U.S. patent application number 12/919975 was filed with the patent office on 2011-05-12 for product based on mineral fibers and process for obtaining it.
This patent application is currently assigned to SAINT-GOBAIN ISOVER. Invention is credited to Arnaud Letourmy, Eric Mangematin, Patrice Martins.
Application Number | 20110111198 12/919975 |
Document ID | / |
Family ID | 39938348 |
Filed Date | 2011-05-12 |
United States Patent
Application |
20110111198 |
Kind Code |
A1 |
Letourmy; Arnaud ; et
al. |
May 12, 2011 |
PRODUCT BASED ON MINERAL FIBERS AND PROCESS FOR OBTAINING IT
Abstract
A thermal insulation product based on mineral wool,
characterized in that the fibers have a micronaire of less than 10
l/min, preferably less than 7 l/min and especially between 3 and 6
l/min, and in that the material has a thermal conductivity of less
than 31 mW/mK, especially less than 30 mW/mK. The parameters for
obtaining this product are in particular the pressure of the
burner, the rotation speed of the fiberizing spinner and the daily
fiber output per spinner orifice.
Inventors: |
Letourmy; Arnaud; (Margny
Les Compiegne, FR) ; Mangematin; Eric; (Cires les
Mello, FR) ; Martins; Patrice; (Lamorlaye,
FR) |
Assignee: |
SAINT-GOBAIN ISOVER
Courbevoie
FR
|
Family ID: |
39938348 |
Appl. No.: |
12/919975 |
Filed: |
February 27, 2009 |
PCT Filed: |
February 27, 2009 |
PCT NO: |
PCT/FR2009/050326 |
371 Date: |
December 7, 2010 |
Current U.S.
Class: |
428/220 ;
181/284; 428/221; 65/460 |
Current CPC
Class: |
C03B 37/04 20130101;
D04H 1/4374 20130101; C03B 37/048 20130101; Y10T 428/249921
20150401; D04H 1/74 20130101; C03B 37/045 20130101; D04H 1/4209
20130101; D04H 1/4226 20130101; D04H 1/4218 20130101 |
Class at
Publication: |
428/220 ;
428/221; 65/460; 181/284 |
International
Class: |
B32B 17/04 20060101
B32B017/04; B32B 5/02 20060101 B32B005/02; C03B 37/04 20060101
C03B037/04; E04B 1/88 20060101 E04B001/88 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 28, 2008 |
FR |
0851281 |
Claims
1. A thermal insulation product comprising fibers of mineral wool,
wherein the fibers have a micronaire of less than 10 L/min and
product has a thermal conductivity of less than 31 mW/mK.
2. The thermal insulation product of claim 1, having a density of
at least 30 kg/m.sup.3.
3. The thermal insulation product of claim 1, wherein the fibers
are essentially parallel to length dimensions of the product.
4. The thermal insulation product of claim 1, wherein a structure
of the mineral wool comprises the fibers, bound together by a
binder, in proportions of 5 to 8% by weight of the product.
5. The thermal insulation product of claim 1, having a thickness
equal to or greater than 30 mm.
6. The thermal insulation product of claim 1, in the form of a cut
panel, optionally comprising several layers.
7. An acoustic insulation system comprising thermal insulation
product of claim 1.
8. The thermal insulation product of claim 1, comprising glass
fibers with a proportion of unfiberized material of less than
1%.
9. The thermal insulation product of claim 1, obtained from an
internal centrifugation fiberizing process.
10. A wall and/or roof lining comprising the product of claim
1.
11. A process for manufacturing mineral wool with an installation
comprising an internal centrifugation device that comprises a
spinner capable of rotating about an axis X, and the peripheral
band of which is drilled with a plurality of orifices for
delivering filaments of a molten material, a high-temperature gas
attenuating unit in the form of an annular burner, which attenuates
the filaments into fibers, and a receiving belt associated with
suction device for receiving the fibers, said process comprising
controlling a combination of parameters, these being, at least, the
pressure of the burner between 450 and 750 mmWC, rotation of the
spinner at a speed greater than 2000 revolutions/minute, and daily
fiber output per spinner orifice, which is at most 0.5 kg.
12. The process of claim 11, wherein a throughput of molten
material entering the spinner is less than 18 tonnes/day for a
spinner having at least 32 000 orifices.
13. The process of claim 11, wherein the spinner has a diameter of
between 200 and 800 mm, and the fiber output per orifice is adapted
to the diameter of the spinner.
14. The process of claim 11, wherein the spinner has an
orifice-perforated band height of at most 35 mm.
15. The process of claim 11, wherein a diameter of the spinner
orifices is between 0.5 and 1.1 mm.
16. The process of claim 11, wherein the orifices of the spinner
are distributed in several annular zones, and the orifices have,
from one zone to another, rows of orifices of different diameter,
and the diameter per annular row decreases, in a centrifugation
position, from a top of a peripheral band of the spinner toward the
bottom.
17. The process of claim 16, wherein a distance between centers of
neighboring orifices in a same annular zone may or may not be
constant throughout an annular zone, and this distance varies from
one zone to another by at least 3%, and, in the centrifugation
position, decreases from the top of the peripheral band of the
spinner toward the bottom, with a distance between 0.8 mm and 2
mm.
18. The process of claim 11, wherein the installation further
comprises a conveyor that extends the receiving belt, the run speed
of the conveyor being greater than the run speed of the receiving
belt, by more than 10%.
19. The thermal insulation product of claim 1, wherein the fibers
have a micronaire of less than 7 L/min.
20. The thermal insulation product of claim 1, wherein the fibers
have a micronaire of between 3 and 6 L/min.
Description
[0001] The invention relates to products based on mineral wool,
such as glass wool, intended especially for making up thermal and
possibly acoustic insulation products, more particularly for the
lining of walls and/or roofs.
[0002] In the insulation market, suppliers always wish to provide
products of ever greater performance in terms of thermal
insulation. The thermal performance of a product is generally
obtained by knowing the thermal conductivity .lamda.. It will be
recalled that the thermal conductivity .lamda. of a product is the
capacity of the product to let through a heat flux: .lamda. is
expressed in W/mK. The lower this conductivity, the more insulating
the product, and therefore the better the thermal insulation.
[0003] Commercially available products based on mineral fibers,
which are made of rock wool or glass wool, have a thermal
conductivity between 0.040 and 0.035 W/mK, or at best 0.032 W/mK.
Unless otherwise specified, the thermal conductivity is that
measured conventionally at 10.degree. C. according to the ISO 8301
Standard.
[0004] Other approaches enable a thermal conductivity of 0.032
W/mK, or even 0.031 W/mK, to be obtained, but these involve
completely different products, such as those based on special
expanded polystyrenes. However, the invention lies solely within
the field of products based on mineral fibers.
[0005] Products based on mineral wool, particularly glass wool, are
obtained by a known internal centrifugation process combined with
attenuation by a high-temperature gas stream.
[0006] This fiber-forming process consists in introducing a molten
glass stream into a spinner, also called a fiberizing dish,
rotating at high speed and pierced around its periphery by a very
large number of orifices through which the glass is ejected in the
form of filaments owing to the effect of the centrifugal force.
These filaments are then subjected to the action of an annular
high-velocity high-temperature attenuating gas stream produced by a
burner and hugging the wall of the spinner, which gas stream
attenuates said filaments and converts them to fibers. The fibers
formed are entrained by this attenuating gas stream to a receiving
device, generally consisting of a gas-permeable belt which is
combined with suction means. A binder needed to bind the fibers
into a wool product is sprayed onto the fibers while they are being
drawn to the receiving device. The accumulation of fibers on the
receiving device under the effect of the suction provides a fiber
mat, the thickness of which may vary depending on the final product
to be obtained.
[0007] This process for converting glass into fibers is extremely
complex and requires a large number of variable parameters to be
balanced. In particular, the pressure of the burner and the
velocity of the attenuating gas play an important role in fiber
refining optimization. The design of the fiberizing spinner is also
an important factor.
[0008] In general, the fibers obtained by internal centrifugation
have an average diameter of 3 .mu.m, which corresponds to a
micronaire of 3 under 5 grams, or else an average diameter of 2
.mu.m, which corresponds to a micronaire of 2.8 under 5 grams.
[0009] It will be recalled that the fineness of fibers is
determined by the value of their micronaire (F) under 5 g. The
micronaire measurement, also called "fineness index" measurement,
takes into account the specific surface area by measuring the
aerodynamic pressure drop when a given quantity of fibers extracted
from an unsized blanket is subjected to a given pressure of a gas,
in general air or nitrogen. This measurement is standard practice
in mineral fiber production units, is carried out according to the
DIN 53941 or ASTM D 1448 Standard and uses what is called a
"micronaire apparatus".
[0010] However, such an apparatus has a measurement limit as
regards a certain fiber fineness. For very fine fibers, the
fineness (micronaire) may be measured in l/min using a known
technique described in patent application WO 2003/098209. This
patent application specifically relates to a device for determining
the fineness index of fibers and comprises a device for measuring
the fineness index, said fineness index measurement device being
provided, on the one hand, with at least a first orifice connected
to a measurement cell designed to receive a specimen consisting of
a plurality of fibers and, on the other hand, with a second orifice
connected to a device for measuring the differential pressure on
either side of said specimen, said differential pressure
measurement device being intended to be connected to a fluid flow
production device, characterized in that the fineness index
measurement device includes at least one volume flow meter for
measuring the volume of fluid passing through said cell. This
device provides correspondences between micronaire values and
liters per minute (l/min).
[0011] By way of indication, according to the document WO
2003/098209, a correspondence relationship between micronaire value
and average diameter of the fiber specimen may be noted. In
general, a micronaire value of about 12 l/min corresponds to an
average diameter of 2.5 to 3 .mu.m, a 13.5 l/min value corresponds
approximately to an average diameter of 3 to 3.5 .mu.m, and finally
an 18 l/min value corresponds to an average diameter of about 4 to
5 .mu.m.
[0012] Fine fibers with an average diameter of about 3 .mu.m have
been produced for certain applications.
[0013] In particular, to obtain glass webs a few millimeters in
thickness for the purpose of producing aerosol filters or battery
separators, document WO 99/65835 provides an internal
centrifugation device which thus permits fibers with a diameter of
about 3 .mu.m to be obtained. The device of the above document
comprises a spinner provided with orifices arranged in rows, at
least two adjacent rows having orifices of different diameters and
the height over which fibers are formed by the spinner is equal to
or less than 35 mm. However, this type of application for filters,
which also uses very thin products, is very far from the
application to thermally insulating products and in no way makes
reference to the concept of thermal conductivity.
[0014] For another application, for the purpose of producing
insulation products, document EP 1 370 496 discloses an internal
centrifugation device that delivers fine fibers, the average
diameter of which is not greater than 3.5 microns, with 2.1 .mu.m
as the smallest diameter obtained.
[0015] For this purpose, the burner of the above device has certain
specific features in combination with a particular configuration of
the spinner. The spinner thus comprises at least two annular zones,
the number of orifices per unit area of which differs by an amount
of 50 or more, the distance between the centers of the closest
neighboring orifices of a given annular zone being approximately
constant over the entire given annular zone, and this distance
varying from one zone to another by at least 3%, decreasing in the
centrifugation position of the spinner from the top downward.
[0016] Such a device, which generates finer fibers, improves the
thermal conductivity of the products obtained for a density
equivalent to that of the usual products. The example given in the
above document is a product with a thickness of 80 mm providing, at
low density (9 kg/m.sup.3), quite a good conductivity (41.2
W/mK).
[0017] However, it is always desirable to improve the thermal
conductivity of a product so as to achieve a satisfactory
insulation performance without correspondingly using an excessively
high thickness. This is because, depending on the thermal
conductivity of the material constituting the product, the
thickness of the product must be adapted in order to provide a
highest possible performance, expressed by a thermal resistance
(denoted by R).
[0018] It is clear that with the product disclosed in the above
document EP 1 370 496, the wish to increase the thermal resistance
necessitates increasing the thickness of the product significantly,
something which would not be compatible with certain building
insulation applications.
[0019] The object of the invention is therefore to provide a
thermal insulation product based on mineral fibers that has
improved thermal insulation properties so that it can be used in
reasonable thicknesses for the building application to which this
product is intended.
[0020] According to the invention, the thermal insulation product
based on mineral wool is characterized in that the fibers have a
micronaire of less than 10 l/min, in particular at most 9 l/min,
preferably less than 7 l/min and especially between 3 and 6 l/min,
and in that the product has a thermal conductivity of less than 31
mW/mK and preferably less than 30 mW/mK.
[0021] The product is thus characterized by an average fiber
diameter of less than 2 .mu.m or even less than 1 .mu.m.
[0022] According to the invention, it turns out that, for a
specific thermal insulation application, a product containing even
finer fibers than in the prior art can be successfully manufactured
with a structure such that the product is characterized by an even
better thermal conductivity than in the prior art. The product of
the invention incontestably enables better thermal insulation
performance to be achieved and, because of the fineness of its
fibers, is also a softer product which is pleasant to handle.
[0023] According to one feature, the density of the product is at
least 30 kg/m.sup.3, preferably between 35 and 60 kg/m.sup.3, and
in particular between 40 and 55 kg/m.sup.3.
[0024] Advantageously, the fibers are essentially, especially in a
proportion of at least 75%, approximately parallel to the long
dimensions of the product, which is substantially of rectangular
parallelepipedal shape. The term "approximately parallel" is
understood to mean a parallelism to within plus or minus 30.degree.
with respect to the planes forming the long dimensions of the
product. This parallel arrangement of the fibers thus resists the
transmission of heat through the thickness of the product
(perpendicular to said planes). The proportion of fibers oriented
along the thickness of the product (perpendicular to the long
dimensions) is minimized, with the result that heat transmission
via the air passages in the form of fibers chimneys lying between
these fibers is prevented.
[0025] The structure is essentially a mineral wool structure
composed of fibers, particularly glass fibers, bound together by a
binder, in proportions of 5 to 8% by weight of the product.
[0026] It is desirable, in view of the application of the product,
to add standard additives of the oily type, in order to pick up
dust, of the antistatic type or of the water-repellent type, such
as silicone.
[0027] According to another feature, the thickness of the product
is at least 30 mm, especially from 40 to 150 mm, depending on the
intended application and the desired thermal resistance.
[0028] To obtain a product of suitable thickness, the product may
take the form of a cut panel, optionally composed of several
layers.
[0029] The product is used more particularly for the lining of
walls and/or roofs in the building industry.
[0030] This thermally insulating product may also be integrated
into an acoustic insulation system.
[0031] Preferably, the product is based on glass fibers, the
proportion of unfiberized material not exceeding 1% in order to
limit heat transfer even better.
[0032] The product of the invention is preferably obtained by an
internal centrifugation fiberizing process, using a fiberizing
installation having fiberizing parameters adapted so as to provide
fibers with the desired fineness index.
[0033] According to the invention, the mineral wool manufacturing
process employs an installation that comprises an internal
centrifugation device that comprises a spinner capable of rotating
about an axis X, especially a vertical axis, and the peripheral
band of which is drilled with a plurality of orifices for
delivering filaments of a molten material, a high-temperature gas
attenuating means in the form of an annular burner, which
attenuates the filaments into fibers, and a receiving belt
associated with suction means for receiving the fibers, and is
characterized in that said process consists in controlling a
combination of parameters, these being, at least, the pressure of
the burner between 450 and 750 mmWC (water column), the rotation of
the spinner at a speed greater than 2000 revolutions/minute and the
daily fiber output per spinner orifice, which is at most 0.5 kg and
preferably at most 0.4 kg.
[0034] For a given spinner configuration according to the
invention, the pressure of the burner is thus 500 mmWC and at most
750 mmWC, so as for example to generate fibers with a micronaire of
5.5 l/min and 3.4 l/min respectively. These pressure values do not
cause excessive turbulence, allow the fiber layers to be stacked
uniformly on the receiving belt and deliver fiber which is highly
advantageously slightly longer.
[0035] According to one feature, the process of the invention is
such that the throughput of molten material entering the spinner is
less than 18 tonnes/day for a spinner having at least 32 000
orifices, and preferably in a combination of throughput of at most
14 tonnes/day and of a spinner with at least 36 000 orifices.
[0036] Spinners with a diameter of 600 mm generally do not have
more than 32 000 orifices. In contrast, the invention provides a
spinner having substantially more orifices than in the prior art,
by increasing the number of orifices per unit area.
[0037] The diameter of the spinner is a diameter of between 200 and
800 mm, the fiber output per orifice being adapted to the diameter
of the spinner.
[0038] The height of the perforation band of the spinner preferably
does not exceed 35 mm.
[0039] The spinner contains two or more annular zones superposed
one above the other, the spinner orifices having, from one zone to
another, rows of orifices of different diameter, and the diameter
per annular row decreasing, in the centrifugation position, from
the top of the peripheral band of the spinner toward the bottom.
The diameter of the orifices is between 0.5 and 1.1 mm.
[0040] According to yet another feature, the distance between the
centers of neighboring orifices in the same annular zone may or may
not be constant throughout an annular zone, and this distance
varies from one zone to another by at least 3% or even by at least
10%, and, in the centrifugation position, decreases from the top of
the peripheral band of the spinner toward the bottom, with in
particular a distance between 0.8 mm and 2 mm.
[0041] The process of the invention thus provides, by the
adjustments, essentially in the pressure of the burner, in the
rotation speed of the spinner and, unexpectedly, in the daily
output of molten material per spinner orifice, a product composed
of fibers that are particularly fine, with a micronaire of less
than 10 l/min, and, for more than 65% of the fibers, with an
average diameter of less than 1 .mu.m, accompanied by a thermal
conductivity of less than 31 mW/mK, even less than 30 mW/mK,
something not offered by the prior art.
[0042] Furthermore, to contribute to the consequent lowering of the
thermal conductivity, the process of the invention provides the
flattest possible arrangement of fibers, i.e. in a fiber
arrangement parallel to the long dimensions of the product.
[0043] This arrangement is in particular obtained by
characteristics relating to the receiving of the fibers and to the
removal thereof by the conveyor that extends the receiving belt.
For this purpose, the process of the invention consists in
regulating the run speed of a conveyor butted onto the receiving
belt which is greater than the run speed of said receiving belt, in
particular by more than 10% and preferably by at least 15%.
[0044] Other advantages and features of the invention will now be
described in greater detail with regard to the appended drawings in
which:
[0045] FIG. 1 illustrates a schematic vertical cross-sectional view
of a fiberizing installation according to the invention; and
[0046] FIG. 2 illustrates a schematic vertical cross-sectional view
of the fiberizing device of the installation.
[0047] FIG. 1 shows schematically a cross-sectional view in a
vertical plane of an installation 1 for forming a mineral wool
blanket.
[0048] The installation 1 comprises, in a known manner from
upstream to downstream, or from the top down, along the direction
of flow of the attenuable material in the molten state, an internal
centrifugation device 10 that delivers filaments of an attenuable
material, an attenuation device 20 delivering a gas stream that
converts the filaments into fibers, which fall in the form of a web
2, an annular inductor 30 placed beneath the centrifugation device
10, a binder supply device 40, and a belt 50 for receiving the
fibers, on which the fibers accumulate so as to form the blanket.
The blanket is then conveyed to an oven in order to cure the fibers
and the binder by means of a conveyor belt 60 that extends the
receiving belt 50 in the same plane.
[0049] FIG. 2 illustrates the devices 10, 20 and 30 of the
fiberizing installation in greater detail.
[0050] The centrifugation device 10 comprises a spinner 11, also
called a fiberizing dish, rotating at high speed, having no bottom
in its lower part, and pierced around its peripheral wall 12 by a
very large number of orifices via which the molten material is
ejected in the form of filaments owing to the centrifugal
force.
[0051] The bottomless spinner 11 is fastened to a hub held on a
vertically mounted hollow shaft 13 rotating about an axis X, the
shaft being driven by a motor (not shown).
[0052] A basket 14 with a solid bottom is connected to the spinner,
being placed inside the spinner, so that its opening faces the free
end of the hollow shaft 13 and its wall 15 is substantially away
from the peripheral wall or band 12.
[0053] The cylindrical wall 15 of the basket is perforated by a
small number of relatively large orifices 16, for example having a
diameter of around 3 mm.
[0054] A stream of molten glass feeds the spinner, passing through
the hollow shaft 13 and flowing out into the basket 14. The molten
glass, by passing through the basket orifices 16, is then delivered
in the form of primary streams 16a directed toward the inside of
the peripheral band 12, from where they are expelled in the form of
filaments 17a through the spinner orifices 17 owing to the
centrifugal force.
[0055] The attenuation device 20 consists of an annular burner that
delivers a high-temperature high-velocity gas stream, said stream
hugging the spinner wall 12. This burner serves to maintain the
high temperature of the spinner wall and contributes to the
attenuation of the filaments so as to convert them into fibers.
[0056] The attenuating gas stream is generally channeled by means
of a surrounding cold gas sheath. This gas sheath is produced by a
blowing ring 21 that surrounds the annular burner. Said cold gas
sheath also helps to cool the fibers, the strength of which is thus
improved by a thermal quenching effect.
[0057] The annular inductor 30 heats the underside of the
centrifugation device so as to help to maintain the thermal
equilibrium of the spinner 11.
[0058] The binder supply device 40 consists of a ring through which
the web of fibers 2 flows. The ring includes a multiplicity of
nozzles that spray the web of fibers with binder. Usually, the
binder that helps to provide mutual cohesion of the fibers includes
anti-dust agents, of the oily type, and antistatic agents.
[0059] The mineral material that is converted into fiber is
preferably glass.
[0060] Any type of glass convertible by the internal centrifugation
process may be suitable.
[0061] It may for example preferably be a lime-borosilicate glass
containing significant amounts of boron.
[0062] According to the invention, fine fibers are obtained by
regulating various parameters, in particular:
[0063] the pressure of the burner 20;
[0064] the rotation speed of the spinner 11; and
[0065] the daily output of fibers delivered by each spinner orifice
17.
[0066] The annular burner 20 is of standard design. The temperature
of the gas jet at its outlet is between 1350 and 1500.degree. C.,
preferably around 1400.degree. C.
[0067] According to the invention, the pressure of the burner is
set between 450 and 750 mmWC (it will be recalled that 1 mmWC=9.81
Pa) so as to generate an attenuating gas jet best suited to the
desired fiber fineness, in combination with the other
aforementioned parameters. Although usually the pressure of a
burner is 500 mmWC, it is possible according to the invention to
choose to increase the pressure so as to make thinner fibers.
However, this requires more energy. There has to be a compromise
between the various abovementioned parameters in order to obtain
the desired product depending on the economic and energy factors to
be taken into account.
[0068] According to the invention, the rotation speed of the
spinner is more rapid than the usual 1900 revolutions per minute
(rpm). The spinner of the invention rotates at a speed of greater
than 2000 rpm, for example 2200 rpm.
[0069] According to the invention, the fiber output per spinner
orifice is at most 0.5 kg/day and preferably does not exceed 0.4
kg/day. The daily fiber output per orifice corresponds to the
throughput of molten material passing through each orifice per
day.
[0070] This output is of course dependent on the throughput of
molten material delivered upstream of the spinner and on the number
of orifices drilled in the spinner. According to the invention, the
throughput of molten material does not exceed 19 tonnes per day
(t/day) and preferably does not exceed 14 t/day. In comparison, the
usual output of a furnace delivering molten glass is generally
around 23 to 25 tonnes per day. The spinner itself has at least 32
000 orifices, preferably at least 36 000 orifices, and therefore a
larger number than in a standard spinner, which is generally 31
846.
[0071] The spinner has a diameter of between 200 mm and 800 mm, the
number of orifices and the output of molten material delivered
being adapted accordingly. The fiber output delivered by a spinner
will be lower the smaller the diameter of the spinner. The diameter
is preferably 600 mm.
[0072] The spinner contains two or more annular zones superposed
one above the other, each zone being provided with one or more
annular rows of orifices. Certain particular features relating to
the spinner can also help to obtain fine fibers.
[0073] The perforated band height of the spinner--the height over
which the orifices are spread--does not exceed 35 mm.
[0074] The spinner orifices have, from one zone to another, rows of
orifices with different diameters, and the diameter per annular row
decreasing, in the centrifugation position, from the top of the
peripheral band of the spinner downward. The diameter of the
orifices is between 0.5 and 1.1 mm.
[0075] The distance between the centers of neighboring orifices in
the same annular zone is essentially constant throughout an annular
zone, this distance varying from one zone to another by at least
3%, or even at least 10%, and decreasing, in the centrifugation
position, from the top of the peripheral band of the spinner
downward, in particular with a distance of between 0.8 mm and 2
mm.
[0076] According to the invention, the metered amount of binder
delivered by the ring 40 is advantageously between 5 and 8% and
preferably between 5 and 7%. The amount of binder customarily
necessary in the usual products and in proportions of 8%, or
higher, is here replaced by the amount of fiber; the product thus
has a higher weight of fiber, leading to an increase in the thermal
conductivity .lamda..
[0077] Finally, the lowering of the thermal conductivity .lamda. is
also dependent on the arrangement of the fibers in the blanket.
More than 75%, or even more than 85%, of the fibers are arranged so
as to be approximately parallel to the long dimensions of the
product. For this purpose, the run speed of the conveyor belt 60
is, according to the invention, faster than the speed of the
receiving belt 50 by more than 10% and preferably by at least
15%.
[0078] This change in speed with acceleration makes the fibers lie
as flat as possible in the run plane of the belts, being therefore
oriented substantially parallel to the longest dimensions of the
fiber blanket obtained, i.e. horizontally to the plane of the belts
to within plus or minus 30.degree..
[0079] An example of a product according to the invention obtained
in accordance with the method of the invention is presented
below.
[0080] The installation comprised a fiberizing spinner 600 mm in
diameter with 36 000 orifices, having an arrangement of orifices
and diameter of the orifices as described above.
[0081] The daily output per orifice was 0.4 kg.
[0082] The rotation speed of the spinner was 2200 rpm.
[0083] The pressure of the burner was 500 mmWC.
[0084] The speed of the conveyor 60 was 15% higher than that of the
receiving belt.
[0085] The product obtained had the following characteristics:
[0086] a fiber fineness index of 5.5 l/min;
[0087] more than 65% of the fibers had an average diameter of less
than 1 .mu.m;
[0088] a thermal conductivity of 29.6 mW/mK, measured at 10.degree.
C. according to the ISO 8301 Standard;
[0089] a density of 45 kg/m.sup.3;
[0090] a binder content of 5% by weight of the product;
[0091] a thickness of 45 mm; and
[0092] more than 80% of the fibers were substantially parallel to
the long dimensions.
[0093] The orientation of the fibers was determined in the
following manner: several (especially at least six)
parallelepipedal specimens, of the same size and with the same
thickness as the product, were removed from said product. They were
cut by means of a cutting instrument, such as a blade producing a
sharp cut without dragging fibers in the cutting direction, thus
not disturbing the fiber arrangement forming the product before
cutting. Each specimen was observed edge-on, the observed surface
was divided into small unitary areas, the fibers being detected
visually in each unit area, the angle made between the fiber
direction and a horizontal direction parallel to a long dimension
of the product was recorded and the average angle in each of the
areas was calculated. An image acquisition tool coupled to image
processing software was used for this purpose. For each specimen,
the fraction of fibers having an angle of orientation falling
within a given angular sector was thus determined. The average of
the data for each specimen was then averaged so as to express the
orientation of the fibers in the product. In this example, it was
found that 80% of the recorded angles lay within the
0.degree.-30.degree. and 150.degree.-180.degree. sectors
(horizontal fibers), whereas 15% of the recorded angles lay within
the 30.degree.-60.degree. and 120.degree.-150.degree. sectors
(oblique fibers) and 5% of the recorded angles lay within the
60.degree.-90.degree. and 90.degree.-120.degree. sectors (vertical
fibers).
[0094] Stable production of this product is obtained under
conditions meeting the requirements of the EN 13162 Standard, the
stated thermal conductivity value expressing the limit representing
at least 90% of the production, determined with a 90% confidence
level.
[0095] It is also possible to obtain a product with an even lower
micronaire of 3.4 l/min with the burner pressure increased to 750
mmWC.
[0096] This product may be compared with a product obtained in a
more standard fashion using the same 600 mm spinner, but one having
31 846 orifices and a daily fiber output per orifice of 0.7 kg, the
burner pressure being 500 mmWC and the spinner rotation speed being
1900 rpm.
[0097] The comparative product produced had the following
characteristics:
[0098] a fiber fineness index of 2.8 under 5 g, which represents a
value of greater than 10 l/min;
[0099] an average fiber diameter of 2 .mu.m;
[0100] a thermal conductivity of 34 mW/mK;
[0101] a density of 50 kg/m.sup.3; and
[0102] a thickness of 50 mm.
[0103] To provide a thicker product, for example with a thickness
of 90 mm or more, thus giving a thermal resistance of 3 or more,
the invention proposes to assemble at least two layers of the
product that has just been described. This superposition of layers
may be achieved before crosslinking the binder, by combining two
plies between reception and the oven, especially between the
conveyor belt 60 and the oven. Cohesion of the two plies is
provided by the sharing of the uncrosslinked binder present at the
interface between the two plies and by crosslinking the binder
throughout the product in the oven.
[0104] Consequently, the configuration of the fiberizing
installation according to several specific features, dependent most
particularly on the rotation of the fiberizing spinner, on the
burner and the fiber output, and additionally dependent on the
receiving belt and on the conveyor following it, have made it
possible, in a non-obvious manner, to obtain the thermal insulation
product of the invention, which hitherto has not existed.
[0105] The product of the invention, because of its very fine
fibers, offers the advantage of a softer feel, making it much less
disagreeable to handle.
[0106] The product, through its considerably lowered thermal
conductivity, provides even better thermal insulation and achieves
an optimum thermal resistance for reasonable thicknesses.
[0107] Finally, the product of the invention, through its density
preferably greater than 30 kg/m.sup.3, takes the form of relatively
rigid sheets which furthermore, because of a standard thickness,
can thus be easily handled and can be easily cut and positioned as
required against the walls to be insulated. In addition, as may be
seen in the case of the comparative example, it is possible to
reduce the density of the product, the product therefore being
lighter, to reduce its thickness and to achieve a better thermal
conductivity.
* * * * *