Thermally expandable preparations

Abstract

The subject matter of the present application is a thermally expandable preparation that can be pumped at application temperatures below 70° C., containing (a) at least one first epoxy resin E1 that has an epoxy equivalent weight of at most 280 g/eq and a viscosity of at most 1250 Pa*s at 25° C., (b) at least one second epoxy resin E2 that has an epoxy equivalent weight of at least 300 g/eq and a viscosity of at most 250 Pa*s at 25° C., (c) at least one hardener that can be thermally activated, (d) at least one propellant that can be thermally activated, and (e) at least 1 wt. % of organic fibres having a fibre length of 0.2 mm to 10 mm.

Claims

1. A thermally expandable preparation pumpable at application temperatures below 70° C., comprising (a) at least one first epoxy resin E1 that has an epoxy equivalent weight of at most 280 g/eq and a viscosity at 25° C. of at most 1250 Pa*s, (b) at least one second epoxy resin E2 that has an epoxy equivalent weight of at least 300 g/eq and a viscosity at 25° C. of at most 250 Pa*s, (c) at least one thermally activatable hardener, (d) at least one thermally activatable blowing agent, (e) at least 1 wt. % organic fibers having a fiber length from 0.2 mm to 10 mm, and (f) at least 20 wt. % fillers.

2. The preparation according to claim 1, characterized in that it contains at least 30 wt. % fillers, based in each case on the total application preparation.

3. The preparation according to claim 1, characterized in that the at least one filler is a lightweight filler.

4. The preparation according to claim 1, characterized in that the at least one filler is an inorganic filler.

5. The preparation according to claim 1, characterized in that the at least one filler is surface-treated silicon dioxide.

6. The preparation according to claim 1, characterized in that it contains less than 1.5 wt. %, based on the total application preparation, of an epoxy resin that is solid at 25° C.

7. The preparation according to claim 1, characterized in that the first epoxy resin E1 has an epoxy equivalent weight of at most 200 g/eq, and/or has a viscosity at 25° C. of at most 20 Pa*s, and/or is contained in the preparation in a quantity from 10 to 55 wt. %, based on the total application preparation.

8. The preparation according to claim 1, characterized in that the second epoxy resin E2 has an epoxy equivalent weight of at least 400 g/eq, and/or has a viscosity at 25° C. of at most 200 Pa*s, and/or is contained in the preparation in a quantity from 5 to 35 wt. %, based on the total application preparation.

9. The preparation according to claim 1, characterized in that it contains at least one impact modifier and/or at least one flame retardant.

10. A method for stiffening and/or reinforcing components having thin-walled structures, in particular tubular structures, characterized in that a thermally expandable preparation pumpable at application temperatures below 70° C. according to one of claims 1 to 9 is applied at a temperature below 70° C., at a pump pressure of less than 200 bar, onto the surface of the structure to be reinforced, and said preparation is cured at a later point in time at temperatures above 130° C.

11. A component having a thin-walled structure, which component has been stiffened and/or reinforced with a thermally expandable preparation pumbable at application temperatures below 70° C. according to one of claims 1 to 9, in the cured state.

12. The preparation according to claim 1, characterized in that the filler is hollow glass spheres.

13. The preparation according to claim 1, characterized in that the filler is chalk.

Description

EXEMPLARY EMBODIMENTS

(1) 1 Production of the Formulations

(2) The following thermally expandable preparations were produced.

(3) Unless otherwise specified, the quantitative data are expressed as percentages by weight.

(4) TABLE-US-00003 TABLE 1 Formulation Raw material F1 F2 F3 F4 F5 F6 DER ® 331 5.0 25.0 25.0 50.0 25.0 25.0 DER ® 736 25.0 10.0 — — — — Prepolymer A 20.0 — 10.0 10.0 20.0 10.0 DER ® 32 — 10.0 — — — — Thioplast ® EPS-25 — 10.0 — — — — Adeka ® QR-9466 5.0 5.8 — — 12.0 — Flexibilize ® DY-965 5.0 — 15.0 — — 13.1 Kevlar ® 1F561 — — 5.0 — 7.0 1.5 Kevlar ® 1F1464 — 5.0 — 7.0 — — Kevlar ® 1F107 2.5 — — — — — Omyacarb ® 4HD 15.0 11.0 23.5 13.7 14.0 34.0 3M GB ® VS5500 15.0 15.0 15.0 10.0 15.0 10.0 Cab-o-Sil ® TS720 2.0 2.0 2.0 2.0 2.0 2.0 Dyhard ® 100SH 4.2 4.9 3.2 6.0 3.7 3.1 Fenuron 0.3 0.3 0.3 0.3 0.3 0.3 Expancel ® 909 DU80 1.0 1.0 1.0 1.0 1.0 1.0 Total 100.0 100.0 100.0 100.0 100.0 100.0

(5) In addition, the following thermally expandable preparation according to the invention was produced, which additionally contains flame retardant:

(6) TABLE-US-00004 Formulation F7 Quantity [wt. %] DER ® 331 37.7 Prepolymer A 14.0 Exolit ® OP930 10.0 Exolit ® AP422 4.0 Exolit ® RP6500 2.0 Martinal ® ON313 14.0 3M GB VS5500 7.5 Kevlar ® 1F1464 2.5 Cab-o-Sil ® TS-720 2.0 Dyhard ® 100SH 5.0 Fenuron 0.3 Expancel ® 909 DU80 1.0 Total 100.0
2. List of Commercial Products Employed

(7) TABLE-US-00005 3M GB ® hollow glass spheres; manufacturer 3M; density VS5500 0.38 g/cm.sup.3 Adeka ® QR- modified polyurethane resin; manufacturer Adeka 9466 Cab-o-sil ® silicon dioxide, pyrogenic amorphous silica, TS-720 manufacturer Cabot DER ® 331 reaction product of bisphenol A with epichlorohydrin; EEW approx. 187 g/eq; viscosity at 25° C. 12.5 Pa * s; manufacturer Dow DER ® 732 reaction product of epichlorohydrin with poly- propylene glycol; EEW approx. 320 g/eq; viscosity at 25° C. 0.034 Pa * s; manufacturer Dow DER ® 736 reaction product of epichlorohydrin with poly- propylene glycol; EEW approx. 190 g/eq; viscosity at 25° C. 0.079 Pa * s; manufacturer Dow Dyhard ® 100SH 1-cyanoguanidine; approx. 94.8% purity; manufacturer Evonik Degussa Exolit ® AP422 ammonium polyphosphate; manufacturer Clariant Exolit ® OP930 organophosphorus salt; manufacturer Clariant Exolit ® RP6500 microencapsulated red phosphorus (approx. 43-47 wt. %) in epoxy resin (approx. 52-57 wt. %); manufacturer Clariant Expancel ® 909 expandable hollow microspheres comprising DU80 acrylonitrile, methacrylonitrile and methyl methacrylate copolymers; manufacturer Expancel Flexibilizer ® reactive impact modifier for epoxy resins; DY-965 manufacturer Huntsman Kevlar ® 1F107 Kevlar fibers having a nominal length of 6.4 mm; manufacturer DuPont Kevlar ® 1F1464 Kevlar fibers having a nominal length of 2.7 mm; manufacturer DuPont Kevlar ® 1F561 Kevlar fibers having a nominal length of 1.5 mm; manufacturer DuPont Martinal ® ON313 aluminum hydroxide (purity 99.6%; particle size 11-15 μm); manufacturer Albemarle Omyacarb ® 4HD calcium carbonate; pulverized limestone; manufacturer Omya GmbH Prepolymer A reaction product of bisphenol A diglycidyl ether and alkyl polyoxyalkylene amine; EEW approx. 450 g/eq; viscosity at 25° C.: 160 Pa * s; Thioplast ® epoxy-terminated, aliphatic polysulfide; EEW EPS-25 approx. 550 g/eq; viscosity at 25° C. 2.8 Pa * s; manufacturer Akzo Nobel

(8) To produce the preparations, the resins were each charged into an unheated planetary mixer and homogenized for at least 20 min under a vacuum of less than 100 mbar at a mixing rate of 100 rpm. The fillers were then added stepwise and the resulting mixtures were each mixed at max. 50 rpm until homogeneous materials were present. The mixtures were then homogenized for a further 20 min under a vacuum of less than 100 mbar at a mixing rate of 100 rpm. The remaining raw materials were then added to the formulations and mixed at max. 50 rpm until homogeneous materials were present. Finally, the mixtures were homogenized for a further 10 min under a vacuum of less than 100 mbar at a mixing rate of 100 rpm and packed into cartridges. Throughout the entire mixing and homogenizing processes, it was ensured that the preparation did not become hotter than 60° C. as a result of any heat of mixing that occurred.

(9) 3 Determination of the Properties of the Preparations

(10) 3.1 Determination of Flow Rate

(11) To determine the flow rate, 310 ml of each of the preparations were packed according to Table 1 into aluminum cartridges with a capacity of 310 ml and an internal diameter of 46 mm and preheated there for 45 minutes at 60° C. The preparations were then each discharged at a temperature of 60° C. with a pressure of 6 bar through the discharge outlet of the cartridge, which had been produced using a cartridge-piercing tool (punch) with an external diameter of 9.0 mm, without using a nozzle. The measuring interval was selected in each case as a function of the flow rate of the system to be measured. Thus, for preparations with a flow rate of at least 1000 g/min, the entire cartridge was emptied and the time needed for this was determined; for very high flow rates, the cartridges emptied so rapidly that only an approximate value could be established. For preparations with a flow rate below 1000 g/min, a measuring interval of 15 seconds in each case was selected.

(12) 3.2 Determination of Tensile Shear Strength

(13) The preparations according to the invention were applied from the cartridges onto untreated steel plates cleaned with ethyl acetate (grade DC05; layer thickness 1.5 mm; width 25 mm). The steel plates treated with the preparations according to the invention were brought into contact with one another in such a way that an overlap region of 10 mm was obtained. The specimens were pressed to the bonding gap thickness (using glass spheres having a diameter of 200 μm as spacers), fixed with clamps and then cured for 30 min at 170° C. The measurement took place on the following day at 25° C. and using a pulling speed of 10 mm/min. In all cases, a cohesive fracture behavior was observed for the preparations according to the invention (referred to in the table as “c.f.”).

(14) 3.3 Determination of Non-Sag Properties

(15) To determine the non-sag properties of the formulations, their sliding behavior was investigated. To this end, using a triangular nozzle as employed e.g. for applying PUR-based windshield adhesives, beads of adhesive with a height of 13 mm and a width of 8 mm were applied onto cleaned steel plates. The plates were then placed in an oven for 30 min at 120° C. at an angle of 90° in such a way that the beads of adhesive stood vertical to the ground. At the end of the test, it was determined how far the beads of adhesive had moved from their original position. A slide of up to 3 mm was tolerated here and evaluated as “acceptable” (“OK”), while a greater slide was marked as “not acceptable” (“n.OK”).

(16) 3.3 Test Results

(17) TABLE-US-00006 TABLE 2 Preparation F1 F2 F3 F4 F5 F6 Flow rate [g/min] 1130 >4000 235 1150 460 >2400 Non-sag properties OK OK OK OK OK OK Tensile shear 9.3 13.5 14.2 15.1 14.0 11.3 strength [MPa] (c.f.) (c.f.) (c.f.) (c.f.) (c.f.) (c.f.)

(18) The results shown in the above table clearly demonstrate that formulations (F1 to F6) according to the invention have good application properties (recognizable by the flow rate in [g/min]) together with good non-sag properties (i.e. low slip).