Radiation imagery chemistry: process – composition – or product th – Radiation sensitive product – Silver compound sensitizer containing
Reexamination Certificate
2001-02-02
2002-10-29
Baxter, Janet (Department: 1752)
Radiation imagery chemistry: process, composition, or product th
Radiation sensitive product
Silver compound sensitizer containing
C430S619000, C430S631000
Reexamination Certificate
active
06472139
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to certain nonionic oligomeric surfactants, in particular such surfactants based on vinyl systems having an amido function, especially acrylamide, methacrylamide or a derivative of either of these, and to their use as coating aids, especially for use in the manufacture of aqueous coated photographic products.
BACKGROUND OF THE INVENTION
Coating aids facilitate the coating process. For example, coating aids are used in the manufacture of photographic products, such as photographic films and the like, for controlling coating uniformity after the application of the coated layers onto a product support (such as film or paper), for the period the coating remains fluid. After the coating point, the coated layers pass through a chill box. During their passage through this section the coated layers set to a rigid gel. Hence, the coated layers remain fluid from their application point to a position somewhere inside the chill box section. This period of fluidity amounts to a period of seconds at current coating speeds. During this period, the coating is subject to the impact of disturbances or perturbations which result from vibrations or air currents, present as part of the mechanics of the coating process.
Amongst commonly known coating aids, saponin is unusual insofar as it provides control of post-coating flow over a wide range of concentrations. However, in the multilayer coating of colour photographic products, it is typical for the lower layers to possess dynamic surface tensions <35 mN.m
−1
due to the surface activity of the dispersing aids used therein, e.g. dispersants for colour couplers such as Alkanol XC™ (DuPont) which leads to surface tension values in the range 32-35 mN.m
−1
. To remain spread, the uppermost layer needs to possess a lower surface tension than any of the underlying layers. Unfortunately, saponin is not very effective at lowering surface tension insofar as its limiting surface tension in aqueous gelatin solution is about 38 mN.m
−1
. Hence it is clear, that in such cases, saponin cannot be used in isolation in the uppermost layer to improve coating uniformity, for if it is used, coating quality becomes unacceptable due to retraction of the top layer over the underlying ones. Furthermore, this deficiency cannot be overcome by using saponin in combination with a more surface-active regular coating aid, like Aerosol OT™ (Cytec), as such materials cause substantive increases in the susceptibility of the coating to disturbances due to vibrations or air currents. Therefore, the ability to manipulate surface tension to values <35 mN.m
−1
whilst maintaining good coating uniformity would be of substantial benefit in simultaneous multi-layer coating where the relative dynamic surface tensions between layers is critical as described above.
It is well known in the art that gelatin coatings show a tendency to become electrostatically charged on separation from surfaces that they come into contact with, such as transport rollers. The nature of the electrostatic charging depends on the relative triboelectric properties of the two contacting surfaces and the conditions prevailing at the time of the charging, such as: speed of contact and separation processes; pressure of contact; temperature; relative humidity; and so on. It is also well known in the art that gelatin-based coatings containing fluorocarbon surfactants often tend to charge electrically in the opposite direction to those containing hydrocarbon-based surfactants. Hence it is common practice to coat mixtures of fluorocarbon and hydrocarbon surfactants in the uppermost layers of photographic products in order to minimise the electrostatic charging from a triboelectric point of view.
SUMMARY OF THE INVENTION
The present invention, in one of its aspects, provides hydrophobically capped oligomeric acrylamides or pyrrolidones, in particular the compounds of the general formula
in which
R, R
1
and R
2
are hydrophobic groups, in particular are each independently selected from aliphatic hydrocarbyl, aryl-(aliphatic hydrocarbyl) and (aliphatic hydrocarbyl)-aryl groups, which groups may be unsubstituted, partially fluorinated or fully fluorinated,
L is a sulphur atom or a linking group that contains a sulphur atom that is attached to the T group, and
T is a hydrophilic oligomeric group obtained by the oligomerisation of one or more vinyl monomers having an anido function.
The present invention also provides, in a further aspect thereof, a coating composition that comprises a liquid medium that contains a hydrophilic colloid and a surfactant, wherein the said surfactant is a compound of the present invention as defined above.
The present invention, in another aspect, provides a method of coating a substrate, which comprises applying to the substrate a coating composition of the present invention. The invention also extends to the coated substrates so produced, especially such coated substrates that may be used in or as photographic products, such as photographic films.
The present invention, in yet another aspect thereof, provides the use of a compound of the present invention, as defined above, as a coating aid in a liquid coating composition.
DESCRIPTION OF EXEMPLARY EMBODIMENTS
The preferred compounds of the present invention are defined by either of the following formulae:
The number of hydrophobic groups, R or (R
1
+R
2
), depends on the linking group L. The hydrophobic group or groups each comprise an aliphatic hydrocarbyl, aryl-(aliphatic hydrocarbyl) or (aliphatic hydrocarbyl)-aryl group, wherein, in each case, the aliphatic hydrocarbyl group may be saturated or unsaturated and may be straight or branched. These groups may be non-fluorinated, completely fluorinated or partially fluorinated. Preferred aliphatic hydrocarbyl groups are alkyl and alkenyl groups and preferred aryl moieties are phenyl and naphthyl groups. Typically, each of the groups R, R
1
and R
2
contains from 8 to 21 carbon atoms. In certain preferred embodiments R
1
and R
2
together have a total of from 8 to 21 carbon atoms. R
1
and R
2
may be the same or different.
The linking entity L is either a sulphur atom (—S—) or a linking group that contains a sulphur atom through which it is attached to T, in other words a linking group that is linked to the or each hydrophobic group by a simple chemical bond and to the oligomeric moiety T by a thio-link (—S—).
Certain preferred sub-groups of the present compounds are represented by the following general formulae, in which formulae (3), (4) and (5) contain typical linking groups for compounds with one hydrophobic group and formulae (6), (7) and (8) contain typical linking groups for compounds with two hydrophobic groups:
R—S—T (3)
R—O—OC—CH
2
—S—T (4)
R—NH—OC—CH
2
—S—T (5)
In the above formulae (4), (5), (7) and (8), other simple chemical groups, in place of the ester or amide link, may also come into consideration.
The oligomeric group T is preferably based on the oligomerisation of vinyl monomers with an amido function, the vinyl part providing a route to oligomerisation and the amido part providing a nonionic polar group to constitute the hydrophilic functional group (after oligomerisation). The oligomeric group T can be constituted from a single monomer source or a mixture of two or more monomers, provided that the resultant oligomeric chain is sufficiently hydrophilic to render the resulting surface-active material soluble in water or other medium. A mixture of monomers may give rise to a group T that is a random co-oligomer. Preferred monomers used to make the oligomeric chain T are acrylamide and derivatives of acrylamide, although methacrylamide and derivatives of methacrylamide can be used too. The monomer 2-vinylpyrrolidone may also be used, although it is less favoured owing to the possibility of adverse photographic effects sometimes found with polyvinyl pyrrolidone (PVP) materials.
Certain suitable monomers can be represented by the two general formulae
wherei
Moon Alice G.
Pitt Alan R.
Simister Elizabeth A.
Wear Trevor J.
Baxter Janet
Eastman Kodak Company
Walke Amanda C.
Wells Doreen M.
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