IL184897A - Foamed polyurethane compositions - Google Patents

Description

POLYURETHANE COMPOSITIONS The present invention relates to copper-impregnated polyurethane foams with antimicrobial, antifungal and antiviral properties. More particularly, the present invention relates to a process for the production of polyurethane foams which can be either soft or hard and which have antibacterial, anti-fungal, anti-viral and anti-mite qualities.

As is known, polyurethane is any polymer consisting of a chain of organic units joined by urethane links. It is widely used in flexible and rigid foams, durable elastomers and high performance adhesives and sealants, fibers, seals, gaskets, condoms, carpet underlay, and hard plastic parts.

BACKGROUND Polyurethanes, also known as polycarbamates, belong to a larger class of compounds called polymers. Polymers are macromolecules made up of smaller, repeating units known as monomers. Generally, they consist of a primary long-chain backbone molecule with attached side groups. Polyurethanes are characterized by carbamate groups (-NHC02) in their molecular backbone. Synthetic polymers, like polyurethane, are produced by reacting monomers in a reaction vessel. In order to produce polyurethane, a step also known as condensation-reaction is performed. In this type of chemical reaction, the monomers that are present contain reacting end groups. Specifically, a diisocyanate (OCN-R-NCO) is reacted with a diol (HO-R-OH). The first step of this reaction results in the chemical linking of the two molecules leaving a reactive alcohol (OH) on one side and a reactive isocyanate (NCO) on the other. These groups react further with other monomers to form a larger, longer molecule. This is a rapid process which yields high molecular weight materials even at room temperature. Polyurethanes that have important commercial uses typically contain other functional groups in the molecule including esters, ethers, amides, or urea groups.

RAW MATERIALS A variety of raw materials are used to produce polyurethanes. These include monomers, prepolymers, stabilizers which protect the integrity of the polymer, and colorants.

Isocyanates One of the key reactive materials required to produce polyurethanes are diisocyanates. These compounds are characterized by a (NCO) group which are highly reactive alcohols. The most widely used isocyanates employed in polyurethane production are toluene diisocyanate (TDI) and polymeric isocyanate (PMDI). TDI is produced by chemically adding nitrogen groups on toluene, reacting these with hydrogen to produce a diamine, and separating the undesired isomers. PMDI is derived by a phosgenation reaction of aniline-formaldehyde polyamines. In addition to these isocyanates, higher end materials are also available. These include materials like 1 ,5-naphthalene diisocyanate and bitolylene diisocyanate. These more expensive materials can provide higher melting, harder segments in polyurethane elastomers.

Polyols The other reacting species required to produce polyurethanes are compounds that contain multiple alcohol groups (OH), called polyols. Materials often used for this purpose are polyether polyols which are polymers formed from cyclic ethers. They are typically produced through an alkylene oxide polymerization process. They are high molecular weight polymers that have a wide range of viscosity. Various polyether polyols that are used include polyethylene glycol, polypropylene glycol, and polytetramethylene glycol. These materials are generally utilized when the desired polyurethane is going to be used to make flexible foams or thermoset elastomers. Polyester polyols may also be used as a reacting species in the production of polyurethanes. They can be obtained as a byproduct of terephthalic acid production. They are typically based on saturated aromatic carboxylic acids and diols. Branched polyester polyols are used for polyurethane foams and coatings. Polyester polyols were the most used reacting species for the production of polyurethanes. However, polyether polyols became significantly less expense and have supplanted polyester polyols.

Some polyurethane materials can be vulnerable to damage from heat, light, atmospheric contaminants, and chlorine. For this reason, stabilizers are added to protect the polymer. One type of stabilizer that protects against light degradation is a UV screener called hydroxybenzotriazole. To protect against oxidation reactions, antioxidants are used. Various antioxidants are available such as monomeric and polymeric hindered phenols. Compounds which inhibit discoloration caused by atmospheric pollutants may also be added. These are typically materials with tertiary amine functionality that can interact with the oxides of nitrogen in air pollution. For certain applications, antimildew additives are added to the polyurethane product. After the polymers are formed and removed from the reaction vessels, they are naturally white. Therefore, colorants may be added to change their aesthetic appearance. Common covalent compounds for polyurethane fibers are dispersed and acid dyes.

Another way to describe polyurethanes is to refer to them as a class of compounds called reaction polymers, which include epoxies, unsaturated polyesters, and phenolics. As stated hereinbefore, a urethane linkage is produced by reacting an isocyanate group, -N=C=0 with a hydroxyl (alcohol) group, -OH. Polyurethanes are produced by the polyaddition reaction of a polyisocyanate with a polyalcohol (polyol) in the presence of a catalyst and other additives. In this case, a polyisocyanate is a molecule with two or more isocyanate functional groups, R-(N=C=0)n≥ 2 and a polyol is a molecule with two or more hydroxyl functional groups, R'-(OH)n≥ 2- The reaction product is a polymer containing the urethane linkage, -RNHCOOR'-. Isocyanates will react with any molecule that contains an active hydrogen. Importantly, isocyanates react with water to form a urea linkage and carbon dioxide gas; they also react with poly(ether)amines to form polyureas. Commercially, polyurethanes are produced by reacting a liquid isocyanate with a liquid blend of polyols, catalyst, and other additives. These two components are referred to as a polyurethane system, or simply a system. The isocyanate is commonly referred to as the Ά-side' or just the 'iso'. The blend of polyols and other additives is commonly referred to as the 'B-side' or as the 'poly'. This mixture might also be called a 'resin' or 'resin blend'. Resin blend additives may include chain extenders, cross linkers, surfactants, fire retardants, blowing agents, pigments, and fillers.

The first essential component of a polyurethane polymer is the isocyanate. Molecules that contain two isocyanate groups are called diisocyanates. These molecules are also referred to as monomers or monomer units, since they themselves are used to produce polymeric isocyanates that contain three or more isocyanate functional groups. Isocyanates can be classed as aromatic, such as diphenylmethane diisocyanate (MDI) or toluene diisocyanate (TDI); or aliphatic, such as hexamethylene diisocyanate (HDI) or isophorone diisocyanate (IPDI). An example of a polymeric isocyanate is polymeric diphenylmethane diisocyanate, which is a blend of molecules with two-, three-, and four- or more isocyanate groups, with an average functionality of 2.7. Isocyanates can be further modified by partially reacting them with a polyol to form a prepolymer. A quasi-prepolymer is formed when the stoichiometric ratio of isocyanate to hydroxyl groups is greater than 2:1. A true prepolymer is formed when the stoichiometric ratio is equal to 2:1. Important characteristics of isocyanates are their molecular backbone, % NCO content, functionality, and viscosity.

The second essential component of a polyurethane polymer is the polyol. Molecules that contain two hydroxyl groups are called diols, those with three hydroxyl groups are called triols, et cetera. In practice, polyols are distinguished from short chain or low-molecular weight glycol chain extenders and cross linkers such as ethylene glycol (EG), 1 ,4-butanediol (BDO), diethylene glycol (DEG), glycerine, and trimethylol propane (TMP). Polyols are polymers in their own right. They are formed by free radical addition of propylene oxide (PO), ethylene oxide (EO) onto a hydroxyl or amine containing initiator, or by polyesterification of a di-acid, such as adipic acid, with glycols, such as ethylene glycol or dipropylene glycol (DPG). Polyols extended with PO or EO are polyether polyols. Polyols formed by polyesterification are polyester polyols. The choice of initiator, extender, and molecular weight of the polyol greatly affect its physical state, and the physical properties of the polyurethane polymer. Important characteristics of polyols are their molecular backbone, initiator, molecular weight, % primary hydroxyl groups, functionality, and viscosity.

The polymerization reaction is catalyzed by tertiary amines, such as dimethylcyclohexylamine, and organometallic salts, such as dibutyltindilaurate. Furthermore, catalysts can be chosen based on whether they favor the urethane (gel) reaction, such as diazobicyclooctane, or the urea (blow) reaction, such as bis-dimethylaminoethylether, or specifically drive the isocyanate trimerization reaction, such as potassium octoate.

One of the most desirable attributes of polyurethanes is their ability to be turned into foam. Blowing agents such as water, and certain halocarbons, such as HFC-245fa, and hydrocarbons, such as n-pentane, can be incorporated into the poly side or added as an auxiliary stream. Water reacts with the isocyanate to create carbon dioxide gas, which fills and expands cells created during the mixing process. Halocarbons and hydrocarbons are chosen such that they have boiling points at or near room temperature. Since the polymerization reaction is exothermic, they volatilize into a gas during the reaction process, and fill and expand the cellular polymer matrix, creating a foam. It is important to know that the blowing gas does not create the cells of a foam. Rather, they are formed during the mixing process as nucleating sites that the blowing gas fills and expands. In fact, high density microcellular foams can be formed without the addition of blowing agents by mechanically frothing or nucleating the poly blend prior to use.

Surfactants are used to modify the characteristics of the polymer during the foaming process. The are used to emulsify the liquid components, regulate the cell size, and stabilize the cell structure to prevent collapse and surface defects. Rigid foam surfactants are designed to produce very fine cells, and a very high closed cell content. Flexible foam surfactants are designed to stabilize the reaction mass while at the same time maximizing open cell content to prevent the foam from shrinking.

The main polyurethane producing reaction is between a diisocyanate (aromatic and aliphatic types are available) and a polyol, typically a polypropylene glycol or polyester polyol, in the presence of catalysts and materials for controlling the cell structure, (surfactants) in the case of foams. Polyurethane can be made in a variety of densities and hardnesses by varying the type of monomer(s) used and adding other substances to modify their characteristics, notably density, or enhance their performance. Other additives can be used to improve the fire performance, stability in difficult chemical environments and other properties of the polyurethane products.

Though the properties of the polyurethane are determined mainly by the choice of polyol, the diisocyanate exerts some influence, and must be suited to the application. The cure rate is influenced by the functional group reactivity and the number of functional isocyanate groups. The mechanical properties are influenced by the functionality and the molecular shape. The choice of diisocyanate also affects the stability of the polyurethane upon exposure to light. Polyurethanes made with aromatic diisocyanates yellow with exposure to light, whereas those made with aliphatic diisocyanates are stable.

Softer, elastic, and more flexible polyurethanes result when linear difunctional polyethylene glycol segments, commonly called polyether polyols, are used to create the urethane links. This strategy is used to make spandex elastomeric fibers and soft rubber parts, as well as foam rubber. More rigid products result if polyfunctional polyols are used, as these create a three-dimensional cross-linked structure which, again, can be in the form of a low-density foam.

An even more rigid foam can be made with the use of specialty trimerization catalysts which create cyclic structures within the foam matrix, giving a harder, more thermally stable structure, designated as polyisocyanurate foams. Such properties are desired in rigid foam products used in the construction sector.

Polyurethane foam (including foam rubber) is usually made by adding small amounts of volatile materials, so-called blowing agents, to the reaction mixture. These can be simple volatile chemicals such as acetone or methylene chloride, or more sophisticated fluorocarbons which yield important performance characteristics, primarily thermal insulation.

Another common route to produce foams is the addition of water to one of the liquid precursors of polyurethane before they are mixed together. This reacts with a portion of the isocyanate, generating carbon dioxide throughout the liquid, creating relatively uniform bubbles which then harden to form a solid foam as polymerization progresses.

The presence of water means that a small proportion of reactions result in urea linkages— NC(=0)N— , rather than urethane linkages, so that the resulting material should technically be called poly(urethane-co-urea).

Careful control of viscoelastic properties— by modifying the catalysts and polyols used—can lead to memory foam, which is much softer at skin temperature than at room temperature.

There are then two main foam variants: one in which most of the foam bubbles (cells) remain closed, and the gas(es) remains trapped, the other being systems which have mostly open cells, resulting after a critical stage in the foam-making process (if cells did not form, or became open too soon, foam would not be created). This is a vitally important process: if the flexible foams have closed cells, their softness is severely compromised, they become pneumatic in feel, rather than soft; so, generally speaking, flexible foams are required to be open-celled.

The opposite is the case with most rigid foams. Here, retention of the cell gas is desired since this gas (especially the fluorocarbons referred to above) gives the foams their key characteristic: high thermal insulation performance.

A third foam variant, called microcellular foam, yields the tough elastomeric materials typically experienced in the coverings of car steering wheels and other interior automotive components.

Polyurethanes can be produced in four different forms including elastomers, coatings, flexible foams, and cross-linked foams. Elastomers are materials that can be stretched but will eventually return to their original shape. They are useful in applications that require strength, flexibility, abrasion resistance, and shock absorbing qualities. Thermoplastic polyurethane elastomers can be molded and shaped into different parts. This makes them useful as base materials for automobile parts, ski boots, roller skate wheels, cable jackets, and other mechanical goods. When these elastomers are spun into fibers they produce a flexible material called spandex. Spandex is used to make sock tops, bras, support hose, swimsuits, and other athletic apparel. Polyurethane coatings show a resistance to solvent degradation and have good impact resistance. These coatings are used on surfaces that require abrasion resistance, flexibility, fast curing, adhesion, and chemical resistance such as bowling alleys and dance floors. Water based polyurethane coatings are used for painting aircraft, automobiles, and other industrial equipment. Flexible foams are the largest market for polyurethanes. These materials have high impact strength and are used for making most furniture cushioning. They also provide the material for mattresses and seat cushions in higher priced furniture. Semiflexible polyurethane foams are used to make car dashboard and door liners. Other uses include carpet underlay, packaging, sponges, squeegees, and interior padding. Rigid, or cross-linked, polyurethane foams are used to produce insulation in the form of boards or laminate. Laminates are used extensively in the commercial roofing industry. Buildings are often sprayed with a polyurethane foam.

While polyurethane polymers are used for a vast array of applications, their production method can be broken into three distinct phases. First, the bulk polymer product is made. Next, the polymer is exposed to various processing steps. Finally, the polymer is transformed into its final product and shipped. This production process can be illustrated by looking at the continuous production of polyurethane foams.

According to the present invention, there is now provided a polyurethane foam comprising microscopic water insoluble particles of copper oxide incorporated in said foam wherein a portion of said particles in said foam are exposed and protruding from the surface of the foam and wherein said particles release Cu++ when exposed to water or water vapor.

In preferred embodiments of the present invention, said particles are of a size of between 0.5 and 2 microns.

Preferably, said particles are present in an amount of between 0.25 and 10% of the polyurethane weight.

In especially preferred embodiments of the present invention said microscopic water insoluble particles of copper oxide are selected from the group consisting of cupric oxide particles, cuprous oxide particles and mixtures thereof.

In a most preferred embodiment of the present invention said particles in said product are exposed and protrude from the surface of the product and said particles release Cu++ when exposed to water or water vapor.

In another preferred aspect of the present invention there is provided a method of making a polyurethane foam with antibacterial, antifungal and/or antiviral propertied comprising adding copper oxide particles to a reaction mixture of an isocyanate and of a polyol and mixing the same.

Antibacterial fibers are already taught and described in the prior art, and may be used in manufacture of fabrics, condoms, filters, diapers, bed linens, and other articles in which it is desirable to kill or retard growth of bacteria, fungi or viruses. A variety of approaches have been used to produce such fibers. For example, PCT publication WO 98/06508 describes an antibacterial textile in which fibers are plated with a metal or metal oxide. United States patent No. 7,169,402, which is incorporated herein by reference, describes polymers such as polyamide, polyester, and polypropylene which contain microscopic particles of copper oxide and exhibit antibacterial properties.

None of said references however, teach or suggest the production of a polyurethane foam having such properties, and none of said references teach or suggest the possibility of incorporating a copper oxide powder in polyurethane to provide the same with such properties.

More particularly, according to the present invention, it was unexpectedly and surprisingly found that when a copper oxide powder comprising a cupric oxide or a cuprous oxide or a combination thereof, was added to either the isocyanate or the polyols in a weight/weight proportion of 1% or 2% copper oxide to compound a number of things were observed: 1. The powder has a specific gravity of around 5. When added to the liquids which have the viscosity similar to water, the powder did not sink to the bottom as would have been expected, and remained suspended in the liquid during the foaming reaction. The raw powder was added to the compounds and stirred. When the 2 compounds were mixed and stirred lightly for a matter of seconds (not enough to prevent sedimentation) it was observed that the reaction began and the stirring was stopped. 2. The copper oxide did not upset any part of the reaction. As is known to someone familiar in the art, copper oxide compounds are very disruptive to most cross linking compounds or organic compounds as is seen when it is added to latex, polyester, polypropylene, polyamides, etc. 3. The copper oxide did not bind with any of the organic compounds in the foam and remained wholly independent and did not cross link in any way. 4. The dispersement of the copper oxide powder in a particulate size of about 1 micron was evenly spread throughout the resulting foam with no sedimentation on the bottom of the receptacle in which the experiment was conducted and particles of copper oxide were also seen as protruding from the surface of the formed foam.

Polyurethane products have many uses and very well known. Over three quarters of the global consumption of polyurethane products is in the form of foams, with flexible and rigid types being roughly equal in market size. In both cases, the foam is usually behind other materials: flexible foams are behind upholstery fabrics in commercial and domestic furniture. The process of adding a treated foam to a carpet can render the anti-microbial and anti-mite qualities to the carpet without having to use a separate foam backing but now as part of the actual carpet in anything from a thin to a thick foam; rigid foams are inside the metal and plastic walls of most refrigerators and freezers, or behind paper, metals and other surface materials in the case of thermal insulation panels in the construction sector. Its use in garments is growing: for example, in lining the cups of brassieres. The precursors of expanding polyurethane foam are available in many forms, for use in insulation, sound deadening, flotation, packing material, and even cast-in-place upholstery padding. Since they adhere to most surfaces and automatically fill voids, they have become quite popular in these applications.

The reaction of the foam can be retarded by physically removing the gasses as they are formed leaving a flat strong polymeric layer which can be used as a carpet backing or substrate.

While the invention will now be described in connection with certain preferred embodiments in the following examples and with reference to the accompanying figures so that aspects thereof may be more fully understood and appreciated, it is not intended to limit the invention to these particular embodiments. On the contrary, it is intended to cover all alternatives, modifications and equivalents as may be included within the scope of the invention as defined by the appended claims. Thus, the following examples which include preferred embodiments will serve to illustrate the practice of this invention, it being understood that the particulars shown are by way of example and for purposes of illustrative discussion of preferred embodiments of the present invention only and are presented in the cause of providing what is believed to be the most useful and readily understood description of formulation procedures as well as of the principles and conceptual aspects of the invention.

In the drawings: Figs. 1 , 2 and 3 present SEM and X-ray analyses of polyurethane foams produced according to the invention.

Figure 1 shows the control material of a normal rigid polyurethane foam with no copper oxide. The flora of normal elements are identified by the accompanying list of spectrographically identifiable elements. The spectrograph found no copper in or on the surface of the polyurethane.

Figure 2 shows the introduction of 1% of copper oxide powder when mixed weight/weight into the polyols and the resulting dispersion throughout the foam.

The spectrographic readings indicate the percentage of different elements on the surface of the polyurethane foam and copper oxide is clearly identified in the listing.

Figure 3 shows the introduction of 3% of copper oxide powder when mixed weight/weight into the polyols and the resulting dispersion throughout the foam. The spectrographic readings indicate the percentage of different elements on the surface of the polyurethane foam and the copper oxide is clearly identified in the listing. .

Example 1 Polymer reactions 1. At the start of polyurethane foam production, the reacting raw materials are held as liquids in large, stainless steel tanks. These tanks are equipped with agitators to keep the materials fluid. A metering device is attached to the tanks so that the appropriate amount of reactive material can be pumped out. A typical ratio of polyol to diisocyanate is 1 :2. Since the ratio of the component materials produces polymers with varying characteristics, it is strictly controlled. The weight of the polyols was measured and 1% and 3% by weight of the copper oxide powder was added to the agitated liquid In each experiment. The powder was added slowly to the liquid to avoid agglomeration and allowed to stir in the liquid. A change in the color of the liquid was observed. 2. The reacting materials are passed through a heat exchanger as they are pumped into pipes. The exchanger adjusts the temperature to the reactive level. Inside the pipes, the polymerization reaction occurs. By the time the polymerizing liquid gets to the end of the pipe, the polyurethane is already formed. On one end of the pipe is a dispensing head for the polymer. 3. Processing The dispensing head is hooked up to the processing line. For the production of rigid polyurethane foam insulation, a roll of baking paper is spooled at the start of the processing line. This paper is moved along a conveyor and brought under the dispensing head. 4. As the paper passes under, polyurethane is blown onto it. As the polymer is dispensed, it is mixed with carbon dioxide which causes it to expand. It continues to rise as it moves along the conveyor. (The sheet of polyurethane is known as a bun because it "rises" like dough.) . After the expansion reaction begins, a second top layer of paper is rolled on. Additionally, side papers may also be rolled into the process. Each layer of paper contains the polyurethane foam giving it shape. The rigid foam is passed through a series of panels that control the width and height of the foam bun. As they travel through this section of the production line, they are typically dried. It was observed that the color of the finished product changed. When cuprous oxide was added as described in step one, the liquid polyols turned orange but the finished product was a light grey. This would indicate that the oxidation state of the cuprous oxide was changed so that now it was cupric oxide. When cupric oxide was added to the polyols, the color of the liquid was grey and it in the finished product was still grey. Neither form of copper oxide showed any difference in biological activity. 6. At the end of the production line, the foam insulation is cut with an automatic saw to the desired length. The foam bun is then conveyored to the final processing steps which includes packaging, stacking, and shipping.

Fibers having microscopic water insoluble particles of copper oxide exposed and protruding from the surface of the fibers have been demonstrated to have antibacterial, antifungal and antiviral properties (e.g., US Pat. No. 7,169,402). It is clear that polyurethane foams similarly impregnated will have a similar effect. Biological activity can be demonstrated using routine assays including, but not limited to, those described in US Pat. No. 7,169,402. Suitable assays include AATCC Test Method 100 and the HIV proliferation assay described in the aforementioned patent.

Polyurethane foams incorporating 1% and 3% copper oxide according to the present invention, were tested against gram +, and gram - bacteria as well as against a fungus and a virus using test method AATCC 100. The results of these tests are seen in the following table.

As noted from said table, after 2 hours there was more than a 3 log reduction in the amount of pathogens which is equivalent to greater than a 99% reduction while in the control which was placed on an untreated carpet of polyurethane, there was noted an almost two-fold increase in the recovered inoculum.

It will be evident to those skilled in the art that the invention is not limited to the details of the foregoing illustrative examples and that the present invention may be embodied in other specific forms without departing from the essential attributes thereof, and it is therefore desired that the present embodiments and examples be considered in all respects as illustrative and not restrictive, reference being made to the appended claims, rather than to the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.

Claims (6)

1. A polyurethane foam comprising microscopic water insoluble particles of copper oxide incorporated in said foam wherein a portion of said particles in said foam are exposed and protruding from the surface of the foam and wherein said particles release Cu++ when exposed to water or water vapor.

2. A polyurethane foam according to claim 1 , wherein said particles are of a size of between 0.5 and 2 microns.

3. A polyurethane foam according to claim 1 , wherein said particles are present in an amount of between 0.25 and 10% of the polyurethane weight.

4. A polyurethane foam according to claim 1 , wherein said microscopic water insoluble particles of copper oxide are selected from the group consisting of cupric oxide particles, cuprous oxide particles and mixtures thereof.

5. A polyurethane foam comprising microscopic water insoluble particles of copper oxide incorporated in said product wherein a portion of said particles in said product are exposed and protrude from the surface of the product and wherein said particles release Cu++ when exposed to water or water vapor.

6. A method of making a polyurethane foam with antibacterial, antifungal and/or antiviral propertied comprising (i) adding copper oxide particles to a reaction mixture of an isocyanate and of a polyol and mixing the same. For the Applicant WOLFF, BREGMAN AND GOLLER