total polyols.

[0019] Polyols P1 to P5 together constitute at least 95% of the total weight of all polyols. They may together constitute at least 96%, at least 97%, or at least 98% of the total weight of all polyols and may constitute up to 100% of the total weight of all polyols.

[0020] Water, if present, is present in an amount of 0.2% or less of the total weight of the polyol composition. Preferred amounts are 0.15% or less or 0.125% or less of the total weight of the polyol composition.

[0021] The surfactant may be, for example, a silicone surfactant such as a polyether-modified polydimethylsiloxane surfactant. The surfactant may be hydrolyzable or non-hydrolyzable. Useful silicone surfactants are available under the trade names Tegostab® (Evonik), VORASURF™ (Dow, Inc.), or Silstab® (Siltech Corporation). The surfactant is not added to the weight of the polyol. The polyol composition contains 0.1 to 2.5% by weight of the surfactant, and preferred amounts are 0.5 to 2.0% by weight or 0.75 to 1.5% by weight.

[0022] The polyol composition further comprises at least one gelling catalyst. For the purposes of the present invention, a "gelling" catalyst is a catalyst that promotes the reaction of isocyanate groups with alcohol groups more strongly than it promotes the reaction of isocyanate groups with water molecules. The relative catalytic activity of the catalyst for the isocyanate-alcohol reaction versus the isocyanate-water reaction can be determined using titration methods such as those described by van Maris et al., "Polyurethane Catalysis by Tertiary Amines", J. Cellular Plastics 41 (July 2005), pp. 305-322. The catalytic activity for the isocyanate-alcohol reaction is evaluated by reacting 50 mL of a 2,4-toluene diisocyanate solution in benzene at 0.1533 mol / L with 50 mL of a diethylene glycol solution in benzene at 0.1533 mol / L and 5 mL of a catalyst solution in benzene at 0.0735 mol / L at 30°C. Samples are taken at various time points and the unreacted isocyanate is quenched with a solution of n-butylamine in benzene. The residual isocyanate content in each sample is determined by back-titration using a standardized HCl solution. Then, using the NCO content of the sample, the gelling activity is calculated in units of L 2 / g·mol·hr. The diethylene glycol solution is replaced with an aqueous solution in benzene at 0.0752 mol / L and the catalytic activity for the isocyanate-alcohol reaction is evaluated similarly. A "gelling" catalyst is one for which the ratio of foaming:gelling catalyst activity is <0.5. Preferred gelling catalysts are those for which this ratio is <0.2, and more preferred gelling catalysts are those for which this ratio is <0.1 or <0.05.

[0023] Examples of gelling catalysts include hypermethylated alkylenediamines, diethylenetriamine, imidazole, tin, zinc, and metal-containing catalysts such as bismuth carboxylate, especially tin(IV) catalysts, for example dimethyltin dilaurate, dibutyltin dilaurate, dimethyltin dioctoate, dibutyltin dioctoate, and tin(IV) thioglycolate having a structure R2Sn(Tg)2 [wherein each R is independently a C1-10 alkyl and each Tg is independently a thioglycolate ester group in the form of R’OOC-CH2-S- (wherein R’ is a C1-10 alkyl)].

[0024] Specific examples of the gelling catalyst include the following.

[0025]

Table 1

[0026] The polyol composition preferably contains, based on the total weight of the polyol composition, at most 0.1 weight percent of a foaming catalyst. The “foaming” catalyst for the purposes of the present invention is one that exhibits a foaming:gelling catalyst activity ratio of 0.5 or more, as measured according to the above titration method. The polyol composition preferably contains at most 0.05 weight percent of a foaming catalyst, more preferably at most 0.025 weight percent of a foaming catalyst. The polyol composition may contain no foaming catalyst at all.

[0027] For the purposes of the present invention, P4 polyol may exhibit catalytic activity due to the presence of a tertiary amino group, but is not considered to be either a foaming catalyst or a gelling catalyst.

[0028] In a preferred embodiment, the gelling catalyst exhibits a foaming:gelling catalyst activity ratio of less than 0.2, and the polyol composition contains a catalyst having a foaming:gelling catalyst activity ratio of 0.2 or more of 0.1 weight percent or less, 0.05 weight percent or less, or 0.025 weight percent or less.

[0029] Polyol compositions are generally useful for producing rigid polyurethane foams by reacting with polyisocyanates in the presence of physical (endothermic) blowing agents. Such methods for producing rigid polyurethane foams are well known in the art.

[0030] Physical blowing agents have a boiling point (at 1 atm) of 10 °C to 80 °C, preferably 10 °C to 50 °C, and lack one or more compounds having hydroxyl, primary and / or secondary amines, thiols, carboxyl, or other groups other than halogen groups that are reactive towards isocyanate groups under the conditions of the curing reaction. Useful physical blowing agents include hydrocarbons, hydrofluorocarbons, hydrochlorocarbons, hydrofluorochlorocarbons, ethers, etc. having the aforementioned boiling points. For example, hydrofluoroolefins and hydrofluorochloroolefins as described in US Patent Application Publication No. 2007 / 0100010 are also useful. Specific examples thereof are trifluoropropene, 1,3,3,3-tetrafluoropropene (1234ze), 1,1,3,3-tetrafluoropropene, 2,2,3,3-tetrafluoropropene (1234yf), 1,2,3,3,3-pentafluoropropene (1225ye), 1,1,1-trifluoropropene, 1,1,1,3,3-pentafluoropropene (1225zc), 1,1,2,3,3-pentafluoropropene (1225yc), (Z)-1,1,1,2,3-pentafluoropropene (1225yez), 1-chloro-3,3,3-trifluoropropene (1233zd), and 1,1,1,4,4,4-hexafluorobuta-2-ene (1336mzzm). Mixtures of any two or more physical blowing agents may also be used.

[0031] 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(s). The amount of the physical blowing agent may be, for example, at least 12, at least 14, or at least 15 parts by weight on that basis, and may be, for example, up to 25 parts, up to 22 parts, up to 20 parts, or up to 18 parts on the same basis.

[0032] Suitable organic polyisocyanates for use in the present invention include aliphatic, alicyclic, araliphatic, or aromatic polyisocyanates, or any combination of two or more thereof. Aromatic polyisocyanates are generally preferred. Among aromatic diisocyanates and polyisocyanates, 2,4- and 2,6-toluene diisocyanate and the corresponding isomer mixtures, 4,4'-, 2,4'-, and 2,2'-diphenylmethane diisocyanate and the corresponding isomer mixtures, mixtures of 4,4'- and 2,4'-diphenylmethane diisocyanate, polyphenyl polymethylene polyisocyanate, mixtures of 4,4'-, 2,4'-, and / or 2,2'-diphenylmethane diisocyanate and polyphenyl polymethylene polyisocyanate (commonly referred to as "polymeric MDI" in the art), and mixtures of polymeric MDI and toluene diisocyanate are preferred. Modified polyisocyanates, i.e., products obtained by chemical reaction of organic diisocyanates and / or polyisocyanates, may also be used. Specific examples are preferably esters, ureas, biurets, allophanates, uretonimines, carbodiimides, isocyanurates, uretdiones, and / or urethane-containing diisocyanates and / or polyisocyanates containing 33.6 to 15 weight percent, preferably 31 to 21 weight percent, of isocyanate groups based on the total weight of the modified polyisocyanate. The organic polyisocyanates can be used alone or in combination. Polymeric MDI having an isocyanate functionality of 2.2 to 3.3, particularly 2.5 to 3.0, and an isocyanate equivalent of 130 to 140 is particularly preferred.

[0033] The polyol composition is particularly useful for producing fiber-reinforced polyurethane foams. Such fiber-reinforced foams are A) distributing 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, the process being conveniently produced in a process wherein the foam precursor fluid comprises at least one polyisocyanate, at least one physical blowing agent, and the polyol composition of the present invention.

[0034] The reinforcing fibers are conveniently provided in the form of a mat of continuous or discontinuous fibers held together mechanically (e.g., by needle punching, entanglement, etc.) or using a small amount of binder. Particularly preferred mats contain randomly oriented continuous filaments and no binder. 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, and metal fibers.

[0035] The fiber mat can have a weight of 225 - 900 g / m 2 ².

[0036] 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. A preferred fiber mat is conveniently supplied from a roller onto the moving support. In a particularly preferred embodiment, the moving support is the lower belt of a double-belt laminator.

[0037] Sufficient fibers are deposited to provide a fiber content of preferably 5 - 25 wt% or 5 - 15 wt% in the resulting fiber-reinforced polyurethane foam. Multiple layers of the fiber mat may be laminated if necessary to provide the desired fiber content.

[0038] A facing layer may be placed on the support before depositing the fibers.

[0039] Next, the foam precursor fluid is distributed onto the fiber bed via a dispensing device. Spraying and injection methods are generally suitable. The foam precursor fluid may be distributed onto the fiber bed via a dispensing device that applies the foam precursor fluid in multiple streams across the lateral width of the fiber bed. Examples of such dispensing devices are described, for example, in European Patent Application Publication Nos. 2125323(A), 2234732(A), International Publication Nos. 2021 / 045888, 2021 / 046019, 2021 / 046020, 2021 / 046021, and 2012 / 046022. As the foam precursor fluid cures, the multiple streams expand and merge. In a preferred embodiment, the stationary dispensing device continuously distributes the foam precursor fluid onto the fiber bed as the fiber bed is transported through the dispensing device on a moving platform.

[0040] The foam precursor fluid penetrates through the fiber bed, expands and cures to produce a polyurethane foam in which reinforcing fibers are embedded. The advantage of the polyol composition of the present invention is that it reacts somewhat slowly, at least in the initial stages of curing, so that the viscosity does not increase rapidly, and for this reason, it has time to penetrate between the fibers of the fiber bed. This distributes the fibers more uniformly in the product and reduces defects such as dry spots and fiber-free regions.

[0041] The curing conditions are selected such that the blowing agent volatilizes and the reactive components of the precursor fluid for the foam react to produce a polymer foam. The conditions typically include a temperature above the boiling point of the physical blowing agent at the pressure used. The curing reaction is exothermic, and the heat generated by the reaction is often sufficient alone to produce a gas that volatilizes the physical blowing agent and expands the foam. Thus, no special conditions are required to promote curing. The precursor fluid for the foam can be produced by combining the components at approximately room temperature (such as 15 - 30 °C), applying the precursor fluid for the foam to the fibrous bed so that it penetrates the fibrous bed, and then allowing the precursor for the foam to react spontaneously without applying additional heat. It can sometimes be beneficial to accelerate curing by applying heat to the precursor fluid for the foam before and / or after it is distributed to the fibrous bed. This can be done, for example, by heating one or more components of the precursor fluid for the foam before combining them, or by heating the fibrous bed after the precursor fluid for the foam has been distributed over it. In some embodiments, a moving platform carrying the fibrous bed is heated, and alternatively or additionally, an upper surface that restricts the upward movement in the vertical direction during the curing step is heated to provide heat for accelerating curing. When done, it can be heated to a temperature of, for example, 35 - 100 °C, particularly 35 - 50 °C.

[0042] In some embodiments, the precursor fluid for the foam is capable of expanding without being restricted in the vertical direction. However, the advantages of the present invention are seen when, instead, the upward movement in the vertical direction is restricted, particularly when the upward movement in the vertical direction is restricted to a height lower than the height to which the precursor fluid for the foam would rise without restriction. This results in overfilling. Different from other foaming systems, it has been found that when the foam is overfilled, for example, by 1 - 15 wt% or 3 - 10 wt%, there is no loss or a decrease in compressive strength. The amount of overfilling is calculated as follows:

[0043] [Number] [where density発泡体 is the density of the polyurethane foam (excluding the weight of the reinforcing fibers), and the minimum filling density is the density of the foam that rises to the same height in the same process, except under free rise conditions, i.e., in the absence of vertical restraint (this also excludes the weight of the reinforcing fibers). Similarly, the overfill percentage can be calculated as 100 times the ratio of the weight per unit area of the foam at a specific vertical height to the weight per unit area of the foam that rises to the same height in the same process, except under free rise conditions. The foam density is conveniently measured in accordance with ASTM D1622.

[0044] The vertical rise of the foam is conveniently constrained mechanically, i.e., by the placement of a physical barrier that restricts further vertical rise. The vertical expansion of the foam precursor fluid in some embodiments is constrained by the upper belt of a double belt laminator. In such embodiments, the upper and lower belts of the double belt laminator are adjusted to provide a gap therebetween. This gap defines the thickness of the product. The gap is selected such that the foam is overfilled, i.e., the gap is smaller than the height to which the foam would rise vertically if unconstrained. The foam precursor fluid expands and rises as it cures, and the vertical rise is constrained by the belts of the double band laminator, preferably over its entire width, resulting in overfill, a flat top surface, and a rectangular cross-section. The lateral expansion of the foam precursor fluid can be similarly constrained, such as by enclosing the fiber bed and the foam precursor fluid within sidewalls.

[0045] A suitable method for making the foam is described in International Publication No. WO 2020 / 193874. The method of International Publication No. WO 2020 / 193874 further includes using lateral sidewalls to constrain the lateral expansion of the foam precursor fluid.

[0046] When the vertical rise of the foam is constrained, the restraint must remain in place until the foam has cured sufficiently to have a stable vertical dimension.

[0047] If desired, an upper facing layer may be placed on the fiber bed having the dispensed pre-foamed precursor fluid to produce a top facing layer that adheres to the upper surface of the fiber-reinforced polyurethane foam.

[0048] Examples of the facing layer include paper, plywood, decorative films, metal foils and sheets, especially aluminum foil and steel plates. In a preferred embodiment, the facing layer is paper.

[0049] The present invention is particularly suitable for producing insulating panels for low-temperature applications, and more specifically, for producing insulating panels for liquefied natural gas or other liquefied gas storage tanks. These foams can have a thickness of, for example, 200 to 500 mm, and due to this relatively large thickness, they tend to be distinguishable from laminated panels for more general purposes. The fiber-reinforced polyurethane foams useful in these applications can have a foam density of 80 to 150 kg / m 3 . Such a density provides a good balance between thermal insulation and mechanical strength (especially compressive strength). Such foams can be produced with a width in the range of 100 mm to 5 meters, especially 300 mm to 2.5 meters, or 500 mm to 2 meters. In a preferred embodiment, the width is 800 to 1200 mm.

[0050] The method of the present invention may, and preferably does, include one or more downstream steps such as cutting the fiber-reinforced polyurethane foam to a desired length, cooling the foam from the curing temperature, laminating the foams, and packaging the foams or otherwise preparing the foams for shipping or storage.

[0051] The following examples are provided to illustrate the present invention and are not intended to limit the scope of the present invention. All parts and percentages are by weight unless otherwise indicated.

[0052] Polyol A is a propoxylate of sorbitol having a functionality of 6 and a hydroxyl value of 477 mg KOH / g (118 Da equivalent). This is P1 polyol.

[0053] Polyol B is a propoxylated mixture of sucrose and glycerin. Its hydroxyl value is 360 mg KOH / g (156 Da equivalent). Polyol 2 contains approximately 58 wt% of an octafunctional species (P1 polyol) and 42 wt% of a trifunctional species (P2 polyol).

[0054] Polyol C is a propoxylated glycerin. Its hydroxyl value is 665 mg KOH / g (83 Da equivalent) and its functionality is 3. This is P2 polyol.

[0055] Polyol D is a propoxylated glycerin. Its hydroxyl value is 378 mg KOH / g (156 Da equivalent) and its functionality is 3. This is P2 polyol.

[0056] Polyol E is a propoxylated glycerin. Its hydroxyl value is 239 mg KOH / g (235 Da equivalent) and its functionality is 3. This is P2 polyol.

[0057] Polyol F is an aromatic polyester polyol having a hydroxyl value of 240 mg KOH / g (234 Da equivalent) and a functionality of 2. Its viscosity reported by the manufacturer is 2,000 - 4,500 cP at 25°C. Polyol F is P3 polyol.

[0058] AEP is a propoxylated o - toluenediamine having a hydroxyl value of 440 mg KOH / g (127.5 Da equivalent) and a functionality of 4. AEP is P4 polyol.

[0059] DPG is dipropylene glycol, having a hydroxyl value of 834 mg KOH / g (67 Da equivalent) and a functionality of 2.0. DPG is P5 polyol.

[0060] TPG is tripropylene glycol, with a hydroxyl value of 584 mg KOH / g (96 Da equivalent) and a functionality of 2.0. TPG is a P5 polyol.

[0061] DBTDL is dibutyltin dilaurate.

[0062] The polyisocyanate has an isocyanate functionality of 2.7 and an isocyanate equivalent of 136 Da, and is a polymeric MDI containing 40% MDI monomer.

[0063] Example 1 and Comparative Samples A - C A polyol system is prepared by mixing the components listed in Table 1.

[0064]

Table 2

[0065] Non-reinforced foam Example 1 and Comparative Samples A - C are each generated from a polyol system and A - C as follows. The catalyst is mixed with TPG. The remaining components of the polyol system are mixed separately to form a polyol composition. These two mixtures are combined together 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 this blend is mixed with polyisocyanate through a high - pressure machine at an index of 116.1 (iso / OH). When the resulting reaction mixture is dispensed into a 30 cm × 30 cm × 10 cm parallelepiped mold, it rises and cures there to produce a foam having a density of 125 g / L. The results are shown in Table 2 for the case of "without fibers". The name of the sample corresponds to the name of the polyol system.

[0066] Fiber - reinforced panels are produced from polyol system 1 and A - B. Since the compressive strength of the non - reinforced foam made from polyol system C is very low, its formulation is not used to produce fiber - reinforced panels. Paper is used as a facing on both the lower and upper sides of the foam to produce fiber - reinforced panels by a double - belt lamination process. The thickness of the foam is set at 300 mm and the nominal width is 1050 mm.

[0067] Supply the bottom facing to the laminator. Stack six layers of continuous strand glass fiber mat (Unifilo U809, manufactured by Owens Corning) on the bottom facing so as to provide a fiber concentration of about 10 wt% in the resulting composite panel. Process a catalyst / TPG mixture, the remainder of the polyol system, a blowing agent (1,1,1,3,3-pentafluoropropane), and a polyisocyanate (116.1 (iso / OH) index) with a high-pressure foaming machine and continuously cast it onto the stacked glass fiber mat and the bottom facing. The amount of the reaction mixture is selected to freely rise during curing to produce a reinforced foam having a thickness of 300 mm and a density of about 125 g / L. Apply the top facing continuously onto the foaming reaction mixture. Pass this assembly between the heating belts of a double-belt laminator, during which the foaming reaction mixture expands and cures to form a laminated panel having upper and lower paper facing layers and a reinforced foam layer. This represents the case of "0% overfill" ("0% OP") because the upward rise of the foam is not restricted by the belts of the double-belt laminator. This panel does not expand fully to contact the surface of the upper belt over the entire width of the panel, so it has a curved upper surface. Therefore, this panel will require subsequent trimming to produce a uniform rectangular cross-section.

[0068] Produce additional reinforced foam in the same general way except that the line speed is reduced. Reducing the line speed has the effect of increasing the amount of reaction mixture applied per unit area, which results in overfill and slightly reduces the weight of the glass fiber mat per unit area. As a result of these two effects, a reinforced foam overfilled by up to 6% is obtained. The overfilled foam expands fully to contact the upper belt over its entire width and produces a uniform rectangular cross-section that does not require trimming.

[0069] For the "fiberless" foam and the 0% and 6% overfilled reinforced foams, the compressive strength is measured according to EN 826. A total of 27 test specimens are cut along their length (i.e., in the machine direction) from the left, right, and central portions of the foam-reinforced panel. The average compressive strength values of these 27 specimens are reported in Table 2. Additionally, the number of individual specimens having a compressive strength less than 1200 kPa is reported in Table 2. 1200 kPa is considered the minimum acceptable compressive strength for a glass-reinforced foam panel with a density of 125 g / L. 2>

[0070] 2> 2>Also, the thermal conductivity is measured according to ISO 8301 - 1991. 2>

[0071] 2> 2> 2>[Table 3] 2> 2> 2> 2> * 2>Not an example of the present invention. 1 2>The compressive strength of the fiberless foam was not required because it was too low. 2>

[0072] 2> 2>As the "fiberless" data shows, the non-reinforced foams made from polyol systems A and B have a higher compressive strength than the foams made from polyol system 1. However, this advantage of polyol systems A and B is not carried over when using these polyol systems to make reinforced foams. In that case, foam Example 1 made using polyol system 1 shows a significantly better compressive strength than those made using polyol systems A and B. At 0% overfill, the compressive strengths of Comparative Example A and Comparative Example B are actually 5 - 10% lower compared to the fiberless case, despite the presence of the fiberglass reinforcement. This is due to the incomplete and non-uniform penetration of the reaction mixture into the fiber mat in these cases. 2>

[0073] 2> 2>In contrast, the compressive strength of the foam of Fiber-Reinforced Example 1 with 0% overfill is significantly higher than the corresponding fiberless case. 2>

[0074] 2> 2>6% overfill data demonstrates another important and unexpected advantage of the present invention. In the case of Comparative Example A and Comparative Example B, overfilling further reduces the compressive strength by about 3% in the case of Comparative Example A and about 9% in the case of Comparative Example B. In contrast to these results, Example 1 unexpectedly shows a slight increase in compressive strength when overfilled. This is an important practical advantage as it enables the production of foams with uniform cross-sectional dimensions having flat upper and lower surfaces by overfilling. This reduces or even eliminates the need for subsequent trimming processes and associated waste.

Claims

1. A polyol composition, a) P1: One or more nonamine-initiated polyether polyols having a nominal functional value of 4 to 8 and a hydroxyl value of 300 to 600 mg KOH / g, based on the weight of the total polyol, in a weight of 15 to 30 percent. P2: One or more nonamine-initiated polyether polyols having a nominal functional value of 3 and a hydroxyl value of 150-700 mgKOH / g, based on the weight of the total polyol, in an amount of 18-35 weight percent. P3: One or more polyester polyols having a nominal functional value of 2 to 2.5 and a hydroxyl value of 150 to 300 mg KOH / g, based on the weight of the total polyols, in an amount of 15 to 35 weight percent. P4: One or more amine-initiated polyether polyols having a nominal functional value of 4 to 8 and a hydroxyl value of 150 to 300 mg KOH / g, based on the weight of the total polyol, in an amount of 2 to 8% by weight, and P5: One or more diols having a nominal functional value of 2 and a hydroxyl value of at least 550 mg KOH / g, in an amount of 10 to 25 weight percent based on the weight of the total polyols. A polyol containing, Polyols P1 to P5 together constitute at least 95% of the total weight of the polyols, b) 0 to 0.2 weight percent of water based on the weight of the polyol composition, c) 0.1 to 2.5 weight percent of a surfactant based on the weight of the polyol composition, d) A catalytically effective amount of polyurethane gelling catalyst, A polyol composition containing the following:

2. The polyol composition according to claim 1, wherein the polyol composition contains 0.1% by weight or less of a foaming catalyst.

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

4. The polyurethane gelation catalyst is dimethyltin dilaurate, dibutyltin dilaurate, dimethyltin dioctoate, dibutyltin dioctoate, and structure R ２ Sn(Tg) ２ [In the formula, each R is independently C １～１０ It is an alkyl group, and each Tg independently forms R'OOC-CH ２ -S- (where R' is C) １～１０ The polyol composition according to claim 1, comprising one or more tin(IV) thioglycolates having a thioglycolate ester group in the form of an alkyl group.

5. The polyol composition according to 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 glycerin 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 contains 0.125% by weight or less of water.

6. A polyurethane foam produced by a reaction of a polyol composition according to any one of claims 1 to 5 with at least one polyisocyanate in the presence of a physical blowing agent, wherein the reaction is carried out in the presence of 0.2 weight percent or less of water based on the weight of the polyol composition and 0.1 weight percent or less of a foaming catalyst based on the weight of the polyol composition.

7. A method for producing fiber-reinforced polyurethane foam, A) A step of distributing the foam precursor fluid onto a bed of reinforcing fibers, B) A step of curing the foam precursor fluid in the presence of the reinforcing fibers to produce the fiber-reinforced polyurethane foam, Includes, The foam precursor fluid comprises at least one polyisocyanate, at least one physical blowing agent, and a polyol composition, the polyol composition is Polyol P1: One or more nonamine-initiated polyether polyols having a nominal functional value of 4 to 8 and a hydroxyl value of 300 to 600 mg KOH / g, based on the weight of the total polyol, in an amount of 15 to 30 weight percent. Polyol P2: One or more nonamine-initiated polyether polyols having a nominal functional value of 3 and a hydroxyl value of 150-700 mgKOH / g, based on the weight of the total polyol, in an amount of 18-35 weight percent. Polyol P3: One or more polyester polyols having a nominal functional value of 2 to 2.5 and a hydroxyl value of 150 to 300 mg KOH / g, based on the weight of the total polyols, in an amount of 15 to 35 weight percent. Polyol P4: One or more amine-initiated polyether polyols having a nominal functional value of 4 to 8 and a hydroxyl value of 150 to 300 mg KOH / g, based on the weight of the total polyol, in a weight of 2 to 8 percent, and Polyol P5: One or more diols having a nominal functional value of 2 and a hydroxyl value of at least 550 mg KOH / g, in a weight of 10 to 25 percent based on the total weight of polyols. A polyol containing, The polyols P1 to P5 together constitute at least 95% of the total weight of the polyols, A method wherein the foam precursor fluid further contains i) 0.1 to 2.5 weight percent of a surfactant based on the weight of the polyol composition, ii) a catalytically effective amount of a polyurethane gelling catalyst, and iii) 0 to 0.2 weight percent or less of water based on the weight of the polyol composition.

8. The method according to claim 7, wherein the foam precursor fluid contains 0 to 0.1% by weight of a foam catalyst based on the weight of the polyol composition.

9. The method according to claim 7, wherein in step A, the floor of reinforcing fibers is placed on a moving support, and the foam precursor fluid is distributed onto the reinforcing fibers on the moving support.

10. The method according to claim 7, wherein in step B, the foam precursor fluid expands vertically, and the vertical expansion of the foam precursor fluid is constrained to generate overfilling.

11. The method according to claim 10, characterized by an overfilling of 3 to 10% by weight.

12. The method according to claim 9, wherein the moving support is the lower belt of a double-belt laminator, and the vertical expansion of the foam precursor fluid is constrained by the upper belt of the double-belt laminator.

13. The aforementioned fiber-reinforced polyurethane foam has a thickness of 200 to 500 mm and a density of 80 to 150 kg / m². ３ The method according to claim 7, having a foam density and a reinforcing fiber content of 5 to 25% by weight.

14. The method according to claim 7, wherein the reinforcing fiber is a glass fiber.

15. The polyurethane gelation catalyst is dimethyltin dilaurate, dibutyltin dilaurate, dimethyltin dioctoate, dibutyltin dioctoate, and a structure R ２ Sn(Tg) ２ [wherein each R is independently a C1-10 alkyl, and each Tg is independently a thioglycolate ester group in the form of R'OOC-CH ２ -S-(wherein R' is C １～１０ alkyl)] and is one or more of tin(IV) thioglycolates, the P1 polyol is a propoxylate of sucrose, a propoxylate of sorbitol, or a mixture thereof, the P2 polyol is a propoxylate of glycerin 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 contains 0.125% by weight or less of water. The method according to any one of claims 7 to 14.