POLYMER, COMPOSITION AND PROCESS

The invention relates to the field of aqueous polymer dispersions, such as acrylic dispersions, to their use, for example as adhesives, and to the preparation of polymers and their dispersions.

Pressure sensitive adhesives (PSA) form a permanently adhesive film capable of adhering to various surfaces upon slight pressure at ambient temperature. PSAs are used to manufacture self-adhesive products, such as labels, tapes or films.

Alkyl phenol ethoxylates (APE) of the general formula C _z Ha _z +iCeHUtOCHaChyeOH have been used as surfactants for water based acrylic dispersions for several decades. Typical values for 'z' (the length of the alkyl chain) are from about 8 to about 12, with nonyl (z = 9) and octyl (z = 8) predominating. The value for 'e' (the degree of ethoxylation) can also range widely depending on the desired end use of the APE with common values of 'e' being from about 10 to about 15. More information about APE can be found for example in the Kirk Othmer Encyclopaedia of Chemical Technology 4 ^th edition, Vol. 23, pages 510 to 51 1 , the disclosure of which is hereby incorporated by reference. In some countries (particularly in Europe) questions have been raised about the environmental effects of APE, especially nonyl phenol ethoxylates (NPE). Therefore there is a need for alternative means to stabilise acrylic emulsions if the products in which they are used (such as PSAs) are to continue to be seen as environmentally friendly in all countries in which they are used.

It has proved difficult to find an APE-free surfactant system that provides the same performance as surfactant systems using APE surfactants (either alone or part of a mixture of surfactants). This is because the more readily available alternatives to APE that might be tried (such as surfactants having a similar hydrophilic / lipophilic balance or HLB value) do not in fact provide the same level of stability to an aqueous dispersion.

This problem of providing APE-free emulsion has been addressed previously in for example US 6,908,524 (Air Products) and US 6,974,520 (Air Products) which both describe an APE free surfactant system comprising a mixture (in a respective weight range from 4:1 to 1.5:1 ) of an anionic surfactant, sodium laureth sulfate (SLS) with 1-12 moles of ethylene oxide (EO) and a non-ionic surfactant, either a secondary C/.-iβalcohol ethoxylate with 7-30 moles of EO or a branched primary C _7- i ₈ alcohol ethoxylate with 3-30 moles of EO. This surfactant mixture is designed to stabilise emulsion polymer binders that are used to form a bonded and creped non-woven web (such as paper products).

However these APE-free emulsions are unsuitable for use as PSAs. For example the pre-emulsion is unstable, it is difficult to achieve high total solids content, high amounts of coagulum and grit are formed and these formulations do not easily form films.

It is an object of the invention to provide APE-free emulsions which solve some or all of the aforementioned problems to provide PSAs with similar or even improved adhesive and/or cohesive properties to those made with APE surfactants.

Surprisingly the applicants have found a means to replace the APE type of surfactants in emulsions with a benign APE-free surfactant system without compromising either the physical properties of a PSA (e.g. total solids content, partial size distribution) or the PSA performance (e.g. peel, shear, tack).

Therefore broadly in accordance with the present invention there is provided an aqueous dispersion suitable for preparing pressure sensitive adhesive (PSA) where the dispersion comprises:

(a) a monomer composition comprising:

(i) at least one hydrophobic monomer (Component I); (ii) at least one hydrophilic monomer (Component II); and (iii) at least one partially hydrophilic monomer (Component III); and

(b) at least one water-soluble or water-dispersible anionic surfactant of Formula 1

R ¹ (R ² O) _n (A ^q -) _m (C ^p+ ) _qm/p Formula 1 where

R ¹ denotes a hydrocarbo group, 'R ² O' denotes independently in each repeat unit a hydrocarbyloxy group,

'A' denotes one or more anionic substituents of charge -q each independently attached anywhere on Formula 1 , C denotes one or more suitable counter cation(s) of charge +p, n is an integer in the inclusive range from 1 to 8 m is from 1 to 4, q is from 1 to 3, and p is from 1 to 3, with the provisos that the dispersion is substantially (preferably completely) free of alkyl phenol ethoxylate(s) (APE); and when q is 1 , m is 1 and A is phosphate, then n is less than 6.

A further aspect of the invention provides a pressure sensitive adhesive obtainable from the above dispersion, the PSA also being substantially free of APE.

It is an object of the invention to provide compositions that are sufficiently free of APE (as defined above) to be acceptable for sale in those territories that have concerns about APEs

(for example Scandinavia). Many of the surfactant and/or other ingredients that can be used to prepare the present invention comprise mixtures (such as polydisperse polymers with many components) and/or are made by a variety of synthetic routes. It will be appreciated therefore that a theoretical possibility exists that some trace amounts of APE (e.g. from contamination, impurities, side reactions etc.) may exist in compositions of the present invention without departing from the preceding object. The term "substantially free of APE" as used herein means having no APE present insofar as it can be detected and/or if detectable would be at such minute concentrations (e.g. 0.01 % or less by weight) that could not possibly have any negative environmental impact. However nevertheless it is preferred that the compositions of the invention contain neither APE in any amount nor any species that would be converted to APE during the conditions of preparation and/or use of the compositions of the present invention.

The current invention provides a substantially APE-free PSA with high total solids content, low viscosity, moderate shear and moderate peel. The pre-emulsion is stable and no grit or coagulum is observed. Low amounts volatile organic compounds (VOC) and monomer residuals are obtained. The PSAs of the invention are suitable for a wide variety of industrial applications. The surfactant system disclosed in this invention can replace alkyl phenol ethoxylates (APE) in a variety of dispersions that currently are stabilised using APE, but is especially suitable as an APE replacement both for existing commercial PSAs that presently use APE and also to formulate new PSAs.

Surfactant

Preferred anionic surfactants of Formula 1 comprise those where:

R ¹ denotes a Cio-3ohydrocarbyl, more preferably Ci ₂ -i8alkyl, most preferably Ci ₂ -i5alkyl, for example C^alkyl (tridecyl);

'R ² O' denotes independently in each repeat unit a Ci _-4 hydrocarboxy; more preferably Ci_ ₄ alkoxy, most preferably propoxy and/or ethoxy, for example ethoxy A independently represents an anionic substituent derived from a strong acid (i.e. that is fully dissociated in water at room temperature) and is independently attached anywhere on Formula 1 , preferably one or more anions derived from an acid with a pKa of less than 3.0, more preferably one or more anions derived from oxy sulfo acid(s), more preferably (when q is 1 ) is -SO ₃ ^" C denotes one or more optionally substituted quaternary ammonium cation (QAC) and/or a metal cation, more preferably (when p is 1 ) C denotes , Na ⁺ , K ⁺ or NH ₄ ⁺ , most preferably NH ₄ ⁺ ; n is an integer in the inclusive ranges: from 2 to 6, more preferably 2 to 5, most preferably 3 to 5, for example 3 or 4; and/or

m, p and q are each independently in the inclusive range from 1 to 3, more preferably about 1.

Surfactants of Formula 1 useful in an alternative embodiment of the invention are those when n is less than 6; and where A may represent one or more anionic substituent(s) derived from oxy sulfo acid(s) and/or oxy phospho acid(s); and usefully when q is 1 , A may represent -SO3 ^" and/or -PO3 ^" , and the other preferences for components of Formula 1 being those described above.

An embodiment of a suitable anionic surfactant of Formula 1 is that sodium tridecyl ether sulfate with three ethoxy repeat units which is available from Rhodia Inc. under the trade mark Rhodapex ^® EST-30.

Advantageously the dispersions of the invention may comprise one or more additional surfactants preferably non-ionic surfactants (as long as they are not of the APE type) in addition to those of Formula 1. Conveniently the additional non-ionic surfactant(s) may have a hydrophilic / lipophilic balance (HLB) of from 10 to 30, more conveniently from 15 to 25, most conveniently from 16 to 20, for example about 18.

The additional surfactant(s) may also be one or more non-ionic surfactant(s) of Formula 2:

R ³ (R ⁴ O) _x (O) _y H Formula 2 where

R ³ denotes a hydrocarbo group, preferably Ci _0- 3ohydrocarbyl, more preferably Ci _2- i8alkyl, most preferably Ci ₂ -i5alkyl, for example C^alkyl (tridecyl); R ⁴ denotes independently in each repeat unit a hydrocarbyloxy group, preferably

Ci_ ₄ hydrocarboxy; more preferably most preferably propoxy and/or ethoxy, for example ethoxy; x is an integer from 20 to 60, preferably 30 to 50, more preferably 35 to 45, for example about 40; and y is 1 or 0, preferably 0, i.e. where the hydrogen atom is bonded directly to the R ⁴ O moieti(ies).

An embodiment of a suitable non-ionic surfactant of Formula 2 is that aliphatic ether with 40 ethoxy repeat units available from Rhodia Inc. under the trade mark Abex ^® 2535.

Conveniently the non ionic surfactant(s) of Formula 2 may also have a HLB value of from 10 to 30, more conveniently from 15 to 25, most conveniently from 16 to 20, for example about 18.

Surfactants suitable for use in the present invention (such as those of Formulae 1 and/or 2) comprise one or more hydrocarbyloxy moieties (such as R ² O and/or R ⁴ O) as a repeat unit, for example a polyoxyalkylene. Suitable polyoxyalkylene moieties comprise unsubstituted or substituted alkylene groups such as ethylene, propylene, butylene, and isobutylene. The polyoxyalkylene moiety can be a homo-, block or random polymer, or any suitable mixtures thereof.

The total amount of water-soluble or water-dispersible surfactant that may present in the dispersion is at least about 0.1 %, preferably from about 0.1 % to about 5%, preferably about 0.5 to about 2 %, by weight of the total amount of Components I, Il and III.

Monomer composition

Unless otherwise indicated (e.g. for amounts of aryl arylalkylene within Component I) all of the weight amounts described herein for the following monomers are given as weight percentages by the total weight of monomers (Components I, II, III & IV).

Component I

The hydrophobic monomer (Component I) may comprise, conveniently consist essentially of, at least one hydrophobic (meth)acrylate and/or arylalkylene monomer.

Preferably the hydrophobic (meth)acrylate comprises C> ₄ hydrocarbo (meth)acrylate(s) and conveniently the C> ₄ hydrocarbo moiety may be C _4-2 ohydrocarbyl, more conveniently C _4- i ₄ alkyl most conveniently C _4- ioalkyl, for example C _4-8 alkyl.

Suitable hydrophobic (meth)acrylate(s) are selected from: isooctyl acrylate, 4-methyl-2-pentyl acrylate, 2-methylbutyl acrylate, isoamyl acrylate, sec-butyl acrylate, n-butyl acrylate, 2-ethylhexyl acrylate, isodecyl methacrylate, isononyl acrylate, isodecyl acrylate, and/or mixtures thereof, especially 2-ethylhexyl acrylate and/or n-butyl acrylate, for example n-butyl acrylate.

Preferably the arylalkylene comprises (optionally hydrocarbo substituted) styrene and conveniently the optional hydrocarbo may be Ci_iohydrocarbyl, more conveniently Ci _-4 alkyl. Suitable arylalkylene monomers are selected from: styrene, α-methyl styrene, vinyl toluene, t-butyl styrene, di-methyl styrene and/or mixtures thereof, especially styrene.

Optionally Component I consist essentially of only the hydrophobic (meth)acrylate(s).

Component I may be present in a total amount of at least 70%, preferably from about 70% to about 98%, more preferably from about 80% to about 96%, most preferably from about 85% to about 95%.

The currently preferred Component I is n-butyl acrylate from about 85% to about 95% by weight.

Component Il

Suitable hydrophilic monomers of Component Il are those that are copolymerisable with the hydrophobic monomer(s) (Component I) and are water soluble.

Preferred hydrophilic monomers comprise, conveniently consist essentially of, at least one ethylenically unsaturated carboxylic acid. More preferred acids have one ethylenic group and one or two carboxyl groups. Most preferably the acid(s) are selected from the group consisting of: acrylic acid (and oligomers thereof), beta carboxy ethyl acrylate, citraconic acid, crotonic acid, fumaric acid, itaconic acid, maleic acid, methacrylic acid and mixtures thereof; especially acrylic acid, methacrylic acid and mixtures thereof for example acrylic acid.

Component Il may be present in a total amount of at least about 0.2%, preferably from about 0.2% to about 5%, more preferably from about 0.3% to about 2%, most preferably from about 0.5% to about 1.5%, for example about 0.8% to about 1.2% by weight.

The currently preferred Component Il is acrylic acid from about 0.8% to about 1.2% by weight.

Component III

The partially hydrophilic monomers of Component III may also be referred to as partially water soluble monomers.

Preferred partially hydrophilic monomers comprise, conveniently consist essentially of, at least one Ci_ ₂ hydrocarbyl (meth)acrylate, more preferably (meth)acrylate. Most preferred partially hydrophilic monomers are selected from the group consisting of: methyl acrylate, methyl methacrylate, ethyl acrylate, vinyl acrylate and/or mixtures thereof; for example vinyl acrylate, methyl methacrylate and/or mixtures thereof.

Component III may be present in a total amount of at least about 3%, preferably from about 3% to about 20%, more preferably from about 4% to about 15%, most preferably from about 5% to about 14%, for example from about 6% to about 13% by weight.

The currently preferred Component III is methyl methacrylate with optionally vinyl acrylate in a total amount of about 6% to about 13% by weight.

Process

Broadly in accordance with another aspect of the present invention there is provided a process for preparing an aqueous dispersion substantially free of alkyl phenol ethoxylates (APE) the dispersion being suitable for preparing pressure sensitive adhesive (PSA), the process comprising the steps of:

(a) copolymerising a monomer composition comprising: (i) at least one hydrophobic monomer (Component I);

(ii) at least one hydrophilic monomer (Component II); and (iii) at least one partially hydrophilic monomer (Component III); in the presence of at least one water-soluble or water-dispersible anionic surfactant of Formula 1 R ¹ (R ² O) _n (A ^q -) _m (C ^p+ ) _qm/p Formula 1 where

R ¹ denotes a hydrocarbo group,

'R ² O' denotes independently in each repeat unit a hydrocarbyloxy group, 'A' denotes one or more anionic substituent(s) of charge -q, each independently attached anywhere on Formula 1 ,

C denotes one or more suitable counter cation(s) of charge +p, n is an integer in the inclusive range from 1 to 8, with the proviso that when A is a phosphate n is less than 6 m is from 1 to 4, q is from 1 to 3, and p is from 1 to 3, and optionally a non-ionic surfactant of Formula 2:

R ³ (R ⁴ O) _x (O) _y H Formula 1 where

R ³ denotes a hydrocarbo group,

R ⁴ denotes a denotes independently in each repeat unit a hydrocarbyloxy group; x is an integer from 20 to 60, and y is 0 or 1.

(b) neutralising the emulsion so that the pH is from about 5.5 to about 9.0. with the provisos that the dispersion is substantially (preferably completely) free of alkyl phenol ethoxylate(s) (APE); and when q is 1 , m is 1 and A is phosphate, then n is less than 6.

Preferably step (a) is performed in the absence of a redox initiator, more preferably step (a) is performed in the presence of a thermal initiator (such as a suitable persulfate). Most preferably step (a) is a radical co-polymerisation.

Schematic example of a process suitable to prepare polymers of the invention is as follows. De-ionised water and a suitable buffer are added to a reaction vessel. In a first delay vessel a solution of the surfactant(s) described herein and the desired monomer composition are mixed to form a thick, white pre-emulsion. In a second delay tank the initiator (such as a suitable persulfate) is dissolved in de-ionised water. The reactor is heated to a suitable temperature and the initiator solution from the second delay tank is added to the reactor. Immediately after all initiator has been added the pre-emulsion delay is started and added over a suitable period (typically 3 hours) whilst the reaction temperature is maintained. At the end of the delay the reactor is cooled and the rest of the ingredients are added.

Further detail and additional optional ingredients that may be used in the process of he present invention are known to those skilled in the art, for example step (a) may be performed in the presence of a chain transfer agent such as n-dodecyl mercaptane. Suitable methods and optional ingredients are described in the examples herein and also in the applicant's patent applications WO 03/006517, WO 03/006518, WO 04/029171 , WO 04/029172 and WO 05/044880 herby incorporated by reference.

Many other variations embodiments of the invention will be apparent to those skilled in the art and such variations are contemplated within the broad scope of the present invention.

Further aspects of the invention and preferred features thereof are given in the claims herein.

Unless the context clearly indicates otherwise, as used herein plural forms of the terms herein are to be construed as including the singular form and vice versa.

The term "comprising" as used herein will be understood to mean that the list following is non exhaustive and may or may not include any other additional suitable items, for example one or more further feature(s), component(s), ingredient(s) and/or substituent(s) as appropriate.

The terms 'effective', 'acceptable' 'active' and/or 'suitable' (for example with reference to any process, use, method, application, preparation, product, material, formulation, compound, monomer, oligomer, polymer precursor, and/or polymers of the present

invention and/or described herein as appropriate) will be understood to refer to those features of the invention which if used in the correct manner provide the required properties to that which they are added and/or incorporated to be of utility as described herein. Such utility may be direct for example where a material has the required properties for the aforementioned uses and/or indirect for example where a material has use as a synthetic intermediate and/or diagnostic tool in preparing other materials of direct utility. As used herein these terms also denote that a functional group is compatible with producing effective, acceptable, active and/or suitable end products.

Preferred utility of the present invention comprises uses as an adhesive, preferably a pressure sensitive adhesive.

The terms Optional substituent' and/or Optionally substituted' as used herein (unless followed by a list of other substituents) signifies the one or more of following groups (or substitution by these groups): carboxy, sulpho, formyl, hydroxy, amino, imino, nitrilo, mercapto, cyano, nitro, methyl, methoxy and/or combinations thereof. These optional groups include all chemically possible combinations in the same moiety of a plurality (preferably two) of the aforementioned groups (e.g. amino and sulphonyl if directly attached to each other represent a sulphamoyl group). Preferred optional substituents comprise: carboxy, sulpho, hydroxy, amino, mercapto, cyano, methyl, halo, trihalomethyl and/or methoxy.

The synonymous terms Organic substituent' and "organic group" as used herein (also abbreviated herein to "organo") denote any univalent or multivalent moiety (optionally attached to one or more other moieties) which comprises one or more carbon atoms and optionally one or more other heteroatoms. Organic groups may comprise organoheteryl groups (also known as organoelement groups) which comprise univalent groups containing carbon, which are thus organic, but which have their free valence at an atom other than carbon (for example organothio groups). Organic groups may alternatively or additionally comprise organyl groups which comprise any organic substituent group, regardless of functional type, having one free valence at a carbon atom. Organic groups may also comprise heterocyclyl groups which comprise univalent groups formed by removing a hydrogen atom from any ring atom of a heterocyclic compound: (a cyclic compound having as ring members atoms of at least two different elements, in this case one being carbon). Preferably the non carbon atoms in an organic group may be selected from: hydrogen, halo, phosphorus, nitrogen, oxygen, silicon and/or sulphur, more preferably from hydrogen, nitrogen, oxygen, phosphorus and/or sulphur. Convenient phosphorous containing groups may comprise: phosphinyl (i.e. a '-PR3' radical where R independently denotes H or hydrocarbyl); phosphinic acid group(s) (i.e. a '-P(=O)(OH)2' radical); and phosphonic acid group(s) (i.e. a '-P(=O)(OH)3 ' radical).

Most preferred organic groups comprise one or more of the following carbon containing moieties: alkyl, alkoxy, alkanoyl, carboxy, carbonyl, formyl and/or combinations thereof; optionally in combination with one or more of the following heteroatom containing moieties: oxy, thio, sulphinyl, sulphonyl, amino, imino, nitrilo and/or combinations thereof. Organic groups include all chemically possible combinations in the same moiety of a plurality (preferably two) of the aforementioned carbon containing and/or heteroatom moieties (e.g. alkoxy and carbonyl if directly attached to each other represent an alkoxycarbonyl group).

The term 'hydrocarbo group' as used herein is a sub set of a organic group and denotes any univalent or multivalent moiety (optionally attached to one or more other moieties) which consists of one or more hydrogen atoms and one or more carbon atoms and may comprise one or more saturated, unsaturated and/or aromatic moieties. Hydrocarbo groups may comprise one or more of the following groups. Hydrocarbyl groups comprise univalent groups formed by removing a hydrogen atom from a hydrocarbon (for example alkyl). Hydrocarbyl en e groups comprise divalent groups formed by removing two hydrogen atoms from a hydrocarbon, the free valencies of which are not engaged in a double bond (for example alkylene). Hydrocarbylidene groups comprise divalent groups (which may be represented by "R2C=") formed by removing two hydrogen atoms from the same carbon atom of a hydrocarbon, the free valencies of which are engaged in a double bond (for example alkylidene). Hydrocarbylidyne groups comprise trivalent groups (which may be represented by "RC≡"), formed by removing three hydrogen atoms from the same carbon atom of a hydrocarbon the free valencies of which are engaged in a triple bond (for example alkylidyne). Hydrocarbo groups may also comprise saturated carbon to carbon single bonds (e.g. in alkyl groups); unsaturated double and/or triple carbon to carbon bonds (e.g. in respectively alkenyl and alkynyl groups); aromatic groups (e.g. in aryl groups) and/or combinations thereof within the same moiety and where indicated may be substituted with other functional groups

The term 'alkyl' or its equivalent (e.g. 'alk') as used herein may be readily replaced, where appropriate and unless the context clearly indicates otherwise, by terms encompassing any other hydrocarbo group such as those described herein (e.g. comprising double bonds, triple bonds, aromatic moieties (such as respectively alkenyl, alkynyl and/or aryl) and/or combinations thereof (e.g. aralkyl) as well as any multivalent hydrocarbo species linking two or more moieties (such as bivalent hydrocarbylene radicals e.g. alkylene).

Any radical group or moiety mentioned herein (e.g. as a substituent) may be a multivalent or a monovalent radical unless otherwise stated or the context clearly indicates otherwise

(e.g. a bivalent hydrocarbylene moiety linking two other moieties). However where indicated herein such monovalent or multivalent groups may still also comprise optional

substituents. A group which comprises a chain of three or more atoms signifies a group in which the chain wholly or in part may be linear, branched and/or form a ring (including spiro and/or fused rings). The total number of certain atoms is specified for certain substituents for example Ci _-N organo, signifies a organo moiety comprising from 1 to N carbon atoms. In any of the formulae herein if one or more substituents are not indicated as attached to any particular atom in a moiety (e.g. on a particular position along a chain and/or ring) the substituent may replace any H and/or may be located at any available position on the moiety which is chemically suitable and/or effective.

Preferably any of the organo groups listed herein comprise from 1 to 36 carbon atoms, more preferably from 1 to 18. It is particularly preferred that the number of carbon atoms in an organo group is from 1 to 12, especially from 1 to 10 inclusive, for example from 1 to 4 carbon atoms.

As used herein chemical terms (other than IUAPC names for specifically identified compounds) which comprise features which are given in parentheses - such as (alkyl)acrylate, (meth)acrylate and/or (co)polymer denote that that part in parentheses is optional as the context dictates, so for example the term (meth)acrylate denotes both methacrylate and acrylate.

Certain moieties, species, groups, repeat units, compounds, oligomers, polymers, materials, mixtures, compositions and/or formulations which comprise and/or are used in some or all of the invention as described herein may exist as one or more different forms such as any of those in the following non exhaustive list: stereo-isomers (such as enantiomers (e.g. E and/or Z forms), diastereo-isomers and/or geometric isomers); tautomers (e.g. keto and/or enol forms), conformers, salts, zwitterions, complexes (such as chelates, clathrates, crown compounds, cyptands / cryptades, inclusion compounds, intercalation compounds, interstitial compounds, ligand complexes, organo-metallic complexes, non stoichiometric complexes, π adducts, solvates and/or hydrates); isotopically substituted forms, polymeric configurations [such as homo or copolymers, random, graft and/or block polymers, linear and/or branched polymers (e.g. star and/or side branched), cross linked and/or networked polymers, polymers obtainable from di and/or tri valent repeat units, dendrimers, polymers of different tacticity (e.g. isotactic, syndiotactic or atactic polymers)]; polymorphs (such as interstitial forms, crystalline forms and/or amorphous forms), different phases, solid solutions; and/or combinations thereof and/or mixtures thereof where possible. The present invention comprises and/or uses all such forms which are effective as defined herein.

Polymers of the present invention may be prepared by one or more suitable polymer precursor(s) which may be organic and/or inorganic and comprise any suitable

(co)monomer(s), (co)polymer(s) [including homopolymer(s)] and mixtures thereof which comprise moieties which are capable of forming a bond with the or each polymer precursor(s) to provide chain extension and/or cross-linking with another of the or each polymer precursor(s) via direct bond(s) as indicated herein.

Polymer precursors of the invention may comprise one or more monomer(s), oligomer(s), polymer(s); mixtures thereof and/or combinations thereof which have suitable polymerisable functionality.

A monomer is a substantially monodisperse compound of a low molecular weight (for example less than one thousand daltons) which is capable of being polymerised.

A polymer is a polydisperse mixture of macromolecules of large molecular weight (for example many thousands of daltons) prepared by a polymerisation method, where the macromolecules comprises the multiple repetition of smaller units (which may themselves be monomers, oligomers and/or polymers) and where (unless properties are critically dependent on fine details of the molecular structure) the addition or removal one or a few of the units has a negligible effect on the properties of the macromolecule.

A oligomer is a polydisperse mixture of molecules having an intermediate molecular weight between a monomer and polymer, the molecules comprising a small plurality of monomer units the removal of one or a few of which would significantly vary the properties of the molecule.

Depending on the context the term polymer may or may not encompass oligomer.

The polymer precursor of and/or used in the invention may be prepared by direct synthesis or (if the polymeric precursor is itself polymeric) by polymerisation. If a polymerisable polymer is itself used as a polymer precursor of and/or used in the invention it is preferred that such a polymer precursor has a low polydispersity, more preferably is substantially monodisperse, to minimise the side reactions, number of by-products and/or polydispersity in any polymeric material formed from this polymer precursor. The polymer precursor(s) may be substantially un-reactive at normal temperatures and pressures.

Except where indicated herein polymers and/or polymeric polymer precursors of and/or used in the invention can be (co)-polymerised by any suitable means of polymerisation well known to those skilled in the art. Examples of suitable methods comprise: thermal initiation; chemical initiation by adding suitable agents; catalysis; and/or initiation using an optional initiator followed by irradiation, for example with electromagnetic radiation (photo-chemical

initiation) at a suitable wavelength such as UV and/or with other types of radiation such as electron beams, alpha particles, neutrons and/or other particles .

The substituents on the repeating unit of a polymer and/or oligomer may be selected to improve the compatibility of the materials with the polymers and/or resins in which they may be formulated and/or incorporated for the uses described herein. Thus the size and length of the substituents may be selected to optimise the physical entanglement or interlocation with the resin or they may or may not comprise other reactive entities capable of chemically reacting and/or cross linking with such other resins as appropriate.

Examples

The present invention will now be described in detail with reference to the following non limiting examples which are by way of illustration only.

The following abbreviations are used herein for example for various ingredients which are identified by chemical name and/or trade-name and optionally their manufacturer or supplier from whom they are available commercially.

Monomers "AA" denotes acrylic acid. "BA" denotes butyl acrylate. "MMA" denotes methyl methacrylate. "VA" denotes vinyl acetate.

Surfactants

"A102" denotes Aerosol ^® A-102, the anionic surfactant available commercially from Cytec under this trade mark as an aqueous dispersion of 30% total solids by weight of a di-sodium ethoxylated alcohol half ester of sulfosuccinic acid.

® ®

"AB20" denotes Abex AB 20 (also known as Rhodapex AB 20), the anionic surfactant available commercially from Rhodia under these trade names as an aqueous dispersion of 30% total solids by weight of an ammonium fatty alcohol ether sulfate (number of EO repeat units is 9, alkyl radical: Ci ₂ -Is)-

® "AB2535" denotes Abex 2535, the non-ionic surfactant available commercially from

Rhodia under this trade name as an aqueous dispersion of 50% total solids by weight of an aqueous solution of a fatty alcohol ether (number of EO repeat units is 40)

"L22" denotes Rhodapon L-22, the anionic surfactant available commercially from Rhodia under this trade name as an aqueous dispersion of 28% total solids by weight of ammonium lauryl sulfate (ALS).

® "EST EO" denotes Rhodapex EST 30, the anionic surfactant available commercially from

Rhodia under this trade name as an aqueous dispersion of 30% total solids by weight of a sodium fatty alcohol ether sulfate, (number of EO repeat units 3, alkyl radical: C ₁ 3). "RS610" denotes Rhodafac RS-610A-25, the anionic surfactant available commercially from Rhodia under this trade name as an aqueous dispersion of 25% total solids by weigh of an ammonium hexa(oxyethylene) tridecyl ether phosphate (i.e. number of EO repeat units is 6, alkyl radical: C13) .

"DS4" denotes Rhodacal DS-4, the anionic surfactant available commercially from Rhodia under this trade name as an aqueous dispersion of 23% total solids by weight of sodium dodoecyl benzene sulfonate (SDBS).

Other ingredients or abbreviations

"EO" denotes ethoxy (e.g. repeat unit in a polyether moiety).

"KPS" denotes potassium persulfate. "PO" denotes propyloxy (e.g. repeat unit in a polyether moiety).

"t-BHP" denotes tert. butyl hydroxy peroxide.

"SFS" denotes sodium formaldehyde sulfoxylate available commercially from Brueggeman

Chemical under the trade name Bruggolite FF-6.

"SPS" denotes sodium persulfate. "ZFS" denotes the zinc formaldehyde sulfoxylate available commercially from Henkel under the trade name Parolite.

Examples 1 to 3 of the current invention and comparative examples Comp A to F herein were prepared, characterised and tested by the methods given below with reference to Tables 1 to 4 herein.

Preparation of pre-emulsion and optionally polymerisation (see Tables 1 and 2)

The following standard method is used herein to prepare pre-emulsions and then a polymeric latex by emulsion polymerisation of the pre-emulsion if stable.

Standard method

In a two litre jacketed glass reactor equipped with a condenser, thermocouple and an agitator, T g of de-ionised water (DIW), 'ii' g of sodium bicarbonate (Na ₂ COs) and 'iii' g of a suitable persulfate is added. Slowly flowing nitrogen is used to purge the air from the reactor. In a delay container 'iv' g of surfactant 'SV and V g of surfactant 'S2' is dissolved in 'vi' g de-ionised water. In separate container, 'vii' g of monomer 'MV, 'viii' g of monomer 'M2', 'ix' g of monomer 'M3' and 'x' g of monomer 'M4' are pre-mixed. The monomer mixture is dissolved in the aqueous solution of surfactant under agitation for 45 min to form a thick, white pre-emulsion (PE). The reactor is heated to 82°C and when the reactor

temperature reaches 79°C addition of the pre-emulsion (PE) is started at a rate of 'xi' g/min. over 180 minutes, whilst the temperature is maintained at 82.5°C. After the delay complete, the reaction is held for another 45 minutes, after which the reactor is cooled to 60°C, and a redox initiator system of 'xii' g of initiator component '11 ' and 'xiii' g of initiator component 'I2' dissolved in 'xiv' g of de-ionised water is added. After 30 minutes at 60°C the reactor is cooled to the room temperature and the latex is filtered.

The data for preparing the pre-emulsions are set out in Table 1. The amount of surfactant used is given as the weight of the surfactant products described above supplied as aqueous dispersions with the total solid content as specified above. The pre-emulsions (P- E) of Examples 1 to 3 and Comp A to F are formed with reference to the standard method and the data in Table 1 and the stability of each P-E is observed over 24 hours.

The P-E of Comp A to F (using prior art surfactants) are unstable as phase separation was observed after from 1 to 5 hours (as indicated in Table 1 ). Therefore the P-E-of Comp A to

F are insufficiently stable to undergo emulsion polymerisation and no polymer latex could be obtained from them. In contrast the P-E of Examples 1 to 3 of the invention are stable for at least 24 hours and so undergo emulsion polymerisation (see Table 2) to form polymeric lattices which are further characterised (see Table 3). These lattices are then formulated as PSAs whose properties are tested (see Table 4).

Table 1 Formation of pre-emulsion (P-E) and test for stability

Table 2 Polymerisation of stable pre-emulsions (Examples 1 to 3 only)

Characterisation of polymer lattices (see Table 3)

The latex has 'xv % solids content, determined by placing known amount of latex into a weighed aluminium weighing tin, drying at 150°C for 60 minutes, weighing the tin again and calculating the solids. The Brookfield viscosity is 'xvi' cps (spindle #3/30, LVT). The average particle size (av. PS) is 'xvi' nm as measured by a Horiba laser light scattering particle size distribution analyzer model LA-910. The pH was 'xvii' as measured by an Orion model pH meter.

Table 3 Latex properties

In Table 3 the non SI unit 'cps' (centipoise) for viscosity can be converted to the SI unit of Pa. s by dividing the 'cps' value by 1000.

Formulation of PSA and testing (see Table 4)

The latex is neutralized with ammonium hydroxide to a pH of 7.04 and then mixed with 25% (w/w) of hydrocarbon tackifier to form a formulated PSA which is then coated on a 1 mil Mylar film. The film is air dried for 15 minutes and heat dried at 90°C for 5 minutes. The adhesive dry film coated on Mylar is laminated with a release liner.

Peel

Samples of laminated film measuring 1 "x 5" are applied to a substrate, for example stainless steel (SS) or high density polypropylene (HDPP). The laminate is peeled off after 20 min and 24 hours of aging using an lnstron machine with speed 12.57min. The respective peel values in adhesive failure (AF) and cohesive failure (CF) are measured.

Shear

The shear value is determined by applying 0.25" x 0.25" samples of the laminated film to a substrate. The substrate with the laminated film is hung vertically and a 1 Ib weight is hung from the film. The shear is measured by the time taken for the film to be removed from the substrate. In Table 3 'NM' indicates the property was not measured.

Table 4 PSA properties

In Table 4 the non SI unit Ib/in' (pound force per inch) for peel can be converted to the SI unit Nm ^"1 by multiplying the 'Ib/in' value by 175.127 (3 d.p.).