Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Polymers from only ethylenic monomers or processes of...
Patent
1998-11-19
2000-11-14
Nutter, Nathan M.
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Polymers from only ethylenic monomers or processes of...
52623822, 536102, 536106, 536124, 536126, 127 32, 127 33, 127 38, 127 67, 127 70, 127 71, C08B 3100, C08B 3300
Patent
active
061471755
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to the field of biological chemistry and to polysaccharides in particular.
It is more specifically directed to biological products derived from cereal flour and so processed to acquire a vitreous texture and enough hardness to be used as abrasive material.
The present invention hence deals with biological products resulting from polymerizing and crosslinking cereal flours by means of a divalent crosslinking agent.
DISCUSSION OF THE PRIOR ART
From French Patent N.degree. 2 646 621, it has been known that vitreous polysaccharide particles can be obtained from starch. These particles have an apparent hardness intermediate the hardness of the coating to be abraded and the hardness of the substrate bearing said coating whereby selective abrasion is achieved.
These particles are formed of wheat starch which had been annealed beforehand to obtain a solid product having a moisture content in the range of 10 to 70% by weight, reacted mainly with epichlorhydrin as crosslinking agent to yield polysaccharide molecules having intermolecular chemical cross-linkages, and ground such that the resulting solid product forms granular particules of a specified particle size and displays hardness up to 4.0 Moh.
The granules described in the above mentioned patent are comprised of starch of well defined water content, which is amorphous in structure and contains little dextrose. The product has therefore undergone only minor hydrolysis in the course of different treatments in alkaline conditions.
It should also be noted that the crosslinking agent used in this process is one selected besides epichlorhydrin, among sodium tripolyphosphate or sodium trimetaphosphate.
Experimental trials conducted by the applicant have shown that epichlorhydrin is not an effective crosslinking agent because it does not increase the viscosity of the product disclosed in patent N.degree. 2 646 621.
Another significant point is that wheat starch must be subjected to prolonged annealing to undergo complete gelatinization and then to full drying in an oven or extruder following crosslinking. There is obtained in this way a bulk product which becomes hard and glass-like upon cooling to room temperature.
The biological product which is disclosed in the present application hence differs from the one previously described in patent N.degree. 2 646 621 in that it derives not from variably hydrolyzed starch but from flour, in that the crosslinking agent is not epichlorhydrin but is chosen among divalent crosslinking agents selected from the group of halogen-multisubstituted derivatives, aldehyde compounds, divalent aldehyde compounds, and dicarboxylic acid anhydrides, and in that the drying is performed not in an extruder having different heating portions or compartments but in an extruder or oven ensuring thorough drying without crust formation or, by contrast, without formation of products of too brittle a character.
All such differences result in the formation of a biological product the chemical and physical characteristics of which are quite distict from those disclosed in the pior art patent documents. Namely, whereas epichlorhydrin crosslinking generates ether linkages between individual chains of glucose molecules, the use of divalent derivatives such as formalin or maleic anhydride, leads to complex chemical reactions of a different type and is likely not lead to crosslinkage formation if at all.
In French Patent N.degree. 2 250 851, there are disclosed paint coatings based on clay wherein crosslinking is carried out by formalin treatment with the aid of such an agent as a mixture of melamine-formalin. It is not clear in this reaction whether it is formalin or melamine which reacts with starch or whether both reagents react simultaneously. It can be questioned what sort of reaction is most likely to occur between starch anhydroglucose molecules and such a reagent.
As a matter of fact, the action of a crosslinking agent can lead either to ether bond formation on hydroxymethyl groups at position 6
REFERENCES:
patent: 5066335 (1991-11-01), Lane et al.
Bonhoure Jean-Paul
Doumeizel Jacques
Thery Denis
Nutter Nathan M.
Syndicat Interprofessionnel Biodecap
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