POLYURETHANE FOAMS

Abstract: The present invention relates to a polyurethane foam composition derived from a reaction mixture comprising: a hydrogenated polydiene diol having a number average molecular weight from 1,000 to 20,000; an aromatic polyisocyanate; a plasticiser; and a blowing agent. Preferably, the polyurethane composition further comprises a tackifying resin. The present invention further relates to a process for preparing the polyurethane foam and to articles containing the polyurethane foam.

Description: POLYURETHANE FOAMS This invention relates to polyurethane foams, in particular flexible polyurethane foams, containing a polyol and aromatic isocyanates. The invention further relates to a process for preparing polyurethane foams and articles containing polyurethane foams. Polyurethane foams having high resilience are typically produced from a polyether triol and an isocyanate. The polyether triols typically have a number average molecular weight from 4,500 to 6,000 and an average functionality of from 2.4 to 2.7 hydroxyl groups per molecule. Toluene diisocyanate, diphenyl methane diisocyanate, toluene diisocyanate/diphenyl methane diisocyanate mixtures, and modified toluene diisocyanate or diphenyl methane diisocyanate versions are used to produce foams with broad processing latitude. Isocyanate functionality is typically 2.0, and in most cases not higher than 2.3 isocyanate groups per molecule. The polyether triols form resilient foams when combined with isocyanates having from 2.0 to 2.3 isocyanate groups per molecule under conditions which promote foaming. United States Patent No. 4,939,184 described the production of polyurethane foams from polyisobutylene triols and diols which were prepared cationically . The polyisobutylenes are premixed with an isocyanate, namely an isocyanate which is a mixture of meta- and para- isomers of toluene diisocyanate having a functionality of 2.0. Then water was added as a blowing agent to form the polyurethane foam. Foams obtained were of low resilience and were useful in energy absorbing applications . International (PCT) application WO 97/00902 described a high resilience polyurethane foam produced from a polydiene diol. The foam's resiliency was achieved by adding an aromatic polyisocyanate having a functionality of from 2.5 to 3.0 isocyanate groups per molecule to assure adequate crosslin ing. The polydiene diol foams produced showed excellent humid aging properties in comparison to conventional polyurethane foams . United States patent No. 5,710,192, described a high resilience, high tear resistance polyurethane foam produced from a polydiene diol. The foam's resiliency was achieved by selecting an appropriate amount of a aromatic polyisocyanate having a functionality of from 1.8 to 2.5 isocyanate groups per molecule to assure adequate crosslinking. The polydiene diol foams produced showed excellent tear resistance and were near white in color. In the above described foams, difficulty is encountered in both the processability and in the control of cell size and cell distribution. It is desirable to have a highly processable foam with small, uniform cell sizes and distribution while retaining adequate resilient foam properties. Surprisingly, it has been found that the addition of a plasticiser, e.g. up to 50 %w oil, to a polyurethane foam produced from a polydiene diol will result in highly processable foams. The present invention therefore relates to a polyurethane foam composition derived from a reaction mixture comprising: a hydrogenated polydiene diol having a number average molecular weight from 1,000 to 20,000; an aromatic polyisocyanate; a plasticiser; and a blowing agent. The foam has lower viscosity during the manufacturing process and more uniform cell structure in comparison to foams made without oil. According to a further, preferred, embodiment, the present invention relates to a polyurethane foam composition derived from a reaction mixture comprising: a hydrogenated polydiene diol having a number average molecular weight from 1,000 to 20,000; an aromatic polyisocyanate; a tackifying resin; a plasticiser; and a blowing agent. The plasticiser is preferably compatible with the hydrogenated polydiene diol. A plasticiser is compatible with the hydrogenated polydiene diol if, following mixing of the two components in the preferred weight ratio, the components do not separate into two layers within twelve hours, at room temperature. Plasticisers may typically be selected from those known to those skilled in the art. Preferably, the plasticiser is an oil and/or a hydrogenated polydiene mono-ol having a number average molecular weight from 500 to 20,000. Description of the Drawings Figure 1 shows the effect of oil on viscosity. Figure 2 shows the effect of oil on foam density. Figure 3 shows the effect of water content on the density of foams like those of the invention. According to one preferred embodiment the present invention is preferably a resilient polyurethane foam comprising 100 parts by weight (pbw) of a polydiene diol having a number average molecular weight from 1,000 to 20,000, more preferably from 1,000 to 10,000, most preferably from 3,000 to 6,000, from 20 to 55 pbw of an aromatic polyisocyanate, up to 200 pbw of a plasticiser, more preferably, a hydrocarbon processing oil, and a blowing agent. In a preferred embodiment, the hydrogenated polydiene diol has a functionality of from 1.6 to 2, more preferably from 1.8 to 2, hydroxyl groups per molecule, and the polyisocyanate used has a functionality of from 2.5 to 3.0 isocyanate groups per molecule. The isocyanate is preferably added at a concentration which gives close to an equal number of isocyanate groups and hydroxyl groups. Preferably, the NCO:OH molar ratio ranges from 0.9 to 1.2. The polydiene diols used in this invention are typically prepared anionically. Anionic polymerisation is well known to those skilled in the art and has e.g. been described in United States Patents Nos. 5,376,745, 5,391,663, 5,393,843, 5,405,911, and 5, 416, 168. Polymerization of the polydiene diols commences with a monolithium initiator containing a protected hydroxyl group or dilithium initiator which polymerizes a conjugated diene monomer at each lithium site. Due to cost advantages, the conjugated diene is typically 1,3- butadiene or isoprene, although other conjugated dienes will also work well in the invention. When the conjugated diene is 1, 3-butadiene and when the resulting polymer will be hydrogenated, the anionic polymerization is typically controlled with structure modifiers such as diethylether or 1, 2-diethoxyethane to obtain the desired amount of 1, 4-addition. Anionic polymerization is terminated by addition of a functionalizing agent prior to termination. Functionalizing agents used are known to those skilled in the art and are described in United States Patents 5,391,637, 5,393,843, and 5, 418 , 296. The preferred functionalizing agent is ethylene oxide. The polydiene diols are preferably hydrogenated to improve stability such that at least 90%, preferably at least 95%, of the carbon-to-carbon double bonds in the diols are saturated. Hydrogenation of these polymers and copolymers may be carried out by a variety of well established processes including hydrogenation in the presence of such catalysts as RANEY® Nickel, noble metals such as platinum, soluble transition metal catalysts and titanium catalysts as described in U.S. Patent 5,039,755. The hydrogenated polydiene diols provide stable, resilient foams. The polydiene diols preferably have from 1.6 to 2, more preferably from 1.8 to 2 terminal hydroxyl groups per molecule. An average functionality of, for example, 1.8 means that about 80% of the molecules are diols and about 20% of the molecules are mono-ols. Since the majority of the product's molecules have two hydroxyl groups, the product is considered a diol. The polydiene diols of the invention have a number average molecular weight between 1,000 and 20,000, more preferably from 1,000 to 10,000, most preferably from 3,000 to 6,000. Hydrogenated polybutadiene diols are preferred, in particular those having a 1,2-addition between 40% and 60%. The diene microstructures are typically determined by 13 C nuclear magnetic resonance (NMR) in chloroform. It is desirable for the polybutadiene diols to have at least 40% 1, 2-butadiene addition because, after hydrogenation, the polymer will be a waxy solid at room temperature if it contains less than 40% 1, 2-butadiene addition. Preferably, the 1, 2-butadiene content is between 40 and 60%. Isoprene polymers typically have at least 80% 1,4-isoprene addition in order to reduce the glass transition temperature (T g ) and viscosity. The polydiene diols used in the invention typically have hydroxyl equivalent weights between about 500 and about 10,000, more preferably between 500 and 5,000, most preferably between 1,500 and 3,000. Thus, for the polydiene diols, suitable number average molecular weights will be between 1,000 and 20,000, more preferably between 1,000 and 10,000, most preferably between 3,000 and 6,000. The hydrogenated polydiene diol of the Examples had a number average molecular weight of 3300, a functionality of 1.92, and a 1, 2-butadiene content of 54%. The polymer was hydrogenated to remove more than 99% of the carbon to carbon double bonds. This polymer is referred to hereinafter as Diol 1. The polydiene mono-ols used are prepared substantially as already described herein for polydiene diols except that polymerization is initiated with a monolithium initiator. The monohydroxylated polydiene polymers typically have a number average molecular weight of 500 to 20,000, preferably 2,000 to 8,000. The hydrogenated polydiene mono-ol of the Examples had a number average molecular weight of 3850, a functionality of 0.98 and a 1, 2-butadiene content of 48%. The polymer was hydrogenated to remove more than 99% of the carbon to carbon double bonds. This polymer is referred to herein after as Mono-ol 1. The number average molecular weights referred to herein are number average molecular weights measured by gel permeation chromatography (GPC) calibrated with polybutadiene standards having known number average molecular weights. The solvent for the GPC analysis is tetrahydrofuran. The isocyanates used in this invention are aromatic polyisocyanates since they have the desired fast reactivity to make foam. As the saturated polydiene diol has a functionality of about 2 hydroxyl groups per molecule, a polyisocyanate having a functionality of from 1.8 to 3.0, preferably 2.5 to 3.0, is typically used to achieve a crosslink density that results in a stable, high loadbearing and high resilient foam. Using isocyanates of lower functionality results in less stable foams having lower loadbearing capacity and having reduced resiliency. Higher isocyanate functionality will result in foam having a too high closeα cell content which will negatively influence the physical properties. An example of a suitable aromatic polyisocyanate is MOND -'. MR (Bayer) , a polymeric diphenyl methane polyisocyanate which typically has an isocyanate functionality of 2.7. Also used is RUBINATE® 9225 (ICI Americas), a liquid isocyanate consisting of a mixture of 2,4-diphenyl methane diisocyanate and 4,4-diphenyl methane diisocyanate with a functionality of 2.06; however the addition of oil or mono-ol to a foam made with this lower functionality polyisocyanate may result in foam collapse, requiring formulation adjustment. The oils useful in the invention are petroleum based process oils. The compositions of these oils may range from paraffinic through naphthenic to highly aromatic types. Oils are available covering a wide range of viscosities, from 10 to 1000 centipoise at 100°F (38°C) . Preferably, oils to be used in the form of the invention are paraffinic, napthenic or paraffinic/napthenic oils having a viscosity within the above range. An example of a suitable oil for use in the invention is SHELLFLEX® 371 (Shell Oil Company), a paraffinic/naphthenic process oil having a viscosity of 80-100 centipoise at 100°F (38°C) . Because the polydiene diol is a hydrocarbon, it has excellent compatibility with hydrocarbon process oils. Further, there is no tendency for the oil to bleed out of the foam. Addition of oil to the formulation reduces the viscosity, thereby improving processability. Fig. 1 shows how the viscosity of polydiene diol (Diol 1) blended with oil (SHELLFLEX 371; SHELLFLEX is a trademark) depends on the amount of oil in the blend. Oil additions up to 200 parts by weight per hundred parts of polydiene diol resin (phr) will lower the viscosity by a factor of 10 at any given temperature. This reduction in viscosity makes the foams of the present invention easier to make than previous foams, resulting in a more uniform and smaller cell size. Fig. 2 shows the affects of the concentration of oil (SHELLFLEX 371) on the foam density of a polydiene diol (Diol 1) blended with a polyisocyanate (MONDUR® MR) and water. Increasing the oil content from 0 to 200 phr about triples the density. The denser foams have smaller cells and very uniform cell size distributions. The essential components of the polyurethane foams of this invention are the polydiene diol, the aromatic polyisocyanate, a blowing agent such as water, and a plasticiser, preferably oil, and/or a polydiene mono-ol. Optionally, and preferably, the polyurethane foam further comprises a tackifying resin. The tackifying resins useful in the invention are relatively low molecular weight, predominately hydrocarbon polymers characterized primarily by their ring and ball softening points as determined by ASTM standard method E28. Normally, the resins will have softening points in the range of about 80°C to about 120°C. In certain cases, however, lower softening point resins or liquid resins may be advantageous, for example to obtain the best tack at low temperatures. A typical tackifying resin is one made by cationic polymerization of a mixture containing 60% piperylene, 10% isoprene, 5% cyclopentadiene, 15% 2-methyl-2-butene and about 10% dimer, as taught in U.S. Patent No. 3,577,398. A resin of this type is commercially available as WINGTACK® 95 (Goodyear Tire & Rubber Company) and has a 95 °C softening point. The resins may also contain some aromatic character introduced by including styrene or α-methylstyrene in the mixture during polymerization of the resins. Other types of adhesion promoting resins which are useful in the invention include hydrogenated rosins, esters of rosins, polyterpenes, terpenephenol resins, and polymerized mixed olefins. To obtain good thermooxidative and color stability, it is preferred to use a saturated resin such as a hydrogenated dicyclopentadiene resin such as ESCOREZ® 5000 series (Exxon Chemical Company) , or a hydrogenated polystyrene resin such as the REGALREZ© series (Hercules, Inc.). When using a tackifying resin having a high softening point, the resin may increase the viscosity of the reacting mixture to a point were foaming actually does not take place. Processibility of the foam may be improved by the addition of an oil to reduce the viscosity during foaming. Typical oils useful in the invention include paraffinic/naphthenic rubber process oils as described above. An example of an oil suitable for use in the invention is SHELLFLEX 371. The compatibility of this oil with the polydiene diol/tackifying mixture is excellent. Therefore, there is no tendency for the oil to bleed out of the foam, allowing the concentration of oil to be adjusted to give the desired viscosity, foam density, and tack properties . Processibility of the foam may also be controlled by replacing part of the polydiene diol with a polydiene mono-ol . The viscoelastic properties of the foam can be tailored for specific applications by adjusting the ratio of the diol to mono-ol. Adhesive foams containing monc-cl contents of up to 75% by weight of the diol /mono-ol mixture have been found to be suitable. The hydrogenated polydiene diol/plasticiser weight ratio is typically at most 5:1, preferably at most 4:1, more preferably at most 3:1, in particular at most 2:1. The said ratio is typically at least 1:4, preferably at least 1:3, more preferably at least 1:1.5, in particular at least 1:1. The hydrogenated polydiene diol / tackifying resin weight ratio is typically at most 5:1, preferably at most 4:1, more preferably at most 3:1, in particular at most 2:1. The said ratio is typically at least 1:4, preferably at least 1:3, more preferably at least 1:1.5, in particular at least 1:1. Typically, catalysts and a surfactant are needed in the preparation of the foams. Surfactants are often added to improve the miscibility of the components, which in turn promotes the hydroxyl/isocyanate reaction. Further, the surface tension of the mixture is reduced, which influences the cell nucleation and stabilises the expanding foam, leading to a fine cell structure. Preferably, the surfactant is a silicone oil. An example of a suitable commercially available silicone oil is TEGOSTAB-B8404 (TEGOSTAB is a trademark) . A preferred silicone surfactant is DABCO® DC-5160. The surfactant, if present, is normally added in an amount of from 0.01 to 5 parts by weight per 100 pbw of the polydiene diol (0.01-5 phr), preferably from 0.01 to 1 phr. In principle any catalyst known to catalyse one or more of the foaming reactions in the system may be used. Examples of suitable catalysts are described in European patent specification No. 0 358 282 and include amines such as tertiary amines, salts of carboxylic acids, and organometallic catalysts. Examples of suitable tertiary amines are triethylene diamine, N-methylmorpholine, N- ethylmorpholine, diethyl-ethanol-amine, N- cocomorpholine, 1-methyl-4-dimethyl-amino- ethylpiperazine, 3-methoxypropyldimethylamine, N,N,N'- tri-methylisopropyl propylenediamine, 3-diethylamino propyl-diethylamine, dimethylbenzylamine and dimethylcyclohexylamine . An example of a carboxylic acid salt useful as a catalyst is sodium acetate. Examples of commercially available amine catalysts are DABCO® 33-LV and the delayed action amine catalyst DABCO DC-1 from Air Products and Chemicals. Suitable organometallic catalysts include stannous octoate, stannous oleate, stannous acetate, stannous laureate, lead octoate, lead naphthenate, nickel naphthenate, cobalt naphthenate and dibutyltin dichloride. Further examples of organometallic compounds useful as catalyst in the production of polyurethanes are described in U.S. Patent Specification No. 2,846,408 The amount in which the catalyst, or mixture of catalysts, is used normally lies in the range of from 0.01 to 5.0 pbw, preferably in the range of from 0.2 to 2.0 pbw, per 100 parts of polydiene diol. A variety of blowing agents may be used. Suitable blowing agents include halogenated hydrocarbons, aliphatic alkanes, and alicyclic alkanes, as well as water which is often referred to as a chemical blowing agent. Due to the ozone depleting effect of the fully chlorinated, fluorinated alkanes (CFC's), the use of this type of blowing agent is not preferred, although it is possible to use them within the scope of the present invention. The halogenated alkanes, wherein at least one hydrogen atom has not been substituted by a halogen atom (the so called HCFC's) have a lower ozone depleting potential and therefore are the preferred halogenated hydrocarbons to be used in physically blown foams. A very suitable HCFC type blowing agent is 1-chloro-l, 1- difluoroethane . Even more preferred as blowing agents are hydrofluorohydrocarbons which are thought to have a zero ozone depletion potential. The use of water as a (chemical) blowing agent is also well known. Water reacts with isocyanate groups according to the well known NCO/H2O reaction, thereby releasing carbon dioxide which causes the blowing to occur . The aliphatic and alicyclic alkanes, finally, were developed as alternative blowing agents for the CFC's. Examples of such alkanes are n-pentane, isopentane, and n-hexane (aliphatic) , and cyclopentane and cyclohexane (alicyclic) . It will be understood that the above blowing agents may be used singly or in mixtures of two or more. Of the blowing agents mentioned, water and cyclopentane have been found to be particularly suitable as blowing agent for the purpose of the present invention. The amounts wherein the blowing agents are to be used are those conventionally applied, i.e. in the range of from 0.1 to 5 pbw per 100 parts of polydiene diol in case of water and in the range of from about 0.1 to 20 pbw per 100 parts of polydiene diol in case of halogenated hydrocarbons, aliphatic alkanes, and alicyclic alkanes. Preferably, the blowing agent is water. Water is preferably added in an amount of from 0.5 to 3.5 parts by weight (pbw) per 100 parts of polydiene diol. Preferably, distilled or de-mineralised water is used, as impurities may affect the foam reaction. If desired, flame (fire) retardants , fillers, and other additives may be added. It belongs to the skill of the average skilled person in this field to select appropriate additional compounds to be added to the composition to be foamed. Antioxidants and ultraviolet stabilizers may be added to further increase the heat and light stability of the foam. Antioxidants of the hindered phenolic type, such as IRGANOX® 1076 (Ciba Geigy) , are well suited for stabilizing these foams. A combination of an ultraviolet light absorber, such as TINUVIN® 328 (Ciba Geigy) , and a hindered amine light stabilizer, such as TINUVIN® 123 (Ciba Geigy) , are preferably used for the best resistance to degradation by sunlight. The polyurethane foams are preferably prepared by blending all of the components except the polyisocyanate. The polydiene diol and, if present, the polydiene mono-ol are preheated (typically to about 80°C) to reduce viscosity prior to blending. The tackifying resin is preferably also preheated, typically to about 150°C. After blending, the aromatic polyisocyanate is quickly added and briefly stirred before pouring the mixture into a mould to hold the expanding foam. Accordingly, a further aspect of the invention relates to a process for preparing a polyurethane foam composition comprising (i) mixing a hydrogenated polydiene diol having a number average molecular weight from 1,000 to 20,000 with a plasticiser, a blowing agent, and, optionally, a tackifying resin, a surfactant and a catalyst to obtain a mixture; (ii) combining an aromatic polyisocyanate with the mixture to obtain a combination; and (iii) allowing the combination to foam, to obtain the polyurethane foam composition. The polyurethane foam may be subjected to a curing treatment by heating the foam to an elevated temperature, usually between 100 and 160 °C for a certain period of time, typically in the range from 10 minutes to 96 hours, preferably from 30 minutes to 48 hours. Usually, however, the heat generated by the exothermic polyurethane forming reaction is sufficient to ensure complete curing, and the process is carried out adiabatically . A preferred embodiment of the present invention is a resilient polyurethane foam comprising 100 parts by weight of a hydrogenated polydiene diol having a number average molecular weight from 3,000 to 6,000 and a functionality of from 1.8 to 2.0 hydroxyl groups per molecule, from 0.5 to 3.5 parts by weight of water, an aromatic polyisocyanate having a functionality of from 2.5 to 3.0 isocyanate groups per molecule at a concentration which will give close to an equal number of isocyanate and hydroxyl groups, from 20 to 200 parts by weight oil, from 0.4 to 0.8 parts by weight of an amine catalyst, from 0.3 to 0.6 parts by weight of a delayed action amine catalyst, and from 0 to 0.06 parts by weight of a silicon surfactant. The foam shows superior cell size and cell size distribution in comparison to foams made without oil. A further preferred embodiment of the present invention is a resilient polyurethane foam comprising 100 parts by weight of a hydrogenated polydiene diol having a number average molecular weight from 3,000 to 6,000 and a functionality of from 1.8 to 2.0 hydroxyl groups per molecule, from 0.5 to 3.5 parts by weight of water, an aromatic polyisocyanate having a functionality of from 2.5 to 3.0 isocyanate groups per molecule at a concentration which will give close to an equal number of isocyanate and hydroxyl groups, from 50 to 150 parts by weight tackifying resin, from 10 to 100 parts by weight oil, from 0.4 to 0.8 parts by weight of an amine catalyst, from 0.3 to 0.6 parts by weight of a delayed action amine catalyst, and from 0 to 0.06 parts by weight of a silicon surfactant. Yet another preferred embodiment of the present invention is a resilient polyurethane foam comprising 25 to 100 parts by weight of a hydrogenated polydiene diol having a number average molecular weight from 3,000 to 6,000 and a functionality of from 1.8 to 2.0 hydroxyl groups per molecule, 75 to 0 parts by weight of a polydiene mono-ol having a number average molecular weight of from 2000 to 4000, from 0.5 to 3.5 parts by weight of water, an aromatic polyisocyanate having a functionality of from 2.5 to 3.0 isocyanate groups per molecule at a concentration which will give close to an equal number of isocyanate as hydroxyl groups, from 50 to 150 parts by weight tackifying resin, from 0 to 100 parts by weight of oil, from 0.4 to 0.8 parts by weight of an amine catalyst, from 0.3 to 0.6 parts by weight of a delayed action amine catalyst, and from 0 to 0.06 parts by weight of a silicon surfactant. According to a further aspect, the present invention relates to articles containing the polyurethane foam according to the present invention. The following examples are not intended to limit the present invention to specific embodiments although each example may support a separate claim which is asserted to be a patentable invention. Example 1 Eight foams were prepared using polymer, isocyanate (MONDUR® MR), catalyst (DABCO® 33-LV and DABCO® DC-1), surfactant (DABCO® DC-5160), and water in the combinations as shown in Table 1. Samples 2 - 7 also contained a hydrocarbon process oil (SHELLFLEX® 371) and are the samples which demonstrate the invention. Sample 1 is a comparative example which contains no oil. Sample 8 is another comparative example containing oil but using a conventional polyether polyol. In the typical preparation, the polymer and oil were preheated to 80°C. All the components in the formulation except the isocyanate were weighed into a dried can and mixed using a CAFRAMO® stirrer equipped with a 2-inch (5.1 cm), regular pitch impeller. Isocyanate was then added and mixing was continued for about 45 seconds. By this time the mass would begin to foam and was poured into a paper bucket. After the foam stabilized and a skin formed, the foam was postbaked in an oven for ten (10) minutes at 110°C. Specimens were cut from the bun for measurement of foam density, hardness at 40% compression, resilience and hysteresis. Density Density was determined from the weight of a block and its dimensions. Results are given in Table 2. Resilience A 16 mm diameter (16.3 g) steel ball was dropped from a height of 51.6 cm through a 38 mm inside diameter clear plastic tube onto a block of foam measuring 10 x 10 x 5 cm. The rebound height was measured and resilience was calculated as 100 x (rebound height/drop height) . Results are given in Table 2. Compression Hardness and Hysteresis Loss Compression hardness and hysteresis loss were measured on an INSTRON® Machine Model 5565. A foam block measuring 10 x 10 x 5 cm was placed between two parallel plates and compressed 60% then unloaded for four cycles at a crosshead speed of 12.5 cm/min . On the fourth cycle, the force required to compress the foam 40% was recorded, giving a measure of compression hardness of the foam. Hysteresis loss was calculated as the area under the stress/height curve on the fourth cycle relative to the first cycle. Results are given in Table 2. Table 1. Foam Formulations Table 2. Foam Properties Samples 1-5 were similar formulations with increasing oil contents from Sample 1 (oil-free) to Sample 5 (200 phr oil) . Samples 1-5 all contained 1 phr water and so they all foamed to about the same volume, each expanding by a factor of approximately 10. With increasing amounts of oil added to that volume, the densities are seen to increase with increasing oil content. It can be seen that addition of 11 phr oil (Sample 2) has essentially no effect on the properties or qualitative appearance of the foam. Addition of 33 phr oil (Sample 3) reduced the cell size distribution somewhat with only a small effect on density. Additions of 100 to 200 phr oil (Samples 4 and 5) resulted in foams with small cell sizes of very uniform distribution but noticeably denser (heavier) foams. No tendency was seen for the oil to bleed from any of these foams. Samples 5-7 and Figure 3 show the effects of increasing the water content in foams containing 200 phr oil. The higher water content and resultant increase in isocyanate content cause more foaming, thereby reducing the foam density. It is believed that a foam containing 200 phr would reach a density of 110 g/1 at about 4 phr water content, an equivalent density to the oil-free Sample I. However, this high oil foam would be expected to have lower compression hardness and cohesive strength than the oil-free foam of the same density. Sample 8 was a conventional foam based on polyether polyol to which oil was added. It can be seen that these conventional type foams are not suitable for oil additions. The foam has an oily feel and bleeds oil due to the incompatibility of the oil and the polyether polymer . Example 2 Five foams were prepared using Diol 1 or Diol 1/Mono-ol 1 mixtures, isocyanate (MONDUR® MR) , a tackifying resin (WINGTACK 95), catalysts (DABCO® 33-LV and DABCO® DC-1), surfactant (DABCO® DC-5160) , and water in the combinations as shown in Table 3. Two foams contained a hydrocarbon processing oil (SHELLFLEX 371). In the typical preparation, the diol, mono-ol and oil, if present, were preheated to 80°C and the tackifying resin was preheated to 150°C. Subsequently, the procedure of Example 1 was followed. Density, resilience and compression hardness and hysteresis loss were measured as in Example 1. Results are given in Table 4. Table 3. Foam Formulations Table 4 . Foam Properties Sample 1 is an example of a high resilience foam and is used for comparative purposes. At the density of 109 g/1, it has a compression hardness of 28 N and has good resilience and low hysteresis loss. However, being resin-free it has no tack or adhesive character. Samples 9 and 10 examined the effects of adding tackifying resin and oil, and adjusting the water content, to give foams of approximately constant density. Results show that, as is required for pressure sensitive adhesives, these foams are much easier to compress, they have much less resilience and much greater hysteresis loss than comparative Sample 1. Both of foam Samples 9 and 10 were very nice pressure sensitive adhesives; both had good finger tack and both adhered well to paper and painted surfaces. Both could also be peeled cleanly off a substrate, providing examples of a removal adhesive foam. Samples 11-13 show the effects of using a polydiene diol/polydiene mono-ol blend with no oil. Satisfactory foams were not obtained with Samples 11 and 12. However, it is believed that by adjusting preheat temperatures, mixing schedules and catalyst concentrations, satisfactory foams can be made with these two formulations. Sample 13 was a very nice, very soft and tacky foam. Sample 13 was an unusual foam in that it showed no immediate rebound upon compression but, when allowed to stand, it would completely recover its initial shape and dimensions. Thus, the compression hardness was zero and the hysteresis loss was nearly 100% because on the short time scale of the test, there was almost no recovery of the foam after the first compression. In the resilience test, the foam merely dissipated the energy of the falling ball and there was no rebound. While this invention has been described in detail for purposes of illustration, it is not construed as limited thereby but is intended to cover all changes and modifications within the spirit and scope thereof.

Claims: C L I M S 1. A polyurethane foam composition derived from a reaction mixture comprising: a hydrogenated polydiene diol having a number average molecular weight from 1,000 to 20,000; an aromatic polyisocyanate; a plasticiser; and a blowing agent. 2. A polyurethane foam composition derived from a reaction mixture comprising: a hydrogenated polydiene diol having a number average molecular weight from 1,000 to 20,000; an aromatic polyisocyanate; a tackifying resin; a plasticiser; and a blowing agent. 3. A polyurethane foam as claimed in claim 1 or 2, wherein the plasticiser is compatible with the hydrogenated polydiene diol. 4. A polyurethane foam as claimed in claim 3, wherein the plasticiser is an oil and/or a hydrogenated polydiene mono-ol having a number average molecular weight from 500 to 20,000; 5. A polyurethane foam as claimed in any one of the preceding claims, wherein the polydiene diol has a functionality of from 1.6 to 2 hydroxyl groups per molecule, and wherein the polyisocyanate has a functionality of from 1.8 to 3.0 isocyanate groups per molecule. 6. A polyurethane foam as claimed in any one of the preceding claims, wherein the amount of polydiene diol to plasticiser is in the range of from 5:1 to 1:4. 7. A polyurethane foam as claimed in claim 2 wherein the amount of polydiene diol to tackifying resin is in the range of 5:1 to 1:4. 8. A polyurethane foam composition, obtainable by a process comprising the steps of: combining a hydrogenated polydiene diol having a number average molecular weight from 1,000 to 20,000 with an aromatic polyisocyanate, a blowing agent and a plasticiser; and allowing the combined polydiene diol, aromatic polyisocyanate, blowing agent and plasticiser to foam, to obtain the polyurethane foam composition. 9. A polyurethane foam composition as claimed in claim 8, wherein the hydrogenated polydiene diol, the blowing agent, the plasticiser and any other components are mixed prior to combining the mixture with the aromatic polyisocyanate. 10. A polyurethane foam composition as claimed in claims 8 or 9, wherein the process a surfactant and a catalyst is used. 11. A polyurethane foam composition as claimed in any one of claims 8-10, further comprising a tackifying resin. 12. A process for preparing a polyurethane foam composition comprising (i) mixing a hydrogenated polydiene diol having a number average molecular weight from 1,000 to 20,000 with a plasticiser, a blowing agent, and, optionally, a tackifying resin, a surfactant and a catalyst to obtain a mixture; (ii) combining an aromatic polyisocyanate with the mixture to obtain a combination; and (iii) allowing the combination to foam, to obtain the polyurethane foam composition. 13. Articles containing the polyurethane foam composition as claimed in any one of claims 1-11.

Inventors: HERNANDEZ HECTOR, ST CLAIR DAVID JOHN, HERNANDEZ, HECTOR, ST. CLAIR, DAVID, JOHN
Applicants: SHELL INT RESEARCH, SHELL INTERNATIONALE RESEARCH MAATSCHAPPIJ B.V.
Application year: 1998
Main classification: C08G18
IPC codes: C08G18, C08G101, C08K5