EP0197470A2 - Paper spacer for copying - Google Patents

Abstract

The invention relates to microcapsules which within a polymer casing contain at least one hydrophobic substance which is solid at room temperature having a melting point of about 40 to 150 DEG C. The microcapsules conforming to the invention are particularly suitable as so-called spacers in recording systems.

Description

In the simplest case, carbon-free copying systems consist of the top sheet, which is coated on the back with color capsule-containing microcapsules (CB sheet). The underlying sheet has a developer layer (CF sheet) on the top. When copying, the microcapsules in the lettering are destroyed, the color former-containing solution runs out and is transferred to the developer layer underneath, in which the color formers develop into color and thus into copy. If several copies or copies are to be obtained, one inserts between these two sheets the microcapsules containing the developer and the color formers on the underside (CFB sheet). Self-contained papers contain capsules containing developer and developer in a layer on the surface of the sheet. If capsules containing color balance are destroyed during copying, the color or copy is developed in the same coating.

One problem with the production of carbon-free copier papers which contain color formers enclosed in microcapsules is that when the microcapsules are applied to the carrier surface, individual microcapsules protrude from the surface of the applied layer (line). The reason for this can e.g. be that individual microcapsules are too large in diameter, that microcapsules are clustered together to form larger agglomerates, or that, because of the uneven microstructure of the surface of the paper, capsules are fixed on fiber sections protruding from the surface.

If these papers are now loaded in the stack, shifted against each other in the form set, e.g. when rolling or bending a set of forms, or when subjected to local loads, the protruding capsules can break and release the color former solution. The latter then gives a color to the developer layer present and thus leads to the surface of the copy becoming soiled, which can lead to the copy being illegible; i.e. the papers are sensitive to rubbing. For this reason, so-called spacers of the coating containing microcapsules were added at an early stage. The spacers have diameters which are 1.5 to a multiple of the capsule diameter and which therefore protrude from the capsule line and, because of their strength, protect the capsules against unwanted destruction. The known spacers have the disadvantage that they also protect the adjacent capsules if they are to be destroyed when they are copied with a pen (ballpoint pen, pencil) or when they are struck with the lathe of the typewriter. It is known that with increasing content of spacing, the copy becomes more difficult to read and its intensity becomes lower. For this reason, a compromise must ultimately be made between the sensitivity to friction of the layer containing the color formers in microencapsulated form and the quality of the copy or the copy intensity.

The first technically used spacers were short cellulose fibers, also called cellulose fiber cuts. They result in a significant reduction in the sensitivity to friction of the layer containing the encapsulated color formers both in the case of CB and also so-called two-layer papers (self-contained paper).

The coating compositions containing microcapsules and cellulose fibers were first applied to the paper coating supplements with an air brush as an aqueous coating color on paper and dried. This application method has the disadvantage of the lower coating speed. At higher speeds, doctor blades, roller scrapers and smoothing scrapers are required. It was found that the cellulose fibers to form matted masses e.g. in front of the smoothing scraper and therefore an error-free, even coating of the paper is not possible. At the same time, the cellulose cut accumulates in the Sireich color supply.

As a result, other materials were sought to be used as spacers.

DE-OS 19 15 504 describes the use of particles of starch or starch derivatives as spacers, the size of which is 1.5 to 2 times the size of the microcapsules. According to DE-OS 25 25 901, starch grains with grain sizes from 20 to 75 µm from different types of peas are suitable as spacers.

DE-PS 870 837 discloses the use of water-soluble, preferably soy protein particles with 10 to 50% by weight, based on microcapsules.

EP-A-6599 describes polyolefin powder, optionally together with starch granules, as a spacer for layers containing microencapsulated color formers.

From US Pat. No. 4,211,437 it is known to use kaolin particles coated with gelatin, which are stick-shaped and whose diameter is 2 to 12 times larger than that of the microcapsules containing the color formers, as spacers.

US Pat. No. 4,280,718 describes grains of cereal starch with a diameter of 14 to 20 μm crosslinked with urea-formaldehyde as spacers.

According to US Pat. No. 4,327,148, polyolefins, such as polyethylene, polypropylene or polystyrene, and also their copolymers and mixtures with a softening point of at least 70 ° C. in the form of aqueous dispersions, the particles of which have a diameter of 5 to 30 μm, can be used as spacers will.

According to JP-OS 092 591 (1983), particles of amylose inclusion compounds with diameters of 1.5 to 10 times the microcapsule diameter are suitable as spacers.

All of these isometric spherical particles are hard. When used as a spacer, the ratio of improved friction sensitivity to copy intensity is not as good as when using cellulose fibers. The cause may be that the binding of the particles on the paper leaves something to be desired because of their spherical shape, that they are therefore released from the coating when rubbed and destroy capsules when rolled.

According to the information in DE-OS 19 55 542, larger microcapsules (3 to 5 µm), which contain pure solvent, with smaller microcapsules (0.5 to 2.5 µm), which contain color former solutions, in a ratio of 3: 1 mixed and applied to paper. The larger, solvent-only capsules are designed to protect the smaller from accidental destruction. If the larger capsules with the liquid content are destroyed, no discolouration occurs. In the event that all capsules are intentionally destroyed, the color former transfer and thus the development of the color on the CF layer is improved. However, this system has not proven itself. The pressures required to destroy the large capsules are too low, but are usually sufficient to also destroy the color former capsules. In addition, it was found that the additional solvent on middle sheets, i.e. in CFB sheets, diffuses from the underside to the top of the paper, taking color formers with it and enhancing the copy, but at the same time sometimes also the lettering. widened to illegibility. The copying intensity of the last sheet (CF sheet) drops with this combination compared to that of the CFB sheets.

The object of the present invention was to provide particles which can be used as spacers and which do not have the disadvantageous properties of the spacers of the prior art.

This object is achieved according to the present invention in that microcapsules are used as spacers which contain at least one hydrophobic substance which is solid at room temperature as the core.

Accordingly, the invention relates to microcapsules which contain in a shell made of a polymer at least one hydrophobic substance which is solid at room temperature and has a melting point of about 40 to 150 ° C.

The microcapsules according to the invention can be used in the form of an aqueous dispersion or as such in the form of powder.

The microcapsules according to the invention can be admixed with the dispersion of the microcapsules containing color formers, a homogeneous dispersion having virtually unchanged rheological properties. In combination with microcapsules containing color formers, the microcapsules according to the invention give a significantly to considerably higher color intensity, i.e. a significantly to considerably higher yield of color than when using the same amount of color formers containing microcapsules together with spacers of the prior art.

The microcapsules according to the invention, also referred to below as spacer capsules, can be used according to all known encapsulation processes _. Ren are produced, as far as they can be carried out at temperatures above the melting point of the encapsulated, hydrophobic core material. Examples of suitable processes are: gelatin coacervation, interfacial polycondensation to polyesters or polyamides, interfacial polyaddition to polyureas or polyurethanes, the deposition of polymer films by precipitation from polymer solutions or the homo- and mixed condensation of urea and / or melamine with formaldehyde. Encapsulation by polycondensation of melamine with formaldehyde or of precondensates based on melamine-formaldehyde is preferred. To stabilize the resulting capsule dispersions, the suitable water-soluble polymers, for example polyvinyl alcohol, salts of polyacrylic acid, copolymers of polymerizable di- or polycarboxylic acids with vinyl isobutyl ether, ethylene and / or (meth) acrylic esters, cellulose derivatives and polymers or copolymers of monomers bearing sulfonic acid groups can be used. Furthermore, low molecular weight surface-active substances can also be used to stabilize the resulting capsule dispersion. In some cases you can even do without these water-soluble stabilizers.

As to be encapsulated solid hydrophobic sub _- punch are those with melting points of about 40 to 150 ° C, preferably those of 50 to 85 ° C, into consideration. The hydrophobic substances have penetrometer index values of 0.5 to 200, preferably 1 to 120. Waxes or wax-like substances are particularly suitable as solid hydrophobic substances; for example plant waxes that are largely free of higher molecular fatty acids, such as candelilla wax or camauba wax; Hydrocarbon waxes such as paraffins, ozokerite or microcrystalline waxes; higher molecular weight fatty alcohols such as octadecanol or ester waxes, which are free of higher carboxylic acids. Wax-like polymers, for example polyethylene waxes or preferably polyvinyl ether waxes, can also be used as core material for the microcapsules according to the present invention. The waxy substances can be used alone or as a mixture. Mixtures containing low melting substances can also be used. Such mixtures allow the melting point and the penetrometer index, ie the hardness of the wax-like filling, to be varied. For technical reasons, the hydrophobic substances should be as colorless as possible or only slightly colored.

The easiest way to determine the plasticity of the waxes is to use the penetrometer index at 20 ° C in accordance with DGF-M-III 3 (standard of the German Society for Fat Science). It should be between 0.5 to 200, preferably between 1 to 120. The values indicate the penetration depth of a needle in 5 seconds in 1/10 mm. The values are identical to those obtained by the needle penetration method according to ASTM-D-1321-61 T.

However, other methods for characterizing the wax can also be used, which accordingly give different numbers, e.g. the Hoeppler hardness at 20 ° C according to DGF-M-II.3.

The capsules obtained by the above-mentioned processes are isometric or spherical. In terms of shape, they are ideally suited for use on fast-running paper coating systems with e.g. Smooth scrapers can be processed without complications. Due to the fact that the capsules are produced above the melting point of the core material, the wax suffers a considerable volume loss when it cools down and crystallizes out.

This is not compensated for by the capsule shell due to its cross-linking and the usually reduced coefficient of thermal expansion. This is particularly true for the capsule walls made of melamine-formaldehyde condensates. There are therefore dents in the spherical surface of the capsules. The capsules with walls based on melamine-formaldehyde condensates are usually only one or two larger dents. Scanning electron micrographs show that the capsules usually lie on the surface with the DeHe and therefore lie wider and are therefore more firmly bound than exactly spherical particles. The capsules can be in the form of the aqueous dispersions obtained in the preparation as well as in powder form, e.g. after spray drying or after sieving or centrifuging and drying e.g. in a paddle dryer.

The application-related advantage of the wax-containing capsules according to the invention is that the capsules are firm and are real spacers due to their firm, waxy consistency of the core at low pressures, such as occur, for example, when stacking papers in a stack or rubbing the papers against one another Act. They protect the microcapsules containing color formers from destruction. At higher pressures, such as occur during writing, the cores of the microcapsules according to the invention can flow or deform or the capsules can be crushed and thus also enable the capsules containing adjacent color formers to be destroyed. It has been found that with an increasing proportion of the spacer capsules, the sensitivity to friction of a layer containing microencapsulated color former is significantly reduced, but at the same time the intensity and the excellent legibility of the copy are retained. This applies in particular to small microcapsules containing color formers. This is a decisive advantage for the application compared to the spacers of the prior art. As a result, when using the microcapsules according to the invention as spacers, the content of capsules containing color former can be reduced. The ratio of spacer capsules to capsules containing color formers can vary from 0.03: 1 to 2: 1. The ratio is preferably between 0.06: 1 and 0.9: 1. Of course, the size of the spacer capsules in relation to the capsule containing the color former also plays a role. In general, it has been found that the spacer caps reduce the friction sensitivity of the CB layer as the size increases. The spacer capsules according to the invention work well when they are 1.5 to 10 times the diameter of the microcapsules containing color formers, ie the distance Switch capsules should have average diameters of 5 to 50 µm, preferably 6 to 35 µm and especially 7 to 30 µm. Spacer capsules that are too large are disadvantageous since they can reduce the sharpness of the copy image.

By using waxes with low plasticity, the resistance to friction against increasing pressure can be increased. If necessary, the coating color can also be admixed with certain amounts of the hard, non-plastic spacers used hitherto. In this case, one has to accept a decrease in the intensity of the copy or compensate for it by a larger proportion of the capsules containing the color former.

The composition of the coating colors comprising capsules containing binder, binder, spacer capsules and water is not significantly changed by the spacer capsule of the present invention. The proportions of the components must be optimized if necessary.

The previously used coating colors are suitable as binders in the microcapsules: e.g. Polymer dispersions based on homo- and copolymers of vinyl acetate, - (meth) acrylic esters, butadiene, styrene and other ethylenically unsaturated, copolymerizable monomers; In addition, water-soluble high polymers can be used, optionally together with polymer dispersions. The optimal binder can easily be determined by simple series tests.

The following examples are intended to illustrate the invention. additionally explain. The parts and percentages given below refer to the weight.

In the examples, the range of the most common capsule diameters is given not according to the microscopic assessment, but the range. The mean capsule diameter is the arithmetic mean of the two capsule diameters specified.

A) Test procedure

Examination of the capsule line for intensity of copy and sensitivity to rubbing.

A. 1. Preparation of the capsule coating

• a) The coating composition containing microcapsules is generally prepared as follows:
• • 8.25 parts of microcapsule dispersion containing color formers, 40%, 11.75 parts of water
  • 1.30 parts of a 50% commercial binder dispersion based on a copolymer of styrene and butyl acrylate and
  • 1.30 parts spacer 100%
  are added to the jar and mixed. If water-containing spacer dispersions are added, the water content is subtracted from the 11.75 parts of water.
• b) The coating material thus produced is applied by hand to a coating base paper of 40 g / m ² by means of a wire spiral doctor blade — the gap width is between 10 and 30 μm in most cases at 25 μm, depending on the desired application weight the coated paper is then dried for 30 minutes: in the air or with a fan heater in a shorter time.
  Each 100 cm ^{2 of} the uncoated and the coated paper are weighed and the coating weight in g / m ^{2 is} determined from the difference.

A. 2. Intensity of copy

The sheet coated according to A.1) is placed with the coated side on a CF sheet. 2 layers of paper of approx. 40 g / m ^{2 are} placed on top. This stack is clamped in an electric typewriter and with the greatest keystroke a field of 4.2 x 3.4 cm is written with the letter small w, the letters in the line directly next to one another and the lines being arranged one above the other. After 30 minutes of storage, the intensity - (ID) of the copy obtained on the fourth sheet is determined as the difference in the reflection of the blank (Ry _o ) and the described (Ry _m ) CF sheet. The reflection was measured in a reflection photometer with the filter Y (Elrepho @, from Zeiss).

The information is given in relative units (%): ID = Ry _o -Ry _m . The reflection of the blank white CF sheet is generally 85%.

A. 3-Friction sensitivity of the capsule-containing spread

The sheet coated according to A.1) - minimum length: 29 cm - is placed with the coated side up on a flat surface made of synthetic leather that has been sanded on both sides. A CF sheet is placed on top with the slave layer facing down to the capsule-bearing layer. A metal disc 50 mm in diameter and 8 mm in thickness is carefully placed on the CF sheet at one end. The disc has an equal-sized, 2 mm thick felt cover on the lower side. A 106 mm long cylindrical dome with a 5 mm diameter protrudes from the center of the disc (weight of the disc total 137.7 g). 4 metal discs with a 6 mm 0 hole in the middle are put over the dome. Weight per slice: 1000 g. The arrangement loads the paper surface with a pressure of 2.1 N / _cm2 .

To check the sensitivity to friction, the CF sheet is now touched at the end and slowly, by hand, together with the weight on it, is pulled exactly 22 cm far over the capsule-bearing paper with the CB layer. The weight is carefully removed. Under the contact surface, the CF paper is more or less discolored depending on the friction sensitivity of the CB line. The intensity (IR) of the discoloration is measured with the reflection photometer as in A2) and given in relative units (%).

A. 4. Adhesion of the microcapsule and spacer-bearing layer

• Ein Selbsklebeband wurde mit leichtem Fingerdruck auf die mit Kapseln beschichtete Seite geheftet und sofort wieder abgezogen. Die Trübung des Selbsktlebebandes durch aus der Schicht herausgerissene, daran haftende Kapseln und Fasern wurde subjektiv nach Noten bestimmt:
• Die Haftung war in allen in den Beispielen aufgeführten Beschichtungen gut und vergleichbar mit technisch hergestellten CB-Blättern und wird deshalb in den Beispielen nicht gesondert vermerkt.

The adhesion of the layer containing capsules was determined as follows:

• A self-adhesive tape was attached to the side coated with capsules with light finger pressure and removed immediately. The cloudiness of the self-adhesive tape due to capsules and fibers torn out of the layer and adhering to it was determined subjectively according to notes:
• The adhesion was good in all of the coatings listed in the examples and was comparable to industrially produced CB sheets and is therefore not separately noted in the examples.

A. 5. Font sharpness

The sharpness of the lettering and the associated legibility of the copy was subjectively determined in comparison with the sharpness of commercially available carbonless papers. It was good in all cases and comparable to the paper available on the market. The sharpness did not become worse with increasing amount of spacer capsules. It is therefore not noted in the examples.

B. Examples: example 1

In a cylindrical 4 1 stirring vessel, which can be heated from the outside, into which there is a coaxially arranged stirring shaft, which at the end has a helical toothed lock washer (diameter 5 cm) - (Pendraulik laboratory mixer, type LD 50, manufacturer: Pendraulik, Bad Münder), immersed, 940 g of water and 160 g of a 20% solution of poly-2-acrylamido-2-methylpropanesulfonic acid / sodium salt (viscosity: 885 mPas; K value: 129) are mixed with formic acid to pH = 5.0 set and heated to 76 ° C. Then paraffin (melting point 69 to 73 ° C., penetrometer index 9) is slowly added in the form of a melt, the temperature of which is slightly above the melting point. The speed of the toothed disk stirrer is slowly increased to the final value of 4500 rpm with increasing filling level. The pH is checked and, if necessary, adjusted to pH = 5.0. At 4500 rpm, 252 g of a clear solution of 120 g of a partially methylated precondensate (containing about 2.3 CH ₂ O groups per melamine molecule) of 1 mol of melamine and 5.25 mol of formaldehyde in 132 g of water are then added in one hour . The temperature is kept at 76 ° C. and the pH is kept constant at pH = 5.0 by metering in 10% formic acid. After the precondensate has been added, the dispersion is immediately transferred to a stirrer with a propeller stirrer and heated from 76 ° C. in 1 hour to 80 ° C. with intensive stirring (1000 rpm) and stirred at 80 ° C. for 2 hours. Then the dispersion is adjusted to pH = 8.5 with triethanolamine and cooled. The dispersion is sieved through a sieve with a mesh size of 1 mm, leaving a negligible residue on the sieve. The dispersion obtained is colorless, milky and, according to microscopic assessment, contains' individual capsules, predominantly 8 to 18 µm in diameter, individual ones Capsules have a maximum diameter of 40 µm. The solids content is 41.0% (determined by drying a sample at 105 ° C. for 2 hours). As a result of the volume shrinkage during cooling and crystallization of the paraffin, almost all of the capsules have a deep indentation or dent in the otherwise spherical and somewhat fine-grained surface.

Example 2

The procedure is exactly the same as in Example 1, but the speed of the disk stirrer is set to 3700 instead of 4500 rpm, so that larger capsules are formed.

A capsule dispersion with capsules with a common diameter of 10 to 25 μm is obtained. Individual capsules have a diameter of up to a maximum of 40 .mu.m after microscopic measurement. The solids content of the dispersion is 38.0%. These capsules also have a large round dent in their spherical surface.

Example 3

The procedure is as in Example 1, but a paraffin with a melting point of 52 to 54 ° C and a penetrometer index of 30 is encapsulated. Temperature: 60 ° C, pH = 4.5, disc stirrer: 4500 rpm.

A capsule dispersion is obtained, the capsules of which have a common diameter of 8 to 18 μm. Individual capsules have a diameter of up to a maximum of 40 µm. Solids content: 43.0%. The capsules have a larger dent in their spherical surface.

Example 4

The procedure was as in Example 3, but the disk stirrer was set to 2500 rpm. The resulting capsule dispersion has a solids content of 45.2%. The spherical capsules have a common diameter of 10 to 45 µm. Their surface is very slightly roughened and has 1 to 2 deep dents in the spherical surface (diameter of the dent 70 to 80% of the sphere diameter, measured on the sphere surface).

Example 5

The procedure was as in Example 3, but the disk stirrer was set to 6500 rpm. After the pre-condensate had been added, the speed of rotation of the disk stirrer was reduced to 5000 rpm. Then 81.5 g of the 20% solution of poly-2-acrylamido-2-methylpropanesulfonic acid / sodium salt used in Example 1 were added in 2 minutes, and then 252 g of the clear solution containing 120 g of the one given in Example 1 were partially added methylated precondensates from melamine and formaldehyde. The stirrer was then switched off, the dispersion was added to the flask equipped with a propeller stirrer and worked up further as in Example 1.

A capsule dispersion was obtained, the capsules of which contain twice the amount of wall material and which have a common diameter of 2 to 8 μm. Individual capsules have a diameter of up to 12 µm (according to microscopic assessment). Solids content: 41.4%.

Example 6

The procedure was as in Example 5, but the speed of the disk stirrer during the capsule formation was 5500 rpm. Towards the end of the addition of the precondensate, it was raised to 6000 rpm.

When the second portion of the precondensate was fed in, the mixture was stirred at 2500 rpm.

A colorless, milky dispersion, the capsules of which most frequently have a diameter of 4 to 12 μm, was obtained. Individual capsules have a diameter of up to 20 µm. Fixed salary: 42.3%.

C.I. Examination of the paraffin-containing capsule dispersions obtained according to Examples 1 to 6.

The microcapsule dispersion containing color formers indicated below was processed to coating compositions without spacers and the spacer capsules of Examples 1 to 6 and with spacers of the prior art according to A1.a) and applied to paper according to A1.b).

The applied weight was determined on the coated papers obtained, and the intensity of the copy according to A2) and the sensitivity to rubbing according to A3).

The results are summarized in Table 1.

The microcapsule dispersion containing color former used was prepared according to EP-B-26 914, Example 1, but a mixture of dodecylbenzene and diisopropylbenzene in a weight ratio of 1: 1 was used as the solvent for the color former. The capsule provides blue copies. The most common diameter of the capsule is 2 to 5 u.m. Solids content: 40%.

If one considers in Table 1 the copy intensity (ID) and the sensitivity to rubbing - (IR) of the capsule lines which contain spacer capsules according to the invention with practically the same amount of color formers containing microcapsules of 4.5 to 4.7 g / m ² , it is established a clear influence of the diameter of the spacer capsule. With increasing diameter from 2 to 8 µm (coating 5) to 10 to 25 µm (coating 2), the friction sensitivity IR drops from 23 to 15%. The copy intensity (ID) even improved a little from 47 to 51%. The spherical spacers with diameters of 2 to 8 microns are only slightly larger than the capsules containing color formers used with 2 to 5 µm in diameter, so that the spacer capsules cannot protect the latter on the uneven paper surface in all cases from possible destruction when rubbing. The comparison of the IR values shows that spacer capsules of 10 to 25 µm in diameter show the best protective effect. This diameter comes very close to the dimensions of the commercially available spacer cellulose cut with a width of 5 to 15 µm and a length of 20 to 60 µm, but above all the special thickness K with a diameter of 20 to 30 µm. If one compares the intensity and sensitivity to friction of the capsule coating produced with paraffin-containing microcapsules as spacers with those produced with spacers of the prior art, the advantages of the capsules according to the invention are very clear. The drift intensity drops to 51% instead of ID = 45% or 46%. The friction sensitivity, however, is much lower with IR = 15 than that of the others with IR = 20% or 26%.

With the same total order weight, the order for microcapsules containing color formers drops to approx. 2/3. The sensitivity to friction decreases from IR = 30% or 31% to IR = 10 or 8%. The intensity of the copy from ID = 55 (achieved with capsules containing 20% more color formers) or ID = 51 (with capsules containing color formers containing almost the same amount) only drops to 50 to 49%. This means that the capsules according to the invention containing paraffin not only significantly reduce the sensitivity to friction of the CB layer, but also allow the use of smaller amounts of microcapsules containing color formers, with practically the same intensity of copy.

Because of the consistency of the paraffin, the copying capacity hardly increases with increasing amount, the sensitivity to friction of the paper or. the CB layer significantly reduced.

• a) Nach A1.a) und A1.b) wurden Beschichtungsmassen und beschichtete Papiere mit zunehmender Menge an Paraffin enthaltenden Kapseln des Beispiels 2 (Durchmesser 10 bis 25 µm) hergestellt. Die Ergebnisse der Messungen der Intensität der Durchschriften und der Reibempfindlichkeit sind in der Tabelle 2 zusammengestellt.
  

• b) In weiteren Versuchen wurden wie vorstehend bei C.II.a) Beschichtungsmassen - (Streichfarben) mit kleineren Abstufungen im Gehalt an Paraffin enthaltenden Mikrokapseln als Abstandshalter hergestellt. Hierbei wurde der Anteil an Farbbilnder enthaltenden Mikrokapseln um den gleichen Beitrag vermindert. Die Zusammensetzung der Streichfarben und die Ergebnisse der Prüfung auf Intensität der Durchschrift und der Reibempfindlichkeit der mit diesen Streichfarben beschichteten Papiere ist in der Tabelle 3 zusammengefaßt.

C.II. Examination of the influence of the content of paraffin-containing microcapsules on the. Properties of the CB line

• a) According to A1.a) and A1.b), coating compositions and coated papers with increasing amount of paraffin-containing capsules of Example 2 (diameter 10 to 25 μm) were produced. The results of the measurements of the intensity of the copies and the sensitivity to rubbing are summarized in Table 2.
  

• b) In further experiments, coating compositions (coating colors) with smaller gradations in the content of paraffin-containing microcapsules as spacers were produced as in C.II.a. The proportion of microcapsules containing colorants was reduced by the same amount. The composition of the coating colors and the results of the test for the intensity of the copy and the sensitivity to rubbing of the papers coated with these coating colors are summarized in Table 3.

Microcapsules containing color formers were the same as in C.I. used.

Microcapsules produced according to Example 2 were used as spacers.

1.30 parts of the binder specified under A1.a) were used in all coating colors.

Vergleichsbeispiel 1

• a) Durch Kondensation eines Melamin-Formaldehydvorkondensates in Wasser wurden kugelige Melamin-Formaldehyd-Harz-Teilchen hergestellt. Die erhaltenen Teilchen haben weder einen Schmelzpünkt noch haben sie wegen ihrer Härte eine meßbare Eindringtiefe, d.h. der Penetrometerindex ist 0 (null). Die Teilchen haben einen häufigsten Durchmesser von 12 bis 20 µm.

The results in Table 3 show that, in spite of the decreasing amount of microcapsules containing color formers in the line, the sensitivity to friction decreases with increasing amount of spacer capsules according to the invention, but the intensity of the copy changes only slightly. The comparison of the coating comparison 4 and coating 2.5 shows the superior effect of the spacer capsules according to the invention over cellulose grinding.

Comparative Example 1

• a) Spherical melamine-formaldehyde resin particles were produced by condensing a melamine-formaldehyde precondensate in water. The particles obtained have neither a melting point nor a measurable depth of penetration because of their hardness, ie the penetrometer index is 0 (zero). The particles have a common diameter of 12 to 20 µm.

In a second experiment, the small particles from experiment a) were agglomerated very slightly.

Capsule lines were prepared from the capsules obtained after both experiments in accordance with A.1). For comparison, a capsule coating was made with cellulose-cut fiber. A capsule containing black copies with a most common diameter of 3 to 6 μm was used as the capsule containing color formers (produced according to EP-B-26 914, example 6).

The result of the test is shown in Table 4. The values for the sensitivity to friction clearly show that the hard balls worsen the sensitivity to friction. In contrast, the intensity of the copy is not noticeably changed.

Comparative Example 2

Vaseline (white, DAB, penetrometer index> 200) is encapsulated according to the information in Example 3. The speed of rotation of the disc stirrer was 4000 rpm. The resulting capsule dispersion has a solids content of 44.4%. The capsules are spherical with a single dent from time to time. The most common diameter was 5 to 15 µm.

Example 3.1

If you work according to example 3 with paraffin (melting point 52 to 54 ° C.) at 4000 rpm of the disk stirrer, a dispersion with a solids content of 43.0% is obtained. The capsules are spherical with one or two very clear, large indentations. The most common diameter is 5 to 15 u.m.

The capsule dispersions and cellulose fiber cut (Arbocel B 600/15) obtained according to Comparative Example 2 and Example 3.1 were used as spacers for the production of CB coating colors according to A.1) and the papers obtained were tested according to A.2) and A.3). The microcapsule dispersion specified under C.I was used as the microcapsule containing color formers.

The amount applied and the result of the test for the intensity of the copy and the sensitivity to rubbing are summarized in Table 5.

The values for the sensitivity to friction show that the soft, pasty petroleum jelly in encapsulated form is not able to protect the capsules containing color formers from being destroyed. Your sensitivity to friction is high; IR 31%. In comparison, the paraffin-containing capsule has an IR value: Both capsules resist the destruction of the color former capsules when writing less resistance than the cellulose fiber cut, so that the intensity of the copy is significantly higher than that of the cellulose cut (49 and 50 instead of 45%).

Example 7

The procedure is as in Example 3, but a mixture of 35 parts of paraffin with a melting point of 69 to 73 ° C. (penetrometer index: 9) and 66 parts of petroleum jelly (white, DAB, penetrometer index> 200) is used. The mixture has a melt index of 52 to 54 ° C and a penetrometer index of 100. Speed of rotation of the disc stirrer: 4000 rpm. The result is a dispersion with a solids content of 44.6% and spherical capsules of the most common diameter from 5 to 18 u.m. The capsules show significant dents, 1 to 2 per capsule.

The capsule coating produced according to A1.a) and A1.b) has a total application weight of 7.4 glm ² . The copy had an intensity of ID = 49 and a sensitivity to rubbing of IR = 20%. The values correspond to those obtained with cellulose cut as a spacer.

Example 8

The procedure is as in Example 7, except that the disk stirrer has a rotational speed of 3000 rpm at pH = 5.0 and 80 ° C. The feed time of the melamine-formaldehyde precondensate was 30 minutes. A mixture of 60 parts of paraffin (melting point 69 to 73 ° C.) and 34 parts of petroleum jelly (white, DAB, penetrometer index> 200) was encapsulated. The mixture has a melting point of 55 to 62 ° C and a penetrometer index of 41. The resulting dispersion had a solids content of 43.0% and contains spherical capsules with 1, rarely 2 distinct dents with a common diameter of 10 to 30 µm.

The capsule (CB) line produced according to A1.a) and A1.b) has an application weight of 7.4 g / m ³ . The intensity of the copy is ID = 47%, the sensitivity to rubbing IR = 6.

Example 9

The procedure is as in Example 3, but instead of paraffin octadecanol with a melting point of 59 ° C. and a penetrometer index of 2 to 3 is used. So that a melt is present, it was encapsulated at 65 ° C. The disc stirrer runs at 3000 rpm. A capsule dispersion with a solids content of 44.4% was obtained. The spherical capsules have a diameter of 5 to um and have 1 or 2 larger dents in their surface.

Capsule coats according to A1.a) and Ab) were produced with these capsules using the microcapsules containing color formers specified under CI. Total coating weight: 7.5 g / m ^2. Intensity of the copy ID = 47%. Friction sensitivity IR = 16%.

Example 10

The procedure is as in Example 1. However, a relatively hard, colorless and cloudy microcrystalline hydrocarbon wax (Ozokerit GS 21208), (melting point: 64 to 67 ° C; penetrometer index: 18) at 80 ° C, pH = 4.5 and 65 minutes feed time of the melamine-formaldehyde - Pre-condensate encapsulated at 6000 rpm of the disc stirrer.

A colorless, milky dispersion with a solids content of 46.9% was obtained, which contains spherical capsules with a common diameter of 6 to 18 μm. The capsules have 1 to 2 clear, deep dents in their surface.

The spread produced according to A1.a) and A1.b) has a total weight of 7.5 g / m ² . Intensity of the blue copy ID = 49%. Friction sensitivity IR = 14%.

Example 11

Example 10 was repeated, but a brownish, somewhat softer microcrystalline hydrocarbon wax (ozokerite BH 447) - (melting point 60 to 70 ° C., penetrometer index: 23) at 75 ° C., pH = 5.0 and 60 minutes feed time of the melamine Encapsulated formaldehyde precondensate. The high-speed stirrer turned at 6000 rpm.

A slightly yellowish, cloudy dispersion with a solids content of 45.6% was obtained. The spherical capsules had a common diameter of 8 to 30 µm and at least one significant dent.

The spread prepared according to A1.a) and A1.b) has a total weight of 7.5 g / m ² ; Intensity of the blue copy ID = 45%; Friction sensitivity IR = 10%.

Example 12

The procedure was as in Example 11, but a relatively soft, yellowish microcrystalline hydrocarbon wax (Ozokerit GS 2115) - (melting point 66 to 70 ° C., penetrometer index 24) was encapsulated.

The colorless, cloudy dispersion has a solids content of 46.3%. The spherical capsules have a common diameter between 4 and 24 µm and all have at least one indentation.

The spread produced according to A1.a) and A1.b) has a total weight of 7.6 g / m ² . Intensity of the blue copy ID = 49%; Friction sensitivity IR = 17%.

Example 13

The procedure is as in Example 3, but instead of the paraffin a colorless polyvinyl ether wax (M.G. melting point 45 to 48 ° C; penetrometer index from 0 to 1) is encapsulated. The disc stirrer rotates at 5000 rpm.

The resulting colorless, milky dispersion has a solids content of 43.6%. The capsules contained therein have a common diameter of 20 to 45 µm, individual capsules up to 100 µm. The surface of the spherical capsules is rough and shows a small indentation.

The CB line produced according to A1.a) and A1.b) has a total line weight of 7.6 g / m ^2. Intensity of the copy ID = 49%; Friction sensitivity IR = 11%.

Example 14

360 g of water are placed in the apparatus of Example 1. Then 122 g of a solution of 50 g of pig skin gelatin and 72 g of water with 970 g of a solution of 25 g of gum arabic in 945 g of water are added at 60 ° C. The pH is adjusted to pH 5.8 with 10% sodium hydroxide solution. The disperser disk stirs at a speed of 3500 rpm. A melt of 150 g paraffin (melting point 52 to 54 ° C., penetrometer index = 30) is then added in one minute and, after the speed of the disk stirrer has been raised to 5000 rpm, the liquid paraffin is brought to particle diameter in 10 minutes dispersed from 10 to 30 µm. The resulting dispersion is transferred to a glass flask with a propeller stirrer (propeller diameter 1/3 of the cross-section of the container) at a speed of 1200 rpm, in which 360 g of water at 60 ° C. had previously been placed, and the pH slowly became 10% Formic acid reduced to 4.8 within 40 minutes. The gelatin coacervate separates around the individual paraffin melt particles, visible in the microscope. 8 g of 37% formaldehyde solution in water are added, the speed of rotation of the disk stirrer is raised to 1800 rpm and the dispersion is cooled to 5 ° C. with an ice bath. 2 hours after the temperature of +5 _° C. had been reached, the pH was raised to pH = 8.3 with 10% sodium hydroxide solution within half an hour, the ice bath was removed and the dispersion was stirred for a further 2.5 hours.

The dispersion is then sieved through a sieve with a mesh size of 1 mm without any significant residue. The solids content is 12.0%. The paraffin-containing capsules are spherical with a clearly indented surface and have a diameter of 10 to 30 µm.

The CB coating produced according to A1.a) and A1.b) of this capsule has a total coating weight of 8.1 g / m ² ; Intensity of copy ID = 47%; Friction sensitivity IR = 26%.

Example 15

The procedure is as in Example 14, but instead of 50 g of pork skin gelatin and 25 g of gum arabic, 29.0 g of pork skin gelatin and 3.2 g of a carboxymethyl cellulose (Tylose C 1000 from Kalle) were used. Instead of the disk stirrer, a Turrax 45 N from Jahnke & Kunkel with a speed of 8000 rpm is used for the dispersion. The primary capsules with a diameter of 2 to 5 µm agglomerate when the pH is adjusted to 5.18 to spherical to ellipsoidal agglomerates of 20 to 60 µm in diameter. After curing, a dispersion with a solids content of 10.5% is formed.

The CB coating produced according to A1.a) and A1.b) with these agglomerated capsules has a total application weight of 7.4 g / m ² . Intensity of the legible copy ID = 47; Friction sensitivity IR = 20%.

Example 16

In the apparatus of Example 1, 1511 g of water and 366 g of a 15% solution of a polyacrylic acid / sodium salt (K value according to Fikentscher: 165) are mixed with stirring, heated to 80 ° C. and adjusted to pH = 5.0 with formic acid . 458 g of melted paraffins (melting point 69 to 73 ° C., penetrometer index = 9) are dispersed in this mixture at a speed of rotation of the toothed disk stirrer of 4000 rpm. Thereafter, 178 g of a clear solution of 68.6 g of the precondensate of melamine and formaldehyde given in Example 1 in 109.4 g of water are run in at a constant rate in 30 minutes. The pH is kept constant at 5.0, the temperature at 80 ° C and the speed of rotation at 4000 rpm. 5 minutes after the addition, the dispersion is transferred to a flask with an anchor stirrer and condensed at 80 ° C. for 2 hours. Then it is cooled and adjusted to pH = 7.0 with triethanolamine.

After sieving there is only an insignificant sieve residue. The thin, colorless, milky dispersion has a solids content of 23.8%. The spherical, individual microcapsules show dents in the surface and have a common diameter between 12 and 36 µm.

The CB coating produced according to A1.a) and A1.b) with this paraffin-containing microcapsule as a spacer has a total coating weight of 7.6 g / m ² . Intensity of legible copy ID = 47%; Friction sensitivity IR = 8%.

Example 17

Example 16 is repeated with the following change: 957 g of water and 142 g of the solution of the polyacrylic acid / sodium salt are introduced, then 800 g of molten paraffin are introduced and 252 g of the precondensate solution are used for the encapsulation. A low-viscosity dispersion with a solids content of 44.7% and spherical, slightly indented capsules (most common diameter: 6 to 30 μm) was obtained.

The CB coating produced according to A1.a) and A1.b) has a total coating weight of 7.8 g / m ² . Copy intensity ID = 48%; Friction sensitivity IR = 10%.

Example 18

Example 17 is repeated, but instead of the solution of 142 g of polyacrylic acid / sodium salt (15%), a solution of 32 g of a copolymer of vinyl methyl ether and maleic anhydride (1: 1 parts by weight; K value according to Fikentscher: 90, corresponding to a molecular weight 100,000) as the sodium salt in 111 g of water. The toothed disk stirrer has a rotation speed of 5000 rpm.

The slightly viscous dispersion obtained has a solids content of 40.3%. It contains spherical, slightly dented capsules with a common diameter of 6 to 24 µm.

The CB coating produced from this according to A1.a) and A1.b) has a total coating weight of 7.8 g / m ² . It provides a clearly legible copy. Intensity of copy ID = 48%; Friction sensitivity IR = 10%.

Example 19

The procedure is as in Example 17, but the solution of the polyacrylic acid / sodium salt is replaced by 83 g of water (i.e. no water-soluble high polymer is used). The rotational speed of the. Toothed disk stirrer is 6000 rpm. The dispersion obtained was sieved through a sieve with a mesh size of 350 μm and had a solids content of 43.1%. It contains spherical capsules with slight dents, which have a common diameter of 15 to 45 µm.

The CB line made according to A1.a) and A1.b) has a total application weight of 7.3 g / m ² . Intensity of copy ID = 50%; Friction sensitivity IR = 10%.

Example 20

The procedure is as in Example 19, but the pH is adjusted to 4.5 and the precondensate is added at 5000 rpm in the course of an hour.

The dispersion obtained has a solids content of 45.1% and contains slightly indented spherical capsules with a common diameter of 3 to 12 µm.

The CB coating produced according to A1.a) and A1.b) has a total coating weight of 7.5 g / m ² . The legible copy has an intensity ID = 50%; and a sensitivity to friction: IR = 19%.

Example 21

Example 1 is repeated, but the toothed-disk stirrer was operated at 80 ° C. and 3000 rpm.

A 44.5% dispersion with capsules with a diameter between 6 and 42 µm was obtained.

C.III Examination of the influence of the content of spacers on copy intensity and sensitivity to rubbing of the CB line

• a) Zellulosefaserschliff (Arbocel B 600/50)
• b) Stärkekörner (Spezialstärke K)
• c) Paraffinhaltige Kapseln des Beispiels 6
• d) Paraffinhaltige Kapseln des Beispiels 4.
• e) Paraffinhaltige Kapseln des Beispiels 2
• f) Paraffinhaltige Kapseln des Beisiels 21.

Spreads were prepared in accordance with A1.a) and A1.b), the proportion of spacers being gradually increased from 0 to 1.9 parts by weight (approx. 100%). The proportion of microcapsules containing color formers was 4.4 to 4.6 parts. The following were used as spacers:

• a) Cellulose fiber cut (Arbocel B 600/50)
• b) Starch grains (special starch K)
• c) Paraffin-containing capsules from Example 6
• d) Paraffin-containing capsules from Example 4.
• e) Paraffin-containing capsules from Example 2
• f) Paraffin-containing capsules of example 21.

The capsules containing blue color were used as color formers by C.I. used.

In Table 6, the results of copy intensity (ID) and rubbing sensitivity (IR) of CB coatings containing increasing amounts of spacers, namely cellulose pulp, starch granules and paraffin capsule of Example 21, are juxtaposed.

With increasing spacer content, the intensity of the copy decreases in all cases. This decrease is most pronounced in the starch grains. Cellulose cut and paraffin encapsulation show little waste.

The sensitivity to friction also decreases with all spacers. The decrease is about the same for starch and cellulose pulp, but is enormous for paraffin capsules.

Table 7 shows the copying intensities and sensitivity to rubbing of CB lines with different capsules containing paraffin as spacers depending on the amount of spacers in the CB line.

Here, too, the intensity of the copy obtained drops somewhat as the number of spacers increases. The larger the diameter of the spacer capsule, the greater the loss of intensity. Melting point and penetrometer index have a hardly discernible influence. With increasing amount of paraffin spacer capsules the sensitivity to friction sometimes decreases very significantly. The greater the diameter of the spacer capsule and the higher the melting point or the lower the penetrometer index of the encapsulated paraffin, the greater the sensitivity to friction.

Despite its spherical shape, which enables high speeds on paper coating systems, the copy intensity only drops slightly, even with large amounts of spacers. The sensitivity to rubbing and thus the soiling of the papers in the form set is reduced in a way that has not previously been possible.

Claims (9)

1. Microcapsules containing in a shell made of a polymer at least one hydrophobic substance which is solid at room temperature and has a melting point of about 40 to 150 ° C. 2. Microcapsules according to claim 1, characterized in that the hydrophobic substance has a melting point of about 50 to 85 ° C. 3. Microcapsules according to claims 1 or 2, characterized in that the microcapsules have an average particle diameter of 5 to 50 µm, preferably 6 to 35 µm, and in particular 7 to 70 µm. 4. Microcapsules according to claims 1, 2 or 3, characterized in that the solid hydrophobic substance is a wax or a wax-like substance which at 20 ° C has a penetrometer index value of 0.5 to 200, preferably 1 to 120, owns. 5. Microcapsules according to claims 1, 2, 3 or 4, characterized in that the shell is a coacervate based on gelatin, a condensation product based on urea-formaldehyde, urea-melamine-formaldehyde or melamine-formaldehyde or a polyamide, polyester , Polyurea or polyurethane. 6. Microcapsules according to claims 1, 2, 3 or 4, characterized in that the shell is a melamine-formaldehyde condensation product. 7. Use of the microcapsules according to claims 1 to 6 as spacers in coatings containing color formers enclosed in microcapsules. 8. recording system based on selfcontained, CF / CB or CFB, characterized in that the layers contain microcapsules as spacers according to claims 1 to 6. 9. Recording system according to claim 8, characterized in that the layers contain 0.1 to 7.0, preferably 0.5 to 5.0 g / m ^{2 of} the microcapsules according to claims 1 to 6.