Suspension Polymerization of VCM and the Role of PVOH
PVOH is often used as a dispersing stabilizer for the suspension polymerization of vinyl chloride monomer (VCM). The surface active performance in relation to vinyl monomers can be widely optimized by selecting the appropriate grade of PVOH characterized by its polymerization and saponification degree.
The suspension polymerization of VCM is a technique used to produce PVC whose particle size ranges from 50 to 200 μ VCM is suspended in water by means of stirring and use of a dispersing agent and allowing a polymerization reaction to continue for several hours. The powder properties of the resultant PVC, including the size and shape of particles and bulk density, vary depending on the particle forming process during the polymerization.
The role of PVOH in the particle forming process, governing the powder properties of PVC, is very critical. 50 to 80% of the powder properties of PVC depends on the surface activity performance of PVOH.
Furthermore, the properties required of a dispersing agent are constantly changing. For instance, the speed of polymerization has been increasingly high thanks to 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, the residual VCM removal performance.
To respond to a diversity of requests from the market, Nippon Gohsei offers a full line of proprietary dispersants for suspension polymerization of VCM (primary dispersant, secondary dispersant) that have a wide variety of surface active properties.
 |
|
Grade |
Saponification Degree
(mol % ) |
Viscosity
(mPa•s, 4 % ) |
Properties |
|
|
G Type |
GH-23
GH-20
GH-17 |
86.5-89.0
86.5-89.0
86.5-89.0 |
48-56
40-46
27-33 |
• For high BD |
|
K Type |
KH-20
KH-17
KM-11 |
78.5-81.5
78.5-81.5
76.7-79.3 |
44-52
32-38
11.7-14.3 |
• Good polymerization stability |
|
New KH (under development) |
78.5-81.5 |
|
• Accelerated monomer adsorption |
|
KP Type |
KP-08R
KP-06R |
71.0-75.0
71.0-75.0 |
6.0-8.0
5.0-7.0 |
• Good porosity |
|
KX Type |
KX-310
KX-315L*
|
70.0-74.0
70.0-74.0 |
7.7-8.7
7.5-8.7 |
• High porosity (for low-temperature polymerization) |
|
NOTE ) Standard values for new KX: Interim values |
|
|
 |
|
Grade |
Saponification Degree
(mol % ) |
Viscosity
(mPa•s, 4 % ) |
Product form |
|
|
L Type |
LL-02
L-5407
L-7514 |
45.0-51.0
30.0-38.0
34.0-41.0 |
*7.0-10.0
*9.0-13.0
*20.0-28.0 |
powder(Non water soluble type)
powder(Non water soluble type)
powder(Non water soluble type) |
|
LW-100
LW-200
LW-300
LW-400 |
39.0-46.0
46.0-53.0
53.0-60.0
35.0-38.0 |
**1000-2000
**500-2000
**500-2000
**1500-2800 |
35~38 % aq.solution
39~41 % aq.solution
39~41 % aq.solution
35~38 % aq.solution |
|
*10.0 % Methanol-Water solution(blend ratio:Methanol/Water=1/1) at 25 degree C measuered by Hoeppler visocometer.
**40.0 % aq.solution at 25 degree C measuered by B-type visocometer. |
|
|
|
PVC Applications
