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
  • C08F22/00—Homopolymers and copolymers of compounds having one or more unsaturated aliphatic radicals each having only one carbon-to-carbon double bond, and at least one being terminated by a carboxyl radical and containing at least one other carboxyl radical in the molecule; Salts, anhydrides, esters, amides, imides or nitriles thereof
  • C08F22/10—Esters
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08C—TREATMENT OR CHEMICAL MODIFICATION OF RUBBERS
  • C08C19/00—Chemical modification of rubber
  • C08C19/22—Incorporating nitrogen atoms into the molecule
• • 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
  • C08F8/00—Chemical modification by after-treatment
  • C08F8/30—Introducing nitrogen atoms or nitrogen-containing groups
• • 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
  • C08J3/24—Crosslinking, e.g. vulcanising, of macromolecules
  • C08J3/243—Two or more independent types of crosslinking for one or more polymers
• • 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
  • C08J2323/00—Characterised by the use of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Derivatives of such polymers
  • C08J2323/02—Characterised by the use of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Derivatives of such polymers not modified by chemical after treatment
  • C08J2323/04—Homopolymers or copolymers of ethene
  • C08J2323/08—Copolymers of ethene
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
  • Y10T428/00—Stock material or miscellaneous articles
  • Y10T428/13—Hollow or container type article [e.g., tube, vase, etc.]
  • Y10T428/1352—Polymer or resin containing [i.e., natural or synthetic]
  • Y10T428/139—Open-ended, self-supporting conduit, cylinder, or tube-type article

Definitions

• the invention relates to an elastomeric material comprising covalently bonded crosslinking bridges, obtained by non-thermo-reversible permanent chemical crosslinking and, on the other hand, non-covalent bonding crosslink bridges, in particular heat-reversible bridges obtained by modifying the polymer chains in such a way that to make them carriers of associative groups capable of forming said non-covalent bonds. Modification of the chains with the associative groups can be done by functionalization, in particular using functional monomers used during the polymerization or by grafting.
• elastomeric materials find most of their good application properties when they are crosslinked.
• the crosslinking of the elastomers gives them not only an improvement in the mechanical properties, but also an extension of the temperature ranges in which they retain the elastic properties and flexibility that characterize them.
• natural rubber derived from the latex of the rubber tree requires crosslinking to find all its properties of dimensional stability and elasticity; without cross-linking, natural rubber is a tacky material that is of little use in most cases.
• Chemical crosslinking is characterized by the establishment of covalent chemical bonds between polymer chains of the base elastomeric material, for example natural rubber.
• the polymer chains generally quite long, come to form a three-dimensional network often shown in two dimensions in the appearance of a net whose meshes are more or less tightened, depending on the crosslinking density (or the density of crosslinking nodes).
• the crosslinking density has a major influence on the main properties of the elastomeric chemical network, such as tensile or compressive modulus, hardness, tear resistance and properties at break (stress, elongation).
• the non-thermo-reversible chemical crosslinking of elastomers has many advantages in terms of their mechanical and thermal properties, but it involves the disadvantage, sometimes major, of generating heat-set materials which can only be used when only once and this, for a time, sometimes short before the crosslinking reaction. Indeed, the chemical crosslinking being permanent, once the material is crosslinked, it can no longer be reworked or recycled thermomechanically. To overcome this major disadvantage, new technologies have been developed throughout the twentieth century to obtain non-permanent crosslinking elastomeric materials. This is also called reversible crosslinking or physical crosslinking, clearly different from permanent chemical crosslinking.
• thermomechanically especially through implementation techniques conventionally used for polymers, such as extrusion, injection, various molding techniques such as rotational molding, form the family of thermoplastic elastomers.
• One of the most common ways of obtaining thermoplastic elastomeric materials is to manufacture alternately or multi-alternatively block copolymers, non-crosslinked elastomeric flexible segments, and rigid segments.
• block copolymers which can be used as thermoplastic elastomers are styrenic block copolymers such as poly styrene-b-butadiene-b-styrene (SBS), or poly styrene-b-isoprene-b-styrene (SIS). ).
• SBS poly styrene-b-butadiene-b-styrene
• SIS poly styrene-b-isoprene-b-styrene
• the rigid blocks, here the polystyrene blocks are associated with each other constituting, at the operating temperatures (below the glass transition temperature or at the softening temperature of the rigid blocks), nodules within a flexible matrix formed by the soft blocks. This is achieved by adjusting the proportion of both types of blocks.
• the material behaves as a set of elastomeric flexible chains, joined together by the rigid block aggregates which act as nodes of crosslinking.
• rigid blocks can soften and possibly flow by raising the temperature, the material can be destructured and therefore reworked or implemented thermomechanically.
• the crosslinking nodes formed by the rigid blocks are, thus, non-permanent nodes or physical nodes.
• thermoplastic elastomers by dispersion in a non-elastomeric thermoplastic matrix, of a crosslinked elastomeric phase fraction or not.
• This composite strategy makes it possible to provide elasticity and rubbery behavior to a reprocessable thermoplastic matrix.
• Another strategy for forming sites that are capable of physically crosslinking, within the basic polymer chains is that of the chemical modification of these chains by functionalization or by grafting. It is to include, by functionalization using functional monomers introduced during the polymerization or by grafting, preferably covalent grafting, on the basic chains, self-complementary patterns capable of associating with each other via non-permanent physical interactions such as ionic interactions, hydrogen bonds, ion-dipole, dipole-dipole interactions.
• the Applicant has now found that it is possible to crosslink low, medium or high molecular weight polymer chains with both a conventional and therefore permanent chemical crosslinking and a reversible crosslinking, preferably physical and even more preferably based on of hydrogen bonds.
• the result is that of obtaining materials having a good dimensional stability and good mechanical properties thanks to the permanent chemical crosslinking, while being easier to implement and having particular properties, such as for example modular mechanical properties, because of the introduction of a different mode of crosslinking (no permanent) and likely to evolve according to the parameters of the environment of use, as, for example, the temperature or the characteristic time of stress.
• the subject of the invention is therefore an elastomeric material comprising flexible polymer chains associated with one another by crosslinking bridges with permanent covalent bonds and, on the other hand, by non-covalently linked crosslinking bridges.
• cross-linking bridges with permanent covalent bonds is meant for the purposes of the present invention, non-thermoreversible crosslinking bridges, the chemical crosslinking being permanent, once the material is crosslinked, it can no longer be reworked or recycled thermomechanically.
• non-covalent linking crosslinking bridges is meant in the sense of the present invention, crosslinking bridges capable of reversibly dissociating depending on the variation of the parameters of the environment of use, such as temperature or time mechanical stress.
• the term "flexible polymer” is intended to mean a rubbery polymer having a glass transition temperature below its temperature of use, that is to say a flexible polymer material at the temperature of use. Such a material preferably has a Young's modulus, measured at the temperature of use, of between 10 000 Pa and 100 000 000 Pa, and preferably between 50 000 Pa and 10 000 000 Pa.
• the invention also relates to a process for obtaining a material according to the invention
• the materials in accordance with the invention can be obtained by bridging flexible polymer chains according to permanent or non-thermo-reversible chemical crosslinking mechanisms and reversible crosslinking mechanisms.
• the remainder of the description describes in more detail the flexible polymers that can be used according to the invention, the chemical crosslinking of the latter to form permanent chemical crosslinking bridges, as well as the functionalization or grafting of the polymer to form reversible crosslinking bridges.
• polystyrene-b-butadiene SB
• poly styrene-b-butadiene-b-styrene SBS
• poly styrene-b-isoprene-b -styrene SIS
• one or more elastomers chosen from the list below are advantageously used as flexible polymers, which are advantageously suitable for the manufacture of rubber articles.
• the flexible polymer according to the invention may comprise one or more elastomers diene.
• Diene elastomers more specifically mean:
• (1) homopolymers obtained by polymerization of a conjugated diene monomer having from 4 to 22 carbon atoms for example: 1,3-butadiene, 2-methyl-1,3-butadiene, 2,3-dimethyl 1,3-butadiene, 2,3-diethyl-1,3-butadiene, 2-methyl-3-ethyl-1,3-butadiene, 2-chlorobutadiene-1,3, 2-methyl-3-isopropylbutadiene, 1, 3, 1-phenyl-1,3-butadiene, 1,3-pentadiene, 2,4-hexadiene;
• (6) a mixture of several of the aforementioned elastomers (1) to (5) between them.
• the polymers that can be used according to the invention can be obtained according to conventional polymerization techniques well known to those skilled in the art.
• the permanent chemical crosslinking is carried out by conventional means such as sulfur vulcanization, crosslinking with peroxides or crosslinking with at least bifunctional crosslinking agents capable of reacting chemically with reactive sites present in at least two polymer chains. All possible chemical combinations between reactive sites on polymer chains and crosslinking at least bifunctional, are useful when they allow the establishment of chemical crosslinking bridges, permanent covalent bonds between polymer chains.
• a suitable crosslinking agent may be any molecule at least difunctional capable of reacting chemically with these reactive sites, such as, for example, a diamine, a diol, a diepoxy, a diisocyanate, and their respective combinations such as, for example, an alkanolamine.
• the crosslinking agents which are at least difunctional with respect to the epoxies, may be, for example, primary amines, diamines, diols, dicarboxylic acids.
• the established reversible associations are physical associations and according to an even more preferred embodiment of the invention, the physical associations are hydrogen bonds.
• the polymers used in the material which is the subject of the invention are modified in such a way as to these polymers carry associative groups based on nitrogen heterocycle.
• a modifying agent can be reacted with the polymer to be modified. More specifically, the modification of the polymer may be carried out by grafting, that is to say by the reaction of said polymer with a modifying agent bearing, on the one hand, an associative group based on nitrogen heterocycle and, on the other hand, on the other hand, a reactive group, chosen for example from amine, mercaptan, epoxy, isocyanate, anhydride, alcohol, acid, preferably amine groups, said reactive group forming a covalent bond with a reactive function, such as an acid function, anhydride, alcohol, mercaptan, amine, epoxy or isocyanate, preferably anhydride or epoxy, carried by said polymer.
• a reactive group chosen for example from amine, mercaptan, epoxy, isocyanate, anhydride, alcohol, acid, preferably amine groups, said reactive group forming a covalent bond with a reactive function, such as an acid function, anhydride, alcohol, mercaptan,
• sociative groups groups capable of associating with each other by hydrogen, ionic and / or hydrophobic bonds. It is according to a preferred embodiment of the invention groups capable of associating with hydrogen bonds, comprising a nitrogen heterocycle, preferably diazotized, usually 5 or 6 members.
• associative groups which may be used according to this preferred embodiment of the invention are the imidazolidinyl, triazolyl, triazinyl, bis-ureyl and ureido-pyrimidyl groups. The imidazolidinyl group is preferred.
• Another way of modifying the polymers used in the material which is the subject of the invention so that these polymers carry associative groups based on nitrogen heterocycle is the functionalization of the polymer during its polymerization, by means of monomers functional groups capable of copolymerizing and, therefore, of being inserted into the backbone of the polymer chains, while carrying said associative groups based on nitrogen heterocycle.
• monomers that can be used to introduce imidazolidinyl groups into the polymer are ethylimidazolidone methacrylate and ethylimidazolidone methacrylamide.
• the modifying agent can thus respond to any one of the formulas (B1) to (B4):
• R denotes a unit containing at least one reactive group, including a polymerizable group (case of introduction by copolymerization with functional monomers bearing associative groups).
• R denotes a hydrogen atom or any group
• A denotes an oxygen or sulfur atom or an -NH group, preferably an oxygen atom.
• modifying agents are 2-aminoethylimidazolidone (UDETA), 1- (2 - [(2-aminoethyl) amino] ethyl) imidazolidone (UTETA), l- (2- ⁇ 2- [2 -aminoethylamino] ethyl ⁇ amino) ethyl] imidazolidone
• UDETA N- (6-aminohexyl) -N '- (6-methyl-4-oxo-1,4-dihydropyrimidin-2-yl) urea (UPy), 3-amino-1,2,4 triazole (3-ATA) and 4-amino-1,2,4-triazole (4-ATA).
• UDETA is preferred for use in the present invention.
• UDETA, UTETA and UTEPA may be respectively prepared by reacting urea with diethylene triamine (DETA), triethylene tetramine (TETA) and tetraethylene pentamine (TEPA).
• DETA diethylene triamine
• TETA triethylene tetramine
• TEPA tetraethylene pentamine
• the grafting process is carried out by reacting the modifying agent and the polymer carrying reactive functions.
• This step can be carried out in the molten state, for example in an extruder or an internal mixer at a temperature which can range from 50 ° C. to 300 ° C. and preferably from 200 ° to 280 ° C. is mixed with the polymer alone, or with the aid of an additive permitting the impregnation of the solid polymer grains by the modifying agent previously melted.
• the solid mixture before introduction into the extruder or mixer may be made more homogeneous by refrigeration to solidify the modifying agent. It is also possible to determine the latter in the extruder or the mixer after a start of melting of the polymer to be grafted.
• the time at the grafting temperature can range from 30 seconds to 5 hours.
• the modifying agent may be introduced into the extruder as a masterbatch in a polymer which preferably may be the polymer to be grafted.
• the masterbatch may comprise up to 30% by weight of the modifying agent; then, the masterbatch is "diluted" in the polymer to be grafted during the grafting operation.
• the grafting can be carried out by reaction in the solvent phase, for example in anhydrous chloroform.
• the reaction temperature can range from 5 ° C. to 75 ° C. for a period ranging from a few minutes to a day and at pre-graft polymer concentrations of between 1 and 50%. by weight, based on the total weight of the solution.
• the number of associative groups introduced on the polymer must be sufficient to obtain materials having good dimensional stability and good mechanical properties thanks to the permanent chemical crosslinking, while being easier to implement and having particular properties, such as example of the modular mechanical properties, because of the introduction of a different mode of crosslinking (not permanent) and likely to evolve according to the parameters of the environment of use, as, for example, the temperature or the characteristic time of stress.
• This number can be simply adjusted by varying the amount of modifying agent or adjusting the reaction time and temperature. It is generally preferred that the amount of modifying agent is from 0.1 to 20% by weight, more preferably from 0.5 to 10% by weight, based on the weight of the unmodified polymer and / or the average number associative groups per polymer chain is between 1 and 200.
• the degree of modification of the polymer by grafts or comonomers bearing the associative groups is from 0.1 to 20% by weight of modifying agent relative to the polymer.
• the average number of associative groups per polymer chain after modification is between 1 and 200.
• the ratio between the percentage of permanent covalent bond crosslinking bridges and the percentage of non-covalent bond crosslinking bridges is between 99/1 and 1/99, and preferably between 90/10 and 20/80.
• the reactive function carried by the polymer to be modified by grafting is an anhydride function
• it can be created on said polymer, by cyclization of acid functions.
• This cyclization process can advantageously be carried out under basic catalysis conditions.
• the basic catalysts that are preferred are soda and sodium methoxide, CH 3 ONa.
• Cyclisation can be done by passing the polymer carrying acid groups in a single or double screw extruder, in the presence of a catalyst and optionally other additives, such as lubricants, antioxidants, dyes, and / or optical correctors to give gloss and reduce yellowing.
• the extrusion temperature may be between 200 and 300 ° C. and preferably between 250 and 280 ° C.
• One or more extrusion passages may be carried out in order to obtain the desired level of cyclization (for example, formation of glutaric anhydride). .
• the cyclization reaction can be carried out under high vacuum.
• the cyclization rate can be controlled to adjust the level of anhydride functions obtained, which can for example range from 0.1 to 20 mol%.
• the reactive groups of the modifying agent are also capable of causing a permanent chemical crosslinking.
• These reactive groups can be: amine, mercaptan, epoxy, isocyanate, anhydride, alcohol, acid, preferably amine.
• the modifying agent is also capable of causing a permanent chemical crosslinking.
• the covalently bonded permanent crosslinking bridges and the non-covalent bond crosslinking bridges are formed by the modifying agent.
• modification agent of UDETA, which is capable of causing a permanent chemical crosslinking by both the primary amine reactive group and the secondary amine carried by the heterocycle constituting the group. associative.
• the invention therefore also relates to a process for preparing a crosslinked material based on a flexible polymer comprising the following steps: (a) the permanent chemical crosslinking of said polymer,
• Steps a) and b) (i) can take place in any order or be simultaneous.
• additives The material according to the invention can be used as such or in single-phase or multiphase mixtures with one or more compounds such as petroleum fractions, solvents, mineral and organic fillers, plasticizers, tackifying resins, "aids process or aids to implementation, lubricants, anti-oxidants, anti-radiation additives, (anti-UV), pigments and / or dyes.
• additives that may be added to the material according to the invention are in particular:
• lubricants such as stearic acid and its esters, waxy esters (, polyethylene waxes, paraffin or acrylic lubricants - dyes
• inorganic or organic pigments such as those described in the document "Plastics Additives and Modifiers Handbook, Section VIII, Dyes", J. Edenbaum, Ed., Van Nostrand, pages 884-954.
• pigments which can be used, mention may be made of carbon black, titanium dioxide, clay, metal particles or treated mica particles of the IRIODIN® brand marketed by MERCK.
• plasticizers such as stearates of tin, lead, zinc, cadmium, barium or sodium, including the Thermolite ARKEMA,
• co-stabilizers such as epoxidized natural oils, antioxidants, for example phenolic, sulfuric or phosphitic,
• fillers or reinforcements in particular cellulosic fillers, talc, calcium carbonate, mica or wollastonite, glass or metal oxides or hydrates,
• fungicides and biocides blowing agents for the production of expanded parts, such as azodicarbonamides, azobisobutyronitrile, diethyl azobisobutyrate,
• flameproofing agents including antimony trioxide, zinc borate and brominated or chlorinated phosphate esters,
• the material which is the subject of the invention can be used for the manufacture of various articles, in particular by calendering, extrusion, extrusion blow molding, conventional molding, injection molding, rotational molding, thermoforming, etc.
• the basic soft polymer to be chemically and physically crosslinked is a copolymer of ethylene, methyl acrylate and glycidyl methacrylate, sold by ARKEMA under the name LOTADER® AX 8900.
• This base polymer is formulated with using fillers: carbon black and calcium carbonate, a plasticizer that makes the polymer more flexible at room temperature, a lubricant and a "process" aid.
• the typical formulation of the base material and the function of the ingredients are given in Table I.
• the evolution of the rheological properties due to the addition of the UDETA can be followed in a rheometer for measuring, on a pellet of the material, the torque in torsion, at different temperatures or different times.
• the tests can also be performed in dynamic mode with the frequency as a parameter.
• the addition of UDETA to this formulation causes, as a function of temperature or time at a given temperature, an increase in the torque, which can be associated with the grafting of UDETA on the polymer chains, but also with a crosslinking. chemical of these also caused by the UDETA.
• mixture 1 is stoichiometric between amines of UDETA and epoxy units of the polymer.
• Mixtures 2 to 4 correspond to stoichiometries of 0.5, 0.75 and 1.2 expressed in molar ratio UDETA / epoxy respectively.
• the grafting reaction of the primary amine of UDETA on the epoxy units is rapid and occurs at moderate temperatures (typically below 100 ° C.).
• the resulting secondary amine of a first epoxy-UDETA reaction must react, again, with an epoxy group of another polymer chain.
• Another possibility is that it is the hydrogen of the imidazolidone ring which intervenes, after the first epoxy-UDETA reaction, in a second reaction step with an epoxy of another chain. In all cases, the second reaction is slower and occurs at a higher temperature.
• mixtures with very much physical cross-linking show a marked drop in high temperature torque (> 200 ° C.) which is indicative of the advanced dissociation of the physical bonds at this temperature, while that mixtures with good proportion of chemical crosslinking tend to keep a torque virtually constant or lighter decrease.

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