Light-weight sound proofing material having partial tread resistance

BACKGROUND OF THE INVENTION 1. Field of the Invention The invention relates to a lightweight sound-insulating part which is designed as an acoustic mass-spring system and has regions with increased resistance to trapping, as well as a method for producing the same.

In the prior art, molded sound insulation with integrated carpet is known as mass-spring systems with polyurethane foam foams.

DE-AS-20 06 741 discloses a multilayer, sound-absorbing component for a body composed of sheet metal pressed parts. The sound-absorbing component consists of a layer of dynamically soft material, such as foam, which is mounted on the body of the vehicle in a floating manner, a heavy layer which is arranged on the soft material, and a carpet or covering, Heavy layer. This layer arrangement improves the sound insulation and also reduces the transmission of the body body sound into the interior of the vehicle.

US Pat. No. 4,579,764 discloses a shaped, rear-foamed carpet assembly which is used in motor vehicles. The structure comprises a carpet layer having a deployed moldable thermoplastic polymer layer and an acoustically insulating foam layer bonded to the thermoplastic polymer layer. A polyurethane foam having a predominantly open-cell structure is preferably used as a flexible foam insulation material. In order to reduce the weight of the sound insulation part and in order to achieve a better adaptation to the structure to be insulated, the polyurethane foam is preferably only provided in some selected areas under the thermoplastic polymer layer.

The physical laws of sound-insulating parts based on mass-spring systems are described in the literature as, for example, in the company document "Information No. 130" ( "Advanced Sound Insulations for Automobile") by Stankiewicz GmbH (published for the 52nd International Automobile Exhibition , Frankfurt / Main, 11-20 September 1987).

It is known from the abovementioned printed manuscript that acoustically effective foam begins to gradually become effective as an acoustic spring due to its special properties, which are required by modern, highly effective sound-insulating moldings.

Formings made from acoustically effective foam are relatively easy to manufacture and are characterized by high fitting accuracy. The density and / or crosslinking of two-component materials can be influenced specifically by means of the chemical components used in the production of the acoustically effective foam and by the applied reaction conditions.

First, a light foam in the mass-spring system with a density of 70 kg / m was used for sound insulation parts³ Is used. A development aimed at providing improved sound attenuation characteristics in the low-frequency range, eg below 200 Hz, in order to dampen the acoustically harmful ignition frequency influences in the passenger compartment. As a result of this development, a so-called viscoelastic foam having a relatively low elastic modulus in the range of about 10⁵ Nm^-2 At a simultaneously acceptable high loss factor. Using this foam, a significant improvement in sound attenuation values ​​in the low-frequency range could be achieved without having to accept too much deterioration in the high-frequency range.

In the case of sound-insulated parts according to this known prior art, it has hitherto been emphasized that in the frequency range below 300 Hz noise attenuations against the insulation of a naked body panel by the mass-spring systems are avoided. The frequency range below 300 Hz is often excited to vibrate in the case of four-cylinder vehicles due to the speed-dependent ignition frequency.

Four-cylinder vehicles of the newer generation, as well as multi-cylinder versions such as six-cylinder engines, are no longer familiar with the drone noises, or they are only greatly reduced. Instead, increasingly high-frequency noises occur in the frequency range from 300 Hz upwards.

In the frequency range from 300 Hz, conventional polyurethane foam materials used as acoustic springs in mass-spring systems have disadvantages with respect to sound-insulating parts, in which acoustic non-woven fabrics are used as acoustic spring.

The nonwovens used in these systems as an acoustic spring are very soft, which leads to a good acoustic insulation behavior in mass spring systems.

However, the softness of the nonwovens gives the vehicle occupant the feeling, after the feet have been placed on a "spongy floor". This circumstance is considered unpleasant. Furthermore, this softness of the nonwovens leads to a compacting of the nonwoven structure in the shortest possible time. The densified nonwoven structure, however, naturally has considerably impaired sound-absorbing properties. Mass-spring systems, the acoustic spring of which is made of a non-woven material, therefore do not ensure long-term stability.

In the case of sound-impregnation parts with such soft acoustic springs, so-called inserts are usually arranged below the acoustic mass (ie the air-sound-absorbing heavy layer with carpet lamination) in areas which require an increased resistance to running. However, this requires the use of other materials, such as hard foam or foamed polystyrene. The use of various materials in the production of sound-insulating parts makes a subsequent recycling of the sound-insulating parts difficult overall. Furthermore, the use of various materials in the production of sound-insulating parts with the aforementioned construction leads to additional working steps in the production process.

The use of soft acoustic springs, however, advantageously results in a reduction in the weight of the sound insulation part. With these weight savings, economic and ecological advantages in vehicle construction, in particular in the case of passenger cars, are connected. These advantages associated with the use of lighter and softer acoustic springs have hitherto been invariably connected with the aforementioned disadvantage of low mechanical resistance.

US Pat. No. 4,529,639-A discloses a carpet part which is designed for weight-saving purposes from an insulating layer with a laminated carpet, that is to say as a single-layer sound-insulating element which has cushion-like foamings at certain locations adapted to a bodywork course Can By using different mixtures in the pillow-like foams, physical properties of the foam and thus of the end product can be influenced, such as density, flexibility, sound insulation. It is not possible to determine how locally partial traction resistance can be achieved without changing the sound insulation against a sound insulation part without partial resistance.

SUMMARY OF THE INVENTION The object of the invention is therefore to provide a sound insulation part which is both lightweight and has a partial resistance to impact, the disadvantages present in the aforementioned prior art being avoided.

The object is achieved by providing a sound insulation part with the features according to claim 1. Preferred embodiments are described in sub-claims 2-4.

Furthermore, the object is achieved by providing a method for producing the aforementioned sound-insulation part with the features according to claim 5. A preferred embodiment is described in claim 6.

For the purposes of the invention, "polyol" means an organic-chemical compound which has at least two hydroxyl groups. The compound can therefore also have three, four or more hydroxyl groups.

In the context of the invention, "isocyanate" is to be understood as an organic-chemical compound which can have one, two, three or more isocyanate groups.

According to the invention, the term "two-component polyurethane foam" is to be understood as meaning a foam which is produced from the basic components "polyol" and "isocyanate", it being self-evident that a mixture of different polyols or isocyanates, Isocyanates can be used. Furthermore, a "two-component polyurethane foam" may contain the customary auxiliaries such as catalysts, emulsifiers, foam stabilizers, pigments, propellants, aging and flame retardants, etc.

In the context of the invention, a "reaction mixture" is understood as meaning the mixture consisting of polyol and isocyanate and optionally "further auxiliaries, from which the desired polyurethane foam is formed by reaction.

The acoustically effective mass-spring system according to the invention comprises at least one region or several regions with increased resistance to impact as well as regions which are adjacent to these regions and have normal or low impact strength. For example, a textile surface covering for the passenger compartment in the foot region can have an increased resistance to running. The regions of the surface covering, which are adjacent to the foot region, for example, covering, for example, the center console or the side walls of the passenger compartment, etc., can not have an increased resistance to running.

The present invention thus makes it possible to provide a single-piece sound insulation part in which a selected area or several selected areas have an increased resistance to running. The areas with increased tread strength differ from the adjacent areas with normal or low impact strength by a changed mixing ratio of polyol to isocyanate in the reaction mixture for the production of the acoustic spring.

In other words, the entire acoustic spring of the sound-insulating part is composed of the same chemical starting materials, ie polyol or isocyanate. As noted above, the various regions of the sound insulation part differ in terms of the amounts of polyol and isocyanate in the reaction mixture. In this respect, the expensive separation step of the or the non-stationary regions (s) required for conventional sound-insulation parts is omitted from the remaining regions during the disposal of the sound-insulation part according to the invention.

When disposing of motor vehicles, very large quantities of surface linings are produced from the passenger compartment. In view of the present invention, the disposing of these surface linings is greatly simplified and, in particular, also reliable disposal is ensured. An erroneous disposal of the materials constituting the acoustic spring, for example by mixing the various materials, can not take place during the disposal of the sound insulation part according to the invention, since the acoustic spring is constructed entirely from polyurethane and can be disposed of in the entire piece. The present invention thus represents a significant advance in both economic and environmental terms.

Furthermore, the sound insulation part according to the invention not only simplifies disposal, but also simplifies the manufacturing process. The use of the same chemical starting materials in the production of sound insulation parts, both for areas with increased resistance to impact and for areas with normal or low impact strength, leads to a reduction in the number of starting materials required in the production of sound insulation parts. This greatly simplifies process management. Furthermore, since a reduced number of starting materials also simplifies the required storage, the invention also leads to a reduction in the production costs.

In other words, the manufacturer has an economic advantage both in the production and in the disposal of sound-insulating parts according to the invention.

For ecological reasons, it is now generally demanded that the use of composites made of different plastic materials, which can be recycled, if at all, to a recycling process only after an elaborate separation into the individual constituents. In this respect, the present invention also represents a significant advance in this respect. The sound-insulating parts according to the present invention can be fed to a polyurethane preparation in a single step without the need for a further separation step, if necessary after separation of the laminated carpet or covering.

The areas with increased tread strength are produced in the sound insulation part according to the invention by using the same starting materials for the production of the polyurethane foam, the mixing ratio between polyol and isocyanate in the reaction mixture compared to the mixing ratio of the reaction mixture for producing the adjacent areas with normal resp Low impact strength. The proportion of the isocyanate in the reaction mixture is preferably increased in this case in order to produce the region with increased resistance to impact. As a result, a stronger crosslinking of polyol and isocyanate is achieved, which then leads to the formation of a polyurethane foam with greater mechanical resistance, ie, increased tensile strength.

For example, the mixing ratio of polyol to isocyanate in the reaction mixture for producing the increased impact strength range may be 100: 62 parts, while the mixing ratio in the reaction mixture for producing the adjacent ranges of polyol to isocyanate may be 100: 45 parts.

If the mixing ratio in the reaction mixture of polyol to isocyanate is changed, for example, from 100: 45 parts to 100: 55 parts, the elastic modulus increases to four times. For example, with a mixing ratio of polyol to isocyanate in the reaction mixture of 100:45 parts, the elasticity modulus of the obtained polyurethane foam is 71,000 N / m², And at a mixing ratio of polyol to isocyanate of 100: 55 parts, the modulus of elasticity of the resulting polyurethane foam is 287,000 N / m².

Of course, other mixing ratios of polyol to isocyanate can also be adjusted in the reaction mixture. What is important is that the mixing ratio of polyol to isocyanate in the reaction mixture for the production of the region with increased resistance to trapping differs from the corresponding mixing ratio in the reaction mixture for the production of the regions adjacent to the region with increased tensile strength.

It is obvious that, for example, the mixing ratio of polyol to isocyanate in the reaction mixture for the production of a region with increased resistance to impact in the passenger compartment of a passenger car, on which only the feet of the driver or rider are regularly deposited, and a reaction mixture for the production of a Area with increased tread resistance in the corridor of a travel bus, on which the passengers are running, are different from each other. That is, if the region with increased tread resistance is likely to be subjected to greater loads, the proportion of the isocyanate component in the reaction mixture is increased according to these requirements.

Depending on the polyol and isocyanate used in the reaction mixture for the preparation of the region with increased tensile strength, no further substantial improvement in the mechanical resistance of the polyurethane foam occurs from a specific mixing ratio of polyol to isocyanate. Rather, the insulation behavior of the obtained polyurethane foam is no longer satisfactory from a certain degree of crosslinking.

This point, in which a further increase in the isocyanate content in the reaction mixture is no longer advantageous with regard to the parameters "impact strength" and "insulation properties" to be set, depends on the particular polyol or isocyanate components used. The mixing ratios of polyol to isocyanate, which are used in the preparation of the region with increased tensile strength, and which lead to a polyurethane foam having an increased resistance to running and at the same time good insulation properties, can be readily determined experimentally.

In a preferred embodiment of the invention, a light weight polyurethane foam having a density of not more than about 70 kg / m³, In particular with a density between about 50 and about 70 kg / m³, And most preferably with a density of about 60 kg / m³ Is used.

Compared with foams conventionally used in the production of sound-insulating parts, which have a density of about 80 to 120 kg / m³ , The use of the polyurethane foams with a density of not more than about 70 kg / m³ To a significant weight saving. This weight reduction facilitates the handling of the sound-insulating parts, for example, when installed in motor vehicles.

According to a further preferred embodiment, the at least one localized region and the adjoining regions have approximately the same density.

Thus, the sound insulation part according to the invention is extremely light-weight throughout. As fuel consumption increases as the weight of a motor vehicle increases, the provision of a light-weight sound-absorbing part is an important contribution to the reduction of the average weight of the motor vehicle and ultimately to the reduction of the average fuel consumption.

Furthermore, it is preferred that the surface area of ​​the at least one localized region does not exceed approximately 20% of the total area.

If, for example, sound insulation with an integrated carpet (carpet compact insulation) is designed in such a way that approximately 20% of the area is treated with harder polyurethane foam, ie a polyurethane foam with a higher stiffness or compressive hardness, the sound insulation is generally as a function of the frequency Practically not deteriorated. The reaction mixture for producing the harder polyurethane foam has a greater proportion of isocyanate compared to the reaction mixture for the production of the adjacent regions with normal or low impact strength.

Of course, the surface portion of the at least one localized region can also exceed approximately 20% of the total area if a certain deterioration of the sound insulation capacity of the sound insulation part is accepted.

According to a further preferred embodiment, a non-woven layer (non-woven fabric) is arranged between the insulating layer (heavy layer) and the polyurethane foam. The arrangement of a thin non-woven layer between the insulating layer (the heavy layer) and the polyurethane foam or between the carpet layer and the polyurethane foam causes a certain antifoaming or collapsing effect, whereby larger foam densities are obtained.

These larger foam densities are advantageous because they can further improve the mechanical strength in the region with increased resistance to impact. The nonwovens are preferably produced from polyurethane fibers. Of course, the nonwoven fabric can also be made from all conventional materials. The surface mass of the nonwoven fabric can be, for example, between about 10 and about 1000 g / m² lie. Preferably the surface mass is between about 50 and about 500 g / m², More preferably between about 70 and about 200 g / m².

As air-sound-absorbing insulating layers or heavy layers on which the carpet is lined as a decor and on the other hand the back-foaming with the above-mentioned reaction mixture of polyol and isocyanate, surface areas are preferably between about 2.0 and about 5.0 kg / m², In particular between about 3.0 and about 5.0 kg / m², And most preferably between about 4.0 and about 5.0 kg / m² In question.

According to the method according to the invention for the production of an acoustically effective mass-spring system, the liquid components for the at least one localized region and the liquid components for the adjoining regions, which have mutually different mixing ratios of the two components in the reaction mixture, Shape, into which the insulating layer and, if appropriate, the non-woven layer is inserted.

The mixing of the liquid components in the different mixing ratios can take place before injection, during injection or directly in the mold. It is only essential that polyol and isocyanate mix well before the reaction. The setting of the foam densities, ie in particular of low foam densities, in the case of polyurethane foams is possible on the one hand by the chosen composition, for example by the proportion of propellants, and on the other hand by the process control.

As the polyol or isocyanate, all compounds conventionally used in the production of a two-component polyurethane foam can be used.

For example, the isocyanate may be selected from the group consisting of 2,4-toluene diisocyanate, 2,6-toluene diisocyanate, 4,4'-methylene diisocyanate, hexamethylene diisocyanate, phenylene-1,4-diisocyanate, phenylene-1,3- Biphenyl-4,4'-isocyanate, naphthalene-1,5-diisocyanate, isophorone diisocyanate, hexane-1,6-diisocyanate, or mixtures thereof.

The polyol can be, for example, polyhydric polyols, diols (dialcohols) such as, for example, 1,4-butylene glycol, from the group consisting of polyalkylene glycol ethers, polyether polyols which can be prepared simply from dihydric and polyhydric alcohols and epoxides such as propylene oxide and / or ethylene oxide Alcohols such as, for example, glycerol, copolymers of diol and dicarboxylic acid, such as, for example, ethylene glycol and adipic acid, or mixtures thereof.

In the production of the polyurethane foam, for example, the above-mentioned customary auxiliaries can be added. The polyurethane foams can also be produced, for example, by means of reaction injection molding (RIM technique, reaction injection molding). However, it is also possible, of course, to use all further conventional processes which are suitable for the production of polyurethane foam.

EP-0 334 178 ( "Construction for sound insulation, process for its production and its use" (Ambivalentsystem, Stankiewicz GmbH) discloses foaming techniques in which, in the case of bulk spring systems, loosely structured materials, such as, for example, A foam, which is arranged below the weaker layer (acoustic mass). By foaming the foam in the loose structures, the density of the subsequent cellular foam is reduced in the sense of a reduction in the specific weight in the closed mold.

As stated above, in a preferred embodiment of the invention, lightweight polyurethane foams having a density (specific gravity) of between about 50 and about 70 kg / m³ Is used. Depending on the process control during the foaming of the polyurethane foams, dynamic elasticity moduli of <80,000 N / m² Can be achieved. However, dynamic elasticity moduli of <50,000 N / m are also advantageous².

With these low modulus of elasticity, low compressive hardnesses are also achieved which are clearly below 5,500 N / m² , But preferably below 3,000 N / m². The compressive hardnesses are determined in accordance with DIN EN ISO 3386 "Determination of compressive deformation properties".

The loss factor, measured according to DIN 53426 "Determination of the dynamic elastic modulus and the loss factor according to the vibrometer method", these values ​​being proportional to the values ​​from the bending vibration test according to DIN 53440 is no longer of decisive importance for the mass spring systems of the type according to the invention , Since in the present case an improved effect with regard to conventional foams in the frequency range above 300 Hz is achieved. However, the loss factor should be in the range of about 0.2 to 0.3 in order to avoid noticeable disadvantages in the low-frequency ignition frequency range, ie below 300 Hz.

According to a further preferred embodiment, the at least one locally limited region is geometrically limited by plastic or metal plates embedded in the mold, and / or several mixing heads are arranged and formed in each case for injection into the at least one localized region and into the adjoining regions in such a way that The mixing ratio of the two components in the reaction mixture can in each case be set differently.

With appropriate arrangement and control of the mixing heads in or on the mold, the at least one locally limited regions with increased resistance to traction as well as the adjoining regions with normal or low impact strength can be produced without further aids in the sound insulation part to be produced. For example, the area of ​​the respective regions in the sound-insulating part to be produced can be adjusted via the injection times or the times at which the reaction mixtures are fed with different mixing ratios from polyol to isocyanate to the mold.

In a preferred embodiment, areas of the plastic or metal, such as steel, for example, can be geometrically limited in the mold or the closed tool area. The liquid polyol and isocyanate components, together with the additives used, which have already been mentioned above, are introduced into the geometrically limited region and into the adjacent regions by means of a plurality of mixing heads.

By means of this measure, defined regions with higher resistance to impact are generated in the sound insulation part according to the invention compared to the adjoining regions. Since it is not necessary to use reaction mixtures with different components in order to produce polyurethane foams with higher or normal or low impact strength but merely have to change the mixing ratio between polyol and isocyanate in the reaction mixture, the process control and the mechanical effort are simple.

After removal of the sound insulation part, the regions of different strength or compressive hardness are visible because the platelets arranged in the tool leave perforations in the overall foam image.

Example formulation for the production of a polyurethane foam

Polyol component: (A component)

<ul><li>100 parts of trifunctional polyetherpolyol, MW 4800, OHZ 35, such as, for example, Desmophen® 3900 from Bayer</li><li>1 part of water</li><li>1.6 parts of tertiary amine 1, such as, for example, dimethyl ethanolamine (DMEA)</li><li>0.4 parts of tertiary amine 2, such as, for example, 1,4-diazabicyclo [2.2.2] octane</li></ul>

Isocyanate component (B component)

4.4 Methylenedi (phenyl isocyanate) (MDI, NCO 31), such as, for example, Desmodur 44V20, Bayer

100 A: B = 100: 13

Foaming is possible in a characteristic range of 50-120.

In general, the normally liquid raw materials are usually mixed at room temperature. Certain stoichiometric ratios are maintained. The above characteristic figure indicates the percentage ratio of the amount of isocyanate actually used to the stoichiometric, ie, calculated isocyanate amount.

For a characteristic number of 100, the amount of isocyanate used corresponds to the calculated amount. For a characteristic number of 110, the amount of isocyanate used is 10% higher than the calculated amount. With an index of 90, the amount of isocyanate used is 10% lower than the calculated amount.

In the following, the present invention will be explained in more detail with reference to the figures.

1 and 2 show the frequency-dependent course of the sound insulation of different mass-spring systems compared to the insulation of a steel sheet of 0.88 mm thickness (so-called body sheet metal); and

FIG. 3 shows the representation of a tool for producing an end wall insulation of a motor vehicle.

FIG. 1 shows the insulation courses for mass spring systems with polyurethane foam densities (new lightweight foam BarySorb 3192 / 1.VP19) of 50 and 60 kg / m³ In comparison to a conventional foam ( "adhesive foam") with a density of 100 kg / m³ shown. Both in the case of the mass spring systems with a foam density of 50 (dotted line) and 60 kg / m, respectively³ (Thin solid line) as well as in the comparative example (foam density 100 kg / m³) (Thick solid line), a foam layer with a thickness of 30 mm each having a heavy layer of 3.0 kg / m 2 was used as the acoustic spring³ Was covered. The foams have uniform tensile strengths or stiffnesses (compression hardening) over the entire test area. The curve, marked with the symbol "B", shows the course of a bodywork of 0.88 mm thickness.

In the high-frequency range above 300 Hz, a significantly better insulation behavior results for the lighter foams compared to conventional foam.

FIG. 2 shows a sound insulation part according to the invention with a partially increased resistance to traction (curve ▲), a sound insulation part without an increased resistance to running (curve O), an uninsulated body plate with a thickness of 0.88 mm (curve □) and the sound insulation part already known from FIG A foam density ( "adhesive foam") of 100 kg / m³ (Thick solid line). Both the sound-insulating part according to the invention with a partially increased resistance to traction (curve A) and the sound-insulating part without an increased resistance to running (curve O) both have a polyurethane foam layer with a thickness of 30 mm as an acoustic spring, and a heavy layer (Ss) of 4, 5 kg / m² on.

The systems have an even stiffness over the entire surface with normal or low impact strength. In the case of the sound-insulating part according to the invention, approximately 20% of the surface area (approximately 0.3 m × 0.3 m) is formed from a foam having a significantly higher compressive hardness, this surface also having a uniform stiffness.

The density of the polyurethane foam was 55 kg / m in the case of the sound insulation part with a constant compression strength (curve O)³ (Soft light foam VP 3119) and the mixing ratio in the reaction mixture of polyol to isocyanate is 100: 45 parts (ISO 3230).

In the embodiment according to the invention (curve ▲), the density of the polyurethane foam of the sound insulation part was also 55 kg / m³ And the mixing ratio in the reaction mixture of polyol to isocyanate is 100: 45 parts (soft light foam VP 3119 - ISO 3230) for the area with normal or low impact strength and 100: 62 parts (soft light foam VP 3119 - ISO 3230) for the range with (20% of the area).

The curve (curve □), which is marked with B, represents the course of the insulation of a car body with a thickness of 0.88 mm.

FIG. 2 shows that the sound insulation part according to the invention with partial resistance to impact has an insulating property which corresponds to that of a sound insulation part without an increased resistance to running. Furthermore, the sound insulation part according to the invention has a significantly improved insulation capacity compared to conventional sound insulation parts.

FIG. 3 shows the representation of a tool (1) for producing a lightweight sound insulation according to the invention with partial resistance to impact in the end wall area of ​​a personal motor vehicle. Two frames (3) are arranged in the tool (1) for the production of a locally limited area (2) with increased tensile strength. The frame (3), which is shown continuously for illustrative purposes, may consist of individual plates which delimit the non-rigid region (2) to be produced from the adjacent regions. In this region (2), polyol and isocyanate are injected in a different mixing ratio relative to the adjoining regions during the production of the end wall insulation. Thus, a sound insulation part, which is designed as an end wall insulation, is provided with a two-component polyurethane foam, in which regionally limited regions (2) have a greater compressive hardness, ie an increased resistance to walking, compared to the adjoining regions (5). Separate margins can be made at (4). In the exemplary embodiment, these areas (2) serve as a foot area in a passenger compartment lining.