CA1081243A - Process for the preparation of organotin dihalides, and the organotin stabilizers derived therefrom - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE
Organotin compounds of the formula (R)2SnX2, wherein R represents the group

Description

.- ~
~8~3 This application is a divisional ap~lication of copending application No. 247,97S, filed March 16, 1976.
This invention relates to a process for preparing organotin halides starting from metallic tin, and to compounds derived from the organotin halides.
The compounds derived from organotin dihalides pro-duced in accordance with the present invention are suitable for use as stabilizers for polymers such as polyvinyl chloride.
Thus, organotin halides are impor~ant intermediates in the preparation of organotin stabilizers for polymers.
Presently available commercial methods for the prepar-ation of such halides often make use of the Grignard-, the alum-; inium alkyl-, or the Wurtz method, tin chloride being converted into tetraalkyl tin which is subsequently converted into an alkyl :~ tin halide. However, such methods are relatively expensive and, moreover, present some hazard to the people carrying them out.
Another known method, which is less dangerous and elaborate includes the step of reacting tin directly with an alkyl halide to form an alkyl tin halide. Such method is describ-ed, for example, in Metherlands Patent No. 144,283. Such direct route, however, is unattractive from a commercial point of view in that it calls for the use of catalysts at a relatively high temperature and leads to considerable lossses of tin as a result of the formation of by-products.
It has been found that the above-mentioned disadvan-tages may be avoided if, in accordance with the invention of copending application No. 247,975, metallic tin is allowed to react with a hydrogen halide and an olefin of the formula~
~ ., C - C\
.. , R2 R2 , ~l .,' , ~ , . .. .
.
- ' ~'. . '- , ' lZ~L3 wherein Rl, R2, R3 and R4 each represents hydrogen or a hydro-carbon group, provided that at least one of Rl and R2 is an oxygen-containing group, with a carbonyl group adjacent to the olefinic double bond, to form an organotin dihalide of the formula:

C / 1 - Sn Hal2 ~2 12 The reaction between metallic tin, a hydrogen halide and an olefin activated by one or more carbonyl groups gives a high yield, calculated on the basis of the tin, even under normal conditions of temperature and pressure and without the use of a catalyst.
It is preferred that relatively inexpensive hydrogen chloride be used as the hydrogen halide.
The activating carbonyl radical in the olefin may form part of, for example, an acid group, an ester group, an aldehyde group or a keto group. Sultable olefins include:
acrylic acid acryloyl chloride methyl acrylate l,l bis~carboxy ethyl) propylene methyl crotonate methyl vinyl ketone methyl 2-cyclohexyl acrylate mesithyl oxide cinnamic acid - methyl styryl ketone cinnamic methyl ester Accordingly, the process of the invention of copending application No. 247,975 is preferably performed using an olefin, wherein at least one of Rl and R2 is an oxygen-containing group ~;
having the formula: 0 -R5 ~

: 1 :

wherein R5 is hydrogen, hydroxyl, halogen, amino or alkyl, sub-stituted alkyl or alkoxy containing 1 - 18 carbon atoms.
The reaction optionally may be carried out in a solvent.
Suitable solvents include ethers, alcohols, ester~ and chlorin-ated or non-chlorinated hydrocarbons~ An excess of olefin may be used as the solvent.
The metallic tin may be used in any form. It is in principle preferable to use powdered tin because of its increased reaction rate as a result of the large available tin surface.
Direct use may, however, also be made of commercially available granulated tin. In the later case, a moderate increase in re-action temperature is advisable in order to increase the rate of reaction.
The process accordiny to the invention of copending ~ application No. 247,975, normally leads to the formation of a ; functionally su~stituted organotin dihalide having the general formula (R)2Sn Hal2, wherein R represents the above-mentioned group:
Rl / 3 H$ - C -R2 ~ 4 These above compounds form the starting material for the preparation by known techniques of exceptionally good, novel organotin stabilizers for polyvinyl chloride and other polymers, the halogen atoms being replaced by the usual organic residues such as acid, thioester and thioalkyl groups.
According to the present invention there is thus pro-vided an organotin compound having the formula (R)2SnX2, wherein R represents the group Rl /R3 ~C C
R2 ~4 108~ 3 ~herein Rl, R2, R3 and R4 each represents hydro~en or a hydro-carbon group, at least one of Rl and R2 being an oxygen-contain-ing group with a carbonyl group adjacent to HC-, and X represents an organic residue selected from the group -S(CH2)nCOO alkyl and -S(CH2)nOCO alkyl, in which n=l or 2, -S alkyl, -OCO alkyl and -OCOCH=CHCOO alkyl.
From the alkyl tin stabilizer technique, it is known that a mixture of dialkyl tin and monoalkyl tin stabilizers has a synergistic effect.
From previous investigations carried out by applicant, it appears that tin dihalide, hydrogen halide and a carbonyl activated olefin react with each other to form an organotin ; trihalide having the general formula RSnHal3, wherein R has the ~-above meaning.
It has been found that the process according to the invention of copending application No. 247,975, can be so controlled that part of the metallic tin first converts into tin dihalide, which subsequently reacts to form organotin trihalide. Thus, it is possible for a metallic tin to be directly processed into a mixture of (R)2SnHal2 and RSnHal~
which mixture can subsequently be directly converted into the ;
desired synergistic stabilizer mixture.
As will be apparent from the following examples, the amount of trihalide in the organotin halide can be varied within wide limits, for example, from 0-95% by weight. If a mixture is to be obtained, the amount to be used will usually be in the ; range of about 5-60% by weight. ~ ;
For the simultaneous formation in the reaction product ;~
of an arbitrary amount of trihalide, it is essential that the ~ ;~
competing reactions between tin and hydrogen halide on the one hand and between these substances and the activated olefin on the other be influenced in favour of the former reaction. Such , ~ -4-formation may be promo-ted by changing the proportions of the re-actants, the order in which and/or the speed at which the reactants are added, the available tin surface and, to a lesser extent, the temperature.
Thus for example, the use of an excess of olefin, a slow addition of the hydrogen halide and a reduction of the available tin surface will tend to lead to an exclusive formation of the dihalide (R)2SnHal2. Changing the reaction conditions in reverse order will lead to increased formation of the tri- -halide RSnHal3.
Organotin dihalides (R)2SnHal2 mixed, if desired, with RSnHal3, and reacted with acids or mercaptans in the usual manner will result in the formation of excellent stabilizers having the general formula (R)2SnX2 which may be mixed with RSnX3. The organotin salts with acid residue X are perferably formed by reaction with alkyl thiocarboxylic esters, alkyl thiols, , ~
~ , ,,. ~ '~
. I

:

1~8~Z~3 monocarboxylic acids and partial esters of polycarboxylic acids.
Specific examples of good stabilizers derived from the present organotin dihalides include:
Alkyl thiocarboxylates (MeOCOCH2CH2)2Sn(s(cH2)ncOoc3Hl7)2 (BuOCOCH2)2Sn(S(CH2)ncOOc8Hl7)2 t 18 37ococ~2cH2)2sn(s(cH2)ncooc8Hl7)2 (BuOCOCH2CH2)2Sn(S(CH2)nCOOBu)2 wherein n=l (thioacetate) or 2 (thiopropionate).
Alkyl mercaptides (~leococH2cH2)2sn(scl2H25)2 (BuococH2cH2)2sn(scl8H37)2 (Cl2~25OcOcH2cH2)2sn(scl2H25)2 Carboxylates (MeOCOCH2cH2)2sn(OcocllH23)2 (BuOCOCH2CH2)2sn(ococl7H35)2 (BuococHcH2)2sn(ococllH23)2 Partial esters ,: .
(MeOCOCH2CH2)2Sn(OCOCH = CHCOO Bu)2 (BuOCOCH2CH2)2Sn(OCOCH = CHCOO Me)2 ~ ;
; The organotin stabilizers according to the invention will generally lead to polymers, more particularly PVC, having a better heat resistance than polymers with the traditional butyl tin stabilizers.
; In the case of sulphur-containing stabilizers, the odour is found to have been considerably improved. Particularly in the foodstuffs branch tPackaging film and the like), the toxicity of the stabilizer is of great importance. It has been found in this respect that various stabilizers according to the invention are -~
considerably more favourable than the traditional butyl tin stabilizers. Thus the L.D. so-value ~i.e. the dose at which 50%

:~
~ - 5 -: . . : . : .: :
:: . , , , ,, , , ,., .,: , . .

3~81'h43 of the laboratory animals ~ie) of the tradi-tional stabilizer (C4H9)2Sn(SCH2COOC8H17)2 for rats is about 500 mg per kg of body weight. For the compound (MeOCOCH2CH2)2Sn(SCH2COOC8H17)2, however, this value is of the order of magnitude of 12,000 mg/kg.
The following examples are given for the purpose of illustrating the invention. Examples I-XII describe the prepar-ation of the organotin dihalides with or without simultaneous formation of trihalides. Examples ~ VI are concerned with the preparation of stabilizers from such halides. Example XVII
describes a comparative test with the stabilizers incorporated in PVC.
Example I
A 500 ml three-necked flask in a cooling bath and equip-ped with a stirrer, a thermometer, a condenser and a gas inlet tube is charged with 60 g of powdered tin, 87.4 g of methyl acrylate and, as solvent, 140 ml of diethyl ether. Over a period of about three hours and at a temperature of 20C, 87 g of dry hydrogen chloride gas are introduced into the mixture, while stirring. Subsequently,the ether is evaporated, and the residue extracted with 300 ml of hot chloroform. 0.5 g of unreacted tin ` is left, with traces of stannous chloride.
Chloroform is removed from the chloroform extract at 100C and 4 mm Hg, following which there remains 177.2 g of a whitish solid substance. Upon analysis (nuclear spin resonance .. : .
spectroscopy), the substance is found to be a mixture of organotin di- and trihalides, namely C12Sn(CH2CH2COOMe)2 and 27% by weight of C13SnCH2CH2COOMe. The yield is quantitatively based on the reacted tin. After the mixture has been washed with diethyl ether, in which the trichloride is readily soluble, there remains a white, crystalline substance which, upon repeated analysis (infrared and nuclear spin resonance spectroscopy and elementary analysis), is ` found to be pure C12Sn(CH2CH2COOMe)2 having a melting point of 132C.

. ~ . .

-~81Z~3 E~cample I I
Using the method of Example I, 60 g of powdered tin, 95.7 g of methyl acrylate and 110 ml of diethyl ether are charged into the flask, and, during a period of about 14 hours and at 20C, 42 g of dry hydrogen chloride gas are passed into the mixture.
As in Example I, the solvent is removed, and the residue extracted, following which there remains 3.7 g of unxeacted tin;
and 167.2 g of a white solid substance are obtained from the extract. The substance is found to be a mixture of C12Sn(CH2CH2 COO~le)2 and 3.5 ~ by weight of C13SnCH2CH2COOMe. The yield is 98 %, calculated on the amount of tin used.
Example III
Using the method of Example I, 60 g of powdered tin, 37.1 g of methyl acrylate and 140 ml of hexane are charged into the flask and over a period of 12 1/2 hours, and 46 g of dry hydrogen chloride gas were introduced. The reaction mixture was filtered, `
! ,.:
washed with 100 ml of hexane and extracted with hot chloroform, following which there remains 1.5 g of unreacted tin, and the ;
extract yields 173 g of solid matter. Upon analysis the matter ~-is found to be a mixture of C12Sn(CH2CH2COOMe)2 and 15.9 % by l`
weight of C13SnCH2COOMe. The yield was 99 %, calculated on the basis of reacted tin.
Example IV
... . ..
60 g of powdered tin and 95.7 g of methyl acrylate were int_oduced into the flask of Example I. During 45 minutes, 115 g of hydrochloric acid (35.4 %) are added, while stirring, following which stirring is continued for g hours. Subsequently, :~ .
; the reaction mixture is filtered, washed with water and extracted with chloroform. There remains 14.9 g of unreacted tin and, from the extract, there are obtained 103.5 g of solid substance, which upon analysis is found to be pure C12Sn(CH2CH2COOMe)2, the remain- ~ ?
der being contained as tin chloride in the wash water.

Example V
By the method of Example I, 60 g of powdered tin and 174.2 g of methyl acrylate (also serving as solvent) are intro-duced into the flask. Then, during a period of 15 hours, 40 g of dry hydrogen chloride gas are introduced. The reaction mix-ture is filtered and washed with 20 g of methyl acrylate. Upon extraction with chloroform, 5.0 g of unreacted tin are left, and the extract yields 141.2 g of crystalline product of pure C12Sn(CH2CH2COOMe)2 in 84.6 % yield, calculated on the basis of reacted tin. The filtrate is still found to contain 17.3 g of the product, the final yield being 95 %.
I Example VI
In accordance with the procedure used in_Example I, 60 g of powdered tin, 95.7 g of methyl acrylate and 140 ml of diethyl ether are charged into the flask. Subsequently, during a period of 10 1/2 hours, 110 g of dry hydrogen bromide gas are introduced.
After the solvent has been removed, the residue is extracted with 300 ml of hot chloroform and 9.5 g of unreacted tin are left.
Evaporation of the extract yields 196.0 g of solid substance, which is analysed as a mixture of Br2Sn(CH2CH2COOMe)2 having a melting point of 137C and 19.7 per cent by weight of Br3SnCH2CH2COOMe. The yield was quantitative, calculated on the basis of reacted tin.
Example VII
60 g of powdered tin, 99.2 g of mesityl oxide and 140 ml of diethyl ether are introduced into a flask in accordance with Example I. Then, during a period of 10 1/2 hours, 70 g of dry hydrogen chloride gas are introduced into the flask. After filtra-tion and washing with 150 ml of i¢e cold ether, the residue is extracted with 300 ml of chloroform. No tin is left, and the extract yields 84.6 g of light brown, crystalline substance, which ~- is pure C12Sn(CMe2CH2COMe)2 having a melting point of 158C.

.' I .
.

1~81243 The yield, calculated on reacted tin, is 43 ~. After evaporation, the ether filtrate still gives 89.5 g of dark brown product, which is found to contain about 40 per cent by weight ; of Cl2Sn(CMe2CH2COMe)2 and 40 per cent by weight of Cl3SnCMe2CH2 COMe. Thus the final total yield of organotin compounds is approx-imately 80%.
Example VIII
60 g of powdered tin, 78.0 g of methyl vinyl ketone and 140 ml of diethyl ether are introduced into a flask in accordance with Example I. Then, during a period of 14 hours, 54 g of dry hydrogen chloride gas are introduced. The reaction mixture is filtered to remove traces of unreacted tin t~ 0.1 g), and then evaporated at 100C and 4 mm Hg, following which 162.4 g of a ` dark brown solid substance is left. ~pon analysis, the substance is found to contain approximately 40 per cent by weight of Cl2Sn(CH2CH2COMe)2 and 40 per cent by weight of Cl3SnCH2CH2COMe.
The total yield or organotin compounds is approximately 80 %, calculated on the basis of reacted tin.
Example IX
~- 20 60 g of powdered tin, 91.5 g of acryloyl chloride and 140 ml of diethyl ether are charged into a flask in accordance with Example I. During a period of l9 l/2 hours, 60 g of dry hydrogen chloride gas are introduced into the flask. Filtration results in the removal of 24 g of unreacted tin from the reaction mixture, which is subsequently evaporated. The residue is ex-tracted with 300 ml of hot chloroform, following which the extract is boiled down to 103 g of a brown solid substance. Upon analysis, the substance is found to contain mainly Cl3SnCH2CH2COCl in addit-ion to some C12Sn(CH2CH2COCl)2. Accurate determination of the yield is not possible because of the presence of organic material. ~
Example X -- 60 g of powdered tin, 129.6 g of _-butyl acrylate . `' .

~ _ 9 _ r- 1081~4L3 and 140 ml of diethyl ether are introduced into a flask in accor-dance with Example I. During a period of 20 hours, 54 g of dry hydrogen chloride gas are introduced into the flask. Filtration of the reaction mixture results in removing 0.2 g of unreacted tin, following which the filtrate is boiled down to 224 g of a clear, colourless liquid, which, upon analysis, is found to consist mainly of C12Sn(CH2CH2COOC4Hg)2 in addition to a small amount of C13SnCH2CH2COOC4Hg. The total yield is about 97 ~, calculated on the basis of reacted tin. The reaction product being a liquid, the method used in this example is highly suit-able for continuous process operation.
Example XI
60 g oE powdered tin, 101.2 g of methyl methacrylate and 140 ml of diethyl ether are introduced into a flask in accord- , -ance with Example I. Then, during a period of 22 hours, 44 g of dry hydrogen chloride gas are introduced into the mixture. The reaction mixture is evaporated, and the residue extracted with 300 ml of hot chloroform. 33.3 g of unreacted tin are left, L
and the extract untimately yields 67.3 g of crystalline material, 20which upon analysis is found to consist of C12Sn(CH2CHMeCOO~e)2 havlng a melting point of 111C and 57.5 per cent by weight of C13SnCHMeCOOMè. The total yield is 84 ~, calculated on the basis of reacted tin.
Example XII
A flask in accordance with Example I is equipped with a heating jacket, and filled with 60 g of granulated tin and 129.6 g of n-butyl acrylate. The contents of the flask are then heated to 120C, following which, during a period of 12 ho~rs, 78 g of dry hydrogen chloride gas are introduced. The reaction mixture is 30filtered to separate unreacted tin (9.8 g), and the filtrate is evaporated to remove the remaining butyl acrylate and hydrochlor-inated acrylate as the by-product. There remains 179.8 g of a ~ - 10 -.: , . ~: :
. ~ . . . .

8~2~3 clear, practically colourless liauid, which, upon analysis, is found to consist mainly of C12Sn(CH2CH2COOBu)2. The yield is 95 %~ calculated on the basis of reacted tin. The product is slightly contaminated with poly-butyl acrylate.
Example XIII
54-6 g of C12Sn(CH2CH2COOMe)2 (isolated as in Example I), 64.3 g of thioglycolate and, as solvent, 200 ml of tetrahydrofuran are introduced into a 600 ml beaker provided with a stirrer, a thermometer and a heating plate. 26.6 g of anhydrous sodium bicarbonate are added to the mixture, while stirring, followed by heating for 2 hours at 50 - 60C. The resulting -sodium chloride is filtered, and the filtrate boiled down to 104.8 g of a colourless liquid. The hot liquid is again filtered and characterized by analysis as (MeOCOCH2CH2)2Sn(SCH2COOC8H]7)2.
By the above synthesis, it is also possible for a mixture ;~ of organotin di- and trihalides to be formed into a mixture of the corresponding thioglycolate tin compounds.
Example XIV
- . , ~
64.5 g of lauric acid and 12 g of sodium hydroxide dissolved in 250 ml of water are introduced into a flask in accordance with Example I. The temperature is increased to 70 -80C, followed by the addition of 54.6 g of C12Sn(CH2CH2COOMe)2, ; and the increased temperature is maintained for 1 hour. Subse~u-ently, 150 ml of toluene are added and stirring is continued for 5 more minutes. The resulting toluene layer is separated and boiled down to 102 g of a light yellow liquid containing ( OcocH2cH2)2sn(ooccllH23)2- By the same ~rocedure, a mixture of organotin di- and trihalides can be formed into a mixture of corresponding laurate tin compounds.
Example XV

72-7 g of C12Sn(CH2CH2COOMe)2, 80.8 g of lauryl thiol and, as solvent, 250 ml of tetrahydrofuran are charged into a ;' ~ .; '.

' i:

600 ml beaker. After the addition, wi~h stirring, of 42.9 g of anhydrous sodium carbonate, the mixture is heated for 1 hour at 60C. Subsequently, the sodium chloride was filtered, and the filtrate boiled down to 137 g of a colourless liquid, which, upon analysis, is found to be (MeOCOCH2CH2)2Sn(S-C12H25)2. In the same manner, mixtures of di- and tri thiolauryl tin compounds can be obtained.
Example XVI
72-7 g of C12Sn(CH2CH2COO~1e)2, 68.8 g of monobutyl maleate and, as solvent, 250 ml of tetrahydrofuran are introduced into a 600 ml beaker~ After the addition of 33.6 g of anhydrous sodium bicarbonate, the temperature is kept at 60C for 1 hour.
The sodium chloride is filtered, and the filtrate boiled down to 124 g of a colourless liquid containing (MeOCOCH2CH2)2Sn(OCOCH=
CHCOOBu)2. In the same manner, the corresponding organotin di- -and trihalides may be formed into mixtures of di- and trimaleate tin compounds.
- Example XVII
The stabilizing effect of the organotin compounds having the general formula (MeOCOCH2CH2)2SnX2 obtained in Examples XIII through XVI is tested in polyvinyl chloride and compared with that of the known dibutyl stabilizers (C4Hg)2SnX2. In each case, there are added 2 per cent by weight of stabilizer, calculated on (plasticized) PVC and the heat resistance is determined on the basis of discolouration with time at a temperature of 185C. A
test is also carried out on PVC bottles containing 1% by weight of a mixture of the stabilizer according to Example XIII and 10% by weight of the corresponding RSnX3 compounds and on bottles con-taining 1~ by weight of only the last-mentioned compound. The results are summarized in the following table.

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~L~8129~3 X - _. , 3 . .~ ~
X~ ~
u~ ~ h ~ : ~
~: .
X~ . 11 11 O E~ U ~1 ~
O H . ~ ~
. .~, C~ X~ . ,' '~' O . :~

a x w ~ u u u .4 ~ 3 ~ H -- ~ O tJ~ X
O
0 .
.` C) ~ ~ ~ UO ~, ho .~ ~ ' ~ ~ a: . 11 11 11 .` ~1 X ~ ~ O
: .fl ~ _ U :>~ O R
U~ .
.. ~ ~ ~ .
U~ _ ~ U U ~ ~
. ~ lu m E~ O ~ . ~ _ . .
U t ) 1~1 U --1 ~ H ~ ~ .
o _ ~ X ~ ?
u~ ~ E~U o ~ Q ~ _ .
~ o 0 P

,.~ , x ~u ~ ~ ~
.. ~ ~
~ ~ O
:~ ~ ~ ~ ~
N 1~1 U . O ~ .q O a~
~C O
. P~ ~ . ~
_ HO U ~ ~
/ O ~ h O ;
~ / ' . . t~
' ~ / o o o 1' ~ ~
.- ~ o u~ O E~ ~ ' ~-.
.
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- 13 ~ ~
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The -table demonstrates that -the stabilizers according to the invention lead to improved stability. This is particularly evident from the considerably improved "early colour", i.e. little or no change in colour in the first heating period.

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Claims (3)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. An organotin compound having the formula (R)2SnX2, wherein R represents the group wherein R1, R2, R3 and R4 each represents hydrogen or a hydro-carbon group, at least one of R1 and R2 being an oxygen-contain-ing group with a carbonyl group adjacent to HC-, and X repre-sents an organic residue selected from the group -S(CH2)nCOO
alkyl and -S(CH2)nOCO alkyl, in which n=1 or 2, -S alkyl, -OCO alkyl and -OCOCH=CHCOO alkyl.

2. An organotin compound according to claim 1, wherein at least one of R1 and R2 is an oxygen-containing group having the formula wherein R5 represents hydrogen, hydroxyl, halogen, amino or alkyl, substituted alkyl or alkoxy containing 1-18 carbon atoms.

3. An organotin compound according to claim 2, wherein R5 is an alkoxy group, R2 is hydrogen or methyl and R3 and R4 are both hydrogen.