Process of making gel detergent compositions

Details Process of making gel detergent compositions Process of making gel detergent compositions

2002-09-20

2004-09-21

Ogden, Necholus (Department: 1751)

Cleaning compositions for solid surfaces, auxiliary compositions

Cleaning compositions or processes of preparing

For cleaning a specific substrate or removing a specific...

C510S277000, C510S283000, C510S336000, C510S351000, C510S403000, C510S424000, C510S426000, C510S491000

Reexamination Certificate

active

06794347

ABSTRACT:

FIELD OF THE INVENTION
The invention relates to a process of making shear-thinnig gel compositions.
BACKGROUND OF THE INVENTION
Thickened or gel laundry products are preferred by many consumers, over either powder or liquid detergents. Gels provide the advantages of liquid detergents, but also can be used for pretreatment of fabrics, obviating the necessity for purchase of a separate pretreatment product.
Gel detergents have been described. See, for instance, WO 99/06519 and WO 99/27065, Klier et al. (U.S. Pat. No. 5,538,662), GB 2 355 015, Lance-Gomez et al. (U.S. Pat. No. 5,820,695), Hawkins (U.S. Pat. No. 5,952,285), Akred et al. (U.S. Pat. No. 4,515,704), Farr et al. (U.S. Pat. No. 4,900,469).
When a gel is made in a typical thin liquid mixer (i.e., a tank mixer) its shear-thinning characteristic does not allow for homogeneous mixing. The high shear portions of the mixer thin out the gel and are highly mixed areas. The low shear areas barely move—the gel thus creating a disproportionate mixture as ingredients are added. The mixture is made even more disproportionate by the typical method of ingredient addition, e.g. from dilute to rich. The disproportion causes areas of the gel mixture to rise high in viscosity (lumps), thus creating extended and unknown mix times. These typical liquid mixers, their methods of use and the additional mixing needed in them results in entraining air in the gel that cannot or easily be removed. Similar problems exist post mixing. Since the gel is high viscosity at low shear conditions, it is difficult to prime a pump—thus, typical liquid pumps cannot be used. There is also a greater chance of aeration when pumping and moving the gel because of its physical characteristics. Furthermore, if other minor ingredients are post dosed into the gel, extreme methods and/or large amounts of time are required to make a uniform product, due to the gel being shear-thinning. The gel is also harder to clean off the process equipment—thus, increased cleaning times and ingredients needed. Making the gel by using a tank mixer designed for use with shear thinning liquids still involves a myriad of manufacturing issues dealing with post dosing, pumping, storing and aeration.
SUMMARY OF THE INVENTION
The present invention includes a process of making a gel detergent composition, the process comprising mixing ingredients comprising preparing a main mixture and a gelling post-mix, which comprise in total:
(a) from about 8% to about 35%, by weight of the composition, of a surfactant, selected from the group consisting of anionic, nonionic and cationic, and amphoteric surfactants and mixtures thereof;
(b) from about 0.1% to about 5%, by weight of the composition; of a non-neutralized fatty acid;
(c) from about 50 to about 90% of water;
wherein
(i) the mixing is carried out in at least one in-line static or dynamic mixer; and
(ii) the gelling post-mix constitutes from about 1% to about 30% of the composition and comprises an ingredient selected from the group consisting of the non-neutralized fatty acid and an anionic surfactant acid precursor.
Surprisingly, it has been discovered, as part of the present invention, that by employing the gelling post-mix and by mixing in a the in-line mixer, the inventive process results in a better-mixed gel and a more economical process.
DETAILED DESCRIPTION OF THE INVENTION
Except in the operating and comparative examples, or where otherwise explicitly indicated, all numbers in this description indicating amounts of material or conditions of reaction, physical properties of materials and/or use are to be understood as modified by the word “about.” All amounts are by weight of the gel detergent composition, unless otherwise specified.
It should be noted that in specifying any range of concentration, any particular upper concentration can be associated with any particular lower concentration.
For the avoidance of doubt the word “comprising” is intended to mean “including” but not necessarily “consisting of” or “composed of.” In other words, the listed steps or options need not be exhaustive.
“Gel” as used herein means a shear thinning, lamellar gel, with a pouring viscosity in the range of from 100 to 5,000 mPas (milli Pascal seconds), more preferably less than 3,000 mPas, most preferably less than 1,500 mPas. The concept of “gel” in the art is frequently not well defined. The most common, loose definition, however, is that a gel is a thick liquid. Nevertheless, a thick liquid may be a Newtonian fluid, which does not change its viscosity with the change in flow condition, such as honey or syrup. This type of thick liquid is very difficult and messy to dispense. A different type of liquid gel is shear-thinning, i.e. it is thick at low shear condition (e.g., at rest) and thin at high flow rate condition. The rheology of shear-thinning gel may be characterized by Sisko model:
&eegr;=a+b×{dot over (&ggr;)}
n−1
.
Where &eegr; is Viscosity, mPAs,
{dot over (&ggr;)} is shear rate, 1/sec,
a, b are constants, and
n is Sisko Rate index,.
As used herein, “Shear-thining” means a gel with the Sisco rate index less than 0.6.
Shear-thinning rheological properties can be measured with a viscometer or a sophisticated rheometer and the correct measurement spindle. The selection of spindle depends on the type of instrument. Generally, a cylindrical spindle needs a greater volume of sample; less sample is needed for either the disc or cone shape spindles. The protocol involves a steady state flow (SSF). The first step is conditioning step that pre-shears the sample at a set temperature (e.g. 25 OC). The time requirement depends on the type of sample: it generally takes from 30 seconds to an hour. The second step is the steady state flow step, which involves adjusting either shear stress (for a controlled stress rheometer only) or shear rate and collecting data after the sample has reached apparent equilibrium. To determine the flow behavior, the maximum shear rate and the ramp time can be arbitrarily chosen for the test program. During the test, up to 1000 data points can be gathered and the viscosity, shear stress, shear rate, temperature and test time at each point are stored. The plot of viscosity vs. shear rate will reveal whether the sample is shear thinning or not. A mathematical model, such as Sisko model, may be fitted to the data points.
As used herein, “pouring viscosity” means viscosity measured at a shear rate of 21 s
−1
, which can be measured using the procedure described immediately above, or it can be read off the plot of viscosity vs. shear rate.
As used herein, “lamellar” means that liquid crystals within the gel have lipid layers (sheets). Lamellar structures can be detected by polarized light microscope. Furthermore, majority of these lamellar sheets remain in a sheet form and only a very limited portion, say less than 10% of lamellar phase, is rolled up to form onion structure—like of vesicles.
As used herein, “lamellar gels” means gels that have lamellar phase structure, alone, in intermixed with isotropic phase (known as L1).
A sophisticated rheometer, such as AR-series from TA Instruments is needed for the measurement of G′ and G″. First, the Pseudo-linear viscoelastic region (LVR) is determined via an Osillatory Stress Sweep (OSS). The sample is then conditioned via timed pre-shear at a set temperature (e.g. 25° C.) so that its structure can equilibrate and so that the geometry to come to thermal equilibration before data acquisition begins. Next, a Stress Sweep step is performed. For an unknown sample, a good rule of thumb is to test over the allowable shear stress (torque) range of the instrument (e.g. 1-10,000 microN.m) and a frequency of 1 Hz. Finally, an Oscillatory Frequency Sweep is performed. The frequency range may be set between 100 Hz to 0.1 Hz. The % Strain or shear stress should be set to a value within LVR found the OSS step. The G′ value from LVR is used to correlate to the Snap-Back phenomenon.
“Transparent” as used herein includes both transparent and translucent and

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