CA2104856C

CA2104856C - Heat stable part for vehicle interiors

Info

Publication number: CA2104856C
Application number: CA002104856A
Authority: CA
Inventors: Walter Fottinger; Hansjorg Grimm; Gerhard Schaut
Original assignee: Carl Freudenberg KG
Current assignee: Carl Freudenberg KG
Priority date: 1992-08-26
Filing date: 1993-08-25
Publication date: 1997-02-18
Anticipated expiration: 2013-08-25
Also published as: CA2104856A1; BR9302844A; ES2078767T3; EP0584445A1; EP0584445B1; ATE127745T1; DE59300587D1; US5501898A

Abstract

A heat stable part for vehicle interiors, in particular a car canopy carrier, has one or three layers, whereby the layers exposed to heat are made of 25 to 100 wt.% of polybutylene terephthalate fibers and at most 75 wt.% of polyester fibers having a higher melting point. The part has a higher residual bending strength at 90°C than conventional vehicle interior parts which substantially prevents sagging of the part when installed in a vehicle.

Description

21~8S 6 HEAT STABLE PART ~OR VEHICLE INTERIORS

The invention relates to parts for vehicle interiors and in particular to car canopy carriers. Car canopy carriers are the supporting, non-visible portions of car canopies.
There are two basic requirements for parts of vehicle interiors and especially suspended car canopies, namely that they are humidity resistant and able to withstand high temperatures without s~gg~ng. When the vehicle is sub~ected to solar irradiation or during the painting of the vehicle in the manufacturing plant the surfaces of such parta may be sub~ected to temperatures of up to 110C. This applies to both single and 3-layer variants. In the latter, only the two outer layers need be designed to withstand such temperatures.
Conventional parts for vehicle interiors made of fiber fleece which fulfill the above noted requirements include at least 50 wt.X of or are completely made of polyester fibers and derive their heat resistance from an impregnation of the fleece with a thermosetting resin binder. Both 1-and 3-layer variants are compressed into the desired shape under pressure and heat and solidified (possibly together). A product of this type is disclosed in German Patent DE 29 37 399, wherein the resin binder is preferably present in an amount of 400g per square meter area and mm thickness of the finished product. It is thereby assumed that the thickness of the finished product is between 1 and 2.5 mm. The German patent also describes the admixture of glass fibers in an amount of up to 100% by weight in order to further increase the heat stability of the product.
It is a disadvantage of conventional parts for vehicle interiors of the type described that they are not recyclable because of their resin and/or glass fiber content. Especially, it is not possible to melt and regranulate the base material, polyester fibers, into recyclable low grade polyester material. It is also not possible to regenerate polyester of the same quality through alcoholysis, since the a~ d materials which increase the heat stability cannot be sufficiently separated from the polyester material prior to the regenerating process.
However, flat stock of the traditionally used polyethylene terephthalate polyester fiber base material free of any reinforcing binder resin or *

210~856 glass fibers has a bending strength which at realistically high temperatures of about 90 is already 90% lower than at room temperature, which would not be sufficient to prevent sagging.
It is now an ob~ect of the present invention to provide a further developed part for vehicle interiors and particularly a car canopy carrier of the general type described in German Patent 29 37 399, which is easily manufactured by conventional processes and wherein at least those fibrous layers which are sub~ected to heat contain only polyester fibers and are neither impregnated with a binder nor contain binder fibers or glass fibers. It is another object to provide a part ~or vehicle interiors which has a heat stability as required by the car manufacturers which means an elasticity module of more than 30 N/mm2 during bending according to test standard EN 63, at a temperature of 90C, a material thickness of 3 mm and an average weight of 1,000 g/m2, and wherein the drastic loss in bending strength at high temperatures which occurs when polyethylene terephthalate fibers are used is substantially reduced.
These ob~ects are achieved with a part for car interiors, preferably a car canopy carrier~ which is made of polyester fibers, and has one or three layers. All layers are pressed into the intended shape and solidified under pressure and heat. At least those layers of the part which are subjected to heat during the intended use are made of polyester fibers.
Accordingly, the invention provides a heat stable part for vehicle interiors of one or 3 layers of polyester fibers, which layers are pressed into a desired shape, internally solidified and interconnected under pressure and heat. All layers are exclusively made of polyester fibers having a titer of 1.5 to 30 dtex. At least the layers(s) sub~ected to heat during the intended use include polybutylene terephthalate fibers. It is important that all layers are made of polyester fibers having a titer of 1.5 to 30 dtex in order to achieve interconnection of the fibers during the manufacturing process without additional binders and to provide the desired strength. The preferred thickness of a part in accordance with the invention is 1-60 mm.
In accordance with the invention, those fibrous layers which are critical with respect to the influence of heat, i.e. the one layer in a 210~5~

single layer embodiment and the outer layers in 3-layer versions include polybutylene terephthalate fibers. Relative to the total weight, the single layer version includes 8 to 100 wt.% of polybutylene terephthalate fibers and a maximum of 20 wt.% of homogeneously distributed polyester fibers having a melting point above 228C. In the 3-layer version, both outer layers which are sub~ected to heat are made of 25 to 100 wt.% of polybutylene terephthalate fibers and a maximum of 75 wt.X of homogeneously distributed continuous polyester fibers having a melting point above 228C. The sum of the relative weights of the respective fiber portions is always 100% which means that there are no bind~rs or solidifiers added. Thus, parts for vehicle interiors in accordance with the invention are made exclusively of polyester.
In a preferred embodiment of the 3-layer version, the inner layer which is the least subjected to heat can be made of a mixture of about equal parts of polyethylene terephthalate and bi-component fibers (polyethylene terephthalate and a lower melting copolyester). However, the fiber titer and the staple length are the same for those and the fibers in the other layers. The inner layer preferably has a density which is 8 to 40% of the one of the outer layers. This increases the bending strength of the laminate. Smaller densities prevent the transfer of deformation forces from one outer layer to the other and higher density values increase the total weight of the part without increasing the bending strength. Since this middle layer is supported by both outer fiber layers, its heat stability has very little influence on the quality of the part, which is almost exclusively determined by the properties of the polybutylene terephthalate fibers including layer.
It is surprising that a construction in accordance with the invention does not require the use of additional binding components for the achievement of a fiber structure which can be shaped and formed under pressure and heat. Furthermore, the heat stable part in accordance with the invention can be manufactured at a lower weight than if substantial amounts of additional binders, binder fibers and/or heat resistant resins or fibers would have to be admixed. It is also surprising that a heat stable part in accordance with the invention has a higher heat resistance than a part made exclusively of polyethylene terephthalate fibers. This could not have been predicted in view of the glass transition 210~856 temperatures of the respectively used materials, the temperature at which the material starts to soften, which are about 39C for polybutylene terephthalate and 69C for polyethylene terephthalate. If anything, these glass transition temperatures would suggest that a fibrous material made of polybutylene terephthalate would have a lower heat stability than one made of polyethylene terephthalate. Thus, a prediction of the surprising strength of a heat stable part in accordance with the invention was not possible on the basis of known glass transition temperature data.
In accordance with the present invention, the term "polybutylene terephthalate fibers" also includes core/mantle fibers having a core of a polyester material which only has to fulfill the single requirement that its melting range lie above the one of the polybutylene terephthalate material of the fiber mantle. The use of such multi-component fibers for the manufacture of parts in accordance with the invention still provides a residual bending strength at 90C of 35 to 40X. This, in most cases, is sufficient to prevent unwanted sagging under the influence of heat.
Parts including bi-component fibers can be made very light and the use of such fibers is economical.
A heat stable part in accordance with the invention is essentially manufactured using only known process steps and procedures. An additional treatment in a preheating furnace is carried out where polytetrafluoroethylene coated heated metal plates act on the binding fibers. The temperature of the plates is preferably 1 to 15 higher than the melting point of the polybutylene terephthalate (228C). Residence times of l to 5 minutes are thereby appropriate. In a further step, the fleece material is transferred into a mold which has the shape of the finished heat stable part and subjected to a forming pressure of 105 to 2 X 106 Pa. The temperature of the mold is preferably at least 10C below the melting temperature of the polybutylene terephthalate fibers. The residence time is 0.2 to 2 minutes whereafter the finished heat stable part for vehicle interiors is removed from the mold.
It was unexpected that stiff but elastic, shaped heat stable parts which at 90C have a residual bending strength of up to 33% of the initial value at room temperature could be prepared by using polybutylene terephthalate fibers without added lower melting binder fibers, other ~lD48~6 binders, resins or glass fibers. The polybutylene terephthalate fibers alone provides for solidification of all the fibers throughout the respective layer when fibers of the disclosed titer and staple length are used.
The invention will now be further explained in the following by way of example only.

ExamPle A single layer fleece of lOOX commercially available polybu~ylene terephthalate fibers having a titer of 1.7 dtex and 38 mm length was manufactured by carding and conventional needling. The weight/area of the resulting needle fleece was 800 g/m2, the thickness 22 mm and the number of needle holes was 18/cm2. The material was subsequently preheated and pre-compressed between a pair of heated polytetrafluoroethylene coated plates. The upper plate had a temperature of 235C and the lower plate 230C and the distance between the plates was 7 mm. The material was sub~ected to those conditions for 2.2 minutes and immediately after compressed within one minute to a thickness of 3 mm between a pair of plates at ambient temperature. The finished compressed material was sub~ected to a bending strength test according to EN 63 at 23C and 90C. The residual bending strength at 90C was still 33X.
This is sufficient to essentially prevent sagging at corresponding temperatures of a car canopy carrier made in accordanct with the invention. The small weight of the material also reduces the tendency to sag.

Example 2 A 3-layer fleece laminate was manufactured from spun fleece materials. The outer layers were respectively made of 70 wt.%
polyethylene terephthalate fibers and 30 wt.% polybutylene terephthalate fibers respectively having a titer of 7 dtex. The thickness of the outer layers was 0.7 mm respectively and their weight per area was 250 g/m2.
The middle layer was made of a spun fleece needled on both sides which had a weight per area of 500 g/m2 and a thickness of 3 mm. The middle 21û~8~6 layer was made of the same fibers in the same proportions as the outer layers. The fiber titer was 5.6 dtex. The laminate was pre-compressed to 4 mm thickness between a pair of heated polytetrafluoroethylene coated plates which both had a temperature of 250C. The material was sub~ected to these conditions for 2.5 minutes and immediately after compressed within one minute to a thickness of 3 mm between a pair of plates at room temperature.
The f~ni~he~ material was sub~ected to a bending strength test according to standard EN-63 at 23 and 90C. The test results are listed below in Table 1.

ExamPle 3 In another 3-layer variant, outer layers as described in Example 2 were used while a thermally pre-solidified needled fleece made of polyethylene terephthalate fibers was used for the middle layer. This needled fleece which had a thickness of 18 mm and a weight of 500 g/m2 was made of 100 wt.Z of bi-component fibers of a titer of 6 dtex and a staple length of 60 mm. The core of the bi-component fibers was made of stretched polyethylene terephthalate having a melting temperature of 260C and the mantle was made of a co-polyester having a melting temperature of 200C. The 3-layer variant was pre-compressed for 0.5 minutes between a pair of polytetrafluoroethylene coated plates heated to 255C. The resulting material was subsequently compressed between a pair of plates for one minute at room temperature to a thickness of 3 mm and at a pressure of 500 kPa. The bending strength at 23C and 90C is listed in Table 1.

ExamPle 4 A single layer fleece of 100% core/metal fibers was made, whereby the core was made of a polyester which has a higher melting temperature than the polybutylene terephthalate of the mantle. Such fibers are commercially available. The particular fibers used in this example had a titer of 5.5 dtex and a staple length of 55 mm. The manufacture of the single layer fleece included carding and conventional needling. The 21~856 weight per area of the needled fleece obtained was 800 g/m2~ its thickness was 22 mm and the number of needle holes was 18/cm2. This fleece was preheated for six minutes in a continuous dryer at 235C. The materlal was subsequently preheated and pre-compressed between a pair of polytetrafluoroethylene coated plates. The temperature of the plates was 255C and the distance therebetween was adjusted to 8 mm. The material was sub~ected to these conditions for 2.4 minutes and immediately after compressed for one minute between a pair of plates at room temperature to a thickness of 4 mm. The finished, compressed material was sub~ected to a bending strength test according to EN 63 at 23C and 90C. The residual bending strength at 90C was 38.8X. This is sufficient to essentially prevent sagging at corresponding temperatures of a car canopy carrier made in accordance with the invention. The small weight of the material also reduces the tendency to sag.

ComParative ExamPle For comparison, a needled fleece was made of conventional polyethylene terephthalate fibers as follows:
A 3-layer fleece laminate without added binder and resin was made as described in Example 2 by carding, needling and thermal pre-solidification, treated in a preheat furnace for 3 minutes at a circulating air temperature of 170C, and subsequently shaped in the mold at 5 X 105 Pa within 1.5 minutes. The temperature was thereby maintained at 120C. The outer layers were respectively made of 100% of 6 dtex bi-component fibers of a staple length of 60 mm and a core of stretched polyethylene terephthalate fibers having a melting temperature of 260C, and a mantle of copolyester, having a melting point of 200C, which fibers were purchased. The middle layer was made to 80 wt.% of the above described core/mantle fibers, to 10 wt.% of single, stretched polyethylene terephthalate fibers having a titer of 17 dtex and to 10 wt.X of stretched polyethylene terephthalate fibers having a titer of 6 dtex. Subsequently, the bending strength of the material was determined according to EN 63 at 23C and 90C.
The comparison showed that the bending strength of the material made of polyethylene terephthalate fibers at 90C decreases to 10% of the starting value at room temperature. Such a value is not acceptable, since a car canopy of this material would sag at those temperatures in the vehicle and would be qualitatively useless.
The results of the experiments described above are summarized in Table 1.

Table 1 Elasticity module during bending (N/mm2) according to EN 63 weight per area 1000 g/m2, thickness 3mm Example 23C 90C Residual value-X

Comparison 136 14 10

Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE PROPERTY
OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A heat stable part for vehicle interiors of a thickness of 1 to 6 mm, comprising first and second outer layers and an inner layer of polyester fibers sandwiched therebetween, the layers being made of polyester fibers having a titer of 1.5 to 30 dtex, whereby the layers are compressed into a desired shape, consolidated and interconnected under pressure and heat, at least the outer layers which are subjected to the influence of heat during the intended use each including 25 to 100 wt.% of polybutylene terephthalate fibers and a maximum of 75 wt.% of homogeneously distributed continuous polyester fibers having a melting point above 228°C, and the inner layer which is the least subjected to the influence of heat during use having a density of 8 to 40% of the density of the outer layers.

2. A heat stable part for vehicle interiors according to claim 1, wherein the polybutylene terephthalate fibers are core/sheath fibers, the core being a polyester which has a higher melting point than the polybutylene terephthalate sheath portion.

3. A heat stable part for vehicle interiors as defined in claim 1 or 2, which is a car canopy carrier.