Processes and compositions for cleaning mixing devices to improve polymer production

Patent metadata

Field	Value
Publication number	US-9347026-B2
Application number	US-201313774524-A
Country	US
Kind code	B2
Filing date	Feb 22, 2013
Priority date	Feb 28, 2012
Publication date	May 24, 2016
Grant date	May 24, 2016

Abstract

Processes and compositions for cleaning mixing devices are disclosed that improve the production and quality of thermoplastic polymer resins subsequently produced in the mixing device, while reducing the time needed for cleaning and/or change over. A cleaning mixture comprising polymeric resin pellets having a Rockwell R hardness of 85 to 140 externally coated with an aqueous solution containing sulfonate salts, alkyl aryl sulfonate salts, alkyl sulfate salts, C6 to C36 carboxylic acid salts, or mixtures thereof, is used to purge the mixing device. The surfactant salt is present in the aqueous solution at 0.2 to 30 wt % of the solution, the aqueous solution having a pH of 6.0 to 9.0.

First claim

The invention claimed is:

1. A process to clean melt processing equipment used to compound, mold, and/or extrude resins containing a polymer, comprising:
purging the melt processing equipment with a cleaning mixture (purge) comprising:
from 70 to 99 wt % of thermoplastic polymeric resin pellets, the pellets having a Rockwell R hardness of from 85 to 140 as measured by ASTM D785; and
from 1 to 30 wt % of an aqueous solution that contains 0.2 to 30 wt % of a surfactant salt selected from at least one of the following: sulfonate salts, alkyl aryl sulfonate salts, alkyl sulfate salts, C6 to C36 carboxylic acid salts, and mixtures thereof, wherein the aqueous solution has a pH of 6.0 to 9.0; and

running the melt processing equipment at a temperature of from 200 to 380° C. to obtain a purged resin while cleaning the melt processing equipment.

2. The process of claim 1 , wherein the surfactant salt is present in the solution at an amount of 5 to 30 wt % of the solution.

3. The process of claim 1 , wherein the solution is present in the cleaning mixture at 0.2 to 5 wt % of the cleaning mixture.

4. The process of claim 1 , wherein the melt processing equipment is run for a period of from 1 minute to 20 minutes to obtain the purged resin.

5. The process of any of claim 1 , wherein the aqueous solution has a pH of 6.0 to 7.0.

6. The process of claim 1 , wherein the surfactant salt contains an alkali metal cation selected from at least one of the following: sodium, potassium, and mixtures thereof.

7. The process of claim 1 , wherein the aqueous solution has a viscosity of 20 to 1000 centipoise as measured by ASTM D445 at 23° C.

8. The process of claim 1 , wherein the surfactant salt is an alkyl aryl sulfonate salt having at least one of the following structures:

wherein each M is an alkali metal cation; each R is independently alkyl having from 1 to 36 carbon atoms; x is 1 to 5; y is 0 to 5; p is 1 to 3; q is 1 to 3; s is 0 to 3; and t is 0 to 3.

9. The process of claim 8 , wherein x=1 and y=1.

10. The process of claim 8 , wherein the alkyl aryl sulfonate salt is an alkyl benzene sulfonate salt.

11. The process of claim 8 , wherein Formula B has the following structure:

where M is an alkali metal cation; R 1 is an alkyl group containing from 5 to 35 carbon atoms; and R 2 is hydrogen or an alkyl group containing from 1 to 12 carbon atoms, with R 1 and R 2 having no more than 36 total carbon atoms.

12. The process of claim 1 , wherein the surfactant salt is a carboxylic acid salt of Formula (G):
R—COO − M +   Formula (G)

wherein R is alkyl having from 6 to 36 carbon atoms; and M is an alkali metal cation.

13. The process of claim 1 , wherein the surfactant salt is an alkyl sulfate salt of Formula (H):

wherein R is alkyl having from 6 to 36 carbon atoms; M is an alkali metal cation; and n is from 0 to 4.

14. The process of claim 1 , wherein the surfactant salt has less than 10% loss of initial dry weight when measured by thermal gravimetric analysis (TGA) at 250° C., under nitrogen, with a 20° C./minute heating rate.

15. The process of claim 1 , wherein the thermoplastic polymeric resin pellets comprise cylinders with an average length of 2.0 to 6.0 mm and an average diameter of 0.5 to 4.0 mm.

16. The process of claim 1 , wherein the thermoplastic polymeric resin pellets have a bulk density of 0.5 to 0.9 g/cc as measured by ASTM D1895.

17. The process of claim 1 , wherein the thermoplastic polymeric resin pellets have at least one angular face and wherein the surfaces defining the angular face meet at an angle of 60 to 120 degrees.

18. The process of claim 1 , wherein the polycarbonate resin pellets have at least one angular face and wherein the surfaces defining the angular face meet at an angle of 80 to 100 degrees.

19. The process of claim 1 , wherein the thermoplastic polymeric resin pellets comprise a condensation polymer.

20. The process of claim 1 , wherein the thermoplastic polymeric resin pellets comprise an amorphous polymer that has a glass transition temperature (Tg) from 110 to 280° C., as measured by ASTM D3418.

21. The process of claim 1 , wherein the thermoplastic polymeric resin pellets comprise at least one of the following: polyphenylene ethers, polystyrenes, styrene acrylonitriles, acrylonitrile butadiene styrenes, polyetherimides, polysulfones, polyether sulfones, polyphenylene ether sulfones, polyurethanes, amorphous polyesters, and mixtures thereof.

22. The process of claim 1 , wherein the thermoplastic polymeric resin pellets comprise a crystalline polymer that has a melting point temperature (Tm) from 110 to 320° C.

23. The process of claim 1 , wherein the thermoplastic polymeric resin pellets comprise at least one of the following: polyamides, polyacetals, polyesters, liquid crystalline polyesters, polypropylenes, polyethylenes, polyolefins, polyvinyl chlorides, polyphenylene sulfides, polyether ether ketones, polyketones, and mixtures thereof.

24. The process of claim 1 , wherein the thermoplastic polymeric resin pellets in the cleaning mixture have a weight average molecular weight (Mw) at least 10% higher than a weight average molecular weight of the resin being cleaned from the melt processing equipment.

25. The process of claim 1 , wherein the thermoplastic polymeric resin pellets in the cleaning mixture have a weight average molecular weight (Mw) of 15,000 to 100,000 daltons measured according to polystyrene standards.

26. The process of claim 1 , wherein the thermoplastic polymeric resin pellets are the same material as at least one polymeric component of the resin being cleaned from the melt processing equipment.

27. The process of claim 1 , wherein the melt processing equipment is an extruder with a length to diameter (L/D) ratio from 20:1 to 40:1 and has a screw diameter of 0.5 to 8.0 inches, and is run at a speed of 50 to 100 rpm at a temperature of 200 to 380° C.

28. The process of any of claim 1 , wherein the mixing device has a single screw for melt conveying.

29. The process of claim 28 , wherein the mixing device is a single screw extruder having a screw diameter from 0.5 to 8.0 inches that is part of a thermoplastic molding machine.

30. The process of claim 28 , wherein the single screw for melt conveying is part of a molding machine selected from at least one of the following: injection molding machines, blow molding machines, injection-blow molding machines, extrusion-blow molding machines, stretch-blow molding machines, gas assist molding machines, hydraulic molding machines, mechanical molding machines and electric molding machines.

31. The process of claim 1 , wherein the melt processing equipment is contaminated with a colorant selected from at least one of the following: Solvent Green 3, Solvent Green 28, Solvent Green 38, Pigment Green 50, Pigment Green 36, Solvent Red 52, Solvent Red 101, Solvent Red 111, Solvent Red 135, Solvent Red 169, Solvent Red 179, Solvent Red 207, Pigment Red 101, Disperse Red 22, Vat Red 41, Solven

Assignees

• Sabic Global Technologies Bv

Inventors

• Gallucci Robert Russell
• Ehrensbeck Franklin

Classifications

• C11D9/225

  Polymers · CPC title

• C11D1/24

  containing ester or ether groups directly attached to the nucleus · CPC title

• C11D1/146 Primary

  Sulfuric acid esters · CPC title

• B29C2948/9299

  Treatment of equipment, e.g. purging, cleaning, lubricating or filter exchange · CPC title

• C11D3/3715

  Polyesters or polycarbonates · CPC title