GB2386898A

GB2386898A - Aqueous polyurethane dispersion comprising polytetrahydrofuran polyol

Info

Publication number: GB2386898A
Application number: GB0305943A
Authority: GB
Inventors: Philip Cheshire; Richard Follows; David Alan Pears
Original assignee: Avecia Ltd
Current assignee: Avecia Ltd
Priority date: 2002-03-27
Filing date: 2003-03-17
Publication date: 2003-10-01
Also published as: GB0305943D0; GB0207205D0

Abstract

An aqueous polyurethane dispersion comprises a polyurethane obtained by the reaction of: <SL> <LI>(A) an isocyanate-terminated prepolymer formed from components which comprise <SL> <LI>(i) 10 to 25 wt% of polyisocyanate(s); <LI>(ii) 40 to 80 wt% of polytetrahydrofuran polyol(s); <LI>(iii) 0 to 5 wt% of polyol(s) containing ionic or potentially ionic water-dispersing groups having two or more isocyanate-reactive groups; <LI>(iv) 0 to 50 wt% of a component(s) not comprised by (i), (ii) or (iii); where (i), (ii), (iii) and (iv) add up to 100 wt%; </SL> and <LI>(B) an active-hydrogen chain extending compound. </SL> Also claimed are polyurethane dispersions wherein the polyisocyanates comprise a mixture of hexamethylene diisocyanate and isophorone diisocyanate. An adhesive composition according to the formulation is also claimed. The dispersion may be used to form a glove by a dipping process.

Description

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ELASTOMERIC POLYURETHANE DISPERSIONS BASED ON

POLYTETRAHYDROFURAN

This invention relates to aqueous polyurethane dispersions, a process for the manufacture of such dispersions, and films and articles made therefrom. The invention further relates to the use of such dispersions in adhesive compositions.

Many articles for diverse medical and industrial applications, such as gloves, 5 contraceptive devices, catheters, balloons, wound care, tubing and swimming caps, are manufactured from elastomeric materials. Such products have been manufactured from rubber latex but there are inherent problems in consistency of manufacture, bacterial degradation of the latex, and allergic reactions to the natural rubber latex.

Synthetic alternatives to natural rubber latex include polychloropropene, nitrile, lo styrenic thermoplastic elastomers (TPEs) and polyurethanes. Physical properties of the materials which are important include tensile strength, modulus, recovery and stress relaxation, as defined herein.

In addition, the presence on articles of residual accelerator from the polymerization process of, for example, polychloropropene or nitrile is undesirable for toxicity and 15 dermatological reasons. Polyurethane articles and polyurethane coated articles contain no such accelerator residues. WO 99/23129 discloses the preparation of waterborne polyurethanes with film properties comparable to natural rubber latex. Examples therein are based on polyester dials or combinations of polyester and polypropyleneglycol (PPG) dials go Aqueous polyurethane dispersions based on PPGs may be prepared with very low modulus but tend to have inadequate tensile strength, recovery and stress relaxation.

Sterilisation by y-irradiation of articles made from PPG based polyurethane gloves has been found to result in a loss of tensile strength and an increase in stickiness of the polyurethanes caused by the y-irradiation which may be due to chain cleavage.

2s DE 19708451 A1 discloses the preparation of thin-walled flexible articles from polyurethane dispersions which comprise prepolymers formed from polytetrahydrofuran dials and PPGs in combination with dimethylolpropionic acid (DMPA) at levels of at least 2.7 wt%.

It has been found that improved properties can be achieved by using polyurethane 30 compositions which are based on polytetrahydrofuran polyols and which incorporate lower levels of DMPA.Use of polytetrahydrofuran dials allows polyurethane dispersions to be obtained with optimum elastomeric properties and the best balance of high tensile strength, low modulus and good recovery to be achieved.

The invention relates to an aqueous polyurethane dispersion comprising a 35 polyurethane obtained by the reaction of: (A) an isocyanate-terminated pre-polymer formed from components which comprise (i) 10 to 25 wt% of a polyisocyanate(s);

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(ii) 40 to 80 wt% of a polytetrahydrofuran polyol(s); (iii) 0 to 2 wt% of a polyol(s) containing ionic or potentially ionic water-dispersing group(s) having two or more isocyanate-reactive groups; (iv) 0 to 50 wt% of a component(s) not comprised by (i), (ii) or (iii); 5 where (i), (ii), (iii) and (iv) add up to 100 wt%; and (B) an active-hydrogen chain extending compound.

Component (i) may be any aliphatic, cycloaliphatic or aromatic polyisocyanate known in the art. Examples include but are not limited to aliphatic polyisocyantes such as 10 ethylene diisocyanate, hexamethylene diisocyanate (HDI), isophorone diisocyanate (IPDI), cyclohexane-1,4diisocyanate, 4,4'-dicyclohexylmethane diisocyanate (commercially available as Desmodur_ W from Bayer Coating Division), 2,474-trimethyl hexamethylene diisocyante (TMDI) and tetramethylxylene diisocyanate (TMXDI); aromatic polyisocyanates such as polymethylene polyphenyl polyisocyanates for example Is 2,4-toluene diisocyanate, 2,6-toluene diisocyanate, 4,4'-diphenylmethane diisocyanate and its hydrogenated derivatives, 2,4'-diphenylmethane diisocyanate and its hydrogenated derivatives and 1,5-naphthylene diisocyanate; and/or mixtures thereof.

Component (i) is preferably a diisocyanate. More preferably component (i) is selected from hexamethylene diisocyanate and/or isophorone diisocyanate, most preferably o hexamethylene diisocyanate.

Especially preferably component (i) is a mixture of hexamethylene diisocyanate and isophorone diisocyanate. Preferably component (i) comprises a mixture of hexamethylene diisocyanate and isophorone diisocyanate in the molar ratio in the range from 1:10 to 10:1, more preferably in the range from 1:9 to 9:1 and especially in the range 2s from 3:7 to 7:3. Component (i) may also comprise up to 5% by weight of an organic triisocyanate or polyisocyanate.

Preferably component (i) forms 10 to 20 wt% of the isocyanate-terminated prepolymer, more preferably 14 to 18 wt%. Where component (i) comprises an aromatic isocyanate it preferably forms 0 to 13 wt% of the isocyanateterminated prepolymer, more o preferably 0 to 11 wt%, most preferably 0 to 9 wt%.

Preferably component (ii) comprises polytetrahydrofuran polyol(s) having a number average molecular weight in the range from 500 to 4000 Daltons, more preferably in the range from 1000 to 3000 Daltons, most preferably in the range from1500 to 2500 Daltons. An especially preferred polytetrahydrofuran polyol has a number average 3s molecular weight in the range from 1900 and 2100 Daltons. A suitable example includes Polymeg 2000 available from Penn Specialty Chemicals Inc. Preferably component (ii) forms 50 to 75 wt% of the isocyanate-terminated prepolymer, more preferably 60 to 70 wt%. Component (iii) providing ionic water-dispersing groups preferably has two 40 isocyanate-reactive groups. Preferred isocyanate-reactive groups are selected from -OH,

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-NH2, -NH- and -SH. These isocyanate-reactive groups are capable of reacting with an isocyanate group in component (i). Component (iii) may comprise polyols having three or more isocyanate-reactive groups in low levels, preferably not exceeding 5% by weight relative to the total weight of component (i).

s The ionic water-dispersing groups may be cationic, anionic or a mixture of cationic and anionic water-dispersing groups. Preferred ionic waterdispersing groups include cationic quaternary ammonium groups and anionic phosphoric acid groups, sulphonic acid groups and carboxylic acid groups. More preferred ionic water-dispersing groups are sulphonic acid groups, carboxylic acid groups and quaternary ammonium groups. The 0 ionic waterdispersing groups may be incorporated into the polyurethane in the form of low molecular weight monomers, for example polyols or polyamines bearing the appropriate ionic water-dispersing groups. Preferred isocyanate-reactive compounds providing ionic water-dispersing groups are dials having one or more carboxylic acid groups or sulphonic acid groups, where examples include bis(2-hydroxyethyl)-isophthalate-5-sulphonic acid 5 and dibydroxy alkanoic acids, especially 2,2-dimethylol propionic acid and dials having quaternary ammonium groups such as quaternary ammonium salt dials or protonated amine dials, for example dimethanol diethyl ammonium bromide.

The carboxylic acid and sulphonic acid groups may be subsequently fully or partially neutralized with a base to give a salt. If the carboxylic acid or sulphonic acid JO groups are used in combination with a non-ionic water-dispersing group, neutralization may not be required. The conversion of any free acid groups into the corresponding salt may be effected during the preparation of the polyurethane.

Preferably the base used to neutralise any anionic water-dispersing groups is ammonia, an amine or an inorganic base. Suitable amines are tertiary amines, for 2s example triethylamine or triethanolamine. Suitable inorganic bases include alkaline hydroxides, oxides and carbonates, for example lithium hydroxide, sodium hydroxide, or potassium hydroxide. A quaternary ammonium hydroxide, for example N+(CH3)40H-, can also be used. Generally a base is used which gives the required counter ion desired for the aqueous dispersion which is prepared from the polyurethane. For example, suitable so counter ions include Li+, Ma+, K+, NH4+, Cs+ and substituted ammonium salts, including tributylammonium, imidazolium, tetramethyl ammonium, tetraethyl ammonium, tetrabutyl ammonium, tetrabutyl phosphonium and trimethyl sulphonium salts and mixtures thereof.

NH4+ or a mixture of Li+ and Na+ is especially preferred. Preferred polyurethanes comprising component (iii) as described above have an acid value in the range from 0 to 3s 22 mg KOH/g.

Preferably component (iii) forms 0 to 1.8 wt% of the isocyanate terminated prepolymer. However, the level of component (iii) may form up to 0 to 5 wt% of the isocyanate terminated prepolymer if, for example, component (i) comprises a mixture of HMDI and IPDI; or, if the aqueous dispersion of the invention is used as, for example, an 40 adhesive. Thencomponent (iii) preferably forms O to 4 wt% of the isocyanate- terminated

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prepolymer, more preferably O to 3 wt%, especially 0 to 2 wt%, more especially 0 to 1.8 wt%. Component (iv) preferably comprises organic polyols or polyamines having a molecular weight up to 3000, more preferably up to 2000, especially from 250 to 2000.

5 Preferred organic polyols include diols which are free from ionic waterdispersing groups and mixtures thereof. Such diols may be members of any of the chemical classes of polymeric diols used or proposed to be used in polyurethane formulations. In particular the diols may be polyesters, polyesteramides, polyethers, polythioethers, polycarbonates, polyacetals, polyolefins, polysiloxanes or C2'0 diols and/or mixtures thereof. Particularly to preferred diols for the present application include polypropylene glycols, especially those containing random ethylene oxide units such as Acclaim P2220N (available from Bayer) and simliar products.

Further examples of diols which are free from ionic water-dispersing groups include organic diols and polyols having molecular weights below 400. Examples of such lower molecular weight diols and polyols include ethylene glycol, diethylene glycol, tetraethylene glycol, butanediol, hexane dial, neopentyl glycol, propylene glycol, bis(hydroxyethyl) terephthalate, cyclohexane dimethanol, furan dimethanol, polyethylene glycol and polypropylene glycol.

Component (iv) may also comprise isocyanate-reactive compounds providing 20 non-ionic water dispersing groups. Preferred non-ionic waterdispersing groups are in chain, terminal and pendant polyoxyalkylene groups, preferably polyoxypropylene and polyoxyethylene groups. Examples include groups of the formula: RO(CH2CH2O)nH, RO(CH2CH2O)n(CH2CH(CH3)O) yCH2CH(CH3)NH2' or H2NCH(CH3)CH2(CH(CH3)CH2O)y (CH2CH2O)n(CH2CH(CH3)O) yCH2CH(CH3)NR'R,, wherein n = 1 to 100, R is H or CH3, 25 each R' independently is H or a substituted or unsubstituted C, JO alkyl group (especially -CH2CH2-OH) and y = 2 to 15.

Preferably component (iv) forms O to 50 wt% of the isocyanate-terminated prepolymer, more preferably O to 35 wt%, most preferably 0 to 25 wt% and especially 5 to 25 wt%.

30 The active-hydrogen chain extending compound (B) is preferably selected from but not limited to amino-alcohols, primary or secondary diamines or polyamines, hydrazine, and substituted hydrazines. Examples of such chain extenders include but are not limited to alkylene diamines such as ethylene diamine, 1,3-diamino-2-hydroxypropane and rn xylylenediamine; cyclic amines such as isophorone diamine, hydrazine and 1,4 35 diaminocyclohexane; substituted hydrazines such as, for example, dimethyl hydrazine, 1,6-hexamethylene-bis-hydrazine; carbodihydrazide; hydrazides of dicarboxylic acids and sulphonic acids such as adipic acid dihydrazide, oxalic acid dihydrazide and isophthalic acid dihydrazide. Water itself may be effective as an indirect chain extender.

Where the chain extender is other than water, for example a polyamine or 40 hydrazine, it may be added to the aqueous dispersion of the isocyanateterminated

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prepolymer or, alternatively, it may already be present in the aqueous medium when the isocyanate-terminated prepolymer is dispersed therein. The isocyanate-terminated prepolymer may also be chain extended to form the polyurethane while dissolved in organic solvent (usually acetone) followed by the addition of water to the solution until 5 water becomes the continuous phase and the subsequent removal of the solvent by distillation to form an aqueous dispersion.

In a second embodiment of the present invention there is provided an aqueous polyurethane dispersion comprising a polyurethane obtained by the reaction of: (A) an isocyanate-terminated pre-polymer formed from components which comprise 0 (i) 10 to 25 wt% of a mixture of hexamethylene diisocyanate and isophorone diisocyanate in a molar ratio in the range from 1:10 to 10: 1; (ii) 40 to 80 wt% of a polytetrahydrofuran polyol(s); (iii) O to 5 wt% of a polyol(s) containing ionic or potentially ionic water-dispersing group(s) having two or more isocyanate-reactive groups; 5 (iv) 0 to 50 wt% of a component(s) not comprised by (i), (ii) or (iii); where (i), (ii), (iii) and (iv) add up to 100 wt%; and (B) an active-hydrogen chain extending compound.

In a third embodiment of the present invention there is provided an aqueous polyurethane JO dispersion comprising a polyurethane obtained by the reaction of: (A) an isocyanate-terminated pre-polymer formed from components which comprise (i) 10 to 25 wt% of a mixture of hexamethylene diisocyanate and isophorone diisocyanate in a molar ratio in the range from 1:10 to 10:1; (ii) 40 to 80 wt% of a polytetrahydrofuran polyol(s); :5 (iii) 0 to 2 wt% of a polyol(s) containing ionic or potentially ionic water-dispersing group(s) having two or more isocyanate-reactive groups; (iv) O to 50 wt% of a component(s) not comprised by (i), (ii) or (iii); where (i), (ii), (iii) and (iv) add up to 100 wt%; and 30 (B) an activehydrogen chain extending compound.

The use of crosslinkers to improve the properties of films formed from the dispersions of the present invention, particularly sterilium resistance, was also found to be beneficial.

The polyurethane dispersion may therefore additionally comprise at least one cross-linker in an amount in the range from O to 5 wt%, preferably 0 to 3 wt%, more preferably 0 to 2 35 wt% most preferably 0 to 1 wt%, especially preferably around 0.5 wt% based on % solids of the polyurethane. Higher levels of crosslinker may have adverse effects on the tear strength of the films. The cross-linker is preferably selected from but not limited to the group comprising the following types: ureaformaldehyde, melamine-formaldehyde, carbodiimide, aziridine, epoxy, silanes and/or mixtures thereof. More preferably the 40 crosslinker is selected from carbodiimide, urea-formaldehyde or melamine-formaldehyde

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crosslinkers such as CX100 (from Avecia bv.), Cymel_ 3717 (from Cytec Norge KS, Svelleveien,N-2000 Lillestrom, Norway) and/or Dynamin UM15 (also available from Cytec). The polyurethane dispersion may also be selfcrosslinking by incorporation of functional monomers which are mutually reactive on heat curing. In a fourth embodiment 5 of the present invention, there is provided a process for the manufacture of a polyurethane dispersion as described above which comprises the following steps: a) reaction of components (i) to (iv) to form an isocyanateterminated prepolymer; b) dispersion of the isocyanate-terminated prepolymer in water; c) chain extension of the isocyanate-terminated prepolymer by reaction with an to active-hydrogen chain extending compound; and d) optionally adding cross-linker.

For step (a), as is well known in the art, temperatures of from 30 C to 130 C are preferred and the reaction is continued until the reaction between the isocyanate groups and the isocyanate-reactive groups is substantially complete, this being ascertained by Is measuring the NCO content of the isocyanate-terminated prepolymer according to standard methods. The relative amounts of components (i), (ii), (iii) and/or (iv) are preferably selected such that the mole ratio of isocyanate groups to isocyanate-reactive groups is in the range of from 1.1:1 to 2.5:1. Neutralisation of any ionic group(s) on the prepolymer, arising from component (iii), may be carried out directly on the isocyanate 20 terminated prepolymer before it is dispersed in water, or as it is dispersed by mixing the appropriate amount of neutralising agent with the water prior to addition of the isocyanate terminated prepolymer, or by simultaneous addition to the water as the isocyanate terminated prepolymer is added, which has the advantage of avoiding excessive hydrolysis of the isocyanate groups. The dispersion and chain extension steps (b) and (c) 25 may be carried out in either order.

When forming films and/or articles from these compositions, physical properties which are important include tensile strength, modulus, recovery and stress relaxation.

Tensile strength is the maximum stress a material subjected to a stretching load can withstand without tearing. The modulus is the ratio of the increment of a specified form of 30 stress to the increment of a specified strain. Stress relaxation is the load after 10 minutes divided by the initial peak load multiplied by 100. Elongation at break is the percentage increase in length of a material when subjected to a stress just sufficient to cause tearing.

Recovery is the time taken for the material to return to its original length having been elongated by a fixed percentage.

35 A fifth embodiment of the present invention relates to a film derived from a polyurethane dispersion as described above. Such a film preferably has a tensile strength of > 10 MPa, more preferably > 15 MPa, most preferably > 21 MPa. The percentage elongation at break of the film is preferably 400%, more preferably > 500% most preferably > 600%. The stress relaxation of the film is preferably 50%, more preferably > 40 60% most preferably > 70%. The film preferably has a modulus at 100% of < 2. 0MPa,

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more preferably < 1.7MPa, most preferably < 1.4MPa. The film preferably has a modulus at 500% of <5.5 MPa.

A sixth embodiment of the present invention relates to articles formed from a polyurethane dispersion as described above, or to articles coated with such a 5 polyurethane dispersion. Such articles include but are not limited to gloves, contraceptive devices, catheters, balloons, wound care films, tubing and swimming caps. Preferably the article is a glove or a condom.

Articles may for example be formed by electrodeposition or by dipping. When articles according to the invention are gloves or condoms they are preferably formed by to dipping; dipping may be either coagulative dipping or straight dipping, preferably straight dipping is used.

In coagulation dipping an appropriate-shaped former is dipped into a coagulant bath (usually calcium nitrate), dried and then dipped into a latex. The latex is coagulated onto the former very rapidly and the coagulum then goes through various drying and 15 washing cycles. The use of coagulation dipping is well known in the art for dispersions of rubber, nitrite and polychloroprene but for polyurethane dispersions may give poor coalescence and also may cause an undesirable increase in modulus. A method for coaglation dipping has been described (JS Sadowski, Elastomerics, August 1978) but the polyurethane composition was not disclosed. US 5977223 claims a process for fabricating 20 a thin-walled polyurethane article by coagulation dipping by using very large particle size polyurethanes swollen with plasticiser and use of a surfactant.

Particularly preferred in the present invention is straight dipping of the polyurethane dispersion, avoiding the use of coagulant on the former. To avoid the polyurethane dispersion running off the former and to avoid multiple dipping to achieve the 25 required glove thickness the polyurethane dispersion should have a suitable rheology so that when a hand shaped former is dipped into the polyurethane dispersion bath and withdrawn slowly, it does not all run off and leave a very thin film requiring many dips. The desired rheology may be achieved inter alla by using hexamethylene diisocyanate (HDI) in the prepolymer and controlling the solids level of the polyurethane dispersion. A mixture of 30 hexamethylene diisocyanate and isophoronediisocyanate (IPDI) as described above in a ratio of 1:10 to 10:1 was found to give an optimum balance of theological properties and film properties. Furthermore, lower levels of HDI were found to allow a higher solids content to be achieved. Optionally theological aids may be used to increase the low shear viscosity of the polyurethane dispersions such as for example Tafigel_ PUR40 and 35 60 or cellulose/acrylic/metal complexation which is known for use in non-drip latex paint technology. Preferably articles of the present invention are made with 2 dips, more preferably 1 dip. Coating thicknesses may be further controlled by the temperature of the former and the temperature of the polyurethane dispersion in the dip tank as well as the dip speed, solids, pH and rheology of the polyurethane dispersion.

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A seventh aspect of the present invention relates to an adhesive composition comprising an aqueous polyurethane dispersion comprising a polyurethane obtained by the reaction of: (A) an isocyanate-terminated pre-polymer formed from components which comprise 5 (i) 10 to 25 wt% of a polyisocyanate(s); (ii) 40 to 80 wt% of a polytetrahydrofuran polyol(s); (iii) 0 to 5 wt% of a polyol(s) containing ionic or potentially ionic water-dispersing group(s) having two or more isocyanate-reactive groups; (iv) 0 to 50 wt% of a component(s) not comprised by (i), (ii) or (iii); 0 where (i), (ii), (iii) and (iv) add up to 100 wt%; and (B) an activehydrogen chain extending compound.The invention is now described by means of example only.

s Examples

1. Polyurethane dispersions Dispersion 1.1 20 Prepolymer preparation Molten Poly THE 2000 dial (Quaker Oats Polymeg 2000 Mn 1935) (2091.8g), PPG dial with EO (Bayer Acclaim P2220N Mn 2304) (375. 09) and NMethylpyrrolidinone (N M P) (Aldrich) (182.4g) were charged to a 5 litre 4-necked resin flask fitted with a mechanical 25 stirrer, water condenser and under nitrogen. IPDI (Aldrich) (368.79) and HDI (Fluke) (119 5g) were added with stirring at 30 to 35 C. The temperature was raised to 95 C and held for 2 hours. Ground dimethylolpropionic acid (DMPA) (Aldrich) (45.0g) and NMP (60.8g) were added to the reactor and the temperature was held at 95 C for a further 2 hours. A sample was removed for NCO % determination and the NCO % was found to be 30 2.00%. The prepolymer temperature was allowed to fall to 75 C. Triethylamine (TEA) (Aldrich) 27. 1g was then added down the condenser and stirred with the prepolymer for 20 minutes. The neutralised prepolymer was held at 75 C until ready to disperse.

Chain extension Distilled water (4206g) and TEA (1.02g) were charged to a 10-litre baffled, flanged flask equipped with a mechanical stirrer, thermocouple and the temperature was stabilised at 25 C. Neutralised prepolymer prepared in 1.1 above (3222.0 9) was added over 1 hour with stirring whilst maintaining a temperature of 25 C to give a dispersion. After 10 mins, 40 hydrazine monohydrate 34.27g as a 25% aqueous solution was added over 5 minutes

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and washed in with 25g of water. The dispersion was stirred for 4 hours after hydrazine addition and filtered through a 50pm cloth to give Dispersion 1.1.

Analysis of Dispersion 1.1 pH = 7.45 Solids = 39.36% Brookfield Viscosity: Spindle 2 RV Set at 20.0 C = 1.36 kg.m'.s' at 0.5 rpm and 0.203

kg.m'.si at 1 OOrpm o Particle size = 1 83nm.

Polyurethane dispersions 1.2 to 1.4 Three further polyurethane dispersions, 1.2 to 1.4, were prepared in a similar fashion, using the component compositions given in Table 1 below for preparation of the prepolymer, wherein the parts given are parts by weight. Dispersions were all neutralized as above with TEA and extended with hydrazine hydrate.

Table 1

Dispersion number DMPA IPDI HDI mole ratio Acclaim Polymeg IPDI:HDI P2220N 2000

_ 1.2 1.0 16.3 0 15.0 67.7 _

1.3 1.0 4.9 8.7 3:7 18.0 67.4

1.4 1.2 8.4 6.4 1:1 15.0 69.0

2. Cross Linker Addition 2.1 25 0.5% wt Cymel_ 3717 on solids was added to a 100g sample of Dispersion 1.1 as prepared above. After stirring for 30 minutes, the resultant dispersion was filtered through a 50pm cloth to give Dispersion 2.1.

2.2 A sample of dispersion 1.2 was diluted with water to reduce solids to 30%. After stirring 30 for 5 minutes, 1.5% wt of Dynomin UM15 on solids was added to the stirred blend followed by water to reduce solids to 30%. The blend was stirred for 1 hour and filtered through 50pm cloth to give 7403g of dispersion 2.2 2.3 Dispersion 2.3 was made in a similar manner to 2.2 by addition of 1.0% wt of Dynomin 35 UM15 on solids to dispersion 1.3.

2.4

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Dispersion 2.4 was made in a similar manner to 2.2 by addition of 0.5% wt of CX-100 on solids to dispersion 1.4.

3. Rheology Adjustment and Cross Linker Addition 5 TEA was added dropwise to 3 litres of Dispersion 1.1 as prepared above being stirred in a 5 litre flanged flask to pH 7.9, stirring continued for 30 minutes followed by filtration through a 50m cloth.

Brookfeld Viscosity Spindle 3 RV Set at 20.2 C = 7.2 kg.m'.s' at 0.5 rpm and 0.492 kg.m.s' at 100rpm. This rheology adjusted Dispersion 1.1 was stirred mechanically and lo 1 wt% Cymel 3717 was added. Stirring was continued for 30 minutes before filtering through a 50m cloth to give Dispersion 3.1.

4. Film Testing 1 5 Resistances Films were cast from Dispersions 1.1 to 3. 1 onto 230 x 300 mm glass plates using a 300K bar and allowed to dry at room temperature followed by 30 minutes at 120 C in an air circulating fan oven. After cooling to room temperature, 1 Omm wide strips were cut from the film using a scalpel and a steel template. Strips had a film thickness of between 0.100 20 and 0.112 mm. The strips were then tested for their resistance to typical surgeons' alcoholic hand scrubs by manually stretching the strips to 300% elongation in a horizontal plane and placing two drops of Desderman_ or Sterillium_ (available from Schulker & Mayr UK Ltd or Bode Chemie Hamburg) on to the strips. After exposure for 5 minutes the films retained good strength.

Physical Properties Films were cast from Dispersion 1.1 onto 230 x 300 mm glass plates using a 300K bar and allowed to dry at room temperature followed by 30 minutes at 120 C in an air circulating fan oven. After cooling to room temperature, 15mm wide and 50mm sample o length strips were cut from the film using a scalpel and a steel template. The strips were then tested for their modulus, tensile strength and elongation at break at room temperature using a Testometric Micro 250-12.5A)C tensometer using a 500N load cell, 25mm wide pneumatic grips and a speed of 500mm/min.

35 Stress Relaxation Strips prepared as above were stretched to 100% elongation and initial load and load after ten minutes was noted. Final load divided by initial load expressed as a percentage is equal to the stress relaxation.

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1 1 Results Table 2

Dispersion Tensile 100% 500% Stress number strength elongation modulus modulus relaxation (MPa) at break (MPa) (MPa) (%) 1.1 29.5 1129 1. 25 1.94 64.5

1.2 12.4 >1000 1.2 1.44

1.4 13.2 1482 1.05 1.57 54

2.1 25.4 1022 1.21 2.17 72.4

2.2 37.6 >1000 1.56 3.14 68.0

2.3 20.2 715 1.54 57.8

2.4 17.0 1793 1.29 1.79 63

3.1 30.7 911 1.39 4.08 77.1

5. Surnical Glove Preparation 5.1 Straight Dipping - Four Dips lo 2.9 litres of Dispersion 1.1 was left in a 3 litre, tall-form beaker to deaerate. A hand shaped ceramic former was dipped into Dispersion 1.1 and withdrawn at 150mm/min.

The former was removed from the dipping machine, held horizontal androtated slowly manually about 1.5m from a domestic cooling fan for 3 minutes. The former was then placed in a 120 C, air circulating oven for 3 minutes. The former was removed and 15 rotated in front of the fan until cooled to almost room temperature. The process was repeated a further three times. After the fourth dip and 3 minutes in front of the fan and three minutes at 120 C, a bead was rolled on the cuff and the glove was dried for a further 20 minutes at 120 C. The former was removed from the oven and cooled to about 60 C and immersed in distilled water at 60 C containing 0.15% Silicone 200 emulsion.

so The glove was then removed from the former, washed inside and out in the silicone solution followed by draining and drying on each side for 3 minutes at 120 C. The glove was easy to put on, of good appearance, free from defects and could be worn comfortably. There was no hand or finger fatigue when the hand was continually opened and closed.

5.2 Straight Dipping - Two Dips A glove was formed using a similar process to that described above in 5.1, but with only two dips. After the first dip, the former was stood vertically in front of the fan, oven dried

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at 60 C and at 120 C for 5 minutes each. After the second dip the former was fan dried vertically and oven dried at 60 C for 5 minutes each. A bead was rolled on the cuff, followed by oven drying at 90 C for 10 minutes and then 120 C for 20 minutes. The glove was easy to put on, of good appearance, free from defects and could be worn s comfortably. There was no hand or finger fatigue when the hand was continually opened and closed.

5.3 Coagulative Dipping lo A 3 litre, tall form beaker containing 2.9 litres of a 25%w/w aqueous solution of technical grade calcium nitrate and 1.45g Triton X-100 (non-ionic surfactant) was heated to 60 C. A hand shaped ceramic former, heated to 60 C, was dipped into the solution and withdrawn manually. The former was held in a horizontal plane and rotated for 2 minutes. The former was then attached to the dipping machine, lowered quickly into Dispersion 3.1 5 (rheology adjusted, phi 7.9), held for 5 seconds and then raised at 25mm/sec. The former was covered with a smooth, glossy white gel coating. Shrinkage of the wet gel was minimal (2. 5%) and no cracking was observed. The wet gel had good strength, was rinsed with deionised water and left to dry at room temperature. A bead was rolled on the cuff and the former was placed in an air circulating oven at 120 C for 30 minutes. The former 20 was removed from the oven and cooled to about 60 C and immersed in distilled water at 60 C containing 0. 15% Silicone 200 emulsion. The glove was then removed from the former, washed inside and out in the dilute silicone emulsion followed by draining and drying on each side for 3 minutes at 120 C. The glove was easy to put on, of good appearance, free from defects and could be worn comfortably. There was no hand or :25 finger fatigue when the hand was continually opened and closed.

Table 3

Average Glove Thickness Measurements (all thicknesses in,um) straight (4 dips) straight (2 dips) coagulative 25mm from bead 186 181 186 palm 206 206 193 back 237 224 233 finger 250 232 238 6. Adhesive examples Dispersion 4.1 was made according to the method described above for Dispersion 1.1, using the following components: 35 Prepolymer: DMPA (12. 00g), Acclaim P2220N PPG (180.00g), Polymeg 2000 polyTHF (812.15g),

SMC 60506

IPDI (195.85g), NMP (97.30g). The prepolymer was then neutraiised with TEA (9.04g) and 1210.7g of this neutralized prepolymer was then dispersed in distilled water (1385g) and chain-extended with hydrazine (11.22g in 33.69 distilled water followed by 22.29 water wash-in). The polyurethane dispersion was then crosslinked by addition of 1.5% 5 Dynomin UM 15 to form Dispersion 4.1 6.1 Wood The ends of 2 x 600mm lengths of 40 x 18mm pinewood were roughly coated with formulated Dispersion 4.1 to give a100mm overlap and clamped overnight. The joint lo could not be separated with reasonable force (i.e. not even with a chemist weighing 92kg standing on one piece and the other being lifted by a chemist weighing 102kg).

6.2 Cotton 300 x 20mm wide strips of cotton labcoat were cut using a ruler and scalpel. The ends 15 were coated with formulated Dispersion 4.1 from a Pasteur pipette and allowed to soak into the cotton. More dispersion was added and the ends pressed together. The strips were hung to dry overnight. The joint could not be separated with reasonable force.

The formulated Dispersion 4.1 was cast into a film and allowed to dry overnight. A ho suitably sized piece of film was sandwiched between the ends of 2 cotton strips and the sandwich pressed with a hot domestic iron for 30 seconds and allowed to cool. The joint could not be separated with reasonable force.

Claims

SMC 60506 CLAIMS

1. An aqueous polyurethane dispersion comprising a polyurethane obtained by the reaction of: 5 (A) an isocyanate-terminated pre-polymer formed from components which comprise (i) 10 to 25 wt% of a polyisocyanate(s); (ii) 40 to 80 wt% of a polytetrahydrofuran polyol(s); (iii) O to

2 wt% of a polyol(s) containing ionic or potentially ionic water-dispersing group(s) having two or more isocyanate-reactive groups; 10 (iv) 0 to 50 wt% of a component(s) not comprised by (i), (ii) or (iii); where (i), (ii) , (iii) and (iv) add up to 100 wt%; and (B) an active-hydrogen chain extending compound.

5 2. A polyurethane dispersion according to claim 1 wherein component (i) is selected from the group consisting of: hexamethylene diisocyanate, isophorone diisocyanate, dicyclohexylmethane diisocyanate, 2,4,4trimethyl hexamethylene diisocyante, tetramethylxylene diisocyanate and/or mixtures thereof.

20

3. A polyurethane dispersion according to either of claims 1 or 2 wherein component (i) comprises O to 20 vat% of an aromatic polyisocyanate.

4. An aqueous polyurethane dispersion comprising a polyurethane obtained by the reaction of: 25 (A) an isocyanate-terminated pre-polymer formed from components which comprise (i) 10 to 25 wt% of a mixture of hexamethylene diisocyanate and isophorone diisocyanate in a molar ratio in the range from 1:10 to 10:1; (ii) 40 to 80 wt% of a polytetrahydrofuran polyol(s); (iii) O to 5 wt% of a polyol(s) containing ionic or potentially ionic water-dispersing 30 group(s) having tvo or more isocyanate-reactive groups; (iv) O to 50 wt% of a component(s) not comprised by (i), (ii) or (iii); where (i), (ii), (iii) and (iv) add up to 100 wt%; and (B) an active-hydrogen chain extending compound.

5. An aqueous polyurethane dispersion comprising a polyurethane obtained by the reaction of: (A) an isocyanate-terminated pre-polymer formed from components which comprise (i) 10 to 25 wt% of a mixture of hexamethylene diisocyanate and isophorone 40 diisocyanate in a molar ratio in the rangefrom 1:10 to 10:1;

SMC 60506

6. A polyurethane dispersion according to any one of the preceding claims wherein to component (ii) has a number average molecular weight in the range from 500 to 4000 Daltons.

7. A polyurethane dispersion according to any one of the preceding claims wherein component (iv) comprises a polyol selected from the group consisting of polyesters, 15 polyethylene glycols, polycarbonates, C2,0 dials and/or mixtures thereof.

8. A polyurethane dispersion according to any one of the preceding claims where the polyurethane has an acid value in the range from 0 to 22 mg KOH/g.

20

9. A polyurethane dispersion according to any one of the preceding claims wherein the active-hydrogen chain extending compound is selected from the group comprising amino-alcohols, primary or secondary diamines or polyamines, hydrazine, substituted hydrazines and substituted hydrazides.

25

10. A polyurethane dispersion according to any one of the preceding claims which additionally comprises at least one cross-linker in the range from 0 to 5 wt% based on solids of polyurethane.

11. A process for the manufacture of a polyurethane dispersion according to any one 30 of the preceding claims which comprises the following steps: a) reaction of components (i) to (iv) to form an isocyanate- terminated prepolymer; b) dispersion of the isocyanate-terminated prepolymer in water; c) chain extension of the isocyanate-terminated prepolymer by reaction with an active-hydrogen chain extending compound; and 35 d) optionally adding cross-linker.

12. A film obtained from a polyurethane dispersion as described in any of claims 1 to 10. 40

13. A film according to claim 12 with a modulus at 100% of c 2.0 MPa.

SMC 60506

14. An article formed from a polyurethane dispersion according to any one of claims 1 to 10.

5

15. An article coated with a polyurethane dispersion according to any one of claims 1 to 1 0.

16. A glove, formed from a polyurethane dispersion according to any one of claims 1 to 10.

17. A process for forming an article according to any one of claims 14 to 16 comprising a dipping process.

18. An adhesive composition comprising an aqueous polyurethane dispersion 15 comprising a polyurethane obtained by the reaction of: (A) an isocyanate-terminated pre-polymer formed from components which comprise (i) 10 to 25 wt% of a polyisocyanate(s); (ii) 40 to 80 wt% of a polytetrahydrofuran polyol(s); (iii) O to 5 wt% of a polyol(s) containing ionic or potentially ionic water-dispersing 20 group(s) having two or more isocyanate-reactive groups; (iv) O to 50 wt% of a component(s) not comprised by (i), (ii) or (iii); where (i), (ii), (iii) and (iv) add up to 100 wt%; and (B) an active-hydrogen chain extending compound.

19. An aqueous polyurethane dispersion substantially as described in any of the examples herein.

20. A process for forming an article substantially as described in any of the examples herein.

20. An article formed from a polyurethane dispersion substantially as described in any 30 of the examples herein.