Pigmented porous material

Details Pigmented porous material Pigmented porous material

1999-11-16

2002-12-17

Elve, M. Alexandra (Department: 1725)

Stock material or miscellaneous articles

Web or sheet containing structurally defined element or...

Composite having a component wherein a constituent is liquid...

C428S321300

Reexamination Certificate

active

06495250

ABSTRACT:

The present application relates to porous materials given coloured pigmentation with organic pigments localized in their pores and to a process for their preparation, which is characterized by the use of particular thermally activated latent catalysts.
Porous materials are commonly coloured with dyes that are applied, for example, as stains. In order to achieve satisfactory colouring results with this method a requirement is that the porous material to be coloured has a high and uniform affinity for the dye; this requirement, however, is seldom met. Porous materials coloured with dyes possess, moreover, an undesirably low light stability, and in contact with water or organic liquids (beverages, for example) marks may be formed on articles that are in contact with the materials, since the dyes are in some cases leached out again.
Another method of imparting a coloured appearance to some porous materials is to provide them with a pigmented coating. This method, however, has the disadvantage that the pores become sealed by the pigmented coating material, with the result that it becomes difficult if not impossible to perceive visually the nature of the porous material. This is a great disadvantage, especially with natural porous materials, since it is their properties, especially their natural appearance and their permeability, that are the most prized. The properties of the porous material, however, are impaired by a pigmented coating.
EP 648 770 and EP 648 817 disclose carbamate-functional, soluble chromophors which can be converted to the corresponding pigments by heating them to relatively high temperatures, with the ensuing elimination of the carbamate radicals. These compounds are suitable for the mass colouring of polymers and, according to EP 654 711, for the colouring of resists and of polymer coats to which they are applied. Compounds of the same type but with improved properties are known from EP 742 556 and WO 98/32802.
EP 654 711 also discloses the use of acids, bases and compounds capable of forming acids or bases under actinic irradiation, preferably some sulfonium salts, as catalysts.
U.S. Pat. No. 5,243,052 discloses carbonates of quinophthalones, which are of limited solubility and can be used in heat-sensitive recording systems. The leuco dye is embedded within a polymer, preferably in polyethyloxazoline.
Soluble derivatives of triphenylmethane dyes are known from U.S. Pat. No. 4,828,976. They are likewise used in heat-sensitive recording systems, together with a binder such as cellulose acetate-butyrate, polyvinylpyrrolidone or copolymerized ethylene/maleic anhydride.
EP 742 556, furthermore, describes textured pigmentary coatings which are prepared from soluble or meltable precursors and which cover all or part of a substrate surface such as fibres and fabrics. It has been found, however, that these pigmentary coatings fail to meet high requirements in terms, in particular, of their rub fastness.
Also known, finally, are numerous heat-sensitive recording systems in which colourless precursors of colorants—as solids, in the form, for example, of aqueous suspensions, together with binders and with or without fillers—are incorporated as the recording layer. For example, JP 04/123,175 describes leucoindigoid derivatives. Colorants in solid form, however, like conventional pigments, for example, make hardly any entry into the pores but for the most part remain, undesirably, on the surface.
It has now surprisingly been found that porous materials can be coloured without impairing their properties, and especially without clogging the pores, if fragmentable pigment precursors in melted or dissolved form are introduced into the pores and then converted to their insoluble pigmentary form.
Depending on the solvent, pressure, temperature and treatment time it is possible to influence to some extend the depth of penetration of the pigment precursor and so to obtain colorations wherein the pigment is more or less close to the surface. Since in this case the entirety of the pigment contributes to colouring, it is possible to reduce its amount to the minimum necessary for coloration, and the colour of the material core remains unaltered.
For other materials, it is conversely desirable to increase the penetration depth. This is especially the case with organic materials, in particular with natural organic materials wherein at least some of the pores are constituted by cells which are hardly accessible to a solution from the surface. There is a strong wish for a penetration deeper than 2 cells, for example at least 8 cells, preferably for example 20 cells or even more. However, increasing the penetration depth into many materials requires high temperatures. Consequently, porous materials which are themselves altered by heat cannot satisfactory be pigmented in depth. Adding a catalyst such as those described in the prior art in order to decrease the latent pigment's decomposition temperature moreover leads to an even lower penetration depth. This is particularly a disadvantage with naturally occurring organic porous materials such as wood, leather and hair, for example alder, amazakoe, aniegre (
Aningria altissima
), ash, balsa, beech, birch, birds eye maple, cedar, cherry, coralwood, cypress, dibaja (
Triplochiton scleroxylon
), ebony, efok (koto, tay,
Pterygota macrocarpa
), elm, eucalyptus, fir, iroko, izingana (zebrano,
Microberlinia brazzavillensis
), larch, madrona burl, mahogany, maple, movongui, myrtle, oak, obeche (
Obece scuro
), palisander (rosewood, black wood), pear, pine, poplar, sap gum, satinwood, spruce, sugar maple, sycamore, tulip, vavona, walnut or yew wood, similar wood from trees growing on other continents, lace wood, veal or pig leather, wool or camel or human hair, to mention only few natural substrates to which the invention is of course not limited.
It has now surprisingly been found, that the use of particular catalysts under appropriate conditions enables to get porous materials with uniform pigmentation right through, hence allowing them with little or no change in colour to be processed, for example cut, bent or joined—by gluing, for instance. Consequently, either finished articles or raw material, as desired, can be coloured prior to its processing or shaping.
A particularly advantageous result of the invention is an increase in production flexibility, and possibilities for making savings, when producing articles from coloured porous materials. A further great advantage is that following the colouring of the porous material its nature is, surprisingly, still apparent to the eye.
The resulting colorations are also surprisingly strong in colour, fast to weathering, light and heat, rubbing, water and solvent, and are also highly uniform optically provided the material itself is uniform in its porosity. With particular advantage this permits the use of materials whose quality would not enable any satisfactory results to be obtained on conventional colouring, a feature which, especially in the case of naturally occurring organic porous materials of complex structure, such as wood, leather or hair, for example, paves the way for ecologically significant, improved utilization of natural resources.
The present invention accordingly provides a coloured porous material comprising in its pores an effectively colouring amount of an organic pigment which is obtained by fragmenting a meltable or solvent-soluble pigment precursor, characterized in said fragmentation takes place in the presence of an effective amount of a strong acid obtained from a catalyst precursor at a temperature of from 40 to 160° C.
Said temperature is preferably from 60 to 140° C., more preferably from 80 to 120° C. The strong acid resulting from the catalyst precursor's thermal reaction has preferably a pK
a
, of 2 or lower, most preferably a pK
a
of 1 or lower. No lower limit can be given for the pK
a
, as very strong acids having largely negative or not even measurable values are well suitable. In general, an amount of from about 1 to about 100% by weight of the catalyst

Affiliated with

Also associated with

Rating

Pigmented porous material does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Pigmented porous material, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Pigmented porous material will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-2987258