DE1267577B - Process for the production of plastic coatings for the inner surface of pipes - Google Patents

Description

FEDERAL REPUBLIC OF GERMANY

GERMAN

PATENT OFFICE

EDITORIAL

Int. CL:

Number:
File number:
Registration date:
Display day:

B 44 c

German class: 75 c - 6

P 12 67 577.3-45
March 8, 1962
May 2, 1968

The constantly increasing aggressiveness of sewage has already led in various cities to that regulations were enacted through which an internal protection on plastic basis of the sewage leading concrete or iron pipes is required. To reduce pipe damage therefore, various processes have already been developed in which protective layers are applied Based on self-hardening plastics, for example tar or. Bitumen combinations on the inner surface of the pipe can be applied by machine or manually. However, these procedures are technical and economical Disadvantages on.

In order to achieve sufficient chemical and mechanical resistance, one must if possible great durability (if possible about 10 years) can be achieved, which in turn certain layer thicknesses, for example about 3 mm. Such strong plastic layers are in comparison to concrete or iron pipe itself extremely expensive, so that the use of plastics only can be made together with fillers. Although on the one hand by the fillers one Improvement of the coatings can be achieved, but on the other hand, there are often defects, for example, by the formation of gas or air bubbles, by not filling the pore volume etc.

The rust protection painting technique also knows the importance of the critical pigment volume concentration, which results from the pigment volume concentration, i.e. the ratio of the volume of the ground pigment to the total volume of the non-volatile binder and ground pigments, depending on the properties (gloss, bubbles, rust , Permeability) brings (see "Handbook for the rust protection paint", by L. Bierner, 1960). At the critical pigment volume concentration, which roughly corresponds to the lubrication point, the amount of binder is superficially bound to the particles by absorption, ie in the ideal case the pore volume of a dense pigment or filler pack is completely filled. In practice, however, this state cannot be achieved or only approximately achieved when using fillers, since the addition of the appropriate amount of binder results in air inclusions depending on the size and nature of the filler particles and the binder, the air bubbles preferably forming at the interface between filler and Form binders. The formation of these air inclusions at the interface also depends on the method of production
Plastic coatings for the inner surface of
Pipes

Applicant:

German Solvay works

Company with limited liability,

5650 Solingen-Ohligs, Keldersstr. 4th

the aforementioned sizes still depend on the grain sizes (grain size gradation, dust content, etc.), of the respective working temperature and other sizes. In the case of coatings, it must also be used care must be taken that part of the total binder to adhere to the substrate, for example in the case of inner pipe coatings for adhesion to the inner surface of the pipe.

All in all, it is very difficult to do all of them at the construction site or at the other application locations those to achieve the "critical filler volume concentration" with close packing of the filler parts the correct composition of the plastic, the fillers, the Grain size and the like. The aim and object of the present invention was therefore to provide a method where the air inclusions between the boundary layers: filler / binder are reduced or largely avoided.

According to the invention it has been found that the aforementioned disadvantages are avoided and up to 8 mm thick plastic coatings for the inner pipe coating can be obtained if initially a filler of uniform grain size mixed with 2 to 5% of a plastic binder and in the giant-shaped state on the inner wall of the pipe itself is centrifuged in a known manner and after curing the unfilled pore volume with the same or a different binder is filled by centrifuging or pouring.

The binders known per se for these purposes are preferred as binders but epoxy resins or copolymers with epoxy resin, tar-epoxy resin combinations, polyvinyl acetate, self-curing polymerization resins, for example of the coumarone or indene type, are used.

The present process is based, among other things, on the fact that fillers with the most homogeneous possible

809 574/357

voltage - preferably lmm. Diameter - with suitable binders can be easily wetted or coated in a mixer. The viscosity and the amount of binder, e.g. B. a liquid epoxy resin or a polyvinyl acetate dispersion, can be determined depending on the grain size so that all filler grains are evenly coated with a film, which gives this mass the following properties:

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1. No excess binder.

2. Each grain of filler can move due to its weight if there is a point of contact from every other grain.

3. The entire mass is gigantic and takes any shape due to its own weight a, with tight packing of spheres by applying shaking or light mechanical pressure develop.

20th

4. The spherical packings created by pressure remain at layer thicknesses even on vertical surfaces Stable up to about 5 to 6 mm.

5. The process can be carried out by adding lubricants that can be added to the binding agent Accelerate to achieve tight packing of the spheres.

The mass with the properties described in detail above can in a known manner in Pipes are thrown in and remains after the end of the spinning process until complete Stick the drying out homogeneously on the walls of the pipe. Due to the homogeneous grain size and the low proportion of binder creates an easily calculable pore volume, which is subsequently can also be filled with the binding agent by centrifugation or by pouring. The addition of suitable wetting agents facilitates the impregnation process. It is advantageous that the wetting agent solution is sprayed in before the filler is impregnated with the binder.

The dense spherical packing, which consists of the most homogeneous filler grain sizes possible, is obtained Coatings with high mechanical strength because of all pressure and shear stresses caused by contact of the individual spherical particles are given off mutually.

Since the framework of the fillers already takes on a stable form with the first binder, it can be advantageous a second, different binding agent can also be used for impregnation (filling of the pore volume). This second binder can be less valuable or stretched. It is also possible that to build up the first binding agent on a dispersion basis, whereby an adhesion even on damp subsoil, for example on fresh spun concrete pipes.

According to one embodiment, cement is advantageously added to the synthetic resin dispersion first, and then this dispersion is prepainted as an adhesion promoter on concrete. Depending on the use of certain Types of binders can be used at normal temperatures or at the coating process Supply of heat can be made.

To save binder and to increase mechanical strength, filler mixtures with two grain sizes can be used, the grain diameters in a ratio of about 1: 0.4 should.

When using fillers with two inherently uniform grain sizes, their diameter ratio is about 1: 0.4, free flowability of all filler particles is achieved by also the fillers of smaller grain sizes always within an approximately close packing of spheres can be accommodated (so-called slip balls). This increases the strength of the under Plastic coatings produced using these grain sizes, and there is still better processing guaranteed.

Claims (4)

Patent claims: 1. Process for the internal coating of pipes with plastic coatings up to 8 mm thick, characterized in that a filler of uniform grain size is mixed with 2 to 5% of a plastic binder and is thrown in the giant-shaped state onto the inner wall of the pipe in a manner known per se and after curing the unfilled pore volume with the same or one other binder is filled by centrifuging or pouring. .— = 2: Method according to claim 1, characterized in that that before the pores are filled, a wetting agent solution is introduced into the interior of the pipe will. 3. The method according to claim 1, characterized in that fillers with two uniform in itself Grain sizes are used whose diameter ratio is about 1: 0.4. 4. The method according to claim 1, characterized in that when covering concrete pipes on this first an adhesion promoter made of one of the filler-containing binders Plastic dispersion, which contains cement, is applied.