GB1570411A - Creation of Inventions and Patents with Artificial Intelligence

GB1570411A – Manufacture of curable organopolysiloxane compositions
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GB1570411A – Manufacture of curable organopolysiloxane compositions
– Google Patents
Manufacture of curable organopolysiloxane compositions

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Publication number
GB1570411A

GB1570411A
GB37162/77A
GB3716277A
GB1570411A
GB 1570411 A
GB1570411 A
GB 1570411A
GB 37162/77 A
GB37162/77 A
GB 37162/77A
GB 3716277 A
GB3716277 A
GB 3716277A
GB 1570411 A
GB1570411 A
GB 1570411A
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Prior art keywords
component
platinum
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composition
organopolysiloxane
Prior art date
1976-10-15
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GB37162/77A
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Wacker Chemie AG

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Wacker Chemie AG
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1976-10-15
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1977-09-06
Publication date
1980-07-02

1977-09-06
Application filed by Wacker Chemie AG
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Wacker Chemie AG

1980-07-02
Publication of GB1570411A
publication
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patent/GB1570411A/en

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Classifications

C—CHEMISTRY; METALLURGY

C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON

C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS

C08L83/00—Compositions of macromolecular compounds obtained by reactions forming in the main chain of the macromolecule a linkage containing silicon with or without sulfur, nitrogen, oxygen or carbon only; Compositions of derivatives of such polymers

C08L83/04—Polysiloxanes

C—CHEMISTRY; METALLURGY

C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON

C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients

C08K5/00—Use of organic ingredients

C08K5/54—Silicon-containing compounds

C—CHEMISTRY; METALLURGY

C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON

C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS

C08G77/00—Macromolecular compounds obtained by reactions forming a linkage containing silicon with or without sulfur, nitrogen, oxygen or carbon in the main chain of the macromolecule

C08G77/04—Polysiloxanes

C08G77/12—Polysiloxanes containing silicon bound to hydrogen

C—CHEMISTRY; METALLURGY

C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON

C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS

C08G77/00—Macromolecular compounds obtained by reactions forming a linkage containing silicon with or without sulfur, nitrogen, oxygen or carbon in the main chain of the macromolecule

C08G77/04—Polysiloxanes

C08G77/20—Polysiloxanes containing silicon bound to unsaturated aliphatic groups

Description

PATENT SPECIFICATION
( 11) 1 570 411 ( 21) Application No 37162/77 ( 22) Filed 6 Sep 1977 ( 31) Convention Application No 2646726 ( 32) Filed 15 Oct 1976 in( ( 33) Fed Rep of Germany (DE) ( 44) Complete Specification Published 2 Jul 1980 ( 51) INT CL 3 C 08 L 83/04 i, ( 52) Index at Acceptance C 3 T 6 D 1 1 6 F 2 6 K 1 6 K 2 B 6 K 2 C 6 K 3 6 K 5 6 K 8 A ( 54) MANUFACTURE OF CURABLE ORGANOPOLYSILOXANE COMPOSITIONS ( 71) We, WACKER-CHEMIE GMBH, a body corporate organised according to the laws of the Federal Republic of Germany, of 8 Munchen 22, Prinzregentenstrasse 22, Federal Republic of Germany, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following
statement:-
The present invention relates to a process for the manufacture of a curable organopolysiloxane composition, preferably a roomtemperature-curable composition, comprising a compound containing silicon-bonded hydrogen atoms and an organopolysiloxane containing aliphatic unsaturation.
In such a composition, curing (also known as hardening, crosslinking or vulcanising) occurs as a result of the addition of the silicon-bonded hydrogen atoms to be aliphatic multiple bonds This addition can be promoted by means of a platinum catalyst (cf French Patent Specification No 1 480
409 and U S Patent Specification No 3 419
593) Moreover, when using, as the organopolysiloxane containing aliphatic unsaturation, one that contains at least 50 silicon atoms per molecule, curing of the composition can be carried out at toom temperature (cf French Patent Specification No 1 503 189 and U S.
Patent Specification No, 3 814 730).
With a room-temperature curable composition comprising a compound containing silicon-bonded hydrogen atoms, an organopolysiloxane containing aliphatic unsaturation and having at least 50 silicon atoms per molecule and a platinum catalyst, it is desirable so to regulate the rate at which curing occurs that, on the one hand, there is a sufficiently long, and preferably constant, period for handling the composition between preparing the composition and the onset of appreciable curing, for example for applying the composition to a moulding surface, which 45 period is known as the pot life of the composition and that, on the other hand, curing will occur at a temperature below about 40 C, preferably at room temperature, within an acceptably short period These desiderata are 50 especially important for dental impression compositions, which may, for example, comprise a diorganopolysiloxane having triorganosiloxy terminal units each containing at least one vinyl group, an organopolysiloxane con 55 taining at least three silicon-bonded hydrogen atoms per molecule, a platinum catalyst and, optionally, various auxiliaries such as fillers It has been suggested that these desiderata may be met by using a diorganosiloxane copolymer 60 containing vinyl groups in some diorganosiloxane units (cf French Patent Specification No.
2 060 329 and U S Patent Specification No.
3 699 073), but this has the problem that such a diorganosiloxane copolymer can be difficult 65 to obtain and, in any case, the rate of curing often cannot be regulated sufficiently consistently by this method.
The present invention provides a process for the manufacture of a curable organopoly 70 siloxane composition, which comprises mixing together.
(i) a compound containing silicon-bonded hydrogen atoms, (ii) an organopolysiloxane containing ali 75 phatic unsaturation and having at least 50 silicon atoms per molecule, (iii) a platinum catalyst (as hereinafter defined), and (iv) a compound of the general formula 80 CH 2 =CHR 2 Si O (Si R 20)n Si R 2 CH=CH 2 I in which R denotes an unsubstituted or substituted monovalent hydrocarbon radical free 85 of aliphatic unsaturation, and N denotes O or a 1 570411 positive integer not exceeding 6, wherein each of components (iii) and (iv), not previously being mixed with one another, is mixed with component (i) and/or with component (ii), prior to components (i) and (ii) being mixed with one another.
(Throughout this specification, any symbol that occurs more than once in any general formula may have identical or different values on each occurrence) It was surprising to discover that the presence of a compound of the above general formula I, and specially of 1, 3-divinyl-1,1,3,3tetramethyldisiloxane (which it is preferred to use as the compound of the general formula I) in the composition prolongs the pot life of the composition, so as to give a greater period for handling the composition prior to the onset of appreciable curing, because U S Patent Specification No 3 814 730 indicates platinum complexes of the compounds of the general formula 1, and especially of 1,3-divinyl-1,1,3,3tetramethyldisiloxane to be especially effective in promoting the addition of silocin-bonded hydrogen atoms to aliphatic multiple bonds.
The compound containing silicon-bonded hydrogen atoms, component (i), used in the process according to the invention may be such a compound as has been or could have been used in previous processes for the manufacture of curable organopolysiloxane compositions from compounds containing siliconbonded hydrogen atoms and organopolysiloxanes containing aliphatic unsaturation.
This compound is preferably an organopolysiloxane consisting of units of the general formula R’ m Si O ( 4-m)/2 II in which R’ denotes a hydrogen atom or an unsubstituted or substituted monovalent hydrocarbon radical free of aliphatic unsaturation, with the proviso that at least two, and preferably at least three, symbols R’ per molecule each denotes a hydrogen atom, and m denotes 1, 2 or 3, Preferred compounds of this type are those consisting of units of the formulae RH Si O, R 2 Si O and R 35 i 011/2 III and containing one silicon-bonded hydrogen atom for every 3 to 100 silicon atoms with the proviso that there are at least two silicon-bonded hydrogen atoms per molecule, and having a viscosity within the range of from 10 to 50 000 c P at 23 C.
The compound containing silicon-bonded hydrogen atoms may alternatively be an organopolysiloxane of the general formula.
R 2 H Si O(Si R 20)p Si R 2 CH=CH 2 IV in which R is defined as above and p denotes a positive integer such that the organopolysiloxane has a viscosity within the range of from 300 to 5000 c P at 23 C Such a compound is, however, preferably used in addition to rather than instead of an organopolysiloxane consisting of units of the general 70 formula II given above.
The unsubstituted or substituted monovalent hydrocarbon radicals denoted by R and R’ preferably have not more than 18 carbon atoms Examples of such unsubstituted mono 75 valent hydrocarbon radicals are alkyl radicals, for example methyl, ethyl, n-proply, isopropyl and octadecyl radicals; cycloalkyl radicals, for example cyclohexyl and cycloheptyl radicals; aryl radicals, for example a phenyl radical; 80 alkaryl radicals, for example a tolyl radical; and aralkyl radicals, for example benzyl and /-phenethyl radicals Examples of such substituted monovalent hydro-carbon radicals are halogenated hydrocarbon radicals, for example a 3,3,3 85 trifluoropropyl radical and an (o, m or p)chlorophenyl radical, and cyanoalkyl radicals, for example a /-cyanoethyl radical Preferably, at least 50 mole % of the radicals denoted by R and at least 50 mole % of the radicals (as dis 90 tinct from hydrogen atoms) denoted by Rl in the organopolysiloxane are methyl radicals, because such organopolysiloxanes are more readily obtainable.
The organopolysiloxane containing aliphatic 95 unsaturation and having at least 50 silicon atoms per molecule, component (ii), used in the process according to the invention may be such a compound as has been or could have been used in previous processes for the manufacture of 100 curable organopolysiloxane compositions from compounds containing silicon-bonded hydrogen atoms and organopolysiloxanes containing aliphatic unsaturation.
This organopolysiloxane is preferably one 105 consisting of at least 50 units of the general formula R 2 x Si O ( 4-x)/2 V in which R 2 denotes an unsubstituted or substituted monovalent hydrocarbon radical, with the proviso that at least two symbols R 2 per molecule each denotes such a radical containing aliphatic unsaturation, and x denotes 0, 1, 2 or 3, with the proviso that the average value of x is within the ragne of from 0 9 to 2 1.
The statements and examples given above concerning the radicals denoted by R and R’ apply also to aliphatically saturated radicals denoted by R 2 Examples of aliphatically unsaturated radicles denoted by R 2 are ethynyl, allyl, methallyl, butadienyl and, especially, vinyl radicals.
It is apparent from the fact that the average value of x may vary from 0 9 to 2 1, that cured products produced from compositions manufactured according to the invention may be elastic or non-elastic (that is resinous) products: The production of elastic products 1 570 411 (namely elastomers) is, however, preferred and, to this end, this organopolysiloxane is preferably one of the general formula (CH 2 =CH)R 2 Si O(R 2 Si O)y Si R 2 (CH=CH 2) VI in which R is defined as above and y denotes an integer af at least 48 The viscosity of such an organopolysiloxane may be, for example, 10 s c P at 23 C, or more, there being no maximum limit to the value of y.
Components (i) and (ii) are preferably used in the process according to the invention an relative amounts such that there are an average of from 0 1 to 15 silicon-bonded hydrogen atoms per aliphatic multiple bond.
The platinum catalyst, component (iii), used in the process according to the invention may be elemental platinum or a platinum compound or complex capable of promoting the addition of silicon-bonded hydrogen atoms to aliphatic multiple bonds and the term “platinum catalyst” as used herein is to be understood accordingly All platinum catalysts known to be suitable for promoting the addition of silicon-bonded hydrogen atoms to aliphatic multiple bonds may be used in the process according to the invention, Examples of suitable catalysts are finely divided platinum, which may be used per se or in conjunction with a carrier, for example silica, alumina or activated carbon; platinum-halogen compounds, for example platinum chloride Pt C 14, chloroplatinic acid and Na 2 Pt CI 4 n’ H 20; platinum/ olefin complexes, for example complexes with ethylene, propylene and butadiene; platinum/ alcohol complexes; platinum/alcoholate complexes; platinum/ether complexes; platinum/ aldehyde complexes; platinum acetyl acetonate; reaction products of chioroplatinic acid with monoketones, for example cyclohexanone, methyl ethyl ketone, acetone, methyl npropyl ketone, diisobutyl ketone, acetophenone and mesityl oxide; and platinum/vinylsiloxane complexes, for example platinum/ divinyltetramethyldisiloxane complexes, with or without a detectable content or inorganic halogen A mixture of platinum catalysts may be used, for example a mixture of a chloroplatinic acid/cyclohexanone reaction product and a platinum/divinyltetramethyldisiloxane complex free of detectable inorganic halogen.
The platinum catalyst is advantagously used in an amount within the range of from 0 5 to 500 ppm by weight (parts by weight per million parts by weight), preferably from 2 to 500 ppm by weight, calculated as (elemental) Pt and based on the total weight of the composition.
The compound of the general formula I, component (iv), is preferably one in which n denotes 0, 1 or 2 and each radical denoted by R is a methyl radical Examples of such compounds are 1,3-divinyl-1,3-diphenyl-1,3dimethyldisiloxane and 1,3-divinyl-1,1,3,3tetramethyldisiloxane The latter compound is preferred because it has a particularly advantageous effect on prolonging the pot life of the composition The use of this compound also has the advantage that it is easily obtainable in one step by the hydrolysis of vinyldimethylchlorosilane and can, because of its relatively low boiling point, easily be purified by distillation to give a product of consistent purity.
if desired Other compounds of the general formula I in which N denotes O can be prepared in an analogous manner.
A compound of the general formula I in which N denotes a positive integer not exceeding 6 may be produced, for example, by the equilibration of an organopolysiloxane of the general formula HO(R 2 Si O)q H in which R is defined as above and q denotes a positive integer such that the organopolysiloxane has a viscosity of at least 106 c P at 23 C, with 1,3-divinyl-1,1,3,3-tetramethyldisiloxane or 1,3-divinyl-1,3-diphenyl-1,3dimethyldisioxane The resulting product may be used after or without purification.
The compound of the general formula I is advantageously used in an amount within the range of from 1 to 5000 ppm by weight, especially from 1 to 1000 ppm by weight, based on the total weight of the composition.
The greater is the amount of the compound of the general formula I used, the greater is the prolongation of the pot life that is achieved.
In the process according to the invention, the compound of the general formula I, namely component (iv), is mixed with component (i) or with component (ii) or separately with components (i) and (ii), prior to mixing component (i) with component (ii) The catalyst, namely component (iii), is also mixed with component (i) or with component (ii) or separately with components (i) and (ii) The catalyst and the compound of the general formula I may be mixed with the same component or with different components but, in the former case, the catalyst and the compound of the general formula I should not previously be mixed with one another.
Preferably, however, at least some of component (ii) is mixed with the platinum catalyst prior to the addition of the compound of the general formula 1.
The presence of the compound of the general formula I in a composition manufactured according to the invention results in the composition having a prolonged and, in any given case, substantially constant pot life between the mixing of all components together and the onset of appreciable curing and also in curing proceeding at a substantially constant rate after the onset of appreciable curing This is so even when there has been a relatively long time (such as six months or 4 1570411 more) between the mixing of the compound of the general formula I with component (i) and/or (ii) and the mixing of all the components together On the other hand, the pot life of a similar composition but not containing a compound of the general formula I can vary to a considerable extent after storage of the various components, especially after storage at relatively high temperatures By varying the amount of compound of the general formula I used according to the invention, it is thus possible to cary the pot life of the composition as desired for the particular purpose for which the composition is intended It is also possible to use sufficient catalyst in the composition that there is practically no danger of poisoning of the catalyst, that is at least 1 5 ppm by weight, and to compensate for any resultant increase in the speed of curing by increasing the amount of the compound of the general formula I.
The compound of the general formula I may be used as such (that is, in a substantially pure form) or in the form of a paste The use of a paste of the compound can facilitate measurement of the amount of the compound and/or the addition of the compound to other components and/or the distribution of the compound in the composition A suitable paste can be prepared, for example, by mixing the compound with a triorganosiloxy-terminated (especially trimethylsiloxy-terminated) diorganopolysiloxane liquid at room temperature, or with a portion of component (ii), and with silica having a specific surface area of at least m 2 /g (as measured by the nitrogen-adsorption method described in A S T M Special Technical Publication No 52, 1941, pp 95 to 105, generally known as “the BET method”), which silica may be precipitated silica or pryogenic silica (also known as “fumed silica”) and may have been rendered hydrophobic by reaction with, for example, an organohalogenosilane, an organoalkoxysilane or a hexaorganodisilazane.
Various auxiliaries may be used in the process according to the invention, especially such auxiliaries as may conventionally be used in compositions comprising an organopolysiloxane containing vinyl groups, an organopolysiloxane containing at least three silicon-bonded hydrogen atoms and a platiunm catalyst, which compositions are curable to elastic or non-elastic products Examples of such auxiliaries are fillers, pigments, soluble dyestuffs, plasticisers, organopolysiloxane resins, solely organic resins, agents for improving the adhesion of the cured products to supports on which they are produced, crosslinking retardants (other than compounds of the general formula I), flavouring substances and odorisers.
The fillers may be reinforcing fillers (that is fillers having a specific surface area of at least m 2 /g) or non-reinforcing fillers (that is fillers having a specific surface area of less than m 2 /g) Reinforcing fillers may be used in amounts additional to those used in the preparation of pastes of the compound to the general formula I as mentioned above Examples of reinforcing fillers are precipitated silica and 70 pyrogenic silica Examples of non-reinforcing fillers are calcium carbonate, quarts powder, cristobalite powder, diatomaceous earth, aluminium silicate and graphite (an electrically conductive filler) At least part of the filler 75 (reinforcing or non-reinforcing) may have been rendered hydrophobic, as discussed above.
Examples of suitable pigemnts are red iron oxide and pigment-quality titanium dioxide.
Examples of suitable plasticiers are organo 80 polysiloxanes free of aliphatic unsaturation, for example trimethylsioxy-terminated dimethylpolysiloxanes liquid at room termperature, which may be additional to any such compound used in the preparation of a paste of the com 85 pound of the general formula I as mentioned above.
An example of a solely organic resin is pulverulent polyvinyl chloride Examples of organopolysiloxane resins that may be used in 90 the manufacture of compositions curable to elastomers are copolymers of Si O 412 units, (CH 3)3 Si 0112 units and (CH 3)2 (CH 2 =CH)Si O 1/2 units, in which an average of from 0 6 to 1 (CH 3)3 Si 0112 units and (CH 3)2 (CH 2 =CH) 95 Si 0, /2 units are present per Si 0412 unit and in which the content of vinyl groups is from 1 5 to 3 5 % by weight.
An example of an additional crosslinking retardant is benztriazole 100 A composition manufactured according to the invention is preferably curable at room temperature and ambient atmospheric pressure, although a higher or lower temperature and/or a higher or lower pressure may be used 105 for curing if desired.
A composition manufactured according to the invention may be used as an impression or moulding composition, especially a dentalimpression composition; as a casting or em 110 bedding composition for, for example, electronic components (the prolonged and constant pot life achieved according to the invention is of particular advantage in this connection when being used in series-manufacture by machine or 115 in dip-coating by machine); as a sealant; an an insulating agent; for the production of moulded articles, including cable terminals; for the production of adhesive-repellent coatings on paper; for coating a wide variety of fabrics; and for 120 the production of electrical heating elements.
The following Examples 1 to 6 illustrate the process of the invention and compare the properties of the compositions thus obtained with those of prior art compositions Parts and 125 percentages are by weight All viscosities are measured at 23 C unless otherwise stated.
EXAMPLE 1 (a)Amixtureof 130 1 570411 1 570411 480 g of a vinyldimethylsiloxy-terminated dimethylpolysoloxane having a viscosity of 21000 c P, 810 g of cristobalite powder, 9 g of hydrophobic pyrogenic silica and 13 g of pigment-quality titanium dioxide was prepared.
(b) A platinum catalyst solution containing 0.1 % of elemental Pt, was prepared by mixing 0 2 to Pt C 14 in 5 ml of anhydrous ethanol with 113 6 g of a vinyldimethylsiloxy-terminated dimethylpolysiloxane having a viscosity of 1100 c P at 23 C, and distilling off the ethanol at 30 C and 0 2 torr.
(c) 500 g of the mixture prepared under (a) were mixed with 9 35 g of the platinum catalyst solution to give a mixture containing 18 4 ppm of elemental Pt, based on the mixture.
(d) This mixture was then mixed first with 25 ppm, based on the total mixture, of 1,3divinyl-1,1,3,3-tetramethyldisiloxane and then with 3 %, based on the total mixture, of a copolymer of dimethylsioxane units, methylhydrogenisloxane units and trimethylsiloxane units, having a viscosity of 730 c P and containing 0 12 % of silicon-bonded hydrogen.
(e) The pot life or processing time of the composition thus obtained was 2 min 50 sec.
After 8 min the compsoition had cured completely at room temperature to form an elastomer having a Shore A hardness of 52.
(f) For comparison purposes, the procedure of paragraphs (a) to (d) was repeated with the variation that the divinyltetramethyldisioxane was entirely omitted Appreciable crosslinking commenced only 20 sec after beginning to mix in the organopolysiloxane containing silicon-bonded hydrogen That is to say, the composition had a pot life of only 20 sec.
EXAMPLE 2 (a) A platinum catalyst solution was produced as follows:
parts of sodium bicarbonate were added to a mixture of 10 parts of H 2 Pt CI 6 6 H 20, 20 parts of 1,3-divinyl-1,1,3,3-tetramethyldisiloxane and 50 parts of ethanol The mixture was refluxed for 30 min while stirring, and then allowed to stand for 15 h, after which it was filtered The volatile constituents were distilled off from the filtrate at approximately 12 torr.
The residue obtained was 17 parts of a liquid, which dissolved in benzene The solution was filtered and the benzene was distilled off from the filtrate The residue was mixed with a vinyldimethylsiloxy-terminated dimethylpolysiloxane having a visocsity of 1400 c P, as diluent, in such a quantity that the mixture contained 1 % of elemental Pt.
(b) In each case, 9 parts of a mixture of 1000 g of a vinyldimethylsoloxy-terminated dimethylpolysiloxane having a viscosity of 980 c P and 4 g of the platinum catalyst solution prepared under (a) were mixed first with the quantities of 1,3-divinyl-1,1,3,3-tetramethyldisiloxane given in the following Table 1 and the with 1 part of the organopolysiloxane containing silicon-bonded hydrogen described in Example 1 The pot lives of the resulting compositions and the times taken to cure to form an elastomer that is no longer tacky are given in Table 1.
TABLE I amount of divinyltetramethyldisiloxane (mg pot life curing time per 100 g of polysilo of com of comxane having a viscosity position position of 980 c P) 0 4 5 min 10 min 30 min 40 min 1 5 h 2 h 2 h 3 h 5 h 7 5 h EXAMPLE 3 (a) A mixture of 1635 g of a vinyldimethylsiloxy-terminated dimethylpolysiloxane having a viscosity of 960 c P, 1296 g of cristobalite powder, 39 g of hydrophobic pyrogenic silica, and 24 g of the platinum catalyst solution prepared under Example 2 (a) was prepared The resulting mixture contained 80 ppm of elemental Pt.
(b) Portions of the mixture prepared under (a) were then each mixed with a short-chain divinylsiloxane given in Table 2 in the amounts there-given.
(c) A mixture of 1513 g of the vinyldimethylsiloxy-terminated dimethylpolysiloxane having a viscosity of 960 c P, 1370 g of cristobalite powder, 53 g of hydrophobic pyrogenic silica, and 450 g of a copolymer of dimethylsiloxane units, methylhydrogensiloxane units and trimethylsioxane units, having a viscosity of 800 c P and containing 0 125 % of silicon-bonded hydrogen was prepared.
(d) 1 part of each of the mixtures prepared under (b) was then mixed with 1 part of the mixture prepared under (c) The pot lives of the resulting compositions were determined at 24 C and are listed in Table 2 overleaf.
Notes: 1) The first divinylsiloxane listed in Table 2 was a distilled product having a purity of 98 7 %.
2) The second divinylsiloxane listed in Table 2 was produced as follows: 74 g of a dimethylpolysiloxane containing a siliconbonded hydroxyl group in each terminal unit and having a viscosity of 400 c P were mixed with 0 01 ml of a solution of 25 parts of phosphorus nitrile chloride in 75 parts by weight of methylene chloride This mixture was allowed to stand for 16 hours at room temperature and 12 torr The composition TABLE 2 amount of short-chain divinylsiloxane divinylsiloxane pot life of (ppm, based on composition mixture (a)) CH 2 =CH(CH 3)2 Si O Si(CH 3)2 CH=CH 2 91 3 min 35 sec CH 2 =CH(CH 3)2 Si O Si(CH 3)20 Si(CH 3)CH=CH 2 167 3 min 40 sec CH 2 =CH(CH 3)2 lSi O Si(CH 3)2 l 20 Si(CH 3)2 CH=CH 2 500 3 min 50 sec CH 2 =CH(CH 3)2 lSi O Si(CH 3)2 l 40 Si(CH 3)2 CH=CH 2 1000 3 min 10 sec none 0 2 min 10 sec thus obtained, which was solid at room temperature, had added to it 186 grams of 1,3divinyl-1,1,3,3-tetramethyldisiloxane, and the resulting mixture was stirred for 24 hours at room temperature The short-chain divinylsiloxane so obtained had a viscosity of 1 6 c St at 25 C It was used without further purification.
3) The third and fourth short-chain divinylsiloxanes were produced analogously and were likewise used without further purification.
EXAMPLE 4 (a) A mixture of a vinyldimethylsiloxy-terminated dimethylpolysiloxane having a viscosity of 20 000 c P and an amount of the platinum catalyst solution prepared under Example 2 (a) containing 70 ppm of elemental platinum was mixed with 40 ppm of 1,3-divinyl-1,1,3,3tetramethyldisiloxane A portion of the resulting mixture was stored for 24 hours at room temperature and the rest was stored for 24 hours at 100 C in a drying chamber.
(b) The mixtures were then each mixed with %, based on each mixture, of the organopolysiloxane containing silicon-bonded hydrogen described in Example 1.
(c) The procedure of paragraphs (a) and (b) was repeated, for comparison purposes, with the variation that the divinyltetramethyldisiloxane was ommitted.
(d) The pot lives of the resulting compositions were determined at 24 C and are given in Table 3.
TABLE 3 pot life of composition composition storage at storage at room 100 C temperature invention 3 min 15 sec 3 min 30 sec comparison 1 min 55 sec 3 min 25 sec EXAMPLE 5 (a) 500 g of a dimethylpolysiloxane having a 85 silicon-bonded hydroxyl group in each terminal unit and having a viscosity of 400 c P at 25 C were mixed with 8 g of a trimethylsiloxy-terminated methylhydrogenpolysiloxane having a viscosity of 33 c P at 25 C and 0 07 ml of a 90 solution of 4 g of phosphorus nitrile chloride, produced by reacting 2 moles of phosphorus pentachloride with 1 mole of ammonium chloride in 10 ml of methylene chloride This mixture was allowed to stand overnight at room 95 temperature and 12 torr The composition so obtained, which was solid at room temperature, had added to it 10 g of a trimethylsiloxy-terminated dimethylpolysiloxane containing, on average, approximately 12 silicon atoms per 100 molecule, and the resulting mixture was heated at 60 C for 12 h while stirring The organopolysiloxane consisting of methylhydrogensiloxane, dimethylsiloxane and trimethylsiloxane units thus obtained contained approximately 1 sili 105 con-bonded hydrogen atom per 50 silicon atoms and had a viscosity of 9300 c P at 25 C.
(b) 1000 g of the dimethylsiloxane containing a silicon-bonded hydroxyl group in each terminal unit and having a viscosity of 400 c P at 25 C 110 were mixed with 0 15 ml of the solution of phosphorus nitrile chloride described under (a).
This mixture was allowed to stand for 3 h at C and 12 torr 4 2 g of sym-divinyltetramethyldisiloxane and 3 1 g of sym-tetrame 115 thyldihydrogendisiloxane were added to thecomposition thus obtained, which was solid at room temperature, and the resulting mixture was stirred for 24 hours at room temperature.
The dimethylpolysiloxane thus obtained, 120 having per molecule, on average, one vinyldimethylsiloxane unit and one dimethylhydrogensiloxane unit as terminal units, had a viscosity of 2000 c P at 25 C.
(c) In a kneader, 30 g of hexamethyldisilazane, 125 g of water and 150 g of pyrogenic silica having a specific surface area of 130 m 2 /g were mixed with a mixture of 150 g of the organopolysiloxane prepared under (a) The mixture thus obtained was heated to 150 C at 50 torr 130 1 570411 1 570411 whilst kneading further, in order to remove volatile constituents, and, after cooling, was mixed with 300 g of the diorganopolysiloxane prepared under (b).
(d) 90 g of the mixture thus obtained were mixed with 10 g of a vinyldimethylsiloxyterminated dimethylpolysiloxane having a viscosity of 162 c P, which dimethylpolysiloxane had previously been mixed first with an amount of the platinum catalyst solution prepared in Example 2 (a) containing 400 ppm of elemental Pt and then with 7000 ppm by weight of 1,3-divinyl-1,1,3,3-tetramethyldisioxane (The resulting composition contained 40 ppm of elemental Pt and 700 ppm of the divinyltetramethyldisiloxane) (e) The procedure described under (d) was repeated, for comparison purposes, with the variation that the divinyltetramethyldisiloxane was omitted.
(f) The procedure described under (d) was again repeated, for comparison purposes, with the variations that the divinyltetramethyldisiloxane was omitted and that only 15 ppm (instead of 400 ppm) of elemental Pt were used (The resulting composition contained 1.5 ppm of elemental Pt) (g) The pot lives of the compositions prepared under (d), (e) and (f) were determined at 23 C and are given in Table 4.
TABLE 4 ppm of 1,3-divinyl-1,1,3,3-tetramethyldisiloxane, and finally with 2 5 % based on the weight of the portion, of the organopolysiloxane containing silicon-bonded hydrogen described in Example 3 70 (b) For comparison purposes, the procedure described under (a) was repeated with the variation that the divinyltetramethyldisiloxane was omitted.
(c) For further comparison purposes, the pro 75 cedure described under (b) was repeated with the variation that only 3 ppm of elemental Pt were used.
(d) Also for comparison purposes, the procedure described under (a) was repeated with the 80 variation that (corresponding to U S Patent Specification No 3 699 073 mentioned previously) a trimethylsiloxy-terminated copolymer of dimethylsiloxane and vinylmethylsiloxane units in a molar ratio of approximately 4:1, 85 having a viscosity of 100 c P at 23 C, was used in a quantity of 500 ppm, based on the weight of the portion, instead of the divinyltetramethyldisiloxane.
(e) The pot lives of the compositions prepared 90 under (a) to (d) were determined at 23 C as were the times taken to cure to form an elastomer having a Shore A hardness of 48 The results are given in Table 5 9 TABLE 5
Composition pot life curing time (a) 4 min 20 sec 11 min (b) 1 min 40 sec 6 min (c) 4 min 10 sec 35 min (d) 4 min 25 sec 45 min From these figures, it can be seen that the use of 1,3-divinyl-1,1,3,3-tetramethyldisiloxane corresponds to a reduction of the quantity of platinum to 3 75 % of the original quantity.
The elastomer produced from composition (d) was, as a result of the relatively high Pt content, no longer tacky after 24 hours, whereas the elastomer produced from composition (f) was still slightly tacky even after 4 days The elastomer produced from composition (e) was also no longer tacky after 24 hours only if, during the crosslinking, the composition was maintained under a nitrogen or oxygen atmosphere.
EXAMPLE 6 (a) A portion of a mixture of 515 g of a vinyldimethylsiloxy-terminated dimethylpolysiloxane having viscosity of 20000 c P, 725 g of cristobalite powder, and 19 g of hydrophobic pyrogenic silica was mixed first with an amount of the platinum catalyst solution produced in Example 2 (a) containing 35 ppm of elemental Pt, then with These results show that, by means of the use of the compound of the general formula I, a much shorter prolongation of the crosslinking is achieved than that achieved according to the prior art, which is particularly desirable for dental-impression compositions.

Claims (21)

WHAT WE CLAIM IS:

1 A process for the manufacture of a curable organopolysiloxane composition, which comprises mixing together (i) a compound containing silicon-bonded hydrogen atoms, (ii) an organopolysiloxane containing aliphatic unsaturation and having at least 50 silicon atoms per molecule, (iii) a platinum catalyst (as hereinbefore defined), and (iv) a compound of the general formula CH 2 =CHR 2 Si O(Si R 2 0)n Si R 2 CH=CH 2 in which R denotes an unsubstituted or substituted monovalent hydrocarbon radical free of aliphatic unsaturation, and N denotes 0 or a positive integer not exceeding 6, 1 570411 wherein each of components (iii) and (iv), not previously being mixed with one another, is mixed with component (i) and/or with component (ii), prior to components (i) and (ii) being mixed with one another.

2 A process as claimed in claim 1, wherein component (i) comprises an organopolysiloxane consisting of units of the general formula R’ m Si O ( 4 -m)/2 in which R’ denotes a hydrogen atom or an unsubstituted or substituted monovalent hydrocarbon radical free of aliphatic unsaturation, with the proviso that at least two symbols R’ per molecule each denotes a hydrogen atom, and m denotes 1,2 or 3.

3 A process as claimed in claim 2, wherein component (i) comprises an organopolysiloxane consisting of units of the general formulae RH Si O, R 2 Si O and R 35 i 011/2 in which R is defined as in claim 1, and containing one silicon-bonded hydrogen atom for every 3 to 100 silicon atoms with the proviso that there are at least two silicon-bonded hydrogen atoms per molecule, and having a viscosity within the range of from 10 to 50 000 c P at 23 C.

4 A process as claimed in any one of claims 1 to 3, wherein component (i) comprises an organopolysiloxane of the general formula R 2 H Si O (Si R 20)p Si R 2 CH=CH 2 in which R is defined as in claim 1 and p denotes a positive integer such that the ofranopolysiloxane has a viscosity within the range of from 300 to 5000 c P at 23 C.

A process as claimed in any one of claims 1 to 4, wherein component (ii) is an organopolysiloxane consisting of at least 50 units of the general formula R 2 x Si O ( 4-x)/2 in which R 2 denotes an unsubstituted or substituted monovalent hydrocarbon radical, with the proviso that at least two symbols R 2 per molecule each denotes such a radical containing aliphatic unsaturation, and x denotes 0, 1, 2 or 3, with the proviso that the average value of x is within the range of from 0 9 to 2 1.

6 A process as claimed in claim 5, in which component (ii) is an organopolysiloxane of the general formula (CH 2 =CH)R 2 Si O(R 2 Si 0)y Si R 2 (CH=CH 2) in which R is defined as in claim 1 and y denotes an integer of at least 48.

7 A process as claimed in any one of claims 1 to 6, wherein components (i) and (ii) are used in relative amounts such that there are an average of from 0 1 to 15 silicon-bonded hydrogen atoms per aliphatic multiple bond.

8 A process as claimed in any one of claims 1 to 7, wherein component (iii) is finely divided platinum, a platinum-halogen compound, a 70 platinum/olefin complex, a platinum/alcohol complex, a platinum/alcoholate complex, a platinum/ether complex, a platinum/aldehyde complex, platinum acetyl acetonate, a reaction product of chloroplatinic acid with a monoke 75 tone, or a platinum/vinylsiloxane complex.

9 A process as claimed in any one of claims 1 to 8, wherein component (iii) is used in an amount within the range of from 0 5 to 500 ppm by weight, calculated as Pt and based on 80 the total weight of the composition.

A process as claimed in claim 9, wherein component (iii) is used in an amount within the range of from 2 to 500 ppm by weight, calculated as Pt and based on the total weight 85 of the composition.

11 A process as claimed in any one of claims 1 to 10, wherein component (iv) is a compound of the general formula in which n denotes 0, 1 or 2 and each radical denoted by R 90 is a methyl radical.

12 A process as claimed in claim 11, wherein component (iv) is 1,3-divinyl-1,3-diphenyl-1, 3-dimethyldisiloxane or 1,3-divinyl-1,1,3,3tetramethyldisiloxane 95

13 A process as claimed in any one of claims 1 to 12, wherein component (iv) is used in an amount within the range of from 1 to 5000 ppm by weight, based on the total weight of the composition 100

14 A process as claimed in claim 13, wherein component (iv) is used in an amount within the range of from 1 to 1000 ppm by weight, based on the total weight of the composition.

A process as claimed in any one of 105 claims 1 to 14, wherein at least part of component (ii) is mixed with component (iii) prior to the addition thereto of component (iv).

16 A process as claimed in claim 1, carried out substantially as described in any one of 110 Examples 1 to 6 herein.

17 A curable organopolysiloxane composition that has been manufactured by a process as claimed in any one of claims 1 to 16.

18 A process for the manufacture of a 115 cured product, which comprises curing a composition as claimed in claim 17.

19 A process as claimed in claim 18, wherein curing is carried out at room temperature.

A cured product that has been manu 120 factured by a process as claimed in claim 18 or claim 19.

21 A cured product as claimed in claim 20, which is an elastomer.
ABEL & IMRAY, Chartered Patent Agents, Northumberland House, 303-306 High Holborn, London, WC 1 V 7 LH.
Printed for Her Majesty’s Stationery Office by MULTIPLEX techniques ltd, St Mary Cray, Kent 1980 Published at the Patent Office, 25 Southampton Buildings, London WC 2 l AY, from which copies may be obtained.

GB37162/77A
1976-10-15
1977-09-06
Manufacture of curable organopolysiloxane compositions

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1976-10-15
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The addition retarding agent in the addition of Si-bonded hydrogen to at least 50 Si atoms per molecule and organopolysiloxane containing aliphatic multiple bonds, promoted by a platinum catalyst and taking place at room temperature

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Manufacture of curable organopolysiloxane compositions

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1976

1976-10-15
DE
DE2646726A
patent/DE2646726C2/en
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1977

1977-07-27
NL
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1977-09-06
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patent/GB1570411A/en
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1977-09-15
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patent/AU512539B2/en
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Expired

1977-09-30
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US05/838,414
patent/US4096159A/en
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Expired – Lifetime

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AT0733077A
patent/AT378375B/en
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1977-10-13
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FR7730836A
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Granted

1977-10-13
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1977-10-14
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GB2301827A
(en)

1995-06-07
1996-12-18
Gen Electric
Silicone oil – silica paste for liquid injection moulding

GB2301827B
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1995-06-07
1998-09-09
Gen Electric
Silicone oil-silica filler paste useful in liquid injection molding applications

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