CA1330382C - Soft tissue paper - Google Patents
Soft tissue paperInfo
- Publication number
- CA1330382C CA1330382C CA000602759A CA602759A CA1330382C CA 1330382 C CA1330382 C CA 1330382C CA 000602759 A CA000602759 A CA 000602759A CA 602759 A CA602759 A CA 602759A CA 1330382 C CA1330382 C CA 1330382C
- Authority
- CA
- Canada
- Prior art keywords
- tissue paper
- polysiloxane
- surfactant
- starch
- tissue
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Lifetime
Links
Classifications
-
- D—TEXTILES; PAPER
- D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
- D21H—PULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR
- D21H21/00—Non-fibrous material added to the pulp, characterised by its function, form or properties; Paper-impregnating or coating material, characterised by its function, form or properties
- D21H21/14—Non-fibrous material added to the pulp, characterised by its function, form or properties; Paper-impregnating or coating material, characterised by its function, form or properties characterised by function or properties in or on the paper
- D21H21/22—Agents rendering paper porous, absorbent or bulky
- D21H21/24—Surfactants
-
- D—TEXTILES; PAPER
- D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
- D21H—PULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR
- D21H17/00—Non-fibrous material added to the pulp, characterised by its constitution; Paper-impregnating material characterised by its constitution
- D21H17/20—Macromolecular organic compounds
- D21H17/33—Synthetic macromolecular compounds
- D21H17/46—Synthetic macromolecular compounds obtained otherwise than by reactions only involving carbon-to-carbon unsaturated bonds
- D21H17/59—Synthetic macromolecular compounds obtained otherwise than by reactions only involving carbon-to-carbon unsaturated bonds obtained by reactions forming in the main chain of the macromolecule a linkage containing silicon
-
- D—TEXTILES; PAPER
- D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
- D21H—PULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR
- D21H19/00—Coated paper; Coating material
- D21H19/36—Coatings with pigments
- D21H19/44—Coatings with pigments characterised by the other ingredients, e.g. the binder or dispersing agent
- D21H19/54—Starch
-
- D—TEXTILES; PAPER
- D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
- D21H—PULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR
- D21H23/00—Processes or apparatus for adding material to the pulp or to the paper
- D21H23/02—Processes or apparatus for adding material to the pulp or to the paper characterised by the manner in which substances are added
- D21H23/22—Addition to the formed paper
- D21H23/50—Spraying or projecting
Landscapes
- Chemical & Material Sciences (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Paper (AREA)
- Sanitary Thin Papers (AREA)
- Materials For Medical Uses (AREA)
Abstract
SOFT TISSUE PAPER
ABSTRACT
Tissue paper having a soft silky, flannel-like tactile feel throug incorporation of an effective amount of a chemical additive such as, fo example, a polysiloxane. Preferably, less than about 2% of such a chemica additive on a dry fiber weight basis, is incorporated in the tissue paper more preferably, only about 0.3% or less is so retained. Tissue pape embodiments of the present invention may further comprise a quantity o?
surfactant material to enhance softness and/or surface smoothness and/o?
wettability control; and/or a quantity of a binder a material such as starc?
for linting control. For example embodiments which would otherwis?
manifest a significant reduction in wettability due to incorporated chemica?
additives may further comprise sufficient surfactant to at least partially offset the reduction of wettability induced by the chemical additive e.g., for toilet tissue embodiments to be sufficiently wettable to be handled i?
contemporary sewage handling and disposal systems. Additionally, for example, embodiments which would otherwise manifest a significant exacerbation of linting due to such incorporation of chemical additives alone or in combinations with surfactant materials may further comprise an effective amount of a binder such as starch to at least partially offset the linting exacerbation effects of the chemical additives and, if present surfactant materials.
ABSTRACT
Tissue paper having a soft silky, flannel-like tactile feel throug incorporation of an effective amount of a chemical additive such as, fo example, a polysiloxane. Preferably, less than about 2% of such a chemica additive on a dry fiber weight basis, is incorporated in the tissue paper more preferably, only about 0.3% or less is so retained. Tissue pape embodiments of the present invention may further comprise a quantity o?
surfactant material to enhance softness and/or surface smoothness and/o?
wettability control; and/or a quantity of a binder a material such as starc?
for linting control. For example embodiments which would otherwis?
manifest a significant reduction in wettability due to incorporated chemica?
additives may further comprise sufficient surfactant to at least partially offset the reduction of wettability induced by the chemical additive e.g., for toilet tissue embodiments to be sufficiently wettable to be handled i?
contemporary sewage handling and disposal systems. Additionally, for example, embodiments which would otherwise manifest a significant exacerbation of linting due to such incorporation of chemical additives alone or in combinations with surfactant materials may further comprise an effective amount of a binder such as starch to at least partially offset the linting exacerbation effects of the chemical additives and, if present surfactant materials.
Description
Rû8ER~ S. ~PllLSKI :
~nd bOLF~N6 U. SPENDEL
' ": ' '' `
I~A~KGRO~,IND~ ~ THE INV~rIQ~
''"."'~'',"`'`'.";`.
FlElQ OF INVEH~
~ .
This invention r~ es, in general, to tissu~ paper; and, n~ore specifically, to high bulk tissue paper having a soft~ silky, flannel-like tactil~ feel; ~nd @nhanc~d t~ctile perc~ivable bulk, -.. ~; .`.:
and physiological surface sRoothness. - ~
BACKS,~Q~Q lNFORMQT~
Soft tiSSUI~ paper ~s generall~ pre~erred for dlspos~ble paper towels, and facial and ~oil~t tissues. Ho~ver, known ~ethods ~nd ~e~ns for enhanciRg softness o~ tissue paper gen~rally ~dversely affect te~sil~ strength. ~ssue p~per produet deslgn is, .
therefore, generall~ n exercise in bal~ncing softness ag~nst tensile str~ h.
80th ~echanical and che~ic~ seans haYe been ~n~roduc~d in , , the pursuit of ~king soft tissue paper: tissue paper ~hich is ` ~:
per~eived b.r users, through ~heir tactile sense, to h soft. Such tactile perceivable softn~ss ~ay b~ ch~ract~r~2ed by, b~l~ nst ;~
limited to, resilience, fle~ibilit)r, and s~oothne~s; and subiQc~
tive descriptors such as feeling like sil~ or fl;lnnel~ The present inYention p~rt~l ns eo i~proving th~ tacti le parce~v~ble 2S softness of tissue paper -- in part~oulilr high bulk, creped tissue pap~r -- through the incorporation of che~ic~ ditives: in particular, 0~teri~1s ~hich iMp~rt a slll~ or flafln~l-like fel!l to ~33~3~2 the tissue paper without rendering it greasy or oily to the tactile sense of users of products comprising such tissue paper.
Exemplary such chemical additives are, for example, polysiloxane materials which are simply referred to hereinafter as polysiloxanes. Additionally, surfactant material may be added to further enhance softness and/or surface smoothness and/or to at least partially offset any reduction in wettability caused by the polysiloxane; and binder material such as starch may be added to at least partially offset reductions in strength and or increasing in linting propensity that results from the polysiloxane and, if used, the surfactant additive.
Representative high bulk, creped tissue papers ~hich are quite soft by contemporary standards, and which are susceptible to softness enhancement through the present invention are disclosed in the following U.S. Patents: 3,301,746 which issued January 31, 1967 to Lawrence H. Sanford and James B. Sisson; 3~974,025 which issued August 10~ 1976 to Peter G. Ayers; 3,994,771 ~hich issueg November 30, 1976 to George Morgan, Jr. and Thomas F. Rich;
4,191,609 which issued March 4, 1980 t`o Paul D. Trokhan; and 4,637,85~ which issued January 20, 1987 to Paul D. Trokhan. Each of these papers is characterized by a pattern of dense areas:
areas ~ore dense than their respective remainders, such dense areas resulting fro~ being compacted during papermaking as by the crossover knuckles of imprinting carrier fabrics. Other high bulk, soft tissue papers are disclosed in U.S. Patent 4,300,981 ~ ~
which issued November 17, 19~1 to Jerry E. Carstens; and 4,440,597 ~ ~M
which issued April 3, 1984 to Edward R. ~ells and Thomas A.
Hensler. Additionally, achieving high bulk tissue paper through the avoidance of overall compaction prior to final drying is disclosed in U.S. Patent 3,821,068 ~hich issued June 2~, 1974 to D. L. Shaw; and avoidance of overall compaction in combination with the use of debonders and elastomeric bonders in the papermaking furnish is disclosed in U.S. Patent 3,812,000 which issued May 21, 1974 to J. L. Salvucci, Jr.
3 ~ ~
Chemical debonders such as those contemplat~d by Salvu~ci, referred to above, and their operative theory are disclosQd in such representative U.S. Patents as 3,755,220 which issued August . 28, 19~3 to Friemark et al; 3,844,880 which issued October 29, 1974 to Meisel et al; and 4,158,594 ~hich issued January lY, 1979 to Becker et al. Other chemical treat~ents ~hich have been proposed to improYe tissue paper include, for example, that disclosed in German Patent 3,420,940, Kenji Hara et al, to ~it: to impregnate toilet tissue paper ~ith a co~bination of a vegetable~
anima1, or synthetic hydrocarbon oil, and a silicone oil such as dimethylsilicone oil to make it easier to clean and wipe with.
Additionally, a ~ell known mæchanical method of increasing tensile strength of paper made from c~llulosic pulp is by mechanically refining the pulp prior to papermaking. In general, greater refining results in greater tensile strength. However, - - consistent with the foregoing discussion of tissue tensile strength and softness, increased mechanical refining of cellulosic pulp negatively impacts tissue paper softness, all other aspects of the paperm~king furnish and process be~ng unchanged. However, through the use of the present invention, tensile strength can be increased without negatively impacting softness; or, alternatively, softness can be iQproved without negatively impacting tensile strength.
..... ..
SUMMARY QF TH~ ENTION
In one aspect of the invention, tissue paper is provided having a basis weight of fro~ about 10 to about 65 g/m?, fiber density of about 0.6 g/cc or less, and which comprises 2n ~
effective amount of a chemical additiv~ such as, for exa~ple,. P;
polysiloxane to effect enhanced softness. The tissue paper has a hi~h degree of tactile softness and smoothness; and a silky and/ur flannel-llke tactile feel. Preferably, the tissue paper comprises fro~ about 0.094 to about 2 percent of such a chemical 133~
additive, based on the dry fiber weight of the tissue --paper; and, more preferably, the amount of such an additive is from about 0.004 to about 0.3 percent. -: -.
Preferred chemical additives for use in accordance ;
5 with the present invention are polysiloxanes; and -~
preferred polysiloxanes include an amino-functional polydimethylpolysiloxane wherein less than about 10 mole percent of the side chains on the polymer contain an amino-functional group. Directionally, the degree of 10 substitution is indirectly related to the average ~-~
molecular weight; and, because molecular weights of polysiloxanes are difficult to ascertain, the viscosity ~`
of a polysiloxane iæ used as an objectively `~
ascextainable indicia of molecular weight. Accordingly, 15 for example, about 2% substitution has been found to be ~
very effective for polysiloxanes having a viscosity of ~-about one-hundred-twenty-five (125) centistokes; and viscosities of about five-million (5,000,000) centistokes or more are effective with or without substitution. In addition to such substitution with amino-functional groups, effective substitution may be made with carboxyl, hydroxyl, ether, polyether, aldehyde, ketone, amide, ester, and thiol groups. Of -~
these effective substituent groups, the family of groups comprising amino, carboxyl, and hydroxyl groups are more preferred than the others; and amino-functional groups are most preferred.
~ ~ ' Exemplary commercially available polysiloxanes includes DOWTM 8075 and DOWTM 200 which are available from Dow Corning; and SilwetTM 720 and UcarsilTM EPS
which are available from Union Carbide.
~33~3~2 4a ~:
Chemically treated tissue paper of the present invention may further comprise an effective amount of a ::~
surfactant to enhance the tactile perceivable surface smoothness of the tissue paper and/or to at least ~ ~:
5 partially offset any reduction of wettability of the `
tissue paper which would otherwise result from the incorporation of the polysiloxane. Preferably, the amount of surfactant is from about 0.01 to about 2 percent or a dry fiber , , " ' ~' , , ".
:::
'' ~
f'~ ~
h~ ~
~303~2 weight of the tissue paper; and, more preferably, from about 0.05 to about 0.5 percent. Also, preferably~ the surfac~ant is noncationic; and is substan~ially nonmigratory in situ after the . tissue paper has been manufactured in order to substantially s obviate post-manufacturing changes in the tissue paper's properties which might otherwise result from the inclusisn of surfactant. This may be achieved, for instance, through the use of surfactants having melt temperatures greater than the temperatures commonly encountered during storage, shipping, merchandising, and use of tissue paper product embodiments of the invention: for example, melt temperatures of about 50C or higher. -Also, tissue paper comprising a chemical additive in accordance with the present invention may further comprise an effective amount of a binder material such as starch to at least partially offset any reduction of tensile strength or increase in linting propensity which ~ould otherwise result from the incorporation of the S&S modifier and, if presentj surfactant material. The effective amount of binder material is preferably from about 0.01 to about 2 percen~ on a dry fiber ~eight basis of the tissue paper.
A particularly preferred tissue paper embodimænt of the present invention comprises from about O.OO~ to about 0.3 percent of a chemical additive such as polys~iloxane for imparting a silky, flannel-like tactile feel; from about O.I to about 2 percent of surfactant material; and from about 0.1 to about 2 percent of starch, all quantities of these additives being on a dry fiber weight bisis of the tissue paper.
. . . ..
DETAILE QDESCRIPTIOH OF THE INYENTION
Briefly,the present invention provides tissue paper having a silky, flannel-like feel, and enhanced tactile p@rceivable softness through the incorporation of a che~ical additive such as, ~ 3 3 0 3 8 2 for example, a polysilox~ne. Such tissue paper may further include an effective amount of surfactant material and/or a binder material such as starch. Generally speaking, surfactant may be included to enhance tactile perceivable, physiological surface smoothness and/or to assure sufficient ~ettability for the intended purposes of the tissue paper (e.g., as toilet tissue);
and a binder material such as starch may be included to at least partially offset any reduction of tissue paper tensile strength and/or exacerbation of 1inting propensity ~hich would other~ise be precipitated by the addition of the chemical additive and, i~
used, the surfactant. Parenthetically, inasmuch as preferred chemical additives ar~ polysiloxanes, the terms Rchemical additive~ and Rpolysiloxane~ are used somewhat interchangeably hearin albeit it is not intended to thereby limit the scope of the invention to tissue papers comprising polysiloxanes per se, or to limit the term ~chemical additive~ to polysiloxanes per s~.
~hile not wishing to be bound by a theory of operation or to other~ise limit the present invention, tissue paper embodiments of the present invention are generally characteri~ed as being within a tri-parametric domain defined by empirieally determined ranges of the following parameters: first, the ratio of their Total Flexibility to their Total Strength; second, their Physiological Surface Smoothness; and third, their Slip-And-Stick Coefficient of Friction. For example, tests conducted in accordance with the following procedures defined by the present invention's tri-parametric domain as: a ratio of Total Flexibility to Total Tensile Strength of about 0.13 or less; Physiological Surface Smoothness of about 0.95 or less; and a Slip-and-Stick Coefficient of Friction of about 0.0~3 or less for pattern densified tissue papers, and about 0.038 or less for tissue paper embodiments having substantially uniform densities. 8y way of con~rast, all i~
contemporary tissue papers which have been tested ~nd which do not embody the present invention fell outside this tri-parametrk domain. These parameters and tests are discussed below.
, ~ , FLEXIBILITY and TOTAL FLEXIBILITY
Flexibi1ity as used herein is defined as the slope of the secant of the graph-curve derived.from force vs. stretch X data which secant passes through the origin (zero % stretch, zero force) and through the point on the graph-curve where the force - per centimeter of width is 20 grams. For example, ~or a sample which stretches lOX (i.e., O.I cm/cm of length) with 20 ~rams of :`
force per cm of sample width, the slope of the secant through (0%, O) and (lOX, 20) is 2.0 using the formula: -~
Y2 - Yl Slope = ------------X2 Xl ~`
Total Flexibility as used herein means the geometric mæan of the machine-direction flexibility and cross-machine-d`irection ~:
flexibility. Mathematically, this is the square root of the product of the machine-direction flexibility and cross-machine- ~
direction flexibility in grams per c~. :
TOTAL TENSILE STR~NGTH
Total tensile strength as used herein means the geometric . .
mean of the machine and cross-machine breaking strengths in grams per cm of sample width. Mathematically, this is the square root of the product of the machine and cross-machine direction breaking strengths in grams per cm of sample width. :~
~A~Y FACTOR
The ratio of Total Flexibility to Total Tensile Strength has .
been determined to be a factor which characterizes embodiments of the invention as being strong yet having high bulk softness. This ratio is hereby dubbed the ~ABY Factor.
- 133Q~82 Total Flexibility ~ABY Factor ~ ------------------- -- -Total Tensile Strength For instance, a sample having a Total Flexibility of 20 g/cm, and a Total Ten~ile Strength of 154 g/cm has a ~A8Y Factor of 0.13.
BrieFly, tactile perceivable softness of tissue paper is inversel~ related to its ~ABY Factor; and limited empirical data indicate that tissue paper embodiments of the present invention have ~ABY Factors of about Q.13 or less. Also, note that the ~ABY
Factor is dimensionless because both Flexibility and ~otal ~ensile Strength as defined above are in g/cm, their ratio is dimensionless.
PSYSIOLOGICA~ SURFACE SMOOTHNESS
... ~ , Physiological surface s~oothness as used h~rein is a factor (hereinafter the PSS ~ Factor) derived from scanning ~achine~
direction tissue paper samples with a profilometer (described ~ below) having a diamond stylus, the profilometer being installed in a surface test apparatus such as, for example, Surface Tester KES-FB-~ which is available from KAT0 TECH C0., LTD., Karato-Cho, Nishikiyo, ~inami-Ku, Koyota, Japan. In this tester, a sample of tissue is mounted on a motorized drum, and a stylus is gravita-tionally biased towards the drum at the 12 o'clock position. The drum is rotated to provide a sample velocity of one (1) ~i71imeter per second, and moves the sample 2 cm. with respec~ to the probe.
Thus, the probe scans a 2 cm length of the sample. The profilometer comprises means for counterbalancing the stylus to provide a normal force of 270 mg. Basically, the instrument senses the up and down displacements tin mm) of the stylus as a 2 cm length of sample is scanned under the profilometer probe. The resulting s~ylus-amplitude vs. stylus-dis~ance-scanned da~a are digitized, and then converted to a stylus-amplitude vs. fre~uen y spectrum by performing a Fourier Transform using the Proc Spectra standard program available from SAS Institut~ Inc., Post Office Box 10066, Raleigh? North Carolina 2~605. This identifies ~ . .
13~382 spectral components in the sample's topography; and t~e frequency `~
spectral data are then adjusted for human tactile responsiveness as quantified and reported by Verril10 (Ronald r . Yerrillo~
"Effect of Contractor Area on the Vibrotactile Threshold~, The Journal of the Accoustical Society of America, 35, 1962 (1963)).
However, whereas Verrills's data are in the time domain (i.e., cycles per second), and physiological surface smoothness is related to finger-to-sample velocity, Verrillo-type data are converted to a spatial domain (i.e., cycles per millimeter) using 65 mm/sec as a standard finger-to-sample velocity factor.
Finally, the data are integrated from zero (O) to ten (10) cycles per millimeter. The result is the PSS Factor. Graphically, the PSS Factor is the area under the Verrillo-adjusted ~requency (cycles/mm) vs. stylus amplitude curve between zero (O) and ten (10) cycles per mi11imeter. Preferably, PSS Fa~tors are average values derived from scanning multiple samples (e.g., ten samples), both fos.~ard and backward.
The profilometer descr;bed above comprises, more specifically, a Gould Surfanalyzer Equipment Controller #21-1330-20428, Probe #21-3100-465, Diamond stylus tip (0.0127 mm radius) ~21-0120-00 and stylus tip extender ~22-0129-00 all available from Federal Products, Providence, ~I. The profilometer probe assembly is fitted with a counterbalance, and set up as depicted in Figure 22 of United States patent 4,300,981 (referenced hereinbefore).
SlIP-AND-STICK_COEFFICIENT OF FRICTION
Slip-and-stick coefficient of friction (hereinafter S~S COF) is defined as the mean de~iation of the coefficient of friction.
It is dimensionless. It may be determined using commercially available test apparatus such as9 fcr example, the Kato Surface Tester identified above which has been fitted ~ith a stylus which ~ `
i5 configured and disposed to slide on the surface of the sample being scanned: for example, a fritted glass disk. ~hen a sample ~33~332 is scanned as described above, the instrument senses the lateral force on the stylus as the sample is moved thereunder: i.e., scanned. The lateral force is called the frictional force; and the ratio of frictional force to stylus weigh~ is the coefficient of friction, mu. The instrumen~ then solves ~he following equation to determine S~S COF for each scan of each sample.
S&S COF =
in which : ' is the ratio of frictional force to probe loading, ~ ~
. ~
~6~is the average value of ~ ; and -~
- X is 2 cm. -.. ~ .
Returning now to the Detailed Description of The Invention, the present invention -- polysiloxane treated tissue papers having enhanced tactile responsiveness -- includes but is ndt iimited to~
conventionally felt-pressed tissue paper; pattern densified tissue paper such as exemplified by Sanford-Sisson and its progeny; and high bulk, uncompacted tissue paper such as exemplified by Salvucci. The tissue paper may be of a homogenous or multilayered construction; and tissue paper products made therefrom may be of a single-ply or multi-ply construction. The tissue paper preferably has a basis weight of between about 10 g/m2 and abou~ 65 g/m2, and density of about 0.60 g/cc or less. Preferably, basis weight will be below about 35 g/m2 or less; and density will be about 0.30 g/cc or less. Most preferably, density will be between about 0.08 g/cc and about 0.20 g/cc.
Papermaking fibers which may be utilized for the present invention include fibers derived from wood puip. Other cellulosic fibrous pulp fibers, such as cotton linters, bagasse, etc., can be utilized and are intended to be within the scope of this 133~3~2 invention. Synthetio fibers, such as r~yon, polyethylene and polypropylene fibers, may also be utilized in combination ~ith natural cellulosic fibers. One exemplary polyethylene fiber which . may be utilized is PulpexTM, available from Hercules, Inc. (Wil-mington, Delaware~
Applicable wood pulps include chem k al pulps ~ade by the Kraft, sulfite, and sulfate processesi and mechanical pulps including, for example, groundwood, thermomechanical pulp and chemically modified thermomechanical pulp. Chemical pulps, however, are preferred since they impart a superior tactile perceivable softness to tissue sheets made therefrom. Pulps may be utilized which are derived from both deciduous trees which are sometimes referred to as "hardwood~; and coniferous trees which are sometlmes referred to as ~soft~ood~.
In addition to papermaking fibers, the papermaking furnish used to make tissue paper structures may have other components or materials added thereto: for example, wet-strength and temporary wet-strength resins.
Suitable polysiloxane materials which are useful as S&S
modifiers in accordance with the present invention include polymeric, oligomeric, copolymeric, and other multiple-monomeric siloxane ~aterials. As used herein, the term polysiloxane shall include all of such polymeric, oligomeric, copolymeric and other multiple-monomeric siloxane materials. Additionally, the polysiloxane can be either a straight chain, a branched chain or have a cyclic structure.
Preferred polysiloxane materials include those having mono-meric siloxane units of the following structure~
:' ,: ' ,~ . .
(1) - Si - O-~33~382 wherein, Rl and R2 for each siloxane monomeri~ unit can indepen-dently be any alkyl, aryl, alkenyl, alkaryl, aralkyl, cycloalkyl, halogenated hydrocarbon, or other radical. Any of such radicals can be substituted or unsubstituted. Rl and R2 radicals of any particular monomeric unit may differ from the corresponding functionalities of the next adjoining monomeric unit.
Additionall~, the radicals can be either a straight chain, a branched chain, or have a cyclic structure. The radicals Rl and R2 can, additionally and independently, be other silicone functionalities such as, but not limited to siloxanes, polysiloxanes, and polysilanes. The radicals Rl and R2 can also contain any of a variety of organic functionalities including, for example, alcohol, carboxylic acid, and amine functionalities~ ;`
The degree of substitution and the type of substituent have '~j been found to affect the relative degree of soft, silky feeling and hydrophilicity imparted to the tissue paper structure. In general, the degree of soft, silky feeling impar~ed by the polysiloxane increases as the hydrophilicity of the substituted polysiloxane decreases. Aminofunctional polysiloxanes are especially preferred in the present inYention.
Preferred polysiloxanes include straight chain organopoly~
siloxane materials of the following general formula:
~1 / R7 \ Rg\ R4 I I \ I '~
~nd bOLF~N6 U. SPENDEL
' ": ' '' `
I~A~KGRO~,IND~ ~ THE INV~rIQ~
''"."'~'',"`'`'.";`.
FlElQ OF INVEH~
~ .
This invention r~ es, in general, to tissu~ paper; and, n~ore specifically, to high bulk tissue paper having a soft~ silky, flannel-like tactil~ feel; ~nd @nhanc~d t~ctile perc~ivable bulk, -.. ~; .`.:
and physiological surface sRoothness. - ~
BACKS,~Q~Q lNFORMQT~
Soft tiSSUI~ paper ~s generall~ pre~erred for dlspos~ble paper towels, and facial and ~oil~t tissues. Ho~ver, known ~ethods ~nd ~e~ns for enhanciRg softness o~ tissue paper gen~rally ~dversely affect te~sil~ strength. ~ssue p~per produet deslgn is, .
therefore, generall~ n exercise in bal~ncing softness ag~nst tensile str~ h.
80th ~echanical and che~ic~ seans haYe been ~n~roduc~d in , , the pursuit of ~king soft tissue paper: tissue paper ~hich is ` ~:
per~eived b.r users, through ~heir tactile sense, to h soft. Such tactile perceivable softn~ss ~ay b~ ch~ract~r~2ed by, b~l~ nst ;~
limited to, resilience, fle~ibilit)r, and s~oothne~s; and subiQc~
tive descriptors such as feeling like sil~ or fl;lnnel~ The present inYention p~rt~l ns eo i~proving th~ tacti le parce~v~ble 2S softness of tissue paper -- in part~oulilr high bulk, creped tissue pap~r -- through the incorporation of che~ic~ ditives: in particular, 0~teri~1s ~hich iMp~rt a slll~ or flafln~l-like fel!l to ~33~3~2 the tissue paper without rendering it greasy or oily to the tactile sense of users of products comprising such tissue paper.
Exemplary such chemical additives are, for example, polysiloxane materials which are simply referred to hereinafter as polysiloxanes. Additionally, surfactant material may be added to further enhance softness and/or surface smoothness and/or to at least partially offset any reduction in wettability caused by the polysiloxane; and binder material such as starch may be added to at least partially offset reductions in strength and or increasing in linting propensity that results from the polysiloxane and, if used, the surfactant additive.
Representative high bulk, creped tissue papers ~hich are quite soft by contemporary standards, and which are susceptible to softness enhancement through the present invention are disclosed in the following U.S. Patents: 3,301,746 which issued January 31, 1967 to Lawrence H. Sanford and James B. Sisson; 3~974,025 which issued August 10~ 1976 to Peter G. Ayers; 3,994,771 ~hich issueg November 30, 1976 to George Morgan, Jr. and Thomas F. Rich;
4,191,609 which issued March 4, 1980 t`o Paul D. Trokhan; and 4,637,85~ which issued January 20, 1987 to Paul D. Trokhan. Each of these papers is characterized by a pattern of dense areas:
areas ~ore dense than their respective remainders, such dense areas resulting fro~ being compacted during papermaking as by the crossover knuckles of imprinting carrier fabrics. Other high bulk, soft tissue papers are disclosed in U.S. Patent 4,300,981 ~ ~
which issued November 17, 19~1 to Jerry E. Carstens; and 4,440,597 ~ ~M
which issued April 3, 1984 to Edward R. ~ells and Thomas A.
Hensler. Additionally, achieving high bulk tissue paper through the avoidance of overall compaction prior to final drying is disclosed in U.S. Patent 3,821,068 ~hich issued June 2~, 1974 to D. L. Shaw; and avoidance of overall compaction in combination with the use of debonders and elastomeric bonders in the papermaking furnish is disclosed in U.S. Patent 3,812,000 which issued May 21, 1974 to J. L. Salvucci, Jr.
3 ~ ~
Chemical debonders such as those contemplat~d by Salvu~ci, referred to above, and their operative theory are disclosQd in such representative U.S. Patents as 3,755,220 which issued August . 28, 19~3 to Friemark et al; 3,844,880 which issued October 29, 1974 to Meisel et al; and 4,158,594 ~hich issued January lY, 1979 to Becker et al. Other chemical treat~ents ~hich have been proposed to improYe tissue paper include, for example, that disclosed in German Patent 3,420,940, Kenji Hara et al, to ~it: to impregnate toilet tissue paper ~ith a co~bination of a vegetable~
anima1, or synthetic hydrocarbon oil, and a silicone oil such as dimethylsilicone oil to make it easier to clean and wipe with.
Additionally, a ~ell known mæchanical method of increasing tensile strength of paper made from c~llulosic pulp is by mechanically refining the pulp prior to papermaking. In general, greater refining results in greater tensile strength. However, - - consistent with the foregoing discussion of tissue tensile strength and softness, increased mechanical refining of cellulosic pulp negatively impacts tissue paper softness, all other aspects of the paperm~king furnish and process be~ng unchanged. However, through the use of the present invention, tensile strength can be increased without negatively impacting softness; or, alternatively, softness can be iQproved without negatively impacting tensile strength.
..... ..
SUMMARY QF TH~ ENTION
In one aspect of the invention, tissue paper is provided having a basis weight of fro~ about 10 to about 65 g/m?, fiber density of about 0.6 g/cc or less, and which comprises 2n ~
effective amount of a chemical additiv~ such as, for exa~ple,. P;
polysiloxane to effect enhanced softness. The tissue paper has a hi~h degree of tactile softness and smoothness; and a silky and/ur flannel-llke tactile feel. Preferably, the tissue paper comprises fro~ about 0.094 to about 2 percent of such a chemical 133~
additive, based on the dry fiber weight of the tissue --paper; and, more preferably, the amount of such an additive is from about 0.004 to about 0.3 percent. -: -.
Preferred chemical additives for use in accordance ;
5 with the present invention are polysiloxanes; and -~
preferred polysiloxanes include an amino-functional polydimethylpolysiloxane wherein less than about 10 mole percent of the side chains on the polymer contain an amino-functional group. Directionally, the degree of 10 substitution is indirectly related to the average ~-~
molecular weight; and, because molecular weights of polysiloxanes are difficult to ascertain, the viscosity ~`
of a polysiloxane iæ used as an objectively `~
ascextainable indicia of molecular weight. Accordingly, 15 for example, about 2% substitution has been found to be ~
very effective for polysiloxanes having a viscosity of ~-about one-hundred-twenty-five (125) centistokes; and viscosities of about five-million (5,000,000) centistokes or more are effective with or without substitution. In addition to such substitution with amino-functional groups, effective substitution may be made with carboxyl, hydroxyl, ether, polyether, aldehyde, ketone, amide, ester, and thiol groups. Of -~
these effective substituent groups, the family of groups comprising amino, carboxyl, and hydroxyl groups are more preferred than the others; and amino-functional groups are most preferred.
~ ~ ' Exemplary commercially available polysiloxanes includes DOWTM 8075 and DOWTM 200 which are available from Dow Corning; and SilwetTM 720 and UcarsilTM EPS
which are available from Union Carbide.
~33~3~2 4a ~:
Chemically treated tissue paper of the present invention may further comprise an effective amount of a ::~
surfactant to enhance the tactile perceivable surface smoothness of the tissue paper and/or to at least ~ ~:
5 partially offset any reduction of wettability of the `
tissue paper which would otherwise result from the incorporation of the polysiloxane. Preferably, the amount of surfactant is from about 0.01 to about 2 percent or a dry fiber , , " ' ~' , , ".
:::
'' ~
f'~ ~
h~ ~
~303~2 weight of the tissue paper; and, more preferably, from about 0.05 to about 0.5 percent. Also, preferably~ the surfac~ant is noncationic; and is substan~ially nonmigratory in situ after the . tissue paper has been manufactured in order to substantially s obviate post-manufacturing changes in the tissue paper's properties which might otherwise result from the inclusisn of surfactant. This may be achieved, for instance, through the use of surfactants having melt temperatures greater than the temperatures commonly encountered during storage, shipping, merchandising, and use of tissue paper product embodiments of the invention: for example, melt temperatures of about 50C or higher. -Also, tissue paper comprising a chemical additive in accordance with the present invention may further comprise an effective amount of a binder material such as starch to at least partially offset any reduction of tensile strength or increase in linting propensity which ~ould otherwise result from the incorporation of the S&S modifier and, if presentj surfactant material. The effective amount of binder material is preferably from about 0.01 to about 2 percen~ on a dry fiber ~eight basis of the tissue paper.
A particularly preferred tissue paper embodimænt of the present invention comprises from about O.OO~ to about 0.3 percent of a chemical additive such as polys~iloxane for imparting a silky, flannel-like tactile feel; from about O.I to about 2 percent of surfactant material; and from about 0.1 to about 2 percent of starch, all quantities of these additives being on a dry fiber weight bisis of the tissue paper.
. . . ..
DETAILE QDESCRIPTIOH OF THE INYENTION
Briefly,the present invention provides tissue paper having a silky, flannel-like feel, and enhanced tactile p@rceivable softness through the incorporation of a che~ical additive such as, ~ 3 3 0 3 8 2 for example, a polysilox~ne. Such tissue paper may further include an effective amount of surfactant material and/or a binder material such as starch. Generally speaking, surfactant may be included to enhance tactile perceivable, physiological surface smoothness and/or to assure sufficient ~ettability for the intended purposes of the tissue paper (e.g., as toilet tissue);
and a binder material such as starch may be included to at least partially offset any reduction of tissue paper tensile strength and/or exacerbation of 1inting propensity ~hich would other~ise be precipitated by the addition of the chemical additive and, i~
used, the surfactant. Parenthetically, inasmuch as preferred chemical additives ar~ polysiloxanes, the terms Rchemical additive~ and Rpolysiloxane~ are used somewhat interchangeably hearin albeit it is not intended to thereby limit the scope of the invention to tissue papers comprising polysiloxanes per se, or to limit the term ~chemical additive~ to polysiloxanes per s~.
~hile not wishing to be bound by a theory of operation or to other~ise limit the present invention, tissue paper embodiments of the present invention are generally characteri~ed as being within a tri-parametric domain defined by empirieally determined ranges of the following parameters: first, the ratio of their Total Flexibility to their Total Strength; second, their Physiological Surface Smoothness; and third, their Slip-And-Stick Coefficient of Friction. For example, tests conducted in accordance with the following procedures defined by the present invention's tri-parametric domain as: a ratio of Total Flexibility to Total Tensile Strength of about 0.13 or less; Physiological Surface Smoothness of about 0.95 or less; and a Slip-and-Stick Coefficient of Friction of about 0.0~3 or less for pattern densified tissue papers, and about 0.038 or less for tissue paper embodiments having substantially uniform densities. 8y way of con~rast, all i~
contemporary tissue papers which have been tested ~nd which do not embody the present invention fell outside this tri-parametrk domain. These parameters and tests are discussed below.
, ~ , FLEXIBILITY and TOTAL FLEXIBILITY
Flexibi1ity as used herein is defined as the slope of the secant of the graph-curve derived.from force vs. stretch X data which secant passes through the origin (zero % stretch, zero force) and through the point on the graph-curve where the force - per centimeter of width is 20 grams. For example, ~or a sample which stretches lOX (i.e., O.I cm/cm of length) with 20 ~rams of :`
force per cm of sample width, the slope of the secant through (0%, O) and (lOX, 20) is 2.0 using the formula: -~
Y2 - Yl Slope = ------------X2 Xl ~`
Total Flexibility as used herein means the geometric mæan of the machine-direction flexibility and cross-machine-d`irection ~:
flexibility. Mathematically, this is the square root of the product of the machine-direction flexibility and cross-machine- ~
direction flexibility in grams per c~. :
TOTAL TENSILE STR~NGTH
Total tensile strength as used herein means the geometric . .
mean of the machine and cross-machine breaking strengths in grams per cm of sample width. Mathematically, this is the square root of the product of the machine and cross-machine direction breaking strengths in grams per cm of sample width. :~
~A~Y FACTOR
The ratio of Total Flexibility to Total Tensile Strength has .
been determined to be a factor which characterizes embodiments of the invention as being strong yet having high bulk softness. This ratio is hereby dubbed the ~ABY Factor.
- 133Q~82 Total Flexibility ~ABY Factor ~ ------------------- -- -Total Tensile Strength For instance, a sample having a Total Flexibility of 20 g/cm, and a Total Ten~ile Strength of 154 g/cm has a ~A8Y Factor of 0.13.
BrieFly, tactile perceivable softness of tissue paper is inversel~ related to its ~ABY Factor; and limited empirical data indicate that tissue paper embodiments of the present invention have ~ABY Factors of about Q.13 or less. Also, note that the ~ABY
Factor is dimensionless because both Flexibility and ~otal ~ensile Strength as defined above are in g/cm, their ratio is dimensionless.
PSYSIOLOGICA~ SURFACE SMOOTHNESS
... ~ , Physiological surface s~oothness as used h~rein is a factor (hereinafter the PSS ~ Factor) derived from scanning ~achine~
direction tissue paper samples with a profilometer (described ~ below) having a diamond stylus, the profilometer being installed in a surface test apparatus such as, for example, Surface Tester KES-FB-~ which is available from KAT0 TECH C0., LTD., Karato-Cho, Nishikiyo, ~inami-Ku, Koyota, Japan. In this tester, a sample of tissue is mounted on a motorized drum, and a stylus is gravita-tionally biased towards the drum at the 12 o'clock position. The drum is rotated to provide a sample velocity of one (1) ~i71imeter per second, and moves the sample 2 cm. with respec~ to the probe.
Thus, the probe scans a 2 cm length of the sample. The profilometer comprises means for counterbalancing the stylus to provide a normal force of 270 mg. Basically, the instrument senses the up and down displacements tin mm) of the stylus as a 2 cm length of sample is scanned under the profilometer probe. The resulting s~ylus-amplitude vs. stylus-dis~ance-scanned da~a are digitized, and then converted to a stylus-amplitude vs. fre~uen y spectrum by performing a Fourier Transform using the Proc Spectra standard program available from SAS Institut~ Inc., Post Office Box 10066, Raleigh? North Carolina 2~605. This identifies ~ . .
13~382 spectral components in the sample's topography; and t~e frequency `~
spectral data are then adjusted for human tactile responsiveness as quantified and reported by Verril10 (Ronald r . Yerrillo~
"Effect of Contractor Area on the Vibrotactile Threshold~, The Journal of the Accoustical Society of America, 35, 1962 (1963)).
However, whereas Verrills's data are in the time domain (i.e., cycles per second), and physiological surface smoothness is related to finger-to-sample velocity, Verrillo-type data are converted to a spatial domain (i.e., cycles per millimeter) using 65 mm/sec as a standard finger-to-sample velocity factor.
Finally, the data are integrated from zero (O) to ten (10) cycles per millimeter. The result is the PSS Factor. Graphically, the PSS Factor is the area under the Verrillo-adjusted ~requency (cycles/mm) vs. stylus amplitude curve between zero (O) and ten (10) cycles per mi11imeter. Preferably, PSS Fa~tors are average values derived from scanning multiple samples (e.g., ten samples), both fos.~ard and backward.
The profilometer descr;bed above comprises, more specifically, a Gould Surfanalyzer Equipment Controller #21-1330-20428, Probe #21-3100-465, Diamond stylus tip (0.0127 mm radius) ~21-0120-00 and stylus tip extender ~22-0129-00 all available from Federal Products, Providence, ~I. The profilometer probe assembly is fitted with a counterbalance, and set up as depicted in Figure 22 of United States patent 4,300,981 (referenced hereinbefore).
SlIP-AND-STICK_COEFFICIENT OF FRICTION
Slip-and-stick coefficient of friction (hereinafter S~S COF) is defined as the mean de~iation of the coefficient of friction.
It is dimensionless. It may be determined using commercially available test apparatus such as9 fcr example, the Kato Surface Tester identified above which has been fitted ~ith a stylus which ~ `
i5 configured and disposed to slide on the surface of the sample being scanned: for example, a fritted glass disk. ~hen a sample ~33~332 is scanned as described above, the instrument senses the lateral force on the stylus as the sample is moved thereunder: i.e., scanned. The lateral force is called the frictional force; and the ratio of frictional force to stylus weigh~ is the coefficient of friction, mu. The instrumen~ then solves ~he following equation to determine S~S COF for each scan of each sample.
S&S COF =
in which : ' is the ratio of frictional force to probe loading, ~ ~
. ~
~6~is the average value of ~ ; and -~
- X is 2 cm. -.. ~ .
Returning now to the Detailed Description of The Invention, the present invention -- polysiloxane treated tissue papers having enhanced tactile responsiveness -- includes but is ndt iimited to~
conventionally felt-pressed tissue paper; pattern densified tissue paper such as exemplified by Sanford-Sisson and its progeny; and high bulk, uncompacted tissue paper such as exemplified by Salvucci. The tissue paper may be of a homogenous or multilayered construction; and tissue paper products made therefrom may be of a single-ply or multi-ply construction. The tissue paper preferably has a basis weight of between about 10 g/m2 and abou~ 65 g/m2, and density of about 0.60 g/cc or less. Preferably, basis weight will be below about 35 g/m2 or less; and density will be about 0.30 g/cc or less. Most preferably, density will be between about 0.08 g/cc and about 0.20 g/cc.
Papermaking fibers which may be utilized for the present invention include fibers derived from wood puip. Other cellulosic fibrous pulp fibers, such as cotton linters, bagasse, etc., can be utilized and are intended to be within the scope of this 133~3~2 invention. Synthetio fibers, such as r~yon, polyethylene and polypropylene fibers, may also be utilized in combination ~ith natural cellulosic fibers. One exemplary polyethylene fiber which . may be utilized is PulpexTM, available from Hercules, Inc. (Wil-mington, Delaware~
Applicable wood pulps include chem k al pulps ~ade by the Kraft, sulfite, and sulfate processesi and mechanical pulps including, for example, groundwood, thermomechanical pulp and chemically modified thermomechanical pulp. Chemical pulps, however, are preferred since they impart a superior tactile perceivable softness to tissue sheets made therefrom. Pulps may be utilized which are derived from both deciduous trees which are sometimes referred to as "hardwood~; and coniferous trees which are sometlmes referred to as ~soft~ood~.
In addition to papermaking fibers, the papermaking furnish used to make tissue paper structures may have other components or materials added thereto: for example, wet-strength and temporary wet-strength resins.
Suitable polysiloxane materials which are useful as S&S
modifiers in accordance with the present invention include polymeric, oligomeric, copolymeric, and other multiple-monomeric siloxane ~aterials. As used herein, the term polysiloxane shall include all of such polymeric, oligomeric, copolymeric and other multiple-monomeric siloxane materials. Additionally, the polysiloxane can be either a straight chain, a branched chain or have a cyclic structure.
Preferred polysiloxane materials include those having mono-meric siloxane units of the following structure~
:' ,: ' ,~ . .
(1) - Si - O-~33~382 wherein, Rl and R2 for each siloxane monomeri~ unit can indepen-dently be any alkyl, aryl, alkenyl, alkaryl, aralkyl, cycloalkyl, halogenated hydrocarbon, or other radical. Any of such radicals can be substituted or unsubstituted. Rl and R2 radicals of any particular monomeric unit may differ from the corresponding functionalities of the next adjoining monomeric unit.
Additionall~, the radicals can be either a straight chain, a branched chain, or have a cyclic structure. The radicals Rl and R2 can, additionally and independently, be other silicone functionalities such as, but not limited to siloxanes, polysiloxanes, and polysilanes. The radicals Rl and R2 can also contain any of a variety of organic functionalities including, for example, alcohol, carboxylic acid, and amine functionalities~ ;`
The degree of substitution and the type of substituent have '~j been found to affect the relative degree of soft, silky feeling and hydrophilicity imparted to the tissue paper structure. In general, the degree of soft, silky feeling impar~ed by the polysiloxane increases as the hydrophilicity of the substituted polysiloxane decreases. Aminofunctional polysiloxanes are especially preferred in the present inYention.
Preferred polysiloxanes include straight chain organopoly~
siloxane materials of the following general formula:
~1 / R7 \ Rg\ R4 I I \ I '~
(2) R2 -li-0 -Si- -5i-0~ -Si - Rs R3 R8 la R~o/b Rs wherein each ~1 - Rg radical can independently be any Cl - Clo `~
unsubstituted alkyl or aryl radical, and Rlo is any substituted Cl ;~
- Clo alkyl or aryl radical. Preferably each Rl - Rg radical is independently any Cl - C4 unsubstitu~ed alkyl group. Those ; `
skilled in the art will recognize that technically there is no ~ ~ ;
l3 ~330382 difference ~hether, for example, Rg or Rlo is the substituted radical. Preferably the mole ratio of b to (a + b) is between 0 and about 20%, more preferably between 0 and about 10%, and most preferably between about I~ and about 5X.
In one particularly preferred embodiment, Rl - Rg are methyl groups and Rlo is à substituted or unsubsti~uted alkyl, aryl, or alkenyl group. Such material shall be generally described herein as polydimethylsiloxane which has a particular functionality as may be appropriate in that particular case. Exe~plary polydi-methylsiloxanes include, for example, polydimethyls;loxane?
polydimethylsiloxane having an alkyl hydrocarbon Rlo radical and polydimethylsiloxane having one or more a~ino, carboxyl, hydroxyl, ether, polyether, aldehyde, ketone, amide, ester, thiol and/or other RIo functionalities including alkyl and alkenyl ~nalogues of such functionalities. For example, an amino functional alkyl groue as Rlo could be an amino-functional or an a~inoalkyl-functional polydimethylsiloxane. The exemplary listing of these - polydimethylsiloxanes is not meant to thereby exclude others not specifically listed.
Viscosity of polysiloxanes useful for this invention may vary as widely as the viscosity of polysiloxanes in general vary, so long as the polysiloxane is flo~able or can be made to be flowable for application to the tissue paper. This includes, but is not limited to, viscosity as low as about 25 centistokes to about 20,000,000 centistokes or even higher. High ~iscosity poly~
siloxanes which themselves are resistant to flowing can be effectively deposited upon the tissue paper webs by such m*thods as, for example, emulsifying the pol~siloxane in surfactant or providing the polysiloxane in soluticn with the aid of a solvent, such as hexane, listed for exe~plary purposes only. Particular methods for applying polysiloxanes to tissue paper webs are discussed in more detail below.
13303~2 Parenthetically, while not wishing to be bound by a theory of operation, it is believed that the tactile-benefit efficacy of the polysiloxane is directly related to its average molecular weight;
and that viscosity is directly related to molecular weight.
Accordingly, due to the relative difficulty of directly determining molecular weights of polysiloxanes as compared to determining their viscosities, viscosity is used herein as the apparent operative parameter with respect to imparting enhanced tactile response to tissue paper: i.e., softness, silkiness, and flannel-like.
References disclosing polysiloxanes include U. S. Patent 2,826,551, issued March 11, 1958 to Geen; U. S. Patent 3,964,500, issued June 22, 197~ to Drakoff; U.S. Patent ~,364,837, issued December 21, 1982 to Pader; and British Patent 849,433, published September 28, 1960 to ~oolston. Also, Silicon Co~npounds, pp.
181-217, distributed by Petrarch Systems, Inc., -1984, contàins an extensive listing and description of polysiloxanes in general. ~ -:. - - . . .
The polysiloxane can be applied to tissue paper as it is being made on a papermaking machine or thereafter: either while it is wet (i.e., prior to final drying) or dry (i.e., a~ter final drying). Preferably, an aqueous mixture containing the poly~
siloxane is sprayed onto the tissue paper as it courses through the papermaking machine: for example, and not by way of limitation, referring to a papermaking machine of the general configuration disclosed in Sanford-Sisson (referenced hereinbefore), either before the predryer, or after the predryer, or even after the Yankee dryer/creping station although the web is preferably creped after the polysiloxane is applied.
The polysiloxane is preferably applied to the wet-web in an aqueous solution, e~ulsion, or suspension. The polysiloxane can also be applied in a solution containing a suitable, nonaqueous solvent, in which the polysiloxane dissolves or with which the polysiloxane is miscible: for example, hexane. The polysiloxane - ' ~330382 may be supplied in neat form or, preferably, emulsified ~ith a suitable surfactant emulsifier. Emulsified polysiloxane is preferable for ease of appl ication since a neat polysiloxane aqueous solution must be agitated.to inhibit separation into S water and polysiloxane phases. The polysiloxane is preferably applied after web formation has been effec~ed. In a typical process, the web is formed and then dewatered prior to polysiloxane application in order to reduce the loss of polysiloxane due to drainage of free water. The polysiloxane is preferably applied to the wet web at a fiber consistency of greater than about 15% in the manufacture of conventionally pressed tissue paper; and to a wet web having a fiber consistency of between about 20% and about 35% in the manufacture of tissue paper in papermaking machines wherein the newly formed web is transferred from a fine mesh Fourdrinier to a relatively coarse imprinting/carrier fabric. This is because it is preferable to make such transfers at su~ficiently low fiber consistencies that the fibers have substantial mobility during the transfer; and it is preferred to apply the polysiloxane after their mobility has substantially dissipated as water removal progresses through the papermaking machine. Also, addition of the polysiloxane at higher fiber consistencies assures greater retention in and on the paper:
i.e., less polysiloxane is lost in the water being drained from the ~eb to increase its fiber consistency.
Methods of applying the polysiloxane to the web include spraying and gravure printing. Spraying, has been found to be economical, and susceptible to accurate control over quantity and distribution of polysiloxane, so is most preferred. Other ~ethods which are less preferred include deposition of the polysiloxane onto a forming wire or fabric which is then contacted by the tissue ~eb; and incorporation o~ the polysiloxane into the furnish prior to web formation. Equipment suitable for spraying polysiloxane containing liquids onto wet ~ebs include external mix, air atomizing nozzles such as the 2 mm noz~le available from V.l.B. Systems, Inc., Tucker, Georgia. Equipment suitable for ~33~3~2 printing polysiloxane containing liquids onto wet webs includes rotogravure printers.
The polysiloxane should be applied uniform~y to the tissue paper web. A uniform distribution is desirable so that substantially the entire sheet benefits fro~ the tactile effect of polysiloxane. Continuous and patterned distributions are both within the scope of the invention and meet the above criteria.
Polysiloxane can be applied to dry paper webs by the same methods previously discusse~ with respect to wet paper web polysiloxane treatments.
.~ .
It has been found, surprisingly, that low levels of polysiloxane applied to tissue paper structures can provide a softened, silky, flannel-like, nongreasy tactile sense of feel without the aid of additional materials such as oils or lotions Importantly, these benefits can be obtained for many of the embodiments of the present invention in combination with high wettability within the ranges desirable for toil~t paper application. Preferably, tissue paper treated ~ith polysiloxane in accordance ~ith the present invention comprises about 2X or less polysiloxane. It is an unexpected benefit of this invention that tissue paper treate~ ~ith about 2% or less polysiloxane can have imparted thereto substa~tial softness and silkiness benefits by such a low level of polysiloxane. In general, tissue paper having less than about 0.3X polysiloxane, preferably less than about 0.2%, can provide substantial increases in softness and silkiness and flannel-like quality yet remain sufficiently wettable for use as toilet paper without requiring the addition of surfactant to offset any negative impact on ~ettability which results from the polysiloxane.
The minimum level of polysiloxane to be retained by the tissue paper is at least an effective level for imparting a tactile difference in softness or silkiness or flannel-like ~,' e ~ ~
~33~38~
qua1ity to the paper. The minimum effective level may vary depending upon the particular type of sheet, the method of application, the particular type of polysiloxane, and whether the . polysiloxane is supplemented by starch, surfactant7 or other S add;tives or treatments. Without limiting the range o~ applicable polysiloxane retention by the tissue paper, preferably at least about 0.004~, more preferably at least about 0.91%, even more preferably at least about 0.05%, and most preferably at least about O.lX polysiloxane is retained by the tissue paper.
Preferably, a sufficient amount of polysiloxane to impart a tactile sense of softness is disposed in both surfaces of the tissue paper: i.e., disposed on the outwardly facing surfaces of the surface-level fibers. When polysiloxane is applied to one surface of the tissue paper, some of it will, generally, at least partially penetrate to the tissue paper interior. ~n a -preferred embodiment, sufficient polysiloxane to effect a tact;l-è response penetrates through the entire thickness of the tissue paper such that both surfaces have imparted ~hereto the benefits of polysiloxane. One method found to be useful for facilitating polysiloxane penetration to the opposing surface when the polysiloxane is applied to one surface of a wet tissue paper web is to vacuu~ dewater the tissue paper from the other surface of the wet tissue paper at the point of application of the polysiloxane.
In addition to treating tissue paper with polysiloxane as described abcve, it has been found desirable to also treat such tissue paper ~ith surfactant material. This is in addition to any surfactant material that may be present as an emulsifying agent for the polysiloxane. ~ .
Tissue paper having in excess o~ about 0.3Z polysilox~ne is preferably treated with surfactant when contemplated for US@S
wherein high wettability is desired. Most preferably, a non~
cationic surfactant is applied to the wet tissue paper web, in order to ~btain an additional softness benefit, on a constant ~ 3 3 0 3 8 ~ ::
tensile basis, as previously discussed. The amount of surfactant required to increase hydrophilicity to a desired leYel will depend upon the type and level of polysiloxane and the type of surfac~
tant. However, as a general guideline, between about 0.01~ and about 2% surfactant retained by the tissue paper, preferably between about 0.05% and about 0.5%, is believed to be sufficient to provide sufficiently high wettability for most applications, including toilet paper, for polysiloxane levels of about ~% or less. However, the benefit of increased wettability is applicable for polysiloxane levels well in excess of 2%, if a sufficient amount of surfactant is incorporated in the tissue paper.
. - ~
Surfactants which are preferred for use in the present invention are noncationic; and, more preferably, are nonionic.
~owever, cationic surfactants may be used. Noncationic surfactants include anionic, nonionic, amphoteric, and zwitterionic surfactants. Preferably, as stated hereinbefore, the surfactant is substantially nonmigratory in situ after the tissue paper has been manufactured in order to substantially obviate post-manufacturing changes in the tissue paper's properties which mi~ht otherwise result from the inclusion of surfactant. This may be achieved, for instance, through the use of surfactants having melt temperatures greater than the temperatures com~only encountered during storage, shipping, merchandising, and use of tissue paper product embodiments of the invention: for exa~ple, melt temperatures of about 50C or higher. Also, the surfactant is preferably water-soluble when applied to the wet web. ~;
The level of noncationic surfactant applied to wet tissue paper webs to provid~ the afore~entioned softness/tensile benefit ranges from the minimum effective level needed for imparting such benefit, on a constant tensile basis for the end product, to about two (2) percent: preferably between about 0.01% and about 1%
noncationic surfactant retained by the web; more preferably, between about 0.01% and about 0.5%; and, most preferably, between -about 0.05X and about 0.3X.
"', ,"...... '~.':'; ,~
.' .~ ~ . ''', ':~' ....
1~30382 The surfactants preferably have alkyl chains with eight or more carbon atoms. Exemplary anionic surfactants are linear alkyl sulfonates, and alkylbenzene sulfonates. Exemplary nonionic surfactants are alkylglycosides including alkylglycoside esters such as CrodestaTM SL-40 which is available from Croda, Inc. (New York, NY)i alkylglycoside ethers as described in U. S. Patent 4,011,389, issued to W. K. langdon, et al. on March 8, 1977; and .alkylpolyethoxylated esters such as PegosperseTM 200 ML available from Glyco Chemicals, Inc. (Greenwich, CT). The above listings of exemplary surfactants are intended to be merely exemplary in nature, and are not meant to limit the scope of the invent;on.
The surfactant, in addition to any emulsifying surfactant that may be present on the polysiloxane, may be applied by the same methods and apparatuses used to apply polysiloxanes. These methods include spraying and gravure printing. Other methods include application to a forming wire or fabric prior tc`contact with the web. Any surfactant other than polysiloxane emulsifying surfactant material, is hereinafter referred to as ~surfactant~W
and any surfactant present as the emulsifying component of emulsified polysiloxane is hereinafter referred to as ~emulsifying agent~.
The surfactant, may be applied to the tissue paper simultane-ously with, after, or before the polysiloxane. In a typical process, the surfactant is applied subsequent to formation of the wet web and prior to final drying. Preferably, noncationic surfactants are applied at fiber consistency levels of between about 10% and about 75X; and, more preferably, between about 15X
and about 35%. Surprisingly, retention rates of noncationic surfactant applied to wet webs are high even though the surfactant is applied under conditions wherein it is not ionically sub-stantive to the f;bers. Retention rates in excess of about 90X
are expected at the preferred fiber consistencies without the utili2ation of chemical retention aids.
".'` ~" '~.' -' ~ 33~2 As stated hereinbefore, it is also desirable to treat polysiloxane containing tissue paper with a relatively low level of a binder such as starch for lint control. Preferably, the tissue paper is treated with an aqueous solution of starch and, also preferably, the sheet is moist at the time of application.
In addition to reducing linting of the finished tissue paper product, low levels of starch also imparts a modest improvement in the tensile strength of tissue paper ~ithout imparting boardiness (i.e., stiffness) ~hich would result from additions of high levels of starch. A7so, this provides tissue paper having improved strength/softness relationship compared to tissue paper which has been strengthened by traditional methods of increasing tensile strength: for example, sheets having increased tensile strength due to increased refining of the pulp; or through the addition of other dry strength additives. This result is especially surprising since starch has traditionally been used to build strength at the expense of softness in applications wherein softness is not an- important characteristic: for example, paperboard. Additionally, parenthetically, starch has been used as a filler for printing and writing paper to improve surface printability.
In general, suitable starch for practicing the present invention is characterized by water solubility, and hydrophilicity. Exemplary starch materials include corn starch and potato starch, albeit it is not intended to thereby limit the scope of suitable starch materials; and waxy corn starch that is known industrially as amioca starch is particularly preferred.
Amioca starch differs from common corn starch in that it is entirely amylopeetin, whereas common corn starch contains both amplopectin and amylose. Various unique characteristics uf amioca starch are further described in ~Amioca - The Starch From ~axy Corn~ H. H. Schopmeyer, Food Industries, December 1945, pp.
106-108 (Vol. pp. 147~-1478).
~33~382 - ~ ::
The starch can be in granular or dispersed for~ albeit granular form is preferred. The starch is preferably sufficiently cooked to induce swelling of the granules. More preferably, the starch ~ranules are swollen, as by cooking, to a point just prior to dispersion of the starch granule. Such highly swo11en starch granules shall be referred to as being ~fully cooked.- The conditions for dispersion in general can vary depending upon the size of the starch granules, the degree of crystallinity of the granules, and the amount of amylose present. Fully cooked amioca starch, for examp1e, can be prepared by heating an aqueous slurry of about 4X consistency of starch granules at about l90-F (about 88-C) for between about 30 and about 40 minutes.
Other exe~plary starch materials which may be used include modified cationic starches such as those modified to have nitrogen containing groups such as amino groups and methylol groups attached to nitrogen, available from National Starch and Chemical Company, (Bridgewater, New Jersey). Such modified starch materials have heretofore been used primarily 2S a pulp furnish additive to increase wet and/or dry strength. However when applied in accordance ~ith this invention by application to a wet tissue paper web they may have reduced effect on wet strength relative to wet-end addition of the same modified starch materials. Considering that such modified starch ~aterials are more expensive than unmodified starches, the latter have generally been preferred.
The starch should be applied to the tissue paper while the paper is in a moist condition. The starch based material is added to the tissue paper web, preferably when the web has a fiber consistency of about 80X or less. Non-cationic starch ~ateria1s are sufficiently retained in the web to provide an observable effect on softness at a particular strength level relative to in~
creased refining; and, are preferably applied to wet tissue ~ebs having fiber consistencies between about 15X and about 80%.
~ 3 ~
Starch is preferably applied to tissue paper webs in an aqueous solution. Methods o~ application include, the same pre-viously described with reference to application of polysiloxane:
preferably by spraying; and, less preferably, by printing. The starch may be applied to the tissue pap~r web simultaneously with, prior to, or subsequent ~o the addition of polysiloxane and/or surfactant.
At least an effective amount of starch to provide lint control and concomitant strength increase upon drying relative to a non-starch treated but otherwise identical sheet is preferably appl ied to the sheet. Preferably, between about O.OlX and about 2.0% of starch is retained in the dried sheet, calculated on a dry fiber weight basis; and, more preferably, between about 0.2X and about 1.0% of starch-based material is retained.
Analysis of the amounts of treatment chemicals herein re-tained on tissue paper webs can be performed by any method accepted in the applicable art. For example, the level of poly-siloxane retained by the tissue paper can be determined by solvent extraction of the polysiloxane ~ith an organic solvent followed by atomic absorption spectroscopy to determine the level of silicon in the extract; the level of nonionic surfactants, such as alkylglycosides, can be determined by extraction in an organic solvent followed by gas chromatography to detenmine the leYel of surfactant in the extract; the level o~ anionic surfaetants, such as linear alkyl sulfonates, can be determined by water extraction followed by colorimetry analysis of the extract; the level of starch can be determined by amylase digestion of the starch to ~lucose followed by colorimetry analysis to determine glucose level. These methods are exemplary, and are not meant to exclude other methods ~hich may be useful for determining levels of particular components retained by the tissue paper.
~33~38~
Hydrophilicity of tissue paper refers, in general, to the propensity of the tissue paper to be ~etted with water.
Hydrophilicity of tissue paper may be somewhat quantified by . determining the period of time required for dry tissue paper to S become completely wetted with water. This period of time is referred to as ~wetting time.~ In order to provide a consistent and repeatable test ~or wetting time, the fol10wing procedure may be used for wetting time determinations: first, a dry (greater than 90% fiber consistency level) sample uni~ sheet, approximately 4-3/8 inch x 4-3/4 inch (about 11.1 sm x 12 cm) of tissue paper structure is pro~ided; second, the sheet is ~olded into four (4) juxtaposed quarters, and then crumpled into a ball approximately 0.75 inches (about 1.9 cm) to about 1 inch (about 2.5 em) in diameter; third, the balled sheet is placed on the surface of a body of distilled water at 72-F (about 22-C), and a timer is simultaneously started; fourth, the timer is stopped and read when wetting of the balled sheet is completed. Complete wetting is observed visually.
The preferred hydrophilicity of tissue paper depends upon its intended end use. It is desirable for tissue paper used in a variety of applications, e.g., toilet paper, to completely ~et in a relatively short period of time to prevent clogging once the toilet is flushed. Preferably, wetting time is 2 minutes or less More preferably, wetting time is 30 seconds or less. Most preferably, wetting time is 10 seconds or less.
Hydrophi1icity characters of tissue paper embodiments of the present invention may, of course, be determined immediately after manufacture. However, substantial increases in hydrophobicity may occur during the first two weeks after the tiss~e paper is made~
i.e., after the paper has aged two (2) weeks following its manufacture. Thus, the above stated wetting times are preferably measured at the end of such two week period. Accordingly, wetting times measured at the end of a two week aging period at room temperature are referred to as ~two week wetting times.~
.
-~. 2~
~330~82 The density of tissue paper, as that tenm is used herein, is the average density calculated as the basis weight of that paper diYided by the caliper, with the appropriate unit conversions i~ncorporated therein. Caliper of the tissue paper, as used herein, is the thi ckness of the paper when subjeeted to a ~:
compressive load of 95 g/jn2 (15.5 g/cm2).
~HAT IS CLAIMED IS:
"'~
unsubstituted alkyl or aryl radical, and Rlo is any substituted Cl ;~
- Clo alkyl or aryl radical. Preferably each Rl - Rg radical is independently any Cl - C4 unsubstitu~ed alkyl group. Those ; `
skilled in the art will recognize that technically there is no ~ ~ ;
l3 ~330382 difference ~hether, for example, Rg or Rlo is the substituted radical. Preferably the mole ratio of b to (a + b) is between 0 and about 20%, more preferably between 0 and about 10%, and most preferably between about I~ and about 5X.
In one particularly preferred embodiment, Rl - Rg are methyl groups and Rlo is à substituted or unsubsti~uted alkyl, aryl, or alkenyl group. Such material shall be generally described herein as polydimethylsiloxane which has a particular functionality as may be appropriate in that particular case. Exe~plary polydi-methylsiloxanes include, for example, polydimethyls;loxane?
polydimethylsiloxane having an alkyl hydrocarbon Rlo radical and polydimethylsiloxane having one or more a~ino, carboxyl, hydroxyl, ether, polyether, aldehyde, ketone, amide, ester, thiol and/or other RIo functionalities including alkyl and alkenyl ~nalogues of such functionalities. For example, an amino functional alkyl groue as Rlo could be an amino-functional or an a~inoalkyl-functional polydimethylsiloxane. The exemplary listing of these - polydimethylsiloxanes is not meant to thereby exclude others not specifically listed.
Viscosity of polysiloxanes useful for this invention may vary as widely as the viscosity of polysiloxanes in general vary, so long as the polysiloxane is flo~able or can be made to be flowable for application to the tissue paper. This includes, but is not limited to, viscosity as low as about 25 centistokes to about 20,000,000 centistokes or even higher. High ~iscosity poly~
siloxanes which themselves are resistant to flowing can be effectively deposited upon the tissue paper webs by such m*thods as, for example, emulsifying the pol~siloxane in surfactant or providing the polysiloxane in soluticn with the aid of a solvent, such as hexane, listed for exe~plary purposes only. Particular methods for applying polysiloxanes to tissue paper webs are discussed in more detail below.
13303~2 Parenthetically, while not wishing to be bound by a theory of operation, it is believed that the tactile-benefit efficacy of the polysiloxane is directly related to its average molecular weight;
and that viscosity is directly related to molecular weight.
Accordingly, due to the relative difficulty of directly determining molecular weights of polysiloxanes as compared to determining their viscosities, viscosity is used herein as the apparent operative parameter with respect to imparting enhanced tactile response to tissue paper: i.e., softness, silkiness, and flannel-like.
References disclosing polysiloxanes include U. S. Patent 2,826,551, issued March 11, 1958 to Geen; U. S. Patent 3,964,500, issued June 22, 197~ to Drakoff; U.S. Patent ~,364,837, issued December 21, 1982 to Pader; and British Patent 849,433, published September 28, 1960 to ~oolston. Also, Silicon Co~npounds, pp.
181-217, distributed by Petrarch Systems, Inc., -1984, contàins an extensive listing and description of polysiloxanes in general. ~ -:. - - . . .
The polysiloxane can be applied to tissue paper as it is being made on a papermaking machine or thereafter: either while it is wet (i.e., prior to final drying) or dry (i.e., a~ter final drying). Preferably, an aqueous mixture containing the poly~
siloxane is sprayed onto the tissue paper as it courses through the papermaking machine: for example, and not by way of limitation, referring to a papermaking machine of the general configuration disclosed in Sanford-Sisson (referenced hereinbefore), either before the predryer, or after the predryer, or even after the Yankee dryer/creping station although the web is preferably creped after the polysiloxane is applied.
The polysiloxane is preferably applied to the wet-web in an aqueous solution, e~ulsion, or suspension. The polysiloxane can also be applied in a solution containing a suitable, nonaqueous solvent, in which the polysiloxane dissolves or with which the polysiloxane is miscible: for example, hexane. The polysiloxane - ' ~330382 may be supplied in neat form or, preferably, emulsified ~ith a suitable surfactant emulsifier. Emulsified polysiloxane is preferable for ease of appl ication since a neat polysiloxane aqueous solution must be agitated.to inhibit separation into S water and polysiloxane phases. The polysiloxane is preferably applied after web formation has been effec~ed. In a typical process, the web is formed and then dewatered prior to polysiloxane application in order to reduce the loss of polysiloxane due to drainage of free water. The polysiloxane is preferably applied to the wet web at a fiber consistency of greater than about 15% in the manufacture of conventionally pressed tissue paper; and to a wet web having a fiber consistency of between about 20% and about 35% in the manufacture of tissue paper in papermaking machines wherein the newly formed web is transferred from a fine mesh Fourdrinier to a relatively coarse imprinting/carrier fabric. This is because it is preferable to make such transfers at su~ficiently low fiber consistencies that the fibers have substantial mobility during the transfer; and it is preferred to apply the polysiloxane after their mobility has substantially dissipated as water removal progresses through the papermaking machine. Also, addition of the polysiloxane at higher fiber consistencies assures greater retention in and on the paper:
i.e., less polysiloxane is lost in the water being drained from the ~eb to increase its fiber consistency.
Methods of applying the polysiloxane to the web include spraying and gravure printing. Spraying, has been found to be economical, and susceptible to accurate control over quantity and distribution of polysiloxane, so is most preferred. Other ~ethods which are less preferred include deposition of the polysiloxane onto a forming wire or fabric which is then contacted by the tissue ~eb; and incorporation o~ the polysiloxane into the furnish prior to web formation. Equipment suitable for spraying polysiloxane containing liquids onto wet ~ebs include external mix, air atomizing nozzles such as the 2 mm noz~le available from V.l.B. Systems, Inc., Tucker, Georgia. Equipment suitable for ~33~3~2 printing polysiloxane containing liquids onto wet webs includes rotogravure printers.
The polysiloxane should be applied uniform~y to the tissue paper web. A uniform distribution is desirable so that substantially the entire sheet benefits fro~ the tactile effect of polysiloxane. Continuous and patterned distributions are both within the scope of the invention and meet the above criteria.
Polysiloxane can be applied to dry paper webs by the same methods previously discusse~ with respect to wet paper web polysiloxane treatments.
.~ .
It has been found, surprisingly, that low levels of polysiloxane applied to tissue paper structures can provide a softened, silky, flannel-like, nongreasy tactile sense of feel without the aid of additional materials such as oils or lotions Importantly, these benefits can be obtained for many of the embodiments of the present invention in combination with high wettability within the ranges desirable for toil~t paper application. Preferably, tissue paper treated ~ith polysiloxane in accordance ~ith the present invention comprises about 2X or less polysiloxane. It is an unexpected benefit of this invention that tissue paper treate~ ~ith about 2% or less polysiloxane can have imparted thereto substa~tial softness and silkiness benefits by such a low level of polysiloxane. In general, tissue paper having less than about 0.3X polysiloxane, preferably less than about 0.2%, can provide substantial increases in softness and silkiness and flannel-like quality yet remain sufficiently wettable for use as toilet paper without requiring the addition of surfactant to offset any negative impact on ~ettability which results from the polysiloxane.
The minimum level of polysiloxane to be retained by the tissue paper is at least an effective level for imparting a tactile difference in softness or silkiness or flannel-like ~,' e ~ ~
~33~38~
qua1ity to the paper. The minimum effective level may vary depending upon the particular type of sheet, the method of application, the particular type of polysiloxane, and whether the . polysiloxane is supplemented by starch, surfactant7 or other S add;tives or treatments. Without limiting the range o~ applicable polysiloxane retention by the tissue paper, preferably at least about 0.004~, more preferably at least about 0.91%, even more preferably at least about 0.05%, and most preferably at least about O.lX polysiloxane is retained by the tissue paper.
Preferably, a sufficient amount of polysiloxane to impart a tactile sense of softness is disposed in both surfaces of the tissue paper: i.e., disposed on the outwardly facing surfaces of the surface-level fibers. When polysiloxane is applied to one surface of the tissue paper, some of it will, generally, at least partially penetrate to the tissue paper interior. ~n a -preferred embodiment, sufficient polysiloxane to effect a tact;l-è response penetrates through the entire thickness of the tissue paper such that both surfaces have imparted ~hereto the benefits of polysiloxane. One method found to be useful for facilitating polysiloxane penetration to the opposing surface when the polysiloxane is applied to one surface of a wet tissue paper web is to vacuu~ dewater the tissue paper from the other surface of the wet tissue paper at the point of application of the polysiloxane.
In addition to treating tissue paper with polysiloxane as described abcve, it has been found desirable to also treat such tissue paper ~ith surfactant material. This is in addition to any surfactant material that may be present as an emulsifying agent for the polysiloxane. ~ .
Tissue paper having in excess o~ about 0.3Z polysilox~ne is preferably treated with surfactant when contemplated for US@S
wherein high wettability is desired. Most preferably, a non~
cationic surfactant is applied to the wet tissue paper web, in order to ~btain an additional softness benefit, on a constant ~ 3 3 0 3 8 ~ ::
tensile basis, as previously discussed. The amount of surfactant required to increase hydrophilicity to a desired leYel will depend upon the type and level of polysiloxane and the type of surfac~
tant. However, as a general guideline, between about 0.01~ and about 2% surfactant retained by the tissue paper, preferably between about 0.05% and about 0.5%, is believed to be sufficient to provide sufficiently high wettability for most applications, including toilet paper, for polysiloxane levels of about ~% or less. However, the benefit of increased wettability is applicable for polysiloxane levels well in excess of 2%, if a sufficient amount of surfactant is incorporated in the tissue paper.
. - ~
Surfactants which are preferred for use in the present invention are noncationic; and, more preferably, are nonionic.
~owever, cationic surfactants may be used. Noncationic surfactants include anionic, nonionic, amphoteric, and zwitterionic surfactants. Preferably, as stated hereinbefore, the surfactant is substantially nonmigratory in situ after the tissue paper has been manufactured in order to substantially obviate post-manufacturing changes in the tissue paper's properties which mi~ht otherwise result from the inclusion of surfactant. This may be achieved, for instance, through the use of surfactants having melt temperatures greater than the temperatures com~only encountered during storage, shipping, merchandising, and use of tissue paper product embodiments of the invention: for exa~ple, melt temperatures of about 50C or higher. Also, the surfactant is preferably water-soluble when applied to the wet web. ~;
The level of noncationic surfactant applied to wet tissue paper webs to provid~ the afore~entioned softness/tensile benefit ranges from the minimum effective level needed for imparting such benefit, on a constant tensile basis for the end product, to about two (2) percent: preferably between about 0.01% and about 1%
noncationic surfactant retained by the web; more preferably, between about 0.01% and about 0.5%; and, most preferably, between -about 0.05X and about 0.3X.
"', ,"...... '~.':'; ,~
.' .~ ~ . ''', ':~' ....
1~30382 The surfactants preferably have alkyl chains with eight or more carbon atoms. Exemplary anionic surfactants are linear alkyl sulfonates, and alkylbenzene sulfonates. Exemplary nonionic surfactants are alkylglycosides including alkylglycoside esters such as CrodestaTM SL-40 which is available from Croda, Inc. (New York, NY)i alkylglycoside ethers as described in U. S. Patent 4,011,389, issued to W. K. langdon, et al. on March 8, 1977; and .alkylpolyethoxylated esters such as PegosperseTM 200 ML available from Glyco Chemicals, Inc. (Greenwich, CT). The above listings of exemplary surfactants are intended to be merely exemplary in nature, and are not meant to limit the scope of the invent;on.
The surfactant, in addition to any emulsifying surfactant that may be present on the polysiloxane, may be applied by the same methods and apparatuses used to apply polysiloxanes. These methods include spraying and gravure printing. Other methods include application to a forming wire or fabric prior tc`contact with the web. Any surfactant other than polysiloxane emulsifying surfactant material, is hereinafter referred to as ~surfactant~W
and any surfactant present as the emulsifying component of emulsified polysiloxane is hereinafter referred to as ~emulsifying agent~.
The surfactant, may be applied to the tissue paper simultane-ously with, after, or before the polysiloxane. In a typical process, the surfactant is applied subsequent to formation of the wet web and prior to final drying. Preferably, noncationic surfactants are applied at fiber consistency levels of between about 10% and about 75X; and, more preferably, between about 15X
and about 35%. Surprisingly, retention rates of noncationic surfactant applied to wet webs are high even though the surfactant is applied under conditions wherein it is not ionically sub-stantive to the f;bers. Retention rates in excess of about 90X
are expected at the preferred fiber consistencies without the utili2ation of chemical retention aids.
".'` ~" '~.' -' ~ 33~2 As stated hereinbefore, it is also desirable to treat polysiloxane containing tissue paper with a relatively low level of a binder such as starch for lint control. Preferably, the tissue paper is treated with an aqueous solution of starch and, also preferably, the sheet is moist at the time of application.
In addition to reducing linting of the finished tissue paper product, low levels of starch also imparts a modest improvement in the tensile strength of tissue paper ~ithout imparting boardiness (i.e., stiffness) ~hich would result from additions of high levels of starch. A7so, this provides tissue paper having improved strength/softness relationship compared to tissue paper which has been strengthened by traditional methods of increasing tensile strength: for example, sheets having increased tensile strength due to increased refining of the pulp; or through the addition of other dry strength additives. This result is especially surprising since starch has traditionally been used to build strength at the expense of softness in applications wherein softness is not an- important characteristic: for example, paperboard. Additionally, parenthetically, starch has been used as a filler for printing and writing paper to improve surface printability.
In general, suitable starch for practicing the present invention is characterized by water solubility, and hydrophilicity. Exemplary starch materials include corn starch and potato starch, albeit it is not intended to thereby limit the scope of suitable starch materials; and waxy corn starch that is known industrially as amioca starch is particularly preferred.
Amioca starch differs from common corn starch in that it is entirely amylopeetin, whereas common corn starch contains both amplopectin and amylose. Various unique characteristics uf amioca starch are further described in ~Amioca - The Starch From ~axy Corn~ H. H. Schopmeyer, Food Industries, December 1945, pp.
106-108 (Vol. pp. 147~-1478).
~33~382 - ~ ::
The starch can be in granular or dispersed for~ albeit granular form is preferred. The starch is preferably sufficiently cooked to induce swelling of the granules. More preferably, the starch ~ranules are swollen, as by cooking, to a point just prior to dispersion of the starch granule. Such highly swo11en starch granules shall be referred to as being ~fully cooked.- The conditions for dispersion in general can vary depending upon the size of the starch granules, the degree of crystallinity of the granules, and the amount of amylose present. Fully cooked amioca starch, for examp1e, can be prepared by heating an aqueous slurry of about 4X consistency of starch granules at about l90-F (about 88-C) for between about 30 and about 40 minutes.
Other exe~plary starch materials which may be used include modified cationic starches such as those modified to have nitrogen containing groups such as amino groups and methylol groups attached to nitrogen, available from National Starch and Chemical Company, (Bridgewater, New Jersey). Such modified starch materials have heretofore been used primarily 2S a pulp furnish additive to increase wet and/or dry strength. However when applied in accordance ~ith this invention by application to a wet tissue paper web they may have reduced effect on wet strength relative to wet-end addition of the same modified starch materials. Considering that such modified starch ~aterials are more expensive than unmodified starches, the latter have generally been preferred.
The starch should be applied to the tissue paper while the paper is in a moist condition. The starch based material is added to the tissue paper web, preferably when the web has a fiber consistency of about 80X or less. Non-cationic starch ~ateria1s are sufficiently retained in the web to provide an observable effect on softness at a particular strength level relative to in~
creased refining; and, are preferably applied to wet tissue ~ebs having fiber consistencies between about 15X and about 80%.
~ 3 ~
Starch is preferably applied to tissue paper webs in an aqueous solution. Methods o~ application include, the same pre-viously described with reference to application of polysiloxane:
preferably by spraying; and, less preferably, by printing. The starch may be applied to the tissue pap~r web simultaneously with, prior to, or subsequent ~o the addition of polysiloxane and/or surfactant.
At least an effective amount of starch to provide lint control and concomitant strength increase upon drying relative to a non-starch treated but otherwise identical sheet is preferably appl ied to the sheet. Preferably, between about O.OlX and about 2.0% of starch is retained in the dried sheet, calculated on a dry fiber weight basis; and, more preferably, between about 0.2X and about 1.0% of starch-based material is retained.
Analysis of the amounts of treatment chemicals herein re-tained on tissue paper webs can be performed by any method accepted in the applicable art. For example, the level of poly-siloxane retained by the tissue paper can be determined by solvent extraction of the polysiloxane ~ith an organic solvent followed by atomic absorption spectroscopy to determine the level of silicon in the extract; the level of nonionic surfactants, such as alkylglycosides, can be determined by extraction in an organic solvent followed by gas chromatography to detenmine the leYel of surfactant in the extract; the level o~ anionic surfaetants, such as linear alkyl sulfonates, can be determined by water extraction followed by colorimetry analysis of the extract; the level of starch can be determined by amylase digestion of the starch to ~lucose followed by colorimetry analysis to determine glucose level. These methods are exemplary, and are not meant to exclude other methods ~hich may be useful for determining levels of particular components retained by the tissue paper.
~33~38~
Hydrophilicity of tissue paper refers, in general, to the propensity of the tissue paper to be ~etted with water.
Hydrophilicity of tissue paper may be somewhat quantified by . determining the period of time required for dry tissue paper to S become completely wetted with water. This period of time is referred to as ~wetting time.~ In order to provide a consistent and repeatable test ~or wetting time, the fol10wing procedure may be used for wetting time determinations: first, a dry (greater than 90% fiber consistency level) sample uni~ sheet, approximately 4-3/8 inch x 4-3/4 inch (about 11.1 sm x 12 cm) of tissue paper structure is pro~ided; second, the sheet is ~olded into four (4) juxtaposed quarters, and then crumpled into a ball approximately 0.75 inches (about 1.9 cm) to about 1 inch (about 2.5 em) in diameter; third, the balled sheet is placed on the surface of a body of distilled water at 72-F (about 22-C), and a timer is simultaneously started; fourth, the timer is stopped and read when wetting of the balled sheet is completed. Complete wetting is observed visually.
The preferred hydrophilicity of tissue paper depends upon its intended end use. It is desirable for tissue paper used in a variety of applications, e.g., toilet paper, to completely ~et in a relatively short period of time to prevent clogging once the toilet is flushed. Preferably, wetting time is 2 minutes or less More preferably, wetting time is 30 seconds or less. Most preferably, wetting time is 10 seconds or less.
Hydrophi1icity characters of tissue paper embodiments of the present invention may, of course, be determined immediately after manufacture. However, substantial increases in hydrophobicity may occur during the first two weeks after the tiss~e paper is made~
i.e., after the paper has aged two (2) weeks following its manufacture. Thus, the above stated wetting times are preferably measured at the end of such two week period. Accordingly, wetting times measured at the end of a two week aging period at room temperature are referred to as ~two week wetting times.~
.
-~. 2~
~330~82 The density of tissue paper, as that tenm is used herein, is the average density calculated as the basis weight of that paper diYided by the caliper, with the appropriate unit conversions i~ncorporated therein. Caliper of the tissue paper, as used herein, is the thi ckness of the paper when subjeeted to a ~:
compressive load of 95 g/jn2 (15.5 g/cm2).
~HAT IS CLAIMED IS:
"'~
Claims (20)
1. Tissue paper having a basis weight of from about 10 to about 65 grams per square meter, and density of about 0.6 grams or less per cubic centimeter, said paper comprising cellulosic fibers and a quantity of a polysiloxane material, said quantity of polysiloxane being at least about 0.004%
polysiloxane based on the dry fiber weight of said tissue paper.
polysiloxane based on the dry fiber weight of said tissue paper.
2. The tissue paper of Claim 1 wherein said effective amount of polysiloxane is from about 0.004% to about 2% polysiloxane based on the dry fiber weight of said tissue paper.
3. The tissue paper of Claim 1 wherein said effective amount of polysiloxane is from about 0.004% to about 0.3% polysiloxane based on the dry fiber weight of said tissue paper.
4. The tissue paper of Claim 1 wherein said polysiloxane is polydimethylpolysiloxane having a hydrogen bonding functional group selected from the groups consisting of amino, carboxyl, hydroxyl, ether, polyether, aldehyde, ketone, amide, ester, and thiol groups, said hydrogen bonding functional group being present in a molar percentage of substitution of about 20% or less.
5. The tissue paper of Claim 4 wherein said polysiloxane has a molar percentage of substitution of about 10% or less, and a viscosity of about 25 centistokes or more.
6. The tissue paper of Claim 4 wherein said polysiloxane has a molar percentage of substitution of from about 1.0 to about 5%, and a viscosity of from about 25 centistokes to about 20,000,000 centistokes.
7. The tissue paper of Claim 4 wherein said molar percentage of substitution is about 2%, and said viscosity is about 125 centistokes.
8. The tissue paper of Claim 1 further comprising a sufficient quantity of a surfactant material to ensure that said tissue paper, after aging two weeks after its manufacture, has a wetting time of about 2 minutes or less.
9. The tissue paper of Claim 8 wherein said quantity of said surfactant is sufficient to ensure that two-week-aged said tissue paper has a wetting time of about 30 seconds or less.
10. The tissue paper of Claim 1 further comprising a quantity of surfactant material, said quantity being between about 0.01%
and about 2% based on the dry fiber weight of said tissue paper.
and about 2% based on the dry fiber weight of said tissue paper.
11. The tissue paper of Claim 10 wherein said quantity of said surfactant is from about 0.05% to about 0.5% based on the dry fiber weight of said tissue paper.
12. The tissue paper of Claim 1 or 10 wherein said surfactant material is noncationic.
13. The tissue paper of Claim 1 or 10 wherein said surfactant has a melting point of at least about 50°C.
14. The tissue paper of Claim 1, 8 or 10 further comprising an effective measure of a binder material to at least partially offset any reduction of tensile strength or increase in linting propensity of said tissue paper which would otherwise result from the incorporation of said polysiloxane and, if present, said surfactant.
15. The tissue paper of Claim 14 wherein said binder material is starch.
16. The tissue paper of Claim 15 wherein said effective measure of said starch is between about 0.01% and about 2% based on the dry fiber weight of said tissue paper.
17. The tissue paper of Claim 2 or 3 further comprising a quantity of a surfactant, said quantity being between about 0.01% and about 0.5% based on the dry fiber weight of said tissue paper.
18. The tissue paper of Claim 17 further comprising an effective measure of a binder material to at least partially offset any reduction of tensile strength or increase in linting propensity of said tissue paper which would otherwise result from the incorporation of said polysiloxane and, if present, said surfactant.
19. The tissue paper of Claim 18 wherein said binder material is starch.
20. The tissue paper of Claim 19 wherein said effective measure of said starch is between about 0.01% and. about 2% based on the dry fiber weight of said tissue paper.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US20662188A | 1988-06-14 | 1988-06-14 | |
| US206,621 | 1988-06-14 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1330382C true CA1330382C (en) | 1994-06-28 |
Family
ID=22767195
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000602759A Expired - Lifetime CA1330382C (en) | 1988-06-14 | 1989-06-14 | Soft tissue paper |
Country Status (12)
| Country | Link |
|---|---|
| EP (1) | EP0347154B1 (en) |
| JP (1) | JP2806974B2 (en) |
| KR (1) | KR0140223B1 (en) |
| AT (1) | ATE132556T1 (en) |
| AU (1) | AU634963B2 (en) |
| BR (1) | BR8902848A (en) |
| CA (1) | CA1330382C (en) |
| DE (1) | DE68925309T2 (en) |
| ES (1) | ES2081303T3 (en) |
| GR (1) | GR3018609T3 (en) |
| MX (2) | MX170318B (en) |
| NZ (1) | NZ229550A (en) |
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|---|---|---|---|---|
| BR8902858A (en) * | 1989-01-19 | 1990-09-25 | Procter & Gamble | PROCESS TO MAKE SOFT SILK PAPER |
| US4950545A (en) * | 1989-02-24 | 1990-08-21 | Kimberly-Clark Corporation | Multifunctional facial tissue |
| US6080686A (en) * | 1993-01-19 | 2000-06-27 | Th. Goldschmidt Ag | Soft cellulosic nonwovens and a method for softening nonwovens |
| US5449551A (en) * | 1993-06-03 | 1995-09-12 | Kawano Paper Co., Ltd. | Highly water absorbent fibrous web and a process for producing the same |
| JP3297340B2 (en) * | 1997-02-13 | 2002-07-02 | 河野製紙株式会社 | Paper products |
| DE19711452A1 (en) | 1997-03-19 | 1998-09-24 | Sca Hygiene Paper Gmbh | Moisture regulator-containing composition for tissue products, process for the production of these products, use of the composition for the treatment of tissue products and tissue products in the form of wetlaid, including TAD or airlaid (non-woven) based on flat carrier materials predominantly containing cellulose fibers |
| DE19963835C2 (en) * | 1999-12-30 | 2002-03-28 | Sca Hygiene Prod Gmbh | Process for the application of treatment chemicals to sheet-like fiber-based products, in particular tissue, and products made therewith |
| DE19963834C2 (en) * | 1999-12-30 | 2002-03-28 | Sca Hygiene Prod Gmbh | Process for applying treatment chemicals to a flat fiber-based product and products made therewith |
| JP3456956B2 (en) * | 2000-08-10 | 2003-10-14 | 株式会社飾一 | Fiber coating material and coating liquid used for it |
| US6905697B2 (en) | 2001-01-19 | 2005-06-14 | Sca Hygiene Products Gmbh | Lotioned fibrous web having a short water absorption time |
| US6860967B2 (en) | 2001-01-19 | 2005-03-01 | Sca Hygiene Products Gmbh | Tissue paper penetrated with softening lotion |
| US6432270B1 (en) | 2001-02-20 | 2002-08-13 | Kimberly-Clark Worldwide, Inc. | Soft absorbent tissue |
| JP3950400B2 (en) | 2001-10-24 | 2007-08-01 | 河野製紙株式会社 | Fiber web product and method for producing the same |
| US6582558B1 (en) | 2001-11-15 | 2003-06-24 | Kimberly-Clark Worldwide, Inc. | Soft absorbent tissue containing hydrophilic polysiloxanes |
| US6599393B1 (en) | 2001-11-15 | 2003-07-29 | Kimberly-Clark Worldwide, Inc. | Soft absorbent tissue containing hydrophilically-modified amino-functional polysiloxanes |
| US6511580B1 (en) | 2001-11-15 | 2003-01-28 | Kimberly-Clark Worldwide, Inc. | Soft absorbent tissue containing derivitized amino-functional polysiloxanes |
| US6514383B1 (en) | 2001-11-15 | 2003-02-04 | Kimberly-Clark Worldwide, Inc. | Soft absorbent tissue containing derivitized amino-functional polysiloxanes |
| US6576087B1 (en) | 2001-11-15 | 2003-06-10 | Kimberly-Clark Worldwide, Inc. | Soft absorbent tissue containing polysiloxanes |
| US20040084164A1 (en) * | 2002-11-06 | 2004-05-06 | Shannon Thomas Gerard | Soft tissue products containing polysiloxane having a high z-directional gradient |
| US6964725B2 (en) † | 2002-11-06 | 2005-11-15 | Kimberly-Clark Worldwide, Inc. | Soft tissue products containing selectively treated fibers |
| US20040084162A1 (en) | 2002-11-06 | 2004-05-06 | Shannon Thomas Gerard | Low slough tissue products and method for making same |
| US6887348B2 (en) | 2002-11-27 | 2005-05-03 | Kimberly-Clark Worldwide, Inc. | Rolled single ply tissue product having high bulk, softness, and firmness |
| TWI268972B (en) | 2002-11-27 | 2006-12-21 | Kimberly Clark Co | Rolled tissue products having high bulk, softness, and firmness |
| US6936136B2 (en) | 2002-12-31 | 2005-08-30 | Kimberly-Clark Worldwide, Inc. | Amino-functionalized pulp fibers |
| US6896767B2 (en) * | 2003-04-10 | 2005-05-24 | Kimberly-Clark Worldwide, Inc. | Embossed tissue product with improved bulk properties |
| US20040221975A1 (en) * | 2003-05-05 | 2004-11-11 | The Procter & Gamble Company | Cationic silicone polymer-containing fibrous structures |
| US7147752B2 (en) † | 2003-12-19 | 2006-12-12 | Kimberly-Clark Worldwide, Inc. | Hydrophilic fibers containing substantive polysiloxanes and tissue products made therefrom |
| EP1752580A4 (en) * | 2004-06-03 | 2010-03-24 | Daio Seishi Kk | Sanitary thin paper and process for producing the same |
| JP4658056B2 (en) | 2004-08-25 | 2011-03-23 | 大王製紙株式会社 | Household tissue paper |
| JP2007307287A (en) * | 2006-05-22 | 2007-11-29 | Meiko Shoji Kk | Fiber body for cleaning body |
| EP2287396B1 (en) | 2008-03-31 | 2016-03-23 | Nippon Paper Industries Co., Ltd. | Tissue paper for domestic use |
| JP5702926B2 (en) | 2009-10-16 | 2015-04-15 | 東レ・ダウコーニング株式会社 | Treatment composition for wiping paper |
| CN104204344A (en) * | 2012-12-27 | 2014-12-10 | 特种东海制纸株式会社 | Wood pulp for glass plate-isolating paper and glass plate-isolating paper |
| EP3231939A1 (en) | 2016-04-11 | 2017-10-18 | Fuhrmann, Uwe | Multi-layer tissue for reducing the transmission of pathogens |
| JP6235674B1 (en) * | 2016-09-30 | 2017-11-22 | 大王製紙株式会社 | Tissue paper |
| PT115562B (en) | 2019-06-03 | 2021-12-24 | Raiz Instituto De Investig Da Floresta E Papel | EUCALYPTUS GLOBULUS PEEL PULP AND ITS PRODUCTION PROCESS FOR TISSUE PAPER PRODUCTS |
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|---|---|---|---|---|
| US3755220A (en) | 1971-10-13 | 1973-08-28 | Scott Paper Co | Cellulosic sheet material having a thermosetting resin bonder and a surfactant debonder and method for producing same |
| FR2186035A5 (en) * | 1972-05-26 | 1974-01-04 | Rhone Poulenc Sa | |
| US4028172A (en) * | 1974-04-15 | 1977-06-07 | National Starch And Chemical Corporation | Process of making paper |
| JPS597832A (en) * | 1982-07-05 | 1984-01-17 | Matsushita Electric Ind Co Ltd | Installation of interior unit of floor heater |
| US4495226A (en) * | 1982-07-06 | 1985-01-22 | Dow Corning Corporation | Method for preparing silicone-treated starch |
| JPS59225111A (en) * | 1983-06-07 | 1984-12-18 | Kao Corp | Composition for cleaning and wiping skin around anus |
-
1989
- 1989-06-13 ES ES89305940T patent/ES2081303T3/en not_active Expired - Lifetime
- 1989-06-13 EP EP89305940A patent/EP0347154B1/en not_active Revoked
- 1989-06-13 DE DE68925309T patent/DE68925309T2/en not_active Revoked
- 1989-06-13 AT AT89305940T patent/ATE132556T1/en not_active IP Right Cessation
- 1989-06-14 CA CA000602759A patent/CA1330382C/en not_active Expired - Lifetime
- 1989-06-14 NZ NZ229550A patent/NZ229550A/en unknown
- 1989-06-14 AU AU36363/89A patent/AU634963B2/en not_active Expired
- 1989-06-14 BR BR898902848A patent/BR8902848A/en not_active IP Right Cessation
- 1989-06-14 MX MX016456A patent/MX170318B/en unknown
- 1989-06-14 MX MX016457A patent/MX167009B/en unknown
- 1989-06-14 KR KR1019890008183A patent/KR0140223B1/en not_active IP Right Cessation
- 1989-06-14 JP JP1152065A patent/JP2806974B2/en not_active Expired - Lifetime
-
1996
- 1996-01-09 GR GR960400020T patent/GR3018609T3/en unknown
Also Published As
| Publication number | Publication date |
|---|---|
| NZ229550A (en) | 1992-01-29 |
| ATE132556T1 (en) | 1996-01-15 |
| DE68925309T2 (en) | 1996-05-23 |
| JP2806974B2 (en) | 1998-09-30 |
| DE68925309D1 (en) | 1996-02-15 |
| AU634963B2 (en) | 1993-03-11 |
| AU3636389A (en) | 1989-12-21 |
| EP0347154A3 (en) | 1991-05-02 |
| EP0347154A2 (en) | 1989-12-20 |
| EP0347154B1 (en) | 1996-01-03 |
| KR910001168A (en) | 1991-01-30 |
| KR0140223B1 (en) | 1998-07-01 |
| JPH02224626A (en) | 1990-09-06 |
| ES2081303T3 (en) | 1996-03-01 |
| GR3018609T3 (en) | 1996-04-30 |
| MX167009B (en) | 1993-02-22 |
| MX170318B (en) | 1993-08-16 |
| BR8902848A (en) | 1990-03-20 |
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| MKEX | Expiry |
Effective date: 20110628 |