“Pre-gel addition” and “Dry-powder addition”
BK organoclay powder is made up of lamellar structure polymer. To carry out under shear, solvent penetrate capillary gap sheet to wet. This occurs to lamellar structure polymer de-agglomeration effect. Conventionally, the system viscosity increases. This will cause organoclay a partial de-agglomeration of the platelets, but no means complete dispersion. To add a polar activator under shear , these lamellar structure polymer are separated completely , a gel structure is developed by edge-to-edge hydrogen bonding like ”house of card”. It is called “pre-gel addition” In special technique procedure , lamellar structure polymer of organoclay is separated more . The stable gel structure can be formed by solvent wetting, and shear. It can be added as a dry powder addition directly before mill process. It is called “dry-powder addition”.
Using which addition method of BK organoclay rheological additive depends on the characteristics of the resin/solvents employed. For example, it is preferred the “pre-gel addition” when the resin has a poor wetting capacity such as epoxy resin ,polyester resin,short-oil alkyd resin. We can use the “dry-powder addition” when the resin has a good wetting capacity .
(1)¡¢Pre-gel addition
The main points are as follows:
Choose the main solvent to produce the pre-gel
Determine organoclay addition weight 5-10%
¢ÙPreparation of BK pre-gel:
A.Add 85-87% solvents or mixed solvents Mix
B.Add 5-10% BK series organoclay Disperse at high speed (2500rpm) for5-10minutes
C.Add polar activator,3-5% Disperse at high speed (2500rpm) for15-20 minutes
¢ÚAddition of BK pre-gel:
A. For poor-wetting capacity resin systems (epoxy,polyester, short-oil alkyd, acrylic resin, etc.), use in combination with surfactant, and can develop thixotropy structure under shear,addition process is as follows:
1. Charge resin and solvents (mix)
2. BK pre-gel (mix)
3. Surfactant
4. Pigment (disperse)
5. Dilute to desired viscosity
B. For poor wetting capacity resin non-thixotropic grind materials, and using surfactant,addition process is as follows:
1. Charge resin and solvents, mix
2. Surfactant (if required)
3. Pigment
4. Disperse to desired fineness with grinding
5. BK pre-gel
6. Disperse completely to desired fineness
7. Dilute to desired viscosity
(2)¡¢Dry powder addition
¢Ù. It is convenient to add BK-884, BK-286,BK-923etc,by dry powder addition for good wetting capacity resin and grind material systems :
1.Charge Solvents and resin, mix
2.BK organoclay powder, mix for 10 min
3.Polar activator, mix for 10 min
4.Surfactant
5.Pigment (disperse)
6.Dilute to desired viscosity
¢Ú. For poor wetting resin, and can develop thixotropy structure under shear,addition process is as follows:
1.Solvents
2.BK organoclay powder, mix for 10 min
3.Polar activator, mix for 5-10 min
4.Resin (mix)
5.Surfactant
6.Pigment (disperse)Dilute
7.Dilute to desired viscosity
(3).Main points for attention
The complete dispersion is very important to BK series organoclay,pls note as follows:
1.Different organoclays suite different solvents. Choose organoclays according to different solvent polarity.(pls refer table5)
2.Polar activator would help the organoclay form into hydrogen bridge bond , but excess or shortage of it will influence the stability and viscosity of the systems.(pls refer table3) The polar activator usually need to have 5% water content.(95%eth
anol or methanol, propylene carbonate ,acetone)
3.It needs proper shear( stir) force and time.
4.Organoclay needs sufficient water content to develop into gel, usually the moisture content should be 3.5% approx.
5.For the full disperse of organoclay, the polar activator should be added after the organoclay wetted .
6.To avoid the interferance from chemical material. Surfactant and vegetable oil(if needed) should be added after organo
clay form into gel after sufficient dispersion.
7.The organoclay dosage usually is 0.2-2% of the total system approx.
ORGANOCLAY SELECTION CHART BASED ON SOLVENT SYSTEMS
| LOW POLARIT Y → HIGH POLARITY |
| ALIPHATIC |
AROMATIC HYDROCARBONS |
ESTERS, KETONES, AND ALCOHOLS |
| MINERAL OIL *** O.M.S.VM & PNAPHTHA HEXANE HEPTANE |
LOW |
HIGH |
HIGH M.W. |
LOW M.W. |
| PARAFFIN WHITE SPIRITS MINERAL SPIRITS |
TOLUENE XYLENE
STYRENE AROMATIC NAPTHA
|
ETHYLENE ACETATE PROPYLENE ACETATE GLYCOL ETHERS |
PHTHALATE ETHYL METHYL KETONE BUTYL ALCOHOL |
DIMETHYL KETONE DIBUTYL ESTER PROP. CARBONATE |
ALCOHOL PRPYL ALCOHOL BUTYL ALCOHOL HEXONE |
| ¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡ |
| BK-883,BK-881,BK-888 |
|
Conventional Organoclays
(Need Polar Activator) |
| ¡¡ |
| BK-886 |
| ¡¡ |
| ¡¡ |
BK-885 |
¡¡ |
| ¡¡¡¡ |
| ¡¡ |
BK-127,BK-500A |
| ¡¡ |
| BK-883B,BK-886B |
| ¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡¡ |
| |
¡¡¡¡BK-286¡¡¡¡¡¡ |
Unconventional Organoclays
(Activator Free Organoclays) |
| ¡¡ |
| ¡¡ |
BK-884,BK-922 |
|
| ¡¡ |
| ¡¡ |
BK-884A |
¡¡ |
| ¡¡¡¡ |
| BK-886C |
¡¡ |
| ¡¡¡¡ |
| ¡¡ |
BK-886D |
¡¡ |
| ¡¡¡¡ |
| ¡¡ |
BK-100 |
| ¡¡¡¡ |
| ¡¡ |
BK-100A,BK-923 |
| ¡¡¡¡ |
| BK-500 |
¡¡ |
| ¡¡¡¡ |
| BK-388,BK-500B |