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CN-122029211-A - Thermosetting epoxy resin composition suitable for pre-curing process without additional metal bonding technique

CN122029211ACN 122029211 ACN122029211 ACN 122029211ACN-122029211-A

Abstract

The invention relates to a thermosetting one-component epoxy resin composition comprising at least one liquid aromatic epoxy resin A1, at least one solid epoxy resin A2, at least one curing agent B for the epoxy resin, at least one core-shell polymer D1 and at least one end-blocked polyurethane polymer D2. The weight ratio (A1/A2) of the at least one liquid epoxy resin A1 to the at least one solid epoxy resin A2 is from 1.75 to 3.75, and the weight ratio (D1/D2) of the at least one core-shell polymer D1 to the at least one end-blocked polyurethane polymer D2 is from 1.2 to 4. The epoxy resin composition has sufficient lap shear strength after pre-curing without the need for additional metal bonding techniques. In addition, the fully cured epoxy resin composition provides good values of mechanical strength, lap shear strength, impact peel, glass transition temperature (Tg), and fatigue resistance.

Inventors

  • D. Garo

Assignees

  • SIKA技术股份公司

Dates

Publication Date
20260512
Application Date
20241106
Priority Date
20231114

Claims (16)

  1. 1. A thermosetting one-part epoxy resin composition comprising: a) At least one liquid epoxy resin A1 having an average of more than one epoxy group per molecule, preferably in an amount of 37.5 to 55 wt%, more preferably 40 to 52.5 wt%, most preferably 42.5 to 50 wt%, based on the total weight of the thermosetting one-component epoxy resin composition; b) At least one solid epoxy resin A2 having an average of more than one epoxy group per molecule, preferably in an amount of 10 to 25 wt%, more preferably 12.5 to 20wt%, most preferably 13.5 to 17.5 wt%, based on the total weight of the thermosetting one-component epoxy resin composition; c) At least one latent hardener B for epoxy resins, wherein the latent hardener B is selected from dicyandiamide, guanamine, guanidine, anhydrides of polycarboxylic acids and aminoguanidine, preferably dicyandiamide; d) At least one core-shell polymer D1, and E) At least one end-blocked polyurethane polymer D2; wherein the weight ratio (A1/A2) of the at least one liquid epoxy resin A1 to the at least one solid epoxy resin A2 is from 1.75 to 3.75, and wherein the weight ratio (D1/D2) of the at least one core-shell polymer D1 to the at least one end-blocked polyurethane polymer D2 is from 1.2 to 4.
  2. 2. A thermosetting one-component epoxy resin composition according to claim 1, characterized in that the weight ratio (A1/A2) of the at least one liquid epoxy resin A1 to the at least one solid epoxy resin A2 is 1.9-3.25, preferably 2.25-3.25.
  3. 3. A thermosetting one-component epoxy resin composition according to any of the preceding claims, characterized in that the weight ratio (D1/D2) of the at least one core-shell polymer D1 to the at least one end-blocked polyurethane polymer D2 is 1.25-2.75, in particular 1.5-2.25.
  4. 4. A thermosetting one-part epoxy resin composition according to any of the preceding claims, characterized in that the thermosetting one-part epoxy resin composition additionally comprises at least one accelerator C selected from the list consisting of substituted ureas, imidazoles, imidazolines and blocked amines, in particular substituted ureas.
  5. 5. The thermosetting one-component epoxy resin composition as claimed in claim 4, wherein the ratio of accelerator C in grams is preferably 0.1 to 5.0g/mol epoxy groups, especially 0.3 to 3.0g/mol epoxy groups, more preferably 0.5 to 2.0g/mol epoxy groups, most preferably 0.6 to 1.0g/mol epoxy groups per mole of the sum of epoxy groups of liquid epoxy resin A1 and solid epoxy resin A2.
  6. 6. The thermosetting one-part epoxy resin composition as claimed in any of the preceding claims, wherein the proportion of the at least one liquid epoxy resin A1 is 37.5 to 55 wt. -%, more preferably 40 to 52.5 wt. -%, most preferably 42.5 to 50 wt. -%, based on the total weight of the thermosetting one-part epoxy resin composition, and/or, preferably and, the proportion of the at least one solid epoxy resin A2 is 10 to 25 wt. -%, preferably 12.5 to 20 wt. -%, more preferably 13.5 to 17.5 wt. -%, based on the total weight of the thermosetting one-part epoxy resin composition.
  7. 7. A thermosetting one-component epoxy resin composition according to claim, wherein the proportion of the at least one core-shell polymer D1 is from 6 to 12% by weight, preferably from 7 to 11% by weight, more preferably from 8 to 10% by weight, based on the total weight of the thermosetting one-component epoxy resin composition, and/or the proportion of the at least one end-blocked polyurethane polymer D2 is from 3.5 to 8% by weight, preferably from 4 to 7.25% by weight, more preferably from 4.5 to 7% by weight, based on the total weight of the thermosetting one-component epoxy resin composition.
  8. 8. A thermosetting one-component epoxy resin composition as claimed in any of the preceding claims, characterized in that the at least one core-shell polymer D1 has a number average particle size of from 10 to 300nm, preferably from 75 to 250nm, as determined by transmission electron spectroscopy, and/or, preferably, and, the at least one end-blocked polyurethane polymer D2 is an end-blocked polyurethane polymer blocked with blocking groups eliminated at temperatures above 100 ℃.
  9. 9. A thermosetting one-part epoxy resin composition according to any of the preceding claims, characterized in that the thermosetting one-part epoxy resin composition additionally comprises 5-30 wt. -%, preferably 10-25 wt. -%, more preferably 12.5-20 wt. -%, based on the total weight of the thermosetting one-part epoxy resin composition, of at least one filler F, preferably selected from the group consisting of calcium carbonate, calcium oxide and fumed silica.
  10. 10. Use of a thermosetting one-part epoxy resin composition according to any one of claims 1 to 9 as one-part thermosetting adhesive, in particular as a thermosetting one-part body adhesive in motor vehicle construction.
  11. 11. A method of bonding thermally stable substrates comprising the steps of: i) Applying a thermosetting one-component epoxy resin composition according to any one of claims 1 to 9 to a surface of a heat-stable substrate S1, in particular a metal; ii) contacting the applied thermosetting epoxy resin composition with a further heat stable substrate S2, in particular a surface of a metal; iii) The composition is heated to a temperature of 180-230 ℃, especially 190-220 ℃, preferably 200-210 ℃ for 10-180 seconds, especially 20-80 seconds, preferably 30-60 seconds, Iv) preferably heating the composition to a temperature of from 100 to 220 ℃, especially from 120 to 200 ℃, preferably from 140 to 190 ℃, more preferably from 150 to 180 ℃, wherein the composition reaches a temperature of less than 100 ℃, especially less than 60 ℃, preferably from 50 to 20 ℃, between step iii) and step iv); wherein the substrate S2 is composed of the same material as the substrate S1 or a different material.
  12. 12. The method according to claim 11, wherein a period of time of more than 15 minutes, in particular more than 20 minutes, preferably ≡30 minutes, in particular 30 to 300 minutes, is present between step iii) and step iv).
  13. 13. The method of claim 11 or 12, wherein the heating in step iii) is by induction heating.
  14. 14. The method according to claims 11 to 13, wherein in step iv) of heating the composition to a temperature of 100-220 ℃, especially 120-200 ℃, preferably 140-190 ℃, more preferably 150-180 ℃, the composition is left at the above temperature for 10 minutes to 6 hours, 10 minutes to 2 hours, 10 minutes to 60 minutes, 10 minutes to 30 minutes, 10 minutes to 20 minutes, more preferably 10 minutes to 15 minutes, preferably in a paint curing oven, especially preferably in a paint curing oven for a vehicle.
  15. 15. An adhesive bonded article obtained by the method of any one of claims 11 to 14.
  16. 16. Use of a combination of a weight ratio (A1/A2) of at least one liquid epoxy resin A1 to at least one solid epoxy resin A2 of 1.75 to 3.75 and a weight ratio (D1/D2) of at least one core-shell polymer D1 to at least one end-blocked polyurethane polymer D2 of 1.2 to improve the fatigue resistance of a thermosetting one-part epoxy resin composition, wherein the fatigue resistance is measured as described in the experimental section, wherein the improvement of fatigue resistance (number of cycles) is compared to the thermosetting one-part epoxy resin composition without the combination of the weight ratios (A1/A2) and (D1/D2), and wherein the thermosetting one-part epoxy resin composition comprises: -at least one liquid epoxy resin A1 having on average more than one epoxy group per molecule; -at least one solid epoxy resin A2 having on average more than one epoxy group per molecule; at least one latent hardener B for epoxy resins, wherein the latent hardener B is selected from dicyandiamide, guanamine, guanidine, anhydrides of polycarboxylic acids and aminoguanidine, preferably dicyandiamide; at least one core-shell polymer D1, and -At least one end-blocked polyurethane polymer D2; preferably, the improvement in fatigue resistance (number of cycles) is greater than 20%, more preferably greater than 30%.

Description

Thermosetting epoxy resin composition suitable for pre-curing process without additional metal bonding technique Technical Field The present invention relates to the field of thermosetting one-component epoxy resin compositions, in particular for use as vehicle body adhesives. Prior Art One important field of application for thermosetting one-part epoxy resin compositions is in vehicle construction, in particular in the bonding of vehicle body construction. After the epoxy resin composition is applied, the vehicle body is heated in a cathodic electrocoating furnace, with the result that the thermosetting one-component epoxy resin composition is also cured. Currently, the epoxy adhesives are used only in combination with other metal joining techniques, such as welding or riveting, because the bonded parts cannot withstand mechanical stresses prior to curing, for example when transported to a cathodic electrocoating furnace. Partial curing of the epoxy adhesive applied upstream of the cathodic electrocoating furnace, such as by induction heating, would be a quick and inexpensive alternative to the already mentioned expensive and inconvenient thermal and mechanical metal joining techniques. However, a disadvantage of such partial curing operations is that only a limited energy input into the epoxy adhesive is generally possible, which results in a curing process that obtains an excessively low lap shear strength value. In the fully cured state, the epoxy adhesive should also provide good mechanical strength, lap shear strength, impact peel, and glass transition temperature (Tg) values. Furthermore, over time and over the life of the bonded components, the cured adhesive may fatigue and may lead to premature failure due to wear and dynamic movement life. In particular, at high temperatures of 180 ℃ in a cathodic electrocoating furnace, the adhesion of conventional partially cured epoxy adhesives fails without additional metal joining techniques before they reach final cure. WO 2022207411 describes a thermally curable epoxy resin composition containing a curing agent in the form of a mixture of an aromatic dicarboxylic acid dihydrazide and a dihydrazide selected from glutaric acid dihydrazide, adipic acid dihydrazide, pimelic acid dihydrazide, 8, 12-eicosadienoic acid-1, 20-dihydrazide and 4-isopropyl-2, 5-dioxoimidazolidine-1, 3-bis (propionyl hydrazide). The epoxy resin composition is particularly suitable for automotive body-in-white bonding, wherein after induction pre-curing without additional metal joining techniques, the pre-cured adhesive is re-cured in a further step at a temperature of about 180 ℃. Disclosure of Invention It is therefore an object of the present invention to provide thermosetting one-part epoxy resin compositions which have sufficient lap shear strength at room temperature and elevated temperatures, such as 180 ℃, after primary curing (especially 30-60 seconds at 200-210 ℃) without the need for additional metal joining techniques. In addition, the fully cured epoxy resin composition should provide good mechanical strength, lap shear strength, impact peel, glass transition temperature (Tg), and fatigue resistance values. This object is surprisingly achieved by a thermosetting one-component epoxy resin composition as claimed in claim 1. The epoxy resin compositions have particularly good usability as one-component thermosetting adhesives, especially as thermosetting one-component body adhesives in motor vehicle construction. Embodiments of the invention The present invention relates to a thermosetting one-part epoxy resin composition comprising: a) At least one liquid epoxy resin A1 having an average of more than one epoxy group per molecule, preferably in an amount of 37.5 to 55 wt%, more preferably 40 to 52.5 wt%, most preferably 42.5 to 50 wt%, based on the total weight of the thermosetting one-component epoxy resin composition; b) At least one solid epoxy resin A2 having an average of more than one epoxy group per molecule, preferably in an amount of 10 to 25 wt%, more preferably 12.5 to 20 wt%, most preferably 13.5 to 17.5 wt%, based on the total weight of the thermosetting one-component epoxy resin composition; c) At least one latent hardener B for epoxy resins, wherein the latent hardener B is selected from dicyandiamide, guanamine, guanidine, anhydrides of polycarboxylic acids and aminoguanidine, preferably dicyandiamide; d) At least one core-shell polymer D1, and E) At least one end-blocked polyurethane polymer D2. The weight ratio (A1/A2) of the at least one liquid epoxy resin A1 to the at least one solid epoxy resin A2 is 1.75-3.75. The weight ratio (D1/D2) of the at least one core-shell polymer D1 to the at least one end-blocked polyurethane polymer D2 is from 1.2 to 4. In this context, the use of the term "independently" in relation to substituents, radicals or groups should be interpreted such that substituents, radicals or groups having the same reference in the same molec