FI60418B - PAPER MASKINSFILT OCH SAETT FOER DESS FRAMSTAELLNING - Google Patents

Description

RÄ55rTI ΓΒΐ / 111 ANNOUNCEMENT

^ ΜΓα m O1) UTLAGG NINGSSKRI FT OU4TÖ (45) ^ ^ (S1) Kv.ik? /Intxi.3 D 21 F 7/08 FINLAND —FIN LAND (21) P »t * nttlh» k * mu * - PK «Nun * ekning 23 ^ 8/7 ^ (22) Haktmisptivi - An * 6knlnf * dag 0? .08.71 * '^ (23) Alkupllv * —Giltlgl» tfdag 07-08.71 * (41) Tulkit lulktMkii - Bllvlt offmcllg 09 · 02.75

Patent and Registration Office .... .... " ... , , .

_ ^. ,. / 44) DATE OF RECORDING AND DATE OF REVIEW— „„ 0 „

Plttnt- oeh registerstyrelsen Antokin utltjd och utl.tkrlftin publtcind 30.09.81 (32) (33) (31) Requested utuikuu * —Buglrd prlorltet 08.08.73 USA (US) 386636 (Tl) Huyck Corporation, Wake Forest, North Carolina 27587 » USA (US) (72) Eugene Zoltan Fekete, Rensselaer, New York, USA (US) (Jk) Oy Heinänen Ab (5 ^) Paper machine felt and the way to make it - Pappermaskinsfilt och sätt för dess framställning

The present invention relates to felts for use in paper machines, which according to the invention comprise a surface layer made of fibrous material and a layer below the surface layer made of fibrous material made of relatively coarse, rigid and deformable fibers so that the felt is compressed, for example in a press roll the fibers of the underlying layer of a rigid lattice or mesh having a cavity for receiving water and conveying it through the compression crimp. More suitably, such a structure can be used with a surface layer made of relatively fine fibers, the function of which is to come into contact with the paper sheet to be made.

2 60418

When making paper, it is known to use a felt in the press section of a paper machine with a cavity which remains open through the entire gap between the press rolls and thus forms a structure for receiving water to be pressed from the sheet as it passes through the press roll. would cause so-called "curling" or hydraulic disturbance in the intact structure of the track. In this context, the term "paper" is used in the restriction to mean paper, pulp and paperboard. Many different methods have been proposed to achieve the desired result. In this connection, reference may be made to U.S. Pat. Nos. 3,214,327, 3,214,329, 3,214,330, 3,214,331 and 3,27,368. Although the solutions disclosed therein have greatly improved the dewatering process compared to those known in the art, various problems have been encountered in their use. For example, when using a relatively coarse, non-compressible, woven base fabric to create cavities, the non-compressibility of the yarns themselves, which contain the base fabric and occasionally act as support members for the associated fibrous layer, tends to form portions where pressure varies as the fabric passes. as explained in more detail below, the felt is less effective as a water-receiving medium because a smaller portion of the surface area of the paper is effectively subjected to the pressure acting on it than if the fibrous layer were supported more evenly by the underlying fabric. The resulting detrimental effects of the paper sheet, which occur in wetter areas, sheet markings, etc., should be avoided as they may become so severe that they are not only disregarded but adversely affect the acceptable quality of the product being manufactured.

Accordingly, it is an object of the present invention to provide a paper machine felt which will immediately form from the cavity as it passes through the gap between the press rolls while avoiding the significant consequences that have arisen in the past.

These and other objects, which are obvious to a person skilled in the art, can be achieved by using the present invention, the features of which are set out in the appended claims. One embodiment is a paper machine felt having a surface layer made of fibers and wherein the bottom layer is made of fibers that are substantially uncompressible and rigid and coarse with respect to the fibers of the surface layer. cavities are certainly available throughout the gut because the soft surface layer will more efficiently transport water from the paper web in contact with it and thus will form a pad against the paper surface, thus preventing significant marking or other consequences due to pressure unevenness at the nip.

The invention will be more readily understood from the following description with reference to the drawings, in which

Fig. 1 shows a cross-sectional view of an embodiment of the invention in which

Fig. 2 is a partially directed view in the direction of arrows 2-2 in Fig. 1 and

Fig. 3 schematically shows a method of manufacturing paper machine blankets according to the invention.

Figures 1 and 2 show a preferred embodiment of the invention in general. Figure 1 shows a paper machine felt 10 made in accordance with the invention and comprising a surface layer 12 and a layer 14 below it. Figure 1 also shows a base fabric 16 which may optionally be used to implement the basic idea of the invention.

The base fabric 16 shown in Figure 1 may alternatively be either a woven or non-woven structure, such as a compressed structure and a non-perforated plastic strip of a crimping machine such as that described in U.S. Pat. No. 3,214,327. U.S. Pat. No. 3,214,331, a non-woven unfilled or non-woven structure as disclosed, for example, in U.S. Pat. No. 3,320 Π79 or some other structure known per se in the field of paper machine felt. Such a base fabric can usually be used to provide structural strength and stability to the fabric.

When used, it may be prepared by any of a number of methods well known to those skilled in the art. As shown in Figure 1, the base fabric includes woven fabrics and threads or yarns, of which certain yarns 18 are large in the cross-machine direction. at right angles to the direction of travel of the felt when used in a paper machine) and of which the other strands or yarns 19 are oriented in the machine direction. When such a base fabric is used in conjunction with the present invention, it may optionally be suitable in certain locations because of its compressibility properties, as will be apparent from the present invention.

The layer 14 below may suitably be made of fibers 15, most of which are preferably of a known composition containing natural fibers such as wool, but suitably it may also be made wholly or partly of a synthetic material such as nylon, dacron, etc. It should be mentioned that that these fibers are relatively coarse or have a large diameter compared to the fibers used to make the surface layer. In the practice of the invention, these have a diameter of 40 microns, i.e. Π.040 mm or more, so as to obtain large intermediate spaces as shown below. The fibers below are suitably selected on the basis of their stiffness or "strength", i.e., their tendency to resist bending or deformation at the intersections of the fibers, as this increases their ability to form a rigid lattice or mesh as described below.

The surface fibers 11 can be suitably made of a variety of materials, including natural fibers such as wool or synthetic fibers such as nylon, dacron, and the like, or also combinations of some of the above. The surface layer 12 is suitably made of fibers 11 which have a relatively small diameter compared to those fibers which are in the layer below and which in no case have a diameter greater than 27 microns, i.e. 0.027 mm. In a practical embodiment of the invention, the ratio between the diameter of the surface fibers and the diameter of the fibers forming the lower layer 14 must be at least 1.75, i.e. the diameter of the fibers forming the underlying layer 14 should be at least about 1.75 times the diameter of the fibers forming the surface layer 12. For example, in a preferred embodiment of the invention, the diameter of the underlying fibers is about 2.8 times the diameter of the surface layer 12. fiber diameter. In providing cavities throughout the compression die with certain previously known structures, these comprised a base fabric, illustrated at 15 in Figure 1, with pads or nonwoven mats knitted on one side, the base fabric being made of a relatively uncompressed material. Reference is made in this connection to U.S. Pat. No. 2,214,327. However, one of the disadvantages which sometimes appeared to arise with such structures was that the relatively uncompressed yarns of the base fabric tended to form local areas of high pressure on the paper web as the felt passed through the paper machine. This was due to the relatively high incompressibility of the yarns or filaments of the base fabric, a property which is of course desirable in order to preserve the cavities as water tanks into which the water removed from the paper enters as the paper passes through the press crystal. However, the above-mentioned locally coarse pressure had a significant effect in reducing the effectiveness of the felt as a dewatering member and / or caused surface markings on the paper, as pointed out by users. This was partly due to the fact that the relatively uncompressed strands or yarns entering the crimping site in the base fabric not only were relatively uncompressed per se but were also so large compared to the fibers that came in their respective fibrous layer that it could not later effectively create a space between adjacent yarns. or between the strands in the base fabric, van instead they became relatively yielding, especially with free, unprofitable intermediate parts from which they were not directly supported by the yarns or strands of the base fabric. According to the present invention, this drawback is overcome by using the underlying layer made of fibers which are relatively coarse compared to the fibers in the surface layer and which in themselves show high resistance to cross-sectional deformation. Contributing to the random arrangement of these fibers is such that when the entire blanket is subjected to upper and lower pressures, for example as it passes through the crystal crystal, the fibers below come into direct contact with each other and receive large between 6 60418 cavities 17 between fibers. By "stiff" is meant that although the fabric bends in the transverse and longitudinal directions of the machine and can regain its "airiness" or volume when the compression pressure ceases to act, the fibers arriving at the compression point reach a point during the compression step, where each fiber interacts with each other. and because the fibers are suitably selected from materials selected on the basis of their ability to resist cross-sectional deformation or deformation (i.e., the tendency of the fiber cross-section to remain in its original shape when pressure is applied to its sidewalls), still as a whole and keeps the formed lattice or grid in an open state, so that there are large spaces that receive water compressed from the paper.

On top of this underlying layer is a surface layer 12. Since the upper surface of the underlying layer has a number of openings in the anti-fiber surface layer which are relatively small compared to those on the anti-fiber side of previously known compressible-non-compressible fabrics, the surface layer tends to remain more evenly supported by the fibers of the underlying layer, in which case there should be less tendency to follow or bend downward between the unsupported portions of the fibers of the surface layer. This means that not only does the felt pressure profile on the paper become smoother without noticeable locally elevated spots that are believed to provide markings on the paper as above, but the felt is more effective in removing water as most of the paper surface area is effectively exposed to the pressure that the blanket drifts. It will be appreciated that if more water is squeezed out of the paper in a given press than the felt of the press can receive, an excess of water will be generated on the inlet side of the press, which will relatively certainly result in a still relatively brittle paper web counterclockwise and usually "curling" in the paper.

7 60418 Thus, the "cavity volume" or part thereof within its physical limits, which describes the entire felt without regard to the material contained in the felt and which must be available to receive paper water at a given Puri stink level and press pressure load 11a, must be greater than the total volume required to receive this water. plus the water remaining in the felt during maximum compression, however, the void volume as such is not independent of fiber size.

A known illustrative example of this fact is that if cylindrical containers are filled with large non-absorbable small balls or balls, both take up substantially the same volume of water which is introduced into the containers. However, the flow resistance of the water between the balls or spheres will be a function of the surface friction and thus also a function of the surface area, so that the water can drain out more easily, more accurately and faster from a tank with large spheres or spheres. Similar effects occur on the other hand between the fibrous layer containing large fibers (and through the large areas of the space) between the fibrous layers with small fibers. The ease of removal will, moreover, be an inverse function of the thickness of the fiber layer, regardless of the fiber size of the fibers contained in the layer.

Thus, it will be appreciated that using the present invention it is possible to form a felt in which the underlying layer provides a cavity volume with a given compression gap 11a and paper type 1 that curling can be avoided while maximizing the portion of the felt through which water can relatively easily and pass efficiently (i.e., the underlying layer) so that the portion of the felt (i.e., the surface layer) through which it is relatively difficult for water to pass becomes as small as possible. In addition, since the latter part is relatively thin compared to the layer below and is easy to handle, it is possible to clean it relatively easily with known devices such as the suction cleanliness of the felt surface.

Referring again to Figure 1, it will be appreciated that when using the invention with a base fabric 16, it is appropriate in certain cases to provide the base fabric with properties opposite to those of early years using 8,604,188 relatively uncompressed base fibers or yarns to ensure a suitable capacity. In this case, the invention uses relatively compressible strands or yarns that "compress" under the pressure applied to the outer surface, because in the present invention the base fabric primarily provides strength and dimensional stability to the fabric and does not need to be made to form a hollow volume. with a network provided by the fibers in the lower layer 14. Furthermore, in contrast to previously known structures where it was necessary to use a fairly large thickness for the fibers covering the uncompressed base layer so that the tendency of the base layer yarns to mark or otherwise adversely affect the paper being produced is reduced, the surface layer 12 a flat surface on its associated track without the need to use a cushion to eliminate the detrimental effect caused by those components which caused the unevenness in pressure. This therefore means that the dewatering efficiency of the felt can be greatly increased, since it is obvious that the porosity and permeability of a surface layer made of fine fibers is significantly reduced if the thickness of the layer has to be made large. Not only is this possibility in the present invention increasing the dewatering efficiency, but it makes it easier to clean the felt from the water after it has left the paper web and the water is removed therefrom by cleaning equipment and methods known per se.

One embodiment of the present invention includes method steps of (a) forming a fibrous surface layer comprising fibers having a majority of the diameter of 27 microns or 0.027 mm or less, (b) forming an underlying layer of a material comprising randomly placed fibers; most of which have at least 1.5 times the diameter of the surface layer fibers and (c) connect the surface layer and the underlying layer to each other. By way of example, Figure 3 shows a method of carrying out the invention, in which method the underlying layer is first prepared, which may consist of a fibrous underlying layer as described above, or the method may also comprise, according to the above, according to the use of a compressible or contractile substance. A surface layer is attached to this underlying layer with fibers that are small compared to the fibers of the underlying layer, and in the next step the surface layer is attached to the underlying layer by any known technique such as knitting, thermoplastic treatment, gluing or a combination of one or more of the present methods or the like. , into which the underlying layer is introduced in the form of fibers, after which the underlying layer is attached to the surface layer by a method or device known per se.

Example

The base fabric was woven with linite satin fabric and the finished felt contained about 6.3 threads / cm in the machine direction and 5.5 threads / cm in the cross direction. The machine direction yarn was staple spun nylon yarn containing 0.19 grams / meter nylon staple fiber and 342 turns / meter. The transverse yarn comprised 439 grams / meter of nylon staple fiber and 181 turns / meter. The final weight of the base fabric was 373 g / m.

The higher fiber portion of the layer below was made of polyester fibers about 76.2 mm long and 5T microns (T0.051 mm in diameter). The layer was knitted onto the woven base fabric in three layers, each weighing 193.2 g / m 2.

The layer that would come into contact with the sheet was made of fine nylon fibers of about 12 microns, i.

0.012 mm in diameter and 38.1 mm long. The layer was knitted onto a coarser fibrous structure as a single layer weighing 152.4 g / m 2.

The composite fabric was knitted until the desired fabric strength was achieved. The weight of the finished felt was 1,105.0 g / m.

This felt was tested on another ventilated Puri stinkida test paper machine that produced bleached kraft paper weighing 65 g / m at varying speeds and pressed with a pressure standard of 10 6041 8 according to the following table. A comparison was made between this felt and a reference felt containing a four-rivet satin fabric woven base fabric and having a finished felt of 5.51 yarns / cm in the machine direction and 4.72 yarns / cm in the cross direction. The machine direction yarn was a two-ply staple-spun nylon yarn comprising 0.38 g / meter nylon staple fiber at 342 r / m. The transverse yarn comprised 0.36 g / meter of nylon staple fiber at 200 r / meter. The final

O

The weight was about 398 g / m 2. The reference felt had a coarse fibrous portion similar in structure to the portion below the felt described above and used in the present invention, but lacking a fine fibrous sheet-contacting layer. Furthermore, a part made of coarser fibers in the reference felt was made of polyester fibers with a diameter of about 51 microns, i.e. 0.051 and a length of 76.2 mm. This part was knitted into a woven base fabric in five layers, each 2 2 weighing 152.4 g / m 2. The total weight of this felt was 1,105.0 g / m 2.

It has been previously suggested that smaller differences in base fabrics and coarser fiber sections would not significantly affect the test results. Therefore, it is reasonable to assume that in the experimental limits, any difference in behavior may be primarily due to a special effect between the fine layer and the coarse layer of the felt according to the invention.

The test results were as follows:

Machine speed 533 m / min:

Compressive load Dewatering Moisture content 2 kg / width cm 'g / m in felt% 30.4 9.1 18.3 39.3 12.0 19.5

Experimental 50.0 14.5 20.4 blanket 62.5 16.5 22.4 31.2 4.4 39.2

Reference-38.4 5.6 40.2 sieve felt 46.4 7.7 42.6 53.6 9.0 45.0 11 6041 8

It is clear from the above that at a given press load and machine speed the dewatering capacity of the test felt according to the invention was almost twice as high as the reference felt at most points and the moisture percentage remaining in the test felt (which is a function of the efficiency of removing water from , in most cases was less than half of what was left in the reference felt.

It is to be understood that these described and described embodiments, as well as the terms and designations used, are merely illustrative of the invention and do not limit it. In selecting the terms used, it is not intended to exclude any equivalent special case, since it is considered that a person skilled in the art may use the invention in various embodiments within the basic idea of the invention, which is defined in the appended claims.

Claims (14)

A paper machine surface comprising a surface layer of fibrous material 1 and a layer of fibrous material made below the surface layer, characterized in that the surface layer (12) comprises randomly arranged fibers, the predominant part having a diameter of 0.027 mm (27 microns) or less. and that the underlying layer (14) comprises randomly arranged fibers, the diameter of which is at least 1.75 times larger than the diameter of the fibers forming said surface layer (12). 2. Felt according to claim 1, characterized in that the predominant part of the fibers (15) forming the underlying layer (14) in cross section is substantially undeformable. Felt according to claim 2, characterized in that the underlying layer (14) comprises fibers (15), the predominant part having a diameter of 0.040 mm (40 microns) or larger. Felt according to claim 3, characterized in that the underlying layer (14) is formed essentially entirely of said fibers (15). Felt according to claim 4, characterized in that the longitudinal axis of the predominant part of the fibers (11) forming said surface layer (12) at least in the portion of the interface between said surface layer (12) and the underlying layer (14) is substantially completely in the a plane parallel to the plane described by the upper surface of said underlying layer (14). Blanket according to claims 2, 3, 4 or 5, characterized in that the underlying layer (14) comprises a reinforcing bottom cloth (16). Felt according to claim 6, characterized in that said bottom fabric (16) comprises yarn or trees with low resistance to cross-sectional shape change. Blanket according to claims 2, 3, 4, 5 or 7, characterized in that the fibrous surface layer (12) has a thickness less than one-third the thickness of the entire blanket in its uncompressed condition.