Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B32—LAYERED PRODUCTS
  • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
  • B32B9/00—Layered products comprising a layer of a particular substance not covered by groups B32B11/00 - B32B29/00
  • B32B9/04—Layered products comprising a layer of a particular substance not covered by groups B32B11/00 - B32B29/00 comprising such particular substance as the main or only constituent of a layer, which is next to another layer of the same or of a different material
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
  • C08F299/00—Macromolecular compounds obtained by interreacting polymers involving only carbon-to-carbon unsaturated bond reactions, in the absence of non-macromolecular monomers
  • C08F299/02—Macromolecular compounds obtained by interreacting polymers involving only carbon-to-carbon unsaturated bond reactions, in the absence of non-macromolecular monomers from unsaturated polycondensates
  • C08F299/026—Macromolecular compounds obtained by interreacting polymers involving only carbon-to-carbon unsaturated bond reactions, in the absence of non-macromolecular monomers from unsaturated polycondensates from the reaction products of polyepoxides and unsaturated monocarboxylic acids, their anhydrides, halogenides or esters with low molecular weight
  • C08F299/028—Macromolecular compounds obtained by interreacting polymers involving only carbon-to-carbon unsaturated bond reactions, in the absence of non-macromolecular monomers from unsaturated polycondensates from the reaction products of polyepoxides and unsaturated monocarboxylic acids, their anhydrides, halogenides or esters with low molecular weight photopolymerisable compositions
• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09D—COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
  • C09D201/00—Coating compositions based on unspecified macromolecular compounds

Definitions

• a label for instance, is normally comprised of a face stock which may range from paper to a plastic film such as polyester film or even metal; a release liner having a silicone release surface, and a pressure-sensitive adhesive layer, normally rubber or acrylic based in contact with the face stock and the silicone release surface.
• a silicone release may be applied to the face stock opposite the side to which the adhesive is applied.
• Conventional silicone release coatings are essentially
• U.S. Patent 4,288,479 to Brack is directed to release coatings which contain a waxy material of limited compatibility with a liquid monomer or prepolymer. Upo application to a film, the waxy material migrates to the surface. Radiation is applied to cure the polymer.
• the waxy material which include silicones are described as generally non-reactive in the polymerizable liquid but can contain reactive groups.
• Example 65 of the Brack patent there is described a release composition containing a silicone rubber which was a polydimethyl siloxane with some unsaturation. On radiation there was stated to be formed a surface releasable with respect to a removable adhesive. We have found that the composition is not functional for permanent pressure sensitives which differ from removable adhesives in that adhesive bond grows with time. As established here, the combination welded together. See Example 5 herein.
• the present invention is directed to novel formulations of substantially reduced silicone content which display excellent release properties.
• a substrate having bonded thereto a cured release coating having a silicone release surface for contact with a pressure-sensitive adhesive formed by coreaction of components of a coating composition of a silicone comprised of dimethyl siloxane polymers, preferably a reactive silicone and a resin preferably a reactive resin.
• the silicone is present in an amount of from about 1 to about 30 percent by weight of the coating composition and anchored to the coating so as to be substantially non-transferable to a pressure-sensitive adhesive.
• the silicone release surface is functional to release permanent and removable pressure-sensitive adhesive .
• Cure is preferably induced by the action of heat, actinic radiation and/or electron beam radiation, provided in a quantity sufficient to anchor the silicone to the resin whereby the silicone becomes substantially non-transferable to a pressure-sensitive adhesive.
• Ultraviolet and/or electron beam radiation is presently preferred.
• the silicones employed preferably have a molecular weight of at least about 2,000, preferably 10,000 or more.
• the products be formed by curing a coating comprised of from about 1 to about 30 percent by weight, preferably from about 5 to about 30, most preferably from about 5 to about 15 percent by weight, of a reactive silicone dispersed as a discontinuous phase in a reactive resin present in an amount of from about 99 to about 70 percent by weight, preferably from about 95 to about 70 percent by weight, more preferably from about 95 to about 85 percent by weight, of the combination of the reactive silicone and reactive resin.
• the reactive resin contains from about 50 to 100 percent by weight reactive oligomer and from about 50 to 0 percent by weight reactive monomer based as the total weight of reactive oligomer and reactive monomer. The reactive monomer is used to control viscosity prior to cure.
• the dispersion preferably has a viscosity of from about 300 to about 10,000 cps.
• photoinitiators colorants and the like.
• the invention enables tailoring of the silicone release surface to the product.
• Useful products will have TLMI (Tape and Label Manufacturers Institute) peel under Keil conditions of no greater than about 400 N/M.
• the TLMI peel should be no greater than about 400 N/M, more typically 100 to 200 N/M.
• tags and labels a "high release specification has a peel up to about 60 to about 100 N/M; a "medium” release has a TLMI peel of about 20 to about 50 N/M; and a "low release” has a TLMI peel of less than about 20. Again all peel values are reported for Keil conditions, namely after aging at a load of 0.25 psi for 20 hours at 70oC.
• FIG. 1 illustrates Carver release in grams per inch as a function of aging at room temperature for the composition described in Example 1.
• FIG. 2 the Carver release is for the same composition except for aging at 140oF.
• FIG. 3 illustrates the release as a function of silicone content of the coating at the time of cure.
• FIG. 4 illustrates the same release but after aging for 28 days at room temperature.
• FIG. 5 is for the same composition but after aging 28 days at 140oF.
• FIG. 6 shows the effect of concentrations of photo initiator on the release force and its effect with time.
• Attached drawing marked "Prior Art” depicts the accepted effect on a control release additive on a silicone release material.
• the release force remains fairly constant until some point is reached where the force increases dramatically. On the scale, zero designates no control release additive while 1 designates no silicone polymer.
• a substrate having thereon a cured coating of silicone release surface for contact with a pressure-sensitive adhesive.
• the coating is formed by coreaction of a silicone comprised of dimethyl siloxane polymers, preferably a reactive silicone and a resin, preferably a reactive resin comprising a reactive oligomer.
• EB electron beam
• actinic radiation preferably ultraviolet (UV) radiation
• the dimethyl siloxane polymer content of the coating is from about 1 to about 30 percent by weight on the total weight of the constituents of the coating with the anchored silicone preferentially concentrated at the surface provided for contact with a pressure-sensitive adhesive.
• the cured coating may be achieved using silicone-monomer combinationso
• Preferential presence of silicone at the surface may be achieved by partial to total incompatibility of the silicone and the resin, or by structural rearrangement of a silicone-resin surface. What is critical is that the silicone is sufficiently anchored to the surface and substantially non-transferable to a pressure-sensitive adhesive. Anchoring may be mechanical and/or chemical.
• Carver release as defined herein of less than about 100 grams per inch.
• Carver release is determined by applying ScotchTM 610 tape to the release surface under a pressure of 6000 psi for 60 seconds then measuring force required to achieve release at a peel rate of 12 inches per minute.
• sicone there is meant dimethyl siloxane polymers consisting of alternate silicone and oxygen atoms with methyl groups attached to silicon The general structure is: CH 3 CH 3 CH 3
• reactive silicone there is meant a silicone end capped and/or mid-chain substituted with groups reactive on application of heat and/or energy with reactive groups of the resin.
• the presently preferred reactive groups are acrylic, mercapto and/or oxirane.
• the term “resin” there is meant an organic moiety which is combinable with the silicone and reactive with silicone and/or reactive silicone under action of heat, actinic radiation and/or electron beam radiation to cause anchoring, preferably preferential surface anchoring of the silicone to the resin.
• reactive resin there is meant a resin comprising reactive oligomers containing groups which are reactive with the reactive groups of a reactive silicone.
• the presently 'preferred reactive oligomers contain reactive acrylic, mercapto and/or oxirane groups.
• the reactive resin may include a reactive monomer used to control viscosity, although not necessary to utility of the silicones.
• reactive monomer there is meant monomers which coreact with the reactive silicone and/or the reactive oligomer of the reactive resin and which are effective in reducing viscosity of coating composition used to form the end products of this invention. It is preferred that the reactive monomer be a multifunctional monomer preferably a multifunctional acrylate.
• silicon release surface there is meant a surface which will release from a pressure sensitive adhesive substantially without transfer of release material to the adhesive and having a TLMI peel under Keil conditions of no greater than about 400 N/M.
• the products of the invention be formed by coating a substrate such as paper then curing the coating, where the coating is comprised of from about 1 to about 30 percent by weight, preferably about 5 to about 30 percent by weight, more preferably about 5 to about 15 percent by weight, of a reactive silicone dispersed as a discontinuous phase in a reactive resin present in an amount of from about 99 to about 70 percent by weight, preferably from about 95 to about 70 percent by weight, more preferably from about 95 to about 85 percent by weight of the combination of the reactive silicone and reactive resin.
• the reactive resin contains from about 50 to 100 percent by weight reactive oligomer and from about 50 to 0 percent by weight reactive monomer based as the total weight of reactive oligomer and reactive monomer.
• the reactive monomer is used to control viscosity prior to cure. There may also be included in the system as required photoinitiators, colorants and the like. To enable good coatability, the dispersion should have a viscosity of from 300 to about 10,000 cps. Viscosity can, as indicated, be adjusted by the addition of reactive monomers.
• the cured coating is believed similar to block or graft copolymers having oligomer blocks bound to the silicone blocks with preferential presence of silicone at the surface as opposed to the body of the coating.
• the coating typically has a glass transition temperature of at least 0°C, preferably greater than about 20°C.
• Critical to the use of a dispersion is that the proportion of reactive silicone and reactive resin remain as a coatable dispersion in which the reactive silicone is as the dispersed phase and the reactive resin is the continuous phase. Once a certain level of reactive silicone monomer content is reached, phase inversion begins, to the end of forming a system in which the reactive resin is the dispersed phase and the reactive silicone is the continuous phase. When this is complete, the cured product will become rubbery and behave like a conventional silicone release coating which requires a high concentration of silicone before a suitable release level is achieved.
• the dispersion is coated in a conventional manner onto a substrate which may be any grade of paper, including the papers of low grade, cardboard, polymeric films and the like. Cure is to be sufficiently complete, such that substantially no silicone transfers to a pressure-sensitive adhesive to which the silicone release surface contacts. Avoidance of transfer is the result of the silicone being anchored to coating body and not available to transfer to the pressure-sensitive adhesive.
• Electron beam cure has a particular benefit, since it can initiate reaction of resins with substantially non-reactive silicones to produce a functional release surface.
• the ability of the coating to accept colorants is a desirable feature for establishing the presence and uniformity of the release coating.
• What is produced by the practice of the invention is a unique product of low silicone content but having a silicone release surface having excellent release properties.
• the coating is hard and substantially non-stretchable and aggressively bound to the substrate to which it is applied. Substantially complete cure insures against transfer to the adhesive during the lifetime of a laminate or self-wound product.
• the release coatings of this invention provides the advantage that the release force can be relatively constant over broad range of stripping speeds without the silicone substantially transferring to the adhesive surface. High holdout can be achieved on low grade papers and monomers can be used not only to adjust viscosity but also adjust release force.
• TLMI Release is by Test Method VII LD-468 and PSTC Test No. 2.
• Loop Tack is by PSTC - Test No. 5.
• Keil release values are after aging under a force of 0.25 psi for 20 hours at 70oC.
• TLMI means Tape and Label Manufacturers Institute and PSTC means Pressure Sensitive Tape Council.
• the adhesives employed in the Examples were permanent rubber based and/or acrylic based pressure-sensitive adhesives.
• a master batch of a resin coating designated as AE- 508 was formed of 72 parts by weight acrylated epoxy oligomer (Celanese 3703) supplied by Celanese Corp., 16 parts by weight hexanedioldiacrylate (HDODA) and 12 parts by weight diethoxyacetophenone (DEAP). From 80-95 parts of the master batch was mixed with 20-5 parts
• DehesiveTM VP-1530 a mixture acrylated and thiol and functional polysiloxanes, available from Stauffer-Wacker Silicones Co. (S-1530 herein). The mixtures were prepared in select increments of weight percent silicone.
• the coating mixtures were applied on clay coated gloss paper.
• the coated paper was exposed to the UV radiation given off by two medium pressure mercury vapor lamps at 200 watts/inch at web speed of 50 feet per minute. This corresponds to an energy input of about 5 kilojoules per square meter. Exposure resulted in cure to a hard glossy film which was dry to the touch. Completeness of cure was determined by laminating ScotchTM 610 tape manufactured by 3M, under pressure and measuring the force required to delaminate the construction or remove the tape. Release which is stable and low over time without substantially detackifying the adhesive is one indication of complete cure.
• Cured coatings with varying amounts of S-1530 were tested using the Carver release test which consists of laminating the cured release liner to ScotchTM 610 tape under a pressure of 6,000 psi for 60 seconds, and measuring force required to achieve release at a peel rate of 12 inches per minute (ipm). Release measurements were modified to include a 1200 inches per minute (ipm) rate.
• the release test as applied to aged samples was after aging with the test tape applied just before measuring release values.
• the initial formulation consisted of 90% AE 508 and
• Carver Release values were between 80-100 grams. Aging at room temperature or 140°F, resulted in a rapid decline to a stable release level within the range of 20-50 grams.
• FIGS. 3, 4 and 5 show the results of varying the concentration of S-1530 on Initial Peel (FIG. 3) after room temperature (RT) aging (FIG. 4) and elevated temperature aging (FIG. 5).
• the results display a phenomenon that appears to be related to phase transition. As silicone content increases there is reached a point where a transition to a rubbery phase occurs. The system then behaves in a conventional way, with release force decreasing with an increase in silicone content.
• FIG. 3 shows the initial Carver Release results and shows low initial releases (both 12 and 1200 ipm) in the range of 3%-5% S-1530.
• initial release values increase, with 1200 ipm releases actually appearing to be lower than 12 ipm.
• S-1530 12 ipm release values decline while 1200 ipm releases increase rapidly and appear to level off above 50% S-1530.
• FIGS. 4 and 5 show the Carver release values for samples aged 28 days at RT and 140°F.
• Formulations in the 5%-20% S-1530 range yield release values in the range of 20-40 grams with minimal differences between 12 and 120 ⁇ ipm releases. Above about 30% S-1530, the release values climb rapidly, peak, and then decline as the percentage of S-1530 increases beyond 40%. The range beyond 60% S-1530 is again characterized by a marked difference between 12 and 1200 ipm release values. The region up to 20 percent is hard and glassy with desirable release values. Above about 30% S-1530 a phase inversion occurs to a rubbery phase which is characteristic of conventional release liners.
• the concentration of photoinitiator diethyl acetophenone (DEAP) in the formulation has a significant effect on the initial Carver release values of lab samples. As shown in FIG. 6, the formulation with an excessive amount of DEAP (20%) yields initially high Carver release values, which subsequently age down to a level similar to formulations with 1%-5% DEAP. This is similar to the aging down observed in FIGS. 1 and 2 are for formulations having a concentration of 10.8% DEAP. Constructions using a rubber based hot melt removable adhesive and a high tack, high peel rubber based hot melt adhesive, were made and found to have acceptable low release from the surface to 10% S-1530. Constructions using 4, 6 and 10% S-1530 were prepared using a removable adhesive. Formulations using 6 and 10% S-1530 had low release whereas the formulation using 4% silicone had tighter release as measured by subjective testing.
• DEAP photoinitiator diethyl acetophenone
• the control was a standard thermally cured silicone release liner.
• the reactive silicones were S-450, an end acrylated silicone known as RC-450 supplied by Goldsmith Chemical Corporation; S-1559, a mixture of acrylated and mercapto functional silicone known as DehesiveTM VP-1559 supplied by Stauffer Wacker-Silicone Corp.; S-4818, an end and in chain acrylated silicone known as IC-4818-38 supplied by Lord Chemical Company and S-5360 and S-6350, each end and in chain acrylated silicones known respectively as Ebecryl 19- 6360 and 19-6350, supplied by U.C.B. Radcure Inc.
• Table 1 shows performance with an acrylic adhesive while Table 2 shows performance with a rubber based adhesive.
• homopolymer means 100% of the reactive silicone; copolymer means 80% by weight AE-508 and 20% by weight reactive silicone. In each instance the coating was formed on a super calendered kraft paper and EB cured at a dosage of 30 kGy.
• the adhesive employed was a tackified Kraton-1107, a styrene-isoprene, styrene-isoprene-styrene resin rubber manufactured and sold by Shell Chemical Company.
• the formulation in each instance was 70% by weight resin or monomers, 20% by weight hexanedioldiacrylate (HDODA) and 10% by weight S-1559.
• Cure was by electron beam at a dosage of 30 kGy in the presence of 200-250 ppm oxygen. Results shown in Table 3 established that epoxy, urethane and polyester oligomers gave low release values whereas an aliphatic oligomer gave higher release.
• Control -- -- 850 650 EXAMPLE 4 In Example 65 of U.S. Patent 4,228,479 to Brack, there is disclosed a potential formulation for a release surface. The formulation was prepared with certain substitutions made because of the lack of availability of components. The substitutions were not believed to modify the performance as the controlling ingredient was the silicone employed. The base formulations are shown in Table 4.
• formulation A When formulation A was used with the silicones of the instant invention, namely formulations C and D, they as well as formulations E to H at all times a functional release surface formed under both UV and EB conditions.
• a master batch of all components except the silicone formulation was prepared.
• the various formulations were prepared by taking a portion of the master batch and adding the silicone and photo-initiators as required. Samples were coated on super-calendared kraft paper and cured by either UV or EB radiation. The cured samples were then laminated to freshly prepared dry adhesives on polyester films.
• EXAMPLE 5 Formulation AE-508 was as a base formulation employing GE 479-1866 an experimental epoxy functional silicone provided by General Electric Company, Silicone Products Division. The formulations are shown in Table 7 and Carver release results reported after UV cure using 2 lamps at 200 watts per inch at a web speed of 50 feet per minute are shown in Table 8. Results are high average or highest value.
• Celrad 3201 an acrylated polyester from Celanese, Inc., 10 parts N-vinylpyrrolidone and 1.5 parts S-6350 and 2 parts photo initiator was coated onto crepe paper and cured with enough actinic (UV) radiation to give a hard dry film.
• the release liner was Keil aged against a permanent rubber based pressure sensitive adhesive. The Keil release forces were 80-150 N/M with minimal loss of adhesive tack.

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• 1988
  • 1988-04-01 EP EP19880903727 patent/EP0309557A4/en not_active Withdrawn
  • 1988-04-01 AU AU15943/88A patent/AU1594388A/en not_active Abandoned
  • 1988-04-01 WO PCT/US1988/001160 patent/WO1988007931A1/en not_active Application Discontinuation
  • 1988-04-01 JP JP63503442A patent/JPH01503544A/ja active Pending
  • 1988-04-01 BR BR888806894A patent/BR8806894A/pt unknown
  • 1988-12-09 KR KR1019880701633A patent/KR890700470A/ko not_active Application Discontinuation
  • 1988-12-09 FI FI885706A patent/FI885706A/fi not_active IP Right Cessation

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