1. A chemical blowing agent for foaming a thermoplastic polymer precursor, for example
PVC plastisol or a polymer resin in an extrusion process,
said chemical blowing agent comprising a functionalized particulate bicarbonate, wherein said functionalized particulate bicarbonate contains at least one additive, and
wherein said additive in the functionalized particulate bicarbonate is at least one following compound;
one or more polymers;
one or more amino acids, any derivative thereof, and salts thereof;
one or more inorganic salts;
one or more oils;
one or more fats;
one or more resin acids, any derivative thereof, and salts thereof;
one or more fatty acids, any derivative thereof, and salts thereof;
a carboxylic or polycarboxylic acid, derivative thereof (such as esters), or salts
thereof;
one or more soaps;
one or more waxes; or
any combinations thereof
2. The chemical blowing agent according to Claim 1, wherein the blowing agent does not contain any further blowing agent which is an exothermic blowing agent.
3. The chemical blowing agent according to Claim 1 or 2, wherein the chemical blowing agent does not contain a compound which liberates nitrogen gas during heating,
4. The chemical blowing agent according to any of Claims 1 to 3, wherein the chemical blowing agent does not contain a compound which liberates ammonia gas during heating.
5. The chemical blowing agent according to any of Claims 1 to 4, wherein the additive in the functionalized particulate bicarbonate is at least one compound selected from the group consisting of an amino acid, derivative thereof, or salt thereof, preferably at least one compound selected from the group consisting of casein, gelatin, glycine, proline, hydroxyproline, glutamic acid, alanine, arginine, aspartic acid, lysine, pectin, serine,

leucine, valine, phenylalanine, threonine, isoleucine, hydroxylysine, methionine, histidine, tyrosine and combinations thereof, more preferably leucine.
6. The chemical blowing agent according to any of Claims 1 to 4, wherein the additive in the functionalized particulate bicarbonate is at least one compound selected from the group consisting of a fatty acid, derivative thereof (such as ester), or salt thereof, preferably at least one compound selected from the group consisting of lauric acid, stearic acid, glycerol mono stearate and combinations thereof, more preferably lauric acid.
7. The chemical blowing agent according to any of Claims 1 to 4, wherein the additive in the functionalized particulate bicarbonate is at least one polymer selected from the group consisting of polyoxyalkylenes and derivatives thereof including polyethylene glycols, poly(meth)acrylates and derivatives thereof, polyvinylalcohol, polysaccharides and combinations thereof, preferably polymer selected from the group consisting of polyvinylalcohol and polyoxyalkylenes and derivatives thereof including polyethylene glycols.
8. The chemical blowing agent according to Claim 7, wherein the polysaccharides are selected from the group consisting of modified, in particular hydrolyzed starch, maltodextrin, arabic gum and combinations thereof, more preferably maltodextrin.
9. The chemical blowing agent according to any of Claims 1 to 4, wherein the additive in the functionalized particulate bicarbonate is at least one resin acid, any derivative thereof, and salts thereof, more preferably rosin acid.

10. The chemical blowing agent according to any of Claims 1 to 4, wherein the additive in the functionalized particulate bicarbonate is at least one oil, preferably a vegetable oil or any derivative thereof, more preferably epoxidized soy bean oil.
11. The chemical blowing agent according to any of claims 1 to 4, wherein the additive in the functionalized particulate bicarbonate is at least one wax selected from the group consisting of beeswax, carnauba wax and combinations thereof.
12. The chemical blowing agent according to any of Claims 1 to 11, wherein the functionalized particulate bicarbonate comprises sodium bicarbonate.

13. The chemical blowing agent according to any of Claims 1 to 12, wherein the functionalized particulate bicarbonate comprises at least 50% by weight and less than 100% by weight of the bicarbonate component, and from 50% or less to 0.02% by weight of at least one of said additive.
14. The chemical blowing agent according to any of Claims 1 to 13, wherein the functionalized particulate bicarbonate comprises at least 65% by weight and less than 100%> by weight of the bicarbonate component, and from 35% or less to 0.02% by weight of at least one of said additive.
15. The chemical blowing agent according to any of Claims 1 to 14, wherein the particles of the functionalized particulate bicarbonate have a particle size distribution of D50 of more than 1 urn and at most 250 um, preferably at most 100 urn, more preferably at most 60 urn, yet more preferably at most 40 um, yet most preferably at most 25 um.
16. The chemical blowing agent according to any of Claims 1 to 14, wherein the particles of the functionalized particulate bicarbonate have a particle size distribution of D50 of at most 1 um.
17. The chemical blowing agent according to any of Claims 1 to 16, wherein the functionalized particulate bicarbonate is obtained by at least one of the following processes:
- by spray-drying (also known as atomization), wherein the additive is dissolved in the
bicarbonate-containing solution.
by grinding or co-grinding (also known as milling or co-milling) with the additive(s) in emulsion or powder form;
- by spray coating and granulation within a fluidized bed,
by spray agglomeration within a fluidized bed,
by spray chilling (e.g., spray cooling, spray freezing),
by roller compaction, and/or
by extrusion, including simultaneous mixing/extrusion.
18. The chemical blowing agent according to Claim 17, wherein the functionalized
particulate bicarbonate is obtained by at least one said process and is further subjected to
milling to reduce its mean particle size.

19. The chemical blowing agent according to any of Claims 1 to 18, further comprising an second compound which liberates C02 upon heating, said second compound being selected from the group consisting of a carboxylic or polycarboxylic acid, derivative thereof (such as esters), or salts thereof.
20. The chemical blowing agent according to Claim 19, wherein said second compound is functionalized with at least one additive which is different or the same as the one in the functionalized particulate bicarbonate, preferably the same additive.
21. The chemical blowing agent according to Claim 19 or 20, wherein said second compound is at least one of:
fumaric acid, - tartaric acid,
citric acid, citrates (such as sodium hydrogen citrate, disodium citrate), or esters of citric acid; or combination thereof.
22. A foamable polymer composition, comprising a polymer, optionally a foaming stabilizer, and the chemical blowing agent according to any of Claims 1 to 21.
23. The foamable polymer composition according to Claim 22, wherein the polymer is a PVC, a polyurethane, a polyolefin, or a polyamide.
24. A foamable PVC plastisol composition, comprising a PVC resin, optionally a foaming stabilizer, and the chemical blowing agent according to any of Claims 1 to 21.
25. The foamable PVC plastisol composition according to Claim 24, which does not contain azodicarbonamide, benzenesulfonylhydrazide, and/or p-toluenesulfonylhydrazide.
26. A process for manufacturing a polymer, comprising heating the foamable polymer composition according to Claims 22 or 23 which comprises the functionalized particulate bicarbonate at a temperature suitable for liberating C02 gas and melting the polymer during a gelation time at a temperature above glass transition temperature Tg and/or above melting temperature Tm of the polymer which is less than 130 seconds.
27. A foamed polymer obtained by the process of Claim 26, wherein the polymer is a PVC, a polyurethane, a polyolefin, or a polyamide.

28. A process for manufacturing a PVC polymer, comprising heating the foamable PVC polymer composition according to Claims 24 or 25 which comprises the functionalized particulate bicarbonate and the PVC resin at a temperature suitable for liberating C02 gas and melting the PVC polymer during a gelation time from 90 seconds to 120 seconds at a temperature from 190 to 210°C, preferably from 200 to 210°C, to provide a foamed PVC polymer. .
29. The process according to Claim 28, wherein the foamable polymer composition is spread coated on a surface before heating and melting, and wherein the foamed polymer has an expansion ratio of at least 270, preferably at least 280, more preferably at least 300 and/or has a density of less than 0.6 g/cm3, preferably less than 0.55 g/cm3, more preferably at most 0.5 g/cm3.
30. A process for manufacturing a polymer, comprising heating the foamable PVC plastisol composition according to Claims 24 or 25 which comprises the functionalized particulate bicarbonate at a temperature suitable for liberating C02 gas and melting the PVC resin during a gelation time, wherein said gelation time with the chemical blowing agent comprising the functionalized particulate is less than the gelation time that would be obtained with a chemical blowing agent liberating N2, all other components in the foamable PVC plastisol composition being the same.
31. A foamed PVC obtained by the process of any of Claims 28, 29 or 30.