DURABLE RETROREFLECTIVE OPTICAL ELEMENTS
A retroreflective optical element is provided in which modified glass beads having a high refractive index are embedded on the surface of a thermoplastic core. The glass beads are heated to a temperature near the softening point of the thermoplastic core and the heated beads and thermoplastic cores are mixed in a fluidized bed. The beads embed into the thermoplastic core and are also chemically bonded thereto through a silane coupling agent provided on the beads.
1 . A retroreflective optical element comprising a reactive thermoplastic core and at least one modified glass bead having a high refractive index embedded on the surface of said thermoplastic core.
2 . The retroreflective optical element of claim 1 , wherein said modified glass bead is chemically bonded to said thermoplastic core.
3 . The retroreflective optical element of claim 2 , wherein said thermoplastic core comprises a maleic modified rosin resin.
4 . The retroreflective optical element of claim 3 , wherein said modified glass bead comprises a coupling agent.
5 . The retroreflective optical element of claim 4 , wherein said coupling agent is a silane coupling agent.
6 . The retroreflective optical element of claim 5 , wherein said silane coupling agent has a functional group selected from the group consisting of amine, acryl, imine, epoxy, isocyanato, mercaptan and salts of acids.
7 . The retroreflective optical element of claim 5 , wherein said silane coupling agent is selected from the group consisting of aminopropyltriethoxy silane, aminophenytriethoxy silane, acrylamidopropyltrimethoxy silane, acryloxypropylmethyldimethoxy silane, 3-(N-allylamino)propyltrimethoxy silane, bis(triethoxypropyl) amine, 2-(carboxymethoxy)ethyltrimethoxy silane, glycidoxypropyltriethoxy silane, 2-(3,4)-epoxycyclohexylethyltriethoxy silane, 3-isocyanatopropyltriethoxy silane, 3-mercaptopropyltriethoxy silane, methacryloxypropyltriethoxy silane, tirmethoxysilylpropyl modified polyethylene imine, N-(trimethoxysilylpropyl)ethylenediamine triacetic acid sodium salt, N(3-triethoxysilylpropyl)-4,5-dihyrdroimidazole, and vinyltriethoxy silane.
8 . A process for manufacturing optical elements comprising the steps of
a. providing a plurality of reactive thermoplastic pellets and a plurality of modified glass beads into a fluidized bed;
b. heating said modified glass beads to a temperature near the softening point of said thermoplastic pellets;
c. mixing said heated beads with said thermoplastic pellets, whereby said glass beads embed within said thermoplastic pellets to form said optical elements; and
d. sieving the mixture to isolate said optical elements.
9 . The process of claim 8 , wherein said beads are embedded into said thermoplastic pellets into a depth of at least 30% and at most 70%.
10 . The process of claim 8 , wherein said beads are mixed with said thermoplastic pellets for a time between 30 seconds and 5 minutes.
11 . The process of claim 8 , wherein said modified glass bead is chemically bonded to said thermoplastic pellet.
12 . The process of claim 11 , wherein said thermoplastic pellet comprises a maleic modified rosin resin.
13 . The process of claim 12 , wherein said modified glass bead comprises a coupling agent.
14 . The process of claim 13 wherein said coupling agent is a silane coupling agent.
15 . The process of claim 14 wherein said silane coupling agent has a functional group selected from the group consisting of amine, acryl, imine, epoxy, isocyanato, mercaptan and salts of acids.
16 . The process of claim 14 wherein said silane coupling agent is selected from the group consisting of aminopropyltriethoxy silane, aminophenytriethoxy silane, acrylamidopropyltrimethoxy silane, acryloxypropylmethyldimethoxy silane, 3-(N-allylamino)propyltrimethoxy silane, bis(tri ethoxypropyl) amine, 2-(carboxymethoxy)ethyltrimethoxy silane, glycidoxypropyltriethoxy silane, 2-(3,4)-epoxycyclohexyl ethyltriethoxy silane, 3-isocyanatopropyltriethoxy silane, 3-mercaptopropyltriethoxy silane, methacryloxypropyltriethoxy silane, tirmethoxysilylpropyl modified polyethylene imine, N-(trimethoxysilylpropyl)ethylenediamine triacetic acid sodium salt, N(3-triethoxysilylpropyl)-4,5-dihyrdroimidazole, and vinyltriethoxy silane.