摘要:
Silica sols which have a large alkali excess, i.e. a low molar ratio SiO.sub.2 to M.sub.2 O, and which contain silica particles with a high specific surface area. The silica sols can be prepared through acidification of a water glass solution and subsequent alkalization of the acid sol to the molar ratio in question. The sols are particularly suitable for use as additives, in combination with cationic polymers, in papermaking.
摘要:
Silica sols having a high content of microgel and aluminum modified particles with high specific surface area. The sols can be prepared by a process comprising acidification of a water glass solution, alkalization at a certain dry substance content, particle growth and aluminum modification. The sols are particularly suitable for use as additives, in combination with cationic polymers, in papermaking.
摘要:
In making paper from an aqueous papermaking stock a binder comprising colloidal silicic acid and cationic starch is added to the stock for improving the paper or the retention of the stock components, or is added to the white water for reducing the pollution problems or recovering values from the white water.The cationic starch of the binder has a degree of substitution of not less than 0.01, and the weight ratio of cationic starch to SiO.sub.2 is between 1:1 and 25:1.
摘要:
In one aspect, the invention provides fluorescent probes and assays. The probes include a fluorophore-quencher pair that undergoes a switch from dark to fluorescent in response to a reaction of the quencher. The switch of the probe from dark to fluorescent is typically mediated by an enzyme that acts directly or indirectly on the quencher, interfering with its ability to quench fluorescence emission from the fluorophore.In another aspect, the invention provides a reporter gene assay system and methods of using this system. The assay system includes a fluorophore-quencher probe and an enzyme that acts directly or indirectly on the quencher, increasing the fluorescent emission of the fluorophore. In still other aspects, the invention provides nucleic acid constructs and cells expressing the peptide products of these constructs.In assays of the invention, the presence of a target substance is detected by the switching of fluorescence mediated by the change in oxidation state of the quencher. The assay systems are of use in numerous assay formats, e.g., confirming the expression of the enzyme that acts on the quencher, and/or detecting a species conjugated to the enzyme.
摘要:
A papermaking process in which an aqueous papermaking stock containing a cellulosic pulp is formed and dried. The stock includes a binder comprising colloidal silicic acid, and cationic starch which is added to the stock before the sheet is formed. The manner of addition involves first adding and intermixing in the stock a portion of the colloidal silicic acid and then the cationic starch and, after an agglomerate has formed, adding and intermixing the remainder of the colloidal silicic acid prior to the formation of the sheet. The method results in improved sheet properties and improved retention of filler and fines on the wire.
摘要:
Cellulose fibre containing products in sheet or web form, such as paper and pulp sheets, are produced from a suspension of cellulose containing fibres, and optional fillers, to which is added anionic inorganic particles, such as bentonite and silica based particles, and a cationic carbohydrate polymer containing aluminum. The cationic carbohydrate polymers are cationic galactomannans or cationic starch. High cationized starch with a degree of substitution of at least 0.07 are especially suitable.
摘要:
A process for the production of paper by forming and dewatering a suspension of cellulose containing fibres, and optional fillers, on a wire. The forming and dewatering is carried out in the presence of a combination of an aluminum compound, a cationic retention agent and a polymeric silicic acid having a high specific surface area. The combination of substances improves dewatering and retention of fines and fillers.
摘要:
The invention relates to a method for the production of needle-punch carpets with improved properties, in which method use is made, in the chemical bonding of the needle-felt, of alkali-stabilized silicic acid sol in combination with a latex of an organic binder which is conventional in this context. The amount of silicic acid is of the order of magnitude of from 1 to 30 weight % calculated as dry SiO.sub.2 on dry polymer and the particle size may vary between 1 and 100 nm.