Patent Application
20230374253
The present invention relates to a method for inducing physico-chemical modification of a polymer composition on demand, and its use for reprocessing/recycling polymers. In what follows, the numbers between brackets ([ ]) refer to the List of References provided at the end of the document.
The use of plastic is widespread and worldwide. In fact, the global plastic production has increased up to more than 4000% between 1960 to 2013. The low cost and the high versatility of plastics leads us to believe that this global plastic production will continue to grow (or at least stagnate) in the future. Unfortunately, the reprocessing, recycling and recovering of plastics cannot match this huge consumption which engenders high environmental problematics. However, plastic reprocessing or recycling is of crucial interest and the proportion of recycling, recovering and landfilling drastically evolves since 2007. To illustrate this, in 2018, 32.5% of plastics wastes were recycled (against 20.4% in 2007), 42.6% were recovered (against 29.2% in 2007) and 24.9% were landfilled (against 50.4% in 2007). The recycling and recovering of plastics can be separated in four different categories.
Thermoplastics constitute around 80% of the plastic wastes generated throughout the world so that their recycling is the keypoint to avoid the landfilling of plastic wastes.
Self-healing is a good way to improve the lifetime of polymers and to reduce their maintenance costs, notably for the healing of cracks. Various strategies have been developed to reach these self-healing properties but all of them require high temperatures to be reached. For instance, PU-based polymers showed good self-healing properties upon heating and it is possible to use a small crosslinker presenting hydroxyl groups to improve reversibility of the bond formation or to use the Diels-Alder reaction which provides an excellent thermal reversibility. Fusible thermoplastic polycaprolactone fibers or polystyrene can also be inserted into the matrix. Under the influence of heat, they will melt and flow to heal the scratch. Another existing way to get self-healing properties is to incorporate graphene oxide or nanoparticles into the polymers to produce an efficient photothermal effect which will lead to the melting of the polymer, providing its local deformation upon NIR light irradiation and resulting in healing of the scratch. It has notably been evidenced that both the nanoparticles concentration and the irradiance could have a dramatic influence on the temperature reached and thus drastically affect healing efficiency. However, this approach suffers the drawback of insoluble bodies (graphene oxide or nanoparticles) and hence non homogenous mixtures.
Therefore, there remains a need for the development of new systems and methods for more efficient recycling/reprocessing and self-healing of polymer compositions, which overcome the aforementioned disadvantages.
Scheme 1. Comparison of the polymer surface (A) heated by conventional oven methods with (B) the new NIR laser diode photothermal approach according to the invention.
Scheme 2. Chemical structures of the monomers (TMPTA, Glyfoma), NIR heat-generating organic dyes (IR-813, SQ) and the photoinitiator (SPBPO) used in the examples.
Scheme 3. Exemplary bonding of two polymer films containing a NIR heater in each film.
Scheme 4. Chemical structures of monomers (Glyfoma, IBOA, TMCHMA, IBOMA, MMA and PEG diacrylate), NIR heater (IR-813) and photoinitiators (TPO-L, BAPO) used in this study.
Scheme 5. (A) Behavior of heater-free polymer upon NIR irradiation; (B) Shaping/reprocessing of a polymer containing a NIR heater upon NIR irradiation.
Scheme 6. Irradiation of Glyfoma-based polymer containing NIR heaters (0.5%wt) upon LED at 810 m (9 W·cm−2); the irradiation starts from t=0 s.
Scheme 7. (A) Shaping cycle of polymer containing NIR heater. (B) Shaping experiment to unfold polymer in order to make it back to its initial shape.
To facilitate an understanding of the present invention, a number of terms and phrases are defined below:
As used herein other than the claims, the terms “a,” “an,” “the,” and/or “said” means one or more. As used herein in the claim(s), when used in conjunction with the words “comprise,” “comprises” and/or “comprising,” the words “a,” “an,” “the,” and/or “said” may mean one or more than one. As used herein and in the claims, the terms “having,” “has,” “is,” “have,” “including,” “includes,” and/or “include” has the same meaning as “comprising,” “comprises,” and “comprise.” As used herein and in the claims “another” may mean at least a second or more.
The phrase “a mixture thereof” and such like following a listing, the use of “and/or” as part of a listing, a listing in a table, the use of “etc” as part of a listing, the phrase “such as,” and/or a listing within brackets with “e.g.,” or i.e., refers to any combination (e.g., any sub-set) of a set of listed components, and combinations and/or mixtures of related species and/or embodiments described herein though not directly placed in such a listing are also contemplated. Such related and/or like genera(s), sub-genera(s), specie(s), and/or embodiment(s) described herein are contemplated both in the form of an individual component that may be claimed, as well as a mixture and/or a combination that may be described in the claims as “at least one selected from,” “a mixture thereof” and/or “a combination thereof.”
In general, the term “substituted” whether preceded by the term “optionally” or not, and substituents contained in formulae of this invention, refer to the replacement of hydrogen radicals in a given structure with the radical of a specified substituent. When more than one position in any given structure may be substituted with more than one substituent selected from a specified group, the substituent may be either the same or different at every position. As used herein, the term “substituted” is contemplated to include all permissible substituents of organic compounds. The term “aliphatic”, as used herein, includes both saturated and unsaturated, straight chain (i.e., unbranched) or branched aliphatic hydrocarbons, which are optionally substituted with one or more functional groups. As will be appreciated by one of ordinary skill in the art, “aliphatic” is intended herein to include, but is not limited to, alkyl, alkenyl, alkynyl moieties.
As used herein, the term “alkyl”, refers to straight and branched alkyl groups. An analogous convention applies to other generic terms such as “alkenyl”, “alkynyl” and the like. As used herein, “lower alkyl” is used to indicate those alkyl groups (substituted, unsubstituted, branched or unbranched) having about 1-6 carbon atoms. Illustrative alkyl groups include, but are not limited to, for example, methyl, ethyl, n-propyl, isopropyl, allyl, n-butyl, sec-butyl, isobutyl, tert-butyl, n-pentyl, sec-pentyl, isopentyl, tert-pentyl, n-hexyl, sec-hexyl, moieties and the like, which again, may bear one or more substituents. Alkenyl groups include, but are not limited to, for example, ethenyl, propenyl, butenyl, 1-methyl-2-buten-1-yl, and the like. Representative alkynyl groups include, but are not limited to, ethynyl, 2-propynyl (propargyl), 1-propynyl and the like.
The term “alicyclic”, as used herein, refers to compounds which combine the properties of aliphatic and cyclic compounds and include but are not limited to cyclic, or polycyclic aliphatic hydrocarbons and bridged cycloalkyl compounds, which are optionally substituted with one or more functional groups. As will be appreciated by one of ordinary skill in the art, “alicyclic” is intended herein to include, but is not limited to, cycloalkyl, cycloalkenyl, and cycloalkynyl moieties, which are optionally substituted with one or more functional groups. Illustrative alicyclic groups thus include, but are not limited to, for example, cyclopropyl, —CH2-cyclopropyl, cyclobutyl, —CH2-cyclobutyl, cyclopentyl, —CH2-cyclopentyl-n, cyclohexyl, —CH2-cyclohexyl, cyclohexenylethyl, cyclohexanylethyl, norborbyl moieties and the like, which again, may bear one or more substituents.
The term “heteroaliphatic”, as used herein, refers to aliphatic moieties in which one or more carbon atoms in the main chain have been substituted with a heteroatom. Thus, a heteroaliphatic group refers to an aliphatic chain which contains one or more oxygen, sulfur, nitrogen, phosphorus or silicon atoms, i.e., in place of carbon atoms. Heteroaliphatic moieties may be branched or linear unbranched. An analogous convention applies to other generic terms such as “heteroalkyl”, “heteroalkenyl”, “heteroalkynyl” and the like.
The term “heterocyclic” or “heterocycle”, as used herein, refers to compounds which combine the properties of heteroaliphatic and cyclic compounds and include but are not limited to saturated and unsaturated mono- or polycyclic heterocycles such as morpholino, pyrrolidinyl, furanyl, thiofuranyl, pyrrolyl etc., which are optionally substituted with one or more functional groups, as defined herein. In certain embodiments, the term “heterocyclic” refers to a non-aromatic 5-, 6- or 7-membered ring or a polycyclic group, including, but not limited to a bi- or tri-cyclic group comprising fused six-membered rings having between one and three heteroatoms independently selected from oxygen, sulfur and nitrogen, wherein (i) each 5-membered ring has 0 to 2 double bonds and each 6-membered ring has 0 to 2 double bonds, (ii) the nitrogen and sulfur heteroatoms may optionally be oxidized, (iii) the nitrogen heteroatom may optionally be quaternized, and (iv) any of the above heterocyclic rings may be fused to an aryl or heteroaryl ring. Representative heterocycles include, but are not limited to, pyrrolidinyl, pyrazolinyl, pyrazolidinyl, imidazolinyl, imidazolidinyl, piperidinyl, piperazinyl, oxazolidinyl, isoxazolidinyl, morpholinyl, thiazolidinyl, isothiazolidinyl, and tetrahydrofuryl. In general, the term “aromatic” or “aryl”, as used herein, refers to stable substituted or unsubstituted unsaturated mono- or polycyclic hydrocarbon moieties having preferably 3-14 carbon atoms, comprising at least one ring satisfying Hückle's rule for aromaticity. Examples of aromatic moieties include, but are not limited to, phenyl, indanyl, indenyl, naphthyl, phenanthryl and anthracyl.
As used herein, the term “heteroaryl” refers to unsaturated mono-heterocyclic or polyheterocyclic moieties having preferably 3-14 carbon atoms and at least one ring atom selected from S, O and N, comprising at least one ring satisfying the Hückel rule for aromaticity. The term “heteroaryl” refers to a cyclic unsaturated radical having from about five to about ten ring atoms of which one ring atom is selected from S, O and N; zero, one or two ring atoms are additional heteroatoms independently selected from S, O and N; and the remaining ring atoms are carbon, the radical being joined to the rest of the molecule via any of the ring atoms, such as, for example, pyridyl, pyrazinyl, pyrimidinyl, pyrrolyl, pyrazolyl, imidazolyl, thiazolyl, oxazolyl, isooxazolyl, thiadiazolyl, oxadiazolyl, thiophenyl, furanyl, quinolinyl, isoquinolinyl, and the like. Examples of heteroaryl moieties include, but are not limited to, pyridyl, quinolinyl, dihydroquinolinyl, isoquinolinyl, quinazolinyl, dihydroquinazolyl, and tetrahydroquinazolyl.
As used herein, the expression “Cx-Cy, preferably Cx1-Cy1, alkylaryl, aralkyl or aryl”, where x, y, x1 and y1 represent integers denoting the number of carbon atoms in the chemical moiety to which it refers (e.g., “alkylaryl”, “aralkyl”, “aryl”)), means “Cx-Cyalkylaryl, Cx-Cyaralkyl or Cx-Cyaryl, preferably Cx1-Cy1alkylaryl, aralkyl or Cx1-Cy1aryl”. Likewise, the expression “Cx-Cy alkylaryl, aralkyl or aryl”, means “Cx-Cyalkylaryl, Cx-Cyaralkyl or Cx-Cyaryl”.
The term “halogen” as used herein refers to an atom selected from fluorine, chlorine, bromine and iodine.
The term “amine” refers to a group having the structure —N(R)2 wherein each occurrence of R is independently hydrogen, or an aliphatic, heteroaliphatic, aryl or heteroaryl moiety, or the R groups, taken together with the nitrogen atom to which they are attached, may form a heterocyclic moiety.
As used herein, the term “independently” refers to the fact that the substituents, atoms or moieties to which these terms refer, are selected from the list of variables independently from each other (i.e., they may be identical or the same).
As used herein, the term “mild light irradiation conditions” or “mild irradiation conditions” refers to irradiation conditions in the near infrared region e.g., λ=625-2500 nm, for example under near infrared light range λ=700-2500 nm, in particular in the near infrared light range λ=700-1500 nm. The light irradiation may be low, moderate or high, depending on the level of exotherm to be achieved. The light irradiation may be with low intensity of a few W/cm2 or even in the mW/cm2 range. For example the near infrared irradiation intensity may range from 50 mW/cm2 to 10 W/cm2, advantageously from 100 mW/cm2 to 7 W/cm2, more advantageously from 200 mW/cm2 to 5 W/cm2, still more advantageously from 300 mW/cm2 to 3 W/cm2. The light irradiation may be moderate to high (for example, the intensity may be as low as 25 mW/cm2 or even lower (for example 25 mW/cm2≤I≤100 W/cm2, for example 25 mW/cm2≤I≤20 W/cm2), or with higher intensity, for example to increase the exotherm generated by the red-to-NIR organic dye, depending on the intended application.
As used herein, the term “photothermal” refers to the ability of red-NIR organic dyes used in the present invention to behave as heat-generator under the triggering action of red to near-infrared irradiation, as further described herein.
As used herein, “about” refers to any inherent measurement error or a rounding of digits for a value (e.g., a measured value, calculated value such as a ratio), and thus the term “about” may be used with any value and/or range. As used herein, the term “about” can refer to a variation of ±5% of the value specified. For example, “about 50” percent can in some embodiments carry a variation from 45 to 55 percent. For integer ranges, the term “about” can include one or two integers greater than and/or less than a recited integer. Unless indicated otherwise herein, the term “about” is intended to include values, e.g., weight %, temperatures, proximate to the recited range that are equivalent in terms of the functionality of the relevant individual ingredient, the composition, or the embodiment.
As used herein, the term “and/or” means any one of the items, any combination of the items, or all of the items with which this term is associated.
As will be understood by the skilled artisan, all numbers, including those expressing quantities of ingredients, properties such as molecular weight, reaction conditions, and so forth, are approximations and are understood as being optionally modified in all instances by the term “about.” These values can vary depending upon the desired properties sought to be obtained by those skilled in the art utilizing the teachings of the descriptions herein. It is also understood that such values inherently contain variability necessarily resulting from the standard deviations found in their respective testing measurements.
As will be understood by one skilled in the art, for any and all purposes, particularly in terms of providing a written description, all ranges recited herein also encompass any and all possible subranges and combinations of subranges thereof, as well as the individual values making up the range, particularly integer values. A recited range (e.g., weight percents or carbon groups) includes each specific value, integer, decimal, or identity within the range. Any listed range can be easily recognized as sufficiently describing and enabling the same range being broken down into at least equal halves, thirds, quarters, fifths, or tenths. As a non-limiting example, each range discussed herein can be readily broken down into a lower third, middle third and upper third, etc.
As will also be understood by one skilled in the art, all language such as “up to,” “at least,” “greater than,” “less than,” “more than,” “or more,” and the like, include the number recited and such terms refer to ranges that can be subsequently broken down into subranges as discussed above. In the same manner, all ratios recited herein also include all subratios falling within the broader ratio. Accordingly, specific values recited for radicals, substituents, and ranges, are for illustration only; they do not exclude other defined values or other values within defined ranges for radicals and substituents.
One skilled in the art will also readily recognize that where members are grouped together in a common manner, such as in a Markush group, the invention encompasses not only the entire group listed as a whole, but each member of the group individually and all possible subgroups of the main group. Additionally, for all purposes, the invention encompasses not only the main group, but also the main group absent one or more of the group members. The invention therefore envisages the explicit exclusion of any one or more of members of a recited group. Accordingly, provisos may apply to any of the disclosed categories or embodiments whereby any one or more of the recited elements, species, or embodiments, may be excluded from such categories or embodiments, for example, as used in an explicit negative limitation.
As will be understood by one skilled in the art, for any and all purposes, particularly in terms of providing a written description, the expression “≤x %” (for example when used to express % w/w contents in components) is equivalent to “x % or <x %”. As such, the expression “≤x %” is understood to provide support for the values “x %” and “<x %”, independently. Likewise for the expression “≥x %”: it will be understood to provide support for the values “x %” and “>x %”, independently.
As noted above, there is a dire need for the development of new systems and methods for more efficient recycling/reprocessing and self-healing of polymer compositions, without the known disadvantages of existing methods.
The inventors have discovered that an appropriately selected Red-to-NIR organic dye system can overcome the aforementioned drawbacks in the field.
In this context, there is provided herein a process for bringing a polymer composition above a threshold temperature on demand, by including in the polymer composition at least one heat-generating organic dye that generates heat above the threshold temperature when exposed to a given range of red to near-infrared irradiation. The polymer composition containing said dye used in the present invention preferably does not comprise any polymer material prepared from cyanoacrylate and usually named cyanoacrylates polymers (adhesive, resins . . . ). More particularly the polymer composition used in the present invention preferably does not contain cyanoacrylate polymers, or monomers, comprising at least one α-cyanoacrylate monomer of the formula:
where R1 represents a straight chain or branched chain alkyl group having 1 to 12 carbon atoms (which may be substituted with a substituent such as a halogen atom or an alkoxy group), a straight chain or branched chain alkenyl group having 2 to 12 carbon atoms, a straight chain or branched chain alkynyl group having 2 to 12 carbon atoms, a C3-C12 cycloalkyl group, a C6-C20 aralkyl group or any C5-C20 aryl group. Specific examples of R1 are a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a pentyl group, a neopentyl group, a hexyl group, an allyl group, a methallyl group, a crotyl group, a propargyl group, a cyclohexyl group, a benzyl group, a phenyl group, a cresyl group, a 2-choroethyl group, a 3-choropropyl group, a 2-chorobutyl group, a trifluoroethyl group, a 2-methoxyethyl group, a 3-methoxybutyl group and a 2-ethoxyethyl group.
For example, the polymer composition may comprise 0,01 to 0,5% weight of at least one heat-generating organic dye that generates heat above the threshold temperature when exposed to a given range of red to near-infrared irradiation, the weight % being expressed with respect to the total weight of the polymer composition.
The process may comprise exposing the polymer composition to red to near-infrared irradiation at a wavelength within the red to near-infrared range where the heat-generating organic dye generates heat above the threshold temperature.
As such, in one aspect, the present invention provides a process for bringing a polymer composition above a threshold temperature on demand, wherein:
Upon absorption of red-to-NIR light irradiation, the organic dye useful in the context of the invention converts a red-to-NIR light into heat (called hereafter “heater” or “heat-generator”). The organic dye therefore generates an exotherm upon exposure to red-to-NIR light irradiation in an appropriately chosen wavelength range. This exotherm may be used for inducing physico-chemical modification of a polymer (softening, melting, depolymerization, decomposition), depending on the temperature of the exotherm.
The threshold temperature may be the glass transition temperature of the polymer composition, the depolymerization temperature of the polymer composition, the melting temperature of the polymer composition, or the decomposition temperature of the polymer composition.
Methods for determining polymer's glass transition temperature, depolymerization temperature, melting temperature, or decomposition temperature are well known in the art. Any conventional method for determining a polymer's glass transition temperature, depolymerization temperature, melting temperature, or decomposition temperature, may be used to determine the threshold temperature to be reached for any given polymer composition. For example, glass transition temperature may be determined by Differential Scanning calorimetry (DSC), and Thermogravimetric analysis (TGA) may be used to measure the decomposition temperature.
A. Threshold Temperature=Glass Transition Temperature
For example, the threshold temperature may be the glass transition temperature of the polymer composition. This variant may find use for inducing physical modification of thermoplastic polymer compositions.
For example, when the polymer composition comprises a thermoplastic polymer, and the threshold temperature is the glass transition temperature of the polymer composition, the process according to the invention may be:
As such, in one aspect, the polymer composition may comprise a thermoplastic polymer, the threshold temperature may be the glass transition temperature of the polymer composition and the process may be for reshaping a thermoplastic polymer article on demand under the triggering action of red to near-infrared irradiation; the process comprising:
In another aspect, the polymer composition may comprise a thermoplastic polymer or an elastomer, the threshold temperature may the glass transition temperature of the polymer composition and the process may be for bonding together two articles made of thermoplastic polymer or an elastomer; under the triggering action of red to near-infrared irradiation; the process comprising:
In a further aspect, the polymer composition may comprise a thermoplastic polymer or an elastomer, the threshold temperature may be the glass transition temperature of the polymer or elastomer composition and the process may be for separating two pieces of a thermoplastic polymer or elastomer article under the triggering action of red to near-infrared irradiation, the process comprising:
In yet another aspect, the polymer composition may comprise a thermoplastic polymer, the threshold temperature may be the glass transition temperature of the polymer composition and the process may be for repairing at least one defect in a thermoplastic polymer article, wherein the polymer composition comprises at least one heat-generating organic dye that generates heat above, for example at least 10° C. above, the glass transition temperature of the thermoplastic polymer when exposed to a given range of red to near-infrared irradiation; the process comprising exposing the region of the article containing the at least one defect to red to near-infrared irradiation at a wavelength within the red to near-infrared range where the heat-generating organic dye generates heat above, for example at least 10° C. above, the glass transition temperature of the thermoplastic polymer; thereby resulting in self-healing of the defect.
For example, the at least one defect may include a crack, creep, a void, a hole, a distortion, a deformation, or a scratch.
B. Threshold Temperature=Glass Transition or Melting Temperature
In still another aspect, the polymer composition may be a composite polymer composition comprising a thermoplastic polymer and reinforcements or fillers. By bringing the polymer composition above its glass transition temperature or melting temperature, the polymer matrix will fluidify/liquefy and it becomes possible to separate the fluid/melted polymer matrix from the reinforcements/fillers, for example by sieving the composite fluid/melted polymer composition through a suitably meshed sieve (i.e. mesh size adapted to the reinforcement/filler size). Thus, in yet a further aspect, the polymer composition may be a composite polymer composition comprising a thermoplastic polymer and reinforcements or fillers, the threshold temperature may be the glass transition temperature or the melting temperature of the polymer composition and the process may be for recycling a composite thermoplastic polymer composition, on demand under the triggering action of red to near-infrared irradiation; the process comprising:
C. Threshold Temperature=Depolymerization Temperature
In another variant, the threshold temperature may be the depolymerization temperature of the polymer composition. This variant may find use for recycling polymer compositions.
For example, when the threshold temperature is the depolymerization temperature of the polymer composition, the process according to the invention may be for recycling a polymer composition on demand under the triggering action of red to near-infrared irradiation; the process comprising:
In step a), the heat-generating organic dye may be made to generate heat for example at least 20-30° C. above the depolymerization temperature of the polymer layer.
D. Threshold Temperature=Decomposition Temperature
In another variant, the threshold temperature may be the decomposition temperature of the polymer composition. This variant may find use for example for separating two articles bonded by a polymer layer.
For example, when the threshold temperature is the decomposition temperature of the polymer composition, the process according to the invention may be for separating two articles bonded by a polymer layer on demand under the triggering action of red to near-infrared irradiation; the process comprising:
In step b), the heat-generating organic dye may be made to generate heat for example at least 20-30° C. above the decomposition temperature of the polymer layer.
Polymer Composition
Generally speaking, the polymer may be a thermoplastic or thermosetting polymer or an elastomer preferably with the exception of cyanoacrylates polymers. In exemplary embodiments, the polymer may be a thermoplastic or a thermosetting polymer preferably with the exception of cyanoacrylates polymers.
Examples of thermoplastic polymers suitable for carrying out the present invention include polyacrylates, polymethacrylates such as poly(methyl methacrylate), polyacrylonitrile butadiene styrene terppolymer, nylon, polylactic acid, polybenzimidazole, polycarbonate, polyestersulfone, polyoxymethylene, polyetherether ketone, polyetherimide, polyethylene, polyphenylene oxide, polyphenylene sulfide, polypropylene, polystyrene, polyvinyl chloride, polyvinylidene fluoride, or teflon. The polyacrylates suitable for carrying out the present invention preferably may not be polymers prepared from a cyanoacrylate compound such as methyl 2-cyanoacrylate.
Examples of thermosetting polymers suitable for carrying out the present invention include epoxy resins, polyureas, phenolic resins, polyester resins, polyurethanes, polyimides, polycyanurates, or vinyl ester resins.
As previously discussed, the polymer composition may be a composite polymer composition. As such, the polymer composition may comprise composite reinforcements or fillers. The composite reinforcements or fillers may be glass fibers, carbon fibers such as carbon fiber fabrics, aramid fibers, basalt fibers, silica fibers, metallic fillers such as metallic nanoparticles, polymer fibers, natural fibers or carbon-based fillers such as carbon black, biochar, carbon fibers, carbon fiber fabrics or carbon nanostructures (such as carbon nanotubes or graphene), or a mixture of two or more of those.
Heat-Generating Organic Dye
Advantageously, the heat-generating organic dye may be any suitable dye that generates heat when exposed to a 625-2500 nm light source (i.e., when exposed to irradiation in the red to near-infrared), for example when exposed to a 625-1500 nm light irradiation. Advantageously, the heat-generating organic dye, when exposed to red to near-infrared irradiation, may generate an exotherm above a threshold temperature which is useful to induce physico-chemical modification of a polymer composition which contains the heat-generating organic dye. The threshold temperature may be the glass transition temperature, the depolymerization temperature, the melting temperature, or the decomposition temperature of the polymer composition. Therefore the exotherm generated by the organic dye upon exposure to red-to-NIR light irradiation in an appropriately chosen wavelength range, may induce softening/fluidization, melting, depolymerization, or decomposition of the polymer matrix of the polymer composition containing the heat-generating organic dye. As the reader will appreciate, the choice of the heat-generating organic dye can be made depending on the application that is targeted/desired, and the temperature that is desired to be achieved. This, together with the fact that low intensity red-NIR irradiation makes it possible to very finely control the temperature, provides to the system according to the present invention a great versatility in terms of fine-tuning the temperature, and the polymerization process, which is a notable advantage over existing systems.
Advantageously, the heat-generating organic dye may comprise a cyclic or acyclic conjugated system containing 1, 2 or 4 heteroatoms selected from N or S, for example 2 or 4 heteroatoms selected from N or S, the lone pair of which may participate in the conjugated system; wherein the heat-generating organic dye generates heat when exposed to a 625-2500 nm light source, for example when exposed to a 625-1500 nm light irradiation. Advantageously, the heat-generating organic dye may comprise:
An example of heat-generating organic dye comprising a cyclic or acyclic conjugated system containing one heteroatom selected from N or S, the lone pair of which may participate in the conjugated system include the squaraine dye SQ-2 shown in
Advantageously, the at least one heat-generating organic dye may be selected from:
The dyes may be tested for their ability to generate heat upon red-NIR irradiation by thermal imaging. For this characterization, an appropriate concentration of red-NIR dye may incorporated in the polymerizable resin or in the ready-to-use polymer composition and irradiated with the red-NIR light. Through thermal imaging experiments, the temperature of the resin can be recorded for different irradiation times. Thermal camera, thermocouple or pyrometer can also be used to record the temperature. Without the presence of the red-NIR-dye the temperature remains almost unchanged showing the role of the red-NIR dye as heater.
As used herein, the term “cyanine dye” does not deviate from the conventional meaning of the term in the art, and refers to a dye having an opened conjugated system where a moiety
and a moiety
are covalently linked via a conjugated system of two or more double bonds, some of which may belong to an aromatic radical. A counter-ion X is typically present to counterbalance the positive charge of the ammonium ion. Advantageously, X may represent Cl−, I−, ClO4−, p-toluenesulfonate, p-dodecylbenzenesulfonate, or a borate anion, such as triphenylbutylborate. Advantageously, the counter ion X may represent a borate anion. For example, X may represent triphenylbutylborate. The expression “opened conjugated system” refers to the fact that the moieties
do not form a cycle together with the conjugated double bonds (i.e, the whole does not piggy-back together to form a cycle). However, the whole system may comprise one or more mono- or polycyclic alicyclic, heterocyclic, aromatic or heteroaromatic radicals. For example, cyanine dyes useable in the context of the invention include as synthetic dyes with the general formula R2N[CH═CH]nCH═N+R2 or R2N+═CH[CH═CH]nNR2 (n is a small number, typically 2-5) in which the nitrogen and part of the conjugated chain usually form part of a heterocyclic system, such as imidazole, pyridine, pyrrole, quinoline and thiazole, e.g. [1] Examples of such cyanine dyes useable as heat-generator according to the present invention include those depicted in
As used herein, the term “squaraine dye” does not deviate from the conventional meaning of the term in the art, and refers to a family of chromophores containing structures such as cyanine dyes, two donor groups conjugated to an electron deficient oxocyclobutenolate core, leading to a highly electron delocalized structure that can be exemplified as zwitterions. Generally, squaraine dyes with donor-acceptor-donor (D-A-D) structures are synthesized by the condensation reaction of 3,4-dihydroxy-3-cyclobutene-1,2-dione (squaric acid) with activated aromatic or heterocyclic components [2] Examples of such squaraine dyes useable as heat-generator according to the present invention include those depicted in
As used herein, the term “push-pull dye” does not deviate from the conventional meaning of the term in the art, and refers to organic pi-systems end-capped with an electron donor (D) and an electron acceptor (A) at each side of the pi-system. Interaction between A and D allows intramolecular charge-transfer (ICT) and a new low-energy molecular orbital is formed. Thus, it is easier to achieve excitation of electrons in the molecular orbital at longer wavelength. Typical electron donors D are represented by the substituents with +M/+I effects such as OH, NH2, OR and NR2, heterocyclic moieties . . . On the other hand, the most used electron acceptors A involve substituents featuring M/I effects such as NO2, CN, CHO, electron deficient heterocyclic compounds . . . [3]. Examples of such push-pull dyes useable as heat-generator according to the present invention include that depicted in
As used herein, the term “BODIPY” does not deviate from the conventional meaning of the term in the art, and refers to boron-dipyrromethene type compounds, which is a class of fluorescent dyes. It is composed of dipyrromethene complexed with a disubstituted boron atom, typically a BF2 unit.[4] An example of such BOPIDY dyes useable as heat-generator according to the present invention include that depicted in
As used herein, the term “dithiolene dye” does not deviate from the conventional meaning of the term in the art, and refers to metal complexes including unsaturated bidentate ligands containing two sulfur donor atoms (e.g., dithiolene ligands attached to a central metal). They may be also referred to as “metallodithiolene dyes”. Generally, the metal used is nickel, palladium or platinum and is in a zerovalent state. Dithiolene ligands are unsaturated bidentate ligand wherein the two donor atoms are sulfur. This formed square planar complexes. Because of the extensive electron delocalization about the dithiolene ring system and the interaction of this delocalized system's available d-orbitals on the central metal, strong NIR absorption is observed with these compounds. [5]
Advantageously, a dithiolene dye useable as heat-generator according to the present invention include:
wherein M represents a metal center that absorbs in the red to near-infrared region of 625-2500 nm, for example a metal atom that absorbs in the range 625-1500 nm, such as Ni; and Ar1, Ar2, Ar3, and Ar4 independently represent a C6-10 aryl; wherein each aryl moiety may be, individually, further substituted with one or more substituents, such as —OH, —OR, halogen atom, —NO2, —CN, —NRA1RA2, —NHC(═O)RA3, —OC(═O)RA3, vinyl, or linear or branched C1-10 alkyl or C6-10 aryl moieties; wherein R and RA3 independently represent a linear or branched C1-10 alkyl or C6-10 aryl moiety; and RA1 and RA2 independently represent H or linear or branched C1-6 alkyl or C6-10 aryl moieties, where RA1 and RA2, taken together with the nitrogen atom to which they are attached, may form a 5- or 6-membered heterocyclic moiety; wherein each of the foregoing aryl moieties may be, individually, further substituted with one or more linear or branched C1-6 alkyl or C6-10aryl moieties. Advantageously, Ar1, Ar2, Ar3, and Ar4 may independently represent a phenyl moiety; wherein each phenyl moiety may be, individually, further substituted with one or more substituents, such as those as described immediately above, preferably linear or branched C1-6 alkyl moieties, including methyl, propyl, butyl, i-propyl. Examples of such dithiolene dyes useable as heat-generator according to the present invention include those depicted in
As used herein, the term “porphyrin dye” does not deviate from the conventional meaning of the term in the art, and refers to conjugated heterocyclic macrocycle metal complexes comprising four modified pyrrole subunits interconnected at their a carbon atoms via methine bridges (═CH—).
Advantageously, a porphyrin dye useable as heat-generator according to the present invention may have a heterocyclic conjugated system having the structure:
wherein M represents a metal center that absorbs in the red to near-infrared region of 625-2500 nm, for example a metal atom that absorbs in the range 625-1500 nm, such as Mg or Cu; and each occurrence of R1, R2, R3, and R4 may independently represent H, —C(═O)OR5, vinyl, a linear or branched C1-10 alkyl or a C6-10 aryl moiety; wherein R5, for each occurrence, may independently represent H or an alkali metal cation such as Na+; and wherein each of the foregoing alkyl or aryl moieties may be, individually, further substituted with one or more linear or branched C1-6 alkyl or C6-10 aryl moieties. Examples of such porphyrin dyes useable as heat-generator according to the present invention include chlorophyllin sodium copper salt depicted in
As used herein, the term “copper complex dye” does not deviate from the conventional meaning of the term in the art, and refers to conjugated oxygen-containing systems (acetylacetonate derivatives) comprising either one of the following basic motifs:
each of which may bear one or more alkyl and/or aryl substituents.
Examples of such copper complex dyes useable as heat-generator according to the present invention include those depicted in
As used herein, the term “phthalocyanine dye” does not deviate from the conventional meaning of the term in the art, and refers to conjugated macrocycles which, depending on how they were synthesized, contain different metal or metalloid inclusions. Advantageously, a phthalocyanine dye useable as heat-generator may have a cyclic conjugated system having the structure:
wherein M represents a metal center, for example Mn, and L1 and L2 independently represent acyloyl ligands or may be absent, depending on the metal atom valency. Examples of such phthalocyanine dyes useable as heat-generator include Manganese (II) phthalocyanine depicted on
Preferably the at least one heat-generating organic dye may be selected from any one or more of the dyes depicted on
Advantageously, the at least one heat-generating organic dye may be a cyanine dye, squaraine or squarylium dye, a push-pull dye, a BODIPY or pyrromethene dye, a porphyrin dye, a copper complex dye, or a phthalocyanine dye, in the form of a borate salt; preferably a cyanine dye in the form of a borate salt or a push-pull dye, more preferably:
most preferably IR-813 or IR-1064.
The dye performance as heat generator may vary with the irradiation wavelength and/or intensity. As such, both parameters (irradiation wavelength and/or intensity) may therefore be used to tune the dye performance for producing a sufficient exotherm.
Advantageously, the heat-generating organic dye may be used in about 0.001% w/w to <0.5% w/w, preferably 0.001-0.4% w/w, preferably 0.001-0.3% w/w, more preferably ≤0.25% w/w, still more preferably ≤0.20% w/w, most preferably ≤0.15% w/w, most preferably ≤0.10% w/w, yet most preferably about 0.1% w/w or even <0.1% w/w, based on the total weight of the polymer composition. For example the heat-generating organic dye may be used in about 0.005% w/w, 0.007% w/w, 0.009% w/w, 0.01% w/w, 0.02% w/w, 0.03% w/w, 0.04% w/w, 0.05% w/w, 0.06% w/w, 0.07% w/w, 0.08% w/w, 0.09% w/w, 0.10% w/w, 0.11% w/w, 0.12% w/w, 0.13% w/w, 0.14% w/w, 0.15% w/w, 0.16% w/w, 0.17% w/w, 0.18% w/w, 0.19% w/w, 0.20% w/w, 0.25% w/w, 0.30% w/w, 0.35% w/w, 0.40% w/w, 0.45% w/w, 0.50% w/w, based on the total weight of the polymer composition. Advantageously, the heat-generating organic dye may be used in about <0.50% w/w, preferably ≤0.40% w/w, preferably ≤0.30% w/w, preferably ≤0.20% w/w, preferably ≤0.15% w/w, preferably ≤0.10% w/w, most preferably ≤0.08% w/w of the total weight of the polymer composition.
Advantageously, the heat-generating organic dye may be used in about 0.01-0.50 wt %, more preferably from 0.01-0.30 wt %, yet more preferably from 0.01-0.20 wt %, even more preferably from 0.01-0.10 wt %, most preferably from 0.05-0.10 wt %, based on the total weight of the polymer composition.
Advantageously, the heat-generating organic dye may be selected from cyanine dyes, squaraine or squarylium dyes, push-pull dyes, BODIPY or pyrromethene dyes, porphyrin dyes, copper complex dyes, or phthalocyanine dyes, adsorbing in the red to near-infrared region; preferably cyanine dyes or squaraine dyes.
Advantageously, the heat-generating organic dye may be selected from any one or more of the following:
Advantageously, the heat-generating organic dye may be selected from
Irradiation Light Source
For purposes of the present invention, any light source known in the art, capable of generating light in the 625-2500 nm region, for example in the range of 625-1500 nm, may be used. For example, light emitted from LED bulbs, laser, laser diode, low pressure mercury and argon lamps, fluorescent light systems, electric arc-light sources, high intensity light sources may be used. Advantageously, the light source may generate light in the red region of the light spectrum (i.e., 625-750 nm). For example, light sources that may be used to that effect include LED bulb, laser, laser diode, fluorescent light system, electric arc light source, high intensity (metal halide 3000K, high pressure sodium lamp), Xenon light, Mercury-Xenon light.
Advantageously, the light source may generate light in the near-infrared region of the light spectrum (i.e., 700-2500 nm, for example 700-1500 nm). For example, light sources that may be used to that effect include NIR LEDs, NIR lasers, low pressure mercury and argon lamps (696-1704 nm) Tungsten light source, tungsten halogen light source, Nd:Yag laser, Nd:YVO4, Nd:CidVO4, Nd:LuVO4, CO2 laser, the intensity of which (especially for the most powerful irradiation light source systems such as lasers (e.g., Nd:Yag lasers)) may be tuned down to a fairly low intensity (e.g., <10 W/cm2).
An important advantage of the invention is that bringing a polymer composition above a desired temperature threshold can be achieved under long wavelength irradiation conditions (i.e., less energetic and safer than UV-type irradiation for example).
Another important advantage include the potentiality of having a tunable heat released: by changing (i) the nature/type of heat-generating organic dye, (ii) its concentration, (iii) the power of the light delivered (irradiance), and/or (iv) the irradiation wavelength, the temperature of the system (and ultimately the control of the physico-chemical modification induced in the polymer matrix) can readily be modulated. This is a stark advantage over existing processes.
Yet another advantage is that red-to-near-infrared irradiation penetrates much deeper within samples, than other commonly used irradiations. Cf.
Advantageously, the light source may be preferably selected as a function of the heat-generating organic dye to be used: most advantageously, the light source may be one that emits light in the wavelength range where the dye most readily absorbs the light to generate an exotherm, which allows to bring a polymer composition above a desired threshold temperature. The heat-generating profiles of organic dyes known to absorb in the red or near infrared range of the light spectrum are known or can be readily determined by running an exotherm vs. wavelength graph using thermal imaging.
Briefly, the heat-generating potential of a red-NIR dye may be determined using an infrared thermal imaging camera, such as (Fluke TiX500) with a thermal resolution of about 1° C. and a spatial resolution of 1.31 mRad by recording the heat released by the red-NIR dye in the resin (polymerizable component) under exposition to the suitable irradiation is described in detail in [6].
As will be readily apparent throughout the teachings of the present document, if a particular organic dye generates low/moderate heat at a given wavelength, one may still proceed with that particular dye at the same given wavelength by increasing the intensity of the light irradiation. This may be done by using a tunable power light source for example, such as commercially available tunable power red to near-infrared light sources.
For illustration purposes, if IR 780 is used as heat-generating organic dye, a NIR laser@785 nm may be used.
As discussed above, it is understood that the light source may be a tunable power light source; that is one that is equipped with tunable power, so as be able to adjust the power of the red to near infrared light irradiation, if needed. Such tunable power light source may also be used to determine the light intensity threshold at which a particular dye starts to absorb at any given wavelength, and therefore to fine-tune the wavelength/irradiation intensity that may be used to obtain optimal conditions for polymerization.
Likewise, the absorbance profiles of dyes known to absorb in the red or near infrared range of the light spectrum are known or can be readily determined by running an absorbance vs. wavelength graph. As will be readily apparent throughout the teachings of the present document, if a particular dye exhibits low/moderate absorbance at a given wavelength, one may still proceed with that particular dye at the same given wavelength by increasing the intensity of the light irradiation. This may be done by using a tunable power light source for example, such as commercially available tunable power red to near-infrared light sources.
The combination of both techniques (heat-generation profile and absorbance profile) allows to identify/select organic dyes that may be suitable for carrying out the present invention, including the preferred irradiation wavelength for optimal exotherm generation.
Preparation Method
Polymer compositions comprising a red-to-NIR heat-generating organic dye may be prepared according to conventional methods that are known to the person of ordinary skill in the art.
For example, such polymer compositions may be prepared by mixing an already prepared polymer composition with the red-to-NIR heat-generating organic dye.
Alternatively, polymer compositions for practicing the present invention may be prepared by polymerizing monomers in the presence of red-to-NIR heat-generating organic dye (bulk synthesis). The reaction conditions and starting materials may be appropriately chosen to minimize the risk for the red-to-NIR organic dye to be involved in the polymerization process and/or to be degraded.
Preparation from Existing Polymer Composition
Polymer compositions for carrying out the present invention may be prepared by a method including a step of mixing at least one heat-generating organic dye and a polymer or a polymer mixture. The heat-generating organic dye may be in solution in a suitable solvent. The polymer or a polymer mixture may also be in solution in a suitable solvent, which may be the same or different from the solvent of the dye solution. Alternatively, the heat-generating organic dye may be added to the polymer or a polymer mixture, or to a solution of polymer or a polymer mixture in a solvent.
The polymer may be any polymer that allows reducing to practice the present invention. It can be selected for example from the group comprising polystyrene; polyolefines, for example polyethylene, polypropylene, poly(alpha-olefine)s, polyisobutene and polypropylene; polyethers; polyesters; polyamides; polyacrylamides; polyacrylates; polysilanes; polysiloxanes.
The polymer may be a thermoplastic polymer selected from polyacrylates, polymethacrylates such as poly(methyl methacrylate), polyacrylonitrile butadiene styrene terppolymer, nylon, polylactic acid, polybenzimidazole, polycarbonate, polyestersulfone, polyoxymethylene, polyetherether ketone, polyetherimide, polyethylene, polyphenylene oxide, polyphenylene sulfide, polypropylene, polystyrene, polyvinyl chloride, polyvinylidene fluoride, or teflon.
The polymer may be a thermosetting polymer selected from epoxy resins, polyureas, phenolic resins, polyester resins, polyurethanes, polyimides, polycyanurates, or vinyl ester resins.
The polymer may be an elastomer.
The polymer may be a linear block copolymer or a statistic copolymer. The person skilled in the art will know how to identify appropriate experimental conditions, and the polymer or polymers to be used, to obtain a composite material having the requisite/desired properties.
“Block copolymers” as used herein refers to a sequenced polymer comprising more than one type of monomer. In a block copolymer, identical monomers are grouped together. Such polymers and methods for their preparation are described for example in Matyjazewski, K.; Eds.; Advances in Controlled/Living Radical Polymerisation, (American Chemical Society 2003) [7] or Hsieh, H. L.; Quirk, R. P.; Eds.; Anionic Polymerisation Principles and Practical Applications, (Marcel Dekker 1996) [8].
“Statistic copolymer” as used herein refers to a polymer in which the various monomers mix depending on their reactivity and concentration. Such polymers and methods for their preparation are described for example in Matyjaszewski, K.; Davies, T. P; Eds.; Handbook of Radical Polymerisation, (Wiley-Interscience 2002) [9] or Fontaine, L.; Initiation à la chimie et à la Physico-Chimie Macromoléculaires (Groupe Français d′Etudes et d′Applications des Polymères volume 12 (Chapitre 3)) [10].
Bulk Preparation by In Situ Polymerization
In another variant, polymer compositions for carrying out the present invention may be prepared by a method including a step of in situ polymerisation of a monomer or a mixture of monomers in the presence of at least one heat-generating organic dye.
The reaction conditions and starting materials may be appropriately chosen to minimize the risk for the red-to-NIR organic dye to be involved in the polymerization process and/or to be degraded. For example, if a photopolymerization process is chosen, the photoinititor (e.g. UV photoinitiator) and the red-to-NIR organic dye may be appropriately selected so that no (or low) overlap of their respective absorptions could exist, avoiding the risk for the NIR dye to be involved in the polymerization process and to be degraded.
Any conventional polymerization method may be used. For example, polymers and methods for their preparation are described for example in Matyjaszeski, K.; Eds. Advances in Controlled/Living Radical Polymerisation, (American Chemical Society 2003) [7]; Hsieh, H. L.; Quirk, R. P.; Eds.; Anionic Polymerisation Principles and Practical Applications, (Marcel Dekker 1996) [8]; Matyjaszewski, K.; Davies, T. P; Eds.; Handbook of Radical Polymerisation, (Wiley-Interscience 2002) [9] or Fontaine, L.; Initiation à la chimie et à la Physico-Chimie Macromoléculaires (Groupe Français d′Etudes et d′Applications des Polymères volume 12 (Chapitre 3)) [10].
When a block copolymer is involved, it can be a 2-block copolymer synthesized for example by controlled radical polymerisation or live anionic polymerisation or live cationic polymerisation, or a statistic copolymer synthesized by controlled radical polymerisation or non-controlled radical polymerisation.
Controlled radical polymerisation (CRP) is a method of choice for preparing well-defined polymers and copolymers with adjustable molar masses and low polymolecularity indexes. Techniques that can be used in the present invention are for example described in Matyjaszewski, K.; Davies, T. P; Eds.; Handbook of Radical Polymerisation, (Wiley-Interscience 2002) [9]
“Live polymerisation” as used herein refers to a polymerisation in which there is neither termination reactions nor transfer reactions, and where polymer chains keep on growing as long as there remains free monomer molecules to be added to chains. Live polymerisation may be cationic or anionic. Such methods are described for example in Matyjaszeski, K.; Eds. Cationic Polymerisation Mechanisms, Synthesis and Applications, (Marcel Dekker 1996) [11] or Hsieh, H. L.; Quirk, R. P.; Eds.; Anionic Polymerisation Principles and Practical Applications, (Marcel Dekker 1996) [8].
Monomers can all be introduced during the step of polymerisation. They also can be introduced separately or in a mixture, continuously or discontinuously. A supplemental monomer can also be introduced at the end of the polymerisation process, to obtain the desired polymer composition.
For example, the polymerizable component or monomer may be any C═C bond-containing compound polymerizable by free radical polymerization. Advantageously, at least one polymerizable component may be an ethylenically unsaturated monomer, the polymerization of which may be achieved by free radical polymerization. As used herein, the term “ethylenically unsaturated monomer” refers to a polymerizable components that contains at least one carbon-carbon double bond. Preferably, ethylenically unsaturated monomers whose polymerization may be effected by free radical polymerization, contains at least one carbon-carbon double bond that is conjugated with an aryl moiety (e.g., phenyl), a carboxyl (C═O) group, or another double bond. Such monomers in this category include for example acrylates —[(ROCO)CHCH2]— (acrylic acid, methyl acrylate, ethyl acrylate, butyl acrylate, etc. . . . ), methacrylates —[(ROCO)C(Me)CH2]— (methacrylic acid, methyl methacrylic acid, etc. . . . ), styrene, ethylene, propylene, N-vinyl acrylamide, N-vinylpyrolidone. For example, at least one polymerizable component may be selected from monomers, prepolymers, dimers, trimers or oligomers containing at least one C═C bond that is conjugated with an aryl moiety, a carboxyl group, or another double bond. For example, at least one polymerizable component may be selected from conjugated carboxylic acids such as acrylic acid, methacrylic acid, itaconic acid, crotonic acid, isocrotonic acid, maleic acid, and esters and amides thereof; or styrene, ethylene, propylene, N-vinyl acrylamide, or N-vinylpyrolidone.
For example, at least one polymerizable component may be an acrylate or methacrylate monomer. For example, at least one polymerizable component may be an acrylate monomer such as trimethylolpropane triacryalate (TMPTA). For example, at least one polymerizable component may be a methacrylate monomer such as (hydroxypropyl)methacrylate (HPMA), 1,4-butanediol dimethacrylate (1,4-BDDMA), 1,6-Bismethacryloxy-2-ethoxycarbonylamino-2,4,4-trimethylhexane (BMATMH) or methacrylate functionalized prepolymers such as aliphatic and aromatic diurethane dimethacrylates, for example UDMA.
Advantageously, the polymerizable component may be a mixture of two or more monomers, prepolymers, dimers, trimers or oligomers containing at least one C═C bond that is conjugated with an aryl moiety, a carboxyl group, or another double bond, as described immediately above. For example, it may be a mixture of at least two compounds selected from methacrylate monomers such as HPMA, 1,4-BDDMA, BMATMH and methacrylate functionalized prepolymers such as aliphatic and aromatic diurethane dimethacrylates (e.g., UDMA). Examples of polymerizable components include mixtures of HPMA, 1,4-BDDMA and aliphatic and aromatic diurethane dimethacrylates such as UDMA, for example Mix-Ma as described herein. For example, the at least one polymerizable component may be selected from acrylates and methacrylates or mixture thereof, such as:
or a mixture of two or more of them, most preferably a 1:1:1 mixture by weight of HPMA, 1,4-BDMA and UDMA.
Methods/processes according to the invention can generally be carried out using conventional methods of preparing the above described polymers according to the present invention in a suitable mixing device such as, but not limited to, stirred tanks, dissolvers, homogenizers, microfluidizers, extruders, or other equipment conventionally used in the field.
Additives that are optionally incorporated during conventional polymerisation methods may be used according to the method of the invention. Thus, initiators, chain transfer agents, catalysts, antioxidants, lubricants, reinforcements/fillers known to the person skilled in the art can be used.
Examples of Suitable Additives Include:
Mixtures of at least two of these additives are also suitable in the context of the invention.
As used herein, the term “tackifier” refers to polymers which increase the tack properties, that is to say, the intrinsic viscosity or self-adhesion, the compositions so that, after a slight pressure a short period, they adhere firmly to surfaces. When the polymerization method is used for the preparation of composites and/or laminated articles, the process may further comprise a step of adding a material/reinforcement designed for this purpose using known methods.
The polymerization method may thus further comprise a step of impregnating composite reinforcements with a mixture of the red-NIR heat-generating dye and at least one polymerizable component, in a mold, such as a silicone mold, prior to effecting polymerization.
The reinforcements/fillers used in composite polymer compositions in the context of the present invention may have a nanometric and/or micrometric size.
“Nanometric size material” a used herein refers to a material whose size is of a few nanometres in at least one of the space dimensions. For example, the size of the material in at least one of the space dimensions is between 1 and 20 nm, preferably between 1 and 2 nm.
“Micrometric size material” a used herein refers to a material whose size is between 1 and 100 microns.
Composite polymer compositions in the context of the present invention may comprise only micrometric size fillers, or only nanometric size fillers, or a mixture of micro and nanometric size fillers.
The composite reinforcements may be any reinforcing conventionally used in the manufacture and implementation of composite materials. For example, the composite reinforcements may be selected from any one or more of:
The composite reinforcements may be for example selected from glass fibers, carbon fibers, aramid fibers, basalt fibers, silica fibers, polymer fibers (such as polyesters, poly (p-phenylene-2,6-benzobisoxazole), aliphatic and aromatic polyamides, polyethylene, polymethyl methacrylate, polytetrafluoroethylene), natural fibers (such as nettle, flax or hemp fibers) . . . Advantageously, composite reinforcements may be glass fibers, carbon fibers such as carbon fiber fabrics, aramid fibers, basalt fibers, silica fibers, metallic fillers such as metallic nanoparticles, polymer fibers, natural fibers or carbon-based fillers such as carbon black, biochar, carbon fibers, carbon fiber fabrics or carbon nanostructures (such as carbon nanotubes or graphene), or a mixture of two or more of those.
Advantageously, the composite reinforcements may be previously disposed in a mold, and then impregnated by a mixture of the red-NIR heat-generating dye and at least one polymerizable component before triggering polymerization.
Alternatively, composite reinforcements may be pre-impregnated with a mixture of the red-NIR heat-generating dye and at least one polymerizable component. Then the resulting mixture may be deposited/spread evenly over the mold, either manually or using an automated robot, in the case of mass production, followed by polymerization.
Uses/Methods
In another aspect, the invention relates to the use of a heat-generating organic dye adsorbing in the red to near-infrared, for:
The practitioner has a well-established literature of synthetic organic and inorganic chemistry and polymer chemistry to draw upon, in combination with the information contained herein, for guidance on synthetic strategies, protecting groups, and other materials and methods useful for the preparaion of the polymer compositions useable in the context of the present invention. For example, the reader may refer to the Exemplification section below, and references cited therein for synthetic approaches suitable for the preparation of some of the compositions and polymer materials described herein. The reader may refer for references to references [17] and [18], which relate to phthalocyanine dyes. These are often simple to synthesize with relatively high yields and have been used as commercial pigments and dyes for decades.
The present invention offers many advantages, including:
Other advantages may also emerge to those skilled in the art upon reading the examples below, with reference to the attached figures, which are provided as non-limiting illustrations.
The representative examples that follow are intended to help illustrate the invention, and are not intended to, nor should they be construed to, limit the scope of the invention. Indeed, various modifications of the invention and many further embodiments thereof, in addition to those shown and described herein, will become apparent to those skilled in the art from the full contents of this document, including the examples which follow and the references to the scientific and patent literature cited herein. It should further be appreciated that the contents of those cited references are incorporated herein by reference to help illustrate the state of the art.
The following examples contain important additional information, exemplification and guidance that can be adapted to the practice of this invention in its various embodiments and the equivalents thereof.
The polymer materials and compositions of this invention and their preparation can be understood further by the examples that illustrate some of the processes by which these polymer materials and compositions are prepared or used. It will be appreciated, however, that these examples do not limit the invention. Variations of the invention, now known or further developed, are considered to fall within the scope of the present invention as described herein and as hereinafter claimed.
In the Examples that follow is illustrated the use of a NIR organic dye (fully soluble in the polymer contrary to fillers such as graphene oxide or nanoparticles) that could be used, subsequent to the polymerization process, for a light-to-heat conversion enabling the increase of the thermoplastic temperature beyond its glass transition temperature. Using this strategy, a modification of the thermoplastic's mechanical properties could be achieved and self-healing of the polymer or the possibility to develop a recycling process based on a bonding/debonding strategy done on demand through NIR irradiation could be promoted. This last strategy constitutes an environment-friendly approach to recycle polymers compared to oven heating. Especially, the main advantage of this photothermal approach is to allow an efficient spatial control of the photothermal effect as illustrated in Scheme 1. More precisely, increase of the temperature is only observed in the irradiated areas e.g. for healing or debonding of multimaterials.
Materials and Methods
Tri methylolpropane triacrylate (TMPTA) was purchased from Sigma-Aldrich, phenyl bis(2,4,6-trimethylbenzoyl)-phosphine oxide (SPBPO) was obtained from Lambson Ltd (UK), IR-813 p-toluenesulfonate (IR-813) was ordered from Tokyo Chemical Industry (TCI-europe) and used as received, crayvallac SLT was provided from Arkema and Glyfoma was supplied from Evonik. The squaraine (SQ) was synthesized according to a procedure recently reported in the literature [19] without modification and in similar yield. Chemical structures of the different monomers and additives are presented in the scheme 2 except that of the crayvallac SLT which is used as a thickener.
Mass spectroscopy was performed by the Spectropole of Aix-Marseille University. ESI mass spectral analyses were recorded with a 3200 QTRAP (Applied Biosystems SCIEX) mass spectrometer. The HRMS mass spectral analysis was performed with a QStar Elite (Applied Biosystems SCIEX) mass spectrometer. Elemental analyses were recorded with a Thermo Finnigan EA 1112 elemental analysis apparatus driven by the Eager 300 software. 1H and 13C NMR spectra were determined at room temperature in 5 mm o.d. tubes on a Bruker Avance 400 spectrometer of the Spectropole: 1H (400 MHz) and 13C (100 MHz). The 1H chemical shifts were referenced to the solvent peak CDCl3 (7.26 ppm), DMSO (2.49 ppm) and the 13C chemical shifts were referenced to the solvent peak CDCl3 (77 ppm), DMSO (49.5 ppm).
Thermoset Polymer
Thermoset polymer samples were prepared to test the heater effect for in-situ embedded NIR dyes.
A multifunctional acrylate monomer (TMPTA, 3 g (98.9% wt)) was mixed with a UV photoinitiator (SPBPO, 0.03 g (1% wt)). In addition, a heat-generating organic dye (0.003 g (0.1% wt))—which is a NIR organic dye (here, IR-813 or SQ, fully soluble in TMPTA)—was incorporated into the photocurable resin before being polymerized under laser diode at 405 nm.
The experiment was repeated using the same amounts of TMPTA (3 g) and SPBPO (0.03 g) but by varying the heat-generating dye concentration/content: 0.01% wt, 0.02% wt, 0.04% wt, 0.05% wt, 0.08% wt, and 0.2% wt. The % wt are expressed with respect of the total weight of the composition.
Thermoplastic Polymer
Once the heater effect was confirmed, thermoplastic samples were prepared. A monomer (Glyfoma, 3 g (96.9% wt)) was selected as a benchmark monofunctional monomer leading to a thermoplastic polymer. A thickener (crayvallac SLT, 0.03 g (1% wt)) was added to control the viscosity of the photocurable sample. Then, the photoinitiator (SPBPO, 0.06 g (2% wt)) and the NIR heater (IR-813 or SQ, 0.003 g (0.1% wt)) were incorporated in the resins.
Likewise, the experiment was repeated using the same amounts of Glyfoma (3 g), crayvallac SLT (0.03 g) and SPBPO (0.06 g) but by varying the heat-generating dye concentration/content: 0.01% wt, 0.02% wt, 0.04% wt, 0.05% wt, 0.08% wt, and 0.2% wt. The % wt are expressed with respect of the total weight of the composition.
The photopolymerization experiments enabling to access to thermosets or thermoplastics were carried out at room temperature upon irradiation with a laser diode at 405 nm (450 mW·cm−2) in a mold. The UV photoinitiator and the two NIR dyes were appropriately selected so that no (or low) overlap of their respective absorptions could exist, avoiding the risk for the NIR dye to be involved in the polymerization process and to be degraded. A Jasco 6600 real-time Fourier transformed infrared spectroscopy (RT-FTIR) was used to follow the C═C acrylate double bond conversion between 6100 and 6200 cm−1 according to the irradiation time of 2 mm thick samples.
1. Infrared Thermal Imaging Camera
In order to follow the heater effect of the NIR dyes in-situ embedded in thermoset or thermoplastic samples, different NIR light sources were used: i) laser diodes @785, 940, 980 and 1064 nm or ii) LED@850 nm. Excitations with the NIR light source were done at a distance of 2 cm for the laser diodes and 6 cm for LEDs. A Fluke TiX500 infrared thermal imaging camera was used to follow in real time the temperature reached by the polymer.
2. UV-VIS Absorption Spectroscopy
A Jasco V-750 spectrophotometer was used to measure the UV-Vis absorption spectra of both IR-813 and SQ in toluene and acetonitrile.
3. Differential Scanning Calorimetry (DSC)
A DSC Mettler Toledo DSC1 coupled to the Star software was used to determine the glass transition temperature of the thermoplastic samples. These latter were heated twice: a first run was carried out to erase their thermal backgrounds and a second run was performed in order to determine the Tg by drawing the tangent of the transition phase.
4. Thermogravimetric Analysis (TGA)
A Mettler Toledo TGA DSC 3+ and the Star software were used to measure the thermal decomposition temperature of the heaters. These latter were heated from 30° C. to 900° C. with a rise in temperature of 10 K·min−1.
5. Optical Microscopy
A PX-8085-919 optical microscope (from Somikon) was used to follow the evolution of scratched thermoplastic samples over irradiation time. This optical microscope has a 200 magnification factor which allows higher quality pictures.
6. Results
Photopolymerizations of TMPTA-based photosensitive resins were recorded by RT-FTIR in order to follow the acrylate function conversion in the presence of different heater contents. The kinetics recorded for different concentrations of IR-813 are depicted in
As shown in
In this Example, we showed that it was possible to in-situ embed a NIR heat-generating organic dye into a polymer film. Specifically, this was achieved by photopolymerizing a TMPTA monomer with a UV-visible photoinitiator (SPBPO) upon excitation at 405 nm. In a second step, NIR heat-generating organic dyes can be used to activate the photothermal effect by irradiation with a NIR light. Indeed, heat-generating organic dyes will release heat by absorbing the NIR light. Various parameters influencing the maximum temperature reached by the polymer films were investigated, namely the irradiance (see
Irradiance
NIR Wavelength
Another factor influencing the maximal temperature reached by the polymer film is the selected NIR wavelength. Indeed, the two NIR dyes can absorb differently in the NIR range and preferential wavelengths can be thus selected to improve the light-to-heat conversion. To illustrate this, by absorbing more light, the NIR can thus produce more heat. Therefore, it is of utmost interest to get a good matching between the emission wavelength of the NIR light used to excite the NIR heat-generating organic dyes and their respective absorptions.
Table 2 summarizes the different temperatures reached by the polymer films at different irradiation wavelengths, for the reference system (without heat-generating organic dye) and the systems comprising a NIR heat-generating organic dye. The presence of a NIR heat-generating organic dye is clearly necessary i.e. without NIR heat-generating organic dye, a very low photothermal effect is found (T<40° C., Table 2).
Two trends can be clearly established from these results; notably that IR-813 is more adapted for irradiations with shorter NIR wavelengths (approximately under 850 nm) i.e. at 785 nm, a temperature as high as 170° C. could be reached. Conversely, the system comprising SQ is more adapted for irradiation with longer NIR wavelengths (approximately over 850 nm) e.g. a temperature above 256° C. could be reached for the SQ-based systems upon excitation at 1064 nm whereas the temperature only reached 38° C. for the IR-813-based system. These results are in perfect agreement with the NIR light absorption properties of the two dyes as it is shown in the
Heat-Generating Organic Dye Concentration
Another parameter governing the temperature reached by the polymer films is the heat-generating organic dye concentration. As shown in
It has been shown that IR-813 is not decomposed before 250° C. (
Some tests have been performed on a thermoplastic material based on Glyfoma in order to reprocess it i.e. self-healing and bonding/debonding applications were first investigated to show the interest of the inventive approach.
As shown above for TMPTA, the photopolymerization of Glyfoma in the presence of SPBPO is not affected by the presence of IR-813 when its content is under 0.1% wt (
To characterize the thermoplastics obtained, DSC measurements have been carried out on the reference system (without heat-generating organic dye) and on systems with NIR heat-generating organic dye in-situ embedded after a first photopolymerization step done at 405 nm. The glass transition temperatures of the prepared glyfoma-based polymers are around 70-80° C. (see
Therefore, to bond two thermoplastics together, a simple experiment has been designed: two polymers were held together and irradiated from the top side. As shown in the
As already mentioned, the advantage of using laser diodes over ovens is the possible spatial control the heated zone (
Some self-healing experiments have also been carried out in order to characterize the ability of the polymer films to recover their initial shape by chain mobility above the Tg. Scratches of around 100 μm depth and 500 μm width were made to Glyfoma-based thermoplastic films of Example 1 and could be very efficiently healed just by irradiating the surface with NIR light. As shown in the
Materials and Methods for Example 5
Isobornyl methacrylate (IBOMA), 3,3,5-trimethyl cyclohexyl methacrylate (TMCHMA) and polyethylene glycol diacrylate (SR610) were obtained from Sartomer-Europe, bis(2,4,6-trimethylbenzoyl)-phosphine oxide (BAPO) and ethyl (2,4,6-trimethylbenzoyl) phenylphosphinate (TPO-L) were purchased from Lambson Ltd (UK), IR-813 p-toluenesulfonate (IR-813) was supplied from Tokyo Chemical Industry (TCI-Europe), MMA and crayvallac SLT were provided from Arkema, glycerol formal methacrylate (Glyfoma) was obtained from Evonik and isobornyl acrylate (IBOA) came from Annex®. Chemical structures of these molecules are presented in the Scheme 4, except that of the crayvallac SLT which was used as a thickener in Glyfoma formulations.
Experimental Conditions for Example 5
Preparation of Polymers
For Glyfoma, IBOA, IBOMA, TMCHMA and PEG diacrylate, 1%wt of BAPO as photoinitiator was used and the LED irradiance was 500 mW·cm−2 whereas 5%wt of TPO-L was used as photoinitiator for MMA and the LED irradiance was 1 W·cm−2.
RT-FTIR Spectroscopy
In order to know the (meth)acrylate function conversion of the photosensitive formulations, photopolymerization experiments have been carried out in a mold at room temperature upon irradiation with a laser diode at 405 nm (450 mW·cm−2). The mold was covered by a polypropylene film to avoid the oxygen inhibition. A Jasco 6600 real-time Fourier transformed infrared spectrometer (RT-FTIR) was used to follow in real time the C═C acrylate double bond conversion between 6100 and 6200 cm−1 during the irradiation time. Final polymers have a thickness of 2 mm.
Thermal Imaging Camera
The sample temperatures reached during the NIR irradiation experiments performed in this study have been followed by the Fluke TiX500 infrared thermal imaging camera. Irradiations with NIR light LEDs were done at a distance of 4 cm with the LED@810 nm and 6 cm with the LED@850 nm (NIR LEDs from Thorlabs).
Phoseon LEDs Panel
For larger irradiations at 810 nm, a Phoseon LEDs panel prototype was used. The light intensity of this prototype goes up to 9 W.
Differential Scanning Calorimetry (DSC)
To determine the glass transition temperature (Tg) of polymers, the DSC Mettler Toledo DSC1 and the Star software were used. A first run was performed out to erase their thermal background and a second one was carried out to determine the Tg with the tangent of the transition phase. DSC tests were performed from 0° C. to 200° C. under air with a rise of temperature of 10° C.·min−1.
Results
The Reprocessing of Thermoplastics
Scheme 5 summarizes the idea of using a NIR heater in-situ embedded in a thermoplastic material. Since the NIR heater is not involved in the polymerization process, it can still be used to photothermally activate the generated polymers upon NIR light. In absence of NIR heater, the polymeric material temperature should not exceed the glass transition temperature (Tg) upon NIR light (See Scheme 5A) whereas this Tg should be reached in the presence of heater (Scheme 5B). Therefore, we can expect the NIR activation of thermoplastics with in-situ embedded heater to allow an efficient shaping/reprocessing of the polymer.
Irradiation of a Glyfoma-based polymer upon NIR light was recorded by thermal imaging camera without NIR-heater (See
Then, this shaping/reprocessing behavior has been investigated for different thermoplastics based on other (meth)acrylate monomers (for IBOA, IBOMA, TMCHMA, MMA based polymers). In the absence of heater, the shaping of all of these polymers was impossible. As for Glyfoma-based polymers, IBOA, IBOMA, TMCHMA and MMA-based polymers could however be shaped under 1 minute of NIR irradiation in the presence of heater. For MMA, a partial degradation was noticed. However, the LED irradiance can be smartly controlled to avoid this degradation and achieve the folding.
The different temperatures reached by all of these polymers in the presence as well as in the absence of NIR heater are depicted in the
Versatility of NIR Dyes for Reprocessing of Thermoplastics
The shaping/reprocessing behavior has also been investigated for other NIR dyes in state of using IR-813, IR-1064 and copper phtalocyanine have been investigated (Scheme 6). The push-pull dye IR-1064 is characterized by an absorption at longer wavelength (@1064 nm). The thermoplastics based Glyfoma have been prepared upon irradiation with the LED@405 nm (1 W/cm2) for 7 min of irradiation and then their behaviors upon NIR light were checked. Scheme 4 clearly show that the shaping can be easily carried out upon irradiation with the LED@810 nm (9 W/cm2). After 1 min 30 sec of irradiation, the polymer based of NIR heaters can change his shape. Indeed, the temperature reached by the NIR heater based polymer is higher than the Tg of Glyfoma which makes the reshaping possible.
An experiment has been specifically designed to show the reversibility of the shaping process. Scheme 7A describes this cycle which can be separated in two parts. The first step consists in folding a polymer, as depicted in Scheme 7B. After this first step, Scheme 7B describes the way how to make the polymer back to its initial shape (defolding) to complete the cycle.
Finally, a folded Glyfoma-based polymer was placed upon irradiation with a LED@850 nm (1 W·cm−2) and followed by thermal imaging camera (See
The results of Examples 2-5 illustrate the range of possible applications for thermoplastics self-healing, shaping and/or reprocessing upon NIR light.
The Examples that precede show that the temperature of different polymers (thermosets or thermoplastics) could be finely tuned by using low NIR heat-generating organic dye content (<0.1% w/w). Specifically, polymeric materials containing a very low amount of stimuli-responsive compound were prepared by using a benchmark UV photoinitiator. An organic dye strongly absorbing in the near infrared region has been selected as the stimuli-responsive compound. When excited by a NIR light, this dye can act as an efficient heat-generator which release heat in a controlled manner to its environment. The heat released by irradiation with an inexpensive and highly penetrating (depth in the cm range) NIR light source allows the development of an unprecedented approach for reprocessing, reshaping, recycling, self-healing and even to modify the structure of thermoplastic polymers. For this purpose, it is important to reach a high temperature to overcome the glass transition temperature (Tg), leading to mechanical properties modification. Several parameters have been studied in order to increase the polymer temperature: the wavelength of the NIR irradiation, the irradiance of the NIR light source, the choice of heater (IR-813 p-toluenesulfonate or a squaraine dye) and the heater concentration.
By mean of a careful selection of the NIR dye structure, the concentration but also the excitation wavelength and the irradiance could be used as efficient tools to control the heat released to the polymer. The good thermal stability of SQ and IR-813 coupled with the low glass transition temperature of the thermoplastic used in the Examples allowed a large flexibility in the operating temperature for reprocessing. Notably, to evidence the pertinence of the strategy, two selected examples were given through bonding/debonding and self-healing applications. IR-813 was found to be more effective upon irradiation at short NIR wavelengths (785-850 nm) whereas SQ was more effective at longer NIR wavelengths (850-1064 nm).
The thermoplastics bonding experiments showed promising results since two pieces of polymers could be pasted together after a short time of NIR irradiation. Reversibility of the bonding was also demonstrated, still while using a NIR light as the activation source. Finally, self-healing ability of the Glyfoma-based thermoplastic was investigated and furnished impressive results even for large scratches. Notably, scratches as deep as 100 μm and with a width as large as 500 μm could be healed after only a few minutes of NIR irradiation.
While we have described a number of embodiments of this invention, it is apparent that the Examples may be altered to provide other embodiments that utilize the compositions and methods of this invention. Therefore, it will be appreciated that the scope of this invention is to be defined by the appended claims rather than by the specific embodiments that have been represented herein by way of example.
| Number | Date | Country | Kind |
|---|---|---|---|
| 20305848.2 | Jul 2020 | EP | regional |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2021/070545 | 7/22/2021 | WO |
