DE1082117B - Photographic base paper and process for its manufacture - Google Patents

Description

GERMAN

The invention relates to a new photographic base paper and a method of its production.

When moistened and dried, normal paper behaves in a way that it does for some purposes makes unsuitable: the dimensions change, in particular the paper shrinks, the surface properties deteriorate, pucker, stain, and so on. Moist also loses Paper retains its stiffness and tensile strength and adsorbs an undesirably large amount of water.

All of these phenomena are extremely troublesome with photographic paper, since in the course of its Processing must be subjected to a wet treatment in which not only water, but also a number of the most varied chemicals act on the paper.

Even when paper is made for photographic use, it comes with water-based ones Mixtures in contact: water-based layers are applied to it, which becomes undesirable Roll of paper can result. Also with the application of the water-based Layers associated moistening and subsequent drying of the paper achieved during calendering Advantages are lost. This has a particular effect in an increase in thickness, a larger one Surface roughness and a reduced gloss of the paper. Different filling of surface fibers of the paper can completely retain the surface gloss achieved by calendering destroy.

The treatment (development) of the paper after exposure leads to complete soaking and therefore also causes increased surface roughness, decreased gloss, one Change in dimensions, etc. All of these phenomena are "on photographic paper extremely annoying.

To overcome these deficiencies, attempts have been made to size photographic paper with substances which increase the strength of the paper when wet and the smoothness of such papers. Papers treated in this way are reasonably sufficient for most purposes, but apart from the fact that they are relatively expensive, they still have a number of disadvantages. They roll in the developing baths and the like and when exposed to humid air. Because they are soaked in water or saline solutions to a considerable extent in the various baths, it takes a long time to wash out the sucked-in substances. In addition, some measures proposed for improving paper impair the photographic properties of the photosensitive layers applied. There is also photographic base paper
and its method of manufacture

Applicant:

Eastman Kodak Company,
Rochester, NY (V. St. A.)

ίο Representative: Dr.-Ing. W. Wolff, patent attorney,

Stuttgart N, Lange Str. 51

Claimed priority:
V. St. v. America April 26, 1956

Glen Gordon Gray,

Joseph Thomas Leone, Rochester, N.Y.,

George Alvin Richter, Pittsford, N.Y.,

and Lloyd Emerson Herdle, Rochester, N.Y. (V. St. A.) ,,

have been named as inventors

in the case of sensitized layers, there is a risk that the sensitizers from the emulsion layer in the Paper felt would migrate, which would discolor the paper and reduce the sensitivity of the emulsion.

The invention relates to a photographic paper which is resistant to the effects of water, in particular with regard to its surface properties. The smooth, glossy surface of the paper should not noticeably be roughened by moistening it with water. These properties should also be retained when the paper is covered with a photographic emulsion. The paper should also remain mechanically strong and dimensionally stable in all wet processes customary in photographic technology, especially in the developing baths. Also, the photographic paper should contain no formaldehyde onnectivity developing \ ^r who come in and of itself appropriate to achieve properties in question, but act detrimental to the applied to the paper photographic emulsions.

The object is achieved by a photographic paper which consists essentially of cellulose, the hydroxyl groups of which are partially substituted by acyl radicals.

It is already known to produce paper from cellulose fibers, some of which are hydroxyl groups are esterified; however, such a material has not heretofore been used for photographic paper.

009 5101/282

As far as plastics such as synthetic fibers have been incorporated into the paper, it has been shown that that the dimensional accuracy was better, but that due to the lack of cross-links in the fibers, the strength such products leaves much to be desired. One tried to do this with the help of a solvent too change, so one came to papers that again left something to be desired with regard to their permeability. Try using whole sheets of moisture-insensitive plastics instead of photographic ones Using papers resulted in products whose properties were closer to those of well-known films Cellulose ester bases resembled a paper. One can of a more horn-like character such Products speak. It has also been shown that such * 5 Products leave something to be desired in terms of water vapor permeability; while photographic Paper, which is supposed to be resistant to liquid water, is known to be permeable to Water vapor to a certain extent and especially for certain special purposes (e.g. in the High-gloss hot drying) required. According to the experiences made with such material, was It is generally to be expected that even a partially acylated cellulose will not be sufficient for water vapor would be permeable. In addition, the higher cost of such material is its use had to appear inappropriate for practical reasons. But it has been shown that because of Due to its excellent properties, photographic base paper made from this material is kept thinner can be than usual for this paper, so that the higher production costs because of quantitative savings are sustainable.

Photographic paper according to the invention resembles paper in its general behavior, but shows decisive improvements in terms of dimensional stability, wet strength, easier removal from photographic processing baths and surface properties during and after wet treatment. For example, the dimensions of the paper according to the invention change less than 1% in the direction of the plane of the paper when the paper is moistened with water for 2 minutes in a Schopper expansion tester. The paper according to the invention shows a shrinkage of less than 1% in the direction of the plane of the paper when the paper is softened in water, dried and then after-treated. It shows a change of less than 15 ¹ Vo in the direction perpendicular to the 5 "plane of the paper when moistened, and after moistening, drying and retreating it shows a change of less than 5%. Its water absorption is less than 0.15 g per 100 cm ² after a 1-minute Cobb test When the paper according to the invention is tested by the valley-size penetration test, it exceeds the value of 2000 seconds, the maximum value up to which this test is carried out Soaking in water shows this paper a steepness at least twice that of normal paper, as measured on a Taber-V-5 stiffness tester. The dry strength of this paper is greater than that of the original glue-free paper, especially in the transverse direction.

It has been found that the paper according to the invention does not significantly change the smoothness when it is soaked and dried; This was shown by a measurement of the dried paper on a device indicating the surface roughness ("Surfindicator"), whereby it was found that the roughness was not more than 2 μ . This is a significant advantage over the known types of paper, which is tear-resistant even in the moist state, in which the moistening and re-drying causes the surface of the paper to be roughened. Also, the reflectivity of the paper according to the invention does not decrease as much as in the case of the known types of paper when the paper is soaked through and dried again. If the paper according to the invention is produced from a paper pulp having a high content of alfa cellulose, its whiteness does not decrease after exposure to ultraviolet light, as can be clearly ascertained by measurement. The known papers that are preferably prepared from pulp having a high alphacellulose content and which are used for the better and more stable types of photographic papers, show a small \ ^r educing its whiteness when they are treated with ultraviolet light. While papers made from a paper pulp with a lower alfa cellulose content previously showed a noticeable reduction in their whiteness when they were irradiated with ultraviolet light, the papers according to the invention made from a paper pulp having a low alfa cellulose content (content of alfa cellulose 85 to 88%) with comparable intensities and exposure times do not show any Yellowing.

The paper according to the invention is produced by esterification of the paper in sheet form, which it imparts an acyl content of 10 to 30%. This esterification can be carried out by subjects the paper to a treatment in which the cellulose of the paper incorporates lower fatty acid radicals which method may include the use of a bath containing lower fatty acid anhydrides and contains an esterification catalyst and preferably also a solvent. These anhydrides can be acetic acid, propionic acid, butyric acid or isobutyric acid anhydride, or but it can be the esterification mixture of lower fatty acids, such as. B. acetic acid, propionic or Butyric acid, and a catalytically active anhydride, such as. B. a chloroacetic anhydride or an alkoxyacetic anhydride. The esterification catalyst used can be perchloroacetic acid, Zinc chloride, phosphoric acid or even sulfuric acid, or it can be a basic catalyst, such as B. an alkali metal acylate, such as potassium acetate, potassium butyrate or the like. Be. When a Solvent is used, a lower fatty acid or an inert organic liquid, such as B. methylene chloride, ethylene chloride, carbon tetrachloride or the like. Can be used. The esterification of the paper sheet can be carried out in one of the known ways, for example by that it is so long immersed in an esterification bath until the desired acyl content at the prevailing temperature is reached. The paper sheet is expediently first treated with a liquid, which causes the cellulose to swell so that it is more accessible to the action of the acid anhydrides is. To produce an acylated paper, the paper is preferably subjected to a process in which the substances are sucked through the paper. For example, the paper becomes a Subjected to water treatment, and the water is then from the sheet by treatment with a lower fatty acid removed. The paper sheet can then undergo treatment in an esterification bath

in which the acid anhydride is a chemical compound of the cellulose of the paper sheet caused with lower fatty acid groups. After the cellulose is esterified in a desired strength is, for example, it is washed by treatment with water and then dried. Preferably drying is carried out by applying pressure, which is the production of the paper according to the invention relieved. The paper sheet thus obtained has a

which is larger than that of the glue-free paper from which it was made. This value was determined on a "Taber V-5" stiffness tester, as it is in the USA. is available. This test is described in the publication "Instrumentation Study No. 14" of the "Institute of Paper Chemistry" of May 27, 1937. In the reported results of this series of tests, L means the value obtained in the machine direction and C the value Acyl content between about 10 and 30% and preferred io that is obtained in the transverse direction of the paper, such as acetyl, propionyl, butyryl or iso-The process according to the invention

butyryl content from 15 to 20%. It is not purposeful- paper shows a stiffness when wet, moderate to exceed an acyl content of 26%, which is at least twice that of the glue-free especially when the acyl group is an acetyl group of the paper from which it is made. The paper is while on the other hand the desired rigidity in the wet state is determined by with an acetyl content below 15% less that the paper samples remain in water for 3 minutes are pronounced. 22.8 to 23.9 ° C and then the

If the paper is acylated, it can be pressure-dried on a "Taber-V-5" stiffness slurry using stiffness values if the measuring device has a sensitivity in the range of 0 to 10 Acylation following washing is complete, or the 20 can be determined.

Paper can be dried in the known manner. The changes in length of the invention

re-moistened and then applying paper in water will be less than 1% in the to be dried by pressure. The treated, acy-direction of the plane of the paper, which took place in a 2-minute Paper should have a liquid content, for example when tested with the help of a Schopper extensometer of water or acetone, of at least 25 was correct. In this exam, a paper-12%, for example, 12 to 50%, of the paper pulp strip from about 15 cm in length and 15 mm in width exhibit. The paper that is after acylation and the transverse direction of the paper used the washing out of the in these procedural steps. This sample is carefully clamped The fabrics used are attached to the device in a wrinkled manner so that they do not generally have a high water content and are under tension or flexing. The sample can immediately afterwards a dry press is then ge for 2 minutes in a water jug

procedure. However, if the acylated paper has been dried beforehand, it should be before be moistened after dry pressing, for example by soaking with a water 35 mixing liquid, such as B. water, acetone, alcohol or the like. Or by spraying the Paper with an appropriate amount of a liquid. The paper treated in this way is then heated and immersed, and at the end of this time a scale is read. The scale indicates the extent of the stripe when moist in percent.

The paper according to the invention shows a shrinkage of less than 1% in the direction of the plane of the paper. This value was after the first treatment of the paper was determined in an atmosphere of 50% relative humidity. From this it is then on

presses while at least one of its surfaces in 40 partitioned the paper a given length. That is in contact with a polished metal surface. Paper is then dipped in water, dried, and this process can be carried out by again exposing the paper to moisture between two polished metal rollers in a 50% relative atmosphere. The length divided on the sample through or over a polished metal roller is then measured, and the percentage that is guided against which a pressure roller presses, or shrinkage can be determined from this, the paper can be pressed against a polished metal surface shows after it is pressed. The temperature applied was humidified, a change of less than should be at least 93 ° C and preferably 150 ° C or 15% in the direction perpendicular to the plane of the paper. This more and the mechanical pressure should be between 21 kg value is obtained when the paper is one per cm ² and 70 kg per cm ² . The paper is measured 50 gauge, then completely immersed in water by this treatment to a moisture content and then returned again with the gauge no more than 5%. When the heated device is checked. The difference between the two metal rollers used is for the reducing readings showing the change in the direction perpendicular to the moisture content to 5% or less to the plane of the paper when wet. If the paper is useful more than one pass. The obtained 55 is dried again, a thickness measurement shows a paper is resistant to the effects of moisture difference of less than 5% between this measurement, has a permanent smooth surface solution and that before the treatment, and thus gives a product with for many applications The water absorption of the paper according to the purposes advantageous properties. Finding is measured by a "1-Minute Cobb-Size" - The 60 test obtained by the method described above and is less than 0.15 g per

If necessary, paper can be coated with various aqueous coating compositions, for example with clear dye solutions or compounds containing barium oxide or with a known light-sensitive

100 cm ² . In this test, the water is allowed to act on a paved surface of paper for a certain period of time, and the amount of water absorbed is determined by the increase in the weight of the sample.

silver halide emulsion is coated, so 65 is correct (see "Tappi method T-441m"). If that

that a photographic paper is obtained. The paper according to the invention with Valley's Pen-

The held product has a wet strength smoothness and a trations test is tested, the obtained exceeds

just such a shine. Value of 2000 seconds, which is the largest reading in

The paper according to the invention shows this test when dry. The P ruf instrument was a Valley

Condition a stiffness, especially in the transverse direction, 70 size tester, and in this test it was approximately

5 x 5 cm paper sample placed between two cells of the device. The adjusting screws are tightened the lever on the back was raised and the time was measured with a clock. The result is pressing in the number of seconds it takes for the current to reach the required number of seconds Has milliamps. The solution used in the valley size tester consisted of the following components :

Distilled water 516 cm ³

Sodium chloride 24 g

Glycerine 60 cm ³

an intermediate pigment layer directly by applying a photosensitive silver halide emulsion layer is sensitized. After this treatment, the paper according to the invention retains its gloss.

In the manufacture of photographic paper, one of the most feared properties is tilt to roll. Rolling can be done before, during or after any treatment and drying of the ίο paper occur. For example, a paper coated with a photographic emulsion can be used drying either immediately or after the treatment, for example after a few days of storage In an atmosphere of relatively low humidity, the resistance of the surface properties of the 15 curl, making it inconvenient for handling Paper is often determined by the fact that the paper is. The paper may curl during treatment, Exposed to ultraviolet light for 2 hours when it was in the developer solution, in the stop bath is, with a mercury vapor lamp "Ge-UA-2" between the developer and the fixer or in of 250 W at a temperature of 32 to 43 ° C, the washing water is introduced after fixing, is applied inside the housing. The »Tappi- 20 The paper can become in Standard T-452 «describes this method for loading against the emulsion layer or in one Mood of reflectivity in percent. Roll the direction away from this one. In a photograph according to the invention Paper made from pulp paper according to the invention shows that which has a lower alfa cellulose containing product with very improved properties has than the known papers, which as im 25 plus the rolling both when the paper at ultraviolet light resistant papers used are stored in lower humidity, as well as then, showed in this test that they if the paper with properties in the course of its treatment retained. For example, different aqueous baths have come into contact. Paper pulp with an alfa cellulose content of 85 to In the tests that were carried out to the 89% papers made according to the invention. This 30 roll inclination of known photographic paper papers retained in the test with ultraviolettem pieren with the properties of the invention

To compare photographic papers, round disks 10 cm in diameter were made from the Paper cut out and laying on a tight grid

tion of a paper with a comparable consistency of the emulsion placed upwards in a room, opposed the action of ultraviolet light, its temperature 38 ° C and its relative humidity

18%. After a desired period of exposure the tendency to curl is measured by taking the distance between the upturned high alfa cellulose (90 to 95%) made 40 ends of the samples in centimeters and measures these will show a brightness of at least 90% value of 10 the original diameter of the Reflectivity peel off slices after exposure of this paper. So when the ends of the sample touch with ultraviolet light in a GE spectrophoto in a full roll, you get the meter at 456 millimicron wavelength. With this value 10. If the specimen bends even more, Test setup was the total length of the 45, then you get a value that goes beyond 10. Ultraviolet lamp 16.2 cm, the distance between some typical results of such a comparison As seen, the lamp and the holder of the ultraviolet irradiated paper were 30.5 cm.

The paper according to the invention is also resistant to roughening during moistening and subsequent drying. A paper that is moistened and dried and then tested in a "brush" surface measuring device, as is the case in the USA. is common, has a roughness not exceeding 2.15μαη, which is a considerable improvement over the papers previously used for purposes where they got wet. While an inventive paper upon wetting and drying is a roughness in a test in this device that is not greater than 215 60-10 ~ ⁶ cm, the roughness is at a

good standard paper 310 x 10 ~ ⁶ cm or more. The values in the column labeled "New"

The paper according to the invention with its high were obtained after the slices were cut Brightness shows when it has been moistened and re-moistened and for 18 hours at 18% room humidity is dry, were held in a test with a "Gardner" - 65.

Gloss meter at least 25 reflection units. The values in the columns "After 8 days" and

Such a paper according to the invention retains its "After 16 days" were obtained after the Shine even when exposed to water. photographic paper 8 or 16 days at 35% This property is particularly good with photographic room humidity and a temperature of 49 ° C important, where the paper was stored without any 70; then the samples were cut

Light their reflectivity at the same size as the original paper before treatment with ultraviolet Had light. It used to be necessary for the profit

to use a pulp that had a much higher content of alfa cellulose. Manufactured according to the invention Papers made from pulp with very

are the following:

Rollability at 18% humidity

Kind of photo
graphic
Paper New
(18%
space
humidity) To
8 days To
16 days 18%
Space-
damp
after 70%
space
damp Known ....
Acetylated ... 3.7
2.2 6.1
2.5 9.7
3.0 20+
9.5

and stored at 38 ° C and 18% humidity for 18 hours and then measured.

For the values in the last column, the targets were displayed according to the one shown in the “New” column Measurement placed overnight in a room with a temperature of 21 ° C and a relative humidity of 70% and then again stored at 18% relative humidity for 18 hours and then measured.

When comparing the curability during processing between a normal photographic Paper and acetylated photographic paper were sheets 20.3 x 25.4 cm for 2 minutes a developer bath (1) and rinsed in water after this development (2). In case (1) it rolled normal photographic paper about 1.5 times around itself in the direction of the emulsion to a tube, while the acetylated photographic paper remained essentially flat. In case (2) it rolled normal paper about 1.5 times in the direction away from the emulsion, while the acetylated paper im essential just remained.

To compare the curling after processing the photographic paper according to the invention with normal photographic paper of appropriate weight were made from each type of paper Samples are taken and after treating and drying for 18 hours at 18% relative humidity stored. The values of curability of the normal photographic paper which are commercially recognized as good Quality were twice as great as the values of the photographic paper according to the invention.

It has been found to be partially acylated paper containing a photographic emulsion is coated, has advantages which are particularly desirable for photographic purposes.

This paper is valuable in making the photographic paper of the present invention. A paper of this type has a higher strength and a lower expansion when wet, which results in better dimensional stability, it rolls less and retains less water, since it absorbs fewer salts during the treatment than is the case with papers produced by the known manufacturing processes the case is. For example, papers chemically given a low acyl content can have a dry strength that is essentially good or better than that of the normal size-free papers from which they are made. While the wet strength of the size-free paper approaches zero, the wet strength of the acylated paper is between 44 and 100% of the strength that this esterified paper has in the dry state. With normal size-free paper, the paper can retain 70 percent or more of water, while a small percentage of acyl incorporated into the paper greatly reduces the retention of water, dropping it to 30 percent or even lower if the acyl content is higher. While the wet expansion of the size-free paper is about 4.0% or more, the partially acylated paper has a wet expansion of the order of 1.0 to 2.0%, and this expansion can still be increased by enhancing the acylation can be further reduced. The dry strength of the paper can be essentially the same as that of the size-free paper before acylation, whereas the wet strength of the partially acylated paper is always much greater than that of the original paper. In the esterification of the size ηα- free paper, which is generally considered unsuitable for photographic purposes, it is possible to obtain a product which has a dry strength that is almost as great as that of the known commercially available photographic papers and the when wet, the properties in terms of expansion and strength are significantly improved.

The degree of acylation involved in the manufacture of backing papers for photographic purposes is desirable depends on a number of factors including the type of acyl group introduced, the specific properties of the paper to be esterified. For some purposes like z. B. Reducing the amount of retained salt during development, can help achieve it the desired improvement in properties is sufficient, 1 to 2% of the hydroxyl groups to esterify with butyryl radicals. A slightly higher degree of esterification may be required to get the obtain the same results with acyl groups of low carbon content.

For general use as a carrier for photographic papers, a level of isobutyrylation of 8 to 15% is considered to be optimum, since esterification beyond this level brings less improvement in benefits than economically is desirable. On the other hand, it requires the introduction of acyl groups of low carbon content a slightly higher degree of esterification, e.g. B. up to 25% of the hydroxyl groups if the same change the properties of the paper is to be achieved. It is clear that even if the isobutyrylation from 8 to 15% of the hydroxyl groups of the paper support is considered optimum, a lower one Esterification also causes a marked improvement in paper properties, and the invention is not limited to compliance with this higher esterification optimum.

The paper used for photographic purposes can be partially used in various ways acylated, the choice of which will be determined by practical aspects of the process. the For example, cellulose can be partially acylated by a hot process in which the Paper a lower fatty acid anhydride, such as. B. acetic anhydride, butyric anhydride, isobutyric anhydride or the like. The hot acylation is preferably carried out using a basic one Catalyst carried out. In the case of acetic anhydride, for example, potassium acetate can advantageously be used as Catalyst can be used while isobutyric anhydride and potassium isobutyrate are satisfactory work. The temperature of the treatment is preferably 100 ° C or more.

The paper that is acylated can either be moistened beforehand, e.g. B. with methyl alcohol, or the air-dried paper can be used in this form. It was found that the Pretreatment with methyl alcohol greatly accelerates the absorption of the acyl content by the paper. That Paper is then immersed in a bath for a certain period of time in order to give it the desired acyl content Inserted anhydride, which contains the catalyst. For example, if a pre-soak with methyl alcohol is carried out, the paper soaked with methyl alcohol can be placed directly in the anhydride bath be introduced at a temperature of 150 ° C, whereby the methyl alcohol evaporates and the Paper absorbs an acyl content. For example

009 510/282

a glue-free paper dipped in methyl alcohol can be introduced into hot isobutyric anhydride containing 2% potassium isobutyrate and 1% isobutyric acid. After 5 minutes approximately 5% and after 10 minutes approximately 11% of the hydroxyl groups are esterified. Without the pre-impregnation with methyl alcohol, under the same conditions, after 5 minutes only 1.4% and after 10 minutes only 2.1% of the hydroxyl groups are esterified. In acylation processes where lower temperatures are used, other types of catalysts can also be used, for example perchloric acid, Zinc chloride, phosphoric acid, or the like. Even sulfuric acid can be used, but it has been used found that the physical properties of the paper thus obtained show reductions that cannot be obtained with other types of catalysts. When using the acid catalyst is it is expedient that the acylation temperature does not rise above 70 ° C .; preferably be lower Temperatures, for example around 35 to 40 ° C, are used.

After the partially acylated paper is made, it can be used in different ways from the rest Liquid can be freed, the most convenient method depending on the size of the acylating group and the method by which the acylation was carried out. The acylated paper can be used in in some cases immediately washed with water and then dried. In those cases where a noticeable part of the esterification liquid does not mix easily with water, it can be useful before washing with water, washing in a suitable solvent soluble in both to be switched on, for example in a suitable alcohol or in a suitable fatty acid.

When the acylated papers are made by a hot process using acidic catalysts are not used, most of the excess liquid can evaporate immediately are removed by passing the paper through hot rollers, and the Washing with water at the end of the process is very simplified because of the contamination of the washing water with the esterification liquids is greatly reduced in this way.

It is expedient that the paper treated by the process according to the invention should be free from glue Paper is. However, this does not preclude the use of a different paper such as e.g. B. a paper made of is sized or treated with a wet strength agent for better economy however, there is no reason to use paper other than glue-free.

After the paper is partially acylated, a layer of a photographic emulsion, z. B. a photosensitive silver halide gelatin emulsion, applied as is normally the case with photographic papers. It can It may be useful to first apply a layer of baryta to the paper, as you would when making one photographic paper is common; this layer is either available as a suspension of barium sulfate in gelatin or a suspension of barium sulfate in a solution of gelatin and a styrene-butadiene emulsion It has been found that the use of these aqueous layer-forming mixtures on the surface of the paper no noticeable deleterious effect on the physical The paper has properties because it withstands the effects of water and aqueous solutions that it comes into contact with. The paper therefore retains its original dimensions and does not show any rolling. Also, wetting the paper has no adverse effect on its dry strength, as by comparison a glue-free paper not acylated in the manner described here was recognized. That so photographic paper obtained also has no adverse effect on the sensitivity of the Emulsion layer that was applied to the paper, and after exposure, it can easily be in Treat developing and fixing bath solutions further. The paper doesn't take on too much salt from solutions and can be easily handled in the following procedures.

In the production of a partially acylated paper according to the invention, if necessary, an Instead of an anhydride, a mixture of anhydrides can be used, for example acetic acid and butyric anhydride.

The following examples illustrate the partial acylation:

example 1

Size-free paper was dipped in methyl alcohol at 25 ° C for 15 seconds, then the remainder Liquid squeezed out, then it was immersed in isobutyric anhydride, the 2% potassium isobutyrate and contains 1% isobutyric acid and its temperature was 150 ° C. The paper was then made with alcohol and then washed with water and air dried. The esterification times and properties of the paper obtained were as follows:

Esterification time Esterification percentages Water retention
after. 16 hours Wet strength
(in ° / o the again
gained dryness
strength) Ashcroft dry
strength (in ° / o des
original
unesterified paper) Original paper
5 minutes
10 mins
15 minutes
30 minutes
60 minutes 0
5.8
11.2
14.4
20.6
31.2 70
34
29
25th
28
33 0
100
100 100
81
81
85
96
100

Example 2 temperature of 150 ° C immersed, the 2% potassium

Air-dried, glue-free paper with 5% moist isobutyrate and 1% isobutyric acid. That

Activity was in isobutyric anhydride with a 70 paper was first with isopropyl alcohol and then

washed with water and finally dried at 50 ° C. The following table gives the esterification times and the properties of the paper obtained:

Esterification time Esterification percentages ^ S & sser reluctance
after 2 minutes Wet strength
(in% of again
gained dryness
strength) Ashcroft dry
strength (in%> des
original
unesterified paper) Original paper
5 minutes
10 mins
20 minutes
30 minutes 0
1.4
2.1
3.3
4.0 60
38
37 0
44 100
108
111
111
104

was refluxed. The paper was then washed with alcohol and finally with water and dried at 50 ° C. The esterification and immersed in acetic anhydride, the 1.55% ao times and the properties of the papers obtained Potassium acetate and 1%> acetic acid and 140 ° C is shown in the following table:

Example 3 Size-free paper was air dried

Esterification time Esterification percentages Water retention
after 2 minutes Wet strength
(in%> the again
gained dryness
strength) Ashcroft dry
strength (in ° / o des
original
unesterified paper) Original paper
30 seconds
1 minute
1.5 minutes
2.0 minutes
2.5 minutes 0
2.1
4.0
5.9
7.0
8.7 60
55
51
46
44
42 0
0
4th
12th
15th
22nd 100
100
100
100
104
104

Example 4 contained isobutyrate and 1% isobutyric acid and at

Air-dried, size-free paper was refluxed in a 145 ° C. That Solution of equal parts isobutyric anhydride 4 ° Paper was mixed with alcohol and then with water. and acetic anhydride dipped, the 2% potassium wash and finally dried at 50 ° C.

Esterification time Esterification percentages
(as acetate) ■ Water retention
after 2 minutes Wet strength
(in ° / o the again
gained dryness
strength) Ashcroft dry
strength (in ° / o des
original
unesterified paper) Original paper
1 minute
3 minutes
5 minutes
10 mins 0
2.3
5.2
8.9
15.2 60
56
43
37 0
0
19th
35 100
111
96

The partially esterified papers described in Examples 1 to 4 are all for photographic use Purposes.

The water retention test was carried out as follows:

2 Minutes of Water Retention: Air-dried paper samples were soaked in distilled water Immersed at 30 ° C for 2 minutes, removed, placed between individual blotting sheets and then under Pressure passed through a set of stainless steel rollers. The samples were then weighed, Made touch dry, weighed again, and the percentage of water retention was based on the dust-dry cellulose. The 16 hour water retention was made in the same way

measured, but the samples were immersed in water for 16 hours instead of 2 minutes.

Example 5

An unsized sheet of paper made from a paper pulp with a high content of alfa cellulose was immersed in a bath consisting of equal parts of acetic anhydride and acetic acid and containing ^{0.45 g of perchloric acid per 100 cm 3.} The paper sheet was immersed in the 60 ° C mixture for 30 seconds and then most of the acetic acid was removed by drying and washing in cold running water overnight. The product had a yield of 114%, based on the weight of the original sheet, which has an acetyl content of other

results in approximately 15%. The sheet shows a wet strength of 53 units on the "Ashcroft" tester im Comparison with 0 units of wet strength of the original sheet. The sheet was in the dark with a photographic gelatin silver halide emulsion to give photographic paper of good properties.

Example 6

An unsized sheet of paper pulp with a high content of alfa cellulose was immersed for 1 minute in a 63 ° C. bath of acetic anhydride containing 1.8 g of sulfuric acid per 100 cm ^{3 of} the bath. The sheet obtained was then washed in cold running water overnight. The paper gave a yield of 107%, which corresponds to 8% acetyl groups. The paper had a wet strength of 48 units, measured with the "Ashcroft" tester, and was coated with a photographic emulsion layer in the dark. A photographic paper with good properties was obtained.

Example 7

A size-free paper sheet made from alfa cellulose pulp was immersed for 1 minute in a 63 ° C. mixture of equal parts by volume of esic acid and acetic anhydride, the bath containing 1.8 g of sulfuric acid per 100 cm ³ . The resulting product was washed in cold running water overnight and dried on a steam drum. The sheet gave a yield of 114% based on the original weight of the sheet, which corresponds to an acetyl content of approximately 15%. The paper had a wet strength of 5 units on the "Ashcroft" tester compared to 0 units of the wet strength of a non-acetylated paper.

After applying a light-sensitive silver halide emulsion in the dark, a was obtained photographic paper of good properties.

The following examples illustrate the manufacturing process of the papers according to the invention.

Example 8

The paper used was made from wood pulp, 50% from hardwood sulfite pulp and too 50% consisted of softwood pulp. The pulp was dispersed in water and used in the papermaking process adjusted with aluminum chloride to an acid content of 3 milliequivalents per liter. 3% melamine-formaldehyde resin were added to the paper pulp, based on the cellulose, added to give it sufficient firmness in moist State to give. This became in a known manner by spreading the paper pulp on the The sieve of the paper machine was made, which was dried on steam-heated rollers. Leaves from the 8 inches by 10 inches from this paper were acetylated by the following procedure:

^{1. 500 cm 3 of} water, then 500 cm ^{3 of} glacial acetic acid and finally 500 cm ^{3 of} acetic anhydride, which contained 5% phosphoric acid, were drawn through the leaves. The temperature of the reagents used was about 23 ° C and the contact times for each treatment were 15 to 20 seconds using a vacuum of 2.1 cm of mercury.

The sheets were then removed and placed in an acetic anhydride bath at a temperature of was about 23 ° C and contained 5% phosphoric acid (85%). After 1 hour the sheets were out of this Took out the bath and then sucked the following liquids through it:

Three rinses with 200 to 300 cm ^{3 of} alcohol, three rinses with 200 to 300 cm ^{3 of} water and, where it appeared appropriate, two rinses with 200 to 300 cm ^{3 of} acetone.

The following samples were produced:

A. Untreated comparative sample.

B. Soaked with water, then pressed dry in a hydraulic press.

C. Finally, acetylated, rinsed with water, then in a commercially available dryer (e.g. »Pako«) dried.

D. Acetylated, finally rinsed with acetone, dried in a "Pako" dryer.

₃ g of E. acetylated, finally rinsed with water, pressed dry in a hydraulic press.

F. Acetylated, finally rinsed with A-reton, in one hydraulic press dry-pressed.

G. Acetylated, finally rinsed with water, dried in a "Pako" dryer and then in pressed in a hydraulic press.

H. Acetylated, finally rinsed with water, dried in a "Pako" dryer, then again moistened with water and dried in a hydraulic press.

The hydraulic press used was a 30 ton press with polished metal contact surfaces.

The »Pako« dryer contains a drum with a smooth, unpolished metal surface over which the paper is guided over a length of about 1.5 m at a temperature of 121 ° C. The paper is held on the drum by a belt that presses the paper only enough to ensure contact between the paper and the drum. The paper samples, which are finally cooled with water, are driven through squeeze rollers in order to remove the excess water from the surface. The acetone-rinsed samples were not driven through such rollers. The wet sheets have about 30% water or acetone and, when a hydraulic press is used, are placed between polished chrome-plated plates and pressed for ^{10 minutes at about 150 ° C and 49 kg per cm 2.} The pressure was interrupted periodically so that the steam could escape.

Upon completion of this treatment, the sheets were cut in half and one series was designated A ₁ to H ₁ and the other series A ₂ to H ₂ . The paper sheets of the series A ₁ to H ₁ were stored at 48% relative humidity. The sheets of series A ₂ to H ₂ were immersed in water at 24 ° C for 30 minutes, after which they were dried in the air at 24 ° C and 48% room humidity. The samples were then tested for gloss by visual inspection and measurement, surface roughness, cross-directional expansion in water, breaking strength when dry (or Mullen), and strength when wet. The following values were obtained:

description

Thick
Measurement 25 ⁰ C shine
45 ° C difference Roughness expansion
in cross
direction
° / o Mullen Strength,
wet 4.7
5.5 1.42
1.42 1.20
1.24 0.22
0.18 65
83 1.65
1.60 22nd
20th 9 V ₂
8 ^3/4 4.1
4.4 1.45
1.45 1.15
1.20 0.30
0.25 60
64 1.30
1.25 20th
23 8 ^3/4
8 »/ 4 7.3
7.5 1.44
1.43 1.27
1.28 0.17
0.15 HO
115 0.80
0.75 ia
18th 9 ^3/4
10 ^3/4 7.5
7.6 1.43
1.44 1.28
1.26 0.15
0.16 113
127 0.60
0.60 21
21 H ¹ A
12th 5.1
5.3 1.46
1.42 1.14
1.20 0.32
0.22 65
82 0.45
0.50 20th
18th 10 Vi
10 5.5
5.5 · 1.43
1.42 1.18
1.20 0.25
0.22 80
78 0.50
0.45 19th
21 11V ₂
9 ^3/4 5.3
6.0 1.42
1.41 1.21
1.23 0.21
0.18 93
83 0.85
0.85 17th
17th 8th
8th 4.3
4.9 1.43
1.41 1.14
1.19 0.31
0.22 65
78 0.55
0.88 18th
15th 7V4
6V ₂

The specimens were divided into the following groups with regard to gloss by eye shine:

Highest gloss: B ₁ , E ₁ , F ₁ , H ₁ .
Next highest group: A ₁ , G ₁ , E ₂ , F ₂ , H ₂ .
Some shine: B ₂ .
Essentially no gloss: C ₁ , D ₁ , A ₂ , C ₂ , D ₂ , G ₂ .

The intensity of the reflective light in density units (logarithmic) is used as a measure of the gloss. taken. The difference between the measured values at 25 and 45 ° C is the logarithm of the ratio from specular reflection to diffuse reflection. A difference of 0.02 is already considered clear perceptible.

■ The roughness was measured with a surface indicator (»Surfindicator«). The instrument setting was: range 762 x 10 ~ ⁶ cm and closure 0.076 cm.

The transverse expansion was determined with a "Schopper" extensometer.

The Mullen value or tensile strength was measured on a "Perkins" tester,. »Tappi standard T-403M-41 «measured. The strength in the wet state was measured using a "Minden-Wet-Strength" Testers measured.

Example 9

The paper used here was made from a mixture of different paper stocks and had a basis weight of 125 g per m ² . The paper pulp suspension was adjusted to an acid content between 3 and 5 milliequivalents per liter with aluminum chloride. In order to obtain sufficient strength when wet, 1% melamine-formaldehyde resin, based on the dry cellulose, was added. All sheets of paper were treated as follows:

The 20.3 x 25.4 cm sheets of paper were pretreated by sucking 500 cm ^{3 of} distilled water and then 500 cm ^{3 of} glacial acetic acid through the paper. The temperature of the water and acid was about 23 ° C and the contact time was 15 to 20 seconds each time under a vacuum of 2.1 cm Hg.

The sheets were then acetylated by drawing through the paper 500 cm ^{3 of} acetic anhydride at a temperature of HO ⁰ C, which contained 5% phosphoric acid (85%). The contact time with the anhydride was 15 to 20 seconds at a vacuum of 2.1 cm Hg.

The reaction was usually stopped immediately by drawing water at about 23 ° C. through the sheets. This was followed by three washes with 200 to 300 cm ^{3 of} alcohol, three washes with 200 to 300 cm ^{3 of} water and, where indicated, two washes with 200 to 300 cm ^{3 of} acetone. The individual samples were treated as follows:

A. Untreated comparative sample.

B. Treated with water for comparison, dried on the »Pako« dryer, then on one hydraulic press dry-pressed.

C. Treated with water for comparison, dry-pressed while wet on a hydraulic press.

D. Acetylated, finally rinsed with water, dried on the »Pako« dryer.

E. Acetylated, then washed with acetone, dried on the "Pako" dryer.

F. Acetylated, · finally washed with water, dried on the "Pako" dryer, then again moistened and pressed dry on a hydraulic press.

G. Acetylated, finally washed with water, on a hydraulic press in the wet state dry pressed.

The drying press was the same as that in the previous example. The moisture content at the start of the treatment was in each case approximately 50%. When dry pressing, the paper was treated for about 10 minutes with pressure being applied intermittently to allow the steam to escape. The sheets obtained were cut in half and divided into two groups, A ₁ to G ₁ and A ₂ to G ₂ . The samples were treated as in the previous example and then tested. The tests gave the following results:

009 5101/282

description

Thick
Measurement 25 ° C shine
45 ⁰ C Differe 6.3
7.3 1.44
1.43 1.25
1.25 0.19
0.18 7.2
7.4 1.46
1.44 1.29
1.27 0.17
0.17 4.9
5.0 1.47
1.44 1.20
1.19 0.27
0.25 9.6
9.8 1.45
1.46 1.29
1.30 0.16
0.16 9.8
10.0 1.46
1.46 1.29
1.29 0.17
0.17 5.5
6.0 1.47
1.46 1.07
1.14 0.40
0.32 5.5
5.5 1.46
1.45 1.07
1.16 0.39
0.29

Roughness

expansion
in the transverse direction
»/ Ο

Mullen

Firmness, wet

81
101

105
103

74
78

134

141

132
136

49
62

65
65

2.15
2.50

2.20
2.40

1.80
2.05

1.15
1.10

0.85
0.85

0.85
0.90

0.65
0.75

42
42

41
43

47
46

25th
28

34
34

35
39

40
38

12 V ₂ 13V ₂

12th
13th

11
12 ³ A

10 ³ at
9 ¹ U

17 V4
14 V *

15th

17 V4

18 ³ U
19th

at room temperature

Partially acetylated paper can be made in a number of ways; for example, one method creates sheets (20.3 x 25.4 cm) using a vacuum treated by about 50 cm of water on both sides of the sheet and reagent following through the paper sucked through.

1. 250 ³ tap water at room temperature cm (10 seconds).

2. 250 cm ^{3 of} glacial acetic acid
(10 seconds).

3. 250 cm ^{3 of} a mixture of acetic acid and acetic anhydride (3: 1) containing 0.3% perchloric acid; Temperature 61 ° C (15 seconds).

4. 250 cm ^{3 of} glacial acetic acid at room temperature (10 seconds).

5. Tap water at room temperature (15 to 20 seconds.

The paper was then dry pressed and found to be suitable for use in manufacture of photographic papers according to the invention is very suitable. Other esterification catalysts, such as B. sulfuric acid, phosphoric acid, methanesulfonic acid, zinc chloride or the like., Can expedient used in the manufacture of partially acetylated paper. The rate of esterification can by increasing the concentration of the catalyst and / or the anhydride content and / or the temperature can be increased.

In another case, partially acetylated paper was made by placing rolls of paper on it a stainless steel support and these by dipping and stirring in a Series of glass cylinders were treated as follows:

1. Pretreat the paper in water containing 2 percent by volume phosphoric acid (5 minutes).

2. Distilled water with glacial acetic acid (5 minutes). Distilled water a second time (5 minutes).

3. Reaction of the paper with acetic anhydride, which contains 5 percent by volume of phosphoric acid. The temperature is held between about 43 and about 60 ° C for 1 to 2 hours.

4. Wash with benzene (5 minutes).

5. Wash with alcohol (5 minutes).

6. Wash with running water (30 to 60 minutes), press dry.

The paper thus obtained was suitable for use in the manufacture of photographic papers.

Highly sensitive chlorobromide enlargement papers can be used particularly well (glossy) and made with simple weight from partially esterified paper, with the paper first at normal temperatures and pressures through a supercalender was passed through. The paper was coated with a layer of clay using gelatin and then calendered and by applying a light-sensitive special emulsion to harmless Sensitized to light. The sensitometric properties, the quality, the tendency to curl and the behavior high gloss heat drying were good. In addition, the paper showed improved properties the resistance to soaking in and treatment with water and to the rolling that occurs during treatment. Photographic papers made in accordance with the present invention remain flat while not so Treated photographic papers roll themselves into the shape of a tube, both when the paper is in treated with the developer and after the paper has been rinsed in water after developing.

Example 10

Various 25 cm paper webs of esterified paper made according to the process just described above were calendered through a step of a supercalender which had a highly polished metal surface. The temperature was above 93 ° C. and the pressure was greater than 21 kg per cm ² ; the paper had a moisture content of 25% at the start of the process. It was treated so that the moisture content fell to less than 5%. These paper strips were then immediately coated with a photographic silver halide gelatin layer. The paper obtained was tested both for curling before and for curling after treatment in the manner described above, and the same results as given above were obtained.

The physical properties of the esterified and dry-pressed paper were compared with the proprietary

Shafts of a known normal paper compared, both having a weight of about 132 g per m ² .

A comparison of the properties of the two papers showed the following:

Transverse expansion
Vo Swelling
"/O Bulk
° / o Mullen
kg per cm ² Firmness, wet
kg per cm ² Acetated dry tears 0.85
2.30 15.9
41.4 3.2
14.3 2.6
2.8 0.98
0.75 normal

The percentages of transverse expansion and swelling of the papers in the table are based on the Change in the values obtained when the papers transition into the wet state. The increase in size bulk is the increase in thickness between the dry state and the state that is obtained after moistening and re-drying.

The papers of the invention were made with gelatin top layers coated, whereby these have been subjected to the high-gloss heat-drying process so that they can be get a smooth surface. The ones coated with gelatin Papers were then treated with photographic chemicals, washed and then attached to the Air dried. A comparison of the surface of the gelatin layers of those produced according to the invention Papers with the surfaces of the gelatin layers of the known photographic papers after moistening and re-drying showed that the first-mentioned papers had their smoothness and mostly theirs too Retain gloss, while the gelatin layers of known photographic papers are rough and matt became. This shows that the dimensional stability of the papers according to the invention in the vertical direction is good compared to the known photographic papers.

The papers of the invention are against yellowing by ultraviolet light as compared with more resistant than the normal known papers, and in some cases the reflectivity of the Paper after the treatment with ultraviolet light is even better than before the treatment. this applies also in the case of the partially acylated papers described here, both in the case that the paper was dry pressed as well as in the case where the paper was not dried under pressure. That Reflectivity of the paper was in each case before and after its exposure in an ultraviolet Light measured with a GE spectrophotometer; this test was, as already described above, carried out.

A paper that is made from a mixture of equal parts from a softwood pulp with an alfa cellulose content of 88% and a hardwood paper pulp with an alfa cellulose content of 89%, had a reflectance of 90.3%, and after exposure to ultraviolet light of 80.1%. This same paper was acetylated to have an acetyl content of approximately 20%; it achieves a reflectivity of 90.6% before exposure to ultraviolet light and after treatment with ultraviolet light of approximately 91.5%. To show a loss with normal papers To avoid reflectivity, it was previously necessary to use a wood mass with a high content of alfa cellulose to use. For example, a paper was made from a softwood pulp with a high alpha cellulose content (94% alfacellulose) in known manner for use as a support for a photographic Layer produced using hand-made sizing and machine sizing; the paper had a reflectance of 89.7% before the ultraviolet light treatment and after the ultraviolet light Treatment of 86.9%.

The expression "dry pressing" is used in the description for the treatment of a partially acylated paper at elevated temperature and pressure against a polished metal surface (at least 93 ° C and 21 kg per cm ² ), the paper being at least 12% water-miscible liquids contained.

It is clear that the use of an original waterproof paper in the manufacture of the invention Paper makes handling easier. If the sheet of paper is supported while it is wet, a paper without glue of any kind can be used. The type of paper used can be selected at will according to the convenience of papermaking. If that Paper has been treated according to the method according to the invention, it has a high strength in damp condition.

Partially acylated paper retains its properties even under severe climatic conditions Well. For example, samples of acylated paper (about 20% acetyl), samples of a glue-free one Papers with high alfa content and good photographic papers arranged in trays and 2 weeks buried in the tropics in a mixture of equal parts of deciduous humus, surface soil and coarse sand. The water content of the buried material was 27 to 29% and the temperature was 27.8 held up to 28.3 ° C. The temperature of the surrounding earth was maintained at 26.6 to 27.2 ° C. Of the The Ph "value of the buried material was 6.9. After excavating the samples, it was found that the acylated paper was white and not significantly degraded, whereas the samples of the photographic The paper and the watermark paper were broken or dissolved and discolored, for example red, green or purple spots or the like.

Claims (11)

Patent claims: 1. Photographic base paper based on cellulose, characterized in that it is essentially consists of cellulose, the original hydroxyl groups of which are partially esterified with acyl residues are. 2. Photographic paper according to claim 1, characterized in that the acyl radicals 2 to Contains 4 carbon atoms. 3. Photographic paper according to one of Claims 1 and 2, characterized in that 1 to 50%, in the case of isobutyryl residues, preferably 8 to 15%, in the case of acetyl residues preferably at least 15 to 20% of the original hydroxyl groups are esterified. 4. Photographic paper according to any of the preceding Claims, characterized in that it is glue-free. 5. Photographic paper according to one of the preceding claims, characterized in that that it was dried under pressure. 6. Photographic paper according to claim 5, characterized in that it is a baryta layer contains, over which the photosensitive layer is arranged. 7. Paper according to one of the preceding claims, characterized in that it consists of one Paper pulp is made which has a content of at least 85% UV-resistant alfa cellulose having. 8. A method for producing a paper according to any one of the preceding claims, which is im essential permanent surface properties and good resistance to the effects of Having moisture, characterized in that a paper web is subjected to a treatment is, in which the cellulose of the paper up to a content of 10 to 30% of low Fatty acid radicals at least partially acylated 24 and that the paper is then soaked in a water-miscible liquid so that it has at least 12% moisture, and then heated and pressed (with at least one of its surfaces resting against a polished metal surface) until its moisture content is at a Has decreased value which is not greater than 5 ^fl / o. 9. The method according to claim 8, characterized in that that the paper is acetylated to an acetyl content of at least 15 to 20%. 10. The method according to claim 8, characterized in that the acylation is conducted so that the paper has a content of 10 to 30% fatty acid radicals with 2 to 4 carbon atoms. 11. The method according to any one of claims 8 to 10, characterized in that a pressure of at least 21 kg per cm ² and a temperature of at least 93 ° C is applied during dry pressing. Considered publications:
German patent specifications No. 752 308, 752 630. When the registration was announced, 2 priority documents were displayed.