Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
  • B41N—PRINTING PLATES OR FOILS; MATERIALS FOR SURFACES USED IN PRINTING MACHINES FOR PRINTING, INKING, DAMPING, OR THE LIKE; PREPARING SUCH SURFACES FOR USE AND CONSERVING THEM
  • B41N7/00—Shells for rollers of printing machines
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
  • B41F—PRINTING MACHINES OR PRESSES
  • B41F13/00—Common details of rotary presses or machines
  • B41F13/08—Cylinders
  • B41F13/193—Transfer cylinders; Offset cylinders
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
  • B41F—PRINTING MACHINES OR PRESSES
  • B41F17/00—Printing apparatus or machines of special types or for particular purposes, not otherwise provided for
  • B41F17/001—Pad printing apparatus or machines
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
  • B41N—PRINTING PLATES OR FOILS; MATERIALS FOR SURFACES USED IN PRINTING MACHINES FOR PRINTING, INKING, DAMPING, OR THE LIKE; PREPARING SUCH SURFACES FOR USE AND CONSERVING THEM
  • B41N2207/00—Location or type of the layers in shells for rollers of printing machines
  • B41N2207/02—Top layers
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
  • B41N—PRINTING PLATES OR FOILS; MATERIALS FOR SURFACES USED IN PRINTING MACHINES FOR PRINTING, INKING, DAMPING, OR THE LIKE; PREPARING SUCH SURFACES FOR USE AND CONSERVING THEM
  • B41N2207/00—Location or type of the layers in shells for rollers of printing machines
  • B41N2207/04—Intermediate layers
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
  • B41N—PRINTING PLATES OR FOILS; MATERIALS FOR SURFACES USED IN PRINTING MACHINES FOR PRINTING, INKING, DAMPING, OR THE LIKE; PREPARING SUCH SURFACES FOR USE AND CONSERVING THEM
  • B41N2207/00—Location or type of the layers in shells for rollers of printing machines
  • B41N2207/14—Location or type of the layers in shells for rollers of printing machines characterised by macromolecular organic compounds
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
  • F16C—SHAFTS; FLEXIBLE SHAFTS; ELEMENTS OR CRANKSHAFT MECHANISMS; ROTARY BODIES OTHER THAN GEARING ELEMENTS; BEARINGS
  • F16C13/00—Rolls, drums, discs, or the like; Bearings or mountings therefor

Definitions

• the present invention relates to novel compressible rolls useful for printing or pad printing and comprising a flexible portion of silicone foam.
• silicon foam or "silicone foam” refers to a polyorganosiloxane composition in the form of foam. Silicone foams are well known in the art and their preparations are described in a number of patents.
• US-A-3467009 discloses the manufacture of a flexible printing roll comprising a roll core, an intermediate layer of polyurethane foam, natural rubber or neoprene, and at least one prepared compressible outer layer from fibrous materials impregnated with elastomeric substances.
• EP-A-577920 discloses a compressible roll comprising a roll core, an intermediate layer of nitrile / polyvinyl chloride foam and an outer layer comprising a polyurethane seal.
• a problem encountered in the manufacture of these rolls relates to manufacturing defects related to an uncontrolled foaming of the foam intermediate layer generating defects related to the presence of bubbles of too large sizes and whose distribution within the material foamed is heterogeneous thus impacting on the mechanical properties of the roll.
• the foams used in the prior art no longer comply with the constraints imposed by new industrial manufacturing processes.
• a field such as the manufacture of rolls for pad printing
• centrifugation techniques which impose new foaming constraints, thus affecting the size and the distribution of the bubble size of the foamed material, a key element of roll for printing.
• Pad printing is an indirect printing process.
• the pattern to be printed is previously etched on a support, the plate is then fixed on a tampograph machine; then the ink is deposited in the etched portions to transfer the pattern onto the object to be printed by means of a silicone foam pad or roll.
• the silicone foam pad or roll be small sized bubbles and that the bubble size distribution within the material be homogeneous so that the The ink can be uniformly deposited and transferred onto the receiving layer supported by the silicone foam layer while allowing accurate reproduction of the etching.
• small bubbles bubbles whose width (or diameter) is less than or equal to about 1 mm, with “medium size bubbles” the width (or diameter) is between 1 and 1.5 mm , whereas for “big bubbles” the width (or diameter) is greater than 1, 5 mm.
• the need to obtain foams having small bubbles and a uniform distribution of bubble sizes is particularly sought after for this application.
• the preparation of the foamed portion of the rolls for flexible printing is therefore the subject of particular attention in the field of printing.
• a first technique implements a condensation reaction with release of volatile by-products. This is particularly the case for systems using the SiH-SiOH type condensation reaction which releases hydrogen which then acts as a blowing agent.
• French Patent No. FR-A-2,589,872 discloses a silicone foam precursor composition comprising an organosilicon polymer comprising siloxane units having silicon-bonded hydroxyl groups, an organosilicon polymer comprising siloxane units having silicon-bonded hydrogen atoms, a catalyst, for example a tin compound , and a finely divided filler comprising silica that has been treated to become hydrophobic.
• compositions cure by a polycondensation reaction and, although satisfactory in many respects, the tin-catalyzed compositions described in French Patent No. FR-A-2,589,872 are considered unsatisfactory because of their use of a tin catalyst which can exert certain undesirable toxic effects.
• compositions may further comprise a polydiorganosiloxane carrying silicon-bonded vinyl groups which simultaneously crosslink by polyaddition reactions with polydiorganosiloxanes bearing silicon-bonded hydrogen atoms thereby participating in the construction of the silicone foam network.
• silicone foams are prepared from a composition comprising water, a polydiorganosiloxane carrying silicon-bonded vinyl groups, a polydiorganosiloxane containing hydrogen atoms bonded to silicon and carried by patterns in the chain and not only at the end of the chain to be able to play a role of crosslinking.
• the water reacts with the hydride functional polysiloxane thus producing hydrogen gas and a silanol.
• silanol then reacts with the hydride-functional polydiorganosiloxane by a condensation reaction thus generating a second molecule of hydrogen gas while another polydiorganosiloxane carrying silicon-bonded vinyl groups will simultaneously react with one addition reaction with another.
• polydiorganosiloxane hydride function thereby participating in the construction of the network of silicone foam.
• the main contribution made by this technique is that hydrogen gas is produced without the addition of silanol and with the addition of a small amount of water.
• silicone foams are prepared from compositions comprising a polydiorganosiloxane, a resin, a platinum-based catalyst, an organohydrogensiloxane, a polyorganosiloxane carrying hydroxyl groups on the end-chain units, a filler and an organic alcohol.
• silanol as a pore-forming agent source tend to give foams with densities too high for many applications, for example those intended for the printing industry.
• foams of medium density are obtained, this is most often at the expense of mechanical properties (tensile strength, tear resistance, ).
• azo-type derivatives for example azodicarbonamide, which will make it possible to release nitrogen, carbon dioxide and ammonia.
• This type of blowing agent despite the fact that it is widely used for other materials, poses serious problems of toxicity (hydrazine release),
• phase change gas liquid
• compositions prepared in the examples are all greater than 190,000 mPa.s.
• the problematic considered here can therefore be summed up as the search for a technical compromise between specifications, a priori antinomic, for the preparation of a precursor composition of silicone foam having a low viscosity, that is to say less than 30. 000 mPa.s and precursor of a silicone foam which has a low density, that is to say less than 0.25 g / cm 3 , good mechanical properties, bubble sizes less than or equal to 1 mm and a uniform distribution of bubble sizes within the foamed material.
• the desired foams should no longer present problems related to the intervention of new techniques, such as centrifugation, in industrial manufacturing processes of the printing rollers.
• the present invention therefore aims to provide a new compressible roller useful for printing whose foamed portion is prepared from an organopolysiloxane composition of low viscosity, that is to say less than 30,000 mPa.s, which, after crosslinking and / or hardening, makes it possible to generate a low density silicone foam, that is to say less than 0.25 g / cm 3 , while obtaining silicone foam having good mechanical properties, bubble sizes whose width or diameter is less than or equal to about 1 mm and a uniform distribution of bubble sizes within the material.
• the present invention therefore aims to provide a new compressible roll (1) comprising:
• an outer layer (4) consisting of a silicone elastomer and covering said intermediate layer (3)
• said roll being characterized in that said an intermediate layer (3) of silicone foam is prepared by cross-linking and / or curing an organopolysiloxane composition X comprising:
• At least one polyorganosiloxane A having a viscosity of between 10 and 300,000 mPa.s and having, per molecule, at least two silicon-bonded C 2 -C 6 alkenyl groups,
• At least one polyorganosiloxane B having a viscosity of between 1 and 5000 mPa.s and having, per molecule, at least two ⁇ SiH units and preferably at least three SiH units,
• porogenic agent D which is water or an aqueous emulsion
• the viscosity of said organopolysiloxane composition X is less than 30,000 mPa.s and preferably less than 25,000 mPa.s.
• a foaming composition according to the invention comprising, as a porogenic agent, water or an aqueous emulsion, makes it possible to prepare rolls for printing. having less defect related to the appearance of large bubbles in its foamed portion thus improving the industrial weakness of the manufacturing processes of these rolls.
• This new compressible roller has the advantage of being composed of an intermediate layer (3) made of silicone foam having a density of less than 0.25 g / cm 3 , having good mechanical properties, bubble sizes of which the width or diameter is less than or equal to about 1 mm and whose bubble size distribution within the material is homogeneous.
• the organopolysiloxane composition X used for the preparation of this intermediate layer makes it possible to avoid the problems related to the new constraints encountered in the recent processes for manufacturing these printing rolls, such as for example those related to the use of the centrifugation techniques. Indeed, during the foaming step to prepare this layer of the roll, the organopolysiloxane composition X no longer generates defects related to the appearance of large bubbles in certain areas of this layer.
• the pore-forming agent D according to the invention is water or an aqueous emulsion. It can be introduced in the form of a direct silicone oil-in-water emulsion or a water-in-oil reverse silicone emulsion comprising a silicone oily continuous phase, an aqueous phase and a stabilizer.
• Direct emulsions can be obtained by emulsification processes well known to those skilled in the art, the process consists in emulsifying in an aqueous phase containing a stabilizer, for example a surfactant, a mixture of constituents. An oil-in-water emulsion is then obtained. Then the missing constituents can be added, either directly to the emulsion (case of the water-soluble constituents), or later in the form of emulsion (case of the constituents soluble in the silicone phase).
• the particle size of the emulsion obtained can be adjusted by conventional methods known to those skilled in the art, in particular by continuing the stirring in the reactor for a suitable period.
• Inverse silicone emulsions consist of water droplets in a continuous silicone oil phase. They can be obtained by emulsification processes well known to those skilled in the art and which involve the mixing of a aqueous phase and an oily phase without or with grinding, ie under high shear.
• the stabilizer is preferably selected from the group consisting of:
• nonionic, anionic, cationic or even zwitterionic surfactants are nonionic, anionic, cationic or even zwitterionic surfactants
• solid particles preferably silica particles optionally in combination with at least one co-stabilizer, preferably selected from nonionic, anionic, cationic or even zwitterionic surfactants;
• HLB HLB
• hydrophilic lipophilic balance refers to the ratio of the hydrophilicity of the polar groups of the surfactant molecules to the hydrophobicity of their lipophilic part.
• HLB values are reported in various basic manuals such as the "Handbook of Pharmaceutical Excipients, The Pharmaceutical Press, London, 1994".
• the water / silicone emulsions can also be stabilized via silicone polyethers (Surfactant Silicone - Surfactant Science V86 series Ed Randal M. Hill (1999).
• the organopolysiloxane composition X is prepared from a two-component system P characterized by:
• organopolysiloxane composition X in that it is in two distinct parts P1 and P2 intended to be mixed to form said organopolysiloxane composition X and comprising said constituents A, B, C, D, E, F, G and H as defined above; , and
• one of the portions P1 or P2 comprises the catalyst C and the porogen D and does not comprise the polyorganosiloxane B.
• the outer layer (4) consisting of a silicone elastomer is prepared by crosslinking and / or curing an organopolysiloxane composition X 'comprising:
• At least one polyorganosiloxane A ' having, per molecule, at least two silicon-bonded C 2 -C 6 alkenyl groups
• At least one polyorganosiloxane B ' having, per molecule, at least two ⁇ SiH units and preferably at least three SiH units,
• a catalytically effective amount of at least one catalyst C which is a compound derived from at least one metal belonging to the platinum group; optionally at least one diorganopolysiloxane E oil blocked at each end of its chain by a triorganosiloxy unit whose organic radicals bonded to the silicon atoms, are chosen from alkyl radicals having from 1 to 8 inclusive carbon atoms, such as methyl groups, ethyl, propyl and 3,3,3-trifluoropropyl, cycloalkyl groups such as cyclohexyl, cycloheptyl, cyclooctyl and aryl groups such as xylyl, tolyl and phenyl,
• the roll core (2) is made of metal.
• the roll core (2) is cylindrical, rigid, hollow and comprises an orifice network in which the diameter of each orifice is between 0.1 and 50 mm and preferably between 1 and 10mm.
• this roll core structure makes it possible to introduce the composition into the hollow core and, when a centrifugal force is applied, to pass the organopolysiloxane compositions X or X 'through the orifices so as to form, after crosslinking, the intermediate layer (3) or the outer layer (4).
• the thickness of the intermediate layer (3) is between 1 and 100 mm, preferably between 1 and 50 mm and even more preferably between 5 and 20 mm.
• the thickness of the outer layer (4) consisting of a silicone elastomer is between 0.1 and 10 mm and preferably between 0.5 and 5 mm.
• the polyorganosiloxanes A and A ', each having, per molecule, at least two alkenyl groups, C 2 -C 6 bonded to silicon, and having a viscosity of between 10 and 300 000 mPa.s, can be formed:
• Y is a C 2 -C 6 alkenyl, preferably vinyl
• R is a monovalent hydrocarbon group having no adverse effect on the activity of the catalyst and is generally selected from alkyl groups having from 1 to
• polyorganosiloxanes A and A ' are the following compounds: dimethylvinylsilyl-terminated dimethylpolysiloxanes, (methylvinyl) (dimethyl) polysiloxane copolymers with trimethylsilyl ends, (methylvinyl) (dimethyl) polysiloxane copolymers with dimethylvinylsilyl ends.
• the polyorganosiloxane A contains terminal vinyl siloxy units.
• polyorganosiloxane B or polyorganosiloxane B ' having, per molecule, at least two silicon-bonded hydrogen atoms and preferably at least three SiH units and having a viscosity of between 1 and 5000 mPa.s are those comprising :
• X is a monovalent hydrocarbon group having no adverse effect on the activity of the catalyst and is generally selected from alkyl groups having 1 to 8 carbon atoms inclusive such as methyl, ethyl, propyl and 3, 3,3-trifluoropropyl, cycloalkyl groups such as cyclohexyl, cycloheptyl, cyclooctyl and aryl groups such as xylyl, tolyl and phenyl,
• Suitable polyorganosiloxanes B or B ' are polymethylhydrogensiloxanes.
• Catalyst C composed of at least one metal belonging to the platinum group is also well known.
• the platinum group metals are those known as platinoids, which includes, in addition to platinum, ruthenium, rhodium, palladium, osmium and iridium.
• the platinum and rhodium compounds are preferably used.
• platinum complexes and an organic product described in US-A-3 159 601, US-A-3 159 602, US-A-3,220,972 and European patents can be used.
• the most preferred catalyst is platinum.
• the preference is for the Karstedt solution or complex, as described in US-A-3,775,452.
• Component E is for example a linear polydimethylsiloxane, non-functionalized, that is to say to repeating units of formula (CH 3) 2 Si02 / 2 and having at its two ends (CH 3) 3 SiO / 2.
• mineral filler F include reinforcing and filling charges. However, the nature and amount of the charge will be determined so as to obtain, after mixing all the components, a viscosity of the composition of less than 30,000 mPa.s. Thus some charges will be discarded because of too much viscosity.
• These fillers can be in the form of very finely divided products whose mean particle diameter is less than 0.1 m. These fillers include, in particular, fumed silicas and precipitated silicas; their specific surface is generally greater than 10 m 2 / g and is most often in the range 20-300 m g. These fillers may also be in the form of more coarsely divided products having an average particle diameter greater than 0.1 m.
• fillers examples include, in particular, the crushed quartz, diatomaceous earth silicas, calcined clay, rutile-type titanium oxide, iron, zinc, chromium, zirconium, magnesium oxides, various forms of alumina (hydrated or not) , boron nitride, lithopone, barium metaborate; their specific surface area is generally less than 30 m 2 / g. Fillers may have been surface-modified by treatment with the various organosilicon compounds usually employed for this purpose.
• these organosilicon compounds may be organochlorosilanes, diorganocyclopolysiloxanes, hexaorganodisiloxanes, hexaorganodisilazanes or diorganocyclopolysilazanes (French Patents FR-A-1 126 884, FR-A-1 136 885, FR-A-1 236 505, English Patent GB-A-1,024,234).
• the treated fillers contain, in most cases, from 3 to 30% of their weight of organosilicic compounds.
• the charges can be treated before or after their incorporation into the formula.
• the charges may consist of a mixture of several types of charges of different particle sizes.
• metal filler F may make it possible to improve the resistance to combustion of the foams.
• metallic fillers F for example:
• a platinum mixture in the form of a complex or a platinum compound and a FeO / Fe 2 O 3 mixture
• a platinum mixture in the form of a complex or a platinum compound and an oxide and / or cerium-IV hydroxide
• a platinum mixture in the form of a complex or a platinum compound and a constituent consisting of a combination of the oxide and / or cerium-IV hydroxide with titanium oxide TiO 2 ;
• a platinum mixture with at least one rare-metal oxide in particular a platinum mixture with cerium-IV CeO 2 oxide as described in the applications
• titanium oxide for example the products marketed by Degussa under the appellation Aeroxide ®, for example the product "Aeroxide ® ⁇ 02 PF2", and
• additive G it is possible in particular to incorporate a catalyst inhibitor in order to retard the crosslinking. It is possible in particular to use organic amines, silazanes, organic oximes, diesters of dicarboxylic acids, acetylenic ketones and acetylenic alcohols (see, for example, FR-A-1,528,464, 2,372,874 and 2,704,553). .
• the inhibitor when one is used, may be employed in an amount of 0.0001 to 5 parts by weight, preferably 0.001 to 3 parts by weight, per 100 parts of polyorganosiloxane A.
• Phosphines, phosphites and phosphonites are also included inhibitors usable in the invention. Mention may in particular be made of the compounds of formula P (OR) 3 described in US Pat. No. 6,300,455. All these compounds are known to those skilled in the art and are commercially available. For example, the following compounds may be mentioned:
• R - R ' is a linear or branched alkyl radical, or a phenyl radical
• R " is a hydrogen atom or a linear or branched alkyl radical, or a phenyl radical, the radicals R ', R" and the carbon atom located at a of the triple bond may optionally form a ring;
• R 'and R " being at least 5, preferably from 9 to 20.
• acetylenic alcohols examples that may be mentioned include:
• diallyl maleate or derivatives of diallyl maleate are examples of diallyl maleate.
• inhibitors are added in an amount by weight of between 1 and 50,000 ppm relative to the weight of the total silicone composition, especially between 10 and 10,000 ppm, preferably between 20 and 2000 ppm.
• Polyorganosiloxane resins H are oligomers or polymers
• branched organopolysiloxanes well known and commercially available. They are in the form of solutions, preferably siloxanes.
• oligomers or branched organopolysiloxane polymers include resins MQ, resins "MDQ”, resins "TD” and resins "MDT", alkenyl functions that can be carried by siloxyl units M, D and / or T.
• the skilled person in the field of silicones commonly uses this nomenclature which represents the following siloxyl units:
• R3S1O1 / 2 M pattern
• RS1O32 T pattern
• R 2 Si0 22 D pattern
• Si0 4/2 Q pattern
• the polyorganosiloxane resins H that are particularly useful according to the invention are silicone resins with "Si-alkenyl” functions, that is to say resins with vinyl, allyl and / or hexenyl functional groups. According to a preferred embodiment of the invention, the resins
• Polyorganosiloxanes H are vinylated silicone resins.
• they comprise in their structures from 0.1 to 20% by weight of group (s) alkenyl (s).
• the alkenyl groups may be located on M, D or T siloxyl units.
• These resins may be prepared, for example, according to the process described in US Pat. No. 2,676,182. A certain number of these resins are available. in commerce, most often in the state of solutions.
• the polyorganosiloxane resin H comprises:
• the symbols Z which may be identical or different, each represent a non-hydrolysable monovalent hydrocarbon group, which has no adverse effect on the activity of the optionally halogenated catalyst and is preferably chosen from alkyl groups as well as from aryl groups, and
• a is 1 or 2, preferably 1, b is 0, 1 or 2 and the sum a + b is 1, 2 or 3,
• the polyorganosiloxane resin H is a resin which comprises Si-Vi units (with "Vi" meaning a vynyl group) and is chosen from the group consisting of the following silicone resins:
• Vl siloxyl unit of formula (R2) (vinyl) SiOi / 2
• the groups R which are identical or different, are monovalent hydrocarbon-based groups 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 that xylyl, tolyl and phenyl
• the polyorganosiloxane resin H is added to the composition according to the invention in the form of a mixture in at least one polyorganosiloxane oil.
• the vinylated polyorganosiloxane resin H is present in the silicone elastomer composition before crosslinking up to 25%, preferably up to 20% and even more preferentially between 1 and 20% by weight. weight relative to the total weight of the composition according to the invention.
• the vinyl polyorganosiloxanes A or A ', the polyorganosiloxane resins H and the polyorganosiloxanes with hydride function B or B', are in such quantities that a molar ratio between the function ⁇ SiH and the functions ⁇ SiVi of between 0.5 is ensured. and 10 and preferably between 1 and 6. According to a particular embodiment of the invention, the composition
• Organopolysiloxane X comprises:
• Another subject of the invention relates to a method of manufacturing a compressible roller (1) according to the invention and as defined above, useful for pad printing, said method comprising the steps of:
• the method according to the invention comprises the steps of:
• Static and dynamic mixers are well known and commercially available.
• Another object of the invention relates to a compressible roll (1) obtainable by the methods according to the invention and described above.
• the last object of the invention relates to a use of a compressible roll (1) according to the invention and as described above for printing or pad printing.
• the attached single figure shows a compressible roll (1) comprising:
• an outer layer (4) consisting of a silicone elastomer and covering said intermediate layer (3).
• All the viscosities referred to herein correspond to a dynamic viscosity quantity which is measured, in a manner known per se, at 25.degree.
• the viscosities are measured using a BROOKFIELD viscometer according to the indications of standard AFNOR NFT 76 106 of May 1982.
• These viscosities correspond to a dynamic viscosity quantity at 25 ° C called "Newtonian", that is to say ie the dynamic viscosity which is measured, in a manner known per se, at a sufficiently low shear rate gradient so that the measured viscosity is independent of the speed gradient.
• the present invention will now be described in more detail using embodiments given by way of non-limiting example.
• a vinylated polyorganosiloxane resin comprising siloxyl units M, D V
• and Q (or "MD" Q ") with Vi vinyl group, M: (CH 3) 3 SiO / 2, Q: S1O4 / 2, D vi:
• b2_ polydimethylsiloxane blocked with (CH 3 ) 2 ViSiOi / 2 units and whose viscosity is 10,000 mPa.s at 25 ° C.
• - cl Silica combustion treated with a silicone oil having a specific surface of 30m 2 / g (BET), sold under the trade name AEROSIL ® RY50.
• - C2 Diatomaceous earth marketed under the trade name CLARCEL ® FD marketed by the company CECA.
• polydimethylsiloxane oil terminated at each of the chain ends by a (CH 3) 3 SiO / 2 having a viscosity of 1000 mPa.s at 25 ° C
• Table 1 below describes compositions tested. Table 1: Compositions - Parts by weight.
• organopolysiloxane compositions X precursors of foam which will be tested as follows:
• a cylindrical mold (length 132 cm, outer diameter 46 cm) of stainless steel is mounted on a cylindrical, rigid, hollow core of roll (2) and comprising an orifice network whose diameter of each orifice is approximately 4 mm so that the main axis is horizontal;
• an organopolysiloxane composition X ' is introduced inside the cavity of the roll core (2) which is obtained by mixing parts A and B of a polyaddition RTV-2 (sold under the name Rhodorsil or BlueSil for pad printing application by Bluestar Silicones France) using a static mixer, c) centrifugation is rotated around the horizontal main axis of the cylindrical mold so that the organopolysiloxane composition X 'passes through the openings of the core roll (2) and forms the outer layer (4) uncrosslinked on the inner wall of the cylindrical mold,
• the mold is heated at a temperature of 40 ° C. for 1 to 4 minutes so that the layer formed cross-links,
• the organopolysiloxane compositions X precursors of foam and described above are introduced inside the cavity of the roll core (2) by means of a dynamic mixer (invention, preparation route 1) or a mixer static (comparative route of preparation 2).
• Example 1 Comparative 1, butanol foaming agent
• R / R means the breaking strength, in MPa according to the AFNOR NF T 46002 standard
• the abbreviation hardness DS00 means Shore 00 hardness
• a / R means the elongation at break in% according to the preceding standard
• R / d tear strength in N / mm

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