Thermosetting epoxy resin compositions useful as structural reinforcement or structural foam

Abstract

Thermosetting epoxy resin compositions on the one hand at room temperature in the incompletely cured state exhibit extremely slight alteration in shape and on the other hand develop a high surface tack, and, moreover, in the fully cured state are of high impact strength and at the same time exhibits high adhesion, particularly to metallic substrates. These compositions are ideally suited to the production of self-adhesive reinforcing elements.

Claims

1. A thermosetting epoxy resin composition comprising from 17.5 to 30 weight % of at least one liquid epoxy resin A having on average more than one epoxide group per molecule; from 1 to 5 weight % of at least one hardener B for epoxy resins which is activated by elevated temperature; from 0 to 2 weight % of at least one accelerator C; from 5 to 12 weight %, of at least one polymeric impact modifier D, which is a terminally blocked polyurethane prepolymer; from 1 to 5 weight % of at least one polyisoprene E; from 5 to 10 weight % of at least one carboxyl- or epoxide- terminated acrylonitrile/butadiene copolymer F which is liquid at room temperature; from 15 to 20 weight % of at least one carboxyl- or epoxide- terminated acrylonitrile/butadiene copolymer G which is solid at room temperature; based on a total weight of the epoxy resin composition.

2. The thermosetting epoxy resin composition according to claim 1, further comprising at least one physical or chemical blowing agent H in an amount of from 0.1 to 3 weight %, based on the total weight of the epoxy resin composition.

3. A structural foam obtained by heating the thermosetting epoxy resin composition according to claim 2.

4. The thermosetting epoxy resin composition according to claim 1, wherein the thermosetting epoxy resin composition is tacky at room temperature.

5. The thermosetting epoxy resin composition according to claim 1, wherein the thermosetting epoxy resin composition has a viscosity at 80 C. in a range of from 900 to 5 000 Pa.Math.s, the viscosity being determined oscillographically by a rheometer with heatable plate (MCR 201, Anton Paar) (1000 m gap, measurement plate diameter: 25 mm (plate/plate), deformation 0.01 at 5 Hz, temperature: 80 C.).

6. The thermosetting epoxy resin composition according to claim 1, wherein the thermosetting epoxy resin composition has a viscosity at 30 C. in a range of from 5 000 to 50 000 Pa.Math.s, the viscosity being determined oscillographically by a rheometer with heatable plate (MCR 201, Anton Paar) (1000 m gap, measurement plate diameter: 25 mm (plate/plate), deformation 0.01 at 5 Hz, temperature: 30 C.).

7. The thermosetting epoxy resin composition according to claim 1, wherein the at least one accelerator C comprises at least one substituted urea selected from the group consisting of 3-(3-chloro-4-methylphenyl)-1,1-dimethylurea (chlortoluron), p-chlorophenyl-N,N-dimethylurea (monuron), 3-phenyl-1,1-dimethylurea (fenuron), 3,4-dichlorophenyl-N,N-dimethylurea (diuron), N,N-dimethylurea, N-isobutyl-N,N-dimethylurea, and 1,1-(hexane-1,6-diyl)bis(3,3 -dimethylurea).

8. The thermosetting epoxy resin composition according to claim 1, comprising from 0.3 to 0.5 weight % of the at least one accelerator C.

9. The thermosetting epoxy resin composition according to claim 1, wherein the at least one impact modifier D is a terminally blocked polyurethane prepolymer represented by formula (I); ##STR00009## where R.sup.1 is a p-valent residue of a linear or branched polyurethane prepolymer PU1, terminated with isocyanate groups, following the removal of the terminal isocyanate groups; p is from 2 to 8; and R independently at each occurrence is a substituent selected from the group consisting of ##STR00010## where R.sup.5, R.sup.6, R.sup.7 and R.sup.8 each independently of one another are an alkyl or cycloalkyl or aralkyl or arylalkyl group, or R.sup.5 together with R.sup.6, or R.sup.7 together with R.sup.8, form part of a 4- to 7-membered ring which is optionally substituted; R.sup.9, R.sup.9 and R.sup.10 each independently of one another are an alkyl or aralkyl or arylalkyl group or are an alkyloxy or aryloxy or aralkyloxy group; R.sup.11 is an alkyl group, R.sup.12, R.sup.13 and R.sup.14 each independently of one another are an alkylene group having 2 to 5 C atoms which optionally has double bonds or is optionally substituted, or are a phenylene group or are a hydrogenated phenylene group; R.sup.15, R.sup.16 and R.sup.17 each independently of one another are H or are an alkyl group or are an aryl group or an aralkyl group; and R.sup.18 is an aralkyl group or is a mono- or polycyclic, substituted or unsubstituted aromatic group which optionally has aromatic hydroxyl groups; R.sup.4 is a residue of an aliphatic, cycloaliphatic, aromatic or araliphatic epoxide containing a primary or secondary hydroxyl group, after the removal of the hydroxyl and epoxide groups; and m is 1, 2, or 3.

10. The thermosetting epoxy resin composition according to claim 1, wherein the at least one polyisoprene E is a polyisoprene which is liquid at room temperature.

11. The thermosetting epoxy resin composition according to claim 1, comprising from 1 to 3 weight % of the at least one polyisoprene E.

12. The thermosetting epoxy resin composition according to claim 1, wherein the at least one carboxyl- or epoxide-terminated acrylonitrile/butadiene copolymer F which is liquid at room temperature is an epoxide-terminated acrylonitrile/butadiene copolymer having an elastomer fraction of from 35 to 45 weight %.

13. The thermosetting epoxy resin composition according to claim 1, wherein the at least one carboxyl- or epoxide-terminated acrylonitrile/butadiene copolymer G which is solid at room temperature is an epoxide-terminated acrylonitrile/butadiene copolymer having an elastomer fraction of from 25 to 35 weight %.

14. The thermosetting epoxy resin composition according to claim 1, comprising from 16 to 20 weight % of the at least one carboxyl- or epoxide-terminated acrylonitrile/butadiene copolymer G.

15. The thermosetting epoxy resin composition according to claim 1, wherein the at least one carboxyl- or epoxide-terminated acrylonitrile/butadiene copolymer G is an epoxide-terminated acrylonitrile/butadiene copolymer that is a reaction product of at least one acrylonitrile/butadiene copolymer and a solid epoxy resin that is bisphenol A-based solid resin, bisphenol F-based solid resin, or both.

16. An article having a three-dimensional extent comprising the thermosetting epoxy resin composition according to claim 1.

17. A method for reinforcing outer surfaces or hollow cavities of structural components, comprising the steps of i) placing the thermosetting epoxy resin composition according to claim 1 onto outer surfaces or into cavities of structural components; ii) heating the thermosetting epoxy resin composition to a temperature of 100-220 C.

18. A reinforced article obtained from the method according to claim 17.

19. A method for reinforcing heat-stable materials, comprising the steps of i) placing the thermosetting epoxy resin composition according to claim 1 onto heat-stable materials; ii) heating the thermosetting epoxy resin composition to a temperature of 100-220 C.

20. A fully cured epoxy resin composition obtained by heating a thermosetting epoxy resin composition according to claim 1 to a temperature of 100-220 C.

Description

EXAMPLES

(1) Set out below are a number of examples which further illustrate the invention but are in no way intended to restrict the scope of the invention. Unless indicated otherwise, all proportions and percentages are by weight.

(2) Raw materials used for preparing the impact modifier SM 1 and the compositions Ref.1-3 and Ex.1-14 were as follows:

(3) TABLE-US-00001 Raw materials used Description Supplier HDI Hexamethylene diisocyanate Sigma-Aldrich PolyTHF2000 Polytetramethylene ether glycol BASF Phenol Phenol Sigma-Aldrich Dibutyltin dilaurate Catalyst Thorson (DBTL) Aerosil R202 Pyrogenic silica Evonik Polycal OS325 Calcium oxide Fitz Chem Corp. Winnofil SPT Calcium carbonate Solvay TRACEL OBSH Oxybisbenzenesulfonyl Tramaco hydrazide (Blowing agent H) Dicyandiamide Dicyandiamide (Hardener B) Sigma-Aldrich N,N-Dimethylurea (Accelerator C) Sigma-Aldrich Araldite GY 250 Bisphenol A-based liquid Huntsman epoxy resin (liquid epoxy resin A) HyPox RA840 Epoxide-terminated Emerald acrylonitrile/butadiene Performance copolymer liquid at RT Materials LLC HyPox RK84L Epoxide-terminated Emerald acrylonitrile/butadiene Performance copolymer liquid at RT Materials LLC
Preparation of the Impact Modifier (SM1)

(4) 300.0 g of PolyTHF2000 (BASF) and 56.7 g of hexamethylene diisocyanate (HDI) were mixed together with 0.04 g of dibutyltin dilaurate (DBTL) in a vessel. After mixing had taken place under reduced pressure at 60 C. for 2 hours, an NCO content of 4.1% was measured. The NCO-terminated polyurethane polymer thus formed was admixed with 39.3 g of phenol (Aldrich), stirred further under reduced pressure at 100 C. for 3 hours and stored at 70 C. for 12 hours. Thereafter the NCO content measured was 0%

(5) Determination of the Isocyanate Content

(6) The isocyanate content in weight % was determined by back-titration using di-n-butylamine employed in excess and 0.1 M hydrochloric acid. All of the determinations were performed semi-manually on a Mettler-Toledo DL 50 Graphix titrator with automatic potentiometric endpoint determination. For this purpose, 600-800 mg of the particular sample were dissolved in each case with heating in a mixture of 10 ml of isopropanol and 40 ml of xylene, and then reacted with a solution of dibutylamine in xylene. Excess di-n-butylamine was titrated with 0.1 M hydrochloric acid, and from this the isocyanate content was calculated.

(7) The respective compositions Ref.1-3 and also Ex.1-14 were mixed in a batch size of 300 g on a planetary mixer and then pressed into sheet-like structures between silicone release films. Immediately after bringing the compositions Ref.1-3 and also Ex.1-14 the sheet-like form, the below mentioned properties (LSS LV, LSS HB and the viscosity) were determined in accordance with the test methods below.

(8) Lap Shear Strength (LSS) (DIN EN 1465)

(9) Cleaned metal test panels measuring 10025 mm and made from hot-dip galvanized steel (0.8 mm thick) were bonded to an adhesive surface of 1225 mm using 1 mm thick Teflon spacers in a layer thickness of 1 mm with the compositions described, and full curing took place under the specified curing conditions: Curing conditions LB (low bake): 10 min at 170 C. oven temperature Curing conditions HB (high bake): 30 min at 205 C. oven temperature

(10) The lap shear strength was determined on a tensile machine with a pulling speed of 10 mm/min in a 5-fold determination in accordance with DIN EN 1465. The results of these tests are compiled in tables 2 and 4, respectively.

(11) Determination of the Viscosity

(12) The viscosity was measured oscillographically by means of a rheometer having a heatable plate (MCR 201, AntonPaar) (gap 1000 m, measuring plate diameter: 25 mm (plate/plate), deformation 0.01 at 5 Hz, temperature: 80 C., heating rate 10 C./min).

(13) The results of these tests are compiled in tables 2 and 4, respectively.

(14) The viscosity of all the compositions was between 8 000-16 000 Pa.Math.s at 30 C. All compositions at room temperature had a surface tack such that after the surface of a sample with an intrinsic weight of 50 g had been pressed with a thumb, exerting a pressure of 5 kg for 1 second, said sample could be lifted up for at least 5 seconds.

(15) The compositions of Ref.1-3 and also Ex.1-6 are set out in tables 1 and 2. Thus, for example, the composition Ref.1 consists both of the components in table 1 listed under Ref.1, and also of the components of table 2 listed under Ref.1. The measured properties (LSS LB, LSS HB and viscosity) are evident from table 2.

(16) The compositions of Ex.7-14 are set out in tables 3 and 4. Thus, for example, the composition Ex.7 consists of the components in table 3 listed under Ex.7-14, and also of the components in table 4 listed under Ex. 7.

(17) The properties measured (LSS LB, LSS HB and viscosity) are evident from table 4.

(18) As a further comparative example of the state of the art, the viscosity of the examples 1 and 2 in table 3 from EP 1916269 A1 was measured according to the method mentioned before. Example 1 as well as example 2 shows a viscosity at 30 C. of less than 3 000 Pa.Math.s and a viscosity at 80 C. of less than 600 Pa.Math.s.

(19) TABLE-US-00002 TABLE 1 Ref. 2, Ref. 3, Ref. 1 Ex. 1-Ex. 6 Raw materials used (wt %) (wt %) Aerosil R202 6.23% 5.00% Polycal OS325 3.11% 2.50% Winnofil SPT 44.82% 36.00% OBSH (Blowing agent H) 0.12% 0.10% Dicyandiamide (Hardener B) 3.98% 3.20% N,N-Dimethylurea (Accelerator C) 0.25% 0.20%

(20) TABLE-US-00003 TABLE 2 Ref. 1 Ref. 2 Ref. 3 Ex. 1 Ex. 2 Ex. 3 Ex. 4 Ex. 5 Ex. 6 (wt %) (wt %) (wt %) (wt %) (wt %) (wt %) (wt %) (wt %) (wt %) Raw materials used SM1 (Impact modifier D) 9.86% 12.12% 7.60% 7.50% 12.00% 10.93% 7.50% 8.36% 8.00% Araldite GY 250 (Liquid epoxy resin A) 7.50% 15.00% 15.49% 20.00% 20.00% 17.96% 19.50% 17.5% 20.00% HyPox RA840 (Copolymer F liquid at RT) 12.00% 5.88% 9.91% 7.55% 5.00% 8.05% 10.00% 9.58% 5.00% HyPox RK84L (Copolymer G solid at RT) 12.12% 20.00% 20.00% 17.96% 16.00% 16.07% 16.00% 17.75% 20.00% Measurement values LSS LB [MPa] 5.87 6.881 7.387 8.101 8.125 8.126 7.95 8.151 7.811 LSS HB [MPa] 5.577 6.013 5.652 6.903 6.794 6.573 6.478 6.553 7.147 Viscosity at 80 C. [Pa .Math. s] 5354 2609 2661 2268 1668 1956 2540 2540 2555

(21) TABLE-US-00004 TABLE 3 Raw materials used Ex. 7-14 (wt %) SM1 (Impact modifier D) 10.96% Araldite GY 250 (Liquid epoxy resin A) 20.00% HyPox RA840 (Copolymer F liquid at RT) 5.65% HyPox RK84L (Copolymer G solid at RT) 16.39% Aerosil R202 6.41% Polycal OS325 2.50% Winnofil SPT 34.59%

(22) TABLE-US-00005 TABLE 4 Ex. 7 Ex. 8 Ex. 9 Ex. 10 Ex. 11 Ex. 12 Ex. 13 Ex. 14 (wt %) (wt %) (wt %) (wt %) (wt %) (wt %) (wt %) (wt %) Starting products OBSH 0.01% 0.01% 0.01% 0.01% 0.25% 0.25% 0.25% 0.25% (Blowing agent H) Dicyandiamide 3.48% 3.36% 3.23% 2.99% 3.24% 3.12% 2.98% 2.75% (Hardener B) N,N-Dimethylurea 0.01% 0.13% 0.26% 0.50% 0.01% 0.13% 0.27% 0.50% (Accelerator C) Measurement values LSS LB [MPa] 8.1 6.9 7.3 7.6 8.0 7.5 8.2 7.9 LSS HB [MPa] 6.9 6.0 5.1 7.5 6.8 5.5 6.1 7.2 Viscosity at 80 C. 3402 3610 2860 3756 3155 2636 2690 3749 [Pa .Math. s]