CS198566B1 - Manufacturing process of room-size elements of polyester plastic concretes - Google Patents

Description

The invention solves a method of manufacturing spatial components made of polyester plastics, intended primarily for housing components and installations in the building industry or as parts of machines and other equipment in engineering, transport and joints, or elsewhere.

Polyester plastics, high-filled polyester resins, are a promising casting material with good physical and mechanical properties, good workability and very low production costs without investment requirements. Usually, these materials are mainly used to produce simple planar shapes, cladding boards, flooring, preferably at least some curved or slightly curved panels without internal edges. More complicated shapes or even rectangular cabinets with higher demands on accuracy cannot be produced from these materials due to the volume contraction of the binder, which, even in the optimal curing mode, destroys the part in the mold and damages so that its proper function cannot be guaranteed. Moreover, it is precisely due to this contraction that it is very difficult to remove particularly deeper profiles from the solid mold and usually leads to the destruction of the workpiece or the entire molding device. These disadvantages are eliminated by a method of manufacturing the spatial components of the polyester polymer concrete according to the invention, which is characterized in that after vibration initiated and homogenised casting mixture monitors the exothermic temperatures during the polymerization of binders in the range t _{min 1} - t _MAT - t _{min 2} and workpiece is sensed from the positive part of the mold in a semi-solid, not zeele polymerized state. This removal must be rapid and must be completed within 45 minutes of the time it was

198 566

198 5B8 product surface temperature of ₂ + 5 ° C is achieved, provided that ₁ and Snin 2 ^are equal.

To simplify and accelerate the manufacturing process, a thermocouple is incorporated directly into the manufacturing mold to determine the optimum scanning time. During the polymerization of the polyester binder, an exothermic reaction occurs, which results in a relatively rapid increase in the temperature of the casting composition. In the course of this reaction, there is first a linear, later a spatial crosslinking of the material. Volume contraction is primarily due to spatial strengthening and occurs only in the second phase of polymerization. A number of technological tests and measurements have shown that the plastic concrete casting retains a certain degree of elasticity and plasticity until about 85 to 90% of the styrene monomer is incorporated. Further curing leads to increasing contractions, the material hardens and to some extent brittle. This then results in the article cracking at the points of greatest internal stress, usually at corners, edges, weakened points, or at places where the wall thickness changes. If the cause of the stress is eliminated before the stress can be fixed, no cracking occurs. The basic problem of the solution is to find the right moment for removing the solid part, ie at the time when my part already has the necessary stiffness, so that it does not get damaged during the scanning and on the other hand the stiffness that enables this removal. volume contraction. The result is a relationship where t _{min 1} is the initial, workshop temperature of the casting mixture, t _fflax is the maximum external temperature and t _{min 2 is the} workshop temperature of the finished concrete after cooling. To simplify the relationship, it is assumed that the temperatures before and after the exotherm are equal, which makes it possible to determine in a timely manner a suitable moment for removal of the workpiece at t _min + 5 ° C. This time was found empirically and verified on several thousand samples.

The advantages of the method are, in particular, that it allows a substantial expansion of polyester plastics production for a wide range of applications, for which it has been necessary to use either more expensive epoxy or polyester casting resins or metals. Due to the very low cost and easy availability of the base material (about 75% of the base material is conventional graded sand), it is possible to produce very cheaply applications where cast iron or other low-quality ferrous materials have been used so far. The material has very good electroinsulating properties, it is not subject to corrosion, it is waterproof, it can be treated in non-flammable or self-extinguishing form, or it can be produced with antistatic treatment.

Case 1

The cable box for 300 x 300 x 500 mm connection installations was cast as usual in a two-piece metal mold, vibrated and left to polymerize at 20 ° C. In the form of a built-in thermocouple, the temperature of the base liquid mixture was measured equal to the temperature of the workplace, ie also 20 ° C. Within 30 minutes after casting, the exothermic temperature of the plastic concrete reached 45 ° C (measured by thermocouple and TERMOFIL touch thermometer). The panel was removed by free pulling from the mold when the temperature on the surface of the back cast wall reached 25 ° C. After removal, the panel was placed on a flat support and left for molding without further polymerization.

Claims (1)

Method for the production of spatial components of polyester plastics, characterized in that after the vibration initiated and homogenized casting mixture during the polymerization the binder is in the range t. , - t_ _ - t. ₉ and the workpiece is removed from the positive part of the mold in a semi-rigid, not completely mismatched d. at least 45 minutes after the product surface temperature t _{mln 2} + 5 ° C has been reached, provided that t _{min 1} and _{min 2} are equal.