SILICONE MODIFIED POLYURETHANES

Abstract: Silicone modified polyurethane compositions having low surface energy characteristics comprise a polyurethane matrix in which 1-30 % of a silicone compound is dispersed. The low surface energy of surface coatings comprised of these silicone modified polyurethanes provides environmentally safe and effective means of managing the effects of marine growth on vessels and static marine structures by the formation of a fouling release surface which enables simple and effective removal of marine organisms without damage to the surface coating. Silicone modified polyurethanes according to the invention also provide a useful alternative to polyester gel coats in fibreglass reinforced plastic boats and the like.

Description: TITLE Silicone Modified Polyurethanes. This invention relates to novel silicone modified polyurethanes. The silicone modified polyurethanes find particular use as coating compositions and especially as marine paints. The modified polyurethanes can also be moulded or cast to form a variety of articles or films. The silicone modified polyurethanes have low surface energy and thus have good anti-stick properties making them suitable for fouling release paint compositions and anti-graffiti paint compositions. Protective coating compositions such as paints are ever increasing in their complexity due in part to the large variety of substrates which need to be coated. Diverse articles or structures such as public buildings, aircraft, and marine vessels often require regular painting to resist environmental attack and to provide an aesthetic appearance. With large buildings in particular, maintenance of the exterior surface is both expensive and time consuming and any reduction in the maintenance of a building (ie. cleaning or painting thereof) is a distinct advantage. Management of surfaces exposed to a marine environment is a major problem insofar as the cost of management of marine growths are concerned. Between hull cleaning operations, marine growths contribute greatly to hull drag and increased fuel consumption. For static marine structures, such as oil rigs, marine growths can contribute to corrosion problems. Various attempts have been made to overcome the problems associated with marine growth as cleaning is both time consuming and expensive. One common method is to provide a paint comprising inorganic or organometallic compounds which exhibit controlled release properties from the surface of the paint thereby providing the painted surface with toxic properties. A serious disadvantage of this type of paint however, is that the inorganic or organometallic compounds are leached out of the paints into the water systems and can result in pollution of marine organisms and creatures as well as coastal or inland waters where a large number of boats are used. The use of toxins to control the fouling of underwater structures by marine life is unacceptable. Alternative non-toxic low surface energy coatings have been developed and field trailed over the last decade. These coatings have proved successful as fouling release coatings, however their use to date has been limited because of difficulties with application, durability and resistance to abrasion. The maintenance of painted surfaces such as the walls on buildings has also become an increasing problem due in part to the increased levels of pollution in the environment. An additional problem affecting the maintenance of painted surfaces is vandalism in the form of graffiti. Graffiti on painted walls is normally carried out using aerosol paint cans, liquid paint, inks, felt pens or the like. By far the most common form of graffiti is using aerosol spray paint cans. Previously it has been difficult to remove such graffiti from painted surfaces as the aerosol paint is formulated to adhere strongly to most surfaces. To remove such graffiti it is necessary to either vigorously scrub the paint work with the aid of solvents or to repaint the whole surface, both of which are time consuming and expensive. Yet another form of painted surface comprises particles of polytetrafluoroethylene ("TEFLON" (trade mark)) bound in a paint matrix to confer low friction qualities to a painted surface. Low friction surfaces may be desirable to reduce wear in pipes or conduits carrying fluids, in particular fluids with solids in suspension. Similarly, in the handling of partiσulate materials such as grains, powdered chemical material and the like, the inner surface of storage hoppers, silos, road and rail freight containers may be coated with a PTFE containing paint in an endeavour to improve the flow characteristics of the particulate material over the surface of the container. Polymeric compositions containing anti-slip or anti-block agents are known in the art and are commonly used as mould release agents. Typically, the polymer composition contains an amount of silicone oil which bleeds out from the, composition to provide the mould release properties. The rate of bleeding of the silicone oil can be controlled by the viscosity of the oil. The silicone is not bound within the polymeric matrix and can migrate to the surface of the composition. While this is desirable for mould release properties, such "bleeding" of the silicone compound from the polymeric composition results in difficulty in an application of a protective or " decorative surface finish to the moulded article. A further disadvantage with these compositions is that while the presence of the silicone compound at or near the surface of the polymer composition can confer flexibility and resistance to weathering, these properties are relatively short lived due to the continual "bleeding". United States Patent 4,500,688 discloses a melt processable pseudo-interpenetrating network of silicones in thermoplastic matrices. The composition is formed from separate batches of thermoplastic pellets, one of which contains a vinyl siloxane complexed with a platinum catalyst and the other containing a silicone hydride composition. The interpenetrating network is formed by mixing and extruding the pellets in a suitable plastics extruder. There is no disclosure of the use of liquid components and the use of the components as coatings. United States Patent No. 4,302,553 describes an interpenetrating network of chemically different crosslinking polymers which do not react together. The structure is described as entangled macroσylic polymeric chains. The patent discloses the formation of a macrocylic structure comprising poly (dimethylsiloxane) and poly (urethane-urea) wherein aqueous emulsions of cross-linked polyurethane and hydroxy terminated poly (dimethylsiloxane) are intermixed to form an homogeneous mixture with sulphur and zinc oxide as cross-linking agents and butylated bisphenol A as an antioxidant. The mixture is cured at elevated temperatures of around 120°C whereby cross-linking is effected by chain extension of the respective polyurethane and poly (dimethylsiloxane) polymers. European patent application 329375 discloses a composition to control marine fouling. The composition includes a curable polyorganosiloxane, an agent capable of curing the polyorganosiloxane to an elastomer, a polyisocyanate and a polyol. The cured polymer composition has a low surface energy due to the polyorganosiloxane elastomer which provides a fouling release. The specification further states that the cured product generally consists of domains of polyurethane within a network of cross-linked polyorganosiloxane. The amount of polyurethane should not exceed 40% by weight as it is stated that above this value the composition will not give a sufficiently low surface energy to prevent marine fouling. It is therefore evident that the composition of European patent specification 329375 is directed to a urethane modified polysiloxane with the urethane as the minor component. It has now been found surprisingly that silicone modified polyurethanes having low surface energy can be formed with a major amount of polyurethane and a minor amount of polysiloxane. In one form the invention resides in a curable liquid silicone modified polyurethane comprising (a) a polyol, (b) a polyisocyanate or polyisothioσyanate, (c) a polysiloxane comprising silicone hydride groups and (d) an unsaturated polysiloxane, wherein the amount of (σ) and (d) is between 1 to 30% by weight of the polyurethane. In another form, the invention resides in a curable liquid silicone modified polyurethane comprising (a) a polyol, (b) a polyisocyanate or polyisothioσyanate, (c) 1- 30% by weight of the polyurethane of a cross-linkable and unsaturated organosiloxane polymer comprising silicone hydride groups. In yet another form, the invention resides in a method for forming curable liquid silicone modified polyurethanes comprising premixing the unsaturated polysiloxane and polysiloxane comprising silicone hydride groups, adding the mixture to the polyol, and adding the polyisocyanate or polyisothiocyanate. The silicone modified polyurethanes can be blended with other resins or fillers to confer desirable properties such as increased flexibility or strength to the silicone modified polyurethane. For example, pitch or tar can be incorporated into the silicone modified polyurethane compositions to provide increased flexibility and durability to the composition or coatings prepared therefrom. The silicone modified polyurethanes can be cured by the addition of catalysts and/or heating. The choice of the catalysts varies depending on the type of component used. Typically, a metal catalyst such as H 2 PtCl 6 is used to polymerise the polysiloxane components. Alternatively, free radical producing catalysts such as organic or inorganic peroxides can be used with the application of heat to generate free radicals. Polymerisation of the polyisocyanate or polyisothiocyanate component with a polyol is well known in the art, and can be catalysed by any suitable catalyst. Catalysts for this type of polymerisation comprise tertiary amines or metal salts or mixtures thereof. The type of catalysts and the conditions to react the isocyanate or isothioσyanate with the polyol will be well apparent to a person skilled in the art. The platinum catalyst can conveniently be premixed with the unsaturated polysiloxane before addition to the remaining compounds although this is not essential. It is preferred that the platinum catalyst is not premixed with the polysiloxane comprising the silicone hydride groups. If a free radical catalyst is used, these can suitably be premixed as described above however, additional care needs to be taken that the catalyst does not decompose into free radicals prematurely. If a catalyst is used to promote the reaction between the polyisocyanate or polyisothiocyanate and the polyol, it is preferred that this is added immediately prior to curing. The unsaturated polysiloxane is suitably selected from ethylenically unsaturated components such as hexenyl or from other terminally unsaturated groups, although other forms of unsaturation are also envisaged. The remaining substituents on the polysiloxane are preferably alkyl groups and an especially preferred alkyl group is the methyl group. However, it is also envisaged that groups such as aromatic groups, long chain alkyl groups or σycloalkyl groups can advantageously be used. A preferred unsaturated polysiloxane is a vinyl end grouped polydimethylsiloxane. The silicone hydride containing polysiloxane is preferably a polymethylsiloxane containing a number of silicone hydride groups along the backbone of the polymer. It is also possible for the hydride and the unsaturated group to be present on the same siloxane polymer backbone. Alternatively, it is also possible to employ a "one-component" organosiloxane component. The organosiloxane would be required to be capable of cross-linking preferably in a non-condensation reaction in the presence of a catalyst. The polyol component can be chosen from any compound comprising at least two hydroxy groups which are reactive to isocyanate or isothiocyanate groups. Suitable polyols include hydroxy (meth)acrylic acid, or esters thereof, polyesters, polyethers, polythioethers, polyacetals, polycarbonates, polyester-amides all of which contain at least two reactive hydroxy groups. Branched polyalkyls with ester and ether groups may also be used. These polyols may be provided with additional functionality such as amino, thiol, or carboxylic groups. The polyisocyanate or polyisothiocyanate can include acyclic, cyclic, cycloaliphatic or aromatic compounds. Additionally the isocyanate or isothiocyanate can be provided with hetero atoms in addition to the isocyanate or isothiocyanate nitrogen, and can also include unsaturated isocyanate or isothiocyanate. Polyphenyl-polymethylenes polyisocyanate and polyisothiocyanate including σarbodiimide, allophanate, isoσyanusate, urethane, acylated urea, urea or buiret groups and polyisocyanate prepoly ers or any mixtures of the above may be suitable for the invention. The considered useful ratio of polysiloxane to polyurethane is between 1 - 30% by weight with a preferred ratio of about 10% by weight polysiloxane to polyurethane. The silicone modified polyurethanes of the invention can be prepared by admixing the polysiloxane, polyol and polyisocyanate in any order. Thus, the polyurethanes can be prepared by admixing the polysiloxane containing hydride groups, the unsaturated polysiloxane, the polyol and the polyisocyanate together in appropriate amounts. Alternatively, the polysiloxanes can be premixed and added to the polyol after which the polyisocyanate is added. In a further alternative method, one of the polysiloxane components can be premixed with the polyol while the other of the polysiloxane components can be premixed with the polyisocyanate or polyisothioσyanate and the two premixtures can be admixed together. In yet another method, the polysiloxanes can be premixed with the polyisoσyanate and the polyol added thereto. The polyurethane σan be in the form of a single component prepolymer σomposition σontaining the polyol and polyisoσyanate or in the form of a two σomponent composition σontaining the polyol and polyisoσyanate as separate σomponents. In a similar manner, the polysiloxanes σan be in the form of a single σomponent prepolymer σontaining both siloxanes or a two σomponent σomposition σontaining the polysiloxane comprising hydride groups and the unsaturated polysiloxane respectively. The polyurethane and polysiloxane can be admixed in any of the above manners, for instance, the two component polyurethane σomposition σan be admixed with the single or two component polysiloxane or viσe versa. The invention will be more fully illustrated by reference to the following examples and comparative examples. The components of the compositions are identified as follows: DESMOPHEN 651 - A branched hydroxy containing polyester sold by BAYER AUSTRALIA LTD. DESMOPHEN A365 A hydroxy σontaining polyacrylate sold by BAYER AUSTRALIA LTD. DESMOPHEN 670 - A slightly branched hydroxy containing polyester sold by BAYER AUSTRALIA LTD. DESMOPHEN 90OU - A branched hydroxy containing polyether sold by BAYER AUSTRALIA LTD. DESMOPHEN A160 - A hydroxy containing polyacrylate sold by BAYER AUSTRALIA LTD. DESMODUR N75 - An aliphatic polyisocyanate sold by BAYER AUSTRALIA LTD. DESMODUR L75 - An aromatic polyisocyanate sold by BAYER AUSTRALIA LTD. BRAMITE SILICONE 2018 PART A - Unsaturated polysiloxane liquid sold by Bramite Limited BRAMITE SILICONE 2018 - PART B - Polysiloxane liquid containing silicone hydride groups sold by Bramite Limited BRAMITE SILICONE 2155 - A reactive unsaturated silicone having silicone hydride groups manufactured by BRAMITE LIMITED. BRAMITE SILICONE 2063 - A silicone oil having a viscosity of 1000 centistokes SYLGARD 184 PART A - unsaturated polysiloxane liquid sold by DOW CORNING. SYLGARD 184 PART B - Polysiloxane liquid σontaining siliσone hydride groups sold by DOW CORNING. SILICONE RTV615A - Liquid siliσone rubber sold by THE GENERAL ELECTRIC COMPANY. SILICONE RTV615B - Liquid siliσone rubber sold by THE GENERAL ELECTRIC COMPANY. MODAFLOW RESIN MODIFIER - A flow and levelling agent sold by MONSANTO AUSTRALIA LTD. BYK P-104S - A wetting and dispersion agent sold by HATRICK AUSTRALIA LTD. RUTILE R-HD2 - A rutile pigment sold by TIOXIDE AUSTRALIA PTY LTD. TALC TS15 - Hydrous Magnesium Silicate sold by COMMERCIAL MINERALS LTD. BLANC FIXE "N"-SACHTLEBEN - A barium sulfate extender sold by A VICTOR LEGGO & CO PTY LTD. CASTOR OIL HYDROGENATED - A vegetable oil sold by HARCROS CHEMICALS PTY LTD. SPECIAL PITCH NO.4 - A pitch sold by THE SWIFT WATTS WINTER COMPANY. EXAMPLE 1 Component A Parts (% weight) 1. Des ophen 651 67% in a 1:1 mixture of methoxy propyl acetate and xylene 28 2. Modaflow 5% in methoxy propylacetate 1 3. Byk P-104S 1 4. Rutile R-HD2 24 5. Solvent (equal ratios of methyl isobutyl ketone, methylethyl ketone, methoxy propyl acetate and toluene) 16 6. 10:1 ratio of Bramite 2018 part A (containing a Pt catalyst) and Bramite 2018 part B 8 Component B Des odur N75 75% in methoxy propylacetate 22 The unsaturated polysiloxane (Bramite 2018 part A) containing a platinum catalyst and the polysiloxane comprising siliσone hydride groups (Bramite 2018 part B) are premixed in the speσified ratio (10:1). The mixture is added to the remaining compounds of σomponent A and is mixed for 3-10mins at ambient temperatures using low shear mixing. This mixture is left at ambient temperatures for 2-4 weeks or until the visσosity of the mixture no longer increases. Component B is added to the mixture, with stirring to form the siliσone modified polyurethanes. The mixture can be applied to a surface and cured to form a coating. If neσessary, a solvent mixture σan be utilized as a thinning mixture to faσilitate the formation of σoating. EXAMPLE 2 Component A Parts (% weight) 1. Desmophen A365 65% in a 3:1 ratio of butylaσetate and Xylene 41 2. Modaflow 5% in methoxypropylaσetate 1 3. Byk P-104S 1 4. Rutile R-HD2 24 5. Solvent - equal ratios of methoxy isobutyl ketone, methyl ethyl ketone, methyl propyl aσetate and toluene 8 6. Bramite 2018 part A (σontaining a Pt catalyst) and Bramite 2018 part B in a 10:1 ratio 8 7. Bramite Silicone 2063 1 Component B 1. Desmodur N75 16 The method of example 1 is used with the exσeption that the addition of the Bramite Silicon 2063 fluid eliminates the requirement of leaving the mixture for 2-4 weeks and σomponent B of the example σan be immediately added . EXAMPLE 3 Component A Parts (% weight) 1. Desmophen A365 65% in 3:1 ratio of butylaσetate/Xylene 40 2. Desmophen 670 1 3. Modaflow 5% in methoxy propyl acetate 1 4. Byk P-104S 1 5. Rutile R-HD2 24 6. Solvent-equal ratios of methyl isobutyl ketone, methyl ethyl ketone, methoxy propyl acetate and toluene 8 7. 10:1 ratio of Bramite 2018 part A (σontaining 8 a Pt catalyst) and Bramite 2018 part B. 8. Bramite Silicon 2063 1 Component B Desmodur N75 - 75% in methoxy propyl acetate 16 The method of example 2 is used to form the silicone modified polyurethanes. EXAMPLE 4 Component A Parts (%weiqht) 1. Desmophen 900U 22 2. Rutile R-HD2 22 3. Solvent - equal ratios of methoxypropyl acetate methyl isobutyl ketone, and methylethyl ketone 24 4. Siliσone RTV615A (containing a Pt catalyst) and Silicone RTV615B in a 10:1 ratio 10 Component B 1. Desmodur L75 - 75% in ethyl aσetate. 22 The σomponents are reacted using the method of example 1. EXAMPLE 5 Component A Parts (%weiqht) 1. Desmophen 900U 14 2. Byk P-104S 1 3. Special Pitch No. 4 20 4. Talσ TS15 4 5. Blanσ Fixe "N ιr - Saσhtleben 16 6. Castor oil Hydrogenated 2 7. Solvent - equal ratios of methyl isobutyl ketone, methyl ethyl ketone and methoxy propyl aσetate 15 8. Sylgard 184 part A (σontaining a Pt σatalyst) and Sylgard 184 part B 10:1 ratio 7 Component B 1. Desmodur L75, 75% in ethyl aσetate 19 2. Toluene 2 The σomponents are reaσted using the method of example 1 . EXAMPLE 6 Component A Parts (%weiqht) 1. Desmophen A160 60% in Xylene 44 2. Rutile R-HD2 24 3. Solvent 2: 1 ratio of Xylene and methoxy propyl acetate 12 4. Bramite 2018 Part A (containing Pt catalyst) and Bramite 2018 part B in a 10:1 ratio 4 Component B 1. Desmodur N75 10 2. Toluene 6 The σomponents are reaσted using the method of example 1. Component A 1. Desmophen A365 - 65% aσetate/Xylene 3:1 2. Rutile R-HD2 3. Solvent-equal parts of methyl isobutyl ketone, methyl ethyl ketone, Toluene and ethyl glyσol acetate 15 4. Silicone - Bramite Silicone 2155 6 18 Component B Desmodur N75 75% in methoxy propyl aσetate 16 The σompounds of σomponent A were admixed and 50ppm (relative to the polysiloxane) of a platinum σatalyst H2 Pt Clg was added. After stirring at ambient temperature for 3-10 minutes σomponent B was added to give the siliσone modified polyurethanes. EXAMPLE 8 Component A Parts (%weiqht) 1. Desmophen A160 60% in Xylene 44 2. Modaflow 5% in methoxy propyl aσetate 1 3. Byk P-1045 1 4. Rutile R-HD2 24 5. Solvent 2: 1 ratio of Xylene and methoxy propyl aσetate 12 6. Siliσone-Bramite Siliσone 2155 4 Component B 1. Desmodur N75 10 2. Toluene 6 The components are reaσted using the method of Example 7. EXAMPLE 9 One pack moisture cured system 1. Desmodur N75 60 parts 2. Xylene 30 parts 3. Dibutyltin dilaurate 0.3 parts 4. Siliσone RTV615A and Siliσone RTV615B 10:1 ratio 9.7 parts Admixture of the above σompounds gave a one paσk moisture σured system. COMPARATIVE EXAMPLE 1 This formulation is identical to example 1 without the Bramite 2018 part A and Bramite 2018 part B. The solvent σomponent is increased to 24 parts. COMPARATIVE EXAMPLE 2 This formulation is identical to example 2 without the Bramite 2018 part A and Bramite 2018 part B and Bramite Silicone 2063. The solvent component is increased to 16 parts. It is believed that the Bramite Silicone 2063 can be partially or totally substituted by polyphenylmethyl siloxane fluids or fluorinated hydrocarbons with low surface energy. Other silicone elastomers such as RTV3110 (produced by DOW CORNING as a two part mixture) σan be used. These silicones are σatalysed by dibutyltin dilaurate or stannous octanoate. Although the silicones are of high viscosity, thinning with appropriate solvents can be carried out prior to incorporation into the polyol. The silicone modified polyurethanes σan be formed as a single σomponent by inclusion of a polyurethane prepolymer which σures by reaσtion with atmospheric moisture. A suitable prepolymer is Desmodur E21 sold by BAYER AUSTRALIA LTD. Alternatively, a one component moisture cured silicone modified polyurethane σan be formed based on an aliphatiσ polyisoσyanate suσh as Desmodur N75. Although the above examples have used hydroxy containing polyaσrylates and other polyol compounds sold by BAYER AUSTRALIA, these σompounds may be substituted by hydroxy σontaining polyacrylates from HOECHST AUSTRALIA LTD under the trade mark MACRYNAL SM series and hydroxy σontaining polyacrylates from CRAY VALLEY PRODUCTS LTD U.K. whiσh are sold under the trade name SYNOCURE. Similarly, an aliphatiσ polyisoσyanate designated as HARTBEN A75 sold by A VICTOR LEGGO AND CO PTY LTD is σonsidered a suitable alternative to Desmodur N75. The silicone modified polyurethane system of example 3 σontaining a small perσentage of Desmophen 670 has been used for coating a product sold by FERRO CORPORATION (AUST) PTY LTD under the trade name VULKEM whiσh is used to provide a very flexible substrate on pools. The siliσone modified polyurethane σompositions of example 5 inσorporating the pitσh provides heavy duty coatings with improved weathering properties in terms of gloss retention. Polyurethane pitσh or tar formulations not inσluding silicone modification suffer from loss of gloss within six months of exposure. The siliσone modified polyurethanes of the examples σan be unpigmented and these formulations usually have UV stabilizers present as well as the levelling agent MODAFLOW. Suitable stabilizers inσlude Tinuvin 292 and Tinuvin 900 (trade mark CIBA-GEIGY AUSTRALIA LTD) as a 10% solution in xylene and whiσh are added in two parts and four parts respectively to the formulation. An alternative method of forming the siliσone modified polyurethane compositions of the examples is to premix the polyol and polyisocyanate or polyisothiocyanate at ambient temperature together with the desired solvent mixture and additives using low shear mixing conditions. The unsaturated polysiloxane (containing platinum σatalyst) and the polysiloxane containing silicone hydride groups are premixed and then added to the polyol/isocyanate or isothioσyanate mixture over a period of 3-10 minutes at ambient temperatures and using low shear mixing σonditions. This mixture σan be applied to a substrate in the form of a σoating to σure at room temperature. Table 1 lists various properties of σertain of the exemplified siliσone modified polyurethanes σompared with identiσal polyurethanes not σontaining εiliσone. Unless otherwise speσified, the siliσone modified polyurethane σoatings have been tested to Australian Standards 2602- Paints for steel struσtures: full gloss polyurethanes. The tests were carried out in accordance with Australian Standards 1580 - Methods of Test for Paints and Related Materials. Although the silicone polymers prepared by Bramite Limited, Dow Corning and General Electriσ for use in the examples above are generally similar in properties, the polymers manufaσtured by Bramite Limited are preferred in praσtiσe. TABLE 1 TABLE 1 (cont) P=PASS F=FAIL PROPERTY TEST METHOD COMPARATIVE EXAMPLE 1 COMPARATIVE EXAMPLE 2 EXAMPLE 1 EXAMPLE 2 EXAMPLE 3 EXAMPLE 8 9. Taber abrasion resistanσe 31 38 46 (weight loss in mg) (CS17, lOOOg, 500 cycles) C 10. Coefficient of friction (u) 0.04 0.10 0.04 IJIΪ 11. Gloss (60 * exposure head) 90 89 94 C 12. Durability (atmospheric N3 H **- weathering) :12 months - assessment of 10 10 10 individual defects r.*ι - colour change (HE) 0.7 0.7 0.7 - gloss 90 84 86 13. durability (QUV accelerated weathering) ; 800 hours - assessment of individual 10 10 10 defects - colour change (VE) 1.4 1.8 1.7 - gloss 28 26 35 TABLE 1 (cont) P=PASS F=FAIL PROPERTY TEST METHOD COMPARATIVE EXAMPLE 1 COMPARATIVE EXAMPLE 2 EXAMPLE 1 EXAMPLE 2 EXAMPLE 3 EXAMPLE 8 98 96 6B 8A 10 19. 1 14.2 38 45 17. 1 13.2 20. Surface profile 0.3 0.8 0.5 0.8 - centre line average (urn) 21. Durability (Atlas Weatherometer accellerated weathering) : 1,000 hours UV - assessment of gloss AS1580.481.1 NOTES - TABLE 1 (1) AS2602 requires testing to AS1580-214.1. (2) AS2602 requires testing within 24 hours of application of second coating. This was extended to 7 days "normal" curing, the 24 hour cure time being insuffiσient. (3) Using a black enamel paint that might commonly be used for graffiti purposes. Tested after 7 days. 1. Application properties Modified coatings σan be applied by brushing, conventional air spraying and roller coating without any evidence of film defects. The presence of the silicone aids the flow, spreading, levelling and lapping properties compared to the unmodified coating. 2. Pot life This test was carried out aσσording to AS1580-214.2 (σonsistenσy - Flow Cup) following the procedure outlined in AS2602. Both the siliσone modified polyurethane and the polyurethane σoatingε were thinned using spraying thinners, so as to give a flow time of 22 seσonds. After a period of 3 hours at 25°C, flow time was measured at 23-24 seσonds for both the silicone modified polyurethanes and the unmodified polyurethanes. The results indicate suitability of both systems with respect to pot life and indirectly suggests minimal, if any, reaction between the siliσone and SUBSTITUTE polyurethane components. 3. Surface dry This test indicates minimal difference between the silicone modified and unmodified polyurethanes. Indirectly this suggests some degree of curing of the siliσone has oσσurred prior to addition of polyisoσyanate σomponent. 4. Bend test This test is considered an indication of flexibility and adhesion of the coatings. 5. Scratch resistance The curing properties of the polyurethanes is assessed by measuring the scratch resistance; the film having cured for 7 days in accordance with AS1580-403.1 should withstand a load of 1.5kg. The scratch resistance of the produσt of Example 1 is slightly down from all other σoatings trialled. 6. Adhesion (knife test) Due to the problem of adherence of pressure-sensitive tape over cuts made in the film (see AS1580-408.4 Adhesion-cross cut) the knife test method was used. A rating of 4 represents traσe peelings or removal along inσisions, in other words, adhesion to the substrate is very good. 7. Reσoatin properties A standard σure period of 7 days was used. Results σlearly show the ability of the siliσone modified polyurethanes to be reσoated. 8. Overcoating properties A variation of 7 above was used to examine the effect of applying a black enamel paint that might be used by graffiti artists. Results clearly demonstrate the inability of the black enamel to form a strong chemiσal bond with the siliσone modified polyurethane σoatings. The enamel film, when applied to the silicone modified polyurethane σoatings, showed σonsiderable film defeσts due to fish-eyeing, etσ. 9. Abrasion resistanσe The abrasion resistanσe of all the coatings was excellent. 10. Coefficient of friction The test method used is a variation of ASTM D4581 in that a 500gm vertical load was plaσed on each coated coupon through a 9.5mm diameter steel ball. The coated coupon sample was mounted on a flat steel plate that could advance on low friction bearings. The plate was pulled forward at a speed of 50mm/minute by the cross-head of a JJ Lloyd testing machine by means of a nylon cord. The forσe required to propel the plate was measured by means of a load σell. Results clearly show a signifiσant reduσtion in εurfaσe friσtion σoeffiσient of the siliσone modified polyurethane coatings. 11. Gloss (6Q Q exposure head) Specular gloss was measured for those samples prepared for acσelerated QUV weathering. All coatings met the minimum requirement of AS2602, in that speσular gloss shall not be less than 85 gloss units. 12. Durability After a weathering period of 12 months, property defeats suσh as erosion, σraσking, σheσking, flaking and peeling, delamination, rusting with blisters, rusting and blistering were not observed and the highest rating of 10 was noted. These results are to be expected and the minimum requirement of AS2602 is that a rating of 10 be attained during the first 48 months. Results do show that no adverse effects are noted for the siliσone modified polyurethane systems. 13. Durability (QUV aσcelerated weathering - 800 hours) The σoatings were subjected to aσσelerated weathering using a fluorescent ultraviolet (UV) and σondensation apparatus to simulate the deterioration σaused by sunlight and water as rain or dew. Repeated cyσles of 4hrs UV light followed by 4hrs condensation were used. Results indicate that the siliσone modified polyurethanes of examples 2,3 and 8 perform better, in terms of gloss retention than Comparative Example 2 or Example 1. 14. Surface drag The interior surface of PVC pipes of 6 metres in length, 50mm in diameter, were coated with the product of Comparative Example 2 and of Example 2. One pipe was left unσoated. Pressure drop was measured over a 5 metre distance, veloσity of the water being measured at 4.0m/s, nominal flow being 7.34 kg/s. Pressure drop for the PVC pipe was 100mm Hg. Results have been correσted to a diameter of 50.0 mm. Results suggest that the siliσone modified polyurethane σoating will also effect a reduσtion in drag for sailing vessels and other marine σraft, not to mention improving the efficiency of pumping systems, etc. 15. Water resistance In this - test, the effectiveness of the silicone-modified polyurethane σoating of Example 2 in improving the water resistanσe rating (with respeσt to blistering) of a gel- σoated laminate was asσertained. The procedure differed to AS1838 in that a temperature of 65°C was maintained for 300 hours and not 100°C for 100 hours. The gel-coat laminate was known to have a degradation rating of 5 or, as assessed by AS1580-481.2, a rating of 4C. The siliσone modified polyurethane coating significantly improved the blister rating of the gel-coat and showed an improvement with respect to the polyurethane system of the Comparative Examples. It should be noted that there was no sign of blistering or any other film defeσt when σoatings were applied to polyester DMC (dough moulded compound) panels. Results indicate improved water resistance of the siliσone modified σoating and suggests that the appliσation of suσh σoatings to fibreglass vessels will provide increased protection with respect to osmosis. 16. Durability and resistanσe to fouling in water These tests were σarried out in an area of heavy fouling activity and where temperature of the water remains temperate. Unmodified polyurethane and silicone modified polyurethane test panels allowed to sit in this environment for a total of 12 months, show fouling very much to the same degree. The silicone modified urethane coatings are non- toxic and will therefore foul. However, on cleaning the test panels it is observed that the silicone modified polyurethane coatings are easily cleaned with no evidence of individual defects whereas the unmodified coatings are quite difficult to clean and, where barnacles have been present, damage to the coating occurs. 17 . Tensile strength Re sul t s were obtained after plaques were prepared approximately 1mm thick. 18. Elongation Results indicate an increase in flexibility of the silicone modified polyurethane. These values can be compared with an unpigmented silicone elastomer (110%), the unpigmented polyurethanes of Comparative Examples 1 or 2 (59%) and the unpigmented siliσone modified polyurethanes of Examples 1,2,3 and 8 (66%) . 19. Tear strength Results indiσate a decrease in tear strength for the silicone modified polyurethanes. These results can be compared with an unpigmented silicone elastomer (6.7), the unpigmented polyurethanes of Comparative Examples 1 or 2 (12.8) and the unpigmented silicone " modified polyurethanes of Examples 1,2,3 and 8 (11.5) . 20. Surface pro ile Tests carried out on coatings sprayed under optimum conditions with respect to thinning of paint system. Surface texture was assessed using a Taylor Hobson Talysurf measuring device which draws a stylus needle over a measured length of σoating. 21. Durability (Atlas Weatherometer accelerated weathering - 1,000 hours uv) Results indicate an improvement in gloss retention of the siliσone modified polyurethanes. Partiσularly advantageous properties of σoatings prepared from the silicone modified polyurethanes of the examples are listed below: EXAMPLE PROPERTIES 1 Good light stability; gloss retention; outdoor resistance, and σhemiσal resistanσe. 2 Exσellent fouling release properties when used as a marine paint. 3 Exσellent fouling release properties, good flexibility. 4 Good fouling release properties and anti- σorrosion properties. 5 Exσellent industrial coatings, heavy duty marine coatings. 6 Good resistance to weathering, water, detergent solutions and σhemiσals. 7 Rapid air drying finish, good weather resistanσe, light stability, solvent and petrol resistance. A particular advantage of the σoatings of the examples resides in their low surfaσe energy properties. Advantage is taken of these low surfaσe energy properties in the use of siliσone modified polyurethane σompositions as a means of effectively and safely managing the effects of marine growth on vessels such as commercial ships, pleasure craft, ferries and the like as well as statiσ marine structures such as oil rigs, jetty piles, etc. Although these silicone modified polyurethane compounds are inherently non toxic to marine organisms and otherwise preserve the integrity of the marine environment, their low surfaσe energy σharaσteristiσs provide a fouling release σoating whiσh inhibits the degree of adhesion of marine organisms. This in turn permits simple and inexpensive underwater σleaning operations to be carried out or otherwise less time consuming slipping of vessels for removal of marine growth. The fouling release coatings enable ready removal of marine growth by less rigorous scrubbing or high pressure hosing without damaging the coating surface. Few organic substances will bond strongly to the surfaσe of the σoatings and thus the σoating σan be used as anti-graffiti σoatings on buildings, railway σarriages or other surfaσes likely to be disfigured by graffiti artists. In addition they may be used as fouling release σoatings on marine vessels. Dirt piσk up is reduced and therefore surface tracking is also reduced. When used as a decorative and/or proteσtive coating on buildings, the coatings have a low coeffiσient of friction and together with the reduced adhesion of dirt of other particles the σoating is easily σleansed by rain or washing. The σoatings are more flexible and softer than σonventional σross-linked paint σoatings and thus exhibits improved sσratσh resistanσe. The coatings while having an anti-stick surface can be recoated with a second σoat having good adhesion properties to the first σoat. Thus, it is not neσessary to strip the first σoat. Further, the σoatings σan be applied directly to a substrate without requiring primer σoats or "tie" σoats. In an endeavour to ascertain the physical struσture of the silicone modified polyurethane compositions, a number of tests were carries out. These tests included:- Pyrolysis/Gas Chromatography Tests conduσted on both modified and unmodified polyurethane systems suggest that no interaction occurs between the urethane and silicone component. The modified system showed no peaks associated with the silicone component and this was considered to be a most unusual result. Polyurethane traces in both cases were identical. Thermal Analysis Thermal analysis using a differential spectral calorimeter showed that the glass transition state (Tg) of the silicone elastomer, the modified and the unmodified urethane acryliσ σompositions were substantially identiσal. Physical Tests Tensile elongation and tear strength measurements all showed reduced values for siliσone modified systems. While not wishing to be bound by speculation, investigations suggest that the silicone modified polyurethanes of the invention comprise domains of at least partially cured polysiloxanes within a network of polyurethane. It is possible that an amount of inter- penetration and/or chemical bonding oσσurs along the interfaσe between the siliσone domains and the polyurethane. However, it is also possible that some degree of chemical coupling ocσurs between the siliσone and polyurethane to give cross-linked, and/or graft polymers or bloσk polymers. It is also possible that the polyol may reaσt with a siliσone hydride funσtionality to link at least a portion of the polyurethane resin to the polysiloxane domains. The siliσone hydride σontaining polysiloxane may reaσt with a polyol to form polar segments whiσh may aggregate into miσelle-like partiσles with siliσone polymer chains extending into the surrounding polyurethane matrix. It is also considered that the respective densities and polarities of the polysiloxanes and the polyol may have a profound bearing on the type of product formed. The polysiloxanes typically have a low solubility in the polyol/solvent mixture and thus tend to form an emulsion or colloidal suspension of fine droplets of the silicone in the polyol upon mixing. The hydroxy containing polyaσrylates (eg. Desmophen A365) can form an emulsion with the unsaturated polysiloxane (eg. Bramite 2018 Part A) and silicone hydride containing polysiloxane (eg. Bramite 2018 part B) which is stable for a period of about three weeks after which time appreciable phase separation had ocσurred. In this example it was observed that the density of the polysiloxanes and solvents approximated the density of the polyol and it is believed that this σontributes to the stability of the emulsion. Addition of additives suσh as pigments appear also to inhibit phase separation. As the polyurethane system σomprises a polyol with a number of hydroxyl groups which normally react with the isoσyanate groups, it is possible that some of these hydroxyl groups reaσt with hydrosilane funσtional groups to σhemiσally bond the siliσone domains within the polyurethane matrix. Alternatively, these σould be formed as polymer σhains having a polyurethane funσtion at one end and a siliσone funσtion at the other. A further postulation is that through inhibition of polymerisation of the silicone monomers, the proportion of uncross-linked silicone monomer may be free to migrate through the polyurethane matrix. That being the case, it is likely through surface tension effects, that there ocσurs a greater conσentration of silicone monomers near the exposed surface of the polyurethane matrix. This concentration may then allow cross-linking of the siliσone monomers in an interpenetrating network as steriσ inhibition is reduσed. Although there is no definite evidenσe to support any partiσular postulation of the moleσular struσture of the siliσone modified polyurethane systems aσσording to the invention, the most likely struσture is believed to σomprise micelle-like domains of silicone polymer with silicone chains extending into the surrounding polyurethane matrix. These extended silicone chains probably bind to the polyurethane matrix by a combination of chemiσal bonding between siliσone hydride and the polyol hydroxy groups as well as interpenetration of the polyurethane molecules. The silicone modified polyurethane compositions aσσording to the invention may have appliσation in a wide range of fields. The silicone modified polyurethanes have partiσular appliσation as non-toxiσ environmentally safe fouling release σoatings for marine appliσations inσluding all manners of marine vessels and marine struσtures suσh as oil rigs and the like. Heavy duty σoatings σomprising pitσh or tar may be used as anti-σorrosion σoatings in marine and land based struσtures particularly where marine fouling release properties are required. Other applications include enhanced slip coatings for σontainers of partiσulate materials such as grains, cement powders, and stiσky substanσes suσh as sugar and molasses and where non-toxiσ low friσtion σoatings are required. Suσh non-toxiσ low friction coatings are also suitable for the interior of pipes and other σonduits. These non-toxiσ σoatings σould be used for example in the pumping of town water or in the food industry such as in conveyanσing of beverages. In other applications such as the pumping of cooling water in condensers of power stations, substantial improvement in pump effiσienσy by reduσtion of head losses can be expected. Application of the siliσone modified polyurethane σoatings aσσording to the invention in aeronautic appliσations is expeσted to lead to increased fuel savings due to reduced air drag on aeroplanes and the like. A particularly advantageous application of the silicone modified polyurethane compositions is in the manufacture of fibreglass (FRP) products such as boats. As an alternative to conventional polyester gel σoats, compositions aσσording to the invention provide a means of overcoming, many of the traditional gel coat problems suσh as σraσking, blistering, osmosis and water absorption. The greater flexibility and improved resistanσe to moisture absorption impart improved impaσt resistanσe, resistanσe to abrasion whiσh otherwise in more brittle polyester gel σoats leads to "star" σraσking whiσh in turn allows water to penetrate the gel σoat/fibreglass struσture, often with disastrous effeσts. At the same time, the low surfaσe energy of the σompositions provides an environmentally sound, non- toxic fouling release surface for above and below water surfaces. In yet further modifications of the invention there are provided mouldable or σastable siliσone modified polyurethane compositions applicable in the field of medicine, such as surgical prostheses, or in other fields such as automotive components, cast films, polymeric laminates for automotive and domestic upholstery and the like. It should be appreσiated that various other σhanges and modifications may be made to the examples without departing from the spirit and scope of the invention as defined in the appended claims.

Claims: CLAIMS : 1. A σurable liquid siliσone modified polyurethane σomposition σomprising (a) a polyol, (b) a polyisocyanate or polyisothiocyanate (c) a polysiloxane σomprising siliσone hydride groups, and (d) an unsaturated polysiloxane, wherein the amount of (σ) and (d) is between 1-30% by weight of the polyurethane. 2. The σomposition as σlaimed in σlaim 1, wherein the amount of (σ) and (d) is between 5-15%. 3. The composition as claimed in claim 2, wherein the amount of (c) and (d) is about 10%. 4. The σomposition as claimed in σlaim 1, wherein the amount of said polyol is between 10-60%. 5. The σomposition as σlaimed in claim 1, wherein the amount of said polyisoσyanate or polyisothiocyanate is between 10-20%. 6. The composition as claimed in claim 1, wherein the ratio of (c) to (d) is between 8:1 to 12:1. 7. The σomposition as σlaimed in claim 6, wherein the ratio of (c) to (d) is about 10:1. 8. The composition as claimed in claim 1, wherein said polyol is selected from . hydroxy containing polyesters, hydroxy containing polyacrylates and hydroxy containing polyethers. 9. The composition as claimed in claim 1, wherein said polysiloxane comprising silicone hydride groups comprises one or more of said siliσone hydride groups. 10. The σomposition as σlaimed in σlaim 1, wherein said unsaturated polysiloxane σomprises one or more vinyl groups. 11. The σomposition as σlaimed in σlaim 1, wherein said polyisocyanate of polyisothiocyanate is selected from. aliphatic or aromatic polyisocyanates or polyisothioσyanateε. 12. A method of forming a σurable liquid silicone modified polyurethane σomposition as σlaimed in σlaim 1, comprising the steps of mixing said polysiloxane comprising siliσone hydride groups, said unsaturated polysiloxane and said polyol as a first σomponent and adding said polyisoσyanate or polyisothioσyanate as a seσond σomponent to said first σomponent. 13. A method of forming a σurable liquid siliσone modified polyurethane σomposition as σlaimed in σlaim 1, comprising the steps of mixing said polysiloxane comprising siliσone hydride groups, said unsaturated polysiloxane and said polyisoσyanate or polyisothioσyanate as a first σomponent and adding said polyol as a seσond σomponent to said first σomponent. 14. A method of forming a σurable liquid siliσone modified polyurethane σomposition as σlaimed in σlaim 1, comprising the steps of mixing said polyol, said polyisocyanate or polyisothiocyanate, said polysiloxane comprising silicone hydride groups and said unsaturated polysiloxane as separate components. 15. A method of forming a σurable liquid siliσone modified polyurethane σomposition as σlaimed in claim 1, σomprising the steps of mixing said polyol and said polyisocyanate or polyisothiocyanate as a first component, mixing said polysiloxane comprising silicone hydride groups and said unsaturated polysiloxane as a second σomponent and admixing said σomponents. 16. A method of forming a σurable liquid siliσone modified polyurethane σomposition as σlaimed in σlaim 1, comprising the steps of mixing said polyol, said polyisocyanate or polyisothioσyanate and said polysiloxane σomprising siliσone hydride groups as a first component and adding said unsaturated polysiloxane as a second component to said first σomponent. 17. A method of forming a σurable liquid siliσone modified polyurethane σomposition as σlaimed in σlaim 1, σomprising the steps of mixing said polyol, said polyisoσyanate or polyisothioσyanate and said unsaturated polysiloxane as a first σomponent and adding said polysiloxane σomprising siliσone hydride groups as a seσond component to said first σomponent. 18. A method of forming a σurable liquid siliσone modified polyurethane σomposition as σlaimed in claim 1, comprising the steps of mixing said polyol and said polysiloxane comprising silicone hydride groups as a first component, mixing said polyisoσyanate or polyisothioσyanate as a seσond σomponent and admixing said σomponents. 19. A method of forming a σurable liquid siliσone modified polyurethane composition as σlaimed in σlaim 1, comprising the steps of mixing said polyol and said unsaturated polysiloxane as a first σomponent, mixing said polyisoσyanate or polyisothiocyanate as a second component and admixing said components. 20. The composition as claimed in claim 1, comprising 1-25% of a reinforcing agent. 21. The composition as σlaimed in σlaim 20, wherein said reinforσing agent is seleσted from partiσulate fillers, fibrous fillers and cross-linkable polymeric materials. 22. A σoating σomposition σomprising the σomposition as σlaimed in σlaim 1. 23. A non-toxiσ fouling release σomposition for σoating surfaσes exposed to a marine environment σomprising the σomposition as σlaimed in σlaim 1. 24. An anti-slip σoating σomprising the σomposition as σlaimed in σlaim 1. 25. An anti-graffiti σoating σompriεing the σomposition as claimed in claim 1. 26. A moulded article comprising the composition as claimed in claim 1. 27. A cast sheet-like material or laminate comprising the composition as claimed in claim 1.

Inventors: BRIDGES ROBERT DEAN, STRUDWICK KENNETH ROY, WALLIS ROBERT CHARLES, BRIDGES, ROBERT, DEAN, STRUDWICK, KENNETH, ROY, WALLIS, ROBERT, CHARLES
Applicants: BRAMITE LTD, BRAMITE LIMITED
Application year: 1989
Main classification: C09D3
IPC codes: C08G18, C09D175