AU5935699A

AU5935699A - Parting agent

Info

Publication number: AU5935699A
Application number: AU59356/99A
Authority: AU
Original assignee: Rhein Chemie Rheinau GmbH
Current assignee: Rhein Chemie Rheinau GmbH
Priority date: 1998-11-11
Filing date: 1999-11-11
Publication date: 2000-05-18
Also published as: AR021151A1; BR9905350A; JP2000141376A; EP1000989A2; HUP9904224A2; HUP9904224A3; EP1000989A3; SK154099A3; DE19851945A1; CA2289137A1; PL336493A1; ZA997026B; CN1256995A; HU9904224D0; KR20000035403A

Description

Our Ref: 7461829/PS Regulation 3.2

AUSTRALIA

Patents Act 1990 COMPLETE SPECIFICATION FOR A STANDARD PATENT

(ORIGINAL)

Name of Applicant: Address for Service: RHEIN CHEMIE RHEINAU GMBH Dusseldorger Str. 23-27, D-68219 Mannheim, GERMANY DAVIES COLLISON CAVE, Patent Attorneys Level 10, 10 Barrack Street, Sydney, 2000 Invention Title: "Parting Agent" The following statement is a full description of this invention, including the best method of performing it known to me: RC 210-Foreign Countries Bg/klu/NT -1- PARTING AGENT FIELD OF THE INVENTION This invention relates to a filler-free parting agent comprising an aqueous emulsion which contains silicone systems which react with each other and which contains a silica sol, and which in addition imparts good sliding properties to the surface which is treated. The parting agent is particularly suitable as a parting agent for the production of tires and of other rubber articles, and is used during the molding and vulcanization of said articles.

BACKGROUND OF THE INVENTION According to the prior art, tires are molded and vulcanized by inserting the tire blank in a mold and pressing it against the mold using a heating membrane (bladder or blister membrane), whereupon it is vulcanized by the effect of heat. The heating membrane has to slide within the blank and has to be separable from the tire after vulcanization. The tire blanks are therefore introduced into a spray booth in which they are set in rotation by means of a mechanical device. A spray gun with which a 20 solution of a parting agent is distributed inside the blanks is introduced into said rotating blanks. The overspray is mostly removed via a water curtain and is taken up in the water. This is followed by the molding and vulcanization of the blank in a vulcanization press by means of the heating membrane, the function of which is to heat the tire blank and to press the tire under a high pressure into the negative mold.

ooooo Aqueous organopolysiloxane emulsions and the use thereof as parting agents in tire molding and vulcanization operations are known from the prior art. US-4,184,880 describes parting agent emulsions, which, however, contain quite large amounts of inorganicsilicates as fillers which have been treated with organosilicon compounds in order to render their surface hydrophobic.

RC 210-Foreign Countries -2- US-4,431,452 describes an aqueous parting agent composition consisting of: 1) a polydimethylsiloxane which comprises SiOH terminal groups and which has a viscosity of up to 25,000,000 centistokes at 25 0

C;

2) a polydimethylsiloxane which comprises SiOH terminal groups and which has a viscosity of up to 120,000 centistokes at 3) a polyalkylene glycol; 4) a bentonite clay; and r a surface-active agent.

US -4,359,340 describes aqueous parting agent preparations for use in tire molding.

These emulsions consist of: 1) a polydimethylsiloxane with a viscosity of up to 25,000,000 centistokes at 0

C;

2) a methyl hydrogen silane with a viscosity of 20 to 40 centistokes or a dimethyl hydrogen silane with a viscosity of 80 to 120 centistokes; 3) a metal salt of an organic acid, and 4) a surface-active agent.

EP-A-0,279,372 describes aqueous organopolysiloxane emulsions which can be used as parting agents in tire molding and vulcanization, particularly for coating the bladder, and which are composed of: RC 210-Foreign Countries -3- 1) a polydimethylsiloxane polymer which comprises SiOH terminal groups and which has a plasticity of 50 to 100; 2) an organohydrogen polysiloxane comprising at least 2 Si-bonded hydrogen atoms per molecule; 3) a lubricant with a melting point of 25 to 80 0

C;

4) an inorganic silicate (mica); a thickener; r 6) a surface-active agent; and 7) water.

The disadvantages of the aqueous parting agent compositions which have been described hitherto are first, they contain relatively large amounts of inorganic silicates as fillers, which have a negative effect on the stability of the emulsion, and second, they crosslink via the reaction of an SiOH group with SiH, with the separation of hydrogen; this is undesirable due to the risk of an explosion.

EP-A-0,635,559 describes a parting agent composition for tire molding, which acts without this unwanted generation of hydrogen. The emulsion described is used for coating the bladder, and consists of 1) at least one non-reactive polydimethylsiloxane which has a kinematic viscosity between 50 and 30,000,000 mm sec' at 25 0

C;

2) at least one reactive polydimethylsiloxane which has a kinematic viscosity between 15 and 5,000,000 mm sec'; RC 210-Foreign Countries -4- 3) a crosslinking agent; 4) a surface-active agent; and water.

EP-A-0,111,100 describes a silicone-based parting agent for tire production, which is not only dissolved in an organic solvent and has to be used thus, but which also has to contain kaolin, chalk, powdered rock, hydrated silicas, carbon black or graphite, if the heating membrane does not already have a roughness from the outset which is sufficient to ensure the satisfactory escape of air.

A satisfactory sliding and parting effect can be achieved with lubricants alone, e.g.

silicone oils or silicone oil emulsions, but total "de-airing", i.e. the escape of air between the bladder and the tire blank, cannot, unfortunately, be achieved.

.go.

i ~Air, included between the bladder and the tire blank means reject tires, since satisfactory vulcanization does not occur under the air bubble.

Fillers (mineral fillers or other types) are required as spacers between the bladder and S"the tire blank, so that air can escape before vulcanization.

"i It has not been possible, mainly on account of the need for de-airing, to employ filleroooo• 25 free inner solutions consisting of combinations of lubricants or parting agents only.

Fillers perform the function of a spacer between the bladder and the inner liner of the tire blank.

The use of conventional silicone oils has hitherto resulted in troublesome separation phenomena at the tire faces.

RC 210-Foreign Countries SUMMARY OF THE INVENTION There is accordingly a need, as before, for an aqueous, solvent-free parting agent, which can be sprayed on to the inside of the tire blank and/or on to the surface of the bladder, which parting agent fulfils all the requirements for vulcanization, namely sliding, separation and de-airing, and which at the same time does not exhibit the disadvantages described above, such as a content of fillers and/or crosslinking with the separation of hydrogen. In addition, separation phenomena at the tire faces should be prevented.

The present invention relates to parting agents comprising, in an aqueous emulsion, a system consisting of at least two silicone components which react with each other with crosslinking, said system being selected from the group consisting of silicone components which react with each other by condensation, or silicone components which react with each other by addition, and 20 an aqueous colloidal hydrated silica (silica sol).

Accordingly, the present invention also relates to a process for vulcanizing pneumatic tires, which is characterized in that the parting agent composition according to i the invention is applied to the bladder and/or to the tire surface before vulcanization.

06000 DETAILED DESCRIPTION OF THE INVENTION The process according to the invention is extremely environmentally friendly, since it employs only 10 of the effective solids content of the parting substances used in conventional, prior art processes and is accordingly more economical as a whole.

RC 210-Foreign Countries -6- The silicone systems and according to the invention, which react with crosslinking, comprise mixtures of emulsions of silicone components which react (crosslink) with each other by condensation or mixtures of emulsions of silicone components which react (crosslink) with each other by addition, and are described in detail below. Both these reaction systems are catalyzed by suitable catalysts.

A. Silicone systems which crosslink with each other by condensation These systems are mixtures of aqueous emulsions of polydimethyl-siloxanes (A-l) which comprise SiOH terminal groups, and of alkoxy-functional silicones The emulsion of the polydimethylsiloxane which comprises SiOH terminal groups contains the siloxane in an amount of 20 to 80 by weight, preferably 30 to 60 by weight, with respect to emulsion A-1.

The emulsion of the alkoxy-functional silicone which is capable of crosslinking contains the siloxane in an amount of 20 to 80 by weight, preferably 25 to 9 by weight, with respect to emulsion A-2.

The two emulsions are mixed with each other in a quantitative ratio of A-i to A-2 9 which ranges from 20:80 to 80:20, preferably from 40:60 to 60:40. Both emulsions, of course, contain suitable emulsifiers as determined by the manner in which they are produced.

Emulsion A, which is produced from emulsion A-i and emulsion A-2, contains 20 to 80 by weight, preferably 30 to 60 by weight, of silicone with respect to emulsion A.

RC 210-Foreign Countries -7- A-l: Emulsions of polydimethylsiloxanes which comprise SiOH terminal groups: The polydimethylsiloxanes which comprise SiOH terminal groups are polymers of general formula I HO[Si(CH3)2-O]PH

(I)

where p 400 to 3000, preferably 800 to 2000.

The production of emulsions of long chain silicone oils which comprise SiOH terminal groups by emulsion polymerization is known to one skilled in the art from US-- 2,891,920 or GB-A-1,024,024, for example. The process disclosed in GB-A- 1,024,024, which employs an alkyl-benzenesulphonic acid as a catalyst, is most preferably used, since the emulsifier and polymerization catalyst are present as one substance here. After polymerization is complete, the acid is neutralized, so that the catalyst properties are subsequently blocked whilst the emulsifier properties are completely retained or are even enhanced. Accordingly, the concentration of emulsitfier can be kept low, and after production of the emulsion is complete there are no 0' troublesome extraneous molecules from the catalyst in the finished product. N-alkylsulphonic acids can also be used instead of the aforementioned alkyl-benzenesulphonic acids. It is also possible to use other emulsifiers as co-emulsifiers in addition a to the catalytically active sulphonic acid.

Co-emulsifiers of this type can be either of a non-ionic nature or of an anionic nature.

25 Suitable anionic co-emulsifiers include salts of the aforementioned n-alkyl- or alkylbenzenesulphonic acids. Non-ionogenic co-emulsifiers are polyoxyethylene derivatives of fatty alcohols, fatty acids and the like. Examples of emulsifiers of this type include POE (3)-lauryl alcohol, POE (20)-oleyl alcohol, POE (7)-nonylphenol and POE (10)-stearate (the nomenclature POE (3)-lauryl alcohol means that 3 units of ethylene oxide have been added to one molecule of lauryl alcohol, with the number 3 constituting an average value). Non-ionogenic emulsifiers of this type are familiar in RC 210-Foreign Countries -8principle to one skilled in the art. These added co-emulsifiers firstly increase the stability of the emulsion which results after emulsion polymerization, and secondly they simultaneously have an effect on the chain length of the long chain silicone oil which comprises SiOH terminal groups and which is formed by the polymerization process.

In general, silicone oils such as these, which are formed by emulsion polymerization in the presence of non-ionogenic co-emulsifiers, have lower molecular weights than those for which no co-emulsifier was used. The molecular weight of a silicone oil which comprises SiOH terminal groups and which is formed by emulsion polymerization can also be controlled via the temperature at which equilibrium occurs between the siloxane, water and the silanol which is first formed by ring opening of the siloxane.

The process described below is particularly preferred for the production of an emulsion of a long chain silicone oil which comprises OH terminal groups.

Octamethylcyclotetrasiloxane (D 4) is used as the monomer, in an amount such that a emulsion is formed. The sulphonic acid which acts as a catalyst for the emulsion polymerization is an n-alkylsulphonic acid. 4 of this sulphonic acid is used 20 with respect to the amount of D 4. The Na salt of the sulphonic acid which is used as the catalyst, as well as POE (5)-lauryl alcohol, are employed as co-emulsifiers. The temperature during emulsion polymerization is 60°C, and neutralization is effected with triethanolamine.

25 One particularly preferred emulsion of a polydimethylsiloxane which is blocked by terminal groups is a 40 by weight emulsion of a polydimethylsiloxane of formula I, wherein p is between 800 and 2000.

RC 210-Foreign Countries -9- A-2: Emulsions of alkoxy-functional silicone oils: The silicone oil which is contained in emulsion A-2 according to the invention, and which is capable of crosslinking, consists of units which have the general structure RR'mSiO( 4 2

(II)

wherein R denotes identical or different hydrocarbon radicals or hydrocarbon oxyradicals, which are optionally substituted and which each comprise 1 to 18 carbon atoms, R' denotes identical or different Si-C-bonded, substituted hydrocarbon radicals which contain polar groups, n is an integer with a value of 0, 1, 2 or 3, and m is an integer with a value of 0, 1, 2 or 3, wherein the sum ofn m has an average value from 1.8 to 2.2, and m is selected so that the polyorganosiloxane comprises at least one R' radical.

Preferably, the sum of n m has an average value from 1.9 to 2.1. Examples of hy- 25 drocarbon radicals R include alkyl radicals such as methyl, ethyl, n-propyl, isopropyl, n-butyl, iso-butyl, tert.-butyl, n-pentyl, iso-pentyl, neopentyl or tert.-pentyl radicals; hexyl radicals such as the n-hexyl radical; heptyl radicals, such as the nheptyl radical; octyl radicals such as the n-octyl radical and iso-octyl radicals such as the 2,2,4-tri-methylpentyl radical; nonyl radicals such as the n-nonyl radical; decyl 30 radicals such as the n-decyl radical; dodecyl radicals, such as the n-dodecyl radical; octadecyl radicals such as the n-octadecyl radical; alkenyl radicals such as vinyl, allyl RC 210-Foreign Countries and 5-hexen-l-yl radicals; cycloalkyl radicals. such as cyclopentyl, cyclohexyl and cycloheptyl radicals and methylcyclohexyl radicals; aryl radicals such as phenyl, naphthyl, anthryl and phenanthryl radicals; alkaryl radicals such as m- or p-tolyl radicals, xylyl radicals and ethylphenyl radicals; and aralkyl radicals, such as benzyl radicals and alpha- and P-phenylethyl radicals.

Examples of hydrocarbon oxyradicals R, which may optionally be substituted, include substituted and unsubstituted hydrocarbon radicals R according to the aforementioned examples which are bonded via an oxygen atom which is directly bonded to a silicon atom, particularly alkoxy radicals comprising 1 to 1 8 carbon atoms and phenoxy radicals, especially methoxy, ethoxy, n-propoxy, iso-propoxy and phenoxy radicals. It is preferred that 10 at most of the radicals R are hydrocarbon oxyradicals which are optionally substituted.

The radicals R are preferably methyl, ethyl, phenyl, methoxy and/or vinyl radicals.

On account of their more ready accessibility, 50 the radicals R, particularly at least 80 of the radicals R, are preferably methyl radicals.

R' can be selected from the group comprising the radicals R. R' is preferably selected 20 from the group comprising amino-functional hydrocarbon radicals, for example aminoalkyl radicals, such as the y-aminopropyl radical and the P-aminoethyl-yaminopropyl radical; aminoaryl radicals; or Si-C-bonded, cyclic amino-functional S* radicals.

25 Examples of preferred amino-functional radicals R' include radicals of general formula

-R'-[NR

2

(CH

2 )a]bNHR 2

(III)

wherein

R

1 denotes a divalent C, to C 8 hydrocarbon radical, RC 210-Foreign Countries 11-

R

2 denotes a hydrogen atom or a C, to hydrocarbon radical which is optionally substituted, a has the value 2, 3, 4, 5 or 6, and b has the value 0, 1, 2, 3 or 4.

Examples of the divalent C, to hydrocarbon radicals R 1 include saturated straight-chain, branched-chain or cyclic alkylene radicals such as methylene and ethylene radicals, as well as propylene, butylene, pentylene, hexylene, 2methylpropylene, cyclohexylene and octadecylene radicals, or unsaturated alkylene or arylene radicals such as hexenyl radicals and phenylene radicals, wherein the npropylene radical and the 2-methyl-propylene radical are particularly preferred.

The examples given for R constitute examples of C, to C, 8 hydrocarbon radicals R 2 which are optionally substituted.

The meanings of the constituents of the above general formula (III) are preferably as 20 follows: R' denotes a divalent C 2 to C 6 hydrocarbon radical,

R

2 denotes a hydrogen atom, or a methyl or cyclohexyl radical, oooQ o go o *oo* oo oo a denotes the values 2 or 3, and b denotes the values 0 or 1.

RC 210-Foreign Countries -12- Silicones which are capable of crosslinking and which also contain amino groups, and which are particularly preferred, are partially branched polydimethylsiloxanes of structure O(SiMe 2 )xOR" R Si-O(SiMe 2

)OR"

O(SiMe 2 )xOR" where R' H 2

N(CH

2 2

NH(CH

2 3 or H 2

N(CH,)

3

CH

3 and where R" C 2 H, or -C-CH 2

H

and where Me CH 3 x=20 to 200.

Reference is made to EP-A-0,646,618 for the production of compounds of this type and of suitable emulsifiers.

In addition, the emulsion which contains the alkoxyfunctional silicone which is capable of crosslinking may also contain 2 to 20 by weight, preferably 5 to 15 by weight, of an alkoxy-functional silicone resin of formula V

R

3 dSi(OR 4 )e0 4

(V)

wherein

R

3 is a monovalent hydrocarbon radical comprising 1 to 14 C atoms, preferably a methyl radical, *•go RC 210-Foreign Countries 13-

R

4 is a monovalent hydrocarbon radical comprising 1 to 18 C atoms, preferably a methyl radical, d has a value from 0.75 to 1.5, preferably of about 1, and e has a value from 0.2 to 2, preferably from 0.4 to 1.2.

The viscosity of this resin ranges from 2 to 2000 mPa.s, preferably from 20 to 200 mPa.s.

The production of these alkoxy-functional silicone resins is known and is effected by the reaction of corresponding alkyl- and/or arylchlorosilanes with alcohol and water (see GB-A-685,173, DE-A-958,702, FR-A-1,475,709, US-3,668,180, DE-A- 2,061,189, DE-A-2,444,529, DE-A-2,532,887, EP-A-0,003,610 and DE-A- 3,000,782, for example).

The most preferred methyl-methoxy silicone resin is produced by the reaction of methyltrichlorosilanes with methanol and water. Mixtures of methyltrichlorosilane and other alkyl- and/or arylchlorosilanes and/or tetrachlorosilanes can also optionally 20 be used for the production of the alkoxy-functional silicone resins, without impairing the stability of the emulsion according to the invention. Mixtures of different alcohols can also be used for the production of the resin and/or different alkoxy-functional silicone resins can be mixed with each other without impairing the stability of the emulsion.

The preparation of emulsions of the alkoxy-functional silicone resins described above is known from DE-A- 3,323,909.

Suitable catalytically active substances (catalyst emulsions) for the crosslinking re- 30 action between the polydimethylsiloxanes which comprise terminal Si-OH groups and the amino-functional silicones in the emulsion are those which are described in RC 210-Foreign Countries -14the known literature for condensation and esterification reactions. The catalysts are used in the customary concentrations which are described in said literature.

B. Silicone systems which crosslink with each other by addition These systems constitute an emulsion B which comprises a mixture of an emulsion which contains an organopolysiloxane B-l comprising at least two unsaturated hydrocarbon groups, and an emulsion which contains a methyl hydrogen polysiloxane B-2 in addition to a catalyst.

Emulsion B, which is produced from emulsions B-l and B-2, contains 20 to 80 by weight, preferably 30 to 60 by weight, of silicone with respect to emulsion B.

The organopolysiloxane B-l which comprises at least two unsaturated hydrocarbon groups in the sense of the invention is preferably a cyclic, linear or branched polysiloxane which contains units of general formula 6 )hSiO,( 4 h (VI), 20 where R' C 2

-C

8 alkenyl and/or unsaturated C 3

-C

10 ether radicals, such as vinyl, ~allyl, 1-butenyl, 1-hexenyl and/or -CH 2

-CH

2

CH

2

OCH

2 CH CH 2 etc.,

R

6 a monovalent, saturated hydrocarbon radical which is optionally substituted and which comprises up to 10 carbon atoms, from the group comprising substituted and 25 unsubstituted alkyl, aryl and arylalkyl radicals, wherein f and h are integers within the following limits: 0<f<3 or 0<h<3 and 0<f+h4 and each individual R 5 or R 6 within the molecule can be identical or different.

*°oo*

R

5 is preferably vinyl or allyl, most preferably vinyl.

RC 210-Foreign Countries Examples of R 6 include methyl, ethyl, propyl, isopropyl, butyl, octyl, etc., cyclobutyl, cyclopentyl, cyclohexyl, etc., phenyl, tolyl, xylyl, naphthyl, etc., benzyl, phenylethyl and phenylpropyl. In one embodiment of the invention, some or all of the hydrogen atoms of the R 6 alkyl, aryl, and arylalkyl radicals are replaced by fluorine, chlorine, bromine or iodine atoms and/or by cyano radicals. In this situation, for example, R 6 corresponds to chloromethyl-, trifluoropropyl, chlorophenyl, dibromophenyl-, p-cyanoethyl, P-cyanopropyl or y-cyanopropyl radicals. At least 90% of the

R

6 radicals are preferably methyl, however.

In one preferred embodiment of the invention, f equals 0 or 1.

Using nomenclature which is familiar to one skilled in the art, namely M (CH) 3 SiO,, D =(CH 3 2 SiO22 T (CH 3 )SiO3/ 20 (CH 2

=CH)(CH

3 2 SiO,2, and D (CH 2 =CH) (CH 3 )SiO,, the following examples of component B-1 can be given: 25 M 2 DiooD 3

MV

2

D

1 0 Mvi 1 DlooDvi 3 TsDssoM",, T 3 DooM' 2

M

3 and/or

T

6

D

3 ooD"M 4 M4.

The molar proportion of unsaturated radicals of type R 5 can be selected arbitrarily.

30 In component B-l, the molar proportion of unsaturated radicals of type R should preferably be between 0.01 and 10 mmole/g, more preferably between 0.05 and RC 210-Foreign Countries -16- 1 mmole/g, and most preferably 0.1 to 0.7 mmole/g of component B-1. The viscosity of component B-1 is preferably between 10 and 100,000 mPa.s, most preferably 50-10,000 mPa.s, at In one preferred embodiment of the invention, the organopolysiloxanes described in DE-A-43 28 657 are used as component B-I, since these are branched, the ratio of the number of diorganosiloxy units (D units) to the number of branching locations is between 15 and 40 on average there, at least one triorganosiloxy unit (M unit) and a maximum of half of all the M units are free from unsaturated radicals there and the remaining M units only comprise one unsaturated radical, and the content of unsaturated radicals ranges from 0.1 to 1 mmole/g.

The branching locations of component B-1 are preferably monoorganosiloxy units, i.e. tri-functional siloxy units (T units), which, however, can also be replaced in part by tetra-functional siloxy units (SiO4 units, Q units).

The terminal groups of the branched organopolysiloxane which are free from unsaturated radicals perform the function of an internal plasticizer. The flexibility of the crosslinked film can be controlled via the number terminal groups which are free 20 from unsaturated radicals (M units).

S* Examples of compounds which are preferred as component B-l are compounds of formulae S: 25 TSD 20 oo 0

IM

2

T

7

D

2 8 0Mi5M 4

T

6 DIs 8

D

2 M M 4 and/or T 8

D

25

OM'

7

M

3 Branched organopolysiloxanes B-l which comprise at least two unsaturated hydrocarbon groups can be produced by customary methods, such as the hydrolysis of 30 chlorosilanes and subsequent polymerization with low molecular weight cyclic diorganopolysiloxanes.

RC 210-Foreign Countries -17- The methyl hydrogen polysiloxane B-2 preferably contains units of general formula Hj(R')kSiO( 4 -jky (VII) where R 7 monovalent, saturated hydrocarbon radicals, which are optionally substituted and which comprise up to 10 carbon atoms, from the group comprising substituted and unsubstituted alkyl, aryl, arylalkyl and/or C 2 alkenyl radicals, wherein j and k are integers, where 0 k 5 3, 0 j 2 and 0 j+k 4, preferably 0 5 j 1.

The methyl hydrogen polysiloxanes B-2 are preferably linear. At least half the D units preferably comprise hydrogen atoms which are directly bonded to silicon

(H(CH

3 )SiO groups). The number of groups comprising hydrogen atoms which are directly bonded to silicon is preferably between 70 and 85 of the di-functional units.

20 Within the scope of the aforementioned structural limitations, the molar proportion of hydrogen atoms which are directly bonded to a silicon atom in component B-2 can be selected arbitrarily.

In component B-2, the molar proportion of hydrogen atoms which are directly 25 bonded to a silicon atom is preferably between 0.01 and 17 mmole, more preferably between 0.1 and 17 mmole and most preferably between 1 and 17 mmole/g component B-2.

Examples of component B-2 include compounds of formulae RC 210-Foreign Countries -18-

M"

2

D

1 o, M 2 DioD 10 o, MH 2

DH

2 0Do,

M"

2 D I I and/or M 2 D 3

DH

8 where MH= H(CH 3 2 SiO,, and DH H(CH 3 )SiO22.

Components B-l and B-2 are preferably present in aqueous emulsion B in a quantitative ratio such that the molar ratio of hydrogen atoms which are directly bonded to a silicon atom (SiH) in component B-2 to the unsaturated radicals (Si-vinyl) in component B-l is between 0.05 and 20, more preferably between 0.5 and 10 and most preferably between 1 and 3.

In addition, emulsion B may also contain an organopolysiloxane which comprises units of general formula

(R

7 ),SiO( 4

(VIII),

wherein

R

7 represents monovalent, hydrocarbon radicals which are optionally substituted and 20 which comprise up to 10 carbon atoms, from the group comprising substituted and unsubstituted alkyl, aryl, and arylalkyl radicals, and which can be the same or different within the molecule, and wherein r can assume the value of integers between 0 and 3.

25 The preferred organopolysiloxane is a linear polydimethylsiloxane which comprises trimethylsiloxy terminal groups, such as that sold by Bayer AG under the description Baysilone®-Ole M, for example. The use of Baysilone®-Ole M such as these which have a viscosity between 50 mm 2 sec' and 5000 mm 2 sec' is particularly preferred.

30 Emulsion B also contains a catalyst from the platinum group, preferably the elements platinum, rhodium, iridium, nickel, ruthenium and/or palladium, in elemental form, RC 210-Foreign Countries -19on a support or in the form of compounds thereof. Platinum compounds or platinum complexes are preferred, such as H 2 PtCl 6 platinum-olefine complexes, platinum-alcohol complexes, platinum-vinylsiloxane complexes or even elemental platinum on a support substance, such as activated carbon, A1 2 0 3 or SiO 2 A platinum-vinylsiloxane complex is particularly preferred as the catalyst. Said platinum-vinylsiloxane complexes preferably have at least 2 olefinically unsaturated double bonds in the siloxane entity. They are described in US-3,715,334, for example.

The term siloxanes includes polysiloxanes, i.e. it also includes vinylpolysiloxanes.

The proportion of catalyst with respect to the sum of all the constituents is preferably between 1 and 1000 ppm, more preferably between 1 and 500 ppm and most preferably between 25 and 250 ppm.

A catalyst from the platinum group can also be pre-dissolved in part of polymer B-1, for example.

Emulsion B may also contain an inhibitor, suitable emulsifiers, thickeners and/or customary additives and adjuvant substances (but no fillers). Reference is made to 20 EP-A-0,819,735 for the production of emulsion B Aqueous colloidal hydrated silica The aqueous colloidal hydrated silica (silica sol) is an aqueous colloid containing o* 25 to 40 by weight, preferably 25 to 35 by weight, of hydrated silica with an average particle diameter of 6 to 50 nm, preferably 7 to 15 nm. Colloidal hydrated silica systems of this type are known to one skilled in the art from the literature and are commercially available.

The aqueous parting agent emulsion according to the invention contains 5 to 35 by weight, preferably 8 to 24 by weight, of silicone emulsion A or B as described RC 210-Foreign Countries above, as well as 0.5 to 5 by weight, preferably 0.8 to 4 by weight, of aqueous colloidal hydrated silica as described above, with respect to the total emulsion.

The total silicone content in the parting agent according to the invention ranges from 2 to 20 by weight, preferably 5 to 15 by weight, with respect to the parting agent.

The emulsion according to the invention may additionally contain, independently of each other, germ prevention agents, rot prevention agents (bactericides), additional wetting agents, thickeners, stabilizers, additional emulsifiers, anti-foaming agents, corrosion inhibitors and colorants, preferably organic colorants and particularly colorants which can be activated by UV light.

In particular, the emulsion according to the invention may contain 0 0.01 to 0.1 by weight, preferably 0.03 to 0.06 by weight, of customary germ prevention agents, 0.1 to 1 by weight, preferably 0.3 to 0.7 by weight, of thickeners/stabilizers, particularly polysaccharides, V, 0 0.1 to 2 by weight, preferably 0.3 to 0.6 by weight, of wetting agents, preferably non-ionic wetting agents, which give rise to a homogeneous distribution (spray pattern) when surfaces are sprayed, due to the improved wetting thereof, 0.5 to 4 by weight, preferably 0.8 to 2 by weight, of polyethylene waxes, S: particularly hard polyethylene waxes having an average particle size of 1 to 9 lm and a melting point between 90 and 110C, 0.1 to 4 by weight, preferably 0.3 to 2 by weight, of polytetrafluoroethylene micro-powders (waxes) which are known from DE-A-4,024,565, for example and which have a molecular weight between 30000 and 200,000 and an average parti- •cle size of 1 to 20 jim.

RC 210-Foreign Countries -21 The parting agent emulsions according to the invention can be mixed together from the respective individual components by customary methods known to one skilled in the art.

The emulsion as used has a viscosity (DIN 5321 1, 4 mm Ford Cup) of 20 to 80 seconds, preferably of 30 to 60 seconds.

The composition according to the invention is preferably used as a parting agent for vulcanization. In this application, the parting agent is sprayed on to the bladder (heating membrane) and/or on to the inner liner of the tire blank before the bladder is inserted in the interior of the (green) tire blank. The amount of parting agent which is deposited is between 8 and 50 g/m 2 preferably between 11 and 25 g/m 2 of the surface which is sprayed. The requisite amount of sprayed-on parting agent for a conventional private car tire is 6 to 40 g, preferably 8 to 18 g.

The bladder is subsequently inserted in the tire. The heating membrane heats the tire blank and simultaneously presses it, under high pressure, into the negative mold, oooo where it is vulcanized. The bladder is then removed from the tire again.

The use of the composition according to the invention as a parting agent in the process described above for the vulcanization of tires has the advantages that not only can S• the bladder easily be inserted in and subsequently removed again from the tire blank, but also that air escapes completely from the intermediate space between the bladder and the tire inner liner, due to the formation of fine fissures in the semi-elastic coat- 25 ing which is formed. Included air means reject tires, since satisfactory vulcanization does not take place under an air bubble. Moreover, the bladder can be separated from the vulcanized tire without problems. Furthermore, if a variable spraying technique is used with the parting agent compositions according to the invention it is possible that each tyre does not have to be sprayed. Due to the use of silicone components which crosslink under vulcanization conditions, separation phenomena at the tire faces can be eliminated. In addition, part of the coating is formed on the bladder and has a RC 210-Foreign Countries -22positive effect on bladder life. It is also possible to apply. an additional coating to new bladders, in order to facilitate the start of new bladders in the press.

As a whole, the use of the parting agents according to the invention can not only improve the quality of tires and the tire reject rate, but can also drastically reduce both the cost per tire and the amount of contaminants (soiling of the production installation/reduction of waste), as a direct consequence of the smaller amount of spray solutions which are used.

The invention is explained in more detail by the following examples.

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o* *i RC 210-Foreign Countries -23-

EXAMPLES

Example 1 (Prior art parting agent composition aqueous dispersions of a tire inner spray solution).

Silicone oil emulsions: by weight Silicone oil, viscosity (1-1000 m 2 /s) 100 100,000 cSt Fillers: carbon black mica, French chalk, etc.

5-15% 1-2% 20 40 r Glycols, wetting agents 10 20 Water balance Amount sprayed on per private car tire blank 16 30 g 22 g on average of a prior art aqueous inner spray solution containing about 40 of active ingredient (all the constituents apart from water) were uniformly sprayed into a private car tire blank. This corresponded to about 11 g of active ingredients per private car tire. Subtracting the amount of overspray of about 25 30 which did not reach the tire blank leaves a remainder of about 8 g of active ingredients per private car tire. The individual constituents, which are given below in the form of a Table in g/private car tire, fulfil the following requirements: RC 210-Foreign Countries -24- Molding Demolding Active ingredi- g/private car Sliding De-airing Parting ef- Bladder ents tire blank effect fect/sliding ef- service life fect Silicone oil about 0.96 X X X Glycols about 1.44 X X X +surfactants Mineral fillers about 5.6 X carbon blacks Total about The following components were used in the experiments detailed below: Propel® GXL is a bactericide (a commercial product ofICI).

Kelzon® D is a polysaccharide which acts as a thickener and stabilizer (a commercial product of Langer Co.).

Levasil® 200A30 (a commercial product of Bayer AG) is a silica sol which contains 30 by weight SiO 2 and which has a specific surface of 200 m 2 Its particle size ranges from 7 to 15 nm. Levasil® 200A30 promotes better curing of the formulation and on dilation contributes to the formation of fissures in the coating, which in turn has a positive effect on de-airing.

Lanco® Wachs PEW 1555 (a commercial product of Langer Co.) is a hard polyethylene wax with an average particle size of 2.5 tm and a melting point of 102°C.

9 9b 9 9**99 RC 210-Foreign Countries Rewopal® LA 6 (a commercial product of Rewo) is a non-ionic wetting agent which results in a homogeneous distribution (spray pattern) on spraying due to improved wetting of the inner liner compound.

Oil emulsion 1 (see Example 2) is Baysilon® N (Bayer AG) Oil emulsion 2 (see Example 3) is Baysilon® VP AI 3632 (Bayer AG) Oil emulsion 3 (see Example 3) is Baysilon® VP AI 3628 Z 343 (Bayer AG) Oil emulsion 4 (see Example 3) is Baysilon® VP Al 3629 Z 344 (Bayer AG) o* *e Example 2: Experiment using the condensation crosslinking system Constituents by weight water 83.10 Proxel® CXI 0.05 (germ prevention agent) Kelzan® D 0.45 (thickener) Rewopal® LA 6 0.40 emulsifier) oil emulsion 1 6.50 il emulsion 2 6.50 Lanco® PEW 1555 1.00 Levasil® 200 A 30 2.00 In experiments with the composition according to Example 2, about 13 g of product were sprayed on. The content of active ingredients (percentage of all the constituents in the composition apart from water) was about 10 If the amount of overspray of RC 210-Foreign Countries -26about 25 30% is taken into account, there remained about 1.0 g of active ingredients/tire blank.

Molding Demolding Active in- g/private Sliding De-air- Parting ef- Bladder gredients car tire effect ing fect/sliding durability blank effect Silicone 0.8 X X X X polymers Surfactants 0.2 X X X Total In a production trial in a tire factory, about 3000 private car tires of all tire sizes were produced using the condensation crosslinking system according to the invention. All the vulcanized tires were of the best quality.

An aspect which should be emphasized is the total transparency of the inner tire, which enabled markings (such as bar codes) to be identified. No marks or other defects could be ascertained, even during possible overspraying on to the outside.

The silicone polymers formed an extremely thin layer which polymerized during vulcanization, whereby any separation effect was partly eliminated (no separation at the splice). This effect was confirmed by separation loading tests according DIN 53539.

The function of de-airing, which in prior art systems which contain fillers is performed by the fillers, was also observed as a result of the parting layer formed by the condensation crosslinking system according to the invention.

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55 S 555a e RC 210-Foreign Countries -27- Comparison of the amounts sprayed on to private car tires Tire inner spray solutions (solids content of the amounts sprayed on per private car tire blank) Prior art composition Composition according to according to Example I Example 2 Solids content/private car tire blank Solids content/private car tire blank about 11 g about 1.0 g Silicone oil/private car tire blank Silicone polymers/private car tire blank about 1.32 g about 0.8 g The solids content which had to be sprayed on per tire blank in order to achieve the desired effects was reduced by about 90 (from 11 g to 1.0 If the proportion of silicone oil is compared with that of the silicone polymer, a reduction of about 40 was achieved (from 1.32 g to 0.8 g).

This means that the water loading due to overspray (overspray about 25 30 the total amount sprayed) in spraying installations is reduced to the said amounts in total, 40 for the silicone oil or polymer), i.e. the pollutant burden is reduced by the same ratio.

o* *e RC 210-Foreign Countries -28- Example 3: Experiment using a Pt-catalyzed addition system Constituents by weight Water 77.05 Proxel® GXL 0.05 Kelzan® D Rewopal® LA 6 0.4 oil emulsion 3 oil emulsion 4 Lanco® PEW 1555 Levasil® 200A30 *9 a. 9S*** About 200 private car tires of different popular sizes were sprayed and vulcanized.

These results corresponded to those which were also obtained for the condensation crosslinking system. The tires were all of the best quality.

These examples clearly show that, compared with prior art parting agent systems, 10 better results are obtained, with the use of lesser amounts of active ingredients, by employing the crosslinking silicone systems according to the invention.

Although the invention has been described in detail in the foregoing for the purpose of illustration, it is to be understood that such detail is solely for that purpose and that variations can be made therein by those skilled in the art without departing from the spirit and scope of the invention except as it may be limited by the claims.

Throughout this specification and the claims which follow, unless the context requires otherwise, the word "comprise", or variations such as "comprises" or "comprising", will be understood to imply the inclusion of a stated integer or step or group of integers or steps but not the exclusion of any other integer or step or group of integers or steps.

Claims

1. A parting agent comprising, in an aqueous emulsion, i) a system comprising at least two silicone components which react with each other with crosslinking, said system being selected from the group consisting of silicone components which react with each other by condensa- tion, or silicone components which react with each other by addition, and ii) an aqueous colloidal hydrated silica (silica sol).

2. A parting agent according to Claim 1, wherein a silicone component system which reacts by condensation comprises, in an aqueous emulsion, a poly- dimethylsiloxane which comprises Si-OH terminal groups, and a sili- 20 cone which is capable of crosslinking.

3. A parting agent according to Claim 1, wherein a silicone component system which reacts by condensation comprises, in an aqueous emulsion, an or- ganopolysiloxane which comprises at least two unsaturated hydrocarbon 25 groups, and a methyl hydrogen polysiloxane

4. A parting agent according to Claim 1, wherein the aqueous colloidal hydrated S" silica comprises, with respect to the silica sol, 15 to 40 by weight of hy- drated silica with an average particle size from 6 to 50 nm.

RC 210-Foreign Countries A parting agent according to Claim 1, comprising 5 to 35 by weight of an emulsion of silicone components which react with each other by conden- sation and 0.5 to 5 by weight of aqueous colloidal hydrated silica, with re- spect to the total amount of parting agent in each case.

6. A parting agent according to Claim 1, comprising 5 to 35 by weight of an emulsion of silicone components which react with each other by addition and 0.5 to 5 by weight of aqueous colloidal hydrated silica, with respect to the total amount of parting agent in each case.

7. A parting agent according to Claim 1 comprising additional constituents which are selected from the group consisting of germ prevention agents, rot prevention agents, wetting agents, thickeners, stabilizers, anti-foaming agents, corrosion inhibitors and colorants.

8. A process for vulcanizing pneumatic tires, comprising the step of applying a parting agent to the bladder and/or to the tire blank before vulcanization, 66 wherein said parting agent comprises, in an aqueous emulsion, •o i) a system comprising at least two silicone components which react with each other with crosslinking, said system being selected from the group consisting of silicone components which react with each other by condensa- S 25 tion, or silicone components which react with each other by addition, and S" ii) an aqueous colloidal hydrated silica (silica sol).

9. A process according to Claim 8, wherein said application is effected by spray- ing or brushing.

RC 210-Foreign Countries -31 A process according to Claims 8, wherein the amount of parting agent which is applied ranges from 5 to 50 g/m 2

11. An aqueous emulsion comprising a parting agent comprising in an aqueous emulsion, i) a system comprising at least two silicone components which react with each other with crosslinking, said system being selected from the group consisting of silicone components which react with each other by condensa- tion, or silicone components which react with each other by addition, and ii) an aqueous colloidal hydrated silica. SS

12. An aqueous emulsion according to Claim 11 for the production of pneumatic 20 tires.

13. An aqueous emulsion according to Claim 11 for coating the bladder and/or the inner liner before the vulcanization of the tire blank. 0* 9 j

14. An aqueous emulsion according to Claim 13 wherein an amount of 8 to 25 g/m 2 of the surface is to be coated. A parting agent and products containing the same, substantially as hereinbefore described with Sreference to the Examples. DATED this 9th day of November 1999 RHEIN CHEMIE RHEINAU GmbH By its Patent Attorneys DAVIES COLLISON CAVE