CA1070038A - Adhesive repellent coatings and substrates coated therewith - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE
Coating compositions are provided for the manufacture of a non-stick coating. The compositions comprise (1) vinyl siloxy-terminated diorganopolysiloxanes having a plasticity within the range of from 300 to 800 mkp, (meter kilo pond), as determined in a Brabender Plastograph at 25°C and at 60 revolu-tions per minute in which from 3 to 30 mole percent of the nonterminal siloxane units are diphenylsiloxane units and at least 50 mole percent of the remaining organic radicals on the siloxane units are methyl radicals, (2) organohydrogenopolysiloxanes having at least 3 Si-bonded hydrogen atoms per molecule, (3) catalysts which promote the addition of Si-bonded hydrogen atoms to the vinyl groups and (4) an inert organic solvent. These coating compositions may be applied to cellulosic materials and other substances to impart varying degrees of adhesive repellency thereto.

Description

3~3 Thls invention relates to coating compositions which will impart varying degrees of adhesive repellency to substrates, such as, for example9 cellulosic substrates, and to a process for preparing the same. More particularly, the invention is concerned with a process for rendering cellulosic or other substrates substantially non-adherent to norma].ly adherent materials such as, for exam.ple, asphalts, bitumen, tars, waxes, paraffin solids, foodstuffs, pastes, adhesives .

~(~7~(~313 and other high molecular weight po:Lymers which may come in contact with the substrates.
It is well known that cellulosic materials ~nd other substrates may be treated with silicones and a host of other materials containing a variety of siloxane polymers, particularly siloxane fluids and resins to render these substrates adhesive repellent, i.e., non-adhesive or easily released from adhesive or sticky material. (See, for example, W. Noll, "Chemie und Technologie der Silicone"~. However, the repellency of various types of substrates such as, for example, smooth or coarse paper will vary with the adhesive; thereEore, it is necessary to com-pensate for the varying degrees of repellency of the coated substrates in order to achieve the desired degree of repellency. Moreover, since these adhesive repellent coatings are used in various applications, it is essential that the coatings have varying degrees of so-called "separating force level". For example, the packaging of sticky foods such as, for example, meat generally requires a high level of repellency, i.e., a low separating force level, while self-adhesive labels or carriers intended to transfer adhesive coatings by means of a so-called "transfer process" require a lesser degree of repellency in order to prevent, for example, the self-adhesive labels from detaching from the base to which they have been affixed prior to use.
Adhesive repellent coatings containing (1) diorganopolysiloxanes having Si-bonded vinyl groups in the terminal units in which from 3 to 30 mole percent of the nonterminal siloxane units are diphenylsiloxane units and at least 50 mole percent of the organic radicals of the remaining siloxane units are methyl radicals, . :. ,: . ~ .
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(2) organopolysiloxanes whlch contain at least 3 Si-bonded hydrogen atoms per molecule and (3) catalysts which promote the addition of Si-bonded hydrogen to the vinyl groups and subsequent crosslinking of the organo-polysiloxanes (1) are known in the art. (See Vnited States Patent No.

3,81~,731, to Nitzsche et al). This patent discloses that adhesive repellency decreases as the percentage of diphenylsiloxane units increases. In other words, various concentrations oE diphenylsiloxane units in the diorganopolysiloxanes (1) result in various levels of adhe-sive repellency. However, the compositions of aspects of this invention which contain diorganopolysiloxanes having terminal Si-bonded vinyl groups, organopolysiloxanes having at least 3 Si-bonded hydrogen atoms per molecule and catalysts which promote the addition of Si-bonded hydrogen to vinyl groups, generally require a greater proportion of diorganopolysiloxanes having terminal Si-bonded vinyl groups than organo-polysiloxanes which have at least 3 Si-bonded hydrogen atoms per molecule.
Therefore in order to obtain various levels of adhesive repellency by means of varying the concentration of diphenylsiloxane units in the diorganopolysiloxanes having terminal Si-bonded vinyl groups, it is necessary to produce and store large quantities of various, relatively high viscous diorganopolysiloxanes. However, the present invention in its various aspects only requires the preparation and storage of rela-tively small quantities of various organopolysiloxanes having a relatively low viscosity and containing at least 3 Si-bonded hydroven atoms per molecule in order to achieve various levels oE adhesive repellency.
Moreover, it is possible to achieve a lower level of adhesive repellency with small amounts of relatively difficult to obtain organopolysiloxanes containing diphenylsiloxane units.

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In addition, even aLter 2~ hours after ap~lication, tlle com-positions of aspects of this invention yield coatings which show the same or practically the same level of adhesive repellency as coatings made from freshly prepared mixtures. Also, the compositions of aspects of this invention have a very long "pot-life"; however, even with a long "pot-life", they rapidly crosslink at temperatures generally used in most applications. Moreover, continuously operating coating equip-ment can be used without any precautions to prevent migration of the coatings. Furthermore, the adhesive repellent properties of the coatings of as spects of this invention remain unaltered or practically unaltered over a period of several months.
It is therefore an object of one aspect of this invention to provide coating compositions which will impart release properties to r substrates coated therewith.
An object of another aspect of this invention is to provide coating compositions which will impart non-adherent properties to sub- b' strates coated therewith when contacted with adhesive materials.
~n object of another aspect of this invention is to provide compositions having a longer "pot-lifei'. t An object of still another aspect of this invention is to pro-vide compositiQns which cure rapidly when applied to substrates.
An object of a further aspect of this invention is to provide coatings which have varying degrees of repellency when contacted with adhesive materials.
~n object of a still further aspect oE tiliS invention is to ~J
provide a process for preparing adhesive repellent coatings. r j, .

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By a broad aspect of this invention, compositions for the manufacture of a non-stick coating comprises (1) vinyl-slloxy-terminated diorganopolysiloxanes in which 3 to 30 mole percent of the nonterminal siloxane units are diphenylsiloxane units and at least 50 mole percent of the remaining organic radicals on the siLoxane units are methyl radicals, the diorganopolysiloxanes (1) having a plasticity within the range of from 300 to 800 mkp (meter kilo ~ond) as determined in a Brabender Plastograph at 25~C. and at 60 revolutions per minute ; (2) organohydrogenpolysiloxanes having at least 3 Si-bonded hydrogen atoms per molecule; (3) a catalyst which promotes the addition of Si-bonded hydrogen atoms to the vinyl groups and (4) an inert organic solvent.
[Brabender Plastograph is a registered Trade Mark. The apparatus is described in an article by J.B. DeCoste SPEJ. 21, 764 (1965~].
These coating compositions are applied to substrates and then heated to a temperature of at least 80C. to remove the solvent and pro-mote crosslinking of the organopolysiloxanes.
Ln one variant, the diorganohydrogenopolysiloxanes (1) have an mkp value of from 360 to 730 as determined by a Brabender Plastograph at 25C. and at 60 revolutions per minute.
In another variant, such diorganopolysiloxanes (1) having terminal Si-bonded vinyl groups in which 3 to 30 mole percent of the non-terminal siloxane units are diphenylsiloxane units and at least 50 mole percent of the o,rganic radicals of the remaining siloxane units are methyl radicals, may be represented by the general formula:
(~H2-CH)R2SiO [ (C6H5) 2SiO]m (R2SiO)nSiR~ (CH=CH2) ; wherein R which may be the same or different represents monovalent hydro-carbon radicals and substituted monovalent hydrocarbon radicals, with the provision that at least 50 mole percent of the ~ radicals are methyl radicals, ' ' ~ :

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m and n each represent .Lnteger such that the amount of diphenylsiloxane units in the dior~c~nopolysiloxane is within the range of 3 t~ 30~ o~ the total c~mount of nonterminal siloxane units and such -that the sum results in t~

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the diorganopoly~iloxanes (1) havLng a mklp value of fr~m 300 to 800 as determined by a Brabender Plastograph at 25C and at 60 rev~lutions per r minute.
By another variant, the nontermunal di~henylsiloxane units are present in ~he diorganopolysilo~anes in an amount of from 5 to 20 mole percent.
By a further variant, the organohydr~genopolysilo~anes (2) have the general formula r C1~13 ~ R~ 1 C113 R' ~ O lSi--~ Si --R
C1~3 Rl C113 wherein R' is selected from the group consi.sting of hydrogen, lcwer alkyl radicals and aryl radicals, in which the amount of silicon bonded hydrogen atcms ranges from 0.10 to 1.66 percent by weight, exce~t that only one hydrogen atom is bonded to any one silicon atom and p is an integer of from 20 to 500, especially where p is an integer of frcm 20 to 100.
By c~nother variant, at least 70 mole percent of the oryanic ~0 radicals on the re~aining siloxane units of the diorganopolysiloxanes (1) are methyl radicals.
By another varian-t,all non-terminal siloxane um ts in the dior~
ganopolysilo~ane are free of v myl grou~.
By a further variclnt, all non-ter~lnal siloxane units Ln the diorganopolysilo~ane are ~ree of aliphatic unsaturation. '~
By a variant thereo~, ~' is .selected from the group consisting of hydrogen, methyl, ethyl or phenyl.
By c~nother varic~nt, R' is selected from methyl, ethyl or phenyl.
By still another varic~nt, all hydrogenosiloxane units in the . .

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3~3 organohydrogenpolysiloxane are methylhydrogenosiloxane units.
By yet another variant, the mole ratio of the siloxane units having one Si-bonded hydrocarbon radical to the siloxane units having two Si-bonded hydrocarbon radicals in the organohydrogenpolysiloxanes (2) is from 10:0 to 1:10, while in still another variant, the organohydrogenpoly-siloxanes (2) are present in an amolmt of from 1 to 20 percent by weight based on the weight of the diorganopolysiloxanes (1), especially in an - amount of 4 - 8%.
In a still further variant, the catalyst (3) contains platinum, or a platinum compound, or a platinum complex, especially where it is present in an amount of from 0.001 to 0.1 percent by ~eight especially 0.01 to 0.5% of elemental platinum based on the weight of the diorgano-polysiloxanes (1). In a variation thereof, the catalyst is a platinum-ketone complex.
By another variant thereof, the organic solvent is anhydrous or substantially anhydrous.
By another variant, the organic solvent is present in an amount of from 200 to 5000 percent by weight based on the weight of the diorganopolysiloxanes (1)~
By still another variant, the composition includes at least one of a pyrogenic silica and an agent to prevent or retard crosslinking at room temperature.
By a variation thereof, the agent is benztria~ole, a dialkyl-formamide, an alkylthiourea or methyl ethyl ketoxime.
By another aspect of this invention, a process is provided for preparing a composition for the preparation of a non-stick coating which ` ~ - 6 a -,, '. , ~. ~' ,, .

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comprises: dissol~ing, in an organic solvent, vinylsiloxy-terminated diorganopolysiloxanes ~1) in which 3 to 30 mole percent of the nontermlrkal siloxane units are diphenylsiloxane units and at least S0 mole percent of the remaining organic radicals on the siloxane units are methyl radicals, the diorganopolysiloxanes (1) having a plastic:ity within the range of from 300 to 800 mkp as determined in a Brabender Plastograph at 25C and at 60 re~lutions per minute and a catalyst (3) capable of pr~moting the addition of Si-bonded hydrogen atoms to vinyl groups to form a solution; and there- L~
after adding organohydrogenopolysiloxanes (2) having at least 3 Si-konded hydrogen atons per molecule to the solution.
By one variant o~ this process, the diorganopolysiloxanes (1) have an mkp value of from 360 to 730 as determined by a Brabender Plasto-graph at 25C and at 60 revDlutions per m mute and they may have the general formula 2 ) 2 (C6H5)2Si m ~R2sio)nsiR2(cH=cH2) wherein R is selected form the group consisting of monovalent hyclro~arbon f' radicals and substituted monovalent hydrocarbon radicals, in which at least 50 mole percent of the R radicals are methyl radicals, m and n each repre- , sent an integer such that the amount o~ diphenylsiloxane units in the ~-diorganopolysiloxane is within the range of 3 to 30% of the total amount of non-terminal siloxane units and such that the sum results in the c~organo-polysiloxanes (1) having an mkp value of Erom 300 to 800 as determined by a Brabender Plastograph at 25C and at 60 revolutions per minute.
By yet another varia~t,of ~his process, the nonter0inal cdiphenyl-siloxane units are present in the diorganopolysilo~anes in an amount of from 5 to 20 mole percant.
By a further variant, at least 70 mDle F~rcent of the organic ra~icals on the rema.umng siloxane units of the diorganopolysiloxanes (1) are methyl radicals.

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By a still further variant the organohydrogenopolysilox~anes (2) are present in an amDunk of from 1 to 20 percent by weight based on the weight of the diorganopolysiloxanes (1).

By a still further variant, the cataly9t (3) contains platinumt or a platinum compound, or a plat mum cc~plex, e.g. a platinum~ketone com~
plex, especially where the organic solvent is present in an amount of f~cm 200 to 5000 percent by weight based on the weight of the diorganopoly-siloxanes (1).
By another aspect of this invention, a process is provided for the nanufacture of a non-stick coating on a substrate which oGmprises:
applying to the substrate a coating composition containing (1) vinylsiloxy-terminated diorganopolysiloxanes in which 3 to 30 mole percent of th2 nonterminal siloxane units are diphenylsiloxane w~ts and at least 50 mole percent of the remaining organic radicals on the siloxane wnits are methyl radicals, the diorganopolysiloxanes (1) having a plasticity wlthin t~e range o~ from 3~0 to 800 mkp as~determined in a Brabender Plastograph at 25C, and at 60 revolutions per minute; (2) organohydrogenopolysiloxanes having at least 3 Si-bonded hydrogen atoms per mDlecule; (3) a catalyst which promotes the addition of Si-bonded hydrogen at~ms to the vinyl gr~ups and (4) an inert organia sol~ent, and thereafter heating the coated suk~

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strate to a temperature o~ at least 80C.
By on~ vari~nt, the surface of the substrate i~ absorbent, and the oomposition is applied m such an amDunt that the total amount of diorganopolysilo~no and organohydrogenopolysiloxane applied is within the range of fram 0.1 to 0.5 g~ ~2 By another variant, the ~urface of ~he substxate is absorbent and the composition is applied ~ ~ ~ an amount that the total amDunt of ;-diorganopolysilo~ane and organ~hydrDgenopolysiloxane a~plied is within the ~r~nge of fram 1 to 5 g m2 6 a - -, ' ' :
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By a variant of this aspec-t, the substrate is first treated wi-th a pore sealing compound, particularly polyvinyl alcoholO
~y a further variant, the coated substrate is heated to a tempera-ture up to 250C.
By another variant, the substrate is paper.
By still another aspect of this invention, a novel substrate is provided w~ich is treated as defined above, F~lrticularly where the diorgano-polysiloxanes and organohydrogenopolysiloxanes are absorbed in an amount of from 0.1 to 5 g/m2.
me organopolysiloxane form~La illustrated above may contain within or along the siloxane chain units other than t~e diorganosiloxane units shown above, iOe., units corresponding to the formLlae (C6HS)2SiO t and R2Sio. Examples of other siloxane units which are present generally r onIy as impurities, are those corresponding to the formuLae RSiO3/2, R3Sio1~ and Sio~/2, where R is the same as above. mese other siloxane units are preferably present in an amoun-t of less than 10 mole percent and more preferably not more than 1 mole percent.
Examples of organic radicals other than the methyl radicals, phenyl radicals and termlnal ~inyl radicals which may be prese;nt in ~he diorganopolysiloxanes (1) are saturated hydrocarbon radicals such as, for e~ample, alkyl radicals having up to 18 carbon atoms, e.g., ethyl, n-propyl t isopropyl and radicals up to and inc:Luding octadecyl radicals; cycloalipha-tic hydrocarbon radicals, such as, for example, th~ cyclohexyl radical, aryl radicals, such as, for example, the phenyl radicaL; aLkaryl radicals such as, for exa~ple, the tolyl radical and araIkyl radicals such as, for example, h the benzyl radical. An e~ample of a ~ubstituted hydrocarbon radical is the 3,3,3-tri$1uo~opropy1 radical. Other ~? ~ 6 d -.
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In order to obtain flexible coatings, it is preferred that the nonter-minal hydrocarbon radicals in the diorganopolysiloxanes (1) be saturated hydrocarbon radicals, iOe., free of aliphatic unsaturation such as, for example, vinyl radicals.

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It is preferred that from 5 to 20 mole percent of the siloxane units which are nonterminal ~mits be diphenylsiloxane units. Moreover, it is preferred that at least 70 mole percent of the nonterminal siloxane units be dimethylsiloxane units. The hydrocarbon radicals which are present in the other siloxane units can be the same or difEerent, regardless of whether they are linked to t:he same or different silicon atoms.
If all the organic radicals in the diorganopolysiloxanes (1) are methyl radicals except the terminal vinyl groups, then varying the concentra~ion of Si-bonded hydrogen in the organopolysiloxanes (2) does not produce any distinguishable variation in the level of adhesive repellency with respect to identical adhesive substances.
As a matter of fact, the degree of adhesive repellency of the coatings prepared pursuant to aspects of this invention increases when the proportion of phenyl groups and especially the content of diphenyl-siloxane units in the diorganopolysiloxanes (1) inc~eases.
The diorganopolysiloxanes (1) may contain identical copolymers or mixtures of various copolymers which have the same degree of poly-merization, or mixtures of identical or different copolymers which have different degrees of polymerization. The diorganopolysiloxanes (1) can be copolymers having a random distribution of the various units or block-copolymers.
If the diorganopolysiloxanes (1) do not have a Brabender Plasto-graph value of from 300 to 800 mkp at 25C. and at 60 revolutions per minute, which corresponds to a viscosity far in excess of 106 cP at 25C., then it is virtually impossible to achieve any variation in '' ;

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I!centration of Si-bonded hydrogen in the organopolysiloxanes (2). A
¦¦Brabender Plastograph is for example illustrated in the text by IIK. Frank, "Prufungsbuch fur Kautschuk und Kunststoffe", (Stuttgart ~1955), page 25.
The preparation of diorganopolysiloxanes (1) having llterminal Si-bonded vinyl groups in which 3 to 30 mole percent of j¦the nonterminal siloxane units are diphenylsiloxane units and at I¦least 50 mole percent of the organic radicals in the remaining silnxane units are methyl radicals and which have an mkp factor of from 300 to 800 as determined in a Brabend~r Plastograph at 25C
and at 60 revolutions per minute, is generally known. These di-jorganopolysiloxanes c~n be prepared for example by the hydrolysis l of a mixture of from 3 to 30 mole percent of diphenyldichlorosilane ¦ and 97 to 70 mole percent of dimethyldichlorosilane and very small ¦amounts of vinylmethyldichlorosilane, in the presence of an aqueous jalkali hydroxide solution containing from 3 to 20 mole percent by !weight of alkali hydroxide based on the total weight of water and . lalkali hydroxide and the cond~nsation and equil;bration of the I hydrolysate is conducted in the presenoe of phosphoronitrile ¦ chloridesO `
ll The organopolysiloxanes (2) which haYe at least 3 Si-bonde,d .¦hydrogerl atoms per molecule are the same organopolysiloxanes which llhave been used heretofore in the preparation of adhesive repellent coatings containing vinyl terminated diorganopolysiloxanes, organo- ~
~polysiloxanes having at least 3 Si-bonded hydrogen atoms per molecule ~ 8 ~07~38 and catalysts which promote the addition of Si-bonded hydrogen to vinyl groups.
Organopolysiloxanes (2) which have at least 3 Si bonded hydrogen atoms per molecule and the valences of the silicon atoms which are not saturated with hydrogen atoms or siloxane oxygen atom~s, are pre-ferably saturated with lower alkyl radicals such as, for example, methyl or ethyl radicals or aryl radicals, such as, for example, the phenyl radical. These organopolysiloxanes (2) may be represented by the follow-ing general formula:

ICH3 - ~ - CIH3 R~ - Si - O - - Sl - O- - Si - R~
CH3 R' p CH3 wherein R' represents hydrogen or a lower alkyl radical such as, for example, methyl, ethyl, or an aryl radical such as, for example, a phenyl radical; however, only one hydrogen atom may be bonded to any one silicon atom and the amount of Si-bonded hydrogen atoms in the organopolysiloxanes corresponding to the above formula ranges from 0.10 to 1.66 mole percent by weight, and p is a number of from 20 to 500 and more preferably a 20 number of from 20 to 100. Because of their availability, methyl radicals are preferred as the hydrocarbon raidcals which are linked to silicon atoms which contain Si-bonded hydrogen atoms.
Examples of diorganopolysiloxanes (23 which correspond to the above forrnula are copolymers consisting of dimethylhydrogensiloxane, methylhydrogensiloxane, dimethylsiloxane and trimethylsiloxane units;
copolymers of methylhydrogensiloxane and trimethylsiloxane units;
copolymers of methylhydrogensiloxane, dimethylsiloxane and trimethyl-siloxane units; copolymers of methylhydrogensiloxane, : 30 ~ .
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copolymers of methylhydrogensiloxane, phenylmethylsiloxane, trimethyl-siloxane and/or dimethylhydrogensiloxane units and copolymers of methyl-hydrogensiloxane, dimethylsiloxane, diphenylsiloxane and trimethyl-siloxane and/or dimethylhydrogensiloxane units.
The higher the proportion of Si-bonded hydrogen groups in the organopolysiloxanes (2), the lower the level of adhesive repellency.
It is preferred that the mole ratio of the siloxane units having one Si-bonded hydrocarbon radical in relation to the siloxane units having two Si-bonded hydrocarbon radicals in the organopolysiloxanes (2) may range from 10:0 to 1:10. It is preferred that the organopoly-siloxanes (2) have a viscosity of 30 to 80 cP at 25C.
Organopolysiloxanes (2) including those of the pre~erred type, are generally known. Such organopolysiloxanes (2) can, for example, be prepared by the co-hydrolysis of dimethyldichlorosilane, methyldichloro-silane, dimethylchlorosilane and/or trimethylchlorosilane. However, it is preferable that the organopolysiloxanes employed in accordance with aspects of this invention be prepared by equilibrating trimethylsiloxy or dimethylhydrogensiloxy terminated methylhydrogensiloxanes, with dimethylsiloxanes and/or diphenylsiloxanes and/or phenylmethylsiloxanes which are endblocked with trimethylsiloxy groups, in the presence of an acid equilibration catalyst.
The organopolysiloxanes (2) are preferably employed in amounts of from 1 to 20 mole percent by weight, and more preferably . .

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in amounts of from 4 to 8 mole percent by weight, based on the weight of the diorganopolysiloxanes (1).
By varying the percentage of Si-bonded hydrogen groups in the organopolysiloxanes (~), it is possible to obtain adhesive repellent coatings having various levels of adhesive repellency while maintaining the same weight ratio between organopolysiloxanes (2) and diorganopoly-siloxanes (1).
Catalysts which promote the addition of Si-bonded hydrogen to vinyl groups employed in various aspects of this invention are the same catalysts as those which have been used heretofore in the preparation of adhesive repellent coatings based on vinyl-terminated diorganopolysilox-anes, and organopolysiloxanes having at least 3 Si-bonded hydrogen atoms per molecule. Examples of suitable catalysts are platinum, ruthenium, rhodium, palladium, iridium and compounds or complexes of these elements, such as, for example, PtC14, chloroplatinic acid, platinum-o:lefin com-plexes, platinum-ketone complexes and platinum-vinylsiloxane complexes as well as iron carbonyls, nickel carbonyls and cobalt carbonyls.
Platinum-ketone complexes are preferred, particularly the reaction pro-ducts o~ chloroplatinic acid and ketones, such as, for example, cyclo-hexanone, methyl ethyl ketone, acetone, methyl-n-propyl ketone, methyl-îso~butyl ketone, methyl-n-amyl ketone, diethyl ketone, ethyl-n butyl ketone, ethyl-iso-amyl detone, diisobutyl ketone, acetophenone and mesityl oxide. The preparation of such platinum-ketone complexes is described in United States Patent No. 3,814,731, to Nitsche et al.
When platinum or platinum compounds and/or platinum complexes are employed as catalysts to promote the addition of Si-bonded hydrogen to vinyl gFOUpS, these catalysts should be used in amounts ..

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` Organic solvents ~4) which have been used heretofore in the preparation of adhesive repellent coatlngs based on vinyl endblocked diorganopolysiloxanes, organopolysiloxanes having at least 3 Si-bonded hydrogen atoms per molecule and catalysts which promote the addition of Si-bonded hydrogen to vinyl groups may be used in -arious aspects of this invention. Pre~erably, the organic solvents are substantially free of water an~ are inert with respec-t to the other ingredients of the coating composition. Fu~thermore, it is preferred that these organic solvents evaporate very rapidly at a temperature of from 70 to 180C and at a pressure of 760 mm Hg (abs). Examples of suitable organic solvents and hydrocarbons, such as, for example, low boiling naphtha, alkane mixtures having a boiling range of from 80 to 110C
at 760 mm Hg (abs), benzene, toluene and xylene, halogenated hydrocar-bons having from 1 to 6 carbon atoms such as, for example, methylene chloride, trichloroethylene and perchloroethylene; ethers such as, for example, di-n-butylether; esters ~uch as, for examllet, ethylace-tate and ketones such as 3 for example, methyl ethyl ketone and cyclo-hexanone. A low boiling naphtha is the preferred organic solvent because of its availability.
The organic solvents should be el~ployed in amounts of from 200 to 5,000 mole percent based on the weight of the diorganopolysilox-anes (1).
If desired, the coating compositions of aspects of this inven-tion may contain in addition to the diorganopolysiloxanes (1), the organopolysiloxanes (2), the catalysts (3) and the organic solvents (4), o~her materials which are sultable additives for such compositions.

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- ~7~3~3 Suitable additives are materials which retard the crosslinking of the organopolysiloxanes ~1) at room temperature, such as, for example, benzo~riazole, dialkylformamide and alkylthiourea, as well as methyl ethyl ketoxime and pyrogenically produced silicon dioxide.
In preparing the coating compositions of aspects of this invention, it is preferred that the diorganopolysiloxanes (1) be mixed with organic solvent (4) and catalyst (3) ~hich promotes the addition of Si-bonded hydrogen to vinyl groups and thereafter oxganopolysiloxanes (2) which contain at least 3 Si~bonded hydrogen atoms per molecule are then added. The solutions thus prepared can be stored at room tempera-ture for at least 7 days without any substantial gelling of the solution and without any substantiai decrease in the crosslinking ability of the diorganopolysiloxanes (1).
When the surfaces which are to be rendered adhesive repellent are nonabsorptive or only slightly absorptive, then the coating con-ditions and especially the concentration oE solvent and the manner in ~hich it is applied are selected so that the diorganopolysiloxanes ~
and the organopolysiloxanes (2) are absorbed in an amount of from 0.1 to 0.5 g/m2. Conversely, if the surfaces which are to be rendered :
adhesive repellent are highly absorptive, then coating conditions are ; selected so that the diorganopolysiloY.anes (1) and the organopolysilox-anes (2) are absorbed by the surface in an amount of from 1 to 5 g/m .
The need for a greater amount of organosilicon compo~lnds for absorptive `
surfaces can be substantially avoided if these surfaces are first pre-treated with pore sealing compounds, such as, for example~ a solution of polyvinyl alcohol, particularly polyvinyl alcohol in which the degree of hydrolysis is f~om 74.5 ~o ~L~7~3~

100 mole percent, and more prefera~ly from 85 to 90 mole percent! and has a viscosity based on a 4 percent by weight aqueous solution in water or polyvinyl acetate in an organic solvent of from 3 to 40 cP
and more preerably from 16 to 32 cP at 20C. The coating compositions of aspects of this invention may be applied to the surfaces which are to be rendered adhesive repel.lent by any suitable means known in the art for preparing coatings from fluid substcmces, such as, for example, by i~nmersion, coating, pouring, spra~ing, calendering, printing, knife or blade coating as well as by a Meyer Rod.
The diorganopolysiloxanes (1) can be crosslinked in the same manner as has been used heretofore for the preparation of adhesive repellent coatings which contain vinyl endblocked diorganopolysiloxanes, organopolysiloxanes having at least three Si-bonded hydrogen atoms per molecule and catalysts which promote the addition of Si-bonded hydrogen to vinyl groups. Crosslinking is achieved by heating to at least 80C
while substantially simultaneously removing the organic solvent. In order to avoid any damage to backings on which adhesive repellency is to be induced and/or the coatings which are to be made adhesive repellent, i~ is preferred that the temperature not exceed 250C during the heating step. Generally, heating to a temperature range of from 140 to 160C is preferred. A heating period of from 5 to 180 seconds is generally sufficient to achieve adequate crosslinking.
As a result of the teachings of various aspects o this inven-tion, it is possible to prepare adhesive repellent coatings on various types of surfaces, such as, for example, paper, board, including boards made of asbestos, wood, cork, plastic, such as, for example, those made from polyethylene, ' ' .

fabrics made from natural or synthet~c f~bers, metals, glass, and ceramic ob~ects. ~or example, the paper may be of an inferior quality, such as, for example, absorptive papers, including raw kraft paper, i.e., kraft paper which has not been pretreated with chemicals and/or polymeric substances9 kraft paper having a weight of from 60 to 150 g/m2, unsized papers, papers having a low degree of grinding, papers containing particles of wood, non-satinated or non-calendered papers 9 uncoated papers, recycled papers or expensive types of paper, such as, for example, non-absorptive papers, sized papers, papers with a high degree of grinding, wood-free papers5 calendered or satinated papers, parchment papers or coated papers. The boards may be of elther type as well.
Also the coating compositions of aspects of this invention may be applied to carpet felt, i.e. paper that is placed under carpets, and "simultaneous run papers" including "simultaneous run papers" which are used during the manufacture of "molded" films or decorating films or the manufacture of foamed plastics. The compositions are also suitable for the manufacture of "simultaneous run cardboard" films and cloths, for application to the undersides of self~adhesive bands and self-adhesive films or the printed side of self-adhesive labels, as well as for packaging material, such as, for example, papers, cardboard boxes~ metal films and fibers, for example,cardboard, plastic material9 wood, lron and other solid materials sued for the storage and/or transportation of adhesive materials, such as, for example, food, e.g.
cakes, honey, candy and meat; bi~umen, asphalt, grease-coated metal parts, and raw rubber, as well as for the coating of carriers which transfer adhesive coatings by means of the so-called "transfer process".

0~70~ ~

In the follo~ing examples all parts or percentages are by !
w~ght unless otherwise specified~ ¦
The catalyst soluticn employed in the following examples ~s prepared by adding 1 part of ohloroplatinic acid to 200 parts of¦
yclohexanone ~hich has been heated to 800. The solution thus obtained is ~aintained at 80~ for 45 minutes and then subsequently dr~ed with the aid of anhydrous sodium sulfate~
Where possible, all units in the copolymers employed in I the following examples, are randomly distributed.
¦ The Brabender Plastograph values arc determined on solven~
¦ ~r~e diorganopolysiloxanes at 25C and at 60 revo7utions per minute.!
~ - EXAMPI.E 1 ., ! . . ~
a) To about 300 parts of a toluene solution containing 25 weight percent o~ vinyldî~ethylsiloxy endblooked diorganopoly-~ 15 s~loxanes consisting of 89 mole percent of dimethylsiloxane units : and 11 mole percent of diphenylslloxane units and havîng a Brabender Plæstograph value of 420 mkp, are added about 118~ parts of an . alkane wixture having a boiling range of from 80 to 110O at 760 mml -Hg (~bs) and 6.0 parts of the catalyst solutlon described above-.
b3 To several eompositions, each containing about 100 parts of the solutian prepared above are added 0.5 part of or~anopolly-s~loxanes having a viscosi~y of from 40 to 60 cP at 25C wh~ch . cons~sts of 4 mole percent of trimethylsiloxane units and methyl- ~
. hydrogensiloxane units and dimethylsiloxane units in the mole peroent ¦shown ln Table I, and applied to im~tation parchment paper having a¦
'.. I . ' . ~ I
.. .. ~ - : ~
: ~`
:

~7~
weight of 75 g/m2, by means of a doctor blade which consists of a s-tainless s-teel rod having 0.3 mm -thick stainless st~el wire wound thereon. The diorganopolysiloxane crosslink in an oven a-t 150C within 2 minutes.
The coated papers are -then tested -to determine -the level of adhesive repellency. ~-Two strips of 3 cm wide selE-adhesive -tape ("Tesafilm rot" No. 154, Beiersdorf AB, Hamburg, German Federal Republic. r "Tesa" is a registered Trademark) which has an adhesive power of approximately 150 p/cm on -the uncoated paper are placed on the coa-ted paper and pressed on-to the latter wi-th a rubber roller with a force of 15 kp/cm2. Af-ter hea-ting for 20 hours a-t 70C under a weight of 20 p/cm and then cooling to 20C, -the two adhesive tapes are separa-ted a-t an angle o:F 180 with a speed of 30 cm/minu-te. The force required -to separate the tape from the paper is measured. The resul-ts are illustrated in Table 1 !

1, .
!

.
,.,.... .
~17 ~-. A~....................... .
,, " ,,, , . .. . .. .. . ~ _ . ..

.
:, .
~ .

__ _ . . _ _ _ . _ _ _ _ _ _,. _. _ _. _. .,__ ~ ~_.~_~._~_ ~L:h.. ~ ~_~. _._ . .,~___ ~7~ ~ 3 TABLE I

~ r- I
Organopolysiloxanes containing Separating Residual Si-bonded hydrogen force adhesiv~
l (p/cm) strengt~
1 . of tape i _ _ _ _ MethylhydrogenDimethyl- Si-bonded siloxane unitssiloxane hydrogen (mole percent) units (percent) l (mole percent) ,,,, _ .
96 o 1.66 113 llo 86 lo 1.46 111 tl7 72 2~ 1,18 loO lo l 64 32 1.03 91 12 1 5O 40 o.gl 76 125 48 48 o .75 47 1 1 . 56 0.59 31 133 32 64 û .48 27 1 29 24 72 o .36 lo 120 14 82 0.2û 7 114 .
_ -- ~ - -t ,, ~ 1:

About 20 parts of a toluene solution containing 25 weight~
: percent of vinyldlmethylsiloxy endblocked diorganopolysiloxanes con~
ta~ning ~4.3 mole percent of dimethylsiloxane units and 6.7 mole percent of diphenylsiloxane units and having a Erabender Plastograp~
v~lue of 730 ~kp are diluted with 79 parts of an alkane mixture ~ 0'7~ 3 ~

: having a boiling range of from 80 to 110C at 760 mm Hg (abs) and then mixed with 0.4 part uf the catalyst solution described above.
The solution thus obtained is mixled with 0.5 part of organopolysiloxanes contai.ning 4 mole percent trimethylsiloxane lunits. 72 mole percent methylhydrogensiloxane units and 24 mole percent dimethylsiloxane units and app7ied either immediately or lafter an elapsed period of time as shown in Table II to imitation I.
¦parchment paper with the aid of the doctor blade described in ¦Example 1. ~r~sslinkina of the dior~anopolysiloxan~s occurs within 12 minutes in an oven at a temperature of 150C.
The coated papers are then tested in accordance with the procedure described in Exarnple 1 to determine their leYel of adhesiv e ¦repellency. The results are illustrated in Table II

~ TABLE II
. _ _. . _ - .
IElapsed time between preparation of solution Separating Residual adhesive and coating of paper . force power of tape ~Hours) (p/cm) (p/cm) 1~ - .

I 1 34 1 20 -~ .

.3 39 132 . 4 ~2 129 ; 2~ ll . ~ 3~ 12 7 3~ 142 .__ _ _ . _ 135 il - - !
l g -\

~ 38 ., : I . 100 parts o~f the solution prepared in accordance l~with Example 1 (a) are mixed with 0.6 part of organopolysiloxanes jjcontainin9 4 mole percent of trimethylsiloxan units, 64 mole per- ¦
¦icent methylhydrogensiloxane units and 32 mole percent of dimethyl-¦~siloxane units and applied to 6 specimens of imitation parchment ¦¦paper having a weight of 75 g/m2 using the doctor blade described In¦
¦IExample 1. Crosslinking of the diorganopolysiloxanes occurs withln ¦
I,2 minùtes in a drying oven.
ll The coated papers are crosslinked and tested aFter an ¦elapsed time with respect-to their level of adhesive repellency in accordance with the procedure described in Example 1. The resul ts . .
are illustrated in Table III

. TAELE III
. .
. . ~
¦Elapsed time between crosslinking Required separatin and testing force (p/cm) I . . .
. ¦ 0 days 91 --¦
I 3 days 94 ¦ 1 week 98 ¦ :
: I 2 weeks 95 j 3 weeks 96 -4 weeks 98 _ t ~ 2 I ~f~7~3~3 I . . I

. a~ To ahout 3Q0 parts ~f a toluene solution containing 2S
.~ welght percent of vinyldimethylsiloxy endblocked copolymers contain-~
: - ~ng ~0~3 mole percent diphenylsiloxane units and 79.7 mole percent di~ethylsiloxane units and ha~ln~ a Brabender Plastograph value of 3C0 mkp are added 1185 parts of an alkane mixture having a boiling range of from 80 to 110C at 760 mm Hg (abs). The resultant solution then mlxed with 6 parts of the catalysE solution described above.
.. b) Several compositions each containing about 100 parts oF the solution prepared in Example 4 ta) above and 0.5 part oF
¦¦organopolysiloxanes which have a viscosity of from 40 to 6Q cP at 2~C and contain 4 mo~e percent of tr~methylsiloxan~ units and . . ~thylhydrogensiloxane units and dimethylsiloxane units in the ~ole !
~ percentages shown in Table IV are prepared and applied to imitation parchment paper having a wei~ht of 75 g/m , by ~eans of the doctor blade descr~be~ ~n Example 1. Crosslinking o~ the diorganopoly-. ¦s~loxanes occurs within 2 minutes ~n a drying oven.
¦ The coated papers are tested wTth respect to their adhesive repellency in accordance with the procedure described in ~Exa~ple 1. The resu1ts are shown in lable IY
` :. ! ~
.. I . . ~ ,.
., . .
. ,. . , . ~ ...
I .................... , ., . ~ .
. 'l ~ ~ -I , .: ~ 21-. ' ' '' ,: ' , , . , :
,' ''." , . . ', , , , , ,',~

10~7003 ITABLE IV

¦lOrganopolysiloxanes containing Separating Residual !¦Si-bonded hydrogen force adhesive~li (p/c~) strength 11 of tape 1.1 I ~ I
Methylhydrogen Dimethyl- Si-bonded siloxane units siloxane hydrogen I(mole percent) units (percent) (mole percent) ~ . . _ _ 96 o 1.~6 114 1~7 64 32 1.03 103 13 56 40 o.gl 92 12~
48 ~8 ~.75 7~ 139 ~o 56 o o59 53 1 36 32 64 ~.48 39 127 24 72 0.3~ 23 l26 14 1 82 1 o.o I 9 ll46 ~_ . _ ~'.' ZO ¦! Several compositions, each containing 100 parts o~ the j! catalyzed sol uti on prepared i n accordance wi th the procedure ¦Idescribed in Example 4 (a) above, and 0.5 part of organopolysiloxanqs ¦each of which çonsists of 4 ~ole percent of trimethylsiloxane units jand methylhydrogensiloxane units and diphenylslloxane units in the ~,mole percentages shown in Table Y are prepared and then applied to ~imitation parehment paper having a weight oF 75 g/cm by means of - 2~
!l ' . :'. ~

.

1~ 00~ 1 ll ¦the doctor blade described in Example 1. Crosslinking of the di-llorganopolysiloxanes occurs in the drying oven within 2 minutes.
¦! The coated papers are then tested in accordance with the !procedure described in Example 1 to determine their level o~
~adhesive repellency.

li The results are illustrated in Table V

¦l TABLE V
l l ..... __ ...................................... ..... ..
Organopolysiloxanes containing Separating Residual~
. Si-bonded hydrogen force adhesive (p/cm) strength~
. ~p/cm~
_ .. .. ___ l~ethylhydrogen Diphenyl- Si-bonded ¦
siloxane unitssiloxane hydrogen (mole percent)units (percent) (mole percent) I . . ~ . ,. .......... .
,j 90 6 1.26 95 1~6 il 78 18 0.68 91 ~1 jj 69 27 0.~1 53 122 : Il 64 32 0.23 24 105 1l .` . . I
_ . -- '' 'I
. .. ..... . , . . .. _._ I
- 1 .
2~ 1 .
~.
' - -. I

Claims (40)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A composition for the manufacture of a non-stick coating com-prises (1) vinylsiloxy-terminated diorganopolysiloxanes in which 3 to 30 mole percent of the nonterminal siloxane units are diphenylsiloxane units and at least 50 mole percent of the remaining radicals on the siloxane units are methyl radicals, said diorganopolysiloxanes (1) having a plasticity within the range of from 300 to 800 mkp as determined in a Brabender Plasto-graph at 25°C and at 60 revolutions per minute; (2) organohydrogenopoly-siloxanes having at least 3 Si-bonded hydrogen atoms per molecule; (3) a catalyst which promotes the addition of Si-bonded hydrogen atoms to the vinyl groups and (4) an inert organic solvent.

2. m e composition of Claim 1 wherein the diorganopolysiloxanes (1) have an mkp value of from 360 to 730 as determined by a Brabender Plastograph at 25°C and at 60 revolutions per minute.

3. The composition of Claim 1 wherein the diorganopolysiloxanes (1) have the general formula (CH2=CH)R2SiO (C6H5)2SiO m (R2SiO)nSiR2(CH=CH2) wherein R is selected from the group consisting of monovalent hydrocarbon radicals and substituted monovalent hydrocarbon radicals, in which at least 50 mole percent of the R radicals are methyl radicals, m and n each repre-sent an integer such that the amount of diphenylsiloxane units in the diorganopolysiloxane is within the range of 3 to 30% of the total amount of nonterminal siloxane units and such that the sum results in the diorgano-polysiloxanes (1) having an mkp value of from 300 to 800 as determined by a Brabender Plastograph at 25°C and at 60 revolutions per minute.

4. The composition of Claim 1 wherein the nonterminal diphenyl-siloxane units are present in the dlorganopolysiloxanes in an amount of from 5 to 20 percent.

5. The composition of claim 1 wherein at least 70 mole percent of the organic radicals on the remaining siloxane units of the diorgano-polysiloxanes (1) are methyl radicals.

6. The composition of claim 1 wherein all nonterminal siloxane units in the diorganopolysiloxane are free of vinyl group .

7. The composition as claimed in claim 1 wherein all nonterminal siloxane units in the diorganopolysiloxane are free of aliphatic unsatura-tion.

8. The composition of claim 1 wherein the organohydrogenopoly-siloxanes (2) have the general formula wherein R' is selected from the group consisting of hydrogen, lower alkyl radicals and aryl radicals, in which the amount of silicon-bonded hydrogen atoms ranges from 0.10 to 1.66 percent by weight, except that only one hydrogen atom is bonded to any one silicon atom and p is a number of from 20 to 500.

9. The composition of claim 8 wherein R' is selected from the group consisting of hydrogen, methyl, ethyl or phenyl.

10. The composition of claim 8 wherein one said R' is hydrogen, and the other said R' is selected from methyl, ethyl or phenyl.

11. The composition of claim 8 wherein all hydrogen siloxane units in the organohydrogen polysiloxane are methylhydrogenosiloxane units.

12. The composition of claims 9, 10 or 11 wherein p denotes an integer from 20 to 100.

13. The composition of Claim 1 wherein the mole ratio of the siloxane units having one Si-bonded hydrocarbon radical to the siloxane units having two Si-bonded hydrocarbon radicals in the organohydrogenopoly-siloxanes (2) is from 10:0 to 1:10.

14. The composition of Claim 1 wherein the organohydrogenopoly-siloxanes (2) are present in an amount of from 1 to 20 percent by weight based on the weight of the diorganopolysiloxanes (1).

l5. The composition of Claim 14 wherein the weight ratio is 4 -8%.

16. The composition of Claim 1 wherein the catalyst (3) is platinum, a platinum compound or a platinum complex.

17. The composition of Claim 16 wherein the catalyst is a plati-num-ketone complex.

18. The composition of Claim 16 wherein the catalyst (3) is pre-sent in an amount of from 0.001 to 0.1 percent by weight of elemental platinum based on the weight of the diorganopolysiloxanes (l).

19. The composition of Claim 18 wherein the catalyst is present in an amount of 0.01 to 0.5%.

20. The composition of Claim 1 wherein the organic solvent is anhydrous or substantially anhydrous.

21, The composition of Claim 20 wherein the organic solvent is an alkane mixture having a boiling range of 80 to 110°C at 760 tor.

22. The composition of Claims 20 or 21 wherein the organic solvent is present in an amount of from 200 to 5000 percent by weight based on the weight of the diorganopolysiloxanes (1).

23. The composition of Claim 1 including at least one of pyro-genic silica and an agent to prevent or retard crosslinking at room temperature.

24. The composition of Claim 23 wherein said agent is benztrio-zole, a dialkylformamde. an alkylltriourees or methyl ethyl ketone.

25. A process for preparing a composition for the preparation of a non-stick coating which comprises: dissolving, in an organic solvent, vinylsiloxy-terminated diorganopolysiloxanes (1) in which 3 to 30 mole percent of the nonterminal siloxane units are diphenylsiloxane units and at least 50 mole percent of the remaining organic radicals on the siloxane units are methyl radicals, said diorganopolysiloxanes (1) having a plasticity within the range of from 300 to 800 mkp as determined in Brabender Plastograph at 25°C and at 60 revolutions per minute and a cata-lyst (3) capable of promoting the addition of Si-bonded hydrogen atoms to vinyl groups to form a solution; and thereafter adding organohydrogenopoly-siloxanes (2) having at least 3 Si-bonded hydrogen atoms per molecule to the solution.

26. The process of Claim 25 wherein the diorganopolysiloxanes (1) have an mkp value of from 360 to 730 as determined by a Brabender Plasto-graph at 25°C and at 60 revolutions per minute.

27. The process of Claim 25 wherein the diorganopolysiloxanes (1) have the general formula (CH2=CH)R2SiO (C6H5)2SiO m (R2SiO)nSiR2(CH=CH2) wherein R is selected from the group consisting of monovalent hydrocarbon radicals and substituted monovalent hydrocarbon radicals, in which at least 50 mole percent of the R radicals are methyl radicals, m and n each represent an integer such that the amount of diphenylsiloxane units in the diorganopolysiloxane is within the range of 3 to 30% of the total amount of nonterminal siloxane units and such that the sum results in the diorgano-polysiloxanes (1) having an mkp value of from 300 to 800 as determined by a Brabender Plastograph at 25°C and at 60 revolutions per minute.

28. The process of Claim 25 wherein the nonterminal diphenyl-siloxane units are present in the diorganopolysiloxanes in an amount of from 5 to 20 mole percent.

29. The process of Claim 25 wherein at least 70 mole percent of the organic radicals on the remaining siloxane units of the diorganopoly-siloxanes (1) are methyl radicals.

30. The process of Claim 25 wherein the organohydrogenopolysilox-anes (2) are present in an amount of from l to 20 percent by weight based on the weight of the diorganopolysiloxanes (l).

31. The process of Claim 25 wherein the catalyst (3) contains platinum, a platinum compound or a platinum complex.

32. The process of Claim 25 wherein the organic solvent is present in an amount of from 200 to 5000 percent by weight based on the weight of the diorganopolysiloxanes (1).

33. A process for the manufacture of a non-stick coating on a substrate which comprises: applying to the substrate a coating composition containing (1) vinylsiloxy-terminated diorganopolysiloxanes in which 3 to 30 mole percent of the nonterminal siloxane units are diphenylsiloxane units and at least 50 mole percent of the remaining organic radicals on the siloxane units are methyl radicals, said diorganopolysiloxanes (1) having a plasticity within the range of from 300 to 800 mkp as determined in a Brabender Plastograph at 25°C and at 60 revolutions per minute; (2) organo-hydrogenopolysiloxanes having at least 3 Si-bonded hydrogen atoms per mole-cule; (3) a catalyst which promotes the addition of Si-bonded hydrogen atoms to the vinyl groups and (4) an inert organic solvent; and thereafter heating the coated substrate to a temperature of at least 80°C.

34. The process of Claim 33 wherein the surface of the substrate is absorbent, and the composition is applied in such an amount that the total amount of diorganopolysiloxane and organohydrogenopolysiloxane ap-plied is within the range of from 0.1 to 0,5 g/m2.

35. A process as claimed in Claim 33 wherein the surface of the substrate is absorbent and the composition is applied in such an amount that the total amount of diorganopolysiloxane and organohydrogenopolysilox-ane applied is within the range of from 1 to 5 g/m2.

36. The process of Claim 33 wherein the coated substrate is heated to a temperature up to 250°C.

37. The process of Claim 33 wherein the substrate is first treated with a pore-sealing compound.

38. The process of Claim 33 wherein the pore-sealing compound is polyvinyl alcohol.

39. The process of Claim 33 wherein the substrate is paper.

40. The substrate treated in accordance with the process of Claim 33.