Liquid formulation
View Patent ↗A formulation for foaming a thermoplastic polymer, for example PVC, comprises a carrier, exothermic and endothermic chemical blowing agents and 1 wt %, preferably less than 0.2 wt % of water. The liquid formulation can readily be used for foaming PVC and other thermoplastics.
1. A liquid formulation for foaming a thermoplastic polymer, said formulation comprising:
a carrier; and
chemical blowing agents, wherein the total amount of chemical blowing agents in said formulation is at least 60 wt %;
wherein said formulation includes at least 25 wt % of one or more endothermic chemical blowing agents;
wherein said formulation includes at least 25 wt % of one or more exothermic chemical blowing agents; and
wherein said formulation includes less than 0.3 wt % of water.
2. A formulation according to claim 1 , wherein said formulation includes less than 0.13 wt % water.
3. A formulation according to claim 1 , wherein the total amount of chemical blowing agents is at least 65 wt %.
4. A formulation according to claim 1 which includes 60 wt % or less of said one or more exothermic chemical blowing agents.
5. A formulation according to claim 4 , wherein said one or more exothermic chemical blowing agents are selected from azodicarbonamide (ADC) and oxybissulphonylhydrazide (OBSH).
6. A formulation according to claim 5 , which includes at least 20 wt % ADC, dispersed in said carrier.
7. A formulation according to claim 5 which includes at least 20 wt % OBSH dispersed in said carrier.
8. A formulation according to claim 1 , which includes an activator which comprises a transition metal oxide.
9. A formulation according to claim 1 , which includes at least 30 wt % and 60 wt % or less of said one or more endothermic chemical blowing agents.
10. A formulation according to claim 1 , wherein said one or more endothermic blowing agents comprises a bicarbonate.
11. A formulation according to claim 10 , which includes at least 10 wt % of a bicarbonate.
12. A formulation according to claim 9 , wherein the ratio of the sum of the wt % of exothermic blowing agents to the sum of the wt % of endothermic blowing agents in said formulation is in the range 0.5 to 2.
13. A formulation according to claim 1 , wherein the formulation comprises from 50-85 wt % solids.
14. A formulation according to claim 1 , wherein said carrier comprises one or a plurality of oils.
15. A formulation according to claim 1 , which includes less than 35 wt % of carrier.
16. A formulation according to claim 1 , which includes
15 to 40 wt % carrier;
one or a plurality of exothermic chemical blowing agents, wherein the total amount of such blowing agents is in the range 25 to 45 wt %;
one or a plurality of endothermic chemical blowing agents, wherein the total amount of such blowing agents is in the range 25 to 45 wt %;
less than 0.13 wt % of water.
17. A formulation according to claim 1 , which includes:
20 to 30 wt % mineral oil;
azodicarbonamide and oxybissulphonylhydrazide, wherein the total amount of such blowing agents is in the range 30 to 40 wt %;
a bicarbonate, wherein the total amount of bicarbonate in the formulation is in the range 30 to 40 wt %;
less than 0.13 wt % of water.
18. A formulation according to claim 1 , which includes a desiccant dissolved or dispersed in said carrier of said liquid formulation.
19. A formulation according to claim 1 , which includes at least 1 wt % of a surface active agent.
20. A formulation according to claim 19 , wherein said surface active agent is a polymeric dispersant with amine anchor.
21. A method of preparing a liquid formulation according to claim 1 , the method comprising:
contacting said carrier, said one or more exothermic chemical blowing agents, and said one or more endothermic chemical blowing agents; and
either (1) treating the formulation after preparation to reduce the level of water contained within the formulation; or (2) contacting the carrier with a desiccant.
22. A method of preparing a foamed thermoplastic polymer, the method comprising contacting said liquid formulation according to claim 1 with a thermoplastic polymer or a precursor of a thermoplastic polymer.
23. A method according to claim 22 , wherein said thermoplastic polymer comprises PVC.
24. A method according to claim 22 , said method being for making an extruded foam material, the method comprising contacting said thermoplastic polymer and said liquid formulation according to claim 1 in an extruder under such conditions that the liquid formulation produces gas which foams the polymer.
25. A method according to claim 24 , wherein the extruded foam material is made from PVC.
26. A liquid formulation as claimed in claim 1 , wherein said liquid formulation as made has a viscosity at 20-25° C. of no more than 5300 cP when measured using a Brookfield DV-I viscometer with spindle 4 at 20 rpm.
27. A liquid formulation as claimed in claim 1 , wherein the rise in viscosity of said liquid formulation measured at 20-25° C. after incubation of said formulation at 50° C. for 6 weeks is no more than 2100 cP when measured using a Brookfield DV-I viscometer with spindle 4 at 20 rpm.