Classifications

• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
  • C08J3/00—Processes of treating or compounding macromolecular substances
  • C08J3/02—Making solutions, dispersions, lattices or gels by other methods than by solution, emulsion or suspension polymerisation techniques
  • C08J3/03—Making solutions, dispersions, lattices or gels by other methods than by solution, emulsion or suspension polymerisation techniques in aqueous media
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
  • B29C41/00—Shaping by coating a mould, core or other substrate, i.e. by depositing material and stripping-off the shaped article; Apparatus therefor
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
  • B29C41/00—Shaping by coating a mould, core or other substrate, i.e. by depositing material and stripping-off the shaped article; Apparatus therefor
  • B29C41/003—Shaping by coating a mould, core or other substrate, i.e. by depositing material and stripping-off the shaped article; Apparatus therefor characterised by the choice of material
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29D—PRODUCING PARTICULAR ARTICLES FROM PLASTICS OR FROM SUBSTANCES IN A PLASTIC STATE
  • B29D7/00—Producing flat articles, e.g. films or sheets
  • B29D7/01—Films or sheets
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
  • C08J5/00—Manufacture of articles or shaped materials containing macromolecular substances
  • C08J5/18—Manufacture of films or sheets
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
  • C08L53/00—Compositions of block copolymers containing at least one sequence of a polymer obtained by reactions only involving carbon-to-carbon unsaturated bonds; Compositions of derivatives of such polymers
  • C08L53/02—Compositions of block copolymers containing at least one sequence of a polymer obtained by reactions only involving carbon-to-carbon unsaturated bonds; Compositions of derivatives of such polymers of vinyl-aromatic monomers and conjugated dienes
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
  • C08L53/00—Compositions of block copolymers containing at least one sequence of a polymer obtained by reactions only involving carbon-to-carbon unsaturated bonds; Compositions of derivatives of such polymers
  • C08L53/02—Compositions of block copolymers containing at least one sequence of a polymer obtained by reactions only involving carbon-to-carbon unsaturated bonds; Compositions of derivatives of such polymers of vinyl-aromatic monomers and conjugated dienes
  • C08L53/025—Compositions of block copolymers containing at least one sequence of a polymer obtained by reactions only involving carbon-to-carbon unsaturated bonds; Compositions of derivatives of such polymers of vinyl-aromatic monomers and conjugated dienes modified
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
  • B29C71/00—After-treatment of articles without altering their shape; Apparatus therefor
  • B29C71/02—Thermal after-treatment
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29K—INDEXING SCHEME ASSOCIATED WITH SUBCLASSES B29B, B29C OR B29D, RELATING TO MOULDING MATERIALS OR TO MATERIALS FOR MOULDS, REINFORCEMENTS, FILLERS OR PREFORMED PARTS, e.g. INSERTS
  • B29K2009/00—Use of rubber derived from conjugated dienes, as moulding material
  • B29K2009/06—SB polymers, i.e. butadiene-styrene polymers
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29K—INDEXING SCHEME ASSOCIATED WITH SUBCLASSES B29B, B29C OR B29D, RELATING TO MOULDING MATERIALS OR TO MATERIALS FOR MOULDS, REINFORCEMENTS, FILLERS OR PREFORMED PARTS, e.g. INSERTS
  • B29K2096/00—Use of specified macromolecular materials not provided for in a single one of main groups B29K2001/00 - B29K2095/00, as moulding material
  • B29K2096/04—Block polymers
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29K—INDEXING SCHEME ASSOCIATED WITH SUBCLASSES B29B, B29C OR B29D, RELATING TO MOULDING MATERIALS OR TO MATERIALS FOR MOULDS, REINFORCEMENTS, FILLERS OR PREFORMED PARTS, e.g. INSERTS
  • B29K2105/00—Condition, form or state of moulded material or of the material to be shaped
  • B29K2105/0058—Liquid or visquous
  • B29K2105/0064—Latex, emulsion or dispersion
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
  • C08J2353/00—Characterised by the use of block copolymers containing at least one sequence of a polymer obtained by reactions only involving carbon-to-carbon unsaturated bonds; Derivatives of such polymers
  • C08J2353/02—Characterised by the use of block copolymers containing at least one sequence of a polymer obtained by reactions only involving carbon-to-carbon unsaturated bonds; Derivatives of such polymers of vinyl aromatic monomers and conjugated dienes

Definitions

• the present invention relates to high-strength films prepared from aqueous dispersions of block copolymers of vinyl aromatic monomers and conjugated dienes.
• Block copolymers of the conventional A-B-A type form strong films when cast from solutions in organic solvents.
• the use of aqueous dispersions or latices to form films or articles of intricate design is preferred to the use of casting from solutions because no objectionable fumes are released during the drying step.
• films of comparable thickness prepared by casting from their aqueous dispersions or latices are generally weak.
• U.S. Patent 3,360,599 taught the use of an annealing procedure. Disadvantageously, this annealing procedure requires elevated temperatures and/or long annealing times. As a consequence, the resulting films often have inferior strength properties, due to polymer degradation, and/or the time required for film formation is unacceptably long.
• U.S. Patent 4, 199,490 taught the addition of a second aqueous dispersion comprising a rubber, synthetic resin or a mixture thereof to enable the formation of films upon drying at room temperature. In the absence of such additive, the block copolymer dispersion did not possess adequate film forming properties at moderate or low temperatures.
• U.S. Patent 3,238,173 there was disclosed the preparation of concentrated aqueous dispersions by contacting the dilute latex with an aliphatic hydrocarbon that is a non-solvent for the non-elastomeric block, removing the hydrocarbon and concentrating the latex. The use of such non-solvents is undesirable, due to the added complexity of the process and the presence of residual organic contaminants in the resulting films.
• the present invention comprises an aqueous dispersion which is capable of forming a coherent, elastomeric, solid film which, after drying and annealing at 80°C for 30 minutes, demonstrates a tensile strength of about 1 1.0 M Pa or greater wherein the dispersion comprises (a) one or more block copolymer(s) corresponding to the formula
• each A is a polymer block consisting essentially of a monoviny lidene aromatic monomer and, ODtionally, a conjugated diene
• each B is a polymer block consisting essentially of a conjugated diene
• X isthe remnant of a multifunctional coupling agent
• m is O or 1
• n is an integer from 1 to 5
• each monovinylidene aromatic monomer block having a weight average molecular weight from 8,000 to 15,000 Daltons
• each conjugated diene block having a weight average molecular weight from 50,000 to 200,000 Daltons
• the present invention comprises an aqueous dispersion of a block copolymer, a process for preparing a coherent, elastomeric film from such aqueous dispersions, and the resulting films
• the block copolymer corresponds to the formula:
• each A is a polymer block of a monovinylidene aromatic monomer
• each B is a polymer block of a conjugated diene
• X is the remnant of a multifunctional coupling agent
• m is 0 or 1
• n is an integer from 1 to 5
• each monovinylidene aromatic monomer block having a weight average molecular weight from 5,000 to 20,000 Daltons
• each conjugated diene block having a weight average molecular weight from 40,000 to 240,000 Daltons
• the total A content being from 5 to 25 percent by weight of the block copolymer
• said A block having an effective phase volume from 10 to 18 5 percent of the block copolymer
• the invention comprises a high-strength film comprising the block copolymer described above, optionally, the diluent described hereinbefore and a residual amount of the surfactant described hereinbefore, wherein the film exhibits a tensile strength at break of about 1 1 0 Pa or greater after annealing at 80°C for 30 minutes
• the invention comprises a process for preparing a film which comprises (1) forming an aqueous dispersion from the block copolymer, water, diluent and surfactant as described hereinbefore, (2) depositing a coating of the aqueous dispersion to form a film, and (3) annealing the film under conditions such that the film exhibits tensile strength at break of about 1 1 0 MPa or greater after annealing at 80°C for 30 minutes
• the invention also comprises films prepared by the process described Surprisingly, such block copolymers readily form thin films by deposition onto solid surfaces from an aqueous dispersion Such films may be dried to form coherent, elastomeric, solid film articles having high annealed strength properties using short annealing times and mild annealing temperatures Examples of such articles include surgical gloves, examination gloves, condoms, catheters, balloons and other thin elastomeric articles If a tackifier and optionally other formulants known to one skilled in the art are combined
• block copolymers are t ⁇ block copolymers, that is, n in formula (I) is equal to 1
• the block copolymers may be partially tapered, fully tapered or untapered polymers
• tapered is meant that the B block changes gradually from diene rich or pure diene homopolymer in the center to include increasing proportions of monovinylidene aromatic monomer in a gradual conversion towards the junction of the monovinylidene aromatic block of the block copolymer and terminates in pure homopolymer of the monovinylidene aromatic monomer (the A block)
• the conversion may be symmetrical or unsymmet ⁇ cal with respect to the center of the B block T ⁇ block copolymers possessing taperness at only one junction are referred to as "half-tapered" polymers
• Preferable monovinylidene aromatic monomers for use herein include styrene and alkyl substituted derivatives of styrene Examples include styrene, ⁇ -methylstyrene, vinyl and toluene
• a more preferred monovinylidene aromatic monomer is styrene
• Conjugated dienes suitably employed in the present invention include 1 ,3-butad ⁇ ene, isoprene or mixtures thereof
• the conjugated diene is iso ⁇ rene
• the amount of monovinylidene aromatic monomer in the hydrocarbon phase is from 10 percent to 20 percent by weight
• the monovinylidene aromatic monomer block has a weignt average molecular weight from 8,000 to 15 000 Daltons, and the conjugated diene block has a weight average molecular weight from 50,000 to 120,000 Daltons
• the diene blocks' weight average molecular weight can range
• a blend of two or more block copolymers may be used in this invention All of the block copolymers used preferably have A blocks which have weight average molecular weights in the range of from 8,000 to 15,000
• the composition weighted average styrene content of the blended copolymers is preferably from 5 to 25 percent by weight
• One or more of the components may have a styrene content outside of the stated range, provided the average is within the stated range
• the styrene content be about 35 weight percent or less and, more preferably, about 30 weight percent or less
• the total amount of block copolymer having a styrene content above about 25 percent by weight is about 35 percent by weight or less and, more preferably, about 30 percent by weight or less
• the block copolymers can be blended in bulk and thereafter emulsified
• the block copolymers may be blended in bulk and thereafter emulsified
• the block copolymers may be blended in bulk and thereafter emulsified
• the one or more block copolymers may have an effective phase vol ume of the A block which is greater than desired
• a diluent may be blended with the block copolymer to reduce the effective phase volume of the A block in the hydrocarbon phase to the require ⁇ or desired level
• Diluents useful in the invention are materials which are compatible with the B block, that is, such diluents are soluble in the B block or form a single phase with the B block wnen the diluent is mixed with one or more block copolymers
• useful diluents do not degrade the properties of the films prepared from the aqueous emulsions of the invention such that the tensile strengths are less than 1 1 0 MPa when the films are annealed at 80°C for 30 minutes
• preferred diluents are hydrocarbon oils, naphthenic oils, polymers or oligomers derived from monomers having olefinic
• Effective phase volume or volume percent of the monovinylidene aromatic monomer blocks may be less than the weight percent of monovinylidene aromatic monomers in such copolymers Especially if one or more of the polymers is tapered, the monovinylidene aromatic monomer blocks are more compatible and therefore more soluble in the diene polymer phase of the resulting multiple phase structure compared to pure monovinylidene aromatic homopolymer blocks Due to such solubility, the volume of the phase segregated monovinylidene aromatic polymer is less than the content of such monovinylidene aromatic monomer expressed by weight Accordingly, the percentage of the monovinylidene aromatic monomer block in the block copolymer or hydrocarbon phase, measured as a volume percent, is less than the percentage thereof measured by weight In order to determine the volume percent of the monovinylidene aromatic polymer block, the corresponding weight percentage of monovinylidene aromatic monomer is divided by a correction factor The correction factor is a value equal to the sum of ratios of each monomer
• D a and D b are the respective densities of homopolymers, the monovinylidene aromatic monomer and diene monomer
• the effective phase volume of the A block in the hydrocarbon phase is represented by formula III
• Dd is the density of the diluent present
• the above numerator is further multiplied by a correction factor equal to 1-t (where ⁇ is the degree of taperness) to account for the isolated monovinylidene aromatic polymer content
• the degree of taperness in the block copolymer is the percentage of total monovinylidene aromatic polymer units that are isolated
• Such isolated monovinylidene aromatic polymer units are those segments of monovinylidene aromatic polymer surrounded on both sides by conjugated diene polymer units and are easily determined by the use of nuclear magnetic resonance spectroscopy as disclosed in Mochel, Rubber Chemistry and Technology, V 40, p 1200 (1967) Because such isolated polymer units do not contribute significantly to the phase represented by the monovinylidene aromatic polymer block, tapered block copolymers possess an effective monovinylidene aromatic polymer phase volume that is significantly less than the weight percent monovinylidene aromatic monomer content
• the tensile properties of the resulting films are unacceptably low
• the dispersion does not readily form films, especially at mild temperatures from 25°C to 90°C
• films from such polymers require longer periods of time under annealing conditions and/or higher annealing temperatures to achieve maximum tensile strength properties
• Such films are subject to polymer degradation resulting in films possessing poor tensile properties, especially ultimate tensile strength
• the weight average molecular weight (M w ) of the block copolymers is from 60,000 to 240,000 Daltons, more particularly, from 65,000 to 200,000 Daltons and, most preferably, from 70,000 to 200,000 Daltons
• the weight average molecular weight is preferably about 300,000 or less
• the technique employed is that of gel permeation chromatography (GPC) using polystyrene standards
• the B block of the block copolymers employed herein comprises a high 1 ,4-content polymer of a conjugated diene
• the 3,4-v ⁇ nyl functionality (or 1 ,2-v ⁇ nyl functionality in the case of butadiene) of the resulting conjugated diene polymer block is preferably below about 10 weight percent for blocks not containing butadiene or, in the case of blocks comprising butadiene, preferably below about 25 weight percent
• Block copolymers and techniques for their preparation are well-known in the art
• Such polymers may be prepared by sequential anionic polymerization utilizing alkyllithium initiators, such as n-butyllithium and sec-butyllithium They may also be prepared by coupling of living block copolymers or by using soluble difunctional lithium initiators such as 5 1 ,3-phenylene-b ⁇ s(3-methyl-1 -phenylpentyl ⁇ dene)-b ⁇ s-(l ⁇ th ⁇ um), or similar initiator as disclosed in U S Patent 4, 196, 154
• the block copolymers may be tapered or untapered That ⁇ s, the junction between the separate blocks may be gradual or abrupt Untapered block copolymers may be formed by completely polymerizing each monomer component before adding the next block forming monomer to the reaction medium containing the living polymer anion Tapered 0 block copolymers may be formed by copolyme ⁇ zing a mixture of the monomers using the previously mentioned difunctional initiators Due
• the surfactant is present in a sufficient amount to emulsify the block copolymer(s) and optional diluent If too much surfactant is used to prepare the aqueous emulsions, films prepared from the aqueous emulsions will not demonstrate the desired tensile properties The reason is that a significant amount of the surfactant will remain in the film which is formed from the aqueous emulsion
• the maximum amount of surfactant useful is related to how much surfactant is retained in the film More than this amount may be used if the excess portion is removed prior to film formation or can be leached from the film prior to annealing
• about 0 5 percent by weight or more of surfactant is present and, more preferably, 1 percent by weight or more is present and, even more preferably, about 2 percent by weight or more is present
• about 10 percent by weight or less surfactant is used, more preferably, about 8 percent by weight is used and, even more preferably, about 6 percent by weight or less is used
• the film thickness is determined by the ultimate use
• the desired film thickness 0 for the uses for which the films of the invention may be used are well-known in the art
• the films have a thickness of about 13 mm or greater and, more preferably, about 20 mm or greater
• the films are about 3 0 mm or less and, most preferably, about 30 mm or less
• the films of this invention preferably exhibit a tensile strength at oreak of about 1 1 0 MPa or greater after annealing at 80°C for about about 30 minutes More 5 preferably, the films exhibit a tensile strength of about 16 5 MPa or greater and, most preferably, about 22 MPa or greater when annealed under such conditions
• Films having adhesive properties may be prepared by incorporating a suitable tackifier, usually a low molecular weight organic polymer such as a polyterpene or similar compound, in the film Additional formulants such as oils may also be added to modify the 0 adhesive properties of the resulting film
• the tackifiers and other formulants may be added to the polymer solution or incorporated into the latex
• the resulting modified latex may be further concentrated and coated onto a substrate such as a masking tape backing
• the substrate/film combination may thereafter be dried and optionally annealed to form the final product 5 Having described the invention, the following examples are provided as further illustration and are not to be construed as limiting Unless stated to the contrary, parts and percentages are expressed on a weight basis Effective phase volumes were calculated using the previously disclosed formulae (II and III) For such calculations, the densities of the Example 1 Films of Styrene/lsoprene/Styrene Block Copolymer
• An aqueous dispersion was formed from a cyclohexane solution of a
• films having good tensile strength properties can be formed according to the present invention without the use of additives such as additional copolymer latices or aliphatic solvents even at relatively low annealing temperatures from 40°C to 80°C
• Length A dispersion was made from a styrene/isoprene/ styrene block copolymer having M w of 205,000 Daltons and having a styrene content of 1 5 weight percent and 13 volume percent
• the polystyrene endblocks had molecular weights of 15,300 Daitons
• the polyisoprene centerblock molecular weight was 174,000 Daltons
• Tne dispersion used in making the films had a solids content of 54 weight percent
• the films were annealed at 80°C for the times identified in Table II Film formation ana testing were according to the techniques of Example 1 Results are contained in Table II
• a dispersion of a styrene-isoprene-styrene block copolymer was prepared as in
• Example 1 The tr ⁇ block copolyme r had a M w of 85,000 Daltons and had a styrene content of 16 weight percent and 15 volume percent The polystyrene endblock molecular weight was 6800
• the polyisoprene block molecular weight was 71 ,000 Daltons
• Film samples were prepared by deposition onto glass and annealed at 80°C, as in Example 1 Results are contained in Table III
• Example 1 A dispersion of a four-armed styrene-isoprene block copolymer coupled with silicon tetrachlonde was prepared as in Example 1
• the polymer had an apparent molecular weight by gel permeation chromatography (GPC) of 227,000 Daltons
• the styrene content was 15 weight percent, 13 2 volume percent
• the polystyrene endblock weight average molecular weight was 1 1 ,300 Daltons
• the polyisoprene radial block apparent weight average molecular weight was 182,000 Daltons
• Film samples were prepared by deposition onto glass and annealed and tested as in Example 1 Results are combined in Table IV
• Films of a symmetrically tapered styrene-isoprene-styrene block copolymer containing 26 weight percent styrene, an overall molecular weight (M w ) of 228,000 Daltons, a measured isolated styrene is 52 percent and effective phase volume styrene content of approximately 1 1 percent were prepared as in Example 1
• the polystyrene endblock molecular weight was measured by degradation analysis and GPC to be 9700 Daltons Films were cast on glass slides, dried at room temperature and annealed as in Example 1 Strength properties were tested according to ASTM-D-412 after annealing at 80°C and at various temperatures Results are contained in Tables VA and VB Table VA Strenqth as a Function of Annealing Time minutes 0 4 1 6 30
• Dispersions were prepared from a toluene solution of a styrene/butadiene/styrene triblock copolymer.
• the polymer weight average molecular weight was approximately 100,000 Daltons.
• the polystyrene content was 30 weight percent, 29 volume percent.
• the polystyrene endblock molecular weight was 15,000 Daltons.
• the polybutadiene block molecular weight was 70,000 Daltons.
• a dispersion was prepared from a cyclohexane solution of KratonTM 1 1 1 1 1 styrene-isoprene-styrene block copolymer containing nominally 22.7 percent styrene having a molecular weight of 147,000 and styrene endblock length of 16,700.
• the film was annealed at 80°C for various times, the results are compiled in Table VI.
• a dispersion was made from a cyclohexane solution containing 35 percent by weight of a styrene-isoprene-styrene block copolymer containing 18 percent by weight polystyrene (15 9 volume percent) with the structure polystyrene-polyisoprene-polystyrene being 10,000-1 10,000-10,000
• This solution was dispersed into water using A pal TM CO-436 surfactant at a level of 3 0 percent by weight based on polymer solids
• the solvent was removed under vacuum to give a dispersion that was 59 percent by weight solids
• Films were cast onto glass plates in two layers and dried 2-16 hours at room temperature to provide a dried film thickness of approximately 25 mm These films were cut into samples, annealed at 80°C for various times and tested according to ASTM-D-412 The results are compiled in Table VIII
• Example 1 A dispersion of styrene-isoprene-styrene block copolymers was prepared as in Example 1 Polymer A was 14 percent styrene (12 4 volume percent styrene) with a structure polystyrene-polyisoprene-polystyrene of 9500-109,000-9500. Polymer B was 15 percent styrene (13.2 volume percent styrene) with a structure polystyrene-polyisoprene-polystyreneof 15,300-154,400-15,300. Film samples were prepared on glass and annealed as described in Example 1. The results are compiled in Table IXA.
• a dispersion was prepared from a cyclohexane solution of a styrene-butadiene-styrene triblock copolymer containing 17 weight percent styrene having a molecular weight of 145,000. This corresponds to 16.5 volume percent styrene.
• the molecular weight of the polystyrene endblocks was 12,300. After drying at room temperature, samples of the film were annealed in a forced-air oven at 80°C for various times. The results are compiled in Table X.
• Example 8 Dispersions were prepared from both toluene and cyclohexane solutions of a styrene-isoprene-styrene triblock copolymer containing 15 weight percent styrene. This corresponds to 13.2 volume percent styrene. After drying at room temperature, samples were annealed in a forced-air oven at 80°C for various times. This shows that either aliphatic or aromatic solvents may be used to prepare dispersions which anneal to high strengtns. The results are compiled in Table XI.

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• 1994
  • 1994-01-06 CA CA002150482A patent/CA2150482A1/en not_active Abandoned
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