Process for the preparation of a mercapto-terminated liquid polymer

1. A process for the preparation of a mercapto-terminated liquid polymer comprising the steps of:

a) reacting (para)formaldehyde with a halo-alcohol to form a reaction mixture comprising bis(2-dihaloalkyl)formal and

b) reacting the reaction mixture of step a) with either (i) sodium polysulfide or (ii) a combination of sodium hydrosulfide and sulfur,

wherein a branching agent is present in step a) and/or step b), said branching agent being selected from the group consisting of di-aldehydes and their corresponding acetals and hemiacetals.

2. The process according to claim 1 wherein the branching agent is a di-aldehyde with the formula (O═)(H)C(CH 2 ) n C(H)(═O), where n is in the range 0-8.

3. The process according to claim 1 wherein the branching agent is a hemi-acetal with the formula (O═)(H)C(CH 2 ) n C(H)(OR 1 )(OH) or (OH)(OR 1 )(H)C(CH 2 ) n C(H)(OR 1 )(OH), in which n is in the range 0-8 and each R 1 is independently selected from alkyl groups with 1-10 carbon atoms.

4. The process according to claim 1 wherein the branching agent is an acetal with the formula (O═)(H)C(CH 2 ) n C(OR 1 )(OR 2 ) or (OR 1 )(OR 2 )(H)C(CH 2 ) n C(H)(OR 1 )(OR 2 ), in which n is in the range 0-8 and each R 1 and R 2 is independently selected from alkyl groups with 1-10 carbon atoms.

5. The process according to claim 2 wherein n is in the range 0-3.

6. The process according to claim 3 wherein each R 1 is independently selected from alkyl groups with 1 or 2 carbon atoms.

7. The process according to claim 4 wherein the acetal is selected from the group consisting of glyoxal dimethyl acetal, glyoxal bis(dimethyl acetal), malonic aldehyde bis(diethyl acetal), and glutaric aldehyde bis(dimethyl acetal).

8. The process according to claim 1 wherein the branching agent is present in step a).

9. The process according to claim 8 wherein branching agent is added during step b).

10. The process according to claim 1 wherein the branching agent is used in an amount of 0.01 to 10 mol %, relative to (para)formaldehyde (calculated as CH 2 O).

11. The process according to claim 1 wherein the halo-alcohol is a chloroalcohol.

12. The process according to claim 1 wherein step b) is conducted in the presence of a dihaloalkane.

13. The process according to claim 1 wherein step a) is conducted in the presence of a polyol.

14. A process for the preparation of a mercapto-terminated liquid polymer comprising the steps of:

a) reacting (para)formaldehyde with a halo-alcohol to form a reaction mixture comprising bis(2-dihaloalkyl)formal and

b) reacting the reaction mixture of step a) with either (i) sodium polysulfide or (ii) a combination of sodium hydrosulfide and sulfur,

wherein a branching agent is present in step a) and/or step b), said branching agent being selected from the group consisting of di-aldehydes and their corresponding acetals and hemiacetals, and

wherein step b) is conducted in the presence of a pre-polymer with the structure

X—(R 2 —O) n —CH 2 —O—(R 1 —O) m —CH 2 —(O—R 2 ) p —X

wherein R 1 and R 2 can be the same or different and are selected from alkane chains containing 2-10 carbon atoms, X is a halogen atom selected from Cl, Br and I, and n, m, and p are integers that can be the same or different and have a value in the range 1-6.

15. The process according to claim 14 wherein X is Cl, R 1 is —CH 2 —CH 2 —, and R 2 is —CH 2 —CH 2 —, —CH 2 —CH 2 —CH 2 —, or —CH 2 —CH 2 —CH 2 —CH 2 —.

16. The process according to claim 3 wherein n is in the range 0-3.

17. The process according to claim 4 wherein n is in the range 0-3.

18. The process according to claim 4 wherein each R 1 and/or R 2 is independently selected from alkyl groups with 1 or 2 carbon atoms.