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Application
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Stabilizer |
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3. Characteristics and advantages of each grade
KURARAY Primary Suspending Agents
400-grades : 420, 420H, 422H and 424H
These grades of PVAs have relatively high degree of hydrolysis and high degree of polymerization.
- Polymerization proceeds stably when one of the 400-grades is used. It is easy to control grain size of PVC resin especially when a secondary suspending agent is combined.
L-grades : L-8, L-9, L-9-78, L-10, L-11, L-12 and L-508
These grades of PVAs have relatively low degree of hydrolysis and low degree of polymerization.
- The amount of the PVA needed in the suspension polymerization can be reduced compared with that of 400-grades.
- High porosity resin can be obtained with keeping relatively high bulk density. Therefore, plasticizer absorption speed, fish eye level and residual VCM level can drastically improved and excellent processability can be achieved.
- Particle size distribution of the PVC resin becomes sharp and each grain tends to be spherical.
- L-9-78 can be suitably used in a hot charge process, because of its high cloud point.
- With L-508, higher gelation speed of PVC resin can be obtained.
High hydrolysis grades : 224, 224E, 624
These grades of PVAs have very high degree of hydrolysis and very high degree of polymerization.
- High bulk density resin can be obtained when one of the PVAs is used with a conventional primary suspending agent such as 400-grade or another alternative grade.
KURARAY Secondary Suspending Agents
- LM-grades are self-dispersible in cold water. No organic solvent, such as methanol, is needed to disperse them.
- LM-grades can be charged into a reactor as a dispersion. Therefore, they are quite suitable for so called " closed system".
- High porosity and an excellent plasticizer up-take property can be obtained with keeping bulk density.
High viscosity grades : LM-10HD
Low viscosity grades : LM-25, LM-20, LM-22
- Low viscosity grades have better self-dispersibility than high viscosity grades.
- Low viscosity grades can be prepared with a wide range of degree of hydrolysis
KURARAY Anti-Dryfoaming Agents
In the PVC industry, a reactor equipped with a condenser has been commonly used to cut back the reaction time. However, when a condenser is used, reaction mixture tends to foam vigorously during the polymerization. Especially, the foam which forms just before or after the reaction pressure drops is called " dry-foam", and it is extremely difficult to be controlled.
Kuraray developed anti-dryfoaming agents to cope with the problems. Charging one of the ACM grades during the polymerization, the dry-foam in the reactor is instantly disappeared.
ACM grades : ACM-3
- These grades comprise special kinds of PVA.
- These grades of materials are very effective in reducing " dry-foam" during the PVC polymerization.
- There should be no bad influence on PVC qualities when these materials are used.
HOW TO USE The Kuraray Anti-Dry foaming Agent
The Kuraray Anti-Dry foaming Agent should be added into the reactor during the polymerization as a solution after dry foam forms. In General, dry foam can be seen just before or after the pressure of the reaction drops. The concentration of the solution of the Kuraray Anti-Dry foaming Agent should be 0.1 - 3.0 wt%, and the amount should be 0.01 - 0.02 % per VCM as a solid basis.
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