Polyol composition for the production of polyurethane foams suitable for filling hollow core insulators

Abstract

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

Description

Technical Field

[0001] The present invention is directed to polyol compositions which, when combined with polyisocyanates, give polyurethane foams. The present invention also relates to the use of polyurethane foams for filling hollow core insulators.

Background Art

[0002] Hollow core insulators play an important role in various application fields for high voltage insulation techniques (specifically, outdoor power plants, substations, and electrical equipment). Originally, ceramic-based hollow core insulators were basically used, but on the other hand, the use of hollow core composite insulators has been increasing.

[0003] A hollow core insulator typically consists of a hollow-wound inner tube or body that provides support and insulation for electrical wires and equipment, upper and lower flanges, and a silicone rubber shed.

[0004] The body of such a hollow core insulator is usually filled with nitrogen or sulfur hexafluoride as an electrical insulating material to avoid internal flashover. On the other hand, it is difficult to firmly confine such gases within the insulation system over a long period while the temperature changes. The use of such gas dielectrics requires a very sophisticated monitoring system to detect any leakage in the hollow core insulator during operation. Otherwise, the gas pressure can drop and moisture can enter the hollow core insulator, reducing the insulation strength of the insulation system. Furthermore, sulfur hexafluoride, which is a fluorine-containing compound, is one of the greenhouse gases and is therefore very problematic from an ecological point of view.

[0005] On the one hand, it is impossible to easily replace the gas with another electrical insulating material. The reason is that the dimensions of high-voltage insulators are large, and their length can reach up to 10 m at most. If conventional solid dielectric materials were used, it is assumed that the total weight of the insulator would become extremely large, which would not be practical for the above-mentioned applications.

[0006] To solve this problem, the use of dielectric foams has been proposed. For example, Patent Document 1 discloses the use of a dry sintered tacticular foam based on poly(acrylonitrile-co-vinylidene chloride-co-methyl methacrylate) hollow microspheres as an ultra-light filler in a hollow core insulator. However, since these foams contain a significant amount of halogen, they are environmentally unfriendly products.

[0007] Patent Document 2 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 non-halogen polyurethane foam. Polyurethane foam is most preferred. On the other hand, the authors do not touch on the composition of such polyurethane foams.

[0008] Polyurethane foams are well known and are used in various applications. Polyurethane foams can be produced by reacting polyisocyanate with polyol in the presence of various additives. Polyurethane foams provide a wide variety of physical properties and dielectric properties desirable for use in insulation systems. Furthermore, the light weight of polyurethane foams promotes their application in high-voltage insulation. Compared with the gases traditionally used, polyurethane foams make it much easier to seal in insulation systems and eliminate the potential risk of gas leakage.

[0009] Patent Document 3 discloses a polyurethane foam for use in a high-voltage resin-impregnated paper bushing to fill the gap between a capacitor core and an outer hollow insulator. The polyurethane foam is prepared from (A) a polyol composition containing a polyether polyol, a polyolefin polyol, and a polyester polyol that can be obtained by epoxidation of an unsaturated fatty acid ester and subsequent ring-opening reaction with a compound containing active hydrogen, and (B) a polyisocyanate compound. While this composition is very useful as a foam for high-voltage bushings, it is somewhat over-engineered, making it too costly for use in larger-volume applications (such as filling a hollow core insulator). Furthermore, the composition contains a polyolefin polyol, specifically a polybutadiene-based polyol, which is in conflict with the Chemical Weapons Convention and thus not globally available. Additionally, some of the components used in this composition (such as Sovermol 1111) are not REACH-registered by the manufacturer and are therefore no longer available.

[0010] Therefore, there is a need to provide a new polyurethane foam suitable for filling a hollow core insulator based on a composition where all components are available and none of them conflict with the Chemical Weapons Convention.

[0011] There is also a need to provide a new polyurethane foam for filling a hollow core insulator that is more environmentally friendly, specifically halogen-free, preferably with an increased content of renewable raw materials and thus a reduced carbon footprint.

[0012] For filling a large-volume hollow core insulator, it is also desirable that the new polyurethane foam be cost-effective.

[0013] Another important factor is to provide a composition having storage stability. In fact, the two components, a polyol compound and a polyisocyanate component, are usually mixed immediately before the production of the polyurethane foam. Since the polyol compound often contains various additives dispersed therein in addition to some polyols, such mixtures often tend to cause sedimentation of solid components. Therefore, the storage stability of the polyol component is a requirement to be met.

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

[0015] This composition not only makes it possible to avoid all the drawbacks of the prior art compositions, but also makes it possible to prepare polyurethane foams with improved properties in an unexpected way.

Prior Art Documents

Patent Documents

[0016]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

[0017] The present invention relates to a polyol composition (A), which, 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 more than 2, a2) 10% to 50% by weight of castor oil, a3) 5% to 30% by weight of one or more mineral oils, and a4) 0.05% to 10% by weight of one or more foam stabilizers, and containing At least 80% by weight of the total weight of the polyols in the composition is provided by the polyether polyol a1) and the castor oil a2).

[0018] Advantageously, the polyether polyol a1) is selected from linear or branched polyethylene oxide, polypropylene oxide, hydroxy-terminated ethylene oxide / propylene oxide block copolymers, and mixtures thereof.

[0019] According to a preferred embodiment, the polyether polyol is a mixture of a polyether polyol having a hydroxyl value of 200 mg KOH / g or less and a polyether polyol having a hydroxyl value of more than 200 mg KOH / g.

[0020] Advantageously, the mineral oil a3) is a naphthenic mineral oil.

[0021] According to a preferred embodiment, the polyether polyol a1) contains 5% to 20% by weight of one or more polyether polyols having a hydroxyl value of more than 200 mg KOH / g and 30% to 70% by weight of one or more polyether polyols having a hydroxyl value of 200 mg KOH / g or less, based on the total weight of the composition.

[0022] Advantageously, the polyol composition according to the present invention further contains additives selected from epoxy components, rheology modifiers, surfactants, flame retardants, fillers, catalysts, dehydrating agents, dyes, pigments, flame-resistant agents, softeners, heat degradation stabilizers, thixotropic agents, foaming agents, and mixtures thereof.

[0023] Advantageously, the epoxy component is polypropylene glycol diglycidyl ether.

[0024] Advantageously, the rheology modifier is fumed silica.

[0025] According to a preferred embodiment, the polyol composition (A) according to the present invention does not contain a polyolefin polyol. The present invention further relates to a two-component composition, which two-component composition comprises · component (A), which is the above polyol composition, and · component (B), which is a polyisocyanate having an average NCO functionality of more than 2, and at least contains.

[0026] Advantageously, component (B) contains at least methyl diphenyl diisocyanate.

[0027] Advantageously, the molar ratio of the NCO groups of component (B) to the total of the reactive hydrogen atoms in component (A) is in the range of 0.80:1 to 1.75:1.

[0028] The present invention also relates to a polyurethane foam obtained by reacting the polyol composition (A) and component (B) of the above composition, specifically in the presence of a blowing agent.

[0029] The present invention also relates to the use of a composition for filling a hollow core insulator, the composition comprising component (A), which is a polyol composition, wherein the polyol composition is based on the total weight of the composition a1) one or more polyether polyols having an average hydroxyl functionality of more than 2 and being 35% to 90% by weight, and a2) castor oil being 10% to 50% by weight, and containing component (A), wherein at least 80% by weight of the total weight of the polyols in the composition is provided by the polyether polyol a1) and the castor oil a2), and component (B), which is a polyisocyanate having an average NCO functionality of more than 2, and at least contains.

[0030] The present invention Component (A) which is a polyol composition, wherein this polyol composition is based on the total weight of the composition, a1) one or more polyether polyols having an average hydroxyl functionality of more than 2, in an amount of 35% to 90% by weight, a2) castor oil in an amount of 10% to 50% by weight, and component (A) wherein at least 80% by weight of the total weight of the 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 more than 2, and also relates to a hollow core insulator filled with a polyurethane foam obtained by reacting them.

Mode for Carrying Out the Invention

[0031] The term "consisting essentially of" following one or more features means that, in addition to the explicitly recited components or steps, components or steps that do not substantially affect the properties and characteristics of the present invention may be included in the process or material of the present invention.

[0032] The expression "contained in X to Y" includes the boundaries unless otherwise explicitly stated. This expression means that the target range includes the X value and the Y value as well as all values between X and Y.

[0033] Polyol Composition (A) A first object of the present invention is a polyol composition (A) for preparing a polyurethane foam, and the polyol composition is based on the total weight of the composition, a1) one or more polyether polyols having an average functionality of more than 2, in an amount of 35% to 90% by weight, a2) castor oil in an amount of 10% to 50% by weight, a3) one or more mineral oils in an amount of 5% to 30% by weight, a4) one or more foam stabilizers in an amount of 0.05% to 10% by weight, and At least 80% by weight of the total weight of the polyols in the composition is provided by polyether polyol a1) and castor oil a2).

[0034] Preferably, at least 90% by weight, more preferably at least 95% by weight, and most preferably 98% by weight of the total weight of the polyols in the polyol composition (A) is provided by polyether polyol a1) and castor oil a2). Advantageously, the polyol composition (A) according to the invention does not contain polyolefin polyol.

[0035] "Does not contain polyolefin polyol" means that, based on the total weight of the polyol composition, the content of one or more polyolefin polyols in the polyol composition is less than 5% by weight, preferably less than 2% by weight, more preferably less than 1% by weight. 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.

[0036] In a preferred embodiment, the polyol composition (A) according to the invention does not contain polyisoprene polyol and / or polybutadiene polyol.

[0037] Advantageously, compounds a1), a2), a3), and a4) correspond to 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).

[0038] Advantageously, the polyol composition (A) according to the invention, based on the total weight of the composition, a1) one or more polyether polyols having an average functionality greater than 2 and accounting for 35% to 90% by weight, a2) castor oil accounting for 10% to 50% by weight, a3) one or more mineral oils accounting for 5% to 30% by weight, a4) One or more foam stabilizers in an amount of 0.05% to 10% by weight, and consists essentially of.

[0039] Advantageously, the polyol composition according to the invention further comprises one or more additives a5) selected from those commonly used in the preparation of polyurethane foams.

[0040] The Applicant has found that the polyol composition according to the invention remains stable when stored over a long period, for example, when stored for up to 1 month, preferably up to 6 months, more preferably up to 12 months.

[0041] The Applicant has surprisingly also found that by carefully selecting this polyol composition, it is possible to produce polyurethane foams with a decrease in the reaction enthalpy and an increase in the reaction time compared to the compositions according to the prior art. Such advantages are particularly interesting in the case of the use of polyurethane foams for filling large-volume insulation systems, specifically, hollow-core insulators.

[0042] Furthermore, it has been found that the polyurethane foam prepared from the polyol composition according to the invention is very soft and exhibits low-temperature flexibility, which is also a desirable characteristic for use as a filler in hollow-core insulators.

[0043] a1) Polyether Polyol The polyether polyols suitable for the polyol composition according to the present invention can be selected from polyether polyols based on ethylene oxide, polyether polyols based on propylene oxide, the corresponding ethylene oxide / propylene oxide copolymers which can be either 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 copolymer can vary within a wide range. Thus, for example, it is possible to react only the terminal hydroxyls of the polyether polyol with ethylene oxide.

[0044] According to one embodiment, the polyether polyol is a linear or branched polyethylene oxide or polypropylene oxide, or a mixture thereof.

[0045] According to another embodiment, the polyether polyol is a hydroxy-terminated ethylene oxide / propylene oxide block copolymer.

[0046] According to another embodiment, the polyether polyol is a mixture of linear or branched polyethylene oxide and / or polypropylene oxide and a hydroxy-terminated ethylene oxide / propylene oxide block copolymer.

[0047] The polyether polyol used in the polyol composition according to the present invention has an average hydroxyl functionality of more than 2. Preferably, the polyether polyol has an average hydroxyl functionality in the range of 2.5 to 4, preferably 2.5 to 3.5. According to a preferred embodiment, the polyether polyol has an average hydroxyl functionality of 3.

[0048] Such 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 propylene oxide, ethylene oxide, and / or a mixture of propylene oxide and ethylene oxide). The polyfunctional active hydrogen initiators are all those commonly used in the preparation of polyether polyols having more than two functionalities, preferably two to four functionalities, and include, for example, water, aliphatic polyhydroxy compounds having two or three hydroxy groups, cycloaliphatic polyhydroxy compounds, or aromatic polyhydroxy compounds (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, on pages 31 - 38, 304, and 305 of Ullmann’s Encyclopedia of Industrial Chemistry, 4th Edition, Volume 19, 1980.

[0049] Polytetrahydrofuran can also be used, and polytetrahydrofuran is commercially available, for example, under the trade name POLYMEG (registered trademark).

[0050] Advantageously, the polyether polyols according to the invention have a molecular weight in the range of 100 - 2000 g / mol, preferably 200 - 1000 g / mol, more preferably 300 - 600 g / mol.

[0051] Advantageously, the polyol composition according to the invention contains 40 wt% - 80 wt% of one or more polyether polyols, based on the total weight of the polyol composition (A).

[0052] According to a preferred embodiment of the present 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.

[0053] As used herein, the term "hydroxyl value" refers to the number of milligrams of potassium hydroxide corresponding to the hydroxyl content in one gram of polyether polyol, as determined by the test method DIN53240-2. The unit of hydroxyl value is expressed as mg of KOH per g of polyether polyol.

[0054] "Polyether polyol having a low hydroxyl value" means a polyether polyol having a hydroxyl value within the range of 200 mg KOH / g or less, preferably within the range of 10 - 200 mg KOH / g, more preferably within the range of 15 - 100 mg KOH / g, and most preferably within the range of 20 - 50 mg KOH / g.

[0055] "Polyether polyol having a high hydroxyl value" means a polyether polyol having a hydroxyl value exceeding 200 mg KOH / g, preferably within the range of 250 - 500 mg KOH / g, preferably within the range of 300 - 450 mg KOH / g.

[0056] Advantageously, the polyol composition according to the present invention contains 5 wt% - 20 wt%, preferably 8 wt% - 15 wt% of one or more polyether polyols having a high hydroxyl value, and 30 wt% - 70 wt%, preferably 40 wt% - 60 wt% of one or more polyether polyols having a low hydroxyl value.

[0057] 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 contained in 300 - 450 mg KOH / g, and one or more polyether polyols having an average functionality of 3 and a hydroxyl value contained in 20 - 50 mg KOH / g.

[0058] According to the most preferred embodiment, the polyether polyol contains 5 wt% to 20 wt% of one or more polyether polyols having a hydroxyl value of 300 to 450 mg KOH / g and 30 wt% 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).

[0059] a2) Castor Oil 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.

[0060] Castor oil is a natural oil polyol derived from castor beans. Chemically, castor oil is a triglyceride in which the three hydroxyl groups of glycerol are esterified mainly with 12-hydroxyoctadec-9-enoic acid (known as ricinoleic acid) as a fatty acid.

[0061] Preferably, the castor oil according to the present invention is unmodified castor oil.

[0062] "Unmodified castor oil" means castor oil that has not been subjected to any treatment process other than purification.

[0063] Preferably, the castor oil according to the present invention has an average functionality number of 2.0 to 2.7, more preferably 2.2 to 2.7.

[0064] Preferably, the castor oil according to the present invention has an average hydroxyl value in the range of 30 to 170 mg KOH / g, more preferably 100 to 160 mg KOH / g.

[0065] Preferably, the polyol composition according to the present invention contains 15 wt% to 40 wt% of castor oil with respect to the total weight of the polyol composition (A).

[0066] Advantageously, the weight ratio of the polyether polyol(s) to the castor oil ranges from 10:1 to 1:5, preferably from 5:1 to 1:1, and most preferably from 4:1 to 1:1.

[0067] a3) Mineral Oil The mineral oil according to the present invention is advantageously selected from aliphatic saturated hydrocarbons, cycloaliphatic saturated hydrocarbons, and branched aliphatic saturated hydrocarbons distilled from petroleum, containing 5 to 24 carbon atoms, preferably 5 to 18 carbon atoms.

[0068] Preferably, the mineral oil is selected from naphthenic oils and paraffinic oils. According to a preferred embodiment, the mineral oil is a naphthenic oil.

[0069] Advantageously, the mineral oil has a viscosity in the range of 50 to 200 cSt at 40 °C, preferably 70 to 150 cSt at 40 °C, and more preferably 80 to 120 cSt at 40 °C according to ASTM 445.

[0070] Advantageously, the polyol composition according to the present invention contains 7% to 20% by weight of mineral oil based on the total weight of the polyol composition (A).

[0071] Preferably, the polyol composition according to the present invention contains 7% to 20% by weight of naphthenic oil based on the total weight of the polyol composition (A).

[0072] a4) Foam Stabilizer The polyol composition according to the present invention contains a foam stabilizer.

[0073] The foam stabilizer can be selected from the group consisting of polydimethylsiloxane, organofunctional polydimethylsiloxane, siloxane polyether copolymer, block copolymer having a silicone block and an organic block, and mixtures thereof.

[0074] According to a preferred embodiment, the foam stabilizer is selected from the group of polyether-modified polysiloxanes (specifically, polysiloxane-polyoxyalkylene block copolymers). Such stabilizers are described, for example, in US6,166,098 and EP-A936240 and are commercially available under the trade name TEGOSTAB®.

[0075] According to another preferred embodiment, the foam stabilizer is selected from the group of block copolymers having a silicone block and an organic block, and the organic block is based on, for example, caprolactone or other lactones (such as Genioperl® W35 (Wacker Chemie AG, Munich, Germany)).

[0076] Advantageously, the foam stabilizer corresponds to 0.5% to 8% by weight, more preferably 1% to 6% by weight, based on the total weight of the polyol composition (A).

[0077] a5) Additional Additive The additive is a minor addition compound that promotes the improvement of the polyol composition and / or the polyurethane foam prepared therefrom.

[0078] Advantageously, the polyol composition according to the invention further comprises optional additives selected from epoxy components, catalysts, surfactants, dehydrating agents, fillers, dyes, pigments, flame retardants, softeners, heat degradation stabilizers, thixotropy modifiers or rheology modifiers, blowing agents, and mixtures thereof.

[0079] Suitable catalysts include, for example, tertiary amines (such as N-methyldiethanolamine, triethylenediamine, triethanolamine, pentamethyldiethylenetriamine, tetramethylethylenediamine, dibenzylmethylamine, N-ethyImorpholine, N-methylmorpholine, 1-methyl-4-dimethylaminoethylpiperazine, N,N-diethyl-3-diethylaminopropylamine, 1-(2-hydroxypropyl)imidazole, or diazabicyclooctane, etc.), or organotin compounds (such as dibutyltin laurate, etc.).

[0080] Suitable flame retardants can be selected from phosphate compounds (such as tricesyl phosphate or dimethylmethanephosphonate, etc.), halogenated compounds, non-halogenated compounds, or combinations thereof. Preferably, the flame 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, etc.) can also be used.

[0081] The heat degradation stabilizer suitable for the polyol composition according to the present invention can be, for example, an aliphatic glycidyl ether (such as polypropylene glycol digylcidyl ether, etc.).

[0082] Suitable fillers can be selected from, for example, particles (such as carbonates, aluminum oxide, and silica, etc.) and natural and synthetic fibers, or mixtures thereof.

[0083] The total content of the additives in the polyol composition according to the present invention is advantageously in the range of 0.01 wt% to 30 wt%, preferably 0.05 wt% to 10 wt% based on the total weight of the polyol composition (A).

[0084] According to a preferred embodiment, the polyol composition according to the present invention contains a thixotropy modifier or a rheology modifier which is fumed silica. Preferably, the fumed silica has a surface area of 120 - 280 m2 It is hydrophilic fumed silica or hydrophobic fumed silica having a specific surface area of / g. Preferably, the polyol composition according to the present invention contains 0.01% by weight to 5% by weight of fumed silica based on the total weight of the polyol composition (A).

[0085] According to a preferred embodiment, the polyol composition according to the present invention contains an epoxy component. Preferably, the epoxy component is polypropylene glycol diglycidyl ether. Preferably, the polyol composition according to the present invention contains 0.01% by weight to 5% by weight of the epoxy component based on the total weight of the polyol composition (A).

[0086] It should be emphasized that the present invention encompasses any specific compound or any combination of groups of compounds described above herein for components a1), a2), a3), and a4).

[0087] According to a preferred embodiment, the polyol composition according to the present invention - 35% to 90% by weight of a polyether polyol having an average hydroxyl functionality in the range of 2.5 to 4, preferably 2.5 to 3.5, - 10% to 50% by weight of castor oil, - 5% to 30% by weight of a mineral oil, preferably a naphthenic mineral oil, - 0.05% to 10% by weight of a foam stabilizer, - Optionally, 0.01% to 5% by weight of additional additives selected from the group consisting of an epoxy component, a catalyst, a surfactant, a dehydrating agent, a filler, a dye, a pigment, a flame retardant, a softening agent, a heat degradation stabilizer, a thixotropy modifier or a rheology modifier, a foaming agent, and mixtures thereof, and preferably consists essentially of them.

[0088] According to the most preferred embodiment, the polyol composition according to the present invention - A hydroxyl value of more than 200 mg KOH / g, preferably within the range of 250 to 500 mg KOH / g, more preferably within the range of 300 to 450 mg KOH / g, and 5% to 20% by weight of a polyether polyol, - A hydroxyl value of 200 mg KOH / g or less, preferably within the range of 10 to 200 mg KOH / g, more preferably within the range of 15 to 100 mg KOH / g, most preferably within the range of 20 to 50 mg KOH / g, and 30% to 70% by weight of a polyether polyol, - 10% to 50% by weight of castor oil, - 5% to 30% by weight of a mineral oil, preferably a naphthenic mineral oil, - 0.05% to 10% by weight of a foam stabilizer, - Optionally, 0.01% to 5% by weight of an additional additive selected from the group consisting of an epoxy component, a catalyst, a surfactant, a dehydrating agent, a filler, a dye, a pigment, a flame retardant, a softening agent, a heat degradation stabilizer, a thixotropy modifier or a rheology modifier, a blowing agent, and mixtures thereof, and preferably consisting essentially of these.

[0089] Advantageously, the polyol composition (A) according to the invention has a viscosity in the range of 1000 to 3000 mPa·s at 25°C, preferably in the range of 1500 to 2500 mPa·s.

[0090] Curable Two-Component Composition In the production of the polyurethane foam according to the invention, the above polyol composition (A) is reacted with a polyisocyanate component (B).

[0091] Therefore, another aspect of the invention is to provide a two-component curable composition comprising the above polyol composition (A) and one or more polyisocyanate components (B) having an average NCO functionality of more than 2.

[0092] "Two-component composition" means a composition containing a polyol composition and a polyisocyanate component, and these two components are provided as two pack systems (or kits), where the polyol composition (A) is part (1) and the polyisocyanate is part (2). Such compositions in the two parts are designed for immediate mixing of the two polyurethane foam-forming compositions just before curing.

[0093] "Curable composition" means a composition containing a polyol composition (A) and a polyisocyanate component (B), and these two components can form a cured solid polyurethane by forming a chemical bond called crosslinking when they are mixed / blended together and cured.

[0094] Polyisocyanate Component (B) Polyisocyanate components useful for the production of 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 can be aromatic, cycloaliphatic, or aliphatic, and can be a monomeric compound or an oligomeric compound.

[0095] Advantageously, the polyisocyanate component has an NCO functionality of 2 or more, preferably in the range of 2.1 to 3.2.

[0096] Isocyanate "functionality" is the number of reactive NCO groups per molecule in an isocyanate molecule or a polymeric isocyanate. For example, most polyisocyanates, specifically MDI-type polyisocyanate compounds, contain a blend of monomeric MDI and polymeric MDI, and the isocyanate functionality is the average functionality over different molecules and polymer species.

[0097] As used herein, "MDI" refers to methylenediphenyl diisocyanate (also called 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" also refers to polymeric MDI and may include polymeric MDI. Polymeric MDI is a compound having a chain of three or more benzene rings linked to each other by methylene bridges, with isocyanate groups attached to each benzene ring.

[0098] 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.

[0099] Commercially available diisocyanates often contain dimers (uretdiones), trimers (triazines), and oligomeric compounds. In the compositions according to the present invention, such mixtures of monomers and oligomers can be used without separation or purification of by-products.

[0100] According to a preferred embodiment of the present invention, the polyisocyanate component (B) is selected from methylene diphenyl diisocyanate (MDI) (including any or all of its isomers), polymeric methylene diphenyl diisocyanate, and / or mixtures thereof.

[0101] According to the most preferred embodiment, the polyisocyanate component (B) includes 2,2'-methylene diphenyl diisocyanate (2,2'-MDI), 4,4'-methylene diphenyl diisocyanate (4,4'-MDI), and polymeric methylene diphenyl diisocyanate.

[0102] Polyurethane Foam Formation A further object of the present invention is to provide an improved polyurethane foam obtained by mixing and curing the above two-component curable composition.

[0103] The polyurethane foam of the present invention can be prepared in a conventional manner, specifically, by mixing and / or blending the two components together.

[0104] According to a preferred preparation mode of such a polyurethane foam, the polyol composition (A) and the polyisocyanate component (B) are reacted in an amount such that the molar ratio of the total NCO groups of the polyisocyanate component (B) to the total reactive hydrogen atoms of component (A) is in the range of 0.85:1 to 1.75:1, preferably 0.8:1 to 1.3:1, more preferably 1.0:1 to 1.2:1. This corresponds to a ratio in the range of 85% to 175%, preferably 80% to 120%, more preferably 100% to 130%, and most preferably 100% to 120% of the stoichiometric ratio.

[0105] "The reactive hydrogen atoms of component (A)" means the total reactive hydrogen atoms provided by the polyols contained in the polyol composition (A), specifically, at least the total reactive hydrogen atoms provided by the polyether polyol a1) and the castor oil a2).

[0106] Generally, a blowing agent is added and / or supplied during the polyurethane forming reaction. The blowing agent can be air, nitrogen, argon, carbon dioxide, or any other inert gas. The blowing agent can also be water (which reacts with isocyanate to produce carbon dioxide in situ) or a fluorinated hydrocarbon (such as chlorodifluoromethane, 1,1-dichloro-1-fluoroethane, 1-chloro-1,1-difluoroethane, 2,2-dichloroethane, or the like). Non-fluorinated organic compounds (such as pentane and acetone) can also be used as blowing agents.

[0107] According to a preferred embodiment, the polyurethane foam according to the present invention is prepared by reacting a polyol composition (A) and a 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 can vary depending on the desired foam density. Appropriate blowing agent levels are known to those skilled in the art. According to a preferred embodiment, the blowing agent is used in an amount such that a polyurethane foam density in the range of 100 kg / m 3 ~700 kg / m 3 is obtained.

[0108] According to the most preferred embodiment, the blowing agent is air and is supplied during the mixing / blending of the two-component composition (for example, by stirring the mixture at 1,500 to 10,000 rpm for 10 to 30 seconds). Such stirring conditions are sufficient to introduce air and achieve foam formation.

[0109] Advantageously, when mixed together, the polyol composition and the polyisocyanate according to the present invention form a composition having a viscosity in the range of 1,000 to 2,000 mPa·s, preferably 1,200 to 1,800 mPa·s, at 25°C before curing. For example, the viscosity can be measured 10 to 15 minutes after the mixing of the polyol composition and the polyisocyanate according to the present invention.

[0110] Advantageously, after mixing / blending the above components (A) and (B), the resulting foam is cured.

[0111] The applicant has found that the two-component composition of the present invention according to the present invention has a slow curing reaction, and thus low reactivity, and can be cured at a relatively low temperature.

[0112] Advantageously, the polyurethane foam is cured at a temperature in the range of 10 to 50 °C, preferably 20 to 40 °C.

[0113] Advantageously, the polyurethane foam is cured in a time range of 15 minutes to 96 hours, preferably 30 minutes to 72 hours.

[0114] Advantageously, when mixed together to form a polyurethane foam, the polyol composition (A) and the polyisocyanate component (B) according to the present invention form a composition that reaches 5 Pa·s at 25 °C in a time of 40 minutes or more, preferably 45 minutes or more.

[0115] The low reactivity of the composition according to the present invention is also characterized by a long gelation time with respect to the composition according to the prior art. Specifically, the gelation time preferably occurs in more than 200 minutes, preferably more than 300 minutes, more preferably more than 400 minutes, after mixing the polyol composition and the polyisocyanate according to the present invention at 25 °C.

[0116] Preferably, the gelation time occurs in more than 120 minutes, preferably more than 160 minutes, more preferably more than 200 minutes, after mixing the polyol composition and the polyisocyanate component according to the present invention at 40 °C.

[0117] Preferably, the gelation time occurs in more than 60 minutes, preferably more than 90 minutes, more preferably more than 100 minutes, after mixing the polyol composition and the polyisocyanate according to the present invention at 60 °C.

[0118] The composition according to the present invention has a low viscosity before curing, has the ability to cure at a relatively low temperature, and has a low reactivity. Therefore, the composition is easy to handle, applicable to a hollow core insulator, and can be easily cured there.

[0119] Advantageously, the polyurethane foam according to the present invention has a Shore hardness (A) of 60 or less, preferably 50 or less, more preferably 20 to 50.

[0120] Advantageously, the polyurethane foam according to the present invention has a density in the range of 250 to 500 kg / m 3 and preferably has a density of about 400 kg / m 3 .

[0121] Advantageously, the polyurethane foam according to the present invention has a Tan delta included in the range of 5 to 20% at 23 °C when measured according to IEC62631-2-1.

[0122] Advantageously, the polyurethane foam according to the present invention has a dielectric constant included in the range of 5 to 12 F / m, preferably 6 to 10 F / m.

[0123] Advantageously, the polyurethane foam according to the present invention has a volume resistivity included in the range of 5 * 10 9 to 5 * 10 12 Ω·cm.

[0124] Advantageously, the polyurethane foam according to the present invention has a specific reaction enthalpy included in the range of 40 J / g to 50 J / g.

[0125] Use of the Composition According to the Invention According to another aspect, the present invention relates to the use of a two-component composition and / or a polyurethane foam prepared therefrom for filling a hollow core insulator, specifically for filling the body of a hollow core insulator, and the composition - Component (A), which is a polyol composition, wherein the polyol composition is based on the total weight of the polyol composition, a1) one or more polyether polyols having an average hydroxyl functionality of more than 2, in an amount of 35% to 90% by weight, a2) castor oil in an amount of 10% to 50% by weight, and contains at least 80% by weight of the total weight of the polyols in the composition is provided by the polyether polyol a1) and the castor oil a2), Component (A); - Component (B), which is a polyisocyanate having an average NCO functionality of more than 2, and contains at least

[0126] The hollow core insulator filled with the polyurethane foam described in detail above is preferably produced by a process comprising at least the following steps. - Supplying a hollow core insulator, - A polyol composition (A), which is a polyol composition, wherein the polyol composition is based on the total weight of the polyol composition, a1) one or more polyether polyols having an average hydroxyl functionality of more than 2, in an amount of 35% to 90% by weight, a2) castor oil in an amount of 10% to 50% by weight, and contains at least 80% by weight of the total weight of the polyols in the composition is provided by the polyether polyol a1) and the castor oil a2), Polyol composition (A); - A polyisocyanate component (B), which is a polyisocyanate having an average NCO functionality of more than 2, Supplying a two-component composition containing at least - Reacting the two components, specifically in the presence of a blowing agent, to produce a polyurethane foam, - Filling the body of the hollow core insulator with the polyurethane foam, - Curing the polyurethane foam in the hollow core insulator.

[0127] According to a preferred embodiment of the use according to the present invention, the polyol composition (A) corresponds to the above disclosure in the chapter of "Polyol Composition (A)".

[0128] According to a preferred embodiment of the use according to the present invention, the polyisocyanate component (B) corresponds to the above disclosure in the chapter of "Two-Component Curable Composition".

[0129] The body of the hollow core insulator can be filled with the foam by spraying, pouring, or injecting the polyurethane foam into the body. It will be understood that while filling the body of the hollow core insulator, the foam is still in a manageable uncured form that can fill the hollow core insulator.

[0130] In an alternative embodiment, the body can be filled with a combination of the polyurethane foam according to the present invention and one or more other insulating foam materials (such as insulating gases like SF6).

[0131] The body of the hollow core insulator can have any suitable degree of filling. Advantageously, at least 70% by volume, preferably at least 90% by volume of the body is filled with the polyurethane foam according to the present invention. According to a particularly preferred embodiment of the present invention, the body of the hollow core insulator is completely filled with the polyurethane foam, i.e., the degree of filling of the body is at least 95% by volume, preferably 100% by volume.

[0132] Advantageously, by curing the polyurethane foam at a temperature in the range of 10 to 50°C, preferably in the range of 20 to 40°C, a cured polyurethane foam is obtained. Preferably, the polyurethane foam is cured at ambient temperature.

[0133] Advantageously, the polyurethane foam is cured over a period of time in the range of 15 minutes to 96 hours, preferably 30 minutes to 72 hours.

[0134] Advantageously, the cured polyurethane foam according to the present invention has a glass transition point of less than -40°C, preferably a glass transition point of -40°C to -70°C.

[0135] The polyurethane foam according to the present invention can also be applied as a low-temperature flexible and low-stress encapsulation system for electronic components.

[0136] According to another aspect, the present invention relates to a hollow core insulator filled with a polyurethane foam prepared by reacting the above polyol composition (A) and the above polyisocyanate component (B).

[0137] Suitable hollow core insulators include, but are not limited to, composite insulators, ceramic insulators, and hybrid insulators.

[0138] In addition to the polyurethane foam according to the present invention, the hollow core insulator may optionally also contain other electrical insulating materials such as nitrogen or sulfur hexafluoride. Embodiments

[0139] In the following examples, unless otherwise specified, contents and percentages are given by mass.

[0140] I - Raw Materials I-1) Polyether Polyol: - Baygal K55 supplied by Bayer. This is a trifunctional polyether polyol having a viscosity of about 600 mPas and a hydroxyl value of 370 - 400 mg KOH / g. - Lupranol 2007 / 1 supplied by BASF. This is a trifunctional highly reactive polyether polyol having primary hydroxyl end groups. It has a viscosity of about 1227 mPas and a hydroxyl value (DIN 53 240) of 27 mg KOH / g. - Lupranol 2095 supplied by BASF. This is a trifunctional polyether polyol with primary hydroxyl end groups. It has a viscosity of approximately 850 mPas and a hydroxyl value (DIN 53 240) of 35 mg KOH / g.

[0141] I-2) Polyolefin Polyol (Comparison): - Polybd R45 HTLO supplied by SARTOMER. This is a hydroxyl-terminated polybutadiene having 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%.

[0142] I-3) Polyester Polyol: - Castor oil supplied by Nidera Handelscompagnie BV. - Sovermol 1111 (comparison) supplied by BASF. This is a branched polyether ester having a viscosity (DIN 53015) of 300 - 700 mPas at 25 °C. According to the document "From vegetable oils to polyurethanes: synthetic routes to polyols and main industrial products" (manuscript LMSC-2011-0133.R1) in the "Polymers Review" journal, such materials are obtained by epoxidizing natural oils and then ring-opening the epoxides by nucleophilic attack of an alcohol (e.g., CH3OH). Then, in a third step, transesterification with the same alcohol is carried out on the hydroxylated oil.

[0143] I-4) Mineral Oil: - Nyflex 820 supplied by Nynas GmbH. A severely hydrotreated process oil having a viscosity (ASTM 445) of 90 - 110 cSt at 40 °C.

[0144] I-5) Foam Stabilizer: -TEGOSTAB B8863Z supplied by Evonik. This is a polyether-modified polysiloxane.

[0145] I-6) Polyisocyanate -Suprasec 2447 supplied by Huntsman Polyurethanes.

[0146] I-7) Other Additives: -HR1862 (DY3601) supplied by Huntsman. This is a polypropylene-glycol-diglycidyl ether having an epoxy index (ISO 3001) of 2.47 - 2.60 eq / kg. -Cab-O-sil M5 supplied by Cabot Specialty Chemicals and Aerosil 200 supplied by Evonik. These are fumed silica.

[0147] II - Preparation of Polyol Composition (A) All the components of the compositions of the examples are shown in Table 1. Except for the polyisocyanate component Suprasec 2447, these components were put into metal cans of sufficient size at given ratios to obtain a 200 g polyol composition mixture. Then, the mixture was prepared by stirring the components at 23 °C for about 2 minutes using a propeller stirrer to obtain the polyol composition (A).

[0148] Example 1 is according to the present invention.

[0149] Example 2 is for comparison and corresponds to Example 1 according to the disclosure of US2018 / 0051124.

[0150] III - Preparation of the Reactive Mixture of Polyol Composition (A) and Polyisocyanate (B): After placing about 150 g of Component A and the corresponding amount of Component B according to Table 1 into a metal can, they were mixed at ambient temperature for 2 minutes using a propeller stirrer. Then, 80 g of this reactive mixture was used to generate foam, and the remainder was subjected to a gelation time test and used to produce tan delta and other test plates as described below.

[0151] IV - Production of Polyurethane Foam 80 g of the polyol / isocyanate mixture was placed into a 200 ml cup and then mixed at 2000 rpm for 30 seconds using a small high-shear disperser mixer. This shear in this equipment is sufficient to introduce an amount of air that achieves an approximately 30% volume increase due to foam formation. Then, the resulting foam was cured at 23 °C for 72 hours. Subsequently, the condition of the cured foam sample was examined for uniformity. The requirement for passing this foam stability test is not to show signs of collapse.

[0152] V - Characteristic Measurement Test Storage Stability of Polyol Composition (A): The storage stability was evaluated at room temperature over a period of one month. The composition is considered stable if there are no signs of separation and the uniformity is maintained. Compositions showing incompatibility of components usually exhibit multiple phases after some time.

[0153] Viscosity Measurement: The polyol composition (A) and the mixture of Component A and Component B were subjected to a Rheomat viscometer, and the viscosity development was followed until a viscosity of 5 Pas was reached. The time required to achieve 5 Pas was recorded. The viscosity was measured in accordance with DIN53019.

[0154] Tan Delta and Tg Measurement: The dielectric loss factor Tan delta was determined in accordance with the international standard IEC62631-2-1. A mixture of component A and component B was poured into a mold (without foam formation), and plates with thicknesses of 1 mm and 2 mm were produced by curing the mixture at 90 °C for 4 hours. Then, Tan delta was measured on the 2-mm-thick plate. Starting from -80 °C, the glass transition temperature Tg was measured by DSC, and the midpoint was evaluated.

[0155] Measurement of Volume Resistivity: The volume resistivity was determined in accordance with the international standard IEC62631-3-1.

[0156] Measurement of Specific Reaction Enthalpy The specific reaction enthalpy was determined by examining approximately 20 mg of a polyol composition / polyisocyanate mixture in a DSC instrument. The mixture was heated from ambient temperature to approximately 260 °C at a constant heating rate of 10 K / min. The heat flow signal was integrated between approximately 60 °C and 236 °C, and the resulting heat of release was divided by the precise mass of the test material. This result finally becomes the specific reaction enthalpy value (J / g).

[0157] VI - Test Results

Table 1-1

Table 1-2

[0158] Example 3 (comparative): This example reproduces the form according to the prior art WO2021 / 058500, which discloses a method of filling a hollow core insulator with thermally expandable hollow spheres. Poly(acrylonitrile-co-vinylidene chloride-co-methyl methacrylate) sold under the name Expancel® supplied by Nouryon was used. Despite the fact that this composition contains halogen and its cost is much higher than that of the composition of the present invention in Example 1, it was revealed that this composition requires a high temperature (about 160 °C) to activate the expansion of the hollow spheres in the hollow core insulator.

[0159] VII - Discussion of Results The results summarized in Table 1 show that the polyol composition (Example 1) according to the present invention has storage stability, a high bio-content, and is composed of components that are particularly available without being restricted by the Chemical Weapons Convention, as compared with the compositions according to the prior art. This composition is also the least costly.

[0160] When combined with a polyisocyanate component, the polyol composition according to the present invention enables the formation of a mixture that can be applied and cured at 23 °C. Based on the results in Table 1, the curable composition according to the present invention has the following. - Inhibition of the curing reaction (i.e., 61 minutes as opposed to 32 minutes in the case of Comparative Example 2) and an increase in the gelation time at different temperatures, and thus a decrease in reactivity. The lengthening of the reaction time in this way is particularly interesting for use as a filler for filling large-volume hollow core insulators. - An increase in the glass transition temperature - A decrease in the specific reaction enthalpy, i.e., 44 J / g as opposed to 67.9 J / g in the case of Comparative Example 2 - An increase in flexibility, i.e., Shore A hardness = 35 as opposed to Shore A hardness = 69 in the case of Comparative Example 2 - Good temperature flexibility

Claims

1. A polyol composition (A), 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 more 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, comprising at least 80% by weight of the total weight of the polyols in the composition is provided by the polyether polyol a1) and the castor oil a2), the polyol composition (A).

2. The polyol composition according to claim 1, wherein the polyether polyol a1) is selected from linear or branched polyethylene oxide, polypropylene oxide, hydroxy-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 200 mg KOH / g or less and a polyether polyol having a hydroxyl value of more than 200 mg KOH / g.

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

5. The polyol composition according to any one of claims 1 to 4, wherein the mineral oil a3) is a naphthenic mineral oil.

6. The polyol composition according to any one of claims 1 to 5, wherein the foam stabilizer a4) is selected from the group consisting of polydimethylsiloxane, organofunctional polydimethylsiloxane, siloxane-polyether copolymer, block copolymer having a silicone block and an organic block, and mixtures thereof.

7. The polyol composition according to any one of claims 1 to 6, further comprising an additive selected from an epoxy component, a rheology modifier, a surfactant, a flame retardant, a filler, a catalyst, a dehydrating agent, a dye, a pigment, a flame-resistant agent, a softening agent, a thermal degradation stabilizer, a thixotropic agent, a blowing agent, and mixtures thereof.

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

9. The polyol composition according to 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 a polyolefin polyol.

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

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

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

1.

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

15. Use of a two-component composition and / or a polyurethane foam prepared therefrom to fill a hollow core insulator, wherein the composition is - Component A), which is a polyol composition, and the polyol composition is based on the total weight of the composition, a1) One or more polyether polyols having an average hydroxyl functionality of more than 2 and accounting for 35% to 90% by weight, a2) Castor oil accounting for 10% to 50% by weight, Including, At least 80% by weight of the total weight of the polyols in the composition is provided by the polyether polyol a1) and the castor oil a2), the component A), - Component B), which is a polyisocyanate having an average NCO functionality of more than 2, The use described above, comprising at least.

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

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