DE4438764A1 - Cheap, lightweight, noise-absorbing laminate for use in automobiles - Google Patents

Abstract

Laminate for use in the automobile industry has a core layer of porous wood fibre fleece and at least 2 covering layers of fleece, in which the flexural strength of the core is less than that of each covering layer. Also claimed is the mfr. of laminate.

Description

The invention relates to a composite material for the car Mobile industry with a multi-layer structure.

Nonwovens are a commonly used con in the automotive field structural material with a wide range of properties. Example wise, phenolic resin-bonded textile fleece has long been under because of its good damping properties as a material for load-bearing and clad parts (pure or as a composite material) used in the automotive industry in the construction of cars and trucks. This product initially served as a low-cost flat product exclusively upholstery. Recently it turned out however, this material is available in a number of variants, and is very versatile. Molded parts are particularly preferred.

Phenolic resin-bonded textile fleece is available in bulk densities of 50 to 1000 kg / cm³ with thicknesses of 5 to 30 mm commercially available. It is a so-called pore composite, consisting of three phases (Cotton, hardened phenolic resin and air) to describe - a Construction material with a wide range of properties Limits can be modified. Cotton has the fiber shape,  Phenolic resin is punctiform, also as a kind of net surface Matrix before.

Wood fiber nonwoven materials are also known as a wood material that is machined and chopped Waste wood with the help of steam pressure and heat to a pulp processed. Some cellulose bonds are released sen. The porridge is usually mixed with small amounts of bandage synthetic resin (e.g. phenolic, alkyd, urea), Flame retardants, pesticides (against insects and fungal attack) and the like, forms the porridge on Formma machines to mostly plate-shaped fiberboard and dewatered.

Such wood fiber nonwovens are used as insulation against Cold, warmth and sound, as partitions, table and floor Coverings etc. also painted and coated with synthetic resin film.

In the course of the manufacturing process, the wood fiber material shaped, compressed and pressed. Here the Ver felting of the fibers and their natural binding power. By adding binders and water repellents as well as by The bandage can be subjected to thermal and other post-treatments increase strength. So the physical and the firm speed properties are adapted to the intended use.

According to DIN 68 753, a distinction is made between the following types of wood fiber materials:
hard wood fiber boards with a bulk density of more than 800 kg / m³,
medium hard wood fiber boards with a bulk density of more than 350 kg / m³ to 800 kg / m³ and
porous wood fiber nonwovens, also called insulation or insulation boards, with a bulk density of 250 to 350 kg / m³.

From Derwent Abstract 90-168 964 and the corresponding one renden JP-A-0 211 15 03, moldings are known which are made of wood fibers and binders as well as glass fiber mats in one lamination  condition. The molded body is used for interior lining use parts of automobiles and electrical cabinets det. The material is good dimensional stability and better strength and acoustic absorption properties attributed to.

The wood-like molding material is produced by adding 5 up to 30 wt .-% of a phenolic binder for binding the woody fibers. Glass fiber mats are obtained in that they are also impregnated with a phenolic resin solution and then dries. The glass fiber mats are then on a porous plate and placed the wood-like molding material on the Mat sprayed on. After the woody molding material he has reached the desired thickness, the spraying is stopped and a plate is applied to obtain a composite material. This becomes a force in a mold under pressure Vehicle headlining base material shaped.

DE 32 33 385 A1 describes a multi-layer fiber mat and a Processes for their preparation are known.

A specially constructed multi-layer fiber mat is described ben, which consist of two outer layers of fibers with high quality Duroplast impregnation and a middle layer from given if short-fiber wood products with particularly inexpensive thermoplastic binder additives, and which in this structure and composition special use offers opportunities for molded parts in the automotive industry, and both for their manufacturing process and quality of the end product itself.

For the production of load-bearing composite materials in the automobile multi-layer pressed cotton fleece set, however, due to the high density a great weight and have poor sound absorption properties. So it is necessary to use up to eight layers of cotton fleece with flats use weights of 1 kg / m² each to ensure a load-bearing capacity  Spare wheel cover of a cargo floor of a car is available deliver.

In contrast, the object of the present invention is in the provision of an inexpensive and as light as possible Composite material for the automotive industry, the beyond good sound absorption properties with a suitable bend strength with the lowest possible weight and volume combined with each other.

The above task is described in a first embodiment Form of the present invention solved by a composite material for the automotive industry with a multi-layer structure a core layer made of porous wood fiber fleece material and little at least two cover layers made of nonwoven, the flexural strength core layer is less than the bending strength of the respective top layers.

The composite material according to the invention is special Properties like low weight with the same rigidity pressed nonwovens or plastic sheets from known art fabrics such as glass fiber reinforced polypropylene, or the like Consider materials. In addition, the acoustic Properties resulting from the porosity and the layer structure of the material result, the materials of the prior art clearly superior. Furthermore, there is a comparable acoustics and a corresponding fire behavior with other composite materials not known with the same price / performance ratio.

In a preferred embodiment of the present invention the composite material consists of a three-layer structure, wherein the core layer of the porous wood fiber nonwoven material with two top layers made of hard-pressed lami cotton fiber fleece is nated.

The acoustics and the Strength of the composite material can be particularly controlled.  

Particularly preferred materials for producing the nonwoven fes are glass fiber reinforced or glass grid reinforced fiber materials, in particular textile fleeces containing binders, preferably those that consist of a cotton blend. These fleeces are opened by pressing at an elevated temperature brought the desired strength.

The special properties and performance of these the latter product group can be explained from the chemical and morphological structure of the cotton, as well as the thermoset character of the cured phenolic resins, commonly called Binders of the cotton blend nonwovens are used. Other influencing factors are the deformability, the ironability of cotton, the statistical frequency of binding points and also the laminate and / or cladding effect along the fibers adhering and thus also condensed binder molecules.

The cotton survives the manufacturing process practically without Change in their physicochemical characteristics. It gives the product special quality features such as sound Absorbency, good mechanical strength, impact toughness and splinter resistance in the cold.

Particularly preferred binders for the nonwovens are out selects from phenol-formaldehyde resins, epoxy resins, polyester resins zen, polyamide resins, polypropylene, polyethylene and / or ethyl vi nyl acetate copolymers. Phenolic resins have the after curing typical thermoset properties that affect the finished product transfer. The textile fleece is made from the tear cotton and the Powdery phenolic resin usually dry poses. Curing takes place either in the heating duct or via the unhardened semi-finished product as an intermediate stage in the press. For the parts that are to be used in the vehicle compartment selected textile used.

To achieve a high flexural strength, one should, if possible high binder content can be selected. In the event, however, that  the lowest possible bending strength is to be achieved it prefers the lowest possible proportion of binder adjust. Particularly preferred in the sense of the present Invention is therefore the proportion of binder in the outer layers in the Range from 10 to 65 vol.%, In particular in the range from 10 to 30 vol%, based on the respective top layer.

The thickness of the cover layers and also the thickness of the core layers can be set practically arbitrarily depending on the material will. The specifications of the automobile manufacturer are decisive here lers, so it is particularly preferred the thickness of the deck layers each in the range of 1 to 10 mm, especially in Range from 1 to 3 mm with a basis weight of 1 each up to 2 kg / m².

The acoustic properties of the composite structure according to the invention are of particular importance. It is accordingly required the density of the top layers on an area adjust the acoustic effectiveness of these layers in coordination with the core layer. As is known are the properties of acoustics to those of strength common. So are particularly hard-pressed nonwoven materials acoustically ineffective. In the same way, good ones are acoustic effective nonwovens characterized by low strength net. It is an essential object of the present invention therefore in making a compromise between these properties to achieve the special choice of fabrics. With basis weights in The acoustic properties of the range from 1 to 2 kg / m² Cover layers are sufficient, while materials with weight in the range of more than 3 kg / m² only insufficient acoustics have specific properties.

The core layer of the porous wood fiber nonwoven material exists in particular from wood fibers or lignose cellulose-containing company sermaterial, in particular due to matting of the fibers are bound due to their natural binding power. The production These materials are the specialist from the paper and Pappher  position especially known as the wet process. Here it is however, it is also possible that the porous wood fiber nonwoven material also contains binders, which are essentially in the state of the Technology are known. These are particularly preferably selected from phenol-formaldehyde resins, alkyd resins, urea resins and Melamine resins, particularly in an amount of 1 to 3 wt .-%, based on the wood fiber nonwoven material used can be. The type and amount of binders also determines here primarily the flexural strength, which moreover from the selected fiber length of the fiber material is dependent. Dement speaking it is required in the sense of the present invention Lich to choose the type and amount of binders such that the bending strength of the core layer, d. H. of the porous Holzfa servlies material is less than the bending strength of the Nonwoven cover layers. This is particularly through a set of a porous wood fiber nonwoven material with a density of 200 to 250 kg / m³ reached.

As with the above cover layers, this also plays with the porous wood fiber nonwoven material the acoustic property special role. Here too are the acoustic and strength properties opposing product properties that it requires make a compromise. Due to the The porous wood fiber fleece has a higher density of the wood fibers materials already have a higher basis weight. However is the elasticity of this material compared to the material of the Cover layers reduced. The good acoustic properties However, this material results from the cavities that are in the wood fiber nonwoven material is available in large numbers.

The thickness of the wood fiber nonwoven material can be practically can be set as desired, with thicknesses of 3 to 40 mm, ins special 5 to 30 mm with a basis weight of 2 to 5 kg / m² are particularly preferred in the sense of the present invention.

If in the following the relative bending strength of the core layer and the cover layers are discussed, then this is gone  going to understand that bending strengths with the same layer thicknesses of core layer and cover layer compared will. Accordingly, it is particularly preferred Embodiment of the present invention preferred that the Bending strength of the core layer a quarter to a twelfth, in particular a tenth, the flexural strength of the cover layers is.

A porous wood fiber non-woven material is particularly preferred, the a bending strength measured according to DIN 53 423 from 1.2 to 2.5 N / mm², in particular 2 N / mm².

In the same way, it is particularly preferred that the respective Top layers have a bending strength measured according to DIN 53423 12 N / mm² to 22 N / mm².

To improve the acoustic properties it is in the sense the present invention particularly preferred, the Holzfa Servlies material before connecting to the cover layers perforate. On the one hand, the number and size of the hollow rooms enlarged. It also finds a better ver binding of the cover layers with the core layer around the perforier th cavities instead if the material of the nonwoven fabric claws in the cavities. Furthermore, the Per foration the weight of the core layer and thus of the whole Composite lowered.

Another embodiment of the present invention exists in the process for producing the composite material defined above when. The nonwovens are used as top layers with a Core layer of a porous wood fiber nonwoven material by entanglement kung increased temperature pressed together. Especially before a temperature range of 180 to 250 ° C is given if necessary using hot melt adhesives, dispersion adhesives or also two-component adhesives, which means that the cover layers with the core layer are laminated. Here is also an easy one  Deformation of the object to be manufactured in the press tool possible Lich.

In the manufacture of the composite materials according to the invention it is possible to change the bending strengths of the cover layers respectively set differently. So it is possible through appropriate Procedure management during pressing, especially by un Different pressing of the individual cover layers, different to achieve bending strengths of the cover layers. This leaves by using spacers, for example or by applying compressed air on one side during the Enable pressing.

The composite materials according to the invention can be as they are be used in the automotive sector. Beyond that it is but also preferred in the sense of the present invention, this with decorative layers, for example carpeting, to ver see.

Another embodiment of the present invention exists in the special use of the composite structure defined above fabrics in the automotive sector. He is particularly preferred Composites according to the invention for acoustic damping in Areas bonnet, bulkhead (both sides), tunnel, door, roof, Footwell and the ventilation duct, as well as if necessary load-bearing basis for interior linings for valve covers, Tunnel linings, door linings, backrest linings and spare wheel covers as well as for parts with double function as Headlining, parcel shelf, filler, trunk mat and wheel arch cladding used.

Claims (17)

1. Composite material for the automotive industry with more layered structure of a core layer made of porous Wood fiber fleece material and at least two decks layers of nonwoven, the flexural strength the core layer is less than the bending strength the respective top layer. 2. Composite material according to claim 1, characterized records that the core layer with the cover layers is laminated in a three-layer structure. 3. composite material according to claim 1 or 2, characterized ge indicates that the cover layer is made of a nonwoven a glass fiber reinforced or glass grid reinforced ten fiber material, a binder-containing Textile fleece, especially a cotton blend fleece exists. 4. The composite material according to claim 3, characterized records that the binder of the nonwoven fabric choose from phenol-formaldehyde resin, epoxy resin, Polyester resin, polyamide resin, polypropylene, polyethylene len and / or ethyl vinyl acetate copolymers. 5. Composite material according to claim 3, characterized records that the binder portion of the deck layer (s) 10 to 65 vol .-%, in particular 10 to 30 vol .-%, based on the top layer. 6. The composite material according to claim 1, characterized shows that the thickness of the outer layers is 1 up to 10 mm, in particular 1 to 3 mm for a surface weight of 1 to 2 kg / m².   7. The composite material according to claim 1, characterized records that the core layer of wood fiber fleece or Lignose cellulose-containing fiber material, which especially by matting the fibers due to the natural binding power. 8. The composite material according to claim 7, characterized records that the porous wood fiber nonwoven material contains small amounts of binder selected are made of phenol-formaldehyde resins, alkyd resins, Urea resins and melamine resins, especially in an amount of 1 to 3 wt .-% based on the wood nonwoven material. 9. The composite material according to claim 7, characterized records that the density of the porous wood fiber fleece material is 200 to 250 kg / m³. 10. The composite material according to claim 7, characterized records that the thickness of the porous wood fiber fleece material 3 to 40 mm, in particular 5 to 10 mm a basis weight of 2 to 5 kg / m². 11. The composite material according to claim 1, characterized indicates that the bending strength of the core layer A quarter to a twelfth, especially a tenth, the bending strength of the cover layers is. 12. The composite material according to claim 1, characterized records that the flexural strength of the porous Holzfa Servlies material measured according to DIN 53 423 1.2 is up to 2.5 N / mm², in particular 2 N / mm². 13. The composite material according to claim 1, characterized records that the flexural strength of each Cover layers measured according to DIN 53 423 12 N / mm² to Is 22 N / mm².   14. The composite material according to claim 1, characterized records that the respective cover layers and / or the core layer is perforated. 15. Process for the production of composite materials according to one or more of claims 1 to 14, characterized characterized in that at least two nonwovens as a top layer with a core layer a porous Wood fiber nonwoven material due to increased exposure Temperature laminated together. 16. The method according to claim 15, characterized in that at a temperature of 180 to 250 ° C, especially using hot melt adhesives, Dispersion adhesives or two-component adhesives laminated. 17. Use of composite materials in the automotive sector according to one or more of claims 1 to 16 acoustic damping in the areas of the bonnet, Front wall (both sides), tunnel, door, roof, footwell and ventilation duct and as self-if necessary base for interior linings, especially for Valve covers, tunnel coverings, door covers clothing, backrest coverings and reserve wheel covers as well as parts with double function especially as a headliner, parcel shelf, filler, Trunk mat or wheel arch trim.