Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B44—DECORATIVE ARTS
  • B44D—PAINTING OR ARTISTIC DRAWING, NOT OTHERWISE PROVIDED FOR; PRESERVING PAINTINGS; SURFACE TREATMENT TO OBTAIN SPECIAL ARTISTIC SURFACE EFFECTS OR FINISHES
  • B44D7/00—Preserving paintings, e.g. by varnishing

Definitions

• the present invention provides a system utilizing silicone compositions for restoring and preserving works of art. Both the reverse and the face of a painting can be restored by utilizing reinforcing materials as well as silicone release coatings and pressure sensitive adhesives.
• a current method of restoration of deteriorated canvas and loosened flaking paint is to force beeswax into the art work with a hot flat iron.
• the use of heat and pressure distorts the painting and flattens the original perspective, thereby resulting in the board-like effect discussed above.
• Some paintings that have been restored in this manner have thereafter been subjected to heat when they are on display, causing the beeswax to flow and puddles and drips to form on and below the painting.
• Silicones are man made materials in which organic and inorganic substances are chemically combined.
• the element silicon is present in sufficient amount to affect the properties of the material and provide desirable characteristics unavailable from organic materials. Silicones offer outstanding resistance to heat, cold, chemicals and weathering.
• Silicone Pressure Sensitive Adhesives are made from inert high molecular weight silicone gum and a silicone resin. The mixture of gum and resin is condensed under controlled conditions to develop cohesive strength in the adhesive. The finished product being highly condensed has very low reactivity and is chemically neutral. The condensed adhesive will go through further chemical cleavage only through the use of a very strong catalyst and or high temperature (300-350F) in the presence of a peroxide.
• silicone pressure sensitive adhesives When applied from a high solids solution the gelatinous property of silicone pressure sensitive adhesives prevents migration of the adhesive into porous materials, e. g. , glass cloth, canvas teflon coated fabric. To obtain penetration it is necessary to thin the adhesive to a low solids concentration and viscosity with an aromatic solvent. Thinned adhesives are used to reinforce fabrics and for heat and pressure laminating.
• Silicone adhesives are resistant to weather, radiation, bacteria, fungi and time. They do not become brittle at temperatures of plus 500 F. In a non-cured cross-linked state the adhesive can always be resolubilized with aromatic solvents or softened (swelled) with aliphatic solvents. When the solvent is removed the adhesive will return to its original form. When cross-linked with a catalyst the adhesive will not solubilize in solvents, but is affected by swelling and softening. When the solvent is evaporated from the cured adhesive it also will regain its original adhesive properties.
• the ratio of gum and resin used allows for making silicone adhesives having a wide range of tackiness and physical properties.
• High gum content adhesives are very sticky and are used for making pressure sensitive masking and electrical insulation tapes.
• High resin content adhesives are non-sticky when the solvent is evaporated. They develop very high bond strength when applied from the solvent solution of when heat activated after solvent removal.
• Silicone pressure sensitive adhesives bond to both high energy and low energy surfaces, e.g., silicone rubber, etched teflon, polyester, kapton, glass cloth and silicone release coated paper. No heat or destructive mechanical methods are needed for restoring paintings with silicone adhesives.
• a tacky pressure sensitive adhesive is applied to the new reinforcing backing material by a transfer or direct deposition method. The adhesive is protected from dirt contamination with easy to remove silicone release coated paper until it is ready for use. It has been found that teflon coated glass fabric makes excellent backing material for strengthening of the canvas.
• An electrostatic hot table which replaces the formerly used vacuum hot table is used as the means for leveling deformities in a painting. By utilizing electrostatics at low heat, e.g.
• the electrostatic table with a variably controlled electronic static attraction and heating function built in beneath the table top, provides the necessary source of low warmth for some treatments, . and a steady-state attraction function that evenly and firmly holds paintings, linings, or any other type of sheet material against the table top.
• adhesion of the painting to the silicone coated backing takes place. Because the silicone is "pressure sensitive" (adhering on contact), adhesion is achieved immediately without heat or destructive pressure.
• the lining remains removable at any future time upon application of solvent naphtha, allowing stress-free peel off. In this type of lining the painting remains completely pristine and uncontaminated by any foreign material.
• This silicone adhesive in a solvent solution is made to thoroughly penetrate the surface, front to back, by electrostatic deposition, a process which forces the adhesive through and around the paint particles and canvas fibers.
• electrostatic deposition a process which forces the adhesive through and around the paint particles and canvas fibers.
• Through electric charging of the silicone adhesive it can be applied over a wide area or to a specific repair area with ease. Excess silicone is removed with solvent after the paint particles have been flattened and reattached. The teflon or other reinforcing lining can then follow as usual.
• Tears and punctures in a canvas can be mended using a temporary silicone coated reinforcing tissue or fabric. Applied to a tear in a painting, it holds the edges together until it can be permanently joined. This temporary reinforcement can be left on canvases with no ill effects, then removed with naphtha after permanent repairs are made.
• the present invention provides processes for restoring works of art.
• the reverse side of a work of art can be restored and preserved by applying a pressure sensitive silicone adhesive coating to a substrate which is suitable for reinforcing the back of the work of art.
• a substrate can desirably be teflon coated glass fabric as well as any synthetic fabric having a life expectancy greater than the canvas backing or other surface of the work of art or painting to be restored.
• the silicone adhesive is coated on the reinforcing substrate, it is cured in place upon the substrate by well-known means.
• the adhesive coated reinforcing substrate can be laminated to the work of art by utilizing a moderate amount of non-destructive pressure which activates the pressure sensitive silicone adhesive properties of the coating composition. This can be accomplished through the use of a light roller or similar pressure applicator.
• An alternative process for restoring the reverse side of the work of art utilizes a transfer adhesive system.
• a first substrate which ordinarily may be any kind of non-porous film or hard surfaced paper, and preferably will be super-calendared kraft paper, is coated with an MQ resin modified solventless silicone release coating (later described as Release Coating B) which is capable of releasing an aggressive high-phenyl content silicone pressure sensitive adhesive which is also later described.
• Release Coating B is cured upon the first substrate by well-known means.
• the high-phenyl content silicone pressure sensitive adhesive is applied upon the release coating and is cured in place such that the first substrate now has two coatings upon it, namely, the silicone Release Coating B and the high-phenyl silicone adhesive.
• This doubly coated first substrate is then laminated to a second substrate, which is suitable for reinforcing and preserving the work of art.
• This second substrate is the same or similar to those reinforcing substrates described above such as teflon coated glass fabric and others.
• a transfer adhesive system suitable for reinforcing the reverse side of a work of art at any desired future point in time. The restoration takes place merely by separating the first substrate with its Release Coating B from the second substrate which retains the high-phenyl silicone pressure sensitive adhesive, since the aggressive adhesive is much more adherent to the second substrate than it is to the release coating to which it was in contact.
• the first substrate, which is coated with the silicone Release Coating B can be selected from the above-described hard surfaced papers as well as the teflon and polyester films, and plastic crepe, etc.
• the obverse side of a work of art that is to say the artistic or painting side
• the obverse side of a work of art can be restored and preserved by first pre-treating the obverse side with any means which compensate for deterioration suffered by the work of art to date.
• This deterioration would ordinarily take the form of chipped, flaked, cracked, cupped or crazed paint or particles of paint and the pre-treating can be accomplished by any of several means well-known in the art restoration such as utilizing heat to soften the chips and flakes and moderate stretching of the canvas, or electrostatic forces applied to the surface of a painting and combinations thereof.
• a zero-tack silicone adhesive (which is later described as Silicone PSA-B) to the pre-treated obverse side or any portion thereof.
• the silicone adhesive can be applied directly or it may be carried by an effective amount of non-destructive solvent.
• the zero-tack silicone adhesive is brought into intimate content with the chipped, flaked and cupped particles of paint and this may be accomplished by utilizing a light brush or squeegee or electrostatic forces or combinations thereof, at which time the adhesive completely surrounds the particles of paint and fixes them to the canvas. Once the adhesive dries the painting is in a restored state. If a solvent is used with the zero-tack adhesive a further step in the process, of course, would be the removal of any excess solvent.
• zero-tack adhesive it is meant that a particular silicone adhesive utilized in this aspect of the invention does not show any adhesive properties at room temperature after it has been air dried. This offers the advantage of allowing the painting to remain clean by not picking up dirt and other particles, which would mar and detract from the restored painting.
• the silicone materials which are particularly- well-suited for the art restoration processes of the present invention are any of various chemical compositions which characteristically have a plurality silicon to oxygen bonds in a chain or lattice framework. Silicon has a valence of four but when there are less than four oxygen atoms attached to the silicon, the remaining valences are ordinarily filled with substituted or unsubstituted organo groups. Depending upon the particular combination of silicon, oxygen and organo substituents, a wide range of silicone fluids and resins can be produced, each of which has different desirable properties. Thus, there are an extremely large number of silicone compositions, some of which are available from several manufacturers and some of which are proprietary with a single manufacturer.
• a release coating is a silicone composition which can be coated on a substrate (ordinarily paper) and when cured thereon it will adhere vigorously. However, the exposed surface of the cured release coating can be coated or contacted with an adhesive or an adhesive coated second substrate yet will not aggressively adhere thereto. Thus, the release coated first substrate can be peeled away from the adhesive coated second substrate, leaving the adhesive intact on the second substrate. By this means it would be an easy matter to laminate an adhesive coated reinforcing substrate to the back of a painting o.r other work of art.
• a silicone release coating is that described by Eckberg in U. S. Patent Application S. N. 40, 015 filed May 17,.1979, and which is hereby incorporated by reference.
• Eckberg's silicone release coating is basically a combination of (a) diorganopolysiloxane base polymer having up to approximately 20% by weight alkenyl or silanol functional groups and having a viscosity ranging from approximately 50 to approximately 100, 000 centipoise at 25 o C; (b) a polymethylhydrogen siloxane fluid cross-linking agent having up to approximately 100% by weight SiH groups and having a viscosity in the range of approximately 25 to approximately 1000 centipoise at 25 0 C; (c) an effective amount of precious metal catalyst for facilitating an addition cure hydrosilation reaction between said base polymer and said cross-linking agent; and (d) an amount of dialkyl carboxylic ester effective to inhibit the precious metal catalyzed hydrosilation cure reaction of said silicone composition at temperatures below the
• a more specific example of a silicone release coating which can be used in the present invention is one which contains (a) a vinyl chain-stopped polydimethyl-methylvinyl siloxane gum containing approximately 20% by weight vinyl groups and having a viscosity of approximately 100, 000 centipoise at 25 0 C; (b) a t r i-methyl chain-stopped polymethyl hydrogen siloxane cross-linking fluid having approximately 10 to 100% by weight SiH groups and a viscosity of approximately 25 to 1000 centipoise at 25 0 C; (c) approximately 10 to 500 ppm platinum in the form of a platinum complex catalyst; and (d) approximately 0.1% to 0.5% by weight diallyl maleate.
• This silicone release coating is representative of a number of such release coatings known in the art. It is available from the Silicone Products Division of the General Electric Company, and for the sale of convenience it will hereinafter be referred to as Release Coating A.
• This release coating can be modified in order to provide different properties.
• an MQ resin refers to a polysiloxane product having primarily monofunctional and quadri- or tetra-functional structural units.
• the MQ resin is obtained from condensed waterglass or sodium silicate and is made up of M units (R 3 SiO 1/2 ) and Q units (Si0 2 ) having an M to Q ratio of approximately 0.5 to 1.0 and preferably about 0.65.
• the R group denotes monovalent hydrocarbon radicals, especially lower alkyl groups like methyl.
• Release Coating A When Release Coating A is modified with approximately 2.0 to 10 parts by weight of the above-described MQ resin it becomes particularly effective for releasing a high-phenyl content silicone adhesive which will hereinafter be described.
• This MQ modified version of Release Coating A will be referred to as Release Coating B.
• silicone adhesives available today, many of which are useful with the process of the present invention, especially silicone pressure sensitive adhesives.
• a silicone pressure sensitive adhesive see U.S. Patent 3,929,704 - Horning, which is hereby incorporated by reference.
• Such adhesives can have various substituent ingredients in order to provide desirable properties for different application. It is well-known, for example, that many silicone products have excellent wide range temperature flexibilities.
• These adhesives will ordinarily contain a silicone resin, a silicone gum and a catalytic amount of curing agent.
• Various peroxides are well-known catalysts for these systems.
• plasticizers extending fillers and process aids.
• Silicone pressure sensitive adhesives are ordinarily made up of a high viscosity polydimethylsiloxane gum in combination with a triorgano-chain-stopped MQ silicone resin.
• 100 parts by weight of a silanol chain-stopped polydimethyl siloxane gum having a viscosity ranging from approximately 100, 000 to 100 million can be combined with approximately 50 to 200 parts by weight based on the gum of an MQ resin as hereinbelow described, to form the basis of a silicone pressure sensitive adhesive having a viscosity determined by the gum.
• the ratio of resin to gum will also determine the adhesive's ultimate tack, peel, adhesion and dryness properties.
• Any of several catalyst systems can be utilized, for example, the peroxides and amines. Especially useful are benzoyl peroxide and 2,4 dichloro benzoyl peroxide.
• a so-called high-phenyl content silicone pressure sensitive adhesive can be provided in accordance with the methods taught by O'Malley in U.S., Patent 4, 039, 707 which is hereby incorporated by reference.
• the expression "high-phenyl content” refers to the fact that these adhesives have, in addition to the polydimethyl siloxane gum described above, significant amounts of alkylaryl- polysiloxane gum.
• the adhesive may be obtained as the intercondensation product of a mixture of organopolysiloxane resin and at least one alkylaryl polysiloxane gum.
• a suitable high-phenyl content silicone pressure sensitive adhesive is the intercondensation product of a mixture containing an organopolysiloxane resin comprised of Si0 2 units and (CH 3 ) 3 SiO 1/2 units, and a silanol-stopped polysiloxane copolymer gum having a viscosity from about 200, 000 to 15, 000, 000 centipoise at 25 0 C wherein the gum is comprised of diphenylsiloxane and dimethylsiloxane units, there being up to approximately 75% silicon-phenyl linkages of the total silicon-organic linkages.
• Zero-tack refers to the property of the adhesive that allows it to become tack-free or non-sticky when it has dried. This is a useful property for treating the obverse or face side of a painting. Like many silicone PSA's, this adhesive is made from a base containing a mixture of dimethylpolysiloxane gum plus MQ silicone resin. However, in order to provide the tack-free properties there is an extraordinarily high MQ to gum ratio. For example, a 2 to 1 MQ to gum ratio will deliver satisfactory zero-tack properties.
• the adhesive can be applied by itself or may be carried by a solvent, and when it dries there remains a tack-free adhesive bond between a substrate such as a canvas and the adhered moieties, such as paint particles.
• a portion of super-calendared kraft paper had cured upon it a coating of a silicone Release Coating B which was modified with 5 parts by weight silicone MQ resin.
• a silicone Release Coating B which was modified with 5 parts by weight silicone MQ resin.
• Such a release coating is available from the General Electric Company.
• To this coated paper was applied a coating of a high-phenyl content silicone pressure sensitive adhesive having 75% phenyl-silicon linkages, which is also available from the General Electric Company.
• the exposed adhesive was then contacted with a teflon coated glass fabric, which is suitable for reinforcing the reverse side of a work of art. Since the bond to the teflon was stronger than to the release surface, when the kraft paper was removed the adhesive remained transferred upon the teflon coated glass fabric.
• the glass fabric was then laminated to the canvas backing of the work of art with the use of light roller pressure.
• Sample A was a high viscosity aggressive silicone adhesive having vinyl and phenyl gum constituents which is ordinarily useful for high temperature and electrical tape applications.
• Sample B was a silicone pressure sensitive adhesive made primarily from MQ resin and methyl gum, which was suitable for various tape applications and having moderate tack and cohesive and adhesive strengths. The adhesive also contained a small amount of rare earth octoate as a heat stabilizer. Both of these adhesives were coated and cured upon the teflon fabric whereupon they were laminated to the reverse side of works of art with moderate amounts of non-destructive pressure effective for initiating their pressure sensitive adhesive characteristics. Both samples were demonstrated to be suitable for reinforcing canvas backed paintings.
• the obverse side of a work of art was pre-treated with mild heat and moderate stretching in order to prepare the particles of flaked, chipped and cupped paint for re-attachment to the surface of the canvas.
• a zero-tack silicone adhesive having an MQ resin to methyl gum ratio of approximately 2 to 1 and which had been thinned with toluene to a concentration of approximately 20% solids was lightly squeegeed against the entire surface of the painting in order to bring the adhesive into intimate contact with the paint particles and the canvas substrate.
• a moderate electrostatic charge was applied to assist the contacting of the adhesive with the particles. The excess solvent was removed and the adhesive was allowed to dry, thereby forming a zero-tack adhesive bond between the paint particles and the canvas.

Landscapes

• Adhesives Or Adhesive Processes (AREA)
• Adhesive Tapes (AREA)

Applications Claiming Priority (2)

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Cited By (1)

Citations (1)

• 1981
  • 1981-01-08 EP EP81300080A patent/EP0033193A1/de not_active Withdrawn
  • 1981-01-22 NO NO810208A patent/NO810208L/no unknown

Patent Citations (1)

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