PRODUCT AND METHOD FOR MANUFACTURING SPRAY PLASTER

Abstract: In a dry product for manufacturing plaster (German: Sandspachtel) when mixing the product with water, the component, which upon the mixing with water forms the consistency of the plaster, consists of water-soluble, organic thickening and binding agent in powder state mixed in the product and having such easy-dissolving properties in water and consistency forming, that, as distinguished from the plaster being manufactured batchwise in accordance with prior art, plaster of the same consistency and quality can be manufactured in a continuous process in a continuously operating high-speed mixer. The product makes accordingly possible a method for manufacturing plaster continuously in a rapid mixing process.

Description: PRODUCT AND METHOD FOR MANUFACTURING SPRAY PLASTER TECHNICAL FIELD The present invention relates to a product and a method for manufacturing spray plaster (German: Sandspachtel) . PRIOR ART A spray plaster is a product, which during more than 25 ye has been in use as a thin coat p aster for treatment of fairly smooth interior surfaces of concrete, light weight concrete, gypsum board, etc., prior to painting or wall¬ papering. It is also used as a textured finishing coat on said type of surfaces. Such spray plaster is built up by granular components havi a maximum grain size usually less than 0,5 mm, often less than 0,25 mm, and is formed by mixing the components with water into a paste-like spray plaster consistency. A plast of principally the same composition but with a somewhat lower water content is also known, giving it a consistency suitable for application by hand. A water-soluble organic thickening and binding agent is included in the components in such an amount that the desired plaster consistency is obtained. Since thickening agents are expensive compared with binding agents, a thickening agent mixed with a bindi agent is often used. There are also binding agents which normally serve as thickening agents. Moreover, binding age in the form of plastic dispersions can also be added. The water content is usually 20-28% of the weight of the ready mixed plaster. The plaster is usually manufactured in factory and delivered as finished product to the building • site. However, a product not containing water, i.e. dry plaster is aJ so often manufactured in factory and delivere to the building site, where the dry product is mixed with water in mixers, whereupon the wet-mixed product is trans¬ ferred to a spray equipment or is applied by hand. This last mentioned procedure has compared with the manufactur of finished product in factory the advantage, that carria or freight charges for the delivery from factory become l due to the reduced weight (20-28%) of the product not con ing water / and furthermore the risk for frost during tran sport and storage is eliminated. However, this procedure has the disadvantage, that the treatment time for obtaini correct plaster consistency is rather long. At work sites with manufacture of plaster in said mixers the treatment time is from about five minutes and ' up to about twenty minutes. Moreover, if the plaster is to be sprayed, a tra fer from the mixer to a spray equipment is required. As distinguished from the manufacture of spray plaster sa disadvantage with long treatment time does not exist when manufacturing finishing mortar or gypsum plaster. Even if there are certain similarities in components and applicat between finishing mortar and spray plaster, these product however differ from each other in a great degree. Spray plaster contains organic thickening and binding agents in such an amount, that the paste-like consistency is obtain Finishing mortar such as gypsum plaster, cement-lime mort or the like have quite another consistency and are charac ized in that they are substantially built up by inorganic binding agents and often contain aggregates with a grain size up to 3 a 4 mm. Also organic binding agents can be added but then in a very small amount compared with the content in the paste-like spray plaster (a tenth or less) and this small admixture is made in order to intimately b the additive water and prevent too rapid loss thereof aft application. The problem as to the comparatively long pre ration time existing when mixing a plaste-like p aster consistency does accordingly not exist when mixing a fini shing mortar. When dry mortar is mixed " with water, a water-mixed product ready for use is rapidly and directly obtained. This " fact has made it possible to spray the wat - ixed product on the surface to be covered immediatelv after th,e rapid mixing of the product. Continuously operating rapid mixers for finishing mortar and gypsum plaster with or -without connected spray equipment have also been constructed and -used for several years, for instance mixers described and shown in the book "Spritz- beton-Spritzmδrtel-Spritzputz" by " Gurither Brux, Richard Linder and Gϋnter Ruffort, published 1981 by Verlags- gesellschaft Rudolf Mϋller, Kδln-Braunsfeld, West Germany. Thus, according to prior art it is when manufacturing finishing mortar or gypsum plaster possible to obtain rapidly and directly a product ready for use by spraying. However, with methods known up to now for the manufacture of a spray plaster from the components dry plaster and water, a comparatively long preparing time has been re¬ quired before a homogeneous paste-like plaster ready for application, for instance by spraying, has been ' obtained. DESCRIPTION OF THE INVENTION The object of the present invention is to make it possible in a continuous operation to add water to a dry product andobtain rapidly a plaster having the same consistency and homogeneity as the plaster that has been previously produced batchwise, and thereby admit a more rational handling of the material flow than what has previously been the case. This object has according to the invention been achieved by using a dry product, which as distingui¬ shed from products, known up to now for the manufacture of plaster is characterized in that the component for form¬ ing the consistency of the plaster upon the admixture with water is in powder state with a solubility rapid enough in a continuous mixing process with water in a continuously operating mixer to yield therefrom discharge- able plaster directly ready for use. Thus, it has surprisingly been established, that plaster, contrary to the conception existing during many years, can by using a product according to the invention be pro¬ duced in corresponding way and substantially equally rapid as finishing mortar {< 1 minute) and obtain a perfe plaster product of the same consistency as has been pre- viosly manufactured by batchwise production in a p aster factory. The manufacture of the plaster can take place at the work site or in a factory. Besides the above mentione advantages in the first mentioned case, also the advantag concerning an essentially cheaper transport to the work s are obtained (weight reduction of 20-28% corresponding to the weight of added water) , avoiding of risk for frost during transport and storage in winter time, rational han ing at the work site by the fact that the dry product can be handled in closed containers, from which it in known manner can continuously be conveyed in closed system to the place for the application of the plaster, and the possibility of a rational handling in bulk from factory to work site, whereby handling in piece packing with belonging.costs in all stages is avoided. The rapid continuous mixing by using a product according to the invention has been proved to be able to be carried out in known high-speed mixers, for instance mixers as disclosed in above mentioned book "Spritzbeton-Spritzmδrt Spritzputz", thus in continuous mixing process with con¬ tinuous discharge of plaster ready for use. This also makes possible a direct connection of a spray equipment to the mixer when application of plaster by spraying is desired.. For instance, a continuous flow mixer (German: Durchlaufmischer) has proved to be well adapted. In this mixer a continuous feeding of the dry product and the water takes place, during the mixing. B using a product according to the invention the total manufacturing procedure can furthermore take place con¬ tinuously in the factory, wherein the dry product is mixe in continuously operating mixers and thereafter continuou ly fed to the continuously operating mixer for mixing wit water and continuous discharge of finished plaster there¬ from, whereby accordingly a continuous manufacture* o plaster starting from the basic components is obtained. Cellulose derivate in powder state can advantageously be used as easy—dissolving binding agent. However, also othe products giving easy dissolving, homogenizing and plaster consistency can be used. In tests carried out in order to control the correctness of the inventive idea the dry product has for example consisted of: dolomite 67% chalk 3.2% bentonite 1.2% zinc oxide 0.13% cellulose derivate 0.8% plastic dispersion 0.6% Moreover, a suitable rust inhibitor, for instance sodium nitrite, and suitable preservative may also be added. In case the product is not delivered in wet-mixed form, it is also possible, that the factory-mixed product can contain hydraulic binders, for instance cement. When manu- facturing plaster in wet state it has not been possible to deliver to the building site a pre-fabricated product containing such hydraulic binder. In cases a plaster with higher water resistance has been pursued, one has been forced to accomplish this either by adding the hydraulic binder immediately prior to plastering or by using a high content of plastic dispersion, which has made the product more expensive.

Claims: CLAIMS 1. A product for manufacturing plaster by mixing the _ product with water, which product is in dry state and contains conventional components including component for forming the consistency of the plaster upon the mixing with water and consisting of water soluble, organic thickening and binding agent, c h a r a c t ¬ e r i z e d in that said component is an easy-dissolv¬ ing powder, which in a continuous mixing process with water in a continuously operating mixer yields from the mixer dischargeable plaster directly ready for use. 2. Product according to claim 1, c h a r a c t e r ¬ i z e d in that said component at least partly is cellulose derivate. 3. Product according to claim. 1 or 2, c h a r a c t e r¬ i z e d in that a hydraulic binder, for instance cement, also is added to the product. 4. A method for manufacturing plaster by mixing a product according to any of the preceding claims with water, which product includes a component consisting of easy-dissolving, organic, thickening and binding agent in powder state for forming the consistency of the plaster, c h a r a c t e r i z e d in supplying the product and water to a continuously operating mixer and continuous discharge therefrom of the plaster ready for use. 5. Metπod according to claim 4, c h a r a c t e r ¬ i z e d in a continuous feed of the product and the water during the mixing. O & v.I ■ 6. Method according to claim 4 or 5, wherein the plaster is manufactured in a. completely continuous manufacturing process, c h a r a c t e r i z e d in mixing the compo¬ nents of the product in a continuously operating mixer and continuous feed of the mixed product to the continuou ly operating mixer for said mixing with water and said discharge therefrom of plaster ready for use.

Inventors: ANDERSSON OLOF, BAUER WERNER, ANDERSSON, OLOF, BAUER, WERNER
Applicants: STRAOBRUKEN AB
Application year: 1983
Main classification: C09D5
IPC codes: C04B26, C04B28, C09D5