CA2036272A1 - Solid silicone compositions having an agricultural biological action - Google Patents

Abstract

Company called: RHONE-POULENC AGROCHIMIE

SOLID SILICONE COMPOSITIONS HAVING AN
AGRICULTURAL BIOLOGICAL ACTION
ABSTRACT

Solid compositions having an agricultural biological action. They comprise a matrix of silicone elastomer in which a water-soluble active substance having an agricultural biological action and a water-soluble auxiliary agent are dispersed.
Application in agriculture.

Description

Solid silicone compositions havinq an aqricultural bioloqical action The present invention relates to solid, silicone-based compositions having an agricultural biological action, their preparation and their use for the treatment of plants.
The treatment of plants and especially of crops in order ~o promote their growth often requires the po~sibility of progres~ively salting out the substances having a biological action from a solid carr~er onto or towards the plants.
Numerous techniques have been proposed combining the polymer material and some active substances, in particular agrochemical or fertiliser active substances. In fact, these techniques have found limited practical application or have not found sufficient outlets because:of ~everal disadvantages, of which the main di~advantage i3 the difficulty in controlling the release kinetics of the active substance and consequently in reliably obtaining a predetermined effect for a given content of active substance.
Other dlsadvantages also lie in the fact that the polymer~ are not sufficiently harmless for the plants to be treated and for the environment, and also in their cost and their implementation.
The aim of the present invention is to alleviate these disadvantages and to provide '~ ,.

compositions having a progressive biological action permitting the release of agricultural active substances in a controlled manner at low cost, and without disadvantage for the plants to be treated and for the environment.
More precisely, the invention relates to solid, polymer-based compositions having an agricultural biological action in order to promote the growth of plants, wherein said compositions consist of a predominant amount of a silicone material, which may or may not be crosslinked and iB permeable to water vapour, and a minor amount of an active substance having an agricultural biological action and a solubility in water of at least 0.5 g/l, and a water-soluble auxiliary agent, di3persed homogeneously in thesilicone material, and without an inhibitory effect on the crosslinking of the silicone, the silicone material, the water-soluble form of the active substance and the auxiliary agent being such that the release kinetics of the active substance by the silicone matrix are of the order of zero.
The invention relates more particularly to compositions of the above type wherein the ~ystem comprising active substance plu8 auxiliary agent is present in an amount of 5 to 50, preferably 15 to 40, parts by volume per 100 parts by volume of organopolysiloxane ~tarting material.
In general, the ratio by volume of the active .,. . ~: .

3 20362~2 substance to the auxiliary agent may vary from 1~10 to 10/1, preferably from 1/5 to 5/1.
Several groups of silicones may be mentioned as silicones which can be used as materials in the compositions according to the invention.
A first ~roup comprises silicone compositions containing (A) a diorganopolysiloxane gum, (B) a reinforcing filler (sl), which is preferably siliceous, and/or an organic peroxide (B2).
Preferred compositions comprise:
- (A): 100 parts by weight of a diorgano-poly~iloxane gum having a viscosity higher than 1 million mPa.s at 25C, and - (B): 5 to 130 parts by weight of a reinforcing siliceous filler (B1) chosen from pyrogenic silicas and silicas produced by precipitation.
Advantageously, the gum (A) has the general formula R3,(R'O).SiO(R2SiO)DSi(OR')~R3 " in which the symbols Rr which may be identical or different, represent C1-C8 hydrocarbon radicals, which are unsubstituted or substituted by halogen atoms or cyano radicals; the symbol R' represents a hydrogen atom or a C1-C~ alkyl radical, the ~ymbol a re~re~ents zero or one, the symbol n represents a number having a value sufficient to obtain a viscosity of at least 1 million mPa.~ at 25C, and at least 50 % by number of the radicals represented by R are methyl radicals.
Preferably, O.OOS to 0.5 mol% of the R2SiO

units involved in the structure of the gum (A) are chosen from those of formulae (CH2=CH)(R)SiO and ~C~2=CH)R2-a(RO~)asioo~s The gum (A) ha~ing a viscosity of at least ~. million mPa.s at 25C, and preferably of at least 2 million mPa.s at 25C, is made up, along its chain, of R2SiO units and is blocked at each end of its chain by an R3 aR(O)~SiOo 5 unit; however, the presence, in a mixture with these unit3, of units having a different structure, for example of formula RSiOlS and SiO2, is not excluded in a proportion of at most 2 % relative to the total number of R2SiO and R3~(RO'),SiOos units.
The symbol R repre~ents a ~l-C8 hydrocarbon radical which i~ unsubstituted or substituted by halogen atoms or cyano radicals; more specifically, it encompasYes:
- Cl-C5 alkyl radicala which are un~ubstituted or substituted by halogen atoms or cyano radicals, such a~ methyl, ethyl, propyl, i~opropyl, butyl, isobutyl, pentyl, 3,3,3-trifluoropropyl, beta-cyanoethyl and gamma-cyanopropyl radical~, - C2~C~ alkenyl radical~, such as vinyl, allyl and but-2-enyl radical~, and - C~-C~ monocyclic aryl radicalR which are unsubstituted or substituted by halogen atomR, such as phenyl, chlorophenyl, tolyl and trifluoromethylphenyl radicals.
The Cl-C~ alkyl radicals represented by the 2~36272 symbol R' relate more specifically to methyl, ethyl, propyl, isopropyl, butyl and secondary butyl radicals.
At least 50 % by number, and preferably at least 70 ~, of the radicals represented by R are methyl radicals.
Moreover, vinyl radicals are preferably also present, in an appropriate amount, in the gum (A); they lead to units of formula CH2=CH(R)SiO and CH2=CH(R2~)(RO~)~SiOo5, the number a of which represents 0.005 to 0.5 mol%, and preferably 0.01 to 0.45 mol%, of the units of general formulae R2SiO and R3~(RO')~SiOos, as a whole, which are involved in the structure of the gum (A)-Specific examples which may be mentioned of units making up the gums (A) are those of formulae:
( CH3 ) 2SiO, CH3 ( CH2=CH ) SiO ~ CH3 ( C5H5 ) SiO ~
(C6H,)2SiO, CH3(C2H5)SiO, CH3CH2-CH2(CH3)SiO, CH3(n-C3H7)SiO, (CH3)3SiOo.5, (cH3)2cH2=cHsioo.5~ CH3(C6H5)2si0.5~ -CH3(C6H,)(CH2=CH)SiOo.5, HO(cH3)2siOo.5~ CH30(CH3)2si0.5~
2 0 C2H50 ( CH3 ) 2SiO~ 5, n-c3H7o ( CH3 ) 2SiOo 5, HO ( CH2=CH ) ( CH3 ) SiOo 5.
The gums (A) are marketed by silicone manufacturers and, on the other hand, they may easily be produced employing techni~ues widely described in the chemical literature.
In the ma~ority of casQs, methylvinyl-dimethylpolysiloxane gums having (CH3)2SiO and CH2=CH(CH3)SiO units along their chain and units chosen from those of formulae:

(CH3)2(CH2=CH)SiOo 5, HO(cH3)(cH2=cH)si (CH3)3siOo.5/ C6H5(CH3) (CH2=cH)sio~ 5~ HO(CH3)2SiOo 5 at the end of their chain, or dimethylpolysiloxane gums blocked at each end of their chain by one of the above units containing a vinyl radical, are used.
They generally have a viscosity of at least 2 million mPa.s at 25DC.
The fillers (B1), which are preferably reinforcing silicas, are used in an amount of 5 to 130 parts of the diorganopoiysiloxane gums (A). They are chosen from silicas produced by combu~tion and silicas produced by precipitation.
They have a specific surface area, determined by the BET methods, of at least 50 m2/g and preferably of more than 70 m2/g, an average size of the primary particles of les~ than 0.1 ~m (micrometre) and an apparent density of less than 200 g/litre.
These silicas may be incorporated as such or after having been treated with organosilicon compound~
customarily used for this application. These compounds include methylpolysiloxanes, ~uch a~ hexamethyl-disiloxane and octamethylcyclotetrasiloxane, methylpolysilazanes, such a~ hexamethyldisilazane and hexamethylcyclotrisilazane, chlorosilane~, such as dimethyldichlorosilane, trimethylchlorosilane, methylvinyldichlorosilane and dimethylvinyl-chlorosilane, and alkoxysilanes, such as ~ , 7 2~36272 dLmethyldLmethoxysilane, dLmethylvinylethoxysilane and trLmethylmethoxysilane.
- During this treatment the silicas may increase their initial weight by a proportion of up to 20 %, preferably about 18 %.
The compo~itions according to the invention, that is to say the silicone compositions of the first group (i.e. A ~ B) mixed with the active substance C, may be malaxated cold as such and be extruded in very diverse forms. The silicone composition forms obtained may be cut to the desired length ~uch that the cut form contains a sufficient equivalent amount of active substance for salting out over the desired period.
Surprisingly, it has been discovered that these non-crosslinked silicone compositions have adequate physical characteristics for the applications envi~aged and salt out the active ~ubstance continuously and in a controlled manner.
Within the framework of the present invention, an organic peroxide (B2) may be used in addition to (Bl) or instead of (Bl). It is then necessary to crosslink the elastomer composition at elevated temperature.
The organic peroxides (B2) are used in an amount of 0.1 to 6 parts, prefarably 0.2 to 5 parts, per 100 parts of the gums (A). They are well known to those skilled in the art and comprise, more particularly, benzoyl peroxide, 2,4-dichlorobenzoyl " 8 2036272 peroxide, dicumyl peroxide, 2,5-bis(t-butylperoxy)-~,5-dLmethylhexane, t-butyl perbenzoate, t-butyl and isopropyl peroxycarbonate,-di-t-butyl peroxide and 1,1-bis(t-butylperoxy)-3,3,5-trLmethylcyclohexane.
These various peroxides decompose at temperatures and at rates which are ~ometLmes different. They are chosen depending on the curing conditions required.
The silicone compositions according to the invention may also comprise, per 100 parts of gum ~A), from 0.1 to 6 part~ of a structuring agent lD) which is a fluoro-organic polymer in the form of a pulverulent solid.
The fluorinated polymers (D) are used in an 15 amount of from U.l to 6 parts, preferably 0.15 to 5 parts, per 100 parts of the diorganopolysiloxane gums (A). These compound~ are well-known to those-skilled in the art; they are prepared by polymerisation or copolymerisation of monomers chosen, for example, from 20 the group comprising tetrafluoroethylene, chlorotri- .
fluoroethylene, vinylidene fluoride and -hexafluoropropene.
These are, therefore, polymers or copolymers consisting of units derived from the above monomers;
thus, polytetrafluoroethylenes, binary copolymers of the polytetrafluoroethylene~beta-fluoropropene type or of the vinylidene fluoride/hexafluoropropene type, and ternary copolymers of the vinylidene :

203~272 fluoride/hexafluoropropene/tetrafluoroethylene type may be used.
These compounds may be introduced into the compositions of the invention in the form of powders having an average particle diameter of less than 100 micrometres, for example having a diameter ranging from 25 to 65 micrometres.
Preferably, when the crosslinking agents (B2) are used, up to 90 % by weight of the reinforcing silicas (Bl) may be replaced by semi-reinforcing or packing fillers, the particle diameter of which is greater than 0.1 ~m, such as ground quartz, calcined clays and diatomaceous earths.
The silicone compositions may also comprise from l to lO parts of dimethylpolysiloxane oil (E) having silanol ends and having a viscosity at 25C of between 10 and 5,000 mPa.s, preferably from 30 to 1,000 mPa.s, per 100 parts of gum (A). Their use i~
recommended in particular when the amounts of reinforcing fillers (Bl) are high.
The preparation of the compositions according to the invention is effected with the aid of known mechanical means, for example kneaders, cylinder mixers or ~crew mixers.
The various constituents are incorporated in this equipment in a sequence which may be arbitrary.
However, it is recommended to charge the gum (A), then, in sequence, the siliceous fillers (Bl) and the active substance (C), where appropriate the additive (E) and, finally, the compound (D) and (Bz).
The compositions o~tained are stable on storage; moreover, they mould and extrude easily, which allows very varied forms to be produced. Those compositions which contain peroxide (B2) are crosslinked by heating. The heating time obviously varies with the temperature, the pressure and the nature of the crosslinking agents. It i~ generally of the order of several minutes at about 150-250C and a few seconds at about 250-350C.
The ela~tomers thu~ formed may sub~equently be post-heated if nece~sary, especially those obtained by moulding for a period of at least one hour at a temperature of between 190 and 270C, with the aim of completing their crosslinking.
However, from the end of their first crosslinking stage, that is to say before any post-heating stage, these ela~tomers have physical characteristics ade~uate for the envisaged application.
The optionally crosfilinked silicone compositions are advantageou~ly in varied solid forms.
The amount of active substance and the salting out period are determined for a given presentation.
A second ~roup of silicones which may be used according to the invention comprises vulcani~able, and preferably hot-vulcanisable, silicone compositions containing:

(A) a diorganopolysilo~;ane gum having, per molecule, at least two vinyl groups bondPd to the silicon and a viscosity at 25DC of at least 500,000 mPa.s, (B) at least one organohydrogenopolysiloxane having, per molecule, at least three hydrogen atoms bonded to the silicon, (C) a reinforcing filler, and (D) a catalytically effective amount of a catalyst which is a compound of a metal of the platinum group.
More precisely, the pre~ent invention relates to a silicone composition compri~ing:
- (A): 100 parts of a diorganopolysiloxane gum having, per molecule, at least two vinyl groups bonded to the ~ilicon and a visco~ity at 25-C of at least 500,000 mPa.s, - (B): at least one organohydrogeno-polysiloxane having, per molecule, at least 3 hydrogen atoms bonded to the silicon, in an amount such that the ratio by number of hydride functional groups in (B) to vinyl groups in (A) is between G.4 and 10, - (C): 5 to 130 parts of a reinforcing filler which is preferably siliceous and is chosen from 25 pyrogenic silica~ and silicas produced by precipitation, and - (D): a catalytically effective amount of a catalyst which is a compound of a metal of the platinum . ..~

group.
The ratio by number of hydride groups in (B) to vinyl groups in (A) may be very variable. It is generally between 0.4 and 10, preferably between 1.1 and 4.
More particularly, the diorganopolysiloxane gum (A) has the general formula R3 ~(R'O)~SiO(R2SiO)nSi(OR' )~R3 ~, in which the symbols R, which may be identical or different, represent C1-C~
hydrocarbon radicals which are unsubstituted or substituted by halogen atoms or cyano radicals; the symbol R' represents a hydrogen atom or a Cl-C~ alkyl radical, the symbol a represent~ zero or one, tha symbol n represents a number having a value sufficient to obtain a viscosity of at least 500,000 mPa.s at 25C, and at least 50 % by number of the radicals represented by R are methyl radicals.
Preferably, 0.005 to 0.5 mol% of the units involved in the ~tructure of the gum (A) are chosen from those of formulae ~CH2=CH)(R)SiO and/or ( CH2=CH ) RZ . ( RO ' ) ~si0.5 -The gum (A) having a viscosity of at least 500,000 mPa.~ at 25C and preferably of at least 1 million mPa.s at 25-C is made up of RzSiO units along its chain and it is blocked at each end of its chain by an R3,R(O),SiOo 5 unit; however, the presence, in a mixture with these units, of units of different structure, for example of formula RSiO~ 5 and SiO2, is ~ , :

13 2~3~272 not excluded in a proportion of at most 2 ~ relative to the total number of R2SiO and R3a(RO )aSiO05 units.
The symbol R represents a Cl-C8 hydrocarbon radical which is unsubstituted or substituted by halogen atoms or cyano radicals; more specifically, it encompasses:
- Cl-C5 alkyl radicals which are unsubstituted or substituted by halogen atoms or cyano radi~als, quch as methyl, ethyl, propyl, isopropyl, butyl, i~obutyl, pentyl, 3,3,3-trifluoropropyl, beta-cyanoethyl and gamma-cyanopropyl radical~, - C2-C~ alkenyl radicals, such as vinyl, allyl and but-2-enyl radicals, and - C6-C~ monocyclic aryl radicals which are unsubstituted or substituted by halogen atoms, such as phenyl, chlorophenyl, tolyl and trifluoromethylphenyl radicals.
The Cl-C~ alkyl radical~ repre~ented by the symbol R~ relate more ~pecifically to methyl, ethyl, propyl, isopropyl, butyl and secondary butyl radicals.
At least 50 % by number and preferably at lea~t 70 ~ of the radical~ R are methyl radicals.
Moreover, -~inyl radical~ are preferably al~o preqent, in an appropriate amout, in the gum ~A); they lead to units of formula CH2=CH(R~SiO and CH2=CH(R2~)(RO')~SiOos, the number of which represents O.OOS to O.S mol%, preferably 0.01 to 0.45 mol~ of the units of general formulae R2SiO and R3,(RO')~SiOo5 a~ a whole which are involved in the structure of the gum ~A).
- Specific examples which may be mentioned of units making up the gums (A) are those of formulae:
(CH3)2SiO, CH3(CH2=CH)SiO, C~3(C~Hs)si~
(C6H5)2SiO, CH3tc2H5)sio, CH3CH2-CH2(CH3)SiO, CH3(n-C3H7)5iO, (CH3)3SiOo.5, (cH3)2(cH2=cH)siOo5~ CH3(C6~s)2siosr CH3(C6H5) (CH2=CH)SiOo.5, Ho(cH3)2sioo.5~ CH3(CH3~2sia.s~
C2Hs(cH3)2si0.5~ n-C~H70(CH3)2SiOO5 and HO(CH2=CH)(CH3)SiOo.s-The gum~ (A) are marketed by silicone manufacturer~ and, on the other hand, they may easily be produced employing techniques widely described in the chemical literature.
In the ma~ority of cases, methylvinyl-dimethylpolysiloxane gums having ICH3)2SiO and CH2-CH(CH3)SiO units along their chain and unit~ chosen from those of formulae:
(CH3)2(CH2=CH)SiOo.5~ HO(CH3)(cH2=cH)si (CH3)3SiOo 5, C~H5(CH3)(CH2=CH)SiOo5 and HO(CH3)2SiOo 5 at the end of their chain, or dimethyl-polysiloxane gums blocked at each end of their chain by one of the above units containing a vinyl radical, are used.
They generally have a visc03ity of at least 2 million mPa.s at 25~C.
The organohydrogenopolysiloxane (B) has a siloxane unit of average general formulas ' 203627~
(H~c (R )dSiO5-d-c in which R~ represents methyl, phenyl and vinyl radicals, at least 50 % of these radicals being methyl radicals, c represents any number from 0.01 to 1 :inclusi~e and d represents any number from 0.01 to 2 inclusive.
These organohydrogenopolysiloxanes (B) are chosen from straight-chain, branched or cyclic polymerY
made up of units chosen from those of formulae:
R"2SiO, ~(R")SiO, H(R" )2sioo 5~ HSiOl 5, R~SiO~5SiO2 and RNSiOo 5.
They may be liquid, gum-like or resinous.
They contain at least 3SiH per molecule.
Specific examples of products (B) widely mentioned in the literature are described in detail in US Patents US-A-3 220 972, US-A-3 284 406, US-A-3 436 366 and US-A-3 697 473, which are cited as reference~.
The filler~ (C), which ara preferably reinforcing silicas, are u~ed in an amount of 5 to 130 parts of the diorganopolysiloxane gum~ (A). They are chosen from ailicas produced by combustion and silicas produced by precipitation. ~hey have a specific ~urface area, determined by the BET methods, of at least 50 m2~g and preferably more than 70 m2/g, an average size of the primary particles of less than 0.1 ~m (micrometres) and an apparent density of les~ than 200 g/litre.

These silicas may be incorporated as such or after having been treated with organosilicon compounds customarily used for this application. These compounds imclude methylpolysiloxanes, such as hexamethyl-S disiloxane and octamethylcyclotetrasiloxane, methyl-polysilazanes, such as hexamethyldisilazane and hexa-methylcyclotrisilazane, chlorosilanes, such as dLmethyldichlorosilane, trLmethylchlorosilane, methylvinyldichlorosilane and dimethylvinyl-chlorosilane, and alkoxysilanes, such as dLmethyl-~ ethoxy~ilane, dimethylvinylethoxysilane and trimethylmethoxysilane.
During this treatment the silicas-may increase their initial weight by a proportion of up to 20 %, preferably about 18 %.
It i~ desirable to add a catalytically effective amount of a hydrosilylation catalyst (D), which is a platinum group compound, preferably platinum, in an amount of 0.001 to 1 %, preferably of 0.05 to 0.5 %, calculated as weight of catalytic metal relative to the weight of the gum (A) and of the organo-hydrogenopolysiloxane (B).
All of the platinum compounds widely described in the literature as hydrosilylatlon catalysts may be used, in particular chloroplatinic acid H2PtCl6, the reaction product~ of chloroplatinic acid with alcohols, ethers or aldehydes (US Patent US-A-3 220 972) and the reaction products of 17 203627~
chloroplatinic acid with vinylpolysiloxanes, which may be untreated or treated with an alkaline agent in order at least partially to remove the chlorine atoms (US
Patents US-A-3 419 593, US-A-3 775 452 and US-A-3 814 730).
Up to 90 % by weight of the reinforcing silicas (C) may be replaced by semi-reinforcing or packing fillers, the particle diameter of which is greater than 0.1 ~m (micrometre), such as ground ~uartz, calcined clays and diatomaceous earths.
The silicone compositions may also comprise from 1 to 10 part~ of dimethylpolysiloxane oil~ (F) having silanol ends and a viscosity at 25C of between 10 and 5,000 mPa.s, preferably from 30 to 1,000 mPa.s, per 100 parts of gum (A). Their use is recommended in particular when the amounts of reinforcing fillers (C) are high.
The preparation of the compositions according to the invention i8 effected with the aid of known mechanical means, for example kneader3, cylinder mixers or ~crew mixers.
The various constituents are incorporated in thi~ equipment in a sequence which may be arbitrary.
However, it i~ recommended to charge the gum (A), than, in sequence, the siliceous fillers (C) and the active substance (E), where appropriate the additive (F) and, finally, the compound (D). If the composition must be stored before its extrusion and/or moulding, it is :`
, desirable to add an effective amount of an agent which inhibits the catalytic action of platinum and disappears at elevated temperature during the vulcanisation of the composition. Thus, inhibitors which may be used are, in particular, organic amines, silazanes, organic oxLmes, diesters of carboxylic diacids, acetylenic ketones and vinylmethylcyclopoly-siloxanes ~see in particular US-A-3 445 420 and US-A-3 989 667).
The inhibitor is used in an amount of from 0.005 to 5 parts, preferably 0.01 to 3 parts, per 100 parts of constituent (A).
The compositions obtained mould and extrude easily, which allows very varied forms to be produced.
~he can also be cured to give elastomers by heating under pressure or in amb1ent air at temperatures of the order of 100 to 350C.
The heating time o~viously varies with the temperature, the pressure and the nature of the crosslinking agents. It i~ generally of the order of several minutes at about 150-250-C and of a few seconds at about 250-350C.
The elastomers thus formed may, if appropriate, subsequently be post-heated, especially those obtained by moulding for a period of at least one hour at a temperature of between 190 and 270C with the aim of completing their crosslinking.
However, from the end of their first crosslinking stage, that is to say before any post-heating stage, these elastomers have physical characteristics adequate for the envisaged application.
Thus, the compositions according to the invention may be malaxated cold as such and be extruded and/or moulded and then vulcanised into very varied shape~.
A ~hird arouD of silicones which may be used according to the invention comprise~ diorganopoly-siloxane compositions which may be cured to give asilicone elastomer by polycondensation reactions, comprising:
- (A): at least one diorganopolysiloxane oil having at each end of the chain at lea~t two condensable or hydrolysable groups or a single hydroxyl group, - (B): a polycondensation catalyst for the oil, and - (C): a silane comprising at least three condensable or hydrolysable groups, when (A) i8 an oil having hydroxyl ends.
In the following and the foregoing text, unles~ indicated to the contrary, percentages and parts are by weight.
The diorganopolysiloxane oils (A) which may be used in the compo~itions according to the invention are more particularly those of formula (1):
YDS i3_DO ( SiR2 ) ~SiR3 DYD ( 1 ) o 2036272 in which:
R represents identical or different monovalent hydrocarbon radicals, Y represents identical or different hydrolysable or condensable groups, or hydroxyl groups, n is chosen from 1, 2 and 3, where n = 1 if Y
i5 a hydroxyl, and x is an integer higher than 1 and preferably higher than 10.
The viscosity of the oils of formula (1) is between 50 and lo6 mPa.s at 25C. The following may be mentioned as example~ of radical~ R: alkyl radic ls having from 1 to 8 carbon atoms, such a~ methyl, ethyl, propy~, butyl, hexyl and octyl, vinyl radicals and phenyl radicals.
The following may be mentioned as examples of substituted radical~ Rs 3,3,3-trifluoropropyl, chlorophenyl and beta-cyanoethyl radicals.
In the products of formula (1) which are generally used industrially, at least 60 % by number of the radicals R are methyl radicals, the other radicals generally being phenyl and/or vinyl radicals.
The following may be mentioned as examples of hydrolysablo groups Y: amino, acylamino, aminoxy, ketiminoxy, iminoxy, enoxy, alkoxy, alkoxy-alkyleneoxy, acyloxy and phosphato groups.
The following may be mentioned as examples of amino groups Y: n-butylamino, sec-butylamino and cyclohexylamino groups; as examples of N-substituted .

.

21 203~272 acylamino groups: the benzoylamino group; as examples of aminoxy groups: dimethylaminoxy, diethylaminoxy, dioctylaminoxy and diphenylaminoxy groups; as examples of Lminoxy and ketLminoxy groups Y: those derived from S acetophenone oxime, acetone oxLme, benzophenone oxLme, methyl ethyl ketoxime, diisopropyl ketoxLme and chlorocyclohexanone oxLme.
Alkoxy groups Y which may be mentioned are the groups having from 1 to 8 carbon atoms, such as the methoxy, propoxy, isopropoxy, butoxy, hexyloxy and octyloxy groups, and an alkoxy-alkyleneoxy group Y
which may be mentioned is the methoxy-ethyleneoxy group.
Acyloxy groups Y which may be mentioned are the groups having from 1 to 8 carbon atoms, such as the formyloxy, acetoxy, propionyloxy and 2-ethylhexanoyloxy groups.
Phosphato groups Y which may be mentioned are those which are derived from dimethyl phosphate, diethyl phosphate and dibutyl phosphate groups.
Condansable groups Y which may be mentioned are the hydrogen atoms and the halogen atoms, preferably chlorine.
When, in the above formula (1), the groups Y
are hydroxyl groups and n is then egual to 1, it is necessary, in order to prepare the polyorganosiloxane elastomers from the polymers of formula (1) above, to use, in addition to the condensation catalysts, 22 2~3~27~
crosslinking agents (D) which have already been indicated and which are silanes of general formula:
R4~Si Y'~ (2) in which:
R has the meanings given above for formula (1) and Y' represents identical or different hydrolysable or condensable groups, and a is 3 or 4.
The examples given for the ~roups Y are applicable to the groups Y'.
It is desirable to use silanes of formula (2) e~en in the case where ~ in the oil (A) is not a hydroxyl group.
In this case it is desirable to use groups Y
in the oil ~A) which are identical to the Y' in the silane (D).
The alpha, omeya-dihydroxy-diorganopoly-siloxanes of formula (1) are generally oils, the vi~cosity of which varies from 500 mPa.s at 25C to 500,000 mPa.s at 25DC, preferably 800 mPa.s to 400,000 at 25C, that is ~traight-chain polymers essentially consisting of diorganosiloxy units of formula (R2SiO).
Howe~er, tha presence of other units, generally present as impurities, such a~ R SiO3/2, R SiO"2 and S~O~2, is not excluded in a proportion of at most 1 % relative to the number of diorganosiloxy units.
The organic radicals, which are bonded to the ~ilicon atoms of the base oils and are represented by 203627~

the symbol R, may be chosen from alkyl radicals having from 1 to 3 carbon atoms, such as the methyl, ethyl and n-propyl radicals, the vinyl radical, the phenyl radical, the 3,3,3-trifluoropropyl radical and the beta-cyanoethyl radical.
At least 60 ~ of all of the radicals R are methyl radicals; at most 1 % are vinyl radicals.
By way of illustration of units represented by the formula RzSiO, those of the following formulae may be mentioned:
(CH3)ZSiO; CH3(CHZ=CH)SiO; CH3(C8,H5)SiO;
CF3CH2CH2 ( CH3 ) SiO; NC-CH2CH2 ( CH3 ) SiO; NC-CH2 ( C6H5 ) SiO .
The great majority of these base oils are marketed by silicone manufacturers. On the other hand, lS their production techniques are well known and are found described, for example, in French Patents FR-A-1 134 005, FR-A-1 198 749 and FR-A-l 226 745.
The following may be mentioned more particularly as examples of ~ilane monomers (D) of formula (2): polyacyloxysilanes, polyalkoxysilanes, polyketiminoxy~ilane~ and polyiminDxysilanes, and in particular the following 6ilanes:
' CH3Si(OCOCH3)3; C2H5Si(OCOC~3)3;
(CH2 = CH)Si(OCOCH3)3; C5H,Si(OCOCH3)3;
CF3CH2CH2Si(OCOCH3)3; NC-CH2CH2Si(OCOCH3)3;
CH2ClSi(OCOCH2CH3)3; CH3Si(ON=C(CH3)C2H5)2OCH2CH2OCH3 and CH3Si(ON=CH-CH3)zOCH2CH2OCH3.
The above silanes (D) in combination with the :

24 2~3~272 alpha, omega-dihydroxy-polydiorganosiloxanes of formula ~1) may be used in one-component compositions which are ~table in the absence of air.
Examples which may be mentioned of silane monomers of formula (2) which, in combination with alpha, omega-dihydroxy-polydiorganosiloxanes of formula (1), may advantageously be used in two-component compositions are polyalkoxysilanes and in particular those of formulae:
Si(OC2H5)4; Si(O-n-C3H~)~; Si(O-isoc3H7)~;
Si ~ OC2H"OCH3 ) ~; CH3Si ( OCH3 ) 3; CH2=CHSi ~ OCH3 ) 3;
CH3Si ( OC2H"OCH3 ) 3; ClCH2S i ( OC2Hs ) 3; CH2 = CHSi ( OCzH40CH3 ) 3 .
All or part of the silane monomer~ described above may be replaced by polyalkoxypolysiloxanes, each molecule of which carries at least two and preferably three atoms Y'; the other silicon valencies are satisfied by the siloxPne bonds.SiO and SiR.
An example which may be mentioned of a polymer crosslinking agent i~ ethyl polysilicate.
Generally from 0.1 to 20 parts by weight of crosslinking agent of formula (2) are u~ed per 100 parts by weight of polymer of formula (1).
The ~olyorganosiloxane compositions which are curable to an elastomer of the type described above comprise from 0.001 to 10 parts by weight, preferably from 0.05 to 3 parts by weight, of condensation catalyst (C) per 100 parts by weight of polysiloxane of formula (1).

The condensation catalyst content in the one-component compositions is generally very much lower than that used in the two-component compositions and is generally between 0.001 and 0.05 parts by weight per 100 parts by weight of polysiloxane of formula (2).
The crosslinking agents (D) of formula (2), which may be used to prepare either one-component or two-component compositions, are products available on the silicone market; moreover, their use in compositions which cure from ambient temperature is known: they are cited in particular in French Patents FR-A-l 126 411, FR-A-l 179 969, FR-A-l 189 216, PR-A-l 198 749, FR-A-l 248 826, FR-A-l 314 649, FR-A-l 423 477, PR-A-l 432 799 and FR-A-2 067 636.
The compositions according to the in~ention may al~o comprise reinforcing or ~emi-reinforcinq or packing fillers (E), which are preferably chosen from the siliceous fillers, silica~ produced by combustion and ~ilicas produced by precipitation.
They have a specific surface area, determined by the BET methods, of at least 50 m2/g and preferably more than 70 m2~g, an average size of the primary particles of less than 0.1 ~m (micrometre) and an apparent density of less than 200 g/litre.
These silicas may be incorporated as such or after having been treated with the organosilicon compounds customarily used for this application. These compounds include methylpolysiloxanes, such as ':

26 20~27~
hexamethyldisiloxane and octamethylcyclotetrasiloxane, methylpolysilazanes, such as hexamethyldisilazane and hexamethylcyclotrisilazane, chlorosilanes, such as dimethyldichlorosilane, trimethylchlorosilane, S methylvinyldichlorosilane and dLmethylvinyl-chlorosilane, and alkoxysilanes, such as dLmethyldi-methoxysilane, dimethylvinylethoxysilane and trimethyl-methoxysilane.
During this treatment the silicas may i~ se their initial weight by a proportion of up to 20 %, preferably about 18 %.
The semi-reinforcing or packing fillers have a particle diameter greater than O . l ~m (micrometre) and are chosen from ground quartz, calcined clays and diatomaceous earths.
In general from 0 to 100 parts, preferably from 5 to 50 parts, of filler (E) may be used per 100 parts of oil (A).
The bases of siiicone composition~ generally defined above are well known to those skilled in the art. They are described in detail in the literature, in particular in numerou~ patents, and the ma~ority are a~railable commercially.
These compositions cros~link at ambient temperature in the presence of moisture supplied by atmospheric humidity and/or contained in the composition. They are subdivided into two large groups.
The first group is made up of the one-component . ~ ' ' .

composi~ions, or compositions in a single packaging, which are stable on storage in the absence of atmospheric humidity and crosslink to form an elastomer in the presence of atmospheric humidity. In this case, the condensation catalyst (C) used is a metal compound, generall~ a tin, titanium or zirconium compound.
Depending on the nature of the condensable or hydrolysable groups, these one-component compositions are termed acid, neutral or basic.
Acid compositions which may be mentioned are, for examplç ? the compositions described in the patents US-A-3 035 016, US-A-3 077 465, US-A-3 133 891, US-A-3 409 573, US-A-3 438 g30, US-A-3 647 917 and US-A-3 886 118.
Neutral compositions which may be used are, for example, the compositions described in the patents US-A-3 065 194, US-A-3 542 901, US-A-3 689 454, US-A-3 779 986, GB-A-2 052 540, US-A-4 417 042 and EP-A-69 256.
Basic compositions which may be used are, for example, the compositions described in the patent~
US-A-3 378 520, US-A-3 364 160, US-A-3 417 047, US-A-3 i64 951, US-A-3 742 004 and US-A-3 758 441.
According to a preferred variant, it is also po~sible to use the free-flowing one-component compositions such as those described in the patents US-A-3 922 246, US-A-3 956 280 and US-A-4 143 088.
The second group, which is the preferred group within the framework of the present invention, is made up of the two-component compositions, or compositions contained in two packagings, generally comprising an alpha, omega-dihydroxydiorganopoly-siloxane oil (A), a silane (D) or a product resultingfrom the partial hydrolysis of this 6ilane, and a catalyst (C), which is a metal compound, preferably a tin compound, and~or an amine.
Examples of such compo~itions are described in the patents US-A-3 678 002, US-A-3 888 815, US-A-3 933 729, US-A-4 064 096 and GB-A-2 032 936.
Amongst these compositions, those preferred more particularly are the two-component compositions comprising:
- ~A): 100 part~ of an alpha, omega-dihydroxydiorgsnopolysiloxane oil which has a vi~osity of 50 to 300,000 mPa.s and in which the organic radicals are chosen from..methyl, ethyl, vinyl, phenyl and 3,3,3-trifluoropropyl radical~, at least 60 ~ by number being methyl radical~, up to 20 ~ by number being phenyl radicals and at most 2 % being vinyl radicals, (C)s 0.01 to 1 part (calculated as weight of tin metal) of a catalytic tin compound, - (D): 0.5 to 15 parts of a polyalkoxysilane or polyalkoxysiloxane, and - (E): 0 to 100 parts, preferably 5 to 50 parts, of siliceous inorganic filler.

~. ~

The tin catalysts (C) are widely described in the above literature and this catalyst may be, in particular, a tin salt of a monocarboxylic or dicarboxylic acid. These tin carboxylates are described in particular in the publication by NOLL (Chemistry and Technology of Silicones, page 337, Academic Press, 1968, 2nd edition).
Dibutyltin naphthenate, octanoate, oleate, butyrate and dilaurate and dibutyltin diacetate may be mentioned in particular.
The catalytic tin compound used may also be the product of the reaction of a tin salt, in particular of a tin dicarboxylate, with an ethyl polysilicate as described in the patent US-A-3 186 963.
It is also possible to use the product of the reaction of a dialkyldialkoxysilane with a tin carboxylate as de~cribçd in the patent US-A-3 862 919.
It is also possible to use the product of the reaction of an alkyl silicate or of an alkyltri-alkoxysilane with dibutyltin diacetate as described inBelgian Patent B~-A-824 305.
Amongst the cros~linking agents (D), those more particularly preferred are alkyltrialkoxysilanes, alkyl ~ilicate~ and alkyl polysilicates, in which the organic radicals are alkyl radicals having from 1 to 4 carbon atoms.
The alkyl silicates may be chosen from methyl silicate, ethyl silicate, isopropyl silicate and 203~272 n-propyl silicate, and the polysilicates chosen from the partial hydrolysis products of these silicates;
these are polymers consisting of a significant proportion of units of formula ~R40~3Sioo 5r R40Sio~ 5, S (R40)2Sio and SiO2; the symbol R4 representing methyl, ethyl, isopropyl and n-propyl radicals. The characterisation of these compounds is customarily based on their silica content, which is established by determination of the hydrolysis product of a sample.
In particular, the polysilicate used may be a partially hydrolysed ethyl silicate marketed under the name "Ethyl Silicate-40"R by Union Carbide Corporation, or a partially hydrolysed propyl silicate.
The compositions according to the invention may be shaped, extruded or, in particular, moulded into varied forms and then cured at ambient temperatu~e to give an elastomer under atmospheric humidity or by the addition of water. Slight heating to a temperature of 20 to 150C may accelerate curing.
Surpri~ingly, it has been discovered that these crosslinked silicone compositions have phy~ical characteri~tics adequate for the applications envisaged.
A fourth arou~ of silicones which may be used according to the invention in effect relates to a polyaddition silicone composition which may be cured to form an ela~tomer by hydrosilylation reactions, which comprises:

- 203g27~

- ~A): at least one organopolysiloxane having, per molecule, at least two vinyl groups bonded to the silicon, - (B): at least one organopolysiloxane having, per molecule, at least three hydrogen atoms bonded to the silicon, and - ~C): a catalytically effective amount of a catalyst which is a compound of a platinum group metal~
In the followinq and foregoing text, unles~
indicated to the contrary, percentages and parts are by weight.
The amounts of (A) and (B) are generally chosen such that the molar ratio of the hydrogen atoms bonded to the silicon in (B) to the vinyl radicals bonded to the silicon in ~A) i5 generally between 0.4 and 10 and preferably between 0.6 and 5.
The vinyl group~ in (A) and the hydrogen atoms in (B) are generally bonded to different silicon atoms.
These compositions crosslink by an addition .reaction (also termed hydrosilylation reaction), cataly~ed by a compound of a platinum group metal, of a vinyl group in the organopolysiloxane (A) with a hydride group of the organopolysiloxane (D).
The vinyl-containing organopoly~iloxane (1) may be an organopolysiloxane having siloxy units of formula:

"'`' :~

Yl. Zb S iO( ~ b ) ( 1 ) in which Y is a vinyl group and Z is a monovalent hydrocarbon group which does not have an adverse action on the activity of the catalyst. Z is generally chosen from alkyl groups having from 1 to 8 carbon atoms inclusive, such as methyl, ethyl, propyl and 3,3,3-trifluoropropyl groups, and aryl groups, such as xylyl, tolyl and phenyl, a is 1 or 2, b is 0, 1 or 2 and a + b is between 1 and 3, all of the other units optionally being units of average formula:

ZcSiO~-c (2) in which Z has the same meaning as above and c has a value between 0 and 3.
The organopolysiloxane (B) may be an organohydrogenopolysiloxane comprising siloxy units of formula:

HdW.SiO~ -d--(3) in which W is a monovalent hydrocarbon group which does not have an adverse action on the activity of the catalyst and has the same definition as Z, d is 1 or 2, e is 0, 1 or 2 and d + e has a value between 1 and 3, all of the other units optionally being units of average formula:

w~SiO~-~ (4 in which W has the same meaning as above and g has a value between 0 and 3.
All of the lLmiting values-for a, b, c, d and g are inclusive.
The organopolysiloxane (A) may be formed solely of units of formula (1) or may also contain units of formula (2).
The organopolysiloxane (A) may have a straight-chain, branched, cyclic or network structure.
The degree of polymerisation is 2 or more and is generally below 5,000. Moreover, if the organopoly~iloxane (A) i8 straight-chain, it ha~ a viscosity at 25C of less than 500,000 mPa.s.
Z i~-generally chosen from methyl, ethyl and phenyl radicals, at least 60 molar % of the radicals Z
being methyl radicals.
The organopolysiloxanes (A) and (B) are well known and are described, for example, in the patents US-A-3 220 972, US-A-3 284 406, US-A-3 436 366, US-A-3 697 473 and US-A-4 340 709.
Examples of siloxy units of formula (1) are the vinyldimethylsiloxy unit, the vinylphenylmethyl-siloxy unit, the vinylsiloxy unit and the vinylmethyl-25 siloxy unit.
Examples of siloxy units of formula (2) are .~ . . .

, . . .
.~
. ..

the SiO4~2, dLmethylsiloxane, methylphenylsiloxane, diphenylsiloxane, methylsiloxane and phenylsiloxane u~its.
Examples of organopolysiloxane (A) are the dimethylpolysiloxanes having dimethylvinylsiloxy ends, the methylvinyldimethylpolysiloxane copolymers having trimethylsiloxy ends, the methylvinyldimethylpoly-siloxane copolymers having dimethylvinylsiloxy ends and the cyclic methylvinylpolysiloxanes.
The organopolysiloxane (B) may be formed solely of units of formula (3) or additionally contains units of formula (4).
The organopolysiloxane (B) may have a straight-chain, branched, cyclic or network structure.
The degree of polymerisation is 2 or more and is generally below 5,000.
The group W has the same meaning as the group Z above.
Examples of unit~ of formula (3) are:
H(CH3)2SiOlt2, HCH3SiO2~2, H(C0Hs)si2~2-The examples of units of formula (4) are the same a~ those given above for the units of formula ~2).
Example~ of organopolysiloxane (B) ares - the dimethylpolysiloxanes having hydrogenodimethylsilyl end~, the dimethylhydrogeno-methylpoly~iloxane copolymer~ having trimethylsiloxy ends, the dimethylhydrogenomethylpolysiloxane copolymers having hydrogenodimethylsiloxy ends, the hydrogenomethylpolysiloxanes having trLmethylsiloxy ends and the cyclic methylvinylpolysiloxanes.
- The ratio of the number of hydrogen atoms bonded to the silicon in the organopolysiloxane (B) to the number of groups having an alkenyl unsaturation in the organopolysiloxane (A) is between 0.4 and 10, preferably between 0.6 and 5. This ratio may, however, be between 2 and 5 if it is desired to make elastomer foams.
The organopolysiloxane (A) and/or the organopolysiloxane (2) may be diluted in a non-toxic organic solvent compatible with silicones.
The organopolysiloxanes (A) and (B) having a network ~tructure are commonly ~ermed silicone resins.
The bases of polyaddition silicone compositions may comprise only straight-chain organopolysiloxanes tl) and (2), such as, for example, those described in the abovementioned US patents:
US-A-3 220 972, US-A-3 697 473 and US-A-4 340 709, or simultaneously comprise organopolysiloxanes (A) and (B) which are branched or have a network structure, such as, for example, those described in the abovementioned US paterts: US-A-3 284 406 and US-A-3 436 366.
The catalysts (C) are also well known.
Platinum and rhodium compounds are preferably used.
In particular, it is possible to use the complexes of platinum and an organic product described .

in the US patents US-A-3 159 601, US-A-3 159 602, US-A-3 220 972 and the European patents EP-A-57 459, EP-A- I88 978 and EP-A- l 90 530, or the complexes of platinum and vinyl-containing organopolysiloxane described in the US patents: US-A-3 419 593, US-A-3 715 334, US-A-3 377 432 and US-A-3 814 730.
In particular, it is possible to u~e the rhodium complexes described in the British patents:
GB-A-l 421 136 and GB-A-l 419 769.
The generally preferred catalyst is platinum.
In this case the amount by weight of catalyst (C), calculated as weight of platinum metal, is generally between 2 and 600 ppm, in general between 5 and 200 ppm, based on the total weight of the organopolysiloxanes (A) and (B).
The preferred co~po~itions within the framework of the present invention are those which comprise:
- (A): 100 parts of a diorganopolysiloxane oil blocked at each end of its chain by a vinyldi-organosiloxy unit, the organic radicals of which, bonded to the silicon atoms, are chosen from methyl, ethyl and phenyl radicals, at least 60 molar ~ of these radicals being methyl radicals, having a viscosity of 100 to 500,000, preferably of 1,000 to 200,000 mPa.s at 25-C, - (B): at least one organohydrogenopoly-siloxane chosen from the liquid homopolymers and copolymers which are straight-chain or have a network structure, which have, per molecule, at least 3 hydrogen atoms bonded to different silicon atoms and the organic radicals of which, bonded to the silicon atoms, are chosen from methyl and ethyl radicals, at least 60 % of these radicals being methyl radicals and the product (B) being used in an amount such that the molar ratio of the hydride groups to the vinyl groups is between 1.1 and 4, - (C): a catalytically effective amount of a platinum catalyst.
Still more preferentially, up to 50 % by weight of the polymer (A) i8 replaced by a copolymer having a network structure and comprising the trimethylsiloxy, methyl~inylsiloxy and SiO~/2 units, in which 2.5 to 10 molar % of the silicon atoms carry a vinyl group and in which th~ molar ratio of the trimethyl~iloxy groups to the SiO~/2 group is between 0.5 and 1.
The compositions according to the invention ~ay also comprise reinforcing or semi-reinforcing or packing fillers (E), which are preferably chosen from the ~iliceous fillers.
The reinforcing fillers are chosen from the silicas produced by combustion and the silicas produced by precipitation. They have a specific surface area, determined by the BET methods, of at lea3t 50 m2/g and preferably more than 70 m2/g, an average size of the prLmary particles of below 0.1 ~m (micrometre) and an apparent density of less than 200 g/litre.
These silicas may be incorporated as such or after having been treated with the organosilicon compounds customarily used for this application. These compounds include methylpolysiloxanes, such as hexamethyldisiloxane and octamethylcyclotetrasiloxane, methylpolysilazanes, such as hexamethyldisilazane and hexamethylcyclotrisilazane, chlorosilanes, such as dLmethyldichlorosilane, trLmethylchlorocilane, methyl-~rinyldichlorosi ~ne and dLmethylvinylchlorosi?ane, and alkoxysilane~, such as dimethyldimethoxysilane, dimethylvinylethoxysilane and trimethylmethoxysilane.
During this treatment, the silicas may increase their initial weight by a proportion of up to 20 %, preferably about 18 %.
The ~emi-reinforcing or packing fillers have a particle diameter of more than 0.1 ~m (micrometre) and are preferably chosen from ground quartz, calcined clays and diatomaceous earths.
Generally from 5 to 100 parts, preferably from 5 to 50 parts, of filler (E) may be used per 100 parts of the sum of the organopolysiloxanes (A) + (B).
The polyaddition compositions are generally 3tored in two packaging~. In fact, they crosslink from the time at which all of these constituents are mixed.
If it is desired to delay this crosslinking in order to obtain good homogenisation of the active substance, it 39 2~36272 is possible to add an inhibitor for the platinum catalyst to the composition.
These inhibitors are well known. In particular, it is possible to use organic amines, S silazanes, organic oxLmes, diesters of carboxylic diacids, acetylenic alcohols, acetylenic ketones or vinylmethylcyclopolysiloxanes (see, for example, US-A-3 445 420 and US-A-3 989 667). The inhibitor is used in an amount of 0.005 to 5 parts, preferably 0.01 to 3 parts, per 100 parts of the constituent (A).
In order to obtain a good distribution homogenisation of the active substance, it is in fact desirable for the silicone matrix to have a certain viscosity of the order of 5,000 to 30,000 mPa.s at 25~C.
Such a vlscosity may be obtained by pre-crosslinking, this pre-crosslinking being blocked at the desired viscosity by the addition of an inhibitor.
Sufficient time is then available to homogenise the active substance well within the silicone matrix.
Crosslinking is then completed by heating the matrix to a temperature such that the inhibitor no longer has an effect on the catalytic action of the platinum.
The compositions according to the invention may be malaxated cold as such and be shaped, in particular moulded into various form~.
The water-soluble auxiliary agent which may be used according to the invention must at one and the same time be highly soluble in water and chemically inert towards the active substance and the silicone material. This auxiliary agent may be an inorganic or organic salt, preference being given to the inorganic salts, in particular the alkali metal and alkaline earth metal salts of strong acids, such as, for example, sulphuric, hydrohalic or nitric acid. The following may be mentioned by way of example: alkali metal, in particular sodium or potassium, and ammonium chlorides, iodides, sulphates or nitrates.
The four groups of silicones described above have the same property, that is to say when they contain an active substance and an auxiliary salt a defined above, dispersed in a uniform manner, the compositions obtained are able to release the active substance in a controlled manner into an aqueou~ medium or into a humid atmosphere, as well as into the plant to be treated over a prolonged period.
Processes for the production of the compos~tions according to the invention by intimate mixing of the polysiloxane base~ with the active substance in water-soluble and preferably solid form, followed by production of the filled elastomer have been described. This latter technique is preferred but any other technique enabling these compositions to be obtained may be used~
The considerable advantage afforded by the 41 2~3~272 silicone matrix is therefore that it is very easy to extrapolate the continuous diffusion of the active substance after measurement of the amount released representing 10 to 15 % of the initial substance, ~ince it is known that the diffusion kinetics are of the order of 0 and that at least 80 ~ of the active substance will be released in accordance with these kinetics.
The composition according to the invention compri~ing the ~ilicone material containing the active su~stance and the auxiliary salt may be in the rigid or to a greater or le~ser extent elastic solid form. It may be in very varied shapes, depending on the envisaged applications, particularly for the active lS substance, and the shape of the plant to be treated as well as on the problem to be resolved.
It may, in particular, be in the form of a sheet, tape or ~trip which may be applied either entirely against any part of the plant to be treated or at a distance from but in the vicinity of the latter, in a gaseous atmo~phere, preferably in humid air, or in an aqueou~ liquid medium.
It may also be advantageous to use the composition according to the invention in the form of units of small dimen~ions and of variou~ shape~, such as cubes, parallelepipeds, rectangles, cylinders or ~pheres, the fundamental parameter~ of which are as follo~Js:

- the nature of the active substance, - the average diameter (particle size) p of the particles of the acti~e substance in the preferred case where the latter is a solid, - the concentration c of the active substance in the matrix, - the ratio r of the surface area to the volume of the unit, - and, in a general manner, according to the geometry of the system.
The nature of the active substance and its particle size determine its rate of diffusion R through the matrix.
The smaller i~ p the slower is R, and vice versa.
The higher i~ c the higher is the flow of the active substance, a~d vice versa.
The higher is r the higher i~ the flow of active substance eluted, and vice verqa.
8y means of routine experiments, those skilled in the art are able, without difficultr, rapidly to arrive at the desired result by extrapolating the theoretical elution time which will correspond to the actual diffusion time of the active 2S substance.
Active substances which may be mentioned which have an agricultural biological action and are insoluble or soluble in water are aqrochemical active 43 ~03~272 substances such as fungicides, bacteriocides, algicides, molluscicides, insecticides, nematicides, herbicides, growth regulators or manures or fertilisers.
The following may be mentioned as examples of agrochemical active substances: fungicides, such as sodium tris-O-ethylphosphonate, calcium tris-O-ethyl-phosphonate or aluminium tris-O-ethylphsophonate (Phosethyl-Al), salts of phosphorous acid, in particular the alkali metal and alkaline earth metal salts, growth regulators, herbicides, such as substituted phenoxyacetic or phenoxypropionic acids, such as 2,4-dichlorophenoxyacetic acid (2,4-D), 2-chloro-4-methylphenoxyacetic acid (MCPA), 2,4-dichlorophenoxy-2-propionic acid (2,4-DP) and 2-chloro-4-methylphenoxy-2-propionic acid (MCPP or mecoprop), and their alkali metal, alkaline earth metal or amine or alkanolamine salts, inorganic alkali metal, alkaline earth metal or amine salts, or N-(phosphono-methyl)glycine alkanolamine (glyphosate) and bipyridyldiylium halides (diquat and paraquat), and insecticides such as aldoxycarb.
The following examples illustrate the compositions according to the invention and their application, without thi~ illustration restricting the scope of the invention.

` 44 2~3~272 Example 1:
Preparation of the composition:
The following ingredients are intimately mixed with the aid of a malaxator: -S * a dimethylmethylvinylpolysiloxane gum (A) (100 parts) blocked at each of its two ends by a trimethylsiloxy unit and comprising in its chain 99.8 molar % of dimethylsiloxy units and 0.2 molar ~ of vinylmethylsiloxy units and having a visc08ity of 10 million mPa.s at 25C;
* filler tB) (43.5 parts), which is a treated silica produced by combustion D4 (ocatamethylcyclo-tetrasiloxane) having a BET specific surface area of 300 m2/g;
* a straight-chain dimethylpolysiloxane (1 part) blocked at its two ends by dimethylhydroxy-~iloxane groups and having a viscosity of 50 mPa; 8;
* octamethyltetracyclosiloxane (0.2 part);
and * micronised aluminium ethylphosphite (c) (36.1 parts).
Malaxating is stopped 30 minutes after the end of the introduction of the silica. The homogeneous composition which has just been prepared and which is termed the ma~ter mixture (M~) i8 removed from the malaxator.
The ~M is transferred to a cylinder mixer in order to incorporate, per 100 parts of MM:

- 203~272 * 2,5-dLmethyl-2,S-di(tert-butylperoxy)hexane tO.5 part).
The catalysed composition detaches easily from the cylinders of the mixer.
It is then injected under a pressure of 5,000 to 20,000 psi into a mould having the following dimensions: 1 20 cm, b = 20 cm, d = 0.2 cm.
Crosslinking is carried out at 150C for a few minutes.
Strips 5 cm long and 2.5 cm broad are then cut for the in vitro release test.
Two in vitro release tests are carried out:
* release in water, and * release in a humid atmosphere.
Ex~erimental protocol for the determination of the elution kinetics in water:
The matrix i~ placed in a vessel containing 100 ml of distilled water, thermostat-controlled at 2~C.
The vessel is fitted with a magnetic stirrer system which i~ set in 810w rotary motion (100 r~v/min) ensuring the homogeneity of the solution. It is covered by a cover in order to minimise the evaporation of water.
1 ml samples are taken daily during the initial elution period and weekly at the end of 15 days of elution.
The concentration of aluminium ethylphosphite ,. ~

- ~

46 203~272 is determined by determination of aluminium by atomic absorptlon.
The results for the elution kinetics are collated in Table 1.
s TLme (days) QJQo 0.3 0.8 2 5.5 6 11.74 9 15.72 13 20.63 25.08 42 44.57 The controlled release curve is given in the \ appended Figure 1.
ExDerimental protocol for the determination of the elution kinetics in a humid atmosphere:
In order to confirm that the active principle incorporated in the elastomer is able to be dispensed into the ambient humid medium, the following test wa~
carried out:
The matrix i~ suspended with the aid of a stainle~s steel boat in a confined medium where an atmosphere of 100 ~ relative humidity is maintained.
The release is monitored by determination of aluminium in the aqueous phase (100 ml) contained in ~he said .

; .
.: -;:

vessel.
The results for the elution kinetics are collated in Table 2.

TLme (days)Q/Qo (%) 42 2.55 5.05 79 13.17 84 13.66 91 14.06 There is a 42 day latent period before elution of the active qubstance.
Example 2:
PreDaration of the com~osition:
The following ingredients are intimately mixed with the aid of a malaxator:
~ a dimethylmethylvinylpolysiloxane gum (A) (100 parts) blocked at each of its two ends by a trimethyl~iloxy unit and comprising in its chain 99.8 molar % of dimethylsiloxy unit3 and 0.2 molar % of vinylmethylsiloxy units and having a visco~ity of 10 million mPa.s at 25-C;
* filler (~) (43.5 parts)~ which is.a treated silica produced by combustion D4 (octamethylcyclo-tetrasiloxane) having a BET specific ~urface area of 300 m2/g;

~. :
:

48 20362~2 * a straight-chain dimethylpolysiloxane (1 part) blocked at its two ends by dLmethylhydroxy-siloxane groups and having a viscosity of 50 mPa.s;
* octamethyltetracyclosiloxane (0.2 part);
* micronised aluminium ethylphosphite (c) (44.4 parts); and * ammonium sulphate (33.3 parts) having a particle size smaller than 50 ~m.
Malaxating i9 stopped 30 minutes after the end of the introduction of the silica. The homogeneous composition which has ~ust been prepared and which is termed the master mixture (MM) is removed from the malaxator.
The MM i8 transferred to a cylinder mixer in order to incorporate, per 100 parts of MM:
* 2,5-dimethyl-2,5-dittert-butylperoxy)hexane ~0.5 part).
The catalysed composition detaches easily from the cylinders of the mixer.
It i3 then in~ected under a pressure of 5,000 to 20,000 psi into a mould having the following dimen~ions: 1 20 cm, b = 20 cm, d = 0.2 cm.
Crosslinking is carried out at 150C for a few minutes.
Strip~ 5 cm long and 2.5 cm broad are then cut for the in vitro release test.
Two in vitro release tests are carried out:
* release in water, and * release in a humid atmosphere.
_lution kinetics in water:
The procedure is as in Example 1.
The results for the elution kinetics are collated in Table 3.

TLme (days) QfQo (%) _ 1 3.31 2 7.72 3 7.87 4 8.25 7 11.79 34.11 .
I5 14 51.52 17 60.20 21 . 69.55 _ The controlled release curve is given in the appended ~igure 1.
Elution kinetic~ in a humid atmosphere:
The procedure i8 as-in Example 1.
The results for the elution kinetics are collated in Table 4. It can be seen that the latent period has ~ubstantially declined.

~.

`- 203~272 .TLme (days) Q/Qo 1 0.00 2 0.42 3 0.51 4 0.6 7 2.66 5.59 14 7.35 17 8.2 21 9.54 24 ~ 11.95 12.77 31 13.46 38 14.56 51 26.64 59 . 30.41 , The corresponding elution curve i~ qiven in Figure 2.
Exam~le 3: Composition:
The following ingredients are intimately mixed with the aid of a malaxator:
~ a dimethylmethylvinylpolysiloxane gum ~A) (100 part~) blocked at each of its two ends by a trimethylsiloxy unit and comprising in it~ chain 99.8 molar % of dimethylsiloxy units and 0.2 molar % of '~ :

`

51 203~2~2 vinylmethylsiloxy units and having a viscosity of 10 million mPa.s at 25C;
* filler (B) (43.5 parts), which is a treated silica produced by combustion D4 (ocatamethylcyclo-tetrasiloxane) having a BET specific surface area of 300 m2/g;
* a straight-chain dimethylpolysiloxane (1 part) blocked at its two ends by dimethylhydroxy-siloxane groups and having a viscosity of 50 mPa.s;
* octamethyltetracyclosiloxane (0.2 part);
* micronised aluminium ethylphosphite (c) (48.1 parts); and * ammonium sulphate (48.1 parts) having a particle size smaller than 50 ~m.
Malaxating is ~topped 30 minutes after the end of the introduction of the silica. The homogeneous composition which has ~ust been prepared and which is termed the master mixture (NN) is removed from the malaxator.
~he M~ is transferred to a cylinder mixer in order to incorporate, per 100 parts of M~:
* 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane (0.5 part).
As in Example 2, strips 5 cm long and 2.5 cm broad are prepared for the in vitro release test.
Two in vitro release tests are carried out:
* release in water, and * release in a humid atmosphere.

' Elution kinetics in water:
The procedure is as in Example 1.
The results for the elution kinetics are c:ollated in Table 5.
s Time (days) Q/Qo 1 3.30 2 7.84 3 7.76 4 14.72 7 25.55 38.24 14 59.54 17 65.46 21 j 72.85 The controlled.release curve i~ given in the appended Figure 1.
Elution kinetics in a humid atmospheret The procedure is as ~n Bxample 1.
The results for the elution kinetic~ are collated in Table 6. It can be seen that the latent period is virtually non-existent.

_ . TLme (days) Q/Qo (%
_ 1 0.00 2 0.57 3 0.89 4 1.52 7 4.57 7.4~
14 7.93 17 10.43 21 9.90 24 10.42 29 13.49 51 25.52 ~9 32.56 i . .
\ The corresponding elution curve is given in Figure 2.
ExamPle 4:
The procedure is as in Example 3 except that ammonium sulphate (48.1 parts) is replaced by potassium sulphate (48.1 parts) having a diameter smaller than 50 ~m.
Rinetics in water:
The procedure is as in Example 1. The results for the elution kinetics are collated in Table 7.

.
.,, .`'' ' TLme (days) Q/Qo (%) 1 4.13 2 8.61 3 11.93 4 15.61 7 20.46 23.14 L0 14 32.5 17 34.98 21 39.21 The controlled release curve is given in the appended Figure l.
Elution kinetics in a humid atmosDhere:
The procedure is as in Example l.
The re~ults for the elution kinetics are collated in Table 8.

Time (days) QJQo (%) .
O . 00 2 0.00 3 0.00 4 0.00 7 2.09 4.44 14 5.91 17 8.77 ~1 11.95 24 13.04 29 18.28 31 18.17 ~:
38 23.24 51 30.26 59 .. 33.88 The latent period is slightly longer with this ~alt than with ammonium sulphate.
The corre~ponding elution curve i~ given ~n Figure 2.
Example 5:
* Preparation of comPonent A:
The following constituents are homogenised at ambient temperature in a malaxator:
a) Silicone resin (25 parts) comprising 40 molar % of , (C~3)3 SiOl~ units, 6 molar % of ~CH3) (CH2 = CH)SiO2~2 units and 53.5 ~ of SiO4/12 uni.ts, b) a dimethylpolysiloxane oil (75 parts) blocked at each of the ends of its chain by a (CH3) (CH2 = CH)SiO"2 unit and having a viscosity of 3,500 mPa.s at 25C, and c) platinum metal (40 ppm calculated by weight), supplied by a 0.25 % solution of hexachloroplatinic acid prepared by stirring hexachloroplatinic acid ~0.6 part), isopropanol (10 parts), xylene (55 parts) and - 1~ 1,1,3,3-tetramethyl-1,3-divinyldisiloxane (6 parts) at ambient temperature.
* Preparation of component B:
The following constituents are homogenised at ambient temperature in a malaxator:
d) liquid hydrogenated silicone resin (45 parts) prepared by hydrolysis of ethyl silicate and (CH3) 2 HSiCl. in amounts corresponding to one mole of SiO per two moles of (CH3.)2 ~SiCl in solution in toluene. This resin therefore has a theoretical molar ratio of (CH3)HSiO1/2 units of 2 and an actual molar ratio of 2.23, e) the resin a) (12.5 parts) from portion (A), and f) the vinyl-containing oil b) (37.5 parts) from portion (A).
The elastomer composition is obtained by mixing component A (10 parts) with component B
(1 part).

.

203627~

* Preparation of the com~osition of ExamPle 5:
Aldoxycarb (25 parts) having an average particle size of less than 50 ~m is incorpoxated into 1:he elastomer composition (lOQ parts). The mixture is <;tirred, under vacuum, for 15 minutes in order to degas the mixture. The whole is then poured into a mould preshaped to the required dimensions, that is to say:
l = 5 cm, b = 2.5 cm, d = 0.2 cm.
The mixture is heated for one hour at 60 J C .
Two in vitro release tests are carried out:
* release in water, and * release in a humid atmosphere.
Elution kinetics in water:
The procedure i8 as in Example 1. The release of the active substance is monitored by determination of aldoxycarb by liquid chromatography.
- The resu}ts for the elution kinetics are-collated in Table 9.

203~272 .Time (days) Q/Qo (~) _ 1 0.6 2 0.78 3 0.98 4 1.12 7 1.~6 11 1.89 21 2.68 31 3.5 37 3.86 43 4.25 It can be pointed out that the elution is very slow.
Blution kinetics_in a humid atmosphere: -The procedure i8 as in Example 1 and the release of the active substance is determined by determination of the aqueous phase by liquid chromatography. Under these conditions, no trace of active sub tance is observed at the end of 45 days.
Example 6:
Aldoxycarb (28.6 parts) having a particle qize of less than 50 ~m and sodium chloride ~14.3 parts) having a particle size of less than 50 ~m are added to the elastomer composition (100 parts) prepared in accordance with Example 5.

~' . ,. ' ' ~ ,,.
. . .

2~36272 Matrices having the following dLmensions are prepared in accordance wi~h Example 5: 1 = 5 cm, b = 2.5 cm, d = 0.2 cm, wh~.ch are then placed in water and in a humid atmosphere for elution.
Elution kinetics in water:
The results for the elution kinetics are collated in Table 10.

Time ~days) Q/Qo 1.4 4 ~.39 8 7.6 12 12.2 15.7 19 18.9 22 21.0 22.2 29 24.3 27.0 __ _ It may be pointed out that in the presence of NaCl the elution is greatly accelerated (factor of close to 7).
Elution kinetics in a humid atmosphere:
In the presence of salt, the olution of aldoxycarb is possible in a humid atmo~phere. However, a latent period of 4 days is observed.

The results for th~ elution kinetics are collated in Table 11.

Time (days) Q/Qo (%) 1 0.0 4 0.04 8 0.09 12 0.08 10 15 0.34 19 0.4 22 0.4 0.38 29 0.77 15 35 3.1 ' - However, the elution remains very slow.
,Example 7:
Aldoxycarb (33.3 parts) having a particle size of le3s than 50 ~m and sodium chloride (33.3 parts) having a particle size of less than 50 ~m are added to the elastomer composition (100 part3) prepared in accordance with Example 5.
Matrices having the following dimensionss 1 = 5 cm, b = 2.5 cm, d = 0.2 cm, are prepared in accordance with Example 5, which are then placed in water and in a humid atmosphere for elution.

203~72 Elution kinetics in water: ~
The results for the elution kinetics are :
collated in Table 12.

STLme ~days) Q/Qo (%) 1 1.6 4 6.1 8 12.5 12 17.2 20.3 19 22.7 Exam~le 8: Biological efficacy on plants.
Silicone collars ~1 = 60 cm, b = 2.75 cm, d = 0.2 cm; weight - 40 g) obtained by the method described in Bxample 2 but containing the active subqtance in an amount of 25 % (55.5 parts, which is 10 q, of aluminium tri-O-ethylphosphonate) and the co-salt in an amount of 15 % (33.3 parts, which is 6 g, of ammonium ~ulphate) are fixed on 10 trees (clementines) at the level of the graft point (10 further trees not provided with these collars serve as controls) at time Tl.
Six collars are fixed in a superimposed manner on each tree in order to have a dosage of 60 g of active substance per tree.
At time Il = Tl + 15 days; or 15 days after positioning of the collars, several inoculations with phytophthora citrophthora (3 to 5 inoculations per tree) are carried out on all of the 20 trees by incrustation of a mycelium fragment in the sub-cortical S zone of the larger branches. The initial diameter of the canker is of the order of 1 cm.
The growth of the pathogenic fungus is checked at I1 + 2 months and Il + 5 months. The length reached by the canker is then measured; this length is expressed in cm in the form of average length for each of the two series of 10 trees.
The table giving the following results is then obtained:

EFFICACY AVERAGE LENGTH OF THE
CANRERS (cm) ~Inoculation .

Il = Tl + 15 days) Il + 60 Il + 150 Control tree~ (10) 7.9 ~ 10 Trees treated with the invention (10) 4.3 4.9 A reduction in the rate of implantation of the canker is observed in the first few months tfactor of 2) and the arrest of the propagation of the fungus is observed in the longer term (factor of 2).

203~27~

The treatment as carried out with the product of the invention proves effective in terms of immediate activity but also over time tcontrolled and continuous release of the active principle).
It proved possible to confirm this prolonged release by measurement of the residues of the active substance and its metabolite in the leaves of the tree, which also proves the passage of the active substance into the vital system of the tree.

Claims (54)

1. A solid, polymer-based composition having an agricultural biological action in order to promote the growth of plants, consisting of a predominant amount of a silicone material, which is not crosslinked or at least partially crosslinked and is permeable to water vapour, and an active substance which has an agricultural biological action and is slightly soluble in water, dispersed homogeneously in the silicone material and not having an inhibitory effect on the crosslinking of the silicone, the silicone material and the water-soluble form of the active substance being such that the release kinetics of the active substance by the silicone material in a non-liquid, in particular an optionally divided solid, medium or in a gaseous medium is essentially of the order of zero, in which composition the active substance chosen has a solubility in water of at least 0.5 g/l and which composition also contains a water-soluble auxiliary agent such that its dispersion is homogeneous in the silicone material and such that its presence does not inhibit the crosslinking of the silicone and promotes release kinetics of the active substance by the silicone material, in a non-liquid, in particular an optionally divided solid, medium or in a gaseous medium, essentially of the order of zero.

2. The composition according to claim 1, wherein the system comprising the active substance and the auxiliary agent is present in an amount of 5 to 50 parts per 100 parts of organopolysiloxane starting material.

3. The composition according to claim 1, wherein the active substance is present in an amount of 15 to 40 parts by volume per 100 parts by volume of organopolysiloxane.

4. The composition according to one of claims l to 3, wherein the active substance/auxiliary agent ratio is between 1/10 and 10/1.

5. The composition according to claim 4, wherein the active substance/auxiliary agent ratio is between 1/5 and 5/1.

6. The composition according to one of claims 1 to 5, wherein the silicone matrix is a silicone composition comprising (A) a diorganopoly-siloxane gum and (B) a reinforcing filler (B1) and/or an organic peroxide (B2).

7. The silicone composition according to claim 6, wherein the compound (B1) is a siliceous reinforcing filler.

8. The composition according to one of claims 6 and 7, which comprises:
- (A): 100 parts by weight of a diorganopolysiloxane gum having a viscosity higher than l million mPa.s at 25°C, and - (B): 5 to 130 parts by weight of a reinforcing siliceous filler (B1) chosen from pyrogenic silicas and silicas produced by precipitation.

9. The composition according to one of claims 6 to 8, wherein the gum (A) has the general formula R3-a(R'O)aSiO(R2SiO)nSi(OR')aR3a, in which the symbols R, which may be identical or different, represent C1-C8 hydrocarbon radicals, which are unsubstituted or substituted by halogen atoms or cyano radicals; the symbol R' represents a hydrogen atom or a C1-C4 alkyl radical, the symbol a represents zero or one, the symbol n represents a number having a value sufficient to obtain a viscosity of at least 1 million mPa.s at 25°C, and at least 50 % by number of the radicals represented by R are methyl radicals.

10. The composition according to claim 9, wherein preferably 0.005 to 0.5 mol% of the units involved in the structure of the gum (A) are chosen from those of formulae (CH2=CH)(R)SiO and (CH2=CH)R2 a(RO')aSio 0.5.

11. The composition according to one of claims 6 to 10, wherein it also comprises from 0.1 to 6 parts of a structuring agent (D) which is a fluoro-organic polymer in tha form of a pulverulent solid.

12. The composition according to one of claims 6 to 11, wherein it also comprises, in addition to a reinforcing filler (B1),from 0.1 to 6 parts (B2) of an organic peroxide.

13. The composition according to claim 12, wherein up to 90 % by weight of the reinforcing silicone filler (B1) is replaced by semi-reinforcing or packing fillers.

14. The composition according to one of claims 6, 12 and 13, cured by heating to form an elastomer.

15. The composition according to one of claims 1 to 5, wherein the silicone matrix is a silicone composition which is vulcanisable at elevated temperature and comprises (A) a diorganopolysiloxane gum having, per molecule, at least two vinyl groups bonded to the silicon and a viscosity at 25°C of at least 500,000 mPa.s, (B) at least one organo-hydrogenopolysiloxane having, per molecule, at least three hydrogen atoms bonded to the silicon, (C) a reinforcing filler, and (D) a catalytically effective amount of a catalyst which is a compound of a metal of the platinum group.

16. The silicone composition according to claim 15, wherein the compound (C) is a siliceous reinforcing filler.

17. The composition according to one of claims 15 and 16, which comprisess - (A): 100 parts by weight of a diorganopolysiloxane gum having, per molecule, at least two vinyl groups bonded to the silicon and a viscosity at 25°C of at least 500,000 mPa.s, - (B): at least one organohydrogenopolysiloxane having, per molecule, at least three hydrogen atoms bonded to the silicon, in an amount such that the ratio by number of hydride functional groups in (B) to vinyl groups in (A) is between 0.4 and 10, - (C): 5 to 130 parts by weight of a reinforcing filler which is preferably siliceous and is chosen from pyrogenic silicas and silicas produced by precipitation, and - (D): a catalytically effective amount of a catalyst which is a compound of a metal of the platinum group.

18. The composition according to one of claims 15 to 17, wherein the gum (A) has the general formula R3,(R'O),SiO(R2SiO)nSi(OR')aR3a, in which the symbols R, which may be identical or different, represent C1-C8 hydrocarbon radicals which are unsubstituted or substituted by halogen atoms or cyano radicals; the symbol R' represents a hydrogen atom or a C1-C4 alkyl radical, the symbol a represents zero or one, the symbol n represents a number having a Yalue sufficient to obtain a viscosity of at least 1 million mPa.s at 25-C, and at least 50 % by number of the radicals represented by R are methyl radicals.

19. The composition according to claim 18, wherein preferably 0.005 to 0.5 mol% of the units involved in the structure of the gum (A) are chosen from those of formulae (CH2=CH)(R)SiO and (CH2=CH)R2 a(RO')aSio0.5.

20. The composition according to one of claims 15 to 19, which comprises from 0.1 to 6 parts of an organohydrogenopolysiloxane (B) having a siloxane unit of average general formula:

in which R" represents methyl, phenyl and vinyl radicals, at least 50 % of these radicals being methyl radicals, c represents any number from 0.01 to 1 inclusive and d represents any number from 0.01 to 2 inclusive.

21. The composition according to any one of claims 15 to 20, wherein the organohydrogeno-polysiloxanes are chosen from straight-chain, branched or cyclic polymers made up of units chosen from those of formulae:
R"2SiO, H(R")SiO, H(R")2SiO0.5, HSiO1.5, R"SiO1.5SiO2 and R"SiO0.5 and are added in an amount such that the ratio by number of hydride.groups in (B) to the vinyl groups in (A) is between 1.1 and.4.

22. The composition according to any one of claims 15 to 21, wherein up to 90 % by weight of the reinforcing siliceous filler (C) is replaced by semi-reinforcing or packing fillers.

23. The composition according to any one of claims 15 to 22, which is cured by heating to form an elastomer.

24. The composition according to any one of claims 1 to 5, wherein the matrix is a diorgano-polysiloxane composition curable by polycondenstion reactions to give a silicone elastomer, which comprises:
- (A): at least one diorganopolysiloxane oil having at each end of the chain at least two condensable or hydrolysable groups or a single hydroxyl group, - (B): a polycondensation catalyst for the oil, and - (C): a silane comprising at least three condensable or hydrolysable groups, when (A) is an oil having hydroxyl ends.

25. The composition according to claim 24, wherein the diorganopolysiloxane (A) has the general formula (1):
YnSi3-n0(SiR20)xSiR3-nYn (1) in which:
R represents identical or different monovalent hydrocarbon radicals, Y represents identical or different hydrolysable or condensable groups, or hydroxyl groups, n is chosen from 1, 2 and 3, where n = 1 if Y is a hydroxyl, and x is an integer higher than 1 and preferably higher than 10.

26. The composition according to claim 25, wherein the radical R is chosen from C1-C8 alkyl, vinyl, phenyl and 3,3,3-trifluoropropyl radicals, at least 60 % by number of the radicals R being methyl radicals.

27. The composition according to one of claims 25 and 26, wherein Y is chosen from amino, acylamino, aminoxy, ketiminoxy, iminoxy, enoxy, alkoxy, alkoxyalkyleneoxy, acyloxy and phosphate groups.

28. The composition according to one of claims 24 to 27, wherein it comprises a silane (D) in the case where the condensable or hydrolysable groups are not hydroxyl groups and wherein the silane (D) has the formula:
R4-aSi Y'a (2) in which R is a monovalent hydrocarbon radical, Y' represents identical or different hydrolysable or condensable groups and a is 3 or 4.

29. The composition according to one of claims 24 to 28, which is one-component.

30. The composition according to one of claims 24 to 28, which is two-component.

31. The composition according to claim 30, which comprises:
- (A): 100 parts by weight of an alpha, omega-dihydroxydiorganopolysiloxane oil which has a viscosity of 50 to 300,000 mPa.s and in which the organic radicals are chosen from methyl, ethyl, vinyl, phenyl and 3,3,3-trifluoropropyl radicals, at least 60 % by number being methyl radicals, up to 20 % by number being phenyl radicals and at most 2 % being vinyl radicals, - (B): 0.01 to 1 part (calculated as weight of tin metal) of a catalytic tin compound, - (C): 0.5 to 15 parts of a polyalkoxysilane or polyalkoxysiloxane, and - (D): 0 to 100 parts, preferably 5 to 50 parts, of siliceous inorganic filler.

32. The composition according to one of claims 1 to 5, wherein the silicone matrix is a polyaddition silicone composition which may be cured to form an elastomer by hydrosilylation reactions, which comprises:
- (A): at least one organopolysiloxane having, per molecule, at least two vinyl groups bonded to the silicon, - (B): at least one organopolysiloxane having, per molecule, at least three hydrogen atoms bonded to the silicon, and - (C): a catalytically effective amount of a catalyst which is a compound of a platinum group metal.

33. The composition according to claim 32, wherein the molar ratio of the hydrogen atoms bonded to the silicon in (B) to the vinyl radicals bonded to the silicon in (A) is generally between 0.4 and 10.

34. The composition according to one of claims 32 and 33, which comprises:
- A) at least one organopolysiloxane having siloxy units of formula:
(1) in which Y is a vinyl group, Z is a monovalent hydrocarbon group which does not have an adverse action on the activity of the catalyst, a is 1 or 2, b is 0, 1 or 2 and a + b is between 1 and 3, all of the other units optionally being units of average formula:

(2) in which Z has the same meaning as above and c has a value between O and 3.
- B) at least one organopolysiloxane comprising siloxy units of formula:

(3) in which W has the same definition as above for Z, d is 1 or 2, e is 0, 1 or 2 and d + e has a value between 1 and 3, all of the other units optionally being units of average formula:
(4) in which W has the same meaning as above and g has a value between 0 and 3, and - C) a catalytically effective amount of a platinum compound.

35. The composition according to one of claims 32 to 34, which comprises:
- (A): 100 parts of a diorganopolysiloxane oil blocked at each end of its chain by a vinyldiorganosiloxy unit, the organic radicals of which, bonded to the silicon atoms, are chosen from methyl, ethyl and phenyl radicals, at least 60 molar % of these radicals being methyl radicals, having a viscosity of 100 to 5000,000 mPa.s at 25°C, - (B): at least one organohydrogenopolysiloxane chosen from the liquid homopolymers and copolymers which are straight-chain or have a network structure, which have, per molecule, at least 3 hydrogen atoms bonded to different silicon atoms and the organic radicals of which, bonded to the silicon atoms, are chosen from methyl and ethyl radicals, at least 60 % of these radicals being methyl radicals and the product (B) being used in an amount such that the molar ratio of the hydride groups to -the vinyl groups is between 1.1 and 4, - (C)s a catalytically effective amount of a platinum catalyst.

36. The composition according to claim 35, wherein 50 % by weight of the polymer (A) is replaced by a copolymer having a network structure and comprising the trimethylsiloxy, methylvinylsiloxy and SiO4/2 units, in which 2.5 to 10 molar % of the silicon atoms carry a vinyl group and in which the molar ratio of the trimethylsiloxy groups to the SiO4/2 group is between a . 5 and 1.

37. The composition according to one of claims 32 to 36, wherein it also comprises from 5 to 100 parts of reinforcing or semi-reinforcing siliceous fillers per 100 parts of the sum of the organopolysiloxanes (A) + (B).

38. The composition according to one of claims 32 to 37, previously cured to form an elastomer.

39. The composition according to one of claims 1 to 38, wherein the active substance is a fungicide.

40. The composition according to one of claims 1 to 38, wherein the active substance is a bacteriocide.

41. The composition according to one of claims 1 to 38, wherein the active substance is an insecticide.

42. The composition according to one of claims 1 to 38, wherein the active substance is a herbicide.

43. The composition according to one of claims 1 to 38, wherein the active substance is a plant growth regulator.

44. The composition according to one of claims 1 to 38, wherein the active substance is a fertiliser.

45. The composition according to claim 39, wherein the active substance is aluminium tris-O-ethylphosphonate.

46. The composition according to one of claims 1 to 45, wherein the auxiliary agent is a water-soluble salt.

47. The composition according to claim 46, wherein the auxiliary agent is an inorganic salt.

48. The composition according to claim 47, wherein the inorganic salt is an alkali metal or alkaline earth metal salt of a strong inorganic acid.

49. A method for the treatment of plants with a substance having an agricultural biological action, characterised by one of claims 1 to 48.

50. The treatment method according to claim 49, wherein the composition is applied against all or part of the plant for a period sufficient to supply an effective amount of active substance.

51. The treatment method according to claim 49, wherein the composition is placed in the vicinity of the plant for a period sufficient to supply an effective amount of active substance.

52. The treatment method according to claim 51, wherein the composition and the plant or part of the plant to be treated are in a gaseous medium.

53. The treatment method according to claim 51, wherein the composition and the plant or part of the plant to be treated are in a humid gaseous atmosphere.

54. The treatment method according to claim 51, wherein the composition and the plant are in a divided solid medium, preferably the soil.