Title of Invention

"CROSSLINKABLE MIXTURES AND A PROCESS FOR PREPARING THEM"

Abstract

Crosslinkable mixture comprising as components a) at least one polysiloxane which contains at least two olefmically or acetylenically unsaturated multiple bonds, b) at least one poly hydro siloxane which contains at least two hydrogen atoms bonded directly to the silicon, c) at least one substance catalyzing hydrosilylation. d) at least one phosphorus compound of the general formula where R1, R2, R3, R4, R5=H, CnH2n+1 and n = 1-15, CaH2a+1 and a = 3-15 and/or CnF2n+1, where R1, R2, R3, R4 and R5 can be identical or different and not all radicals R1, R2, R3, R4 and R5 = H, and in which the aliphatic radicals are linear or branched and the hydrogen atoms they contain may have been replaced where appropriate by groups selected from -NHa, COOH, -F, -Br, -Cl, -CN, -C6H5, -C2H2CH5), and e) optionally further auxiliary substances.

Full Text

The present invention relates to crosslinkable mixtures and a process for preparing them. When using addition crosslinking silicone rubber systems, the problem generally arises that the reactive mixture, once prepared, has a finite rate of curing even at room temperature. This can be a nuisance, in particular when the machines have to be shut down for a relatively long time due to technical difficulties or for other reasons. In this case, reactive silicone rubber mixtures left in the machines crosslink even at room temperature which means that very costly cleansing procedures have to be performed before the process can be started up again. For this reason, there has long been a market need for addition crosslinking silicone rubber systems which ideally do not cure at room temperature at all and have the highest possible rate of reaction under the processing conditions. In order to achieve this objective, so-called inhibitors are normally added to the rubber systems. One group of inhibitors comprises organophosphorus compounds. Thus, for example, in DE-A-3 635 236, the use of cyclometallised platinum phosphite complexes for increasing the storage-stability at room temperature is described. The catalyst inhibitor complexes mentioned there do increase the pot life at room temperature, but they have the disadvantage that they are complicated to prepare, which is associated with additional production costs. EP-A-662 490 describes general organophosphorus compounds as inhibitors in addition crosslinking silicone systems. The aliphatic and aromatic phosphines mentioned there, however, have the disadvantage that they cause a clear reduction in the rate of reaction under the processing conditions (T = 120 to 170°C). DE-P 19532316.5 describes crosslinkabls addition crosslinking mixtures which contain, in addition to a hydrosilylation catalyst, an organophosphorus compound and an inhibitor. The adjustment described there, using a 2-component system, however, is complicated. Mixtures which are fully inhibited at room temperature and in which there is no effect on the rate of reaction under the conditions of curing with an additive, have not hitherto been disclosed. There is therefore the object of providing suitable mixtures for lowering the activity of the catalyst at room temperature, even in rapid, addition crosslinking silicone systems, without extending the curing times under the reaction conditions. In addition, the mixture should be as simple as possible, i.e. it should comprise the smallest possible number of components. It has now been found, that the problems in addition crosslinking polysiloxane mixtures can be solved if these contain Pt compounds or elemental Pt or any other hydrosilylation catalysing substance and at least one sterically complicated substituted triaryl phosphite of the type described in more detail below. The mode of action of the organophosphorus compound as inhibitor becomes closer to that of an ideal inhibitor (switch function, threshold characteristic) the more sterically complicated is the aromatic group R. According to the present invention there is provided a crosslinkable mixture comprising as components a) at least one polysiloxane which contains at least two olefmically or acerylenically unsaturated multiple bonds, b) at least one polyhydrosiloxane which contains at least two hydrogen atoms bonded directly to the silicon, 4 c) at least one substance catalyzing hydro silylation. d) at least one phosphorus compound of the general formula (Formula Removed) where R1, R2, R3, R4, R5=H, CnH2n+1 and n = 1-15, CaH2a+1 and a = 3-15 and/or CnF2n+1, where R1, R2, R3, R4 and R5 can be identical or different and not all radicals R1, R2, R3, R4 and R5 = H, and in which the aliphatic radicals are linear or branched and the hydrogen atoms they contain may have been replaced where appropriate by groups selected from -NH2, COOH, -F, -Br, -Cl, -CN, -C6H5, -C6H4(CH3), and e) optionally further auxiliary substances. The invention therefore provides crosslinkable mixtures containing the following components a) at least one polysiloxane, which contains at least two olefinically or acetylenically unsaturated multiple bonds, b) at least one polyhydrogensiloxane, which contains at least two hydrogen atoms bonded directly to the silicon atom, c) at least one substance for catalysing the hydrosilylation, d) at least one phosphorus compound of the general formula (I): P(OR)3 where R=C7-C31-alkylaryl, wherein R may have different definitions within one molecule, and e) optionally further auxiliary substances. Component a) in the context of the invention is preferably a cyclic, linear or branched polysiloxane which is built up from units of the general formula (II) (Formula Removed) Here, R3 represents a C2-C8-alkenyl radical, e.g. vinyl, allyl, 1-butenyl, 1-hexenyl etc. The alkenyl radicals may be bonded to silicon atoms within the chain or right at the end. R4 is a monovalent, saturated hydrocarbon radical with up to 10 carbon atoms from the group of substituted and unsubstituted alkyl, aryl, and arylalkyl radicals. Examples of these monovalent radicals R4 are methyl, ethyl, propyl, isopropyl, butyl, octyl, etc., cyclobutyl, cyclopentyl, cyclohexyl, etc., phenyl, tolyl, xylyl, naphthyl, etc., benzyl, phenylethyl, phenylpropyl. The following conditions are placed on the integers a and b : 0 Using nomenclature which is familiar to a person skilled in the art: M: (CH3)3SiO1/2 D: (CH3)2Si02/2 T: (CH3)Si03/2 Mvi: (CH2=CH)(CH3)2SiO1/2 DVi; (CH2=CH)(CH3)Si02/2 the following may be cited as examples of component a): (Component Removed)The molar proportion of unsaturated radicals of the type R3 may be chosen to have any value. The molar proportion of unsaturated radicals of the type R3 in component a) should preferably be between 10-3 and 10 mmol per gram. The expression 'between' always includes the particular limiting values cited, both here and in the text which follows. The viscosity of component a) is preferably between 10-3 and 1.000.000 Pa.s at 25°C. Component b) in the context of the present invention is a polysiloxane which is built up from units of the general formula (III) (Formula Removed) wherein R3 is defined in the same way as above and R4 may optionally also be defined in the same way as R-*. The stoichiometric indices c and d are integers where 0 Using nomenclature which is familiar to a person skilled in the art Q: Si04/2 MH: H(CH3)2SiO1/2 DH: H(CH3)SiO2/2 the following may be cited as examples of component b): Component Removed) (M, D, M vi and Dvi are defined in the same way as for component a)). The molar proportion of hydrogen atoms directly bonded to a silicon atom in component b) may be chosen to have any value at all. In component b), the molar proportion of hydrogen atoms directly bonded to a silicon atom is preferably between 0.01 and 17 mmol, more preferably between 0.1 and 17 mmol and in particular is between 1 and 17 mmol per gram of component b). In the overall mixture described, components a) and b) are preferably present in a ratio by amounts such that the molar ratio of hydrogen atoms directly bonded to a silicon atom (SiH) in component b) to unsaturated radicals (Si-vinyl) in component a) is preferably between 0.05 and 20, more preferably between 0.5 and 10 and in particular between 1 and 5. Component c) in the context of the invention preferably includes the elements platinum, rhodium, indium, nickel, ruthenium and/or palladium, as the element on a support substance or in the form of their compounds. Platinum compounds or platinum complexes such as, for example, H2PtCl6, platinum/olefin complexes, platinum/alcoholate complexes, platinum/vinylsiloxane complexes or also elemental platinum on a support substance such as e.g. activated carbon, Al2O3 or SiO2 are preferred. Component c) is, in particular, a platinum/vinylsiloxane complex. Platinum/vinylsiloxane complexes preferably contain at least 2 olefmically unsaturated double bonds in the siloxane, see e.g. US-A 3715 334. The expression siloxane also includes polysiloxanes, i.e. for example also vinylpoly-siloxanes. The proportion of component c) in the overall mixture is preferably between 1 and 1000 ppm, more preferably between 1 and 500 ppm and in particular between 1 and 100 ppm. Component d) in the context of the invention is an organophosphorus compound of the type P(OR)3. R may represent different entities within one molecule. A compound of the following formula is preferred: (Formula Removed) where R1, R2, R3, R4, R5 = H, CnH2n+1 and n = 1-15, CaH2a-1 and a = 3-15 and/or cnF2n+l, wherein Rl, R2, R3, R4 and R5 may be identical or different and not all of the radicals Rl R2, R3, R4 and R5 represent H. The aliphatic radicals mentioned may be linear or branched, the H atoms contained therein may optionally be substituted by groups such as -NH2, -COOH, -F, -Br, -Cl, -CN, -C6H5, -C6H4(CH3). Sterically complicated radicals in the context of the invention are also substituted or unsubstituted heteroaromatic compounds as well as substituted or unsubstituted poly-aromatic compounds as well as polyaromatic compounds containing heteroatoms. Component d) in the present invention is preferably added in an amount by weight of 1 ppm to 50 000 ppm, with reference to the total weight of mixture, more preferably 10 ppm to 10 000 ppm and in particular between 20 ppm and 2000 ppm. Components d) can be prepared, for example, by the processes described in Methoden der organ. Chemie, Houben-Weil, vol. XII/2, 1964, 4th ed. p. 59-61. Auxiliary substances (component e) in the context of the invention are, for example, polysiloxane resins which are built up from fundamental units of the general formula (II) and (III), fillers which have a positive effect on the mechanical and electrical properties of the cured mixture in accordance with the invention such as, for example, pyrogenic and precipitated silicas with a BET surface area of 50 to 500 m2/g. These types of fillers may be surface-modified, for example with organosilicon compounds. Modification may also be achieved during incorporation into the polymer by adding, for example, ,ω-OH terminally stopped oligosiloxanes or polysiloxanes or hexa-methyldisilazane or l,3-divinyl-l,l,3,3-tetramethyldisilazane while adding water. Furthermore, substances such as, for example, diatomaceous earths, finely divided quartz powder, amorphous silica or carbon black, as well as A1(OH)3 or oxides which can be ceramicised, etc., may be used as fillers. In another embodiment, mixtures according to the invention also contain water or an organic solvent. In a preferred embodiment of the invention, components a) and b) are preferably present in a ratio by weight such that: the ratio SiH: Si-vinyl is between 0.1 and 10, the concentration of component c) is between 1 and 1000 ppm, the concentration of component d) is between 0.0001 and 5 %, wherein data referring to amounts are each with reference to the total weight of the mixture. This invention also provides a process for preparing crosslinkable mixtures according to the invention. In this, components a) and d) are preferably mixed and then component c) and finally component b) are added. It is also possible to mix components a) and d) and add component b) and lateron component c). The addition of component c) ensures (apart from the composition) that the rate of reaction is reduced. The invention also provides use of phosphorus compounds of the formula I as an inhibitor and the use of a mixture of at least one phosphorus compound of the formula I and a Pt compound or elemental Pt to control the rate of crosslinking in addition crosslinking silicone systems. The following examples are used to explain the invention. The invention is not, however, restricted to the examples. Working example In the following examples, all data relating to weight and percentages, unless stated otherwise, are with reference to the weight of the entire mixture. The compounds used can be defined as follows: (TableRemoved) The basic mixture used consists of: 55 wt.% of polysiloxane A, 19 wt.% of polysiloxane B and 26 wt.% of surface-modified pyrogenic silica. The inhibitor mix used is composed as follows: 99.915 wt.% of basic mixture and 0.085 wt.% of an organophosphorus compound of the type P(OR)3 and the catalyst mix used consists of: 99.88 wt.% of polysiloxane D and 0.22 wt.% of Pt (in the form of a vinylsiloxane complex) Example 1 The amounts of inhibitor mix and catalyst mix specified below were added to the parts of basic mixture given in Table 1. The amount of catalyst mix was selected so that the concentration of metallic Pt in all the mixtures was 10 ppm, with reference to the weight of the entire mixture. The amount of inhibitor mix was selected so that the molar ratio of organophosphorus compound to Pt complex was 2 : 1 in all the mixtures. Finally, 1.3 g of polysiloxane C were added. The molar ratio of vinyl groups directly bonded to Si atoms to H atoms directly bonded to Si atoms was 1:2.5 in all the mixtures. Table 1: Amounts used, given as parts by wt. (Table Removed) All the mixtures had a pot life of more than four weeks at room temperature. Cure-meter curves were plotted for each of these mixtures at temperature T = 140 °C and the t60-times were determined. Table 2 gives the chemical structure of R in the organophosphorus compound of the type P(OR)3 and also gives the t60-time at T = 140 °C. Table 2:(Table Removed) The systems are faster the more sterically complicated is the radical R in the organophosphorus compound of the type P(OR)s. We Claim 1. Crosslinkable mixture comprising as components a) at least one polysiloxane which contains at least two olefinically or acetylenically unsaturated multiple bonds, b) at least one polyhydrosiloxane which contains at least two hydrogen atoms bonded directly to the silicon, c) at least one substance catalyzing hydrosilylation. d) at least one phosphorus compound of the general formula (Formula Removed) where R1, R2, R3, R4, RS=H, CnH2n+1 and n = 1-15, CaH2a+1 and a = 3-15 and/or CnF2n+1, where R1, R2, R3, R4 and R5 can be identical or different and not all radicals R1, R2, R3, R4 and R5 = H, and in which the aliphatic radicals are linear or branched and the hydrogen atoms they contain may have been replaced where appropriate by groups selected from -NH2, -COOH, -F, -Br, -Cl, -CN, -C6H5, -C6H4(CH3), and e) optionally further auxiliary substances. 2. Crosslinkable mixture as claimed in Claim 1, wherein component c) is a Pt compound or platinum complexes or elemental platinum on a support substance. 3. Crosslinkable mixture as claimed in one of Claims 1 and 2, wherein component c) is a platinum/vinylsiloxane complex in which the siloxane contains at least two olefinically unsaturated double bonds. 4. Crosslinkable mixture as claimed in one or more of Claims 1 to 3, wherein it may further comprise water. 5. Crosslinkable mixture as claimed in one or more of Claims 1 to 3, wherein it may further comprise an organic solvent. 6. Crosslinkable mixture as claimed in one or more of Claims 1 to 5, wherein components a) and b) are present in a quantitative ratio such that the ratio SiH:Si-vinyl is between 0.01 and 300, the concentration of component c) is between 0.1 and 1000 ppm, the concentration of component d) is 0.0001 % to 5%, the quantity figures being based in each case on the total weight of the mixture. 7. Process for preparing a Crosslinkable mixture as claimed in one or more of Claims 1 to 6, wherein components a) and d) are mixed, then components c) and finally component b) are added. 8. Crosslinkable mixture substantially as herein described with reference to the foregoing examples.

Documents:

3700-del-1997-abstract.pdf

3700-del-1997-assignment.pdf

3700-del-1997-claims.pdf

3700-del-1997-correspondence-others.pdf

3700-del-1997-correspondence-po.pdf

3700-del-1997-description (complete).pdf

3700-del-1997-form-1.pdf

3700-del-1997-form-13.pdf

3700-del-1997-form-19.pdf

3700-del-1997-form-2.pdf

3700-del-1997-form-3.pdf

3700-del-1997-form-4.pdf

3700-del-1997-form-6.pdf

3700-del-1997-gpa.pdf

3700-del-1997-pct-338.pdf

3700-del-1997-pct-409.pdf

3700-del-1997-petition-137.pdf

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