Process for preparing a polyurethane material

ES 2 247 161 T3

DESCRIPTION

Procedure for preparing a polyurethane material.

The present invention relates to a process for preparing a polyurethane material. More specifically, the present invention relates to a process for preparing a polyurethane material using a polyoxyethylene polyoxypropylene polyol with a high content of oxyethylene and a polyisocyanate with a high content of 4,4'-diphenylmethane diisocyanate (4,4 ' -MDI).

WO 98/00450 describes the preparation of polyurethane materials with a high content of hard blocks from polyols with a high content of oxyethylene, polyisocyanates comprising at least 85% by weight of 4,4'-MDI or a variant of it and water. The materials that are manufactured are elastomers and therefore have a glass transition temperature of less than 25 ° C. Furthermore, in EP 608626 the production of shape memory polyurethane foams is described by reacting a polyisocyanate comprising a high amount of 4,4'-MDI and a polyol with a high oxyethylene content with water. The foams have a glass transition temperature above 25 ° C; the amounts of crosslinker and chain extender used are relatively low, resulting in products with limited hard block content, providing products that are not as rigid as would sometimes be desired.

Surprisingly, it has now been found that if a polyol with a high oxyethylene content and a high level of primary hydroxyl groups is used together with a sufficient amount of a crosslinker or chain extender to provide a high hard block ratio, one obtains a polyurethane material with a glass transition temperature of at least 25 ° C and exhibiting high stiffness at a given density. The resulting material has fewer surface defects (improved mixing, fewer bubbles) and relatively high "ductility" (ie, it is not brittle). The combination of components used to produce these materials shows good wetting of fibrous materials and particularly glass fibers which make the process particularly suitable for reactive injection molding (RIM), especially for reinforced RIM (RRIM). and the structural RIM (SRIM).

The present invention therefore relates to a process for preparing a polyurethane material having a glass transition temperature of not less than 25 ° C, which process comprises reacting a polyisocyanate and an isocyanate-reactive composition, optionally in the presence of water in an amount less than 5% by weight of the following isocyanate-reactive composition, in which the reaction is carried out with an isocyanate index of 80 to 140, the polyisocyanate consisting of a) 80-100% by weight of diphenylmethane diisocyanate comprising at least 40%, preferably at least 60% and most preferably at least 85% by weight of 4,4'-diisocyanate of diphenylmethane and / or a variant of said diphenylmethane diisocyanate, variant that is liquid at 25 ° C and has an NCO value of at least 20% by weight (polyisocyanate a), and b) 20-0% by weight of another polyisocyanate (polyisocyanate b), and wherein the isocyanate-reactive composition consists of a) 80-100% by weight of a polyether polyol with an average nominal functionality of 3-8, an average equivalent weight of 200-2000, an average molecular weight of 600-8000, an oxyethylene (EO) content of 50-100% and preferably 75-100% by weight and a primary hydroxyl content of 70-100% calculated with respect to the number of primary or secondary hydroxyl groups in the polyol, b) an isocyanate reactive crosslinker and / or chain extender in an amount such that the hard block ratio is 0.60 or more and preferably at least 0.65 and c) 20-0% by weight of one or more of other isocyanate-reactive compounds excluding water, the amount of polyol a) and of isocyanate-reactive compound c) being calculated with respect to the total amount of this polyol a) and compound c).

The materials prepared according to the present invention do not have any glass transition temperature, Tg, less than 25 ° C and preferably not less than 60 ° C.

Tg is defined as the temperature at which the tangent δ of the curve reaches its maximum value as measured by mechanical dynamic thermal analysis (DMTA) at 1 Hz and a heating rate of 3 ° C / min.

In the context of the present invention the following terms have the following meaning:

1) Isocyanate index or NCO index or index:

The ratio of NCO groups to isocyanate-reactive hydrogen atoms present in a formulation, given as a percentage:

[NCO] x100 [active hydrogen] (%)

In other words, the NCO number expresses the percentage of isocyanate actually used in a formulation relative to the amount of isocyanate theoretically required to react with the amount of isocyanate-reactive hydrogen used in a formulation.

ES 2 247 161 T3

It should be noted that the isocyanate index, as used herein, is considered from the point of view of the polymerization process itself that prepares the elastomer involving the isocyanate component and the isocyanate-reactive components. Any isocyanate group consumed in a preliminary stage to produce modified polyisocyanates (including such isocyanate derivatives referred to in the art as prepolymers) or any active hydrogen consumed in a preliminary stage (e.g., reacted with isocyanate to produce modified polyols or polyamines) does not they are taken into account in the calculation of the isocyanate index. Only free isocyanate groups and free isocyanate-reactive hydrogens (including those of water) present in the polymerization phase itself are taken into account.

2) The term "isocyanate-reactive hydrogen atoms", as used herein for the purpose of calculating the isocyanate index, refers to the total of active hydrogen atoms in hydroxyl and amine groups present in the reactive compositions. ; This means that for the purpose of calculating the isocyanate index in the polymerization process itself, a hydroxyl group is considered to comprise a reactive hydrogen, a primary amine group is considered to comprise a reactive hydrogen, and a water molecule is considered to comprise two active hydrogens.

3) Reaction system: a combination of components in which the polyisocyanates are kept in one or more containers separate from the isocyanate-reactive components.

4) The term "polyurethane material", as used herein, refers to cellular or non-cellular products obtained by reacting polyisocyanates with isocyanate-reactive hydrogen-containing compounds, optionally using foaming agents, and in particular includes cellular products obtained with water as a reactive foaming agent (which involves a reaction of water with isocyanate groups, obtaining urea and carbon dioxide bonds and producing polyurea-urethane foams) and with polyols, amino alcohols and / or polyamines as compounds. isocyanate reactive.

5) The term "average nominal hydroxyl functionality" is used herein to indicate the number average functionality (number of hydroxyl groups per molecule) of the polyol or polyol composition, assuming this is the number average functionality (number active hydrogen atoms per molecule) of the initiator (s) used in their preparation, although in practice this will often be somewhat lower due to some terminal unsaturation.

6) The word "average" refers to the average in number unless otherwise stated.

7) The term "hard block ratio" refers to the amount (in parts by weight) polyisocyanate + isocyanate reactive materials with a molecular weight of 500 or less (in which polyols having a weight molecular weight greater than 500 incorporated in polyisocyanate) divided by the amount (in parts by weight) of all polyisocyanate + isocyanate reactive materials used.

8) The glass transition temperature is measured according to dynamic mechanical thermal analysis (DMTA) according to ISO / DIS 6721-5 at 3 ° C / min.

Preferably, the polyisocyanate a) is selected from 1) a diphenylmethane diisocyanate comprising at least 40%, preferably at least 60% and most preferably at least 85% by weight of diphenylmethane 4,4'-diisocyanate and the following preferred variants of said diphenylmethane diisocyanate: 2) a variant of polyisocyanate 1) modified with carbodiimide and / or uretonimine, the variant having an NCO value of 20% by weight or more; 3) a urethane-modified variant of polyisocyanate 1), the variant having an NCO value of 20% by weight or more and being the reaction product of an excess of polyisocyanate 1) and of a polyol having nominal hydroxyl functionality 2-4 average and an average molecular weight of at most 1000; 4) a prepolymer having an NCO value of 20% by weight or more and which is the reaction product of an excess of any of the aforementioned polyisocyanates 1-3) and of a polyol having an average nominal functionality of 2 -6, an average molecular weight of 2000-12000 and preferably a hydroxyl number of 15 to 60 mg KOH / g, and 5) mixtures of any of the aforementioned polyisocyanates. Polyisocyanates 1), 2), 3) and mixtures thereof are preferred.

Polyisocyanate 1) comprises at least 40% by weight of 4,4'-MDI. Such polyisocyanates are known in the art and include pure 4,4'-MDI and isomeric mixtures of 4,4'-MDI and up to 60% by weight of 2,4'-MDI and 2,2'MDI.

It should be noted that the amount of 2,2'-MDI in the isomeric mixtures is fairly at an impurity level and will generally not exceed 2% by weight, the remainder being 2,4'-MDI and 4,4'-MDI . Polyisocyanates such as these are known in the art and are commercially available; for example Suprasec^MR Huntsman Polyurethanes MPR, which is a company of Huntsman International LLC (owner of the Suprasec trademark).

The variants of the polyisocyanate 1) above modified with carbodiimide and / or uretonimine are also known in the art and are commercially available; for example, Suprasec 2020 from Huntsman Polyurethanes.

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The polyisocyanate variants 1) above modified with urethane are also known in the art, see for example The ICI Polyurethanes Book by G. Woods 1990, 2^to ed., pp. 32-35. The aforementioned prepolymers of polyisocyanate 1) with an NCO value of 20% by weight or more are also known in the art. Preferably, the polyol used to obtain these prepolymers is selected from polyester polyols and polyether polyols and especially from polyoxyethylene / polyoxypropylene polyols having an average nominal functionality of 2-4, an average molecular weight of 2500-8000, and preferably an index of hydroxyl of 15-60 mg KOH / g and preferably either an oxyethylene content of 5-25% by weight, oxyethylene which is preferably at the end of the polymeric chains, or an oxyethylene content of 50-90% by weight, oxyethylene which is preferably randomly distributed throughout the polymer chains.

Mixtures of the above-mentioned polyisocyanates can also be used, see, for example, The ICI Polyurethanes Book by G. Woods 1990, 2nd ed., Pp. 32-35. An example of such a commercially available polyisocyanate is Suprasec 2021 from Hunstman Polyurethanes.

The other polyisocyanate b) can be selected from aliphatic, cycloaliphatic, araliphatic and preferably aromatic polyisocyanates, such as toluene diisocyanate in the form of its 2,4 and 2,6 isomers and mixtures thereof and mixtures of diphenylmethane diisocyanates ( MDI) and oligomers thereof with an isocyanate functionality greater than 2 known in the art as "crude" or polymeric MDI (polymethylene polyphenylene polyisocyanates). Mixtures of toluene diisocyanate and polymethylene polyphenylene polyisocyanates can also be used.

If prepolymers having an NCO value of 20% by weight or more made from polyols having a molecular weight of 2000-12000 are used, the amount of these polyols in the prepolymers compared to the total amount of these polyols that have such a molecular weight used in making the polyurethane material is preferably less than 50% and more preferably less than 30% by weight.

The polyol 1) having a high EO content and a high primary hydroxyl content is selected from those having an EO content of 50-100% and preferably 75-100% by weight calculated on the weight of the polyether polyol and a primary hydroxyl content of 70-100% and preferably 80-100% calculated on the number of primary and secondary hydroxyl groups in the polyol. These polyether polyols can contain other oxyalkylene groups such as oxypropylene and / or oxybutylene groups. These polyols have an average nominal functionality of 3-8 and more preferably 3-6, an average equivalent weight of 200-2000 and preferably 2001800 and a molecular weight of 600-8000, preferably 600-5000. As long as there are enough oxyethylene groups at the end of the polymer chains to meet the requirement for primary hydroxyl content, the distribution of the oxyethylene groups and other oxyalkylenes (if present) on the polymer chains can be of the type of a random distribution, a distribution of block copolymers or a combination thereof. Mixtures of polyols can be used. Methods for preparing such polyols are known and such polyols are commercially available; example are Caradol^MR Shell 3602, Lupranol^MR 9205 from BASF, Daltocel F526 from Huntsman Polyurethanes (Daltocel is a trademark of Huntsman International LLC) and G2005 from Uniqema.

Isocyanate reactive chain extenders, having a functionality of 2, can be selected from amines, amino alcohols, and polyols; polyols are preferably used. Furthermore, chain extenders can be aromatic, cycloaliphatic, araliphatic, and aliphatic; aliphatics are preferably used. Chain extenders have a molecular weight of 500 or less. Most preferred are aliphatic diols with a molecular weight of 62-500, such as ethylene glycol, 1,3-propanediol, 2-methyl-1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6 -hexanediol, 1,2-propanediol, 1,3-butanediol, 2,3-butanediol, 1,3-pentanediol, 1,2-hexanediol, 3-methylpentane-1,5-diol, 2,2-dimethyl-1 , 3-propanediol, diethylene glycol, dipropylene glycol and tripropylene glycol, and propoxylated and / or ethoxylated products thereof. Crosslinkers are isocyanate-reactive compounds with an average molecular weight of 500 or less and a functionality of 3-8. Examples of such cross-linkers are glycerol, trimethylolpropane, pentaerythrole, sucrose, sorbitol, mono, di, and triethanolamine, ethylenediamine, toluenediamine, diethyltoluenediamine, polyoxyethylene polyols with an average nominal functionality of 3-8 and an average molecular weight of 500 or less as glycerol. ethoxylate, trimethylolpropane, pentaerythrole, sucrose and sorbitol with said molecular weight, and polyether diamines and polyether triamines with an average molecular weight less than 500; the most preferred crosslinkers are polyol crosslinkers.

The amount of crosslinkers and / or chain extenders used is such that the hard block ratio is 0.60 or more, and preferably at least 0.65.

The other isocyanate-reactive compounds, which can be used in an amount of 0-20% by weight and preferably 0-10% by weight, can be selected from polyether polyamines, polyester polyols and polyether polyols (other than those described above) having a molecular weight of 500 and, in particular, of other polyether polyols such that they can be selected from polyoxyethylene polyols, polyoxypropylene polyols, polyoxyethylene-polyoxypropylene polyols having an oxyethylene content of less than 50% by weight and polyoxyethylene-polyoxypropylene polyols having a primary hydroxyl content of less than 70%. Preferred polyoxyethylene polyoxypropylene polyols are those having an oxyethylene content of 5-30% and preferably 10-25% by weight, in which all oxyethylene groups are at the end of the polymer chains (referred to as EO-terminated polyols ) and those that have an oxyethylene content of 60-90% by weight and that have all oxyethylene groups and oxypropylene groups randomly distributed and a primary hydroxyl content of 20-60%, calculated relative to the number of primary and secondary hydroxyl groups in the polyol. Preferably, these other polyether polyols have a functionality

ES 2 247 161 T3 average nominal 2-6, more preferably 2-4 and an average molecular weight of 2000-10000, more preferably 2500-8000.

Still further, the other isocyanate-reactive compounds can be selected from polyesters, polyesteramides, polythioethers, polycarbonates, polyacetals, polyolefins, or polysiloxanes. Polyester polyols that can be used include hydroxyl-terminated reaction products of dihydric alcohols such as ethylene glycol, propylene glycol, diethylene glycol, 1,4-butanediol, neopentyl glycol, 1,6-hexanediol or cyclohexanedimethanol or mixtures of such dihydric alcohols, or dicarboxylic acids. their ester-forming derivatives, for example succinic, glutaric and adipic acids or their dimethyl esters, sebacic acid, phthalic anhydride, tetrachlorophthalic anhydride or dimethyl terephthalate or mixtures thereof. Polyesteramides can be made by including amino alcohols such as ethanolamine in polyesterification blends.

Polythioether polyols that can be used include products obtained by the condensation of thiodiglycol alone or with other glycols, alkylene oxides, dicarboxylic acids, formaldehyde, amino alcohols, or aminocarboxylic acids. Polycarbonate polyols that can be used include products obtained by the reaction of diols such as 1,3-propanediol, 1,4-butanediol, 1,6-hexanediol, diethylene glycol or tetraethylene glycol with diaryl carbonates, for example diphenyl carbonate, or with phosgene. Polyacetal polyols that can be used include those prepared by reacting glycols, such as diethylene glycol, triethylene glycol, or hexanediol, with formaldehyde. Suitable polyacetals can then be prepared by polymerization of cyclic acetals. Suitable polyolefin polyols include hydroxyl terminated butadiene homo and copolymers and suitable polysiloxane polyols include polydimethylsiloxanediols.

Mixtures of the other isocyanate-reactive compounds mentioned above can also be used. Preferably, the other isocyanate-reactive compounds are polyols selected from the above preferred ones.

The polyols may comprise dispersions or solutions of addition or condensation polymers in polyols of the types described above. Such modified polyols, often referred to as "polymeric polyols" have been described in detail in the prior art and include products obtained by the in situ polymerization of one or more vinyl monomers, for example styrene and / or acrylonitrile, in the polyether polyols. above, or by the in situ reaction between a polyisocyanate and an amino and / or hydroxyl functional compound, such as triethanolamine, in the above polyol. Polyoxyalkylene polyols containing from 1 to 50% dispersed polymer are particularly useful. Particle sizes of the dispersed polymer less than 50 microns are preferred.

In recent years, various methods have been described for preparing polyether polyols with a low level of unsaturation. These developments have made possible the use of polyether polyols at the upper end of the molecular weight range, since such polyols can now be prepared with an acceptably low level of unsaturation. Polyols according to the present invention having a low level of unsaturation can also be used.

Still further, the following optional components can be used: catalysts that enhance urethane bond formation like tin catalysts like tin octoate and tin dibutyldilaurate, tertiary amine catalysts like triethylene diamine and imidazoles like dimethylimidazole and other catalysts like maleate esters and acetate esters; surfactants; foam stabilizers such as siloxane-oxyalkylene copolymers; flame retardants; smoke suppressants; UV stabilizers; colorants; microbial inhibitors; organic and inorganic fillers; internal mold release agents. Additional external mold release agents can be used. A particularly preferred class of catalysts is an alkali metal or alkaline earth metal carboxylate salt. The catalyst can be a salt or any metal of groups IA and IIA of the periodic table, although alkali metal salts such as potassium and sodium salts, especially potassium salts, are generally preferred. If desired, mixtures of such salts can be used, such as a mixture of a potassium salt and a sodium salt.

A catalytically effective amount of the salt will normally be in the range of 0.1 to 10, preferably 0.2-5 parts by weight per 100 parts by weight of reagents.

Although other polyurethane catalysts can be used in conjunction with carboxylate salt catalysts, such as tertiary amine catalysts and tin catalysts which are generally known, it is preferred that the materials are made in the absence of other catalysts, particularly in absence of tin and tertiary amine catalysts.

The carboxylate can be selected from aliphatic carboxylates having 2-10 carbon atoms, such as acetate, hexanoate, 2-ethylhexanoate, and octanoate.

Especially, the carboxylate can be selected from those having the formula REA-COO- in which

A is a hydrocarbon diradical with 1-6, preferably 1-3 carbon atoms;

OR

II

Ees -O- or -OC-; Y

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R is XR₁- (OR₂)_n- where X is CH₃- or OH-, Ri is a hydrocarbon diradical with 1-8 and preferably 1-4 carbon atoms, R₂ is a hydrocarbon diradical with 2-4 and preferably 2 or 3 carbon atoms and n is 0 to 10, preferably 0-5.

A can be selected from diradicals such as -CH₂-, -CH₂CH₂-, -CH₂CH₂CH₂-, -CH = CH-CH₂-, -CH₂-CH-CH₃,

-CH = CH-, -CH = C-CH₃ and CH₂= C-CH₂-. The most preferred diradical is -CH = CH-, or -CH₂-C = CH₂.

Ri can be selected from those radicals mentioned for A and from radicals obtained by removing two hydrogen atoms from, for example, butane, pentane, hexane and octane. The most preferred radicals for Ri are methylene, ethylene, trimethylene, tetramethylene and propylene.

R2 can be selected from ethylene, trimethylene, tetramethylene, ethylethylene, and propylene. The most preferred groups are ethylene and propylene.

Such catalysts and their preparation are known as such, see EP 294161, EP 220697 and EP 751114.

Examples of catalysts are sodium acetate, potassium acetate, potassium hexanoate, potassium 2-ethylhexanoate, potassium ethoxyacetate, sodium ethoxyacetate, the potassium salt of the hemiester of maleic acid and ethoxyethane, ethoxyethoxyethane, ethylene glycol, diethylene glycol, triethylene glycol, triethylene glycol , propylene glycol, dipropylene glycol, tripropylene glycol, methanol, ethanol, propanol or butanol and the potassium salt of the half ester of such hydroxyl-containing compounds with malonic acid, succinic, glutaric, adipic or fumaric. Mixtures of these catalysts can also be used.

The polyurethane material can be a solid or expanded (microcellular) material. Microcellular materials are obtained by carrying out the reaction in the presence of a blowing agent, such as hydrocarbon, hydrofluorocarbons, hydrochlorofluorocarbons, gases such as N₂ and CO₂ and water. Most preferably, water is used as the blowing agent. The amount of blowing agent will depend on the desired density. The amount of water will be less than 5 and preferably less than 3 and most preferably less than 1% by weight; calculated on the weight of the isocyanate-reactive composition.

The reaction to prepare the material is carried out with an NCO number of 80-140 and preferably 90-130 and more preferably 90-110.

The density of materials is greater than 25 kg / m³ and preferably greater than 50 kg / m³ and more preferably greater than 500 kg / m³.

The materials are preferably made in a mold. The process can be carried out in any type of mold known in the art. Examples of such molds are the molds commercially used to make polyurethane shoe soles, automobile parts, such as steering wheels, armrests, door panels, and rear shelves. Preferably the reaction is carried out in a closed mold. The components used to obtain the material are introduced into a mold at a temperature of from room temperature to 80 ° C and preferably up to 70 ° C, the mold being kept at a temperature of from room temperature to 80 ° C and preferably up to 70 ° C. during the procedure. The mold release time is relatively short despite the fact that isocyanate-reactive compounds containing amine groups are preferably not used; Depending on the amount of catalyst, mold release times may be less than 10 minutes, preferably less than 5 minutes, more preferably less than 3 minutes, and most preferably less than 1 minute.

The molding process can be carried out according to the reactive injection molding (RIM) process and the casting process. The procedure was carried out in particular according to the RRIM and SRIM procedures.

In general, the isocyanate-reactive components are premixed, optionally together with the optional components, prior to contacting the polyisocyanate.

The materials according to the invention are particularly suitable for use in applications where materials with high stiffness, non-brittle, highly impact resistant and low density are desired, such as shoe soles and automotive parts such as armrests, panels of the doors, rear shelves and visors.

The present invention is illustrated by the following examples.

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Examples 1 and 2

The following components were mixed on a workbench (amounts in parts by weight) and poured into an aluminum mold (20 x 15 x 1.5 cm), which was subsequently closed. The components were allowed to react and a polyurethane material according to the present invention was obtained with the following properties:

<td>Example</td><td> 1</td><td> 2</td>

<td>Caradol SA 3602</td><td> 26,81</td><td> -</td>

<td>Polyol 1</td><td> -</td><td> 26,89</td>

<td>1,4-butanediol</td><td> 15,11</td><td> 12,78</td>

<td>DABCO EG</td><td> 0,3</td><td> 0,1</td>

<td>Polyisocyanate</td><td> 57,78</td><td> 60,23</td>

<td>Hard blocks ratio,%</td><td> 72,9</td><td> 73</td>

<td>Density, kg / m³ (DIN 53420)</td><td> 929</td><td> 957</td>

<td>Shore D (DIN 53505)</td><td> 70</td><td> 77</td>

<td>Tg, ° C (Ihz, 3 ° C / min DMTA)</td><td> 70</td><td> 87</td>

The polyols used were not dried before use and probably contained a minimal amount of residual water, which is why a density of 929 and 957 kg / m was obtained.³.

Caradol^MR SA 3602, from Shell is a polyol having a nominal hydroxyl functionality of 3, an OH number of 36 mg KOH / g, an oxyethylene content of approximately 77% by weight and a primary hydroxyl content of approximately 90 %. DABCO EG is an amine catalyst from Air Products.

The polyisocyanate is a polyisocyanate with an NCO value of 26.2% by weight and which is a mixture of 1) a polyisocyanate obtained by reacting 42.55 parts by weight of MDI comprising more than 95% by weight of 4.4 'MDI and 5.05 parts by weight of a mixture of tripropylene glycol, Propylene glycol and 1,3-butanediol (59 / 18.79 / 22.21, / w / w / w) and 2) Suprasec 2020 (52.4 parts by weight) (a uretonimine modified MDI from a polyisocyanate comprising more than 95% by weight of 4,4'-MDI with an NCO value of 29.5% by weight from Huntsman Polyurethanes). Polyol 1 is a sorbitol-initiated polyoxyethylene polyol with an OH number of 187 mg KOH / g and a molecular weight of 1800.