NO155667B - LATEX OF INTERNAL SOFTENED ADDITION POLYMER PARTICLES AND USE OF IT IN A WATER POLISHING MATERIAL. - Google Patents

Description

The present invention relates to a latex of internally softened addition polymer particles, for use in coating materials, adhesives and binders, containing (A) an early stage polymer and (B) a later stage polymer formed by polymerization in the presence of an emulsion of polymer particles containing the polymer (A), wherein each of the polymers (A) and (B) constitutes at least 10% by weight of the amount of polymer in the particles.

The invention also relates to the use of the latex in an aqueous polishing material capable of forming a coating having a Knoop hardness number of at least 0.5.

It is necessary that the polymer in a film-forming latex be soft enough to form a film of good integrity, yet hard enough that the film has high tenacity, low dirt absorption and a number of other related properties dependent on the particular application. It is known that if the glass transition temperature (T ) for a polymer is below the temperature at which the film is formed, a film with good integrity, i.e. which is not "cheesy", is obtained by drying a layer of the latex. But the great softness of the latex particles, which leads to good film formation, means that the produced film tends to be soft or sticky as opposed to strong, hard, wear-resistant and tough. The usual way out of this dilemma is to add to a relatively hard polymer film forming aids which are volatile enough to leave the film after film formation has taken place. With greater consideration for air pollution, it is preferred to omit the volatile film-forming aids. Omission of the film-forming aids also represents a cost saving.

Another solution to producing polymers with a high glass transition temperature and a low minimum film dust formation temperature is to embed a high proportion of hydrophilic monomers (eg those with hydroxyl, amine or carboxyl functions) in the polymer. This introduces water swelling into the latex particles, which softens the particles in the latex. But in normal polymer concentrations, swelling is accompanied by very high viscosities, especially if the pH during storage or use is such that the carboxyl groups or amine groups are neutralized in whole or in part. Another disadvantage is the water sensitivity of the finished film and its sensitivity to acidic or basic solutions. Polymers of hydrophilic monomers produced by solution polymerization and applied in solution are known from US patent 3,935,368, for use in coating vinyl chloride floor coverings.

Another solution to the problem of producing a hard coating in the form of a film with good integrity is known from US Patent 3,949,107, from which it is known to apply a polishing agent containing an aqueous dispersion of a resin with a T of 30 -80°C on a floor, whereby either the polishing agent or the floor has been preheated to a temperature above the T of the resin. The latex according to the present invention is characterized in that the polymer (A) contains at least 10% by weight of units formed by hydrophilic monomer units of which at least 10% by weight are non-ionic, and the polymer (B) is less hydrophilic than the polymer (A), and that either (i) the polymer (B) has a higher Tg than the polymer (A) and at least 0.5% of the hydrophilic

units in the polymer (A) are ionic and the interpenetration parameter

to the polymer (A) is at most 8 units greater than for the polymer (B), as the polymer (A) contains units formed from monoethylenically unsaturated monomers, or (ii) the polymer particles have a T of more than 15°C while the latex has a viscosity of less 5000 cP measured at 20% dry matter content over a pH range of 4 to 10 and has a minimum film formation temperature that is more than 5°C lower than the calculated T of the polymer particles.

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It is produced by polymerizing usually relatively hard (high T g ), relatively hydrophobic polymers on previously prepared, usually relatively soft (low T g ) # copolymer latex particles with hydrophilic functionality, to form latex particles which, for the sake of convenience, will be named latex particles of internal plasticized polymer particles. This produces a latex that has a low viscosity, but still forms a film at a temperature that is low compared to the calculated T of the polymer in the particles. The viscosity and minimum film formation temperature (MFT) are measured under conditions of normal use, i.e. neutral to high pH for acid-containing polymers and neutral to low pH for base-containing polymers. Preferably, the latex is produced by producing a water-swellable addition polymer under normal emulsion polymerization conditions. This water-swellable polymer may also be water-soluble at a suitable pH and is usually soluble at high pH when it contains acidic groups or at low pH when it contains basic groups. Under the polymerization conditions, however, it does not dissolve in the aqueous medium, but is retained as a latex. A second polymer is then formed by polymerization in the presence of the latex and may interact with and eventually penetrate the first. This is achieved by adding to the first latex a monomer which will form a polymer which is less water sensitive, i.e. less hydrophilic, and usually harder than the monomer in the first latex, and then carrying out polymerisation. The second monomer system is chosen so that it has sufficient compatibility with the first polymer to swell it. By interacting with the first polymer, the second polymer causes limitation of the water swellability of the first polymer. The product can thus be regarded as a hydro-plastic first polymer, which is made more hydrophobic and usually harder by the second polymer, or alternatively as a usually hard, hydrophobic second polymer which is made more hydro-plastic, and usually softer, by means of the first polymer. The internal plasticized polymer that is formed has properties that are different from the properties of one of the component polymers, nor are the properties simply the sum or average of the component properties. If e.g. the first polymer is completely soluble at high pH, it has been found that after the internal softened polymer is formed, this first polymer portion is no longer soluble even at very high pH values.

A highly water-swellable component polymer would be expected to produce a highly viscous latex, although the minimum film formation temperature was low compared to T . According to the present invention, the modification of the properties of the water-swellable polymer from the first stage with the polymer from the second stage results in relatively low viscosity for the latex.

The preferred latexes according to the invention comprise at least the unit of one of the monomer units acrylate, methacrylate, vinyl ester and vinyl aromatic. Preferred hydrophilic, ionic monomer units (if present) in the polymers are monomer units with carboxylic acid groups. Preferred hydrophilic nonionic monomer units in the polymer are monomer units of hydroxyalkyl esters of carboxylic acids or vinyl alcohol monomer units.

The internal softened polymer in the latex according to the invention can be produced by polymerization of a first ethylenically unsaturated monomer system containing a relatively hydrophilic monomer, usually by emulsion polymerization, and then, in the presence of the resulting latex, emulsion polymerization of a second batch of the ethylenic unsaturated monomer, as this rate will by itself form a

harder and more hydrophobic polymer than the polymer from the first batch.

The polymer formed in the first batch (stage) is retained as an emulsion even if it is water-swellable or water-soluble. By "water-soluble" here is meant soluble in water when the water's pH is regulated by the addition of acid or base so that the polymer is completely or partially neutralized. By "water swellable" it is meant here that the polymer absorbs water or can be made to absorb water by such pH regulation. It is preferred that the pH range considered to be useful is from 4 to 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 dry polymer, is preferably greater than two , preferably greater than six.

It is believed that the mode of action of the hydrophilic monomer, which is present in amounts of from approx. 10 to 100 parts per 100 parts of the monomer from the first step is understood. It appears that the hydrophilic monomer when polymerized can act so that it binds any amount of water introduced into the material, e.g. by hydration. Any monomer which can be polymerized in the mixture and which is hydrophilic enough to bind water effectively is therefore useful. Suitable hydrophilic monomers are, for example: acrylonitrile, methacrylonitrile, hydroxy-substituted alkyl and aryl acrylates and methacrylates, polyether acrylates and methacrylates, alkyl phosphato-alkyl acrylates and methacrylates, alkylphosphono-alkyl acrylates and methacrylates, acrylic acid, methacrylic acid, maleic acid , maleic anhydride, N-vinylpyrrolidone, alkyl and substituted alkyl amides of acrylic acid, methacrylic acid, maleic acid (mono- and diamides), fumaric acid (mono- and diamides), itaconic acid (mono- and diamides), acrylamide, methacrylamide, also other half-acid forms of the above mentioned dibasic acids, such as half esters, amino monomers such as amino substituted alkyl acrylates and methacrylates, vinyl pyridines and amino alkyl vinyl ethers, as well as ureido monomers including those with cyclic ureido groups. The hydrophilic monomer can also be introduced in another way into the monomer mixture, such as e.g. when the hydrophilic monomer units are formed in situ or afterwards. E.g. a monomer which is not itself hydrophilic, but which is changed during processing or in a subsequent step, e.g. by hydrolysis, to achieve hydrophilicity. Anhydride- and epoxide-containing monomers are examples.

Preferred suitable hydrophilic monomers are acrylic compounds, especially the amides and hydroxyalkyl esters of methacrylic and acrylic acids, amides and hydroxyalkyl esters of other acids are also preferred, but less so than the corresponding methacrylates and acrylates which are also easier to polymerize. Monomers containing carboxylic acid groups are also preferred, particularly acrylic acid, methacrylic acid and itaconic acid. Other preferred groups of hydrophilic monomers are represented by particular examples of potential hydrophilic monomers which produce the relevant hydrophilic monomer units in the polymer upon 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 monomer units in the polymer. The preferred monomer among these is vinyl acetate.

Polymerized together with the hydrophilic monomer in the first step can be another monomer which is carefully chosen so that other desirable properties are achieved in the finished polymer. Any polyethylene unsaturated monomer is, if it exists, of the type where the various ethylenic groups, i.e. the addition-polymerizable unsaturated groups, participate in the polymerization at approximately the same rate. Preferably, no crosslinking or graft polymer forming polyethylene unsaturated monomer is present in the first stage monomer system. The term graft-forming monomer is defined in column 4, line 66, to column 5, line 20, in US Patent 3,796,771. Preferably, the first step contains a monoethylenically unsaturated monomer.

It is desirable that the first stage polymer is softer than the second stage polymer. The hardness in the first step can be regulated by the choice of the hydrophilic monomer and of any copolymer used together with it. Suitable comonomers which form soft polymers in the presence of free radical catalysts are primary and secondary alkyl acrylates with alkyl substituents down to 18 or even more, carbon atoms, primary or secondary alkyl methacrylates with alkyl substituents of at least 5, e.g. 18 or more, carbon atoms, or other ethylenically unsaturated compounds that are polymerizable by means of free radical catalysts to form soft, solid polymers, including vinyl esters of saturated monocarboxylic acids with more than 2 carbon atoms. The preferred ethylenically unsaturated compounds are the specified acrylates and methacrylates, and among these the most practical esters are those with alkyl groups of at most 8 carbon atoms.

The preferred monomers which by themselves give soft polymers can be anqis with the formula

where R' is hydrogen or the methyl group and Rx is, when R<1> is methyl,

a primary or secondary alkyl group of 5-18 carbon atoms, or, when R' is hydrogen, an alkyl group of not more than 18 carbon atoms, preferably of 1-8 carbon atoms, preferably of 1-4 carbon atoms.

Typical compounds according to the definition given above 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-trimethylhexyl acrylate, 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, as well as those with substituted alkyl groups such as butoxyethyl acrylate or methacrylate.

As polymerizable, ethylenically unsaturated monomers such as av

themselves form hard polymers, alkyl methacrylates can be used which have alkyl groups with no more than 4 carbon atoms, i.e. tert-amyl methacrylate, tert-butyl or tert-amyl acrylate, cyclohexyl, benzyl or isobornyl acrylate or methacrylate, acrylonitrile or methacrylonitrile. These constitute a preferred group of the monomers which form hard polymers by themselves. Styrene, vinyl chloride, chlorostyrene, vinyl acetate and p-methylstyrene, which also form hard polymers, can be used.

Preferred monomers which by themselves form hard polymers can be indicated by the formula

where R' is hydrogen or the methyl group, and where X is one of the groups

-CN, phenyl, methylphenyl, ester-forming groups, -COOR", where R"

is cyclohexyl, or, when R' is hydrogen, a tert-alkyl group of 4 or 5 carbon atoms, or, when R' is methyl, an alkyl group of from 1 to 4 carbon atoms. Some typical examples of these have already been indicated. 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 can also be used as monomers to add hardness to the copolymer.

These monomers may contain other functional groups

for other purposes, such as to effect cross-linking in the polymer during curing or increased 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-alkylamido and alkylolamido, epoxy, hydroxy, amino including oxazolidinyl and oxazinyl as well as ureido. In most cases, these functional groups are also hydrophilic groups, and many of the monomers are hydrophilic.

Another group of monomers which can be used according to the invention and which by polymerisation themselves give soft polymers are butadiene, chloroprene, isobutene and isoprene. These are monomers which are usually used in rubber latexes together with monomers which produce hard polymers and which are also applicable according to the present invention, such as acrylonitrile, styrene and other hard monomers as indicated above. The olefin monomers, especially 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 which are useful according to the invention are polymers of esters of vinyl alcohol, such as vinyl formate, vinyl acetate, vinyl propionate, vinyl butyrate and vinyl versitate. Polyvinyl acetate and copolymers of vinyl acetate with one or more of the following monomers are preferred: vinyl chloride, vinylidene chloride, styrene, vinyl toluene, acrylonitrile, methacrylonitrile, acrylate or methacrylate esters as well as the above-mentioned monomers with functional groups. In the polymers which are largely vinyl ester polymers, it is preferred that

the first four stage polymers contain at least 30 wt.

percent vinyl acetate units, while at least 80% is particularly preferred. Before polymerization of vinyl alcohol esters is complete, some hydrolysis to vinyl alcohol monomer units usually takes place or is carried out deliberately. The vinyl alcohol monomer units thus formed are hydrophilic and are considered here to be derived from vinyl alcohol monomers. The degree of hydrolysis can be controlled by regulating the time, temperature and pH of the reaction, to produce the desired amount of vinyl alcohol in the product. Longer periods of time, higher temperatures, very acidic or very alkaline conditions all serve to increase the degree of hydrolysis and thus the amount of vinyl alcohol in the final product. The degree of hydrolysis can be determined by acid-base titration in water or in suitable solvent systems.

A preferred latex according to the invention is a latex

where the monomer units in the first step contain 65-85% by weight (C-^C^)-alkyl acrylate, (C^-C^j)-alkyl methacrylate and/or styrene, 5-10% acrylic acid, methacrylic acid and/or itaconic acid and 10- 25% hydroxy-(C1~C4)-alkyl acrylate and/or hydroxy-(C1~C4)-alkyl methacrylate, and the monomer units in the polymer in the last step contain methyl methacrylate and/or styrene. Another preferred material is a material where the monomer units in the first step contain 50-85% by weight vinyl acetate (for subsequent hydrolysis), 1-10% acrylic acid, methacrylic acid, itaconic acid and/or maleic acid (producible from maleic anhydride), as well as 8-25% vinyl alcohol , and the monomer units in the later stage contain 70-100% by weight methyl methacrylate and/or styrene and 0-30% by weight, preferably 10-20% by weight, acid-containing monomer units, such as acrylic, methacrylic and/or itaconic acid monomer units. It is desirable that the acid monomer units in the first stage contain up to 5%, calculated by the weight of the first stage polymer, of maleic anhydride or maleic acid, 0.2-2% being preferred. As used herein, by "monomer unit" is meant the addition polymer which is derived from the specified monomer by addition to the double bond.

In general, the preferred hydrophilic monomers used according to the present invention are monomers with a solubility of at least 6 g per 100 g of water, as those with a solubility of at least 20 g per 100 g of water is preferred, while those in which at least 50 g of the monomer is soluble in 100 g of water are most preferred. The first stage polymer contains at least 10% hydrophilic monomer units, with 10-70% being preferred, at least 25% being more preferred and the range 25-35% being most preferred. Of the hydrophilic monomer content, it is desirable to have at least 0.5% of ionic, hydrophilic monomer units in the form of acidic monomer units, such as monomer units containing carboxyl groups, or basic groups such as amino groups, in either unneutralized or neutralized form. ig At least 10% of the hydrophilic monomer units are non-ionic, i.e. non-ionizable, such as hydroxyethyl acrylate or -methacrylate, which can be formed in situ, such as non-ionic monomer units from hydroxyethyl ester and vinyl alcohol monomer units.

The last stage polymer is more hydrophobic and preferably harder than the first stage polymer. Hydrophobic means that the last-stage polymer alone is less water-swellable than the first-stage polymer alone. Harder means that the modules in the last-stage polymer are greater than in the first-stage polymer, whereby measurements are carried out on polymer samples immersed in water. It is preferred that the last stage monomer is monoethylenically unsaturated.

The inner softened polymer is produced

appropriate according to known emulsion polymerization processes where a multi-step serial technique is used. But they can also be produced by a continuous polymerization where the monomer material that is supplied is continuously changed, either stepwise or continuously, during the polymerization. In such polymerization, any sudden or discontinuous change in the composition of the monomer feed can be regarded as a step termination. 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 can be considered to represent one stage and the second half to represent a second stage. In the simplest form of latex according to the invention, the hydrophilic monomer is formed in a first step, and the more hydrophobic polymer is formed in a second step. Any of the component polymers can themselves also be serially polymerized, i.e. consist of several steps. The monomers in the first step, together with initiators, soaps or emulsifiers, polymerization ion modifiers or chain transfer agents, are mixed into the initial polymerization mixture and polymerized,

e.g. by means of heating, mixing, cooling as required,

in a well-known and completely conventional manner until the monomers are largely used up. The monomers in the second and, in turn, in any subsequent stages are then added together with the suitable other materials so that the desired polymerization in each stage takes place in series until the monomers are mostly used up. It is preferred that in each step after the first, the amounts of initiator and soap, if such are used, are kept at such a level that polymerization takes place on existing particles and that no significant number of new particles or "seeds" are formed

in the emulsion.

When polymerisations are carried out in multi-stage serial processes, there may further be stages which in composition and proportion are a combination of two distinct stages and which produce polymers which have properties that lie between these. The hydrophilic first stage is at least 10%, preferably 20-80%, more preferably 30-70% and most preferably 40-60% of the total polymer. There may of course be other steps before, between or after the two that are of main interest. These second steps always constitute smaller weight shares of the whole polymer than both main component polymers when they cannot be considered to be part of one or the other of the main component polymers due to their composition. It is preferred that the polymer according to the invention is a two-stage polymer. Those skilled in the art will typically prepare few internal plasticized polymer latex samples with differing weight ratios between the first and second stages and select the sample that has the best properties for a given application. An equal weight ratio is the usual starting point for these tests, which usually consist of a higher and a lower ratio with the spread of the ratios selected based on consideration of the desired end properties, e.g. hardness, minimum film formation temperature, latex viscosity and tack-free time.

The polymer is preferably produced by emulsion copolymerization of the monomers in the correct proportions. Conventional emulsion polymerization techniques are known from US Patents 2,754,280 and 2,795,564. The monomers can thus be emulsified with anionic, cationic or non-ionic dispersants, of which 0.5-10% is usually used, calculated on the weight of total monomer. When a water-soluble monomer is used, the dispersant serves to emulsify any other monomer. A polymerization initiator of the free radical type, such as ammonium or potassium persulfate, can be used alone or together with an accelerator, such as potassium metabisulfite or sodium thiosulfate. The initiator and accelerator, usually referred to as catalyst, may be used in amounts of ^-2% each, based on the weight of the monomer to be copolymerized. The polymerization temperature can be from room temperature to 90°C or more as appropriate.

Examples of emulsifiers or saps which are suitable for the polymerization according to the present invention are alkali metal and ammonium salts of alkyl, aryl, alkaryl and aralkyl sulphonates, sulphates and polyether sulphates, the corresponding phosphates and phosphonates as well as ethoxylated fatty acids, esters , alcohols, amines, amides and alkylphenols.

Chain transfer agents, such as mercaptans, polymer captans and polyhalogen compounds, are often desirable in the polymerization mixture.

Another way to describe and define the first- and second-stage monomers according to the invention is to use the solubility parameter concept. "Polymer Handbook", 2nd edition, J. Brandrup and E. H. Immergut, (John Wiley and Sons, Nev? York 1975) section IV, part 15 entitled "solubility parameter values" by H. Burrell, pages IV-337-IV-359 , defines solubility parameter, describes how it is determined or calculated, contains tables of solubility parameters and provides further references to scientific literature on solubility parameters. The solubility parameter is the square root of the cohesion energy density, which in turn is the numerical value of the potential energy in 1 cm 3 of the material. The potential energy arises from the van der Walls forces of attraction between the molecules in a liquid or in a solid. Burrell describes different ways to calculate the solubility parameters from experimentally determined physical constants and two ways to calculate them from a molecule's structural formula. The structural formula methods are usually used when data for the calculation based on physical constants is not available or is considered to be particularly unreliable. When calculating from the structural formula, tables for molar group attraction constants such as those indicated on page IV-339 of the "Polymer Handbook" are used. Small's table is preferred.

The concept of solubility parameter can be considered to be an extension of the old rule "like dissolves like" known in the early days of chemistry. A non-crosslinked polymer will usually dissolve in a solvent with a similar solubility parameter, and a crosslinked polymer will usually be swollen by a solvent with a similar solubility parameter. Conversely, solvents with solubility parameters far from the polymers' solubility parameters will neither dissolve nor swell the polymer. As indicated by Burrell, the solubility parameters of polymers can be determined

among other things by measuring the swelling of the polymer in a variety of solvents. The solubility parameter for polymers can also be estimated by calculation from the above-mentioned molar group attraction constants. In the usual situation, it appears that the solvents with a range of solubility parameters around the solubility parameter of the polymer will dissolve the uncrosslinked polymer. Those skilled in the art have added the further refinement of classifying solvents as solvents with weak, moderate and strong hydrogen bonds. It has been shown that the area

of solubility parameters to dissolve a given uncrosslinked polymer differs from one class to the next although considerable overlap has been observed. Burrell's Table 4 beginning on page IV-349 indicates ranges of solubility parameters for solvents with weak, moderate and strong hydrogen bonds, for dissolving a large number of polymers. In table 5, which begins at

page IV-3 54, solubility parameters are given for a number of polymers determined by calculation and according to other methods.

For the production of the inner softened polymer for the latex according to the invention, the first-stage polymer and the monomers in the later stage are selected so that they interact to an appropriate degree. There are both upper and lower limits to the degree of desirable compatibility between the first stage polymer and the monomers in the subsequent stages (second, later or final stage as indicated above). It has been shown that the appropriate degree of compatibility can be expressed numerically by means of a property based on the solubility parameter and here referred to as the interpenetration parameter (lp). The interpenetration parameter can be regarded as a solubility parameter which is regulated to place solvents with strong, moderate and weak hydrogen bonds on the same scale. For a given molecule, the interpenetration parameter is defined as the solubility parameter plus a hydrogen bond growth value given below. Solubility parameters for various molecules, including a number of monomers, are given in Tables 1 and 2 of Burrell, beginning on page IV-341. These tables also indicate the hydrogen bonding group for the given molecule. The growth values, a new doctrine according to this invention,

is 17.2 for molecules with strong hydrogen bonds, 7.2 for molecules with moderate hydrogen bonds and 2.8 for molecules with weak hydrogen bonds.

The table below contains a list of monomers and values for their solubility parameter, interpenetration parameter and water solubility. The hydrogen bonding class of the polymer is also indicated. The solubility parameter values and hydrogen bond class for most of these monomers are those given in Table 1 of Burrell. Vinyl alcohol is a special case because of this monomer, which is known to be unstable. Polymers containing monomer units corresponding to vinyl alcohol can be prepared by hydrolysis of a polymer containing the corresponding vinyl ester monomer unit, such as vinyl acetate. The solubility parameter for this hypothetical monomer is calculated according to the method of Small as indicated above. Values for other monomers not listed in Burrell's table are determined or calculated according to the teachings given by Burrell. Dimensions for the solubility parameters given in the table are the usual ones, the square root of calories per cm <3>. The interpenetration parameter has the same dimensions. Water solubility is indicated in grams of monomer per 100 g of water at 25°C. The hydrogen bond class strong, moderate or weak is derived by using the method of C. M. Hansen, Journal of Paint Technology, volume 39, pages 104-117 and 505-514 (1967).

For a latex; according to the present invention

the interpenetration parameter in the first stage will be greater than in the second stage, preferably at least one unit (calorie per cm 3 ) greater. But the interpenetration parameter for the first step must not be too much larger than that for the second step. The difference is not more than 8, and it is desirable that it is not more than 6, preferably from 1 to 6 units. When the first-stage polymer contains 65 percent by weight or more of a C₁-C₂-alkyl acrylate, C₂-C₂-alkyl methacrylate, styrene or a mixture thereof, it is desirable that the first-stage lp is no more than 6 units greater than that of the later stages , with a difference of from 1 to 4 units being preferred and from 2 to 3 units being most preferred. When the first-stage polymer contains 50 percent by weight or more of vinyl acetate, it is desirable that the first-stage lp is from 1 to 8 units greater than for the later stage, with a difference of

from 2 to 6 units is preferred and from 4 to 5 units is most preferred. It should be understood in this context that the second step or the later step may contain some hydrophilic monomers and still be in accordance with these rules for the difference between the interpenetration parameter for the first step and for the second step.

As indicated above, the first step according to a preferred embodiment contains acidic, preferably carboxyl, monomer units as well as the other hydrophilic monomer units. The carboxyl monomer units preferably come from the monomers acrylic acid, methacrylic acid or itaconic acid. The other hydrophilic monomer units are preferably hydroxy-C 1 -C 4 -alkyl methacrylate, hydroxy-C 1 -C 4 -alkyl acrylate or vinyl alcohol units.

The viscosity of the produced polymer emulsion can be measured

in any known manner, preferably with the Brookfield Synchro-Letric viscometer model LV 1, whereby when selecting the spindle and speed combinations are preferably selected which will result in a reading in a middle range. Measurements, at 20°C, are carried out at pH values in the range from 3 to 10 of emulsions that have been regulated with water to a solids content of 20%. The pH in acid-containing copolymer emulsions is usually regulated using a mineral base, an organic base, such as an amine, or ammonia, the latter being preferred. Internally plasticized polymer latexes containing basic groups, such as amino groups or quaternary ammonium groups, can have their pH adjusted using mineral acids, such as hydrochloric acid, or organic acids such as acetic acid. The viscosity of the latex over the pH range from 3 to 10 is usually below 5000 cP, preferably below 500 cP, more preferably below 150 cP and even better below 40 cP, preferably below 10 cP. The lower values are particularly desirable for wet applications, such as floor polishes.

The minimum film formation temperature (MFT) should be measured on a film formed from the latex with 20% solids content and a pH of from 7.% to 9 for ammonia-neutralized acid-containing polymers and from 3 to 4 for acetic acid-neutralized base-containing polymers. The procedure according to ASTU D2354-68 is followed. The MFT is more than 5°C below the calculated glass transition temperature (T^) for the polymer when Tg is above 5°C. Minimum film formation temperatures below 18°C are preferred for polymers having a T calculated for the entire polymer material above 25°C. The term MFT as used herein to define certain polymers refers to the value determined for a latex at pH and solids content which indicated above. In some examples set forth below, MFT values determined under other conditions are provided for comparison purposes only and do not apply to or refer to the MFT used to define the polymers of the invention.

Hardness is expressed as the Knoop hardness number (KHN), and is determined using the Tukon microhardness tester on a film formed by applying the latex to a solid substrate, such as a glass panel. It is preferred that the polymers have a KHN of over 3, whereby over 5 is more preferred and over 8 most preferred.

The calculated T^ for each step and for the total polymer is determined by calculation based on the glass transition temperature of homopolymers of individual monomers, as described by Fox, Bull. Am. Physics Soc., 1, 3, page 123 (1956). Tables

for the glass transition temperature of homopolymers is given in "Polymer Handbook", Chapter III, Part 2, by W. A. Lee and R. A. Rutherford. The desired, calculated glass temperature for the first stage is lower than 40°C, with less than 5°C being preferred and less than -10°C being most preferred. The desired, calculated glass temperature for the second stage is above 35°C, with above 75°C being preferred and above 100°C being most preferred. The calculated T ^ for the polymer based on the entire polymer material is above 15°C, preferably above 20°C, with above 30°C being preferred for floor polishes and similar uses. For some other applications, such as adhesives, binders and paints, polymers with calculated T values below approx. 40 C, including values below 0, suitable.

Internally plasticized polymer emulsions of the invention can have a remarkable combination of properties, particularly (1) low minimum film formation temperature together with high hardness and high Tg, and (2) low polymer emulsion viscosity even when neutralized. Comparatively hard latex polymer systems can thus be used with much less film-forming aid than usual or without any film-forming aid at all. This is particularly valuable in situations where the film-forming aid causes secondary disadvantages. Due to this absence or minimization of added film-forming aid in the formulation, coatings which develop hardness at a very high rate can be produced from polymers according to the invention. Other advantages that arise from the elimination of added plasticisers, film-forming aids or organic solvents are cost reduction, reduced flammability during processing and reduced emission of toxic and polluting gases during and after application. These properties are particularly important in the formulation and use of water-based industrial coatings, both clear and pigmented. In printing ink technology, the advantages of very fast drying and non-flammability of internally softened polymers are very important. In commercial grade coatings, the combination of high hardness and low minimum film formation temperature results in a blocking-resistant, air-drying coating. A further advantage of the latex according to the invention is that the formulation is very easy, which results in a significant cost saving due to the four components and that these are easy to mix in a mixing plant. The ease of mixing is probably due to the fact that the latex produced according to the present invention is resistant to the so-called "shock" phenomenon, i.e. that the latex does not easily flocculate or gelatinize when it is mixed with another component in the formulation. The components can thus usually be mixed in any order in ordinary mixing plant equipment, and in addition the equipment itself is left in a much cleaner state than with ordinary latexes.

As described above, the polymer latex according to the invention is particularly useful for replacing the systems latex plus plasticizer or latex plus film-forming aid, which comprise a number of formulations that are used for many different applications of polymer latexes. These latexes are applicable for the production of free films and for the formation of coating agents such as in paints, varnishes, powder coatings and the like. The latexes according to the invention are also usable as impregnating agents and adhesives for both natural and synthetic substances, such as paper, textiles, wood, plastic, metal and leather and as binders for non-woven cloth. They can be used to lower the minimum film formation temperature or to assist during film formation in other latex systems when this is used in combination with them. Pigments, dyes, fillers, antioxidants, antiozonants, stabilizers, flow control agents, surfactants or other possible components can be used in the polymer materials according to the invention.

The latex according to the invention can be applied with or without a solvent by permanent or removable application on a suitable substrate, particularly for use as coating agents, fillers or adhesives. Application by ironing, floating, dipping, spraying and other known methods can be used to apply the latex according to the invention. One of the special advantages of the present invention is that reactive polymers can be prepared for use as air-drying or thermally drying coating agents, fillers or adhesives without the need for organic solvents, film-forming aids or plasticizers, although small amounts of these materials may be desirable. This is particularly valuable because the elimination of volatile solvents or other volatile substances, such as film forming aids, lowers a potential ecological risk.

It is of particular importance that the acid groups, hydroxyl groups or other functional groups in the first step of the polymerization remain available for further reaction, such as neutralization or cross-linking. This availability is due to the internal softened polymer latex from a latex where a second or later stage thus cooperates or interacts with the first stage to lower or eliminate the availability of the functional groups in the first stage for subsequent reactions. Said cross-linking can be any of the usual ones, such as a coordination cross-linking, ionic cross-linking or the formation of covalent bonds. In general, the reactions of these latexes can be ionic or covalent reactions. Ionic reactions are illustrated by the ionic cross-linking in the use of these latexes in floor polishes as stated below. The formation of covalent bonds by reaction with aminoplasts, epoxies, isocyanates and beta-hydroxyethyl esters is well known in the field.

The polymer latexes according to the invention are particularly useful in formulating floor polishes and are advantageously used in the floor polishes according to US patents 3,328,325, 3,467. 610 and 3,573,239.

In general, polishing agents in which the polymers according to the invention are used can be defined by the following amounts of the main constituents:

The sum of A, B and C should be 100.

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

For a non-polishable, self-polishing material, the wax should not exceed 35 parts by weight, preferably from 0 to 25 parts by weight of 100 parts total of polymer plus wax according to the above table. Satisfactory non-polishable wax polishes have been prepared without the addition of wax. Wax is thus not an essential component of a self-polishing agent. For a dry, polishable polish, the wax should make up at least 35 parts by weight of this total. Examples of wetting and dispersing agents are alkali metal and amine salts of higher fatty acids having from 12 to 18 carbon atoms, such as sodium, potassium, ammonium or morpholino oleate or ricinoleate, as well as the usual non-ionic surfactants. Additional wetting agent improves the spreading effect of the polishing agent.

For polishing floors, the coating formed by the material preferably has a Knoop hardness number of from 0.5 to 20 when measured on a film of 12.7-63.5 microns thick on glass. This hardness range provides good resistance to grinding and wear and can be achieved by the correct choice of monomers to be polymerised.

Preferred embodiments of the invention will be described below using examples where parts and percentages are by weight unless otherwise stated.

Example 1

Production of internal softened polymer emulsion.

A latex with first stage, second stage and average Tg values of -14°C, 105°C and 34°C respectively was prepared as follows:

A. Equipment.

A 5-liter four-necked flask equipped with condenser, stirrer, thermometer and monomer addition pumps. Heating, cooling and nitrogen sprinkler devices were used.

C. Procedure.

1. The water and the surfactant were introduced into the flask

and stirring and nitrogen sparging started.

2. The materials for each of the monomer batches were combined and

mixed well to produce stable monomer emulsions.

3. The flask was heated to 82-84°C with continued stirring

and nitrogen sprinkling.

4. Catalyst solution was introduced into the flask, and the addition of monomer step 1 was started at such a rate that the addition was completed within approx. 50 minutes. The temperature was maintained at 82-04°C throughout the polymerization. 5. After the monomer step 1 addition was complete

the temperature was maintained at 82-84°C for 15 minutes.

6. After this period of time, the addition of monomer batch step 2 was started at such a rate that the addition was completed within approx. 60 minutes. The temperature was maintained at 82-84°C throughout the polymerization. 7. After the addition of monomer batch step 2 was complete, the temperature was kept at 82-34°C for 30 minutes, after which it was cooled and filtered.

A sample of the latex was neutralized to pH 9 with ammonia. The MFT was below 15°C and the viscosity was 15 cP (Brookfield viscosity, 20% solids). A film of the neutralized latex had a hardness of 12.1 KHN.

Example 2

Rate ratio.

By the same general procedure as in example 1, three internal softened polymer latexes were produced which had the same composition in the first and second stages, but which differed in terms of the weight ratio between the first and second stages. Details are given in Table I.

It was found that the balance of properties, low minimum film formation temperature and at the same time low viscosity in the emulsion was sensitive to the weight ratio between the hard hydrophobic second stage charge and the soft hydrophilic first stage charge. This makes it clear that for a given monomer composition, a few simple experiments may be necessary to determine the rate ratio necessary to obtain a product according to the invention. Table I shows the effects of changing the rate ratio. Run 2B had a low minimum film formation temperature, low neutral viscosity and a high T . It appears that trial 2B is a latex polymer according to the invention, while trial 2A has too high a viscosity at pH 9 and 2C too high a minimum film formation temperature. Trials 2A and 2C are therefore only for comparison purposes.

Example 3

Polymerization.

The difference between a single emulsion copolymer, an internally softened polymer and a physical mixture of two polymers can be seen from the data in Table II. All the polymers were prepared by emulsion polymerization by substantially following the procedure of Example 1 with the exception that there is no other batch in the execution of Experiments 3A and 3C which were therefore only carried out for comparison. The total composition of each of the three samples was the same. The calculated T was 47°C.

It appears from Table II that the polymer from trial 3A with a single batch had a minimum film formation temperature close to the calculated T . The physical mixture, i.e. Experiment 3C, a mixture of an emulsion having the composition of the polymer from the first step in Experiment 3B with one having the composition from the second step in Experiment 3B, was so viscous at high pH that the emulsion gelatinized even after dilution to 20% dry matter content before pH regulation. Note that neutralized to a pH of 9, the inner plasticized polymer had a much lower minimum film formation temperature and only a moderately higher viscosity than the single batch polymer.

Example 4

Balance between hydrophilic and hydrophobic character in the steps.

Using the polymer emulsion from Experiment 23 as a control, the composition ratio of the water-starved first stage polymer to the second stage polymer was varied. Interaction between the first-stage polymer and the second-stage polymer was demonstrated in achieving internal softening, at controlled viscosity, of sequentially charged (1) soft, hydrophilic and functional and (2) hard and hydrophobic copolymers. This internal softening was found to depend on the balance between hydrophobic and hydrophilic character of the two monomer chargers by the data given in Table III.

The results in table III show that compared to experiment 4a, the hydrophobic, i.e. less hydrophilic, first stage polymer, 4B, is good, that a more hydrophilic first stage, 4C, leads to high viscosity, that a too hydrophobic second stage, 4D, leads to very high viscosity at high pH, too high for most applications.

Example 5

Interpenetration parameter.

Emulsion polymers with several compositions, which differed in interpenetration parameter (lp) for the two steps, were prepared by the method of Example 1 (experiments 5A-r5D, 5F-5H, 5J^5L and 5N-5R) or Example 8 (experiments 5E, 51 and 511) as indicated below. Determinations of emulsion viscosity and MFT, carried out with the emulsion neutralized to a pH of 7.5-8.5 with ammonia and diluted to 20% polymer solids, and of the film hardness show which of the materials have formed internal softened polymers. Tables IV.A and B indicate these data.

I w w vj w f Notes to Table IV.B: 1) The viscosity was measured with the 20% solids content latex brought to a pK of 9 with ammonia with the exception of experiment 5H which was at pH 3 with acetic acid.

2) MFT in °C, latex with 20% solids content regulated to

pH 9 with ammonia with the exception of experiment 5H (pH 3 as above). 3) Hardness was Knoop hardness number (KHN) determined by the method set forth in Resin Review, Volume XVI, No. 2, from page 9 (1966), a publication of the Rohm and Haas Company.

4) Tg was calculated for a high polymer by the method

to Fox, v.s. "(1)" and "(2)" represent first and second or later stages and "average" the value calculated for the material as a whole. 5) lp was calculated for the first stage (1) and the second stage (2). The difference between these Ip values was indicated under "(1-2)".

Data in Table IV.B show that an intrinsically softened polymer, indicated by the glass transition temperature, minimum film formation temperature, emulsion viscosity, and hardness value, is obtained when the interpenetration parameter value of the first stage polymer is greater than that of the second stage polymer, but not too much higher. Test 5J, a known polymer latex, does not contain internal softened particles, as evidenced by T^ being up to MFT.

As indicated in Table IV.A, this polymer contains only 7% hydrophilic monomer units in the first stage polymer. Test 5K does not contain internal softened particles according to the invention, which is evident from the high viscosity. As indicated in Table IV.B, its composition is such that there is an undesirably high difference in lp between the polymers from the two stages. Experiment 5L is not according to the invention, its viscosity is so high that a gel is formed. Note that the Ip difference between the polymers in the two stages is too low, it is below 0. Experiments 5Q and 5R, known polymer latexes, have MFT values above the T^ values. None of them contain non-ionic, hydrophilic monomers in the first step.

Example 6

Floor polish.

A floor polish was prepared by mixing the ingredients of the following recipe (with the exception of Experiments 6A and 6E as noted below):

The floor polish was applied and tested by the method described in detail in "P.esin Review", Volume XVI, No. 2, 1966, published by the Rohm and Haas Company, except where a different method is indicated. The polymer emulsions used and the test results obtained are given in Tables V.A and V.B. 1)<:> Experiment 6A is illustrative of the known technique. In this, a floor polishing agent-polymer emulsion containing 1.6 5% zinc ions was used as a cross-linking agent. This polish was prepared by mixing the ingredients in the following recipe: 2) Application of the floor polishes is described in ASTM D14 3 6-64, method B. Test methods, in parentheses, are given below. 3) Trial 6D was formulated with 1.25% zinc ions calculated from the emulsion polymer solids. 4) The recipe for the polish in trial 6E differed from the recipe for 6B, 6C and 6D in that the wax and antifoam were omitted while two parts of the film forming aid, diethylene glycol monomethyl ether, were added.

Test methods for Table V.A, indicated in parentheses in the table: 1. Slip: ASTM Method 02047-72, the panels were conditioned at 25°C and 55% relative humidity.

2. Pulverization: ASTM Method D2048-69.

3. 60° Gloss: ASTM Method D1455-64, Vinyl Tile ("Kentile" No. R-44). used instead of OTVA chips in this sample. 4. Water resistance: ASTM method D1793-66, dynamic test execution. 5. Rubber Full Mark Resistance: CSMA Method 9-7 3 (Chemical Specialties Manufacturers Association, Washington, D.C.), the sample modified by rotating for 15 minutes in each direction. 6. Detergent resistance was performed on black vinyl asbestos tile using 10 ml of 5 percent aqueous "Forward" detergent, 50 cycles in the 1 day test, 75 in the 3 day test and 100 cycles in the 7 day test. 7. Removeability was performed with 75 cycles using 10 ml of 3 percent Spic and Span and 1 percent aqueous ammonia on black vinyl asbestos tile.

Abrasion tests were carried out in a corridor having a vinyl-asbestos tile floor subjected to a daily traffic load of from 3500 to 4000 pedestrian crossings. A section of the corridor (approx. 3.5 m wide and approx. 7.3 m long) was cordoned off, residual polish was removed and the section was re-polished as a janitor would typically do as follows: Dust on the floor was mopped for removal of loose dirt by applying a 1:1 aqueous solution of "Step-Off" using a string mop in an amount of approx. 24 5 cm 2/l. After a soaking period of 5 minutes, the floor was scrubbed with an approx. 41 cm black floor polishing pad "Scotch Brite Slim Line Floor Pad" No. 61-6520-0101-0 on a floor machine with 300 rpm. (Mercury Floor Machines Inc., Englewood, New Jersey, Model H-15-c), the plastered floor was thoroughly sprinkled twice by steam mopping with clean water and allowed to dry. The plastered floor was divided into sections of approx. 1.8 meters perpendicular to the normal direction of traffic in the corridor.

On each of these sections, a coat of the polish to be tested was applied with a string mop, one amount of approx.

490 cm 2/l. After drying this coat of polish for one hour, a second coat was applied in the same manner. The appearance of the polishes was rated at the beginning and after 1 and 2 weeks of heavy traffic. The results from these observations and other tests, obtained by the methods used to obtain the data in table V.A, appear in table V.B:

Example 7

Lacquer and paint.

The polymer latex in example 1 was formulated as follows: Experiment 7A: The latex with 40% solids content was adjusted to pH 9 with 14% aqueous ammonia.

Experiment 7B: To 100 parts by weight of the latex which had been adjusted to pH 8.5 with 14 percent aqueous ammonia, a mixture of 9.7 parts water and 15.3 parts butoxyethanol was added.

Experiment 7C: The following ingredients were mixed:

The mixture was torn in a rapid dispersing apparatus (about 1250 rpm) for 15 min. and thinned while stirring with:

Polymer latex 7 0.4

Key varnish and paint properties were determined following the usual procedures in the paint industry. The results of the determinations on films produced from the materials when applied to metal sheets are given in Table VI.

^ Results determined on approx. 38.1 micron thick films baked for 1 hour at 121°C for samples of the film unless otherwise stated.

2' ) Air-dried films have values of 0.9/0.45.

Data in Table VI.A show that the latex in test 7A dries very quickly to full hardness, whereby a film is formed which is both hard and elastic without the aid of a film-forming aid. Film forming aid slows hardness development and has a detrimental effect on some of the durability properties. Burning is necessary to maximize certain properties. The resistance properties are good in general although the water wetting and alcohol resistance results are not as good as the other results.

Experiment 7C shows that the latex from example 1 can be used for the production of pigmented films with relatively little film-forming aid. The physical properties of the formed films are parallel to the properties of the unpigmented films. Other samples of the formed film from Experiment 7C showed: moderate rusting for a sample exposed for 5 days in a humidity cabinet, signs of failure after 3 days in a salt spray chamber and gloss change after 32 hours at 38°C in a "Cleveland" condensing cabinet as follows:

Example 8

Inner softened polymer emulsion based on vinyl acetate.

A latex with first-stage, second-stage and average Tg values of 25, 100 and 58°C respectively and Ip values of 17.5 and 12.1 for the first and second stage respectively was prepared as follows:

A. Equipment.

A 5-liter four-necked flask was equipped with a condenser, an efficient stirrer, a thermometer, addition funnels, and heating, cooling, and nitrogen sparging devices.

B. Material rates.

C. Procedure.

The monomer batches and flask batches were weighed separately and each mixed to form an emulsion. The initiator mixture was prepared and introduced into the flask. Effective stirring in the flask was carried out throughout the reaction. The reaction heat drives the flask temperature from 22°C to a maximum, approx. 60°C during approx.

7 minutes. At the maximum temperature, addition of monomer batch 1 was commenced at a rate of 13 ml/min, and addition of the catalyst solution and activator solution was commenced as separate feed streams at a rate of 1 ml/min. The reaction temperature was kept at approx. 62°C all the time. After the addition of half of monomer batch 1 was completed (approx. 22 minutes), batch IA was mixed with the rest of the monomers from batch 1 and the addition continued. After 45 minutes the addition of this monomer batch (1 + IA) was complete and the flask contents were held at 62°C for 15 minutes. Addition of monomer batch 2 was then commenced at a rate of 13 ml/min. This second addition was completed within 1 hour, and the flask contents were maintained at 62°C

for 10 minutes while the addition of the catalyst and activator batches was completed. The reaction mixture was held at 62°C for an additional 15 minutes and then allowed to cool to 55°C. The chain transfer agent was now added rapidly and the reaction mixture held at 50-60°C for 15 minutes. The product was allowed to cool to room temperature and was packaged.

A sample of the product latex was neutralized to pH 8.5

with ammonia and was found to have a viscosity of 40 cP (20% solids, Brookfield Synchro-Lectric viscometer model LVl, spindle 1 at 60 rpm) and an MFT below 15°C. A film of this sample had a hardness of 17 KHN.

Example 9

Inner softened polymer emulsion with an acid-containing final step.

A latex with a first-stage, second-stage and average T value of 28, 112 and 65°C, respectively, and an Ip value of 17.5 and 14.5 for the first and second stage, respectively, was produced using the same equipment as in example 8 and a similar procedure as follows:

Material rates.

Approach

1. The flask was charged and the temperature was regulated to 20-22°C, and it was sprinkled with l^.

2. Batch 1 was prepared and 231 g introduced into the flask.

3. Maleic anhydride in water and methacrylic acid (batch IA) was added to the remainder of monomer batch 1, and it emulsified.

4. Initiator was added and ^ sprinkler was turned off.

5. During several minutes of initiator addition, an exothermic reaction occurred with a temperature peak of 55-60°C. 6. At the temperature peak, addition of monomer batch 1 and half of the catalyst and activator was started. The temperature was allowed to rise to 62°C and was maintained at 62°C throughout the addition. 7. The addition of Batch 1 took 4 0-4 5 minutes. After batch 1 and half of the catalyst and activator had been added, the system was held at 62°C for 20 minutes. 8. After 20 minutes, addition of batch 2 and of catalyst and activator began. 9. Addition of rate 2 took approx. 55 minutes while addition of catalyst and activator took another 10 minutes.

10. The temperature was maintained at 62°C for 30 minutes.

11. After this time it was cooled to 55°C and the chain transfer agent was added, after which the temperature was held for 10 minutes before cooling to room temperature. 12. At room temperature, the pH was adjusted to 4.5-5.0 with a 10% aqueous NH^HCO^ solution.

A sample of the latex had a viscosity of 19 cP (20% solids, Brookfield Synchro-Lectric viscometer model LVl, spindle 1 at 60 rpm) and an MFT of 37°C. A film formed from this sample had a hardness of 14 KHN. By adding 1% Zn<2+>

(as Zn(NH^)^(HCO^)2) calculated from the polymer solids, such that according to US Patent 3.3 28.3 25, the hardness of the film was 15.5 KHN.

Example 10

Effect of the level of hydrophilic monomer.

By following the procedure in example 9, it was prepared

a group of polymer emulsions that had the compositions listed in Table VII. Floor polishes were prepared from these emulsions by mixing the ingredients in the following recipe:

Each floor polishing agent was applied and tested according to the methods described in example 6. The results are given in Table VII, where the good polishing agent properties of 10D and 10E appear.

"AC-392" was prepared at 35% solids as indicated below, and was thinned to 15% solids with water.

The first five ingredients were added to form a 50 percent concentrate in a pressure reaction vessel where stirring was carried out. Stirring was started, it was heated to 95°C with the valve open. The valve was closed and heating was continued to 150°C for h hour. 43 parts of water at 95°C was added to the reaction vessel while the temperature was at 150°C, and it was then cooled to room temperature with stirring as quickly as possible. 500 ppm formaldehyde preservative was added.

Example 11

Effect of acid variations.

According to the method in example 9, a group of polymer emulsions was prepared which is indicated in table VIII. From these emulsions, floor polishes were produced which were tested as described in example 10. The results of these tests are given in table VIII where it appears that example 11A has no distinct weaknesses and that the copolymers where maleic anhydride is used are not unclear.

Example 12

Variations of the ratio between the first step and the last step.

By the method according to Example 9, polymer emulsions were produced which had a range of weight ratios between the first and last stages which are shown in Table IX. The composition of the first step for each was EA/VAc/VOH/MAn/MAA = 11/7 5.6/11.2/0.8/ 1.4 and had a T (1) of 27.7°C and an Ip(l) of 17.5. The last step of each was polystyxene which had a Tg(2) of 100°C and an Ip(2) of 12.1. The Ip(1) - Ip(2) value for each latex polymer was thus 5.4. Floor polishes were prepared from these emulsions and tested as described in examples 6 and 10. The test results appear in Table IX.

Example 13

Maleic anhydride/ methacrylic acid levels.

The method of Example 9 produced polymer emulsions with a range of maleic anhydride and methacrylic acid levels in the first step as shown in Table X. Each last step was polystyrene and made up 50% by weight of the polymer. The polymer in run 13A was the same as in run 11A. As the differences in composition were relatively small, the T - values and Ip values for the other three polymers deviated little from the corresponding ones for test 13A. Polishes prepared from these emulsions were tested as in Examples 6 and 10 and gave the performance results shown in Table X. A wide range of removeability and detergent resistance was obtained, which was remarkable in view of the vinyl acetate content of the polymer.

Example 14

Acid in the last step.

The polish in trial 14A was made from the same polymer latex as the polish in trial 11A. A film of this polymer was found to have a Knoop hardness number of 10. The polish in Experiment 14B was prepared from the polymer latex of Example 9 and was crosslinked with 1% Zn 2+ , calculated on the polymer dry matter, added as Zn(NH 3 ) 4 (HC0 3 )2. The polishing agent in Experiment 14C was prepared from a sample of the polymer latex in Experiment 6A, Table V.A, Note 1. A film of this polymer had a KHN of 13. These polishing agents were tested as in Examples 6 and 10. The results appear in Table XI. Note the balance achieved between removeability and detergent resistance while maintaining the high level of other properties.

Claims (18)

1. Latex of internally softened addition polymer particles, for use in coating materials, adhesives and binders, containing (A) an early stage polymer and (B) a late stage polymer formed by polymerization in the presence of an emulsion of polymer particles containing the polymer (A), each of the polymers (A) and (B) make up at least 10% by weight of the amount of polymer in the particles, characterized in that the polymer (A) contains at least 10% by weight of units formed from hydrophilic monomer units of which at least 10% by weight are non-ionic, and the polymer (B) is less hydrophilic than the polymer (A), and that either (i) the polymer (B) has a higher Tg than the polymer (A) and at least 0.5% of the hydrophilic units in the polymer (A) are ionic and the interpenetration parameter of the polymer (A ) is at most 8 units greater than for the polymer (B), as the polymer (A) contains units formed from monoethylenically unsaturated monomers, or (ii) the polymer particles have a Tg of more than 15°C while the latex has a viscosity of less than 5000 cP measured with 20 wt% solids content over a pH range of from 4 to 10 and has a minimum film formation temperature that is more than 5°C lower than the calculated Tg of the polymer particles. 2. Latex in accordance with claim 1, characterized in that the calculated Tg of the polymer particles is above 20°C. 3. Latex in accordance with claim 1 or 2, where the viscosity is below 5000 cP and the polymer particles have a Tg of over 30°C, characterized in that the latex polymer is such that a film formed from it has a Knoop hardness number of at least 5. 4. Latex in accordance with one of the preceding claims, characterized in that of the hydrophilic units, from 0.5 to 90% by weight are acidic or basic units, and that the latex has a viscosity of less than 150°C. 5- Latex in accordance with one of the preceding claims, characterized in that the viscosity is below 40 cP, that the latex polymer is such that a film formed from it has a Knoop hardness number of at least 8, and that the polymer (A) contains ionic units of carboxyl groups. 6. Latex in accordance with claim 5, where the viscosity is below 10 cP, characterized in that from 50 to 90% of the hydrophilic units originate from monomer units of hydroxyalkyl ester of o.6 unsaturated acid. 7. Latex in accordance with claim 6, characterized in that the units in the addition polymer originate from acrylate, methacrylate, vinyl ester and/or vinyl aromatic monomers. 8. Latex in accordance with claim 3, where each of the polymers (A) and (B) constitutes at least 30% by weight of the latex polymer and the viscosity of the latex is below 150cP, characterized in that the polymer (A) contains from 10 to 70% by weight of hydrophilic units, and that the polymer (B) has a calculated T of at least 10°C above the calculated T for the polymer (A). 9. Latex in accordance with claim 8, characterized in that the minimum film formation temperature is at most 18°C, that a film formed by the latex polymer has a Knoop hardness number of at least 5, that the calculated T for the polymer (A) is at most 40°C and that the polymer (B) is harder than the polymer (A). 10. Latex in accordance with claim 9, with a viscosity of less than 40 cP, characterized in that the Knoop hardness number for a film formed by the latex polymer is at least 8, that T for the polymer (A) is at most 5°C and that T for the polymer ( B) is at least 75°C. 11. Latex in accordance with claim 10, where the viscosity is below 10 cP and each of the polymers (A) and (B) constitutes at least 40% by weight of the latex polymer, characterized in that the Tg for the polymer (A) is at most -10°C , and that the Tg for the polymer (B) is at least 100°C. 12. Latex in accordance with claim 11, characterized in that at least 0.5% by weight of the hydrophilic units is formed by carboxylic acid monomers. 13. Latex in accordance with claim 12, characterized in that the latex polymer contains units of one or more of the following monomers: acrylate esters, methacrylate esters, vinyl esters and vinyl aromatic monomers. 14. Latex in accordance with claim 13, characterized in that the units in the polymer (A) comprise from 65 to 85% by weight (C1~C4)-alkyl acrylate, (C-^-C^)-alkyl methacrylate and/or styrene units, from 5 to 10% by weight of acrylic acid, methacrylic acid and/or itaconic acid units and from 10 to 25% by weight of hydroxy-(C1"C4)-alkyl methacrylate and/or hydroxy-(C-^-C^)-alkyl acrylate units, and that the units in the polymer (B) comprise methyl methacrylate and/or styrene units. 15. Latex in accordance with claim 13, characterized in that the units in the polymer (A) comprise from 50 to 85% by weight of vinyl acetate units, from 1 to 10% by weight of acrylic, methacrylic, itaconic and/or maleic acid units and from 8 to 2 5% by weight vinyl alcohol units, and that the units in the polymer (B) comprise from 100 to 70% by weight methyl methacrylate and/or styrene units and from 0 to 30% by weight acidic units. 16. Latex in accordance with claim 15, characterized in that the units in the polymer (A) comprise from 1 to 4% by weight acid units of which from 0.2 to 2% by weight are units of maleic acid, from 0 to 20% by weight (C^- C 1 )-alkyl acrylate units, from 65 to 80% by weight of vinyl acetate units and from 10 to 20% by weight of vinyl alcohol units, and that the units in the polymer (B) comprise from 10 to 20% by weight of acid units. 17. Latex in accordance with one of the preceding claims, characterized in that the interpenetration parameter of the polymer (A) is at least from 1 to 6 units higher than that of the polymer (B). 18. Use of the latex according to one of claims 1-17 in an aqueous polishing material capable of forming a coating having a Knoop hardness number of at least 0.5.