Thermally expandable compositions

Abstract

The present application relates to a thermally expandable composition containing an endothermic chemical blowing agent, to shaped bodies containing said composition and to a method for sealing and filling cavities in components, for strengthening or reinforcing components, in particular hollow components, and for bonding movable components using shaped bodies of this type.

Claims

1. A thermally expandable composition containing at least one endothermic chemical blowing agent, at least one reactive binder, anhydride containing copolymers present in an amount of 5 wt. % to 20 wt. % and at least one of a curing agent and an accelerator.

2. The thermally expandable composition according to claim 1, wherein the at least one endothermic chemical blowing agent is selected from bicarbonates, solid polycarboxylic acids, solid polycarboxylic acid salts and mixtures thereof; and the at least one reactive binder is selected from the group consisting of epoxies, rubbers, peroxide-crosslinkable polymers and combinations thereof.

3. The thermally expandable composition according to claim 2, wherein the endothermic chemical blowing agent contains a bicarbonate of formula XHCO.sub.3, wherein X is a cation.

4. The thermally expandable composition according to claim 3, wherein X is selected from Na.sup.+, K.sup.+, Zn.sup.2+, Mg.sup.2+, Ca.sup.2+ and mixtures thereof.

5. The thermally expandable composition according to claim 2, wherein the endothermic chemical blowing agent contains a mixture of 2 or more bicarbonates.

6. The thermally expandable composition according to claim 2, wherein the solid polycarboxylic acids are selected from organic di-, tri-, tetra-acids and combinations thereof.

7. The thermally expandable composition according to claim 2, wherein the solid polycarboxylic acids comprise hydroxyl-functionalized and/or unsaturated di-, tri-, tetra- or polycarboxylic acids.

8. The thermally expandable composition according to claim 2, wherein the endothermic chemical blowing agent is selected from citric acid, tartaric acid, malic acid, fumaric acid, maleic acid, salts of citric acid, tartaric acid, malic acid, fumaric acid, maleic acid and mixtures thereof.

9. The thermally expandable composition according to claim 1, wherein the endothermic chemical blowing agent contains a mixture of sodium bicarbonate with citric acid and/or citrate.

10. The thermally expandable composition according to claim 1, wherein the composition contains the endothermic chemical blowing agent in an amount of 0.1 to 35% by weight, based on the total composition.

11. The thermally expandable composition according to claim 1, wherein the composition contains less than 0.05% by weight of exothermic blowing agents.

12. The thermally expandable composition according to claim 1, wherein upon activation the blowing agents do not produce formamide, formaldehyde or nitrosamines.

13. The thermally expandable composition according to claim 2, wherein the endothermic chemical blowing agent contains a bicarbonate of formula XHCO.sub.3, wherein X is a cation.

14. A method for sealing and filling cavities in components and shaped bodies, for strengthening or reinforcing components, or for bonding movable components comprising steps of introducing into a cavity of a component or shaped body or applying to a surface of a component, a thermally expandable composition comprising at least one endothermic chemical blowing agent selected from bicarbonates, solid polycarboxylic acids, solid polycarboxylic acid salts and mixtures thereof; at least one reactive binder selected from the group consisting of epoxies, rubbers, peroxide-crosslinkable polymers and combinations thereof; and at least one of a curing agent and an accelerator; wherein the thermally expandable composition contains less than 0.05% by weight of azodicarbonamide and 4,4-oxybis (benzenesulfonyl hydrazide); and activating the composition such that the thermally expandable composition expands and seals, fills, strengthens or reinforces the component.

15. The method according to claim 14 for sealing and filling cavities in components, for strengthening or reinforcing components, wherein a shaped body comprising the thermally expandable composition is introduced into a component, and then is heated to a temperature above 110 C. such that the thermally expandable composition expands and seals, fills, strengthens or reinforces the component.

16. The thermally expandable composition according to claim 1, wherein the thermally expandable composition comprises calcium oxide.

17. The thermally expandable composition according to claim 1, wherein the thermally expandable composition comprises guanidines, substituted guanidines, melamine resins, guanamine derivatives, cyclic tertiary amines, aromatic amines and/or mixtures thereof.

Description

EXEMPLARY EMBODIMENTS

(1) General Test Procedure/Preparation of the Formulations:

(2) In order to prepare the thermally expandable preparations according to the invention, the solid polymers contained therein were processed at RT in a kneader with fillers until a homogeneous dough was obtained, heating to up to 150 C. if necessary. Liquid polymers and/or resins and further fillers, carbon black, stabilizers and plasticizers were then successively added and kneading was continued until the formulation was smooth.

(3) At below 60 C., all the reactive components such as for example accelerators, peroxides, sulfur, activators and catalysts, zinc oxide, calcium oxide and blowing agents were then added and the mixture was slowly kneaded until the adhesive had been homogeneously mixed. In order to adjust the viscosity, further plasticizers or liquid polymers may be added and kneaded in towards the end of the preparation step.

(4) FOG Analysis

(5) The FOG analysis is a thermodesorption analysis of organic emissions to characterize non-metallic motor vehicle materials according to VDA 278. During this analysis, the volatile substance content of a very small material sample is determined at 120 C. by means of GC Headspace. The organic compounds are determined individually and the content thereof in the total emission is ascertained. Identification takes place using a mass spectrometer.

(6) Determination of the Expansion

(7) In order to determine the expansion, test specimens having the dimensions 40 mm40 mm4 mm were cut from the prepared panels of example formulations A, C and D and were placed in a circulating air oven that was heated to the temperatures specified in the tables (heat-up time approximately 7 to 10 min), and the test specimens were then left at this temperature for the length of time specified in the tables. The expansion at 180 C. corresponds to the ideal conditions that are achieved in the context of curing in vehicle construction. The expansion at 160 C. simulates the conditions of under-cure, and the expansion at 200 C. simulates the conditions of over-cure.

(8) Pumpable products consisting of example formulations B are applied in line form to an aluminum sheet (24 cm).

(9) The degree of expansion was determined by means of the water displacement method according to the formula

(10) $\mathrm{Expansion}=\frac{m2-m1}{m1}100$ m1=mass of the test specimen in the original state in deionized water m2=mass of the test specimen after curing in deionized water
Odor Evaluation

(11) To evaluate the odor of the formulations, test specimens were cured for 25 min. at 180 C. and were stored at RT for 24 h. The test specimen is selected such that approximately 50 cm.sup.3 of sample material exists after expansion.

(12) For test purposes, the specimen is placed in a 1 l glass and the latter is stored in a tightly closed manner at 80 C. for 2 h. After removal from temperature storage, the test vessel is cooled to a test temperature of around 60 C. before at least 3 people independently evaluate the odor according to the following assessment:

(13) 1=imperceptible

(14) 2=perceptible, not obtrusive

(15) 3=clearly perceptible but not yet obtrusive

(16) 4=obtrusive

(17) 5=very obtrusive

(18) 6=unbearable

(19) The arithmetic mean of the individual tests is specified.

(20) Aging Test According to VDA 621-415

(21) The aging test according to VDA 621-415 describes an artificial aging method for adhesive bonds which is standardized in the automobile industry. 24 h salt spray according to DIN EN ISO 9227-NSS (505 g/l NaCl, 352 C.) +4 d condensation/alternating climate according to DIN EN ISO 6270-2 (8 h, 403 C. at 100% relative humidity+16 h, room temperature 18-28 C.) +2 d room temperature 18-28 C. according to DIN 50014/ISO 554 =7 d=1 cycle

(22) TABLE-US-00001 TABLE 1 Example formulation A (solid elastomer, sulfur-crosslinking) Recipe 1A Recipe 2A Recipe 3A according according according Substance name/ Comparative Comparative to the to the to the group (generic name) recipe 1A recipe 2A invention invention invention SIS copolymer (20% 11.5 11.5 11.5 11.5 11.5 styrene content, MFI 4 g/10 min (190 C., 2.16 kg), Tg 13 C.) SIS copolymer (20% 18.5 18.5 18.5 18.5 18.5 styrene content, MFI 5 g/10 min (190 C., 2.16 kg), Tg 8 C.) Ethylene/vinyl acetate 12.5 12.5 12.5 12.5 12.5 copolymer (28% VA content, MFI 400 g/10 min (190 C., 2.16 kg)) Talc (BET 3.5 g/m.sup.2, 32 29.7 29.7 29.7 29.7 2-20 m) (filler) Aliphatic hydrocarbon 8 8 8 8 8 resin (softening point 97-103 C.) Diisononyl phthalate 8 8 8 8 8 (phthalate plasticizer) Zinc oxide (activator for 2 2 2 2 2 vulcanization) 4-Methylphenyl, 1 1 1 1 1 reaction product with dicyclopentadiene and isobutylene (melting point 115 C.) (antioxidant) Carbon black 0.3 0.3 0.3 0.3 0.3 Sulfur (vulcanizing 0.4 0.4 0.4 0.4 0.4 agent) Benzothiazyl-2- 0.4 0.4 0.4 0.4 0.4 dicyclohexylsulfenamide (accelerator from the sulfenamide class) TETRAMETHYL 1.2 1.2 1.2 1.2 1.2 THIURAMDISULFIDE (accelerator from the thiuram class) DIBENZOTHIAZYL 0.4 0.4 0.4 0.4 0.4 DISULFIDE (accelerator from the thiazyl sulfide class) Activated 2.3 0 0 0 azodicarbonamide (gas yield 220 ml/g, decomposition temp. 205-213 C.) (exothermic blowing agent) Diphenyloxide-4,4- 4.6 0 0 0 disulfohydrazide (exothermic blowing agent) Sodium hydrogen 4.6 carbonate (endothermic blowing agent) Mixture of sodium 4.6 hydrogen carbonate/ citric acid/citrate (endothermic blowing agent) Sodium hydrogen 4.6 carbonate (endothermic blowing agent) Urea (activator for 1.5 1.5 1.5 1.5 1.5 accelerator) TOTAL 100 100 100 100 100 FOG [g/g] according to 4030 4070 2480 2219 VDA 278 Expansion [%] 15 min @ 160 C. 552 391 377 342 304 25 min @ 180 C. 596 302 455 380 346 40 min @ 200 C. 589 36 473 408 367 Odor note 1-6 4 2 3 3 2 Aging 10 cycles VDA 100% cf 100% cf 100% cf 100% cf 100% cf 621-415, galvanized zinc, oiling: 3 g/m.sup.2 Fuchs Anticorit PL 3802-39S Foam structure, optical small pores very large medium to small pores large pores evaluation pores, bubbly large pores

(23) TABLE-US-00002 TABLE 2 Example formulation B (standard rubber base, sulfur-crosslinking) Recipe 1B Recipe 2B Recipe 3B Recipe 4B according according according according Substance name/group Comparative to the to the to the to the (generic name) recipe 1B invention invention invention invention Cis-1,4-polybutadiene solid 7.80 7.80 7.80 7.80 7.80 rubber (Mooney viscosity ML 1 + 4, 100 C., 47 MU, 96% cis-1,4) Liquid vinyl-1,2- 2.20 2.20 2.20 2.20 2.20 polybutadiene (Mn 1800, viscosity 400-700 dPas (35 C.), vinyl-1,2 45-55%) Polybutadiene with active 1.30 1.30 1.30 1.30 1.30 carboxyl anhydride groups, Mn 1000, acid content 68-80 mgKOH/g, viscosity 1500-6000 dPas 25 C.) Liquid cis-1,4-polybutadiene 24.48 24.48 24.48 24.48 24.48 (Mn 2600 g/mol, viscosity 700-800 mPas (20 C.), cis- 1,4 75%) Liquid cis-1,4-polybutadiene 3.00 3.00 3.00 3.00 3.00 with active carboxyl anhydride groups (Mn 1800-2400 g/mol, viscosity 6000-9000 mPas (20 C.), acid content 70-90 mgKOH/g) Coated chalk 18.80 18.80 18.80 18.80 18.80 Zinc oxide 1.50 1.50 1.50 1.50 1.50 Chalk (filler) 32.60 31.70 31.70 31.70 31.70 Calcium oxide 2.50 2.50 2.50 2.50 2.50 Sulfur (vulcanizing agent) 2.50 2.50 2.50 2.50 2.50 DIBENZOTHIAZYL 1.00 1.00 1.00 1.00 1.00 DISULFIDE (accelerator from the thiazyl sulfide class) Azodicarbonamide (gas 1.00 yield approx. 220 ml/g) (exothermic blowing agent) Sodium hydrogen carbonate 2.00 (endothermic blowing agent) Mixture of sodium hydrogen 2.00 carbonate/citric acid/ citrate (endothermic blowing agent) Sodium hydrogen carbonate 2.00 (endothermic blowing agent) Sodium hydrogen carbonate 2.00 (endothermic blowing agent) Benzenesulfinic acid Zn salt 0.10 (activator for azodicarbonamide) Physical blowing agent 0.62 0.62 0.62 0.62 0.62 (methylbutane in acrylonitrile/methacrylonitrile copolymer, particle size 38-44 m, start temperature 110-120 C.) 4-Methylphenol, reaction 0.30 0.30 0.30 0.30 0.30 product with dicyclopentadiene and isobutylene (melting point 115 C.) (antioxidant) Carbon black 0.30 0.30 0.30 0.30 0.30 Total 100.00 100.00 100.00 100.00 100.00 Expansion [%] 20 min @ 140 C. 32 76 60 59 59 15 min @ 160 C. 87 162 130 154 169 25 min @ 180 C. 114 104 119 106 108 40 min @ 200 C. 178 98 113 105 111 Odor note 1-6 5 3.5 3.5 4 4 Foam structure, optical small pores small pores small pores small pores small pores evaluation

(24) TABLE-US-00003 TABLE 3 Example formulation C (EVA-based, peroxide-crosslinking) Recipe 1C Recipe 2C Recipe 3C Recipe 4C Substance name/ according to according to according to according to group (generic Comparative the the the the name) recipe 1C invention invention invention invention Ethylene/vinyl 19.77 17.77 17.77 17.77 17.77 acetate copolymer (38-42% VA content, MFI 3 g/10 min (190 C., 2.16 kg)) Ethylene/vinyl 13.18 12.18 12.18 12.18 12.18 acetate copolymer (28% VA content, MFI 0.7 g/10 min (190 C., 2.16 kg)) Ethylene/vinyl 39.54 36.75 36.75 36.75 36.75 acetate copolymer (27.2-28.8% VA content, MFI 5.3-6.7 g/ 10 min (190 C., 2.16 kg)) Carbon black 1.37 1.37 1.37 1.37 1.37 Mixture of saturated 1.32 1.32 1.32 1.32 1.32 C16-C18 fatty acids Polyethylene (MFI 10.97 9.96 9.96 9.96 9.96 0.3 g/10 min (190 C., 2.16 kg), density 0.93 g/cm.sup.3) 4-Methylphenyl, 0.90 0.90 0.90 0.90 0.90 reaction product with dicyclopentadiene and isobutylene (melting point 115 C.) (antioxidant) Activated 7.22 azodicarbonamide (gas yield 160-180 ml/g, decomposition temp. 142-154 C.) (exothermic blowing agent) Sodium hydrogen 14.00 carbonate (endothermic blowing agent) Mixture of sodium 14 hydrogen carbonate/ citric acid/citrate (endothermic blowing agent) Sodium hydrogen 14 carbonate (endothermic blowing agent) Sodium hydrogen 14 carbonate (endothermic blowing agent) Dicumyl peroxide on 4.35 4.35 4.35 4.35 4.35 chalk (content 38-42%, active oxygen content 2.2-2.5%) (peroxide crosslinker) 1,1-Di-(tert- 1.40 1.40 1.40 1.40 1.40 butylperoxy)-3,3,5- trimethylcyclohexane (content 39-41%, active oxygen content 10.6%) (peroxide crosslinker) 100.00 100.00 100.00 100.00 100.00 Expansion [%] 20 min @ 140 C. 12 14 49 19 18 15 min @ 160 C. 1058 356 160 231 350 25 min @ 180 C. 1017 365 244 328 416 40 min @ 200 C. 1089 349 320 334 259 Odor note 1-6 3 3 3 3 2 Foam structure, large pores small pores small pores small pores medium to optical evaluation large pores

(25) TABLE-US-00004 TABLE 4 Example formulation D (EVA-based, peroxide-crosslinking) Recipe Recipe Recipe Recipe Recipe 1D 2D 3D 4D 5D Substance name/ according according according according according group (generic Comparative to the to the to the to the to the name) recipe 1D invention invention invention invention invention Ethylene/vinyl 84.00 acetate copolymer (18-19.5% VA content, 2-5 g/ 10 min at 190 C./ 2.16 kg, melting point 85-89 C.) Ethylene/vinyl 39.55 39.66 acetate copolymer (18% VA content, MFI 1.7 g/10 min (190 C., 2.16 kg)) Ethylene/vinyl 72.6 acetate/methacrylic acid terpolymer (28% VA content, MFI 4.5-7.5 g/ 10 min (190 C., 2.16 kg)) Vinyl/butyl 40 76.05 39.66 acrylate copolymer (30% butyl acrylate, MFI 4.5-7.5 g/10 min (190 C., 2.16 kg)) Ethylene/N-butyl 72 acrylate/glycidyl methacrylate terpolymer (melting point 72 C., MFI 12 g/10 min (190 C., 2.16 kg)) Randomized 7 7 ethylene/acrylic acid ester/glycidyl methacrylate terpolymer (24% methyl acrylate, MFI 6 g/10 min (190 C., 2.16 kg)) LDPE (low density 4.99 v polyethylene Talc (filler) 3.26 Benzenesulfinic 0.40 acid Zn salt (activator for azodicarbonamide) Trimethylolpropane 1.60 1.00 1.00 trimethacrylate (co-crosslinker) Di-(tert- 1.00 butylperoxy- isopropyl)benzene (40% on chalk/silicic acid) (peroxide crosslinker) Di-tert-butyl- 1.25 1.25 0.66 1,1,4,4- tetramethylbut-2- in-1,4-ylene diperoxide on chalk (content 45%) (peroxide crosslinker) Dibenzoyl 0.7 1.2 peroxide on chalk (content 45%) (peroxide crosslinker) Bis-(3,3-bis-(4- 0.12 0.2 0.2 0.3 0.3 0.2 hydroxy-3-tert- butylphenyl)- butanoic acid) glycol ester (antioxidant) Diphenyloxide- 1.00 4,4- disulfohydrazide (decomposition temperature 140-160 C., gas yield 130-140 ml/g) (exothermic blowing agent) Azodicarbonamide 3.61 (gas yield approx. 220 ml/g) (exothermic blowing agent) Sodium hydrogen 3 carbonate (gas yield 130 ml/g) (endothermic blowing agent) Sodium hydrogen 3.72 carbonate (gas yield 130 ml/g) (endothermic blowing agent) Sodium hydrogen 2.5 3 3 carbonate (gas yield 165 ml/g) (endothermic blowing agent) Sodium hydrogen 15 16 16 carbonate in polyethylene (active substance content 60%, gas yield 90-100 ml/g) (endothermic blowing agent) Citric acid 16 20 (endothermic blowing agent) TOTAL 100.00 100.00 100.00 100.00 100.00 100.00 15 min @ 160 C. 462 541 652 697 561 556 25 min @ 180 C. 580 673 908 548 535 658 40 min @ 200 C. 484 683 809 504 533 562 Odor note 1-6 3 2 2 2 2 2 Foam structure, small pores small small pores small small small optical evaluation pores pores pores pores

(26) The tests according to the invention show a reduced emission behavior, as can be demonstrated with reference to comparative series A. At the same time, the results in terms of the expansion behavior were able to be improved or at least kept constant relative to the conventional blowing agents. The examples according to the invention show an improvement in terms of odor, with the aging behavior and pore structure being comparable between the comparative examples and the examples according to the invention.