Method for in-mold lamination of foils
View Patent ↗A method is described for the back-moulding of sheets ( 7 ) with thermoplastics, in particular of printed sheets to protect the decorated surface against scratching or detachment, in which a sheet ( 7 ) that is initially separated from the moulded-article wall is pressed against the moulded-article wall by the melt front ( 3 ).
1. Method for the back-moulding of sheets printed on their rear side with thermoplastic, in an injection-moulding device having mould cavity ( 1 ) with a wall ( 9 ) and an opposite wall ( 5 ), characterised in that the sheet ( 7 ) is place in the mould cavity ( 1 ) of the injection-moulding tool ( 2 ) in such a way that it is initially applied, before the molten plastic enters, with its edge ( 4 ) that meets the front of the melt ( 3 ) against the opposite wall ( 5 ) of the mould cavity ( 1 ), whereas the rest of the sheet is kept separated from the wall ( 9 ), and in that the part ( 6 ) of the sheet ( 7 ) that is separated from the wall ( 9 ) is pressed against the opposite wall ( 5 ) by the incoming melt front advancing in the mould cavity ( 1 ), the support of the sheet ( 7 ) being released the same time, so that the rest of the sheet ( 7 ) is also applied against the opposite wall ( 5 ) of the mould cavity ( 1 ).
2. Method according to claim 1 , characterised in that, before the melt ( 3 ) enters the mould cavity ( 1 ), the sheet is applied against the wall ( 5 ) of the mould cavity ( 1 ) with the aid of a depressor ( 8 ), and in that the depressor ( 8 ) is retracted when the melt enters.
3. Method according to claim 1 , characterised in that the sheet material is a plastic selected from the list: polycarbonate, polyurethane, polyester, polyvinyl chloride.
4. Method according to claim 1 , characterised in that the thermoplastic is selected from the list: polyamide, polyester, polyurethane, styrene copolymer, polyphenylene oxide, polycarbonate, polyethylene sulfide, polyvinyl chloride, polyurethane or possible mixtures of the said polymers.
5. Method according to claim 3 , characterised in that polycarbonate is used as the sheet material.
6. Method according to claim 4 , characterised in that polyamide or polycarbonate is used as the thermoplastic.
7. Method according to claim 1 , characterised in that that, before the melt ( 3 ) enters, the sheet is held at its lower part ( 6 ), which faces away from the melt front ( 3 ), against the wall ( 9 ) of the mould cavity ( 1 ) opposite the wall ( 5 ), and is released as the melt front ( 3 ) advances in the mould cavity ( 1 ).
8. Method according to claim 1 , characterised in that, before the melt enters, the sheet is positioned at its lower end, which faces away from the melt front, with the aid of at least one stop ( 11 ) that can be withdrawn from the mould cavity ( 1 ).
9. The method according to claim 7 , characterised in that that the sheet is held at its lower part using a sintered block ( 10 ) under reduced pressure.