Thermally expandable formulations

Abstract

The present specification relates to thermally expandable formulations comprising (a) at least one peroxidically crosslinkable binary copolymer comprising at least one monomer unit selected from vinyl acetate, (meth)acrylic acids and derivatives thereof, the binary copolymer having a melt flow index of not more than 3 g/10 min, as determined in accordance with DIN EN ISO 1133 and with a test load of 2.16 kg and a test temperature of 190 C., (b) at least one peroxide, (c) at least one chemical blowing agent, and (d) at least one polymer based on one or more diene monomers, and (e) at least one terpolymer based on at least one first monomer selected from singly or multiply unsaturated hydrocarbons, and on at least one second monomer selected from (meth)acrylic acids and derivatives thereof. The thermally expandable formulations exhibit a high level of persistence during the heating of the material as required for curing/expansion.

Claims

1. A thermally expandable composition, comprising: (a) at least one peroxidically crosslinkable binary copolymer containing at least one monomer unit, selected from vinyl acetate, (meth)acrylic acids and derivatives thereof, wherein the binary copolymer has a melt flow index of no more than 3 g/10min, which is determined in accordance with DIN EN ISO 1133 with a test load of 2.16 kg and a test temperature of 190 C., (b) at least one peroxide, (c) at least one chemical blowing agent and (d) at least one polymer based on one or more diene monomers and (e) at least one terpolymer based on at least one first monomer selected from the mono-or polyunsaturated hydrocarbons, and at least one second monomer selected from the (meth)acrylic acids and derivatives thereof.

2. The thermally expandable composition according to claim 1, wherein the peroxidically crosslinkable polymer (a) is selected from ethylene-vinyl acetate copolymers, functionalized ethylene-vinyl acetate copolymers, ethylene-butyl acrylate copolymers, functionalized ethylene-butyl acrylate copolymers, ethylene-methyl acrylate copolymers, ethylene-ethyl acrylate copolymers, ethylene-(meth)acrylic acid copolymers and ethylene-2-ethylhexyl acrylate copolymers and mixtures thereof.

3. The thermally expandable composition according to claim 1, comprising as component (a) an ethylene-vinyl acetate copolymer.

4. The thermally expandable composition according to claim 1, comprising as component (c) a sulfonic acid hydrazide and/or azodicarbonamide.

5. The thermally expandable composition according to claim 1, wherein the polymer (d) is selected from polybutadiene homopolymers, polyisoprene homopolymers and butadiene-isoprene copolymers.

6. The thermally expandable composition according to claim 1, wherein the polymer (d) has a syndiotactic structure.

7. The thermally expandable composition according to claim 1, wherein the terpolymer (e) has a third monomer unit selected from styrene, glycidyl (meth)acrylic acid esters and maleic acid anhydride.

8. The thermally expandable composition according to claim 1, wherein the composition additionally contains at least one low-molecular multifunctional acrylate.

9. The thermally expandable composition according to claim 1, wherein the composition is essentially free of low-molecular multifunctional acrylates.

10. The thermally expandable composition according to claim 1, wherein the composition additionally contains at least one hydrocarbon resin.

11. The thermally expandable composition according to claim 1, comprising: 50 to 80% by weight of (a) the at least one peroxidically crosslinkable binary copolymer, 0.2 to 2% by weight of (b) the at least one peroxide, 5 to 18% by weight of (c) the at least one chemical blowing agent, and wherein the terpolymer (e) is selected from: styrene-butadiene-(meth)acrylate acids, styrene-butadiene-(meth)acrylic acid esters, ethylene-(meth)acrylic acid ester-glycidyl (meth)acrylic acid ester and/or ethylene-(meth)acrylic acid ester-maleic acid anhydrides.

12. A baffle part for sealing a cavity of a component, wherein the baffle part has a shape adapted to a cavity to be sealed and includes a thermally expandable composition according to claim 1.

13. The baffle part according to claim 12, wherein the baffle has at least one fastening element, which permits anchoring of the baffle in the cavity.

14. The baffle part according to claim 12, wherein the baffle does not have a carrier structure.

15. A method for sealing a cavity of a component wherein a baffle part according to claim 11 is introduced into a cavity and is then heated to a temperature above 130 C. such that the thermally expandable composition expands and seals the cavity.

Description

EXEMPLARY EMBODIMENTS

(1) 1. Preparation of the Formulations

(2) The raw materials Escorene Ultra UL 00218 CC 3 and RB 810 were first mixed in a kneading mixer at 130 C. according to the specifications in Table 1 until a homogeneous composition was obtained. Next, the other raw materials were added, one after the other, whereupon the mixture was cooled, so that the mixture was not heated to temperatures above 99 C.

(3) 2. Determination of the Expansion

(4) To determine the expansion, test bodies with the dimensions 240 mm240 mm6 mm were cut from the finished sheets and were then inserted into a circulating air oven, which was heated to the temperature listed in Table 1 (heating time approx. 7 to 10 min) and the test bodies where then left at this temperature for the period of time listed in Table 1. The expansion at 170 C. corresponds to the ideal conditions, which are achieved as part of curing in automotive engineering. Expansion at 150 C. simulates the underbaking conditions, while expansion at 190 C. simulates overbaking conditions.

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

(6) $\mathrm{Expansion}=\frac{\left(m2-m1\right)}{m1}100$ m1=mass of the test body in the original state, in deionized water m2=mass of the test body after baking, in deionized water
3. Determination of the Runoff Behavior

(7) To determine the runoff behavior, test bodies with the dimensions 10 mm10 mm4 mm were cut from finished sheets and then melted on a horizontal oiled metal plate (galvanized zinc, oiling with 3 g/m.sup.2) for 5 minutes at 100 C. in a circulating air oven. After cooling, the sheet metal prepared in this way was positioned vertically for 30 minutes at 175 C. in a circulating air oven, so that the product would expand. After removing the sheet metal from the oven and then cooling it, the runoff and/or slippage of the resulting foam was evaluated in comparison with the starting position.

(8) 4. Formulations and Measurement Results

(9) 4.1 Table Summary

(10) The quantitative amounts are understood to be percent by weight (wt %), unless otherwise indicated.

(11) TABLE-US-00001 TABLE 1 W1 W2 W3 W4 E1 E2 E3 Elvax 470A 71.1 69.8 73.9 71.4 59.4 58.9 Escorene Ultra 59.4 UL 00218 CC3 RB 810 2.8 5.00 2.8 5.0 5.0 5.0 Novares TL 100 10.5 10.8 10.4 10.4 10.4 10.5 Necires LF 220 10.5 Zinc oxide Activox 2.8 2.8 2.9 2.8 2.7 2.7 2.8 B Monarch 280 0.2 0.2 0.2 0.2 0.2 0.2 0.2 Perkadox BC 0.6 0.6 0.6 1.3 1.3 1.3 1.3 40BGR DD Celogen AZ 130 11.1 11.1 11.6 11.1 11.1 11.1 11.1 Lotader AX 8900 9.9 9.9 10.0 Sartomer SR 350 0.9 0.2 TOTAL 100 100 100 100 100 100 100 Expansion at 1500- 1500- 1200- 1200- 1800- 1600- 1400- 30 min @ 150 C. 1600 1600 1300 1300 1900 1700 1500 (%) Expansion at 1400- 1400- 200- 2000- 2500- 2100- 1950- 30 min @ 170 C. 1500 1500 300 2100 2600 2200 2000 (%) Expansion at 500- 750- 200- 800- 2400- 1800- 1700- 30 min @ 190 C. 600 800 300 900 2500 1900 1800 (%) Runoff behavior no heavy heavy heavy no no no runoff, runoff runoff runoff runoff, runoff, runoff, no heavy no no no slippage slippage slippage slippage slippage
4.2 Index of Commercial Products Used Celogen AZ 130 Azodicarbonamide (Safic Alcan) Elvax 470A Ethylene-vinyl acetate copolymer (approx. 18% by weight vinyl acetate content in the copolymer, melting point 89 C., melt flow index 0.7 g/10 min at 190 C. under a load of 2.16 kg) (DuPont) Escorene Ultra UL 00218 CC3 Ethylene-vinyl acetate copolymer (approx. 18% by weight vinyl acetate content in the copolymer, melting point 86 C., melt flow index 1.7 g/10 min at 190 C. and a load of 2.16 kg) (Exxon Mobil) Lotader AX 8900 Terpolymer of ethylene, acrylic acid ester and glycidyl methacrylate with a random arrangement (acrylic acid ester content 24% by weight, glycidyl methacrylate content 8% by weight) (Arkema) Monarch 280 Carbon black (degree of purity at least 99%) (Cabot) Necires LF 220 Hydrocarbon resin; polymerization product of cycloaliphatic and alkylaromatic monomers (Rttgers Chemicals) Novares TL 100 Hydrocarbon resin; polymerization product of unsaturated aromatic C.sub.9 to C.sub.10 hydrocarbons (Rttgers Chemicals) Perkadox BC 40BGR DD Dicumyl peroxide on a chalk-silica carrier approx. 40% by weight active substance content (Akzo Nobel) RB 810 Syndiotactic 1,2-polybutadiene homopolymer (melt flow index 3 g/10 min at 150 C. and a load of 2.16 kg; melting point 71 C.) (Japan Synthetic Rubber) Sartomer SR 350 Trimethylolpropane trimethacrylate (Sartomer) Zinc oxide Activox B Zinc oxide (degree of purity 99.9%) (NRC Nordmann Rassmann)
4.3 Evaluation

(12) The exact compositions of the various formulations as well as the results of the determination of the expansion behavior and the runoff behavior under various baking conditions were summarized in Table 1.

(13) Whereas the preparations E1 to E3 according to the invention have expansion values of 1400-2600% under the tested conditions, in particular advantageous values of 1950-2600% under standard conditions and overbaking conditions, the comparative formulations VV1-VV4 show a definitely lower expansion volume of 200-2100%. In particular in the case of overbaking conditions, expansion values of the comparative formulations VV1-VV4 of only max. 900% are achieved.

(14) With all the baking conditions tested, however, the expansion values of all the formulations E1-E3 according to the invention remain at a consistently high level of more than 1400%, while the comparative formulations W1-W4 have much greater fluctuations. Shrinkage of the comparative formulations is observed In particular with overbaking conditions (30 min at 190 C.), which can result in leakage in the application field.

(15) Based on the consistently high expansion values of the compositions E1-E3 according to the invention, it is possible to seal cavities completely and reliably by using these compositions.

(16) In addition, the results in Table 1 indicate that the compositions E1-E3 according to the invention do not run off, slip or sag during baking. In particular in the vertical position, the foams remain stable during the baking process. However, the comparative formulations VV2-VV4 exhibit great runoff and slippage during baking, so that in a vertical position, a cavity cannot be filled completely using these formulations. VV1 does not exhibit any runoff/slippage during baking, but the expansion is inadequate, in particular under overbaking conditions, because the foam shrinks unfavorably.