CZ284239B6 - Process for producing tissue paper by applying chemical additives employed in paper industry - Google Patents

Abstract

Disclosed is a process for making soft tissue paper which includes providing a dry tissue web and then applying a sufficient amount of a chemical papermaking additive from a thin film to the dry web. The chemical papermaking additives are added to the surface of the tissue paper to enhance properties of the paper such as strength, softener, absorbency, and/or aesthetics. The chemical papermaking additive application process includes the steps of diluting the chemical papermaking additive with a suitable solvent, applying the diluted chemical solution to a heated transfer surface, evaporating the solvent from the dilute solution to form a film, and then transferring the film to the tissue by contacting the dry tissue web with the heated transfer surface. Preferably, the tissue web is dried to a moisture level below its equilibrium moisture content before application of the papermaking additive.

Description

Technical field

The invention generally relates to a method of making tissue paper, and more particularly to a method of applying a small amount of chemical paper additive to a tissue surface to improve the paper's properties, such as strength, softness, absorbency, or aesthetic appearance.

BACKGROUND OF THE INVENTION

Consumer products, such as toilet paper, paper towels and soft tissue paper for wiping the face cream, made from cellulose belt, are strongly penetrating modern society. Generally speaking, these products must have certain basic physical characteristics that customers consider acceptable. Although the precise combination of the essential properties and the absolute value of the individual properties varies depending on the type of product, however, softness, wet and dry strength, absorbency and aesthetic appearance are universally desirable properties. Softness is an aspect of the fibrous web that induces a tactile reaction and ensures that the product is not coarse or rough when touched with human skin or other delicate surfaces. Strength is the ability of a structure to maintain its physical cohesion in use. Absorbency is a property of the fibrous structure that allows the fluid to be contacted to be retained and retained for an acceptable period of time. The aesthetic appearance refers to the psychovisual reaction that occurs when a customer views either the product itself or the product in the context of its environment. The most common method of making tissue paper is leaching. First, a fine suspension of the individual fibers is formed in the thin aqueous slurry. The slurry is then deposited on a screen where heavy parts of water are removed from the screen and a thin, relatively homogeneous initial web is formed. This initial web is then pressed or dried in various ways to form the final paper web. In part of this process, the compressed or dried web is usually adhered to the drying drum and then creped on the surface of the drying drum to obtain the desired properties.

Products made by known alluvial processes form part of the prior art described. Examples of such bands that are soft, solid, and absorbent and contain at least two density micro-regions are disclosed in U.S. Patent 3,301,746, issued January 31, 1967, in the name of Lawrence H. Sanford and James B. Sisson; No. 3,974,025, issued August 10, 1976 to Peter G. Ayers; No. 3,994,771, issued Nov. 30, 1976, in particular to George Morgan Jr. and Thomas F. Rich; No. 4,191,609, issued Mar. 4, 1980, to Paul B. Trokhan; and 4,637,859, issued Jan. 20, 1987, in the name of Paul B. Trokhan. Each of these paper webs is characterized by a repeating pattern of a dense and less dense region. The dense areas may be either discontinuous or continuous. The dense areas of the paper web are the result of local compression in its manufacture by raised areas of the carrier fabric or web.

Other bulky soft tissue papers are disclosed in U.S. Patent 4,300,981, issued November 17, 1981, to at least Jerry E. Carstens; and 4,440,597, issued April 3, 1984, to Edward R. Wells and Thomas A. Hensler. In addition, a method of achieving bulky, soft, and absorbent tissue paper excluding total compression prior to final drying is disclosed in U.S. Patent 3,821,086, issued June 28, 1974, in particular to D. L. Shaw. and excluding total compression in combination with the release agent and the elastomeric binder in the paper furnish, it is disclosed in US Patent 3,812,000. issued May 21, 1974 to J.L. Salvucci, Jr. The chemical disintegrants disclosed herein and their theory of action are included as typical examples in the US patent

No. 3,755,220, issued August 28, 1973 to Friemark et al., 3,844,880, issued October 29, 1974 to Meisel et al .; and 4,185,594, issued Jan. 19, to Becker et al.

Tissue paper is also treated with cationic as well as non-cationic surfactants to increase softness. By way of example, U.S. Patent 4,959,125, issued September 25, 1990 to Spendel; and 4,940,513, issued July 10, 1990 to Spendel, which include methods for enhancing the softness of tissue paper by treating it with non-cationic, especially nonionic, surfactants.

It has been found that the softness of tissue paper, especially bulky tissue patterned compacted paper, can be improved by various agents such as vegetable, animal or synthetic oils, and in particular polysiloxane materials, commonly referred to as silicone oils. As an example, U.S. Patent 5,059,282, issued October 22, 1991 to Ampulski et al. This patent discloses a method of adding a polysiloxane compound to a wet web of tissue paper (particularly with a fiber consistency of from 20% to 35%) that imparts a soft silk feel to the paper.

Although the methods described create generally acceptable product properties, these properties can be further improved. However, methods for making conventional articles and potentially improved articles have some drawbacks. For example, the chemicals used to increase the strength of the paper webs are often added to the fiber suspension in the thin aqueous slurry prior to initial leaching to the forming screen. This is quite convenient and, in terms of cost, an effective way of introducing ingredients. However, other chemicals which help to increase absorbency or softness are also commonly added to the so-called wet portion of the tissue paper process. Because a set of individual chemicals is used to create the desired basic properties, they often interact and result in the opposite. They can cooperate successfully to maintain the desired properties of cellulosic fibers, as well as destroy the properties that are natural to these fibers. For example, softening chemicals often reduce the natural tendency of fibers to bond to one another and therefore reduce the effective strength of the resulting web. Both the method and the product are obtained when the amount of additives added to the wet portion of the tissue paper process is minimized.

As already mentioned, in most known processes, the web is adhered to the drying drum and then creped on the surface of the drying drum. Creping typically produces a paper web with improved softness and, importantly, improved extensibility. In order to perform the creping proper, it is important that the belt is securely attached to the drum surface. Many chemicals added in the wet portion of the paper machine to allegedly improve the basic properties eventually cause interference and interfere with the adhesion of the belt to the drying drum and have an adverse effect on the creping process and the quality of the paper produced. The creping operation proceeds optimally when the adhesive used to secure the web to the creping surface does not interfere with the non-creping chemicals and those chemicals that are added in the wet portion of the paper machine when performing the tissue paper manufacturing process.

Additives added in the wet portion of the paper machine must be retained by the cellulose fibers if they are to be effective. This is usually done by using chemicals having an ionic charge, in particular a positive ionic charge, which is attracted to the inherent negative ionic charge in cellulose. Many additives that could improve the properties of the paper web do not contain charge. The introduction of these chemicals into the fiber suspension in the thin aqueous slurry in the wet portion of the paper machine results in poor retention and causes the aforementioned interference problems.

A further drawback of adding any chemicals to the wet part of the machine while doing this causes them to penetrate the paper web when held. In a number of cases it is desirable

Only apply active ingredients to the surface of the belt. This may be desirable, for example, in fatty softening materials. Applying them only to the surface ensures the efficient use of these materials, since there is only tactile interaction of users with the surface of the product. The surface coating also avoids interference with other materials, such as strength enhancers, which are to be contained mainly in the middle portion of the web.

SUMMARY OF THE INVENTION

The above-mentioned drawbacks are overcome by the process of the present invention, which aims to provide an improved method of introducing chemical papermaking additives into a tissue web which improves softness, strength, absorption and aesthetic appearance, or combines these properties without causing creping interference or disturbing the delicate water balance. system or loss of advantageous properties achieved by other means.

Another object of the invention is to provide an improved method for introducing chemical papermaking additives into a tissue web, which can usually be slightly retained when added in the wet portion of the papermaking machine.

It is a further object of the invention to provide a method of adding papermaking chemicals to a dry web of a calender. Another object of the invention is to provide an improved method for applying diluted chemical papermaking additives to ensure controlled application of small amounts of additives to a heated conveying surface to preferentially evaporate solvent or carrier material while the mixture is only on the conveying surface but more concentrated prior to addition to the dry web. a blend of additives and solvent on the surface of the tissue paper web than originally applied to the shipping surface.

Another object of the invention is to provide an improved method for applying chemical papermaking additives to a tissue web by the method as described above, wherein the vapor pressure of the carrier material or solvent is higher than the additive material pressure so that the carrier is preferably emptied after the additives have been applied to the heated transport surface. This emptying of the carrier also occurs, in particular, before the additives are applied to the tissue paper web.

Said objects are achieved by a process for the production of a soft, solid, absorbent and aesthetically pleasing tissue paper according to the invention, which consists in diluting the chemical papermaking additive with a solvent to form a dilute chemical solution which is then applied to the heated transport surface. a portion of the solvent from the heated conveying surface to form a film containing chemical papermaking additives, and the film is then transferred from the heated conveying surface to at least one outer surface of the tissue paper web by contacting the outer surface of the web with the heated conveying surface while retaining an amount of 0.004% to 2.0 % chemical papermaking additive, based on the dry fiber weight of the tissue paper web.

The solvent is preferably water.

According to a preferred embodiment of the invention, the chemical papermaking additives are selected from additives for increasing strength, absorbency, softness, aesthetics and mixtures thereof. It is also preferred that the softening additives are selected from lubricants, plasticizers, cationic disintegrants, non-cationic disintegrants, and mixtures thereof.

Lubricants may be polysiloxanes.

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According to another preferred embodiment of the invention, the non-cationic disintegrant is selected from sorbitan esters, ethoxylated sorbitan esters, propoxylated sorbitan esters, and mixtures thereof.

It is further preferred that the strength enhancing additives are selected from permanently wet strength resins, in particular polyamide epichlorohydrin resins, polyacrylamide resins and mixtures thereof, from temporarily wet strength resins, in particular starch-based resins, temporarily strengthening wet strength, dry strength additives, and mixtures thereof.

It is also preferred that the absorbency enhancers are selected from polyethoxylates, alkylethoxylated esters, alkylethoxylated alcohols, alkylpolyethoxylated nonylphenols, and mixtures thereof, especially alkylethoxylated alcohols.

According to a further preferred embodiment of the invention, an additive is applied to the tissue web in an amount of 0.01% to 2.0%. based on the dry fiber weight of the tissue paper web.

It is further preferred that the absorbency enhancers are non-cationic surfactants, especially an alkylethoxylated alcohol having a melting point of at least 50 ° C.

It is also preferred that additives are applied to the tissue web to increase its strength in an amount of 0.01% to 2.0%, based on the dry fiber weight of the tissue web.

By solvent is meant a liquid that completely dissolves a chemical paper additive, or a liquid that is used to emulsify a chemical paper additive, or a liquid that is used to suspend a chemical paper additive. The solvent may also be a carrier or transfer agent containing chemical additives or chemical transfer aids. All of these references are interchangeable and are not limiting. The solution is a liquid containing chemical papermaking additives. By a solution is meant a true solution, emulsion or suspension. For purposes of the invention, all of these terms may be used interchangeably and are not limiting. When the solvent is water, the hot strip is dried to a moisture level below equilibrium moisture (under standard conditions) before contact with the papermaking additive film. However, this method can be applied to tissue paper even at equilibrium moisture if most of the moisture evaporates from the conveying surface. The amount of chemical papermaking additive retained by the tissue web is preferably 0.01% to 1.0% of chemical papermaking additive based on the dry fiber weight of the tissue web. The resulting tissue paper has a basis weight of about 10 to 80 g / m ² and a fiber density of less than 0.6 g / cm ³ .

As already mentioned, the papermaking additives are applied to the web, especially after it has been dried and creped. Adding papermaking additives to the web after drying and creping does not interfere with the glue on the Yankee Dryer Drum, which can cause omitted creping or misalignment of the web. Further, the papermaking additives applied in this manner do not cause interference in the aqueous papermaking system as they are not added to the wet portion of the papermaking machine. Another advantage of this method is that the additives need not be substantive to the paper. That is, it need not include a cationic charge for bonding to the anionic charge of cellulosic paper fibers. In particular, the papermaking additive is applied to the hot creped web after leaving the creping scraper and before being wound on the parent roll. Surprisingly, it has been found that significant increases in softness, strength, absorbency or aesthetic appearance of tissue paper with a small amount of chemical papermaking additive can be achieved by diluting it with a solvent, applying it to a heated conveying surface to vaporize the solvent carrier and then transfer the papermaking additives to the hot strip before processing. The advantage of said method is that the amount of residual solvent transferred to the paper web is significantly low, so that it does not deteriorate other properties

-4GB 284239 B6 of this product. In addition, the amount of paper additive used is rather low, so that it is economically advantageous. Also, tissue paper treated with a small amount of chemical softeners such as polysiloxanes retains a large amount of moisture, which is an important feature of the tissue paper product. Preferred paper softening additives according to the present invention comprise aminofunctional polydimethylpolysiloxanes, with less than 10 mole percent of the side chains of the polymer containing an aminofunctional group. In addition to this substitution with aminofunctional groups, effective substitution with carboxyl, hydroxyl, ether, polyether, aldehyde, ketone, amide, ester and thiol groups can be effected. Of these important groups, the group consisting of amino, carboxyl, and hydroxy groups is preferred over other groups, with amino-functional groups being most preferred. Examples of commercially available polysiloxanes include DOW 8075 and DOW 200 from DOW Coming and Silvet L720 and Ucarsil EPS from Union Carbide.

Other preferred softness enhancers useful in the present invention include nonionic surfactants selected from sorbitan esters, ethoxylated sorbitan esters, propoxylated sorbitan esters, mixed ethoxylated and propoxylated sorbitan esters, and mixtures thereof.

The method of making tissue paper by treating chemical softening agents such as polysiloxane or nonionic surfactants as described may further comprise the operation of adding an effective amount of ingredients to increase the tactile perceptible surface softness of the tissue paper, or at least partially compensate for the wettability reduction of the tissue paper. which could otherwise be caused by the use of polysiloxanes or other chemical emollients. Of course, the wettability of paper without chemical softening agents can be increased by adding suitable absorbent enhancing additives, such as a surfactant. An effective amount of a surfactant is such that, in particular, 0.01% to 2.0% based on the dry fiber weight of the tissue paper web is retained by the tissue paper, and more preferably 0.05% to 1.0%. The surfactant is also preferably non-cationic and remains substantially in place after the tissue paper has been manufactured to prevent its post-production changes in properties that may be caused by the surfactant. This can be achieved, for example, by the use of a surfactant having a melting point above the temperatures conventionally used in the storage, shipping, sale and use of tissue paper products according to the invention: for example, the melting point is greater than 50 ° C.

The tissue papermaking process of the present invention may further comprise the operation of adding an effective amount of strength enhancing additives, such as starch-based material, to at least partially eliminate the tensile strength reduction or fibrous dust tendency that would otherwise be caused by chemical additives to the to increase softness, or to increase the absorbency when added. An effective amount of the strength enhancing additive is such that, in particular, 0.01% to 2.0% of the additive relative to the dry fiber weight of the tissue paper web is retained by the tissue paper.

All percentages, ratios and proportions herein are by weight unless otherwise indicated.

Overview of the drawings

BRIEF DESCRIPTION OF THE DRAWINGS The invention will now be described in more detail with reference to the accompanying drawings, in which: FIG.

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DETAILED DESCRIPTION OF THE INVENTION

The process of the invention produces tissue paper with increased softness, perceptible tactile achieved by the addition of chemical softeners, an increased strength achieved by the addition of strength enhancers, and an increased absorbency achieved by the addition of enhancers. absorbency, or with improved aesthetic properties, achieved by adding ingredients such as ink, dyes, perfumes, to a dry tissue paper web to enhance aesthetic appearance. These properties can be improved by applying these and other chemical papermaking additives alone or in combination to dry tissue paper. In particular, the tissue web is dried to a moisture level below equilibrium moisture prior to application of the papermaking additive to the web. Surprisingly, it has been found that the method of the invention can achieve a significant increase in the softness of tissue paper by adding very small amounts of chemical papermaking additives, for example polysiloxane softeners, applied to the dry web of tissue paper. Importantly, the amount of softener used to soften the web was small enough that the tissue paper maintained its high wettability. Since the tissue paper is particularly overdried and has an elevated temperature during application of the papermaking additive, and since the fluid carrier is emptied on the heated transport surface, no further drying is desirable. In this application, the hot paper web refers to a tissue paper web having an elevated temperature that is higher than room temperature. In particular, the elevated temperature of the web is at least 43 ° C and more preferably at least 65 ° C.

The moisture content of the tissue paper web is related to the temperature of the tissue paper web and the relative humidity of the environment where the web is located. The term dried tissue paper web as used refers to a tissue paper web that has been dried to moisture below equilibrium moisture under standard test conditions, at 23 ° C and 50% relative humidity. The equilibrium moisture content of the tissue paper web, placed in standard test conditions at 23 ° C and 50% relative humidity, is approximately 7%. The tissue web produced according to the invention can be dried by elevated temperature using conventional drying means such as a Yankee drying drum. The overdried web will preferably have a moisture content of less than 7%, more preferably from 0 to 6%, and most preferably will have a moisture content of from 0 to 3% by weight.

Paper exposed to normal environments has an equilibrium humidity in the range of 5 to 8%. When the paper is dried and creped, the equilibrium moisture in the web is typically less than 3%. After its manufacture, the paper product absorbs moisture from the atmosphere. In a preferred embodiment of the method according to the invention, the advantage arises from the low moisture of the paper when leaving the creping scraper. In applying a paper papermaking solution to dried paper, the remainder of the water added to the paper is less than the amount of water normally taken from the atmosphere. Therefore, no further drying is required and there is no apparent loss of tensile strength except that normally would occur when absorbing moisture from the air.

The method of the invention is generally applicable to tissue paper, including conventional pleated tissue paper, tissue patterned compacted paper, as exemplified by Sanford-Sisson products and its affiliates, and bulk non-pressed tissue paper, 45 as exemplified by company products. Salvucci. The tissue paper may have a homogeneous or multilayer structure, and the tissue paper products may be single or multi-fold. The tissue paper has a basis weight of preferably 10 g / m to 80 g / m ² and a density lower than 0.6 g / cm ³ tissue paper, more preferably has a basis weight less than 35 g / m ² and a density lower than 0.30 g / cm ³ . In a most preferred embodiment, the 50 has a density in the range of 0.04 g / cm ³ to 0.20 g / cm ³ .

Conventional pressed tissue paper and a process for its production are known in the art. Such paper is usually made by depositing the furnish on a forming screen. This forming screen is often referred to in the prior art as a longitudinal screen of a paper machine

-6GB 284239 B6 (Fourdrinier sieve). When the furnace is deposited on a forming screen, it is referred to as a belt. The strip is dewatered by pressing and drying at elevated temperature. Special techniques and conventional devices for making the belt in the manner just described are well known to those skilled in the art. In a conventional method, a low consistency pulp furnish is prepared in a pressure headbox. The headbox has an opening for supplying a thin layer of pulp furnish to the longitudinal screen of a paper machine to form a wet web. The web is then typically dewatered to a fiber density in the range of from about 7% to about 45% (total web basis weight) by vacuum dewatering and is further dried by compression where the web is pressurized by opposing mechanical means such as roller rollers. The dewatered web is further compressed and dried by a steam drum apparatus known as a Yankee drying drum. The pressure at the Yankee dryer drum can be exerted by mechanical means, such as an opposing roller drum, which compresses the web. Multiple Yankee drying drums may also be used, with optional additional compression being set between the drums. The tissue webs formed are hereinafter referred to as conventional pressed tissue paper structures. Such sheets of paper are considered to be molded because the web is subjected to substantially total mechanical compressive forces when the fibers are wet and then dried in a compressed state.

The tissue patterned compacted paper is characterized by relatively bulky regions of relatively low fiber density and a set of compacted regions of relatively high fiber density. The bulky region is alternatively referred to as a cushion-shaped region. The compacted region is alternatively referred to as an elbow-shaped region. The compacted regions may be spaced discontinuously in bulky regions, or may be joined either fully or partially in bulky regions. Preferred methods of making a web of tissue patterned compacted paper are disclosed in U.S. Patent 3,301,746, issued to Sanford and Sisson on January 31, 1967, 3,874,025, issued to Peter G. Ayers on August 10, 1976, and 4,191,609, issued to Paul D Trokhan on March 4, 1987, which are incorporated herein by reference. Generally speaking, a silk patterned compacted web is mainly produced by depositing a furnish on a forming screen, such as a longitudinal screen of a paper machine to form a wet web, which is then aligned against a plurality of supports. The web is compressed against the web of webs, resulting in densified areas on the web at locations that correspond to the contact points between the web of webs and the wet web. The remainder of the belt that was not compressed during this operation is called a bulky area. The bulky areas may further be dewatered by fluidized compression, for example by a vacuum device or a blow dryer, or by mechanically compressing the web against a group of supports. The strip is dewatered and optionally pre-dried so as to substantially prevent compression of the bulk regions. This is done in particular by fluid compression, for example by a vacuum device or blow dryer, or alternatively by mechanical compression of the strip against a plurality of supports. The dewatering, pre-drying, and densified area forming operations may be combined or partially combined to limit the total number of stages in the web processing. Subsequent to the formation of the compacted areas, drainage and optional pre-drying, the web is finished dried, preferably still without mechanical compression. In particular, about 8% to 65% of the tissue surface comprises densified nodes with a relative density of at least 125% of the density of the bulk regions. In particular, the set of supports consists of a marking textile carrier, on whose surface patterned spaced nodes are formed, which act as a set of supports, facilitating the formation of compacted areas by applying pressure. The knee pattern is formed by said set of supports. Marking textile carriers are disclosed in U.S. Patent 3,301,746, issued Jan. 31, 1967 to Sanford and Sisson, 3,821,068. issued May 21, 1974 in the name of Salvucci Jr. et al. No. 3,974,025, issued August 10, 1976 to Ayers, 3,573,164, issued March 30, 1971 to Friedberg et al., 3,473,576, issued October 21, 1969 to Amneus, 4,239,065, issued December 16, 1980 to Trokhan; and 4,528,239 , issued July 9, 1985 to Trokhan, all of which are incorporated herein by reference.

In particular, the furnace is formed into a wet web shape on perforated forming carriers such as a longitudinal screen of a paper machine. The belt is drained and transferred to a marking textile carrier. In an alternative embodiment, the insert can first be placed on a perforated support carrier,

Which also acts as a marker textile carrier. After forming, the web is dewatered and, in particular, heat-dried to a selected fiber density of from 40% to 80%. In particular, the dewatering is carried out with suction boxes or other vacuum equipment or with a blow dryer. The markers of the marker carrier are pressed into the paper web before it is finally dried, as already mentioned. One method of this embodiment is mechanical compression. It can be carried out, for example, by pressing the nip roller which supports the marking textile carrier against the face of a drying drum, such as a Yankee drying drum, wherein the belt is arranged between the nip roller and the drying drum. The web is also preferably formed against the marking carrier prior to fluid compression drying by means of a vacuum device such as a suction box or blow dryer. Fluid compression can be used to push the compacted areas during the initial dewatering as a separate downstream processing step or as a combined step.

Non-densified tissue paper structures without patterned densification are described in U.S. Patent 3,812,000, issued May 21, 1974, in the name of Joseph L. Salvucci, Jr. et al. and Peter N. Yiannos, and 4,208,459, issued June 17, 1980 in the names of Henry E. Becker, Albert L. McConnell and Richard Schutte, all of which are incorporated herein by reference. Generally speaking, uncompressed tissue webs without pattern compaction are manufactured by depositing a furnish on a perforated forming screen, such as a longitudinal screen of a paper machine, dewatering the web and removing additional water without mechanical compression until the web has a fiber density of at least 80%. Water is removed from the belt by vacuum dewatering and heat drying. The resulting structure is a soft but weak bulky web of relatively uncompressed fibers.

In particular, the binder is added to the portions of the strip prior to creping. Densified tissue paper structures without patterned densification are commonly known in the art as conventional tissue paper structures. Generally speaking, densified non-patterned tissue paper structures are produced by depositing a furnish on a perforated screen, such as a longitudinal screen of a papermaking machine to form a wet web, dewatering the web and removing additional water by uniform mechanical compression (compression) until the web has a fiber density. % to 50% by transferring the web to a heat dryer such as a Yankee drying drum and creping the web. The total amount of water is removed from the belt by vacuum means, mechanical compression and thermal means. The resulting structure is strong and usually of the same density, but with very low bulk density, absorbency and softness.

The papermaking fibers used in the process of the invention normally include wood pulp fibers. Cellulose fibers such as cotton linter, bagasse, etc. may also be used, which are intended to be within the scope of the invention. Synthetic fibers such as rayon, polyethylene and polypropylene fibers can also be used, which can also be used in combination with natural cellulose fibers. An example of polyethylene fibers that may be used is Pulpex ™, commercially available from Hercules, Inc., Wilmington. Delavare. Useful wood pulp fibers include pulp such as kraft and sulphite pulp, as well as wood pulp and wood pulp, including, for example, wood pulp, thermomechanical pulp and chemically modified thermomechanical pulp. However, pulp is preferred because it imparts the best tactile feel to the tissue paper made from it. Pulps obtained from both deciduous trees, hereinafter referred to as hardwood, and conifers, hereinafter referred to as softwood, may be used.

Also useful are recycled paper fibers, which may include some or all of the above categories, as well as non-fibrous materials such as fillers and adhesives used to facilitate initial paper production.

In addition to papermaking fibers, the papermaking furnishings. used to make tissue paper, include other components or filler materials that may be known or which may become known later. The types of additives required may depend upon the particular uses of the tissue paper web. For example, products such as toilet paper, paper

Towels, soft tissue paper for wiping the face cream, and other similar products, high wet strength is required. Therefore, it is often desirable to add chemical substances known as wet strength resins to the paper furnish. A general discussion of the types of wet strength resins used in papermaking can be found in TAPPI monograph, No.29, Wet Paper and Cardboard, Technical Association of Pulp and Paper Industry, New York, 1965. more commonly used wet strength resins have cationic properties. It has been found that polyamide-epichlorohydrin resins, which are cationic, have a particular functional value as a wet strength resin. Suitable types of such resins are described in U.S. Patent 3,700,623, issued October 24, 1972 and 3,772,076, issued November 13, 1973 in the name of Keim, which are incorporated herein by reference. One available source of useful polyamide epichlorohydrin resins is Hercules, Inc., Wilmington, Delavare, which sells these resins under the trademark Kymene ™ 557 H. Polyacrylamide resins have also been found to be useful as wet strength enhancing resins. These resins are disclosed in U.S. Patent 3,556,932, issued January 19, 1971 to Coscia et al., And 3,556,933, issued January 19, 1971 to Williams et al., Which are incorporated herein by reference. One commercially available source of polyacrylamide resins is Cyanamid Co., Stanford, Connecticut, which markets these resins under the brand name Parez ™ 631 NC.

Still other water-soluble cationic resins that are useful in the process are urea formaldehyde and melamine formaldehyde resins. The most common functional groups of these polyfunctional resins are nitrogen-containing groups as well as nitrogen-linked amino and methyl groups. Polyethyleneimine resins may also be beneficial. In addition, temporary wet strength resins such as Caldas, manufactured by Japan Carlet, and CoBond 1000, manufactured by National Starch and Chemical Company, may be used in the process of the invention. It should be noted that the addition of chemical compounds such as wet strength resins and temporary wet strength resins to the pulp furnish is optional and is not necessary in the practice of the process.

In the practice of the present invention, the papermaking additive is applied after drying and creping the tissue paper web, and in particular at elevated temperature. It has been found that the addition of some chemical papermaking additives to the tissue paper web prior to drying and creping may cause interference in the dryer coating, i.e., the adhesive coating on the Yankee dryer drum, and may also result in omitted creping or misfeed in the paper web control. These problems are eliminated by the method of the invention, wherein the chemical papermaking additive is applied to the web after drying and creping. In particular, the chemical papermaking additive is applied to the dried and creped tissue paper web prior to being wound onto the parent roll. In a preferred embodiment of the method of the invention, the chemical papermaking additive is applied to the hot, dried web after its creping, but before the paper passes through the calender rolls.

The chemical papermaking additives are preferably applied to the hot transport surface as an aqueous solution, emulsion or suspension. The chemical papermaking additive may also be applied in a solution containing a suitable non-aqueous solvent in which the chemical papermaking additive is dissolved or miscible. for example hexane. The chemical papermaking additives may be supplied in pure form or, preferably, as an emulsion with a suitable surfactant emulsifier. Emulsified chemical papermaking additives are advantageous for ease of application, since aqueous solutions of pure chemical papermaking additives must be mixed to suppress separation between the aqueous phase and the chemical papermaking phase.

The chemical papermaking additive should be applied to the heated transport surface in a macroscopically uniform shape for subsequent transfer to the tissue paper web so that substantially the entire web can benefit from the chemical papermaking additive. In particular, the solvent evaporates after leaving the chemical paper additive on the heated transport surface and leaves

A thin film on the surface containing chemical papermaking additives. By thin film is meant any thin coating, haze or fog on the conveying surface. The film may be microscopically continuous, discontinuous or may be arranged in a pattern, but should be macroscopically uniform. On a microscopic scale, the chemical papermaking additive can be distributed in a uniform, irregular, discontinuous, patterned, and continuous or discontinuous configuration. The deposition of chemical additives in a continuous configuration in a pattern is within the scope of the invention and satisfies the above criteria. Chemical papermaking additives may also be added to either side of the tissue paper web or to both sides.

Methods of macroscopically uniform deposition of chemical papermaking additives on a hot transfer surface include spray and gravure deposition. Spraying has been found to be economically advantageous and capable of accurately controlling the amount and distribution of chemical papermaking additives, thus providing the most preferred method. In particular, an aqueous composition comprising emulsified chemical papermaking additives is applied from the conveying surface to the dried creped tissue paper web after it has passed through a Yankee drying drum and before being wound onto a parent roll.

FIG. 1 shows an example of a preferred embodiment of a method of applying chemical papermaking additives to a tissue paper web. According to the figure, the wet tissue web 1 deposited on the textile carrier 14 is guided around the first roller 2 and is transferred to the Yankee drying drum 5 by the pressure of the pressure roller 3, while the textile carrier 14 passes the second roller 66. adhesive is applied to the cylindrical surface of the Yankee drying drum 5 with an adhesive sprayer 4. Drying is performed with a Yankee drying drum 5, heated by steam and hot air, which is heated and circulated in the drying cover 6. The tissue paper web 1 is then removed from the drying drum. Then, it is referred to as a creped paper web 15. Next, an aqueous mixture containing emulsified chemical papermaking additives is applied to an upper heated transporting surface, referred to as an upper calender roller 10, or a lower heated transporting conveyor. a surface designated as a lower calender roller H, by means of spraying devices 8 and 9, depending on whether the chemical papermaking additions are to be applied to both sides or only to one side of the creped paper web 15. After evaporation of a portion of the solvent, the creped paper web 15 passes between the upper calender roller 10 and the lower calender roller 11, touching their heated surfaces. The treated web 15 then passes around a portion of the periphery of the take-up roll 12 and is then wound onto the parent disc 13. A suitable device for spraying liquids containing chemical papermaking additives onto hot shipping surfaces is external agitation air spray nozzles such as a 2 mm nozzle commercially available at VIB Systems, Inc., Tucker, Georgia. A suitable device for the printing of liquids containing chemical papermaking additives on hot transport surfaces is an intaglio or flexographic printing device.

The following is a description of the typical conditions encountered in operations during papermaking and their effect on the process of the present invention without being bound by theory or in any way limiting this invention. The Yankee 5 Dryer Drum raises the tissue web temperature and removes moisture . The steam pressure in the drying drum is maintained at 750 kPa. This pressure is sufficient to raise the cylinder temperature to about 173 ° C. The temperature of the paper on the roller increases when water is removed from the paper web. The temperature of the paper web downstream of the creping rasp 7 may be higher than 120 ° C. The belt passes through the space to the calender and the take-up roll, losing part of its temperature. The measured temperature of the paper web on the take-up roll is 65 ° C. The paper web is eventually cooled to room temperature. This can be done at any time of the day, depending on the size of the roll paper. When the paper cools, it also absorbs atmospheric moisture. As noted, the humidity of the paper web depends on the temperature of the web and the relative humidity of the environment where the paper is located. For example, the equilibrium moisture content of a web, placed under standard test conditions of 23 ° C and 50% relative humidity, is approximately 7%. An increase in web humidity above 7% may have detrimental effects on the tensile strength of the web.

- 10GB 284239 B6 paper. For example, increasing the humidity to 9% may cause a 15% reduction in the tensile strength of the paper web.

One of the very surprising properties of chemical softeners such as polysiloxane is their ability to increase softness in a very small layer on the paper surface. However, the chemical softener must be truly evenly distributed on the surface of the paper in order for the user to recognize an increase in softness. From the paper processing point of view, there was no previously satisfactory method of uniformly applying a small amount of a chemical softener to a web of paper progressing at high speed. In modern high-speed paper machines, the typical belt speed is 10,700 to 100Om / min. The webs advancing at this speed typically have an air interface on their surface. One method of applying a small amount of fluids is to use an air and fluid pressure setting. For example, low flow rates with high air pressure can be used. This usually results in extremely small particles. These small particles are difficult to impart sufficient momentum to penetrate the air interface as they flow to the surface of the paper at high speed. In addition, when the particle size of the liquid to be sprayed increases, they can penetrate the air interface at a lower speed and the surface coverage becomes uneven.

In one commonly used method of applying small layers of active material, the material 20 is first diluted with a solvent. Spraying methods can then be set to deliver larger material particles at a higher flow rate. Larger particles can penetrate the air interface. However, the problem of having to remove the solvent from the paper has to be avoided. Volatile solvents are generally not used in the paper industry as they pose a fire or environmental hazard. Water can be used as solvents for water-soluble paper additives. Water may also be used as solvents or rather diluents for non-water-soluble papermaking additives, such as organic oils, polymers and polysiloxanes, when non-water-soluble papermaking additives, such as polysiloxane, are first emulsified with a suitable surfactant. substance. Although water cannot carry the same manufacturing hazards as organic solvents, it can cause degradation of the product, resulting in reduced tensile strength or creped state. Water must therefore be removed from the paper. One means to solve this water problem is to apply diluted chemical papermaking additives to the dried paper. The amount of water added to the paper with chemical papermaking additions in this process is usually less than the amount of water that the paper would normally absorb from the atmosphere upon cooling to room temperature. Therefore, no further drying is required and there is no reduction in tensile strength by the addition of water. However, the aqueous solution has the ability to penetrate the entire web so that the active material expands within the web rather than remaining on the surface where it is more effective. This method is further limited to the overdried web, which presents difficulties in using the paper during its processing (outside the paper machine) without adding an additional drying step. Another limitation of this method 40 is the limited range of dilution and the range of use of the chemical paper additive emulsion due to the emulsion properties (i.e., high concentrations tend to have high viscosity, while low concentrations increase the amount of water sprayed onto the web).

The tissue manufacturing process of the present invention solves these problems by first spraying a 45 dilute aqueous solution of chemical papermaking additive or an emulsified solution of water-insoluble chemical papermaking additive onto a heated transfer surface and evaporating the solvent from the chemical papermaking solution before transferring it to a dry web. of paper.

An example of a typically commercially available silicone emulsion chemical diluent is Dow Coming ^R Q2-7224 from Dow Coming Corporation. This material usually contains about 35% by weight of an aminofunctional polysiloxane emulsified in water. This silicone emulsion is diluted with water to a concentration of less than 20% by weight before being applied to the heated transport surface. In a more preferred embodiment, the chemical paper additive emulsion,

Used in the field method of the present invention first dilute with water to a concentration of less than 15% by weight prior to application to the heated transport surface. Examples of suitable materials for the heated transport surface are metals (e.g. steel, stainless steel and chromium) and non-metals (e.g. suitable polymers, ceramic materials, glass) and rubber. When spraying a dilute silicone emulsion of this type onto a hot transport surface formed by a steel calender roll, it was surprisingly found that in this process little or no water was transferred to the web. In fact, one set of production conditions expected that the moisture of the strip could increase by 4% to 5% after injection. However, it was found that moisture did not increase at all, although the silicone content of the paper web had increased to its expected concentration. Furthermore, it was surprisingly found that an attempt to increase the web humidity by 3.5% (i.e., increase the web humidity from 4% to 7.5%) resulted in an increase in humidity of 0.7%, i.e. the measured humidity was only 4.7%. This was very surprising because the cylinder temperature was 80 ° C (20 ° C below the boiling point of water) and the time between application and transfer was 0.1 s. Surprisingly, it was found that in these conditions more than 50 % water, where a thin film of polysiloxane emulsion remained on the roll. The film was calculated to have a thickness of 0.25 x ^{10 6} m. The film in the method of the invention has a thickness of less than 10 x 10 ^-6 m and more preferably less than about 1.10 ^-6 m.

Preferably, at least 50% and more preferably at least 80% of the water is evaporated from a dilute solution of chemical papermaking additives that are applied to the heated transport surface prior to being passed onto a dry tissue web. Thus, a thin film of a calculated thickness of 0.075.10 ^-6 m remains. In the most preferred embodiment, more than 95% of the water evaporates from the solution on the heated conveying surface, leaving a thin film of a calculated thickness of about 0.05.10 ^-6 m. . The temperature of the heated transport surface is preferably below the boiling point of the solvent. Thus, when the solvent is water, the temperature of the heated transport surface should be between 50 ° C and 90 ° C, more preferably between 70 ° C and 90 ° C.

Heating the conveying surface may also cause a decrease in the viscosity of the chemical papermaking additives, and hence an increase in their ability to spread as a thin film on the conveying surface. This film is then transferred to the surface of the web by contacting the web with the transport surface. Surprisingly, it has been found that the transfer efficiency of chemical papermaking additives to the web is quite high. Typical transfer efficiency is in the range of 40% to 80% of the output of these chemical papermaking additives from the spray nozzles to the transfer surface to the measured amount on the web. In addition, the method is not limited to dried paper. Depending on the amount of water removed from the spray mixture by the hot conveying surface, it is also possible in this way to supply the chemical papermaking additives to dry paper with an equilibrium moisture content. However, it is preferable to apply it to a superheated web to ensure that the residual water in the film does not interfere with the properties of the paper.

Another additional advantage in applying a chemical paper additive solution to an overheated web paper is that reducing the viscosity of the solution helps to ensure uniform application of the solution over the entire surface of the web. (Lower viscosity solution is believed to be more mobile).

Chemical stationery additives

In particular, the chemical papermaking additives for use in the inventive method of making tissue paper are selected from the groups of additives for enhancing strength, absorbency, softness, aesthetics, and mixtures thereof. Each of these ingredients will be described below.

- 12GB 284239 B6

A) Strengthening Ingredients

The strength enhancing additives are selected from the group of permanently wet strength enhancing resins, the temporarily wet strength enhancing resins, the dry strength enhancing additives, and mixtures thereof.

When sustained wet strength is desired, chemical papermaking additives are selected from the following chemical groups: polyamide-epichlorohydrin, polyakiylamides, styrene-butadiene latices, undissolved polyvinyl alcohols, urea-formaldehyde resins, polyethyleneimine and chitosan polymers. Polyamide epichlorohydrin resins are wet strength cationic resins which have been found to be particularly useful. Suitable types of these resins are described in U.S. Patent 3,700,623, issued October 24, 1972 and 3,772,076, issued November 13, 1973 in the name of Keim. Both publications are incorporated herein by reference. A commercially available source of useful polyamide-epichlorohydrin resins is Hercules. Inc., Wilmington, Delavare, which markets these resins under the trademark Kymene ™ 557 H. Polyacrylamide resins have been found to be useful as wet strength resins. These resins are described in U.S. Patent 3,556,932, issued January 19, 1971 to Coscia et al., And 3,556,933, issued January 19, 1971 to Williams et al. Both publications are incorporated herein by reference. A commercially available source of polyacrylamide resins is American Cyanamid Co., Stanford. Coonecticut, which is sold under the brand name Pařez ™ 632 NC.

Other water-soluble cationic resins which find use in the present invention are urea-formaldehyde resins and melamine-formaldehyde resins. The most common functional groups of these polyfunctional resins are nitrogen-containing groups, such as amino-linked and nitrogen-linked methylol groups. Polyethyleneimine resins may also find use in the present invention.

When temporary wet strength is desired, chemical papermaking additives can be selected from the following chemical groups. A starch-based cationic dialdehyde resin (such as Caldas, manufactured by Japan Carlet and CoBond 1000, manufactured by National Starch), a dialdehyde starch, or a resin disclosed in U.S. Patent 4,981,557. issued January 1, 1991 to Bjorquist, which is incorporated herein by reference.

When dry strength is desired, chemical papermaking additives can be selected from the following groups of chemicals. Polyacrylamides (such as the combination of Cypro 514 and Accostemgth 711, manufactured by American Cyanamid, Wayne, NJ), starch (such as corn starch or potato starch), polyvinyl alcohol (such as Airvol 540, manufactured by Air Products Inc., Allentown, PA) ), guar or carob gum, polyacrylate latexes, or carboxymethyl cellulose (such as Aqualon CMC-T from Aqualon Co., Wilmington, DE). A suitable starch for use in the present invention is characterized by water solubility and hydrophilicity. Examples of suitable starches include, but are not limited to, corn starch and potato starch, and waxy corn starch, which is industrially known as amioca starch. Amioca starch differs from conventional corn starch because it consists only of amylpectin, while conventional corn starch consists of both amylpectin and amylose. The various extraordinary properties of amioca starch are further described in the article. Amioca - Waxy Corn Starch, H.H. Schopmeyer, Food Industries, December 1945, pp. 106-108 (pages 1476-1478). The starch may be in the form of granules or in dispersed form, although granules are preferred. In particular, the starch should be sufficiently cooked to swell the granules. In a more preferred embodiment, the granules are swollen by boiling to the point just prior to disintegration of the starch granule. These highly swollen starch granules are labeled as fully cooked. The degradation conditions may vary depending on the size of the starch granules, the degree of crystallinity of the granules, and the amount of amylose present. Fully cooked amioca starch can be prepared, for example, by heating an aqueous slurry with a consistency of about 4%

Starch granules at about 88 ° C, for about 30 to 40 minutes. Other examples of starches that may be used include modified cationic starches, such as nitrogen-starch starches such as amino-linked and nitrogen-bonded methylol groups, which are commercially available from National Starch and Chemical Company of Bridgevater, New Jersey. These modified starch materials have previously been used as pulp furnish additives to increase wet or dry strength. However, when used in the method of the present invention for depositing on a dried web, they could have a limited effect on wet strength due to the addition of the same modified starch materials in the wet portion of the paper machine. Since these modified starch materials are more expensive than unmodified starches, unmodified starches are generally preferred. These wet and dry strength resins may be added to the pulp furnish in addition to being added in the process of the invention. Obviously, the addition of chemical compounds such as permanent wet strength resins and temporary wet strength resins to the pulp furnish as described is optional and is not necessary in the practice of this method.

In particular, for the purposes of the present invention, the strength enhancers are applied in the form of an aqueous solution to the heated transfer roller. The deposition methods include the deposition methods of the other chemical ingredients, in particular by spraying, and in a less preferred embodiment by printing. The strength enhancers may be applied to the tissue web separately, simultaneously, before or after the application of the enhancers, absorbency, softness or aesthetic appearance. At least an effective amount of a strength additive, in particular starch, is applied to the paper web to regulate the formation of fibrous dust and to increase the drying strength concurrently, as compared to an otherwise identical web but untreated binder. In particular, about 0.01% to 2.0% strength-enhancing agents based on dry fiber weight are retained in the dried web, and more preferably about 0.1% to 1.0% strength-enhancing agents, especially starch based.

B) Softeners

The chemical softening ingredients are selected from the group consisting of lubricants, plasticizers, cationic and non-cationic disintegrants, and mixtures thereof. Preferably, the disintegrating agents used in the method of the invention are non-cationic, and more preferably non-anionic surfactants. However, cationic surfactants can also be used. Non-cationic surfactants include anionic, non-anionic, amphoteric, and zwitterionic surfactants. The surfactant remains substantially at the original location of the tissue paper after it has been manufactured to prevent its post-production changes in properties that may be caused by the surfactant. This can be achieved, for example, by the use of a surfactant having a melting point higher than those commonly used in the storage, shipping, sale and use of tissue paper products of the invention: for example, the melting point is greater than 50 ° C. In particular, the surfactant is water-soluble when applied to a wet web.

The amount of non-cationic surfactant applied to the tissue web to achieve said softness or strength enhancement ranges from the minimum effective amount required to achieve such an advantage at a constant strength level of the resulting product that about up to 2%, especially about 0.01 % to about 2% of the non-cationic surfactant is retained by the band, more preferably about 0.05% to about 1.0%, and most preferably about 0.05% to about 0.3%. Surfactants have an alkyl chain of eight or more carbon atoms. Examples of anionic surfactants are linear alkylsulfonates and alkylbenzenesulfonates. Examples of non-anionic surfactants are alkyl glycosides including alkyl glycoside esters such as Crodesta ™ SL-40, which is commercially available from Croda, Inc, New York, NY, the alkyl glycoside ethers described in U.S. Patent 4,011,389. issued March 8, 1977 in the name of W. K. Langdon et al., alkylpoly

- 14E 284239 B6 ethoxylated esters such as Pegosperse ™ 200 ML, which is commercially available from Glyco Chemicals, Inc., Greeiiwich, CT, alkylpolyethoxylated ethers and esters such as Neodol ^R 25-12, which is commercially available from Shell Chemical Co, sorbitan esters such as Span 60 from ICI America, Inc., ethoxylated sorbitan esters, propoxylated sorbitan esters, mixed ethoxylated and propoxylated sorbitan esters, and polyethoxylated sorbitan alcohols such as Tween 60, also from ICI America, Inc. . Particularly preferred in the papermaking process of the present invention are alkyl polyglycosides. Listed examples of surfactants are merely exemplary and do not limit the scope of the invention.

Surfactants can be applied to the hot transport surface by spraying, gravure printing or flexo printing. Any surfactant other than the emulsifying surfactant of the chemical papermaking additive will hereinafter be referred to as a surfactant, and any surfactant referred to as the emulsifying component of the emulsified chemical papermaking additive will be referred to as an emulsifier. The surfactants may be applied to the tissue web separately or simultaneously, after or before the application of other chemical papermaking additives. In a typical process, when other chemical papermaking additives are present, the surfactants are applied to the dried web simultaneously with the other additives. It may also be desirable to treat the tissue paper containing the release agent with a relatively small amount of binder to control the formation of fibrous dust or increase the tensile strength. The term binder as used herein refers to various wet and dry strength additives known in the art. The binder may be applied to the tissue web at the same time, after or before the application of the release agents and absorbency enhancers, if used. The binders are added to the dried tissue web at the same time as the release agent (i.e., the binder is contained in a dilute release agent solution applied to the heated transfer surface).

When chemical softeners are required which act primarily to produce a slippery sensation, they may be selected from the following groups of chemicals. Organic materials (such as mineral oils or waxes, such as paraffin or cerium wax or lanolin) and polysiloxanes (such as those described in U.S. Patent 5,059,282 issued to Ampulski and incorporated herein by reference). Surprisingly, it has been found that a small amount of polysiloxane, applied to a hot, over-dried tissue paper web, may give the tissue paper a non-greasy soft silk or flannel feel without the aid of other materials such as oils or lotions. It is important that this advantage can be obtained in many embodiments of the invention in combination with high wettability to the extent required for toilet paper. The tissue paper, in particular treated with the polysiloxane of the present invention, contains about 0.75% or less of the polysiloxane. The process of the invention provides the unexpected advantage that a tissue paper treated with polysiloxane in an amount of 0.75% or less can produce such a soft silk feel with such a small amount of polysiloxane. In general, tissue paper containing less than 0.75% polysiloxane, in particular less than 0.5%, may produce a substantial increase in soft silk or flannel feel while maintaining sufficient wettability without requiring the addition of a surfactant to eliminate the negative effect on the tissue. wettability which is induced by polysiloxane.

The minimum amount of polysiloxane to be retained by the tissue paper is at least an effective amount to impart a tactile difference in the feeling of soft silk or flannel on the tissue paper. The minimum effective amount may vary depending on the particular type of belt, the method of application, the type of polysiloxane and whether the polysiloxane is supplemented with starch, a surfactant or other additives, or a processing method. In particular, without limiting the useful tissue retention of the polysiloxane with the tissue paper, the tissue paper retains at least 0.004%, more preferably at least 0.01%, most preferably at least 0.05% polysiloxane. A sufficient amount of polysiloxane to impart a feeling of softness is distributed evenly on both tissue surfaces, i.e., on the outer surfaces of the surface fibers. When the polysiloxane is applied to one surface of the tissue paper, a little of it

It penetrates at least partially into the tissue paper web. However, the polysiloxane is usually applied to both sides of the tissue paper to impart advantageous properties to both sides. In addition to treating the tissue paper with the polysiloxane as described, it has been found desirable that the tissue paper also be treated with additives to enhance absorbency. That is, in addition to any surfactant that may be present as an emulsifier for the polysiloxane. In some cases, it has also been found desirable that the polysiloxane be omitted from the additive solution and that the tissue paper be treated with a surfactant alone to enhance wettability or softness. Tissue paper containing more than about 0.3% polysiloxane is preferably treated with a surfactant when it is intended to be used where high wettability is desired. In a most preferred embodiment, the non-cationic surfactant is applied to the hot, overdried tissue paper web to obtain additional softness, at a constant tensile strength as previously described. The amount of surfactant to increase hydrophilicity to the desired level will depend on the type and amount of polysiloxane and the type of surfactant. In general, when a tissue paper retains about 0.01% to 2% of a surfactant, and in particular about 0.05% to 1.0%, it is considered sufficient to provide a sufficiently high wettability for most applications, including toilet paper. at a level of polysiloxane of about 0.75% or less.

When chemical softening agents that primarily act to plasticize the structure are desired, they can be selected from the following chemical groups: polyethylene glycol (such as PEG 400), dimethylamine or glycerin. When chemical softeners are required that act primarily on disengagement, they may be selected from the following groups: cationic quaternary compounds such as hydrogenated beef tallow and dimethylammonium methylsulfate (DTDMAMS) or hydrogenated beef tallow and dimethylammonium chloride (DTDMAC) products Sherex Corporation, Dudlin, OH, and Berocel 579, manufactured by EKA Nobel, Stennungssund, SE, and the materials described in U.S. Patent 4,351,699 and 4,447,294 issued to Osbom and incorporated herein by reference, or diester derivatives of DTDMAMS or DTDMAC.

C) Absorbency enhancing additives

When additives are required to increase the degree of absorbency, they may be selected from the following groups of chemicals: polyethoxylates such as PEG 400, alkylethoxylated esters such as Pegosperse 200ML from Lonza Inc, alkylethoxylated alcohols such as Neodol ^R , alkylpolyethoxylated nonvlphenols such Igepal CO, manufactured by Rhone-Poulenc / GAF, or the materials described in U.S. Patent Nos. 4,959,125 and 4,940,513 issued to Spendel and incorporated herein by reference. In cases where surfactant disintegrating agents reduce wettability, a wettability enhancing agent may be added to the deposition solution. for example another surfactant. Thus, for example, a sorbite ester with stearic acid can be mixed with an alkylpolyethoxylated alcohol to produce a soft wettable paper.

When additives are required to reduce the degree of absorption, they may be selected from the following groups of chemicals: alkyl ketendimers such as Aquapel ^R 360XC Emulsion, manufactured by Hercules Inc .. Wilmington, DE, fluorocarbons such as Scoth Guard. manufactured by 3M Minneapolis, MN.

Absorbency enhancing additives may be used alone or in combination with strength enhancing additives. Starch-based strength enhancers have been found to be preferred binders for use in the method of the invention. In particular, the tissue paper is treated with an aqueous starch solution and, as already mentioned, the web is dried over the deposition time. In addition to reducing the formation of fibrous dust in the manufacture of tissue paper, a small amount of starch also imparts a slight improvement in tensile strength to the tissue paper, without increasing the stiffness that may be caused by the addition of large amounts of starch. So be it

- 16GB 284239 B6 produces tissue paper with an improved strength-to-softness ratio compared to tissue paper that has been strengthened by conventional methods of increasing tensile strength, for example, webs of increased tensile strength caused by pulp refining or the addition of other dry strength additives . This result is particularly surprising because starch has been commonly used to increase strength at the expense of softness where softness is not an important property, for example in cardboard. In addition, starch is used as a filler in printing and writing paper to improve its printability.

D) Additives to improve aesthetic appearance

When additives to enhance aesthetic appearance are desired, chemicals, inks, dyes, perfumes, opacifiers (such as TiO ₂ or calcium carbonate), optical brighteners, and mixtures thereof can be selected from these groups.

The aesthetic appearance of the paper can also be improved by the method of the invention. Inks, dyes or perfumes are preferably added to the fluid which is subsequently applied to the hot transfer roller. The aesthetics may be applied alone or in combination with the wettability, softness or strength enhancers.

Analytical methods

The analysis of the amount of paper-processing chemicals that are retained on the tissue paper can be performed by any method that is recognized as applicable. For example, the amount of siloxane poles retained by the tissue paper can be determined by solvent extraction of the polysiloxane with an organic solvent, followed by atomic absorption spectroscopy to determine the amount of siloconone in the extract. The amount of nonionic surfactants such as alkyl glycosides can be determined by extraction in an organic solvent followed by gas chromatography to determine the amount of surfactant in the extract. The amount of anionic surfactants, such as linear alkyl sulfonates, can be determined by aqueous extraction followed by colorimetric analysis of the extract. The amount of starch can be determined by amylase digestion of starch to sugar followed by colorimetric analysis to determine glucose levels. These methods are given by way of example only and do not exclude other methods that may be useful in determining the amount of individual components retained by tissue paper.

The hydrophilicity of tissue paper generally refers to the tendency of tissue paper to wet with water. The hydrophilicity of the tissue paper can be quantified by determining the time for which the dry tissue paper is completely wetted with water. This is referred to as the wetting time. In order to create a consistent and repeatable wettability test, the following procedure must be performed to determine the wetting time: first, a modified sample of tissue paper unit of approximately 11.1 x 12 cm is prepared (environmental conditions for testing paper samples are 23-1 ° C and 50 ± 2% relative humidity according to TAPPI method T402), then fold the sample into four (4) quarters aligned and crumble into a ball approximately 1.9 cm to 2.5 cm in diameter, then place the sample on the surface distilled water at a temperature of 23 ± 1 ° C, placed in the vessel, and at the same time the time is measured. The time measurement ends when the ball is fully wetted. Total wetting is observed visually.

The recommended hydrophilicity of tissue paper depends on its intended use. For tissue paper intended for various uses, such as toilet paper, it is desirable to be completely wetted within a relatively short period of time to prevent clogging of the toilet after it has been flushed. Wetting time is maximum 2 minutes. In a more preferred embodiment, the wetting time is at most 30 seconds and in the most preferred embodiment the wetting time is at most 10 seconds.

- 17GB 284239 B6

Of course, the hydrophilic properties of the tissue paper according to the invention can be determined immediately after manufacture. However, during the first two weeks after manufacture, hydrophobia can be substantially increased in paper. Therefore, said wetting time is preferably measured at the end of the second week after manufacture. Therefore, the wetting time, measured at the end of the second week after manufacture, is referred to as the wetting time after two weeks. The density of tissue paper, as used herein, is the average density calculated from the basis weight divided by the thickness of the paper, with appropriate conversion of the appropriate units. The thickness of the tissue paper used in this case is its thickness under a compressive load of 15.5 g / cm < 3 >.

Example 1

The purpose of this example is to illustrate one example of a method that can be used to produce soft tissue treated tissue webs according to the invention. A longitudinal sieve paper machine (Fourdrinier machine) was used to carry out this method. The papermaking machine has a headbox where the upper chamber, the intermediate chamber and the lower chamber are arranged one above the other. In its use, as will be further indicated below, the method described also applies to the previously described examples. The first fibrous slurry, preferably composed of short papermaking fibers, is pumped simultaneously from the upper and lower chambers, the second fibrous slurry, preferably composed of long papermaking fibers, is pumped from the middle chambers and stacked successively on the longitudinal screen of the paper machine to form three-layer starter strip. The first slurry has a fiber density of about 0.11% with hard eucalyptus kraft pulp fibers. The second slurry has a fiber density of about 0.15% with the fibers of northern softwood kraft pulp. Dewatering is performed on the longitudinal screen of the paper machine. The longitudinal screen is 5-shed with satin weave in an arrangement of 87 threads per 2.464 cm in the longitudinal direction and 76 threads per 2.464 cm in the transverse direction. The initial web is transferred from a longitudinal sieve with a fiber density of about 22% at the point of transfer to a textile carrier that is 5-shed with satin weave in a configuration of 35 threads per 2.464 cm in the longitudinal direction and 33 threads per 2.464 cm in the transverse direction. The belt is carried by a textile carrier through a vacuum dewatering box, a blow dryer, and is then transferred to a Yankee drying drum. After passing through the vacuum dewatering cabinet, the fiber density is about 27% and under the influence of the pre-dryer about 65% before transferring to the Yankee drying drum. The creping adhesive containing 0.25% aqueous polyvinyl alcohol solution is applied by spraying with applicators. The fiber density is increased to an estimated 99% prior to dry creping of the web with a crepe scraper. The creping rasp has a bevel angle of about 24 degrees and is inclined relative to the Yankee dryer at an angle of about 83 degrees. The Yankee Dryer Drum has an operating speed of about 177 ° C and a peripheral speed of about 244 m / min. The heated calender rolls are sprayed with the chemical softener emulsion described below using a 2 mm spray nozzle. The web then passes between the two heated calender rolls. The two calender rolls are biased relative to one another and have a peripheral speed of about 201 m / min.

The spray solution is prepared by diluting the C12-25 linear primary alcohol known as Neodo® 25-12 Shell Chemical to 5% by weight with water. The surfactant solution is then sprayed onto a heated steel calender roll. The flow rate of the aqueous solution through the nozzle is about 25 l / h per m in the transverse direction.

More than 95% of the water is evaporated from the calender rolls, leaving a chemical softener film of a calculated thickness of less than 0.07.10 ' ⁶ m. A dry web of about 1% moisture touches the hot calender rolls. The chemical softener compound is transferred to the dry web by direct pressure transfer. Efficiency of chemical plasticizer transfer. applied to the web is usually about 45%.

The resulting tissue paper has a basis weight of 30 g / m ² , a density of 0.10 g / cm 2 and contains 0.17% by weight of the alkylpolyethoxylated alcohol compound and has an initial non-equilibrium

- 18GB 284239 B6 Humidity 1.2%. It is important that the resulting tissue paper produces a tactile feeling of softness compared to paper that has not been treated.

Example 2

The purpose of this example is to explain one example of a method that can be used to produce softening and starch treated tissue paper bands of the invention.

A three-ply paper web is prepared according to the described method 1. The tissue paper web is treated with Crodesta ™ SL -40 (an alkyl glycoside polyester non-anionic surfactant sold by the crop company) and fully cooked amioca starch prepared as described above. The surfactant and starch are applied simultaneously to the heated transfer roller as part of the aqueous solution by spraying with a paper machine nozzle. The concentration of Crniesta ™ SL-40 non-anniotic agent in the aqueous solution is adjusted such that the amount of surfactant retained is about 0.15% based on the dry fiber weight. Similarly, the concentration of starch in the aqueous solution is adjusted such that the amount of starch retained is about 0.2%, based on the dry fiber weight.

The surface treatment mixture is sprayed onto the upper and lower heated transfer rollers. The water evaporates from the rollers and the surfactant and binder are transferred to both sides of the tissue paper web. The flow rate of the upper and lower nozzles on the heated rollers is about 12.5 l / h per m in the transverse direction. The resulting tissue paper has a basis weight of 30 g / m ² , a density of 0.10 g / cm ^J and contains 0.15% by weight of the non-anionic Crodesta ™ SL-40 and 0.2% by weight of cooked amioca starch. It is important that the resulting tissue paper produces an improved tactile feel of softness and has a higher wettability and less tendency to form dust as compared to paper that has not been treated.

Example 3

The purpose of this example is to explain one example of a method that can be used to produce soft tissue paper webs, wherein the tissue paper is processed by the method of the invention adapted to a two-layer product.

A two-ply paper web is produced by the method of Example 1, with the following exceptions. The flow rate through the nozzles is about 13.3 liters / hour, per 1 m in the transverse direction. The film thickness after evaporation of 95% water is calculated to be about 0.035 x ^{10 6} m. The resulting single layer tissue paper web has a basis weight of 16 g / m < 2 >.

In the subsequent paper production, two strips of paper having a treated surface are joined together with the treated surfaces facing outwardly.

The resulting two-ply paper product has a basis weight of 32 g / m ² . a density of 0.10 g / cm ^{< 3} > and contains 0.17% by weight of the alkyl polyethoxylated alcohol.

It is important that the resulting tissue paper produces an improved tactile feeling of softness.

Example 4

The purpose of this example is to explain one example of a method that can be used to produce soft tissue paper webs, wherein the tissue paper is treated with a surfactant mixture comprising a surfactant additive and an absorbent enhancing agent.

- 19GB 284239 B6 capability. The process of Example 1 produces a three-ply paper web. An aqueous plasticizer dispersion is prepared from 11.9% GLYCOMOL-S CG (sorbitol ester stearate surfactant mixture, manufactured by Lonza, Inc), 3.2% Neodol ^R 23-6.5T (ethoxylated C12-C13 linear) an alcohol dispersion surfactant manufactured by Shell Chemical Company), 0.8% additive DOW 65 (silicone polymer foam restrictor manufactured by Dow Coming Corporation) and 84.1% distilled water.

The processing mixture is sprayed onto a lower heated calender (transport roller). Water is evaporated from the cylinder and the active softener and absorbent are transferred to one side of the tissue paper web. The nozzle flow rate is adjusted so that the paper web retains about 0.6% of the plasticizer (Glycomul-S CG). The resulting tissue paper has a basis weight of 30 g / m ² , a density of 0.10 g / cm ^3, and contains about 0.6% by weight of Glycomul-S CG surfactant. Importantly, the resulting tissue paper produces an improved tactile feel of softness and has a high wettability.

Example 5

The purpose of this example is to explain one example of a method that can be used to produce soft tissue paper webs, wherein the tissue paper is treated with a biodegradable quaternated aminoester softener compound. The method of Example 1 produces a three-ply web. A 1% aqueous dispersion of a plasticizer is prepared from a mixture of a diester derivative of hydrogenated tallow and dimethylammonium chloride (DEDTDMAC) (ie ADOGEN DDMC from Sherex Chemical Company) and polyethylene glycol as a wettability enhancer (ie PEG-400 from Union Carbide Company). The solution is prepared according to the following procedure: 1. Weigh the equivalent molar concentration of DEDTDMAC and PEG-400;

2. PEG is heated to about 70 ° C; 3. DEDTDMAC is dissolved in PEG as a molten solution. 4. Using a shear stress, a homogeneous mixture of DEDTDMAC in PEG is formed; 5. Adjust the pH of the water to be diluted to 3 by addition of hydrochloric acid; 6. Heat the dilution water to about 70 ° C. 7. Dilute the DEDTDMAC / PEG-400 mixture to a 1% solution. 8. Apply shear to form an aqueous solution containing a suspension of the DEDTDMAC / PEG-400 mixture.

The processing mixture is sprayed onto the lower heated calender (transport) roller. The water is evaporated from the cylinder and a softening compound and an absorbent enhancing agent are transferred to one side of the tissue paper web. Adjust the flow rate through the spray nozzles so that about 0.05% of the softener (DEDTDMAC) is retained by the tissue paper web. The resulting tissue paper has a basis weight of 30 g / m ² , a density of 0.10 g / cm ^3, and contains about 0.5% by weight of the DEDTDMAC softener. It is important that the resulting tissue paper produces an improved tactile feeling of softness and has a high wettability.

PATENT CLAIMS

Claims (12)

A method of making tissue paper by applying chemical papermaking additives to a dry tissue web, characterized in that the chemical papermaking ingredients are diluted with a solvent to form a dilute chemical solution, which is then applied to the heated transport surface, further evaporating at least a portion of the solvent. a heated conveying surface to form a film containing chemical papermaking additives, and the film is then transferred from the heated conveying surface to at least one outer surface of the tissue paper web by contacting the outer % Of this strip having a heated conveying surface at a retention rate of 0.004% to 2.0% by weight; chemical paper additives, based on the dry fiber weight of the tissue paper web. 2. The process of claim 1 wherein the solvent is water. Method according to claims 1 and 2, characterized in that the chemical papermaking additives are selected from additives for increasing strength, absorbency, softness, aesthetic appearance and mixtures thereof. The method of claim 3, wherein the softness enhancing agents are selected from lubricants, plasticizers, cationic disintegrants, non-cationic disintegrants, and mixtures thereof. The method of claim 4, wherein the lubricants are polysiloxanes. The method of claim 4, wherein the non-cationic disintegrant is selected from sorbitan esters, ethoxylated sorbitan esters, propoxylated sorbitan esters, and mixtures thereof. Method according to claim 3, characterized in that the strength enhancing additives are selected from permanently wet strength resins, in particular polyamide epichlorohydrin resins, polyacrylamide resins and mixtures thereof, temporary wet strength resins, in particular from resins, starch, temporary wet strength enhancers, dry strength additives and mixtures thereof. Method according to claim 3, characterized in that the additives for increasing the absorbency are selected from polyethoxylates, alkylethoxylated esters, alkylethoxylated alcohols, alkylpolyethoxylated nonylphenols and mixtures thereof, in particular alkylethoxylated alcohols. Method according to claims 4 to 6, characterized in that additives for improving the absorbency are applied to the tissue paper in an amount of 0.01% to 2.0% by weight, based on the weight of the dry fibers of the tissue paper. Method according to claim 9, characterized in that the absorbency enhancers are non-cationic surfactants, in particular an alkylethoxylated alcohol having a melting point of at least 50 ° C. Method according to claims 4 to 6 or 8 to 10, characterized in that additives for increasing its strength are applied to the tissue paper in an amount of 0.01% to 2.0% by weight, based on the dry fiber weight of the tissue paper. Method according to claims 1 to 11, characterized in that the heated conveying surface is a calender roller.