DE102007012691A1 - Plate e.g. high density fiber plate, manufacturing method, involves blowing up wood fiber bonding agent mixture by air flow from reservoir to conveyor under spatial adjustment of fibers in desired thickness - Google Patents

Abstract

The method involves blowing up a wood fiber bonding agent mixture by an air flow from a reservoir to a conveyor under spatial adjustment of binding fibers e.g. thermoplastic synthetic resins, in desired thickness, where the bonding agent is a condensation resin. The mixture is heated up and pressed in a pressing device using hot-pressing procedure. The condensation resin is selected from a group consists of urea-formaldehyde, melamine urea-formaldehyde, melamine-urea-phenol-formaldehyde, methyl disocyanate and polymeric diphenylmethane disocyanate resins.

Description

The The invention relates to a process for the production of wood fiber boards with lower plate thickness and lower densities and LDF, MDF or HDF boards produced by the process according to the invention.

It is known from the prior art that the carrier plates in the low LDF range have a density of 250 to 450 kg / m ³ , in the MDF range of 550 to 750 kg / m ³ and in the HDF range of 800 to 1000 kg / m ³ own. In the production of the known MDF or HDF boards, the wood fibers are glued and mixed with a binder, preferably a synthetic resin, and the mixture is sprinkled on a screen belt without pressure. Thereafter, the sprinkled mixture is compacted and pressed in a hot pressing process under high pressure and heat, whereby the resin hardens. Such plates require large quantities of material, both wood fibers and binders. Due to the high weight, the resulting products cause enormous transport costs and make the laying of such boards difficult.

The high densities of finished products are necessary to meet the requirements to the finished products z. B. when used in the floor to meet. Despite high density, it was not possible under a certain Plate thickness to go. So it was with HDF plates with thicknesses of 5 mm and less not possible in a spring connection a neat connection during processing to create panels. Such profiles go under stress time apart.

at the production of MDF boards below a certain thickness this no longer transportable in the previous scattering of the feed since it with the high mileage of Siebbinder at the press inlet due to the layered structure of the scattered material a partial blowing away of the fibers comes. Committee on the plates is preprogrammed.

Of the Invention is based on the object, a process for the preparation of boards of wood fibers lowering the density and lesser Plate thickness without reducing the quality parameters to create.

The The object is achieved by the characterizing features of claim 1, as well as the claims 12-14 solved.

According to the invention Wood fiber-binder mixture on the screen belt three-dimensionally aligned, the orientation of the fibers substantially until compression is maintained. The fibers are interwoven.

According to the desired composition and field of use, the individual components are weighed and blown with air with intensive mixing in a reservoir. When discharged from the reservoir mixing is still ongoing. From the reservoir, the wood fiber-binder mixture is uniformly inflated on a wire conveyor belt across its width. The amount of wood fiber-binder mixture depends on the desired layer thickness and the desired bulk density of the LDF, MDF or HDF plates to be produced. The thicknesses of the plates to be produced u. Ä. Are between 1-15 mm, preferably between 1-5 mm. The densities for the LDF boards according to the invention are 100 to 400 kg / m ³ , preferably 100-300 kg / m ³ for MDF boards at 400 to 650 kg / m ³ , preferably 400-550 kg / m ³ and for HDF Plates at 650 to 1300 kg / m ³ , preferably 650-850 kg / m ³ .

When Wood fibers are preferably the MDF wood fibers known per se used. The binders are the usual condensation resins such as UF, MUF, MUPF, MDI or PMDI resins used. Preferably they are used as precondensates. The aforementioned binders may alternatively or in a wide variety of combinations are used.

Next The condensation resins can also be used in admixture with these thermoplastic resins. In a particular embodiment of the invention, the thermoplastic Synthetic resins used in the form of binding fibers.

Around caking of the thermoplastic binders and fillers To prevent the pressing tools, the wood fiber binder mixture can Release agents are added or applied to the pressing tools become.

The Further processing of the spread on the wire conveyor belt wood fiber-binder mixture takes place in a known hot pressing process.

Despite lower densities in the individual products, the same or better quality features are achieved as are known from the products known hitherto. Thus, the new manufacturing process makes it possible to produce MDF boards with layer thicknesses down to 1 mm. Due to the three-dimensional orientation of the fibers, there is no unwanted blowing away of the fibers in the press inlet even at high transport rates. Become LDF, MDF or HDF boards desired with the hitherto known for such plates technical properties, the process of the invention, a smaller amount of wood fibers and thus also on binders, which represent a high cost factor, are used.

Would plates produced with the previously known densities by the process according to the invention, that would be the technical characteristics of these products are significantly better over the products prepared by known methods. When used as floor panel would become with consistent quality the weight loss of the plates during laying clearly noticeable do.

Of Furthermore, it is possible with the method according to the invention, too LDF, MDF, and HDF sheets with a flowing density gradient of a large-scale page to the other large-scale side to make the plates. This is the wood fiber-binder mixture another filler, the one higher specific gravity than the wood fibers added. When such fillers come sand, ground quartz waste, resin granules, like them for example, when recycling plastic particles from the dual System incurred u. ä. in question. When the mixture is blown onto the belt, a desired sighting occurs one. The heavy fillers fly on and store themselves thereby increasingly directly on the tape from. Depending on the blowing pressure, the raw density gradient of the plate to be produced be set.

Of Further can the fillers on the one hand or in part on a sieve conveyor belt inflated wood fiber binder mixture are sprinkled. To the others it is also possible the fillers sprinkle all or in part on the wire conveyor belt before the wood fiber-binder mixture inflated onto the wire conveyor belt becomes.

In another variant can the fillers both before and after inflation of the wood fiber-binder mixture on the Screen conveyor belt are sprinkled. The subsets of fillers, the before or after or with the wood fiber binder mixture together be applied depend on the desired properties of the final product.

By the use of fillers receives For example, you plates, on their top a completely different Sound behavior opposite have the bottom.

The Field of application of the process according to the invention produced Products is very diverse. Besides the use as plates can as wall coverings, as thin ones Walls, so-called Japan walls be used. In addition, the use in furniture or in the manufacture of flooring, z. B. laminate floors possible.

One Another field of application arises when the hot pressing performed as compression molding becomes. It can be packaging or "honeycomb" as a substitute for the known Making paper or cardboard honeycombs in the construction of lightweight panels.

The Invention will be explained in more detail by way of examples.

example 1

For the production of a thin MDF board with a thickness of 2 mm, twelve parts of condensation resin, for example MUF resin, with 88 parts of classic MDF wood fibers with intensive mixing by air in a reservoir and from this on a wire conveyor belt to a bulk density blown from 450 kg / m ³ . During mixing, the wood fibers become entangled and form a three-dimensional system with the attached condensation resins. Even at high feed rates of 200 m / min, there is no segregation or blowing away of the fibers before the press inlet. In the press by hot pressing the condensation of the resins and you get the desired plate.

Example 2

For the production of 4 mm thick HDF board, 17 parts of a condensation resin, for example, UF resin and four parts of a thermoplastic resin in fiber form containing 79 parts of wood fibers previously treated with flameproofing agents are given as in Example 1 mixed and inflated on a wire conveyor belt to such a height that a bulk density of 580 kg / m ^{3 is} achieved. The thermoplastic binder fibers used have a high melting point, so that they contribute intensively to the bonding of the wood fibers only during hot pressing. When blending the starting materials, the thermoplastic binder fibers contribute to the intense three-dimensional orientation of the system. In order to avoid caking of the thermoplastic binder fibers or corresponding fillers on the pressing tools release agent can be added to the mixture.

As well can the release agents are applied directly to the pressing tools.

The resulting plates are comparable in their mechanical properties with known HDF plates having a bulk density of 780 kg / m ³ . The plates according to the invention are not only lighter than the conventional plates for the same purpose, but also cost-effective due to the material savings.

Example 3

For the production MDF or HDF sheets with a flowing density gradient of a large-scale page to the other large-scale side the plate are, for example, as indicated in Examples 1 and 2, the wood fibers with the synthetic resins in the specified quantity ranges mixed and in addition five parts added to fillers. As fillers resin resin pellets are preferably used. When inflating of the starting mixture, the resin granules are due to the higher Weight similar fly on an air sifting and propagated on the underside of the plate to come to rest on the wire conveyor belt.

Also Here it may be advantageous to work with additional release agents, the caking of the thermoplastic binder fibers or fillers prevent the pressing tools.

To the hot pressing receives you plates, opposite the conventional one Plates show a lower natural vibration behavior. Likewise will improves the sound behavior.

Claims (17)

A process for the production of LDF, MDF and HDF boards, characterized in that after intensive mixing of the starting materials, the wood fiber-binder mixture is inflated by means of an air flow from the reservoir to a conveyor belt with spatial alignment of the fibers in the desired thickness and then in a pressing device is heated and pressed in a hot pressing process. Method according to claim 1, characterized in that the binder content is 8 to 25% by weight. Method according to Claims 1 and 2, characterized that as a binder condensation resins, preferably in the form of Precondensates are used. Method according to at least one of claims 1 to 3, characterized in that as condensation resins UF, MUF, MUPF, MDI or PMDI resins alone or mixed with each other be used. Method according to at least one of claims 1 to 4, characterized in that as a binder mixtures of condensation resins and thermoplastic resins. Method according to claim 5, characterized in that that the thermoplastic synthetic resins are preferably used as binding fibers to be used. Method according to at least one of claims 1 to 6, characterized in that the wood fiber-binder mixture fillers be added. Method according to at least one of claims 1 to 7, characterized in that as fillers preferably sands, ground glass waste and Resin granules, preferably those in the recycling of plastic particles arising from the dual system, are used. Method according to at least one of claims 1 to 8, characterized in that the fillers in total or in Partial quantities on the wood fiber-binder mixture blown onto the wire conveyor belt be scattered. Method according to at least one of claims 1 to 8, characterized in that the fillers in total or in Aliquots prior to inflation of the wood fiber-binder mixture on the wire conveyor belt be scattered. Method according to at least one of claims 1 to 8, characterized in that the fillers in total or in Subsets before and after inflation of the wood fiber-binder mixture be sprinkled on the screen conveyor belt. Method according to at least one of claims 1 to 11, characterized in that the starting materials release agent be added, which is a caking of the thermoplastic binder and fillers prevent the pressing tools. Method according to at least one of claims 1 to 11, characterized in that the pressing tools release agent against the caking of the thermoplastic binders and fillers be applied. LDF board produced by a process according to claims 1 to 11, characterized by a thickness of 1 to 15 mm and a bulk density of 100 to 400 kg / m ³ , preferably a thickness from 1 to 5 mm and a bulk density of 100 to 300 kg / m ³ . MDF board produced by a process according to claims 1 to 11, characterized by a thickness of 1 to 15 mm and a bulk density of 400 to 650 kg / m ³ , preferably a thickness of 1 to 5 mm and a bulk density of 400 to 550 kg / m ³ . HDF board produced by a process according to claims 1 to 11, characterized by a thickness of 1 to 15 mm and a bulk density of 650 to 1300 kg / m ^3, preferably a thickness of 1 to 5 mm and a bulk density of 650 to 850 kg / m ³ . Plate according to one of claims 12 to 14, characterized by a density gradient from one large area side to the other large area side the plate.