MXPA97007094A - Copolymers of block polidiorganosiloxano-poliurea de dibloque and triblo - Google Patents

Abstract

Block copolymers of diblock (B-A) and triblock (B-A-B) polydiorganosiloxane-polyurea comprising a non-functional polydiorganosiloxane B terminal block and a polyurea A block. When used to provide release coatings, block copolymers allow easier release compared to traditional block copolymers of the (AB) n type having comparable amounts of polydiorganosiloxane. Articles incorporating the copolymers as a release material are also described.

Description

COPOLYMERS OF BLOCK POLIDIORGANOSILOXANO- POLIUREA DE DIBLOQUE AND TRIBLOQUE FIELD OF THE INVENTION The present invention relates generally to polydiorganosiloxane-polyurea materials and, more specifically, to diblock and triblock copolymers thereof. The invention further relates to release materials based on. these block copolymers as well as various articles comprising the block copolymers.

BACKGROUND OF THE INVENTION Pressure sensitive adhesive (PSA) articles such as tapes, labels and other types of PSA coated sheets often require the use of either a release liner or a backing that has a low load. adhesion (LAB). The release liners and LABs provide a surface whereby the adhesive does not adhere permanently, so that the adhesive is released therefrom before use.

REF: 25579 A backing having a LAB is particularly useful for providing an adhesive article such as a tape in a roll form. In this case, the adhesive is coated on the side of the backing opposite the LAB so that when the backing coated with the adhesive is rolled up, the adhesive contacts the LAB. The adhesive adheres sufficiently well to the LAB so that the roll does not come undone or "compress" one in a way that the tape can not be unwound. The release liners can be used in a wide variety of ways to provide numerous types of adhesive articles. In some cases, the release liner functions as a support for a layer of adhesive. For example, a layer of adhesive may be coated on the release surface of the release liner to provide a transfer ribbon. In this case, the back side of the release liner can also have a LAB so that the transfer belt can be provided in the roll form. In other cases, the release liner functions as a protective surface for the adhesive. For example, the release liner can be releasably adhered to the adhesive surface of a tape, label, or other adhesive article. The release liner is removed from the adhesive article prior to application of the article to a surface. The release liner or LAB comprises a release liner that is expected to provide an appropriate level of release of the adhesive of interest. The level of release is measured by the amount of force required to remove the release liner or the LAB from the adhesive. The release levels within the range of 1.0 N / dm to 40 N / dm are typical for LABs used to provide adhesive articles in the roll form. Release levels below 2.0 N / dm are generally preferred for release liners to provide a smooth and easy release and are considered to be of "premium quality". The release coatings may comprise a wide variety of materials such as silicones, epoxysilicon, polyolefins (such as polyethylene or polypropylene), fluorocarbon polymers, acrylic polymers and copolymers, urethane polymers and copolymers, and the like. An additional discussion of release coatings can be found in Handbook of Pressure Sensitive Adhesives, Satas, 1989, Van Nostrand Reinhold, pages 585-626. One type of release coating that is known to be suitable for a wide variety of PSA comprises segmented block copolymers of polydiorganosiloxane-polyurea of type (AB) n. US Pat. No. 5,214,119 (Leir) discloses this segmented block copolymer of (AB) n, wherein A represents a segment of polydiorganosiloxane and B represents a segment of polyurea. This reference discloses that the segmented copolymers can be adapted to have a wide range of radiation release properties in the segment ratio, the nature of the chain extenders used to form the segments, and the molecular weight of the segment of polydiorganosiloxane. While the aforementioned release coatings based on block copolymers of (AB) n have proven to be acceptable for numerous applications, other release coatings that provide the advantages over the prior art are investigated.

BRIEF DESCRIPTION OF THE INVENTION The present invention provides block copolymers of diblock (B-A) and triblock (B-A-B) polydiorganosiloxane-polyurea that can be used, for example, to provide release materials. In general, blends of diblock and triblock copolymers are typically provided, the mixture which is preferably predominantly triblock copolymer (B-A-B). In these block copolymers, B comprises a terminal block of non-functional polydiorganosiloxane and A comprises a block of polyurea. As used herein, the term "non-functional" means that the block is not reactive to the isocyanate. The term "polyurea block" is defined as a block having at least a portion of urea, urethane or thiourea attached to the block. Surprisingly, the diblock and triblock copolymers of the present invention can provide "unique advantages over type block copolymers (AB) n where the block (B) of polydiorganosiloxane is typically internal to the block copolymer. In the preparation of release coatings, the diblock BA and triblock BAB copolymers allow for easier release compared to traditional block copolymers of the (AB) r type having comparable amounts of polydiorganosiloxane In addition, the block copolymers of the present invention which comprising relatively low levels of segment B provides release levels that are typically only exhibited by 100% silicone release coatings.In addition, diblock BA and triblock BAB copolymers can be easily adapted for specific applications by incorporating various groups in segment A. This ability to adapting the block copolymer allows a variety of applications to be used including, for example, protective coatings and protective films. In one embodiment, the diblock and triblock copolymers of the present invention can be described by the formula BAX wherein B comprises a terminal block of non-functional polydiorganosiloxane, A comprises a block of polyurea and X is selected from the group consisting of hydrogen, a terminal block of non-functional polydiorganosiloxane, or an isocyanate radical. More preferably, B has a structure: and A has a structure In the case of the diblock, X is hydrogen or has a structure: -C-N- 2-N- * C-0 H In the case of the triblock, X has a structure In all the structures presented above, D, Y, R, n, m, Z, A 'and B' are defined as follows: Each D is selected individually from the group consisting of hydrogen, an alkyl radical having from 1 to 10 carbon atoms, and a phenyl radical; Each Y is selected individually in the group consisting of an alkylene radical having from 1 to 10 carbon atoms, an aralkyl radical, and an aryl radical; Each R is selected individually from the group consisting of a monovalent alkyl radical having from 2 to 12 carbon atoms, a substituted alkyl radical having from 2 to 12 carbon atoms, a vinyl radical, a phenyl radical, and a radical substituted phenyl, with the proviso that at least 50% of the number of radicals R are methyl; Each n is an integer that is 5 or greater; m is an integer that is 1 to approximately ; each Z is selected from the group consisting of aromatic, aliphatic, araliphatic and cycloaliphatic divalent radicals; each A 'is selected from the group consisting of -O -.- N- I G and -S- where G is selected from the group consisting of hydrogen, an alkyl radical having from 1 to carbon atoms, a phenyl radical, and a radical which when combined with B 'forms a heterocycle; and each B 'is selected from the group consisting of aromatic, aliphatic, araliphatic and cycloaliphatic radicals, polyethylene oxide, polypropylene oxide, polytetramethylene oxide, polyethylene adipate; polycaprolactone, polybutadiene, polyamide, polysiloxane, mixtures thereof, and a radical that completes a ring structure with A 'to form a heterocycle.

It is noted that when D, Y, R, n, Z, A 'and B' appear more than once from a structure of diblock and triblock, they may be the same or different. Preferably, each D is a hydrogen; each Y is selected from the group consisting of alkylenic radicals having from 1 to 10 carbon atoms, more preferably having from 1 to 3 carbon atoms, most preferably propylene; each R is methyl; each n is a number from 40 to 400; m is a number from 5 to 15; each Z is selected individually from the group consisting of hexamethylene, methylene-bis- (phenylene), tetramethylxylylene, isophorone, tetramethylene, cyclohexylene and methylenedicyclohexylene; and A 'is selected from the group -N-y and -O-. I The present invention also provides release materials comprising these diblock and triblock copolymers and articles comprising these release materials. The article may comprise a backing having at least one layer of release material applied thereto. The article may additionally comprise a layer of adhesive coated on the backing. The adhesive layer can be coated on the side of the backing opposite the release material, or directly on the release material. The present invention also provides a laminated construction wherein a release liner removably adheres to an adhesive article such as a tape. Preferably, the adhesive is a rubber resin adhesive or other adhesive having a low acid content of less than about 2% by weight.

DETAILED DESCRIPTION OF THE INVENTION The diblock B-A and triblock B-A-B copolymers of the present invention can be produced by mixing, under reactive conditions, a monoamine functional polydiorganosiloxane, a diamine and / or dihydroxy chain extender and a diisocyanate. The terminal segment of non-functional polydiorganosiloxane is derived from the polydiorganosiloxane with monoamine functional groups, while the polyurea segment is derived from the diisocyanate and the diamine and / or dihydroxy chain extender. The combined molar ratio of the polydiorganosiloxane with monoamine functional groups and the diamine and / or dihydroxy chain extender to the isocyanate in the reaction is that suitable for the formation of a block copolymer with desired properties. Preferably, the ratio is maintained in the range of about 0.95: 1.0 to 1.0: 0.95 with 1.0: 1.0 which is most preferred.

Polydiorganosiloxane with monoamine functional groups The polydiorganosiloxane with monoamine functional groups has the following general structure: where D, Y, R and n are as defined above. The polydiorganosiloxane with monoamine functional groups can be prepared by a variety of methods. A useful means of synthesizing these materials is via a platinum catalyzed hydrosilation reaction of a polydiorganosiloxane terminated with mono-SiH and an alpha-olefinic alkylamine compound. This method is described by Clouet et al., In Journal of Polymer Science: Part A: Polymer Chemistry, Vol. 31, 3387-3396 (1993). Care must be exercised during the preparation of the polydiorganosiloxane with monoamine functional groups to avoid side reactions that could lead to unwanted impurities in the material that would carry them in the final block copolymer products. For example, the SiH groups can be hydrolyzed in the presence of water, and the platinum catalyst to form a silanol group. These polydiorganosiloxanes with silanol functional groups could be impurities that could adversely affect the elastomeric properties and release characteristics of the copolymers of. diblock and triblock formed. A discussion of the detrimental effects of these silanol-terminated species that may be present in the elastomeric silicone-polyurea block copolymers can be found in US Patent No. 5,290,615 (Tushaus et al.). A preferred means for preparing the polydiorganosiloxane with monoamine functional groups can be found in U.S. Patent No. 5,091,483 (Mazurek et al.). This method comprises the use of a fluorosilane substituted with amine to terminate the anionic polymerization product of a cyclic siloxane monomer.

Diisocyanates Any suitable organic diisocyanate, such as an aromatic, cycloaliphatic, aliphatic or araliphatic diisocyanate, can be used either alone or in mixtures of two or more. Suitable aromatic diisocyanates include 2,4-toluene diisocyanate, 2,6-toluene diisocyanate, a toluene diisocyanate dimer (available under the trademark Desmodur ™ TT from Miles Coating Division), diphenylmethane-4,4 '-diisocyanate. (MDI), 1,5-diisocyanato-naphatalene, 1,4-phenylene diisocyanate, 1,3-phenylene diisocyanate > and mixtures thereof. Examples of cycloaliphatic diisocyanates include dicyclohexylmethane diisocyanate (Hi2MDI, commercially available as Desmodur ™ W from Miles Coating Division), isophorone diisocyanate (IPDI), 1,4-cyclohexane diisocyanate (CHDI), 1,4-cyclohexane bis (methylene) isocyanate) (BDI), 1,3-bis (isocyanato-methyl) cyclohexane (H6XDI), and mixtures thereof. Examples of useful aliphatic diisocyanates include hexamethylene-1, 6-diisocyanate (HDI), 1, 12-dodecane-diisocyanate, 2,2,4-trimethyl-hexamethylene-diisocyanate (TMDI), 2,4-trimethyl-hexamethyl -diisocyanate (TMDI), 2-methyl-l, 5-pentamethylene-diisocyanate, dimeryl-diisocyanate, hexane-diisocyanate urea, and mixtures thereof. Examples of useful araliphatic polyisocyanates include m-tetramethyl-xylylene-diisocyanate (m-TMXDI), p-tetramethyl-xylylene-diisocyanate (p-TMXDI), 1-xylene-diisocyanate (XDI), 1,3-xylene-diisocyanate , and mixtures thereof. Preferred diisocyanates, generally include those selected from the group consisting of isophorone diisocyanate, toluene diisocyanate, dicyclohexylmethane-4, -diisocyanate, 1,4-cyclohexane diisocyanate, m-tetramethyl-xylylene diisocyanate, p-tetramethyl- xylylene diisocyanate, derivatives of all those mentioned above, and mixtures thereof.

Chain Extenders Suitable chain extenders include diamine and dihydroxy chain extenders. The chain extenders can be short chain diamines such as hexamethyl diamine, xylylene diamine, 1,3-di (4-piperidyl) propane (DIPIP), N-2-aminoethyl-propylmethyldimethoxysilane (DAS), 1,3 -dia inopentane (DAMP), 1, -diaminopentane, piperazine, piperidylpropane and the like, with the 1,3-di (4-piperidyl) propane and 1,3-diaminopentane which are most preferred. Examples of useful dihydroxy chain extenders include, but are not limited to, those selected from the group consisting of 1,4-butanediol, ethylene glycol, diethylene glycol, dipropylene glycol, neopentyl glycol, 1-6-hexanediol, 1,4- cyclohexanedimethanol, and mixtures thereof. Polymeric diamines as well as polymeric glycols can also be used. Useful polymeric diamines include those having a 2.0 approaching functionality such as polyethylene oxide diamines; polypropylene oxide diamines; and ethylene polytetra oxide diamines having a molecular weight in the range of 300 to 10,000, with a molecular weight in the range of 400 to 5,000 which are most preferred. These polytetramethylene oxide diamines and the methods for manufacturing them can be found in US Pat. No. 4,933,396 (Leir et al.). Other useful polymeric diamines are polyester diamines, sold under the trademark JEFFAMINE, available from Huntsman Chemical Co. Suitable polymeric diols include polytetramethylene oxide glycol, polyethylene oxide glycol, polyethylene adipate glycol, polypropylene oxide glycol, polybutadienglicol, polycaprolactone-glycol, and the like. It is also possible to incorporate polysiloxane into segment A of the block copolymer by using a diamine or diol-polysiloxane chain extender. These chain extenders typically have molecular weights from about 500 to about 35,000, more preferably from about 1,000 to about 20,000. Extending examples of the polysiloxane chain with diol functional groups, useful include triblock copolymers comprising a middle block of polydimethylsiloxane and a terminal block of polyethylene oxide terminated with hydroxyl functionality. This material is commercially available from Dow Corning Co. under the trade designation DC Q4-3667. Extenders of the polysiloxane chain with diamine functional groups can be prepared by a variety of methods known in the art, most preferably according to the methods described in U.S. Patent No. 5,214,119 and WO 95/03354. The physical properties of the resulting block copolymer (such as tensile strength, hardness, abrasion resistance, glass transition temperature, flexibility, etc.) are affected by the selection of the chain extender. In general, low molecular weight chain extenders can be used to increase the tensile strength, hardness and abrasion resistance of the block copolymer, while polymeric diamines and polymeric glycols can be used to provide copolymers of soft, flexible and elastic blocks. For example, when a diisocyanate is combined with large quantities of the chain extenders with a relatively low molecular weight (preferably having a molecular weight of less than 300), the hard character of the block copolymer is improved and an leathery product. By way of another example, when the block copolymer comprises high levels of polydiorganosiloxane and polymeric diamines or polymeric glycol, chain extenders are used, and soft or flexible materials are formed which can be used as sealants or additives. By way of yet another example, when diamine or diol-polysiloxane chain extenders are used, the polysiloxane is incorporated into both the terminal block and the segments of the middle block of the resulting block copolymer. This allows for increased flexibility in the adaptation of the release materials to provide a desirable level of release. A discussion of the effects of the various types of chain extenders on the mechanical properties of block copolymers can be found on page 172 in Abouzahr, S. and Wilkes, G.L. "Segmented Copolymers with Emphasis on Segmented Polyurethanes" in Processing, Structure and Properties of Block Copolymers, Folkes, M.F., Elsevier, New York. Preferably, the segments resulting from the chain extender comprise less than about 50% by weight of the copolymer formulation, depending on the properties of the resulting copolymer desired.

Preparation of diblock and triblock polydiorganosiloxane-polyurea copolymers The diblock and triblock copolymers of the present invention are prepared from the reaction of mixtures of polydiorganosiloxane with monoamine functional groups and the chain extender, with approximately stoichiometric amounts of diisocyanate. The reactions are carried out in a dry solvent, or mixtures of solvents, protected from atmospheric humidity. The solvents are preferably non-reactive with the diisocyanates and the chain extender. The starting materials in the final products remain preferably completely visible in the solvents during and after the polymerization. Suitable solvents include polar liquids, such as alcohols, ethers, esters, and chlorinated hydrocarbons, with tetrahydrofuran and methylene chloride which are especially useful. The preferred solvents are determined by the nature of the reagents. For example, when all reagents are amine functional groups and reacted with aliphatic diisocyanates, secondary alcohols such as isopropanol or 2-butanol are preferred, either alone, or in combination with non-polar solvents such as toluene or cyclohexane. For reactions comprising aromatic diisocyanates [for example, diphenylmethane-4,4'-diisocyanate (MDI)], tetrahydrofuran containing from 10 to 25% of an aprotic, bipolar co-solvent such as dimethylformamide is preferred. The reaction conditions of the processes for the preparation of the block copolymers will also vary depending on the nature of the reagents. For reactions comprising only starting materials with amine functional groups, it is preferred to run the polymerization in two steps in order to ensure complete incorporation of the polydiorganosiloxane ("polysiloxane") with monoamine functional groups in the final product. In the first step, the polysioxane, either pure or in solution, is added to a solution of at least a four-fold molar excess of diisocyanate to provide a solution of a mixture of ureido monoisocyanate of polydiorganosiloxane and diisocyanate. In the second step, the remaining diisocyanate, if any, is added, followed by a solution of the other diamine reagents. The preferred molar ratio of the total amines to the diisocyanates are in the range from 0.95: 1.0 to 1.0 to 0.95, more preferably in a ratio of 1.0: 1.0 in order to provide the maximum molecular weight of the final block copolymer product . These reactions can be carried out at temperature from 0 to 150 ° C. The reaction is preferably carried out at room temperature at 50 ° C. The reaction of the amines with diisocyanates is exothermic, and no catalyst is required. For compositions incorporating diols in the formulation, a two step process for the preparation is also preferred. Again, it is preferred to add the polysiloxane to a solution of excess diisocyanate in a non-hydroxylic solvent, more preferably tetrahydrofuran. This mixture is added to the diols and a small amount of a catalyst such as stannous octoate or dibutyltin dilaurate, and heated to reflux for 1 to 2 hours, or until the reaction is finished. The preferred molar ratio of the amine plus the diols to diisocyanates is 0.95: 1.0 to 1.0: 0.95. It is also possible to carry out or run the reaction initially at lower molar ratios of 0.70-0.90: 1.0 to provide mixtures of urethane oligomers terminated with isocyanate. Then, the polymerization is terminated by the addition of the diamine chain extender, sufficient to the reaction to bring the final molar ratio of amine / alcohol to diisocyanate to 0.95-1.0: 1.0, more preferably 1.0 to 1.0. The diblock and triblock copolymers of this invention can be prepared to have a wide range of useful properties by varying the weight ratio of segment B to segment A, the nature of the chain extenders and other polymers used, and the molecular weight of the polysiloxane end blocks. The block copolymers of this invention, for most applications, do not require curing to achieve their desired properties, but produce films molded with solvents, hard on drying. When additional stability, resistance to solvents is desired, the silicone block copolymers can be crosslinked after coating molding by any of the conventional methods known in the art, such as by electron beam radiation, or the use of peroxides. The diblock and triblock copolymers of the present invention are suitable for use as release coatings for a variety of pressure sensitive adhesives. They have good stability in solution, are film formers, and have an unusually high strength plus desirable mechanical and elastomeric properties. In addition, they do not require a high temperature cure or long processing times, a decided advantage in the manufacture of pressure sensitive tapes. The block copolymers of this invention can be prepared to give varying amounts of release through variations in the ratio of the silicone segments to the non-silicone segments (ie, the ratio of B to A), the amount and nature of the extended chain extenders, and the molecular weight of the polydiorganosiloxane block.

In general, the release amount may vary from 1.0 N / dm or less to about 35 N / dm. Certain copolymers are especially useful as low adhesion fillers (LAB) for pressure sensitive adhesive tapes such as adhesive tapes. LABs for roll tapes typically exhibit release values in the range of from about 6 to about 35 N / dm. The preferred content of the non-functional polydiorganosiloxane segment for the copolymers of the present invention used as release coatings for pressure sensitive adhesives is from about 1 to about 50 weight percent, the preferred ranges which are dependent on the specific adhesive and its end use. In general, thin film coatings of copolymers comprising 1 to about 50 weight percent polydiorganosiloxane exhibit the necessary combination of proper unwinding in the fresh belt with only a moderate increase in the unwinding force after adverse aging conditions. of heat and humidity. For top-quality release coatings (i.e., release coatings having release values of less than about 2 N / dm), a higher content of polydiorganosiloxane in the formulation is required, preferably from about 25 to 50% by weight of polydiorganosiloxane. In applications where moderate release values are acceptable, the polysiloxane content can be reduced to lower levels, for example, 15% by weight and lower. The number average molecular weights, typical for the terminal block of the block copolymers proposed for use in release materials are in the range from 5,000 to about 30,000. The number average molecular weight of the middle block can vary over a wide range depending on the chain extender used to make this block. The polysiloxane-polyurea diblock and triblock compositions of this invention, depending on their viscosity, can be coated via any of a variety of conventional coating methods, such as roll, blade, or curtain coating, or extrusion coating. These compositions can be applied to at least a portion of at least one main surface of a suitable flexible or inflexible backing material and dried to produce the sheet materials coated with release. Flexible, useful backing materials include paper, plastic films such as poly (propylene), poly (ethylene), poly (vinyl chloride), poly (tetrafluoroethylene) ", polyester [eg, poly (ethylene-terephthalate)] , polyamide film such as DuPont's Kapton ™, cellulose acetate and ethylcellulose.The backs can also be made of woven material formed from strands of synthetic and natural materials such as cotton, nylon, rayon, glass, or ceramic material, and can be non-woven material. fabric such as meshes deposited with air of natural or synthetic fibers or mixtures of these.In addition, suitable backings can be formed of metal, metallized polymeric film, or ceramic sheet material.The coated laminate materials can take the form of any conventionally known article. which is used with PSA compositions, such as labels, tapes, transfer tapes (comprising a PSA film held in a at least one release liner), signals, covers, marking signals, and the like. You can use captors, but they are not always necessary. This invention is further illustrated by the following examples which are not intended to be limiting in scope. Unless indicated otherwise, molecular weights refer to number average molecular weights. All parts, percentages and ratios are by weight unless otherwise specified.

EXAMPLES TEST METHODS Aged Release Value This test measures the effectiveness of the silicone release composition after a period of aging with heat. The aged release value is a quantitative measure of the force required to move a flexible adhesive tape from a substrate coated with the test composition. The aged release test was carried out using a commercially available tape sample of 3M Co. , as general purpose adhesive tape No. 232. This tape comprises a pressure sensitive adhesive of natural rubber with improved tack coated on a pleated paper backing impregnated with resin and a width of 1.27 cm. The tape was wound with 5 steps of a 2 kg rubber roller on a 2.54 cm by 25 cm strip of the release coated substrate prepared according to the following examples and allowed to be in intimate contact for three days at 65 ° C. . These laminates were then aged for at least 6 hours at 22.2 ° C and a relative humidity of 50% and then the side of the tape adhered to the stage of a slip tester / release apparatus from Instru entors, Inc., (Model 3M90) with double coated tape. The force required to remove the No. 232 adhesive tape at an angle of 180 ° C and a speed of 228.6 cm / min was measured.

Aged Readiness Aged readhesions were measured by adhering the freshly detached tape from the previous test to a clean glass plate and measuring the release adhesion using the same sliding / detaching instrument tester, indicated above, again the detachment 228.6 cm / min and at an angle of 180 ° detachment, after allowing the test tape to be on the glass plate for 30 seconds. These measurements were taken to determine whether a fall in adhesion value occurred due to undesirable contamination of the adhesive surface by the transfer of unincorporated silicone into the release coating. The readhesions are reported as a percentage of the force required to remove the aged sample from a clean glass plate against the force required to remove a sample of control tape and a clean glass plate that has not adhered to the release coating. Preferably, the readhesion values are 100% indicating that there is no transfer of silicone in the release liner to the belt. The readhesion values of approximately 80-90%, however, are acceptable.

Abbreviations 5K Polydimethylsiloxane terminated with onoaminoalkyl having a theoretical molecular weight of 5,000 10K Polydimethylsiloxane terminated with monoaminoalkyl having a theoretical molecular weight of 10,000 20K Polydimethylsiloxane terminated with monoaminoalkyl having a theoretical molecular weight of 20,000 D-400 JeffamineMR D400, an extender of the a,? - diaminopropyl-poly (propylene oxide) chain having an approximate number average molecular weight of 400, commercially available from Huntsman Chemical Co.

(Continued) Abbreviations D-4000 Jeffamine ™ D4000, a chain extender of α, β-diaminopropyl-poly (propylene oxide) having an approximate number average molecular weight of 400, commercially available from Huntsman Chemical Co. DAMP 1, 3-diaminopentane DU700 Jeffamine ™ DU700, an extender of the α, α-diaminopropyl-poly (propylene oxide) chain containing internal urea groups having an approximate number average molecular weight of 900, commercially available from Huntsman Chemical Co. IPDI Isophorone diisocyanate Mn Number average molecular weight 5K DIAMINE Polydimethylsiloxane terminated with diaminoalkyl having a theoretical molecular weight of 5,000.

EXAMPLE 1 Preparation of the Aminoalkyl Fluorosilane Termination Agent.

A round bottom flask with three necks 500 ml, was loaded with 49.6 g of l, 3-bis (3-aminopropyl) tetramethyldisiloxane, 29.6 g of ammonium fluoride, and 300 ml of cyclohexane. While heating under reflux, the water was removed by means of a Dean-Stark trap. After 18 hours, 4.4 ml of water had been collected, and the clear, colorless solution was transferred while hot in a round bottom flask and 500 ml neck. The solvent was distilled in a rotary evaporator to provide 165 g of the white solid. This dissolved in 200 ml of methylene chloride; 30 g of hexamethyldisilazane were added; and the mixture was stirred and heated under reflux for 5 hours. The flask was equipped for distillation and the solvent was removed under vacuum with a vacuum cleaner. The product was distilled (boiling point 70 ° C) under vacuum aspirator to provide (3-aminopropyldimethyl-fluorosilane as a clear, colorless oil.) The yield was 54 g (100%), which was determined to be pure by vapor phase chromatography. The structure was confirmed by NMR spectroscopy.

EXAMPLE 2 Preparation of Aminopropyl-terminated Polydimethylsiloxane N-Butyllithium (10 ml, 2.5 M) was added to 7.4 grams of octamethylcyclotetrasiloxane under argon to form a lithium silanolate initiator. After stirring for 30 minutes, a solution of 250 grams of hexamethylcyclotrisiloxane in 250 grams of dry tetrahydrofuran was added, and the reaction was stirred at room temperature for 18 hours. To the resulting viscous syrup was added 3.4 grams of 3-aminopropyldimethyl fluorosilane, a terminating agent, described in Example 1. The viscosity decreased rapidly. After stirring for 2 hours, the solvent was completely distilled in a rotary evaporator. The product was filtered to remove the lithium fluoride and provide 250 grams of silicone monoamine as a clear, colorless oil. Trituration with 1.0 N HCl gave a number average molecular weight, Mn, of 9400 (theoretical Mn = 10, -000). Using this procedure, but varying the reaction time and using a molar excess of the terminating agent to the cyclic siloxane, polydimethylsiloxanes terminated with aminopropyl terminated with theoretical Mn of 5,000 (number average molecular weight = 5,038) and 20,000 ( average molecular weight titled number = 19,274).

EXAMPLE 3 Preparation of Diblock and Triblock Polysiloxane-Polyurea In a 100 ml round bottom flask, 0.10 grams of the macromonomer of the aminopropyl terminated polysiloxane of Example 2 (Mn = 9400) and 2.9 grams of Jeffamine ™ DU700 were combined. After heating this mixture to 100 ° C under vacuum, 25 ml of isopropyl alcohol were added to this mixture. In a second flask equipped with a metal stirrer, 5.02 grams of IPDI was mixed with 25 ml of isopropyl alcohol. The contents of the first flask were then added to the contents of the second flask and the combined contents were stirred for 10 minutes. Then 1.98 grams of DAMP were dissolved in 40 ml of isopropyl alcohol and added in one portion to the second flask. This mixture was stirred for several hours. Then it is. added enough isopropyl alcohol to result in a 5% solution of the block copolymer product. This 10% solids solution was then coated directly onto a 15.24 cm x 1 m strip of a 0.038 mn (1.5 mil) polyester film using a # 6 Mayer rod and tested for release and re-adhesion as described above. The results of these tests were recorded and can be found in Table 1.

EXAMPLES 4-7 Block copolymers were prepared by the method of Example 3 by varying the amounts of aminopropyl-terminated polysiloxane, Jeffamine ™ DU700, IPDI and DAMP in the polymerization mixture. The ratios of these starting materials are given in Table 1. Release compositions were prepared and coated as in Example 3 except using a 5% solids solution. The results of the release and re-adhesion test are given in Table I.

EXAMPLES 8-9 To demonstrate the effect of molecular weight on the polydiirimethylsiloxane endblocks of the compositions of the present invention, two analogs of Example 5 were prepared using starting materials of low molecular weight aminopropyl-terminated polydimethylsiloxane (Mn-5,038) and high molecular weight.

(Mri = 19,274) of Example 2. The ratios of these starting materials are given in Table I. Release compositions were prepared and coated as in Example 3. The results of the release and re-adhesion test are given in Table I.

EXAMPLE 10 Example 10 illustrates the use of the higher molecular weight polymer chain extender, D4000. A mixture comprising 25 percent by dry weight of an aminoalkyl-terminated polydimethylsiloxane (Mn = 9.257), 50 percent by weight of IPDI / DAMP, and 25 percent by weight of D4000, was prepared, coated and tested in accordance with the methods of Examples 8-9 except using a # 3 Mayer rod. The results of the release and re-adhesion test are given in Table I.

COMPARATIVE EXAMPLE C-l A segmented silicone-polyurea block copolymer was prepared using the method of US Patent No. 5,214,119 (Leir et al.). The block copolymer comprised 20 weight percent of a silicone diamine (Mn = 10,000) prepared from • < according to the two step method of US Pat. No. 5,214,119 using a tetramethylammonium silanolate catalyst, 60 weight percent IPDI / DAMP and 20 weight percent DU700. A release composition was prepared and coated as in Example 3. The release and adhesion tests were carried out and the results are in Table I.

Table I 1 Polysiloxane terminated with diaminoalkyl used in place of the polysiloxane macromonomer terminated with aminoalkyl.

Table I illustrates that a full range of release characteristics were obtained by varying the amounts and molecular weights of the various components used to make the block copolymer of the present invention. Surprisingly, the release coating compositions, useful in the range of moderate to firm release (ie, release values in the range of 10-40 Mn) were prepared using neither as 1-5% by weight of the macromonomer of polysiloxane. High quality release values (ie, release values less than 2 N / dm) were observed for compositions having only 35% by weight of the monofunctional polysiloxane component. These low release values are typically seen only at ',. compositions with 100% silicone. Additionally, Example 6 and Comparative Example C-1 clearly demonstrate the effect of the different polymer architectures (B-A and B-A-B copolymers of the present application against segmented block copolymers).

(A-B) n of C-1) in the release performance of the coatings comprising the same amount of polydiorganosiloxane. At the same polysiloxane, diisocyanate and chain extender content, the copolymers of the present invention possess a significantly lower release adhesion than their segmented counterparts.

EXAMPLES 12-14 To further demonstrate the release properties of the compositions of the present invention, the coatings of Examples 8-10 were measured for release and re-adhesion as described above using an alternative tape sample (styrene-isoprene block copolymer adhesive -styrene (SIS) with improved tack on a polypropylene backing, commercially available as 3M Co. high performance box sealing tape No. 375). The results of these tests are recorded later in Table II.

These examples show that a range of release levels can be obtained for adhesives comprising SIS block copolymers, with improved tack.

EXAMPLE 15 Preparation of an Organopolysiloxane-diamine Chain Extender A solution of 14.79 g of bis- (3-aminopropyl) tetramethyl-disiloxane and 352.9 g of octamethylcyclotetrasiloxane was purged with argon during minutes and then heated to 150 ° C; 0.06 g (100 ppm) of 50% aqueous cesium hydroxide was added and heating continued for 6 hours until aminopropyl disiloxane was consumed. The reaction was cooled to 70 ° C, neutralized with excess triethylamine and acetic acid, and heated under high vacuum to remove cyclic siloxane for a period of at least 5 hours. After cooling to room temperature and filtration to remove the cesium acetate, an isolated diaminopropyl-terminated polydimethylsiloxane product having a theoretical molecular weight of 5,000 was obtained (number-average molecular weight titrated - 5.276). .

EXAMPLE 16 Example 16 demonstrates the use of the combination of monoaminopropyl-terminated polydimethylsiloxane of Example 2 (Mn = 5.038) and the chain extender is silicone-diamine of Example 15 (Mn = 5.276). These mixed polysiloxanes with aminopropyl functional groups, each used in the proportion of 10 weight percent, were combined as in Example 3 with 25 weight percent of the extender of the polymer chain of D400 and 55 weight percent of IPDI / DAMP. These compositions were coated and tested as in Example 3. The results of these tests are given in Table III.

Table III This example illustrates that near-prime release levels can be achieved at a low polysiloxane content (20 weight percent) by combining both polysiloxane end blocks and middle blocks in the block copolymer when using polysiloxane starting materials terminated in both monoaminoalkyl and nonalkyl day.

EXAMPLE 17-18 Example 17 was prepared by making a block copolymer solution using the same procedure of Example 3 except for the use of both polysiloxane terminated with monoaminoalkyl (Mn = 5,038) of Example 2 and diaminoalkyl-terminated polysiloxane (Mr. = 5.276) Example 15. Example 18 was prepared by making a block copolymer solution using the same procedure as in Example 3 except for the use of both monoaminoalkyl-terminated polysiloxane (Mn-10,489) made using the same procedure of Example 2 and polysiloxane-terminated diaminoalkyl (Mn = 5.276) of Example 15. The block copolymer solutions were coated according to the procedure given in Example 3 and tested for release and re-adhesion using the procedure of Examples 12-14. The results of these tests are recorded later in Table IV.

This example illustrates that first quality release levels can be achieved using 20% and 50% polysiloxane contents when both the terminal blocks and the middle blocks comprise polysiloxane.

It is noted that in relation to this date, the best method known by the applicant to carry out the present invention, is the conventional one for the manufacture of the objects to which it refers. Having described the invention as above, the content of the following is claimed as property:

Claims (10)

1. A block copolymer, characterized in that it has the structure BAX, wherein B comprises a terminal block of non-functional polydiorganosiloxane, derived from a polydiorganosiloxane with monoamine functional groups, A comprises a block of polyurea, and X is selected from the group consisting of of hydrogen, a terminal block of non-functional polydiorganosiloxane, and an isocyanate radical.

2. A block copolymer according to claim 1, characterized in that: B has the structure: A has the structure X is selected from the group consisting of hydrogen and the following structures: H wherein: each D is individually selected from the group consisting of hydrogen, an alkyl radical having from 1 to 10 carbon atoms, and a phenyl radical; each Y is a divalent radical individually selected from the group consisting of an alkylene radical having from 1 to 10 carbon atoms, an aralkylene radical, and an arylene radical; each R is individually selected from the group consisting of a monovalent alkyl radical having from 2 to 12 carbon atoms, a substituted alkyl radical having from 2 to 12 carbon atoms, a vinyl radical, a phenyl radical, and a phenyl radical replaced, with the proviso that at least 50% of the number of R radicals are methyl; each n is an integer that is 5 or greater; m is an integer that is 1 to about 25; each Z is individually selected from the group consisting of aromatic, aliphatic, araliphatic and cycloaliphatic divalent radicals; each A 'is selected individually from the group consisting of I G and -S- where G is selected from the group consisting of hydrogen, an alkyl radical having from 1 to 10 carbon atoms, a phenyl radical, and a radical which when combined with B 'forms a -heterocycle; and each B 'is a divalent radical selected individually from the group consisting of aromatic, aliphatic, araliphatic and cycloaliphatic radicals, polyethylene oxide, polypropylene oxide, polytetramethylene oxide, polyethylene adipate, polycaprolactone, polybutadiene, polyamide, polysiloxane, mixtures thereof and a radical terminating a ring structure with A 'to form a heterocycle.

3. A block copolymer according to claim 2, characterized in that: each D is hydrogen; each Y is selected individually from the group consisting of hydrogen, alkylene radicals having from 1 to 10 carbon atoms; each R is methyl; each n is an integer from 40 to 400; m is an integer from 5 to 15; each Z is selected individually from the group consisting of hexamethylene, ethylene-bis- (phenylene), tetramethyl-xylylene, isophorone, tetramethylene, cyclohexylene, and methylen-dicyclohexylene; and each A 'is selected individually from the group consisting of I H

4. A block copolymer according to claim 1, characterized in that it comprises from about 1 to about 50 weight percent of non-functional polydiorganosiloxane.

5. A block copolymer according to claim 1, characterized in that it is prepared by reacting a polydiorganosiloxane with monoamine functional groups, a chain extender and diisocyanate.

6. A block copolymer according to claim 5, characterized in that the chain extender is selected from the group consisting of diamine, diamine-polysiloxane, diol-polysiloxane, and diol chain extenders and mixtures thereof.

7. A block copolymer according to claim 5, characterized in that the combined molar ratio of the polydiorganosiloxane with monoamine functional groups and the chain extender to the diisocyanate is 0.95: 1.0 to 1.0: 0.95.

8. An article, characterized in that it comprises a backing having at least one release material applied thereto, the release material comprising a block copolymer according to claims 1-7.

9. An article according to claim 8, characterized in that the backing comprises a material selected from the group consisting of paper, poly (propylene), poly (ethylene),. poly (vinyl chloride), poly (tetrafluoroethylene), polyester, polyamide, cellulose acetate, ethylcellulose, cloth and non-woven fabric.

10. An article according to claim 12, characterized in that the backrest further comprises at least one layer of adhesive applied thereto.