MXPA04010175A - Roll with stress and/or temperature-indicating cover. - Google Patents

Abstract

a substantially cylindrical core and a cover overlying the adhesive layer. The cover comprises a polymeric top stock layer. The top stock layer comprises a mixture of a polymeric material and at least one of a piezochromic material and a thermochromic material. In this configuration, the pressure and/or temperature experienced by the roll cover at any location thereon can be determined visually, without the need for external equipment.

Description

ROLLER WITH TENSION AND / OR TEMPERATURE INDICATOR COVER FIELD OF THE INVENTION The present invention relates generally to industrial rollers, and in particular to covers for industrial rollers.

BACKGROUND OF THE INVENTION Cylindrical rollers are used in a number of industrial applications, especially those related to papermaking. Such rollers are typically used in demanding environments in which they may be exposed to dynamic loads and elevated temperatures and aggressive or corrosive chemicals. As an example, in a typical paper mill, the rolls are used not only to transport a sheet of fibrous tape between processing stations, but also, in the case of calendering rolls and press section, to process the sheet itself. paper tape. Usually, the rollers used in papermaking are constructed taking into account the location within the papermaking machine, since rolls are required that reside in different positions within the papermaking machines to perform different functions . Because papermaking rolls can have many different performance demands, and because the replacement of a complete metal roll can be very expensive, many papermaking rolls include a polymeric cover that surrounds the circumferential surface of a paper. typically metallic core. By varying the material used in the cover, the cover designer can provide the roller with different operating characteristics as required by the papermaking application. In addition, the repair, repeated rectification or replacement of a cover on a metal roller can be considerably less expensive than the replacement of a complete metal roller. Exemplary polymeric roofing materials include natural rubber, synthetic rubbers such as neoprene, styrene-butadiene (SBR), nitrile rubber, chlorosulfonated polyethylene ("CSPE" - also known under the name HYPALON® from DuPont, EDMP (the name given to an ethylene-propylene terpolymer formed of ethylene-propylene diene monomer) polyurethane, thermosetting mixed materials, and mixed thermoplastic materials In many cases, the roller cover will include at least two different layers: a base layer covering the core and provides a bond with it, and a layer of upper pulp that covers and joins the base layer and serves the outer surface of the roller (some rollers will also include an intermediate "connecting" layer inserted into the layers of base and upper pulp.) The layers for these materials are typically selected to provide the cover with a prescribed set of physical properties. icas for operation. These can include the necessary strength, elastic modulus, and resistance to high temperature, water, and strong chemicals to support the papermaking environment. In addition, the covers are typically designed to have a predetermined surface hardness that is suitable for the process they are going to perform, and they usually require the sheet of paper to "peel off" from the cover without damage to the sheet of paper. In addition, in order to be economical, the cover must be resistant to abrasion and wear. Some rollers are present as "pressed" rollers, where two or more rollers are placed in such a way as to form a "pass" through which a belt can pass. Often, said rollers are found, for example, in the press section of a papermaking machine. The rollers are pressed against the belt at a prescribed pressure in order to advance the processing. However, in some cases, the rollers may apply pressure unevenly on the belt. The application of non-uniform pressure, can result from many circumstances, including (a) that the cover of one or more rollers is slightly "oval", (b) that a roller is mounted so that its axis is not parallel to that of its coupling roller, or (c) localized wear increased on one of the roller covers. Regardless of the cause of non-uniform pressure, their presence can negatively impact the processing of the tape, and in extreme cases, can damage the cover or even cause it to fracture. In addition, the temperature of a roller can influence the processing. Uneven or undesirable temperature distributions can be created in a roller by some of the same mechanisms described above for non-uniform pressure application. Some systems are available to try to detect the pressure or temperature inside a roller. A system includes a flexible strip on which are mounted multiple pressure sensors that can be placed between the rollers and provide pressure and / or temperature readings (see for example, U.S. Patent No. 5,953,230 to Moore). Another system employs sensors that are embedded in the roller cover itself and provide signals to an external processor (see, for example, U.S. Patent No. 5,699,729 to Moschel et al.). However, each of these systems includes electrical or electronic communication equipment and data that may require processing, maintenance and the like and that may malfunction or interfere with operations. As such, it would be advisable to provide an alternative system to detect levels and distribution of pressure and / or temperature in rollers.

BRIEF DESCRIPTION OF THE INVENTION The present invention can provide rollers and polymer roll covers that are capable of indicating pressure levels and / or temperatures present in the cover without the need for additional or external devices. Said roller includes a substantially cylindrical core and a cover that extends over the core. The cover includes at least one layer (typically the upper pulp layer) comprising a mixture of a polymeric material and at least one of a piezochromic material and a thermochromic material. In this configuration, the pressure and / or temperature experienced by the roller cover at any location thereof can be determined visually, without the need for external equipment.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a fragmented perspective view of an industrial roller and roller cover of the present invention; Figure 2 is a sectional view taken through lines 2-2 of Figure 1.

DETAILED DESCRIPTION OF THE INVENTION In the following, the present invention will be described more fully, in which preferred embodiments of the invention are shown. However, this invention can be modalized in different ways and should not be interpreted as limited to the modalities set forth herein. Rather, these embodiments are provided so that this description is complete and complete, and that it fully transmits the scope of the invention to those skilled in the art. In the drawings, similar numbers refer to similar elements, and the thicknesses and dimensions of some components or features may be exaggerated for reasons of clarity. It will be understood that when an element or layer is referred to as "connected" or "coupled to" or "covering" another element or layer, it may be directly connected or coupled to the other element or layer, or intermediate elements or layers may be present. . In contrast, when an element is referred to as "directly connected" or "directly coupled" to or "directly covering" another element or layer, there are no intermediate elements or layers present. Referring now to the drawings, a papermaking roller, broadly designated 10, is illustrated in Figures 1 and 2. The roller 10 includes in superposed relation a core 12 (typically metallic), an adhesive layer 14, and a cover 16. Each of these components are discussed in more detail below.

The core 12 is a hollow, substantially cylindrical structure typically formed of steel, some other metal, or even a mixed material. The core 12 usually has between approximately 3.81 and 1016 centimeters in length and 2.54 and 177.8 centimeters in diameter, with lengths between approximately 254 and 1016 centimeters and diameters between approximately 50.8 and 177.8 centimeters being preferred. In these preferred length and diameter scales, the core 12 usually has walls between about 2.54 and 12.7 centimeters thick. Generally, components such as journals and bearings (not shown) are included in the core 12 to facilitate assembly and rotation in a papermaking machine. The surface of the core 12 can be treated by jetting, dusting with sand, sandblasting of sand or the like to prepare the surface for attachment to the adhesive layer 14. Referring again to FIGS. 1 and 2, the adhesive layer 14 comprises a adhesive (typically an epoxy adhesive) that can bond the core 12 to the cover 16. Of course, the adhesive comprising the adhesive layer 14 must be selected to be compatible with the materials of the core 12 and the base layer 18 of the cover 16 (that is, it must provide a high integrity joint between these structures without unduly damaging any material); preferably, the joint has a tensile strength of between about 84.36 and 351.5 kg / cm2. The adhesive can have additives, such as curing agents, which facilitate the physical and healing properties. Exemplary adhesives include Chemlok 220X and Chemlok 205, which are epoxy adhesives available from Lord Corporation, Raleigh, North Carolina. The adhesive layer 14 can be applied to the core 12 in any known manner that is suitable for those skilled in the art to apply a thin layer of material. Exemplary application techniques include spraying, brushing, dipping, scraping, and the like. It is preferred that if a solvent-based adhesive is used, the adhesive layer 14 is applied so that the solvent can evaporate prior to the application of the cover 16 in order to reduce the occurrence of trapped solvent which may cause "currents". of air "during the healing procedure. Those skilled in the art will appreciate that the adhesive layer 14 may comprise multiple adhesive coatings, which may comprise different adhesives.; for example, two different epoxy adhesives with slightly different properties can be employed. It should also be noted that in some embodiments, the adhesive layer can be omitted completely, so that the cover 16 is attached directly to the core 2. Still referring to FIGS. 1 and 2, the cover 16 comprises, in superposed relation, a base layer 18 and a top pulp layer 22. In the illustrated embodiment, the base layer 18 is adhered to the adhesive layer 14. The base layer 18 comprises a polymeric compound (preferably an elastomeric compound) which usually includes fillers and other additives. Exemplary elastomeric compounds include polyurethane, natural rubber and synthetic rubbers such as SBR, EPDM, CSPE, nitrite rubber, neoprene, isoprene, silicone, and fluoroelastomers, and combinations and copolymers thereof, including combinations with polyvinyl chloride (PVC) . An exemplary polymeric material that may be suitable for use in the base layer is epoxy. To increase the polymerization, additional monomers and coagents of monomers, such as trimethyl propane trimethacrylate and 1,3-butylene glycol dimethacrylate, can also be added to the base layer. The fillers are usually added to the base layer 18 to modify the physical properties of the compound and / or reduce its cost. Exemplary filler materials include inorganic oxides such as aluminum oxide (AI2O3), silicon dioxide (SiO2), magnesium oxide (MgO), calcium oxide (CaO), zinc oxide (ZnO) and titanium dioxide (Ti02). ), carbon black (also known as black oven), silicates such as clays, talc, wollastonite (CaSi03), magnesium silicate (MgSi03), anhydrous aluminum silicate, and feldspar (KAISi308), sulfates such as barium sulfate and calcium sulfate, metal powders such as aluminum, iron, copper, stainless steel, or nickel, carbonates such as calcium carbonate (CaCo3) and magnesium carbonate (MgCo3), mica, silica (natural, fuming, hydrated, anhydrous, or precipitate) and nitrides and carbides, such as silicon carbide (SiC) and aluminum nitride (AIN). These fillers may be present in virtually any form, such as powder, pellet, fiber or sphere.

In addition, the base layer 18 may optionally include other additives, such as initiators, polymerization accelerators and accelerators, curing or vulcanizing agents, plasticizers, heat stabilizers, antioxidants, and antiozonants, coupling agents, pigments, and the like, which they can facilitate processing and increase physical properties. These components are generally combined in the polymer prior to the time of application of the base layer 18 to the adhesive layer 14 or directly to the core 12. Those skilled in this art will appreciate that the identity and amounts of these agents and their use in a layer Bases are generally known and do not need to be described in detail herein. The base layer 18 can be applied by any manner known to those skilled in the art which is convenient for the application of polymers to an underlying surface. Preferably, the base layer 18 is applied through an extrusion process in which the strips of the base layer 18 are extruded through an extrusion die, subsequently, while still hot, they extend over the layer Adhesive 14 while it is still a bit sticky. The base layer strips are preferably between about 0.07 and 0.31 centimeters thick and are applied in an overlapping manner, resulting in a total thickness of the base layer 18 typically between about 0.15 and 0.63 centimeters. Those skilled in the art will appreciate that in some embodiments, the base layer 18 may be omitted so that the upper pulp layer 22 adheres directly to the adhesive layer 14, or in the absence of an adhesive layer, to the core 12. In the illustrated embodiment, the upper pulp layer 22 extends and, unless one or more connecting layers are included as described below, it adheres to the base layer 18. The upper pulp layer 22 comprises a polymeric compound that usually includes fillers and other additives. Exemplary elastomeric compounds for the upper pulp layer 22 include polyurethane, natural rubber and synthetic rubber such as SBR, EPDM, CSPE, nitrile rubber, neoprene, isoprene, silicone and fluoroelastomers, and combinations and copolymers thereof, including combinations with polyvinyl chloride (PVC). Other exemplary polymeric compounds include epoxies. As mentioned above, the upper pulp layer 22 includes thermochromic or pyzochromic compositions within the polymeric formulation. As used herein, a "thermochromic composition" is a substance that changes color when subjected to different levels of temperature or heat, either reversibly or irreversibly. Exemplary thermochromic compositions include those comprising an electron donor component, an acidic material and an organic solvent or medium (see, for example, U.S. Patents 4,666,949 to Shimizu et al., 5,688,592 to Shibahashi et al.), Those that include a electron donor color former, an electron acceptor warhead and a color change temperature controlling agent (see for example, U.S. Patent No. 4,681, 791 to Shibahashi et al.), and liquid crystals such as chiral crystals cholesteric, biphenyl and related liquid crystals (see, for example, U.S. Patent Nos. 5,194,183 to Münch et al. and 5,690,857 to Osterried et al.). As used herein, a "piezochromic composition" is a substance that changes color when subjected to different levels of pressure, either reversibly or irreversibly. Exemplary piezochromic compositions include: 9- (p-nitrophenylphenylmethylene) xanthene, diflavin, dehydrodiantrone, hexaphenylbiimidazolyl, tetraphenylvinyl dimer, phthalocyanine-cobalt complex and hydroxycarboxylic acid derivatives, spirobenzopyranoxadiazoline derivatives and spiropyranthiopyrans, both commonly referred to briefly as spiropyrans (see U.S. Patent No. 5,320,784 for Miyashita), samarium sulfides (such as samarium monosulfide and disamarin trisulfide) (see U.S. Patent No. 6,132,568) for Jin et al.), and three-dimensionally periodic materials (such as those described in US Patent No. 6,261,469 to Zakhidov et al.). The piezochromic materials are preferably included in an amount between about 0.001 and 10 parts (preferably between about 0.01 and 5 parts) by weight to 100 parts of polymer from the upper pulp layer 22, and preferably provide an identifiable color change to a pressure of between about 101.9 and 1054.5 kg / cm2 (preferably between about 140.6 and 703 kg / cm2). The thermochromic materials are preferably included in an amount of between about 0.001 and 10 parts (preferably between about 0.01 and 5 parts) by weight to 100 parts of polymer of the upper pulp layer 22, and preferably provide a color change identifiable at a temperature between about 40 and 180 ° C (preferably between about 70 and 160 ° C). An upper pulp layer 22 may include both piezochromic and thermochromic materials, but these must be selected so that their color changing characteristics are compatible with each other. Preferably, the piezochromic and / or thermochromic materials are microencapsulated prior to inclusion in the upper pulp layer 22. It is also preferred that these materials are generally homogeneously distributed over the surface of the upper pulp layer 22, unless throughout the upper pulp layer 22, in order to provide a more accurate indication of the pressure and / or temperature experienced by the cover 16. The upper pulp layer 22 typically also includes fillers that are added to modify and improve the physical and processing properties and / or to reduce the cost of the upper pulp layer 22. Exemplary fillers include silicon dioxide, carbon black, clay, and titanium dioxide (Ti02) as well as others discussed above Typically, fillers are included in an amount between about 3 and 70% by weight of the upper pulp layer 22. Fillers can have virtually any shape, including powder, pellet, bead, fiber, sphere, or the like. The upper pulp layer 22 also usually includes other additives, such as initiators, polymerization accelerators and accelerators, curing or curing agents, plasticizers, heat stabilizers, antioxidants, coupling agents, pigments, and the like, which can facilitate processing and improve physical properties. Those skilled in the art will understand the types and concentrations of additives that are suitable for inclusion of the upper pulp layer 22, so that these do not need to be discussed in detail herein. The upper pulp layer 22 can be applied over the base layer 18 by any technique known to those skilled in the art which is convenient for the application of elastomeric materials on a cylindrical surface. Preferably, the components of the upper pulp layer 22 are mixed separately, then combined in a mill. The mixed material is transferred from the mill to an extruder, which extrudes upper pulp material feeder strips onto the base layer 18. Preferably, the upper pulp layer 22 is applied so as to have between approximately 2.54 and 6.35 centimeters of thickness (to a greater thickness, multiple steps of material may be required). It is also preferred that the thickness of the upper pulp layer 22 is between about 50 and 75% of the total cover thickness (i.e., the total thickness of the combined base and top pulp layers 18, 22). Alternatively, either or both of the base and top pulp layer 18, 22 can be applied through the coating of calendered sheets of material. The elastomeric compounds of the base layer 18 and the upper material 22 can be selected so that the base layer 18 has a higher hardness value than the upper pulp layer 22. As an example, the base layer 18 can have a hardness of between approximately 5 and 16 P &J, and the upper pulp layer 22 can have a hardness of between about 170 and 230 P &J. The concept of a graduated module can reduce the shear stresses of the joining line that can occur due to the irregularities of the elastic properties (such as elastic modulus and Poisson's ratio) of the various layers in the roof constructions. This reduction in shear stress of the interface can be important to maintain the integrity of the sheath. Those skilled in the art will also appreciate that the roller 10 can be constructed with a connecting layer inserted into the base layer 18 and the upper pulp layer 22, so that the connecting layer extends directly below the layer. of upper pulp 22. The typical properties of a connecting layer are known to those skilled in the art and do not need to be described in detail herein.

After the upper pulp 22 has been applied, the roller 10 is subsequently cured, typically in an autoclave, during a suitable curing period (generally between about 16 and 30 hours). After curing, it is preferred to rough any crust that has developed on the surface of the upper pulp layer 22, and that the upper pulp layer 22 is ground for dimensional correction. Roller covers formed from the compositions described above can be employed in press rolls or other roll positions within papermaking machines or other devices. In position, and during operation of the machine, the roller cover, due to the presence therein of a thermochromic and / or piezochromic composition, can provide information about the temperature and / or pressure experienced by the roller cover. As such, undesirable circumstances, such as non-uniform application of pressure, wrong misalignment or crimping of press rolls, inadequate roll profile, roller overload beyond a preselected limit, presence of "hot spots" on the cover, wear localized, or similar, can be discerned visually during operation. In addition, photographs of the cover can be taken and can be purchased with other photographs taken later to determine if the processing conditions have changed. Any of these techniques may be preferable for the use of external devices, particularly in places of a machine that are difficult to access. It should also be noted that in some embodiments, the cover may include a connecting layer or other intermediate layer comprising a thermochromic or piezochromic material, and the upper pulp layer is transparent to allow visual examination of the intermediate layer. The foregoing is illustrative of the present invention and will not be construed as limiting thereof. Although exemplary embodiments of this invention have been described, those skilled in the art will readily appreciate that many modifications to the exemplary embodiments are possible without departing materially from the teachings and novel advantages of this invention. Accordingly, all such modifications are intended to be included within the scope of this invention as defined in the claims. The invention is defined by the following claims, to include equivalents of the claims herein.

Claims (9)

NOVELTY OF THE INVENTION CLAIMS

1. - An industrial roller, comprising: a substantially cylindrical core; and a cover extending over said core, said cover comprises a layer extending over said core and comprising a mixture of a polymeric material and at least one of a piezochromic material and a thermochromic material.

2. - The roller according to claim 1, further characterized in that the cover comprises a layer of upper pulp, and wherein the upper pulp layer is the layer comprising the mixture of a polymeric material and at least one of a piezochromic material and a thermochromic material.

3. The roller according to claim 1, further characterized in that the mixture comprises 100 parts of polymeric material by weight and between about 0.001 and 10 parts of piezochromic material by weight.

4. The roller according to claim 1, further characterized in that the mixture comprises 100 parts of polymeric material by weight and between about 0.001 and 10 parts of thermochromic material by weight. 5 - . 5 - The roller according to claim 1, further characterized in that the polymeric material comprises a rubber material. 6. - The roller according to claim 1, further characterized in that the piezochromic material is selected and included in such an amount that displays an identifiable color change at a pressure of between about 0.9 and 1054.5 kg / cm2. 7. - The roller according to claim 1, further characterized in that the thermochromic material is selected and included in such an amount that it displays an identifiable color change at a temperature of between about 40 and 180 degrees centigrade. 8. - The roller according to claim 2, further characterized in that the cover additionally comprises a base layer, the base layer extends over the core and is subjacent to the upper pulp layer. 9. - The roller according to claim 8, further characterized in that the cover further comprises a connecting layer between the base layer and the upper pulp layer. 10. - The roller according to claim 1, further characterized in that it additionally comprises an adhesive layer between the core and the cover. 11. - The roller according to claim 1, further characterized in that the layer comprising the mixture is an intermediate layer that extends over the core, and wherein the cover comprises a layer of transparent upper pulp that extends over the intermediate layer. 12. - An industrial roller, comprising: a substantially cylindrical core; and a cover extending over said core, said cover comprises a base layer, a connecting layer extending over the base layer, and a top pulp layer extending over the connecting layer, one of the upper base, connecting and pulp layers comprises a mixture of a polymeric material and at least one of a piezochromic material and a thermochromic material. 13. - The roller according to claim 12, further characterized in that the layer comprising the mixture is the upper pulp layer. 14. - The roller according to claim 12, further characterized in that the layer comprising the mixture is the connecting layer. 1

5. - The roller according to claim 12, further characterized in that the mixture comprises 100 parts of polymeric material by weight and between about 0.001 and 10 parts of piezochromic material by weight. 1

6. - The roller according to claim 12, further characterized in that the mixture comprises 100 parts of polymeric material by weight and between about 0.001 and 10 parts of thermochromic material by weight. 1

7. - The roller according to claim 12, further characterized in that the polymeric material comprises a rubber material. 1

8. - The roller according to claim 12, further characterized in that the piezochromic material is selected and included in such an amount that it displays an identifiable color change at a pressure between about 101.9 and 1054.5 kg / cm2. 1

9. The roller according to claim 12, further characterized in that the thermochromic material is selected and included in an amount such that it displays an identifiable color change at a temperature between about 40 and 180 degrees centigrade.