EP0171665B2 - Method and device for the continuous production of inorganically bonded processing materials, in particular of processing boards - Google Patents

Description

The invention relates to a process for the continuous production of inorganically bound materials, in particular of material plates, from mixtures of substances of binders hardening by hydrate formation, reinforcement and optionally auxiliary materials having a pourable or scatterable consistency, the special material properties and usability of which are achieved by a permanent and irreversible structure compaction , whereby one forms a plate strand from the mixture of substances, which is then compressed and calibrated by exerting a surface pressure. The invention also relates to a device for carrying out this method.

With the invention, a technologically simplified principle for the continuous production of inorganically bound materials, for. B. slabs, from mixtures of binders hardening by hydrate formation, reinforcement materials and optionally active and inactive auxiliaries, which are forced by a pressure that mostly affects the properties of use, permanent and irreversible structure compaction, which acts during the entire hardening process.

It is known to produce materials from mixtures of bindable and reinforcing substances. Binder, reinforcement material and possibly other active and inactive substances are mixed according to predetermined ratios in a suitable device, poured into a fleece or scattered and compacted in a pressing device. The pressure required for this is dependent on the properties of the starting materials which cause the deformation modulus of the mixture, the ratio of the plate fleece densities before and after the compression process, the deformation modulus of the fleece which changes as a function of time, and the compression speed.

Plates with organic binders, the hardening of which causes polycondensation or addition usually takes place by supplying heat, are heated in heatable floor presses or continuous presses, such as. B. known from DE-AS-1 007 497 and DE-AS-1 938 280. Due to the use of material mixtures of high reinforcement material and low binder concentration, the deformation modules and the required compression pressures are relatively high, which requires the development and use of compression systems of heavy and complex design. However, the effects of pressure and heat can usually be coordinated so that curing takes place during a relatively short dwell time in the press. The required length of the known continuous compression plants can be kept within economically justifiable limits. The state of the art in this area is determined by the Hydro Dyn press from Bison and the continuous press from Contipress, Federal Republic of Germany.

Mixtures with inorganic binders, such as cement and gypsum, are significantly rich in binders and contain fewer reinforcing materials. They harden due to hydrate formation, i.e. that is, phases of the binder with less water are converted into water-rich compounds by reaction with water. This process is called hydration, it is exothermic and depends on the reactivity of the binder with the water. Are this two-material binder-water chemically non-neutral reinforcement, z. B. wood, mixed, the reactions between the different phases of the binder and the water reactions are often disturbed. Most wood ingredients act as hydration and crystallization inhibitors, i.e. that is, they delay the hardening process. In contrast, accelerating influences of wood constituents are very rare. In order to counteract these undesirable influences of the wood, hydration accelerating or retarding additives (adjusting agents) are used. Because of their unfavorable side effects (deterioration of the physical properties of the plates, blooming phenomena), they are usually not applicable to the technologically desirable extent. For this reason, the less problematic hydrothermal acceleration effect is often used in the manufacture of cement-bound boards. The hardening processes of gypsum-bound boards cannot be activated in this way.

Despite these various possibilities of influencing the reaction sequence of such material systems in a targeted manner, a technological optimum cannot be achieved in most cases. This means that the production systems have to absorb certain fluctuations in this regard. In the case of discontinuous production, this takes place through an extended dwell time in the press, which is at the expense of capacity, or through intermediate storage of the plates in complex clamping stands, which transfer the pressure entered by the pressing process to the stack packages at least until the end of hydration. With increasing hydration time and capacity requirements, the necessary number of clamping frames increases and the investment costs increase. The economy and efficiency of such systems are accordingly low.

Continuous production plants must have a considerable length to make the compaction irreversible and, depending on the capacity, to absorb larger fluctuations in hydration time. This means that solutions for industrial plants that are ready for application have so far been available not known.

wiedergeben. Setzt man die Plattenstrangbreite bp = konst. (zweckmäßigerweise 1 m), so läßt sich diese Beziehung linearisieren und als Nomogramm darstellen, wie b Fig. 1 gezeigt. Es veranschaulicht daß progressive Kapazitätserwartungen eine größere Länge der Preß- und Kalibriervorrichtung sowie einen entsprechend höheren Investitionsaufwand voraussetzen. Zur Verringerung der Anlagekosten werden bei den bekannten Anlagen zur Herstellung von Werkstoffen auf organischer Bindemittelbasis Mehrberaichspressen bevorzugt, d. h., der Druck wird in den einzelnen Zonen der Presse etwa entsprechend dem zeitabhängigen Verformungsmodul des Plattenstranges differenziert. Darüber hinaus ist es durch die DE-PS-2 126 935 bekannt, daß bei der Herstellung kunstharzgebundener Spanplatten in beheizbaren Anlagen verbesserte Oberflächengüten und höhere Festigkeiten erzielt werden können, wenn die Spanplattenvliese am Beginn der Pressung auf eine geringere Dicke als die Bewünschte Enddicke verdichtet und anschließend bei der gewünschten Enddicke fertiggepreßt werden.The relationship between the length of the pressing and calibrating device I _v , the capacity K and the hydration time t _H can be determined by the relationship

play. If one sets the plate strand width bp = constant (expediently 1 m), this relationship can be linearized and represented as a nomogram, as shown in FIG. 1. It illustrates that progressive capacity expectations require a greater length of the pressing and calibration device and a correspondingly higher investment. In the known systems for the production of materials based on organic binders, multi-area presses are preferred in order to reduce the system costs, ie the pressure in the individual zones of the press is differentiated approximately according to the time-dependent deformation module of the plate strand. In addition, it is known from DE-PS-2 126 935 that improved surface qualities and higher strengths can be achieved in the production of synthetic resin-bonded particle boards in heatable systems if the particle board non-wovens at the start of compression compresses to a thickness less than the desired final thickness and then pressed to the desired final thickness.

In addition, the following prior art references are given: Kossatz, G. and K. Lempfer: For the production of gypsum-bonded chipboard in a semi-dry process. Wood as raw and material 40 (1982), pp. 333 - 337; Technical information: The continuous Hydro Dyn press - another step forward. Holz-Zentralblatt 56/57, Stuttgart May 11, 1983; Kossatz, G., Lempfer, K. and H. Sattler: Inorganically bonded wood-based panels. FESYP business report 1982/83, pp. 98 - 198; Bücking, G .: The production of gypsum-bonded chipboard in an endless process. Wood as raw and material 41 (1983), pp. 427 - 430; Ahrweiler, K .: The disturbance in the thickness and density of chipboard in a continuous press. Conference report from the 6th wood technology. Colloquium 1980 in Braunschweig; and Hübner, J.E .: Semi-dry process for the production of gypsum-bonded chipboard. Conference report from the 7th Wood Technology Colloquium 1983 in Braunschweig.

The special physical effect of stress relaxation and its potential for use in the manufacture of much simpler and cheaper manufacturing systems has not been recognized so far. a. it can be attributed to the fact that in the production of resin-bonded chipboard, dry mixtures of materials with significantly higher deformation moduli are used. Accordingly, all known compression systems have the disadvantage in common that the devices required for the compression of the nonwoven sheet have to generate and transmit relatively high pressures during the entire hardening time and therefore require a complicated and heavy design. To circumvent such costly solutions such. B. discontinuous and therefore less effective manufacturing techniques applied in the production of cement-bound chipboard (BISON cement board plant).

From AT-B-123 984 (page 2, lines 7 to 9, FIGS. 4 and 5) it is known to compress the plate strand so strongly that the strand at the pressing point has a considerably smaller height than in the setting chamber. Behind a pair of press rolls, the fiber material begins to relax again in the press strand. The pressure is chosen so that the height of the relaxed strand is only slightly larger than the distance for the strand in the setting chamber. However, this measure is only sufficient for the production of the well-known cement-bound wood wool building boards and not for reinforcement materials that have a pourable or scatterable consistency.

It is therefore an object of the invention to make a continuous process and a continuously operating device available for the production of materials on the basis of inorganic binders, which process is more economical and thus less investment-intensive and more efficient and with which the other disadvantages set out above are overcome.

This object is achieved by the combinations of features of claims 1 and 2.

With the features it is achieved in particular that the installation of expensive, preferably hydraulic, pressure generating and transmission devices, such as are required for carrying out the pre-sealing phase or in the compression device, is limited to a relatively small area because the compression zone becomes relatively short, while the longest part (usually 10 to 25 times the compression zone) can be designed as a technically simple calibration device without active pressure. In the invention, the calibration device has only the task of absorbing the restoring forces of the plate strand compressed in the press of the compression device or in the compression phase, which are reduced in the manner described, and of keeping them at the desired thickness until completion of the hydration. Such a continuous calibration device is z. B. realizable by the arrangement of cascaded calibration rollers. The conversion of the line pressure between the calibration rollers and the plate strand into a surface pressure can be achieved by a suitable stiffening of the forming belt or accessible by inserting suitable transport plates. To adjust the device according to the invention to different plate strand thicknesses, a corresponding adjustability of the gap of the pressing and calibration device can be provided. This procedure and this structure of the device is based on the fact that the compression process and the relaxation process required to reduce the restoring forces take place before or at the latest during the initial phase of the hydration. A disturbance of the structure and strength building process is excluded.

Developments of the invention are specified in the subclaims.

• Figur 1 ein NOMOGRAMM zur Ermittlung der Gesamtlänge von Verdichtungs- und Kalibrierzone I_v in Abhängigkeit von der Hydratationszeit von Gips t_H und der Anlagenkapazität K bei 1 m Plattenstrangbreite, worin Klammerwerte der K-Leiter der Kapazität bei 2,5 m Plattenstrangbreite und Klammerwerte der t-Leiter der etwa zu erwartenden Verarbeitungszeit des Gipses t_v entsprechen;
• Figur 2 eine Darstellung der funktionalen Zuordnung des Druckverlaufes bei der Verdichtung eines Plattenstranges zur Herstellung von Gipsspanplatten zum Hydratations- bzw. Erhärtungsverlauf des Stoffgemisches, wobei im Gegensatz zur Erfindung ein Verdichten mit niedrigem Druck entsprechend der zu erreichenden Solldicke des Plattenstrangs und ein Kalibrieren mit aktiver Druckeinwirkung erfolgt; und
• Figur 3 eine Darstellung der funktionalen Zuordnung des Druckverlaufs bei der Verdichtung eines Plattenstrangs zur Herstellung von Gipsspanplatten zum Hydratations- bzw. Erhärtungsverlauf des Stoffgemisches, wobei gemäß der Erfindung ein Verdichten mit höherem Druck, das eine entsprechende Unterschreitung der Solldicke des Plattenstrangs bewirkt, und ein Kalibrieren ohne aktive Druckeinwirkung erfolgen.

The invention is explained in more detail below using exemplary embodiments with reference to FIGS. 1 and 2 of the drawing; show it:

• 1 shows a NOMOGRAM for determining the total length of compression and calibration zone I _v as a function of the hydration time of gypsum t _H and the system capacity K for a 1 m plate strand width, wherein bracketed values of the K-conductor capacity at 2.5 m plate strand width and bracketed values of t-conductor corresponds to the expected processing time of the plaster t _v ;
• Figure 2 is a representation of the functional assignment of the pressure curve in the compression of a plate strand for the production of gypsum chipboard for the hydration or hardening course of the mixture, in contrast to the invention, compression with low pressure according to the desired thickness of the plate strand to be achieved and calibration with active pressure he follows; and
• 3 shows a representation of the functional assignment of the pressure profile during the compression of a plate strand for the production of gypsum chipboard for the hydration or hardening profile of the substance mixture, wherein according to the invention a compression with higher pressure, which causes a corresponding drop below the target thickness of the plate strand, and a calibration done without active pressure.

To carry out a process for the continuous production of materials from mixtures of binders hardening by hydrate formation, reinforcement and, if appropriate, auxiliaries, pourable or scatterable consistency with permanent and irreversible structural compression, so that a sheet strand is formed from the mixture of materials, which is then compressed and calibrated , whereby the plate strand is compressed before calibration in a compression phase with such a high pressure that its thickness after the compression falls below the target value of the finished plate strand, but the density exceeds this and both are so large that the compressed plate strand immediately without active pressure application can be calibrated in a calibration phase, the specific deformation or compressibility behavior of the material mixtures used for the material production is used. A comparison between FIGS. 2 and 3 explains how this is done:
the maximum pressure P max in the pressure curve according to FIG. 2 for generating the target thickness and target bulk density of the material is only required at the beginning of the compression phase for a relatively short time. Thereafter, the pressure p rapidly decreases as the deformation module drops to a value of Pk = 0.4 P _max . If, on the other hand, as illustrated in FIG. 3, the maximum pressure is increased to a value P ' _max ≈ 1.5 P _{max in} accordance with the solution according to the invention, the plate target thickness is undercut by a small amount (approximately 10%) and p' _k is reduced as a result of Relaxation about 40% smaller than _Pk ; that is, the higher pressure P ' _max expended in a very short compression phase leads in an extremely favorable manner to a considerable reduction in the required calibration pressure p' _k during the very long calibration phase, namely to such a low calibration pressure that calibration takes place without active pressure can.

• (a) Verdichtungszone, Druckerhöhung von p = o auf p = p'_max ≈ 1,5 p_max
  Länge I_v vorzugsweise maximal 5 m (unabhängig von der Anlagenkapazität)
• (b) Kalibrierzone ohne aktive Druckeinwirkung (nur zur Aufnahme des relativ kleinen inhärenten Rückstelldruckes von p'_k ≦ 0, 15 p'_max ≈ 0,60 ^p _k ≦ 0,22 p_max

notwendige Länge:

The specific compatibility behavior of the mixtures of substances used can therefore be used to manufacture a technically much simpler and more cost-effective continuous production system which consists of two corresponding zones for pre-sealing and calibrating the plate strand:

• (a) Compression zone, pressure increase from p = o to p = p ' _max ≈ 1.5 p _max
  Length I _v preferably a maximum of 5 m (regardless of the system capacity)
• (b) Calibration zone without active pressure (only to absorb the relatively small inherent reset pressure of p ' _k ≦ 0.15 p' _max ≈ 0.60 ^p _k ≦ 0.22 p _max

necessary length:

The installation of expensive, preferably hydraulic, pressure generating and transmission devices is thus limited to the relatively small area of the compression zone, while the relatively very long calibration device does not require any active pressure, that is to say can be produced with only relatively low system costs.

• Für die Herstellung gipsgebundener holzspanbewehrter Bauplatten werden Stoffgemische verwendet, deren Hydratationszeit t_H minimal 6 Minuten (siehe Fluchtlinie 1 in Figur 1 ) und maximal 12 Minuten (Figur1, Fluchtlinie 2) beträgt (6 - t_H - 12). Die Plattenstrangbreite soll 2,5 m, die Fertigungskapazität K soll 500 m²/h betragen.
• Für das Stoffgemisch mit der kurzen Hydratationszeit ist ein Versteifungsbeginn nach 4 Minuten und dementsprechend ein Hydratationsende nach 10 Minuten, für das mit der längeren Hydratationszeit ein Versteifungsbeginn nach 8 Minuten und ein Hydratationsende nach 20 Minuten zu erwarten. Die für die Bestimmung der notwendigen Länge der Verdichtungsanlage als Rechenwert zugrundezulegende Hydratationszeit ergibt sich aus der Differenz des spätesten Hydratationsendes (20 Minuten) und des kürzesten Versteifungsbeginns (4 Minuten) zu 16 Minuten.

The advantage of the solution according to the invention will be explained in more detail using the following example:

• For the production of gypsum-bound wood-chip-reinforced building boards, mixtures of materials are used whose hydration time t _{H is at} least 6 minutes (see escape line 1 in Figure 1) and a maximum of 12 minutes (Figure 1, escape line 2) is (6 - t _H - 12). The board strand width should be 2.5 m, the production capacity K should be 500 m ² / h.
• For the substance mixture with the short hydration time, a start of stiffening can be expected after 4 minutes and accordingly an end of hydration after 10 minutes, for the longer hydration time, a start of stiffening after 8 minutes and an end of hydration after 20 minutes can be expected. The hydration time to be used as a calculation value to determine the necessary length of the compression system results from the difference between the latest end of hydration (20 minutes) and the shortest start of stiffening (4 minutes) to 16 minutes.

• (a) Verdichtungszone: 2,5 m
• (b) Kalibrierzone: 53 m lang

This means that the compression system must have a length of at least 53 m (FIG. 1, escape line 3) to compensate for such hydration time fluctuations if, according to FIG. 2, compression is carried out with a pressure at which the target thickness and density of the plate strand never or below. are exceeded, since a relatively high pressure must be applied to the plate strand without taking into account the solution according to the invention during the long path of the plate strand specified above, this compression system is very expensive in terms of material and costs. When using the solution according to the invention, the following lengths can be used, for example determine the differentiated compression and calibration zone:

• (a) Compression zone: 2.5 m
• (b) Calibration zone: 53 m long

The example shows that in the invention, the longest part of the compression system can be designed as a calibration device without active pressure, which means that the system manufacturing costs can be significantly reduced compared to other systems. It is advantageous that for the press (compression zone) with a standardized sheet strand width, only one size, which is dependent on the design requirements, is required, regardless of the system capacity. To satisfy different capacity requirements, it is sufficient to construct and offer the variable length calibration device downstream of the press or compacting device. A segment design that makes it possible to assemble systems of high performance from modules of lower performance appears particularly expedient for this purpose. This results in particularly favorable conditions for later retrofitting to larger capacities.

In a nutshell, the invention relates to a technically simplified and cost-effective process and a technically simplified and inexpensive device for the continuous production of materials, in particular plates, from mixtures of binders hardening by hydrate formation, reinforcement and, if appropriate, auxiliaries of pourable or scatterable consistency, which have their essential material properties obtained by a pressure which usually begins before the hardening reactions and continues until the end of hydration. In order to meet the usual capacity requirements, continuous production systems must have considerable lengths, which has a negative effect on the system costs, especially when long-term use of high pressures. According to the invention, the specific deformation or compressibility behavior of the material mixtures used is used to effect such a reduction in the restoring forces emanating from the compressed sheet fleece that the time-consuming hardening processes during calibration are caused by a higher initial compression than is required to produce the desired thickness and density without active pressure and the system costs can be significantly reduced.

Claims (6)

1. Process for the continuous production of inorgan- ically bonded materials, particularly material plates, from substance mixtures of binding agents hardening by hydrate formation, reinforcing agents and optionally adjuvants having a pourable or strewable consistency, whose specific materials characteristics and usability are attained by a permanent and irreversible structural compression, with a plate strand being formed from said substance mixture, which is then compressed and calibrated by the exertion of an area pressure,
characterized in
that, in a compression stage prior to calibration, said plate strand is compressed at a pressure so high that its thickness after compression is below the value desired for the finished plate strand and that its density exceeds, however, the desired value while the two values are so high that the compressed plate strand is adapted to be calibrated to its desired thickness and density immediately thereafter without the active application of pressure in a calibration stage, with a compression stage being applied which lasts for a period independent of the hydration time of said bringing agent and substantially shorter than said calibration stage.

2. Apparatus for performing the process according to Claim 1,
characterized in that

(a) the compression device connected upstream of calibration device, in the direction of plate strand movement, compresses said plate strand at an area pressure higher than necessary for achieving the desired thickness and density of the finished plate strand for compressing said plate strand to a thickness smaller than its desired thickness, such that a subsequent active pressure application is not necessary;

(b) that the calibration device immediately joining said compression device is a calibrating device operating without active pressure application onto said plate strand, in which device, on account of the stress relaxation taking place to a substantially greater extent due to the thorough moistening of said substance mixture in said plate strand, such a reduction of the resetting forces is achieved that active calibrating pressures are superfluous; and

(c) that the length of said compression device is substantially smaller than the length of said calibration device so that the higher pressure required for compression is applied only during a short compression stage whereas in the longer calibration device the time-consuming hardening processes, which require a correspondingly long calibrating stage, take place without active pressure application.

3. Apparatus according to claim 2, characterized in that in the compressing device is provided a press regulatable with respect to its passage speed and its press gap and whose length is determined independently of the capacity of the apparatus and solely according to the constructional requirements of the compressing device.

4. Apparatus according to claim 3, characterized in that the press length is max 5 m.

5. Aparatus according to one of the claims 2 to 4, characterized in that the calibrating device directly following the compressing device has a minimum length I_K, which results from the hydration time t_H, the apparatus capacity K and the plate strand width bp in accordance with the following relation

so that the calibrating device which is regulatable with regards to the passage speed and the calibrating gap is able to absorb hydration time fluctuations of the binder.

6. Apparatus according to one of the claims 2 to 5, characterized in that the calibrating device, if its length extends beyond a given system size, is formed from individual, similar components and is consequently adaptable to different capacity and subsequent extension requirements.

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