EP0275015B1 - Curtain coating process - Google Patents

Description

The invention relates to a method for producing webs coated with a plurality of layers, the bottom or top layer being a layer containing an instant hardening agent (hardening layer).

A hardening of the layers is required for the production of photographic materials, the layers containing binders based on proteins and / or polymers. The following methods are known for hardening:

The conventional hardening with additives such. B. Triacrylformal, which are added to the casting solutions before the application for the web. The hardening of the applied layer structure is only completed after the rail has been stored for several weeks. Disadvantages are the large storage costs and the uneven quality, caused by the different hardening caused by different storage conditions.

The rapid hardening process also uses additives, e.g. certain vinyl sulfones, which are added to the casting solutions. The hardening of the layer dressing is completed after one day at the earliest and after 8 days at the latest, which is fundamentally advantageous, but there are very high demands on the drying process and the residual moisture of the products, since otherwise the product quality will deteriorate due to post-curing.

The instant hardening process differs fundamentally from the other two processes. Immediate hardeners are understood to mean compounds which crosslink suitable binders in such a way that the hardening is completed immediately after coating or at the latest after 24 hours, preferably after 8 hours, to the extent that no further change in the sensitometry and the swelling of the layer structure occurs as a result of the crosslinking reaction . Swelling is understood to mean the difference between the wet film thickness and the dry film thickness during the aqueous processing of the film (Photogr. Sci. Eng. 8 (1964), 275: Photogr. Sci. Eng. 16 (1972), 449). The instant hardeners are known per se, e.g. from DE-C-2 408 814 or DE-A-2 225 230.

Because of the immediate start of hardening, the instant hardener cannot be mixed with the usual gelatin-containing casting solutions, i. H. after a short time the production process would have to be interrupted for cleaning due to hardening on the casting device.

For this reason, in the instant hardening process, which is very advantageous for the product quality, the hardener substance in a separate casting solution which contains 0 to 4% by weight of gelatin or gelatin derivatives, preferably 0.5 to 1% by weight as an additional layer or as a layer in a layer package in which the adjacent layers likewise only have gelatin concentrations of at most 4% by weight. When using gelatin derivatives, a higher concentration in the neighboring layers is possible.

Without the above-mentioned restrictions in the gelatin concentration, only technically more complex solutions are conceivable e.g. the hardening solution can be applied to a second pouring vial after the first order has dried or through a separate machine pass. All of the aforementioned disadvantages are avoided by the invention described below.

The invention is therefore based on the object of improving the instant hardening process in such a way that the hardener solution can be applied together with all other layers and thus also with the gelatin-rich casting packs in one coating process with a glazier.

It has surprisingly been found that the instant hardener solution can be applied together with the layer package using the curtain coaster described in EP-A-0 017 126 or in DE 3 238 905 without any curing. The two references describe a curtain caster in which some of the coating solutions flow on an inclined surface to the edge of the caster and cover the path from there to the web to be coated as a free-falling curtain.

Opposite the inclined surface there is a negatively inclined surface on which at least one further coating solution flows hanging downwards, which meets the other coating solutions at the pouring edge. This leads to more favorable flow conditions at the foundry edge and thus to an improved casting. According to the invention, the hardener solution is now supplied to the layer package via the negatively inclined surface and contacts the layer package at the foundry edge. Surprisingly, there are no casting problems or quality losses at the pouring edge, where the hardener solution and layer package come together.

The invention therefore relates to a process for producing a web coated with at least two layers, at least one layer containing binders based on protein and / or polymer, according to the curtain pouring process with the V-caster, to which the web is continuously passed, one layer applied simultaneously with the binder-containing layer on the negatively inclined sliding surface of the V-caster, the binder-containing layer is guided on the opposite sliding surface of the V-caster and both layers are combined on the casting edge to form a layer package and as a free-falling curtain on the web to be coated applied, wherein the layer applied to the negatively inclined casting surface becomes the bottom or top layer of the applied layer package, characterized in that the layer applied to the negatively inclined casting surface is a hardening layer and contains an instant hardening agent.

The V-caster is preferably combined with a curtain holder with integrated liquid supply according to US-A-4 479 987. This curtain holder has the additional advantage that, due to the continuous rinsing, hardening and incrustation caused by the hardener cannot occur.

With the measure according to the invention of applying an immediate hardener solution and layer package in one casting process, the acceleration or wetting layer described in DE 3 238 905 C2 can also be saved, since the hardener solution also takes on this task. This is possible by selecting the web guide so that the hardener solution is arranged under the layer package as a connecting layer between the layer package and the surface of the web (see FIG. 1, solid web running direction). As an alternative to this, it can be arranged as the uppermost layer due to the opposite direction of web travel (see FIG. 1, dashed web running direction) and thus used as a top layer with surface-specific additives.

Significant and surprising advantages of the method according to the invention are the saving of a second coating station or a second machine pass for the application of the hardener solution or the avoidance of low-gelatin neighboring layers and the saving of expensive hardener substance, since the amount of hardener can be reduced to about half without that a loss of hardening effect is observed.

Figure 1 shows a section through a curtain coating device of the type "V-caster". The caster consists of blocks 13 and 14 which are screwed together and delimited by end plates. The face plates and the fixture of the foundry on a frame are not shown. The hardener solution 7 and the liquid casting solutions 8 for the layer package 11 are fed into the distribution chamber 5 with the aid of known metering devices and lines (not described in more detail here) from one end face. The outlet slots 9.1 to 9.5 in connection with the distribution chambers 5 ensure a uniform distribution of the casting solutions 8 and the hardener solution 7. The casting solutions 8 for the layer package emerge from the outlet slots 9.2-9.5 and flow on the cascade surfaces 3 at an angle α 1 as a result of Gravity down. The layer package 11 finally flows over the surface 15 to the lowermost V-shaped casting block 14 and to the casting edge 4.

The hardener solution 7 is fed to the distributor chamber 5 between the foundry blocks 13 and 14 and exits through the outlet slot 9.1 onto a sliding surface 16 which is negatively inclined at the angle α₂. It follows the sliding surface 16 and flows from the other side of the casting block 14 to the common pouring edge 4. At the pouring edge 4, the free-falling curtain 12 is formed from the first-mentioned layer package 11 and the hardener layer 7, which reaches the web 1 to be coated in a fraction of a second over the height h and lies on top of it. The moving web 1 is supported in the impact area of the curtain 12 by the casting roller 6 and the edges are in a known manner by curtain guides held (not shown). In order to avoid possible hardening here, too, an aqueous inert layer can be arranged between the curtain guides and layers.

The curtain 12 coats the web 1 over its entire width, the excess of casting material at the edges being able to be drained off by collecting trays in a manner not described in any more detail. The result is webs without an edge section that are coated with the casting solutions over the entire width and have no edge loss.

Advantageously, however, the web 1 is only coated almost up to the web edges, the curtain 12, as is known, being guided by curtain guide elements almost reaching the web and thus being prevented from contracting by the surface tension. In this way, less of the valuable casting solution is lost. The cast web 1 with the coating 2 is then not coated over the full width and must be trimmed, the uncast edges and the edge beads being separated.

Figure 1 shows a dashed and a solid web running direction, which are to be understood as alternatives. Depending on requirements or needs, the hardener layer 7 can be placed under the layer package 11 or on the layer package 11.

Although the instant hardener contacts the layer package 11 in the curtain 12 and on the pouring edge 4, no curing or deterioration of the casting quality occurs. The high coating speeds disclosed in DE 3 238 905 C 2 are retained.

The hardening layer preferably has a viscosity of 1 to 30 mPa.s and a wet layer thickness of 3 to 30 µm; the remaining layers preferably have viscosities of 10 to 500 mPa.s and wet layer thicknesses of 5 to 100 microns.

At least one of the remaining layers preferably contains gelatin and a light-sensitive silver halide, while the hardening layer contains 0 to 4% by weight, preferably 0.5 to 1% by weight, of gelatin.

The pouring edge is in particular 10 to 100 mm above the surface of the web to be coated.

worinSuitable examples of instant hardeners are compounds of the following general formulas:

wherein

R₁ denotes alkyl, aryl or aralkyl,

verknüpft ist, oderR₂ has the same meaning as R₁ or means alkylene, arylene, aralkylene or alkaralkylene, the second bond having a group of the formula

is linked, or

R₁ and R₂ together represent the atoms necessary to complete an optionally substituted heterocyclic ring, e.g. a piperidine, piperazine or morpholine ring, the ring e.g. can be substituted by C₁-C₃-alkyl or halogen,

oder ein Brückenglied oder eine direkte Bindung an eine Polymerkette steht, wobeiR₃ for hydrogen, alkyl, aryl, alkoxy, _NR₄-COR₅, _ (CH₂) _m -NR₈R₉, _ (CH₂) _n -CONR₁₃R₁₄ or

or a bridge link or a direct bond to a polymer chain, wherein

R₄, R₆, R₇, R₉, R₁₄, R₁₅, R₁₇, R₁₈, and R₁₉ are hydrogen or C₁-C₄-alkyl,

R₅ is hydrogen, C₁-C₄-alkyl or NR₆R₇,

R₈ _COR₁₀

R₁₀ NR₁₁R₁₂

R₁₁ C₁-C₄ alkyl or aryl, especially phenyl,

R₁₂ is hydrogen, C₁-C₄ alkyl or aryl, especially phenyl,

R₁₃ is hydrogen, C₁-C₄ alkyl or aryl, especially phenyl,

R₁₆ is hydrogen, C₁-C₄-alkyl, COR₁₈ or CONHR₁₉,

m is a number 1 to 3

n is a number 0 to 3

p is a number 2 to 3 and

Y is O or NR₁₇ or

R₁₃ and R₁₄ together represent the atoms necessary to complete an optionally substituted heterocyclic ring, for example a piperidine, piperazine or morpholine ring, which ring can be substituted by C₁-C₃-alkyl or halogen, for example,

Z the C atoms and required to complete a 5- or 6-membered aromatic heterocyclic ring, optionally with a fused benzene ring

worinX ^{⊖ is} an anion which is omitted if an anionic group is already linked to the rest of the molecule;

wherein

worinR₁, R₂, R₃ and X ^{⊖ have} the meaning given for formula (a);

wherein

R₂₀, R₂₁, R₂₂, R₂₃ C₁-C₂₀-alkyl, C₆-C₂₀-aralkyl, C₅-C₂₀-aryl, each unsubstituted or by halogen, sulfo, C₁-C₂₀-alkoxy, N, N-di-C₁-C₄-alkyl -substituted carbamoyl and, in the case of aralkyl and aryl, substituted by C₁-C₂₀-alkyl,

R₂₄ mean a group cleavable by a nucleophilic agent and

gegebenenfalls unter Einschluß weiterer Heteroatome wie O oder N auch zu einem oder zwei gesättigten, 5-7-gliedrigen Ringen vereint sein können;
X ^{⊖ has} the meaning given for formula (a), where
2 or 4 of the substituents R₂₀, R₂₁, R₂₂ and R₂₃ together with a nitrogen atom or the group

optionally including other heteroatoms such as O or N, can also be combined to form one or two saturated, 5-7-membered rings;

(d) R₂₅-N = C = N-R₂₆
wherein

R₂₅ is C₁-C₁₀-alkyl, C₅-C₈-cycloalkyl, C₃-C₁₀-alkoxyalkyl or C₇-C₁₅-aralkyl,

steht, wobeiR₂₆ has the meaning of R₂₅ or for a radical of the formula

stands where

R₂₇ C₂-C₄ alkylene and

R₂₈, R₂₉ and R₃₀ are C₁-C₆-alkyl, where one of the radicals R₂₈, R₂₉ and R₃₀ can be substituted by a carbamoyl group or a sulfo group and two of the radicals R₂₈, R₂₉ and R₃₀ together with the nitrogen atom to form an optionally substituted heterocyclic ring, for example, a pyrrolidine, piperazine or morpholine ring can be linked, the ring for example can be substituted by C₁-C₃-alkyl or halogen, and

worinX ^{⊖ has} the meaning given for formula (a);

wherein

X ^{⊖ has} the meaning given for formula (a),

R₂₄ has the meaning given for formula (c),

R₃₁ C₁-C₁₀-alkyl, C₆-C₁₅-aryl or C₇-C₁₅-aralkyl, in each case unsubstituted or substituted by carbamoyl, sulfamoyl or sulfo,

R₃₂ and R₃₃ represent hydrogen, halogen, acylamino, nitro, carbamoyl, ureido, alkoxy, alkyl, alkenyl, aryl or aralkyl or together the remaining members of a ring condensed with the pyridinium ring, in particular a benzo ring,
in which

R₂₄ and R₃₁ can be linked together if

worinR₂₄ is a sulfonyloxy group;

wherein

R₁, R₂ and X ^{⊖ have} the meaning given for formula (a) and

worinR₃₄ is C₁-C₁₀ alkyl, C₆-C₁₄ aryl or C₇-C₁₅ aralkyl;

wherein

R₁, R₂ and X ^{⊖ have} the meaning given for formula (a),

R₃₅ is hydrogen, alkyl, aralkyl, aryl, alkenyl, R₃₈O_, R₃₉R₄₀N, R₄₁R₄₂C = N_ or R₃₈S_,

R₄₄-SO₂ oderR₃₆ and R₃₇ alkyl, aralkyl, aryl, alkenyl,

R₄₄-SO₂ or

R₄₅-N = N_ or together with the nitrogen atom the remaining members of a heterocyclic ring or the grouping

worinR₃₈, R₃₉, R₄₀, R₄₁, R₄₂, R₄₃, R₄₄ and R₄₅ alkyl, aralkyl, alkenyl, R₄₁ and R₄₂ furthermore hydrogen, R₃₉ and R₄₀ or R₄₁ and R₄₂ furthermore the remaining members of a 5- or 6-membered, saturated carbocyclic or mean heterocyclic ring;

wherein

R₄₆ is hydrogen, alkyl or aryl

R₄₇ acyl, carbalkoxy, carbamoyl or aryloxycarbonyl;

R₄₈ is hydrogen or R₄₇

R₄₉ and R₅₀ are alkyl, aryl, aralkyl or, together with the nitrogen atom, the remaining members of an optionally substituted heterocyclic ring, for example a piperidine, piperazine or morpholine ring, the ring being e.g. can be substituted by C₁-C₃-alkyl or halogen, and

worinX ^{⊖ has} the meaning given for formula (a);

wherein

R₅₁ is an optionally substituted heteroaromatic ring which contains at least q ring C atoms and at least one ring O, ring S or ring N atom, and

q is an integer ≧ 2.

worinThe heteroaromatic ring represented by R₅₁ is, for example, a triazole, thiadiazole, oxadiazole, pyridine, pyrrole, quinoxaline, thiophene, furan, pyrimidine or triazine ring. In addition to the at least two vinylsulfonyl groups, it may optionally contain further substituents and optionally fused-on benzene rings, which in turn may also be substituted. Examples of heteroaromatic rings (R₅₁) are listed below.

wherein

r is a number from 0 to 3 and

R₅₂ is C₁-C₄-alkyl, C₁-C₄-alkoxy or phenyl.

Finally, the compounds described in Japanese Patent Laid-Open Nos. 38 540/75, 93 470/77, 43 353/81 and 113 929/83 and in US Pat. No. 3,321,313 are suitable as immediate hardening agents.

Unless otherwise defined, alkyl is in particular C₁-C₂ Hydrox-alkyl optionally substituted by halogen, hydroxy, sulfo, C₁-C₂₀-alkoxy.

Aryl, unless otherwise defined, is in particular optionally substituted by halogen, sulfo, C₁-C₂₀-alkoxy or C₁-C₂₀-alkyl C₆-C₁₄-aryl. Aralkyl, unless otherwise defined, is especially C durch-C₂₀-aralkyl substituted by halogen, C₁-C₂₀-alkoxy, sulfo or C₁-C₂₀-alkyl. Alkoxy, unless otherwise defined, is in particular C₁-C₂₀ alkoxy.

X ^⊖ is preferably a halide ion such as Cl ^⊖ , Br ^⊖ or BF₄ ^⊖ , NO₃ ^⊖ , (SO₄ ^2⊖ ) _1/2 , ClO₄ ^⊖ , CH₃OSO₃ ^⊖ , PF₆ ^⊖ , CF₃SO₃ ^⊖ .

Alkenyl is especially C₂-C₂₀ alkenyl. Alkylene is especially C₂-C₂₀ alkylene; Arylene in particular phenylene, aralkylene in particular benzylene and alkaralkylene in particular xylylene.

Suitable N-containing ring systems, which can stand for Z, are shown on pages 16 and 17. The pyridine ring is preferred.

R₃₆ and R₃₇ form together with the nitrogen atom to which they are attached, in particular a pyrrolidine or piperidine ring substituted by 2 oxo groups bonded in the o- and o'-position, which are benzo, cyclohexeno- or [2.2.1] -bicyclohexenocondensed can.

Acyl is especially C₁-C₁₀ alkylcarbonyl or benzoyl; Carbalkoxy is especially C₁-C₁₀ alkoxycarbonyl; Carbamoyl is especially mono- or di-C₁-C₄ alkylaminocarbonyl; Carbaroxy is especially phenoxycarbonyl.

Groups R₂₄ which can be split off by nucleophilic agents are, for example, halogen atoms, C₁-C₁₅ alkylsulfonyloxy groups, C₇-C₁₅ aralkylsulfonyloxy groups, C₆-C₁₅ arylsulfonyloxy groups and 1-pyridinyl radicals.

Preferred hardeners are listed below:

Compounds of formula (a)

The compounds can be prepared in a simple manner known from the literature. The secondary amines are e.g. with phosgene, the carbamic acid chlorides, which are then reacted with aromatic, heterocyclic nitrogen-containing compounds in the absence of light. The preparation of compound 3 is described in Chemical Reports 40, (1907), page 1831. Further information on the synthesis can be found in DE-OS 2 225 230, DE-OS 2 317 677 and DE-OS 2 439 551.

Compounds of formula (b)

Methods for the synthesis of these compounds are described, for example, in DE-A 2 408 814:

Compounds of formula (c)

Methods for the synthesis of these compounds are described in more detail in Chemistry Letters (The Chemical Society of Japan), pages 1891-1894 (1982). Further information on the synthesis can also be found in EP-A-162 308.

Compounds of formula (d)

Methods for the synthesis of these compounds are described in more detail in JP-OS en 126 125/76 and 48 311/77.

Compounds of formula (e)

Methods for the synthesis of these compounds are described in more detail in JP-OS en 44 140/82 and 46 538/82 and JP-PS 50 669/83.

Compounds of formula (f)

Methods for the synthesis of these compounds are described in more detail in JP-OS 54 427/77.

Compounds of formula (g)

The synthesis of these compounds is described in U.S. Patent 4,612,280.

Compounds of the formulas (h)

The preparation of these compounds is described in DD 232 564 A1.

Compounds of formula (i)

Methods for the preparation of these compounds are described in DE-OS 35 23 360.

Other suitable instant hardeners correspond to the following formulas

η = Viskosität

(mPa.s)

σ = Oberflächenspannung

(mN/m)

δ = Naßauftrag auf der Bahn

(µm)

ν = Bahngeschwindigkeit

(m/min)

h = Vorhanghöhe

(mm)

The symbols used in the following table have the following meaning:

η = viscosity

(mPa.s)

σ = surface tension

(mN / m)

δ = wet application on the web

(µm)

ν = path speed

(m / min)

h = curtain height

(mm)

A coating device according to FIG. 1 (V-caster) was used for an eight-layer coating (an instant hardener layer, 7-layer photographic layer package).

The casting dates of the individual layers were:

The direction of web travel was chosen so that the instant hardener layer was applied as the top layer of coating 2 (Fig. 1, web run dashed line). A PE paper base was used as the web.

eingesetzt.The casting quality was very good, there was no curing on the foundry. An aqueous solution of the compound of the formula was used as the instant hardener solution

used.

When using 2 pouring points or with 2 machine passes, the same casting quality was only achieved with a hardener application of 12 µm, according to the invention with 7 µm.

According to the invention, fewer or more than 8 layers can be cast. The method is particularly suitable for casting 2 to 20 layers.

Claims (9)

1. A process for the production of a web coated with at least two layers, at least one layer containing binders based on proteins and/or synthetic polymers, by the curtain coating method using a V-coater past which the web is continuously guided, a layer applied at the same time as the binder-containing layer being guided at the negatively inclined sliding surface of the V-coater, the binder-containing layer being guided at the opposite sliding surface of the V-coater and the two layers being combined at the coating edge to form a layer packet which is applied as a freefalling curtain to the web to be coated, the layer applied at the negatively inclined surface becoming the lowermost layer or uppermost layer of the layer packet applied, characterized in that the layer applied at the negatively inclined surface is a hardening layer and contains an instant hardener.

2. A process as claimed in claim 1, characterized in that the hardening layer has a viscosity of 1 to 30 mPa.s and a wet layer thickness of 3 to 30 µm.

3. A process as claimed in claim 1, characterized in that at least one of the other layers contains gelatin and a photosensitive silver halide.

4. A process as claimed in claim 1, characterized in that the instant hardener is applied in a coating solution containing 0 to 4% by weight gelatin.

5. A process as claimed in claim 1, characterized in that the instant hardener is applied in a coating solution containing a gelatin derivative.

6. A process as claimed in claim 1, characterized in that the coating edge is situated 10 to 100 mm above the surface of the web to be coated.

7. A process as claimed in claim 1, characterized in that the curtain is held by a curtain holder with integrated liquid supply.

8. A process as claimed in claim 1, characterized in that the web is coated with 2 to 20 layers.

9. A process as claimed in claim 1, characterized in that the instant hardener corresponds to the following general formula

in which
R₁ is alkyl, aryl or aralkyl,
R₂ has the same meaning as R₁ or represents alkylene, arylene, aralkylene or alkaralkylene, the second bond being attached to a group corresponding to the formula

or
R₁ and R₂ together represent the atoms required to complete an optionally substituted heterocyclic ring, for example a piperidine, piperazine or morpholine ring, the ring optionally being substituted, for example, by C₁₋₃ alkyl or halogen,
R₃ is hydrogen, alkyl, aryl, alkoxy, _NR₄-COR₅, _(CH₂)_m-NR₈R₉, _(CH₂)_n-CONR₁₃R₁₄ or

or is a bridge member or a direct bond to a polymer chain,
R₄, R₆, R₇, R_9, R₁₄, R₁₅, R₁₇, R₁₈ and R₁₉ being hydrogen or C₁-C₄ alkyl,
R₅ being hydrogen, C₁₋₄ alkyl or NR₆R₇,
R₈ being _COR₁₀,
R₁₀ being NR₁₁R₁₂,
R₁₁ being C₁₋₄ alkyl or aryl,
R₁₂ being hydrogen, C₁₋₄ alkyl or aryl,
R₁₃ being hydrogen, C₁₋₄ alkyl or aryl,
R₁₆ being hydrogen, C₁₋₄ alkyl, COR₁₈ or CONHR₁₉,
m being a number of 1 to 3,
n being a number of 0 to 3,
p being a number of 2 to 3 and
Y being O or NR₁₇ or
R₁₃ and R₁₄ together representing the atoms required to complete an optionally substituted heterocyclic ring, for example a piperidine, piperazine or morpholine ring, the ring optionally being substituted, for example, by C₁₋₃ alkyl or halogen, Z being the C atoms required to complete a 5-membered or 6-membered aromatic heterocyclic ring, optionally with a fused benzene ring, and
X^⊖ is an anion which is unnecessary where an anionic group is already attached to the rest of the molecule.

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