Improved structural bonding adhesive

Abstract

A material comprising an epoxy / elastomer adduct, polymer particles, from about 0.05 to about 20% by weight of an epoxy / diacid adduct, and optionally an amine reaction product.

Description

[0001] This application is a divisional application of a Chinese application with an application date of October 29, 2019, an application number of 201980072079.X, and an invention title of "Improved Structural Adhesives". Technical Field

[0002] This teaching generally relates to activatable materials, methods of forming activatable materials, and methods of using activatable materials to adhere components of articles such as motor vehicles. The activatable materials provide improved adhesion for individual substrates (especially when exposed to environmental stresses), improved adhesion between different substrates, and improved fracture toughness, improved failure strain, and improved adhesion durability. Background Art

[0003] For many years, industry, particularly the transportation industry, has been concerned with the bonding and strengthening of articles such as motor vehicles. Of particular concern is the production of lightweight, fuel-efficient vehicles in response to government regulations and the pressure of other widespread industry demands. In turn, industry has developed a wide variety of activatable adhesion and sealing materials for use in such lightweight, improved fuel economy vehicles. One way to reduce vehicle weight includes replacing heavy components with counterparts composed of lighter materials than those currently in use, such as replacing galvanized steel with aluminum or polymer composites.

[0004] In addition, multi-material combinations (such as steel and aluminum) typically require fastening means different from traditional welding. Different materials pose significant challenges to traditional welding processes, and thus adhesives are often used instead of welding. To meet the need for bonding different materials, these adhesives typically need to have highly specific physical properties while also adhering to a variety of different substrates.

[0005] One problem with using such adhesives is the large difference in the coefficients of thermal expansion between components composed of different materials. For example, the coefficient of thermal expansion of aluminum is approximately twice that of steel. Thus, when heating a motor vehicle to cure coatings and adhesives, problems such as delamination, warping, flaw propagation, or other types of assembly deformations occur. Therefore, a suitable adhesive material must have sufficient failure strain to compensate for the increased relative displacement due to the difference in the coefficients of thermal expansion of the materials being bonded to each other.

[0006] Another problem when different metals are in proximity to each other is galvanic corrosion (e.g., the result of ion transfer that can occur when the interface of two metals is exposed to the environment (e.g., a hot, wet, and corrosive environment)). Therefore, a suitable activatable material must have sufficient adhesion durability in hot, wet, and corrosive environments.

[0007] Some other desired properties of these materials include high fracture toughness, an appropriate tensile modulus, improved wash resistance before activation (e.g., in its green state), and improved ease of dispensing when the material is on a surface before activation. These properties, including failure strain and adhesion durability, generally have an inverse relationship, where an increase in one follows a decrease in the other. Thus, providing simultaneous improvement in both properties is a significant challenge.

[0008] Accordingly, the present teachings are directed to providing a material that, compared to existing activatable materials, has improved failure strain, adhesion, T-peel, and wedge impact and / or durability after activation while maintaining an appropriate tensile modulus (e.g., a relatively consistent modulus in the temperature range of -40°C to 80°C), ease of dispensing, and wash resistance (before activation). Summary of the Invention

[0009] The teachings herein provide a material comprising an epoxy / elastomer adduct, polymer particles, from about 0.05 to about 20 wt% of an epoxy / diacid adduct, and an optional amine reaction product.

[0010] The material can have a T-peel of at least 14. The material can have a failure strain greater than 8%. The material can have a glass transition temperature as defined by ASTM D 7028-07 of at least 80°C. The material can include an amine reaction product. The epoxy / elastomer adduct can comprise a polydisulfide polymer. The epoxy elastomer adduct can be present in an amount of at least about 5 wt% but less than about 50 wt% or even at least about 15 wt% but less than about 30 wt%. The polymer particles can be present in an amount of at least about 3 wt% but less than about 60 wt% or even at least about 27 wt% but less than about 32 wt%. The epoxy / diacid adduct can be present in an amount of from about 0.2 wt% to about 15 wt% or even from about 2 wt% to about 5 wt%.

[0011] The amine reaction product can be present in an amount of from about 0.01 wt% to about 15 wt% or even from about 0.5 wt% to about 5 wt%. The amine reaction product can be present in an amount sufficient such that the material exhibits a T-peel strength of from about 6 N / mm to about 30 N / mm. The amine reaction product can be selected from 1-naphthylamine, 2-naphthylamine, ethanolamine, phenethylamine, oleylamine, or combinations thereof. The amine reaction product can be adducted with the epoxy resin.

[0012] The material can comprise phenoxy dissolved in the epoxy resin in the range of from about 2 wt% to about 10 wt% of the material. The material can comprise a silane-modified epoxy resin in the range of from about 8 wt% to 18 wt% of the material.

[0013] The material may include a curing agent. The material may include a toughening agent. The epoxy component of the epoxy / diacid adduct may include bisphenol-F diglycidyl ether (DGEBF) epoxy resin. The diacid component of the epoxy / diacid adduct may be one or more of C18 or C36 diacids. The epoxy resin may be selected from bisphenol-F diglycidyl ether (DGEBF) epoxy resin, silane-modified epoxy resin, or a combination thereof.

[0014] The material may have a failure strain of at least 16%. The material may have a modulus of at least 900 MPa.

[0015] The polymer particles may include a core modifier of polybutadiene, styrene-butadiene rubber, or a combination thereof. The polymer particles may include core / shell rubber particles with an average size of about 100 - 200 nm. The polymer particles may be substantially free of agglomerated particles. The elastomer in the epoxy / elastomer adduct may be selected from polydisulfide polymers, CTBN, ETBN, Epoxonic 328, or any combination thereof.

[0016] The material may include a curing accelerator in the range of about 0.5 wt% to about 5.0 wt% of the material. The material may include a curing agent in the range of about 2 wt% to about 7 wt% by weight of the material. The material may exhibit a tensile modulus of about 900 MPa to about 1700 MPa upon curing. The material may exhibit a lap shear strength of at least about 20 MPa upon curing. When cured, the material may exhibit a T-peel strength of about 6 N / mm to about 18 N / mm.

[0017] The material may include one or more reinforcing components. The one or more reinforcing components may be selected from silica, diatomaceous earth, glass, clay (e.g., including nanoclay), glass beads or bubbles, carbon or ceramic fibers, nylon, aramid or polyamide fibers (e.g., Kevlar), pyrophyllite, zinc montmorillonite, talc, nontronite, wollastonite, or montmorillonite. The material may include silica and / or calcium-based reinforcing components. The silica-based reinforcing component may be fumed silica.

[0018] The ratio of epoxy / elastomer adduct to reinforcing component can be about 1 to 30 parts of epoxy / elastomer adduct per about 1 to 4 parts of reinforcing component. The ratio of epoxy / elastomer adduct to reinforcing component can be about 15 to 30 parts of epoxy / elastomer adduct per about 1 to 2 parts of reinforcing component. The ratio of epoxy / elastomer adduct to epoxy / diacid adduct can be about 1 to 6 parts of epoxy / elastomer adduct per about 1 to 4 parts of epoxy / diacid adduct. The ratio of epoxy / elastomer adduct to epoxy / diacid adduct can be about 3 to 7 parts of epoxy / elastomer adduct per about 1 to 3 parts of epoxy / diacid adduct. The ratio of epoxy / diacid adduct to amine reaction product can be about 1 to 12 parts of epoxy / diacid adduct per about 1 to 3 parts of amine reaction product.

[0019] The teachings herein also relate to materials comprising less than about 30 wt% of polymer particles, an epoxy / elastomer adduct, and an amine reaction product, wherein the polymer particles comprise core / shell rubber particles dispersed in an epoxy resin, and the core / shell rubber particles are present at a concentration of at least 20% of the polymer particles.

[0020] The material can include a silane-modified epoxy resin. The material can include a reinforcing component. The material can include an epoxy / diacid adduct. The material can have a failure strain greater than 8% and a modulus of at least 900 MPa. The material can include a curing agent. The material can contain about 15 wt% to about 30 wt% of the epoxy / elastomer adduct. The material can have a failure strain of at least 16%. The material can have a modulus of at least 1100 MPa. The ratio of epoxy / elastomer adduct to silane-modified epoxy resin can be about 1 to 20 parts of epoxy / elastomer adduct per about 1 to 13 parts of silane-modified epoxy resin. The ratio of epoxy / elastomer adduct to reinforcing component is about 1 to 30 parts of epoxy / elastomer adduct per about 1 to 4 parts of reinforcing component.

[0021] The teachings herein also relate to the use of the materials described herein as adhesives. The teachings herein also relate to the use of the materials described herein for adhering components in a transport vehicle. The teachings herein also relate to the use of the materials described herein for adhering steel to aluminum. The teachings herein also relate to the use of the materials described herein for adhering steel to a polymer composite or for adhering aluminum to a polymer composite.

[0022] The teachings herein also contemplate a method for adhering a first substrate to a second substrate, comprising: applying the material according to any one of the preceding claims to the first substrate; then contacting the material with the second substrate after activating the material; and activating the material. Description of the Drawings

[0023] Figure 1A graph is shown depicting the storage modulus as a function of temperature for identifying the glass transition temperature of exemplary materials in accordance with the present teachings. DETAILED DESCRIPTION

[0024] The explanations and illustrations presented herein are intended to acquaint others skilled in the art with the present teachings, its principles, and its practical applications. The specific embodiments of the present teachings set forth are not intended to be exhaustive or to limit the present teachings. The scope of the present teachings should be determined with reference to the appended claims and the full scope of equivalents to which those claims are entitled. The disclosures of all articles and references (including patent applications and publications) are incorporated by reference for all purposes. Other combinations are possible as will be gathered from the appended claims, which are also incorporated by reference into this written description. Unless otherwise indicated, percentages herein are by weight.

[0025] This application is related to U.S. Provisional Application No. 62 / 751,786, filed Oct. 29, 2018, the content of which is incorporated herein by reference for all purposes.

[0026] The present teachings are set forth based on providing improved materials (e.g., activatable materials) and articles incorporating such materials. The activatable materials can contribute to providing adhesion on the surface of a structure or to one or more structural members of an article. As used herein, the term activatable material includes any material that can be activated by environmental conditions or other conditions to melt, flow, cure (e.g., thermoset), or combinations thereof. For example, upon exposure to conditions such as heat, pressure, chemical exposure, or combinations thereof, the material can flow, melt, cure, or combinations thereof.

[0027] Activatable materials generally include epoxy / elastomer adducts, polymer particles, epoxy / diacid adducts, amine reaction products, toughening agents, phenoxy resins, curing agents, curing accelerators, and one or more reinforcing fillers.

[0028] The activatable materials of the present teachings can be applied to a variety of articles to increase the structural integrity of portions or components of the article. Examples of such articles include, but are not limited to, household or industrial appliances, furniture, storage containers, buildings, structures, etc. The activatable materials can be applied to portions of a transportation vehicle, which includes boats, trucks, trains, airplanes, motor vehicles, etc. The material can be used in a motor vehicle, for example, in conjunction with the body or frame members (e.g., vehicle frame rails) of the motor vehicle.

[0029] The material can be formulated to include an adduct, which can be an epoxy / elastomer adduct. The epoxy / elastomer adduct imparts flexibility and the ability to produce a separate phase of the activatable material upon curing and the ability to absorb energy during plastic deformation, and can impart the ability to produce phase separation. Such phase separation can improve fracture toughness. A variety of adducts can be used in the present teachings. The content of the epoxy / elastomer adduct can be up to about 75 wt% of the activatable material. The epoxy / elastomer adduct can be about at least about 5 wt%, more typically at least about 10 wt%, more typically at least about 15 wt%, and even more typically at least about 20 wt% of the activatable material. The epoxy / elastomer adduct can be about 75% or less by weight of the activatable material, more typically about 70% or less by weight, more typically about 65% or less by weight, and even more typically 60% or less by weight. The epoxy / elastomer adduct can be a combination of two or more specific adducts. At a temperature of 23 °C, the adduct can be a solid adduct, a liquid adduct, or a semi-solid, or can also be some combination thereof. The adduct can consist essentially of one or more adducts that are solid at a temperature of 23 °C (i.e., at least 70%, 80%, 90% or more). The adduct (if solid) can be in a dissolved form to facilitate incorporation during mixing operations. The adduct can be used with polymer particles, such as core / shell materials, styrene-butadiene rubber (SBR) or polybutadiene (PBd), epoxy / diacid adducts, and amine reaction products, which can achieve the desired adhesion properties and physical properties over a wide temperature range, even when using a relatively small amount of the adduct.

[0030] The adducts themselves generally include from about 1:5 to 5:1 parts of epoxy resin to elastomer, more preferably from about 1:3 to 3:1 parts of epoxy resin to elastomer. More typically, the adducts include at least about 10%, more typically at least about 20% and / or even at least about 30% elastomer, and also typically include no greater than about 60% elastomer, although higher or lower percentages are possible. The elastomeric compounds suitable for the adducts can be thermosetting elastomers, but this is not necessary. Exemplary elastomers include, but are not limited to, natural rubber, SBR (styrene-butadiene rubber), polyisoprene, polyisobutylene, PBd (polybutadiene), isoprene-butadiene copolymer, chloroprene, nitrile rubber, butyl rubber, carboxyl-terminated polymers (such as carboxyl-functional butadiene-acrylonitrile), polydisulfide polymers, acrylic elastomers, acrylonitrile elastomers, silicone rubber, polysiloxane, polyester rubber, diisocyanate-linked condensation elastomers, EPDM (ethylene-propylene-diene rubber), carboxyl-terminated polymers, carboxyl-terminated butadiene-acrylonitrile (CTBN), chlorosulfonated polyethylene, fluorinated hydrocarbons, etc. Examples of additional or alternative epoxy resin / elastomer or other adducts suitable for the present teachings are disclosed in U.S. Patent Publication 2004 / 0204551.

[0031] An example of a preferred adduct or preferred component for producing an epoxy / elastomer adduct is an epoxidized polydisulfide polymer, such as the products sold under the trade names Thioplast TM G and Thioplast TM EPS. A particularly preferred grade of epoxy / elastomer adduct is Thioplast TM G10 and Thioplast TM EPS-80. Another example is Hypro TM 1300X13NA (CTBN), which is commercially available from Emerald Performance and is adducted with bisphenol F diglycidyl ether. Yet another example of a preferred epoxy / elastomer adduct is Hypro TM 1300X63 (ETBN (glycidyl esters of butadiene and butadiene-acrylonitrile)). Another example of a preferred epoxy / elastomer adduct can be prepared using Epoxonic 328.

[0032] Adducts containing elastomers can be included to modify the structural properties of the activatable material, such as strength, failure strain, fracture toughness (G 1C) Peel, adhesion durability, stiffness, or other properties. CTBN can be particularly useful for developing adhesion to contaminated surfaces, especially to stamping lubricants typical in the automotive industry. The material can include a carboxyl-terminated polymer adduct. The carboxyl-terminated polymer adduct can impart to the activated material an improved failure strain of greater than about 2% or even greater than about 3%.

[0033] For illustrative purposes, Table A is made below to illustrate exemplary compositions for producing epoxy / elastomer adduct reaction products.

[0034] Table A

[0035]

[0036] Generally, the activatable material preferably includes at least one type of polymer particle. Such polymer particles can be used to improve fracture toughness (G 1C ) Peel resistance and impact resistance. As used herein, the term "polymer particle" is defined as a particle containing a polymer material. Like any other component of the present teachings, the term "polymer particle" can include one or more polymer particles. A variety of polymer particles can be used in the practice of the present teachings and generally include one or more elastomers. The polymer particles are typically preferably at least 4 wt% of the activatable material, more typically at least 7 wt%, even more typically at least 10 wt%, still more typically at least 13 wt%, even still more typically at least 16 wt%, and the polymer particles are preferably less than 90 wt% of the activatable material, more typically less than 40 wt%, even more typically less than 30 wt%, although higher or lower amounts can be used in specific embodiments.

[0037] The polymer particles can include one or more core / shell polymers, which can be pre-dispersed in an epoxy resin. The method of forming the core-shell material in a liquid epoxy resin avoids the agglomeration of the core-shell particles, which can be common for "dry" core-shell polymer particles (e.g., agglomeration may occur during the drying process). Examples of products prepared by this method can be described in one or more of the following U.S. patents: U.S. Patent Nos. 3,984,497; 4,096,202; 4,034,013; 3,944,631; 4,306,040; 4,495,324; 4,304,709; and 4,536,436. The polymer particles can be formed by an emulsion polymerization method. The method can include adding a solvent to the resin. Due to the incompatibility between the resin / solvent and water, when the core-shell particles move into the resin, water settles out of the material, resulting in reduced agglomeration. Alternatively, high-speed dispersion can effectively depolymerize the core / shell material. However, surfactants can remain after spray drying or coagulating the core / shell material. Such residual surfactants can be harmful to the tolerance of the material to environmental exposure conditions involving water (e.g., salt spray and moisture). Materials not exposed to environmental exposure conditions generally will not show a difference between dry and liquid, provided that the dry material is sufficiently depolymerized. The polymer particles can include one or more core / shell polymers pre-dispersed in an epoxy resin such as bisphenol-A type or bisphenol-F type epoxy resin.

[0038] As used herein, the term core / shell polymer can denote a polymer material, where a majority (e.g., greater than 30 wt%, 50 wt%, 70 wt% or more) of the polymer material can consist of a first polymer material (i.e., the first or core material), and the first polymer material can be substantially completely encapsulated by a second polymer material (i.e., the second or shell material). As used herein, the first polymer material and the second polymer material can consist of one, two, three or more polymers, which are combined and / or reacted together (e.g., sequential polymerization), or can be part of separate or identical core / shell systems. The core / shell polymer should be compatible with the formulation and preferably have a ductile core and a rigid shell that has favorable adhesion to other components of the activatable material.

[0039] The first and second polymer materials of the core / shell polymer can include elastomers, polymers, thermoplastic materials, copolymers, other components, or combinations thereof. The first polymer material, the second polymer material, or both can include (e.g., at least 70 wt%, 80 wt%, 90 wt% or more) one or more thermoplastic materials or can consist essentially entirely of (e.g., at least 70 wt%, 80 wt%, 90 wt% or more) one or more thermoplastic materials. Exemplary thermoplastic materials include, but are not limited to, styrenics, acrylonitriles, acrylates, vinyl esters, polyamides, polyethylenes, PBd (polybutadiene), SBR (styrene-butadiene rubber), or combinations thereof.

[0040] Examples of useful core-shell graft copolymers can be those in which a hard compound (e.g., styrene, acrylonitrile, or methyl methacrylate) is included and can be grafted onto a core made of a polymer of a soft or elastomeric compound (e.g., butadiene or butyl acrylate). U.S. Patent No. 3,985,703 describes useful core-shell polymers, the core of which is made of butyl acrylate, but can be based on ethyl isobutyl, 2-ethylhexyl, or other acrylic alkyl esters or mixtures thereof. The core polymer can also include other copolymerizable compounds, such as styrene, vinyl acetate, methyl methacrylate, butadiene, isoprene, etc. The core polymer material can also include crosslinking monomers having two or more non-conjugated double bonds with approximately equal reactivity, such as ethylene glycol diacrylate, butanediol dimethacrylate, etc. The core polymer material can also include graft-linking monomers having two or more non-conjugated double bonds with unequal reactivity, such as diallyl maleate and allyl methacrylate.

[0041] The shell portion can be polymerized from methyl methacrylate such as methyl acrylate and optional other (meth)acrylic acid alkyl esters and (meth)acrylates such as ethyl acrylate, butyl acrylate or mixtures thereof. Up to 40 wt% or more of the shell monomers can be styrene, vinyl acetate, vinyl chloride, etc. Additional core-shell graft copolymers useful in the examples of this teaching are described in U.S. Patent Nos. 3,984,497; 4,096,202; 4,034,013; 3,944,631; 4,306,040; 4,495,324; 4,304,709; and 4,536,436. Examples of core-shell graft copolymers include, but are not limited to, MBS (methacrylate-butadiene-styrene) polymers made by polymerizing methyl methacrylate in the presence of PBd (polybutadiene) or a polybutadiene copolymer rubber. MBS graft copolymer resins generally can have an SBR (styrene-butadiene rubber) core and a shell of an acrylic polymer or copolymer. Examples of other available core-shell graft copolymer resins include PBd (polybutadiene), ABS (acrylonitrile-butadiene-styrene), MABS (methacrylate-acrylonitrile-butadiene-styrene), ASA (acrylate-styrene-acrylonitrile), all acrylics, SA EPDM (styrene-acrylonitrile grafted onto an elastomeric backbone of ethylene-propylene-diene monomer), MAS (methacrylic acid-acrylic rubber styrene), and mixtures thereof.

[0042] Examples of available polymer particles include, but are not limited to, those sold under the trade name Kane Ace TM and commercially available from Kaneka Americas Holding, Inc. Particularly preferred grades of Kane Ace TM are sold under the trade names MX-134 and MX-267. The average size of the polymer particles can be not less than 50 nm and not greater than 300 nm. The polymer particles can be about 5 wt% to about 30 wt% of the activatable material.

[0043] The material can include an epoxy / diacid adduct. The use of the term diacid can refer to any polyfunctional molecule having two carboxylic acid moieties. Some diacid compounds are introduced into the epoxy backbone to increase the flexibility and toughness of the formulation and the ability to phase separate. The diacid component of the epoxy / diacid adduct can be a C8-C40 or higher diacid compound adducted to the epoxy. The epoxy component of the epoxy / diacid adduct can be DGEBF (bisphenol F diglycidyl ether). The diacid can be saturated or unsaturated. Preferably, the diacid is derived from an unsaturated fatty acid. Examples of preferred epoxy / diacid adducts are The esterification product of YDF-172LV (DGEBF) and C18 diacid. Another example of a preferred epoxy / diacid adduct is one that can be obtained from Emerald Performance obtained DA323 (DGEBA and dimer fatty acid adduct).

[0044] The adduct typically comprises from about 1:6 to 6:1 parts of diacid and epoxy resin, more preferably from about 1:4 to 4:1 parts of diacid and epoxy resin. More typically, the adduct comprises at least about 10%, more typically at least about 20%, even more typically at least about 40% diacid, and typically comprises no more than about 60% diacid, although higher or lower percentages are possible.

[0045] The material can include an amine reaction product. Such a reaction product can be used to improve peel resistance and impact resistance without adversely affecting other properties such as lap shear, modulus measured by ASTM D 7029-07, ultimate strength, etc. The amine reaction product can include an amine moiety and a hydrophobic moiety. The hydrophobic moiety can be aliphatic, cyclic, or a combination thereof. The hydrophobic moiety can be C36 or less, C18 or less, C10 or less, or C4 or less. The amine reaction product can be selected to include one or more low molecular weight components. As a non-limiting example, the amine reaction product can include 1-naphthylamine, 2-naphthylamine, ethanolamine, phenethylamine, oleylamine, or a combination thereof. The amine reaction product can be adducted to the epoxy resin. The amine reaction product can be adducted to bisphenol-F epoxy resin, silane-modified epoxy resin, or a combination thereof. Examples of suitable epoxy resins can include YDF 172LV (DGEBF). Another example of a suitable epoxy resin can include Epokukdo KSR-177 (bifunctional silane-modified epoxy resin). The amine reaction product can be adducted to the epoxy resin before being added to the material. High molecular weight components can be selected as long as the detrimental effects on the material viscosity are minimized (e.g., such that the material can still flow as needed during application).

[0046] For illustrative purposes, Table B is made below to illustrate exemplary compositions for producing an amine reaction product with an epoxy resin.

[0047] Table B

[0048]

[0049] The material can include a toughening agent. The use of the term toughening agent can relate to a single toughening agent or a combination of different toughening agents. Although other toughening agents can be used, preferred toughening agents include amine-modified, epoxy-modified, urethane-modified polymers or any combination thereof. These polymers can include thermoplastics, thermosets or thermocurable materials, elastomers, combinations thereof, etc. These polymers can be modified with urethanes, aromatic or non-aromatic epoxy resins, and / or can be modified with bisphenol-F type, bisphenol-A type, combinations thereof or other types of epoxy resins. Examples of preferred toughening agents (which can be toughening agents based on phenol-terminated urethanes) are EP 1820 (available from Innovative Resin Systems).

[0050] Examples of other preferred toughening agents are polyurethane-modified epoxy resins sold under the trade names GME-3210 and GME-3220, which are commercially available from GNS Technologies. Without being bound by theory, it is believed that when a polyurethane-modified epoxy toughening agent is included, the activatable material can substantially maintain impact strength (e.g., impact resistance) at low temperatures while minimizing the decrease in glass transition temperature (Tg) (e.g., compared to other toughening agents). Additional examples of preferred toughening agents are epoxy-capped polyethers or amine precursors for producing epoxy-capped polyethers, such as the JEFFA M series or SD series available from Huntsman and DER 732 available from the Dow Chemical Company. Toughening agents based on cashew nut shell liquid such as epoxidized liquid Cardolite NC-514 and Cardolite Lite2513HP are also available toughening agents. Unless otherwise stated, all of the individual toughening agents discussed herein can be used alone or in combination with each other in the materials of the present invention.

[0051] Generally, the toughening agent is at least 1 wt% of the material, more typically at least 2 wt%, and even possibly at least 5 wt%, but generally less than 50 wt% of the material, more typically less than 35 wt%, and even possibly less than 20 wt%, although higher and lower values are possible unless otherwise stated.

[0052] The materials described herein can include an epoxy resin. The epoxy resin can be added to the activatable material to increase the adhesion, flowability or both of the material. An exemplary epoxy resin can be a phenolic resin, which can be a novolac type or other type of resin. An example of a suitable epoxy resin is YDF 172LV (DGEBF) is available from Aditya Birla. Other preferred epoxy resin-containing materials can include modified epoxy resins. The epoxy resin can be a silane-modified epoxy resin or a silane-free epoxy resin. For example, a silane-modified epoxy resin can help allow the activatable material to adhere to metals, such as aluminum. The silane-modified epoxy resin can be a reaction product between at least one epoxy resin and a silane compound. An example of a suitable silane-modified epoxy resin is Epokukdo KSR-177 (bifunctional silane-modified epoxy resin) available from Kukdo Chemical. Additionally, various mixtures of several different epoxy resins can also be used. The epoxy resin can be present in other formulation components, such as epoxy / elastomer adducts, polymer particle dispersions, and epoxy / diacid adducts. The concentration and type of epoxy resin present in the formulation components vary according to the manufacturer and the specific grade. The epoxy resin can be present in the formulation components as an adduct, unreacted epoxy resin, or both.

[0053] The material can include a phenoxy resin component. The phenoxy resin is a high molecular weight thermoplastic condensation product of bisphenol A and epichlorohydrin and their derivatives. The phenoxy resin that can be used can have the following basic formula:

[0054]

[0055] where n is typically from 30 to 100, preferably from 50 to 90. Modified phenoxy resins can also be used. Examples of phenoxy resins that can be used are products sold by Gabriel Performance Products. Examples of suitable materials are PKHB, PKHC, PKHH, PKHJ, PKHP pellets and powders. Alternatively, phenoxy / polyester hybrids and epoxy / phenoxy hybrids can be used. To increase the yield of the activatable material, it is preferred to supply the phenoxy resin as a solution to the other components. Although any solvent can be used, it is particularly preferred to use a low molecular weight epoxy resin as the solvent, as this can also be helpful for the adhesion properties upon activation.

[0056] In certain embodiments, it may be desirable to include one or more thermoplastic polyethers and / or thermoplastic epoxy resins in the activatable material. When included, one or more thermoplastic polyethers preferably make up from about 1 wt% to about 90 wt% of the activatable material, more preferably from about 3 wt% to about 60 wt% of the activatable material, and even more preferably from about 4 wt% to about 25 wt% of the activatable material. However, as with other materials, more or less thermoplastic polyether can be used depending on the intended use of the activatable material.

[0057] Thermoplastic polyethers typically include pendant hydroxyl moieties. The thermoplastic polyethers can also include aromatic ether / amine repeating units in their main chain. For a sample weighing 2.16 kg at a temperature of about 190 °C, the thermoplastic polyethers of the present teachings preferably have a melt index of about 5 to about 300, more preferably about 30 to about 250 grams per 10 minutes. Of course, the thermoplastic polyethers can have higher or lower melt indices, depending on their intended applications. Preferred thermoplastic polyethers include, but are not limited to, polyetheramines, poly(amino ethers), copolymers of monoethanolamine and diglycidyl ether, combinations thereof, and the like.

[0058] According to one embodiment, the thermoplastic polyethers are formed by reacting a primary amine, a bis(secondary) diamine, a cyclic diamine, combinations thereof, etc. (e.g., monoethanolamine) with a diglycidyl ether or by reacting an amine with an epoxy-functionalized poly(alkylene oxide) to form a poly(amino ether). According to another embodiment, the thermoplastic polyethers are made by reacting a bifunctional amine with a diglycidyl ether or a diepoxy-functionalized poly(alkylene oxide) under conditions sufficient to react the amine moiety with the epoxy moiety to form a polymer backbone having amine bonds, ether bonds, and pendant hydroxyl moieties. Optionally, the polymer can be treated with a monofunctional nucleophile, which can be or can not be a primary or secondary amine.

[0059] Additionally, it is contemplated that amines having one reactive group (e.g., one reactive hydrogen) (e.g., cyclic amines) can be used to form the thermoplastic polyethers. Advantageously, such amines can help control the molecular weight of the thermoplastic ether formed.

[0060] Examples of preferred thermoplastic polyethers and methods for their formation are disclosed in U.S. Patent Nos. 5,275,853; 5,464,924 and 5,962,093, which are incorporated herein by reference for all purposes. Advantageously, the thermoplastic polyethers can provide various desired properties to the activatable materials, such as the desired physical and chemical properties for various applications, as further described herein.

[0061] One or more curing agents and / or curing agent accelerators can be added to the activatable materials. The amounts of the curing agent and the curing agent accelerator can vary widely within the activatable materials, depending on the desired structural properties, etc. of the activatable materials. Exemplary ranges of the curing agent present in the activatable materials are from about 2 wt% to about 7 wt%. Exemplary ranges of the curing agent accelerator present in the materials are from about 0 wt% to about 5 wt%.

[0062] Preferably, the curing agent helps the activatable material to cure by crosslinking of polymers, epoxy resins, or both. The categories of curing agents available are materials selected from the following: aliphatic or aromatic amines or their respective adducts, amidoamines, polyamides, cycloaliphatic amines, acid anhydrides, polycarboxylic acid polyesters, isocyanates, phenolic resins (e.g., those of phenol or cresol novolac resins, copolymers such as phenol terpene, polyvinyl phenol, or bisphenol-A formaldehyde copolymers, dihydroxyphenyl alkanes, etc.) or mixtures thereof. Particularly preferred curing agents include modified and unmodified polyamines or polyamides, such as triethylenetetramine, diethylenetriamine, tetraethylenepentamine, cyanoguanidine, dicyandiamide, etc. A promoter for the curing agent (e.g., modified or unmodified urea, such as methylene diphenyl bisurea, imidazole, or combinations thereof) can also be provided to prepare the activatable material.

[0063] Examples of suitable curing agents can be polyamide curing agents, such as those available from Evonik ResourceEfficiency GmbH CG 1200 (micronized dicyandiamide curing agent). Examples of suitable curing promoters can be substituted urea promoters, such as those available from Emerald Performance obtained U-52M (phenyl-substituted urea).

[0064] The activatable material can also include one or more reinforcing components. Preferably, the reinforcing components include materials that generally do not react with other components present in the activatable material. It is contemplated that the reinforcing components can also impart properties such as strength and impact resistance to the activatable material.

[0065] Examples of reinforcing components include wollastonite, silica, diatomaceous earth, glass, clay (e.g., including nanoclay), glass beads or bubbles, carbon or ceramic fibers, nylon, aramid, or polyamide fibers, etc. Examples of suitable fillers can be fumed silica, such as TS-720 (fumed silica surface-treated with polydimethylsiloxane) available from Cabot Corporation.

[0066] When used, the reinforcing components in the activatable material can be from 10 wt% or less to 90 wt% or more of the activatable material, but more typically about 20 wt% to 55 wt% of the activatable material. According to some embodiments, the activatable material can include from about 0 wt% to about 30 wt%, more preferably slightly less than 10 wt% of the reinforcing components.

[0067] Other additives, reagents, or property modifiers can also be included in the activatable material as needed, including but not limited to UV-resistant agents, flame retardants, heat stabilizers, colorants, processing aids, lubricants, etc.

[0068] It is contemplated that most any additional chemical, material, or other substance can be added to the activatable material, provided they are suitable for the activatable material and for the selected application of the activatable material.

[0069] It is possible that certain combinations and relative amounts of one or more of the materials described herein may contribute to providing improved values for one or more of tensile modulus, adhesion durability, T-peel, failure strain, or lap shear (all after activation). As another example, a combination of an epoxy / elastomer adduct and an epoxy / amine adduct may contribute to imparting improved strain failure rate and adhesion durability. The ratio of epoxy / elastomer adduct to epoxy / amine adduct is about 1 to 9 parts epoxy / elastomer adduct to about 1 to 3 parts epoxy / amine adduct. The ratio of epoxy / elastomer adduct to epoxy / amine adduct can be about 3 to 7 parts epoxy / elastomer adduct to about 1 to 3 parts epoxy / amine adduct. As another example, a combination of an epoxy / elastomer adduct and a silane-modified epoxy resin may contribute to imparting improved adhesion durability. The ratio of epoxy / elastomer adduct to silane-modified epoxy resin is about 1 to 10 parts epoxy / elastomer adduct to about 1 to 7 parts silane-modified epoxy resin. Another example is that a combination of an amine adduct and a diacid adduct can improve peel resistance and impact resistance.

[0070] When determining the appropriate components of the activatable material, it may be important to form the material such that it activates (e.g., flows, melts, cures, or otherwise changes state) only at the appropriate time or temperature. For example, in some applications, it is not desirable for the material to be reactive at room temperature or at the ambient temperature in a production environment. More typically, the activatable material becomes activated to flow and produce adhesion at a higher exposure temperature. As an example, the temperatures encountered, for instance, in an automotive assembly plant may be suitable, especially when the activatable material is being processed with other components at an elevated temperature or a higher applied energy level (e.g., during a paint preparation step). The temperatures encountered in many coating operations (e.g., in a paint and / or electrocoating curing oven) are in the range of up to about 250 °C or higher, for example.

[0071] The formation of the activatable material can be achieved according to various new or known techniques. Preferably, the activatable material is formed as a material having a substantially uniform composition. However, it is contemplated that various combination techniques can be used to increase or decrease the concentration of certain components in certain locations of the activatable material.

[0072] According to another embodiment, the activatable material can be formed by heating one or more components (such as polymer-based materials) that are generally more easily softened or liquefied to bring these components into a mixable state. Thereafter, the remaining components can then be mixed with the softened components. Melt processing operations such as twin screw, two-arm mixers, or planetary mixers can be used to compound the materials.

[0073] Depending on the components used, it may be important to ensure that the temperature of the components is kept below certain activation temperatures that could cause the activatable material to cure before the intended cure time. In cases where it is desired to keep the activatable material at a lower temperature, it may be desirable to use pressure or a combination of pressure and heat to keep the components in a semi-solid or viscoelastic state to mix the components of the activatable material. Various machines have been designed to avoid applying heat, pressure, or both to the material.

[0074] After the activatable material is formed, the material is typically applied to a surface and activated. When applied to a surface, the material can be in the form of a paste, film, solid extrudate, liquid, or patch. The material can be applied by a robotic application device, which can be a robotic extrusion device.

[0075] It should be understood that depending on the intended application, the activatable material can be applied and activated in different ways and at different times. Accordingly, exemplary uses of the activatable material will be discussed below to illustrate preferred methods of application and activation of the activatable material. In particular, the activatable material can be used for strengthening, adhesion, etc.

[0076] According to one embodiment, it can be expected that the activatable material according to the present teachings can be used as a structural adhesive material. In such an embodiment, the material is typically activated and cured (e.g., at temperatures common in electrophoretic coating or automotive painting operations) to adhere to a first member and a second member. Contact with the attachment surfaces of the first and second members can occur before or during activation and curing of the material. Examples of structural adhesive applications are disclosed in U.S. Patent Application Serial Numbers 10 / 234,902; 10 / 386,287; 60 / 451,811, which are incorporated herein by reference for all purposes.

[0077] When measured according to the ASTM D638 Type IV test method, certain activatable materials formed according to the present teachings have exhibited a post-activation tensile modulus greater than about 900 MPa, greater than about 1200 MPa, and possibly even greater than about 1500 MPa. In addition, the post-activation activatable material, especially when provided as a solid, is generally not prone to cracking (e.g., chipping, etc.).

[0078] When measured according to ASTM D5868, certain activatable materials formed according to this teaching have exhibited lap shear strengths after activation greater than about 30 MPa, greater than about 35 MPa, and possibly even greater than 40 MPa.

[0079] Certain activatable materials formed according to this teaching have exhibited post-activation failure strains greater than about 1%, greater than about 5%, greater than 8%, and possibly even greater than 15%. The failure strain is measured by conducting a tensile test (such as ISO 527), while using an extensometer to record the amount of deformation, which is then used to calculate the material strain.

[0080] When measured according to ASTM D 7028-07, certain activatable materials formed according to this teaching have exhibited glass transition temperatures (T G ) greater than 80 degrees Celsius, greater than 85 degrees Celsius, and even greater than 90 degrees Celsius. The glass transition temperature determined by this test method (referred to as the dynamic mechanical analysis Tg or "DMA Tg") may be different from the glass transition temperature reported by other measurement techniques on the same test sample. This test method is commonly used to determine the upper use temperature of composite materials. Figure 1 The storage modulus as a function of temperature for an exemplary material of this teaching is shown. The glass transition temperature is determined as the temperature at which the storage modulus begins to decrease more rapidly.

[0081] For exemplary purposes, Tables C to D are presented below to illustrate two exemplary formulations for forming activatable materials.

[0082] Table C

[0083]

[0084] Table D

[0085]

[0086]

[0087] The comparative examples shown below demonstrate changes in the physical properties based on the inclusion / removal of certain components of the materials disclosed herein.

[0088] Table E

[0089] Sample 1 Sample 2 Sample 3 Sample 4 CTBN adduct 8.72 8.72 8.72 Silica 1.00 1.00 1.00 1.00 Diacid adduct 2.50 3.50 5.00 Phenoxy resin 1.625 2.18 1.62 1.625 Polymer particles 10.87 11.61 10.87 10.25 Silane-modified epoxy resin 11.30 15.70 13.55 12.98 Bisphenol F epoxy resin 46.215 41.18 41.27 42.705 Polyurethane-based toughening agent 5.44 6.00 5.44 5.44 Polysulfide adduct 5.00 7.00 5.00 Epoxy 328 adduct 5.45 5.00 5.45 5.45 Curing agent 5.97 5.97 6.20 5.97 Accelerator 0.76 0.76 0.78 0.76 Pigment 0.10 0.10 0.10 0.10 Total 100.00 100.00 100.00 100.00 Steel / steel lap shear strength (MPa)* 42.7 39.9 36.3 43.3 Steel / aluminum lap shear strength (MPa)** 41.6 39.5 38.8 41.5 Aluminum lap shear strength (MPa)*** 42.5 36.6 36.1 38.9 Steel / steel lap shear strength after 21-day salt spray (MPa)* 32.1 33.8 30.2 21.1 Steel / aluminum lap shear strength after 21-day salt spray (MPa)** 32.9 29.4 24.5 24.5 Aluminum lap shear strength after 21-day salt spray (MPa)*** 30.2 25.2 14.8 19.7 T-peel (N / mm)**** 15.4 15.0 14.1 13.0 Peak stress (MPa) 36.5 35.3 33.2 36.1 Modulus (MPa) 1491 1580 1219 1561 Elongation (%) 21.5 14.0 15.7 12.8 Wedge impact @ 22°C – Energy (J) 17.7 17.6 17.6 19.4 Wedge impact at 22°C – Average peel load (N / mm) 41.3 43.9 44.1 40.9 Wedge impact at -40°C – Energy (J) 18.1 16.4 17.4 17.6 Wedge impact at -40°C – Average peel load (N / mm) 43.5 38.0 42.0 37.0 Tg (°C) 82.1 90.9 103 95.7

[0090] *0.060” EG60 / 0.060 EG60; **0.060” EG60 / 0.080” Alu 6061; ***0.080” Alu / 0.080” Alu 6061 ****0.030” EG60

[0091] Table F

[0092]

[0093]

[0094] *0.060” EG60 / 0.060 EG60; **0.060” EG60 / 0.080” Alu 6061; ***0.080” Alu / 0.080” Alu 6061 ****0.030” EG60

[0095] As shown in Table E, Sample 1 includes all components except the amine reaction product. Sample 2 does not contain the CTBN adduct and exhibits lower elongation and reduced wedge impact resistance at -40 °C. Sample 3 does not contain the polysulfide adduct and exhibits lower T-peel and reduced salt spray resistance of aluminum-to-aluminum adhesion. Sample 4 does not contain any diacid adduct and exhibits reduced elongation.

[0096] As shown in Table F, compared to Samples 6-10, Sample 5 is a control sample that does not include the amine reaction product or the diacid adduct. Sample 6 includes the diacid adduct. Sample 7 includes both the amine reaction product and the diacid adduct. Sample 8 includes only the amine reaction product. Sample 9 includes both the amine reaction product and the diacid adduct but does not contain polymer particles. Sample 10 includes both the amine reaction product and the diacid adduct but does not contain the polysulfide adduct, toughener, or epoxy adduct (e.g., does not contain elastomeric material). Sample 7 exhibits the best physical properties. The presence of the amine adduct shows a significant improvement in T-peel. Due to the respective lack of polymer particles and elastomeric components, both Samples 9 and 10 show overall reduced physical properties.

[0097] As used herein, unless otherwise specified, this teaching contemplates that any member of a genus (list) can be excluded from a subgenus; and / or any member of a Markush group can be excluded from the group.

[0098] Unless otherwise indicated, any numerical values recited herein include all values from the lower value to the higher value in increments of one unit, provided that there is a separation of at least two units between any lower value and any higher value. As an example, if a value for a component amount, property, or process variable (such as temperature, pressure, time, etc.) is stated to be, for example, from 1 to 90, preferably from 20 to 80, more preferably from 30 to 70, then the intervening range values (such as from 15 to 85, from 22 to 68, from 43 to 51, from 30 to 32, etc.) are intended to be within the teachings of this specification. Similarly, the individual intermediate values are also within this teaching. For values less than 1, a unit is considered to be 0.0001, 0.001, 0.01, or 0.1 as appropriate. These are merely examples of specific intentions, and all possible combinations of numerical values between the recited lowest and highest values are considered to be expressly stated in this application in a similar manner. It can be seen that the teachings of amounts expressed herein as “parts by weight” also contemplate the same ranges expressed as weight percentages. Thus, an expression in the range of “‘x’ parts by weight of the resulting polymer blend composition” also contemplates the teachings of the same recited amounts of ‘x’ in terms of weight percentages of the resulting polymer blend composition.

[0099] Unless otherwise indicated, all ranges include both endpoints and all numbers between the endpoints. The use of “about” or “approximately” in connection with a range applies to both endpoints of the range. Thus, “about 20 to 30” is intended to cover “about 20 to about 30”, including at least the specified endpoints.

[0100] The disclosures of all articles and references (including patent applications and publications) are incorporated herein by reference for all purposes. The term “consisting essentially of” used to describe a combination shall include the identified elements, ingredients, components, or steps, as well as such other elements, ingredients, components, or steps that do not materially affect the basic and novel characteristics of the combination. The use of the term “comprising” or “including” herein to describe a combination of elements, ingredients, components, or steps also contemplates embodiments consisting of or consisting essentially of the elements, ingredients, components, or steps.

[0101] A plurality of elements, ingredients, components, or steps may be provided by a single integrated element, ingredient, component, or step. Alternatively, a single integrated element, ingredient, component, or step may be divided into separate plural elements, ingredients, components, or steps. The disclosure of “a” or “an” for an element, ingredient, component, or step is not intended to exclude additional elements, ingredients, components, or steps.

[0102] It should be understood that the above description is intended to be illustrative and not restrictive. After reading the above description, many embodiments and many applications other than the examples provided will be apparent to those skilled in the art. Accordingly, the scope of the present invention should not be determined with reference to the above description, but should be determined with reference to the appended claims and the full scope of equivalents to which such claims are entitled. The disclosures of all articles and references (including patent applications and publications) are incorporated by reference for all purposes. The omission of any aspect of the subject matter disclosed herein from the appended claims is not a waiver of such subject matter, nor should it be considered that the inventors do not consider such subject matter to be part of the disclosed inventive subject matter.

Claims

1. A curable material comprising: An epoxy / elastomer adduct; Polymer particles dispersed in an epoxy resin and present in an amount of at most 30% by weight of the curable material; An epoxy / diacid adduct present in an amount of about 0.05% to about 20% by weight of the curable material; A silane-modified epoxy resin; A curing agent; An amine reaction product optionally adducted to the epoxy resin and selected from the group consisting of 1-naphthylamine, 2-naphthylamine, ethanolamine, phenethylamine, oleylamine, and combinations thereof; and A phenoxy resin component; Wherein, When cured, the material exhibits a failure strain of at least 8% measured according to ISO 527 and a tensile modulus of about 900 MPa to about 1700 MPa measured according to the ASTM D638 Type IV test method.

2. The material according to claim 1, Wherein, When cured, the material has a T-peel of at least 14.

3. The material according to claim 2, Wherein, When cured, the material has a glass transition temperature of at least 80 °C as defined by ASTM D7028-07.

4. The material according to claim 1, Wherein, The amine reaction product is adducted to the epoxy resin.

5. The material according to claim 1, Wherein, The elastomer of the epoxy / elastomer adduct comprises a polydisulfide polymer.

6. The material according to claim 4, Wherein, The epoxy / elastomer adduct is present in an amount of about 5% to about 50% or about 15% to about 30% by weight of the curable material.

7. The material according to claim 2, Wherein, The polymer particles are present in an amount of about 3% to 30% or about 20% to 30% by weight of the curable material.

8. The material according to claim 1, Wherein, The epoxy / diacid adduct is present in an amount of about 0.2% to about 15% or about 2% to about 5% by weight of the curable material.

9. The material according to claim 1, Wherein, The amine reaction product is present in an amount of about 0.01% to about 15% or about 0.5% to about 5% by weight of the curable material.

10. The material according to claim 9, Wherein, The amine reaction product is present in an amount sufficient such that when cured, the material exhibits a T-peel strength of about 6 N / mm to about 30 N / mm.

11. The material according to claim 1, Wherein, The phenoxy resin component is dissolved in an additional epoxy resin and is present in an amount of about 2% to about 10% by weight of the curable material.

12. The material according to claim 1, Wherein, The silane-modified epoxy resin is present in an amount of about 8% to 18% by weight of the curable material.

13. The material according to claim 1, Wherein, It further comprises a toughening agent.

14. The material according to claim 1, Wherein, The epoxy component of the epoxy / diacid adduct comprises a bisphenol-F diglycidyl ether (DGEBF) epoxy resin.

15. The material according to claim 16, wherein, the diacid component of the epoxy / diacid adduct comprises at least one of C18 diacid and C36 diacid.

16. The material according to claim 5, wherein, the amine reaction product is adducted with an epoxy resin selected from the group consisting of bisphenol-F epoxy resin, silane-modified epoxy resin, and combinations thereof.

17. The material according to claim 1, wherein, upon curing, the material has an elongation of at least 12%.

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