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Technical Information by Appication

PVC Applications

Suspension Polymerization of VCMs and Role of PVOH

Water-soluble polymers are often used as dispersing stabilizers for the suspension polymerization of vinyl chloride monomers (VCMs). In particular, PVOH is a suitable agent optimizing the surface-active performance of a vinyl monomer by selecting appropriate degrees of polymerization and saponification.

The suspension polymerization of VCMs is a technique used to produce PVC with a particle size of 50 to 200 μm. A VCM is suspended in water by means of stirring and use of a dispersing agent, and then polymerized for several hours to achieve PVC. The properties of the resultant PVC powder, including the size and shape of particles and bulk density, vary depending on the particle forming process during the polymerization.
In the particle forming process, the role of PVOH, which governs the properties of PVC powder, is very critical, where 50% to 80% of the properties of PVC powder depend on the surface activity performance of PVOH.

Furthermore, required properties of a dispersing agent constantly change. For instance, the speed of polymerization has been accelerated because of improved heat removal efficiency during the suspension polymerization process. Therefore, the need is mounting for a PVOH capable of satisfying requirements in both productivity and environmental protection, without limiting performance, for example, residual VCM removal.

To respond to a wide range of requests from the market, Nippon Gohsei offers a full line of proprietary dispersants for suspension polymerization of VCMs (i.e., primary and secondary dispersants) that have a variety of surface-active properties.

Role of PVOH

Primary Dispersants
Grade Saponification Degree
(mol % )
Viscosity
(mPa・s, 4 % )
Properties
GH-23 86.5-89.0 48-56 For high BD
GH-22 86.5-89.0 45-52
GH-20 86.5-89.0 40-46
GH-17 86.5-89.0 27-33
KH-20 78.5-81.5 44-52 Good polymerization stability
KH-17 78.5-81.5 32-38
KP-08R 71.0-75.0 6.0-8.0 Good porosity

 

Secondary Dispersants
Grade Saponification Degree
(mol % )
Viscosity
(mPa・s, 4 % )
Product form
LL-810 45.0-51.0 *7.0-10.0 powder(Non water soluble type)
LL-920 30.0-38.0 *9.0-13.0 powder(Non water soluble type)
LL-940 34.0-41.0 *20.0-28.0 powder(Non water soluble type)
LW-100 39.0-46.0 **500-2,500 35~38 % aq.solution
LW-200 46.0-53.0 **500-2,000 39~41 % aq.solution

*10.0 % Methanol-Water solution(blend ratio:Methanol/Water=1/1) at 25℃ measuered by Hoppler viscometer.
**39 %~41 % aq.solution at 25℃ measuered by B-type viscometer.

SUMMARY OF PVOH FOR PVC SUSPENSION



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