U.S. patent number RE36,756 [Application Number 08/580,941] was granted by the patent office on 2000-06-27 for glass-mat-reinforced thermoplastic panels.
This patent grant is currently assigned to BASF Aktiengesellschaft. Invention is credited to Helmut Vogel, Ludwig Wahl.
United States Patent |
RE36,756 |
Wahl , et al. |
June 27, 2000 |
**Please see images for:
( Certificate of Correction ) ** |
Glass-mat-reinforced thermoplastic panels
Abstract
Semifinished material consisting of symmetrically-needled
glass-fiber mat impregnated with a thermoplastic polymer. The glass
mat can be made by, for instance, needling continuous filament web
from above and below at the same time with a double needling
machine.
Inventors: |
Wahl; Ludwig (Schifferstadt,
DE), Vogel; Helmut (Bramsche, DE) |
Assignee: |
BASF Aktiengesellschaft
(Ludwigshafen, DE)
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Family
ID: |
6342176 |
Appl.
No.: |
08/580,941 |
Filed: |
December 29, 1995 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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Reissue of: |
281853 |
Dec 9, 1988 |
04885205 |
Dec 5, 1989 |
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Foreign Application Priority Data
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Dec 9, 1989 [DE] |
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37 41 667 |
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Current U.S.
Class: |
442/180; 156/148;
28/107; 28/112; 428/902; 442/388; 442/391 |
Current CPC
Class: |
B29C
70/24 (20130101); B29C 70/543 (20130101); D04H
3/004 (20130101); D04H 3/105 (20130101); D04H
13/00 (20130101); D04H 18/02 (20130101); D04H
1/4218 (20130101); Y10T 442/67 (20150401); Y10T
442/687 (20150401); Y10T 442/2992 (20150401); Y10T
442/667 (20150401) |
Current International
Class: |
D04H
3/08 (20060101); D04H 3/10 (20060101); D04H
13/00 (20060101); B32B 015/00 (); B32B
027/00 () |
Field of
Search: |
;428/280,284,285,290,300,301,85,95,96 ;156/148 ;28/107,112
;442/180,388,391 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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0 319 832 B1 |
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Jun 1989 |
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EP |
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1570793 |
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Jun 1969 |
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FR |
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26 30 514 |
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Jan 1978 |
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DE |
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30 29 442 C2 |
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Feb 1981 |
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DE |
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203 577 |
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Oct 1983 |
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DE |
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Other References
Notice of Opposition for EP 319 832. .
Decision of European Patent Office and Final European Claims of EP
319 832..
|
Primary Examiner: Bell; James J.
Attorney, Agent or Firm: Oblon, Spivak, McClelland, Maier
& Neustadt, P.C.
Claims
We claim:
1. Fiber-reinforced thermoformable semifinished material consisting
of .Iadd.two layers of needled glass-fiber mats impregnated with
.Iaddend.a thermoplastic polymer .[.and at least one layer of
needled.]..Iadd., wherein the .Iaddend.glass-fiber .[.mat that
has.]. .Iadd.mats have .Iaddend.been symmetrically needled.
2. Fiber-reinforced semifinished material as claimed in claim 1
wherein .Iadd.at least one of .Iaddend.the glass-fiber .[.mat.].
.Iadd.mats .Iaddend.has been needled in such a way that the numbers
and lengths of the fiber ends protruding from both sides of the mat
are practically the same and the average length of the protruding
fiber ends is less than 2 mm.
3. Fiber-reinforced semifinished material as claimed in claim 1
wherein the glass-fiber .[.mat has.]. .Iadd.mats have .Iaddend.a
breaking strength of from 10N to 50N for a strip 100 mm wide.
4. Fiber-reinforced semifinished material as claimed in claim 1
wherein the glass-fiber .[.mat has.]. .Iadd.mats have .Iaddend.an
areal mass of from 200 g/m.sup.2 to 2500 g/m.sup.2.
5. A process for the manufacture of fiber-reinforced semifinished
material as claimed in claim 1 wherein .[.the.]. .Iadd.at least one
of the two .Iaddend.glass-fiber .[.mat is.]. .Iadd.mats are
.Iaddend.first needled from one side then turned and needled once
more from the other side and the .[.mat so needled is.]. .Iadd.mats
are .Iaddend.impregnated with a thermoplastic polymer.
6. A process for the manufacture of fiber-reinforced semifinished
material as claimed in claim 1 wherein .[.the.]. .Iadd.at least one
of the two .Iaddend.glass-fiber .[.mat.]. .Iadd.mats .Iaddend.is
needled by means of needles that have both downward-pointing barbs
and upward-pointing (reversed) barbs and that the .[.mat so needled
is.]. .Iadd.mats are .Iaddend.impregnated with a thermoplastic
polymer.
7. A process for the manufacture of fiber-reinforced semifinished
material as claimed in claim 1 wherein .[.the.]. .Iadd.at least one
of the two .Iaddend.glass-fiber .[.mat.]. .Iadd.mats .Iaddend.is
needled by means of a board carrying both needles with
downward-pointing barbs and needles with upward-pointing barbs and
the .[.mat so needled is.]. .Iadd.mats are .Iaddend.impregnated
with a thermoplastic polymer.
8. A process for the manufacture of fiber-reinforced semifinished
material as claimed in claim 1 wherein .[.the.]. .Iadd.at least one
of the two .Iaddend.glass-fiber .[.mat.]. .Iadd.mats .Iaddend.is
needled by means of two boards in succession, one carrying needles
with downward-pointing barbs and the other needles with
upward-pointing barbs, and the .[.mat so needled is.]. .Iadd.mats
are .Iaddend.impregnated with a thermoplastic polymer.
9. A process for the manufacture of fiber-reinforced semifinished
material as claimed in claim 1 wherein .[.the.]. .Iadd.at least one
of the two .Iaddend.glass fiber .[.mats.]. .Iadd.mats .Iaddend.is
needled from above and below simultaneously by means of a double
needling machine and the .[.mat so needled is.]. .Iadd.mats are
.Iaddend.impregnated with a thermoplastic polymer.
10. A process for the manufacture of semifinished material as
claimed in claim 5 or claim 9 wherein needling is carried out with
crown needles having three downward-pointing barbs on the
triangular shaft of the needle at the same distance above the
point.
Description
The present invention relates to fiber-reinforced thermoformable
semifinished material with improved flow when press molded
consisting of a thermoplastic polymer and at least one layer of
needled glass-fiber mat.
Glass-mat-reinforced thermoplastics (GMT) are being used
increasingly for the manufacture of moldings, particularly of
moldings used in automotive construction. The molding is carried
out in a press at a temperature above the softening temperature of
the thermoplastic. If the molding is at all complicated, for
instance, if it has ribs, deep indentations, or steep sides, the
material as a whole must be capable of flow, that is to say, the
glass-fiber mat must be extensible enough to ensure that the
features mentioned are reinforced by fibers.
GMT capable of flow is obtained if needled glass-fiber mat such as
that described in, for instance, DE-A-31 12 496 (U.S. Pat. No.
4,335,176) is used. Needling has two effects on the mat, which
generally consists of continuous or chopped-strand glass fibers
crossing at random. In the first place it fixes the mat, that is to
say it imparts cohesion and sufficient strength to allow handling
and processing. In the second place it makes the mat more open, and
it makes it extensible enough for molding by controlled rupture of
glass fibers.
The needling process causes individual fiber ends to be thrust down
at right angles to the plane of the mat by barbs on the needles.
Increasing the number of penetrations per unit area and the
coarseness of the barbs increases the number of fibers whose
orientation is changed and the number that are ruptured, and thus
affects the strength and extensibility of the mat. The use of
needles with barbs pointing upwards, that is to say, with reversed
barbs, as described in DE-A-30 29 442 (U.S. Pat. No. 4,277,531),
has similar effects, except that the fiber ends are drawn upwards
out of the mat.
Whichever way the barbs point, needled mat is formed with two
different surfaces, one comparatively smooth, the other having a
multitude of protruding fiber ends or spikes.
It is necessary that the needles should completely penetrate the
mat and protrude several millimeters on the other side (the
underside), especially when GMT is produced as described in DE-A-31
12 196, so that sufficient fibers are ruptured all through the mat.
The result is that the underside has many spikes and that these are
comparatively long (cf. the illustrations in DE-A-31 12 496). This
leads to problems when the thermoplastic panel is processed. When
the panel is manufactured, by pressing the mat with a plastic melt,
the thickness of the mat is reduced, and it is fixed by the plastic
when this has hardened by cooling; when the panel is reheated, to
soften it before it is molded, the mat tends to recover its
original thickness. This unwanted expansion, which is troublesome,
increases as the number and length of the spikes increase.
The aim of the present invention was therefore to avoid these
problems and to provide panels that can be easily processed, giving
moldings of uniform structure with good mechanical properties and
smooth surfaces.
We achieved this aim by the use of symmetrically needled
glass-fiber mat. The mat is needled in such a way that at each face
of the mat the numbers and lengths of the spikes are practically
the same and the average length is preferably less than 4 mm, in
particular less than 2 mm.
The needled mat is preferably made from the usual continuous
filament or chopped strand, but staple fiber can also be employed.
The glass fibers are coated with the usual sizes, which should be
suited to the polymers with which the mat is to be impregnated. The
fibers are formed into a web, which is then needled in one of
several different ways.
In one process the glass mat is first needled from one side, then
turned and needled once more from the other side. The second time
it can be passed through the same needling machine or go to another
machine in series with the first.
In another process needles having both downward-pointing barbs and
upward-pointing barbs (reversed barbs) are used.
It is also possible to work with a needle board provided with both
needles with downward-pointing barbs and needles with reversed
barbs, or with two needle boards, one behind the other, one having
the one kind of barbed needles, one the other kind. The fiber ends
drawn out of the glass mat by needles with reversed barbs are
generally somewhat longer than those thrust out of the glass mat by
needles with downward-pointing barbs.
In a preferred embodiment of the invention the glass mat is needled
from above and below at the same time by means of a double needling
machine. It
is then especially advantageous to employ crown needles, which have
three downward-pointing barbs on the triangular shaft of the needle
at the same distance (3 mm, for instance) above the point.
A common feature of each of the needling methods mentioned is the
fact that it is sufficient if the needles penetrate through the mat
comparatively slightly. If the needling were from one side only
this would not give adequate rupture of the fibers, except on that
side; this would lead to uneven strength, and impregnation on the
side where the needles emerge would be not so easy as on the side
where they go in. These disadvantages do not arise with symmetrical
needling: with less intensive and shallower needling it is possible
to obtain thin mat of adequate strength that is easy to impregnate
and flows out well during molding. Both sides of the mat are
uniform and have few, comparatively short spikes that do not
interfere with molding.
A criterion for the quality of the needled mat is its breaking
strength. The test is carried out with a specimen consisting of a
strip about 100 mm wide and about 200 mm long held by grips 100 mm
apart whose jaws are about 100 mm wide. The grips are drawn apart
and the force at which the strip ruptures is measured. This force
should be between 10N/(100 mm) and 50N/(100 mm), preferably between
15N/(100 mm) and 30N/(100 mm).
If the breaking strength is too low there is a danger that the mat
will be pulled apart during processing, for example, when it is
taken off the roll, and when the mat is impregnated in the
double-band press it loses its structure and disintegrates. If the
breaking strength is too high the extensibility of the mat may
become inadequate when the GMT is molded.
The breaking strength of the mat can be influenced by various
factors, such as the number of penetrations per unit area and the
depth of penetration; the number and coarseness of the barbs also
affect it. The kind of size on the glass also has an effect; if it
is brittle more fibers rapture, which reduces the breaking
strength.
The novel semifinished material can be manufactured by means of
usual impregnation processes. The method of choice is to sandwich
two lengths of needled mat between three layers of the hot
thermoplastic emerging from slotted extruder dies and to impregnate
them by, for instance, lamination in a double-band press as
described in DE-A-29 48 235. All the common thermoplastic polymers
are suitable, but those preferred are polypropylene, polyamides,
thermoplastic polyesters such as poly(ethylene terephthalate),
polysulfones, polyether ketones, and mixture of these. The polymers
can contain the usual additives. The mass fraction of glass fibers
in the semifinished material should preferably be between 25% and
50%. In general the material is from 2 mm to 5 mm thick.
The novel semifinished material can be press molded by usual
methods at temperatures above the softening point of the polymer,
yielding moldings for automotive construction, machines, and
household goods.
EXAMPLE
A web was formed from glass rovings coated with a size suitable for
polypropylene and fed through a needling machine. The width of the
web was 1200 mm. The needle board carried 2 rows of close-barb
felting needles on the feed side, followed by 14 rows of crown
needles and 14 rows of reversed-barb needles. Needling was carried
out with 49 penetrations per square centimeter, the needles
descending 11 mm. The areal mass of the mat produced was 700 g/m2
and the breaking strength was about 30N/(100 mm). Two lengths of
such mat were impregnated by lamination to three lengths of
polypropylene at elevated temperature and pressure. The GMT panels
obtained were 3.8 mm thick and the mass fraction of glass was
32%.
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