CA1247274A - Erasable inks containing thermoplastic block copolymers - Google Patents
Erasable inks containing thermoplastic block copolymersInfo
- Publication number
- CA1247274A CA1247274A CA000413487A CA413487A CA1247274A CA 1247274 A CA1247274 A CA 1247274A CA 000413487 A CA000413487 A CA 000413487A CA 413487 A CA413487 A CA 413487A CA 1247274 A CA1247274 A CA 1247274A
- Authority
- CA
- Canada
- Prior art keywords
- ink
- blocks
- solubility parameter
- block copolymer
- cal
- 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
Links
Classifications
-
- C—CHEMISTRY; METALLURGY
- C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
- C09D—COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
- C09D153/00—Coating compositions based on block copolymers containing at least one sequence of a polymer obtained by reactions only involving carbon-to-carbon unsaturated bonds; Coating compositions based on derivatives of such polymers
- C09D153/02—Vinyl aromatic monomers and conjugated dienes
-
- C—CHEMISTRY; METALLURGY
- C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
- C09D—COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
- C09D11/00—Inks
- C09D11/16—Writing inks
- C09D11/18—Writing inks specially adapted for ball-point writing instruments
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
- Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10S525/00—Synthetic resins or natural rubbers -- part of the class 520 series
- Y10S525/901—Radial block
Abstract
ABSTRACT
An erasable ink containing a thermoplastic block copolymer, pigment particles, and a solvent. In a preferred embodiment an erasable ink requiring little or no pressuri-zation is provided by empolying a mixture of radial adn linear block copolymers and a mixed solvent system falling within a specific range of solubility parameter. Polybutene and poly-alpha-methylstyrene are preferred additive to decrease smearing tendency.
An erasable ink containing a thermoplastic block copolymer, pigment particles, and a solvent. In a preferred embodiment an erasable ink requiring little or no pressuri-zation is provided by empolying a mixture of radial adn linear block copolymers and a mixed solvent system falling within a specific range of solubility parameter. Polybutene and poly-alpha-methylstyrene are preferred additive to decrease smearing tendency.
Description
I:R~\SI~',I,E I~IK'; ' CO~ 'r~T~ Rt/lO'~'L/~',TIC ~sLOCK C(~L'O[.'~'lr:r~S
BACKGROU~D OF T~-~E INV~IITION , ,.", .~
: !
1. Field of the In~enLion The present invention relates to an erasable ink, and more particularly, to an erasable ink containing a i thermoplastic block copolymer.
. . .. ..
BACKGROU~D OF T~-~E INV~IITION , ,.", .~
: !
1. Field of the In~enLion The present invention relates to an erasable ink, and more particularly, to an erasable ink containing a i thermoplastic block copolymer.
. . .. ..
2~ Description of the Prior Art In choosing a writing instrument, line intensity and erasability must be taken into account. Until recently, the choice was between these two factors since it was impos-sible to have both hish line intensity and high erasability in the s~me writing instrument. Writin~ instruments such as pencils possess high erasability (i.e., the written line can be removed readily) but are relatively lo~ in line intensity (i.e., the contrast between the written line and the paper is low~. B~cause of this, a xerograp~ic copy of a document written in pen-il is typ1c211y a poor reproduc~ion. In contrast, writing instruments such as ball pOiIlt pens, fountain pens, and s-oft- or porous-type pens produce written lines which are relatively intense but lack any slgnificant degree of erasability without damage to the underlying writing surface, or require additional material to mas~ the unwant~d lines.
~ ccordingly, the prior art contain~ nume~ous ~tt pts a- writing instrll-cnts containing In~s which produce I . .. . ~ I
Il .' l ' ~,f~ i3~ ." , I
. ~ 7 ~
a ~rittcn line of hiyh int:~nsit:y, and yct ar~ crasabk for at lcast th~ firs~ fc~ ours aftcr b~ing placcd upon th~
writing surf~ce. This combina~ion produces ~ writt~n docurncn~
havin~ all the desirable attributes of both syst~ms, and within ~ short period of ti~e after being written, possess the permanency typically desired in written documents.
One such system is describ d in U.S. Patent
~ ccordingly, the prior art contain~ nume~ous ~tt pts a- writing instrll-cnts containing In~s which produce I . .. . ~ I
Il .' l ' ~,f~ i3~ ." , I
. ~ 7 ~
a ~rittcn line of hiyh int:~nsit:y, and yct ar~ crasabk for at lcast th~ firs~ fc~ ours aftcr b~ing placcd upon th~
writing surf~ce. This combina~ion produces ~ writt~n docurncn~
havin~ all the desirable attributes of both syst~ms, and within ~ short period of ti~e after being written, possess the permanency typically desired in written documents.
One such system is describ d in U.S. Patent
3,875,105 to Daugherty et al., issued on April 1, 197~.
That patent describes an erasable writing medium suitable for use in ball poinl pens having a discontinuous phase of a solid colorant and a homo~eneous continuous phase including a matrix material having cohesive properties exceed ns its property to adhere to the substratum being written upon. ¦
The ink consists of a pisment, stabilized with adsorbed surfactant, dispersed in a multicomponent solvent system containing a pclyvinyl methyl ether elastomer. On transfer to paper, the low boiling toluene evaporates into the air or penetrates into the paper causing a YiSCOslty increase and enhancement of the elastic characteristics of the pigment dispersion. Adhesion between the elast~mer and pigment remains greater than that betw~en the elastomer and paper until certain com~nents of the solvent system migrate into the paper, at which time polymer adhesion increases and erasability decreases. The erasability ~f the ink is stated to depend in part on the rapid e~aporation of at least one o$ the components of the continuous phase. Accordingly, the ~olatile component is stated to he one preferably with an evaporation rate o 3 to lS on a relati~e numerical scale on l .. ~ _ , .-,. '. '' which ethyl ether is assigned an evaporation rate of 1, such as toluene which is stated to have a rate of 6.1. The volatile component is employecl in a range from 24.0 to 29.0'~. The line intensity of that ink is dependent upon the relative quantity of pigment used. As stated in that patent, it may be necessary to dispense the ink in a pressurized ball pen depending upon the relative quantity of pigment used since at higher levels of pigment the ink may not flow with sufficient rapidity through the feed passageways of the conventional, gravity fed balIpoint pen.
Moreover, in an ink of such a high level of volatile component, some means must be provided to prevent the volatile component from evaporating into the atmosphere which would increase the viscosity of the ink while in the pen.
U.S. Patent 4,097,290 to Muller et al. describes a ballpoint writing instrument capable of writing with an intense line which is easily erasable by mechanical means for an initial period of several hours but eventually becomes non-erasable.
These properties are attained by an ink composition containing certain specific rubbers and volatile solvents which control erasability. The rubbers employed are natural or of a chemical structure essentially duplicating that of natural rubber. In addition, ~he ink contains a volatile low boiling organic solvent having a boiling point less than 108C and exhibiting 100%
evaporation within 60 minutes, and a high boiling organic liquid solvent having a boiling point of greater than 300C. The volatile low boiling organic solvent is included to . . . I
rapidly incrc~s~ th~ viscosity o t;)lC ink in th~ ~ritt~n linc ther~by minimiziny p~n~tration by the ink in~o thc paper. Although the inl~ ylelds a very int~nse line with /o/
; ~ood erasability for the~f~w hours after it is written, it S suffers from the same disadvantage as that set forth previ-ously for the Daugherty et al. Patent. Namely, it possesses a relatively high concentration c)f a low boiling, rapidly vaporizable solvent, and a relati~ely high concentration of pigment such that means for subjecting the ink to super-O atmospheric pressure is necessary to facilitate the flow andsupply of ink to the ball. In addition, the rubber must be milled prior to its incorporation into the ink to produce an . a~erage molecular weight of between 100,000 and 930,000 and preferably bet~-een 400,000 and 750,000. The milling process is somewhat difficult to control in that milling too rapidly, or for too long a time, will produce rubber particles unsui~
able for use in the ink.
There are often also problems in addition ~o time and expens~ when ink must be supplied under pressure. If . ¦ the ball doesn't fit almost perfect y in the ball seat, point bleed can occur, and will become worse as the ball seat wears with writing. ~riting sm~o~hness is also affected ; by pressuri~ation bèc~use the ball must be pushed into its seat, and ~he ink pressure must be counteracted in order to get ink flow. Another major disad~antage of prior art erasable in~ is that the written line is easil~ smeared.
Accordingly, a need e.~ists for an erasable in~ for us n ballpoint pcns uhicl~ ill produ~e a line of high ; r~
~ 7~
erasabi:Lity a~lcl higl-l line intenC;ity~ which does not depencl upon a high level of volatile solvent, does not smeclr, is reclcliL~
prepared without the necessity of controlled milling oL the rubber component, and requires little or no pressurization.
SUMMARY OF TFlE INVENTION
The presen-t inverltion comprises an erasable ink for use in a ball-point writing instrument consisting essen-tially of a pigmented organic solvent solution containing a thermoplas-tic block copolymer having an arrangement of A (thermoplastic) and B
(rubbery) blocks selected frozn the class consisting of ABA
(AB) X and (-AB)- ; in which the thermoplastic blocks are selected Erom the class consisting of styrene, ester and urethane blocks; in which the rubbery blocks are selected from the class consisting of butadiene, isoprene and ethylene-butylene blocks;
in which the weight ratio of the rubbery blocks to the thermoplastic bloc]cs is from 60:40 to 90:10; in which the solubility parameter of the organic solvent is from about 7 to about 10.5 (cal/cm3)1/2; and containing an effective amoun-t up to about 10% by weight of the solution of an additive to increase erasability selected from -the class consisting of polybutenes and poly-alpha-methylstyrene.
DETAILED DESCRIPTION OF THE INVENTION
It has now been found that an erasable ink producing a written line of high intensity and high erasability can be produced withou-t employing a high volatility solvent or high levels of pressurization, by the use of thermoplastic block copolymers in place oE the matrix material of Daugherty et al. or the rubbers of Muller et al.
~'~3 5.
The block copolymer~; of the present invention are be3t de~7cribed a9 thermopLastic ela~tomers which hclve an ABA, (AB)nX, or (-AB)-n arrangement oE A (thermopla~stic) and U
(rubbery) blocks. The harcl ~ blocks may be glassy te.g., polystyrene) or crystalline (e.g., polyester, polyurethane); the soft s blocks must be elastomeric (e.g., polybutadiene, polyisoprene). When the hard segments are incompatible wi-th the soft segments, the domains or regions of hard blocks act as reinforcing physical cross-links for the rubbery matri~. In contrast to chemically cross-linked rubbers, the physical l ~ - 5a -~ '727~
nctwork is thcrm~lly rcvcrsiblc. ~Icn t.hc polymc~ i~ hea~ccl ~bove th~ Tg (or Tm) of th~ hard block, thc h~l blocks ~often and allow thc rubber to ~low and to be proccsscd as thermoplastic.
The manufacture of block copoiymer ther~oplastic elastomers depends upon the type and arrangement of the blocks. For example, styrene-butadiene ABA and (AB)nX block copolymers are conveniently prepared by alkylithium initiated anionic polymerization. Thermoplastic ~A-Bjn polyur~thanes are synthesized ~y step-srowth addition copolymerization of dihydroxy compounds such as polytetlamethylene ether glycol and toluene diisocyanate. The copolyester-ether 'A-Btn copolymers are produced by the polycon~ensation o~ dicar-boxylic acids (e.g., terephthalic acid) with glycols or . polyethP~ slycols. The preferred block copolymers of the present invention are Lhose made from styrene-diene comonomers having a block arrangement of ABA or (AB)nX such as those sold under the trade ~me~ Kraton ~Shell Chemical~ and , - ¦
Solprene (Phi.lli~s Chemical Company).
A preferred block copolymer for use iZl the preser~t invention is a styrene-isoprene-styrene block copolymer.
Each molecule consists of an individual chain of three blocks, - an elastomeric ~lock in the center (isopr~ne) a~d a thermoplastic block on each end (styrene). The polystyrene i ~nd bloc~s form a discrete phase which locks the continuous phase isoprene midblocks into al~ elastomeric network.
Because mechanical cross-links ra~ler than chemical cross-lin~s are present, thc copolymers can be dissolved in many ~ !
7~
co~non hydrocarbon solvcnts without I~r(rl~a~;tication. By diGsolving thc polystyrene domains, ~hc nct~rork is unlockcd ~rmitting rni~.in~ with oth~r materlals. Sincc such xubbcrs arc low in molecular weic3ht (typicc?lly .less th~n 100,000 to about 150,000), th~ solutions produced have low viscosity even with high solids content.
Another type of preferred ~lastomer is a "radial"
(AB)nX block copolymer consisting of styrene and isoprene blocks. In a linear arrangement such as that d~scribed above, each molecllle contains two styrene blocks at the ends of an isoprene midblock. In contrast, the preferred radial structure contains four isoprene ~idbloc~s which are all joined at a common center, with a styrene block at the outer ena of each isoprene block. Compared to linear block copol- I
~mersJgenerally~ the radial block copolymers at similar ~f molecular wei~ht and monomer ratio produce lower solution viscosities. For example, the viscosity of a 20% and ~5% by weight solution in toluene of a linear polymer having a _ moleculax weight of about 150,000 is 600 centipoises and 1600 ce~ti~?ises respectively. I~ contrast, solu~ions of a - I radial polymer having a molecular weight of between 175,000 and 275,000 at the same concent ation in toluene have ~iscos-ities of 570 centipoises and ~650 centipoises respectively The typical ran~e of molecular weights of radial polymers is ~bout 150,000 to about 300,000. t While the use of either linear or radial block copolymers alone results in an acceptable ink, i~ is preferred to blelld the two toge~her in a range of radial to linear of about 7:1 ~o 1:1. Th~ prcfcrr~d bl~ndiny is in ~l ratio of about 3 to 1 r~dial to lin~ar.
Bloclc copolymers havin~ butadiene or isoprcne miclblock~s are preferred, although block copolymers having ethylene-butylene midblocks can also be used in pressuriz~d ~ystems. The range of concentra~ion for the block copolymer is bet~en about 10~ and about ~G% by weiyht. Higher concen-- !
trations can be used but contribute little to erasability and result in rap'idly increasing viscosity with a concomitant increase in pressurization requirements. The ratio of diene to styrene is typically between abouk 60:40 and about 90:10.
The molecular weight of the rubbers empioyed in ~he presen~ ~nvention is low, typically less than 300,000, ¦ ' as compared to general purpose rubbers such as styre~e-; butadier.e rubber, polyisoprene rubber, and natural rubber even after natural ru~ber is broken down by milling. Natural rubbers used in the prior art typlc~lly have mol~cular 1, weigh~s between about 400!000 and about 750,000. With block copolymers, breakdown is neither desired nor reguired.
Instead, the polystyrene domains'are softened by solvating which~permits the polymer to t-low unde~ shear. 'Dissolution and solvent release~re quite rapid with such block copol-.ymers. -They dissolve or disperse readily in common hydro-carbon solvents to yield high solids, low viscosity solutions.
Depending upon which solvent is used, the interaction betw~en hard ~glassy) and soft (rubbery3 segments o~ a ~hexmoplastic block will b~ affected. This in turn strongly influcnces t,he visco~lastic b~havlor of the rubb~r.
1~ -Il . - .
7'1L
Three general factors must be considered in preparing inks according to the present invention: solubility parameter, volatility, and critical pigment concentration (CPC). These factors require greater consideration when preparing a pcn needing low Jevels (less than 1.0 psi~ or no pressurization.
Each of these factors will be discussed generally before focusing on how each affects pressurization requirements.
In determining which solvents to employ in the ink of the present invention, the solubility parameter (represented by ~ ), which is a measure of the total forces holding the molecules of a solid or a liquid together, is a useful guide. It has the units of (cal/cm3)1/2. Every compound is characterized by a specific value of solubility parameter. Materials having about the same solubility parameter tend to form homogeneous mixtures or to be miscible. Those with different solubility parameters tend to form separate layers or to be mutually insoluble.
Discussions of solubility parameter concepts are presented in (I) Encyclopedia of Polymer Science and Technology, Interscience, New York (1965), Vol. 3, Pg. 833; (2) Encyclopedia of Chemical Technology, Interscience, New York (1971), Sup. Vol., Pg. 889;
(3) Polymer Handbook, J. Brandrup and E.H. Immergut, Inter-science, New York (1966), pgs. IV-337 to IV-341; and (4) I.T.
Smith~ review of Current Literature on the Paint and Allied Industries, Vol. XXXYI, No. 247, (January 1963), pgs. 1-4.
7~
The block copolymers in the present invention will dissolve in most or~anic solvents havine ~solubility pararrleters between about 7 and about 10.5. In the case of inlss that will be subject to pressurization, low boilin~, high volatility solvents such as toluene, naphtha, and the other low boiling solvents in the Muller et al. Patent can be advantageously employed. ln such an embodiment, the solubility parameter of the organic solvent combination need only fall within the outer limits of the solubility parameter of about 7 to about 10.5.
It will often be desirable to use a combination of solvents in the ink of the present invention since the resulting mixed solven~ system acts as a solvent for the polymer, as a dispersant for the pigment7 and as a plasticizer for the polymer or polymers. The formula to use in determining the solubility parameter for such a mixed solvent system is r 3 = ~ mole :~ra;:t- oni*~i The value for a particular soivent is reaclily obtained by consulting one of the reference texts referenced above.
To give sufficient intensity to the written line produced by the ink of the present invention, finely divided pig,nenting materials are added. By finely divided, reference is made to particle sizes within the range of about 0.01 microns to about 5 microns, the lower figure being a limita-tion as to visibili~y ~nd th~ uppcr figurc bciny limi~cd hy b~llpoint clcaranc~; that is, the cgap bctwee~ t~lC b~ n~
thc rct~ining lip of the sockct.
l'he pigment is typically addecl to the oth~r cornpo-nents of the ink in the form of a dispersion containing 50-60% of dioctyl phthalate. A typical blue ink would cont~in 12.6% Victoria Blue having a particle size of about 0.025 m~crons and about 5.7% Phthalocyanine Blue having a partic~ size of about ~.015 microns. Unless an unpressurized 0 ink is desired as discussed below, the dispersion would then be diluted with an egual vol~me o~ toluene or other similar solvent.
For every pigment/solvent system, as well as for every pigment/solvent/polymer system, there is a "critical pigme~t ~oncentration" (CPC), below which no pressure is ¦
required to initiate flow. Above the ~PC, constant pressure is required for pigment/solvent systems and the pressuriza-. tion of pigment/solvent/polymer systems increases in propor-tion to increases in pigment concentration, signifying a !0 pigment-polymer interactior.. Each particular pigment, . polymer and solvent combination has its own CPC. Tnus it is difficult to predict what the CPC for any particular system will be.
For inks requiring no pressurization, low volatility ~5 solvents are employed. Low volatility solvents are defined as those having a value of not greater than 10 on a scale of O~to 100 where ~utyl acetate is used as a stan~ard and has a value of 100 s measurcd ac-ording to the ~ti~nal Println~
~1 ,: , , 7~
Ink Research Institute Raw Materials Handbook, Volume 1, Organic Solvents. Page 9 of that volurne provides data for various solvents.
To produce a pen requiring a low level (less than 1.0 psi) or no pressurization, each of the above factors must be controlled within a relatively narrow range, and care must be exercised in choosing the block copolymer or copolymers. each of these factors will now be discussed in connection with refills requiring little or no pressurization.
~lock copoJymers having butadiene or isoprene mid-blocks, and mixtures of radial and linear block copolymers are preferred when preparing refills requiring little or no pres-surization. For gravity flow with no pressurization, such biock ; copolymers must be used in conjunction with an organic solvent or a mixture of organic solvents having a solubility parameter between about 8.1 and about 8.7. Where no pressurization is involved, such solvent or solvents must also possess low volatil-ity as defined above. Preferred low volatility solvents for use in inks of the present invention are set forth in Table I below.
One or more solvents from Group 1 are mixed with one or more solvents from Group 2 to produce a combination having a solubil-ity parameter in the appropriate range.
Finally, the CPC must be considered. It has generally been found that the CPC of most pigment/solvents/polymer systems is 9-10% or less. Choosing the exact pigment concentration is readily accomplished by one skilled in the art after selecting a mixed solvent system and a particular block copolymer.
_ 12 -1: r ~i ~
7fa . ~
~131,R 1 Solvcnt & Chcmical Solubility Boiling Evaporation Manu~acturcr Description . 'Paramcter Point,C ~3tc~
. .
GROUP l . .
Isopar M Heavy isoparaffinic naphtha 7.2 207 ~lO. .
(Exxon) Cll Cl7 .
~agicSol 47 Oil SMagie) Hydrotreated middle distillate 7.2 238 ~ l 1102 Oil (~itco) ~ight vacuum gas oil 7.2 266 < l MagieSol 44 Oil (Magie) ~ydrotreated midd].e distillate 7.5 226 2 1108 Oil i (Witco) ~Iydrotreated middle distillate 7.3 280 ~ l Norpar 13 Normal paraffin . 7.4 , 229 . <lO
(Exxon) ~ Cll ~17 c~ . .
Dodecane C~2 hydrocarbon ~ 7.8 2l6 med.low ~r''~ ?.~ .
. Aromatic l50 : (Exxon). Heavy aromatic naphtha . 8.7 183 ~lO
. -. DXE
(Gulf) . 1,l-di(ortho-xylyl)ethane 8.8 335 v.low Han Aromatic ~iddle : .
(Exxon) distillate extract 8.~ l69 ~lO
DOP . ~~ dicctylphthalate 8.9 38b ~ O
. ,, .
. - - - - - ' ' - _ _ . .
a. Relative evi~poration rates ~here butyl acetate = lOO . .
1~ 7Z'7~
Pressuri~ation is required for the erasabIe inks of the present invention which are too visous to flow at a s~lfficicnt rate under the force of gravity alone. Prior art erasabIc inks often require 10 psi to produce an acceptable written line. In contrast, the inks of the present invention typically require less than 1.0 psi to produce a written line of similar quality.
The amount of pressure required depends on several factors including temperature, the particle size of the pigment, the polymer employed, and the ~ap between the ball and the lip of the ball-retainin~ socket. The pressure for any particular combina-tion is readiJy determined by one skilled in the art. Various means for applying appropriate pressure are well known in the prior art including U.S. Patent 3,000,354; U.S. Patent 3,099,252;
and U.S. Patent 3,425,779.
A preferred additive to the ink of the present inven-tion is polybutene to enhance the cohesive strength of par-ticularly styrene-isoprene-styrene elastomers. The polybutene has no effect on pressurization or line intensity, but increases the erasability of inks when used in concentrations up to about 10% by weight. Polybutenes are a series of butylene polymers composed predominantly of high molecular weight mono-olefins (85-98%), the balance being isoparaffins. Preferred polybutenes have a viscosity of about 3026-3381 centistokes at 210F and average molecular weight of about 2060. Polybutenes are made by polymer-izing an isobutylenerich butene stream with a metal halidecatalyst.
72~
Thc polymc~r backhorle structtlrc r~ scmblc~ olyisobll~y].crl~, alt:houyh mor~ 1- and 2~ butcnes a.re i~orporated in t~le ! lo~lcr molcc:ular-~cight; fract:ions. Thc olcfin structurc is I prcdominently the trisubstitu~cd t~p~ (R-C~I~C'R2). Only j minor amounts of vinylidene (R-CH2-~ R) and terminal vinyl I (~-CH=CH2) structures are prescnt. A preferred poly~utene ~' , ~ i5 sold under the trade1~ffle Indopol H-1500 by ~moco Chemicals Corporation, 200 East Randolph Drive, Chicayo, IL 60601.
Another preferred additive is poly-alpha-methylstyrene which can be used alone or in conjunction with polybutenes.
With this addi~ive, line intensity is unchanged, but eras-¦ ability is increased with increasing concentration. However, the pressure to write increases proportionately with concen-I tration such that poly-alpha-methylstyrene is useful only in L5 I pressuri3ed inks and is t~ically used in concentratiGns up . to aboui 10% by wei~ht.
It has been found ~lat the addition of polybutene and poly-a'pha-methylstyrene dramatically reduces the tendency to smearing of prior art erasabl~ inks whic~ is seen initi~lly after writing.
~rasability can be evaluated by manual erasure and visual observation, but this involves personal fact~rs such a~ pressure applie~, size of surface being erased, etc. A
mor~ accurate evaluation can be conducted by applying the trace by a standard writing test method in which the paper is advanced beneath the writing instrument at a rate of 11.5 ~m. per 10 cycles and at the same ra~e under an erasing head provided with an Eberhard-Faber Pink Pearl Pencil Eraser .
; 15 -~ ;7,27 ~tlOl (S~orc ~3~ Durom~ter hardrl~ss, ~SI~ D 22~0), ~1pplied to ~}~c p~pcr bcaring thc tr.lcc unc1er ~ load o 375 ~Jranls upvn Gurfacc m~suring 9 m~. by 23.~ rnm. in thc directior1 of tr~vel, the ~rasing head reciprocating ~lt a ratc o 80 cycles per ~inut~, thc.lcngth of each stroke being 63.5 mm. I
Each trace is thus subjected to 7 cycles of erasing and .
results can be visually observed.or rated by photometer .
readings.
Smearing can be tested by taking Ross micro ~ax ~1365, obtained from Frank B. Ross Company, Inc., 6-lO Ash Street, Jersey City, 1~ew Jersey and ~orming it into plugs.
the size of a standard eraser, placing i~ into an erasing . machine as described above and running over a fresh tracing five cycles. This produces a reasonably uniform sm~ar ~Ihich can ~hen be placed into a reflectometer and r.easured against the reflectance of the same paper without ink on it.
. The equation used. to de~ermine the percent smear~.ng . i~ . o , ,, % smearing =.~ nS x lO0 , ~7here Ru is the re lectance of the unm~rked paper, ~ is th~ re-flectance of the mar~ed pa~er, and RS is the reflectance of ~he smeared area~
-- While the major c~mponents of the ink have been stressed ~bove, the presence in the ink of additives such as corrosion inhibitors, lubricants such as lauric acid or stearic acid, preservatives, parting com~ounds (between ink in a reservoir and a gaseous ~ressuri~ing agent), and dispers- ;
ing agents, is not precluded.
. -16 . ..
The inv~ntion will ~c furthc~ illustratcd by consider~tion of thc following cY.amplcs which ar~ intend~d . to be purely exemplary of the use of the invention.
. . ' ', .
EXAMPLE I .
.. ' .' . '.
An ink employin~ a radial styrene-isoprene-styrene block ~opol~ner sold under the trademark Solprene 418 by Phillips Chemical Company, Borger,.Texas, having a styrene/
isoprene ratio of 15/85 was used to prPpare an erasable ink . requiring no pressurization. 20 gr~ms of the block copol~ner 1.0 was dissolved in 49.8 grams of dodecane and 10.2 grams of dixylylethane. To this was added 20 grams of a pi~nent . dispersion OI 31.6% Victoria ~lue, 14 1% Phthalo Blue, and ¦ 54.2% dioctyl phthalate. The combination of solv~nts produced .
. a solubility parameter of 8.1. The resultin~ ink prod~ced a written trace with acceptahle line intensity and erasability.
~^' "' -, '''- . I
~ ~... EX~MPLE Il , - - .
- Example I was repea'ed with 10 grams-of a linear ~lock ~opol~ner having a styrene/isoprene xatio of 14~86 .sold by Shell Chemical Company, Houston, Texas, and a mixed ~olvent system of 67.2 grams of isobutyl isobutyrate having solubility parameter of 8.1, ~.~ gxams of methyl ethyl ketone having a solubility parameter of 9.3, and 20 grams of th~ pigme~t dispersion of Example I. Thc resulting combina~
¦~ tio f sol\el~ts ha~ a solubility par~loeter of B.7. The I . ". I
. .' ~ .
7 ~
r~sult:ir~(3 irlk produccd cl wri~tcn ~racc wit~l acccp~ablc lirlc int~nsity and cr~sability, ; E~MPLE IlI
' ': ' .
~n ink employing a styrene-ethylene/butylene-styrenc block copol~er sold under the trademark Kraton G1650 by Shell Chemical Company, Houston, Texas, having a styrene to ru~ber ratio of about 28 to 72 was prepared by mixing 10% by weight of block copolymer with $0% by weight of toluene.
The dissolved polymer was then mixed with a pigment dispersion D consisting of 60% by weight of toluene, 21.7% dioctyl ph~halate, 12.6% Victoria Blue and 5.7~ Phthaloc.yanine Blue~
¦ The resulting ink was placed in a conventional ref~
¦ c:artridge ar.d pressurized to a pressure of 0.6 psi. The ¦ resulting ink produced a written trace with acceptable line ¦ intensity and moderate erasa~ility.
I' ..i - .. ..
l _ EXAMPLE IV
.-.................. , .
Exam~le III was rep~ated with a styrene-isoprere-styrene block copoly~er sold under t~e trademark Kraton 1101 by Shell Chemical Company, Houston, Texas, having a styrene to rubber ratio of 30 to 70 in place of the styrene-ethylene/
butylene~styrene bloc~ copoly~ller. The resulting ink produced a written trace wi~h acceptable line intensity and good erasability~
- la . ... ...
~ ~ ~'72'~'~
Ex~ r.r, V
. ''' " '~ .
A xe111 capable of ~r.iti.ng ~ hout pressuriz.l~ion was prepared employing an ink ~ontaining the ~ollow.ing ingredients by weight: 4.0% Indoast Violet; 5.0% Kraton. .
1107, a linear styrene-isoprene-styrene block copolymer having a styrene/isoprene rat.io of 14/86 sold by Shell Chemical Company, Houston, Texas; 1~.0% Solprene ~23, a radial styrene-isoprene-styrene block copolymer having a styrene/isoprene ratio of 15/85; 5.0% Indopol H 1500, a polybutene sold by Amoco Chemicals Co., Chicago, Illinois;
6% dioctyl phthalate; and a mixed solvent of 49% l,l-di(ortho-xylyl)ethane and 16% MagieSol 44 to produce a ~ of approxi-mately 8.4. Tke resulting ink produced a written line of good line intensity and good erasability.
. , ' - , ' . .
j EXP~LE VI
~' ~
A refill re~uiring a ~ressurization of about 0;3 psi and h~ving good line intensity and good erasabili~y was produced by the following formulation:
Inqredient~ ~,w~
~` Kraton 1107 5,0 .
S~lprene 423 15.0 I~ldopol 1500 5,~
Poly-alpha-methylstyrene . 6.0 Aromatic 150 ) .
) ~.s. to~
S ¦ MagieSol 44 l ~ 19 .l . ~
. . Victoria ~.luc 15.0 Dioctyl phthal~ 15.0 .
. , '.
.. . EX~PLES VXI & VIII
'''`: ' . . ' ' '-- ' .
~ Ex~mples VII and VIII illustrate t:he beneficial effect of polybutene arld poly-al~-ha-methy].styr~ne on smearing tendency.
.' . ' .' ' INK COMPCSITION (percent by weight~ .
Exampl~ VTI Exam~le VIII
10. Solprene 423 16.2 14O7.
¦ Kraton 1107 5.4 ~Og ~n~opol H-1500 . ~;- 3,0 Resin 18-210 (1) --- 6.0 Lauric Acid . 1.4 . 1.1 Stearic Acid 0~5 0.4 . Toluene ~26.5 lg.5 Dioctyl phthalate 27.1 27.1 . BT-264D (2~15.8 15.B
BT-427D ~ 7.1 7~1 _, ~ ' '' '' .... ~
.
~0 ~1) Poly-alpha-methylstyrene sold by AmOCQ Chemicals Corp., Chicago, Illinois.
- 20 - . .
. 11, ~ I
lZ4'72~7~
. ~) Victoria ~luc sol~ by E. I, DuPont, ~ilmington, Dcl~arc.
. (3) ~hthalocy~lnine Bluc sold by E. I. Du~ont, Wlllni.ncJ~on, :; . Dcla~arc.
: : . The inks of Examples VII and VIII were compared using the smearing test descrioed a~ove. The smeariny tendency of the ink of Example VIII was about two-thirds ', that of Example VII and the inks of the prior art.
.' .' ,. ' ' .
. , , ~~'' ' ''' ' "
~ ~
. " ,~. .
~21~
., . .
`I
That patent describes an erasable writing medium suitable for use in ball poinl pens having a discontinuous phase of a solid colorant and a homo~eneous continuous phase including a matrix material having cohesive properties exceed ns its property to adhere to the substratum being written upon. ¦
The ink consists of a pisment, stabilized with adsorbed surfactant, dispersed in a multicomponent solvent system containing a pclyvinyl methyl ether elastomer. On transfer to paper, the low boiling toluene evaporates into the air or penetrates into the paper causing a YiSCOslty increase and enhancement of the elastic characteristics of the pigment dispersion. Adhesion between the elast~mer and pigment remains greater than that betw~en the elastomer and paper until certain com~nents of the solvent system migrate into the paper, at which time polymer adhesion increases and erasability decreases. The erasability ~f the ink is stated to depend in part on the rapid e~aporation of at least one o$ the components of the continuous phase. Accordingly, the ~olatile component is stated to he one preferably with an evaporation rate o 3 to lS on a relati~e numerical scale on l .. ~ _ , .-,. '. '' which ethyl ether is assigned an evaporation rate of 1, such as toluene which is stated to have a rate of 6.1. The volatile component is employecl in a range from 24.0 to 29.0'~. The line intensity of that ink is dependent upon the relative quantity of pigment used. As stated in that patent, it may be necessary to dispense the ink in a pressurized ball pen depending upon the relative quantity of pigment used since at higher levels of pigment the ink may not flow with sufficient rapidity through the feed passageways of the conventional, gravity fed balIpoint pen.
Moreover, in an ink of such a high level of volatile component, some means must be provided to prevent the volatile component from evaporating into the atmosphere which would increase the viscosity of the ink while in the pen.
U.S. Patent 4,097,290 to Muller et al. describes a ballpoint writing instrument capable of writing with an intense line which is easily erasable by mechanical means for an initial period of several hours but eventually becomes non-erasable.
These properties are attained by an ink composition containing certain specific rubbers and volatile solvents which control erasability. The rubbers employed are natural or of a chemical structure essentially duplicating that of natural rubber. In addition, ~he ink contains a volatile low boiling organic solvent having a boiling point less than 108C and exhibiting 100%
evaporation within 60 minutes, and a high boiling organic liquid solvent having a boiling point of greater than 300C. The volatile low boiling organic solvent is included to . . . I
rapidly incrc~s~ th~ viscosity o t;)lC ink in th~ ~ritt~n linc ther~by minimiziny p~n~tration by the ink in~o thc paper. Although the inl~ ylelds a very int~nse line with /o/
; ~ood erasability for the~f~w hours after it is written, it S suffers from the same disadvantage as that set forth previ-ously for the Daugherty et al. Patent. Namely, it possesses a relatively high concentration c)f a low boiling, rapidly vaporizable solvent, and a relati~ely high concentration of pigment such that means for subjecting the ink to super-O atmospheric pressure is necessary to facilitate the flow andsupply of ink to the ball. In addition, the rubber must be milled prior to its incorporation into the ink to produce an . a~erage molecular weight of between 100,000 and 930,000 and preferably bet~-een 400,000 and 750,000. The milling process is somewhat difficult to control in that milling too rapidly, or for too long a time, will produce rubber particles unsui~
able for use in the ink.
There are often also problems in addition ~o time and expens~ when ink must be supplied under pressure. If . ¦ the ball doesn't fit almost perfect y in the ball seat, point bleed can occur, and will become worse as the ball seat wears with writing. ~riting sm~o~hness is also affected ; by pressuri~ation bèc~use the ball must be pushed into its seat, and ~he ink pressure must be counteracted in order to get ink flow. Another major disad~antage of prior art erasable in~ is that the written line is easil~ smeared.
Accordingly, a need e.~ists for an erasable in~ for us n ballpoint pcns uhicl~ ill produ~e a line of high ; r~
~ 7~
erasabi:Lity a~lcl higl-l line intenC;ity~ which does not depencl upon a high level of volatile solvent, does not smeclr, is reclcliL~
prepared without the necessity of controlled milling oL the rubber component, and requires little or no pressurization.
SUMMARY OF TFlE INVENTION
The presen-t inverltion comprises an erasable ink for use in a ball-point writing instrument consisting essen-tially of a pigmented organic solvent solution containing a thermoplas-tic block copolymer having an arrangement of A (thermoplastic) and B
(rubbery) blocks selected frozn the class consisting of ABA
(AB) X and (-AB)- ; in which the thermoplastic blocks are selected Erom the class consisting of styrene, ester and urethane blocks; in which the rubbery blocks are selected from the class consisting of butadiene, isoprene and ethylene-butylene blocks;
in which the weight ratio of the rubbery blocks to the thermoplastic bloc]cs is from 60:40 to 90:10; in which the solubility parameter of the organic solvent is from about 7 to about 10.5 (cal/cm3)1/2; and containing an effective amoun-t up to about 10% by weight of the solution of an additive to increase erasability selected from -the class consisting of polybutenes and poly-alpha-methylstyrene.
DETAILED DESCRIPTION OF THE INVENTION
It has now been found that an erasable ink producing a written line of high intensity and high erasability can be produced withou-t employing a high volatility solvent or high levels of pressurization, by the use of thermoplastic block copolymers in place oE the matrix material of Daugherty et al. or the rubbers of Muller et al.
~'~3 5.
The block copolymer~; of the present invention are be3t de~7cribed a9 thermopLastic ela~tomers which hclve an ABA, (AB)nX, or (-AB)-n arrangement oE A (thermopla~stic) and U
(rubbery) blocks. The harcl ~ blocks may be glassy te.g., polystyrene) or crystalline (e.g., polyester, polyurethane); the soft s blocks must be elastomeric (e.g., polybutadiene, polyisoprene). When the hard segments are incompatible wi-th the soft segments, the domains or regions of hard blocks act as reinforcing physical cross-links for the rubbery matri~. In contrast to chemically cross-linked rubbers, the physical l ~ - 5a -~ '727~
nctwork is thcrm~lly rcvcrsiblc. ~Icn t.hc polymc~ i~ hea~ccl ~bove th~ Tg (or Tm) of th~ hard block, thc h~l blocks ~often and allow thc rubber to ~low and to be proccsscd as thermoplastic.
The manufacture of block copoiymer ther~oplastic elastomers depends upon the type and arrangement of the blocks. For example, styrene-butadiene ABA and (AB)nX block copolymers are conveniently prepared by alkylithium initiated anionic polymerization. Thermoplastic ~A-Bjn polyur~thanes are synthesized ~y step-srowth addition copolymerization of dihydroxy compounds such as polytetlamethylene ether glycol and toluene diisocyanate. The copolyester-ether 'A-Btn copolymers are produced by the polycon~ensation o~ dicar-boxylic acids (e.g., terephthalic acid) with glycols or . polyethP~ slycols. The preferred block copolymers of the present invention are Lhose made from styrene-diene comonomers having a block arrangement of ABA or (AB)nX such as those sold under the trade ~me~ Kraton ~Shell Chemical~ and , - ¦
Solprene (Phi.lli~s Chemical Company).
A preferred block copolymer for use iZl the preser~t invention is a styrene-isoprene-styrene block copolymer.
Each molecule consists of an individual chain of three blocks, - an elastomeric ~lock in the center (isopr~ne) a~d a thermoplastic block on each end (styrene). The polystyrene i ~nd bloc~s form a discrete phase which locks the continuous phase isoprene midblocks into al~ elastomeric network.
Because mechanical cross-links ra~ler than chemical cross-lin~s are present, thc copolymers can be dissolved in many ~ !
7~
co~non hydrocarbon solvcnts without I~r(rl~a~;tication. By diGsolving thc polystyrene domains, ~hc nct~rork is unlockcd ~rmitting rni~.in~ with oth~r materlals. Sincc such xubbcrs arc low in molecular weic3ht (typicc?lly .less th~n 100,000 to about 150,000), th~ solutions produced have low viscosity even with high solids content.
Another type of preferred ~lastomer is a "radial"
(AB)nX block copolymer consisting of styrene and isoprene blocks. In a linear arrangement such as that d~scribed above, each molecllle contains two styrene blocks at the ends of an isoprene midblock. In contrast, the preferred radial structure contains four isoprene ~idbloc~s which are all joined at a common center, with a styrene block at the outer ena of each isoprene block. Compared to linear block copol- I
~mersJgenerally~ the radial block copolymers at similar ~f molecular wei~ht and monomer ratio produce lower solution viscosities. For example, the viscosity of a 20% and ~5% by weight solution in toluene of a linear polymer having a _ moleculax weight of about 150,000 is 600 centipoises and 1600 ce~ti~?ises respectively. I~ contrast, solu~ions of a - I radial polymer having a molecular weight of between 175,000 and 275,000 at the same concent ation in toluene have ~iscos-ities of 570 centipoises and ~650 centipoises respectively The typical ran~e of molecular weights of radial polymers is ~bout 150,000 to about 300,000. t While the use of either linear or radial block copolymers alone results in an acceptable ink, i~ is preferred to blelld the two toge~her in a range of radial to linear of about 7:1 ~o 1:1. Th~ prcfcrr~d bl~ndiny is in ~l ratio of about 3 to 1 r~dial to lin~ar.
Bloclc copolymers havin~ butadiene or isoprcne miclblock~s are preferred, although block copolymers having ethylene-butylene midblocks can also be used in pressuriz~d ~ystems. The range of concentra~ion for the block copolymer is bet~en about 10~ and about ~G% by weiyht. Higher concen-- !
trations can be used but contribute little to erasability and result in rap'idly increasing viscosity with a concomitant increase in pressurization requirements. The ratio of diene to styrene is typically between abouk 60:40 and about 90:10.
The molecular weight of the rubbers empioyed in ~he presen~ ~nvention is low, typically less than 300,000, ¦ ' as compared to general purpose rubbers such as styre~e-; butadier.e rubber, polyisoprene rubber, and natural rubber even after natural ru~ber is broken down by milling. Natural rubbers used in the prior art typlc~lly have mol~cular 1, weigh~s between about 400!000 and about 750,000. With block copolymers, breakdown is neither desired nor reguired.
Instead, the polystyrene domains'are softened by solvating which~permits the polymer to t-low unde~ shear. 'Dissolution and solvent release~re quite rapid with such block copol-.ymers. -They dissolve or disperse readily in common hydro-carbon solvents to yield high solids, low viscosity solutions.
Depending upon which solvent is used, the interaction betw~en hard ~glassy) and soft (rubbery3 segments o~ a ~hexmoplastic block will b~ affected. This in turn strongly influcnces t,he visco~lastic b~havlor of the rubb~r.
1~ -Il . - .
7'1L
Three general factors must be considered in preparing inks according to the present invention: solubility parameter, volatility, and critical pigment concentration (CPC). These factors require greater consideration when preparing a pcn needing low Jevels (less than 1.0 psi~ or no pressurization.
Each of these factors will be discussed generally before focusing on how each affects pressurization requirements.
In determining which solvents to employ in the ink of the present invention, the solubility parameter (represented by ~ ), which is a measure of the total forces holding the molecules of a solid or a liquid together, is a useful guide. It has the units of (cal/cm3)1/2. Every compound is characterized by a specific value of solubility parameter. Materials having about the same solubility parameter tend to form homogeneous mixtures or to be miscible. Those with different solubility parameters tend to form separate layers or to be mutually insoluble.
Discussions of solubility parameter concepts are presented in (I) Encyclopedia of Polymer Science and Technology, Interscience, New York (1965), Vol. 3, Pg. 833; (2) Encyclopedia of Chemical Technology, Interscience, New York (1971), Sup. Vol., Pg. 889;
(3) Polymer Handbook, J. Brandrup and E.H. Immergut, Inter-science, New York (1966), pgs. IV-337 to IV-341; and (4) I.T.
Smith~ review of Current Literature on the Paint and Allied Industries, Vol. XXXYI, No. 247, (January 1963), pgs. 1-4.
7~
The block copolymers in the present invention will dissolve in most or~anic solvents havine ~solubility pararrleters between about 7 and about 10.5. In the case of inlss that will be subject to pressurization, low boilin~, high volatility solvents such as toluene, naphtha, and the other low boiling solvents in the Muller et al. Patent can be advantageously employed. ln such an embodiment, the solubility parameter of the organic solvent combination need only fall within the outer limits of the solubility parameter of about 7 to about 10.5.
It will often be desirable to use a combination of solvents in the ink of the present invention since the resulting mixed solven~ system acts as a solvent for the polymer, as a dispersant for the pigment7 and as a plasticizer for the polymer or polymers. The formula to use in determining the solubility parameter for such a mixed solvent system is r 3 = ~ mole :~ra;:t- oni*~i The value for a particular soivent is reaclily obtained by consulting one of the reference texts referenced above.
To give sufficient intensity to the written line produced by the ink of the present invention, finely divided pig,nenting materials are added. By finely divided, reference is made to particle sizes within the range of about 0.01 microns to about 5 microns, the lower figure being a limita-tion as to visibili~y ~nd th~ uppcr figurc bciny limi~cd hy b~llpoint clcaranc~; that is, the cgap bctwee~ t~lC b~ n~
thc rct~ining lip of the sockct.
l'he pigment is typically addecl to the oth~r cornpo-nents of the ink in the form of a dispersion containing 50-60% of dioctyl phthalate. A typical blue ink would cont~in 12.6% Victoria Blue having a particle size of about 0.025 m~crons and about 5.7% Phthalocyanine Blue having a partic~ size of about ~.015 microns. Unless an unpressurized 0 ink is desired as discussed below, the dispersion would then be diluted with an egual vol~me o~ toluene or other similar solvent.
For every pigment/solvent system, as well as for every pigment/solvent/polymer system, there is a "critical pigme~t ~oncentration" (CPC), below which no pressure is ¦
required to initiate flow. Above the ~PC, constant pressure is required for pigment/solvent systems and the pressuriza-. tion of pigment/solvent/polymer systems increases in propor-tion to increases in pigment concentration, signifying a !0 pigment-polymer interactior.. Each particular pigment, . polymer and solvent combination has its own CPC. Tnus it is difficult to predict what the CPC for any particular system will be.
For inks requiring no pressurization, low volatility ~5 solvents are employed. Low volatility solvents are defined as those having a value of not greater than 10 on a scale of O~to 100 where ~utyl acetate is used as a stan~ard and has a value of 100 s measurcd ac-ording to the ~ti~nal Println~
~1 ,: , , 7~
Ink Research Institute Raw Materials Handbook, Volume 1, Organic Solvents. Page 9 of that volurne provides data for various solvents.
To produce a pen requiring a low level (less than 1.0 psi) or no pressurization, each of the above factors must be controlled within a relatively narrow range, and care must be exercised in choosing the block copolymer or copolymers. each of these factors will now be discussed in connection with refills requiring little or no pressurization.
~lock copoJymers having butadiene or isoprene mid-blocks, and mixtures of radial and linear block copolymers are preferred when preparing refills requiring little or no pres-surization. For gravity flow with no pressurization, such biock ; copolymers must be used in conjunction with an organic solvent or a mixture of organic solvents having a solubility parameter between about 8.1 and about 8.7. Where no pressurization is involved, such solvent or solvents must also possess low volatil-ity as defined above. Preferred low volatility solvents for use in inks of the present invention are set forth in Table I below.
One or more solvents from Group 1 are mixed with one or more solvents from Group 2 to produce a combination having a solubil-ity parameter in the appropriate range.
Finally, the CPC must be considered. It has generally been found that the CPC of most pigment/solvents/polymer systems is 9-10% or less. Choosing the exact pigment concentration is readily accomplished by one skilled in the art after selecting a mixed solvent system and a particular block copolymer.
_ 12 -1: r ~i ~
7fa . ~
~131,R 1 Solvcnt & Chcmical Solubility Boiling Evaporation Manu~acturcr Description . 'Paramcter Point,C ~3tc~
. .
GROUP l . .
Isopar M Heavy isoparaffinic naphtha 7.2 207 ~lO. .
(Exxon) Cll Cl7 .
~agicSol 47 Oil SMagie) Hydrotreated middle distillate 7.2 238 ~ l 1102 Oil (~itco) ~ight vacuum gas oil 7.2 266 < l MagieSol 44 Oil (Magie) ~ydrotreated midd].e distillate 7.5 226 2 1108 Oil i (Witco) ~Iydrotreated middle distillate 7.3 280 ~ l Norpar 13 Normal paraffin . 7.4 , 229 . <lO
(Exxon) ~ Cll ~17 c~ . .
Dodecane C~2 hydrocarbon ~ 7.8 2l6 med.low ~r''~ ?.~ .
. Aromatic l50 : (Exxon). Heavy aromatic naphtha . 8.7 183 ~lO
. -. DXE
(Gulf) . 1,l-di(ortho-xylyl)ethane 8.8 335 v.low Han Aromatic ~iddle : .
(Exxon) distillate extract 8.~ l69 ~lO
DOP . ~~ dicctylphthalate 8.9 38b ~ O
. ,, .
. - - - - - ' ' - _ _ . .
a. Relative evi~poration rates ~here butyl acetate = lOO . .
1~ 7Z'7~
Pressuri~ation is required for the erasabIe inks of the present invention which are too visous to flow at a s~lfficicnt rate under the force of gravity alone. Prior art erasabIc inks often require 10 psi to produce an acceptable written line. In contrast, the inks of the present invention typically require less than 1.0 psi to produce a written line of similar quality.
The amount of pressure required depends on several factors including temperature, the particle size of the pigment, the polymer employed, and the ~ap between the ball and the lip of the ball-retainin~ socket. The pressure for any particular combina-tion is readiJy determined by one skilled in the art. Various means for applying appropriate pressure are well known in the prior art including U.S. Patent 3,000,354; U.S. Patent 3,099,252;
and U.S. Patent 3,425,779.
A preferred additive to the ink of the present inven-tion is polybutene to enhance the cohesive strength of par-ticularly styrene-isoprene-styrene elastomers. The polybutene has no effect on pressurization or line intensity, but increases the erasability of inks when used in concentrations up to about 10% by weight. Polybutenes are a series of butylene polymers composed predominantly of high molecular weight mono-olefins (85-98%), the balance being isoparaffins. Preferred polybutenes have a viscosity of about 3026-3381 centistokes at 210F and average molecular weight of about 2060. Polybutenes are made by polymer-izing an isobutylenerich butene stream with a metal halidecatalyst.
72~
Thc polymc~r backhorle structtlrc r~ scmblc~ olyisobll~y].crl~, alt:houyh mor~ 1- and 2~ butcnes a.re i~orporated in t~le ! lo~lcr molcc:ular-~cight; fract:ions. Thc olcfin structurc is I prcdominently the trisubstitu~cd t~p~ (R-C~I~C'R2). Only j minor amounts of vinylidene (R-CH2-~ R) and terminal vinyl I (~-CH=CH2) structures are prescnt. A preferred poly~utene ~' , ~ i5 sold under the trade1~ffle Indopol H-1500 by ~moco Chemicals Corporation, 200 East Randolph Drive, Chicayo, IL 60601.
Another preferred additive is poly-alpha-methylstyrene which can be used alone or in conjunction with polybutenes.
With this addi~ive, line intensity is unchanged, but eras-¦ ability is increased with increasing concentration. However, the pressure to write increases proportionately with concen-I tration such that poly-alpha-methylstyrene is useful only in L5 I pressuri3ed inks and is t~ically used in concentratiGns up . to aboui 10% by wei~ht.
It has been found ~lat the addition of polybutene and poly-a'pha-methylstyrene dramatically reduces the tendency to smearing of prior art erasabl~ inks whic~ is seen initi~lly after writing.
~rasability can be evaluated by manual erasure and visual observation, but this involves personal fact~rs such a~ pressure applie~, size of surface being erased, etc. A
mor~ accurate evaluation can be conducted by applying the trace by a standard writing test method in which the paper is advanced beneath the writing instrument at a rate of 11.5 ~m. per 10 cycles and at the same ra~e under an erasing head provided with an Eberhard-Faber Pink Pearl Pencil Eraser .
; 15 -~ ;7,27 ~tlOl (S~orc ~3~ Durom~ter hardrl~ss, ~SI~ D 22~0), ~1pplied to ~}~c p~pcr bcaring thc tr.lcc unc1er ~ load o 375 ~Jranls upvn Gurfacc m~suring 9 m~. by 23.~ rnm. in thc directior1 of tr~vel, the ~rasing head reciprocating ~lt a ratc o 80 cycles per ~inut~, thc.lcngth of each stroke being 63.5 mm. I
Each trace is thus subjected to 7 cycles of erasing and .
results can be visually observed.or rated by photometer .
readings.
Smearing can be tested by taking Ross micro ~ax ~1365, obtained from Frank B. Ross Company, Inc., 6-lO Ash Street, Jersey City, 1~ew Jersey and ~orming it into plugs.
the size of a standard eraser, placing i~ into an erasing . machine as described above and running over a fresh tracing five cycles. This produces a reasonably uniform sm~ar ~Ihich can ~hen be placed into a reflectometer and r.easured against the reflectance of the same paper without ink on it.
. The equation used. to de~ermine the percent smear~.ng . i~ . o , ,, % smearing =.~ nS x lO0 , ~7here Ru is the re lectance of the unm~rked paper, ~ is th~ re-flectance of the mar~ed pa~er, and RS is the reflectance of ~he smeared area~
-- While the major c~mponents of the ink have been stressed ~bove, the presence in the ink of additives such as corrosion inhibitors, lubricants such as lauric acid or stearic acid, preservatives, parting com~ounds (between ink in a reservoir and a gaseous ~ressuri~ing agent), and dispers- ;
ing agents, is not precluded.
. -16 . ..
The inv~ntion will ~c furthc~ illustratcd by consider~tion of thc following cY.amplcs which ar~ intend~d . to be purely exemplary of the use of the invention.
. . ' ', .
EXAMPLE I .
.. ' .' . '.
An ink employin~ a radial styrene-isoprene-styrene block ~opol~ner sold under the trademark Solprene 418 by Phillips Chemical Company, Borger,.Texas, having a styrene/
isoprene ratio of 15/85 was used to prPpare an erasable ink . requiring no pressurization. 20 gr~ms of the block copol~ner 1.0 was dissolved in 49.8 grams of dodecane and 10.2 grams of dixylylethane. To this was added 20 grams of a pi~nent . dispersion OI 31.6% Victoria ~lue, 14 1% Phthalo Blue, and ¦ 54.2% dioctyl phthalate. The combination of solv~nts produced .
. a solubility parameter of 8.1. The resultin~ ink prod~ced a written trace with acceptahle line intensity and erasability.
~^' "' -, '''- . I
~ ~... EX~MPLE Il , - - .
- Example I was repea'ed with 10 grams-of a linear ~lock ~opol~ner having a styrene/isoprene xatio of 14~86 .sold by Shell Chemical Company, Houston, Texas, and a mixed ~olvent system of 67.2 grams of isobutyl isobutyrate having solubility parameter of 8.1, ~.~ gxams of methyl ethyl ketone having a solubility parameter of 9.3, and 20 grams of th~ pigme~t dispersion of Example I. Thc resulting combina~
¦~ tio f sol\el~ts ha~ a solubility par~loeter of B.7. The I . ". I
. .' ~ .
7 ~
r~sult:ir~(3 irlk produccd cl wri~tcn ~racc wit~l acccp~ablc lirlc int~nsity and cr~sability, ; E~MPLE IlI
' ': ' .
~n ink employing a styrene-ethylene/butylene-styrenc block copol~er sold under the trademark Kraton G1650 by Shell Chemical Company, Houston, Texas, having a styrene to ru~ber ratio of about 28 to 72 was prepared by mixing 10% by weight of block copolymer with $0% by weight of toluene.
The dissolved polymer was then mixed with a pigment dispersion D consisting of 60% by weight of toluene, 21.7% dioctyl ph~halate, 12.6% Victoria Blue and 5.7~ Phthaloc.yanine Blue~
¦ The resulting ink was placed in a conventional ref~
¦ c:artridge ar.d pressurized to a pressure of 0.6 psi. The ¦ resulting ink produced a written trace with acceptable line ¦ intensity and moderate erasa~ility.
I' ..i - .. ..
l _ EXAMPLE IV
.-.................. , .
Exam~le III was rep~ated with a styrene-isoprere-styrene block copoly~er sold under t~e trademark Kraton 1101 by Shell Chemical Company, Houston, Texas, having a styrene to rubber ratio of 30 to 70 in place of the styrene-ethylene/
butylene~styrene bloc~ copoly~ller. The resulting ink produced a written trace wi~h acceptable line intensity and good erasability~
- la . ... ...
~ ~ ~'72'~'~
Ex~ r.r, V
. ''' " '~ .
A xe111 capable of ~r.iti.ng ~ hout pressuriz.l~ion was prepared employing an ink ~ontaining the ~ollow.ing ingredients by weight: 4.0% Indoast Violet; 5.0% Kraton. .
1107, a linear styrene-isoprene-styrene block copolymer having a styrene/isoprene rat.io of 14/86 sold by Shell Chemical Company, Houston, Texas; 1~.0% Solprene ~23, a radial styrene-isoprene-styrene block copolymer having a styrene/isoprene ratio of 15/85; 5.0% Indopol H 1500, a polybutene sold by Amoco Chemicals Co., Chicago, Illinois;
6% dioctyl phthalate; and a mixed solvent of 49% l,l-di(ortho-xylyl)ethane and 16% MagieSol 44 to produce a ~ of approxi-mately 8.4. Tke resulting ink produced a written line of good line intensity and good erasability.
. , ' - , ' . .
j EXP~LE VI
~' ~
A refill re~uiring a ~ressurization of about 0;3 psi and h~ving good line intensity and good erasabili~y was produced by the following formulation:
Inqredient~ ~,w~
~` Kraton 1107 5,0 .
S~lprene 423 15.0 I~ldopol 1500 5,~
Poly-alpha-methylstyrene . 6.0 Aromatic 150 ) .
) ~.s. to~
S ¦ MagieSol 44 l ~ 19 .l . ~
. . Victoria ~.luc 15.0 Dioctyl phthal~ 15.0 .
. , '.
.. . EX~PLES VXI & VIII
'''`: ' . . ' ' '-- ' .
~ Ex~mples VII and VIII illustrate t:he beneficial effect of polybutene arld poly-al~-ha-methy].styr~ne on smearing tendency.
.' . ' .' ' INK COMPCSITION (percent by weight~ .
Exampl~ VTI Exam~le VIII
10. Solprene 423 16.2 14O7.
¦ Kraton 1107 5.4 ~Og ~n~opol H-1500 . ~;- 3,0 Resin 18-210 (1) --- 6.0 Lauric Acid . 1.4 . 1.1 Stearic Acid 0~5 0.4 . Toluene ~26.5 lg.5 Dioctyl phthalate 27.1 27.1 . BT-264D (2~15.8 15.B
BT-427D ~ 7.1 7~1 _, ~ ' '' '' .... ~
.
~0 ~1) Poly-alpha-methylstyrene sold by AmOCQ Chemicals Corp., Chicago, Illinois.
- 20 - . .
. 11, ~ I
lZ4'72~7~
. ~) Victoria ~luc sol~ by E. I, DuPont, ~ilmington, Dcl~arc.
. (3) ~hthalocy~lnine Bluc sold by E. I. Du~ont, Wlllni.ncJ~on, :; . Dcla~arc.
: : . The inks of Examples VII and VIII were compared using the smearing test descrioed a~ove. The smeariny tendency of the ink of Example VIII was about two-thirds ', that of Example VII and the inks of the prior art.
.' .' ,. ' ' .
. , , ~~'' ' ''' ' "
~ ~
. " ,~. .
~21~
., . .
`I
Claims (5)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. An erasable ink for use in a ball-point writing instrument consisting essentially of a pigmented organic solvent solution containing a thermoplastic block copolymer having an arrangement of A (thermoplastic) and B (rubbery) blocks selected from the class consisting of ABA, (AB)nX and (-AB)-n; in which said thermoplastic blocks are selected from the class consisting of styrene, ester and urethane blocks; in which said rubbery blocks are selected from the class consisting of butadiene, isoprene and ethylene-butylene blocks; in which the weight ratio of said rubbery blocks to said thermoplastic blocks is from 60:40 to 90:10; in which the solubility parameter of said organic solvent is from about 7 to about 10.5 (cal/cm3)1/2;
and containing an effective amount up to about 10% by weight of said solution of an additive to increase erasability selected from the class consisting of polybutenes and poly-alpha-methylstyrene.
and containing an effective amount up to about 10% by weight of said solution of an additive to increase erasability selected from the class consisting of polybutenes and poly-alpha-methylstyrene.
2. An erasable ink as described in claim 1 in which said block copolymer has butadiene or isoprene midblocks.
3. An erasable ink as described in claim 1 in which said block copolymer has butadiene or isoprene midblocks and in which the solubility parameter of said organic solvent ranges from about 0.1 to about 8.7 (cal/cm3)1/2.
4. An erasable ink as described in claim 1 in which said block copolymer has butadiene or isoprene midblocks and in which said organic solvent is a mixture of at least two organic solvents, at least one of which has a solubility parameter of about 7.2 to about 7.8 (cal/cm3)1/2, at least one other of which has a solubility parameter of about 8.7 to about 8.9 (cal/cm3)1/2 and in which said mixture has a solubility parameter of about 8.1 to about 8.7 (cal/cm3)1/2.
5. An erasable ink as described in claim 1 in which said block copolymer has butadiene or isoprene midblocks, in which the solubility parameter of said organic solvent ranges from about 8.1 to about 8.7 (cal/cm3)1/2 and in which the concentration of pigment does not exceed about 10% by weight.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US06/318,307 US4391927A (en) | 1981-11-05 | 1981-11-05 | Erasable inks containing thermoplastic block copolymers |
| US318,307 | 1989-03-03 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1247274A true CA1247274A (en) | 1988-12-20 |
Family
ID=23237605
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000413487A Expired CA1247274A (en) | 1981-11-05 | 1982-10-15 | Erasable inks containing thermoplastic block copolymers |
Country Status (3)
| Country | Link |
|---|---|
| US (1) | US4391927A (en) |
| CA (1) | CA1247274A (en) |
| PH (1) | PH20710A (en) |
Families Citing this family (20)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO1984000174A1 (en) * | 1982-07-01 | 1984-01-19 | Bic Corp | Erasable ink composition and process for forming erasable script |
| US4721739A (en) * | 1982-07-01 | 1988-01-26 | Bic Corp. | Erasable ink compositions |
| JPS5980476A (en) * | 1982-10-29 | 1984-05-09 | Pilot Pen Co Ltd:The | Erasable ink for ball-point pen |
| US4847326A (en) * | 1985-12-19 | 1989-07-11 | The Dow Chemical Company | Copolymer blends |
| US4988123A (en) * | 1986-09-15 | 1991-01-29 | The Gillette Company | Erasable system including marking surface and erasable ink composition |
| MY109293A (en) * | 1991-12-18 | 1996-12-31 | Gillette Co | Fiber marker including an erasable ink |
| US5599853A (en) * | 1993-01-29 | 1997-02-04 | The Gillette Company | Erasable inks |
| CA2076318A1 (en) * | 1992-03-23 | 1993-09-24 | Andree Santini | Erasable marking composition |
| US5300538A (en) * | 1992-06-02 | 1994-04-05 | The Gillette Company | Solid marking compositions |
| USH1517H (en) * | 1993-07-12 | 1996-02-06 | Shell Oil Company | Radiation curable printing ink composition |
| IL111305A (en) * | 1993-10-18 | 2000-02-17 | Gillette Co | Non-erasable liquid ink and marking instrument containing it |
| US5852072A (en) * | 1994-12-16 | 1998-12-22 | Bic Corporation | Erasable ink composition containing a waterborne polyurethane urea |
| US5900445A (en) * | 1994-12-20 | 1999-05-04 | Bic Corporation | Erasable ink composition containing a polymer dye obtained from ethylenic monomers and marking instrument containing same |
| US5661197A (en) * | 1994-12-20 | 1997-08-26 | Bic Corporation | Erasable ink composition containing a polymer-encapsulated colorant derived from monomer containing dissolved colorant |
| US5852073A (en) * | 1994-12-21 | 1998-12-22 | Bic Corporation | Erasable ink composition containing a polymer-encapsulated colorant obtained by polymerizing monomer in the presence of solid colorant particles |
| US5916357A (en) * | 1997-03-25 | 1999-06-29 | The Gillette Company | Eradicable inks |
| KR100642350B1 (en) | 1998-12-03 | 2006-11-03 | 파일롯트 잉크 가부시키가이샤 | Rubber-erasable aqueous ink for writing material composition and ball point pen and marking pen with the ink contained therein |
| US6224284B1 (en) | 1999-10-12 | 2001-05-01 | Dri Mark Products Incorporated | Metallic ink composition for wick type writing instruments |
| US6797748B2 (en) | 2001-06-08 | 2004-09-28 | Bic Corporation | Polyurethane based inks for writing instruments |
| US6890972B2 (en) * | 2003-01-09 | 2005-05-10 | Advance Watch Company, Ltd. | Erasable ink for a writing implement |
Family Cites Families (13)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB1092563A (en) * | 1965-01-06 | 1967-11-29 | Shell Int Research | Thermoplastic elastomeric composition incorporating a block copolymer |
| US3875105A (en) * | 1968-08-12 | 1975-04-01 | Scripto Inc | Erasable writing medium suitable for use in ball point pens |
| US3880953A (en) * | 1969-03-17 | 1975-04-29 | Goodyear Tire & Rubber | Adhesive composition |
| US3784587A (en) * | 1972-07-31 | 1974-01-08 | Goodyear Tire & Rubber | Adhesive composition containing an a-b-a block copolymer,poly alpha-methyl styrene and a tackifying resin |
| US4097290A (en) * | 1974-08-09 | 1978-06-27 | The Gillette Company | Ball-point instruments writing with improved transitorially erasable trace and ink compositions therefor |
| US4011178A (en) * | 1974-12-23 | 1977-03-08 | The Goodyear Tire & Rubber Company | Resins and polymer mixtures thereof |
| US3993613A (en) * | 1975-02-24 | 1976-11-23 | Phillips Petroleum Company | Adhesive composition |
| US4244862A (en) * | 1976-02-05 | 1981-01-13 | Denki Kagaku Kogyo Kabushiki Kaisha | Compositions for paints and printing inks |
| US4059554A (en) * | 1976-05-28 | 1977-11-22 | Xerox Corporation | Stabilized emulsion inks |
| US4101484A (en) * | 1976-10-04 | 1978-07-18 | Phillips Petroleum Company | Sealant based on thermoplastic elastomer and mixed modifying resins |
| US4101482A (en) * | 1976-10-04 | 1978-07-18 | Phillips Petroleum Company | Sealant based on mixture of unsaturated and hydrogenated block copolymers |
| US4229338A (en) * | 1979-05-11 | 1980-10-21 | Shell Oil Company | Suede-look shoe soles |
| US4329262A (en) * | 1981-03-25 | 1982-05-11 | Scripto, Inc. | Initially erasable ink composition for a ball point writing instrument |
-
1981
- 1981-11-05 US US06/318,307 patent/US4391927A/en not_active Expired - Lifetime
-
1982
- 1982-10-15 CA CA000413487A patent/CA1247274A/en not_active Expired
- 1982-10-27 PH PH28048A patent/PH20710A/en unknown
Also Published As
| Publication number | Publication date |
|---|---|
| US4391927A (en) | 1983-07-05 |
| PH20710A (en) | 1987-03-30 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| CA1247274A (en) | Erasable inks containing thermoplastic block copolymers | |
| CA1246766A (en) | Erasable inks containing thermoplastic block copolymers | |
| US4389499A (en) | Erasable inks containing thermoplastic block copolymers | |
| US4349639A (en) | Method of making and the composition for an initially erasable ink for a ball point writing instrument | |
| US4329262A (en) | Initially erasable ink composition for a ball point writing instrument | |
| US4721739A (en) | Erasable ink compositions | |
| JPH03237171A (en) | Erasable aqueous ink composition | |
| US4329264A (en) | Ballpoint writing instrument containing an initially erasable ink | |
| EP0890620A1 (en) | Water base ink having metallic luster for ball-point pen and aqueous pigment ink | |
| CA2076318A1 (en) | Erasable marking composition | |
| US4410643A (en) | Method of making and the composition for an initially erasable ink for a ball point writing instrument | |
| US5629363A (en) | Aqueous-based, shear-thinning, erasable ink and roller-ball pen containing same | |
| US4606769A (en) | Erasable black ink composition for ball-point pens | |
| US4367966A (en) | Erasable ink for ball point pens comprising trifluoroethylene and vinyl acetate polymers | |
| EP0092578B1 (en) | Erasable inks containing thermoplastic block copolymers | |
| US4419464A (en) | Erasable ink for ball point pens | |
| WO1994010251A1 (en) | Erasable marking medium composition | |
| EP0721485B1 (en) | Correction and marking materials | |
| WO1997016499A1 (en) | Aqueous-based, shear-thinning, erasable ink and roller-ball pen containing same | |
| US9809722B2 (en) | Transitorially erasable ink compositions and writing instruments containing same | |
| AU1778783A (en) | Erasable ink composition and process for forming erasable script | |
| JP2003237279A (en) | Follower for non-aqueous ball point pen | |
| JPS63273676A (en) | Oily pigment ink for writing utensils | |
| JPH1030074A (en) | Recording liquid composition | |
| JPS60190481A (en) | Ink for ball-point pen |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |