Method for Pre-forming a Curved Thermoplastic Laminate and Pre-formed Thermoplastic Laminate

Abstract

A method for pre-forming a curved thermoplastic laminate to be incorporated in composed automotive windows, the method including the processing steps of; providing a thermoplastic laminate, clamping said thermoplastic laminate from opposite flat sides between a first and a second flexible clamping layer, applying a clamping force to the thermoplastic laminate, heating the clamped thermoplastic laminate, forming the clamped and heated thermoplastic laminate, and cooling the thermoplastic laminate. The invention also relates to a pre-formed thermoplastic laminate that is pre-formed by such method as well a system for pre-forming such a thermoplastic laminate.

Claims

1. A method for pre-forming a curved thermoplastic laminate to be incorporated in composed automotive windows, the method comprising the processing steps of; a) providing a thermoplastic laminate, said thermoplastic laminate comprising at least one thermoplastic film and preferably at least one adjacent layer of bonding material, b) clamping said thermoplastic laminate from opposite flat sides between a first and a second flexible clamping layer, c) applying a clamping force to the thermoplastic laminate, said clamping force having at least a component perpendicular to the thermoplastic laminate situated between the first and second clamping layer, d) heating the clamped thermoplastic laminate to a predefined temperature, e) forming the clamped and heated thermoplastic laminate in contact with at least one mould part, wherein the contact surface of the mould part is a double-curved contact surfaces, and f) cooling the thermoplastic laminate, wherein the clamping force applied during processing step c) is at least partially maintained during processing step d).

2. The method for pre-forming a curved thermoplastic laminate according to claim 1, wherein the flexible clamping layers are substantially gas impermeable.

3. The method for pre-forming a curved thermoplastic laminate according to claim 1, wherein during processing step c) the clamping force is applied to the thermoplastic laminate from opposite sides of the thermoplastic laminate by the first and second flexible clamping layer.

4. The method for pre-forming a curved thermoplastic laminate according to claim 1, wherein during processing step c) the clamping force is applied over substantially the entire surface of at least one flat side, preferably both the opposite flat sides of the thermoplastic laminate.

5. The method for pre-forming a curved thermoplastic laminate according to claim 1, wherein the flexible first and second clamping layer are attached to individual frames and said frames are moved between a clamping position, wherein the frames are pressed together, and an inactive position, wherein the frame parts are placed apart.

6. The method for pre-forming a curved thermoplastic laminate according to claim 1, wherein during processing step c) the clamping force is increased by creating a vacuum between the flexible first and second clamping layers, causing an vacuum pressure on the opposite flat sides of the thermoplastic laminate.

7. The method for pre-forming a curved thermoplastic laminate according to claim 6, wherein gas is extracted from the space enclosed by the clamped together flexible first and second clamping layer via vacuum hose is attached to this space.

8. The method for pre-forming a curved thermoplastic laminate according to claim 6, wherein during processing step f) the thermoplastic laminate is cooled by forcing a cooling gas through at least one of the mould parts.

9. The method for pre-forming a curved thermoplastic laminate according to claim 6, wherein the thermoplastic laminate comprises at least two thermoplastic films.

10. The method for pre-forming a curved thermoplastic laminate according to claim 9, wherein at least one, preferably both of the sides of the thermoplastic films facing towards each other are coated by a conductive material, preferably Indium Tin Oxide (ITO).

11. The method for pre-forming a curved thermoplastic laminate according to claim 9, wherein in between the at least two thermoplastic films the thermoplastic laminate comprises a dispersed liquid crystal formula, and/or a suspended-particle devices, and/or a electro chromic substrate.

12. The method for pre-forming a curved thermoplastic laminate according to claim 9, wherein during processing step d) the thermoplastic laminate is heated to a temperature situated between 80? C. and 160? C., preferably between 115? C. and 135? C.

13. The method for pre-forming a curved thermoplastic laminate according to claim 9, wherein during processing step e) at least two collaborative mould parts are used, both mould parts having double-curved contact surfaces.

14. The method for pre-forming a curved thermoplastic laminate according to claim 9, wherein the contact side of at least one of the flexible first or second clamping layers is provided with an antistick layer, wherein the antistick layer preferably has a deairing surface structure.

15. The method for pre-forming a curved thermoplastic laminate according to claim 9, wherein step e) is in particular forming the clamped and heated thermoplastic laminate between two opposite mould parts, wherein the contact surfaces of the mould parts are double-curved contact surfaces.

16. A pre-formed thermoplastic laminate, wherein the thermoplastic laminate is pre-formed by the method according to claim 1.

17. A system for pre-forming a thermoplastic laminate, wherein the system is configured for executing the method according claim 1.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0030] The terms Fig., Figs., Figure, and Figures are used interchangeably to refer to the corresponding figures in the drawings.

[0031] The present invention will further elucidated with reference to the non-limitative embodiments shown in the following figures. Herein shows:

[0032] FIG. 1 a schematical side view of a system for executing the method; and

[0033] FIG. 2 a schematical perspective and partially exploded view of the system.

DESCRIPTION OF THE INVENTION

[0034] FIG. 1 shows a schematic side view of a first mould halve 1 and a second mould halve 1, wherein a surface 2 of the first mould halve 1 that is facing towards a thermoplastic laminate 5 is a double curved surface, in particular a convex double curved surface. The thermoplastic laminate 5 is depicted to be positioned between a first flexible clamping layer 3 and a second flexible clamping layer 3. The first and second flexible clamping layers 3, 3 are both stretched and attached to a respective first and second frame part 4, 4. In the illustrated situation there is no clamping force exerted onto the laminate 5 by the clamping layers 3, 3. However, a vacuum hose 6 that is attached to the first clamping layer 3 could be activated in order to extract air that is enclosed by the first and second clamping layer 3, 3 and the frame portions 4, 4. If an under pressure is realized between the clamping layers 3,3, these clamping layers 3, 3 will exert a clamping force onto the thermoplastic laminate 5. Since the clamping force in this non-limitative embodiment is induced by the vacuum that is generated in the space enclosed by both the clamping layers 3, 3 and the frame parts 4, 4 the clamping force is automatically exerted from opposite sides of the thermoplastic laminate.

[0035] FIG. 2 depicts a schematic and exploded perspective view of a process step in the pre-forming of a curved thermoplastic laminate wherein the corresponding elements with the representation in FIG. 1 are referred to with identical reference signs. In this figure the laminate 5 is positioned onto the clamping layer 3. Subsequently, once the laminate 5 is correctly positioned onto the clamping layer 3, the top and bottom frame part 4, 4 are moved towards each other, as indicated by the arrows 6, 6. Once the two frame parts 4, 4 are brought together, (in line with the situation represented in FIG. 1) a clamping force may be applied onto the laminate 5 to maintain the mutual orientation of individual layers of the laminate 5. After the clamping force is applied, the laminate 5 is heated, after which the two mould halves 1, 1 are pressed together by moving them towards each other (see arrows 7, 7). After the mould halves being pressed together, and thereby force the laminate 5 to follow the shape of the mould surfaces 2, 2, the laminate 5 is cooled, e.g. by forcing cooling gas through the mould 1, 1 to stabilize the laminate 5 in this position.