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EP 0 776 395 B1 |
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EUROPEAN PATENT SPECIFICATION |
(45) |
Mention of the grant of the patent: |
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02.02.2000 Bulletin 2000/05 |
(22) |
Date of filing: 03.08.1995 |
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International Patent Classification (IPC)7: D21F 1/48 |
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International application number: |
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PCT/FI9500/413 |
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International publication number: |
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WO 9605/370 (22.02.1996 Gazette 1996/09) |
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(54) |
WATER REMOVAL ELEMENT IN A PAPER MACHINE AND METHOD OF MANUFACTURING SUCH AN ELEMENT
ENTWÄSSERUNGSELEMENT IN EINER PAPIERMASCHINE UND VERFAHREN ZUR HERSTELLUNG EINES SOLCHEN
ELEMENTS
ELEMENT D'ELIMINATION DE L'EAU POUR MACHINE A PAPIER, ET SON PROCEDE DE FABRICATION
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(84) |
Designated Contracting States: |
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AT CH DE FR GB IT LI SE |
(30) |
Priority: |
17.08.1994 FI 943777
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(43) |
Date of publication of application: |
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04.06.1997 Bulletin 1997/23 |
(73) |
Proprietor: VALMET CORPORATION |
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00620 Helsinki (FI) |
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(72) |
Inventor: |
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- TELAMA, Ari
FIN-40520 Jyväskylä (FI)
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Representative: Hovi, Simo et al |
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Seppo Laine Oy,
Itämerenkatu 3 B 00180 Helsinki 00180 Helsinki (FI) |
(56) |
References cited: :
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- DIALOG INFORMATION SERVICES, File 347, Japio Database, Accession Number 01903166,
MITSUBISHI HEAVY IND LTD: "Manufacture of Sliding Material for Paper Machine"; & JP,A,61
117 266, 04-06-86.
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Note: Within nine months from the publication of the mention of the grant of the European
patent, any person may give notice to the European Patent Office of opposition to
the European patent
granted. Notice of opposition shall be filed in a written reasoned statement. It shall
not be deemed to
have been filed until the opposition fee has been paid. (Art. 99(1) European Patent
Convention).
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[0001] The invention relates to a fixed water removal element according to the preamble
of claim 1 in a paper or board machine, said element being adapted to squeegee the
wire or press felt of the machine from the side opposite to the sheet side of the
wire/felt.
[0002] The invention also concerns a method of manufacturing such a water removal element.
[0003] water removal elements are subjected to high wearing stresses. As web speeds in modern
paper machines are today in the range 1000 - 1500 m/min, a wire or felt travelling
over the surface of the water removal element hurls past the element at a substantial
velocity. The wear is increased by the fillers used in papermaking such as clay, talc
and chalk, and by unwanted impurities of the papermaking process. Fixed water removal
elements are located at the wet end of the paper machine along its wire section and
press section. Passing over the water removal element in the wire section is a wire
woven from polymer monofilament, whereby the wire permits drainage of water from the
paper sheet of high moisture content at this stage. The water removal elements squeegee
water off the wire or impose a vacuum or pressure shocks on the wire. In the press
section water is removed from the felt by suction.
[0004] Different types of water removal elements are required in varying applications. The
simplest of such elements are planar slices extending over the width of the web aligned
so as to support and squeegee the wire. If the trailing edge of the slice relative
to the machine direction is chamfered, a slice is obtained capable of imposing a pressure
shock on the moving web. Suction boxes are used to remove water from the wire by a
vacuum, and the box cover resting against the wire may comprise slice-like elements
or a drilled surface. Besides these, sliding shoes can be adapted about the wire so
as to opposedly support and press the wire(s). Such sliding shoes may also be employed
to deflect the web and subject it to pressure shocks. The sliding surface of such
shoe elements must be manufactured to close tolerances with a design which is most
durable under the wear imposed by the moving wire or felt and which simultaneously
is very gentle to the wire or felt. Ceramic materials have been found optimally compatible
with these requirements.
[0005] Conventionally, ceramic water removal elements are fabricated by assembling a long
slice comprising adjoining ceramic pieces. The length of the slice is determined by
the web width of the machine. The slice may be prepared from pieces machined to exact
dimension that are mounted onto a precision pedestal, whereby a relatively smooth
surface of the slice results. However, a better end result is achieved by means of
a structure in which the ceramic pieces are adjacently glued to each other and the
ready-assembled slice is ground to correct shape, whereby no height differences remain
between the pieces. The most common materials for the pieces are aluminium oxide,
silicon carbides and zirconium oxide.
[0006] However, a slice structure assembled from ceramic pieces has several shortcomings.
Even if the water removal element is assembled from pieces, the pieces become relatively
massive and thus rather vulnerable to thermal shocks. Temperature variations in a
piece pressed against a web moving at a high speed may be substantially rapid at,
e.g., loss of water film lubrication between the piece and the web. Such thermal shocks
cause local fractures of the pieces and erosion of the piece surfaces which increases
the wear rate of the wire massively. A slice assembled from pieces may become deformed
due to wear or displacement of the pieces. Shape defects of the slices cause disturbances
in water removal and can ruin the sheet being manufactured.
[0007] Yet, the greatest problems plaguing water removal elements made from ceramic pieces
are associated with the inferior chemical and thermal resistance of adhesives used
for joining the pieces. The adhesive applied to the joint has insufficient resistance
to the wide temperature variations and strong chemicals occurring in a paper machine.
The heaviest thermal loads occur when the wire travels without lubrication, that is,
the machine is running dry. In this case the heat of friction can elevate the surface
temperature of the ceramic piece in a few minutes by 120 - 200 °C. Since the thermal
expansion coefficients of the ceramic material, the adhesive and the glass-fiber reinforced
plastic body are different and the temperature profile of the slice is not homogeneous,
substantial thermal stresses will develop in the slice that may detach the ceramic
pieces from each other or totally separate them from the slice body.
[0008] Adhesives employed for bonding the ceramic pieces are not sufficiently resistant
to the warm waters of the paper machine which are chiefly detached from the web being
dried. The degrading effect of the waters is amplified by the residual chemicals of
the papermaking process contained in the waters. Experimental tests on the strength
of an adhesive-bonded joint indicated that already after 200 hours of aging the bond
strength of almost all adhesives was lowered by tens of percent and in some adhesive
grades even below half of their initial strength during this aging period. Because
the strength impairment of the adhesive bond may result in the detachment of the ceramic
pieces, such a drastic loss of bond strength is not acceptable. The ceramic pieces
may also rise above the slice surface which results in a so-called keyboard effect.
Then, the elevated pieces mark the web with detrimental streaks. Hence, a water removal
element requiring no adhesive bonds in its manufacture would be desirable.
[0009] The WO 93/00473 describes a water removal element having a thin wear plate of stainless
steel. The plate is coated by a ceramic coating and it is attached to a support structure
by screws. The plate is thin, whereby it has to be fixed to the support structure
at very short intervals in order to prevent deformation of the plate. Also, the nuts
for the screws are welded into the plate. The drawback of this element is its complicated
structure that is laborious to manufacture mainly because of above mentioned screw
attachment.
[0010] It is an object of the present invention to achieve a cost-efficient and easy-to-manufacture
water removal element having a continuous ceramic sliding surface.
[0011] The goal of the invention is accomplished by manufacturing the water removal element
from a continuous section of metal having its one side covered with a ceramic coat
applied by thermal spray-coating and its interior filled with a cast thermoset plastic
compound.
[0012] More specifically, the water removal element according to the invention is characterized
by what is stated in the characterizing part of claim 1.
[0013] Furthermore, the manufacturing method according to the invention is characterized
by what is stated in the characterizing part of claim 7.
[0014] The invention offers significant benefits.
[0015] The invention is capable of entirely avoiding the use of an adhesive in the manufacture
of a water removal element with a ceramic surface. The vulnerability of the element
to damage is reduced as no piece can become detached therefrom under use. The thin,
ceramic surface of the water removal element is most resistant to thermal shocks,
this making it less sensitive to damage under rapid variations of the element temperature
as compared with conventional ceramic elements. By means of spray-coating, a continuous
surface is obtained, whereby the keyboard effect is avoided which plagues water removal
elements assembled from ceramic pieces. The element has a relatively good inherent
stiffness, because the metallic continuous section forms a shell structure with good
resistance to stresses about the thermoset plastic compound core. Hence, the bodies
of the water removal elements can have a relatively lightweight construction and dispose
of the need for a separate plastic body for ceramic pieces. Due to the corrosion resistance
requirement imposed on a water removal element, stainless steel or other corrosion-resistant
material must be employed in its manufacture. The element structure according to the
invention is capable of minimizing the use of required expensive, stainless material
to a very small amount, whereby a cost-efficient construction results. Hence, the
present type of water removal element may be used in applications where conventional
embodiments made from ceramic pieces have been too costly. The porous coat made by
thermal coating is sealed, whereby good wear resistance and advantageous friction
properties are obtained.
[0016] In the following, the invention will be examined in more detail with reference to
the attached drawings, in which:
Figure 1 is the cross section of a water removal element according to the invention
after its first manufacturing step;
Figure 2 is the cross section of the element illustrated in Fig. 1 after its second
manufacturing step; and
Figure 3 is the cross section of the element illustrated in Figs. 1 and 2 after its
third manufacturing step;
[0017] Referring to the diagrams, a complete water removal element comprises a U-shaped
continuous section 1 having, e.g., a ceramic coat 5 applied onto the base part 3 of
the U-shaped continuous section so as to form a wear-resistant surface, and a thermoset
plastic compound core 6 cast into the continuous section 1. A T-slot is machined into
the thermoset plastic compound core 6, in the area between the legs of the U-shape,
for mounting the water removal element.
[0018] In the embodiment illustrated herein, the continuous section of the water removal
element body is made from stainless steel having its cross section comprising a base
part 3 of the U-shaped continuous section forming a plane to which the legs 2 of the
continuous section are joined extending orthogonally upward from the base part 3.
The joining edge between the base part 3 and the legs 2 is provided with a chamfer
8, and the legs 2 end at inward bent flanges 4. The entire interior of the continuous
section is filled by a thermoset plastic compound core 6.
[0019] A water removal element with the above-described structure is manufactured in the
following manner. A ceramic coat 5 is applied onto the base part 3 of the continuous
section 1 cut to a suitable length by means of thermal spray-coating. Next, the coat
is sealed by impregnating the coat with a low-viscosity material having a high penetration
capability into the coat. Subsequent to the sealing step, the interior of the continuous
section is filled by casting it full of a thermoset plastic compound which is cured,
whereby it adheres to the interior walls of the continuous section 1 thus stiffening
the continuous section 1. To assure good adherence of the plastic compound 6, the
interior walls of the continuous section 1 may be sand-blasted or cleaned by any other
suitable method. After the curing of the plastic compound 6, a mounting slot 7 is
machined into the cast compound for mounting the water removal element at the desired
place in the paper machine by means of a support frame. Finally, the outer surface
of the coat is precision ground to correct shape.
[0020] The water removal element according to the invention may be made from a variety of
different materials. While the optimal material for the base part continuous section
1 is stainless steel, also aluminium, brass, duplex steel and other corrosion-resistant
materials may be employed. The ceramic coat can be made from the following materials
or mixtures thereof: Al
2O
3, Cr
2O
3, ZrO
3, TiB
2, SiO
2, TiO
2, WC and Cr
2C
3. However, when applied by thermal spray-coating, these materials remain more porous
and softer than ceramic pieces made by sintering. Such a porous coat may wear down
paper machine wires by the cutting action of the edges of the pores and the abrading
action imposed on the wire by the filler particles and impurities lodging in the pores.
To avoid such undesirable effects and improve the wear resistance of the coat, the
pores may be sealed with a suitable auxiliary material. Suitable materials are, e.g.,
organic resins and inorganic compounds. Of organic materials, the most suitable are
low-viscosity epoxy resins which can be made to impregnate almost the entire porous
volume of the coat. Moreover, such a sealing treatment improves the durability of
the coat. Of inorganic materials can be used, e.g., phosphate compounds which are
impregnated into the coat from aluminium hydroxide and phosphoric acid solutions.
These compounds are then converted into crystalline form by a heat treatment. Also
these compounds are capable of improving the wear resistance of the coat and their
friction properties may further be enhanced by complementing the sealing treatment
by auxiliary compounds with fluorinated resins. The selection of suitable sealing
compounds is wide and at least phenolic resins, fluorinated resins, epoxy resins,
phosphate compounds and methacrylate resins are well suited for use as sealing compounds.
[0021] Thermal spray-coating can be used for applying coats on metallic surfaces only. Since
the body of a water removal element must be of a non-rusting material, it would become
excessively expensive with respect to competing solutions when made on, e.g. a solid
stainless steel beam. According to the invention, this problem is overcome by manufacturing
the body from a thin-walled continuous section which is stiffened by filling it with
a thermoset plastic compound. In this manner the element can be made both stiff, lightweight
and cost-efficient. Several different types of thermoset plastics are suitable for
use as the fill material of the continuous section including epoxy resins, methacrylate
resins, polyester resins, vinyl ester resins, phenolic resins and mixtures thereof.
To improve the stiffness of the fill material and lower its thermal expansion coefficient,
the resin may be reinforced with, e.g., chopped glass fiber or ceramic particles.
[0022] The above-described type of water removal element is suited for use as a water removal
element squeegeeing a wire or felt. Naturally, the invention may also be applied to
other water removal elements of a paper machine that are in contact with a moving
wire or felt. Then obviously the shape of the element must be modified to suit the
application. As a person versed in the art can readily fabricate elements of different
shape for varied applications on the basis of the foregoing exemplary description,
detailed illustration of such modified shapes will be omitted herein. Also the shape
of the continuous section can be widely varied and, for instance, the use of a continuous
section with a closed perimeter is possible. Then, the outer surface of the section
may be contoured so as to provide the mounting facility of the water removal element.
1. A water removal element in a paper or board machine, said element comprising a body
(1, 6) and a ceramic wear-resisting coat (5),
characterized in that
- said body (1, 6) comprises
- an elongated continuous section forming a bounded space into which a flowing material
(6) can be cast, and at least one surface formed to accommodate the adherence of said
wear-resisting coat (5),
- a thermoset plastic compound fill (6) cast to fill said bounded space at least partially,
and
- said ceramic wear-resisting coat (5) is formed by a ceramic coat (5) applied onto
a surface of the continuous section body (1) by thermal spray-coating.
2. A water removal element as defined in claim 1, characterized in that said continuous section (1) constituting the casting mould has an open cross-sectional
shape, advantageously approximating a U-shape having its interior at least partially
filled with a thermoset plastic compound and having said ceramic coat (5) adhered
to its base part (3).
3. A water removal element as defined in any of claims 1 and 2, characterized by a slot (7) machined into the thermoset plastic compound fill (6) for mounting
the element to a support frame.
4. A water removal element as defined in any of claims 1 - 3, characterized by having the coat (5) made from one of the following compounds: Al2O3, Cr2O3, ZrO3, TiB2, SiO2, TiO2, WC and Cr2C3, or a mixture thereof.
5. A water removal element as defined in any of claims 1 - 4, characterized by having the coat (5) sealed by impregnation with, e.g., a compound selected from
the group of the following compounds: phenolic resins, fluorinated resins, epoxy resins,
phosphate compounds and methacrylate resins.
6. A water removal element as defined in any of claims 1 - 5, characterized by having the fill compound of the continuous section (1) selected from one of the
following groups of compounds: epoxy resins, methacrylate resins, polyester resins,
vinyl ester resins and phenolic resins.
7. A method of manufacturing a water removal element,
characterized in that said method comprises at least the following steps:
- providing a body comprising an elongated continuous section forming a bounded space,
- a ceramic coat (5) is applied onto at least one surface of the continuous section
(1) by thermal spray-coating, and
- the interior of the continuous section (1) is filled at least partially with a thermoset
plastic compound fill (6).
8. A method as defined in claim 7, characterized in that the ceramic coat (5) is sealed by impregnating with a sealing compound.
9. A method as defined in claim 7 or 8, characterized in that a mounting slot (7) is machined into said thermoset plastic compound fill
(6) after the curing step of the plastic compound.
1. Entwässerungselement in einer Papier- oder Kartonmaschine, umfassend einen Körper
(1, 6) und eine keramische Verschleißfläche (5),
dadurch
gekennzeichnet, daß
- der Körper (1, 6)
- ein längliches kontinuierliches Profilstück, das einen begrenzten Raum bildet, in
welchen fliessendes Material (6) gegossen werden kann, und mindestens eine zur Anhaftung
der Verschleißfläche (5) angeordnete Fläche, und
- eine hitzehärtbare Kunststoffmassenfüllung (6) zum zumindest teilweisen Auffüllen
des begrenzten Raumes umfaßt, und
- die keramische Verschleißfläche (5) durch eine im Wärmesprüh-Streichverfahren auf
eine Fläche des kontinuierlichen Profilstücks des Körpers (1) aufgetragene keramische
Strichschicht (5) gebildet ist.
2. Entwässerungselement gemäß Anspruch 1, dadurch gekennzeichnet, daß das die Gußform bildende kontinuierliche Profilstück (1) eine offene, vorzugsweise
einer U-Form angenäherte Querschnittsform aufweist, deren Inneres zumindest teilweise
mit einer hitzehärtbaren Kunststoffmasse ausgefüllt ist und an deren Basisteil (3)
die keramische Strichschicht (5) anhaftet.
3. Entwässerungselement gemäß einem der Ansprüche 1 und 2, gekennzeichnet durch eine in der hitzehärtbaren Kunststoffmassenfüllung (6) einbearbeitete Ausschlitzung
(7) zum Anbringen des Elementes an einen Stützkörper.
4. Entwässerungselement gemäß einem der Ansprüche 1 - 3, dadurch gekennzeichnet, daß die Strichschicht (5) aus einer der folgenden Verbindungen besteht: Al2O3, Cr2O3, ZrO3, TiB2, SiO2, TiO2, WC und Cr2C3, oder aus einer Mischung derselben.
5. Entwässerungselement gemäß einem der Ansprüche 1 - 4, dadurch gekennzeichnet, daß die Strichschicht (5) durch Impregnieren mit z.B. eines aus der Gruppe der folgenden
Stoffe ausgewählten Stoffes abgedichtet ist: Phenolharze, Fluorharze, Epoxydharze,
Phosphatverbindungen und Methacrylharze.
6. Entwässerunselement gemäß einem der Ansprüche 1 - 5, dadurch gekennzeichnet, daß das Füllmittel des kontinuierlichen Profilstücks (1) aus einer der folgenden
Gruppen von Stoffen ausgewählt ist: Epoxydharze, Methacrylharze, Polyesterharze, Vinylesterharze
und Phenolharze.
7. Verfahren zur Herstellung eines Entwässerungselementes, dadurch
gekennzeichnet, daß das Verfahren mindestens die folgenden Schritte umfaßt:
- Bereitstellen eines Körpers umfassend ein längliches kontinuierliches Profilstück,
das einen begrenzten Raum bildet,
- Auftragen einer keramischen Strichschicht (5) auf mindestens eine Fläche des kontinuierlichen
Profilstücks (1) durch Wärmesprüh-Streichverfahren, und
- zumindest teilweises Auffüllen des Inneren des kontinuierlichen Profilstücks (1)
mit einer hitzehärtbaren Kunststoffmassenfüllung (6).
8. Verfahren gemäß Anspruch 7, dadurch gekennzeichnet, daß die keramische Strichschicht (5) durch Impregnieren mit einem Dichtungsmaterial
abgedichtet wird.
9. Verfahren gemäß Anspruch 7 oder 8, dadurch gekennzeichnet, daß nach dem Erhärten der Kunststoffmasse eine Montierungsausschlitzung (7) in der
hitzehärtbaren Kunststoffmassenfüllung (6) einbearbeitet wird.
1. Elément destiné à éliminer l'eau dans une machine à papier ou à carton, ledit élément
comprenant un corps (1, 6) et un revêtement (5) de céramique résistant à la corrosion,
caractérisé en ce que :
- ledit corps (1,6) comprend
- une section continue allongée formant un espace délimité dans lequel un matériau
fluide (6) peut être coulé, et au moins une surface ayant une forme convenable pour
permettre l'adhérence dudit revêtement (5) résistant à l'usure,
- un remplissage de composé plastique (6) thermodurci coulé de façon à remplir ledit
espace délimité au moins partiellement, et
- ledit revêtement (5) de céramique résistant à la corrosion est formé par un revêtement
(5) de céramique appliqué sur une surface du corps de section continue (1) par revêtement
par pulvérisation thermique.
2. Elément destiné à éliminer l'eau suivant la revendication 1, caractérisé en ce que
ladite section continue (1) constituant le moule de coulée présente une forme à section
droite ouverte, avantageusement proche d'une forme en U dont l'intérieur est au moins
partiellement rempli d'un composé plastique thermodurci et ayant ledit revêtement
(5) de céramique collé à sa partie de base (3).
3. Elément destiné à éliminer l'eau suivant l'une quelconque des revendications 1 et
2, caractérisé par une fente (7) usinée dans le composé plastique thermodurci de remplissage
(6) pour le montage de l'élément sur un cadre de support.
4. Elément destiné à éliminer l'eau suivant l'une quelconque des revendications 1 à 3,
caractérisé en ce que le revêtement (5) est fabriqué à partir d'un des composés suivants
: Al2O3, Cr2O3, ZrO3, TiB2, SiO2, TiO2, WC et Cr2C3, ou d'un mélange de ceux-ci.
5. Elément destiné à éliminer l'eau suivant l'une quelconque des revendications 1 à 4,
caractérisé en ce que le revêtement (5) est rendu étanche par imprégnation avec, par
exemple, un composé choisi dans le groupe des composés suivants ; résines phénoliques,
résines fluorées, résines époxy, composés de type phosphate et résines méthacryliques.
6. Elément destiné à éliminer l'eau suivant l'une quelconque des revendications 1 à 5,
caractérisé en ce que le composé de remplissage de la section continue (1) est choisi
dans l'un des groupes suivants de composés : résines époxy, résines méthacryliques,
résines polyester, résines d'ester vinylique et résines phénoliques.
7. Procédé de fabrication d'un élément destiné à éliminer l'eau, caractérisé en ce que
ledit procédé comprend au moins les étapes suivantes :
- la fourniture d'un corps comprenant une section continue allongée formant un espace
délimité,
- l'application d'un revêtement (5) de céramique sur au moins une surface de la section
continue (1) par revêtement par pulvérisation thermique, et
- le remplissage de l'intérieur de la section continue (1) au moins partiellement
avec un remplissage de composé plastique thermodurci (6).
8. Procédé suivant la revendication 7, caractérisé en ce que le revêtement (5) de céramique
est rendu étanche par imprégnation avec un composé d'étanchéité.
9. Procédé suivant les revendications 7 ou 8, caractérisé en ce qu'une fente de montage
(7) est usinée à l'intérieur dudit remplissage (6) de composé plastique thermodurci
après l'étape de durcissement du composé plastique.