ITMI20010861A1 - PROCEDURE FOR THE PREPARATION OF POLYOLIC BASED COMPOSITIONS CONTAINING A FINELY DIVIDED AND STABLE POLYMER CHARGE - Google Patents

Description

Title: Process for the preparation of polyol-based compositions containing a finely divided and stable polymeric filler.

The present invention relates to a process for the preparation of compositions based on polyols containing a finely divided and stable polymeric filler.

More particularly, the present invention relates to a process for the preparation of polyol-based compositions containing a finely divided and stable polymeric filler, to the compositions thus obtained and to their use in the preparation of polyurethane resins.

Methods for preparing polyol compositions containing in dispersion, or partially grafted to the chains, polymeric solid particles prepared in situ by polymerization of the corresponding monomers are known in the scientific literature. In US patent 4,357,430, for example, a process is described for preparing stable dispersions of polymers in polyethers which essentially consists in then imerising a mixture of acrylonitrile and styrene, in a weight ratio between 80:20 and 20:80, in a polyol base consisting of a polyether polyol with a molecular weight Mn of at least 500 and a polyether polyol obtained as a reaction product between a polyether polyol, with functionality greater than 2, and a polyisocyanate in such proportions that the ratio between the groups hydroxyl and isocyanic groups is greater than 1. The composition thus obtained can be used as a polyol component in the preparation of polyurethane foams.

In US patent 6,013,731 a process is described for the preparation of stable dispersions of polymeric fillers in polyol bases which envisages partially modifying the polyol chains so that they can contain ethylene unsaturations in a concentration lower than 0.02 meq / g and then polymerize in situ, in the polyol thus modified, one or more vinyl monomers.

The Applicant has now found a new process for the preparation of polyol-based compositions containing a polymeric filler characterized by a high concentration of solid, a remarkable stability and an average particle size of the polymeric particles capable of allowing the filterability of the compositions through filters. from 40 micrometers.

Therefore, the object of the present invention is a process for the preparation of polyol-based compositions containing a finely divided and stable polymeric filler which comprises: a) then polymerizing at least one vinyl monomer into a polyol component with functionality greater than or equal to 2 and of weight average molecular weight between 1000 and 8000 in the presence of a stabilizing agent obtained from the reaction between at least one polyether polyol terminated with at least one amino group, of average molecular weight between 1500 and 8000, and an anhydride comprising at least one unsaturated cyclic anhydride and in which the concentration of amino groups of the polyoxy polyether is such that at the end of the reaction with the anhydride the T / C ratio between the double bonds of the trans type (T) and the double bonds of the cis type (C) is between 0 , 1 and 10;

b) eliminating the unreacted monomers from the reaction mixture.

According to the present invention, the polymerization of the vinyl monomer is carried out in a polyol base. The polyol base is essentially of the ether or ester type and can be selected from polyether polyols, polyether polyols containing ester groups, polyether polyols containing amino groups, polyester polyols. The preferred polyol base is that consisting of one or more polyether polyols obtained by condensation of C2-C6 olefin oxides on compounds (starters) having at least two active hydrogen atoms. Ethylene oxide, propylene oxide or their mixtures are preferred as olefinic oxides.

Condensation occurs on starters such as glycols, triols, tetrols, amines, canol amine, polyamines or their mixtures.

Representative examples of polyether polyols to be used according to the present invention are those based on ethylene oxide and / or propylene oxide and in which the starter is a glycol such as propyl englene or a propylene oxide oligomer with a molecular weight lower than 500; a triol such as glycerin or trimethylolpropane; a tetrol such as pentaerythritol; one of amine such as ethylenediamine; one of aromatic amine such as ortho-toluenediamine; one amine canol as tri ethanol amine; or a hydroxy alkane then the functions and as xi litoio, Arab tolo, sorbitol, mannitol.

Any vinyl monomer capable of dissolving in the polyol base can be used in the process object of the present invention. Illustrative examples are acrylic and methacrylic acids, methyl acrylate, methyl methacrylate, ethyl acrylate, acrylamethacrylamide, vinyl chloride and vinylidene chloride, acrylonitrile, methacrylonitrile, styrene, brominated styrenes, butadiene, isoprene, isobutene and mixtures thereof. Further examples of monomers are cited in F. E. Bailey, 3. V. Koleske “Alkylene Oxides and Their Polymers” Marcel Dekker. Preferred products are acrylonitrile and styrene used singly or mixed together in styrene / acrylonitrile ratios including 80: 20-40: 60.

These monomers can be polymerized according to conventional techniques. In particular, they are dissolved in the polyol base in an amount equal to 20-60% by weight of the total and, therefore, reacted at a temperature between 80 and 150'C in the presence of radical initiators and molecular weight regulators or chain transfer agents.

The radical polymerization initiators are added to the polyol base in quantities generally comprised between 0.05 and 3% by weight, with respect to the mixture of vinyl monomers, and can be selected from peroxides, persulfates, perborates, percarbonates and azo derivatives. Examples are dibenzoyl peroxide, lauryl peroxide, di-t-butyl peroxide, t-butyl-peroxy 2-ethylhexanoate, t-amyl-peroxy 2-ethyl hexanoate, dicumyl peroxide, benzoyl hydroperoxide, t-butyl hydroperoxide, cumyl hydroperoxide, 2, 2'-azobis (isobutyronitrile), 2,2'-azobis (2, 4-dimethylvaleronitrile), etc.

The chain transfer agents are added to the polyol base in quantities generally comprised between 0.1 and 2% by weight and can be selected from mercaptans such as dodecyl mercaptan, ethyl mercaptan, propyl mercaptan, butyl mercaptan, hexyl mercaptan, octyl mercaptan, decyl mercaptan , octadecyl mercaptan, 2-mercapto ethanol, etc.

Together with the vinyl monomer, the stabilizing agent is also added in an amount equal to 0.5-20% by weight, preferably 2-10%, with respect to the total. The stabilizing agent is prepared starting from at least one amino terminated polyether polyol, preferably selected from a polyoxyethylene glycol or a polyoxyethylene glycol terminated polyethylene glycol, containing at least one primary terminal amino group, preferably from 1 to 3 primary terminal amino groups. These polyols are commercially available under the name JEFFAMINE from HUNTSMAN POLYURETHANES or can be industrially prepared with conventional techniques described, for example, in the text "Saunders & Frisch - Poiyurethanes, Chemistry and Technology" Interscience, New York, 1964 or in the text by Bailey and Kuleske previously quoted.

The stabilizing agent is prepared by reaction of the amino polyol terminated with an unsaturated cyclic anhydride, i.e. with mixtures containing both an unsaturated and saturated cyclic anhydride in unsaturated / saturated anhydride molar ratios greater than or equal to 0.5, preferably between 1 and 10. Examples of unsaturated anhydrides can be maleic, citraconic, 2,5-dimethylmaleic anhydride, etc. The reaction is carried out by operating in bulk at a temperature between 60 and 180 ° C, preferably between 100 and 150 ° C, keeping the reactants in contact for times between 1 and 8 hours. The molar ratios between the amino groups and the anhydride are between 5 and 1.

At the end of the reaction the free carboxy groups can be transformed into hydroxyl groups by reaction with epoxides, such as ethylene oxide, propylene oxide, butene oxide, hexene oxide, epichlorohydrin, glycidol, or with alkyl carbonates such as ethylene carbonate or propylene carbonate. The reaction is carried out in bulk, under basic catalysis conditions and at a temperature between 60 and 180 ° C.

Once the polymerization of the vinyl monomer is completed, the unreacted monomers are eliminated by known techniques, for example by stripping with an inert gas or by evaporation under vacuum at 80-140 ° C. The final compositions thus obtained have a solid filler content between about 20% and about 60% by weight, an average particle size of the solid particles, measured with a "Light Scattering" apparatus according to the Fraunhofer optical model, of less than 5 micrometers and complete filterability through a 40 micrometer mesh filter. Kept in a closed container for 28 days, they did not give rise to any form of sediment.

The polyol-based compositions containing a finely divided and stable polymeric filler object of the present invention can be used in the preparation of polyurethane resins and, in particular, in the preparation of rigid or flexible polyurethane foam resins, in combination with conventional isocyanic reagents.

According to the present invention any at least bifunctional organic isocyanate can be used in combination with the present polyol compositions. in particular, low or medium molecular weight diisocyanates of general formula (I) can be used:

(THE)

where R represents a cycloalkyl or aromatic alkyl radical (iso) possibly substituted with alkyl radicals Examples of such products are hexamethylene diisocyanate, meta and / or paraphenylene diisocyanate, 2,4-toluene diisocyanate (TDI), either alone or mixed with the isomer 2,6-toluene diisocyanate, 4,4'-diphenylmethane-diisocyanate (NIDI), optionally in mixture with the isomer 2,4 ', 4,4'-dicyclohexyl methane diisocyanate, l-isocyanate-3isocyanatomethi1-3,3, 5-trimethylcyclohexane, etc.

Alternatively, high molecular weight polyisocyanates with varying degrees of condensation can be used, obtained from the phosgenation of anilineformaldehyde condensates. These products consist of mixtures of polymethylenepolyphenyl polyisocyanates of general formula

where Φ represents a phenyl group and n is an integer greater than or equal to 1.

Preferred medium or high molecular weight polyisocyanates according to the present invention are polymethylenepolyphenyl polyisocyanates having an average functionality comprised between 2.6 and 2.8. These products are commercially available under different names such as "TEDIMON 31" (ENICHEM S.p.A.), "SUPRASEC DNR" (HUNTSMAN POLYURETHANES) or DESMODUR 44 V20 (BAYER).

Further examples of polyisocyanates are the isocyanic prepolymers obtained by reacting an excess in equivalents of one or more isocyanates of general formula (I) or (II) with at least one polyether and / or polyester polyol, optionally containing mixed ether or ester groups and / or groups of an animine nature, having a functionality between 2 and 8 and an equivalent weight between about 50 and In the preparation of polyurethane resins, in particular of expanded polyurethane resins, in addition to the traditional reagents, the reaction mixture also includes further additives commonly used for this type of polymerization such as amine catalysts, such as triethylenediamine, and / or metal such as stannous octoate, cell regulators, thermo-oxidation stabilizers, pigments, etc. Details on the polymerization of polyurethanes are described in the text “Saunders & Frisch -Polyurethanes, Chemistry and Technology” Interscienee, New York, 1964.

In the production of polyurethane foams, the expansion agent consists mainly of water which can be used alone or in combination with secondary expansion agents. In the preparation of polyurethane foams, water has a critical function as through it there is the formation of urea bonds associated with the development of carbon dioxide which causes the process of expansion / swelling of the polyurethane resin with the obtainment of flexible foams. Amounts of water between 3 and 6 parts by weight compared to 100 parts of the polyol component are the most commonly used.

According to conventional technology, therefore, for the expansion of the polyurethane resin, carbon dioxide developed in situ for the chemical reaction between water and the NCO groups of the polyisocyanate is preferably used as the primary agent. The method for introducing the primary expander into the polymerization mass must not, however, be construed as limiting as other gases and other techniques can be used, such as, for example, bubbling of air, nitrogen or other inert gas, into the reaction mass. by injection from the outside, which allow to obtain similar products.

However, in the preparation of polyurethane foams with reduced density, for example having a density equal to or lower than 25 Kg / m3, the expanding function of the water alone may not be sufficient to reach these density values without incurring problems (burning or "scorching" ) due to the exothermic reaction between water and isocyanic groups. For this reason, the expanding action of water can be supported by expanding agents of a physical nature, chosen from hydrofluoro alkanes, liquid CO2, hydrocarbons such as n-pentane , ipentane, cyclopentane, etc., dimethylcarbonate, or their mixtures.

In order to better understand the present invention and to put it into practice, some illustrative and non-limiting examples are given below.

EXAMPLE 1

B0.2 g (7.5 mmol) of poly (propylene glycol) bis (2- aminopropyl ether) of molecular weight 4000 and 1.47 g (15 mmoles) of maleic anhydride. After stopping the nitrogen flow, the reaction mixture is heated to 130 ° C for 24 hours.

The final product has a l / C ratio equal to 2. EXAMPLE 2

In a 100 ml AISI 316 steel autoclave, 50 g of a reaction mixture was introduced, the synthesis of which is reported in Example 1, containing 0.22 meq / g of carboxylic groups. 0.62 g (11 mmoles) of KOH were then introduced and the reactor was charged with nitrogen until the pressure was brought to a value of 2 atm. 5 g (115 mmoles) of ethylene oxide were then introduced and the reaction mixture was gradually heated to 125 ° C for 2 hours.

The final product has a l / C ratio of 2.5.

EXAMPLE 3

In a two-necked flask equipped with a tap for the introduction of nitrogen, a fitting connected to a bubble counter and magnetic stirring, 30 g (7.5 mmol) of poly (propylene glycol) bis (2-aminopropyl ether) are introduced under nitrogen flow. ) of molecular weight 4000 and 1.49 g (15 mmoles) of maleic anhydride and 0.009 g (0.5% by weight) of Irganox 1010. After stopping the nitrogen flow, the reaction mixture is heated to 180 ° C for 4 hours.

The final product has a T / C ratio of 2.8

EXAMPLE 4

30.2 g (7.5 mmol) of poly (propylene glycol) bis (2- aminopropyl ether) of molecular weight 4000 and 1.47 g (15 mmoles) of maleic anhydride. After stopping the nitrogen flow, the reaction mixture is heated at 130 ° C for 4 hours.

The final product has a T / C ratio of 0.2.

EXAMPLE 5

In a pressure-resistant glass reactor equipped with a manometer and magnetic stirrer, the following are respectively introduced:

10.41 g (52.5% by weight) of a three-function polyether polyol with an average molecular weight MW of 3500 (Glendion FG 3504 from ENICHEM),

1.42 g (7% by weight) of stabilizer of example 1, 5.7 g (28% by weight) of styrene,

2.39 g (12% by weight) of acrylonitrile,

0.06 g of dodecantiol,

0.062 g of benzoyl peroxide.

The reactor is closed and the mixture is heated to 110 ° C for 360 minutes. The reaction mixture is left to cool and the volatile products that have not reacted are eliminated by initially holding under vacuum at 50 ° C for 90 minutes and then under vacuum at 100 ° C for another 360 minutes, the final product appears as a viscous dispersion. white in color.

EXAMPLE 6

We operate as in example 5 using the following formulation.

10.51 g (52.5% by weight) of a trifunctional polyether polyol (Glendion FG 3504 by ENICHEM),

1.42 g (7% by weight) of stabilizer of example 1, 6.4 g (32% by weight) of styrene,

1.6 g (8% by weight) of acrylonitrile,

0.05 g of dodecantiol,

0.061 g of benzoyl peroxide.

EXAMPLE 7

We operate as in example 5 using the following formulation.

10.96 g (54.5% by weight) of a trifunctional polyether polyol (Glendion FG 3504 by ENICHEM),

1.03 g (5% by weight) of stabilizer of example 1,

5.6 g (28% by weight) of styrene,

2.41 g (12% by weight) of acrylonitrile,

0.06 g of dodecantiol,

0.062 g of benzoyl peroxide.

EXAMPLE 8

We operate as in example 5 using the following formulation.

11.33 g (56.5% by weight) of a trifunctional polyether polyol (Glendion FG 3504 by ENICHEM),

0.6 g (3% by weight) of stabilizer of Example 1,

5.6 g (28% by weight) of styrene,

2.4 g (12% by weight) of acrylonitrile,

0.05 g of dodecantiol,

0.062 g of benzoyl peroxide.

EXAMPLE 9

We operate as in example 5 using the following formulation.

8.5 g (42.5% by weight) of a trifunctional polyether polyol (Glendion FG 3504 from ENICHEM),

1.4 g (7% by weight) of stabilizer of example 1, 7.08 g (35% by weight) of styrene,

2.92 g (15% by weight) of acrylonitrile,

0.05 g of dodecantiol,

0.061 g of benzol peroxide.

EXAMPLE 10

We operate as in example 5 using the following formulation.

8.9 g (44.5% by weight) of a trifunctional polyether polyol (Glendion FG 3504 by ENICHEM),

1.02 g (5% by weight) of stabilizer of example 1,

7.1 g (35% by weight) of styrene,

2.92 g (15% by weight) of acrylonitrile,

0.06 g of dodecantiol,

0.066 g of benzol peroxide.

EXAMPLE 11

We operate as in example 5 using the following formulation.

6.57 g (32.5% by weight) of a three-function polyether polyol (Glendion FG 3504 from ENICHEM),

1.42 g (7% by weight) of stabilizer of example 1,

8.44 g (42% by weight) of styrene,

3.56 g (18% by weight) of acrylonitrile,

0.06 g of dodecantiol,

0.062 g of benzol peroxide.

EXAMPLE 12

We operate as in example 5 using the following formulation.

10.51 g (52.5% by weight) of a three-function polyether polyol (Glendion FG 3504 from ENICHEM),

1.46 g (7% by weight) of stabilizer of example 1,

8.02 g (40% by weight) of styrene,

0.08 g of dodecantiol,

0.062 g of benzoyl peroxide.

EXAMPLE 13

In a pressure-resistant glass reactor equipped with a manometer and magnetic stirrer, the following are respectively introduced:

10.47 g (52.5% by weight) of a trifunctional polyether polyol (Glendion FG 3504 by ENICHEM),

1.42 g (7% by weight) of stabilizer of example 1,

8.0 g (40% by weight) of styrene,

0.05 g of dodecantiol,

0.095 g of benzoyl peroxide.

After having loaded the polyol, the stabilizer, the styrene, the dodecantiol and 0.047 g of benzoyl peroxide, the reactor is closed and the mixture is heated at 125 ° C for 300 minutes. Subsequently, the reaction mixture is allowed to cool and after having discharged the residual pressure, 0.048 g of benzoyl peroxide are added to the reactor under a nitrogen flow. The mixture is heated to 125 ° C for another 300 minutes. The volatile products which have not reacted are eliminated by initially holding under vacuum at 50 ° C for 90 minutes and then under vacuum at 100 ° C for a further 360 minutes.

EXAMPLE 14

We operate as in example 5 using the following formulation.

10.52 g (52.5% by weight) of a trifunctional polyether polyol (Glendion FG 3504 by ENICHEM),

1.41 g (7% by weight) of stabilizer of example 3,

5.61 g (28% by weight) of styrene,

2.45 g (12% by weight) of acrylonitrile,

0.05 g of dodecantiol,

0.066 g of benzoyl peroxide.

EXAMPLE 15

We operate as in example 5 using the following formulation.

10.52 g (52.5% by weight) of a trifunctional polyether polyol (Glendion FG 3504 by ENICHEM),

1.41 g (7% by weight) of stabilizer of example 4,

5.61 g (28% by weight) of styrene,

2.42 g (12% by weight) of acrylonitrile,

0.05 g of dodecantiol,

0.064 g of benzoyl peroxide.

COMPARATIVE EXAMPLE A

into a pressure-resistant glass reactor equipped with a manometer and magnetic stirrer, the following are respectively introduced:

9.0 g (44.5% by weight) of a three-functional polyether polyol (Glendion FG 3504 from ENICHEM), 0.964 g (0.24 mmoles) of poly (propylene glycol) bis (2 aminopropyl ether),

0.038 g (0.48 mmol) of acrylic acid

7.07 g (35% by weight) of styrene,

2.91 g (15% by weight) of acrylonitrile,

0.07 g of dodecantiol,

0.061 g of benzol peroxide.

The reactor is closed and the mixture is heated to 110 ° C for 360 minutes. The reaction mixture is allowed to cool and the volatile products which have not reacted are removed by initially holding under vacuum at 50 ° C for 90 minutes and then under vacuum at 100 ° C for a further 360 minutes. The final product appears as a viscous yellow dispersion.

COMPARATIVE EXAMPLE B

In a flask are respectively introduced:

0.041 g (0.73 mmol) of KOH in tablets,

0.1 g of polyether polyol (Glendion FG 3504), 0.041 g of distilled water

The solution is placed under magnetic stirring until KOH is completely dissolved and then 0.2 g of polyol are added to obtain an emulsion at the end.

107 g of Glendion FG 3504 and the emulsion described above are introduced into a pressure-resistant glass reactor equipped with a pressure gauge and magnetic stirring. The reaction mixture is heated to an internal temperature of 105 ° C and nitrogen is bubbled through a capillary for 4 hours. Then after allowing the mixture to cool under nitrogen, 1.79 g (18.2 mmoles) of maleic anhydride are added. The mixture is heated at 120 ° C for 8 hours. the final product has a T / C ratio of 0.

COMPARATIVE EXAMPLE C

In a pressure-resistant glass reactor equipped with a pressure gauge and magnetic stirrer, the following are respectively introduced:

10.4 g (52.5% by weight) of a trifunctional polyether polyol (Glendion FG 3504 by ENICHEM),

1.4 g (7% by weight) of stabilizer of comparative example B,

5.7 g (28% by weight) of styrene,

2.4 g (12% by weight) of acrylonitrile,

0.05 g of dodecantiol,

0.061 g of benzoyl peroxide.

the reactor is closed and the mixture is heated at 110 ° C for 360 minutes. The reaction mixture is left to cool and the volatile products that have not reacted are eliminated by initially holding under vacuum at 50 ° C for 90 minutes and then under vacuum at 100 ° C for another 360 minutes, the final product appears as a viscous dispersion. yellow in color.

The following table shows the properties of the polyols containing the polymeric filler as described in the previous examples.

EXAMPLE 16

In a one-liter reactor, equipped with an internal stirrer and lines for the vacuum and for the nitrogen supply, 40 g of stabilizer from Example 1 and 254 g of three-function polyether polyol (Glendion FG

3504 of ENICHEM). The following formulation is then loaded into the reactor, maintained at 110 ° C in 2 hours:

235.2 g of styrene,

- .100.8 g of acriIoniters! And,

2.1 g of dodecantiol,

0.99 g of benzoyl peroxide,

169.6 g of Glendion FG 3504.

At the end of the reaction, the residual monomers are removed by stripping under vacuum for 90 minutes. The product has a viscosity of 24,000 mPa.sec at 25 ° c.

EXAMPLE 17

In a one-liter reactor, equipped with an internal stirrer and lines for vacuum and nitrogen feeding, 16 g of stabilizer from Example 1 and 320 g of three-function polyether polyol (Glendion FG 3504 from ENICHEM) are fed. The following formulation is then loaded into the reactor, maintained at 110 ° C in 2 hours:

168 g of styrene,

72 g of acrylonitrile,

1.5 g of dodecantiol,

0.71 g of benzoyl peroxide,

224 g of Tercarol 909SAO (MW = 3600, functionality = 3).

At the end of the reaction, the residual monomers are removed by stripping under vacuum for 90 minutes, the product has a viscosity of 2260 mPa.sec at 25 ° C.

Claims (24)

CLAIMS 1. Process for the preparation of polyol-based compositions containing a finely divided and stable polymeric filler which comprises: a) then imerising at least one vinyl monomer in a polyol component with functionality greater than or equal to 2 and with an average molecular weight between 1000 and 8000 in the presence of a stabilizing agent obtained from the reaction between at least one polyether polyol terminated with at least one amino group, with an average molecular weight between 1500 and 8000, and an anhydride comprising at least one unsaturated cyclic anhydride and in which the concentration of amino groups of the polyoxy polyether is such that at the end of the reaction with the anhydride the ratio T / C between the double bonds of the trans type (T) and the double bonds of the cis type (C) is between 0.1 and 10; b) eliminating the unreacted monomers from the reaction mixture. 2. Process according to claim 1, wherein the polyol base is essentially of the ether or ester type and is selected from polyethers polyethers, polyethers polyethers containing ester groups, polyethers polyethers containing amino groups, then the polyester oils. 3. Process according to claim 2, wherein the polyol base is that consisting of one or more polyether polyethers obtained by condensation of C2-C6 olefinic oxides on compounds (starters) having at least two active hydrogen atoms. 4. Process according to claim 3, in which the olefinic oxide is selected from ethylene oxide, propylene oxide or their mixtures. 5. Process according to any one of the preceding claims, in which the polyether polyols are those based on ethylene oxide and / or propylene oxide and in which the starter is a glycol, a triol, a tetrol, a diamine, an aromatic diamine, an alkanolamine or a then functional hydroxy alkane. 6. Process according to any one of the preceding claims, in which the vinyl monomer capable of solubilization in the polyol base is selected from acrylic and methacrylic acid, methyl acrylate, methyl methacrylate, ethyl acrylate, acrylamide, methacrylamide, vinyl chloride and vinylidene chloride, acrylonitrile, methacrylonitrile, styrene, brominated styrenes, butadiene, isoprene, isobutene and their mixtures. 7. Process according to claim 6, wherein the vinyl monomer is selected from acrylonitrile and styrene used singly or mixed together in styrene / acrylonitrile ratios including 80: 20-40: 60. 8. Process according to any one of the preceding claims, in which the vinyl monomers are dissolved in the polyol base in an amount equal to 20-60% by weight of the total and reacted at a temperature between 80 and 150 ° C in the presence of radical initiators and molecular weight regulators or chain transfer agents. 9. Process according to any one of the preceding claims, in which the stabilizing agent is added in an amount equal to 0.5-20% by weight, preferably 2-10%, with respect to the total. 10. Process according to any one of the preceding claims, in which the stabilizing agent is prepared starting from at least one amino terminated polyether polyol, selected from a polyethylene glycol or a polyoxypropylene glycol containing from 1 to 3 primary terminal amino groups. 11. Process according to any one of the preceding claims, in which the stabilizing agent is prepared starting from mixtures containing both an unsaturated and saturated cyclic anhydride in unsaturated / saturated anhydride molar ratios greater than or equal to 0.5. 12. Process according to any one of the preceding claims, in which the stabilizing agent is obtained at a temperature between 60 and 180 ° C, keeping the reagents in contact for times between 1 and 8 hours. 13. Process according to any one of the preceding claims, in which the stabilizing agent is prepared by operating with molar ratios between the amino groups and the anhydride between 5 and 1. 14. Process according to any one of the preceding claims, in which at the end of the preparation reaction of the stabilizing agent the free carboxylic groups are transformed into hydroxyl groups by reaction with epoxides or alkyl carbonates. 15. Process according to claim 14, in which the reaction is carried out in bulk, under basic catalysis conditions and at a temperature between 60 and 180 ° C. 16. Process according to any one of the preceding claims, wherein the unreacted vinyl monomers are removed by stripping with an inert gas or by evaporation under vacuum at 80-140 ° C. 17. Polyol compositions containing a finely divided polymeric filler obtainable with the process described in any one of the preceding claims. 18. Polyol compositions according to claim 17, wherein the solid filler content is between about 20% and about 60% by weight. 19. Polyol compositions according to claim 17 or 18, wherein the solid charge has an average particle size of the solid particles, measured with a "Light Scattering" apparatus, lower than 5 micrometers. 20. Use of the polyol-based compositions containing a finely divided and stable polymeric filler according to any one of the preceding claims, in the preparation of rigid or flexible expanded polyurethane resins in combination with isocyanates. 21. use according to claim 21, wherein the isocyanates are at least bifunctional and are selected from low or medium molecular weight diisocyanates of general formula (I): where R represents an (iso) alkyl radical C1-C12, cycloalkyl C5-C15 or aromatic C6-C18, optionally substituted with alkyl radicals ^ -04, and those with various degrees of condensation, obtained from the phosgenation of aniline-formaldehyde condensates, of general formula (II): where Φ represents a phenyl group and n is an integer greater than or equal to 1. Use according to claim 20 or 21, wherein the isocyanates are selected from the isocyanic prepolymers obtained by reacting an excess in equivalents of one or more isocyanates of general formula (I) or (II) with at least one polyether polyol and / or polyester, optionally containing mixed ether or ester groups and / or groups of an amino nature, having a functionality comprised between 2 and 8 and an equivalent weight comprised between about 50 and 2000. 23. Use according to any one of the preceding claims from 20 to 22, in which the polyol composition comprises water used alone or in combination with secondary expansion agents. Use according to claim 23, wherein the polyol composition comprises water in amounts ranging from 3 to 6 parts by weight with respect to 100 parts of the polyol component.