GB1597611A - Internally plasticized polymer latex - Google Patents

Abstract

Successive suspension polymerisations in at least two stages are used to prepare aqueous suspensions or latices containing particles whose middle part is made of hydrophilic and relatively soft polymer while the outer part is made of hydrophobic and relatively hard polymer, the two types of polymer interpenetrating to a sufficient degree to result in an internal plasticisation of the latex particles. These latices can be employed for preparing compositions of the polish type which make it possible to form hard, glossy coatings with a very high chemical and mechanical resistance on floors or parquets.

Description

(54) INTERNALLY PLASTICIZED POLYMER LATEX (71) We, ROHM AND HAAS COMPANY, a corporation organized under the laws of the State of Delaware, United States of America, of Independence Mall West, Philadelphia, Pennsylvania 19015, United States of America, do hereby declare the invention for which we pray that a patent may be granted to us, and the method by which it is to be performed to be particularly described in and by the following statement: This invention is concerned with novel polymer latexes useful in the formation of coatings, adhesives and binders. The latexes are particularly useful to replace combinations of polymers and coalescents in polish and other coatings compositions. The resulting polishes or coatings may be suitable for application to either hard or soft surfaces and to floor and wall surfaces to form clear coatings having a glossy appearance. The invention is also concerned with the coating, adhesive and binder compositions containing the latexes of the invention and in the polishing methods and polished articles associated therewith.

The polymer in a film-forming latex is required to be soft enough to form a film of good integrity yet hard enough that the film has high strength, low dirt pick-up and a myriad of other related properties depending on the specific application. It is known that if the glass transition temperature (Tg) of the polymer is below the temperature at which the film is being formed, a film of good integrity, that is, not "cheesy", is normally produced on drying a layer of the latex. However, the very softness of the latex particles which leads to good film formation means that the produced film tends to be soft or tacky as opposed to being strong, hard, wear resistant and tough. The conventional way out of this dilemma is to add, to a relatively hard polymer, coalescents volatile enough to leave the film after film formation has occurred. With greater concern about air pollution, it is preferred to eliminate the volatile coalescents. Elimination of the coalescents also represents a cost saving.

Another approach toward preparing high Tg polymers with low minimum film formation temperatures (MFT) is the incorporation of a high proportion of hydrophilic monomers (for example those with hydroxyl, amine or carboxyl functions) in the polymer. This induces water swelling of the latex particles which softens the particle in the latex. However, at normal polymer concentrations, the swelling is accompanied by very high viscosities particularly if the storage or use pH is such that the carboxylic groups or amine groups are neutralized or partially neutralized. A further disadvantage is water sensitivity of the final film as well as sensitivity to acidic or basic solutions. Polymers of hydrophilic monomers made by solution polymerization procedures and applied in solution are taught in U.S.

Patent 3,935,368 for use in coating vinyl chloride flooring materials.

Still another solution to the problem of getting a hard coating in the form of a well integrated film is that of U.S. Patent 3,949,107 which teaches applying a polish containing an aqueous dispersion of a resin with a Tg of 30"C. to 800C. to a floor, either the polish or the floor having been preheated to a temperature above the Tg of the resin.

In the present invention we sequentially form, by polymerization, relatively hard (high Tg), relatively hydrophobic polymer on preformed, relatively soft (low Tg), hydrophilic functionalized copolymer latex particles, to form latex particles, which for convenience we call internally plasticized polymer latex particles. This can produce a latex low in viscosity yet film-forming at a temperature low in comparison to the calculated Tg of the polymer in the particles. The viscosity and the minimum film forming temperature MFT) are measured under normal use conditions, i.e. neutral to high pH for acid containing polymers and neutral to low pH for base-containing polymers. Preferably, the latex of internally plasticized polymer particles is made by preparing a water-swellable addition polymer under normal emulsion polymerization conditions. This water swellable polymer may also be water soluble at an appropriate pH and normally is soluble at high pH when containing acidic groups or at low pH when containing basic groups. Under the conditions of polymerization, however, it does not dissolve in the aqueous medium but is maintained as a latex. A second polymer is then formed by polymerization in the presence of the latex and interpenetrates the first. This is achieved by the addition to the first latex of monomer which will form polymer less water sensitive, i.e. less hydrophilic, and harder than that of the initial latex, and subsequent polymerization. The second monomer system is chosen to have sufficient compatibility with the initial polymer so as to swell the initial polymer. The second polymer in its interaction with the first serves to limit the water swellability of the first polymer. Thus, the product can be considered to be a hydroplastic first polymer, made more hydrophobic and hardened, by the second polymer; or alternatively a, hard, hydrophobic second polymer made, more hydroplastic, and softer, by the first polymer.

The internally plasticized polymer formed has properties unlike the properties of either component polymer nor are the properties simply the sum of average of the properties of the components. For example, if the first polymer is one which is completely soluble at high pH it is found that after the internally plasticized polymer is formed this first polymer portion is no longer soluble even at very high pH values.

A highly water swell able component polymer would be expected to produce a high viscosity latex, even though the MFT might be low compared to the Tg. In this invention, the modification of the properties of the water swellable first stage polymer by the second stage results in the relatively low viscosity of the latex.

According to this invention there is thus provided a latex of internally plasticized addition polymer particles comprising (A) early stage polymer and (B) later stage polymer formed by polymerisation in the presence of an emulsion of polymer particles comprising polymer (A), polymers (A) and (B) each making up at least 10% by weight of the polymer in the particles, polymer (A) containing at least 10% by weight hydrophilic mers of which at least 10% by weight are nonionic and polymer (B) being less hydrophilic than polymer (A) wherein polymer B is of higher Tg than polymer (A) and, of the hydrophilic units in polymer (A), at least 0.5% are ionic and the interpenetration parameter of polymer (A) is greater than that of polymer B by at most eight units, polymer (A) comprising units of monoethylenically unsaturated monomer.

The preferred polymers of this invention comprise at least one of acrylate, methacrylate, vinyl ester and vinyl aromatic mer units. Preferred hydrophilic ionics mers (if any) in the polymers comprise mers with carboxylic acid groups. Preferred hydrophilic nonionic mers in the polymer comprise mers of hydroxyalkyl esters of carboxylic acids or vinyl alcohol mers.

The internally plasticized polymer of this invention may be formed by polymerization of a first ethylenically unsaturated monomer system comprising comparatively hydrophilic monomer, usually by emulsion polymerization and then, in the presence of the resulting latex, emulsion polymerizing a second charge of ethylenically unsaturated monomer which charge, by itself, would form harder and more hydrophobic polymer than the first charge polymer. The polymer formed by the first charge (or stage) is maintained as an emulsion although it is water swellable or water soluble. By "water soluble", in this specification we mean soluble in water when the pH of the water is adjusted, by the addition of acid or base, to completely or partially neutralize the polymer. By "water swellable" in this specification we mean that the polymer imbibes water or can be made to imbibe water by such a pH adjustment. It is preferred that the pH range considered useful be from about 4 to about 10.

The swelling ratio of the swellable polymer, i.e., the volume of the polymer swollen in a large excess of water divided by the volume of the polymer when dry, is preferably greater than two and more preferably greater than six.

We believe we understand the mode of operation of the hydrophilic monomer, included in amounts ranging from about 10 to about 100 parts per hundred parts of first charge monomer, but this invention is not to be limited by any such theoretical considerations. It appears that the hydrophilic monomer may serve, when polymerized, to bind whatever amounts of water are transmitted into the composition, by way of water of hydration for example. Any monomer which can be polymerized in the mix and which is hydrophilic enough to bind water effectively is therefore useful. Among suitable the hydrophilic monomers, for example, are: acrylonitrile, methacrylonitrile, hydroxy-substituted alkyl and aryl acrylates and methacrylates, polyether acrylates and methacrylates, alky-phosphatoalkyl acrylates and methacrylates, alkyl-phosphono-alkyl acrylates and methacrylates, acrylic acid, methacrylic acid, maleic acid, maleic anhydride, N-vinyl pyrrolidone, alkyl and substituted alkyl amides of acrylic acid, methacrylic acid, maleic acid (mono- and di-amides), fumaric acid (mono-and di-amides), itaconic acid (mono- and di-amides), acrylamide methacrylamide, also other half acid forms of the above dibasic acids such as half esters, amino monomers such as amino-substituted alkyl acrylates and methacrylates, vinyl pyridines and amino alkyl vinyl ethers, and ureido monomers, including those with cyclic ureido groups. The proper scope of the invention should also be interpreted to include variations on the inclusion of the hydrophilic monomer in the monomer mix, such as, for example, when the hydrophilic monomeric units are formed in situ or subsequently formed. For example a monomer may be included in the polymerization mix which is not itself hydrophilic but is altered in processing or in a subsequent step, e.g. by hydrolysis, to provide hydrophilicity; anhydride- and epoxide-containing monomers are examples.

Preferred suitable hydrophilic monomers include acrylic compounds, particularly the amides and hydroxy alkyl esters of methacrylic and acrylic acids, amides and hydroxy alkyl esters of other acids are also preferred, but less so than the corresponding methacrylates and acrylates which are more readily polymerized. Monomers containing carboxylic acid groups are also preferred particularly acrylic acid, methacrylic acid and itaconic acid.

Another preferred group of hydrophilic monomers are represented by specific examples of potential hydrophilic monomers which produce the actual hydrophilic mer units in the polymer on hydrolysis. These monomers include esters of vinyl alcohol such as vinyl formate. vinyl acetate, vinyl propionate, vinyl butyrate, and vinyl versitate. Hydrolysis of these monomers produces hydrophilic vinyl alcohol mer units in the polymer. The preferred monomer among these is vinyl acetate.

Polymerized with the hydrophilic monomer in the first charge may be other monomer carefully chosen to give other desirable properties to the final polymer. Any polyethylenically unsaturated monomer, if present, is preferably of the type in which the various ethylenic groups, i.e. the addition polymerizable unsaturated groups, participate in the polymerization at about the same rate. Preferably no such crosslinking or graftlinking polyethylenically unsaturated monomer is present in the first stage monomer system. The term graftlinking monomer is defined in column 4 line 66 to column 5 line 20 of U.S. Patent 3,796,771 which definition is hereby incorporated by reference. Preferably the first charge comprises monoethylenically unsaturated monomer.

It is necessary that the first charge polymer be softer than the second charge polymer.

The hardness of the first charge can be controlled by the choice of the hydrophilic monomer and of any comonomer used therewith. Suitable comonomers which form soft polymers in the presence of free radical catalysts include primary and secondary alkyl acrylates, with alkyl substituents having up to eighteen, or even more, carbon atoms, primary or secondary alkyl methacrylates with alkyl substituents of at least five, for example to eighteen or more carbon atoms, or other ethylenically-unsaturated compounds which are polymerizable with free radical catalysts to form soft solid polymers, including vinyl esters of saturated monocarboxylic acids of more than two carbon atoms. The preferred ethylenically unsaturated compounds are the stated acrylates and methacrylates and of these the most practical esters are those with alkyl groups of at most 8 carbon atoms.

The preferred monomers which by themselves yield soft polymers may be summarized by the formula

wherein R' is hydrogen or the methyl group and RX represents, when R' is methyl, a primary or secondary alkyl group of 5 to 18 carbon atoms, or, when R' is hydrogen, an alkyl group of not over 18 carbon atoms, preferably of 1 to 8 carbon atoms and more preferably 1 to 4 carbon atoms.

Typical compounds coming within the above definition are methyl acrylate, ethyl acrylate, propyl acrylate, isopropyl acrylate, butyl acrylate, isobutyl acrylate, sec-butyl acrylate, amyl acrylate, isoamyl acrylate, hexyl acrylate, 2-ethylhexyl acrylate, octyl acrylate, 3,5,5-trimethylhexylacrylate, decyl acrylate, dodecyl acrylate, cetyl acrylate, octadecyl acrylate, octadecenyl acrylate, n-amyl methacrylate, sec-amyl methacrylate, hexyl methacrylate. 2-ethylbutyl methacrylate, octyl methacrylate, 3,5 ,5-trimethylhexyl methacrylate, decyl methacrylate, dodecyl methacrylate, octadecyl methacrylate, and those with substituted alkyl groups such as butoxylethyl acrylate or methacrylate.

As polymerizable ethylenically unsaturated monomers, which by themselves form hard polymers, there may be used alkyl methacrylates having alkyl groups of at most four carbon atoms, also tert-amyl methacrylate, tert-butyl or tert-amyl acrylate, cyclohexyl, benzyl or isobornyl acrylate or methacrylate, acrylonitrile, or methacrylonitrile, these constituting a preferred group of the monomers which by themselves compounds form hard polymers.

Styrene, vinyl chloride, chlorostyrene, vinyl acetate and p-methylstyrene, which also form hard polymers, may be used.

Preferred monomers, which by themselves form hard polymers, may be summarized by the formula

wherein R' is hydrogen or the methyl group and wherein X represents one of the groups - CN, phenyl, methylphenyl, and ester-forming groups, -COOR", wherein R" is cyclohexyl or, when R' is hydrogen, a tert-alkyl group of four or five carbon atoms, or, when R' is methyl, an alkyl group of one to four carbon atoms. Some typical examples of these have already been named. Other specific compounds are methyl methacrylate, ethyl methacrylate, propyl methacrylate, isopropyl methacrylate, isobutyl methacrylate, n-butyl methacrylate, sec-butyl methacrylate, and tert-butyl methacrylate. Acrylamide and methacrylamide may also be used as monomers to contribute hardness to the copolymer.

These monomers may contain other functional groups for other purposes such as to produce crosslinking in the polymer on curing or enhanced adhesion to a substrate.

Examples of such functional groups are carboxyl, in the form of the free acid or salt, amido including substituted amido, such as alkoxy alkyl amido and alkylol amido, epoxy, hydroxy, amino including oxazolidinyl and oxazinyl, and ureido. In most instances these functional groups are also hydrophilic groups, and many of the monomers are hydrophilic.

Another group of monomers useful in this invention and which if polymerised by themselves yield soft polymers are butadiene, chloroprene, isobutene, and isoprene. These are monomers commonly used in rubber latices along with monomers which produce hard polymers and also useful in this invention, such as acrylonitirile, styrene, and other "hard monomers" as given above. The olefin monomers, particularly ethylene and propylene, are suitable "soft monomers". Particularly useful first stage copolymers are ethylene/ethyl acrylate copolymers and ethylene/vinyl acetate copolymers containing added hydrophilic monomers.

A further class of polymers useful in this invention are polymers of esters of vinyl alcohol such as vinyl formate, vinyl acetate, vinyl propionate, vinyl butyrate and vinyl versatate.

Preferred is poly(vinyl acetate) and copolymers of vinyl acetate with one or more of the following monomers; vinyl chloride, vinylidene chloride styrene, vinyl toluene, acrylonitrile, methacrylonitrile, acrylate or methacrylate esters, and the functional group containing monomers given above. In the largely vinyl ester polymers it is preferred that the first stage polymers contain at least 10% and preferably at least 30% by weight vinyl acetate units with at least 80% being most preferred. Before polymerization of vinyl alcohol esters is complete some hydrolysis to vinyl alcohol mer units normally occurs or is deliberately accomplished.

The vinyl alcohol mer units so produced are hydrophilic and considered here as though derived from vinyl alcohol monomer. The amount of hydrolysis can be controlled by means of control of the time, temperature and pH of the reaction to produce the desired amount of vinyl alcohol in the product. Longer time, higher temperatures, very acidic or very alkaline conditions all serve to increase the amount of hydrolysis and thus the amount of vinyl alcohol in the final product. The amount of hydrolysis can be determined by acid-base titration procedures in water or in suitable solvent systems.

A preferred composition of this invention is one in which the mers of the first stage comprise by weight 65 to 85% (C1-C4)-alkyl acrylate, (C1-C4)-alkyl methacrylate and/or styrene, 5 to 10% acrylic acid, methacrylic acid, and/or itaconic acid, and 10 to 25% hydroxy (C1 - C4) - alkyl acrylate and/or hydroxy (C1 - C4) - alkyl methacrylate, and the mers of the later stage polymer comprise methyl methacrylate, and/or styrene. Another preferred composition is one in which the mer units of the first stage comprise, by weight, 50 to 85% vinyl acetate (for subsequent hydrolysis), 1 to 10% acrylic acid, methacrylic acid, itaconic acid and/or maleic acid (derivable from maleic anhydride), and 8 to 25% vinyl alcohol, and the mer units of the latter stage comprise 70 to 100% methyl methacrylate and/or styrene and 0 to 30%, preferably 10 to 20%, by weight acid - containing mers, such as acrylic, methacrylic and/or itaconic acid mers. It is desirable that the acid mers in the first stage comprise up to 5%, based on the first stage polymer weight, of maleic anhydride or maleic acid with 0.2 to 2 per cent being preferred. In this usage, the term "mer" means the unit, in the addition polymer, derived from the named monomer by addition to the double bond.

In general the preferred hydrophilic monomers used in this invention are monomers with a solubility of at least six grams per 100 grams of water, those with a solubility of at least 20 grams per 100 grams of water are more preferred and most preferred are those in which at least 50 grams of the monomer is soluble in 100 grams of water. The first stage polymer contains at least 10% hydrophilic mers, 10% to 70% being preferred, at least 25% is more preferable with the range 25% to 35% being most preferable. Of the hydrophilic monomer content it is necessary to have at least 0.5% ionic hydrophilic mers such as acidic mers, such as mers containing carboxyl or basic groups such as amino groups, in either the unneutralized or neutralized form. It is also necessary that at least 10 of the hydrophilic mers be nonionic, i.e. not ionizable, such as hydroxyethyl acrylate or methacrylate, which may be produced in situ such as nonionic mer units from hydroxyethyl ester and vinyl alcohol mer units.

The last stage polymer is more hydrophobic and harder than the first stage. By more hydrophobic is meant that the later stage polymer alone is less water-swellable than is the first stage polymer alone. By harder is meant that the modulus of the later stage polymer is greater than that of the first stage polymer, measurements being conducted on polymer samples immersed in water. It is preferred that the last stage monomer be monoethylenically unsaturated.

The internally plasticized polymers of the present invention are conveniently prepared by known emulsion polymerization procedures utilizing a multi-stage, sequential technique.

However, they may also be prepared by a continuous polymerization in which the composition of monomer being fed continuously is changed, either step-wise or continuously, during the polymerization. In such a polymerization any abrupt or discontinuous change in the composition of the monomer feed may be regarded as a stage terminal. If there are no such changes in the feed composition to indicate a change from one stage to another, the first half of the polymer feed may be regarded as representing one stage and the second half as representing a second stage. In the simplest form of the latexes of the invention, the hydrophilic polymer is formed in a first stage and the more hydrophobic polymer is formed in a second stage. Either of the component polymers can themselves also be sequentially polymerized, i.e. consist of multiple stages. The monomers of the first stage, together with initiators, soap or emulsifier, polymerization modifiers or chain transfer agents, are formed into the initial polymerization mix and polymerized, e.g., by heating, mixing, cooling as required, in well known and wholly conventional fashion until the monomers are substantially depleted. Monomers of the second and, in turn, of any subsequent stage are then added with appropriate other materials so that the desired polymerization of each stage occurs in sequence to substantial exhaustion of the monomers.

It is preferred that in each stage after the first, the amounts of initiator and soap, if any, are maintained at such a level that polymerization occurs on existing particles, and no substantial number of new particles, or "seeds" forms in the emulsion.

When polymerizations are conducted in multi-stage, sequential processes, there can additionally be stages which are, in composition and proportion, the combination of the two distinct stages, and which produce polymers having properties which are intermediate therebetween. The hydrophilic first stage is at least 10%, preferably 20% to 80%, more preferably 30% to 70% and most preferably 40% to 60% of the total polymer. There may of course, be other stages before, between or after the two of principal interest. These other stages are always smaller weight proportions of the whole polymer than either of the principal component polymers when they cannot be considered a portion of one or the other of the principal component polymers by virtue of their composition. It is preferred that the polymer of the invention be a two stage polymer. Those skilled in a given art field will usually prepare a few internally plasticized polymer latex samples differing in first to second stage weight ratio and select the one with the best properties for the given application. The equal weight ratio is the usual starting point for these trials which usually consist of one higher and one lower ratio with the spread of the ratio being chosen by consideration of the final properties desired, for example hardness, MFT, latex viscosity, tack-free time.

The copolymer is preferably made by the emulsion copolymerization of the several monomers in the proper proportions. Conventional emulsion polymerization techniques and described in United States patents 2,754,280 and 2,795,564. Thus the monomers may be emulsified with anionic, cationic, or nonionic dispersing agent, about 0.5% to 10% thereof usually being used, based on the weight of total monomer. When water-soluble monomer is used, the dispersing agent serves to emulsify any other monomer. A polymerization initiator of the free radical type, such as ammonium or potassium persulfate, may be used alone or in conjunction with an accelerator, such as potassium metabisulfite, or sodium thiosulfate. The initiator and accelerator, commonly referred to as catalyst, may be used in proportions of 1/2 to 2% each based on the weight of monomer to be copolymerized. The polymerization temperature may be from room temperature to 90"C. or more as is conventional.

Examples of emulsifiers or soaps suited to the polymerization process of the present invention include alkali metal and ammonium salts of alkyl, aryl, alkaryl, and aralkyl sulfonates, sulfates, and polyether sulfates; the corresponding phosphates and phosphonates; and ethoxylated fatty acids, esters, alcohols, amines, amides and alkyl phenols.

Chain transfer agents, including mercaptans, polymercaptans, and polyhalogen compounds, are often desirable in the polymerization mix.

Another way of describing and defining the first and second stage monomers of this invention is by use of the solubility parameter concept. "Polymer Handbook", 2nd Edition, J. Brandrup and E. H. Immergut, editors (John Wiley and Sons, New York 1975) Section IV Part 15 entitled "Solubility Parameter Values" by H. Burrell, on pages IV-337 to IV-359, herein incorporated by reference, defines solubility parameter, describes how it is determined or calculated, contains tables of solubility parameters and gives further references to the scientific literature on solubility parameters. The solubility parameter is the square root of the cohesive energy density which in turn is the numerical value of the potential energy of 1 cc. of material, the potential resulting from the van der Waals attraction forces between the molecules in a liquid or solid. Burrell describes a number of ways of calculating solubility parameters from experimentally determined physical constants and two ways of calculating them from the structural formula of a molecule. The structural formula methods are normally used when the data for the calculation from physical constants are not available or are considered particularly unreliable. Calculation from the structural formula utilizes tables of group molar attraction constants such as those given on page IV-339 in the "Polymer Handbook". The table of Small is preferred.

The solubility parameter concept may be considered an extension of the old rule "like dissolves like" recognized from the early days of chemistry. A non-crosslinked polymer will normally dissolve in a solvent of similar solubility parameter and a cross-linked polymer will normally be swollen by a solvent of similar solubility parameter. Conversely, solvents with solubility parameters far from those of the polymers will neither dissolve nor swell the polymer. As given by Burrell the solubility parameter of polymers may be determined, among other ways, be measuring the swelling of the polymer in a series of solvent.

Solubility parameter for polymers may also be estimated by calculation from the group molar attraction constants as mentioned above. In the usual situation, it is found that solvents with a range of solubility parameters around that of the polymer will dissolve the uncrosslinked polymer. Those skilled in the art have added the further refinement of classifying solvents as poorly, moderately and strongly hydrogen bonded. It is found that the range of solubility parameter for dissolving a given uncrosslinked polymer differs from one class to the next although usually considerable overlap is observed. Burrell's Table 4 starting on page IV-349 gives ranges of solubility parameters for poorly, moderately and strongly hydrogen bonded solvents used to dissolve a large number of polymers. In Table 5 starting on page IV-354, there is given solubility parameters of a number of polymers determined by calculation and by other methods.

To form the internally plasticized polymer system of this invention the first stage polymer and monomers of the later stage are chosen so as to interact to an appropriate degree.

There are both upper and lower limits to the degree of compatibility desired between the first stage polymer and the monomer charges of subsequent (second later or last as hereinabove described) stages. It is found that the appropriate degree of compatibility may be expressed in numerical terms by a property based on solubility parameter and herein named the interpenetration parameter, Ip. The interpenetration parameter may be regarded as a solubility parameter adjusted so as to put strongly, moderately and weakly hydrogen bonding solvents on the same scale. For a given molecule, the interpenetration parameter is defined as the solubility parameter plus the hydrogen bonding increment value given below. Solubility parameters of various molecules, including a number of monomers, are given in Tables 1 and 2 of Burrell starting on page IV-341. These tables following examples, in which the part and percentages are by weight unless otherwise indicated.

The words "Triton", Nopco", "Zopaque", "Abex" and "Carbitol" used in the Examples are Registered Trademarks and the word "Versatate" used in this specification is a derivative of the Registered Trademark "Versatic".

EXAMPLE 1 Preparation of internally plasticized polymer emulsion A latex with first stage, second stage and average Tg values of - 14"C., 105"C., and 34"C. respectively, is prepared as follows: A. Equipment A five liter, four-necked flask is equipped with a condenser, stirrer, thermometer and monomer addition pumps. Heating, cooling and nitrogen sparging facilities are provided.

B. Material charges Kettle Monomer Charges Raw Material Charge Stage 1 Stage 2 Water 2008 g 400 g 400 g Sodium lauryl sulfate (surfactant) 16 2 2 Butyl acrylate (BA) - 600 Methyl methacrylate (MMA) - 140 1000 Methacrylic acid (MAA) - 60 Hydroxyethyl methacrylate (HEMA) - 212 Sodium persulfate in 100 g Water (catalyst) 12 C. Procedure 1. Add kettle charge water and surfactant to the kettle and start agitation and nitrogen sparge.

2. Combine the materials of each of the monomer charges and thoroughly mix to create stable monomer emulsions.

3. Heat the kettle to 8284"C. with continued agitation and nitrogen sparging.

4. Add the catalyst solution to the kettle and start the addition of monomer charge stage 1 at such a rate that the addition is completed in about 50 minutes. Maintain the temperature at 82-84"C. throughout the polymerization.

5. When monomer charge stage 1 addition is completed hold for 15 minutes at 82-84"C.

6. After the hold period start the addition of monomer charge stage 2 at such a rate that the addition is completed in about 60 minutes. Maintain the temperature at 82-84"C. throughout the polymerization.

7. When monomer charge stage 2 addition is completed, hold for 30 minutes at 82-84"C., then cool and filter.

A sample of the latex is neutralized to a pH of 9 with ammonia; the MFT is below 15"C. and the viscosity is 15 centipoise (Brookfield Viscosity; 20% solids). A film cast from the neutralized latex has a hardness of 12.1 KHN.

EXAMPLE 2 Following the general procedure of Example 1 on internally plasticized polymer latex was prepared according to details given in Table I.

TABLE I Polymer Tg Composition MFT/Viscosity (20% Solids) Example BA/MMA/MAA/HEMA//MMA* (1) (2) Avg. pH 3 pH 9 2 23/6/6/15//50 4 105 47 40/6 10/140 *A double slash (//) is used to indicate separation between the first and second stage.

MFT is in degrees Celcius/Viscosity in centipoise at 20 C.

Tg is calculated, in degrees Celcius, for the first stage (1), second stage (2) and overall polymer-Avg. bonding class appropriate for the monomer. The solubility parameter values and hydrogen bonding class of most of these monomers are those given in Table 1 of Burrell. Vinyl alcohol is a special case because, as is well known, this monomer does not have a stable existence. Polymers containing mer units corresponding to vinyl alcohol may be prepared by hydrolysis of a polymer containing the corresponding vinyl ester, such as vinyl acetate, mer unit. The solubility parameter of this hypothetical monomer is computed by the method of Small as indicated above. Values for other monomers not in Burrell's table are determined or computed following the teachings in Burrell's writings v.s. Dimensions for the solubility parameters given in the table are the usual ones, square root of (calories per cubic centimeter). The interpenetration parameter has the same dimensions. Water solubility is given in grams of monomer per 100 grams of water at 25 C. The hydrogen bonding class strong, moderate or poor is ascertained by using the method of C. M.

Hansen, Journal of Paint Technology, Vol. 39, p. 104-117 and 505-514 (1967).

Solubi- Interpene- Water lity Hydrogen tration Sol- Abbre Monomer Parameter Bonding Parameter ubility viation Acrolein 9.8 S 27.0 40 Acr.

Acrylic Acid 12.0 S 29.2 CM AA Acrylonitrile 10.5 P 13.3 25-30 AN o-bromostyrene 9.8 P 12.6 BrSt 1.3-butadiene 7.1 P 9.9 Bd i-butyl acrylate 8.5 M 15.2 0.2 iBA n-butyl acrylate 8.8 M 16.0 0.2 BA Butyl methacrylate 8.2 M 15.4 0.01 BMA Chlorostyrene 9.5 P 12.3 ClSt i-decyl acrylate 8.2 M 15.4 0.01 iDA Dichloroethylene 9.1 P 11.9 0.01 DCE Ethyl acrylate 8.6 M 15.8 1.51 EA Ethylene oxide 11.1 M 18.3 CM EO Ethylene epichlorohydrin 12.2 S 29.4 EEPC Dimethylamino ethyl methacrylate 7.0 S 24.2 CM DMAEMA Dihydroxypropyl methacrylate 9.0 S 26.2 CM DHPMA Ethylhexyl acrylate 7.8 M 15.0 EHA Ethyl methacrylate 8.3 M 15.5 0.1 EMA 1-hexene 7.4 P 10.2 hex Solubi- Interpene- Water lity Hydrogen tration Sol- Abbre Monomer Parameter Bonding Parameter ubility viation Hydroxyethyl methacrylate 8.0 S 25.2 HEMA Isoprene 7.4 P 10.2 Ipn Maleic anhydride 13.6 S 30.8 16.3(79)1 MAn Methacrylic acid 11.2 S 28.4 CM MAA Methyl acrylate 8.9 M 16.1 5.2 MA Methyl methacrylate 8.8 M 16.0 1.6 MMA 2-methylstyrene 8.5 P 11.3 MeSt Styrene 9.3 P 12.1 ST Vinyl acetate 9.0 M 16.2 2.3 VAc Vinyl chloride 7.8 M 15.0 VCl Vinyl toluene 9.1 P 11.9 Vtol (Vinyl alcohol) 8.4 S 25.6 (CM) VOH S = Strong P = Poor M = Moderate CM = Completely Miscible As maleic acid For a latex polymer of this invention, the interpenetration parameter of the first stage will be greater than that of the second stage, preferably at least one unit (calorie per cubic centimeter) greater. However, the interpenetration parameter of the first stage must not be too much greater than that of the second stage. The difference is not more than 8 and is desirably not more than 6, preferably 1 to 6 units. When the first stage polymer contains 65% or more, by weight, of C1-C4 alkyl acrylate, C1-C4 alkyl methacrylate, styrene or a mixture thereof, it is desirable that the first stage Ip be not more than 6 units greater than that of the later stage with a difference of 1 to 4 units being preferred and 2 to 3 units most preferred. When the first stage polymer contains 50% or more, by weight, of vinyl acetate it is desirable that the first stage Ip be 1 to 8 units greater than that of the later stage with a difference of 2 to 6 units being preferred and 4 to 5 units most preferred. It should be appreciated in this context that the second stage or the later stage may contain some hydrophilic monomers and still conform to these rules for the difference between the interpenetration parameter of the first stage and that of the second stage.

As stated above, in a preferred embodiment, the first stage contains acidic, preferably carboxylic, mer units as well as the other hydrophilic mer units. The carboxylic mer units are preferably obtained from the monomers acrylic acid, methacrylic acid or itaconic acid.

The other hydrophilic mer units are preferably hydroxy C1-C4 alkyl methacrylate, hydroxy C1-C4 alkyl acrylate or vinyl alcohol units.

The viscosity of the polymer emulsion produced may be measured by any of the known procedures. preferably by Brookfield Synchro-Letric Viscometer model LV 1 with preference in choice of spindle and speed being given to the combinations which will result in a mid-range reading. Measurements, at 20"C, are made at pH values in the range of 3 to 10 on emulsions adjusted, with water, to 20% solids content. The pH of acid-containing copolymer emulsions is generally adjusted by the use of a mineral base, an organic base, such as an amine, or ammonia with the latter being preferred. Internally plasticized polymer latices containing basic groups, such as amine groups or quaternary ammonium groups, may have their pH adjusted by the use of mineral acids, such as hydrochloric acid, or organic acids such as acetic acid. The latex viscosity, over the pH range 3 to 10, is preferably below 5,000 centipoises, better still below 500 centipoises, better still below 150 centipoises, better still below 40 centipoises, and most preferably below 10 centipoises; the lower values being particularly desirable for certain applications, such as floor polishes.

The minimum film temperature (MFT) may be measured on a film cast from the latex at 20% solids and a pH of 7-1/2 to 9 for ammonia-neutralized, acid-containing polymers and of 3 to 4 for acetic acid neutralized base containing polymers. The procedure of The American Society for Testing Materials method D2354-68 is followed. The MFT is preferably more than 5C" below the calculated glass transition temperature (Tg) of the polymer when the Tg is about 5"C. Preferred are MFTs below 18"C. with polymers having a Tg calculated for the entire polymer composition of greater than 25"C. The term MFT, as used herein to define certain polymers, refers to the value determined on a latex at the pH and solids just given.

In some of the examples given later, MFT values determined under other conditions are given only for comparison purposes and do not apply or refer to the MFTs used in defining the polymers of this invention.

Hardness is expressed as Knoop Hardness Number (KHN) and is determined by means of the Tukon Microhardness Tester on a film formed by casting the latex on a solid substrate such as a glass panel. It is preferred that the polymers have a KHN greater than 3 with greater than 5 being more preferred and greater than 8 most preferred.

The calculated Tg of each stage and that of the overall polymer may be determined by calculation based upon the Tg of homopolymers of individual monomers as described by Fox, Bull. Am. Physics Soc. 1, 3, page 123 (1956). Tables of the Tg of homopolymers are given in "Polymer Handbook" Section III, Part 2 by W. A. Lee and R. A. Rutherford. The desired calculated Tg of the first stage is less than 40"C. with less than 5"C. being preferred and less than -100C. being most preferred. The desired calculated Tg of the second stage is greater than 35"C. with greater than 75"C. being preferred and greater than 100"C. being most preferred. The calculated Tg of the polymer based on the overall polymer composition is preferably greater than 15"C., more preferably greater than 20"C. with greater than 30"C. being most preferred for floor polish and similar uses. For some other uses, such as adhesives, binders and paints, polymers with calculated Tg values below about 40"C, including subzero values, are suitable.

Internally plasticized polymer emulsions of this invention may have a noteworthy combination of properties especially (1) low minimum film temperature coupled with high hardness and high Tg; and (2) low polymer emulsion viscosity even when neutralized. Thus, comparatively hard latex polymer systems can be used with much less coalescent than usual, or no coalescent at all. This is particularly valuable in situations in which the coalescent gives rise to secondary disadvantages. Because of the absence or minimization of added coalescent in the formation, coatings which develop hardness at a very high rate can be made from the polymers of this invention. Further advantages implied by the elimination of added plasticizer, coalescent or organic solvent are cost reduction, reduced flammability during processing and decreased emission of toxic and polluting vapors during and following application. These properties are of particular importance in the formulation and use of water based industrial coatings, both clear and pigmented. In ink technology, the extremely fast drying and non-flammability advantages of internally plasticized polymers are of great importance. In trade sales coatings, the combination of high hardness and low minimum film temperature makes for a block resistant air drying coating. A further advantage of the latex of this invention is that formulation is very easy, which results in a considerable cost saving, because of the fewer ingredients and the ease of mixing in the plant operation. The ease of mixing probably results from the latex made by this invention being resistant to the so-called "shocking" phenomenon; that is, the latex is not easily flocculated or gelled when mixed with another component of the formulation. Thus, ingredients usually may be mixed in any order in the usual plant equipment and, in addition, the equipment itself is left in a much cleaner condition than with ordinary latexes.

As described above, the polymer latexes of this invention are particularly useful to replace the latex plus plasticizer of latex plus coalescent systems which comprise a number of formulations used in a wide variety of applications for polymer latexes. These latexes are useful in forming free films as well as in forming coatings such as in paints, lacquers, varnishes, powdered coatings, and the like. The latexes of this invention are also useful as impregnants and adhesives for both natural and synthetic materials such as paper, textiles, wood, plastics, metal and leather and as binders for nonwoven fabrics. They may be used to lower the minumum film forming temperature or to aid in film formation of other latex systems when used in combination therewith. Pigments, dyes, fillers, antioxidants, antiozonants, stabilizers, flow control agents, surfactants or other optional ingredients may be included in the polymer compositions of the invention.

The polymer compositions of this invention can be applied with or without a solvent by casting permanently or removably onto a suitable substrate, particularly for use as coatings, fillers or adhesives. Application by brushing, flowing, dipping, spraying and other known means may be used to apply the latex of this invention. One of the particular advantages of the present invention is that reactive polymers can be prepared for use as air cured or thermally cured coatings, fillers or adhesives without requiring organic solvents, coalescents or plasticizers although small amounts of these materials may be desired. This is particularly valuable because elimination of volatile solvents or other volatiles, such as coalescents, decreases a potential ecological hazard.

It is of especial importance that the acid groups, hydroxyl groups, or other functional groups incorporated in the first stage of the polymerization remain available for further reaction such as neutralization or crosslinking. This availability distinguishes the internally plasticized polymer latex from a latex in which a second or later stage so coats or interacts with the first stage as to decrease or eliminate the availability of first stage functional groups for subsequent reactions. The crosslinking referred to may be by any of the usual means, such as coordination crosslinking, ionic crosslinking or the formation of covalent bonds. In general, the reactions of these latices may be ionic or covalent reactions. Ionic reactions are illustrated by the ionic crosslinking in the application of these latices to floor polishes as taught below. The formation of covalent bonds by reaction with aminoplasts, epoxies, isocyanates and beta hydroxyethyl esters are well known in the art.

The polymer latexes of the present invention are particularly useful in formulating floor polish and are advantageously used in the floor polishes taught by U.S. 3,328,325 Fiarman, U.S. 3,467,610 and U.S. 3,573,239.

In general polishing compositions using the polymers of the present invention can be defined in terms of the following proportions of the main constituents: Constituent: Proportion (A) Water-insoluble internally plasticized addition polymer, parts by weight 10-100 (B) Wax ........................................ do.. 0- 90 (C) Alkali-soluble resin do 0- 90 (D) Wetting, emulsifying and dispersing agents . ............. ............ . . .............. percent 0.5-20 (E) Polyvalent metal compound .. .....................do.. 0-50 (F) Water to make total solids 0.5% to 45% preferably 5 to 30%.

(D) is in weight percent on weight of A+B+C (E) is in weight percent on weight of A.

The total of A. B and C should be 100.

The amount of C, when present may be up to 90% of the weight of the copolymer of A, and preferably from about 5% to 25% of the weight of the copolymer of A.

For a nonbuffable, self-polishing composition, the wax should not be over 35 parts by weight, preferably 0 to 25 parts by weight in 100 parts total of polymer plus wax according to the above table. Satisfactory nonbuffable floor polish formulations have been prepared without the inclusion of a wax. Thus wax is not an essential component of a self-polishing composition. For a dry buffable polish composition, the wax should be at least 35 parts by weight on such total. Examples of wetting and dispersing agents include alkali metal and amine salts of higher fatty acids having 12 to 18 carbon atoms, such as sodium, potassium, ammonium, or morpholine oleate or ricinoleate, as well as the common nonionic surface active agents. Additional wetting agent improves the spreading action of the polish.

For polishing floors, the coating obtained from the composition preferably has a Knoop hardness number of 0.5 to 20 when measured on a film thereof 0.5-2.5 mils thick on glass.

This range of hardness provides good resistance to abrasion and wear and can be obtained by the appropriate selection of monomers to be polymerized.

Preferred embodiments of the invention will now be described, for illustration only in the EXAMPLE 3 Polymerization process The difference between a single emulsion copolymer, an internally plasticized polymer and a physical blend of two polymers is seen in the data in Table II. All of the polymers were prepared by emulsion polymerization following essentially the procedure of Example 1 except for there being no second charge in the preparations of Runs 3A and 3C which were therefore for comparative purposes only. The overall composition of each of the three examples is the same; the calculated Tg is 47 C.

TABLE II Polymer Composition BA/MMA/MAA/ MFT/Viscosity Run HEMA/MMA Description pH 3 pH 9 3A (Comparative) 23/56/6/15//0 single charge, 52/3 46/55 simple copolymer 3B b 23/6/6/15//50 internally plas- 40/6 10/140 ticized polymer 3C (Comparative) 23/6/6/15//50 physical blenda 10/10 10/ gellation aPhysical blend 50:50 of (BA/MMA/MAA/HEMA: 46/12/12/30) and (MMA: 100). bThe polymer of Run 3B is the same as that of Run 2B.

It is seen, in Table II, that the single charge polymer of Run 3A has an MFT in the neighborhood of the calculated Tg and this is undesirable. The physical blend, i.e. Run 3C: a blend of an emulsion having the composition of the first stage of the Run 3B polymer with one having the second stage Run 3B composition, is so viscous at high pH that the emulsion gels even when diluted to 20% solids before pH adjustment. Note that neutralized to a pH of 9 the internally plasticized polymer has a much lower MFT and only a moderately higher viscosity than the single charge copolymer.

EXAMPLE 4 Balance of hydrophilelhydrophobe character of stages Using the polymer emulsion of Run 23 as a control, the compositional relationship between the water-swelled first stage polymer and that of the second stage is varied.

Interaction of the first stage polymer with the second stage is shown by achievement of internal plasticization, with controlled viscosity, by sequentially charged (1) soft, hydrophilic and functionalized and (2) hard and hydrophobic copolymers. This internal plasticization is demonstrated to depend on the balance of hydrophobe/hydrophile character of the two monomer charges by the data in Table III.

TABLE III Tg MET/Viscosity Run Composition (1) (2) Avg. pH 3 pH 9 4A* BA/MMA/MAA/HEMA//MMA 4 100 47 40/ 10/ 23/6/6/15//50 6 140 4B BA/MMA/MAA/HEMA//MMA-13 105 35 30/ 10/ 29/0/6/15//50 10 70 4C EA/MAA/HEMA//MMA 14 105 53 55/ 10/ 29/6/15//50 10 1400 *The polymer emulsion of Emulsion 4A is the same as that of Example 2.

The results, in Table III, show that vs. Run 4A a more hydrophobic, i.e. less hydrophilic first stage polymer is good, 4B; a more hydrophilic first stage, 4C, leads to high viscosity.

EXAMPLE S Interpenetration parameter Emulsion polymers of a number of compositions, differing in interpenetration parameter (Ip) of the two stages, are prepared by the procedure of Example 1 (Runs SA to SD, SF to SH, SJ to SL and SN to SR or Example 8 (Runs SE, SI and SM) given hereinafter.

Determinations of the emulsion viscosity and MFT, done to the emulsion neutralized to a pH of 7.5 to 8.5 with ammonia and diluted to 20% polymer solids, and of the film hardness show which of the preparations have formed internally plasticized polymers. Tables IV.A and B present these data.

TABLE IV.A Run Composition Ratio 5A BA/MMA/MAA/HEMA//MMA 23/6/6/15//50 SB BA/MMA/MAA/HEMA//MMA 30/7/3/10//50 5C BA/MMA/MAA/HEMA//MMA 30.5/9/3/7.5//50 5D BA/MMA/MAA/HEMA//MMA 34.8/9.4/4.3/8.5//43 5E EA/VAc/VOH/MAn/AA//ST 5.5/37.8/5.6/0.4/0.7//50 5F BA/MMA/MAA/DHPMA//MMA 25/11.5/6/7//50 5G BA/MMA/MAA/VAc/VOH//MMA 23/6/6/13.5/1.5//50 5H BA/MMA/DMAEMA//MMA 18/17/15//50 5I EA/VAc/VOH//ST 23/23.9/2.1//50 5J BA/MMA/MAA//ST/AN 25/21.5/3.5//30/20 (Comp) 5K BA/MMA/MAA/HEMA//ST 22.5/6.5/6/15//50 (Comp) 5L MMA//BA/MMA/MAA/HEMA 50//2.3/6/6/15 (Comp) 5M BA/VOH/VAc//MMA 24/2.1/23.9//50 5N BA/MMA/MAA/DHPMA//MMA 25/11.5/6/7.5//50 50 BA/MMA/MAA/HEMA//MMA 30/7/3/10//50 5P BA/MMA/MAA/HEMA//MMA 30.5/8.25/3.75/7.5//50 SO BA/MMA/MAA//ST/AN 25/19/6//30/20 (Comp) 5R EA/ST/MAA//ST 21/24/5//50 (Comp) TABLE IV.B Viscosity Tg4 Ip 5 Run cps. MFT KHN (1) (2) Avg. (1) (2) (1-2) 5A 140 < 10 18 4 105 47 20.2 16.0 4.2 5B 5 < 15 12 -14 105 34 18.6 16.0 2.6 5C 3 18 13 -14 105 34 18.1 16.0 2.1 5D 5 18 12 -14 105 28 18.3 16.0 2.3 5F 25 < 10 15 4 105 47 19.0 16.0 3.0 5G 140 20 14 - 1 105 43 17.8 16.0 1.8 5H 720 < 15 -- 6 105 48 18.5 16.0 2.5 5E 40 < 15 18 25 100 58 17.5 12.1 5.4 5I 95 < 15 -- 3 100 44 16.4 12.1 4.3 5J (Comp) 20 42 9 6 99 46 16.9 12.6 4.3 5K (Comp) 30,000 < 10 16 7 100 47 20.3 12.1 9.2 5M 4,250 < 15 -- 3 105 46 16.4 16.0 0.4 5N 25 < 10 18 4 105 47 19.0 16.0 3.0 5L (Comp) Gel < 10 -- 105 5 47 16.0 20.3 -4.3 5O 5 < 15 9 -14 105 34 18.6 16.0 2.6 5P 5 < 15 9 -14 105 34 18.3 16.0 2.3 5Q (Comp) 35 50 10 8 99 49 17.5 12.6 4.9 5R (COMP) 30 73 16 42 100 69 17.2 12.1 5.1 Notes for Table IV.B 1. Viscosity is measured on the latex at 20% solids brought to a pH of 9 with ammonia except for Example SH which is at pH of 3 with acetic acid.

2. MFT, in degrees Celcius, latex at 20% solids and adjusted to pH 9 with ammonia except Example 5H (pH3 as above).

3. Hardness is Knoop Hardness Number (KHN) determined by the procedure given in Resin Review, Vol. XVI, No. 2, p. 9 ff (1966), a publication of the Rohm and Haas Company.

4. Tg is calculated for a high polymer by the procedure of Fox, v.s. "(1)" and "(2)" represent first and second or later stage and "Avg." the value calculated for the composition as a whole.

5. Ip is calculated for the first stage (1) and the second stage (2). The difference between these Ip values is tabulated under "(1-2)".

The data in Table IV.B show that an internally plasticized polymer is obtained, as indicated by the glass transition temperature, minimum film temperature, emulsion viscosity and hardness values, when the interpenetration parameter value of the first stage polymer is greater than that of the second but not too much greater. Run SJ, a polymer latex of the prior art, is not one of internally plasticized particles as this polymer has only seven percent hydrophilic mer units in the first stage polymer. Run 5K is not of internally plasticized particles of this invention; as indicated in Table IV, B is composition is such that an undesirably high difference in the Ip exists between the polymers of the two stages. Run SL is not of this invention, note that the Ip difference between the polymers of the two stages is too low, it is below zero. Runs 5Q and SR, are polymer latexes of the prior art; neither contains nonionic hydrophilic monomers in the first stage.

EXAMPLE 6 Floor polish A floor polish is prepared by mixing ingredients in the following recipe (except Runs 6A and 6E as noted below): Role Material Charge Vehicle Polymer emulsion -- 15% solids 100.0 parts Wax Poly EM-40 - 15% solids 15.0 parts (Trademark, Cosden Oil & Chemical Co.) Wetting aid Fluorad FC128 - 1% solids 0.5 parts (Trademark, 3M Co.) Leveling Tributoxyethyl phosphate - 0.5 parts aid 100% active Defoamer SWS-211 - 50% solids (Trademark 0.01 parts Stauffer Wacker Silicone Corp.) Base Ammonia - 10% aqueous to pH 8 The floor polish is applied and tested by the procedure described in detail in Resin Review, Volume XVI, No. 2, 1966 published by Rohm and Haas Company, Philadelphia, Pennsylvania 19105 except when another procedure is specified. Polymer emulsions used and the test results obtained are in Table V.A. and V.B.

TABLE V.A.

(Comparative) Run 6A 6B 6C 6D 6E Polymer emulsion (note 1) Example 2 Run 50 Run SP Run SE (note 3) (note 4) Test (note 2) Visual gloss One coat g-vg vg vg vg g-vg Two coats vg vg- vg- vg- vg exc. exc. exc.

Leveling One coat exc. exc. exc. exc. exc.

Two coats exc. exc. exc. exc. exc.

60"C gloss (TM 3) 71 82 79 80 77 Heel mark resistance (TM 5) vg- g-vg vg vg- fair exc. exc.

Water resistance (TM 4) One hour good exc. exc. exc. exc.

One day g-vg exc. exc. exc. exc.

Detergent resistance (TM 6) One day vg good good vg - Three days vg-exc. -- -- -- fair Seven days vg-exc. vg vg- vg- - exc. exc.

Removability (TM7) vg exc. exc. exc. fair Static coeff. of friction (TM 1) 0.5 0.6 0.6 0.6 - Powdering (TM 2) slight nil nil nil - Notes for TABLE V.A.

1. Run 6A is illustrative of the state of the art. It employs a floor polish polymer emulsion having 1.65% zinc ion crosslinker. This polish is prepared by mixing ingredients in the following recipe: Role Material Charge Vehicle BA/MMA/MAA copolymer emulsion 80 parts - 15% solids Wax Poly EM-40 - 15% solids 15 parts (Trademark, Cosden Oil and Chemical Co.) Alkali Solu- low molecular weight all acrylic 5 parts ble Resin resin - 15% solids Coalescent diethyleneglycol monomethylether 4 parts Plasticizer dibutyl phthalate 1.0 part Wetting aid Fluorad FC-128 - 1% solids 0.4 parts (Trademark, 3M Co.) Leveling aid tributoxyethyl phosphate 1.0 part - 100% active Defoamer SW-211 - 50% solids 0.01 parts (Trademark, Stauffer Wacker Silicone Co.) 2. Applicaton of the floor polishes is described in ASTM method D1436-64, Method B.

(ASTM - American Society for Testing Materials, Philadelphia, Pennsylvania). Test methods, identified in brackets, are listed below.

3. Run 6D is formulated with 1.25% zinc ion on emulsion polymer solids.

4. The recipe for the polish of Run 6E differs from that for 6B, C and D in the omission of wax and defoamer and the addition of 2 parts of coalescent, diethyleneglycol monomethylether.

Test Methods for TABLE V.A. - given in brackets in the table.

1. Slip: ASTM method 02047-72; panels conditioned at 250C. and 55% relative humidity.

2. Powdering: ASTM method D2048-69.

3. 60 gloss: ASTM method D1455-64 - Vinyl tile (Kentile No. R-44, Kentile Floors, Inc.) substituted for OTVA tile in this test.

4. Water resistance: ASTM method D1793-66, dynamic test procedure.

5. Rubber heel mark resistance: CSMA method 9-73 (Chemical Specialties Manufacturers Association, Washington, D.C.), test modified by rotating 15 minutes in each direction.

6. Detergent resistance is run on black vinyl asbestos tile using 1 of corridor traffic flow. To each of these sections a coat of polish to be tested is applied, with a string mop, at a rate of ca. 2,000 square feet/gallon. After allowing one hour for the initial polish to dry a second coat is applied in the same manner. The appearance of the polishes is rated initially and after one and two weeks of heavy traffic. The results of these observations and other tests, following the procedures used in obtaining the Table V.A. data, are in Table V.B.

TABLE V.B.

Run 6A 6B 6C 6D Initial: Gloss (visual) vg vg vg+ vg+ Leveling exc exc exc exc Recoatability exc vg-exc vg-exc exe One week traffic: Gloss (visual) g-vg vg vg vg+ Dirt pick-up resistance exc exc exc exc Black heel mark resistance vg-exc vg vg-exc vg Scuff resistance vg-exc vg+ vg-exc vg Two week traffic: Gloss (visual) good good good+ good+ Dirt pick-up resistance vg vg vg vg Black heel mark resistance vg vg- vg vg Scuff resistance g-vg g-vg g-vg g-vg The abbreviations used in Tables V.A and V.B are: exc = excellent; vg = very good; g = good; + = plus; - = minus except when used between abbreviations, where is means "to".

EXAMPLE 7 Lacquer and paint The polymer latex of Example 1 is formulated as follows: Run 7A: Adjust the 40% solids latex to pH 9 with 14% aqueous ammonia.

Run 7B: To 100 parts by weight of the latex, adjusted to pH 8.5 with 14% aqueous ammonia, is added a mixture of 9.7 parts of water and 15.3 parts of butoxyethanol.

Run 7C: The ingredients are mixed as follows: Parts by Weight Water 4.7 Tamol 165 (22% aqueous) 1.3 (Rohm and Haas Co.) Triton CF-10 (100%) 0.16 (Rohm and Haas Co.) Nopco NXZ (Diamond Shamrock) 0.05 Zopaque RCL-9 (TiO pigment) 18.8 (SCM Corp; Glidden-Durkee Division Grind on high speed disperser (4,000 ft/min.) for 15 min. and letdown under agitation with: Polymer latex 70.4 Water 1.8 Butoxyethanol 2.8 TOTAL 100.0 Key lacquer and paint properties are determined by following the usual paint industry procedures. Results of the determinations, on films made from the formulations by coating metal sheets, are in Table VI.

TABLE VI Property (l) Run 7A Run 7B Run 7C Dry to touch/tack free time (min. at 25 C and 40% R.H.) 19/21 Air dry hardness KHN, 1 hr. at 25 C and 40% R.H. 6.5 ca. 1 Ultimate hardness KHN 6.5 6.5 (baked 30 min.) Hot print (600 C/16 hr./ 4 pal) (baked 250 F/60') none none v.sl.trace Mandrel flexibility (1.5 mil/B-1000/1 hr. at 250 F) (1/2, 1/4, 1/8 inch blends) 0/1/1 //1 //7-8 Impact In-Lb (D/R) Alodine 1200S* 50/16(2) T-Bend T - T1 Water Soak (16 hr. at 1000F) moderate moderate moderate rust, no rust, mod rust, mod blisters blisters blisters Cleveland Condensing Cabinet sl. rust, (16 hours at 40 C) no blisters Chemical and stain resistance: Alcohol (16 hours) moderate moderate moderate attack attack attack Ink (30 minutes) no attack Mustard (30 minutes) no attack Lipstick (30 minutes) no attack Gasoline (30 min.) slight sl. to sl. to attack moderate moderate attack attack 1Results determined on 1.5 mil thick films baked 1 hour at 250 F. for film tests unless other conditions are noted.

2Air dried films have values of 2/1.

The data in Table VI.A indicate that the Run 7A latex dries very rapidly to full hardness, to form a film which is both hard and flexible, without the aid of a coalescent. Coalescent slows hardness development and has a deleterious effect on some resistance properties.

Baking is required to maximize certain properties. The resistance properties are good in general although water soak and alcohol resistance results are not as good as the other results.

Run 7C shows that the latex of Example 1 can be employed to form pigmented films with comparatively little coalescent. The physical properties of the film formed parallels that of the unpigmented film. Other tests on the film formed from Run 7C indicate: moderate rusting of a sample exposed five days in a humidity cabinet, signs of failure after three days in a salt spray cabinet and a change in gloss after 32 hours at 380C. in a Cleveland Condensing Cabinet as follows: Initial (200/600/800) gloss 54/77/88 Final (200/600/800) gloss 21/60/72 EXAMPLE 8 An internally plasticized polymer emulsion based on vinyl acetate A latex, with first stage, second stage and average Tg values of 25, 100 and 58 degrees Celcius respectively and Ip values of 17.5 and 12.1 for the first and second stages respectively, is prepared as follows: A. Equipment A five liter, five-necked flask is equipped with a condensor, an efficient agitator, a thermometer, addition funnels and heating, cooling and nitrogen sparging facilities.

B. Material charges Monomer Charge Kettle Raw Material 1 1A 2 Charge deionized water 166.3g 154 g 883.7g octylphenoxy poly (39) ethoxyethanol 3.4 5.1 1.7 Abex 18S (33%) (Alcolac Inc) 8.5 12.8 4.3 sodium dodecylbenzene sulfonate (23%) 6.8 10.2 3.4 ethyl acrylate 37.8 - 19.1 vinyl acetate 298.5 - 150.8 styrene - 517.5 maleic anhydride 4.1 - acrylic acid - 7.2 - Initiator: Fe++ (0.15% FeSO4.6H2O) 6.4 ml 0.26g ammonium persulfate (APS) in 8g water.

0.26g sodium sulfoxylate formaldehyde in 8g water.

Catalyst: 1.92g APS and 0.32g t-butyl hydroperoxide (tBHP) in 110g water.

Activator: 1.92g NaHSO3 in 110g water.

Chaser: 0.52 g tBHP in Sg water.

0.39g sodium sulfoxylate formaldehyde in Sg water.

C. Procedure The monomer charges and kettle charges are weighed separately and each is mixed to form an emulsion. The initiator mix is prepared and charged to the kettle. Efficient kettle stirring is maintained throughout the entire reaction sequence. The heat of reaction drives the kettle temperature from 22"C to a maximum (ca 60"C in ca. 7 min.). At the temperature maximum, monomer charge 1 addition is begun at a rate of 13 ml/min and addition of the catalyst solution and activator solution is begun as separate feed streams at a rate of 1 ml/min. The reaction temperature is maintained at ca. 620C throughout. When one half of the monomer charge 1 addition is completed (ca. 22 min) charge 1A is mixed with the remaining monomers of charge 1 and the addition continued. After about 45 minutes this monomer charge (1 + 1A) addition is completed and the kettle contents are maintained at 62"C for 15 minutes. Monomer charge 2 addition is then begun at a rate of 13 ml/min. This second addition is completed in about one hour and the kettle contents are maintained at 62"C for 10 minutes while the catalyst and activator charges are completed. The reaction mixture is held at 620 for an additional 15 minutes and then allowed to cool to 550C. The chaser is now charged rapidly, and the reaction mixture maintained at 50-600C for 15 minutes. The product is allowed to cool to room temperature and is packaged.

A sample of the product latex is neutralized to a pH of 8.5 with ammonia and is found to have a viscosity of 40 centipoise (20% solids Brookfield Synchro-Lectric Viscometer Model LV1 Spindle 1 at 60 rmp) and a MFT below 15"C. A film cast from this sample has a hardness of 17 KHN.

EXAMPLE 9 An internally plasticized polymer emulsion having an acid-containing last stage A latex, with first stage, second stage and average Tg values of 28, 112 and 65 degrees Celcius respectively and Ip values of 17.5 and 14.5 for the first and second stages respectively, is prepared using the same equipment as Example 8 and a similar procedure as follows: Material Charges Monomer Charge Kettle Raw Material 1 1A 2 Charge deionized water 154.0 g. 64 g. 154.0 g. 832 g. octylphenoxy poly (39) ethoxyethanol 5.1 5.1 Abex 26S )33%) (TM Alcolac Inc) 12.8 12.8 sodium dodecylbenzene sulfonate (23%) 10.3 10.3 ethyl acrylate 56.9 - Vinyl acetate 449.3 - styrene - 440.0 methacrylic acid 7.2 77.6 maleic anhydride - 4.1 - Initiator: Foe++ (0.15% FeSO4.6H2O) 6.4 ml 0.26 g ammonium persulfate (APS) in 8g water.

0.26g sodium sulfoxylate formaldehyde in 8g water.

Catalyst: 1.92g APS and 0.32g t-butyl hydiopernxide (tBHP) in 110g water.

Activator: 1.92g NaHSO3 in 110 g water.

Chaser: 0.52g tBHP in Sg water.

0.39g sodium sulfoxylate formaldehyde in Sg water.

Procedure 1. Charge kettle and adjust temperature to 20-220C; sparge with N2.

2. Prepare charge 1 and add 231 g. to kettle.

3. Add maleic anhydride in water and methacrylic acid (charge 1A) to remainder of monomer charge 1 and emulsify.

4. Add initiator; turn off N2 sparge.

5. Within several minutes of initiator addition, an exothermic reaction occurs, with the temperature peaking at 55-600C.

6. At the peak, start addition of monomer charge 1 and half of the catalyst and activator. Allow temperature to rise to 62"C and hold at 62"C throughout addition.

7. Charge 1 addition takes 40-45 minutes; when charge 1 and half of the catalyst and activator have been added, hold system at 62" for 20 minutes.

8. After 20 minutes, start addition of charge 2 and of catalyst and activator.

9. Addition of charge 2 takes about 55 minutes; addition of catalyst and activator takes an additional 10 minutes.

10. Hold for 30 minutes at 62"C.

11. After hold period, cool to 55" then add chaser and hold for 10 minutes before cooling to room temperature.

12. At room temperature, adjust pH to 4.5-5.0 with 10% NH4HCO3 aqueous solution.

A sample of the product latex has a viscosity of 19 centipoise (20% solids Brookfield Synchro-Lectric Viscometer model LV1 spindle 1 at 60 rpm) and a MFT of 37"C. A film cast from this sample has a hardness of 14 KHN; when 1% Zn++ (as ZN(NH3)4(HCO3)2) on polymer solids is admixed, as taught in US 3,328,325, the hardness of a film is 15.5 KHN.

EXAMPLE 10 Effect of hydrophilic monomer level Following the procedure of Example 9, the group of polymer emulsions are prepared having the compositions and properties given in Table VII. From these emulsions floor polishes are prepared by mixing ingredients in the following recipe: Role Material Charge Vehicle Polymer emulsion--15% solids 90.0 parts Wax AC 392--15% solids 10.0 parts (Trademark, Allied Chem. Corp.) Wetting aid Fluorad FC128--1% solids 0.5 parts (Trademark, 3M Co.) Leveling Tributoxyethyl phosphate-- 0.5 parts aid 100% active Coalescent Methyl Carbitol 4.0 Base Ammonia--10% aqueous to pH 7.5 Each floor polish is applied and tested by the procedure described in Example 6. The results are in Table VII where the superior polish properties of 10D and 10E are noted.

The AC-392 is prepared at 35% solids, as follows, and is diluted to 15% solids with water.

Formulation Parts by Weight A-C Polyethylene 392 40 Octylphenoxy poly(9)ethoxyethanol 10 KOH (90% Flake) 1.2 Sodium Meta Bisulfite 0.4 Water (1) to 50% Solids 50 Water (2) to 35% Solids 43 Charge the first five ingredients to produce the 50% concentrade into a stirred pressure reactor. Begin agitation and heat to 95"C (2030F) with the vent open. Close the vent and continue heating to 1500C (302"F) for 1/2 hour. Add water (43 parts) at 950C (203"F) to the reactor while the temperature is at 1500C (302 ) and then cool to room temperature with agitation as quickly as possible. Add 500 ppm formaldehyde preservative.

TABLE VII Run 10A 10B 10C 10D 10E Polymer emulsion Composition Vac/VOH//ST VAc/VOH/MAA//ST VAc/VOH/MAA//ST EA/VAc/VOH/MAA//ST EA/VAc/VOH/MAA//ST Weight ratio 49.5/0.5//50 46.75/2.0/1.25//50 45.5/2.5/2.0//50 5/39.1/3.4/2.5//50 10/32.2/2.8/5//50 Tg (1), C 30 33 34 31 30 Tg (2), C 100 100 100 100 100 Tg - average, C 57 59 60 57 56 MFT, C below 15 below 15 below 15 below 15 below 15 Ip (1) 16.2 16.5 16.7 17.4 17.9 Ip (2) 12.1 12.1 12.1 12.1 12.1 Ip(1) - Ip(2) 4.1 4.4 4.6 5.3 5.8 Polish properties Viscosity(cps)/pH 2.0/8.2 3.6/8.0 4.5/8.3 3.5/7.2 3.7/7.0 Visual gloss poor poor fair good good Leveling fair very good very good excellent excellent Visual haze severe severe moderate-severe slight-moderate slight EXAMPLE 11 Effect of acid variations Following the procedure of Example 9, a group of polymer emulsions is prepared as given in Table VIII. Floor polishes are prepared from these emulsions and are tested as described in Example 10. Results of these tests are in Table VIII wherein it is seen that Example 11A does not have pronounced weaknesses and that the copolymers utilizing maleic anhydride are not hazy.

TABLE VIII Run 11A 11B 11C 11D Polymer Emulsion Composition - - - all expressed as EA/VAc/VOH/MAn/MAA//ST - - Weight ration 5.5/37.8/5.6/0.4/0.7//50 5.5/40.3/3.5/0/0.7//50 5.5/39.7/4.4/0.4/0//50 5.5/42.7/1.8/0/0//50 Tg(1), C 27.7 26.4 26.2 25 Tg(2), C 100 100 100 100 Tg - average, C 60 59.2 59.1 58.3 MFT, C 23 24 24 - Ip (1) 17.5 17.0 17.1 16.5 Ip (2) 12.1 12.1 12.1 12.1 Ip(1) - Ip(2) 5.5 4.9 5.0 4.4 viscosity*(cps) 24 18 20 20 Polish properties Viscosity(cps)/pH 3.0/7.5 2.8/7.2 3.4/7.5 3.0/7.2 Visual haze nil slight(sl) nil sl-mod Leveling very good(vg) vg-excellent vg good *At 40% solids and a pH of 5.

TABLE VII (cont'd.) Run 11A 11B 11C 11D Polish Properties Visual gloss good good-vg good fair Detergent resistance fair-good vg-excellent vg-excellent excellent Removability fair poor poor poor EXAMPLE 12 First stagellast stage ratio variations Polymer emulsions are prepared, by the procedure of Example 9, having a range of first stage to last stage weight ratios as shown in Table IX. The composition of the first stage of each is EA/VAc/VOH/MAn/MAA = 11/75.6/11.2/0.8/1.4 and has a Tg(1) of 27.7"C and an Ip(1) of 17.5. The last stage of each is polystyrene having a Tg(2) of 100"C and an Ip(2) of 12.1. Thus the Ip(1) - Ip(2) value of each latex polymer is 5.4. Floor polishes are prepared from these emulsions and tested as described in Examples 6 and 10; test results are in Table IX.

TABLE IX Run 12A 12B 12C 12D 12E Polymer emulsion First//last stage 70//30 60//40 50//50 40//60 30/M0 (by weight) MFT "C 19 21 23 24 80 viscosity*(cps) 22 21 24 20 17 Tg-average "C 46.3 53.0 60.0 67.3 75.0 Polish properties Visual haze nil nil nil slight moderate Visual gloss good good+ good good fair-gd Leveling vg vg+ vg vg vg Detergent resistance fair fair fair good vg Removability fair fair fair poor poor Heel mark resistance good good good good good Overall wear good good good+ good good resistance *At 40% solids and a pH of 5.

EXAMPLE 13 Maleic anhydride/methacrylic acid levels Polymer emulsions are prepared, by the procedure of Example 9, with a range of maleic anhydride and methacrylic acid levels in the first stage as shown in Table X. Each last stage is polystyrene and represents 50 weight percent of the polymer. The polymer of Run 13A is the same as that of Run 11A. The compositional differences being comparatively small the Tg values and the Ip values for the other three copolymers are but little different from those for Run 13A. Polishes prepared from these emulsions are tested as in Examples 6 and 10 to give the performance results recorded in Table X. A wide range of removability and of detergent resistance is achieved; remarkable in view of the vinyl acetate content of the polymer.

TABLE X Run 13A 13B 13C 13D Polymer emulsion Composition - - - - first stage is EA/VAc/VOH/MAn/MAA - - - Weight ration 5.5/37.8/5.6/0.4/0.7 5.5/37.2/6.0/0.4/0.3 5.3/37.0/6.2/0.2/0.7 5.5/36.9/6.5/0.8/0.7 MFT, C 23 23 26 24 viscosity*(cps) 24 22 18 40 Polish properties Visual haze nil nil nil nil Visual gloss good good good fair-good Leveling very good)vg) vg vg good-vg Detergent resistance fair-good vg-excellent fair-good poor Removability fair poor fair-good excellent *At 40% solids and a pH of 5.

EXAMPLE 14 Acid in the last stage The polish of Run 14A is prepared from the same polymer latex as that of Run 11A. A film of this polymer is found to have a Knoop Hardness Number of 10. The polish of Run 14B is prepared from the polymer latex of Example 9 and is crosslinked with 1% On++, on polymer solids, added as Zn(NH3)4(HCO3)2. The polish of Run 14C is prepared from a sample of the polymer latex of Run 6A, Table V. A, Note 1; a film of this polymer has a KHN of 13. These polishes are tested as in Examples 6 and 10; the results are in Table XI.

Note the balance of removability and detergent resistance obtained while maintaining a high level of performance in other properties.

TABLE X1 Run 14A 14B 14C Polish properties Leveling vg-exc. vg vg-exc.

Visual gloss* one coat g-vg/g g-vg/g-vg. vg/g-vg two coats vg-exc/vg+ exc/vg-exc. vg-exc/exc.

Visual haze nil nil nil Detergent resistance fair vg vg-exc.

Removability good vg-exc. exc.

*Recorded as results on vinyl tile/on OTVA tile see Test Method 3 of Table V. A. Example 6.

Our copending application number 23561/80 (Serial No. 1597612) divided herefrom claims a latex of internally plasticized addition polymer particles comprising (A) early stage polymer and (B) later stage polymer formed by polymerisation in the presence of an emulsion of polymer particles comprising polymer (A), polymers (A) and (B) each making up at least 10% by weight of the polymer in the particles, polymer (A) containing at least 10% by weight hydrophilic mers of which at least 10% by weight are nonionic and polymer (B) being less hydrophilic than polymer (A) and wherein the polymer particles have a Tg above 15"C and the latex has a viscosity below 5000 centipoises when measured at 20% by weight solids over the pH range 4 to 10 and has a minimum film temperature more than 5"C below the calculated Tg of the polymer particles and attention is directed to the claims thereof under Section 9 of the Patents Act 1949.

Claims (24)

WHAT WE CLAIM IS:

1. A latex of internally plasticized addition polymer particles comprising (A) early stage polymer and (B) later stage polymer formed by polymerisation in the presence of an emulsion of polymer particles comprising polymer (A), polymers (A) and (B) each making up at least 10% by weight of the polymer in the particles, polymer (A) containing at least 10% by weight hydrophilic mers of which at least 10% by weight are nonionic and polymer (B) being less hydrophilic than polymer (A) wherein polymer B is of higher Tg than polymer (A) and, of the hydrophilic units in polymer (A), at least 0.5% are ionic and the interpenetration parameter of polymer (A) is greater than that of polymer B by at most eight units, polymer (A) comprising units of monoethylenically unsatured monomer.

2. A latex as claimed in Claim 1 wherein the polymers (A) and (B) each make up at least 20% by weight of the latex polymer.

3. A latex as claimed in Claim 2 containing no stages other than polymers (A) and (B).

4. A latex as claimed in any preceding Claim wherein the polymer is such that a film formed therefrom has a Knoop Hardness Number of at least 5.

5. A latex as claimed in any preceding Claim wherein, of the hydrophilic units, 0.5 to 90% by weight are acid or basic units.

6. A latex as claimed in any preceding Claim wherein the latex polymer is such that a film formed therefrom has a Knoop Hardness Number of at least 8 and polymer (A) contains ionic units comprising units containing carboxyl groups.

7. A latex as claimed in Claim 6 in which the and SQ to 90% of the hydrophilic mers are mers of hydroxyalkyl ester of a,ss-unsaturated acid.

8. A latex as claimed in Claim 7 in which the mers in the addition polymer comprise mers of acrylate, methacrylate, vinyl ester, and/or vinyl aromatic monomer.

9. A latex as claimed in Claim 4 in which polymer (A) comprises 10% to 70% by weight hydrophilic mers and polymer (B) has a calculated Tg at least 100C, above the calculated Tg of polymer (A); polymers (A) and (B) each being at least 30% by weight of the latex polymer.

10. A latex as claimed in Claim 9 in which a film formed from the latex polymer has a Knoop Hardness Number of at least 5, the calculated Tg of polymer (A) is at most 400C, and polymer (B) is harder than polymer (A).

11. A latex as claimed in Claim 10 wherein the Knoop Hardness Number of a film formed from the latex polymer is at least 8, the Tg of polymer (A) is at most 50C and the Tg of polymer (B) is at least 750C.

12. A latex as claimed in Claim 11 in which polymers (A) and (B) each make up at least 40% by weight of the latex polymer, the Tg of polymer (A) is at most -- 10"C and the Tg of polymer (B) is at least 1000C.

13. A latex as claimed in Claim 12 in which, of the hydrophilic mers, at least 0.5% by weight are carboxylic acid mers.

14. A latex as claimed in Claim 13 in which the latex polymer comprises units of one or more of the following monomers: acrylate esters, methacrylate esters, vinyl esters and vinyl aromatic monomers.

15. A latex as claimed in Claim 14 in which the units of polymer (A) comprise by weight, 65 to 85% (C1-C4)-alkyl acrylate, (C,-C4)-alkyl methacrylate and/or styrene units; 5 to 10% acrylic acid, methacrylic acid and/or itaconic acid units; and 10 to 25% hydroxy-(C,-C4)-alkyl methacrylate and/or hydroxy (C1-C4)-alkyl acrylate units, and the units of polymer (B) comprise methyl methacrylate and/or styrene units.

16. A latex as claimed in Claim 14 in which the units of polymer (A) comprise, by weight, 50 to 85% vinyl acetate units; 1 to 10% acrylic, methacrylic, itaconic and/or maleic acid units; and 8 to 25% vinyl alcohol units; and the units of polymer (B) comprise 100 to 70% methyl methacrylate and/or styrene units and 0 to 30% acidic units, by weight.

17. A latex as claimed in Claim 16 in which the units of polymer (A) contain, by weight, 1 to 4% acid units, of which 0.2 to 2%, by weight of polymer (A), are units of maleic acid, 0 to 20% (C1-C4)-alkyl acrylate, 65-80% vinyl acetate and 10 to 20% vinyl alcohol units; and the units of polymer (B) comprise 10 to 20% acid units, by weight.

18. A latex as claimed in any of Claims 1 to 8 wherein the polymers (A) and (B) each make up at least 30% by weight of the latex polymer.

19. A latex as claimed in any preceding Claim wherein the interpenetration parameter of polymer (A) is greater than that of polymer (B) by 1 to 6 units.

20. An internally plasticised polymer as defined in any preceding Claim in finely divided or other physical form.

21. An aqueous polish composition capable of forming a coating having a Knoop Hardness Number of at least 0.5 and containing: (a) 10 to 100 parts by weight of polymer as claimed in Claim 20.

(b) 0 to 90 parts by weight of alkali-soluble resin in an amount of at most 90% by weight of the weight of (a), (c) 0 to 90 parts by weight of wax, (d) wetting, emulsifying and dispersing agents in an amount of 0.5 to 20% by weight of the total of (a), (b) and (c), (e) polyvalent metal compound in an amount of 0 to 50% by weight of (a), (f) water to make total solids of 0.5 to 45%.

22. A processs of polishing a hard surface comprising coating the surface with a composition as claimed in Claim 21 and drying the coating or allowing the coating to dry.

23. A polished hard surface prepared by a process as claimed in Claim 22.

24. A process for producing alatex of internally plasticized addition polymer particles comprising: (a) forming by polymerisation an emulsion of polymer particles comprising polymer (A) as defined in any one of Claims 1 to 19 and (b) forming by polymerisation, in the presence of that emulsion, polymer (B) as defined in any one of Claims 1 to 19 as a later stage polymer on the particles comprising polymer (A); the amount of monomer for each of polymers (A) and (B) being so chosen that each makes up at least 10% by weight of the polymer in the particles.