CN-121986147-A - Two-component thermally conductive adhesive with low E-modulus

Abstract

The present invention relates to a two-component adhesive formulation comprising an isocyanate component and a polyol component, the isocyanate component comprising greater than 50 wt% of a thermally conductive filler, wherein at least one of the isocyanate component and the polyol component further comprises a plasticizer, wherein at least one of the isocyanate component and the polyol component further comprises a mono-alcohol, and wherein the two-component adhesive has an E-modulus of less than 35 MPa.

Inventors

• S. Glender
• I. Kadras
• G-G. Bang Bu
• S. Schmatroch

Assignees

• DDP特种电子材料美国有限责任公司

Dates

Publication Date

20260505

Application Date

20240819

Priority Date

20230927

Claims (15)

1. 1. A two-component adhesive formulation comprising a base and a plurality of adhesive layers, the two-component adhesive formulation comprises: An isocyanate component comprising greater than 50wt% of a thermally conductive filler, and A polyol component; Wherein at least one of the isocyanate component and the polyol component further comprises a plasticizer; wherein at least one of the isocyanate component and the polyol component further comprises a monol, and Wherein the two-component adhesive has an E-modulus of less than 35 MPa.
2. 2. The two-part adhesive formulation of claim 1, wherein both the isocyanate component and the polyol component comprise a plasticizer.
3. 3. The two-component adhesive formulation of any of the preceding claims, wherein the plasticizer is a trialkyl phosphate.
4. 4. The two-component adhesive formulation of any of the preceding claims, wherein the plasticizer-containing component comprises from 0.1% to 40% of the plasticizer, based on the weight of the component.
5. 5. The two-component adhesive formulation of any of the preceding claims, wherein the polyol component comprises a monol.
6. 6. The two-component adhesive formulation of claim 5, wherein the polyol component comprises 0.1% to 20% of the monol based on the total weight of the polyol component.
7. 7. The two-component adhesive formulation of any of the preceding claims, wherein the mono-alcohol is a fatty acid alcohol alkoxylated with polypropylene oxide, polyethylene oxide, or mixtures thereof.
8. 8. The two-component adhesive formulation of any of the preceding claims, wherein the monol is a fatty acid alcohol initiated polypropylene oxide polyether.
9. 9. The two-component adhesive formulation of any of the preceding claims, wherein the polyol component has a mass ratio between the plasticizer and the monol of between 1:1 and 1:2.
10. 10. The two-component adhesive formulation of any of the preceding claims, wherein the two-component adhesive has an E-modulus of less than 20 MPa.
11. 11. The two-component adhesive formulation of any of the preceding claims, wherein the two-component adhesive has an E-modulus of less than 10 MPa.
12. 12. The two-component adhesive formulation of claim 2, wherein the mass ratio between the plasticizer present in the isocyanate component and the plasticizer present in the polyol component is about 5:1.
13. 13. A two-component adhesive formulation according to claim 3, wherein the plasticizer contains a branched C8 alkyl group.
14. 14. The two-component adhesive formulation according to any of the preceding claims, Wherein the volume ratio between the isocyanate component and the polyol component ranges from 2:1 to 1:2.
15. 15. The two-component adhesive formulation according to any of the preceding claims, Wherein the volume ratio between the isocyanate component and the polyol component is about 1:1.

Description

Two-component thermally conductive adhesive with low E-modulus In the last decade, the automotive industry has a trend to reduce the weight of vehicles. This trend is driven by regulations that reduce CO 2 emissions from fleets. In recent years, the increase in the number of electrically driven vehicles has further driven lightweight construction strategies. In order to provide longer range, batteries with high energy density are required. All long-lasting and durable battery cells require adequate thermal management. In order to thermally connect the battery cells or the modules housing the battery cells to the cooling unit, a thermal interface material or a thermally conductive adhesive is required. The battery cells generate heat during charge and discharge. The unit should be maintained at an appropriate operating temperature (preferably 25-40 ℃) to avoid efficiency losses, overheating and dangerous thermal runaway reactions. For this reason, active cooling is typically used. An effective active cooling method involves pumping a cooled water-glycol mixture through the channels to cool the metal bottom of the cooling plates on which the cells or modules are disposed. The battery cells or cartridges may be directly bonded to the cooling plate with a thermally conductive adhesive. This provides good mechanical fixation and thermal connection. The battery cells may be pouch battery cells, prismatic battery cells, or cylindrical battery cells, all of which require cooling. The cooling unit may be bonded to the bottom of the battery cell with an adhesive, or to the side of the battery cell with a thermally conductive adhesive. The key requirement of the thermally conductive adhesive is a thermal conductivity of not less than 1.5W/mK. In addition, lap shear strength > 1.5 MPa is required. The cooling unit and battery cells/cartridges are typically made of aluminum covered with a polyethylene terephthalate (PET) film or similar polymeric material. Therefore, good adhesion between the thermally conductive adhesive and the PET film is required. For some battery applications, a foam or potting composition is applied to fill the battery case for better rigidity to avoid rupture of the PET film from the battery cell in the event of physical impact to the vehicle. In these applications, the modulus of the thermally conductive adhesive applied between the battery cell casing and the cooling unit must be lower than the modulus of the potting composition or foam, so that the energy of any physical impact will be transferred from the adhesive to the foam and thus maintain the integrity of the PET film. Typically, the E-modulus of the thermally conductive adhesives should be as low as possible, and in most cases they should remain below 35 MPa. There are a variety of potential materials that can be used to formulate thermally conductive adhesives. Two-component polyurethane adhesives are distinguished among other candidates in that they have good mechanical properties and elongation at break as well as good cure kinetics. However, since high levels of filler are typically used in these polyurethane adhesives, generally available two-component polyurethane adhesives typically exhibit high E-modulus. It is desirable to have a two-component polyurethane thermally conductive adhesive formulation with a low E-modulus even when the filler content in the adhesive formulation exceeds 70 wt% of the total formulation. Disclosure of Invention The present invention relates to a thermally conductive adhesive having an ultra low e-modulus of less than 35 MPa, preferably less than 20 MPa, and more preferably less than 10 MPa, and most preferably less than 7 MPa, while having a thermally conductive filler of greater than 50 wt% based on the total weight of the adhesive formulation. The present invention provides such low e-modulus adhesive formulations by including a plasticizer and a mono-alcohol in the formulation and by carefully maintaining the critical mass ratio between the two. More specifically, the present invention provides a two-part adhesive formulation comprising an isocyanate component comprising greater than 50 wt% of a thermally conductive filler, and a polyol component, wherein at least one of the isocyanate component and the polyol component further comprises a plasticizer, wherein at least one of the isocyanate component and the polyol component further comprises a mono-alcohol, and wherein the two-part adhesive has an E-modulus of less than 35 MPa. Detailed Description To achieve a thermal conductivity greater than 1.5W/mK, the two components of a two-component adhesive formulation typically require at least 50% to 95% of a thermally conductive filler by weight of the components. In one embodiment, each component of the adhesive formulation independently comprises 50% to 85% by weight of the component of the thermally conductive filler. In another embodiment, each component of the adhesive formulation independently co