US3515568A - Processing of erasing from a thermographic element - Google Patents

Description

United States Patent 3,515,568 PROCESSING OF ERASING FROM A THERMOGRAPHIC ELEMENT Martin Goldman and William J. Staudenmayer, Rochester, N.Y., assignors to Eastman Kodak Company, Rochester, N.Y., a corporation of New Jersey No Drawing. Filed July 3, 1967, Ser. No. 650,634 Int. Cl. B41m 5/14; H01j 37/22 US. Cl. 117-2 11 Claims ABSTRACT OF THE DISCLOSURE This invention relates to thermographic processes and elements. In a particular aspect it relates to a novel method for erasing an image from thermographic copying materials to make the material reusable. In another aspect it relates to a novel method of preparing thermographic copying materials which can be erased.

Ther-mographic copying materials and methods have been previously described in a number of domestic and foreign patents. These materials frequently have the advantage of simplicity over certain photographic processes in that they produce a direct positive image of the original upon exposure to radiant energy (e.g., infrared radiation). However, certain of these known thermographic materials possess properties which make them of limited utility in the production of facsimile copies on a commercial scale. For example, certain of these thermographic materials are only slightly sensitive to heat, and therefore require prolonged exposures. Other materials contain metallic ions which may stain the material upon which the heat-sensitive layer is coated. Yet other thermographic materials have the disadvantage of being excessively sensitive to visible light, and hence these materials must be handled in the dark until they are first exposed. Still other heat-sensitive copying materials exhibit thermotrophy and therefore lose their developed color when the heat-sensitive material is cooled to ambient temperature.

Many of the aforementioned defects have been overcome by a thermographic copying material disclosed in Crevling et al. US. Pat. 2,899,334. The thermographic materials disclosed in that patent comprise a p-quinone compound and dihydroxybenzene compound which are maintained in physically distinct but chemically interactive relationship, so that upon exposure to heat they react with one another and undergo a rapid color change. These thermographic materials are particularly preferred over other thermographic materials disclosed in the prior art because they do not require prolonged exposure, they are not sensitive to visible light, and upon cooling the heat induced color change is intensified.

The thermographic materials disclosed in Crevling et al. US. Pat. 2,899,334 have the further advantage that the images formed on exposure to heat can be erased and the heat-sensitive element regenerated. Commonly assigned Fierke et al. US. patent application Ser. No. 506,325, filed Nov. 4, 1965 now US. Pat. 3,414,423 discloses a process for erasing and regenerating the thermographic materials of the Crevling et al. patent in 3,515,568 Patented June 2, 1970 ice which exposed materials are treated with certain solvents to convert the colored quinhydrone complex to the pquinone compound and dihydroxybenzene compound. This regeneration process is extremely useful in that it permits the same element to be used a number of times. However, the solvent treatment step sufiers from the ditficulties associated with any wet processing procedure, and it would be desirable if a dry process for erasing and regenerating thermographic materials could be obtained.

Accordingly, it is an object of this invention to provide a process for regenerating exposed thermographic material.

It is a further object of this invention to provide a novel process in which exposed thermographic material is erased and regenerated without using a solvent.

It is a still further object of this invention to provide a novel process for preparing thermographic materials which can be erased and regenerated.

It is another object of this invention to provide novel thermographic materials which can be erased and regenerated by a dry process.

These and other objects of this invention will be apparent to those skilled in the art from the further dis cussion of the invention which follows.

In accordance with the present invention, we have discovered that the colored quinhydrone complex which is formed by the reaction of a p-quinone compound and a dihydroxybenzene compound can be erased by heating the quinhydrone complex to a temperature between C. and C. When heated to a temperature within this range, it has been found that the dark quinhydrone complex dissociates and is converted back to the pale colored mixture of the p-quinone compound and the dihydroxybenzene compound. The particular temperature within this range at which the dissociation occurs will vary with the particular pair of p-quinone and dihydroxybenzene compounds which are employed. However, dissociation will generally occur at a narrow temperature range within the broader range of 60 C. to 100 C. If the dark colored quinhydrone complex is heated to a temperature below this selected narrow temperature range, it will not dissociate and will not change color; if the complex is heated to a temperature above the selected range, it will initially dissociate to the pale mixture, but upon cooling will revert to the dark colored quinhydrone complex.

The ability of certain elements containing the p-quinone compound and the dihydroxybenzene compound to be converted to the quinhydrone and then reconverted to the p-quinone and the dihydroxybenzene compounds solely by the application of heat, permits these elements to be used in a wide variety of applications. For example, an element containing the p-quinone compound and the dihydroxybenzene compound can be exposed to heat in an imagewise manner to cause formation of the quinhydrone complex in image areas, thereby giving a dark image on a light background. After this image has served its purpose, the entire sheet can be raised to a temperature at which the quinhydrone complex reconverts to the p-quinone compound and the dihydroxybenzene compound. The sheet can then be reused, and this cycle can be repeated several times.

In an alternative procedure, an element in which the quinhydrone complex has been uniformly formed, either by heat or by a procedure which will be described hereinafter, can be exposed to heat in an imagewise manner to heat the element to a temperature at which the quinhydrone complex is converted to the p-quinone and the dihydroxybenzene compound. Thus, there is obtained a light image on a dark background. After the image has served its purpose, it can be erased by heating the sheet to a temperature above that at which the quinhydrone complex is converted to the p-quinone compound and the dihydroxybenzene compound. Upon cooling, the sheet again has the uniform dark color of the quinhydrone complex. This procedure can be repeated several times.

Thus, the capability of these elements to be exposed, erased and regenerated solely by the application of heat permits the preparation of a uniformly dark element, a uniformly light element, an element having light image areas on a dark background and an element having dark image areas on a light background. Other applications utilizing this capability of these elements will be apparout to those skilled in the art.

The dihydroxybenzene compounds useful in practicing our invention comprise the hydroquinones, pyrocatechols, pyrogallols, etc. These dihydroxybenzenes can contain one or more of the conventional substituents of the type common in organic chemistry. We have found that these substituents do not generally interfere with the colorforming reaction upon which the instant therrnographic process depends. A particularly useful group of dihydroxybenzene compounds comprise those represented by the following general formula:

wherein R and R each represents a hydrogen atom, an *alkyl group (e.g., methyl, ethyl, n-propyl, isopropyl, nbutyl, isobutyl, tert-butyl, n-amyl, isoamyl, tert-amyl, nhexyl, isohexyl, 2-ethylbutyl, n-octyl, isooctyl, tert-octyl, n-nonyl, n-decyl, n-lauryl, n-hexadecyl, sec-hexadecyl, noctadecyl, etc.), an alkenyl group (e.g., allyl, crotyl, etc.), a halogen atom (e.g., chlorine, bromine, etc.), a hydroxyl group, an acyl group (e.g., acetyl, =butyryl, caprylyl, palmitoyl, etc.), an acyloxyl group (e.g., acetoxyl, benzoxyl, etc.), a carbamyl group (e.g., carbamyl, N-ethylcarbamyl, N-methylcarbamyl, N-Z-aminoethylcarbamyl, etc.), or an aryl group (e.g., phenyl, p-chlorophenyl, p-nitrophenyl, 11-, or p-tolyl, etc.); R represents a hydrogen atom, or R and R together represent the groups necessary to complete an aromatic ring (which can contain substituents, such as methyl, ethyl, hydroxyl, bromine, chlorine, etc.).

The p-quinone compounds which have been found to be especially useful in practicing our invention include those represented by the following general formula:

1| a R4 I i wherein R and R each represents a hydrogen atom, an alkyl group (e.g., methyl, ethyl, n-propyl, isopropyl, nbutyl, isobutyl, tert-butyl, n-amyl, isoamyl, tert-amyl, n-hexyl, isohexyl, Z-ethylbutyl, n-octyl, isooctyl, tertoctyl, n-nonyl, n-decyl, n-lauryl, n-hexadecyl, sec-hexadecyl, n-octadecyl, etc.), an alkenyl group (e.g., allyl, crotyl, etc.), a halogen atom (e.g., chlorine, bromine, etc.) a hydroxyl group, an acyl group (e.g., acetyl, butyryl, caprylyl, palmitoyl, etc.), an acyloxyl group (e.g., acetoxyl, benzoyl, etc.), a carbamyl group (e.g., car- 'barnyl, N-ethylcarbamyl, N-methylcarbamyl, N-2-aminoethylcarbamyl, etc.), or an aryl group (e.g., phenyl, pchlorophenyl, p-nitrophenyl, o-, n-, or p-tolyl, etc.); R represents a hydrogen atom, or R and R together represent h g oup necessary to f rm an a o a ic ring 4 (which can contain substituents, such as methyl, ethyl, hydroxyl, bromine, chlorine, etc.).

Certain p-quinone and dihydroxybenzene compounds are especially preferred because these compounds do not induce a dermatitic reaction in individuals handling them, as do certain other of the p-quinone and dihydroxyben- Zene compounds described above. These nondermatitic p-quinone and dihydroxybenzene compounds include those wherein at least one of R and R and at least one of R and R represents a carboxyalkyl group (e.g., carboxybutyl, carboxypropyl, carboxypentyl, etc.), a carboxyaryl group (e.g., carboxyphenyl, carboxynaphthyl, etc.), an acyloxyalkyl group (e.g., succinoxypropyl, malonoxyethyl, etc.), or an acyloxyaryl group (e.g., succinoxy-phenyl, malonoxyphenyl, etc.).

Typical of the p-quinone and dihydroxybenzene compounds which are useful in the practice of the present invention are those which are tabulated in columns 3 and 4 of Crevling et al. US. Pat. No. 2,899,334. Other pquinone and dihydroxybenzene compounds which are useful in the practice of the present invention and which are not specifically referred to in the Crevling et a1. patent are: 2 (w-carboxypentyl)-5-n-octylhydroquinone, Z-(wcarboxypentyl) 5 n octylquinone, 2 (w carboxypropyl)-5-n-octylhydroquinone, 2 (wcarboxypropyl)-5- n-octylquinone, 2 (w-carboxypentyl) 5 methylhydroquinone, 2 (w carboxypropyl)-5-methylhydroquinone, 2,5 di (w-carboxypropyl) hydroquinone, 2,5-di-(w-carboxypropyl)quinone, 2 (o carboxyphenyl) hydroquinone, 2 ('y-succinoxypropyl)-5-n-octylhydroquinone and 2,5-di- (B-malonoxyethyl) hydroquinone.

Not all elements in which the quinhydrone complex is formed upon heat exposure exhibit the dissociation reaction of the quinhydrone to the quinone and dihydroxybenzene compounds. The proportions in which the quinone and dihydroxybenzene compounds are present in the element affects this reaction. Similarly, if a binder is employed, the particular binder chosen affects both the color-forming reaction and the dissociation reaction.

While the quinhydrone will form upon heating over a wide range of proportions of quinone compound and dihydroxybenzene compound, the dissociation reaction of quinhydrone decomposing to quinone compound and dihydroxybenzene compound will take place only above a particular ratio of quinone compound to dihydroxybenzene compound initially present in the element. For this dissociation to occur, there must be a molar excess of quinone compound present in the element. That is, there should be at least 1.1 moles of the quinone compound initially present in the element for each mole of dihydroxybenzene compound. Ratios of 1.3 to 2.5 moles of quinone compound per mole of dihydroxybenzene compound are preferred.

The binders which are employed in coating the quinone and dihydroxybenzene compounds in an element affect both the color-forming reaction between the quinone and dihydroxybenzene compounds to form the quinhydrone complex and the dissociation reaction in which the quinhydrone complex reverts to the quinone and dihydroxybenzene compounds. The dissociation reaction does not take place in all binders. Those binders in which the dissocciation reaction can occur are primarily the polymeric resins. However, certain polymeric resins hinder the color-forming reaction if sufiicient quinone compound is not present. These resins contain a large number of free hydroxyl groups which compete with the dihydroxybenzene compound for the quinone compound, thus tying up the quinone compound and inhibiting the formation of the colored quinhydrone complex. If these binders are used, it is necessary to provide in the element a sufficient excess of quinone compound to react both with the free hydroxyl groups of the binder and with the dihydroxybenzene compound. Therefore, it is preferred that the polymeric binders employed contain less than one mole of free hydroxyl groups per mole of quinone compound present in the element. Typical polymeric resins which are useful in the practice of the present invention as binders include: polyvinyls (e.g., polystyrene, polyvinyl chloride, polyvinyl acetate, polyvinyl butyral, etc.), polyesters (e.g., polyethylene terephthalate, polyethylene terephthalate-isoterephthalate, cellulose acetate'butyrate etc.), polycarbonates (e.g., poly[4,4 (2-norbornylidene) diphenyl carbonate], the polycarbonate formed by the reaction of bisphenol A with diphenyl carbonate, etc.), and the like.

In one embodiment of this invention a dark colored element containing the quinhydrone complex can be formed by coating a mixture of a p-quinone compound and a dihydroxybenzene compound in a binder, such as is described above, using certain solvents. The colored element thus formed, can be used directly to prepare negative light colored images on a dark background without having to uniformly heat the element to form the quinhydrone complex. In the practice of this embodiment the element is prepared and then heated in image areas to a temperature at which the dissociation reaction occurs, thus giving a light image on a dark background. The solvents which exhibit this ability to cause the quinone and dihydroxybenzene compounds to complex as the quinhydrone upon coating are the coordinate solvents such as halogenated hydrocarbons (e.g., carbon tetrachloride, methylene chloride, 1,1-dichloroethane, chloroform, etc.), toluene, cyclohexane, and the like.

Elements useful in the practice of the present invention can be prepared in any well-known manner. For example, a dispersion of the p-quinone and dihydroxybenzene in a suitable binder can be coated on a support by any of the well-known coating procedures, such as dip coating, hopper coating, doctor-blade coating, etc. As described in Crevling et al. US. Pat. 2,899,334, the pquinone and dihydroxybenzene compounds can be dispersed in separate binders and the two dispersions then combined prior to coating, or the p-quinone and a dihydroxybenzene compounds can be dispersed together in a single binder and then coated on a support. Suitable supports for the elements of this invention include paper, polyethylene coated paper, metal foils, polymeric film base such as cellulose acetate, cellulose acetate-butyrate, cellulose acetate-propionate, polyethylene terephthalate, etc., and the like.

In the practice of the invention an element containing the quinhydrone complex is exposed to heat in an imagewise manner to raise the temperature of the element in image areas to a temperature between 60 C. and 100 C. at which the dissociation reaction occurs. This can be accomplished in a variet of manners. For example, the element can be contacted with an image which is maintained at the temperature at which the dissociation reaction takes place. Alternatively, the element can be contacted with an original containing infrared-absorbing image areas and the element in contact with the original can be exposed to infrared radiation for a period of time sufficient to heat the areas of the element in contact with the image areas to the temperature at which the dissociation reacion occurs. In both of these instances a negative copy of the original is obtained. That is, the element contains light-colored image areas on a dark background. To achieve this there must be used a uniformly dark element containing the quinhydrone complex. This element can be obtained either by heating an element containing the quinone compound and the dihydroxybenzene compound to a temperature at which the quinhydrone complex is formed, or the quinhydrone complex can be formed in the element by the method described above in which the quinone compound and the dihydroxybenzene compound are coated from a solvent.

ment can be obtained by the coating process described in the Crevling et al. patent, or a dark-colored element containing the quinhydrone complex can be heated uniformly to a temperature at which the dissociation reaction occurs. The element can then be exposed to heat in the manner described above to form the quinhydrone complex in image areas. Thus a dark positive image on a light background will be obtained.

The image formed in the elements of our invention can be erased and the element rendered suitable for reuse by a relatively simple procedure. Depending upon whether a uniformly clear element is desired or a uniformly colored element is desired, the element can be heated either to the temperature at which the dissociation reaction occurs or to a temperature above this temperature. In the first instance, the quinhydrone complex will dissociate to the quinone and dihydroxybenzene compounds thus giving a uniformly light colored element. In the second instance the quinhydrone complex will initially dissociate to the p-quinone and dihydroxybenzene compounds, but upon cooling the quinhydrone complex will reform uniformly in the element.

From the above discussion it is readily apparent that the elements and processes of our invention are suitable for a wide variety of uses in which it is desirable to employ a reusable element on which can be formed an erasable image.

The following non-limiting examples further illustrate the practice of our invention.

EXAMPLE 1 A coating solution is prepared by mixing 3 g. of 2,5- di-n-octylquinone, 2 g. of 2,5 -di-n-octylhydroquinone and 10 g. of polystyrene (Koppers 8X, sold by Koppers Co., Pittsburgh, Pa.) in 100 m1. of methyl chloroform. This solution is coated at a thickness of .005 inch on a polyethylene terephthalate film base which is subbed with a terpolymer of methylacrylate, vinylidene chloride, and itaconic acid. After drying at approximately 70 C. a blue coated element is obtained. A strip of the coated film is then contacted with a heated surface which varies in temperature along its length from approximately 50 C. to approximately 100 C. at a rate of approximately 7 C. per inch of length. While in contact with the heated surface, the areas of the strip which are below approximately 74 C. remain blue while the area above 74 C. clear to a pale yellow color. Upon removal of the coated film from the variable temperature surface and cooling, the pale yellow section of the film reverts to the blue color except for a narrow band which had been exposed to a surface temperature of between 74 C. and 76 C. This narrow band remains pale yellow in color.

EXAMPLE 2 A coated element is prepared as described in Example 1. The element is then heated uniformly to a temperature of 75 C. in an oven. There is thus obtained a pale yellow element. This element is then placed in contact with an original containing black infrared absorbing image areas on a white background and is exposed by passing the element in contact with the original through an exposure unit containing a 1350 watt infrared lamp at a distance of 1 cm. from the element. There is thus obtained a positive copy of the original document having dark blue image areas on 'a light background. This copy is erased by again heating the element to 75 C. to obtain a uniformly pale yellow element. This exposure anderasure procedure is repeated several times. After each exposure a positive blue copy on a pale yellow background is obtained.

EXAMPLE 3 A coated element is prepared as described in Example 1. The dark blue element is placed in contact with an original containing black infrared image areas on a white background and is exposed by passing the element in contact with the original through the exposure unit described in Example 2 to heat the image areas to a temperature of approximately 75 C. There is thus obtained a negative copy having pale yellow image areas on a dark blue background. The image is erased by heating the element to 100 C. and cooling to 40 C. to produce a uniform blue coating. This exposure and erasure procedure is repeated several times, and after each exposure a negative light-colored image on a blue background is obtained.

EXAMPLE 4 A coated element is prepared by the procedure described in Example 1, using 3 g. of 2-(w-carboxy-npentyl)-5-methyl hydroquinone and S g. of Z-(w-carboxyn-pentyD-S-n-octyl quinone as the heat-sensitive components, and 5 g. of polystyrene (Koppers 8X, sold by Koppers Co., Pittsburgh, Pa.) as the binder. The element thus obtained is treated and exposed as described in Example 2. A positive copy of the original is obtained. This element is erased and exposed several times. After each exposure a good positive copy is obtained.

EXAMPLE 5 A coated element is prepared as described in Example 1, using the heat-sensitive components of Example 4 and 5 g. of a polyester of terephthalic acid and a mixture of ethylene glycol (1 part by weight) and 2,2-bis(4-hydroxyethoxyphenyl)propane (9 parts by weight) (Vitel PIE-101 sold by Goodyear Tire and Rubber Co., Akron, Ohio) as the binder. This element is exposed as described in Example 3, and a negative copy of the original is obtained. The element is erased and exposed several times. After each exposure a good negative copy is obtained.

This invention has been described in detail with particular reference to preferred embodiments thereof, but it will be understood that variations and modifications can be effected within the spirit and scope of the invention as described hereinabove and as defined in the appended claims.

We claim:

1. A process for erasing from a thermographic element a quinhydrone complex in a polymeric resin binder, the quinhydrone complex being formed from a dihydroxybenzene compound having the formula:

wherein R is a member selected from the group consisting of a hydrogen atom, an alkyl group, an alkenyl group, a halogen atom, a hydroxyl group, an acyl group, an acyloxyl group, a carbonyl group, an aryl group, a carboxyalkyl group, a carboxyalkryl group, an acyloxyalkyl group, and an acyloxyaryl group; R is a member selected from the group consisting of a hydrogen atom and groups which together with R represent the atoms necessary to complete an aromatic ring; and R when R represents a hydrogen atom, is a member selected from the group consisting of a hydrogen atom, an alkyl group, an alkenyl group, a hydroxyl group, a halogen atom, an acyl group, an acyloxy group, an aryl group, a carboxyalkyl group, a carboxyaryl group, an acyloxyalkyl group and an wherein R is a member selected from the group consisting of a hydrogen atom, an alkyl group, an alkenyl group, a halogen atom, a hydroxyl group, an acyl group, an acyloxyl group, a carbonyl group, an aryl group, a carboxyalkyl group, a carboxyaryl group, an acyloxyalkyl group, and an acyloxyaryl group; R is a member selected from the group consisting of a hydrogen atom and groups which together with R represent the atoms necessary to complete an aromatic ring; and R when R represents a hydrogen atom, is a member selected from the group consisting of a hydrogen atom, an alkyl group, an alkenyl group, a hydroxyl group, a halogen atom, an acyl group, an acyloxyl group, an aryl group, a carboxyalkyl group, a carboxyaryl group, an acyloxyalkyl group, and an acyloxyaryl group, there being present initially at least 1.1 mole of the quinone compound for each mole of the dihydroxybenzene compound, said process comprising heating the element to a temperature of between 60 C. and C. to convert the quinhydrone complex to the quinone compound and the dihydroxybenzene compound.

2. A process as defined in claim 1, wherein the quinhydrone complex is present in the element in the form of an image and heating of the element is in a uniform manner to erase the quinhydrone image.

3. A process as defined in claim 1 wherein the quinhydrone complex is uniformly present in the element and heating is in an imagewise manner to erase the quinhydrone complex only in image areas.

4. A process as defined in claim 3 wherein the quinhydrone complex is formed in the element by coating the quinone compound and the dihydroxybenzene compound onto a support from a coordinate solvent.

5. A process as defined in claim 1 wherein the polymeric resin binder is substantially free of hydroxyl groups.

6. A process as defined in claim 5 wherein the polymeric resin binder is a polystyrene.

7. A process as defined in claim 5 wherein the polymeric resin binder is a polyethylene terephthalate.

8. A process for erasing from a thermographic element a quinhydrone complex carried in a po ymeric resin binder which is substantially free from hydroxyl groups, said quinhydrone complex being formed from 2,5-di-noctyl quinone and 2,5-di-n-octyl hydroquinone, there initially being present at least 1.1 mole of the quinone compound for each mole of the hydroquinone compound, the process comprising heating the element to a temperature of between 74 C. and 76 C. to convert the quinhydrone complex to the quinone compound and the dihydroxybenzene compound.

9. A process for erasing from a thermographic element a. quinhydrone complex carried in a polymeric resin binder which is substantially free from hydroxyl groups, said quinhydrone complex being formed from 2-(w-carboxy-npentyD-S-methyl hydroquinone and 2-(w-carboxy-npentyl) -5-n-octyl quinone, there initially being present at least 1.1 mole of the quinone compound for each mole of the hydroquinone compound, the process comprising heating the element to a temperature of between 72 C. and 77- C. to convert the quinhydrone complex to the quinone compound and the dihydroxybenzene compound.

10. A process for preparing a thermographic element uniformly coated with a quinhydrone complex which comprises coating a support with a mixture in a coordinate solvent of 1.1 mole of a quinone compound per mole of a clihydroxybenzene compound, and evaporating the solvent from the element, said dihydroxybenzene compound having the formula:

wherein R is a member selected from the group consisting of a hydrogen atom, an alkyl group, an alkenyl group, a halogen atom, a hydroxyl group, an acyl group, an acyloxy group, a carbonyl group, an aryl group, a carboxyalkyl group, a carboxyaryl group, an acyloxyalkyl group, and an acyloxyaryl group; R is a member selected from the group consisting of a hydrogen atom and groups which together with R represent the atoms necessary to complete an aromatic ring; and R when R represents a hydrogen atom, is a member selected from the group consisting of a hydrogen atom, an alkyl group, an alkenyl group, a hydroxyl group, a halogen atom, an acyl group, an acyloxy group, an aryl group, a carboxyalkyl group, a carboxyaryl group, an acyloxyalkyl group and an acyloxyaryl group, and said quinone compound having the formula:

R3 R4 w wherein R is a member selected from the group consisting of a hydrogen atom, an alkyl group, an alkenyl group, a halogen atom, a hydroxyl group, an acyl group, an acyloxyl group, a carbonyl group, an aryl group, a carboxyalkyl group, a carboxyaryl group, an acyloxyalkyl group, and an acyloxyaryl group; R is a member selected from the group consisting of a hydrogen atom and groups which together with R represent the atoms necessary to complete an aromatic ring; and R when R represents a hydrogen atom, is a member selected from the group consisting of a hydrogen atom, an alkyl group, an alkenyl group, a hydroxyl group, a halogen atom, an acyl group, an acyloxyl group, an aryl group, a carboxyalkyl group, a carboxyaryl group, an acyloxyalkyl group, and an acyloxyaryl group.

11. A process as defined in claim 10 wherein the solvent is selected from the group consisting of carbon tetrachloride, methylene chloride, 1,1-dichloroethane, chloroform, toluene and cyclohexane.

References Cited UNITED STATES PATENTS 2,899,334 8/1959 Crevling et a1. 11736.8 2,953,454 9/1960 Berman 11736.8 3,414,423 12/1968 Fierke et a1. 11736.8

MURRAY KATZ, Primary Examiner US. Cl. X.R.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION 3,5 5,56 Dated June 2, 1970 Patent No.

Inventor) Martin Goldman and William J. Staudenmayer It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 7, line 66 carboxyalkryl" should read carboxyaryl