NO753050L - - Google Patents

Description

The invention relates to molding compounds that can be stored

in the absence of water and which hardens to form elastomers in the near-

of water at room temperature off

(a) diorganopolysiloxanes with terminally placed SiOH-

groups,

(b) siloxane-modified polyurethane prepolymers

polyurethane prepolymers with end-placed

groups bonded through urea bridges and

(c) a silicone compound with at least three hydrolysables

groups attached to the Si atom.

Molding compounds of organopolysiloxanes that can be stored

in the absence of water and which hardens to form elastomers in the presence of water at room temperature, so-called "one-component-mix-

ingers" are known (compare e.g. W. Noll, Chemie und Tech-

nologie der Silicone, 1968, page 3^1, Verlag Chemie, Weinheim/Bergstrasse). Although the vulcanizates have properties of typical organopolysiloxane elastomers, including thermal stability and flexibility at low temperatures, the cured products do not have the mechanical strength or high elongation required for certain applications.

The purpose of the present invention is to provide a one-component system which satisfies the following requirements for economic and technical reasons:

(a) Preparation of the one-component masses shall'' not

involve extra expenditure in connection with appa-

rate or application of high temperatures, in other words, manufacturing must be able to be carried out in

standard commercial mixers; and

(b) the one-compChent system shall be a dissolution-

agent-free liquid mass with adequate stability

during storage in the absence of moisture, but shall -

ensure■vulcanization to form a uniform elastomer under the influence of moisture.

There has been no shortage of proposals for the production of similar systems. However, the problem has not yet been satisfactorily resolved.

US Patent No. 3-632,557 relates to manufacture

of polyurethanes with end-positioned organosilyl-urea groups. However, these products which are formed by the addition of yaninopropyl-trimethoxysilane to NCO prepolymers do not contain any polysiloxane blocks and consequently do not have the necessary combination of properties of polyurethane and polysiloxane.

Furthermore, DOS Nos. 2,155,258, 2,155-259 and 2,155,260 relate to polyaddition products of the α-aminomethyl-alkoxysilane and NCO compounds., This system, with the necessary for the presence of stabilizing solvents, enables siloxane blocks

to be incorporated by condensation with polysiloxanes which

ends in silanol groups. However, as the solvent is usually undesirable one-component mixtures (evaporation of the solvent results in shrinkage of the one-component rubber) this system is completely unsuitable for use in one-component silicone rubber compounds.

It has now surprisingly been found that molding compounds produced by mixing, for example, in the absence of solvents, the usual kneaders, (a) di-organopolysiloxanes with end-placed silanol groups with (b) polyurethane prepolymers or siloxane-modified polyurethane prepolymers, containing end-placed _„ groups, connected through urea bridges

R

and (c) a silicone compound having at least three hydrolyzable radicals attached to a Si atom, vulcanizes at room temperature in the presence of moisture to form a uniform elastomer.

Single-component masses produced in this way do not show any of the disadvantages referred to above when stored in the absence of moisture.

Accordingly, the invention relates to one-component compounds based on polysiloxane-polyurethane copolymers, which are characterized by containing:

(a) diorganopolysiloxanes with terminally placed SiOH groups, corresponding to the general formula:

in which

R means H, alkyl, alkenyl, aryl, haloalkyl and

n is greater than 3;

(b) polyurethane prepolymers or end-placed siloxane-modified polyurethane prepolymers

R

CHpSiOR' groups connected through urea bridges

R

and corresponding to the general formula:

in which

R' means C 1 -C 8 alkyl or C 8 -C 1 -cycloalkyl radical;

R" means an optionally halogen- or cyano-substituted C-1-C-C-1-Q-alkyl, C-1-<C>-Q-cycloalkyl or C8-C10-aryl radical;

R"' means H, methyl or phenyl,

R"" means H or an optionally halogen- or cyano-substituted C-j^-C-^g-alkyl 13 C^-C-^-cycloalkyl 1 or Cg-C<->^<-a>ryl radical;

Q' means a divalent alkyl radical with from 4 to 36 carbon atoms, a divalent C^-C-^-cycloalkyl radical, Cy-C^<g->aralkyl radical, Cg-ClI(-aryl radical or Cy-C^g-alkaryl radical;

X means 0, NH or N-Y (where Y means C₁-C₆-alkyl₁),

Q means a divalent radical derived by removing hydrogen atoms from a compound containing ester, ether, urethane, urea, carbonate, amide and additionally siloxane groups and with a molecular weight in the range from 200 to 80,000,

a means 1 or, greater than 1,

b means 1 to 8, preferably 2 or 3,

and

(c) a silicone compound containing at least three -

hydrolyzable groups attached to the Si atom.

The radicals R, R', R", R""<:> preferably have

following meaning:

R means a methyl, vinyl, phenyl or chloromethyl radical,

R' means a methyl, ethyl or cyclohexyl radical,

R" means one methyl or phenyl radical and

R"" means an isobutyl, cyclohexyl or phenyl radical.

Diorganopolysiloxanes which are suitable for use in accordance with the invention are the same as those usually used as basic diorganopolysiloxane in the production of mixtures which harden to elastomers at room temperature based on diorganopolysiloxanes, network formers and condensation catalysts. The polysiloxanes. preferred viscosity is from 100 to 500,000 cP/25°C.

Polyurethane prepolymers or siloxane-modified polyurethane prepolymers of formula (II) can be prepared by adding

(a) NCO prepolymers; or (b) siloxane-modified NCO prepolymers

with α-aminoalkyldimethyl-monoethoxysilanes, the NCO prepolymers can be obtained by reacting diisocyanates with hydroxy-functional polyethers or polyesters, the reaction being carried out in a known manner, possibly in the presence of catalysts (Polyurethanes: Chemistry and Technology, Saunders and Frisch, Intersc. Publishers , New York 1963 (Part I)

and 1964 (Part II).

Siloxane-modified NCO prepolymers can be prepared: (a) by reacting NCO prepolymers with one polysiloxane■content- end α-aminoalkyl end groups:

and/or a hydroxyalkyl polysiloxane:

in which

R means H, an alkyl, preferably methyl, alkenyl, preferably vinyl, aryl, preferably phenyl or haloalkyl, preferably chloromethyl radical and

n = 0 - 20;

to achieve the end-placed NCO group and

(b) by reacting a,w-dihydroxypolyether with diisocyanate in the presence of aminoalkyl-polysiloxane and/or hydroxyalkyl-polysiloxane.

The compounds according to formula (II) can be prepared

by reacting the α-aminoalkyl-dimethylmono-alkoxysilane with isocyanate prepolymers at a temperature from -20 to 150°C, possibly in the presence of a solvent. The quantitative ratios between the compound containing isocyanate groups and the aminoalkylsilane derivative are calculated so that equivalent amounts are used, in other words an isocyanate group is reacted with

an amino group. The adducts formed, which contain hydrolyzable SiOR groups connected through a urea bridge at the chain ends, are low- to high-viscosity liquids or waxes with viscosities from 500 to 500,000 cP/25°C, preferably from 5,000 to 100,000 cP.

α-Aminoalkyl 1-silane derivatives can be prepared in accordance with DOS Nos. 1,812,504 and 1,812,562.

It is preferred to use compounds with the general formula

as. can be obtained by turnover

with dimethyl-chloromethylethoxysilane.

Examples of diisocyanates corresponding to the general formula:

are known aliphatic, cycloaliphatic, araliphatic and aromatic isocyanates, for example 1,6-hexamethylene diisocyanate, 2,4- and 2,6-toluene diisocyanate, also mixtures of these isomers, diphenylmethane-4,4'-diisocyanate and l- isocyanato-3,3,5-trimethyl-5-isocyanato-methylcyclohexane.

It is of course also possible to use mixtures

of the above-mentioned polyisocyanates.

In general, it is particularly preferred to use the commercially readily available diisocyanates, e.g. 2,4-and 2,6-toluylene diisocyanate, also mixtures of these isomers.

Examples of connections:

includes any compounds containing OH,

NH"2, NHR and ether, esters, urethane, urea, carbonate and amide groups and which have molecular weights from 200 to 80,000.

The NCO prepolymers may additionally contain siloxane segments, connected to the polyether or polyester through urethane and/or urea bridges.

Preferred compounds are addition products of diisocyanates with polyethers, containing two hydroxyl groups based on propylene oxide or ethylene oxide or mixed blocks of both or polyesters obtained by reacting adipic acid with 1,6-hexanediol.

The NCO prepolymer is preferably prepared by reacting the compounds containing hydroxyl groups with diisocyanates in an NCO:OH ratio of from 2.0 to 1.01.

Network forming substances suitable for use - according to the invention are those which are usually used in the production of systems which form networks at room temperature. The network-forming substances that are preferably used, above all because of their easy availability, are silicone compounds corresponding to the formula: (V) R Si in which X means a hydrolysable radical' with at least three hydrolysable radicals connected through oxygen, such as alkoxy, oximato. .or hydrocarbon radicals connected through nitrogen, such as alkyl, cycloalkyl or acid radicals such as acetoxy or acid amide radicals and possibly mixtures of the above-mentioned compounds. The network forming agents are preferably used in amounts of from 1.0 to 15% by weight, based on the total weight of the mass.

Particularly preferred cross-linking agents are: methyl-tris-butanone oxime silane, methyl-tris-cyclohexylamine silane, methyl monoethoxy-bis-benzamidosilane, methyltriacetoxysilane, ethyltriacetoxysilane and vinyltriacetoxysilane. The one-component compounds according to the invention based on polyurethane copolymers are produced -i. absence of moisture and - the solvent by mixing the polydiorganosiloxanes (I) which end in a silanol group, with the compounds (II) in a standard mixer, preferably at room temperature and subsequent addition of a network forming agent with at least three hydrolyzable radicals connected to the Si atom.

The quantitative ratio between diorganopolysiloxane (I) and polyurethane prepolymer (II) is not critical and can surprisingly vary within wide limits, which was not predictable. This one-component composition with viscosities in the range of 10,000 to 1,000,000 cP at 25°C can be easily prepared with plasticizers, fillers and catalysts to form molding compositions which cure in the presence of moisture to give elastomers.

The masses according to the invention are stable in absence

of humidity. Consequently, they can be stored for longer periods without undergoing adverse changes. During storage, the masses do not undergo any noticeable changes in their physical properties either. This is particularly decisive commercially because it ensures that, following the production of a mass with a certain consistency and hardening time, this mass does not undergo any significant changes during storage. Stability during storage is one of the properties that make the compounds according to the invention particularly valuable as a one-component compound which vulcanizes at room temperature.

The plasticizers used are liquid, inert organopolysiloxanes, for example dimethylpolysiloxanes which end in trimethylsiloxy groups, used in amounts from 5 to 70% by weight, based on base diorganosiloxane with end-placed SiOH groups.

The fillers used are fillers that usually

is used in the production of siloxane-based one-component compounds, especially SiO2-produced pyrogen in gas phase, large-surface precipitated SiO2, silazane-treated SiO2 and lime. If desired, metal oxides such as Ti02, Fe20^, Al20 and ZnO can be used.

The condensation catalysts used are known condensation catalysts such as amines or organotin

salts, such as dibutyltin dilaurate and dibutyltin salts of aliphatic carboxylic acids&r.

The one-component compounds according to the invention are stable during storage in the absence of moisture and can be used for many known purposes, for example as sealing compounds, insulating materials for electrical, apparatus and for

position of elastomeric articles.

The method according to the invention shall be explained in more detail with the help of some examples where the parts mean by weight

parts.

Examples 1 to 4.

■1.145 g (0.562 mol) of a polyether based on propylene oxide with an OH number of 54.8 is dehydrated for 1 hour by;

120°C in oil pump vacuum, then reacted at 100°C with 196 g (1.124 mol) of an isomeric mixture of 2,4- and 2,6-toluylene diisocyanate and 0.02 g of dibutyl tin dilaurate to form a, (j-diisocyanate prepolymer. After cooling to 30°C, 242 g (1.124 mol) of a cyclohexylaminomethyl-dimethylmonoethoxy-■silane are added over a period of one hour, which causes an increase in the temperature of the mixture to 40°C. After stirring in for a further 2 hours it is not possible to detect free NCO groups by IR analysis The product has a viscosity of 11,540 cP at 25°C Mixtures listed in the following table are prepared in standard machines from the product obtained which at each end of the chain contains a hydrolyzable SiOC^H^ group connected through urea groups:

The vulcanized mixtures 1 to 4, with increasing replacement of the diorganopolysiloxanes, show higher tensile strength compared to the comparative example which consists exclusively of polysiloxanes.

The other examples show (for the same formulation 4) that it is possible to achieve higher expansion values in relation to comparative examples by varying polyurethane prepolymer or siloxane-modified polyurethane prepolymer with terminal SiOR groups.

Example 5.

760 g (0.45 mol) of a polyester of adipic acid, hexanediol and neopentyl glycol with an OH number of 66.5 is reacted with 113 g (0.365 mol) of toluylene diisocyanate to form an NCO prepolymer. The addition of. 46 g (0.214 mol) of cyclohexyl-amihomethyl-dimethylmonoethoxysilane, followed by reaction with 110 g. (0.2 mol) of an α,oo-dihydroxypolysiloxane, gives a colorless product with a viscosity of 31-000 cP at 25°C . The mixture is carried out in accordance with example 4. The Vulkani seat shows the following properties according to DIN:-

Example 6.

918 g (0.45 mol) of the polyether used in example 1 is reacted with 113 g (0.65 mol) of an isomeric mixture of toluylene diisocyanate to form a prepolymer. Subsequent reaction with 46 g (0.214 mol) of cyclohexylaminomethyl-dimethylmonoethoxysilane is followed by the addition of 110 g (0.2 mol) of a short polysiloxane ending in a silanol group. The product has a viscosity of 18,100 cP at 25°C. 31 parts of this compound, 30 parts of a diorganopolysiloxane with terminal SiOH groups (viscosity 45.000 cP at 25°C) are mixed in a kneader at room temperature with 2-4 parts of a polysiloxane which ends in a trimethylsiloxy group ( 1000. cP), 5 parts of butanone oxime netformer, 10 parts of aerosil and 0.05 parts of dibutyltin dilaurate. The mixture is stable during storage in the absence of moisture.

This mixture cures in air to form an elastomer with the following properties:

Example 7.

If, in example 6, the isomeric mixture of toluylene diisocyanate is replaced by hexamethylene diisocyanate, a vulcanizate with the following properties is obtained:

Example 8.

If, in example 7, hexamethylene diisocyanate is replaced by isophorone diisocyanate, a vulcanizate with the following properties is obtained:

Example' 9 • 92 g (0.528 mol) of an isomeric mixture of 2,4- and 2,6-toluylene diisocyanate and 0.02 g of dibutyltin dilaurate are added to 900 g (0.44l mol) of an a,.w-dihydroxy- polyether based, on propylene oxide (OH number 54.8) after dehydration at 120°C. The NCO prepolymer that is formed is reacted at room temperature with 18.75 g (0.087 mol) of cyclohexylaminomethyl-dimethylmono-ethoxysilane. The colorless product formed has a viscosity of 55,000 cP at 25°C. 31 parts by weight of this compound are mixed in a kneader in the absence of moisture with 30 parts by weight of a polydimethylsiloxane with an end-placed silanol group (viscosity 45-000 cP), 24 parts by weight of a polysiloxane ending in a trimethylsiloxane group, 5 parts by weight of methyl-tris-butanone-oximsilane, 10 parts aerosil and 0.05 part dibutyltin dilaurate. This mixture is stable during storage in the absence of moisture. In air, toughness disappears after 30 minutes and the product hardens into an elastomer that has the following properties:

Example 10.

612 g (0.3 mol) of the dehydrated polyether used in example 1 is mixed at room temperature with 324 g (0.15 mol) of a polysiloxane containing a cyclohexylaminomethyl end group and corresponding formula:

followed by the addition of 113 g (0.65 mol) of toluylene diisocyanate and 0.02 g of dibutyltin dilaurate. The reaction mixture is stirred for 1 hour at 50°C and heated briefly (10 minutes) at 90°C. This is followed by the addition at room temperature of 46 g (0.2 mol) of cyclohexylaminomethyl-dimethylmonoethoxysilane. The product with a viscosity of 12,000 cP is made up to form a one-component mass according to example 4. The vulcanizate has the following properties:

Example 11.

Uncertain, in the previous example, amine.osiloxane is replaced by a polysiloxane must end in a hydroxymethyl group and corresponds to the formula: Under the same reaction conditions, a product with the following properties is obtained:

Example 12.

An a,u)-diisocyanato prepolymer is prepared in the same way as in example 1 and the cyclohexylaminomethyldimethylethoxysilane is replaced by benzylaminomethyldimethylethoxysilane (product A) and anilinomethyldimethylethoxysilane (product B).

The mixtures are prepared according to example 4. The vulcanizates show the following properties:

Claims (13)

1. Molding compound3 characterized in that it comprises: (a) at least one diorganopolysiloxane corresponding to it general formula (I): in which R means a hydrogen atom or an alkyl, alkenyl, aryl or haloalkyl radical and n is greater than 3; (b) at least one optionally siloxane-modified polyurethane prepolymer corresponding to the general formula (II): wherein R' means a C-L-C8 alkyl or C8-C4 cycloalkyl radical; R" means an optionally halogen- or cyano-substituted C-C-C-Q-alkyl, C-C-C-Q-cycloalkyl or Cg-C-Q-aryl radical; R"' means a hydrogen atom or a methyl or phenyl group; R"" means a hydrogen atom or an optionally halogen- or cyano-substituted C -C -C -C -alkyl, C -C -C -cycloalkyl or C -C -C -aryl radical; Q' means a divalent C^ -C^ g-alkyl radical, a divalent Cj-C-^-cycloalkyl, Cy-C/ jg-aralk<y>l , Cg-C-^ -aryl or Cy-C^ g -alkaryl radical, X means -O-, -NH- or the group -NY-, in which Y means a C1 -C8 alkyl radicalj Q means a divalent radical formed by removing the hydrogen atom from a compound containing at least one ester, ether, urethane, urea, carbonate or amide group and, in addition, at least one siloxane group and with a molecular weight of from 200 to 80,000; a is at least 1 and b is from 1 to 8;- ° g (c) at least one silicone-containing compound with at least 3 hydrolyzable groups connected to a Si atom. 2. Mass according to claim 1, characterized in that b means 2 or 3- 3.. Mass according to claim 1 or 2, characterized in that R represents a methyl, vinyl, phenyl or chloromethyl radical; R' means a methyl, ethyl or cyclohexyl radical; R" means- a methyl or phenyl radical and - R"" means an isobutyl, cyclohexyl or phenyl radical -. 4. Mass according to one of claims 1 to 3, characterized in that the viscosity of component (a) is from 100 to 500,000 cP/25°C. 5- Mass according to one of claims 1 to 4, characterized in that the viscosity of component (b) is from 500 to 500,000 cP/25°C. 6. Mass according to claim 5, characterized in that the viscosity is from 5,000 to 100,000 cP/25°C 7. Mass according to one of claims 1 to 6, characterized in that component (c) corresponds to the following general formula (V): in which X means a hydrolysable radical and R has the same meaning as stated in claim 1. 8. Mass according to one of claims 1 to 7, characterized in that component (c) is present in an amount from 1.0 to 15% by weight, based on the total weight of the mass. 9- The composition of claims 1 to 8, characterized in that component (c) is selected from methyl-tris-butanone oxime silane, methyl-tris-cyclohexylamine silane, methyl-monoethoxy-bis-benzamidosilane, methyltriacetoxysilane, ethyltriacetoxysilane and vinyltriacetoxysilane . 10. Mass according to one of claims 1 to 9j, characterized in that it has a viscosity of from 10,000 to 1,000,000 cP/25°C. 11. Mass according to one of claims 1 to 10, . characterized in that it additionally comprises a plasticizer and/or a filler and/or a catalyst. 12. Porm mass essentially as described here under reference to one of the examples. 13. Molding compound according to one of claims 1 to 12, hardened. by the impact of water.