Classifications

• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
  • C08F265/00—Macromolecular compounds obtained by polymerising monomers on to polymers of unsaturated monocarboxylic acids or derivatives thereof as defined in group C08F20/00
  • C08F265/04—Macromolecular compounds obtained by polymerising monomers on to polymers of unsaturated monocarboxylic acids or derivatives thereof as defined in group C08F20/00 on to polymers of esters
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
  • C08F255/00—Macromolecular compounds obtained by polymerising monomers on to polymers of hydrocarbons as defined in group C08F10/00
  • C08F255/02—Macromolecular compounds obtained by polymerising monomers on to polymers of hydrocarbons as defined in group C08F10/00 on to polymers of olefins having two or three carbon atoms

Definitions

• the present invention is directed to
• substantially non-crossl inked ethylene-methylaerylate copolymers grafted with a grafting agent as well as processes for their preparation.
• an ethylene-methylacrylate copolymer is combined with a grafting agent and a free-radical initiator under conditions sufficient to cause
• Such grafted copolymers are particularly useful as barrier layers and have particular utility in food packaging, etc. Moreover, because of their enhanced adhesion properties these grafted copolymers can be attached to aluminum foil which can then be used as food wraps. In the preparation of these grafted
• the grafting is generally conducted by employing a free-radical
• initiator generally in amounts exceeding 1 percent by weight relative to the polymer.
• grafted products are preferably prepared in an extruder in order to achieve higher product quality as well as to minimize costs. See, for instance, "Modern Plastics", July 1985, pages 56 et seq.
• extruder reactions are by necessity done in the absence of solvent. Thus lies the heart of the problem.
• solvents In order to obtain the benefits of products prepared in the extruder it is necessary to avoid the use of solvents; on the other hand, the absence of solvents results in levels of crosslinking which renders the product
• substantially non-crosslinked grafted polymers can be prepared from either reaction in a solvent, see, for instance, Poreiko et al., Journal of Polymer Science, A-I, 5, 1563 (1967), or from solvent extraction of a crosslinked and non-crosslinked mixture.
• solvents in process preparations necessitates that such processes not be conducted in an extruder.
• organic solvents in either process preparation or in extraction processes poses environmental hazards and remaining traces of the organic solvent are invariably retained in the grafted product which can leach from the product over a period of time. This latter problem is particularly troublesome where the product is in contact with food stuffs and may result in the incorporation of trace amounts of organic solvents into the foodstuff which when
• a particularly useful copolymer that finds application in foodwraps, etc. is a copolymer of ethylene and methacrylate.
• a grafting agent such as maleic
• the resulting product has enhanced adhesion properties which not only allows it to be bound to aluminum but additionally allows for printing to be done on its surface.
• the present invention is directed to
• the present invention is directed to a process which comprises combining in the absence of a solvent an ethylene-methylacrylate copolymer, a grafting agent, and a free-radical initiator wherein the concentration of the free-radical initiator in the reaction mixture is
• the present invention is directed to a process for preparing a substantially non-crosslinked maleic anhydride grafted ethylene-methylacrylate copolymer which comprises a) combining in an extruder in the absence of solvent
• concentration of maleic anhydride in the reaction mixture is maintained at about 2.0 weight percent or less relative to the
• a free-radical initiator wherein the concentration of said free-radical initiator in the reaction medium is maintained at less than about 0.2 weight percent relative to the copolymer of i) above, under conditions sufficient to cause decomposition of the free- radical initiator and above both the ceiling- temperature of the grafting agent and the melt temperature of the polymer; and b) removing any unreacted maleic anhydride from the grafted copolymer.
• the present invention is directed to a
• ethylene-methylacrylate copolymer free of grafting solvent and substantially free of nitrogen, phosphorus, and sulfur.
• ethylene- methylacrylate copolymers as well as to processes for their preparation.
• a free-radical initiator i.e., less than about 0.2 weight percent relative to the copolymer
• this result appears to be specific for the ethylene-methylacrylate copolymer insofar as the use of other polymers or copolymers in place of ethylene-methylacrylate copolymer in the process of this invention results in
• Ethylene-methylacrylate copolymers - - refer to copolymers of ethylene and
• methylacrylate methylacrylate.
• the specific ethylene-methylacrylate copolymer employed in the process of the present invention is not critical and can include copolymers containing high weight percentages of methylacrylate or high weight percentages of ethylene. However, preferably, these copolymers contain from about 10-60 weight percent methylacrylate and from about 90-40 weight percent ethylene; and more preferably from about 15-30 weight percent methylacrylate and 85-70 weight percent ethylene. Suitable copolymers
• melt index of about 0.1 to about 200; preferably from about 1 to 30; and more preferably from about 2 to 10.
• suitable ethylene-methylacrylate copolymers can also contain stabilizers, such as UV stabilizers, anti-oxidants, coloring agents, etc., as well as minor amounts, i.e., 5% or less, of one or more saturated or unsaturated hydrocarbon components, such as propylene, butylene, hexa-1,4-diene, etc., provided that these additional components do not alter the basic properties of the
• copolymer including its reaction properties set forth in the present invention.
• the copolymer contains no more than adventurous amounts of such saturated or unsaturated components.
• Suitable copolymers are commercially available. For example, a suitable copolymer containing about 80 weight percent ethylene and 20 weight percent
• methylacrylate is available as PE-2207 from Chevron Chemical Company, San Francisco, Ca.
• the preparation of ethylene-methylacrylate copolymers is disclosed in U.S. Patent No.
• ethylene-methylacrylate copolymers are ethylene-methylacrylate copolymers obtained by chemical modification of the base copolymer, e.g., chlorosulfonated, chlorinated, oxidized, etc., ethylene-methylacrylated copolymers.
• “Grafting agent” - - refers to a conjugated unsaturate carboxylic acid or anhydride compound capable of undergoing addition to saturated hydrocarbon polymers, copolymers, terpolymers, etc., in the presence of a free-radical initiator. Such saturated hydrocarbon polymers, copolymers, terpolymers, etc., in the presence of a free-radical initiator. Such saturated hydrocarbon polymers, copolymers, terpolymers, etc., in the presence of a free-radical initiator. Such saturated
• hydrocarbons can include minor amounts of unsaturation, i.e., 5% or less, and include hydrocarbon polymers such as polyethylene, polypropylene, polybutylene,
• Suitable grafting agents include maleic anhydride. acrylic acid, methacrylic acid and the like. Other suitable grafting agents are well known in the art. It is also contemplated that the grafting agent can be mixed with other materials.
• grafting agents are maleic anhydride and acrylic acid; with maleic anhydride being particularly preferred.
• Maleic acid may be used in lieu of maleic anhydride in reactions carried out at about 140oC or higher since the acid is converted to the anhydride under these conditions.
• the resultant polymer has carboxyl functionality (as either the free acid groups or as the anhydride in the case of maleic anhydride) which imparts improved adhesion properties to the polymer.
• Gramted ethylene-methylacrylate copolymer - - refers to the product obtained by the addition of a grafting agent to the ethylene-methylacrylate copolymer in the presence of a free-radical initiator. In general, the addition of the qrafting agent to the
• copolymer will result in a product having a grafting agent content of from about 0.05 to about 5 weight percent, preferably from about 0.1 to about 1 weight percent, and more preferably from about 0.3 to about 0.6 weight percent of the grafting agent relative to the copolymer.
• the percent by weight of grafting agent on the polymer is determined by base titration as described in Chemical Reactions on Polymers, ACS Symposium Series, 364, 438 (1988) which is incorporated herein by
• substantially non-crosslinked grafted ethylene-methylacrylate copolymers - - means that the product obtained from the free-radical addition of a grafting agent to the backbone of this copolymer by the process of this invention does not have substantial amounts of cross-linking.
• most prior art free-radical grafting reactions not only result in the addition of grafting agents onto the backbone of the polymer but also result in the formation of a covalent bond between two heretofore unconnected polymers. See, for instance, Gaylord et al.. Journal of Polymer Science, 26 , 1189-1198 (1988). The resulting formation of a covalent bond between the two heretofore unconnected polymers is referred to in the art as
• substantially non-crosslinked grafted copolymers prepared by the process of this invention will contain less than about 5% crosslinked copolymers, preferably less than about 1% crosslinked copolymers, and even more preferably, less than about 0.5% crosslinked copolymer.
• Free-Radical Initiator - - refers to a compound which is a free-radical precursor and is generally stable at ambient conditions but under reaction conditions will decompose to form a free-radical which initiates the grafting reaction. In general, the free-radical is generated from the free-radical initiator by exposing the free-radical
• each free-radical initiator will have its own decomposition temperature and the initiator so selected for a particular reaction will of course depend on the reaction temperature to be used.
• the free-radical initiators which are useful in the practice of this invention have half-lives of less than about 30 minutes and preferably less than about 3 minutes at the reaction temperature and include acyl peroxides such as benzoyl peroxide, dialkyl or aralkyl peroxides such as di-t-butyl peroxide, dicumyl peroxide, cumyl butyl peroxide, 1,1- di-t-butyl peroxy-3,5,5-trimethylcyclohexane, 2,5-dimethyl-2,5-di-t-butylperoxyhexane, and bis(alpha-t-butyl peroxyisopropylbenzene), peroxyesters such as t-butyl peroxypivalate, t-butyl peroctoate, t-but
• hydroperoxide, pinane hydroperoxide, and cumene hydroperoxide and ketone peroxides such as cyclohexanone peroxide and
• a particularly preferred free-radical initiator is 2,5-dimethyl-2,5-di-t-butylperoxyhexane which is commercially available under the trade name Lucidol 101 (Pennwalt, Buffalo, New York). On the other hand, any free-radical initiator having the desired half-life at the reaction temperature may be used. More detail
• the free-radical initiator is employed at a concentration of 0.1 weight percent or less relative to the ethylene-methylacrylate copolymer.
• “Ceiling temperature of the grafting agent” - - refers to the temperature at or above which the grafting agent will not homopolymerize. In general, if the reaction is conducted at a temperature below the ceiling temperature of the grafting agent, then the grafting agent can homopolymerize, i.e., the grafting agent polymerizes onto itself in addition to adding to the polymer.
• the ceiling temperature is a function of the grafting agent concentration and can be readily determined by the skilled artisan for a particular grafting agent at a particular concentration. See, for instance, Russel. Journal of Polymer Science, Part A: Polymer Chemistry, 26, 2273-2280 (1980) for a discussion of the ceiling temperature of maleic anhydride.
• “Grafting solvent” - - refers to either the solvent employed to prepare a substantially non-crosslinked grafted polymer, if the grafting process is conducted in a solvent, or to the solvent employed in the isolation of the substantially non-crosslinked grafted polymer, if this product is separated by solvent extraction from the cross-linked product.
• Suitable grafting solvents are known in the art and include xylene, chlorobenzene and the like.
• melt index is calculated in accordance with ASTM test D1238-86 using the following conditions - 190oC and a weight of 2.16 kg on the piston of the plastometer. The melt index is reported in gram/10 minutes.
• Melt temperature - - refers to the
• polyethylene melts at about 137°C the melt temperature of the copolymer is by necessity less than 137oC.
• "Psia” - - refers to pounds per square inch atmospheric.
• a mixture of free-radical initiator and grafting agent are mixed with the ethylene-methylacrylate copolymer under reaction conditions.
• Suitable reaction conditions include the reaction temperature which is selected so as to be above the ceiling
• the ceiling temperature of the grafting agent will vary with the grafting agent as well as with its concentration, i.e., as the concentration of the grafting agent lowers, its ceiling temperature also lowers.
• Reaction temperatures of about 180oC or more generally are above the ceiling temperatures of any concentration of grafting agent used in this invention.
• reaction temperatures of about 120oC are sufficient to be at or above the ceiling temperature.
• the reaction is generally conducted at a temperature of from about 140oC to about 250oC and preferably at about 180oC.
• reaction temperature should also be above the melt temperature of the particular ethylene-methylacrylate copolymer used as well as at or above the decomposition temperature of the particular free-radical initiator used in the reaction. Because the melt temperatures of such copolymers are generally less than the ceiling temperature of the grafting agent, the melt temperature is generally of secondary concern. However, care should be taken to ensure that in each instance the reaction is conducted at or above the melt temperature of the particular ethylene-methylacrylate
• Such a free-radical initiator having a decomposition temperature appropriate for the reaction temperature selected.
• a free-radical initiator should have a half-life of less than about 30 minutes at the reaction temperature selected, i.e., one-half of the free-radical initiator will decompose at the reaction temperature in less than 30 minutes, preferably less than 3 minutes, and more preferably, less than 1 minute.
• the free-radical initiator employed in the present process must be maintained at less than about 0.2 weight percent relative to the ethylene- methylacrylate copolymer in order to prevent substantial crosslinking of the copolymer from occurring.
• the free-radical initiator is maintained at a concentration of about 0.1 weight percent or less relative to the copolymer. Because the free-radical initiator is decomposing at the reaction temperature, it is possible and indeed
• concentration of free-radical initiator of about 0.2 weight percent or greater relative to the ethylene-methylacrylate copolymer.
• the additional amounts of free-radical initiator can be added batchwise at selected intervals designed so as not to result in too large a concentration of free-radical initiator in the reaction mixture, i.e., periodically the concentration of the free-radical initiator in the reaction mixture can be determined by actual analysis or estimated by its
• the additional amounts of free- radical initiator can be added continuously by matching the addition rate to the
• crosslinking See, for instance. Examples 9-14, 19-20, 23, 25 and 28-31 herein as well as Gaylord, U.S. Patent No. 4,506,056, which sets forth in several of its examples that the use of small amounts of free-radical initiator, i.e., less than 0.5 weight percent relative to the polymer, in the grafting reaction with maleic anhydride and a polymer (albeit not ethylene-methylacrylate) in the absence of solvent and a donor molecule results in substantial amounts of
• the grafting agent is employed in the present process in amount sufficient so as to provide a grafted ethylene-methylacrylate copolymer having a grafting agent content of from about 0.05 to about 5 weight percent relative to the copolymer, preferably from about 0.1 to about 1 weight percent, and even more preferably, from about 0.3 to about 0.6 weight percent.
• the grafting agent will either react with the copolymer or be lost by evaporation. In either case, the concentration of reactable grafting agent diminishes over time. Accordingly, it is possible and indeed preferable during the reaction to add additional amounts of grafting agent to the reaction mixture.
• the additional amounts of grafting agent can be added batch wise at selected intervals in an amount which approximates reactable grafting agent
• the additional amounts of grafting agent can be added continuously by matching the addition rate to the sum of the evaporation and reaction rates. In either case, because a portion of the grafting agent added to the reaction mixture is lost by evaporation, it is desirable to add more grafting agent into the reaction mixture than is intended to be incorporated into (grafted onto) the copolymer.
• the additional amounts of grafting agent can be added continuously by matching the addition rate to the sum of the evaporation and reaction rates. In either case, because a portion of the grafting agent added to the reaction mixture is lost by evaporation, it is desirable to add more grafting agent into the reaction mixture than is intended to be incorporated into (grafted onto) the copolymer. In general, the
• concentration of grafting agent in the reaction mixture is maintained at about 8 weight percent or less, preferably at about 5 weight percent or less, and even more
• the concentration of the grafting agent is about 2 weight percent or more relative to the copolymer, it may be necessary to limit the reaction time to less than about 10 minutes in order to avoid undesirable
• additional grafting agent In a preferred embodiment, the additional amounts of grafting agent are added simultaneously with the additional amounts of free-radical initiator.
• unreacted maleic anhydride can be removed from the grafted copolymer by evaporation, i.e., heating the product to a temperature of about 140°C or greater, or by treatment with water.
• evaporation i.e., heating the product to a temperature of about 140°C or greater, or by treatment with water.
• the anhydride groups appended to the polymer are converted to carboxylic acid groups on
• the grafted polymer may be freed of unreacted maleic anhydride by solution in a suitable solvent and
• a suitable mixing device such as a Brabender Plasticorder, a roll mill, a single or multiple screw extruder or any other of the well-known mechanical mixing equipment normally used in the mixing, compounding, processing or fabrication of low or high molecular weight thermoplastic, elastomeric or thermosetting polymers or mixtures thereof in the absence of solvent.
• An extruder having one or more ports is a particularly desirable reaction vessel, although it is by no means necessary insofar as the grafting reaction can be done in the absence of solvent in other reaction vessels.
• the solid polymer e.g., pellets or powder
• the solid polymer may be premixed with the grafting agent and the free-radical initiator, and the resulting mixture added to the mixing device.
• the mixture of reactants may be added to the molten polymer.
• the ixture of grafting agent and free- radical initiator is prepared in the
• the powder, slurry or paste may be converted to a liquid by heating above the melting point of grafting agent and/or the free-radical initiator.
• the mixture is dropped continually or intermittently onto the surface of the melted polymer.
• the mixture may be added mechanically, e.g., from a hopper, or may be blown in with an inert gas.
• the mixture is a paste, slurry or fluid, it may be added mechanically or may be pumped and sprayed onto the surface of the melted
• polymer or a roll mill, or may be pumped and injected into one or more parts in an
• reaction vessels, mills and extruders are well known to those skilled in the art and may be used in the practice of this invention.
• the mixture is generally added continuously or in several portions over a period of time to promote homogeneous distribution of
• the carboxylation reaction is extremely rapid and occurs to a major extent when the mixture comes in contact with the heated polymer. However, the reaction can continue when the molten polymer is conveyed away from the point of injection, particularly if the free-radical initiator's half life is at least 10 seconds at the reaction
• reaction is conducted from about 10 seconds to about 20 minutes.
• reaction is conducted for a period of at least 30 seconds.
• the concentration of the grafting agent is about 2 weight percent or more relative to the copolymer, it may be necessary to limit the reaction time to less than about 10 minutes in order to avoid undesirable crosslinking.
• An extruder containing an entry port for the addition of the polymer, one or more reduced pressure zones with injection orifices at points where the polymer is molten for
• the extrudate may be removed as ribbon or rod and cut into pellets or as fibers or extruded or blown film.
• the film may be utilized as a self-supporting film or may be extrusion laminated onto a substrate such as paper, aluminum foil or an unoriented or oriented polymeric film, or may be coextruded with a thermoplastic polymer to form a
• extruder pressures will generally be in the range of about 500 to 7000 psia.
• the product of this invention is by necessity free of such
• the process of the present invention does not utilize a donor molecule, which is defined by Gaylord, U.S. Patent No. 4,506,056, as sulfur, nitrogen or phosphorus containing compounds or a chain-stopping agent, which is defined by Gardiner et al, U.S. Patent No. 4,780,228, as a mercaptan, the product of this invention does not contain added amounts of sulfur, nitrogen or phosphorus.
• a donor molecule which is defined by Gaylord, U.S. Patent No. 4,506,056, as sulfur, nitrogen or phosphorus containing compounds or a chain-stopping agent, which is defined by Gardiner et al, U.S. Patent No. 4,780,228, as a mercaptan
• the product of this invention does not contain added amounts of sulfur, nitrogen or phosphorus.
• nitrogen, phosphorus and sulfur means that no exogenous nitrogen, sulfur or phosphorus has been added to the process for preparing the grafted products of this invention. Any concentration of sulfur, nitrogen and
• phosphorus in the products of this invention results from impurities in the reactants including the ethylene-methylacrylate
• the concentration of sulfur, nitrogen, and phosphorus in the products of this invention are generally less than about 100 parts per million (ppm).
• the products of this invention have a sulfur, nitrogen and phosphorus concentration of less than about 10 ppm; more preferably, less than about 5 ppm; and most preferably, less than about 1 ppm.
• E-M ethylene-methylacrylate copolymer
• E-B ethylene-butylacrylate copolymer
• PE polyethylene
• the surface coating of the pellets was carried out by tumbling the pellets with finely ground maleic anhydride and Lucidol 101 in a closed jar at room temperature for 30 minutes.
• the extruder barrel was heated to 180oC and a one-eighth (1/8) inch diameter continuous strand was extruded at 30 rpm screw speed.
• the strand was cooled to room temperature and cut up into pellets of approximately 3 mm diameter.
• the resulting product is maleic anhydride grafted ethylene-methylacrylate copolymer containing some unreacted maleic anhydride.
• anhydride grafted ethylene-methylacrylate copolymer was 1.4 weight percent.
• Examples 9-14 illustrate grafted polymers which were prepared from polyethylene and accordingly are not examples of this invention. These examples were extruder prepared following the procedures set fo ⁇ -th in Example 1 but with the reagent amounts indicated below in Table I. Because of the extensive amount of cross-linking obtained in comparison Examples 9-14, no determination was made of the weight percent maleic anhydride in the crude and extracted products and no determination was made of the melt index. In any event, this data
• Examples 15-20 below illustrate different grafted polymers. Examples 15-18 were
• copolymer and in particular certain of these examples use reagent amounts outside the scope of this invention. On the other hand.
• Examples 21-23 below illustrate different grafted polymers.
• Examples 21 and 22 were prepared from ethylene-methylacrylate
• Example 23 was prepared from
• polyethylene and is not an example of this invention. These examples were prepared following the procedure set forth in Example 2 above but with the reagent amounts set forth in Table III below.
• Example 24 illustrate different grafted polymers wherein the grafting agent is acrylic acid.
• Example 24 was prepared from ethylene-methylacrylate copolymer and is an example of this invention whereas Example 25 was prepared from polyethylene and is not an example of this invention. These examples were prepared following the procedure set forth in Example 2 above but using acrylic acid in lieu of maleic anhydride and with the reagent amounts set forth in Table IV below.
• Examples 26-31 below illustrate different grafted polymers.
• Examples 26 and 27 were prepared from ethylene-methylacrylate copolymer and are examples of this invention.
• Examples 28 and 29 were prepared from ethylene-butylacrylate copolymer (16% butylacrylate, 0.05% 2,6-di-tert-butyl-4-ethylphenol--antioxidant and having a MI of 2 g/10 minutes) and are not examples of this invention.
• Examples 30 and 31 were prepared from polyethylene and are not examples of this invention. These examples were extruder prepared following the procedure set forth in Example 1 but with the reagent amounts
• grafting reaction is preferably carried out at concentrations of maleic anhydride of less than about 2.0 weight percent although
• concentrations of the maleic anhydride of about 2.0 weight percent and greater, it may be necessary to limit the reaction duration to less than about 10 minutes, i.e., see
• Examples 34-35, 40-43, and 56-57 were subjected to an aluminum adhesion test to test the adhesion characteristics of the grafted products of this invention.
• the grafted polymers of these examples were compression molded at 180oC/25 tons/1 minute between two pieces of aluminum foil. After cooling to room temperature (ten tons), the films were found to adhere very strongly to the aluminum and could be separated only by dissolving the aluminum in dilute HCl. On the other hand, non-grafted ethylene-methylacrylate copolymer films, compression molded in the same manner, could be peeled off easily from the aluminum foil.

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• Chemical & Material Sciences (AREA)
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• Chemical Kinetics & Catalysis (AREA)
• Medicinal Chemistry (AREA)
• Polymers & Plastics (AREA)
• Organic Chemistry (AREA)
• Graft Or Block Polymers (AREA)
• Addition Polymer Or Copolymer, Post-Treatments, Or Chemical Modifications (AREA)

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• 1990
  • 1990-08-02 EP EP19900912629 patent/EP0494875A4/en not_active Withdrawn
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