Claims
- 1. A solvent composition for use in carbonless copy systems in the absence of a halogenated solvent, wherein said solvent consists essentially of a combination of a mono-alkyl naphthalene, wherein said alkyl group contains from 1 to 3 carbon atoms per molecule, and a di-alkyl naphthalene, wherein each of said alkyl groups in said di-alkyl naphthalene contains from 2 to 4 carbon atoms per molecule, said mono-alkyl naphthalene being present in an amount between about 25 and about 40% by weight of the alkylated naphthalenes present in said solvent.
- 2. The solvent composition of claim 1 wherein said composition contains between about 30 and about 35% by weight of said mono-alkyl naphthalene.
- 3. The solvent composition of claim 1 wherein said mono-alkyl naphthalene is monoisopropylnaphthalene and said di-alkyl naphthalene is diisopropyl naphthalene.
- 4. The solvent composition of claim 1 wherein said composition contains below about 10% by weight of material other than mono- and di-alkylnaphthalenes.
- 5. The solvent composition of claim 1 wherein said composition contains a color-forming compound.
- 6. The solvent composition of claim 5 wherein said color-forming compound is a dye precursor material.
- 7. The solvent composition of claim 6 wherein said dye precursor material is crystal violet lactone.
- 8. The solvent composition of claim 6 wherein dye precursor material is benzoyl leuco methylene blue.
- 9. The solvent composition of claim 1 wherein said composition contains a polyfunctional isocyanate cross-linking agent selected from the group consisting of the adducts of 4,4'-diphenyl methane diisocyanate, triphenyl methane triisocyanate and toluene diisocyanate with polyhydric alcohols.
- 10. The solvent composition of claim 9 wherein said polyfunctional isocyanate cross-linking agent is an adduct of toluene diisocyanate and glycerol, pentaerythritol, hexanetriol or trimethylol propane.
- 11. The solvent composition of claim 10 wherein said polyfunctional isocyanate cross-linking agent is an adduct of toluene diisocyanate and trimethylol propane.
- 12. A solvent composition for use in carbonless copy systems in the absence of a halogenated solvent wherein said solvent consists essentially of a combination of monoisopropylnaphthalene and a di-alkyl naphthalene, wherin each of said alkyl groups in said di-alkyl naphthalene contains from 2 to 4 carbon atoms per molecule, said monoisopropylnaphthalene being present in an amount between about 25 and about 40 percent by weight of the alkylated naphthalenes present in said solvent, said solvent composition additionally containing crystal violet lactone.
- 13. The solvent composition of claim 12 wherein said di-alkyl naphthalene is diisopropyl naphthalene.
- 14. The solvent composition of claim 12 wherein said solvent composition additionally comprises benzoyl leuco methylene blue.
- 15. The solvent composition of claim 12 wherein said composition contains a polyfunctional isocyanate cross-linking agent selected from the group consisting of the adducts of 4,4'-diphenyl methane diisocyanate, triphenyl methane triisocyanate and toluene diisocyanate with polyhydric alcohols.
- 16. The solvent composition of claim 15 wherein said polyfunctional isocyanate cross-linking agent is an adduct of toluene diisocyanate and glycerol, pentaerythritol, hexametriol or trimethylol propane.
- 17. The solvent composition of claim 16 wherein said polyfunctional isocyanate cross-linking agent is an adduct of toluene diisocyanate and trimethylol propane.
- 18. A solvent composition for use in carbonless copy systems in the absence of a halogenated solvent, wherein said solvent composition consists essentially of a combination of monoisopropylnaphthalene and diisopropyl naphthalene, said monoisopropylnaphthalene being present in an amount between about 25 and about 40 percent by weight of the alkylated naphthalenes present in said solvent, said solvent composition additionally containing crystal violet lactone and benzoyl leuco methylene blue.
Parent Case Info
This application is a continuation-in-part of U.S. Patent application Ser. No. 353,809 filed Apr. 23, 1973 and now abandoned, to Vincent et al.
This invention relates to alkyl naphthalene solvents. More particularly this invention relates to an alkyl naphthalene solvent involving a combination of a mono-alkyl naphthalene and a di-alkyl naphthalene, wherein the solvent is used for solubilizing colorless chromogenic dye-precursor materials and isocyanate cross-linking agents in the production of mircocapsules for use in pressure-sensitive record material.
Marking systems involving localized contact between a chromogenic compound and a color-developing substance in areas where a colored marking is desired have found widespread acceptance in a variety of commercial applications. For example, transfer copy systems have been devised wherein a colorless dye-intermediate material, such as crystal violet lactone, is dissolved in an oil and encapsulated in order to form minute droplets of dye-intermediate solution and isolate the dye-intermediate material from an electron-accepting material of the Lewis acid type, such as acid-treated clay, which is provided on a separate receiving sheet. Upon the application of localized pressure, the capsules thereunder are ruptured and the dye intermediate is released and transferred to a receiving sheet thereby resulting in a distinctive mark. Such pressure-sensitive mark-forming systems are described, for example, in U.S. Pat. Nos. 3,418,656 and 3,418,250 to A. E. Vassiliades.
One of the most commonly used dye-precursor materials is crystal violet lactone (CVL) which produces an instant blue image on an acidic co-reactant material, such as acidic clays, phenols, resorcinols and the like. Until recent years, polychlorinated biphenyls (PCB) had been widely used as the dye-precursor solvent for CVL, since PCB is a good solvent for dissolving the dyes and is easily retained in the microcapsules. However, due to various difficulties with the PCB, its use has been discontinued and various substitutes have been proposed.
U.S. Pat. No. 3,016,308 to Macaulay discloses the use of a 1:1:1 mixture of chlorinated biphenyl-amylbiphenyl-amylnaphthalene as the solvent for methyl violet butyl ether for use as an encapsulated marking liquid in a coated record sheet. Isopropyl biphenyl has been proposed in U.S. Pat. No. 3,627,581 to Phillips, Jr. as a solvent for CVL which increases the CVL image intensity over that achieved with PCB.
More recently, U.S. Pat. No. 3,806,463 to Konishi et al discloses the use of alkyl naphthalenes as a solvent in a dye composition component of microcapsules for use in carbonless copy paper, as a substitute for the toxic PCB solvent. Patentees disclose alkyl naphthalenes wherein each alkyl group contains from 1 to 4 carbon atoms with the proviso that the total number of carbon atoms in the alkyl groups must be from 4 to 6. Thus, patentees disclose alkyl naphthalenes such as butyl naphthalene, diethyl naphthalene, dipropyl naphthalene, propylmethyl napthalene, etc.
Various microencapsulation processes have been utilized in the formation of microcapsules that are employed in the manufacture of copy sheets. Thus, processes such as those described in U.S. Pat. Nos. 3,418,250 and 3,418,656 have been suggested, which processes involve the formation of microcapsules by a dilution of an admixture comprising a resin wherein the resin is separated in solid particle form from solution to form the microcapsule walls. Other microencapsulation systems involve the phenomenon known as "coacervation" wherein a liquid-liquid separation is effected in the formation of the capsule walls.
More recently, an encapsulation process has been proposed which involves the formation of an emulsion by admixing an aqueous solution of a water-soluble, polymeric film-forming emulsifying agent possessing hydroxyl groups with an oily material, which contains an oil-soluble, nonpolymeric cross-linking agent for the emulsifying agent, in addition to a color-forming dye intermediate material. The cross-linking agent is a polyfunctional isocyanate which interacts with the hydroxyl groups of the polymeric emulsifying agent to from a solid, cross-linked resinous capsule wall which surrounds each of the oily droplets. The isocyanate cross-linking agent is a material such as an adduct of toluene diisocyanate and trimethylol propane. Although alkyl naphthalenes, such as the amylnaphthalene disclosed in the Maculay patent and the various alkyl naphthalenes disclosed in the Konishi et al patent are suitable solvents for dye intermediate materials, such as crystal violet lactone, such materials are unsiutable for use as the solvent in microencapsulation processes involving isocyanate cross-linking agents of the type mentioned previously.
It has been discovered that a solvent composition for use in carbonless copy systems wherein the solvent consists essentially of a combination of a mono-alkyl naphthalene, wherein the alkyl groups contain from 1 to 3 carbon atoms per molecule, and a dialkyl naphthalene, wherein each of the alkyl groups in the dialkyl naphthalene contain from 3 to 4 carbon atoms per molecule, provides not only a solvent having improved dye solubility and dye intensity over the solvents previously proposed, but such solvent provides the solubility for isocyanate cross-linking agents, such as a toluene diisocyanate-trimethylol propane adduct, to permit the utilization of an alkyl naphthalene solvent system for the production of microcapsules involving such isocyanate cross-linking agents.
As will be hereinafter demonstrated, the monobutyl naphthalene and higher naphthalenes of Macaulay and Konish et al provide inadequate solubility on a commercial basis for isocyanate cross-linking agents, such as the toluene diisocyanate-trimethylol propane adduct, while the solvent system of the present invention, such as that including mono-isopropyl naththalene in combination with diisopropyl naphthalene provides a highly suitable solvent for such isocyanates.
The alkyl naphthalene solvent of the present invention when used alone, and in the absence of a halogenated solvent, such as PCB, has far superior properties as a CVL solvent in a record system as compared with PCB. For example, whereas the color intensity obtained in the oil phase consisting of a 1.7% CVL in a 2:1 mixture of isopropyl biphenyl and saturated hydrocarbon oil is 16% higher than that achieved with a 2:1 mixture of PCB (42% chlorine content) and saturated hydrocarbon oil. It has now been found that the alkyl naphthalenes of the present invention yeild 60% greater intensities than those of PCB at a 2.1 CVL concentration.
Another chromogenic dye precursor that is used in the art of pressure-sensitive copy systems is benzoyl leuco methylene blue (BLMB). The color formation of BLMB on acidic clay or silica gel is very slow. Under normal conditions it takes about 6 days to develop to a constant intensity. As will be hereinafter demonstrated, the color intensity obtained using 1.8% BLMB in the oil phase of the alkyl naphthalene solvent composition of the present invention is 85% greater than that produced by 1.8% BLMB in PCB or a 2:1 mixture of PCB and coconut oil. The previously suggested isopropyl biphenyls provide only 35% higher intensity over the PCB. This faster development of the BLMB image enhances the instant CVL image when BLMB and CVL are used in combination. It was still further surprising to discover that the final intensity of the BLMB image produced in the alkyl naphthalenes of the present invention was 44% greater than that produced in PCB, while isopropyl biphenyls displayed only a 20% higher intensity. Thus, the alkyl naphthalenes of the present invention greatly improve the color production efficiency of pressure-sensitive record material.
As previously indicated, the solvent of the present invention consists essentially of a mono-alkyl naphthalene wherein the alkyl groups contain from 1 to 3 carbon atoms per molecule, and a dialkyl naphthalene, wherein each of the alkyl groups in the dialkyl naphthalene contains from 2 to 4 carbon atoms per molecule. Thus, the mono-alkyl naphthalenes have the formula ##STR1## wherein R.sup.1 represents an alkyl group having from 1 to 3 carbon atoms.
Accordingly, the mono-alkyl naphthalenes of the present invention include methyl, ethyl and isopropyl naphthalenes. The mono-alkyl derivatives may be the alpha of beta isomer, or a mixture of both isomers. When R.sup.1 is a 3 carbon atom alkyl group, R.sup.1 may be either n-propyl or isopropyl, with isopropyl being the especially preferred mono-alkyl naphthalene of the present invention.
The dialkyl naphthalenes of the present invention may be a single isomers of di-alkylated naphthalenes or a mixture of di-alkylated isomers. Accordingly, suitable dialkyl naphthalenes have the formula ##STR2## wherein R.sup.2, R.sup.3, R.sup.4 and R.sup.5 each represent an alkyl group having from 2 to 4 carbon atoms per molecule.
Preferred dialkyl naphthalenes include diethyl naphthalenes, diisopropyl naphthalenes, di-sec-butyl naphthalenes, isopropyl methyl napthalenes, and the like.
An especially preferred dialkyl naphthalene is diisopropyl napthalene.
Suitable amounts of mono-alkyl naphthalenes in the solvent composition of the present invention include between about 25 and about 40% by weight of the solvent, preferably between about 30 and about 35% by weight. The remaining portion of the solvent is substantially dialkyl naphthalene, with no more than about 10% by weight of the solvent being tri-alkyl naphthalenes or the like. Accordingly, a preferred solvent consists of 30-35% mono-isopropyl naphthalene, 55-60% diisopropyl naphthalene and the remainder being triisopropyl naphthalene, in an amount, for example, of about 5% by weight.
As previously indicated, the alkyl naphthalene solvent of the present invention may be suitable used as a solvent for various isocyanate cross-linking agents, as well as dye precursor solvents. Thus, according to the present invention, a preferred method for the production of microcapsules comprises admixing:
The admixing of the solvent composition with the aqueous solution of the emulsifying agent is conducted under conditions to form an oil-in-water emulsion, wherein the solvent composition is dispersed in the form of emulsion droplets in an aqueous continuous phase. The cross-linking agent interacts with the hydroxyl groups of the polymeric emulsifying agent to form a solid cross-linked resinous capsule wall surrounding each of the solvent composition droplets.
A preferred isocyanate cross-linking agent is an adduct of toluene diisocyanate with glycerol (3:1 molar), pentaerythritol (4:1 molar), hexanetriol (3:1 molar) or trimethylol propane (3:1 molar). An especially preferred isocyanate cross-linking agent is the adduct of toluene diisocyanate and trimethylol propane.
Suitable hydroxyl group-containing polymers include polyvinyl alcohol, methylcellulose, starch and benzyl-substituted starches. Polyvinyl alcohol is the preferred emulsifying agent.
The alkyl naphthalenes of the present invention are preferably utilized as solvents for CVL and BLMB. Additionally, the present solvents are useful, for example, for other chromogenic compounds, such as Rhodamine B lactone; diaryl phthalides, e.g., Malachite green lactone; leucoauramines, e.g., leucoauramine and N-benzoyl leucoauramine; caumarins, e.g., 7-diethylamino-4-methylcaumarin; and fluorans, e.g., 6-chloro-7-methyl-3-diethylaminofluoran and 6,8-dimethyl-3-diethylaminofluoran.
Any suitable amount of the alkyl naphthalene solvent of the present invention may be used for dissolving the chromogenic dye-precursor material. For example, in the case of CVL and/or BLMB, between about 0.9 and about 5.0, preferably between 1.5 and about 4.0 parts by weight of the blue image yielding chromogenic materials, based upon 100 parts by weight of the naphthalene solvent.
The microcapsules may be coated on or incorporated in a web or substrate, such as paper, and utilized in any form of pressure-sensitive copy system wherein the microcapsules are ruptured under localized pressure to release the dye precursor-containing alkyl naphthalenes for contact with an acidic co-reactant. Thus, for example, the microcapsulebearing substrate may also be coated with the acidic co-reactant, such as an acidic clay. Such system is normally referred to as a "self-contained" or "autogenous" system, since the colorless chromogenic material and the acidic co-reactant are present on the same surface of the substrate. Alternatively, the microcapsules containing the alkyl naphthalenes of the present invention may be coated onto and/or incorporated into a substrate which is used in combination with a separate sheet of substrate which is coated with the acidic co-reactant. This type of copy system is normally referred to as a "transfer copy system", and upon rupture of the capsules by localized pressure the dye precursor contacts a separate acidtype coated sheet upon which a colored mark is thereby provided.
The halogen-free alkyl naphthalene oils of the present invention may be utilized in any copy system where they are isolated along with the dye precursor from the acid co-reactant prior to formation of the desired colored image. Any of the well-known acidic materials including bentonite, kaolin, acidic clays, talc, aluminum silicate, calcium citrate, metal oxides, metal chlorides, or the like may be utilized as acidic co-reactants for the chromogenic compounds.
The invention will be further illustrated by the following Examples. The percentages are by weight unless otherwise specified.
US Referenced Citations (3)
| Number |
Name |
Date |
Kind |
|
3726804 |
Matsukawa et al. |
Apr 1973 |
|
|
3806463 |
Konishi et al. |
Apr 1974 |
|
|
3855146 |
Saeki et al. |
Dec 1974 |
|
Foreign Referenced Citations (7)
| Number |
Date |
Country |
| 2,101,564 |
Mar 1972 |
FR |
| 2,104,444 |
Apr 1972 |
FR |
| 2,120,873 |
Aug 1972 |
FR |
| 2,083,121 |
Dec 1971 |
FR |
| 2,244,484 |
Mar 1973 |
DT |
| 1,329,077 |
Sep 1973 |
UK |
| 1,325,220 |
Aug 1973 |
UK |
Non-Patent Literature Citations (1)
| Entry |
| Derwent Japanese Patent Report, vol. T45, Dec. 2, 1972. |
Continuation in Parts (1)
|
Number |
Date |
Country |
| Parent |
353809 |
Apr 1973 |
|
Patent Grant
4071469
