DE102021212069A1 - Process for manufacturing a multi-layer component - Google Patents

Abstract

The invention relates to a method for producing a component (1) which has a multi-layer structure made up of individual layers (3) stacked one on top of the other, in which the individual layers (3) are stacked one on top of the other in a stacking step with adhesive (5) arranged in between to form the multi-layer structure (10). and the multi-layer structure (10) is pressed to form the component (1) in a pressing step. According to the invention, an additional component of exothermally reacting particles (7) is added to the adhesive (5), which releases heat directly in the multi-layer structure (10), i.e. in the adhesive gap between adjacent individual layers (3), during or after the pressing step with an exothermic reaction.

Description

The invention relates to a method for producing a multi-layer component according to the preamble of claim 1.

With regard to the use of CO2-neutral or -negative as well as renewable materials, components made of wood, for example, are becoming increasingly important.

In a generic method, such a component is produced as a multi-layer structure from individual layers stacked on top of one another. In the process, the individual layers are first stacked in a stacking step with an adhesive in between. This is followed by a pressing step in which the stack is pressed to form the component.

For example, in the production of such a multi-layer component for structural use in automobile construction, among other things, up to 30 individual layers and more (with a thickness per individual layer, for example between 0.8 and 3.0 mm) are joined to form the component in the pressing step in a press . The layers of adhesive arranged between the individual layers are usually cured in a curing process at a curing temperature in the range of up to 200°C. In the prior art, the heat input required for curing takes place via the press tool. After the pressing process, this remains closed for a predefined heating or locking time until the adhesive has hardened.

Due to the high number of individual layers stacked on top of each other and the heat-insulating properties of wood and other CO2-neutral, -negative and/or renewable materials, the heating/holding times in the press are very long. It can take up to 30 minutes for the required curing temperature to be reached inside the multi-layer component.

From the DE 10 2009 022 584 B4 a method for the integral connection of parts with an adhesive is known. From the DE 101 41 674 A1 a reactive adhesive with at least one microencapsulated component is known. From the DE 101 61 349 A1 a fast, activatable polyurethane adhesive is known.

The object of the invention is to provide a method for producing a multi-layer component in which the functionality during the production process is increased compared to the prior art.

The object is solved by the features of claim 1. Preferred developments of the invention are disclosed in the dependent claims.

The invention is based on a method for producing a multi-layer component which has a multi-layer structure made up of individual layers stacked on top of one another. In the process, the individual layers are first stacked in a stacking step with an adhesive in between to form a multi-layer structure. This is followed by a pressing step in which the multi-layer structure is pressed into the component in a press tool. According to the characterizing part of claim 1, an additional component of exothermic particles is added to the adhesive. During or after the pressing step, these can release heat directly in the multi-layer structure, i.e. in the adhesive gap between adjacent individual layers, with an exothermic reaction.

With regard to a perfect joining result after the pressing step, it is preferred if the adhesive located in the multi-layer structure is cured in a curing process. The curing process can preferably take place during the pressing step. In this case, the pressing tool can be kept closed for a predefined heating and/or holding time after the pressing process, until the adhesive in the multi-layer structure has hardened. The curing process can take place at a temperature of the order of up to 200°C.

Due to the exothermic reaction according to the invention directly in the multi-layer structure, the above curing process can be accelerated, specifically in comparison to an external heat input that takes place on the multi-layer structure via a heating system in the press tool. As an alternative to this, the invention also includes a constellation in which an additional external heat effect on the multi-layer structure takes place via the press tool.

The invention is therefore aimed at accelerating the curing process and thus the production of the component and is in principle not limited to a multi-layer structure made of wood veneer parts, but rather can also be used on other multi-layer components that have a layered or multi-layer structure and require heat input for production .

In the case of the invention, the heat is used which occurs during exothermic reactions of organic and/or inorganic particles (size of the particles matched to the adhesive gap, usually less than 500 μm) with moisture/water. In a preferred embodiment, each of the particles can be provided with a water-impermeable be provided with a layer so that the reaction with moisture/water does not take place in advance. For example, organic polymers (for example polycarbonate) or mineral substances (for example silicates) can be considered as the water-impermeable layer. On the other hand, each of the particles can be in a geometric shape that breaks well under pressure into fragments with the largest possible fracture surfaces. There are various ways of using the resulting heat. In addition to a general reaction initiation, acceleration is also conceivable.

In a preferred process scheme described below, the principle is shown using the example of thermal curing of an adhesive layer when gluing wood veneers. To explain the reaction/principle described, the exothermic hydration of gypsum (that is, the mixing of gypsum) should be mentioned here as an example. This is the exothermic crystallization to form calcium sulfate dihydrate, in which water is built into the crystal lattice exothermically. The heat generated during such a reaction can be used to harden the adhesive. The resulting inorganic compound (gypsum) can remain in the adhesive layer without any disruptive influence and without undergoing any further reactions. Fillers in the form of inorganic particles are already used in almost all technical polymers/adhesives in the double-digit percentage range. Another example of an exothermic reaction is the exothermic hydration of calcium chloride.

In the preferred process scheme, the exothermally reacting particles are introduced into an adhesive layer in order to be able to use the heat generated by the reaction directly in the adhesive gap to cure the adhesive. On the other hand, the chemical composition of the particles is selected in such a way that the reacted particles can remain in the adhesive layer.

In a first process step of the above process scheme, the generally pasty adhesive is first applied to the wood veneer. In the second process step, the particles, which react exothermically with moisture and are initially surrounded by a water-repellent layer, are distributed on the adhesive. A first joining partner is thus obtained. In a third process step, a second joining partner, i.e. the next wood veneer, is brought together with the first joining partner. The second joining partner can be treated in the same way as the process steps above. This process is repeated until the desired number of wood veneer layers is reached. The resulting stack is then placed in a press tool. Up to this step, the water-impermeable layer of the particles should be intact enough to prevent the particles from reacting with the moisture in the wood and/or the environment. In the fourth process step, the press tool is now closed, the particles are broken up by the pressure and the water-impermeable layer is destroyed. The particles can then react exothermically with the moisture from the wood veneer and/or the environment. The heat generated by the exothermic process can now be used very efficiently directly in the adhesive layer to harden the adhesive. The resulting particle fragments can, on the one hand, be due to their small size (divided particles/fragments should be less than 100 µm in size) and the inert properties of the organic and/or inorganic compounds (reacted by the reaction with moisture), on which the particles are based, remain in the adhesive layer.

In a comparative example not covered by the invention, particles (so-called Curie particles) which can be excited inductively are introduced into an adhesive layer for direct heating. An electromagnetic field is applied from the outside via an induction unit and the particles introduced are thus excited. The resulting heat can be used to cure an adhesive. In contrast to the comparative example, according to the invention no additional system and no complex tool technology is required (thus no additional investment, no further personnel requirements, no maintenance). In addition, in the comparative example there is the risk of so-called hotspots, which means that significantly higher temperatures can occur locally, which can lead to damage and thus a weakening of the adhesive. In addition, in the comparative example, the inductively excitable particles are generally made of metal, so that anti-corrosion measures have to be taken.

Aspects of the invention are emphasized again in detail below: The exothermically reacting particles can preferably be organic and/or inorganic particles. These can react exothermically with a reaction partner from the process environment, especially water. In a preferred embodiment variant, the individual layers can be provided at least partially from laminated wood layers, ie wood veneer layers. In this case, the exothermally reacting particles in the adhesive can preferably react exothermically with the moisture from the laminated wood layers. The moisture from the laminated wood layers can usually be in a range up to over 25%.

An inorganic or organic reaction product is formed from the exothermic reaction. The reaction product forms a component that remains in the adhesive without any interfering influence or without further reaction. Such components in the form of inorganic materials are already used in almost all technical polymer adhesives in the double-digit percentage range.

With regard to a perfect joining result in the multi-layer component, it is important that the exothermic reaction only starts when the pressing step is carried out, i.e. not before. This can be ensured as follows: The exothermally reacting particles can each have a covering layer which is impermeable to the reaction partner, in particular water-impermeable, and which encases a particle core made of exothermally reactive material. In this case, the process sequence is as follows: Before the pressing step is carried out, the covering layer prevents an exothermic reaction between the exothermally reactive material located in the particle core and the reactant. In the pressing step, the covering layer is destroyed by mechanical action. As a result, the exothermally reactive material in the particle core comes into contact with the reactant and reacts exothermically with it.

By way of example, the exothermic reaction can be an exothermic hydration of gypsum. Here, an exothermic crystallization of calcium sulfate and water to calcium sulfate dihydrate takes place. The water is built into its crystallization lattice exothermically. The gypsum that forms as a reaction product remains in the form of particle fragments as a non-reactive component in the adhesive.

The covering layer, which is impermeable to the reaction partner, can be formed from organic polymers, in particular polycarbonate, or from mineral substances, in particular silicates.

An exemplary embodiment of the invention is described below with reference to the accompanying figures.

• 1 in einer vergrößerten Schnittdarstellung ein fertiggestelltes Mehrlagen-Bauteil;
• 2 bis 10 jeweils Ansichten, anhand derer die Prozessabfolge zur Herstellung des in der 1 gezeigten Mehrlagen-Bauteils veranschaulicht sind.

Show it:

• 1 a finished multi-layer component in an enlarged sectional view;
• 2 until 10 each views, based on which the process sequence for the production of in the 1 multi-layer component shown are illustrated.

In the 1 a section of a finished multi-layer component 1 is shown in a sectional view to the extent necessary for understanding the invention. The multi-layer component 1 consists in the 1 from a total of three wood veneer layers 3, each of which can have a thickness in the range of up to 3.0 mm, which add up to a component thickness s1. The three layers of wood veneer 3 are each adhesive layers 5 interposed.

The following is based on the 2 until 8th a process sequence for producing the in the 1 shown multi-layer component 1 described: So in the 2 first a lower wood veneer layer 3 is provided, on which an adhesive layer 5 is applied. Subsequently, according to 3 a component of exothermically reacting particles 7 is added to the adhesive. In the 3 the exothermically reacting particles 7 are applied, for example, by sprinkling. The exothermic particles 7 can be applied in any other way. For example, the exothermally reacting particles can be metered into the adhesive 5 in a mixer unit, even before the adhesive 5 is applied to the wood veneer layer 3.

Then, in a batch process ( 4 ) the middle wood veneer layer 3 is stacked on the lower wood veneer layer 3 with the interposition of the adhesive layer 5 . After that, according to 5 An adhesive layer 5 is again applied to the middle wood veneer layer 3 and exothermic particles 7 are applied to the adhesive layer 5 ( 6 ). In a final batch step ( 7 ) the top wood veneer sheet 3 is stacked on the middle wood veneer sheet 3 with the adhesive layer 5 interposed. The thus formed, still uncompressed multi-layer structure 10 has in FIG 7 a thickness s2, which can be greater than the component thickness s1. The still unpressed multi-layer structure 10 is placed in a press tool 9 ( 8th ) transferred, in which a pressing process takes place, in which the multi-layer structure 10 is pressed up to the component thickness s1.

The core of the invention lies in the admixture of the exothermally reacting particles 7 to the adhesive 5. With the help of the exothermically reacting particles 7, heat can be released directly in the multi-layer structure 10, i.e. in the adhesive gap between adjacent wood veneer layers 3, during and after the pressing step with an exothermic reaction . With the heat released, the adhesive 5 can harden more quickly, compared to an external heat effect on the multi-layer structure 10, which takes place via the press tool 9. It should be emphasized that the invention also includes a configuration in which an additional external heat effect on the multi-layer structure 10 takes place, for example via the press tool 9 .

With regard to a perfect joining result, it can be important that the exothermic Reaction does not take place in advance of the pressing step, but only takes place when the pressing step is carried out. This is the following based on the 9 indicated material structure 10 of the exothermically reacting particles 7 is reached. In the 9 the adhesive layer 5 before the pressing step is shown in an enlarged, schematic view. Accordingly, the exothermically reacting particles 7 are distributed in the adhesive 5 . The exothermally reacting particles 7 each have a water-impermeable covering layer 11 which encases a particle core 13 made of exothermally reactive material. Before performing the pressing step ( 8th ) the enveloping layer 11 prevents an exothermic reaction between the exothermically reactive particle core material 13 and the moisture in the wood veneer layers 3. In the pressing step, the pressing force F acts on the material structure 10 and thus on the enveloping layer 11 of the particles 7, as a result of which it is destroyed ( 10 ). The exothermally reactive material in the particle core 13 therefore comes into contact with the moisture in the wood veneer layers 3, so that the exothermic reaction starts.

By way of example, the exothermic reaction can be an exothermic hydration of gypsum. Here, an exothermic crystallization of calcium sulfate and water to calcium sulfate dihydrate takes place. The water is built into its crystallization lattice exothermically.

In the 9 is the grain size k1 of the exothermically reacting particles 7 located before the pressing step. In contrast, the grain size k2 of the particle fragments 15 that are produced after the pressing step is significantly smaller. The particle fragments 15 form a filler which remains in the adhesive 5 without any disruptive influence or without any further reaction.

Reference List

1

multi-layer component

3

wood veneer layers

5

adhesive layer

7

exothermic particles

9

press tool

10

unpressed multi-layer structure

11

cladding layer

13

particle core

15

particle fragments

s1

component thickness

s2

Thickness of the still unpressed multi-layer structure

k1

grain size of the particles

k2

Grain size of the particle fragments

f

press force

QUOTES INCLUDED IN DESCRIPTION

This list of documents cited by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent Literature Cited

• DE 102009022584 B4 [0006]
• DE 10141674 A1 [0006]
• DE 10161349 A1 [0006]

Claims (9)

Method for producing a component (1), which has a multi-layer structure made up of individual layers (3) stacked one on top of the other, in which the individual layers (3) are stacked one on top of the other with an adhesive (5) arranged in between to form the multi-layer structure (10), and in a pressing step the multi-layer structure (10) is pressed to form the component (1), characterized in that the adhesive (5) is admixed with a component of exothermally reacting particles (7) which, during or after the pressing step, generate heat directly in the multi-layer structure (10 ), i.e. in the adhesive gap between adjacent individual layers (3). procedure after claim 1 , characterized in that the method has a curing step in which the adhesive (5) in the multi-layer structure (10) is cured, and that in particular as a result of the exothermic reaction taking place directly in the multi-layer structure (10) the curing step is accelerated, compared to an external heat effect on the multi-layer structure (10), and/or that, in addition to the exothermic reaction taking place directly in the multi-layer structure (10), there is an external heat effect on the multi-layer structure (10), for example via the press tool (9). procedure after claim 1 or 2 , characterized in that the exothermally reacting particles (7) are organic and/or inorganic particles which react exothermally with a reactant from the process environment, in particular moisture or water. Method according to one of the preceding claims, characterized in that the individual layers (3) are at least partially wood layers or wood veneer layers, so that the exothermally reacting particles (7) react exothermically in particular with the moisture from the wood layers, or that the individual layers (3) generally are made of CO ₂ -neutral, CO ₂ -negative and/or renewable materials. Method according to one of the preceding claims, characterized in that the exothermic reaction produces an inorganic or organic reaction product which forms a component which remains in the adhesive (5) without any disruptive influence or without further reaction. Method according to one of the preceding claims, characterized in that the exothermic reaction only starts with or shortly before the pressing step is carried out, and in that in particular the exothermally reacting particles (7) each have a covering layer (11) which is impermeable, in particular water-impermeable, to the reaction partner a particle core (13) made of exothermally reactive material. procedure after claim 6 , characterized in that before carrying out the pressing step, the shell layer (11) prevents an exothermic reaction between the exothermally reactive material and the reactant, and in the pressing step the shell layer (11) is destroyed by mechanical action, so that the exothermally reactive material in the particle core ( 13) reacts exothermically with the reactant. Method according to one of the preceding claims, characterized in that the exothermic reaction is an exothermic hydration of gypsum, in which an exothermic crystallization of calcium sulfate and water to form calcium sulfate dihydrate takes place, in whose crystallization lattice the water is incorporated exothermally, and/or that gypsum is the reaction product arises, which remains as a reactive component in the adhesive (5). Method according to any of the preceding Claims 6 until 8th , characterized in that the covering layer (11) which is impermeable to the reaction partner is formed from organic polymers, in particular polycarbonate, or from mineral substances, in particular silicates.

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