The present invention relates to UV curable epoxy resin compositions.

Background of the Invention Reactive diluents are substances, which reduce the viscosity of a resin for processing and become part of the resin during its subsequent curing via copolymerization. Dilu ents, also called thinners, are usually added to resins to reduce their viscosity and, thereby, to adjust the rheology of the resins. In thermal cured resins, such diluents added are volatile substances evaporating from the resin during drying. In the case of radia- ti on-curing resins, for example, for UV curing epoxy resins, the volatile diluents should be avoided.

US2011250415A discloses an ultraviolet curable resin composition which includes 25 to 45 parts by weight of a modified epoxy acrylate oligomer; and 10 to 25 parts by weight of a urethane acrylate oligomer. Further provided is a metal sheet that is trans parent and corrosion resistant, impact resistant, scratch resistant, adhesive, anti-corro sive, and bendable (workable) by forming a coating film on the surface of a metal ma terial such as a steel material, specifically a steel sheet, using the UV curable resin com position mentioned above.

WO17017128A1 discloses a composition, comprising A) a photo-curable component; B) a photo-initiator; and C) a polymer-containing coating, wherein the component A is physically mixed with component C, or is chemically bonded to the polymer of compo nent C. The present invention further relates to a process for preparing the composition and a process for applying the composition, and the coating film obtained therefrom.

US2009227698A discloses a surface coating for moulded articles, especially for the automotive industry, said surface coating comprising at least 40 percent by weight of one or more resin components to achieve the requisite product properties, up to 60 per- cent by weight of one or more reactive diluents and between 0.3 percent and 1.5 percent by weight of UV initiators, the viscosity of the surface coating at the processing tem perature being between 500 and 2500 mPa s; and also the use of a surface coating for coating moulded articles of wood in an IMC machine under UV irradiation. Furthermore resins of this type are also used for other purposes. One such purpose is for re-lining pipes, typically in water supply systems or sewer systems. A well-known method is to impregnate a flexible- typically woven tube with an epoxy resin. Thereafter the flexible tube is inserted or drawn into the pipe to receive a new lining. The tube is expanded in-situ against the inner wall of the pipe. In this position the epoxy resin is allowed to set, thereby creating a new inner pipe liner. This method although finding wide-spread use has a number of drawbacks. Typically the epoxy resin used must be a two-component epoxy resin in order to achieve desired strength characteristics and suf ficient liquid tightness. However as soon as the two components are mixed the chemical hardening process will commence. Some of the epoxy systems used have slow harden- ers, which may be activated or accelerated by using heating in-situ- which requires a subsequent process following installing the liner which already is in the process of hard ening. Others just have regular hardeners whereby the epoxy hardening process is going on while the liner is being inserted into the pipe. This naturally puts stress on the whole process, as it is necessary to complete the installation in the time allowed by the hard- ener before the epoxy resin hardens.

A further challenge is the fact that some of the epoxy resins used in the art also shrink during the hardening process. This is especially true for heat hardening epoxy resins. Of cause when the resin shrinks, the flexible tube liner will also shrink, thereby in some instances not be in complete contact with the inner side of the pipe in which it is in stalled. This may cause problems in that water (or other liquids) may flow between the liner and the pipe wall, thereby causing renewed trouble.

Object of the Invention The objective of this invention is to disclose high strength UV curable epoxy resin com positions that have high resistance against the organic solvents. The addition of reactive diluents facilitates the processing of UV curing epoxy resins, allows the addition of more fillers and improves the wetting behaviour on the substrate. By replacing volatile diluents with reactive diluents, flammability, smell, skin irritation and environmental compatibility are improved.

The object is therefore also to alleviate the problems with prior art uses as described above and make the epoxy resin useful in other applications as well. Other uses may include reinforcement of tanks, pools or other vessels. Also with respect to wind turbine blades/wings or boat hulls the present invention may find use.

Description of the Invention

Since reactive diluents are incorporated into the resin during curing and remain in it after the curing is completed, they influence not only the viscosity of the uncured epoxys, but also its physical properties after curing. Therefore, the choice of the reactive diluent has an influence on adhesion of a resin to a substrate, its compatibility with a binder, flexibility of a cured layer, volatility of the composition and its environmental compatibility.

Reactive diluents used are low-viscosity, mono-, bi- or polyfunctional monomers or oligomers. In general, several different monomers are combined so that one monomer can compensate for the undesired properties of another monomer. Monofunctional mon omers offer a low viscosity but are quite volatile and tend to smell. With an increasing number of functional groups of a monomer, its volatility decreases while viscosity and crosslinking of the final varnish increase.

Reactive diluents for the UV curable epoxy resin compositions can be styrene, epoxides and acrylates. Especially, a specific combination of 3 various diacrylates is found to be particularly useful, resulting in a coating of superior mechanical strength and superior resistance against organic solvents.

The UV curable epoxy resin composition is to be used in industries such as pipe tech nology for stocking lining/feeding and in wind industry, among other industries. Detailed Description of the Invention

In the description below and in the claims, various intervals expressed in mass% are recited. It should be noted that it is not the intention that selecting the max content of every compound shall add up to 100%. However, the skilled person will recognise that the various compounds shall be selected within the given ranges such that the combina tion of compounds constituting the inventive resin achieves a mass% of 100%.

In one embodiment, a UV curing epoxy resin composition, comprising 50-70 mass% of an energy curable resin and 20-30 mass% of a first reactive diluent, and 5-10 mass% of a second diluent being different from the first diluent is disclosed.

In a further embodiment, the energy curable resin is an epoxy acrylate such as Bi-sphe- nol A-epichlorohydrin acrylate. In a further embodiment, the first reactive diluent is being selected from glycol diacry lates, preferably, said first glycol diacrylate is dipropylene glycol diacrylate (DPGDA).

In a further embodiment, the composition wherein the second reactive diluent, being different from the first reactive diluent, is an amino acrylate.

In a still further embodiment, the second reactive diluent is selected from glycol diacry lates, different from the first glycol diacrylate, preferably, said second reactive diluent is polyethylene glycol diacrylate. In a further embodiment, the composition further comprises 0-10 mass% of a curing agent.

In yet a further embodiment, the curing agent comprises pentaerythritol or its derivative or a Hexanediol.

In a further embodiment, the composition is further characterised by comprising 0-1 mass% of a third reactive diluent, being different from the first reactive diluent and the second reactive diluent. In yet a further embodiment of the invention, the third reactive diluent is selected from diacrylates, preferably, the third reactive diluent being hexamethylene diacrylate a Hex- anediol diacrylate or a polyether amine. In a further embodiment, the composition is further comprising 0-1 mass% of a pho toinitiator or a sensitiser; preferably, the photoinitiator or the sensitizer being a phenyl bis phosphine oxide.