GB1571186A

GB1571186A - Process for the preparation of stable heterogenous dispersions of stable heterogenous dispersions of polyisocyanate polyaddition products

Info

Publication number: GB1571186A
Application number: GB2175479A
Authority: GB
Original assignee: Bayer AG
Current assignee: Bayer AG
Priority date: 1976-06-16
Filing date: 1976-11-10
Publication date: 1980-07-09

Description

(54) PROCESS FOR THE PREPARATION OF STABLE HETEROGENOUS DISPERSIONS OF POLYISOCYANATE POLY-ADDITION PRODUCTS (71) We, BAYER AKTIENGESELL SCHAFT, Zentralbereich Patente, Marken Und Lizenzen, 509 Leverkusen, Germany, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by wh ich it is to be performed, to be particularly described in and by the following statement:- This invention relates to an improved process for the preparation of finely divided, stable and relatively low viscosity heterogenous dispersions of polyisocyanate polyaddition products in compounds which have hydroxyl groups, and the use of such dispersions as starting components for the production of polyurethane resins.

Our co-pending Patent Application No.

46744/76 (Serial No. 1,571,183) relates to a process for the in situ preparation of a stable dispersion of a non-ionic polyisocyanatepolyaddition product in a hydroxyl compound as dispersing agent, in which the polyaddition product is produced in situ in the polyhydroxyl compound in the presence of from 4 to 35( by weight, based on the total quantity of reaction mixture of water.

The properties of polyurethane resins produced from such dispersions can be further modified in a commercially advantageous manner if, instead of using water as in the process according to our copending application, there is used a corresponding quantity of an aqueous polymer latex, for example, an aqueous polyurethane dispersion, or the aqueous solution of an ionic polyurethane or a polymer latex or a dispersion of a polycondensation product. The polymer latex or solution should have a solids content of from 1 to 60"it by weight, preferably 5 to 55 n by weight, so that the ratio by weight of solids content of the polymer latex to a polyaddition product prepared in situ is between 1:99, and 99:1 preferably between 10:90 and 90:10, most preferably between 25:75 and 75:25.

The present invention thus relates to a process for the in situ preparation of a stable dispersion of a polyisocyanate polyaddition product in a hydroxyl-containing compound used as external continuous phase, by reacting, 1. an organic polyisocyanate with 2. a compound having primary and/or secondary amino groups and/or primary hydroxyl groups in 3. a compound having at least one hydroxyl group which hydroxyl group is. less reactive towards isocyanate groups than the isocyanate reactive groups of component 2, compounds 3 having secondary hydroxyl groups, if compounds 2 have primary hydroxyl groups and the starting components being reacted together in the presence of from 4 to 35 /n by weight of water, based on the reaction mixture including water, the water being subsequently removed in known manner if indicated, in accordance with our copending application No. 46744/76, the process being characterised in that the polyisocyanate-polyaddition reaction is carried out in the presence of an aqueous polymer latex other than the external continuous phase, or in the presence of an aqueous solution of an ionic linear polyurethane.

When choosing a suitable latex for the process according to the invention from the known aqueous latices of polymers, polycondensates, polyaddition products or mixtures thereof, it is necessary to take into account their compatibility with the compound which carries alcohol groups which is used as external continuous phase.

Aqueous polyurethane dispersions are particularly widely applicable.

Numerous processes have become known for the preparation of polyurethane dispersions in water. A summarizing report has been given, for example by D. Dieterich and H. Reiff in "Die Angewandte Makromolekulare Chemie" 26 (pages 85106); by D. Dieterich et al in "Angewandte Chemie", 82 1970 (pages 53-63) and by D.

Dieterich et al in J. Oil Col. Chem. Assoc.

1970, 53, (363-379). These reports also give a comprehensive survey of the literature. In practice, the most popular method for preparing aqueous polyurethane dispersions comprises reacting an isocyanate prepolymer dissolved in an organic solvent with a chain lengthening agent. In this process, either the prepolymer or the chain lengthening agent contains ionic groups or groups capable of ion formation. These groups capable of ion formation are converted into ionic groups either during the polyaddition reaction or subsequently.

Formation of the aqueous dispersion is carried out at the same time or subsequently by the addition of water and removal of the organic solvent by distillation.

Both cationic and anionic and non-ionic polyurethane dispersions may be used in the process according to the invention.

Aqueous polyurethane dispersions which give rise to polyurethane foils with elastic properties when dry are preferred for the purpose of the invention, particularly rubbery elastic or, at least high impact resistant polyurethanes, polyureas or polyhydrazodicarbonamides which have a ball pressure hardness below 1400 kp/cm2 (60 seconds according to DIN 53 456) and preferably a Shore hardness D of less than 55 and most preferably a Shore hardness A of less than 98. Dispersions of harder polyurethanes may, of course, be used in individual cases, for obtaining foams which have special properties.

As already mentioned above, aqueous polyurethanes dispersions suitable for the process according to the invention may be obtained quite generally by including in the preparation of the polyurethanes components which contain ionic groups or groups capable of ion formation and, in addition, at least one isocyanate group or at least one hydrogen atom which is reactive with isocyanate groups.

Methods of preparation of cationic polyurethane dispersions have been described for example, in German Auslegeschriften Nos. 1,184,946; 1,178,586; 1,179,363 and 1,270,276; U.S. Patent Specification No. 3,686,108 and Belgian Patent Specification No. 653,223; 658,026 and 636,799.

The anionic polyurethane(urea) dispersions may also be prepared by known methods. Suitable anionic polyurethanes have been described, for example, in German Auslegeschrift No. 1,237,306 and German Offenlegungsschriften Nos.

1,570,5651,720,639 and 1,495,847.

Other ionic polyurethane dispersions which may be used according to the invention are described for example, in German Auslegeschriften Nos. 1,495,745, No. 1,282,962 and No. 1,694,129 (British Patent No. 1,158,088) and in German Offenlegungsschriften Nos. 1,595,687, No.

1,694,148, No. 1,729,201 (British Patent No.

1,175,339) and No. 1,770,068.

As already mentioned above, non-ionic, self-emulsifying aqueous polyurethane dispersions may also be used for the process according to the invention in addition to cationic and anionic polyurethane dispersions.

The preparation of non-ionic, emulsifierfree polyurethane dispersions which are suitable for the process according to the invention may be carried out, for example, by the process according to German Offenlegungsschrift Nos. 2,141,807; 2,314,512; 2,314,513 and 2,320,719.

Suitable polymer latices include, for example, those based on natural or synthetic rubber, styrene-butadiene copolymers, neoprene, styrene-acrylonitrile copolymers, polyethylene chlorosulphonated or chlorinated polyethylene, butadiene-acrylonitrile copolymers, butadiene-methacrylate copolymers, polyacrylic acid esters, PVC and copolymers of ethylene and vinyl acetate which may be partially saponified.

Examples of such polymer latices may be found, for example, in U.S. Patent No.

2,993,013 and German Offenlegungsschrift No. 2,014,385.

As examples of polycondensate dispersions may be mentioned the aminoplastic or phenoplast dispersions which may contain ionic groups as described in German Offenlegungsschrift No. 2,324,134. Methylolated polycondensate dispersions prepared using an excess of formaldehyde may also be used. According to a special embodiment of the present invention, the polymers or polycondensates may first be prepared in situ in the dispersing agent containing hydroxyl groups and the polyisocyanatepolyaddition reaction may then be carried out in the same reaction vessel.

Although the polyurethanes, polymers, polycondensation products or mixtures thereof are preferably used in the form of their aqueous dispersions or solutions in the process according to the invention, they may also be introduced into the reaction vessel as dispersions or solutions in nonaqueous dispersing agents or solvents, water being then added before the polyisocyanatepolyaddition reaction, e.g. together with the amino compounds.

The non-aqueous dispersing agents or solvents, if used, are preferably the same as those used as dispersing agent for the in situ polyaddition reaction, in other words low molecular weight polyols or higher molecular weight polyethers, polyesters, polycarbonates and polyacetals containing hydroxyl groups, which compounds have been described in detail in co-pending application No. 46744/76 (Serial No.

1,571,183). In special cases, organic or aqueous organic solvents or dispersing agents (preferably with boiling points below 150 C) may be used, for example an acetonic solution or dispersion with or without the addition of water for dilution.

The great advantage of the process according to the invention is that, with the aid of the simple process of the polyisocyanate polyaddition reaction, the polyurethane resins produced from the dispersions obtainable according to the invention can be optimally improved and modified in their properties exactly as desired by suitable choice of their starting compounds because of the very wide range of possible reactants available for selection.

In another variation of the process according to the invention, aqueous solutions of ionic polyurethanes are used instead of aqueous polymer dispersions, for example those described in the publication mentioned above by D. Dieterich et al in Angewandte Chemie 82, 1970, pages 5363.

The various starting compounds used in the process according to the invention are selected according to the proposed use of the polyurethanes prepared from the modified polyhydroxyl compounds obtainable according to the invention and according to the desired modification or improvement in their mechanical properties or possible methods of application. If, for example, it is desired to modify a relatively hard, brittle polyurethane in order to increase its impact strength, an aqueous dispersion of a highly elastic polyurethane, polymer or polycondensate should be used.

It is thereby possible not only substantially to reduce the general brittleness of the end product but also to increase the elasticity of the surface zones which are particularly liable to be damaged by impact, for example in the case of a foam product.

It is, of course, also possible to proceed conversely on the same principle and to modify a relatively soft polyurethane product by means of a dispersion of a relatively hard polyurethane, polymer or polycondensate product. It is possible in this way to optimise both the hardness and the tensile strength of the end product. In addition, the stability of the product to light can be improved, for example when using finely dispersed particles of polyhydrazodicarbonamides.

Foams with ionic groups which have increased hydrophilic character can be obtained by using polyhydroxyl compounds which contain ionic polymers.

Foams which have been rendered hydrophilic in this way can be wetted more easily, for example, and depending on their hydrophilic character, they can also absorb larger quantities of water than conventional foam products. They may also be used as ion exchangers, for example.

A further advantage of the process according to the invention is that when polyhydroxyl compounds containing, for example, ionic polyisocyanate polyaddition products are used in the production of polyester urethane foams, the emulsifying agents normally required can be omitted.

The ionic polyurethane molecules introduced into the reaction mixture evidently act as internal dispersing agents.

According to another possible variation of the present invention, polyisocyanate polyaddition products dispersed in the polyhydroxyl compounds are subsequently cross-linked with formaldehyde in known manner in the presence of catalytic quantities of acids. It is surprisingly found that cross-linked dispersions of this kind are also finely dispersed and stable in storage.

The special importance of the present invention lies in the fact that all the abovementioned improvements and modifications in the properties of polyurethane resins can be obtained using the usual raw materials and conventional, in most cases standardised, formulations.

The following examples serve to explain the process according to the invention. The figures given refer to parts by weight or percentages by weight unless otherwise indicated.

Example I 20% Dispersion of PHD/SAN (polyhydrazodicarbonamide/styrene - acrylonitrile copolymer) in trifunctional polyether. Ratio of solids contents PHD:SAN=l :1.

Formulation 824.00 Parts by weight of a polyether of propylene oxide and ethylene oxide started on tri methylolpropane, hydroxyl number of polyether 34 and containing about 80% of primary hydroxyl groups (hereinafter referred to "polyether I") as external continuous phase.

257.50 Parts by weight of a 40 'n aqueous styrene-acrylonitrile dispersion (ratio by weight of styrene:acrylonitrile=72.28, here inafter referred to as "SAN Latex"); 25.25 parts by weight of hydrazine monohydrate (99%); 87.00 parts by weight of tolylene diisocyanate (isomeric mixture 2,4:2,6=80:20, hereinafter referred to as "T 80"); Index (KZ)=NCO/NH. 100=100; water content: 13.7% by weight based on reaction mixture (including water).

General Method of Preparation The polyether preheated to 60 to 750C, aqueous polymer latex and hydrazine hydrate are combined in a vessel equipped with stirrer and reflux condenser. Into this mixture, which is at 75"C, the diisocyanate is introduced directly through an inlet tube at a rate such that the temperature is raised to 85 to 95"C by the exothermic polyaddition reaction. The pressure may then be gradually reduced so that the water derived from the polymer latex and the water of hydration are distilled off. Towards the end of this distillation, the temperature is raised to 100--1200C/2040 Torr. The practically anhydrous dispersion is discharged hot through a 100 ,um sieve.

The viscosities at 250C (at solid contents of 20% and 10%, respectively) are 4650 and 1780 cP.

Example la 40 /n PHD/SAN dispersion in Polyether I.

Ratio of solids contents=l:l.

The formulation and method are the same as in Example 1 but using only 309 parts by weight of polyether I and a water content of 24.1 by weight.

The finely divided dispersion has a viscosity of 68.500 (3200, 1470) cP at 250C when the solids content is 40% (20%; 10%) and, particularly in its highly concentrated form, it is suitable for use as "masterbatch" for mixing with polyesters containing hydroxyl groups.

Example 2 20% PHD/SBR (polyhydrazodicarbonamide/polybutadiene) dispersion in polyether I.

Ratio of solids contents PHD/SBR=1:1.

Formulation 824.00 parts by weight of polyether I as external continuous phase; 229.00 parts by weight of a 45 'n aqueous polybutadiene latex; 25.25 parts by weight of hydrazine monohydrate (99%); 87.00 parts by weight of diisocyanate "T 80"; Index=100; water content 11.69 by weight.

The method of procedure is the same as described in Example 1.

The anhydrous 20% (10%) dispersion has a viscosity of 4480 (1880) cP at 250C.

Example 3 20% PHD/ABS (graft copolymer) dispersion in branched polyether.

The ratio of solids contents=l:l.

824 parts by weight of a polyether of propylene oxide and ethylene oxide started on trimethylolpropane (hydroxyl number of polyether=3 1; about 70% primary hydroxyl groups; hereinafter referred to as polyether II) as external continuous phase; 312.00 parts by weight of a 33% aqueous dispersion of 70% by weight styrene-acrylonitrile copolymer and 30% by weight of graft copolymer of polybutadiene, styrene and acrylonitrile (hereinafter referred to as "ABS dispersion"); 25.25 parts by weight of hydrazine monohydrate (99%); 87.00 parts by weight of tolyene-2,4 diisocyanate (hereinafter referred to as "T 100"); Index=100; water content: 17.5% by weight.

The method of procedure is the same as described in Example 1. The 20% (10%) anhydrous stable dispersion has a viscosity of 6,900 (1790) cP at 25".

Example 4 20% PHD/PE (polyethylene) dispersion (ratio of solid contents 1:1) in polyether II.

The formulation and method of procedure are the same as in Example 3 except that 257.5 parts by weight of a 40% PE dispersion are used instead of the ABS dispersion. The water content during the diisocyanate polyaddition is 13.7% by weight.

The 20% (10%) dispersion has a viscosity of 8450 (2160) cP at 25"C.

Example 5 20% dispersion of PDH(OH) > (polyhydrazodicarbonamide containing hydroxyl groups)/PUR elastomer dispersion in Polyether III. Ratio of solids contents; 15:5.

Formulation 1267 parts by weight of a linear polypropylene glycol containing secondary hydroxyl groups (hereinafter referred to as polyether III"), hydroxyl number 56, as external continuous phase; 188.6 parts by weight of a 40% anionic aqueous PUR dispersion of a polyester of hexandiol, neopentyl glycol and adipic acid (molecular weight 1800), hexamethylene-1,6 diisocyanate, ethylenediamine and adiaminosulphonate of the formula H2NCH2CII2NHCH2CH2SOe3Na (Shore hardness A 60); 50.5 parts by weight of hydrazine monohydrate (99%); 13.0 parts by weight of ethanolamine; 192.5 parts by weight of toluene-2,4 diisocyanate; Index (NCO/NH). 100=100; water content; 11.8% by weight; Index (NCO/NH+OH). 100=91.

Method External continuous phase, aqueous PUR dispersion and NH compounds are introduced into the reaction vessel as described in Example 1 and the mixture is heated to 950C before introduction of the diisocyanate is begun. Distillation of water at reduced pressure may be started immediately after addition of the diisocyanate.

The anhydrous, stable dispersion has a viscosity of 590 cP at 250C and shows a pronounced Tyndall effect.

Example 5a 40 Sn PHD(OH)PUR dispersion.

Example 5 is repeated but using only 475 parts by weight of polyether III and a watercontent of 13.9% by weight.

The 40% (20 /n) dispersion has a viscosity of 4310 (575) cP at 25"C.

Example 6 200n PHD(OH)2/PUR dispersion in branched polyether. Ratio of solids contents=15:5.

1267.0 parts by weight of a polyethylene glycol started on trimethylolpropane and having a hydroxyl number of 550 (polyether 188.6 parts by weight of a cationic 40 /n aqueous cross-linked PUR dispersion of a polyester of adipic acid, phthalic acid and diethylene glycol (molecular weight of polyester 1700), about equal parts of tolylene diisocyanate and hexamethylene diisocyanate, N methyldiethanolamine, diethylene triamine and dimethylsulphate as quaternising agent (Shore A hardness 85); 50.5 parts by weight of hydrazine monohydrate (99%); 13.0 parts by weight of ethanolamine; 192.5 parts by weight of tolylene diisocyanate (mixture of isomers 2,4:2,6=4:1); Index (NCO/NH). 100=100; water content: 11.8% by weight; Index (NCO/NH+OH). 100=91.

The finely divided 20% dispersion prepared as described in Example 5 has a viscosity of 2100 cP at 250C.

Attention is directed to our co-pending application No. 46745/76 (Serial No.

1,571,184) which is directed to a similar process to that of the present invention, but differs in that the dispersed polyaddition products prepared in situ contain ionic groups.

WHAT WE CLAIM IS: 1. A process for the in situ preparation of a stable heterogeneous dispersion of a nonionic polyisocyanate polyaddition product in a hydroxyl-containing compound used as external continuous phase, by reacting in the presence of from 4 to 35% by weight of water based on- the reaction mixture including water, I) an organic polyisocyanate with 2) a compound having primary and/or secondary amino groups and/or primary hydroxyl groups in 3) a compound having at least one hydroxyl group which hydroxyl group is less reactive towards isocyanate groups than the isocyanate reactive groups of Component 2, Compound 3 having secondary hydroxyl groups if Compound 2 has primary hydroxyl groups, which reaction is carried out in the presence of an aqueous polymer latex other than the external continuous phase or in the presence of an aqueous solution of an ionic linear polyurethane.

2. A process as claimed in Claim 1 in which the aqueous polymer latex is an aqueous polyurethane dispersion.

3. A process as claimed in Claim 1 or Claim 2 in which water is removed from the reaction mixture after the polyisocyanate polyaddition reaction.

4. A process as claimed in Claim 1 in which the aqueous polymer latex or ionic polyurethane solution is added to the hydroxyl containing external continuous phase and the polyisocyanate polyaddition product is then produced in situ.

5. A process as claimed in any of Claims 1 to 4 in which the polymer dispersion is an

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. Formulation 1267 parts by weight of a linear polypropylene glycol containing secondary hydroxyl groups (hereinafter referred to as polyether III"), hydroxyl number 56, as external continuous phase; 188.6 parts by weight of a 40% anionic aqueous PUR dispersion of a polyester of hexandiol, neopentyl glycol and adipic acid (molecular weight 1800), hexamethylene-1,6 diisocyanate, ethylenediamine and adiaminosulphonate of the formula H2NCH2CII2NHCH2CH2SOe3Na (Shore hardness A 60); 50.5 parts by weight of hydrazine monohydrate (99%); 13.0 parts by weight of ethanolamine; 192.5 parts by weight of toluene-2,4 diisocyanate; Index (NCO/NH). 100=100; water content; 11.8% by weight; Index (NCO/NH+OH). 100=91. Method External continuous phase, aqueous PUR dispersion and NH compounds are introduced into the reaction vessel as described in Example 1 and the mixture is heated to 950C before introduction of the diisocyanate is begun. Distillation of water at reduced pressure may be started immediately after addition of the diisocyanate. The anhydrous, stable dispersion has a viscosity of 590 cP at 250C and shows a pronounced Tyndall effect. Example 5a 40 Sn PHD(OH)PUR dispersion. Example 5 is repeated but using only 475 parts by weight of polyether III and a watercontent of 13.9% by weight. The 40% (20 /n) dispersion has a viscosity of 4310 (575) cP at 25"C. Example 6 200n PHD(OH)2/PUR dispersion in branched polyether. Ratio of solids contents=15:5. 1267.0 parts by weight of a polyethylene glycol started on trimethylolpropane and having a hydroxyl number of 550 (polyether 188.6 parts by weight of a cationic 40 /n aqueous cross-linked PUR dispersion of a polyester of adipic acid, phthalic acid and diethylene glycol (molecular weight of polyester 1700), about equal parts of tolylene diisocyanate and hexamethylene diisocyanate, N methyldiethanolamine, diethylene triamine and dimethylsulphate as quaternising agent (Shore A hardness 85); 50.5 parts by weight of hydrazine monohydrate (99%); 13.0 parts by weight of ethanolamine; 192.5 parts by weight of tolylene diisocyanate (mixture of isomers 2,4:2,6=4:1); Index (NCO/NH). 100=100; water content: 11.8% by weight; Index (NCO/NH+OH). 100=91. The finely divided 20% dispersion prepared as described in Example 5 has a viscosity of 2100 cP at 250C. Attention is directed to our co-pending application No. 46745/76 (Serial No.

aqueous polymer dispersion having a solids content of from 5 to 55% by weight.

6. A process as claimed in any of Claims 1 to 5 in which the polymer, dispersed in a non-aqueous organic medium, is added to the hydroxyl containing external continuous phase and the polyisocyanate polyaddition reaction is allowed to proceed after the addition of water.

7. A process as claimed in Claim 1 substantially as herein described with reference to the Examples.

8. A dispersion of a polyisocyanate polyaddition product when produced by a process as claimed in any of Claims I to 7.

9. A process for the production of a polyurethane resin which comprises using as a starting component a dispersion as claimed in Claim 8.