Claims
- 1. In a process wherein a polyetherurethane foam is prepared by foaming polyether polyols and polyiosocyanate in the presence of water of low-boiling propellant and a polyalkyleneglycol-polysiloxane mixed block polymer foam stabilizer, the improvement which comprises that the mixed block polymer foam stabilizer has the general formula ##STR25## wherein the mixed block polymer comprises dimethylpolysiloxane units wherein m has a value between 4 and 7, provided the number of units wherein m = 5 or 6 is at least twice the number of units wherein m = 4 and 7;
- n .gtoreq. 2,
- R.sup.1 is saturated alkyl of 1 - 8 carbon atoms,
- R.sup.2 is saturated alkyl of 1 - 8 carbon atoms, the group POA or R.sub.3.sup.1 Si--,
- M is a divalent group which links the adjacent silicone atoms to POA,
- Poa corresponds to the formula (C.sub.r H.sub.2r O).sub.s R.sup.3 and is composed of polyoxyethylene and polyoxypropylene units in the weight ratio of from 50 : 50 to 30 : 70,
- r is an integer whose specific value or range is a corollary function of the specific value of said weight ratio and
- R.sup.3 is saturated alkyl of 1 - 8 carbon atoms or phenyl, and
- s is an integer whose specific value or range is a corollary function of the POA block mole weight,
- Poa has a block mole weight of from 1400 - 3000, said stabilizer prepared by adding a polydimethylsiloxanediol having the formula ##STR26## with a tertiary amine to a compound having the formula ##STR27## wherein X is a group which is reactive towards SiOH and then removing any residue of the X groups by adding compounds having the formula R.sup.2 OH to the reaction mixture.
- 2. The improvement of claim 1, wherein R.sub.3.sup.1 Si is (CH.sub.3).sub.3 Si.
- 3. The improvement of claim 1, wherein said POA block mole weight is between 1600 - 2200.
- 4. The improvement of claim 1, wherein R.sup.2 is ethyl or isopropyl.
- 5. The improvement of claim 2, wherein R.sup.1 = methyl.
- 6. The improvement of claim 1, wherein M is oxygen or (CH.sub.2).sub.t --O--, wherein t = 1 to 3.
- 7. The improvement of claim 1, wherein s = 24 - 60.
- 8. In a process, wherein a polyetherurethane foam is prepared by foaming polyether polyols and polyisocyanate in the presence of water or low-boiling propellant and a polyalkyleneglycol-polysiloxane mixed block polymer foam stablizer, the improvement which comprises that the mixed block polymer foam stabilizer has the general formula ##STR28## wherein the mixed block polymer comprises dimethylpolysiloxane units wherein m has a value between 4 and 7, provided the number of units wherein m = 5 or 6 is at least twice the number of units wherein m = 4 and 7,
- n .gtoreq. 2,
- R.sup.1 is saturated alkyl of 1 - 8 carbon atoms,
- R.sup.2 is ethyl or isopropyl,
- M is a divalent group which links the adjacent silicone atom to POA,
- Poa corresponds to the formula (C.sub.4 H.sub.2r O).sub.s R.sup.3 and is composed of polyoxyethylene and polyoxypropylene units in the weight ratio of from 50 : 50 to 30 : 70,
- r is an integer whose specific value or range is a corollary function of the specific value of said weight ratio and
- R.sup.3 is saturated alkyl of 1 - 8 carbon atoms of phenyl, and
- s is an integer whose specific value or range is a corollary function of the POA block mole weight,
- Poa has a block mole weight of from 1400 - 3000.
Priority Claims (1)
| Number |
Date |
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| 2208149 |
Feb 1972 |
DT |
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CROSS-REFERENCE TO PRIOR APPLICATIONS
This ia a continuation-in-part of Ser. No. 515,260, filed Oct. 16, 1974 which, in turn, is a continuation of Ser. No. 333,155, filed Feb. 16, 1973, and both now abandoned.
The invention is directed to a procedure for the preparation of polyetherurethane foams by foaming polyether alcohol and polyisocyanate in the presence of water or low-boiling propellant and a foam stabilizer, the latter being a polyalkyleneglycol-polysiloxane mixed block polymer.
The use of polyoxyalkylene-polysiloxane mixed block polymers as foam stablizers for polyetherurethane foams has previously been proposed in a large number of patents and publications of which German Pat. No. 1,233,133 may be mentioned as an example. A summarizing presentation of the preparation of such polyurethane foams and of mixed block polymers, which may be used as foam stabilizers for such foams, is contained in "Polyurethanes Chemistry and Technology" by Saunders and Frisch, Volume XVI of the series "High Polymers", published by Interscience Publishers, New York, London Tl. 1 (1962) and Tl. 2 (1964).
A characteristic which is common to all mixed block polymers previously used for this purpose is that the polysiloxane block is not uniform within each molecule. Rather, the block comprises dimethylsiloxy units of widely different chain lengths. This, of course, means that in addition to low molecular polysiloxane groups, the block contains units of average chain length as well as those of extremely high mole weight, to wit, units having very long chains. In several prior art patents and publications it is suggested to use polysiloxane blocks whose statistical chain length distribution corresponds to the statistical equilibrium which is obtained by subjecting the polysiloxane blocks to an equilibration reaction.
It is the primary object of the invention to provide a foam stabilizer for use in the preparation of polyetherurethane foams which is superior to prior art foam stabilizers of the indicated kind.
Briefly, and in accordance with the invention, it has now surprisingly been ascertained that superior foam stabilizers, having a markedly improved foam stabilizing activity, are polyalkyleneglycol-polysiloxane mixed block polymer of the general formula ##STR2## wherein
m is uniform or approximately uniform within each siloxane block unit of each molecule and has a value of 5 or 6;
R.sup.1 is a saturated alkyl with 1 - 8 carbon atoms;
M is a divalent group which, in a manner known per se bridges the silicon atom with the POA group;
POA corresponds to the formula (C.sub.r H.sub.2r O).sub.s R.sup.3 and is composed of polyoxyethylene and polyoxypropylene units in the weight ratio of 50:50 to 30:70;
r is an integer whose specific value or range is thus a corollary function of the specific value of said weight ratio;
s is an integer whose specific value or range is a corollary function of the POA block mole weight;
POA has a block mole weight of from 1400 - 3000, preferably of from 1600 - 2200.
The preferred R.sub.3.sup.1 Si-- group is (CH.sub.3).sub.3 Si.
As will be apparent from the above, the value for s is between 24 and 60.
It will be appreciated from the above that the crux of the present invention thus resides in the use of polyalkyleneglycol-polysiloxane mixed block polymer for the indicated purpose, wherein the dimethylpolysiloxane blocks are of uniform chain length within each molecule or unit, the chain length of each unit being determined by the index m = 5 or 6 as indicated in the formula. In this context it should, however, be noted that the improved characteristics of the foam stabilizer are retained if, instead of using equilibrium products of a wide molecular weight distribution, substantially uniform blocks are used, wherein the index m fluctuates between 4 and 7, with the majority of the units having an m value of 5 and 6. As a matter of fact, the number of units wherein m is 5 and 6, must then be at least twice that of the number of units wherein m has a value of 4 and 7. This can be made clear and illustrated by way of the molecular weight distribution curve, which in ordinary cases appears in the form of a wide flat curve (Gauss distribution) while, by contrast, in the present invention the curve corresponds to a narrow section with a narrow base and greater height.
It should be appreciated that the terms "uniform chain length" and "uniform", as used herein, are directly solely to the siloxane moiety of the molecule, and not the entire molecule. In this context the following should be considered:
All foam stabilizers of the polysiloxane polyoxyalkylene mixed copolymer type consist of molecule moieties, which are exclusively formed from siloxanes, and of molecule moieties, which are formed from polyether units. By chemical linking of these two different moieties, a large molecule is formed which exerts surface-active activities and which, provided certain selection rules are adhered to, is frequently useful for the stabilization of polyurethane foams.
The chemical reactions which lead to the two vastly different molecule moieties which, if linked together, in turn form the total stabilizer molecule, are inherently reactions that do not form uniform end products. The end products rather exhibit a wide-ranging molecular weight distribution. In respect of the siloxane moiety, the reaction is in the nature of a cohydrolysis with optionally following equilibration or it is an equilibration in which linear siloxane chains, jointly with cyclic siloxanes, can be used as starting products. In respect of the polyether moiety, alkylene oxides, such as, for example, ethylene oxide or propylene oxide, form an adduct with a starting compound which contains at least one reactive hydrogen atom, the adduct being formed by a polyaddition reaction.
It should be emphasized that, in accordance with the present invention, it is rendered possible for the first time to obtain uniformity of the siloxane blocks or moieties and thus to increase the effect of the foam stabilizers. However, no uniformity of the entire, total molecule is suggested in accordance with this invention, since this would also require uniformity of the polyether blocks or moieties. Such stabilizers, to wit, stabilizers in which the entire molecule is uniform, are not the subject matter of this invention, particularly, since uniform polyether blocks with average molecular weights as they are required as building blocks for foam stabilizers for the stabilization of polyurethane foams, cannot be produced according to the present state of the art.
The inventive realization that foam stabilizers of the indicated kind, having uniform or approximately uniform dimethylpolysiloxane groups or units, exhibit superior foam stabilizing effects run counter to that which could have been reasonably expected from the present state of the art and experience gained in other uses of surfactants. Thus, the superior foam stabilizing effect certainly could not have been predicted and is unexpected, since it is generally known that in the use of surface-active substances, mixtures of compounds of differing chain length exhibit better characteristics than the relatively pure substances. It thus can be fairly stated that the present invention successfully overcomes a prejudice of the art against the use of compounds of the kind proposed in this invention.
The polyoxyalkylene block (POA) should generally have a mole weight of from 1400 - 3000. The optimum mole weight is dependent on several factors, such as the nature of the starting substances employed for the foaming and also the particular process conditions. It should be appreciated that under certain circumstances the use of mixed block polymers may be of particular advantage wherein the molecular weight range previously indicated is exceeded or is below the above indicated lower limit of 1400. However, the range of 1400 - 3000 reflects that range which, from a practical point of view, is the most important one. Particularly preferred is a range of 1600 - 2200. The polyosyalkylene block is composed of polyoxpropylene and polyoxyethylene units, the polyoxyalkylene block containing 50-70% by weight of polyoxypropylene groups.
The group POA corresponds then to the formula (C.sub.r H.sub.2r O).sub.s R.sup.3, wherein the value for r is determined by the propyleneoxyde content while s is an integer whose specific value or range is a corollary function of the POA block mole weight, and R.sup.3 is preferably stands for alkyl with 1 - 8 carbon atoms or is phenyl. R.sup.3, however, may also stand for any other suitable chain limiting group. The specific value for s is thus between 24 - 60.
R.sup.1 is preferably methyl. However, also other alkyl groups, to wit, those having 2 - 8 carbon atoms may be considered which are then present either alone or in mixture, preferably in mixture with the methyl group.
R.sup.2 is preferably ethyl or isopropyl.
The above explanations are also applicable if R.sup.2 stands for a polyoxyalkylene group. The group R.sup.2 may also comprise the grouping (CH.sub.3).sub.3 Si as a chain limiting terminal member. However, as it will be appreciated by the skilled art worker, other chain limiting terminal members may be selected for this purpose.
In respect of the group M, it is noted that M is the linking or bridging member between a silicon atom and the polyoxyalkylene group. The meaning for the symbol M is of secondary importance. It may stand for oxygen, but M may also be an alkyleneoxy group with 1 - 3 carbon atoms. Persons skilled in this art know that mixed block polymers wherein the silicon atom is connected to the polyoxyalkylene group via an alkyleneoxy group are more resistant to hydrolysis than those wherein the polyoxyalkylene group is linked to the silicon atom through oxygen. Other linking principles are known, which however, from a practical point of view have lesser importance. Thus, for example, the groups ##STR3## may be used wherein the carbon atom is linked with the silicon atom and wherein the terminal oxygen atom is connected to the polyoxyalkylene group.
Another bridging member has the structure ##STR4## Also in this instance the terminal carbon atom is connected with the silcon atom and the terminal oxygen atom with the POA group. R.sub.3 stands then for hydrogen or methyl.
The preparation of such foam stabilizers to be used in accordance with the invention and having the inventive uniform or substantially uniform polysiloxane block may be carried out as follows: ##STR5##
The polydimethylsiloxanediols of the mentioned formula, which are used as starting product may be readily synthesized by hydrolysis of the corresponding .alpha..omega.dichloropolydimethylsiloxanes of the formula ##STR6## in an aqueous medium. For the purpose of preventing the formation of local concentrations of hydrochloric acid, acid acceptors, such as amines, are added to the medium and the medium is vigorously agitated during the hydrolysis. The polydimethylsiloxanediols thus obtained and, after having been well washed, may, if necessary, again be distilled through a column under reduced pressure.
(2) Synthesis of compounds of the formula ##STR7## wherein X is a group which is reactive towards SiOH and preferably stands for chlorine or ##STR8## These silanes may be prepared by an addition reaction between polyethers having terminal olefinic groups, such as for example polyethers with terminal allyl groups, and silanes of the formula ##STR9## by hydrosilation, for example, in the presence of platinum catalysts. In this manner, silanes are formed in which the polyether block POA is linked to the silicon atom through an alkyleneoxy group. Silanes in which the polyether POA is connected with the silicon through oxygen may, by contrast, be prepared by reacting polyethermonols in the presence of acid acceptors, such as tertiary amines, with silanes of the formula R.sup.1 --Si--X.sub.3. These silanes are then used in a great excess amount and the excess is removed after the reaction by distillation.
(3) The inventive mixed block polymers may then be prepared by adding, in dropwise manner and under effective agitation, a mixture of the polydimethylsiloxanediols of (1) above and tertiary amines to the silanes of (2) above. The reaction is preferably carried out in the presence of inert solvents. Further, it is advantageous to dissipate the reaction heat by cooling. The weight relationship between the components in the preparation of the inventive mixed block polymer should preferably be as follows:
Silanes of (2): n + 1 moles
Polydimethylsiloxanediols of (1): n moles
Tertiary amines (mixed with the polydimethylsiloxanediols of (1):2 n + 2 moles.
It is advantageous if the tertiary amines are used in excess.
In the reaction of the silanes (2) with the polydimethylsiloxanediols (1) in the indicated mole ratio, a residue of X groups remains first in unreacted form. This residue is ultimately brought to reaction in the final stages by adding to the reaction mixture compounds of the formula R.sup.2 OH. Also in this case it is advantageous to use a certain excess so as to make sure that the SiX groups, which upon hydrolysis split off acid, are completely removed. After the reaction, the salts are removed by filtration and ultimately the inventive products are obtained by removing excess ingredients together with the inert solvents by distillation to the extent this is feasible.
The improved foam stabilizing characteristics of the mixed block polymers to be used for foaming purposes in accordance with the invention are primarily demonstrated by the fact that the amounts of foam stabilizers which are necessary to achieve satisfactory stabilization of the foam, both during its formation and also after it has been completely formed, are considerably less than the quantities required when prior art stabilizers are used. Customarily, in the production of such foams not less than 0.5% by weight of stabilizer, calculated on the foaming system, have been used in the past. By contrast, if inventive substances are employed, it is frequently sufficient to add only 0.1% by weight.
The invention will now be described with reference to the following Examples, it being understood, however, that these Examples are given by way of illustration and not by way of limitation and that many changes may be effected without affecting in any way the scope and spirit of the invention as recited in the appended claims.
US Referenced Citations (7)
Continuations (1)
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| Parent |
333155 |
Feb 1973 |
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Continuation in Parts (1)
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515260 |
Oct 1974 |
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Patent Grant
4090987
