US 2944931 A
Description (OCR text may contain errors)
g [2,944,931 SANITARY PAPER AND rnocnss oFMc THE'SAME hristenH.-'C. Yang, 'Camas, Wash assignor to Crown Zellerbach Corporation, San Francisco, Calif., a corporation of Nevada No Drawing. Filed .Dec. 13, 1957,-Ser. No. 707,450
Claims. 01. 162-179) posable sanitary purposes. These papers are absorbent, bulky and have a rough finish. They include such grades as facial tissue, toilet tissue, paper napkins, towelsa'nd the like. 7
Many attempts have been made in the past to improve softness and surface feel of such papers in order to satisfy use requirements. Such attempts include mechanical treatments of paper, such as embossing, calendering, etc., as well as incorporation into the paper of a variety of chemical agents, usually referred to as softeners, plasticizers or humectants by means of impregnation or saturation of paper. Examples of such agents are glycerine, sorbital, urea,-invert sugars and the like. These materials have the :ability of absorbing and holding water. Since water alone is a good lubricant or plasticizer of cellulosic Y fibers, papers containing such humectants are characterized by being able to hold moisture therein at low relative humidities and in this way they keep the paper soft through the action of Water.
While improvement in softness of certain grades of paper, particularly glassine or grease-proof papers, has been realized by impregnation with the above mentioned agents, such agents are not entirely satisfactory for the treatment of sanitary papers since they do not produce a softening effect desired by the trade. Moreover, such agents are applied to the finished sheet of paper by spraying, coating or impregnation; such impregnation procedures for paper require special equipment and give a paper product in which the humectant is unevenly distributed therein.
Accordingly, the present invention has as a principal object .an improved process of making sanitary paper by incorporating lanolin inform of an aqueous emulsion into an aqueous slurry of papermaking fibers in such a manner that many of the disadvantages enumerated above are avoided. a
Another object of. this invention is to provide a process .for the incorporation of an aqueous emulsion of lanolin into an aqueous papermaking slurry in such a manner that the addition of lanolin emulsion does not interfere with the conventional method of making paper on standard paper-making equipment.
Still another object of this invention is to provide a sanitary paper characterized by excellent softness and surface feel.
Still further objects (and advantages of the present invention will be obtained from the following description and the appended claims.
The process .of this invention of making sanitary papers having improved softness and surface feel broadly comp prises providing a mixture of an aqueous slurry of celis well known, sanitary papers are used for disass st Patented Jul-y f2, 1960 a 2 lulosicgpapermaking fibers and an aqueous emulsion of lanolin used in an amount suflicient to impart the desired improvement in softness of the resultingpaper. Precautions are taken at this point to insure that a substantial proportion of the lanolin content in the emulsion will be retained by-the fibers.
Accordingly, the invention is based on the discovery that it is possible to produce a sanitary paper characterized by a marked improvement in softness by incorporating lanolin into an aqueous system containing papermaking fibers under such conditions that small, discrete lanolin particles will be deposited or adsorbed on individual fibers and such fibers will retain their property of felting or forming into a paper web on conventional papermaking equipment. The resulting paper has lanolin particles uniformly distributed throughout in contrast with papers which have received a surface treatment to improve softness. 1 Aqueous emulsions of lanolin may be prepared in the presence of a suitable emulsifying or dispersing agent. Although it is preferred to employ a cationic emulsifier in the preparation of such emulsions, non-ionic or anionic emulsifiers may also be used in certain cases. When a.
non-ionic or anionic aqueous emulsion of lanolin is to be added to the fibrous slurry, it may be desirable to incorporate into the slurry a cation-active substance in order to enhance the adsorption or deposition of lanolin particles on the cellulosic fibers which are normally of anionic character and thus attain a still greater softening effect of the resulting paper.
In accordance with the preferred embodiment of this invention, a cationic aqueous emulsion of lanolin is prepared using a cationic emulsifier inconjunction with lanolin and water. The cationic emulsifiers which may be employed in preparing a. suitable lanolin emulsionin water are quaternary ammonium salts or bases, long chain amine salts, tertiary sulfonium salts or bases, quaternary sulfonium salts or bases, and the like. These may be used either singly or in combination with each other or with other well-known cationic emulsifiers. The quaternary ammonium compounds are examples of especially satisfactory emulsifiers; exemplary of these is a quaternary ammonium salt containing two long straight hydrocarbon chains Within the same molecule.
, Similarly, a wide variety of non-ionic emulsifiers may be used. Such emulsifiers are, in general, derivatives of aliphatic alcohols containing at least one free hydroxy group, panticularly aliphatic polyhydroxy. substances or polyhydric alcohols incompletely 'esterified with higher molecular weight aliphatic acids, particularly fatty acids; such compounds include monostearin, stearic acid monoester of diethylene or triethylene glycol, polyoxyethylene sorbitan stearates, and the like.
Typical anionic emulsifiers comprise the soaps of aliphatic acids, alkyl aryl sulfonates, alkyl aryl polyether sulfonates, fatty alcohol sulfates, sulfonated aliphatic compounds, and the likes A wide variety of papermaking fibers may be used the process of this invention. Such fibers in form of aqueous slurries may be derived from softwoods, hardwoods or annual plants including bagasse, cerealstraws and the like. These various fibrous materials may be produced by conventional chemical pulping procedures such as sulfite, kraft,soda, as well as by mechanical treatment to produce groundwood.
An aqueous emulsion of lanolin of the cationic type, which is the preferred type of lanolin emulsionaccording to the present invention, may be prepared by simply adding lanolin, preferably in the molten condition, to cold watertogether .with a suitable cationic emulsifier. The mixture is then vigorously agitated in a suitable mixing apparatus, such as a colloid mill or a homogenizer until a uniform emulsion is obtained.
In addition to the two essential ingredients of the aqueous emulsion, namely lanolin and a cationic emulsilien-two auxiliary ingredients may be incorporated therein, if desired. V V
Y First, an emulsion stabilizer may 'be'added-in'order to enhance the shelf-life and stability characteristics of the emulsion. Such stabilizers include several types of nonionic surfactants, cellulose derivatives, proteins, phosphatides, lecithin, and the like. S'e'condly, a certain quantity of an oil may be incorporated into' the mixture, primarily in order to improve the papermachine operation, for example, by extending the life of the c'reping blade on the Yankee drier. Suitable oils compn'semineral, vegetable or animal oils having a specific gravity at 60 F. in the range of 0.80-0.99. Examples of mineral oils are lubricating oils, produced by distillation ofcrude oil and having constituents boiling from about 600 F. at atmospheric pressure; light oils having a Saybolt viscosity at 100 F. of less than 175 and heavy oils of viscosity higher than 175 are satisfactory. Examples of vegetable oils are soya beanjcottons'eed, and the like; examples of animal oil. are whale oil; wool oil, lard oil, etc.
' The respective amounts of the various ingredients described hereinabove which may be used in the preparation of the lanolin emulsion are shown in the following Table I in which the figures are expressed in percent It will be understood that water is present in the emulsion in. an amount sufficient to produce an emulsion having a desired solids concentration which may range boar'dly from 0.1 to 50% and preferably from to 25% by weight.
' The aqueous emulsion of lanolin may be added to the aqueous slurry of papermaking fibers at any point prior to the paper web formation. Thus it may be added at the beater, mixing chest, or paper machine headbox. A very convenient method of adding the emulsion to the pulp slurry is by pumping it continuously into the paper machine headbox where adequate mixing of the components occurs rapidly and the particles of lanolin are instantly deposited on vor adsorbed bythe cellulosic fibers. It will be appreciated that the amount of lanolin emulsion added to the pulp. slurry may vary depending upon the type of fibers employed in the manufacture of the sanitary paper as well as on the degree of softness desired for such a paper. Generally the amount of lanolin added to the pulp slurry should'be sufficient to improve softness and surface feel of the resulting paper. Usually an amount of from 0.1 to 40 pounds of lanolin and preferably from 0.5 to pounds of lanolin per ton of oven-dry pulp will produce satisfactory improvement in softness of the resulting paper.
.Also, if desired, other materials conventionally used 4 position of lanolin particles takes place at any pH level between about 2 and 9. As a result, the choice of pH will depend primarily on such factors as the character of the pulp and the presence or absence of wet-strength resins and colorants.
The lanolin-treated aqueous .pulp slurry is then run on the paper machine wire or "cylinder and .the resulting paper is passed through heated drying rolls in the usual manner. Other desirableproperties may be obtained by creping and/or calendering the'paper.
The herein described invention be further illustrated by means of the following examples which are intended to be descriptive of the invention in preferred embodiments .thereof, percentages or parts being expressed by weight unless otherwise specified.
Example 1.-An aqueous emulsion'of lanolin was prepared by placing in a mixing vessel 50 parts of anhydrous lanolin (U. S.P. grade) together with 50 parts of a cationic emulsifier, a quaternary ammonium salt containing two straight hydrocarbon chains of 16-18 carbon atoms in length. within the'sam'e molecule, and mixing the two ingredients while heatingat 120 F. to melt the mixture. The molten mixture was poured slowly into a vessel equippedwith an agitator and containing 900 parts of cold water and mixed vigorously for 10 minutes at which time a coarse emulsion having a temperature of about 70 F. was formed. The resulting emulsion, having a solids content of 10%, was tranferred to a colloid mill and treated therein until a stable, fine emulsion of lanolin was obtained.
To an aqueous fibrous slurry of 1% consistency, suitable forthe manufacture of toweling, prepared by beating bleached softwood kraft pulp to 550 cc. Canadian Standard Freeness, there was added sufficient of the resulting emulsion to incorporate 1% of lanolin based on ovendry pulp, corresponding to 20 pounds of lanolin per ton of oven-dry pulp.- The mixture was agitated and formed into handsheets having a basis weight of 30 pounds per ream in accordance with the standard TAPPI procedure. For comparison, control handsheets were also made from the same pulp without lanolin emulsion added thereto. The resulting papers were tested for softness in the Handle-O-Meter, supplied by the Thwing Albert Instrument Co., Philadelphia, Pennsylvania. The following table indicates the values obtained on the untreated controls and the lanolin-treated papers. It will be noted that the lower the value the better is the softness of the paper.
Control Lanolin- Paper treated Paper softness, grams/4 inches 31 21 Thus the addition of a' cationic lanolin emulsion to pulp slurry increased the softness of the resulting paper by approximately 32%, as compared to untreated paper. Moreover, the lanolin-treated paper had a markedly improved surface feel and slightly improved absorbency.
" Example 2.-In' a manner essentially similar to that described in Example 1, an aqueous, cationic emulsion of lanolin was prepared. In addition to the two essential ingredients of Example 1, a mineral oil, Nujol, characterized by specific gravity of 0.88/0.90 at 60 F. and Sayas pulp additives may be incorporated into the Pulp mix- Such materials may include wet-strength resins bolt viscosity of 360/390 at F., was employed. The ingredients were admixed in amounts sufficient to give a 10% aqueous emulsion (solids basis) containing 30% of lanolin, 50% of cationic emulsifier and 20% of oil.
The emulsion was incorporated into the same papermaking fiber slurry as described in Example 1 in an amount corresponding to 0.6% of lanolin based on ovendry pulp, or. 12 pounds of lanolin per ton of oven-dry P p-:3 a. a 7
ssoftness tests carried out in thesame manner as in Example 1 gave the following results:
5 together with the-same paper untreated with the "lanolin emulsion. jThezresults were as follows:
Control Lanolln- Control Lanolln- Paper treated 5 :Paper treated Paper Paper 'Softness, grams/4 inches 31 22 softness, grams/inchXm as 34 Hence, the softness of the lanolin-treated paper was 6 I The resulting lanolin-treatedtissue had an increased increased by about 29% and its examination indicated a l. significant improvement'in surface feel, as compared to 1 the untreated control paper.
Example .3.- .An aqueous, cationic lanolin emulsion was prepared as indicated in Example v1, except that a non-ionic stabilizer, namely polyoxyethylene sorbitan monostearate, having a specific gravity of 1.08 at 25 C. and viscosity of 300 centipoises at 40 C. was added thereto. The ingredients were employedin amounts sufficient to provide a 10% aqueous emulsion (solids basis) containing 50% lanolin, 40% of cationic emulsifier and 10% of stabilizer. I
' The emulsion was added to the same kraft pulp slurry asemployed in Example 1 in amount sufficient to provide 1% of lanolin based on the oven-dry pulp, corresponding to 20 pounds of lanolin per ton of oven-dry pulp. r
The results of softness tests performed hereinabove were as follows:
as indicated The resulting lanolin-containing paper had an increased softness by about 36% and markedly improved surface feel, as compared to the untreated control paper.
Example 4.--A stable, cationic, aqueous emulsion of lanolin having 20% solids was prepared as indicated above using the ingredients employed in the preceding examples in their respective quantities as follows: lanolin 27%, cationic emulsifier 42%, stabilizer 17% and oil 19%.
The emulsion was added to an aqueous pulp slurry of 0.5% consistency, comprising as a fibrous furnish 60% of bleached softwood kraft, 20% of bleached hardwood kraft and 20% of softwood groundwood, in an amount sufficient to provide 0.1% of lanolin based on ovendry pulp, corresponding to 2 pounds of lanolin per ton of oven-dry pulp. The pulp mixture was formed into a creped tissue grade of paper having 13.8 pounds/ream I basis weight. The results of softness tests performed on this paper were as follows:
Thus, the lanolin-containing tissue paper had an increased softness by about 29% and markedly improved surface feel, compared to the untreated control paper.
Example 5.'To the same pulp slurry as indicated in Example 4 there was added an aqueous cationic emulsion of lanolin containing the same constituents as in Example 4, but used in the following amounts: lanolin 33%, cationic emulsifier 33%, non-ionic stabilizer 17%, and oil 17%.. 'The amount of the emulsion added was suflicient to give 0.07% of lanolin, oven-dry 'pulp basis 1.4 pound per ton of pulp).
The creped paper of 13.5 pounds/ream basis weight, formed from the above mixture, was tested for softness softness by about 11% and improved surface feel, as compared to the untreated control.
Example 6.-Three stable aqueous emulsions of lanolin having 20% solids, namely, a cationic, an anionic and a non-ionic emulsion, were prepared inthe manner described hereinabove. 'The emulsions, designated A,'B and C, respectively, contained the following ingredients in their respective proportionsi (A) lanolin 20%, cationic emulsifier (the same as employed in Example 1) 51%, stabilizer (the same as employed in Example 3) 7%, and mineral oil (the same as employed in Example 2) 22%; (B) lanolin 20%, anionic emulsifier, e.g., N-octadecyl tetrasodium N-(l,2-dicarboxyethyl sulfo-succinate) 30%, stabilizer e.g., polyoxyethylene sorbitan monolaurate, 27%, and the same mineral oil 23% (C) lanolin 20%, emulsifier, e.g., a mixture of 51% of polyoxyethylene sorbitan monolaurate and 7% of-sorbitan monolaurate, and the same mineral oil 22%. V V
Each of the above identified emulsions was added separately to an aqueous pulp slurry of 1% consistency, comprising as a fibrous furnish bleached softwood kraft, in amounts sufiicient to provide 0.2% of lanolin based on oven-dry pulp, corresponding to'4 pounds of lanolin per ton of oven-dry pulp, followed by addition of papermakers alum solution in amount sufficient to reduce the pH of the mixture to 5.0. The pulp mixtures were then formed into toweling paper grades of about 30 pounds/- ream basis weight.
Another series of paper sheets was also made using the same lanolin-containing pulp slurn'es, to which cationic melamine-formaldehyde wet-strength resin was added in an amount of 1% (solids basis) on oven-dry pulp. Paper of the same basis weight was formed in the same manner as set forth hereinabove.
The results of softness tests performed on the resulting papers and on papers containing no lanolin were as follows: 7
Control Lanolin- Lanolin- Lanolin- Paper treated treated treated Paper (A) Paper (B) Paper (0) softness, grams/4 inches: No wet strength resin-. 42 28 38 32 With wet-strength resin 44 28 32 29 were improved significantly by incorporation to pulp of a lanolin emulsion.
Example 7.-'An aqueous, cationic emulsion of lanolin having a 20% solids content and containing 21% of lanolin, 17% of cationic emulsifier, 8% of non-ionic stabilizer and 54% mineral oil (all the ingredients being the same as in the-preceding examples) was added continuously at the paper machine headbox to an aqueous slurry of fibers having 0.3% consistency and comprising 50% bleached softwood sulfite, 20%. bleached softwood kraft, 20% hardwoodfgroundwood and,'10%..bleached hardwood kraft, at such a rate as to provide 0.4% of lanolin, oven-dry pulp basis, corresponding to 8 pounds of lanolin per ton of oven-dry pulp.
' The resulting pulp mixture was convertedinto creped household toweliiig paper grade having aba'sis weight of 35.2pounds perream.
8 ing oil 52%. This may be combinedwith a pulp slurry for papermaking at the r'ate'of 0.1 pound of lanolin per ton of pulp (oven-dry weight basis). Example 10.-Lanolin 80% and cationic emulsifier (the same as in Example 1) 20%. This may be combined with a pulp slurry for papermaking atthe rate of Another papermachine run was'lma'd'e reproduce, as
a control, the same grade ofpaperr withoutaddir' g the 1 Machine direction. 1 Gross-machine direction.
Thus the'lanolin-treated .toweling had an increased softness by about 29% and was characterized by a markedly improved surfacefee], as compared to the untreated control. Moreover, the lanolin-containing pulpslurry ran well on the paper machine and produced toweling which had other desirable properties required by -:the trade, such as absorbency, caliper, tensile and stretch. In addition, the creping blade on the Yankee drier lasted twice as long during the manufacture of lanolin-treated paper than during the manufacture of the untreated control paper. p
Example 8.-Two similar paper machine runs were made using the same lanolin emulsion, as indicated in Example 7, but making facial tissue grade having 10.4 pounds/ream basis weight. Prior to the addition of the lanolin emulsion, 1% of a urea formaldehyde wetstrength resin (dry fiber basis) and suflicient papermaking alum to adjust the pH of the pulp mixture to 5.5 were added to the slurry, which was composed of 50% bleached softwood sulfite and 50% b1eached hardwood kraft.
The lanolin emulsion was added continuously at-the headbox at such a rate as to incorporate into the pulp 0.5% lanolin (oven-dry pulp basis), corresponding to pound-s of lanolin per ton of oven-dry pulp.
. lanolin emulsion. The test resultswe re as, followsf The resulting pulp mixture was run on the paper machine, creped on the Yankee drier and passed through two calender nips.
For comparison, the same grade of paper was made under the same conditions but Without adding the lanolin emulsion.
The results of softness tests were as follows:
Paper treated Paper Softness,grams/8inohes:
D 5 3 OMD 18 V 8 Total 23 11 The lanolin-treated tissue paper had an increased softness by about 52% and significantly improved sur-' The following working examples illustrate other embodiments of the invention: 1
Example 9.--Lanolin 22%; cationic emulsifier (a long chain. amine salt), hexadecylarnine acetate 16%, stabilizer, polyoxyethylene sorbitan tristerate 10%; saturat- 605 pound of lanolin per ton of pulp (oven-dry weight basis).
' Example. 11.La1 1olin 15% and cationic emulsifie'f (the samev as in Example. 1) 85%. This may be combiried with a pulpslurry for papermaking at'the rate of '35' pounds of lanolin per ton' of pulp (oven-dry weight basis).
Example 12.--Lanolin 30%; cationic emulsifier (another quaternary ammonium salt), N-cetyhN-ethyl morpholiniuni ethosulfate 30%; stabilizer (the same as in Example 9) 20%; Nujol oil 20%. This mayv be combined with a pulp slurry for papermak ing at the rate of 0.5 pound of lanolin per ton of pulp (oven-dry weight basis). 3 f V H Example 13.-Lanolin 40%; anionic emulsifier (alkyl aryl polyether sulfonate), sodium salt of alkyl aryl polyether sulfonate 40%; stabilizer (the same as in Example 9) 10%; Nujol oil 10%. This maybe combined with a pulp slurry for papermaking 'at' the rate of 3 pounds of lanolin per tonof pulp (oven-dry weight basis).
\ Example.14.-Lanolin non-ionic emulsifier, sorbitan mono-'oleate 25%.. This may be combined with a pulp slurry for papermaking at the rate of 12 pounds of lanolin per ton of pulp (oven-dry weight basis).
Example 15.-Lanolin 50%; cationic emulsifier (the same as in Example 1) 40%; stabilizer, lecithin 10%. This may be combined with a pulp slurry for papermaking at the rate of 40 pounds of lanolin per ton of pulp (oven-dry weight basis).v
Example 16.-Lanolin 50%; cationic emulsifier (the same as in Example 1) 40%; vegetable oil (cottonseed) 10%. This may be combined with a pulp slurry for papermaking at the rate of 10 pounds of lanolin per ton of pulp (oven-dry weight basis).
Example 17.Lanolin 50%; cationic emulsifier (the same as in Example 1) 40%; animal oil (lard) 10%. This may be combined -with a pulp slurry for papermaking at the rate of 10 pounds of lanolin per ton of pulp (oven-dry weight basis).
Accordingly, it is apparent that by the present invention I have provided an improved process for the manufacture of sanitary papers which process includes incorporation into an aqueous pulp slurry of an aqueous lanolin emulsion. Through interaction of a cationic emulsifier, the process results in a rapid, uniform and more complete deposition of discrete lanolin particles on the fibers which in turn results in the formation of paper products characterized by excellent softness, surface feel and other properties prerequisite for such paper grades, as tissue, toweling, napkinand the like.
5,1. The process of improving the softness and surface feel of sanitary paper, which comprises adding to an aqueous slurry of paperrnaking fibers a stable, aqueous emulsion of 190% '-by weight of lanolin and 1099% by weight of a cationic emulsifier selected from the group consisting of quaternary ammonium salts, quaternary ammonium bases, quaternary sulfonium salts, quaternary sulfonium bases, long chain amine salts and tertiary sulfonium bases, said slurry and said emulsion being at substantially room temperature, whereby a substantial proportion 'of lanolin particles and emulsifier contained in said emulsion is deposited onto said fibers while said fibers are suspended in water, and thereafter forming a paper web from the resulting slurry, the amount of lanolin and emulsifier deposited on the'fibers being sufiicient to improve the softness and surface feel of the resulting paper but being insufi'icient to permit said lanolin from being rubbed off on said paper.
2. Sanitary paper product produced in accordance with the process of claim 1.
3. The process of claim 1 wherein the amount of lanolin added to the slurry of papermaking fibers is from 0.1 to 40 pounds per ton of oven-dry pulp.
4. The process of claim 1 wherein the amount of lanolin added to the slurry of papcrmaking fibers is from 0.5 to 10 pounds per ton of oven-dry pulp.
5. The process of claim 1 wherein the emulsion is prepared by adding a molten mixture of the lanolin and of the emulsifier to cold water and vigorously agitating the resulting aqueous mixture until a finely divided emulsion is obtained.
6. The process of claim 1 wherein the emulsion comprises essentially 15-80% by Weight of lanolin and 20-50% by weight of the emulsifier. v
7. The process of claim 1 wherein the emulsion has a solids content of 0.1-50% by weight.
8. The process of claim l'wherein the emulsion has a solids content of 5-25 by weight.
9. The process of claim 1 wherein the emulsifier is a quaternary ammonium compound.
10. The process of claim 1 wherein the emulsifier is a quaternary ammonium salt containing two long straight hydrocarbon chains within the same molecule.
References Cited in the file of this patent UNITED STATES PATENTS 2,173,243 Young Sept. 19, 1939 2,442,972 Edelstein June 8, 1948 2,601,598 Daniel June 24, 1952 2,637,662 Russell May 5, 1953 2,832,357 Powers Apr. 29, 1958 2,877,115 Wemyss et al. Mar. 10, 1959 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No 944,931 July 12, 1960 Christen H. C, Yang It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.
Column 3 line 45 for "'-b0a1rdly"' read broadly column 8 line 75 for "on" read of Signed and sealed this 13th day of December 1960,
( SEAL) Attest:
KARL H, AXLINE ROBERT C. WATSON Attesting Oflicer Commissioner of Patents