SOUND ABSORBING MATERIAL

MATERIAU D'ISOLATION PHONIQUE

English Abstract

The invention relates to a sound absorbing material, made from a microfilament
non-woven
fabric with a mass per unit surface area of 40 to 300 g/m2, whereby a non-
woven fabric made from
a melt-spun and drawn multi-component endless filament with a titre of 1.5 to
5 dtex is directly
bonded to form a web and the multi-component endless filaments are optionally
spread with and
fixed to micro-endless filaments with a titre of 0.1 - 1.2 dtex, up to a
degree of 80 % by means of a
prefixing process.

French Abstract

L'invention concerne un matériau d'isolation phonique composé d'un non-tissé à microfilaments ayant un grammage de 40 à 300 g/m<2>. Ledit non-tissé est composé de filaments sans fin à plusieurs constituants, filés à chaud, étirés et directement disposés sous forme de non-tissé, lesdits filaments sans fin ayant un titre de 1,5 à 5 dtex. Après un pré-durcissement, ces filaments sans fin à plusieurs constituants sont éventuellement divisés et durcis à au moins 80 % pour former des microfilaments sans fin ayant un titre de 0,1 à 1,2.

Claims

CLAIMS:
1. Use of a microfilament nonwoven fabric having a basis weight in the range
from
40 to 300 g/m2 and consisting of continuous multicomponent filaments having a
linear density in
the range from 1.5 to 5 dtex which are spun on the melt, stretched and
directly laid down to form a
web and optionally subjected to a preconsolidating operation before being at
least 80% split into
continuous microfilaments having a linear density in the range from 0.1 to 1.2
dtex and
consolidated, as a sound absorption layer in the construction of roof liners,
in the construction of
column, door and boot linings, in the construction of dashboards, in the
region of an engine
compartment or floor lining.
2. Use of a microfilament nonwoven fabric having a basis weight in the range
from
40 to 300 g/m2 and consisting of continuous multicomponent filaments having a
linear density in
the range from 1.5 to 5 dtex which are spun on the melt, stretched and
directly laid down to form a
web and optionally subjected to a preconsolidating operation before being at
least 80% split into
continuous microfilaments having a linear density in the range from 0.1 to 1.2
dtex and
consolidated, as a tufting base for an automotive carpet.
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Description

SOUND ABSORBING MATERIAL
Description
The invention relates to a sound absorbing material, consisting of a
microfilament
nonwoven with surface weights of 40-300g/m2.
Interior finish parts for automotive vehicles such as vehicle roofs are known
from
documents EP 0 909 680 and US 4,851,283, which have sound absorbing
properties. They consist of
a staple fibre nonwoven layer in which preferably polyester fibres are
consolidated with the help of
binder fibres and are coated with at least one foam layer.
Damping and sound protecting materials are also known from documents DE 197 26
965
and DE 197 08 188, which consist of staple fibre nonwovens, especially of
polyester fibres and are
consolidated by mechanical as well a thermal processes.
In the course of the increasing demands of the automotive industry, new
requirements are
imposed on the supplier. Thus, the lining parts used in the interior of a
motor vehicle should have a
decor with attractive optic and haptic. The parts should be recyclable, should
have a very high color
consistency and light resistance, especially hot light resistance, a low
tendency to soiling, a high
abrasion resistance, humidity resistance, flame resistance, cleanability and
very good deep drawing
ability, and furthermore accommodate the growing requirements for sound
protection with the goal
of increased comfort for the motor vehicle passengers.
It is an object of the invention to provide a sound absorbing material which
accommodates
the mentioned requirements and a process for its manufacture.
This object is achieved in accordance with the invention with a sound
absorbing material,
which consists of a microfilament nonwoven with surface weights of 40-300
g/m2, whereby the
nonwoven is made of meltspun, drawn multicomponent endless filaments with a
titre of 0.15-5dtex
which are immediately laid into a nonwoven web, is split, preferably after a
preconsolidation, at
least to 80% into micro endless filaments with a titre of 0.1-1.2dtex, and is
consolidated. The sound
absorbing material has a high specific fibre surface at a comparatively low
surface weight and a high
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opacity. The fineness of the filaments allows a good printability and
embossability and therefore a
good decoration of the material.
The sound absorbing material is preferably one wherein the nonwoven is made of
meltspun,
aerodynamically drawn multicomponent endless filaments with a titre of 1.5-
3dtex, which
multicomponent endless filaments are immediately laid into a nonwoven web and
split to at least
80% into micro endless filaments with a titre of 0.1-0.3dtex, and
consolidated. The sound absorbing
material has an isotropic filament distribution in the nonwoven web, whereby
the further processing
is rendered relatively independent from the machine direction and is thereby
very advantageous for
the utilization of the material.
Preferably, the sound absorbing material is one wherein the multicomponent
endless
filament is a bicomponent endless filament of two incompatible polymers,
especially a polyester and
a polyamide. Such a bicomponent endless filament has a good splittability into
micro endless
filaments and results in an advantageous ratio of strength to surface weight.
At the same time, the
sound absorbing material in accordance with the invention can be easily
cleaned and wiped off and
has a high abrasion resistance because of the polymers used and their filament
structure, which
means it is easy-care.
Preferably, the sound absorbing material is one wherein the multicomponent
endless
filaments have a cross-section with a multi-segment structure called orange
type or also "pie",
whereby the segments altematingly include respectively one of the two
incompatible polymers.
Besides this orange-type multi-segment structure of the multicomponent endless
filaments, a "side-
by-side" (s/s) segment positioning of the incompatible polymers in the
multicomponent endless
filament is also possible, which is preferably used for the generation of
curled filaments. Such
segment arrangements of the incompatible polymers in the multicomponent
endless filament have
shown to be very well splittable. The sound absorbing material has a good deep
drawing ability or
deformability, which is manifested in the mid-range strength values at a high
stretchability and
comparatively low module values.
Preferably, the sound absorbing material is one in which at least one of the
incompatible
polymers forming the multicomponent endless filament includes an additive in
an amount up to 10%
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per weight, such as color pigments, permanently active anti-statics, flame
protection agents and/or
additives which influence the hydrophobic properties. Static charges can be
prevented or reduced
with these additives and the hot light resistance improved. Hot light
consistencies of >6, determined
according to DIN EN 20105-A02 were achieved with subsequently colored
products.
The process in accordance with the invention for the manufacture of a sound
absorbing
material consists in that multicomponent endless filaments are spun from the
melt, drawn and
immediately layed into a nonwoven web, a preconsolidation is carried out, and
the nonwoven is
consolidated by high pressure fluid jets with the simultaneous splitting into
micro endless filaments
with a titre of 0.1-1.2dtex. The sound absorbing material obtained has a very
even thickness, an
isotropic tread distribution and low tendency to delamination.
Preferably, the process for the manufacture of the sound absorbing material is
carried out in
such a way that the consolidation and splitting of the multicomponent endless
filaments is achieved
in that the possibly preconsolidated nonwoven is impacted at least once on
each side with high
pressure water jets. The sound absorbing material thereby has a good surface
and a degree of
splitting of the multicomponent endless filaments >80%.
Preferably, the sound absorbing material in accordance with the invention is
also subjected
to a point calendaring, to increase the abrasion resistance. The split and
consolidated nonwoven is
therefore fed through heated rollers of which at least one roller has
protrusions which lead to a point
form melting together of the filaments.
The sound absorbing material in accordance with the invention is suitable for
the
manufacture of motor vehicle roof linings, door linings, column linings, hat
rests andlor trunk
linings as well as wheel well linings, because of its properties such as good
printability, high
abrasion resistance and a good hot light resistance, thermal formability in
deep drawn processes and
the haptic shape. When a very high weight savings is to be achieved, one can
also omit an additional
foam covering, without suffering large losses in sound absorption properties.
The sound absorbing material is suitable as sound absorption layer in the
construction of
roof linings, in the construction of column, door and trunk linings, in the
construction of dashboards,
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in the region of the engine compartment and/or the floor lining, whereby it
has good sound
absorption values at lower surface weights compared to known materials.
The sound absorbing material is especially suited as tuft can-ier for motor
vehicle carpets
which at a significantly lower material use has at least the same sound
absorption properties as
conventional motor vehicle carpets, since one can do away with heavy carpet
backing layers.
Example 1
A filament web with a surface weight of 138 g/m2 is produced from a side by
side (s/s)
polyester-polyamide 6.6 (PES-PA 6.6) bicomponent endless filament with a titre
of 2.3 dtex and a
weight ratio of PES/PA 6.6 of 60/40, and subjected to a waterjet needling on
both sides and at
pressures of 230 bar. The bicomponent endless filaments after the waterjet
needling, which leads to
a simultaneous splitting of the starting filaments, had a titre of <1.2dtex
and a thickness of 0.73mm.
A tear resistance in machine direction of 391N and in transverse direction of
372N was determined.
Example 2
A filament web with a surface weight of 115g/m2 was produced from a 16 segment
(pie)
polyester-polyamide 6.6 (PES-PA 6.6) bicomponent endless filament with a titre
of 2.4dtex and a
weight ratio of PES/PA 6.6 of 55/45, and subjected on both sides to a waterjet
needling at pressures
of 230 bar. The bicomponent endless filaments after the waterjet needling,
which leads to
simultaneous splitting of the starting filaments, had a titre of <0.15dtex and
after a final smoothing a
thickness of 0.48mm. A tear resistance in machine direction of 302N and in
transverse direction of
303N was determined.
Comparative Example I
A commercially available single-layer needled nonwoven of polyester (motor
vehicle
sealing material) and about 1.1mm thick was used.
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Comparative Example 2
A laminate made of a knitted fabric (about 0.6mm thick) and a foam base (about
1.6mm
thick), which is typically used as motor vehicle sealing material, was tested.
Comparative Example 3
A laminate consisting of a knitted fabric (about 0.6mm thick) and a polyester
needle
nonwoven (about 1.9mm thick), which is typically used as motor vehicle sealing
material, was
tested.
Comparative Example 4
A laminate consisting of a knitted fabric (about 0.6mm thick), a foam
intermediate layer
(about 4.4mm thick) and a nonwoven base (about 0.3mm thick), which is
typically used as motor
vehicle roof lining material, was tested.
The results of the sound absorption properties (measured in a tube according
to DIN 52215)
at different frequencies are summarized in Table 1.
Ex. 500 625 800 900 1000 1120 1250 1400 1600
No. HZ HZ HZ HZ HZ HZ HZ HZ HZ
1 6% 12% 28% 33% 39% 46% 51% 70%
2 1% 8% 24% 34% 50% 74% 91% 95% 95%
CE1 1% 5% 10% 12% 14% 16% 21% 29%
CE2 2% 6% 11% 12% 14% 16% 10% 27%
CE3 5% 11% 20% 24% 28% 35% 38% 54%
CE4 5% 10% 20% 25% 30% 33% 34% 71% 76%
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