FI93561C - Process for chemical processing of paper-making viruses - Google Patents

Description

93561

Method for the chemical treatment of papermaking fabrics

FIELD OF THE INVENTION The present invention relates generally to methods of making durable, soft and absorbent paper products. The invention also relates to a papermaking method using a papermaking wire coated with a photosensitive polymer resin, and to a method of chemically treating a resin-coated wire during a papermaking operation.

Background of the invention

One of the predominant features of the daily life of today's industrialized communities is the use of disposable products, especially paper disposables. Paper towels, handkerchiefs, sanitary napkins, toilet paper and the like are in almost constant use. The manufacture of these highly sought-after products has, of course, become one of the 20 largest industries in industrialized countries in the 20th century. The high demand for disposable paper products has also created a demand for improved variants of these products and their manufacturing methods. Despite 25 major advances in papermaking, research and development is ongoing to improve both these products and their manufacturing methods.

Disposable products, such as paper towels, handkerchiefs, sanitary napkins and toilet paper, are made from one or more paper webs. If these products are to perform their functions and gain widespread acceptance, they and the paper webs used in their manufacture must have certain physical characteristics. The most important of these properties are durability-35 durability, softness and absorbency.

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Durability refers to the ability of a paper web to maintain its physical integrity during use.

Softness signifies the pleasant tactile sensation experienced by product users when wrinkling paper 5 in their hands and using it for their intended purposes.

Absorbency refers to the property of paper associated with the reception and retention of flowable media, especially water and aqueous solutions and suspensions. When assessing the absorbency of a paper, not only is the exact amount of fluid absorbed by a given amount of paper relevant, but also the rate at which the paper absorbs the fluid. In addition, when the paper is formed into a drive medium such as a towel or wipe, the absorbency of the paper with respect to the fluid is important, resulting in a dry and clean wiped surface.

Methods for making disposable paper towel and sanitary products generally include making an aqueous slurry of paper fibers, after which water is removed from the product while rearranging the fibers in the slurry to form a paper web. Various machines can be used to remove water. Today, most manufacturing processes use machines known as Fourdrinier wire paper machines or double (Fourdrinier) wire paper machines. In Fourdrinier wire paper machines, the paper slurry is fed to the top surface of the endless conveyor wire, which serves as the machine's original papermaking surface. In twin wire machines, the slurry is sandwiched between two converging Fourdrinier wires, where the initial dewatering and rearrangement of the fibers in the papermaking process takes place. After the initial formation of the paper web in the Fourdrinier wire or 35 wires, the paper web is moved to run in both 3 y O o! in machine types through a drying process or processes on top of another fabric in the form of an endless wire, this wire often being different from the Fourdrinier wire or wires. Several different combinations of Fourdrinier wire (-5 wires) and drying fabric (s) have been used successfully and less successfully. The drying process or processes may include mechanical sealing of the paper web, vacuum dewatering, blowing hot air through the paper web, and other types of drying processes.

As described above, papermaking fabrics or fabrics have different names depending on their intended use. Fourdrinier wires, also known as Fourdrinier belts, forming wires 15 or fabrics are used in the original forming zone of a paper machine. The aforementioned drying fabrics transfer the paper web to pass through the drying section of the paper machine. Other types of wires or fabrics may be used. Most previously used papermaking fabrics are generally made of a woven piece of fabric, the ends of which are joined together to form an endless belt. Woven papermaking fabrics usually comprise a plurality of longitudinally spaced warp yarns and a plurality of transverse discrete weft yarns woven together in a manner consistent with a particular weave pattern. Previously known wires have included a single fabric layer (made of warp and weft yarns), multilayer fabrics, and fabrics provided with a plurality of interwoven warp and weft yarn layers. The yarns of papermaking fabrics were originally made of materials such as copper, stainless steel, brass, or combinations thereof. Various materials were often placed on and attached to the tissues to enhance the dewatering process. Recently, in the field of papermaking 93561 4, it has been found that synthetic materials can be used in whole or in part to form the underlying wire structures, these wires being superior in quality to forming wires made of metal yarns. Such synthetic materials have included Nation, polyesters, acrylic fibers, and copolymers. Although a number of different processes, tissues, and combinations of these tissues have been used, only a few such processes, tissues, and combinations of these tissues have resulted in commercially successful paper products.

An example of paper webs that have gained widespread consumer acceptance is webs made by the method described in U.S. Patent No. 3,301,746 to Sanford and Sisson, issued January 31-May 15, 1967. Other generally accepted paper products have been made according to the method described in U.S. Patent No. 3,994,771 to Morgan and Rich, issued November 30, 1976. However, despite the high quality of the paper products produced according to these two methods, efforts are still being made to continuously improve the products, as stated above.

Another commercially significant improvement has been made to the aforementioned paper webs by the method described in U.S. Patent No. 4,529,480 to Trokhan, issued July 16, 1985. This improvement included the use of a paper web wire or belt (called a "deflection member") comprising a perforated woven member surrounded by a cured photosensitive resin-30 frame. This resin frame was provided with several separate insulated channels called "deflection pathways". The method using this deflection member included, among other steps, attaching an embryonic web of papermaking fibers to the top surface of the deflector member 35 and applying a vacuum or other fluid pressure differential to the web from the rear side of the deflector member (machine contact side). . The papermaking wire used in this connection was called a "deflection member" because the papermaking fibers 5 became deflected and rearranged during the application of the pressure difference of the fluid flowing into the deflection channels of the cured resin frame. This deflection member was made according to the method described in U.S. Patent No. 4,514,345, issued to Johnson et al., April 30, 1985,. This method included the following steps: (1) coating the perforated woven element with a photosensitive resin; (2) a thickness control of the photosensitive resin to a predetermined value; (3) exposing the resin to light passing through a mask having opaque and transparent regions having an activating wavelength; and (4) removing the uncured resin. Finally, using the above-mentioned improved papermaking method, it was possible to produce paper with predetermined preselected properties. Paper made by the process described in U.S. Patent No. 4,529,480 is characterized in that it includes two physically separate areas on its surface; the first region comprising a network of relatively high-density and internally quite durable continuous image images; while the second region comprises several domed formations which are quite low in density and internal durability (compared to the network) and which are completely surrounded by the network.

Paper made by this method was clearly more durable, softer and more absorbent than paper made by previously known methods due to several factors. The durability of this paper was increased due to the rather high internal durability provided by the domain. The softness of the paper, on the other hand, increased due to several low-density dome-shaped formations on its surface. The absorbency of the paper increased due to the fact that the paper generally had a lower density, with an increase in the absorption rate due to the ability of the network to distribute the absorbed liquids into absorbent low-density dome-shaped formations in a regular manner.

Although the above-mentioned improved method has worked quite well, it has been found that the cured photosensitive resin contained in the papermaking wire deteriorates rapidly over time, resulting in premature wear of the wires. The principal deterioration mechanism for these deflection members (papermaking fabrics) is the oxidation of the photopolymer resin. To delay this oxidation, it is necessary to add antioxidant chemicals, such as high molecular weight blocked phenols, to the liquid photopolymer resin prior to final polymerization by wavelength activating light (e.g., ultraviolet light). However, there is an upper limit to the number of chemicals that can be included in a liquid resin for three reasons: (a) these chemicals have a negative effect on the resin's rate of light (reaction rate), (b) solubility limits in the resin, and (c) resin structure is degraded by polymer. transition. In addition, as the paper machine operates, these materials wear and / or are removed as they protect against oxidation. When the concentration of antioxidant decreases or this substance becomes eliminated, the resin becomes susceptible to deterioration and the wire is soon destroyed. Thus, there is a need for a method for replacing chemical compounds consumed from a wire during a papermaking operation.

The present invention relates to a method for increasing the life of a wire by continuously adding chemical compounds to 35 wires containing a solid polymeric resin during papermaking. In more detail, when t1: 93561 7 is added, when suitable antioxidant chemicals are added to the wire during papermaking, the life of the wire can be greatly extended. This technique overcomes the current limitations on the amount of antioxidants that can be added to the unpolymerized liquid resin. This technique also resists the inherent wear of the antioxidant in the resin during a normal papermaking operation.

It is an object of the present invention to provide a method for extending the life of papermaking fabrics containing a solid polymeric photosensitive resin by continuously adding an effective amount of a chemical compound to the papermaking fabric during papermaking.

Another object of the present invention is to provide a method for continuously increasing low concentrations of antioxidant chemicals on the paper-contacting surface of these resin-containing papermaking fabrics during their use, thereby protecting the resin from oxidation.

These and other objects are achieved by the present invention as described below.

Summary of the Invention

The present invention relates to a method for improving the service life of papermaking fabrics containing solid photosensitive polymeric resins, and to an improved method of making paper using these papermaking fabrics. The improvement in wire life is generally achieved by the continuous addition of an effective amount of a chemical compound or compounds to the wire during papermaking. These chemical compounds preferably comprise antioxidants capable of preventing or delaying the oxidation of the polymeric resin and the subsequent detrimental effects.

β 93561

The papermaker's fabric, in its preferred form, comprises two main components: (1) a solid polymeric resin frame made solid by exposing a photosensitive liquid resin to wavelength-5 delta active light, the first surface of which is in contact with the fibrous webs to be dried, and the second, first p the surface is in contact with the dewatering apparatus used in connection with the dewatering operation, and (2) a resin-10 reinforcing structure having slits, which may comprise a perforated woven member, interposed between the first surface of the frame and at least a portion of the second surface of the frame. The resin frame preferably includes a plurality of ducts for conducting water from the first surface through the resin frame to the second surface.

Suitable photosensitive resins can be readily selected from a variety of commercially available resins. Examples of such photosensitive polymer resins are urethane acrylates (e.g. methacrylated urethane), styrene-butadiene copolymers, acrylic esters, epoxy acrylates, acrylated aromatic urethanes and acrylated polybutadienes. Particularly preferred liquid photosensitive resins are included in the Merigraph series of methacrylated urethane manufactured by Hercules Incorporated, Wilmington, Delaware, USA. The most recommended resin is Merigraph resin EPD 1616B.

In the preferred method for carrying out the present invention, antioxidants are continuously added to the papermaking fabrics during papermaking to protect the papermaking fabrics from oxidation and to extend their service life. Surprisingly, it has been found that papermaking wire absorbs antioxidants when these agents are added to the wire during its use. This is an unexpected 35 result because of the fast moving papermaking fabrics ti.

93561 9 make one revolution in about three seconds and pass through cleaning jets and vacuum boxes removing the fluid during each revolution. Thus, antioxidant chemicals generally have less than 5 seconds to absorb or adhere to the resin surface (before being flushed out by the cleaning jets and / or removed by vacuum boxes) and to make the wire oxidation resistant.

Suitable antioxidants can be readily selected from a variety of commercially available antioxidants. Preferred antioxidants are primary antioxidants, such as blocked phenols, which are capable of scavenging free radicals and interrupting oxidation chain reactions. A more detailed description of these types of antioxidants that can be used in the present invention will be provided later.

The present invention also relates to a method of making paper using the papermaking fabrics of the present invention. The method of making a paper web of the present invention comprises: (a) forming an aqueous dispersion of papermaking fibers; (b) forming an embryonic web 25 of papermaking fibers from this aqueous dispersion on the torn member; (c) contacting said embryonic web with a papermaking wire comprising a frame including a first surface 30 in contact with the paper, a second surface opposed thereto, and ducts extending from the first surface to the second surface; and a frame reinforcing structure interposed between the first surface of the frame and at least a portion of the second surface of the frame, said reinforcing structure including a reinforcing component having slots; (D) deflecting at least a portion of the papermaking fibers within the embryonic web within said ducts and removing water from the embryonic web through the ducts and rearranging the papermaking fibers to form an intermediate web under conditions under which said deflection is initiated at least simultaneously with dewatering; (e) pre-drying the intermediate web associated with the papermaking wire to a consistency of about 25 to about 98% to form a pre-dried web of papermaking fibers.

In connection with the papermaking process described above, an effective amount of a chemical compound, preferably an emulsion containing a dissolved antioxidant chemical, is continuously added to the wire during papermaking. This method of continuously adding chemical compounds to papermaking fabrics while in use is described in more detail below.

All percentages and ratios are given in this context as weights, unless otherwise indicated.

20 Brief Description of the Drawings

Fig. 1 schematically shows an embodiment of a continuous paper machine showing a method for adding chemicals to a papermaking fabric according to the present invention; Fig. 1A shows a simplified schematic cross-sectional view of an embryonic web partially formed of papermaking fibers prior to being deflected into the duct of the papermaking wire;

Fig. 1B is a simplified cross-sectional view of a portion of the embryonic web shown in Fig. 1A after the fibers of the embryonic web have been deflected into one of the ducts of the papermaking wire;

Figure 1C shows a simplified top view of a portion 35 of a paper web according to the present invention; 93561 11

Fig. ID shows a machine direction sectional view of a portion of the paper web shown in Fig. 1C taken along line ID-ID;

Fig. IE shows a cross-sectional view of a portion of the paper web shown in Fig. 1C taken along line IE-IE, transverse to the machine direction;

Figure 2 shows a plan view of a papermaking wire without a reinforcing structure;

Fig. 3 is a cross-sectional view of a portion of the papermaking wire shown in Fig. 2 taken along line 3-3;

Figure 4 shows a plan view of a fully assembled embodiment of a papermaking wire;

Fig. 5 is a cross-sectional view of the embodiment of the papermaking wire shown in Fig. 4 taken along line 5-5, the rear surface of this wire being provided with a character pattern;

Fig. 6 is an enlarged schematic view of a preferred duct gap geometry; Fig. 7 is a plan view showing a preferred woven multilayer reinforcement structure that may be used in a papermaking fabric;

Fig. 8 is an enlarged sectional view taken along line 8-8 of Fig. 7; Fig. 9 is an end sectional view of the woven reinforcement structure of Fig. 7;

Fig. 10 is a sectional view taken along line 10-10 of Fig. 7;

Fig. 11 shows a sectional view taken along line 11-11 of Fig. 7.

Fig. 12 is a sectional view taken along line 12-12 of Fig. 7;

Figure 13 schematically shows a basic apparatus for making a papermaking line used in accordance with the present invention.

12 93561

Detailed description of the invention

Although the claims of this specification clearly define the subject matter of the invention, it is believed that the invention may be better understood by reference to the following detailed description with reference to the accompanying drawings and application examples.

This description is divided into four parts: (1) a detailed description of the papermaking process and the continuous addition of chemical compounds to the papermaking fabric of the present invention; (2) a description of the paper webs made according to the papermaking method; (3) a description of preferred papermaking fabrics; (5) a description of recommended papermaking fabric manufacturing methods.

1. A method of making paper and adding chemical compounds to a wire 20 The method of the present invention for increasing the life of papermaking fabrics containing solid photosensitive polymer resins and a method of making paper using such resin-coated fabrics may be described in detail below, although other methods may be used. A preferred method of making paper using the photosensitive resin coated papermaking wire of the present invention is detailed in U.S. Patent 4,528,239, entitled "Deflection Member", issued to Paul D. Trokhan on July 9, 1985, and U.S. Patent No. 4,598,239. 4,529,480, entitled "Tissue Paper", issued to Paul. To D. Trokhan on July 16, 1985, both of which are incorporated herein by reference.

Il 93561 13

A well-known papermaking process comprising the process of the present invention for the chemical treatment of resin-coated fabrics comprises a plurality of steps or operations which take place in the chronological order described below. However, it is to be understood that the steps described below are intended to assist the reader in understanding the method of the present invention, and that the present invention is not limited to methods comprising only a limited number of steps. Each step is described in detail below with reference to Figure 1.

Figure 1 shows a simple schematic view of an embodiment of a continuous paper machine that may be used in connection with the present invention. The paper machine shown in Figure 1 is a Fourdrinier wire machine similar in shape and wire arrangement to the paper machine described in U.S. Patent No. 3,301,746 issued to Sanford and Sisson on January 31, 1967, the disclosure of which is incorporated herein by reference. . It will also be appreciated that the twin wire paper machine of Figure 1 of U.S. Patent No. 4,102,737, issued to Morton on July 25, 1978 (which is also incorporated herein by reference), could also be used in connection with the present invention.

First phase

The first practical step in the papermaking process is to form an aqueous dispersion of papermaking fibers 14. Useful papermaking fibers include cellulosic fibers, commonly referred to as wood pulp fibers. Fibers derived from soft wood material (bare-seeded or coniferous) and hard wood materials (bean-seeded or hardwood) are suitable in the context of this invention. The specific species of wood in which these fibers are obtained is not essential.

Cellulose-containing fibers of various natural origins can also be used, including short cotton fibers, esparto hay fibers, sugar cane crushing waste, hemp, curd moss, and flax. Recycled cellulosic fibrous materials (e.g., wood pulp fibers) can be used and are within the scope of the invention. In addition, man-made fibers such as rayon, polyethylene, and polypropylene fibers can also be used in conjunction with natural cellulosic fibers. One exemplary useful polyethylene fiber is Pulpex® sold by Hercules Inc. (Wilmington Delaware, USA).

15 Wood pulp fibers can be made from natural wood by any conventional fiberization process. Chemical processes such as sulfite, sulfate (including kraft paper) and soda processes are suitable. Mechanical processes such as thermomechanical (or Asplun-20 din) processes are also suitable. In addition, a variety of semi-chemical and chemical-mechanical processes can be used. Bleached and unbleached fibers are useful. When the paper web of the present invention is to be used with absorbent articles such as paper towels, fibers made from bleached northern softwood kraft pulp are preferred.

Any equipment commonly used in the art for dispersing fibers can be used to prepare an aqueous dispersion of papermaking fibers. The aqueous dispersion of papermaking fibers 14 is prepared in an apparatus, not shown in the figures, provided with a headbox 13, which may have any suitable structure. The aqueous dispersion 14 of papermaking fibers 14 is fed from a headbox 13 to a forming surface or wire, generally comprising a Fourdrinier wire, generally designated 93561 15 15, to perform the second step of the papermaking process. The Fourdrinier wire 15 is supported by a chest roll 16 and a plurality of counter rolls marked 17 and 17a. The Fourdrinier wire 15 is moved forward 5 in the direction of arrow A conventional drive means, not shown in Figure 1. An auxiliary units and devices which are normally associated with paper machines, and a Fourdrinier wires, including muodostuspöy-DAT, hydrofoils, vacuum boxes, tension support rollers, 10 wire cleaning jets and the like are also not shown in Figure 1.

The fibers in the aqueous dispersion are normally dispersed at a consistency of about 0.1 to about 0.3% at the end of the first stage.

In addition to papermaking fibers, the aqueous dispersion may contain a variety of additives commonly used in papermaking. A list of possible additives contained in column 4, lines 24-59 of U.S. Patent 4,529,480, issued July 16, 1985, is incorporated herein by reference.

The moisture content of the various dispersions, webs and the like described in connection with this specification is expressed as a percentage composition. The percentage composition is determined as the quotient obtained by dividing the weight of dry fibers in the system by the total weight of the system, multiplied by one hundred. In this context, the fiber weight is always expressed on the basis of the oven-dry fibers.

Second Step 30 The second step of the papermaking process is to form an embryonic web 18 of disinfectant fibers on a perforated surface (such as a Fourdrinier wire 15) from the aqueous dispersion 14 prepared in the first step.

16 93561 In connection with this description, said embryonic web 18 comprises a fibrous web which, during the papermaking process, is undergoing rearrangement on the papermaking fabric 10, as will be described below.

The embryonic web 18 is formed from an aqueous dispersion of papermaking fibers 18 by depositing this dispersion on a perforated surface and removing a portion of the aqueous dispersion medium by techniques well known to those skilled in the art. Suction-10 boxes, forming tables, discharge strips and the like can be used to remove water. The fibers contained in the embryonic web 18 are generally high in water, with the water content of these fibers normally being from about 5% to about 25%. The embryonic web 18 is usually too weak to exist without the support provided by an external element such as a Fourd rinier wire 15. Regardless of the technique by which the embryonic web 18 is formed, it must be held together by the papermaking wire 10 while being reorganized by bonds 20 that are weak enough to allow the fibers to be reorganized under the influence of the forces described below.

Any of a number of techniques commonly known to those skilled in the art of papermaking can be used to form an embryonic web. The precise method by which the embryonic web 18 is formed is not essential in the context of the present invention, as long as this embryonic web 18 has only the properties described above. In practice, continuous papermaking processes are desirable, although batch processes, such as those associated with hand-made test sheets, may also be used. Processes useful in this step are described in several reference publications, such as U.S. Patent 3,301,746 to Sanford and 35 Sisson on January 31, 1974, and U.S. Patent No. 9,3561 to 17,994,771 issued to Morgan and Rich on November 30, 1976, both of which are incorporated herein by reference. being incorporated herein by reference.

Once the embryonic web 18 is formed, it passes 5 together with the Fourdrinier wire 15 around the counter roll 17 and is moved in the vicinity of the second papermaking wire 10.

The third stage

The third step in the papermaking process is to attach the embryonic web 18 to a papermaking wire 10, sometimes referred to in previous patents as a "deflection member" due to its function. The purpose of this third step is to contact the embryonic web 18 with the papermaking fabric 10, on which it is then deflected, rearranged and further dried. The properties of the papermaking wire 10 are described in more detail in the following section of this specification. At this point, however, it should be noted that the papermaking fabric 10 includes a plurality of channels or ducts into which the fibers of the embryonic web 18 are deflected and rearranged.

papermaking belt according to the present embodiment shown in Figure 1 passes to the invention the direction of arrow B in 25. The papermaking wire 10 passes around the papermaking wire counter rolls 19a and 19b, the printing spacer roll 20, the papermaking wire counter rolls 19c, 19d, 19e and 19f and the emulsion dispensing roll 21 (which dispenses the emulsion 22) from the papermaking wire 10 to the emulsifying wire 10. Wire cleaning jets 102 and 102a, respectively, are placed between the papermaking counter rolls 19c and 19d and also the papermaking rolls 19d and 19e. The purpose of these wire cleaning jets 102 and 102a is to clean the papermaking wire 10 of all 35 papermaking fibers, binders, durability enhancers, and the like adhering to a portion of the papermaking wire 10 during its use after the final step of the papermaking process. The loop along which the papermaking-5 wire 10 of the present invention passes also includes means for applying pressure differential fluid to a paper web, which in a preferred embodiment of the present invention comprises a vacuum catcher shoe 24a and a vacuum box such as a multi-slot vacuum box 24. various miscellaneous support rollers, counter rollers, cleaning means, drive means and the like not shown in Fig. 2 are commonly used in paper machines and are well known to those skilled in the art.

The embryonic web 18 is contacted with the papermaking wire 10 of the present invention via a Fourdrinier wire 15 when the Fourdrinier wire 15 is placed close to the present papermaking wire 10 adjacent the vacuum capture shoe 24a.

In connection with the third step, the method of the present invention is described, namely, the continuous addition of an effective amount of a chemical compound to the wire during papermaking. While it is clear that this method of adding chemical compounds to extend the life of the wire does not depend on any particular step in the papermaking process, it is only described in connection with the third step for convenience. In fact, chemical compounds can be added to the papermaking wire at any point during papermaking, although it is desirable that these compounds be added to the surface of the wire in contact with the paper at a specified point during the rotation of the wire so that the wire does not support the paper web. This addition generally occurs after the pre-dried paper web 27 has been removed from the papermaking wire 10 through the Yankee drying drum 28 and the wire has passed through the cleaning jets 102 and 102a, but before the wire has returned to contact with the second embryonic web 18 (e.g., near the emulsion dispensing roll 21). ).

5 The term "effective amount of a chemical compound" as used herein means the amount of a chemical compound that slows the rate of deterioration of a photosensitive resin over time. This means that an effective amount of a chemical compound is the amount of a compound capable of increasing the life of a papermaking wire coated with a polymeric resin compared to a papermaking wire that does not contain that chemical compound. The effective amount of a chemical compound will, of course, depend on the large amount of compound used and the process conditions to which the papermaking wire is subjected.

As used herein, the term "continuous addition" means the addition of chemical compounds to the surface of a resin-coated papermaking wire at a specified point or points during each round of the wire. These chemical compounds are preferably added evenly to the top surface of the wire so that the area of the wire substantially in contact with the entire paper benefits from this chemical treatment.

As used herein, the term "chemical compound" means any chemical that, when continuously added to a papermaking resin-coated papermaking wire, extends the life of the wire. Examples of typical chemical compounds suitable for use in the process of the present invention include antioxidants (described in more detail below), reducing agents, chelating agents, preservatives, emollients, ultraviolet light stabilizers, and emollients. Reducing agents are chemical compounds that oxidize more readily than brittle bonds in a polymeric resin (e.g., other bonds). These reducing agents include, for example, sulfite ions, mercaptans, and stannous chloride. Chelating agents include chemical compounds such as EDTA, complex oxidation catalysts (e.g., transition metals). Preservatives are chemical compounds that inhibit or slow the growth of microorganisms that may damage polymeric resins. These compounds include, for example, fungicides and antimicrobials. The release agents are chemical compounds that modify the surface anergy of the polymer resin coated wire to prevent waste from adhering to the wire surface and to allow efficient transfer of the web from the wire to the dryer. Examples of well-known emitters are oils (hydrocarbons and silicones, fluoroplastics and waxes). Ultraviolet light stabilizers include chemical compounds such as 2-hydroxyphenylbenzotriazole, which protects polymer resin coated fabrics from photodegradation. Plasticizers are chemical compounds that improve the flexibility of papermaking fabrics. Plasticizers include, for example, glycerin, di-2-ethylhexyl phthalate and dipropylene glycol dibenzoate. This list of chemical compounds is given by way of example only and is not intended to be exhaustive. Other types of chemical compounds known to those skilled in the art of papermaking to be capable of extending the life of polymeric resin coated papermaking fabrics are also within the scope of this invention.

In a preferred embodiment of the present invention, the chemical compounds are selected from suitable antioxidants. As used herein, the term "antioxidants" refers to organic compounds that can be used in low concentrations to prevent or retard the disappointment and consequent deterioration effects of the cured resin frame in the papermaking wire. Deterioration means a sequential process that includes an initial, duration, and termination phase. The formation of free radicals initiates polymer oxidation. Factors leading to the formation of free radicals include the presence of reactive peroxides or ketones during polymerization and the presence of chemical and cellulosic wastes, which accumulate on the surface of the wire during the papermaking operation. This fact, coupled with the thermal mechanical stress on the wire, eventually causes the belt to wear out due to oxidation. To provide protection against oxidation, the concentration of antioxidant in the cured resin frame should be from about 0.001% to about 5.0% by weight (based on the weight of the resin frame) and preferably from about 0.05% to about 1.5%. The best possible concentration will, of course, depend on the antioxidant used and the process conditions to which the wire is subjected.

There are two types of antioxidants, namely primary and secondary antioxidants. Primary antioxidants, such as blocked phenols and secondary amines, purify free radicals and interrupt oxidation chain reactions. Oxidation of polymeric resins often involves the formation of a hydroperoxide intermediate. When metastable hydroperoxide decomposes, it can disrupt the structure of the polymer and form more free radicals. Secondary antioxidants such as phosphates, phosphites, or sulfur-containing compounds (such as thioesters) and secondary sulfides safely decompose hydroperoxide intermediates into stable by-products (e.g., alcohols). This prevents the peroxides from decomposing into free radicals and oxidizing the polymer resin. The combination of these two types of antioxidants can provide a synergistic effect.

Preferred types of antioxidants of the present invention are primary antioxidants, the best of which are blocked phenols. Blocked phenols purify free radicals by the transfer of labile hydrogen from the hydroxyl group. A variety of blocked phenolic antioxidants are available in molecular weight and cost. High molecular weight blocked phenols usually provide greater long-term stability, with correspondingly more expensive prices. On the other hand, lower molecular weight blocked phenols provide poorer long-term stability due to their higher volatility, although some such low molecular weight antioxidants have been advantageously approved by the FDA. Examples of suitable commercially available blocked phenols for use in the present invention include: tetrakis-20 [(methylene (3,5-di-tert-butyl-4-hydroxyhydrocinnamate)] - methane, Irganox 1010 marketed by Ciba Geigy , 2,6-di-t-butyl-4-methylphenol (BHT), 1,3,5-triazine-2,4,6- (1H, 3H, 5H) -trione, Cyanox 1790 marketed by Amercian Cyanamid Company, and 2, 2 Methylenebis (4-methyl-6-tert-butylphenol), Cyanox 2246, manufactured by American

Cyanamid Company also markets. Mixtures of blocked phenolic antioxidants can be used in the context of the present invention. Further information on blocked phenolic antioxidants can be found, inter alia, in Johnson, "Antioxidant Syntheses and Applications", p. 3-58 (1975), and Capolupo and Chucta, "Antioxidants," Modern Plastics Encyclopedia, p. 127-128 (1988), both of which are incorporated herein by reference.

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93561 23

Another type of primary antioxidant that can be used in the present invention are secondary amines. Secondary amines purify radicals via a hydrogen transfer -NH group and are superior to hindered phenols for high temperature stabilization. However, amines tend to cause staining and color fading and can only be used when darker colors can be accepted or disguised.

10 In addition, amines have only limited FDA approval. An example of a secondary amine antioxidant is 4-4'-bis (α, α-dimethylbenzyl) diphenylamine, Naugard 445, manufactured by Uniroyal Inc. Secondary amine antioxidants are described in more detail in Johson's Antioxidants Synthesis. and Applications ", pp. 60-79 (1975), which is incorporated herein by reference. Mixtures of secondary amines and blocked phenols can be used to protect the papermaking wire from ha-20 disappointment.

Secondary antioxidants break down peroxides into stable by-products (e.g., alcohols). They are considered cost-effective as they can replace some of the more expensive primary antioxidants and work just as effectively. However, one drawback is their tendency to hydrolysis. Suitable types of secondary antioxidants for use in the present invention include phosphites, thioesters, and mixtures thereof. Examples of commercially available phosphites include Tris (monononylphenyl) phosphite, Naugard P, marketed by Uniroyal Inc., and Tris (2,4-di-tert-butylphenyl) phosphite, Naugard 524, marketed by Uniroyal Inc. Inc. also markets. An example of a commercially available thio-35 ester is dilauryl thiodipropionate, 24 93561

Cyanox LDTP marketed by American Cyanamid. A more detailed description of secondary antioxidants, including phosphites and thioesters, is provided in Johnson, "Antioxidants Syntheses and Appli-cations," p. 106-147 (1975), which is incorporated herein by reference.

Combinations of primary and secondary antioxidants are particularly preferred in the context of the present invention. Most preferred are combinations of blocked phenols and thioesters.

Chemical compounds (e.g., antioxidants) are added to the polymer resin-coated papermaking wire as an aqueous solution, emulsion, or suspension. The chemical compounds may also be added as a solution containing a suitable non-aqueous solvent to which these compounds may be mixed; although an emulsion containing chemical compounds is desirable in the context of the present invention. The chemical compounds are preferably uniformly applied to the top side of the resin-coated wires so that substantially all of the surface in contact with the paper benefits from this chemical treatment.

Surprisingly, it has been found that chemical compounds (e.g., antioxidants) are effective when applied to the surface of a papermaking fabric during papermaking. This is particularly unexpected due to the fact that the wires travel at a high speed, usually 2,500 rpm, which means one full revolution every three seconds. In addition, in the preferred embodiment 30, the wires pass through the wire cleaning jets 102 and 102a during each cycle and over the fluid removal vacuum boxes 24a and 24. Thus, the chemical compounds have very little time (i.e., generally less than three seconds) to absorb into the resin 93561 25 and to form a protective topcoat and increase the life of the wire.

Any technique known in the art that distributes chemical compounds evenly at the desired rate of 5 to the papermaking wire 10 can be used. These application techniques for the continuous addition of chemical compounds include transfer roll coating, spraying, and gravure printing. Transfer roll coating has been found to be a cost-effective and accurate method for controlling the amount and distribution of compounds and is therefore the most preferred. Any of the cylindrical dispensing means or coating rolls commonly used in connection with paper machines can be used. Suitable devices for spraying chemical compounds on papermaking rolls include external mixing devices, air-spray nozzles, such as a 2 mm nozzle sold by V.I.B. Systems, Inc., Tucker, Georgia, USA. Suitable devices for printing solutions or emulsions containing dissolved chemical compounds include rotogravure printing machines. One particularly preferred method of continuously adding chemical compounds to a papermaking wire is to use an emulsion dispensing roll 21 and an emulsion bath 23 as shown in FIG. In this preferred method, the chemical compound is dissolved in at least one emulsion step 22 comprising three primary substances, namely water, oil and surfactant, although it will be appreciated that other or additives may be used. The emulsion 22 containing dissolved chemical compounds (e.g. antioxidants) is applied to the papermaking wire 10 via the above-mentioned emulsion distribution roller 21. The emulsion 22 can also be applied to the papermaking fabric 10 by means of cleaning jets 102 and 102a.

An example of a particularly preferred emulsion-35 composition includes water, an oil for a high speed turbine 26 93561 known as "Regal Oil", dimethyldistearylammonium chloride, cetyl alcohol and an antioxidant phenol inhibitor called "Cyanox 1790" sold by American Cyan. As used herein, the term "Regal Oil" means a blend comprising about 87% saturated hydrocarbons and about 12.6% aromatic hydrocarbons and some additives, manufactured under part number R & 0 68 Code 702 Texaco Oil Company, Houston, Texas, USA. The purpose of Regal Oil 10 in the above composition is to act as an "emulsion emulsion". By "release emulsion" is meant that it forms a coating on the papermaking wire 10, whereby the formed paper is released from (and does not adhere to) after the steps of the method of the invention have been performed on the paper web.

Dimethyldistearylammonium chloride is sold under the tradename AROSURF TA 100 by Sherex Chemical Company, Inc., Rolling Meadows, Illinois, USA. Dimethyldistearylammonium chloride is hereinafter referred to as AROSURF for convenience. AROSURF is used in the emulsion as a surfactant for emulsifying or stabilizing oil components in water (e.g. Regal Oil). As mentioned above, the term "surfactant" means a substance in which one part is hydrophilic and the other part water-refractory and regroups at the interface of this hydrophilic ingredient and the hydrophilic ingredient to stabilize the two ingredients.

As used herein, the term "cetyl alcohol" refers to a C16 linear fatty alcohol Cetyl alcohol 30 is manufactured by Procter & Gamble Company, Cincinnati, Ohio, USA Cetyl alcohol, as well as AROSURF, is used as a surfactant in the emulsion used in the preferred embodiment of the present invention.

n 27 93561

The relative percentages of the composition of the emulsion in its preferred embodiment are shown in the following table: 5 Component Volume Weight (gal.) (Pounds)

Water 518 4 320.0 REGAL OIL 55 421.8 10 AROSURF N / A * 24

Cetyl alcohol N / A * 16

Cvanox 1790_N / A * _5.3 * The N / A component has been added in solid form.

15 The fourth step

The fourth step of the papermaking process is deflecting the fibers in the embryonic web 18 into the ducts 36 of the papermaking wire 10 and removing water from the embryonic web 18, for example by applying a fluid separation pressure 20 to the embryonic web to form a papermaking fiber intermediate web 25. One preferred method of applying fluid separation pressure is to subject the embryonic web 18 to a vacuum such that the web becomes vacuum through a passage 36 by applying a vacuum to the papermaking wire 10 on its bottom surface side 12. Figure 1 shows this preferred method using a vacuum trapping shoe 24a and a multi-slit vacuum box 24. Alternatively, positive pressure in the form of air or vapor pressure 30 may be applied to the embryonic web 18 in the vicinity of the trapping shoe 24a or vacuum box 24 via a Fourdrinier wire 15. Conventional means for this alternative pressure alignment are not shown in Figure 1.

The deflection of the fibers within the ducts 36 is shown in Figures 1A and 1B. Figure 1A is a simple cross-sectional view of a portion of the papermaking wire 10 and the embryonic web 18 after the embryonic web 18 is joined to the papermaking wire 10, but before deflecting the fibers into the ducts 5 36 by applying a fluid separation pressure. As shown in Figure 1A, the embryonic web 18 is still in contact with the Fourdrinier wire 15. Only one of the ducts 36 is shown in Figure 1A; the embryonic web 18 being connected to the first side surface 10a of the papermaking wire 10. The first side mesh surface 34a is described in more detail in the papermaking wire section of this specification.

Fig. 1B is a simplified cross-sectional view of a portion of the papermaking wire 10, similar to Fig. 1A. However, this view shows the embryonic web 18 after its fibers have been deflected by applying the separation pressure of the fluid flowing into the roadway 36. It should be noted that a substantial portion of the fibers in the embryonic web 18, and thus the embryonic web 18 itself, have been moved below the first lateral mesh surface 34a and within the duct 36 to form the intermediate web 25. The rearrangement of the fibers in the embryonic web 18 (not shown) occurs during deflection and water is removed through the passage 36, as described in more detail below.

It should be noted that either when the fibers are deflected into the ducts, or after this deflection, dewatering begins from the embryonic web 18 through the ducts. The dewatering takes place, for example, by means of a separation pressure of the fluid 30. However, it is important that essentially no dewatering occurs from the embryonic web 18 prior to deflection of the fibers into the ducts 36. To facilitate this situation, the ducts 36 are quite isolated from each other. This isolation or compartmentation of the ducts 36 35 is important to ensure teas; 93561 29 that a deflecting force, such as a vacuum, is applied quite abruptly and in a sufficient amount to deflect the fibers.

In the machine shown in Figure 1, the water is initially removed at the catcher shoe 24a and the vacuum box 24. Since the ducts are open over the entire thickness of the papermaking wire 10, the water withdrawn from the embryonic web 18 passes through the ducts and out of the system by, for example, a vacuum 10 applied to the bottom surface of the papermaking wire 10. The dewatering continues until the consistency of the web associated with the duct 36 increases from about 20% to about 35%.

After vacuum application, the embryonic web 18 is in a state where it has been under vacuum pressure 15 but from which water has not been completely removed, so that it is now referred to as "intermediate web 25".

The fifth step

The fifth step of the papermaking process is to dry the intermediate web 25 to form the paper web 20 of the present invention. Any of the conventional means known in the papermaking art can be used to dry the intermediate web 25, for example, blow dryers and Yankee dryers, alone or in combination.

The preferred method of the intermediate web 25 kuivattamisek-25 si shown in Figure 1. After leaving 25 passes around papermaking belt 10 return roll 19a and travels in the direction of arrow b in the direction of the papermaking belt 24 a vacuum box 10 connected to the vicinity of the välirai-na. The intermediate web 25 first passes through a pre-dryer 30 26 acting as an alternative accessory. This pre-dryer may comprise a conventional blow dryer (hot air dryer) well known to those skilled in the art.

The amount of water removed from the pre-dryer 26 is controlled so that the consistency of the pre-dried web 27 leaving the pre-dryer 26 is from about 30% to about 98%. The pre-dried 30,93561 web 27, still connected to the papermaking wire 10, passes around the counter roll 19b of the papermaking wire 10 in the area of the printing roll 20.

The pre-dried web 27 passes through a contact surface formed by the pressure roll 20 and the Yankee-5 drying drum 28, whereby a mesh pattern formed on the upper surface of the papermaking wire 10 (described in more detail below) is printed on the pre-dried web 27 to form a printed web 29. This printed web 29 is attached to the surface of a Yankee dryer 28 where it is dried to a consistency of at least about 95%.

The portion of the wire 10 that has carried the web passes around the counter rolls 19c, 19d, 19e and 19f of the papermaking wire 10 and through the cleaning jets 152 and 102a therebetween. This portion of the wire passes from the jets to the emulsion roll 21, where it receives the second emulsion device 22 before coming into contact with the second embryonic web 18.

Sixth Step 20 The sixth step of the papermaking process is to pre-shorten the dried web (printed web 29). This sixth step is an alternative but highly recommended step.

As used herein, the term "pre-shortening" means shortening the length of a dry paper web that occurs when energy is applied to the dry web so that the length of the web is shortened and the fibers in the web are rearranged as the bonds between the fibers break. Pre-shortening can be performed in any of a number of generally known ways. The most common and recommended method is wrinkling.

In connection with the crimping operation, the dried web 29 is attached to the surface and then removed from this surface by means of a scraper blade 30. The surface to which the web is attached usually also acts as a drying surface and generally comprises 93561 31 the surface of a Yankee dryer. Such an arrangement is shown in Figure 1.

The attachment of the printed web 29 to the surface of the Yankee drying drum 28 is facilitated by the use of a shirring binder. Type 5 wrinkle binders are based on polyvinyl alcohol. Specific examples of suitable binders are set forth in U.S. Patent No. 3,926,716, issued to Bates on December 16, 1975, which is incorporated herein by reference. The binder 10 is applied either to the pre-dried web 27 immediately before it passes through the contact surface described above or to the surface of the Yankee dryer 28 of the filter mixer before the web is pressed onto the surface of the Yankee dryer 28 via the printing roll 20. (Neither of the 15 adhesive application means is shown in Figure 1; any application technique commonly known to those skilled in the art, such as spraying, may be used). Generally, only the non-deflected portions of the web connected to the top surface plane 11 of the papermaking wire 10 are attached directly to the surface of the Yankee dryer 28. The paper web attached to the surface of the Yankee drum 28 and dried to at least about 95% consistency is removed (i.e., crimped) from this surface by a scraper blade 30. Energy is thus applied to the web and the web is pre-shortened. The exact pattern of the surface of the net-25 and its orientation with respect to the scraper blade 30 largely determines the amount and nature of wrinkling applied to the web.

The paper web 31 obtained by this method can alternatively be calendered and 30 is either post-rolled (with or without differential speed post-printing) or cut and stacked by means not shown in Figure 1. The paper web 31 is then ready for use.

32 93561 2. Improved paper

An improved paper web, sometimes referred to in the art as a tissue paper web, is prepared according to the method described above. As shown in Figures 2C and 2D, this improved paper web 31 is characterized in that it includes two separate areas.

The first area comprises a network area 100 which is continuous and forms a preselected pattern. It is referred to as a "network area" because it comprises a line system with essentially the same physical properties, these lines crossing, interleaving and transversely with each other like a mesh fabric. It is said to be "continuous" because the lines of this network run mainly uninterrupted over the surface of the web. (Of course, the Pa-15 peri is never completely uniform by nature, for example microscopically. The substantially uniform lines are practically uniform and also continuous.) The domain is said to form a preselected pattern because these lines 20 provide a certain shape or shapes in a repetitive (unlike random) figure.

Figure 1C shows a plan view of a portion of the improved paper web 31. The web area 100 is thereby forming modified diamond patterns, although it will be appreciated that other preselected shapes 25 may be used in connection with the present invention. Fig. 1D is a cross-sectional view of the paper web 31 taken along line ID-ID of Fig. 1C.

The second area of the enhanced tissue paper web comprises a plurality of dome-shaped formations 101 over the entire network area 100. As shown in Figure 1C, these domes are distributed throughout the network area 100, each substantially surrounded by the area 100. The shape of these domes (in the paper web plane) is limited by the area 100. gives the reason why the second region of the paper web is called 35 the region of several "domes". Domes 101 appear to extend 93561 33 (projecting) 100 formed by the domain level toward an imaginary observer who looks at the direction of the arrow Z x. When this imaginary observer whereas Figure ID the arrow Z2 direction, the second region comprises Priva-5 Enclosed are biting the cavities or wells. The second area of the paper web is thus called the area of several "domes" for convenience.

Fig. IE shows a sectional view of the paper web 31 taken along the lines IE-IE of Fig. 1C (machine direction section). Figure IE shows the ridges 104 formed in the paper web 31 during the crimping process. The paper structure forming the figures 101 may be intact, or as shown in Figure ID, it may also be provided with one or more holes or openings, such as a hole 103, extending mainly through the paper web 31 structure. through.

In one embodiment of this improved paper, the basis weight of the domes 101 and the network 100 is substantially the same, however, the density (weight / volume unit) of the network 100 is high compared to the density of the domes 101.

In another embodiment, the improved pa-20 peri includes a relatively low basis area 100 relative to the basis weight of the domes 101. This means that the fiber weight in any region extending to the plane of the paper web 31 of the web region 100 is less than the fiber weight in the corresponding region 25 extending into the region of the domes 101. In addition, the density of the network area 100 (weight / volume unit) is high compared to the density of the domes 101.

The preferred paper webs of this invention have a device density (or pulp or gross density) of from about 0.020 to about 0.150 grams / cm 3, most preferably from about 0.040 to about 0.100 g / cm 3. The density of the web 100 is preferably from about 0.200 to about 0.800 g / cm 3, most preferably from about 0.500 to about 0.600 g / cm 3. The average density of the domes 101 is preferably from about 0.040 to about 0.150 g / cm 3. preferably 35 from about 0.060 to about 0.100 gm / cm3. The recommended total basis weight of the paper web 93561 34 is from about 9 to about 95 g / m 2. Given the amount of fibers contained in the unit area extending into that web area, the ratio between the basis weight of the network area and the average basis weight of the domes is from about 0.8 to about 1.0.

The paper web of this invention can be used in any application where soft and absorbent tissue webs are required. One particularly preferred area of use for the paper web of this invention is towel products. For example, the two paper webs of the present invention can be bonded together by gluing together as described in U.S. Patent No. 3,414,459, issued to Wells on December 3, 1968, which is incorporated herein by reference, to form two-ply paper towels.

3. Papermaking wire

As described above, there is a need for an improved paper having the above properties. In order to produce such paper, a papermaking wire 10 with certain properties must be used in connection with the papermaking process, which transfers the desired properties to the paper web. The desired properties of the papermaking wire 10 are described below.

A detailed description of a papermaking wire that does not include the improvements described herein is provided in U.S. Patent 4,528,239, entitled "Deflection Member", issued to Paul 30 D. Trokhan on July 9, 1985, and incorporated herein by reference, although other structures may also be used in the manufacture of improved paper. In this connection, reference is made in particular to column 6, line 20 and column 10, line 60, of this Trokhan patent for a thorough description of the previously known papermaking wire.

As mentioned above, in the embodiment shown in Figure 1, the papermaking wire 10 is in the form of an endless wire-5 belt. Although the preferred embodiment of the papermaking wire used in the present invention is an endless wire belt, several other wire shapes may be used in the present invention, including, for example, solid sheets for making test sheets or rotating drums for use in other types of continuous processes. The papermaking wire 10, regardless of its physical form, generally has certain physical properties.

The papermaking fabric 10 generally includes two opposing surfaces 15, referred to herein as the paper contacting surface 11 and the machine contacting surface 12. The papermaking contact surface is also referred to herein as the "top surface," the top surface ", and the" work surface. " "," surface in contact with the embryonic web "," paper side "or" front side "because this surface of the papermaking wire 10 is in contact with the paper web to be dewatered and rearranged. The opposite surface 25 (i.e., the machine contact surface 12) is also referred to herein and in the references as a "bottom surface", a "bottom surface", a "surface in contact with the machine" or simply the "back side" of the papermaking wire 10 because this surface passes through papermaking equipment such as the papermaking process. over and in contact with the counter rolls 19a, 19b, 19c and the vacuum box 24 of the papermaking wire. It will be appreciated that although the paper-contacting surface of the papermaking wire is sometimes referred to as the top surface of the wire, this orientation of the paper-contacting surface may be such that it faces down the return path in the paper machine because it is in the form of an endless wire belt. Similarly, it is clear that although the surface in contact with the machine of the papermaking wire is sometimes referred to as the bottom surface of the wire, the orientation of the surface in contact with this machine may be such that it is directed upward in the return path in the paper machine.

The papermaking fabric 10 generally comprises two main elements: a solid polymeric resin frame 32 and a reinforcing structure 33, both of which are shown in Figure 4. The resin frame 32 comprises a first surface 34 for contact with the fibrous webs to be dried, a first surface 34 opposite the first surface 34 for contact with a dewatering operation. with dewatering devices (such as a vacuum box 24 and papermaking counter rollers 19a, 19b, 19c), and ducts passing between the first surface 34 and the second surface 35 to channel water from the fibrous webs on the first surface 34 to the second surface 35 and form areas where the fibrous web fibers can be formed. deviate and rearrange. A reinforcing structure 33 is interposed between the first surface 34 and 25 of the frame 32 at least a portion of the second surface 35 of the frame 32 of the papermaking wire 10.

In a preferred embodiment, the reinforcing structure 33 includes slots 39. With the exception of portions of the reinforcing structure 33, the slits 39 (i.e., the solid portion) are referred to herein as the reinforcing structure component 40 or simply as the reinforcing component. The reinforcing structure includes a protruding open area delimited by the projection of the area delimited by the slits and a protruding reinforcing component delimited by the projection of the reinforcing component.

li 93561 37

In addition, in a preferred embodiment, the second surface 35 of the frame 32 of the papermaking fabric 10 includes passages 37 which cause surface pattern irregularities, generally indicated at 38 (best shown in Figure 5) and spaced apart from the ducts 36. These passages form an uneven surface that allows at least partial removal of the vacuum pressure from the dewatering devices, such as the vacuum box 24, through the sieve 10 in contact with the machine of the papermaking wire 10. The surface pattern irregularities 38 result in an uneven surface for contact with the papermaking equipment.

The first surface 34 of the frame 32 and the paper contacting surface 1115 of the papermaking wire 10 generally comprise the same elements. This is usually the case with most embodiments of the present invention because the reinforcement structure 33 is interposed between the first surface of the frame 34 and at least a portion of the second surface of the frame 32 (i.e., the first surface of the frame 32 generally covers one side of the reinforcement structure 33). However, the second surface 35 of the frame 32 of the papermaking wire 10 and the surface 12 of the papermaking wire 10 in contact with the machine do not necessarily comprise the same elements. As mentioned above, the reinforcing structure 35 is interposed between the first surface 34 of the first frame 32 and at least a portion of its second surface 35. Thus, the second surface 35 may either completely cover the reinforcing structure 33 or only a part of the second surface 35 covers the reinforcing structure 33. In the former case, the second surface 35 of the frame 32 and the surface 12 of the papermaking wire 10 in contact with the machine are the same. In the latter case, the surface of the papermaking wire 10 in contact with the machine comprises, on the one hand, the second surface 35 of the frame 32 and, on the other hand, the exposed part of the reinforcing structure 33.

93561 38

In the following description, the characteristics of the frame 32 and the ducts 36 passing through the frame 32 of the papermaking wire 10 will be considered first, followed by alternative variations 5 of the reinforcing structure 33 and the reinforcing structure 33. The general characteristics of the frame, and in particular of its first surface 34, are best seen in Figure 2. It can first be seen from Figure 2 that in papermaking, directions are generally expressed as machine direction (MD) or machine transverse direction (CD). Machine-10 direction means a direction parallel to the direction of travel of the paper web through the apparatus. The direction transverse to the machine direction, on the other hand, is perpendicular to the machine direction. These directions are indicated by arrows in Figure 2 and several other figures.

Fig. 2 shows a plan view of the first surface of the resin frame 32 without the reinforcing structure 33 to facilitate explaining the properties of the resin frame 32. Although the papermaking fabric can be made without this reinforcing structure, the most useful papermaking fabric for the papermaking method 20 of the present invention includes some form of reinforcing structure to maintain stability. As will be described in more detail below, the most suitable material for forming the resin frame 32 is a liquid light-sensitive resin which can be made solid by exposing it to activating light (e.g. ultraviolet light) of wavelength. By controlling the exposure of the photosensitive resin to activating light of wavelength, the properties of the resulting polymeric resin frame can be varied.

The portion of the frame 32 that is exposed on the top surface of the papermaking wire 10 and comprising the integral portion of the first surface 34 of the frame 32 resembles a net in appearance and is referred to as a "top side net surface 35". The exposed portion on the back side of the papermaking wire 10 93561 39 is again referred to as the "back side mesh surface". As shown in Figures 2 and 4, the topsheet web 34a is macroscopically monolithic, patterned, and continuous. The terms used above to describe the web surface of the cover page (i.e., "macroscopically monolithic, patterned, and continuous") are the same as those used in the references U.S. Patent Nos. 4,514,345, 4,528,239, 4,529,480, and 4,637,859, which are incorporated herein by reference. concepts. Thus, "macroscopically monolithic" means that when a portion of the side of the papermaking wire 10 in contact with the paper is placed in a planar shape, the mesh surface is substantially flush. It is said to be "substantially" on the same level to account for the fact that deviations from absolute uniformity are allowed, but not recommended, as long as these deviations are not too great to adversely affect the papermaker's product. The mesh surface is said to be "continuous" because the lines contained in the mesh surface must form at least 20 substantially uninterrupted mesh-like patterns. This pattern is said to be "substantially" continuous to account for the fact that interruptions in this figure are permitted, as long as these interruptions are not too significant to adversely affect the product formed on the papermaking wire 25.

It can be seen from Figure 2 that the paper contacting surface 11 of the papermaking wire 10 includes a plurality of ducts 36 passing through the frame 32 to the second surface 35. Each duct 36 includes defined portions as follows: a channel portion or hole usually numbered 41; a channel orifice, such as a first channel orifice 42 formed on the first surface 34 of the frame 32; a mouth opening of the duct, such as a second duct opening 43 formed on the second surface 35 of the frame 35 32; and duct walls, generally designated 93561 40, which define the dimensions of the duct in the interior of the frame (i.e., in the portion between the first surface 34 and the second surface 35).

Although the openings of the ducts 36 may be arbitrary in shape and arbitrarily distributed, they preferably have a uniform shape and are distributed in a manner according to a repetitive preselected pattern. In practice, these shapes include circles, ovals, and polygons with up to six pages. The tubular openings need not be regular polygons in shape and the sides of the openings need not be straight; but openings with curved sides, for example three-block shapes, can also be used. Although there is an unlimited range of possible geometric shapes for the mesh surface and the openings of the ducts, certain guidelines for selecting this geometric shape can nevertheless be set. Without being bound by any theory, it is believed that ducts of regular shape and order are important for the physical properties of the final paper web. The more random the order of these ducts and the more complex their geometry, the greater their effect on the appearance of the web. The maximum staggering of the ducts tends to produce isotropic paper webs (i.e., paper webs having the same properties as measured along all axes in all directions). If anisotropic paper webs are desired, the staggering of these ducts should be reduced.

The shape and order of the ducts 36 shown in Figure 2 is particularly preferred. The shape and order of the road-30 hyeau openings shown in Figure 2 are referred to as the "linear Idaho pattern." In more detail, the preferred shape and order of these channel openings is referred to herein as the "300 linear Idaho pattern with 35% articulation." The first 35 digits of this designation represent the number of ducts per square inch of the frame. The second part of the designation (i.e. 35% with articulation area) denotes the projection area of the top side mesh surface. The designation "linear Idaho" is based on the fact that the cross-section of the ducts forming this pattern originally resembled a potato in shape. However, the walls on the four sides of the ducts are generally formed by straight lines, so this pattern is called a "linear Idaho pattern" instead of the Idaho pattern alone. As shown in Figure 2, the cross-sectional shape of these ducts 10 is approximately a modified parallelepiped. The shape of these ducts is said to resemble a modified parallelepiped, since in this plan view each duct has four sides, each opposite pair of sides being parallel, whereby the corners between adjacent sides are not straight, with the corners between adjacent sides being rounded.

The dimensions of this figure are best seen in Figure 6, where the reference letter "a" represents the length in the machine direction (MD) or simply the "length" of aperture 20 shown in the figure, "b" the aperture length measured in the transverse direction (CD), or the aperture "width". "c" is the distance between two adjacent openings in the direction between the MD and CD directions, "d" is the distance in the CD direction between adjacent openings, and "e" is the distance in the MD direction between two adjacent openings. In a particularly preferred embodiment, "a" has a size of 1.6892 mm, "b" 1.2379 mm, "c" 0.28153 mm, "d" 0.92055 mm and "e" 0.30500 mm. The open mesh area of the upper surface 30 of the papermaking wire 10 formed according to this geometry is about 65%. These dimensions can be changed in a directly proportional manner for use in other applications.

Referring to Figure 2 and additionally to Figure 3, again, it can be seen that the conduits form the inside of the sel-35 nät 44 taper inwardly from the frame 32 of the top facet 34 93 561 42 35 toward the bottom surface. This narrowing of the walls is controlled (as can be seen in the part of this specification relating to the manufacture of the papermaking wire 10) by aligning the light used to cure the photosensitive resin. The walls are preferably tapered so that the surface area of the web is about 35% of the total projection area of the top surface of the papermaking wire and 65% of the total projection area of the bottom surface of the papermaking wire 10 (before patterning the back side, as described below). The reason why the walls of the ducts taper in such a 35/65 ratio is that a larger amount of resin is needed near the back of the papermaking wire 10 to mechanically bond it to the reinforcement structure 33. As shown in the figures and as described in more detail below, the reinforcement structure is in the preferred embodiment set closer to the back side of the papermaking wire than to the top side thereof. One reason why the reinforcing structure 33 is placed closer to the rear side of the papermaking wire 10 is that the portion of the resin network on top of the reinforcing 20 structure 33 (hereinafter referred to as "overload resin") is needed to form the ducts in the desired pattern and their depth so that these ducts sufficient to fulfill its function of forming an area into which the fibers in the paper web 25 can be deflected for rearrangement of this paper web.

When it is said that the reinforcing structure 33 is placed closer to the back side of the papermaking wire, the dimensions in question may vary. In a preferred embodiment of the papermaking wire 10, the thickness of a typical woven member comprising stacked warp yarns is 10 to 37 thousandths of an inch. The thickness of the overload resin (i.e., the portion of the resin network placed over the top surface plane of the reinforcing structure) is usually 1 to 30 inches to 93561 43 parts per thousand. This results in a papermaking wire 10 having a thickness of 11 to 67 thousandths of an inch.

The openings or channels formed by the ducts extend over the entire thickness of the papermaking wire 10 and form the necessary continuous passages 5 connecting its two surfaces as described above. As shown in Figures 2-5, the ducts 36 are made separately except for the base (as described below), which has a back side pattern. This means that the final shape of the 10 depends on the pattern selected for the network, which is formed in the network, and they are separate with respect to each other. In other words, the mesh surface surrounds these ducts in a separate circumferential manner. This separation is particularly evident from the plan view 15 of Figure 2. They are also shown insulated so that there is no connection between the ducts in the body of the papermaking wire 10. This isolation of the ducts from each other is particularly evident from the cross-sectional view shown in Figure 3. Thus, the transfer of material (e.g., dewatering from the paper web) to one of the ducts is not possible unless this transfer is performed outside the body of the papermaking fabric or, as described below, along the back side of the papermaking fabric.

Figures 4 and 5 are similar to Figures 2 and 3, but show a more useful and preferred papermaking wire 10 that includes a reinforcing structure 33 for reinforcing the frame 32. Fig. 4 is a plan view of a portion of the papermaking wire 10. Fig. 5 is a cross-sectional view of this portion of the papermaking wire 10 shown in Fig. 4 taken along line 5-5. The reinforcing structure 33 is shown in Figures 4 and 5 as a woven element of monofilament yarn for simplicity. Although the present invention can be applied using a monofilament woven element as a reinforcing structure 3335, a multilayer woven element (comprising more than one set of yarns running either in the machine direction or in the transverse direction) is more preferable. Figures 4 and 5 generally show situations in which the reinforcing structure comprises a woven element, the structural elements 40a comprising machine direction warp reinforcement strands, generally designated 53, and machine direction transverse weft reinforcement strands, generally designated 53. As can be seen from these Figures 10, the reinforcing strands 53 and 54 are round and are formed as a square woven belt around which a frame 32 is made. Any suitable filament size and shape can be used in any conventional fabric, as long as the flow through the ducts is not significantly impeded during web processing and the overall integrity of the papermaking wire 10 can be maintained. Although the structural material of these filament yarns is not critical, polyester is the preferred material. Other suitable materials from which filament-20 yarns can be made include polypropylene, Nation, and any other materials commonly used in papermaking fabrics.

Although in the above preferred embodiment of the invention the structure of the wire is formed by a perforated woven element, this structure could be different in several ways. It could comprise a nonwoven element, belt or plate (made of metal or plastic) pierced or drilled with a series of holes, as long as such element is only capable of sufficiently reinforcing the hart-30 frame and includes a suitable open projection area for the operation of drainage devices, and allows the passage of water removed from the pericardium through the cracks it contains.

In connection with the description of the properties of the perforated woven element 35 shown in Figures 4 and 5, several different related concepts have been used. It can be seen that the structural components 40a of the reinforcing structure 33 are generally referred to as yarns, threads, filaments or fibers when the reinforcing structure 33 comprises 5 woven elements. It is clear that these concepts: yarns, threads, filaments and fibers mean the same thing. In addition, some yarns that include a reinforcing structure 33 are referred to as warp yarns 53 and others as weft yarns 54. As used herein, the term "warp yarn" 10 refers to yarns that are generally machine-oriented when the papermaking wire 10 is installed on a paper machine. As used herein, the term "weft yarn" means yarns that are transverse to the machine direction when the papermaking fabric 10 is installed on a paper machine.

As mentioned above, although a fibrous woven element may be used as the reinforcing structure 33 in the present invention, a multilayer woven element is more preferable. Most preferred are those multilayer fabrics that contain multiple warp yarns or machine direction filament yarns because the repeated passage of the papermaking wire over the rolls in the machine direction puts considerable strain on the machine direction due to this endless flow and papermaking transfer method. This heat and stress tends to stretch the papermaking wire 10. If the papermaking wire 10 were to stretch out of shape, its ability to fulfill its intended purpose would be reduced to otherwise unusable.

The preferred reinforcing structure 33 comprises a multilayer woven wire characterized by warp yarns which are generally stacked in a vertical direction directly on top of each other. These vertically stacked warp yarns 35 increase the stability of the wire in the machine, i.e. process, process, and at the same time do not reduce the open project area of the wire required for the use of the wire in blow-dried papermaking processes.

Figures 7-12 show one such preferred multilayer wire that may be used in connection with the present invention. The reinforcing structure shown in Figures 7-12 comprises a highly permeable multilayer reinforcing structure for use in a papermaking fabric or as such as a papermaking fabric having increased fabric stability in the machine direction. As shown in Figures 8 and 9, this preferred wire includes a paper support side 51 and a roll contact side 52 that facilitates its passage as an endless belt in the machine direction.

The wire fabric shown in Figs. , 53 £, 53g and 53h, these yarns running in the machine direction on the roll contact side 52 of the wire fabric. As best seen in Figures 9-12, the individual yarns of the first yarn layer C and the second yarn layer D form stacked warp yarn pairs E, F, G and H arranged usually in vertically stacked overlapping positions. Looking in more detail, it can be seen that the warp yarns 53a and 53e form a stacked warp yarn pair E; 30 warp yarns 53b and 53f a stacked warp yarn pair F; warp yarns 53c and 53g stacked warp yarn pair G; and warp yarns 53d and 53h of the stacked warp yarn pair H. Adjacent stacked warp yarn pairs are spaced apart in a machine direction transverse direction vii-35 93561 47 to form a desired open area of cellular tissue. The warp yarn balancing weft yarn, 53a in Fig. 9, 54b in Fig. 10, 54c in Fig. 11, and 54d in Fig. 12 are woven together with the first and second warp yarn layers 5 to bond the respective individual warp yarns in the first and second warp yarn layers of the stacked pairs. These weft yarns balancing the warp yarns are also numbered repeatedly in the wire fabric. The warp yarn balancing the warp yarns is woven together with pairs of warp yarns stacked in the equilibrium weaving pattern of the warp yarns 10, keeping the warp yarns stacked on top of each other and generally in a vertical alignment in this weaving pattern. The wire fabric thus formed has increased fabric stability in the machine direction as well as high openness and permeability.

The wires and hinge areas of the reinforcing structure 33 further form a plurality of planes that may be of interest in explaining the location and properties of the surface irregularities 38 on the second surface 35 of the frame 32. These surface pattern irregularities 38 (or back side pattern) in the preferred embodiment of the papermaking wire 10 are best seen in Figure 5. "Back side pattern" location or are independent of it. By "not necessarily dependent" is meant that the location of this backside pattern is not necessarily in any way related to the location of the reinforcement structure 33.

The back side pattern irregularities 38 comprise the same material as the frame 32, so the surface pattern may include any irregularities, discontinuities, or interruptions in the resin material forming the second surface mesh 35a or in the portions of the back side mesh surface from which the resin has been removed.

4. Method of making a papermaking wire

As mentioned above, the shape of the papermaking line can be different in several ways. Although the method of making the paper-making wire 10 is insignificant as long as it has the above-mentioned properties, the following methods have been found to be useful. A detailed description of a method of making a papermaking wire 10 without improvement is described in U.S. Patent 4,514,345, entitled "Method of Making a Foraminous Member", issued to Johnson et al. On April 30, 1985, which is incorporated herein by reference. . One method of manufacturing the papermaking wire 10 will be described below.

An embodiment of an apparatus useful in the present invention for making the papermaking wire 10 of the present invention in the form of an endless wire belt 20 is shown schematically in Figure 13. To provide an overview of the entire papermaking wire apparatus of the present invention, Figure 13 has been simplified to some extent. The general method 25 shown in Fig. 13 generally comprises coating the reinforcing structure 33 with a photosensitive resin 70 as the reinforcing structure 33 passes over the forming unit 71 or table 51 covered with a support film 76 which, among other things, prevents contamination of the operating surface 72 of the forming unit 71 from the resin; monitoring the thickness of the photosensitive resin 70 to a predetermined value; exposing the resin 70 to an activating light of wavelength (from light source 73) through a mask 74 having opaque areas 74a and transparent areas 74b; and removing the uncured resin 75.

93561 49

As shown in Figure 13, the forming unit 71 includes a drive surface 72, this unit comprising a circular element, preferably in the form of a drum. The diameter of the drum and its length are chosen appropriately. Its diameter 5 should be large enough so that the support film 76 and the reinforcing structure 33 are not adversely curved during the process. Its diameter must also be large enough to leave a sufficient distance around its surface to carry out the necessary method steps as the drum 10 rotates. The length of the drum is selected according to the width of the fabric manufacturing wire to be produced. The forming unit 71 is rotated by an actuator not shown in the figure. Alternatively and from the preferred work surface 72, it absorbs light of an activating wavelength.

As mentioned above, the forming unit 71 is covered with a support film 76 which prevents the operating surface 72 of the forming unit 71 from becoming dirty with resin. Another purpose of the backing film 76 is to facilitate the removal of the partially complete papermaking wire 10 from the forming unit. This backing film can generally be made of any flexible, flat and smooth material, such as polyethylene or polyester sheet. The backing film is preferably made of polypropylene and has a thickness of about 0.01 to about 0.1 millimeters (mm). The backing film 76 also preferably absorbs light of a wavelength of activating light.

shown in Figure 13, the device support film 76 is supplied to the system of the backing film supply roll 77 by winding and causing it to travel in the direction of the arrow D2. After unwinding-30, the support film 76 comes into contact with the operating surface 72 of the forming unit 71 and becomes temporarily forced against the operating surface 72 (by the means described below). The support film 76 of this passes together with the forming unit 71 as the forming unit 71 35 rotates. The support film 76 is finally separated from the drive surface 93561 50 72 and passes to the support film receiving roll around which it is rewound. In an embodiment of the method according to Figure 13, the support film is intended to be disposable, after which it is discarded. In the case of the alternative arrangement 5, the support film is in the form of an endless belt running around a set of counter rolls, where it is suitably cleaned and re-used. The required drive means, guide rollers and the like are not shown in Figure 13.

The forming unit 71 is preferably provided with a means for ensuring that the support film 76 remains in close contact with the operating surface 72. For example, the support film 76 may be affixed to the use surface 72 by gluing, or the forming unit 71 may be provided with means for attaching the support film 15 76 to the use surface 72 by a vacuum applied to a plurality of adjacent small openings formed on the use surface 72 of the forming unit 71. by means of a tightening means-20 not shown in Fig. 13.

Another step of the present invention is to make a reinforcing structure for connection to a papermaking wire. As mentioned above, the reinforcing structure 33 is made of the material from which the papermaking wire 10 25 is made. The preferred reinforcement structure 33 shown in Figures 7-12 comprises a woven multilayer fabric characterized in that the warp yarns are stacked vertically on top of each other. These vertically stacked warp yarns provide additional stability to the fabric in the machine-30 or process direction, while not simultaneously reducing the open projection area of the fabric required to use the fabric in papermaking drying processes.

Since the pa-35 fabric 10 made by the apparatus of Fig. 13 is in the form of an endless wire belt.

51 95561 the reinforcing structure 33 should also be in the form of an endless belt. As shown, reinforcing structure 33 travels in the direction of the arrow D around the counter roll 78a up, and fas-forming units 71 and counter-rolls 78b and 78c. The other 5 guide and counter rollers, drive means, support rollers and the like are not shown in Fig. 13.

The third step of the present invention is to place the reinforcing structure 33 on the operating surface 72 of the forming unit 71 (or, in more detail in the illustrated embodiment, causing the reinforcing structure 33 to pass over the operating surface 72 of the forming unit 71). As mentioned above, the support film 76 is used to keep the operating surface 72 of the forming unit 71 free of resin 70. In this case, the third step comprises placing a reinforcing structure 33 15 adjacent the support film so that the support film 76 is interposed between the reinforcing structure 33 and the forming unit 72.

The desired special structure of the papermaking wire 10 accurately determines the setting point of the reinforcing structure 33 with respect to either the operating surface 72 of the forming unit 71 or the support film 76. In one embodiment of the present invention, the reinforcing structure 33 is placed in direct contact with the support film 76. In another embodiment of the present invention, the reinforcing structure 33 may be set at a predetermined distance from the support film 76 by any suitable means. A situation in which the reinforcing structure 33 is placed at a distance from the operating surface 72 of the forming unit 71 (or, when using a support film from the surface of the support film 76) occurs as described below when a photosensitive liquid resin is applied to the rear side 52 of the reinforcing structure 33.

The third step of the method is to apply a liquid photosensitive resin coating 70 over the reinforcing structure 33. Any technique by which the liquid material 35 can be applied to the reinforcing structure 33 is suitable. However, in the preferred method, this liquid photosensitive resin is applied to the reinforcing structure 33 in two steps. The first application step of the resin takes place via the extrusion head 79. The resin is applied via the extrusion head 79 together with the application of the resin in the second stage by means of a nozzle 80. The extrusion head 79 is used in the first step to fill the gaps in the reinforcement structure 33 from the rear side. This allows a suitable amount of photosensitive resin 10 to adhere to the back side of the reinforcement structure 33, whereby this resin can be applied for patterning the back side in connection with the steps described below. It is necessary that the liquid photosensitive resin 70 be spread evenly across the width of the reinforcing structure 15 33 and that the required amount of material be placed in the slots 39 and all existing voids of the reinforcing structure 33 as required by the structure of the papermaking wire 10.

Suitable photosensitive resins for coating the reinforcing structure 33 can be easily selected from a variety of commercially available resins. Useful photosensitive materials are usually polymers that cure or crosslink under the influence of radiation, usually ultraviolet light (UV). Examples of photosensitive polymeric resins include: acrylated urethanes (e.g. methacrylated urethane), styrene-butadiene copolymers, acrylic esters, epoxy acrylates, acrylated aromatic urethanes, acrylated polybutadienes and methybutadienes. Reference publications containing a more complete description of suitable liquid photosensitive resins include Green et al., "Photocross-linkable Resin Systems", J. Macro-Sci. Revs. Macro Chem. C21 (2), 187-273 (1981-82); Bayer, "A Review of Ultraviolet Curing Technology," 35 Pin Paper Synthetics Conf. Proc., September 25-27, 1978, 53 yäb6 * i ss. 167 - 172; and Schmidle, "Ultraviolet Curable Flexible Coatings," J. of Coated Fabrics, 8, 10-20 (July, 1978). All three of these patents are incorporated herein by reference. Particularly Recommended 5 liquid photosensitive resins are included in the Merigraph series of methacrylated urethane resins manufactured by Hercules Incorporated, Wilmington, Delaware, USA. The most preferred methacrylated resin is Merigraph resin EPD 1616B.

In the preferred method of the present invention, antioxidants are added to the resin to protect the final papermaking wire 10 from oxidation and to extend its life. Any suitable antioxidants may be added to the resin. Preferred antioxidants include Cyanox 1790, sold by American Cyanamid, Wayne, New Jersey 07470, USA, and Irganox 1010, manufactured by Ciba Geigy, Ardsley, New York 10502, USA. In the preferred method of making the papermaking wire 10, both of these antioxidants are added to the resin. These antioxidants are added in the following amounts, Cyanox 1790 0.10% and Irganox 101 0.40%. Both antioxidants are added to protect the papermaking wire 10 from a variety of oxidizing agents.

The next (i.e., fifth) step of the method is to control the thickness of the coating to a predetermined value. This preselected value corresponds to the desired thickness of the papermaking wire 10. This thickness is, of course, in accordance with the intended use of the papermaking wire. When the papermaking wire is to be used in the following papermaking process to be described, it is desirable that it be about 0.01 to about 3.0 mm thick. Other applications, of course, require thicker papermaking fabrics, which may be 3 cm or more thick. Any suitable means for controlling the thickness can be used. Fig. 13 of Fig. 35 shows the use of a leaving roller 81, which also acts as a mask guide roller. The clearance between the leaving roller 81 and the forming unit 71 can be monitored mechanically by conventional means not shown in the figure. The leaving roller 81, together with the mask 74 and the mask guide roller 82, tends to smooth the surface of the liquid photosensitive resin 70 and control its thickness.

The sixth step of the method comprises contacting the mask 74 with a liquid photosensitive resin 70. The purpose of the mask 74 is to protect certain areas of the liquid photosensitive resin 10 from the effects of light. Of course, if some areas are protected, others will be left unprotected, causing the liquid photosensitive resin 70 in these unprotected areas to subsequently be exposed to activating light and cure. The protected areas generally comprise a preselected pattern formed by the ducts 36 in the cured resin frame 32.

The mask 74 can be made of any suitable material into which the opaque areas 74a and the transparent areas 74b can be formed. A material similar to a photographic film that is flexible in nature is suitable. This flexible film can be made of polyester, polyethylene, cellulose or any suitable material. The opaque areas 74a may be formed on the mask 74 74 in any suitable manner, such as by photography, engraving, flexography, or circular wire printing. The mask 74 may comprise an endless loop or may be fed from a single feed roll transverse to the system to a take-up roll, neither of which is shown in the figures. The mask 74 travels in the direction of arrow D 3 in the direction of rotating the nip roll 81 where it is brought into contact with the liquid photosensitive resin 70 surface, and then maskiohjaustelaan 82 in the vicinity of which it is removed from contact with the resin 70. In this particular embodiment 93561 55, the control of the thickness of the resin and the setting of the mask take place simultaneously.

The seventh step of the method comprises exposing the liquid photosensitive resin to light of wavelength Akti-5, whereby the resin cures in areas aligned with the transparent areas 74b of the mask. In the embodiment shown in Fig. 13, the support film 76, the reinforcing structure 33, the liquid photosensitive resin 79, and the mask 74 form a unit 10 that travels together from the output roller 81 in the vicinity of the mask guide roller 82. The spacer roller 81 and the mask guide roller 82 are placed where the support film 76 and the reinforcing structure 33 are still adjacent to the forming unit 71, and the liquid photosensitive resin 70 is exposed to light of wavelength Akti-15 emitted from the radiation lamp 73. The radiation lamp 73 is generally selected to provide suitable for curing liquid photosensitive resin 70. This wavelength is in accordance with the properties of the liquid photosensitive resin 70. Any suitable lighting source, such as mercury arc, pulsed xenon, electrodeless lighting sources, and fluorescent lamps, can be used. As described above, when the liquid photosensitive resin is exposed to light of a suitable wavelength, the portions of the resin 70 under this influence cure. This curing usually manifests itself as solidification of the resin in areas exposed to light. On the other hand, the covered parts remain liquid.

The illuminance and its duration depend on the degree of curing required for exposed areas. The absolute values of the intensity and duration of exposure to light depend on the chemical nature of the resin, its light properties, the thickness of the resin coating and the pattern chosen for use. In addition, the intensity of the exposed light and the angle of incidence of the light have a significant effect on the presence or absence of narrowing of the walls contained in the preselected pattern of paths.

In a preferred embodiment of the present invention, the angle of incidence of light is harmonized for more efficient curing of the photosensitive resin in the desired areas and to achieve the desired taper angle in the walls of the final papermaker's fabric. Other means of controlling the direction and intensity of curing radiation are refracting means (i.e., lenses) 10 and reflecting means (i.e., mirrors). In a preferred embodiment of the present invention, a subtractive collimator (i.e., an angle division filter or a collimator that filters or prevents the passage of ultraviolet light rays in non-desired directions) is used. Any suitable device can be used as a subtractive collimator. A dark, preferably black, metal-colored medium in the form of a series of channels through which light directed in the desired direction can pass is recommended. In a preferred embodiment of the present invention, the dimensions of the collimator are such that it transmits light, wherein the projection area of the cured resin web is 35% on the top side and 65% on the back side of the papermaking wire.

The eighth and final step of the method comprises substantially removing all of the uncured liquid photosensitive resin from the reinforcing structure 33. That is, the resin protected from light is removed from the system.

In the embodiment shown in Figure 13, at a location adjacent to the mask guide roller 30, the mask 74 and support film 76 are physically separated from the combination comprising a reinforcing structure 33 and now a partially cured resin 70a. The combination of the reinforcing structure 33 and the partially cured resin 70a passes in the vicinity of the first resin removal-35 shoe 83a. A vacuum is applied to one surface of this compound in the first resin removal shoe 83a, whereby a substantial amount of liquid (uncured) photosensitive resin is removed from said combination.

As this combination continues, it is moved in the vicinity of the resin wash shoe 85 and the resin wash station drain 85, where the combination is thoroughly washed with water or other suitable liquid to remove virtually all of the remaining liquid (uncured) photosensitive resin 75a from the system. At the second resin removal shoe 83b, all remaining washing liquid and liquid resin are removed from the combination by applying a vacuum. At this stage, the combination now mainly comprises a reinforcing structure 33 15 and an associated frame 32 and represents a papermaking wire 10 which is a product of this method. Alternatively and preferably, as shown in Figure 13, the resin may be exposed a second time to activating light to complete the curing of the resin 20 and to increase the hardness and durability of the cured resin frame.

The process continues until the full length of the reinforcing structure 33 has been processed and converted into a papermaking wire 10.

If it is desired to manufacture a member provided with different overlapping patterns or patterns of different thickness, this member can be set to pass through the process several times. Multiple passes through the process can also be used to make relatively thick papermaking fabrics.

A preferred method of making an improved papermaking wire 10 having a patterned backsheet involves the use of a woven element (or nonwoven element) made of filament yarns having different ultraviolet light transmission properties. This method 93561 58 is called "differential transfer casting". This differential transfer molding produces a perforated woven element such that the filaments at the top of this perforated woven element transmit a large amount of ultraviolet light, while the filaments at the bottom or back do not transmit ultraviolet light but instead absorb it. This causes ultraviolet light to pass through the photosensitive resin network in the portion of the network located below the base wires. As a result, the light-sensitive resin under these base yarns does not cure and can be removed in the last step described above, leaving behind a series of recesses in the back side of the papermaking wire 10 located below the light absorbing filament yarns.

It is believed that the solvent addition method of the present invention, in which chemicals are added to a resin-coated papermaking wire to extend the life of that wire, can be understood from the above detailed description. It will be appreciated, however, that various changes may be made in the form, structure and arrangement of the parts of this method without departing from the spirit and scope of the invention or without departing from the essential advantages thereof, with only 25 preferred or exemplary embodiments.

For the sake of clarity, but without limitation, the following examples are provided.

Example I

A test scale Fourdrinier paper machine 30 is used in connection with the present invention. The headbox comprises a fixed roof suction roll frame. The blend used contains 100% northern softwood kraft pulp fibers along with about 10 pounds of Kymene ™ 557H wet strength additive / 1,000 pounds of oven dry fibers 35 (Hercules, Inc ,, Wilmington, Delaware, USA manufactures Kymene 59

? ό56 I

ne ™ 557H). An aqueous fibrous slurry having a fiber content of about 0.15% is deposited on a Fourdrinier wire. Dewatering takes place via a Fourdrinier wire and is assisted by a baffle plate and vacuum boxes. The fourdrinier wire-5a is a five-wire satin fabric structure with 33 machine direction and 30 machine direction transverse monofilament yarns per centimeter, respectively. The embryonic wet web is transferred from the Fourdrinier wire at a fiber content of about 18% at the transfer site to another papermaking-10 wire. This second papermaking wire comprises an endless wire belt, preferably including a mesh surface and deflection channels, described in connection with Figures 2 and 5 above. The papermaking fabric is formed around a perforated woven element 15 made of polyester and containing 14 machine direction (MD) and 12 machine direction (CD) filaments / cm in a four-viral two-layer structure (as shown in Figures 7-12) as described in U.S. Patent No. 4,514,345. in accordance with the method. The MD-20 through-yarns measure about .22 mm and the CD yarns measure about .28 mm. The resin used in the wire production process is Migrigr resin EPD1616B, a methacrylated urethane resin sold by Hercules Incorporated, Wilmington, Delaware, USA. The thickness of the papermaking wire containing the cured photosensitive resin is about 1.1 mm.

The embryonic web passes on the papermaking fabric past the vacuum dewatering boxes and through blow dryers, after which the web is transferred to a Yankee dryer. Other process and machine conditions are described below. The fiber content is about 27% after the vacuum dewatering box and due to the operation of the pre-dryers about 65% before transfer to the Yankee dryer. The creasing binder comprising an aqueous solution of 0.25% polyvinyl alcohol is sprayed through applicators to increase the fiber content to about 99% before 93561 60 as the web is dry creased with a scraper blade. The bevel angle of the scraper blade is about 24 degrees and is set relative to the Yankee dryer so that a collision angle of about 83 degrees is formed. The Yankee dryer is operated at about 350 ° F 5 (177 ° C) at a speed of about 800 feet per minute (about 244 meters per minute). The dry crumpled web is then set to pass between two calendar rolls. These calender rolls are moved together by roll weight and operate at a surface speed of 660 feet per minute (approximately 201 10 meters per minute). The calendered web is wound onto a roll (which also operates at a surface speed of 660 feet per minute), after which the web is ready for use.

The aqueous solution containing the antioxidant emulsion is continuously applied to the paper-contacting surface of the papermaking wire via the emulsion dispensing roller before the papermaking wire comes into contact with the embryonic web (see, e.g., the location of the emulsion dispensing roller in Figure 1). The aqueous emulsion 20 applied to the deflection member of the distribution roller contains five ingredients: water, Regal Oil (a high-speed turbine oil marketed by the Texas Oil Company), AROSURF TA 100 (a surfactant in the form of dimethyl distearearyl ammonium chloride, marketed by Sherex Chemical Company), cetyl alcohol (C16 linear fatty alcohol marketed by Procter & Gamble Company), and Cyanox 1790, a blocked phenol-type primary antioxidant sold by Amercian Cyanamid Company. The interrelationships of these five ingredients are as follows: 10 wt% Regal Oil, 1 wt% Arosurf, 0.9 wt% cetyl alcohol, 1.25 wt% Cyanox 1790 oil and the rest water. When preparing the emulsion, Cyanox 1790 is first dissolved in Regal Oil by heating this oil to 165 ° F for five minutes. Subsequently, the oil step of the emulsion is mixed with the above-mentioned 93561 61 surfactants and finally with water. The volumetric flow rate of the aqueous solution applied to the papermaking fabric is about 0.50 gal / h transverse foot (about 6.21 1 / h meter).

5 An aqueous solution containing an antioxidant emulsion is continuously applied to the surface in contact with the wire paper throughout its life. This ensures that the amount of antioxidant contained in the papermaking fabric is sufficient to protect the papermaking fabric containing resin 10 from oxidation (an amount of about 0.1% antioxidant is considered optimal). Thus, the service life of the papermaking wire is extended due to this method.

Claims (10)

93561 A method for extending the life of papermaking fabrics, wherein the fabrics comprise a solid polymeric resin made solid by exposing a liquid photosensitive resin to activating light of a wavelength, characterized in that the method comprises the steps of: a) preparing a papermaking wire comprising a polymeric resin made solid by exposing the liquid photosensitive resin to activating light of a wavelength; b) continuously adding an effective amount of a chemical compound capable of preventing or retarding the rate of oxidation of this solid polymeric resin to the papermaking wire when the wire is used in a paper machine, at a point where the wire is not in contact with the paper web, said chemical compound comprising antioxidants, chelating agents, reducing agents and mixtures thereof. A method according to claim 1, characterized in that the chemical compound comprises an antioxidant chemical. A method according to claim 1 or 2, characterized in that the papermaking wire comprises: a frame comprising a first surface in contact with the paper, a second surface opposite to said first surface 30 and ducts extending between the first and second surfaces, said frame being made of solid polymer resin; and a reinforcing structure for reinforcing said frame, said reinforcing structure being positioned between the first surface of the frame „93561 and at least a portion of the second surface of the frame. Method according to Claim 3, characterized in that the reinforced structure is a perforated woven element. A method according to any one of claims 2 to 4, characterized in that the antioxidant chemical is applied to the surface of the papermaking wire in contact with the paper. A method according to claim 5, characterized in that the antioxidant chemical is dissolved in a release emulsion containing water, oil and a surfactant, and that the release emulsion containing this dissolved antioxidant chemical is continuously applied to the paper-contacting surface of the papermaking wire. Process according to Claim 6, characterized in that the antioxidant chemical is dissolved in the oil stage of the effluent emulsion. Process according to any one of claims 1 to 7, characterized in that said solid polymeric resin comprises acrylated urethane, preferably methacrylated urethane. Process according to any one of claims 2 to 6, characterized in that the antioxidant chemical comprises a primary antioxidant selected from blocked phenols, secondary amines and mixtures thereof, preferably a blocked phenol. Process according to any one of Claims 2 to 7, characterized in that the antioxidant chemical further contains a secondary antioxidant selected from phosphites, thioesters and mixtures thereof, preferably thioesters. 93561