Polyvinyl alcohol mixture gels
Polyvinyl alcohol gels, particularly hydrogels, which are produced by methods and formulas and are provided with a characteristic profile that is adjustable to a large extent, e.g. outstanding mechanical properties with moduli of elasticity of 30 MPa and stiffnesses of 25 MPa at a breaking elongation of 550 percent, or full transparency in a wide range of water contents.
1. A polyvinyl alcohol gel comprising at least two different polyvinyl alcohols and a swelling agent, each polyvinyl alcohol being of the type selected from the group consisting of PVA1, PVA2 and PVA3, wherein the degrees of polymerisation (“DP”) of PVA1 and PVA3 are >1000 and the degree of polymerisation (“DP”) of PVA2 is in the range of 50-1000 and wherein PVA1 and PVA2 are predominantly linear whereas PVA3 has a fraction of long-chain branchings.
2. The polyvinyl alcohol gel according to claim 1 , wherein the gel has a modulus of elasticity E and/or a strength sm in MPa is >5.
3. The polyvinyl alcohol gel according to claim 2 , wherein the modulus of elasticity E and/or strength sm is >10.
4. The polyvinyl alcohol gel according to claim 3 , wherein the modulus of elasticity E and/or strength sm is >15.
5. The polyvinyl alcohol gel according to claim 2 , wherein the modulus of elasticity E and/or strength sm is >20.
6. The polyvinyl alcohol gel according to claim 1 , wherein the gel is obtained from a mixture of polyvinyl alcohol and swelling agent, wherein the viscosity of the mixture during forming is >10,000 mPa.
7. A process for preparing the gel of claim 6 , including extruding the mixture to obtain a gel formation.
8. The process according to claim 7 , including storing the gel formation at a temperature above the freezing point.
9. The polyvinyl alcohol gel according to claim 1 , wherein
a) the degree of hydrolysis of PVA1, PVA2 and PVA3 in mole % is >95;
b) the 1,2-glycol content of PVA1, PVA2 and PVA3 in mole % is <3; and
c) the number of short-chain branchings of PVA1, PVA2 and PVA3 per monomer unit is <10 −2 .
10. The polyvinyl alcohol gel according to claim 1 , wherein
a) the degree of hydrolysis of PVA1, PVA2 and PVA3 in mole % is >98;
b) the 1,2-glycol content of PVA1, PVA2 and PVA3 in mole % is <1; and
c) the number of short-chain branchings of PVA1, PVA2 and PVA3 per monomer unit is <10 −3 .
11. The polyvinyl alcohol gel according to claim 1 , wherein
a) the degree of hydrolysis of PVA1, PVA2 and PVA3 in mole % is >99;
b) the 1,2-glycol content of PVA1, PVA2 and PVA3 in mole % is <0.5; and
c) the number of short-chain branchings of PVA1, PVA2 and PVA3 per monomer unit is <10 −4 .
12. The polyvinyl alcohol gel according to claim 1 , wherein
a) the degree of hydrolysis of PVA1, PVA2 and PVA3 in mole % is >99.8;
b) the 1,2-glycol content of PVA1, PVA2 and PVA3 in mole % is <0.2; and
c) the number of short-chain branchings of PVA1, PVA2 and PVA3 per monomer unit is <10 −6 .
13. The polyvinyl alcohol gel according to claim 1 , wherein
a) PVA1 and PVA3 have a degree of polymerisation DP >1000; and
b) PVA2 has a degree of polymerisation DP in the range of 50-1000.
14. The polyvinyl alcohol gel according to claim 1 , wherein
a) PVA1 and PVA3 have a degree of polymerisation DP >2000; and
b) PVA2 has a degree of polymerisation DP in the range of 60-500.
15. The polyvinyl alcohol gel according to claim 1 , wherein
a) PVA1 and PVA3 have a degree of polymerisation DP >3000; and
b) PVA2 has a degree of polymerisation DP in the range of 70-300.
16. The polyvinyl alcohol gel according to claim 1 , wherein
a) PVA1 and PVA3 have a degree of polymerisation DP >5000; and
b) PVA2 has a degree of polymerisation DP in the range of 75-200.
17. The polyvinyl alcohol gel according to claim 1 , wherein
a) the fraction of PVA2 relative to PVA in wt. % is in the range of 1-95;
b) the fraction of PVA3 relative to PVA in wt. % is in the range of 1-80; and
c) the fraction of PVA relative to PVA and swelling agent in wt. % is in the range of 5-90.
18. The polyvinyl alcohol gel according to claim 1 , wherein
a) the fraction of PVA2 relative to PVA in wt. % is in the range of 2-90;
b) the fraction of PVA3 relative to PVA in wt. % is in the range of 2-60-; and
c) the fraction of PVA relative to PVA and swelling agent in wt. % is in the range of 7-95.
19. The polyvinyl alcohol gel according to claim 1 , wherein
a) the fraction of PVA2 relative to PVA in wt. % is in the range of 3-85;
b) the fraction of PVA3 relative to PVA in wt. % is in the range of 3-50; and
c) the fraction of PVA relative to PVA and swelling agent in wt. % is in the range of 10-80.
20. The polyvinyl alcohol gel, according to claim 1 , wherein the gel has a degree of swelling Q in water in the range of 1.01-3.
21. The polyvinyl alcohol gel, according to claim 1 , wherein the gel has a degree of swelling Q in water in the range of 1.03-2.
22. The polyvinyl alcohol gel, according to claim 1 , wherein the gel has a degree of swelling Q in water in the range of 1.05-1.5.
23. The polyvinyl alcohol gel according to claim 1 , wherein the gel is transparent and free of organic solvents.
24. A process according to claim 7 , including preparing the gel into a biomedicine.
25. A process according to claim 7 , including preparing the gel into an agriculture product.