MXPA98004599A

MXPA98004599A - Polyurethane elastomers

Info

Publication number: MXPA98004599A
Application number: MXPA/A/1998/004599A
Authority: MX
Inventors: Willem Leenslag Jan; James Hamilton Alan; Jozef Bleys Gerhard
Original assignee: Imperial Chemical Industries Plc
Priority date: 1995-12-08
Filing date: 1998-06-08
Publication date: 1999-01-11

Abstract

An elastomer based on polyisocyanate is provided having a storage modulus ratio (E ') at 20 ° C and a storage modulus (E') at 120 ° C of between 0.75 and 1.5, and so at 100 ° C less of 0.1 and a maximum value of tan of more than 0.8, tan is the ratio of the loss modulus (E ") and the storage modulus (E)

Description

DESCRIPTION The present invention relates to novel polyurethane elastomers and methods for the preparation thereof. Polyurethane elastomers are made by reacting diisocyanates, such as toluene diisocyanate (TDI), 1,5-naphthalene diisocyanate (NDI) or 4,4'-diphenylmethane diisocyanate (4,4 '-MDl), with polyols of high molecular weight, such as polyester polyols or polyether polyols, and low molecular weight polyols or polyamines such as ethylene glycol or butanediol. The high molecular weight polyether polyols used are mainly polytetrahydrofuran or propylene oxide. It is also known to prepare elastomeric polyurethanes from polyether polyols containing minor amounts of ethylene oxide (EO) groups, see, for example, EP-A-13487. The formulations comprising high amounts of 4.4 '-MDl and polyether polyols having high contents of EO have already been used to prepare flexible polyurethane foams, see, for example, EP-A-547764, EP-A-547765 and EP-A-549120. However, none of the known isocyanate-based elastomers shows satisfactory dynamic modulus behavior over a wide temperature range. Now a new class of polyurethane elastomers has been found which exhibit an almost perfect elastomeric behavior over a wide temperature range. Therefore, the present invention relates to polyisocyanate-based elastomers having a storage module ratio (E1) at 20 ° C and the storage module (E1) at 120 ° of between 0.75 and 1.5, a tan d of 100 ° C or less than 0.1 and a maximum value of tan d of more than 0.8, so d is the ratio of module loss (E ") and storage modulus (E1) .Preferably, the maximum value of tan d is more than 1.0 The ratio of the storage module (E1) at 20 ° C and the storage module (E ') at 120 ° C is preferably between 0.8 and 1.2, and more preferably between 0.85 and 1.1. gives 100 ° C of less than 0.05.

More preferably, the tan d at 100 ° C is less than 0.03. The maximum value of tan d is preferably presented at a temperature lower than 0 ° C, more preferably lower than the storage and loss modulus are measured by dynamic mechanical thermal analysis (DMTA, measured in accordance with ISO / DIS 6721-5) . These novel polyurethane elastomers can be manufactured from formulations containing polyols having high oxyethylene contents or polyol blends containing polyester polyols and high concentrations of polyols having high contents of oxyethylene, 4,4 '-MDl substantially pure or a derivative thereof, and a low molecular weight chain extender and optionally a crosslinking agent. Therefore, according to the invention, there is also provided a method for the preparation of polyurethane elastomers from a reaction mixture comprising a polyisocyanate component, a polyol composition, a chain extender and optionally a crosslinking agent. wherein the polyisocyanate component contains at least 85% by weight of 4,4'-diphenylmethane diisocyanate or a variant thereof, the polyol composition comprises at least one polyoxyalkylene polyol containing oxyethylene residues, the polyol composition it has an average nominal hydroxyl functionality from 2 to 4, an average hydroxyl equivalent weight from 500 to 7000 and an average oxyethylene content of between 50 and 85% by weight, and the chain extender has an average hydroxyl equivalent weight of up to 250.

The polyisocyanate component used in the invention can be any aromatic or aliphatic polyisocyanate such as TDI, NDI or pure 4,4'-diphenylmethane diisocyanate, or mixtures of that diisocyanate with one or more different organic polyisocyanates., especially other isomers of diphenylmethane diisocyanate, for example, the 2,4'-isomer optionally in conjunction with the 2,2'-isomer. The polyisocyanate component can also be a variant of MDl derived from a polyisocyanate composition containing at least 85% by weight of 4,4'-diphenylmethane diisocyanate. MDl variants are well known in the art and, for use in accordance with the invention, include particularly liquid products obtained by introducing uretonimine and / or carbodiimide groups into the polyisocyanate composition and / or reacting with one or more polyols. As the preferred polyisocyanate component are the polyisocyanate compositions containing at least 90% by weight of 4,4'-diphenylmethane diisocyanate. Most preferred are polyisocyanate compositions containing at least 95% by weight of 4,4'-diphenylmethane diisocyanate. The polyol composition may consist of one or more polyether polyols optionally mixed with other polyols such as polyester polyols. The composition may comprise a simple polyoxyalkylene polyol which is preferably a poly (oxyethylene-oxypropylene) polyol having the required functionality, equivalent weight and oxyethylene content. Such polyols are known in the art and can be obtained in a conventional manner by reacting ethylene and propylene oxides simultaneously and / or secondarily in any order with an initiator such as water, a polyol, a hydroxylamine, a polyamine and the like having 2. to 4 active hydrogen atoms. Alternatively, the polyol composition may comprise a mixture of two or more polyoxyalkylene polyols such that the total composition has the required average functionality, equivalent weight and oxyethylene content. The polyoxyalkylene polyols present in such mixtures are preferably poly (oxyethylene-oxypropylene) polyols, but one or more polyoxyethylene polyols and / or polyoxypropylene polyols may also be present. Preferred polyether polyol compositions comprise: (a) from 75 to 100% by weight of a first polyol component comprising at least one polyoxyalkylene polyol containing oxyethylene residues, the polyol component having an average nominal hydroxyl functionality from 2 up to 4, an average hydroxyl equivalent weight from 1000 to 5000 and an average oxyethylene content from 60 to 85% by weight, and (b) from 25 to 0% by weight of another polyol component.

The polyol component (b) suitably has an average functionality from 2 to 4, an average equivalent weight from 1000 to 3000 and can be, for example, a polyoxypropylene polyol, a polyoxyethylene polyol or a poly (oxyethylene-oxypropylene) polyol. ) containing less than 60% or more than 85% by weight of oxyethylene residues. The term "average nominal hydroxyl functionality" is used herein to indicate the average functionality (number of hydroxyl groups per molecule) of the polyol composition on the assumption that the average functionality of the polyoxyalkylene polyols present therein is identical that the average functionality (number of active hydrogen atoms per molecule) of the initiator or initiators used in its preparation, although in practice it will often be a little lower due to some terminal unsaturation. It is preferred that the average nominal hydroxyl functionality of the polyol composition be from 2 to 3. If desired, the polyoxyalkylene polyol (or one or more of the polyoxyalkylene polyols when a mixture is used) may contain dispersed polymer particles. Such polymer modified polyols have been fully described in the prior art and include products defined by the in situ polymerization of one or more vinyl monomers, for example acrylonitrile and styrene, in polyoxyalkylene polyols or by the in situ reaction between a polyisocyanate and a compound with amino or hydroxy functionality, for example triethanolamine, in the polyoxyalkylene. Also suitable as the polyol (b) are the polyester polyols. Polyester polyols which may be used include hydroxyl-terminated reaction products of polyhydric alcohols such as ethylene glycol, propylene glycol, diethylene glycol, dipropylene glycol, 1,4-butanediol, bis (hydroxyethyl) terephthalate, glycerol, trimethylolpropane, hexanediol, neopentyl glycol, methylpentanediol, pentaerythritol, or polyether polyols or mixtures of such polyhydric alcohols and polycarboxylic acids, especially dicarboxylic acids or their ester-forming derivatives, for example, succinic, glutaric and adipic acids or their dimethyl esters, sebasic acid, phthalic anhydride, anhydride tetrachlorophthalic or dimethyl terephthalate, or mixtures thereof. Preferred polyesters have an average number of molecular weight of 750-4000, especially 750-2500, and an average nominal functionality of 2-3. Suitable chain extenders include low molecular weight diols, aminoalcohols or diamines such as ethylene glycol, diethylene glycol, dipropylene glycol, tripropylene glycol, propanediol, butanediol, pentanediol, hexanediol, 3-methylpentan-1,5-diol, ethanolamine or diethyltoluenediamine.

Low molecular weight isocyanate-reactive compounds having an average functionality of 3 or more, such as glycerol, pentaerythritol or triethanolamine can be added as crosslinking agents. It is preferred to add small amounts of water, more preferably less than 2% by weight, based on the total weight of the isocyanate reagent, to the formulation. The isocyanate index of the reaction system, considering the composition polyol, water and any other species reactive with isocyanate, for example chain extenders and optionally crosslinking agents, can be as low as 85 or as high as 120. Preferably the index of isocyanate is between 90 and 110. The most preferred isocyanate index is between 95 and 105. The elastomer-forming reaction mixture may contain one or more of the conventional additives to such reaction mixtures. Such additives include catalysts, for example tertiary amines and tin compounds, surfactants and foam stabilizers, for example siloxane-oxyalkylene copolymers, flame retardants, organic and inorganic fillers, pigments and internal mold release agents. The invention further provides a reaction system comprising: (a) a polyisocyanate component containing at least 85% by weight of 4,4'-diphenylmethane diisocyanate or a variant thereof; (b) a polyol composition comprising at least one polyoxyalkylene polyol containing oxyethylene residues, the polyol composition has an average nominal hydroxyl functionality of 2 to 4, an average nominal hydroxyl equivalent weight of 500 to 7000 and a content of average oxyethylene between 50 and 85% by weight; (c) a chain extender having an average hydroxyl equivalent weight of up to 250, and optionally, (d) water, (e) a crosslinking agent, and (f) one or more conventional additives to elastomer formulations. This reaction system is used to make polyurethane elastomers. In carrying out the method of the invention, the known techniques of a shot, semi-prepolymer or complete prepolymer can be applied together with mixing equipment conventionally used in the preparation of elastomers. The elastomers according to the invention are particularly suitable for use in applications where good energy absorption and fatigue resistance properties are required, and good elastomeric behavior over a wide temperature range, for example in the automotive industry and of footwear. The invention is illustrated by the following examples in which all parts, percentages and proportions are by weight. The following glossary of materials is included to identify reaction components that are not otherwise identified in the examples.

GLOSSARY Polyisocyanate I 4.4 '-MDl pure (Suprasec MPR, commercially available from Imperial Chemical Industries PLC; Suprasec is a trademark of ICI PLC).

Polyisocyanate II: MDL modified with uretonimine (Suprasec 2020, commercially available from Imperial Chemical Industries PLC).

Polyisocyanate III: MDl-based prepolymer ((Suprasec 2433, commercially available from Imperial Chemical Industries PLC).

Polyisocyanate IV: Isocyanate prepolymer manufactured by reacting polyisocyanate I and polyol B (NCO content = 8.66%).

Polyol A: triol EO / PO that has 70% random EO groups; OH value of 42 mg KOH / g and approximately 45% of primary OH groups.

Polyol B: EO / PO diol having 75% random EO groups and an OH value of 27 mg KOH / g.

Polyol C: 70/30 mixture of an EO / PO diol (22% Eo-end, OH value = 35 mg KOH / g) and an EO / PO triol (15% EO-end, OH value = 32 mg of KOH / g).

Polyol D: polymer modified polyol (polyol initiated with glycerol having a value of OH = 34 mg KOH / g, 15% end EO: 75% primary OH groups and containing 20% styrene copolymer particles - acrylonitrile).

Polyol E: EO / PO diol having 27% EO-end and an OH value of 30 mg KOH / g.

Catalyst 1 Dabco EG; commercially available from Air Products.

Catalyst 2 Niax Al; commercially available from Union Carbide.

EG: ethylene glycol EXAMPLES Examples 1. 2. 3 and 4 and comparative examples 1 v 2 The elastomers are mixed in the cabinet and molded in a 15 x 10 x 1 cm mold in a conventional manner using the formulations provided in Table I and the properties indicated in Table I were measured.

Table I * N.M. = not measured The ratio E1 (20 ° C) / E (120 ° C) of the elastomers according to the comparative examples is greater than 1.5 and its maximum value of tan d is less than 0.8.

DMTA Test Measurements were carried out in accordance with ISO / DIS 6721-5 on a Rheometric Scientific DMTA apparatus using a 3-point bending method. The sample test dimensions were: length 1.0 cm, width 1.3 cm, thickness 0.4 cm. Applied voltage amplitude 64 x 10"4 cm, frequency 1 Hz, heating speed 2 ° C / min The elastomer samples were preconditioned at 23 ° C / 50% relative humidity for 24 hours before the test. of elastomer were suspended at -120 ° C (cooling rate 8.5 ° C / min) and kept at this temperature for 5 minutes before the heating of the sample was started, Figures 1-4 show the DMTA curves of Examples 1-4 The figures of DMTA of Comparative Examples 1 and 2 are shown in Figures 5 and 6. It is noted that in relation to this date, the best method known to the applicant to carry out the aforementioned invention, is the conventional for the manufacture of the objects to which it refers The invention having been described as above, is claimed as property contained in the following:

Claims

1. An elastomer based on polyisocyanate that has a ratio of the storage modulus (E1) at 20 ° C and the storage modulus (E1) at 120 ° C between 0.75 and 1.5, one tan gives 100 ° C of less than 0.1 and a maximum value of the tan d of more than 0.8, so d is the ratio of the loss modulus (E ") and the storage modulus (E1).

2. The elastomer according to claim 1, characterized in that the polyisocyanate contains at least 90% by weight of 4,4'-diphenylmethane diisocyanate.

3. The elastomer according to claim 2, characterized in that the polyisocyanate contains at least 95% by weight of 4'-diphenylmethane diisocyanate.

. The elastomer according to any preceding claim, characterized in that it has a ratio of storage modulus (E ') at 20 ° C and storage module (E') at 120 ° C of between 0.8 and 1.2.

5. The elastomer according to claim 4, characterized in that it has a storage module ratio (E ') at 20 ° C and the storage module (E1) at 120 ° C between 0.85 and 1.1.

6. The elastomer according to any of the preceding claims, characterized in that it has a tan d at 100 ° C of less than 0.05.

7. The elastomer according to claim 6, characterized in that it has a tan d at 100 ° C of less than 0.03.

8. The elastomer according to any of the preceding claims, characterized in that it has a maximum value of tan d of more than 1.0.

9. The elastomer according to any of the preceding claims, characterized in that it has a maximum value of tan d at a temperature below 0 ° C.

10. The elastomer according to claim 9, characterized in that it has a maximum value of tan d at a temperature below -10 ° C.

11. A method for the preparation of elastomers according to any of the preceding claims, from a reaction mixture comprising a polyisocyanate component, a polyol composition, a chain extender and optionally a crosslinking agent, wherein the component polyisocyanate contains at least 85% by weight of 4,4'-diphenylmethane diisocyanate or a variant thereof, the polyol composition comprises at least one polyoxyalkylene polyol containing oxyethylene residues, the polyol composition has an average nominal hydroxyl functionality from 2 to 4, an average hydroxyl equivalent weight from 500 to 7000 and an average oxyethylene content of between 50 and 85% by weight, and the chain extender has an average hydroxyl equivalent weight of up to 250.

12. The method according to claim 11, characterized in that the polyol composition comprises at least one poly (oxyethylene-oxypropylene) polyol.

13. The method according to claim 12, characterized in that the polyol composition comprises: (a) from 75 to 100% by weight of a first polyol component comprising at least one polyoxyalkylene polyol containing oxyethylene residues, the polyol component it has an average nominal hydroxyl functionality from 2 to 4, an average hydroxyl equivalent weight from 1000 to 5000 and an average oxyethylene content from 60 to 85% by weight, and (b) from 25 to 0% by weight of another polyol component.

14. The method according to any of claims 11 to 13, characterized in that the polyol composition has an average nominal hydroxyl functionality from 2 to 3.

15. The method according to any of claims 11 to 14, characterized in that the reaction mixture further comprises water.

16. The method according to claim 15, characterized in that the amount of water is less than 2% by weight, based on the total weight of the isocyanate-reactive compounds.

17. The method according to any of claims 11 to 16, characterized in that it is carried out at an isocyanate index of 90 and 110.

18. The method according to claim 17, characterized in that it is carried out at an isocyanate index between 95 and 105.

19. A reaction system, characterized in that it comprises: (a) a polyisocyanate component containing at least 85% by weight of 4,4'-diphenylmethane diisocyanate or a variant thereof; (b) a polyol composition comprising at least one polyoxyalkylene polyol containing oxyethylene residues, the polyol composition having an average nominal hydroxyl functionality of 2 to 4, an average nominal hydroxyl equivalent weight of 500 to 7000 and an average oxyethylene content of between 50 and 85% by weight; (c) a chain extender having an average hydroxyl equivalent weight of up to 250, (d) water, (e) a crosslinking agent, and (f) one or more conventional additives to elastomer formulations. RESTJMEN OF THE TUVENTION An elastomer based on polyisocyanate having a storage modulus ratio (E1) at 20 ° C and a storage modulus (E1) at 120 ° C between 0.75 and 1.5, and so at 100 ° C of less than 0.1 is provided and a maximum value of tan d of more than 0.8, so d is the ratio of the loss modulus (E ") and the storage modulus (E ').