CS214740B2 - Pressure-sensitive, self-adhesive copying material and manufacturing method - Google Patents

Abstract

The invention relates to a self-contained pressure-sensitive copying material comprising a sheet material coated with particles of a mineral colour developing material and microcapsules enclosing a solution of a colourless colour forming component which is reactive with the colour developing material to form a coloured product. The essence of this material is that the microcapsules and the colour developing material are contained in one layer, this layer also containing a means for preventing premature colour development. The material according to the invention can be used in making copies of written text

Description

The invention relates to a self-contained pressure-sensitive copying material comprising a sheet material coated with particles of a mineral color developing material and microcapsules enclosing a solution of a colorless color forming component which is reactive with the color developing material to form a colored product. The invention also relates to a method of making the material.

In the pressure-sensitive copying systems known to date, the underside of the top sheet is coated with microcapsules containing a solution of a colorless color-forming component, and the top side of the bottom sheet is coated with a color-developing material, for example, acid clay or phenolic resin. Several intermediate sheets are also usually used, each of which is coated on its lower surface with microcapsules and on its upper surface with a color-developing material. Pressure exerted on the sheets during handwriting or typing breaks the microcapsules, thereby releasing the solution of the colorless color-forming component, which thus comes into contact with the color-developing material, whereby a dye is formed at the points where the pressure was applied.

Such a system has the disadvantage that it is necessary to produce at least two and usually three types of laminated sheets, that is, top and bottom sheets and intermediate sheets.

To overcome the disadvantages of this system, the use of a so-called separate system has been proposed. In this system, the microcapsules and the color developing material are applied to one side of a sheet, and by hand-writing or typing on a second sheet, which is placed on the first sheet thus coated, the walls of the microcapsules are broken and the colorless color forming component is released, which then reacts with the color developing material to form a dye at the points where the pressure has been applied.

The disadvantage of this stand-alone system is that until now it was necessary to coat the first sheet twice. First, a mixture containing microcapsules is applied to it, and only then a layer of color developing material is applied to the resulting layer.

It would probably be simpler and cheaper to apply the microcapsules and the color developing material simultaneously. Such a method is described, for example, in the description of the invention in U.S. Patent No. 2,730,457. However, it has been shown that in this case the color development occurs either when the suspension of microcapsules is mixed with the dispersion of the color developing material before applying this mixture to the sheet, or only after applying the mixture to the sheet.

The reasons for the premature development of the colorless color former are probably very complex and are not fully understood at present. One reason for the premature development of the colorless color former is probably that the microcapsule suspension contains some unencapsulated solution of the colorless color former, which reacts rapidly with the color developing material to form the dye.

It has also been found that premature development of the colorless color-forming component can occur even when the microcapsule suspension does not contain unencapsulated colorless color-forming component (for example, when the unencapsulated colorless color-forming component is removed before the microcapsules are mixed with the color-developing material). The reason for the premature development of the colorless color-forming component in this case is not entirely clear, but research suggests that it may be due to the interaction between the microcapsules and the color-developing material particles. The exact mechanism of this interaction is not yet known. /

Finally, it was found that even when an uncolored coating mixture of microcapsules and particles of color developing material was obtained, the paper coated with this mixture became colored either immediately upon drying or several days after coating. Even in this case, the reason for the premature development of the color-forming component is not entirely clear.

It has now been newly discovered that the above-mentioned premature development of the colorless color-forming component can be substantially avoided by suitable chemical treatment of the color developing material and/or microcapsules.

The above-mentioned disadvantages are not overcome by a separate pressure-sensitive copying material according to the invention, comprising a sheet material coated with particles of a mineral color developing material and microcapsules enclosing a solution of a colorless color-forming component that is reactive with the color developing material to form a colored product, the essence of which is that the microcapsules and the color developing material are contained in one layer, this layer also containing an agent for preventing premature color development from the group consisting of a self-crosslinkable polymer, for example a self-crosslinkable wet strength paper agent, an anionic surfactant, a fluorine-containing paper size, a non-crosslinkable wet strength paper agent, for example a polyethyleneimine resin, and a substance effective in reducing the mutual attraction between the microcapsules and the particles of the color developing material.

The self-contained pressure-sensitive copying material according to the invention preferably contains an aminoplast polymer, for example a urea-formaldehyde or melamine-formaldehyde polymer, as the self-crosslinkable polymer.

The separate copying material according to the invention also preferably contains an epichlorohydrin polymer, for example an aminoepichlorohydrin polymer or a copolymer of amide and aminoepichlorohydrin, as the self-crosslinkable polymer.

As a surfactant, the self-contained pressure-sensitive copying material of the invention preferably contains a sulfate-containing surfactant, for example a lauryl sulfate salt, or a sulfonate-containing surfactant, for example a sulfonated derivative of ricinoleic acid, a dodecylbenzene sulfonate salt, or a dibutyl ester or dioctyl ester of sulfosuccinic acid.

The invention also provides a method for producing the above-mentioned separate pressure-sensitive copying material, in which a sheet material, for example paper, is coated with a coating mixture comprising particles of a mineral color developing material and microcapsules enclosing a solution of a colorless color-forming component that is reactive with the color developing material to form a colored product, the essence of which is that the particles of the color developing material and optionally also the microcapsules are brought into contact with a protective agent for preventing premature color development from the group consisting of a self-crosslinkable polymer, for example a self-crosslinkable wet strength paper enhancer, an anionic surfactant, a fluorine-containing paper size, a non-crosslinkable wet strength paper enhancer, for example a polyethyleneimine resin, and a substance effective for reducing the mutual attraction between the microcapsules and the particles of the color developing material.

In the process according to the invention, an aminoplast polymer, for example a urea-formaldehyde or melamine-formaldehyde polymer, is preferably used as the self-crosslinkable polymer.

As a self-crosslinkable polymer, an epichlorohydrin polymer, _and for example an aminoepichlorohydrin polymer or a copolymer of amide and aminoepichlorohydrin, can also be advantageously used in the process according to the invention.

In the method according to the invention, it is possible to advantageously use _as the surfactant a sulfate-containing surfactant, for example a lauryl sulfate salt, or a sulfonate-containing surfactant, for example a sulfonated derivative of ricinoleic acid, a dodecylbenzene sulfonate salt or a dibutyl ester or dioctyl ester of sulfosuccinic acid.

The advantage of the invention is that in a stand-alone pressure-sensitive copying system, there is no premature development of the colorless color-forming component during its manufacture and thus no deterioration thereof.

The particles of mineral color developing material are preferably made of acid clay, for example clay found in Japan, which is known to those skilled in the art as Japanese acid clay.

Particles of mineral color developing material can be treated with a preservative by simply mixing a suspension of this material with the preservative.

The protective agent may be a self-crosslinking polymer, in which case it is advantageous to heat the resulting mixture of this polymer with the color developing material before mixing it with the microcapsules.

It is also advantageous to adjust the color of the developing material and the microcapsules before mixing them together. However, in the case where premature development of the colorless color-forming component does not occur immediately upon mixing the microcapsules with the color developing material, it is possible to add the preservative after mixing them.

The term "self-crosslinkable polymer" includes not only polymers with a large number of repeating structural units, but also so-called prepolymers or precondensates, which have only a limited small number of these repeating structural units.

The self-crosslinkable polymer may be a resin or precondensate which is used in the paper industry for wet strengthening of paper tissue. Examples of such resins are epichlorohydrins and aminoplast resins or precondensates. Examples of suitable epichlorohydrins are polyaminoepichlorohydrin resins and polyamidopolyaminoepichlorohydrin resins.

Examples of suitable aminoplasts are melamine formaldehyde resins or precondensates or urea formaldehyde resins or precondensates thereof. Melamine formaldehyde resins have been found to be most effective against premature development of the color-forming component.

When the protective agent is a self-crosslinking polymer, the method of treating the color developing material depends on the nature of this polymer. The selection of suitable conditions for treating this polymer does not present any problem for the person skilled in the art,

In the case of a developing material based on acid clay, melamine formaldehyde resin with a reactive resin content of 1000% and a dry matter of 93% and a methylated modified melamine formaldehyde precondensate with a reactive resin content of 80 _% and a dry matter of 69%, the treatment is preferably carried out by heating a suspension of clay with a solution of said resin or said precondensate (the weight of resin or precondensate is 10% in relation to the weight of dry matter of acid clay) for 2 hours at a temperature of 90 ° C. In the case of polyaminoepichlorohydrin resins and a developing material based on acid clay, the treatment is preferably carried out by mixing the clay with an aqueous solution of the resin (the weight of resin is 10% in relation to the weight of dry matter of clay) and stirring for several minutes at a pH of 8 or 7. Heating is not necessary here.

The microcapsules may also optionally be treated with a self-crosslinkable polymer, preferably a crosslinkable polymer that is used to adjust the color of the developing material.

A non-crosslinkable wet strength paper enhancer, such as polyethyleneimine resins, can also be used as a protective agent.

Other materials that can be used as a preservative are anionic surfactants, especially anionic surfactants, especially anionic surfactants that contain a sulfate or sulphate group. An example of anionic surfactants containing a sulfate group is a lauryl sulfate salt, such as sodium lauryl sulfate.

Anionic surfactants containing a sulfate group include dodecylbenzene sulfate salts, sulfosuccinic acid dibutyl ester, sulfosuccinic acid dioctyl ester, and sulfonated ricinoleic acid derivatives.

An example of anionic surfactants that are useful as a preservative but do not contain a sulfate or sulfonate group is ethylenediaminetetraacetic acid.

Other plasticizers, which are anionic surfactants, such as dibutyl phthalate, di-2-ethylhexyl adipate and dibutyl maleate, are also effective as preservatives. However, the disadvantage of these substances is that they cause oil stains on the coated sheet and therefore the use of these substances is only envisaged as a last resort when other types of preservatives are not available and when high demands are not placed on the quality of the obtained copy.

Another group of materials that can be used as a protective agent are fluorine-containing paper sizes, which are designed to make paper hydrophobic.

A mixture of preservatives may also be used. In some cases, the use of such a mixture of preservatives provides certain advantages over the use of a single type of preservative. For example, mixtures of fluorine-containing sizing agents and a self-crosslinking polymer have better protective properties than the sizing agents or self-crosslinking polymers alone.

The amount of protective agent depends on the nature of the microcapsules used and the color developing material used. The optimum amount of this agent is easily determined by a person skilled in the art. The following examples may be used as a guide in this regard.

Preferably, microcapsules for use in a separate pressure-sensitive copying material must have thicker walls, that is, these walls must be stronger than the walls of the microcapsules used in the copying system used to date.

Although it is advantageous to use microcapsules with walls that are stronger than those of the microcapsules used in the stand-alone copying system, it has been found that even with the use of the relatively less strong microcapsules used in the past, a reduction in premature development of the colorless color-forming component is achieved if the particles of the color developing material are treated with a self-crosslinkable polymer before being mixed with the suspension of said microcapsules. However, the coating mixture thus obtained is relatively well colored despite the said reduction, so that this method can be used in cases where high demands are not placed on the copies obtained.

Microcapsules suitable for use in the self-contained copying material of the invention may have walls of synthetic materials such as melamine formaldehyde resin, urea formaldehyde resin, and acrylamide acrylic acid copolymer. Other synthetic materials that may be used as microcapsule wall materials include polyacrylates, polyurethanes, polyureas, or aminoplasts.

Microcapsules may also have walls of coacervated hydrophilic colloids, for example a mixture of gelatin, gum arabic or carboxymethylcellulose and copolymers of polyvinyl methyl ether and maleic anhydride.

To achieve sufficient strength of the microcapsule walls, it is necessary to choose a lower weight ratio of the solution of the colorless color-forming component to the aqueous solution of the microcapsule wall material during their production.

If microcapsules conventional in previously known copying systems are used, then the use of a protective agent in the manner of the invention results in less blueing of the sheet than when no protective agent is present, but the degree of blueing is still too high to be acceptable for making quality copies.

Cases with synthetic walls, such as aminoplasts, are stronger and less <

soluble than gelatin coacervate type casings. Synthetic casings therefore show less premature blueing than gelatin coacervate type casings. However, it has been found that it is desirable to protect not synthetic wall casings even when the difference in whiteness between the protected and unprotected copy paper is small. Even small differences in whiteness are readily observable and even a small reduction in the whiteness of copy sheets can greatly affect the commercial acceptability of these sheets.

Not all protective agents of the previously mentioned types are suitable for all types of capsules. For example, anionic surfactants leach the contents of microcapsules with walls of gelatin coacervate type, but are on the contrary applicable to capsules with aminoplast synthetic walls. However, the choice of protective agent for a given type of microcapsule does not present any problem for the person skilled in the art.

Also, some materials which seemed to be suitable for use as preservatives are in fact unsuitable. Cationic and nonionic surfactants, which might be expected to have the same effect as anionic surfactants, act as poisons for the color developing material, that is, they limit its ability to develop the colorless color-forming component. Retention agents used in papermaking, which are chemically similar in some respects to wet strength agents, also appear to be useful as preservatives, but in practice they have been found to cause flocculation of the coating compositions. However, methods are known to overcome these problems.

The invention is not limited to the use of particular color-forming components or particular solvents for color-forming components. Examples of color-forming components that can be used are phthalide derivatives such as crystal violet lactone, fluoran derivatives, diphenylamine derivatives, spiropyran derivatives, phthalimidine derivatives, and benzoyl leuco derivatives of various dyes.

Examples of the solvents used are mixtures of partially hydrogenated terphenyls, chlorinated paraffins, biphenyl derivatives, diarylmethane derivatives, alkylnaphthalenes, mixtures of dibenzylbenzenes, phthalate esters, phosphoric acid esters or linear alkylbenzenes with 10 to 14 carbon atoms. These solvents can be used in a mixture with a diluent such as kerosene.

If both the microcapsules and the color of the developing material need to be modified, then the modification conditions ODet depend on the nature of the microcapsules and the nature of the color of the developing material. The choice of modification conditions in a given case does not present any problem for a person skilled in the art. The specific cases given in the following examples may serve as a guide.

The coating composition may also contain a filler to improve the rheological properties of the coating composition and to increase the whiteness of the coated sheet. Suitable fillers include kaolin and calcium carbonate. It is known that the said fillers sometimes have a weak color developing effect. However, this effect is not so strong as to be disruptive; otherwise, the filler can be treated with a preservative which is used to treat the color of the developing material. For example, the conditions for treating kaolin would be almost the same as those for treating an acidic color developing clay.

Therefore, some care must be taken in selecting a suitable binder for the coating composition. Some binders which are commonly used in prior art copying systems may have a colour developing effect or other undesirable properties and are therefore not suitable for use in the stand-alone copying system of the invention. For example, a starch binder may reduce the reactivity of the colour developing material by forming a film on the surface of the colour developing material particles. On the contrary, it has been found that highly hydrolysed polyvinyl alcohol is particularly suitable as a binder for the coating composition of the copying system of the invention.

The coating composition according to the invention may also contain a dispersant, preferably a dispersant which also serves to adjust the pH of the coating composition. Such dispersants are well known and examples thereof are sodium silicate and sodium hydroxide, which also serve, as mentioned above, to adjust the pH. The optimum pH is preferably adjusted to be most suitable for developing a colourless colour-forming component. For example, if the colour-forming component is crystal violet lactone and an acid clay is the colour-developing material, then a suitable pH of the coating composition is around pH 10.

The coating composition may also contain an agent to protect the sleeves from premature breakage during storage and transportation of the coated paper web. The use of such protective agents, often known as reinforcing material, is well known in pressure-sensitive copying papers.

Two examples of suitable reinforcing materials are fibrous cellulose flakes and wheat starch grains.

The usual surface weight of the dry applied layer is from 10 to 15 g/m ² .

In the production of a separate pressure-sensitive copying material, conventional coating methods are used, such as, for example, ruler coating, air-wipe coating or roller coating. It has not been possible to apply coating compositions containing only microcapsules under operational conditions using a ruler, since in this way it is generally not possible to apply a coating with a low basis weight. The method according to the invention makes this possible, since a coating containing both microcapsules and a color developing material can have a higher basis weight, since in this case only a single coating is applied instead of two coatings previously applied, where one coating contained microcapsules and the other coating contained a color developing material. The possibility of this application considerably speeds up production.

The mechanism by which the preservative prevents premature development of the color-forming component in the coating composition for the stand-alone copying material of the invention is not fully understood. It is believed that the preservative causes a reduction in the mutual attraction between the color-developing material and the microcapsules.

In the following description, the invention will be described with reference to the accompanying drawings, in which Fig. 1 is an enlarged cross-sectional view of a sheet of a separate pressure-sensitive copying material, and Fig. 2 is a flow chart showing an exemplary method of manufacturing the material of Fig.

1.

It is apparent from Fig. 1 that a separate pressure-sensitive copying material comprises a paper backing 1 carrying a layer 2 containing microcapsules 3 and particles 4 of the colour of the developing material. The remaining components of the layer are not shown in Fig. 1 in order to keep the picture clear. One such component is a protective agent, the exact location of which is not known.

It is apparent from Fig. 2 that particles 4 of color developing material, a suspension 5 of microcapsules 3, fillers 13 and a mixture 14 comprising a binder, a dispersant and a pH adjusting agent are mixed to form a coating mixture 6.

Before mixing, the color developing material and optionally the microcapsules 3 and/or the filler 13 are treated with a protective agent. If necessary, the filler 13 can be mixed with the color developing material particles 4 before being treated with a protective agent.

These options are shown in dashed lines in Fig. 2. The coating mixture 6 is then coated onto a paper backing in a coating step 7. The resulting material is then dried in a drying step 8 to form a separate pressure-sensitive copying material 9.

The invention will be explained in more detail in the next part of the description using the following examples.

Example 1 aj Preparation of microcapsules

382 g of a 9.1% gelatin solution with a pH of 6.4 is placed in a Varing mixer. At low speed, 274 g of the internal phase, that is, the material to be encapsulated, is added. The internal phase is a mixture (9:1) of linear alkylbenzenes with 10 to 14 carbon atoms and a phthalate material, containing

1.8% crystal violet lactone and 1.4% benzoyl leucomethylene blue. The mixer is left running until a droplet size of less than 3 micrometers is achieved.

g of a 17.6% aqueous solution of gum arabic and 422 g of deionized water are then added to 218 g of the gelatin solution with the internal phase emulsion. The pH of the mixture is adjusted to

8.7 potassium hydroxide and 8 g of a 5% aqueous solution of polyvinyl methyl ether and maleic anhydride are slowly added. 14.7% acetic acid is then added to lower the pH to 4.3, thereby precipitating the coacervate which clumps around the droplets of the internal phase. The emulsion is then cooled to 10°C, then 3.3 ml of 50 _% glutaraldehyde are added to crosslink the coacervate.

A further 10 g of a 5% aqueous solution of polyvinyl methyl ether and maleic anhydride is added to prevent agglomeration of the microcapsules. Then 6 g of a 12.5% aqueous solution of sodium carbonate is added as a buffer solution. The pH is then raised very slowly with sodium hydroxide to a value of 10.

bj Preparation of the coating mixture and coating g of acidic color developing clay is dispersed in water to approximately 36% dry matter content of the mixture. Then 3 g of methylated modified melamine formaldehyde precondensate are added as a preservative. The resulting suspension is heated with stirring to a temperature of 90 ° C and maintained at this temperature for 2 hours and then cooled.

g of kaolin is dispersed in sufficient water to obtain a dry matter content of approximately 36% in the mixture. 1 g of methylated modified melamine formaldehyde precondensate with a reactive resin content of 80 _% and a dry matter content of 69% is added to the mixture as a preservative and the suspension is heated to 90°C, maintained at this temperature for 2 hours and then cooled.

The color developing clay and kaolin thus treated are mixed and the pH of the mixture is adjusted to 10 with sodium hydroxide solution.

132 ml of the microcapsule suspension prepared as described above is then added to the clay suspension, followed by the addition of 30 g of 10% polyvinyl alcohol binder. The resulting mixture is then coated to a thickness of 9 g/m ² onto 49 g/m ² paper using a laboratory coating machine and, after drying, the paper is tested for whiteness using an opacimeter (for example, the Bausch and Lomb opacimeter described in U.S. Patent No. 1,950,975). The test involves measuring the reflectance of the sheet and comparing the value obtained with the reflectance of a standard white surface (a powdered magnesium oxide surface). The result is expressed as:

____reflectance of the coated sheet x 100_ reflectance of a standard white surface.

The higher the value obtained, the whiter the surface of the coated sheet.

The test is performed on several different locations on the sheet and the average is then calculated. A difference of just a few percent may seem insignificant, but such a difference is easily visible to the eye and can greatly affect the marketability of the coated material produced.

An average of 93% was obtained and the sheet appeared white. When a plain sheet of paper was placed on the thus coated sheet and written on, a bright blue copy of the written text was produced on the coated sheet.

To demonstrate the effect of the melamine formaldehyde precondensate, a similar experiment was conducted in which neither the acid color developing clay nor the kaolin was treated with the melamine formaldehyde precondensate.

g of acidic color developing clay and 10 g of kaolin are dispersed in sufficient water to give a dry matter content of about 40% in the mixture. The pH of the mixture is then adjusted to 10 with sodium hydroxide solution.

132 ml of the microcapsule suspension prepared as above was added together with 30 g of 100% polyvinyl alcohol binder. The resulting mixture was bluish and when coated on paper at a coating weight of 9 g/m ² , the sheet was pale blue and had an average reflectance of 81%. Example 2

In this embodiment, different self-crosslinking polymers are used as a protective agent.

³ g of polyaminoepichlorohydrin resin is dissolved in 60 g of water. 30 g of acidic color developing clay and 10 g of kaolin are dispersed in this solution. 2 g of 1% dispersing agent are added to the mixture to prevent flocculation. The pH value is slowly adjusted to 10 by adding sodium hydroxide solution.

132 ml of a suspension of microcapsules prepared as described in Example 1 are then added to the mixture, followed by 30 g of 10% polyvinyl alcohol binder.

The resulting color of the mixture was a faint pale blue and when paper was coated with this mixture at a basis weight of 8 g/ ^m2 , a pale blue sheet with a reflectance of 87% was obtained. This was an improvement over the untreated acid color developing clay which, as shown in Example 1, gave a reflectance of 81%.

When the procedure was repeated using a different solution of the colorless color-forming component, the sheet with the acid color-developing clay treatment had an average reflectance of 88%.

When a plain sheet of paper was placed on two coated sheets, produced by the processing procedures described above, and written on by hand, a bright blue copy of the written text was produced on both coated sheets.

Example 3

a) Preparation of microcapsules

First mix:

aj 19 g of cationic urea-formaldehyde resin with a reactive resin content of 45% and a dry matter content of 35%;

bj 42 g of a 20% solution of a copolymer of acrylamide and acrylic acid, having a viscosity average molecular weight of 40,000 and an acrylic acid content;

cj 200 g deionized water.

The mixture is then heated to 55°C and maintained at this temperature for 45 minutes. 12 g of methylated modified melamine formaldehyde precondensate are then added and the pH is lowered to 4.4 by adding acetic acid.

89 g of the color-forming component solution is then added to the mixture and the dispersion thus formed is ground into droplets of 4 to 5 micrometers in size. 20 g of deionized water is added and the mixture is stirred for one hour at 35 °C and then for a further 2 hours at 55 ^° C, after which the mixture is allowed to cool overnight and to ambient temperature. The following morning the pH is raised to 10 by adding 1θο/ _ο sodium hydroxide solution. The dry matter content of the resulting microcapsule suspension is 30 o/oa and the phase ratio, i.e. the ratio of the weight of the colorless color-forming component solution to the weight of the microcapsule wall material, is equal to 3.4:1.

bj Preparation of the coating mixture and coating g of acidic color developing clay is dispersed in sufficient water to form a 40% solids content in the mixture and then 1.5 g of methylated modified melamine formaldehyde precondensate is added as a preservative.

The mixture is then heated to 90°C, held at this temperature for 2 hours and then allowed to cool. The pH of the mixture is adjusted to 10 with sodium silicate.

ml of microcapsule suspension (dry weight of microcapsules is 5.5 g) is then mixed with 0.55 g of methylated modified melamine formaldehyde resin, used as a preservative, after which the mixture is heated to 70 °C, maintained at this temperature for 1 hour and then allowed to cool.

The modified color developing clay dispersion and the modified microcapsule suspension are then mixed and 15 ml of 10% polyvinyl alcohol binder are added to the resulting mixture with stirring, then 15 g of kaolin are added with constant stirring. The resulting mixture is then coated onto a sheet of paper in the manner described in Examples 1 and 2 except that the basis weight of the layer is 12.5 g/m ² .

The sheet was tested for whiteness and found to have an average reflectance of 93.5%. When a plain sheet of paper was placed on the coated sheet and handwritten, a bright blue copy of the written text was produced on the coated sheet.

After 10 days, the leaf whiteness measurements were repeated and an average reflectance of 98% was found.

Example 4

a) Preparation of microcapsules

This preparation is carried out as in Example 3 except that after adding the color-forming component solution and after it is pulverized, 40 g of deionized water and 10 g of methylated modified melamine formaldehyde precondensate are added. The remaining steps are the same as in Example 3. The methylated modified melamine formaldehyde precondensate had a reactive resin content of 80% and a dry matter of 69%.

b) Preparation of the coating mixture and coating g of acidic color developing clay is dispersed in sufficient water to form a mixture with a 40% dry matter content and then 2 g of methylated modified melamine formaldehyde precondensate with a reactive resin content of 80% and a dry matter of 69% are added as a preservative. The mixture is then heated to 90°C for 2 hours, then allowed to cool. The pH is then adjusted to 10 with sodium silicate.

g of kaolin is dispersed in sufficient water to form a mixture with a dry matter content of 50%, and then 1.5 g of methylated modified melamine formaldehyde precondensate with a reactive resin content of 80 _% and a dry matter content of 69% is added as a preservative. The mixture is heated to 90°C, maintained at this temperature for 2 hours and allowed to cool.

The dispersion of the modified color developing clay and the dispersion of the modified kaolin are then mixed.

ml of microcapsule suspension (dry weight is 5.8) is then mixed with 0.58 g of methylated modified melamine formaldehyde precondensate with a reactive resin content of 80% and a dry weight of 69%, used as a preservative, and the mixture is heated to 70 °C, maintained at this temperature for 1 hour and allowed to cool. The thus treated microcapsule suspension is then added to the treated clay dispersion.

15 ml of 10% polyvinyl alcohol binder is then added to the mixture with stirring.

The resulting mixture is coated onto a sheet of paper in the manner described in the previous examples except that the basis weight of the coating is 14 g/m ² .

The sheet was then tested for whiteness, and an average reflectance of 97% was found. When a plain sheet of paper was placed on the coated sheet and handwritten, a bright blue image of the written text was formed on the coated sheet. After 10 days, the whiteness measurement of the sheet was repeated, and an average reflectance of 96% was determined.

Example 5

The microcapsules used in this example are the same as in Example 4 except that they are not treated with melamine formaldehyde.

g of acidic color developing clay is dispersed in sufficient water to form a mixture with a 40% solids content and then 1.5 g of melamine formaldehyde resin with a reactive resin content of 100% and a solids content of 93'% is added as a preservative. The mixture is heated to a temperature of 90 ⁰ Celsius, maintained at this temperature for 2 hours and then allowed to cool. The pH is then adjusted to 10 with sodium silicate.

ml of microcapsule suspension (dry weight of microcapsules is 5.8 g) is added and then 15 ml of _100/0 polyvinyl alcohol binder and 15 g of kaolin are added with stirring.

The resulting mixture is then coated onto a sheet of paper in the manner described in the preceding examples, except that the coating weight is 13.6 g/m ² . The sheet is tested for whiteness and an average reflectance of 96.5% is found. When a plain sheet of paper is placed on the thus coated sheet and written on by hand, a bright blue copy of the written text is produced on the coated sheet.

After 10 days, measurements of the whiteness of Ušt were repeated, and an average reflectance of 96% was found.

Example 6

In this example, microcapsules are used that were prepared according to the procedure described in Example 4, but were not subsequently treated with melaminoformaldehyde.

g of acidic color developing clay is dispersed in sufficient water to form a mixture with a 40% solids content. The pH is then adjusted to 10 with sodium silicate.

The dispersion is then divided into 2 parts, one of which is treated with a methylated modified melamine formaldehyde precondensate with a reactive resin content of 80% and a dry matter of 69%, used as a preservative, according to the procedure described in Example 4.

ml of microcapsule suspension (dry weight of microcapsules is 7 g) is added to each portion of the clay dispersion, then 15 ml of 10% polyvinyl alcohol binder is added with stirring. The resulting mixtures, both colorless, are then coated on a sheet of paper in the manner described in the previous examples so as to obtain a surface weight of the applied layer of 8 g/m.

The color of the sheet with the modified clay mixture is white and has an average reflectance of 95%, while an average reflectance of 91% was found for the untreated clay mixture.

When ordinary sheets of paper were placed on both Uštěch coated in this way and written on by hand, a bright blue image of the written text was created on both sheets, but on the sheet with the modified clay, this image was clearer.

After 10 days, the average reflectance measurements were repeated, and an average reflectance of 85 _% was found for the sheet with untreated clay; the sheet with treated clay had an average reflectance of 92%.

Example 7

This example illustrates the use of aminoepichlorohydrin resin as a preservative instead of melamine formaldehyde resin or melamine formaldehyde precondensate.

The casings used in this example are prepared as described in Example 4, but are not treated with melamine formaldehyde.

g of acidic color developing clay is dispersed in sufficient water containing 1.5 g of polyaminoepichlorohydrin resin as a preservative to give a 30% solids content in the mixture. The pH of the mixture is adjusted to 8 with sodium hydroxide and the mixture is stirred at ambient temperature for several minutes.

The pH of the mixture is then adjusted to 10 with sodium hydroxide. 20 ml of microcapsule suspension (7 g dry weight of microcapsules) and 15 ml of 10% polyvinyl alcohol binder are added to the mixture with stirring. The resulting mixture is then coated onto a sheet of paper at a coating weight of 8 g/m ² . The sheet color was white and when the whiteness measurement was made, an average reflectance of 93 percent was found.

When a regular sheet of paper was placed on the coated sheet and written on by hand, a bright blue image of the written text was created on the coated sheet.

After 10 days, the whiteness measurements were repeated, and an average reflectance* of 92.1% was found.

It should be noted that it is not necessary to heat the polyaminoepichlorohydrin resin, as was done with the melamine formaldehyde resins mentioned above. In addition, the release of formaldehyde fumes is minimized.

Example 8

This example illustrates the production of a separate pressure-sensitive copying material by coating on an in-house coating device.

a) Preparation of microcapsules

This preparation is carried out at a phase ratio of 2.7:1 in the following manner.

kg of hot deionized water is mixed with 16.8 kg of acrylamide-acrylic acid copolymer, after which the temperature is increased to 55 °C.

Then 7.6 kg of urea-formaldehyde resin are added and the mixture is stirred for 40 minutes, while maintaining the temperature at 55 ° C. Then 8.9 kg of methylated modified melaxin formaldehyde precondensate with a reactive resin content of 76% and a dry matter of 71% are added and the pH is adjusted to 4.4 with acetic acid. Then

36.4 kg of a colorless color-forming component solution and the dispersion thus formed are ground to a droplet size of 4 to 5 microns. The pH of the mixture is then adjusted to 4 with acetic acid and the mixture is heated to 55 °C and maintained at this temperature for 3 hours. The pH of the mixture is then increased to 10 and the mixture is stirred overnight.

The dry matter content of the resulting microcapsule emulsion is 29.5%.

b) Preparation of the coating mixture and coating

100 l of water is added to a galatite kettle and 50 kg of acidic color developing clay is dispersed in this water. Then 5 kg of methylated modified melamine formaldehyde precondensate with a reactive resin content of 80% and a dry matter of 69% is added as a preservative and the mixture is kept at a temperature above 90 °C for 2 hours with stirring. The mixture is then transferred to a rod mill and the process is repeated with another 50 kg of acidic color developing clay.

100 kg of kaolin is treated in the manner described for the acid color developing clay and the resulting mixture is also transferred to the aforementioned rod mill.

Then 13 kg of 50% sodium silicate is added and the resulting clay suspension is transferred to a storage vat.

11 kg of polyvinyl alcohol binder is added to 136 liters of water in a galatite kettle. The water is then heated to 90°C to dissolve the polyvinyl alcohol and the resulting solution is then transferred to another rod mill.

liters (47 kg of microcapsule dry matter) of the microcapsule suspension, prepared as described in paragraph a) above, is then added to the galatite kettle. 4.7 kg of methylated modified melamine formaldehyde precondensate with a reactive resin content of 80 percent and a dry matter of 69 o/o is then added as a preservative and the mixture is heated to 70 °C for 1 hour with stirring. This mixture is added to the polyvinyl alcohol binder in a rod mill. After stirring, the resulting mixture is added to the clay suspension in the storage tank.

After overnight storage, several papers were coated with this mixture using an air-wiper coating machine to obtain different basis weights of the resulting coating. The average reflectance measurement results are summarized in Table 1.

TABLE 1

Weight per unit area (g/ ^m2 ) 17

Average reflectance (°/o) 95.9

When a plain sheet of paper was placed on the coated sheet and written on, a bright blue image of the written text was formed on the coated sheet.

After 10 days, the whiteness measurements of the sheet were repeated for a sample with a basis weight of 14 g/m ² and an average reflectance of 94% was found.

After 14 months, the whiteness measurements of the sheet with a surface area of 14 g/ ^m2 were repeated and the average reflectance was determined

93.4%.

Example 9

It illustrates the production of a separate pressure-sensitive copying material by coating on an in-process coating device using a different self-crosslinkable polymer than that used in the previous example.

a) Preparation of microcapsules

The microcapsules used in this example are prepared as described in Example 8.

b) Preparation of the coating mixture and coating kg of polyaminoepichlorohydrin resin, used as a protective agent, and 50 kg of dispersant are dissolved in 210 liters of water in a rod mill. 75 kg of acidic color developing clay and 25 kg of kaolin are then dispersed in this water. The pH of the mixture is slowly adjusted to 10 with 1% sodium hydroxide solution.

178 kg (55 kg dry weight of microcapsules) of the microcapsule suspension prepared as described in paragraph a above are then added to the clay and kaolin suspension. 30 kg of styrene-butadiene latex binder (15 kg dry weight) are then added to the mixture and, after mixing the mixture, the mixture is transferred to a storage vat.

The mixture is coated onto several papers using an air-dried coater20

17 16.7 8.3 96.2 97 96.4 16.7 96.9 14 95.3 14.7 96.7 what; the results obtained are shown in Table 2. are summarized in the TABLE 2 Coating weight (g/m ² ) 5 4 6 Average reflectance (%) 96 96 97

When a plain sheet of paper was placed on the coated sheet and written on, a bright blue image of the written text was formed on the coated sheet.

After 12 days, the whiteness measurements of the sheet with a surface weight of the applied layer of 6 g/m ² were repeated, and an average reflectance of 95% was found.

After 10 weeks, the whiteness measurements of the sheet were repeated with a surface weight of the applied layer of 6 g/m ² and an average reflectance of 96% was found.

Example 10 g of acidic color developing clay and 3 g of kaolin are dispersed in 20 ml of water and one of the preservatives listed in Table 3 below is added. The pH of the mixture is slowly adjusted to 10 with sodium hydroxide solution. Then 38 ml (17% dry matter content) of microcapsule suspension (prepared as described in Example 1) is added. 1% polyvinyl alcohol binder (10 g) is also added. The resulting mixture is then coated onto a paper sheet to achieve a surface weight of 10 g/m ² ; the surface weight of the paper sheet is 49 g/m ² .

After drying, the reflectance is measured at various locations on the leaf using an opacimeter as described in the previous section and the average reflectance value is calculated. The results obtained, together with the results of a control experiment in which no preservative was used, are shown in the following Table 3.

TABLE 3 Protective agent Amount of preservative based on clay weight (%) Average reflectance (%) initial after 10 days None (check) 84.5 81.8 Polyaminoepichlorohydrin resin 10 87.8 85.1 Polyethyleneimine resin 10 91.3 90.7 Fluorine containing paper glue 10 91.2 89.7 Dibutyl ester of sulfo- amber 10 89.4 83.5 Self-crosslinking polymer 5 88.8 84.2 Fluorine containing paper glue 0.5 88.8 84.2

Each coated sheet, treated with a protective agent, was placed under a plain sheet of paper, which was then written on. In all cases, a bright blue image of the written Wxt was produced on the coated sheet.

Example 11

a) Preparation of microcapsules g of acrylamide and acrylic acid copolymers are added to 170 g of deionized water and the mixture is heated to 55 °C. 19 g of resin is added and the mixture is maintained at 55 °C for 40 minutes. Then 105 g of deionized water and 179 g of a solution of a colorless color former are added. The resulting mixture is ground to a droplet size of 4 to 5 microns and cooled to 15 °C. Then 40 g of methylated modified melamine formaldehyde precondensate with a reactive resin content of 76% and a dry matter of 71% and 125 g of deionized water are added and the pH of the dispersion is adjusted to 4.15 with acetic acid. The temperature is maintained at 15 ^° C for 1 hour and then increased to 55 °C and maintained at this temperature for another hour. Finally, the pH is increased to

8.5 sodium hydroxide solution,

b) Preparation of the coating mixture and coating

22.5 g of acidic color developing clay and 7.5 g of kaolin are dispersed in 40 ml of water and one of the preservatives listed in Table 4 below is added to this dispersion. The pH of the mixture is slowly adjusted to 10 with sodium hydroxide solution. Then 65 ml of a suspension of microcapsules with a 30% dry matter content are added. Furthermore, 225 g of wheat starch granules are added to protect the microcapsules against premature breakage together with 15 g of styrene-butadiene binder. The resulting mixture is coated onto a paper sheet to achieve a surface weight of the applied layer of 10 g/m ² ; the paper sheet has a surface weight of 49 g/m ² .

After drying (at 105 °C for 20 seconds), the reflectance of the leaf was measured using an opacimeter at various locations on the leaf and the average reflectance was calculated. The results obtained, together with those of a control experiment in which no preservative was used, are given in Table 4 below.

TABLE 4

Protective agent Amount of preservative based on clay weight (%) Average reflectance (%) initial after 10 days None (check) 0 93.2 92.6 Polyaminoepichlorohydrin resin 10 95 93.9 Sulfonated acid derivative castor oil 10 95.1 94.1 Self-crosslinking polymer 5 94.7 93.3 Fluorine containing paper glue 0.5 Polyethylene emulsion (10% dry polyethylene) 95.1 93.9

Each of the coated sheets treated with the protective agent was placed under a plain sheet of paper, which was then written on. A bright blue image of the written text was created on all of the coated sheets.

Example 12

Example 11 was repeated using some 23 k anionic surfactants as a preservative. For comparison, the test with polyaminoepylchlorohydrin resin and a sulfonated ricinoleic acid derivative was also repeated, as was a control experiment in which no preservative was used. The results obtained are shown in the following Table 5.

TABLE 5

Protective agent Amount of preservative based on clay weight (%) Average reflectance (°/o) initial after 10 days None (check) 0 93.3 92.1 Polyaminoepichlorohydrin resin 10 95.3 94.5 Sulfonated ricinoleic acid derivative 10 95 94.5 Sodium salt of dodecylbenzenesulfonic acid 10 95.1 94.4 Ethylenediaminetetraacetic acid 10 93.9 94.3 Dibutyl sulfo- succinic acid ester 10 95.9 95.3 Dioctyl sulfo- succinic acid ester 10 95.1 94.5 Sodium lauryl sulfate 10 95.3 94.7

Each of the coated sheets treated with the protective agent was placed under a plain sheet of paper, which was then written on. A bright blue image of the written text was formed on all of the coated sheets.

Example 13

22.5 g of acidic color developing material and 7.5 g of kaolin are dispersed in water and one of the preservatives listed in Table 6 below is added to the dispersion thus obtained. The pH of the dispersion is slowly adjusted to 10 with sodium hydroxide solution. Then 65 ml of a suspension of microcapsules with a dry matter content of 30% (prepared in the same way as in Example 11) are added. 22.5 g of wheat starch in grains and 15 g of styrene-butadiene latex binder are further added to the mixture. A sheet of paper is then coated with the resulting mixture to achieve a surface weight of the applied layer of 10 g/m ² ; the paper had a surface weight of 49 g/m ² .

After the leaf has dried, the reflectance is measured at various locations on the leaf using an opacimeter and the average reflectance is calculated. The results obtained, together with the results of a control experiment in which no protective agent was used, are summarized in the following Table 6.

TABLE 6

Protective agent Amount of protective agent based on the initial weight of clay (%) Average reflectance (%) after 10 days

None (check) 0 95.2 94.3 Polyaminoepichlorohydrin resin 10 96.3 95.8 Polyamidopolyamlnoepichloro- hydrin resin 10 95.9 94.9 Self-crosslinking polymer 10 95.9 95.1 Self-crosslinking polymer 15 95.9 95.2 Self-crosslinking polymer 5 95.7 94.9 Fluorine containing paper glue 0.5 Sulfonated acid derivative castor oil 10 96.1 95.3 Self-crosslinking polymer 3 Fluorine containing paper glue 0.3 95.9 95.4

Sulfonated ricinoleic acid derivative 3

Each of the protective coated sheets was placed under a plain sheet of paper, which was then written on.

A bright blue image of the written text was created on all sheets.

Example 14

In this example, microcapsules prepared according to German Patent Specification DOS No. 2,529,427 were used.

22.5 g of acidic color developing clay, 7.5 g of kaolin, one of the preservatives listed in Table 7 below and 40 g of water are mixed and the pH of the resulting mixture is adjusted to 10 with sodium hydroxide solution. Then 50 g of microcapsule suspension with a 40% dry matter content is added, then

22.5 g wheat starch and 15 g styrene-butadiene latex binder. The resulting mixture is coated onto 49 g/m ² paper to give a coating weight of 10 g/m ² ; the coating is dried at 105°C for 20 seconds.

The results obtained are shown in the following Table 7 together with the results of a control experiment in which no preservative was used.

Protective device

No

Polyaminoepichlorohydrin resin

Polyethyleneimine Resin Fluorine Containing Paper Size

Derivative of sulfonated ricinoleic acid

Sodium lauryl sulfate

Sodium salt of secondary alkyl sulfate

Mixture of sodium alkylbenzenesulfonate, sodium ethoxysulfate alcoholate and nonionic alcohol ethoxylate

TABLE 7

Amount of preservative based on clay weight (%) Average reflectance (%) initial after 10 days 0 76.4 64.3 10 90 85.9 10 84.8 81.8 10 85.7 79.5 10 85.7 79.9 10 87 72.3 10 86.4 78 10 85.8 73

Each of the coated sheets, treated with a protective agent, was placed under a plain sheet of paper, which was then written on. A bright blue image of the written text was created on all of the sheets.

by the fact that 65 ml of microcapsule suspension was prepared as in Example 11, and these were used instead of the microcapsule suspension used in Example 14. The results obtained are shown in the following Table 8.

Example 15

The procedure according to example 14 is repeated with the

TABLE 8 Protective agent Amount of preservative based on clay weight (%) Average reflectance (% j initial after 10 days None (control) Polyaminoepichlorohydrin 0 94.9 94.3 resin Sulfonic acid derivative 10 95.4 95 castor oil Sodium salt of secondary 10 96.1 95.6 alkyl sulfate Sodium salt of secondary alkyl- 10 96.2 95.5 17 carbon sulfate 10 96.5 95.8

Each of the coated sheets treated with a protective agent was placed under a plain sheet of paper, which was then written on.

A bright blue copy of the written text was created on all sheets.

Example 16

In this exemplary embodiment, a separate pressure-sensitive copying material is produced using an in-process coating device.

Microcapsules were prepared as described in Example 11, but higher amounts of the individual components were used and the mixture was maintained at 55°C overnight after cooling to 15°C.

22.5 kg of polyaminoepichlorohydrin resin and 296 liters of water are mixed in a propeller melter, then 225 kg of acidic color developing clay is dispersed in the resulting mixture.

The pH of the mixture is then increased to 8 by adding 13.7 g of 47% sodium hydroxide solution. 500 kg (139 kg dry weight) of microcapsule suspension is then added, 225 kg of wheat starch and 75 kg of kaolin are dispersed in the resulting mixture and 150 kg of styrene-butadiene latex binder (75 kg dry weight) is added to the dispersion. The resulting mixture is coated onto a base paper with a basis weight of 47 g/m ² to achieve a basis weight of the applied layer of 14 g/m ² .

Immediately after coating, the average reflectance of the coated sheet was determined.

96.1%, after 10 days 96% and after seven months 94.5%.

When a plain sheet of paper was placed on the coated sheet and written on, a blue image of the written text was formed on the coated sheet.

Example 17

This example shows the use of the method according to the invention for a previously known type of microcapsule. As previously mentioned, the use of these microcapsules does not result in an acceptably light sheet. However, the results obtained using the method according to the invention show that this method provides increased resistance to premature development of the colorless color-forming component at any wall thickness of the microcapsules used.

The microcapsules used in this example were prepared in accordance with the method described in the specification (Example 1) of British Patent Specification No. 1,053,935 except that carboxymethylcellulose was used instead of gum arabic. The microcapsule suspension was divided into 3 doses, namely dose

a), dose b] and dose cj.

The batch is treated with a solution of methylated modified melamine formaldehyde precondensate with a reactive resin content of 80% and a dry matter of 69%, used as a preservative, at a temperature of 60°C for 30 minutes, then allowed to cool.

g of acidic color developing clay is dispersed in sufficient water to form a mixture with a 40% solids content, then the pH of this mixture is adjusted to 10 with sodium silicate.

100 ml of microcapsule suspension is added to the above mixture with stirring and the resulting mixture is coated onto a sheet of paper. A dark blue sheet with an average reflectance of 19% is obtained. Batch b)

The microcapsule suspension is prepared in the same way as in the case of dose a).

g of acidic color developing clay is dispersed in sufficient water to form a mixture with a 40% solids content. To the dispersion obtained, 4 g of methylated modified melamine formaldehyde precondensate with a reactive resin content of 80% and a solids content of 69%, used as a preservative, are added and the mixture is heated to boiling point and then allowed to cool. The pH is then adjusted to 10 with sodium silicate.

10 ml of the microcapsule suspension was then added to the mixture with stirring and the resulting mixture was coated onto a sheet of paper as described above. The paper was again blue and had an average reflectance of 30%, which is better than the 19% determined for the sheet coated with the mixture without the preservative. Dose c)

The microcapsule suspension in this case was not pretreated.

g of polyaminoepichlorohydrin resin, used as a preservative, are added to 60 g of water. 40 g of acidic color developing clay are dispersed in this solution to form a mixture with a 40% dry matter content. The pH of the mixture is adjusted with sodium hydroxide solution while stirring for several minutes.

Then 100 ml of the microcapsule suspension is added with stirring and the resulting mixture is coated on a sheet of paper as described above. The sheet is again blue and an average reflectance of 39% was determined by calculating the average of the reflectances measured at different locations on the sheet. This value is also better than the average reflectance value determined for the sheet coated with the mixture that was not treated with the protective agent (19%).

Microcapsule suspension is adjusted 13%

Claims (8)

SUBJECT A separate pressure-sensitive copying material comprising a sheet material overlaid with mineral color developing material particles and a microcapsule enclosing a colorless coloring agent solution that is reactive with the color developing material to form a color product, characterized in that the microcapsules and the color developing material are contained in The layer also comprises a means for preventing premature color development from the group comprising a self-crosslinkable polymer, for example a self-crosslinkable wet strength agent, anionic surfactant, a fluorine-containing paper sizing agent, a non-crosslinkable wet strength agent , for example, a polyethyleneimine resin, and a substance which is effective to reduce the mutual attraction between the microcapsule and the color developing material particles. Separate copying material according to claim 1, characterized in that it comprises an aminoplast polymer, for example a urea-formaldehyde or melamine-formaldehyde polymer, as a self-crosslinkable polymer. 3. A separate copying material according to claim 1, wherein the self-crosslinkable polymer comprises an epichlorohydrin polymer, for example an aminoepichlorohydrin polymer or an amide-aminoepichlorohydrin copolymer. 4. A separate copying material as claimed in claim 1, wherein the surfactant is a sulfate-containing surfactant, e.g., a lauryl sulfate salt, or a sulfonate containing a surfactant, e.g. acid. 5. A process for producing a separate pressure-sensitive copier of the invention according to items 1 to 4, wherein the sheet material, such as paper, is coated with a coating composition comprising mineral color developing material and a microcapsule enclosing a solution of a colorless coloring agent reactive with a color developing material to form a color product, characterized in that the particles of the color developing material and optionally also the microcapsules are contacted with a protective agent for preventing premature color development from the group comprising a self-crosslinkable polymer, for example a self-crosslinkable wet strength a surfactant, a fluorine-containing paper sizing agent, a non-crosslinkable wet strength agent, such as a polyethyleneimine resin, and a substance that is effective to reduce mutual attraction between the microcapsules and the particles of the color developing material. 6. Process according to claim 5, characterized in that an aminoplast polymer, for example urea-formaldehyde or melamine-formaldehyde polymer, is used as the self-crosslinkable polymer. 7. A process according to claim 5, wherein the self-crosslinkable polymer is an epic-chlorohydrin polymer, for example an amino-epichlorohydrin polymer or an amide-amino epichlorohydrin copolymer. 8. The method of claim 5, wherein the surfactant is a sulfate-containing surfactant, e.g., a lauryl sulfate salt, or a sulfonate containing a surfactant, e.g., a sulfonated ricinoleic acid derivative, dodecylbenzenesulfonate salt or dibutyl ester or dioctyl sulfosuccinate.