Spray drying of solid epoxy resin or phenoxy resin

Abstract

A high molecular weight solid epoxy resin or phenoxy resin is dissolved in a mixture of an alcohol solvent and an aprotic solvent, and the resulting solution is spray dried in a closed-loop spray dryer to form a powdered epoxy resin or phenoxy resin.

Description

[0001] Cross-reference to related applications

[0002] This application claims the benefit of U.S. Provisional Patent Application Serial No. 63 / 111,325, filed on November 9, 2020. The contents of the above application are incorporated herein by reference. Technical Field

[0003] The present application relates to the spray-drying of solid epoxy or phenoxy resins. More specifically, a high molecular weight solid epoxy or phenoxy resin is dissolved in a mixture of an alcoholic solvent and an aprotic solvent, and the resulting solution is spray-dried in a closed-cycle spray drying apparatus to form a powdered epoxy or phenoxy resin. Background Art

[0004] High-molecular-weight epoxy or phenoxy resins are generally considered thermoplastics and are commonly used in applications such as injection molding, extrusion, coatings, and adhesives. A common organic solvent for dissolving epoxy or phenoxy resins is methyl ethyl ketone (MEK). However, epoxy or phenoxy resins dissolved in MEK do not spray dry well. Similarly, other solid epoxy or phenoxy resin solutions have not been spray dried effectively in the past.

[0005] Powdered resins have been formed by cryogenically grinding polymers as an alternative to spray drying. However, the average particle size achieved is about 200 micrometers (μm), much larger than required for powdered epoxy or phenoxy resins, and the process is energy-intensive and expensive.

[0006] Until now, in practice, high molecular weight epoxy resins or phenoxy resins have been synthesized in the presence of a solvent, the solution is washed with water to remove the salts formed during the reaction, and the solvent is removed to obtain solid pellets. The solvent removal is accomplished using a device. However, the amount of solvent that can be removed in this manner is limited, and the start-up of the process typically results in an initial high-color product and charred material that must be disposed of as waste. In addition, pellets are not as useful as powdered epoxy or phenoxy resins. Summary of the Invention

[0007] The present invention generally provides a method for forming a dry powder thermoplastic resin composition, comprising dissolving a solid thermoplastic resin selected from a solid epoxy resin and a solid phenoxy resin in a mixture of a protic solvent and an aprotic solvent to form a slurry; and spray drying the slurry to form the dry powder thermoplastic resin composition. The present invention also provides a dry powder thermoplastic resin composition obtained by the above method, the thermoplastic resin composition comprising a plurality of particles selected from epoxy resin particles and phenoxy resin particles, the particles having an average particle size of approximately 150 microns or less. The dry powder thermoplastic resin composition of the present invention can be used, for example, in coatings, adhesives, plastics, composite materials, and electronic components. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] Figure 1 is a flow chart illustrating a method of forming a powdered epoxy resin or phenoxy resin according to one embodiment of the present invention; and

[0009] Figure 2 A spray drying apparatus used in one embodiment of the present invention is shown. DETAILED DESCRIPTION

[0010] The following terms shall have the following meanings:

[0011] The term "comprising" and its derivatives are not intended to exclude the presence of any additional ingredients, steps or procedures, whether or not disclosed herein. For the avoidance of any doubt, all compositions claimed herein using the term "comprising" may include any additional additives or compounds unless otherwise stated. In contrast, the term "consisting essentially of," if used in this application, excludes any other ingredients, steps or procedures from the scope of any subsequent statement, except those that are not essential for operability. The term "consisting of," if used, excludes any ingredient, step or procedure not specifically delineated or listed. The term "or," unless otherwise stated, refers to each of the listed members and in any combination.

[0012] The articles "a" and "an" used in this application refer to one or more than one (i.e., at least one) of the grammatical object of the article. For example, "a protic solvent" means one protic solvent or more than one protic solvent. The phrases "in one embodiment", "according to one embodiment" and similar expressions generally mean that the specific feature, structure or characteristic following the phrase is included in at least one embodiment of the present invention and may be included in more than one embodiment of the present invention. Importantly, such phrases do not necessarily refer to the same aspect. If the specification indicates that a component or feature "may" or "can" be included therein or has a certain feature, it is not required that the specific component or feature be included or have that feature.

[0013] As used herein, the term "about" may allow for a certain degree of variability in a value or range, for example, within 10%, 5% or 1% of a stated value or the stated limit of a range.

[0014] The terms "preferred" and "preferably" refer to embodiments that may offer certain benefits under certain circumstances. However, other embodiments may also be preferred, under the same or other circumstances. Furthermore, the description of one or more preferred embodiments does not imply that other embodiments are not useful, nor is it intended to exclude other embodiments from the scope of the invention.

[0015] The term “optional” or “optionally” means that the subsequently described event, circumstance or material may or may not occur, may or may not exist, and that the description includes instances where said event, circumstance or material occurs or exists and instances where it does not.

[0016] Numerical values ​​expressed in range format should be interpreted in a flexible manner to include not only the numerical values ​​explicitly recited as limits of the range, but also all individual numerical values ​​or sub-ranges contained within the range, as if each numerical value and sub-range were explicitly recited. For example, a range such as from 1 to 6 should be considered to have specifically disclosed sub-ranges such as from 1 to 3, from 2 to 4, from 3 to 6, etc., as well as individual numbers within that range, such as 1, 2, 3, 4, 5, and 6. This applies regardless of the breadth of the range.

[0017] The term "substantially free" refers to a composition in which the specified compound or moiety is present in an amount that has no substantial effect on the composition. In some embodiments, "substantially free" may refer to a composition in which the specified compound or moiety is present in an amount less than 2% by weight, or less than 1% by weight, or less than 0.5% by weight, or less than 0.1% by weight, or less than 0.05% by weight, or even less than 0.01% by weight, based on the total weight of the composition, or the specified compound or moiety is not present in any amount in the corresponding composition.

[0018] The term "dry powder thermoplastic resin composition" generally refers to a composition characterized, among other features, by a residual moisture content that is preferably sufficiently low to prevent the formation of aggregates that would reduce or prevent the flowability of the powder. As used herein, the term "residual moisture content" (or "residual moisture") refers to the total amount of solvent present in the dry powder thermoplastic resin composition. The total amount of residual moisture can be determined by any suitable method known in the art, such as a Karl-Fischer titration technique or a thermal gravimetric analysis (TGA) method. In one embodiment, the dry powder thermoplastic resin composition according to the present invention has a residual moisture content of 10% (by weight, w / w) or less, or 9% (w / w) or less, or 8% (w / w) or less, or 7% (w / w) or less, or 6% (w / w) or less, or 5% (w / w) or less, or 4% (w / w) or less, or 3% (w / w) or less, or 2% (w / w) or less, or 1% (w / w) or less, or 0.5% (w / w) or less, or even 0.25% (w / w) or less. In another embodiment, the residual moisture content of the dry powder thermoplastic resin composition is between about 0.01% (w / w) to about 5% (w / w), or from about 0.01% (w / w) to about 3% (w / w), or from about 0.01% (w / w) to about 2% (w / w), or from about 0.01% (w / w) to about 1.5% (w / w), or from about 0.01% (w / w) to about 1.25% (w / w), or from about 0.01% (w / w) to about 1% (w / w), or from about 0.01% (w / w) to about 0.75% (w / w).

[0019] The term "average particle size" as used herein refers to the particle diameter corresponding to 50% of the particles in the distribution curve, where the particles are accumulated in the order from the smallest particle to the largest particle. Here, the total number of particles accumulated is 100%. The average particle size can be measured by methods known to those skilled in the art. For example, the average particle size can be measured with a particle size analyzer, or measured using a transmission electron microscope (TEM) or scanning electron microscope (SEM) image. As an example of another measurement method, the average particle size can be measured using a measuring device using dynamic light scattering. According to this method, the number of particles within a predetermined size range can be counted and the average particle diameter calculated therefrom.

[0020] like Figure 1As shown, an exemplary method for forming a powdered epoxy or phenoxy resin includes providing a solid epoxy or phenoxy resin at step 10; dissolving the solid epoxy or phenoxy resin in a mixture of an alcohol solvent and an aprotic solvent at step 20; and spray drying the resulting solution in a closed-cycle spray dryer to form a powdered epoxy or phenoxy resin at step 30. A closed-cycle dryer is used in step 30 because an inert atmosphere is ideal because the solvent is atomized in the drying chamber.

[0021] The exemplary method is directed to a high molecular weight solid resin having an average molecular weight of at least 1,000 Daltons, preferably at least 10,000 Daltons, more preferably at least 30,000 Daltons, more preferably at least 50,000 Daltons, and most preferably between about 50,000 and about 55,000 Daltons.

[0022] The alcohol solvent in step 20 of this exemplary method has a molecule having 2 to 6 carbon atoms. Examples of alcohol solvents include ethanol, propanol, isopropanol, butanol, pentanol, and hexanol. A preferred alcohol solvent is butanol.

[0023] Examples of aprotic solvents for step 20 of this exemplary method include methyl ethyl ketone, methyl isobutyl ketone, toluene, xylene, dichloromethane, and tetrahydrofuran. A preferred aprotic solvent is toluene.

[0024] In the mixture of step 20 of this exemplary method, the weight ratio of the alcohol solvent to the aprotic solvent can be, for example, between about 30:70 (w / w) and about 70:30 (w / w), preferably between about 40:60 (w / w) and about 60:40 (w / w), and more preferably about 50:50 (w / w).

[0025] The solution obtained in step 20 of the exemplary method contains, for example, about 1 wt % to about 10 wt % of the epoxy resin or phenoxy resin, preferably about 5 wt % to about 10 wt % of the epoxy resin or phenoxy resin, based on the total weight of the obtained solution.

[0026] The powdered epoxy or phenoxy resin obtained by this exemplary method contains, for example, no more than about 5 wt % residual solvent, preferably no more than about 1.5 wt % residual solvent, more preferably no more than about 0.5 wt % residual solvent, and most preferably no more than about 0.3 wt % residual solvent, based on the total weight of the powdered epoxy or phenoxy resin.

[0027] The average particle size of the powdered epoxy or phenoxy resin obtained by this exemplary method is, for example, no greater than about 20 microns, and preferably no greater than about 12 microns.

[0028] Compared to the typical practice of removing solvents using thin-film devices under high heat and vacuum conditions, spray drying allows for solvent removal at lower temperatures because atomization of the solvent significantly increases the surface area and improves evaporation efficiency. It is believed that the choice of solvent significantly influences the ability to spray dry solid epoxy or phenoxy resin solutions, which has not been effective in the past. Spray drying epoxy or phenoxy resins dissolved in a mixture of alcoholic and aprotic solvents allows for processing through the spray drying apparatus without "stringing" and produces powders with relatively small particle sizes.

[0029] The powdered epoxy or phenoxy resin obtained by the spray drying step 30 of the exemplary method is highly advantageous relative to the pellets typically obtained to date. Removing the solvent by spray drying reduces heat exposure compared to using a thin film apparatus. This significantly improves quality because there are no longer any black specks or yellowing caused by heat exposure. Furthermore, the powdered epoxy or phenoxy resin dissolves faster in, for example, solvents, liquid epoxies, amines, acrylates, and polyols than the pellets typically obtained to date. This is a manufacturing advantage and also reduces the cycle time for the production of waterborne and solventborne derivatives. As a specific example, the powdered epoxy or phenoxy resin dissolves almost twice as fast as the pellets, resulting in a 40% reduction in the production of the derivative. Furthermore, the lower percentage of residual solvent in the powdered epoxy or phenoxy resin reduces concerns about future regulatory risks related to residual solvents, a factor in markets such as electronics, composites, and thermoplastic additives.

[0030] According to another embodiment, a method for forming a dry powder thermoplastic resin composition is provided, comprising the steps of dissolving a solid thermoplastic resin selected from a solid epoxy resin and a solid phenoxy resin in a mixture of a protic solvent and an aprotic solvent to form a slurry, and spray drying the slurry to form the dry powder thermoplastic resin composition. The method according to the present invention can be performed in bulk or as a continuous process. In one embodiment, the method is performed as a continuous process.

[0031] In one embodiment, the solid thermoplastic resin is a solid epoxy resin. The solid epoxy resin may be solid or semi-solid at room temperature (25° C.) and may soften when the temperature rises, but may not exhibit a rapid decrease in viscosity. In one embodiment, the molecular weight of the solid epoxy resin may be about 1000 grams per mole (g / mol) or more, or about 2000 grams per mole or more, or about 5000 grams per mole or more, or about 10,000 grams per mole or more. In another embodiment, the molecular weight of the solid epoxy resin may be about 60,000 grams per mole or less, or about 50,000 grams per mole or less, or about 40,000 grams per mole or less, or about 30,000 grams per mole or less. In yet another embodiment, the molecular weight of the solid epoxy resin may be between about 1,000 g / mole and about 55,000 g / mole, or between about 2,500 g / mole and about 45,000 g / mole, or between about 5,000 g / mole and about 35,000 g / mole, or between about 10,000 g / mole and about 25,000 g / mole.

[0032] In yet another embodiment, the solid epoxy resin may have an epoxy equivalent weight (EEW) of about 250 g / eq to about 3000 g / eq, or about 300 g / eq to about 2000 g / eq, or about 325 g / eq to about 1500 g / eq, or about 350 g / eq to about 1200 g / eq, or about 360 g / eq to about 1100 g / eq, or about 500 g / eq to about 1000 g / eq. In other embodiments, the softening point of the solid epoxy resin at room temperature may be between about 40° C. and 120° C., or between about 50° C. and 110° C., or between about 60° C. and 100° C.

[0033] Various solid epoxy resins can be used without particular limitation as long as they are solid or semi-solid at room temperature. Examples include, but are not limited to, bisphenol A epoxy resins, bisphenol F epoxy resins, bisphenol AF epoxy resins, o-cresol novolak epoxy resins, phenol novolak epoxy resins, modified phenol epoxy resins, naphthyl epoxy resins, trisphenol methane epoxy resins, alkyl-modified trisphenol methane epoxy resins, triazine nucleus-containing epoxy resins, dicyclopentadiene epoxy resins, glycidylamine epoxy resins, biphenyl epoxy resins, biphenylaralkyl epoxy resins, hydrogenated bisphenol A epoxy resins, aliphatic epoxy resins, stilbene epoxy resins. resins), triglycidyl ether of trisphenol methane, isocyanate-modified bisphenol A epoxy resin, isocyanate-modified bisphenol F epoxy resin, isocyanate-modified bisphenol AF epoxy resin, and bisphenol A novolak epoxy resins, bisphenol F novolak epoxy resins or bisphenol AF novolak epoxy resins.

[0034] In another embodiment, the solid thermoplastic resin is a solid phenoxy resin. The solid phenoxy resin can be obtained by a condensation reaction between a dihydric phenol compound and epichlorohydrin, or a polyaddition reaction between a dihydric phenol compound and a difunctional epoxy resin.

[0035] Examples of the dihydric phenol compounds used in the production of solid phenoxy resins include hydroquinone, resorcinol, 4,4-dihydroxybiphenyl, 4,4′-dihydroxybenzophenone, 2,2-bis(4-hydroxyphenyl)propane, 1,1-bis(4-hydroxyphenyl)cyclohexane, 1,1-bis(4-hydroxyphenyl)-3,3,5-trimethylcyclohexane, bis(4-hydroxyphenyl)methane, 1,1-bis(4-hydroxyphenyl)ethane, 2,2-bis(4-hydroxyphenyl)butane, 1,1-bis(4-hydroxyphenyl)-1-phenylethane, bis(4-hydroxyphenyl)diphenylmethane, 2,2-bis(4-hydroxy-3-methylphenyl)propane, 2,2-bis(3-phenyl-4-hydroxyphenyl)propane, 2,2-bis(4-hydroxy-3-tert-butylphenyl)propane, 1,3-bis(2-(4-hydroxyphenyl)propyl)benzene, 1,4-bis(2-(4-hydroxyphenyl)propyl)benzene, 2,2-bis(4-hydroxyphenyl)-1,1,1-3,3,3-hexafluoropropane, 9,9'-bis(4-hydroxyphenyl)fluorene, etc. can be mentioned. Among them, 4,4-dihydroxybiphenyl, 4,4'-dihydroxybenzophenone, 2,2-bis(4-hydroxyphenyl)propane or 9,9'-bis(4-hydroxyphenyl)fluorene is particularly preferred.

[0036] The bifunctional epoxy resins used to produce solid phenoxy resins include epoxy oligomers obtained by the condensation reaction of the above-mentioned dihydric phenol compounds and epichlorohydrin, for example, hydroquinone diglycidyl ether, resorcinol diglycidyl ether, bisphenol S type epoxy resin, bisphenol A type epoxy resin, bisphenol F type epoxy resin, methylhydroquinone diglycidyl ether, chlorohydroquinone diglycidyl ether, 4,4'-dihydroxydiphenyl oxide diglycidyl ether, 2,6-dihydroxynaphthalene diglycidyl ether, dichlorobisphenol A diglycidyl ether, tetrabromobisphenol A type epoxy resin, 9,9'-bis(4)-hydroxyphenyl)full orangeglycidyl ether, and the like. Among them, bisphenol A type epoxy resin, bisphenol S type epoxy resin, hydroquinone diglycidyl ether, bisphenol F type epoxy resin, tetrabromobisphenol A type epoxy resin or 9,9'-bis(4)-hydroxyphenyl) all-orange glycidyl ether is preferred.

[0037] The production of solid phenoxy resin can be carried out in the absence of a solvent or in the presence of a reaction solvent, and the reaction solvent used can be, for example, an organic solvent such as methyl ethyl ketone, dioxane, tetrahydrofuran, acetophenone, N-methylpyrrolidone, dimethyl sulfoxide, N,N-dimethylacetamide, sulfolane, toluene, etc. The phenoxy resin obtained using the reaction solvent can be subjected to a solvent removal treatment using an evaporator or similar device to obtain a solid resin free of the reaction solvent. In other embodiments, the reaction solvent is not removed but is used as part of the mixture that is subsequently spray-dried.

[0038] The average molecular weight (g / mol) of the solid phenoxy resin may be about 1,000 or more, or about 5,000 or more, or about 10,000 or more. In other embodiments, the average molecular weight of the solid phenoxy resin may be about 500,000 or less, or about 200,000 or less, or about 150,000 or less, or about 100,000 or less. In other embodiments, the average molecular weight (g / mol) of the solid epoxy resin may be between about 10,000 and about 250,000, or between about 20,000 and about 150,000, or between about 25,000 and about 80,000.

[0039] In another embodiment, the hydroxyl equivalent weight (g / eq) of the solid phenoxy group can be between about 50 and about 1000, or between about 100 and about 750, or between about 200 and about 500.

[0040] According to another embodiment, the solid phenoxy resin may have the formula

[0041]

[0042] wherein n is an integer from about 8 to about 400, and X is selected from:

[0043]

[0044]

[0045] In a specific embodiment, n is an integer between about 20-400, or an integer between about 25-150, or an integer between about 35-100, or an integer between about 38-60. In another embodiment, X is

[0046]

[0047] In the first step of the process, a solid epoxy resin or a solid phenoxy resin is dissolved in a mixture comprising a protic solvent and an aprotic solvent to form a slurry. As used herein, a "protic solvent" generally refers to a solvent having hydrogen atoms bound to oxygen atoms (such as in hydroxyl groups) or nitrogen atoms (such as in amine groups), so that it can primarily donate protons (H + In one embodiment, the protic solvent may be C1-C6-alkanol, C2-C4-alkanediol, ether alkanol, water, acetic acid, formic acid, and mixtures thereof.

[0048] C1-C6-alkanols generally include methanol, ethanol, propanol, isopropanol, n-butanol, sec-butanol, and tert-butanol. Preferred C1-C4-alkanols include ethanol, n-propanol, isopropanol, and n-butanol. Particularly preferred is n-butanol.

[0049] C2-C4-alkanediols include ethylene glycol or propylene glycol. Ether alkanols include diethylene glycol.

[0050] In one embodiment, the protic solvent is a C1-C4-alkanol. It has surprisingly been found that the use of a C1-C4 alkanol as one of the solvents in the mixture is particularly advantageous in terms of the ability to spray dry solid thermoplastic resins and produce powders with relatively small average particle sizes.

[0051] In one embodiment, the mixture comprises about 1 wt % or more of a protic solvent, based on the gross weight of the mixture. In other embodiments, the mixture comprises about 5 wt % or more, or about 10 wt % or more, or about 20 wt % or more, or about 30 wt % or more of a protic solvent, based on the gross weight of the mixture. In other embodiments, the mixture comprises about 99 wt % or less, or about 90 wt % or less, or about 80 wt % or less, or about 70 wt % of a protic solvent, based on the gross weight of the mixture.

[0052] The mixture also includes an aprotic solvent. As used herein, an "aprotic solvent" refers to a solvent that cannot donate a proton. In one embodiment, the aprotic solvent is selected from aromatic solvents, alkane solvents, ether solvents, ester solvents, acetone, acetonitrile, dimethylformamide, and mixtures thereof.

[0053] In one embodiment, the aromatic solvent is benzene, toluene, xylene (n-xylene, m-xylene or p-xylene), mesitylene, chlorobenzene (MCB), 1,2-dichlorobenzene, 1,3-dichlorobenzene, 1,4-dichlorobenzene, or a mixture thereof. Preferred aromatic solvents are selected from toluene, xylene (n-xylene, m-xylene or p-xylene), chlorobenzene, and a mixture thereof.

[0054] The alkane solvent includes aliphatic hydrocarbons such as pentane, hexane, heptane, cyclohexane, petroleum ether, or mixtures thereof, and halogenated hydrocarbons such as dichloromethane, chloroform, or mixtures thereof.

[0055] Ether solvents include open-chain and cyclic ethers, in particular diethyl ether, methyl tert-butyl ether (MTBE), 2-methoxy-2-methylbutane, cyclopentyl methyl ether, 1,4-dioxane, tetrahydrofuran (THF), 2-methyltetrahydrofuran (CH3-THF), or mixtures thereof.

[0056] Ester solvents include carboxylic acid esters, such as ethyl acetate or butyl acetate.

[0057] In one embodiment, the aprotic solvent is selected from toluene, xylene (n-xylene, m-xylene or p-xylene), chlorobenzene, heptane, tetrahydrofuran, 2-methyltetrahydrofuran, methyl tert-butyl ether, 1,4-dioxane, ethyl acetate, butyl acetate, acetone, acetonitrile, and mixtures thereof.

[0058] In a particular embodiment, the aprotic solvent is an aromatic solvent. It has surprisingly been found that the use of an aromatic solvent as the aprotic solvent in the mixture is particularly advantageous in terms of the ability to spray dry the solid thermoplastic resin and produce a dry powder having a relatively small average particle size.

[0059] In another embodiment, the mixture comprises about 1 wt % or more of an aprotic solvent, based on the total weight of the mixture. In other embodiments, the mixture comprises about 5 wt % or more, or about 10 wt % or more, or about 20 wt % or more, or about 30 wt % or more of an aprotic solvent, based on the total weight of the mixture. In other embodiments, the mixture comprises about 99 wt % or less, or about 90 wt % or less, or about 80 wt % or less, or about 70 wt % of an aprotic solvent, based on the total weight of the mixture.

[0060] In other embodiments, the mixture comprises a protic solvent and an aprotic solvent in a weight ratio of about 10:90 (w / w) to about 90:10 (w / w) (protic solvent:aprotic solvent). In other embodiments, the mixture comprises a protic solvent and an aprotic solvent in a weight ratio (protic solvent:aprotic solvent) of about 25:75 (w / w) to about 75:25 (w / w), or about 30:70 (w / w) to about 70:30 (w / w), or about 40:60 (w / w) to about 60:40 (w / w), or about 45:55 (w / w) to about 55:45 (w / w).

[0061] In one embodiment, a solid epoxy resin or a solid phenoxy resin is dissolved in the mixture to form a slurry containing about 1% by weight or more of the epoxy resin or phenoxy resin, based on the total weight of the slurry. In other embodiments, a solid epoxy resin or a solid phenoxy resin is dissolved in the mixed liquid to form a slurry containing about 3% by weight or more, or about 5% by weight or more, or about 7% by weight or more, or about 10% by weight or more, or about 15% by weight or more of the epoxy resin or phenoxy resin, based on the total weight of the slurry.

[0062] In another embodiment, a solid epoxy resin or a solid phenoxy resin is dissolved in the mixture to form a slurry containing about 20% by weight or less of the epoxy resin or phenoxy resin, based on the total weight of the slurry. In other embodiments, a solid epoxy resin or a solid phenoxy resin is dissolved in the mixed liquid to form a slurry containing about 17% by weight or less, or about 15% by weight or less, or about 12% by weight or less, or about 10% by weight or less of the epoxy resin or phenoxy resin, based on the total weight of the slurry.

[0063] In yet another embodiment, a solid epoxy resin or a solid phenoxy resin is dissolved in the mixture to form a slurry containing from about 1% to about 15% by weight of the epoxy resin or phenoxy resin, based on the total weight of the slurry. In other embodiments, a solid epoxy resin or a solid phenoxy resin is dissolved in the mixed liquid to form a slurry containing from about 2% to about 13% by weight, or from about 3% to about 12% by weight, or from about 5% to about 10% by weight of the epoxy resin or phenoxy resin, based on the total weight of the slurry.

[0064] The slurry is then spray-dried to form a dry powder thermoplastic resin composition comprising a plurality of thermoplastic resin (i.e., epoxy resin or phenoxy resin) particles. The term "particles" refers to individual solid particles of the dry powder thermoplastic resin composition. The individual particles of the dry powder thermoplastic resin composition are preferably physically separated from each other, i.e., the individual particles constituting the dry powder are in loose and reversible contact with each other (as opposed to irreversible connections between the individual particles).

[0065] As used herein, the term "spray drying" refers to a process that typically involves breaking up a liquid into small droplets (atomization) and rapidly removing the solvent from the droplets in a spray drying apparatus where a strong driving force is provided for evaporating the solvent from the droplets. The strong driving force for solvent evaporation is typically provided by a high surface to mass ratio of the droplets and by maintaining the solvent partial pressure in the spray drying apparatus well below the solvent vapor pressure at the temperature of the dried droplets. This can be achieved, for example, by maintaining the pressure in the spray drying apparatus in a partial vacuum, or by mixing the droplets with a warm drying gas, or a combination of the two. As a result of the spray drying process, particles are obtained, preferably dry particles, more preferably in the form of a dry powder composition.

[0066] Typically, the slurries comprising solid thermoplastic resin and mixed solvent are first broken down into a plurality of droplets, which can be suspended in a gas or gas mixture (such as air). The droplets obtained and the mixture of gas are commonly referred to as "spray" or "mist". The process of slurries being broken down into droplets is referred to as "atomization", and any suitable equipment (atomizer) known in the art can be used to realize. Various types of atomizers known in the art are suitable for method of the present invention, such as rotary atomizers, pressure nozzles, two-fluid nozzles, fountain nozzles (fountain nozzles), ultrasonic atomizers and vibrating orifice aerosol generators (vibrating orifice aerosol generators).

[0067] In one embodiment, atomization of the slurry produces spherical droplets. As used herein, the term "spherical" includes not only geometrically perfect spheres, but also less regular shapes such as spheroidal, ellipsoid, oval, or round droplets.

[0068] Once the slurry is atomized, the resulting spray droplets mix with the drying gas, causing the solvent mixture to evaporate rapidly in the drying chamber. Rapid evaporation typically produces a cooling effect, so the dried particles do not reach the temperature of the drying air, which is particularly advantageous for drying heat-sensitive materials. The drying chamber can be of any shape and can include one or more chambers. The drying gas can at least partially absorb the solvent evaporated from the droplets and can be introduced into the drying chamber through an inlet, such as a disperser. The disperser can be located in the upper half of the drying chamber, for example, near the atomizer, so that the drying gas and droplets can mix rapidly. The drying gas stream leaves the drying chamber through an outlet, which can be located at the bottom of the drying chamber.

[0069] Among other things, the characteristics of the drying chamber can be matched with the atomizer used, etc. In order to ensure uniform quality of the product, the droplets can only contact the surface of the drying chamber when they are fully dried. The dry powder can be collected at the bottom of the drying chamber. In one embodiment, the drying chamber is designed as a cone, and the outlet of the dry air flow is located at the center of the cone, where the cool and moist air can be discharged from the drying chamber. This design of the cone and the outlet acts as a cyclone separator and causes the dry powder to accumulate at the bottom of the drying chamber. Cyclone separation is preferably used to separate dry particles or fine droplets from the drying gas. In some embodiments, a filter is not required and vortex separation is performed. For this purpose, a high-speed rotating flow is preferably established in a cylindrical or conical container of the cyclone separator. Typically, the dry gas flows from the top (wide end) of the cyclone separator to the bottom (narrow end) in a spiral shape, and then leaves the cyclone separator in a straight flow through the center of the cyclone separator. Larger or denser particles in the rotating flow do not follow the tight curve of the flow, but instead hit the outer wall and fall to the bottom of the cyclone where they can be collected. Alternatively, a filter, such as a bag filter, or a combination of a cyclone and a filter can be used to separate the dry powder and the drying gas.

[0070] Depending on the type of flow, i.e. the relative position of the atomizer and the drying gas inlet, or, respectively, the relative movement of the spray and the drying gas, several types of spray drying apparatus can be distinguished, all of which can be used in the method according to the invention. In one embodiment, the spray drying apparatus is configured as a co-current flow apparatus (the spray and the drying gas move in the same direction), a counter-current flow apparatus (the spray and the drying gas move in opposite directions) or a mixed flow apparatus (co-current and counter-current flow combined). In one embodiment, the spray drying apparatus is a co-current apparatus.

[0071] In addition, spray drying apparatuses can be classified according to the type of drying gas cycle employed. For example, a spray drying apparatus can be an open cycle apparatus (drying gas entering the spray drying apparatus through an inlet is exhausted to the atmosphere through an outlet) or a closed cycle spray dryer (drying gas entering the spray drying apparatus through an inlet is exhausted through an outlet and is recovered and reused). In one embodiment, the spray drying apparatus is a closed cycle spray dryer.

[0072] The drying gas may be any suitable gas or mixture of gases. In one embodiment, an inert gas is used as the drying gas. The inert gas may be, for example, nitrogen, nitrogen-enriched air, helium, CO 2 or argon.

[0073] In one embodiment, the spray drying apparatus reduces the residual moisture content of the dry powder thermoplastic resin composition to a desired level as defined herein after one pass through the system. If the residual moisture content of the dry powder thermoplastic resin composition after one cycle is higher than the desired level, the residual moisture content can be further reduced by a second (or several) drying stages until the desired residual moisture content is reached.

[0074] Figure 2 An example of a spray drying apparatus is shown in Figure 2, which further illustrates the principle of spray drying. A slurry input stream 1 is sprayed into a drying air stream 3 through a nozzle 2 and evaporated. After entering the drying air stream 3, the droplets are cooled due to the evaporation of the solvent in the slurry. Solid spherical particles are formed, and the water quickly leaves the droplets. In order to achieve a sufficiently small droplet size (atomizer) and to maximize the rate of heat transfer and solvent evaporation, a nozzle is used. The solid spherical particles are further dried and separated in a cyclone separation device 4. The dried spherical particles are cooled and collected in a collection container 5 connected to the separation device 4, ready for packaging in different forms.

[0075] The final product is collected as mentioned above, preferably in the form of dry powder, and this dry powder comprises the thermoplastic resin spherical particles limited in the application.In one embodiment, the mean grain diameter of the thermoplastic resin spherical particles is approximately 150 microns or less, or approximately 125 microns or less, or approximately 100 microns or less, or approximately 75 microns or less, or approximately 50 microns or less, or approximately 25 microns or less, or approximately 20 microns or less, or approximately 10 microns or less or approximately 5 microns or less.In other embodiments, the mean grain diameter of the thermoplastic resin spherical particles is approximately 1 micron or larger, or approximately 5 microns or larger, or approximately 10 microns or larger, or approximately 15 microns or larger, or approximately 25 microns or larger.In other embodiments, the mean grain diameter of the thermoplastic resin spherical particles is between approximately 0.5 micron to approximately 150 microns, or between approximately 1 micron to approximately 100 microns, or between approximately 2 microns to approximately 50 microns, or between approximately 3 microns to approximately 25 microns, or between approximately 4 microns to approximately 15 microns.

[0076] The dry powder thermoplastic resin compositions can be used in a variety of applications / formulations including, but not limited to, automotive, industrial, aerospace construction, marine, civil engineering, personal protective equipment, coatings, consumer or do-it-yourself products, laminated films, plastics, tape coatings, rigid and flexible packaging coatings, epoxy baking primers, maintenance primers, zinc-rich primers, shop and heavy equipment primers, appliance and coil coating primers, chemical resistant finishes, wood coatings, pipe coatings, flexibility modifiers for phenol or poly(ethylene terephthalates), cellophane, polystyrene, aluminum foil, polycarbonate, paperboard, poly(methyl methacrylate), kraft paper, canvas duck cloth, "B" grade phenolic impregnated paper, fiberglass cloth, and felt.

[0077] Example

[0078] Prepare a sample of phenoxy resin at a concentration of approximately 10% (w / w) as a starting solution. Mix 10 grams of solid phenoxy resin with 90 grams of a 50:50 (w / w) mixture of n-butanol / toluene solvent. Stir the slurry for approximately 10 minutes until a clear solution is obtained. Transfer 50 grams of the slurry to a 50 ml glass beaker containing a magnetic stir bar. Continue stirring the slurry during the spray drying process. Seal the beaker with Parafilm foil to prevent any solvent evaporation during the drying process.

[0079] The slurry was spray-dried in a closed-loop spray dryer. Nitrogen was used as the drying gas. The drying gas flow rate was approximately 140 liters / minute, resulting in an internal pressure of approximately 60 millibars. The laminar drying gas flow and piezoelectric atomization resulted in gentle evaporation. The inlet temperature varied between 20°, 25°, 30°, 35°, and 40°C. The outlet temperature and nozzle temperature also varied depending on the selected spray cap size. A 60% spray rate was used. After reaching the inlet temperature, a 50:50 weight ratio (w / w) mixture of n-butanol / toluene was sprayed to stabilize the outlet temperature. The slurry was then sprayed, and the dry powder was collected in an electrostatic particle collector. Scanning electron microscopy (SEM) was used to determine the morphology and particle size of the solid phenoxy resin particles in the dry powder, revealing spherical particles with an average particle size of approximately 10 microns. The moisture content was determined using an infrared moisture analyzer B-302 and was found to be approximately 1% (w / w).

[0080] From the above, it will be understood that many modifications and variations can be realized without departing from the true spirit and scope of the novel concept of the present invention. It should be understood that no limitation to the specific embodiments illustrated and described is intended and should not be inferred.

Claims

1. A method for forming a dry powder thermoplastic resin composition, the method comprising: dissolving a solid thermoplastic resin selected from a solid epoxy resin and a solid phenoxy resin in a mixture of a protic solvent and an aprotic solvent to form a slurry, wherein the protic solvent is a C1-C4-alkanol and the aprotic solvent is an aromatic solvent, wherein the amount of the aprotic solvent exceeds the amount of the protic solvent by at least 1% by weight; and The slurry is spray-dried to form the dry powder thermoplastic resin composition, and The dry powder thermoplastic resin composition has a residual solvent content of 5 wt % or less.

2. The method according to claim 1, wherein the solid epoxy resin comprises bisphenol A epoxy resin, bisphenol F epoxy resin, bisphenol AF epoxy resin, o-formaldehyde epoxy resin, phenol novolac epoxy resin, modified phenol epoxy resin, naphthyl epoxy resin, trisphenol methane epoxy resin, alkyl-modified trisphenol methane epoxy resin, epoxy resin containing a triazine core, dicyclopentadiene epoxy resin, glycidylamine epoxy resin, biphenyl epoxy resin, biphenyl alkyl epoxy resin, hydrogenated bisphenol A epoxy resin, aliphatic epoxy resin, distyrene epoxy resin, triglycidyl ether of trisphenol methane, isocyanate-modified bisphenol A epoxy resin, isocyanate-modified bisphenol F epoxy resin, isocyanate-modified bisphenol AF epoxy resin, isocyanate-modified bisphenol A novolac epoxy resin, bisphenol F novolac epoxy resin, bisphenol AF novolac epoxy resin, or a combination thereof.

3. The method according to claim 1, wherein the structural formula of the solid phenoxy resin is wherein n is an integer from 8 to 400, and X is selected from:

4. The method of claim 1, wherein the slurry comprises 5 to 10 wt% of the epoxy resin or phenoxy resin based on the total weight of the slurry.

5. The method according to claim 1, wherein the solid phenoxy resin is obtained by a condensation reaction between a dihydric phenol compound and epichlorohydrin, or a polyaddition reaction between a dihydric phenol compound and a bifunctional epoxy resin.

6. The method according to claim 5, wherein the solid phenoxy resin is obtained in the presence of a reaction solvent.

7. The method according to claim 6, wherein the reaction solvent comprises dioxane, tetrahydrofuran, acetophenone, N-methylpyrrolidone, dimethyl sulfoxide, N,N-dimethylacetamide, sulfolane or toluene.

8. The method of claim 1, wherein the slurry is spray dried in a closed cycle spray drying apparatus.

9. A dry powder thermoplastic resin composition obtained by the method of claim 1, wherein the dry powder thermoplastic resin composition comprises a plurality of particles, and the plurality of particles are selected from epoxy resin particles and phenoxy resin particles. 10 . The dry powder thermoplastic resin composition according to claim 9 , wherein the average particle size of the plurality of particles is 150 μm or less.

11. The dry powder thermoplastic resin composition according to claim 10, wherein the average particle size is 20 microns or less.

12. Use of the dry powder thermoplastic resin composition according to claim 9 in coatings, adhesives, plastics, composite materials, or electronic components.

13. A method for forming a dry powder thermoplastic resin, the method comprising: dissolving a solid thermoplastic resin selected from a solid phenoxy resin in a mixture of a protic solvent and an aprotic solvent to form a slurry, wherein the protic solvent is a C1-C4-alkanol and the aprotic solvent is an aromatic solvent, wherein the amount of the aprotic solvent exceeds the amount of the protic solvent by at least 1% by weight; and The slurry is spray-dried to form the dry powder thermoplastic resin composition, wherein the dry powder thermoplastic resin composition comprises a plurality of phenoxy resin particles, the average particle size of the plurality of phenoxy resin particles is between 3 microns and 25 microns, the residual solvent content is between 0.01 weight percent and 1.5 weight percent, and the spray drying is performed in a closed-cycle spray drying device.

14. A method of forming a powdered epoxy resin or phenoxy resin, the method comprising: Providing a solid epoxy resin or phenoxy resin having an average molecular weight of at least 1000 Daltons; dissolving the solid epoxy resin or phenoxy resin in a mixture of an alcohol solvent and an aprotic solvent to form a resulting solution, wherein the alcohol solvent is a C1-C4-alkanol, the aprotic solvent is an aromatic solvent, the alcohol solvent and the aprotic solvent in the mixture have a weight ratio, wherein the amount of the aprotic solvent exceeds the amount of the alcohol solvent by at least 1 weight percent, and the resulting solution has between 1 weight percent and 10 weight percent of the epoxy resin or phenoxy resin based on the total weight of the resulting solution; as well as The obtained solution is spray-dried in a closed-cycle spray drying apparatus to form the powdered epoxy resin or phenoxy resin, and The residual solvent content of the powdered epoxy resin or phenoxy resin is 5 wt % or less.

15. The method of claim 14, wherein the solid epoxy or phenoxy resin has an average molecular weight of at least 10,000 Daltons.

16. The method of claim 14, wherein the solid epoxy or phenoxy resin has an average molecular weight of at least 30,000 Daltons.

17. The method of claim 14, wherein the solid epoxy or phenoxy resin has an average molecular weight of at least 50,000 Daltons.

18. The method according to claim 14, wherein the alcohol solvent is selected from ethanol, n-propanol, isopropanol and n-butanol. The method according to claim 18 , wherein the alcohol solvent is n-butanol.

20. The method of claim 14, wherein the obtained solution contains 5 to 10 wt% of epoxy resin or phenoxy resin.

21. The method of claim 14, wherein the powdered epoxy or phenoxy resin comprises no more than 4 weight percent residual solvent based on the total weight of the powdered epoxy or phenoxy resin.

22. The method of claim 14, wherein the powdered epoxy or phenoxy resin comprises no more than 1.5 weight percent residual solvent based on the total weight of the powdered epoxy or phenoxy resin.

23. The method of claim 14, wherein the powdered epoxy or phenoxy resin comprises no more than 0.5 weight percent residual solvent based on the total weight of the powdered epoxy or phenoxy resin.

24. The method of claim 14, wherein the powdered epoxy or phenoxy resin comprises no more than 0.3 weight percent residual solvent based on the total weight of the powdered epoxy or phenoxy resin.

25. The method of claim 14, wherein the powdered epoxy or phenoxy resin has an average particle size of no greater than 20 microns.

26. The method of claim 14, wherein the powdered epoxy or phenoxy resin has an average particle size of no greater than 12 microns.

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