Roll Composition

Abstract

A roll for use in a nip defining relationship with another roll, including an inner core, an elastomeric layer around the inner core and an outer shell wrapping core consisting of a nonwoven mat bonded with a thermosetting resin. Preferred mats for the present invention are acrylic nonwoven mats, and preferred resins are those of the epoxy resin family.

Parent Case Text

This application is a continuation-in-part of my copending application, Ser. No. 784,606, filed Dec. 18, 1968.

Description

BACKGROUND OF THE DISCLOSURE

In a number of industries, the high speed transfer of continuous webs of material is accomplished with the use of rolls which either support the web itself or support endless belts which carry the webs. In some instances, the particular characteristics of the rolls are important if the precise conditions necessary for the handling of the material are to be met.

Of particular importance are those rolls which are used in nip-defining relationship with other rolls, such as where a web might be passed between two rolls for pressing, surface conditioning, embossing, dewatering, and the like. A corollary condition to the nip-defining relationship is that condition where one or more of the rolls contain a plurality of grooves in the surface to permit the release of fluids expelled by the nip pressure from the web.

Prior art rolls have been manufactured from iron for a great number of years, and recently, it has been possible to provide steel rolls. Also, rubber-covered rolls, granite rolls and other composition rolls have been employed in various parts of the paper making industry and other industries.

However, metal rolls are expensive to manufacture and are not resistant to corrosion in any degree. Stainless steel and other metals which resist corrosion are particularly difficult and expensive to groove, thereby raising the cost of the roll to a point which becomes prohibitive.

Rubber-covered rolls or other synthetic materials of that type are relatively easy to manufacture but are not capable of sustained high speed nip pressures and are therefore limited to applications at low speed and/or low nip pressure. Rubber rolls normally are effected by a self-aggravating condition where a high spot load will cause a buildup of heat due to energy loss from hysteresis, which causes that portion to expand, which in turn causes more heat due to energy loss from hysteresis, etc. Roll failure is common under these circumstances.

Particular areas where rolls become important are in the forming zones of relatively new forming devices for paper machines and in the press area in a number of industries such as paper, textiles, nonwoven fabrics, and the like. In a press section, two or more rolls are placed in operative relationship with each other to define a nip between which a material such as a web is passed. Efficient conditions for operation require sustained high speeds and nip pressures such as up to 6,000 feet per minute of web travel with nip pressures in excess of 600 pounds per linear inch of roll. At the same time, a resiliency is needed which enables the roll to deform and reform rapidly, such as when a piece of "broke" or other extraneous material is carried by the web through the nip. These deformations and reformations require low hysteresis or the self-aggravating condition mentioned above occurs. High thermoconductivity is necessary to dissipate any heat which is generated.

It is particularly important that with these high speeds and high nip pressures that the rolls be grooved, as for example, in an instance where the traveling web of material passes through a nip and contains moisture or other fluids associated with a web. This moisture, which is being pressed so that the moisture may be removed, oftentimes rewets the web after the web passes through the nip. Grooved rolls substantially lessen the rewetting of the web, thereby permitting higher speeds and pressures.

THE INVENTION

It has now been discovered that rolls may be prepared which are capable of operation at high speed and at high nip pressure without substantial expense in the manufacture thereof. These rolls have a high degree of resiliency, are able to deform and reform without buildup of heat, are totally resistant to chemical attack, are easy to machine for proper surfacing of the rolls and are readily grooved for use in instances where grooved rolls are required. Basically, the invention comprises the use of a roll including an inner core, an elastomeric or rubbery layer around the core and an outer shell wrapping the elastomeric layer consisting of a nonwoven mat bonded with a thermosetting resin. The outer surface may be machined to achieve the proper smoothness and grooving of the rolls, a preferred embodiment, is a relatively simple tooling operation and may be accomplished with a high degree of accuracy.

The rolls of the present invention may be manufactured from any fiber substance that may be formed into a nonwoven mat. It is preferred, however, that the mat itself has a tensile strength of at least five pounds per inch. Typical examples of materials which may be formed into suitable fibrous mats are nylon fibers, paper or paperboard of sufficient strength, acrylic fibers, polyester fibers, cellulose acetate and other acetate fibers, asbestos fibers, cotton and sisal fibers, polyamide fibers, rayon fibers, polyolefin fibers, and the like. Particularly suitable rolls have been prepared from acrylic nonwoven mats.

The thermosetting resins employed to bond the nonwoven mat are broadly defined as condensation polymers or copolymers formed through the reaction of the functional groups of the organic compound, with the possible elimination of water or similar byproducts. A wide variety of thermosetting resins may be employed. An example of these are phenolic resins which are the reaction product of phenols with aldehydes, such as phenol and formaldehyde.

Urea and melamine resins are also suitable and are formed from the reaction between the hydrogen of the amine groups of urea or melamine and the hydroxyl of the hydrated formaldehyde.

Two other closely related classes of thermosetting resins which may be employed are alkyds and polyesters, otherwise known as modified and unmodified polyester resins. Polyester resins are prepared by reacting a polybasic acid such as adipic acid, sebacic acid, etc., with a polyfunctional component such as glycol, glycerol, and the like. Modified or alkyd resins are formed by the reaction of a fatty glyceride or fatty acid such as linoleic acid with the unmodified resin.

The most preferred class of thermosetting resins are the epoxy resins. Epoxy resins are formed from a basic epoxide which contains epoxy groups which are then cured with either diamines or diabasic anhydrides. Epoxides are prepared in a number of ways, such by the reaction of phenol and acetone to produce Bisphenol-A, which in turn is reacted with ephichlorohydrin to yield the epoxy intermediate. Diamine or diabasic anhydride then reacts with the intermediate to produce the final resin.

Another preferred class of thermosetting resins are the acrylic resins. Acrylic resins are acrylate or methacrylate ester polymers, although they may include acrylonitrile and chloroacrylate polymers. These polymers are polymerized along or with other comonomers to give the acrylate resin.

In my copending application having Ser. No. 784,606, filed Dec. 18, 1968, certain rolls are disclosed using the nonwoven mat and thermosetting resin of the present invention, the disclosure of which is incorporated herein by reference. This invention relates to an improvement thereon, said improvement consisting of the addition of the elastomeric middle layer as described in detail herein.

As has been stated above, the nonwoven mat is wrapped around the roll core after being saturated with the resin in a conventional manner. Polymerization of the resin to bond a nonwoven mat results in the formation of the roll. Simple machining of the surface and conventional grooving may then be done to yield a grooved roll.

Typical groove dimensions for use in a wide variety of applications are as follows. The grooves are preferably from approximately 0.005 inches to about 0.080 inches wide. A preferred range of groove width ranges from 0.015 to 0.025 inches. The depth of the groove may range from as little as 0.025 inches to as great as 0.400 inches or greater. Preferably, the groove depth will range from 0.050 to 0.150 inches. The number of grooves per inch of axial length of the roll will vary, depending upon the particular application and the other dimensions of the groove. Normally, it is preferred to have from two to 32 grooves per inch of longitudinal length, while a more preferred range is from six to 12 grooves per inch of axial length.

For a more complete understanding of the operation of the rolls of the present invention, and for a better understanding of the necessity for resistance to corrosion and high nip pressures and speeds, reference is hereby made to the drawings in which:

FIG. 1 represents a perspective view of a roll according to the present invention; and

FIG. 2 is an enlarged section view of a section in a typical roll.

As shown in FIG. 1, the roll of the present invention is most simply shown by the inner core 10 which may be manufactured from iron, steel, or other suitable materials. Around the inner core 10 is wrapped an elastomeric middle layer 12. Depending upon the particular use for which the roll is intended, a wide variety of elastomeric materials may be employed as the middle layer of the present invention. For example, the layer may be natural rubber or any of the synthetic rubbers such as polybutadiene, S. B. R., neoprene, butyl rubber, nitrile rubber, polysulfide rubber, and other materials such as some forms of polyethylene-polypropylene, polyurethane and the like. All that is required is that the material be resilient to some degree to provide the cushion effect or resiliency as set forth herein. Pores or grooves in the elastomeric layer should be provided to permit compression of the layer, since rubber cannot be compressed when totally confined.

Surrounding the middle elastomeric layer 12 is an outer shell 14 which consists of a nonwoven mat bonded with a thermosetting resin. The resin may be machined in a conventional manner to provide any surface which is desired. Grooves may be installed in the outer shell by a simple tooling process.

In FIG. 2, an enlarged section view of the roll having a plurality of grooves is shown. The inner core 10 has a middle elastomeric layer 12 surrounding the core 10. An outer shell 14 comprising a nonwoven mat bonded with a thermosetting resin is then provided. On the surface 16 of the outer shell 14 are a plurality of grooves 17 which may range in the dimensions as set forth herein previously. The grooves 17 may have a depth of from 0.025 inches to 0.40 inches or greater. The width 20 of the groove 17 are preferably from approximately 0.005 inches to about 0.080 inches wide, with a preferred range of groove width ranges from 0.015 to 0.025 inches. The width 22 of the land surface area 16 will vary considerably, depending upon the width of the grooves and the number of grooves per inch. Generally, from 2 to about 32 grooves per inch of longitudinal length are sufficient, while it is more preferred to include from about 6 to about 12 grooves per inch of axial length. Thus if the grooves were about 0.02 inches in width and there were 10 grooves per inch, the width 22 of the land area 16 would be about 0.8 inches. Also shown in FIG. 2 are voids or pores 24 which permit the elastomeric layer 12 to compress when the roll is under load.

Claims

Having thus described the invention, what I claim is:

1. In a roll for use in a nip-defining relationship with another roll, said roll having an inner core and an outer shell comprising a nonwoven mat bonded with a thermosetting resin, the improvement comprising:

an elastomeric middle layer around said core and being wrapped by said outer shell.

2. The roll of claim 1 wherein said elastomeric layer contains a plurality of pores.

3. The roll of claim 2 wherein said shell has a plurality of grooves on the exterior surface thereof.

4. The roll of claim 1 wherein said nonwoven mat is a nonwoven mat derived from acrylic fibers, polyester fibers and mixtures thereof.

5. The roll of claim 1 wherein said thermosetting resin is an epoxy-type resin.