KR100284677B1 - How to apply chemical paper additive from thin film to thin paper - 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

[Name of invention]

How to apply chemical paper additive from thin film to thin paper

Detailed description of the invention

[Technical Field]

The present invention is generally a method for producing thin paper; More specifically, the present invention relates to a method of applying a small amount of chemical papermaking additives to thin paper and surfaces in order to improve the properties of the thin paper, such as strength, flexibility, absorbency and / or aesthetics.

[Background of invention]

Consumer products such as tissue paper, towels and toilet paper made from cellulose webs are widespread in the modern world. In general, these products should have some key physical properties that will be acceptable to the consumer. The precise mixing of key properties and the absolute value of individual properties depends on the nature of the product, but flexibility, wet and dry strength, absorbency and satisfactory aesthetics are commonly required properties. Flexibility is a property of the fibrous web that elicits a satisfactory tactile response and ensures that the product is not rough or abrasive when in contact with human skin or other fragile surfaces. Strength is the ability of a structure to maintain its physical form in use. Absorbency is a property of the fibrous structure that allows absorbing and retaining fluid in contact within an acceptable time. Aesthetics refers to the psychological-visual response that occurs when a consumer views a product, either alone or with the product's surroundings.

The most common method of making thin paper products is wet laid papermaking. In this method, the individual fibers are first suspended in a slurry which is diluted with water. This slurry is then poured onto a perforated screen to remove large amounts of water and to produce an initial web of thin, relatively uniform weight. The initial web is molded and / or dried in various ways to produce the final lamination web. As part of this method, the molded and / or dried web is usually adhered to a drying drum and then creped from the surface of the dryer to impart the desired properties.

Products manufactured by several existing wet laid methods fall under the above description. Examples of such webs that are flexible, strong, absorbent, and include more than one small density region can be found in the following US patents: Lawrence H. Sanford and James B. Sisson, dated January 31, 1967. 3,301,746 to 3,974,025, issued to Peter G. Ayers on August 10, 1976; 3,994,771 to Morgan, Jr. and Thomas F. Rich, issued November 30, 1976; 4,191,609, issued to Paul D. Trokhan, March 4, 1980; And 4,637,859, issued to Trocan on January 20, 1987, each of these leaflets is characterized by a repeating pattern of dense and less dense areas. Dense zones may be discontinuous or continuous. This dense zone results from the local compression of the web upon papermaking by the raised zone of the indented conveying fabric or belt.

Other bulky and flexible leaf papers are US Patent No. 4,300,981 issued to Jerry E. Carstens on November 17, 1981; And US Patent No. 4,440,597, issued to Edward R. Wells and Thomas A. Hensler, on April 3, 1984.

In addition, bulky and flexible absorbent leaf paper obtained by not totally compressing before finally drying is disclosed in US Pat. No. 3,821,068 to D. L. Shaw, dated June 28, 1974; A bulky, flexible absorbent leaf paper obtained by total compression without the use of debonders and elastomeric binders in paper stock, to Salbutucci, J. (J, L. Salvucci, Jr.), dated May 21, 1974. US Patent No. 3,812,000.

As mentioned above, chemical debonders such as those contemplated by Salbutchi and their principle of action are described in U.S. Patent Nos. 3,755,220 to Friemark et al. On August 28, 1973; United States Patent No. 3,844,880, issued October 29, 1974 to Meisel et al .; And representative patents, such as US Pat. No. 4,158,594, issued to Becker et al. On January 19, 1979.

In order to improve the flexibility, the leaf paper has been treated with cationic surfactants and non-cationic surfactants. U.S. Patent No. 4,959,125 to September 25, 1990, which discloses a method for improving its flexibility by treating thin paper with, for example, a non-cationic, preferably nonionic surfactant; And US Pat. No. 4,940,513, issued to Spencer on July 10, 1990.

It has been found that treatment with various agents such as polysiloxane materials, typically referred to as vegetable oils, animal oils or synthetic oils, in particular silicone oils, can improve the flexibility of thin paper, particularly bulky pattern dense thin paper. See, for example, U.S. Patent No. 5,059,282 to Ampulski et al. On October 22, 1991. Ampulsky's patent discloses polysiloxane compounds in a wet leafy web (preferably between about 20% and about 35%). (In% fiber consistency) is disclosed. These polysiloxane compounds impart a smooth and soft touch to the thin paper.

Although the acceptable product characteristics are usually obtained by the method described above, the characteristics of the product can be further improved. However, current and methods of making products that can be improved have several disadvantages. For example, chemicals used to reinforce thin paper webs are often added to a thin slurry of water and fibers prior to first pouring into a forming screen. This is a relatively convenient and cost effective way to introduce additives. However, other chemicals for improving the absorbency or for improving the flexibility are also commonly added to the so-called wet ends of the thin paper manufacturing process. Because of the complex nature of the individual chemicals used to characterize their key properties, they often react with each other in a counterproductive way. They not only compete with each other to be preferably retained in cellulose fibers but can also destroy the properties inherent in the fibers. For example, softeners reduce the natural tendency of the fibers to bind to other fibers, thereby reducing the strength of the resulting web. When chemical papermaking additives are introduced at the wet end, both process and product benefits are kept to a minimum.

As described above, in most conventional thin paper manufacturing methods, the web is brought into close contact with the surface of the drying drum and then the web is creped from the dryer surface. Creping typically results in a web with improved flexibility and importantly also improves the stretchability of the web. To creep properly, the web must be firmly attached to the drum surface. Many chemicals added to the wet end of the machine to improve the core properties on the surface prevent the web from adhering to the drying drum, adversely affecting the creping process and the quality of the tissue produced. The creping process works optimally when the adhesive used to bond the web to the creping surface is not disturbed by chemicals not involved in creping, such as being added to the wet end of the entire lamination process. .

The additives introduced at the wet end of the process must be retained by the cellulose fibers when the chemical is functional. This can be done conventionally by using chemicals with ionic charges, most preferably positive charges, having a attraction to the intrinsic negative charge of cellulose. Many additives that can improve the properties of the web are not charged. The introduction of these chemicals into thin fiber slurries at the wet end of the process leads to poor retention and the aforementioned interaction problems.

Another disadvantage of adding chemicals to the wet end of the process is the distribution of retained chemicals throughout the web. In many cases, it is desirable to apply the active ingredient (s) only to the surface of the web. This may be desirable, for example, in lubricity softeners. Since the consumer only touches the surface, applying it only to the surface allows for efficient use of the softener. Applied only to the surface will also not react with other materials, such as strength additives, which are best contained in the center of the sheet. The present invention overcomes all of the aforementioned disadvantages and presents the desired additional advantages.

Accordingly, it is an object of the present invention to provide an improved method of incorporating chemical papermaking additives into thin paper webs that enhance flexibility, strength, absorbency and aesthetics or a combination of these properties.

Another object of the present invention is to provide flexibility, strength, absorbency and aesthetics or a combination of these properties without disturbing the creping process or without destroying the sensitive aqueous equilibrium or by losing other advantageous means. It is to provide an improved method of incorporating an improving chemical papermaking additive into a thin paper web.

It is a further object of the present invention to provide an improved process for incorporating chemical paper additives into the thin paper web which are typically hardly retained when added to the wet end of the papermaking process.

It is another object of the present invention to provide a method of adding chemical papermaking additives to a dry web in a calender stack.

It is another object of the present invention to apply a diluted chemical papermaking additive (diluted to adjust and apply a small amount of additive) to a heated moving surface to maintain the mixture on the moving surface and also before adding it to the dry web or solvent or medium. An improved method is to evaporate the bay and then apply a mixture of additives and solvents more concentrated than the one initially applied to the moving surface to the surface of the lamination web.

It is another object of the present invention to provide an improved method of applying a chemical papermaking additive to a thin paper web by the above-described method in which the vapor pressure of the medium or solvent is higher than the vapor pressure of the additive so that only the medium is removed after it is applied to the heated moving surface. will be.

As can be seen in the following more detailed description, these and other objects are achieved using the present invention.

[Overview of invention]

The present invention includes a method for producing a flexible, strong, absorbent and aesthetically pleasing lamination paper. The method includes applying a sufficient amount of chemical papermaking additive to the dry web after providing the dry leaf paper web. More specifically, the softener application method comprises the steps of diluting the chemical papermaking additive compound with a suitable solvent to prepare a diluted papermaking additive solution; Applying the diluted papermaking additive solution to the heated moving surface, for example by spraying; And evaporating some of the solvent from the heated moving surface to produce a film containing papermaking additive. A sufficient amount of papermaking additive is then moved by contacting at least one of the outward surfaces of the dry foil paper contact with the heated moving surface such that 0.004% to about 2% of the papermaking additive is retained in the foil. By solvent is meant a fluid which completely dissolves the chemical papermaking additive, or a fluid used to emulsify the chemical papermaking additive, or a fluid used to suspend the chemical papermaking additive. The solvent may be a medium or delivery means containing chemical additives or assisting in the delivery of chemical papermaking additives. These terms are compatible and not restrictive. The solution is a fluid containing chemical papermaking additives. By solution is meant a true solution, emulsion and / or suspension. For the purposes of the present invention, all terms are compatible and non-limiting. If the solvent is water, preferably the web is dried to a moisture content below the equilibrium moisture content (at standard condition) before contacting the paper additive film, but equilibrium if most of the water evaporates from the moving surface This process can also be used for thin paper having a moisture content of.

The amount of papermaking additive retained in the thin paper is preferably from 0.01% to about 1.0% by weight of the dry fiber of the thin paper. The resulting leaf paper preferably has a basis weight of about 10 to about 80 g / m ² and a fiber density of less than about 0.6 g / cc.

As mentioned above, the papermaking additive is preferably applied to the web after drying and creping the web. The addition of the papermaking additive to the web after drying and creping is not impeded in close contact with the Yankee dryer, which would result in skip creep and / or control of the sheet. In addition, the papermaking additives applied by the method described in the present invention do not cause any disruption in the papermaking system, since they are not added to the wet end of the papermaking machine. Another advantage of the method is that the additive does not have to be independent of the lamination paper. That is, they do not need to contain a positive charge to bind to the negative charge of the cellulose papermaking fibers. Preferably, the papermaking additive is applied to the web after the hot creped web leaves the doctor blade and before it is wound onto the main drive roll.

Surprisingly, when a paper additive is diluted with a solvent and applied to a heated moving surface to evaporate the solvent, transfer the paper additive to a hot web, and then switch operation, the thin paper is significantly softened by a small amount of chemical paper additive and the strength, It has been found to exhibit absorbent and / or aesthetic benefits. An advantage of the method disclosed herein is that the amount of residual solvent transferred to the thin paper web is low enough to not degrade other product properties. In addition, the amount of papermaking additive used is sufficiently economical. In addition, leaf paper treated with small amounts of chemical softeners, such as polysiloxanes, retains a high level of wetting, an important feature of leaf paper products.

Preferred flexible additives used in the process of the present invention include amino-functional polydimethylpolysiloxanes in which less than about 10 mole% of the side chains of the polymer contain amino-functional groups. In addition to being substituted with amino-functional groups, they can be effectively substituted with carboxyl, hydroxyl, ether, polyether, aldehyde, ketone, amide, ester and thiol groups. Among these effective substituents, classes comprising amino, carboxyl and hydroxyl groups are more preferred than others; Most preferred are amino-functional groups.

Exemplary commercial polysiloxanes include the Dow 8075 and Dow 200, available from Dow Corning; And Silwet L720 and Ucarsil EPS, available from Union Carbide.

Other preferred flexible additives suitable for the present invention include nonionic surfactants selected from sorbitan esters, ethoxylated sorbitan esters, propoxylated sorbitan esters, mixed ethoxylated / propoxylated sorbitan esters, and mixtures thereof. do.

Methods of making thin paper treated with chemically flexible additives, such as polysiloxanes and / or nonionic surfactants discussed above, add an effective amount of an absorbent additive to enhance the softness of the surface of the thin paper that can be sensed by touch and / or fleece. The method may further comprise at least partially offsetting the reduction in the weeping paper wettability that may be caused by incorporating siloxane or other chemical emollients. Of course, by adding suitable absorbent additives such as surfactants, wetting can be improved without chemically flexible additives. The effective amount of the surfactant is preferably about 0.01 to about 2% by weight of the dry fiber of the foil paper; More preferably, about 0.05 to about 1.0% is retained in the thin paper. In addition, preferably the surfactant is noncationic; In order to substantially eliminate the post-production changes in the thin paper properties that may occur due to the incorporation of surfactants, the thin paper is not moved substantially in situ after the thin paper is produced. This can be accomplished, for example, by using surfactants having a melting point higher than the temperatures typically encountered during storage, transportation, distribution and use of the inventive leaf paper product embodiments, such as at least about 50 ° C.

In addition, the method for preparing the thin paper according to the present invention is to add an effective amount of strength additives such as starch-based materials to avoid the increase in lintability and / or decrease in tensile strength which may occur due to the incorporation of chemically flexible additives and absorbent additives, if present. At least partially canceling. The effective amount of the strength additive is preferably such that about 0.01 to about 2% is retained in the foil, based on the dry fiber weight of the foil.

Unless stated otherwise, percentages, ratios, and ratios herein are all based on weight.

[Brief Description of Drawings]

1 is a schematic diagram illustrating a preferred embodiment of the method of the present invention for adding chemical papermaking additives to thin paper.

The present invention is explained in more detail below.

Detailed description of the invention

Briefly, the present invention provides improved flexibility that can be sensed by touch by adding chemically flexible additives, improved strength by adding strength additives, improved absorbency by adding absorbent additives, and / or aesthetic additives such as inks, dyes and flavorings. Incorporation into dry leaf paper provides a leaf paper with improved aesthetics. These properties can be improved by applying these and other chemical papermaking additives, alone or in combination, to the dry leaf paper web. Preferably, the thin paper web is dried to a moisture content below the equilibrium moisture content before the chemical papermaking additive is applied to the web.

Surprisingly, it has been found that very small amounts of chemical additives, such as polysiloxane softeners, provide a significant thinning softening effect when applied to a dry thinning web in accordance with the present invention. Importantly, it has been found that the amount of flexible additive used to soften the foil paper is low enough to have a high wettability. Furthermore, since the thin paper web is preferably excessively dried at elevated temperatures when applying the papermaking additive, and also because the water, which is the medium, is removed from the hot moving surface, there is no need to further dry.

As used herein, high temperature lamination webs refer to lamination webs that are at elevated temperatures above room temperature. Preferably the temperature rise of a web is 43 degreeC or more, More preferably, it is 65 degreeC or more.

The moisture content of the thin leaf web is related to the temperature of the web and the relative humidity of the environment in which the web is located. As used herein, the term “overly dried leaf web” refers to a leaf paper web dried to a moisture content below the equilibrium moisture content at standard test conditions of 23 ° C. and 50% relative humidity. The equilibrium moisture content of the thin paper web, placed under standard testing at 23 ° C and 50% relative humidity, is about 7%. By using a conventional drying means such as a Yankee dryer, it can be excessively dried by raising the temperature of the thin paper web of the present invention to an elevated temperature. Preferably, the overly dried leaf web has a moisture content of less than 7%, more preferably from about 0% to about 6%, most preferably from about 0% to about 3% by weight.

The leaf paper exposed to the general environment typically has an equilibrium moisture content of 5 to 8%. The moisture content of the sheet is usually less than 3% when drying and creping the thin paper. After manufacture, the leaf paper absorbs water from the atmosphere. In the preferred method of the present invention, the leaf paper has the advantage that the moisture content of the leaf paper is low when it leaves the doctor blade. By applying the chemical papermaking additive solution to the overly dried leaf paper, the remaining water added to the leaf paper is less than normally absorbed from the atmosphere. Therefore, there is no need to further dry, and no loss of tensile strength other than that normally occurs when the leaf paper absorbs moisture from the air.

The present invention is a conventional felt-pressing leaf paper; Pattern dense laminations such as those exemplified by Sanford-Sieson and derived therefrom; And bulky, uncompressed foils, such as exemplified by Salbutch, can be used in conventional foils. The leaf paper may be homogeneous or multi-layered; The leaf paper products made from them may have a single or multiple layers of structure. The thin paper preferably has a basis weight of 10 g / m ² to about 80 g / m ² , and a density of about 0.60 g / cc or less. Preferably, the basis weight is about 35 g / m ² or less; The density is about 0.30 g / cc or less. Most preferably, the density is from 0.04 g / cc to about 0.20 g / cc.

Existing pressed leaf paper and methods for making such leaf paper are known in the art. Typically, such thin paper is produced by depositing a paper stock on a perforated forming wire. This forming wire is often referred to in the art as Fourdrinier wire. Once the raw material is deposited on the forming wires it is called a web. The web is dehydrated by pressurizing the web and drying at elevated temperature. The specific techniques and typical devices for making webs according to this process are well known to those skilled in the art. In a typical process, low consistency pulp stock is provided to the pressurized headbox. The headbox has openings for transferring thin deposits of pulp stock onto podlinear wires to form a wet web. The web is then dewatered by vacuum dewatering to a fiber consistency of about 7% to about 45% (based on the total web weight) and a pressurization process that exerts pressure on the web by opposing mechanical members, such as cylindrical rolls. Further drying. The dehydrated web is further pressurized and dried by a steam drum apparatus known in the art as a Yankee dryer. In Yankee dryers, pressure may be generated by mechanical means such as opposing cylindrical drums that press against the web. By using several Yankee dryer drums, it is possible to optionally additionally pressurize between the drums. The produced leaf paper is hereinafter referred to as conventional pressurized leaf paper. Such sheets are thought to be compressed because the web is almost entirely subjected to mechanical compression and dried in the compressed state while the fibers contain moisture.

The patterned dense leaf paper is characterized by having relatively bulky zones of relatively low fiber density and dense zones of relatively high fiber density. The bulky zone is alternatively characterized as the zone of the pillow zone. The dense zone is otherwise referred to as the Knuckle zone. The densified zones may be discontinuously located within the bulky zones or may be fully or partially connected within the bulky zones. Preferred methods for making pattern dense thin paper webs are described in US Pat. No. 3,301,746 to Sanford and Sison, on January 31, 1967; U.S. Patent No. 3,974,025 to Ayers on August 10, 1976; And US Pat. No. 4,191,609, issued to Trocan on March 4, 1980; And US Pat. No. 4,637,859 to Trocan, issued January 20, 1987: all of which are incorporated herein by reference.

Generally, pattern dense webs are preferably prepared by depositing paper stock on a perforated forming wire, such as a pod linear wire, to produce a wet web and then paralleling the web to a series of supports. Pressing the web towards a series of supports creates a dense zone in the web at a location corresponding to the point of contact between the series of supports and the wet web. The remainder of the web that is not compressed during this process is referred to as bulky zone. This bulky zone can be further inflated by applying fluid pressure, such as by using a vacuum device or a blow dryer, or by mechanically pressing the web towards a series of supports. The web is dewatered and optionally pre-dried in such a way that the bulky zone is not substantially compressed. This is preferably done by mechanical pressure of the web towards a series of supports by fluid pressure, such as using a vacuum type apparatus or a blow dryer, or otherwise without compressing a bulky area. The total number of process steps carried out can be reduced by integrating or partially integrating the dehydration, optional predrying, and the manufacturing process of the densified zones. After preparation, dehydration and optional predrying of the dense zone, the web is preferably completely dried without mechanical pressure. Preferably, about 8% to about 65% of the foil paper surface has a dense knuckle having a relative density of at least 125% relative to the density of the bulky area.

The series of supports is preferably a press-in conveying fabric with a patterned knuckle distribution. It acts as a series of supports that allow the compacted zone to be easily manufactured when under pressure. The pattern of knuckles constitutes the series of supports described above. Stamped conveying fabrics are disclosed in U.S. Patent Nos. 3,301,746 to Sanford and Sison on January 31, 1967; United States Patent No. 3,821,068 to Salbutch, Jr., et al., May 21, 1974; U.S. Patent No. 3,974,025 to Ayers on August 10, 1976; United States Patent No. 3,573,164, issued to Friedberg et al. On March 30, 1971; United States Patent No. 3,473,576 to Amnus, dated October 21, 1969; U.S. Patent No. 4,239,065 to Trocan, issued December 16, 1980; And US Pat. No. 4,528,239 to Trocan, issued July 9, 1985, all of which are incorporated herein by reference.

Preferably, the raw material is first molded into a wet web on a perforated forming medium such as a pod linear wire. The web is dewatered and transferred to a stamped fabric. Alternatively, the raw material may first be deposited on a perforated support medium that acts as a stamped fabric. After the wet web is prepared, it is dehydrated and preferably preheated by heat to a selected fiber consistency of about 40% to about 80%. Dehydration is preferably carried out using a suction box or other vacuum device or a blow dryer. The knuckle of the stamped fabric is pressed into the web as described above before the web is completely dried. One way to do this is to apply mechanical pressure. This can be done, for example, by pressing a nip roll that supports the fabric pressed against the surface of the drying drum, such as a Yankee dryer, in which case the web lies between the nip roll and the drying drum. In addition, the web is preferably formed against the pressed fabric prior to complete drying using a vacuum device, such as a suction box, or by applying fluid pressure using a blow dryer. In individual subsequent process steps or combinations thereof, fluid pressure may be applied to induce a stamp of the densified zone upon initial dewatering.

Uncompressed pattern-undensified leaf paper US Pat. No. 3,812,000 issued to Salbutch, Junior and Peter N. Yiannos on May 21, 1974, and Becker, McConnell on June 17, 1980. (US Pat. No. 4,208,459 to Albert L, Mcconnell and Richard Schutte). Generally, an additional amount of paper is produced by depositing paper stock on a perforated forming wire, such as a pod linear wire, after draining the web, and without mechanically squeezing until the web has a fiber consistency of at least 80%. The water is removed, and the web is creped to produce a laminate that is not compressed and is not pattern-dense. Water is removed from the web by vacuum dehydration or thermal drying. The resulting structure is a flexible but weak, bulky sheet of relatively uncompressed fiber. The bonding material is preferably applied to a portion of the web before creping.

Compacted pattern-dense thin paper is known in the art as conventional thin paper. Typically, papermaking materials are deposited on perforated wires, such as podliner wires, to form a wet web, drain the web, and then mechanically compress (press) it uniformly until the web has a 25-50% consistency. By removing some water and moving the web to a heat dryer, such as a Yankee dryer, and then creping the web, compressed pattern-non-dense lamination paper is produced. All water is removed from the web by vacuum, mechanical pressurization and thermal means. The resulting structure is strong and usually has a single density but very small in volume and very low in absorbency and flexibility.

Papermaking fibers used in the present invention typically include fibers derived from wood pulp. Other cellulose fibrous pulp fibers, such as cotton linters, bagasses and the like, can be used, which are also within the scope of the present invention. Synthetic fibers such as rayon, polyethylene, and polypropylene fibers can also be used with natural cellulose fibers. One exemplary polyethylene fiber that can be used is Pulpex ^™ , available from Hercules, Inc. (Walmington, Delaware).

Suitable wood pulp includes chemical pulp such as kraft, sulfite and sulfate pulp, and mechanical pulp including, for example, groundwood, thermomechanical pulp and chemically modified thermomechanical pulp. However, chemical pulp is preferred because these pulp impart an excellent flexible touch to the thin paper sheets produced. Pulp derived from deciduous trees (hereafter referred to as "hardwood") and conifers (hereafter referred to as "softwood") can be used. Also used in the present invention are fibers derived from recycled paper, which not only contain all of the fibers in this category but also contain other non-fibrous materials such as fillers and adhesives used to facilitate the initial papermaking process. Can be.

In addition to papermaking fibers, the papermaking raw materials used to make the thin paper may have other ingredients or materials that may be known in the art or later known. Preferred forms of additives depend on the particular end use of the intended leaf paper sheet. For example, high wet strength is a desirable property in products such as tissue paper, paper towels, toilet paper and other similar products. Therefore, it is desirable to add a chemical component known in the art as a "wet strength" resin to the paper stock.

Extensive research reports on the types of wet strength resins used in the paper industry can be found in TAPPI Paper Series 29 (Wet Strength in Paper and Paperboard, Technical Association of the Pulp and Paper Industry, New York, 1965). The most useful wet strength resins are usually cationic in nature. Polyamide-epichlorohydrin resins are cationic wet strength resins known to have specific applications. Suitable forms of such resins are described in US Pat. No. 3,700,623, issued October 24, 1972, and US Pat. No. 3,772,076, issued November 13, 1973, all of which are issued to Keim and are herein incorporated by reference. Cited for reference. A commercially available company of useful polyamide-epichlorohydrin resins is Hercules, Inc., Wilmington, Delaware, which is marketed under the trade name Kymeme ^™ 557H.

Polyacrylamide resins are also known to be useful as wet strength resins. These resins are described in US Pat. No. 3,556,932, issued to Coscia on January 19, 1971, and US Pat. No. 3,556,933, issued to Williams, et al., On January 19, 1971. Is incorporated herein by reference. A commercial company of polyacrylamide resins is American Cyanamid Co. of Stanford, Connecticut, which is marketed under the trade name Parez ^™ 631 NC.

Other water soluble cationic resins useful in the present invention are urea formaldehyde and melamine formaldehyde resins. More common functional groups of these multifunctional resins are groups containing nitrogen, namely amino groups and methylol groups bonded to nitrogen. Polyethylenimine type resins may also be useful in the present invention. In addition, temporary wet strength resins such as Caldas (Japan Carlit) and CoBond 100 (National Starch and Chemical Company) are used in the present invention. It may be. The addition of compounds such as the wet strength and temporary wet strength resins described above to the pulp stock is optional and is not necessary to practice the present invention.

In the process of the present invention, after the thin paper web is dried and creped, the chemical papermaking additive is preferably applied while still maintaining the elevated temperature. Adding some chemical papermaking additives to the lamination web prior to drying and creping the web may interfere with the coating on the dryer (ie, the tight coating on the Yankee dryer) and also cause skip crepe and make the sheet uncontrollable Was found. This problem is eliminated by using the method of the invention in which the chemical papermaking additive is applied to the web after the web is dried and creped. Preferably, the chemical papermaking additive is applied to the dried and creped thin paper web before the web is wound onto the main drive roll. Thus, in a preferred embodiment of the present invention, a chemical papermaking additive is applied to a hot overdried leaf paper web after creping the web, but before the web passes through the calender roll.

Chemical papermaking additives are preferably applied to hot moving surfaces as aqueous solutions, emulsions or suspensions. The chemical papermaking additive may also be applied as a solution containing a suitable non-aqueous solvent such as hexane, which may dissolve or be mixed with the chemical papermaking additive. The chemical papermaking additive can be supplied in pure form or more preferably by emulsification with a suitable surfactant emulsifier. Pure chemical papermaking additives are preferred because emulsified chemical papermaking additives are easy to apply because they must be stirred to prevent separation into water and chemical papermaking additive phases.

The chemical papermaking additives are applied to the heated moving surface in a visually uniform manner for subsequent transfer to the thin paper web, such that the entire sheet benefits from the effect of the chemical papermaking additives. After application to the heated moving surface, the solvent is preferably evaporated to leave a thin film containing the chemical papermaking additive. Thin film means a thin coating, haze or mist on a moving surface. The thin film may be microscopically continuous, discontinuous or patterned, but should be visually uniform. On a microscopic scale, chemical papermaking additives can be distributed in a uniform, non-uniform, individual, patterned, continuous or discontinuous manner. The application of chemical papermaking additives in thin paper to have a continuous distribution and a patterned distribution is all within the scope of the present invention and meets the above criteria. Similarly, chemical papermaking additives may be added to one side or both sides of the thin paper web.

Methods of visually and uniformly applying chemical papermaking additives to hot moving surfaces include spraying and gravure printing. Spraying is most preferred because it has been found to be economical and easy to precisely control the amount and distribution of chemical papermaking additives. Preferably, after the Yankee dryer and before the main drive roll, the aqueous mixture containing the emulsified chemical papermaking additive is applied from the moving surface to the dried and creped foil web.

1 illustrates a preferred method of applying chemical papermaking additives to a thin paper web. In FIG. 1, the wet lamination web 1 is on the conveying fabric 14 passing through the turning roll 2 and is moved to the Yankee dryer 5 by the action of the pressure roll 3 and the conveying fabric 14. ) Moves past the turning roll 16. The thin paper web is attached to the cylindrical surface of the Yankee dryer 5 by the adhesive applied by the sprayer 4. It is completely dried by hot air which is heated by a steam-heated Yankee dryer 5 and by means not shown and circulated through the drying hood 6. The web is then dry creped from the Yankee dryer 5 by the doctor blade 7, which is then referred to as crumpled lamination sheet 15. Upper heated moving surface and / or lower calender roll 11, referred to as upper calender roll 10, by nebulizer 8 and 9, depending on whether the chemical papermaking additive is applied to both or one side of the lamination web. An aqueous mixture containing the emulsified chemical papermaking additive compound is sprayed onto the bottom heated moving surface called). After some of the solvent has evaporated, the foil sheet 15 is in contact with the heated moving surfaces 10 and 11. The processed web is moved around the circumferential portion of the rail 12 and wound around the main drive roll 13. Suitable devices for spraying chemical papermaking additive-containing liquid onto hot moving surfaces include external mixers and V.B. Air atomizing nozzles such as 2 mm nozzles available from V.I.B Systems, Inc .; Apparatuses suitable for forcing chemical papermaking additive-containing liquids onto hot moving surfaces include rotogravure or flexographic printers.

In a sense bound by theory or not otherwise limited by the present invention, typical process conditions of the papermaking process and their effects on the process described herein are described below. The Yankee Dryer raises the temperature of the thin paper sheet and removes moisture. The steam pressure of the Yankee dryer is around 110PSI (750kPa). This pressure is sufficient to raise the temperature of the cylinder to about 173 ° C. The temperature of the foil on the cylinder rises when the water in the sheet is removed. The temperature may be higher than 120 ° C. when the sheet exits the doctor blade. The sheet moves some space up to the calendar and the rear, and loses some of this column. The temperature of the leaf paper wound on a rail is measured to be about 65 degreeC. Eventually the foil sheet is cooled to room temperature. This may take several hours to several days depending on the size of the thin paper roll. As the leaf paper cools, the leaf paper absorbs moisture from the atmosphere. As mentioned above, the moisture content of the sheet is related to the sheet temperature and the relative humidity of the environment in which the leaf paper is located. For example, the moisture content of a sheet placed at 23 ° C and 50% RH in a standard test condition is about 7%. If the moisture content of the sheet is higher than 7%, it may have a detrimental effect on the tensile strength of the thin paper. For example, if the moisture is increased to 9%, the tensile strength of the thin paper may be reduced by 15%.

One very surprising feature of chemical softeners such as polysiloxanes is that they can improve flexibility with very small amounts on the surface of the lamination paper. However, chemical softeners must be distributed very uniformly on the surface of the lamination paper in order for the consumer to feel improved flexibility. In view of the process, the method of uniformly applying a small amount of chemical softener to the thin leaf web moving at high speed was previously unsatisfactory. Belt speeds of 700 to 1000 m / min (25 to 40 miles / hour) are typical of modern high speed paper machines. Webs traveling at this speed typically have an air boundary layer on their surface. One way to apply a small amount of liquid is to use a spray system and adjust the air and / or liquid pressure. For example, the flow rate can be lowered by using high air pressure. This usually produces very small particles. It is extremely difficult to give these small particles enough moments to penetrate the moving air boundary layer on the surface of the fast moving leaf web. In addition, the surface coating becomes uneven when the particle size of the spray fluid is increased so that the particles can penetrate the air boundary layer at a low flow rate.

One commonly used method of applying a small amount of active substance is to first dilute the substance with a solvent. The spray system can then be adjusted to allow larger particle sizes to be delivered at higher flow rates. Larger particles can penetrate the air boundary layer. However, there is now a problem of removing the solvent from the thin paper. Typically, volatile organic solvents are not used in papermaking because they can cause fire hazards or environmental problems. Water may be used as the solvent of the water-soluble papermaking additive. Water can be used as a solvent or more suitably as a diluent of water-insoluble papermaking additives such as organic oils, polymers and polysiloxanes when the water-insoluble papermaking additive such as polysiloxane is first emulsified with a suitable surfactant system. Water does not have the same process hazards as organic solvents, while water may degrade the product and lose creep and / or tensile strength. Water must also be removed from the leaf paper.

One way to solve the problem associated with the use of water is to apply a diluted chemical papermaking additive during excessive drying of the leaf paper. By this method, the amount of water added to the paper by the chemical papermaking additive is usually less than the amount the paper normally absorbs from the atmosphere when the paper is cooled to room temperature. Thus, no additional drying step is necessary, and no loss of tensile strength by the addition of water is seen. However, the water solution can penetrate the entire sheet and spread it inside the sheet rather than having the active material stay on the surface of the paper where it is most effective. Moreover, this process is limited to overdried sheets, making it difficult to apply to paper during processing (off-paper process) without applying additional drying steps to the process. A further limitation of this process is the limited dilution range and application range of the chemical papermaking additive emulsion, which is defined by the emulsifying properties (ie high concentrations lead to high viscosity while low concentrations increase the amount of water sprayed onto the sheet).

The present invention solves the above-mentioned problems by first spraying a diluted water soluble chemical paper additive or emulsified non-aqueous chemical paper additive solution onto the hot moving surface and evaporating the solvent from the chemical paper additive additive solution before moving it to the dry web. did.

For illustrative purposes, a representative commercial silicone emulsifying chemical emollient is Dow Corning ^R Q2-7224 conditioning agent commercially available from Dow Corning Corporation. This material generally contains about 35% by weight amino-functional polysiloxane emulsified in water. Before the silicone aqueous emulsion is applied to the heated moving surface, it is diluted to a concentration of less than about 20% by weight with water. More preferably, the chemical papermaking additive emulsion used in the present invention is first diluted to a concentration of less than about 15% by weight with water prior to application to the moving surface.

Examples of suitable materials for heated moving surfaces include metals (eg, steel, stainless steel, and chromium), nonmetals (eg, suitable polymers, ceramics, glass), and rubber.

When spraying a diluted silicone emulsion of the type disclosed above onto a hot moving surface such as a steel calender roll, it was surprisingly found that water was not transferred to the thin paper web by the present invention. In fact, it was expected that the moisture content of the sheet would increase about 4-5% after spraying under a set of process conditions. However, it was found that the silicon content in the web increased to the expected concentration, but the water content did not increase at all. More surprisingly, attempts to increase sheet moisture by 3.5% (i.e. increase in sheet moisture from 4% to 7.5%) resulted in a moisture increase of 0.7% (i.e. only 4.7% of measured moisture content). Revealed.

Most surprising is that the roll temperature is about 80 ° C. (20 ° C. lower than the boiling point of water) and the time difference between the point of application and the point of travel is about 0.1 seconds. It was surprisingly found that over 50% of water was evaporated from the rolls under these conditions leaving a thin polysiloxane emulsion. The thickness of this thin film was calculated to be about 0.25 μ (1 μ = 10 ⁻⁶ m). The thickness of the film of the present invention is preferably less than about 10 microns, and more preferably less than about 1 microns.

In the process of the present invention, at least about 50%, more preferably at least about 80% of water is evaporated from the diluted chemical papermaking additive solution and applied to the heated moving surface, after which the surface is transferred to a dry lamination web. . Thus, a film with a calculated thickness of about 0.075 μ remains. Most preferably, at least about 95% of the water is evaporated from the solution on the heated moving surface to leave a calculated film thickness of about 0.05 μ for transferring to the foil web.

The temperature of the heated moving surface is preferably lower than the boiling point of the solvent. Thus, when the solvent is water, the temperature of the heated moving surface should be lower than 100 ° C. When water is used as the solvent, the temperature is preferably 50 to 90 ° C, more preferably 70 to 90 ° C.

Heat on the moving surface also lowers the viscosity of the chemical papermaking additive, thereby increasing the ability of the additive to spread into the thin film on the moving surface. The membrane is then transferred to the web surface by contacting the foil web with the moving surface. Surprisingly, the efficacy of the transfer of chemical papermaking additives into the web has been found to be very high. Efficacy of about 40 to 80% is typical based on the flow from the spray nozzle to the moving surface and the amount was measured on the lamination web. Moreover, this process is not limited to overly dried paper. Depending on the amount of water removed from the spray mixture by the hot moving surface, the method can also be used to deliver chemical papermaking additives to the equilibrium dry paper. However, it is desirable to apply to hot overdried webs so that any residual water in the film does not interfere with any paper properties.

A further advantage of applying the chemical papermaking additive solution to the hot overdried web is that the reduced viscosity of the solution helps to ensure that the solution is applied uniformly along the web surface (low viscosity solutions are more mobile).

[Chemical Paper Additives]

Chemical papermaking additives for use in the improved process of the present invention are preferably selected from the group consisting of strength additives, absorbent additives, flexible additives, aesthetic additives and mixtures thereof. Each of these types of additives will be described below.

A) strength additive

Strength additives are selected from the group consisting of permanent wet strength resins, temporary wet strength resins, dry strength additives, and mixtures thereof.

If permanent wet strength is desired, chemical papermaking additives can be selected from the following chemical groups:

Polyamide-epichlorohydrin, polyacrylamide, styrene-butadiene latex; Insoluble polyvinyl alcohol; Urea-formaldehyde; Polyethyleneimine, and chitosan polymers.

Polyamide-epichlorohydrin resins are cationic wet strength resins that have been found to be particularly useful. Suitable resins of this type are disclosed in US Pat. No. 3,700,623, issued October 24, 1972 and US Pat. No. 3,772,076, issued November 13, 1973, all of which are issued to Keim, Which is incorporated herein by reference. One commercially available polyamide-epichlorohydrin resin is Hercules, Inc., Wilmington, Delaware, which is marketed under the trademark Kymene ^™ 557H.

Polyacrylamide resins have also been found to be useful as wet strength resins, which have been assigned to U.S. Patent No. 3,556,932 to Cossia et al. On January 19, 1971 and to Williams, et al. On January 19, 1971. US Pat. No. 3,556,933, which is incorporated herein by reference. One commercially available polyacrylamide resin is American Cyanamide Company, Stanford, Connecticut, which is marketed under the trademark Parez ^™ 631 NC.

Water soluble cationic resins that have been found to be useful in the present invention are urea formaldehyde and melamine formaldehyde resins. More common functional groups of such multifunctional resins are nitrogen containing groups such as amino groups and methylol groups bonded to nitrogen. Polyethylenimine type resins may also be useful in the present invention.

If temporary wet strength is desired, chemical paper additives can be selected from the following chemical crowds:

Cationic dialdehyde starch base resins (e.g., Caldas manufactured by Japan Carlet or Cobond 1000 manufactured by National Starch); Dialdehyde starch; And / or resins disclosed in US Pat. No. 4,981,557, issued January 1, 1991 to Bjorkquist, which is incorporated herein by reference.

If dry strength is desired, chemical paper additives may be selected from the following chemical crowd.

Polyacrylamide (a combination of Cypro 514 and Accostrength 711, manufactured by American Cyanamide, Wayne, NJ); Starch (eg corn starch or potato starch); Polyvinyl alcohol (eg, Airvol 540 available from Air Products Inc., Allentown, PA); Guar or locust bean gum; Polyacrylate latex; And / or carboxymethyl cellulose (eg, Aqualon CMC-T, available from Aqualon Company, Wilmington, Delaware).

In general, starches suitable for carrying out the present invention are characterized by water solubility and hydrophilicity. Starch materials include, for example, corn starch and potato starch, but this is not considered to limit the range of suitable starch materials; Particular preference is given to waxy corn starch industrially known as amioca starch. Unlike conventional corn starch in that conventional corn starch contains amylopectin and amylose, amiocar starch is made entirely of amylopectin. Several unique features of Amioka starch are also described in “Amioca-The Starch From Waxy Corn”, H. H. Schopmeyer, Food Industries, December 1945, pp. 106-108 (Vol. Pp. 1476-1478). Starch may be granular or dispersed, but granular is preferred. The starch is preferably cooked sufficiently to induce swelling of the granules. More preferably, the starch granules are swelled just before the starch granules are dispersed, for example by cooking. These highly swollen starch granules are said to be "cooked sufficiently." In general, the dispersion conditions may vary depending on the size of the starch granules, the crystallinity of the granules and the amount of amylose present. Fully cooked Amioka starch can be prepared, for example, by heating an aqueous slurry of starch granules of about 4% consistency at about 190 ° F. (about 88 ° C.) for about 30 to 40 minutes. Other exemplary starch materials that can be used are modified cationic starches such as modified with nitrogen-containing groups such as amino groups and methylol groups bound to nitrogen (National Starch and Chemical Company of Bridgewater, NJ). and Chemical Campany). Until now, these modified starch materials have been used primarily as pulp material additives to increase wet and / or dry strength. However, when applied by application to overdried thin paper webs according to the present invention, they may have a reduced effect on wet strength compared to the wet end addition of denatured starch material. Unmodified starch is generally preferred given that the modified starch material is more expensive than unmodified starch. In addition to adding the wet and dry strength resin by the method disclosed in the present invention, it may be added to the pulp material. The addition of chemical compounds to the pulp material, such as the wet strength and transient wet strength resins discussed above, is optional and not critical to the practice of the present invention.

In the present invention, the strength additive is preferably applied to the transfer roll heated in the form of an aqueous solution. Application methods include the methods described above with reference to the method of applying other chemical additives, preferably spraying and less preferably printing. The strength additives may be applied alone to the thin paper web and may be applied before, or simultaneously with, the addition of the flexible, absorbent and / or aesthetic additives. It is preferred to apply a minimum effective amount of strength additive, preferably starch, to the sheet, which provides lint suppression and concomitant increase in strength when dried compared to the same sheet except not treating the binder. When calculated on the basis of dry fiber weight, it is desirable to retain from about 0.01% to about 2.0% by weight strength additives in the dried sheet, and from about 0.1% to about 1.0% strength additive material, preferably starch based material More preferably retained.

B) flexibility additives

Chemical flexible additives are selected from the group consisting of lubricants, plasticizers, cationic debonders, noncationic debonders and mixtures thereof. Preferred debonders for use in the present invention are noncationic debonders and more preferably nonionic surfactants. However, cationic surfactants can also be used. Non-cationic surfactants include anionic, nonionic, amphoteric and zwitterionic surfactants. The surfactant is preferably substantially non-movable in situ after the manufacture of the foil to substantially prevent post-production changes in the foil properties that may otherwise occur after incorporation of the surfactant. This can be achieved, for example, by using surfactants having a higher melting temperature (eg, greater than or equal to about 50 ° C.) and the thin paper product aspects of the present invention than temperatures commonly encountered during storage, transportation, and sale. In addition, the surfactant is preferably water soluble when applied to a wet web.

The amount of noncationic surfactant applied to the thin paper web to provide the aforementioned flexibility / tensile benefits is from the minimum effective amount to about 2% necessary to provide the benefits, on a constant tensile basis for the final product: preferably about 0.01% to about 2% of the noncationic surfactant is retained by the web, more preferably about 0.05% to about 1.0%, most preferably about 0.05% to about 0.3%. The surfactant preferably has an alkyl chain having 8 or more carbon atoms. For example anionic surfactants include linear alkyl sulfonates and alkylbenzene sulfonates. Nonionic surfactants include, for example, alkyneglycosides including alkylglycoside esters such as Crodesta ^™ SL-40 available from Croda Inc., New York, NY; W. March 8, 1977. K. Alkylglycoside ethers such as those disclosed in US Pat. No. 4,011,389 to WK Landon et al .; Alkylpolyethoxylated esters such as Pegosperse ^™ 200 ML available from Glyco Chemicals, Inc. of Connecticut Greenwich; Neodol sold by Shell Chemical Co 25-12 and each are alkylpolyethoxylated ethers and esters; Sorbitan esters, such as Span 60 from ICI America, Inc., ethoxylated sorbitan esters, propoxylated sorbitan esters, mixed ethoxylated / propoxylated sorbitan Polyethoxylated sorbitan alcohols such as esters and IC America, Inc., Tween 60. Alkylpolyglycosides are particularly preferred for use in the present invention. The above list of exemplary surfactants is for illustration only and is not meant to limit the scope of the invention.

Surfactants can be applied to hot moving surfaces by spraying, gravure printing or flexographic printing. Any surfactant other than chemical papermaking additives that emulsify the surfactant material is hereinafter referred to as "surfactant" and any surfactant present as an emulsifying component of the emulsified chemical papermaking additive is hereinafter referred to as "emulsifier". The surfactant may be applied to the thin paper alone or at the same time as or before or after the addition of other chemical papermaking additives. In a typical process, if another additive is present, the surfactant is applied to the excessively dried web simultaneously with the other additive (s). It may also be desirable to treat relatively small amounts of binder to debonder containing thin paper for lint inhibition and / or to increase tensile strength. The term "binder" as used herein refers to a variety of wet and dry strength additives known in the art. The binder (if used) may be applied to the lamination simultaneously with or before the addition of the debonder and the absorbent aid. Preferably, the binder is added to the overly dried leaf paper web simultaneously with the debonder (ie, the binder is included in a dilute debonder solution applied to the heated moving surface).

If you want chemical emollients that work primarily by imparting a slippery feel, you can choose from the following chemical crowd:

Organic materials (eg mineral oils or waxes such as paraffin or carnuba or lanolin); And polysiloxanes (eg, compounds disclosed in US Pat. No. 5,059,282 to Ampulski, which is incorporated herein by reference).

Surprisingly, it has been found that small amounts of polysiloxanes applied to hot, overdried leaf paper webs can provide the leaf paper with a flexible, silky flannel-like feel to the leaf paper without the aid of additional materials such as oils or lotions. Importantly, this benefit can be obtained in many aspects of the present invention with high wettability within the range desirable for toilet paper applications. Preferably, the leaf paper treated with polysiloxane according to the present invention comprises up to about 0.75% polysiloxane. An unexpected advantage of the present invention is that the thin paper treated with up to about 0.75% polysiloxane is provided with considerable flexibility and silkiness by the small amount of polysiloxane. In general, thin paper having polysiloxanes of less than about 0,75%, preferably less than about 0.5%, can provide a significant increase in flexibility, silkiness, and flannel-like features, and can provide any increase in wettability resulting from polysiloxanes. It does not require the addition of surfactants to counteract the bad impact and still remain wet enough for use as toilet paper.

The minimum amount of polysiloxane to be retained by the thin paper is at least an effective amount to impart a touch difference in softness or silky or flannel-like properties to the thin paper. The minimum effective amount may vary depending on the particular type of sheet, the method of application, and whether the particular type of polysiloxane and polysiloxane is supplemented by starch, surfactants or other additives or treatments. Without limiting the amount of applicable polysiloxane retention by the thin paper, preferably at least about 0.004%, more preferably at least about 0.01% and most preferably at least about 0.05% of the polysiloxane is retained by the thin paper. Sufficient amount of polysiloxane is evenly distributed on both sides of the foil, i.e., on the outer surface of the flat fiber, to provide a pliable feel. If polysiloxane is applied to one surface of the foil, generally a portion of the polysiloxane will at least partially penetrate into the foil. Preferably, however, the polysiloxane is applied to both sides so as to ensure the benefit of the polysiloxane on both sides of the foil paper. In addition to treating polysiloxanes with thin paper as described above, it has been found that treating the thin paper with an absorbent additive may be desirable. In addition to any surfactant material it may be present as an emulsifier for the polysiloxane. In some cases it has also been found to be desirable to treat only the surfactant material to the lamination to remove polysiloxane from the additive solution and provide wettability and / or flexibility. If it is intended for use in applications where high wettability is desired, it is preferred to treat surfactants with thin paper having about 0.3% excess polysiloxane. Most preferably, as noted above, non-cationic surfactants are applied to hot, overly dried leaf paper webs to obtain additional flexibility benefits on a constant tensile basis. The amount of surfactant required to increase the hydrophilicity to a desired degree will vary depending on the type and amount of polysiloxane and the type of surfactant. However, as a general baseline, for polysiloxane contents of about 0.75% or less, from about 0.01% to about 2% of the surfactants retained by the foil paper, preferably from about 0.05% to about 1.0% of the surfactant, including toilet paper It is believed to be sufficient to provide sufficiently high wettability for use.

If a chemical softener that acts primarily by softening the structure is desired, the softener may be selected from the following chemical crowd.

Polyethylene glycol (eg PEG 400); Dimethylamine; And / or glycerin.

If cationic chemical softeners which function primarily by debonding are desired, the softener can be selected from the following chemical crowd.

Cationic quaternary compounds (e.g., dihydrogenated tallow dimethyl ammonium methyl sulfate (DTDMAMS) or dihydrogenated tallow dimethyl ammonium chloride (DTDMAC) manufactured by Sherex Corporation of Dudlin, OH; Berocel 579, manufactured by Eka Nobel of Sund; materials disclosed in US Pat. Nos. 4,351,699 and 4,447,294 to Osborn, which are incorporated herein by reference; and / or DTDMAMS Or diester derivatives of DTDMAC).

C) Absorbent Additives

If you want an absorption aid that increases the rate of absorption, you can choose from the following chemical crowds:

Polyethoxylates (eg PEG 400); Alkyl ethoxylated esters (eg, Pegosperse 200ML, available from Lonza Inc.); Alkyl ethoxylated alcohols (eg Neodol ^R ); Alkyl polyethoxylated nonylphenols (e.g., Igepal CO from Rhone-Poulenc / GAF) and / or US Patents issued to Spendel, which is incorporated herein by reference. Materials disclosed in US Pat. Nos. 4,959,125 and 4,940,513. If the surfactant debonder softener reduces the wettability, a wetting agent, for example another surfactant, may be added to the application solution. For example, sorbitan stearate esters can be mixed with alkyl polyethoxylated alcohols to produce flexible wettable papers.

If an absorbent adjuvant that reduces the rate of absorption is desired, the adjuvant may be selected from the following chemical crowd.

Alkylketene dimers (e.g. Aquapel ^R 360XC emulsion from Hercules Incorporated, Wilmington, Delaware): Fluorocarbons (e.g., Skach Guard, available from 3M, Minneapolis, Minnesota) (Scotch Guard)).

Absorbent additives may be used alone or in combination with strength additives. Starch base strength additives have been found to be preferred binders for use in the present invention. Preferably, the thin paper is treated with an aqueous solution of starch and the sheet is excessively dried when applied as mentioned above. In addition to reducing the lintability of the final thin paper product, a small amount of starch also optimally improves the tensile strength of the thin paper without imparting the cardboard properties (i.e., stiffness) that can be caused by adding a large amount of starch. In addition, it has increased tensile strength due to the addition of thin paper, such as increased pulp tablets or other dry strength additives, with improved strength / flexibility relative to thin paper reinforced by conventional tensile strength increasing methods. Provide a sheet. This result is particularly surprising because starch has traditionally been used to increase strength at the expense of flexibility in applications where flexibility is not an important characteristic, eg cardboard. In addition, starch has been used as a filler for printing paper and printing paper to improve surface printability.

D) aesthetic additives

If an aesthetic additive is desired, the additive may be selected from the following chemical crowd ink; dyes; Fragrances: brighteners (eg TiO ₂ or calcium carbonate), fluorescent brighteners and mixtures thereof.

The aesthetic characteristics of the leaf paper can also be improved by using the methods disclosed herein. Inks, dyes and / or flavors are preferably added to the application fluid and then applied to the hot transfer roll. Such aesthetic additives may be applied alone or in combination with wetting, softening and / or strength additives.

[Method of Analysis]

Analysis of the chemical throughput herein retained in the thin paper can be performed by any method acceptable in the field of application. For example, the amount of polysiloxane retained by the leaf paper can be determined by solvent extraction of the polysiloxane with an organic solvent followed by atomic absorption spectroscopy to determine the amount of silicon in the extract; The amount of nonionic surfactant, such as alkylglycoside, can be extracted in an organic solvent and then measured by gas chromatography to determine the amount of surfactant in the extract; The amount of anionic surfactant, such as linear alkyl sulfonate, can be determined by colorimetric analysis of the extract after water extraction; The amount of starch can be measured by measuring the amount of glucose by warming the amylase with glucose, followed by colorimetric analysis. This method is exemplary and does not mean that it excludes other methods that may be useful for measuring the amount of certain components carried by the leaf paper.

The hydrophilicity of thin paper generally refers to the tendency of thin paper to wet. The hydrophilicity of a thin leaf paper can be quantified to some extent by measuring the time required for the dry leaf paper to fully wet with water. This time is called "wetting time." To provide a consistent and repeatable test for wetting time, the following process can be used to measure wetting time: first, about 4-3 / 8 inches × 4-3 / 4 inches (about 11.1 cm ×) of the thin paper structure. 12 cm) (with environmental conditions for testing paper samples being 23 ± 1 ° C. and 50 ± 2% RH as listed in TAPPI Method T 402); Secondly, fold the sheets in quarters side by side. It is then decorated with a ball of about 0.75 inches (about 1.9 cm) to about 1 inch (about 2.5 cm) in diameter. Thirdly, the ball-shaped sheet is placed on the sieve surface of distilled water at 23 ± 1 ° C. and a timer is operated simultaneously; Fourth, stop and read the timer when the ball sheet is finished wet. Complete wetting is observed by eye.

The preferred hydrophilicity of the thin paper varies depending on the end use of the thin paper. In order to prevent clogging when squirting water in the toilet, it is desirable that the lamination paper used in various applications, for example, toilet paper, be completely wet in a relatively short time. Preferably the wet time is 2 minutes or less. More preferably, the wet time is 30 seconds or less. Most preferably the wetting time is 10 seconds or less.

The hydrophilic properties of the thin leaf aspect of the present invention can of course be measured immediately after preparation. However, a significant increase in hydrophobicity can occur during the first two weeks after the manufacture of the leaf paper (ie, after making the leaf paper and aged for two weeks). Therefore, the above-mentioned wet time is preferably measured at the end of the two-week period. Thus, the wet time measured at the end of the maturation time of 2 weeks at room temperature is referred to as “2 weeks wet time”.

As used herein, the term "density of thin paper" is the average density calculated by dividing the basis weight of the thin paper by the thickness, and appropriate unit conversion is included herein. The thickness of the thin paper as used herein is the thickness of the paper when applied to a compressive load of 95 g / in ² (15.5 g / cm ² ).

Example I

The purpose of this example is to illustrate one method that can be used to produce a flexible lamination sheet treated with a flexible additive according to the present invention.

A pilot scale pod linear paper machine is used in practicing the present invention. The paper machine has a stacked headbox having an upper chamber, a central chamber and a base chamber. As shown in the examples below, the processes described below also apply to later examples as the case may be. In simple terms, the fibrous slurry, consisting primarily of short papermaking fibers, is pumped through the upper and base headbox chambers, and at the same time another fibrous slurry, consisting mainly of long papermaking fibers, is pumped through the central headbox chamber and placed on the podlinear wire In a stacked relationship to form a three-layer initial web thereon. The first slurry has a fiber consistency of about 0.11% and its fiber content is Eucalyptus Hardwood Kraft. The second slurry has a fiber consistency of about 0.15% and its fiber content is Northern Softwood Kraft. Dehydration takes place through the podlinear wire, and the deflector and vacuum box are auxiliary devices. The podlinear wire has 87 machine-direction single yarns and 76 transverse machine-direction single yarns per inch, and has a 5-ply, satin-like shape. When the initial wet web is about 22% fiber consistency in travel, it is moved from the podlinear wire to a conveying fabric having 35 machine direction single yarns and 33 transverse machine direction single yarns per inch and 5 ply satin weave. The web is placed on a conveying fabric through a vacuum dehydration box through a blower predryer and then transferred onto a Yankee dryer. The fiber consistency is about 27% after passing through the vacuum dehydration box, about 65% by the action of the predryer before moving to the Yankee dry gas phase, and spraying the creping adhesive comprising 0.25% aqueous solution of polyvinyl alcohol by the applicator Apply; Fiber consistency increases to about 99% prior to dry creping the web with the doctor blade. The doctor blade has a tilt angle of about 24 ° and is positioned relative to the Yankee dryer to provide an impact angle of about 83 °; The Yankee dryer is operated at about 350 ° F. (177 ° C.); The air dryer operates at about 800 fpm (feet / minute) (about 244 meters / minute). The chemical softener emulsion, which is further described later, is sprayed onto the heated calender rolls using a 2 mm spray nozzle. The web is then passed between two heated calender rolls. The two calender rolls are inclined together according to the roll weights and operate at a surface speed of 660 fpm (about 201 meters / minute).

Spray solution is Neodol 25-12 shell chemical is prepared by dilution to 5% by weight with water. The surfactant solution is then sprayed onto a heated steel calender roll. The capacity flow rate of the aqueous solution through the nozzle is about 2 gal / hour-cross section (ft) (about 25 liters / hour-meter).

At least about 95% of the water is evaporated from the calender rolls leaving a calculated chemical softener film thickness of less than 0.07 μ. A dry web having a moisture content of about 1% is contacted with a hot calender roll. The chemical softener compound 뭍 is transferred to the drying web by direct pressure transfer. The migration efficacy of the chemical softeners applied to the web is generally about 45%.

The resulting leaf paper has a basis weight of 30 g / m ² , a density of 0.10 g / cc, contains 0.17% by weight of alkylpolyethoxylated alcohol compound, and has an unbalanced initial moisture content of 1.2%. Importantly, the resulting leaf paper has improved feel compared to the untreated control.

Example II

The purpose of this example is to illustrate one method that can be used to make flexible foil paper sheets treated with softening additives and starch.

A three-layer lamination sheet was prepared according to the method described above in Example I. Crodesta ^TM SL-40 (alkyl glycoside polyester nonionic surfactant commercially available from Crodesta Inc.) and thinly cooked ami prepared as disclosed in the thin paper web Process with orca starch. The surfactant and starch are simultaneously applied onto a heated transfer roll as part of the aqueous solution sprayed through the paper machine spray nozzle. The concentration of the Crodesta ^™ SL-40 nonionic surfactant in the aqueous solution is adjusted so that the amount of surfactant retained is about 0.15% based on the weight of the dry fibers. Similarly, the starch concentration in the aqueous solution is adjusted such that the retained amioka starch concentration is about 0.2% by dry fiber weight.

The treatment mixture is sprayed onto the top and bottom of the heated transfer roll. Water is evaporated off the roll and the active surfactant and binder are transferred to both sides of the lamination web. The capacity flow rate sprayed on the roll heated through the upper and lower spray nozzles is about 1 gal / hr cross-sectional ft. The combined flow rate through both nozzles is 2 gal / hr cross section ft.

The resulting leaf paper has a basis weight of 30 g / m ² , a density of 0.10 g / cc, contains 0.15% by weight of Crodesta ^™ SL-40 nonionic surfactant and 0.2% by weight of cooked amioca starch. Laminated paper has increased tactile flexibility and has higher wetting and lower lint tendency than untreated paper.

Example III

The object of this example illustrates one method that can be used to produce a flexible leaf paper sheet for treating the leaf paper and processing it into a two-ply product according to the present invention.

Two-layered paper sheets were prepared according to the method described above in Example I, with the following exceptions. The capacity flow rate through the nozzle is about 1.05 gal / hour-cross sectional feet (about 13.3 liters / hour-meter). The film thickness was calculated to be about 0.035 μ after 95% of the moisture had evaporated. The resulting single ply leaf paper has a basis weight of 16 g / m ² .

After papermaking, two sheets of treated lamination are combined with the treated surface facing out.

The resulting two-ply thin paper product has a basis weight of 32 g / m ² , a density of 0.10 g / cc and contains 0.17% by weight of alkylpolyethoxylated alcohol.

Importantly, the resulting leaf paper has increased hand softness.

Example IV

The purpose of this example is to illustrate one method that can be used to produce flexible foil paper sheets treated with foil paper with softener additives and absorbent enhancer mixed surfactant systems. A three-layer paper sheet is prepared according to the method described in Example I. Softener water dispersion was added to GLYCOMUL-S-Suji (Lonza, Inc., mixed sorbitan stearate ester surfactant) 11.9%, neodol 23-6.5T (ethoxylated Cl ₁₂ -C ₁₃ linear alcohol dispersing surfactant and wetting agent manufactured by Shell Chemical Company) 3.2%, Dow 65 additive (silicone polymer defoaming agent manufactured by Dow Corning Corporation) 0.8% and distilled water 84.1% Prepared from.

The treatment mixture is sprayed onto a low heated calender (moving) roll. Water is evaporated from the rolls and the active softener and the absorbent enhancer are transferred to one side of the foil. The flow rate through the spray nozzle is adjusted to ensure that about 0.6% of the softener (glyco water-sea seed) is retained by the sheet. The resulting leaf paper has a basis weight of 30 g / m ² , a density of 0.10 g / cc and contains about 0.6% by weight glyco-S-sea seed surfactant.

Importantly, the resulting thin paper has increased hand softness and high wettability.

Example V

It is an object of the present invention to illustrate one method that can be used to produce a flexible foil paper sheet that is treated with a biodegradable quaternized amine-ester softening compound. Three-layer paper sheets are prepared according to the method described above in Example I. The softener 1% aqueous dispersion was subjected to diester dihydrogenated tallow dimethyl ammonium chloride (DEDTDMAC) (i.e., ADOGEN DDMC from Sherex Chemical Company) and polyethylene glycol wetting agent (i.e., PEG from Union Carbide Company). -400). This solution is prepared according to the following procedure: 1. Weigh DEDTDMAC and PEG-400 at equal molar concentrations; 2. Heat PEG to a temperature below about 180 ° F .; 3. Dissolve DEDTDMAC in PEG to prepare a molten solution; 4. Shear stress is applied to produce a homogeneous mixture of DEDTDMAC in PEG; 5, adjust the pH of the dilution water to about 3 by adding hydrochloric acid, 6. Heat the dilution water to about 180 ° F .; 7. Dilute the melt mixture of DEDTDMAC / PEG 400 with 1% solution; 8. Apply shear stress to prepare an aqueous solution containing bubble suspension of the DEDTDMAC / PEG-400 mixture.

The treatment mixture is sprayed onto a bottom heated calender roll. Water is evaporated from the rolls and the active softening compound and absorbent are transferred to one side of the foil web. The flow rate through the spray nozzle is adjusted so that about 0.05% of softener (DEDTDMAC) is retained by the sheet. The resulting leaf paper has a basis weight of 30 g / m ² , a density of 0.10 g / cc and contains about 0.05% by weight of DEDTDMAC softener.

Importantly, the resulting thin paper has increased hand softness and high wettability.

Claims (14)

a) providing a dry lamination web; b) diluting the chemical papermaking additive with a suitable solvent to form a diluted chemical solution; c) applying the diluted chemical solution to a heated moving surface; d) evaporating at least a portion of the solvent from the heated moving surface to form the chemical papermaking additive containing film; And e) contacting at least one outwardly facing surface of the foil paper web with the heated moving surface such that 0.004% to 2.0% by weight of the chemical papermaking additive is based on the dry fiber weight of the foil paper web. Drying the chemical papermaking additive from the heated moving surface to at least one outward surface of the lamination web by moving a sufficient amount of the chemical papermaking additive to be retained by the web. How to apply to the lamination web. The method of claim 1 wherein the solvent of step (b) is water. The method of claim 1 or 2, wherein the chemical papermaking additive is selected from strength additives, absorbent additives, flexible additives, aesthetic additives, and mixtures thereof. 4. The method of claim 3, wherein the flexible additive is selected from lubricants, plasticizers, cationic debonders, noncationic debonders, and mixtures thereof. The method of claim 4, wherein the lubricant is polysiloxane. The method of claim 4, wherein the noncationic debonder is selected from sorbitan esters, ethoxylated sorbitan esters, propoxylated sorbitan esters, mixed ethoxylated / propoxylated sorbitan esters, and mixtures thereof. 4. The method of claim 3 wherein said strength additive is selected from permanent wet strength resins, temporary wet strength resins, dry strength additives, and mixtures thereof. 4. A process according to claim 3, wherein said absorbent additive is selected from polyethoxylates, alkylethoxylated esters, alkylethoxylated alcohols, alkylpolyethoxylated nonylphenols and mixtures thereof, preferably alkyl ethoxylated alcohols. . The method of claim 4, wherein a sufficient amount of absorbent additive is applied to the web such that 0.01% to 2.0% by weight of the absorbent additive, based on the dry fiber weight of the foil paper, is retained by the web. The method further comprises a step. 10. The process according to claim 9, wherein the absorbent additive is a nonionic surfactant, preferably an alkylethoxylated alcohol having a melting point of at least 50 ° C. 7. A sufficient amount of strength additive is applied to the web according to any one of claims 4 to 6, based on the dry fiber weight of the foil paper, so that 0.01% to 2.0% by weight of the strength additive is retained by the web. Further comprising the step of: The method of claim 1, wherein the heated moving surface is a calender roll. 8. The method of claim 7, wherein the permanent wet strength resin is a polyamide-epichlorohydrin resin, a polyacrylamide resin, and mixtures thereof. 8. The method of claim 7, wherein the temporary wet strength resin is a starch based temporary wet strength resin.