Adhesive composition with Anti-corrosion and low baking shrinkage properties

Abstract

A novel structural adhesive having a low baking shrinkage with excellent anti-corrosion characteristics relating the substrates and the method of making thereof.

Description

[0001] DI83927

[0002] ADHESIVE COMPOSITION WITH ANTI-CORROSION AND LOW BAKING SHRINKAGE PROPERTIES

[0003] During the assembly of automotive vehicles, coatings are frequently applied by dipping a partially- or entirely assembled body frame into a coating bath and then baking the coated assembly to cure the coating material. The baking step exposes the body frame to temperatures that are nominally about 160°. However, significant temperature gradients exist in the oven. Upper regions of the oven, for example, tend to be significantly hotter than other areas. Localized temperatures within the oven may reach 180-210°C. In recent years, the industry has turned to structural adhesives to reduce the number of welds, or to eliminate welding altogether. However, some of the traditional structural adhesives made from epoxy and polyurethane resins tend to shrink during this baking process, causing undesirable structural and dimensional changes. Furthermore, when the structural adhesives are applied to the automotive parts substrate, the traditional adhesives may cause substrate corrosion problems such as rust, oxidation, and other types of corrosion.

[0004] Therefore, there is a need to develop a new structural adhesive that can have a low baking shrinkage which having excellent anti-corrosion characteristics relating the substrates. It is also important to keep the viscosity of such new structural adhesives low in order to make them suitable for various applications.

[0005] Summary of the Invention

[0006] This invention provides an adhesive composition comprising: A) one or more non-rubber-modified epoxy resins and one or more rubber-modified epoxy resins; B) one or more reactive urethane group-containing toughener; C) a mixture of mineral fillers; D) a plasticizer comprising oil; and E) one or more curing agent. This invention also provides an adhesive composition comprising: A) one or more non-rubber-modified epoxy resins and one or more rubber-modified epoxy resins; wherein these two epoxy resins constitute about 12 to 45 wt.% of the adhesive composition; B) one or more reactive urethane group-containing toughener; wherein the toughener constitutes 5 to 30 wt.% of the adhesive composition; C) a mixture of mineral fillers comprising calcium oxide, calcium metasilicate, calcium carbonate, hydrated magnesium silicate, silicon dioxide, polydimethylsiloxane modified silicon dioxide, and titanium dioxide; wherein the mixture of the mineral fillers constitutes 22 to 28 wt.% of the adhesive composition; D) aDI83927

[0007] plasticizer comprising soybean oil wherein the soybean oil constitutes 15 to 17 wt.% of the adhesive composition; and E) one or more curing agent comprising dicyandiamide; wherein the curing agent constitutes 1 to 1.5 wt.% of the adhesive composition.

[0008] The present invention also provides method of making these novel adhesive compositions.

[0009] Detailed Description of the Invention

[0010] 1. Epoxy resins

[0011] The adhesive contains at least one non-rubber-modified epoxy resin, by which it is meant that, prior to curing, the epoxy resin is not chemically bonded to a rubber as described below. A wide range of epoxy resins can be used as a non-rubber-modified epoxy resin. The epoxy resin should have an average of at least 1.8, preferably at least 2.0, epoxide groups per molecule. The epoxy equivalent weight may be, for example, 75 to 350, preferably 140 to 250 and in some embodiments 150 to 225. If a mixture of non-rubber-modified epoxy resins is present, the mixture should have an average epoxy functionality of at least 1.8, preferably at least 2.0, and an epoxy equivalent weight as in the previous sentence, and more preferably each epoxy resin in the mixture has such an epoxy functionality and epoxy equivalent weight.

[0012] Suitable non-rubber-modified epoxy resins include diglycidyl ethers of polyhydric phenol compounds such as resorcinol, catechol, hydroquinone, biphenol, bisphenol A, bisphenol AP (l,l-bis(4-hydroxylphenyl)-l-phenyl ethane), bisphenol F, bisphenol K and tetramethylbiphenol; diglycidyl ethers of aliphatic glycols such as the diglycidyl ethers of C2-24 alkylene glycols; polyglycidyl ethers of phenol-formaldehyde novolac resins (epoxy novolac resins), alkyl substituted phenol-formaldehyde resins, phenolhydroxybenzaldehyde resins, cresol-hydroxybenzaldehyde resins, dicyclopentadienephenol resins and dicyclopentadiene-substituted phenol resins; and any combination of any two or more thereof.

[0013] Suitable epoxy resins include diglycidyl ethers of bisphenol A resins such as are sold by Olin Corporation under the designations D. E. R.® 330, D. E. R.® 331, D. E. R.® 332, D. E. R.® 383, D. E. R. 661 and D. E. R.® 662 resins.

[0014] Epoxy novolac resins can be used. Such resins are available commercially as D. E. N.® 354, D. E. N.® 431, D. E. N.® 438 and D. E. N.® 439 from Olin Corporation. Other suitable epoxy resins include oxazolidone-containing compounds as described in U. S.DI83927

[0015] Patent No. 5,112,932. In addition, an advanced epoxy-isocyanate copolymer such as those sold commercially as D. E. R. 592 and D. E. R. 6508 (Dow Chemical) can be used.

[0016] The non-rubber-modified epoxy resin preferably is a bisphenol-type epoxy resin or mixture thereof with up to 10 percent by weight of another type of non-rubber-modified epoxy resin. The most preferred epoxy resins are bisphenol-A based epoxy resins and bisphenol-F based epoxy resins. These can have average epoxy equivalent weights of from about 170 to 600 or more, preferably from 225 to 400.

[0017] A rubber-modified epoxy resin for purposes of this invention is a compound having at least two epoxide groups separated by an aliphatic chain of at least 300 g / mol, preferably at least 500 g / mol. The aliphatic chain may be, for example, an alkylene group; an alkenyl group; a diene polymer or copolymer; or a polyether such as a poly(propylene oxide), a poly(ethylene oxide) or a copolymer of propylene oxide and ethylene oxide. The rubber-modified epoxy resin may have, prior to curing, a glass transition temperature of -20°C or lower, preferably -30°C or lower.

[0018] One useful type of rubber-modified epoxy resin is an epoxy-terminated polyether, which contains one or more polyether segments that each has a weight of at least 300 g / mol, preferably at least 500 g / mol. The polyether segment(s) each may have a weight of up to 10,000, up to 3,000 or up to 2,000 g / mol. One type of useful epoxy-terminated polyether is a diglycidyl ether of a polyether diol. The polyether diol may be, for example, a poly(propylene oxide), a poly(ethylene oxide), or a propylene oxide / ethylene oxide copolymer. Commercially available epoxy-terminated polyethers that are useful include those sold as D. E. R.® 732 and D. E. R.® 736 by Olin Corporation.

[0019] A second useful type of rubber-modified epoxy resin is a reaction product of any of the non-rubber-modified epoxy resins described before with at least one liquid rubber that has epoxide-reactive groups, such as amino or preferably carboxyl groups. The resulting adduct has reactive epoxide groups which allow the adduct to react further when the structural adhesive is cured. It is preferred that at least a portion of the liquid rubber has a glass transition temperature (Tg) of -40°C or lower, especially -50°C or lower, as measured by differential scanning calorimetry (DSC). Preferably, each of the rubbers (when more than one is used) has a glass transition temperature of -25°C or lower. The rubber Tgmay be as low as - 100°C or even lower.

[0020] An example of this second type of rubber-modified epoxy resin is a reaction product of an amine -terminated polyether and an excess of a polyepoxide. The polyepoxide caps the amino groups of the amine -terminated polyether and forms freeDI83927

[0021] epoxide groups on the reaction product. The amine-terminated polyether preferably has 2 or 3 amino groups per molecule, prior to reaction with the polyepoxide. The amine-terminated polyether may have a weight of at least 300 g / mol, preferably at least 500 g / mol, up to 10,000, up to 3,000 or up to 2,000 g / mol. The polyepoxide may be any of the non-rubber modified epoxy resins mentioned above, among which the glycidyl ethers of polyphenols are preferred.

[0022] The second type of rubber-modified epoxy resin may be a reaction product of an excess of a polyepoxide with a homopolymer or copolymer of a conjugated diene, especially a diene / nitrile copolymer. The conjugated diene is preferably butadiene or isoprene, with butadiene being especially preferred. The preferred nitrile monomer is acrylonitrile. Preferred copolymers are butadiene -acrylonitrile copolymers. The rubbers preferably contain, in the aggregate, no more than 30 weight percent polymerized unsaturated nitrile monomer, and preferably no more than about 26 weight percent polymerized nitrile monomer. The rubber preferably contains from about 1.5, more preferably from about 1.8, to about 2.5, more preferably to about 2.2, of epoxide-reactive terminal groups per molecule, on average. Carboxyl-terminated rubbers are preferred. The molecular weight (Mn) of the rubber (prior to reaction with the polyepoxide) is suitably from about 2000 to about 6000, more preferably from about 3000 to about 5000.

[0023] Suitable carboxyl-functional butadiene and butadiene / acrylonitrile rubbers are commercially available from Noveon under the tradenames Hycar® 2000X162 carboxyl-terminated butadiene homopolymer, Hycar® 1300X31, Hycar® 1300X8, Hycar® 1300X13, Hycar® 1300X9 and Hycar® 1300X18 carboxyl-terminated butadiene / acrylonitrile copolymers. A suitable amine-terminated butadiene / acrylonitrile copolymer is sold under the tradename Hycar® 1300X21.

[0024] Other rubber-modified epoxy resins include epoxidized fatty acids (which may be dimerized or oligomerized), and elastomeric polyesters that are modified to contain epoxy groups.

[0025] At least one of non-rubber-modified epoxy resins and rubber modified epoxy resins must be present in the adhesive. In a preferred embodiment, both are present. The combined weights of epoxy resins constitute 12 to 45 wt.%, preferably 15 - 40 wt.%, more preferably 20 to 35 wt.% based on the total weight of the adhesive.

[0026] In a most preferred embodiment, the epoxy resin of the adhesive is a combination of butadiene-carboxy-terminated acrylonitrile bisphenol A glycidyl ether polymer,DI83927

[0027] epichlorohydrin bisphenol A polymer, and an epoxy-terminated polyether such as polypropylene glycol diepoxide.

[0028] 2. Tougheners

[0029] The present adhesive contains one or more reactive urethane group- and / or urea group-containing tougheners. The toughener may be conveniently made in a process that includes the steps of forming an isocyanate -terminated polyether or diene rubber and capping the isocyanate groups with a phenol or polyphenol. The isocyanate-terminated polyether or diene rubber may be made by reacting a hydroxyl- or amine-terminated polyether or hydroxyl- or amine -terminated diene rubber with an excess of a polyisocyanate, to produce adducts that have urethane or urea groups and terminal isocyanate groups. If desired, the isocyanate-terminated polyether or diene rubber can be chain-extended and / or branched prior to performing the capping reaction.

[0030] The polyether portion of the isocyanate-terminated polyether may be a polymer or copolymer of one or more of tetrahydrofuran (tetramethylene oxide), 1,2-butylene oxide, 2,3-butylene oxide, 1,2-propylene oxide and ethylene oxide, with polymers or copolymers of at least 70 weight-%, based on the total weight of the polymer or copolymer, of tetrahydrofuran, 1,2-butylene oxide, 2,3-butylene oxide and 1,2-propylene oxide being preferred. Polymers of at least 80 weight-% tetrahydrofuran, based on the total weight of the polymer or copolymer, are especially preferred.

[0031] The isocyanate-terminated polyether is conveniently prepared by the reaction of a hydroxyl- and / or amine -terminated polyether with a polyisocyanate, at a ratio of at least 1.5 equivalents, preferably 1.8 to 2.5 equivalents or 1.9 to 2.2 equivalents, of polyisocyanate per equivalent of hydroxyl and / or primary or secondary amino groups on the starting polyether. The starting polyether preferably has 2 to 3, more preferably 2, hydroxyl and / or primary or secondary amino groups per molecule. The polyisocyanate preferably has 2 isocyanate groups per molecule. The isocyanate-terminated polyether preferably has 2 to 3, more preferably 2, isocyanate groups per molecule. The starting polyether preferably has a number average molecular weight of 900 to 800, more preferably 1500 to 6000 or 1500 to 4000. The polyisocyanate preferably has a molecular weight of up to 300.

[0032] The isocyanate-terminated diene polymer is conveniently prepared by the reaction of a starting hydroxyl- or amine-terminated diene polymer with a polyisocyanate, at a ratio of at least 1.5 equivalents, preferably 1.8 to 2.5 equivalents orDI83927

[0033] 1.9 to 2.2 equivalents, of polyisocyanate per equivalent of hydroxyl groups on the starting diene polymer.

[0034] The starting diene polymer preferably has a glass transition temperature, prior to reaction with the polyisocyanate, of no greater than -20°C and preferably no greater than -40°C. The diene polymer is a liquid homopolymer or copolymer of a conjugated diene, especially a diene / nitrile copolymer. The conjugated diene is preferably butadiene or isoprene, with butadiene being especially preferred. The preferred nitrile monomer is acrylonitrile. Preferred copolymers are butadiene -acrylonitrile copolymers. The rubbers preferably contain, in the aggregate, no more than 30 weight percent polymerized unsaturated nitrile monomer, and preferably no more than about 26 weight percent polymerized nitrile monomer.

[0035] The starting diene polymer preferably has 2 to 3, more preferably 2, hydroxyl and / or primary or secondary amino groups per molecule. The polyisocyanate preferably has 2 isocyanate groups per molecule. The isocyanate -terminated diene polymer preferably has 2 to 3, more preferably 2, isocyanate groups per molecule. The starting diene polymer preferably has a number average molecular weight of 900 to 800, more preferably 1500 to 6000 and still more preferably 2000 to 3000. The polyisocyanate preferably has a molecular weight of up to 300.

[0036] The isocyanate -terminated polyether and isocyanate -terminated diene polymer can have aromatic or aliphatic isocyanate groups. When the isocyanate -terminated polymers are made in the process described above, the polyisocyanate may be an aromatic polyisocyanate such toluene diamine or 2,4’- and / or 4, 4’- diphenylmethane diamine, or an aliphatic polyisocyanate such as isophorone diisocyanate, 1,6-hexamethylene diisocyanate, hydrogenated toluene diisocyanate, hydrogenated methylene diphenylisocyanate (H12MDI), and the like.

[0037] The reaction to form the isocyanate-terminated polymers can be performed by combining the starting polyether or diene rubber with the polyisocyanate and heating to 60 to 120°C, optionally in the presence of a catalyst for the reaction of isocyanate groups with the isocyanate -re active groups of the polyether or diene polymer. The reaction is continued until the isocyanate content is reduced to a constant value, or to a target value, or until the amino- and or hydroxyl groups of the starting polyether or diene polymer are consumed.DI83927

[0038] In a preferred embodiment, the reactive toughen used in the present invention is an aliphatic based urethane polymer with is isocyanate group capped with dially bisphenol A.

[0039] The adhesive typically contains 5 to 30 wt.%, preferably 10-25 wt.%, more preferably 10-20 wt.%, and most preferably 15 to 20 wt.% of a reactive toughener.

[0040] 3. Mineral fillers

[0041] The adhesive preferably contains one or more mineral fillers. These can perform several functions including acting as an anti-corrosion agent, functioning as an oxidation / humidity scavenger to prevent corrosion redox (oxidation-reduction) reactions. Examples of suitable mineral fillers include calcium carbonate, calcium oxide, calcium metasilicate, talc, carbon black, textile fibers, glass particles / beads or fibers, aramid pulp, boron fibers, carbon fibers, mineral silicates such as hydrated magnesium silicate, mica, powdered quartz, hydrated aluminum oxide, bentonite, wollastonite, kaolin, fumed silica, silica aerogel, polyurea compounds, polyamide compounds or metal powders such as aluminum powder or iron powder, silicon dioxide, polydimethylsiloxane modified silicon oxide, and titanium oxide.

[0042] In a preferred embodiment, the mineral filler is a mixture of calcium oxide, calcium metasilicate, calcium carbonate, hydrated magnesium silicate, silicon dioxide, polydimethylsiloxane modified silicon dioxide, and titanium dioxide.

[0043] The mineral filler(s) may constitute, 8 to 40 wt.%, preferably 15 to 35 wt.%, more preferably 20 to 30 wt.%, and most preferably 22 to 28 wt.% of the total weight of the adhesive composition.

[0044] 4. Plasticizer

[0045] The adhesive of the present invention contains a plasticizer which can provide low viscosity and anti-corrosion protection by forming an oil film on the adhesive. This material may also minimize shrinkage during curing. Suitable plasticizer used in the present invention may include vegetable oil, soybean oil, cashew nut oil or other similar oils, or a mixture thereof. In the present adhesive, soybean oil is present at about 5 to 40 wt.%, preferably 10 to 30 wt.%, more preferably 12 to 20 wt.%, and most preferably 15 to 17 wt.%, based on the total weight of the adhesive.

[0046] 5. Curing agentDI83927

[0047] The adhesive of the present invention contains a carefully designed curing combination to decrease the shrinkage during the curing process. Many different chemicals may be used alone or in combination with each other for this purpose. These include aliphatic / aromatic amines, anhydrides, isocyanates, silane coupling agents, alkylphenol resins etc.

[0048] In a preferred embodiment, dicyandiamide is used as the curing agent. In another preferred embodiment, dicyandiamide is used in combination with 2-hydroxy-N-[2-[(2Z)-2-(6-oxocyclohexa-2,4-dien-l-ylidene)imidazolidin-l-yl]ethyl]benzamide to function as a curing mixture.

[0049] The curing agent is typically present in the present adhesive at 0.5 to 5.5 wt.%, preferably 0.5 to 3.5 wt.%, more preferably 0.5 to 2 wt.%, and most preferably 1 to 1.5 wt.%, based on the total weight of the adhesive.

[0050] 6. Other Ingredients

[0051] The adhesive may in addition contain one or more optional commonly used ingredients in the art such as catalyst. The adhesive can further contain other additives such as dimerized fatty acids, diluents, plasticizers, extenders, pigments and dyes, fireretarding agents, pigment, thixotropic agents, expanding agents, flow control agents, adhesion promoters and antioxidants.

[0052] Examples and Testing

[0053] To further illustrate the present invention, an inventive example and a comparative example were prepared with their relative compositions as listed in Table 1. The examples are prepared by simply mixing all the raw materials in Table 1 in room temperature. The material tradenames, their sources and functions are listed in Table 2.

[0054] Table 1. Composition details of the inventive and comparative examples

[0055] Comparative Inventive Example (wt.%) Example (wt.%) Butadiene-carboxy-terminated 33.2 32.89 acrylonitrile bisphenol a glycidyl ether

[0056] polymer and epichlorohydrin bisphenol a

[0057] polymer

[0058] Aliphatic based urethane polymer and 34.6 16.37

[0059]

[0060] diallyl bisphenol a polymerDI83927

[0061] Polypropylene glycol diepoxide 7.02 6.95 Calcium oxide 6.52 6.47 Calcium metasilicate 6.02 5.97 Calcium carbonate 5.67 5.58 Hydrated magnesium silicate 0.50 0.50 Silicon dioxide (glass bead) 0.30 0.29 Polydimethylsiloxane modified silicon 3.51 3.48 dioxide

[0062] Dicyandiamide 1.30 1.29

[0063] Blue pigment araldite DW0135 0.20 0

[0064] 2-hydroxy-N-[2-[(2Z)-2-(6-oxocyclohexa- 0.70 0

[0065] 2,4-dien-1-ylidene)imidazolidin-1- yl]ethyl]benzamide

[0066] 9-[2-(2-Methoxyethoxy)ethoxy]-9-[3- 0.50 0 (oxiranylmethoxy)propyl]-2,5,8,10,13,16- hexaoxa-9-silaheptadecane

[0067] Titanium dioxide 0 3.80

[0068]

[0069] Soybean oil 0 16.50

[0070] Table 2. Functions and sources of the materials used for the Examples

[0071] Trade Name Sources Functions Butadiene-carboxy-terminated INT 170300 DUPONT Epoxy acrylonitrile bisphenol a glycidyl ether BULK resin polymer and epichlorohydrin bisphenol a

[0072] polymer

[0073] Aliphatic based urethane polymer and INT FLEX DY HUNTSMAN Toughener diallyl bisphenol a polymer 965

[0074] Polypropylene glycol diepoxide DER 732 OLIN Epoxy CHEMICAL resin Calcium oxide QUICKLIME MISSISSIPPI Filler LIME CO.

[0075] Calcium metasilicate Nyad 200 IMERYS Filler Calcium carbonate H ubercarb IMERYS Filler Hydrated magnesium silicate Talc IN MIAL M& S Filler LUISONI

[0076] Silicon dioxide (glass bead) GLAS-SHOT PQ Filler CORPORATION

[0077] Polydimethylsiloxane modified silicon TS720 Cabot Filler dioxide

[0078] Dicyandiamide AMICURE CG Evonik Cure 1200G Industries agent Blue pigment araldite DW0135 ARALDITE HUNTSMAN Pigment DW0135

[0079] BLUE

[0080] 2-hydroxy-N-[2-[(2Z)-2-(6-oxocyclohexa- ACCELERINE CELERITY LLC Cure 2,4-dien-1-ylidene)imidazolidin-1- CEL 2191 agent yl]ethyl]benzamide

[0081] 9-[2-(2-Methoxyethoxy)ethoxy]-9-[3- FK RAM 1087 HUNTSMAN Cure (oxiranylmethoxy)propyl]-2,5,8,10,13,16- agent hexaoxa-9-silaheptadecane

[0082] Titanium dioxide TiPure R900 ACCI Filler Soybean oil Soybean Oil Stratas Foods Plasticizer

[0083]

[0084] 101051DI83927

[0085] During baking, the adhesive compositions undergo a significant increase in density and a corresponding reduction in volume after baking. This is commonly referred to as “baking shrinkage.” In this test, the shrinkage was evaluated by measuring the change in density after baking the compositions at various temperatures. To illustrate the difference in shrinkage between the Comparative and Inventive examples, two curing conditions were selected: (350°F / 30 minutes) for nominal baking and (400°F / 30 minutes) for over-baking. The comparison results, as shown in Table 3, indicate that the Inventive Examples exhibited only 2-6% shrinkage after baking, significantly lower than that of the Comparative Examples withl9 -20% shrinkage. This reduced shrinkage helps decrease the internal stress of the adhesive after baking, resulting in stable mechanical properties and reducing the possibility of shrink crack.

[0086] Table 3. Shrinkage of Comparative and Inventive Examples

[0087] Comparative Inventive Example Example Shrinkage of after baking at 350 °F / 30 min 20% 2%

[0088]

[0089] Shrinkage of after baking at 400 °F / 30 min 19% 6%

[0090] Redox (oxidation-reduction) reactions usually occur at the metal surface and the interface between the adhesive and the metal, leading to corrosion of the adhesive and the metal substrate. Salt spray aging accelerates this corrosion and contributes to adhesive failure (AF), while effective anti-corrosion performance results in cohesive failure (CF). In this test, with results shown in Table 4, both Comparative and Inventive Examples were tested for up to 5 weeks, with the failure mode directly reflecting the anti-corrosion performance under salt spray conditions. As shown in Table 4, the Inventive Examples maintained a 100% cohesive failure mode throughout the 5 weeks, but the Comparative Examples began to exhibit adhesive failure mode after 2 weeks and this becomes predominant after 4 weeks. This indicates that the Inventive Examples possess excellent anti-corrosion performance compared to the Comparative Examples. The high anti-corrosion performance of the Inventive Examples is attributed to the unique combination of filles, which function as a redox scavenger, along with the protective effect of a hydrophobic surface due to oil migration.

[0091] Table 4. Failure mode of Comparative and Inventive Examples after salt spray aging corrosion testingDI83927

[0092] Comparative Inventive Example Example Unaged 100% CF 100% CF Salt spray aging for 1 week 70%CF / 30%AF 100% CF Salt spray aging for 2 week 50%CF / 50%AF 100% CF Salt spray aging for 3 week 20%CF / 80%AF 100% CF Salt spray aging for 4 week 100%AF 100% CF

[0093]

[0094] Salt spray aging for 5 week 100%AF 100% CF Note: CF: cohesive failure mode AF: adhesion failure mode

[0095] Viscosity is a crucial factor in determining the processability and application of adhesives. High viscosity can limit the adhesive's usability and may introduce defects, such as air bubbles, during application. Conversely, low viscosity not only enhances processability but also allows manufacturers to improve production efficiency by enabling faster adhesive application. In certain applications, such as paintability, only low viscosity adhesives can meet the required specifications. A parallel plate rheometer was used in this testing of the Inventive and Comparative Examples, conducting viscosity measurements under varying temperature conditions. As shown in Table 5, it is evident that the Inventive Examples exhibited significantly lower viscosity than the Comparative Examples at different temperatures. Notably, at an increased temperature of 30°C, the viscosity could be as low as 272 Pa·s for the Inventive Example, demonstrating excellent flowability and enabling high-throughput transfer during manufacturing and application, as well as potential paintability.

[0096] Table 5. Viscosity of comparative and inventive examples at different temperature (3 s-1 shear rate)

[0097] Viscosity (Pa.s.) Comparative Inventive Example Example Viscosity at 10 °C 8327 1470 Viscosity at 15 °C 5121 886 Viscosity at 20 °C 3287 566

[0098]

[0099] Viscosity at 30 °C 1431 272DI83927

[0100] In the present invention, different plasticizers may also have an impact of the properties of adhesives of the present invention. Table 6 provides the comparations of properties of two Inventive Examples with different oil resource - soybean oil for Inventive Example 1 and cashew nut oil for Inventive Example 2. Both oils are used at the same amounts as in the inventive example of the composition in Table 1. In comparison to soybean oil, examples utilizing cashew nut oil demonstrated superior lap shear performance and elongation. However, this enhancement came at the expense of modulus and hardness, likely attributable to the variations in molecular weight and molecular weight distribution of the oil polymer chains. Furthermore, it is important to note that different oils impart varying viscosities to the compound, indicating that the combination of different oils is a viable strategy to meet the viscosity requirements for diverse application needs.

[0101] Table 6. Mechanical propertied of Inventive Examples 1 and 2 with different oil resource (soybean oil / cashew nut oil)

[0102] Inventive Example 1 Inventive Example 2 Viscosity (15C) 877 552

[0103] Lap shear max stress (Mpa) 2.8 5.9 hardness 47 36 Elongation (%) 100 235 Strength (Mpa) 2.4 2.3

[0104]

[0105] Modulus (Mpa) 4.6 1.6

Claims

DI83927WHAT IS CLAIMED IS:

1. An adhesive composition comprising:A) one or more non-rubber-modified epoxy resins and one or more rubber-modified epoxy resins;B) one or more reactive urethane group-containing toughener;C) a mixture of mineral fillers;D) a plasticizer comprising oil; andE) one or more curing agent.

2. The adhesive composition of claim 1, wherein the mineral fillers are selected from calcium carbonate, calcium oxide, calcium metasilicate, talc, carbon black, textile fibers, glass particles / beads or fibers, aramid pulp, boron fibers, carbon fibers, mineral silicates, mica, powdered quartz, hydrated aluminum oxide, bentonite, wollastonite, kaolin, fumed silica, silica aerogel, polyurea compounds, polyamide compounds or metal powders, silicon dioxide, polydimethylsiloxane modified silicon oxide, and titanium oxide.

3. The adhesive composition of claim 2, wherein component B) is a mixture of calcium oxide, calcium metasilicate, calcium carbonate, hydrated magnesium silicate, silicon dioxide, polydimethylsiloxane modified silicon dioxide, and titanium dioxide.

4. The adhesive composition of any one of the preceding claims wherein component B) is present at 8 to 40 wt.% of the composition, based on total weight of the composition.

5. The adhesive composition of Claim 4, wherein component B) is present 22 to 28 wt.% of the composition, based on total weight of the composition.

6. The adhesive composition of any one of the preceding claims wherein component D) is selected from vegetable oil, soybean oil, or a mixture thereof.DI839277. The adhesive composition of claim 6, wherein component D) comprises soybean oil.

8. The adhesive composition of any one of the preceding claims wherein component D) is present at 5 to 40 wt.% of the composition, based on total weight of the composition.

9. The adhesive composition of claim 8, wherein component D) is present at 15 to 17 wt.% of the composition, based on total weight of the composition.

10. The adhesive composition of any one of the preceding claims wherein component E) is selected from aliphatic / aromatic amines, anhydrides, isocyanates, silane coupling agents, and alkylphenol resins.

11. The adhesive composition of any one of the preceding claims wherein component E) comprises dicyandiamide.

12. The adhesive composition of claim 11, wherein component E) further comprises 2-hydroxy-N-[2-[(2Z)-2-(6-oxocyclohexa-2,4-dien-l-ylidene)imidazolidin-l-yl]ethyl]benzamide.

13. The adhesive composition of any one of the preceding claims, wherein component E) is present at 0.5 to 5.5 wt.% of the composition based on total weight of the composition.

14. The adhesive composition of claim 13, wherein component E) is present at 1 to 1.5 wt.% of the composition, based on total weight of the composition.

15. An adhesive composition comprising:A) one or more non-rubber-modified epoxy resins and one or more rubber-modified epoxy resins; wherein these two epoxy resins constitute about 12 to 45 wt.% of the adhesive composition;B) one or more reactive urethane group-containing toughener; wherein the toughener constitutes 10 to 20 wt.% of the adhesive composition;DI83927C) a mixture of mineral fillers comprising calcium oxide, calcium metasilicate, calcium carbonate, hydrated magnesium silicate, silicon dioxide, polydimethylsiloxane modified silicon dioxide, and titanium dioxide; wherein the mixture of the mineral fillers constitutes 22 to 28 wt.% of the adhesive composition;D) a plasticizer comprising soybean oil wherein the soybean oil constitutes 15 to 17 wt.% of the adhesive composition; andE) one or more curing agent comprising dicyandiamide; wherein the curing agent constitutes 1 to 1.5 wt.% of the adhesive composition.

15. A method of making an adhesive composition by mixingA) one or more non-rubber-modified epoxy resins and one or more rubber-modified epoxy resins;B) one or more reactive urethane group-containing toughener;C) a mixture of mineral fillers;D) a plasticizer comprising oil; andE) one or more curing agent.

Images