EP1048782A1 - Soft roll and process for making such a roll - Google Patents

Abstract

The calender roller, to polish the surface of a paper web, has a hard metal core (1) and an elastic outer cladding (2). The cladding (2) is composed of a matrix material (3) with filling materials (6,7) at least partially of longitudinally-drawn and especially rod-shaped particles (6), with a length which is less than the radial thickness of the elastic cladding (2). The particles have a length:thickness ratio of 20:1 to 5:1 and especially 15:1 to 7:1 and pref. 10:1 and/or they are in a statistical distribution radially and/or axially in the matrix material (3). The majority of the particles (6) are on a radial alignment in the matrix (3) or they are in a statistical alignment distribution. The particles (6) are of a heat conductive mate with a thermal conductivity which is higher than the material of the matrix (3) and/or part of the particles (6) extend radially inwards to the surface (9) of the metal core (1) and/or the particles (6) have a thermal expansion coefficient which is lower th the matrix (3). The particles (6) are stiffer than the matrix material (3) and/or part of the particles (6) extends radially outwards to the outer surface (8) of the elastic cladding (2) and/or the particles (6) have an average length of 200-600 mu m an especially 300-500 mu m and pref. 400 mu m and/or the particles (6) are of wollastonite and/or calcium silicate. Fibers (4) of g and/or carbon are embedded in the matrix (3), in addition to the particles (6), in a fiber layer (5) or in radially successive f layers spaced apart or against each other. The elastic cladding (2) contains 5-100 fiber layers (5), and especially 20-70 layers pref. 30-40 layers and/or the particles are between the separate fiber layers (5). The cladding has an outer functional layer an inner bonding layer, to bond it to the roller core. The particles are mainly in the functional layer. The matrix material (3) is heat-setting or thermoplastic and/or is a combined resin/hardener. An Independent claim is included for the prodn. of a cladded roller where the elastic matrix material is augmented by longitudinally drawn and especially rod-shaped particles, with a shorte length than the radial thickness of the cladding. Fibers are also added to the matrix material. Preferred Features: To produce t cladding layer, at least one bundle of a number of fibers is wound round the roller core in a number of overlaid layers. The particles are added between the wound fiber layers and/or between the fiber layer and the roller core surface and/or between the fiber layer and the outer cladding surface. The fiber bundle is formed by one or more fiber rovings and/or a fiber web. The rovi is composed of a number of adjacent fibers of the same type and/or the fiber bundle is formed by a web. Before winding, the fibe bundle is coated with a matrix material, especially through a bath which contains the particles in the bath, and the saturated bundle is wound round the core. Or the fiber bundle is dry, on winding round the roller core, and is treated with the matrix material during or after winding so that the fibers are wholly embedded in the matrix.

Description

The present invention relates to a roller, in particular for smoothing of paper webs, with a hard one consisting in particular of metal Roll core, on the outside with an elastic reference layer is provided, which is made of an elastic matrix material and in the There is matrix material embedded fillers. Furthermore, the invention directed to a method of making such a roller.

Elastic rolls of this type are used, for example, when satinizing paper webs. An elastic roller forms a press nip together with a hard roller through which the paper web to be processed is passed. While the hard roller has a very smooth surface, for example made of steel or cast iron, and is responsible for smoothing the side of the paper web facing it, the elastic roller acting on the opposite side of the paper web causes the paper web to be leveled and compressed in the press nip. The size of the rollers is 3 to 12 m in length and 450 to 1500 mm in diameter. They withstand line forces up to 600 N / mm and compressive stresses up to 130 N / mm ² .

Since the tendency in papermaking is that the satin in Online operation takes place, i.e. that the the paper machine or coating machine leaving the paper web directly through the paper smoothing device (Calender) is guided to the rollers of the smoothing device higher demands in particular with regard to temperature resistance than previously posed. Due to the high required in online operation Transport speeds of the paper web and the associated high rotational speeds of the calender rolls, their nip frequency, that is the frequency at which the reference compresses and again is relieved, increased, which in turn leads to increased roller temperatures leads. These high temperatures, which arise in online operation, lead to problems with known elastic rollers until destruction of the plastic covering. On the one hand are known Plastic coverings maximum temperature differences of about 20 ° C over the The width of the roller is permissible and on the other hand they are for the coating Usually plastics used are much higher Thermal expansion coefficients than those commonly used Steel rollers or chill cast rollers, so that by an increase in temperature high axial tensions between the steel roller or chilled iron roller and the associated plastic coating occur.

Due to these high voltages associated with particular points occurring heating points within the plastic coating So-called hot spots can occur, at which a detachment or even the plastic layer bursts open.

These hot spots occur especially when in addition to mechanical stresses and the relatively high temperature crystallization points in the form of, for example, faulty bonds, deposits or above-average indentations of the elastic covering, for example due to folds or foreign bodies on the paper web, available. In these cases, the temperature at these crystallization points rise from the usual 80 ° C to 90 ° C to over 150 ° C, whereby the aforementioned destruction of the plastic layer takes place.

To control the properties of the elastic reference layer Powdery fillers and / or fibers introduced into the matrix material. Depending on the amount and physical properties of these fillers or the fibers, the physical properties of the elastic Reference layer dominated or influenced by the fillers or the fibers.

An effect that is usually undesirable with satin, black satin, is used for the production of tracing paper. With this Manufacturing process are rolls with reference layers of higher rigidity used so that the fibers of the paper web inserted into the press nip collapse due to the increased pressure, causing the desired Transparency arises.

However, a general increase in the stiffness of the reference layer increases the likelihood of uneven pressurization in the Press nip, which can reduce the quality of the transparent paper.

It is an object of the present invention to provide a manufacturing method an elastic roller of the type mentioned and a specify appropriate roller, at which the risk of occurrence of Hot spots is reduced. At the same time, the roller for the production of high quality tracing paper.

The part of the task relating to the roller is based on the invention solved by a roller of the type mentioned in that at least some of the fillers as elongated, in particular rod-shaped particles is formed and that the length of the particles is smaller than the radial thickness of the elastic reference layer. A corresponding one The method according to the invention is characterized in that that in the elastic matrix material at least one filler in the form of elongated, in particular rod-shaped particles introduced whose length is smaller than the radial thickness of the elastic reference layer is.

Due to the elongated particles introduced into the matrix material both the thermal conductivity and the rigidity of the elastic Reference layer improved. Due to the increased thermal conductivity the overheating heat occurring at critical points is dissipated more quickly so that the critical temperature and thereby preventing hot spots from occurring. It is special the elongated formation of the particles for rapid heat dissipation advantageous from critical points, for example in the direction of the roll core.

The elongated shape of the particles also causes them to Particles that are oriented essentially in the radial direction, selectively increase the stiffness of the elastic cover layer. Through the The elastic reference layer thus has an elongated particle Variety of points with increased stiffness, so that with a corresponding equipped roller transparent paper can be produced. Since the Particle length less than the radial thickness of the elastic reference layer the elongated particles do not extend from the Surface of the reference layer down to the roll core, but it can be found areas between individual particles that are free of the particles, so that a certain elasticity of the reference layer is retained, whereby the quality of the transparent paper produced compared to a complete rigid coating is increased. Are also in axial Direction of the roller between the punctiform rigid points elastic Areas that are essentially free of the fillers, so that at a uniform distribution of the elongated particles both in radial as well as optimized in the axial direction within the reference layer A combination of rigidity and elasticity is created.

Such an optimized combination is with the known powder Filling materials consisting of essentially round particles are not reachable. The improved thermal conductivity is also known Filling materials are not given because each of the essentially round particles thus included in the thermally poorly conductive matrix material is that heat dissipation, for example, in the direction of the roll core is practically not given.

The elongated ones designed according to the invention preferably have Particles have a ratio of their length to their thickness of between approximately 20: 1 and 5: 1, in particular of approximately 15: 1 and 7: 1, preferably of approximately 10: 1. With these preferred ratios become an ideal combination between Stiffness and elasticity of the cover layer achieved. The elongated Particles are advantageous in radial in the matrix material and / or essentially statistically distributed in the axial direction, whereby uniform rigidity with uniform elasticity of the cover layer is reached over the length of the roller.

Furthermore, a predominant part of the elongate is particularly advantageous Particles in the matrix material are essentially radial Direction aligned so that through the majority of the particles the stiffness of the elastic reference layer is defined. Basically it is also possible that the particles in the matrix material essentially statistically distributed, i.e. evenly aligned in all directions are. In this case the stiffness of the reference layer is lower, but at the same time the thermal conductivity of the reference layer in axial direction is increased.

According to a preferred embodiment of the invention, the particles are formed from thermally conductive material, the thermal conductivity of the particles is higher than that of the matrix material. Depending on the amount brought in Particles will have the thermal conductivity of the reference layer this way increased, in particular by the radial direction aligned elongated particles a derivative of excess Heat within the reference layer to the metallic roll core takes place so that unwanted heat within the reference layer quickly to the roller core and can be discharged laterally via this. In principle, the particles forming the fillers can all be made from the same Material or be made of different materials.

According to a further advantageous embodiment of the invention Coefficient of thermal expansion of the particles smaller than that of the matrix material. In this way it is achieved that the total coefficient of thermal expansion the reference layer is smaller than that of the matrix material, so that the total coefficient of thermal expansion at the coefficient of thermal expansion of the roll core can be adjusted. Thereby the longitudinal stresses that occur when the roller is heated reduced between the reference layer and the roll core.

According to a preferred embodiment of the invention, a Part of the particles radially outwards to the surface of the elastic reference layer. The elongated particles can already do this be introduced into the reference layer so that they are up to extend their surface. If the surface of the reference layer sanded after being applied to produce a high surface smoothness the elongated particles cannot at first reach all the way to the surface of the reference layer. After grinding the The ends of the elongated particles ultimately lie freely on the surface the surface so that they have the desired points of rigidity form.

Advantageous values for average lengths of the invention elongated particles are between approximately 200 and 600 μm, in particular between about 300 and 500 microns, preferably at about 400 microns. The elongated Particles therefore have a length that is clearly below that Length of in the elastic reference layer, for example as reinforcement layers provided fibers, for example carbon fibers. Prefers the particles consist of wollastonite and / or calcium silicate. In principle, however, other materials with comparable ones can also be used Properties are used.

In addition to the particles in the matrix material, fibers are preferred embedded. These fibers can be in rovings or as nonwoven on the Roll core are applied and are usually used for reinforcement the elastic reference layer.

According to a further preferred embodiment of the invention, the Fibers arranged in radially successive layers of fibers. These fiber layers can be spaced from one another or directly abut each other. Furthermore, in the elastic reference layer between about 5 and 100, in particular between about 20 and 70, preferred 30 to 40 fiber layers are available. Depending on the thickness of the elastic However, the reference layer can also have more or fewer fiber layers his.

The fiber layers reinforce the elastic reference layer achieved, since usually consists only of a matrix material Reference layer does not have the rigidity required for the satin finish. If the elastic reference layer is formed from several However, there is a risk of fiber layers if the connection is insufficient there is a tendency for the fiber layers to separate between the individual fiber layers exists.

Especially when the elongated particles are arranged between The individual fiber layers counteract such a tendency to detach, because the elongated particles are particularly radial an additional connection between the individual fiber layers create. Thus, in addition to the increased punctual stiffness for the black satin finish and the improved thermal conductivity as well the compensating thermal expansion coefficient also the service life a reference layer designed according to the invention by reduced Transfer tendency to be improved.

Fig. 1

einen Teillängsschnitt durch eine erfindungsgemäß ausgebildete Walze mit elastischer Bezugsschicht und

Fig. 2

eine weitere Ausführungsform einer erfindungsgemäß ausgebildeten Walze.

Further advantageous embodiments of the invention are specified in the subclaims. The invention is described below using an exemplary embodiment with reference to the drawing; in this show:

Fig. 1

a partial longitudinal section through an inventive roller with elastic reference layer and

Fig. 2

a further embodiment of a roller designed according to the invention.

Fig. 1 shows a part of a cut in the longitudinal direction, for example existing steel or cast iron roll core 1, the outside with an elastic reference layer, also shown in section 2 is provided.

The reference layer 2 consists of an elastic matrix material 3, in particular from a resin / hardener combination, in which a variety of Fibers 4 are embedded. In the case of the fibers 4, for example around carbon fibers or around glass fibers or a mixture of Trade carbon and glass fibers. The fibers 4 are essentially in Axial direction of the roller core 1 aligned and form a fiber layer 5, which is applied, for example, by winding on the roll core 1 has been. The fibers 4, on the one hand, increase the rigidity of the reference layer 2 compared to a reference layer made of pure plastic increased and at the same time, especially when using carbon fibers, improves thermal conductivity in the axial direction.

In addition to the fibers 4, there are fillers in the elastic matrix material 3 intended. For one, these fillers include elongated, rod-shaped particles 6 and on the other hand fine-grained, the filler forming fine particles 7. While the fine particles are substantially quasi-spherical are formed and a diameter of, for example Have 10 to 20 microns, have the elongated rod-shaped particles a length of about 400 microns, for example. Some of the elongated ones Particles 6 each extend with one end to the surface 8 of the reference layer 2, while others of the elongated particles 6 with their respective ends up to the surface 9 of the roll core 1 extend. All elongated particles 6 are however so formed so that its length is shorter than the radial thickness of the reference layer 2nd

The particles 6 reaching to the surface 8 of the reference layer 2 form 8 punctiform points 10 with increased rigidity on this surface, that with a uniform distribution of the particles 6 in the reference layer 2 accordingly evenly over their entire surface 8 are distributed. In particular with an essentially radial alignment the particle 6 becomes the stiffness of the reference layer at the points 10 2 significantly increased over their remaining areas. To this The roller shown in FIG. 1 can be used for the production of transparent paper be used.

Since the length of the particles 6 is shorter than the radial thickness of the reference layer 2, an increase in stiffness is only in some areas along given the length of the respective particles 6. Over the entire thickness the reference layer 2 retains a certain elasticity since even at exactly radially aligned particles 6 between their lower ends and the surface of the roll core 1 each have a certain amount of flexible Matrix material 3 is present. Through the combination shown elongated rod-shaped particles 6 and elastic matrix material 3 in the manner shown in FIG. 1 thus becomes an optimal combination between selective stiffness and global elasticity of the reference layer reached.

In addition, due to the elongated ponds 6, the thermal conductivity of the reference layer 2 increases because the particles 6 have better thermal conductivity possess than the matrix material 3 Direction or inclined particles 6 in particular the Thermal conductivity of the reference layer 2 improved in the radial direction, so that in addition to the improved thermal conductivity by the fiber layer 5 in the axial direction an improvement in a perpendicular to it direction.

Occasional so-called overheating points occur within the reference layer 2 Hot spots on, so the unwanted heat along the elongated particles in the radial direction to the roll core 1 and can be removed axially via this, for example. Basically it is also conceivable that the heat supplied to the roller core radially after is continued on the inside to either be axially discharged inside or for example cooling medium present in the interior of the roller to be included.

While the fibers are oriented essentially in the axial direction 4 of the fiber layer 5 only heat transfer in the axial direction can, can thus be undesirable via the elongated particles 6 Heat is dissipated perpendicular to it. This is especially why advantageous because the unwanted heat much faster in radial Direction can be removed from the reference layer 2 because of the thickness the reference layer 2 is typically between 1 mm and 3 cm, while the axial length can be between 3 to 12 m. A timely one Dissipation of unwanted heat in the axial direction over the Fiber layer 5 is practical due to the axial length of the reference layer 2 not possible.

If the particles 6 are chosen from a material that is a material of the roll core 1 has a similar coefficient of thermal expansion, the total thermal expansion coefficient approaches the reference layer 2 to the coefficient of expansion of the roll core 1. this applies especially when a large number of the particles 6 are oblique or essentially are arranged extending in the axial direction. Because the matrix material 3 usually a significantly higher coefficient of thermal expansion owns than the roll core 1 can by reducing of the total thermal expansion coefficient of the reference layer 2 due to the elongated particles 6 when the roller is heated longitudinal stresses occurring between the roll core 1 and the reference layer be reduced.

The punctiform fine particles 7 can also be adapted of the coefficient of thermal expansion of the reference layer 2 to the coefficient of thermal expansion serve the roll core 1 or other desired Define physical properties of the reference layer. Possibly the fine particles 7 can also be completely eliminated.

The fiber layer 5 can, for example, by winding fiber rovings or Nonwoven fabric can be produced on the roll core 1. This is more clearly shown in Fig. 2 can be seen where two fiber layers arranged radially spaced apart 5 ', 5' 'are shown schematically. The fibers or fiber rovings can be in the liquid state before winding Matrix material 3 can be applied, for example, by a Matrix bath are drawn. However, it is also possible that the fibers or the fiber rovings are wound dry on the roll core 1 and soaked during or after winding with matrix material until you are completely surrounded by it. To be a smooth Reaching surface 8 of the roller after the winding process top layer of the matrix material 3 is sanded off, creating a multitude of the elongated particles 6 come to the surface 8 and thus form the punctiform points 10 of increased rigidity.

The two fiber layers 5 ′, 5 ″ are connected to one another via the matrix material 3 connected, the lower fiber layer 5 '' also via the matrix material 3 is connected to the surface 9 of the roll core 1. While the Reference layer 2 in the area of the fiber layers 5 ', 5' 'due to the interlocking Fibers 4 is very stable, consists of the dashed Lines 11, 12 indicated areas between the fiber layers 5 'and 5' ' or between the fiber layer 5 ″ and the surface 9 of the roll core 1 the risk that the reference layer will become detached if subjected to the appropriate stress 2 of the roll core 1 or of the two the fiber layers 5 ', 5' ' containing partial areas of the reference layer 2 from each other.

Through the elongated rod-shaped particles 6 is just in the endangered areas 11, 12 the connection of the different Sub-layers of the reference layer 2 improved. The elongated particles 6 form reinforcing bridges in the radial direction, so that the overall stability the reference layer 2 increased significantly in the radial direction becomes. The tendency to detachment described is according to the invention trained reference layer 2 is therefore not given.

By improving heat dissipation, it is possible to have larger nip widths to produce, thereby reducing the quality of the paper web being treated is further improved.

Reference list

1

Roll core

2nd

Reference layer

3rd

Matrix material

4th

Fibers

5, 5 ', 5' '

Fiber layers

6

elongated rod-shaped particles

7

Fine particles

8th

Surface of the reference layer

9

Surface of the roll core

10th

punctiform places

11

dashed line

12th

dashed line

Claims (15)

Roller, in particular for smoothing paper webs, with a hard roller core (1) consisting in particular of metal, which is provided on the outside with an elastic reference layer (2) which is made of an elastic matrix material (3) and embedded in the matrix material (3) Fillers (6, 7),
characterized,
that at least some of the fillers (6, 7) are designed as elongated, in particular rod-shaped particles (6) and that the length of the particles (6) is less than the radial thickness of the elastic reference layer (2). Roll according to claim 1,
characterized,
that the particles (6) have a length to thickness ratio of between approximately 20: 1 and 5: 1, in particular between approximately 15: 1 and 7: 1, preferably approximately 10: 1 and / or that the particles (6) are essentially statistically distributed in the matrix material (3) in the radial and / or in the axial direction. Roller according to claim 1 or 2,
characterized,
that a particular predominant part of the particles (6) in the matrix material (3) is oriented essentially in the radial direction or that the particles (6) in the matrix material (3) are oriented essentially statistically. Roller according to one of the preceding claims,
characterized,
that the particles (6) are made of thermally conductive material, the thermal conductivity of the particles (6) being higher than that of the matrix material (3) and / or that some of the particles (6) extend radially inwards to the surface (9) of the roll core (1) and / or that the coefficient of thermal expansion of the particles (6) is smaller than that of the matrix material (3). Roller according to one of the preceding claims,
characterized,
that the particles (6) have a higher rigidity than the matrix material (3) and / or that part of the particles (6) extends radially outwards to the surface (8) of the elastic reference layer (2) and / or that the particles (6) have an average length of between approximately 200 and 600 μm, in particular of between approximately 300 and 500 μm, preferably of approximately 400 μm and / or that the particles (6) consist of wollastonite and / or calcium silicate. Roller according to one of the preceding claims,
characterized,
that in addition to the particles (6), fibers (4) are embedded in the matrix material (3), in particular that the fibers (4) are arranged in a fiber layer (5) or in radially successive fiber layers (5 ', 5''), the fiber layers (5 ', 5'') preferably being spaced apart from one another or the fiber layers abutting one another. Roller according to claim 6,
characterized,
that between about 5 and 100, in particular between about 20 and 70, preferably about 30 to 40, fiber layers (5, 5 ', 5'') are present in the elastic reference layer (2) and / or that the particles (6 ) are arranged between the individual fiber layers (5 ', 5''). Roller according to one of the preceding claims,
characterized,
that the reference layer comprises radially outer functional layer and a radially inner connecting layer for connecting the functional layer to the roller core and that the particles are arranged at least in the functional layer. Roll according to one of claims 6 to 8,
characterized,
that the fibers (4) are designed as glass and / or as carbon fibers. Roller according to one of the preceding claims,
characterized,
that the matrix material (3) is a plastic, in particular a thermoset or a thermoplastic and / or that the matrix material (3) consists of a resin / hardener combination. Method for producing an elastic roller with a hard roller core, in particular made of metal, and an elastic reference layer consisting of an elastic matrix material, in particular for producing a roller according to one of the preceding claims,
characterized,
that at least one filler is introduced into the elastic matrix material in the form of elongated, in particular rod-shaped particles, the length of which is smaller than the radial thickness of the elastic reference layer. A method according to claim 11,
characterized,
that fibers are embedded in addition to the particles in the elastic matrix material. Method according to claim 12,
characterized,
that to produce the reference layer, at least one fiber bundle consisting of a plurality of fibers, in particular in several fiber layers one above the other, is wound on the roller core and the particles between adjacent fiber layers and / or between fiber layer and the surface of the roller core and / or between fiber layer and the surface the reference layer are introduced, in particular the fiber bundle being formed by one or more fiber roving and / or by a nonwoven fabric, a roving in each case consisting of a plurality of adjacent fibers of the same type, and / or the fiber bundle being formed by a nonwoven fabric. A method according to claim 13,
characterized,
that the fiber bundle is surrounded by the matrix material before being wound up on the roll core, in particular is drawn through a matrix bath, and that the particles are already contained in the matrix material, in particular in the matrix bath, and / or are introduced into the matrix material surrounding the fiber bundle during winding , or that the fiber bundle is wound up essentially dry on the roll core and is loaded with the matrix material during or after winding, in particular is completely embedded in the matrix material, and that the particles are already contained in the matrix material and / or after or during loading with matrix material. Method according to one of claims 12 to 14,
characterized,
that glass and / or carbon fibers are used as fibers.

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