EP0785053B1 - Process for the continuous production of chip- or fibreboards - Google Patents

Description

The invention relates to a process for continuous production of chipboard or fiberboard made from lignocellulose Raw materials according to the preamble of claim 1.

An external release agent in the sense of claim 1 understood a release agent, which is either on the pressing allowances, so the tapes, press plates u. Like., Before pressing is applied. Another way is this external release agent on the two surfaces of the scattered and Apply pre-sealed mat if necessary. Internal release agents are on the other hand release agents that are introduced into the interior of the mat are, so the entire chips and / or fiber material z. B. in Connection to the glue can be added. The usage of these two types of release agent is from Deppe / Ernst "paperback der Spanplattenentechnik ", 3rd edition 1991, p. 60, is known.

A method according to the preamble is from US 4,131,662 A known. The external release agent is called talc directly Powder, d. H. applied dry to the pressing allowances. This Procedure is in US 4,131,662 but in many ways described disadvantageously. It is said to be cumbersome and wasteful be and to an uneven distribution of the talc as well lead to damage to health. To use the good properties of talc as a releasing agent while eliminating this Disadvantages are proposed in US 4,131,662 A, talc in a stable suspension in a stable emulsion of water and convert to an organic solvent, which then on the pressing allowance is applied. Such a solvent leaves continuously growing residues on the pressing supplements back.

From US 5,302,330 it is known to use an aqueous solution Foaming agent and a foaming agent and the Foam onto the surface of the mat before hot pressing apply. Various substances known as release agents should be able to be used. Chemical are listed active release agent in liquid form. Those are preferred Release agents that also act as foaming agents. Talc is an inert mineral substance that does not turn into an aqueous Solution is convertible and does not act as a foaming agent.

A process for the continuous production of chip or Fiberboard made from raw materials containing lignocellulose, in which the Raw materials in chip and / or fiber form with an NCO group containing binder glued, formed into a mat and under the influence of heat to the chipboard or fiberboard be pressed, with an external release agent in particular the pressing allowance is applied before pressing is also known from GB 1,148,016. The press allowances are with a treated external release agent. Organic release agents Substances containing free hydroxyl groups, for example glycerin, ethylene glycol, polyester and polyether.

From DE-OS 26 47 488 a method for improving the Demolding process in the production of chipboard or Chip moldings by pressing the raw materials with an NCO group having known binders, with the press supplements before the introduction or application of the glued chips Press temperature essentially non-volatile substance, if necessary. in the form of a solution or dispersion, which is applied at the pressing temperature an adhesive consisting of discrete particles Layer. This external release agent, which an adhesive layer consisting of discrete particles leaves, consists of at least two components, namely a non-volatile surfactant and one finely divided filler. In addition, there is generally a solution or dispersant, if the surface-active substance is not liquid anyway. Come as a surfactant Soaps, in particular soft soap. As fine-grained Fillers are oxides, carbonates, silicates, sulfates, fine particles Minerals, e.g. B. also talc, clays, expanded mica, diatomaceous earth, etc. suitable. However, the use of surfactants is essential Substance. The desired granular structure of the release agent can also be used without a filler achieve. This note as well as the examples given causes in practice the use of a filler was dispensed with and the surface-active substance, in particular Soft soap, used as the actual active ingredient alone has been. This can also be seen in Deppe / Ernst, p. 60.

The use of soft soap as an external release agent is in the relatively low press temperatures below about 200 ° C. applicable. At higher press temperatures up to around 250 ° C however, decomposition takes place, with the press supplements a well adhering but difficult to remove covering forms, especially in continuously operating presses grows in an uncomfortable way since it is continuously cannot be removed mechanically. This coating worsens the Heat transfer into the glued chip material, which is disadvantageous Way requires longer pressing times. Business interruptions at mechanical removal of the covering is a necessary consequence. As the thickness of the covering increases over time, the covering thickness is not constant, it is still necessary to have larger ones Grinding allowances to be taken into account, including not only that Production efficiency suffers, but also the complicate subsequent processing steps. The covering structure can eventually lead to lower forcibly Apply pressing temperatures and thus extended pressing cycles have to.

The use of suitable release agents on the one mentioned here Area is particularly in use with isocyanate as Binder a well-known and upcoming Problem. Not only has a significant effort been made, to develop internal release agents (DE 31 08 537 A1), but also searched for other ways. So it is from DE 38 20 376 C2 known in the manufacture of a multilayer chipboard in the core layer and in the top layers isocyanate as a binder to use and in addition outside separating cover layers that are bound with phenolic resin, apply and after curing remove again. Through these separating cover layers prevents the isocyanate from contacting the pressing additives comes. The removal of the separating cover layers and the partial The cover layers are removed by a grinding process.

The invention has for its object a method according to Show preamble of claim 1 that is easy to handle and in which a disruptive build-up on the press supplements is not he follows.

According to the invention, this is done with a method according to claim 1 reached.

The invention is based on the knowledge that this is in the state of the Technology in the production of chipboard also as a filler known talc in its sole use, that is without surface-active substances, becomes the active ingredient and thereby Signs of decomposition and the structure difficult to remove Avoid deposits even if with comparatively increased Press temperatures is worked. The invention avoids continue to use an organic release agent and uses the inexpensive mineral talc in an economical way as an active ingredient. Talc is also under in its application World viewpoints unproblematic. It even leaves his continuous use without building a covering occurs. With continuous presses there is also a continuous one Cleaning of the press allowances instead. This well-known continuous cleaning, which is available anyway, is sufficient completely to keep the press supplements clean. This results in a uniform heat transfer, and the pressing device can operated with high performance and constant speed become. Production does not have to go through separate cleaning cycles to be interrupted. The thickness tolerances to be taken into account the plates can advantageously be kept small, since constant, reproducible, even in continuous operation Conditions exist. The application of the talc can done in the usual way, for example by sprinkling, Spray on, roll up or the like. The talcum reaches the Pressing allowances, including the various pressing tools, such as sheets, plates, strips or the like and on the other hand also the means of transport for the glued raw material, especially the Belts, rollers, rolls u. Like. To be understood.

It when the talc in the form of aqueous suspension is applied to the pressing supplements. The Suspension of talc in water enables easy Preparation and handling of the suspension. The advantages are in economical consumption, while maintaining an even Press allowances are covered. When using any Avoidance of dust. Adequate arises Liability on the press allowances. Due to the effects of temperature evaporates the water during the pressing, being advantageous the adhesion of the talc to the press allowances is reduced and at the same time the separating effect is retained. Consequently it is possible to use the known press allowances Cleaning devices to clean without a deposit on builds up the press allowances. The use of talc in the form of Suspension has no adverse effect on the other process steps in the manufacture of such Spanoder Fiberboard. The other conditions of the manufacturing process can remain unchanged. Also the known binders containing NCO groups, in particular polymeric diphenylmethane diisocyanate (PMDI) used alone or mixed with polyols can still be advantageous to be used. Such binders are due to the reaction with the hydroxyl groups of the wood also as a polyurethane binder (PUR) called.

The talc can be in a proportion of about 5 to 40 wt .-% preferably about 20 wt .-% -, based on the total weight of the Suspension can be used. This is also an economical one Use ensured what was in relation to the already inexpensive Release agent has double effects. One with these proportions defined suspension has sufficient stability, is easy to handle and has an excellent separation effect. With high degrees of glueing, one also becomes comparative higher proportion by weight of talc in the suspension choose.

The suspension is kept in motion during application and thus a foam is formed, which is an even application of talc on the press allowances. It won't only signs of settling are avoided, but the foam is considered Means of transport and used as a distributor to keep the even Order to achieve the press allowances. The foaming on the suspension is achieved by stirring or pumping.

Particularly good results were achieved when using the talc an average grain size of about 10 microns is used. This means that a substantial proportion of the talc in this Grain size range should be, with finer ingredients do not bother. When using coarser talc - for example in one Grain size of> = 100 µm - the properties of the suspension, especially the ability to form the foam increasingly lost; the suspension also becomes increasingly unstable, so that the uniformity of those arising on the press allowances Protective layer deteriorated.

It is also useful to apply the suspension during application Add water. This can be done in steps or continuously to compensate for evaporation losses and to promote the application of a uniform layer thickness.

It is particularly advantageous to use talc as an external release agent Connection with a continuous pressing one with a binder containing chip or NCO groups Insert fiberboard. Then it is possible to use the suspension also apply continuously to the pressing allowances and the Press allowances continuously with known cleaning devices clean off.

The method according to the invention is illustrated by the following Examples further explained and clarified:

Example 1 :

An aqueous suspension of talc is prepared by several approaches can be combined into one batch. For each 40 kg of water with a temperature of about 20 ° C. are added submitted and added 10 kg of talc. The addition of the Talc is carried out in 5 portions of 2 kg one after the other. The talc has a grain size of 30 µm. The servings are under Use a high-speed mixer in the Water introduced. Then 20 such batches of 50 kg each become the batch united.

Example 2:

An aqueous suspension of talc is prepared by several approaches can be combined into one batch. For each Approach 160 kg of water with a temperature of about 25 ° C. submitted and 40 kg talc added. The addition of the Talc is carried out in 5 portions of 8 kg one after the other. The talc has a grain size of 20 µm. The servings are under Use a high-speed mixer in the Water introduced. Then 5 such batches of 200 kg each become the batch united.

Example 3:

It becomes an aqueous suspension of talc in one batch made by 700 kg of water with a temperature of about Submitted 50 ° C and 300 kg of talc is added. The addition the talc is carried out in 6 50 kg portions in succession. The talc has a grain size of 10 µm. The servings are introduced into the water using a paddle stirrer. The paddle stirrer is at the highest possible speed driven.

Claims (6)

1. A process for the continuous production of chip- or fibre-boards of lignocellulose containing raw materials, in which a binder comprising NCO-groups is applied to the raw materials having the form of chips and/or fibres, in which the raw materials are formed into a mat and in which the raw materials are compressed into the chip- or fibre-board under the influence of heat, talcum being applied as an outer release agent particularly to the compressing layers, i.e. to the belts, press plates and the like, prior to the compressing step, characterized in that the talcum release agent is applied in form of a suspension in water without an organic solvent.
2. The process according to claim 1, characterized in that the talcum is used in an amount of about 5 to 40 % per weight, preferably about 20 % per weight, related to the total weight of the suspension.
3. The process according to claim 1, characterized in that the suspension is agitated during its application so that a foam is formed, which allows a uniform application of the talcum to the compressing layers.
4. The process according to claim 1, characterized in that the talcum is used with an average particle size of about 10 µm.
5. The process according to claim 1, characterized in that water is added to the suspension during its application.
6. The process according to claim 1, characterized in that the chip- or fibre-board is continuously compressed, and that the suspension is continuously applied to the compressing layers.