Classifications

• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
  • C08G18/00—Polymeric products of isocyanates or isothiocyanates
  • C08G18/06—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen
  • C08G18/28—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen characterised by the compounds used containing active hydrogen
  • C08G18/40—High-molecular-weight compounds
  • C08G18/48—Polyethers
  • C08G18/4833—Polyethers containing oxyethylene units
  • C08G18/4837—Polyethers containing oxyethylene units and other oxyalkylene units
  • C08G18/4845—Polyethers containing oxyethylene units and other oxyalkylene units containing oxypropylene or higher oxyalkylene end groups
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
  • C08G18/00—Polymeric products of isocyanates or isothiocyanates
  • C08G18/06—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen
  • C08G18/08—Processes
  • C08G18/10—Prepolymer processes involving reaction of isocyanates or isothiocyanates with compounds having active hydrogen in a first reaction step
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
  • C08G18/00—Polymeric products of isocyanates or isothiocyanates
  • C08G18/06—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen
  • C08G18/28—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen characterised by the compounds used containing active hydrogen
  • C08G18/40—High-molecular-weight compounds
  • C08G18/48—Polyethers
  • C08G18/4825—Polyethers containing two hydroxy groups
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
  • C08K3/00—Use of inorganic substances as compounding ingredients
  • C08K3/34—Silicon-containing compounds
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
  • C08G2110/00—Foam properties
  • C08G2110/0083—Foam properties prepared using water as the sole blowing agent

Definitions

• This invention is related to production of antibacterial polimers for use in medical and industrial applications. Particularly this invention is about preparation methods for biomedical grade polyurethane based composites, in a variety of forms such as films, fibers and foams containing ionic silver impregnated zeolites with low or high SiO 2 /Al2 ⁇ 3 ratios.
• Such composites can be used in a wide variety of applications as follows: textiles (upholstery, or clothing fabrics, socks), paint industry ( automotive, marine and household paints) , coating material for metals, ceramics or wood, or coatings for items used in public places, such as escalators, shopping car holders, elevator buttons, steering wheels or stick shifts in cars, keyboards, paper industry (magazines, newspapers) household hygene items (detergents, soaps, shampoo), cosmetics (moisturizer creams), hospital floors, beds and stretchers.
• the composites prepared may be water soluble or resistant. Water resistant composites are mechanically strong, relatively cheaper and possess increased antibacterial properties when compared to composites containing metallic silver in their composition.
• Polyurethanes (PU) are polymeric biomaterials that are widely used in the biomedical field due to their mechanical properties and their perfect compatibility with blood and tissue as well as the fact that they can be easily modified for certain applications. Besides their wide use in industry, they polyurethanes also find wide use in the medical field in a variety of applications such as artificial veins, catheters, artificial heart valves and parts, stent coatings, and skin grafts. Since polyurethanes can be synthesized in different chemical compositions, they cam be tailored to have desired physical an mechanical properties.
• Polyurethanes are synthesized through poiycondensation reactions of isocyanates and polyhydroxy compounds.
• the most widely used isocyanates in polyurethane synthesis are toluene diisocyanate (TDI), diphenyl methylene diisocyanate (MDl), p-phenylene diisocyanate (PDI), and naphthalene diisocyanate (NDI).
• the widely used polyhydroxy compounds are polyether and polyester glycols containing hydroxy groups with a molecular weight of 400-5000 Da. Isocyanates form the hard units of the PU structure, while glycol cahins in the form of polyols form the soft units. When both units co-exist in the micro phase separations, the structure becomes elastomeric.
• Zeolites are known to be considered mainly in 3 groups according to their silica/alumina ratios. These are zeolites with low (i.e.,zeolite A and X), medium (i.e., zeolite X and mordenite), and high (i.e.: zeolite Beta and ZSM-5) SiO 2 ZAI 2 O 3 ratios. To date all antibacterial materials with zeolite and PU have been with zeolites having low or medium SiO 2 ZAI 2 O 3 ratios. Antibacterial zeolite with a high SiO 2 ZAI 2 O 3 ratio has not been studied yet, moreover there are reports that they can not be made antibacterial.
• the aims of developing a process to produce medical grade PU films, fibers and sponges containing antibacterial zeolites and their preparation methods include :
• FIGURES Figure 1 SEM (Scanning Electron Microscope) photomicrographs of silver ion loaded zeolite Beta (a) and Zeolite A (b).
• FIG. 1 SEM photomicrographs of silver ion loaded nano sized Zeolite A crystals.
• Figure 3. SEM photomicrographs of Polyurethane sponge Figure 4. Chemical structure of Polyurethane synthesized from TDI and polypropylene.
• This invention involves preparation of biomedical grade PU with various elastomeric properties by reacting toluene diisocyanide (TDI) and polypropylene ethylene diisocyanide (polyol) without any additives, and making these materials antibacterial with the incorporation of zeolites. Since no additional catalyst or chain modifier compounds are used in PU synthesis, the toxic effects of such ingredients are eliminated.
• This product is of biomedical grade and can be tailored to have desired mechanical properties, so it is a strong candidate for the development of biomedical devices . Zeolite crystal containing silver ions are incorporated into the polyurethane structure so the composite becomes antibacterial.
• the sponge form is obtained by adding water into the viscous polyurethane prepolymer. Only water is used in this step and no other chemical is present, and this is significant in the sense that biomedical grade purity of PU is not affected.
• the formation of the sponge-like structure at first the isocyanide groups reacts with water to give an unstable carbamic acid (Equation 2). Carbamic acid then decomposes into an amine and gaseous carbon dioxide which causes the spongy structure (Equation 3).
• the amine molecules react with isocyanates and urea groups form in the chain (Equation 4), This process forms the spongy polyurethane-polyurea foam.
• PU is also prepared in a spongy form and silver ion loaded zeolites are incorporated into this structure forming an antibacterial composite.
• Examples are, by addition of various chemicals, [i.e., N-(fluorodichloromethylthio)- phthalimide, 2-benzimidazole carbamic acid lower alkylester and/or 2-(4-thiazolyl)- benzimidazole (USPTO Patent Application #: 20050245627 - Patent Class: 521099000)] by addition of organic dyes (methylene blue, toluidine blue, methylene violet, azure A, azure B, azure C, brilliant cresol blue, thionin, methylene green, bromcresol green, gentian violet, acridine orange, brilliant green, acridine yellow, quinacrine, trypan blue, trypan red (European Patent No:1490140 Medical Devices Exhibiting Antibacterial Properties), or through coating with or adding particles of metallic silver (Schierholz et al., J.
• Silver can be used in the form of metallic silver (Ag) or in ionic form
• Zeolites are homogenous four faced crystalline aluminosilicates composed silica [SiO 4 ] and alumina [AIO 4 ] " groups (or other oxides) linked by shared oxygen atoms. They contain micro or nanoporous channels of uniform size linked in a 2-dimenisonal or 3- dimensional network, and this structure enables them to have very large surface areas per unit mass.
• the size and shape of zeolitic pores as well as the cage-like structure of the crystal determines the property of the zeolite. As the relative amount of alumina tetrahedra is increased the structure becomes more negatively charged. This results in increasing the amount of positively charged metal cations in the pores that would balance the crystal.
• zeolites are classified according to their SiO 2 /AI 2 O 3 ratios. In general they can have low (zeolite A and X), medium (X, mordenite), or high (Beta, ZSM-5) silica/alumina ratios. This property of zeolites controls their capacity to have silver ions in the structure, and their compatibility with the organic material while making the composite, as well as their antibacterial efficacy. Thus, the resulting composite can be tailored to have the antibacterial and mechanical properties desired for the specific application.
• Antibacterial efficacy of zeolites is significant for sterilization purposes.
• Antibacterial zeolite powders can be added into the microstructure of various materials that are handled daily (i.e, toilet seats, paper money, keyboards, etc.), or into household cleaners, fabrics, and biomedical devices to prevent buildup of bacteria on these materials.
• This invention involves synthesis of two different types of antibacterial zeolites with different SiO 2 /AI 2 O 3 ratios, preparation of the PU prepolymers in various physical forms, and combining these two in a composite structure.
• the resulting composite material resembles the polymer in thermal properties, but shows superior mechanical performance than the pure polymer.
• adjusting the parameters in preparation of both the polymer and zeolite i.e., chemical composition, crystal structure, pore size, etc
• the properties of the resulting product is controlled in the desired direction.
• This invention involves the ability of tailoring the zeolite synthesis and its crystaline and chemical properties, optimizing the synthesis parameters (temperature, time), and their compatibility with polymers, resulting in an improved poylymer-zeolite composite.
• resulting composites are mechanically stronger than polyurethanes currently used.
• Zeolites containing silver ions are incorporated into a biocompatible polymer for the first time, and the resulting composite material can have wide potential applications in many areas, such as medical devices, paper, textile, plastics, and detergents.
• this invention for the first time describes preparation of an antibacterial zeolite ( Zeolite Beta) with a high SiO 2 ZAI 2 O 3 ratio, and a large pore size, and the resulting product is incorporated into biomedical grade polyurethane for the first time, resulting in a new composite material. Moreover, this material is more compatible with the polymer, and the resulting composite is stronger than pure polyurethane.
• zeolites a property of Zeolite Beta is its high SiO 2 /AI 2 O 3 ratio, and for this reason it is highly hydrophobic than zeolites with low or medium SiO 2 /AI 2 O 3 ratios. Therefore Zeolite Beta is more compatible with polymer, and can have a homogeneous distribution in the composite.
• Zeolites are synthesized as micron and nanosized crystals and they are made antibacterial by loading with silver ions. In most cases materials are made antibacterial by adding metallic silver nanoparticles into the structure. However the antibacterial effect of metallic silver is less than ionic silver. Since micro and nanosized zeolite crystals are loaded with silver ions this will minimize the amount of silver used and the resulting product is much less costly. In literature it is reported that chitosan is made antibacterial by adding silver nanoparticles and zeolite A loaded with silver ions, and about 10 % less silver was needed in case of using zeolite A instead of silver nanoparticles. Moreover composites prepared with silver nanoparticles were mechanically weaker, since these were not distributed homogeneously in the structure.
• the composites composed of antibacterial zeolite and biomedical grade polyurethane film, fiber and sponges that are described in this invention are prepared by the following processing steps. • Synthesis of polurethane prepolymer,
• Biomedical grade polyurethane is synthesized from diisocyanide (DDI) and polyol with no other additives.
• PU Synthesis is done in a closed reactor under vacuum where a predetermined amount of DDI can be added. After polyol is heated to 70°C-150°C and the reactor is evacuated, DDI is added and polymerization starts and continues 70-150 0 C while the mixture is being stirred. Thus polyurethane prepolymer at a low viscosity is obtained.
• various amounts of DDI is added into the polyol in order to change the polyol/DDI ratio.
• the pure polyurethane produced has different mechanical properties depending on its synthesis conditions and the ratios of materials used. If desired, additives to extend the chain length (chemicals containing carbon and hydrogen, or oxygen, nitrogen and sulfur) can be used.
• PU synthesis involves using various diisocyanides and polyols at different ratios resulting in polymers with different mechanical properties.
• diisocyanides DI
• TDI toluene diisocyanide
• MDI 4-4 diphenyl diisocyanide
• HDl hexamethylene diisocyanide
• polyols polypropylene ethylene glycol (PPEG), polypropylene glycol
• DI diisocyanide
• TDI toluene diisocyanide
• MDI 4-4 diphenyl diisocyanide
• HDI hexamethylene diisocyanide
• NDI naphthalene-1 ,5 diisocyanide
• XDI xylene diisocyanide
• PICM dicyclohexylmethane diisocyanide
• IPDI isofurane diisocyanide
• Hi 2 MDI 4,4'- methyldicyclohexane diisocyanate
• CHDI 1,4-cyclohexane diisocyanate
• polyurethane and polyol other polymeric materials such as other carbon and hydrogen containing monomers and polymers, as well as the ones containing oxygen, nitrogen, sulfur, fluorine and chlorine containing monomers and polymers can be used.
• the temperature for synthesis reaction can vary in the range 50 to 200 0 C.
• Zeolite Beta with a high SiCVAI 2 O 3 ratio is synthesized hydrothermally from gel solutions.
• colloidal silica as a silica source (sodium silicate, sodium metasilicate pentahydrate, sodium metasilicate nonahydrate, fumed silica, precipitated silica, tetramethylorthosilicate, and tetraethylorthosilicate can be used as alternatives); sodium aluminate as an aluminate source (aluminum metal, aluminum nitrate, aluminum sulfate, aluminum hydroxide, aluminum isopropoxide can be used as alternatives); sodium hydroxide powder as a soda source; and tetraethyl ammonium hydroxide solution is used as the organic structure directing agent.
• the autoclaves were kept statically at 150 0 C in a conventional oven for 8 days.
• the resulting solid particles were vacuum-filtered, washed with deionized water and dried before storing.
• the SiO 2 /AI 2 O 3 ratio of the zeolite Beta synthesis gel composition is set at 20. This ratio is higher than any other ratios of the similar zeolite materials, such as zeolite A and X, as stated in other related studies and patents.
• sodium mathasilicate pentahydrate as a silica source (colloidal silica, sodium silicate, sodium metasilicate pentahydrate, sodium metasilicate nonahydrate, fumed silica, precipitated silica, tetramethylorthosilicate, and tetraethylorthosilicate can be used as alternatives); sodium aluminate as an aluminate source (aluminum metal, aluminum nitrate, aluminum sulfate, aluminum hydroxide, aluminum isopropoxide can be used as alternatives); sodium hydroxide powder as a soda source; and tetraethyl ammonium hydroxide solution is used
• tetraethylorthosilicate as a silica source
• aluminum isopropoxide as an aluminate source
• sodium hydroxide powder as a mineral source
• tetraethyl ammonium hydroxide solution is used as the organic structure directing agent.
• the clear gel compositions are prepared according to 0.6 Na 2 O: 1.8 AI 2 O 3 : 11.25 SiO 2 : 13.4 (TMA) 2 O: 700 H 2 O molar compositions. After keeping zeolite solutions at high temperature (80-100 0 C), the synthesized nano-zeolite crystals are obtained after high speed centrifugation, filtration and drying.
• the cation-exchange process is done using AgNO 3 to the synthesized zeolites in
• Step 2 Zeolite samples are put into a solution of AgNO 3 and the resulting solution is is stirred in the dark for some time in order to achieve the exchange of ions.
• the silver loaded zeolite powders are vacuum filtered and dried.
• the ion exchanged zeolite Beta is calcined afterwards in order to remove the organic structure directing agent, which is not necessary for other types of zeolites.
• Figure 1 and 2 are showing the scanning electron electron micrographs of silver loaded zeolit Beta ( Figure 1-a) and zeolite A ( Figure 1-b).
• Zeolite Beta is shown for the first time to possess an antibacterial effect, despite the relatively high SiO 2 ZAI 2 O 3 ratio, in spite of the fact that it exhibits less silver ion with respect ot the other well known antibacterial zeolites types. Furthermore, in the current invention, a nano-sized zeolite sample ( ⁇ 1 ⁇ m) was shown to exhibit antibacterial activity for the first time.
• Zeolites that were prepared as described in steps 2 and 3 were dried at 80 0 C, sieved (Sieve No. 100) to break up zeolite lumps and added to the freshly prepared viscous prepolymer. Desired amount of zeolite can be added into the mixture. Preferably, depending on the property of the polymer, %0.01-50 weight percent of zeolite is added to the prepolymer.
• the homogeneous mixture is prepared in the petri dishes after which it is placed in a vacuum oven and cured. At the end of the process, the prepared composites are taken out of the petri dishes, which are made ready for use.
• silver ion exchanged zeolites were added into a biomedical grade polyurethane, and this biomedical grade polyurethane composite was shown to possess antibacterial properties.
• a high SiO2/AI2O3 ratio zeolite Beta was used for composite making purposes for the first time, which shows superior mechanical properties with respect to the pure polyurethane.
• the same properties were obtained by using nano sized zeolite A instead of zeolite Beta.
• the present invention provides an antibacterial polymer article prepared by adding a high silica zeolite or a nano sized zeolite having antibacterial properties similar, which was prepared without using chemical linkers between the organic-inorganic materials.
• a great variety of polymers can be used with different variety of high silica and/or nano sized zeolites.
• polyurethane film compositions prepared from different diisocyanate and polyol types with different mole ratios are given in the table below.
• DDI TDI for T samples
• DD! MDI for M samples
• DDI HDI for D samples.
• M PPG is used as a polyol with molecular weight of 1025 g mol '1 in the sample notation of (1).
• b 2 PPG is used as a polyol with molecular weight of 2025 g mol "1 in the sample notation of (2).
• polypropylene ethylene glycol was used as the polyol and no chain extender was used.
• characteristic signals observed for polyurethane are at 3300 cm “1 and 1726-1705 cm “1 wavelenghts. All polyurethanes synthesized form diisocyanate and polyol have shown these characteristic FTIR signals.
• the signal at 3297cm “1 is the presence of structure hardening hydrogen bonding N-H stretching vibration.
• the signals at 2968 cm '1 and 2866 cm “1 corresponds to C-H bond asymmetric and symmetric stretching in polyurethane structure.
• DDI TDI for T samples
• DDI MDI for M samples
• DDI HDI for D samples.
• b 1 PPG is used as a polyol with molecular weight of 1025 g mol "1 in the sample notation of (1).
• b2 PPG is used as a polyol with molecular weight of 2025 g mol "1 in the sample notation of (2).
• 0 C defines the presence of chain extender. For all other samples, polypropylene ethylene glycol was used as the polyol and no chain extender was used.
• diisocyanates form the hard segments and polyols form the soft segments. Presence of hard segments in the structure increases materials resistance to deformation while soft segments effects the elongation upon tension.
• polyurethane structure when the amount of hard segments increases, ultimate elongation values are expected to decrease because of an increase in crosslinking. An increase in modulus and decrease in ultimate elongation was observed as the TDI content increases for TPU2.5T - TPU10T samples prepared from TDI. It is observed from the table that the use of chain extender increased the mechanical properties in polyurethane synthesis.
• chain extenders were not preferred in the current innovation and the desired mechanical properties were arranged by increasing the amount of diisocyanate.
• the selected polyol type as the molecular weight decreases from 2025 PPG to 1025 PPG, elastic modulus increases and elongation of materials decreases.
• MDI based polyurethanes had shown higher elastic modulus and lower elongation due to the stiffness of MD! aromatic ring. MDl produces stiffer polyurethanes in comparison with TDI.
• MPU10M and TPU10T samples it was observed that MPU 10M has higher elastic modulus.
• any other polymeric material such as any monomers and polymers containing either only carbon and hydrogen in their structure; or the ones containing oxygen, nitrogen, sulphur, florine, and chlorine in addition to carbon and hydrogen can be used.
• the antibacterial properties of zeolite powder samples with silver ion were tested on the most well known pathogenic Escherichia coli bacteria type.
• Ag + - zeolites were placed in the bacterial solutions prepared with deionized water. After waiting for 24 hours, they were taken from these solutions and placed in the feeding medium. The concentration of the solutions were arranged to make them 500 ppm.
• the antibacterial properties of Ag + - zeolites were examined by controlling the bacterial growth on agar plates.
• Figure 7-a shows the blank solution containing only E. Coli in deionized water, which was used to observe the normal growth of the bacteria on agar plates.
• Figures 7-b and c show the growth of bacteria on zeolite Beta and zeolite A without any silver ion loading; whereas Figures 7-d and e show the growth of bacteria on zeolite Beta and zeolite A with silver ion loading and thus were induced antibacterial properties.
• the embedded close-up figures are optical microscopy images of the agar surfaces. These tests clearly show that zeolites with no silver loading had no effect on the growth of E. Coli, while silver loaded zeolites showed antibacterial property even at low concentrations (500 ppm).
• Example 6 Antibacterial tests - Composite samples The effect of zeolite films and sponge composites with antibacterial properties on the bacterial growth were examined by disc diffusion test. For that purpose, the composite samples were placed on the agar plates containing bacterial colonies as described in Example 5, and the bacterial growth inhibition zones were observed around the composite samp ⁇ es.
• Figure 8 shows the diffusion test results carried out to examine the antibacterial properties of the composites.
• Figures 8-a , b, c, and d are showing the diffusion test results of pure polyurethane fiber (a), film (b), sponge (c) and after removal of sponge (d) from the media and their effects on the bacteria.
• Figure 8-a', b', c' and d' show the same materials prepared as composites with addition of silver ion loaded zeolite Beta and their effects on E. coli medium. Because of the porous structure of the sponge composites their adhesion on the feeding surface is small, and therefore the antibacterial effect is more clearly seen (d 1 ) after the removal of the material. As seen from the photograph the growth of the bacteria is prevented in the mentioned area.
• the composites of polyurethane fiber and films (a,b) obtained with addition of no water and the composites prepared with addition of silver ion containing zeolites (a' and b') are also shown.

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