Reactive mixture for coating molded objects by means of reaction injection molding and coated molded object

Abstract

The present invention relates to a reactive mixture for coating mouldings by means of reaction injection moulding, comprising at least 40% by weight of (meth)acrylates having at least two double bonds, the reactive mixture comprising at least one photoinitiator and at least one thermal initiator. The present invention furthermore describes a coated moulding comprising a moulding which is obtainable by injection moulding processes and comprises at least one polymer selected from the group consisting of polymethyl methacrylate, polymethylmethacrylimide, styrene-acrylonitrile copolymer, styrene-maleic acid copolymer and polymethyl methacrylate copolymers, and a coating which is obtainable by polymerization of (meth)acrylates having at least two double bonds, the coating having an adhesive strength rating of not more than 1 according to the cross hatch test and a decrease in gloss at 20° after a scratch resistance test according to ASTM 1044 (12/05) (applied weight 500 g, number of cycles=100) of not more than 10%.

1 . A reactive mixture for coating mouldings by means of reaction injection moulding, comprising at least 40% by weight of (meth)acrylates having at least two double bonds, wherein the reactive mixture comprises at least one photoinitiator and at least one thermal initiator. 
   
   
       2 . The reactive mixture according to  claim 1 , wherein the reactive mixture comprises at least 60% by weight of (meth)acrylates having at least two double bonds. 
   
   
       3 . The reactive mixture according to  claim 2 , wherein the reactive mixture comprises at least 90% by weight of (meth)acrylates having at least two double bonds. 
   
   
       4 . The reactive mixture according to  claim 1 , wherein the reactive mixture comprises at least one (meth)acrylate having three or more double bonds. 
   
   
       5 . The reactive mixture according to  claim 4 , wherein 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. 
   
   
       6 . The reactive mixture according to  claim 5 , wherein the proportion of (meth)acrylates having three or more double bonds is at least 50% by weight, based on the weight of the reactive mixture. 
   
   
       7 . The reactive mixture according to  claim 1 , wherein the reactive mixture comprises not more than 75% by weight of monomers having two or less double bonds. 
   
   
       8 . The reactive mixture according to  claim 1 , wherein the reactive mixture has a dynamic viscosity in the range of 1 to 200 mPa·s at 25° C. 
   
   
       9 . The reactive mixture according to  claim 1 , wherein the reactive mixture comprises 0.01% by weight to 3% by weight of photoinitiator, based on the weight of the reactive mixture. 
   
   
       10 . The reactive mixture according to  claim 1 , wherein the reactive mixture comprises 0.03% by weight to 5% by weight of thermal initiator, based on the weight of the reactive mixture. 
   
   
       11 . The reactive mixture according to  claim 1 , wherein the weight ratio of photoinitiator to thermal initiator is in the range of 20:1 to 1:5. 
   
   
       12 . The reactive mixture according to  claim 1 , wherein the reactive mixture comprises 1,6-hexanediol diacrylate, trimethylolpropane triacrylate and/or pentaerythrityl tetraacrylate. 
   
   
       13 . The reactive mixture according to  claim 12 , wherein the reactive mixture comprises trimethylolpropane triacrylate and 1,6-hexanediol diacrylate, the weight ratio of trimethylolpropane triacrylate to 1,6-hexanediol diacrylate being in the range of 5:1 to 1:5. 
   
   
       14 . The reactive mixture according to  claim 12 , wherein the reactive mixture comprises trimethylolpropane triacrylate and pentaerythrityl tetraacrylate, the weight ratio of trimethylolpropane triacrylate to pentaerythrityl tetraacrylate being in the range of 5:1 to 1:5. 
   
   
       15 . The reactive mixture according to  claim 12 , wherein the reactive mixture comprises pentaerythrityl tetraacrylate and 1,6-hexanediol diacrylate, the weight ratio of pentaerythrityl tetraacrylate to 1,6-hexanediol diacrylate being in the range of 5:1 to 1:5. 
   
   
       16 . The reactive mixture according to  claim 1 , wherein the reactive mixture comprises a lubricant. 
   
   
       17 . The reactive mixture according to  claim 1 , wherein the reactive mixture comprises colorants, metallic pigments, UV stabilizers, fillers or nanomaterials. 
   
   
       18 . A process for the production of coated mouldings, wherein the moulding material is injected into an injection mould and cooled to give a moulding, the injection mould is changed so that a space forms between that surface of the moulding which is to be coated and the inner surface of the injection mould, the resulting space is filled by injection moulding with a reactive mixture according to  claim 1 , and the reactive mixture is first thermally cured and, after the thermal curing, cured by irradiation. 
   
   
       19 . The process according to  claim 18 , wherein the moulding material comprises at least one polymer selected from the group consisting of polymethyl methacrylate, polymethylmethacrylimide, styrene-acrylonitrile copolymer, styrene-maleic acid copolymer and polymethyl methacrylate copolymers. 
   
   
       20 . The process according to  claim 19 , wherein the moulding material comprises at least 50% by weight of polymethyl methacrylate, polymethyl methacrylimide and/or polymethyl methacrylate copolymers. 
   
   
       21 . The process according to  claim 18 , wherein the thickness of the coating is in the range of 5 μm to 75 μm. 
   
   
       22 . The process according to  claim 18 , wherein the moulding material is injected into the injection mould at a temperature in the range of 220 to 330° C. 
   
   
       23 . The process according to  claim 18 , wherein the moulding material is cooled to a temperature in the range of 70 to 150° C. before the reactive mixture is injected into the space. 
   
   
       24 . The process according to  claim 18 , wherein the reactive mixture is thermally cured at a temperature in the range of 80 to 130° C. in the injection mould. 
   
   
       25 . The process according to  claim 18 , wherein the thermally cured reactive mixture is cured by irradiation at a temperature in the range of 10 to 40° C. 
   
   
       26 . The process according to  claim 25 , wherein the thermally cured reactive mixture is cured using UV radiation. 
   
   
       27 . A coated moulding comprising a moulding which is obtainable by injection moulding processes and comprises at least one polymer selected from the group consisting of polymethyl methacrylate, polymethylmethacrylimide, styrene-acrylonitrile copolymer, styrene-maleic acid copolymer and polymethyl methacrylate copolymers, and a coating which is obtained by polymerization of (meth)acrylates having at least two double bonds, wherein the coating has an adhesive strength rating of not more than 1 according to the cross hatch test and a decrease in gloss at 20° C. after a scratch resistance test according to ASTM 1044 (12/05) (applied weight 500 g, number of cycles=100) of not more than 10%. 
   
   
       28 . The moulding according to  claim 27 , wherein the coating is obtained by curing a reactive mixture which is applied to the surface of the moulding at a temperature in the range of 75 to 120° C. and is thermally cured. 
   
   
       29 . The moulding according to  claim 27 , wherein the coating has a thickness in the range of 5 μm to 75 μm. 
   
   
       30 . The moulding according to  claim 29 , wherein the coating has a thickness in the range of 10 μm to 40 μm. 
   
   
       31 . The moulding according to  claim 27 , wherein the decrease in the gloss of the moulding at 20° C. after a scratch resistance test according to ASTM 1044 (12/05) is not more than 6%. 
   
   
       32 . The moulding according to  claim 27 , wherein the moulding shows an increase in the haze value after a scratch resistance test according to ASTM 1044 (12/05) to not more than 25% after exposure to a xenon arc for 2000 hours. 
   
   
       33 . The moulding according to  claim 27 , wherein the coating of the moulding shows an adhesive strength rating of 0 according to the cross hatch test. 
   
   
       34 . An injection moulding machine, wherein the machine comprises a reactive mixture according to  claim 1 .