EP-4739725-A1 - TOUGHENING AGENTS WITH IMPROVED MODULUS RETENTION

Abstract

A solid, epoxy adduct comprising the reaction product of a solid carboxylated nitrile rubber (XNBR) and at least one epoxy functional resin.

Inventors

• CZAPLICKI, MICHAEL
• PAQUET, DONALD
• MADAUS, KEITH
• BEDNARSKI, JEANNE

Assignees

• Zephyros, Inc.

Dates

Publication Date

20260513

Application Date

20240708

Claims (1)

1. Claims Claim 1: A solid, epoxy adduct comprising the reaction product of: (i) a solid carboxylated nitrile rubber (XNBR); and (ii) an epoxy functional resin. Claim 2: The adduct of claim 1 , wherein a carboxylic acid content of the solid carboxylated nitrile rubber is less than 2% by weight. Claim 3: The adduct of claim 1 , wherein a carboxylic acid content of the solid carboxylated nitrile rubber is less than 1% by weight. Claim 4: The adduct of any of the preceding claims, wherein the solid carboxylated nitrile rubber (XNBR) is present in an amount of at least 10% by weight. Claim 5: The adduct of the preceding claims, wherein the solid carboxylated nitrile rubber (XNBR) is a carboxylated cold polymerized butadiene acrylonitrile terpolymer. Claim 6: The adduct in any of the preceding claims, wherein the epoxy functional resin for the adduction reaction comprises a solid epoxy resin. Claim 7: The adduct in any of the preceding claims, wherein the epoxy functional resin for the adduction reaction comprises a liquid epoxy resin. Claim 8: The adduct of any of the preceding claims, wherein the adduct is free of any carboxyl terminated butadiene acrylonitrile (CTBN) material. Claim 9: The adduct of any of the preceding claims, wherein the adduct comprises polyvinyl butyral. Claim 10: The adduct of claim 9, wherein the polyvinyl butyral is present in an amount of at least 5%, or even at least 10%. Claim 11 : The adduct of any of the preceding claims, wherein the adduct comprises at least two different epoxy-functional resins. Claim 12: The adduct of any of the preceding claims, wherein the adduct comprises at least three different epoxy-functional resins. Claim 13: The adduct of any of the preceding claims, wherein the adduct comprises a solvent. Claim 14: The adduct of any of the preceding claims, wherein the adduct is free of any solvent. Claim 15: The adduct of any of the preceding claims, wherein the adduct comprises a metal carbonate. Claim 16: An epoxy-based composition comprising the adduct of any of claims 1 through 15. Claim 17: The composition of claim 16, wherein the composition is foamable upon exposure to a stimulus. Claim 18: The composition of claim 16, wherein the composition is foamable upon exposure to elevated temperatures (e.g., 120 °C to 200 °C). Claim 19: The composition of any of claims 16 through 18, wherein the composition has an improved storage modulus (e.g., an improvement of at least 10%, at least 20%, or even at least 30%) as compared to a composition that includes a carboxyl terminated butadiene acrylonitrile (CTBN)-based adduct and no XNBR-based adduct. Claim 20: The composition of any of claims 16 through 19, wherein the composition is free of any carboxyl terminated butadiene acrylonitrile (CTBN)-based adducts. Claim 21 : The composition of any of claims 16 through 20, wherein the composition comprises a blowing agent, a curing agent, or both. Claim 22: The composition of any of claims 16 through 21 , wherein the composition comprises a polymeric particle. Claim 23: The composition of any of claims 16 through 22, wherein the composition has adhesive properties. Claim 24: The composition of any of claims 16 through 22, wherein the composition has sealing properties. Claim 25: The composition of any of claims 16 through 22, wherein the composition has structural properties. Claim 26: The composition of any of claims 16 through 22, wherein the composition is a pressure-sensitive adhesive. Claim 27: The composition of any of any of claims 16 through 26, wherein the solid carboxylated nitrile rubber adduct provides for a tensile modulus as measured in accordance with ASTM D638 that is within 10% or less of the tensile modulus of the same composition with a carboxyl terminated butadiene acrylonitrile (CTBN)-based adduct. Claim 28: The composition of any of any of claims 16 through 27, wherein the modulus of the composition at room 20 °C to 25 °C does not decrease by more than 60% when exposed to temperatures of more than 80 °C. Claim 29: The composition of any of any of claims 16 through 28, wherein the volume expansion of the composition is greater with the solid carboxylated nitrile rubber adduct than with a carboxyl terminated butadiene acrylonitrile (CTBN)-based adduct. Claim 30: A solid, epoxy adduct comprising the reaction product of: (i) a solid carboxylated nitrile rubber (XNBR); (ii) a first epoxy functional resin; (iii) an optional second epoxy functional resin; and (iv) a polyvinyl butyral additive.

Description

TOUGHENING AGENTS WITH IMPROVED MODULUS RETENTION CLAIM OF PRIORITY [001] This application claims the benefit of the filing date of United States Provisional Application No. 63/525,598, filed July 7, 2023, the contents of that application being incorporated by reference herein in its entirety and for all purposes. FIELD OF THE INVENTION [002] The present teachings relate generally to solid carboxylated nitrile rubber-epoxy adducts useful as toughening agents in epoxy-based compositions for improving the modulus retention at elevated temperatures. BACKGROUND OF THE INVENTION [003] For many years industry, and particularly the transportation industry, has been concerned with acoustic attenuation, adhesion, and reinforcement of articles of manufacture such as automotive vehicles. In turn, industry has developed a wide variety of materials for providing such sound baffling, adhesion, and reinforcement. Some of the more desirable properties for adhesion and reinforcing materials include high tensile modulus, high strain to failure, and adhesion durability. [004] Epoxy thermosets, formulated with liquid carboxy terminated nitrile rubber (CTBN) containing toughening agents, are materials that satisfy most requirements. During curing most of the CTBN agents become incompatible with the curing epoxy and form separate low glass transition temperature (Tg) elastomeric domains which improve the fracture toughness of the cured thermoset material. The portion of the CTBN material that does not phase separate bonds into in the continuous epoxy matrix. This can lead to a reduction in the modulus or Tg due to the presence of low Tg elastomeric material in the matrix. When properly formulated, these thermoset materials provide an acceptable balance of properties such as adhesion, tensile modulus, strain to failure, peel resistance, and fracture toughness at ambient temperatures. [005] One continuing challenge with these materials is the ability to maintain performance at elevated temperatures. Methods to increase the modulus at elevated temperatures, such as increasing crosslink density or decreasing the amount of CTBN toughening agents, often result in reduced performance in other properties at ambient temperatures (e.g., about 20 °C to about 25 °C). It is desirable to have a material that provides increased tensile modulus at elevated temperatures, while maintaining or improving adhesion and reinforcement performance at ambient temperatures. [006] The present invention, therefore, seeks to provide an improved toughening agent material for baffling, adhesion, and/or reinforcement that provides for increased tensile modulus retention at elevated temperatures, as compared to existing materials. [007] Carboxylated solid nitrile rubbers (XNBRs) have been used to toughen thermoset formulations. Unlike CTBN with a low molecular weight and carboxyl groups at the ends of the polymer chain, XNBRs are high molecular weight polymers with carboxylic groups randomly spaced along the polymer chain. This can lead to adduct gelation during synthesis or storage and greatly limits the use of XNBR toughening agents. Co-pending United States Provisional Application No. 63/359,513 filed on July 8, 2022 (which is incorporated by reference herein in its entirety for all purposes) discloses the use of epoxy adducts of low acid containing XNBRs as storage stable toughening agents. [008] Bascom et al. (W.D. Bascom, R.Y. Ting, R. J. Moulton, C. K. Riew, and A. R. Siebert, J. of Mat. Sci., 16, 2657-2664, 1981) utilized CTBN- and XNBR- epoxy adducts separately and in combination to demonstrate their effectiveness in improving the fracture toughness of epoxy thermosets. While they identified a difference in the way CTBN and XNBR improved toughness, they did not disclose any information regarding elevated temperature behavior. [009] We have surprisingly discovered that solid XNBR adducts provide acceptable performance at ambient temperatures while improving modulus retention at elevated temperatures. Without being bound by theory, we believe the smaller domain size, identified by Bascom et al, arising from the higher molecular weight of XNBRs with their random acid functionality provides sufficient bonding to the continuous epoxy matrix while still being phase separated. This leads to less homogeneous elastomeric material in the continuous phase and subsequently improved tensile modulus retention at elevated temperatures. SUMMARY OF THE INVENTION [0010] The teachings herein provide for a solid rubber adduct derived from a carboxylated nitrile rubber useful in toughening epoxy-based compositions with improved modulus retention at elevated temperatures. [0011] The teachings herein are further directed to a solid, epoxy adduct comprising the reaction product of a solid carboxylated nitrile rubber (XNBR) and an epoxy functional resin. [0012] A carboxylic acid content of the solid carboxylated nitrile rubber may be less than 2% by weight. [0013] A carboxy