CA1265414A - Silane dispersing agent for magnetic media - Google Patents

Abstract

SILANE DISPERSING AGENT
FOR MAGNETIC MEDIA

ABSTRACT

Ferromagnetic particles are dispersed for use in magnetic coatings by a novel dispersing agent containing either silylated alkylene oxide copolyethers or isocyanatoalkyl silanes in combination with phosphate esters.

Description

~%~
^ 1 -SILANE DISPERSING AGENT
FOR MAGNETIC MEDIA
BACKGROUND OF THE INVENTION
This invention relates to a novel sil~ne-contalning dispersing agent in~ended for use in the dispersion of ferromagnetic particles employed ~n magne~ic coating. More particularly, this in~ent~on relates to novel compositions contalning silylated copolyethers or isocyanato silanes wi~h phosphate esters as the silane-containing dispersing agent.
PRIOR ART
Audio and video tape and other informat~on-storing magnetlc media, can be prepsred by coat~ng MylarTM or some other non-magnetic substrate with a solvent-based magnetic coating cont~ining ~ine ~errom~ tic p~rticles dispe~sed in a suitable polymeric binder. In conventional practice, the acicular (needlelike) ferromsgnet1c particles are orien~ed ~n a magnetlc field and the solvent is evaporated.
The current trend in the electronics industry is toward higher information density which can be achieved with suitable dopants (often cobalt) and by the use o~ progressively ~-maller ferromagnetic partlcles of h~gh coerclve strength.
These ~actors increase dispers~on viscosity enormously. Consequently, effectlve dispersing agents are needed to sch~eve the high partlcle loading densi~y required.
Prlor art teachin8 dlsperslng agent~ for magnetlc media da~es back 15-20 years. U.S. Pa~ent

2 -

3,144,352 describes the use of lecithin British Patent 1,080,614 describes the use of oleic acid lubricant ~nd monobutyl phosphate dispersant. ~er.
Offen. 2,543,962 teaches ~he use of aminosilanes for improved dispersibility and abrasion resistance.
U.S. Patent 4,076,890 teaches a range of organofunctional silanes as dispersing agen~s (including alkyl, amino, mercapto, epoxy, vinyl, chloro~ in magnetic media for abrasion resistance and reduced drop-out.
Organo$unctlonal silanes have likewise been reported as improving the squareness ratio in magnetic coatings. Japanese Kokai 81 49 767 and CA
g5-995~6.
Phosphate dispersants are widely reported in the literature. Sodium metaphosphate (CA
86-19g032). Potassium dihydrogen phosphate (~apanese Kokai 79,143,894). Polyethylene-polypropylene glycol monoether phosphates (J~p~nese Kokai 82,205,461). Dioctylphosphate (European Patent Application 48456). Phosphoric acid alkyl ester (U.S. Patent No. 4,244,987). Lecithin (U.S.
Patent Nos. 3,144,352 and 4,196,258).
Combinations of aminosil~nes with surfactant are disclosed in Japanese Kokai 58,1559517 and U.S. Patent No. 4,244,987.
In broad strokes, the prior art mentions the use of ~ range of organofunctional silanes for various benefits in magnetic coating. Notably absent, however, ~re re~erences to polyether silanes or isocyanato ~ilanes. Cited dlspersing agents ~lso include a rangP o~ candidates, chiefly the phosphates.

The frag~le needle-llke ferromagnetlc particles have an unusually high propensity to form strong aggregates primarily because of magnetic attraction between particles. To a lesser degree, part~cle asymmetry, surface area, surface roughness and sorbed species (air, water) slso favor agglomerat~on. When an inappropriate dispersing agent is used, mechanics~ d~spersion can fracture the ferromagnet~c particle causing a performance loss. This is of particular concern with fine ferromagnet~c particles designed for higher information densi~y. Thus an effectlve dispersing agent, such as presently set forth, performs an important unction.
This present inventlon ~s novel in th~t it provides the use of a combination of a polyether silane or isocyanato silane and an organophosphate ester as an effective dispersing agent for use in magnetic coatings. Unexpected benefits in the reduction of viscoslty is an impor~ant aspect of this invention not previously descrlbed in the prior art.
SUMMARY OF THE INVENTION

The novel composition of a silylated copolyether or ~n isocyanato silane with Rn orgsnophosphate este~ outperformed "state of the art" dispersing agents. The novel dlspersant of the present invention w~s found to be ef~ectlve when integrally added or pretreated on the ferromagnet~c particle. Because dispersion viscosity is effectively reduced, higher pigment lo~dings without the loss of ~ilm integrity; reduced grinding times;
reduced sur~actant demand; magnetic co~tings with improYed tensile strength, squareness (ratio of remnant magne~ic flux density to satura~ion magnetic flux density) magnetic proper~ies, surface appearance and less migration of dispersing agent to the surface of the magnetic coating are expected as concom~tant benefits.
DETAILIED DESCRIPTION~ OF THE INVENTIO~

In accordance with the ins~ant invention there is provided a novel dispersing composition useful in the dispersion of ferromagnetic partlcles in the manufacture of magnetic coatings. This dispersing composition comprises a silylated copolyether or ~n isocyana~o silan~ with a phosphate ester.
The s~lylated copolyether employed as a component in the dispersing agent of the present invention is of th~ general formula:

R2 ~4 [~30(CmH2m-cHo)x~cH2-cH~o)y CWH2W~ 2 Si [ ~ 4-(2 a) ~here Rl ls indivldually a hydrogen atom, an alkyl group having from 1 to 12 carbon atoms, an alkoxy slkyl group having from 2 to 12 carbon atoms, or sn acyl group having from 6 to 12 carbon a~oms; R2is individually a hydrogen atom, sn alkyl group h~ving from 1 to 18 carbon atoms or ~n aryl group having ~2~

from 6 to 18 carbon atoms; R3 is indlvldually a hydrogen atom, an alkyl group having from 1 to 12 carbon atoms, an aryl group having from 6 to 18 carbon atoms or an aryl alkyl group having from 7 to 18 carbon atoms; R is individually an alkyl group having l to 4 carbon atoms; the sum of x + y has a value of from 2 to 100, preferably 10 to 60; z has a vAlue o$ 1 ~ ? or 3 and preferably is equal to 1; w has a value 0 to 6, preferably 3; m has a value of 1, 2 or 3; and a has a value of O or 1.
Exemplary silylated copolyethers which are useful in practicing the present invention include, but are not limited to, C,H3 CH30(CH2-C-0)27(CH2-cH2-0)24 C3H6si(0CH3)3 C4HgO(CH2-C~0)5C3H6Si(OcH3)3 H
C~3 C4HgO(CH2-C-O~gC3H6Si(OCH3)3 H

CH30(CH2-CH2O312~3H6S~(OcH3)3 C4H9o~cH2-cH25))l2c3~l6si(ocH3)3 CH30(CH2-CH20) 1oC3H6Si (OCH3 )3 ,CH3 CH30(CH2-C-0)2C3H6sl~OcH3)3 H

~-O( CH2 -C -O ) 4 ( CH2 -CH20 ) 4C3H6S i ( OC2Hs ) 3 and H

C9Hlg-~-o(cH2-cH2-o)lo-c3H6si(ocH2-cH2ocH3)3 C, H3 / CH3 CH -O(CH2-C-0)2~CH2-CH20)24C3H6Si(OcH3)2 :

CH C(O)O(CH2-C-0)5C3H~, Si(OCH3)3 , ~2~

C~3 C2~Hs ~H o~cH~-c-o)4o(cH~-cH2o)24c3H6si~ocH3~2 Generally, the s~lyla~ed copolyethers are commercially ava~lable or they may be prepared by reacting a hydroxyl end capped polyether wlth allyl chloride followed by the hydrosllylatlon of the adduct, l.e., as ~aught in U.S. 2,868,~24 and U.S.
2,846,458.
The isocyanRto sllane employed ~s an alternat1ve to the sllylated copolyether component in the d1spersing agent is of the general formula II.
~6 OCN-R -Si-~OR )3-b where R6 is indivlduslly an alkyl group having 1 to 4 carbon a~oms; R7 is lndividually a hydrogen atom, an alkyl group having from 1 ~o 12 carbon atoms, an alkoxy alkyl group having from 2 to 12 carbon a~oms or an acyl group hav~ng from 6 to 12 carbon Rtoms; b is O, 1, 2 or 3; and R is an alkylene, arylene or aralkylene grou~ havlng from 1 to 18 carbon atoms or a group o the ~ormula:

.

H O

~ N - C - NH - C3H6-CH3 ~

OCN

Exemplary isocyanato silanes include but, are not limi~ed to, C,H3 OCN -:C3H~ - Si - (OC~3)2 OCN - C2H6 - Si - ~OCH3)3 l_ O
OCN ~ ~ N C - HN - C3H6 - Si (OCH3) OCN ~ (C3H6) Si (OCH3)3 o, m, p isomer OCN - C3H6 - Si (OC2Hs)3 The isocyanato silanes are commercially available or they may be prepared by forming the carbamate adduct of an alkylchloroformate with an aminoalkyltrialkoxy silane and cracking the carbamate to form the isocyanato silane~and alkanol. See for instance U.S. Patent 3,607,901.

~L2~
_ 9 The phosphate ester employed as a second component in the dispersing agent of the present invention is of the general formula:

III.

[R8((:~CH2-C )c(oc~2-cH2)do~e P [OA~v where R is a hydrogen atom or an alkyl group containlng from 1 to 1~ carbon atoms; R is a hydrogen atom, an alkyl group containing from 1 to

4 carbon atom, an aryl group containing from 6 to 18 carbon atoms; or an alkylaryl group containing from 7 to 17 carbon atoms; the sum of c ~ d has a ~alue of from 2 to 100 and preferably c is at least 1; e has a value of 1 or 2; v has a value of 1 or 2; and A is a hydrogen, sodium, potassium or lithium atom or an NH4 group.
Exemplary phosphate esters which are useful in practicing the present inv~ntion include, but are not limited to, ..
C4H9(o-cH2-c)2oo-p-oH
H OH

..
C4Hg(O-CH2-C)sO-P-OH
H OH

C, H3 ,O, C4Hg (O-CH2-C)440-P-OH
H OH
C~13 C4Hg ( O - CH2 - C ~ 2 ( OCH2 - CH2 ) ;~ 50 -P -OH
H Off ~H3 ,, 4Hg (o-cH2-c)l4(ocH2-cH2)l9~-p-oH
H OH

GH3 ..
4Hg ~O-CH~-C)34(0cH2-c~2)450-P-oH
H OH

4Hg ( OCH2- C ) 10 ( OCH2 ~ CH2 ) 42 ~P, OH
H OH

, 3 "
H3 (OCH2-C)s O P - O Na H OH

~-1467g o CH3 .. I ,.
CH3 C (ocH2-c)2(ocH2c~2)2~5 P ONH4 OH

Generally, the phosphate es~ers may be prepared by the phosphorylation of a hydroxy endblocked polyalkylene oxide with polyphosphoric acid or phosphorus pentoxide. It is believed that phosphorylation is preferably conducted in such a manner as to maximize mono-ester formation and minimize ~ormation of diorgano phosphate esters and free phosphoric acid. See U.S. Patent 3,235,627 and U.S. Patent 4 t 4161830.
In addition to the silylated copolyethers and the phosphate es~ers, the dispersin~ agent may optionally contain the followlng:
(a) Ancillary wetting agents ~e.g.
lecithin);
(b) Acid scavengers (e.g. propylene oxtde);
~ c) Organomodified silicone fluids to modify surface tension, surface lubricity or reduce static charge; and ~ d) Adhesion promoters.
The ratio of silylated copolyethers to phosphate esters is from 10:90 to 99:1, preferably 25:75 to 75:25.
The ratio of isocyanato silane to phosphate ester is from 35:65 to 99:1 preferably 50:50 to ~0:10, The manner in which the dispersing agent acts to disperse the ferromagnetic particles is . .

~: i;5~

sllb~ect to scientific con3ecture and may lnvolve two separate stages, each requiring a speci~ic componen~. The understanding o~ ~his mechanism ia not, however, a critical aspect o~ thls inventlon.
One component of this present invention ls a low molecular weight anionic polyether ester acid phosphate which ia sorbed on the ferromagnetic particle. In this firs~ stage sorption, the erromagnetic par~lcles acquire a greater charge and are subsequen~ly separated by electrostatic repulsion which counteracts the usual magnetic forces of at~rac~ion. Because most magnetic coating formulations are typic~lly nonaqueous9 thls electrokinetic e~fect resides close to the ferromagnetic partlcle surface. Consequently this first stage sorption gives ~ quic~ but short range separation that ~nitia~es the deagglomeration process .
This limited separation exposes ferromagnetic particle surface area to a second stage sorption of a higher molecul~r welgh~
polyether silane which may ultimately covalently bond to the ferromagnetic particle via Si-O
linkages. The bulky silylated polyether acts to further increase an~ maintain ferromagnetic part~cle separation. Since the force of magnetic attraction diminishes wlth the distsnce of pa~ticle sepsration, agglomerates are effectively deagglomerated and ~he ~ndency to reagglomerate is diminlshed.
Additional f~ctors may also be involved.
The polyalkylene oxide mo~ety present in either component of the lnvention i~ believed to facilit~te desorption of air and wster from the ferromagnetic D-1467~

., , .. .. .... - -particle surface, render the particle surface more organophilic and therefore more susceptible to wetting by the organic solvent and/or the polymer binder.
Other agents used in the preparation of the magnetic coating include, but are not limited to organic solvents (acetone, MEK, THF, DMF); thermo-plastic polymeric binder (polyurethane, PVC, phenoxy resin, acrylic resin, cellulosic resins); thermoset resins (epoxy); electron beam curable oligomers (urethane acrylates~; cross linkers or curing agents (polyisocyanates); lubricating agents (silicone fluids, organomodified silicone fluids, fatty acids and corresponding derivatives); antistatic agents (halo- and quarternary nitrogen compounds);
conductive pigments (carbon black); wetting agents (lecithin, "Aerosol OTT~"), and additional silanes to improve adhesion or other properties.
The dispersing agent may be either pretreated onto the ferromagnetic particles from aqu~ous or organic solvent slurry or integrally added to the coating formulation.
In general the magnetic recording medium consists of a support having thereon a magnetizable recording layer in which the ferromagnetic particles are dispersed in a binder, the contained ferromagnetic particles having been processed with the dispersing agent of the present invention.
The magnetizable powders which can be used in the present invention include the generally known and conventional ferromagnetic powders. Suitable ferromagnetic powders are y-Fe203, Co doped ~2~5'~

y-Fe2O3, Fe3O4, Co-doped Fe3O4, CrO2, ferromagnetic alloy powders or mixtures thereof. Specific Pxamples of these ferromagnetic alloy powders are as follows: Fe-Co, Fe-Ni, Fe-Co-Ni-, Fe-Ni-Zn, Fe-Mn-Zn, Fe-Co-Ni-B, Fe-Co-Ni-Cu-Zn, Fe-Co-Ni-Cr, Fe-Co-Ni-P, Fe-Ga-As, Fe-As-Te, Fe-Mn, Zn-Cr, Ni-Co, Ni-Cu, Ni-Cr, Co-Mn, Co-Mg, Ni-Co-As-Sb, Ni-Co-As-Sb, Cr-Ga-As, Cr-As-Te, and Cr-As-Sb, and the like.
These alloys are well-known in the art and are described in U.S. Pat. Nos. 3,026,215;
3,031,341; 3,1Q0,194; 3,242,005 and 3,389,014;
British Pat. Nos. 752,659; 782,762 and 1,007,323;
French Pat. No. 1,107,654; German Pat. No. OLS
1,281,334. These ferromagnetic powders are generally used at about 300 parts by weight in a binder at a level of about 50 to sbout 200 parts by wt., preferably 70 to 150 parts by wt. The particle size range of the ferromagnetic powder generally employed is a particle size of 0.2 to 2 micrometers in length, with an aspect ratio of 1/1 to 20/1.
Solid additive particles generally present in the magnetizable layer are inorganic particles such as carbon black, graphite, molybdenum disulfide, tungsten disulfide, clay, silica, carbonates, alumina powder, abrasive materials, metal oxides, etc., and these are particularly effective. Organic particles such ~s fine powders of $1uorine-contRining resins, polyolefin resins, polyamide resins, etc., can also be incorporated with no particular detrimental influences. The fluorine-containing resins gener&lly ha~e a molecular weight from about 80,000 to about 120,000 L L~

and are materi~ls such as trifluorochloroethylene, tetrafluorethylene, etc., the polyoleÇins reslns generally have a molecular weight o~ abou~ 800,000 to about 1,200,000 and are materials such 8S
po~yethylene, polypropylene, e~c., and the polyam~de resins generally have a molecular weight of abou~

5, ono to about 200~000 and are materials such as

6-nylon, 6~6-nylon, 6,10-nylon, 7-nylon, 9-nylon, ll-nylon, and ~he like. These materials are described in Japanese Patent Publicat~on Nos.
40461/71 and 3~001/7~. These solid additive particles are added, in part~cular, as antistatic agents, lubricants, surace-ma~ting agents or a tape dursbility-improving agents as described in U.S.
Pat. Nos. 3,2.~3,n66; 2,~58,106; 3,312,563; 3,517,378 and 3,630,914. They are o~ten utilized generally in the production o~ tapes a~ a level of ~bout 0.1 to 25 wt.~, preferably 0.2 to 13 wt.~, of the inorganic or organic particles per 100~ by wt. of the ferromagnetic powder; with particle sizes of about 0.02 to about 2 microns, preferably 0.08 to 1 micrometers, being generally used.
As the binder used fo~ the recordlng layer in the present invention, 8 conventionally known thermoplastic resin, thermosetting resin, (or reaction-type resin) or mixtures thereof are used.
As the thermoplastic resins, those having softening point o less th~n 150C, a mean molecul~r weight of about 10,000 to about 200,000 Rnd a copolymerization degree of about 400 to about 500, such as vinyl chloride-vinyl acetate copolymers, vinyl chloride-vinylidene chloride copolymers, vinyl chloride-~crylonitrlle copolymers, ~-14679 -- -- .

~ ~s~

acrylate-acrylonitrile copolymers, acrylate-vinylidene chloride copolymers, acrylate-stryene copolymers, methacrylate-acrylonitrile copolymers, me~hacrylate-Yinylidene chloride copolymers, meehacrylate-styrene copolymers, urethane elastomers, polyvinyl Eluorides, vlnylldene chloride-acrylonitrile copolymers J
bu~adiene-acrylonitrile copolymers, polyamide resins, polyvlnyl bu~yrals, cellulose derivatives (such as cellulose diacetate cellulose triaceta~e, cellulose propionate, cellulose acetate butyrflte, nitrocellulose etc.), styrene-butadiene copolymers, polyester resins, chlorovinyl ether-acrylate copolymers, amino resins, various synthetlc rubber thermoplastic resins, and the like, are used.
The thermose~ting resin or resction-type resin used pre~erably has a molecular weight of les~
than about 200l000 in the state of a coating solution and, upon heat~ng after coating and drying, the molecular weight becomes infinite due to the reaction of condensatlon, addition, etc. Of ~hese resins, those which are not softened or melted be~ore the thermal condensation are preferred. To be specific, there are, for example, phenol resins, urea resins, melam~ne resins, alkyd resins, ~illcone resins, acrylic reactive resins, epoxy-polyamide resins, a mix~ure of a high molecular weight polyester resin and an isocyanate prepolymer, 8 mixture of a methacrylate copolymer and a diisocyanate prepolymer 9 a mixture of polyester polyol and a polylæocyanate, urea-formaldehyde ~2~5~

resins, ~ mixture of ~ low molecul~r weight glycol/high moler:ular weight diol/triphenylmethane-isocyanate, polyamide resins and mixtures thereof~
The magnetic record~ng layer may be formed by dissolving the above-descr~bed composition in sn organic solvent and applying the resulting coating snlut~on to the base support. As the organic solvent used upon coat~ng, there can be employed ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, etc., alcohols such as me~hanol, ethanol, propanol, butanol, etc., esters such as methyl acetste, ethyl acetate, butyl acetate, proply aceta~e, amyl ace~ate, ethyl lactate, glycol acetate monoethyl ether, etc.;
ethers; glycol ethers such as glycol dimethyl ether, glycol monoethyl ether, dioxane, etc.; aromatic hydrocarbons such as benzene, toluene, xylene, etc.;
chlorlnated hydrocarbons such as methylene chloride9 ethylene chloride, carbon tetr~chloride, chloroform, trichloroethane, dichlorobenzene, and the like. The magnetic recording layer may also be a water-borne formulation or an electron beam curable formulation.
Suitable support~ which can be used ~n the p~esent inven~ion ~re those having a th~ckness of about 5 to 50 ~, preferably 10 to 40 ~, and suitable examples of supports are supports o~
polyesters such as polyethylene terephthalate;
polyolefins such 8S polypropylene; cellulose deriva~ves such as cellulose triacetate, cellulose diacetate; polycarbonate, and the like.

5~

Whereas the exact scope of the instant invention is set forth in the appended claims, the followlng specific examples illustrate certain aspects of the present invention and, mor~
particularly, point out methods o~ evaluating the same. However, the examples are set forth for illustration only and are not to be cons~rued as limitations on the present ~nvention except ~ set forth ~n the appended cl~ims. All p~rts and percen~ages are by weight unless otherwise specified.

ExamPles:

~ ow viscosity values ~re ~ measure of effective performance and probably indicative of one or more of the following concomit~nt advant~ges:
R) higher loading of magnetic iron oxide. (i.e., higher information stor&ge dens~ty), b) reduced grinding time, and/or c) reduced surfact~nt demand.

DEFINITIONS
A. G~f~c RE-610; MW 800 A mixture containing the following componen~s wlth typical concentration~:

HlgCg ~3 OH

Cg~ ~ ~OCH2cH2)Il ~ ~ -P-OH (26 mole%) MW ~ 800 ~2~ g Free Phosphoric Acid (11 mole %) o HO-P-OH
bH

Water 0.5 wt% max B. Soya Lecithin (Central 3F-UB or Centrolexl~ P
from Central Soya Corp.) A mixture. A phophatide residue from manu-facture o~ soybean oi]..

A major ~~ 60-70%) component o CH3 11 1+
H C O P OCH2 C~l2 3 OH-O I
~¦ OH CH3 ~-Phosphatidylcholine R = typically C16-C 18 '~

~i5~ L~

Gandidate DisPersants S-l ( C3H6)27(OC2H4)24OC3H6Si(OMe)3 S-2 - y-Isocyanato$rlethoxys~1ane S-3 - y-Aminopropyltriethoxysil~ne S 4 CH~o(c~H4o)l2(cH2)3si(o ~3)3 S-5 - C4HgO (C3H6O)5(CH2)3 ( 3 3 S-6 - CH~CCH3COO(CH2)3Si(OCH3)3 S-7 - 1:1 wt blend of S-6 ~nd S-8 S B CH3O(cH2cH2O)75 3 6 S 3)3 P-l Bu(OC3H6)20 O 1 40 - 85 mole~
OH
MW ~ 1,300 Corresponding Diorganic ~ster 2 - 20 mole~
Free Phosphoric Acid 2 - 45 mole~

P-2 - Composi~lon prepared by phosphoryl~tion f~C3H6)17 O
MW ~ 1040 P-3 - C4Hg O(cH~cH2o)l8(~2ct-o~l4H
H

O CH O
ll 1 3 11 P-4 - (Cyclophos PV4): HOP O (CH2CH20)4(CHCH2)250 1 OH
OH
The results are attached as follows:

PROCEDURE I
PREPARATION OF ~AGNETIC COATINGS

WET GRIND

2.06 grams of the dispersant candidate is first dissolved in 32.2 grams of cyclohexanone solvent. To this solution are added 51.4 grams dry magnetic iron oxide and 25.0 grams Polyurethane Solution (15.0 wt.% "EstaneT~" 5701F-l in a cyclohexanone solvent). Initial premixing is done with a hand spa~ula to wet all ingredients. The resultant slurry is then ground at 3,500 rpm for 30 minutes on an Eiger Mini-50 Motor Mill.

LET DOWN

To the Wet Grind, 32.0 grams of Polyurethane Solution are slowly added while grinding. Then grinding is continued at 3,500 rpm for additional 30 minutes on the Eiger Mini-50 Motor Mill.
The final dispersion contains 4.00 wt.%
dispersant candidate based upon the weight of contained magnetic iron oxide.

~`~

Final DisPersion Cast Film Wt.% ol.~ Wt.~ Vol.
Compon~nt Magnetic Iron Oxide 36.03 10.41 82.9 54.5 Polyureth~ne Binder 5.99 6.72 13.8 35.2 Dispersant Candidate 1.44 1.96 3.3 10~3 CyGlohexanone Solvent 56.54 80.91 -~
10~.O 100.0 1~0.O100.O
PROCEDURE II
PREPARATION OF CAST FILMS

A 50 mil wet film ls ~ast on silicone-coa~ed release paper and air dried for one week. The dried fllm is stripped rom the release paper, cut into test strips and allowed to air dry for an additional week.

PROCEDURE III
PREPARATION OF ~I.ECTRON B~AM
CURA~LE MAGNETIC COATING

WET GRIND

1.63 grams of the dispersant candidate is first dissolved in 15.00 grsms af cyclohexanone solvent. To ~his solution are added 34.09 grfims of dry magnetic iron oxide and 19.44 grams of an electron beam curable polyurethflne resin solution (RD 4345-63 from Lord Gorp, a medium molecular weight resin as a 58 wt.~ solution in cyclohexanone). Initlsl premixing is done with a hard spatula to wet all in8redients. The resultant slurry is ~hen ground at 3500 rpm for 30 minute~ on an Eiger-Mini-50 motor m~ll.

~s~
- ~3 -I.ET DOWN

To the Wet Grlnd an additional 29.84 gram~
of cyclohexanone are slowly added while grinding.
Then g~inding ts cont~nued at 3500 rpm for an additional 30 minutes on the Eiger Mini-50 motor mill.
The final dispersion contains 4.7~ wt.
dispersant candidate based on the weight of contained magne~ic iron oxide.

Final Formulstion Final DisPersion Cast Film Component Wt.%Vol.~ Wt.% Vol.~
Magnetic Iron Oxide 34.09 9.77 7~.53 39.84 Polyurethane Reætn Solids 11.2812.56 24.00 51.20 Dispersant Candidate 1.63 2.20 3.47 8.96 Cyclohexanone 53.0075.47 --- ---100.00100.00 100.00100.00 TYPes of Ma~etic Iron Oxide A = Hercules TMOG-642. High coercive strength ~Coercive Force = 650 Oersteds), Cobalts Doped y-Fe~03. Acicular particle, length = 0.20 micrometers, sspect ration = 8-10.

B = Pflzer "Pferrox" 22~HC, y-Fe2O3 with no cobalt dopant. Coercive orce (oersteds) J 350; Speciftc Magnetization (emulg), 74; Average length D-14~7~

. " ,. . . .

~2 E;~
- 24 ~

(micrometers), 0.35; Average width (microme~ers), 0.06; Acicul~rity ~atio, 6; Poder Density (g/cm3), 0.8; Particle Density ~g/cm3), 4.7; pH, 3.0; Oil Absorption (mlJ100 g), 50; Specific Surface Area (m Ig), 24.

PolYmeric Binder "Estane" 5701F-l is ~ block copolymer having a gl~ss transition temperature of -28C. It consists o~ 60% soft block and 40~ hard block. The sof~ block ~s ~2,000 MW polyes~er of Adipic ~cid and 1,4-But~nediol. The hard block is ~1,500 MW polyurethane prepared from 4,4'-Diisocyanate Diphenyl Methane and 1,4-Butanediol.

Method of Introducln~ DisPersant C = Integral Addition, i.e., dissolving of dispers~ng agent in cyclohexanone olvent prior to addltion of untreated magnetic iron oxide and polyurethane binder.
Formulation detail in Procedure I.

D = Pretreatment of dispersing agent on magn2t1c iron ox~de in ~oluene slurry.
Pretrea~ed oxide is vscuum dried for two hours @ 120C. In prepsring subsequent disper$10n (Procedure I) magnetic iron oxide content corrected for weight of dispersing agent pretreatment.

D-14$79 E = Pretreatment of dispersing agent on magnetic iron oxide in water slurry.
Same drying conditions and dlspersion preparation considerations as for (~).

TABLE I - Viscosity values achieved with various disper~ing agents made from Procedure I obtained at 25C us~ng a Wells-Brookfield cone and plate viscometer. Shear thinning index is viscosity at 1 reciprocal second divided by viscosity a~ 200 reciprocal seconds. The thixotropic degree represents the hysterysis of the rheogram.

TABLE II - Cast film properties achieved on ~ilms made from with various disperslng agents mad~. from Procedure I. The films are made by Procedure II.

TABLE III - Y~scosi~y values achleved with various dispersing agents made from Procedure III.

TAB~E IV - Provldes a gene~ic description of the m~gnetic iron oxide, polymeric binder, candida~e organosili~-on dispersing agents and dispersing agen~s ~valuated. Mode of introducing candidate d~sper~ant also deflned.

~Çi5~

TABLE I

E CANDIDATE DISPERSANT METHOD TYPE DlSPERSlON RHEOLOGY
~ OF OF
A Candidate WT X INTRO- MAGNETIC VIS. VIS. SHEAR OEGREE
MBASED DUCING IRON (cps.) (cps.) THINNING OF
PON DISPER- OXIDE @ @INDEX THIXO-LMAGNETIC SANT USED 1.0 200TROPY
EOXIDE _ SEÇ.-l SEC.-l X
A N~ne - - A113,0003,650 31.0 45 8 None - - B61,4001,400 42.6 10 1 S-l (2.0X) P-l (2.0X~ 4.0 C A15,700 950 16.5 17 2 S-l (2.0Y.) P-l (2.0%) 4.0 D A18,900 940 20.0 17 3 S-l (2.0%) P-l (`2.0X) 4.0 E A14,200 660 21.4 22 4 S-l (2.0%) P-l (2.0%) 4.0 C B9,440 440 21.4 22 C "Gafac'~'`
RE-610 4.0 C A44,0001,460 30.1 11 D "Gafacr~"
RE-610 4.0 C B20,500870 23.6 31 E P-l 4~0 C A39,2001,270 30.9 20 E S-l 4.0 C A55,0002,340 23.5 P-l ~2.0X) S-2 (2.0%) 4.0 C A31,400 1,770 17.7 BO
G P-l (2.0æ) S-3 (1.0%) P-3 (l.OZ) 4.0 C A23,600 1,720 13.7 93 6 P-l (2.0Z) S-4 (2.0%) 4.0 C A34,600 1,450 Z3.9 14 A`

~6S~

~L__E I (CONT'D.) E CANDIDATE DISPERSANT METHOD TYPE DISPERSION RHEOLOGY
X OF OF
A Candidate WT % INTRO- MAGNETIC VIS. VIS. SHEAR DEGREE
M BASED DUCING IRON (cps.) (cps.) THINNING OF
P ON DISPER- OXIDE @ @ INDEX THIXO-L MAGNETIC SANT USED 1.0 200 TROPY
F OXIDE SEC.-l SEC.-l X

7 P-l (2.0%) S-5 (2.0%) 4.0 C A 56,600 2,330 24.3 25 H Soya Leci thi n ( Z . 0~0) S-l (2.0%) 4~0 C A 70,800 2,850 25.0 56 I GaFac'~ RE-610 (2.0%) S-l (2.0%~ 4.0 C A55,100 1,860 Z9.6 11

8 P-2 (2.0%) S-l (2.0~.) 4.0 C A56,500 2,220 25.4 11

9 P-2 (2.0%) S-l (2.0%) 4.0 C A70,000 2,320 30.5 4 J "Cyclophos" (2.0%) S-l (2.0%) 4.0 C A 31,500 1,420 22.2 50

10 S-l (l.OX) p_l ( 1 ~ 0%) "Gafac~" RE-610 (2.0~) 4.0 C A 17,300 63027.5 27 S-2 4.0 C A 42,400 1,990 21.3 59

11 S-3 (2.0X) P-3 (2.0%) 4.0 C A44,000 1,750 25.1 21 L Soya Lecithin 4.0 C A40,900 1,670 24.5 27

12 1.0% P-l 3.0% S-l 4.0 C A22,000 1,650 13.3 85

13 2.0% P-l 2.0% S-l 4.0 C A15,700 77120.4 50 ~:65~

TABLE I ( GONT ' D . ) E CANDIDATE DISPERSANT METHOD N PE DISPERSION RHEOLOGYX OF OF
A Ca~d;date WT S INTRO- MAGNETIC YIS. VIS. SllAR DEGRE
BASED DUCING IRGN ~cps.~ (cps.) THINNING OF
P ON DISPER- OXIDE ~ e INDEX THIXO-L MAGNETIC SANT USED 1.0 2~0 TROPY
E OXIDE _ _ SEC.-I_ SEC.-I

14 3.0S P-l 1.0~ S-l4.0 C A 31,500 1,000 31.5 10

15 3.0~ S-2 1.0~ P-l4.0 C A 18,9D0 76U 24.9 67

16 2.0~ ~-2 2.0% P-l4.0 C A 26,700 849 32 12

17 2.0~ S-2 2.0% P-l4.0 C A 31,40D 1770 17.7

18 1.0~ S-2 ~0~ P-l 4.0 C A 3~,300 1,340 29.4 40 ~26~
_ ~9 _ TABLE I I

E CANDIDATE DISPERSANT METHOD TYPE CAST FILM PROPERTIES
X OF OF
A Candidate WT ~ INTRO- MAGNETICGl~ssT~nsil~
M ~ASED DUCING IRON ~ Str~ngth P 0~ DISPER- OXIDE 60 (psi) L MAGNETICSANT USED
E _ ~X I DE
I S-l (2.0~) P-l (2~0~) 4.0 C A 47.1 799 2 S-l (2.0~
P-l (2.0S) 4.0 D A
3 S-l (2.0~) P-l (2.Q%) 4.0 E A
4 S-l (~.0~) P-l (2.C~ 4.0 C B
C "6~
R 4 104.0 C A 81.7 553 P-l 4.0 C A 29.3 445 F S-7 4.0 C A 24.7 P-l (2.0%) S-2 (2.CS) 4.0 C A 11.9 571 6 P-l (2.0~) S-3 (1.00 P-3 (I.QS) 4.0 C A 33.0 ~59L~

TABLE~ CONT ' D.

-E CANDIDATE DISPERSANT METHOD TYPE CAST FILU PROPERTIES
X OF OF
A Candida~e WT S INTRO- MAGNETIC Gloss Tensi 19 ~ i~ASED DUCIN6 IRON ~S~r~ngth P ON DISPER- OXIDE 60 (psi) L MAGNETICSANT USU
E OXIi~E
I Ga~c R-610 t2.0%) S-l t2.G%~ 4.0 C A 63 8S6 8 P-2 l2.0~) S-l t2.0~) 4.0 C A 61.4 P-2 ~2.G~) S-l t2.0a~ 4.0 C A 4B.5 J ~Cyclophos~ t2.00 S-l t2.0~ 4.0 C A 15.6 S-l tl.O~) p_ I ~ I .OX) nGa~acn RE-610 t2.0~) 4.0 C A 31.6 531-K S-2 4.0 C A 13.6 737 I I p_3 ~2.CS) S-3 t2.0$) 4.0 C A 40.3 593 ~ . . . .

~2Ç~

TABLE I I I

.
E CANDIDATE DISPERSANT METHOD TYPE DISPERSION RHEOLOGY
X OF OF
A Cand;d3ts ~T ~ INTRO- MAGNETIC YIS. VIS. SHEAR DEGREE
M BASED DUCING IRON (cps.) tcps.) THINNING OF
P ON DISPER- OXIDE ~ ~ INDEX THIXO-L MAGNETIC SANT USED 1.0 200 TROPY
E OXIDE SEC~-I SEC.-I _ S
M Non9 - - A73,900 417 177 N ~C9ntrol~x P" C A 15,700 330 47.6 60 LQclthin Fr x t~ntrol Soya 4.78 i9 S-l (2.39) P-l (2.39) 4.78 C A 4,720 181 26.166 0 ~6~fac RE610~
4.78 C A 7,865 î97 40.060 P P-l 4.78 C A7, K 5 189 41.740 Q S-2 4.78 C A12,600 236 53.450 R S-l 4.78 C A14,200 354 40.133 S S-6 4.78 C A26,7t~ 393 68.029 T S-3 4.78 C A28>300 684 41.4î61 U S-7 4.78 C A31,500 629 50.03D
S-2 (2.39) P-l (2.39) 4.78 C A 9,439 244 38.7 33 21 S-2 t~.59) P-l (1.19) 4.78 C A î5,731 346 45.5 30

Claims (18)

1. A dispersing agent comprising (a) a silane selected from the group consisting essentially of a silylated copolyether of the general formula:

where R1 is individually a hydrogen atom, an alkyl group having from 1 to 12 carbon atoms, an alkoxy alkyl group having from 2 to 12 carbon atoms, or an acyl group having from 6 to 12 carbon atoms; R is individually a hydrogen atom, an alkyl group having from 1 to 18 carbon atoms or an aryl group having from 6 to 18 carbon atoms; R3 is individually a hydrogen atom, an alkyl group having from 1 to 12 carbon atoms, an aryl group having from 6 to 18 carbon atoms or an aryl alkyl group having from 7 to 18 carbon atoms; R4 is individually an alkyl group having 1 to 4 carbon atoms; the sum of x + y has a value of from 2 to 100; z has a value of 1, 2 or 3;
w has a value 0 to 6; m has a value of 1, 2 or 3;
and a has a value of 0 or 1;
and an isocyanato silane of the general formula:

where R6 is individually an alkyl group having 1 to 4 carbon atoms; R7 is individually a hydrogen atom, an alkyl group having from 1 to 12 carbon atoms, an alkoxy alkyl group having from 2 to 12 carbon atoms or an acyl group having from 6 to 12 carbon atoms; b is 0, 1, 2 or 3; and R5 is an alkylene, arylene or aralkylene group having from 1 to 18 carbon atom or a group of the formula:

and (b) a phosphate ester of the general formula:

where R8 is a hydrogen atom or an alkyl group containing from 1 to 18 carbon atoms; R9 is a hydrogen atom, an alkyl group containing from 1 to 4 carbon atoms, an aryl group containing from 6 to 18 carbon atoms; or an alkylaryl group containing from 7 to 17 carbon atoms; the sum of c + d has a value of from 2 to 100; e has a value of 1 or 2; v has a value of 1 or 2; and A is a hydrogen, sodium, potassium or lithium atom or an NH4 group; where the ratio of silane to phosphate ester is 10:90 to 99:1 when the silane is a silylated copolyether and 35:65 to 99:1 when the silane is an isocyanato silane.

2. The dispersing agent of claim 1 wherein the ratio of silane to phosphate ester is 25:75 to 75:25 when the silylated copolyether is employed and 50:50 to 90:10 when the isocyanato silane is employed.

3. The dispersing agent of claim 1 wherein the silane is a silylated copolyether where R1 and R3 are alkyl groups, R2 is hydrogen, z is 1, w is 3 and a is 0.

4. The dispersing agent of claim 1 wherein the silane is an isocyanato silane where R1 is an alkyl group, b is 0 and R5 us ab alkylene group.

5. The dispersing agent of claim 3 wherein the silane is:
CH3O(C3H6O)27(C2H4O)24C3H6Si(OCH3)3

6. The dispersing agent of claim 3 wherein the silane is:

CH3O(C2H4O)12(CH2)3 - Si(OCH3)3

7. The dispersing agent of claim 3 wherein the silane is:

C4H9O(C3H6O)5(CH2)3 - Si(OCH3)3

8. The dispersing agent of claim 3 wherein the silane is:

CH3O(C2H4O)75 - C3H6 - Si(OCH3)3

9. The dispersing agent of claim 4 wherein the silane is isocyanatotriethoxysilane.

10. A process of dispersing ferromagnetic particles which comprises the use of a dispersing agent comprising (a) a silane selected from the group of silanes consisting essentially of silylated copolyethers of the formula:

where R1 is individually a hydrogen atom, an alkyl group having from 1 to 12 carbon atoms, an alkoxy alkyl group having from 2 to 12 carbon atoms, or an acyl group having from 6 to 12 carbon atoms; R2 is individually a hydrogen atom, an alkyl group having from 1 to 18 carbon atoms or an aryl group having from 6 to 18 carbon atoms; R3 is individually a hydrogen atom, an alkyl group having from 1 to 12 carbon atoms, an aryl group having from 6 to 18 carbon atoms or an aryl alkyl group having from 7 to 18 carbon atoms; R4 is individually an alkyl group having 1 to 4 carbon atoms; the sum of x + y has a value of 1, 2 or 3; w has a value 0 to 6, m has a value of 1, 2 or 3; and a has a value of 0 or 1;

and isocyanato silanes of the formula:

where R6 is individually an alkyl group having 1 to 4 carbon atoms; R7 is individually a hydrogen atom) an alkyl group having from 1 to 12 carbon atoms, an alkoxy alkyl group having from 2 to 12 carbon atoms or an acyl group having from 6 to 12 carbon atoms; b is 0, 1, 2 or 3; and R5 is an alkylene, arylene or aralkylene group having from 1 to 18 carbon atoms or a group of the formula:

and (b) a phosphate ester of the formula:

where R8 is a hydrogen atom or an alkyl group consisting from 1 to 18 carbon atoms; R9 is a hydrogen atom, an alkyl group containing from 1 to 4 carbon atoms, an aryl group containing from 6 to 18 carbon atoms; or an alkylaryl group consisting from 7 to 17 carbon atoms; the sum of c + d has a value of from 2 to 100; e has a value of 1 or 2; v has a value of 1 or 2; and A is a hydrogen, sodium, potassium or lithium atom or an NH4 group.

11. The dispersing agent of claim 10 wherein the ratio of silane to phosphate ester is 25:75 to 75:25 when the silylated copolyether is employed and 50:50 to 90:10 when the isocyanato silane is employed.

12. The dispersing agent of claim 10 wherein the silane is a silylated copolyether where R1 and R3 are alkyl groups, R2 is hydrogen, z is 1, w is 3 and a is 0.

13. The dispersing agent of claim 10 wherein the silane is an isocyanato silane where R7 is an alkyl group, b is 0 and R5 is an alkylene group.

14. The dispersing agent of claim 12 wherein the silane is:

CH3O(C3H6O)27(C2H4O)24C3H6Si(OCH3)3

15. The dispersing agent of claim 12 wherein the silane is:

CH3O(C2H4O)12(CH2)3 - Si(OCH3)3

16. The dispersing agent of claim 12 wherein the silane is:

C4H9O(C3H6O)5(CH2)3- Si(OCH3)3

17. The dispersing agent of claim 12 wherein the silane is:

CH3O(C2H4O)75 C3H6 - Si(OCH3)3

18. The dispersing agent of claim 13 wherein the silane is isocyanatotriethoxysilane.