Activatable Polymer Composition Comprising At Least Two Carboxylic Acids as Blowing Agent

Abstract

The invention relates to a curable volume expandable polymer composition comprising an organic acid component, wherein the organic acid component comprises a first organic acid, a second organic acid, and optionally one or more additional organic acids; wherein said polymer composition, when being heated to an activation of expansion temperature above room temperature, undergoes volume expansion. When the organic acid component is heated to the activation of expansion temperature, the first organic acid and/or the second organic acid and/or the optionally present one or more additional organic acids decarboxylate and thus release carbon dioxide. The polymer composition traps the thus released carbon dioxide thereby causing the polymer composition to undergo volume expansion.

Claims

1: A curable volume expandable polymer composition comprising: an organic acid component, wherein the organic acid component comprises a first organic acid, and a second organic acid; wherein said polymer composition, when being heated to an activation of expansion temperature above room temperature, undergoes volume expansion due to decarboxylation of the first organic acid and/or the second organic acid and wherein the relative weight ratio of the first organic acid to the second organic acid is within the range of from 10:1 to 1:10.

2: The polymer composition according to claim 1, wherein the first organic acid and/or the second organic acid independently of one another have a molecular weight of at most 500 g/mol, or even at most 300 g/mol.

3: The polymer composition according to claim 1, including one or more additional organic acids having a molecular weight of at most 300 g/mol.

4: The polymer composition according to claim 1, wherein the content of the organic acid component is at least 0.1 wt.-%, relative to the total weight of the polymer composition.

5: The polymer composition according to claim 1, wherein the content of the organic acid component is at least 5.0 wt.-%, relative to the total weight of the polymer composition.

6: The polymer composition according to claim 1, wherein the content of the organic acid component is within the range of from 5.0 to 30 wt.-%, relative to the total weight of the polymer composition.

7: The polymer composition according to claim 2, wherein the content of the organic acid component is within the range of 107.5 wt.-%, or 105.0 wt.-%, or 102.5 wt.-%, or 12.510 wt.-%, or 12.57.5 wt.-%, or 12.55.0 wt.-%, or 12.52.5 wt.-%, or 1512.5 wt.-%, or 1510 wt.-%, or 157.5 wt.-%, or 155.0 wt.-%, or 152.5 wt.-%, or 17.512.5 wt.-%, or 17.510 wt.-%, or 17.57.5 wt.-%, or 17.55.0 wt.-%, or 17.52.5 wt.-%, or 2010 wt.-%, or 207.5 wt.-%, or 205.0 wt.-%, or 202.5 wt.-%, or 22.57.5 wt.-%, or 22.55.0 wt.-%, or 22.52.5 wt.-%, or 255.0 wt.-%, or 252.5 wt.-%, or 27.52.5 wt.-%, relative to the total weight of the polymer composition.

8: The polymer composition according to claim 1, wherein the organic acid component consists essentially of the first organic acid and the second organic acid.

9. (canceled)

10: The polymer composition according to claim 1, wherein the first organic acid and/or the second organic acid and/or optionally one or more additional organic acids independently of one another are hydrocarbons comprising no functional groups other than carboxylic acid groups (C02H), carbonyl groups (C(=0)-), hydroxyl groups (OH) and vinylogous carboxylic acid groups (C(=0)-CCOH).

11: The polymer composition according to claim 1, wherein the first organic acid is selected from (i) monocarboxylic acids, dicarboxylic acids, tricarboxylic acids, tetracarboxylic acids, hydroxycarboxylic acids, aminocarboxylic acids and ketocarboxylic acids; and/or (ii) saturated or unsaturated aliphatic carboxylic acids; and/or (iii) aliphatic carboxylic acids, cycloaliphatic carboxylic acids, heterocycloaliphatic carboxylic acids, aromatic carboxylic acids or heteroaromatic carboxylic acids.

12: The polymer composition according to claim 1, wherein the second organic acid is selected from (i) monocarboxylic acids, dicarboxylic acids, tricarboxylic acids, tetracarboxylic acids, hydroxycarboxylic acids, aminocarboxylic acids and ketocarboxylic acids; and/or (ii) saturated or unsaturated aliphatic carboxylic acids; and/or (iii) aliphatic carboxylic acids, cycloaliphatic carboxylic acids, heterocycloaliphatic carboxylic acids, aromatic carboxylic acids or heteroaromatic carboxylic acids.

13: The polymer composition according to claim 3, wherein the one or more additional organic acids independently of one another are selected from (i) monocarboxylic acids, dicarboxylic acids, tricarboxylic acids, tetracarboxylic acids, hydroxycarboxylic acids, and ketocarboxylic acids; and/or (ii) saturated or unsaturated aliphatic carboxylic acids; and/or (iii) aliphatic carboxylic acids, cycloaliphatic carboxylic acids, heterocycloaliphatic carboxylic acids, aromatic carboxylic acids or heteroaromatic carboxylic acids.

14: The polymer composition according to claim 3, wherein the first organic acid and/or the second organic acid and/or the one or more additional organic acids is a saturated or unsaturated aliphatic monocarboxylic acid, which may optionally comprise at least one carbonyl group and/or which may optionally comprise at least one hydroxyl group.

15: The polymer composition according to claim 14, wherein the first organic acid and/or the second organic acid and/or the one or more additional organic acids is an alpha-keto acid having the general formula R<1>C(=0)-C02H, wherein R<1> means H, saturated or unsaturated C1-C8-alkyl, saturated or unsaturated C3-C8-cycloalkyl, saturated or unsaturated heterocycloalkyl, C6-C1o-aryl or C1-C9-heteroaryl.

16: The polymer composition according to claim 15, wherein the alpha-keto acid is glyoxylic acid or pyruvic acid.

17: The polymer composition according to claim 14, wherein the first organic acid and/or the second organic acid and/or the one or more additional organic acids is a beta-keto acid having the general formula R<2>C(=0)-CR<3>R<4>C02H, wherein R<2>, R<3> and R<4> independently of one another mean H, saturated or unsaturated C1-C8-alkyl, saturated or unsaturated C3-C8-cycloalkyl, saturated or unsaturated heterocycloalkyl, C6-C1o-aryl or C1-C9-heteroaryl.

18: The polymer composition according to claim 17, wherein the beta-keto acid is acetoacetic acid.

19: The polymer composition according to claim 14, wherein the saturated or unsaturated aliphatic monocarboxylic acid is selected from the group consisting of formic acid, acetic acid, propionic acid, butyric acid, valeric acid, caproic acid, enanthic acid, caprylic acid, pelargonic acid, capric acid, undecylic acid, lauric acid, tridecylic acid, myristic acid, pentadecylic acid, palmitic acid, margaric acid, stearic acid, nonadecylic acid, arachidic acid, acrylic acid, methacrylic acid, lactic acid, glycolic acid, pyruvic acid, and acetoacetic acid.

20-92. (canceled)

93: The polymer composition according to claim 1, which comprises (i) the organic acid component; (ii) an olefin acrylate copolymer, preferably selected from (E/MA), (E/EA), (E/PA), (E/BA), (E/MMA), (E/EMA), (E/PMA), (E/BMA), and mixtures thereof; (iii) optionally, an olefin acrylate terpolymer, preferably selected from (E/MA/GA), (E/EA/GA), (E/PA/GA), (E/BA/GA), (E/MMA/GA), (E/EMA/GA), (E/PMA/GA), (E/BMA/GA), (E/MA/GMA), (E/EA/GMA), (E/PA/GMA), (E/BA/GMA), (E/MMA/GMA), (E/EMA/GMA), (E/PMA/GMA), (E/BMA/GMA), and mixtures thereof; (iv) an olefin vinylacetate copolymer, preferably selected from (E/VA), (E/VA/MAH), and mixtures thereof; (v) optionally, a tackifyer, preferably an aliphatic tackifying resin; and (vi) optionally, one or more fillers.

94-110. (canceled)

111: The polymer composition according to claim 1, wherein the composition: (i) is dry to the touch at room temperature; (ii) becomes adhesive at elevated temperature. (iii) is heat curable; and (iv) is cured when being heated to an activation of cure temperature.

Description

EXAMPLES

[0257] The invention is further illustrated by the following examples which are not to be construed as limiting its scope.

Example 1Volume Expansion

[0258] Volume expansion is measured using this method: [0259] Cut in the material at least 3 samples with 25253 mm dimensions [0260] Determine uncured material volume V1 by obtaining its weight in air and water using a specific gravity balance. [0261] Record results [0262] Bake uncured material as specified (30 minutes at 165 C.) [0263] Determine material volume V2 by obtaining its weight in air and water using a specific gravity balance [0264] Record results [0265] Obtain % volume change using equation: [(V.sub.2V.sub.1)/V.sub.1]100 [0266] Calculate the average of volume expansion of the three samples

[0267] A standard formulation comprising the following components is prepared:

TABLE-US-00003 component weight content Lotryl copolymer of ethylene 66 g 22.00 wt.-% 35BA40 and butyl acrylate (E/BA) Lotader random terpolymer of 18 g 6.00 wt.-% AX8900 ethylene, acrylic ester and glycidyl methacrylate (E/MA/GMA) Evatane copolymer of ethylene 69 g 23.00 wt.-% 28-05 and vinylacetate (E/VA) Escorene copolymer of ethylene 27 g 9.00 wt.-% MVO2514 and vinylacetate (E/VA) Omya calcium carbonate 14.4 g 4.80 wt.-% Calibrite Escorez aliphatic tackifying 45 g 15.00 wt.-% 5690 resin Raven 410 carbon black 0.6 g 0.20 wt.-%

[0268] Thus, the standard formulation contains neither blowing agents nor blowing agent accelerators nor free radical polymerization initiators.

[0269] In an alternative embodiment, the random terpolymer of ethylene, acrylic ester and glycidyl methacrylate (E/MA/GMA) (e.g. Lotader AX8900) can be replaced by a copolymer of ethylene and vinylacetate grafted with maleic anhydride (ENA/MAH) (e.g. Fusabond MC190D) and a peroxide, optionally together with a coagent.

[0270] Aliquots of 240 g of the above standard formulation are mixed with various organic acids in various amounts. All components are blended and heated to a temperature of 80 C. at which no volume expansion occurs. The samples are allowed to cool to room temperature. The initial volume of each sample is determined.

[0271] All samples are heated to 165 C. thereby inducing volume expansion. The samples are kept at a temperature of 165 C. until no additional volume expansion can be observed. The expanded samples are allowed to cool to room temperature. The final volume of each sample is determined.

[0272] In the following table, the composition of the tested examples as well as the relative volume expansion upon heating (calculated in vol.-% as [final volumeinitial volume].Math.100/initial volume) are summarized:

Comparative Examples (Single Carboxylic Acid)

[0273]

TABLE-US-00004 C-1 C-2 C-3 C-4 C-5 C-6 C-7 C-8 C-9 valeric acid 5.00 wt.-% pyruvic acid 5.00 wt.-% ascorbic acid 15.00 wt.-% maleic acid 15.00 wt.-% glutaric acid 15.00 wt.-% malonic acid 15.00 wt.-% malic acid 15.00 wt.-% oxalic acid 15.00 wt.-% citric acid 15.00 wt.-% Volume Expansion 22 vol.-% 61 vol.-% 29 vol.-% 79 vol.-% 119 vol.-% 125 vol.-% 130 vol.-% 247 vol.-% 272 vol.-% 30 @ 165 C. 2 vol.-% 3 vol.-% 1 vol.-% 5 vol.-% 6 vol.-% 17 vol.-% 5 vol.-% 51 vol.-% 15 vol.-%

Inventive Examples (Mixture of 2 or 3 Carboxylic Acids)

[0274]

TABLE-US-00005 I-1 I-2 I-3 I-4 I-5 I-6 pyruvic acid 5.00 wt.-% 2.00 wt.-% ascorbic acid 2.00 wt.-% maleic acid 15.00 wt.-% malonic acid 5.00 wt.-% malic acid 2.00 wt.-% citric acid 15.00 wt.-% 15.00 wt.-% 15.00 wt.-% oxalic acid 15.00 wt.-% 15.00 wt.-% 5.00 wt.-% 3.00 wt.-% 3.00 wt.-% 3.00 wt.-% Volume Expansion (%) 596 vol.-% 645 vol.-% 712 vol.-% 505 vol.-% 526 vol.-% 556 vol.-% 30 @ 165 C. 17 vol.-% 33 vol.-% 41 vol.-% 15 vol.-% 21 vol.-% 3 vol.-%

[0275] It becomes clear from the above experimental data that the combinations of organic acids according to the invention (I-1 to I-6), under otherwise identical experimental conditions, provide higher volume expansions than one would expect based upon the comparative data for the individual single organic acids.

[0276] For example, the inventive combination I-1 of 5 wt.-% pyruvic acid and 15 wt.-% oxalic acid provides a volume expansion of 596 vol.-%, whereas that sum of the volume expansion of comparative example C-2 (5 wt.-% pyruvic acid alone, 61 vol.-%) and comparative example C-8 (15 wt.-% oxalic acid alone, 247 vol.-%) would indicate an expected volume expansion of only 308 vol.-% (61 vol.-%+247 vol.-%).

[0277] Likewise, the inventive combination I-2 of 5 wt.-% malonic acid and 15 wt.-% oxalic acid provides a volume expansion of 645 vol.-%, whereas that sum of the volume expansion of comparative example C-6 (15 wt.-% malonic acid alone, 125 vol.-%) and comparative example C-8 (15 wt.-% oxalic acid alone, 247 vol.-%) would indicate an expected volume expansion of less than 372 vol.-% (125 vol.-%+247 vol.-%), taking into account that the formulation of comparative example C-6 contains thrice the amount of malonic acid (15 wt.-%) contained in the formulation of inventive example I-2 (5 wt.-%).

Example 2Curing

[0278] The measurements are done using a planer plane rheometer. The measuring system has a diameter of 25 mm with a gap of 0.88 mm. A Normal force of 0.1 N and a strain of 1% amplitude with a frequency of 1 Hz are applied. The temperature varies between 70 C. and 165 C. with a rate of 20 C./min.

[0279] FIGS. 1 and 2 show the evolution of the storage modulus G and loss modulus G with the temperature. G and G curves have in both FIG. 2 intersections: The first intersection is at about 90 C. where the material is transformed from the solid state to the molten state (G is higher than G). The second intersection is at about 150 C. that is related to the gel point. At this point, the material has crosslinked and has the behavior of a solid.