COMPOSITION FOR SILICONE RUBBER COMPOUNDS

Abstract

A curable composition comprising a polyorganosiloxane, a silane-based crosslinker, a heterocyclic azasilane and an organophosphonic acid, and a process for preparing the curable composition and its use is provided.

Claims

1.-15. (canceled)

16. A curable composition, comprising (a) a polyorganosiloxane of the formula HO(SiR.sup.lR.sup.mO).sub.oH, wherein each R.sup.l and R.sup.m independently represents an optionally substituted alkyl, alkenyl or alkynyl residue; an optionally substituted cycloaliphatic residue, aryl residue or aralkyl residue; or an optionally substituted heteroalicyclic residue or heteroaryl residue; and o is an integer from 5 to 5000, (b) a crosslinker of the formula Si(R).sub.m(R.sup.a).sub.4m, wherein each R independently represents an optionally substituted alkyl, alkenyl or alkynyl residue; an optionally substituted cycloaliphatic residue, aryl residue or aralkyl residue; or an optionally substituted heteroalicyclic residue or heteroaryl residue; m is an integer from 0 to 2; each R.sup.a is independently selected from the group consisting of (b1) a hydroxycarboxylic acid ester residue of the formula (I): ##STR00015## wherein each R.sup.b and R.sup.c independently of each other represents hydrogen; an optionally substituted alkyl, alkenyl or alkynyl residue; an optionally substituted cycloaliphatic residue, aryl residue or aralkyl residue; or an optionally substituted heteroalicyclic residue or heteroaryl residue; each R.sup.d independently represents an optionally substituted alkyl, alkenyl or alkynyl residue; an optionally substituted cycloaliphatic residue, aryl residue or aralkyl residue; or an optionally substituted heteroalicyclic residue or heteroaryl residue; each R.sup.e independently represents carbon; an optionally substituted cycloaliphatic residue, aryl residue or aralkyl residue; or an optionally substituted heteroalicyclic residue or heteroaryl residue; and n is an integer from 1 to 10, (b2) a hydroxycarboxamide residue of the formula (II): ##STR00016## wherein each R.sup.n, R.sup.o, R.sup.p and R.sup.q independently of one each other represents hydrogen; an optionally substituted alkyl, alkenyl or alkynyl residue; an optionally substituted cycloaliphatic residue, aryl residue or aralkyl residue; or an optionally substituted heteroalicyclic residue or heteroaryl residue; R.sup.r independently of each other represents carbon; an optionally substituted cycloaliphatic residue, aryl residue or aralkyl residue; or an optionally substituted heteroalicyclic residue or heteroaryl residue; and p is an integer from 1 to 10, (b3) a carboxylic acid residue OC(O)R.sup.f, (b4) an oxime residue ONCR.sup.gR.sup.h, and (b5) to a carboxylic acid amide residue N(R.sup.i)C(O)R.sup.j, wherein each R.sup.f, R.sup.g, R.sup.h, R.sup.i and R.sup.j independently of one each other represents hydrogen; an optionally substituted alkyl, alkenyl or alkynyl residue; an optionally substituted cycloaliphatic residue, aryl residue or aralkyl residue; or an optionally substituted heteroalicyclic residue or heteroaryl residue; (c) a heterocyclic azasilane in which N and Si are ring atoms and are directly linked to each other; and (d) an organophosphonic acid of the formula RPO(OH).sub.2, wherein R is an optionally substituted alkyl, alkenyl or alkynyl residue; an optionally substituted cycloaliphatic residue, aryl residue or aralkyl residue, or an optionally substituted heteroalicyclic residue or heteroaryl residue.

17. The composition according to claim 16, wherein the amount of organophosphonic acid, based on the total amount of crosslinker, is 0.3-30 mol %.

18. The composition according to claim 17, wherein the amount of organophosphonic acid, based on the total amount of crosslinker, is 1-10 mol %.

19. The composition according to claim 16, wherein the organophosphonic acid is an alkylphosphonic acid having 2 to 12 carbon atoms.

20. The composition according to claim 19, wherein the organophosphonic acid is an octylphosphonic acid.

21. The composition according to claim 16, further comprising: a metal catalyst.

22. The composition according to claim 21, wherein the metal catalyst does not contain tin.

23. The composition according to claim 21, wherein the metal of the metal catalyst is selected from the group consisting of Na, Zn, Sc, Nd, Ti, Zr, Hf, V, Fe, Pt, Cu, Ga, and Bi.

24. The composition according to claim 21, wherein the metal of the metal catalyst is selected from the group consisting of Zn, Ti, Zr, Hf, V, Fe and Bi.

25. The composition according to claim 21, wherein the metal of the metal catalyst is Zr.

26. The composition according to claim 21, wherein the metal catalyst is a metal siloxane of the formula
R*.sub.ASi.sub.BO.sub.CM.sub.D, wherein each R* is independently selected from the group consisting of optionally substituted C1 to C20 alkyl, optionally substituted C3 to C6 cycloalkyl, optionally substituted C2 to C20 alkenyl, optionally substituted C6 to C10 aryl, OH and O(C1 to C20 alkyl), M is the metal, A is an integer from 4 to 19, B is an integer from 4 to 10, C is an integer from 8 to 30, and D is an integer from 1 to 8.

27. The composition according to claim 26, wherein the metal siloxane is a polyhedral metal silsesquioxane.

28. The composition according to claim 27, wherein the metal siloxane is a polyhedral titanium and/or zirconium silsesquioxane.

29. The composition according to claim 16, wherein the crosslinker each R.sup.a is independently selected from the group consisting of (b1) a hydroxycarboxylic acid ester residue of formula (I) wherein the residues are as defined in claim 16, and (b2) a hydroxycarboxylic acid amide residue of formula (II) wherein the residues are as defined in claim 16.

30. The composition according to 16, wherein the crosslinker R.sup.a is a hydroxycarboxylic acid ester residue of the formula (I), and wherein n=1.

31. The composition according to claim 16, wherein the heterocyclic azasilane is a compound of the formula ##STR00017## wherein a=0, 1 or 2; n=0-6; each R.sup.K, R.sup.L, R.sup.M, R.sup.O, R.sup.P and R.sup.Q is independently H or an optionally substituted straight-chain or branched C1 to C20 alkyl group, an optionally substituted straight-chain or branched C2 to C20 alkenyl group, an optionally substituted C3 to C20 cycloalkyl group, an optionally substituted C4 to C20 cycloalkenyl group, an optionally substituted straight-chain, branched or cyclic C4 to C20 alkynyl group or an optionally substituted, straight-chain or branched C2 to C20 heteroalkyl group, an optionally substituted, straight-chain, branched or cyclic C3 to C20 heteroalkenyl group or an optionally substituted C4 to C14 aryl or heteroaryl group, or two residues R.sup.K, R.sup.L, R.sup.M, R.sup.O, R.sup.P and R.sup.Q together form a 5- to 8-membered ring.

32. The composition according to claim 16, wherein the heterocyclic azasilane is N-n-butyl-1-aza-2,2-dimethoxy-2-silacyclopentane, 2,2-diethoxy-1-(3-triethoxysilylpropyl)aza-2-silacyclopentane and/or 2,2-diethoxy-1-(trimethylsilyl)aza-2-silacyclopentane, preferably N-n-butyl-1-aza-2,2-dimethoxy-2-silacyclopentane.

33. The composition according to claim 16, wherein the polyorganosiloxane is polydimethylsiloxane.

34. A process for preparing a curable composition according to claim 16, wherein the components (a) to (d) are mixed.

35. A use of a curable composition according to claim 16 as a sealant, glue, coating agent, jointing material, potting compound, adhesive or in paints.

Description

EXAMPLES

Example 1

[0269] A silicone rubber compound is produced according to the following formulation: 570 g alpha-omega hydroxyl-terminated polydimethylsiloxane with a viscosity of 80,000 cSt [0270] 270 g polydimethylsiloxane with viscosity 100 cSt [0271] 50 g highly dispersed silica untreated [0272] 50 g highly dispersed silica hydrophobized [0273] Mixture of 40.7 g methyl-tris(ethyl lactato)silane and 8.7 g tetraethyl lactatosilane [0274] 12.0 g adhesion promoter butyldimethoxycyclosilane (BDC, N-n-butyl-1-aza-2,2-dimethoxy-2-silacyclopentane) [0275] 0.5 g catalyst iBu-POSSZr-OEt [0276] 1.5 g octylphosphonic acid

[0277] The sealant has been exposed to air after application: [0278] a skin formation time of 5 min [0279] a bonding time of 35 min [0280] early stress after 180 min [0281] complete curing after 24 hours [0282] a transparent appearance [0283] a Shore hardness A of 18 [0284] good adhesion to wood, painted wood, varnished wood, aluminum, powder-coated aluminum, glass, PVC, polyamide, steel, concrete, etc.

[0285] The sealant is also characterized by its excellent storage stability.

After 8 weeks of storage at 50 C. in the cartridge, the sealant still has the same properties as when it was first applied.

Example 2

[0286] A silicone rubber compound is produced according to the following formulation: [0287] 570 g alpha-omega hydroxyl-terminated polydimethylsiloxane with a viscosity of 80,000 cSt [0288] 270 g polydimethylsiloxane with viscosity 100 cSt [0289] 50 g highly dispersed silica untreated [0290] 50 g highly dispersed silica hydrophobized [0291] 49.4 g methyl-tris(ethyl lactato)silane [0292] 12.0 g adhesion promoter butyldimethoxycyclosilane (BDC, N-n-butyl-1-aza-2,2-dimethoxy-2-silacyclopentane) [0293] 1.0 g catalyst iBu-POSSZr-OEt [0294] 1.5 g octylphosphonic acid

[0295] The sealant has been exposed to air after application: [0296] a skin formation time of 11 min [0297] a bonding time of 65 min [0298] an early stress after 280 min [0299] complete curing after 24 hours [0300] a transparent appearance [0301] a Shore hardness A of 17 [0302] good adhesion to wood, painted wood, varnished wood, aluminum, powder-coated aluminum, glass, PVC, polyamide, steel, concrete, etc.

[0303] The sealant is also characterized by its excellent storage stability.

After 8 weeks of storage at 50 C. in the cartridge, the sealant still has the same properties as when it was first applied.

[0304] For detailed examination and comparison with an established silicone sealant, the following example 3 and the comparative example were examined in detail.

Example 3

[0305] Analogous to examples 1 and 2, a silicone rubber compound was prepared according to the following formulation:

TABLE-US-00001 Fabric Weight % 1 Polymer 80,000 cSt 57.1 (--dihydroxy-dimethyl-polysiloxane) 2 Plasticizer 100 cSt 26.45 (polydimethylsiloxane) 3 Crosslinker 1: 3.6 (methyl-tris(ethyl lactato)silane) 4 Crosslinker 2: 1.4 (tetra(ethyl lactato)silane) 5 Pyrogenic silica, hydrophobic 5.0 (BET surface area 130-150 m.sup.2/g) 6 Pyrogenic silica, untreated 5.0 (BET surface area 130-150 m.sup.2/g) 7 Adhesion promoter: BnDC 1.2 (benzyldimethoxycyclosilane, N-benzyl-1-aza-2,2- dimethoxy-2-silacyclopentane) 8 Catalyst: iBuPOSSZrOEt 0.1 9 Stabilizer octylphosphonic acid 0.15

Comparative Example (Prior Art)

TABLE-US-00002 Component Weight % 1 a,-dihydroxy-dimethyl-polysiloxane 52.1 80,000 cSt 2 Polydimethylsiloxane (PDMS) 100 cSt 32.9 3 Crosslinker 1: Vinyl-tris(ethyl lactato)silane 2.5 4 Crosslinker 2: Methyl-tris(ethyl lactato)silane 2.5 5 Aminopropyltriethoxysilane (AMEO) 0.2 6 Pyrogenic silica, untreated 8.5 BET surface area 130-150 m.sup.2/g 7 Catalyst 1:1 (w/w) Mixture of dialkylzine oxide and 0.1 tetraalkoxysilane 8 Adhesion promoter: N-n-butyl-1-aza-2,2-dimethoxy-2- 1.2 silacyclopentane (BDC) (BDC)

[0306] The optical properties of the compositions from examples 1 to 3 and the comparative example were comparable on application, as were the mechanical properties after curing. However, the silicone rubber compounds according to examples 1 to 3 were found to have improved storage stability and adhesion compared to the reference example. The composition according to examples 1 to 3 was still colorless after storage at 50 C. after eight weeks, whereas the composition of the comparative example was yellowish after eight weeks at 50 C. In terms of adhesion, the composition according to examples 1 to 3 exhibited improved adhesion to Plexiglas, polycarbonate and polystyrene compared to the comparative example. An additional advantage of the above examples according to the invention is that toxic tin could be dispensed with.

[0307] Compared to the sealant of the above comparative example, the above examples show that the mechanical properties of the compositions according to the invention are equally good compared to known silicone rubber compounds and at the same time the storage stability and adhesion to plastics such as Plexiglas, polycarbonate or polystyrene could be improved.