GB1574892A - Indicator compositions - Google Patents

Description

(54) INDICATOR COMPOSITIONS (71) We, BRENT CHEMICALS INTERNATIONAL LIMITED, a British Company, of Ridgeway, Iver, Buckinghamshire, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement:- Known methods of visually locating surface flaws or cracks in test bodies or parts include the application of a dye penetrant composition to the surface, removing excess composition but leaving composition in the flaws or cracks, optionally applying a developer composition to draw penetrant in the flaws or cracks up to the surface, and inspecting the surface. The dye is chosen so that with appropriate lighting those areas where penetrant composition was trapped in flaws or cracks are made readily visible or detectable.This general method is well known to those experienced in the art. The removal of excess composition is normally conducted by washing, and this washing has to be conducted carefully since if there is inadequate washing, composition containing dye remains on the surface even where there are no flaws or cracks, whilst if there is too much washing penetrant composition may be removed from the flaws or cracks.

Traditional penetrant compositions comprise dyes and surfactants dissolved in solvents or carriers. More recently compositions have been proposed which contain little or no solvent and which are more tolerant to variations in the duration or vigour of washing. These compositions gel significantly upon contact with a small amount of water but then are removed by washing upon contact with larger amounts of water. Thus once washing starts the composition begins to gel so that the composition on the surface is removed whilst the composition in the cracks and flaws tends to remain.

Various formulations for these watergellable compositions have been proposed, but generally those that have the best combination of wash resistance due to gelling combined with water-washability tend to be based on surfactants that are not very readily available or are nonbiodegradable or upon carefully chosen mixtures of surfactants.

Another type of dye penetrant composition is one which is waxy but which becomes fluid on heating. Such compositions are described in, for instance, U.S. Patent Specification No. 3,607,333, but of course work on an entirely different principle from the wash-resistant waterwashable compositions that gel in contact with water.

A wash-resistant water-washable penetrant composition according to the invention is a liquid and comprises one or more dyes and at least 700 by weight surfactant, and at least 30% by weight of the composition is a liquid ethylene oxide propylene oxide block copolymer surfactant.

These compositions gel as described above when contacted with a small amount of water, but are washed away with larger amounts of water. They may contain solvents or carriers but these are generally introduced for reasons of economy and must be used in amounts insufficient to impair substantially the wash-resistant and water-washable properties of the composition. Thus there is always less than 30%' by weight solvents or carriers and preferably there is much less, and most preferably no solvents or carriers. Thus preferred compositions comprise at least 80% surfactants and preferably at least 95 /n surfactants.

The composition may contain minor amounts, for example less than 10% and usually less than 5, of one or more minor additives such as corrosion inhibitors, wetting agents, anti-foamants, defoamers, biocides and biostats. Sarkosyl 0 supplied by Ciba-Geigy Ltd. is an example of such a corrosion inhibitor. Preferably the compositions consist solely of one or more of these together with dyes and surfactants.

The amount of dye is preferably from 0.05 to 20%, most preferably from 0.1 to 10%, by weight. Preferably the ethylene oxide propylene oxide block copolymer surfactant is at least 50 /O by weight of the composition and more preferably at least 80% by weight.

Mixtures of this surfactant with other surfactants can be used, but preferably such other surfactants are present in an amount of less than 50, and generally less than 20%, by weight of the total surfactant present in the composition. Preferred compositions of the invention consist solely of ethylene oxide propylene oxide block copolymer surfactant, one or more minor additives such as discussed above and dye.

Preferably the composition contains at least 95 4 by weight of the ethylene oxide propylene oxide block copolymer surfactant.

It is essential that both the composition and the ethylene oxide propylene oxide block copolymer should be liquid, that is to say liquid at room temperature (200 C).

Accordingly waxy materials, such as those described in U.S. Patent Specification No.

3,607,333 cannot be used.

For best results the ethylene oxide propylene oxide block copolymer has a molecular weight below 4000, preferably from 1500 to 3500, and most preferably 1800 to 3100. The relative proportions of ethylene oxide and propylene oxide in the block copolymer affect its properties and preferably the proportion of ethylene oxide units in the polymer is from 10 to 60, most preferably 15 to 55 /n molar. When the copolymer has a molecular weight in the middle of the preferred range the percentage of ethylene oxide units is preferably at the lower end of the preferred range, whilst if the molecular weight is near either end of the preferred range the percentage of ethylene oxide units is preferably higher, e.g. above 35%.

Preferably when the molecular weight is from 2100 to 2600 the copolymer contains 15 to 350/,, most preferably 20 to 30%, ethylene oxide units, whilst if the molecular weight is 1800 to 2100 or 2600 to 3100 the copolymer contains from 30 to 55, most preferably 40 to 50 /O ethylene oxide units.

Suitable copolymers are commercially available. Suitable copolymers are copolymers having molecular weights of about 2000 or 2950 and containing 40 ethylene oxide (for instance those sold under the trade names "Pluronic" L.44 and L.64 respectively), copolymers having a molecular weight of 1900 and containing 50 /n ethylene oxide units (e.g. "Pluronic" L.35) and copolymers having the molecular weight of 2500 and containing 30% ethylene oxide units, e.g. "Monolan" 2500 E/30, and copolymers having a molecular weight of about 1500 or 2200 and containing about 25% ethylene oxide units, e.g. "Pluronic" L.42 or L.62 respectively. The surfactants sold under the trade mark "Pluronic" are available from Ugine Kuhlmann Chemicals Limited, and those under the trade mark "Monolan" are available from Lankro Chemicals Limited.

The preferred surfactants have a viscosity measured in cSt at 200C of less than 800, and which have a pour point of -40 to +180C, most preferably -4 to +160C.

The dyes used may be dyes which fluoresce in "black" light, for example, Calcofluor OR Yellow, "Azosol" Brilliant Yellow 6GB. Alternatively dyes may be used which fluoresce in "black" light and also exhibit a marked non-fluorescent colour in day light, for example Rhodamine B550, or non-fluorescent dyes may be used, e.g. Oil Red "O". Mixtures of dyes may also be used. "Azosol" is a Trade Mark.

After the dye penetrant composition has been applied and allowed to "dwell" in the usual way, the article nay be washed with water and then examined but if desired a developer composition, for example a dry powder or a solvent or water based developer may be used before examination.

The compositions of the invention may be made merely by mixing the ingredients together. Preferably the dyes are first dissolved in the surfactants with appropriate warming and stirring and then any minor ingredients such as corrosion inhibitors and/or biocides are blended into the mixture.

The following are examples of the invention that may be made in this manner.

(1) (2) (3) Monolan 2500 E/30 98.0 Pluronic L42 60.0% 50.0 / Pluronic L62 37.4"/, 35.0"//, Ethylan CD913 13.0 AzO Brilliant Yellow 6B 1.6% 2.0 / Oil Red '0' 2.0 S Sarkosyl'O' 1.0% All ' by weight "Ethylan" CD913 is an ethoxylate of a primary linear aliphatic alcohol containing 9 to 11 carbon atoms with 2.9 moles ethylene oxide. "Ethylan" is a Trade Mark.

The compositions may be applied to the surface to be tested in conventional manner and rinsed off, and the surface then examined. Particularly good results are achieved if the rinse water used for these, and also for other compositions of the invention, has a temperature above 15"C.

WHAT WE CLAIM IS: 1. A liquid wash-resistant water-washable penetrant composition comprising one or more dyes and at least 70% by weight surfactant, at least 30% by weight of the composition being a liquid ethylene oxide propylene oxide block copolymer surfactant.

2. A composition accordance to Claim 1 consisting of at least 80% by weight surfactant, 0.1 to 10% by weight dye and 0 to 10% by weight of an additive selected from corrosion inhibitors, wetting agents, antifoamants, defoamers, biocides and biostats.

3. A composition according to Claim 1 or Claim 2 in which at least 50% by weight of the surfactant is ethylene oxide propylene oxide block copolymer.

4. A composition according to any preceding claim in which substantially the only surfactant present in the composition is the ethylene oxide propylene oxide block copolymer surfactant.

5. A composition according to any preceding claim containing at least 95% by weight of the ethylene oxide propylene oxide block copolymer.

6. A composition according to any preceding claim in which the block copolymer has a molecular weight below 4000 and the proportion of ethylene oxide units in the polymer is from 10 to 60 /n molar.

7. A composition according to Claim 6 in which the molecular weight is from 1500 to 3500 and the proportion of ethylene oxide units is 15 to 55 /n molar.

8. A composition according to Claim 1 substantially as herein described with reference to the Example.

9. A method of detecting flaws in the surface of an object which comprises applying to the surface a composition according to any preceding claim, washing the surface and thereby gelling the composition in the flaws, and observing the gelled composition.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (9)

**WARNING** start of CLMS field may overlap end of DESC **. The compositions may be applied to the surface to be tested in conventional manner and rinsed off, and the surface then examined. Particularly good results are achieved if the rinse water used for these, and also for other compositions of the invention, has a temperature above 15"C. WHAT WE CLAIM IS:

1. A liquid wash-resistant water-washable penetrant composition comprising one or more dyes and at least 70% by weight surfactant, at least 30% by weight of the composition being a liquid ethylene oxide propylene oxide block copolymer surfactant.

2. A composition accordance to Claim 1 consisting of at least 80% by weight surfactant, 0.1 to 10% by weight dye and 0 to 10% by weight of an additive selected from corrosion inhibitors, wetting agents, antifoamants, defoamers, biocides and biostats.

3. A composition according to Claim 1 or Claim 2 in which at least 50% by weight of the surfactant is ethylene oxide propylene oxide block copolymer.

4. A composition according to any preceding claim in which substantially the only surfactant present in the composition is the ethylene oxide propylene oxide block copolymer surfactant.

5. A composition according to any preceding claim containing at least 95% by weight of the ethylene oxide propylene oxide block copolymer.

6. A composition according to any preceding claim in which the block copolymer has a molecular weight below 4000 and the proportion of ethylene oxide units in the polymer is from 10 to 60 /n molar.

7. A composition according to Claim 6 in which the molecular weight is from 1500 to 3500 and the proportion of ethylene oxide units is 15 to 55 /n molar.

8. A composition according to Claim 1 substantially as herein described with reference to the Example.

9. A method of detecting flaws in the surface of an object which comprises applying to the surface a composition according to any preceding claim, washing the surface and thereby gelling the composition in the flaws, and observing the gelled composition.