GB2028348A - Improved urethanic polymerisation by use of chelating agent is used as catalyst or cocatalysts - Google Patents

Abstract

A process of urethanic polymerisation is disclosed, in which a chelating agent is used as catalyst or cocatalyst. Preferred chelating agents for such use include hydroxyethylethylenediaminetriacetic acid and its salts and 2-hydroxy-1,3- diaminepropylenetetraacetic acid and its salts. Other suitable chelating agents include alkali metal salts of nitrile triacetic acid, ethylenediamine tetra- acetic acid, diethylene triamine-penta- acetic acid and N,N-di(2 - hydroxyethyl) glycine.

Description

SPECIFICATION Improved urethanic polymerisation by use of chelating agents acting as catalysts or cocatalysts This invention relates to the improvement of urethanic polymerisation by chelating agent(s) acting as catalyst(s) or cocatalyst(s). Particularly, the present invention relates to the use of organic chelating agents as catalysts in polyurethanic reactions between hydroxyls and isocyanates groups.

According to the present invention there is provided a process for urethanic polymerisation, the improvement which comprises using a chelating agent as a catalyst or cocatalyst, in which an isocyanate reacts with hydroxylic compound to the catalysts presence, wherein the catalyst(s) and/or cocatalyst(s) used is/are a compound(s) able to form complex with metallic ions so that they do not show standard reactions in the presence of reacting compounds. The invention also provides products whenever obtained by the process of the present invention. Chelating agents here considered are preferably organic compounds such as mono and polycarboxylic amino derivates, where the carboxyl or the carboxyls are preferably neutralised partially or completely with metallic cations in order to form the correspondent metallic salts.

The best known of this class of compounds is the ethylenediaminetetraacetic acid (EDTA H4) and its sodium salts. Among these it is preferable to use the partially salified salts, as example EDTA Na3 or EDTA No3.5.

Another compound of this class and still more efficient as catalyst is the nitriletriacetate sodium salt (NTA Na3). The superior catalytic efficiency of this last compound is due to the fact that the nitrogen is less sterically blocked and accordingly the catalysis mechanism acts easier. It is thought in fact that this mechanism proceeds by the formation of an entity between amine derivate and isocyanate; this entity is formed easier if the nitrogen is stericallyfree. For example, this reaction can be represented by the general equation, for the reaction together of isocyanate and n itriletriacetate sodium salt:

(intermediate compound) Other compounds of this class that can be used as catalysts in the polyurethane reactions are, by way of example, diethylene triaminepentacetic acid (DTPA) and its salts, preferably the tetrasodium salt.

Other exemplary compounds that can be used with good result, and particularly interesting for their solubility also in non-aqueous solvent, are hydroxyethylethyl enediaminetriacetic acid (HEEDTA) and its salts, preferably the trisodium salt, and 2 - hydroxy- 1,3 - diaminepropylenetetraacetic acid (HPDTA) and its salts, preferably the trisodium salt.

Another compound of this class is sodium salt dihydroxyethylglycine. These compounds of this class are compounds containing in their-molecule a 1- or 2-hydroxyl group and accordingly, to their catalytic activity, is added the reaction between the functional OH group and the functional NCO group.

Also, mixed salts of heavier metals and alkali metals can be advantageously used as catalysts; they can delay the starting of reaction (giving longer cream time) and accelerate the final polymerisation, as will be seen hereinafter. Among these mention may be made of the iron and sodium salt, and the manganese and sodium salt of the hydroxyethylethylenediaminetriacetic acid.

The hypothesis is that the catalysis by the complex formation explains the catalytic action of this class of compounds, which chelating action is due, as it is well known, to the complex formation. As is well known in polyurethane chemistry, the metallic cations and the basic medium favour the urethanic polymerisation.

The alkaline cations, when present in these chelating salts, have a more controlled action than other alkaline salts derivated by different acids (organic or inorganic). The salts of these chelating compounds containing also heavier metals, because of their increased solubility and stability, can develop a greater catalytic action when compared to other organic and inorganic forms of these metals. The catalytic action controlled by chelating metals could be attributed as follows: the chelated metal works as a metallic ions reserve and there is a balance between the chelated metal, the chelating agent and the free metallic ion. If the free metallic ion is consumed or annulled in the reaction, other ions are released from the chelate and the low initial concentration of the metal is constant.Thus, the more controlled reaction rate can be explained by the constant and well controlled concentration of catalyst present in the chelating agent.

As already stated, this group of compounds that are herein used as catalysts for polyurethanic reactions have a particular characteristic that makes them greatly interesting in the polyurethanic reactions, generally, and above all in the polyurethane reactions with formation of expanded or microcellular products. This characteristic consists in the slowing down of initial reaction times without extending, on the contrary shortening, in some cases, the rise time and the demoulding time when particular moulded products are in question. In this last case, where today the need of speedier moulding cycles is demanded, the use of these types of catalysts can allow an increase of the reactivity of the compounds without interference with good flushing of the material in the mould.Furthermore, in some types of foam formulations, the so called "cold" foams, based on activated polyols, and especially when the isocyanate used is toluenediisocyanate, the use of a catalyst in accordance with the present invention allows one to obtain easier expanded products without collapse or shrinkage due to closed cells of the foam. When, instead of these catalyst members of a chelating family, a classic catalyst based on triethylenediamine and/or tin compound is used, it is very difficult to find a right balance between collapse and shrinkage.

The best results, as regards the fast reaching of final polymerisation, are obtained using these chelating catalysts in conjunction with other catalysts of the amine type, already used in the polyurethanic reactions, for example triethylamine or dimethylethanolamine. Good results of fast polymerisation can be obtained using the chelating catalyst more than one amine catalyst, including among these also triethylenediamine, or a usual combination of catalysts. In this last case, the action of the chelating agent has essentially the function of cream time delayer and accelerator offinal polymerisation.

When the foaming material is normally formulated with tin octpate and aminic catalysts, the chelating agent can replace in this case the aminic catalysts.

The choice of the more suitable chelating compound depends from the formulation. If water is pre sent -- as in the case of flexible and semirigid foam it is possible to choose a chelating compound without OH groups. In fact, the chelating compounds are soluble only in water. For formulations without water, it is necessary to use the products containing OH and soluble for example in dipropyleneglycol.

Furthermore, if it is necessary to adjust the pH of the formulated, the necessary quantity of a non-salified chelating could be added at the sodium salt of the chelating agent. If the alkaline cation presence - in some formulations for use in block production where part temperature of the block is very high negatively influences the mechanical properties of the foam, it can be convenient to add a little quantity (forexamplefrom 1 two3%) oforganichalogenic compound, for example, a chlorinated paraffin or tridibromopropylphosphate, already generally used in foams when a greater flame protection is demanded.

The halogenic compound can give halogenic acid able to decrease the alkalinity and thus avoid disorderly reactions; besides, it can react with free radicals, decreasing compression set figures of the foam.

EXAMPLES Two comparative formulations of semirigid foam cold cured are given, where, in Formula No. 1 a solution of triethylenediamine art 33% in dipropyleneglycol (commercial name Dabco 33LV) has been used, and in Formula No. 2 the Dabco has been replaced by the chelating compound nitrile-triacetate sodium salt. This one is a formulation based on an activated polyol and methylenediphenyldiisocyanate crude type.

Formulations: No. 1 No. 6 Triol M.W. 4800 (Daltocel 32/75) 88 p.b.w. 88 p.b.w.

Triethanolamine 5 p.b.w. 5 p.b.w.

Water 3 p.b.w. 3 p.b.w.

Dabco 33LV 0,3 p.b.w. 0,3 p.b.w.

Nitriletriacetate sodium salt 1 p.b.w.

Triethylamine 0,5 p.b.w. 0,5 p.b.w.

Methylenediphenyldiisocyanate (Suprasec DNR) Index 105 p.b.w. 105 p.b.w.

As known, by index is meant the isocyanate quantity used with reference to the stechiometric quantity. For example, index 100 means stechiometric quantity and index 105 means a 5% excess on stechiometric quantity. Formulations: No. 1 No. 2 Cream Time (seconds) 20 28 Rise time (seconds) 70 70 Demoulding time (minutes) 3 3 As an example of flexible foam for cushions, a foam of the so-called "cold" type and based on activated polyol and on toluenediisocyanate is described. A comparison has not been made between the chelating compound and triethylenediamine or other kinds of catalysts, because the chelating compound allowed a moulding facility that the Applicants have not obtained without the chelating compound. In this case, hydroxyethyethylenediaminetriacetate sodium salt was used added to an amine catalyst of the trade, namely Polycat 21.

Formulation No. 3 Triol M.W. 4800 (Daltocel 32/75) 70 p.b.w.

Triol copolymer M.W. 6000 (Niax 31-28) 30 p.b.w.

Water 2,8 p.b.w.

Hydroxyethylethylenediaminetriacetate sodic (HEEDTA Na) 0,3 p.b.w.

Polycat 21 0,8 p.b.w.

Tridibromopropylphosphate 2 p.b.w.

Silicon DC 11630 0,05 p.b.w.

TDI, index 105 p.b.wf- These products in some cases can act as synergics of catalysts. Nextthere is described an example (Formulation No. 4) where nitriletriacetate sodium salt is used in order to improve the reaction times (cream time longer and demoulding time shorter), together with classic catalysts, thus demonstrating a synergistic catalytic effect.

Formulations No. 4 No. 5 Polyol triol M.W. 4800 (Daltocel 32/75) 100 p.b.w. 100 p.b.w.

Diethanolamine 1,5 p.b.w. 1,5 p.b.w.

Tetrol NOH520 5 p.b.w. 1,5 p.b.w.

(Caradol 520) Water 2,8 p.b.w. 2,8 p.b.w.

Dabco powder 0,1 p.b.w. 0,1 p.b.w.

Triethylamine 0,5 p.b.w. 0,5 p.b.w.

Silicon 3043 0,8 p.b.w. 0,8 p.b.w.

Nitriletriacetate sodic 1 p.b.w.

Blending isocyanates: 50 p. methylenediphenyldiisocyanate 50 p. toluenediisocyanate 80/20 Index 102 p.b.w. 102 p.b.w.

Cream time seconds 12 14 Rise time seconds 130 105 In the Formulation No. 5, the nitriletriacetate sodium salt chelating agent is used as synergin in order to improve the reaction time. In following Formulation No. 6, there is an example of flexible foam standard formulation for slab-stock production; in this formulation, the hydroxyethylethylenediaminetriacetate sodium salt (HEED TANa) is used with tin octoate.

Formulation No. 6 Triol M.W. 3600 (Voranol CP 3322) 100 p.b.w.

Water 4 p.b.w.

Silicon oil (L 540) 0,8 p.b.w.

HEEDTANa 0,06 p.b.w.

Tin octoate 0,20 p.b.w.

Tridibromopropylphosphate 2 p.b.w.

TDI Index 105 p.b.w.

Herein, "p.b.w." means parts by weight.

Claims (18)

1. In a process for urethanic polymerisation, the improvement which comprises using a chelating agent as a catalyst or cocatalyst, in which an isocyanate reacts with hydroxylic compound to the catalysts presence, wherein the catalyst(s) and/or cocatalyst(s) used is/are a compound(s) able to form complex with metallic ions so that they do not show standard reactions in the presence of reacting compounds.

2. A process according to Claim 1, wherein the chelating agent(s) used as catalyst and/or cocatalysts is/are selected from esters or salts of aminocarboxylic acids, aminopolycarboxylic acids, alkyl enediaminopolyearboxyl ic acids, hydroxyalkylaminocarboxylic acids and hydroxyalkylal kylenediaminopolycarboxylic acids.

3. A process according to Claim 2, wherein alkali metal salts of aminocarboxylic or polyaminocarboxylic acids and hydroxyaminocarboxylic acids are used.

4. A process according to Claim 1, 2 or 3, wherein chelating agent(s) used as catalyst or cocatalyst is/are selected from alkali metal salts of nitriletriacetic acid, ethylenediaminotetraacetic acid, hydroxyethylethylenediaminotriacetic acid, diethylenetriaminopentacetic acid, 2-hydroxy, 1-3 diaminepropylenetetraacetic acid and N, N - di (2 - hydroxyethyl) glycine.

5. A process according to any one of the preceding claims, wherein said catalyst(s) and/or cocatalyst(s) is/are employed in a dose generally used in such polymerisation for catalysts or cocatalysts.

6. A process according to any one of the preceding claims, the chelating agent(s) employed as catalyst(s) or cocatalyst(s) are used alone or in conjunction with usual aminic catalyst(s).

7. A process according to any one of the preceding claims, wherein one or more of aminopolycarboxylic acids and hydroxyaminocarboxylic acids is/are used as they are, that is not salified, to adjust the pH of the reaction mixture.

8. A process according to any one of the preceding claims, wherein the chelating agent(s) is used in conjunction with tin octoate.

9. A process according to any one of Claims 1 to 7, wherein the chelating agent(s) is used in conjunction with organic tin compound(s) other than tin octoate.

10. A process according to any one of Claims 6 to 9, wherein a halogen compound is added as cocatalyst.

11. A process for urethane polymerisation, substantially as hereinbefore described with reference to Formulation No. 1.

12. A process for urethane polymerisation, substantially as hereinbefore described with reference to Formulation No.2.

13. A process for urethane polymerisation, substantially as hereinbefore described with reference to Formulation No. 3.

14. A process for urethane polymerisation, substantially as hereinbefore described with reference to Formulation No.4.

15. A process for urethane polymerisation, substantially as hereinbefore described with reference to Formulation No. 5.

16. A process for urethane polymerisation, substantially as hereinbefore described with reference to Formulation No. 6.

17. A polyurethane whenever polymerised by the process of any one of the preceding claims.

18. Any novel feature or combination of features described herein.