WO2023164639A1

WO2023164639A1 - In-mold coating containing conductive particles to provide emi shielding

Info

Publication number: WO2023164639A1
Application number: PCT/US2023/063255
Authority: WO
Inventors: Siddhartha Asthana; Ranjit PACHHA; Axel Lachenmaier
Original assignee: Magna Exteriors Inc.
Priority date: 2022-02-24
Filing date: 2023-02-24
Publication date: 2023-08-31

Abstract

Process for manufacture of an electrically shielded molded vehicle part comprising the steps of: a. Providing a mold having a cavity for forming a vehicle part from a moldable material, wherein the vehicle part includes an inner surface and an outer surface; b. Molding of the part using a thermoset or thermoplastic material; c. Injecting a mixture of a carrier and a particulate shield mixture into the mold cavity for dispersing and coating of at least the inner of the outer surface of the part with an electronic shielding material; and, d. Curing the part for producing and electrically shielded vehicle part.

Description

IN-MOLD COATING CONTAINING CONDUCTIVE PARTICLES TO PROVIDE EMI SHIELDING

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a PCT International Patent Application and claims benefit of United States Provisional Patent Application Nos. 63/313,429, filed February 24, 2022, and 63/313,921 , filed February 25, 2022. The disclosures of the above applications are incorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates to an in-mold coating containing conductive particles to provide EMI shielding.

BACKGROUND OF THE INVENTION

Composite battery covers are being considered for Battery Electric Vehicles (BEV) to replace steel and aluminum covers. A composite battery cover is lighter in weight and provides better thermal insulation compared to steel and has better flame/thermal insulation compared to aluminum covers. Metal covers do not need additional EMI shielding whereas composite covers need additional Electromagnetic Interference (EMI) shielding to be useful in BEVs. Metal foil bonded to composite covers is typically used. However additional steps of pre-forming metal foil for a 3D geometry and bonding to a composite battery cover are required. Spray coating consisting of metallic flakes is also known, however post molding spray coating involves additional cycle times and metallic flakes are expensive.

It is an object of the present invention to introduce the in-mold conductive coating in the compression molding and injection molding process thereby eliminating the need for additional post molding process to incorporate EMI shielding.

Spray coating with conductive metallic flake is too expensive for large battery cover, additional capital for spray booth and cycle time for spraying and drying are required.

Woven and non-woven conductive fabric-co-molding of conductive fabric caused fabric to disintegrate during molding.

Metal mesh does not provide the 60 DB EMI shielding required for automotive application. Metal foil-aluminum foil-challenge with pre-forming aluminum foil in a 3D geometry. Metal aluminum foil can also crack during integration onto SMC, transportation or installation at the OEM.

It is thus a goal in the present invention to provide an efficient cost-effective method to produce an EMI shielded vehicle part such as a battery box or the like.

SUMMARY OF THE INVENTION

In accordance with the present invention there is provided a process for molding an EMI shielding of a polymer based automotive component such as a battery box for an electric vehicle. The process includes the steps of: a. Providing a mold having a cavity for forming a vehicle part from a moldable material, wherein the vehicle part includes an inner surface and an outer surface; b. Molding of the part using a thermoset or thermoplastic material; c. Injecting a mixture of a carrier and a particulate shield mixture into the mold cavity for dispersing and coating of at least the inner of the outer surface of the part with an electronic shielding material; and, d. Curing the part for producing an EMI shielded vehicle part.

Since the coating is introduced in the compression molding process, additional post molding processes, like spraying of EMI shielding coatings, is not required. Conductive coating used in an IMC process is able to evenly cover complex part geometries, unlike metal foils which are difficult to conform to complex part geometry. Depending on the final part and extent of shielding desired, graphene, carbon nano tubed, metal flake, micro metallic spheres and/or rods can be used to provide an EMI shielded final part. Shielded electric vehicle parts can be produced cost effectively utilizing the present process.

Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating the preferred embodiment of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention. BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will become more fully understood from the detailed description and the accompanying drawing, wherein Figure 1 is a schematic view of the process of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The following description of the preferred embodiment(s) is merely exemplary in nature and is in no way intended to limit the invention, its application, or uses.

In the present invention there is provided a process for manufacture of an electromagnetic interference shielded molded vehicle part comprising the steps of: a. Providing a mold having a cavity for forming a vehicle part from a moldable material, wherein the vehicle part includes an inner surface and an outer surface; b. Molding of the part using a thermoset or thermoplastic material; c. Injecting a mixture of a carrier and a conductive particulate shield mixture into the mold cavity for dispersing and coating of at least the inner or the outer surface of the part with an EMI shielding material; and, d. Curing the part for producing an EMI shielded vehicle part.

In the first step a mold generally shown at 10 is provided for molding of a vehicle part. Mold 10 includes a lower platen 12 and upper platen 14. The lower platen has a female part mold surface cavity 16 and the upper platen 14 includes a male mold portion which forms the back side of the part. A press 20 is attached for compressing the sheet mold composition charge into a vehicle part such as a battery box for an electro voltaic vehicle.

As shown in Figure 1A the mold uses heat and pressure to form the vehicle part 24. The part is allowed to cure enough such that it retains its shape as the mold is separated. For thermoplastic material is injection molded and allowed to fill the part.

Thereafter, as shown in Figure 1 C. The mold is opened such that a layer of a carrier material containing a shielding material is forced into the mold cavity on either the female or male side of the mold or both. This forces the carrier and EMI shielding material 26 along the female surface (or male surface as selected or both) and forms a layer of shielding on the part. The part and the shielding layer are then allowed to cure.

The SMC battery cover is molded in a compression molding tool. Typical cycle time of 90-120 sec and pressure of 1000 psi. Once the SMC is cured, the in-mold coating (IMC) based on conductive coating containing graphene, carbon nano tubes (CNT), metallic flakes (or in combination) is injected into the tool, the conductive coating flows and covers the entire surface of the part (still held within the mold), conductive coating starts to cure and once the curing is completed the tool is opened. The cycle time of IMC is 90 sec. Introducing high conductive particles like graphene, CNT and metallic flake/balls/rods in IMC provides EMI shielding to the composite part. There are two ways the in-mold coating may be introduced: 1 ) the tool is slightly cracked open, and the in-mold coating can be injected, 2) the tonnage is reduced to 25-50% and then the in-mold coating is injected. The carrier and mixture include from about 30% to 90% by weight of a moldable carrier material and from about 0.1 % to about 20% of a particulate electrically conductive material with the remainder comprising at least one of the group including fillers, release agents, catalysts, reinforcing agents, inhibitors and mixtures thereof. Preferably the carrier is an epoxy and urethane mixture. In a preferred embodiment the carrier comprises: from about 10-60% and preferably from about 30-50% by weight Urethane acrylate oligomer of the entire mixuture; from about 5-20% and preferably from about 7-15% Epoxy acrylate oligomer; and, from about 10-30% and preferably 15-25% Monomer content.

Conductive materials used in the coating must be of a size which is suitable for injection into the mold. Suitable graphene materials include graphenes available from AGP-such as AGNP-10 and AGNP-35 or those available from XGHS such as C-300, or R-10. Graphene and carbon nano tubes are also available from these sources. Suitable carbon nano tubes are available from suppliers such as OCSiAl under the trademark Tuball.

In operation manufacturing environment the benefits of this process are as follows. Since the coating is introduced in the compression molding process, additional post molding processes, like spraying of EMI shielding coatings, is not required. Conductive coating used in IMC process is able to evenly cover complex part geometries, unlike metal foils which are difficult to conform to complex part geometry.

1 Graphene based in-mold coating.

Carbon Nano Tube based in-mold coating.

2 Metallic flake incorporated in in-mold coating. Balls/rods based in-mold coating.

3 Application of in-mold coating for composite (thermoplastic or thermoset) to provide EMI shielding. In operation the process of the present invention provides an in-mold coating containing Graphene and/or Conductive Nano Tubes as conductive material to provide EMI shielding.

As stated above the in-mold coating containing metal flake as conductive material to provide EMI shielding.

With this process there is a method for applying an in-mold coating containing conductive material after compression molding or injection molding to provide EMI shielding.

Example

An SMC battery covers areas molded in a compression molding tool. Cycle times of 90-120 sec at a pressure of 1000 psi is used. Once the SMC is cured, the In-Mold Coating (IMC) based on conductive coating containing graphene is formulated as follows. a. Urethane acrylate oligomer: 10-60% (30-50%) b. Epoxy acrylate oligomer: 5-20% (7-15%) c. Monomer: 10-30% (15-25%) d. Graphene, metallic Flake, Carbon Nano tubes (CNT): 0.1-15% e. Filler-Calcium Carbonate: 0-15% f. Mold release agent-Zinc Stearate: 1-2% g. Cobalt Octoate: .25-1 .0% h. Catalyst-TBPB: 1-2.5% i. Inhibitor- Tert butyl catechol-0.02-0.1 %- 0.03-0.08%

Carbon nano tubes (CNT), metallic flakes (or in combination) are also used as a replacement for graphene in the above formula and as an alternate.

The various ranges of materials set forth above are used and are found effective for producing EMI shielded battery box parts.

Pressure in the mold is reduced and the above mixture is injected into the tool. The conductive coating flows and covers the entire surface of the part (still held within the mold). The conductive coating starts to cure and once the curing is completed the tool is opened. The cycle time of IMC is 90 sec. The result is a part in this case a battery box including a coating of high conductive particles like graphene, CNT and metallic flake/balls/rods in IMC. This coating is found to provide EMI shielding to the composite part. Conductive materials used in the coating must be of a size which is suitable for injection into the mold. Suitable graphene materials include graphenes available from AGP-such as AGNP-10 and AGNP-35 or those available from XGHS such as C-300, or R-10. Graphene and carbon nano tubes are also available from these sources. Suitable carbon nano tubes are available from suppliers such as OCSiAl under the trademark Tuball.

The description of the invention is merely exemplary in nature and, thus, variations that do not depart from the essence of the invention are intended to be within the scope of the invention. Such variations are not to be regarded as a departure from the spirit and scope of the invention.

Claims

CLAIMS What is claimed is:

1 . A process for manufacture of an electrically shielded molded vehicle part comprising the steps of: a. Providing a mold having a cavity for forming a vehicle part from a moldable material, wherein the vehicle part includes an inner surface and an outer surface; b. Molding of the part using a thermoset or thermoplastic material; c. Injecting a mixture of a carrier and a particulate shield mixture into the mold cavity for dispersing and coating of at least the inner or the outer surface of the part with an electronic shielding material; and, d. Curing the part for producing and electrically shielded vehicle part.

2. The process of claim 1 wherein the thermoset material is a sheet molding composition.

3. The process of claim 2 wherein the particulate shielding material is selected from graphene, carbon nano tubes (CNT), metallic flakes, metallic balls, metallic rods and combinations thereof.

4. The process of claim 3 wherein the carrier is a thermosettable liquid carrier material.

5. The process of claim 3 wherein the carrier is a thermoplastic liquified carrier.

6. The process of claim 1 wherein the part is molded under pressure in the mold and at least partially cured, the pressure in the mold is at least partially released before injection of the mixture into the mold.

7. The process of claim 6 wherein the mixture is injected for covering both an outside and an inside of the part.

8. The process of claim 1 wherein the mold is opened, and the mixture is placed inside the mold and the mold pressurized for dispersing of the particulate shielding material.

9. The process of claim 1 wherein the carrier material is a thermoplastic material.

10. The process of claim 1 wherein the carrier material is a thermoset material.

11. The process of claim 1 wherein the carrier material comprises an epoxy material.

12. The process of claim 1 wherein the part is made from a glass filled thermoplastic polyolefin material.

13. A process for manufacture of an electrically shielded molded vehicle part comprising the steps of: a. Providing a mold having a cavity for forming a vehicle part from a thermoset or thermoplastic moldable material, wherein the vehicle part includes an inner surface and an outer surface; b. Molding of the part under pressure and allowing the part to at least partially cure; c. Injecting a mixture of a carrier and a particulate shield mixture into the mold cavity for dispersing and coating of at least the inner or the outer surface of the part with an electronic shielding material; wherein the mixture includes from 30% to 90% by weight of a moldable carrier material and 0.1 % to about 20% of a particulate electrically conductive material with the remainder comprising at least one of the group including fillers, release agents, catalysts, reinforcing agents, inhibitors and mixtures thereof; and, d. Curing the part for producing and electrically shielded vehicle part.

14. The process of claim 13 wherein the moldable carrier material is a sheet molding composition.

15. The process of claim 13 wherein the particulate electromagnetic shielding material is selected from graphene, carbon nano tubes (CNT), metallic flakes, metallic balls, metallic rods and combinations thereof.

16. The process of claim 13 wherein the carrier is a glass filled thermoplastic olefin carrier.

17. The process of claim 13 wherein the part is molded under pressure in the mold and at least partially cured, the pressure in the mold is at least partially released before injection of the mixture into the mold.

18. The process of claim 17 wherein the mixture is injected for covering both an outside and an inside of the part.

19. The process of claim 13 wherein the mold is opened, and the mixture is placed inside the mold and the mold pressurized for dispersing of the particulate shielding material.