U.S. patent application number 10/558153 was filed with the patent office on 2007-08-02 for method for producing compressed, plastic-coated rovings.
This patent application is currently assigned to SIA ABRASIVES INDUSTRIES AG. Invention is credited to Donat Frei, Christian Jentgens, Kurt Lehmann, Theo Staheli.
Application Number | 20070175570 10/558153 |
Document ID | / |
Family ID | 33459812 |
Filed Date | 2007-08-02 |
United States Patent
Application |
20070175570 |
Kind Code |
A1 |
Jentgens; Christian ; et
al. |
August 2, 2007 |
Method for producing compressed, plastic-coated rovings
Abstract
The invention relates to a method for producing compressed
plastic-coated fibres or fibre strands, consisting of essentially
parallel filaments, from fibre strands consisting of filaments
coated with plastic. The invention is characterised in that fibre
strands or a composite of a plurality of such fibre strands
consisting of essentially parallel filaments to which the plastic
is applied in a melted or liquid state, optionally as powder, are
guided, following the coating, by means of a rotating device (6)
which is used to carry out a local rotation of the fibres. The
invention also relates to the use of the inventive individual
filaments for producing saw threads, tapes and prepegs,
fibre-reinforced plastic granulated material and fibre-reinforced
preforms, or fibre-reinforced pultruded or extruded profiled
elements. The invention further relates to a device for carrying
out the inventive method.
Inventors: |
Jentgens; Christian;
(Wallenwil, CH) ; Lehmann; Kurt; (Frauenfeld,
CH) ; Frei; Donat; (Frauenfeld, CH) ; Staheli;
Theo; (Reinach, CH) |
Correspondence
Address: |
SHOEMAKER AND MATTARE, LTD
10 POST OFFICE ROAD - SUITE 110
SILVER SPRING
MD
20910
US
|
Assignee: |
SIA ABRASIVES INDUSTRIES AG
FRAUENFELD
CH
|
Family ID: |
33459812 |
Appl. No.: |
10/558153 |
Filed: |
May 21, 2004 |
PCT Filed: |
May 21, 2004 |
PCT NO: |
PCT/CH04/00311 |
371 Date: |
September 12, 2006 |
Current U.S.
Class: |
156/181 ;
156/441 |
Current CPC
Class: |
B29C 70/50 20130101;
B29B 15/122 20130101; B23D 61/185 20130101 |
Class at
Publication: |
156/181 ;
156/441 |
International
Class: |
D04H 3/08 20060101
D04H003/08 |
Foreign Application Data
Date |
Code |
Application Number |
May 23, 2003 |
CH |
0931/03 |
Claims
1. A method for producing compressed, plastic-coated fibers or
rovings, consisting of substantially parallel filaments, starting
from rovings consisting of plastic-coated filaments, characterized
in that rovings, or a plurality of such rovings as a composite,
consisting of substantially parallel filaments on which the plastic
applied, optionally as a powder, is present in the molten or liquid
state, are passed, after the coating, through a rotating device by
means of which local rotation of the fibers is executed so that the
individual threads in the method are twisted with one another in
the form of rotations, starting from the rotating device, backward
along the threads in the direction of the coating device, it being
the case, however, that after passing through the rotating device
there are no longer any rotations or there are rotations only to a
small extent, so that, after passing through the rotating device,
the filaments have no spiral revolutions per meter or only a small
number thereof and are arranged substantially parallel and linear
or straight.
2. The method as claimed in claim 1, characterized in that the
rotating device consists of a rotating sizing die.
3. The method as claimed in claim 1 or 2, characterized in that
thin threads are produced.
4. The method as claimed in any of claims 1-3, characterized in
that the rovings obtained are subsequently coated in a subsequent
coating procedure additionally with mineral powders or metal
powders at temperatures above the melting point of the coating
polymer, or with plastic, optionally as a mixture with mineral
powders, and then hardened or allowed to solidify.
5. The method as claimed in any of claims 2-4, characterized in
that the sizing die is rotated at such a high speed that all excess
coating material is spun off at the die edge.
6. The method as claimed in claim 5, characterized in that the
rotating sizing die is fixed in a hollow shaft and rotated together
with this solid shaft, preferably at a speed of at least 500
revolutions per minute (rpm), preferably at least 2000 rpm,
preferably at least 7000 rpm, and preferably at about 10 000
rpm.
7. The method as claimed in any of claims 2-6, characterized in
that the sizing die is heated to at least the melting point of the
fiber coating, and the polymer coating of the fiber is in the
heated liquid state.
8. The method as claimed in any of claims 2-7, characterized in
that a plurality of rotating sizing dies are connected in series
and the fibers are passed through these devices and thus sized and
compressed.
9. The method as claimed in any of claims 2-7, characterized in
that the sizing die has an internal diameter in the range of
100-2000 .mu.m, preferably in the range of 150-600 .mu.m and in
particular in the range of 200-350 .mu.m, preferably 200-240
.mu.m.
10. The method as claimed in any of claims 1-8, characterized in
that the roving has about 5 to 50 spiral revolutions per meter,
preferably about 10 to 30 spiral revolutions per meter, preferably
about 10 to 20 revolutions per meter, before the first rotating
device, backward in the direction of the coating device.
11. The method as claimed in any of claims 1-9, characterized in
that, after leaving the rotating device, the roving consists of
substantially parallel filaments which preferably have about 3 to
10 revolutions per meter and preferably about 2 to 5 revolutions
per meter.
12. The method as claimed in any of claims 1-11, characterized in
that the fibers from which the rovings are formed are synthetic
inorganic fibers, in particular glass fibers, C fibers, plastic
fibers, in particular aramid fibers (aromatic polyamide), zylon
fibers (PBO), preferably zylon 28 dtex, or natural fibers, in
particular cellulosic fibers, and the filament thickness thereof is
preferably 5 .mu.m to 20 .mu.m and about 100 tex-4800 tex
(0.1g/m-4.8 g/m), preferably 600 tex-2400 tex.
13. The method as claimed in any of claims 1-12, characterized in
that the fibers are coated with at least one synthetic
thermoplastic polymer having a softening point of 100.degree. C. or
higher, preferably in the range from 140.degree. C. to 390.degree.
C. and in particular in the range from 150.degree. C. to 50.degree.
C.
14. The method as claimed in any of claims 1-12, characterized in
that the fibers are coated with at least one thermosetting plastic
in the form of polycondensates, preferably curable
phenol/formaldehyde plastics, curable bisphenol resins, curable
urea/formaldehyde plastics, polyimides, BMI molding materials and
polybenzimidazole (PBI); with at least one thermosetting plastic in
the form of polyadducts, preferably epoxy resins, molding materials
comprising unsaturated polyester resins, DAP resins, MF molding
materials, preferably curable melamine/phenol/formaldehyde molding
materials, or crosslinked polyurethanes.
15. The method as claimed in any of claims 1-14, characterized in
that mineral, preferably crystalline, compounds, optionally as a
mixture with further plastic, are applied in the subsequent
coating, preferably inorganic compounds, preferably oxides,
carbides, metal powders, preferably in powder form, preferably
magnesium oxide, aluminum oxide, silicon carbide, substances of
great hardness, preferably crystalline carbon, preferably diamonds,
in particular industrial diamonds, the average particle size
thereof being in the range of 5 .mu.m-300 .mu.m, preferably in the
range of 10 .mu.m-100 .mu.m and in particular in the range of 10
.mu.m-30 .mu.m.
16. A thread, saw thread, tape, prepreg, fiber-reinforced plastic
granule, fiber-reinforced shaped article, or fiber-reinforced
pultruded or extruded profile produced as claimed in any of claims
1-15.
17. The use of the individual filaments produced as claimed in any
of claims 1-15, or the corresponding individual rovings as a
composite, for producing threads and saw threads and for producing
tapes and prepregs, fiber-reinforced plastic granules and
fiber-reinforced shaped articles or fiber-reinforced pultruded or
extruded profiles and for fabrics which are woven from coated
rovings and then optionally pressed.
18. A device for carrying out the method as claimed in any of
claims 1-15, comprising at least one coating device (3) for coating
the roving or the rovings in the melt coating method or in the wet
coating method or in the dry coating method, at least one IR oven
(4) as a continuous device (for the wet and in the dry coating
method) for fixing the coating, optionally a subsequent coating
device (5), optionally associated with a further IR oven (4), and
at least one conditioning device (9), consisting of a cooling
device and optionally a heating device for final conditioning of
the coated thread, characterized in that at least one rotating
device (6) by means of which the rovings, or a plurality of such
rovings as a composite, are compressed and preferably
simultaneously sized is mounted in the region after the coating
device (3) but before the conditioning device (9) and before any
subsequent coating device (5) is present.
Description
[0001] The present invention relates to a method for producing
compressed, plastic-coated fibers or rovings, consisting of
substantially unidirectional parallel filaments. In particular, the
present invention relates to a method for producing sized and
compressed thin threads or tapes which consist of substantially
parallel filaments which are used, for example, for producing sized
thin threads, in particular saw threads for cutting out precise
workpieces in the electronics industry, or for producing tapes and
prepregs, fiber-reinforced plastic granules and fiber-reinforced
shaped articles, and in extrusion.
[0002] The production of plastic-coated fibers and rovings which
preferably consist of substantially parallel filaments, also in the
form of tapes or prepregs, is known per se. Usually, rovings which
consist of filaments are coated with a plastic or a mixture of
plastics which may contain various additives and are processed in
further processing stages, depending on the intended use, to give
threads, granules, fiber-reinforced shaped articles or pultruded or
extruded profiles.
[0003] Thus, it is known that rovings to be coated in the melt
coating method can be passed through the melt of a thermoplastic,
then allowed to cool and then further processed. When this method
is used in practice, in particular in the case of a high proportion
of fibers and increasing fiber length, however, a large variation
in the strength values and numerous local weak points in the shaped
article are found. Owing to the high shear forces, such as those
which occur in melt impregnation, fine filaments, for example
comprising carbon fibers, are broken and filament damage or tearing
of threads occurs in the process. A similar situation is
encountered with the use of wet coating methods, i.e. of a liquid
impregnating bath in which the plastic is dissolved in a solvent,
in this case the difficulties associated with the evaporation of
the solvent occurring in addition.
[0004] In the dry coating method, the rovings to be coated are
preferably moved through a fluidized bed. This fluidized bed
consists as a rule of a thermoplastic polymer powder in which
additives are optionally incorporated (compounded), or of a curable
thermosetting plastic powder or plastic powder premix, this being
absorbed onto the fibers as a coating. It is also possible to apply
the individual components of the coating in the fluidized bed
method uniformly and directly to the fibers in the desired
composition, the individual coating components present in the
fluidized bed optionally additionally being mixed in the fluidized
bed so that separation of the individual components is virtually
prevented. Thereafter, the coated fibers are at least partly
melted, preferably in a continuous oven, for example by means of IR
radiation, and then cooled again. An improved distribution of the
plastic on the fiber is thus achieved. However, this dry coating
method has the disadvantage that a part of the powder used for the
coating falls off the fiber again after emergence from the coating
unit, with the result that the powder application and hence the
proportion of resin and/or the proportion of filler in the end
product is limited, which adversely affects the quality of the end
product. However, the coating powder also falls off in the
continuous oven and decomposes in contact with the overheated oven
surface, resulting in the formation of decomposition products which
enter the venting unit and the environment via the waste air. In
addition, these particles, in the form of dust or in the form of
decomposition products, also enter other parts of the production
plant, in particular the filters of the venting unit, and block the
filters of the venting unit there. This in turn leads to imbalances
in the operating procedure and the operating conditions, which
adversely affects the quality of the coated rovings.
[0005] In all cases of said coating methods, a large variation in
the strength values and numerous local weak points in the thread
formed and hence also in the shaped article occur in practical use,
in particular in the case of a high proportion of fiber. In
particular, there are also local differences in the thread diameter
and in the roundness or in the degree of roundness of the fiber and
in the coating thereof with plastic, which subsequently causes said
disadvantages. There is therefore a need to reduce or completely
eliminate these disadvantages.
[0006] For the production of thin threads, in particular of saw
threads for the electronics industry for cutting precise shaped
articles, for example shaped articles which consist of silicon
carbide, or wafers, chips and related shaped articles, or in the
production of solar collectors, it is furthermore necessary for
these threads to have been processed so as to be as thin as
possible and very precise, i.e. of the same diameter along their
entire length, the diameter of these threads being in the micron
range, preferably in the range of 100-1000 microns (.mu.m), and the
variation in the linear deviation of the diameter from the required
value should be within only a few microns. In this context, a very
exact sizing of the threads is necessary, i.e. both the diameter
and the roundness of the thread along the entire thread length are
exactly established and monitored within the specified
dimensions.
[0007] For the coating of rovings, in particular in powder coating,
preferably linear unidirectional rovings are used, also in the
present invention, i.e. rovings in which the filaments are arranged
substantially parallel and substantially straight or
plane-parallel. These rovings can be more easily fanned out and
hence more uniformly coated in the coating process.
[0008] It has now been found that thin plastic-coated continuous
threads (consisting of a multiplicity of individual filaments) or
those comprising plastic-coated fibers or rovings, consisting of
substantially parallel filaments, are obtained if the rovings on
which the plastic, optionally applied as powder, is present in the
molten or liquid state are passed, after the coating, through a
rotating device by means of which local rotation of the fibers is
executed. As a result of such a local high rotation, the fibers are
compressed to a high degree. In the process, the threads are
twisted with one another, starting from the rotating device,
backwards along the individual threads in the direction of the
coating device. After passing through the rotating device, however,
there are no longer any rotations or there are rotations only to a
small extent, so that, after passing through the rotating device,
the filaments have no spiral revolutions per meter or only a small
number thereof but are arranged substantially parallel, linear and
straight. Such threads can then be further processed, for example
additionally coated with a suitable plastic and/or optionally with
mineral particles and then hardened.
[0009] In a particular embodiment of the present invention, the
rotating device consists of a rotating sizing die. By means of the
rotating sizing die according to the invention, the fiber composite
is additionally sized and particularly highly homogenized, and at
the same time compressed, the enclosed gases being forced out of
the composite. Sized rovings which have been processed to have an
exact diameter along their entire length and have only a small
linear deviation in the desired diameter length and hence a high
degree of roundness and moreover are very compact or compressed
result.
[0010] This gives excellent saw threads or coated rovings which
have been processed exactly in the diameter or in the degree of
roundness along their entire length, the variation in the linear
deviation of the diameter from the required value being small.
These saw threads are suitable in particular for producing shaped
electronic articles, such as wafers, chips and related shaped
articles.
[0011] In addition, there are the advantages that the material
applied during the coating of the filaments is better distributed
in the roving owing to the effect of the rotating device.
Consequently, no material or only very little material falls off
the coated fiber on entry into the continuous oven. As a result,
material losses are reduced, the material consumption is optimized
and the environment is protected, which is evident in particular on
heating or on hardening the coating materials.
[0012] If a rotating sizing die is used, any melt cone is spun away
by the rotating sizing die at its die edge and is not deposited
dropwise on the thread. In accordance with the design of a sizing
die, as shown below in FIG. 2a, any melt cone is spun away at the
die exit. A sized thread of high density and free of air inclusions
results.
[0013] By means of the method according to the invention, the
proportion of filler in the coating premix can be substantially
increased so that products having a lower proportion of fibers and
higher proportion of fillers can be produced. The bulk density and
the flowability of granules produced from such threads compressed
according to the invention are also substantially increased, and
the formation of tufts during granulation is considerably
reduced.
[0014] By means of the method according to the invention, the
tensile strength of the coated rovings in the production method
itself is also increased to a surprisingly great extent and can
readily be doubled. Thread breaks in the method, in particular in
the area between the coating device and the rotating unit, are thus
very substantially avoided even at high thread tension.
[0015] These unexpected advantages make it possible to carry out
the entire method under significantly greater thread tension, which
in turn permits a more balanced procedure and increased
productivity of the production plant. Surprisingly, as a result of
the local rotational effect produced by the rotating device, even
relatively coarse powder particles having a particle size up to 300
.mu.m remain enclosed in the composite in dry coating, so that
uneconomical very fine milling of the polymers with narrow particle
size spectrum can be dispensed with.
[0016] The invention is defined in the patent claims. In
particular, the invention relates to a method for producing
compressed, plastic-coated fibers or rovings, consisting of
substantially parallel filaments, starting from rovings consisting
of plastic-coated filaments, characterized in that rovings, or a
plurality of such rovings as a composite, consisting of
substantially parallel filaments on which the plastic applied,
optionally as a powder, is present in the molten or liquid state,
are passed, after the coating, through a rotating device by means
of which local rotation of the fibers is executed so that the
individual threads in the method are twisted with one another in
the form of rotations, starting from the rotating device, backward
along the threads in the direction of the coating device it being
the case, however, that after passing through the rotating device
there are no longer any rotations or there are rotations only to a
small extent, so that, after passing through the rotating device,
the filaments have no spiral revolutions per meter or only a small
number thereof, but are arranged substantially parallel and linear
or straight.
[0017] The invention also relates to a particular embodiment for
producing compressed, plastic-coated fibers or rovings, consisting
of substantially parallel filaments, which is characterized in that
the rotating device consists of a rotating sizing die, sized and
compressed threads being obtained.
[0018] The roving treated in this manner or a plurality of such
rovings as a composite can be subjected to further coating or
subsequent coating. In this context, the invention also relates to
a method which is characterized in that the rovings compressed
according to the invention are subsequently coated in a subsequent
coating procedure additionally with mineral powders or metal
powders at temperatures above the melting point of the coating
polymer, or with plastic, optionally as a mixture with mineral
powders, and then hardened or allowed to solidify.
[0019] The present invention also relates to the use of the rovings
compressed according to the invention, or a plurality of such
rovings as a composite, for producing saw threads which are
suitable, for example, for producing shaped electronic articles,
preferably wafers, chips and related shaped articles, and for
producing tapes and prepregs, fiber-reinforced plastic granules and
fiber-reinforced shaped articles or fiber-reinforced pultruded or
extruded profiles. Included therein are also fabrics which are
woven from coated rovings and optionally then pressed. Tapes also
comprise continuously produced fiber-reinforced tapes. Prepregs
comprise unidirectional and fabric-reinforced prepregs.
[0020] The present invention also relates to the threads, saw
threads, tapes, prepregs, fiber-reinforced plastic granules,
fiber-reinforced shaped articles, fiber-reinforced pultruded or
extruded profiles produced in this manner. The present invention
furthermore relates to a device for carrying out the method
according to the invention.
[0021] Said coated individual filaments or individual rovings as a
composite may have been coated in the melt coating method, in the
wet coating method and/or in the dry coating method, preferably in
the dry coating method. The compression of the individual filaments
or of the individual rovings as a composite is carried out in such
a way that, after the coating process, the coated, individual
filaments or individual rovings as a composite are passed through
at least one rotating device, preferably a device which
simultaneously sizes and compresses, such as, for example, a
rotating sizing die, with the result that these filaments or the
individual rovings as a composite are compressed on passing through
or are simultaneously both sized and compressed by the rotating
sizing die.
[0022] A suitable rotating device as indicated in FIG. 1 and shown
more exactly in FIG. 2 may consist, for example, of two cooled
shafts provided with V-grooves, which are arranged one behind the
other at an angle of less than 90.degree. (<90.degree.),
preferably at an angle in the range from 5.degree. to 20.degree..
Preferably, the 1st shaft is arranged at an angle of more than or
less than 90.degree. to the thread direction, preferably at an
angle of at least 91.degree. or 89.degree. (>1.degree.),
preferably at an angle in the range from 600 to 120.degree.. The
second grooved shaft is arranged at right angles to the thread
running direction. The coated roving runs through, for example,
above the first shaft and below the second shaft, i.e. the rovings
are passed over the first shaft and then under the second shaft, in
each case in the V-grooves thereof. In this case, the first shaft
rotates counterclockwise and the second shaft clockwise. The
V-groove of the first shaft is laterally offset in the thread axis
by at least 1 mm, preferably at least 5 mm, so that the thread runs
laterally over the oblique flanks of the first shaft. The thread is
pressed against the V-flanks as a result of the angular arrangement
of the shafts and as a result of the offset of the grooves and is
rotated by the component acting perpendicularly to the thread axis,
so that a clockwise or counterclockwise rotation of the thread
results. The number of rotations (stated as rotations per meter) is
determined primarily by the angle opening of the 1st shaft. The
rotation of the grooved shafts is achieved by the friction with the
coated rovings or additionally by an external drive. The number of
rotations per meter is product-dependent and is determined by
optimizing the angular arrangement and the friction of the coated
roving in the V-grooves, which presents no problem for the person
skilled in the art.
[0023] The rotating shafts are preferably mounted or installed
after the first or optionally after a further continuous oven. The
rotation acts uniformly, as already described above, over the
entire length of the roving or rovings, back to the location where
the roving leaves the coating device or, for the present example,
the first rotating shafts. After passing through the rotating
device, the rotations cease again and give the thread according to
the invention with substantially parallel fibers, which have no
rotations per meter or only a few thereof.
[0024] If a sizing die is used, it rotates at such a high speed
that the individual filaments or individual rovings as a composite
are compressed and also sized. All excess coating material which
forms as a melt cone at the die exit is spun away during the
sizing. The diameter of the sizing die is set so that the desired
thread diameter is obtained. As already mentioned, the threads in
the method are rotated from the rotating sizing die in each case
along the thread backward in the direction of the coating device.
After passing through the rotating sizing die, there are, however,
no longer any rotations in the forward direction or only a part of
the rotations persist, so that, after passing through the rotating
sizing die, the threads (filaments) have no spiral revolutions per
meter or only a small defined number thereof.
[0025] The rotating die is preferably mounted or fixed in a hollow
shaft and rotates together with this hollow shaft at a suitable
speed of, as a rule, at least 500 revolutions per minute (rpm),
preferably at least 2000 rpm, preferably at least 7000 rpm and
preferably at about 10 000 rpm. A range from 7000 rpm to 15 000 rpm
is preferred. The die, preferably produced from hard metal, is
preferably heated to at least the melting point of the fiber
coating, i.e. as a rule to at least about 100.degree. C. and
preferably to about 150-180.degree. C.
[0026] The polymer coating of the fiber must be liquid during
passage through the rotating device, i.e. must be heated to a
temperature which as a rule is at least 100.degree. C. and
preferably at least 150-200.degree. C. or about 50.degree. C. above
the melting point of the polymer. The heating can be effected, for
example, by means of IR radiation or hot air.
[0027] It is also possible to connect a plurality of individual
rotating sizing dies one behind the other in series and to pass the
fibers through these devices. As a result, the fibers are even more
accurately sized and compressed to a greater extent. Preferably,
the sizing dies connected one behind the other have decreasing
internal (sizing) diameters.
[0028] Preferably, the rotating sizing die has an internal diameter
in the range of about 100-2000 .mu.m (micrometers, microns),
preferably in the range of about 150-600 .mu.m and in particular in
the range of about 200-350 .mu.m, for example about 200-240 .mu.m,
with the result that a sized and compressed or homogenized and
compressed strand produced according to the invention and having a
corresponding diameter is obtained. The average linear deviation
from the required value of the diameter of the hardened thread is
as a rule less than 6 % and preferably less than 4 %, and is
likewise in the micron range, which results in a very high degree
of roundness.
[0029] The rotating device exerts a local torque on the fiber when
it passes through. The rotating device is adjusted so that the
roving has locally, for example depending on the rotational speed
of the sizing die, about 5 to 50 spiral revolutions per meter,
preferably about 10 to 30 spiral revolutions per meter, preferably
about 10 to 20 revolutions per meter, before the rotating device.
After leaving the rotating device, this local comparatively large
number of revolutions per meter no longer exists, so that a roving
comprising substantially parallel and straight filaments results.
This means that the roving preferably has about 3 to 10 revolutions
per meter and preferably still about 2 to 5 revolutions per meter.
If a roving in which the individual filaments are arranged in
parallel form was coated, the mutual parallel line of the
individual threads is substantially retained in the compressed,
preferably in the sized and compressed, roving.
[0030] Regardless of the compression, preferably sizing and
compression, according to the invention of the roving or of the
rovings, the sized and compressed rovings or thin threads can
additionally be further processed in a manner known per se, for
example to give thicker and stronger threads.
[0031] According to the invention, all fibers known per se which
are known for the production of fiber-reinforced materials can be
used as fibers from which the rovings are formed. Examples are
synthetic inorganic fibers, in particular glass fibers, C fibers,
plastic fibers, in particular aramid fibers (aromatic polyamide),
zylon fibers (PBO) 28 dtex (0.028 g/m), or natural fibers, in
particular cellulosic fibers. The filament thickness is preferably
about 5 .mu.m to 20 .mu.m and about 100 tex-4800 tex (0.1 g/m-4.8
g/m), preferably 600 tex-2400 tex, as usually used.
[0032] According to the invention, thermoplastics known per se (as
compound or as a premix) and/or thermosetting molding materials
known per se (preferably as a premix) can be used as plastic for
the coating. Thermoplastic molding materials or plastics and
additives thereof are known in large numbers from the literature.
Synthetic thermoplastic polymers are preferably selected from the
group consisting of the polyolefins, preferably polyethylene, in
particular HDPE, or polypropylene (PP); polycarbonates;
polyoxymethylenes (POM); polyethylene terephthalates (PET);
polybutylene terephthalates (PBT); polyethylene sulfides (PES);
polyphenylene oxides (PPO); polyphenylene sulfides (PPS); PSO;
PVDS; thermoplastic polycondensates, preferably polyesters and
polyamides, such as polyamide 66, polyamide 12 and the like;
polyvinyl acetates; polystyrenes; polacrylates; polymethacrylates;
alkylene/acrylic acid copolymers or alkylene/methacrylic acid
copolymers, preferably ethylene/acrylic acid copolymers; PEEK and
PEK, alkylene/maleic anhydride copolymers; or alkylene/vinyl
alcohol copolymers. HDPE, PP, polycarbonates, POM, PET, PBT, PES,
PEEK, PEAK, PPO, PPS, PSO, PVDS, and thermoplastic polyamides are
preferred. Synthetic polymers having a softening point of
100.degree. C. or higher, preferably in the range from 140.degree.
C. to 390.degree. C. and in particular in the range from
150.degree. C. to 350.degree. C. are preferred.
[0033] Thermosetting plastics in the form of polycondensates are,
for example, curable phenol/formaldehyde plastics (PF casting
resins), curable bisphenol resins, curable urea/formaldehyde
plastics (UF molding materials), polyimides (PI), BMI molding
materials and polybenzimidazoles (PBT). Thermosetting plastics in
the form of polyadducts are, for example, epoxy resins (EP),
molding materials comprising unsaturated polyester resins (UP
molding materials), DAP resins (polydiallyl phthalate), MF molding
materials, e.g. curable melamine/phenol/formaldehyde molding
materials or crosslinked polyurethanes (PU).
[0034] For example, in addition to the resin/curing
agent/accelerator system for thermosetting plastics, additives for
thermosetting plastic molding materials or plastics and
thermosetting plastics in the form of polycondensates or
polyadducts are mold release agents, lubricants, fillers, pigments,
adhesion promoters, stabilizers and inhibitors. Such compounds are
known per se, as are the compositions preferably to be used for the
coatings according to the present invention.
[0035] Said plastics may be applied to the rovings in the melt
method or directly from the melt or in the wet method, i.e. in
solution in a suitable solvent, or in the dry coating method, as
described at the outset, as a coating, by means of a suitable
apparatus known per se. Such devices and the process conditions are
known to the person skilled in the art.
[0036] If the rovings which have been compressed, preferably sized
and compressed, according to the invention, or a plurality of such
rovings as a composite, are subjected to subsequent coating, said
plastics and said coating methods can be used independently of one
another, depending on suitability and choice. The plastic may
additionally be used as a mixture with mineral or metallic,
preferably crystalline, compounds and may serve as a binder for the
mineral substances. Such subsequent coating is necessary in
particular for producing saw threads. Such mineral substances are
preferably crystalline compounds, preferably inorganic compounds,
preferably oxides, carbides, metal powders, preferably in powder
form. For example, inorganic compounds, such as oxides, carbides,
preferably in powder form, such as, for example, magnesium oxide,
aluminum oxide, silicon carbide, or other substances of great
hardness, such as, for example, crystalline carbon, preferably
diamonds, in particular industrial diamonds, preferably in the form
of diamond powder, are preferred. The particle size of the powder
is preferably in the range of about 5 .mu.m-300 .mu.m (microns),
preferably in the range of about 10 .mu.m-100 .mu.m and in
particular in the range of about 10 .mu.m-30 .mu.m. Synthetic
polymers having a softening point of 100.degree. C. or higher,
preferably in the range from 140.degree. C. to 390.degree. C. and
in particular in the range from 150.degree. C. to 350.degree. C.
are preferred for the subsequent coating, the process temperatures
used being the same as those described herein for the coating
device.
[0037] The attached FIG. 1 illustrates a diagram of a device for
the coating and subsequent coating, according to the invention, of
a roving, containing three rotating sizing dies which are connected
in series which, for example, first size the thread to 300 .mu.m
and then to 260 .mu.m and then to 240 .mu.m and simultaneously
compress it.
[0038] FIG. 2 shows a rotating device containing two cooled shafts
which are provided with V-grooves and are arranged one behind the
other at an angle of less than 90.degree..
[0039] FIG. 2a shows a rotating sizing device, containing the
rotating sizing die, in cross section.
[0040] FIG. 3 and FIG. 3A show a rotating sizing die with shear
part, consisting of a cone for the melt cone A, the centering hole
B, the transverse hole X, the shallow channel C, the bearings E and
F and the toothed ring G. The roving coated with the molten premix
passes through the centering hole B into the die, expands in the
transverse hole D and emerges again through the shallow channel C.
For filaments particularly sensitive to breaking or for exact
sizing, only round dies are used, in order thereby to keep shear
forces small. In this process, the die rotates at 6000 to 15 000
revolutions per minute. The changed cross section results in a
shear effect and exertion of a rotational force. The inner
filaments are substantially better opened up. A homogeneous strand
having uniform resin content is thus obtained. This is more compact
and can be granulated to give better granules. The density of the
strand is higher. The coated strand is compressed by the rotation
and by the shallow channel up to the coating, so that the coated
strand passes through the IR oven without loss of coating
particles. The toothed ring makes it possible to arrange different
sizing dies in a line side by side in a small space and to drive
them mutually. Analogous results are obtained with a rotating
device according to FIG. 2.
[0041] FIG. 4 shows a further embodiment of the sizing die,
analogous to that shown in FIG. 3 and FIG. 3A, but the shallow
channel B is narrower than the channel designated as sizing hole
C.
[0042] The device (1) shown as attached FIG. 1 consists of an
unwinding device (2), the coating device (3), the IR ovens (4), the
subsequent coating device (5), the rotating devices (6) according
to FIG. 2 or 2a, the rotating device (6) preferably being a
rotating device according to FIG. 2a, the conditioning device (9)
and the winding unit (10). The first rotating device is mounted
directly after the coating device (3). Further rotating devices or
sizing devices are then mounted at the first IR oven (4).
[0043] If the coating device (3) is a device for the dry coating
method in the fluidized bed, the particle size distribution of the
coating component or of the coating components in the dry coating
is preferably in the range of 30 .mu.m-250 .mu.m, preferably in the
range of 50 .mu.m-300 .mu.m. The average particle size is chiefly
preferably about 50 .mu.m-150 .mu.m.
[0044] For the coating, according to the invention, of rovings in
the dry coating method with a reaction resin, such as, for example,
an epoxy resin, a melting point in the range of 60.degree.
C.-300.degree. C., preferably 70.degree. C.-220.degree. C., a roll
temperature of 10.degree. C.-200.degree. C., preferably 20.degree.
C.-50.degree. C., and a thread speed of 3-200 meters per minute,
preferably 50-150 meters per minute, are preferably used. The
processing conditions for the various plastics are known per se and
also depend on the size of the apparatus used and can readily be
correctly applied by the person skilled in the art for the
respective plastic used or for the respective resin used.
[0045] In the powder coating method itself, the rovings are unwound
from a roving rack, preferably from the outside of the roller, and
fed into the coating unit, where they are preferably fanned out and
passed through the fluidized-bed bath. The fluidized-bed bath
comprises in principle a trough and contains the feed for the
coating component or coating components, and the fluid base, which
preferably consists of sintered aluminum or ceramic and through
which the air supply to the fluidization tank, i.e. the fluidizing
air for maintaining the fluidized bed, is introduced. The diameter
of the perforations in the perforated intermediate base (fluid
base) is less than the particle size of the coating powder used or
of the coating components or of the granules. Air or inert gas is
blown in from below through the perforations, so that an undulating
bath of powder or of granules or a fluidized bed forms. A plurality
of deflection rollers or deflection rods for fanning out and
tautening the fibers is present in the fluidized-bed bath. The
coating unit can be provided with a device for additional thorough
mixing of the coating components, for example a mixing device for
additional mechanical mixing of the coating components.
[0046] The temperature of the air supply to the fluidizing tank,
i.e. the conditioning of the fluidizing air, is controlled in
proportion to the melting point of the polymer powder. Thus, the
amount of powder applied can be controlled. A fluid base comprising
sintered aluminum or ceramic is preferably used. The conditioning
of the fluidizing air makes it possible to preheat those plastic
powders having a high melting point during the coating itself to
below the softening temperature and thus to reduce the required
heat-up time. Thus, the productivity in the case of thermoplastics
having a high melting point can be considerably increased. However,
the heating during the conditioning may be effected in the case of
reactive resin mixtures only to sufficiently below the temperature
(onset temperature) at which the exothermic curing process of the
resin mixture starts.
[0047] After the coated rovings have left the fluidized-bed bath,
they pass through the rotating device according to FIG. 2 or the
rotating device according to FIG. 2a. The rotating device according
to FIG. 2a is a rotating sizing device containing a rotating sizing
die (7) which is produced from hard metal and by means of which the
filaments are simultaneously both sized and compressed while
passing through. The sizing die (7) is fixed in a hollow shaft and
rotates together with this hollow shaft. The rotating hollow shaft
can be driven by electric drive or compressed-air drive known per
se. The sizing dies can also be integrated in gear wheels, the
individual gear wheels engaging in one another in line and driving
one another. That design of the sizing device or sizing die which
is shown in FIG. 2a is only one of the possible embodiments.
[0048] After the first rotating device or sizing device (6), the
coated rovings are passed through an IR oven (4) or a continuous
oven, where they are heated. For this purpose, the continuous oven
preferably contains an infrared heater. The coating becomes
slightly liquid or pasty, but not so liquid that it can drip off
the fibers. In this state, further coating material or granules
which consists of consist of inorganic powder or of inorganic
powder mixed with organic polymer, or of organic polymer, as
described above, can be applied, optionally by means of subsequent
coating, in a further coating device (5). The coated, heated thread
can also be passed in this manner through fluidized mineral or
metal powder, this powder being entrained by the softened coating
polymer. The temperature and the residence time determine the layer
thickness of the applied material. Subsequently, treatment can be
effected in a further IR oven. In this way, the desired amount of
plastic and/or inorganic material which is to be applied to the
fibers can be reached. It is thus possible to obtain thread weights
with a very low proportion of glass, for example threads having a
proportion of only 15% by weight of glass fibers. The subsequent
coating can also serve as insulation.
[0049] After the rovings have been coated, sized and compressed and
optionally subsequently coated, they are then passed through a
conditioning device (9) which consists of a cooling device and
optionally a heating device. If an epoxy resin mixture was applied
as a coating, the rovings are optionally heated again, the epoxy
resin mixture undergoing pregelling or precrosslinking, but not
being cured. The cooling is necessary in particular because the
fiber/plastic composite is subsequently drawn through a pair of
rolls which transports this composite. At the location of the pair
of rolls, the fiber/plastic composite must be in a solid state,
since otherwise the plastic may adhere to the rolls of the pair of
rolls, with the result that these would become soiled and in
certain circumstances reliable transport of the fiber/plastic
composite would be hindered. Preferably, the fiber/plastic
composite also passes through a heating device in which the
temperature required for the granulation or winding is determined.
The coated roving obtained can then be wound up or granulated.
[0050] If a pultrusion die is used, the apparatus preferably has
the following structure:
[0051] Creel.fwdarw.coating bath.fwdarw.IR
oven.fwdarw.rotating/sizing device.fwdarw.pultrusion
die.fwdarw.profile take-off unit.
[0052] The present invention also relates to a device for carrying
out the method according to the invention, comprising at least one
coating device (3) for coating the roving or the rovings in the
melt coating method or in the wet coating method or in the dry
coating method, at least one IR oven (4) as a continuous device
(for the wet and in the dry coating method) for fixing the coating,
optionally a subsequent coating device (5), optionally associated
with a further IR oven (4), and at least one conditioning device
(9), consisting of a cooling device and optionally a heating device
for final conditioning of the coated thread, characterized in that
at least one rotating device according to the invention, preferably
a sizing device (6), are installed in the region after the coating
device (3), but before the conditioning device (9) and before any
subsequent coating device (5) present, the coated individual
filaments from which the respective roving is formed, or the
roving, or a plurality of such rovings as a composite, being
compressed, or compressed and sized, by the rotating device or
sizing device (6), immediately after leaving the coating device
(3), and forming a compact closed strand. The following examples
illustrate the invention.
EXAMPLE 1
[0053] PBO roving containing 160 filaments having a filament
diameter of in each case 0.005 mm, 0.012 mm and 0.014 mm (5 .mu.m,
12 .mu.m and 14 .mu.m) are coated in the dry coating method with a
matrix which contains a customary bisphenol resin (Araldit.RTM.)
and curing agent (Durez.RTM.) from Hunstmann und Durez, (50.0% of
the total coating), and customary mold release agents, lubricants,
fillers and pigments (50.0%) in a customary composition. The
components of the matrix are mixed in a mixer and have a particle
size distribution in the range from 30 .mu.m to 200 .mu.m. The
coating method is carried out an apparatus described above in the
description, a coating unit described in EP-A-0 680 813 being used.
A sizing device containing a rotating die mounted in a hollow tube
and intended for the continuous simultaneous sizing and compression
of the rovings is installed directly after the coating unit. This
sizing device corresponds to the device shown in FIG. 2a. The die
has an internal diameter of 300 .mu.m. A second and a third such
sizing device having in each case a die diameter of 260 .mu.m and
240 .mu.m are mounted in series after the continuous IR oven.
[0054] Glass rovings are unwound from a roving rack, preferably
from the outside, fanned out and passed via four deflection rods to
the fluidized-bed bath. The coated rovings then pass through a
sizing device, then the continuous infrared oven at a temperature
of 180.degree. C. and then the two further rotating sizing devices
connected in series. The coated rovings are then conditioned in the
conditioning unit and cooled so that the plastic becomes solid.
[0055] Coated rovings having a diameter of 240 .mu.m and a
deviation of the diameter over the length of the thread of less
than 0.5% were obtained. Virtually no evolution of smoke from
decomposed coating material in the continuous oven and in the
conditioning unit was observable. The thread speed (throughput) was
140 meters per minute.
EXAMPLE 2
[0056] Example 1 is repeated, with the proviso that, instead of the
sizing devices according to FIG. 2a, (i) only one rotating device
according to FIG. 2 and (ii) first a rotating device according to
FIG. 2 and then a sizing device according to FIG. 2a are installed.
Here too, good results analogous to those in example 1 are
obtained.
EXAMPLE 3 (COMPARATIVE EXAMPLE)
[0057] Example 1 is repeated, with the proviso that the
installation of the sizing device (6) is dispensed with. Coated
rovings having a diameter of about 300 .mu.m and a deviation of the
length of the thread of 15% were obtained. Evolution of smoke from
decomposed coating material in the continuous oven and in the
conditioning unit was observable. The thread speed (throughput) was
80 meters per minute.
EXAMPLE 4
[0058] Example 1 is repeated, with the proviso that the bisphenol
resin and the curing agent and the additives are replaced by a
PEEK-HT (Vitrex.RTM., from Victrex) having a melting point of
370.degree. C. Results analogous to those stated in example 1 are
obtained.
EXAMPLE 5
[0059] Example 1 is repeated, with the proviso that the bisphenol
resin and the curing agent and the additives are replaced by a
thermoplastic polyamide 11 powder having a melting point of
180.degree. C. Results analogous to those stated in example 1 are
obtained.
EXAMPLE 6 (COMPARATIVE EXAMPLE)
[0060] The examples 1, 2, 4 and 5 are repeated, with the proviso
that the installation of the rotating device or of the rotating
sizing devices according to the invention is dispensed with. Here
too, the results from examples 1, 2, 4 and 5 are substantially
superior to the results from example 6. In the method according to
examples 1, 2, 4 and 5, the thread quality and the loss of coating
material were considerably smaller than in example 6. The bulk
density of granules obtained according to examples 1, 2, 4 and 5
was also markedly higher than that according to example 5. The
throughput, too, is substantially higher in examples 1, 2, 4 and 5
in comparison with example 6.
* * * * *