Patent Application
20050261160
1. Field of the Invention
This invention relates to wetting agents, and, more particularly, to a stable wetting concentrate, and aqueous wetting compositions thereof, which exhibit superior wetting and spreading properties.
2. Description of the Prior Art
Kolazi S. Narayanan, in U.S. Pat. Nos. 5,424,072; 5,508,249; 5,470,508; and 5,409,639; has described the use of N-octyl pyrrolidone (Surfadone® LP 100) (International Specialty Products) in several applications, particularly for agricultural chemicals. N-octyl pyrrolidone (NOP) however, is costly compared to other surfactants.
Accordingly, it is an object of this invention to provide a stable, superior wetting agent with NOP at a reduced cost.
What is described herein is a wetting concentrate comprising, by wt.,
In the preferred forms of the invention, (b) contains 2 or 3 EO units, the weight ratio of (a):(b) is about 80:20, (c) is sodium lauryl sulfate or sodium laureth sulfate, and (c) is about 2.5%. and (d) is about 1.5%.
A stable wetting composition includes the wettable concentrate and water of dilution, wherein the water of dilution, in parts concentrate to water of is 1:50 to 1:5000, preferably 1:1000 to 1:2000.
A typical use wetting formulation herein includes the wetting concentrate and water of dilution, which is useful, e.g. as an agricultural spray solution, a surface cleanser, a car wash or a fountain wash.
N-octyl pyrrolidone (Agsol® Ex 8 or Surfadone® LP 100) is used commercially in several applications, either neat or in conjunction with other formulated compositions. The main advantage of N-octyl pyrrolidone is its high solvency for hydrophobic molecules. It can also form mixed micelles with several other surfactants, especially with anionic emulsifiers such as sodium lauryl sulfate (SLS) and sodium laureth sulfate. N-octyl pyrrolidone is unique in also being a surface active solvent and thus it can function as an interfacial solvent. This property is advantageous in many consumer formulations e.g. to control the release of organic fragrances and to provide additional wetting on surfaces in spray solutions.
The wetting concentrate of the invention includes (a) octyl or dodecyl pyrrolidone, (b) an ethoxylated alcohol, e.g. ethoxylated nonyl alcohol, (c) is a compatabilizer, preferably an anionic emulsifier, or polyol, and, optionally (d) water.
Preferably, in the wetting concentrate, (b) contains 2 or 3 EO units; the weight ratio of (a):(b) is about 80:20; and (c) is sodium lauryl sulfate or sodium laureth sulfate.
A stable wetting composition of the invention comprises the wetting concentrate and water of dilution, wherein the water of dilution ratio of concentrate to water is about 1:50 to 1:5000; preferably about 1:1000 to 1:2000.
Typical use formulations of the invention includes the wetting concentrate in an agricultural spray solution, a surface cleanser, a car wash or a fountain wash.
Use formulations of the invention can have wetting times <30 sec. and a spreading area on Parafilm® surfaces (hydrophobic surface) 6.25× that of water (20 microliter).
Materials Used
The wetting concentrates were prepared by weighing accurately the appropriate amounts of each ingredient to produce 100 g of stock solutions.
Table 1 below shows the invention ternary compositions containing Agsol® Ex 8, Tomodol® 1-3, aqueous sodium laureth sulfate 2 EO, and/or aqueous sodium laureth sulfate 3 EO. These compositions were prepared by adding increasing amounts (from 0-25%) of commercially available aqueous sodium laureth sulfate to the base mixture of Agsol® Ex 8 and Tomidol® 1-3 (20:80).
These stock solutions were used to prepare for serial dilutions as follows.
SW 1 diluted with distilled water.
Similarly, the rest of the stock solutions at dilutions: 1/100,1/1000, 1/2000, and 1,5000 were prepared as above. All diluted solutions were used for the following tests.
50 ml of each diluted solution was transferred to a Nessler color comparison tube and each solution was observed from time zero to 10 days. The results are shown in Table 2 below.
C) Wetting Time (Drave's Method)
About 300 ml of each dilution (higher dilution first) was transferred into a 250 ml volumetric cylinder. The weight was Hooked on to a cotton skein, then transferred into the cylinder slowly with weight at the lower end. Once the weight was placed at the bottom of the cylinder, a stop watch was started immediately, and the position of cotton skein was observed. The time was recorded when the cotton skein fell to the bottom of the cylinder. This procedure was repeated several times and an average of the wetting time for each solution was recorded. Typically reproducibility was within 10% of reported values, as shown in Table 3. The aqueous solutions of Agsol Ex 8 were acidified with conc HCl to pH˜1.2 to solubilize Agsol Ex 8. In all other compositions using Agsol Ex 8, no acid was added.
D) Spreading Efficacy
A fine-mm graph paper was inserted between two 12 inch×12 inch glass plates. 20 microliter of each solution was transferred on a para-film wax paper mounted on the glass plate. The time and diameter of each drop was immediately recorded by observing it through a magnifying glass with ˜20× magnification. The diameter of the same drop was again measured after three minutes. This procedure was repeated at least three times for each drop. The average diameter after three minutes was recorded. Similarly the average diameter of a drop of distilled water was recorded after three minutes. The ratio of the square of the radius of each set of droplets and the radius of a water droplet was calculated as a measure of spreading efficacy, as shown in Table 4.
E) Foam
A 50 ml solution was accurately transferred into a 100 ml-measuring cylinder, stoppered, and the solution was inverted at a 180° angle 25 times. The volume height of the foam was recorded for fifteen minutes from time zero to a 1-minute interval and the foam volume height was recorded. This procedure then was repeated and an average of two readings for each minute was recorded in mm length. Similarly foam heights of all diluted stock solutions were measured (see Table 5-relative foam heights for compositions 6 and 7 or SW 1 and SW 2).
Table 2 shows the physical stability of selected compositions of Table 1 upon dilution with at ratios of 1/100, 1/500, 1/1000, and 1/2000. All compositions remained clear even after 10 days. However, on dilution in water, the base composition not containing any anionic surfactant (SW 1) separated into two phases within 24 h at 1/100 dilution. However, addition of 5% aqueous sodium laureth sulfate (either with 2 EO or with 3 EO) was sufficient to improve its stability on dilution.
The wetting, spreading and foaming properties of the blends of Agsol® Ex 8, Tomadol® 1-3 and aq Rhodapex® ES-2, or, and Standapol® ES-3, at dilutions at 1/100, 1/500, 1/1000, 1/2000, and 1/5000 were determined. The results are shown in Tables 3 through Tables 5.
*Water system- Spreading data: Spreading droplet area ratio on paraffin-area ratio of 20 microliter droplet on Parafilm compared to water
Ternary blends of (N-octyl or N-dodecyl pyrrolidone), ethoxylated noninol with 2 EO and 3 EO and aqueous sodium lauryl sulfate or sodium laureth sulfate exhibited excellent properties of clarity, wetting, spreading, and foam on dilution with water. Superior wetting (cotton) and spreading on Parafilm® surfaces were observed with the blends. The most favorable clarity was observed for ternary blends, i.e. in the presence of an anionic emulsifier e.g. sodium laureth or sodium lauryl sulfates. The inventive compositions find application where wetting and spreading on hydrophobic surfaces is necessary, e.g. tank mix additives in agricultural formulations, and additives in cleaning compositions. Ternary blends with sodium laureth sulfate showed properties comparable to ternary blends with aqueous sodium lauryl sulfate; however sodium laureth sulfate is particularly advantageous for personal care products because of lower skin irritation of sodium laureth sulfate compared to sodium lauryl sulfate.
While the invention has been described with particular reference to certain embodiments thereof, it will be understood that changes and modifications may be made which are within the skill of the art. Accordingly, it is intended to be bound only by the following claims, in which:
