Thermally expandable compositions comprising urea derivatives

Abstract

The present application relates to a thermally expandable composition containing at least one peroxide cross-linking polymer, at least one peroxide and at least one endothermic, chemical blowing agent, the blowing agent comprising at least one solid, optionally functionalized, polycarboxylic acid or the salt thereof and at least one urea derivative according to the formula (I) as defined herein; as well as shaped bodies containing the 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 cross-linking polymer; b) at least one peroxide; and c) at least one endothermic chemical blowing agent comprising at least one carboxylic acid or salt thereof, and at least one urea derivative of formula(I)
R.sub.1—NH—C(═X)—NR.sub.2R.sub.3  (I), wherein X denotes O or S; and R.sub.1, R.sub.2 and R.sub.3 independently denote H, unsubstituted alkyl, substituted or unsubstituted cycloalkyl, substituted or unsubstituted aryl or —C(O)—R.sub.4, where R.sub.4 denotes H or substituted or unsubstituted alkyl; wherein the thermally expandable composition comprises less than 0.1 wt. % of hydrogen carbonates and carbonates.

2. The thermally expandable composition according to claim 1, wherein the at least one peroxidically cross-linking 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-acrylic ester copolymers, and polyolefins.

3. The thermally expandable composition according to claim 2, wherein the at least one peroxidically cross-linking 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 3, wherein said at least one carboxylic acid comprises at least one solid, optionally functionalized, polycarboxylic acid or salt thereof.

5. The thermally expandable composition according to claim 4, wherein the at least one solid, optionally functionalized, polycarboxylic acid or the salt thereof is selected from hydroxy-functionalized or unsaturated dicarboxylic, tricarboxylic, tetracarboxylic or polycarboxylic acids and the salts thereof.

6. A thermally expandable composition, comprising: a) at least one peroxidically cross-linking polymer; b) at least one peroxide; and c) at least one endothermic chemical blowing agent comprising at least one carboxylic acid or salt thereof, and at least one urea derivative of formula (I)
R.sub.1—NH—C(═X)—NR.sub.2R.sub.3  (I), wherein in the urea derivatives of formula (I): (i) X denotes O; and (ii) R.sub.2 and R.sub.3 are selected from H and unsubstituted alkyl functional groups, optionally comprising C.sub.1-4 alkyl functional groups; and (iii) R.sub.1 is selected from H; unsubstituted alkyl functional groups, optionally comprising C.sub.1-4 alkyl functional groups; substituted or unsubstituted aryl functional groups, optionally comprising substituted or unsubstituted phenyl functional groups.

7. The thermally expandable composition according to claim 1, wherein the urea derivative is a bis-urea derivative according to formula (II):
H.sub.2C(phenyl-NH—C(═X)—NR.sub.2R.sub.3).sub.2  (II).

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

9. The thermally expandable composition according to claim 8, wherein the urea derivative is selected from: urea; N,N-dimethylurea; N,N-diethylurea; N,N′-dimethylurea and N,N′-diethylurea.

10. The thermally expandable composition according to claim 1, further comprising at least one tackifying resin.

11. The thermally expandable composition according to claim 10, wherein the at least one tackifying resin comprises at least one aromatic, aliphatic or cycloaliphatic hydrocarbon resin and/or modified or hydrogenated derivatives thereof.

12. The thermally expandable composition according to claim 10, wherein the at least one tackifying resin comprises at least one liquid C9/C10 aromatic hydrocarbon resin.

13. A shaped body comprising a thermally expandable composition according to claim 1.

14. 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 a site of application 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.

15. The method according to claim 14 wherein the thermally expandable composition is present as the shaped body and 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.

16. The method according to claim 15 wherein in step 1) the site of application 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.

17. A product comprising a component according to the method of claim 14 wherein said product is a vehicle, airplane, rail vehicle, household appliance, furniture, building, wall, partition or boat.

18. The thermally expandable composition of claim 1, wherein the at least one urea derivative of formula (I) and the at least one carboxylic acid or salt thereof is present at a ratio of 0.1:1 to 0.1:20.

19. The thermally expandable composition of claim 1, wherein the at least one urea derivative of formula (I) and the at least one carboxylic acid or salt thereof is present at a ratio of 0.1:2 to 0.1:10.

20. A thermally expandable composition, comprising: a) at least one peroxidically cross-linking polymer; b) at least one peroxide; and c) at least one endothermic chemical blowing agent, wherein the at least one endothermic chemical blowing agent comprises at least one solid, optionally functionalized, polycarboxylic acid or the salt thereof, and at least one urea derivative of formula (I)
R.sub.1—NH—C(═X)—NR.sub.2R.sub.3  (I), where X denotes O or S, R.sub.1, R.sub.2 and R.sub.3 independently denote H, substituted or unsubstituted alkyl, substituted or unsubstituted heteroalkyl, substituted or unsubstituted cycloalkyl, substituted or unsubstituted aryl or —C(O)—R4, where R4 denotes H or substituted or unsubstituted alkyl; wherein the weight ratio of the urea derivative to the solid polycarboxylic acid is from 0.1:1 to 0.1:20; and the thermally expandable composition comprises less than 0.1 wt. % of hydrogen carbonates and carbonates.

Description

EXEMPLARY EMBODIMENTS

(1) General Execution of Experiment/Production of the Formulations:

(2) To produce the thermally expandable preparations according to the invention, the polymers were processed with fillers at room temperature in a kneader or, where necessary, by applying heat up to 150° C., to form a homogeneous dough. The further non-reactive components such as fillers, carbon black, stabilizers and plasticizers, where present, were then successively added and kneading was continued until the formulation was smooth.

(3) All reactive components, such as accelerators, peroxides, activators and catalysts, zinc oxide, calcium oxide and blowing agents, were then added at less than 70° C. and slowly incorporated by way of kneading until the adhesive was homogeneously mixed. Some of the blowing agents were used in the form of a masterbatch.

(4) Determination of the Expansion

(5) To determine the expansion, test specimens having the approximate dimensions 20 mm×20 mm×3 mm were cut from the finished panels of the exemplary formulations and then inserted into a circulating air oven, which was heated to the temperatures listed in the tables (heating time approx. 7 to 10 min), and the test specimens were then left at this temperature for the period of time listed in in tables (including heating time). The expansion at 175° C. corresponds to the ideal conditions, which are achieved as part of curing in vehicle construction. The expansion at 160° C. simulates the under-baking conditions, while the expansion at 200° C. simulates the over-baking conditions.

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

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

(8) To determine the water absorption, test specimens having the approximate dimensions 20 mm×20 mm×3 mm were prepared analogously to the method for determining the expansion and then expanded and cured in the circulating air oven at predefined temperatures analogously to the method for determining the expansion, as indicated in the tables. Thereafter, the test specimens thus expanded were conditioned for 24 hours under normal climate (23° C., 50% relative humidity); the mass determination “m” was carried out directly after conditioning.

(9) For storage in a water bath, the test specimens were kept for 24 hours at 23° C. approximately 5 to 10 cm beneath the water surface in a container filled with water. After removal, the test specimens were drained, dried on the surface with an absorbent cloth and then weighed again m.sub.0. Thereafter, the test specimens were again stored for 24 hours under normal climate (23° C., 50% relative humidity), and weighed again m24.

(10) The water absorption [wt. %] was calculated according to the following equation:

(11) $\mathrm{Water}\mathrm{absorption}=\frac{m_i-m}{m}\times 100$
m: mass of the test specimen prior to storage in water in the dip bath
m.sub.i: mass of the test specimen after storage in water in the dip bath after the time i

(12) i=0: measurement directly after removal

(13) i=24: measurement after 24 hours under normal climate (23° C., 50% relative humidity)

(14) Exemplary formulations were made using as components:

(15) TABLE-US-00001 EVA polymer 1 EVA, 16.5 to 19.5% VA content, melting point 82 to 90° C., MFI 1.5 to 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-acrylate-glycidyl methacrylate terpolymer, methyl acrylate content 24 wt. %, glycidyl methacrylate content 8 wt. %, melting point 65° C., MFI 6 g/10 min (190° C., 2.16 kg If present, in Citric acid Particle size 10 to 15 μm the form of NaHCO.sub.3 Particle size 10 to 15 μm masterbatch Talc Talc EVA EVA (17 to 19% VA, melting point 85 to 89° C., MFI approx. 1.5 polymer 2 to 4 g/10 min, 190° C., 2.16 kg) Peroxide 1 Di-(2-tert-butylperoxyisopropyl)benzene, 95% peroxide, 8.98% active oxygen 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 with chalk, 4.96% active oxygen content, half-life temperature 1 h = 147° C., t90 = 175° C. (rheometer t90 Antioxidant Bis[3,3-bis-(4′-hydroxy-3′-tert-butylphenyl)butanoic acid] glycol ester, molecular weight 794 g/mol, melting point 167 to 171° C.

(16) In the table below, Comp. Formula 1, 2, 3 are comparative formulations. Inventive Formula 1, 2, 3 are formulations according to the invention.

(17) Exemplary Formulation (EVA-Based, Peroxide Cross-Linking)

(18) TABLE-US-00002 Substance designation/group Comp. Comp. Comp. Inventive Inventive Inventive (generic names) Formula 1 Formula 2 Formula 3 Formula 1 Formula 2 Formula 3 EVA polymer 1 51.70 51.90 51.70 51.10 63.35 63.35 Terpolymer 1 10.00 10.00 10.00 10.00 10.00 10.00 Terpolymer 2 2.00 2.00 2.00 2.00 2.00 2.00 Citric acid 17.50 17.50 21.00 21.00 17.50 17.50 NaHCO.sub.3 3.50 3.50 — — — — Talc 5.25 5.25 5.25 5.25 5.25 5.25 EVA polymer 2 8.75 8.75 8.75 8.75 — — Peroxide 1 — 0.20 — — — — Peroxide 2 1.00 0.60 1.00 1.00 1.00 1.00 Antioxidant 0.30 0.30 0.30 0.30 0.30 0.30 Urea — — — 0.60 0.60 — N-N-dimethylurea — — — — — 0.6 TOTAL 100 100 100 100 100 100 Expansion 20 min, 160° C. 511 527 168 849 679 825 25 min, 175° C. 656 667 845 1174 921 947 40 min, 200° C. 962 990 801 1093 1025 957 Foam structure Homo- Homo- Cracks in the Homo- Homo- Homo- geneous, fine geneous, surface geneous, geneous, geneous, fine fine fine fine Water absorption 24 dip; directly after removal in % 20 min, 160° C. 6.0 4.8 3.4 4.5 4.8 4.3 25 min, 175° C. 4.5 4.0 10.5 4.3 3.6 4.7 Theoretical gas 2520 2520 2520 2520 2100 2100 volume (% absolute) Effective gas yield 26 26 34 47 44 45 at 175° C. (% relative)

(19) The experiments according to the invention show that the use of urea derivatives and citric acid allows homogeneous, fine foams having low water absorption to be obtained. At the same time, the results with respect to the expansion behavior and the gas yield were able to be improved.

(20) TGA Measurements

(21) The following table shows TGA measurements of the pure substances and mixtures:

(22) TABLE-US-00003 Decomposition temperature Decomposition (° C.) rate Citric acid 170 Very slow Citric acid:urea (mass ratio 10:0.18) 150 Fast Citric acid:urea (mass ratio 10:0.36) 145 Fast Citric acid:urea (mass ratio 10:0.70) 135 Fast Citric acid:bicarbonate (mass ratio 5:1) 156 Slow

(23) These experiments show that, compared to the use of citric acid alone, the use of urea derivatives and citric acid allows the decomposition temperature to be lowered considerably (in all experiments by up to 35° C.), and that even comparatively small amounts show a significantly more pronounced reduction in the decomposition temperature than with the use of hydrogen carbonate. At the same time, the decomposition rate is considerably increased compared to the two references.

Exemplary Embodiment 4, in Particular for Manual Application

(24) As in the above exemplary embodiments, to produce the thermally expandable preparation 4 according to the invention, the polymers were processed with fillers at room temperature in a kneader or, where necessary, by applying heat up to 150° C., to form a homogeneous dough. The further non-reactive components such as fillers, carbon black, stabilizers and plasticizers, where present, were then successively added and kneading was continued until the formulation was smooth. All reactive components, such as accelerators, peroxides, activators and catalysts, zinc oxide, calcium oxide and blowing agents, were then added at less than 70° C. and slowly incorporated by way of kneading until the adhesive was homogeneously mixed. For this purpose, 12.5 parts of an ethylene-acrylate-glycidyl methacrylate terpolymer (methyl acrylate content 24 wt. %, glycidyl methacrylate content 8 wt. %, melting point 60° C., MFI 6 g/10 min (190° C., 2.16 kg)), 3.2 parts carbon black, 8.3 parts of a pre-crosslinked butyl rubber, 45.5 parts of an aromatic C9/C10 carbon resin that is liquid at room temperature, 2.3 parts zinc oxide, 0.6 parts urea, 16 parts citric acid, 3 parts dicumyl peroxide, 3 parts TMPTMA, 0.3 parts antioxidant, and 5.3 parts polyisobutylene were used.

(25) The resulting thermally expandable composition was flexible, tacky and stable at room temperature. Moreover, this composition was excellently suited for manual application. After foaming at 175° C. for 25 minutes, a fine homogeneous foam is obtained, which exhibits low water absorption. The resulting foam has particularly good adhesion on a wide variety of materials.