Method for connecting molded bodies by injecting a single-component heat-curing epoxy resin composition into cavities

Abstract

A method of bonding two shaped bodies S1 and S2 including the steps of: a) providing shaped body S1; b) arranging shaped body S2 wherein shaped body S1, forming cavity between two shaped bodies, c) introducing one-component thermosetting epoxy resin compositions into cavity, wherein one-component thermosetting epoxy resin composition is one-component thermosetting epoxy resin composition including: at least one epoxy resin A having average of more than one epoxy group per molecule; at least one curing agent B for epoxy resins activated by elevated temperature; at least one polyester polyol PP obtainable by reaction of at least one diol having structure HO—(CH.sub.2).sub.x′—OH the value of x′=2-10, and —at least one dicarboxylic acid having structure HOOC—(CH.sub.2).sub.y′—COOH and derivatives of dicarboxylic acid, value of y′=8-18, and wherein proportion of polyester polyol PP is 1.5% to 20% by weight, based on total weight of one-component thermosetting epoxy resin composition.

Claims

1. A method of bonding two shaped bodies S1 and S2, said method comprising the steps of: a) providing a shaped body S1, b) arranging a shaped body S2 with respect to the shaped body S1, forming a cavity between the two shaped bodies S1 and S2, c) introducing a one-component thermosetting epoxy resin compositions into the cavity, wherein the one-component thermosetting epoxy resin composition is a one-component thermosetting epoxy resin composition comprising at least one epoxy resin A having an average of more than one epoxy group per molecule; at least one curing agent B for epoxy resins which is activated by elevated temperature; and at least one polyester polyol PP obtainable by the reaction of at least one diol having the structure HO—(CH.sub.2).sub.x′—OH where the value of x′=2 to 10, and at least one dicarboxylic acid having the structure HOOC—(CH.sub.2).sub.y′—COOH and derivatives of this dicarboxylic acid, where the value of y′=8 to 18, and wherein the proportion of the polyester polyol PP is 1.5% to 20% by weight, based on the total weight of the one-component thermosetting epoxy resin composition.

2. The method as claimed in claim 1, wherein the cavity is an open cavity.

3. The method as claimed in claim 1, wherein there is essentially no change in the distance in the cavity between the two shaped bodies after the step b) of arranging a shaped body S2 with respect to the shaped body S1.

4. The method as claimed in claim 1, wherein any change in distance between the two shaped bodies alongside the cavity after step b) is 0-100 mm.

5. The method as claimed in claim 1, wherein the one-component thermosetting epoxy resin composition is introduced through at least one introduction opening in at least one of the two shaped bodies.

6. The method as claimed in claim 1, wherein the cavity is a bonding site for a composite of the two shaped bodies.

7. The method as claimed in claim 1, wherein the cavity is a material recess in at least one of the two shaped bodies.

8. The method as claimed in claim 1, wherein the method additionally comprises step d) of curing the one-component thermosetting epoxy resin composition for at least 10 min.

9. The method as claimed in claim 1, wherein the one-component thermosetting epoxy resin composition on introduction in step c) is at a temperature of 40-100° C.

10. The method as claimed in claim 1, wherein the one-component thermosetting epoxy resin composition on introduction in step c) is at a temperature of not more than 20° C., below the melting point of the polyester polyol PP.

11. The method as claimed in claim 1, wherein the one-component thermosetting epoxy resin composition on introduction in step c) has a viscosity of <3,000 Pas, determining the viscosity by oscillography by means of a rheometer with a heatable plate (Anton Paar MCR 302) (1000 μm gap, measurement plate diameter: 25 mm (plate/plate), deformation 0.01 at 5 Hz).

12. The method as claimed in claim 1, wherein the one-component thermosetting epoxy resin composition has a viscosity at 23° C. of >5,000 Pas, determining the viscosity by oscillography by means of a rheometer with a heatable plate (Anton Paar MCR 302) (1000 μm gap, measurement plate diameter: 25 mm (plate/plate), deformation 0.01 at 5 Hz).

13. The method as claimed in claim 1, wherein the proportion of the polyester polyol PP is 2-15% by weight, based on the total weight of the one-component thermosetting epoxy resin composition.

14. The method as claimed in claim 1, wherein any change in distance between the two shaped bodies alongside the cavity after step b) is 0-30 mm.

15. A method comprising applying a one-component thermosetting epoxy resin composition into a cavity between two shaped bodies S1 and S2 arranged with respect to one another and bonding the two shaped bodies S1 and S2 to one another, wherein the one-component thermosetting epoxy resin composition comprises: at least one epoxy resin A having an average of more than one epoxy group per molecule; at least one curing agent B for epoxy resins which is activated by elevated temperature; and at least one polyester polyol PP obtainable by the reaction of at least one diol having the structure HO—(CH.sub.2).sub.x′—OH where the value of x′=2 to 10, and at least one dicarboxylic acid having the structure HOOC—(CH.sub.2).sub.y′—COOH and derivatives of this dicarboxylic acid, where the value of y′=8 to 18, and wherein the proportion of the polyester polyol PP is 1.5% to 20% by weight, based on the total weight of the one-component thermosetting epoxy resin composition.

16. A method comprising applying a polyester polyol PP in a one-component thermosetting epoxy resin compositions for reducing escape characteristics through lateral openings in cavities on introduction of the one-component thermosetting epoxy resin compositions into cavities having lateral openings, wherein the at least one polyester polyol PP is obtainable by the reaction of at least one diol having the structure HO—(CH.sub.2).sub.x′—OH where the value of x′=2 to 10, and at least one dicarboxylic acid having the structure HOOC—(CH.sub.2).sub.y′—COOH and derivatives of this dicarboxylic acid, where the value of y′=8 to 18, and wherein the proportion of the polyester polyol PP is 1.5% to 20% by weight, based on the total weight of the one-component thermosetting epoxy resin composition.

Description

EXAMPLES

(1) There has been a search for epoxy resin compositions that, on injection into an open cavity, spread out predominantly in the cavity intended for the epoxy resin compositions and have sufficiently low spread into lateral openings that this need not be prevented by sealing elements. For this purpose, a test method was developed in order to examine such spreading characteristics in thermosetting one-component epoxy resin compositions.

(2) Test Method for Spreading Properties:

(3) The test method uses a composite of two shaped bodies consisting of a base element 5 and a transparent outer element 6 as shown in FIG. 2a. The rectangular base element 5 consists of polyamide and has a length of 400 mm, a width of 80 mm and a height of 30 mm. The base element 5 has a recessed channel 7 running down the middle and having a rectangular cross section and a depth of 3 mm and a width of 20 mm. This is apparent, for example, in FIG. 2b.

(4) On the base element 5, a boundary marker 12 that runs parallel to the channel 7 has been applied at a distance of 12 mm from the broad side (or 18 mm measured from channel 7). Spread markers 13 run at right angles to the boundary marker 12, each at a distance of 10 mm. The first boundary marker begins in the middle of the base element 5, and the rest of the boundary markers are arranged along the boundary marker up to the outer edge of the base element.

(5) Spacers 8 are disposed between base element 5 and outer element 6, and these ensure a gap (with a uniform width) between base element and outer element. This is apparent, for example, in FIG. 2c. The height of the gap is adjustable by means of washers as spacers 8 and is 1 mm. Base element and outer element are held together by means of 8 fixing screws 10.

(6) The transparent outer element 6 consists of polymethylmethacrylate (PMMA) and has a length of 400 mm, a width of 80 mm and a thickness of 10 mm. An introduction opening 9 having a diameter of 10 mm has been sunk into the middle of the cover element 6 (gap of 35 mm from each long side, and of 195 mm from each broad side). In the assembled state, the introduction opening 9 comes to rest exactly over the middle of the channel 7 of the base element 5.

(7) The epoxy resin composition is introduced from the outside through the introduction opening 9 into the channel 7 at the injection rate, or injection pressure, and injection temperature displayed below.

(8) The figures FIG. 3a and FIG. 3b show a top view of the composite of base element 5 and transparent outer element 6 that has been assembled with 8 fixing screws 10. They show an introduced epoxy resin composition 11 which has spread along the channel 7. FIG. 3a shows a situation in which the introduced epoxy resin composition 11 has spread laterally up to the boundary marker 12. Once the epoxy resin composition reaches the boundary marker 12, the injection is stopped and the spread markers 13 are used to determine the spread in channel direction in the number of spread markers, with the spread markers in the middle of the base element serving as the starting point and not being counted. The spread markers attained +1 serves as the value of the “squeeze-out ratio”.

(9) In the example of FIG. 3a, the 10th boundary marker is attained, which corresponds to an extent of 100 mm, or a squeeze-out ratio of 11 (marker 10+1).

(10) FIG. 3b shows a situation in which the already introduced epoxy resin composition 11 has spread predominantly along the channel 7. During the injection, the epoxy resin composition has not reached the boundary marker 12 before exit from the end of the channel. This corresponds to a spread of more than 200 mm, or a squeeze-out ratio of >20.

(11) As described hereinafter, it has been found that, surprisingly, some of the epoxy resin compositions of the invention in the test method show behavior according to FIG. 3b. The heated epoxy resin compositions of the invention spread predominantly in the direction of the channel 7 and flow at least partly into the gap having a thickness of 1 mm between base element 5 and outer element 6. By virtue of the gap being smaller than the distance between a base of the channel 7 and the transparent outer element 6, the epoxy resin composition cools down more quickly in the gap than in the region of the channel 7 and solidifies as a result of this cooling in the region of the gap. This leads to a self-sealing function of the epoxy resin composition in the region of the gap.

(12) An attempt was first made to influence the spreading properties of the epoxy resin composition by means of adjustment of the viscosity and/or of the thixotropic recovery time.

(13) Epoxy resin compositions according to table 1 (tab. 1) were produced.

(14) TABLE-US-00003 TABLE 1 Parts by Raw materials weight Liquid epoxy resin, D.E.R. 331 50 (bisphenol A diglycidyl ether), Dow Reactive diluent, hexanediol glycidyl ether, 1 Denacol EX-212, Nagase America Toughness improver D-1 35 Curing agent, dicyandiamide (=“Dicy”) 4.67 Accelerator, substituted urea 0.22 Fumed silica 5

(15) Preparation of a Toughness Improver (“D-1”)

(16) 150 g of poly-THF 2000 (OH number 57 mg/g KOH) and 150 g of PolyBD R.sup.45V (OH number 46 mg/g KOH) were dried under reduced pressure at 105° C. for 30 minutes. Once the temperature had been reduced to 90° C., 61.5 g of IPDI and 0.14 g of dibutyltin dilaurate were added. The reaction was run under reduced pressure at 90° C. until the NCO content was constant at 3.10% after 2.0 h (calculated NCO content: 3.15%). Subsequently, 96.1 g of cardanol were added as blocking agent. Stirring was continued at 105° C. under vacuum until it was no longer possible to detect any free NCO. The product was used as such as toughness improver D-1. The following raw materials were used for the purpose:

(17) TABLE-US-00004 Poly-THF 2000 (difunctional polybutylene glycol) (OH equivalent weight = about 1000 g/OH equivalent), BASF PolyBD R45V (hydroxyl-terminated polybutadiene) (OH equivalent weight = about 1230 g/OH equivalent), Cray Valley lsophorone diisocyanate (=“IPDI”), Evonik Cardolite NC-700 (cardanol, meta-substituted alkenylmonophenol), Cardolite

(18) The epoxy resin composition according to table 1 has a viscosity η from 0-5000 and a thixotropic recovery time to 50% of the starting structure of 5-15 seconds. The complex viscosity η* was determined using a rheometer (Physica MCR 302, Anton Paar) by means of rotational measurement (gap: 1 mm, plate/plate, plate diameter: 25 mm, shear rate: 0.1 s−1) at a temperature of 20° C.

(19) Based on this composition, epoxy resin compositions with different viscosity η and/or different thixotropic recovery time were produced. By varying the proportions in % by weight of reactive diluent and the thixotropic agent (fumed silica) and in some cases by exchanging the fumed silica for organophilic sheet silicates, it was possible to obtain epoxy resin compositions with different viscosity η and/or different thixotropic recovery time.

(20) TABLE-US-00005 TABLE 2 Viscosity 15000-30000 10 10 (Pa * s)  5000-15000 10 10 10   0-5000 10 11 11 (Tab. 1) 0-5 5-15 15-50 Thirxotropic recovery time 50% (s)

(21) The spreading properties, i.e. the squeeze-out ratio, of the aforementioned epoxy resin compositions were determined at an injection temperature of 60° C. and an injection pressure of 2 bar.

(22) It was found that, surprisingly, neither the viscosity η nor the thixotropic recovery time has a significant influence on the squeeze-out ratio. Moreover, the spreading properties of all epoxy resin compositions with a value of 10-11 are unsatisfactory.

(23) Also examined was whether the proportions of the raw materials used in the epoxy resin compositions have an influence on the spreading properties. For this purpose, in the epoxy resin composition from table 1, the amount of liquid resin and of the toughness improver D-1 was varied.

(24) TABLE-US-00006 TABLE 3 Squeeze- Squeeze- out-ratio out-ratio 60° C., 60° C., Formulation Variation 2 bar 1 bar (Tab.1)   50 parts by weight of D.E.R. 331, 11 n.d.   35 parts by weight of D-1 INJ-1 +20 parts by weight of D.E.R 331, 10 11 −20 parts by weight of D-1 INJ-2 −20 parts by weight of D.E.R 331, 11 12 +20 parts by weight of D-1

(25) The spreading properties, i.e. the squeeze-out ratio, of the compositions were determined at an injection temperature of 60° C. and an injection pressure of 1 bar or 2 bar.

(26) It was found that, surprisingly, the proportions of the raw materials used in the epoxy resin compositions do not have any significant influence on the squeeze-out ratio. Moreover, the spreading properties of all epoxy resin compositions with a value of 10-12 are unsatisfactory.

(27) Also examined was whether the injection temperature or injection pressure, or the injection rate, have an influence on the spreading properties. For this purpose, epoxy resin compositions with different viscosities η (based on the epoxy resin composition from table 1) were used. The viscosity was determined by rotation by means of a rheometer (MCR 302, Anton Paar) (gap: 1000 μm, measurement plate diameter: 25 mm (plate/plate), shear rate: 0.1 s−1, temperature 20° C.).

(28) TABLE-US-00007 TABLE 4 Injection η Injection temperature Formulation (Pa*s) pressure 23° C. 60° C. INJ-3  1750 2 bar 8 11 6 bar 8 11 (Tab. 1)  2020 2 bar 8 11 6 bar 8 10 INJ-4  6930 2 bar 8 10 6 bar 8 11 INJ-5 10300 2 bar not n.d. pumpable 6 bar 8 10 INJ-6 27720 2 bar not n.d. pumpable 6 bar 8 10 “n.d.” = not determined

(29) It was found that, surprisingly, neither the injection temperature nor the injection pressure, or the injection rate, has a significant influence on the squeeze-out ratio. Moreover, the spreading properties of all epoxy resin compositions with a value of 8-11 are unsatisfactory.

(30) Also examined was whether the use of additional raw materials in the epoxy resin compositions has an influence on spreading characteristics. Various raw materials of this kind were tested. These are detailed in table 5.

(31) TABLE-US-00008 TABLE 5 Viscosity rise Ratio in Mixing (150° C. to Mixture Type Structure Product Manufacturer liquid resin M.p. conditions Miscibility 25° C.) A Polyester Terephthalic acid and Dynacoll 7340 Evonik 1:2 96° C. 30′ 140° C. YES slow polyol hexanedioic acid with hexane-1,6-diol B Polyester Hexanedioic acid with Dynacoll 7360 Evonik 1:2 55° C. 30′ 100° C. YES slow polyol hexane-1,6-diol C Polyester Dodecanedioic acid with Dynacoll 7380 Evonik 1:2 70° C. 30′ 120° C. YES fast polyol hexane-1,6-diol D Polyester Dodecanedioic acid with Dynacoll 7330 Evonik 1:2 85° C. 30′ 130° C. YES fast polyol ethylene glycol E Diamide wax Diamide wax Thixatrol MAX Elementis 1:4 100-120° C. 30′ 150° C. YES slow Polyester Esters of montanic acids Licolub WE 40 P Clariant 1:4 73-79° C. 30′ 130° C. NO* n.d. Polyester Ester wax based on Licolub WE 4 P Clariant 1:4 79-81° C. 30′ 130° C. NO* n.d. montanic acids Polyester Ester wax based on Licowax E P Clariant 1:4 79-83° C. 30′ 130° C. NO* n.d. montanic acids F Polyester Fineplus HM Dic 1:2 85° C. 30′ 130° C. YES fast polyol 3123 *= not homogeneous after cooling, n.d. = not determined

(32) Measurement of Miscibility:

(33) Mixtures of these raw materials with liquid epoxy resin were created in order to determine the mixing characteristics. This was done by mixing the raw materials at about 40° C. above the melting point for about 30 minutes with liquid epoxy resin (liquid epoxy resin, D.E.R. 331 (bisphenol A diglycidyl ether), Dow) in accordance with the ratio displayed in table 5 until a clear mixture was formed. In the case of mixing with Dynacoll 7380, for example, “1:2” means 33.3% by weight of polyester polyol and 66.6% by weight of liquid epoxy resin.

(34) This mixture was then cooled down to 25° C. In the case of the mixtures with the polyesters Licolub WE 40P, Licolub WE 4P and Licowax EP, it was found that no homogeneous mixture formed after cooling. These are unsuitable as additions for thermosetting epoxy resin compositions of the invention.

(35) For the rest of the raw materials, the mixture was homogeneous after cooling. The viscosity characteristics of these compositions were then determined on cooling from 150° C. to 25° C.

(36) Measurement of Viscosity Characteristics:

(37) The method consists of three phases. During the first phase, the mixture is at a temperature of 150° C., meaning that the added raw material is in the liquid state. In the second phase, the temperature cools down to 25° C. at a constant cooling rate. In the third phase, the mixture is left at a temperature of 25° C. By this method, it is possible to determine the solidification characteristics of the mixture, the “sharpness” of the transition, and the time at which the solidification of the mixture occurs.

(38) A rheometer was used (Physica MCR 302, Anton Paar) by means of oscillographic measurement (gap: 200 μm, plate/plate, plate diameter: 25 mm, frequency: 5 Hz, target deformation: 0.01) within a temperature range of 25-150° C. (cooling rate: −23° C./min, heating rate: +53° C./min) measured.

(39) Phase 1: The mixture is brought to a temperature of 150° C. and left there for 265 seconds.

(40) Phase 2: The mixture was brought to a temperature of 25° C. at a cooling rate of −23° C./min. In other words, the mixture was cooled uniformly and constantly from 150° C. to 25° C. within 325 seconds at a uniform and constant cooling rate of −23° C./min.

(41) Phase 3: Leaving the mixture at a temperature of 25° C.

(42) The magnitude of the complex viscosity η* was determined on the basis of the oscillographic measurement. FIGS. 4a-4d show the magnitude of the complex viscosity η*. The progression of the magnitude of the complex viscosity η* as a function of the time [t in seconds] for the mixtures A (◯), B (□), C (Δ), D (.circle-solid.), E (.square-solid.) and F (.Math.) is shown in FIGS. 4a-4d. FIGS. 4c and 4d show the magnitude of the complex viscosity η* shown in a logarithmic plot.

(43) The above-described rheometer, and the above-described oscillographic measurement were used. The mixtures were brought to a temperature of 150° C. and the measurement was started. The commencement of the recording of the measurements is shown in FIGS. 4a-4d from 130 seconds after the start of measurement. 265 seconds after the start of measurement, the mixture was cooled down from a temperature of 150° C. at a cooling rate of −23° C./min to a temperature of 25° C. 590 seconds after commencement of measurement, the temperature of 25° C. was attained. The mixture was left at 25° C. until about 1500 seconds after commencement of measurement.

(44) For mixtures C (Δ), D (.circle-solid.), E (.square-solid.) and F (.Math.), a high and rapid rise in viscosity is apparent. They attain more than 80% of the rise in viscosity, proceeding from the magnitude of the complex viscosity η* on commencement of the measurement at 150° C. to the maximum value for the magnitude of the complex viscosity η*, within 20 seconds.

(45) Moreover, they attain the maximum value for the magnitude of the complex viscosity η* within 80-280 seconds after commencement of the cooling of the mixtures from 150° C. at a cooling rate of −23° C./min, especially prior to the attainment of a temperature of 25° C.

(46) Mixture E (.square-solid.) shows a slow increase in viscosity, and mixtures A (◯) and B (□) show a slow and slight increase in viscosity.

(47) Based on mixture C, mixtures with different proportions by weight of Dynacoll 7380 based on the total weight of the mixtures of Dynacoll 7380 with liquid epoxy resin were produced (33% by weight, 7% by weight, 3% by weight, 2% by weight).

(48) The mixture with 2% by weight of Dynacoll 7380 reached a maximum value for the magnitude of the complex viscosity η* of 39′000. Moreover, this mixture attained more than 80% of the rise in viscosity to 39′000, proceeding from the magnitude of the complex viscosity η* on commencement of the measurement at 150° C., within 50 seconds.

(49) The other mixtures reached a maximum value for the magnitude of the complex viscosity η* of more than 100′000. Moreover, the mixtures with 33% by weight and 7% by weight attained more than 80% of the rise in viscosity to 100′000, proceeding from the magnitude of the complex viscosity η* on commencement of the measurement at 150° C., within 10 seconds.

(50) Using raw materials C, D and F, the spreading characteristics of thermosetting one-component epoxy resin adhesives based on the epoxy resin composition from table 1 with different viscosity, different amount of the toughness improver D-1 and optionally additionally comprising a solid epoxy resin were produced. Composition Z-1 additionally contains 15 parts by weight of solid epoxy resin and 20 rather than 35 parts by weight of toughness improver D-1 and has a viscosity of 2500 Pas. Composition Z-2 contains 20 rather than 35 parts by weight of toughness improver D-1 and has a viscosity of 1000 Pas. Composition Z-3 additionally contains 10 parts by weight of solid epoxy resin and 15 rather than 35 parts by weight of toughness improver D-1 and has a viscosity of 3500 Pas. To compositions Z-1, Z-2 and Z-3 was added 5% by weight of Dynacoll 7380, Dynacoll 7330 or Fineplus HM 3123, based on the total weight of the corresponding composition.

(51) Table 6 shows that compositions Z-1, Z-2 and Z-3 comprising raw material C (Dynacoll 7380) having a melting point of 70° C. show very good spreading characteristics at an injection temperature of 60° C. However, raw materials D (Dynacoll 7330) and F (Fineplus HM 3123), owing to their higher melting point of 85° C. in each case, show unsuitable spreading characteristics at an injection temperature of 60° C.

(52) TABLE-US-00009 TABLE 6 Injection rate 47 ml/min, injection temperature 60° C., Raw 5% by weight of raw material material Z-1 Z-2 Z-3 C >20 >20 >20 D 9 9 9 F 9 9 9

(53) When the same experiment was conducted with an injection temperature of 80° C. rather than 60° C., all epoxy resin adhesives showed good spreading characteristics. It is therefore advantageous when the one-component thermosetting epoxy resin composition comprising the raw material on injection has a temperature of not more than 20° C., not more than 15° C., preferably not more than 10° C., below the melting point of the raw material.

(54) Different proportions by weight of Dynacoll 7380 were added to the epoxy resin composition according to table 7 and the propagation characteristics were determined. Moreover, tensile shear strength (TSS) and impact peel strength (I-peel) were determined.

(55) TABLE-US-00010 TABLE 7 Raw materials (parts by weight) Z-4 Z-5 Z-6 Z-7 Z-8 Z-9 Liquid epoxy resin, D.E.R. 331 50 50 50 50 50 50 (bisphenol A diglycidyl ether), Dow Reactive diluent, hexanediol glycidyl 1 1  1  1 1 1 ether, Denacol EX-212, Nagase America Toughness improver D-1 35 35 35 35 35 35 Curing agent, dicyandiamide (=“Dicy”) 4.6 4.6  4.6  4.6 4.6 4.6 Accelerator, substituted urea 0.2 0.2  0.2  0.2 0.2 0.2 Fumed silica 5 5  5  5 5 5 Dynacoll 7380 0 2.5   5*   10** 20 30 Dynacoll 7380 (% by weight) 0 2.5  5.0  9.5 17.3 23.8 Total (parts by weight) 95.8 98.3 100.8 105.8 115.8 125.8 Injection rate: 47 ml/min Injection temperature: 60° C. 11 19 >20   >20   >20 >20 Squeeze-out-ratio: TSS 35′ 175° C. RT MPa 24.8 20.8  20.6  16.0 10.0 7.2 I-Peel 35′ 175° C. RT N/mm 33.3 35.0  33.7  24.1 5.7 3.8 I-Peel 35′ 175° C. −30° C. N/mm 34.9 37.5  33.9  23.1 0.2 0.2 *= maximum lateral spread in the gap <10 mm, **= maximum lateral spread in the gap <1 mm.

(56) Table 7 shows that epoxy resin compositions containing an amount of more than 20% by weight of Dynacoll 7380 are no longer suitable as structural adhesives. It has been found that, surprisingly, epoxy resin compositions containing 2.5% by weight of Dynacoll 7380 have particularly high I-peel values, especially at −30° C.

(57) Test Methods:

(58) Tensile Shear Strength (TSS) (DIN EN 1465)

(59) Cleaned test specimens of Elo H420 steel (thickness 1.2 mm) that had been reoiled with Anticorit PL 3802-39S were bonded with the adhesive over a bonding area of 25×10 mm with glass beads as spacer in a layer thickness of 0.3 mm, and cured at oven temperature 175° C. for 35 min. The tensile shear strength was determined on a tensile testing machine at a pull rate of 10 mm/min in a triple determination according to DIN EN 1465.

(60) Impact Peel Strength (I-Peel) (to ISO 11343)

(61) The specimens were produced with the adhesive and DC04+ZE steel with dimensions of 90×20×0.8 mm. The bonding area here was 20×30 mm at a layer thickness of 0.3 mm with glass beads as spacer. The samples were cured for 35 minutes at oven temperature 175° C. Impact peel strength was measured in each case at the temperatures specified (23° C., −30° C.) as a triple determination on a Zwick 450 impact pendulum. The impact peel strength reported is the average force in N/mm under the measurement curve from 25% to 90% to ISO011343.