GB2278350A - Hydroxylation of diglycerides and triglycerides - Google Patents

Abstract

A partially unsaturated hydroxylated diglyceride or triglyceride of one or more long-chain ethylenically unsaturated fatty acids is characterised in that a proportion a of the ethylene moieties of said fatty acid(s) have been di-hydroxylated to form vic diol moieties, a proportion b of said ethylenic moieties remain in the diglyceride or triglyceride and optionally a proportion c of said ethylenic moieties have formed inter- or intramolecular crosslinks, wherein a>c and b>c. The diglycerides or triglycerides may be of the formula: <IMAGE> wherein: Z is H, CO.A-B-D or CO.E where E is a C5-C30alkyl group, A is a C1-C30 alkylene group, B is -CR(OH)-CR(OH)-,-CR=CR-, -CR(L)-CR(OH)-, or -CR(L)-CR(L)- in molar proportions a, b, c1 and c2 respectively wherein each R is independently H or a C1-C6 alkyl group and L is part of an ether linkage to a similar B moiety on the same or a different glyceride moiety, D is H or a C1-C30 hydrocarbyl group, and each A, each B and each D may be the same or different; subject to the provisos that a>c1+c2, b>c1+c2, at least two Z moieties per glyceride are CO>A-B-D and each D moiety having two or more C atoms may optionally include one or more B moieties. Glycerides containing vic diol groupings may be obtained by a process involving the hydroxylation of ethylenically unsaturated glycerides e.g. rapeseed oil with H2O2 in a two-phase aqueous-organic liquid system in the presence of a catalyst comprising a lipophilic onium cation and a peroxo transition metal heteropolyanion, the aqueous phase being acidified with phosphoric acid in a predetermined concentration range (Figure 1). The product can be reacted with diisocyanate to form polyurethanes for cable joint insulation. <IMAGE>

Description

Hyydroxylated diglycerides and triglycerides, method of production thereof and use method in the production of polyurethanes The present invention relates to a method of di-hydroxylating water-insoluble diglycerides and triglycerides of ethylenically unsaturated fatty acids, and also relates to partially unsaturated hydroxylated diglycerides and triglycerides of long-chain ethylenically unsaturated fatty acids, as well as to a method of producing polyurethanes from such glycerides and to electric cable joints insulated with such polyurethanes. Furthermore the invention relates to the use of certain diglycerides and triglycerides as a substitute for castor oil in polymerisation reactions in general.

Polyurethanes for cable joint insulation are currently produced from castor oil and 4,4 diphenylmethane diisocyanate (MDI). Castor oil is a naturally occurring oil whose main component is the triglyceride:

The three hydroxyl groups in the acyl chains react with the diisocyanate to form a relatively rigid crosslinked polyurethane. It is believed that the C=C double bonds in the acyl chains contribute to the rigidity of the polyurethane.

It has been proposed to prepare a substitute for castor oil by transesterifying the cheaper and more readily available rapeseed oil with glycerol. However the product, being composed of diglycerides and triglycerides in which the acyl chains remain unsaturated, forms a very different polyurethane structure from castor oil and is unsatisfactory.

Luong, Schriftman and Swern, Z Amen 017 emzsts Soc. 47 pp 316320 (1967) discloses the di-hydroxylation of oleic in high yield with hydrogen peroxide and tungstic acid. However when Luong et alattempted the di-hydroxylation of olive oil (iodine number 84) with hydrogen peroxide and tungstic acid a nearly fully saturated product was obtained, having an iodine number of 3 and a 1,2 glycol content of only 55%. Olive oil consists mainly of the triglyceride of oleic acid, which is also a major constituent of rapeseed oil. The main side reaction in this process involves the formation of inter-molecular and intra-molecular ether cross-linkages between the acyl chains.Accordingly such a process is considered to be unsatisfactory for di-hydroxylating the ethylenic double bonds of diglycerides and triglycerides.

EP-A-146,374 (which is incorporated herein by reference) discloses a process for the preparation of water-soluble vk diols involving the vigorous agitation of a two-phase aqueous liquid-organic liquid system comprising the corresponding olefin in the organic phase and hydrogen peroxide in the aqueous phase, in the presence of a catalyst comprising a specified lipophilic onium cation and a peroxo tungstate heteropolyanion of formula XW40.4 h, wherein X is P or As and n is 0, 1 or 2. The aqueous phase is acidified to pH 0-3 with e.g. sulphuric, phosphoric or sulphonic acid. Sulphuric acid is stated to be preferred and is utilised in all 7 Examples.When however we attempted to hydroxylate rapeseed oil using the above process, a polymeric product was obtained which appeared to contain inter- and/or intramolecular ether crosslinkages as in the contaminating product of the Luong et aS process (supra). Accordingly neither of the above prior art dihydroxylation processes appear to be applicable to diglycerides or triglycerides.

A novel process has now been found which enables the ethylenic bonds of diglycerides and triglycerides to be dihydroxylated in high yield. The products are considered to be novel.

Accordingly in one aspect the invention provides a partially unsaturated hydroxylated diglyceride or triglyceride of one or more long-chain ethylenically unsaturated fatty acids wherein a proportion a of the ethylenic moieties of said fatty acid(s) have been di-hydroxylated to form vic diol moieties, a proportion b of said ethylenic moieties remain in the diglyceride or triglyceride and optionally a proportion c of said ethylenic moieties have formed inter- or intra-molecular crosslinks, wherein a > c and b > c. A minor proportion of the acyl chains may optionally be saturated The long-chain fatty acid may for example be a CS-C30 fatty acid. The invention encompasses mixtures of such glycerides.

The invention provides a diglyceride or triglyceride of general formula:

wherein: Z is H, CO.A-B-D or CO.E where E is a C5-C30 alkyl group, A is a r Cl-C30 alkylene group, B is -CR(OH)-CR(OH)-, -CR=CR-, -CR(L)-CR(OH)-, or -CR(L)-CR(L)- in molar proportions a, b, cl and c2 respectively, wherein each R is independently H or a Cl-C6 alkyl group and L is part of an ether linkage to a similar B moiety on the same or a different glyceride moiety, D is H or a C-C30 hydrocarbyl group, and each A, each B and each D may be the same or different; subject to the provisos that a > cl+c2, bscl+c2, at least two Z moieties per glyceride are CO.A-B-D and each D moiety having two or more C atoms may optionally include one or more B moieties.

Preferably R is H, A is -(CH2)7 or -(CH2) 1 and D is (CH,)7Me (in which case the triglyceride can be obtained by di-hydroxylating rapeseed oil); or R is H, A is -(CR2)7 and D is CH..B(CH2)4Me, CH2.B.CH2.B.C:H .Me or B.B.(CH2)3Me (corresponding to the dihydroxylated triglycerides of linoleic, linolenic and eleostearic acids respectively). In practice it is preferred to dihydroxylate naturally occurring oils which are mixtures of glycerides of the above acids; in particular soya oil, linseed oil and tung oil as well as rapeseed oil are suitable. The hydroxylated diglyceride or triglyceride preferably contains 2% to 10%, more preferably 3R to 8% by weight hydroxy groups.

Partially dihydroxylated rapeseed oil, which contains a significant proportion of acyl chains of the same length as the acyl chains in castor oil, is a particularly preferred substitute for castor oil and indeed its I.R. spectrum is strikingly similar to that of castor oil. This correlates with a similar chemical behaviour in polymerisation reactions and accordingly it can be used as a castor oil substitute in a variety of polymerisation reactions, including but not limited to polyurethane formation. It can be used in polymerisation reactions involving esterification for example.

In another aspect the invention provides a method of producing a polyurethane comprising reacting a di- or polyisocyanate with a diglyceride or triglyceride as defined by the first aspect of the invention, e.g. in the presence of an organo-tin or amine catalyst. Preferably said di- or polyisocyanate is of formula: X(NCO)n wherein X is a Q-C, hydrocarbyl group (e.g. an alkyl, aryl, alkaryl or aralkyl group) optionally containing one or more -0-, -CO.O-, -NH.CO.NH- or -NH.CO.Olinkages and the mean value of n is in the range 1.5 to 4 (preferably 1.9 to 2.1), X being free of active hydrogen atoms. The most preferred isocyanate is 4,4 diphenylmethane diisocyanate (MDI).

As stated above, the glycerides of the invention can be produced by a novel method.

In another aspect, the invention provides a method of di-hydroxylating some or all of the ethylenic bonds of a water-insoluble diglyceride or triglyceride of an unsaturated fatty acid to form a corresponding water-insoluble vic diol, comprising vigorously agitating a two-phase aqueous liquid-organic liquid system comprising said diglyceride or triglyceride in the organic phase thereof and hydrogen peroxide in the aqueous phase thereof, in the presence of a catalyst system comprising a lipophilic onium cation and a peroxo transition metal heteropolyanion, said aqueous phase being acidified and the major acid component thereof being phosphoric acid. The catalyst may optionally be formed in Preferably said heteropolyanion is a peroxo tungsto-phosphate, tungsto-arsenate, molybdo-phosphate or molybdo-arsenate union.

Preferably rapeseed oil, linseed oil, soya bean oil or tung oil is partially di-hydroxylated to a hydroxy content of 2% to 10% (more preferably 3% to 8%, desirably 4% to 6%) by weight of the product.

Preferably said heteropolyanion is a peroxo tungsto-phosphate or molybdo-phosphate anion and the concentration of phosphoric acid in said aqueous phase is 0.5M to 3M, more preferably 0.75M to 3M in the case of rape or soya bean oil and 0.8M to 1.8M in the case of linseed oil.

The process can be carried out at atmospheric or at elevated pressure.

Preferably the catalyst is formed by oxidising said transition metal with hydrogen peroxide and combining the product with phosphoric or arsenic acid and then a salt of said lipophilic onium cation. Alternatively the catalyst can be formed by combining an oxide (usually the trioxide) of said transition metal with aqueous hydrogen peroxide and combining the product with phosphoric or arsenic acid and then a salt of said lipophilic onium cation.

Preferably said lipophilic onium cation is of general formula [MR43+ wherein M is N, P, As or Sb, R is H or a monovalent hydrocarbyl group of up to 30 carbon atoms, each R being the same or different and the total number of carbon atoms in the R moieties being up to 80.

Preferably the catalyst is present in an amount of 0.5% to 2% by weight relative to the organic phase, which is generally less than the amount taught in the Examples of EP-A-146,374, and the reaction mixture preferably contains less than 20% organic solvent by weight relative to said diglyceride or triglyceride. Normally it will be possible to dispense with solvent. Incidental non-glyceride components of naturally occurring oils which are hydroxylated by the method of the invention are not considered to be a "solvent" in this context. The reaction temperature can be in the range 550C to 1100C (preferably 90 C to 98OC) for example.

In the accompanying drawings: Figure 1 shows two plots of hydroxyl content in products of the invention: phosphoric acid concentration in the reaction mixture in the case of rapeseed oil and linseed oil respectively; Figure 2 is an I.R. spectrum of hydroxylated rapeseed oil in accordance with the invention, and Figure 3 is an I.R. spectrum of castor oil.

Preferred embodiments of the invention are described below with reference to the drawings and the following non-limiting Examples.

Examplel 11.04g tungsten metal powder was mixed with 42ml water at 250C (controlled with a waterbath) and then 90ml 30cwlw hydrogen peroxide (AR) was carefully mixed into the suspension. After the initial reaction had subsided the resulting solution was heated to SO0C to clear, then allowed to cool and made up to 270ml with water and 2.13g 88%wtv phosphoric acid (AR).This solution was then emulsified with a solution of 17.34g acetone-washed dimethyl[dioctadecyl(76%) + dihexadecyl(24%)] ammonium chloride (commercially available as Arquad 2HT-75) in 240ml dichioromethane. The catalyst was recovered from the organic layer of the emulsion by evaporation under vacuum (m.p. 216-220'C with slight decomposition).

The powdered catalyst(0.lg) was mixed with 10g rapeseed oil (low erucic acid). The resulting mixture was then emulsified sequentially with 17ml water, 5g 88% orthophosphoric acid (AR) and 4.4ml 30%ww hydrogen peroxide (AR). The emulsion was stirred continuously and the temperature carefully raised to approximately 100 C (very slow reflux) to complete the reaction within 6 hours. The cooled mixture was allowed to separate and the aqueous phase discarded. The organic phase was washed with water to constant pH, in the presence or absence of dichloromethane and the partially dihydroxylated product was isolated and dried at 800C under vacuum. Yield: 95-100%. Analysis: 4.8% hydroxy content by weight of the product.

Example 2 Linseed oil was processed using an emulsion containing 0. Ig of the catalyst of Example 1, 10g linseed oil, 19.5ml water, 2.5g 88% orthophosphoric acid and 4.4ml 30%w/w hydrogen peroxide. The procedure of Example 1 was repeated and partially dihydroxylated linseed oil was recovered in high yield. Yield: 95-100%.

Analysis: 6.2% hydroxy content.

Example3 Tungsten metal powder (50mg) was mixed with 0.2ml distilled water at 250C (controlled with a waterbath). Hydrogen peroxide (30% w/w Analar, 0.46ml) was carefully mixed into the suspension. After the initial reaction had subsided the temperature was raised to 50 C to give a clear solution. This was cooled to 20 C and 0.4 ml water added, together with 30mg 88% orthophosphoric acid (Analar).

Arquad 75-2HT (as used in Example 1) was washed with acetone to give a dry white powder, then 80mg was dissolved at 400C in Ig rapeseed oil (low erucic acid) and emulsified with the above tungsten solution. The emulsion was mixed sequentially with 10g rapeseed oil, 16ml water, 5g orthophosphoric acid and 4.4ml 30% wlw hydrogen peroxide. The emulsion was stirred continuously and the temperature raised to approximately 1000C (very slow reflux) to complete the reaction within 6 hours. The cooled mixture was allowed to separate and the aqueous layer was discarded. The organic layer was washed with water to constant pH, in either the presence or absence of dichloromethane.Finally the product was isolated and dehydrated under vacuum at 80 C. Analysis: 5.3% hydroxy content.

Example 4 Molybdenum trioxide (52mg) was dissolved at 400C in 0.42ml of 30% wlw hydrogen peroxide, then added to 0.6ml water and 30mg 88% orthophosphoric acid. This solution was substituted for the "tungsten solution" of Example 3 and the procedure of Example 3 repeated. The transmittance I.R. spectrum of the product is shown in Figure 2 and the absorption peak at 3412.8cm-1 (due to OH attached to the acyl chains of the triglyceride) is very similar in shape and position to to the corresponding peak at 33999cm'I in the spectrum of castor oil as shown in Figure 3 demonstrating that the hydroxy content is similar to that of castor oil.

In fact the two spectra are almost identical, demonstrating a) the virtual absence of inter- or intra-molecular ether crosslinkages and b) the similarity of the product to castor oil. Yield: 95-100%. Analysis: 5% hydroxy content.

Example 5 Example l was repeated, using different phosphoric acid concentrations and using the catalyst as described in Example 1 in a proportion of 1% by weight relative to the rapeseed oil and hydrogen peroxide in a proportion of 5% by weight relative to the aqueous phase. The reaction temperature was 950C and the final hydroxyl content was measured by I.R. spectroscopy in each case, after 400 minutes. The results are plotted in Figure la), and it can be seen that the optimum yield occurs at about 1.8M phosphoric acid, although useful results are obtained over a range of 0.75M to 3M.

Example 6 Example 5 was repeated, using linseed oil in place of rapeseed oil. The results are plotted in Figure lb) and it will be seen that the optimum yield occurs at about 1.OM phosphoric acid, although useful results are obtained over the range 0.5M to 2.0M.

Example 7 A three-part cable joint encapsulation kit comprising i) a container containing 164 parts by weight sand (filler), ii) a sachet containing a mixture of 100 parts by weight partially hydroxylated rapeseed oil obtained by a method in accordance with the invention (containing 4.5% by weight hydroxyl groups) and 0.03 parts by weight of dibutyl tin dilaurate catalyst and iii) a sachet containing 45 parts by weight MDI was provided. The hydroxylated rapeseed oil contained about 5 wt.% 4A grade molecular sieve in order to absorb any water present in the oil. The partially hydroxylated rapeseed oil, filler and MDI components were mixed at 20 C and the resulting mixture was immediately poured into an enclosure containing the junction of three 50mm diameter cables. The mixture set rapidly to a semi-rigid polyurethane, forming an encapsulated cable joint.

Claims (23)

1. A partially unsaturated hydroxylated diglyceride or triglyceride of one or more long-chain ethylenically unsaturated fatty acids wherein a proportion a of the ethylenic moieties of said fatty acid(s) have been di-hydroxylated to form vic diol moieties, a proportion b of said ethylenic moieties remain in the diglyceride or triglyceride and optionally a proportion c of said ethylenic moieties have formed inter- or intramolecular crosslinks, wherein a > c and b > c.

2.A diglyceride or triglyceride of general formula:

wherein: Z is H, CO.A-B-D or CO.E where E is a C5-C30 alkyl group, A is a Cl-C30 alkylene group, B is -CR(OH)-CR(OH)-, -CR=CR-, -CR(L)-CR(OH)-, or -CR(L)-CR(L)in molar proportions a, b, ct and c2 respectively, wherein each R is independently H or a C1-C6 alkyl group and L is part of an ether linkage to a similar B moiety on the same or a different glyceride moiety, D is H or a Cl-C30 hydrocarbyl group, and each A, each B and each D may be the same or different; subject to the provisos that a > cl+c2, b > cl+c2, at least two Z moieties per glyceride are CO.A-B-D and each D moiety having two or more C atoms may optionally include one or more B moieties.

3.A diglyceride or triglyceride according to claim 2 wherein A is -(CH2) or -(CH2)11, D is (CH2)7Me, CH2.B(CH2)4Me, CH2.B.CH2.B.CH2Me or B.B.(CH2)3Me and R is H.

4.A diglyceride or triglyceride according to any preceding claim wherein hydroxy groups comprise 2% to 10% by weight thereof.

5.Use as a substitute for castor oil in a polymerisation reaction of a diglyceride or triglyceride as claimed in claim 3 wherein A is -(CH2)7 and D is (CH2)Me.

6.A method of producing a polyurethane comprising reacting a di- or polyisocyanate with a glyceride as claimed in any of claims 1 to 4.

7.A method as claimed in claim 6 wherein said di- or polyisocyanate is of formula: XtNCOn wherein X is a C2-C30 hydrocarbyl group optionally containing one or more -0-, -CO.O-, -NH.CO.NH- or -NH.CO.O- linkages and the mean value of n is in the range 1.5 to 4, X being free of active hydrogen atoms.

8.A method as claimed in claim 7 wherein X(NCO)n is:

9.An electric cable joint having polyurethane electrical insulation which has been produced by a method as claimed in any of claims 6 to 8.

10.A method of di-hydroxylating some or all of the ethylenic bonds of a water-insoluble diglyceride or triglyceride of an unsaturated fatty acid to form a corresponding water-insoluble vic diol, comprising vigorously agitating a two-phase aqueous liquid-organic liquid system comprising said diglyceride or triglyceride in the organic phase thereof and hydrogen peroxide in the aqueous phase thereof, in the presence of a catalyst system comprising a lipophilic onium cation and a peroxo transition metal heteropolyanion, said aqueous phase being acidified and the major acid component thereof being phosphoric acid.

ll.A method as claimed in claim 10 wherein said heteropolyanion is a peroxo tungsto-phosphate, tungsto-arsenate, molybdo-phosphate or molybdo-arsenate amnion.

12.A method as claimed in claim 10 or claim 11 wherein rape oil or linseed oil or soya bean oil is partially hydroxylated to a hydroxy content of 2% to 10% by weight of the product.

13.A method as claimed in claim 12 wherein said heteropolyanion is a peroxo tungsto-phosphate or molybdo-phosphate anion and the concentration of phosphoric acid in said aqueous phase is 0.5M to 3M.

14.A method as claimed in claim 13 wherein rape oil or soya bean oil is partially hydroxylated and said concentration of phosphoric acid is 0.75M to 3M, or linseed oil is partially hydroxylated and said concentration of phosphoric acid is 0.8M to 1.8M.

15.A method as claimed in any of claims 10 to 14 wherein the catalyst is formed by oxidising said transition metal with hydrogen peroxide and combining the product with phosphoric or arsenic acid and then a salt of said lipophilic onium cation.

16.A method as claimed in any of claims 10 to 14 wherein the catalyst is formed by combining the trioxide of said transition metal with aqueous hydrogen peroxide and combining the product with phosphoric or arsenic acid and then a salt of said lipophilic onium cation.

17.A method as claimed in claim 15 or claim 16 wherein the catalyst is formed m situ.

18.A method as claimed in any of claims 10 to 17 wherein said lipophilic onium cation is of general formula [MR4]+ wherein M is N, P, As or Sb, R is H or a monovalent hydrocarbyl group of up to 30 carbon atoms, each R being the same or different and the total number of carbon atoms in R4 being up to 80.

19.A method as claimed in any of claims 10 to 18 wherein the reaction temperature is in the range 55 C to 110 C.

20.A method as claimed in any of claims 10 to 19 wherein the catalyst is present in an amount of 0.5% to 2% by weight relative to the organic phase.

21.A method as claimed in any of claims 10 to 20 wherein the reaction mixture contains less than 20% organic solvent by weight relative to said diglyceride or triglyceride.

22.A method of partially hydroxylating a diglyceride or triglyceride substantially as described hereinabove with reference to any of Examples 1 to 6 or a method of encapsulating a cable joint substantially as described hereinabove with reference to Example 7.

23.A diglyceride or triglyceride as claimed in any of claims 1 to 4 when prepared by a method as claimed in any of claims 10 to 22.