HU214780B - Process for applying chemical papermaking additives to a dry tissue paper web - 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

The present invention relates generally to a process for making paper tissue; more specifically, a method of applying a small amount of a chemical papermaking additive to the surface of a tissue paper to improve the properties of the paper, such as strength, softness, absorbency and / or aesthetic properties.

Products used by consumers, such as toilet paper, wipes and facial wipes made of cellulosic fabrics, are commonplace in modem society. These products should generally have some of the essential characteristics considered acceptable by consumers. While the exact mixing of the essential properties and the absolute value of each attribute will vary depending on the nature of the product, softness, wet and dry firmness, suction and attractive aesthetic qualities are generally required. Softness is a property of fibrous web that gives a pleasant feel to the paper and ensures that the product is not rough or abrasive when in contact with human skin or other delicate surfaces. Strength is the ability of a paper structure to maintain its physical integrity during use. Suction capacity is a property of the fibrous structure that enables it to absorb and retain contacting liquids within a reasonable time. The aesthetic character refers to the psycho-visual reaction that occurs when the consumer sees the product by itself or in relation to its environment.

The most common method for the production of paper fabrics is the wet laid paper production process. In such a process, individual fibers are first suspended in a dilute suspension in water. This suspension is then layered on a perforated sieve to remove most of the water and form a thin, relatively uniform starting material. This starting fabric is then pressed and / or dried in various ways to form the final paper web. As part of this process, the pressed and / or dried fabric is usually glued to a drum dryer and then creped from the surface of the dryer to give the fabric favorable properties.

Many of the existing wet layered products fall within the scope described above. Examples of such tissue webs which are soft, solid, and of good color and contain at least two microregions of density are disclosed in U.S. Patent Nos. 3,301,746, 3,974,255, 3,994,771, 4,191,609 and 4,637,859. Each of these papers is characterized by a repetitive pattern of dense and less compact sites. The compact spaces can be discrete or continuous. These compact locations result from the partial compression of the paper web during the papermaking process by the indentation of the embossed portions of a printer transfer screen or ribbon.

Other high-volume soft tissue fabrics are described in U.S. Patent Nos. 4,300,981 and 4,440,597.

U.S. Pat. No. 3,821,068 discloses the production of high specific volume, soft and absorbent paper webs without the need for full compaction prior to final drying; and U.S. Pat. No. 3,812,000 disclose the avoidance of total compaction in combination with the use of loosening agents and elastomeric binders in a papermaking fiber machine.

Chemical release agents such as those proposed by Salvucci (U.S. Pat. No. 3,812,000) and their theory of operation are described, for example, in U.S. Patent Nos. 3,775,220, 3,844,880, and 4,158,594.

The paper tissues were also treated with cationic and non-cationic surfactants to enhance softness. For example, U.S. Patent Nos. 4,959,125 and 4,940513 disclose processes for enhancing the softness of paper tissue by treatment with non-cationic, preferably nonionic, surfactants.

It has been found that the softness of paper tissue, especially of high specific volume, patterned paper tissue, can be improved by treatment with various agents such as vegetable, animal or synthetic oils, and in particular polysiloxane materials, typically silicone oils (cf. U.S. Pat. No. 5,059,282). patent). This specification describes a process for adding a polysiloxane compound to a wet paper web (preferably having a fiber density of about 20% to about 35%). These polysiloxane compounds give a silky soft feel to the paper web.

Although the aforementioned processes generally give acceptable product characteristics, the product properties can be further improved.

However, processes that provide widespread and potentially improved products have several disadvantages. For example, chemicals used to strengthen paper webs are often added to a dilute suspension of water and fibers before they are layered on a forming screen. This is a relatively convenient and cost-effective way of administering additives. However, other chemicals to improve absorbency and softness are generally also introduced in the so-called wet phase of the papermaking process. Due to the complex nature of the individual chemicals used to provide the essential properties, they are often adversely affected. The chemicals may compete with one another for the desired retention of the cellulosic fibers and may destroy the properties inherent in the fibers. For example, plasticizers often reduce the natural tendency of fibers to bind other fibers, thereby reducing the functional strength of the paper web produced. It is advantageous for both process and product to keep the amount of chemical papermaking additives added in the wet stage to a minimum.

As mentioned above, in the known papermaking process, the fabric is glued to a tumble dryer surface and the fabric is then creped from the tumble dryer surface. Creping usually produces better softness of the fabric and significantly improves the extensibility of the fabric. H2

EN 214 780 Β for the crepe to work properly, it is necessary that the paper tissue is securely attached to the surface of the drum. Many chemicals that are applied during the wet phase of the machine to apparently improve the basic properties will ultimately reduce the adhesion of the fabric to the tumble dryer and thus adversely affect the creping process and the quality of the paper fabric produced. The creping operation is optimally performed when the adhesive used to glue the fabric to the creping surface does not interact with non-creping related chemicals, such as those applied by the papermaker's wet process.

Additives added at the wet stage of the process must be retained by the cellulosic fibers if the chemicals have a function. This is usually provided by the use of chemicals that have an ionic charge; most preferably, a positive ionic charge is attracted to the negative ionic charge inherent in the cellulose. Many additives that can improve the properties of the fabric are not charged. The introduction of such chemicals into the dilute fiber suspension at the wet stage of the process results in poor chemical retention and exacerbates the above mentioned interaction problems.

Another disadvantage of introducing chemicals at the wet stage of the process is that the chemical, when retained by the paper tissue, is distributed throughout the tissue. In many cases, it is desirable that the active ingredient (s) be applied only to the surface of the tissue. This may be useful, for example, for lubricating plasticizers. The application ensures effective use of the material only on the surface as consumers only come into contact with the surface. Application to the surface avoids interaction with other materials, such as strength-enhancing additives, which are best placed inside the arc. The present invention overcomes all of the above-mentioned drawbacks and provides further desirable advantages.

It is an object of the present invention to provide an improved process for incorporating chemical papermaking additives into paper tissue, which enhances softness, strength, suction capacity and aesthetic appearance, or combinations of these properties.

It is a further object of the present invention to provide an improved process for incorporating chemical papermaking additives into paper tissue that enhances softness, strength, absorbency and aesthetic appearance, or combinations of these properties, without interfering with the creping process or destabilizing the delicate water system. of the invention.

Another object of the present invention is to provide an improved process for incorporating chemical papermaking additives into tissue paper, which is generally retained by the paper in small amounts when introduced in the wet stage of the papermaking process.

Another object of the present invention is to provide a process for introducing chemical papermaking additives into dry paper webs in a calender roll.

It is a further object of the present invention to provide an improved process for using diluted chemical papermaking additives (dilution providing controlled delivery of a small amount of additive) on a heated carrier, such that the solvent or carrier is preferably evaporated while the mixture is on the carrier. and then applying a more concentrated mixture of additive and solvent to the surface of the tissue than was previously applied to the delivery surface.

Finally, it is an object of the present invention to provide an improved process for introducing chemical papermaking additives into paper tissue by the above-described process wherein the carrier or solvent has a higher vapor pressure than the additive so that the carrier is preferably evaporated upon application to the heated delivery surface.

This evaporation of the support material preferably takes place before the dry tissue paper is treated.

The above and other objects have been achieved by the use of the present invention as will be apparent from the following detailed description.

The present invention relates to a process for producing a soft, solid, absorbent and aesthetically pleasing paper web. This process involves preparing the dry paper web and then applying sufficient amounts of chemical papermaking additive to the dry paper web. More specifically, the process employing the plasticizer comprises the steps of: diluting the chemical papermaking additive compound with a suitable solvent to form a diluted papermaking additive solution; applying the diluted papermaking additive solution, for example, by spraying onto a heated delivery surface; and evaporating a portion of the solvent from the heated delivery surface to form a film containing the papermaking additive. Thereafter, at least one outer surface of the dry tissue web is contacted with the heated delivery surface, which results in that surface transferring sufficient amount of papermaking additive to retain from 0.004 to 2% by weight of papermaking additive. By solvent is meant a liquid that completely dissolves a chemical papermaking additive, or a liquid that is used to emulsify a chemical papermaking additive, or a liquid that is used to suspend a chemical papermaking additive. The solvent may be a carrier or vehicle that contains the chemical additive or aids in the delivery of the chemical papermaking additive. All of the above references are interchangeable and non-restrictive. The solution is the liquid that contains the chemical papermaking additive. Solution means a real solution, emulsion and / or suspension. For the purposes of the present invention, all terms are interchangeable and non-limiting. If the solvent is water, the hot paper web is preferably dried to a moisture content below the equilibrium moisture content (under standard conditions) prior to contact with the papermaking additive film, but this process can be applied to the web at equilibrium moisture content or even when most of the water is evaporated. from the interface.

HU 214 780 Β

Preferably, the amount of papermaking additive retained by the paper web is between 0.01% and 1.0% by weight based on the dry weight of the paper web. The paper web produced preferably has a basis weight of 10 to 80 g / cm ² and a fiber density of about 0.6 g / ml.

As mentioned above, the papermaking additive is preferably introduced into the paper web after the paper web has been dried and creped. When the papermaking additive is added to the tissue after drying and creping, there is no interference with the adhesive on the Yankee dryer, which causes skipping in creping and / or degrades sheet control. Furthermore, when used as described in the process of the invention, the papermaking additives do not interfere with the papermaking water system since they are not introduced in the wet stage of the papermaking machine. A further advantage of the process according to the invention is that the additives do not have to be substantive to the paper. This means that the cationic charge associated with the anionic charge on the cellulosic papermaking fibers need not be included. Preferably, the papermaking additive is added to the hot, creped paper web after it has left the scraper blade and rolled onto the carrier roll.

Surprisingly, it has been found that significant benefits in terms of softness, strength, absorbency, and / or aesthetic appearance of paper web can be achieved with a small amount of chemical papermaking additive by diluting the papermaking additive with a solvent and applying a carrier solvent to the carrier. the additive is transferred to the hot paper tissue prior to the processing operation. An advantage of the process according to the invention is that the amount of residual solvent that has entered the paper web is low enough not to impair the other properties of the product. In addition, the amount of papermaking additive used is low enough to be economical. Paper tissue that is treated with a small amount of chemical plasticizer such as polysiloxane retains a high degree of wettability (hydrophilicity), which is an important feature of a paper tissue product.

Preferred plasticizers for use in the process of the present invention are amino-functional polydimethylpolysiloxanes in which less than about 10 mol% of the side chains on the polymer contain an amino function. In addition to this substitution containing amino-functional groups, effective substitution with carboxy, hydroxy, ether, polyether, aldehyde, ketone, amide, ester and thiol may also be performed. Of these effective substituent groups, the family of amino, carboxy and hydroxy groups is more preferred than the others; and amino function groups are most preferred.

Examples of commercially available polysiloxanes are DOW 8075 and DOW 200, which are products of Dow Corning; and Silwet L720 and Ucarsil EPS available from Union Carbide.

Other preferred plasticizer additives useful in the process of the present invention include nonionic surfactants such as sorbitan esters, ethoxylated sorbitan esters, propoxylated sorbitan esters, mixed ethoxylated / propoxylated sorbitan esters, and mixtures thereof.

The process for producing a paper tissue treated with a chemical plasticizer such as the above-mentioned polysiloxane and / or nonionic surfactants may further comprise the step of adding an effective amount of a suction enhancer to the tissue to provide a tactile surface softness to the tissue. stepping up and / or at least partially compensating for the reduction in the wettability of the paper tissue that would otherwise be caused by incorporation of polysiloxane or other chemical plasticizer. Of course, the paper's wetting ability without the chemical plasticizer additive can be enhanced by the use of a suitable absorbent additive such as a surfactant. The surfactant is preferably present in an amount of 0.01% to 2% by weight based on the dry weight of the paper web; and more preferably the paper tissue retains 0.05 to 1.0% by weight. Preferably, the surfactant is non-cationic and substantially non-migrating in situ after the paper web has been manufactured in order to substantially avoid any change in the properties of the paper web after manufacture that would otherwise occur due to the mixing of the surfactant. This can be achieved, for example, by the use of surfactants having higher melting temperatures than those encountered during storage, transport, sale and use of the paper web products of the present invention, such as preferably at or above 50 ° C.

The process for producing a paper web according to the invention may further comprise the step of introducing an effective amount of a strength enhancing additive, such as a starch based material, to at least partially avoid a reduction in tensile strength and / or an increase in dusting tendency. resulting from incorporation of the chemical softener and, if present, the suction enhancer. The strength enhancing additive retained by the paper web is 0.01 to 2% by weight based on the dry weight of the paper web.

Unless otherwise stated, all percentages, ratios and proportions are by weight unless otherwise stated.

Figure 1 is a schematic representation illustrating a preferred embodiment of the process of the invention by adding chemical papermaking additives to the paper web.

The process of the invention will be described in detail below.

Briefly, the process of the present invention results in a paper web that is tactile with increased softness, improved strength with added plasticizer, enhanced absorbency with added absorbency enhancer and / or added with aesthetics, dyes, for dry tissue paper, improved aesthetic owner don4

HU 214 780 Β

He's got some. These properties can be improved by adding these and other papermaking additives alone or in combination to a dry tissue paper. Preferably, the tissue paper is dried to a moisture content below the equilibrium moisture content before the chemical papermaking additive is added to the tissue.

Surprisingly, it has been found that a very small amount of a chemical additive, such as a polysiloxane plasticizer, significantly improves the softness of the paper web when added to the dry paper web by the process of the present invention. It has also been found to be relevant that the amount of plasticizer additives used to soften the paper web is low enough to maintain the wettability of the paper web. Further, since the paper web is preferably over-dried and high-temperature when the papermaking additive is introduced, and since the carrier water evaporates from the hot transport surface, no further drying is required.

As used herein, hot paper web refers to a paper web having a temperature above room temperature. The higher temperature of the paper web is preferably at least 43 ° C, preferably at least 65 ° C.

The moisture content of the tissue paper is related to the temperature of the tissue tissue and the moisture content of the environment in which the tissue tissue occupies. As used herein, the term "over-dried paper tissue" refers to a paper tissue that has been dried under standard conditions to a moisture content of less than about equilibrium moisture content, measured at 23 ° C and 50% relative humidity. The equilibrium moisture content of the paper tissue placed under standard conditions of 23 ° C to 50% relative humidity is about 7% by weight. In the process of the invention, the paper web can be over-dried by raising its temperature to a higher level using conventional drying devices such as a Yankee dryer. The moisture content of an overdried paper tissue is preferably less than 7% by weight, more preferably about 0-6% by weight and most preferably about 0-3% by weight.

The paper typically has an equilibrium moisture content of 5-8% by weight when exposed to normal ambient conditions. When the paper is dried and creped, the moisture in the sheet is generally less than 3% by weight. After making the paper, it absorbs water from the atmosphere. In a preferred process according to the invention, the low moisture content of the paper when leaving the scraper blade is preferred. When using a chemical papermaking additive solution on overdried paper, the remaining water added to the paper is less than would normally be taken from the atmosphere. Thus, no further drying is required, and the extensibility does not deteriorate more than would normally occur if the paper absorbed moisture from the air.

The process of the invention is applicable to paper fabrics in general, including, but not limited to, conventionally felted paper fabrics; patterned paper webs, such as those described in U.S. Patent No. 3,301,746, and derivatives thereof; and high specific volume, non-compacted paper webs, such as those described in U.S. Patent 3,812,000. The paper web may be homogeneous or multilayer, and the paper products made thereof may be single or multilayer. Preferably, the web has a basis weight of between 10 g / cm ² and 80 g / cm ² and a density of about 0.60 g / ml or less. Preferably, the basis weight is less than or equal to 35 g / m ² and the density is about 0.30 g / m ² or less. Most preferably, the density is between 0.04 g / ml and 0.20 g / ml. Conventionally pressed paper fabrics and the process for making such papers are well known in the art. These papers are generally made by applying the pulp of papermaking pulp to a perforated forming screen. This sheet forming screen is often referred to in the literature as a Fourdrinier screen. From the time the pulp is placed on the forming screen, this is referred to as (paper) fabric. The tissue is dewatered by squeezing and drying at elevated temperature. The specific methods and typical equipment for making tissue paper by the process described above are well known to those skilled in the art. In a typical process, low-density cellulosic pulp is prepared in a high-pressure overhead cabinet. The overhead cabinet has an opening through which the pulp is deposited in a thin layer onto a Fourdrinier sieve and forms a wet tissue there. The fabric is then generally dewatered in vacuo to a fiber density of about 7% to 45% by weight (to the total weight of the fabric) and further dried by compression operations, whereby the fabric is pressurized by opposing mechanical members, e.g. rollers. The dewatered fabric is then further pressed and dried using a drum dryer known in the art as the Yankee dryer. The Yankee dryer may be mechanically pressurized to compress the fabric with a counter-cylindrical drum. Multiple Yankee drying drums can be used with additional pressure between the drums, if appropriate. The paper web structures that are formed are hereinafter referred to as conventional pressed paper web structures. These sheets are compacted as the paper tissue is subjected to a thorough, comprehensive mechanical compression force while the fibers are wet and then dried in a compressed state.

Patterned compacted tissue is characterized by the fact that some of its surface consists of zones of relatively low fiber density, relatively high specific volume, and the rest of its surface consists of compacted zones of relatively high fiber density. The surface area with a high specific volume can also be characterized as the surface of the "pama" fields. Compressed zones are regions of the so-called "knuckle". Compressed zones may be located individually in the high specific volume field or may be fully or partially interconnected within the high specific volume field. Preferred methods for making patterned paper webs are disclosed in U.S. Pat. No. 3,301,746;

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U.S. Patent Nos. 4,191,609; and 4,637,859.

Preferably, the sample compacted paper webs are generally made by applying a papermaking pulp to a sheet forming screen, such as a Fourdrinier screen, forming a paper web, and then placing the paper web next to a carrier system. The paper web is pressed onto the carrier system to form compacted zones in the paper web at locations that correspond to the contact points between the carrier system and the wet web. The remainder of the paper web that is not pressed during this operation is a high specific volume surface. This high specific volume portion can be further loosened by applying a fluid pressure, such as a vacuum type device or a blow dryer, or by mechanically pressing the fabric against the carrier system. The tissue paper is dewatered and optionally pre-dried so as to substantially avoid compressing the high specific volume field. This is preferably accomplished by fluid pressure, such as a vacuum-type device or a blow dryer, or by mechanically pressing the paper web against the carrier system while not compressing the high specific surface area. The dewatering, pre-drying, if any, and compaction zones may be combined or partially combined to reduce the number of operations performed. After forming the compacted zones, dewatering and possibly pre-drying, the paper web is completely dried, preferably again without mechanical pressure. Preferably, about 8% to about 65% of the surface of the paper web contains compacted mesh knots having a relative density of at least 125% of the density of a high specific volume surface.

Preferably, the carrier system is a printer transfer screen with patterned screen knots, which acts as a carrier system to facilitate the formation of compacted zones under pressure. The pattern of the mesh knots forms said carrier system. Printer transfer screens are described in U.S. Patent Nos. 3,301,746, 3,828,068,3,940,255, 3,573,164, 3,473,576, 4,239,065, and 4,528,339.

The pulp is first formed into wet tissue on a perforated sheet forming substrate, such as a Fourdrinier sieve. The tissue is dewatered and transferred to a printer screen. Alternatively, the pulp may be placed on a perforated substrate which also functions as a printer screen. After forming, the tissue is dewatered and preferably thermally pre-dried to a fiber density of about 40% to about 80%. The dewatering is preferably carried out using a suction cupboard or other vacuum apparatus or a blow dryer. The printing of the screen of the printer screen is pressed into the paper web as described above before the paper web is completely dried. One way of performing this operation is by applying mechanical pressure. This can be done, for example, by pressing a tension roller holding the printer screen onto the surface of the dryer drum, such as the Yankee dryer, while the paper web is located between the tension roller and the Yankee dryer. Preferably, the tissue paper is pressed onto the screen of the printer before it is completely dried using a hydrostatic pressure, such as ^a suction cup or blow-through dryer. The hydrostatic pressure may be applied to initiate the impregnation of the compacted zones during initial dewatering, followed by a separate process operation, or combined.

Non-printed, non-patterned paper tissue structures are described in U.S. Patent Nos. 3,812,000 and 4,208,459. Unprinted, non-pattern compacted paper web structures are generally prepared by applying a papermaking pulp to a perforated forming screen, such as a Fourdrinier screen, to form a wet paper web, dewatering the web, and removing any remaining water without mechanical pressure to dry the paper web. 80%, and then the tissue paper is creped. Water is removed from the tissue by vacuum drying and thermal drying. The resulting structure has a high specific volume curve of soft but weak, relatively uncompressed fibers. Preferably, the binder is added to the tissue web portions prior to creping.

Printed, non-patterned tissue structures are known in the art as conventional tissue structures. Printed, non-pattern compacted paper web structures are generally prepared by applying a papermaking pulp to a perforated screen, such as a Fourdrinier screen, to form a wet web, extracting the water from the web, and removing any remaining water by uniform mechanical pressure (pressing) until the tissue density is 25-50%, then the tissue is transferred to a thermal dryer such as a Yankee dryer and creped. The water is completely removed from the tissue by vacuum, mechanical pressing and thermal methods. The resulting structure is strong (solid) and generally singular in density but has a very low specific volume, suction capacity and softness.

The papermaking fibers used in the present invention are generally those derived from wood pulp. Other cellulosic fibers, such as cotton waste, bagasse (leached sugar beet or cane), etc., are used in the process of the invention. can also be used and are within the scope of the invention. Fibrous plastics such as rayon, polyethylene and polypropylene fibers can also be used in combination with natural cellulosic fibers. An example of a polyethylene fiber that can be used is Pulpex ™, available from Hercules Inc. (Wilmington, Delaware).

Suitable wood pulps include chemical pulps such as kraft pulp, sulphite and sulphate pulps, and mechanical pulps such as wood pulp, thermomechanical and chemically modified thermomechanical pulps. However, chemical pulps are preferred because they give the sheets of paper made therefrom a tactile softness. In the process, both deciduous trees (also called hardwoods) and coniferous trees (to6

EN 214 780 Β also referred to as softwoods). Fibers derived from recycled paper, which may include some or all of the above categories, as well as other non-fibrous materials, such as fillers and binders, used to facilitate the production of the original paper, may also be used in the process of the invention.

The papermaking fiber used in the manufacture of paper web structures may contain other components or materials as well as blends, as known in the art or later known, in addition to the papermaking fibers. The types of additives required depend on the intended specific end use of the sheet of paper. For example, in products such as toilet paper, paper towels, face wipes and the like, high wet strength is a desirable property. Thus, it is often desirable to add to the papermaking pulp chemicals known in the art as wet strength resins.

A general description of the types of wet strength resins used in papermaking is given in the TAPPI monograph series (No. 29, Wet Strength in Paper and Paperboard, Technical Association of Pulp and Paper Industry, New York 1965). The most commonly used wet strength resins are generally cationic. It has been found that polyamide epichlorohydrin cationic wet strength resins are the ones which are particularly useful. Suitable types of such resins are disclosed in U.S. Patent Nos. 3,700,623 and 3,77,776. Useful polyamide epichlorohydrin resins are available from Hercules Inc. of Wilmington, Delaware, which markets such resin under the trade name Kymeme ™ 557H.

It has been found that polyacrylamide resins can also be used as wet strength resins. These resins are disclosed in U.S. Patent Nos. 3,569,632 and 3,569,633. A commercial source of polyacrylamide resins is the American Cyanamid Co. of Stanford, Connecticut, which markets such a resin under the tradename Parez ™ 631 NC.

Still other water-soluble cationic resins useful in the process of the invention are urea / formaldehyde and melamine / formaldehyde resins. The most common functional groups of these polyfunctional resins are nitrogen-containing groups such as amino groups and nitrogen-linked methylol groups. Polyethyleneimine-type resins may also be useful in the present process. In addition, temporary wet strength resins such as Caldas (manufactured by Carlit Japan) and CoBond 1000 (manufactured by National Starch and Chemical Company) can be used in the process of the invention. It is noted that the addition of chemical compounds such as the wet strength and temporary wet strength resins described above to the cellulosic pulp is optional and not necessary in the practice of the present invention.

In the process of the present invention, the chemical papermaking additives are added to the paper web after it has been dried and creped, and preferably at elevated temperatures. It has been found that adding chemical papermaking additives to the tissue before drying and creping the tissue can cause interference with the coating on the dryer (such as the adhesive coating on the Yankee dryer), and can cause skipping crepe and impair arc control. These problems are overcome by the process of the invention, wherein the chemical papermaking additives are added to the paper web after it has been dried and creped. Preferably, the chemical papermaking additives are added to the dried and creped paper web before the paper web is wound onto the support roll. In a preferred embodiment of the process of the invention, the chemical papermaking additives are added to the hot, over-dried paper web after the paper web has been creped, but before the web passes through the calender rolls.

The chemical papermaking additives are preferably applied to the hot transport surface from an aqueous solution, emulsion or suspension. The chemical papermaking additives may also be used in a solution containing a suitable non-aqueous solvent in which the chemical papermaking additive is soluble or with which the chemical papermaking additive is miscible. An example of such a solvent is hexane. The chemical papermaking additive may be incorporated in pure form or, more preferably, emulsified with a suitable surfactant emulsifier. Emulsified chemical papermaking additives are advantageous in terms of ease of handling because a pure aqueous solution of the chemical papermaking additive must be stirred to prevent separation into water and chemical papermaking additive phases.

The chemical papermaking additive is applied to the heated delivery surface in a macroscopically uniform manner so that it is transferred to the paper web so that substantially the entire sheet has the beneficial effect of the chemical papermaking additive. After application of the additive to the heated delivery surface, at least a portion of the solvent is evaporated and a thin film containing the chemical papermaking additive remains. By thin film is meant any thin coating, vapor or mist, on the transport surface. This thin film may be microscopically continuous, discrete or patterned, but must be macroscopically uniform. Microscopically, the distribution of the chemical papermaking additive may be uniform, irregular, discrete, patterned, continuous or discontinuous. Applying the chemical papermaking additive to the tissue paper in a continuous and patterned manner, both methods are within the scope of the invention and meet the above requirements. The chemical papermaking additive may be applied to one or both sides of the tissue paper.

Methods for macroscopically uniform application of the chemical papermaking additive to the hot transport surface include spraying and gravure printing. We have found that spraying is economical and that the amount and distribution of the chemical papermaking additive

EN 214 780 szabályozás, so it is most advantageous. Preferably, an aqueous mixture of the emulsified chemical papermaking additive is applied from the delivery surface to the dried, creped paper web after the Yankee dryer and before the holding roll.

Figure 1 illustrates a preferred method of applying a chemical papermaking additive to a paper web. Referring to Figure 1, the wet paper web 1 passes through the transfer screen 14 next to the rotating roller 2 and is transferred to the Yankee dryer 5 by means of the press roller 3 while the transfer screen 14 passes through the lower rotating roller. The paper tissue adheres securely to the cylindrical surface of the Yankee dryer 5 by means of the spray applied from the dispenser 4. Perfect drying is accomplished by steam-heated Yankee dryer 5 and hot air, which is heated and circulated through the drying jacket 6 by means not shown. The tissue is then dry-creped from the Yankee dryer 5 with the scraper blade 7 to obtain a crepe sheet 15. The aqueous mixture containing the emulsified chemical papermaking additive is sprayed onto an upper heated conveyor surface 10 and / or a lower heated conveyor surface 11 lower calender roll by spraying with the applicators 8 and 9, respectively. the chemical papermaking additive is applied to both sides of the tissue paper or to one side only. The sheet 15 is then contacted with the heated transport surfaces 10 and 11 after a portion of the solvent has evaporated. The treated paper web passes along the circumference of the pre-winder 12 and then rolls onto the support roll 13. Suitable equipment for spraying liquids containing chemical papermaking additive onto hot surfaces includes an external mixer, air atomized nozzles such as a 2mm nozzle sold by V. I. B. Systems Inc., Tucker, Georgia. Devices suitable for printing liquids containing a chemical papermaking additive onto hot surfaces are rotogravure or rubber press printers.

The invention is not intended to be bound by theory or otherwise limited, and the following description of typical process conditions found in the papermaking operation and their effect on the process of the invention is provided. The Yankee dryer raises the temperature of the sheet of paper and removes moisture. The vapor pressure in the Yankee dryer is 750 kPa (110 psi). This pressure is sufficient to raise the cylinder temperature to about 173 ° C. The temperature of the paper on the roller rises when the water leaves the sheet. The arc temperature when leaving the scraper blade may exceed 120 ° C. The arc passes through the square to the calender and pre-winder and loses something from this temperature. The temperature of the paper wrapped in the pre-winder is approximately 65 ° C. Finally, the paper sheet cools down to room temperature. This may take several hours or days depending on the size of the roll of paper. As the paper cools, it absorbs moisture from the atmosphere. As mentioned above, the moisture content of the sheet depends on the temperature of the sheet and the relative humidity of the environment in which the paper is placed. For example, the arc at 23 ° C and 50% relative humidity under standard test conditions has an equilibrium humidity of about 7%. Increasing the moisture content of the sheet to above 7% may adversely affect the tensile strength of the paper. For example, increasing the moisture content to 9% may reduce the tensile strength of the paper by 15%.

A very surprising property of chemical plasticizers, such as polysiloxane, is their ability to improve the elasticity of the paper surface in very small amounts. However, the chemical softener must be distributed evenly over the paper surface to allow the consumer to perceive a softer surface. From the point of view of the process, there was previously no satisfactory method of uniformly applying small amounts of the chemical plasticizer to high-speed paper webs. 700-1000 meters / min web speed is common on modem high speed paper machines. Paper webs moving at this speed generally have an air boundary layer on their surface. One way of applying small amounts of fluid is by applying a spray system and adjusting air and / or fluid pressures. For example, low flow rates can be used using high air pressures. This usually results in very small particles. It is difficult to give these small particles sufficient momentum to penetrate the air boundary layer passing through the surface of fast moving tissue paper. In addition, if the particle size of the spray liquid is increased to penetrate the air boundary layer at low flow rates, the surface coating will not be uniform.

In a commonly used method, a small amount of the active ingredient is first diluted with a solvent. Spray systems can then be adjusted to provide higher particle size at high flow rates. Larger particles can penetrate the air boundary layer. However, there is the problem of removing solvent from the paper. Volatile organic solvents are generally not used in papermaking because they are flammable and harmful to the environment. Water can be used as a solvent for water-soluble papermaking additives. Water may also be used as a solvent or, more preferably, as a diluent for non-water-soluble paper-making additives such as organic oils, polymers and polysiloxanes, if the water-insoluble paper-making additive such as polysiloxane is pre-emulsified with a suitable surfactant system. Although water does not present the same process risks as an organic solvent, water can degrade the product, thus impairing creping and / or tensile strength. In addition, water must be removed from the paper.

The only help to the water problem is to add diluted chemical papermaking additive to the paper while it is over-dried. The amount of water added to the paper with this chemical papermaking additive is usually less than what the paper would normally absorb from the atmosphere when cooled to room temperature. Thus, no further drying is required and the addition of water does not cause any deterioration in tensile strength. However, the aqueous solution can pass

EN 214 780 Β across the arc, and thus distributes the active ingredient inside the arc rather than on the paper where it is most effective. Further, this process is limited to an overdried sheet, which makes it difficult to handle the paper during a processing process (an additional machine process) if no further drying operation is included in the process. Another limiting feature of this process is the limited dilution range and application range of the chemical papermaking additive emulsion caused by the emulsion properties (i.e., high concentrations tend to have high viscosity while low concentrations increase the amount of water sprayed on the sheet).

The process of the present invention solves the above problems by first spraying a dilute solution of a water-soluble chemical papermaking additive or an emulsified solution of a non-water-soluble chemical papermaking additive onto a hot surface and evaporating the solvent from the paper papermaking additive solution to dryness. .

By way of example, a typical commercially available silicone emulsion chemical softener is Dow Corning ™ 02-7224 Conditioner, marketed by Dow Corning Corporation. This material generally contains about 35% by weight of an amino-functional polysiloxane emulsified in water. This silicone emulsion composition is diluted with water to a concentration below about 20% by weight before being applied to the heated delivery surface. More preferably, the chemical papermaking additive emulsions used in the process of the invention are first diluted with water to a concentration of less than 15% by weight before being applied to the delivery surface.

Suitable materials for the heated transport surface include metal (e.g., steel, stainless steel and chromium), non-metal (e.g., suitable polymers, ceramic materials, glass) and rubber.

When a diluted silicone emulsion of the type described above was sprayed onto the hot conveying surface, the most surprising feature of the steel calender roller was that this process carried little or no water to the paper web. In fact, according to one of the process conditions, it was expected that the humidity of the arc after spraying would increase from the 4-5% base. However, it was found that the moisture content did not increase at all while the silicone content increased to the expected concentration in the tissue. It was also surprising that the experiment to increase the arc moisture content by 3.5% (i.e., increase the arc moisture content from 4% to 7.5%) resulted in only 0.7% increase in humidity. , so the measured moisture content was only 4.7%.

This is very surprising since the temperature of the roll is about 80 ° C (20 ° C below the boiling point of water) and the time between handling and transport is about 0.1 sec. It was surprising to find that more than 50% of the water evaporated from the cylinder under these conditions, leaving a thin film of polysiloxane emulsion on the cylinder. This thin film was calculated to be 0.25 microns thick (1 micron = 10- ⁶ m). The films formed in the process of the invention are preferably less than 10 micromolar in thickness and more preferably less than 1 micron in thickness.

In the process of the invention, it is preferred that at least 50%, more preferably at least 80% of the water is evaporated from the dilute solution of the chemical papermaking additive which is applied to the heated delivery surface before being transferred to the dry tissue. This leaves a film with a calculated thickness of about 0.075 microns. Most preferably, about 95% of the water evaporates from the solution on the heated delivery surface, leaving a film of about 0.05 microns thick for transfer to the tissue web.

The temperature of the heated transport surface is preferably below the boiling point of the solvent. Thus, if the solvent is water, the temperature of the heated transport surface should be below 100 ° C. The temperature is preferably between 50 ° C and 90 ° C, and more preferably between 70 ° C and 90 ° C when water is used as the solvent.

The surface heating can also cause the chemical papermaking additive to decrease in viscosity, thereby increasing its ability to form a thin film when dispersed on the surface. This film is then transferred to the surface of the paper web by contacting the web with the transport surface. Surprisingly, it has been found that the transfer efficiency of the chemical papermaking additive to the paper web is quite high. Efficiency is generally about 40-80%, based on the amount of spray nozzle discharged to the transport surface and the amount measured on the paper web. In addition, the process is not limited to overdried paper. Depending on the amount of water removed from the spray mixture by the hot conveyor, the present process also allows the use of a chemical papermaking additive for balanced dry paper. However, it is preferable to apply it to a hot, over-dried paper tissue, ensuring that the water remaining in the film does not adversely affect the properties of the paper.

The use of a chemical papermaking additive solution on a hot, over-dried paper also has the advantage that the reduced viscosity of the solution helps to ensure that the solution is evenly distributed over the surface of the tissue. (We believe that a solution with a lower viscosity is more mobile.)

Chemical additives for paper making

The chemical papermaking additives used in the improved process of the present invention are preferably selected from strength enhancers, absorbency enhancers, emollients, aesthetic enhancers, and mixtures thereof. Each type of additive is described below.

A) Strengthening additives

The strength enhancing additive is selected from permanent wet strength resins, temporary wet strength resins, dry strength resins, and mixtures thereof.

HU 214 780 Β

If desired to achieve a durable wet strength, the chemical papermaking additive may be selected from the group consisting of polyamide epichlorohydrin, polyacrylamides, styrene-butadiene latexes, insoluble polyvinyl alcohol, urea-formaldehyde, polyethyleneimine and chitosan polymers. The polyamide-epilorohydrin resins are cationic wet strength resins which have been found to be particularly useful. Suitable types of these resins are disclosed in U.S. Patent Nos. 3,700,623 and 3,7,720,776. A commercially available source of polyamide-epichlorohydrin resins is Hercules Inc. of Wilmington, Delaware, which markets such resin under the trade name Kymeme ™ 557H.

Polyacrylamide resins have also been found to be useful as wet strength resins. These resins are disclosed in U.S. Patent Nos. 3,556,932 and 3,556,933. A commercial source of polyacrylamide resins is the American Cyanamid Co. of Stanford, Connecticut, which markets one such resin under the tradename Parez ™ 631 NC.

Other water-soluble cationic resins useful in the process of the invention are urea-formaldehyde and melamine-formaldehyde resins. The most common functional groups of these polyfunctional resins are nitrogen-containing groups, such as amino groups and nitrogen-linked methylol groups. Polyethyleneimine type resins can also be used in the process of the invention.

To obtain temporary (intermittent) wet strength, the chemical papermaking additive can be selected from the following chemical groups: cationic dialdehyde starch-based resins (such as Caldas, manufactured by Cariond Japan, or Cobond 1000, manufactured by National Starch), dialdehyde starch and / or the resin described in U.S. Patent 4,981,557.

To achieve dry strength, the chemical papermaking additive may be selected from the group consisting of polyacrylamide (such as combinations of Cypro 514 and Accostrength 711, manufactured by American Cyanamid of Wayne, N.J.); starches (such as corn starch and potato starch); polyvinyl alcohol (such as Airvol 540, manufactured by Air Products Inc. of Allentown, PA); guar or locust bean gum, polyacrylate latexes and / or carboxymethylcellulose (such as Aqualon CMC-T from Aqualon Co., Wilmington, DE). In the practice of the process according to the invention, the corresponding starch is characterized by water solubility and hydrophilicity. Suitable starches include, but are not limited to, corn starch and potato starch; and waxy corn starch, which is known in the industry as amyloid starch, and is highly preferred. Amioca starch differs from common corn starch in that it consists entirely of amylopectin while common corn starch contains amylopectin and amylose. Various unique properties of amyloid starch have been described in the literature [, Α-mioca - The Starch From Waxy Com], Η. H. Schopmeyer, Food Industries, December 1945, p. 106-108 (Vol. Pp. 1476-1478)]. The starch may be in granular or dispersed form, but granular form is preferred. Preferably, the starch is cooked sufficiently to cause the granules to swell. More preferably, the granules, for example by cooking, swell to the point just before the starch granulate disperses. Such highly swollen starch granules are referred to as "fully cooked" starch granules. The conditions for the dispersion will generally vary, depending on the size of the starch granules, the degree of crystallinity of the granules, and the amount of amylose present. For example, a fully cooked amyloid starch may be prepared by heating an aqueous suspension of starch granules having a density of about 4% at about 88 ° C (190 ° F) for about 30 to 40 minutes. Other useful starches include modified cationic starches, such as those modified to contain nitrogen-containing groups such as amino groups and nitrogen-linked methylol groups, which are manufactured by the National Starch and Chemical Company of Bridgewater, New Jersey. Such modified starches have already been used, primarily as additives in cellulosic pulp, to increase wet and / or dry strength. However, when used in the process of the invention for the treatment of overdried paper tissue, the effect on wet strength may be reduced compared to the same modified starches being introduced in the wet section. Considering that these modified starches are more expensive than non-modified starches, the latter are generally preferred. The wet and dry strength resins may be added to the cellulosic pulp in addition to the additives added according to the invention. It should be noted that the addition of chemical compounds such as the aforementioned wet strength and temporary wet strength resins to the cellulosic pulp is optional and not necessary in the practice of the present process.

For purposes of the present invention, the strength enhancing additive is preferably applied in an aqueous solution to the heated transport roller. The methods of application are the same as those mentioned for other chemical additives, preferably by spraying and less preferably by printing. The strength enhancing additive may be applied to the tissue paper alone or simultaneously with, before, or after the plasticizer, suction and / or aesthetic enhancers. Preferably, at least an effective amount of a strength enhancing additive, preferably starch, is applied to the sheet to provide control of the dusting of the paper and at the same time to increase the strength after drying relative to the untreated but otherwise identical sheet. Preferably, the dry sheet retains from about 0.01% to about 2.0% strength enhancing additive, based on the dry weight of the dry fiber; and more preferably from about 0.1% to about 1.0%

EN 214 780 Β in strength retaining additives, preferably with starch base.

B) Plasticizer additives

The chemical plasticizer additives are selected from the group consisting of lubricants, plasticizers, cationic release agents, non-cationic release agents, and mixtures thereof. The release agents preferably used in the process of the invention are non-cationic, preferably nonionic surfactants. However, cationic surfactants may also be used. Non-cationic surfactants include anionic, nonionic, amphoteric and zwitterionic surfactants. Preferably, the surfactant is non-migrating in situ after the paper web has been manufactured to substantially avoid post-production changes in paper web properties that would otherwise result from the introduction of the surfactant. This can be achieved, for example, by using a surfactant having a melting point higher than the temperature generally encountered during storage, transport, sale and use of the paper web products of the present invention; for example, the melting temperature is about 50 ° C or higher. The surfactant is preferably water-soluble when applied to a wet paper web.

The amount of non-cationic surfactant used in the paper webs to provide the above mentioned softness / extensibility ranges, is the minimum effective amount required to achieve this based on the constant extensibility of the final product; paper tissue preferably retains 0.01% to 2% non-cationic surfactant; more preferably 0.05 to 1.0%; and most preferably retains 0.05-0.3% surfactant. The surfactants preferably contain alkyl chains of eight or more carbon atoms. Examples of anionic surfactants are linear alkyl sulfonates and alkyl benzene sulfonates. Nonionic surfactants include alkyl glycosides including alkyl glycoside esters such as Crodesta ™ SL-40, a product of Croda Inc. (New York, NY); alkyl glycosidate ethers disclosed in U.S. Patent 4,011,389; alkyl polyethoxylated esters such as Pegosperse ™ 200 ML, manufactured by Glyco Chemicals Inc. (Greenwich, CT); alkyl polyethoxylated ethers and esters, such as Neodol 25-12, manufactured by Shell Chemical Co.; sorbitan esters such as Span 60 from ICI America Inc.; ethoxylated sorbitan esters, propoxylated sorbitan esters, mixed ethoxylated / propoxylated sorbitan esters, and polyethoxylated sorbitan alcohols such as Tween 60, also from ICI America Inc. Alkyl polyglycosides are particularly preferred in the process of the invention. The above exemplary list of surfactants is illustrative only and is not intended to limit the scope of the invention.

The surfactant may be applied to the hot delivery surface by spraying, gravity blasting, or rubber printing. All surfactants, with the exception of the surfactant emulsifying the chemical papermaking additive, are hereinafter referred to as "surfactant" and the surfactant present as the emulsifying component of the emulsifying chemical papermaking additive is hereinafter referred to as "emulsifying grains". The surfactant may be applied to the tissue paper, either alone or simultaneously with other chemical papermaking additives, either before or after. In a typical process, even if other additives are present, the surfactant is added to the over-dried paper web simultaneously with the other additive (s). It may be desirable to treat a paper web containing a release agent with a relatively small amount of binder to control dusting and / or increase tensile strength. As used herein, the term "binder" refers to various additives known in the art to increase wet and dry strength. The binder may be added to the tissue paper at the same time as, before, or after the release agent and, if used, the absorbency enhancer. The binders are preferably added to the over-dried paper webs at the same time as the release agent (i.e., the binder is added to a dilute solution of the release agent which is applied to the heated delivery surface).

If you need a chemical softener that gives you a primarily slippery feel, this can be selected from the next group of chemicals. Certain organic materials are suitable (such as mineral oils or waxes, such as paraffin or kamauba wax or lanolin); and polysiloxanes (such as those described in U.S. Patent No. 5,059,982). Surprisingly, it has been found that adding a small amount of polysiloxane to hot, over-dried paper webs gives the paper web a softer, silky, flannel-like, non-greasy feel without the aid of other materials such as oils or washing liquids. These advantages are substantially achieved in many embodiments of the process of the invention, combined with a high degree of wettability, to the extent desired for toilet paper use. Preferably, the polysiloxane-treated paper tissue of the present invention contains about 0.75% or less polysiloxane. An unexpected advantage of the process of the present invention is that the paper tissue treated with about 0.75% or less polysiloxane has such a remarkable amount of softness and silky effect with such a small amount of polysiloxane. The soft, silky and flannel-like nature of paper tissue containing less than about 0.75%, preferably less than about 0.5%, of polysiloxane generally improves substantially, yet retains sufficient wettability for toilet paper use without the need for the addition of a surfactant. , which would compensate for the negative effect of polysiloxane on wettability.

The minimum amount of polysiloxane retained by the paper tissue is at least the effective amount that gives the paper a tactile difference in terms of softness, silkiness, or flannel. The minimum effective amount may vary depending on the specific type of arc, the mode of application, the specific type of polysiloxane and the degree of polysiloxane release11.

EN 214 780 Β whether starch, surfactant or other additives or other treatments are added. Without limiting the range of polysiloxane retained by the tissue paper, the tissue tissue preferably retains at least 0.004%, more preferably at least 0.01%, most preferably at least 0.05% polysiloxane.

Sufficient amounts of polysiloxane, which provide a soft tactile feel, are preferably uniformly applied to both sides of the paper web, i.e. to the outer surface of the fibers on its surface. When polysiloxane is applied to one surface of a paper web, a portion of it will generally at least partially penetrate the paper web. Preferably, however, the polysiloxane is applied to both sides of the tissue, thereby ensuring that both surfaces of the tissue benefit from the polysiloxane. In addition to treating the paper tissue with polysiloxane as described above, it has been found advantageous to treat the paper tissue with an absorbency enhancer. This is added in addition to any surfactant which may be present as an emulsifier for polysiloxane. In some cases, it has also been found advantageous to omit the polysiloxane from the additive solution and treat the paper web only with a surfactant to improve wettability and / or softness. Paper tissue containing more than about 0.3% polysiloxane is preferably treated with a surfactant when it is intended for use in which high wettability is desired. Most preferably, a non-cationic surfactant is used for the hot, over-dried paper web, so that softness is preferably enhanced with constant extensibility, as noted above. The amount of surfactant required to increase the hydrophilicity to the required level will depend on the type and amount of polysiloxane and the type of surfactant. However, as a general guideline, it is believed that from about 0.01% to about 2%, preferably from about 0.05% to about 1%, of the surfactant retained by the paper tissue is sufficient to provide a sufficiently high wetting capability for most applications, including toilet paper containing about 0.75% or less polysiloxane.

When a chemical plasticizer is used that primarily serves to plasticize the structure, it is selected from the group consisting of polyethylene glycol (such as PEG-400), N, N-dimethylamine and / or glycerol.

If a cationic chemical plasticizer that primarily functions as a laxative is required, it may be selected from the group consisting of cationic quaternary compounds (such as dihydrogenated tallow dimethylammonium methyl sulfate (DTDMAMS) or dihydrogenated tallow dimethylammonium). chloride (DTDMAC), both manufactured by Sherex Corporation of Dudlin, OH; Berocel 579 (manufactured by Eka Nobel of Stennungsund, Sweden), materials disclosed in U.S. Patent Nos. 4,351,699 and 4,447,294, and / or Diester derivatives of DTDMAMS and DTDMAC.

C) Adsorption additives

If a sorbent enhancer is required to increase the rate (s) of absorption, it may be selected from the group consisting of: polyethoxylates (such as PEG-400); alkyl ethoxylated esters (such as Pegosperse 200ML from Lonza Inc.); alkyl ethoxylated alcohols (such as Neodol®); alkyl polyethoxylated nonylphenols (such as Igepal CO, a product of Rhone-Poulenc GAF) and / or materials disclosed in U.S. Patent Nos. 4,959,125 and 4,940,513. In cases where the surfactant softener reduces the wetting ability, a wetting agent such as a second surfactant may be added to the treatment solution. For example, a sorbitan stearate ester may be blended with an alkyl polyethoxylated alcohol to produce a soft wettable paper.

If a desiccant reducing agent is required, it may be selected from the group consisting of alkyl ketene dimers (such as Aquapel® 360XC Emulsion, a product of Hercules Inc., Wilmington DE; and fluorine). carbons (such as Scotch Guard by 3M of Minneapolis, MN).

The absorbency enhancer may be used alone or in combination with a strength enhancer. It has been found that starch based strength enhancing additives are preferred binders in the process of the invention. Preferably, the tissue paper is treated with an aqueous solution of starch and, as already mentioned, the sheet is over-dried upon treatment. In addition to reducing the dusting tendency of the paper web finished product, a small amount of starch also slightly improves the tensile strength of the paper web without making it stiff, which would result from the intake of large amounts of starch. This method results in a paper web having a better strength / softness ratio than that strengthened by conventional methods of enhancing tensile strength; for example, increasing the tensile strength of the sheets by enhanced purification of cellulose; or other dry strength additives. This result is surprising primarily because starch has traditionally been used to provide strength at the expense of softness in applications where softness is not an important property, such as cardboard papermaking. Starch is also used as a filler for printing papers and writing papers to improve the printability of the surface.

D) Aesthetic additives

If an aesthetic additive is to be used, it may be selected from the group consisting of paints, dyes, fragrances, opacifiers (such as titanium dioxide or calcium carbonate), optical brighteners and mixtures thereof.

The aesthetic appearance of the paper can be improved as described in the process of the invention. The inks, dyes and / or fragrances are preferably added to the treatment fluid, which is then applied to the hot conveyor

HU 214 780 Β. The aesthetic additive may be used alone or in combination with wetting agents, softeners and / or strength enhancers.

Analytical methods

The amount of treatment chemicals retained by the tissue paper can be analyzed by any of the methods accepted in the field of application. For example, the amount of polysiloxane retained by the paper tissue can be determined by extracting the polysiloxane with an organic solvent and then determining the amount of silicon in the extract by atomic absorption spectroscopy; the amount of nonionic surfactants, such as alkyl glycosides, can be determined by extracting the nonionic surfactants with an organic solvent and then determining the amount of surfactant in the extract by gas chromatography; the amount of anionic surfactants, such as linear alkyl sulfonates, can be determined by extracting the surfactant with water and then analyzing the extract colorimetrically; the amount of starch can be determined by converting the starch to glucose by digestion with amylase and determining the amount of glucose by colorimetric analysis. These methods are exemplary only and do not exclude the use of other methods that may be used to determine the amount of special components retained by the tissue.

The hydrofilming of paper tissue generally refers to its tendency to be wetted with water. The hydrophilicity of the paper tissue can be quantitatively determined by the amount of time required for the dry tissue paper to be completely moistened with water. This period is called the "wetting time". In order to provide a constant and repeatable test of the wetting time, the following procedure may be used to determine the wetting time: first, prepare a uniform conditioned paper sample (ambient conditions for testing paper samples: 23 ± 1 ° C and 50 ± 2% relative humidity; as defined by TAPPI Method T 402), which is a paper tissue structure of about 11.1 x 12 cm (4-3.8 inch * 4-¼ inch); then bending the arc into four adjacent quarters and crimping the arc into a sphere of about 1.9 to 2.5 cm (0.75 to 1 inch); third, placing the curled curve on the surface of a distilled body of water at 23 ± 1 ° C and simultaneously activating the stopper; fourth, the stopper is stopped and read when the paper ball is completely wet. Total wetting is determined visually.

The preferred hydrophilicity of the tissue paper depends on what it is intended to use at the end. For many uses of tissue paper, such as toilet paper, it is desirable to wet it completely over a relatively short period of time to avoid clogging the toilet when rinsed with water. The wetting time is two minutes or less. More preferably, the wetting time is 30 seconds or less. Most preferably, the wetting time is 10 seconds or less.

Of course, the hydrophilic properties of the paper webs of the present invention can be determined immediately after manufacture. However, the hydrophobicity may increase significantly during the first two weeks after the papermaking process, that is, after two weeks after the papermaking process. Therefore, the above wetting times are preferably measured at the end of this two-week period. Accordingly, the wetting times measured at room temperature at the end of the two-week aging period are referred to as "two-week wetting times".

Density of a paper web in this specification is the average density of the paper, calculated from the basis weight of the paper divided by its thickness. The caliper of a paper web is the thickness measured under a compressive load of 15.5 g / cm ² (95 g / in ² ).

The following examples illustrate the process of the invention.

Example 1

The purpose of this example is to illustrate a method that can be used to produce soft tissue webs treated with a plasticizer additive according to the present invention.

In the practice of the invention, a half-size Fourdrinier papermaking machine is used. The papermaking machine has a layered float box having an upper chamber, a central chamber and a lower chamber. If the procedure described below can be applied to the following examples, as indicated, it will be used for subsequent examples. First, a fiber suspension containing mainly short papermaking fibers is aspirated through the upper and lower chambers of the riser, and at the same time, a fiber suspension containing primarily long papermaking fibers is aspirated through the middle chamber of the inflation chamber, and the suspension is suctioned one by one. The first suspension has a fiber density of 0.11% and a fiber content of eucalyptus hardwood kraft cellulose. Dewatering is performed on a Fourdrinier sieve with a deflector (baffle) and suction cup. The Fourdrinier sieve is a 5 shed fine satin fabric configuration that contains 87 longitudinal and 76 transverse monofilaments per inch. The starting wet paper web having a fiber density of 22% at the transfer point is transferred from a Fourdrinier screen to a transfer screen, 5 shed fine satin fabric, with 35 longitudinal and 33 transverse monofilaments per inch. After the vacuum dehumidifier cabinet, the tissue paper is transferred to the transfer screen through the blow-through pre-dryers, and then the tissue tissue is transferred to the Yankee dryer. The fiber density is 27% after the vacuum dehumidifier cabinet and 65% using a pre-dryer before being transferred to the Yankee dryer; spraying a creping adhesive containing 0.25% aqueous polyvinyl alcohol onto the tissue paper using nozzles; the fiber density increases to about 99% before the paper tissue is creped dry with a scraper. The scraper blade is inclined at 24 ° and has an angle of entry of 83 ° relative to the Yankee dryer.

HU 214 780 Β is placed; operating the Yankee dryer at a temperature of 177 ° C (350 ° F) and a surface speed of 244 meters / minute (800 feet per minute). Spray onto the heated calender rollers using the chemical softening emulsion described below using a 2 mm nozzle. The paper web is passed between the two heated calender rolls. The two calender rollers are preloaded together in the weight of the roll and are operated at a surface speed of 201 meters / minute (660 feet per minute).

The spray solution was prepared by diluting Neodol® 25-12 (Shell Chemical) with water to 5% by weight. The surfactant solution is then sprayed onto a heated steel calender roller. The volumetric flow rate of the aqueous solution through the nozzle is 25 liters / hour-meter (2 gal / hr cross-direction ft).

More than 95% of the water evaporates from the calender rolls, leaving a film of chemical softener with a calculated thickness of less than 0.07 microns. The dry tissue paper, which has a moisture content of about 1%, comes into contact with the hot calender rollers. The chemical softener is delivered by direct pressure to the dry paper web. The chemical softener used in paper tissue generally has a transfer efficiency of 45%.

The resulting tissue paper has a basis weight of 30 g / m ² , a density of 0.10 g / ml, and 0.17% by weight of an alkyl polyethoxylated alcohol compound and an unbalanced initial moisture content of 1.2%. Importantly, the paper tissue produced has better tactile softness compared to untreated control.

Example 2

The purpose of this example is to illustrate a method that can be used to produce soft paper webs by treating the paper web with a softener and starch.

By the procedure described in Example 1, a three-layer sheet of paper is prepared. The tissue paper is treated with Crodesta ™ SL-40 (an alkyl glycoside polyester nonionic surfactant marketed by Croda Inc.) and fully cooked amyloid starch as described herein. The surfactant and starch are simultaneously applied to the heated transport roller as part of the aqueous solution which is sprayed through the nozzle of the papermaking company. The concentration of Crodesta ™ SL-40 nonionic surfactant in the aqueous solution is adjusted so that the amount of retained surfactant is 0.15% by weight of dry fiber. Similarly, the starch concentration in the aqueous solution is adjusted so that the retained amyloid starch is 0.2% by weight of the dry fibers.

The treatment mixture is sprayed onto an upper and a lower heated transport roller. The water evaporates from the rollers and the effective surfactant and binder are transferred to both sides of the tissue. The volumetric flow rate through the upper and lower nozzles to the heated cylinders is approximately 12.5 liters / hour-meter (1 gal / hr cross-direction ft). The combined flow rate through both nozzles is 25 liters per hour (2 gal / hr cross direction ft).

The paper web produced had a basis weight of 30 g / m ² , a density of 0.10 g / ml, and 0.15 wt% Crodesta ™ SL-40 nonionic surfactant and 0.2 wt% boiled amyloid starch. It is important that the paper web produced has increased tactile softness, improved wetting ability and reduced dusting tendency compared to untreated paper web.

Example 3

The purpose of this example is to illustrate a method that can be used to produce soft paper webs by treating the paper web with the process of the present invention and converting it into a bilayer product.

The double-layer paper was prepared according to the procedure described in Example 1 with the following differences.

The volumetric flow rate through the nozzle is about 13.3 liters / hour-meter (1.05 gal / hr crossdirection foot). The film thickness after evaporation of 95% water was calculated to be about 0.035 microns. The resulting monolayer paper web has a basis weight of 16 g / m ² .

After papermaking, two sheets of treated paper are joined to the outside with their treated surface.

The resulting bilayer paper web has a basis weight of 32 g / m ² , a density of 0.10 g / ml and 0.17% by weight of alkyl polyethoxylated alcohol.

Example 4

The purpose of this example is to illustrate a method that can be used to make soft paper webs by treating a paper surfactant system blend containing a paper softener and a sorbent.

A three-layered sheet of paper is prepared by the method described in Example 1. An aqueous softener dispersion was prepared from 11.9% Glycomul-SCG (mixed sorbitan stearate ester surfactant, product of Lonza Inc.), 3.2% Neodol® 23-6.5T (ethoxylated C12-13 straight chain alcohol, dispersant). surfactant and wetting agent, manufactured by Shell Chemical Company), 0.8% DOW 65 (silicone polymer antifoam, manufactured by Dow Corning Corporation) and 84.1% distilled water.

The treatment mixture is sprayed onto the lower heated calender roll (conveyor roll). The water is evaporated from the roll and the active plasticizer and absorbent are applied to one side of the tissue. The flow rate is adjusted through the spray nozzle so that the sheet of paper retains about 0.6% plasticizer (Glycomul-SCG). The paper web produced had a basis weight of 30 g / cm ² , a density of 0.10 g / ml and 0.6% by weight of Glycomul-SCG surfactant. It is important that the paper tissue produced has increased tactile softness and very good wetting ability.

Example 5

The purpose of this example is to illustrate a method that can be used to produce soft paper webs by treating the paper web with a biodegradable quatemerized amine ester softening compound.

HU 214 780 Β

A three-layered sheet of paper is prepared by the procedure described in Example 1. A 1% aqueous plasticizer dispersion, diester dihydrogenated tallow dimethyl ammonium chloride (DEDTDMAC) (i.e. ADOGEN DDMC from Sherex Chemical Company) and a polyethylene glycol wetting agent (i.e. PEG-400 from Union Carbide Company) are prepared. ). The solution is prepared as follows: 1. measure the molar concentration of DEDTDMAC and PEG-400; 2) heating the PEG to about 82.5 ° C (180 ° F); 3. dissolving DEDTDMAC in PEG to form a melt solution; Using a shear stress to form a homogeneous mixture of DEDTDMAC and PEG; 5. adjusting the pH of the diluent water to about 3 by addition of hydrochloric acid; 6. the dilution water is then heated to about 82.5 ° C (180 ° F); 7. diluting the molten mixture of DEDTDMAC / PEG to a 1% solution; Using a shear stress of 8, an aqueous solution containing an air bubble suspension of the DEDTDMAC / PEG-400 mixture is prepared.

The treatment mixture is sprayed onto the lower heated calender roll (conveyor roll). The water is evaporated from the roll and the active compound softener and absorbent are transferred to one side of the tissue. The flow rate is adjusted through the spray nozzle so that the arc retains 0.05% softener (DEDTDMAC). The paper web produced had a basis weight of 30 g / m ² , a density of 0.10 g / ml, and approximately 0.05% by weight of DEDTDMAC plasticizer. It is important that the paper tissue produced has increased tactile softness and high wettability.

Claims (12)

PATENT CLAIMS A method for applying chemical papermaking additives to dry tissue paper, comprising the steps of: a) providing a dry tissue paper; b) diluting a chemical papermaking additive with a suitable solvent to form a dilute chemical solution; c) applying this dilute chemical solution to a heated delivery surface; d) evaporating at least a portion of the above solvent from the heated transport surface to form a film containing said chemical papermaking additive; and e) transferring said film from the heated delivery surface to at least one outer surface of the paper web by contacting the outer surface of the paper web with the heated delivery surface, thereby transferring a sufficient amount of chemical papermaking additive such that 0.004 to 2.0% by weight of retains papermaking additive based on the dry weight of the paper web. A process according to claim 1, wherein the solvent for step b) is water. Method according to claim 1 or 2, characterized in that the chemical papermaking additive is used in the form of strength enhancing additives, absorbent additives, plasticizer additives, aesthetic additives or mixtures thereof. 4. The method of claim 3 wherein the plasticizer is lubricants, plasticizers, cationic release agents, non-cationic release agents, or mixtures thereof. 5. The process of claim 4 wherein the lubricant is polysiloxanes. The process according to claim 4, wherein the non-cationic release agent is sorbitan esters, ethoxylated sorbitan esters, propoxylated sorbitan esters, mixed ethoxylated / propoxylated sorbitan esters or mixtures thereof. 7. The process according to claim 3, wherein the strength enhancing additive is a resinous wet strength resin, preferably a polyamide-epichlorohydrin resin, a polyacrylamide resin or a mixture thereof, a temporary wet strength resin, preferably a starch based, temporary wet strength resin. , dry strength additives or mixtures thereof. 8. The process according to claim 3, wherein the absorbent enhancer is polyethoxylates, alkyl ethoxylated esters, alkyl ethoxylated alcohols, alkyl polyethoxylated nonyl phenols or mixtures thereof, preferably alkyl ethoxylated alcohols. 9. A process according to any one of claims 1 to 4, wherein the paper web is also treated with a sufficient amount of a suction enhancer to retain from 0.01% to 2.0% by weight of the suction enhancer based on the dry weight of the paper web. Process according to claim 9, characterized in that a nonionic surfactant, preferably an alkyl ethoxylated alcohol having a melting point of at least 50 ° C, is used as a sorbent enhancer. 11. or 8-10. A process according to any one of claims 1 to 4, wherein the paper web is also treated with a sufficient amount of a strength enhancing additive so that the web retains 0.01 to 2.0 wt% of the strength enhancing additive, based on the dry weight of the paper web. 12. A method according to any one of claims 1 to 3, characterized in that the heated conveying surface is a calender roller.