GB2032405A

GB2032405A - Vanadium pentoxide colloidal solution

Info

Publication number: GB2032405A
Application number: GB7921904A
Authority: GB
Original assignee: Eastman Kodak Co
Current assignee: Eastman Kodak Co
Priority date: 1978-06-23
Filing date: 1979-06-22
Publication date: 1980-05-08
Also published as: DE2925370C3; JPS6326375B2; GB2032405B; IT7923737A0; JPS555982A; DE2925370A1; NL7904917A; FR2429252B2; FR2429252A2; DE2925370B2; IT1165102B

Abstract

An antistatic composition is made by heating to a temperature of at least 100 degrees C above the melting point of vanadium pentoxide a mixture which contains at least 80 per cent by weight of vanadium pentoxide and a remainder consisting of an alkali metal, transition metal or rare earth element oxide and pouring the molten mixture into water to form a colloidal solution. The composition so made may be diluted with a water-miscible organic solvent and may contain a binder to improve the mechanical properties of an antistatic layer produced therefrom. An antistatic layer formed from a composition of the invention is useful for a variety of articles and especially for the supports of photographic and magnetic recording materials.

Description

SPECIFICATION Antistatic compositions and articles comprising antistatic coatings prepared therefrom This invention relates to a method of making antistatic compositions.

It is well known that the surfaces of articles made from electrically insulating substances, such as plastics materials, tend to become electrically charged and that such charges can have harmful effects.

For example, a static discharge occurring during the manufacture or use of a sensitive photographic film may be recorded by the film to produce an unwanted image. The tendency for static charges to be generated, and for them to persist after generation, can be reduced or overcome by coating the surface concerned with a layer of relatively high electrical conductivity formed from an antistatic composition.

In French patent specification No. 2,318,4442 there is described a method of making an antistatic composition which comprises heating vanadium pentoxide, or a mixture containing at least 80% by weight of vanadium pentoxide, the remainder comprising a glass former such as a phosphate or polyphosphate of sodium, and optionally comprising another oxide such as molybdenum trioxide, to a temperature at least 100 degrees C above the melting point of vanadium pentoxide and pouring the molten mass rapidly into distilled water at room temperature so as to form a colloidal solution. For this result to be obtained, the molten mass should enter the water at a temperature well above (say, at least 50 degrees C above) its melting point.

We have found that if this fusion-quenching technique is applied to a mixture containing at least 80% by weight of vanadium pentoxide and another oxide (the nature of which is specified below) a glass-former need not be present.

According to the present invention there is provided a method of making an antistatic composition which comprises heating to a temperature at least 100 degrees C above the melting point of vanadium pentoxide a mixture which contains at least 80% by weight of vanadium pentoxide and a remainder which consists of an alkali metal, transition metal or rare earth element oxide and pouring the molten mixture into water to form a colloidal solution.

Also provided in accordance with the invention is an antistatic composition made by the method of the invention and an antistatic layer made by coating a surface with, and drying, a layer of an antistatic composition of the invention.

In carrying out a method of the invention it is preferred to use distilled water and for the water to be initially at the ambient temperature. It is also preferred for the temperature of the melt to be high enough for the molten mixture to enter the water at a temperature at least 50 degrees C above the melting point (6900C) of vanadium pentoxide. A temperature of at least 100000 is preferred.

An antistatic layer of the invention may contain, for a given resistivity, approximately half the quantity of vanadium pentoxide contained in a layer made by the method described in the French patent specification No. 2,318,442. Some of the antistatic layers of the invention exhibit such a low coloration that their optical densities are not measurable. Layers containing lithium or silver oxides have rather low resistivity values, 0.2 GQ for lithium (5 mg of V205 per m2) and 0.35 GQ for silver (7.2 mg of V20s per m2).

The alkali metal, transition metal, or rare earth element oxide may be provided by a compound, preferably an oxalate or carbonate, which decomposes at the fusion temperature to give that oxide. The quantity of compound used is such as to give a maximum of 20% by weight of the corresponding oxide in the fused mixture.

Lithium is preferably used as an alkali metal; chromium, manganese, copper, zinc, niobium and silver are preferably used as transition metals; and neodymium, samarium, gadolinium, ytterbium and europium are preferably used as rare earth metals.

The resulting aqueous solutions may be diluted by organic solvents. The presence of organic solvents in the antistatic compositions makes it possible to incorporate therein various binders consisting of natural, artificial or synthetic high polymers that improve their mechanical properties, and may impart specific properties such as the possibility of being removable during photographic processing, and a friction coefficient adapted for a particular use. The presence of a binder may be desirable to facilitate the adhesion of the layer to the support or to a subsequent overcoating. However, the addition of binders to the antistatic compositions is not essential for layer formation because the antistatic substances have the properties of a polymer.Useful binders include, for instance, cellulose derivatives such as cellulose acetate, cellulose acetophthalate, cellulose etherphthalate, methylcelluloses, soluble polyamides, styrene and maleic anhydride copolymers, copolymers prepared as emulsions such as methyl acrylate, vinylidene chloride and itaconic acid polymers.

The fusion of the pulverised substances can be carried out in any appropriate device, especially in a muffle furnace or in a solar furnace.

In carrying out the invention, the mixture of vanadium pentoxide and the other oxide is melted at a temperature at least 10000 above the melting temperature of vanadium pentoxide. The melting temperature is preferably about 1 000 C, a temperature for which the resulting layers exhibit the lowest surface resistivity values.

The melt can be poured preferably in an amount giving a concentration of up to 60 grams per litre, continuously into distilled water. The height of the fall of the melt is conveniently between 2 m and 1 5 cm. While the melt is being poured, the water is vigorously stirred by any appropriate device.

A gel is obtained that may then be diluted with water or with a water organic solvent mixture, such as a water and acetone mixture. The concentration of the antistatic substance may be varied according to the properties desired. Satisfactory results are obtained with a concentration of 0.1% by weight of antistatic substance.

An antistatic layer according to the invention may be coated on a large variety of supports, e.g.

cellulose ester supports such as cellulose acetate and cellulose acetobutyrate supports, polyester supports such as those of poly(ethylene terephthalate) and supports of polycarbonates, poly(ethylene and 1 ,4-cyclohexanedimethanol terephthalate-co-isophthalate) and polyolefins.

Various methods may be used to coat the antistatic coating composition on the chosen support. It is possible to use a dip roll which is immersed in the composition to be coated and a roller around which the support to be coated is passed thereby creating a coating bead of solution at the nip. Any conventional methods may also be used, such as hopper coating, air knife coating or brush coating.

The antistatic layers according to the invention are preferably coated on the support concerned at coverages lower than 10 mg of vanadium pentoxide per square metre in order to eliminate or substantially reduce pollution hazards.

The antistatic layers produced by the method of the invention may be permanent or temporary, according to the use for which the products bearing them are intended. To render the layers permanent or to improve their mechanical properties, in particular the friction coefficient, it is possible to overcoat them with a composition capable of imparting the desired properties, e.g. a lubricant or a composition containing a binder, such as a cellulose derivative (e.g. cellulose etherphthalate). A protective coating may contain both a lubricant and a binder as well as other compounds such as a matting agent.

The antistatic compositions of the invention are very suitable for use on photographic film supports and magnetic film supports. They may be coated on the side of the support that does not carry a sensitive layer, or as an underlayer or over the sensitive layer.

The following examples illustrate the invention.

EXAMPLE 1 Control Test A Vanadium pentoxide was placed in a platinum crucible and heated at 1 0000C for 5 minutes in a muffle furnace, then the melt was poured into vigorously stirred distilled water. A quantity of the colloidal solution so produced containing 0.1 g of vanadium pentoxide was incorporated as a colloidal dispersion into a hydroketonic solution containing 10 parts of distilled water to 90 parts of acetone by volume.

The resulting composition was coated on a cellulose triacetate film at a coverage of 19 mg per m2.

Control Test B A coating composition as used for test A was coated on a cellulose triacetate support at a coverage of 8 mg/m2.

The surface resistivity values of the layers obtained from Control tests A and B are given in Table I.

TABLE I

Surface resistivity Coverage in (G# Element mg of Tests added V20Jm2 15% RH 50% RH 19 1 0.9 (Control) B - 8 3 2 (Control) Tests 1 to 4 For each test, 40 g of an intimate mixture of pulverised vanadium pentoxide and silver oxide in the relative proportions quoted in table II was placed in a platinum crucible and heated for 5 minutes in a muffle furnace at 10000 C. The melt was then poured rapidly into one litre of vigorously stirred distilled water.

Each colloidal dispersion só obtained, was diluted to a concentration of 0.1% by weight of antistatic substance in a water/acetone mixture (10:90 by volume). The resulting solution was coated on a cellulose triacetate support.

The surface resistivity values are given in table II.

TABLE II (muffle furnace)

Surface resistivity Quantity by Coverage | (Gi2) Element weight/100 g in mg of Test added of V2O5 V2O5/m2 15% RH 50% RH 1 Ag 0.5 g 7.6 3 1 (oxide) 3 2 Ag 4.4 g 7.6 0.8 0.3 (oxide) 3 Ag 6.2 g 7.7 0.4 0.26 (oxide) 4 Ag 8.8 g 7.2 0.35 0.1 (oxide) EXAMPLE 2 In the test of this example, pulverised vanadium pentoxide and transition metal oxides or carbonates were intimately mixed. These mixtures were melted and poured into water as described in Example 1. Each resulting colloidal dispersion was diluted to obtain a concentration of 0.1% by weight of antistatic substance in a water/acetone mixture (10:90 by volume). The resulting solutions were coated on a poly(ethylene terephthalate) support. The quantities by weight of oxides or carbonates added to 1 00 g of V20s, the coverage ratios (in mg of V205 per m2) and the resistivity values are set forth in Table Ill.

TABLE Ill

Surface resistivity Quantity by Coverage (GQ) Element weight/100 g in mg of 15% RH 50% RH Test added of V2Os V2Os/m 5 Cr 5.9 g 9.4 3 0.8 (oxide-Cr203) 6 Cr 6.6 g 6 2 1.6 (oxideCr203) 7 Mn 1.3 g 6.8 0.75 0.75 (carbon ate-Mn CO3) 8 Cu 4.5 g 4.4 0.7 - (oxi de-Cu20) 9 Zn 4g 8 2 0.9 (oxide) ZnO 10 Nb 16 g 7 0.5 0.4 (oxide)Nb2O5 The layers obtained with chromium, manganese or zinc were not so yellow as those that contained only vanadium pentoxide and exhibited a lower optical density.

EXAMPLE 3 A colloidal dispersion was prepared by the process of Example 2 from 1 g of lithium oxide (Li203) for 100 g of vanadium pentoxide. As in that Example, it was diluted and the resulting solution was coated on a poly(ethylene terephthalate) support, at a coverage of 5 mg of vanadium pentoxide per m2.

The surface resistivity at 15% RH was 0.2 GQ.

EXAMPLE 4 In the tests of this Example, rare earth metal oxides, oxalates or carbonates were used. The process for preparing the layers was that of Example 2. The quantities in grams per 100 g of vanadium pentoxide and the surface resistivity values are set forth in Table IV.

TABLE IV

Surface resistivity Quantity by Coverage (GQ) Element weight/100 g in mg of /0RH Test added of V2O, V2Os/m2 15% RH 50% RH 13 Nd 12.6 g 6 7 2 (Carbonate) Nd2(CO,)3, 8H2O 9 1 0.5 14 Sm 9.9 g 6 2 0.4 (Oxal ate) Sm2(C204)3, 10H2O 7 0.6 0.09 15 Gd 9.6 g 5 3 0.3 (Oxal ate) Gd2(C204)3. 10H2O 9 0.7 0.2 16 Yb 9.1 g 4 4 0.1 (Oxal ate) Yb#(C204)3, 1 H2 17 Eu 4.6 g 4 0.3 0.5 (Oxide) Eu2O3

Claims

1. A method of making an antistatic composition which comprises heating to a temperature at least 100 degrees C above the melting point of vanadium pentoxide a mixture which contains at least 80% by weight of vanadium pentoxide and a remainder which consists of an alkali metal, transition metal or rare earth element oxide and pouring the molten mixture into water to form a colloidal solution.

2. A method according to claim 1 wherein the remainder consists of the oxide of the alkali metal lithium.

3. A method according to claim 1 wherein the remainder consists of an oxide of one of the transition metals chromium, manganese, copper, zinc, niobium and silver.

4. A method according to claim 1 wherein the remainder consists of an oxide of one of the rare earth elements neodymium, samarium, europium, gadolinium and ytterbium.

5. A method according to any of the preceding claims wherein the remainder is provided by a compound which decomposes at the heating temperature to give the alkali metal, transition metal or rare earth element oxide.

6. A method according to claim 5 wherein the said compound is an oxalate or carbonate.

7. A method according to any of the preceding claims wherein the mixture is heated to a temperature of at least 10000 C.

8. A method according to any of the preceding claims wherein the colloidal solution is mixed with a solution of a polymeric binder.

9. A method according to claim 8 wherein the solution of the polymeric binder contains a watermiscible.organic solvent.

10. A method according to claim 1 substantially as described in any of the Examples 1 to 4 herein.

1 1. An antistatic composition made by a method according to any of claims 1 to 10.

12. A method of making an antistatic layer which comprises coating a substrate with a layer of a composition according to claim 11.

13. An article comprising an antistatic layer formed from a composition made by a method according to any of claims 1 to 10.

14. An article according to claim 13 wherein the antistatic layer contains less than 10 mg of vanadium pentoxide per square metre.

1 5. An article according to claim 13 or 14 which comprises a film of artificial or synthetic polymeric material.

16. An article according to claim 15 wherein the polymeric material is cellulose triacetate or poly(ethylene terephthalate).

17. An article according to claim 15 or 16 which is a sensitive photographic material comprising at least one radiation-sensitive layer coated on the film of polymeric material.

18. An article according to claim 15 or 16 which is a recording material comprisig a magnetic recording layer coated on the film of polymeric material.