Measuring and testing – Liquid analysis or analysis of the suspension of solids in a... – Viscosity
Patent
1998-09-10
2000-05-23
Larkin, Daniel S.
Measuring and testing
Liquid analysis or analysis of the suspension of solids in a...
Viscosity
G01N 1114
Patent
active
060653302
DESCRIPTION:
BRIEF SUMMARY
The present invention is concerned with a rheometer for assessing characteristics, such as flow characteristics, of materials.
Rheometers are used in a wide variety of chemical and material processing industries including pharmaceuticals, food processing, agrochemicals, paint and pigment manufacture, paper manufacture, catalysts, ceramics and cosmetics for determining and comparing characteristics, such as flow characteristics, of materials such as powders, liquids and semi-solids such as pastes, gels, ointments and the like. These materials generally combine the properties of a viscous liquid and an elastic solid, that is they are visco-elastic. The response of such materials to mechanical force is important for their proper manufacture and use and as a result rheometry is an important tool in their development, production and quality control.
Viscometers and rheometers are well known for assessing the characteristics of liquids and some semi-solids. However, these known instruments have limitations and are not suitable for many kinds of semi-solid materials. In particular, they are not suited to assessing the characteristics of powders when or while being mixed with other materials such as solid or liquid binders, surfactants or air. Known twin rotor mixing machines have been modified to carry out this assessment and a number of "mixer torque rheometers" are available commercially. These apparatus employ complex rotors, have a poor volumetric efficiency and lack sensitivity and repeatability. The lack of sensitivity and repeatability are due to the dependence of these apparatus on material being squeezed between two rotor blades rotating at different speeds.
The torque transient associated with this squeezing is recorded and used to assess the flow characteristics of the material. However, the amount of material trapped between the rotor blades is not consistent and leads to variable results. Only the speed of the rotors can be varied so that there is limited scope for sensitively testing materials having widely different characteristics.
Some torque rheometers have rotors that do not overlap, and the torque required to rotate one of the counter-rotating shafts is used to characterise the material. However, this type of torque rheometer has poor sensitivity and requires significant amounts of material in order to complete a test.
The poor volumetric efficiency of the known apparatus can lead to a significant proportion of the material remaining unmixed and this is a further cause of variability in the results. Additionally, poor volumetric efficiency renders the apparatus unsuited for assessing small quantities of material which is an important requirement for drug formulation.
A further problem with known apparatus is the difficulty of cleaning the bowl and rotors after use. Cleaning is important to avoid cross-contamination and in some cases to ensure recovery of as much material as possible.
U.S. Pat. No. 5,118,439 describes a viscometer in conjunction with a helipath stand in which a rotating shearing spindle describes a helical path through a test sample.
GB-A-2 092 308 describes a paddle arrangement for measuring the workability of concrete. The paddle is rotated in the concrete and the torque required to turn the paddle when immersed in fresh concrete is measured.
U.S. Pat. No. 4,530,701 describes the use of a Brookfield viscometer with helipath attachment in which spindles in the form of wire tees traced out helical patterns through fresh, unsheared volumes of sample. WO-A-9203719 describes a rheometer in which a cylindrical spindle is rotated in a cylindrical sample chamber. U.S. Pat. No. 3,935,729 describes a coaxial cylinder rheometer in which a cylindrical rotor rotates within an outer cylinder which contains a material to be tested. The rotor is movable axially as well as rotationally. WO-A-9509353 describes a viscometer in which the rotor can be changed automatically.
It is therefore an object of the present invention to provide a rheometer which eliminates or at least ameliorates the above
REFERENCES:
patent: 3935729 (1976-02-01), McCarthy
patent: 4148214 (1979-04-01), Madsen
patent: 4530701 (1985-07-01), Koskan et al.
patent: 5118439 (1992-06-01), Urfer et al.
patent: 5357785 (1994-10-01), Hemmings et al.
patent: 5531102 (1996-07-01), Brookfield et al.
International Search Report Jul. 4, 1997.
European Search Report Jun. 25, 1998.
"Brookfield Synchro-Electric Viscometer", product brochure, Brookfield Engineering Laboratories, Jan. 1970.
Freeman Reginald Edward
Iles Christopher Martin
Dorman Ira S.
Larkin Daniel S.
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