Catalyst and its use for the synthesis of polyol polyethers

Details Catalyst and its use for the synthesis of polyol polyethers Catalyst and its use for the synthesis of polyol polyethers

1999-11-12

2001-03-13

Truong, Duc (Department: 1711)

Synthetic resins or natural rubbers -- part of the class 520 ser

Synthetic resins

Treating polymer containing material or treating a solid...

C528S488000, C528S495000, C502S104000

Reexamination Certificate

active

06201101

ABSTRACT:

The present invention relates to a catalyst having general formula (I) and a process for the synthesis of polyol polyethers which uses this catalyst.
Polyol polyethers are very versatile compounds which can be used as such or as intermediates in the production of compounds of industrial interest such as polyurethanes, detergents or additives for oils.
Polyol polyethers are usually prepared by reacting an alkylene oxide, especially propylene oxide, ethylene oxide or their mixtures, with a compound having active hydrogen atoms (initiator) in the presence of an acid, metal or basic alkoxylation catalyst.
Acidic catalysts, typically Lewis acids such as aluminum trichloride, boron trifluoride, tin tetrachloride, zinc chloride, cause a high formation of low-boiling cyclic oligomers (Meerwein et al., 1939, J. Prakt. Chem., 154, 83). The use of cocatalysts such as water, alcohols or alkyl halides leads to an improvement in the conversion to polymer, but in such a quantity that these systems cannot be used on an industrial scale (Merral et al., 1960, Can. J. Chem. 82).
Metallic catalysts, based on metals such as iron, zinc or aluminum, have a good catalytic activity.
Examples of metal catalysts are iron chloride (U.S. Pat. No. 2,706,181), optionally activated with water, zinc or aluminum alcoholates (Osgan et al., 1959, J. Polym. Sci. 34, 153), mixtures of aluminum alcoholates with zinc chloride (Miller et al., 1960, J. Polym. Sci. 46, 455), the Vandenberg catalyst, consisting of an aluminoxane complexed with acetylacetone (Vandenberg, 1976, Pure Appl. Chem., 48, 295).
These catalysts act with a coordination mechanism and produce materials generally consisting of two distinct fractions: an amorphous polyether with a relatively low molecular weight and a polyether with a high molecular weight, stereoregular and crystalline.
As a liquid polyol is required for the synthesis of polyurethanes, and therefore not stereoregular and with a moderate molecular weight (normally less than 10,000), these catalysts are not deemed suitable, even though with these systems one of the end groups of the polyols is a halogen or an alkyl group, which is not polymerizable in reactions with isocyanates (F. E. Bailey, J. V. Kolesske, “Alkylene oxides and their polymers”, Marcel Dekker Inc. (1991, chapter 4).
Basic catalysts, in particular potassium hydroxide, are used in industrial processes for the preparation of polyol polyethers which can be used as intermediates for the preparation of polyurethanes. These catalysts however, have a moderate catalytic activity and consequently relatively long reaction times are required for obtaining complete conversion of the propylene oxide.
A further disadvantage relates to the formation of unsaturated end groups, due to secondary reactions caused by the alkalinity of the medium.
Another group of catalysts proposed in patent literature is that of metal cyanometallates, particularly zinc hexacyanoferrate and zinc hexacyanocobaltate, as such (U.S. Pat. No. 4,4725,60) or modified (EP-743.093).
These catalysts produce liquid, amorphous polyol polyethers with a suitable molecular weight and with a low unsaturation degree. Their preparation however is extremely complex (Kuyper et al., 1987, J. Catal., 105, 163) and the experimental parameters adopted in their preparation (temperature, concentration of the solutions, order and rate of the products added) can substantially influence their catalytic activity. It has, in fact, been observed that in numerous cases even inert products are obtained. In addition, these catalysts have long and non-reproducible induction times causing problems relating to reaction control and safety of the plant.
It has now been found that it is possible to overcome the drawbacks of the known art mentioned above by means of a new group of catalysts based on metal antimoniates.
In particular the use of these catalysts has the following advantages: (i) good catalytic activity, no induction time, good selectivity and easy preparation.
In accordance with this the present invention relates to a group of catalysts having general formula (I)
M[SbO
n
(OH)
2(3-n)
]
x
  (I)
wherein: M represents at least one cation of an element selected from earth-alkaline metals belonging to groups IIA, IIIA, VA, or transition metals belonging to groups IIB, IIIB, VB or VIIIB; n represents an integer between 0 and 2 and x is an integer between 2 and 5.
M is preferably selected from magnesium, calcium, strontium, barium, aluminum, tin, titanium, cobalt, iron, zinc or combinations of these. Particularly preferred for the purposes of the present invention are zinc and aluminum or combinations of these.
The catalysts (I) of the present invention can be prepared with known techniques starting from a hydroxy-antimoniate of an alkaline metal and an organic or inorganic salt of a metallic cation M.
The synthesis of the catalysts having general formula (I) is typically carried out by putting the components in contact under light stirring, in an aqueous solution , at a temperature ranging from 25 to 100° C., preferably between 50° C. and 90° C., for a period of 0.1 to 3 hours.
The way in which the various components are put in contact with each other, is not critical; however in the preferred embodiment this is achieved by dissolving in water a soluble salt of hexahydroxyantimonic acid at a final weight concentration of 0.1 to 10%, and adding a salt of the metal (M) to the resulting solution, with a molar ratio M/Sb ranging from 10 to 1, preferably between 5 and 1.
The suspended solid is then separated by filtration. The compound thus obtained can be washed with an organic solvent to totally or partly remove the imbibition and/or crystallization water. At the end the catalyst is dried at temperatures ranging from 20° C. to 80° C. and for times of 1 to 24 hours.
The catalyst of the present invention is active in synthesis processes of polyol polyethers by the reaction of an alkylene oxide with one or more compounds, indicated with the term initiators, capable of promoting the formation of hydroxyalcohol end groups.
The alkylene oxides are selected from epichlorohydrin, propylene oxide, ethylene oxide, butene oxide or their mixtures.
The quantity of oxide used in the process is selected in relation to the molecular weight desired for the polyol polyethers.
The initiators are water or polyfunctional alcohols with from 2 to 20 carbon atoms, in particular from 2 to 10 carbon atoms, or polyols with a molecular weight of less than 1,000 daltons.
Examples of initiators are: glycols such as for example, ethylene, propylene, butylene glycol; diols such as 1,3-propanediol, 1,4-butanediol, 1,6-hexane-diol, cyclohexanediol, cyclohexanedimethanol, benzene-dimethanol; aromatic diols such as hydroquinone, methylhydroquinone, catechol, resorcinol, naphthalenediol, dihydroxybiphenyl; aliphatic polyfunctional alcohols such as glycerine, pentaerythritol, trimethylolpropane or aromatics such as for example pyrogallic acid; sugar derivatives (pentose or hexose) such as sorbitol, mannitol, glucitol, xylitol, adonitol, etc.
Alternatively, it is also possible to use polyfunctional acids such as succinic, glutaric, malonic, adipic acid or hydroxyacids such as hydroxyacetic, hydroxypropionic, hydroxybutanoic, hydroxyhexanoic, hydroxybenzoic, citric, tartaric acid. Finally polyfunctional amines can also be used, such as ethylenediamine, tetramethylenediamine, hexamethylenediamine, isophoronediamine, benzenediamine, diaminobiphenyl, etc.
The selection of the appropriate initiator also depends on the polymer to be prepared.
For example, bifunctional initiators are particularly suitable for the preparation of polyol polyethers which can be used for the production of polyurethane elastomers.
The quantity of catalyst used can vary within wide limits, but generally ranges from 0.001 to 0.01 moles per mole of monomer.
The polymerization can be carried out without or in the presence of a hydrocarbon solvent such as, for example, toluene, benzene, xylene, ethylbenzene, cumene or an ether solvent such as

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