Minute polymeric capsules

(54) Title: Procedure for polymer capsules

INC., APPLETON, WIS. US W Brown and PS Phillips jr., Production of extremely smfi

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The invention relates to a process for the mass production of extremely small polymer capsules in a liquid manufacturing medium by in situ polymerization. In particular, the process according to the invention comprises liquid-liquid phase separation of a relatively concentrated solution of polymeric material to be used in the formation of the walls of the extremely small capsules.

Many combinations of materials have been used over the years in the exploration of compositions which provide certain physical properties to the capsule walls or which allow the implementation of the encapsulation process under certain desired or necessary conditions. Examples of desirable capsule properties are small size, the impermeability of the capsule walls with respect to diffusion and the strength of the capsule walls to withstand normal handling stresses.

As examples of desirable process conditions, relatively high pH, ​​relatively short times, relatively high yields and high concentration are important.

The present invention offers many advantages over prior art processes, including the substantially complete utilization of the starting materials.

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- 2 I to form the condensation polymer which constitutes the wall material and a decidedly less coloration of the capsule batches obtained when they contain a basic chromogenic material.

According to the invention there is thus provided a process for the mass production of extremely small polymer capsules by in situ polymerization of water-soluble starting materials in an aqueous medium in which particles or droplets of a substantially water-insoluble capsule core material have been dispersed, the polymerization being carried out in the presence of a negatively charged polymer. polyelectrolyte with a linear aliphatic hydrocarbon chain having on average two carboxyl or anhydride groups for every fourth or sixth carbon atom, characterized in that said starting material is selected from a) melamine and formaldehyde, b) monomer methylol melamine or a polymer thereof low molecular weight or c a polymer of low molecular weight thereof and d) mixtures of any of these starting materials.

According to the process of the present invention, various starting materials can be used to form the condensation polymer which builds up the resulting capsule walls. Thus, in one embodiment of the invention, the wall-forming polymer is formed by polycondensation of melamine with formaldehyde in the presence of said polymeric polyelectrolyte. In other embodiments of the invention, methylol melamines, such as trimethylol melamine or methylated methylol melamines, may be used in an in situ polymerization reaction in the presence of said polymeric polyelectrolyte to obtain the desired condensation polymer.

It may be worth noting that the reaction of melamine with formaldehyde to form capsule walls in the present invention is carried out in the absence of urea. This polymerization between melamine and formaldehyde, carried out in the presence of said polymeric polyelectrolyte, allows encapsulation in a wider range of molar ratios of the reactants and in pH ranges unattainable in the processes using urea and formaldehyde as starting materials.

The methylol melamines used in the present invention are commercially available. Examples are the melamine resins marketed by Monsanto, 7714554-8 - V under the brand name "Resimene". The chemical structure for example for trimethylolmelamine is as follows:

HOCI-L-HN-C C-NH-CH_O0H ² II ²N. N

V

NH-CH₂0H

The methylated methylol melamines are commercially marketed in the same manner under different names. Methylated methylol melamines that can be used in the present invention include those marketed under the following brands:

Valmel 40 (United Merchants)

Parez 613 and 707 (American Cyanamid)

Cymel 300-301 (American Cyanamid)

Cymel 385 (American Cyanamid)

Resloom M-75 or RM-441 (Monsanto)

Resloom RT-183 or RT-202 (Monsanto)

Resloom RM-442 (Monsanto)

Resimene (Monsanto)

Cascomel PR-601 or PR-609 (Borden Chemical)

Genetically, the chemical structure of said preferred methylated methylol melamines is as follows:

RI NO. I

RN ^ NR

I II II

R- N— C CN-CH.OCH

Y ² wherein R is H, CH 2 OH. ZZ v

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It will be apparent from the foregoing that in addition to the use of melamine with formaldehyde, the capsule walls can be prepared using melamines which are methylolated with 1-6 methylol groups and of these methylol groups one or more and even all may be preferred. In addition, the present invention may be successfully practiced with each of the compounds or mixtures of the compounds within the indicated scope or with oligomers or mixtures of oligomers of these melamine compounds, for example containing five or six monomeric units thereof. Compounds with a lower degree of methylolation and etherification are generally preferred because they have greater water solubility and faster reactivity.

Commercially available methylol melamines and methylated methylol melamines are usually mixtures of monomers and oligomers, i.e. polymers with lids. molecular weight and they may contain small amounts of free formaldehyde and unreacted melamine. Commercially available methylated methylol melamines may also contain some non-etherified methylol melamine. Consequently, some of these commercially available products may contain all the starting materials. The concentration of these materials in the aqueous phase should preferably be 5-20 °.

The polymeric polyelectrolyte acts as a system modifier in the polymerization reaction of the starting materials used in the present invention. Its role is not fully understood and it is especially difficult to understand because the modifier is not included in the final capsule walls in significant amounts. The system modifier seems to take some active part in the polymerization reaction that occurs, but still the finished canister walls retain only a small residual proportion of system modifiers. The system modifier should be present in the encapsulation system before the polymerization reaction begins.

Examples of suitable system modifiers include hydrolyzed maleic anhydride copolymers which are preferred, for example polyethylene-maleic anhydride copolymer (EMA), polymethylvinylether-maleic anhydride copolymer (PVMMA), polypropylene-maleic anhydride copolymer (PMA),

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The preferred polyethylene-maleic anhydride copolymer should have a molecular weight in excess of 1,000 and the polymethylvinyl ether-maleic anhydride copolymer in excess of 250,000 and polyacrylic acid in excess of 5,000.

The amount of system modifier in the encapsulation system should be sufficient to ensure some disturbance of the condensation reaction to form the polymer. If the system modifier is present in very high concentrations, the viscosity of the system will of course be too high to function. As a general rule, the encapsulation system should preferably contain at least 0.4% system modifier. With regard to the second extreme, it must be borne in mind that the amount of suitable material prevents the establishment of an exact general upper limit due to differences in the viscosity of the solution. It can be said that more than 10% is rarely used or needed. However, if desired, an amount of system modifier of up to about 15% can be used. Qualities with different molecular weights of the same system modifier can advantageously be combined in some cases and different system modifiers can also be combined.

It can generally be argued that the amount of system modifying material used is the amount sufficient to modify the polymerization of the melamine with the formaldehyde in one embodiment or polymerization of the methylol melamine or polymers thereof, low molecular weight methylated methylol melamine or polymers thereof, in a low molecular weight. another embodiment of the invention for the purpose of forming polymer capsule walls thereof.

In the encapsulation systems of the present invention, the amount of material present in the aqueous manufacturing medium can be varied over a wide range. Such systems in which the aqueous content is less than 60% or even 45% or less by volume of the total system can easily be used. Furthermore, depending on the choice of system modifier, viscosities of less than 300 cp have been achieved in systems containing these low volume percentages of the aqueous content.

The materials enclosed by the capsule walls formed according to this invention,

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ο i.e. the capsule core material, is relatively irrelevant to the practice of the invention and may be any material, solid, liquid or gaseous. It must be substantially water-insoluble and not affect the material regardless of the canister wall or any other components of the encapsulation system that are detrimental to the process. Of the materials which can be used as core materials in the capsules, the following may be mentioned among others: water-insoluble or substantially water-insoluble liquids, such as olive oil, fish oils, vegetable oils, spermacetol oil, mineral oil, xylene, toluene, kerosene, chlorinated biphenyl and methyl salicylate; similar substantially water-insoluble materials of solid but digestible nature such as naphthalene and coconut butter; water-insoluble metal oxides and salts; fibrous materials, such as cellulose or asbestos, water-insoluble synthetic polymeric materials; mineral; pigment; glass; flavors, odorants; reactants; biocidal compositions; physiological compositions and fertilizer compositions.

The method of the present invention preferably comprises, as an embodiment, first a preparation of a single aqueous solution of the system modifier in which solution the material intended for the capsule core is dispersed. The capsule core material should be substantially insoluble in the solution and substantially chemically inert in the dissolved constituents and starting materials for polycondensation, ie the melamine and formaldehyde or the methylol melamine or the methylated methylol melamine. The polycondensation reaction proceeds, preferably but not necessarily, under heating and / or stirring to form a polymer which separates from the solution as a liquid solution phase. The separated liquid phase containing said condensation polymer hydrates and encloses particles of the dispersed capsule core material, thereby forming embryos into capsules with liquid walls. Continued polycondensation reaction results in solid and substantially water-insoluble capsule walls. It is important to note the following: a / that there is no dilution step in the process after the system has been established and the capsule wall-forming condensation reaction has begun: b / the presence of the system modifier enables a high concentration of condensation polymer to be obtained at a relatively low viscosity; c) the formed system with high concentration and low viscosity enables liquid phase separation and subsequent polymerization to solid phase with the intention of mass-producing capsules with a volume concentration in

₇ 7714554-8 in the manufacturing means which has not been possible in the prior art processes.

Alternatively, the process can be modified and the various system components can also be combined in any order, with the only limitation that the system modifier must be present in the system when the polymerization reaction is in progress. The capsule core material can be dispersed in the system at any time, before the separated liquid phase of the polymeric material changes to solid form or becomes so polymerized that dispersed capsule core particles are not enclosed by the polymer formed.

Even when modified by the system modifier, the polymerization reaction is a polycondensation performed in an acidic medium. The condensation can be carried out in an aqueous system having a pH between 4.3 and 6, adjusting the time and temperature required to optimize the reaction. As an effect of the system modifier and its relation to the polycondensation reaction, a suitable pH for the practice of this invention is 4.5 to 6.0, and the most preferred pH is 5.3 for the melamine-formaldehyde and methylol melamine systems. When methylated methylol melamine is used, the appropriate pH is 4.3-5.6, with a pH of 4.8 being preferred.

Suitable operating temperatures are between about 20 - 100 ° C, with about 50-60 ° C being preferred.

In an embodiment of the invention where melamine and formaldehyde are used as starting material, it has been found that molar ratios of formaldehyde to melamine lying within a wide range can be used. However, a molar ratio of between 2: 1 and 3: 1 is preferred.

When the reaction has progressed to a stage when the capsule walls have solidified and the capsule production in this regard is completed, the capsules can be separated from the manufacturing medium by filtration and then washed with water. The canister walls are dried by placing the canisters in an air stream from a dryer. However, it should be apparent that the capsules do not need to have dried walls

7714554-8 ₈ or even separated from the liquid medium before use. If desired for any particular purpose, the capsule product of the present invention may be administered in the form of a suspension of capsules in a liquid carrier, which may be the manufacturing medium, for example for use in a paper coating composition, in a paint or in a composition for insect repellent.

The individual capsules made according to the present invention are substantially spherical and can be manufactured with diameters from less than 1 .mu.m to 100 .mu.m, the preferred range for the diameter size being between 1 .mu.m and 50 .mu.m.

By regulating the degree of agitation, droplets of any size of the liquid capsule core material can be made. In addition, the amount of the material intended for capsule cores can be varied, in order to change the amount of finished capsules, which is the internal phase, in batch to capsule wall material. Capsules can usually be manufactured with less than 50% internal phase up to 95% internal phase or more.

In the following examples, all percentages and sub-indications refer to percentages by weight and parts by weight, and all solutions are aqueous solutions unless otherwise indicated.

Example 1.

A solution was prepared from a mixture of 100 g of a 10% aqueous solution of a polyethylene-maleic anhydride copolymer which contains approximately equal moles of ethylene and maleic anhydride and which has a molecular weight of about 75,000-90,000 and is marketed under the trademark "EMA-31" water. The pH of this solution is raised to 4.5 using 20% ​​sodium hydroxide solution. To this solution is emulsified 200 ml of capsule core material comprising a solution of 1.7% of 3,3-bis (4-dimethylaminophenyl) -6-dimethylaminophthalide, 0.55% (2'-anilino-3'-methyl-6'-diethylaminofluorane) and 0.55% of 3,3-bis (1-ethyl-2-methylindol-3-yl) phthalide in a mixture of solvents containing benzylated ethylbenzene and a high boiling hydrocarbon oil having a distillation range of 204-260 ° C. The emulsion is placed with stirring in a water bath at 55 ° C and a solution is prepared by heating a mixture of 26.5 g

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37% formaldehyde reading and 20 g of melamine are added. After 2 hours, the heat is turned off and the capsule batch is kept under stirring in the cooling water bath overnight.

Because the capsule sizes are so small and the intended use of the capsules is in carbonless copy paper, the capsules are tested according to methods relating to the effectiveness of the capsules when used in copy paper. As a general description, a sheet of paper called a CB sheet (coated backing sheet) is coated with the capsules and tested together with a standardized receiving sheet of paper called a CF sheet (coated backed sheet). The coating on the CB sheet contains about 75% capsules, 18% hydrogen starch and 7% rubber binder such as e.g. hydroxyethyl ether of maize starch or other water-soluble starch derivatives and prepared by mixing 100 parts of an aqueous capsule suspension containing 40% capsules, 125 parts water, 10 parts wheat starch and 40 parts of a 10% aqueous solution of the rubber binder, adjusting the pH of the slurry to a value around 9. The coating is applied by means of a wire-wound rod, adapted to apply a wet film coating of 0.03 kg per m.

Coatings on a typical CF sheet made sensitive to reaction with the dye indicator in the capsules include a metal-modified phenolic resin, kaolin clay, other additives and a binder.

When a CB sheet and a CF sheet are placed with the coated sides facing each other and subjected to pressure, capsules from ruptures in the CB sheet and capsule-containing material will be transferred to and react with the acidic constituents in the CF sheet, whereby a staining occurs. One sample associated with such capsule rupture and the appearance of staining is the Typewriter Intensity Test (TI) and the TI values ​​indicate the ratio of the reflection of characters transferred to the CF sheet of a typewriter to the background reflection of the paper. A high value indicates a low degree of color development while a low value indicates a high degree of color development.

yj _ The reflection from printed characters _χ“The background reflection

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A related capsule quality test is a typewriter test that measures the degree of reduction in the ability of capsule-coated paper to produce transfer pressure after storing the coated paper in an oven at a given temperature for a given time. It is valuable to perform a routine typewriter transfer test with a continuous CB / CF 2 pair, by placing the CB sheet in an oven at 95 ° C for 18 hours and then repeating the imaging transfer test after storage. In accordance with this test, it has been shown that bad capsules will lose most or all of their ability to produce a transfer pressure during such furnace storage and that good capsules will withstand this storage with little or no loss in its ability to provide a print. One of the essential advantages of the present invention is that good capsule quality is achieved accordingly Over a wide range of the formaldehyde to melamine ratio. These satisfactory results are reflected in the table below where the ratio F: M (formaldehyde to melamine), initial typewriter intensity (III) before oven storage and typewriter intensity (II) after oven storage are given for capsules made according to the procedure described in this example:

<td>F; M</td><td>ITI</td><td>TI after storage overnight at 95OC________________</td>

<td> 2.06</td><td> 63</td><td> 66</td>

<td> 4.14</td><td> 54</td><td> 59</td>

In contrast, the quality of capsules made from urea formaldehyde polymeric material in the presence of an anhydride copolymer is entirely dependent on the molar ratio of formaldehyde to urea.

Example 2

This example is identical to Example 1, except that 180 grams of core material is added to the system modifier solution and 27 grams of 37 # formaldehyde solution and 12.6 grams of dry melamine are added to the emulsion. Capsules of good quality are obtained.

Example 3

A solution of 100 g of water and 50 g of 10% aqueous solution of polymethyl vinyl ether, 7714554-8 maleic anhydride copolymer, marketed under the trademark Gantrez AN-119 is adjusted to a pH of 4.73 with a 20% NaOH solution. Then, 100 ml of the standard core material of Example 1 is emulsified in the reading and the resulting emulsion is placed in a 55 ° C water bath. A 23.3 g portion of a solution of 80 g of melamine in 196 g of 37% formaldehyde solution is added to the emulsion with stirring. Stirring is stopped and the heat to the water bath is turned off after one hour and 40 minutes.

Capsule wall formation is determined by the so-called CF drip test. The emulsion containing all the capsule-forming ingredients is coated on a reactive CF paper. The color formation occurs by reaction of the dye which occurs when the emulsion is coated at a later time and measured with an opacimeter to give the reflection of the coated surface. The reflectance of a drop on a CF sheet after 22 hours was 65%.

Example 4

A solution of 280 g of water and 20 g of 50% aqueous solution of polyacrylic acid, marketed under the trademark Good-rite K-732 was adjusted to a pH of 5.12 with a 20% NaOH solution. The solution emulsifies 200 ml of standard core material. The emulsion is placed in a water bath at 55 ° C and a portion amounting to 46.6 g of a solution of 80 g of melamine in 106 g of 37% formaldehyde solution was added thereto with stirring. Heating and stirring were allowed to proceed for 19 hours.

At the end of the 19 hours, the reflection reading for a drip gave a value of 70%.

Example 5

A solution of 111.5 g of water and 38.5 g of 13% aqueous solution of polybutadiene maleic anhydride copolymer, marketed under the trademark Maldene 285 is adjusted to a pH of 5.12 with a 20% NaOH solution. The solution emulsifies 100 ml of standard core material. The resulting emulsion is placed in a 55 ° C water bath and a 23.3 g portion of a solution of 100 g of melamine in 132.5 g

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37% solution of formaldehyde is added with stirring. Stirring is stopped after 4 hours but the heating is allowed to continue for a total time of hours.

At the end of the 21 hours, the reflection of a drop on a CF sheet was 60%.

Example 6.

A solution of 154.5 g of aqueous solution of polyethylene-maleic anhydride copolymer according to Example 1 and 309 g of water is adjusted to a pH of 4.5 with 20% NaOH solution. To this solution is emulsified 520.7 g of standard core material according to Example 1.

Sample A

A 318.5 g solid portion of the emulsion described above is placed in a 55 ° water bath with stirring and 32.4 g of 60% solution of methylol melamine resin, marketed under the trademark Resimene 814 ”is added thereto.

Sample B

Same procedure as described in Sample A except that a methylol melamine resin marketed under the trademark Resimene 817 was used.

^{Sample c}

The same procedure as described for sample A is followed, except that a methylol melamine resin, marketed under the trademark “Resimene 836” was used.

All three batches are stirred in the water bath overnight. The heat to the bath is switched off after tv8 hours.

Good quality capsules are obtained from all three batches as shown by the color obtained on a CF sheet after three hours.

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Opacimeter reading after drip p8 CF sheet

Sample A Sample B Sample C

69 68

All these three batches were mixed together and coated in a conventional manner to obtain satisfactory CB sheets.

Example 7

A solution of 50 g of 10% aqueous solution of polymethyl vinyl ether-maleic anhydride copolymer (Gantrez AAN-119) and 100 g of water is adjusted to a pH of 4.5 with a 20% NaOH solution, 35 g of 60% solution of a methylol melamine resin marketed under the trademark Resimene 814 is added to the solution and 150 ml of standard core material is emulsified therein. The emulsion is placed in a 55 ° water bath with stirring.

Successful capsules were obtained after 90 minutes, as indicated by an opacimeter reading of 71 obtained after a drop on a CF sheet.

Example 8 The pH of a mixture of 100 g of 10% aqueous solution of polyethylene-maleic anhydride copolymer (EMA-31) and 200 g of water is adjusted to 4.0 with sodium hydroxide. To this solution is emulsified 200 ml of core material from Example 1. This emulsion is placed in a water bath at 55 ° C and with stirring is added 64.6 g of a methylated methylol melamine resin marketed under the trademark Resloom M-75. After 2 hours, the heating of the water bath is stopped but the batch is stirred overnight in the cooling water bath. During the encapsulation process, the pH rises to about 4.8. The origin of the encapsulation reaction is followed by dripping samples from the batch at various time intervals after the addition of the preferred methylol melamine, on an acidic CF coating and measuring the resulting color intensity by means of an opacimeter. In the following, a typical measurement of such drip intensities is described with a capsule batch made according to this example. For comparison, a urea-formaldehyde-based capsule kit made according to the procedure described in Swedish p.ans has been included. No. 7507803.

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Opacimeter reading of drip on CF.

<td>Time after mixing</td><td>5 minutes</td><td>15 min.</td><td>30 min.</td><td>1 h</td><td>11 h</td>

<td>Capsule system with methylated methylol melamine</td><td> 44</td><td> 29</td><td> 84</td><td> —</td><td> —</td>

<td>Capsule system with urea-formaldehyde</td><td> 36</td><td> 32</td><td> 23</td><td> 27</td><td> 70</td>

When the opacimeter reading in this test is about 60 or greater, the oil droplet is assumed to have been protected and the encapsulation has been successful. It should be apparent from the above data that at 55 ° C the present invention provides protection for the core material much earlier than the urea-formaldehyde system does. This phenomenon can be modified so that protection can be obtained at a lower temperature at the same time:

Opacimeter reading for drip on CF.

Time after addition of components 1 h 2 h

Present example at 40 ° C 33 80

If desired, the present invention can be practiced without the need to resort to additional heat at all. The time needed to achieve protection is of course longer.

Opacimeter reading for drip on CF.

<img file="SE414583B_D0001.tif" />

Present example at 24 ° C 49 47 h 18 h

67

When the above two batches prepared at lower (than 55 ° C) temperatures are tested alongside representative samples of the present invention and urea formaldehyde capsules in situations where the results obtained are related to the capsule wall quality, the lower batch prepared capsule batches are at least as good as those prepared under use of previous procedures.

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Change αν TI units after storage of CB samples for weeks under the specified conditions

60 ° C, oven Climate control at 32 ° C-90% relative humidity.

urea-formaldehyde capsules made at 55 ° C -3 + 1

Present Example -40 at 55^ISLANDC

Present Example -1 + 3 at 40^islandC

Present Example -40 at 24^ISLANDC

According to oven tests, CB samples deteriorate at 95 ° C. The present invention provides acceptable capsules at room temperature within a reasonable reaction time while the urea-formaldehyde capsule system does not provide equally good capsules under equivalent conditions.

CB storage 1 95^OC oven

Process temperature ΙΤΪ 1-3 days

Present Example 24 ° C 59 66 urea-formaldehyde- 21 ° C 64 100 capsules

Example 9

A solution of 100 g of 10% aqueous solution of polymethyl vinyl ether-maleic anhydride copolymer (Gantrez AN-119 "), 100 g of water and 65 g of 60% solution of methylated methylol melamine resin marketed under the trademark Resloom M-75 is adjusted to a pH of about 4.8 with a 20% NaOH solution. 180 g of standard core material are emulsified in the solution. The emulsion is placed in a 55 ° C water bath with stirring to allow satisfactorily good capsules after about 30 minutes.

Example 10

A solution containing 40 g of 25% aqueous solution of polyacrylic acid having a molecular weight of less than about 150,000, marketed under the trademark Acrysol A-3 and 160 g of water is adjusted to a pH of about 4.0 with 20% NaOH solution. To this is added 50 g of 80% preferred methylol melamine resin solution, marketed under the trademark Resimene 714. Thereafter, 180 g of standard core material is emulsified in the solution.

7714554-8 ₁₆ the emulsion is placed in a 40 ° C water bath which is heated to 55 ° C in about 15 minutes. Acceptable capsules are obtained after heating and stirring for 45 minutes.

Example 11

A solution of 50 g of 10% solution of polypropylene-maleic anhydride copolymer, as system modifier and 100 g of water is adjusted to a pH of 4.0 with 20% NaOH solution. In this solution, 100 ml of standard core material from Example 1 are emulsified. Then 25 g of an 80% solution of methylol melamine resin marketed under the trademark "Resimene 714" are added. The emulsion is placed in a 55 ° C water bath with stirring.

Successful capsules are obtained after 25 minutes, as indicated by an opacimeter reading of 70 obtained on a drip test on a CF sheet.

Example 12

A solution of 38 g of 13% aqueous solution of polybutadiene-maleic anhydride copolymer, marketed under the trademark Maldene 285 and 77 g of water is adjusted to a pH of 4.0 with NaOH. To this solution is added 25 g of 80% solution of methylated methylol melamine resin, marketed under the trademark “Resimene 714” and 100 ml of standard core material emulsified therein. The emulsion is placed in a 55 ° C bath.

Successful capsules are obtained as evidenced by an opacimeter reading of 74 obtained in a drip test on a CF sheet after 40 minutes of walking.

Example 13

A 10% aqueous solution of polyvinyl acetate-maleic anhydride copolymer (PVAMA) is prepared by dissolving the polymer in water by steam blowing and partial neutralization with about 0.5 ml of 20% sodium hydroxide solution per gram of polymer to give a reading with a pH of about 4.0. A solution of 50 g of said PVAMA solution, 100 g of water and 25 g of methylated methylol melamine resin ("Resimene 714") is then prepared and 100 ml (90 g) of standard core material are emulsified therein. The emulsion is placed in a 55 ° C water bath.

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After 2 hours, a sample coated on a CF test strip gave a reflection value of 74%.

Example 14

A solution of 20 g of methylol melamine resin (Resimene 817), 9.5 g of 37% formaldehyde solution and 5.5 g of water is mixed and stirred at room temperature between 45 minutes and 1 hour until the solution thins and becomes homogeneous. The pH of the resulting solution is about 6.0.

Then 20 g of 25% solution of polyacrylic acid (Acrysol A-3) and 130 g of water are combined and the pH is adjusted to 4.5. The previously prepared solution of methylol melamine resin is added and 100 ml (90 g) of standard core material are emulsified in the mixture. The emulsion is placed in a 55 ° C water bath.

After 1 hour and 45 minutes, a sample of the emulsion coated on a CFt strip had a reflection of 53%. A comparative sample coated on a non-reactive paper had a reflection of 59%.

Example 15

A solution of 20 g of methylol melamine resin (Resimene 817) and 15 g of 37% formaldehyde solution was mixed and stirred at room temperature for 45 minutes to one hour until the solution thinned and became homogeneous. The pH of the resulting solution is about 6.0.

Then 20 g of 25% solution of polyacrylic acid (Acrysol A-3) are combined and 130 g of water and the pH is adjusted to 4.5. The previously prepared solution of methylol melamine resin is added thereto and 100 ml (90 g) of standard core material are emulsified in the mixture. The emulsion is placed in a 55 ° C water bath.

After 1 hour and 15 minutes, a sample of the emulsion coated on a CF test strip had a reflection of 51%. A comparative sample coated on a non-reactive paper had a reflection of 61%.

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Example 16

A solution of 40 g of 13 # aqueous solution of polybutadiene-maleic anhydride copolymer (Maldene 285) and 65 g of water is adjusted to a pH of 4.5 with a 20% NaOH solution. To this is added a solution of 17.5 g of methylol melamine resin (Resimene 814) dissolved in 17.5 g of water. Then 100 ml (90 g) are emulsified.¹ standard core material as in Example 1 of the mixture. The emulsion is placed in a 55 ° C water bath.

After one hour and 25 minutes, a sample of this emulsion coated on a CF test strip gave a reflection reading of 62%.

Example 17

In the same manner as described in Example 8, a solution of 35 g of 10% aqueous solution of polyethylene-maleic anhydride copolymer (EMA-31), 65 g of a 10% aqueous solution of polyethylene-maleic anhydride copolymer (EMA-1103) and 157 g of water are added to a pH pa 4.0 with 20% NaOH solution. To this solution is emulsified 270 g of standard core material and 50 g of methylated methylol melamine resin (Resimene 714) is added, making a solids concentration of about 55% in the system.

The resulting emulsion is placed in a 55 ° C water bath and stirred therein for 2 hours, at which time the heating of the bath is turned off. Stirring of the system in the bath may continue overnight.

After adjusting the pH with NH 4 OH to 7-8, the resulting capsules can be mixed in for coating in a manner known per se and coated on a substrate material to provide carbonless CB sheets.

Example 18

This example shows that a successful encapsulation can be obtained even without stirring after the components have been combined.

A solution of 35 g of 10% aqueous solution of polyethylene-maleic anhydride copoly7714554-8 merisate (EMA-31) _t 65 g of 10% aqueous solution of polyethylene-maleic anhydride copolymer (EMA-1103) and 170 g of water are adjusted to a pH of 4 by 20%

NaOH solution. In this solution 270 g of standard core material are emulsified and 50 g of methylated methylol melamine resin (Resimene 714) are added.

The resulting emulsion is placed in a 70 ° water bath without stirring. Successful capsules acceptable for use in carbonless copy paper are obtained without any agitation of the system. Drip drops on CF test sheets show the formation of capsules, with the opacimeter reading reaching at least 70 after one hour.

Comparative example

This example shows that successful capsules cannot be obtained by using the starting reactants of the present invention alone without using the system modifier.

In a solution of 125 g of methylated methylol melamine resin (Resloom M-75) and 75 g of water, 225 ml of standard core material from Example 1 were emulsified. The pH of the emulsion was lowered to 4.0 with glacial acetic acid. The emulsion was added with stirring to a 45 ° C water bath. After 1 hour and 10 minutes, the batch appeared as a single solid mass.