Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Reissue Patent
1999-07-15
2001-01-30
Cain, Edward J. (Department: 1714)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Processes of preparing a desired or intentional composition...
C524S357000, C524S401000, C524S428000, C524S504000, C524S505000, C524S523000
Reissue Patent
active
RE037036
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to polymer blends useful, e.g., as adhesives, primers, inks, and paints.
2. Description of the Background Art
Low surface energy substrates such as polyethylene, polypropylene, and other polyolefins are characterized as having critical surface tensions of wetting of about 35 dynes/cm or less. Such surfaces are generally unreceptive to inks, paints, and adhesives due to their poor wettability. There is a need to improve adhesion to such surfaces, as well as to high energy surfaces.
SUMMARY OF THE INVENTION
The present invention relates to a blend comprising (a) a modified block copolymer comprising (i) a polystyrene block and (ii) a polydiene block or a hydrogenated polydiene block, said polydiene block or hydrogenated polydiene block being modified to contain an average of one or more carboxyl groups; (b) a polymer comprising a polymerization reaction product of two or more mono-ethylenically unsaturated monomers in which (i) at least one of the monomers is an acrylic or methacrylic acid ester of a non-tertiary alcohol having 1 to 14 carbon atoms, inclusive and (ii) at least one of the monomers has carboxylic acid functionality and is present in an amount ranging from about 1 to about 15 parts by weight, based on 100 parts by weight of polymer (b); polymer (b) does not comprise a nitrogen-containing monomer.
The invention also relates to a method of priming a substrate comprising applying to the substrate a blend comprising (a) a modified block copolymer comprising (i) a polystyrene block and (ii) a polydiene block or a hydrogenated polydiene block, said polydiene block or hydrogenated polydiene block being modified to contain an average of one or more carboxyl groups; (b) a polymer comprising a polymerization reaction product of two or more mono-ethylenically unsaturated monomers in which (i) at least one of the monomers is an acrylic or methacrylic acid ester of a non-tertiary alcohol having 1 to 14 carbon atoms, inclusive and (ii) at least one of the monomers has carboxylic acid functionality and is present in an amount ranging from about 1 to about 15 parts by weight, based on 100 parts by weight of polymer (b); polymer (b) does not comprise a nitrogen-containing monomer.
In particular, the present invention also relates to a method of enhancing adhesion between a substrate and an adhesive (for example, a pressure-sensitive adhesive, a thermosetting adhesive, a thermoplastic adhesive) comprising the steps of priming said substrate by applying to said substrate a blend comprising (a) a modified block copolymer comprising (i) a polystyrene block and (ii) a polydiene block or a hydrogenated polydiene block, said polydiene block or hydrogenated polydiene block being modified to contain an average of one or more carboxyl groups; (b) a polymer comprising a polymerization reaction product of two or more monoethylenically unsaturated monomers in which (i) at least one of the monomers is an acrylic or methacrylic acid ester of a non-tertiary alcohol having 1 to 14 carbon atoms, inclusive and (ii) at least one of the monomers has carboxylic acid functionality and is present in an amount ranging from about 1 to about 15 parts by weight, based on 100 parts by weight of polymer (b); polymer (b) does not comprise a nitrogen-containing monomer; and applying an adhesive to the primed substrate. In some preferred embodiments, the substrate is a low energy substrate. As used herein, “low energy substrate” refers to a substrate having a critical surface tension of wetting no greater than about 35 dyncs/cm. Examples include polyolefin polymers such as polyethylene and polypropylene.
The invention provides polymer blends that exhibit good adhesion to both low energy surfaces (e.g., polyolefins such as polyethylene and polypropylene), as well as higher energy surfaces (i.e., having surface energies greater than 35 dynes/cm such as metal and glass). The blends are useful as primers (e.g., for paints and coatings), adhesives (e.g., for use as tie layers), pressure sensitive adhesives, inks, and paints.
DETAILED DESCRIPTION OF THE INVENTION
The invention features blends comprising (a) a modified block copolymer and (b) a polymer, as set forth in the Summary of the Invention section.
The block copolymer comprises one or more polystyrene blocks. If one or two polystyrene blocks are present, the block copolymer can be designated as an AB block copolymer (containing one polystyrene block) and an ABA block copolymer (containing two polystyrene blocks), “A” designating polystyrene and “B” designating polydiene or hydrogenated polydiene.
Examples of a polydiene block or hydrogenated polydiene block include, e.g., a polybutadiene, polyisoprene, ethylene/butylene, or ethylene/propylene block. The term “polydiene” refers to repeating units of a diene monomer. The hydrogenated polydiene block preferably has a residual unsaturation of less than 10%, more preferably less than 5%, based on the original amount of ethylenic unsaturation of the polydiene block. Examples of compounds which may be reacted with the polydiene block or the hydrogenated poly diene block to provide the substituent carboxyl groups include carboxylic acids and anhydrides (e.g., maleic acid and maleic anhydride).
A particularly preferred block copolymer is a maleated styrene-ethylene/butylene-styrene block copolymer. The term “maleated” means that the polydiene or hydrogenated polydiene block is modified, for example, with maleic acid or maleic anhydride so that the polydiene or hydrogenated polydiene block contains an average of one or more carboxyl groups. An example of a preferred copolymer is a styrene-ethylene/butylene-styrene triblock copolymer containing 2% by weight succinic anhydride (the source of the carboxyl groups) (commercially available from Shell Chemical Company, Houston, Tex., under the trade designation “Kraton FG-1901X”). “Kraton FG-1901X” has a tensile strength of about 5000 psi, a percent elongation of about 500, a Shore A hardness of about 75, a specific gravity of about 0.91, and a Brookfield viscosity of about 1250 cps at 77° F. (25° C.).
Block copolymer (a) has a ratio, by weight, of polystyrene block to polydiene block or hydrogenated polydiene block typically ranging from about 5:95 to 95:5, preferably 10:90 to 50:50.
Polymer (b) comprises a polymerization reaction product of two or more mono-ethylenically unsaturated monomers in which (i) at least one of the monomers is an acrylic or methacrylic acid ester of a non-tertiary alcohol having 1 to 14 carbon atoms, inclusive and (ii) at least one of the monomers has carboxylic acid functionality and is present in an amount ranging from about 1 to about 15 parts by weight, based on 100 parts by weight of polymer (b); and polymer (b) does not comprise a nitrogen-containing monomer.
The non-tertiary alcohol preferably includes methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 1-pentanol, 2-pentanol, 3-pentanol, 2-methyl-1-butanol, 1-methyl-1-butanol, 1-methyl-1-pentanol, 2-methyl-1-pentanol, 3-methyl-1-pentanol, 2-ethyl-1-butanol, 3,5,5-trimethyl-1-hexanol, 3-heptanol, 2-octanol, 1-decanol, or 1-dodecanol. A particularly preferred ester monomer is iso-octyl acrylate.
In a preferred embodiment, the homopolymer of the acrylic or methacrylic acid ester has a T
g
less than 20° C. A polymeric moiety having a T
g
greater than 20° C., a weight average molecular weight above 2,000, and capable of associating with one or more of the blocks of the block copolymer (e.g., a polystyryl moiety as described in Groves, U.S. Pat. No. 5,143,972 entitled “Pressure-Sensitive Adhesive Composition” which is hereby incorporated by reference) may be polymerized with the acrylic or methacrylic acid ester portions of the polymer. In this case, association is believed to occur between this polymeric moiety and the phenyl groups of the styrene blocks.
Examples of monomers having carboxylic functionality include acrylic acid, methacrylic acid, itaconic acid, maleic acid, maleic anhydride, fumaric acid, and citraconi
3M Innovative Properties Company
Cain Edward J.
Hayworth Melissa M.
Knecht Harold C.
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