GB2068004A - Dichlorobutadiene copolymer for coating a hydrophobic film support - Google Patents

Abstract

A copolymer for coating a hydrophobic film support to provide a halogen-containing subbing layer thereon comprises from 73% to 96% by weight of 2,3-dichlorobutadiene, 2% to 10% by weight of at least one hydrophilic monomer, and 2% to 25% by weight of at least one hydrophobic copolymerizable monomer, the glass transition temperature of the copolymer being at least 18 DEG C. The subbing layer is used for improving the adhesion of a gelatin-silver halide emulsion layer to a polyethylene terephthalate film support in dry as well as in wet state.

Description

SPECIFICATION Sheet material comprising a hydrophobic film support directly coated with a halogen-containing subbing layer and halogen-containing copolymer therefor The present invention relates to sheet material comprising a hydrophobic film support directly coated with a halogen-containing subbing layer. In particular the present invention relates to a photographic material wherein the adhesion of (a) hydrophilic colloid layer(s) to a hydrophobic film support with said subbing layer is improved.

It is known from the United States Patent Specification 4,123,278 to provide an adhesive bond between a polyester film support and a hydrophilic colloid layer by means of an adhesive layer consisting essentially of about 25~60% by weight of a chlorine-containing copolymer, 1 5-40% by weight of a butadiene copolymer, and 2-1 0% by weight of a water-soluble melamine-formaldehyde or hydantoin-formaldehyde resin, the said layer being free of gelatin. Normally the chlorine-containing copolymer comprises both vinyl chloride units and vinylidene chloride units.

It has now been found that instead of a chlorine-containing copolymer and butadiene copolymer it is possible to use only one copolymer namely a copolymer containing 2,3-dichloro-butadiene units in a subbing layer for a sheet material with hydrophobic film support, particularly a hydrophobic polyester e.g. polyethylene terephthalate film support.

The halogen-containing copolymer according to the present invention is a copolymer formed from 73% to 96% by weight of 2,3-dichloro-butadiene,2% to 10% by weight of at least one hydrophilic monomer, and 2% to 25% by weight of at least one hydrophobic copolymerizable monomer, the glass transition temperature of the copolymer being at least 1 80C.

The subbed sheet material according to the present invention comprises a hydrophobic film support having directly coated thereon a subbing layer comprising a chlorine-containing copolymer characterized in that the subbing layer contains a major proportion by weight (more than 50%) of a copolymer formed from 73% to 96% by weight of 2,3-dichlorobutadiene,2% to 10% by weight of at least one hydrophilic monomer, and 2% to 25% by weight of at least one copolymerizable hydrophobic monomer, the glass transition temperature of the copolymer being at least 1800.

With copolymers having the defined amount of 2,3-dichlorobutadiene units a Tg of at least 1 800 is obtainable which is particularly advantageous for the manufacture of subbed polyester films of which the subbing layer is coated from an aqueous dispersion (latex). Relatively high drying temperatures (100--1200C) can be applied such being in favour of production speed and enabling the use of shorter drying channels. Further, the Tg of at least 1800 is in favour of the production of less tacky subbing layers. The subbing layers as defined in the present invention are particularly suited for improving the adhesion of a gelatin-silver halide emulsion layer to a polyethylene terephthalate film support in dry as well as in wet state.

With butadiene monomer yielding a homopolymer having a Tg of -850C and with monochlorobutadiene monomer yielding a homopolymer having a Tg of --500C, it will be very difficult for double side subbing of resin supports to produce copolymers having a softening point high enough to avoid sticking of the subbing layer to the rollers of the drying chamber.

By the use of 2,3-dichlorobutadiene one single chlorine-containing monomer provides in the copolymer sufficient chlorine atoms for a good adherence of the copolymer to hydrophobic polyester resins and sufficient double bonds for offering adherence to a hydrophilic colloid e.g. gelatin.

The preparation of the present copolymers may proceed by the emulsion polymerization of the different comonomers according to known emulsion polymerization techniques. The so-called primary dispersion directly formed upon emulsion polymerization may be used as such, or after adaptation of its concentration. Greatly varying concentrations can be used depending on the final concentration and viscosity needed in the coating composition. The copolymers can be prepared in particular analogously to the preparation of Example 1 of Research Disclosure 18 564, September 1979 and analogously to the emulsion copolymerization described in United Kingdom Patent Specification 1,234,755. In the emulsion polymerization of the copolymer a reactive emulsifier as described in United Kingdom Patent Specification 1,511,533 may be used.

The hydrophilic monomer used may be acrylic acid, methacrylic acid, crotonic acid, maleic acid, fumaric acid, itaconic acid, an amide of acrylic and methacrylic acid, a mono-alkyl ester of maleic acid, vinyl pyrrolidone, or an ethylenically unsaturated compound comprising a sulpho group in salt form, for instance as described in United Kingdom Patent Specification 1,453,057, more particularly the sodium salt of p-sulphoethylmethacrylate and the sodium salt of acrylamido-2-methylpropane sulphonic acid.

The said other hydrophobic copolymerizable monomer which may be used include esters of acrylic or methacrylic acid e.g. methyl, ethyl, butyl, and cyanoethyl acrylate or methacrylate, acrylonitrile, styrene, and further vinyl esters such as vinyl acetate and the vinyl ester of versatic acid, which is sold by Shell Chemical Co., under the Trade Mark VEOVA 10 and which is a branched chain vinyl carboxylic acid ester having a molecular weight of 198 and corresponding to the formula:

wherein R1, R2 and R3 are alkyl groups having together from 7 to 9 carbon atoms, and wherein only one of R1, R2 and R3 is a methyl group.

According to one embodiment of the present invention said copolymer of 2,3-dichlorobutadiene is used in a single adhesive layer for adhering directly a mainly gelatin-containing layer e.g. gelatin-silver halide emulsion layer to a hydrophobic polyester film support.

For a single adhesive layer, preferably gelatin is used in admixture with the copolymer. In such layer the gelatin content is less than 50% by weight and is usually from 5% to 30% by weight.

Although a subbing layer produced from a said copolymer of 2,3-dichlorobutadiene and gelatin has already a good flexibility such may further be improved to obtain an easier stretching by incorporating a plasticizer for gelatin. The plasticizer is added e.g. in an amount of 1 0% to 80% by weight with respect to the total weight of the gelatin.

The term "plasticizer" as used herein relates to plasticizing compounds that are soluble or dispersible in water and photographically inert and that have the property of allowing layers formed from mixtures of gelatin and said 2,3-dichlorobutadiene copolymers to be more easily stretched, such layers after having been stretched and heated at relatively high temperatures remaining completely transparent. The action of these plasticizers is not only based on the known effects shown by external plasticizers, as described i.a. in the book "Plasticizatlon and Plasticizer Processes", Advances in Chemistry, Series 48~American Chemical Society, Washington D.C. - 1965.Probably this action results also in an improvement of the miscibilizy between gelatin and the chlorine-containing copolymer, so that the chlorine-containing copolymer in fact acts as a real external plasticizer for gelatin.

Suitable plasticizers acting as stretch-improving agents are aliphatic polyhydroxy compounds such as glycerol, tri(P-hydroxyethyl)giycerol. 1,1,1 -tri(hydroxymethyl)propane, 2-nitro-2-ethyl-l ,3- propanediol, I ,3-dichloro-2-propanol, 1 ,2,4-butanetriol, 3-hydroxymethyl-2,4-dihydroxypentane, 1,2,6- hexanetriol,2-hydroxymethyl-4-hydroxy-amyl alcohol, glycerol-aldehyde, sorbitol, mannitol and polyvinyl alcohol.

Equally suitable compounds are caprolactam and N,N'-dimethylurea. Other suitable plasticizers are aliphatic carboxylic or sulphonic acids such as glutaric acid, adipic acid, azelaic acid, sebacic acid, mono- and dichloro-acetic acid, 1 2,3-propene tricarboxylic acid, acrylic acid, methacrylic acid, maleic acid, fumaric acid, itaconic acid, and 2-sulpho-ethyl methacrylate; further aromatic acids such as phthalic acid, o-sulphobenzoic acid, o-nitrobenzoic acid, o-aminobenzoic acid, n-hydroxybenzoic acid, and salicylic acid.

In order to improve the electric conductivity of the subbing layer to avoid electrostatic charge accumulation a metal-complexing antistatic agent e.g. in an amount up to 30% by weight of the dry subbing layer may be added.

Suitable mecal complexing antistatic agents are e.g. sulphosalicylic acid, 2,5disulphohydroquinone, the sodium salt of ethylene diamine tetra-acetic acid, ethanolaminodiacetic acid, the sodium salt of N(o-hydroxybenzyl)-aminodiacetic acid, the monosodium salt of vanadic acid, 3,5disulphopyrocatechin, phosphono-acetic acid, ethylene-1 ,2-diphosphonic acid, butylene-1,4diphosphonic acid, ascorbic acid, and other compounds of that type described in the United States Patent Specification 4,123,278.

In the preparation of a single adhesive coating composition the 2,3-dichlorobutadiene-containing copolymer is preferably mixed in the form of a primary dispersion i.e. as latex obtained by emulsion polymerization and in the proportions indicated above with an aqueous gelatin solution, whereafter a plasticizer and possibly an antistatic agent are dissolved in water and mixed therewith. The viscosity of the coating composition thus formed can be adapted as desired and known coating aids are added to the composition. Finally the coating composition is applied in known manner to a hydrophobic resin film serving as support.

According to a modified embodiment of the invention the coating composition of a single adhesive layer, does not contain gelatin and is formed by mixing the chlorine-containing copolymer in the form of an aqueous primary dispersion with an aqueous solution of melamine-formaldehyde or of hydantoinformaldehyde resin, whereupon optionally an antistatic agent, a stretch-improving agent and/or a matting agent is added thereto. Suitable stretch-improving agents are the plasticizers in particular the aliphatic polyhydroxy compounds referred to hereinbefore. The melamine-formaldehyde resin or hydantoin-formaldehyde resin is preferably used in an amount of 2 to 10% by weight of the dry layer.

The plasticizer is preferably used in an amount of 5 to 40% by weight with respect to the total weight of the dry adhesive layer.

According to a second embodiment, in order to ensure a perfect adhesion of a hydrophilic colloid layer such as a photographic gelatino-silver halide emulsion layer to a hydrophobic film support, a layer of said copolymer of 2,3-dichlorobutadiene is applied as a first subbing layer called primary layer in direct contact with the hydrophobic film support and a second layer called second subbing layer including a rather large amount (at least 30% by weight) of gelatin in admixture with a polymer or copolymer of ethylenically unsaturated monomers of hydrophobic nature is applied from a latex.

Examples of such latices are described in the United States Patent Specification 3,649,336 which is to be read in conjunction herewith. Said subbing layer preferably comprises in a ratio of 1:3 to 1:0.5 by weight a mixture of gelatin and a copolymer of 30 to 70% by weight of butadiene and at least one copolymerizable ethylenically unsaturated monomer preferably a halogen-free monomer selected from the group consisting of acrylonitrile, styrene, an acrylic acid ester, methacrylic acid ester and acrolein.

Optionally the mixture of said latex (co)polymer and gelatin contains a plasticizer for gelatin as referred to hereinbefore such as a polyethylene oxide, glycerol or sorbitol.

The coating of the primer layer and of the subbing layer proceeds by means known to those skilled in the art.

The thickness of primer layer and likewise of the above described single adhesive layer may vary between 0.10 and 2 ym. The thickness of the second adhesive layer (subbing layer) may vary between 0.10 and 20cm.

Although the present invention mainly relates to the bonding of hydrophobic polyester film supports such as a polyethylene terephthalate film support to a hydrophilic colloid layer containing gelatin the present sheet material may contain other kinds of hydrophobic supports e.g. may be a film ol cellulose triacetate, polycarbonate resin, polystyrene or polymethacrylic acid ester. The adhesive layer(s may be applied to both sides of the support.

To the coating composition of the adhesive layer(s) may be added known coating aids such as dispersing agents, spreading agents, antiseptic agents for the gelatin and thickening agents, which in general are highly viscous water-soluble poiymers having as sole object to adapt the viscosity of the 5 coating composition to the desired degree. A survey of the thickening of latices and of the thickening agents that niay be used has been given by Houben-Weyl in "Methoden der organischen Chemie", Makromolekulare Stoffe, 14/1, pages 519 and 536, Georg Thieme Verlag, Stuttgart (1961).

As desired adhesion-improving agents may be incorporated in the adhesive layer(s) from an aqueous solution, e.g. resorcinol, pyrocatechol, dihydroxytoluene, and chloral hydrate. Other useful ingredients that may be added are, e.g., surface-active coating agents, colloidal silica and embossing agents for creating microscopic protrusions of less than 3 #m for obtaining a thin air space between the subbed material and a material touching it, e.g. during transport of the film. Such embossing agents can be known matting agents, e.g. those described in the European Patent Application 79/200053.1.

Any of the light-sensitive layers containing a photosensitive substance in a hydrophilic colloid medium can be adhered very well to the present subbed hydrophobic support. The hydrophilic colloid layer may contain as photosensitive substances photosensitive silver halide grains, photosensitive iron salts or complexes e.g. iron(lll)ammonium oxalate or diazonium compounds. Other non-light-sensitive hydrophilic colloid layers e.g. gelatin antihalation layers can be adhered likewise very well to a subbed support according to the present invention.

The 2,3-dichlorobutadiene copolymer coating composition may be applied to a polyester film support either before or after it has been stretched or oriented. It can be applied to the unstretched or only monoaxially stretched film support.

Where a 2,3-dichlorobutadiene copolymer is applied in a primer layer this layer is preferably applied onto the unstretched amorphous polyester film support. After drying the primer coating, the coated film is longitudinally stretched e.g. in a temperature of from 80 to 1 000C with a stretch ratio in the range of 2.5:1 to 4.0:1. The thus primed support is then coated with a second layer called hereinbefore second subbing layer. After drying of that layer the film is stretched in the transverse direction e.g. in the temperature range of from 80 to 900C with a stretch ratio of 3.5:1.

In accordance with the present invention completely clear subbed polyester films are formed.

Hydrophilic layers, such as gelatin-containing silver halide emulsion layers will tenaciously adhere to a support subbed in that way. Indeed the adhesion of a hydrophilic gelatin-silver halide emulsion layer to the polyester film in dry as well as in wet state during the treatment of the photographic material in the different photographic processing baths is very good.

The examples hereinafter are especially directed to the use of a subbed polyethylene terephthalate film support containing in its subbing composition a 2,3-dichlorobutadiene copolymer but the adhesive layer can, however likewise be applied to other polyester films, e.g. polyesters resulting from the polycondensation of glycol, or mixtures of glycols with terephthalic acid or mixtures of terephthalic acid with minor amounts of other dicarboxylic acids such as isophthalic acid, diphenic acid, and sebacic acid. The polyester film may contain pigments or dyes and when used as base for X-ray film it is e.g.

tinted blue.

In the following table copolymers used according to the invention are defined by their ratio by weight of repeating units and glass transition temperature (Tg).

TABLE

Copolymer I A (%) B (%) C (%) D (%) Tg ('C) 1. 88 10 2 - 23 2. 88 10 - 2 20 3. 88 8 4 - 19 4. 86 10 4' - 19 5. 84 10 6 - 19 6. 84 14 2 19 A = 2,3-dichlorobutadiene B = methylacrylate C = itaconic acid D = acrylic acid The present invention is illustrated by the following examples wherein all ratios and percentages are by weight unless indicated otherwise.

EXAMPLE 1 A blue-tinted amorphous polyethylene terephthalate film having a thickness of 2.0 mm was formed by extrusion of molten polyethylene terephthalate at a temperature of about 28000 on a quench drum and was chilled to a temperature of 840C at which temperature the film was stretched longitudinally in a stretch ratio of 3.3:1.

The thus stretched film was double-side coated with a primer layer at a coverage of 100 sq.m/litre applying the following coating composition: 15% aqueous dispersion of emulsion polymerised copolymer 1 of table 800 ml ULTRAVON W (trade name) (10% aqueous solution) 16 ml SYTON W 30 (trade name) 40 ml water 144 ml ULTRAVON W is a trade name of Ciba Geigy A.G., Switzerland, for the disodium salt of 2heptadecylbenzimidazole disulphonic acid.

SYTON W 30 is a trade name of Monsanto Chemical Company, St. Louis, Mo., U.S.A. for a 30% colloidal dispersion of silica in water (average particle size 120 nm).

The coated layer was dried in a drying channel with a hot (1000C) air-current.

The primed film was stretched transversally in a stretch ratio of 3.5:1 at a temperature of 9000 whereupon the film was heat-set at 22000.

Onto the biaxially stretched film a subbing layer was double-side coated at a coverage of 30 sq.m/litre from the following composition: 10% aqueous gelatin solution 80 ml SYTON W 30 (trade name) 66 ml 20% aqueous dispersion (latex) of copoly (butadiene/methylmethacrylate) (50/50) 50 ml ULTRAVON W (trade name) (10% aqueous solution) 7.5 ml disodium salt of sulphosalicylic acid (10% aqueous solution) 15 ml methanol 100 ml water 681.5 ml After drying onto the subbed film a gelatin silver halide emulsion layer was double-side coated for use in X-ray recording. In the thus obtained photographic material the silver halide emulsion layer adhered very well to the polyester support in wet as well as in dry state.

The adhesion in wet state was checked by scratching the material superficially and trying to rub off the gelatin containing layer with a finger after each step of the photographic processing (development, rinsing, fixing, rinsing). The gelatin containing layer could not be removed with this rubbing.

EXAMPLE 2 A colourless amorphous polyethylene terephthalate film having a thickness of 1.1 mm was obtained by extrusion at a temperature of 2800C and quenching on a quench drum.

The cooled amorphous film was double-side coated with a primer layer at a coverage of 40 sq.m/litre applying the following coating composition: 15% aqueous dispersion of emulsion polymerised copolymer 2 of the table 800 ml ULTRAVON W (trade name) (10% aqueous solution) 16 ml SYTON W 30 (trade name) 40 ml water 144 ml After drying the primed film was stretched longitudinally in a stretch ratio of 3.3:1 at a temperature of 840 C.

Onto the dried film a subbing layer was double-side coated from the following composition: 10% aqueous gelatin solution 25 ml 10% aqueous malonic acid 10 ml AMBITERIC H (trade name) (10% solution in water) 1 ml matting agent according to European Patent Applica tion 79/2.00053.1 (6% dispersion in water) 1.5 ml water 962.5 ml AMBITERIC H is a trade name of Glovers Chem. Ltd. for a 85% by weight aqueous solution of R2 R1-N±R3-COO I R4 wherein R' and R2 each are lower alkyl, R4 is C8-C18 alkyl, and R3 is lower alkylene.

The thus coated film was after drying the subbing layer transversally stretched in a draw ratio of 3.3:1 at 900C and heat-set at 2200C.

The subbed polyester film was used as a support for the production of a photographic gelatinsilver halide emulsion material used in the graphic art and having at one side a coloured gelatin antihalation layer and at the other side a gelatin-silver halide emulsion layer of the type used in lithdevelopment. The adhesion of said both layers was very well in wet as well as in dry state.

EXAMPLE 3 Example 1 was repeated with the proviso however, that the primer layer being applied at both sides of the polyester film was built up by means of the following composition: 1 5% aqueous dispersion of emulsion-polymerised copolymer 3 of the table 570 ml sorbitol (10% aqueous solution) 100 ml disodium sulphosalicylic acid (10% aqueous solution) 136 ml melamine-formaldehyde resin (40% solution in water) 13 ml HOSTAPAL BV (trade name) (20% aqueous solution) 4 ml water 177 ml HOSTAPAL BV is a trade name of Farbwerke Hoechst A.G. Frankfurt-W.Germany for a dispersing agent being an alkyl aryl polyglycol ether sodium sulphonate.

The subbing layer was dried with a stream of hot air.

The film carrying at both sides a single subbing layer was double-side coated with a photosensitive gelatin-silver halide emulsion suited for medical X-ray recording. The adherence of the emulsion layer in dry as well as in wet state to the described subbing layer and of that subbing layer to the polyethylene terephthalate support was very good. The presence of the subbing layer had no disadvantageous influence on the photographic properties of the emulsion layer.

Claims (21)

1. Sheet material comprising a hydrophobic film support having directly coated thereon a subbing layer comprising a chlorine-containing copolymer characterised in that the subbing layer contains a major proportion by weight of a copolymer formed from 73% to 96% by weight of 2,3dichlorobutadiene, from 2% to 10% by weight of at least one hydrophilic monomer, and from 2% to 25% by weight of at least one copolymerizable hydrophobic monomer, the glass transition temperature of the copolymer being at least 1 80C.

2. A sheet material according to claim 1, wherein the said chlorine-containing copolymer is the only chlorine-containing copolymer in the subbing 'ayer.

3. A sheet material according to claim 1 or 2, wherein the said film support is a hydrophobic polyester film support.

4. A sheet material according to claim 3, wherein the film support is a polyethylene terephthalate film support.

5. A sheet material according to any of claims 1 to 4, wherein the hydrophilic monomer is acrylic acid, methacrylic acid, crotonic acid, maleic acid, fumaric acid, itaconic acid, an amide of acrylic or methacrylic acid, a mono-alkyl ester of maleic acid, vinyl pyrrolidone, or an ethylenically unsaturated compound containing a sulpho group in salt form.

6. A sheet material according to any of claims 1 to 5, wherein the said copolymerizable hydrophobic monomer is an ester of acrylic or methacrylic acid, acrylonitrile, styrene, vinyl acetate or the vinyl ester of versatic acid.

7. A sheet material according to any of claims 1 to 6, wherein the copolymer is one described in the table of the disclosure.

8. A sheet material according to any of claims 1 to 7, wherein the sid subbing layer is a single adhesive layer for adhering a hydrophilic colloid layer to the hydrophobic film support.

9. A sheet material according to claim 8, wherein said single adhesive subbing layer contains in admixture with said copolymer up to 30% by weight on the total weight of the layer, of gelatin.

10. A sheet material according to claim 9, wherein the said adhesive layer comprises a plasticizer for gelatin.

11. A sheet material according to claim 8, wherein said single adhesive subbing layer is free from gelatin and contains in admixture with said copolymer from 2 to 10% by weight based on the total weight of the subbing layer of a melamine-formaldehyde or a hydantoin-formaldehyde resin.

12. A sheet material according to any of claims 8 to 11, wherein said adhesive layer contains a metal-complexing antistatic agent.

13. A sheet material according to claim 11, wherein said adhesive subbing layer contains a stretch-improving agent and/or a matting agent.

14. A sheet material according to any of claims 1 to 7, wherein said subbing layer comprises a first subbing primer layer and a second subbing layer containing at least % by weight of gelatin and a polymer or copolymer of hydrophobic ethylenically unsaturated monomers applied from a latex.

15. A sheet material according to claim 14, wherein said copolymer is derived from 30 to 70% by weight of butadiene and at least one halogen-free copolymerisable ethylenically unsaturated monomer.

16. A sheet material according to claim 14 or 15, wherein said second subbing layer contains a plasticizer for gelatin.

17. A sheet material according to any of the claims 1 to 16, wherein the subbing lyaer(s) are coated with a light-sensitive gelatin-silver halide emulsion layer.

1 8. A sheet material according to claim 1 7, wherein the polyester film contains pigments of dyes.

19. A copolymer formed from 73% to 96% by weight of 2,3-dichlorobutadiene, from 2% to 10% by weight of at least one hydrophilic monomer, and from 2% to 25% by weight of at least one copolymerizable iiydrophobic monomer, the glass transition temperature of the copolymer being at least 1 80C.

20. The copolymer according to claim 19, wherein the hydrophilic monomer is acrylic acid, methacrylic acid, crotonic acid, maleic acid, fumaric acid, itaconic acid, an amide of acrylic or methacrylic acid, a monoalkyl ester of maleic acid, vinyl pyrrolidone, or an ethylenically unsaturated compound containing a sulpho- group in salt form.

21. The copolymer according to claim 19 or 20, wherein the said hydrophobic copolymerizable monomer is an ester of acrylic or methacrylic acid, acrylonitrile, styrene, vinyl acetate or the vinyl ester of versatic acid.