Lamination process

Abstract

A lamination process is disclosed. The process is useful for silicone based lamination adhesive compositions, in particular those which cure at or around room temperature.

Claims

1. A process for making a laminate assembly comprising a cured lamination adhesive sandwiched between two substrates, said process comprising the steps of: (i) providing a dam of sealant around a periphery of a first substrate; (ii) introducing a flowable silicone based lamination adhesive onto the first substrate having the dam of sealant around the periphery thereof; (iii) placing a second substrate on top of the first substrate to form a pre-cured assembly, trapping the flowable silicone based lamination adhesive between the first and second substrates; (iv) applying a vacuum to the pre-cured assembly of step (iii); (v) pressing the pre-cured assembly of step (iv) at a pre-determined pressure while maintaining the vacuum; (vi) releasing the pre-determined pressure of step (v) while maintaining the vacuum for a period sufficient to ensure that there is provided a continuous layer of flowable silicone based lamination adhesive between the first and second substrates as defined by the peripheral dam of sealant; and (vii) repeating step (v) and then release the pressure and vacuum and cure the pre-cured assembly; wherein the flowable silicone based lamination adhesive is made by mixing a multiple part condensation curable lamination adhesive composition, the composition comprising: (i) at least one condensation curable silyl terminated polymer having at least one, optionally at least 2 hydrolysable and/or hydroxyl functional group(s) per molecule; (ii) a cross-linker selected from the group consisting of silanes having at least 2 hydrolysable groups, optionally at least 3 hydrolysable groups, per molecule group; and/or silyl functional molecules having at least 2 silyl groups, each silyl group containing at least one hydrolysable group; and (iii) a condensation catalyst selected from the group consisting of titanates and zirconates; wherein polymer (i) is not stored in the same part as cross-linker (ii) and catalyst (iii); wherein condensation catalyst (iii) is present in a molar amount which is at least 50% of the moisture present cumulatively in the parts of the composition; wherein the molar ratio of silicon bonded hydroxyl groups in polymer (i) to hydrolysable groups in cross-linker (ii) is above 0.5; and wherein the molar ratio of the silicon bonded hydroxyl groups in polymer (i) to condensation catalyst (iii) M-OR functions is greater than 10, where M is titanium or zirconium and R is an aliphatic hydrocarbon group.

2. The process in accordance with claim 1, wherein the flowable silicone based lamination adhesive in the pre-cured assembly is allowed to cure at room temperature or at a temperature above 60° C. to cure the silicone composition or by a UV exposure treatment to cure the silicone composition.

3. The process in accordance with claim 2, wherein the cure at a temperature above 60° C. takes place in a continuous furnace.

4. The process in accordance with claim 1, wherein an edge region of the laminate assembly is subsequently cut to remove any optical transition near the edge.

5. The process in accordance with claim 1, wherein the dam of sealant is made from a polyisobutylene (PIB) rubber seal, silicone hot melt material or optically clear silicone sealant.

6. The process in accordance with claim 1, wherein one or more objects are attached to the first or second substrate prior to step (iii) so that the object(s) is/are effectively encapsulated within the cured lamination adhesive layer in the laminated assembly.

7. The process in accordance with claim 6, wherein the objects are selected from decorations, electronics, photovoltaic cells or wires and/or other connectors.

8. The process in accordance with claim 1, wherein the sealant forming the dam is retained as an external protective seal around the outside of the laminate assembly.

9. The process in accordance with claim 1, wherein step (iv) of the process has a duration of from 15 seconds to 1.5 minutes.

10. The process in accordance with claim 1, wherein the time period for step (v) will be a period of from 45 seconds to 3 minutes.

11. The process in accordance with claim 1, wherein the time period for step (vi) is similar to that of step (iv) and likewise the time period for step (vii) is similar to that of step (v).

12. The process in accordance with claim 1, wherein the pressure applied in both steps (vi) and (vi) is in the range of 10,000 Pa to 400,000 Pa.

13. The process in accordance with claim 1, wherein the substrates are made from glass, wood, stones, plastics, composites, metals, or ceramics.

14. The process in accordance with claim 13, wherein at least one substrate is made of glass.

15. The process in accordance with claim 1, wherein the flowable silicone based lamination adhesive consists of components (i), (ii) and (iii) and one or more additives selected from the group consisting of pigments, dyes, adhesion promoters, light diffusing particles, siloxane resins and/or particles with fire resistant properties.

16. The process in accordance with claim 1, wherein the multiple part condensation curable lamination adhesive composition further comprises pigments, dyes, light diffusing particles and/or fire resistance properties.

17. The process in accordance with claim 1, wherein the molar ratio of silicon bonded hydroxyl groups in polymer (i) to hydrolysable groups from cross-linker (ii) is >0.15 for polymers having a viscosity ≤30,000 mPa.Math.s at 25° C. and >0.5 for polymers having a viscosity >30,000 mPa.Math.s at 25° C.

18. A laminated assembly obtained by the process in accordance with claim 1.

19. The laminated assembly in accordance with claim 18, wherein the assembly comprises two glass substrates and wherein the assembly is cold bended to create a curved glass product.

Description

EXAMPLES

(1) All viscosity measurements were made using a Brookfield cone plate viscometer RV DIII with the most appropriate cone plate at 25° C. unless otherwise indicated.

(2) The compositions used in the following examples were made by mixing part A and part B together in a speedmixer. The part A and Part B were introduced into a speedmixer and were then mixed for four periods of 30 seconds at a speed of 2000 revolutions per minute (rpm). Dimethyl OH terminated polydimethylsiloxane (viscosity ca 50,000 mPa.Math.s) exhibits a typical average molecular weight in number of 63,000 g/mol. Trimethoxysilyl terminated polydimethylsiloxane (viscosity ca 56,000 mPa.Math.s) exhibits a typical average molecular weight in number of 62,000 g/mol. OH terminated polydimethylsiloxane (viscosity ca 2,000 mPa.Math.s) exhibits a typical average molecular weight in number of 22,000 g/mol. Dimethyl OH terminated polydimethylsiloxane (viscosity ca 13,500 mPa.Math.s) exhibits a typical average molecular weight in number of 43,000 g/mol. Trimethoxysilyl terminated polydimethylsiloxane (viscosity ca 2,000 mPa.Math.s) exhibits a typical average molecular weight in number of 22,000 g/mol.

(3) Formulation A

(4) The flowable silicone based room temperature cure adhesive was prepared by mixing two component together the base (Part A) was added at a ratio in weight of 3:1 over the curing agent (Part B). The base is composed of a 50,000 mPa.Math.s silanol terminated polydimethyl siloxane. The curing agent is composed of 100 weight parts of a 56,000 mPa.Math.s trimethoxysilyl terminated polydimethylsiloxane and 0.2 weight parts of tetra n-butyl titanate. Part A and Part B were introduced into a speedmixer and were then mixed for four periods of 30 seconds at a speed of 2000 revolutions per minute (rpm).

(5) Process Description

(6) 200×200×4 mm.sup.3 laminated glass panes were assembled using two float glass panes as the first and second substrates. The dam is prepared using a silicone hot melt (Dow Corning® Instantglaze III Window Assembly Adhesive) deposited at the periphery of the first pane. The bead thickness is about 2 mm thick. The interior of the dam was filled with flowable silicone based room temperature cure adhesive in the center of the pane. The flowable silicone based room temperature cure adhesive flows gently to form a disc.

(7) After application both panes are put on top of each other thereby sandwiching the adhesive between them to form a pre-cured assembly and the panes are put in a VAC® Company vacuum apparatus (HVV90500) and vacuum is pulled out for the defined time (see table) using a vacuum pump. Once the time is reached, the pressurizing plate is utilised to apply pressure to the pre-cured assembly with a pressure of 80,000 Pa for the defined time. The pressure is subsequently released whilst the vacuum is maintained for a given time after which pressure is re-applied for a given time. At the end, the vacuum is released to atmospheric pressure and the pane is allowed to complete the cure process at room temperature.

Examples with Formulation A

(8) TABLE-US-00001 Comp. Comp. Example 1 Example 2 Example 3 Example 4 example 1 example 2 (3 units) (3 units) (1 unit) (1 unit) (1 unit) (3 units) Formulation A A A A A A Dimensions 200 × 200 × 6.1.6 200 × 200 × 6.1.6 200 × 200 × 6.1.6 200 × 200 × 6.1.6 200 × 200 × 6.1.6 200 × 200 × 6.1.6 Shape of flowable material Strips Center Center Center Center two faces disk disk disk disk Time vacuum (s) 30 30 30 30 30 30 Time compression + vacuum (s) 60 60 60 300  60 60 Time vacuum (s) 30 30 30 30 30 150 Time compression + vacuum (s) 120  120  60 60  0 0 Leaks no no no no no no Appearance after 24 h No No No No Voids at 4 Voids at 4 bubble bubble bubble bubble corners corners Comp. Comp. Comp. Comp. Comp. Comp. Comp. Comp. example 3 example 4 example 5 example 6 example 7 example 8 example 9 example 10 (1 unit) (1 unit) (1 unit) (1 unit) (2 units) (1 unit) (3 units) (1 unit) Formulation A A A A A A A A Dimensions 200 × 200 × 200 × 200 × 200 × 200 × 200 × 200 × 200 × 6.1.6 200 × 6.1.6 200 × 6.1.6 200 × 6.1.6 200 × 6.1.6 200 × 6.1.6 200 × 6.1.6 200 × 6.1.6 Shape of Center Center Center Center Center Strips Center Center flowable disk disk disk disk disk two faces disk disk material Time 300 0  0 600 420 420 300 120 vacuum (s) Time 60 60 60 no 120 60 60 120 180 compression + vacuum vacuum (s) Time 30 30 30 0 0 0 0 0 vacuum (s) Time 120 120 120  0 0 0 0 0 compression + vacuum (s) Leaks no yes yes Yes yes no yes no Appearance Voids at Bubbles Bubbles Bubbles Voids at Bubbles Voids at Voids at after 24 h 2 corners 4 corners 4 corners 4 corners

Examples with Formulation A

(9) Examples and Comparative (Comp.) examples are showing that a one compression step process is not leading to a void free and to a leak free assembly. The first compression is useful to prevent leaks in the barrier occurring later on in the process. The vacuum stage in between the two compression steps is useful to drive the product from the center to the edges. A one step process might be successful by chance but will not provide a consistent quality in the units produced. FIG. 1a attached hereto depicts a laminate made by the process as hereinbefore described.

(10) One of the resulting units was tested for impact with a 5 kg mass falling from 3 meters. No glass parts were ejected from the impact and after the impact, the glass parts were still holding together (FIG. 2), which emphasize the good adhesion of the lamination product with all parts of the laminate.

(11) A laminated glass unit containing inserts such as plastics fabrics were made successfully as well.

(12) Laminated glass unit containing inserts such as plastics fabrics SEFAR® Architecture Vision CU 140/70 and SEFAR® Architecture Vision CU 260/25 were made successfully as depicted in FIG. 1b.