PROCESS FOR FUNCTIONALISING POLYMERS

Abstract

Process for functionalizing a polymer by treating said polymer at a temperature in the range 80-250 C. with a monoazide of the formula wherein m is 0 or 1, n is 0 or 1, n+m=1 or 2, X is a linear or branched, aliphatic or aromatic hydrocarbon moiety with 1-12 carbon atoms, optionally containing heteroatoms, R.sub.b is selected from the group consisting of hydrogen, linear and branched alkyl groups with 1-6 carbon atoms optionally substituted with O, S, P, Si, or N-containing functional groups, alkoxy groups with 1-6 carbon atoms, and halogens, and each R.sub.a is individually selected from hydrogen, linear or branched alkyl groups with 1-6 carbon atoms, or may form a saturated or unsaturated aliphatic or aromatic ring structure with at least one other R.sub.a.

##STR00001##

Claims

1. Process for functionalizing a polymer by treating said polymer at a temperature in the range 80-250 C. with a mono-azide of the formula ##STR00010## wherein Y is ##STR00011## m is 0 or 1, n is 0 or 1, n+m=1 or 2, X is a linear or branched, aliphatic or aromatic hydrocarbon moiety with 1-12 carbon atoms, optionally containing heteroatoms, R.sub.b is selected from the group consisting of hydrogen, linear and branched alkyl groups with 1-6 carbon atoms optionally substituted with O, S, P, Si, or N-containing functional groups, alkoxy groups with 1-6 carbon atoms, and halogens, and each R.sub.a is individually selected from hydrogen and linear or branched alkyl groups with 1-6 carbon atoms, or may form a saturated or unsaturated aliphatic or aromatic ring structure with at least one other R.sub.a.

2. Process according to claim 1, wherein the treated polymer is further reacted with a substance comprising one or more functionalities selected from amine, anhydride, alcohol, thiol, and aldehyde functionalities.

3. Process for crosslinking a polymer comprising the steps of: a. functionalizing said polymer according the process of claim 1 to form a functionalized polymer and b. reacting the functionalized polymer with a substance comprising two or more functionalities selected from amine, anhydride, alcohol, thiol, and aldehyde functionalities.

4. Process according to claim 1 wherein R.sub.b is hydrogen.

5. Process according to claim 1 wherein n+m=1.

6. Process according to claim 1 wherein each R.sub.a is hydrogen.

7. Process according to claim 6 wherein the mono-azide is succinimidobenzene sulfonylazide.

8. Process according to claim 1 wherein the substance has one or more amine functionalities.

9. Process according to claim 2 wherein the substance is selected from aminoacids, furfurylamine, polyether monoamines, and aminofunctional silanes.

10. Process according to claim 1 wherein the substance is selected from the group consisting of bis(hexamethylene)triamine, tris(2-aminoethyl)amine, 1,6-hexanediamine, isophorone diamine, 4-aminophenylether, maleinized polybutadienes, and polyethylene glycol.

11. Process according to claim 1 wherein the polymer is an elastomer.

12. Process according to claim 11 wherein the elastomer is selected from the group consisting of natural rubber (NR), styrene butadiene rubber (SBR), butadiene rubber (BR), butyl rubber (IIR), ethylene propylene copolymer elastomer (EPM), ethylene propylene diene terpolymer elastomer (EPDM), and ethylene vinylacetate copolymer (EVA).

13. Process according to claim 1 wherein the polymer is a polyolefin.

14. Process according to claim 13 wherein the polyolefin is selected from the group consisting of polyethylene, polypropylene, and polyolefin elastomers.

15. Process for de-crosslinking a polymer obtainable by the process of claim 1, wherein the crosslinked polymer is heated to a temperature higher than the temperature that was used for its crosslinking.

16. Process according to claim 15 wherein the crosslinked polymer is heated to a temperature in the range 180-250 C.

17. Process according to claim 15 wherein an aliphatic primary monofunctional amine is present during said heating.

Description

EXAMPLES

Example 1

Preparation of 4-(2,5-dioxopyrrolidin-1-yl)benzenesulfonyl azide (succinimidobenzene sulfonylazide)

[0065] 40.0 g 4-acetamidobenzenesulfonyl azide (ex Sigma Aldrich) was dissolved in 160 ml concentrated hydrochloric acid. The solution was stirred and heated to 80 C. for a maximum of 30 min. The clear solution was cooled to room temperature. At 70 C., a precipitate formed. The cooled mixture was added to ice-water (200 g) in order to dissolve all components and the resulting solution was added to 1000 gram of a 20% aqueous sodium carbonate solution. The product was extracted twice with 150 ml dichloromethane and the combined extracts were dried over sodium sulfate, filtered and concentrated in vacuum, and finally dried in air to remove all volatiles. This resulted in 30 gram of solid 4-aminobenzenesulfonyl azide:

##STR00007##

[0066] To a solution of 16.5 gram of 4-aminobenzenesulfonyl azide in 120 ml dichloromethane, 16.6 g succinic anhydride was added and the mixture was stirred for 3 hours at reflux temperature. The solids formed were isolated by filtration, rinsed with diethylether (60 ml) and dried at room temperature. This resulted in 24.7 g (99%) of 4-((4-(azidosulfonyl)phenyl)amino)-4-oxobutanoic acid as a white solid:

##STR00008##

[0067] To 24.5 gram of 4-((4-(azidosulfonyl)phenyl)amino)-4-oxobutanoic acid were added 160 g acetic anhydride and 0.8 g sodiumacetate. The resulting suspension was stirred and heated to 85 C. for 90 minutes. The clear solution was cooled to room temperature, added to 1000 g ice and stirred until solids were formed. The formed solids were isolated by filtration, twice washed with water and dried at room temperature. The resulting white/yellowish solid was 16.8 g (73% yield) 4-(2,5-dioxopyrrolidin-1-yl)benzenesulfonyl azide:

##STR00009##

Example 2

Modification of a Polymer

[0068] 50 grams of styrene-butadiene rubber (Buna VSL 4720-0 HM, styrene content 19.5%; vinyl content 47.5%, s-SBR), 1 gram of the succinimidobenzene sulfonylazide of Example 1, and 0.1 grams of tertbutyl-hydroquinone (TBHQ) were blended on a two-roll mill and intimately mixed. This blend was treated in an internal Banbury type mixer at 130-160 C. to allow grafting of the azide onto the s-SBR. During this grafting step the temperature of the mixture was allowed to rise to 160 C. within 20 minutes.

[0069] In an internal Banbury type mixer, the resulting compound was mixed with the components listed in Table 1. The silica (Ultrasil 7000 GR) was added to the rubber in two separate portions at 120 C. while allowing the temperature to rise to 150 C. for a maximum of 10 minutes.

[0070] The experiment was repeated with non-functionalized polymer, both with and without the further addition of Si69; a bifunctional, sulfur-containing organosilane ex-Evonik.

TABLE-US-00001 TABLE 1 Invention Comparative 1 Comparative 2 Functionalized polymer (g) 23.5 Non-functionalized 23.5 22.6 polymer (g) Ultrasil 7000 GR (g) 18.4 18.8 18.0 treated distillated aromatic 6.9 7.0 6.8 extract oil (Vivatec 500) Si69 (g) 2.0

[0071] After addition of the silica and other additives to the SBR, a curative package based on sulfur and sulfur accelerators was added to a portion of the silica-filled rubber on a two-rol-mill. The cure pack is displayed in Table 2.

TABLE-US-00002 TABLE 2 Invention Comparative 1 Comparative 2 Silica-filled rubber (g) 40 40 40 Insoluble sulfur (Crystex 0.25 0.25 0.24 HS OT10) (g) N-tert-butyl-2-benzothiazyl 0.25 0.25 0.24 sulfenamide (TBBS) (g) Tetrabenzyl 0.06 0.06 0.05 Thiuramdisulfide (TBzTD) (g) ZnO (g) 0.57 0.57 0.55 Stearic acid (g) 0.19 0.19 0.18

[0072] The resulting formulations were compared using the so-called Payne-effect-test, as described in The science and technology of rubber, 3.sup.rd edition, J. E. Mark, 2005, page 388. This test measures the Payne-effect of a filled system using a dynamic viscoelastic measurement. According to this experiment, a filled SBR rubber sample is subjected to periodic shear strain at 100 C. and 0.7 Hz. The strain is varied from 0.3% to 100%. The measurement is performed on a rubber analyzer, a Visco Elastograph ex Gottfert. This test measures the relationship between the sample's elasticity modulus and the subjected strain on the sample and thereby evaluates the interaction between the rubber and the filler by measuring the interaction between the filler particles. The filler-filler interaction is a good indication for the filler-rubber interaction: a high filler-filler interaction indicates a low filler-rubber interaction and vice versa.

[0073] Table 3 shows the results of the Payne test on uncured compounds. Comparative experiment 1 shows a high elasticity modulus (G) at low strain values and a fast breakdown to low G values at high strain. This breakdown indicates the breakdown of the filler network and shows a strong filler-filler interaction and a poor filler-rubber interaction. The experiment according to the invention shows a low G at low strain values and a gradual breakdown at high induced strain to G values higher than those of comparative experiment 1. This proofs that modification with an azide according to the present invention leads to lower filler-filler interaction and higher filler-rubber interaction. This is particularly inferred from the higher modulus values at high strain, which indicate the presence of bound rubber. Bound rubber is a portion of the rubber that is irreversibly bound to the filler particles.

TABLE-US-00003 TABLE 3 elasticity modulus (G) in kPa strain (%) Invention1 comp1 comp2 0.3 619 1758 458 0.4 671 1923 485 0.6 712 2031 497 0.7 740 2097 509 1.4 778 2143 495 2.8 780 1788 465 4.2 760 1302 430 5.6 731 981 398 7.0 697 804 373 11.2 575 535 312 14.0 515 449 281 27.9 327 244 186 41.9 242 175 144 55.8 192 140 117 69.8 161 119 99 83.7 137 106 84 100.0 118 99 72

[0074] Because the filler-rubber interaction of the cured compounds are of utmost importance for the ultimate properties of the tire, this interaction has also been evaluated after cure of the compounds for 30 minutes at 160 C. (see Table 4). The same conclusions as for the uncured compounds can be drawn: the filler-rubber interaction is much stronger in the case of the azide-modified s-SBR according to the present invention.

TABLE-US-00004 TABLE 4 elasticity modulus (G) in kPa strain (%) Invention1 comp1 0.3 2222 2982 0.4 2183 3010 0.6 2163 3046 0.7 2142 3077 1.4 2075 3153 2.8 1990 2506 4.2 1928 2175 5.6 1883 1979 7.0 1840 1857 11.2 1706 1677 14.0 1560 1473

[0075] The better filler-rubber interaction results in a better dispersion of the filler and improved mechanical properties. This can be observed in Table 5 where the mechanical properties are compared. These mechanical data have been recorded after full crosslinking of the silica-filled SBR compounds in a heated mould at 160 C. for 30 minutes with a dimension 1010 cm and a thickness of 2 mm, producing sheets with thickness of 2 mm. The mechanical properties were evaluated according to the following ISO standard: ISO 37:1995 Tensile stress-strain properties (tensile strength and elongation at break)

TABLE-US-00005 TABLE 5 max R 100 200 (200/ 300 500 N/mm2 % N/mm2 N/mm2 100)*2 N/mm2 N/mm2 IRHD Inv. 13.9 450 2.3 4.7 4.09 8.2 14.2 79.0 Comp1 10.0 496 2.6 4.01 3.08 5.78 9.87 99.0 Comp2 13.3 251 4.5 10.1 4.49 79.0

[0076] Table 5 clearly shows the effects of the polymer modification: increased tensile strength ( max) while maintaining proper elongation at break (R). The modulus values 100 and 200 indicate tensile properties at 100 and 200% elongation and allow calculation of the reinforcement parameter (200/100)*2. This reinforcement results from enhanced interaction between the elastomer and the filler, which is clearly stronger in the experiment according to the invention than in comparative experiment 1.

[0077] The better dispersion of the filler can also be observed by the hardness of the compound as indicated by the IRHD value. This hardening of the rubber after cure is measured by the IRHD hardness (International Rubber Hardness Degrees, ISO 48). Table 5 shows that with the same silica content (80 phr), the composition made by the process according to the invention has lower hardness after cure than the composition of comparative experiment 1. Comparative experiment 2, making use of a silane coupling agent, also shows the lower hardness but at the expense of a lower elongation at break. The higher hardness in comparative experiment 1 is probably due to so-called flocculation: agglomeration of the dispersed silica particles. This agglomeration leads to tough structures, adding to the increased hardness of the compound. Flocculation further makes processing of the silica compound more difficult, lowers the shelf life of the silica-filled compound, and leads to undesirable and unpredictable mechanical properties of the end product. The compound prepared in accordance with the present invention has no or only a marginal flocculation, which is probably due to the improved dispersion of the silica in the rubber, and due to the increased interaction between the rubber and the silica, resulting in a decreased filler-filler interaction.

Example 3

Filler Rubber Interaction

[0078] The functionalized rubber of Example 2 and the non-functionalized rubber were mixed with the components listed in Table 6 in an internal Banbury type mixer. Silica (Ultrasil 7000 GR) was added in two separate portions to the rubber at 120 C. while allowing the temperature to rise to 150 C. for a maximum of 10 minutes.

TABLE-US-00006 TABLE 6 Invention Comparative Functionalized polymer (g) 23 Non-functionalized polymer (g) 23 Ultrasil 7000 GR (g) 18 18.4 treated distillated aromatic 6.8 6.9 extract oil (Vivatec 500) (g) 3-aminopropyl-triethoxysilane 0.9 0.9 (APTS) (g)

[0079] The resulting compounds were cured as described in Example 2 and the filler-filler interaction was evaluated by observing the Payne effect after cure of the compounds for 30 minutes at 160 C. (see Table 7). The Payne effect and therefore the filler-filler interaction is more pronounced in the comparative composition, as seen from the increasing elastic modulus values at low strain. The composition according to the invention shows a much lower Payne effect indicating an improved filler-rubber and lower filler-filler interaction (i.e lower flocculation).

TABLE-US-00007 TABLE 7 elasticity modulus (G) in kPa strain (%) Invention Comparative 0.3 1247 2406 0.4 1270 2450 0.6 1284 2486 0.7 1289 2508 1.4 1299 2539 2.8 1279 2366 4.2 1256 2057 5.6 1235 1857 7.0 1178 1721 11.2 1116 1432 14.0 n.d. 1246

Example 4

Filler-Rubber Interaction

[0080] Example 2 was repeated, except that magnesium hydroxide was used instead of silica. Magnesium hydroxide is a very polar filler with a poor compatibility with elastomers. Table 8 shows the compound recipes. Magnesium hydroxide was mixed into the modified sSBR using in an internal Banbury type mixer operated at 130 C. for a maximum of 15 minutes while allowing the temperature to rise to 150 C.

TABLE-US-00008 TABLE 8 Invention Comparative total recipe (phr) BUNA VSL 4720-0-HM 100 100 Succinimidobenzene sulfonylazide 2 Tert-butyl hydroquinone (TBHQ) 0.2 Magnesium dihydroxide 200 200 (Magshield UF NB-10)

[0081] The resulting compound was tested for filler dispersion using the Payne test as described above. Table 9 shows the high elasticity modulus (G) as function of the imposed strain. This breakdown indicates the breakdown of the filler network and is clearly more significant in the comparative sample than in the sample of the invention. This indicates that magnesium hydroxide is more properly dispersed in the sample of the invention.

TABLE-US-00009 TABLE 9 elasticity modulus (G) in kPa strain (%) Invention Comparative 0.3 831 1410 0.4 879 1501 0.6 874 1478 0.7 867 1423 1.4 824 1084 2.8 761 792 4.2 717 656 5.6 683 569 7.0 655 513 11.2 584 405 14.0 540 357 27.9 386 235 41.9 292 176 55.8 230 140 69.8 188 117 83.7 156 100 100.0 129 82

Example 5

Crosslinking

[0082] 50 grams of EPDM were mixed with 1 g (2 phr) succinimido-benzene sulfonylazide and added to an internal mixer, preheated to 180 C., with a rotor speed of 50 rpm, for 12-15 minutes.

[0083] An amine (either bis(hexamethylene)triamine or 1,6-hexanediamine) was added to the functionalized EPDM using a temperature controlled two-roll mill, operating at a temperature between 20 and 40 C. Table 10 indicates the amount of amine functionalities in molar equivalents, i.e. the total number of primary amine groups originating from the amine relative to the total number of succinimide groups on the polymer.

[0084] Rheometer (Alpha Technologies MDR2000) data, recorded at 150 C. for 30 minutes, were obtained according to ISO 6502-1991 (Measurement of vulcanization characteristics with rotorless curemeters). The parameters indicated in the table are: t90 (time to 90% of maximal torque) and delta S. Delta S is an indicator for the ultimate crosslink density achieved.

TABLE-US-00010 TABLE 10 1 2 3 4 5 6 7 8 9 EPDM 100 100 100 100 100 100 100 100 100 Succinimido-ben- phr 2 2 2 2 2 2 2 2 2 zene sulfonylazide bis(hexametylene) Eq. 0 0.5 1 2 4 triamine 1,6-hexanediamine Eq. 0 0.5 1 2 4 Rheometer data: t90 min 22.8 15.2 14.6 13.3 7.1 17.3 16.8 19.1 10.7 delta S Nm 0.05 0.09 0.14 0.27 0.21 0.05 0.08 0.17 0.24

[0085] Table 10 shows that, for optimal crosslinking (highest delta S), more than 1 molar equivalent of amine-functional substance is desired. It also shows that there is an optimum in the amount of said substance. The latter is probably due to its action as chain stopper, if overdosed.

[0086] Table 10 further shows that the cure speed (t90) increases with the amine content. This is probably due to the fact that the crosslinking is base catalysed.

Example 6

De-crosslinking

[0087] The excess of the amine-functional substance, and the reversible character of the formed imide link, can be used to induce de-crosslinking to allow recycling of the crosslinked polymer. The following table shows that polymers crosslinked by the process of the present invention can be de-crosslinked by subjecting them to higher temperatures.

TABLE-US-00011 TABLE 11 Crosslinked polymer of Example 5, experiment: 3 4 9 bis(hexametylene) triamine Eq 1 2 1,6 hexanediamine Eq 4 crosslinking T [ C.] 150 150 150 crosslinking time [min] 30 30 30 de-crosslinking T [ C.] 200 200 200 de-crosslinking time [min] 60 60 60 de-crosslinking % [%] 19 54 80

[0088] The de-crosslinking was determined by rheometry on a Gotffert Visco Elastograph applying the following method: the torque difference after crosslinking at 150 C. for 30 minutes (see Table 11) was taken as a measure for the crosslink density. The same sample was then heated to 200 C. for 60 minutes to allow de-crosslinking, and the crosslinking was again measured at 150 C. to determine the residual torque in the rheometer. The relative drop in torque compared to the original torque is the amount of de-crosslinking.

[0089] These experiments show that, after heating at 200 C., up to 80% of the crosslinks disappeared.

[0090] There is no re-crosslinking when continuously heating at 150 C. after de-crosslinking, which indicates that the de-crosslinking seems to be the result of the reaction of excess amine with succinimide functionalities, thereby cleaving the reversible crosslinks, and forming end-functionalities (as a kind of chain stoppers which prevent re-crosslinking).