EP0465486A1

EP0465486A1 - Process for the production of a surface-glazed body, using an at least latently hydraulic binder

Info

Publication number: EP0465486A1
Application number: EP19900904602
Authority: EP
Inventors: Ivan Odler
Original assignee: KERASAL OBERFLACHENSCHUTZ GmbH
Current assignee: KERASAL OBERFLACHENSCHUTZ GmbH
Priority date: 1989-04-06
Filing date: 1990-03-21
Publication date: 1992-01-15
Also published as: JPH05500792A; DE3911117C1; WO1990011983A1

Abstract

Procédé de fabrication d'un objet à surface vernie avec un liant au moins potentiellement hydraulique.Method for manufacturing an object with a varnished surface with an at least potentially hydraulic binder.

Description

Process for the production of a body glazed on the surface based on an at least latent hydraulic binder

B e s c h r e i b u n

The invention relates to a method for producing a body glazed on the surface based on an at least latently hydraulic binder.

The term "body" encompasses molded parts of all kinds, such as containers, pipes, plates, but also monolithic structures that are either to be glazed in-situ on their surface or provided with a coating from which the glaze is then formed.

The term "inorganic, latent hydraulic binder" stands for known binders and binder systems, for example made of or based on Portland cement, alumina cement or the like, with or without additives (e.g. blastfurnace slag, raft, fly ash) and / or additives. To this extent, the invention also encompasses processes for the production of glazed concrete bodies.

The term organic binder also stands for known binders of this type such as starch, dextrin, lignin, polyvinyl alcohol etc. The glazing of a conventional concrete using conventional cements, in particular Portland cement, has recently been proposed (Interbrick, Vol. 3, No. 2, 1987, 30). However, the method described there is practically not feasible.

A glaze, such as is used, for example, for coating ceramic molded parts, must be heated to temperatures between 900 and 1100 ° C. during glazing in order to achieve a melting phase. However, if one were to glaze a cement-bound base body, produced using conventional inorganic binders such as Portland cement, in such a temperature range over a corresponding time interval, this would lead to decomposition of the calcium silicate hydrates formed in the concrete body, and tests have shown that a loss of strength of the concrete body of 80% and more occurs from about 300 ° C. It is obvious that a stable molded body cannot be obtained in a glazing process which takes a few hours. The water released from the calcium silicate hydrates also creates bubbles which also do not allow a uniform glaze application.

If quartz is proposed as an additive in the aforementioned publication, this additive will ultimately also lead to a disturbance of the base body made of concrete during the glazing due to the known quartz jump.

If it is suggested in the Japanese publication, the (considerable) loss of strength in the glaze To accept fire first and then to put the concrete body in water in order to achieve rehydration, this proposal also appears to be purely theoretical and practically impractical because, among other things, that which was dehydrated to CaO in the previous temperature treatment Material after water absorption with the formation of calcium hydroxide must lead to (known) driver phenomena and thus mechanical destruction of the base body.

The proposal for the production of a glazed concrete body disclosed in Japanese Patent Application 86 / 160,558 is also practically impracticable because, on the one hand, the lead-borate frit used there is extremely unstable and, moreover, a liming drive cannot be prevented here either.

On the other hand, there is an urgent need to glaze basic bodies from inorganic binders, on the one hand for the production of corresponding molded parts, and on the other hand also for repair purposes. Concrete tanks such as those used in water treatment, for example, may be mentioned here. These containers are damaged over time as a result of the action of the stored water on the concrete and need to be repaired. Glazing such containers could help here, especially since the use of steel containers, for example, is often out of the question for both technical and financial reasons.

In this respect, the invention is based on the object of demonstrating a possibility of how a body is based on a at least latent hydraulic, especially inorganic binders can be glazed while maintaining the strength as far as possible. In particular, the aim is to be able to use conventional binders.

The invention is based on the knowledge that this aim can be achieved in two alternative, but closely related ways, in each case a glaze melting at high temperature can be applied to a hydraulically bound and consequently only to a limited extent thermally stable body, if instead of the whole Body only the layer intended for melting (the subsequent surface glaze) is heated. It was also recognized that the mass (filler) provided as glaze must be bound to the surface of the base body using a binder. When organic binders are used, they are thermally broken down during glazing; in the case of inorganic binders, constituents of the binder remain in the glaze. If an inorganic binder is used, appropriate additives, which form a eutectic with the binder even under short-term temperature stress and at temperatures well below the melting temperature of the hydrated binder, can be used to lower the temperature for the formation of the glaze. Even a brief exposure to temperature of only a few seconds is usually sufficient to form the melt phase, as a result of which the material underneath is not subjected to any significant temperature stresses, as a result of which the loss of strength described at the outset can be avoided.

In this connection it is important that the components forming the melt phase are free of quartz in order to prevent a volume increase due to the quartz crack, which would lead to an "in-situ destruction" of the glaze The part to be glazed can either be the surface of the body itself or a coating applied to a preformed body. In the first case, an in-situ glazing is practically achieved, while the second variant requires a two-stage process, in which a body is first formed and then a coating is applied to this body.

If an organic binder is used, the two-stage procedure is recommended. A coating of the organic binder (component A) and a low-melting material (component B) in a mixture with a liquid such as water is applied to a given body, the melting temperature of component B, however, being equal to or higher than the decomposition temperature of the organic binder so that it can burn out during the subsequent temperature treatment. Accordingly, the organic binder primarily serves to hold the coating on the body (to bind). Subsequent drying improves the bond between the coating and the body.

The methods are described in detail by the features of claims 1 and 2.

Advantageous designs result from the features of the subclaims.

These first name suitable surcharges as a component

B, namely feldspar, blast furnace slag and / or slag sand, feldspar is preferred. While a hydrated inorganic cement or concrete has a melting temperature of well above 1,300 ° C, the addition of the substances mentioned leads to a reduction in the temperature at which a first melting phase is formed to about 900 ° C and lower. The same applies if a ceramic frit, in particular a frit containing Pb, is used as component B. Frits or glass powder mixtures are particularly advantageous in the sense of the invention, especially since individual frits have melting temperatures of only 700 ° C. to 1,000 ° C.

In order to increase the reactivity between the binder and the component forming the melt phase, the component forming the melt phase should have a grain size of less than 1 mm, preferably in powder form. The finer the material, the more reactive it is. In this case, a few seconds are enough to form a melt phase in the outer surface area of the body.

Since it is desirable when using an inorganic binder to achieve a melt in the short term with the lowest possible melting temperature in the surface region, it is further proposed to set the proportion of the component forming the melt phase to at least 30% by weight. Experiments have shown that a proportion of 75% by weight, based on the total mass, is particularly favorable in the sense of the invention. However, even when an organic binder is used as component A, the proportions can be chosen accordingly, as described above.

A major advantage of the process is that conventional binders can be used. Portland cement or alumina cement are mentioned as examples of inorganic binders and dextrin or lignin as organic binders. A combination of both binder systems is also possible. Other inorganic, at least latently hydraulic, binders can also be used. For example, some of the cement can be replaced by fly ash or other pozzolana materials. It is also possible to add inert additives to the binder phase in order to form a mortar or concrete, in particular when using the in-situ method according to claim 2. Basalt, corundum, wollastonite, broken bricks or the like are suitable as inert additives . The aggregate can be processed in a conventional manner, in particular in lumpy or granular form.

A certain proportion of iron oxide in these supplements also has a positive effect in the sense of lowering the melting temperature in the surface of the body, since iron oxide also acts as a flux.

In addition to the inorganic binders mentioned, special binders can also be used. A water glass in combination with a silicon fluoride is mentioned as an example. The silicon fluoride is preferably a sodium or potassium silicofluoride, in particular a sodium silicon hexafluoride.

Such a binder shows the following reaction mechanism

2Na ₂ 0 '(Si0 ₂ ) _χ + Na ₂ SiFg = 6NaF + (2x + 1) Si0 ₂

The binder then forms a highly dispersed three-dimensional framework made of amorphous silica, which is suitable for achieving favorable strength values.

2 namely bending tensile strengths of over 5 N / mm and compressive

2 strengths of over 50 N / mm. A binder proportion of between 20 and 30% by weight is assumed. The use of the latter binder leads to a treatment as is known from concrete technology. The mixing of the binder with the additive leads to plastic masses which can easily be cast into molded parts. It is particularly advantageous that the hardening takes place in only a few hours and is completed after 48 hours at the latest.

It is also possible to mix water glass and / or silicon fluoride in certain proportions with the conventional binder.

The coating applied to a body can be very thin, for example less than 1 mm. During the temperature treatment, the layer then melts to the surface of the (base) body.

If inorganic binders are used, however, a thicker coating (for example greater than 2 mm) can also be applied, so that after the glaze has melted between the glaze and the (base) body there is still a non-melted transition area. remains.

The heat treatment of the body produced by the process and thus the glazing can be carried out in various ways.

This means that a flame can be applied directly to the surface. However, infrared radiation or electrical heating is also possible. A method is particularly preferred in which the heating unit is continuously guided over the surface of the body formed, in such a way that individual surface sections of the body are only exposed to the temperature load for a few seconds, for example 3 to 10 seconds. this time being sufficient to form a smelting phase on the surface which, after the heating device has continued, cools to form a solid glaze.

In this way, repair measures can also be carried out particularly easily. It was already pointed out at the beginning that there is an urgent need to repair damaged concrete surfaces in such a way that a further chemical attack is reduced. In this case, the defective concrete part can be coated with a coating according to claims 1 or 2. When setting, the newly applied layer connects to the base material. After the coating has been hydrated and hardened, it is glazed - as described above - and in this way a closed, dense glazed surface is formed, which makes the corresponding part particularly resistant to chemical attacks in particular.

The invention thus offers a surprisingly simple possibility of producing glazed bodies or forming a base body with a glazed surface, and that - as stated - not only for the production of new molded parts, but also for the repair of existing bodies. In this case, the strength of the hydrated base material is practically completely maintained due to the briefly reduced temperature effect compared to conventional ceramic glazing processes. Bodies produced by the method according to the invention can be used in a wide variety of areas. They can be produced inexpensively, since conventional binders or concretes can be used, and the production is unproblematic since both the preparation and the glazing do not require any special devices or production techniques. Experiments have shown that when a binder system with 25% by weight Portlandzemeπt and 75% by weight feldspar is flamed at a temperature of 1,050 ° C, a closed glaze layer of approximately 0.5 to 1 is applied after only 3 to 5 seconds mm thickness can be achieved without a noticeable destruction of the hydrate phases of the binder system in the base body, obviously due to the short heat treatment and a very steep temperature gradient resulting therefrom.

Claims

Patent claims

1. A method for producing a body glazed on the surface based on an at least latent hydraulic binder, comprising the following steps:

1.1 a coating of component A (inorganic, at least latent hydraulic binder and / or organic binder), component B (below the melting temperature of the inorganic binder, quartz-free material forming a quartz-free material) and a liquid is applied to the body,

1.2 then or after the binder has set, the coating is dried,

1.3 then a heat source is directed onto the surface of the coating for a few seconds until a melting phase has formed at least in the area of the coating,

1.4 then the heat source is removed or switched off, after which the melting phase cools to form a closed glaze layer. 2. Method for producing a body glazed on the surface on the basis of an at least latently hydraulic, inorganic binder with the following steps:

2.1 the binder (component A), which contains a portion of a quartz-free material (component B) forming the melting phase below the melting point of the binder, is mixed with a liquid and shaped in order to

2.2 then hydrate and harden

2.3 thereafter, a heat source is directed onto the surface of the body formed for a few seconds until a melting phase has formed in the area of the body,

2.4 The heat source is then removed or switched off, after which the melting phase cools to form a closed glaze layer.

3. The method according to claim 1 or 2 with the proviso that feldspar, blast furnace slag or blast furnace slag is used as component B forming the melt phase.

4. The method according to any one of claims 1 or 2 with the proviso that a ceramic frit or a glass powder is used as the component forming the melt phase.

5. The method according to any one of claims 1 to 4 with the proviso that component B forming the melt phase is used in a grain size of less than 1 mm.

6. The method according to claim 5 with the proviso that the melt phase forming component B is used in powder form.

7. The method according to any one of claims 1 to 6 with the proviso that component B forming the melt phase is used in an amount of at least 30% by weight, based on the total mass.

8. The method according to claim 7 iL provided that the component forming the melt phase is used in an amount of at least 75% by weight, based on the total mass.

9. The method according to any one of claims 1 to 8 with the

Provided that Portland cement or alumina cement is used as the inorganic binder (component A).

10. The method according to any one of claims 1 to 8 with the proviso that starch, lignin and its derivatives, dextrin, polyvinyl alcohol or polyvinyl acetate is used as the organic binder (component A).

11. The method according to any one of claims 1 to 10 with the proviso that the temperature treatment is carried out by direct flame irradiation.

12. The method according to any one of claims 1 to 11 with the proviso that the temperature treatment is carried out by infrared radiation.

13. The method according to any one of claims 1 to 11 with the

Provided that the temperature treatment is carried out by electrical heating.

14. The method according to any one of claims 1 to 13 with the proviso that the heat source is continuously guided over the surface of the body.

15. The method according to any one of claims 1 to 14 with the proviso that the surface of the body or the coating when using an inorganic binder ^* as component A to a temperature greater than 700 ° C, but below the melting temperature of the pure binder or binder system is heated.

16. The method according to any one of claims 1 to 14 with the proviso that when using an organic binder as component A, the coating is heated to a temperature at which the organic binder burns out.