P35641PC00/MKO Title: A method for sealing an electrical cable joint or termination with an electrically- insulating multicomponent polyurethane resin composition Technical Field The current invention concerns a method for sealing an electrical cable joint or termination with an electrically-insulating multicomponent polyurethane resin composition, the electrically- insulating multicomponent polyurethane resin composition for sealing an electrical cable joint or termination, and an electric cable joint or termination comprising a housing that encloses at least one cable and substantially filled with the cured electrically-insulating multicomponent polyurethane composition. More in particular, it relates to a resin composition that may be applied professionally without requiring special training and that is preferably label-free. Background Cable joints and terminations are typically sealed with an electrically-insulating resin composition. A housing, which may be rigid or flexible, or formed by tape, and which contains one or more electric power cables is filled with a resin composition. The resin composition is subsequently allowed to harden (cure). Once the resin has cured, it provides mechanical protection and electrical insulation. The multicomponent resin composition is often employed in the form of a two pack composition. For instance, WO2011012918 describes a resin composition wherein the first pack contains a (meth)acrylate ester monomer and a curing agent, and the second pack contains a filler and a radical catalyst. In WO2014126473 a user-friendly disposable and collapsible bag is disclosed, wherein separate components are separated with a temporary seal, and wherein the contents, after mixing, may be discharged from the bag by hand or with a pump. Details on the resin composition are not disclosed. In WO2021228857 a method for sealing an electric cable joint is disclosed, wherein use is made of a prefabricated sealing assembly. In this case a liquid resin compound, after mixing, is introduced via a resin compound transfer member into the space delimited by the sealing assembly, whereby a cable joint becomes embedded in the resin compound, which resin compound hardens thereafter. Particularly suitable electrically-insulating resin compositions are based on polyurethane (“PU”) resin. A PU resin combines excellent electrically insulating properties with excellent mechanical properties. Moreover, as any isocyanate component remaining in the housing and/or on equipment that was used reacts with water, there is no residual isocyanate component left. Thus, after application there is no risk to staff of irritation by skin contact. In this respect a PU resin advantageously does not have the disadvantages of an epoxy resin, where staff need to remain alert against repeated skin contact. The Filobox™ cable joint kit, for instance, is suitable for sealing underground cable connections. The Filobox T40 + PU resin contains a 2K polyurethane resin. The PU resin cures to a hard high quality sealing compound which creates a durable seal around the cable connection. Such cable joints are especially suitable for outdoor- and underground applications or in a humid environment where an IP68 or IP67 sealing is required. Such resins typically consist of polyol and isocyanate components. 2 part polyurethane cable jointing resin compositions are provided by Filoform, but also by companies such as 3M (e.g. Scotchcast™ 40), W T Henley (using a hardener and resin in twin pouch with ruptureable membrane or in a three-part version), Electrolube and Birkett Electric (e.g., Swishpak™ 2 part PU resin compound). For instance, in EP2767983 is disclosed a polyurethane resin composition for electrical insulation, a sealing member formed of the polyurethane resin composition for electrical insulation, and an electrical component that has been resin-sealed with the sealing member. Unfortunately, PU resin compositions may contain hazardous or regulated components, and isocyanates in particular. Therefore special precautions are required when such PU resin compositions are used. Regulatory information can be found in the Code of Federal Regulations Title 21 (Food and Drugs) and Title 40 (Protection of the Environment). In Europe, health and safety information is available from ISOPA the European Diisocyanate and Polyol Producers Association. Indeed, as from 24 August 2023, a mandatory training on the safe use of diisocyanates will be required when using a PU resin composition for cable joints and terminations. WO2007062812 relates a method of applying a coating layer comprising a non-isocyanate polyurethane (NIPU) on an elongated metal wire. This product is therefore different from the regular PU resins, based on the reaction of isocyanates and polyols (components B and A of a 2K resin). Moreover, the application as coating differs from that of the present invention, wherein the resin needs to provide a durable seal around the cable connection. WO2021202876 suggests adding a diluent in the form of a plasticizer to a polyurethane prepolymer composition to lower the viscosity. In this particular case the polyurethane prepolymer composition comprises at least one alkyl benzoate as plasticizer. US2018148534 concerns blocked isocyanate terminated prepolymers with improved handling and processing properties. Blocked polyisocyanates are polyisocyanates in which each isocyanate group has been reacted with a protecting or blocking agent to form a derivative which will dissociate on heating to remove the protecting or blocking agent and release the reactive isocyanate group. These may be prepared from isocyanate terminated prepolymers with very low free isocyanate monomer content. However, such resin compositions require heating to remove the blocking group first. Resin compositions for cable joints and terminations, however, require cure at ambient temperature, e.g., in the range of 10-30 °C (normally about 20 °C). In a post in Engineering Plastics, on July 12, 2021, “The importance of curing, heat and time”, it is indicated that cure time depends both on cure temperature and size of the object to be cured. The cure time of the present resin is defined by the time required for 300 ml to gel at about 20 °C, which is 5 hours or less. Whereas additional training is always a benefit, it would be highly desirable to have access to a PU resin composition for cable joints and terminations that does not contain hazardous amounts of regulated components, and free isocyanates in particular, allowing the safe use of such compositions without the mandatory training. If hazardous amounts of regulated components are present in a composition for cable joints and terminations, then such resin compositions must labeled in accordance with the Globally Harmonized System of Classification and Labelling of Chemicals (GHS), which is an internationally agreed-upon standard managed by the United Nations that was set up to replace the assortment of hazardous material classification and labelling schemes previously used around the world. This includes the European Union, which has implemented the United Nations' GHS into EU law as the CLP Regulation, and United States Occupational Safety and Health Administration standards. Ideally the resin composition contains no hazardous amounts of regulated components, and is therefore exempt from the labelling schemes around the word (hereafter “label-free”). Summary of the Invention Accordingly, a method is provided for sealing an electrical cable joint or termination, which method comprises mixing a multicomponent PU resin composition, introducing the mixed PU resin composition into a housing comprising one or more electric cables and allowing the resin composition to cure, wherein the multicomponent PU resin composition has a free isocyanate content of not more than 0.1% by weight, and a viscosity that is less than 8000 mPa.s at 25 °C. The free isocyanate content, consisting of isocyanate monomers, is preferably close to zero. Preferably the multicomponent PU resin may be used professionally without special training. Also provided is an insulated electrical cable joint or termination, comprising the cured multicomponent PU resin composition. Moreover, a multicomponent electrically-insulating PU resin composition is provided, for cable joints and terminations, as well as a kit comprising the multicomponent electrically-insulating PU resin composition and a housing. Preferably the composition is label-free. Detailed description of the Invention PU resin compositions with a free isocyanate content of not more than 0.1% by weight are known for various uses. In such cases, free isocyanate, typically in the form of monomeric diisocyanate, is removed from the isocyanate terminated prepolymer, typically by vacuum distillation. The viscosity of so-called Low-Free isocyanate-terminated prepolymers, i.e., with a free monomer content of <0.1%, and that are not considered hazardous, is generally very high and not suitable for handling, such as mixing and introducing the mixed composition in a housing, to seal an electrical cable joint or termination. For instance, the viscosity of Adiprene LFG 740D is 35,000 mPa.s at 25°C. Surprisingly, it has been found that isocyanate-terminated prepolymers with a free isocyanate content below 0.1% can be used for sealing an electrical cable joint or termination provided -if their viscosity is too high- they are used together with a diluent. A single Low-Free isocyanate-terminated prepolymer or a mixture of such prepolymers may be used. Such products include Adiprene™ Low-Free TDI systems from Lanxess with a free TDI content below 0.1%. In addition to the LFG 740D grade mentioned above, also Adiprene™ FG 964A may be used, which is a TDI-terminated polyether prepolymer, based on PPG polyether, with an NCO content in the range of 5.80-6.20%. A further suitable example is Adiprene™ FG 963. These Low Free TDI systems are considered harmless and “label free”. Adiprene™ Low-Free TDI systems prepolymers are developed for use at elevated temperatures, for the production of polyurethane products such as shoe soles, rubber boots, rollerblade wheels, etc., but also granules for thermoplastic elastomers. That such Low-Free isocyanate-terminated prepolymers could be used for electrical cable joint or termination, was not known. Prepolymers based on HDI and PPDI with levels of free isocyanate below 0.1% are also available. These alternative Low-Free systems can also be used without the restrictions of use: e.g. Desmodur™ N3300, an aliphatic HDI trimer from Bayer with an NCO content of 21.8 +/- 0.3%, and Lupranat™ 5025 from BASF, a low free NCO prepolymer based on pure MDI with an NCO content of 12.9 wt%. Furthermore, Tolonate™ HDT-LV from VencoreX, may be used, which is based on hexamethylene diisocyanate oligomers and already has a very low viscosity. Even with a low free isocyanate content, some additional safety requirements may be applicable, as appears to be the case for Tolonate™ HDT-LV (considered harmful, irritant if inhaled, and may cause allergic skin reactions). The selection of components is preferably such as to be allowed for the DIY market. Preferably, the Low-Free isocyanate-terminated prepolymer has no restrictions on its use (“label-free”). Indeed, the multicomponent electrically-insulating PU resin composition of the present invention, contains no hazardous amounts of regulated components necessitating a warning of possible carcinogenic effects and/or harmful to health, more preferably contains no hazardous amounts of regulated components necessitating a warning of possible allergic reactions, such as possible irritation of the skin and/or the respiratory tract. Preferably, the multicomponent electrically-insulating PU resin composition is label-free. For the use in cable joints and terminations, the Low-Free isocyanate-terminated prepolymer or mixture may have to be diluted. Various diluents may be used. Preferably a non-reactive diluent is used. Suitably this is a fatty acid ester of a polyol. More preferably the non-reactive diluent has a viscosity of at most 400, more preferably at most 200, still more preferably at most 50 mPa.s at 20°C. Suitably, the Low-Free isocyanate-terminated prepolymer or mixture is diluted with for instance Sovermol™ 1058. This non-reactive diluent is a fatty acid ester type diluent with a viscosity of about 5 mPa.s at 25°C. A combination of non-reactive diluents may be used. Optionally one or more polyols may be added. Preferably, the component of the resin composition containing the Low-Free isocyanate- terminated prepolymer(s) and the diluent(s), optionally containing one or more polyols, generally referred to as the B-component, has a viscosity less than 8000 mPa.s, preferably less than 5000 mPa.s, more preferably less than 3000 mPa.s at 25°C. The amount of non-reactive diluent (or combination of diluents) depends on the viscosity of the isocyanate-terminated prepolymers. A suitable amount is added to reduce the viscosity of the B-component to less than 8000 mPa.s, preferably less than 5000 mPa.s at 25 °C. For example, the non-reactive diluent or mixture of diluents may be added in an amount or combined amount in the range of 5 to 25, preferably 7.5 to 20 parts by weight based on 100 parts by weight of the isocyanate-terminated prepolymer(s). The component of the resin composition containing the Low-Free isocyanate-terminated prepolymer(s) and the diluent(s), is mixed with at least one other component of the multicomponent resin composition, e.g. the A-component, comprising one or more polyols and other ingredients of the resin composition. Typically, an A-component of a multicomponent resin composition comprises at least one polyol or another crosslinker for an isocyanate-terminated prepolymer. Generally, the A- component and optional additional components of the multicomponent resin composition have viscosity of less than 3000 mPa.s, preferably less than 2000 mPa.s at 25°C. The A-component may comprise a single polyol, but preferably a combination of polyols and other crosslinkers. This allows a fast cure in combination with a suitable hardness of the polyurethane so formed. Preferably, the hardness is 40 shore D or more. For instance a low molecular diol or triol may be used, e.g. with a molecular weight of 1000 or less, preferably 300 or less, more preferably 200 or less in combination with a polyether polyol having two or more hydroxy groups and a molecular weight in the range of 1000 to 10,000. For instance, a mixture may be used comprising a C2-6 alkanediol, in label-free amounts, in combination with a polyether polyol of ethylene oxide and/or propylene oxide. Suitable, the polyol or mixture is used in an amount or combined amount in the range of 5 to 200 parts by weight based on 100 parts by weight of the isocyanate-terminated prepolymer(s). In addition, one or more amine-based crosslinkers, including amine-based polyols, may be used. Such components may be very effective chain extenders for isocyanate pre-polymers. These include materials such as ethylenediamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, and several cycloaliphatic amines, acting as curing agents. These curing agents as a class offer low viscosities and ambient temperature cures. A further example of a curing agent is 4,4'-methylene-bis(o-chloroaniline), also known as MbOCA or MOCA, and commercially available as Vibracure™ A133. Preferably the selected curing agent and/or chain extender, if any, is considered harmless and/or is used in amounts that do not require labelling. Suitable, the amine-based crosslinker, if any, is used in an amount in the range of 0 to 10 parts by weight based on 100 parts by weight of the isocyanate-terminated prepolymer(s). Amine-based polyols, such as Lupranol™ 1002/1 from BASF or Petol™ 450 T3 from Ottchim may be used in an amount in the range of 0 to 70 parts by weight, based on 100 parts by weight of the isocyanate-terminated prepolymer(s). Use of such polyols is very advantageous, as they are autocatalytic and may reduce the amount of (potentially harmful) catalysts. Again, the amine-based polyol, if any, is preferably considered harmless. It is also possible to use a castor oil-based polyol as the polyol component. Examples of the castor oil-based polyol include castor oil and castor oil derivatives. Examples of the castor oil derivatives include castor oil fatty acid; hydrogenated castor oils such as those obtained by adding hydrogen to castor oil or castor oil fatty acid; products obtained by an ester interchange reaction of castor oil with other oils; reaction products of castor oil and polyhydric alcohol; esterification products of castor oil fatty acid and polyhydric alcohol; and products obtained by alkylene oxide addition polymerization. As the castor oil-based polyol, the use of hydrogenated castor oil is preferable. More preferably, the polyol component contains polybutadiene polyol and castor oil-based polyol. In this case, the proportion of the polybutadiene polyol and castor oil-based polyol is, when the total amount of polybutadiene polyol and castor oil-based polyol is defined as 100% by weight, (polybutadiene polyol):(castor oil-based polyol) = 90:10% by weight to 50:50% by weight, and more preferably 90:10% by weight to 70:30% by weight. The use of a castor oil-based polyol as the polyol component having the above proportion may result in an improved compatibility with polyisocyanate component, and reduced viscosity of the polyurethane resin composition for electrical insulation, whilst maintaining excellent operability. A castor oil-based polyol may be used, if at all, in an amount in the range of 0 to 1000 parts by weight based on 100 parts by weight of the isocyanate-terminated prepolymer(s). Preferably, the A-component or additional component(s) comprise a catalyst for the formation of the polyurethane. Preferably a catalyst is used that allows for the fast cure of the multicomponent resin composition. The curing time is important for use as an insulating resin for cable joints and terminations. For instance, for application in cable joints the curing time is preferably less than 1 hour. Most ideal is a curing time of 15 - 30 minutes at 20ºC. A suitable catalyst is dibutyltin dilaurate (DBTL), supplied as Dabco™ T by Evonic. Alternatively, a bismuth carboxylate metal catalyst may be used, such as Kosmos™ MB 19, supplied by Evonic. However, any other catalyst or combination of catalysts known in the art may be used. Preferably, the selected catalyst is considered harmless. Moreover, the person skilled in the art is well aware of the suitable amount of catalyst, typically in the range of 0.5 parts by weight or less compared to 100 parts by weight of the isocyanate-terminated prepolymer(s). For instance, a catalyst may be used in an amount in the range of 0.005 to 0.25 parts by weight on 100 parts by weight of the isocyanate-terminated prepolymer(s). Advantageously, the A-component or additional component(s), if any, comprise additional ingredients such as one or more moisture scavengers and/or one or more thixotropic agents and/or one or more fillers. These ingredients may be used in amounts typically used in multicomponent resin compositions. For instance, the one or more moisture scavenger(s) may be used in an amount or combined amount in the range of 0 to 5 parts by weight on 100 parts by weight of the isocyanate-terminated prepolymer(s). The one or more thixotropic agents may be used in an amount or combined amount in the range of 0 to 5 parts by weight on 100 parts by weight of the isocyanate-terminated prepolymer(s). The fillers, such as chalk, may be used in minor or significant amounts, depending on the level of hardness that is desired and limited by the viscosity of the mixture. For example, an amount or combined amount in the range of 0 to 60 parts by weight on 100 parts by weight of the isocyanate- terminated prepolymer(s) may be used. The viscosity of each component in the multicomponent resin composition is preferably less than 8000 mPa.s at 25°C. Indeed, when the components of the multicomponent resin composition are mixed, the viscosity of the mixture is preferably less than 5000 mPa.s, more preferably less than 3000 mPa.s, ideally between 1000 and 2500 mPa.s at 25°C. If thixotropic agents are added, then the lower limit may even be less than 1000 mPa.s at 25°C. Depending on the viscosity of the components they may be mixed manually, e.g., as in a kneading pack, or with the aid of a pump. Depending on the viscosity of the mixture, the mixed resin composition may be poured, hand-pressed, or pumped into the housing comprising one or more electric cables, thus forming a cable joint or termination. In particular if the mixed multicomponent resin composition will be poured into a housing, then preferably the viscosity is in the range of 1000 and 4000 mPa.s at 25°C. Suitably the multicomponent resin composition is in the form of a 2-component kneading package. Alternatively, and/or at higher needed pressures, for instance in housings formed by tape, the multicomponent resin composition may be introduced by way of a static mixer or using a hand pump. In such cases the viscosity is preferably less than 3000 mPa.s at 25°C. Packages and housings typically used in the preparation of cable joints and terminations may be used. Preferably such packages and housings are used that reduce the risk of waste of materials, and exposure of the resin composition to staff working with the same. Indeed preferably a kit is used comprising a housing and a multicomponent resin composition contained within a package adapted for safe introduction of the resin composition into the housing. Examples The following chemical components have been used: Suitable formulations for cable joint or termination can be produced in accordance with the formulations set out in Table 1. All amounts are in parts by weight. In the comparative example, a formulation is provided as is used for hot casting. This formulation has a very high viscosity and hence is not at all suitable for sealing an electrical cable joint or termination. Moreover, it contains a curing agent in an amount that requires labelling. The multicomponent polyurethane resin compositions of Examples 1-5 on the other hand may be introduced into a housing that encloses at least one cable in any conventional manner, without requiring training. Moreover, Examples 1-3 are label-free and preferred. Example 5 is also considered of interest, from a cost-perspective. It may be further improved by reducing the amount of curing agent. :