Compositions of resin-linear organosiloxane block copolymers

1. A hot melt composition comprising the reaction product of:

A) a resin linear organosiloxane block copolymer comprising:

40 to 90 mole percent disiloxy units of the formula [R 1 2 SiO 2/2 ],

10 to 60 mole percent trisiloxy units of the formula [R 2 SiO 3/2 ],

0.5 to 35 mole percent silanol groups [≡SiOH];

wherein:

each R 1 , at each occurrence, is independently a C 1 to C 30 hydrocarbyl,

each R 2 , at each occurrence, is independently a C 1 to C 20 hydrocarbyl;

wherein:

the disiloxy units [R 1 2 SiO 2/2 ] are arranged in linear blocks having an average of from 10 to 400 disiloxy units [R 1 2 SiO 2/2 ] per linear block,

the trisiloxy units [R 2 SiO 3/2 ] are arranged in non-linear blocks having a molecular weight of at least 500 g/mole, at least 30% of the non-linear blocks are crosslinked with each other,

each linear block is linked to at least one non-linear block; and

the organosiloxane block copolymer has a weight average molecular weight of at least 20,000 g/mole; and

B) a capping agent of the formula R 5 SiX 3

wherein R 5 is a C 1 to C 12 hydrocarbyl, an organohydrogensiloxane, or a vinyl functional organosiloxane;

X is a hydrolyzable group chosen from —OR 6 , Cl, —OC(O)R 6 , —N(R 6 ) 2 , or —ON═CR 6 2 ,

wherein R 6 is hydrogen or a C 1 to C 6 alkyl group.

2. The hot melt composition of claim 1 , wherein the resin linear organopolysiloxane is prepared by:

I) reacting

a) a linear organosiloxane having the formula

R 1 q (E) (3-q) SiO(R 1 2 SiO 2/2 ) n Si(E) (3-q) R 1 q ,

wherein each R 1 , at each occurrence, is independently a C 1 to C 30 hydrocarbyl,

n is 10 to 400,

q is 0, 1 or 2,

E is a hydrolyzable group containing at least one carbon atom, and

b) an organosiloxane resin comprising at least 60 mole % of [R 2 SiO 3/2 ] siloxy units in its formula, wherein each R 2 , at each occurrence, is independently a C 1 to C 20 hydrocarbyl,

in c) an organic solvent;

to form a resin-linear organosiloxane block copolymer;

wherein the amounts of a) and b) used in step I are selected to provide the resin-linear organosiloxane block copolymer with 40 to 90 mole % of disiloxy units [R 1 2 SiO 2/2 ] and 10 to 60 mole % of trisiloxy units [R 2 SiO 3/2 ], and

wherein at least 95 weight percent of the linear organosiloxane used in step I is incorporated into the resin-linear organosiloxane block copolymer; and

II) reacting the resin-linear organosiloxane block copolymer from step i) and organosilane having the formula R 6 q SiX 4-q , wherein R 6 is a C 1 to C 8 hydrocarbyl or a C 1 to C 8 halogen-substituted hydrocarbyl, X is a hydrolyzable group, and q is 0, 1, or 2;

to crosslink the trisiloxy units of the resin-linear organosiloxane block copolymer sufficiently to increase the weight average molecular weight (M W ) of the resin-linear organosiloxane block copolymer by at least 50%.

3. The hot melt composition of claim 1 , wherein the organosilane is an alkyltriacetoxysilane.

4. The hot melt composition of claim 1 , wherein the capping agent is an alkyltriacetoxysilane or an alkyltrialkoxysilane.

5. The hot melt composition of claim 1 , wherein the resin linear organopolysiloxane is prepared by:

I) reacting

a) a linear organosiloxane having the formula

R 1′ q R 3 (3-q) SiO(R 1 2 SiO 2/2 ) n SiR 3 (3-q) R 1′ q ,

wherein:

each R 1′ , at each occurrence, is independently a C 1 to C 30 hydrocarbyl free of aliphatic unsaturation,

each R 3 , at each occurrence, is independently H, R 1′ , or R 4 , wherein each R 4 , at each occurrence, is independently a C 2 to C 12 hydrocarbyl group having at least one aliphatic unsaturated bond, and

n is 10 to 400, q is 0, 1, or 2;

b) an organosiloxane resin having the average formula:

[R 2′ 2 R 3 SiO 1/2 ] a [R 2′ R 3 SiO 2/2 ] b [R 3 SiO 3/2 ] c [R 2′ SiO 3/2 ] d [SiO 4/2 ] e ,

wherein:

each R 2′ , at each occurrence, is independently a C 1 to C 20 hydrocarbyl free of aliphatic unsaturation,

each R 3 , at each occurrence, is independently H, R 1′ , or R 4 , wherein each R 4 , at each occurrence, is a C 2 to C 12 hydrocarbyl group having at least one aliphatic unsaturated bond,

the subscripts a, b, c, d, and e represent the mole fraction of each siloxy unit present in the organosiloxane resin and range as follows:

a is about 0 to about 0.7,

b is about 0 to about 0.3,

c is about 0 to about 0.8,

d is about 0 to about 0.9,

e is about 0 to about 0.7,

with the provisos that a+b+c>0, c+d+e≧0.6, and a+b+c+d+e≈1, with the proviso that at least one R 3 substituent is H on either of the linear organosiloxane or organosiloxane resin, and at least one R 3 substituent is R 4 on the other organosiloxane; and

c) a hydrosilylation catalyst;

in an organic solvent;

to form a resin-linear organosiloxane block copolymer;

wherein the amounts of a) and b) used in step I are selected to provide the resin-linear organosiloxane block copolymer with 40 to 90 mole % of disiloxy units [R 1′ 2 SiO 2/2 ] and 10 to 60 mole % of [R 2′ SiO 3/2 ] and/or [SiO 4/2 ] siloxy units, and wherein at least 95 weight percent of the linear organosiloxane added in step I is incorporated into the resin-linear organosiloxane block copolymer;

II) reacting the resin-linear organosiloxane block copolymer from step I) to crosslink the [R 2′ SiO 3/2 ] and/or [SiO 4/2 ] siloxy units of the resin-linear organosiloxane block copolymer sufficiently to increase the weight average molecular weight (M W ) of the resin-linear organosiloxane block copolymer by at least 50%.

6. The hot melt composition of claim 5 , wherein component

a) has the average formula:

H(CH 3 ) 2 SiO[(CH 3 ) 2 SiO 2/2 )] n Si(CH 3 ) 2 H

 where n may vary from 10 to 400,

and component b) has the average formula

[(H 2 C═CH)(CH 3 ) 2 SiO 1/2 ] a [(C 6 H 5 )SiO 3/2 ] d [SiO 4/2 ] e

where the subscripts a, d, and e are as defined in claim 1 ; or

component a) has the average formula

(H 2 C═CH)(CH 3 ) 2 SiO[(CH 3 ) 2 SiO 2/2 )] n Si(CH 3 ) 2 (HC═CH 2 )

 where n may vary from 10 to 400,

and component b) has the average formula

[H(CH 3 ) 2 SiO 1/2 ] a [SiO 4/2 ] e

where the subscripts a and e are as defined in claim 1 .

7. The hot melt composition of claim 5 , wherein the capping agent has the formula:

H(CH 3 ) 2 SiOSi(CH 3 ) 2 CH 2 CH 2 Si(OCH 3 ) 3 .

8. The hot melt composition of claim 5 , wherein a crosslinker is added in step II) and/or in step I), wherein the crosslinker has the formula:

R 1′ q R 3 (3-q) SiO(R 1′ 2 SiO 2/2 ) m SiR 3 (3-q) R 1′ q

wherein each R 1′ , at each occurrence, is independently a C 1 to C 30 hydrocarbyl;

m varies from 0 to 50, q is 0, 1, or 2;

each R 3 , at each occurrence, is independently H, R 1′ , or R 4 , wherein each R 4 , at each occurrence, is a C 2 to C 12 hydrocarbyl having at least one aliphatic unsaturated bond.

9. The hot melt composition of claim 8 , wherein the crosslinker is tetramethyldisiloxane or divinyltetramethyldisiloxane.

10. The hot melt composition of claim 5 , wherein step II) further comprises adding an organosilane having the formula R 5 q SiX 4-q , where R 5 is a C 1 to C 8 hydrocarbyl or a C 1 to C 8 halogen-substituted hydrocarbyl, X is a hydrolyzable group, and q is 0, 1, or 2.

11. The hot melt composition of claim 10 , wherein the organosilane is an alkyltriacetoxysilane.

12. The hot melt composition of claim 11 , wherein the alkyltriacetoxysilane is a mixture of two alkyltriacetoxysilanes.

13. The hot melt composition of claim 12 , wherein the mixture of two alkyltriacetoxysilanes comprise methyltriacetoxysilane and/or ethyltriacetoxysilane.

14. The hot melt composition of claim 5 , wherein the organosiloxane resin is chosen from:

[H(CH 3 ) 2 SiO 1/2 ] a [(C 6 H 5 )SiO 3/2 ] d ;

[H(CH 3 ) 2 SiO 1/2 ] a [(CH 3 ) 2 SiO 2/2 ] b [(C 6 H 5 )SiO 3/2 ] d ;

[H(CH 3 ) 2 SiO 1/2 ] a [(C 6 H 5 ) 2 SiO 2/2 ] b [(C 6 H 5 )SiO 3/2 ] d ;

[H(CH 3 ) 2 SiO 1/2 ] a [(C 6 H 5 )(CH 3 )SiO 2/2 ] b [(C 6 H 5 )SiO 3/2 ] d ;

[H(CH 3 ) 2 SiO 1/2 ] a [(C 6 H 5 )SiO 3/2 ] d [SiO 4/2 ] e ;

[H(CH 3 ) 2 SiO 1/2 ] a [(CH 3 ) 2 SiO 2/2 ] b [SiO 4/2 ] e ;

[H(CH 3 ) 2 SiO 1/2 ] a [SiO 4/2 ] e ; and

combinations thereof.

15. The hot melt composition of claim 5 , wherein the organosiloxane resin is chosen from:

[Vi(CH 3 ) 2 SiO 1/2 ] a [(C 6 H 5 )SiO 3/2 ] d ;

[Vi(CH 3 ) 2 SiO 1/2 ] a [(CH 3 ) 2 SiO 2/2 ] b [(C 6 H 5 )SiO 3/2 ] d ;

[Vi(CH 3 ) 2 SiO 1/2 ] a [(C 6 H 5 ) 2 SiO 2/2 ] b [(C 6 H 5 )SiO 3/2 ] d ;

[Vi(CH 3 ) 2 SiO 1/2 ] a [(C 6 H 5 )(CH 3 )SiO 2/2 ] b [(C 6 H 5 )SiO 3/2 ] d ;

[Vi(CH 3 ) 2 SiO 1/2 ] a [(C 6 H 5 )SiO 3/2 ] d [SiO 4/2 ] e ;

[Vi(CH 3 ) 2 SiO 1/2 ] a [(CH 3 ) 2 SiO 2/2 ] b [SiO 4/2 ] e ;

[Vi(CH 3 ) 2 SiO 1/2 ] a [SiO 4/2 ] e ; and

combinations thereof.

16. The hot melt composition of any of the above claim 1 , further comprising a cure catalyst, wherein the cure catalyst is a titanate.

17. The hot melt composition of claim 16 , wherein the titanate is tetra-n-butyl titanate.

18. The cured product of the composition of claim 1 .

19. An LED encapsulant comprising the cured product of claim 18 .

20. The cured product of the composition of claim 1 , which is produced by exposing the compositions to moisture.