MXPA98009100A - Imprimation coating for reinforced tapes with poliolef - Google Patents

Abstract

A primer coating composition for use in pressure sensitive tape with polyolefin reinforcement comprising a modified chlorinated polyolefin of maleic anhydride covalently bonded to a modified maleic anhydride thermoplastic copolymer is disclosed. A pressure sensitive tape with polyolefin reinforcement employing the primer coating composition and a method for manufacturing a pressure sensitive tape with polyolefin reinforcement employing the primer coating composition.

Description

IMPRIMATION COATING FOR REINFORCED TAPES WITH POLIOLEFIN BACKGROUND OF THE INVENTION The present invention relates to a primer composition for coating pressure sensitive tapes reinforced with polyolefin to improve the bond between the polyolefin substrate and the adhesive. Polyolefins, particularly polypropylene, are useful as a reinforcing material for the pressure sensitive tape. However, polyolefins usually have a very low surface energy which makes it difficult to securely apply a coating such as a pressure sensitive adhesive (PSA) to the surface of the polyolefin substrate. Traditionally, the surface of the polyolefin substrate is treated with, for example, corona discharge to increase the surface energy of the substrate. This treatment improves the bond between the adhesive and the substrate, but only to a limited extent. Chlorinated polyolefin primer coatings have also been employed in the pressure sensitive adhesive tape reinforced with polypropylene. While these primer coatings adhere well to the polypropylene substrate, they do not bond well to pressure sensitive adhesives. Accordingly, it is convenient to provide a pressure sensitive adhesive tape reinforced with polypropylene which exhibits improved bonding between the polypropylene substrate and the pressure sensitive adhesive. SUMMARY OF THE INVENTION According to the invention, a primer coating composition for use in a pressure-sensitive adhesive tape reinforced with polyolefin comprises a chlorinated functionalized polyolefin of maleic anhydride, a functionalized thermoplastic copolymer of maleic anhydride and at least an interlacing compound. The chemical composition of the functionalized chlorinated maleic anhydride polyolefin and the functionalized maleic anhydride thermoplastic copolymer are different and it is assumed that in the film formation reaction process, similar groups associate and subsequently form a two-layer film. In this two-ply film, the functionalized chlorinated maleic anhydride polyolefin significantly improves the adhesion of the primer to the polyolefin substrate and the functionalized maleic anhydride thermoplastic copolymer significantly improves primer adhesion of the primer to the pressure sensitive adhesive thereby providing a tape pressure sensitive reinforced with polyolefin where the adhesive bonds securely to: polyolefin substrate. According to the invention, the maleic anhydride functional groups of the chlorinated polyolefin and the thermoplastic copolymer react with the crosslinking compounds.

Accordingly, it is an object of the invention to provide a pressure sensitive adhesive tape reinforced with polyolefin having a substantially improved bond between the reinforcing layer and the adhesive. It is another object of the invention to provide a primer coating composition applied between the polyolefin backing and the adhesive wherein the bonding of the adhesive to the backing is substantially improved. It is still another object of the invention to provide a method for manufacturing a polyolefin reinforced pressure-sensitive adhesive tape wherein the bond between the reinforcement and the adhesive is substantially improved. DETAILED DESCRIPTION OF THE INVENTION The primer coating composition of the invention comprises a functionalized chlorinated polyolefin of maleic anhydride covalently bonded to a functionalized thermoplastic copolymer of maleic anhydride by reacting the functional groups of maleic anhydride on the chlorinated polyolefin and the thermoplastic copolymer with at least one entanglement compound such that the functionalized chlorinated polyolefin of maleic anhydride and the copolymer Functionalized thermoplastic maleic anhydride form an interlaced layer. The primer coating composition is useful in the application of various coatings to a substrate having a very low surface energy such as polyolefin films. The two-layer primer coating composition is particularly useful in pressure-sensitive adhesive tapes reinforced with polypropylene to improve the bond between the polypropylene backing and the adhesive. Usually, the pressure-sensitive adhesive tape reinforced with polyolefin is manufactured by applying, to a surface of a polyolefin substrate, a primer coating composition comprising a functionalized chlorinated polyolefin of maleic anhydride, a functionalized thermoplastic copolymer of maleic anhydride, and by at least one entanglement compound wherein the maleic anhydride functional groups on the chlorinated polyolefin and the thermoplastic copolymer react with the entanglement compounds such that the functionalized chlorinated maleic anhydride polyolefin is covalently bound to the functionalized maleic anhydride copolymer and applies a pressure sensitive adhesive to the polyolefin substrate so that the coating composition of the initiator resides between the polyolefin substrate and the pressure sensitive adhesive. Typically, the primer coating composition comprises from about 20 to 80 wt.% Dry of functionalized chlorinated maleic anhydride polyolefin and about 20 to 80 wt.% Of functionalized maleic anhydride thermoplastic copolymer and + 40% of a stoichiometric ratio of crosslinking compound to form reactive sites of anhydride. The primer coating can be applied to the polyolefin substrate according to standard procedures for example using a rotogravure coater. Preferably, the primer coating is applied to the polyolefin substrate at a coating weight of about 0.22 to 3.5 kg / ream (10000m). The chlorinated polyolefin component of the functionalized chlorinated maleic anhydride polyolefin is intended to include chlorinated polyethylene, chlorinated polypropylene, chlorinated polybutene, and the like. It may be convenient to choose the functionalized chlorinated maleic anhydride polyolefin on the substrate or reinforcement for the pressure sensitive tape. For example, a functionalized chlorinated polyethylene of maleic anhydride with a polyethylene support can be used. Typically, the functionalized chlorinated maleic anhydride polyolefin will contain about 0.1 to 10% by weight of maleic anhydride [or other functionality measurement], have a chlorine content of about 10 to 50% by weight and have a molecular weight on the scale of approximately 1,000 to 500,000. Representative examples of modified chlorinated polyolefins of maleic anhydride contain Hypalon CP 826 available from DuPont and Eastman CP-343-1 available from Eastman Chemical Company. The functionalized maleic anhydride thermoplastic copolymer component should be compatible with the adhesive used in the pressure-sensitive adhesive tape of the invention and. normally, it includes a block copolymer A-B-A wherein A represents a thermoplastic polystyrene and B represents a middle block of polyisoprene rubber, polybutadiene, poly (ethylene / butylene), etc. Typically, the functionalized maleic anhydride thermoplastic polymer contains from about 1 to 5% by weight of maleic anhydride. A particularly useful functionalized thermoplastic copolymer is Kraton FG19OIX, a functionalized maleic anhydride rubber available from Shell Development Co. Houston, Texas. In addition to the functionalized chlorinated maleic anhydride polyolefin and the functionalized maleic anhydride thermoplastic copolymer, the primer coating composition contains at least one entanglement compound capable of reacting with the maleic anhydride functionality. As crosslinking agents, the polyfunctional isocyanates such as methanediphenyl diisocyanate, toluene diisocyanate, polyaromatic polyisocyanates, polyether polyisocyanates (average molecular weight of about 700-5,000), polyester polyisocyanates (average molecular weight of about 700 - 5,000), polyamides such as diethylenetriamine, triethylenetetramine, N-aminoethylpiperadine, diaminophenylmethane, metaphenylenediamine, polyamide resins having an amine value of about 200 to 400, melamines such as trimethylol melamine, hexamethylol melamine, alkylated methylol melamines (eg, methyl-methylol melamine, ethyl-methylol melamine or butyl) -methylol melamine), polyfunctional epoxy resins having an average molecular weight of 800 to about 4,000, a smoothing point of about 60 ° C to about 160 ° C and an epoxy equivalent of about 400 to 3,000 can be used. The entanglement agent is present in the primer coating composition in an amount to provide an effective interlacing bond between the functionalized chlorinated maleic anhydride polypropylene and the functionalized maleic anhydride thermoplastic copolymer. Normally, the crosslinking agent is present in an amount of about + 40% of a stoichiometric ratio of the crosslinking compound to the reactive sites of maleic anhydride. In a preferred aspect of the invention, the primer coating composition contains an activator that improves the crosslinking reaction. Useful activators include para-toluene sulphonic acid, hydrochloric acid, phosphoric acid or any Bronsted acid which is capable of lowering the pH of the coating to a value of 0.5-5.0. The substrate of the pressure sensitive tape can be any of the materials commonly used in the industry and typically include biaxially oriented polypropylene (PPOB), machine oriented polypropylene (PPOM), polyethylene, polyethylene teraphthalate (PET) and Similar. Preferably, the support of biaxially oriented polypropylene or polypropylene oriented in the machine direction. Conventional pressure sensitive adhesives may be used in the tape of this invention. A representative example of a suitable adhesive is described in the U.S. Patent. No. 3,239,478, incorporated herein by reference. EXAMPLE In a typical example of the pressure-sensitive adhesive tape with polyolefin reinforcement of the invention, a machine-oriented polypropylene (PPOM) reinforcement of 101.6 μm is coated with a primer coating composition using a coating method of rotogravure The primer coating contains 6.20% by weight of Hypalon CP826 (a modified chlorinated polypropylene of maleic anhydride from DuPont). 80.81% by weight of toluene, 3.10% 3n by weight of Cymel 303 (an American Cyanamid melamine crosslinking agent), 3.10% by weight of Kraton FG1901X (maleic anhydride modified ethylene / butadiene-styrene (block copolymer of Shell rubber S-EB-S), 0.26% by weight of para-toluenesulfonic acid and 0.63% by weight of Rubinate M (a polymeric MDI available from ICi Polyurethanes, used as a secondary entanglement agent). an oven at 132.2 ° C for 30-90 seconds before applying the adhesive A layer of SIS block copolymer pressure sensitive adhesive is coated on the primer-coated polypropylene substrate. 7.5 kg / ream (10000 m) Having described the intention in detail and by reference to the particular embodiments thereof, numerous modifications and variations will be possible without departing from the scope of the invention as defined by the following claims.

Claims (22)

1. CLAIMS 1. A primer coating composition for use in a pressure sensitive tape with polyolefin reinforcement, the composition comprising a functionalized chlorinated maleic anhydride polyolefin, a functionalized maleic anhydride thermoplastic copolymer and at least one entanglement agent. The composition of claim 1, wherein the functionalized chlorinated maleic anhydride polyolefin is covalently bonded to the functionalized maleic anhydride thermoplastic copolymer to form a bilayer. The composition of claim 2, wherein the entanglement agent is melamine-formaldehyde resin, a polyfunctional isocyanate, a polyamide, a polyamide resin or a polyfunctional epoxy resin. 4. The composition of claim 1, wherein the composition additionally contains an activator. The composition of claim 4, wherein the activator is para-toluene sulphonic acid, hydrochloric acid, phosphoric acid, or any Bronsted acid that is capable of lowering the pH of the coating to a value of 0.5-5.0. The composition of claim 1, wherein the composition comprises from about 20 to 80% by weight of functionalized chlorinated maleic anhydride polyolefin from about 20 to 80% by weight of functionalized maleic anhydride copolymer and about + 40% by weight. a stoichiometric ratio of crosslinking agent to reactive sites of maleic anhydride. The composition of claim 1, wherein the maleic anhydride functionalized chloride polyolefin is a chlorinated polypropylene functionalized maleic anhydride. 8. A pressure sensitive tape with polyolefin reinforcement comprises: a polyolefin substrate; a release liner; a pressure sensitive adhesive; and a primer coating composition between the polyolefin substrate and the pressure sensitive adhesive, the composition comprising a functionalized chlorinated maleic anhydride polyolefin, a functionalized maleic anhydride thermoplastic copolymer, and a coating agent. 9. The tape of claim 8, wherein the functionalized chlorinated maleic anhydride polyolefin is covalently bonded to the functionalized maleic anhydride thermoplastic copolymer to form a bilayer, the functionalized chloralised polyolefin layer of maleic anhydride of the bilayer forming a bond with the polyolefin substrate at the interface thereof, and the functionalized thermoplastic maleic anhydride copolymer layer of the bilayer forming a bond with the adhesive at the interface thereof. 10. The tape of claim 8, wherein the entanglement agent is melamine-formaldehyde resin, a polyfunctional isocyanate, a polyamide, a polyamide resin, or a polyfunctional epoxy resin. The tape of claim 8, wherein the composition additionally contains an activator. 12. The tape of claim 11, wherein the activator is a para-toluenesulfonic acid. The tape of claim 8, wherein the functionalized maleic anhydride polyolefin is a functionalized maleic anhydride polypropylene. A method for manufacturing a pressure sensitive tape with polyolefin reinforcement comprising: providing polyolefin substrate, a release coating, applying to a surface of the polyolefin substrate a primer coating, the primer coating comprising a chlorinated polyolefin functionalized maleic anhydride, a functionalized maleic anhydride thermoplastic copolymer and an entanglement agent; and applying a pressure sensitive adhesive to said polyolefin substrate having the initiator coating applied so that the initiator coating resides between the polyolefin substrate and the pressure sensitive adhesive. 15. The method of claim 14, wherein the entanglement agent is a melamine-formaldehyde resin, a polyfunctional isocyanate, a polyamide, a polyamide resin or a polyfunctional epoxy resin. 16. The method of claim 14, wherein the reaction of the crosslinking compounds is activated by an activator. 17. The method of claim 16, wherein the activator is para-toluene sulphonic acid. The method of claim 14, wherein the maleic anhydride functional groups on the functionalized chlorinated maleic anhydride polyolefin and the functionalized maleic anhydride thermoplastic copolymer react with the crosslinking agent to form a bilayer, the functionalized chlorinated polyolefin layer of maleic anhydride of the bilayer forming a bond with the polyolefin substrate at the interface thereof and the functionalized thermoplastic maleic anhydride copolymer layer of the bilayer forming a bond with the adhesive at the interface thereof. The method of claim 14, wherein the primer coating comprises about 20 to 80% by weight of functionalized chlorinated maleic anhydride polyolefin, about 20 to 80% by weight functionalized maleic anhydride copolymer, and about + 40% of a stoichiometric ratio of the crosslinking compounds to reactive sites. 20. The method of claim 16, wherein the primer coating comprises approximately one activator that is capable of lowering the pH of the coating to a value of 0.5-5.0. The method of claim 14, wherein the functionalized chlorinated maleic anhydride polyolefin is functionalized chlorinated polypropylene maleic anhydride. 22. The method of claim 14, wherein the primer coating composition is applied at a coating weight of about 0.22 to 1.35 kg / ream (10000 m).