Agents for reworkable epoxy resins

Abstract

Compounds of formula I, uses as crosslinking agents or curing agents thereof, and resins obtained by using the compounds as crosslinking agents.

Claims

1. An epoxy resin composition comprising: an epoxy resin; and a polyamine curing agent comprising a compound having Formula (I): ##STR00023## wherein: m is 2, 1, or 0; n is 2, 3, or 4; the sum of m and n is 4; each R.sup.1 is independently hydrogen, alkyl, cycloalkyl, heterocycle, heterocycloalkyl, alkenyl, cycloalkenyl, aryl, heteroaryl, alkyloxyalkyl, or alkynyl; each A is independently unsubstituted ethylene, propylene, isopropylene, butylene, iso-butylene, hexylene, ethylene-oxy-ethylene, ethylene-amino-ethylene, ##STR00024## each R.sup.2 is independently NHR.sup.3, wherein each R.sup.3 is independently hydrogen, alkyl, aminoalkyl, alkylaminoalkyl, cycloalkyl, heterocycle, alkenyl, aryl, or heteroaryl; or, every two O-A-R.sup.2 groups, together with the carbon atom to which they are attached to, can independently form an dioxanyl ring with no less than 4 ring members and one or more of the ring carbon atom(s), other than the carbon atom to which the two O-A-R.sup.2 groups are attached, are independently substituted with one or more independent amino group or aminoalkyl wherein each amino is independently a primary or secondary amino group.

2. An adhesive material comprising the epoxy resin composition of claim 1.

3. A coating material comprising the epoxy resin composition of claim 1.

4. A composite matrix material comprising the epoxy resin composition of claim 1.

5. The composition of claim 1, wherein R.sup.1 is independently hydrogen, alkyl, or aryl.

6. The composition of claim 1, wherein R.sup.1 is independently hydrogen or methyl.

7. The composition of claim 1, wherein the compound is: ##STR00025## ##STR00026## ##STR00027## ##STR00028## ##STR00029## ##STR00030##

8. The composition of claim 1, wherein the compound is: ##STR00031##

9. A composite comprising a cross-linked epoxy resin in contact with a substrate, wherein the cross-linked polymer comprises cleavable links derived from a cross-linking agent comprising a compound having Formula (I): ##STR00032## wherein: m is 2, 1, or 0; n is 2, 3, or 4; the sum of m and n is 4; each R.sup.1 is independently hydrogen, alkyl, cycloalkyl, heterocycle, heterocycloalkyl, alkenyl, cycloalkenyl, aryl, heteroaryl, alkyloxyalkyl, or alkynyl; each A is independently unsubstituted ethylene, propylene, isopropylene, butylene, iso-butylene, hexylene, ethylene-oxy-ethylene, ethylene-amino-ethylene, ##STR00033## each R.sup.2 is independently NHR.sup.3, wherein each R.sup.3 is independently hydrogen, alkyl, aminoalkyl, alkylaminoalkyl, cycloalkyl, heterocycle, alkenyl, aryl, or heteroaryl; or, every two O-A-R.sup.2 groups, together with the carbon atom to which they are attached to, can independently form an dioxanyl ring with no less than 4 ring members and one or more of the ring carbon atom(s), other than the carbon atom to which the two O-A-R.sup.2 groups are attached, are independently substituted with one or more independent amino group or aminoalkyl wherein each amino is independently a primary or secondary amino group.

10. The composite of claim 9, wherein R.sup.1 is independently hydrogen, alkyl, or aryl.

11. The composite of claim 9, wherein R.sup.1 is independently hydrogen or methyl.

12. The composite of claim 9, wherein the compound is: ##STR00034## ##STR00035## ##STR00036## ##STR00037## ##STR00038## ##STR00039##

13. The composite of claim 9, wherein the compound is: ##STR00040##

14. A cross-linked epoxy matrix derived from an epoxy resin and cross-linking group derived from a polyamine curing agent having the structure of Formula (I): ##STR00041## wherein: m is 2, 1, or 0; n is 2, 3, or 4; the sum of m and n is 4; each R.sup.1 is independently hydrogen, alkyl, cycloalkyl, heterocycle, heterocycloalkyl, alkenyl, cycloalkenyl, aryl, heteroaryl, alkyloxyalkyl, or alkynyl; each A is independently unsubstituted ethylene, propylene, isopropylene, butylene, iso-butylene, hexylene, ethylene-oxy-ethylene, ethylene-amino-ethylene, ##STR00042## each R.sup.2 is independently NHR.sup.3, wherein each R.sup.3 is independently hydrogen, alkyl, aminoalkyl, alkylaminoalkyl, cycloalkyl, heterocycle, alkenyl, aryl, or heteroaryl; or, every two O-A-R.sup.2 groups, together with the carbon atom to which they are attached to, can independently form an dioxanyl ring with no less than 4 ring members and one or more of the ring carbon atom(s), other than the carbon atom to which the two O-A-R.sup.2 groups are attached, are independently substituted with one or more independent amino group or aminoalkyl wherein each amino is independently a primary or secondary amino group.

15. The epoxy matrix of claim 14, wherein R.sup.1 is independently hydrogen, alkyl, or aryl.

16. The epoxy matrix of claim 14, wherein R.sup.1 is independently hydrogen or methyl.

17. The epoxy matrix of claim 14, wherein the compound is: ##STR00043## ##STR00044## ##STR00045## ##STR00046## ##STR00047## ##STR00048## ##STR00049## ##STR00050## ##STR00051## ##STR00052##

18. The epoxy matrix of claim 14, wherein the compound is: ##STR00053##

19. A method of recycling a cross-linked polymer, comprising: (a) degrading the cross-linked polymer under an acidic condition into smaller, soluble molecules and/or polymers; (b) and removing the degraded the cross-linked polymer, wherein the cross-linked polymer comprises cleavable links derived from an acid-labile cross-linking agent comprising a compound selected from: ##STR00054## ##STR00055## ##STR00056## ##STR00057## ##STR00058## ##STR00059##

20. The method of claim 19, wherein R.sup.1 is independently hydrogen, alkyl, or aryl.

21. The method of claim 19, wherein R.sup.1 is independently hydrogen or methyl.

22. The method of claim 19, wherein the compound is: ##STR00060##

Description

DETAILED DESCRIPTION OF THE INVENTION

(1) The present invention provides compounds of Formula I:

(2) ##STR00015##
wherein m is 2, 1, or 0; n is 2, 3, or 4; the sum of m and n is 4; each R.sup.1 is independently hydrogen, alkyl, cycloalkyl, heterocycle, heterocycloalkyl, alkenyl, cycloalkenyl, aryl, heteroaryl, alkoxyalkyl, or alkynyl; each A is independently alkyl, alkylene, alkenene, alkylene-hetero-alkylene, alkylene-heterocyclo-alkylene, carbonyl, thiocarbonyl, alkylene-oxy-alkylene, 1,4-alkyl substituted piperazine, aryl, or heteroaryl. Each R.sup.2 is independently NHR.sup.3, heterocycloalkyl, or SH, wherein each R.sup.3 is independently hydrogen, alkyl, cylcoalkyl, heterocycle, alkenyl, aryl, or heteroaryl. Alternatively, every two O-A-R.sup.2 groups, together with the carbon atom to which they are attached to, can independently form an dioxanyl ring with no less than 4 ring members and one or more of the ring carbon atom(s), other than the carbon atom to which the two O-A-R.sup.2 groups are attached, are independently substituted with one or more independent amino group or aminoalkyl wherein each amino is independently a primary or secondary amino group.

(3) These compounds include di-, tri-, or polyvalent cleavable links between the core and the nucleophilic end groups. As such, they can be used as hardeners or cross-linkers for curing thermosetting polymers such as epoxies (due to the terminal nucleophilic groups), but can also enable the breakdown or degradation of the cured resins (due to the cleavable bonds). These compounds can include the functionality of formal, ketal, acetal, orthoester, or orthocarbonate and they tend to be acid labile. See below the general structural schemes of such compounds.

(4) ##STR00016##

(5) Although synthesis of tertiary aminoorthoesters has been described in the art (see, e.g., U.S. Pat. No. 3,786,029), the synthesis of aminoorthoesters that contain primary- or secondary-amines has not been previously reported. As such, another aspect of this invention provides methods for making the compounds of Formula I (e.g., aminoorthoseters that contain primary- or secondary amines, thiolorthoseters, and thiolorthocarbonates).

(6) The present invention also encompasses the use of the compounds of Formula I as amino- or thiol hardeners for curing epoxy resins to give degradable cross-linked resins. U.S. Pat. No. 5,932,682 disclosed the use of ketal containing diepoxides cured with anhydrides, for reworkable epoxy systems. However, the curing of ketal, orthoester or orthocarboante-based epoxy resins with amine- or thiol-based hardeners and their mild acid degradation has hitherto not been disclosed. As such, another aspect of this invention is that it provides a method for curing ketal, acetal, orthoester, or orthocarbonate resins of the general types shown below, with amine- or thiol-based hardeners of this invention used for the production of reworkable epoxy compositions. Resins cured in such a way are also within the scope of this invention.

(7) ##STR00017##

(8) The use of orthoester and orthocarbonate linkage is also suitable for thiol-based hardeners. Thiol hardeners serve as the basis for fast curing systems, commonly with set times of less than 15 minutes.

(9) The present invention includes, as non-limiting examples, fully acid recyclable hardeners, acid recyclable hardener-resin compositions, ultra-fast setting thiol-based reworkable epoxies, reworkable epoxies, wash-away epoxies, reworkable ultra clear epoxies, reworkable epoxy pastes, and reworkable epoxy putties, and other such compositions. Such compositions can be degraded in acidic conditions, especially weakly acidic conditions. The present invention further includes, as non-limiting examples, recyclable hardener-resin compositions that are resistant to degradation under weekly acidic conditions, and can only be readily dissolved or reworked under more strongly acidic conditions. The advantages of the present invention include, without limitation, the ability to form easily acid-degradable epoxy compositions using compounds of Formula I where the ability to remove, reverse or otherwise recycle the epoxy composition or the component(s) in contact with the epoxy compositions is desired. For example, a composition provided by the present invention can be used to seat an electronic component in an epoxy coating and then that component can be recovered, removed or recycled at a later time by removing the epoxy composition under conditions that do not damage the component or mother structure. As another example, a composition provided by the present invention that can only be dissolved under more strongly acidic conditions can be used to manufacture carbon fiber composites, which at a later time the carbon fiber can be recovered by removing the epoxy matrix under conditions that do not significantly adversely affect the properties of the carbon fiber. As another example, a composition provided by the present invention that can only be dissolved under more strongly acidic conditions can be used in commercial or residential construction applications such as in epoxy flooring or epoxy countertops, which at a later time can be recycled. As another example, the thiol orthoesters of this invention could be used with an existing epoxy resin to produce a fast curing epoxy system whose excess could be easily wiped away by, e.g., an unskilled user needing to bond two components together in their home, office, place of work, automobile, nautical craft, etc. A further advantage of the present invention is the ability to recycle devices that contain high-value material components that can be reused or reutilized. For example, indium or indium-tin-oxide can be recovered from thin-films held together in devices typically employing epoxy adhesives, such as cellular telephones, portable television screens, and the like.

(10) The compounds of Formula I can be used as hardeners in epoxy compositions to achieve cured compositions that can be degraded in acidic conditions, ranging from weakly to strongly acidic conditions. Such a strategy is attractive because it allows common resins to be combined with novel hardeners for the formation of epoxies with a variety of mechanical, adhesive, electronic, thermal etc. properties, while enabling them to be disassembled, dissolved, or reworked. The development of epoxy systems employing acid-labile hardeners where the cured resin can rapidly disassemble under mildly acidic conditions while maintaining mechanical and adhesive integrity in the ambient environment, as described in this invention, are unknown in the prior art. As such, the present invention also provides: (1) the use of orthoesters to produce hardener components of epoxy compositions that enable useful degradation properties including degradation under mildly acidic conditions; (2) the use of formal, ketal, acetal moieties, suitable derivatives, and analogs as hardener component in epoxy compositions; (3) the use of orthocarbonate moieties, suitable derivatives, and analogs as hardener component in epoxy compositions, (4) the use of ketal, acetal, orthoester, or orthocarbonate based epoxy resins with non degradable polyamine or polythiol hardener components to provide compositions that enable useful degradation properties including degradation under mildly acidic conditions.

(11) Set forth below are examples of the compounds of this invention and methods of making and using them. They are intended to be illustrative and not to be constructed as limiting the scope of this invention in any way.

Example 1

Synthesis of Amino Ketal

(12) ##STR00018##

(13) N-(6-hydroxyhexyl)pthalimide (50 g, 202 mmol), 2,2-dimethoxypropane (21 g, 202 mmol), and a catalytic amount of p-toluene sulfonic acid monohydrate (192.3 mg, 1 mmol, 0.005 equiv.) were placed in 200 mL of toluene in a 500 mL Round Bottom Flask equipped with a 25 mL Dean Stark apparatus. The reaction was heated to reflux and the Dean Stark column emptied every 5 hours. After 20 hours, the reaction mixture was cooled to ambient temperature and concentrated under reduced pressure. The resulting crude residue was dissolved in 50 mL of THF and then 80% hydrazine hydrate (80 g, 1280 mmol) was added and the reaction mixture was heated to reflux again. After 10 hours, the reaction was cooled to room temperature, filtered and concentrated under reduced pressure. The resulting crude oil was dissolved in dichloromethane, the solution washed with water and brine, dried with Na.sub.2SO.sub.4, and then concentrated under reduced pressure to give 20 g of the title compound (72% yield).

(14) .sup.1H NMR (CDCl.sub.3, 400 MHz): 3.39 (t, J=6.8 Hz, 4H), 2.68 (t, J=6.8 Hz, 4H), 1.56-1.51 (m, 4H), 1.47-1.42 (m, 4H), 1.34 (bs, 14H), 1.20 (bs, 4H). .sup.13C NMR (CDCl.sub.3, 100 MHz):99.5, 60.6, 42.2, 33.8, 30.1, 26.8, 26.3, 25.0.

Example 2

Synthesis of Amino Orthoesters

(15) ##STR00019##

(16) N-(6-hydroxyhexyl)pthalimide (140 g, 567 mmol), triethyl orthoacetate (31 g, 195 mmol), and a catalytic amount of p-toluene sulfonic acid monohydrate (31.9 mg, 0.168 mmol, 0.0009 equiv.) were placed in 700 mL of cyclohexane. The reaction mix was heated to reflux and the evolved ethanol removed via distillation of the cyclohexane/ethanol azeotrope (vapor temperature 60-80.5 C.). After the reaction vapor temperature reached 80.5 C., the reaction mixture was heated for additional 30 minutes. Subsequently, the solution was cooled to ambient temperature and the solvent removed under reduced pressure. The resulting crude residue was dissolved in 800 mL of THF and then 80% hydrazine hydrate (222.3 g, 3.8 mol) was added and the reaction heated to reflux. After 10 hours, the reaction was cooled to room temperature, filtered, and concentrated under reduced pressure. The resulting crude oil was dissolved in dichloromethane, the solution washed with water and brine, dried with Na.sub.2SO.sub.4, and then concentrated under reduced pressure to give 36 g of the title compound (49% yield).

(17) .sup.1H NMR (CDCl.sub.3, 400 MHz): 3.45 (t, J=6.8 Hz, 6H), 2.68 (t, J=6.8 Hz, 6H), 1.60-1.54 (m, 6H), 1.49-1.29 (m, 27H); .sup.13C NMR (CDCl.sub.3, 100 MHz): 114.0, 61.8, 42.0, 33.6, 29.6, 26.7, 26.1, 20.1.

Example 3

Synthesis of Amino Orthocarbonates

(18) ##STR00020##

(19) N-(6-hydroxyhexyl)pthalimide (20 g, 80.8 mmol), tetraethyl orthocarbonate (4.13 g, 20 mmol), and a catalytic amount of p-toluene sulfonic acid monohydrate (3.4 mg, 0.0179 mmol, 0.0009 equiv.) were placed in 100 mL of cyclohexane. The reaction mix was heated to reflux and the evolved ethanol removed via distillation of the cyclohexane/ethanol azeotrope (vapor temperature 60 C.). After the reaction vapor temperature reached 80.5 C, the reaction was heated for an additional 30 min. Subsequently, the solution was cooled to ambient temperature and the solvent removed under reduced pressure. The resulting crude residue was dissolved in 50 mL of THF and then 80% hydrazine hydrate (36 g, 576 mmol) was added and the reaction heated to reflux. After 10 hours, the reaction was cooled to room temperature, filtered, and concentrated under reduced pressure. The resulting crude oil was dissolved in dichloromethane, the solution washed with water and brine, dried with Na.sub.2SO.sub.4, and then concentrated under reduced pressure to give 4.5 g of the title compound (47% yield).

(20) .sup.1H NMR (CDCl.sub.3, 400 MHz): 3.49 (t, J=6.8 Hz, 8H), 2.68 (t, J=6.8 Hz, 8H), 1.63-1.56 (m, 8H), 1.48-1.32 (m, 24H), 1.17 (s, 8H).

(21) .sup.13C NMR (CDCl.sub.3, 100 MHz): 119.5, 62.6, 42.1, 33.7, 29.2, 26.7, 26.1.

Example 4

Synthesis of Thiol Orthoseters

(22) ##STR00021##

(23) 6-Chlorohexan-1-ol (100 g, 735 mmol), triethyl orthoacetate (36 g, 204 mmol), and a catalytic amount of p-toluene sulfonic acid (38 mg, 0.221 mmol) were placed in 700 mL of cyclohexane. The reaction mix was heated to reflux and the evolved ethanol removed via distillation of the cyclohexane/ethanol azeotrope (vapor temperature 60-80.5 C.). After the reaction vapor temperature reached 80.5 C., the reaction mixture was heated for additional 60 minutes. Subsequently, the solution was cooled to ambient temperature and the solvent removed under reduced pressure. The resulting crude residue was dissolved in 1000 mL of DMF and then K.sub.2CO.sub.3 (191.6 g, 1.39 mol) was added. After stirring for 20 hours, the reaction solution was filtered, concentrated under reduced pressure, then water was added, extracted with DCM, washed with brine, dried over anhydrous Na.sub.2SO.sub.4, and then concentrated under reduced pressure. The resulting crude residue was dissolved in 144 mL of THF and 50% hydrazine hydrate (72 g, 0.72 mol) was added and the reaction was heated to 35 C. After 12 hours, the reaction was cooled to room temperature and concentrated under reduced pressure. The resulting crude oil was dissolved in dichloromethane, the solution washed with water and brine, dried with Na.sub.2SO.sub.4, and then concentrated under reduced pressure to give 32 g of the title compound (41.8% yield).

(24) .sup.1H NMR (CDCl.sub.3, 400 MHz): 1.34 (t, J=7.6 Hz), 1.36-1.43 (m), 1.43 (s), 2.52 (q, J.sub.av=7.4 Hz), 3.43 (t, J.sub.av6.6 Hz).

Example 5

Synthesis of Thiol Orthocarbonates

(25) ##STR00022##

(26) The mixture of S-6-hydroxyhexyl ethanethioate (20 g, 114 mmol), tetraethyl orthocarbonate (4.2 g, 21.9 mmol), and a catalytic amount of p-toluene sulfonic acid (8 mg, 0.047 mmol) was heated to 150 C. and the evolved ethanol removed via distillation (vapor temperature 35-78 C.). After the reaction, vapor temperature reached 78 C. and the reaction mixture was heated for additional 60 minutes. Subsequently, the solution was cooled to ambient temperature, K.sub.2CO.sub.3 (2 g, 14.5 mmol) was added and the solvent removed under reduced pressure. The resulting crude residue was dissolved in 300 mL of THF and 80% hydrazine hydrate (19 g, 0.304 mol) was added and the reaction was heated to 50 C. After 3 hours, the reaction was cooled to room temperature and concentrated under reduced pressure. The resulting crude oil was dissolved in dichloromethane, and the solution was washed with water and brine, dried with Na.sub.2SO.sub.4, and then concentrated under reduced pressure to give 6.5 g of the title compound (54.6% yield). .sup.1H NMR (CDCl.sub.3, 400 MHz): 1.34 (t, J.sub.av=7.8 Hz), 1.37-1.42 (m), 1.56-1.65 (m), 2.52 (q, J.sub.av=7.4), 3.49 (t, J=6.8 Hz).

Example 6

Curing of Bisphenol A Dyglycidyl Ether with Amine Hardeners

(27) Bisphenol A dyglycidyl ether [BPADGE] is a standard resin used in the epoxy industry. BPADGE (epoxide equivalent weight=180-182) was mixed with the different cleavamine hardeners and then dispensed in 53 mm circular aluminum pan. The samples were cured at 100 C. in the oven, and then the resin was removed from the pan.

Example 6a

(28) The same procedure as described immediately above was carried out with 100 parts BPADGA and 38 parts amino ketal from example 1 to give a hard tack-free solid.

Example 6B

(29) The same procedure as described immediately above was carried out with 100 parts BPADGA and 35 parts amino orthoester from example 2 to give a hard tack-free solid.

Example 6C

(30) The same procedure as described immediately above was carried out with 100 parts BPADGA and 33 parts amino orthocarbonante from example 3 to give a hard tack-free solid.

Example 7

Curing of Bisphenol A Dyglycidyl Ether with Amine Thiol Hardeners

(31) Different thiol hardeners were mixed with BPADGE (epoxide equivalent weight=185-192) and 2,4,6-tri(dimethylaminomethyl)phenol [TDMAP] was used as the accelerator. The samples were cured at ambient temperature in a plastic dish. Gelling of the formulation was apparent in less than one hour.

Example 7a

(32) The same procedure as described immediately above was carried out with 100 parts BPADGA, 75 parts thiol otrthoester from example 4 and 8 parts TDMAP to give a hard, tack-free solid.

Example 7B

(33) The same procedure as described immediately above was carried out with 100 parts BPADGA and 72 parts thiol orthocarbonate from example 5 and 8 parts TDMAP to give a hard, tack-free solid.

Example 8

Disassembly of BPADGE/CLEAVAMINE Resins

(34) The cured epoxy resins were placed in a solution of water/ethanol/acetic acid (50/45/5 percent respectively), but could also be placed in water/ethanol (50/50 percent respectively), at 50 C. After 12 h, the resins were examined. Samples 6A, 6B, and 6C had all completely dissolved in the 12-hour period in the acid solution, with 6D only remaining in small gel-like pieces. In drastic contrast, all of the resins remained as hard, tack free resins after the prolonged immersion in the non-acid solution, with no weight loss detected after immersion.

Example 9

(35) An example of the novel characteristics of this degradable epoxy was demonstrated. A porcelain teacup that had broken in two pieces was glued back together using a cleavamine-HT/BPADGE formulation. After curing, noticeable amounts of hard cured resin existed on surface surrounding the joint closure. After immersion of the teacup in a solution of 10% acetic in ethanol/water (1:1 mixture), the spilled-over resin dissolved or could be wiped from the surface, with the bonding of the joint remaining steadfast. The newly bonded joint could not be pulled apart by hand.

Example 10

(36) An example of the novel characteristics of this degradable epoxy was demonstrated. A quartz glass tube that had broken in two pieces was glued back together using a mercaptocleave-HQ/BPADGE formulation (as in example 7b). After curing, the hardened epoxy that spilled from the pressed joint was easily removed after the quartz tube had been immersed in a 1:1 mixture of ethanol and white vinegar for two hours. Any epoxy that did not dissolve was easily wiped from the quatz with a paper towel. The bonded joint remained intact after the immersion.

Other Embodiments

(37) The invention has been described above with the reference to specific examples and embodiments. It is understood that various modifications and additions can be made to the specific examples and embodiments disclosed without departing from the spirit of the invention, and all such modifications and additions are contemplated as being part of the present invention.