DE2718036A1 - PAPER MAKING FELT AND METHOD FOR MAKING IT - Google Patents

Description

Papermaker's felt and process for its manufacture

The invention relates to a papermaker's felt as well as a Process for its manufacture.

Papermaking felts are commercially available in a variety of varieties to have. Woven felts are made by weaving wool or wool and synthetic yarn, after which the fabric is shrunk or felted to obtain the desired properties and dimensions for a particular application. Although such Woven felts are still used on a large scale, needle felts are becoming more and more popular. So far, needle felts produced by needling a fibrous web onto a fabric substrate. The fabric substrate is usually on top of a Woven felt chair. The fibrous web is formed by carding or carding fibers and the finished web is then made immediately placed on the fabric substrate prior to passage through a needle loom. Several successive web layers can be used can be used, the felt being passed through the needle loom again after each laying of a web. Also can on such webs are needled onto one or both sides of the fabric substrate.

The surface quality of a papermaker's felt is directly responsible for the quality and finish of the paper formed on it. A difficulty with the known papermaker's felts occurs, consists in the surface bumps or irregularities caused by the structure of the fabric or in the case of a needle felt, through the structure of the fabric substrate develop. The crossing points of the cross and weft threads are protruding points, which are impressions on the paper to be formed leave behind. It has already been proposed, by omitting the transverse threads in the fabric substrate of a needle felt, the upper

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To improve the surface quality of the felt, see US Pat. No. 3,458,911. The instruction given to use this in the form of a soluble material. After the needling process, the transverse threads were removed by dissolving. The omission of the longitudinal threads has not been suggested, as these threads are generally considered to be essential for the tensioning of the Felt on the paper machine and for the stability of the felt in the machine direction. aside from that would, if one were faced with the question of omitting the longitudinal threads or the transverse threads of a fabric substrate of a needle felt, also because of this the transverse threads are omitted, since these are the threads that normally reduce the drainage resistance and increase the occlusion of the felt.

Unexpectedly, it has been found that the lengthways threads in a papermaker's needle felt are unnecessary when the cross threads are in place stay.

The papermaker's felt according to the invention is thus characterized that he only uses transverse threads and at least one non-woven, porous layer of textile fibers needled with them The invention also includes intermediate felts which correspond to the Processed papermaker's felts according to the invention as the end product can be.

In addition to maintaining sufficient elasticity and directional stability in the machine direction, the papermaking felts of the present invention have improved Strength and stability in the transverse direction compared to felts without transverse threads, as well as an excellent porosity, a low one Drainage resistance and a more even cross-directional mass distribution than a nonwoven felt, and reduce them the accumulation of impurities from the paper pulp.

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The invention also encompasses a method of making such Papermaker's felts, a fabric substrate made of longitudinal threads, which are soluble in a certain solvent, and transverse threads, which are insoluble in this solvent, is produced that then on this substrate at least one textile fiber web is needled and then the longitudinal threads are dissolved in the solvent.

Monofilament yarns are preferably used for transverse threads, which advantageously improve the strength of the felt in the transverse direction. It was found that in the invention Method the mechanical contraction of the felt during the needling process can be controlled better than with one that cannot woven felt.

The term "longitudinal threads" is intended to denote those threads or yarns which run in the working direction (direction of movement) of the felt on the paper machine while printing "Cross threads" are intended to denote those threads or yarns which run transversely to the working direction of the felt in the paper machine.

The invention is explained in more detail below with reference to the drawings. It shows:

Fig. 1 is a perspective view of a portion of an endless papermaking felt, the needling of a shown is a nonwoven layer with a fabric substrate;

Fig. 2 is a perspective partial view of the needle felt, which according to Fig. 1 was produced;

FIG. 3 shows a view like FIG. 2, but after the longitudinal threads have been removed from the fabric substrate, and

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Figure 4 is a view similar to Figure 3 of a differently constructed papermaking felt according to the invention.

Figure 3 is a perspective, partially broken away view of a papermaker's felt having transverse threads 14 upon which an upper nonwoven web 15 made of textile fibers and a lower nonwoven web 16 made of textile fibers is needled. The one shown in FIG Felt is further characterized by the lack of longitudinal threads that are otherwise interwoven with the transverse threads 14. The cross threads 14 can be yarns that are commonly used as a component of a fabric substrate for needle felts and the desired Strength, rigidity, bending properties and the desired Have weight. Conventional yarn materials can also be used for the transverse threads 14 are used, which in a preferred embodiment monofilament fibers made of synthetic polymer resins such as Polyethylene, polypropylene and like polyolefins, polyamides, polyimides, polyesters and the like. Fiberglass and metallic Single threads can also be used.

The webs 15, 16 can be made of non-woven wool or synthetic fibers or from mixtures of wool and synthetic textile fibers, which are commonly used in the manufacture of papermaker's needle felts be used. For example, the upper panel 15 can be made of wool fibers while the lower panel 16 is synthetic Contains textile fibers, such as polypropylene fibers. The resulting felt consists of a mixture of wool and synthetic polymer resin fibers and embedded transverse threads.

The papermaker's felt of Fig. 3 can be made by that the webs 15 and 16 are needled with the transverse threads 14 in successive needling operations. This allows a Usual needle looms are used, with the transverse threads are held at a distance from each other on a forming loom during the needling process.

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According to a method according to the invention, the webs are first 15 and 16 are needled onto a fabric substrate which contains longitudinal threads which are soluble in a certain solvent, as well as Cross threads that are not soluble in this solvent. This first step is illustrated in Figure 1, using a fabric substrate 10 in the form of an endless belt or tube on a needle loom 17 with a non-woven web or layer is provided. After needling the layer 15 on the base fabric Further layers can be needled one after the other with the upper surface of the base fabric 10. The lower layer 16 is also with The base fabric 10 is needled and here, too, further layers can be needled with the underside of the base fabric 10. Through the In the needling process, all layers are firmly connected to one another and to the base fabric 10 in order to form a firm and compact web, in which the longitudinal threads 12 and the transverse threads 14 of the base fabric 10 are contained. This web is an intermediate felt in a second process step is treated to the invention To form papermaker's felt.

Fig. 2 shows an intermediate felt in a perspective partial view. The upper and lower needled layers 15 and 16 are connected to form a web which contains the longitudinal threads 12 and the transverse threads 14 previously described. The longitudinal threads 12 can be single or multifilament yarns made of any conventional material which is soluble in a given solvent, but which, when the yarns 12 dissolve, has no adverse effect on the properties of the transverse threads 14 or the layers 15 needled therewith. The longitudinal threads 16 can for example consist of calcium alginate, sodium alginate, polystyrene, ethyl cellulose, polycarbonate and similar materials. Such yarns are known as well as the solvents that dissolve in the inventive process, see for example US-PS 2,539,244, 3,311,928 and 3 458 911. consist In a preferred embodiment of the invention, the longitudinal threads 12 of polyvinyl alcohol-plied yarns, which are soluble in water at room temperature.

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The second process step consists in breaking up the longitudinal threads 12, whereby these are removed from the intermediate felt without removing the layers 15, 16 or the transverse threads 14 or essential to solve. The terms "substantially insoluble" and "without substantially dissolving" are intended to mean that the solvent does not have sufficient dissolving power to negatively affect the desired properties of the transverse threads 14 and the layers 15, 16 influence. The detachment of the longitudinal threads 12 takes place in that the intermediate felt according to FIG. 2 in the suitable solvent is washed. The finished papermaker's felt is then watered, dried and using conventional techniques completed.

Fig. 4 is a partial perspective view of a modified papermaking felt similar to the embodiment of Fig. 3; However, it differs from this in that a homogeneous layer of wool fibers with the layer 15 and the underlying layer Structure is needled to give the felt a certain surface quality.

The following example describes a preferred method of making and using the papermaker's felt of the invention, however, the invention is not limited to this example:

An example

First, an endless fabric substrate is produced, which consists of a single-layer flat fabric. The transverse threads consist of polyamide single fibers with a diameter of 0.2 mm and they are arranged at 8 per cm. The longitudinal threads are polyvinyl alcohol -Mehr fasergar ne with a weight of about 20 g / 100 m and they are woven in a number of 7 per cm. The woven substrate is heat-cured at 143 ⁰ C, in a length which is equal to the length of felt in the loom.

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The woven, thermoset substrate is placed on a needle loom and oriented in the longitudinal and transverse directions Sheets made from a mixture of polyamide, polyester and polypropylene staple fibers are applied to the substrate in the usual manner needled. This needle felt is then washed at 83 ° C in a soapy water solution, the felt at a speed of about 37 m / min, is pulled about 100 times through the wash tank. The washed felt, which is now free of longitudinal threads, which in the wash water were dissolved, is now dried on drying cylinders and to the correct length and tension stretched. The finished felt has the following properties:

2 Weight per unit area: 1400 g / m

3 2

Air permeability: 12.8 m / min / m at 12.7 mm water column

Pressure drop 2 density: 0.255 g / cm with one load

of 22 g / cm

Porosity (proportion of voids): 0.653 at 24 atmospheres Thickness: 3.5 mm at 24 atmospheres

LXZ test: At a pressure of 24 atmospheres and

an approach speed of 28 m / s:

L - direction: 0.41 per m χ 10

X - direction: 0.55 per m χ 10

Z - direction: 0.59 per m χ 10

(vertical direction).

The LXZ text simulates the conditions on a papermaker's felt in the middle of the press zone, where the pressure drop per unit length of a felt is measured in the L, X and Z planes, see the thesis by T. N. Kershaw "A Three Dimensional Study of The Factors Affecting the Water Permeability of Wet Felts ", Rensselaer Polytechnik Institute, Troy, New York, U.S.A., June 1972.

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Claims (8)

PATENTANWÄLTE Ing.EberhardtSPEIDEL · - I,. — _ DAAl 9TUHTiC Postfach 1320 ... *, “. - - * 'I V U V V D-8035 Gautlng 2 Patent Attorneys Speldel. W »*» m * m + mer '·' Postfach 1320. 0-6035 Gautlng 2 Office: Dianastr. 1 Telephone: Munich (0 89) 8 50 50 88 Telegram: Germarkpat Gauting Telex: 523818 blue Date: Your reference: Our reference: A 1041 Albany International Corp.,, N.Y., U.S.A. Patent claims 1. Papermaker's felt, characterized in that it has only transverse threads and at least one with has this needled, non-woven, porous layer of textile fibers. 2. Papermaker's felt according to claim 1, characterized in that that the transverse threads are monofilament threads. 3. papermaker's felt according to claim 1, characterized in that the textile fibers are a mixture of wool and synthetic Polymer resin fibers are or consist exclusively of synthetic polymer resin fibers. 4. papermaker's felt according to claim 3, characterized in that it also has a homogeneous layer of wool fibers. 5. papermaker's felt according to claim 3, characterized in that it also has a homogeneous layer of synthetic textile fibers. 709846/0806 ORIGINAL INSPECTED 6. A method for making a papermaker's felt according to claim 1, characterized in that first a fabric substrate made of longitudinal threads in a certain solvent are soluble, and transverse threads, which are insoluble in this solvent, is produced that then on this Substrate at least one textile fiber web is needled and then the longitudinal threads are dissolved in the solvent. 7. The method according to claim 6, characterized in that monofilament threads are used as transverse threads. 8. The method according to claim 6, characterized in that those made of polyvinyl alcohol are used as longitudinal threads. 709846/0806