MXPA01006783A - Process for improving cellulosic material - Google Patents

Abstract

The wet strength softness absorbency, absorbency rate and other valuable properties in paper products, tissues, wipes, towels, etc. can be improved by using, in the paper forming process, a cellulosic material comprising a carboxymethyl cellulose material associated with a monomeric or polymeric cationic additive material. A process of the invention comprises a fiber surface carboxymethylation and an aqueous medium followed by blending the modified fibers with a cationic additive under varying conditions and wet forming the tissue and towel products. The additive is typically a cationic additive that preferentially associates with a carboxymethyl group on the cellulose surface. The affinity between the positively charged cationic groups in the polymeric or monomeric additive material to the negatively charged carboxyl group in the carboxymethyl cellulose modified fiber improves various attributes of the paper products.

Description

i PROCESS TO IMPROVE CELLULOSE MATERIAL Field of the invention The invention relates to chemically modified cellulosic materials which may have improved properties such as moisture resistance, softness, absorbency, absorbency rate and others. The invention relates to a chemically modified cellulosic product and to a process for improving the cellulosic material.

BACKGROUND OF THE INVENTION Wet laid cellulosic fibers that are not treated prior to sheet formation typically have substantially unacceptable properties for use in towels, wipes and tissue. Important properties include moisture resistance, softness, absorbency, absorbency rate, and so on. In other words, the moisture resistance of the material can be such that, when submerged in water, the paper can lose a large part of its tensile strength in both dimensions of the sheet, it can become a non-stable pulpy mass , may not have soft tissue as the term is understood, may have very little absorbency or may have a very low absorbency rate until saturation is reached. Such sheet-like materials may have little or no appeal to consumers in the market due to the substantial lack of utility in many operations in which the moisture resistance and absorbency of the tissue paper or cleaning cloth is of critical importance.

The use of additives to improve the properties of wet laid leaves is well known. Such additives include sizing agents, dry strength additives, wet strength additives, surface treatments, coatings, and all are well known. Such materials include resin-based sizing materials, cellulose reactive sizing materials, wax emulsions, fluorochemicals and others. Dry strength additives are typically polymeric materials that include such compositions as polyacrylamides, vegetable gums, starches and others. Wet strength additives are commonly understood as formaldehyde urea resins, formaldehyde melanin resins, polyamide epichlorohydrin amino resins, polymeric amine epichlorohydrin resins, modified aldehyde resins and others. Surface treatments of cellulosic fabrics typically include pigments, resin coatings and lamination sheets.

One type of improved moisture resistance material is a carboxymethyl cellulose polymer. Such materials are used as aggregate additives applied directly to a typical cellulose sheet. Carboxymethyl cellulose is often used as a type of polymer of type one such as a polyalkylene polyamine or a polyamide amine which can be post reagent with epichlorohydrin to produce a useful additive material. The application of sodium carboxymethyl cellulose with other cationic additives to a cellulose sheet is a useful strategy of moisture resistance additive that has some measure of success. Such processes are described in U.S. Patent No. 5,525,664 issued to Miller et al., And U.S. Patent No. 5,316,623 issued to Espy. In addition, US Pat. No. 3,103,462 issued to Griggs et al. Teaches a partially acylated cellulose fiber which is followed by the use of a cationic thermosetting resin. U.S. Patent No. 4,248,595 issued to Lask et al. Teaches a crosslinked fiber. The cellulose is converted using a carboxyalkylated etherifying agent and then reacted with a crosslinking agent in an aqueous medium. The patent of the United States of America No. 3,657, 066 awarded to Chene et al., Teaches a carboxylated cellulosic material with resistance to moisture. In the patent granted to Chene et al., The underlying cellulosic fiber is oxidized to produce carboxyl groups which are then crosslinked with a formaldehyde resin of melanin. These references are mainly directed to crosslinked materials having covalently bonded crosslinked agents that directly bind a cellulosic fiber half to a second cellulosic fiber half through substantially increasing the molecular weight of the resulting material. This is also an accepted regimen to improve the properties of cellulosic materials. While this is a useful process, the cost and properties of the resulting product can be a problem in the market.

For the purpose of this patent application, the term "carboxymethyl cellulose material" indicates a cellulosic fiber that has been modified with a chemical reagent to introduce carboxymethyl ether groups directly linked to a hydroxyl site which introduces a carboxymethyl ether. carboxyl terminal group in the cellulose moiety. For the purpose of this patent application, a cationic additive material, whether a small polymeric or monomeric molecule, is a positively charged nitrogen containing additive material that is ionically associated with the carboxymethyl cellulose groups in the paper product. The materials described in this application and the products of the application process are not covalently crosslinked in molecular weight cellulosic materials. The association of the carboxymethyl groups ionically with the cationic additive materials improves the physical properties of the materials without the covalent binding.

Brief Description of the Drawings Figures 1 to 4 show that wet triethylamine, moisture resistance, dry triethylamine and dry strength of a sheet material are all improved by the processes of the compositions of the invention.

Detailed description of the invention A conventionally pressed tissue paper and similar wet laid cellulosic sheets and methods for making such sheets are used in the compositions of the invention. Such sheets of paper are typically made by depositing a supply for making paper in a foraminous forming wire. The forming wire is often referred to in the art as a fourdrinier wire. Once the supply is deposited in the forming wire, it is referred to as a fabric. The tissue is dehydrated by pressing the tissue and drying the tissue at elevated temperatures. The particular techniques and typical equipment for making such fabrics are, according to the processes described, well known to those of skill in the art. In a typical process, a supply of low consistency pulp is provided in a pressurized headbox. The head box has an opening for supplying a thin deposit of a supply of pulp in a fourdrinier wire to form a wet tissue. The fabric is then typically dehydrated at a fiber consistency of between about 7% and about 25% (basis weight of total fabric) by vacuum dewatering and further drying by pressing operations wherein the fabric is subjected to the pressure developed by opposing mechanical members, for example, felts or cylindrical rolls. The dehydrated fabric is then further pressed and dried in a current drum apparatus known in the art as a Yankee dryer. The pressure can be developed in the Yankee dryer by mechanical means such as an opposing cylindrical drum that presses against the tissue. Multiple Yankee drying drums can be employed, which additional pressing is optionally incurred between the drums. The sheet structures which are formed are conventionally referred to as pressed paper or sheet structures. Such sheets are considered as being compact since the fabric is subjected to the substantial and mechanical compressive forces while the fibers are wetted and then dried while compressed.

The products and products of the inventive processes of the invention are typically made from a pulp that is prereacted with a carboxymethyl forming reagent prior to the sheet forming processes.

Carboxymethyl cellulose physically prepared in an alkali metal form using potassium or sodium cations is anionic (due to the introduction of carboxyl groups in the fiber), hydrophilic, sometimes water soluble cellulosic ether. A very range Broad substitution of carboxyl groups in cellulose can be achieved. The most widely used types are in the range of about 0.1 to about 0.5 SD where the solubility to water is achieved while the DS approaches 0.6. Useful insoluble fibers typically have a DS less than 0.6. The low molecular weight also tends to increase the solubility. The common method for making carboxymethyl cellulose is the reaction of sodium chloroacetate with an alkali cellulose complex. Such complexes are typically represented as R cell 0H: NaOH. The chlorine moiety of sodium chloroacetate typically reacts with a hydroxyl group on the alkali cellulose complex to form an ether group which replaces the carboxylmethyl group of the hydroxyl group originally on a cellulosic substrate. Carboxymethyl cellulose is a typically used cellulosic ether material and has a wide variety of applications. More commonly, the hydroxymethyl cellulose is used as a solution or a dispersant of maal in aqueous solutions. Applications include food, pharmaceuticals, cosmetics, additive coatings, training, etc. for paper products, such as adhesives, in ceramics, deents and textiles. Similar processes can be used to form carboxyalkyl celluloses, however, these reagents are less reactive and of limited value.

Therefore, cationic materials suitable for the practice of this invention can be selected from the group consisting of common cationic fabric softening agents, such as certain substantive quaternary ammonium fiber compounds; common moisture resistant additives, such as formaldehyde resins of melanin and urea formaldehyde; the reaction products of aminopolyamide with epichlorohydrin, such as the commercially available resin, Kymene, from Hercules, Inc., and the cationic materials obtained by the reaction of polyalkylene polyamines with polysaccharides, such as starch, Irish moss extract, gum, tragacanth, dextrin, Veegum, carboxymethyl cellulose, locust grain gum, Shiraz gum, Zanzibar gum, Karaya gum, agar agar, guar gum, psyllium seed extract , gum arabic, acacia gum, Senegal gum, algin, British gum, flax seed extract, ghatti, Icelandic moss extract and quince seed extract. These and other appropriate fiber substantive additives are described in the following patents of the United States of America, which are incorporated herein by reference: US Pat. Nos. 3,409,500 (November 5, 1968) and 3,448,005 (US Pat. June 3, 1969); 2,926,116 (February 23, 1960); 3,520,774 (July 14, 1970); 3,469,569 (March 14, 1972); and 3,686,025 (August 11, 1972). Among the most preferred cationic materials are Parez-630 NC, a modified polyacrylamide obtained from American Cyanamid, Kymene, formaldehyde resins of melamine and formaldehyde of urea, quaternary ammonium compounds such as ammonium chloride of bis (dimethyl) quaternary octadecyl. The present invention may contain about 0.01% about 2.0%, more preferably from about 0.03% to about 0.5% by weight, on a basis weight of dry fiber, of a quaternary ammonium compound having the formula: In the structure noted above Rlf R2, R3 and R4 is an aliphatic hydrocarbon radical selected from the group consisting of alkyl having from about 1 to about 18 carbon atoms, coconut and tallow. X is a compatible anion, such as a halide (for example, chloride or bromide) or a methyl sulfate. Preferably, X is a methylsulfate. As used above, "coco" refers to the alkylene and alkyl halves derived from coconut oil. The recognized that coconut oil is a mixture that occurs naturally that has, like all materials that occur naturally, a range of compositions. Coconut oil contains mainly fatty acids (of which the alkyl and alkylene moieties of the quaternary ammonium salts are derivatives) having from 12 to 16 carbon atoms, although fatty acids having fewer or more carbon atoms are carbon are also present. Mr. Swern, Ed in Industrial Oil and Bailey's Fat Products, third edition, John ile and Sons (New York 1964) in Table 6.5 suggests that coconut oil typically has from about 65 to 82% by weight of its fatty acids in the range of 12 to 16 carbon atoms with about 8% of the total fatty acid content that is present as unsaturated molecules. The main one of the unsaturated fatty oil in coconut oil is oleic acid. Blends of "coconut" that occur naturally as well as synthetic fall within the scope of this invention.

Sebum, as is the coconut, is the naturally occurring material that has a variable composition. The board 6. 13 in the previously identified reference edited by Swern indicates that typically 78% or more of the tallow fatty acids contain 16 or 18 carbon atoms. Typically, half of the fatty acids present in sebum are unsaturated, mainly in the form of oleic acid. Natural "talums" as well as synthetic ones fall within the scope of the present invention. Preferably, each R1 is C16-C18 alkyl, more preferably each R1 is a straight C18 alkyl chain. Examples of quaternary ammonium compounds suitable for use in the present invention include the well-known dialkyl dimethyl ammonium salts such as ditallowdimethylammonium chloride, ditallowdimethylammonium methyl sulfate.; di (hydrogenated tallow) dimethylammonium chloride; with di (hydrogenated tallow) methylsulfate dimethylammonium is preferred. This particular material is commercially available from Sherex Chemical Company Inc. of Dublin, Ohio under the brand name "Varisoft® 137".

Optional ingredients Other chemicals commonly used to make paper can be added to the paper supply provided they do not significantly or adversely affect the softness, absorbency, and moisture resistance actions of the three chemicals required. For example, surfactants can be used to treat the tissues of tissue paper of the present invention. The level of surfactant, if used, is preferably from about 0.01% to about 2.0 percent by weight, based on the weight of dry fiber for the tissue paper. The surfactants preferably have alkyl chains with eight or more carbon atoms. Exemplary anionic surfactants are linear alkyl sulfonates, and alkylbenzene sulfonates to exemplary nonionic surfactants are alkyl glycosides including alkyl glycoside esters such as Crodesta ™ SL-40 which is available from Croda, Inc. (New York, New York); the alkylglycoside esters as described in U.S. Patent No. 4,011,389 issued to .K. Langdon et al. On March 8, 1977; and alkylpolyethoxylated esters such as Pegosperse ™ 200 ML available from Glyco Chemicals, Inc. (Greenwich, CT) and IGEPAL RC-520 available from Rhone Poulenc Corporation (Caranbury, N.J.). Other types of chemicals which can be added include dry strength additives to increase the tensile strength of tissue tissues. Examples of dry strength additives include carboxymethyl ama cellulose and cationic polymers of the ACCO chemical family such as ACCO 771 and ACCO 514, with carboxymethyl cellulose being preferred. This material is commercially available from the Hercules Company of Wilmington, Delaware under the brand name HERCULES® CMC. The level of near strength additive, if used, is preferably from about 0.01% to about 1.0%, by weight, based on the dry fiber weight of the tissue paper.

The novel leaf products of the invention are prepared by a process of mixing sufficient cellulose pulp in water to form a typical supply. Sufficient sodium chloroacetate is added to the supply to produce a carboxymethyl cellulose having a ds of about 0.01 about 6. High molecular weight fibers are preferred resulting in substantially modified insoluble cellulose. While some soluble materials may be inherently formed, most cellulosic feed to the process is typically modified but remains insoluble. Prior to the reaction between the fiber and the sodium chloroacetate, a modified cellulose of sodium hydroxide is prepared by mixing the cellulose with an appropriate amount of sodium hydroxide in a mixer capable of intimately contacting the sodium hydroxide with the reduced fiber. Once the sodium hydroxide is fully incorporated into the caustic modified fiber, the mixture is heated to a higher temperature than the environment, but typically not higher than about 100 ° C and the heated material reactivated with a chloroacetate solution. Sodium added in sufficient quantity to result in a ds of about 0.01 to about 6. Cellulose and reacted with the chloroacetate solution for a sufficient period of time to produce the fiber modification typically less than 16 hours. The modified surface fibers are then washed with water and diluted in acetic acid until the resulting pH of the effluent is about 6 about 7.5. The carboxyl content of the fiber can then be determined to ensure that the fiber remains in the soluble sheet forming material. The modified fibers can then be mixed with mixtures or cationic additive of cationic additives depending on the purpose of the preparation. The cationic additives can be a resin of moisture resistance of, a separating agent, a softening agent, a dehydrating agent, a sizing agent, or any other additive that can provide a property or attribute to the subsequently formed sheet. Such materials can be vigorously used as a tissue or a towel or a cleaning cloth. We have found that modified fiber as described when compared to untreated fibers, dry strength, moisture resistance, dry triethylamine and wet triethylamine hand sheets are significantly improved using the ionically associated additive of carboxymethyl cellulose materials. The level of aggregate, from about 0.5 to about 5% by weight, improvement in drying resistance, moisture resistance and wet triethylamine has been observed from hand sheets made from carboxymethyl-assisted cellulosic fibers with a carboxyl content of about 1 about 20 milliequivalents per 100 grams of fiber, commonly the carboxyl content ranges from about 5 to about 15 milliequivalents per 100 grams of fiber. The aggregate of cationic material is typically used in about a stoichiometric amount of cationic charge in the cationic additive to the anionic charge of the carboxyl group in the modified cellulosic material. Less than that amount of cationic material produces less than optimal results while substantially large amounts do not provide improvement.

The preferred products made with the sheet forming method of the application relate to the manufacture of towel and tissue. Tissues and towels can have a single layer or multiple layers of material. In the multiple layers, the layers may comprise the product or formed sheet of the invention or conventional sheets in combination with the modified sheets made in accordance with the processes of the invention. Such tissue may be flat, embossed, creped or otherwise modified to improve the physical profile of the surface of the paper product.

Example 1 A source of wood pulp made contact with service water for a sufficient period of time to saturate the pulp with water and soften the pulp. After balancing, the excess water was expelled from the pulp. The pulp was in the range of about 20 to 50% by weight of pulp in an aqueous pulp product. The wet fiber was mixed with an appropriate amount of sodium hydroxide in a sigma batter mixer for 20 to 60 minutes at room temperature to form a modified sodium hydroxide pulp material. For a calculated amount of sodium chloroacetate solution to produce a substitution of about 0.01 to about 6 was added to the caustic modified pulp. The resulting mixture was mixed until uniform and heated to a temperature of between 40 to 100 ° F for between 5 to 16 hours depending on the concentration of sodium chloroacetate. After the reaction was complete, the modified carboxymethylated surface of wood fiber was washed and then with dilute acetic acid to yield the pH to be approximately neutral, a pH of from 6 to 7.5. The carboxyl content of the fiber was determined and the fiber was found to be a substantially insoluble carboxymethyl cellulosic material. The modified carboxymethyl cellulose fibers were then washed with at least one cationic additive or a mixture of cationic additives and then introduced into a common method for making towel or sheet forming tissue.

Detailed Description of the Drawings Figures 1 to 4 show that wet triethylamine, moisture resistance, near triethylamine and dry strength of a sheet material are all improved by the processes of the compositions of the invention.

Claims (14)

R E I V I N D I C A C I O N S

1. A process to improve the performance of the leaf of a product made of a cellulose fabric placed in wet, said process comprises: a) chemically attaching anionic groups through etherification to the surface of the cellulose tissue fiber resulting in an anionic modified sheet forming fiber; Y b) adding one or more cationic additives, prior to wet formation, to the anionic fiber to form an ionic association between the cationic additive and the anionic fiber; Y c) forming a wet laid sheet; wherein the ionic interactions between the anionic and cationic groups are increased.

2. The process as claimed in clause 1 characterized in that the anionic groups comprise carboxymethyl groups.

3. The process as claimed in clause 2 characterized in that the carboxymethyl groups are added through an alkaline treatment comprising sodium chloroacetate.

4. The process as claimed in clause 1 characterized in that the cationic additive is selected from the group consisting of a wet strength resin, a binder such as a softening agent, a drain aid and a sizing agent.

5. The process as claimed in clause 1 characterized in that the cationic additive is selected from the group consisting of urea-formaldehyde resin and acylated chitin.

6. A process to improve the functioning of cellulosic tissues, said process comprises the steps of: a) subject the smoked cellulose fibers to an alkaline treatment; b) adding surface carboxymethyl groups to the cellulosic fibers; c) washing the fibers to achieve a pH of about 6 to 8; d) mixing with one or more cationic additives; Y e) form a sheet placed wet.

7. The process as claimed in clause 6 characterized in that the alkaline treatment comprises a sodium hydroxide solution.

8. The process as claimed in clause 6 characterized in that the surface carboxymethyl groups are added through heating with sodium chloroacetate.

9. The process as claimed in clause 6 characterized in that the step of washing fibers comprises dilute aqueous acetic acid.

10. The process as claimed in clause 6 characterized in that the cationic additive is selected from the group consisting of wet strength resin, a binder, a softening agent, a drain aid and a sizing agent.

11. The process as claimed in clause 6 characterized in that the cationic additive is selected from the group consisting of urea-formaldehyde resin and acylated chitin.

12. A process to improve the functioning of cellulosic tissues, said process comprises the steps of: a) subjecting the smoked cellulose fibers to an alkalinity treatment comprising the aqueous sodium hydroxide; b) adding surface carboxymethyl groups to the cellulosic fibers by treatment with sodium chloroacetate. c) washing the fibers with dilute aqueous acetic acid to achieve a pH value of about 6 to 7.5; d) mixing with one or more cationic additives.

13. The process as claimed in clause 12 characterized in that the cationic additive is selected from the group consisting of a wet strength resin, a binder such as a softening agent, a drain aid and a sizing agent.

14. The process as claimed in clause 12 characterized in that the cationic additive is selected from the group consisting of urea-formaldehyde resin and acylated chitin.