HIGHLY TRANSPARENT COATED CELLULOSE TRIACETATE FILM AND DISSOLVER MEDIUM

Abstract

A coated, highly transparent film based on cellulose triacetate, is proposed that includes a) a support film acting as support layer and a cellulose triacetate or a mixture of cellulose esters and cellulose triacetate as main component, the cellulose triacetate or mixture being defined by a haze value of <0.5%, measured on the cellulose triacetate or mixture drawn out to a film after having been dissolved in dichloromethane or acetone, and b) a multi-functional coating applied in a coating solution to one or both sides of the support film. A dissolver medium can also be used as an enclosure medium. The highly transparent films of the invention can be used as window film, sunglasses film, laminating film, furniture foil, enclosing film, slide film for microscopy, cover slip replacement film and/or protective film, adhesive to glass, wood, metal, ceramic, cellulose derivative films or plastics following incipient dissolution or heat treatment.

Claims

1.-16 (canceled)

17. A highly transparent film based on cellulose triacetate, comprising, a) a support film acting as a support layer comprising cellulose triacetate or a mixture of cellulose esters and cellulose triacetate as a primary component, wherein the cellulose triacetate or the mixture is defined by a haze value of <0.5%, and b) a coating applied on one side or both sides of the support film in a coating solution and comprising the following components: b.sub.1) one or more solvents selected from the following group of solvents consisting of alcohols, organohalogen solvents, ethers, esters, ketones, aromatics, deep eutectic solvents (DES) based on quaternary ammonium compounds and hydrogen bond donors. b.sub.2) at least one acrylate copolymer having a refractive index at 20 C., between 1.30 and 1.60, an average molecular weight M.sub.W between 10,000 g/mole and 300,000 g/mole, a glass transition temperature of at least 35 C. and a solubility or swellability in at least one solvent; b.sub.3) at least one or more cellulose derivatives which are either identical to the cellulose derivative optionally used in the surface layer of the support film or have a solubility of at least 10 g/liter in a solvent; b4) one or more plasticizers in an amount of between 0.01% by mass and 15% by mass.

18. The highly transparent film according to claim 17, wherein the support a) further comprises, a.sub.1) as raw material base: cotton linters and/or wood pulp, a water content of 1%, a proportion of free acetic acid of 300 ppm, a proportion of gel-forming components of 0.5%, a very slight yellow coloration, characterized by a low Hazen color number (APHA value) 70 (determined on a 16% solution of cellulose triacetate, dissolved in methylene chloride according to the ASTM D-1209 method), a proportion of <0.5% of foreign fibers and over- or under-derivatized particles having a size of 540 m, and a.sub.2) at least one organic or inorganic substance, which is effective as bonding agent and spacer between the molecular chains of cellulose triacetate and acts as a plasticizer, so that this substance, in addition to an improved removability of the solvents, also causes improved flexibility and elasticity of the films, a.sub.3) to improve the contact angle and/or the scratch resistance of the support film, a surface layer disposed on one side or both sides and based on a cellulose derivate or cellulose derivate mixture that is fully dissolved or initially dissolved in halogen alkanes, ketones, ethers, esters, deep eutectic solvents or alcohols and/or an acrylate mixture which is crosslinkable with UV light, chemically or by supplying thermal energy, a.sub.4) optionally further functional additives from the following groups in a proportion between 0.001 mass % and 15 mass %: organic or inorganic substances with a transmission-influencing absorptive function in the wavelength range of 300 nm to 2,500 nm, microscale or nanoscale additives to improve adhesion, slip or electrostatic properties, crosslinking agents, stabilizers and/or antioxidants.

19. The highly transparent film according to claim 17, wherein substances used as plasticizer component according to a.sub.2) and b.sub.4) are selected from the group consisting of phosphoric acid esters, phthalic acid esters, carboxylic acid esters, glycols, deep eutectic solvents and/or polyesters and having a boiling point greater than 60 C.

20. The highly transparent film according to claim 19, wherein the cellulose derivatives are one or more selected from the group consisting of cellulose acetate (CA), cellulose diacetate (CDA), cellulose triacetate (CTA) cellulose acetate butyrate (CAB) cellulose acetate propionate (CAP) methyl cellulose (MC), ethyl cellulose (EC) and hydroxypropyl cellulose (HPC).

21. The highly transparent film according to one of claims 17, wherein the coating solution comprises at least one solvent which dissolves the acrylate copolymer used for the coating and also initially dissolves or swells the cellulose triacetate used for the support film and has a boiling point greater than 35 C.

22. The highly transparent film according to claim 17 or 18, wherein the coating solution comprises one or more acrylate copolymers having an average molecular weight between 10,000 g/mole and 300,000 g/mole, which are selected from the group consisting of methyl methacrylate copolymers, ethyl acrylate copolymers, ethyl meth acrylate copolymers, butyl acrylate copolymers and butylmethacrylate copolymers.

23. The highly transparent film according to claim 22, wherein the multifunctional coating is obtained based on a coating solution which contains maximally two plasticizers according to claim 3, maximally two cellulose derivatives according to claim 4, maximally two solvents according to claim 5 and maximally two acrylate copolymers according to claim 6.

24. The highly transparent films according to claim 23, wherein the thickness of the support film is 40 m to 350 m, and the dry thickness of the coating is between 0.5 m to 100 m.

25. The highly transparent film according to claim 24, wherein the multifunctional coating is obtained based on a coating solution, which contains: only one plasticizer according to claim 3, only one cellulose derivative according to claim 4 maximally two solvents according to claim 5, only one acrylate copolymer according to claim 7.

26. The highly transparent film according to claim 25, wherein the coating has a dry film thickness of 5 m to 35 m, and the film has a total thickness in a range from 120 m to 270 m.

27. The highly transparent film according to claim 26, wherein the coating surface has a defined surface structure, embossed with two-dimensionally repeating geometric patterns of hexagonal honeycombs, rhomboids, diamonds, squares, rectangles, circles, sinusoidal circular arcs and/or triangles with an inner diameter or pitch of 10 m to 500 m, a ridge height of the lines of 2 m to 15 m, and a ridge width of 1 m to 200 m.

28. A dissolver medium for dissolving a multifunctional coating of a highly transparent film according to claims 17 before bonding to a surface of glass, wood, metal, ceramic, cellulose derivatives or plastics, comprising, one or more low-toxicity carboxylic acid esters, one or more low-toxicity ethers, and one or more low-toxicity alcohols.

29. The dissolver medium according to claim 28 for use as cover medium, further comprising an additional proportion of an acrylate copolymer, which is selected from the substance class of the acrylate copolymer used in the coating according to claim 1, b).

30. The dissolver medium according to claim 29, wherein the dissolver medium has the following composition: one or more low-toxicity carboxylic acid esters, preferably from the group of acetic acid alkyl esters and/or from the group of carbonic acid alkyl esters, and/or from the group of lactic acid alkyl esters having a boiling point of less than 225 C. and a refractive index>1.35, and present in the solution in a mass fraction of at least 10% and/or one or more low-toxicity ethers, preferably from the group of glycol ethers and/or from the group of alkylphenyl ethers, having a boiling point of less than 250 C. and a refractive index>1.35, and present in the solution in a mass fraction of the total mass of at least 10%, and one or more low-toxicity alcohols with a boiling point of less than 100 C. and a refractive index>1.35, and present in the solution in a mass fraction of the total mass of at least 10%, and an acrylate copolymer with an average molecular weight M.sub.W between 10,000 g/mole and 300,000 g/mole and a refractive index>1.35, which preferably originates from the substance class of the acrylate copolymer used in the coating and is contained in the solution in a mass fraction of the total mass of not more than 65%.

31. A dissolver medium according to claim 30, wherein the dissolver medium has the following properties at 20 C.: refractive index: 1.40 to 1.50, dynamic viscosity: <500 mPa, color: colorless, density: <1.05 g/cm3, water content: <0.5%, and solids content: <65%.

32. The highly transparent film according to claim 17, wherein the alcohols are selected from the group consisting of methanol, ethanol, propanol butanol hexanol; wherein the organohalogen solvents are selected from the group consisting of chloroform, dichloromethane, trichloromethane, tetrachloromethane, trichloroethane; wherein the ethers are selected from the group consisting of dimethyl ether, diethyl ether, dipropyl ether, polyether, glycol ether, tetrahydrofuran, dioxane; wherein the esters are selected from the group consisting of carboxylic esters, methyl acetate, ethyl acetate, propyl acetate, butyl acetate, gamma-butyrolactone, gamma-valerolactone, carbonic acid dimethyl ester, ethyl lactate, cyclohexanol acetate; wherein the ketones are selected from the group of acetone, methyl ethyl ketone butyl methyl ketone; wherein the aromatics are selected from the group consisting of benzene, toluene, xylene, ethylbenzene; wherein the deep eutectic solvents are selected from the group consisting of choline chloride/urea; choline acetate/urea; tetrabutylammonium chloride/oxalic acid and choline chloride/glycol.

33. A method of using one or more highly transparent films according to claims 17, as a window film, sunglasses film, laminating film, furniture film, cover film, slide film for microscopy, cover glass replacement film and/or protective film capable of bonding to glass, wood, metal, ceramics, cellulose derivative films or plastics after dissolution or thermal treatment.

34. The dissolver medium according to claim 28, wherein one or more low-toxicity carboxylic acid esters are selected from the group consisting of methyl acetate, ethyl acetate, propyl acetate, butyl acetate, carbonic acid dimethyl ester and ethyl lactate; one or more of the low-toxicity glycol ethers selected from the group consisting of diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, propylene glycol-1-methyl ether, dipropyleneglycol methyl ether; a methyl phenyl ether; and one or more low toxicity alcohol selected from the group consisting of ethanol, isopropanol and butanol.

35. The highly transparent film according to claim 17, wherein the b.sub.2) solvent is selected from the group consisting of aromatic solvents, organohalogen solvents, esters, ethers, ketones, deep eutectic solvents or alcohols;

36. The highly transparent film according to claim 17, wherein the b.sub.3) solvent is selected from one of the solvent groups consisting of halogen alkanes, ketones, ethers, esters, deep eutectic solvents and alcohols.

Description

EXEMPLARY EMBODIMENT 1

[0179] Multifunctional coated colored cellulose triacetate film with improved bondability to surfaces made of glass, wood and metals

[0180] A film with a layer thickness of 80 m, consisting of a cellulose triacetate with a lowest possible haze value0.4%, a plasticizer (triphenyl phosphate) in a concentration of 12% and dye additives (for example Orasolrot 395 from the company Kremer Pigments) in a concentration<1% is coated as follows: [0181] Preparing a 10% cellulose derivative solution consisting of 10% cellulose acetate propionate, dissolved in a mixture of 39% acetone and 1% methyl ethyl ketone and 60% methyl acetate and thereafter applying the solution with a doctor blade with a wet film thickness of max. 20 m on the 80 m -CTA film, followed by intensive convective drying for fastest possible removal of the solvent, [0182] Preparing a coating solution consisting of the following components which are together stirred and homogenized at a temperature of 30 C. for at least 12 hours: [0183] 75 mass % solvent mixture, consisting of 45% Toluene, 40% methoxypropanol. 15% dichloromethane, [0184] 22 mass % acrylate copolymer mixture, consisting out 75% Paraloid B48N and 25% Paraloid B72, [0185] 1.5 mass % cellulose acetate propionate (CAP), [0186] 1.5 mass % plasticizer mixture, consisting of 80% triphenyl phosphate (TPP) and 20% tris(2-chloroethyl) phosphate (TCEP).

[0187] At the end of the stirring time, the coating solution is applied on the primary coated side of the CTA film with a doctor blade to a wet film thickness of about 30 m and subsequently intensively dried at temperatures of at least 120 C. for 20 min.

[0188] The so produced highly transparent coated colored CTA films can now be bonded onto a glass surface, a wood surface or a metal surface by initially dissolving the coating with acetone or toluene and applying a window film doctor blade, without causing the film to detach from of the surface independently. The multifunctional coating enables also the application of thermal energy for bonding the film, i.e. a permanent and yet reversibly releasable adhesion of the CTA film can already be realized by briefly placing an iron or a similar heating unit followed by briefly pressing the film onto the surface.

[0189] In contrast to an uncoated colored CTA film, the adhesion on the above-mentioned surfaces is significantly improved while retaining the high transparency of the starting material.

EXEMPLARY EMBODIMENT 2

Multifunctional Coated Cellulose Triacetate Film For Application As A Cover Film In the Field of Microscopy

[0190] A highly transparent film (haze value<0.5%) with one layer thickness in the range from 120 to 130 m, consisting of cellulose triacetate and a plasticizer (triphenyl phosphate) in a concentration of 12% is coated as follows: [0191] Preparing a coating solution consisting of the following components which are stirred together and homogenized at a temperature of 30 C. for at least 8 hours: [0192] 70 mass % solvent mixture, consisting of 75% ethyl acetate and 25% methoxypropanol, [0193] 22 mass % acrylate copolymer mixture consisting of 50% Paraloid B99 and 50% Paraloid B72, [0194] 1.5 mass % cellulose acetate propionate (CAP), [0195] 1.5 mass % cellulose acetate butyrate (CAB), [0196] 5 mass % plasticizer mixture, consisting of 50% diethyl phthalate and 50% diisononyl phthalate.

[0197] At the end of the stirring time, the coating solution is applied onto the CTA film with a doctor blade with a wet film thickness of about 65 m and subsequently intensively dried at 125 C. for 45 min.

[0198] It was found to be advantageous to apply in this context a 3D surface structure on the coated side of the filmfor example by using several pressure rollers with a defined roughness and/or surface geometry.

[0199] The so produced coated CTA films can now be cut to the required size for application as a cover filmfor example as a single cut 50 mm24 mm or as a roll 75 m24 mm. These assembled cover films can be stored and transported at a temperature from 5 C.-35 C. for at least 12 weeks, without degrading the product.

[0200] The coating can be dissolved by dropwise applying 3-5 drops xylene or ethylbenzene from a 5 ml disposable pipette onto the coated side and the film can then be immediately bonded on a microscope slide, on which the microscopy object has already been placed. The use of a rubberized roll as pressure roll for affixing the film uniformly on the glass slide is hereby recommended.

[0201] The objects can subsequently be immediately examined microscopically, wherein no interference of the observation matrix occurs due to the high transparency of the CTA film and the coating.

[0202] Long-term preservation of the covered objects for at least 12 weeks can be attained by storing these covered slides at a temperature of 20 C. to 25 C. and a relative humidity from of about 50%, without optically detectable degradation of the object undergoing microscopic examination.

[0203] Even after a storage time of several months the film can be detached again very quickly from the slide by briefly inserting the covered slide in acetone (for about 30 seconds). The object to be examined is then again available for further investigations.

[0204] A comparison with current commercially available cover films from different manufacturers has demonstrated that coated CTA films produced in accordance with this exemplary embodiment have comparable application and storage properties which appear to make feasible the use of the cover film in the field of microscopy and with coverslipper machines.