Jettable compositions
View Patent ↗A fully curable jettable composition having a viscosity less than 30 cps at a temperature within the range of 15-180° C., more preferably at a temperature of 15-100° C., e.g. 60-80° C. the composition comprising: (A) at least one low viscosity reactive resin selected from the group consisting of compounds containing an oxetane ring, cycloaliphatic epoxy resins, tetrahydrofurans, hexahydropyrans and mono-functional (meth)acrylates, said resin having a molecular weight of not greater than 300 Daltons, e.g. 250 Daltons or less, and a viscosity at a temperature in the said range of less than 30 cps, e.g. 5 to 15 cps; (B) at least one higher viscosity resin selected from the group consisting of epoxy resins, compounds containing an oxetane ring and acrylates, which resin acts to thicken the low viscosity resin and strengthen a jetted deposit of the composition, the higher viscosity resin having: a viscosity greater than twice that of the low viscosity resin at the said temperature in the range stated above, and a functionality of greater than or equal to 2; (C) at least one curable toughener, preferably having a functionality of at least 2, such as hydroxy, epoxy, acrylic or other reactive functionalised polymer/oligomer (e.g. derived by functionalising poly(tetrahydrofuran), polycaprolactone, polycarbonate diol, or a dendrimeric polyol; (D) at least one initiator for the polymerisation of the resins, and (E) at least one stabilizer for delaying the curing of the resins of the composition; wherein the low viscosity resin is slower to react than the higher viscosity resin and acts to solvate the higher viscosity resin prior to curing and at least partly during curing and wherein at least 30% of the components A and B are cationically curable resins. The composition can be jetted from piezo electric printing heads under the control of a computer program to form a multi-layered article, e.g. a three dimensional article, in which the adjacent droplets merge and are cured homogeneously together.
1. A method for depositing a composition on a substrate comprising:
(a) jet depositing successive droplets of the jettable composition whereby adjacent droplets merge together; and
(b) irradiating the droplets to cure the jettable composition and form a shaped deposit on the substrate wherein the jettable composition has a viscosity of less than 30 cps at a temperature within the range of 15° C.-180° C. and comprises: at least one low viscosity reactive resin consisting of one or more oxetane compounds wherein the low viscosity resin has a molecular weight of not greater than 300 Daltons and a viscosity of less than 30 cps at a temperature within the range of 15° C.-180° C.; at least one high viscosity resin selected from the group consisting of one or more epoxy resins, one or more compounds containing a reactive oxetane ring, and one or more multifunctional acrylates wherein the high viscosity resin has a functionality of greater than or equal to 2 and a viscosity greater than twice the viscosity of the low viscosity reactive resin at a temperature within the range of 15° C.-180° C.; at least one curable toughener comprising a polymer or oligomer having a hydroxy, epoxy or acrylic group; at least one initiator; and at least one stabilizer and wherein the low viscosity resin is slower to react than the high viscosity resin and wherein two or more jettable compositions are used to form the shaped deposit, each jettable composition having the same low viscosity reactive resin but differing high viscosity resin.
2. The method of claim 1 wherein the merged droplets are irradiated immediately upon deposition on the substrate.
3. The method of claim 1 wherein the merged droplets are irradiated during flight to partially cure the droplets prior to deposition on the substrate.
4. The method of claim 1 wherein successive layers of merged droplets are deposited on the substrate to form a multi-layered shaped deposit.
5. The method of claim 1 wherein the substrate is a bed made of curable powder.
6. The method of claim 1 wherein the substrate is paper, textile, metal powder, paste or a prior layer of the jettable composition.