NO166638B - PROCEDURE FOR THE MANUFACTURING OF QUATERNARY ESTERAMINES AND THEIR USE. - Google Patents

Description

The present invention relates to a method for the production of continuous, opaque films which are impermeable and micro-porous, but which do not contain pigments, which are generally used in the production of opaque films.

Opaque films are usually produced by the addition of a pigment, which acts to dissolve a film-forming material,

which would otherwise become colorless or transparent when cast as a film, opaque. The necessity of the addition of an agent which

makes the film opaque, increases the cost of the produced film. Moreover, such films will not have greater porosity than the non-pigmented films.

Optical opacity, e.g. coverage in a paint film, is achieved either by absorption of the incident light or by scattering of the incident light or by a combination of these two.

Thus, black is opaque because it absorbs the incident light, and white is opaque because it reflects the incident light scattered. The light is either absorbed or scattered before it reaches the substrate. The ideal white pigment is therefore one that has no absorption and maximum scattering.

The absorption depends primarily on the electron structure of the molecule as well as on the pigment particle size in relation to the light's wavelength. The dispersion depends on the relative refractive indices of pigment and carrier as well as on the particle size of the pigment in relation to the wavelength of the incident light.

A simple description of the relationship between the scattering and the absorption and the resulting reflection is given by Kubelka and Munk. For full extinction, the following equation applies:

where R^ is the reflectance of a film so thick that a further increase in thickness does not change the reflectance, K is the absorption coefficient and S is the Kubelka-Munk scattering coefficient. Surface reflections are not taken into account, and the equation only applies to internal reflection.

The contributions for more than one pigment in a system are additive, as shown by the following equation:

where , C2 and refer to concentrations of pigment 1, 2, 3, etc.

When the extinction is incomplete, the following equation applies:

where R is the resulting internal reflection, Rg is the reflection of the substrate, a is (S + K)/S, b is (a<2> - 1)1//2, S is the scattering coefficient f i-

the sieten, and X is 1/25.4 times the thickness of the film measured in [ im.

The Kubelka-Munk diffusion coefficient can be calculated by the following equation:

where Ro is the reflection over a black substrate with 0 percent reflection, a can be found from the equation: and b is calculated as above. In this equation, R corresponds to the reflectance over a white substrate, and Rg is the reflectance of the coated substrate, or a can be found from the equation:

K can be found from the equation K = S(a—1).

The Kub elka-Munk analysis is discussed further by D. B. Judd in "Color in Business, Science and Industry", John Wiley and Sons,

New York 1952, pp. 314-338, and by D. B. Judd and J. Wyszecki in "Color and Business, Science and Industry", 2nd ed., John Wiley and Sons, New York 1963, pp. 387-413-

Different methods are described in this subject area for the production of opaque films whose opacity depends on the presence of a large number of voids in the film. Such films can be prepared by skimming a film from an emulsion, i.e. either an oil-in-water emulsion (U.S. Patent 3,108-009) or a water-in-oil emulsion (U.S. Patent 2,739-909). When a water-in-oil emulsion is used, i.e. one in which very small water droplets are dispersed in a continuous phase of a film-forming material, the emulsion is precipitated as a coating, and the organic solvent which forms the continuous phase of the emulsion is evaporated. This causes gelatinization of the film-forming material and entrapment of the dispersed water droplets. The water evaporates from there, leaving microscopic voids in the film structure.

When an oil-in-water emulsion is used, its film-forming mechanism corresponds to that described above. A film-forming material dissolves in water. An organic liquid, which cannot be dissolved in the film-forming material and which is not miscible with water, is then emulsified in the aqueous phase. The emulsion is cast as a film and the water is evaporated, whereby the film-forming material gelatinizes and encloses small drops of the organic liquid. This liquid is then evaporated, whereby quite small voids are created in the film structure.

Another technique for obtaining porous, opaque, non-pigmented films consists of preparing an aqueous dispersion of a film-forming polymer containing a water-soluble organic solvent in an amount sufficient to dissolve the polymer (U.S. Patent 2,848,752) . This aqueous dispersion is cast as a film, and the water is evaporated, whereby small droplets of the organic solvent are trapped in the polymer. The film is then washed too

to dissolve the trapped small droplets of the solvent, and the film is dried.

However, the use of emulsions presents certain problems precisely because of the nature of the emulsions. For example, when handling an emulsion, steps must be taken to ensure its stability, i.e. ensure that it does not break, before it is used to refine a film. This often requires the use of emulsifiers. However, emulsifiers present in the film reduce its physical properties, such as its water repellency and its abrasion resistance. Furthermore, only film-forming materials that are able to emulsify easily can be used in such a system. Furthermore, the size of the formed voids in the film when these are formed from emulsions depends on the size of the droplets in the emulsion, which are trapped in the film. This results in a certain limitation of how small voids can be achieved in the film.

It is the purpose of the present invention to provide microporous, opaque, unpigmented films, a method for producing such films, which does not depend on the use of emulsions or solvent extraction.

These and other objects are achieved by the application of the present invention which, described briefly, comprises the production of a continuous, opaque film containing closed cells by

a method comprising (a) applying to a substrate a preparation comprising a film-forming, gelatinizable polymer and a solvent mixture for this film-forming material, comprising at least two miscible liquids of which at least one is not a solvent

solvent for the polymer and has a lower volatility than the other liquids in this mixture, the amount of the liquid with the lowest volatility in the mixture being at least sufficient to,

upon removal of the solvent mixture from the preparation, to provide a film having a Kubelka-Munk scattering coefficient greater than 12.7 reciprocal µm at 4400 angstroms and greater than 2.54 reciprocal µm at 56oO angstroms and less than those obtained upon removal of the solvent the solvent mixture from the composition produces a discontinuous film, and (b) removing the solvent mixture from the applied composition on the substrate.

The film-forming, gelatinizable polymers which can be used in carrying out the invention are well known to those skilled in the art. These include thermoplastic and thermosetting synthetic as well as natural polymers. The only limitations of the film-forming polymers are that they must be soluble in (i.e. miscible with) the particular solvent mixture used, and they must be capable of gelatinizing (i.e. being converted from a liquid phase to a solid phase) by evaporation of part of the solvent system.

Examples of film-forming, gelatinizable polymeric materials that can be used include cellulose derivatives (e.g. ethyl cellulose, nitrocellulose, cellulose acetate, cellulose propionate and cellulose acetate butyrate), acrylic resins, (e.g. homopolymers and copolymers with each other or with other monomers of methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, butyl acrylate, butyl methacrylate , acrylic acid and methacrylic acid), polyolefins (e.g. polyethylene and polypropylene), nylon, polycarbonates, polystyrene, copolymers of styrene and other vinyl monomers, such as acrylonitrile, vinyl polymers, such as homopolymers and copolymers of vinyl acetate, vinyl alcohol , vinyl chloride and vinyl butyral, homopolymers and copolymers of dienes, such as polybutadiene, butadiene-styrene copolymers and butadiene-acrylonitrile copolymers. You can also use condensation polymers such as alkyd resins, which are produced by condensation of a polyhydric alcohol and a polycarboxylic acid. Examples of polycarboxylic acids that can be used in the production of the alkyd resin,

are phthalic acid, phthalic anhydride, succinic acid, adipic acid, maleic acid, itaconic acid, isophthalic acid, terephthalic acid and similar acids. The polyhydric alcohols that can be used in the production of the alkyd resin can include glycols, such as ethylene glycol, propylene glycol and the like

compounds, glycerol, sorbitol, erythritol, pentaerythritol and similar alcohols. Epoxy resins can also be used as film-forming polymers. Epoxy resins include condensation products of bisphenol and epichlorohydrin, epoxidized drying oils, glycidole ethers of glycerol, epoxidized novolak resins and similar compounds. Phenolic resins, such as those produced by the reaction between phenol

and formaldehyde, can also be used.

The film-forming polymer materials can also be an aminoplast, produced by reaction between a compound containing a number

-NF^ groups (e.g. urea, melamine, guanamine or benzoguanamine)

with an aldehyde or a compound that acts like an aldehyde (e.g. formaldehyde, benzaldehyde or paraformaldehyde). In the production of aminoplasts, the aldehyde or its equivalent is usually dissolved in an alkanol, such as butanol, and at least part of the N-methylol groups in the aminoplast are converted to -N-oxyalkyl groups with the formula:

These groups are distributed as side chains in the resin molecules. Butanol can be replaced with other monohydric aliphatic alcohols containing from approx. 1 to approx. 8 carbon atoms, and examples of this include methanol, ethanol, propanol, isopropanol, butanol, isobutanol, pentanol, hexanol and octanol. All of these are primary or secondary alcohols. Such resins contain -N-CH2OH groups and -N-CT^O-alkyl groups where the unit denoted by "alkyl" usually contains from 3" to about 8 carbon atoms.

A preferred group of film-forming materials which can be used in carrying out the present invention are carboxylic acid amide interpolymers of the type described in U.S. Pat. patents

Nos. 3,037,963 and 3.H8,853- These interpolymers are prepared by forming an interpolymer of an unsaturated carboxylic acid amide, such as acrylamide or methacrylamide, with at least one other polymerizable ethylenically unsaturated monomer, whereupon the interpolymer is reacted with an aldehyde, such as formaldehyde , in the presence of an alcohol, such as butanol. The exact mechanism by which amide interpolymers are produced is not known with certainty, but it is believed that the process begins with the formation of a relatively short-chain, soluble interpolymer with an approximate structure as follows, using acrylamide as an example:

where M is a unit of a monomer that can be polymerized with acrylamide, and n is an integer greater than 1. If there e.g. as the other polymer is styrene, M would be the unit:

The short-chain interpolymer is then reacted with an aldehyde, e.g. formaldehyde, during formation of the structure:

where M and n are as stated above.

If the aldehyde is used in the form of a solution in butanol or another alcohol, an ether ring will take place so that at least part of the methylol groups in the above structure will be converted into groups with the formula:

where R is an unsaturated, lower aliphatic hydrocarbon radical with its free valences on a single carbon atom, and R"<*>" is hydrogen or the radical that appears when the hydroxyl group is removed from the alkanol.

It is desirable that at least approx. 50% of the methylol groups are etherified as preparations with less than 50% of the methylol groups in the etherified state will tend to be unstable and prone to gelatinization. Butanol is the preferred alcohol for use in the etherification process, although any alcohol can also be used, such as methanol, ethanol, propanol, pentanol, octanol, decanol and other alkanols containing up to approx. 20 carbon atoms, as well as aromatic alcohols, such as benzyl alcohol or cyclic alcohols.

Although it is preferred to use either acrylamide or methacrylamide for use in forming the interpolymer compound, any unsaturated carboxylic acid amide may be used. Examples of such other amides include itaconic acid diamide, α-ethyl acrylamide, crotonamide, fumaric acid diamide, maleic acid diamide and other amides of α, β-ethylenically unsaturated carboxylic acids with up to approx. 10 carbon atoms. Maleic acid and its esters and imide derivatives, such as N-carbamylmaleimide, can also be used.

An arbitrarily polymerizable monomer compound containing i

at least one

can be polymerized with the unsatd

carboxylic acid amide. Examples of such monomers include styrene, isobutylene, vinyl chloride, vinylidene chloride, vinyl acetate, methyl methacrylate, ethyl acrylate, acrylic alcohol, acrylonitrile, methacrylic acid and similar monomers.

The preparation of the amide interpolymer is described in detail in U.S. Pat. patents 2,870,116 and 2,870,117.

The amide interpolymer resin prepared by the process in the above-mentioned patents is reacted with an aldehyde, preferably in the presence of an alcohol. It is particularly preferred to use formaldehyde in aqueous solution (formalin) or dissolved in an alkanol, such as butanol, or a formaldehyde-forming compound, such as paraformaldehyde, trioxymethylene or hexamethylenetetramine. However, other aldehydes can also be used, such as acetaldehyde, butylaldehyde, furfural and similar aldehydes which preferably only contain carbon, hydrogen and oxygen. Dialdehydes, such as glyoxal, are preferably not used as they have a tendency to cause the amide interpolymer resin to gelatinize.

The interpolymeric compound will contain repeating groups in the polymer chain with the following structure:

where R is hydrogen or a lower aliphatic hydrocarbon radical, and

R<1> is hydrogen or the radical produced by removing the hydroxyl group from an alcohol. When the reaction is carried out in the presence of an alcohol, this reacts in such a way that at least some, and preferably more than approx. 50% of the radicals R<1> will represent the radical that can be produced from the alcohol. When aldehyde is used alone, i.e. not in an alcoholic solution, the radical R^ will of course be hydrogen. The free valences in the above-mentioned structure can be filled with hydrogen or hydrocarbon, depending on the amide used in the interpolymerization reaction. These resins give strongly cross-linked structures upon subsequent oven drying, as the positions where cross-linking takes place include functional groups in other polymers present in the system, if such are used.

Aldehyde-modified and etherified amide interpolymers can also be prepared by first reacting the unsaturated amide with an aldehyde and, if desired, with an alcohol to form an N-alkylol- or an N-alkylol-substituted amide. The N-substituted amide is then interpolymerized with the other monomer or the other monomeric compounds as described above, whereby interpolymers with the aforementioned repeating groups are produced without further reactions being necessary. Another method using N-Alkoxyalkyl substituted amides is described in U.S. Pat. patent No. 3,079,434.

Beneficial properties can often be obtained by using mixtures of the above-mentioned amide interpolymer resins with other resin-like materials, such as many of those mentioned herein.

For example, nitrocellulose, polyethylene, alkyd resins, epoxy resins, aminoplast resins and other similar compounds can be used for this purpose.

Another large group of film-forming materials that can be used in carrying out the present invention are interpolymers of hydroxyl esters of unsaturated acids with at least one other polymerizable, ethylenically unsaturated monomer. Such interpolymers are produced by interpolymerization of a mixture of monomers, comprising at least 2% by weight of a hydroxyalkyl ester of an ethylenically unsaturated carboxylic acid and at least one other ethylenically unsaturated monomer that is copolymerizable therewith. in many cases, more than one hydroxyalkyl ester is included in the interpolymeric compound, and usually several monomers are used in addition to the hydroxyalkyl ester or esters. These interpolymeric compounds are produced in a manner known per se by using common methods and catalysts. Free-radical-producing catalysts are generally used, but catalyst systems that work by other mechanisms can also be used. The used time, temperature and similar conditions under which these interpolymerizations are carried out are likewise those commonly used and depend to a large extent on the catalyst in question.

Preferred monomer systems used in the production of these interpolymers are those containing hydroxyalkyl esters in which the alkyl group has up to approx. 12 carbon atoms.

Particularly preferred esters are acrylic acid and methacylic acid esters of glycol and 1,2-propylene glycol, i.e. hydroxyethyl acrylate and methacrylate and hydroxypropyl acrylate and methacrylate. Combinations of these esters are also commonly used. However, corresponding esters of other unsaturated acids can also be used, e.g. ethacrylic acid, crotonic acid and similar acids with up to approx. 6 carbon atoms, as well as esters containing other hydroxyalkyl radicals, such as hydroxybutyl esters and hydroxylauryl esters.

In addition to esters of unsaturated monocarboxylic acids, mono- or diesters of unsaturated dicarboxylic acids can also be used, such as maleic acid, fumaric acid and itaconic acid, in which at least one of the esterifying groups is hydroxyalkyl. Examples of such esters include bis-(hydroxyethyl) maleate, bis-(hydroxypropyl) fumarate and corresponding bis-(hydroxyalkyl) esters, as well as mixed alkyl hydroxy alkyl esters, such as butyl hydroxyethyl maleate and benzyl hydroxypropyl maleate. Monoesters, such as mono-(hydroxyethyl) and mono-(hydroxypropyl) esters of maleic acid and corresponding acids can also be used.

The monomeric compound or compounds with which the hydroxyalkyl ester is interpolymerized can be arbitrary ethylenic compounds that are copolymerizable with the ester, the polymerization taking place over the ethylenic unsaturated bonds. Examples of this include monoolefinic and diolefinic hydrocarbons, halogenated monoolefinic and diolefinic hydrocarbons, unsaturated esters of organic and inorganic acids, esters of unsaturated acids, nitriles, unsaturated acids and similar compounds. Examples of such monomers include styrene, butadiene-1,3,2-chlorobutene, α-methylstyrene, α-chlorostyrene, 2-chlorobutadiene-1,3,1,1-dichloroethylene, vinyl butyrate, vinyl acetate, allyl chloride , dimethyl maleate, divinylbenzene, diallyl litaconate, triallyl cyanurate and similar compounds.

The most useful interpolymers of this type can be prepared by interpolymerization of one or more hydroxyalkyl esters with one or more alkyl esters of ethylenically unsaturated carboxylic acids or a vinyl aromatic hydrocarbon, or both. Among these preferred comonomers are ethyl, methyl, propyl, butyl, hexyl, ethylhexyl and lauryl acrylates and methacrylates, as well as the corresponding esters with up to approx. 20 carbon atoms in the alkyl group. Among the commonly used vinyl aromatic hydrocarbons can be mentioned styrene and α-alkylstyrene or vinyltoluene. The preferred monomeric systems may comprise an ethylenically unsaturated nitrile, such as acrylonitrile or methacrylonitrile, and in many cases an ethylenically unsaturated carboxylic acid is present, of which the preferred ones are acrylic acid and methacrylic acid. The particular comonomers that are often used are methyl methacrylate, ethyl acrylate, styrene, vinyl toluene, acrylonitrile, methacrylonitrile, methacrylic acid, acrylic acid, 2-ethylhexyl acrylate, butyl acrylate, butyl methacrylate and lauryl methacrylate.

Examples of catalysts that are usually used in interpolymerization are peroxygen compounds, such as benzoyl peroxide, cumene hydroperoxyd, hydrogen peroxide and t-butylperoxyisopropylcarbonate, and azo compounds, such as a,a'-azobis-(isobutyronitrile) and p-methoxyphenyl-diazothio-(2 -naphthyl) ether.

Films and coatings are usually produced from the above-mentioned interpolymers of hydroxyalkyl esters by cross-linking these interpolymers with other compounds containing functional groups which are reactive with the hydroxyl group in the interpolymer compound. Examples of such coreactive substances are polyisocyanates, such as toluene diisocyanate and isocyanate-containing polymeric products, aminoplast resins, such as hexa-(methoxymethyl)-melamine and other compounds described above, epoxy resins, such as polyglycidyl ethers of bisphenol A and other compounds, e.g. silicone resins.

Naturally occurring polymeric materials that can be used in the practice of the present invention include casein, shellac and gelatin.

The film-forming polymeric materials can be added and dissolved

in the solvent system as such. Alternatively, the corresponding monomer or the corresponding monomers can be dissolved

ning solvent system, and the film-forming material can then be formed in situ by polymerization of the monomers in the solvent system. Polymerization catalysts, such as organic peroxides, and polymerization modifiers, such as tertiary dodecyl mercaptan and carbon tetrachloride, may be used in accordance with well known practice. If the system contains a polymer containing free hydroxyl groups, a cross-linking agent such as an organic diisocyanate or a common aminoplast can be used. Ethylenically unsaturated monomers can be polymerized in the solvent system in the presence of a preformed polymer, in which case there can be either graft polymerization of the monomer onto the preformed polymer or,

if the preformed polymer contains ethylenic acid, crosslinking of the preformed polymer.

The solvent system used in carrying out the present invention comprises a mixture of at least two miscible liquids. It is not necessary that any of the liquids used in the solvent system, taken alone, be a solvent for the film-forming polymer, so long as the polymer is soluble in them in mixture. However, at least one of the liquids in the solvent system must be a non-solvent for the polymer, and this liquid must have a substantially lower volatility than the other liquids in the solvent mixture.

The term "non-solvent" is used to denote

a liquid in which the polymeric compound does not dissolve to any particular extent.

The amount of low volatility non-solvent in the solvent system shall be sufficient to produce, upon removal of the solvent mixture from a film prepared from the formulation, a Kubelka-Munk scattering coefficient greater than 12.7 reciprocal (im at 4400 Å and greater than 2.54 reciprocal µm at 5600 Å. The amount of non-solvent present in the solvent system must, however, be less than that which, on removal of the solvent mixture from a film formed from the preparation, would produce a discontinuous film, i.e. a film containing interconnected open cells or discontinuities or spaces as opposed to a continuous film containing cells that are not interconnected.

When these conditions are met, and a film is formed of the preparation, the more volatile liquid evaporates at a greater rate than the non-solvent of low volatility. After a portion of the solvent mixture is evaporated, the film-forming polymer gelatinizes, and then the low-volatility non-solvent precipitates as small droplets in the polymeric matrix forming a rigid structure. The non-solvent then evaporates, leaving microscopic voids in the rigid structure. These microscopic voids cause light scattering and opacity, and cause the film to become micro-porous and have a Kubelka-Munk scattering coefficient, which was previously def inert.

If sufficient non-solvent of low volatility is not present in the system, the film formed by the formulation will dry as a clear or hazy film with a Kubelka-Munk scattering coefficient less than 12.7 reciprocal \ xm at 44oo Å and less than 2 .54 reciprocal nm at 56oo Å and will not be sufficiently micro-porous. If, however, too much non-solvent of low volatility is present in the system, the polymer may precipitate from the mixture before it gelatinizes, and a film formed from such a preparation will be discontinuous.

The relationship between the quantities of the miscible liquids included in the solvent mixture can best be understood by drawing the relevant composition of a three-component system in a triangle diagram. The composition of such a system is shown in Figure 1 where the concentration of the higher volatility liquid, methyl ethyl ketone (MEK) is calculated from tip G, the concentration of the non-solvent for the lower volatility polymer, high flash aromatic naphtha (HFAN), is calculated from the tip A and the concentration of the film-forming, gelatinizable polymer, a copolymer containing 90% methyl methacrylate and 10% methacrylic acid (MMA-MAAc), is calculated from the tip M. The line E-B is the gel structure line, and the line B-A is the precipitation line. All preparations within the surface GEA contain the polymer in the liquid phase. All preparations outside this range contain the polymer in a gel stage. Films with compositions along the line E-F are, upon removal of all solvent, continuous and have Kubelka-Munk scattering coefficients less than 12.7 reciprocal [ iia at 4400 Å and less than 2.54 reciprocal (im at 5600 Å. Films with compositions along the line B-F is, upon removal of all solvent, continuous and white with Kubelka-Munk scattering coefficients greater than 12.7 reciprocal |im at 4400 Å and greater than 2.54 reciprocal \m at 5600 Å. Films with compositions along the line B-A are, upon removal of all solvent, discontinuous. The coating preparations according to the invention are, in the special system shown in Figure 1, those that lie within the area BFG. A film formed by a preparation within this area, such as a preparation represented at point I, dries as a very white, tough, continuous film However, a film formed from a preparation within the range ERG, as represented by point J, will dry as a continuous, non-white film, which describes above, and a film formed by a preparation within the region ABG, as represented by point H, will dry as a discontinuous, possibly white film.

The invention will be explained in more detail with reference to the generalized phase diagram shown in Figure 2.

This diagram shows three clearly separated zones which depend on the concentrations of the materials in the preparations. Coating deposited by a preparation that lies within zone A is continuous, transparent and, for the most part, non-porous. When the preparation approaches the border of zone B, the precipitated coatings show a veil. Coatings made from preparations within zone C form opposites to those falling within zone A, in that the preparations dry as a polymer containing open cells of interconnected voids or as a precipitated, powder-like, white, discontinuous film. However, coatings made from preparations in zone B are continuous and exhibit many of the macro properties of the polymer itself and exhibit Kubelka-Munk dispersion coefficients as previously defined. When the preparations within zone B approach the border of zone C, the precipitated overcoats upon removal of all solvent become whiter and exhibit higher Kubelka-Munk scattering coefficients. Therefore, the preparations according to the invention are those which fall within zone B and pass through the line B-R upon removal of the solvent. The lines G-F and G-B can be approximated by straight lines when the rate of evaporation of the actual solvent is much greater than that of the non-solvent.

The particular liquids used in the solvent mixture depend on the film-forming polymer used. A liquid that is the more volatile component in one system may be the low-volatility non-solvent in the other system. Examples of groups of liquids that can be used include ketones, esters, alcohols, aliphatic, aromatic and chlorinated hydrocarbons and similar compounds. In the examples given below, a number of more precisely defined systems are illustrated.

The preparations according to the invention may contain other ingredients which do not interfere with the relationship between the film-forming, gelatinizable polymer and the solvent mixture, which contains at least two miscible liquids. Thus, one or more additional polymers can be included to modify the properties of the finished film, which polymers do not need to have the above-mentioned solvent properties in relation to the solvent system, i.e. e.g. they need not be insoluble in liquids of lower volatility. If it is desired to obtain a film with a color other than white, pigments or dyes can be included in the preparations.

The preparations according to the invention can be formed into a film by methods that are well known to those skilled in the art. thus they can be applied to a substrate by brushing, spraying, dipping, roller application, knife application or calendering.

Film produced from the preparations according to the invention can be air-dried, vacuum-dried or oven-dried at elevated temperatures.

Film produced using the present invention is characterized by the presence of a large number of separate, closed cells. Practically all of these cells or voids are less than 1 µm and preferably less than 0.5 µm in size. The size of the cells varies down to the size of the film-forming polymer molecule. Films produced from many of the preparations according to the invention contain closed cells, practically none of which are larger than 0.1 (im. In other films, the average size of the cells may be 0.25 (im.

Unless a color-forming material is included in the preparation, such as a dye or pigment, the films according to the invention are opaque and white, colored films can be produced by incorporating small amounts of dyes or pigments. Smaller amounts of dye or pigments are required to produce a colored film than are required when using ordinary coating preparations.

The coating preparations according to the invention can e.g. used for the final surface treatment of vehicles and appliances and for corresponding coverings for protective and decorative purposes. Such covers can have a thickness of up to 0.25k mm. Many of the covers according to the invention, especially the strongly cross-linked films, are extremely tough and resistant to wear.

A film with an apparent thickness of e.g. 0.254 mm will have a truly fixed thickness corresponding to the sum of the thicknesses of each wall between the separated cells lying along a line perpendicular to the outermost flat surface of the film, which e.g. only amounts to 0.0254 mm. This property makes the films according to the invention, especially those with an average cell size of less than 0.1 (im), usable as vapor or liquid permeable membranes, which can be used for a number of purposes, such as desalination processes.

The film thus has sufficient apparent thickness to provide the required strength. Even so, the total thickness of the solid polymer through which a molecule must pass (ie the cell walls) is relatively small.

Furthermore, the diffusion per time unit of a vapor or a liquid through a unit area of any of the films according to the invention significantly greater than that which can be achieved with the hitherto available non-porous films.

The films according to the invention reflect light of wavelengths below 3800 Å, which makes them useful as reflectors for ultra-violet light. Moreover, these films have such a whiteness that they can be used as white reflection standards.

The following examples illustrate some ways in which the present invention can be used. In many of these examples, polymeric materials are referred to by means of designations listed in the following overview, and other constituents are abbreviated in the manner described in the following overview.

In the above overview, the viscosity of the cellulose acetate-butyrate polymers is determined by ASTM Method D-1343-54T in the solution described as Formula A, ASTM Method D-871-54T and the viscosities in poise are converted to ASTM seconds corresponding to the values obtained by ASTM method D-871-48- The viscosity of the cellulose acetate polymers was determined using ASTM method 4-1343-56 in the solution described as Formula A, ASTM method D-871 -56.

Example 1

A solution (500 g) of a copolymer consisting of 89.75% by weight methyl methacrylate, 10% by weight lauryl methacrylate and 0.25% by weight methacrylic acid, the acid groups in the copolymer being reacted with an organic imine so that aminoethyl ester ends appear, with a solids content of 35% in a solvent mixture of 73% toluene and 27% methyl ethyl ketone is mixed with methyl ethyl ketone (200 g). Odorless aliphatic mineral turpentine (100 g) is slowly added to this solution. A film cast from this mixture is initially transparent but becomes opaque upon drying. The dried film is continuous and microporous and has a Kubelka-Munk scattering coefficient greater than 12.7 reciprocal µm at 4400 Å and greater than 2.54 reciprocal µm at 5600 Å.

Example 2- 15

In these examples, a film-forming polymer of the type and in the amount stated in the second column of Table 1 is dissolved in the type of solvent and in the amount thereof stated in the third column of Table 1. Non-solvent is then added for the film-forming polymer of the type and in the amount indicated in the fourth column of Table 1. In Examples 2-14, the film is drawn from the formed solutions, and in Examples 15a and 15b, the solutions are sprayed onto a substrate to form a film. The films are described in the table's fifth column. In examples 2a, 3a, 4a, 5a and 6a, for comparison, films have been cast from the solution of the film-forming polymer before the addition of non-solvent. All the films described as white are microporous, contain a large number of closed cells most of which are less than 0.5 µm in size and have Kubelka-Munk scattering coefficients greater than 12.7 reciprocal µm at 4400 Å and greater than 2.54 reciprocal [im at 5600 Å.

Example 16

A mixture is prepared containing Hercules Powder Company nitrocellulose (17 g) type RA-56 different viscosity (70% solids, 30% ethanol), toluene (40 g) and butyl acetate (43 g), from which a sample is taken and a film is drawn . After drying, the film is ready. Acetone (40 g) is then added to this solution and another film is drawn. This film is also ready. Aromatic naphtha is then added. high flash point (60 g) to the solution, and a film is drawn from this. This film is white after drying.

Example 17

Cellulose acetate butyrate (P-2) (100 g) is dissolved in acetone (900 g), and xylene (300 g) is then added there. The solution is diluted with xylene in an amount of 13 parts solution to 1 part xylene and sprayed with 2.1 kg/cm 2 pressure onto an unprimed steel substrate. One coat is white with fairly good coverage, and two coats are white with excellent coverage and adhesion.

Example 18 - 79

For each of these examples, the ingredients listed in Table 2 under the column "step 1" are mixed at the beginning under the specified conditions. The component or components listed in the column with the heading "step 2" are then added under the specified conditions. If additional materials are added,

they are listed in the column with the heading "stage 3" under the stated conditions. The final preparation is then applied to a substrate and dried. The film is described in the column with the heading "description of film". All films described as white are microporous and have Kubelka-Munk scattering coefficients greater than 12.7 reciprocal [im at 4400 Å and greater than 2.54 reciprocal (im at 56oO Å.

In table 2, the polymer or polymer solution and the other components are identified by the names and abbreviations mentioned earlier.

The following example illustrates the execution of the present

end invention with a solvent system in which none of the liquids individually is a solvent for the polymer, but is a solvent for the polymer when mixed together.

Example 81

A solution consisting of toluene (700 g), ethanol (200 g), xylene (100 g) and cellulose acetate butyrate (P-1) is prepared there.

(100 g). After application as a film, the first evaporation is mainly ethanol and toluene. When a sufficient amount of this mixture has been removed from the system, gelatinization occurs. After gelatinization, continued evaporation mainly of this mixture eventually causes phase separation, in which the xylene and some of the toluene precipitate as very small droplets. Final solvent evaporation produces a continuous, opaque white film.

When the above example is repeated under the substitution of de

100 g of cellulose acetate butyrate used in the example, with 50 g of cellulose acetate butyrate, a discontinuous film is obtained there.

Example 82

To a part of the coating preparation prepared according to ex-

empel 19 (300 g) is added a magenta dye (3 g) and acetone (300 g). The preparation is sprayed onto a substrate and dried. The dry microporous film has a rose-red colour.

Example 83-90

In these examples, the ingredients listed in table 3 under the heading "step 1" are mixed and boiled under reflux for 1 hour. The substances listed in the column headed "step 2" are then added over a period of 4 hours during which the mixture is maintained at approximately reflux temperature. After this addition, the mixture is further boiled under reflux for 1 hour.

A sample of approx. 0.5 liters of the preparation obtained at the end of step 2, and to the rest add the material indicated in the column with the heading "step 3"• A film is formed of the preparation obtained at the end of step 2 (film A) and another film of the preparation obtained at the end of step 3- The formed films are described in the column headed "description of film". All films that are white are microporous.

Example 91

A solution containing acrylamide (37.5 g), styrene

(206 g), methacrylic acid (18.7 g), ethyl acrylate (487 g), tertiary dodecyl mercaptan (7.5 g), methyl ethyl ketone (1320 g), high flash point aromatic naphtha (195 g), azobisisobutyronitrile (0.94 g ) and cellulose acetate butyrate (P-1) (375 g) are refluxed for 15 minutes. Heating under reflux is continued for 3.75 hours. At intervals of 45 minutes, 1 hour and 45 minutes, 2 hours and 45 minutes and 3 hours and 34 minutes, further portions of azobisisobutyronitrile (0.94 g) in aromatic naphtha with a high flash point (10 g) are added thereto. Together with the last addition, a 40% butylform cell solution in butanol (80 g), maleic anhydride (1 g) and aromatic naphtha with a high flash point (80 g) are also added, and the mixture is boiled under reflux for 3 hours. Further aromatic naphtha with a high flash point (237 g) is added, and a film is drawn from the solution. The film becomes very white when it dries.

Example 92

Part of the preparation prepared according to the preceding example (33.8 9)> is mixed with aromatic naphtha with a high flash point (52.6 g), and a film is drawn there. After drying, the film is white.

Example 93

Methyl methacrylate (1600 g), high flash aromatic naphtha (1200 g), xylene (800 g), tertiary dodecyl mercaptan (32 g), tertiary butyl peroxyisopropylcarbonate (4 g), and azobisisobutyronitrile (4 g) are mixed, heated and refluxed in 1 hour. Xylene (800 g) and azobisisobutyronitrile (4 g) are then added over the course of 4 hours, and the mixture is refluxed for 1 hour. Part of this solution (200 g) is mixed with a solution consisting of 20% by weight of cellulose acetate butyrate (P-1) in acetone (200 g) and with further acetone (200 g). A green pigment paste (1.60 g) consisting of 12% heliogen green pigment, 30% acrylic copolymer (50% solids), 55.5% xylene and 2.5% butanol is added to a portion of this solution (100 g). , and the preparation is thoroughly mixed. A film sprayed from this mixture turns an opaque green upon drying.

Example 94

The above procedure is repeated using instead of the green pigment paste an aluminum pigment (0.63 g) consisting of 30% aluminum ("Alcoa 1595" pigment), 16.17% xylene, 25% acrylic copolymer (50% solids) and 2.53 % butanol, and the preparation is sprayed, whereby an opaque gray film is obtained.

Example 95

A film is drawn from a preparation consisting of 14% by weight cellulose acetate butyrate (P-1), 43% by weight aromatic naphtha with a high flash point and 43% by weight methyl ethyl ketone. The film is drawn onto a plate, and the weight of plate plus film is determined at periodic intervals. The results of these measurements are shown in table 4.

After drying, the film measured 38.0 mm in length, 33.0 mm in width, 33.0 x 10 - 3 mm in thickness and occupied a volume of 4.14 x 10 -2 cm 3 and weighed 1.12 x 10 - 2 g. The specific weight of the film was thus 0.283 g/cm 3 . In contrast, the specific weight of a corresponding film of cellulose acetate butyrate (P-1) produced by conventional methods is 1.240 g/cm 3 . It is therefore seen that a film produced according to the present invention is significantly less dense than a film produced by conventional methods. In reality, most of the volume of the non-solvent for the cellulose acetate butyrate (ie, the high flash point aromatic naphtha) results in the formation of voids in the film. This can be shown by comparing the actual specific gravity of the film (0.283 g/cm ) with the theoretical specific gravity, i.e. the specific gravity that the film would have if the total amount of high flash aromatic naphtha had resulted in the formation of voids. This theoretical specific gravity can be calculated as follows: The volume of cellulose acetate butyrate (P-1) per lOO g original coating preparation = 11.30 cm.

The volume of aromatic naphtha with a high flash point per 100 g original coating preparation = 48.20 cm 3.

Total film volume produced from 100 g of the original coating preparation after evaporation of methyl ethyl ketone, and assuming that no evaporation of the aromatic naphtha with a high flash point has taken place = 59.50 cm .

Volume percentage of cellulose acetate butyrate (P-1) in the film, prepared from 100 g of original coating preparation, after evaporation of methyl ethyl ketone, and assuming that no

evaporation of aromatic naphtha with high

The theoretical specific gravity (actual specific gravity of cellulose acetate butyrate times the percentage, calculated above, divided by

Figure 3 shows the data listed in table 4. The resulting curve illustrates the evaporation rate of solvent mixture from the drawn film. In the area AB, most of the weight loss is due to the evaporation of methyl ethyl ketone. At some point along the line AB, the cellulose acetate butyrate gelatinizes, and at a later time the high flash point aromatic naphtha precipitates as small droplets in the cellulose acetate butyrate matrix. The evaporation of most of the aromatic naphtha with high flash points occurs along the line BC. After all the aromatic naphtha with a high flash point has evaporated, an opaque, micro-porous film of cellulose acetate butyrate remains.

Example 96 - 107

In these examples, a number of preparations are prepared with different concentrations of cellulose acetate butyrate (P-1), methyl ethyl ketone (MEK) and aromatic naphtha with a high flash point (HFAN). The percentage by weight of each of these components is listed for each example in table 5-

The preparations according to each of Examples 96 - 107 are plotted in a triangular diagram shown in Figure 4 - In this figure, the concentration of the higher-volatile liquid, methyl ethyl ketone (MEK), is calculated from tip G, the concentration of the lower-volatility non-solvent for the polymer , aromatic naphtha with a high flash point (HFAN), from tip A, and the concentration of the film-forming, gelatinizable polymer, cellulose acetate butyrate (P-1), from tip M. The drawn points correspond to the preparations according to examples 96 - 107-

Still referring to Figure 4, preparations in the approximate range ABG dry as discontinuous films, preparations in the approximate range BFG as continuous white films with Kubelka-Munk scattering coefficient greater than 12.7 reciprocal p,m at 4400 Å and greater than 2.54 reciprocal (im at 5600 Å, and preparations in the approximate range EFG as continuous films with Kubelka-Munk scattering coefficients less than 12.7 reciprocal yim at 4400 Å and less than 2.54 reciprocal (im at 5600 Å The word "about" is necessary because of the possible variations in the film drying conditions (such as humidity, temperature and atmospheric pressure).

The preparations according to examples 96 - 100, 102, 104, 106 and 107 are applied with different controlled film thicknesses over white and black glass and over steel plates and allowed to dry thoroughly. The total reflection as well as the non-specular reflections are measured with a recording spectrophotometer equipped with a digital tristimulus integrator (abbreviated to TSI). The reflections are recorded for each

200 Å interval from the digital output signal from TSI for the film over white, R, films over black, Ro and for the white glass substrate, Rg. All measurements are made in relation to the pressed BaSO^-white standard, which has an average absolute reflection corresponding to around 97.5%. All readings are corrected to absolute reflectance by multiplying by 0.975. (More correctly, an exact correction should be made for each wavelength, but the error by using 0.975 is at most only about 1%).

Corrections are made for the surface reflection using the following equation:

where R''" is the total reflection, R is the internal reflection (used in the Kubelka-Munk equation), k^ is the first surface Fresnel reflection (gloss), and k2 is the correction for the reflection from the underside of the surface-air interface. Values of 0.04 for k^ and 0.40 for k2 are used in these calculations. (See also Saunderson, J. L., J. Opt. Soc. Am. 22, 727-36 (1942)).

The scattering and absorption coefficients are calculated from equation 4 for 16 wavelengths, from 4000 to 7000 Å at 200 Å intervals. Ti02~pigment is also measured and calculated in a similar way for comparison. For comparison purposes, the scattering coefficients are calculated for a film thickness of 0.0254 mm. TiO2 is calculated for 100% dry pigment by weight, with a thickness of 0.0254 mm forming the basis for the comparison. Table 6 gives an overview of the results obtained at three selected wavelengths, 4400 Å (violet), 5600 Å (yellow-green)

and 6800 Å (red).

Rø,, is determined from a-b except for Ti02 in which case it is measured. The materials according to the invention are whiter when fully covered than Ti02.

The apparent absorption coefficient, K, is assumed

not a true absorption except for TiO 2 at 44oo Å and lower wavelengths. What appears to be absorption is presumably light loss as a result of multiple scattering.

Record of log S in relation to the wavelength is a straight line for the materials in the examples, so that the curves can be extrapolated from the three values listed in the table.

Example 108

A preparation consisting of acetone (200 g), cellulose acetate butyrate (P-7) (100 g), an acrylic polymer containing 4% hydroxypropyl methacrylate, 4% hydroxyethyl methacrylate and 2% methacrylic acid with a solids content of 50% in a 90/10 xylene/butanol mixture (120 g), a butylated melamine resin with 50% solids content in a 50/50 xylene/butanol mixture (80 g) and water (100 g) is prepared. This preparation gives, when sprayed and dried, a white glossy film which, after oven drying at 149°C for 30 minutes, results in a hard, solvent-resistant coating preparation in which the melamine resin has successfully cross-linked a significant portion of the hydroxy groups in the cellulose acetate butyrate and in the acrylic polymer.

Claims (2)

1. Procedure for the production of continuous, opaque films by applying to a substrate in the form of a wet film a film-forming material containing at least one film-forming gelable polymer and a solvent mixture for the polymer, which solvent mixture consists of two mutually miscible liquids, of which at least one is a non-solvent for the polymer with lower volatility than the other liquid in the solvent mixture, and as the solvent mixture and the polymer form a single phase, after which the solvent is removed from the film on the substrate, characterized in that the amount of non-solvent with lower volatility is adjusted in the mixture so that, after removal of the solvent mixture from the film-forming material applied to the substrate is sufficiently great to form a film with a Kubelka-Munk scattering coefficient greater than 12.7 reciprocal (im at 4400 Å and greater than 2.54 reciprocal [ im at 56oO Å, and which have separate, closed cells that make the film opaque. 2. Method according to claim 1, characterized in that the separated, closed cells of the film are given an average cell size of less than 1.0 µm.