GB1577767A

GB1577767A - Liquid diphenylmethana diisocyanate formulation

Info

Publication number: GB1577767A
Application number: GB1905377A
Authority: GB
Original assignee: Elastogran GmbH
Current assignee: BASF Polyurethanes GmbH
Priority date: 1976-05-07
Filing date: 1977-05-06
Publication date: 1980-10-29
Also published as: FR2350331B3; ES458536A1; DE2620222A1; FR2350331A1; DK198377A; IT1078197B

Description

(54) LIQUID DIPHENYLMETHANE DIISOCYANATE FORMULATION (71) We, ELASTOGRAN GmbH, a German Company, of 2844 Lemförde Federal Republic of Germany, do hereby declare the invention, for which we pray that a Patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following Statement:- The present invention relates to liquid diphenylmethane diisocyanate formulations.

When manufacturing high quality polyurethane elastomers and polyurethane foams, the use of diphenylmethane diisocyanate (hereinafter referred to for brevity as pure MDI) as the isocyanate component has proved very advantageous in many cases. However, the disadvantage of pure MDI is that it is solid at room temperature and can therefore only be processed with difficulty. Attempts have, therefore, already been made to convert pure MDI to a liquid form. German Patent 1,092,007 proposes heating pure MDI above 50"C whereby a part of the diisocyanate groups present are consumed by the formation of a carbodiimide. The remaining NCO groups react with the carbodiimide groups formed, in part with the formation of a uretonimine, so that the liquid products obtained are no longer diisocyanates but polyisocyanates, and this manifests itself in the mechanical properties of the polyurethanes, manufactured from such products, being less good.

German Patents 1,618,380 and 1,593,665 disclose a process for liquefying pure MDI, by reacting it partially with tri- or poly 1,2 - propylene ether glycols or with dipropylene glycol and a little phosphoric acid. This gives mixtures, which are liquid at room temperature, of pure MDI and the corresponding prepolymers thereof with diols.

It is a disadvantage of the above process that the polyisocyanate mixtures obtained still have relatively high crystallization points so that the products solidify to crystals especially on prolonged storage at fairly low temperatures, and then must be remelted when being processed. This is not only laborious and time-consuming, but also expensive. This disadvantage manifests itself adversely above all when processing minor amounts of polyisocyanate, for example when producing polyurethane coatings, since in that case the small amounts of polyisocyanate required are not delivered in heated tankers but, as a rule, in barrels.

The present invention seeks to provide liquid diphenylmethane diisocyanate formulations having a crystallization point which is so low that the products do not solidify to crystals even if stored for several months at around the freezing point, or even below.

According to one aspect, the invention provides a storage-stable, liquid diphenylmethane diisocyanate formulation which contains an adduct manufactured by reacting 1 molar proportion of 4,4'- and/or 2,4' - diphenylmethane diisocyanate with from 0.1 to 0.3 molar proportion of P,P' dihydroxy - dipropyl sulfide. The formulation may, for example consist solely of said adduct.

According to a second aspect, the invention provides a process for the manufacture of a liquid diphenylmethane diisocyanate formulation wherein 1 molar proportion of 4,4'- and/or 2,4' - diphenylmethane diisocyanate is reacted with from 0.1 to 0.3 molar proportion of A,,B' - dihydroxy - dipropyl sulfide which may or may not be mixed with one or more diand/or poly - 1,2 - propylene ether glycols.

Surprisingly, these very small amounts of P,P' - dihydroxy - dipropyl sulfide suffice to ensure that the reaction with 4,4'- and/or 2,4' - diphenylmethane diisocyanate gives a liquid diisocyanate which even after prolonged storage at fairly low temperatures remains liquid. The diphenylmethane diisocyanate formulation manufactured according to the invention has a low viscosity and is therefore very readily processable. It is a further advantage that it has a very low vapor pressure and is thus physiologically safe.

As has already been explained, the liquid diphenylmethane diisocyanate formulations are manufactured by reacting 1 molar proportion of 4,4'- and/or 2,4' - diphenylmethane diisocyanate with from 0.1 to 0.3 molar proportion of P,P' - dihydroxy dipropyl sulfide. If less than 0.1 mole proportion of ,B,p' - dihydroxy - dipropyl sulfide is used per mole of diphenylmethane diisocyanate, the crystallization point of the diphenylmethane diisocyandte formulation is again lowered, but frequently by an insufficient amount, so that on prolonged storage at low temperatures the formulation deposits crystals. Of course, it is also possible to employ more than 0.3 mole of ss,ss' - dihydroxy - dipropyl sulfide per mole of diphenylmethane diisocyanate, but it is a disadvantage of such formulations that they are not only more expensive but also more viscous and more difficult to process.

For some fields of application it can be of advantage to use a mixture of ,l,' - dihydroxy - dipropyl sulfide with one or more di- and/or poly - propylene ether glycols or molecular weights from 134 to 1,000, preferably from 134 to 400. It has proved advantageous in such cases to use from 0.1 mole to 5 moles, preferably from 0.5 to 2 moles, of di- and/or poly propylene ether glycol per mole of ,p' dihydroxy - dipropyl sulfide.

The process may be carried out, for example, by introducing ,p' - dihydroxy dipropyl sulfide, which may or may not be mixed with di- and/or poly - propylene ether glycol(s), at from 40 to 700C into the fused 4,4'- and/or 2,4' - diphenylmethane diisocyanate whilst stirring, and completing the reaction at a higher temperature, e.g.

80"C, in the course of from 0.5 to 5 hours, preferably from 1 to 2 hours.

The liquid diphenylmethane diisocyanate formulations of the invention have crystallization points of from +50 to -300C, preferably from -40 to -300C, and isocyanate contents of from 15 to 25% by weight. The difference between the isocyanate content of the pure crystalline 4,4'- and/or 2,4' - diphenylmethane diisocyanate and the product of the present process corresponds to the amount of /3,p' dihydroxy - dipropyl sulfide employed.

The products may be used for a great diversity of poly-addition reactions, especially to produce polyurethane foam moldings or coatings. Examples are the manufacture of 2-component coating compositions, integral foams for shoe soles and automobile fenders.

EXAMPLE 1 2,500 parts (10 moles) of 4,4' - diphenylmethane diisocyanate are fused and 341 parts (2.27 moles) of A,ss' - dihydroxy dipropyl sulfide are added slowly at 700 C.

Hereupon the temperature rises to 800 C, and is kept at this value for 2 hours. After cooling to room temperature, a pale yellowish liquid having a viscosity of 1,360 cp/25 C, an NCO content of 22.0 /,, by weight and a crystallization point of -30"C is obtained.

EXAMPLE 2 2,500 parts (10 moles) of 4,4' - diphenylmethane diisocyanate are fused and reacted, by the method described in Example 1, with a mixture of 200 parts (0.5 mole) of a polypropylene ether glycol having a hydroxyl number 280, and 265 parts (1.77 moles) of , - dihydroxy - dipropyl sulfide. The end product had an NCO content of 21 /" by weight, a viscosity of 1,650 cp/25 C and a crystallization point of -19 C.

EXAMPLES 3 " If the method described in Example 1 is followed, but the content of p,p dihydroxy - dipropyl sulfide is varied, the diphenylmethane diisocyanate formulations listed in the Table are obtained.

COMPARATIVE EXAMPLES I-V If the method described in Example I is followed, but the nature and amount of the di- and poly-propylene ether glycols used are varied, the end products listed in the Table are obtained.

TABLE Moles of glycol per mole of 4,4'- Diphenylmethane diisocyanate formulation diphenylmethane NCO content Viscosity Crystalliza Examples Glycol diisocyanate /" by weight cp/250C tion point (0C) 1 P,P'-dihydroxy- 0.227 22.0 1,364 -30 dipropyl sulfide 2 Mixture of,B,p'- 21.0 1,650 -19 dihydroxy-dipropyl 0.177 sulfide and poly- 0.05 propylene glycol, OH-number 280 3 ss,p'-dihydroxy- 0.206 22.8 792 -4 dipropyl sulfide 4 " 0.185 23.6 396 +4 Comparative Examples I Dipropylene glycol 0.207 22.5 730 15 II ,, 0.226 22.2 1,900 13 III ,, 0.254 20.2 4,700 10 IV Polypropylene glycol 0.167 16.3 968 12 OH-number 112 V Higher-functional 0.156 20.4 3,520 13 polypropylene glycol OH-number 420 The Table shows that the crystallization point of the diphenylmethane diisocyanate formulations of the invention, which are based on P,P' - dihydroxy - dipropyl sulfide, are substantially lower than those of the products used hitherto. This becomes particularly clear when products of identical or similar viscosity are compared with one another. This is important in practice since for processing purposes the viscosity should be kept as low as possible.

The accompanying drawing shows graphically the interrelation of viscosity and crystallization temperature. Curve I shows diphenylmethane diisocyanate formulations according to the invention which have been liquefied with various amounts of P,P' dihydroxy - dipropyl sulfide, whilst in the case of Comparative Curve II dipropylene glycol was used to liquefy the diphenylmethane diisocyanate. The Figure clearly shows the unexpectedly great effect to be found with the diphenylmethane diisocyanate formulations of the invention.

Using a process within the invention it is possible to manufacture diphenylmethane diisocyanate formulations which, for example, have a viscosity of less than 1400 cp, e.g. about 1,000 cp, at 250C, which is still easily manageable on machinery, coupled with a crystallization point of about -20"C.

Such products do not deposit any crystals even on prolonged storage at low temperatures, so that all heating and fusing equipment can be dispensed with.

WHAT WE CLAIM IS: 1. A storage-stable, liquid diphenylmethane diisocyanate formulation which contains an adduct manufactured by reacting 1 molar proportion of 4,4'- and/or 2,4' - diphenylmethane diisocyanate with from 0.1 to 0.3 molar proportion of ss,ss' dihydroxy - dipropyl sulfide.

2. A process for the manufacture of a liquid diphenylmethane diisocyanate formulation, wherein 1 molar proportion of 4,4'- and/or 2,4' - diphenylmethane diisocyanate is reacted with from 0.1 to 0.3 molar proportion of ss,ss' - dihydroxy dipropyl sulfide.

3. A process as claimed in claim 2, wherein the reaction with the ss,ss' - dihydroxy - dipropyl sulfide is carried out in the absence of other active hydrogen compounds reactive with the diphenylmethane diisocyanate.

4. A process as claimed in claim 2, wherein the reaction with the ss,ss' - dihydroxy - dipropyl sulfide is carried out in the presence of one or more di- and/or poly - 1,2 - propylene ether glycols.

5. A process as claimed in claim 4, wherein the molecular weight of the diand/or poly-propylene ether glycol(s) present is from 134 to 1,000.

6. A process as claimed in claim 4 or 5, wherein from 0.5 to 2 moles of di- and/or poly-propylene ether glycol(s) are used per mole of ss,ss' - dihydroxy - dipropyl sulfide.

7. A process as claimed in any of claims 2 to 6, wherein the ss,ss' - dihydroxy dipropyl sulfide is introduced into fused diphenylmethane diisocyanate at from 40 to 70"C whilst stirring and the reaction is completed at higher temperature.

8. A process for the manufacture of a liquid diphenylmethane diisocyanate

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

Claims

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

TABLE Moles of glycol per mole of 4,4'- Diphenylmethane diisocyanate formulation diphenylmethane NCO content Viscosity Crystalliza Examples Glycol diisocyanate /" by weight cp/250C tion point (0C) 1 P,P'-dihydroxy- 0.227 22.0 1,364 -30 dipropyl sulfide

2 Mixture of,B,p'- 21.0 1,650 -19 dihydroxy-dipropyl 0.177 sulfide and poly- 0.05 propylene glycol, OH-number 280

3 ss,p'-dihydroxy- 0.206 22.8 792 -4 dipropyl sulfide

4 " 0.185 23.6 396 +4 Comparative Examples I Dipropylene glycol 0.207 22.5 730 15 II ,, 0.226 22.2 1,900 13 III ,, 0.254 20.2 4,700 10 IV Polypropylene glycol 0.167 16.3 968 12 OH-number 112 V Higher-functional 0.156 20.4 3,

520 13 polypropylene glycol OH-number 420 The Table shows that the crystallization point of the diphenylmethane diisocyanate formulations of the invention, which are based on P,P' - dihydroxy - dipropyl sulfide, are substantially lower than those of the products used hitherto. This becomes particularly clear when products of identical or similar viscosity are compared with one another. This is important in practice since for processing purposes the viscosity should be kept as low as possible.

The accompanying drawing shows graphically the interrelation of viscosity and crystallization temperature. Curve I shows diphenylmethane diisocyanate formulations according to the invention which have been liquefied with various amounts of P,P' dihydroxy - dipropyl sulfide, whilst in the case of Comparative Curve II dipropylene glycol was used to liquefy the diphenylmethane diisocyanate. The Figure clearly shows the unexpectedly great effect to be found with the diphenylmethane diisocyanate formulations of the invention.

Using a process within the invention it is possible to manufacture diphenylmethane diisocyanate formulations which, for example, have a viscosity of less than 1400 cp, e.g. about 1,000 cp, at 250C, which is still easily manageable on machinery, coupled with a crystallization point of about -20"C.

Such products do not deposit any crystals even on prolonged storage at low temperatures, so that all heating and fusing equipment can be dispensed with.

WHAT WE CLAIM IS: 1. A storage-stable, liquid diphenylmethane diisocyanate formulation which contains an adduct manufactured by reacting 1 molar proportion of 4,4'- and/or 2,4' - diphenylmethane diisocyanate with from 0.1 to 0.3 molar proportion of ss,ss' dihydroxy - dipropyl sulfide.
2. A process for the manufacture of a liquid diphenylmethane diisocyanate formulation, wherein 1 molar proportion of 4,4'- and/or 2,4' - diphenylmethane diisocyanate is reacted with from 0.1 to 0.3 molar proportion of ss,ss' - dihydroxy dipropyl sulfide.
3. A process as claimed in claim 2, wherein the reaction with the ss,ss' - dihydroxy - dipropyl sulfide is carried out in the absence of other active hydrogen compounds reactive with the diphenylmethane diisocyanate.
4. A process as claimed in claim 2, wherein the reaction with the ss,ss' - dihydroxy - dipropyl sulfide is carried out in the presence of one or more di- and/or poly - 1,2 - propylene ether glycols.
5. A process as claimed in claim 4, wherein the molecular weight of the diand/or poly-propylene ether glycol(s) present is from 134 to 1,000.
6. A process as claimed in claim 4 or 5, wherein from 0.5 to 2 moles of di- and/or poly-propylene ether glycol(s) are used per mole of ss,ss' - dihydroxy - dipropyl sulfide.
7. A process as claimed in any of claims 2 to 6, wherein the ss,ss' - dihydroxy dipropyl sulfide is introduced into fused diphenylmethane diisocyanate at from 40 to 70"C whilst stirring and the reaction is completed at higher temperature.
8. A process for the manufacture of a liquid diphenylmethane diisocyanate

formulation carried out substantially as described in any of the foregoing Examples I to 4.
9. A liquid diphenylmethane diisocyanate formulation when manufactured by a process as claimed in any of claims 2 to 8.
10. A liquid diphenylmethane diisocyanate formulation having a viscosity of less than 1400 cp at 250C, a crystallization point of from -4"C to -300C and an isocyanate content of from 15 to 25 /n by weight. ~~~~~~~~~~~~~~~~~~
11. A polyurethane coating or foam molding when made from a liquid diphenylmethane diisocyanate formulation as claimed in claim 1, 9 or 10.