PVA-containing compositions
View Patent ↗An extrudable PVA-containing composition is disclosed, which enables PVA articles to be manufactured on conventional extrusion apparatus. The composition includes a lubricant, such as a fatty acid amide, and is formed into pellets by cold pressing. The compositions are suitable for manufacturing a variety of products.
1. A polymer feedstock in the form of a cold-pressed tablet or pellet for use in the extrusion of an extruded product containing PVA and a filler, the cold-pressed tablet or pellet comprising, by weight of the feedstock, a blend of:
40 to 80% PVA;
up to 20% plasticizer;
up to 5% lubricant; and
5 to 50% solid particulate filler.
2. A polymer feedstock according to claim 1 comprising at least 5% plasticizer.
3. A polymer feedstock according to claim 1 comprising at least 8% plasticizer.
4. A polymer feedstock according to claim 1 comprising up to 2.5% lubricant.
5. A polymer feedstock according to claim 1 comprising at least 0.5% internal lubricant and at least 0.0001% external lubricant.
6. A polymer feedstock according to claim 4 comprising at least 0.5% internal lubricant and at least 0.0001% external lubricant.
7. A polymer feedstock according to claim 5 wherein the internal lubricant comprises a fatty acid amide.
8. A polymer feedstock according to claim 7 wherein the fatty amide is a straight or branched C12-C24 fatty acid amide.
9. A polymer feedstock according to claim 1 wherein the plasticizer is selected from the group consisting of ethylene glycol, glycerol, triethylene glycol, polyethylene glycols and C2-C8 amides.
10. A polymer feedstock according to claim 1 wherein the filler comprises inert, inorganic material or a superabsorbent material.
11. A polymer feedstock according to a claim 1 wherein the filler comprises both an inert, inorganic material and a superabsorbent material.
12. A polymer feedstock according to claim 1 wherein the inorganic filler comprises calcium carbonate.
13. A polymer feedstock according to claim 5 wherein the external lubricant comprises a stearate.
14. A PVA-containing polymer feedstock in the form of a cold-pressed tablet or pellet comprising, by weight of the feedstock:—
40 to 80% PVA;
5 to 50% solid particulate filler;
5 to 20% plasticizer; and
0.0001 to 5% lubricant.
15. A polymer feedstock according to claim 14 , comprising, by weight of the feedstock:—
40 to 70% PVA;
8 to 20% plasticizer; and
0.5 to 2.5% lubricant.
16. A polymer feedstock according to claim 15 comprising at least 0.5% internal lubricant and at least 0.0001% external lubricant.
17. A polymer feedstock according to claim 16 wherein a fatty acid amide is provided as internal lubricant.
18. A polymer feedstock according to claim 16 wherein stearate is provided as external lubricant.
19. A polymer feedstock according to claim 14 comprising, by weight of the feedstock:—
50 to 70% PVA:
5 to 50% stearate-coated calcium carbonate as said filler;
8 to 20% glycerol; and
at least 0.5% fatty acid amide and at least 0.0001% stearate as lubricant.
20. A polymer feedstock according to claim 1 prepared without liquefying the bulk of the polymer granules.
21. A polymer feedstock according to claim 1 having a moisture content less than about 10% by weight of the feedstock but greater than 0.01% to bind the pellets or tablets.
22. A method of making a PVA-containing polymer feedstock according to claim 1 comprising blending the PVA with the plasticizer, the internal lubricant, the external lubricant and the filler, said internal lubricant including a fatty acid amide, in the presence of an amount of moisture sufficient to bind the polymer feedstock into tablets or pellets upon cold pressing and cold pressing the feedstock into tablets or pellets.
23. A method according to claim 22 comprising blending, in a high speed blender, the PVA and the internal lubricant.
24. A method according to claim 22 comprising adding moisture to the components to be blended.
25. A method according to claim 22 wherein PVA and lubricant are fed into a high speed mixer gravimetrically.
26. A method of making a PVA-containing polymer feedstock according to claim 22 , wherein the filler comprises a superabsorbent material.
27. A method of extruding a PVA-containing polymer feedstock comprising forming a feedstock according to claim 1 and extruding the feedstock into a product, wherein the feedstock is prepared without liquefying the bulk of the polymer granules.