MXPA96004686A - Continuous process for finely divided, low viscosity, small average particle size, highly stable polymeric polyols preparation - Google Patents

Abstract

The present invention describes a continuous process for finely divided, low viscosity, small average particle size, highly stable polymeric polyols preparation, wherein in first stage an intermediate is prepared by reacting (1) an styrene and acrylonitrile mixture, in a mixture of (2) a polyoxyalkylenepolyetherpolyol and (3) a macromere, in presence of (4) a free radical initiator, (5) a dissolvent having a moderated chain transference activity, and optionally (6) a reaction moderator, at a temperature of at least 100øC, so that intermediate contains a high macromere concentration, at least of about 12 percent, and preferably at least about 15 percent with respect to polyol mixture, and intermediate solid materials content is lower than about 30 percent, preferably lower than about 25 percent, and at least about 15 percent by weight. Intermediate, which works as a seed for ulterior polymerization, is subsequently reacted in one or more series-stirred tank reactors, with a mixture of styrene and acrylonitrile, in a polyol and optionally a macromere, in presence of a dissolvent, initiator and reaction moderator, which are distributed among remaining reactors.

Description

CONTINUOUS PROCESS FOR THE PREPARATION OF HIGHLY VISIBLE, LOW VISCOSITY, SMALL AVERAGE PARTICLE SIZE POLYMERIC POLYOLIC POLYOLES, HIGHLY DIVIDED, POLYMER POLYOLS and their use in the preparation of polyurethane foams are known. Polymeric polyols are polyols that are modified or added with polymers or copolymers of ethylenically unsaturated monomers. They are prepared by the in situ polymerization of one or more vinyl monomers, in a polyether polyol, in the presence of a radical-forming polymerization initiator. The polyurethanes prepared from such polymeric polyols are distinguished by their improved properties, in particular, the hardness and load-bearing capacity of flexible polyurethane foams. Polymeric polyols are, ideally, dispersions of the polymer or copolymer of relatively low viscosity, finely divided, not sedimenting, in a substantially stable polyol. The stabilization of the dispersions of the polymer polyols against sedimentation is achieved by the incorporation or grafting of a portion of the polyol molecules into the polymer matrix, which is formed in situ. The preferred polymer is a styrene-acrylonitrile graft copolymer. Two basic processes have been used to produce polymeric polyoles; semi-batches and continuous. Prepared products REF: 23249 Rados via the two methods are distinguished by their particle size distribution. The particle size distribution is narrow for the polymer polyols prepared via a semi-batch process, while it is broad for the polymeric polyols prepared via a continuous process. In the semi-batch process, most of the particles are generated in the initial stage of the reaction. The subsequent polymerization favors the growth of the existing particles. In a continuous process, the broad particle size distribution is the result of the combination of the competitive growth of the existing particles and the formation of new particles, as well as the continuous rotation, or run-off of the particles in the reactor. The aspects that characterize the ability to be processed from polymeric polyols are their viscosity, storage stability (resistance to sedimentation), and filterability. The parameters that have a particularly important influence on the quality of the product are the proportion of the monomer in the starting mixture and the relations of the monomers. The trend towards the use of mixtures of monomers with a high content of styrene and polymer polyols with a high content of solid materials has resulted in polymeric polyols that have less than ideal properties (low viscosity, stable, no agglomerate material, small average particle size). ).

It has been shown that the stability of the polymer polyols, particularly at high levels of styrene, can be increased by the polymerization of the monomer mixture in a polyol or mixture of polyols containing a particular level of induced unsaturation. The polyol containing induced unsaturation, often called macromer or ma-chromonomer, stabilizes the polymer dispersion by incorporating suitable amounts of the polyol into the polymer matrix via addition polymerization. Chain transfer agents or polymer control agents have been used in the preparation of polymeric polymer compositions as reaction moderators, or to control the molecular weight of the copolymer, resulting in stable, low viscosity products. Various reaction moderators have been suggested, including mercaptans, alkyl halides, alcohols, halogens and enol ethers. One of the many improvements in the preparation of polymeric polyols is provided by US 4,148,840, wherein a process for producing highly stable and filterable polymer polyol compositions is described., by polymerizing the monomer or monomers in situ, in a polyol mixture containing a minor amount of preformed polymeric polyol. Another improved process for the preparation of polymeric polyols is described in US 4,242,249. The use of preformed stabilizers allows the preparation of polymeric polyols having higher styrene contents and higher contents of solid materials, and using smaller molecular weight polyols. These preformed stabilizers typically have viscosities greater than 40,000 centipoise (40,000 mPas) at 25 ° C, and formed by the polymerization of styrene-acrylonitrile mixtures in a polyol containing induced unsaturation. The preformed stabilizer is used in small amounts, 5% or less, in the preparation of the final product. US 5,233,570 provides a process for the preparation of dispersions of polymer polyols of broad particle size distribution, without viscosities that fluctuate wildly. The method comprises preparing an intermediate containing less than 30% by weight of solid materials in a continuous process, to achieve a broad particle size distribution. The intermediate is then used as a seed for a subsequent polymerization in a semi-batch process, to increase the content of solid materials to more than 30% by weight. A continuous process is described in US 5,364,906, to produce polymeric polyols of low viscosity, with improved dispersion stability. The method uses a two-stage continuous process, wherein the first reaction product is formed by the reaction of less than 50% of the mixture in more than 50% of the total polyol (preferably all of the polyol), which contains a most of a macromer and a polymer control agent. In a second reactor, the remaining raw materials are added to the first reaction product. The deposition of the polymer on the wall of the reactor, or scaling of the reactor, is known in the polymerization of olefinic monomers. Three methods to minimize or eliminate reactor fouling are: (1) coating the reactor with a material that provides resistance to polymer deposition, (2) reactor design improvements (eg better mixing), and (3) control the monomer / polymer concentrations. US 4,956,427 provides a method for the prevention of reactor fouling during the polymerization of olefinic monomers by coating the surface of the reactor with a moisture curable amino silicone fluid. The coating is used to prevent fouling, especially during the polymerization of ethylene, propylene and mixtures thereof, In J 54133582, the preparation of polymeric polyols without adhesion to the reactor wall is described, using a special reactor, equipped with an agitator. helical sheets and extraction tubes, and that recycles the contents of the reactor at a speed of 50-200 times faster than that of the loaded starting material.

In another approach, US 4,794,151 provides a continuous process for the preparation of ethene copolymers, which uses a circular tube reactor with specified monomer / polymer concentrations, to stop the coating of the polymer on the reactor wall. t None of the references disclose the importance of forming a highly stabilized intermediate or seed of small average particle size, which is ideally suited for further polymerization, in the preparation of highly stable, finely divided, low viscosity, size polymer polyols of small average particle, using a series of stirred tank reactors. None of the related art would suggest to one of ordinary skill in the art that the scale of the reactor, or deposition of the polymer on the reactor wall, can be eliminated or substantially reduced by the preparation method described in the present invention. Indeed, the processes for the preparation of polymeric polyols have not advanced beyond the need for further improvement. There is a clear demand for polymer polyols with improved dispersion stability (particularly at high levels of styrene), polymer polyols with minimal viscosity (especially at high solids content), and polymer polyols that are finely divided (without agglomerated material), with a small average particle size. There is also a desire to develop sensible processes, that maximize the use of the reactor, and minimize the time of shutdown of activities due to embedding of the reactor. The polymeric polyols, and the processes described in the present invention satisfy these criteria. The present invention is directed to a continuous process using a series of stirred tank reactors for the preparation of highly stable, finely divided, low viscosity polymer polymers of small average particle size. In a preferred embodiment, an intermediate is formed which is ideally suited for a subsequent polymerization. The intermediate is formed by reacting a mixture of styrene and acrylonitrile in a polyol mixture consisting of a polyether polyol and a polyol containing induced unsaturation, or the so-called macromer, wherein the macromer is at least about 12%, and preferably at least about 15% by weight of the polyol mixture, and the solid content of the intermediate is less than about 30%, preferably less than about 25%, and at least about 15% by weight. The intermediate, which functions as a seed for a subsequent polymerization, is subsequently reacted in one or more consecutive reactors, with a mixture of styrene and acrylonitrile in a polyol, and optionally a macromer, in the presence of a solvent, initiator and a moderator. of reaction, which are distributed among the remaining reactors. In another preferred embodiment of the present invention, the concentration of monomer is minimized throughout the polymerization reactors, via the distribution of the starting materials, so that the amount of monomer added to any reactor is less than about 30. % of the content of the reactor, and preferably is approximately equal in each of the polymerization reactors. According to another aspect of the present invention, the use of a solvent with moderate chain transfer activity is also preferred. The process of the present invention results in the elimination or substantial reduction of scaling of the reactor, or deposition of the polymer on the wall of the reactor. The invention also relates to the highly stable, finely divided, low viscosity polymer polyols obtained from the described process, and to their use in the preparation of polyurethane foams. According to the present invention, an intermediate, having a small average particle size, ideally suitable for a subsequent polymerization, is prepared by reacting (1) a mixture of styrene and acrylonitrile in a mixture of (2) a polyoxyalkylene polyether polyol and (3) a macromer in the presence of (4) a free radical initiator, (5) a solvent having a moderate chain transfer activity, and optionally (6) a reaction moderator, such that the intermediate contains a high level of macromer, at least about 12%, and preferably at least about 15 7"with respect to the polyol mixture, and the solid content of the intermediate is less than about 30%, preferably less closely of 25%, and at least about 15% by weight. The intermediate, which functions as a seed for a subsequent polymerization, is then reacted in one or more tank reactors agitated in series, with a mixture of styrene and acrylonitrile in a polyol and optionally a macromer, in the presence of solvent, initiator and a reaction moderator, which are distributed among the remaining reactors. In another preferred embodiment of the present invention, the distribution of the raw materials between the polymerization reactors minimizes the monomer concentration, so that the amount of monomer added to any reactor is less than about 30% of the content of the reactor. , and preferably it is approximately equal in each of the reactors where the monomer is added. The last reactor in a series of stirred tank reactors is usually, but not necessarily, used exclusively as a post reactor, to increase the conversion of monomer to polymer. The temperature at which the polymerization is carried out should be at least 100 ° C, preferably 100 ° to 140 ° C, and more preferably 120 ° to 130 ° C. The content of each reactor is mixed well, with a time of residence of at least 20 minutes, preferably in the range of 30 to 90 minutes. The reaction can be carried out at the pressure that becomes established at the operating temperature, in a system that is hermetically sealed from external pressure, or can be carried out in an open system, at atmospheric pressure. Atmospheric oxygen must be purged from the entire apparatus with an inert gas, such as nitrogen or argon. During the process an inert atmosphere must be maintained in the system constantly. The product is released from volatile constituents, in particular from the solvent and from monomer residues, by the usual vacuum distillation method, optionally in a thin film or falling film evaporator. The monomers suitable for in situ graft polymerization are mixtures of styrene and acrylonitrile in proportions by weight in the range of from about 100/0 to 20/80, preferably more than 50% of styrene. Other commonly used ethylenically unsaturated monomers may be used, in minor portions, together with styrene and / or acrylonitrile, or as replacements for either styrene and / or acrylonitrile. Examples include, but are not limited to: methylacrylonitrile, d-methyl styrene, methylstyrene, butylstyrene, unsaturated monocarboxylic acids (such as acrylic acid, methacrylic acid, maleic acid, fumaric acid or itaconic acid), and substituted unsaturated monocarboxylic monomers (such as methyl acrylate, 2-hydroxypropyl acrylate, methyl methacrylate, 2-hydroxyethyl methacrylate, and isopropyl methacrylate) and the like. The polyols that can be used according to the invention include the known addition reaction products of cyclic ethers. Examples include, ethylene oxide, propylene oxide, butylene oxide, tetrahydrofuran and mixtures thereof with starting compounds having at least two active hydrogen atoms in the molecule, for example, those described in "Polyurethanes: Chemis -try and Technology ", Volume XVI, Part I, by JH Saunders and KC Frisch, Robert E. Krieger Publishing Co. , Malabar, FL, 1983, pages 32-44. Suitable starting materials include polyhydroxyl compounds such as alkylene glycols, glycerin, trimethylolpropane, pentaerythritol, sorbitol, glucose, and sucrose. Other examples of suitable starting compounds include water, ammonia, amino alcohols (such as ethanolamine, diethanolamine, triethanolamine) and primary and / or secondary amines or polyamines (such as ethylenediamine, aniline and toluenediamine). The polyether polyols used in the present invention for the preparation of polymeric polyoles have a molecular weight from 500 to 12,000, preferably from about 2,000 to 8,000, and a hydroxyl functionality from 2 to 6. The polyether chains are generally they are formed of units of propylene oxide and ethylene oxide. The oxides can be mixed with the addition, or they can be added separately to form blocks or layers. The resulting polyols may be in the range from having predominantly primary hydroxyl groups to predominantly secondary hydroxyl groups, depending on the sequence and amounts of the respective oxides. Macromers that can be used according to the present invention include, but are not limited to, the reaction product of a polyol with the following reactive unsaturated compounds: maleic anhydride, fumaric acid, 1,1-dimethyl-m-isopropenyl- benzyl isocyanate, isocyanatoethyl methacrylate, 2-buten-l, 4-diol, l-butene-3, 4-diol, hydroxyethyl methacrylate, hydroxypropyl acrylate, methyl methacrylate, acrylic and methacrylic acid, meta-chryloyl chloride, glycidyl methacrylate, and allyl glycidyl ether. If an acid or polycarboxylic anhydride is employed, it is preferred to react the unsaturated polyol with an alkylene oxide, to reduce the acid number, by replacing the carboxyl groups with hydroxyl groups before using it in the present invention. The polyol reagent is preferably a polyoxyalkylene polyether polyol as described above, having a molecular weight of at least 4,500, and a hydroxy functionality of at least 3. In the preparation of the macromer, it is preferred to use an amount of reactive unsaturated compound in the range of 0.3 to 1.5 moles per mole of polyol, preferably 0.5 to 1.2 moles per mole of polyol, The amount of macromer used is that which is required to adequately stabilize the polymer against settling. In general, the total amount of macromer in the final product is in the range from 2% to 10% by weight with respect to the polyol mixture, but may require more in some cases, to stabilize the dispersion. The initiation of the polymerization is carried out using initiators that form typical free radicals. Initiators of this type include, for example, organic peroxides (such as benzoyl peroxide and decanoyl peroxide), percarboxylic acid esters (such as t-butylperoctoate and t-amyl 2-ethylhexanoate) and aliphatic azonitrile compounds (such as 2,2'-azo-bis- (iso-butyronitrile) and 2,2'-azo-bis- (2-methylbutanonitri-lo)). The half-life for the thermal decomposition of the initiator should be as low as possible under the polymerization conditions, preferably about 1 minute, to achieve a rapid conversion of monomer to polymer. The initiator is preferably used in amounts of 0.5 to 5% by weight, based on the total amount of monomers.

The polymerization is preferably carried out in an organic solvent that does not dissolve the polymer. Illustrative examples thereof are benzene, toluene, ethylbenzene, xylene, hexane, iso-propanol, n-butanol, 2-butanol, ethyl acetate, butyl acetate, and the like, including those known in the art. which are suitable for the polymerization of vinyl monomers. It is preferred to use a solvent having a normal boiling point, within the range of 100-140 ° C. Solvents with normal boiling points lower than 100 ° C may be used, but require that the reaction be conducted in pressurized reactors. It is also preferred that the solvent has a moderate chain transferase activity. Ethylbenzene and n-butanol are particularly suitable for use as a solvent according to the present invention. The solvent is typically used in amounts of 2% to about 20% by weight, and is removed from the reaction mixture before the polymeric polyol is used to produce polyurethane foams. The addition of a reaction moderator or chain transfer agent or polymer control agent during the polymerization has been found to be useful. The use of such reaction moderators is optional during the preparation of the intermediate, but is essential during the subsequent polymerization, especially at solid material levels greater than 30% by weight. Examples of such reaction moderators include: mercaptans, ketones, alcohols, alkyl halides, and enol ethers. Preferred reaction moderators are the enol ethers of the formula: A = CH-0-R wherein R represents an alkyl group of 1 to 18 carbon atoms, cycloalkyl of 5 to 10 carbon atoms, or benzyl substituted or not replaced, A represents the group: R 'represents either hydrogen or an alkyl group of 1 to 8 carbon atoms. A representative example of a preferred enol ether is Vulkazon AFD, a product of Bayer AG or (cyclohex-3-enyll-denmethoxymethyl) benzene. The reaction moderator is used in an amount from about 0.5% to about 5% by weight with respect to the total monomer. One of the main advantages of the process of the present invention is that the scaling of the reactor is eliminated, or at least substantially reduced, so that the process can be run for several weeks without interruption. The polymer polyols prepared by the process of the present invention are suitable for the production of all types of polyurethane resins, particularly flexible and semi-rigid polyurethane foams. Polymeric polyols are free of coarse articulates which are sedimentation and filtration suscep-tibies, and have a lower viscosity or a smaller average particle size at the same viscosity, compared to similar products prepared by methods known from the prior art. The processes for producing polyurethane foams using polymeric polyols are known. One of the most important applications of polymeric polyols is their use in the production of flexible molded polyurethane foams and agglomerated sheets, as well as semi-rigid, to which impart improved stiffness and weight bearing capacity. The substances also have advantageous effects on other properties of the foams, such as open cell character and resistance to shrinkage of the flexible foams. This invention also relates to a process for the preparation of cellular and non-cellulose polyurethane resins, which comprises reacting (1) a polyisocyanate with (2) a polymeric polyol, and optionally (3) other compounds with a molecular weight in the range from 40 to 1,000, containing hydrogen atoms reactive to the isocyanate, optionally in the presence of (4) catalysts, (5) blowing agents and (6) other known additives.

Isocyanates that can be used include aromatic polyisocyanates, aliphatics, and cycloaliphatics, and combinations thereof. Representative samples of these polyisocyanates include diisocyanates, such as 2,4-to-1,2-diisocyanate, 2,6-toluene diisocyanate, m-phenylene diisocyanate, hexamethylene diisocyanate, tetramethylene diisocyanate, cyclohexan-1, -diisocyanate, hexahydrotoluene diisocyanate. , naph-talen-1,5-diisocyanate, 4,4'-diphenylmethane diisocyanate and 3,3'-dimethyldiphenylmethane-4,4'-diisocyanate; and triisocyanates, such as toluene-2,4,6-triisocyanate and 4'-triphenylmethane triisocyanate, especially 2,4-toluene diisocyanate, mixtures of 2,4-toluene diisocyanate and 2,6-toluene. diisocyanate obtained from the phosgenation of crude toluene diamine; 4, 4 '-difenilemethane diisocyanate and crude diphenylmethane diisocyanate obtained from the phosgenation of crude diphenylmethane diamine.The foam formulation includes polymeric polyols prepared according to the present invention, and may also include with a molecular weight from 400 to 10,000, having at least two hydrogen atoms reactive to the isocyanate.These compounds may contain hydroxy groups, amino groups, thiol groups or carboxyl groups.The preferred compounds are hydroxyl compounds containing from 2 to 6. hydroxyl groups, with a molecular weight from 400 to 10,000, preferably from 1,000 to 8,000 The hydroxyl compounds are preferably polyesters or polyesters. Styres commonly used in the production of polyurethanes. Chain-lengthening agents or cross-linking agents which can be employed according to the present invention include, but are not limited to, water, hydrazine, aromatic and aliphatic diamines (such as phenylenediamine, ethylenediamine, diethylenetriamine, 2,4 - and 2, 6-hexahydro-tolylenediamine), amino alcohols (such as diethanolamine, N-methyldiethanolamine, triethanolamine, and 3-aminopropanol), amino acids, hydroxy acids, glycols (such as ethylene glycol, propylene glycol, glycerin, 1, 4-butanediol, 1,6-hexanediol, and sorbitol) and polyethylene or polypropylene or polybutylene glycols of higher molecular weight, with a molecular weight of up to 400. Suitable catalysts can be used for the preparation of polyurethane foams, including amines tertiary such as, for example, triethylamine, tributylamine, N-methyl-morpholine, N, N, ',' -tetramethylene diamine, 1,4-diazobicyclo- [2.2.2] -octane, N, N-dimethylbenzylamine and N, -dimethylcyclohex xyl amine. Triethanolamine, N-methyldi-ethanolamine, N, N-dimethylethanolamine and their reaction products with alkylene oxides can also be used. Other suitable catalysts include tin (II) salts of carboxylic acids (such as tin (II) acetate, tin (II) octoate, tin (II) ethyl hexanoate and tin (II) laurate) and tin compounds ( IV) (such as dibutyl tin oxide, tin dichloride, dibutyl tin diacetate, dibutyl tin dilaurate, dibutyl tin maleate and dioctyl tin diacetate.) The catalysts mentioned above can, of course, also be used as Mixtures Blowing agents, such as water and / or volatile organic or inorganic substances can optionally be used Suitable organic blowing agents include, for example, acetone, ethyl acetate, cyclopentane, halogenated hydrocarbons (such as methylene chloride, chloroform, trichlorofluoromethane, chlorodifluoromethane, and dichlorodifluoromethane), butane, hexane or diethyl ether Air, CO2 or N ^ O may be used as inorganic blowing agents. The effect of a blowing agent can also be obtained by the addition of compounds that decompose at elevated temperatures, to release gases. Other additives may also be used, including surface active additives, foam stabilizers, reaction retardants, stabilizers, flame retardant substances, plasticizers, colorants, fillers and fungistatic and bacteriostatic substances, according to the invention. Details regarding the use and action of these additives can be found in the "Polyurethane Handbook", Volume VII, by G. Oertel, Carl Hanser Publishers, Munich, 1993, pages 104-127.

Examples Definitions Polyol A: A polyether prepared by reacting a mixture of glycerin and propylene glycol, having a hydroxyl functionality of 2.9, with propylene oxide and ethylene oxide. The polyether has an ethylene oxide content of 10% by weight, contains predominantly secondary hydroxyl groups, and has a hydroxyl number of 56. Polyol B: A polyether prepared by reacting trimethylolpropane with proprietary oxide and ethylene oxide, wherein the ethylene oxide content is 17.5% by weight. The polyether contains 80-90% of primary hydroxyl groups, and has a hydroxyl number of 35. Polyol C: Polyether prepared by reacting trimethylolpropane with propylene oxide and ethylene oxide, wherein the ethylene oxide content is 17.7. % by weight. The polyether contains about 90% of primary hydroxyl groups, and has a hydroxyl number of 28. Polyol D: Polyether prepared by reacting glycerin with propylene oxide and ethylene oxide. The polyether has an ethylene oxide content of 10% by weight, contains predominantly secondary hydroxyl groups, and has a hydroxyl number of 56. Macromer I: Polyether containing induced unsaturation, prepared by reacting Polyol B with maleic anhydride, and subsequently with ethylene oxide. The macromer has an unsaturation of 0.050 meq / g, and a hydroxyl number of 33.9. Macromer II: Polyether containing induced unsaturation, prepared by reacting Polyol C with acrylic acid in the presence of p-toluenesulfonic acid. The macromer has an unsaturation of 0.065 meq / g, and a hydroxyl number of 25.9. Starter: 2, 2 '-azobis- (2-methylbutanonitrile), VazoMR 67, commercially available from DuPont. Moderator: (cyclohex-3-enylidinomethoxymethyl) benzene, Vulkazone MR AFD, commercially available from Bayer AG T: toluene EB: ethylbenzene BU0H: 1-butanol Stabilizer: OS 22 stabilizer, commercially available from Bayer AG Catalyst 1: dimethylethanolamine, Desmorapid MR DMEA, commercially available from Rhein Chemie Catalyst 2: bis (2-dimethylaminoethyl) ether in dipropylene glycol, RC-PUR Activator 108, available commercially from Rhein Chemie, MR Catalyst 3: stannous octoate, Desmorapid "" SO, commercially available from Rhein Chemie TDI: Toluene diisocyanate (80% of 2.4-; 20% of 2.6 toluene diisocyanate), Desmodur M11R1"T80, commercially available from Bayer AG Preparation of Polymer Polyol Polymeric polyols of the Examples were prepared continuously, in a series of stirred tank reactors. The respective reactors were continuously mixed in. The contents of each reactor were mixed well, and the internal temperature was controlled at 125 ° C. All the reactions were conducted under an inert atmosphere. or normal pressure, using a reactor design with overload. The overload of the first reactor enters the second reactor, where additional raw materials are added. Additionally, when desired, other reactors were used in a similar manner, with the distribution of raw materials between the reactors. The last reactor in the series was used as a post reactor, where additional initiator and solvent were added, to increase the conversion of monomer to polymer. The crude products were distilled under vacuum, a < 1019 x 10 kg / cm (1 mbar) and 125 ° C for several hours, to remove the solvent and the residual monomers, before the polymeric polyoles were used to produce polyurethane foams. Preparation of Polyurethane Foams The formulation of a typical easy-to-increase polyurethane foam is listed below. Several of the polymeric polyols described above, and identified in the Examples, were used to prepare easily bulking foams. Easy Volume Increase Foam Formulation Components Parts Polymer Polyol 50 Polyol D 50 Water 4.5 Stabilizer 1 Catalyst 1 0.1 Catalyst 2 0.05 Catalyst 3 0.13 TDI (Index 108) A typical easy-to-increase polyurethane foam is prepared by loading all components (except polyisocyanate) to a container, and mixing them intensely. The polyisocyanate is added with stirring, and the content is subsequently poured into an open mold. The polyurethane foam is allowed to increase in volume and cure at room temperature.

Analysis and Measurements Conversion The conversion of monomer to polymer was calibrated from the distillate Viscosity The viscosity of the polymer polyols was measured on a rotoviscometer equipped with a constant temperature cell. Particle Size The average particle size was determined by dynamic light scattering, a technique for determining particle sizes in the range from 3 nm to 3 lm. The reported values are the average of 6 tests. Residue The waste is a means to evaluate the quality, and eventually the storage stability of the polyol polyol. The test is carried out by first moistening the interior wall of a 10 ml sample vial with 2-3 ml of polymeric polyol. After 24 hours of remaining at room temperature, the glass wall is observed and evaluated based on the clarity of the film, and the number of polymer particles or agglomerated polymer particles of about 5-30 um in diameter. Classification Numerical 0 = very good 1 = good 2 = medium / good 3 = medium 4 = medium / poor 5 = poor Hardness The hardness of the foams was determined according to test method DIN 53577. Elongation The elongation at the breaking point of the foams was determined according to test method DIN 53571. Traction The tensile strength of the foams was determined according to test method DIN 53571.

EXAMPLES The following examples, Examples 1-16 (reported in Table I) clearly illustrate the advantages of the present invention. Examples 1-5 were prepared for comparison, and are not covered under the claims of the present invention. Examples 1-3 were prepared using a simple overload reactor, and are characterized by a large average particle size (more than 1000 nm) and a relatively high viscosity (more than 5000 centipoise (5000 MPas) at 25 ° C. ). Materials prepared via this approach usually exhibit a poor residue test, indicating that the material contains a significant portion of large polymer particles, or agglomerated po-lime particles, which can precipitate from the continuous phase of the base polyol. After 4-6 hours, early signs of scaling in the reactor, accumulation of polymer on the reactor wall in Examples 1 and 2 were observed. The scale of the reactor was improved with the replacement of toluene with ethylbenzene, Example 3 , however, an increase in the viscosity of the final product was noted, see Table I. In Example 4, the reaction mixture was added to two reactors connected in series, with 50% of the reaction mixture added to each reactor. . The resulting product showed an increase in viscosity and average particle size. In Example 5, only the monomer is distributed between the two reactors, while the total amount of polyol and macromer are added to the first reactor. In this example, polymer accumulation was noted in the second reactor after 7 hours. The final product had a similar viscosity (compared to Example 1), the average particle size remains relatively large, and the residue test shows a moderate amount of large polymer particles, or agglomerated polymer particles. The critical process parameters required for the preparation of stable polymer polymers, of low viscosity and of small average particle size, using a series of stirred tank reactors have been identified. The advantages of the present invention are demonstrated in Examples 6-16. Examples 6-9 demonstrate the effect of varying the macromer concentration and the solids content during the preparation of the intermediate on the physical properties of the final polymeric polyol dispersion. By maintaining a high concentration of macromer and a low content of solid materials in the first reactor, a highly stable intermediate is formed, of small average particle size, which is ideally suited for a post-polymerization. In Examples 6, 7 and 9, the concentration of macromer is set at about 15% with respect to the polyol mixture, and the level of solids in the first reactor is varied (20, 30 and 25% by weight, respectively ), resulting in intermediaries with an average particle size of 430, 550 and 505 nm respectively. The final products containing more than 40% solids, have low viscosities and small average particle sizes, see Table 1. In Example 8, a macromer concentration of 12% is used with respect to the polyol, and a content of solid materials of 15% by weight in the first reactor, to form an intermediate with an average particle size of 390 nm. However, the amount of monomer added to the second reactor is undesirably high, resulting in some build up on the reactor wall. Examples 10-16 demonstrate the advantages of the pre-satin invention using three polymerization reactors, so that the monomer can be further distributed to minimize reactor fouling. Materials prepared via this process usually contain very large polymer particles or agglomerated polymer particles, as previously described. Examples 10 and 11 further demonstrate the effect of the macromer concentration during the preparation of the intermediate on the physical properties of the final dispersion. In Example 12, the macromer is distributed in all polymerization reactors, resulting in a polymer dispersion essentially without large polymer particles or polymer agglomerates. A second type of macromer is used in Example 13. Example 14 demonstrates the use of an alternative solvent, 1-butanol. In Example 15, the intermediate is prepared using a lower styrene / acrylonitrile ratio, which results in an intermediate of small average particle size. A higher initiator concentration is used during the preparation of the intermediate in Example 16, which also produces an intermediate of small average particle size.

TABLE t Table I (Continued) or Table I (Continued) I J The Examples described above are for purposes of illustration, and should not be taken as limiting the invention, which is defined in the following claims.

It is noted that in relation to this date, the best method known to the applicant to carry out the aforementioned invention, is that which is clear from the present description of the invention.

Having described the invention as above, property is claimed as contained in the following:

Claims (12)

1. CLAIMS 1. A continuous process for the preparation of highly stable polymer polyols, finely divided, low viscosity, of small average particle size, the process is characterized in that in the first stage an intermediate is prepared by reacting (1) a mixture of styrene and acrylonitrile in a mixture of (2) a polyoxyalkylene polyether polyol and (3) a macromer, in the presence of (4) a free radical initiator, (5) a solvent having a chain transfer activity moderate, and optionally (6) a reaction moderator, at a temperature of at least 100 ° C, such that the intermediate contains a high concentration of macromer, at least about 12%, and preferably at least about 15%, with respect to the polyol mixture, and the solid material content of the intermediate is less than about 30%, preferably less than about 25%, and at least about 15% by weight, and thereafter the i The intermediate, which functions as a seed for a subsequent polymerization, is further reacted in one or more tank reactors agitated in series, with a mixture of styrene and acrylonitrile, in a polyol and optionally a macromer, in the presence of a solvent , initiator and a reaction moderator, which are distributed among the remaining reactors.
2. 2. A process according to claim 1, characterized in that the distribution of the raw materials between the polymerization reactors minimizes the concentration of monomer, in such a way that the amount of monomer added to any reactor is less than about 30%. that reactor content, and preferably is approximately equal in each reactor.
3. 3. A process in accordance with the claims 1 and 2, characterized in that the monomer mixture is a mixture of styrene and acrylonitrile, in proportions by weight in the range from about 100/0 to 20/80, preferably more than 50% of styrene.
4. 4. A process in accordance with the claims 1 and 2, characterized in that the polymeric base polyol is characterized by a molecular weight in the range from 500 to 12,000, preferably from about 2,000 to 8,000, and because it has a hydroxyl functionality from 2 to 6.
5. 5. A compliance process with claims 1 and 2, characterized in that the macromer is prepared either directly or indirectly by the reaction of (1) a polymeric polyol, having a molecular weight of at least 4,800 and a hydroxyl functionality of at least 3, with (2) a reactive unsaturated compound, and in that the amount of the reactive unsaturated compound used in the preparation of the macromer is in the range of 0.3 to 1.5 moles per mole of polyol, and preferably 0.5 to 1.2 moles per mole of polyol,
6. 6. A process according to claims 1 and 2, characterized in that the free radical initiator is used in amounts from 0.5 to 5% by weight, based on the total amount of monomers.
7. 7. A process in accordance with the claims 1 and 2, characterized in that a solvent, preferably ethylbenzene or n-butanol, is used in an amount from about 2 to 20%.
8. 8. A process according to claims 1 and 2, characterized in that the reaction moderator, which is optional for the preparation of the intermediate, but required for the subsequent reaction of the intermediate, is an enol ether of the following formula: A = CH-0-R wherein R represents an alkyl group of 1 to 18 carbon atoms, cycloalkyl of 5 to 10 carbon atoms, or substituted or unsubstituted benzyl, A represents the group R 'represents either hydrogen or an alkyl group of 1 to 8 carbon atoms.
9. 9. A process according to claims 1, 2, and 8, characterized in that the reaction moderator is (cyclohex-3-enylidenemethoxymethyl) benzene.
10. 10. A process according to claims 1, 2, 8 and 9, characterized in that the reaction moderator is used in an amount from about 0.5% to 5% by weight with respect to the total monomer.
11. 11. A highly stable, finely divided polymeric polyol of low viscosity, of small average particle size, characterized in that it is prepared according to claims 1 to 10.
12. 12. A polyurethane product, characterized in that it uses a polyol polymeric prepared according to claims 1 to 10. SUMMARY OF THE INVENTION The present invention describes a continuous process for the preparation of highly stable, finely divided, low viscosity polymer polyols of small average particle size, wherein in the first step an intermediate is prepared by reacting (1) a a mixture of styrene and acrylonitrile, in a mixture of (2) a polyoxyalkylene polyether polyol and (3) a macromer, in the presence of (4) a free radical initiator, (5) a solvent having a moderate chain transfer activity , and optionally (6) a reaction moderator, at a temperature of at least 100 ° C, so that the intermediate contains a high concentration of macromer, at least about 12%, and preferably at least about 15% with respect to the polyol mixture, and the solid content of the intermediate is less than about 30%, preferably less than about 25%, and at least about 15% by weight. The intermediate, which functions as a seed for a subsequent polymerization, is subsequently reacted in one or more stirred tank reactors in series, with a mixture of styrene and acrylonitrile, in a polyol and optionally a macromer, in the presence of a solvent, initiator and a reaction moderator, which are distributed among the remaining reactors.