BRPI0707383A2 - 2,4'-mdi-based nco prepolymer polyurethane casting elastomers, a process for their preparation and use - Google Patents

Abstract

POLYURETHANE CASTING ELASTOMERS OF NCO PREPolymer based on 2,4'-MDI, PROCESS FOR ITS PREPARATION AND USE. The present invention relates to new polyurethane casting elastomers (PUR) of functional NCO prepolymers based on 2,4'-MDI and aminic chain extenders and / or crosslinkers, a process for their preparation and use.

Description

Report of the Invention Patent for "N-2,4-MD PRE-POLYMER PRE-POLYMERTANE CASTING ELASTOMERS, PROCESS FOR PREPARATION AND USE".

The present invention relates to novel polyurethane (PUR) casting elastomers of 2,4'-MDI-based functional NCO prepolymers and amine chain extenders and / or crosslinkers, a process for their preparation and their use.

MDI (diphenylmethanediisocyanate) is a technically important group of polyisocyanates; With regard to its structural formation, it is very heterogeneously composed and comprises types of monomers, which are characterized by the fact that they have two aromatic structural elements, linked through merely a methylene bridge, as well as superior polygomers, which have more than that two aromatic structural elements and more than one methylene bridge, which are referred to as MDI polymer.

In MDI monomer, 4,4'- and 2,4'-isomers prevail conditioned by synthesis. The 2,2 'isomer also occurs at a lower rate less frequently and is technically largely useless.

The ratio of MDI monomer to polymer MDI, as well as the ratios of the 2,4'- and 4,4'-isomers in the MDI monomer, may vary within limits by varying the synthesis conditions for pre-stage preparation.

The separation of the raw MDI obtained from the synthesis of the MDI is carried out extensively in large parts, whereby, depending on the technical expense, both nearly pure isomeric fractions with ratios, for example, of 4,4'-MDI greater than 97.5 wt.% Or also mixtures of isomers with ratios of 4.4 'and 2.4' of approximately 50 wt.% Each.

In the past, due to technical conditions, 2,4'-isomer puron was not commercially available or only in very limited quantities. However, several efforts have recently been made to make these isomers available in high purity. An essential reason for these efforts is in the different reactivity of the NCO groups at position 2 and 4 'of 2,4'-MDI, similar to the differences in reactivity of NCO groups at position 2 and 4 of 2,4-toliolenediisocyanate (TDI).

These reactivity differences allow or facilitate the synthesis of monomer-poor NCO prepolymers. NCO prepolymers are NCO1-terminated polyols which are obtained by reacting a polyol with an NCO1 molar excess polyisocyanate relative to the NCO1-reactive groups at room temperature of up to approximately 100 ° C. NCO prepolymers produced in this manner also always contain free monomer diisocyanate, depending on the molar proportions of application.

The driving force for the preparation of poor NCO prepolymers in monomers to practically monomer-free in the case of 2,4-TDI is their high vapor pressure and the resulting health hazards.

Aliphatic diisocyanate-based NCO prepolymers, for example hexamethylenediisocyanate (HDI) or isophoronediisocyanate (IPDI) should be considered even more critical in this context. This aspect is also present in MDI, however, in a significantly lower proportion based on its lower vapor pressure compared to TDI. In addition, reducing the prepolymer monomer content leads to polyurethanes, which are softer than those, which are produced from monomer-containing NCO prepolymers.

Preparation of monomer-poor NCO prepolymers can be made in a number of ways:

a.) removal of free monomer diisocyanate by thin layer evaporation or technically expensive flash. This is independent of the fact whether diisocyanates were used with differently reacted NCO groups. For this purpose, dragging agents may also be used.

b.) Application of diisocyanates with different reactivity NCO groups or equal reactivity NCO groups and specially selected stoichiometric ratios, eg molar ratios of NCO groups to reactive groups relative to NCO of less than 2: 1 and / or possibly under special catalysis .

c.) Combinations of the two processes, for example, of maneiratal, that the proportion of the free monomer diisocyanate according to process b.) is initially limited to a particular measure and then further minimized by process a.) .

Such combinations may be convenient when it is valid to minimize the viscosity of the prepolymers. The disadvantage of process b.) Is mainly that reactions with stoichiometric ratios especially below 2: 1 lead to an increase in the previous prolongation and thus inherently simulate a clear increase in the viscosity of the reaction product.

WO 01/40340 A2 (Crompton Corp.) provides examples for such combinations where, in a first stage, the diisocyanate is reacted as a co-use of a selectivity enhancing catalyst for an NCO prepolymer which in It is then released from the excess monomer through thin layers.

For particularly critical applications, for example in the food sector, the argument valid for industrial hygiene, which holds true for TDI, is also valid for MDI. The evidence for this is numerous patents, which are also concerned with monomer-poor MDI prepolymers, for example, WO 03/006521 (Henkel KGaA), WO 03/033562 (Henkel KGaA), WO 03/055929 (Henkel KGaA) , WO 03/051951 (HenkelKGaA), WO 93/09158 (Bayer AG) and EP 0 693 511 A1 (Bayer AG).

The object of the present invention, therefore, has been to produce 2,4'-MDI-based polyurethanes, which have advantages over processing, for example in the form of longer melt times, lower prepolymer viscosities, in relation to the state of the art and simultaneously to their mechanical properties, they are at least equal to the state of the art.

Surprisingly, it has now been found that in relation to mechanical properties (eg friction, tensile strength, resistance to subsequent rupture, rupture dilatation), valuable PUR is obtained from 2.4 NCO prepolymers. '-MDI having a 2,4'-isomer content of at least 85 wt% and a proportion of free monomer MDI in the prepolymer of at least 1 wt% to 20 wt%, preferably at least 2 wt% to 18 wt.%, Particularly preferably from 3 to 15 wt.%, Relative to the prepolymer. In addition, the low viscosity of NCO prepolymers is advantageous.

For NCO prepolymers hereinafter, NCO prepolymers made from pure 2,4'-MDI shall be understood to be at least 1% by weight and at most 20% by weight. by weight, relative to the prepolymer, of free extracted and distilled monomer diisocyanate.

By pure 2,4'-MDI is meant hereinafter types of MDI having a 2,4'-isomer content of at least 85 wt.%, Preferably at least 90 wt.%. particularly preferably at least 95 wt%, most particularly preferably at least 97.5 wt%.

The object of the present invention is polyurethane elastomers (obtainable according to the casting process) obtainable from

a) Common diphenylmethanediisocyanate-based NCO prepolymers content of a 2,4'-isomer of at least 85 wt.%, preferably at least 90 wt.%, particularly preferably at least 95 wt. Most particularly preferred is at least 97.5 wt%, wherein the ratio of 2,4'-MDI free monomer implies at least 1 wt% to 20 wt%, preferably 2 to 18 wt%, particularly preferably 3 to 15% by weight relative to NCO prepolymer and OH-index polyols of 20 to 200 mg KOH / g and functionalities of 1.95 to 2.40, preferably 1.96 to 2.20,

b) amino chain extenders and / or crosslinkers, preferably aromatic amino chain extenders and / or crosslinkers;

(c) if necessary adjuvants and additive substances.

The polyuretapes according to the invention are superior to the state of the art because they have particularly favorable combinations of advantageous properties over prepolymer viscosity, casting time, mechanical and mechanical-dynamic properties.

Another object of the invention is a process for preparing the polyurethane elastomers according to the invention by the melt process which is characterized by the fact that

A) Diphenylmethanediisocyanate (MDI) with a 2,4'-isomer content of at least 85 wt.%, Preferably at least 90 wt.%, Particularly preferably at least 95 wt.%, Particularly preferably at least 97.5% by weight, is reacted with polyols with OH indices of 20 to 200 mg KOH / g and functionalities of 1.95 to 2.40 to form NCO prepolymers with a ratio of 2.4'-MDI free monomer of 1 wt.% to 20 wt.%, preferably 2 to 18 wt.%, particularly preferably 3 to 15 wt.%, relative to NCO prepolymer,

B) amine chain extenders and / or cross-linkers and eventually adjuvants and additives are added to the prepolymer of A) for the preparation of the elastomer.

Preparation of elastomers according to the casting process is a generally important application of NCO-terminated prepolymers, either prepolymers being either directly reacted with a chain protractor after preparation or the cooled NCO prepolymers being cooled. and stored at a lower temperature (storage temperature) for the purpose of further chain extension.

In the prepolymer synthesis process, it is favorable that some of the reaction heat is already obtained in the prepolymer synthesis and thus exotherm precipitates less in the formation of the polymer itself. This acts favorably on the rate of molecular weight formation and enables longer casting times, therefore, represents an advantage in processing. In a particularly preferred embodiment of the preparation of PUR elastomers according to the preprocessing process. Polymer, the prepolymers are initially degassed by applying a low pressure at ambient or elevated temperature and then - most often at elevated temperature - are mixed with a chain extender.

In the process according to the invention, the prepolymer is preferably heated to a temperature of 60 ° C to 110 ° C and degassed in a vacuum under stirring. Then the chain extender and / or crosslinker is added in liquid form, which is eventually heated to temperatures typically at least 5 ° C above its melting point. The reaction mixture is poured into preheated molds (preferably 90 ° C). 120 ° C) and heated for about 24 hours at 90 ° C to 140 ° C.

As polyols polyether, polyester, polycarbonate and polyether polyols with hydroxyl indices of 20 to 200 mg KOH / g, preferably 27 to 150, particularly preferably 27 to 120, may be used.

Polyether polyols are produced either by alkali catalysis or by double metal cyanide catalysis or possibly stepwise reaction conduction by alkaline catalysis and double metal decianide catalysis from a starting molecule and epoxides, preferably ethylene and / or propylene oxide and have terminal hydroxy groups. As initiators, in this case, consideration is given to those known to the art with hydroxyl and / or amino groups, as well as water. In this case, the functionality of the primers matters in at least 2 and 4. Of course, mixtures of several primers can also be used. In addition, also mixtures of various polyether polyols may be used as polyether polyols. Polyether polyols may be hydroxyl terminated tetrahydrofuran oligomers.

Polyester polyols are produced in a manner known per se through polycondensation from aliphatic and / or aromatic polycarboxylic acids of 4 to 16 carbon atoms, possibly from their anhydrides as well as possibly from their low-molecular-weight esters, including esters of ring, mainly using low molecular weight polyols of 2 to 12 carbon atoms. In this case, the functionality of the polyol forming polyol forming components is preferably at 2, but in the individual case it may also be greater than 2, and components with functionalities greater than 2 are only used in small quantities. such that the numerical average arithmetic functionality of polyester polyols is in the range of 2 to 2.5, preferably 2 to 2.1.

Polyether polyols are produced by the co-use of polyether polyols with the synthesis of polyester polyol.

Polycarbonate polyols are obtained correspondingly to the state of the art from carbonic acid derivatives, for example dimethyl or diphenylcarbonate or phosgene and polyols, by polycondensation.

Preferred chain extenders are aromatic amine chain extenders such as, for example, diethyltoluenediamine (DETDA), 3,3'-dichloro-4,4'-diamino diphenylmethane (MBOCA), 3,5-diamino benzoate -4-chloro-isobutyl, 4-methyl-2,6-bis (methylthio) -1,3-diaminobenzene (Etha-cure 300), trimethylene glycol di-p-aminobenzoate (Polacure 740M) and 4,4'-diamino dichloro-β-dihyldiphenylmethane (MCDEA). MBOCA and 3,5-diamino-4-chloro-isobutyl benzoate are particularly preferred. Similarly, amino-aliphatic chain extenders may be used or co-used.

In addition, adjuvants and additives may be used, such as, for example, catalysts, stabilizers, ultraviolet protection agents, hydrolysis protection agents, emulsifiers, preferably incorporable dyes, as well as pigments which impart -with color.

Examples of catalysts are trialkylamines, diazabicyclooctane, tin dioctoate, dibutyltin dilaurate, N-alkylmorpholine, zinc octoate, calcium, magnesium, the corresponding naphthenates and p-nitrophenolate.

Examples of stabilizers are Broenstedt and Le-wis acids, such as, for example, hydrochloric acid, benzoyl chloride, organometallic acids, for example dibutyl phosphate, in addition, adipic, acidic acid, succinic acid, pyruvic acid or Citric acid.

Examples of ultraviolet protection agents and hydrolysis protection agents are sterically hindered 2,6-dibutyl-4-methylphenol and carbodiimides.

Incorporatable dyes are those which have zerewitinoff active hydrogen atoms, that is, which can react with NCO groups.

Other adjuvants and additives include emulsifiers, foam stabilizers, cell regulators and fillers. A summary is contained in G. Oertel, Polyurethane Handbook, 2-edition, Carl Hanser Verlag, Munich, 1994, chapter 3.4.

The polyurethane elastomers according to the invention may be used for a variety of different applications: for example as elastic perforated parts which are produced according to the casting process as well as in coatings and glues which are produced. according to common spraying process, such as, for example, parking cover coatings, concrete repairs, corrosion protection.

The invention should be detailed based on the following examples.

Examples

Measurement methods used:

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Chemicals used: polyester polyol 1: poly (ethylene-co-butylene) adipate with an OH index of 56 mg KOH / g, Fa. Bayer MateriaIScience AG; nominal functionality 2.0

4,4'-MDI: 4,4'-diphenylmethanediisocyanate, Desmodur® 44M from Fa.Bayer MateriaIScience AG; 98.5 wt.% 4,4'-isomer

2,4'-MDI: 2,4'-diphenylmethanediisocyanate (laboratory product) from Fa. Bayer MateriaIScience AG; 98.5 wt.% 2,4'-isomer

3,5-diamino-4-chloroisobutyl benzoate: RC-CrossIinker 1604da Fa. Rheinchemie, Rheinau,

Example 1: Preparation of MDIP-based Ester Prepolymers Example preparation of the exemplary prepolymer in the prepolymer example 2 (Table 1):

In a shaker flask, 25 parts by weight of 2,4'-MDI are heated to 70 ° C under nitrogen and rapidly mixed with 100 parts by weight of the dehydrated polyester 1 polyol and heated to 70 ° C. It was allowed to run for 2 hours and the physical properties were determined, see table 1.

Table 1: MDI-based ester prepolymer recipes (according to the invention and comparative examples)

<table> table see original document page 10 </column> </row> <table> <table> table see original document page 11 </column> </row> <table>

V = comparison

Prepolymer 1: 100 parts by weight, polyester polyol 1 and 25 parts by weight, 4,4'-MDI

Prepolymer 2: 100 parts by weight, polyester polyol 1 and 25 parts by weight, 2,4'-MDI

Comparison of viscosity values for MDI prepolymers with a theoretical NCO content of 3.36% by weight shows the advantages of the 2,4'-MDI prepolymer (prepolymer 2 according to invention) with respect to the 4,4'-analogue (prepolymer 1 V, not according to the invention).

Mixing these two prepolymers with additional MDI 6.1% by weight NCO (theoretical) NCO catalysts naturally yields, in all cases, low viscosity prepolymers relative to the starting prepolymers ( prepolymers 3 V, 4 V, 5 and 6 V in table 1). In the following feature, it is shown that the equal low viscosity of prepolymers 3V and 5 (in each case 2900 mPas at 70 ° C) is not sufficient for advantageous processing (e.g. casting time) relative to casting elastomers. Advantageously, only prepolymer 5 was further processed to form an elastomer (see tables 2 and 3).

Example 2: Preparation of foundry elastomers according to the invention from prepolymers 2 and 5 of example 1.

Exemplary preparation prescription for the preparation of melting elastomers in the example of foundry elastomer A:

100 parts of prepolymer 2 were degassed at 90 ° C with slow stirring in vacuo until bubbles were released. Then, 9.05 parts of 3,5-diamino-4-chloroisobutyl benzoate, which was preheated to 100 ° C, and the reagent homogeneous melting mass were poured into preheated molds at 1100C with the corresponding measures. test standards. It was then heated for 24 hours at 110 ° C and the mechanical properties shown in Table 2 were determined.

Table 2: Recipes, preparation and properties of casting elastomers according to the invention

<table> table see original document page 12 </column> </row> <table> <table> table see original document page 13 </column> </row> <table> <table> table see original document page 14 < / column> </row> <table>

Example 3: Preparation of non-invented foundry elastomers from the prepolymers IV, 3V, 4V and 6V of example 1

The preparation was carried out as described in example 2. Table 3: Recipes, preparation and properties of casting elastomers not according to the invention

<table> table see original document page 14 </column> </row> <table> <table> table see original document page 15 </column> </row> <table> <table> table see original document page 16 < / column> </row> <table>

The comparison of tables 2 and 3 makes clear the advantages of the systems according to the invention:

At comparable temperatures of the prepolymers (split temperature) and comparable NCO1 contents ie comparable recipes, the melting times of the prepolymers according to the invention (table 2) are longer around factor 3 than systems not in accordance with the invention (Table 3), which represents a clear processing advantage. Particularly favorable combinations of the "long melt time" and "low viscosity prepolymer" properties are obtained only by the systems according to the invention. In addition, the melt elastomers according to the invention also exhibit advantages with respect to their mechanical properties:

Comparing, for example, in Table 2, PUR prepared from prepolymer 2 (casting elastomer A) with a PUR prepared from prepolymer 1 V (casting elastomer F1 table 3) - both pre- polymers have the same NCO value of 3.36% by weight as NCO - so the system according to the invention has a better tensile strength, rupture swelling, rupture propagation resistance and friction.

Comparing in Table 2 the PUR prepared from prepolymer 5 (casting elastomer E) with a PUR1 prepared from prepolymer 3 V, 4 V and 6 V (casting elastomers G, Η, I, table 3) -all prepolymers have the same NCO value of 6.1% by weight as NCO - so the system according to the invention has a tensile strength, rupture swelling, rupture propagation resistance, comparatively good friction and pressure strain radicals within the scope of measurement accuracy.

This applies in the same way also with respect to dynamic-mechanical properties (storage and loss modulus as well as loss factor).

The systems according to the invention have a unique combination of advantageous properties with respect to prepolymer viscosity, casting time, mechanical and mechanical-dynamic properties.

Claims (5)

1. Polyurethane elastomers obtainable from.) Diphenylmethanediisocyanate-based NCO prepolymers with a 2,4'-isomer content of at least 85% by weight, wherein the proportion of 2,4'-MDI free monomer imports at least 1 to 20% by weight, compared to NCO prepolymer and polyols with OH indices from 20 to 200 mg KOH / g and a functionality of 1.95 to 2.40b.) chain extenders and / or amine cross-linkers and (c)), where appropriate adjuvants and additive substances. Polyurethane elastomers according to claim 1, characterized in that in the case of component b) it is diethyl toluenediamine (DETDA), 3,3'-dichloro-4,4'-diamino diphenylmethane (MBOCA) ), 3,5-Diamino-4-chloro-isobutyl benzoate, 4-methyl-2,6-bis (methylthio) -1,3-diaminobenzene (Ethacure 300), trimethylene glycol di-p-aminobenzoate (Polacure 740M) and 4,4-diamino-2,2,2-dichloro-5,5'-diethyldiphenylmethane (MC-DEA) or mixtures thereof. Process for the preparation of polyurethane elastomers as defined in claim 1 or 2, characterized in that A) diphenylmethanediisocyanate with a content of 2,4'-isomer of at least 85% by weight is reacted with polyols having indices OH from 20 to 200 mg KOH / g and functionalities from 1.95 to 2.40 to form NCO prepolymers with a ratio of 2.4'-MDI free monomer from 1 wt% to 20 wt% to the NCO prepolymers, B) amine chain extenders and / or crosslinkers and eventually adjuvants and additives are added to the A) prepolymer for the preparation of the elastomer. Use of polyurethane elastomers as defined in one of claims 1 or 2 for the preparation of profiled parts, such as adhesive and sealing material. Profiled parts of a polyurethane elastomer as defined in one of claims 1 or 2.