Organic compounds -- part of the class 532-570 series – Organic compounds – Carbohydrates or derivatives
Reexamination Certificate
2001-03-12
2003-07-22
Barts, Samuel (Department: 1623)
Organic compounds -- part of the class 532-570 series
Organic compounds
Carbohydrates or derivatives
C536S123100, C536S102000, C536S107000, C536S110000, C536S047000, C536S128000, C536S004100, C106S206100
Reexamination Certificate
active
06596860
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to an adhesive composition for wallpaper and the like.
Adhesive compositions for wallpaper are mostly based on cellulose derivatives, such as methylcellulose, methylhydroxypropylcellulose, hydroxyethylcellulose, and carboxymethylcellulose, and/or starch derivatives, such as carboxymethylated or hydroxyalkylated starch. The compositions are usually marketed in dry form, e.g. in flake or granulate form, and are formulated into an aqueous paste just before use.
In order to develop a suitable adhesive composition for wallpaper and the like, several factors are to be taken into account. It is desired that the composition, in the dry form wherein it is purchased, can easily be formulated in an aqueous paste. The aqueous paste should have sufficient adhesive strength for a sheet of wallpaper to adhere to a substrate surface when said sheet is applied thereto. Further, the drying time of the composition should not be too long or too short. Also, after drying, the composition should have sufficient adhesive strength to hold the wallpaper into place. However, the adhesive strength after drying should not be too high. It often occurs that a once applied layer of wallpaper is to be removed so that a fresh layer, for instance a wallpaper having a different design, can be applied.
It is an object of the invention to provide an improved adhesive composition for wallpaper, billposters and the like, which meets all the above requirements.
Surprisingly, it has been found that the incorporation of a derivative of a starch having a high amylopectin content into an adhesive composition for wallpaper and the like bestows highly advantageous properties upon said composition. Thus, the invention relates to an adhesive composition comprising a derivative of a starch, which starch comprises at least 95 wt. % of amylopectin, based on dry substance of the starch, wherein the derivative is obtainable by crosslinking, etherification, esterification, or a combination thereof, of the starch.
A great advantage of an adhesive composition according to the invention is that it contains significantly smaller amounts of salts, which are by-products of the preparation of the composition, than conventional adhesive compositions based on starch. This is particularly advantageous in that the presence of salts may lead to staining of wallpaper, that is being adhered to a surface using the adhesive composition. Also, in comparison with adhesive compositions for wallpaper based on derivatives of conventional starches, which comprise at least 10 wt. % based on dry substance of the starch of amylose, a larger surface of wallpaper can be adhered to a substrate using an adhesive composition according to the invention. In addition, it has been found that wallpaper applied to a substrate using the present adhesive composition can be easily removed, for instance when it is desired to apply a fresh layer of wallpaper to the same substrate, while the adhesive strength of the dry composition is high enough to prevent the wallpaper from releasing itself from the substrate after a certain period of time.
As has been indicated above, an adhesive composition according to the invention, is based on a starch which has a very high amylopectin content. Most starch types consist of granules in which two types of glucose polymers are present. These are amylose (15-35 wt. % on dry substance) and amylopectin (65-85 wt. % on dry substance). Amylose consists of unbranched or slightly branched molecules having an average degree of polymerization of 1000 to 5000, depending on the starch type. Amylopectin consists of very large, highly branched molecules having an average degree of polymerization of 1,000,000 or more. The commercially most important starch types (maize starch, potato starch, wheat starch and tapioca starch) contain 15 to 30 wt. % amylose.
Of some cereal types, such as barley, maize, millet, wheat, milo, rice and sorghum, there are varieties of which the starch granules nearly completely consist of amylopectin. Calculated as weight percent on dry substance, these starch granules contain more than 95%, and usually more than 98% amylopectin. The amylose content of these cereal starch granules is thus less than 5%, and usually less than 2%. The above cereal varieties are also referred to as waxy cereal grains, and the amylopectin starch granules isolated therefrom as waxy cereal starches.
In contrast to the situation of different cereals, root and tuber varieties of which the starch granules nearly exclusively consist of amylopectin are not known in nature. For instance, potato starch granules isolated from potato tubers usually contain about 20% amylose and 80% amylopectin (wt. % on dry substance). During the past 10 years, however, successful efforts have been made to cultivate by genetic modification potato plants which, in the potato tubers, form starch granules consisting for more than 95 wt. % (on dry substance) of amylopectin. It has even been found feasible to produce potato tubers comprising substantially only amylopectin.
SUMMARY OF THE INVENTION
In the formation of starch granules, different enzymes are catalytically active. Of these enzymes, the granule-bound starch synthase (GBSS) is involved in the formation of amylose. The presence of the GBSS enzyme depends on the activity of genes encoding for said GBSS enzyme. Elimination or inhibition of the expression of these specific genes results in the production of the GBSS enzyme being prevented or limited. The elimination of these genes can be realized by genetic modification of potato plant material or by recessive mutation. An example thereof is the amylose-free mutant of the potato (amf) of which the starch substantially only contains amylopectin through a recessive mutation in the GBSS gene. This mutation technique is described in, inter alia, J.H.M. Hovenkamp-Hermelink et al., “Isolation of amylose-free starch mutant of the potato (
Solanum tuberosum L
.)”, Theor. Appl. Gent., (1987), 75:217-221, and E. Jacobsen et al., “Introduction of an amylose-free (amf) mutant into breeding of cultivated potato,
Solanum tuberosum L
., Euphytica, (1991), 53:247-253.
Elimination or inhibition of the expression of the GBSS gene in the potato is also possible by using so-called antisense inhibition. This genetic modification of the potato is described in R. G. F. Visser et al., “Inhibition of the expression of the gene for granule-bound starch synthase in potato by antisense constructs”, Mol. Gen. Genet., (1991), 225:289-296.
By using genetic modification, it has been found possible to cultivate and breed roots and tubers, for instance potato, yam, or cassave (Patent South Africa 97/4383), of which the starch granules contain little or no amylose. As referred to herein, amylopectin potato starch is the potato starch granules isolated from potato tubers and having an amylopectin content of at least 95 wt. % based on dry substance.
Regarding production possibilities and properties, there are significant differences between amylopectin potato starch on the one hand, and the waxy cereal starches on the other hand. This particularly applies to waxy maize starch, which is commercially by far the most important waxy cereal starch. The cultivation of waxy maize, suitable for the production of waxy maize starch is not commercially feasible in countries having a cold or temperate climate, such as The Netherlands, Belgium, England, Germany, Poland, Sweden and Denmark. The climate in these countries, however, is suitable for the cultivation of potatoes. Tapioca starch, obtained from cassave, may be produced in countries having a warm climate, such as is found in regions of South East Asia and South America.
The composition and properties of root and tuber starch, such as amylopectin potato starch and amylopectin tapioca starch, differ from those of the waxy cereal starches. Amylopectin potato starch has a much lower content of lipids and proteins than the waxy cereal starches. Problems regarding odor and foaming, which, because of the lipids and/
Bleeker Ido Pieter
Kamminga Willem
Kesselmans Ronald Peter W.
Barts Samuel
Cooperatieve Verkoop-en Productievereniging van Aardappelmeel en
Henry Michael C.
Hoffmann & Baron , LLP
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