United States Patent (19)
`Dunn, Jr.
`
`3,773,706
`(iii.
`(45) Nov. 20, 1973
`
`54) METHOD FOR INDICATING STAGE OF
`CURE OF CROSSLINKED RESNS AND
`COMPOSITIONS RESULTING THEREFROM
`75) Inventor: Harold F. Dunn, Jr., Longmont,
`Colo.
`(73) Assignee: International Business Machines
`Corporation, Armonk, N.Y.
`Nov. 26, 1971
`(22 Filed:
`(21) Appl. No.: 202,589
`
`52 U.S. Cl. ... . . . . . . . . . . . . . . . . . . . . . . . . 260/37 EP, 260/37 N
`(51) Int. Cl............................................. CO8g 51/14
`(58) Field of Search...................... 260/37 EP, 37 N,
`260/40, TN
`
`56
`
`3,287,156
`
`References Cited
`UNITED STATES PATENTS
`l/1966 Griffith................................. 117/72
`
`3,030,329
`3,207,614
`3,390,121
`
`4/1962 Warnsdorfer................... 260/37 EP
`9/1965 Canevari............................. 106/287
`6/1968 Burford et al..................... 260/40R
`
`
`
`Primary Examiner-Lewis T. Jacobs
`Attorney-Donald W. Margolis et al.
`
`ABSTRACT
`57
`This invention discloses the use of phenosafrainin with
`crosslinkable synthetic organic polymer resins as a vis
`ible qualitative degree-of-cure indicator. It also dis
`closes the use of phenosafrainin to enhance visibility of
`thin film of resin and to serve as a visible degree-of
`mixing indicator. This invention also discloses novel
`compositions of matter containing curable synthetic
`organic polymer resins in combination with phenosa
`franin and dye.
`11 Claims, No Drawings
`
`Cooper Ex. 1006
`
`

`

`10
`
`40
`
`BACKGROUND OF THE INVENTION
`
`3,773,706
`2
`1.
`polymers. It is therefore desirable to identify a dye ma
`METHOD FOR INDICATING STAGE OF CURE OF
`terial which has universal application to a broad num
`CROSSLINKED RESINS AND COMPOSITIONS
`ber of crosslinked synthetic organic resin polymers.
`RESULTING THEREFROM
`In order for a dye to be able to fulfill this multitude
`of requirements, it must possess a distinct, strong color
`which color undergoes a change when crosslinking is
`completed, and preferably a separate and distinct color
`1. Field of the Invention
`change at the outset of cross-linking.
`This invention relates to methods of testing the de
`gree-of-cure of crosslinked synthetic polymer resins by
`SUMMARY OF THE INVENTION
`the inclusion of phenosafranin as a stain in the compo
`sition. It also relates to the synthetic curable organic
`In accordance with this invention, a method of test
`resins to which the dye has been added.
`ing the degree-of-cure of crosslinked synthetic polyrner
`2. Description of the Prior Art
`resin systems by the inclusion of phenosafranin stain in
`Various types of crosslinked synthetic organic poly
`the composition is disclosed. As a qualitative test for
`mers are formed by the reaction of one or more compo
`15
`degree-of-cure, phenosafranin is added to a to-be
`nent compounds, with or without a curing agent, and
`cured synthetic resin system in either crystalline pow
`with or without the benefit of heating above ambient
`der form, or previously dissolved in a suitable compati
`temperatures. There are many types of synthetic cross
`ble solvent, or mixed with one or more components of
`linked polymers, with the epoxy family, the phenoxy
`the reaction mixture. When complete mixing of the re
`family, and the polyurethane family being nonlimiting
`20
`examples. Crosslinked polymers are utilized as adhe
`action components is obtained, the composition will
`have a uniform color. At the outset of curing, the mix
`sives and coatings, as well as in a multitude of other
`ture will begin to change color and continue to change
`uses. After the components of a crosslinked polymer
`have been brought together under reactive conditions,
`color until curing is completed.
`As a qualitative test for degree-of-cure, phenosafra
`the crosslinking reaction proceeds at a given speed,
`25
`nin is unexcelled for its speed, ease of application, ease
`usually a function of the temperature, until cross
`of interpretation after standardization, and its stability,
`linking has been completed at all available reactive
`The degree-of-cure is indicated by striking color
`sites... When complete crosslinking has occurred, the
`changes which progress as curing progresses. Further
`polymer is referred to as having been "cured." The
`ability to identify complete curing, as well as the onset
`more, it is completely reproducible for a given system.
`30
`of curing and the progress of curing, is useful.
`The specific color changes observed during curing de
`It is desirable to identify the onset or near completion
`pend upon the type of resin system in which the
`of curing so that application of the resin can be com
`phenosafrainin has been incorporated, and vary from
`pleted before crosslinking has proceeded too far to
`system to system.
`35
`make it workable. It is also useful to be able to identify
`. While the use of phenosafrainin as a degree-of-cure
`when curing of an applied resin has been completed so
`indicator in crosslinked resins is a novel application,
`that one might know when one can rely upon its adhe
`phenosafranin also exhibits distinct advantages over
`sive or coating qualities. Once crosslinking has been
`many commonly used dyes and pigments which are uti.
`completed, the resins are generally tough, hard, intrac
`lized to determine. degree of mixing and completeness
`table and generally insoluble. Therefore, they must be
`of coating. It provides a very intense color in both the
`applied before this cured stage is reached and similarly,
`cured and uncured state making possible the use of low
`once applied, it may be relied upon once this cured
`concentrations of material in various visual applica
`state is reached. It is therefore desirable to be able to
`tions. Furthermore, it exhibits a chemical reactivity
`determine the degree of cure and final curing of a syn
`with the resin system during curing which reactivity
`45
`thetic cross-linked polymer.
`locks in the dye and prevents it from blooming to the
`It has also been taught in the prior art that a dye may
`surface to discolor adjacent components or from being
`be added to one or more components of a multicompo
`washed out under adverse conditions.
`nent synthetic organic resin so that during mixing, com
`The foregoing and other objects, features and advan
`plete mixing can be determined by the uniformity of
`tages of the invention will be apparent from the follow
`50
`distribution of the dye throughout the mixture. In order
`ing more particular description of preferred embodi
`to be useful, such dyes must have a distinct color which
`ments of the invention.
`is not overshadowed by the colors of the components
`of the mixture. Furthermore, it is desirable to add a dis
`DESCRIPTION OF THE PREFERRED
`tinctive color to a polymeric resin which is to be coated
`EMBODIMENTS
`55
`in a very thin layer so that the completeness and uni
`formity of coating can be visually determined.
`It has been found when phenosafranin is incorpo
`Heretofore, a small number of coloring components
`rated into numerous crosslinking synthetic organic
`or families of coloring components have been identi
`resin systems and the resin system submitted to its nor
`fied as being useful as identifying degree-of-cure or de
`mally employed curing cycle, that a striking color
`60
`gree-of-mixing of synthetic organic resins. However,
`change occurs which coincides with the curing of the
`these prior art materials are specific in nature and do
`resin. Phenosafrainin is otherwise known as Safrainin B
`not include phenosafranin. Furthermore, none of the
`Extra or 3,7-diamino-5-phenylphenazinium chloride. It
`dye materials identified as cure or mix indicators in the
`is a basic dye of the safranine family which is lustrous
`prior art have been identified as being useful to identify
`green in its crystalline form and with an empirical mo
`degree-of-cure for a broad spectrum of crosslinked 65
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`Cooper Ex. 1006
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`

`

`3,773,706
`
`4
`sirable to warm the mass to liquify it or to use a suitable
`solvent to accomplish phenosafranin incorporation or
`to utilize a combination of these techniques or of other
`similar techniques to obtain the desired mixing.
`In multiple component resin systems, such as those
`requiring the addition of a curing agent, phenosafranin
`may be added to any or all of the components, as de
`sired; however, if initial incorporation of the dye is into
`only one of the components, the color imparted thereto
`will aid in the thorough mixing of the entire system by
`10
`carrying out mixing in such a manner and for such a
`time that a uniform color is obtained in the reaction
`mixture.
`
`5
`
`20
`
`3.
`lecular formula of CushisClN and a molecular weight
`of 322.79. It also has a Colour Index 2d Edition, Vol
`ume 3 (1957), Number of 50,200 and is commerically
`available from Eastman Organic Chemicals as stock
`number 1 125. It is prepared by dichromate oxidation
`of 1 mole p-phenylinediamine hydrochloride and 2
`moles aniline hydrochloride.
`As detailed hereinafter, phenosafrainin has been
`added to epoxy, phenoxy?epoxy and polyurethane sys
`tems which have undergone curing, and in each in
`stance, it has exhibited a striking color change at both
`the outset of curing and upon final curing. It is postu
`lated that by employing the method of the present in
`vention and adding phenosafranin to any synthetic or
`ganic resin crosslinking system, a color change will take
`place upon curing.
`Normally, but not inclusively, the initial color of the
`phenosafrainin after it is placed into solution or added
`to the reaction mixture is a brillant red or pink. The
`color change is then coincident with the progress of the
`curing reaction, for example, through shades of violet
`to a deep brillant royal blue. Changes from the initial
`red to shades of yellow have also been noted. In each
`instance, once the range of color changes for a system
`25
`have been determined, they can be used as a reliable
`indicator of degree-of-cure as they are highly reproduc
`ible. As would be expected, the higher the curing tem
`perature, where curing is obtained through heating, the
`quicker the curing occurs and the quicker the signature
`curing color is indicated in the resin. As used herein,
`the term "color change" means formation of a different
`color, loss of original color, or intensification of the
`original color,
`The depth or magnitude of intensity of the color of
`35
`the initial mixture and the final resin is simply con
`trolled by controlling the concentration of the phenosa
`fran in and the thickness of the resin film. It has been
`determined that concentrations within in the range of
`about 0.001% to about 2.0% phenosafrainin, by weight
`40
`of solids, is sufficient for most visual and cure indica
`tion uses, while a range of about 0.01% to about 1% is
`preferred. However, there are merely practical limits in
`that lesser concentrations are visible under many cir
`cumstances, and greater concentrations can be used,
`but without adding to the visual effects of this inven
`tion. The use of any amount of phenosafrainin affects
`the color of the resin system, while the concentration
`of the phenosafrainin affects the color intensity,
`The addition of phenosafranin to a curable synthetic
`50
`organic resin does not alter the normally employed cur
`ing procedures or reaction components. It has also
`been found that the addition of phenosafrainin in the
`preferred range of concentration does not affect the
`physical properties of the resin system. The only effect
`observed is the desired effect of providing a visible
`color and inducing a color change coincident with cur
`ing.
`In incorporating phenosafranin into a resin system, it
`is preferably dissolved in the system or in one compo
`60
`nent of the system, although in some cases, it may be
`incorporated as a finely divided dispersed or partially
`dissolved mixture. Mixing of the phenosafranin with
`the resin system or with a component of the resin sys
`tem is most easily done while the system or component
`65
`are in the liquid state. In some instances, it may be de
`
`30
`
`EXAMPLE I
`A commerical proprietary epoxy/phenoxy/curing
`agent mixture dissolved in a solvent and sold by Minne
`sota Mining and Manufacturing Company as EC-2290
`resin was obtained. To a sample of EC-2290 containing
`about 21 percent solids was added a pink alcohol solu
`tion of 2.5 percent phenosafrainin, by weight, in an
`amount such that the phenosafrainin was equal to 0.1
`percent, by weight, of the total solids of the EC-2290
`resin. After thorough mixing, as indicated by a uniform
`pink color throughout the mixture, the resin was uni
`formly coated upon an aluminum surface, with the uni
`formity of coating being apparent from the color of the
`mixture as imparted by the phenosafranin. Three addi
`tional pieces of aluminum were coated in a similar
`manner with the EC-2290-phenosafranin mixture. On
`yet another piece of aluminum, a pink coating of
`phenosafrainin and alcohol was brushed. The several
`pieces of resin coated aluminum were then placed in
`different ovens at temperatures of 60°, 100 and 150
`C, respectively. The aluminum coated with the pink
`phenosafrainin and alcohol solution was also placed in
`the 150 Coven. It was then observed that each of the
`phenosafranin/EC-2290 mixtures progressed through a
`series of color changes from the initial red, through sev
`eral shades of purple and violet, and, ultimately, to a
`final color of brillant royal blue. The time required for
`complete curing in each of these systems exhibited an
`inverse relationship to the temperature, with the 150
`Csample reaching final cure within twenty minutes, the
`100 C sample reaching final cure within 180 minutes,
`and the 60 C sample not obtaining cure until after
`about 3,000 minutes. However, in each case, when
`complete cure was obtained, the color was the same
`brillant royal blue. The sample of aluminum coated
`with the phenosafrainin and alcohol mixture, without
`resin, did not exhibit any color change after 3 hours in
`an oven at 150 C, other than the conversion of the
`pink alcohol solution to green irridescent crystals,
`which are the normal form of dry phenosafrainin.
`EXAMPLES II-V
`Phenosafranin was incorporated with other resin sys
`tems in much the same manner as in Example I, and in
`concentrations of from about 0.001 percent to about 2.
`percent, by weight, of the total solids. The resin systems
`in which the phenosafranin was incorporated and the
`temperature, time of cure, initial color and color upon
`reaching complete cure are noted in Table I, which also
`includes the data from Example I.
`
`45
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`55
`
`Cooper Ex. 1006
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`

`

`3,773,706
`
`TABLE I
`
`Resin System
`
`Example No.
`
`Uncured
`color
`Red------
`-------------- Phenoxylopoxy: 3M, EC-2290--------------------------------. Red------
`Red-----.
`II------------- Epoxy: Shell, Epon 828 epoxy, 10 g. and diethylaminopropyl- Red
`amine, 0.7 g.
`- - - -
`III------------ Sheil, Epon 828 epoxy, 10g.; and Nadic methyl anhydride, 9.0 Red------
`g.; and benzyldimethylanine, 0.4g.
`IV------------ Polyurethane: DuPont, 4.6960 polyester, 10 g.; and DuPont, Red. -----
`'RC-805 isocyanate, 0.5g.
`V- - - - - - - - - - - - - DuPont, Adiprene polyurethanc, 10 g. and methylene bisor- Red.-----
`thochloroaniline, .0 g.
`NoTE.-ND = Not Determined.
`
`6
`
`Time Cured
`Temp.
`(C.) (min.) color
`150
`20 Royal blue.
`00
`180
`D0.
`60
`3,000
`Do.
`150
`i0 Yellow.
`00
`40
`DO.
`60
`500
`Do.
`23
`1,000
`Do.
`100-150
`ND Yellow/orange,
`100-50
`ND Royal blue.
`100-150
`ND
`Do,
`
`25
`
`30
`
`This series of examples is broadly indicative of the
`fact that this invention is applicable to all families of
`curable synthetic organic polymers and that it is inde
`pendent of the type of curing agent that is used.
`As an aid in determining the effect which phenosafra
`nin had on the physical properties of a resin system, the
`following procedure was followed. Phenosafranin was
`dissolved in a sample of EC-2290 phenoxy/epoxy in
`amounts of 0.1 percent and 1 percent, by weight, of the
`solids. Resin sample with no dye added were also pre
`pared. Each of the resins and resin dye mixtures was
`then utilized to laminate foils of 0.006 inch thick
`etched aluminum with a 0.001 inch thick glue line for
`the purpose of testing and comparing the adhesive peel
`strength of the systems with and without dye, in the foll
`lowing manner. Etched aluminum sheets were uni
`formly sprayed with one each of the previously pre
`pared resin systems, dried open-faced under room tem
`perature conditions for about 15 minutes, then at 100'
`C for 15 minutes. Under these conditions, the color of
`the dyed systems remained pink, and the control sys
`tem, without dye, a clear straw color. The systems were
`then bonded to other foils and cured in their laminated
`forms and under flattening pressure at 180° C for 60
`minutes. Following curing, the laminates were cooled
`and tested for peel strength using an Instron Universal
`Tester at a peel rate of 0.5 inch per minute to apply a
`T/peel test. For all of the samples, both with and with
`out phenosafranin added and among those samples .
`45
`having different quantities of phenosafrainin added, the
`peel strength was found to be the same. The resins in
`the cured systems containing phenosafranin exhibited
`a bright blue color indicative of complete curing. The
`resin to which no phenosafrainin had been added ap
`peared to be the same clear straw color it was prior to
`curing.
`It is therefore seen that the addition of phenosafrainin
`
`15 to resin systems would appear to have no effect upon
`their adhesive strength.
`In an effort to determine the stability and extractabil
`ity of the phenosafrainin from both cured and uncured
`resin systems, the following procedure was followed.
`Phenosafrainin was added to a sample of EC-2290 phe
`noxy/epoxy resin. Four sheets of aluminum were
`coated with the resin dye mixtures and cured at 150 C
`for 20 minutes. One each of these pieces of aluminum
`was placed in acetone at room temperature, in water at
`room temperature, in boiling acetone, and in boiling
`water. In each of these four tests, no effect was ob
`served on either the cured resin or upon the dye. The
`resin remained firm and unchanged, and the dye was
`not extracted from the cured resin in any detectable
`amount.
`When four additional plates of aluminum were
`coated with the EC-2290 and phenosafrainin mixture,
`not cured, and subjected to the same solvent and heat
`ing conditions, a substantial change was noted in both
`the resin and the dye. The acetone caused both the un
`cured resin and the dye to dissolve and separate under
`both ambient and boiling conditions. The water caused
`partial dissolution of the dye, but no dissolution of the
`resin under both room temperature conditions and
`boiling conditions. This data is indicative of the fact
`that some form of reaction has occurred between the
`dye and the resin during the curing reaction which
`makes it impossible to extract the dye from the cured
`system. This reaction may also be the cause of the ob
`served color change.
`Finally, measurements were made by differential
`scanning calorimetry to determine whether the resin
`systems exhibited a signature curing exotherm concur
`50
`rent with their final color change. The results are set
`forth in Table II.
`
`35
`
`40
`
`A3LE I...EVALUATIONS BY DIFFERENTIAL SCANNING CALORIMETRY
`Instrunnelt conditions: Perkin-Elmer DSC-1B; scan rate, 20/min.; sensitivity, 32; temperature range of study within -40° C. to 280° C.
`Curing exotherm
`Peak,
`C. Comments and observations
`195 Color change from red to blue coincident with exotherm.
`140 Color change from red-violet (partial dispersion) to yellow
`tone coincident with exothern...
`N D Color change from red to blue coincident with curing.
`
`Range, C.
`Resin System
`3M, EC-2290, phenoxylepoxy------------------------------ 155-240------------
`Shell, Epon 828, epoxy dicthylaminopropylamine pheno- 65-160-------------
`safrainin (1%).
`JuPont, 4.6960 polyester DuPont, RC-805 isocyanate (5%) 60-140 and
`phenosafrainin (1%).
`I40-200.
`NoTE.-N) = Not Deterinined.
`
`Cooper Ex. 1006
`
`

`

`15
`
`20
`
`25
`
`3,773,706
`8
`7
`the final cured product, said mixture indicating by
`It is apparent from the data in this Table that the
`a color change the degree of curing of said resin
`color change is indeed coincident with the curing exo
`therm of the resin system and is a true indication of
`system.
`final curing.
`2. The method of claim 1 wherein the phenosafranin
`The objects, advantages and principles of this inven- 5 constitutes from about 0.001 percent to about 2 per
`tion are broadly applicable and are not limited to the
`cent, by weight of solids, of said system.
`specific steps, methods, compositions or combinations
`3. The method as defined in claim 2 wherein said
`herein described. Other advantages and uses of this in
`cured synthetic organic resin is selected from the group
`vention may be learned by experimentation with the
`consisting of phenoxyfepoxy, epoxy and polyurethane.
`invention and may require optimization for a given sys
`4. The method of claim 3 wherein the synthetic or
`O
`ganic resin is a phenoxy/epoxy.
`tem without departing from the principles of the inven
`tion. In any event, it has been clearly shown that the use
`5. The method according to claim 3 wherein the syn
`of phenosafrainin with a broad range of crosslinkable
`thetic organic resin is epoxy.
`synthetic organic resin systems produces a composition
`6. The method according to claim 3 wherein the syn
`which is useful in enhancing the visibility of thin coated
`thetic organic resin is polyurethane. .
`films, a visible degree-of-mixing indicator when used in
`7. As a composition of matter, a mixture of a curable
`multicomponent systems, and particularly as a visible,
`synthetic organic resin system and phenosafranin, said
`qualitative degree-of-cure indicator.
`resin system capable of inter-action with phenosafrainin
`While the invention has been particularly shown and
`to produce a color change when cured with a substance
`described with reference to preferred embodiments
`which enters into the curing reaction and becomes part
`thereof, it will be understood by those skilled in the art
`of the final cured product.
`that various changes in form and details may be made
`8. The composition of claim 7 wherein said curable
`therein without departing from the spirit and scope of
`synthetic organic resin system is selected from the
`the invention.
`group consisting of phenoxy/epoxy, epoxy and polyure
`What is claimed is:
`thane.
`1. The method of indicating various stages through
`9. The composition of claim 8 wherein the resin sys
`which a curable synthetic organic resin system passes
`tem is phenoxylepoxy.
`comprising:
`10. The composition of claim 8 wherein the resin sys
`mixing a curable synthetic organic resin system with
`tem is epoxy.
`phenosafranin, said resin system during curing ca
`30
`11. The composition of claim 8 wherein the resin sys
`pable of interaction with phenosafrainin to produce
`tem is polyurethane.
`a color change; and then
`curing said resin system with a substance which en
`ters into the curing reaction and becomes part of
`
`35
`
`40
`
`45
`
`50
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`55
`
`60
`
`65
`
`Cooper Ex. 1006
`
`