Thermally expandable compositions comprising polysaccharide

Abstract

The present application relates to a thermally expandable composition containing at least one peroxide cross-linking polymer, at least one peroxide, at least one polysaccharide and at least one endothermic, chemical blowing agent; as well as to shaped bodies containing said composition and to a method for sealing and filling voids in components, for strengthening or reinforcing components, in particular hollow components, and for bonding mobile components using shaped bodies of this type.

Claims

1. A thermally expandable composition comprising: a. at least one peroxidically crosslinked polymer; b. at least one peroxide; c. at least one polysaccharide; and d. at least one endothermic chemical blowing agent; wherein the composition is free of exothermic blowing agents.

2. The thermally expandable composition according to claim 1, wherein the at least one peroxidically crosslinkable polymer a) is selected from styrene-butadiene block copolymers, styrene-isoprene block copolymers, ethylene-vinyl acetate copolymers, functionalized ethylene-vinyl acetate copolymers, functionalized ethylene-butyl acrylate copolymers, ethylene-propylene-diene copolymers, ethylene-methyl acrylate copolymers, ethylene-ethyl acrylate copolymers, ethylene-butyl acrylate copolymers, ethylene-(meth)acrylic acid copolymers, ethylene-2-ethylhexyl acrylate copolymers, ethylene-acryl ester copolymers and polyolefins.

3. The thermally expandable composition according to claim 2, wherein the at least one peroxidically crosslinked polymer a) is a copolymer selected from ethylene-vinyl acetate copolymers and functionalized ethylene-vinyl acetate copolymers.

4. The thermally expandable composition according to claim 1, wherein the at least one polysaccharide includes a starch and a cellulose.

5. The thermally expandable composition according to claim 1, wherein the at least one polysaccharide comprises more than one starch having a gelation temperature in a range of from 40 to 200 degrees C.

6. The thermally expandable composition according to claim 5, wherein the starch is a native potato starch and/or a chemically modified potato starch.

7. The thermally expandable composition according to claim 1, wherein the at least one endothermic chemical blowing agent contains at least one carboxylic acid or a salt thereof.

8. The thermally expandable composition according to claim 7, wherein the at least one carboxylic acid or a salt thereof comprises at least one solid, optionally functionalized, polycarboxylic acid or a salt thereof.

9. The thermally expandable composition according to claim 7, wherein the at least one carboxylic acid or a salt thereof is selected from solid, organic hydroxy-functionalized or unsaturated di-, tri-, tetra- or poly-carboxylic acids and salts thereof.

10. The thermally expandable composition according to claim 7, wherein the at least one carboxylic acid or a salt thereof is selected from citric acid, tartaric acid, malic acid, fumaric acid, maleic acid and salts thereof.

11. The thermally expandable composition according to claim 7, wherein the blowing agent contains at least one bicarbonate.

12. The thermally expandable composition according to claim 7, wherein the blowing agent contains at least one urea derivative of formula (I):
R1-NH—C(═X)—NR2R3  (I), wherein X represents O or S, R1, R2 and R3 independently represent H, substituted or unsubstituted alkyl, substituted or unsubstituted heteroalkyl, substituted or unsubstituted cycloalkyl, substituted or unsubstituted aryl or —C(O)—R4, wherein R4 represents H, substituted or unsubstituted alkyl.

13. The thermally expandable composition according to claim 12, wherein the urea derivative is selected from: urea, N,N-dimethyl urea, N,N-diethyl urea, N,N′-dimethyl urea, N,N′-diethyl urea, 4-chlorophenyl-N,N-dimethyl urea, 4,4′-methylene-bis-(phenyldimethyl urea), 1,1-dimethyl-3-(4-chlorophenyl)urea, 1,1-dimethyl-3-(3,4-dichlorophenyl)urea, isophorone bis(dimethyl urea), 1,1-dimethyl-3-phenyl urea, 1,1-dimethyl-3-(4-ethoxyphenyl)urea, 1,1′-(4-phenylene)-bis-(3,3-dimethyl urea), 1,1-dimethyl-3-(2-hydroxyphenyl)urea and 1,1-dimethyl-3-(3-chloro-4-methylphenyl)urea.

14. The thermally expandable composition according to claim 13, wherein the urea derivative is selected from: urea, N,N-dimethyl urea, N,N-diethyl urea, N,N′-dimethyl urea and N,N′-diethyl urea.

15. The thermally expandable composition according to claim 12, wherein R1, R2, and R3 independently represent H, substituted or unsubstituted alkyl, substituted or unsubstituted cycloalkyl, substituted or unsubstituted aryl or —C(O)—R4, wherein R4 represents H, substituted or unsubstituted alkyl.

16. The thermally expandable composition according to claim 1, wherein c) the at least one polysaccharide comprises two polysaccharides having different gelation temperatures.

17. A shaped body, wherein the shaped body comprises a thermally expandable composition according to claim 1.

18. A method of sealing and filling cavities in components, of reinforcing or stiffening components, of bonding movable components and combinations thereof comprising steps of: 1) applying a thermally expandable composition according to claim 1, optionally said thermally expandable composition being a shaped body, to an application site on a component or in a cavity of a component; and 2) subsequently heating the thermally expandable composition to a selected temperature for a period of time selected such that activation of the blowing agent is thereby induced causing expansion and cure of the thermally expandable composition.

19. The method according to claim 18 wherein the thermally expandable composition is present as the shaped body; step 1) comprises introducing the shaped body into the cavity of the component; and step 2) comprises heating to a temperature greater than 110° C., such that the thermally expandable composition expands and seals, fills, reinforces or stiffens the component.

20. The method according to claim 19 wherein in step 1) the application site is the cavity of the component and wherein the shaped body has a shape that is adapted to the cavity, such that in step 2) the thermally expandable composition expands and seals and/or fills the component thereby acoustically sealing the cavity and/or sealing the cavity from water and/or moisture.

21. A product comprising a component according to the method of claim 18 wherein said product is a vehicle, airplane, rail vehicle, household appliance, furniture, building, wall, partition or boat.

22. A thermally expandable composition comprising: a. at least one peroxidically crosslinked polymer; b. at least one peroxide; c. more than one polysaccharide; and d. endothermic chemical blowing agents present in an amount of 15 to 25 wt. % based on total weight of the composition.

23. The thermally expandable composition according to claim 22, wherein c) comprises two polysaccharides having different gelation temperatures; and d) the endothermic chemical blowing agents are selected from the group consisting of bicarbonates, carboxylic acids, urea derivatives and combinations thereof.

24. A thermally expandable composition comprising: a. at least one peroxidically crosslinked polymer; b. at least one peroxide; c. at least one polysaccharide; and d. chemical blowing agent consisting essentially of endothermic chemical blowing agents present in an amount of 12.1 to 15.9 wt. % based on total weight of the composition, and said endothermic chemical blowing agents are at least two selected from the group consisting of bicarbonates, carboxylic acids and urea derivatives.

Description

PRACTICAL EXAMPLES

(1) General Experimental Procedure/Preparation of the Formulations

(2) In order to prepare the thermally expandable preparations according to the invention, the contained polymers were processed together with fillers at room temperature in a kneader while being heated, if required, up to 150° C., so as to form a homogeneous dough. The further non-reactive components, such as fillers, carbon black, stabilizers and plasticizers, if present, were added one after the other and the formulation was kneaded some more until smooth.

(3) At below 70° C., all reactive components, such as accelerators, peroxides, activators and catalysts, and blowing agents were then added and slowly folded in until the adhesive was homogeneously mixed. The blowing agents were inserted in part as a masterbatch.

(4) Determination of Expansion:

(5) In order to determine the expansion, test pieces having dimensions of approx. 20 mm×20 mm×3 mm were cut from the finished sheets of the example formulations and were introduced into a convection oven, which was heated to the temperatures given in the tables (heating time approx. 7 to 10 min) and the test pieces were then left at this temperature for the period of time given in the tables (including the heating-up time). Expansion at 175° C. corresponds to the ideal conditions which are obtained during curing in vehicle construction. Expansion at 160° C. simulates the underbaking conditions, while expansion at 200° C. simulates the overbaking conditions.

(6) The extent of expansion [%] was determined by means of the water displacement method according to the formula

(7) $\mathrm{Expansion}=\frac{\left(m2-m1\right)}{m1}\times 100$
m1=mass of the test piece in the original state, in deionized water
m2=mass of the test piece after baking, in deionized water.
Determination of Adherence:

(8) In order to determine adherence, test pieces (produced in the same way as for determining expansion) were heated, on galvanized sheets, for 20 minutes at 160° C. in the convection oven. In order to test the adherence of the foamed shaped body, said shaped body is stored for 24 hours at room temperature after being taken out of the convection oven. The foamed shaped body is then mechanically pulled off the metal surface. The remaining residue of the shaped body on the metal surface is assessed and quantified in terms of the wetted surface (% cf).

(9) The foam structure is visually assessed in each case.

(10) In order to determine storability, the above tests are repeated after storage for 28 days at 40° C. and 80% relative humidity.

(11) By way of illustrating the comparison of the values before and after storage, the absolute difference (Ads.Math.Δ) and the relative retention of the expansion in % are given in the following table for the aforementioned conditions.

(12) In the table below, Comp. Formula 1 is a comparative formulation. Formula 1-7 are formulations according to the invention.

Example Formulation (EVA-Based, Peroxide-Crosslinking)

(13) TABLE-US-00001 Substance name/group Comp. Formula Formula Formula Formula Formula Formula Formula (generic name) Formula 1 1 2 3 4 5 6 7 EVA polymer 1 60.65 68.1 68.5 69.6 64.76 69.6 61.1 70.3 Terpolymer 1 10.00 10.8 10.5 10.8 10.33 10.8 16.8 10.0 Terpolymer 2 2.00 3 2.5 3 2.06 3 3 2.0 Citric acid 17.50 13 13 11.5 13.3 11.5 14 13.0 NaHCO.sub.3 3.50 — — — 2.6 — — — Talc 5.25 — — — 2.35 — — — Peroxide 1 0.20 — 0.5 — 0.2 — — 0.2 Peroxide 2 0.60 — 0.6 1.2 0.6 — 1.2 0.6 Peroxide 3 — 1.2 — — — 1.2 — — Antioxidant 0.30 0.3 0.3 0.3 0.3 0.3 0.3 0.3 Urea — 0.6 0.6 0.6 — 0.6 0.6 0.6 Starch 1 — 3 3 — 3 — 1.5 Starch 2 — — — — — 3 1.5 Starch 3 — — — 3 — — — Cellulose — — — — — — — 3.0 Carbon black — — 0.5 — 0.5 — — TOTAL 100 100 100 100 100 100 100 100 Expansion 20 min, 160° C. 527 551 517 490 462 484 530 561 25 min, 175° C. 667 652 624 552 543 562 662 649 40 min, 200° C. 990 770 752 655 715 647 772 733 Adherence 100% 100% 100% 100% 100% 100% 100% 100% cf cf cf cf cf cf cf cf Foam structure fine- fine- fine- fine- fine- fine- fine- fine- pored pored pored pored pored pored pored pored After storage (28d @ 40° C., 80% RH): Expansion 20 min, 160° C. 301 443 437 420 411 376 391 451 25 min, 175° C. 384 608 560 482 464 432 486 472 40 min, 200° C. 412 536 583 503 551 474 537 497 Adherence  80% 100% 100% 100% 100% 100% 100% 100% cf cf cf cf cf cf cf cf Foam structure coarse- fine- fine- fine- fine- fine- fine- fine- pored pored pored pored pored pored pored pored Ads. Δ 20 min, 226 108 80 70 51 108 139 110 160° C. 40 min, 200° C. 578 234 169 152 164 173 235 236 Relative 57 80 85 86 89 78 74 80 retention 20 min, 160° C. Relative 42 70 78 77 77 73 70 68 retention 40 min, 200° C.
Components Used:

(14) TABLE-US-00002 EVA polymer 1 EVA, 16.5-19.5% VA content, melting point 82-90° C., MFI 1.5-6 g/10 min (190° C., 2.16 kg)) Terpolymer 1 Terpolymer (GMA/EBA), reactive ethylene terpolymer, 9 wt. % glycidyl methacrylate, 20 wt. % butyl acrylate, melting point 72° C., MFI 8 g/10 min (190° C., 2.16 kg)) Terpolymer 2 Ethylene-acrylic acid ester- glycidyl methacrylate terpolymer, methylacrylate content 24 wt. %, glycidyl methacrylate content 8 wt. %, melting point 65° C., MFI 6 g/10 min (190° C., 2.16 kg) Citric acid Particle size 10-15 μm NaHCO.sub.3 Particle size 10-15 μm Talc Talc Peroxide 1 Di-(2-tert.-butyl-peroxyisopropyl)benzene, 95% peroxide, 8.98% active substance content, half-life temperature 1 h = 146° C., t90 = 175° C. (rheometer t90 approximately 12 min) Peroxide 2 2,5-dimethyl-2,5-di-(tert.-butylperoxy)hexane, 45% peroxide, powder containing chalk, 4.96% active oxygen content, half-life temperature 1 h = 147° C., t90 = 175° C. (rheometer t90 approximately 12 min) Peroxide 3 Di-tert-butyl-3,3,5-trimethylcyclohexylidene diperoxide, 40% peroxide, powder containing chalk, 4.23% active oxygen content, half-life temperature 1 h = 117° C., t90 = 145° C. (rheometer t90 approximately 12 min) Antioxidant Bis[3,3-bis-(4′-hydroxy-3′-tert-butylphenyl)butanic acid]-glycol ester, molecular weight 794 g/mol, melting point 167-171° C. Starch 1 native potato starch, gelation temperature 55° C. Starch 2 phosphated hydroxypropyl-modified starch based on potato starch, gelation temperature 140° C. Starch 3 phosphated hydroxypropyl-modified starch based on potato starch, gelation temperature 65° C. Cellulose pure white cellulose powder and fibers, cellulose content ~99.5%, loss in drying 5%, sieve residue 32 μm sieve ~5% Carbon black Monarch 580

(15) The tests according to the invention demonstrate that fine foams having good levels of expansion can be obtained by using starch or cellulose, both immediately and after a relatively long period of storage. The results with regard to expansion behavior were able to be significantly improved after storage. The tests further show that the addition of starch makes it possible for adherence to be retained following storage.