Aqueous zinc-containing coating compositions are provided in which the bonding agent is a blend of sodium and/or potassium silicate and lithium polysilicate the latter being in relatively high proportion particularly over 30% up to 70% by weight of silicate. Preferably the composition contains particulate flaked zinc. The composition is of particular value in enhancing corrosion resistance of articles produced from powdered metal or of non-passivated galvanized artefacts.

This invention relates to coating compositions, methods of preparing such compositions and surfaces coated with such compositions. In particular it relates to coatings useful in protection of articles produced by powder metallurgy techniques and otherwise-untreated galvanized articles from corrosion.
While one aspect of preparing a coating for a surface is to provide a decorative finish, even more important is to provide a resistance to environmental and atmospheric conditions. This is particularly true of coatings for metallic surfaces where materials present in the atmosphere, including both natural components such as water vapor and pollutants such as acids and other corrosive materials, can damage the surface of the metal. Many of the most commonly used coating materials contain organic resin materials to provide binding for the pigment and other corrosion resistant materials in the composition. Such organic pigments frequently require organic solvents to ensure their dispersion in the composition, which can create major pollution problems.
A particularly valuable type of anti-corrosion composition is one containing zinc. The outstanding corrosion resistance afforded by galvanizing has made it one of the most effective means for long term protection of steel from oxidation (rusting), and subsequent corrosion. It is the conventional method of providing protection for guard rails, transmission towers, light poles, electrical equipment and dozens of other specific applications. A coating of 5 mils or 125 microns of a galvanizing composition can protect its exposed equivalent for a period in excess of 20 years. Galvanizing coatings can be applied both by hot dipping and electroplating but these techniques have their limitations, particularly in regard to the shape of the article during installation. Typically galvanized products are then post treated to avoid the formation of xe2x80x9cwhite rustxe2x80x9d. In the past such treatments involved use of chromic acid or chromates. Use of these materials is, however, becoming recognized as creating unnecessary environmental hazzards. Today, use of polymer coatings is becoming more common to address this problem Alternatively in some situations, such as water treatment plants, corrosion inhibiting chemicals are being added to water that contacts the galvanized parts. Alternative ways of dealing with the problem are desirable. Coating compositions, sometimes known as zinc rich primers, have been considered to be optimum anti-corrosion coatings on iron or steel substrates. The zinc inhibits rust by reason of an electro-chemical interaction between the zinc and steel substrate. It is desirable to avoid too great a binder component to avoid insulating zinc particles from each other and the substrates but this can mean there are difficulties in application because of settling of the composition. There is a very extensive art on the use of zinc in coating compositions alone or in combination with other components such as glass microspheresxe2x80x94see for example U.S. Pat. No. 5,580,907 Ronald R. Savin.
The use of silicate bonded compositions particularly compositions containing zinc has been suggested for various types of surfaces.
In U.S. Pat. No. 5,792,803 there is described the use of alkyl silicates in an anhydrous alkyl alcohol in combination with epoxy or other polymeric resins as a binding agent.
U.S. Pat. No. 5,888,280 (Montes) describes a composition suitable for forming a protective coating on steel substrates comprising zinc dust, a group 1A metal silicate (preferably potassium silicate), a colloidal silica ingredient modified with a group 1A metal (preferably lithium polysilicate) and a carbonate-containing internal hardener.
U.S. Pat. No. 6,071,624 (Hubbard) describes an aqueous barrier coating for polymerizing substrates comprising a lithium-potassium copolysilicate.
U.S. Pat. No. 4,917,960 (Homberger) describes several different types of coating compositions for coating porous substrates on a metal base particularly for use in heat exchangers. Such substrates may include heat exchangers including a porous coating of bonded metal particles. The coatings applied to such substrates include fugitive materials to ensure that the coating applied to the bonded metal particle layer is also porous. Such fugitive materials maybe comprised of various bonding agents such as sodium or potassium silicates or lithium polysilicate. There is, however, no teaching of the use of a mixture of these materials. The coating may also contain metal particles, preferably particles of the same metal as is used from the substrate, such as aluminum.
British Patent 1,095,191 (Esso Research and Engineering) discloses coating compositions for metal comprising zinc dust and a lithium-sodium silicate solution.
U.S. Pat. No. 4,162,169 (Schutt, assigned to NASA) describes a paint binder for use in protection of ferrous articles or aluminum alloys which comprises a potassium or sodium silicate dispersion having a silicon dioxide to alkali metal molar ratio of 4.8:1 to 6.0:1 which is obtained by using silicon dioxide as a hydrogel and incorporation of a silicone.
It is desirable to use silicates which are soluble in water as distinct from organic silicates which create environmental problems because of the organic solvents.
Potassium silicates have been proposed. Thus for example corrosion-resistant coating can be prepared from zinc and potassium silicate. A powdered material comprising zinc dust, with a small content of mica and zinc oxide (5% or less each) is mixed with a water solution of potassium silicate (20% by weight), potassium hydroxide (0.5 to 5% by weight) and lithium polysilicate (5% by weight) with amorphous silica (5% by weight) and the resulting blend is sprayed onto the surface to be protected. The use of this primarily potassium silicate product has the disadvantage that there is a relatively slow development of water resistance.
The addition of the lithium polysilicate in proportions of 5% to 25% by weight to potassium silicate although found to improve the properties of potassium silicate indicated the contents of any silicate including the lithium polysilicate should be maintained relatively low.
It has now been determined that if sodium silicate or potassium silicate is combined with lithium polysilicate in a composition containing relatively high proportions or both sodium silicate and/or potassium silicate and lithium polysilicate there is obtained a silicate primer system which is both inexpensive and rapidly develops initial impressive water resistance. Lithium polysilicate (SiO2 20%, lithium 2%) is extremely effective as a binder for zinc rich coatings over blasted steel and becomes extremely insoluble in a very short period of time. Its adherence to cold rolled steel, galvanized products and other porous substrates is very poor. When subjected to baking for industrial application with or without zinc dust or zinc flake, lithium polysilicate will not bond satisfactorily to unblasted metallic substrates. There is obtained a coating composition which cured within a reasonable time and provided a composition which was then extremely resistant to corrosion even at relatively elevated temperatures.
According to the invention therefore there is provided a coating composition with a silicate binder in which the silicate binder comprises a sodium silicate or potassium silicate with a relatively high proportion of lithium polysilicate. As an embodiment of the invention there is provided a coating composition comprising zinc in particle form together with, as binding component, sodium or potassium silicate together with a significant proportion of lithium polysilicate composition all being dispersed in an aqueous medium.
Such compositions are of particular use in coating powdered metal artefacts and galvanized products that have not been passivated or pretreated, for example with a chromate or equivalent pretreatment.
In a particularly preferred embodiment of the invention there is dispersed into the coating composition zinc flake alone or combined with a proportion of zinc powder or zinc dust. As described in Savin International patent application number PCT/US99/06647 (U.S. application Ser. No. 09/075,302 filed May 8, 1998) the contents of which are incorporated by reference, the zinc flake material provides superior properties with relatively smaller proportions of zinc than were achievable with zinc powder or zinc dust.
The compositions of the present invention are of use in providing corrosion resistance to porous metal artefacts, for example those produced by powder metallurgy techniques in which metal particles are sintered together under pressure to produce artefacts of a desired shape. Since production of artefacts, for example automobile and aircraft parts such as gears and the like, by such techniques is often cheaper than by other processes, it would be desirable to increase use of powder metal techniques for producing such products. However, powder metal products, especially when made of a carbon steel, are particularly prone to corrosion because of their porous nature. Treatment of such artefacts with the zinc-silicate-polysilicate composition of the present invention provides a means for considerable reduction to their susceptibility to corrosion. I have found that use of an internal hardener such as a carbonate is not necessary for this purpose.
Another major use for the compositions of the invention, with or without the inclusion of zinc flake or dust, is in coating galvanized products to avoid the formation of white rust. The use of the compositions of the invention therefore provided a means.
I have found that it is often preferable to employ potassium silicate rather than sodium silicate when using the composition to treat porous metal articles or non-passivated galvanized products since this permits processing at lower temperatures, for example about 275xc2x0 F. as compared to temperatures in excess of 400xc2x0 F. which may be required with sodium silicate alone. For example, compositions of the present invention can be cured at temperatures in the range 250xc2x0 F. to 350xc2x0 F.
In an alternative embodiment of the invention some or all of the mixture of sodium and/or potassium silicate with lithium polysilicate may be replaced by an alkyl silicate, for example of the type described in my U.S. Pat. No. 5,413,628 which is incorporated herein by reference. Useful alkyl silicates include esters of silicic acid, especially ortho silicic acid with low molecular weight alkanols such as those having up to six carbon atoms. One particular alkyl silicate that may be of use is tetraethyl orthosilicate. When alkyl silicates are present, an additional solubilizing agent such as an alcohol may be of use.
Compositions for use in the invention are prepared as aqueous dispersions. The zinc particles are used in the form of dust or flake. I have found that when flake is used I can achieve good results with substantially lower amounts than with dust. Thus in cases where one is concerned about minimizing any increase in weight to an artefact by application of zinc, zinc flake is preferred. Additionally mixtures of zinc dust and zinc flake may be used. I have found it particularly useful to employ at least 35% of the zinc, for example more than 50% of the zinc, in the form of zinc flake for many applications. I believe that compositions containing zinc flake and a mixture of sodium and/or potassium silicate and lithium polysilicate are novel in that this mixture has not been applied to protect powdered metal parts from corrosion. When used herein the term xe2x80x9czinc dustxe2x80x9d refers to particles of a size of from 3 to 10 microns, having an apparent density above 3. Zinc flake refers to particles having a different aspect ratio than dust and having a particle size of 6-50 microns and an apparent density below 3, for example about 2.4.
The aqueous dispersion is either sprayed on to the articles to be treated or they are dipped into the dispersion. When a vacuum is applied to powdered metal parts, it has been found that the absorption of the compositions of the invention may be improved. For example in certain cases it may be possible to penetrate the whole of the artefact being treated, increasing the impregnating mass by as much as 500% further improving overall corrosion resistance. In some cases air drying of the product may be possible although in others heating, possibly up to 600xc2x0 C. may be necessary to dry the treated artefact.
In some cases agitation may be required in order to bring about good incorporation of all of the components into the composition. I have found particularly useful compositions to be those which include a combination of polyether-modified polydimenthyl siloxane and a silicone antifoaming agent.
Additional materials may be employed in compositions used in the invention. For example, it may be useful to add lithium hydroxide to act as a pH stabilizer for the composition. Suitable concentrations of lithium hydroxide for this purpose are in the range 10 to 30%, preferably 15% to 20%. Another example of possible additives are pigments which may be used to affect the surface appearance of the articles being treated, for example aluminum or, where a black color is desired, a black pigment such as graphite, manganese dioxide or black iron oxide or a mixture of any two or three of these. Coloring of galvanized products has been rare in the past because of the need for passivation. The present invention now permits the coloring of galvanized products for both decorative and functional purposes, for example th coloring of guard rails to alert drivers or the use of orange and white coloring to meet certain Federal Aviation Authority requirements for aircraft warnings
Sodium silicate has the advantage of being a low cost material usually dispersed to approximately 40% by weight in water and has been used in roofing granules baked at 1300xc2x0 F. and in the manufacture of soap and concrete curing compounds.
The use of the sodium silicate with lithium polysilicate give outstanding adhesion to numerous substances including stainless steel, fresh galvanized and other surfaces over which conventional potassium silicate developed inconsistent adhesion.
The precise proportion of sodium or potassium silicate and lithium polysilicate measured in terms of the parts by weight of the two silicates in the final composition can vary substantially depending on the other components and the degree to which the final composition is expected to be resistant to different types of environment. Each of the two silicate types, i.e. (a) lithium polysilicate and (b) sodium and/or potassium silicate measured by dry weight of silica and relative to each other in the final composition will be in the range 1:2 to 2:1 i.e. one third to two thirds of either of the silicate types with the balance being the other type. In a preferred proportion, the lithium polysilicate and sodium silicate and/or potassium silicate will be added by weight in a 1 to 1 proportion by weight to each other in the final composition particularly when one is examining total proportions of silicate close to the outer limits of the ranges for silicates.
I have found that it is preferable to maintain a high molar ratio of SiO2 to alkali metal for example in the range 4 to 7:1 preferably in the range 5 to 6:1.
Typically compositions of the present invention will penetrate a powdered metal artefact to a depth of 10 microns although greater penetration is possible when a vacuum is applied to the artefact being treated.
The sodium silicate is employed in the form of a sodium silicate solution containing approximately 30 to 50% by weight total solids with silicon as SiO2 being from 24 to 30 and sodium as Na2O approximately 9%, the weight ratio of SiO2 to Na2O being about 4. Such material is available commercially from, for example, Chemical Products Corporation and PQ Corporation. The composition will contain 50 to 70%. weight water. One useful composition contains about equal amounts of a 30% aqueous solution of silicate mixture and dust. If zinc flake is used, the amount of zinc used may be reduced to from 10-50%, typically 20-30% of what is required when zinc dust is used.
With this sodium silicate there can then be provided a substantial content of lithium polysilicate which is usually provided in the form of a stabilized colloidal solid containing approximately 20% silicate (SiO2) and 2% lithium as LiO, the lithium polysilicate being dispersed in water. The proportion of lithium polysilicate added will be from 30 to 60% by weight lithium polysilicate as compared to sodium polysilicate. Depending on the intended use, such composition may be combined with a zinc material which can be any of the conventional zinc powders or can be a zinc flake material as described in the above mentioned patent application (Savin). This is a flake material produced by a dry milling process.
In preparing the final compositions dispersing agents may be employed. A surprising aspect of the invention is that addition of certain dry finely divided silicates such as mica which is a natural blend of silica and alumina of low particle size to the composition provides a stable coating composition. The mica should be added to the final composition in a proportion of 2 to 10% by weight of the total composition. Mica typically has an analysis 45.5% silica SiO2, 36% Al2O3, 8.8% potassium oxide and small percentages of ferrous and ferric oxide and is a dry white odorless powder. The mica can be used in the region of 5 to 30 microns, preferably 6 to 10 microns. Other components can be added, for example titanium dioxide or other coloring components. Desirable particles have a median particle of 0.1 to 15 microns.
Use of only silicate as the bonding agent does tend to give a slightly inflexible coating which is perhaps over brittle for certain uses. This can be modified by the addition of small amounts of organic polymeric materials such as water-dispersed lattices of synthetic rubbers, polystyrene, polybutadiene etc., acrylic etc., as well as certain polymers of polyurethanes or possibly glycerols.
The invention will now be described in the accompanying Examples.


An article for providing a visual deterrent against theft of a portable electronic device is provided. The portable electronic device such as a portable computer has a first portion, such as a keyboard and body part and a second portion such as a display hinged for rotation relative to the first portion. The article comprises a body arranged to prevent hinging of the second portion relative to the first portion and a lock for preventing removal of the body of the article from the portable electronic device.

The present invention relates to portable computers and more specifically to devices for deterring theft of portable computers.
As portable computers such as laptop and notebook computers have become more popular and more powerful, they have become increasingly attractive targets for theft, including in the workplace of the computer""s user. Portable computers, such as the ThinkPad laptop from IBM Corporation, are designed to be easily portable and it is this characteristic which also makes them easy to steal (ThinkPad and IBM are trademarks of IBM Corporation). The main factors which make them so easy to steal is that they are relatively small and can be easily concealed in a briefcase, bag or simply carried under the arm. This results in office theft of a portable computer being much simpler than larger equipment such as personal computers.
As such thefts have become more common and more costly, an assortment of devices and systems have been proposed for securing portable computers from theft. Solutions such as password protection on BIOS, hard drive and operating system have been implemented. However, this does not provide a visual deterrent or increase the physical difficulty of stealing a mobile computer. A solution which does provide a visual deterrent is to fix machines to desks but this solution detracts from the advantages of having a portable computer.
U.S. Pat. No. 5,632,165 discloses a security anchor for a laptop computer which is adhesively attached to a surface of a laptop computer. A shaft at the end of a flexible security cable is inserted and locked inside the security anchor,, and cannot be removed until sliders within the security anchor are selectively arranged into a predetermined one of a combination of positions. A disadvantage of this device is that the bulk of the security anchor remains permanently attached to the computer, interfering with storage and positioning of the computer, and detracting from its external appearance.
An alternative security feature is found in certain laptop computers manufactured by International Business Machines Corporation, including the ThinkPad models 560, 760 and 770. An elongated slot in an exterior side surface of the base of the laptop computer accepts a suitably shaped locking pin attached to a security cable. The locking pin is inserted into the slot, rotated, and locked in place so as to prevent its removal from the laptop, thereby attaching the security cable to the computer. Because the components of portable computers are extremely small, the locking pin and security lock are necessarily small as well, and therefore provide only limited protection against theft.
German published patent application number DE 297 20 285 U1, discloses a theft prevention device, having a block attached to a thin carrier which is inserted in the gap between the keyboard and the screen of a laptop computer. The device has a hole for a padlock, securing the carrier to a security chain or steel cable. The carrier is a thin rectangular element, and the block is a rectangular solid extending upwardly from the carrier to prevent the carrier from being pulled from the rear of the computer through the gap between the keyboard and screen. This device can be used only in conjunction with a security chain or steel cable which is permanently affixed to the workplace.
Pending PCT patent application US98/15263 discloses a locking plate which secures a portable computer when open or closed, through a gap between the base and hinged cover and between two risers which extend upwardly from the base. The locking plate includes a thin flat rectangular stem pierced by a hole toward the distal end, and two thin flat flanges coplanar with the stem and extending in opposite directions perpendicularly to the stem. In use the locking plate lies flat on the tops of the key caps of the keyboard. A security cable is attached to the locking plate by a padlock, preventing the locking plate from being withdrawn back through the gap and thereby anchoring the computer. The thickness of the locking plate is sized to fit between the base and cover of the computer when the cover is closed. Alternative locking plates having different combinations of flanges and stems are disclosed, including: one stem and one flange; two stems and one flange; and two stems and three flanges. This device also requires a security chain or steel cable permanently affixed to the workplace.
There is thus a need for a security device as a visual deterrent to reduce the chances of theft of a portable computer without the need for a chain or cable permanently fixed to the workplace. Since portable computers are, by definition, portable, they are frequently used in locations where such a permanently affixed cable or chain is not available.
Accordingly, the present invention provides an article for providing a visual deterrent against theft of a portable electronic device, the device having a first portion and a second portion hinged for rotation relative to the first portion, the article having an open and a closed position, the first portion being substantially in planar contact with the second portion in the closed position and the first portion being in contact with the second portion along substantially one edge only in the open position, the article comprising: a body arranged to prevent hinging of the second portion relative to the first portion from an open position to a closed position; and a lock for preventing removal of the body of the article from the portable electronic device.
The present invention acts as a visual deterrent. Although this may not prevent theft of the computer, it helps to reduce the likelihood of theft. The present invention increases the difficulty of concealing and stealing a portable computer. The locking bar can be seen and is a visual deterrent, unlike passwords etc., which only become visible after theft of the machine when a thief tries to use the machine.
In a first embodiment, the body of the article comprises two portions, which, in use, are joined so as to surround the second portion of the portable electronic device. Such an embodiment may be easily used with an unmodified conventional portable computer.
In a preferred embodiment, the lock is a combination lock.
In a second embodiment, the portable electronic device further comprises a lock for retaining the body of the article and the body of the article is shaped and located so as to prevent hinging of the second portion relative to the first portion. Such an embodiment is more convenient for use by a user, but requires an adapted portable computer.


A livestock facility exhaust system to remove a majority of the dust and other such odorous airborne particulate material from air exhausted by power ventilation equipment from a livestock confinement building and without a significant increase in static pressure within the ventilation system. This is accomplished by a free standing enclosure of high strength air permeable material supported by a hoop structure around the exhaust end of the containment building of the livestock facility. Exhausted air enters the enclosure and is temporarily contained therein. Air circulates around impaction surfaces in the enclosure that promote precipitation of airborne particulates from the air stream. A discharge opening is located at or near the top of the enclosure. Exhaust air rid of most of the airborne particulates moves upward and out through the opening. The enclosure also serves to deflect outside wind from the fan orifices which helps to maintain fan performance.

Livestock is housed in buildings that need to be ventilated, either naturally or through the use of power equipment. Typically, air is exhausted from power ventilated livestock facilities by an appropriate number of 24 to 60 inch, high volume, electrically powered and controlled fans. This provides the appropriate air exchange rate for the animals housed inside the facility in accordance with environmental conditions present. In general, cooler conditions warrant low or minimum ventilation, just to keep air freshened, while warmer weather warrants a much higher ventilation rate to keep animals cool and comfortable. Power ventilation allows air to be pulled in one end or side opening of a building and through the living area of the animals, to be exhausted by the fans at the other end. This creates the air circulation needed.
Odor is inherent in this production system. Odor is generated from the animals, anaerobic degradation and volatilization of manure and urine, and from other sources present. Dust is also produced from sluffed animal dander and movement of feed. Research has shown that dust molecules attract and hold odor molecules such as ammonia, hydrogen sulfide and a wide range of volatile organic compounds.
This system of ventilation effectively removes dust and odors from the living space of animals, creating a better environment within. However air laden with dust and odor is discharged directly to the atmosphere at the fan end of the facility. This often causes a concentrated and objectionable odor plume downwind from these facilities.
The invention pertains to a livestock facility exhaust system to remove a majority of the dust and other such odorous airborne particulate material from air exhausted by power ventilation equipment from a livestock confinement building and without a significant increase in static pressure within the ventilation system.
It has been theorized that up to 90% of odor molecules exiting livestock production facilities are attached to airborne dust particles. Upon removal of a majority of this airborne material with the disclosed invention, odor release to the atmosphere is significantly reduced with less likelihood that downwind receptors will detect offensive odor.
The purpose of the invention is to substantially reduce the dust and odor discharge from livestock facilities employing power ventilation (as opposed to natural ventilation). This is accomplished by a free standing enclosure of high strength woven synthetic material supported by a hoop structure around the exhaust end of the containment building of the livestock facility. Exhausted air enters the enclosure and is temporarily contained therein. Air circulates around impaction surfaces in the enclosure that promote precipitation of airborne particulates from the air stream. A discharge opening is located at or near the top of the enclosure. Exhaust air rid of most of the airborne particulates moves upward and out through the opening. The enclosure also serves to deflect outside wind from the fan orifices which helps to maintain fan performance.
This structure presents numerous opportunities for removing dust from exhaust air. Dust particles are xe2x80x9cscrubbedxe2x80x9d from exhaust air by impaction, redirection and vortex forces created by the design of the enclosure and strategically placed impaction surfaces and material.
The free standing enclosure structure can be as wide as the fan wall itself. It typically extends out approximately 14 feet from the building and 10 feet from the fans, and is typically about 7 to 12 feet high at its highest point near the building. The sides of the enclosure extend to the building exterior wall. The bottom perimeter of the structure is enclosed with a flap that lies on the ground and is covered with gravel.
The enclosure defines a chamber that serves as a collection and impaction area. Exhausted air moves from the fan orifice to an area of lower pressure inside of the enclosure. The air slows in this area as it impacts various permeable surfaces, without causing a static pressure increase and subsequent reduction in fan efficiency. The air, once impacting the inner surfaces of the enclosure, is generally directed toward the ground where it tends to stall in the area furthest from the fan in the enclosure. Many dust particles will fall out of suspension at this point. The air stream, following a path of least resistance (and lowest pressure), reverses direction and exits out the opening in the top of the enclosure. Part of the air stream passes through the porous enclosure wall and dust is trapped by the fabric. Periodic rain events clean the fabric of excess dust. A disposable ground mat with dust retention characteristics can be placed on the floor of the structure to allow for the collection, storage and removal of accumulated dust as needed (likely once annually).
At times a xe2x80x9cVenturixe2x80x9d effect is created when the ambient wind sweeps over the discharge opening of the enclosure with sufficient speed to create a pressure differential. During such occurrences, air will actually be drawn out of the enclosure.

Livestock facility ventilation exhaust air dust removal system


Flexible polyurethane foams are prepared by reacting organic and/or modified organic polyisocyanates (a) with a polyetherol mixture (b) and, if required, further compounds (c) having hydrogen atoms reactive toward isocyanates, in the presence of water and/or other blowing agents (d), catalysts (e) and, if required, further assistants and additives (f), by a process in which the polyetherol mixture (b) consists of

The preparation of polyurethane foams by reacting organic and/or modified organic polyisocyanates and prepolymers with compounds which have a higher functionality and at least two reactive hydrogen atoms, for example polyoxyalkylenepolyamines and/or preferably organic polyhydroxy compounds, in particular polyetherols, having molecular weights of from 300 to 6000, and, if required, chain extenders and/or crosslinking agents having molecular weights of up to about 400, in the presence of catalysts, blowing agents, flameproofing agents, assistants and/or additives is known and has been widely described. A comprehensive overview of the preparation of polyurethane foams is given, for example, in Kunststoff-Handbuch, Volume VII, Polyurethane, 1st Edition 1966, edited by Dr. R. Vieweg and Dr. A. Hxc3x6bchtlen, and 2nd Edition, 1983, and 3rd Edition, 1993, each edited by Dr. G. Oertel (Carl Hanser Verlag, Munich).
For various fields of use, in particular the production of upholstered furniture and reclining furniture, for insulation purposes, in vehicle construction and in applications in the medical and hygiene sector, it is frequently desirable to use foams which are extremely soft and at the same time have a high level of mechanical properties.
EP-A-433889 claims flexible foams which have low compressive strength and are based on block polyoxypropylenepolyoxyethylenepolyol mixtures, the content of primary OH groups being from 3 to 8% by weight. U.S. Pat. No. 4,950,695 describes a soft foam, a correspondingly flexible foam being obtained by the use of monofunctional polyetherols. Up to 25% of monools can be used there. EP-A-422080 likewise mentions the use of monofunctional polyols (up to 80%) for obtaining flexible polyurethane foams. EP-A-703254 claims soft foams which are obtained by a polyol combination with the use of chain extenders and primary amines (up to 1% by weight). These hot foams were prepared with an index of about 70 but must be subjected to a heat treatment at relatively high temperatures after production. EP-A-339369 mentions polyetherols having a higher functionality as cell-opening agents and compositions for improving the foam flexibility. The preferred amount for use is up to 5% by weight. In comparison, EP-A-913414 describes very flexible foams which were prepared using nonylphenol-initiated polyol species. An insufficient level of mechanical property is achieved there. EP-A-547764 claims resilient MDI foams, with the concomitant use of ethylene oxide-rich polyols in amounts of up to 30% by weight. EP-A-547765 describes flexible polyurethane foams based on ethylene oxide-rich polyols ( greater than 50% of ethylene oxide), a random distribution of the ethylene oxide being present within the polyether chain. The isocyanate used comprises  greater than 85% of 4,4xe2x80x2-MDI.
U.S. Pat. No. 4,929,646 describes an ethylene oxide-rich polyol having a high functionality as a cell-opening agent. According to U.S. Pat. No. 3,857,800, up to 15% of ethylene oxide-rich polyols are used in the polyol mixture in order to obtain better cell opening. In WO-A-97/23545, ethylene oxide-rich polyols are used in order to obtain hydrophilic flexible foams. Said polyols have a propylene oxide terminal block, resulting in high proportions of secondary OH groups. U.S. Pat. No. 5,011,908 claims flexible foams which may comprise up to 10% of ethylene oxide-rich polyetherols. Relatively resilient foams are obtained there.
EP-A-731120, EP-A-884338 and DE-A-19508079 describe sorbitol-based polyetherols having a relatively high functionality for the preparation of resilient flexible foams. By using such polyols which carry a terminal ethylene oxide block, the required process safety in the preparation of such resilient flexible foams is achieved. However, the foams thus prepared are relatively rigid. DE-A-19725020 claims resilient flexible foams in which in particular combinations of polyols having a high functionality and an ethylene oxide endcap and polymeric polyols are used. However, substantial rigidity is also obtained in the case of these foams. EP-A-733078 describes resilient foams. Once again, polyetherols having a high functionality are used for the slabstock foams thus produced. The processing latitude is within an index range of from 75 to 120. Ethylene oxide-rich polyols are present as cell-opening agents.
According to EP-A-549120, ethylene oxide-rich polyols and amino-containing chain extenders are used in order to obtain resilient flexible foams. In selected casesxe2x80x94as a rule ethylene oxide-rich polyetherols are also contained in the foam formulationxe2x80x94an attempt is made to establish an insulating character of the foams by special processing, in particular with pronounced undercrosslinking. As a rule, foaming is effected with an index of about 60-80. Thus, DE-A-3710731 describes a flexible foam of this type having sound-insulating and antidrumming properties. It is based on the fact that the elastic properties generally decrease with a decrease in the index.
DE-A-4129666 uses polyols which are incompatible with one another and which slowly separate, in order to establish the acoustic properties. The foams are processed with indices of  less than 80, which can affect the mechanical properties. It is shown that the resilience of the foams decreases with a reduction in the index. Furthermore, the elongation properties deteriorate.
The inventions mentioned in the prior art all permit the preparation of flexible foams having medium hardness, there still being a notable potential for improvement with respect to the properties and the processability in the case of this class of substance.
It is an object of the present invention to provide flexible polyurethane foams which are easy to process, with the use of both tolylene diisocyanate and in particular diphenylmethane diisocyanate isomers, and which are extremely flexible and at the same time have a high level of mechanical properties.
We have found that this object is achieved, surprisingly, by using a polyetherol mixture (b) which consists of at least one polyetherol which is at least difunctional, has an OH number of from 20 to 100 mg KOH/g and is based on propylene oxide and/or butylene oxide and ethylene oxide, having an ethylene oxide content of more than 40% by weight, based on the total amount of alkylene oxide used, and, if required, further at least difunctional polyetherols based on propylene oxide and/or butylene oxide and ethylene oxide and having an OH number of from 20 to 160 mg KOH/g (b1) and at least one difunctional to hexafunctional polyetherol based on propylene oxide and/or butylene oxide and having an OH number of less than 800 mg KOH/g (b2) for the preparation of the flexible polyurethane foams, and preparing the foams with indices of less than 110, the amount by weight of (b1) being greater than that of (b2).
The present invention therefore relates to a process for the preparation of flexible polyurethane foams by reacting organic and/or modified organic polyisocyanates (a) with a polyetherol mixture (b) and, if required, further compounds (c) having hydrogen atoms reactive toward isocyanates, in the presence of water and/or other blowing agents (d), catalysts (e) and, if required, further assistants and additives (f), wherein the polyetherol mixture (b) consists of
b1) at least one polyetherol which is at least difunctional, has an OH number of from 20 to 100 mg KOH/g and is based on propylene oxide and/or butylene oxide and ethylene oxide, having an ethylene oxide content of more than 40% by weight, based on the total amount of alkylene oxide used, and, if required, further polyetherols which are at least difunctional, are based on propylene oxide and/or butylene oxide and ethylene oxide and have an OH number of from 20 to 160 mg KOH/g, and
b2) at least one difunctional to hexafunctional polyetherol based on propylene oxide and/or butylene oxide and having an OH number of less than 800 mg KOH/g
and the foams are prepared with indices of less than 110, the amount by weight of (b1) being greater than that of (b2).
The present invention furthermore relates to flexible polyurethane foams themselves prepared by this process and their use for upholstery purposes, insulation purposes, in vehicle construction and in the medical and hygiene sector.
In our investigations, we surprisingly found that the use of the novel combination of polyols (b) in the stated ratio resulted in a flexible foam whose resilience increases considerably with decreasing index. The person skilled in the art would actually have expected that limp highly insulating foams would result with decreasing index owing to the chain terminations occurring thereby. This principle is used, inter alia, to obtain highly insulating flexible carpet foams which are then processed in an index range of  less than 80.
Regarding the components used according to the invention in the polyol mixture, the following may be stated:
The component (b1) consists of at least one polyetherol which is at least difunctional, has an OH number of from 20 to 100 mg KOH/g and is based on propylene oxide and/or butylene oxide and ethylene oxide, having an ethylene oxide content of more than 40, preferably more than 60, % by weight, based in each case on the total amount of alkylene oxide used.
For example, the following are suitable as (b1): polyetherols based on ethylene glycol, glycerol or trimethylolpropane as initiator with a terminal ethylene oxide block or with random incorporation of the ethylene oxide. Polyetherols based on glycerol and having an ethylene oxide endcap are preferably used, but a propylene oxide endcap may also be employed.
In addition to the polyetherols described, further at least difunctional polyetherols based on propylene oxide and/or butylene oxide and ethylene oxide and having an OH number of from 20 to 160 mg KOH/g can, if required, be concomitantly used.
Examples of suitable initiators for this purpose are glycerol, trimethylolpropane, pentaerythritol and sorbitol.
The polyetherols having an OH number of from 20 to 100 mg KOH/g and an ethylene oxide content of more than 40% by weight should preferably contain at least 60, preferably  greater than 80, % by weight, based on the total amount of the polyetherols (b1) used.
The component (b2) consists of at least one difunctional to hexafunctional polyetherol based on propylene oxide and/or butylene oxide and having an OH number of less than 800, preferably  less than 500, mg KOH/g.
For example, the following are suitable as (b2): polyetherols based on propylene glycol, glycerol, tolylenediamine and sorbitol and propylene oxide. Polypropylene glycol based on propylene glycol or glycerol is preferably used.
According to the invention, the amount by weight of (b1) is greater than that of (b2).
The weight ratio of component (b1) to component (b2) is preferably from 2:1 to 40:1, advantageously from 2:1 to 25:1, particularly preferably from 2:1 to 15:1.
Said polyetherols are prepared by known processes, as described by way of example further below.
The novel flexible polyurethane foams are prepared by reacting organic and/or modified organic polyisocyanates (a) with the polyetherol mixture (b) described above and, if required, further compounds (c) having hydrogen atoms reactive toward isocyanates, in the presence of water and/or other blowing agents (d), catalysts (e) and, if required, further assistants and additives (f).
The foams are prepared, according to the invention, with indices of less than 110, preferably less than 95, particularly preferably less than 75.
Regarding the further starting components to be used, the following may be stated specifically:
Suitable organic polyisocyanates (a) for the preparation of the novel polyurethanes are the aliphatic, cycloaliphatic, araliphatic and preferably aromatic polyfunctional isocyanates known per se.
Specific examples are alkylene diisocyanates having 4 to 12 carbon atoms in the alkylene radical, such as dodecane 1,12-diisocyanate, 2-ethyltetramethylene 1,4-diisocyanate, 2-methylpentamethylene 1,5-diisocyanate, tetramethylene 1,4-diisocyanate and preferably hexamethylene 1,6-diisocyanate; cycloaliphatic diisocyanates, such as cyclohexane 1,3- and 1,4-diisocyanate and any desired mixtures of these isomers, 1-isocyanato-3,3,5-trimethyl-5-isocyanatomethylcyclohexane (IPDI), hexahydrotolylene 2,4- and 2,6-diisocyanate and the corresponding isomer mixtures, dicyclohexylmethane 4,4xe2x80x2-, 2,2xe2x80x2- and 2,4xe2x80x2-diisocyanate and the corresponding isomer mixtures, and preferably aromatic di- and polyisocyanates, e.g. tolylene 2,4- and 2,6-diisocyanate and the corresponding isomer mixtures, diphenylmethane 4,4xe2x80x2-, 2,4xe2x80x2- and 2,2xe2x80x2-diisocyanate and the corresponding isomer mixtures, mixtures of diphenylmethane 4,4xe2x80x2- and 2,2xe2x80x2-diisocyanates, polyphenylpolymethylene polyisocyanates, mixtures of diphenylmethane 4,4xe2x80x2-, 2,4xe2x80x2- and 2,2xe2x80x2-diisocyanates and polyphenylpolymethylene polyisocyanates (crude MDI) and mixtures of crude MDI and tolylene diisocyanates. The organic di- and polyisocyanates can be used individually or in the form of their mixtures.
Tolylene diisocyanate, mixtures of diphenylmethane diisocyanate isomers, mixtures of diphenylmethane diisocyanate and crude MDI or tolylene diisocyanate with diphenylmethane diisocyanate and/or crude MDI are preferably used. Mixtures of diphenylmethane diisocyanate isomers with at least 30% by weight of diphenylmethane 2,4xe2x80x2-diisocyanate are particularly preferably used.
Frequently, modified polyfunctional isocyanates, i.e. products which are obtained by chemical reaction of organic di- and/or polyisocyanates, are also used. Examples are di- and/or polyisocyanates containing ester, urea, biuret, allophanate, carbodiimide, isocyanurate, uretdione and/or urethane groups. Specific examples are organic, preferably aromatic polyisocyanates containing urethane groups and having NCO contents of from 43 to 15, preferably from 31 to 21, % by weight, based on the total weight, diphenylmethane 4,4xe2x80x2-diisocyanate modified by reaction with, for example, low molecular weight diols, triols, dialkylene glycols, trialkylene glycols or polyoxyalkylene glycols having molecular weights of up to 6 000, in particular up to 1 500, modified diphenylmethane 4,4xe2x80x2- and 2,4xe2x80x2 diisocyanate mixtures or modified crude MDI or tolylene 2,4- and 2,6-diisocyanate. The di- and polyoxyalkylene glycols can be used individually or as mixtures, examples being diethylene and dipropylene glycol, polyoxyethylene, polyoxypropylene and polyoxypropylenepolyoxyethylene glycols, -triols and -tetraols. NCO-containing prepolymers having NCO contents of from 25 to 3.5, preferably from 21 to 14, % by weight, based on the total weight, prepared from the polyesterpolyols and/or preferably polyetherpolyols described below and diphenylmethane 4,4xe2x80x2-diisocyanate, mixtures of diphenylmethane 2,4xe2x80x2- and 4,4xe2x80x2-diisocyanate, tolylene 2,4xe2x80x2- and/or 2,6xe2x80x2-diisocyanates or crude MDI, are also suitable. Liquid polyisocyanates containing carbodiimide groups and/or isocyanurate rings and having NCO contents of from 43 to 15, preferably from 31 to 21, % by weight, based on the total weight, for example based on diphenylmethane 4,4xe2x80x2-, 2,4xe2x80x2- and/or 2,2xe2x80x2-diisocyanate and/or tolylene 2,4- and/or 2,6-diisocyanate have furthermore proven useful.
The modified polyisocyanates can be mixed with one another or with unmodified organic polyisocyanates, e.g. diphenylmethane 2,4xe2x80x2- or 4,4xe2x80x2-diisocyanate, crude MDI, tolylene 2,4- and/or 2,6-diisocyanate.
Modified organic polyisocyanates which have proven particularly useful are NCO-containing prepolymers which are advantageously formed from the reaction of the isocyanates (a) with the polyetherols (b) and, if required, compounds of components (c) and/or (d).
In addition to the polyetherol mixture (b) described above and used according to the invention, further compounds (c) having hydrogen atoms reactive toward isocyanates may be present if required.
Compounds having at least two reactive hydrogen atoms are primarily suitable for this purpose. Those having a functionality of from 2 to 8, preferably from 2 to 3, and an average molecular weight of from 300 to 8 000, preferably from 300 to 5 000, are expediently used. The hydroxyl number of the polyhydroxy compounds is as a rule from 20 to 160, preferably from 28 to 56.
The polyetherpolyols used in the components (b) and (c) are prepared by known processes, for example by anionic polymerization with alkali metal hydroxides, e.g. sodium hydroxide or potassium hydroxide, or alkali metal alcoholates, e.g. sodium methylate, sodium ethylate, potassium ethylate or potassium isopropylate, as catalysts and with the addition of at least one initiator which contains from 2 to 8, preferably 2 or 3, reactive hydrogen atoms bonded per molecule, or by cationic polymerization with Lewis acids, such as antimony pentachloride, boron fluoride etherate, etc., or bleaching earth as catalysts or by double metal cyanide catalysis from one or more alkylene oxides having 2 to 4 carbon atoms in the alkylene radical. For special purposes, monofunctional initiators may also be incorporated into the polyether structure.
Suitable alkylene oxides are, for example, tetrahydrofuran, 1,3-propylene oxide, 1,2- and 2,3-butylene oxide, styrene oxide and preferably ethylene oxide and 1,2-propylene oxide. The alkylene oxides can be used individually, alternately in succession or as mixtures.
Examples of suitable initiator molecules are water, organic dicarboxylic acids, such as succinic acid, adipic acid, phthalic acid and terephthalic acid, aliphatic and aromatic, unsubstituted or N-monoalkyl-, N,N-dialkyl- and N,Nxe2x80x2-dialkyl-substituted diamines having 1 to 4 carbon atoms in the alkyl radical, such as unsubstituted or monoalkyl- or dialkyl-substituted ethylenediamine, diethylenetriamine, triethylenetetramine, 1,3-propylenediamine, 1,3- or 1,4-butylenediamine, 1,2-, 1,3-, 1,4-, 1,5- or 1,6-hexamethylenediamine, phenylenediamine, 2,3-, 2,4- or 2,6-tolylenediamine or 4,4xe2x80x2-, 2,4xe2x80x2- or 2,2xe2x80x2-diaminodiphenylmethane. Other suitable initiator molecules are alkanolamines, e.g. ethanolamine and N-methyl- and N-ethylethanolamine, dialkanolamines, e.g. diethanolamine and N-methyl- and N-ethyldiethanolamine, and trialkanolamines, e.g. triethanolamine, and ammonia. Polyhydric, in particular dihydric and/or trihydric, alcohols, such as ethanediol, 1,2- and 2,3-propanediol, diethylene glycol, dipropylene glycol, 1,4-butanediol, 1,6-hexanediol, glycerol, trimethylolpropane and pentaerythritol, are preferably used.
The polyetherpolyols, preferably polyoxypropylene- and polyoxypropylenepolyoxyethylene polyols, have a functionality of, preferably, from 2 to 8, in particular from 2 to 3, and molecular weights of from 300 to 8 000, preferably from 300 to 6 000, in particular from 1 000 to 5 000, and suitable polyoxytetramethylene glycols have a molecular weight of up to about 3 500.
Other suitable polyetherpolyols are polymer-modified polyetherpolyols, preferably graft polyetherpolyols, in particular those based on styrene and/or acrylonitrile, which are prepared by in situ polymerization of acrylonitrile, styrene or preferably mixtures of styrene and acrylonitrile, for example in a weight ratio of from 90:10 to 10:90, preferably from 70:30 to 30:70, expediently in the abovementioned polyetherpolyols, analogously to German Patents 1111394, 1222669 (U.S. Pat. Nos. 3,304,273, 3,383,351, 3,523,093), 1152536 (GB 1040452) and 1152537 (GB 987618), and polyetherpolyol dispersions which contain, as the disperse phase, usually in an amount of from 1 to 50, preferably from 2 to 25, % by weight, for example polyureas, polyhydrazides, polyurethanes containing bonded tertiary amino groups and/or melamine and which are described, for example, in EP-B-011752 (U.S. Pat. No. 4,304,708), U.S. Pat No. 4,374,209 and DE-A-3231497.
The polyetherpolyols can be used individually or in the form of mixtures.
In addition to the polyetherpolyols described, for example, polyetherpolyamines and/or further polyols selected from the group consisting of the polyesterpolyols, polythioetherpolyols, polyesteramides, hydroxyl-containing polyacetals and hydroxyl-containing aliphatic polycarbonates or mixtures of at least two of said polyols may also be used. The hydroxyl number of the polyhydroxy compounds is as a rule from 20 to 80, preferably from 28 to 56.
Suitable polyesterpolyols can be prepared, for example, from organic dicarboxylic acids of 2 to 12 carbon atoms, preferably aliphatic dicarboxylic acids of 4 to 6 carbon atoms, polyhydric alcohols, preferably diols, of 2 to 12, preferably 2 to 6, carbon atoms, by conventional processes. Usually, the organic polycarboxylic acids and/or derivatives thereof and polyhydric alcohols are subjected to polycondensation, advantageously in a molar ratio of from 1:1 to 1:1.8, preferably from 1:1.05 to 1:1.2, in the absence of a catalyst or preferably in the presence of esterification catalysts, expediently in an atmosphere comprising inert gas, e.g. nitrogen, carbon monoxide, helium, argon, etc., in the melt at from 150 to 250xc2x0 C., preferably from 180 to 220xc2x0 C., under atmospheric or reduced pressure, until the desired acid number is obtained, which is advantageously less than 10, preferably less than 2.
Examples of suitable hydroxyl-containing polyacetals are the compounds which can be prepared from glycols, such as diethylene glycol, triethylene glycol, 4,4xe2x80x2-dihydroxyethoxydiphenyldimethylmethane or hexanediol, and formaldehyde. Suitable polyacetals can also be prepared by polymerization of cyclic acetals. Suitable hydroxyl-containing polycarbonates are those of the type known per se, which can be prepared, for example, by reacting diols, such as 1,3-propanediol, 1,4-butanediol and/or 1,6-hexanediol, diethylene glycol, triethylene glycol or tetraethylene glycol, with diaryl carbonates, e.g. diphenyl carbonate or phosgene. The polyesteramides include, for example, the predominantly linear condensates obtained from polybasic, saturated and/or unsaturated carboxylic acids or their anhydrides and polyhydric saturated and/or unsaturated amino alcohols or mixtures of polyhydric alcohols and amino alcohols and/or polyamines. Suitable polyetherpolyamines can be prepared from the abovementioned polyetherpolyols by known processes. The cyanoalkylation of polyoxyalkylenepolyols and subsequent hydrogenation of the nitrile formed (U.S. Pat. No. 3,267,050) or the partial or complete amination of polyoxyalkylenepolyols with amines or ammonia in the presence of hydrogen and catalysts (DE-A-1215373) may be mentioned by way of example.
The compounds of component (c) can be used individually or in the form of mixtures.
The flexible polyurethane foams can be prepared in the presence or absence of chain extenders and/or crosslinking agents, but these are generally not required. The chain extenders and/or crosslinking agents used are diols and/or triols having molecular weights of less than 400, preferably from 60 to 300. For example, aliphatic, cycloaliphatic and/or araliphatic diols of 2 to 14, preferably 4 to 10, carbon atoms, e.g. ethylene glycol, 1,3-propanediol, 1,10-decanediol, o-, m- and p-dihydroxycyclohexane, diethylene glycol, dipropylene glycol and preferably 1,4-butanediol, 1,6-hexanediol and bis(2-hydroxyethyl)hydroquinone, triols, such as 1,2,4- and 1,3,5-trihydroxycyclohexane, triethanolamine, diethanolamine, glycerol and trimethylolpropane, and low molecular weight hydroxyl-containing polyalkylene oxides based on ethylene oxide and/or 1,2-propylene oxide and the abovementioned triols and/or diols are suitable as initiator molecules.
If chain extenders, crosslinking agents or mixtures thereof are used for the preparation of the polyurethane foams, they are expediently used in an amount of up to 10% by weight, based on the weight of the polyol compounds.
The blowing agents (d) used may be the chlorofluorocarbons (CFCs) generally known from polyurethane chemistry as well as highly fluorinated and/or perfluorinated hydrocarbons. However, the use of these substances is greatly restricted or has been completely discontinued for ecological reasons. In addition to chlorofluorocarbons and fluorocarbons, in particular aliphatic and/or cycloaliphatic hydrocarbons, especially pentane and cyclopentane, or acetals, e.g. methylal, are possible alternative blowing agents. These physical blowing agents are usually added to the polyol component of the system. However, they can also be added to the isocyanate component or as a combination of both the polyol component and the isocyanate component. Their use together with highly fluorinated and/or perfluorinated hydrocarbons, in the form of an emulsion of the polyol component, is also possible. Emulsifiers, if used, are usually oligomeric acrylates which contain polyoxyalkylene and fluoroalkane radicals bonded as side groups and have a fluorine content of from about 5 to 30% by weight. Such products are sufficiently well known from plastics chemistry (e.g. EP-A-0351614). The amount of blowing agent or of blowing agent mixture used is from 1 to 25, preferably from 1 to 15, % by weight, based in each case on the total weight of the components (b) to (d).
It is also possible and usual to add water in an amount of from 0.5 to 15, preferably from 1 to 5, % by weight, based on the total weight of the components (b) to (f), as blowing agent to the polyol component. The addition of water can be effected in combination with the use of the other blowing agents described.
For the purposes of the present invention, water is preferably used as the blowing agent.
Catalysts (e) used for the preparation of the flexible polyurethane foams are in particular compounds which greatly accelerate the reaction of the reactive hydrogen atoms, in particular of hydroxyl-containing compounds of components (b), (c) and (d), with the organic, unmodified or modified polyisocyanates (a). Organic metal compounds, preferably organic tin compounds, such as tin(II) salts of organic carboxylic acids, e.g. tin(II) acetate, tin(II) octanoate, tin(II) ethylhexanoate and tin(II) laurate, and the dialkyltin(IV) salts of organic carboxylic acids, e.g. dibutyltin diacetate, dibutyltin dilaurate, dibutyltin maleate and dioctyltin diacetate, are suitable. The organic metal compounds are used alone or, preferably, in combination with strongly basic amines. Examples are amidines, such as 2,3-dimethyl-3,4,5,6-tetrahydropyrimidine, tertiary amines, such as triethylamine, tributylamine, dimethylbenzylamine, N-methyl-, N-ethyl- and N-cyclohexylmorpholine, N,N,Nxe2x80x2,Nxe2x80x2-tetramethylethylenediamine, N,N,Nxe2x80x2,Nxe2x80x2-tetramethylbutanediamine, N,N,Nxe2x80x2,Nxe2x80x2-tetramethylhexane-1,6-diamine, pentamethyldiethylenetriamine, tetramethyldiaminoethyl ether, bis(dimethylaminopropyl)urea, dimethylpiperazine, 1,2-dimethylimidazole, 1-azabicyclo[3.3.0]octane and preferably 1,4-diazabicyclo[2.2.2]octane, and aminoalkanol compounds, such as triethanolamine, triisopropanolamine, N-methyl- and N-ethyldiethanolamine and dimethylethanolamine.
Other suitable catalysts are tris(dialkylaminoalkyl)-s-hexahydrotriazines, in particular tetraalkylammonium hydroxides, such as tetramethylammonium hydroxide, alkali metal hydroxides, such as sodium hydroxide, and alkali metal alcoholates, such as sodium methylate and potassium isopropylate, and alkali metal salts of long-chain fatty acids having 10 to 20 carbon atoms and, if required, OH side groups. From 0.001 to 5, in particular from 0.05 to 2, % by weight, based on the weight of the components (b) to (f), of catalyst or catalyst combination are preferably used.
If required, further assistants and/or additives (f) may also be incorporated into the reaction mixture for the preparation of the novel flexible polurethane foams. Examples are flameproofing agents, stabilizers, fillers, dyes, pigments and hydrolysis stabilizers as well as fungistatic and bacteriostatic substances.
Suitable flameproofing agents are, for example, tricresyl phosphate, tris(2-chloroethyl)phosphate, tris(2-chloropropyl)phosphate, tetrakis(2-chloroethyl)ethylene diphosphate, dimethyl methanephosphonate, diethyl diethanolaminomethylphosphonate and commercial halogen-containing polyol flameproofing agents. In addition to the abovementioned halogen-substituted phosphates, inorganic or organic flameproofing agents, such as red phosphorus, hydrated alumina, antimony trioxide, arsenic oxide, ammonium polyphosphate and calcium sulfate, expanded graphite or cyanuric acid derivatives, e.g. melamine, or mixtures of at least two flameproofing agents, for example ammonium polyphosphates and melamine, and, if required, corn starch or ammonium polyphosphate, melamine and expanded graphite and/or, if required, aromatic polyesters may also be used for flameproofing the polyisocyanate polyadducts. Additions of melamine have proven particularly effective. In general, it has proven expedient to use from 5 to 50, preferably from 5 to 25, parts by weight of said flameproofing agents per 100 parts by weight of the components (b) to (f).
Stabilizers used are in particular surfactants, i.e. compounds which serve for supporting the homogenization of the starting materials and may also be suitable for regulating the cell structure of the plastics. Examples are emulsifiers, such as sodium salts of castor oil sulfates or fatty acids and salts of fatty acids with amines, for example of oleic acid with diethylamine, of stearic acid with diethanolamine and of ricinoleic acid with diethanolamine, salts of sulfonic acids, for example alkali metal or ammonium salts of dodecylbenzene- or dinaphthylmethanedisulfonic acid and ricinoleic acid; foam stabilizers, such as siloxane/oxyalkylene copolymers and other organopolysiloxanes, oxyethylated alkylphenols, oxyethylated fatty alcohols, liquid paraffins, castor oil esters and ricinoleic esters, turkey red oil and groundnut oil, and cell regulators, such as paraffins, fatty alcohols and dimethylpolysiloxanes. Predominantly used stabilizers are organopolysiloxanes which are water-soluble. These are polydimethylsiloxane radicals onto which a polyether chain comprising ethylene oxide and propylene oxide has been grafted.
The surfactants are usually used in amounts of from 0.01 to 5 parts by weight, based on 100 parts by weight of the components (b) to (f).
Fillers, in particular reinforcing fillers, are to be understood as meaning the conventional organic and inorganic fillers, reinforcing agents, weighting agents, compositions for improving the abrasion behavior in paints, coating materials, etc., which are known per se. Specific examples are inorganic fillers, such as silicate minerals, for example sheet silicates, such as antigorite, serpentine, hornblends, amphiboles, chrysotile and talc, metal oxides, such as kaolin, aluminas, titanium oxides and iron oxides, metal salts, such as chalk, barite and inorganic pigments, such as cadmium sulfide and zinc sulfide, and glass, etc. Kaolin (china clay), aluminum silicate and coprecipitates of barium sulfate and aluminum silicate as well as natural and synthetic fibrous minerals, such as wollastonite, metal fibers and in particular glass fibers of different lengths, which, if required, may be sized, are preferably used. Examples of suitable organic fillers are carbon, rosin, cyclopentadienyl resins and graft polymers as well as cellulose fibers, polyamide, polyacrylonitrile, polyurethane and polyester fibers based on aromatic and/or aliphatic dicarboxylic esters and in particular carbon fibers. The inorganic and organic fillers may be used individually or as mixtures and are advantageously incorporated into the reaction mixture in amounts of from 0.5 to 50, preferably from 1 to 40, % by weight, based on the weight of the components (a) to (f), but the contents of mats, nonwovens and fabrics of natural and synthetic fibers may reach values of up to 80.
Further details regarding the abovementioned other conventional assistants and additives appear in the technical literature, for example the monograph by J. H. Saunders and K. C. Frisch, High Polymers, Volume XVI, Polyurethanes, Parts 1 and 2, Verlag Interscience Publishers 1962 and 1964, or the above-cited Kunststoffhandbuch, Polyurethane, Volume VII, Hanser-Verlag, Munich, Vienna, 1st to 3rd Editions.
For the preparation of the novel foams, the organic and/or modified organic polyisocyanates (a), the polyetherol mixture (b) and, if required, further compounds (c) having hydrogen atoms reactive toward isocyanates and further components (d) to (f) are reacted in amounts such that the ratio of the number of equivalents of NCO groups of the polyisocyanates (a) to the sum of the reactive hydrogen atoms of the components (b) to (f) is less than 0.95:1, preferably less than 0.70:1.
Polyurethane foams obtained by the novel process are advantageously prepared by the one-shot method, for example with the aid of the high pressure or low pressure technique, in open or closed molds, for example metallic molds. Continuous application of the reaction mixture to suitable belt lines for producing slabstock foams is also usual.
It has proven particularly advantageous to employ the two-component process and to combine the components (b) to (f) into a polyol component, often also referred to as component A, and to use the organic and/or modified organic polyisocyanates (a), particularly preferably an NCO prepolymer or mixtures of this prepolymer and further polyisocyanates and, if required, blowing agents (d) as the isocyanate component, often also referred to as component B.
The starting components are mixed at from 15 to 90xc2x0 C., preferably from 20 to 60xc2x0 C., in particular from 20 to 35xc2x0 C. and are introduced into the open mold or, if required, under superatmospheric pressure into the closed mold or, in the case of a continuous workstation, are applied to a belt which receives the reaction material. The mixing can be carried out mechanically by means of a stirrer, by means of a stirring screw or by high-pressure mixing in a nozzle. The mold temperature is expediently from 20 to 110xc2x0 C., preferably from 30 to 60xc2x0 C., in particular from 35 to 55xc2x0 C.
The polyurethane foams prepared by the novel process have a density of from 10 to 800, preferably from 30 to 100, in particular from 30 to 80, kg/m3. The indentation hardness is preferably less than 100 N, in particular less than 50 N.
The SAG factor is less than 3.0 and shows that such foams retain their flexible behavior even in the case of a relatively high indentation value. The SAG factor is the ratio of the force at 65% compression to the force at 25% compression, the measurements being effected according to DIN 53577.
In the case of the novel foams, the isocyanate index is inversely dependent on the resilience (DIN 53573). The loss factor (Iso 7626, Part 1,2) decreases with decreasing index. The resilience of the foams thus increases greatly with decreasing index.
The novel polyurethane foams are particularly suitable as upholstery material for seats in the furniture sector, for insulation purposes, in vehicle construction and in the medical and hygiene sector.

Preparation of flexible polyurethane foams

Abstract: b1) at least one polyetherol which is at least difunctional, has an OH number of from 20 to 100 mg KOH/g and is based on propylene oxide and/or butylene oxide and ethylene oxide, having an ethylene oxide content of more than 40% by weight, based on the total amount of alkylene oxide used, and, if required, further polyetherols which are at least difunctional, are based on propylene oxide and/or butylene oxide and ethylene oxide and have an OH number of from 20 to 160 mg KOH/g and

Abstract: and the foams are prepared with indices of less than 110, the amount by weight of (b1) being greater than that of (b2). The flexible polyurethane foams prepared by this process are used for upholstery purposes, and insulation purposes, in vehicle construction and in the medical and hygiene sector.