GB1603239A - Coating compositions and their production - Google Patents

Description

(54) COATING COMPOSITIONS AND THEIR PRODUCTION (71) We, THE MEAD CORPORATION, a corporation organized and existing under the laws of the State of Ohio, United States of America, of Mead World Headquarters, Courthouse Plaza Northeast, Dayton, Ohio, 45463, United States of America, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement:- This invention relates to the production of microcapsular coating compositions.

In accordance with a first aspect of this invention, we provide a process for producing a microcapsular coating composition which comprises the preparation of microcapsules in situ in a radiation curable hydrophilic liquid comprising a radiation curable polar compound.

In a second and alternative aspect of this invention, there is provided a process for producing a microcapsular coating composition comprising the steps of: preparing an emulsion containing droplets of a hydrophobic emulsion component dispersed in a hydrophilic emulsion component, said hydrophobic emulsion component comprising a hydrophobic liquid, and a first wall-forming material soluble in said component and capable of reacting with a second wall-forming material to form a polymeric capsule wall insoluble in said hydrophilic and said hydrophobic emulsion components, and said hydrophilic emulsion component comprising an emulsifier dispersed in a radiation curable hydrophilic liquid comprising a radiation curable polar compound; said emulsion additionally containing said second wall-forming material; and subjecting said emulsion, with stirring, to temperature conditions for a period of time sufficient to substantially completely polymerize said first and second wall-forming materials to form a dispersion of microcapsules in said hydrophilic emulsion component.

We also provide, in accordance with a third alternative aspect of this invention, a radiation curable coating composition comprising microcapsules having a hydrophobic liquid core dispersed in a radiation curable hydrophilic liquid which comprises a polar radiation curable compound.

In one embodiment, the encapsulated hydrophobic liquid contains a chromogenic material soluble therein. A dispersion of such microcapsules can be coated on a substrate and cured by radiation to give a pressure-sensitive carbonless copy sheet having a transfer coating.

The production of microcapsules containing an encapsulated oily (hydrophobic) liquid wherein the microcapsule walls are produced by a polycondensation reaction of polyisocyanate and a second wall-forming material is described in U.S. Patent No.

3,796,669 to Kiritani et al. Both the polyisocyanate wall-forming material and the second wall-forming material are mixed with the oily liquid. The mixed oily liquid is dispersed into an aqueous continuous phase and the temperature is raised to initiate the reaction on the surface of the oil drops to encapsulate the oil drops with the reaction product of the polyisocyanate and second wall-forming material. A catalyst for the reaction may also be added to the oily liquid.

A number of patents propose the production of microcapsules using interfacial condensation polymerization oF two or more reactants to form the microcapsule walls. Typical of these are: U.S. Patent 3,429,827 (1969) to Ruus U.S. Patent 3,432,427 (1969) to Kan et al U.S. Patent 3,464,926(1969) to Vandegaer et al U.S. Patent 3,492,380(1970) to Santo et al U.S. Patent 3,575,882(1971) to Vandegaer et al U.S. Patent 3,577,515 (1971) to Vandegaer U.S. Patent 3,607,776(1971) to Santo et al U.S. Patent 3,726,804 (1973) to Matsukawa et al U.S. Patent 3,875,074(1975) to Vassiliades et al It is important to note that none of the above listed patents or U.S.Patent 3,796,669 to Kiritani disclose the in situ preparation of the microcapsules in a radiation curable hydrophilic liquid containing a radiation curable polar compound.

Carbonless copy paper, briefly stated is a standard type of paper wherein during manufacture the backside of the paper substrate is coated with what is referred to as a CB or transfer coating, the CB coating containing one or more chromogenic materials, generally in capsular form. At the same time the front side of the paper substrate is coated during manufacture with what is referred to as a CF coating, containing one or more chromogenic materials capable of producing a colour with encapsulated CB chromogenic material. Both the chromogenic materials remain in the coatings on the respective back and front surfaces of the paper in substantially colourless form. This is true until the CB and CF coatings are brought into overlying relationship and sufficient pressure, as by a typewriter, is applied to rupture the CB coating to release the encapsulated chromogenic material.At this time the chromogenic material contacts the CF coating and reacts with the chromogenic material therein to form a coloured image.

Carbonless copy paper has proved to be exceptionally valuable image transfer media for a variety of reasons, only one of which is the fact that until a CB coating is placed next to a CF coating both the CB and CF coatings are in an inactive state as the coreactive elements are not in contact with one another until pressure is applied.

Patents relating to carbonless copy paper products include: U.S. Patent 2,712,507 (1955) to Green U.S. Patent 2,730,456 (1956) to Green et al U.S. Patent 3,455,721 (1969) to Phillips et al U.S. Patent 3,466,184(1969) to Bowler et al U.S. Patent 3,672,935 (1972) to Miller et al A disadvantage of coated paper products such as carbonless transfer papers stems from the necessity of applying a liquid coating composition containing the colour forming ingredients during the manufacture process. In the application of such coatings, volatile organic solvents are sometimes used which then in turn requires evaporation of excess solvent to dry the coating thus producing volatile solvent vapours. An alternate method of coating involves the application of the colour forming ingredients in an aqueous slurry, again requiring removal of water by drying.Both methods suffer from serious disadvantages. In particular, the organic solvent coating method necessarily involved the production of generally volatile solvent vapours, creating both a health and fire hazard in the surrounding environment. When using an aqueous solvent system a substantial quantity of water must be evaporated which involves the expenditure of significant amounts of energy and further necessitates a separate drying step requires the use of complex and expensive apparatus to continuously dry a substrate which has been coated with such an aqueous coating composition which may typically comprise 60-85% water. The application of substantial amounts of heat in this way not only is expensive, !snaking the total paper manufacturing operation less cost effective, but also is potentially damaging.

Radiation curable coating compositions and methods of producing these compositions have been previously proposed. Patent proposals concerned with the production and application of liquid resin compositions containing no volatile solvent which are subsequently cured by radiation to a solid film include: U.S. Patent 3,551,235 (1970) to Bassemir et al U.S. Patent 3,551,246 (1970) to Bassemir et al U.S. Patent 3,551,311 (1970) to Nass et al U.S. Patent 3,558,387 (1971) to Bassemir et al U.S. Patent 3,661,614 (1972) to Bassemir et al U.S. Patent 3,720,534 (1973) to Macaulay et al U.S. Patent 3,754,966 (1973) to Newman et al U.S. Patent 3,772,062 (1973) to Shur et al U.S. Patent 3,772,171 (1973) to Savageau et al U.S. Patent 3,801,329(1974) to Sandner et al U.S. Patent 3,819,496(1974) to Roskott et 1 U.S.Patent 3,847,768 (1974) to Kagiya et al U.S. Patent 3,847,769 (1974) to Garratt el al These compositions generally also contain a pigment or dye. Such resin compositions are useful for protective coatings and fast drying inks. U.S. Patent 3,754,966 describes the production of an ink releasing dry transfer element which can be used as a carbon paper or typewriter ribbon.

It is significant to note that for carbonless copying the particular radiation cured coating must be compatible with the reaction of CB and CF chromogenic materials to form a colour. Such colour forming reactions are generally of a sensitive or delicate nature and are not generally compatible with the compositions found in the prior art.

The liquid coating compositions specifically described herein are dispersions of microcapsules having a hydrophobic core liquid in a radiation curable hydrophilic liquid. The coating compositions are prepared by a process in which the microcapsules are formed in situ in the radiation curable hydrophilic liquid which may contain some water, though significantly less to be evaporated than in prior art aqueous drying compositions. The radiation curable hydrophilic liquid cures by radiation (the excess water evaporating) to give a tack-free film containing microcapsules thus omitting the additional complex drying step necessary for the prior art solvent or aqueous based microcapsular coating compositions to remove the very large quantities of solvent or water involved.

The cured continuous phase acts as a binder to adhere the microcapsules to a substrate.

In a preferred arrangement, the microcapsules can contain a chromogenic material in the hydrophobic core liquid.

Coating compositions containing such microcapsules may be used in the preparation of copy papers having a CB transfer coating.

The coating compositions produced by our process essentially dispersions of microcapsules containing a hydrophobic liquid core material in a radiation curable hydrophilic liquid as a continuous phase.

The dispersions of microcapsules are prepared in situ in the radiation curable hydrophilic liquid by a condensation polymerization reaction of a first wallforming material and a second wall-forming material. The coating compositions can be applied as a coating to a substrate such as paper or plastic film and can be cured by radiation to a tack-free resinous film. If the microcapsules contain a chromogenic material, the coated paper is useful as a pressure-sensitive carbonless transfer CB paper. For purposes of this invention, the term "chromogenic" shall be understdod to refer to colour materials such as colour precursors, colour developers, and colour formers.

The coating composition can contain additional materials which function as photoinitiators. Addition of these materials depends upon the particular method of curing the microcapsular coating. Filler materials can also be added to modify the properties of the cured film. Although our products and processes are useful in the manufacture of a variety of microencapsulated products, such as, for example, microencapsulated flavours, foods, pharmaceuticals, insecticides and the like, the preferred use of our processes and products is in the production of a pressuresensitive carbonless transfer sheets such as is described in our co-pending British Patent Application No. 19420/77 (Serial No.

1581756).

Hydrophobic liquids which we have found useful in the process include the nonpolar oils and solvents. In the preferred use of our process, i.e. to prepare pressuresensitive carbonless transfer sheets, the preferred hydrophobic liquids are monoisopropybiphenyl (MIPB), chlorinated paraffins, alkylnaphthalenes, kerosene, petroleum naphtha and mixtures thereof.

Chromogenic materials we have found useful in the practice of the process are the electron-donor type colour precursors.

These include the lactone phthalides, such as crystal violet lactone, and 3,3-bis-(1'ethyl-2-methylindol-3 'yl) phthalide, the lactone fluorans, such as 2 dibenzylamino - 6 - diethylamino - fluoran and 6 - diethylamino - 1,3 dimethylfluoran, the lactone xanthenes, the leucoauramines, the 2 - (omega substituted vinylene) - 3,3 - disubstituted - 3 - H indoles and 1,3,3 - trialkylindolinospirans.

Mixtures of these colour precursors can be used if desired. The colour precursors are soluble in the hydrophobic liquid and are preferably present in such solutions, sometimes referred to as carrier oil solutions, in an amount of from 0.5% to 20.2% based on the weight of the oil solution, and the most preferred range is from 2% to 7%.

The radiation curable hydrophilic liquids we have found useful in the practice of our process comprise the free radical polymerizable ethylenically unsaturated organic compounds. These compounds contain at least one terminal ethylenically unsaturated group or molecule. These compounds are radiation curable polar compounds and function in part as the continuous hydrophilic phase during the in situ preparation of the microcapsules and as a dispersing medium for the microcapsules and other ingredients of the coating composition prior to the coating operation.

They are curable to a solid resin when exposed to ionizing or ultraviolet radiation.

The cured resin acts as a binder for the microcapsules to a substrate such as paper.

Examples of useful radiation curable polar compounds are N- vinyl - 2 pyrrolidone, acrylamide, hydroxyethyl acrylate, hydroxypropyl acrylate, diacetone acrylamide, 2 - acrylamido - 2 - methyl- propanesulfonic acid, acrylic acid, polyethylene glycol monoacrylates, polyethylene glycol polyacrylates, polyvinyl alcohol acrylate, starch acrylate, cellulose acrylate, quaternary ammonium salt derivatives of dimethylaminoethyl acrylate and methacrylate and mixtures thereof. The above radiation curable polar compounds are liquids. However, solid radiation curable polar compounds, such a Nmethylol acrylamide, can be dissolved in water and used as the radiation curable hydrophilic liquid. The preferred polar compounds are N-methylol acrylamide and hydroxyethyl acrylate.

The first wall-forming material is soluble in and forms a part of a hydrophobic emulsion component. It may suitably be either a polyisocyanate or a polyacid halide compound. The polyisocyanates we have found useful in our process are the aliphatic and aromatic polyisocyanates which include, for example, (a) diisocyanates, such as m - phenylmethane - 4,4' diisocyanate; (b) triisocyanates, such as toluene - 2,4,6 - triisocyanate; (c) tetraisocyanates, such as 2,2,5,5 tetraisocyanate; (d) isocyanate prepolymers such as Mondur CB-75 (75% of a high molecular weight adduct of toluene isocyanate and 25% of ethyl acetate produced and sold by Mobay Chemical Company-'Mondur' is a Registered Trade Mark) Desmodur N-100 (a biuret containing aliphatic isocyanate also produced and sold by Mobay Chemical Com any - 'Desmodur' is a Registered Trade Mark) and NIAX SF-50 (a trifunctional aromatic polyurethane prepolymer having a free isocyanate content of 32.5% made and sold by Union Carbide Corporation, New York, N.Y.).

Mixtures of these compounds may be used.

The useful polyacid halides include terephthalyl dichloride, adipyl dichloride, 1,3,5-benzenetricarboxylic acid trichloride, oxalyl dibromide, 1,4 - benzenedisulphonyl dichloride and 4,4' - biphenyldisulphonyl dichloride. Mixtures of these compounds may also be used. The preferred first wallforming materials are NIAX SF-50, Desmodur N-100 and terephthalyl dichloride.

The second wall-forming material suitably can be selected from the group consisting of polyols, polythiols, polyamines, acid anhydrides, and polycarboxylic acids and mixtures thereof The polyols include for example, glycerin, resorcinol, 1,3-naphthalenediol, bisphenol A,1,3 - propylene glycol, and 1,5 pentanediol. Examples of polythiols are thioglycol and thioglycol condensates.

Polyamines include, for example, pphenylenediamine, diethylene triamine, N,N,N',N'. - tetrakis - (2 - hydroxypropyl) ethylene diamine (Quadrol Wyandotte Chemical Corp., Wyandotte, Michigan) and phthalamide. Examples of acid an hydrides include maleic anhydride and succinic anhydride. Examples of polycarboxylic acids are malonic acid, succinic acid and terephthalic acid. The preferred second wall-forming materials are Quadrol (Registered Trade Mark) and diethylene triamine.

A photoinitiator is suitably added to the coating composition if the composition is to be cured by ultraviolet radiation. A wide variety of photoinitiators are available which serve well in the system described.

The preferred photoinitiators are the benzoin alkyl ethers, such as Vicure 30, benzoin methyl ether, a,, azo bisisobutyrontltrile, a,-d'iethoxy- acetophene and zinc carbonate. Other photoinitiators which can be used are benzophenone, 4,4' - bis - (dimethyl amino)benzophenoneferrocene, xanthone,.

thioxanthane, decabromodipheny'l oxide, 1 pentabromonochloro - cyclohexan e, pentachlorobenzene, benzoin ethyl ether, 2ethyl anthraquinone, 1 - (chloroethyl) - naphthalene, desyl chloride, chlorendic anhydride, naphthalene sulphonyl chloride and 2-bromoethyl ethyl ether. The amount of photoinitiator added suitably can be from 0.2% to 10% by weight of the coating composition, with a preferred range from 1% to 4% by weight.

Photoinitiation synergists suitably can also be added to the ultraviolet curable coating compositions. Photoinitiation synergists serve to enhance the initiation efficiency of the photoinitiators. The preferred synergists are the chain transfer agents, such as the tertiary alcoholamines and substituted morpholines, triethanolamine, N - methyldiethanolamine, N,N - dimethylethanolamine and N - methylmorpholine.

The amount of photoinitiation synergist added suitably can be from 0.2% to 10% by weight of the coating composition with a preferred range of from 3% to 4% by weight.

In the preparation of the dispersion of microcapsules, a hydrophobic emulsion component is suitably prepared by dissolving the first wall-forming material in an hydrophobic liquid, as for example, an oil. If the microcapsules are to be used in preparing carbonless copy papers, a chromogenic material is dissolved in a carrier oil.

The hydrophilic emulsion component is suitably prepared by dissolving dispersing an emulsifier in the radiation curable hydrophilic liquid which itself suitably comprises at least one radiation curable polar compound dissolved or dispersed in water. Any of the known emulsifiers can be used including polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose and Triton N-101 (Rohm and Haas, Phildelphia, Pa. - 'Triton' is a Registered Trade Mark). Water increases the polarity of the hydrophilic emulsion component to a point where the two phases, hydrophobic and hydrophilic, are essentially insoluble in each other, thus permitting formation of an emulsion. At this point, the second wall-forming material soluble in the hydrophilic emulsion component can also be dissolved in the hydrophilic emulsion component.

Alternatively, the second wall-forming material can be added to the emulsion formed during the emulsification step. To facilitate mixing the second wall-forming material may be dissolved in additional radiation curable hydrophilic liquid prior to addition to the emulsion.

Alternatively, the second wall-forming material may be added to the hydrophobic emulsion component. In this case, the second wall-forming material is soluble in the hydrophobic emulsion component.

Some second wall-forming materials, for example, diethylene triamine, are soluble in both the hydrophobic and hydrophilic emulsion components. These materials can be added to the hydrophobic and/or hydrophilic emulsion components or to the emulsion formed by the emulsification step.

Preparation of each of these components is easily accomplished by stirring together at room temperature the materials of each component. The Brookfield viscosity of the hydrophilic emulsion component suitably can be from 0.5 cps. to 1,000 cps. The preferred viscosity is from 1 cps. to 500 cps.

and the most preferred viscosity is from 1 cps. to 50 cps.

The hydrophobic and hydrophilic emulsion components prepared as above are suitably mixed together with high agitation to form an emulsion containing droplets of the hydrophobic emulsion component dispersed in the continuous hydrophilic emulsion component. The term "soluble" as used herein is intended to describe wall-forming materials which are only partially soluble in and give hazy solutions in the radiation curable hydrophilic liquid as well as those which are completely soluble in the radiation curable hydrophilic liquid.

After emulsification, the emulsion is stirred for a period of 3 hours to 16 hours at a temperature of 0 C to 700C, preferably room temperature to 400 C, to allow the first and second wall-forming materials to react and form a dispersion of microcapsules having capsule walls which are substantially impermeable to both the hydrophilic and hydrophobic emulsion components used to form the microcapsules. The microcapsules should be from 0.1 micron to 50 microns in diameter. A preferred range is from 5 to 15 microns.

The microcapsular coating composition so produced can be applied to a substrate, such as paper or a plastics film by any of the common paper coating processes such as roll, air knife, or blade coating, or by any of the common printing processes, such as offset, gravure, or flexographic printing.

The rheological properties, particularly, the viscosity of the coating compositions, can be adjusted for each type of application by proper selection of the type, molecular weight and relative amounts of the liquid radiation curable compounds and the amount of water present.

These coating compositions can be set to a solid film by any free radical initiated chain propagated addition polymerization reaction of the terminal ethylenic groups of the radiation curable compounds. These free radicals can be produced by several different chemical processes including ultraviolet induced degradation of a molecular species and any form of ionizing radiation such as alpha-particles, beta-rays (high-energy electrons), gamma-rays, x-rays and neutrons.

The preferred curing process is by exposure of the coating composition to ultraviolet radiation having a wave length of 2000 A to 4000 A. For curing to occur the composition must contain suitable ultraviolet absorbing photoinitiators which will produce polymerization initiating free radicals upon exposure to the radiation source. A typical radiation source suitable for this type of curing process is a Hanovia (Registered Trade Mark) 200 watt medium pressure mercury lamp which produces both ultraviolet and infrared radiation.

Curing efficiencies of the coating composition are dependent on such parameters as the nature of the radiation curable substance, atmosphere in contact with the coating, quantum efficiency of the radiation absorbed, thickness of coating and inhibitory effects of the various materials in the composition. Any water which may be present on the coating composition is evaporated by the infrared radiation from the ultraviolet lamps. It is to be understood that the quantity of heat required is very substantially less than in the prior art arrangements not using radiation curable compositions.

When ionizing radiation induced curing of the coating compositions is used, a specific radiation absorbing material (photoinitiator) is not necessary. Exposure of the coating composition to a source of high energy electrons results in spontaneous curing of the composition to a tough, tackfree coating. Any of a number of commercially available high energy electron beam or linear cathode type high energy sources are suitable for curing these compositions. Parameters such as the atmospheric environment and inhibitory effects of the various materials in the composition play an important role in the determination of the curing efficiency of these compositions.

The following examples further illustrate but do not limit the invention: Example 1 An aqueous phase (hydrophilic emulsion component) was prepared as follows:- In a 250 ml. beaker with magnetic stirring bar on a magnetic stirring ot plate, 40 grams of distilled water, 60 grams of a radiation curable compound, 2hydroxyethyl acrylate, 0.5 gram of carboxymethyl cellulose (grade 7L2, Hercules, Inc., Wilmington, Delaware) and 0.5 gram of hydroxypropyl cellulose (Klucel L, Hercules, Inc. - 'KIucel' is a Registered Mark) were mixed together and then heated to 600C until the solid ingredients were dissolved. After cooling the mixture to room temperature, 0.1 gram of Turkey Red Oil (sulphonated castor oil) and 0.5 gram of triethylene tetramine were stirred in.

An oil phase (hydrophobic emulsion component) was prepared as follows:- In a 100 ml. beaker with magnetic stirring bar on a magnetic stirring hot plate, 24 grams of monoisopropylbiphenyl, 0.83 gram of 3 - (N,N - diethylammo - 7 - (N,N - dibenzylamino)fluoran, and 0.08 gram of 2,3 - (1' - phenvl - 3' - methyl) - 7 (N,N - diethyiamino) - 4 - spirophthalidochromene were heated with stirring at 900C for one hour to dissolve the above colour precursors. To this solution at room temperature, 3 grams of an aliphatic polyisocyanate (Desmodur N-100), 3 grams of an aromatic polyisocyanate (NIAX SF50) and 0.9 gram of a polyol (Quadrol) were added with stirring until homogeneous.

The oil phase in the 100 ml. beaker was added slowly over a one minute period to the first solution in a Waring Blender on low speed, and stirred for five minutes more. A mint green coloured mixture resulted in which capsules I to 4 microns in diameter were observed through a 450 x microscope.

The mixture was placed in a 60"C hot water bath for 30 minutes. An off-white dispersion resulted, with no apparent change in capsule size. 1.5 grams of azobisisobutyronitrile photoinitiator was added, a drawdown was made on 13.5 lb.

per 1300 square feet paper rawstock with a No. 16 Mayer rod and exposed to a 200 watt mercury ultraviolet lamp also producing infrared radiation at a distance of 4 inches for one minute. Excess water evaporated and the resultant cured coating was smooth and tack-free. When pressure imaged against a kaolin/phenolic resin coated CF sheet, a clear, green image was formed on the CF sheet.

Example 2 The example above was repeated except that 0.5 gram of polyvinyl alcohol (grade 5(5, E. I. duPont de Nemours & Co., Inc., Wilmington, Del.) was used in place of hydroxypropyl cellulose. Capsules before heat curing were I to 4 microns as determined by microscopic examination of the dispersion. The image formed was clear but not as intense as in Example 1.

Example 3 An aqueous phase was produced by stirring together 90 grams of a radiation curable compound, N-methylol acrylamide (60% solution in water, from Proctor Chemical Company, Salisbury, N.C. 28144).

0.5 gram of a dispersing agent (Triton N-101 - Rohm and Haas Company, Philadelphia, Pennsylvania), 0.8 gram of sodium carbonate (anhydrous) and 9.3 grams of diethylene triamine.

An oil solution was prepared by dissolving.

the following colour precursors into 19 grams of MIPB (monoisopropylbiphenyl) with heating to 850C: 0.40 gram of crystal violet lactone, 0.10 gram of 3,3 - bis(l' ethyl - 2' - methyl - indol - 3 - yl) phthalide, 0.17 gram of 2,3 - (1' - phenyl 3' - methyl) - 7 - (N,N - diethylamino) 4 - spirophthalidochromeme, and 0.05 gram of 3 - N,N - diethylamino - 7 - (N,Ndibenzylamino) fluoran. When the solution was cooled and filtered, 3 grams of terephthaloyl chloride were dissolved. The oil solution was added to the aqueous phase in a Waring Blender operating at high speed over a 30 second period and was stirred for 5 minutes more. Microscopic examination of the fluid, gray mixture showed capsules of 2 to 10 micron size. Few agglomerates were present, 0.1 gram of benzoin methyl ether photoinitiator was stirred in. The mixture was coated on 13 lb./1300 square feet form bond using a No. 16 Mayer rod and exposed to an ultraviolet lamp also producing infrared radiation as in Example 1. When pressure imaged against kaolin/phenolic coated CF paper with a ballpoint pen, a purple image was formed.

Example 4 An aqueous phase was produced by stirring together 90 grams of a radiation curable compound, N-methylol acrylamide (60% solution in water, from Proctor Chemical Company, Salisbury, N.C. 28144), 1.0 gram of a dispersing agent (Triton N-101 - Rohm and Haas Company, Philadelphia, Pennsylvania), and 1.59 gram of sodium carbonate (anhydrous).

An oil solution containing colour precursors was prepared as in Example 3 and 3 grams of terephthaloyl chloride were dissolved therein. The oil solution was added to the aqueous phase in a Waring Blender operating at high speed over a 30 second period and was stirred for 3 minutes more. To the Waring Blender mixture, 6.19 grams of diethylene triamine was added over a 15 second period and the speed was reduced to low speed for 5 minutes more.

Microscopic examination of the fluid, light pink mixture showed capsules of approximately 2 to 10 microns size. Few agglomerates were present. 0.1 gram of benzoin methyl ether photoinitiator was stirred in. The mixture was coated on 13 lb./1300 square feet form bond using a No.

16 Mayer rod and exposed to an ultraviolet lamp also producing infrared radiation as in Example 1. When pressure imaged against kaolin/phenolic coated CF paper with a ballpoint pen, a purple image was formed.

WHAT WE CLAIM IS: 1. A process for producing a microcapsular coating composition which comprises the preparation of microcapsules in situ in a radiation curable hydrophilic liquid comprising a radiation curable polar compound.

2. A process for producing a microcapsular coating composition comprising the steps of: preparing an emulsion containing droplets of a hydrophobic emulsion component dispersed in a hydrophilic emulsion component, said hydrophobic emulsion component comprising a hydrophobic liquid, and a first wall-forming material soluble in said component and capable of reacting with a second wall-forming material to form a polymeric capsule wall insoluble in said hydrophilic and said hydrophobic emulsion components, and said hydrophilic emulsion component comprising an emulsifier dispersed in a radiation curable hydrophilic liquid comprising a radiation curable polar compound; said emulsion additionally containing said second wall-forming material; and subjecting said emulsion, with stirring, to temperature conditions for a period of time sufficient to substantially completely polymerize said first and second wall-forming materials to form a dispersion of microcapsules in said hydrophilic emulsion component.

3. A process according to Claim 1 or Claim 2, wherein said radiation curable hydrophilic liquid comprises a polar compound having at least one terminal ethylenic group per molecule.

4. A process according to Claim 3, wherein said polar compound is selected from N- vinyl - 2- pyrrolidone, acrylamide, N - methylolacrylamide, hydroxyethyl acrylate, hydroxypropyl acrylate, diacetone acrylamide, 2 acrylamido - 2 - methylpropanesulphonic acid, acrylic, acid, polyethylene glycol monoacrylates, polyethyleneglycol polyacrylate, polyvinyl alcohol acrylate, starch acrylate, cellulose acrylate, quaternary ammonium salt derivatives of dimethylaminoethyl acrylate and methacrylate, and mixtures thereof.

5. A process according to Claim 2 or any claim appendent thereto, wherein said first wall-forming material is an oil soluble compound selected from polyisocyanates and polyacid halides.

6. A process according to Claim 2 or any claim appendent thereto, wherein said second wall-forming material is selected from polyols, polythiols, polyamines, polycarboxylic acids, and mixtures thereof.

7. A process according to Claim 2 or any claim appendent thereto, wherein the step of subjecting said emulsion, with stirring, to temperature conditions is performed at a temperature in the range of 0 C to 70"C for a period of time from 1 hour to 16 hours.

8. A process according to Claim 2 or any claim appendent thereto, wherein said hydrophobic emulsion component includes a chromogenic material.

9. A process according to Claim 2 or any of Claims 3 to 7 when appendent thereto, wherein said hydrophobic emulsion component includes a chromogenic material, said chromogenic material being a colour precursor of the electron-donor type.

10. A process for producing a microcapsular coating composition substantially as hereinbefore described with reference to the Examples.

11. A microcapsular coating composition whenever produced according to any preceding claim.

12. A process for producing a pressuresensitive transfer paper comprising the steps of: producing, according to any of Claims 8 to 10, a coating composition; applying the

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Claims (19)

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   to an ultraviolet lamp also producing infrared radiation as in Example 1. When pressure imaged against kaolin/phenolic coated CF paper with a ballpoint pen, a purple image was formed.

   Example 4 An aqueous phase was produced by stirring together 90 grams of a radiation curable compound, N-methylol acrylamide (60% solution in water, from Proctor Chemical Company, Salisbury, N.C. 28144), 1.0 gram of a dispersing agent (Triton N-101 - Rohm and Haas Company, Philadelphia, Pennsylvania), and 1.59 gram of sodium carbonate (anhydrous).

   An oil solution containing colour precursors was prepared as in Example 3 and 3 grams of terephthaloyl chloride were dissolved therein. The oil solution was added to the aqueous phase in a Waring Blender operating at high speed over a 30 second period and was stirred for 3 minutes more. To the Waring Blender mixture, 6.19 grams of diethylene triamine was added over a 15 second period and the speed was reduced to low speed for 5 minutes more.

   Microscopic examination of the fluid, light pink mixture showed capsules of approximately 2 to 10 microns size. Few agglomerates were present. 0.1 gram of benzoin methyl ether photoinitiator was stirred in. The mixture was coated on 13 lb./1300 square feet form bond using a No.

   16 Mayer rod and exposed to an ultraviolet lamp also producing infrared radiation as in Example 1. When pressure imaged against kaolin/phenolic coated CF paper with a ballpoint pen, a purple image was formed.

   WHAT WE CLAIM IS: 1. A process for producing a microcapsular coating composition which comprises the preparation of microcapsules in situ in a radiation curable hydrophilic liquid comprising a radiation curable polar compound.
2. 2. A process for producing a microcapsular coating composition comprising the steps of: preparing an emulsion containing droplets of a hydrophobic emulsion component dispersed in a hydrophilic emulsion component, said hydrophobic emulsion component comprising a hydrophobic liquid, and a first wall-forming material soluble in said component and capable of reacting with a second wall-forming material to form a polymeric capsule wall insoluble in said hydrophilic and said hydrophobic emulsion components, and said hydrophilic emulsion component comprising an emulsifier dispersed in a radiation curable hydrophilic liquid comprising a radiation curable polar compound; said emulsion additionally containing said second wall-forming material; and subjecting said emulsion, with stirring, to temperature conditions for a period of time sufficient to substantially completely polymerize said first and second wall-forming materials to form a dispersion of microcapsules in said hydrophilic emulsion component.
3. 3. A process according to Claim 1 or Claim 2, wherein said radiation curable hydrophilic liquid comprises a polar compound having at least one terminal ethylenic group per molecule.
4. 4. A process according to Claim 3, wherein said polar compound is selected from N- vinyl - 2- pyrrolidone, acrylamide, N - methylolacrylamide, hydroxyethyl acrylate, hydroxypropyl acrylate, diacetone acrylamide, 2 acrylamido - 2 - methylpropanesulphonic acid, acrylic, acid, polyethylene glycol monoacrylates, polyethyleneglycol polyacrylate, polyvinyl alcohol acrylate, starch acrylate, cellulose acrylate, quaternary ammonium salt derivatives of dimethylaminoethyl acrylate and methacrylate, and mixtures thereof.
5. 5. A process according to Claim 2 or any claim appendent thereto, wherein said first wall-forming material is an oil soluble compound selected from polyisocyanates and polyacid halides.
6. 6. A process according to Claim 2 or any claim appendent thereto, wherein said second wall-forming material is selected from polyols, polythiols, polyamines, polycarboxylic acids, and mixtures thereof.
7. 7. A process according to Claim 2 or any claim appendent thereto, wherein the step of subjecting said emulsion, with stirring, to temperature conditions is performed at a temperature in the range of 0 C to 70"C for a period of time from 1 hour to 16 hours.
8. 8. A process according to Claim 2 or any claim appendent thereto, wherein said hydrophobic emulsion component includes a chromogenic material.
9. 9. A process according to Claim 2 or any of Claims 3 to 7 when appendent thereto, wherein said hydrophobic emulsion component includes a chromogenic material, said chromogenic material being a colour precursor of the electron-donor type.
10. 10. A process for producing a microcapsular coating composition substantially as hereinbefore described with reference to the Examples.
11. 11. A microcapsular coating composition whenever produced according to any preceding claim.
12. 12. A process for producing a pressuresensitive transfer paper comprising the steps of: producing, according to any of Claims 8 to 10, a coating composition; applying the

    resultant dispersion of microcapsules to a paper substrate; and then setting said dispersion by subjecting it to radiation for a period of time sufficient to cure said radiation curable hydrophilic liquid to a tackfree resinous film on said paper substrate.
13. 13. A process according to Claim 12, wherein said dispersion of said microcapsules additionally contains a photoinitiator and said radiation is ultraviolet light.
14. 14. Substantially as herein described with reference to the Examples, a process for producing a pressure-sensitive transfer paper.
15. 15. A pressure-sensitive carbonless transfer paper prepared by a process according to Claims 12, 13 or 14.
16. 16. A pressure-sensitive carbonless transfer paper substantially as hereinbefore described with reference to the Examples.
17. 17. A radiation curable coating composition comprising microcapsules having a hydrophobic liquid core dispersed in a radiation curable hydrophilic liquid which comprises a polar radiation curable compound.
18. 18. A coating composition according to Claim 17, wherein the microcapsules have capsule walls comprising a reaction product of a first wall-forming material and a second wall-forming material.
19. 19. A coating composition according to Claim 17 or 18, wherein said hydrophobic liquid core contains a chromogenic material dissolved therein.