Polyol composition for producing polyurethane foams suitable for filling hollow-core insulators

Abstract

The present invention relates to a polyol composition comprising, based on the total weight of the composition: a1) from 35% to 90% by weight of one or more polyether polyols having an average hydroxyl functionality greater than 2, a2) from 10% to 50% by weight of castor oil, a3) from 5% to 30% by weight of one or more mineral oils, a4) from 0.05% to 10% by weight of one or more foam stabilizers, wherein at least 80% by weight of the total weight of polyols in the composition is provided by polyether polyol a1) and castor oil a2). The invention also relates to a two-component composition for producing polyurethane foams, comprising said polyol composition and a polyisocyanate compound. The invention also relates to the use of a polyurethane foam produced from this composition for filling a hollow-core insulator, and to a hollow-core insulator filled with said polyurethane foam.

Description

[0001] The present invention relates to a polyol composition which, in combination with a polyisocyanate, provides a polyurethane foam. The present invention also relates to the use of the polyurethane foam for filling hollow core insulation. Prior art

[0002] Hollow-core insulators play an important role in various application areas of high-voltage insulation technology, especially in outdoor power stations, substations and electrical equipment. Initially, mainly ceramic-based hollow-core insulators were used; at the same time, hollow-core composite insulators are increasingly used.

[0003] Air core insulators are typically made of a hollow, wound inner tube or body, upper and lower flanges, and a silicone rubber skirt, which provide support and insulation for wires and electrical equipment.

[0004] The body of these hollow core insulators is usually filled with nitrogen or sulfur hexafluoride as electrical insulating material to avoid internal flashovers. However, it is difficult to seal these gases securely within the insulation system over long periods of time and at variable temperatures. The use of these gaseous dielectrics requires complex monitoring systems to detect any leaks in the hollow core insulators during operation. Otherwise, when the gas pressure drops, moisture can penetrate into the hollow core insulator and the dielectric strength of the insulation system decreases. In addition, the fluorinated compound sulfur hexafluoride is a greenhouse gas and is therefore also very problematic from an ecological point of view.

[0005] However, the gas cannot simply be replaced by another electrical insulating material, since due to the large size of the high voltage insulators (which can be up to 10 m in length), using conventional solid dielectric materials would result in an extremely high total weight of the insulator, which is not practical for the above applications.

[0006] In order to solve this problem, the use of dielectric foams has been proposed. For example, WO2021 / 058500 discloses the use of dry synthetic foams based on poly(acrylonitrile-co-vinylidene chloride-co-methyl methacrylate) hollow microspheres as ultra-lightweight fillers in hollow core insulators. However, these foams contain a large amount of halogens, which makes them not environmentally friendly products.

[0007] WO2011 / 089471 discloses filling the hollow core of an insulator with an insulating material selected from closed-cell polyethylene foam, cross-linked polyethylene foam, EVA foam, polystyrene foam and closed-cell halogen-free polyurethane foam. Polyurethane foam is most preferred. However, the author does not mention the composition of these polyurethane foams.

[0008] Polyurethane foams are well known and used in a variety of applications. They can be produced by reacting polyisocyanates with polyols in the presence of various additives. Polyurethane foams provide a variety of physical properties as well as the desired dielectric properties for use in insulation systems. In addition, the light weight of polyurethane foams facilitates their use in high voltage insulation. Polyurethane foams allow for easier sealing in insulation systems compared to conventionally used gases and eliminate the potential risk of gas leaks.

[0009] US2018 / 0051124 discloses a polyurethane foam for a high-voltage resin impregnated paper bushing for filling the gap between a capacitor core and an external hollow insulator. The polyurethane foam is prepared by (A) a polyol composition and (B) a polyisocyanate compound, and the polyol composition includes polyether polyols, polyolefin polyols and polyester polyols (which can be obtained by epoxidation of unsaturated fatty acid esters and subsequent ring-opening reaction with a compound containing active hydrogen). Although the composition is very useful as a foam for a high-voltage bushing, it is over-designed to some extent, and is therefore too expensive for applications (such as filling hollow insulators) for larger volumes. In addition, the composition includes polyolefin polyols, particularly polybutadiene-based polyols, which belong to the scope of the Chemical Weapons Convention and therefore cannot be used globally. In addition, some components used in the composition, such as Sovermol 1111, are not registered by manufacturers for REACH, and are therefore no longer available.

[0010] Therefore, there is a need to provide new polyurethane foams suitable for filling hollow core insulation, based on compositions in which all components are available and in which none of the components fall within the scope of the Chemical Weapons Convention.

[0011] There is also a need to provide new polyurethane foams for filling hollow core insulation which are more environmentally friendly, in particular which are halogen-free and preferably have a higher renewable raw material content, thereby having a lower carbon footprint.

[0012] It would also be desirable for new polyurethane foams to be cost effective for filling large volumes of hollow core insulation.

[0013] Another important factor is to provide a storage-stable composition. In practice, the two ingredients, the polyol compound and the polyisocyanate component, are usually mixed shortly before the polyurethane foam is produced. Since the polyol compound usually contains several polyols and various additives dispersed therein, these mixtures are usually prone to precipitation of solid components. Therefore, the storage stability of the polyol component is a requirement that needs to be met.

[0014] The applicant has surprisingly found that such polyurethane foams can be prepared from (A) a polyol composition and (B) a polyisocyanate component having an average functionality greater than 2, wherein the polyol composition comprises at least one or more polyether polyols having an average functionality greater than 2, castor oil, one or more mineral oils and one or more foam stabilizers.

[0015] The compositions avoid all the disadvantages of the prior art compositions and make it possible in an unexpected manner to prepare polyurethane foams having improved properties. Summary of the invention

[0016] The present invention relates to a polyol composition (A) comprising, based on the total weight of the composition:

[0017] a1) 35% to 90% by weight of one or more polyether polyols having an average hydroxyl functionality of greater than 2,

[0018] a2) 10 to 50% by weight of castor oil,

[0019] a3) 5% to 30% by weight of one or more mineral oils,

[0020] a4) 0.05% to 10% by weight of one or more foam stabilizers,

[0021] At least 80% by weight of the total weight of polyols in the composition is provided by polyether polyol a1) and castor oil a2).

[0022] Advantageously, the polyether polyol a1) is selected from linear or branched polyethylene oxides, polypropylene oxides, hydroxyl-terminated ethylene oxide / propylene oxide block copolymers and mixtures thereof.

[0023] According to a preferred embodiment, the polyether polyol is a mixture of a polyether polyol having a hydroxyl value less than or equal to 200 mg KOH / g and a polyether polyol having a hydroxyl value greater than 200 mg KOH / g.

[0024] Advantageously, the mineral oil a3) is a naphthenic mineral oil.

[0025] According to a preferred embodiment, the polyether polyol a1) comprises 5 to 20% by weight of one or more polyether polyols having a hydroxyl value greater than 200 mg KOH / g and 30 to 70% by weight of one or more polyether polyols having a hydroxyl value less than or equal to 200 mg KOH / g, based on the total weight of the composition.

[0026] Advantageously, the polyol composition according to the invention further comprises additives selected from the group consisting of epoxy components, rheology modifiers, surfactants, flame retardants, fillers, catalysts, desiccants, dyes, pigments, flame retardants, softeners, heat aging stabilizers, thixotropic agents, blowing agents and mixtures thereof.

[0027] Advantageously, the epoxy component is polypropylene glycol diglycidyl ether.

[0028] Advantageously, the rheology modifier is fumed silica.

[0029] According to a preferred embodiment, the polyol composition (A) according to the invention does not contain polyolefin polyols. The invention also relates to a two-component composition comprising:

[0030] Component (A), which is the above-mentioned polyol composition,

[0031] Component (B), which is a polyisocyanate having an average NCO functionality of greater than 2.

[0032] Advantageously, component (B) comprises at least methyl diphenyl diisocyanate.

[0033] Advantageously, the molar ratio of the NCO groups of component (B) to the sum of the reactive hydrogen atoms of component (A) is from 0.80:1 to 1.75:1.

[0034] The present invention also relates to a polyurethane foam obtained by reacting the polyol composition (A) of the above composition with component (B), in particular in the presence of a blowing agent.

[0035] The present invention also relates to the use of a composition for filling a hollow core insulator, the composition comprising at least:

[0036] Component (A), which is a polyol composition, comprises, based on the total weight of the composition:

[0037] a1) 35% to 90% by weight of one or more polyether polyols having an average hydroxyl functionality of greater than 2,

[0038] a2) 10 to 50% by weight of castor oil,

[0039] wherein at least 80% by weight of the total weight of polyols in the composition is provided by polyether polyols a1) and castor oil a2),

[0040] Component (B) is a polyisocyanate having an average NCO functionality of greater than 2.

[0041] The present invention also relates to a hollow core insulation filled with a polyurethane foam obtained by reacting the following components:

[0042] Component (A), which is a polyol composition, comprises, based on the total weight of the composition:

[0043] a1) 35% to 90% by weight of one or more polyether polyols having an average hydroxyl functionality of greater than 2,

[0044] a2) 10 to 50% by weight of castor oil,

[0045] wherein at least 80% by weight of the total weight of polyols in the composition is provided by polyether polyols a1) and castor oil a2),

[0046] Component (B) is a polyisocyanate having an average NCO functionality of greater than 2. DETAILED DESCRIPTION

[0047] The term "consisting essentially of" followed by one or more characteristics means that they can be included in the methods or materials of the present invention, except for the components or steps explicitly listed, components or steps that do not materially affect the nature and characteristics of the present invention.

[0048] Unless expressly stated otherwise, the expression "X to Y" includes boundaries. The expression means that the target range includes the X value and the Y value, as well as all values ​​from X to Y.

[0049] Polyol composition (A)

[0050] A first object of the present invention is a polyol composition (A) for preparing a polyurethane foam, comprising, based on the total weight of the composition:

[0051] a1) 35% to 90% by weight of one or more polyether polyols having an average functionality of greater than 2,

[0052] a2) 10 to 50% by weight of castor oil,

[0053] a3) 5% to 30% by weight of one or more mineral oils,

[0054] a4) 0.05% to 10% by weight of one or more foam stabilizers,

[0055] At least 80% by weight of the total weight of polyols in the composition is provided by polyether polyol a1) and castor oil a2).

[0056] Preferably at least 90 wt. %, more preferably at least 95 wt. %, most preferably 98 wt. % of the total weight of polyols in the polyol composition (A) is provided by polyether polyols a1) and castor oil a2). Advantageously, the polyol composition (A) according to the invention does not contain polyolefin polyols.

[0057] "Free of polyolefin polyols" means that the polyol composition contains less than 5 wt%, preferably less than 2 wt%, more preferably less than 1 wt% of one or more polyolefin polyols based on the total weight of the polyol composition. Specifically, the polyolefin polyol can be selected from polyisoprene polyol, polybutadiene polyol, hydroxyl-terminated polybutadiene-acrylonitrile, hydroxyl-terminated styrene-butadiene liquid rubber or hydrogenated hydroxyl-terminated polybutadiene.

[0058] In a preferred embodiment, the polyol composition (A) according to the invention does not contain polyisoprene polyol and / or polybutadiene polyol.

[0059] Advantageously, compounds a1), a2), a3) and a4) represent at least 80% by weight, preferably at least 90% by weight, most preferably at least 95% by weight, most preferably at least 98% by weight of the polyol composition (A).

[0060] Advantageously, the polyol composition according to the invention consists essentially of:

[0061] a1) 35% to 90% by weight of one or more polyether polyols having an average functionality of greater than 2,

[0062] a2) 10 to 50% by weight of castor oil,

[0063] a3) 5% to 30% by weight of one or more mineral oils,

[0064] a4) 0.05% to 10% by weight of one or more foam stabilizers.

[0065] Advantageously, the polyol composition according to the invention also comprises one or more additives a5) selected from those usually used for the preparation of polyurethane foams.

[0066] The applicant has found that the polyol composition according to the invention remains stable when stored for extended periods of time, for example up to one month, preferably up to 6 months, more preferably up to 12 months.

[0067] The applicant has also surprisingly found that the specific selection of the polyol composition can produce polyurethane foams with lower reaction enthalpy and longer reaction time when compared to prior art compositions. These advantages are particularly attractive in the case of using polyurethane foams to fill large volume insulation systems, especially hollow core insulation.

[0068] Additionally, it has been found that polyurethane foams prepared from the polyol compositions according to the present invention are very soft and exhibit low temperature flexibility, which is also a desirable property for applications as fillers in hollow core insulation.

[0069] a1) Polyether polyol

[0070] The polyether polyols suitable for the polyol composition according to the invention can be selected from polyether polyols based on ethylene oxide, polyether polyols based on propylene oxide, corresponding ethylene oxide / propylene oxide copolymers (which may be random copolymers or block copolymers), and mixtures of these polyether polyols. The ratio of ethylene oxide to propylene oxide in the ethylene oxide / propylene oxide copolymers can vary within wide limits. Thus, for example, it is possible that only the terminal hydroxyl groups of the polyether polyol react with ethylene oxide.

[0071] According to an embodiment, the polyether polyol is a linear or branched polyethylene oxide or polypropylene oxide or a mixture thereof.

[0072] According to another embodiment, the polyether polyol is a hydroxyl-terminated ethylene oxide / propylene oxide block copolymer.

[0073] According to another embodiment, the polyether polyol is a mixture of linear or branched polyethylene oxide and / or polypropylene oxide and hydroxyl-terminated ethylene oxide / propylene oxide block copolymers.

[0074] The polyether polyol used in the polyol composition according to the invention has an average hydroxyl functionality greater than 2. Preferably, the average hydroxyl functionality of the polyether polyol is from 2.5 to 4, preferably from 2.5 to 3.5. According to an advantageous embodiment, the average hydroxyl functionality of the polyether polyol is 3.

[0075] These polyether polyols can be obtained, for example, by reacting one or more polyfunctional active hydrogen initiators with alkylene oxides such as ethylene oxide, propylene oxide, butylene oxide, tetrahydrofuran and mixtures thereof, preferably with propylene oxide, ethylene oxide and / or mixed propylene oxide and ethylene oxide. Polyfunctional active hydrogen initiators are all those commonly used for the preparation of polyether polyols having a functionality greater than 2, preferably 2 to 4, such as water, aliphatic, alicyclic or aromatic polyhydroxy compounds having 2 or 3 hydroxyl groups, such as ethylene glycol, propylene glycol, butanediol, hexanediol, octanediol, dihydroxybenzene or bisphenol, trimethylolpropane or amines. Methods for preparing polyether polyols are known to those skilled in the art and are described, for example, in Ullmann's Encyclopedia of Industrial Chemistry, 4th edition, volume 19, 1980, pages 31-38, 304 and 305).

[0076] Polytetrahydrofuran may also be used and is available, for example, under the trade name Commercially available.

[0077] Advantageously, the polyether polyols according to the invention have a molecular weight of from 100 to 2000 g / mol, preferably from 200 to 1000 g / mol and more preferably from 300 to 600 g / mol.

[0078] Advantageously, the polyol composition according to the invention comprises from 40% to 80% by weight of one or more polyether polyols, relative to the total weight of the polyol composition (A).

[0079] According to an advantageous embodiment of the invention, the polyether polyol is a mixture of one or more polyether polyols having a high hydroxyl value and one or more polyether polyols having a low hydroxyl value.

[0080] As used herein, the term "hydroxyl value" refers to the milligrams of potassium hydroxide equivalent to the hydroxyl content in 1 gram of polyether polyol, as determined by test method DIN 53240-2. The hydroxyl value unit is expressed in mg KOH / g polyether polyol.

[0081] "Polyether polyols having a low hydroxyl value" means polyether polyols having a hydroxyl value less than or equal to 200 mg KOH / g, preferably in the range of 10 to 200 mg KOH / g, more preferably 15 to 100 mg KOH / g, most preferably 20 to 50 mg KOH / g.

[0082] "Polyether polyols having a high hydroxyl value" means polyether polyols having a hydroxyl value greater than 200 mg KOH / g, preferably in the range of 250 to 500 mg KOH / g, preferably 300 to 450 mg KOH / g.

[0083] Advantageously, the polyol composition according to the invention comprises 5 to 20% by weight, preferably 8 to 15% by weight, of one or more polyether polyols having a high hydroxyl value and 30 to 70% by weight, preferably 40 to 60% by weight, of one or more polyether polyols having a low hydroxyl value.

[0084] In a preferred embodiment, the polyether polyol is a mixture of one or more polyether polyols having an average functionality of 3 and a hydroxyl value of 300 to 450 mg KOH / g and one or more polyether polyols having an average functionality of 3 and a hydroxyl value of 20 to 50 mg KOH / g.

[0085] According to the most advantageous embodiment, the polyether polyol comprises 5 to 20 wt. % of one or more polyether polyols having a hydroxyl value of 300 to 450 mg KOH / g and 30 to 70 wt. % of one or more polyether polyols having a hydroxyl value of 20 to 50 mg KOH / g, based on the total weight of the polyol composition (A).

[0086] a2) Castor Oil

[0087] An important aspect of the present invention is the use of renewable natural components. This is achieved by using castor oil in the polyol composition.

[0088] Castor oil is a natural oil polyol derived from castor beans. Chemically, it is a triglyceride in which the three hydroxyl groups of glycerol have been esterified primarily with 12-hydroxyoctadec-9-enoic acid (known as ricinoleic acid) as the fatty acid.

[0089] Preferably, the castor oil according to the invention is unmodified castor oil.

[0090] "Non-modified castor oil" means castor oil that has not been subjected to any processing other than purification.

[0091] Preferably, the castor oil according to the invention has an average number of functional groups of 2.0 to 2.7, more preferably 2.2 to 2.7.

[0092] Preferably, the castor oil according to the invention has an average hydroxyl value of 30 to 170 mg KOH / g, more preferably 100 to 160 mg KOH / g.

[0093] Preferably, the polyol composition according to the invention comprises 15 to 40% by weight of castor oil, relative to the total weight of the polyol composition (A).

[0094] Advantageously, the weight ratio of polyether polyol to castor oil is from 10:1 to 1:5, preferably from 5:1 to 1:1 and most preferably from 4:1 to 1:1.

[0095] a3) Mineral oil

[0096] The mineral oil according to the invention is advantageously chosen from aliphatic, cycloaliphatic and branched aliphatic saturated hydrocarbons distilled from petroleum containing from 5 to 24 carbon atoms, preferably from 5 to 18 carbon atoms.

[0097] Preferably the mineral oil is selected from naphthenic oils and paraffinic oils.According to a preferred embodiment, the mineral oil is a naphthenic oil.

[0098] Advantageously, the mineral oil has a viscosity of 50 to 200 cSt at 40°C, preferably a viscosity of 70 to 150 cSt at 40°C, more preferably a viscosity of 80 to 120 cSt at 40°C, measured according to ASTM 445.

[0099] Advantageously, the polyol composition according to the invention comprises from 7 to 20% by weight of mineral oil, relative to the total weight of the polyol composition (A).

[0100] Preferably, the polyol composition according to the invention comprises 7 to 20% by weight of naphthenic oil, relative to the total weight of the polyol composition (A).

[0101] a4) Foam stabilizer

[0102] The polyol composition according to the invention comprises a foam stabilizer.

[0103] The foam stabilizer may be selected from polydimethylsiloxanes, organofunctional polydimethylsiloxanes, silicone polyether copolymers, block copolymers having silicone and organic blocks, and mixtures thereof.

[0104] According to a preferred embodiment, the foam stabilizer is selected from polyether-modified polysiloxanes, in particular polysiloxane-polyoxyalkylene block copolymers. These stabilizers are described, for example, in US 6166098 and EP-A 936240 and are available under the trade name Commercially available.

[0105] According to another preferred embodiment, the foam stabilizer is selected from block copolymers having silicone and organic blocks, the organic blocks being based, for example, on caprolactone or other lactones, such as W35 (Wacker Chemie AG, Munich, Germany).

[0106] Advantageously, the foam stabilizer represents 0.5 to 8% by weight, more preferably 1 to 6% by weight, based on the total weight of the polyol composition (A).

[0107] a5) Other additives

[0108] Additives are compounds added in small amounts which promote improvements in the polyol composition and / or the polyurethane foams prepared therefrom.

[0109] Advantageously, the polyol composition according to the invention comprises further optional additives selected from epoxy components, catalysts, surface-active substances, desiccants, fillers, dyes, pigments, flame retardants, softeners, heat aging stabilizers, thixotropic or rheological modifiers, blowing agents and mixtures thereof.

[0110] Suitable catalysts are, for example, tertiary amines such as N-methyldiethanolamine, triethylenediamine, triethanolamine, pentamethyldiethylenetriamine, tetramethylethylenediamine, dibenzylmethylamine, N-ethylmorpholine, N-methylmorpholine, 1-methyl-4-dimethylaminoethylpiperazine, N,N-diethyl-3-diethylamine, propylamine, 1-(2-hydroxypropyl)imidazole or diazabicyclooctane or organotin compounds such as dibutyltin laurate.

[0111] Suitable fire retardants can be selected from phosphate compounds such as tricresyl phosphate or dimethylmethanephosphonate, halogenated compounds, non-halogenated compounds or combinations thereof. Preferably, the fire retardant is selected from phosphate compounds, non-halogenated compounds and mixtures thereof. Inorganic flame retardants such as hydrated aluminum oxide, antimony trioxide and ammonium polyphosphate can also be used.

[0112] Suitable heat aging stabilizers for the polyol composition according to the present invention may be, for example, aliphatic glycidyl ethers, such as polypropylene glycol diglycidyl ether.

[0113] Suitable fillers may be selected, for example, from particles such as carbonates, alumina and silica, and natural and synthetic fibers, or mixtures thereof.

[0114] The total content of additives in the polyol composition according to the invention is advantageously from 0.01% to 30% by weight, preferably from 0.05% to 10% by weight, based on the total weight of the polyol composition (A).

[0115] According to an advantageous embodiment, the polyol composition according to the invention comprises a thixotropic or rheological modifier which is fumed silica. Preferably, the fumed silica is a fumed silica having a molecular weight of 120 to 280 m 2 / g of hydrophilic or hydrophobic fumed silica with a specific surface area of ​​1000 g / cm2. Preferably, the polyol composition according to the present invention comprises 0.01 to 5 wt% of fumed silica, based on the total weight of the polyol composition (A).

[0116] According to an advantageous embodiment, the polyol composition according to the invention comprises an epoxy component. Preferably, the epoxy component is polypropylene glycol diglycidyl ether. Preferably, the polyol composition according to the invention comprises 0.01 wt. % to 5 wt. % of the epoxy component, based on the total weight of the polyol composition (A).

[0117] It is emphasized that the present invention comprises any combination of any specific compound or group of compounds mentioned above for components a1), a2), a3) and a4).

[0118] According to a preferred embodiment, the polyol composition according to the invention comprises, preferably consists essentially of:

[0119] 35 to 90% by weight of polyether polyols having an average hydroxyl functionality of 2.5 to 4, preferably 2.5 to 3.5,

[0120] - 10 to 50% by weight of castor oil,

[0121] - 5 to 30% by weight of mineral oil, preferably naphthenic mineral oil,

[0122] - 0.05 to 10% by weight of a foam stabilizer, and

[0123] - Optionally, 0.01 to 5% by weight of other additives selected from the group consisting of epoxy components, catalysts, surface active substances, desiccants, fillers, dyes, pigments, flame retardants, softeners, heat aging stabilizers, thixotropic or rheology modifiers, blowing agents and mixtures thereof.

[0124] According to the most preferred embodiment, the polyol composition according to the invention comprises, preferably consists essentially of:

[0125] 5 to 20% by weight of polyether polyols having a hydroxyl number of more than 200 mg KOH / g, preferably in the range of 250 to 500 mg KOH / g, preferably 300 to 450 mg KOH / g,

[0126] 30 to 70% by weight of polyether polyols having a hydroxyl value less than or equal to 200 mg KOH / g, preferably in the range of 10 to 200 mg KOH / g, more preferably 15 to 100 mg KOH / g, most preferably 20 to 50 mg KOH / g,

[0127] - 10 to 50% by weight of castor oil,

[0128] - 5 to 30% by weight of mineral oil, preferably naphthenic mineral oil,

[0129] - 0.05 to 10% by weight of a foam stabilizer, and

[0130] - Optionally, 0.01 to 5% by weight of other additives selected from the group consisting of epoxy components, catalysts, surface active substances, desiccants, fillers, dyes, pigments, flame retardants, softeners, heat aging stabilizers, thixotropic or rheology modifiers, blowing agents and mixtures thereof.

[0131] Advantageously, the polyol composition (A) according to the invention has a viscosity at 25° C. of 1000 to 3000 mPa.s, preferably 1500 to 2500 mPa.s.

[0132] Curable two-component composition

[0133] In producing the polyurethane foam according to the present invention, the above-mentioned polyol composition (A) is reacted with the polyisocyanate component (B).

[0134] Therefore, another aspect of the present invention is to provide a two-component curable composition comprising the above-mentioned polyol composition (A) and one or more polyisocyanate components (B) having an average NCO functionality greater than 2.

[0135] "Two-component composition" means a composition comprising a polyol composition and a polyisocyanate component, the two components being provided as a two-pack system (or kit), wherein the polyol composition (A) is part (1), and the polyisocyanate is part (2). Such a two-part composition is designed for extemporaneous mixing of the two compositions just before curing begins to form a polyurethane foam.

[0136] "Curable composition" means a composition comprising a polyol composition (A) and a polyisocyanate component (B) which, when mixed / blended together and cured, can form a cured solid polyurethane by forming chemical bonds known as crosslinks.

[0137] Polyisocyanate component (B)

[0138] The polyisocyanate components useful in producing the polyurethane foams according to the present invention are well known in the art and are organic compounds containing more than two isocyanate groups per molecule. The polyisocyanate component may be aromatic, cycloaliphatic or aliphatic and may be a monomeric or oligomeric compound.

[0139] Advantageously, the NCO functionality of the polyisocyanate component is greater than or equal to 2, preferably from 2.1 to 3.2.

[0140] Isocyanate "functionality" is the number of reactive NCO groups per molecule in an isocyanate molecule or polymeric isocyanate. For example, most polyisocyanates, particularly MDI-type polyisocyanate compounds, contain a blend of monomeric and polymeric MDI, and the isocyanate functionality is the average functionality of the different molecular and polymeric species.

[0141] As used herein, "MDI" refers to methylene diphenyl diisocyanate (also known as diphenylmethane diisocyanate) and its isomers. MDI exists as one of three isomers (4,4'MDI, 2,4'MDI and 2,2'MDI) or as a mixture of two or more of these isomers. Unless otherwise specifically stated, "MDI" may also refer to and include polymeric MDI. Polymeric MDI is a compound having a chain of three or more benzene rings connected to each other by methylene bridges, wherein an isocyanate group is connected to each benzene ring.

[0142] Suitable polyisocyanate component (B) according to the present invention may be selected from dodecane-1,12-diisocyanate, 2-ethyltetramethylene-1,4-diisocyanate, 2-methylpentamethylene-1,5-diisocyanate, tetramethylene-1,4-diisocyanate, hexamethylene-1,6-diisocyanate, cyclohexane-1,3-diisocyanate, cyclohexane-1,4-diisocyanate, isophorone diisocyanate, hexahydrotoluene-2,4-diisocyanate, hexahydrotoluene-2,5-diisocyanate, dicyclohexylmethane- 2,2'-diisocyanate, dicyclohexylmethane-4,4'-diisocyanate, dicyclohexylmethane-2,4'-diisocyanate, toluene-2,4-diisocyanate, toluene-2,6-diisocyanate, diphenylmethane-2,2'-diisocyanate (2,2'-MDI), diphenylmethane-4,4'-diisocyanate (4,4'-MDI), diphenylmethane-2,4'-diisocyanate (2,4'-MDI), polyphenyl polymethylene polyisocyanate (crude MDI) and mixtures thereof.

[0143] Commercially available diisocyanates generally contain dimer (uretdiones), trimer (triazines) and oligomeric compounds. In the composition according to the invention, these mixtures of monomers and oligomers can be used without separation of by-products or purification.

[0144] According to a preferred embodiment of the present invention, the polyisocyanate component (B) is selected from methylene diphenyl diisocyanate (MDI) (including any or all isomers thereof), polymeric methylene diphenyl diisocyanate and / or mixtures thereof.

[0145] According to the most preferred embodiment, the polyisocyanate component (B) comprises 2,2'-methylene diphenyl diisocyanate (2,2'-MDI), 4,4'-methylene diphenyl diisocyanate (4,4'-MDI) and polymeric methylene diphenyl diisocyanate.

[0146] Polyurethane foam formation

[0147] Another object of the present invention is to provide an improved polyurethane foam obtained by mixing and curing the above-mentioned two-component curable composition.

[0148] The polyurethane foams of the invention can be prepared in a customary manner, in particular by mixing and / or blending the two components together.

[0149] According to a preferred mode of preparing such polyurethane foams, the polyol composition (A) and the polyisocyanate component (B) are reacted in such an amount that the molar ratio of the NCO groups of the polyisocyanate component (B) to the sum of the reactive hydrogen atoms of the component (A) is from 0.85: 1 to 1.75: 1, preferably from 0.8: 1 to 1.3: 1, more preferably from 1.0: 1 to 1.2: 1. This corresponds to a ratio of 85% to 175%, preferably from 80% to 120%, more preferably from 100% to 130%, most preferably from 100% to 120%, respectively, of the stoichiometric ratio.

[0150] The "reactive hydrogen atoms of component (A)" means the total of reactive hydrogen atoms contributed by the polyol contained in the polyol composition (A), specifically, by the polyol contained in at least the polyether polyol a1) and the castor oil a2).

[0151] Typically, a blowing agent is added and / or provided during the polyurethane forming reaction. The blowing agent may be air, nitrogen, argon, carbon dioxide or any other inert gas. The blowing agent may also be water, which reacts with the isocyanate to generate carbon dioxide in situ, or may be a fluorinated hydrocarbon such as dichlorodifluoromethane, 1,1-dichloro-1-fluoroethane, 1-chloro-1,1-difluoroethane, 2,2-dichloroethane, etc. Non-fluorinated organic compounds such as pentane and acetone may also be used as blowing agents.

[0152] According to a preferred embodiment, the polyurethane foam according to the present invention is prepared by reacting the polyol composition (A) with the polyisocyanate component (B) in the presence of a blowing agent selected from air, nitrogen, carbon dioxide or a mixture thereof. The amount of blowing agent required may vary depending on the desired density of the foam. Suitable levels of blowing agent are known to those skilled in the art. According to a preferred embodiment, the blowing agent is used in an amount that can obtain a density of 100 kg / m 3 Up to 700kg / m 3 The density of the polyurethane foam used.

[0153] According to the most preferred embodiment, the blowing agent is air and is provided during mixing / blending of the two-component composition, for example by stirring the blend at 1500 to 10000 rpm for 10 to 30 seconds. These stirring conditions are sufficient to introduce air to achieve foam formation.

[0154] Advantageously, when mixed together, the polyol composition and the polyisocyanate according to the invention form a composition having a viscosity of 1000 to 2000 mPa.s, preferably 1200 to 1800 mPa.s at 25° C. before curing. For example, the viscosity can be measured 10 to 15 minutes after mixing the polyol composition and the polyisocyanate according to the invention.

[0155] Advantageously, after mixing / blending components (A) and (B) as described above, the foam obtained is cured.

[0156] The applicant has found that the inventive two-component composition according to the invention has a slow curing reaction and thus a low reactivity and can be cured at relatively low temperatures.

[0157] Advantageously, the polyurethane foam is cured at a temperature of from 10 to 50°C, preferably from 20 to 40°C.

[0158] Advantageously, the polyurethane foam is cured for a period of time of from 15 minutes to 96 hours, preferably from 30 minutes to 72 hours.

[0159] Advantageously, when mixed together to form a polyurethane foam, the polyol composition (A) and the polyisocyanate component (B) according to the invention form a composition reaching 5 Pa.s at 25°C within a period of greater than or equal to 40 minutes, preferably greater than or equal to 45 minutes.

[0160] The low reactivity of the composition according to the invention is also characterized by a longer gel time relative to the compositions of the prior art. Specifically, after mixing the polyol composition according to the invention and the polyisocyanate at 25° C., the gel time preferably occurs for more than 200 minutes, preferably for more than 300 minutes, more preferably for more than 400 minutes.

[0161] Preferably, after mixing the polyol composition according to the invention and the polyisocyanate component at 40° C., a gel time of more than 120 minutes, preferably more than 160 minutes, more preferably more than 200 minutes occurs.

[0162] Preferably, after mixing the polyol composition according to the invention and the polyisocyanate at 60° C., a gel time of more than 60 minutes, preferably more than 90 minutes, more preferably more than 100 minutes occurs.

[0163] Since the composition according to the present invention has low viscosity before curing, has the ability to cure at a relatively low temperature and has low reactivity, the composition is easy to handle and can be applied to a hollow core insulator and easily cured therein.

[0164] Advantageously, the polyurethane foam according to the present invention has a Shore hardness (A) of less than or equal to 60, preferably less than or equal to 50, more preferably from 20 to 50.

[0165] Advantageously, the density of the polyurethane foam according to the invention is between 250 and 500 kg / m 3 , preferably a density of about 400 kg / m 3 .

[0166] Advantageously, the polyurethane foam according to the invention has a tan delta measured at 23° C. according to IEC 62631-2-1 of 5% to 20%.

[0167] Advantageously, the dielectric constant of the polyurethane foam according to the invention is between 5 and 12 F / m, preferably between 6 and 10 F / m.

[0168] Advantageously, the volume resistivity of the polyurethane foam according to the invention is 5*10 9 Up to 5*10 12 Ω.cm.

[0169] Advantageously, the specific reaction enthalpy of the polyurethane foam according to the invention is between 40 J / g and 50 J / g.

[0170] Use of the composition according to the invention

[0171] According to another aspect, the invention relates to the use of a two-component composition and / or a polyurethane foam produced therefrom for filling hollow-core insulators, in particular hollow-core insulator bodies, the composition comprising at least:

[0172] - Component (A), which is a polyol composition comprising, based on the total weight of the polyol composition:

[0173] a1) 35% to 90% by weight of one or more polyether polyols having an average hydroxyl functionality of greater than 2,

[0174] a2) 10 to 50% by weight of castor oil,

[0175] wherein at least 80% by weight of the total weight of polyols in the composition is provided by polyether polyols a1) and castor oil a2),

[0176] and

[0177] - component (B) which is a polyisocyanate having an average NCO functionality of greater than 2.

[0178] The hollow core insulation filled with polyurethane foam as detailed above is advantageously manufactured by a method comprising at least the following steps:

[0179] - Provide hollow core insulators,

[0180] - A two-component composition is provided, which comprises at least a polyol composition (A), wherein the polyol composition (A) is a polyol composition comprising the following substances based on the total weight of the polyol composition:

[0181] a1) 35% to 90% by weight of one or more polyether polyols having an average hydroxyl functionality of greater than 2,

[0182] a2) 10 to 50% by weight of castor oil,

[0183] wherein at least 80% by weight of the total weight of polyols in the composition is provided by polyether polyols a1) and castor oil a2), and

[0184] a polyisocyanate component (B) which is a polyisocyanate having an average NCO functionality of greater than 2,

[0185] - reacting the two components, in particular in the presence of a blowing agent, to produce a polyurethane foam,

[0186] -Fill the hollow core insulator body with polyurethane foam,

[0187] - Curing of the polyurethane foam in the hollow core insulation.

[0188] According to an advantageous embodiment of the use according to the invention, the polyol composition (A) corresponds to the above disclosure in the section "Polyol composition (A)".

[0189] According to an advantageous embodiment of the use according to the invention, the polyisocyanate component (B) corresponds to the above disclosure in the section “Curable two-component compositions”.

[0190] The body of the hollow core insulator may be filled with polyurethane foam by spraying, pouring or injecting the foam into the body. It will be appreciated that during filling of the body of the hollow core insulator, the foam remains in a manageable uncured form, which allows for filling of the hollow core insulator.

[0191] In an alternative embodiment, the body may be filled with a combination of the polyurethane foam according to the present invention and one or more other insulating foam materials such as an insulating gas, such as SF6.

[0192] The body of the hollow insulator can have any suitable filling degree. Advantageously, at least 70% by volume, preferably at least 90% by volume of the body is filled with the polyurethane foam according to the invention. According to a particularly preferred embodiment of the invention, the body of the hollow insulator is completely filled with the polyurethane foam, i.e. the filling degree of the body is at least 95% by volume, preferably 100% by volume.

[0193] Advantageously, the polyurethane foam is cured at a temperature of 10° C. to 50° C., preferably 20° C. to 40° C., to obtain a cured polyurethane foam. Preferably, the polyurethane foam is cured at ambient temperature.

[0194] Advantageously, the polyurethane foam is cured for a period of time of from 15 minutes to 96 hours, preferably from 30 minutes to 72 hours.

[0195] Advantageously, the cured polyurethane foam according to the invention has a glass transition temperature below -40°C, preferably from -40°C to -70°C.

[0196] The polyurethane foams according to the present invention can also be used as low temperature flexible, low stress encapsulation systems for electronic components.

[0197] According to another aspect, the present invention relates to a hollow core insulation filled with a polyurethane foam prepared by reacting the above-mentioned polyol composition (A) with the above-mentioned polyisocyanate component (B).

[0198] Suitable hollow core insulators include, but are not limited to, composite insulators, porcelain insulators, and hybrid insulators.

[0199] Besides the polyurethane foam according to the invention, the hollow core insulation may optionally also contain other electrically insulating materials, such as nitrogen or sulfur hexafluoride.

[0200] Example:

[0201] In the following examples, and unless otherwise stated, the contents and percentages are given by mass.

[0202] I-Raw Materials

[0203] I-1) Polyether polyol:

[0204] - Baygal K 55, supplied by Bayer. This is a trifunctional polyether polyol having a viscosity of about 600 mPas and a hydroxyl number of 370-400 mgKOH / g.

[0205] - Lupranol 2007 / 1, supplied by BASF. This is a trifunctional, highly reactive polyether polyol with primary hydroxyl end groups. Its viscosity is about 1227 mPas and its hydroxyl number is 27 mg KOH / g (DIN 53 240).

[0206] - Lupranol 2095, supplied by BASF. This is a trifunctional polyether polyol with primary hydroxyl end groups. Its viscosity is about 850 mPas and its hydroxyl number is 35 mg KOH / g (DIN 53 240).

[0207] I-2) Polyolefin polyol (comparison):

[0208] - Polybd R45 HTLO, supplied by SARTOMER. This is a hydroxyl-terminated polybutadiene with a viscosity of 5 Pas at 30° C., a hydroxyl functionality of 2.5 and a molecular weight Mn of 2800 g / mol. The 1,2 vinyl content is 20%.

[0209] 1-3) Polyester polyol:

[0210] - Castor oil, supplied by Nidera Handelscompagnie BV.

[0211] - Sovermol 1111, supplied by BASF (comparison). This is a branched polyetherester with a viscosity of 300-700 mPas at 25° C. (DIN 53015). According to the document “From vegetable oils to polyurethanes: synthetic routes to polyols and main industrial products” in the journal “Polymers Review” (manuscript LMSC-2011-0133.R1), these materials are produced by epoxidation of natural oils followed by nucleophilic attack of an alcohol (e.g. CH3OH) to open the epoxide ring. Then, in a third step, the hydroxylated oil is transesterified with the same alcohol.

[0212] I-4) Mineral oil:

[0213] - Nyflex 820 supplied by Nynas GmbH. Severely hydrotreated process oil with a viscosity of 90-110 cSt (ASTM 445) at 40°C.

[0214] I-5) Foam stabilizer:

[0215] -TEGOSTAB B 8863Z, supplied by Evonik. This is a polyether-modified polysiloxane.

[0216] I-6) Polyisocyanate

[0217] -Suprasec 2447, supplied by Huntsman Polyurethanes.

[0218] I-7) Other additives:

[0219] - HR 1862 (DY 3601), supplied by Huntsman. This is polypropylene glycol diglycidyl ether with an epoxy index of 2.47-2.60 eq / kg (ISO 3001).

[0220] - Cab-O-sil M5, supplied by Cabot Specialty Chemicals; and Aerosil 200, supplied by Evonik. These are fumed silicas.

[0221] II-Preparation of polyol composition (A)

[0222] All components of each composition of the examples shown in Table 1 were placed in a metal can of sufficient size in a given ratio, except for the polyisocyanate component Suprasec 2447, to produce 200 g of a polyol composition mixture. The mixture was then prepared by stirring the components with a propeller stirrer at 23° C. for about 2 minutes, producing a polyol composition (A).

[0223] Example 1 is according to the present invention.

[0224] Example 2 is comparative and corresponds to Example 1 according to the disclosure of US2018 / 0051124.

[0225] III-Preparation of a Reactive Mixture of Polyol Composition (A) and Polyisocyanate (B):

[0226] About 150 g of component A and the corresponding amount of component B according to Table 1 were placed in a metal can and then mixed for 2 minutes at ambient temperature with a propeller stirrer. 80 g of this reactive mixture was then used to produce foams and the rest was used to test gel time and produce plaques for tan delta and other tests below.

[0227] IV-Production of polyurethane foam:

[0228] 80 g of the polyol / isocyanate mixture was placed in a 200 ml cup and then stirred at 2000 rpm for 30 seconds using a small high shear dispersing mixer. This shear using the equipment was sufficient to introduce such an amount of air that a volume increase of about 30% was achieved due to foam formation. The resulting foam was then allowed to cure for 72 hours at 23° C. The cured foam samples were then checked for uniformity of appearance. The requirement for passing this foam stability test was to show no signs of collapse.

[0229] V-property measurement test

[0230] Storage stability of polyol composition (A):

[0231] Storage stability is evaluated over a period of 1 month at room temperature. A composition is considered stable if it remains homogeneous with no signs of separation. Compositions that exhibit component incompatibility typically exhibit more than one phase after a period of time.

[0232] Viscosity measurement:

[0233] The polyol composition (A) and the mixture of components A and B were tested with a Rheomat viscometer and the viscosity development was followed until 5 Pas was reached. The time required to reach 5 Pas was recorded. The viscosity was measured according to DIN 53019.

[0234] Tanδ and Tg measurements:

[0235] The dielectric loss factor tan δ is determined according to the international standard IEC 62631-2-1. The mixture of components A and B (without foaming) is cast into a mold, and 1 mm and 2 mm thick plates are produced by curing the mixture at 90° C. for 4 hours. The tan δ is then measured on a 2 mm thick plate. The glass transition temperature Tg is measured by DSC starting at -80° C., and the midpoint is estimated.

[0236] Volume resistivity measurement:

[0237] The volume resistivity is measured according to the international standard IEC 62631-3-1.

[0238] Determination of specific reaction enthalpy

[0239] The specific reaction enthalpy is determined by examining about 20 mg of the polyol composition / polyisocyanate mixture in a DSC apparatus. It is heated from ambient temperature to about 260°C at a constant heating rate of 10K / min. The heat flow signal between about 60°C and 236°C is integrated and the resulting heat released is divided by the exact mass of the test material. This ultimately yields a specific reaction enthalpy value (J / g).

[0240] VI-Test Results

[0241] Table 1

[0242]

[0243]

[0244] Example 3 (comparative): This example reproduces a foam according to the prior art WO 2021 / 058500, which discloses a method for filling a hollow core insulation with heat-expandable hollow spheres. A foam supplied by Nouryon under the name It was found that, in addition to the fact that this composition contains halogen and its cost is much higher than the inventive composition of Example 1, it also requires high temperatures (about 160° C.) to activate the expansion of the hollow spheres in the hollow core insulator.

[0245] VII-Discussion of Results

[0246] The results summarized in Table 1 show that the polyol composition according to the invention (Example 1) is storage stable, has a high biocontent, and contains available components, in particular components that are not restricted by the Chemical Weapons Convention, compared to the compositions of the prior art. The composition also has the lowest cost.

[0247] When combined with a polyisocyanate component, the polyol composition according to the present invention can form a mixture that can be applied and cured at 23° C. Based on the results of Table 1, the curable composition according to the present invention has:

[0248] - Slower curing reaction, i.e. 61 minutes (compared to 32 minutes in the case of Comparative Example 2), and longer gel times at different temperatures, thus having lower reactivity. This increased reaction time is particularly attractive for applications as filler for bulk hollow core insulators.

[0249] -Higher glass transition temperature,

[0250] - lower specific reaction enthalpy, namely 44 J / g (compared to 67.9 J / g in the case of Comparative Example 2),

[0251] - higher softness, i.e. Shore A hardness = 35 (compared to Shore A hardness = 69 in the case of Comparative Example 2),

[0252] -Good temperature flexibility.

Claims

1. A polyol composition (A), comprising, based on the total weight of the composition: a1) 35% to 90% by weight of one or more polyether polyols having an average hydroxyl functionality of greater than 2, a2) 10 to 50% by weight of castor oil, a3) 5% to 30% by weight of one or more mineral oils, a4) 0.05% to 10% by weight of one or more foam stabilizers, At least 80% by weight of the total weight of polyols in the composition is provided by polyether polyol a1) and castor oil a2).

2. The polyol composition according to claim 1, wherein the polyether polyol a1) is selected from linear or branched polyethylene oxide, polypropylene oxide, hydroxyl-terminated ethylene oxide / propylene oxide block copolymers and mixtures thereof.

3. The polyol composition according to claim 1 or claim 2, wherein the polyether polyol is a mixture of a polyether polyol having a hydroxyl value of less than or equal to 200 mg KOH / g and a polyether polyol having a hydroxyl value of greater than 200 mg KOH / g.

4. The polyol composition according to claim 3, wherein the polyether polyol a1) comprises 5 to 20% by weight of one or more polyether polyols having a hydroxyl value greater than 200 mg KOH / g and 30 to 70% by weight of one or more polyether polyols having a hydroxyl value less than or equal to 200 mg KOH / g, based on the total weight of the composition. 5 . The polyol composition according to claim 1 , wherein the mineral oil a3) is a naphthenic mineral oil.

6. The polyol composition according to claim 1, wherein the foam stabilizer a4) is selected from polydimethylsiloxanes, organofunctional polydimethylsiloxanes, siloxane polyether copolymers, block copolymers having silicone and organic blocks, and mixtures thereof.

7. The polyol composition according to any one of claims 1 to 6, further comprising an additive selected from the group consisting of epoxy components, rheology modifiers, surfactants, flame retardants, fillers, catalysts, desiccants, dyes, pigments, flame retardants, softeners, heat aging stabilizers, thixotropic agents, blowing agents and mixtures thereof.

8. The polyol composition of claim 7, wherein the epoxy component is polypropylene glycol diglycidyl ether.

9. The polyol composition of claim 7 or claim 8, wherein the rheology modifier is fumed silica.

10. The polyol composition according to any one of claims 1 to 9, which does not contain polyolefin polyol.

11. A two-component composition comprising at least: Component (A), which is the polyol composition according to any one of claims 1 to 10, Component (B), which is a polyisocyanate having an average NCO functionality of greater than 2.

12. The composition according to claim 11, wherein the component (B) comprises at least methyl diphenyl diisocyanate.

13. A composition according to claim 11 or claim 12, wherein the molar ratio of the NCO groups of component (B) to the sum of the reactive hydrogen atoms of component (A) is from 0.80:1 to 1.75:

1.

14. Polyurethane foam obtained by reacting the polyol composition (A) of the composition according to any one of claims 11 to 13 with component (B), in particular in the presence of a blowing agent.

15. Use of a two-component composition and / or a polyurethane foam produced therefrom for filling hollow core insulation, the composition comprising at least: Component A), which is a polyol composition comprising, based on the total weight of the composition: a1) 35% to 90% by weight of one or more polyether polyols having an average hydroxyl functionality of greater than 2, a2) 10 to 50% by weight of castor oil, wherein at least 80% by weight of the total weight of polyols in the composition is provided by polyether polyol a1) and castor oil a2), Component B) which is a polyisocyanate having an average NCO functionality of greater than 2.

16. A hollow core insulator filled with a polyurethane foam obtained by reacting the polyol composition (A) according to claim 15 with component (B).

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