CN1768178A - Acoustically effective nonwoven material for vehicle liners - Google Patents

Abstract

An acoustically effective nonwoven for linings of motor vehicles comprises a porous fibrous skeleton made of coarse fibers. These coarse fibers comprise in particular staple fibers or spun-bonded fibers. A continuously changing weight quota of melted-on microfibrous material is foreseen in a front and/or rear surface region. This melted-on microfibrous material clings to the coarse fibers and bonds these in such a manner that the nonwoven has a predetermined airflow resistance and is stiffened at least in its surface region. The airflow resistance in the surface region has a value of between 200 - 60000 Nsm<-3>, in particular between 800 - 35000 Nsm<-3>, preferably between 1000 - 20000 Nsm<-3>, and mainly about 1400 Nsm<-3>. The bending stiffness of this fibrous nonwoven has a value of between 0.005 and 10 Nm, and in particular a value of between 0.25 and 6.0 Nm.

Description

Nonwovens for sound absorption in automotive linings

The invention relates to a sound-absorbing nonwoven material according to the preamble of claim 1 .

Nonwovens are gradually being widely used in the automotive industry because of the advantages of their sound-absorbing properties, in particular, such properties are the main purpose of the automotive industry using linings that have different sound-absorbing properties depending on the application of the lining performance, light weight, thinner and easier to shape, but also stable, plus easy to recycle. It is therefore desirable to use said liner which fulfills several technical functions while at the same time reducing the cost of materials to benefit.

Known lining components are disclosed, for example, in US-2001/0036788 publication or in EP-0939007 publication, all of which are composite structures with a plurality of individual layers each achieving a different technical functions.

Producing such composite structures has proven to be relatively complex, since the different material layers have to be produced beforehand and subsequently bonded to one another. Furthermore, these composite structures tend to delaminate over time. The effort required to counteract this delamination by gluing the flakes and/or dots is significant and makes the production process more expensive.

It is therefore an object of the present invention to provide a nonwoven with a sound-absorbing effect for lining motor vehicles which does not have the disadvantages of known components. In particular, it is an object of the present invention to provide a porous nonwoven having enhanced and easily adjustable sound-absorbing properties and shape-stabilizing properties. At the same time, the nonwoven should be lightweight and thin, durable and recyclable.

The invention achieves the above object by providing a nonwoven having the features of claim 1, in particular a sound-absorbing nonwoven, which has a predetermined airflow resistance and shape stability , comprising a fibrous framework comprising scaffolds or coarse fibers, into which are added microfibers such that at least some of the microfibers are completely melted. This ensures that the nonwoven is rigid in its surface area, which extends over half the thickness of the nonwoven, preferably over a third of the thickness, and that the nonwoven has a predetermined air flow resistance. The different desired technical properties of the nonwoven according to the invention are thus achieved by introducing microfibers of the same type or of different types in predetermined surface regions of the fiber backbone. Thus, the liner of the invention does not contain separate layers but has a continuously varying weight fraction of microfibrous material incorporated into the fibrous skeleton.

The invention uses known production methods, such as those described in DE-10044694. This publication discloses the production of nonwovens such as for soft and tensile wipe towels. This method of production requires the joining of one layer of spunbond fibers to another layer of meltblown fibers via a hydroentangling process.

In addition, EP-0418493 discloses a two-layer nonwoven for use as a trouser liner or a disposable napkin, the individual layers of which are connected to each other by directing a fine water jet into a specific layer so that the fibers are partly drawn from this directly The impact layer penetrates into the other layer, so that a tear-resistant connection between the two layers is produced.

Nonwovens produced in this way are commonly used in personal or household hygiene products and are generally not particularly suitable for stable, ie self supporting, automotive linings or acoustically effective automotive parts. In particular, in these known nonwovens, the fine fibers are distributed very evenly throughout the fiber skeleton (wiping cloth) or are almost twisted together at the mutual surfaces of the separate layer (cleaning towel).

In contrast to the above, according to the invention all microfibers are transported completely into this surface region, ie less than half the thickness of the fibrous skeleton containing the coarse fibers. The depth of this surface region is determined by the penetration depth of the microfibres, which is defined below by the statistical average penetration depth. Statistically, the weight fraction of the microfibrous material in this surface region changes continuously, for example decreases, with depth.

Therefore, this nonwoven is carried out by arranging a nonwoven containing microfibers (i.e. fibers with a count of 0.01-1.0 dtex, preferably 0.1-0.6 dtex) on top of a nonwoven made of skeleton fibers. The production of the skeleton fiber is also referred to as the fiber skeleton later. The fiber material is chosen such that the matrix fibers have a higher melting temperature than the microfibers. Subsequently, many tiny water jets are directed at the microfibers under high pressure so that the fibers of the microfibrous nonwoven are twisted around the thick fibers of the fiber skeleton. In the subsequent drying stage, the microfiber-rich nonwoven is subjected to a temperature at which the fibers of the microfiber nonwoven are at least superficially Melted - but preferably completely melted - after the heat treatment, the skeleton fibers are connected and hardened in the surface region of the nonwoven.

The production method can be modified so that the microfibers are melted by other heat sources, such as radiant heat from microwave ovens, contact heating or heating by hot steam or other hot fluids. The duration and temperature of these heat sources on the nonwoven are at the discretion of the skilled person.

The product produced by this method is thus characterized by a fibrous backbone whose front and/or rear surface area comprises a constantly changing weight fraction of molten microfibrous material. The skeleton fibers, hereinafter referred to as coarse fibers, have a fineness greater than 1 dtex, preferably 6-7 dtex. Suitable backbone fibers are endless spunbond fibers as well as staple fibers. These fibers can be made of suitable polymers or comprise mineral fibers, especially glass fibers, metal fibers or natural fibers. In a preferred embodiment, such a fibrous skeleton has an areal weight of 20-150 g/m ² . This area weight is determined by the skilled person according to requirements and can also have an area weight of approximately 800 g/m ² . Coarse fibers made of polyethylene terephthalate (PET) are used in a preferred embodiment of this fibrous backbone.

The desired nonwoven is fed in its surface area by adding molten microfibrous material, especially meltblown fibrous material having an average diameter of fibers of 2-8 microns and a length of 2-80 mm. Depending on the length of the fibres, it has been shown to be advantageous to shorten said microfibers to a fibrous skeleton (by means of hydroentangling) before transport, the material of these melted microfibrils being predominantly at the connection points of the coarse fibres, Or also at the individual coarse fiber filaments. According to the invention, these deposits have a statistically continuously changing proportion in the surface area of the nonwoven and decrease in depth. In said preferred embodiment, the total areal weight of the molten fibers is about 5-50 g/ ^m2 (about 10-30% of the areal weight of the fiber backbone) and the material is co-PET Co-PET. The surface area rich in molten microfibrous material (approximately 5-35%, up to 50% of the total thickness of the inventive nonwoven) is also porous and essentially determines the airflow resistance of the entire nonwoven. The nonwovens of the present invention are established in such a way that after the forming extrusion step, the airflow resistance is 200Nsm ^-3 < Rt < 60000Nsm ^-3 , especially at 800-35000Nsm ^-3 , preferably at 1000-20000Nsm ^-3 , mainly is about 1400Nsm ^-3 .

Furthermore, the accumulation of microfibrous material on the coarse fibers leads to a substantial stiffening of the fiber skeleton in its surface region, so that the inventive nonwoven is self-supporting. Especially by having a nonwoven with a skeleton fiber larger than 1 dtex, referred to below as thick fibers, and using the above-mentioned hydrodynamic entanglement method in combination with the melting method, increased stability and shape strength can be obtained, because on the one hand the thick The slight twisting of the fibers leads to a certain reinforcement in the surface area, on the other hand the drop-shaped molten fiber material adheres to the coarse fibers and thus stiffens them when it solidifies, in particular strengthening the connection points. The combination of these stiffening mechanisms leads to the desired flexural stiffness of the nonwoven of the invention, ie to a shape-reinforced and self-supporting nonwoven that can be used by the automotive industry.

The pronounced elasticity and flexibility of the coarse fibers in the interior of the nonwoven combined with the constantly changing hardness in the surface region result in a component with a high sound-absorbing effect. This part acts as a sound-absorbing spring-mass mechanics system, the mass of which is replaced by a porous hardened material in the surface area. By means of such a sound-absorbing system, the unavoidable resonance characteristic of conventional spring-mass mechanical systems can be compensated or avoided.

It should be understood, however, that the particular design of the nonwoven of the present invention depends on its intended application. Thus, the front side of the nonwoven of the present invention may be apertured while the rear side of the nonwoven is breathable.

It is also possible to use a microfibrous nonwoven made from meltblown fibers of variable fineness, different melting points, or a combination thereof. Furthermore, the impingement of the microjet of water delivered to the microfibers, ie the pressure and the duration, can be adjusted so that the penetration depth of the one or other type of microfibres is controllable. This provides a nonwoven that after heat treatment has a sticky nonwoven surface that contains partially fused microfibers that allow another standard nonwoven or the present invention to bonded nonwovens. It will be appreciated that the use of a suitable microfiber blend allows the airflow resistance in the surface area to be easily adjusted.

The advantages of the present invention will be apparent to those skilled in the art below. In particular, the combination of known production methods used in other fields allows the production of nonwovens suitable for lining automobiles, which nonwovens have a predetermined airflow resistance and the required bending stiffness but do not have separate layers. The possibility of obtaining nonwovens suitable for use as automotive linings, which have a hard surface area and areas integrated into this surface area for producing a predetermined airflow resistance, is surprising. Nonwovens produced according to the invention are particularly thin, ie are also lightweight and can be easily adjusted, ie can be designed such that they have a predetermined stiffness and selectable sound absorption efficiency. The nonwovens according to the invention have proven to have the particular advantage of not delaminating even after extensive use over a long period of time. Removing the risk of delamination leads to increased durability of the nonwovens of the present invention. Furthermore, the nonwovens according to the invention can be produced from only one material and still have all the properties used in modern automotive linings. Thus, the nonwovens of the present invention can be produced as a single piece of material allowing inexpensive disposal or recycling.

For clarity, the following does not distinguish between endless filaments of a certain length or fibers, and the term "fiber" includes both. For the skilled person, the term "microfiber" generally means meltblown fibers having a tex of 0.01-1.0, preferably 0.1-0.6, usually 0.2 dtex. The crude fibers here should have a dtex greater than 1.0 and/or also include fibers such as sisal, coir, bark, or glass, metal or mineral fibers.

Further preferred embodiments of the nonwoven according to the invention are characterized by the dependent claims.

In the following, the invention is described in more detail by means of exemplary embodiments and figures.

Fig. 1 shows the method for producing the nonwoven of the present invention;

Figure 2 shows an enlarged view of area A of Figure 1;

Figures 3a-3d show the physical properties of the nonwovens of the present invention;

Figure 4 shows an enlarged portion of a nonwoven of the present invention; and

Figure 5 shows a further improved production method of the nonwoven according to the invention.

In order to produce the nonwoven 1 according to the invention, a coarse fiber nonwoven 2 is covered with a layer of microfibres, as shown in FIG. 1 . This coarse nonwoven 2 preferably comprises spunbond fibers made of polyethylene terephthalate (PET) with a dtex of greater than 1.0. This coarse-fiber nonwoven serves as a fiber skeleton and has the soft spring properties of a sound-absorbing spring-mass system and has good recovery capabilities. This fibrous skeleton can have an areal weight of 20-800 g/m ² and is preferably made of PET material. It will be appreciated that the matrix may also include natural fibres, glass fibres, metal fibers and mineral fibres. In the present example, the covered nonwoven is subjected to the so-called hydroentangling process, which transports the deposited microfibrous layer to the surface area 4 by means of microjets 5 of water. The term "surface area" as used herein defines the area of the nonwoven comprising microfibrous material and extending between one-third and one-half the thickness of the entire nonwoven. During this process, the microfiber slides along and wraps itself around the backbone fibers, or preferably twists around the joints of the fiber backbone. These microfibers have 0.01-1.0 dtex, preferably 0.1-0.6 dtex, usually 0.2 dtex, and are preferably also made of PET or Co-PET. This method allows the penetration depth of the microfibers to be controlled and ensures that the weight fraction of the introduced microfibers is optionally continuously distributed in the surface area of the fibrous skeleton, in particular in a continuously variable manner; this means that all The gradient of the weight fraction of the introduced microfibrous material can be selectively adjusted. The fibrous skeleton 2 thus treated is then subjected to drying and heat treatment, in particular conveyed through a treatment station where the microfibrous material introduced into the surface region 4 of the fibrous skeleton 2 is passed through hot air or some other The heating mechanism 6 is melted. After passing through this treatment station, the shape of the microfibers 3 is changed into a drop shape, so that the coarse fibers are joined together in the regions especially at junctions or intersections, thereby strengthening the fiber skeleton in these regions. This produces porous, dimensionally stable nonwovens, ie self-supporting shaped parts that can produce sound-absorbing effects, such as are used, for example, in the modern automotive industry. It should be understood that the sound-absorbing properties and stiffness of the nonwoven can be determined by the variation and distribution of the fiber material and/or the fineness of the fibers and/or the proportion of selected fibers.

Part A of FIG. 1 is shown in FIG. 2 . From this figure, it is evident how the droplets of molten material 7 are deposited on the coarse fibers 8 of the fibrous skeleton 2 , resulting in hardening of the nonwoven in zone 4 .

Figure 3a shows the relationship between the different properties of the nonwoven 1 according to the invention. The schematically shown nonwoven 1 has three regions: a microporous surface region 4 ; an elastic central region 19 ; and a breathable bottom region 10 . The base region 10 and the surface region 4 are produced in a similar manner but their melted microfibrous material can have different weight fractions and different penetration depths.

Figure 3b shows a graph of the airflow intensity Rt value as a function of the depth d of the nonwoven according to the invention. The characteristic values of the airflow intensity in the surface zone 4 are between 500-5000 Nsm ⁻³ , in the central zone 19 these are about 200 Nsm ⁻³ , and in the bottom zone 10 between 200-10000 Nsm ⁻³ or higher.

The graph in FIG. 3c shows this bending stiffness B as a function of depth d. This bending stiffness depends approximately on the weight fraction of the melted microfibrous material and on the density of the fibers in this surface region. In this example, the slope in the microporous surface region 4 is smaller than the slope in the gas-permeable bottom region 10 . In the nonwovens of the invention, values for bending stiffness may vary between 0.0005 and 10.5 Nm; in particular these values are between 0.025 and 6.0 Nm.

Figure 3d shows the density index K for different fibers and melted fiber materials. Curve a shows the density values for spunbond or coarse fibers, which are present in higher density in the surface area as a result of the hydroentangling process. Curve b shows the density distribution of the molten microfibrous material and shows a curve with a continuous change in its weight fraction. The slope of this fibrous material depends on the duration and water pressure of the hydroentanglement process. The ratio of coarse fibers to micro fibers is in the range of 3:1. Curve c shows the proportion of meltblown fibers which have been introduced into the surface region of the nonwoven but which have not been melted. The airflow resistance can be adjusted in particular by means of the meltblown fibers. These unmelted fibers are meltblown fibers having a dtex of 0.01-1.0, in particular comprising polyester, polyester copolymers, polyamide, polypropylene or similar synthetic materials, preferably PET or Co-PET.

Figure 4 schematically shows a microscopic view of the nonwoven of the present invention. This figure clearly shows how the porous fibrous skeleton made of coarse fibers 8 is filled with molten microfibrous material 7 and unmelted microfibrous material 9 . The weight fraction of the molten fibers directly below the surface is significantly higher than the weight fraction of the molten fibers in the interior of the surface region 4 . The distribution of the non-melted microfibers in this region is also clearly shown. The formation of the microporous stiffening layer in the surface region of the fiber skeleton is important for the nonwoven according to the invention.

It should be understood that the nonwoven 1 of the present invention can be combined with other nonwovens of the same type in order to obtain parts with specific performance properties. Such a production process is schematically shown in FIG. 5 . In this process, nonwovens 11, 12 of different designs are subjected to the known hydroentanglement process (station 13) in order to obtain different intermediate products 14, 15, 16, 17, which are formed in a suitable manner. are stacked and joined together by a known heat treatment process 18 .

It is clear to a person skilled in the art that the fleece according to the invention can be provided with an air-permeable decorative layer or with air-permeable and/or water-permeable foils. Particularly suitable for the decorative layer are woven layers, knitted fabrics, fabrics, decorative nonwovens and/or foam layers.

Claims (12)

1. the nonwoven (1) that is used for the acoustically effective of vehicle liner, comprise the porous fibre skeleton of making by crude fibre (8) (2), particularly including staple fibre or spun-bonded fibre, described fiber reinforcement (2) has the micro fibre material of fusing at front surface area and/or back surface area (4,10) weight quota that continuously changes in, described melted on microfibrous material (7) is connected to that this crude fibre (8) is gone up and these crude fibres is connected and makes described nonwoven (1) have the predetermined air flow resistance and at least at its surf zone (4,10) hardened with predetermined bending hardness in, make this nonwoven oneself support.

2. nonwoven according to claim 1 is characterized in that, this crude fibre (8) has the number greater than 1dtex, particularly at 1-35dtex, is preferably the number of 6-17dtex.

3. according to claim 1 or 2 described nonwovens, it is characterized in that this crude fibre (8) is a spun-bonded fibre and by polyester, polypropylene or polyamide are made, and are preferably made by polyethylene terephthalate.

4. according to each described nonwoven among the claim 1-3, it is characterized in that described nonwoven (1) comprises unfused microfiber (9).

5. nonwoven according to claim 4 is characterized in that, the microfiber of described fusing (9) has the number of 0.01-1.0dtex, and the best number of 0.1-0.8dtex is generally the number of about 0.2dtex.

6. according to each described nonwoven among the claim 1-5, it is characterized in that, this micro fibre material (7) is the melt blown fiber material, particularly by polyester, copolymerization-polyester, polyamide, copolymerization-polyamide, polypropylene, copolymerization-polypropylene etc. are made, and are preferably made by polyethylene terephthalate or copolymerization-polyethylene terephthalate.

7. according to each described nonwoven among the claim 1-6, it is characterized in that the fusing point that described crude fibre (8) has is higher than the fusing point of this micro fibre material (7).

8. according to each described nonwoven among the claim 1-7, it is characterized in that the gas-flow resistance in the surf zone (4) of this fiber non-woven thing (1) is 200-60000Nsm ^-3, particularly at 800-35000Nsm ^-3, be preferably in 1000-20000Nsm ^-3, mainly be about 1400Nsm ^-3

9. according to each described nonwoven among the claim 1-8, it is characterized in that the bending hardness (B) of this fiber non-woven thing (1) is 0.005-10Nm, particularly between 0.025-6.0Nm.

10. according to each described nonwoven among the claim 1-9, it is characterized in that described nonwoven and another nonwoven combination at least.

11., it is characterized in that described nonwoven is provided with air-permeable layer according to each described nonwoven among the claim 1-10.

12., it is characterized in that described nonwoven is provided with decorative layer according to each described nonwoven among the claim 1-11.

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