Note: Descriptions are shown in the official language in which they were submitted.
PROCESS FOR SEPARATING FIB~S FROM COMPO$ITE MATERIA~
The present invention relates to methods and
apparatus for treating waste byproducts of
flbre-reinforced plastic manufacturing processes.
There is widespread use o~ fibre reinforced
plastics which essentially utilize a fibre substrate
impregnated with a thermosetting resin. One of the more
popular fibre reinforcements is glass fibre which may be
utilized in a mat form, either woven or random, or as
chopped fibres distributed within the resin binder.
The manufacturing techniques utilizing fibre
reinforced plastics frequently require trimming of the
completed product. These trimmings and improperly
manufactured products produce a significant waste product
which has to be disposed of as landfill. Moreover, once
the useful life of the product is over, it has to be
disposed of, usually by landfill.
Another product used increasingly in the
automotive industry is known as sheet molded compound
~SMC) which is used to p~od~ce complex shapes for panels,
bumpers and the like. These products are mass-produced
and inevitably some of the product is not of sufficient
quality. Again, therefore, considerable waste product
has to be disposed of, both during manufacture and at the
end of the product life.
Attempts to utilize the waste byproducts of
fibre reinforced plastic have not previously been
successful. This is due in part to the fact that most
processes that seek to reduce the size of the waste
either damage the fibre and/or generate excessive heat
which in turn causes the resin to melt and inhibit the
process. It is, however, recognized that much of the
waste product contains fibre which, if it could be
separated from the resin in a relatively undamaged
condition, could be reused.
- It is therefore an object of the present
invention to provide a method and apparatus for
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separating fibres from fibre reinforced plastic material
which obviates or mitigates the above disadvantages.
According to the present invention, there is
provided a method of separating fibres from a fibre
reinforced plastic material comprising the steps of
shredding said material into a plurality of discrete
pieces, feeding said pieces into a pulverizer to impact
said pieces, and providing an unclassified output ~rom
said pulverizer, separat~ng free fibres from said output
and feeding at least a portion of the balance of said
output to a pulverizer for further diminution thereof.
It has been found that by utilizing a
pulverizer of the vertical shaft swing hamm~r type, known
as a fiberizer, a good separation of the fibres from the
resin is obtained without generation of excessive heat or
undue damage to the fibres.
Preferably, the pulveriser is airswept so that
fibres are entrained with the air stream and moved
effectively through the pulveriser.
The separation of the free fibre after passing
through the pulveriser ensures that the free fibres are
not reprocessed by the pulveriser to maintain the maximum
length of fibre in the recovered fibre.
Preferably, the portion of the balance of the
output that is further processed by the pulveriser is
selected to comprise essential unitary pieces of fibre
reinforced plastic material so that further processing
will separate fibres rather than reprocess already
The use of a shredder to break the material
into small discrete pieces of uniform size that
facilitates operation of the pulverizer. With certain
types of waste there is a significant amount of free
fi~re that can be separated prior to pulverization ,
either prior to or after shredding, and which further
enhances the operation of the pulverizer.
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In one embodiment, the material processed by
the pulverizer is cascaded through progressively finer
sieves with free fibres being removed at each stage. The
resultant byproduct can then be milled to produce a fine
powder that may be used as a resin extender or filler
with characteristics comparable to commercially available
It is preferred in a second embodiment to
utilize a sieve or trommel to separate free fibres after
processing by the pulverizer. A trommel has been found
effective to separate free fibre from larger pieces of
composite and permit the composite pieces to be
recampaigned through a pulverizer.
Embodiments of the invention will now be
described by way of example only with reference to the
accompanying drawings, in which
Figure 1 is a schematic representation of the
process and apparatus for separating fibres from fibre
reinforced plastic material: :
Figure 2 is a section through apparatus used in
the process shown in Figure l;
Figure 2a is a view of a portion of the
apparatus shown in Fi~ure 2 on an enlarged scale;
Figure 3 is a curve comparing the fibre size
distribution for a product recovered during the process
with a commercially available product;
Figure 4 is a schematic representation of an
alternative em~odiment of the process shown in Figure l:
Figure 5 is a sectional view of a further piece
of apparatus used in the process of Figure 3;
Figure 6 is a schematic representation of
further embodiment o~ the process shown in Figures 1 and
Figure 7 is an enlarged schematic
representation of a screen used in the embodiment shown
in Figure 6.
Referring therefore to Figure 1, waste fibre
reinforced plastic material such as fibre glass
composites indicated at 10 is introduced into a shredder
12. The waste material can include solidified resin and
fibre product as well as fibre cloth or felt that has
b~en tri~ed during the manufacturing procecs.
Shredder 12 is a low speed, high torque
shredder of the type utilizing a pair of counter-rotating
shafts carrying a plurality o~ interdigitated hooXed
blades. Such shredders are availa~le from Shred-Tech
Limited of Cambridge, Ontario. The shredder 12 reduces
the waste product to discrete pieces typically in the
form of elongate strips in the order of 8 cm x 8 cm with
the thicXness determined by the original feedstock. It
has been found that the optimum rake angle of the hooked
teeth utilized in the shredder 12 is between 10- and 20-
with a rake angle of 15 proving satisfactory when
operating at a rotational speed of betwee~ 20 rpm and 26
rpm. It has also been found that too great a reduction
of the feedstoc~, for example to 3 cm x 3 cm, in general
leads to a reduction in the recovery of longer fibres.
The shrèdded pieces indicated at 14 are
deposited onto a vibrating non-perforated screen 16.
Screen 16 causes free fibres that have been released in
the shredder 12 to separate from the resin-bound fibres
and may be removed by an airlift 18. This fibre has a
consistency similar to that sold commercially as 36 mm
chopped strand. It has been found that with mixed waste
product such as results from hand lay up manufacture in
the order of 10% of the initial waste may be released as
free fibres by the shredder 12 and extracted through the
airlift 18. Further cleansing of the free fibres is
provided by a willow 20 and it has been found in ~ .
experimental tests that free fibres in the order of 88~ ,
purity have been obtained from the willow 20.
The balance of the waste ~aterial as indicated
at 22 is delivered to a pulverizer 24 for further
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separation. Pulverizer 24 is shown in further dstail in
Figure 2 and is a vertical shaft swing hammer mill
commonly known as a fibreiser. The fibreiser used in the
experimental process illustrated in Figure 1 is a "lab
scale Fibreiser" made by Fournier Steel Works, Blacklake,
Quebec, and identified as model D6624RE. Pulverizer 24
utilizes a vertical shaft 52 having a plurality of
hammers 54 pivotally mounted to the shaft for swinging
movement in a horizontal plane. An imperforate breaker
plate 56 is disposed about the shaft 52 so that product
introduced into the pulverizer is impacted either by the
hammers 54 or against the breaXer plate 56. Stationary
fingers 57 are interposed between the hammers 54. As can
be seen from Figure 2a the radially inner surface of
plate 56 is serrated with the generally radial faces 59
directed against the direction of rotation of the shaft
Each of the hammers 54 includes an enlarged
head S8 with leading and trailing faces 60,61
respectively an end face 62 and upper and lower faces 63.
It is preferred that the included angles at the
intersection of each of the faces 60, 61, 62, 63 is 90-
and that the edges at the intersection are not radiussed
so that a "sharp" edge is provided. It is also preferred
that the faces of the head are face hardened by an
appropriate conventional process. Material is
fed through the pulverizer 24 in a vertical direction
from an inlet 64 to an outlet 66. The flow of material
is enhanced by entrainment with air, indicated by arrows
68, which carries the product past the hammers 54. The
pulverizer 24 does not include a classifying screen as is
commonly used in other types of hammer mill so that the
material at the outlet 66 is unclassified and has
proceeded from the inlet 64 to outlet 66 in a single
pass. It is found surprisingly that the use of an
unclassified vertical shaft swing hammer type mill
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effectively separates the fibres from the resin wlthout
damaging the fibres.
By contrast, when product was introduced into a
ball mill, rod mill or shàtterbox, each of which uses a
classifying screen, the material was not pul~erized but
It is believed that the absence of a
class~fying screen and the consequent single pass
pulverization reduces recirculation within the mill and
so prevents excessive hQating of the material or damage
to the fibres. Moveover, it is believed that the action
of the hammers leads to a breaking of the material along
the fibres and consequently release of the fibres.
In the embodiment of Figure 1, material from
the pul~erizer 24 is fed to a vibrating screen 26. The
vibrating screen 26 is a 10-mesh screen having a 2.03 mm
screen opening defined by .51 mm diameter wires. The
material delivered from the pulverizer is separated on
the screen 26 into the unders indicated at 28 which pass
through the screen, the overs 30 which are too large to
pass through the screen 26 and free fibre which is
extracted by an airlift 32. The free fibre extracted by
airlift 32 may be combined with the output from the
willow 20 to produce a recovered product of relatively
long fibres similar to commercially available 24 mm
The overs 30 from the 10 mesh screen are
returned to the pulverizer 24 for further processing and
eventual separation on the scrsen 26.
Unders 28 are delivered as feedstock 33 to a
35-mesh screen 34 having a 0.51 mm screen opening defined
by a .216 mm diameter wire. Again, the screen separates
the feedstock 33 into unders 36 that pass through the
screen 34, overs 38 which do not pass through the screen
3S 34, and free fibre separated by an airlift 40. In
practice, when using glass fibre reinforced composites,
it has been found that the fibre extracted by the airlift
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40 can be used as an end product having a consistency
similar to that known as 8 mm - 12 mm chopped strand sold
The unders 36 are used as feedstock 37 to a
further vibrating screen 42 having a 60-mesh screen with
a screen opening of .27 mm defined by a .152 mm diameter
wire. The screen 42 separates further free fibre which
is removed through an airlift 44 and delivers the overs
46 and unders 48 to a milling device 50. The fibre
extracted by the airlift 44 has a consistency sim~lar to
3 mm milled fibre and typically is 60% pure when the
waste product is glass fibre rein~orced.
The milling device 50 is a fluid energy mill in
which a pair of jets of air entrained particles are
caused to impact and disintegrate. Such mills are
commonly referred to as micronizers and produce a ~ery
fine powder in the order of lO micron size. The powder
has been found suitable for use as an extender or filler
ln resin used to make fibreglass reinforced products.
From the above, it can be seen that the process
provides free fibres which are comparable with
commercially available virgin fibres and also produces
from the resin a powder suitable for reuse as a filler or
The fibre extracted by the airlift 40 when the
waste product includes glass fibre typically has a purity
of fibre to resin is in the order of 60% although it is
believed that the entrapment of small pieces of resin
within the fibre is not detrimental and may even enhance
the characteristics of the fibre.
As shown in Figure 3, the fibre extracted from
the airlift 44 has comparable fibre length
characteristics to the commercially available 3 mm milled
fibre product and again typically has a 60% purity. The
size distribution was obtained with a ~auer McNett test
using a wet screen classification.
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Further separation of the fibre from the resin
can be obtained utilizing willows similar to those
indicated at 20 in each o~ the fibre lines. However, in
tests it is found that such willows may reduce the length
5 of the ~ree fibres and therefore may not be tesira~le.
In tests conducted to date with glass
reinforced composites, it would appear that between 30% -
40% by weight of the total throughput of the waste i6
recovered as fibre with the majority being recovered from
the 10-mesh screen 26. The output from the mill 50
represents in the order of 20~ by weight of the
throughput. It can be seen, therefore, that in excess of
50% by weight of the initial waste product is recovered
as reusable materials. The above results were obtained
using a pulverizer as described ahove but with radiussed
edges at the intersection of the faces 60,61,62,63 for
the hammers heads and without face hardening. ~he use of
sharp edges and face hardening have been observed to
increase the extraction of the fibre.
A further process is disclosed in Figures 4 and ~'!
5 that has been found particularly beneficial with
SMC-type product although as shown the apparatus may be
used with different types of waste product. Like
reference numerals will be used to denote like components
with a suffix "a" added for clarity.
In the process of Figure 4, the waste SNC
product is first shredded by shredder 12a into smaller
pieces. The output of shredder 12a is discharged onto a
conveyor 69 which is selectively operable to direct
shredded waste to either a pulverizer 24a, a willow 20a
or a cutter 71. Different types of waste have different
characteristics so that, for example, some waste will be
mainly glass mat which is best processed by the cutter
73. Similarly, some waste has an abundance of free fibre
which is best separated by willow 20a. By providing the
dif~erent devices and the conveyor 71, mixed waste may be
processed efficiently and selectively.
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Because the SMC waste has few free fibres, the
output of shredder 12a is fed to pulverizer 24a identical
to that described above. The waste i5 fed after a single
pass through the pulverizer 24a to one of a pair of bins
73 which store the output of the pulverizsr and
recirculate the product within the bins 73 to obtain a
uniform distribution of product within the bin. The
output of willow 20a is also fed to a bin 73a for
sub~equent processing. Product within the bins is then
fed by conveyors 75 to a first separation stage performed
by a trommel 70.
Trommel 70 comprises a stationary housing 72
with a cylindrical sieve 74 rotatably mounted within the
housing 72 for rotation about a generally horizontal
axis. A paddle array 76 including a shaft 78 and paddles
80 is also rotatably mounted within the housing 72 so as
to be coaxial with the sieve 74. A motor rotates sieve
74 in one direction and the paddle array 76 in the
opposite direction so that the ~ieve 74 and paddles 80
contra-rotate. Air is introduced into the centre of the
sieve 74 and flows radially outwardly through the sieve
74 as indicated by the arrow 86.
The output of pulverizer 24a from bin 73 is fed
to the interior of the sieve 74 where the free fibre and
~maller particles of resin pass through the sieve to be
collected at the bottom o~ the housing 72 and discharged
by an auger 82. It has been observed with SMC waste that
the output of the pulverizer 24a includes a relatively
high percentage, typically 5% to 10% by weight, of larger
discrete pieces of SMC product. These pieces,
colloquially referred to as "medallions", ara typically
the size of coins, i.e. 1 c~ to 3 cm diameter and the
thickness of the waste material. The presence o~ the
medallions is believed to inhibit the separation of
3S fibres on an orbital vibrating sie~e but it has been
found surprisingly that the contra-rotation Of the sieve
74 and paddles 80 in the trommel promote the separation
of the fibres. It has been observed that the relatively
aggressive agitation of the waste by the paddles 80 as it
rolls around the sieve 74 allows the fibres to be
orien~ated by the air stream to pass radially through the
S sieve 74 while leaving the medallions within the sieve
74. For optimum separation, the paddles 80 should be
relatively close to the sieve 74 and may touch the sieve
74 if flexible paddle ends are provided. Typically a
spacing of less than 12 mm is preferred although the
spacing may be adjusted in the air flow through the sieve
74 to provide the aggressive action within the sieve and
the orientation of the fibres in the air stream. A 4.5
mesh (approximately ~") sieve has been found effective
for this separation. Thus fibres that may be up to 1"
long will be oriented by the airstream to pass through
the screen but larger pieces or medallions are left.
The medallions are removed from the centre of
the sieve 74 and are recampaigned through a pulverizer
24a. As shown in Figure 4, a second pulverizer 24a may
be used and the product passed through a cyclone
classifier 77 before being fed back to the trommel 70.
The air from the classifier 77 is discharged through bag
filters 79 that collect dust and small particles.
Alternatively, the overs of trommel 70 may be
recampaigned through the first pulverizer 24a and
reprocessed through bins 73. The medallions may
constitute between 5% and 15% of the waste product fed to
the pulverizer 24a.
The unders from the trommel 70 - that is, the
product that passes through the sieve 74 - is fed through
a classifier 81 to a 10 mesh orbital screen 26a similar
to th~t described above. The classifier 81 also receives
the air that flows through the trommel 70 so that any
fibres entrapped in the air stream are further separated
and fed to screen 26a. The screen 26a separates the
flb~es and resin with the free fibre~ being lifted from
the surface of the screen 26a by airlift 32a. The fi~res
recovered are passed through a classifier 83 to separate
dust and are then suitable for further use having a
consistency equivalent to that of 1 inch chopped strand.
The overs 30a from the screen 26a that concist
mainly of resin are fed via a bin 85 to a grinding mill
50a for grinding into a filler. The output of grinding
mill 50a is filtered in a baghouse 87 and the solids
classified in a cyclone classifier 89. The solids below
the cut size o~ the classifier 89 are collected in bin 93
for use as ~ resin filler. The solids larger than the
cut size of the classifier 89 are combined with the
output of bin 85 to provide a feed for grinding mill 50a.
The unders 28a from screen 26a consist of
shorter fibres and resin and are fed to a further
separation device provided by a second trommel 88. The
trommel 88 is similar to trommel 70 and so will not be
described in detzil. The sieve of trommel 88 i8 a 60
mesh sieve and operates to separate the short fibres from
the resin. Again, the action of the trommel 88 has been
found beneficial in achieving an efficient separation
with resin being retained within the sieve and fed to the -
bin 85 of grind ing mlll 50a. The shorter ~ibres that
pass through the sieve are collected a~ter dedusting by
classifier 95 and have been found to have a consistency
equivalent to that of milled fibre.
The waste product from the cutter 71 is fed
directly into a deduster 97 and then applied to 10 mesh
screen 90. Free fibre is air lifted off the screen 90
and collected in bin 92 where it has a consistency of
chopped strand. The unders and overs from screen 90 are
fed back to the bin 73 to serve as a feed stock for the
- trommel 70.
It will be seen therefore that the process
shown in Figure 4 provides a simple continuous process
that effectively recovers fibres from the SMC waste
relying upon mechanical separation at each stage.
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In initial testing with the process of Figure
4, the fibres recovered from airlift 32a were found to be
31% of the waste feed by weight with 7.2~ of the waste
feed being recovered as medallions from the trom~el 70
and 8.5% being recovered from the overs 30a of the 10
mesh screen 26a.
In the subsequent processing in the trommel 88,
10~ - 15% of the feed stock to the trommel was recovered
as fibres and the balance was fed to the mill 50a.
- A further embodiment of a process to separate
glass fibres is shown in Figure 6 with like reference
numerals to those used in Figure 1 denoting like
components with a suffix b added for clarity. The
embodiment shown in Figure 6 is has been used to process
successfully up to 1800 pounds per hour of SMC waste with
in the order of 1500 pounds per hour providing an optimal
throughput. As such, the embodiment of Figure 6 provides
- a useful indication of the performance attainable from
the process described above.
Referring therefore to Figure 6, waste SMC
product is fed to a shredder 12b and into a pulverizer
24b. The nature of the SMC waste is such that
~ignificant free fibre is not produced in the shredder
12b can be ~ed directly to the pulverizer 24b. An
airstream 68b is also fed to the pulverizer 24b and the
unclassified output supplied to a cyclone classifier 97.
A secondary airstream 99 assists in the transportation of
the output from the pulverizer 24b to the classifier 97.
The classifier 97 removes dust from the unclassified
output and transfers it through an air duct 101 to the
The classified output of the separator 97
passès through an airlock 103 and is supplied to the
trommel 70b. Trommel 70b operates as described above
with respect of Figure 4 with the throughs including the
free fibre and the particulate resin being collected and
delivered to a cyclone classifier 81b. Again the
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throughs are collected from the auger 82b and from the
entrainment of fibres in the airstream passing through
the sieve 74b and are combined prior to entry into the
classifier 81b. The overs from the trommel 70b are fed
through the recovery line 105 to a separator 107. The
separator 107 feeds the fine particles through an air
duct 109 to the filter 79b. The output of the separator
107 passes through an airlock 111 and into the feed for
the pulverizer 24b. The recampaigned overs or medallions
can amount to up to 10~ of the feedstock for the
The classifier 81b separates the fine particles
through an air duct 113 for collection in the filter
house 79b. The fibres and particulate resin are fed
through the airlock 115 of classifier 81b to the 10-mesh
As described above with respect to the 10-mesh
screen 26b, the throughs 28b are fed for further
separation of the shorter fibres as described above with
Figure 4 or with Figure 1. The overs 3Ob from the
10-mesh screen are found to be essentially resin
particles and are directed to the mill 50b for reduction
into fine powder. The free fibres are lifted through the
air lift 32b and directed to a separator 83b where the
fine particulate material is extracted and transferred to
the filter house 79b and the fibre product transferred
through the airlock 11~ for use as a recovered product.
The airlift 32b and the operation of the
10-mesh screen 26b is shown in further detail in Figure
Referring therefore to Figure 7, the screen 26b
supports an open mesh 119 and is vibrated to encourage
particulate material to pass through the mesh 119. The
screen 26b is vibrated by means of an orbital motion at
its upper edge and is constrained to move in a generally
reciprocal motion at its lower edge. The particulate
material passing through the mesh 119 is collected in a
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hopper 121 and transferred as the throughs 28b for ' .
The lower edge of the screen 26b is formed as a
perforated plate 12~ with perforations significantly ~~'
greater than those of the mesh 119. An airlift housing
125 is positioned over the perforated plate 123 and has a
pivoted leading flap 127 and a pivoted trailing flap 129
secured to an air duct 131. A fan (not shown) draws air
through the duct 131 to entrain free fibre and lift it
from the screen 26b.
The airlift housing 125 is positioned a
relatively large distance from the surface of the screen
26b typically in the order of six inches and the flaps
127,129 orientated to encourage fibres to be entrained at
the trailing edge, i.e. adjacent the flap 129, of the
screen 26b; In operation it has been found that as the
throughs of the trommel 70b are deposited on the mesh
119, the throughs are separated leaving free fibre and
the overs progressively moving along the mesh 119. As
the free fibre and overs pass across the perforated
plates 123, the overs pass quic~ly through the
perforations 123 thereby increasing the concentration of
the fibres above the mesh 26b. The fibres are lifted
from the trailing edge after maximum separation has
occurred and thus are relatively clean when transferred
to the cyclone separator 83b. Any material left on the
perforated plate is discharged over the trailing edge
beneath the flat 129 for further processing as described
Exemplary results using the apparatus shown in
Figure 6 as set out below.
T,h,rou~hput % of Shredder Output
_ by wei~h~
Output of shredder 100%
Recampaigned tro~mel overs 10%
Net throughput of pulverizer 24b 110~
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(typically 1500 lb/hr)
Trommel overs (medallions) 10%
10 mesh screen airlift 20
~0 mesh overs 15
10 mesh throughs 55%
(fibres + resin)
Dust recovery in filter 79b 10
(from all stages)
~he fibres recovered from the airlift typically
1~ have a 40% glass content by weight and have a consistency
equivalent to that of 25 mm. chopped strand. The
throughs 28b have been found to have a significant glass
content of shorter fibres typically 35% glass content
with the balance being resin and calcium carbonate
The throughs 28b have been further processed on
a 40-mesh screen similar to that shown at 34 in Figure 1
but without an airlift.
The following results were obtained, expressed
as percentages of the shredder output:
40 mesh overs 30%
(fibre + resin)
40 mesh throughs 25
An analysis of the 40-mesh overs shows a glass
content of 35% by weight with a consistency similar to
that of 8 m~ milled fibre, 27% calcium carbonate filler
and 32% resin.
The 40-mesh throughs have a 2B~ glass content
with a consistency similar to a-3 mm milled fibre, 41%
calcium carbonate ~iller and 31% resin.
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Further processing of the 40-mesh overs and
throughs will therefore yield additional glass product
with the resin and filler being processed by the m~ll 50
~or use as a filler.