CA1057640A - Tire sidewalls and method of manufacture - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE
Pneumatic tires with colored sidewalls are produced by applying one or more elastomeric coatings thereto.
A colored polyurethane elastomeric coating may be applied directly to the sidewall, but it may be applied to a primer elastomeric coating which is first applied and the colored coating is applied to it either before or after it is cure. Usually, the elastomeric coatings are applied over a barrier strip that is in the rubber sidewall to prevent stabilizer or other discoloring agent from bleeding from the sidewall and discoloring the primer coating or the colored coating or both.
Barrier strips are well known in the art. They are cured into the rubber during the cure of the tire.
The color of the colored coating may be produced by dyeing or pigmenting.
The one or more coatings which are applied in pro-ducing the colored sidewall are sufficiently flexible to with-stand the flexing of the sidewall of the tire during prolonged use without cracking and must be firmly bonded to the sidewall and to one another so as not to separate during such prolonged flexing. Furthermore, the colored coating must resist deteriora-tion by environmental conditions such as ozone, oxygen, sunlight, etc.

Description

~0576~
White sidewall tires and sidewalls with colored designs have been produced commercially by locating white or other color in rubber from which the sidewall of a tire is formed. The procedure ~s well known in the art, but the production of saturated polyurethane coated sidewalls is novel.
The invention is applicable to pneumatic tire sidewalls ~ormed from natural or synthetic diene rubbers.
U.S. Patent Nos. 3,648,748 of March 14, 1972 and 3,764,455 of October 9, 19?3 to Lovell describe applying poly-urethane sidewàlls but the polyurethane which is applied contains .
unsaturation and does not withstand deterioration caused by theozone in the environment.
The long adhesion of the coatings of this invention to a sidewall is obtained by including an adhesion promoter in a polyurethane prepolymer which provides the required adherence of the polyurethane to the rubber of the tire, and neither of : .
; the foregoing patents refers to the use of polyurethane which includes a~promoter. Of the promoters which provlde a grPater or lesser adherence of the polyurethane to the rubber, only a ;, 20 selectéd fe~ have proved satisfactory, although it is presumed - that many more will be found to be effective. Various adhesion ; promoters discolor the polyurethane and are unsatisfactory for the production of certain colors, although they are satisfactory , l for the production of black and other dar}c colors.
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U.S. Patent No. 2,905j582 of September 22, 1959 to Coleman et al. describes polyurethane rubbers for bonding olefinic rubbers to flexible subs-trates.
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Several companies have developed polyurethane primers `
and PPG Industries has developed both polyurethane primers and , 30 paints to be applied to the primers when used for coating rubber, ~i but tests on such coatinys applied to the sidewalls flex-crack -~-; during short periods of testing. -~;

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The Automativ~ Finishes Division of PPG Industries, Inc. published four bulletins under the general heading "Fini~hed Procedure Bulletins for the Application of PPG Durethane 100 Elastomeric Enamel." These bulletins were:
No. 1 : General Information.
No. 2 : Application to Cast Polyurethane Foam.
No. 3 : Application to Injection-Molded Polyurethane.
No. 4 Application to DuPont-Nordel and other EPDM ~ -. ~, .
- Rubbers. ~
DuPont~s Elastomers Laboratory published a bulletin ~ -entitled, "DuPont Surface Treatment Process for Nordel EPDM ~ -Rubber Parts; Procedure 102." ¦-:; :
The two U.S. Patent Nos. 3,648,748 and 3,764,455 to LovelI reveal a method of curing a polyurethane laminate onto a cured rubber tire. The patents do not describe any testing ;``l . .
o~ the laminate.
Although the application of colors to sidewalls has ~
been the subject of intensive study by the rubber industry or ;
years, results have not been too satisfactory. However, tire ~ ;~
. . .
;~ 20 sidewalls with one or more colored areas as described herein, , s l withstand prolonged 1exing when tested as described herein.
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- 2 -~ . , 10~764 1 DE~XN~ :
I z T'ne term pol~urethan~ as used herein designates both pure polyurethanes and pol~ur~aur~hanes (so~letim~s called :~
polyureapolyure~hanes~. ~ polyurethane is synthesized from a 5 polyol ~ermina~d with a diisocyanate and cured with a diol.
6 Illustrative equations are:

8 . Il 1l ~:~
HO(R)OH ~ 20CNRINCO--S OCNR'N~ICOROCNHR'NCO .;
g . Polyurethane Prep~lymex . . .
0 7i , ' ` ~ Equation No. 1 lll ~ 1 Il R ~.! 13 Prepolymer + 80R"OH - -~P~'IOCN~R'~ICOROCNHR'~ICO~n - Polyur~thane . ~ .
15 . . . . Equation No. 2 .

6 ~
1: 17 A polyureaurethane is synthesi~ed ~rom a polyol wbich has been ~ : 18 terminated wi~h a diisocyanate and curad with a diamine or a i 19 hydroxylamine. ~n illustrative equation ia .
,'"i1, ' ' ~0 , ' ' ' ' ' , ' ' . : ~
:I 21 . .
22 Polyu~ethane Prepolymer -~ H2NR"'NH2 - -~ o ~! 23 ~R'I'NHCN~lR'NHCO~OCNHRlNHC-NH~
Polyureaurethane 25 ~¦ . Equation No. 3 -~

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¦ The s-idewall of any p~esent comm~rcial pneums~ic vehicle ~ ;

3 ~ tire can be colored according to this invention.

4 ¦ T~l~ elastomer of ~he ~ire sid~wall may be essentlall~ ` ;;

5 ¦the vulcanizate o a natural rubber, a synthetic di~ne rubber ,.,I . . , . .

6 ¦such as a homopnlymer or copolymer of a conjugated diene of 4 to 18 carbon atoms or a copolymer o~ such a diene and styren~ or l~ke 8 ¦ole~inic monom~r5 or ~PDM (e~hylene-propylen~ diene ru~ber~ or 9~ ¦other di~e rubber used ln commercial tires~ can be rni~ed lnto ~ -;, lC Ithe syn~hetic or natural rubber without adversely affecting the ll adhes~on. : -12 ~ The pneumatic tire may or may not be provided with an 113 inner tube. It may be of any belted structure. It usually ~ ~ -l4 consists o~ a casing with or wi~hout an inner tube on a s~eel or lS oth~r wheel. Some tires consist only of a heavy one-piece }~ Gasing direcely Dn~a wheel.~
1~ 17 ~ ~-i ' 18 The Sidewall ~
; l9 The invention i~ designed par~icularly for coloring , ~ 20 pass~nger ~ires wi~h con~entional sidewalls; but is appllcable 21 to the sidewalLs o~tires for aircrat and even bosses and trucks ~;1 22 and all other tires to which manufacturers' names, trademarks, I ~ advertising~slogans, etc. may be appl~ed~ in color.
:s; ~ ~ ~; Although designed par~icularly for sidewalls o~
conven~ional rounded contour, there is no reason ~hy~the olorin~
;processes of th:s invention cannot be applied to sidewalls of ¦ unusual sbape,-sucb aL~ for exa~ple, the sidewall.5 dascribed ~ G :
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3576~1 n~U.S. Patent No. 3,840,060 o:E Octob~r 8, 1974 to Tangorra.
. ` The coloring proce~ure of this invention ls applicable 3 to the sidewall o any tire to which i~ adheres durio~ prolonged 4 constant flexing to meet ~he ~est set forth herein.
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6 The Coatln~s .

7 The colored design may be a single colored coating

8 applied directly to the sidewall~ or a primer coating may be

9~ applied first, with the colored coating applled to this. The :
lO Isidewall usualIy includes a barrier to prevent the bleeding ~ ;
11 ¦of discolorant from the sidewall into the applied coatings.
12 ¦ ~ It is known.~hat ~arious antiozonants and antiox~dizing ~:
.~ agents and certain other rubber compounding ingredients used in ' 14 a rubber product will.bleed int~ another elastomer cured adjacent 15 ~to it, and known protective barxier strips are used wh~ch may be 1~ applied to sidewalls to protect the d~iscoloration o~ the colored .; 17 coatings of this invention. These protective barriers may be ` .
: 18 used in carrying out this inventlon, whether made from a synth~tic . 19 ¦ or natural rubber. They include an absorbent material such as is 20 ¦ known ~or use in such strips, for instance, activated carbon, :
21 ¦ to absorb discoloring which bleeds rom the sidewalLs to which .
~; 22 ¦ the coatings of this invention are applied~ This barrier 23 coating whcn used accordin~ to this invention ma~ necessarlLy be as thick as 1/10 ~nch or ~hicker. `
~, 25 It is to be understood that in describing the coatings, . wh~n reEerence is ma~e to in~luding an adhesion promot~r in a ~.
27 1l polyure hane coating whlch i9 eo be apylLed to ~ rubber surface, ¦

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~Los76~0 ~ ~ ~

., the ~quivalent proced~lre ma~ be used which involv~s applylng the 2 ad11~sion promoter to th~ rubber surace to whLch the polyurethane 1 3 coating is to be adhered.
., There are two general proc~dures for applying a .' ~ colored coating to a sidewall~ Thi_ application of a colored coat~ng directly to a sidewall formed of a natural or synthetic . 7 rubber and ~2)~the application of a colared coating to a primer . ~ coa~lng which has been applied to tX~ sidewall. ~ ~ ~
.. The co~r~d coating and the primer coatlng may b~ ;`
0 applied as.a liquid or paste, in any suitable manner, as b~ .
,, ~1 brushing,. rolling, spraying, 10uring~ etc~ They are;often ~:
12 applied by rolling them over a sidewall surface on which the 1 13 design, such as le~tering, etc~, ls raised, or by-ro~ling one ~ ;
or more stripes on a sidewall which may be flat or be pr~vided . I
15~ w:i~h:raised stripes,~so that the roller~aontacts only the .¦ ~-6 raised area or areas. :They~may be applied in other ways. `: :
~i~` 17 Spraying is usually applied after the sidewall is covered by .`

~ masking.;:The details of th~ variou3 m2~hods of applying th~ :
.~ l9 coatings are knot~n to the art. :
,.~ ~ a.. The Colored Coatin~ - The colored coa~ing is .
Sl 21 elastomexic and is preferably a~polyureaurethane but ma~ be :
t;;~ 22 an~ polyurethane derived. from a substantial1y saturated . -.
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t.~ 23~ hydroxy-~erminated-polyol. It may be synthesi~ed from a a4 ¦ composition of polyure~han~ prepo~yme~, dye andlor pigment, curin~ I
~ -:! ' û5 agent and solvent. If applied diri3 tly to a ~ubber sid~wall~

¢ ~ i~the colored coating will include an aclhe5ive p~o~.~t~r, or the : . ¦sidPwaL1 will be f~r:st treated wi~h the~adhesive promot~r. .

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~L057640 1 Usually, however, for such conventional tLre9, the sidewall will b~ coated ~irst with an elas~omeric prim2r coating, and th&n the adhesi.ve promocer is ornitted -~rom the colored coating and includ~c , : :
4 in the primer coating.
b. Tb- r~ The primer coating wîll not .
include any dye or pigment. It is elastomeric and is a pol~urea-. ~` -7 polyurethane o~ other polyurethane and synthesized from a poly- .
8 ure~hane prepolymer as the colored coatlng ls. Lt includes a 9 caring`agent and solvent. If it is to be applied to a rubber .
` 10 sidewall or barrier s~rip, an adhesion promo~er is included. - ~ :
:, 11 ~ The invention is illustra,ted by the accompanying .
draw~ng~ in which~ . . 1:
. 13 Figure 1 is a side view of a tire with a .whi~e . :
. 14 1 sidewall; ~ . ~ .

~ : Fig 2 is an enlarged sectlonal view on the line 2~2 of ! . I
.-~ 16 1 Fig-lre l showing a white sidewall s~perimposed over the primer .

;l 17 ¦¦coating which is on the sidewall o~ the tire;; and . 18 .Figure 3 is a sectional vlew o a whlte sidewall-. ;; .
19 attached directLy to the carcass of the ~ire witho-it the u~e o~ :~

a primer coating. . . :~

~j21 . Figure 1 i5 a sectional view through a tire lO with :
~.,22 beads 12. The carcass 14 and ~read 16 are o~ natural or any - ~:
Y:. 23 synthetic rubber t~re composltion such as is known in the art, ~4 ¦¦ as for example, polybutadiene, polylsop~ene~ butadiene-styrene 25 ¦¦copolymer, etc~ ~ No belt or other reinforc~ment is illustrated, although ~uch structures are inclu~ed. Th~ locat~on o~ the .

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1 ~ hlte side~lclll is illustrated by the groove ~Ihich is coat~d with ¦ t:he primçar coatin" 18 and th~ white sidewall or other colored ~ co~ting . 20. Th~ colored coatLng 20 ia a polyurethane . The . ~.
4 ¦ primer coating ~8 is also a poly~rethane as will be evident rom ~his sp~cification. ~:' ¦ Xn Figure 3 the carcass 14 can be o~ natural ~r 7 syn~he~ic rubber~ such as po1ybutadiene~ polyisoprene or poly .
- 8 butadiene styrene copolymer. Tke white si~ewall or colored .
. coating 20 is applied. ~o the sidewall o"the tire in these cases lo wi~ho~ the use o ~h primer coating~
~ 11 ~ A1though the drawings do not i11ustrate the use oE a 12 gtain barri;er, i~. is to be understood that the invention relates .. ~, 13 to a~plying a co10xed coating to a tire wh1ch has had a stain 1~ barrier cured into or other~e applied to the tire. The stain barrier is u sed to pravent discoloration rom anti.oxldants or 16 ¦:other ingredients used in the compounding of the rubbex. -:~. 17 : :~ . . . ; .-: 18 1. THE APPLIC~TIO~ OF A COLO~ED COATING DIRECTLY
: TO A SID~WALL FORM~D OF A NATURAL OR S~NTHETIG
. 19 . RUBBER, ~20 Various elasto~neric matèrlals may be utillzed in .: æl forming this coating. Thc el~stomer must be firmly bonded to 22 the n~ural or synthetic rubber o~ the sidewall, and or this 23 1¦ purpose the coating is synthesiz~d ~rom a polyurethane pre-, po:lymer, a curing agent" a dye and/or pigment, a promote~
.~, . . .
2~ adhesive and solvent. ~he colored coati~lg is applied in any . . 2~ Ij sultable manner-to provide a thickn2ss of fro~ 2 to 30 mils o~
7 ¦¦ more up to, for example, 1.00 mils or more, depending upon such 1(~5i7~
nside-rations ~s cost, require~ scuEf resistance, etc.
~: The prepolymer ~hich may comprise a triol as well as 3 diol is no~ synthesized from an unsaturated prepolymer pol~Jol 4 such as a,polybutadiene polyol as, for instance, Arco R45M*or 5 Arco CS15*which do not resist environm~ntal deterioration, bu~
6 is synthesized from a substantially saturated difunc~ional 7 hy~roxy-terminated polyol with a molecular weight of 500 to

10,000 or higher, and preferably in the molecular wei~ht range .9 o~ 2,500 to 4~000. The usable polyols include hydrogenated :
polybutadiene diol, h~drogenated s~yrene polybutadiene diol,

11 polyt~trahydrofuran, polypropylene ~lycol, polye9ter diols;

12 whic~ may include triols ctc. The po~yol ~s reacted ~lth a .
substantially saturated aliphatic di~socyanate, for in5tance, 14 hydrogenated m~thylene diphenyl diisocyanate ~H12MDI), hexa-methylene diisocyanate, isophorone diisocyanate or any other 16 aliphatic diisocyanate which produces an environmental resistant 17 ;polyu~ethane. The reaction of the poLyol with a diisocyanate to 18 produce the prepolymex is illustrated-in the following e~uation:
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9 ~ ` ~: .
;~Q(cH~cH2cH2cH2)nol~ocNcl3H22 ;:` 21 . I' ~
Z2 ~ ~(cl3}l22~Qco(cl~2cH2cH2rll2)nocNH(cl3H22)~co . Equation No. 4 : 24 .
~ 2~ ln whlCh C13~l22 is -aCH2~ and n is sufficient to give !. ;~7 l a prepolymer molecular weight o~ substantially ~,~)00 to 4,500.
I * Trademarks ':;''''". ~ _g_ : ~' ~.~ " ,~ ~

~ 105q64 ; ¦ r~ The reaction take9 place vn heat~ng the dilsoc~nate and the polyol at 70 to 80 C. or 5 to 2~ hours. A catalyst -¦ such as dibutyl. t~n dila~rate (DBTDL) or other catalyst ma~ be useci to speed u~ the reac~lon. ,~
5 ¦ ~n synth~sizing the prepoly~er, the diisocyanate is' I ~
6 ¦ reacted wi~h the polyol ~n th~ ratio of 1~2 mo]s to 2~2 mols of ~;;
'' 7 ¦ the diisoc~anate'per l mol of the polyol. The ratio dep~nds ~, ¦ upon the molecula'r weight o~ the polyol, Pre~erably, a'ratio , .
,g ~ o,f around 1.8 mols o diisocyana~e to 1 mol o~ polyol ~s used ,:~
lo I wh~n the polyol molecular welght is in th2 range o 2,500 to 1 ~3jO00 or more. The ~olecular weig4t of the prepolymer is ",,~ ' ~; ' , ' , ' . .; . , :.
~" 12 ' cri~ical. When a~'diamine is used as a curing agent with a .1 , . . . . . . ~ ......................................... . . .
, " prepolymer having'a molecular we~ght below the range of 2,500 ,,, ,, i . , .,, . ., . . ,.. .. ~ . , . .. , .. - .. . . :, ... . - . . ., . ' ,~ 14 ~o 3,500, the ~lex-crack resistance of the col'ored'coating made from the~'prepolymar is not~satisfactory~ as shown,in Table 3. ~ , 16~ ~ If diol'or hydroxyam-ine cùring agent's are,use~'~ much ~ow~-r`, ,~
, 17~ prepolymer,molecul~r wèight~ can ~e tolerated,~and still maintain , 'I~ 18 satlsfactory flex l~e. ' , ; , ,~

' ; Colored coatings containing aromat~c dlisocyanate are , 'apt to discolor in li~t--particularly sunlight. There~ore~
~1 ~he dilsocyanate used to make the prepolymer in the colored X2 coa~ing is preferably aliphatic. ~ ' , 2~ ~ The curing agents used can be diamines, diol~ or I; ~ hydroxyam~nes. ~When the amine ~unction is used, the curing ;, 25 ageD~ is preferably~allphatic if disco~oration in the colored , , y~ ¦ coating is to be avolded. E~amples of curing ~ents that can 27 ¦ b~ useù include: diols - butanediol, ethylene~lycol, ' I : ~ .

576~

p~ntanediol, hexanediol, cyclohexanediol and various isomers thereof and other diols; hydroxyamines - ethanolamine, propanol-amine or other hydroxy amines; and diamines - ethylenediamine, hexamethylenediamine, hydrogenated methylene dianiline, isophorane diamine or other diamines.
a. Use of Aliphatic Diamine With a Blockin~ ~gent --When an aliphatic diamine curing agent is used, it should be blocked to control the rate of its reaction with the diisocyanate. The blocked amine can be prepared by reacting the diamine with a blocking agent such as a keton~ or aldehyde o the formula R2C-O in which R may be hydrogen, methyl, ethyl, propyl, isopropyl, butyl, isobutyl, t-butyl, pentyl, isopentyl, neopentyl, etc. Typical ketone or aldehydes which may be employed are as follows: isobutyraldehyde, t-butylaldehyde, methyl -t-butylketone, methyl isobutyl ketone, ethyl t-butylketone, etc.
The art on blocked diames includes U.S. Patent Nos 3,493,543 of February 3, 1970 to Nazi et al., 3,567,692 of March 2, 1971 to Haggis et al. and 3,784,521 of January 8, 1974 to Finelli et al. which disclose blocked amines which may be used.
- 20 The reaction of the curing agent with the ketone or the aldehydé is performed by refluxing the-two materials in benzene to azeotrope off the water, as shown in the reaction below, in which hydrogenated methylene dianiline is the curing j agent.

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1()576~0 l ! NH2 ~'~Cll2~~ ~ Nl2 ~ 2B7 benzene : 2 Hydrogenated m~th~lene Kctone or clldehyde 4 dianiline .

, , 6 Blocked curing agen~
~` Equa~ion No. 5 ` 8 . .
:The reaction ~f the ab~ve curing agent with tha poly-~:,lO urethane diisocyanata-termlnated prepolymer to form a poly .
- ll ure~hane i~ complete a~er 60 to 5 minutes at ~00 to 140 C. .
i2 The equation for ~h2se reactions is shown below:~ ; ' . ... . .
. ~. 13 . . : . .;
,,,, ,. ~': ' O" ' ., .' 1l ' ' ' '' '.' ' .. 15 ¦ ~C~.C13H~2.NH.CO~CH2CH2CH~HC2~0C.NH.. CH13H22.NC0 + ~ j~
6 ~ ~ R2c-N \ ~ CH2 ~ ~ N-CR2 ~ >

18. ¦ ~CHN.CH13H~.2.NH.C04CH2CH2CH2CH2jnoc~NH~cHl3H2~.~H~cNM- , I
9 I . `
~ 20 I r ~ . . .
! ~ C~2-~ ~ -N~x ~ 2 ~2C 0 -,~; 21 ~ Eq~ation ~o. 6 23 ¦ When diols or hydroxy amin~ ~uring agents are used, ¦ no blocking agent is necessary, but a catalyst~ such as d~butyl i 25 ¦ ti~ dilauxate (DBTDL~t for instance~ sllll ordinarily be used. :
P~ ! The adheslve promoters used in thi5 colored cnating nr ~7 ¦ elSeWhel2 it~ any of the proc~sses discl~sed herein include those s~ ~ . I , .

.
1 kno~rn to the art, both ~:hose applied to the rubber surEace as 2 ~ell as those mixed into ~he colored coating. They incl~lde:
3 1. Those w~lich are used in the colored coatings:
4 l-chloro-l-nitropropane, chloro-nitros~ted polybutadlene, nicrol, 4-nitroso~ mPthyl pentanoic acid,nitrosoyl chloride adduct o 6 dic~clopentadien~, 2-chlo~o-cyclohexanone oxime, l-chloro-l-7 nitroso cyclohexane and other compounds containing chlorine and 8. nitro, oxime or nitroso groups. In~some cases the chlor~ne on ~::
th~ molecule is not needed, for example, when cyclohexanone.
10 ~;irn2 ~îs us~d. .. .
11 ~ 2. Those which are used as surface treatments ~or the 12 rubber: chlorlne, bromine-, nitrosoyl chloride, hydrogen pero~ide~
. suluric acid, hydrochloric acid, hypochlo~ous QCid j ultra viole~ .
.. " .. .. , . . ,.. .. ,.,.,,...,,, . .., light and other know~ to the ar~. U~tra violet light ~ay be used 15 instead of a promoter. . . - . ;
16 ; ~A preferred prOmOtQr i~ l-chloro-l-nitro-propane because 17 it is effective without coloring the coating. . ::
18 I the rubber surface is treated with a promotex . . , . . . ' ' '" ' `
19 adhesive, no adhesion promoter is necessary in the coatiug applied æ~ to it, althou~;h lmproved adhesion may be obtained by the USQ~ of 21 an adhesion promoter .vn the surface and in the coatin~. -2~ The colored coatingS are prepared in . non~polar solvents ::

23 such as benzQne~ toluene~ xylene9 or in anothQr aromatic solven~.

~4 I~Combina~ions with hexane, heptane, octane, acetone, mPthyl etllyl 25 l¦ketonQ, methyl isobutyl ketone, and methyl but~l keton c~n also 2~ llbe used. The~ solv~nts are used to mak~ application o~ the ~7 i! colored coat;ng to the rubber easier, but are not necessary to , .
~8 ¦the application. The more non-polax the solvent is, th~ better iO57640 ~the spr2ading ~f the colored coatln~ onto the non-polar rubber 2 ¦ surface.
3 ¦ The coatlng composition can be applled wi~hout solvent ¦ if thlcker layers are to be applied. In thl5 case~ the pre-¦ polymer, cur~ng a~ent and pigment are mixed and extruded onto the .:.
:- I tire. .
7 ¦ . Pigments may b mi~ed with the other material5 ~o make ¦the colored coatlngs. The plgments are used to give the coating 9 hiding power a~ well as for obtaining a de5ired color. The ` lO be~t p~gment to ùse to obtain a wh~te eoating i.s TiO2. Xf :~
`~ ll ~.olors such as yellDw~ blue and green ~re deslred? adding small .. 12 ~ amou~ts of dyes t~, the coating, with or without TiO2 wil~ g~ve : 15 th~ ~esired effect~ If dark~r colors such as re~s, bror~s~
14 purples ànd blacks axe desired,-other p~gmen~s and/or dyes ar~-~ -; l5 ~ necessary. For dark-colored coatings, eias~omers which discolor ~.
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¦ or.are somëwhat discolored may be utllized and n~ barrie~ strip .
is required; wh~rea5 o~ a whi~e or llght-co~ored coat~ng, : :-~' . 18 prepol~mer~, etc. which discolor are to be avoided. The coa~ngs l9 may con~in reflec~ve bead~, ~ . ~

. THE APPLXCATION OF A COLORED COAT~NG TO A . ~:
.... , 21 P~XME~ CQATIN~ ON THE SID~WAL~. :~
The adhesion and flex-cracking resis~ance of a colored c~ating .
3 to the ~idewall may b~ improved by first applying a primer coating to the sidewa1l and th n applying th2 c~lored coatin ~i~ 25 1l to this. Th~ colored coa~ing usecl ih this trea~ment is iclen~ical ~;

~ i! to that described under the above heading~ The application ~;~
5~ ~7 1~ of a colc~ed coattng di~ectl~ to a sidewall form2d of a natoral f ~ -~057640 1 ¦ or syn~he~ic rubber~"
2 ¦ The prlmer coating ls synthesi~ed from a polyurethane I prepolymer~ a cur~ng agent, an adhesive promoter, sol~ent and 4 ¦ some~imes other co~pounding ingredients. The primer coat~g is ~ .
5 1 usually applied to the cured sidewall by conventional means as 6 ¦ described above. The thickness of the primer coatin~ can vary ~ 7 1 from 0.1 to S mils or more, an~ preerably~ because o the coi~t ; 8. lo~ the materi~ls, a thickness o only about 0.1 to 1.0 mlli~ ~s 9 ¦ desIred. ~he prepoly~r is synthesized rom a diol as described 10 1 ln Eq~ation No~ . . .
~;1 11 ~ Preferably prepolym~rs made from an approsi~ately ~
1, 12 ¦ difunctional hydraxy~terminated polybutadiene or other unsaturatec :~ 15 ~ rubber of substan~ial1y 5.00 to 5,000 molecular weight o~ high~r 14 ¦ is used in the prlm~r coating beca~se it appears to wet the i . ~:
~5 ~ surfa~e o~ the rubber and g~iie better adhesiox ~han other ~ ' l , - - . ~ , ., .
? ~, 16 ¦ pols7m~ric prepolyme~s~ but, other such prepolymers etc. rnay be 17 ¦ used. The p~eferable molecular we~ght range :Eor the prepol)rme~
. , . . I . . . . . ~ . .
18 ¦ is 2,500 to 4,()00. A d~ol is reacted w~t~l a diisocyar.tate such as 19 ¦ toluene diisocyanate (TDX), m~thylen2 diphenyl diisocyanate, :
0 ¦ (~IDI)g methylen diisocyanate thàt has been hydrogenated (HMDI), ~:
21 ¦ isopho~one diisocyanate, hexamethylene diisocyan~te o~ o~her :! 22 ¦ diisocyan~te to form the prepolymer~ ~1 1~' 23 ¦ Cu~in~ Agents F _ the Primer CoatinQ
24 ¦¦ There are thxee types o~ curing agents that can be ~ ~-25 1¦ used for curing the polyurethane prepolymer whether in the coLored ~o,a~ing o~ the primer coating; naln21y, diamines; diols , 27 1l or hydro~yamines. ~hen the amine function is ~sed to cur~ the ,;''~ ~

~Lo57640 1 ~ primer? th~ cur:ing agen~ can be ar~matlc or alipllatic, 2 ¦ The ~iol curing agents includ~ ethylen~lycol~ propane ¦ d:;o]., butanQ ~iol~ pentane diol, hexan2 diol, cyclohexane diol ¦ a~d isomers thereo and other diols. . .
¦ The hydroxyamlne curin~ agents include: ethanol amin~, 6 ¦ propanol amine and othe~ hydroxy amines which are known to be 7 curing agents~ .
8 The diamine curing agents include: -. Aromatic Curin~; Agents A i i~ ci c Cg~e~-s 11) . MOCA, methylene dianiline J hydxogenated. methylen~ :
- ~luene dîamine, phenylene dlaniline, hexamethylene : -~
11 . . diamine diamlne, is~phorone diamlne, 12 ~ / eth~lene diamine . . .

13 Three types o~ diamine curing agznts, namely, aromatlc 1~ (including hindered and non-hinderëd) atid aliphatic, are us2d :
15 depending.upon the diisocyanat2 used in the prepolymer.
16 ~a. ~Us~ ~ LL~__tic Diamines With A~ipha~ic .
17 Diisocyanates - An aliphatic diamine must be blocked to control .
18 I its rate of reaction with the d~isocyanates. This ls effected7 19 as in the colored co~ting, by reaction Oe the curing agent with ~O a ketone or aldehyde. The reaction is effected by reEluxing the 21 two materials in a wa~er-immiseible solvent sach as benz2ne to 22 a~e~trope off the watex, as shown in Equation No. ~, as krown 23 ln the ar~. . :~
2~ ¦ The blockad diamine is react2d with th diisocyanate 25 ¦pr~polymer as shown in Equation No. 6 to yield the cured ~ ~:~
polyureaurethane cvating. . ~
~7 b. Use o~ A omatic Diamines With Blocked ~ ates 28 T~le second type of curing agent i- a non-hindered aromatic diamin . ~ ', ~ , ' .

l ~hat ~.s use~l wlth an ~Iromatic diisocyanate-~erminated prepolym2r.
In ~llis ca.e, bloc~ing a~ents are usu~lly used on the di.isocyanate 3 The blocking a~en-ts that are used include phenol, oximes such as ~, c~clohexanone oxime, etc., which are removed from the amine wh~n the reaction mixture is heated. The blocking agent is reacted ~ith the free NC0 groups on the prepolyrnex as represented by the .:7 ~ollo~ing equation:
8 . 0 o :
CH3 ~-NHCO~H2C~1 CHCH2~ OC~I~ CH3 ~ NOH
I NCO NCO
11 I~CH3~ ~CH2CH C~ICH2~nOCNH~CH3 NHCO-N =O NHCO-N=C>
., . . Il . Il . Equation.No. 7 .

- 15 ¦The biocked dii50cyanate is reacted with any~non-hindered a~omatic .~16 diamine c~ring agent.at a tempe~ature of lO0 to 140 C. for aroun~
;60 to lO minutes, r~spectively, to glve a polyurethane suitable 18 for a primer coa~ing. The bloc~ing agent ~olatilizes during ' 19 hea~ing; liberat.ing the-diisocyanate group which ~hen re~c~s with .
20 -~he curin~ agent, as illustrated in the equa~ion below: ~ ~ . .
~` - 21Product from Equat~on 2~o. 7 ~ H2N~C~12~)~12 > ~:
:. ~ 22 : ~OH :
23 ~ cured polyureaurethane ~+ ~
: 2~Eq-lation No. 8 :' Other dian~ines that m~y he used with.blocked aromatic diisocyanate ~:
~6 1~ prepolymers a~e tolue.ne diamine, phenylene diamine, bis~4-amino-i~~ 27 l~phen~l sulE~ne, napbthylene diamine, allthracene diamine, etc, ¦
s ' ~ 7 .

`;`~ li . .

1 c. Use oE ~rom_tic Diamlnes Wlth ~ tic 2 ~ Prepol~m~rs ~ If al:Lphatic di.lsocyanates _ , , . .
a~e used in prepolymers~ no blocking agent is necessary when the curing agents are aromatic dlamines ~or the re~ction rate 5 ~s slow enough at roo~ temperature to p~r~t a reasonable pot .
6 1 if e of the primer, 7 . d. Use o Hlnder~d Aromatic ~iamines Wlth Aroma_ic :~
Diisocvanate Termlned PrePol~mers - Hlndered dlamlnes such as . ~ ~
;- ~ 4,4'-methylene-bis-(2^chloro anillne)-(MOCA~, 4~4'-me~hylene .
bis~2~thoxyaniline), 4~4'-meth~lene bis ~2-meth~laniline), etc. .
, , . .. .. . ..
. 11 can ~(e reacted with aroma~ic diisocyanate. terminated prepolym2rs .
12. without blocking agent~. C~re times are 120 C. ~or 2 hours, ,, . , ., . , ::
13 . . The prim~r coatings are appLied to the sidewall o~ the .
barrier strip and cured at elevated ten~peratures to form the .
13 elastic polyure~u~ethane film. Colored coatings are tben :
16 1 applied over the cured primer coating and heat-cured.
` 17 1 e . Prim~r Coatin~ That is Not Cured Be~ore ~ .
. , ,, ~ . ~ .. ,..
; 18 ¦ Colored Coatin~ - Another type o~ primer coat:Lng that is no~
19 ¦ cured before t he col.ored coating is applied, is synthesized by ~ ¦ mixing a diisocyanate-te~minated prepolymer, diisocyanate~ ~ :
:` 21 ¦ adhesion pro~oter (if nec~ssary)~ and solvent. This ma~erial is 22 appli~d to the rubber by conventional means~ im~2dia~ely followed . 23 , by applica~ion of ~he colored coatin$. The col~red coating and ~ 24 ~ the primer coating are cured together ~or 60 ~o 10 ~inutes at 25 ¦¦ loo to 140 C., respecti~ly. - -.~ 2~ 1 ~ It is not necessar~ that ~he primer coating b~ com- . .......... ~.
. ~7 ¦ pletely cured if the colored coating is applied to it before the I .
~ - l .
! - ~
,-' `. I : . ~ . . . . `. . ~. .~ .

I ~ ~ 57 ~ ~ . .
!E~e2 :isocyL~n~lte gro~ps in the pr~2r coat:lng have hyclrolyzed, 2 rrhe curing agent .in th~ color~t coa~in~ mi~rates into th2 primer 3 coating and r~ac~s wit:h thf isocyanate grou~?s.
4 .
3. TESTINC, T}IE COLORED COATIN(: O~ TOP : `
or PA~ OM~NO_~~
The thickness o the colored coat1ng may vary ~:
7 depending upon co~s~derations such as cost, scuf resistance, etc.
8 In the colored coàt-lng, an aliphatic diamine is ~.9 preferred o~ reaction w~:th an aliphati~diisocyanate (~or - 10 example, H12MDX, ~sophorone diisocyanate and hexamethylene ~
. ., , . .
11 d~isocyanate) ~o prov~de ligh~ stability, although when th~ ...
12 coatin~ is a very dark color, aromatic d-;amLnes and diisocyanate5 1~ may be used~ The polyol can hav~ a molecular w~ight.of 1,000 ~o ;~

14 5,~00 or higher, usually no lower than 29500. hliphatic d.~amine curing agents are preerred with blocking as discussed above, to 16 control th2 pot life and the rate o the reaction. Non-polar r j solvents are prefexred if the coating is applied t~ a rubber. .:
18 ¦ s~rface. Dyes and/or pigmPnts are included as d~sired. : ~ ;
19 ¦ The coa~ing is usually cuxed from abo~t 60 to 5 minutes o ¦at 100 to 140 C. . ~ ¦~
~1 Table 3 shows tha~ the NCO/OH ratio and/or the ~ ;~
, 22 molecular we~ght o the polyol used ln the preparat~on o the :` prepolymer for the coating composition is very important when 4 ¦d~amine cu~ing agents are used. The polyol's nam~ and its ~ :
I ¦molecular wei~ht are in the f~rst column. In the second column : ::
Z~ lis the NCO/Oi-l ratio. From this data, the calcula~ed mole~ular :
i weight of uhe p~epolymer is given in thP next column. ~eference ~-;
- I . ~ ' '. ' ,..', I . ~'`

.,' , ' . , , - ~ i.s made to tlli.s below ln connec tfon ~ h the Texus flex and ozone 2 t~s~s.
3 ~
A Tex~US Flex-Tester Model No. 31-11 of Test~ng Machines, Inc., Amityville, ~lew Yorlc, ls used ~or laboratory testing of :
6 the flex-crack reslstance o coatings used on rllbber samples.
7 T-shaped samples wi$h a groove in the leg are made of various 8 elastomsric rubbers used in tire sidewalls. The sample~ are .9 clea~ed and painted wi~h either a colored coating or a primer lO coating in combina~ion wlth a colored coating on the opposi~e side s~. , , , 11 ~rom the groove. The painte~ samples are placed m the Texus 12 Flex ~ester on a wheel. The wheel is turned at such a rate as to 1~ caus~ the samples to bend under stra~n 7Z0 times per minute.-he an~le o bend of the rubber is 60 to 70 degrees, with a flex

15 ~elongatlon of 18 to 25~per cent. ~esults of tests on various :

16 l¦coating sarnples are reported in column 4 of Table 3~ A si~ewall~

17 c`oa~ing that withstands 2,000,000 1exes wLthout c~acking ls ~

18 considered s~tisfactory for the purposes of thLs inven~ion. . ;

19 ¦RadLal Crack Tes~ :
~o I Tires wl~h sidewalls to whLch colored coatings and .
~1 prLmer coatings, Lf necessary, have been applLed (and which may 22 ¦be dLferent constructions and sizes) are tested as ollow~ ;
~3 rhe tLres are m~unted on a rlm, in~lated to ~4 psl and ~4 tested on an in~doo~ wheel against a flat, large-wheel surface 2S at 50 mph at 85 per cen~ o the rated load o~ the ~.ire. ~he 2.~ 1 tire de1ects 20 to 30 per cent o the distance betwee~ thP bead :~
7 ~and the tre d on each revolutLon, which ~s a S to 7 peF cent ' ' ' ' ' : ' ~ ' ':, ',' ~ !
,,, . . ~ ..................... .. . .
r . . ' ~

i dec~:case l.n t:~le cli.ame~er. Thc l~umber o revolutions a tire will wi.thstand ~epends upon the sl~e oE the tir~. A ~ire is considered 3 comtllercially satisfactory if it runs 7,UOO,OOO revolutions ~r a large tire and 20,000,000 revolutions for a smaLl tire which is 5 equivalent to 20,000 miles. A tire with a colored coating whlch ~:
i 6 withst.ands ~h~s test is considered commercial, This is the 7 equivalent of an actual ~est: on the road o at least 40, 000 miles because the decrease in diameter due to the deflec~ion produc~d 9 in act~lal driving is much le5s than the 5 to 7 per cent used in ~¦
:. . , , . - - .
the tes~. Tes~s on a machine are given as the test for determin-11 ~ing what is com~ercially sa~isfactory, because actual road tests 12 will~vary wi~h the nature of the :road sur~ace and ~he speed; and 15 consecluently the ~emperature o the tire varies. I)uring and at:e~
: 1~ the test the colored coating is examinëd or cracking and loss of 15 1 adhesion, - : :
16 ¦ Test results on various samp].es.are r~corded in column ~ :
? 6 oi Ta~le 3. . . . . ~ :
18 Ozone Tes~ . - . .
., 19 One-half by six inch strips oE rubber are painted with æo the colored coa~ing or combination o the primer coating and ` :
1 colored coating, and tes~ed in the 50-1.0 static dynamic ozone 22 ~est. The tefiting procedure consi.sts o~ placing ~he colored ~3 rubber sample in an arm of the tester on each side o this slx-I, inch strip, and stretching the strip 20 per cent in an atmosphere o 60 parts l~er lOO~O~O,OUO ozone. ~fter the sample is allo~d to stand 50 minutes in this ozone atmosphere ~ the samples are stretc~
,;1~11 I
J' 27 I ed ~rom 0 t~ 20 per cent elon~gation ~or 10 minutes and if no crac~ Is ~:
'`' li ' - .

. , - . . . . . . . .. .

~ :~L ~ o576~
op durin~ continu2cl testin~ at botll~O and 95 F. for 72 2 ¦hours, it is considered ~ha~ the coatin~ is satisactory Eor use 3 ¦in commercial production. .
Results of this test are r~corded in column 5 of 1 Table 3.
6 Trade Marks and Sources: .
. 7 Adipr2ne LW520 made by duPont de Nenlours and Co. ls a 8 12r~Dl-terminated polytetrafuran diol, : g Polyme~ 1000 is polytetrahydrof~ran ('rl~F).
Niax is a trademark of Union Carblde Co.
11 ~ Niax 737 is a polyester w~th a molecular weig~t of .. 12 ~911.
. ,.................................. . . , .
13 Niax 1025, 2025 and 3025 are polypropylene g~ycols (PYG~
14 f molecular weight of 1025, 2025 and 3025.
i 15 Arco R45M is polybuCacliene diol iden~ified in Sinclair 16. ~etrochemicals Inc. (Arco).Product ~ata ~ulletin No. 505 as 17 ~00 per cent butadiene~ havin~ a viscosity o~ 50 poises at 30 C., I :
:' 18 ~n hydroxyl content of 0.80 me~/gm, an equivalent weight of 1250 ~' nd iodine number of 398. The diol ma~ be prepared by a process ' ~0 uch as disclosed in U. S. 3,333,018 or U. S. 3~673,168 or British .:
; 21 57,788. :~
.~ 22 DOP is a plaf~ticizer, dioctyl phthalate.
23 1 Paraplex G50 is a polyester dispersing agent used to ¦ e~p titanium oxide in suspension.
. 1 2~ 1l llar~ick St~n t:onc 10 PCo3 ~ ~ d:;sper~i.on cont~inln~
~ ~ anium diox.i~le in DOP an~ Paral)lex G50.

.. ~7 1l ;:~
, 1~
~ - 22 -I . .
,~ .

:L ~'x~aratiol~ of ~Iy(ko~ren.lted ~r~ierle Diol:
To a hyclrogF~nat1~n re~ctor ad~ 100 gr~ns oE Arco poly-¦butadiene diol, 1300 gra~s oE h~xane and 0.81 gram~ of nickel 4 ¦hippur~e (made ~rom nickel chloride and hippuric acid -: 5 ¦C6H~C0NHC~2C02~l). Th~ mi~ture is stirred under a hydrogen 6 ¦atmosphere at 160 to 170 psi at 90 C. When the hydrogen - ::
7 ~pressur~ stops dropping the reaction is complete. A three molar ;
¦e~cess of dim~thylglyoxine and 50 grams o~ fil~er aid are added 9 ¦.to th~ reaction and the mixture is stirred. After stlrring,the ;~. 10 ¦ca~alyst and filter aid are filtered off and the hydrogenated 11 ¦Arco i~;.obtained by removing the hexane under vacuum.
12 I r . . . .
. ¦ EXAMPLE~ ........................................... ;
¦ ~ Various prepolymers wexe prepared and tested. Some- . I
' 1~ ¦were tested in pr~mer coatings, some ~n colored coating5 and some ~ .
., 16 1 in both. . ~; :
17 The description which 0110w5 re~ers to the dif~erent . ~:
prepolymers and coatings by numbers given as example numb~rs in .
19 the tabLes which follow.~ .
0 ~Various prepolymers wexe prepared. It was ound that ~:- 21 some were more satisfactory for primer coatings and colored ~ 2 coatings than others and to illustrate the invention, the general ,~
'i ~3 , instruc~ions for preparin~ those utili~ed in tested tlres follo~s:
I , ' ''' ~
¦ ~ ~X~MPLE 1 ,.
General Pr~a____on o the Diisocyanate Termina~ed Prepoly~
"',:1 I _ _..................... --. .
~ To a mixture o~the diisocysn2~e and one drop o i~
'.'`,~- ! . ' ~ . ~
.i,,.~.. , j . .
~ , ~ : lOS769L~ :- ~ ~
,'''' I ~ , 3 : .~
~'';'' 11 ' : . , , 1:
`,.:~.i . . .
..,:. `
.. . . . .

,~'. ~.. . .. .. .
.. ., .. , , , . ,, ,, . ~ ... . .. .. . . .
. ... . , . . - . . . ; ............... . . . - .. . ~ ` .

~ )5 7tj~
dibutyl tin clil.a~lr~lte ~DI3TDL) in 100 milli.~neters o:E dry toluene at 80" C. i.s ~clded with skirrin~ che prepolymer dlol in 100-300 3 mi~limeter~ o ~lry toluene over a period o~ o 2 hours. The .
.~ m:i xtu3:e is stirred at 80 C . for 6 So 24 hours . I~:ter completion, the contents are stored ln the absence of air. Table 1 illust~ate 6 the polyols used, the diisocyanates used. and the amount o each 7 used to synthesi~e the desired prepolymer. The pr~polymers a~e used to make the prlmer and colored coatings as described in g E~camples 3 and 4~
,' 10 :~, "',' .,'', ' ' j'"' ' . , . ., 11 . ' ~ , ,.; ' :. ' ' - ' ~ ' ' . : .
12 : - :
3 . . - :- .

6 ~

a ~ - . - .
~ 19 I ' ' ' " " ' " ' , '.: . . ., ~: 2~
.~, 22 I . . :
~` 23 Ij~ 1 -.1. 25 11 : I . . . - ..

7 11 ~ -.

à~

. , : . .
.. ~

~V57~0 DII~AN~TE-TERMINATED PREPOLY~n~RS

GramS GramS H 2MDI NCO /OH
Num.ber Pol~ol Used ~ Use~ (Molar Ratio) Adiprene LW 520 l7ao 2-. Polymeg 1000 (PolyT~lF) 400 . 157.2 1.5 :
;. 3 ~iax D737 - 2911 291 r 52~4 2 .
4 Niax D737 - 2911 291 52.4 1.8 :-Niax 1025 -(polypropylene~glycol- 70 1.33 6 Nia~ 2025 (PPG) 202.5 47.5 . 1.8 `. 7 Niax.3025 (PPG) 302.5 52.~ 2 :
;, 8 Niax 3025 (PPG) 302.5 47.5 1.8 ~;l 9 ARCO ~45M polybutadiene- . .. . :
2475. 2~7.5 52.4 - 2 : ;~
ARCO R45M-2475 ~ 247.5 47.5 1.8 - ~: 11 75~/O hydrogenated .i . A~G0 R45M 2550 255 55 . 2,1 12 100% hydrogenated ;` . ARC0 R45M 2575 257.5 52.4 2 ~:
; ,. . . .
D 13 1OOV/O hyd~ogen~ted ~, ARCO R45M Z575 257.5 7.5 1.8 .;1 1 - Numbers on Tables 1, 2 and 3 all correspond~
2 - The four-digit number after the name indicates polyol molecular J weight.
' 1 3 - Hl?MDI = hydrogenated methylene diph~nyl isocyanate.

.. . .
.,-.. : - ~ ~ ~ . . -~,'''~, , ' ' ' ' ~ ' ` ' .'.''' ' ' ' '' ~

- ~ 764(1 . E MPI.E 2 2 Pr~ rat ion oE Bl ocked I)iamine s 3 . (~) Add ~2 grams t~ hydrogenated meth~l~ne cl lanilinz 4 tHMDA) and 40 gralns oE lsobutyrald~hyd~ to 100 millime~ers of 5 benzene . Reflua~ the mixture 1 hour or until 7 . 3 grams of water have been aæeotroped of. Strip o~ the ben2ene under vacuum. .
.. . (B) Same procedure ~ts in (~) above except use 4Z grams 8 o methyl isobutyl ketone in place of the aldehyde.
. The blocked amines discussed m~y be used in the prepara- .
lO tion o satis~actory primers and coatinvs. The blocked amine .
~. .
11 ¦prepare~ according to (A) was util~ze~t in preparing all of t~e 12 mate~ ials reported in Ta~le 3. .-13. ~ ; ~-~ . .
14 : EXAMPLE 3 Pre aration o PrimPr Coatin~
.~, - , P . . ___ :I 16 (A) Primzr coating is-used in all of the~ examples i~
:', 17 Table 3. The materials listed below were m~xed together in a .
. 18 bottle, screened and either sprayed, brushed or rolled onto a -~ 19 clean rubber surface and cured onto the rubber at 140~ C. for

20 2-5 minutes. .

21 . . 100 grams of H 2~I terminated A~CO R45~
poly~utadiene polyol (Table 1, No. 9) 23 13 gram~ o iso~utyraldehyde blocked HMD~
:'~' . - . :
.I . 24 ¦ 15 grams of 1 chloro -l-nitropropane -I 25 ¦ . . 300 grams o ~oluene .
i 7~ (B) The following primer coating could also have been ~`, Z7 ¦use~l in testing tbe co~ored coatilg r~ported ilt Table 3, but W-15 ' '"' ' I : ' ' , , : ' ' , ` ~:
",.,, I . ;:
t,,, I . .. . ' ~ .

., ~

l ~76~0 ~ . , .
IlO~ and is repor~ed jus~ t~o give anvt:her example o a primer 2 coating that can be used.

3 T~e ollowing mat:erials are mixed and applied a~ ~,:

4 illuscrated in example (a) above. This primer coating is cured -:

onto the xubber at 140 C. ~or 10 minut~s. . : ¦

6 100 gratns o~ cyclohe~arlone oxim~ blocked ~oluene ~:
diisocyana~e (TDI~ termina~ed ~RC0 R45M
r polybutadiene polyo~ '::

8 6.1 grams o methylene dianilir~e (Ml~) in 6. ~ I ~ 1:
grams.o~ ~HF ~

300 grams o~ toluen~ r ' ' ' ' ~ ' 11 ¦ The ARC0 prepolymer can ,be made by the ~ollo~ing ~-~'i 12 ¦ pro'cedore: To a~28 oz. p~p bottle is added 247 gram~ o A~C0 i3 ¦ ~45M polybutadiene polyol and 34.8 grams of toluene diisoc~anate, The contents are heated ~at 70 C. or four hours with stirring, 1;

¦ ~ l After completion, 300 ml o~ THF is added and the contents are dissolved. Then ~dd 22,6 grams o cyclohexano~e oxime.~and ref1ux 17 1 overnight. Removal of ~the THF yields the cyclohe-~anone o~ime ~ b~1Ocked TDX terminated ARCO pO1ybueadiene pOlyQl~: ..... , .
'`1 : ~ " ' ' 1 . ' ' : ~
0 1 -~ EXAMPLE 4 ........................................... ~:

21 ~ ~ . ~.
:' 22 ~ . The ollowing coatings which are illustrated in Ta~le 2 .~ ~ 23 ~ below are mi~ed, screened and eithe~ sprayed, brushed or rolled onto primed rubber for ~esting as:illustrate~ in Table 3. The 25 ¦ ~oatings are cured a~ 120-140~ C. for 5 to 60 minutes depending I -upon: which prepolynler is use~3. As iLlustrated in Table 3, these i~ ~ 27 ~ prcp~lymer~ are preierably polyuLea-lrethanes. These were applied .. I ;~: ' : ~ ' :. , . ;

0~76~0 1 ¦ ~o prirne~l rul~ber samples. It is also posslbLe to apply these - ¦ coatings t:o non-primed rubber. In this case~ 15 parts of 1 3 1 chloro-l-nitropropane is adcled to the form-lla~:ions outl:lned in ¦ Table 2 to insure adhesiQn o~ the coating to the rubber.
5 1 Usuall~ the use of a primer assures b~tter adhesion and flex-6 ¦ crack resist:ance of the paint, than when no primer is used.

:

:; g I : ' . . . : ~
,; .' 10 ~ " ~' . . ., ~` 11 I ' . ` ' . ~ ' . ' . ~ . .. . , 13 ~ : ~ .
;. ~, 14 1 ~ .

l6 .
,.,, ; . ' , .
7 ! ~
,. , ... I . . , . ; , , . . . . .
19 1 ~
. . , . . . ' .
`` 21 . 22 ~ `
. " . ; ~' 5~

27 1~ . ~:

~ 11 , '' . .

~057~40 ~: ~
, ~" . : .
~ . :
~ o o o o o o o o ,, o ~, C~ ~d ~t ~ ~ `J ~ ~J ~t ~t ~ `;t `* - -V ~,o O O O O O O o O O O ~ ~ O
'. ~ . ,~ .
.; .
O o o o o o o' o o ' C~
~I r~ C"l r-l ~ r-l :~ ~ Ei. d rl O O O O O ~ O O U') U) O O O
.. . .
., ~D ' ' Ei a.) I o o cl O O O C~ O O O . O O O
O O O O C:~ O O O O O ' O ' O O r~ ' . g ~., ~> u~ . ~t ~t ~ ~ ~ ~ ~ r~
;~ E~ ~ , , ~ oo 00 " j 00 0~ ' O C!~
~:~ ~ ~ ~ 0~ O' O ~ C~C~i O C~ i 0 ~`J . C~i .
<~. C~ ~ ~ .~t ~ ~ ~ t ~t ` ~d - . . Ql ~ h C~ ,~ J U ~ g ~ :~
o u ~
~z ~a o o o o o . c~ o c:~ ~ . o o - o Q~

~ : - . , ' ,, ~' ~ ~
~. o a~
O C~' ': ' ' , ~ ' ~ S pr~r~
I~ o . a~ 0 ~ .
.'. ,~ o o 1 ~ ~d ..... r~ n X X ~ c~. a~ I~ I~ ': O O O O ~ ~ ~ ~ .. ,~
u ~ o '` ~ X ~ o c~ ~ o ~0 c~ ~ ~ ~ ~ o :,~' 3 ~ r~ i r~ n ~ O p O ~ r~1 ~ ~ , z :zi z z~; z;, ¢ ¢ ~ ~ ~ sd 4~ ~0 S~
. . ~ E~ ~ ~ V 'O
~ H1--1 H H H H 1-1 H 1-1 H 1-1 H S~ ~ O
h ~ .,1 ~ p. ~
.. - .'a ~ ~1 H H ~ H r-l. ~ ~ r ~ 1 h rd I C~ H

i., . 1~

,~

. . .
, ............................................. . .
:: . - :

.

~ 7640 1 ¦ . E:X~MPLE S
2 I Pa-Lntin~ Tires ~Eavin~ a Sidewall Which is ~ar~ely a Con~u~d 3 1 Diene ~ubber . . ~ .
. 4 ¦ A tire wi~h a stain barrier irl the sidewall was bufed 5 ~ in the arQa to b~ painted. The buffed area was washed with 6 ¦ toluene and primPd by spraying~ brushing or rolling with pr~m~r 7 ¦ prepared with the bloc~ced-amine described in Exan~le 3 (A~.
. 8 ¦ Primer simi].arly prepared from the blocked~amine describ2d in 9 . I Exa~pl~: 3~b~ may be used. The primer was cured. as d~re~ted in .
10 ¦ Example 3. The colored coaking was applied by eikher: spraying, 11 1- brushislg or ~olling onto ~he ~ire and curing as directed in 12 ¦ Example 4. Each~of the colored coatings in Table 2 could bei -:
1~ ¦ used to paint the ~ire but som2 are bet~e~ than others as '' ' '' . ' . ; ..
shown in Table 3. ~ The tire could also be painted without using ¦ a primer provided an adhesion promoter is added ~o the colored 16 ~ coating. . .
17 ~ ~ . .

~ .19 . , . . , ', ' ' '.. , ' .
;20 . ' , ' ' , . , , ';"
21 .......... . . :

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1 4. EXPL~NI~TION_OF TAsLE 3 2 The ~a~le ref~rs to various experitnents which were 3 conducted to procluce co~mercia]. ~ires. Tle test is whether the 4 coat:i.ngs adhered ti~ ly to the sid~walls, and whether the coatings cracked on Elexing. The d~signation "NC" stands for 6 "No Cracks".
7 . The molecular weight o~ the diol and t11e NCO/O~ ra~ia.
8 for making the prepolymers used in synthes.iæing the colored and pri.mer coatings are very-importan`t as ev~denced in Table 3. The .
lQ diol and the diol mo]ecular weight are glven in the firs~ column 1l of the table. The diisocyanate used in all of the examples 12 repo~-ted in Table 3 was hydrogenated methylene diphenylisocyana~e .
13 (H12~DI). The W~O/OH ratio:is given in column 2. .Using.this 14 ratio .and the molecu1ar weight o~ the diol, the average mole~ular ~5 weig~t o the prepol~mer was calculated, and this rnolecular . I :
16. ~7P lgllt Ls shown in column 3. Colored eoatings were prepared l7. sing all of the diols-shown in Table 3 at the NCO/OH ratios. . .
18 ¦ shown. These colored coatin~s which were cured with isobutyr- ::
19 1 aldehyde-blQcked hydrogenated m~thylene dianili~e, were applied .
~o ¦ to rubber samples which had previously been primed ~lth a prime~:
21 ¦ coating. The prim~r coating u5ed was prepared rom H12MDI- ::
22 ¦ t~ermina~ed AFcCO R45M polybutadiene diol which was cured with

23 1 iso~,utyraldehyde~blocked hydrogenated mPthylene aniline.
2~ ¦ ComparLng the average molecular weight of the prepolymer with 25 1 that o the re~sults ob~ained on the Te~US Flex Tester and the 2~ 1ozone test, as sho~7n in Table 3, it is evident that sam~les witl ¦a prepolymer molec~1ar we1gh~ of greater than 3,00~ to 3,500 ~ . ~ ' .' .: I 3 .
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1~ 10576A0 ¦ sho~lld be usecl. Samples o colored coating~: which are made from ~ prepolymers o:f lower molecular weight show extensive cracking in 3 the Texus Flex test as ob~erved in CO~ n 4 of Table 3.
Column S in Table 3 shows the results o~ ~he 50-10 static/clynamic 5 ozone ~est. The cracks obse~ved during this testing ~how a similar tr~nd to the cracks obser~ed ~n the Texus flex testing.
7 Duxing this ozone tes~5 evidently the colored coatin~ derived 8 rom a prepolymer wi~h a moleculr weigh~ less ~han 3~C)00 g ¦ to 3,500 is unsa~isfactory. The~ rubbar under the small cracks i ¦ ormed by this flexing is attacked by the oxone which cluses the il ¦ crack~ lto grow. Xn ~he case where 2~0 cracks are observ~d- ~haJc '-:` l . . . , . : ~.
12 ¦ iS9 ~h~re the p~epolymer molecula~ weight is greate~lth~n 3,000 13 ¦ or in some instances 3"500J the colored coatings prot~cit the ¦ rubbex frorn the oæon~, The colored coatings themselv~s are .
15 ¦ resistant to the attack by ozone with ~he exception o~,the pa-ints synthesized by using a prepolymer that has un5a~uration .1 17 ~n i.ts.baclcbone; for example, Samples 9 and lO in Table 3 18 composed of the prepolymsrs m~de from Arco ~45M polybutadiene 19 ¦ dlol. ~ In thls ~ase, the ozone attacks the olein bond,s in the ~.
0 ¦ colored coating 9 causing the pain~ to crack, . . : . .
Zl Exarnples 11 to 13 o Table 3, usin~ coati~gs similarly 22 j prepared, except tha~ a saturated or substantially. sat~ated ~3 1 prepolymer was used, developed no cracks~ provicl~d th~ molecular weight of ~he prepolymer was high enou~h. The mole uLar ~7~ight 25 ~j o~ the prepolymi~r used in Sample 12 wa~ not sufficiently high : .
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Claims (15)

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A pneumatic tire having sidewalls of a diene rubber and a cured coating formed from a substantially saturated polyurethane on the sidewall thereof; said coating including an adhesion promoter which causes the coating to adhere so tightly to the tire that it does not crack when the tire is subjected to the 50-10 static-dynamic ozone test and is run for the equivalent of at least 20,000 road miles according to the Radial Crack Test.

2. The tire of claim 1, the coating of which is a polyureaurethane which is derived from a substantially saturated polyurethane prepolymer having a molecular weight of at least 3000.

3. The tire of claim 1, in which the coating is a colored coating adhered directly to the sidewall.

4. The tire of claim 1, in which the coating is a colored polyurethane coating, and a polyurethane primer strip is provided between the sidewall and the exposed surface of the design to provide required adherence of the design to the sidewall.

5. The tire of claim 4 in which, between the sidewall and the surface of the inner surface of the colored coating, there is a rubber-polyurethane bond which includes an adhesion promoter.

6. The tire of claim 5, in which the coating comprises an elastomeric colored coating over an elastomeric primer coating and the polyurethane of the colored coating is saturated and the polyurethane of the primer coating is saturated or unsaturated.

7. The tire of claim 5, in which the colored coating is adhered directly to the sidewall, and the colored coating includes an adhesion promoter.

8. The tire of claim 5, in which there is a poly-urethane primer between the colored coating and the sidewall and the primer includes an adhesion promoter.

9. A process of producing a colored coating on the surface of a diene rubber sidewall of a pneumatic tire, which process comprises covering said surface with a coating of colored composition which contains a substantially saturated polyurethane prepolymer, a diisocyanate and a curing agent which is a diamine, a diol or an hydroxyamine, there being an adhesion promoter at the interface between the design and the sidewall, and curing the colored composition and simultaneously adhering it to the tire.

10. The process of claim 9, in which the colored composition of the coating is a polyureaurethane derived from a polyurethane prepolymer with a molecular weight of at least 3000.

11. The process of claim 9, in which the coating comprises a colored polyurethane coating over a polyurethane primer and there is an adhesion promoter in the primer.

12. The process of claim 9, in which the curing agent is an aromatic diamine blocked with a ketone or aldehyde.

13. A process of producing a cured colored coating on the surface of a diene rubber sidewall of a pneumatic tire, which process comprises applying to the sidewall a primer coating of a polyurethane prepolymer, a diisocyanate, a curing agent and an adhesion promoter, applying over this a colored coating of a substantially saturated polyurethane prepolymer, a diisocyanate and a curing agent, both curing agents being a diamine, a diol or an hydroxyamine, and curing the coatings.

14. The process of claim 13, in which the polyurethane of the coatings is a polyureaurethane derived from a substantially polyurethane prepolymer with a molecular weight of at least 3000 when a diamine curing agent is used.

15. The process of claim 13, in which the curing agent is a diamine blocked with a ketone or aldehyde.