TOUGHENED TWO-COMPONENT EPOXY COMPOSITION

Abstract

A two-component epoxy resin composition includes a first component K1 including at least one epoxy resin A that contains on average more than one epoxy group per molecule; and a second component K2 including a hardener B for epoxy resins; wherein the two-component epoxy resin composition contains between 2 and 35 wt.-%, based on the total weight of the composition, of at least one impact modifier I in either one or both of components K1 and K2; wherein the impact modifier I is a reaction product of at least one polymeric diol, at least one polyisocyanate, and cardanol. The two-component epoxy resin composition exhibits excellent toughness and impact peel strength

Claims

1. A two-component epoxy resin composition, comprising a first component K1 comprising at least one epoxy resin A that contains on average more than one epoxy group per molecule; and a second component K2 comprising a hardener B for epoxy resins; wherein the two-component epoxy resin composition contains between 2 and 35 wt.-%, based on the total weight of the composition, of at least one impact modifier I in either one or both of components K1 and K2; wherein the impact modifier I is a reaction product of at least one polymeric diol, at least one polyisocyanate, and cardanol.

2. The two-component epoxy resin composition according to claim 1, wherein the polymeric diol is selected from the group comprising polyether diols, polyester diols, polycarbonate diols, poly(meth)acrylate diols, and polybutadiene diols.

3. The two-component epoxy resin composition according to claim 2, wherein the polymeric diol is a polyether diol.

4. The two-component epoxy resin composition according to claim 1, wherein the polymeric diol has an average molecular weight M.sub.n, measured by GPC against polystyrene standard, of between 300 and 15,000 g/mol.

5. The two-component epoxy resin composition according to claim 1, wherein the polyisocyanate is 4,4′-, 2,4′- or 2,2′-diphenylmethane diisocyanate or arbitrary mixtures of these isomers (MDI).

6. The two-component epoxy resin composition according to claim 1, wherein the impact modifier I has an apparent epoxy equivalent weight of >500 g/eq.

7. The two-component epoxy resin composition according to claim 1, wherein the two-component epoxy resin composition contains the epoxy resin A with an amount of between 5 and 85 wt.-%, based on the total weight of the composition.

8. The two-component epoxy resin composition according to claim 1, wherein the two-component epoxy resin composition contains the hardener B with an amount of between 5 and 40 wt.-%, based on the total weight of the composition.

9. The two-component epoxy resin composition according to claim 1, wherein the two-component epoxy resin composition contains at least one filler with an amount of between 20 and 50 wt.-%, based on the total weight of the composition.

10. The two-component epoxy resin composition according to claim 1, wherein the hardener B comprises di- and/or tri-functional polyamines.

11. The two-component epoxy resin composition according to claim 1, wherein the two-component epoxy resin composition comprising: the first component K1, comprising between 25 and 85 wt.-%, based on component K1, of the at least one epoxy resin A, and between 0 and 15 wt.-%, based on component K1, of at least one epoxy-functional reactive diluent, and between 0 and 25 wt.-%, based on component K1, of at least one filler, and between 5 and 25 wt.-%, based on component K1, of the impact modifier I; the second component K2, comprising between 30 and 70 wt.-%, based on component K2, of the hardener B for epoxy resins, and between 25 and 75 wt.-%, based on component K2, of at least one filler, and between 0.5 and 7 wt.-%, based on component K2, of at least one accelerator for the curing of epoxy resins.

12. A method of manufacturing a two-component epoxy resin composition, the method comprising: introducing a reaction product of at least one polymeric diol, at least one polyisocyanate, and cardanol as an impact modifier or a toughener.

13. The method according to claim 12, wherein the polymeric diol is selected from the group comprising polyether diols, polyester diols, polycarbonate diols, poly(meth)acrylate diols, and polybutadiene diols.

14. The method according to claim 12, wherein the polymeric diol has an average molecular weight M.sub.n, measured by GPC against polystyrene standard, of between 300 and 15,000 g/mol.

15. An adhesively bonded article, wherein the adhesive for the adhesive bond is a two-component epoxy resin composition according to claim 1.

Description

EXAMPLES

[0205] Examples are given below which illustrate the invention further but do not limit the scope of the invention in any way and merely illustrate some of the possible embodiments. “Standard conditions” or “norm climate” (“NK”) refers to a temperature of 23° C. and 50% relative humidity (r.h.).

[0206] Test Methods

[0207] The following test methods were employed:

Tensile Strength (TS), Elongation at Break (EOB) and Elastic Modulus (E-Mod) (DIN EN ISO 527)

[0208] These mechanical properties were determined by applying and curing the mixed adhesive in the standard climate into a silicone mold to form dumbbell-shaped bars (specimen type 1A of DIN EN ISO 527) having a thickness of 4 mm, a length of 150 mm, a land length of 80 mm and a land width of 10 mm. After 4 hours curing time at a temperature of 70° C., the test specimens were released from the mold. The specimens were measured under standard conditions at a pulling speed of 1 mm/min (E-Mod) or 10 mm/min (TS, EOB), respectively. The tensile strength, elongation at break and the modulus of elasticity 0.05-0.25% were determined according to DIN EN ISO 527.

Impact Peel Strength (IPS) (ISO 11343)

[0209] The test specimens were prepared from the example compositions described and with electrogalvanized DC04 steel (eloZn) having dimensions 90×20×0.8 mm, where the adhesion surface area was 30×20 mm with a layer thickness of 0.3 mm. They were cured for 4 h at 70° C. The impact peel strength was measured at 23° C. according to ISO 11343 with an impact velocity of 2 m/s. The failure mode was also determined. “AF” means adhesive failure, “CF” means cohesive failure.

Viscosity

[0210] The viscosity the respective freshly mixed two-component compositions was determined using a viscometer with a plate-plate set-up having a plate diameter of 25 mm. The samples were measured at 23° C., at a gap size of 1 mm and at a shear stress of 10 s.sup.−1. The samples were pre-sheared for 40 seconds and measured for 80 seconds (8 measuring points).

Example Two-Component Epoxy Resin Compositions

[0211] A series of two-component example composition were prepared using the substances listed in Table 1. Tables 2 to 4 show example compositions consisting of components K1 and K2. All amounts are in wt.-% (percent by weight) based on the respective component K1. For components K2, commercially available hardener components of two-component epoxy adhesives were, available from Sika Schweiz AG.

[0212] The individual components K1 in each experiment were prepared by adding the ingredients in their respective amount to a centrifugal mixer and mixing them homogeneously.

TABLE-US-00001 TABLE 1 Employed chemicals and ingredients. Trade name Abbreviation Description (supplier) BADGE Bisphenol A diglycidyl ether (main epoxy resin) D.E.R. ®331 (Olin) Desmocap 11 Branched polymer with ether and urethane Desmocap ® 11 groups; isocyanate groups blocked by (Covestro) nonylphenol (impact modifier) Desmocap 12 Linear polymer with ether and urethane groups; Desmocap ® 12 isocyanate groups blocked by nonylphenol (Covestro) (impact modifier) Desmocap 14 Branched polymer with ether and urethane Desmocap ® 14 groups; isocyanate groups blocked by cardanol CNB (Covestro) (impact modifier) Araldite DY-D Diglycidylether of butanediol (epoxy-functional Araldite ® DY-D reactive diluent) (Huntsman) Silane A-187 Gamma-Glycidoxypropyltrimethoxysilane Silquest* A-187 (adhesion promoter) (Momentive) Silica Pyrogenic, hydrophobic silica (filler) — Chalk Ground, natural chalk (filler) — WTG-1050 (B) Commercial amine-based hardener component Sikadur ® WTG- of Sikadur ® WTG-1280 LD, a toughened two- 1050 (B) (Sika component epoxy adhesive for wind turbine Schweiz AG) blade bonding WTG-1280 (B) Commercial amine-based hardener component Sikadur ® WTG- of Sikadur ® WTG-1280, a toughened two- 1280 (B) (Sika component epoxy adhesive for wind turbine Schweiz AG) blade bonding

[0213] For testing, a homogenous mixture of each respective component K1 and K2 in each example two-component composition was prepared using a stirrer and directly applied to the substrate surfaces used for preparing the test pieces. Immediately after mixing of the components K1 and K2, the testing protocol was employed.

[0214] Test data is shown for each composition in Tables 2 to 5 at the end of the table.

Synthesis of Exemplary Impact Modifier I1

[0215] Under nitrogen atmosphere, 5687 g of Acclaim® 4200 polyol (Bayer MaterialScience) 712 g (2 equivalents) of MDI with the trade name Desmodur 44 MC L (Covestro) and 0.6 g catalyst DABCO 33 LV (Air Products) were heated with constant stirring to 80° C. and left at this temperature to produce an NCO-terminated prepolymer. After one hour of reaction time, a free NCO content was determined by titration. It had reached a content of isocyanate groups of 1.9 wt.-%. Subsequently, 910 g cardanol with the trade name Cardolite NC-700 (Cardolite) were added and stirring was continued for a further 2 hours at 80° C. The reaction was stopped as soon as free isocyanate was no longer detectable by IR spectroscopy (wavenumbers 2275-2230 cm.sup.−1).

Synthesis of Exemplary Impact Modifier I2

[0216] 150 g of isocyanate-terminated prepolymer, produced from 60% by weight PolyTHF® 2000 (BASF), 40% by weight Poly BD® R45V (Cray Calley), Isophorone diisocyanate (Evonik) (0.75 equivalents) and dibutyl tin dilaurate catalyst, was treated with 1 equivalent of dry Epikote® 828LVEL (Hexion). Next, 8.11 mmol phthalic anhydride (Sigma Aldrich) were added, the reaction mixture was mixed and then reacted at 110° C. under vacuum by adding catalyst.

Synthesis of Exemplary Impact Modifier I3

[0217] Impact modifier I3 was synthesized in identical manner as described for impact modifier I1, with the sole exception that an equimolar amount of IPDI was used instead of MDI.

Synthesis of Exemplary Impact Modifier I4

[0218] Impact modifier I4 was synthesized in identical manner as described for impact modifier I3, with the exceptions that as polyol two equivalents of a mixture of 60% by weight PolyTHF® 2000 (BASF) and 40% by weight Poly BD® R45V (Cray Calley) was used instead of Acclaim® 4200 and an equimolar amount of IPDI was used instead of MDI.

Synthesis of Exemplary Impact Modifier I5

[0219] Impact modifier I5 was synthesized in identical manner as described for impact modifier I1, with the sole exception that as polyol two equivalents of a mixture of 60% by weight PolyTHF® 2000 (BASF) and 40% by weight Poly BD® R45V (Cray Calley) was used instead of Acclaim® 4200.

TABLE-US-00002 TABLE 2 Details of compositions C1 and C2. C1 (Ref.) C2 Component K1 BADGE 63 63 Impact modifier I1 — 20 Impact modifier I2 20 — Silane A-187 1 1 Araldite DY-D 6 6 Silica 5 5 Chalk 5 5 TOTAL 100 100 Component K2 WTG-1280 (B) - mixing ratio (w/w) 100:70 (K1:K2) Test data E-Mod [MPa] 2990 2390 IPS [N/mm] 19.3 26.4

TABLE-US-00003 TABLE 3 Details of compositions C3 to C6. C3 (Ref.) C4 C5 C6 (Ref.) Component K1 BADGE 63 63 68 83 Impact modifier I1 — 20 15 — Impact modifier I2 20 — — — Silane A-187 1 1 1 1 Araldite DY-D 6 6 6 6 Silica 5 5 5 5 Chalk 5 5 5 5 TOTAL 100 100 100 100 Component K2 WTG-1050 (B) - mixing ratio (w/w) 100:47 (K1:K2) Test data E-Mod [MPa] 3140 2290 2680 3930 IPS [N/mm] 21.2 27.2 21.8 0.3 Viscosity [Pa s] 89.5 62.03 55.3 41.3

TABLE-US-00004 TABLE 4 Details of compositions C7 to C10. C7 C8 (Ref.) C9 (Ref.) C10 (Ref.) Component K1 BADGE 68 68 68 68 Impact modifier I1 14 — — — Desmocap 11 — 14 — — Desmocap 12 — — 14 — Desmocap 14 — — — 14 Araldite DY-D 6 6 6 6 Silane A-187 1 1 1 1 Silica 5 5 5 5 Chalk 6 6 6 6 TOTAL 100 100 100 100 Component K2 WTG-1280 (B) - mixing ratio (w/w) 100:70 (K1:K2) Test data IPS [N/mm] 14.2 ± 3.1 ± 7.4 ± 2.0 ± 0.5 0.1 0.7 1.4 TS [MPa] 37.9 ± 45.4 ± 47.1 ± 39.2 ± 1.5 1.4 0.5 12.5 EOB [%] 4.1 ± 3.4 ± 3.9 ± 2.6 ± 1.6 1.3 0.5 1.1 E-Mod [MPa] 2180 ± 3030 ± 3210 ± 3070 ± 70 70 70 210

TABLE-US-00005 TABLE 5 Details of compositions C11 to C14. C11 C12 C13 C14 Component K1 BADGE 68 68 68 68 Impact modifier I1 14 — — — Impact modifier I3 — 14 — — Impact modifier I4 — — 14 — Impact modifier I5 — — — 14 Silane A-187 1 1 1 1 Araldite DY-D 6 6 6 6 Silica 7 7 7 7 Chalk 4 4 4 4 TOTAL 100 100 100 100 Component K2 WTG-1050 (B) - mixing ratio (w/w) 100:47 (K1:K2) Test data E-Mod [MPa] 2910 3070 3280 3490 IPS [N/mm] 17.0 11.0 5.2 8.2