PUMPABLE, THERMALLY EXPANDABLE PREPARATION

Abstract

The present application relates to a preparation that is pumpable, thermally curable and expandable at application temperatures, typically in the range of 30 to 120° C., and contains at least one solid rubber, at least one liquid rubber, at least one thermally activatable blowing agent and a curing agent system containing at least one peroxide and at least one quinone, quinone dioxime or dinitrosobenzene, to a method for stiffening structural components having thin-walled structures using such preparations or for sealing cavities in structural components using such preparations, and to the use of these preparations for stiffening such structures or for sealing cavities in structural components.

Claims

1. A thermally expandable preparation that is pumpable at application temperatures in a range of 30 to 120° C., and contains (a) at least one solid rubber; (b) at least one liquid rubber; (c) at least one thermally activatable blowing agent; and (d) a curing agent system containing at least one peroxide and at least one quinone, quinone dioxime or dinitrosobenzene.

2. The thermally expandable preparation of claim 1, wherein the at least one solid rubber is selected from styrene butadiene rubbers and styrene isoprene rubbers and/or is contained in an amount of 1 to 30 wt. %, in each case based on total weight of the preparation.

3. The thermally expandable preparation of claim 1, wherein the at least one liquid rubber is selected from butadiene-isoprene block copolymers and/or is contained in an amount of 1 to 30 wt. %, in each case based on total weight of the preparation.

4. The thermally expandable preparation of claim 1, wherein a sulfonic acid hydrazide and/or azodicarbonamide is contained as the at least one blowing agent, in an amount of 0.1 to 10 wt. %, in each case based on total weight of the preparation.

5. The thermally expandable preparation of claim 1, wherein the curing agent system is contained in an amount of 0.1 to 10 wt. %, in each case based on total weight of the preparation.

6. The thermally expandable preparation of claim 1, further comprising at least one adhesion promoter present in an amount of 2 to 10 wt. %, in each case based on total weight of the preparation.

7. The thermally expandable preparation of claim 1, further comprising at least one peroxidically crosslinkable polymer selected from binary copolymers containing at least one monomer unit selected from vinyl acetate, (meth)acrylic acids, styrene and derivatives thereof, and terpolymers based on at least one first monomer selected from the monounsaturated or polyunsaturated hydrocarbons, and at least one second monomer selected from (meth)acrylic acids and derivatives thereof, and at least one third monomer selected from epoxy-functionalized meth(acrylates), and combinations thereof.

8. The thermally expandable preparation of claim 7, wherein an ethylene/vinyl acetate copolymer, having a melt flow index of greater than/equal to 200 g/min, is contained as at least one peroxidically crosslinkable polymer.

9. The thermally expandable preparation of claim 7, wherein the at least one peroxidically crosslinkable polymer comprises at least one terpolymer based ethylene, (meth)acrylic esters, and epoxy-functionalized meth(acrylates).

10. The thermally expandable preparation of claim 1, further comprising at least one liquid polymer selected from liquid hydrocarbon resins, and liquid polyolefins present in an amount of 5 to 35 wt. %, in each case based on the total weight of the preparation.

11. The thermally expandable preparation of claim 1, further comprising fillers, antioxidants, activators and/or dyes.

12. The thermally expandable preparation of claim 1, comprising: 8 to 20 wt. % of (a) the at least one solid rubber; 8 to 20 wt. % of (b) the at least one liquid rubber; 0.5 to 3.5 wt. % of (c) the at least one thermally activatable blowing agent; and 1 to 3 wt. % of (d) the curing agent system containing at least one peroxide and at least one quinone, quinone dioxime or dinitrosobenzene; and 1 to 15 wt. % of at least one adhesion promoter selected from epoxides, anhydride-grafted polybutadiene isocyanates; amounts in each case based on total weight of the preparation.

13. The thermally expandable preparation of claim 12, further comprising at least one peroxidically crosslinkable polymer selected from binary copolymers containing at least one monomer unit selected from vinyl acetate, (meth)acrylic acids, styrene and derivatives thereof, and terpolymers based on at least one first monomer selected from the monounsaturated or polyunsaturated hydrocarbons, and at least one second monomer selected from the (meth)acrylic acids and derivatives thereof, and at least one third monomer selected from epoxy functionalized meth(acrylates), and combinations thereof.

14. The thermally expandable preparation of claim 13, wherein an ethylene/vinyl acetate copolymer is contained as at least one peroxidically crosslinkable polymer.

15. The thermally expandable preparation of claim 13, wherein the at least one peroxidically crosslinkable polymer comprises at least one terpolymer based ethylene, (meth)acrylic esters, and epoxy functionalized meth(acrylates).

16. The thermally expandable preparation of claim 12, further comprising at least one liquid polymer present in an amount of 5 to 35 wt. % and selected from a. liquid hydrocarbon resins, and b. liquid polyolefins.

17. A method for stiffening and/or reinforcing structural components having thin-walled structures, or for sealing cavities in structural components, in particular tubular structures, wherein a thermally expandable preparation of claim 1, is applied to the surface of the structure to be stiffened and/or reinforced or introduced into the cavity of the structural component to be sealed at a temperature below 120° C., and at a pump pressure of less than 200 bar, and this preparation is cured at a later point in time, at temperatures above 130° C.

18. A structural component, optionally having a thin-walled structure, stiffened and/or reinforced and/or sealed by means of curing using a thermally expandable preparation according to claim 1.

Description

EXAMPLES

[0118] The following thermally expandable preparations were produced. Unless otherwise noted, the quantitative data are given in weight percent.

TABLE-US-00001 COMPONENT Example 1 Example 2 Example 3 Example 4 Solid styrene-butadiene copolymer  5.73  9.12  20  15 Amorphous carbon black  3.88  1.82   2   2 Calcium dioxide  2.82  2.46   2.7   2.7 Coated calcium carbonate  15.53  13.59  13.11  14.24 Ethylene-vinyl acetate copolymer  1.82   2   2 Calcium carbonate  27.21  22.0 Benzoquinone dioxime  0.87  0.77   0.84   3.36 Benzenesulfinic acid zinc salt  0.19  0.17   0.19   0.19 Azodicarbonamide  1.84  6.16  13  16 Expandable hollow microspheres  2.43 Dicumyl peroxide  0.76   0.83   0.83 Bis(tert-butylperoxyisopropyl)benzene  2.17 Dicyandiamide  0.46   0.5   0.5 Epoxy resin  3.65   4.0   4 Maleic anhydride-grafted polybutadiene  6.31 Diisononyl phthalate  3.88  3.4   3.73   3.73 Liquid butadiene-isoprene copolymer  12.14  10.62  11.65 Liquid styrene-butadiene copolymer  10 Aromatic hydrocarbon resin in oil  14.99  23.2  25.45  25.45 TEST RESULTS Expansion rate in % 25 minutes, 160° C. 440 400%  700%  900% 25 minutes, 180° C. 470 500% 1000% 1000% 40 minutes, 200° C. 480 400%  700%  800% Washout resistance  2  2   2   2
Specification of components used:

TABLE-US-00002 Solid styrene-butadiene copolymer SBR with Mw > 300,000 both uncrosslinked and pre-crosslinked Liquid styrene-butadiene copolymer SBR with Mw < 20,000 Ethylene-vinyl acetate copolymer 28% vinyl acetate content, MFR (190° C./2.16 kg) 400 g/10 min, melting point 60° C. Liquid butadiene-isoprene copolymer liquid; Mw 48,000, density 0.88 g/cm.sup.3 Aromatic hydrocarbon resin in oil liquid; melting point 15° C. Benzoquinone dioxime 1,4-para-benzoquinonedioxime in 65% paste Epoxy resin <700 Mw; epoxy group content 5,200-5,500 mmol/kg

[0119] To produce the thermally expandable preparations according to the invention, the polymers and resins contained were processed step-by-step with fillers at RT in a kneader or, if necessary, with heating to up to 90° C. to form a homogeneous dough. The other non-reactive components such as fillers, carbon black, stabilizers and plasticizers, if any, were then added one after the other and kneaded further until the formulation was smooth.

[0120] At below 60° C., all reactive components such as benzoquinone dioxime, peroxides, activators and catalysts, calcium oxide and blowing agent were then added and slowly kneaded in until the adhesive was homogeneously mixed. Finally, the mixtures were homogenized for a further 10 minutes under a vacuum of less than 100 mbar and filled into cartridges.

[0121] All preparations exhibit uniform expansion, with a uniform, fine-pored foam being formed. The foam does not shrink or have any surface cracks.

[0122] Also, as a result of the preparation being stored in a humidity chamber (30° C./85% relative humidity/8 days), the materials do not exhibit any changes in properties and the material does not mushroom, either. The foam adheres to the steel substrates CRS, ELO; HDG, ZnMg very well and has up to 100% cohesive failure. The water absorption (after 24 h in water) of the foams also has an excellent, low weight increase of <5 wt. % in a direct measurement and <0.5 wt. % after re-drying (24 h), the foams from examples 2 to 4 having particularly good values.

Determination of Expansion:

[0123] To determine the expansion, test specimens having dimensions of approximately 20 mm×8-10 mmø round bead portions were pressed out of the cartridges produced from the example formulations at approximately 40-60° C. and these were introduced into a convection oven, which was heated to the temperatures specified in the tables (heating time approximately 7 to 10 minutes). The test specimens were then left at this temperature for the period specified in the tables (including heating time). The expansion at 180° C. corresponds to the ideal conditions that are achieved during curing in vehicle construction. The expansion at 160° C. simulates the underfiring conditions and the expansion at 200° C. simulates the overfiring conditions.

[0124] The degree of expansion [%] was determined by the water displacement method according to the formula

[00001]$\mathrm{Expansion}=\frac{\left(m2-m1\right)}{m1}\times 100$

m1=mass of the test specimen in its original state in deionized water
m2=mass of the test specimen after baking in deionized water.

Determination of Washout Resistance:

[0125] To determine the washout resistance, round beads having a geometry of 150 mm×10 mmø were applied at 40-60° C. to a prepared metal sheet of approximately 200 mm×30 mm and cooled for at least 1 h. The metal sheet prepared in this way is clamped in a holder of a rod agitator having a 12 cm radius, and immersed in a bath at 55° C., the rod agitator is set to a speed of rotation of 60 min.sup.−1 and started. After 10 minutes the stirrer is switched off and the sample holder is lifted out of the water. The samples are removed from the holder and assessed. At least three test specimens are to be made.

[0126] The evaluation is based on the following rating scale:

0=unchanged compared with the initial state
1=little deformation
2=significant deformation without material washout
3=strong deformation, but without material washout
4=very strong deformation with material washout
5=material removal, but the originally wetted area is still covered in material
6=almost complete material removal except for small residual amounts