Method for the production of coated moldings
View Patent ↗The present invention relates to a process for the production of coated mouldings, by injecting a moulding composition into an injection mould and cooling the composition to obtain a moulding, and altering the injection mould in such a way as to produce an intermediate space between a surface to be coated of the moulding and the inner surface of the injection mould, and using injection moulding to charge a reactive mixture to the resultant intermediate space, where the temperature of at least a portion of the injection mould is increased for the curing of the reactive mixture. The present invention moreover describes a system for the conduct of the process described above.
1. A process for the production of a coated moulding, comprising injecting a moulding composition into an injection mould and cooling the composition to obtain a moulding, and altering the injection mould in such a way as to produce an intermediate space between a surface to be coated of the moulding and the inner surface of the injection mould, and charging a reaction mixture to the resultant intermediate space with the injection moulding and the reactive mixture is first thermally cured and after the thermal curing, cured by irradiation, wherein the temperature of at least a portion of the injection mould is increased for the curing of the reactive mixture, wherein the temperature of at least one portion of the injection mould is increased by at least 20° C. within 5 seconds.
2. The process according to claim 1 , wherein one portion of the injection mould is heated and is in contact with the reactive mixture, and one portion of the injection mould is not heated and is not in contact with the reactive mixture.
3. The process according to claim 1 , wherein the temperature of at least one portion of the injection mould is increased by at least 30° C.
4. The process according to claim 1 , wherein the moulding composition comprises at least 50% by weight of polymethyl methacrylate, of poly(meth)acrylimide, or of polymethyl methacrylate copolymers, or mixtures thereof.
5. The process according to claim 4 , wherein the reactive mixture comprises at least 40% by weight of (meth)acrylates having at least two double bonds.
6. The process according to claim 1 , wherein the reactive mixture comprises at least one (meth)acrylate having three or more double bonds and that the proportion of (meth)acrylates having three or more double bonds is at least 25% by weight, based on the weight of the reactive mixture.
7. The process according to claim 1 , wherein the dynamic viscosity of the reactive mixture is in the range of from 1 to 200 mPa·s at 25° C.
8. The process according to claim 1 , wherein the reactive mixture comprises from 0.03% by weight to 5% by weight of thermal initiator or from 0.01% by weight to 3% by weight of photoinitiator, or both, each based on the weight of the reactive mixture.
9. The process according to claim 1 , wherein the thickness of the coating is in the range of from 5 μm to 75 μm.
10. The process according to claim 1 , wherein the moulding composition is injected at a temperature in the range of from 220 to 330° C. into the injection mould, and that the moulding composition is cooled to a temperature in the range of from 70 to 150° C. before the reactive mixture is injected into the intermediate space.
11. The process according to claim 1 , wherein the reactive mixture is thermally cured at a temperature in the range of from 95 to 180° C. in the injection mould.
12. The process according to claim 1 , wherein the thermally cured reactive mixture is cured at a temperature in the range of from 10 to 40° C. by UV irradiation.
13. The process according to claim 1 , wherein at least a portion of the injection mould is heated by electrical current.
14. The process according to claim 1 , wherein the maximum of the heating power which heats the injection-mould surface facing towards the moulding lies within a period which begins at the juncture of the minimum temperature of the uncoated moulding and ends less than one second after injection of the reactive mixture.
15. The process according to claim 1 , wherein the maximum of the heating power which heats the injection-mould surface facing towards the moulding is achieved prior to or during the injection of the reactive mixture.
16. The process according to claim 4 , wherein the reactive mixture comprises at least 60% by weight of (meth)acrylates having at least two double bonds.
17. The process according to claim 1 , wherein the moulding composition is injected at a temperature in the range of from 220 to 330° C. into the injection mould, and that the moulding composition is cooled to a temperature in the range of from 70 to 90° C. before the reactive mixture is injected into the intermediate space.
18. The process according to claim 1 , wherein the reactive mixture is thermally cured at a temperature in the range of from 100 to 140° C. in the injection mould.