Bleaching and dyeing; fluid treatment and chemical modification – Bleaching – Chemical
Patent
1986-12-12
1990-02-27
Lieberman, Paul
Bleaching and dyeing; fluid treatment and chemical modification
Bleaching
Chemical
8101, 8111, 427373, D06L 306
Patent
active
049042734
DESCRIPTION:
BRIEF SUMMARY
DESCRIPTION
The present invention relates to the foam treatment of porous substrates and has particular reference to the foam treatments of textile materials.
Our European Patent No. 47058 describes and claims a method of treating a surface with reagents, which method comprises establishing a reagent in a liquid phase, forming a foam of the liquid phase, applying foam to the surface to be treated and causing or allowing the foam to collapse at the interface with the surface being treated to deposit the reagent thereon, and thereafter removing or deactivating the reagent on said surface when the treatment is completed, whereby the rate of foam collapse is controlled to control the rate of application of the reagent to the surface.
The process forming the subject of this European Patent has been found to be highly beneficial and constitutes a major advance in the art of the treatment of substrates.
The careful control that can be exercised over the amount of reagent applied to a substrate surface has been improved considerably by this invention, but nevertheless the results obtained with this invention still suffer, to some extent, from the disadvantage that there is uneven treatment through the depth of the substrate per se. European Patent No. 47058 describes the application of foam to a surface. The specification then teaches the collapse of the foam upon that surface in a controlled manner to allow release of reagent onto the surface. Thus, the surface areas of the substrate are treated in a controlled manner, but depending upon the variations in the porosity of the substrate, the reagent may or may not permeate into the interstices of porous substrate, thus producing a possible uneveness of effect.
The present invention seeks to overcome this disadvantage by providing an interaction between a reagent not only on the surface of the material, but also within the interstices of the substrate being treated.
According to the present invention, therefore, there is provided a method of treating a porous substrate with a reagent, which method comprises moisture content upon treatment with the foam of up to 130% of the foam transit water content as herein defined thereby surface interfaces and interior interfaces, between foam and substrate enable foam transit through said substrate, and at the interior interfaces and deactivating the reagent.
The foam is preferably a stable foam having a blow ratio within the range of 5 to 80, preferably 10 to 50. The porous substrate may be substantially dry on treatment with the foam or may have a moisture content within the range of the foam transit water content .+-. 30%.
The termination of the treatment may be effected by treatment of the substrate with a heat transfer medium such as, for example, a vapour or gas having a temperature of at least 100.degree. C. In one embodiment of the invention, the reagent may be a bleaching agent.
For the purposes of this specification, the expression "foam transit water content" (FTWC) of a porous substrate is the water content of that substrate, expressed as a percentage of the substrate's dry weight, when a foam containing a treatment agent is passed through a dry porous substrate material substantially perpendicular thereto under the action of a pressure gradient until foam starts to exit from the other side thereof. The determination of the foam transit water content may be effected by preparing a dried sample of the porous material, placing the material on a filter plate of a funnel, covering it with an excess of foam in accordance with the invention, applying strong vacuum to suck foam through the material and removing the sample immediately after the foam has disappeared from the upper side of the sample, determining the amount of liquid present in the sheet material after such treatment as a percentage of the dry weight of the material before the application of the foam.
It will be appreciated from the foregoing that the concept of the invention is to provide reagent in the foam not only at the surfaces of the material to be tr
REFERENCES:
patent: 4099913 (1978-07-01), Walter et al.
patent: 4288475 (1981-09-01), Meeker
Adnovum AG
Lieberman Paul
McNally John F.
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