FI123186B - The roll coating - Google Patents

Description

The roll coating

Field of the Invention

The present invention relates to a roll coating and in particular to a coating suitable for rolls used in the process of making paper, board, tissue paper, pulp or other fibrous web.

Background of the Invention

In the manufacture of paper, board and pulp, polymer roll coatings use mainly three types of polymers, namely rubber, polyurethane and epoxy. Roller coatings require a variety of drive characteristics such as good dynamic strength under high load, wear resistance and process or fiber web properties such as suitable hardness. Depending on the application, the roll profile requirement profile may vary greatly.

With the development of polyurethane coatings, polyurethane coatings are increasingly used in paper industry applications. They are used in particular in suction and press rolls for press parts, coating and surface sizing rolls, and web or fabric guide rolls. Currently, polyurethane coatings are mainly manufactured by nozzle technology as strip molding directly onto the roll surface.

Coatings commonly used in the art include composite roll coatings containing reinforcing fibers such as glass, carbon or aramid fibers, and plastics. Composite roller coatings are typically epoxy based. The advantage of the Kompo pen rollers is e.g. their good heat and strain resistance, stability and low hysteresis. The main use of these rollers is in calender nip rolls, press groove and suction rolls and track guide rolls. The composite rolls o ™ are manufactured by a winding technique in which the fiber reinforcement is wound onto the roll. The fiber Y reinforcement can be wound onto the roll body dry, whereby the epoxy is applied to the roll by means of a nozzle. The fiber reinforcement can also be first wetted into epoxy and then wound g wetted fiber reinforcement onto the roll body.

30 A weakness of the polyurethane coating is its adhesion to metal

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g in the pass if the roll is used in a wet position or if there is a nip load

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> - large. Thus, polyurethane-coated rolls under polyurethane typically use an epoxy-based composite or hard polyurethane as the base layer. The ground floor provides e.g. moisture barrier between the polyurethane surface layer and the roll 35 body, which prevents hydrolysis and rusting, reduces shear forces at 2 interfaces and thus reduces the risk of delamination, but also improves coating adhesion, both under mechanical stress, resulting in better bond strength than metal body / polyurethane interface for thermal stress, especially when using a fiber reinforced base layer. It is important to keep the surface layer on the bottom layer, because the coating that comes off during driving can cause major damage to the paper machine. At present, the aim is to secure the adherence of the various layers of roller coatings by the following means: 1) An epoxy-impregnated / impregnable reinforcing fiber mat / tape, i.e. 10 composite bases, is wound onto the roller body to form a composite base layer. An adhesive is applied to the surface, for example epoxy-based, which may be pre-cured before casting the polyurethane surface layer.

2) The composite base is wound onto a roll body, after which a new layer of epoxy impregnated / impregnable fiber is wound onto the surface 15 using a different epoxy material than the base layer, i.e. the so-called adhesive epoxy which adheres to both the epoxy material and the top layer. The roll is gelled hard and polyurethane is cast on the surface.

Fl Patent Publication 115153 discloses a paper machine roll coating 20 comprising an upper working coating layer and below a base layer on a roll body. In addition, there may be an intermediate layer between the operating coating and the substrate. To provide sufficient adhesion between the coating and the substrate or between the coating and the intermediate, corrosion-resistant particles are introduced into the substrate and / or the intermediate layer which partially submerges in the coating. The disadvantage of the roll coating is that the particles form discontinuities in the plastic matrix, which may in some cases even reduce the adhesion between the layers locally.

Brief Description of the Invention 00 o It has now surprisingly been found that polyurethane is semi-semi-miscible | The partially gelled epoxy can be improved by increasing the compatibility between the polyurethane and the epoxy and thus enhancing the adhesion of the polyurethane coating S to the epoxy based composite base layer. The deeper the urethane chains penetrate before the chemical bonds are fashioned and the three-dimensional structure is locked, the more strongly the polyurethane and epoxy bind to one another. The adhesive layer is made of an epoxy-3 polyurethane copolymer in which the polyurethane has a better miscibility than the pure epoxy used in the prior art.

Thus, one aspect of the invention is a roller coating comprising an epoxy-polyurethane copolymer. The copolymer can either be itself a roller coating 5 or act as an adhesive layer between the epoxy-based composite base layer and the polyurethane coating. The roll coating has the advantage that the adhesion of the copolymer to the metal roll body itself or between the epoxy-based composite base layer and the polyurethane coating can be enhanced. The use of an epoxy-polyurethane copolymer-based adhesive layer 10 instead of an adhesive between the epoxy composite and the polyurethane surface reduces the roll production time by several days and reduces the manufacturing cost.

Another aspect of the invention is a roll of a fiber web machine comprising a roll body and a roll coating according to the invention on top thereof.

Yet another aspect of the invention is the use of an epoxy-polyurethane copolymer in a roll coating.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 shows a roller coating according to the invention. DETAILED DESCRIPTION OF THE INVENTION One aspect of the invention is a roller coating comprising an epoxy-polyurethane copolymer. The roll coating is particularly suitable for rolls used in paper, board and pulp production.

The roll coating according to the invention may comprise, in addition to the epoxy-polyurethane copolymer, another epoxy compound.

In one embodiment of the invention, the epoxy-polyurethane copolymer ™ is itself made into a roll coating.

In another embodiment of the invention, the roll coating comprises an epoxy-based composite base layer 1 on top of the roll body 4 and a functional epoxy-polyurethane copolymer comprising on the base layer 1

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30 coating 3.

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g In one embodiment of the invention, the functional coating comprises at least 50% of an epoxy-polyurethane copolymer.

In yet another embodiment of the invention, the roll coating comprises an epoxy-based composite base layer 1 on top of the body 4, an adhesive layer 2 on epoxy-polyurethane copolymer on a base 35 and a polyurethane functional coating 3 on the adhesive layer 2.

In one embodiment of the invention, the adhesive layer 2 comprises at least 50% of an epoxy-polyurethane copolymer.

In the context of the present invention, the term functional coating refers to the top, i.e., radially outermost, layer of a roll coating that comes into direct contact with a fibrous web, such as pulp, paper or board, or the like in a fiber web machine such as felt or wire.

The epoxy-polyurethane copolymer can be prepared, for example, by the following methods: 1) The isocyanate end groups of the polyurethane prepolymer are converted to epoxy groups by reacting the polyurethane prepolymer with compounds containing a hydroxyl and epoxy group. Such a compound is, for example, glycidol or 2,3-epoxy-1-propanol. The OH group of glycidol reacts with the NCO group of the prepolymer according to Scheme 1. The resulting epoxy component has both polyurethane and epoxy properties. The mutual molar ratios of the starting materials can be used to control how much of the NCO-terminus reacts to the epoxy. In Scheme 1, both isocyanate groups of the polyurethane prepolymer are terminated by glycid.

Scheme 1

OCN NCO + 2 ^ X ^ -OH

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δ ™ o o ί - »

O

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^ 2) The polyurethane prepolymer is reacted with an epoxy compound containing OH groups SiO 2 g. The isocyanate group of the polyurethane prepolymer then reacts with the hydroxyl group of the epoxy, whereby the copolymer

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00 is formed according to Scheme 2 below, wherein the epoxy compound is bisphenol A diglycidyl ether (DGEBA). The mutual molar ratios of the starting materials can be used to control the proportion of NCO groups that react.

Scheme 2 5 ^ -7 - (- j-Yn- + OCN - ^^^ - 'NCO - ^

O OH O

VI-f 1-k V7

O OOCNH O

O OOCNH O

^ - (') n / X

3) An epoxy component such as DGEBA and a suitable accelerator are added to the polyurethane prepolymer. The accelerator may be, for example, 1,3-disubstituted imidazole-2-thione. The epoxy reacts with the isocyanate group according to Scheme 3 below.

Figure 3

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o c / \ / \

R — NCO + CH: —CH — R: -> R, —N O

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The choice of polyurethane prepolymer is important for the properties of the copolymer jr, for example, the choice of the chain length of the polyurethane prepolymer, the type of polyol and the type of isocyanate can influence

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cd for dynamic and dynamic properties.

In one embodiment of the invention, the epoxy-polyurethane copolymer 00 is a copolymer of diglycidyl ether of bisphenol A and polyurethane.

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The copolymer prepared in Schemes 1 and 2 may be cured, for example, with diamines which react with both epoxy and isocyanate groups.

The roller coating according to the invention, and in particular its functional surface layer, may also contain one or more fillers. The filler may be, but is not limited to, an inorganic metallic, ceramic or mineral filler, such as, but not limited to, silica, silicon carbide, alumina, boride, titanium dioxide, silicon dioxide, silicate, chalk, carbon black, or boron nitride, , beads, fibers, sheets, etc. The filler may also be organic, for example, a synthetic polymer such as UHMWPE (very high molecular weight polyethylene), a synthetic fiber such as an aliphatic or aromatic polyamide, or a carbon fiber tube and may be staple fiber, fiber chips or powder. in terms of. The amount of filler in the roll coating may typically be 0.01 to 50% by weight. The size of the filler may vary from nanoscale up to 200 ppm.

The roll coating according to the invention can be manufactured according to the mold or strip molding technique commonly used in the production of polyurethane coatings. In mold casting, the raw material components of the epoxy-polyurethane copolymer, i.e., the epoxy compound and the urethane prepolymer, and optionally a diol and / or amine curing agent and any auxiliary and excipients are mixed at the casting end and led into a molded assembly. The raw material components are selected so that their mixture remains liquid for a sufficient period of time to allow the mixture to spread evenly in the mold. Cure the coating with its after-treatment by heating it in the oven.

In strip casting, the raw materials of the epoxy-polyurethane copolymer are mixed in a mixing chamber and immediately afterwards, the mixture is poured from the die onto a rotating roll body. The nozzle moves from one end of the roll to the other and the coating can be constructed with one or more sweeps, respectively.

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^ or more layers thick. If necessary, the coating is heat treated at a temperature of 80-160 ° C. The raw materials for strip casting are selected so that the viscosity of the raw material blend rises sufficiently in a short time to allow the | the knife can be cast onto the rotating roll as a coating and the mixture does not spill out of the roll.

cd Fast reactive amines may be included in the raw materials as a curing agent

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and catalysts.

The fibrous material may be introduced onto the roll body by winding or winding before or during casting, preferably in synchronization with the movement 7 of the casting head. In the case of staple fiber, the fiber can be premixed with one of the raw materials and / or introduced into the material at the casting stage.

Figure 1 shows an embodiment of a web coating according to the invention. The roll body 4 is provided with a base layer 1, a grip coil 5 and a surface layer 3. Typically, the roll body 4 is a metal, e.g. steel, aluminum, cast iron, wrought iron or sheet metal cylinder. The base layer 1 comprises a reinforcing fiber, which may be glass, carbon, aramid, polyester, polyamide, or the like, or any mixture thereof, in continuous fiber, woven or nonwoven fabric, and a polymeric resin, typically is epoxy. The adhesive layer 2 according to the Kek-10 invention comprises an epoxy-polyurethane copolymer and may further comprise less than 50% epoxy or polyurethane, preferably the same epoxy as the base layer 1 or the same polyurethane as the surface layer 3. The adhesive layer 2 is preferably non-fiber reinforced. The topsheet 3 comprises polyurethane.

To prepare the base layer 1, the epoxy, curing agent and necessary excipients are mixed together and the resulting mixture is further introduced into a nozzle or irrigation basin. The non-woven fabric is wound dry around the rotating roll and the fabric is wetted on the roll by means of nozzles or the non-woven fabric is wetted prior to winding in the pool and / or by means of nozzles and then wound onto a roll. The adhesive layer 2 is fabricated on the base layer in a manner known in the art. It can be applied by brushing, rolling, casting nozzle, etc., but of course can also be applied to the roll by impregnating the fabric, similar to the base layer resin. Preferably, however, the adhesive layer is non-reinforcing.

As mentioned above, the epoxy-polyurethane copolymer itself can be made into a roll coating or the copolymer can act as an adhesive layer 5 for an epoxy-based composite base layer and a polyurethane topcoat.

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^ rose. When the copolymer acts as an adhesive layer, the adhesive layer can be gelled to the desired extent by heating with, for example, infrared radiation ice. In one embodiment of the invention, the adhesive layer is left in beta or gelled to such an extent that the coating has just solidified, the Beta degree cd can be achieved by allowing the curing reaction to proceed at room temperature; or

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raising the temperature of the coating with infrared radiators or placing the roll in the oven. Another aspect of the invention is a roll of a fiber web machine comprising a roll body and a roll coating according to the invention thereon.

8

Yet another aspect of the invention is the use of an epoxy-polyurethane copolymer in a roll coating.

The following examples illustrate the invention.

Comparative Example 5 A composite sheet of polyester fiber and epoxy resin was prepared with an epoxy portion consisting of 90% bisphenol-A based resin and 10% reactive thinner ("90/10"). A mixture of four apathetic and aromatic amines was used as the curing component.

10 Example

An epoxy-terminated urethane prepolymer was prepared by adding Adipre to the RFAIOOO prepolymer with vigorous stirring to such an extent that theoretically all isocyanate groups react with glycidol to form epoxy groups. The epoxy equivalent weight of the polymer was calculated.

A composite sheet of polyester fiber and resin was prepared as in Comparative Example, but half of the bisphenol A resin was replaced with the above epoxy terminated prepolymer ("45/45/10") with the same hardener mixture. The amount of hardener was adjusted so that the stoichiometry was the same as in the 90/10 plate.

The surface of both boards was gelled by heating the boards to such an extent that the epoxy became rigid. Polyurethane was cast on the boards.

The plates were drilled perpendicular to the joint interface with cylindrical test buttons and the joint shear strength was determined by pulling the epoxy and polyurethane layers apart in the direction of the interface. The 90/10 sheet 25 obtained a shear strength of 15.5 MPa and a 45/45/10 sheet of 17.5 MPa, respectively. The results show an improved adhesion between epoxy and surface urethane as a result of urethane modification of the epoxy.

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It will be obvious to a person skilled in the art that as technology advances, the basic idea of the invention can be implemented in many different ways. Thus, the invention and its embodiments are not limited to the above-described examples, but may vary. la within the scope of the claims.

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Claims (7)

A roll of fiber web machine comprising a metal roller body (4) and on top of it a roll coating comprising an epoxy polyurethane copolymer. 2. Vais according to claim 1, comprising on top of the roll body (4) an epoxy-based composite bottom layer (1) and on top of the bottom layer (1) a functional ionic coating (3) comprising an epoxy-polyurethane copolymer. 3. Vais according to claim 1, comprising on top of the roll body (4) an epoxy-based composite bottom layer (1), on top of the bottom layer (1) an adhesive layer (2) comprising an epoxy-polyurethane copolymer and on top of the adhesive layer (2) a functional coating. (3) made of polyurethane. 4. Vais according to claim 2 or 3, wherein the coating (3) or adhesion layer (2) comprises at least 50% epoxy-polyurethane copolymer. 5. Vais according to claim 1, consisting essentially of epoxy polyurethane copolymer. Vais according to any of the preceding claims, wherein the copolymer is a copolymer of bisphenol A's diglycidyl ether and polyurethane. 7. A roller according to any of the preceding claims, which is a press or suction roller, coating roller, surface sizing roller or articulated roller. C \ J δ c \ j i oo o X cc CL CD CD CD LO δ C \ l