EP0052730A1 - Pressure sensitive copy materials - Google Patents

Abstract

Pressure- and thermo-sensitive recording material which has a color-developing coating on a support made of a) a finely divided spherical solid phenolic resin with particle sizes of 5 µm, b) a copolymer as a dispersant from (α) a compound of the formula <IMAGE> in the R¹ C8- C20- Alkyl, phenyl or C1- to C20-alkylphenyl, R² is hydrogen or methyl, n = 2 to 100 and m = 0 to 50, (β) an ethylenically unsaturated copolymerizable carboxylic, sulfonic or phosphonic acid and optionally (γ) another contains ethylenically unsaturated copolymerizable compound different from (α) and (β), c) at least one aliphatic alcohol which is solid at room temperature and optionally d) contains further auxiliaries. The coating, together with color formers encased in microcapsules, gives sharp and intense copies.

Description

The invention relates to pressure- and thermo-sensitive recording material.

As a rule, the carbon paper-free copy papers used today consist of a combination of sheets. The cover sheet contains a coating with microcapsules on the back, the interleaves also have a microcapsule coating on the back (donor side: CB side) and on the front side an acidic compound (electron acceptor), on which the color formers react with color formation (recipient side: CF side). You can also apply the microcapsules with the color donor and the receiver on top of each other on the same sheet side. In this case, when the microcapsules are destroyed, color formation occurs in any case.

The color formers are known. In particular, the following are considered, for example: crystal violet lactone, N-benzoyl leukomethylene blue, malachite green lactone, rhodamine lactones, spirodipyrans or fluorane derivatives (cf. DE-OS 24 22 899, 20 25 171, _{23 18 403} , _{23-23 803} ; _DE - _AS 21 ₅₆ 214; DE-OS 22 43 483 and 2 230 225; GB-PS 1 417 695).

Activated clays, attapulgite, aluminum oxide, bentonite, silton clay, kaolin and other clays can be used as electron acceptors.

It is known from US Pat. Nos. 3,222,557 and 3,488,207 that color development also takes place on solid aromatic carboxylic acids. According to DE-OS 21 52 765, the salts of aromatic carboxylic acids, especially hydroxycarboxylic acids, with polyvalent metals such as magnesium, zinc, calcium, cadmium or aluminum are more effective than the free carboxylic acids. Noe / P

DE-PS 2 252 901 and 2 303 405 describe the use of mixtures of clays, clays and aromatic carboxylic acids and / or their metal salts as acceptors.

The receiving substances are first processed by grinding and mixing and optionally dispersing to form an aqueous dispersion which is then applied to the paper surface with the aid of doctor blades or by printing.

Because of the sensitivity of inorganic consumers to moisture, attempts have been made in recent years to use phenolic resins as consumers. US Pat. No. 3,466,184 describes the use of phenolic polymers which are soluble in oil as the receiving end. As resins are novolaks auf.der based _{p-phenylphenol.} Alkylphenol and alkylphenol acetylene are used which are soluble in ethylene glycol monoethyl ether, n-butanol, ethyl acetate, ethanol, mixtures thereof and similar solvents.

The polymers can be used as an organic solution, e.g. be applied using a flexographic printing unit.

DE-OS-26 31 832 describes low molecular weight condensation products of hydroxybenzene or hydroxynaphthalenecarboxylic acids, phenols and formaldehyde as acceptors, which can be applied to the paper from organic solution. These agents are optionally used together with salts soluble in organic solvents.

Known from US Pat. No. 3,466,184 and DE-OS 26 31 832 have the disadvantage that they have to be applied in the form of a solution in organic solvents, due to the solvent vapors Extraction systems must be available.

In addition, because of the organic solvents, these recipients cannot be applied together with the aqueous microcapsules to produce "self-contained paper", since the microcapsules are generally not stable to solvents and therefore discoloration occurs. A "self-contained paper" can therefore only be produced in such a way that the slave is first applied and the microcapsules are applied in a second step after the solvent has been completely removed. The self-contained paper thus obtained has the disadvantage that it is very sensitive to friction because the capsules lie unprotected on the resin particles.

DE-AS 20 64 155 discloses the use of phenol-formaldehyde resins as recipients, the resin being converted into an aqueous suspension / dispersion in the presence of anionic dispersants. The dispersion is prepared in a conventional manner by wet grinding the resin in an aqueous suspension. The particle size should be 5 _/ um'und less, preferably ≤1μm, so that an effective receiving layer is obtained. The fine particles can also be obtained by dissolving the phenol / formaldehyde resin in alkali hydroxide solution and precipitating the resin from the aqueous solution with acid and then wet grinding. These finely divided resin suspensions / dispersions can be isolated as such by spray drying or in a drum dryer.

The inorganic or organic substances used as recipients often contain sharp-edged agglomerates which, when applied, e.g. cause corrosion and abrasion when printed.

The object of the present invention was to develop a pressure- and thermo-sensitive recording material with a color developing coating, which contains the receiving substance (electron acceptor) in a uniform size and in a non-abrasive form and which the production of "self-contained paper" in one work step allowed.

The object is achieved according to the present invention in that secondary dispersions of phenolic resins which have spherical resin particles of ≤ 5 μm in diameter, preferably of 0.5 to 2 μm in diameter, and aliphatic alcohols which are solid at room temperature are used as the color-developing layer.

• a) ein feinteiliges kugelförmiges festes Phenolharz mit einer Teilchengröße von ≤ 5 µm,
• b) als Dispergiermittel ein Copolymerisat aus
  • α) 5 bis 95 Gew.% einer copolymerisierbaren Verbindung der Formel
    
    in der R^- C₈- bis C₂₀-Alkyl oder gegebenenfalls durch C₁- bis C₁₈-Alkyl substituiertes Phenyl, _R2 Wasserstoff oder Methyl, n = 2 bis 100 und m = 0 bis 50 bedeuten,
  • β) 5 bis 95 Gew.% einer copolymerisierbaren ethylenisch ungesättigten C₃- bis C₅-Carbonsäure oder einer eine polymerisierbare ethylenisch ungesättigte Gruppe tragenden Sulfonsäure oder Phosphonsäure und
  • 0 bis 50 Gew.% mindestens einer copolymerisierbaren ethylenisch ungesättigten Verbindung, die von α) und β) verschieden ist,
• c) mindestens einen bei Raumtemperatur festen aliphatischen Alkohol und gegebenenfalls
• d) weitere in solchen Beschichtungen üblicherweise enthaltene Hilfsmittel enthält,

wobei a) zusammen mit b) in Form einer wäßrig oder wäßrig--organischen Sekundärdispersion angewendet worden sind.It has been found that pressure- and thermo-sensitive recording material with excellent properties is present when used as a color-developing coating

• a) a finely divided spherical solid phenolic resin with a particle size of ≤ 5 µm,
• b) as a dispersant, a copolymer
  • α) 5 to 95% by weight of a copolymerizable compound of the formula
    
    R ^- C ₈ - to C ₂₀ -alkyl or optionally C ₁ - to C ₁₈ alkyl-substituted phenyl, _R 2 is hydrogen or methyl n = 2 to 100 and m = 0 mean to 50,
  • β) 5 to 95% by weight of a copolymerizable ethylenically unsaturated C ₃ to C ₅ carboxylic acid or a polymerizable ethylenically unsaturated saturated group bearing sulfonic acid or phosphonic acid and
  • 0 to 50% by weight of at least one copolymerizable ethylenically unsaturated compound which is different from α) and β),
• c) at least one aliphatic alcohol solid at room temperature and optionally
• d) contains further auxiliaries usually contained in such coatings,

where a) together with b) in the form of an aqueous or aqueous-organic secondary dispersion have been used.

With the color-developing coating according to the invention, pressure-sensitive or thermosensitive recording materials are obtained which, together with color formers embedded in microcapsules, provide sharp and intensive copies / recordings which are stable.

The recording material according to the present invention is obtained by applying an aqueous or aqueous-organic preparation which contains components (a), (b), (c) and optionally (d) to the support material.

The aqueous or aqueous-organic formulation is prepared by mixing the (a) and (b) secondary dispersion with the solid at room temperature, aliphatic alcohol and, optionally, further in such coatings ü _b - SHORT- prepared auxiliaries contained.

The required aqueous or aqueous-organic secondary dispersion of (a) with (b) is carried out by introducing a solution of the phenolic resin (novolak) in a water-miscible solvent in water, which contains the copolymer (b) as a dispersing agent, suspended or suspended, with strong Get mixed. The particle size of (a) can be influenced by the temperature during the precipitation, the solvent used and by the stirrer used, for example propeller stirrer, mixing siren or intensive stirrer. Round particles of (a) in a size of 0.2 to 5 _/ um, preferably of 0.5 to 2 _/ um, are particularly suitable for the recording materials according to the invention. Smaller particles (a), in particular those ≤0.2 µm, disappear between the paper fibers when applied to paper and are therefore no longer or only partially available for color development.

For economic reasons, water-miscible solvents for (a) are: ethanol, n- and i-propanol, methanol, butanol, tetrahydrofuran, acetone or mixtures thereof.

If necessary, all or part of the organic solvent can be removed from the dispersion obtained from the dispersion in a known manner, e.g. by distillation.

in der R¹ C₈- bis C₂₀-Alkyl oder gegebenenfalls durch C₁-bis C₁₈-Alkyl substituiertes Phenyl, R² Wasserstoff oderSuitable dispersants (b) are copolymers which, based on the copolymer, consist of (α) 5 to 95% by weight of a copolymerizable compound of the formula

in which R ^{1 is} C ₈ to C ₂₀ alkyl or phenyl which is optionally substituted by C _{1 to} C ₁₈ alkyl, R ^{2 is} hydrogen or

) 0 bis 5Q Gew.% mindestens einer copolymerisierbaren ethylenisch ungesättigten Verbindung, die von (α) und (ß) verschieden ist, auf gebaut sind.Is methyl, n = 2 to 100 and m = 0 to 50; (β) 5 to 95% by weight of a copolymerizable ethylenically unsaturated C ₃ to C ₅ carboxylic acid or a sulfonic or phosphonic acid containing a polymerizable ethylenically unsaturated group and (

) 0 to 5Q% by weight of at least one copolymerizable ethylenically unsaturated compound which is different from (α) and (ß) are built on.

For R ¹ in the comonomer (α) in particular, for example, are: radicals which are from C ₈ - to C ₂₀ -, in particular from C ₁₀ - to C ₂₀ -alkanols such as octyl, 2-ethylhexyl, nonyl, palmityl, stearyl , Oleyl, lauryl, of phenol or of C ₁ - to C ₂₀ -alkylphenols such as hexylphenol, dodecylphenol,. Derive hexadecylphenyl and octadecylphenol.

For R ^1, radicals are preferred which are derived from tallow fatty alcohol, coconut fatty alcohol or from C ₅ to C ₁₈ alkylphenols.

In the comonomer of the formula (I), n is preferably from 10 to 100; m is preferably 0.

As comonomers (ß) are as C ₃ - to C ₅ -carboxylic acids, for example acrylic acid, methacrylic acid, crotonic acid, vinyl acetic acid, and as. Sulfonic and phosphonic acids, for example vinylsulfonic acid, sulfoethyl (meth) acrylic acid, sulfopropyl (meth) acrylic acid, maleimide-N-ethanesulfonic acid, 2-acrylamido-2-methylpropanesulfonic acid and vinylphosphonic acid.

As comonomers (β) acrylic acid, methacrylic acid and 2-acrylamido-2-methylpropanesulfonic acid are preferred for (b).

Comonomers (f) which may be used are, for. _B. into consideration: (meth) acrylamide, lauryl acrylate, styrene, vinyl acetate, methyl (meth) acrylate, tert.-, sec.- or n-butyl acrylate, hydroxypropyl acrylate, butanediol monoacrylate, vinyl propionate, 2-ethylhexyl acrylate, of which acrylamide, the butyl acrylates, 2-ethylhexyl acrylate, hydroxypropyl acrylate and lauryl acrylate are preferred.

Particularly preferred are copolymers of the acrylate of a reaction product of tallow fatty alcohol with 40 to 90 moles of ethylene oxide, acrylamide and 2-acrylamido-2-methylpropanesulfonic acid as well as copolymers of the modified tallow fatty alcohol acrylate with lauryl acrylate and methacrylic acid, or copolymers of the modified tallow fatty alcohol acrylate and approx. 30% by weight methacrylic acid.

Production of (b) takes place according to the information in DE-OS 27 58 122.

The amount of dispersant (b) is generally 1 to 10, preferably 2 to 8, in particular 3 to 8,% by weight, based on resin (a).

Suitable phenol resins (a) are those of the novolak type which are obtained by the condensation of phenol with formaldehyde or isobutyraldehyde in a molar ratio of 1: 0.5 to 1: 1. The production of these resins is known (see 0. Nouvel, "The industry of phenol-aldehyde resins", Wilh. Knapp-Verlag, Halle (Saale) 1931; Robert W. Martin, "The Chemistry of Phenolic Resins", John Wiley and Sons, Inc. 1956; DE-OS 28 05 763 and 29 18 593).

Aliphatic alcohols which are solid at room temperature are those having 12 to 18 carbon atoms, it being possible for the alkyl radicals to be linear or branched. Mixtures of these alcohols can also be used.

^r The following are examples of alcohols: lauryl alcohol, myristyl alcohol, cetyl alcohol, stearyl alcohol and mixtures which have been prepared from C ₁₁ -C ₁₈ cuts. Cetyl alcohol and myristyl alcohol are preferably used.

Other tools (d) are e.g. means with which the viscosity of the preparation containing (a), (b) and (c) can be adjusted; also binders such as starch, soluble cellulose derivatives, binder dispersions based on copolymers with acrylate or styrene-butadiene, white pigments and fillers such as insoluble starch, insoluble melamine-formaldehyde condensates, hollow microspheres, titanium dioxide, calcium carbonate. and clay.

The coating of (a), (b), (c) and (d) can e.g. in the form of the aqueous or aqueous-organic dispersion are applied to the support in a known manner. If color formers still enclosed in microcapsules are added to the dispersion, so-called "self-contained" recording materials are obtained.

The following examples are intended to explain the invention further.

The parts and percentages given below relate to the weight.

A. Dispersant

• 954 Teile Isopropanol,
• 954 Teile Wasser,
• 315 Teile Acrylat eines Umsetzungsproduktes

1. In a Wittchen pot with a water bath, anchor stirrer, thermometer and N ₂ connection

• 954 parts isopropanol,
• 954 parts of water,
• 315 parts of acrylate of a reaction product

of tallow fatty alcohol with 80 moles of ethylene oxide, 105 parts of 2-acrylamido-2-methylpropanesulfonic acid and 210 parts of acrylamide. The mixture is dissolved under nitrogen with stirring and heating to 60 ° C. Then 21 parts of azodisisobutyronitrile were added and the mixture was kept at 80 ° C. for 3 hours.

The cooled polymer solution had a solids content of 26%. The polymer had a Fikentscher K value of 36 (measured on a 3% solution in dimethylformamide (DMF)).

• 315 Teile Isopropanol,
• 315 Teile Wasser,
• 140 Teile Acrylat eines Umsetzungsproduktes von Talgfettalkohol mit 80 Mol Ethylenoxid,
• 70 Teile Methacrylsäure sowie
• 7 Teile Azobisisobutyronitril verwendet.

2. The procedure was as for dispersant 1, but were

• 315 parts of isopropanol,
• 315 parts of water,
• 140 parts of acrylate of a reaction product of tallow fatty alcohol with 80 moles of ethylene oxide,
• 70 parts of methacrylic acid as well
• 7 parts of azobisisobutyronitrile are used.

The polymer solution obtained had a solids content of 25%; K value nack Fikentscher (3% in DMF) 32.

B. Evaluation of the Recording Material According to the Present Invention

• Ein handelsübliches mit Mikrokapseln beschichtetes Papier (CB-Papier) wurde mit Blättern des erfindungsgemäßen Aufzeichnungsmaterials (CF-Papier) zu einem 8fach Durchschreibesatz zusammengestellt und dieser Satz auf einer elektrischen Schreibmaschine bei der Anschlagstärke 2 auf einer Fläche von 4x4 cm mit dem Buchstaben '"w" beschriftet. Hierbei werden die Buchstaben in der Zeile unmittelbar aneinandergereiht und die Zeilen dicht übereinander angeordnet.

1. Determining the intensity of the copy:

• A commercially available paper coated with microcapsules (CB paper) was put together with sheets of the recording material according to the invention (CF paper) in an 8-copy set, and this set on an electric typewriter at Velocity 2 marked on an area of 4x4 cm with the letter '"w". Here, the letters in the line are lined up directly and the lines are arranged one above the other.

The 8th copy is used to determine the intensity. For this purpose, the reflectance of the blank and the described coated paper was measured in comparison to the reflectance of the white standard (= 100) using a reflectance photometer from Zeiss (®Elrepho) with the filter Y (= relative reflectance).

The intensity of the copy (IG) results from IG ⁼ R _yo -R _ym , where Ry _{o is} the relative reflectance of the blank and R _ym the relative reflectance of the paper described to the white standard (determined with the filter Y).

2. Assessment of font sharpness

• Note 1 = scharfe Durchschrift
• Note 2 = etwas unscharf
• Note 3 = unscharf
• Note '4 = verschmiert
• Note 5 = stark verschmiert.

The 8th copy is used for this, since the blur increases from copy to copy. The assessment was made with grades 1 to 5. Mean

• Grade 1 = sharp copy
• Note 2 = a little out of focus
• Note 3 = out of focus
• Note '4 = smeared
• Grade 5 = heavily smeared.

example 1 a) Dispersion

140 parts phenol-formaldehyde novolak resin (molar ratio phenol: formaldehyde = 1: 0.75; molecular weight 500; softening point: 104 ° C (determined according to the ring-ball Method according to DIN 52011; readily soluble in alkanols and ketones) and 20 parts of cetyl alcohol are dissolved in ethanol. Then 28 parts of the solution of the dispersing _'means 1 (= 7.28 parts dispersing agent) are stirred and submitted to the solution obtained in a device with a dispersant (® Ultra-Turrax) provided vessel. At room temperature, 300 parts of water are slowly added at 6000 rpm (temperature at the end of the addition: approx. 40 ^° C.). The organic solvents are then removed from the dispersion in a distillation apparatus.

A stable phenolic resin dispersion is obtained which is stable for weeks.

Solids content: 36%; Particle diameter of the round particles Æ≈1 µm.

Coating color: 10% starch and 5% of a 50% binder dispersion based on styrene / butadiene are added to the dispersion obtained according to a), based on the solids content. The mixture is then diluted with water so that the paint has a flow time from the Ford cup (DIN cup 4 mm nozzle) of 30 s.

The ink was removed with a doctor blade on paper (40 g / m ² ) (application: ^5.1 g / m ² ).

• IG = 40; Schriftschärfe: Note 1.

With the coated recording material obtained, copies were made in accordance with B1 and the intensity and type of the 8th copy were assessed in accordance with B1 and B2:

• IG = 40; Font sharpness: grade 1.

Examples 2 to 5 a) Dispersion

The procedure is as described in Example la), but a phenol-isobutyraldehyde novolak resin (molar ratio 1: 1; molecular weight 650; softening point 120 ° C. (ring ball according to DIN 52011; readily soluble in alkanols and ketones). The amount of cetyl alcohol dissolved with the resin is shown in the following table.

b) The dispersions were used to produce coating colors in accordance with the information in Example 1b) and the recording material was checked in accordance with B1 and B2 for the intensity of the 8th copy and the typeface.

In combination with commercially available microcapsule papers, sharp and intensive copies are obtained. The best result is achieved when 20 parts of cetyl alcohol are added.

IG = 45, font sharpness: grade 1.

Examples 6 to 9

("self-contained" coating)

a) The resin dispersions of Examples 2a) to 5a) are used.

b) 45 parts of a 50% binder dispersion based on butadiene / styrene, 80 parts cellulose pulp and 13 parts thickener based on polyacrylic acid are introduced into the dispersions of Examples 2a) to 5a) and the homogeneous dispersion is adjusted to pH 8 with sodium hydroxide solution .

The resulting mixtures, based on phenolic resin, are added with enough 40% microcapsule dispersion that the weight ratio resin: microcapsules = 2: 1.

The microcapsule dispersion was prepared by the process described in DE-OS 29 40 786, Example 1.

To produce the coating color, the mixers were diluted with water in such a way that the run-out time from the Ford cup (nozzle: 4 mm) was approximately 30 s. The test of the recording material obtained with the coating colors is summarized in Table I below.

c) If, in the coating color or in the preparation from which the coating color is obtained by dilution to a suitable viscosity, the ratio of resin to microcapsules is increased to 1: 1 or 1: 2, a recording material is obtained, the 8th copy of which is one has a high IG value (IG 49.5 to 62), but the copies are blurred to heavily smeared and therefore practically no longer legible (see Table I, Examples 6.1, 6.2, 7.1 and 7.2).

Claims (8)

1. Printing and thermo-sensitive recording material, consisting of a support with a color former developing coating and optionally one or more color reacting with the coating with color formation, characterized in that the color developing coating a) a finely divided spherical solid phenolic resin with a particle size of ≤5 microns b) as a dispersant, a copolymer α) 5 to 95% by weight of a copolymerizable compound of the formula

in which R ^{1 is} C ₈ to C ₂₀ alkyl or phenyl which is optionally substituted by C ₁ to C ₂₀ alkyl, R ^{2 is} hydrogen or methyl, n = 2 to 100 and m = 0 to 50, β) 5 to 95% by weight of a copolymerizable ethylenically unsaturated C ₃ to C ₅ carboxylic acid or a sulfonic acid or phosphonic acid carrying a polymerizable ethylenically unsaturated group and 0 to 50% by weight of at least one copolymerizable ethylenically unsaturated compound which is different from α) and β), c) at least one 'aliphatic alcohol solid at room temperature and optionally d) contains further auxiliaries customary in such coatings,
where a) together with b) in the form of an aqueous or aqueous-organic secondary dispersion have been used. 2. Recording material according to claim 1, characterized in that the proportion of (b) 1 to 10 wt.%, Based on (a). 3. Recording material according to claim 1 or 2, characterized in that the proportion of (c) 10 to 100 wt.%, Based on (a). 4. Recording material according to claim 1 or 2, characterized in that the proportion of (c) 25 to 50 wt.%, Based on (a). 5. Recording material according to claim 1, 2, 3 or 4, characterized in that cetyl alcohol is used as (c). 6. Recording material according to claim 1, 2, 3, 4 or 5, characterized in that (a) has a particle size of 0.5 to 2 microns. ₇ . Recording material according to claim 1, 2, 3, 4, 5 or 6, characterized in that (b) a copolymer of (α) at least one (meth) acrylate of a reaction product of tallow fatty alcohol, coconut fatty alcohol or of C ₅ - to C ₁₈ -alkylphenol with 10 to 100 moles of ethylene oxide / mole of alcohol or phenol with (ß) acrylic acid, methacrylic acid, 2-acrylamido-2-methylpropanesulfonic acid or mixtures thereof and optionally (δ) acrylamide, butyl acrylates, 2-ethylhexyl acrylate, hydroxypropyl acrylate, lauryl acrylate or mixtures thereof. 8. Recording material according to claim 1, 2, 3, 4, 5 or 6, characterized in that (b) a copolymer of (α) an acrylate of a reaction product of tallow fatty alcohol with 40 to 90 moles of ethylene oxide / mole of alcohol with (ß) 2nd -Acrylamido-2-methylpropanesulfonic acid and (δ) acrylamide, or with (ß) methacrylic acid. and optionally (δ) is lauryl acrylate.