Substituted tartaric acid esters, a process for their production and their use as polymerization initiators

Ethers of 1,2-disubstituted tartaric acid esters proved to be excellent initiators for thermally initiatable radical polymerization reactions. They show a high reactivity even in low concentrations and yield thoroughly hardened products.

This invention relates to new substituted tartaric acid esters, to a 
process for their production from--ketocarboxylic acid esters and 
organohalogen compounds or halogen silanes and to their use as initiators 
for radically initiable polymerization reactions. 
On account of the known dangers of polymerization initiators containing 
peroxide groups, 1,1,2,2-tetraaryl-1,2-dihydroxyethanes, their alkyl and 
silyl ethers have already been proposed as initiators for thermally 
initiatable radical polymerization reactions (German Auslegeschrifts Nos. 
1,216,877 and 1,219,224, German Auslegeschrifts Nos. 2,131,623 and 
2,164,482). Other known initiators include 
1,2-diaryl-1,2-dicyano-1,2-dihalogen ethanes (German Offenlegungsschrift 
No. 2,444,252), 1,2-diaryl-1,1,2,2-tetracarbalkoxy ethanes (U.S. Patent 
No. 3,896,099) and 1,2-diaryl-1,1,2,2-tetramethyl ethanes containing 
partially chlorinated methyl groups (Belgian Patent No. 834,599). It is 
also known that silyl ethers of oligomers containing recurring units with 
the following structure: 
##STR1## 
in which R represents phenyl or alkyl, can be used for initiating 
polymerization reactions, in some cases even at temperatures just above 
40.degree. C. (German Offenlegungsschrifts Nos. 2,632,294 and 2,656,782). 
There is a need for peroxide-group-free initiators which are stable in 
storage at room temperature in the compounds or mixtures to be 
polymerized, show greater reactivity at elevated temperatures than the 
known peroxide-free initiators in as low a concentration as possible in 
the polymerizable system, and give thoroughly hardened products (as 
determined by measuring the residual styrene content). 
It has now surprisingly been found that the ethers of substituted tartaric 
esters defined hereinafter satisfy these requirements. In addition, they 
have the advantage that, on decomposing into radicals, they do not release 
any volatile fractions which could give rise to undesirable bubble 
formation in the polymer. 
Accordingly, the present invention provides ethers of 1,2-disubstituted 
tartaric acid esters corresponding to the following formula (II): 
##STR2## 
in which R.sup.1 and R.sup.2, which may be the same or different, 
represent linear or branched C.sub.1 -C.sub.10 alkyl radicals optionally 
substituted by methoxy, chlorine or fluorine, preferably methyl, ethyl, 
isopropyl, t-butyl, isobutyl, n-butyl, hexyl or octyl; C.sub.5 -C.sub.7 
cycloalkyl radicals optionally substituted by C.sub.1 -C.sub.4 alkyl, 
methoxy, chlorine or fluorine, preferably cyclopentyl or cyclohexyl; 
C.sub.7 -C.sub.10 aralkyl radicals optionally substituted by C.sub.1 
-C.sub.4 alkyl, methoxy, chlorine or fluorine, preferably benzyl; C.sub.6 
-C.sub.12 aryl radicals optionally substituted by C.sub.1 -C.sub.4 alkyl, 
methoxy, chlorine or fluorine, preferably phenyl, tolyl, chlorophenyl, 
dichlorophenyl, naphthyl, biphenylyl or t-butyl phenyl, 
R.sup.3 and R.sup.4, which may be the same or different, represent linear 
or branched C.sub.1 -C.sub.18 alkyl radicals optionally substituted by 
methoxy, chlorine or fluorine, preferably methyl, ethyl, isopropyl, butyl, 
hexyl, octyl, lauryl or stearyl; C.sub.5 -C.sub.7 cycloalkyl radicals 
optionally substituted by C.sub.1 -C.sub.4 alkyl, methoxy, chlorine or 
fluorine, preferably cyclohexyl; C.sub.7 -C.sub.10 aralkyl radicals 
optionally substituted by C.sub.1 -C.sub.4 alkyl, methoxy, chlorine or 
fluorine, preferably benzyl or .beta.-phenyl ethyl; C.sub.6 -C.sub.10 aryl 
radicals optionally substituted by C.sub.1 -C.sub.4 alkyl, methoxy, 
chlorine or fluorine, preferably phenyl, tolyl, chlorophenyl or naphthyl; 
or triorganosilyl radicals containing from 3 to 18 carbon atoms, 
preferably trimethyl silyl, triethyl silyl and triphenyl silyl, 
R.sup.5 and R.sup.6, which may be the same or different, represent 
(1) a hydrogen atom with the proviso that at most one of the two 
substituents is a hydrogen atom; 
(2) C.sub.1 -C.sub.10 alkyl radicals optionally substituted by methoxy, 
chlorine or fluorine, preferably methyl, ethyl, isopropyl, isobutyl, hexyl 
or octyl; C.sub.5 -C.sub.7 cycloalkyl radicals optionally substituted by 
C.sub.1 -C.sub.4 alkyl, methoxy, chlorine or fluorine, preferably 
cyclohexyl; C.sub.7 -C.sub.10 aralkyl radicals optionally substituted by 
C.sub.1 -C.sub.4 alkyl, methoxy, chlorine or fluorine, preferably benzyl 
or .beta.-phenyl ethyl; or 
(3) SiR.sup.7 R.sup.8 (O.sub.n SiR.sup.9 R.sup.10).sub.m R.sup.11 and 
R.sup.7, R.sup.8, R.sup.11, which may be the same or different, represent 
(a) methyl, ethyl, phenyl, benzyl, chloromethyl, hydroxyl, methoxy or 
ethoxy, or 
(b) a radical corresponding to the following formula: 
##STR3## 
R.sup.9 and R.sup.10, which may be the same or different, are as defined 
in (3a), and 
n=0 or 1, 
m=0 or an integer of from 1 to 10; in which the compounds of formula (II) 
in case (3) may contain the component structure: 
##STR4## 
attached through silicon atoms or groups containing silicon atoms from 1 
to 10 times and, in the SiR.sup.7 R.sup.8 (O.sub.n SiR.sup.9 
R.sup.10).sub.m R.sup.11 -radicals, where they function as terminal 
groups, the substituents R.sup.7, R.sup.8 and R.sup.11 may have the 
meanings defined in (3a). 
The compounds according to the invention may be obtained by reacting the 
.alpha.-ketoesters (VI) and (VII): 
##STR5## 
and the corresponding halogen compound in the presence of a substantially 
equivalent quantity of a base metal in an inert aprotic solvent. 
Accordingly, the present invention also provides a process for producing 
the compounds corresponding to formula (II), characterized in that 0.5 
mole of each of the following .alpha.-ketoesters (VI and (VII): 
##STR6## 
is reacted in the presence of a substantially equivalent quantity of a 
base metal with from 0.4 to 1.2 moles, preferably from 0.5 to 1.1 moles, 
of an organohalogen compound (VIII) or (IX): 
EQU R.sup.5 X (VIII) 
EQU R.sup.6 X (IX) 
in which X represents chlorine, bromine or iodine and R.sup.5 and R.sup.6 
are as defined in (2) above, 
or with 
from 0.4 to 1.2 moles, preferably from 0.5 to 1.1 moles, of a 
monochloro-organosilane, disilane or polysilane, disiloxane or 
polysiloxane corresponding to the following formula (X): 
EQU ClSiR.sup.7 R.sup.8 (O.sub.n SiR.sup.9 R.sup.10).sub.m R.sup.11 (X) 
or with 
from 0.3 to 0.8 mole, preferably from 0.4 to 0.6 mole of a 
dichloro-organosilane, disilane or polysilane, disiloxane or polysiloxane 
corresponding to the following formula (XI): 
EQU Cl.sub.2 SiR.sup.7 (O.sub.n SiR.sup.9 R.sup.10).sub.m R.sup.11 (XI) 
or with 
from 0.2 to 0.6 mole, preferably from 0.2 to 0.4 mole, of a 
trichloro-organosilane, disilane or polysilane, disiloxane or polysiloxane 
corresponding to the following formula (XII): 
EQU Cl.sub.3 Si(O.sub.n SiR.sup.9 R.sup.10).sub.m R.sup.11 (XII) 
in which the substituents in formulae (X) to (XII) are each as defined in 
(3a) above and the indices are as 
defined above, or with 
from 0.1 to 0.7 mole, preferably from 0.2 to 0.5 mole, of 
tetrachlorosilane, 
in an inert aprotic solvent until the exothermic reaction is over, the 
resulting reaction product is hydrolysed, the organic phase is separated 
off and the solvent is distilled off. 
The present invention also relates to the use of the compounds of formula 
(II) according to the invention as initiators for radically initiatable 
polymerization reactions. 
In the context of the invention, "base metals" are metals which are capable 
of forming the dianions (XIII): 
##STR7## 
from the .alpha.-ketoesters (VI) and (VII); they are preferably members of 
the First Main Group, Second Main and Subsidiary Group and Third Main 
Group of the Periodic System (U. Hofmann and W. Rudorff, Anorganische 
Chemie, 16th Edition, Friedr. Vieweg & Sohn, Braunschweig, 1966, page 
150). Typical representatives of base metals suitable for use in the 
process according to the invention are lithium, sodium, magnesium, 
calcium, zinc and aluminium. 
The expression "substantially equivalent quantitites" of a base metal means 
that approximately 1 mole of a monovalent metal, approximately 0.5 mole of 
a divalent metal or approximately 1/3 mole of a trivalent metal is used 
per mole of the .alpha.-ketoester (VI) or (VII). 
The compounds VI and VII may be identical, i.e. R.sup.1 =R.sup.2 and 
R.sup.3 =R.sup.4. 
In general, the reaction may be carried out at temperatures of from 
-10.degree. to +70.degree. C. and preferably at temperatures of from 
-5.degree. to +50.degree. C., if necessary with cooling. 
The solvent is generally distilled off at temperatures of from 0.degree. to 
120.degree. C. and preferably at temperatures of from 20.degree. to 
60.degree. C. under a pressure of from 1 to 760 and preferably from 10 to 
200 Torr. 
The compounds (II) according to the invention produced from ketoesters, 
base metals and chloro-silanes, -disilanes, or -polysilanes, -disiloxanes 
or -polysiloxanes may have a molecular weight, determined as a number 
average, of from 500 to 6000 and preferably from 800 to 4000. 
The molecular weight of the silyl ethers (II) according to the invention is 
determined by vapour pressure osmometry up to a molecular weight of 3000 
and by membrane osmometry for molecular weights above 3000, in each case 
using acetone as a solvent. The molecular weights of the individual 
fractions of the reaction mixtures according to the invention may be 
determined by gel chromatography (using standard substances). 
The reaction mixtures obtained during production, which in case (3) contain 
oligomers of different molecular weight, are normally directly used as 
polymerization initiators, i.e. they do not have to be separated into the 
pure substances. 
The combinations listed in the following Table represent preferred examples 
of the base metals, .alpha.-ketoesters and organohalogen compounds of 
chloro-silanes, di- or poly-sil(ox)anes which may be used in accordance 
with the invention: 
TABLE 1 
______________________________________ 
Initi- .alpha.-ketocarboxylic 
Halogen Com- 
ator Base metal acid ester pound 
______________________________________ 
1. magnesium phenylglyoxylic 
metal iodide 
acid methyl ester 
2. magnesium phenylglyoxylic 
isopropyl 
acid methyl ester 
bromide 
3. lithium phenylglyoxylic 
benzyl chloride 
acid methyl ester 
4. lithium phenylglyoxylic 
cyclohexyl 
acid methyl ester 
bromide 
5. magnesium t-butyl glyoxylic 
benzyl chloride 
acid ethyl ester 
6. magnesium pyruvic acid ethyl 
hexyl bromide 
ester 
7. magnesium phenylglyoxylic 
chlorotrimethyl 
acid methyl ester 
silane 
8. magnesium phenylglyoxylic 
dichlorodi- 
acid methyl ester 
methyl silane 
9. magnesium phenylglyoxylic 
trichloro- 
acid methyl ester 
methyl silane 
10. magnesium phenylglyoxylic 
tetrachloro- 
acid methyl ester 
silane 
11. lithium phenylglyoxylic 
diphenyl di- 
acid methyl ester 
chloro silane 
12. lithium phenylglyoxylic 
dichlorodi- 
acid hexyl ester 
methyl silane 
13. calcium phenylglyoxylic 
trichloro- 
acid hexyl ester 
methyl silane 
14. magnesium 4-methylphenyl 
trichloro- 
glyoxylic acid 
methyl silane 
methyl ester 
15. magnesium 4-chlorophenyl 
dichlorodi- 
glyoxylic acid 
methyl silane 
hexyl ester 
16. magnesium phenylglyoxylic 
chlorotri- 
acid lauryl ester 
ethyl silane 
17. aluminium 4-biphenylyl gly- 
tetrachloro- 
oxylic acid ethyl 
silane 
ester 
18. sodium phenylglyoxylic 
chlorotrimethyl 
acid methyl ester 
silane 
19. magnesium pyruvic acid ethyl 
chlorotrimethyl 
ester silane 
20. magnesium pyruvic acid ethyl 
tetrachloro- 
ester silane 
21. magnesium t-butyl glyoxylic 
chlorotriethyl 
acid hexyl ester 
silane 
22. magnesium t-butyl glyoxylic 
trichloro- 
acid hexyl ester 
methyl silane 
23. magnesium cyclohexyl gly- 
chlorotri- 
oxylic acid hexyl 
methyl silane 
ester 
24. magnesium sec-butyl gly- 
trichloro- 
oxylic acid hexyl 
methyl silane 
ester 
25. magnesium n-hexyl glyoxylic 
chlorotri- 
acid methyl ester 
methyl silane 
26. magnesium isopropyl glyoxy- 
dichlorodi- 
lic acid benzyl 
phenyl silane 
ester 
27. magnesium phenyl glyoxylic 
trichloro- 
acid-(octaethylene 
methyl silane 
glycol)-ester 
28. magnesium phenyl glyoxylic 
trichloro- 
acid-(trimethyol 
methyl silane 
propane)-ester, 
etherified with 
4 moles of 
ethylene oxide 
______________________________________ 
Preferred inert aprotic solvents are aromatic and alkyl aromatic compounds, 
such as benzene and toluene; ethers such as diethyl ether, diisopropyl 
ether, dibutyl ether, anisole, tetrahydrofuran, dioxane or 1,2-dimethoxy 
ethane; trialkyl phosphates such as triethyl phosphate or tributyl 
phosphate; N,N-disubstituted amides such as dimethyl formamide, 
N,N'-dimethyl acetamide and phosphoric acid-tris-(dimethyl amide). Other 
suitable inert aprotic solvents are described in "Methoden der Organischen 
Chemie" (Houben-Weyl), Vol. XIII/2a, pages 59-70, Georgh Thieme-Verlag, 
Stuttgart, 1973. Solvents which have proved to be particularly suitable 
consist of from 0 to 80 parts by weight of benzene or toluene, from 1 to 
100 parts by weight of tetrahydrofuran of from 0 to 50 parts by weight of 
triethyl phosphate or phosphoric acid-tris-(dimethyl amide). In order not 
unnecessarily to dilute the reaction mixture, as little solvent as 
possible is generally used. In most cases, a ratio by weight of ketoester 
to solvent of 1:2 is entirely adequate. 
It is advisable to bear in mind that partial decomposition is actually 
possible under the reaction conditions. If, therefore, the compounds (II) 
according to the invention should show low reactivity attributable to 
decomposition of the compounds used as initiators during production, the 
reaction temperature will be reduced. 
The dissociation temperature of the compounds (II) according to the 
invention may be determined by a simple colour reaction. This is because 
the radicals which are formed during thermal decomposition are capable of 
declouring quinoid dyes. To carry out the test, a small quantity of 
quinoid dye, for example methylene blue, thionine or neutral red, is 
dissolved in a solvent which is free from molecular oxygen, for example 
glycol or xylene, and an at least equivalent quantity of the compound (II) 
according to the invention is added to the resulting solution. The 
temperature at which the dye is decoloured is the dissociation temperature 
of the initiator. 
The dissociation temperature is governed to a large extent by the structure 
of the compounds (II). Initiators containing space-filling radicals 
R.sup.1 and R.sup.2 (for example aryl or t-butyl) are distinguished by a 
relatively low dissociation temperature. Initiators in which the 
substituents R.sup.1 and R.sup.2 represent primary or secondary alkyl or 
aralkyl groups only decompose into radicals at relatively high 
temperatures. In addition, however, the other substituents are also of 
importance so far as the tendency of the compounds (II) according to the 
invention towards dissociation is concerned. 
In contrast to peroxides, the compounds or mixtures according to the 
invention decompose without giving off any heat. In addition, in the 
presence of peroxides, the products according to the invention do not lead 
to induced decomposition of the peroxide. Accordingly, they are also 
suitable for subsequently tempering cold-hardened mouldings of unsaturated 
polyester resins and for desensitizing peroxidic initiators. 
Compounds whose polymerization may be initiated by the compounds (II) 
according to the invention include any radically polymerizable compounds 
or mixtures thereof, i.e. for example olefins, such as ethylene; 
conjugated dienes, such as butadiene, isoprene or chloroprene; vinyl 
chloride; vinylidene chloride; aromatic vinyl compounds, such as styrene 
or divinyl benzene; vinyl esters, particularly vinyl acetate and vinyl 
propionate; vinyl ethers, such as vinyl propyl ether or vinyl isobutyl 
ether; acrylic acid and methacrylic acid and derivatives thereof, such as 
esters, particularly with aliphatic alcohols containing from 1 to 5 carbon 
atoms, nitriles, amides, etc.; di(vinylphenyl)-carbonates: diallyl 
phthalate, diallyl carbonate, diallyl furmarate: 
di(allylphenyl)carbonates; polyol poly(meth)acrylates; and 
N,N'-methylene-bis-(methy)acrylamide. 
Particularly preferred substances to the polymerized are unsaturated 
polyester resins, i.e. solutions of .alpha.,.beta.-ethylenically 
unsaturated polyesters in monomers copolymerizable therewith. 
Investigation of the unsaturated polyester resins thermally hardened with 
the compounds (II) according to the invention surprisingly shows that the 
residual styrene contents are lower than where comparable known initiators 
of the dibenzyl type are used. 
Preferred .alpha.,.beta.-ethylenically unsaturated polyesters are the usual 
polycondensation products of at least one .alpha.,.beta.-ethylenically 
unsaturated dicarboxylic acid generally containing 4 or 5 carbon atoms or 
ester-forming derivatives thereof, for example anhydrides, optionally in 
admixture with up to 200 mole percent, based on the unsaturated acid 
components, of at least one aliphatic saturated C.sub.4 -C.sub.10 or 
cycloaliphatic or aromatic C.sub.8 -C.sub.10 dicarboxylic acid or 
ester-forming derivatives thereof, with at least one polyhydroxy compound 
particularly dihydroxy compound, containing from 2 to 8 carbon atoms, i.e. 
polyesters of the type described in the book by J. Bjorksten et al 
entitled "Polyesters and their Applications," Rheinhold Publishing Corp., 
New York, 1956. 
Examples of preferred unsaturated dicarboxylic acids or their derivatives 
are maleic acid or maleic acid anhydride and fumaric acid. However, it is 
also possible to use for example mesaconic acid, citraconic acid, itaconic 
acid or chloromaleic acid. Examples of the aliphatic saturated and 
cycloaliphatic or aromatic dicarboxylic acids or their derivatives which 
may be used in accordance with the invention are phthalic acid or phthalic 
acid anhydride, isophthalic acid, terephthalic acid, hexahydro or 
tetrahydrophthalic acid or their anhydrides, endomethylene 
tetrahydrophthalic acid or its anhydride, succinic acid or succinic acid 
anhydride and succinic acid esters and chlorides, adipic acid and sebacic 
acid. In order to produce flame-resistant resins, it is possible to use 
for example hexachloroendomethylene tetrahydrophthalic acid, 
tetrachlorophthalic acid or tetrabromophthalic acid. Suitable dihydric 
alcohols include ethylene glycol, 1,2-propane diol, 1,3-propane diol, 
diethylene glycol, dipropylene glycol, 1,3-butane diol, 1,4-butane diol, 
neopentyl glycol, 1,6-hexane diol, 2,2-bis-(4-hydroxy cyclohexyl)-propane, 
bis-alkoxylated bisphenol A, perhydro bisphenol and others. It is 
preferred to use ethylene glycol, 1,2-propane diol, diethylene glycol and 
dipropylene glycol. 
Further modifications are possible through the incorporation of monohydric, 
trihydric and tetrahydric alcohols containing from 1 to 6 carbon atoms, 
such as methanol, ethanol, butanol, allyl alcohol, benzyl alcohol, 
cyclohexanol and tetrahydrofurfuryl alcohol, trimethylol propane, glycerol 
and pentaerythritol, by the incorporation of mono-, di- and tri-allyl 
ethers and benzyl ethers of trihydric and higher alcohols containing from 
3 to 6 carbon atoms according to German Auslegeschrift No. 1,024,654 and 
by the incorporation of monobasic acids, such as benzoic acid, or 
long-chain unsaturated fatty acids, such as oleic acid, linseed oil fatty 
acid and ricinene fatty acid. 
The polyesters have acid numbers of generally from 1 to 100 and preferably 
from 20 to 70, OH numbers of from 10 to 150 and preferably from 20 to 100 
and molecular weights M.sub.n, determined as number averages, of from 
about 500 to 5000 and preferably from about 1000 to 3000 (as measured by 
vapour pressure osmometry in dioxane and acetone; in the case of differing 
values, the lower value is regarded as the correct value). 
Suitable vinyl and vinylidene compounds copolymerizable with the 
unsaturated polyesters are the unsaturated compounds commonly encountered 
in polyester technology which preferably contain .alpha.-substituted vinyl 
groups or .beta.-substituted allyl groups, preferably styrene. However, it 
is also possible for example to use nucleus-chlorinated and 
nucleus-alkylated or -alkenylated styrenes, in which case the alkyl groups 
may contain from 1 to 4 carbon atoms, for example vinyl toluene, divinyl 
benzene, .alpha.-methyl styrene, t-butyl styrene or chlorostryrenes; vinyl 
esters of carboxylic acids containing from 2 to 6 carbon atoms, preferably 
vinyl acetate; vinyl pyridine, vinyl naphthalene, vinyl cyclohexane, 
acrylic acid and methacrylic acid and/or their esters (preferably vinyl, 
allyl and methallyl esters) containing from 1 to 4 carbon atoms in the 
alcohol component, their amides and nitriles, maleic acid anhydrides, 
semiesters and diesters containing from 1 to 4 carbon atoms in the alcohol 
component, semiamides and diamides or cyclic imides, such as N-methyl 
maleic imide or N-cyclohexyl maleic imide; allyl compounds, such as allyl 
benzene, and allyl esters, such as allyl acetate, phthalic acid diallyl 
ester, isophthalic acid diallyl ester, fumaric acid diallyl ester, allyl 
carbonates, diallyl carbonates, triallyl phosphate and triallyl cyanurate. 
Some of the compounds (II) according to the invention are active even at 
temperatures above 400.degree. C. Complete and rapid hardening is 
generally obtained with from 0.2 to 1% by weight and preferably with from 
0.05 to 0.8% by weight of the compounds (II) according to the invention, 
based on the substance to be polymerized. 
The polymerization reaction is started by heating a mixture of the 
substance to be polymerized and the compounds (II) according to the 
invention above a particular starting temperature which may readily be 
determined in each individual case. Radically polymerizable systems are 
generally hardened at temperatures of from 60.degree. to 200.degree. C. 
Hardening may be carried out in a single operation, although if desired it 
may even be carried out in stages (cf. British Pat. No. 1,041,641).

The invention is illustrated by the following Examples in which the parts 
quoted represent parts by weight and the percentages are by weight. 
EXAMPLE 1 
0.1 g of HgCl.sub.2, 12.2 g of magnesium chips and 20 g of phenyl glyoxylic 
acid methyl ester are introduced into a solvent mixture of 100 g of 
toluene and 500 g of tetrahydrofuran. A mixture of 144 g of phenyl 
glyoxylic acid methyl ester and 125 g of isopropyl bromide is then slowly 
added dropwise at a temperature of from +5.degree. to +30.degree. C. After 
a short time, the highly exothermic reaction begins and the magnesium 
dissolves as more of the isopropyl bromide-containing solution is added. 
On completion of the reaction, the reaction mixture is stirred for 5 hours 
at 30.degree. C., cooled to +5.degree. C., carefully hydrolysed with 200 
ml of water and acidified with 10 ml of 18% hydrochloric acid. The organic 
phase is diluted with 300 ml of toluene, subsequently separated off and 
washed three times with water. Removal of the solvent by distillation 
leaves 150 g of a residue of which, according to analysis by NMR 
spectroscopy, approximately 25 mole percent consists of 
1,2-diphenyl-1,2-diisopropoxy succinic acid dimethyl ester, approximately 
45 mole percent of 1,2-diphenyl-1-hydroxy-2-isopropoxy succinic acid 
dimethyl ester and 30 mole percent of 1,2-diphenyl tartaric acid dimethyl 
ester. 
EXAMPLE 2 
The procedure was as in Example 1, except that methyl iodide (140 g) was 
added instead od the isopropyl bromide. Yield: 148 g, of which 
approximately 30 mole percent consists of 1,2-diphenyl-1,2-dimethoxy 
succinic acid dimethyl ester, 40 mole percent of 
1,2-diphenyl-1-hydroxy-2-methoxy succinic acid dimethyl ester and 30 mole 
percent of 1,2-diphenyl tartaric acid dimethyl ester. 
EXAMPLE 3 
The procedure was as in Example 1, except that all the phenyl glyoxylic 
acid methyl ester was initially introduced and trimethyl chlorosilane (115 
g) was added dropwise instead of the isopropyl bromide. Yield: 160 g, 
Si-content: 6.2% Composition (as determined by NMR-spectroscopy): 
35 mole percent of 1,2-diphenyl-1,2-bis-(trimethyl siloxy)-succinic acid 
dimethyl ester, 
35 mole percent of 1,2-diphenyl-1-hydroxy-2-trimethyl siloxy succinic acid 
dimethyl ester, 
30 mole percent of 1,2-diphenyl tartaric acid dimethyl ester. 
EXAMPLE 4 
24.3 g of magnesium and 328 g of phenyl glyoxylic acid methyl ester are 
initially introduced into a solvent mixture of 500 g of toluene, 100 g of 
phosphoric acid tris-(dimethyl amide) and 50 g of tetrahydrofuran, 15 g of 
trichloromethyl silane are added at a temperature of from 15.degree. to 
30.degree. C. After the reaction has started (exothermic reaction), 
another 95 g of trichloromethyl silane are added dropwise at 25.degree. to 
35.degree. C. The magnesium dissolves completely. On completion of the 
reaction, the solution is stirred for 4 hours at 30.degree. C., cooled to 
just 5.degree. C. and hydrolyzed with 600 ml of water. During hydrolysis 
the temperature should not exceed +20.degree. C. After stirring for 
another 2 hours at 30.degree. C., the organic phase is separated off, 
washed three times with 400 ml of water and concentrated in a water jet 
vacuum at 30.degree. C., leaving as residue a highly viscous liquid which 
quickly hardens to form a wax-like solid. 
Gel chromatography was carried out with a low-molecular-separating column 
combination filled with Styragel in different pore widths (Waters 
measuring technique); tetrahydrofuran was used as eluent. Calibration was 
carried out with phenyl glyoxylic acid methyl ester. Correlated therewith, 
the following molecular weight distribution is obtained: 
______________________________________ 
Component Molecular weight 
Percentage area 
______________________________________ 
1 164 2.2 
2 330 3.0 
3 400 4.6 
4 480 2.4 
5 700 12.0 
6 800 14.8 
7 1240 34.6 
8 1900 20.3 
9 2200 6.1 
______________________________________ 
EXAMPLE 5 
The procedure is as in Example 4, except that t-butyl glyoxylic acid hexyl 
ester (428 g) is used instead of the phenyl glyoxylic acid methyl ester. 
Working up leaves an oily product which, according to gel chromatography, 
has the following molecular weight distribution: 
______________________________________ 
Component Molecular weight 
Percentage area 
______________________________________ 
1 154 5.5 
2 310 4.2 
3 380 2.7 
4 700 14.4 
5 840 16.0 
6 1200 24.8 
7 1840 14.0 
8 2320 13.7 
9 3000 4.7 
______________________________________ 
EXAMPLE 6 
6 g of sodium in filament form are introduced under pressure into a solvent 
mixture of 250 ml of absolute tetrahydrofuran and 50 ml of triethyl 
phosphate. A solution of 68 g of 4-chlorophenyl glyoxylic acid hexyl ester 
and 18 g of dichlorodimethyl silane in 50 ml of absolute tetrahydrofuran 
is then added dropwise at -5.degree. to 10.degree. C. When all the sodium 
has dissolved, the mixture is stirred for 3 hours and then hydrolyzed with 
300 g of ice. After repeated washing with iced water, the organic phase is 
concentrated in a water jet vacuum at 15.degree. C. 
Removal of the solvent by distillation leaves 101 g of a liquid residue, of 
which approximately 35% by weight consists of triethyl phosphate. 
EXAMPLE 7 
An unsaturated polyester, producted from 11 parts of phthalic acid 
anhydride, 47 parts of maleic acid anhydride and 42 parts of 1,2-propylene 
glycol at 200.degree. C. (acid number 20, OH-number 30, viscosity at 
23.degree. C.: 1500 cP), is dissolved to form a 66% solution in styrene 
and stabilized with 0.01 part of hydroquinone. 1 part of compound (II) 
(cf. pages 10,11) of benzpinacol is dissolved in 100 parts of this 
unsaturated polyester resin. 
1 hour after addition of the initiator, 20 g of a resin mixture are 
introduced into a 16 mm diameter test tube. An iron/constantan 
thermocouple connected to a temperature-time recorder is immersed to a 
depth of 3 cm in the resin and, after the measureing apparatus has been 
switched on, the test tube which is filled to a level of 8 cm is placed in 
a boiling water bath. The hardening time t.sub.H (time taken to reach the 
peak temperature minus the time taken to pass the 65.degree. C. line) and 
the peak temperature (T.sub.m) are determined in accordance with DIN 16 
945. 
The residual styrene contents were iodometrically analysed by the process 
described by B. Alt in Kunststoffe 52, 133 (1962). 
______________________________________ 
Initiator 
t.sub.H (min.) 
T.sub.m (.degree.C.) 
Residual styrene content (%) 
______________________________________ 
1 5.2 230 0.35 
5 9.8 215 0.32 
7 4.8 230 0.28 
9 4.8 230 0.30 
14 4.9 230 0.30 
21 8.7 210 0.45 
23 10.4 190 0.60 
benzpinacol 
11.0 205 0.70 
______________________________________ 
(COMISON TEST) 
EXAMPLE 8 
The procedure was as in Example 7, except that an oil bath thermostatically 
regulated to 140.degree. C. was used as the heating bath. 
______________________________________ 
Initiator t.sub.H (min.) 
T.sub.m (.degree.C.) 
______________________________________ 
6 14.5 210 
19 13.0 225 
23 5.0 250 
24 8.2 240 
______________________________________ 
EXAMPLE 9 
0.2 g of a compound (II) according to the invention is added to 150 g of a 
40% solution of styrene in 1,2-dichloroethane. 
Each sample is boiled under reflux for 4 hours, followed by the addition of 
0.5 ml of a 1% solution of benzoquinone in ethyl acetate. The product is 
then concentrated in a rotary evaporator at a bath temperature of 
35.degree. C. The bath temperature is slowly increased to 60.degree. C. at 
14 Torr and then kept for 4 hours at 95.degree. C. Any residual monomers 
still present are removed by tempering the polymer in a vacuum drying 
cabinet at 140.degree. C. until it is constant in weight. The polystyrene 
left as residue is weighed out. 
The following initiators of the examples given in Table 1 were 
investigated: 
______________________________________ 
Conversion (% of the 
Initiator Polystyrene 
theoretical) 
______________________________________ 
-- 0.2 0.3 
2 14.1 23 
5 7.0 12 
7 16.4 27 
9 13.2 22 
15 14.4 24 
21 6.9 12 
26 3.2 5 
______________________________________ 
EXAMPLE 10 
A 2000 ml stirrer-equipped autoclave was filled with 1 liter of heptane and 
1 g of compound (II) (initiators 12 and 16, see Table 1). The solution was 
purged with nitrogen, after which 430 g of ethylene were introduced under 
pressure at room temperature. The autoclave was slowly heated to 
130.degree. C. The internal pressure initially rose to 450 bars, but fell 
back to 300 and 280 bars over a period of 60 minutes. The autoclave was 
then left for 2 hours at 130.degree. C., cooled and vented. After the 
reactor had been opened, the ethylene polymer was removed with the heptane 
solution, filtered, washed and dried at 50.degree. C. until constant in 
weight. 
In the case of initiator 12, 180 g of polymer melting at 110.degree. to 
113.degree. C. were obtained. In the case of initiator 16, 164 g of 
polymer melting at 110.degree. to 114.degree. C. were obtained.