Tannin-based expanding microspheres

Abstract

This provides tannin-based expandable microspheres. [Solution] The present invention relates to tannin-based thermally expandable microspheres, and also to a method for manufacturing them. The thermally expandable microspheres include a thermoplastic shell surrounding a hollow core, the hollow core containing a foaming agent, and the thermoplastic shell containing tannin.

Description

[Technical Field]

[0001] This invention relates to tannin-based thermally expandable microspheres, and also to a method for producing them. [Background technology]

[0002] Thermally expandable microspheres are known in the art and are described, for example, in U.S. Patent No. 3,615,972, International Publication No. 00 / 37547, and International Publication No. 2007 / 091960. Several examples are marketed under the trademark name ExpanseL®. These can be expanded to form extremely low-weight and low-density fillers and can be found in applications such as foamed resins or low-density resins, paints and coatings, cements, inks, and crack fillers. Consumer products that often contain expandable microspheres include lightweight shoe soles (e.g., for running shoes), textured coatings such as wallpaper, sun-reflective and heat-insulating coatings, food packaging sealants, wine corks, artificial leather, foams for protective helmet liners, and automotive weatherstrips.

[0003] Thermally expandable polymer microspheres typically contain a thermoplastic shell with a hollow core containing a blowing agent that expands upon heating. Examples of blowing agents include low-boiling point hydrocarbons or halogenated hydrocarbons, which are liquid at room temperature but vaporize upon heating. To produce expanded microspheres, the expandable microspheres are heated so that the thermoplastic shell softens, and the blowing agent vaporizes and expands, thus expanding the microspheres. Typically, the diameter of the microspheres can increase by 1.5 to 8 times during expansion. Expandable microspheres are commercially available in various forms, for example, as dry free-flowing particles, as aqueous slurries, or as partially dehydrated wet cakes.

[0004] Expandable microspheres can be produced, for example, by polymerizing ethylenically unsaturated monomers in the presence of a blowing agent using a suspension polymerization process. Typical monomers include those based on acrylates, acrylonitriles, acrylamides, vinylidene dichloride, and styrene. The problem associated with these thermoplastic polymers is that they are typically derived from petrochemicals and not from sustainable sources. In addition, many polymers are non-biodegradable or at least very slowly biodegradable, posing a risk of cumulative accumulation in the environment. However, simply replacing monomers with more sustainably sourced alternatives is not always straightforward, as it is necessary to ensure that acceptable expansion performance is maintained. For example, the polymer must have a suitable surface energy to obtain core-shell particles in the suspension polymerization reaction so that the blowing agent is encapsulated. In addition, the resulting polymer must have good gas barrier properties that can retain the blowing agent. Furthermore, the polymer must have a glass transition temperature T such that the shell can be stretched during expansion. g It is necessary to have suitable viscoelastic properties that surpass those of conventional monomers. Therefore, replacing conventional monomers with bio-based monomers is not straightforward.

[0005] Expandable microspheres are described, in which at least a portion of the monomers forming the thermoplastic shell may be bio-based and derived from renewable resources. For example, International Publication No. 2019 / 043235 describes polymers containing lactone monomers, International Publication No. 2019 / 101749 describes copolymers containing dialkyl itaconate monomers, and International Publication Nos. 2020 / 099440 and International Publication Nos. 2021 / 234010 A1 disclose thermally expandable microspheres made from cellulosic biopolymers.

[0006] However, these bio-based expandable microspheres have been found to have several drawbacks from a commercial standpoint. For example, the reduced commercial availability of the raw materials and their higher price compared to petroleum-based raw materials. Furthermore, from a performance standpoint, the expandable microspheres may not always be flexible or adequate, and may not always be precisely tuned for specific desired applications. Moreover, there is always room for improvement regarding the biodegradability of the thermoplastic shell. In addition, the storage stability of bio-based microspheres, particularly their water resistance, has been found to be unsatisfactory. Therefore, to improve storage stability, additional steps are often required during the production of such known bio-based microspheres, such as additional post-heating steps as described in International Publication No. 2024 / 089208 A1. However, these additional production steps are often cumbersome and expensive.

[0007] Therefore, there remains a need for alternative thermally expandable microspheres in which the thermoplastic shell is at least partially derived from sustainable sources. Furthermore, there remains a need for providing expandable microspheres in which the thermoplastic shell is at least partially derived from sustainable sources and the expandable microsphere has sufficient expandability, more preferably adaptable to the needs. Such alternative thermally expandable microspheres would also be even more desirable if they already have sufficient storage stability, particularly water resistance, so as to avoid additional steps to further improve storage stability during their manufacture. Accordingly, the present invention aims to find improved bio-based thermally expandable microspheres having at least some of the aforementioned desirable properties. [Overview of the Initiative]

[0008] The present invention relates to a thermally expandable microsphere comprising a thermoplastic shell surrounding a hollow core, wherein the hollow core contains a foaming agent and the thermoplastic shell contains tannin. The thermally expandable microsphere described herein solves the above-mentioned problems.

[0009] The present invention also relates to a method for preparing a thermally expandable microsphere comprising a thermoplastic shell surrounding a hollow core, wherein the hollow core comprises a blowing agent and the thermoplastic shell comprises tannin, and the method comprises (i) preparing a mixture comprising tannin and a blowing agent in a solvent, and (ii) spray-drying the mixture obtained in step (i) to obtain a thermally expandable microsphere. [Brief explanation of the drawing]

[0010] [Figure 1A] The differences in microspheres between single-core (Figure 1A) and multi-core (Figure 1B) processors are illustrated. [Figure 1B] The differences in microspheres between single-core (Figure 1A) and multi-core (Figure 1B) processors are illustrated. [Modes for carrying out the invention]

[0011] One aspect of the present invention is a thermally expandable microsphere comprising a thermoplastic shell surrounding a hollow core, wherein the hollow core contains a foaming agent and the thermoplastic shell contains tannin.

[0012] Expanding microspheres are based on a thermoplastic shell containing tannins. Tannins, also called tannoids, are widely distributed in many types of plants, where they can play a role in protecting against predation, for example by acting as insecticides, and in regulating plant growth. The astringency from tannins is what causes a dry and paccoly sensation in the mouth after consuming unripe fruit, red wine, or tea, for example. Similarly, the breakdown or modification of tannins over time plays an important role in determining the optimal harvest time.

[0013] Tannins are a class of polyphenol biomolecules that can typically bind to and precipitate macromolecules such as proteins, as well as a variety of other organic compounds, including amino acids and alkaloids. This ability of tannins to bind to and precipitate macromolecules and a variety of other organic compounds is usually attributable to the hydroxyl groups in tannins, but may also be attributable to additional other suitable groups present in tannins, such as carboxyl groups and aromatic groups. These functional groups can form strong complexes with macromolecules and a variety of other organic compounds, thus resulting in their precipitation. Therefore, in some embodiments, the tannins described herein are polyphenol compounds containing hydroxyl groups and, optionally, other suitable functional groups such as carboxyl groups. As used herein, the term “phenol” or “phenol” describes any compound containing a group comprising a six-membered aromatic carboxylic acid ring substituted with at least one hydroxyl group. In other words, the six-membered aromatic carboxylic acid ring may be further substituted with groups other than hydrogen, such as further hydroxyl or carboxyl groups. Similarly, as used herein, the term “polyphenol” describes any compound containing at least two groups, each comprising a six-membered aromatic carboxylic acid ring substituted with at least one hydroxyl group. As a result, the tannins described in this disclosure can be considered as phenolic polymers containing at least two phenolic groups. Typically, a tannin molecule contains at least six, preferably at least twelve, and more preferably at least eighteen hydroxyl groups. Furthermore, a tannin molecule may typically contain at least five, preferably at least seven, and more preferably at least nine phenyl groups. Therefore, a tannin described in this disclosure may contain at least four, preferably at least six, more preferably at least eight, and particularly preferably at least ten phenolic groups.

[0014] In some embodiments, the tannin may be selected from three main classes of tannins: hydrolyzable tannins, phlorotannins, and condensed tannins.

[0015] Hydrolyzable tannins contain hydrolyzable bonds and are typically based on gallic acid (3,4,5-trihydroxybenzoic acid). In some embodiments, the hydrolyzable tannin contains a base unit of gallic acid that is condensed together. The condensation of the carboxyl group of the first gallic acid molecule and the hydroxyl group of the second gallic acid molecule forms an ester bond linking the two gallic acid molecules. The hydrolyzable tannin may also contain units derived from further components such as hydroxyl and / or carboxyl group-containing molecules, e.g., sugar molecules. In some embodiments, the hydrolyzable tannin is tannic acid. Tannic acid is C, which corresponds to decagalloyl glucose. 76 H 52 O 46 It may have the overall chemical combination formula. However, tannic acid may also be a mixture of polygalloyl glucose or polygalloyl quinate ester with a number of galloyl moieties per molecule ranging from 2 to 12, depending on the circumstances. In a preferred embodiment, tannic acid comprises 1,2,3,4,6-penta-O-{3,4-dihydroxy-5-[(3,4,5-trihydroxybenzoyl)oxy]benzoyl}-D-glucopyranose. In a more preferred embodiment, tannic acid is 1,2,3,4,6-penta-O-{3,4-dihydroxy-5-[(3,4,5-trihydroxybenzoyl)oxy]benzoyl}-D-glucopyranose.

[0016] Condensed tannins contain functional groups, are obtained by condensation, and individual molecular units are linked via carbon-carbon bonds. Usually, condensed tannins are polymers formed by the condensation of flavan-3-ols, flavan-4-ols, or flavan-3,4-diols, especially flavans such as flavan-3-ols. Condensed tannins may have a composition selected from proanthocyanidins, polyflavonoid tannins, catechol-type tannins, pyrocatecollic type tannins, non-hydrolyzable tannins, and flavolans. Condensed tannins usually do not contain sugar residues. Flavan-3-ol-based tannins may have a composition selected from procyanidins, propelargonidins, prodelphinidins, profisetidins, protelacinsidins, progibotrutinidins, or prorobinetidins. Flavan-3,4-diol-based tannins may be leuco-fisetinidins, and flavan-4-ol-based tannins may be 3’,4’,5,7-flavan-4-ol form prolutelol (luteoflorol). One specific type of condensed tannin found in grapes is procyanidin, which is a polymer of 2 to 50 (or more) catechin units linked by carbon-carbon bonds. These are resistant to cleavage by hydrolysis.

[0017] Florotanins are usually based on phloroglucinol (benzene-1,3,5-triol) and may be in the form of polyphloroglucinols.

[0018] In a preferred embodiment, the tannin comprises condensed tannins or hydrolyzable tannins, or mixtures thereof. In an even more preferred embodiment, the tannin comprises hydrolyzable tannins.

[0019] In a particular preferred embodiment, the tannin comprises tannic acid.

[0020] The thermoplastic shell may consist solely of tannins, preferably hydrolyzable tannins, fluorotannins, and condensed tannins, more preferably hydrolyzable tannins and condensed tannins, even more preferably hydrolyzable tannins, and most preferably tannic acid. However, in embodiments, the thermoplastic shell may also consist of further components, such as one or more nonpolymer additives or one or more polymer components. In preferred embodiments, the thermoplastic shell further comprises one or more polymer components.

[0021] In some embodiments, the thermoplastic shell further comprises polymer components (which may be considered a first polymer component if two or more different polymer components are present). The polymer compound is different from tannin.

[0022] In some embodiments, the thermoplastic shell comprises a second polymer component, distinct from the first polymer component, in addition to the first polymer component. The second polymer compound is distinct from tannin.

[0023] In some embodiments, the thermoplastic shell includes, in addition to the first and second polymer components, a further third polymer component distinct from the first and second polymer components. The third polymer compound is different from tannin.

[0024] If the shell contains one or more polymer components, the total content of one or more polymer components may be up to 99.9% by weight, for example, up to 99% by weight, up to 98% by weight, up to 95% by weight, up to 90% by weight, up to 80% by weight, up to 70% by weight, or up to 60% by weight. In further embodiments, the content of one or more polymer components may be up to 50% by weight, for example, up to less than 30% by weight, or up to less than 10% by weight, for example, 9% or less by weight, 5% or less by weight, or even 2% or less by weight. These percentages are based on the total weight of the thermoplastic shell. In some embodiments, the shell contains polymer components in amounts of at least 0.1% by weight, at least 0.5% by weight, at least 1% by weight, at least 5% by weight, or at least 10% by weight. In some embodiments, the shell contains polymer components in amounts ranging from 0.1% to 50% by weight, for example, 0.5% to 50% by weight, 1% to 45% by weight, or 5% to 40% by weight.

[0025] In other embodiments in which the shell includes one or more polymer components, the total content of the one or more polymer components may be 50 to 99.9% by weight, preferably 55 to 99% by weight, more preferably 60 to 98% by weight, and more preferably 70 to 95% by weight, based on the total weight of the thermoplastic shell.

[0026] In some embodiments, the thermoplastic shell may be configured to contain at least 0.1% by weight, for example, at least 0.5% by weight, at least 1% by weight, at least 2% by weight, at least 3% by weight, at least 5% by weight, at least 10% by weight, at least 20% by weight, or at least 30% by weight, at least 50% by weight, at least 60% by weight, at least 70% by weight, or at least 80% by weight, at least 90% by weight, at least 95% by weight, or at least 98% by weight of tannins, preferably hydrolyzable tannins, fluorotannins, and condensed tannins, more preferably hydrolyzable tannins and condensed tannins, even more preferably hydrolyzable tannins, most preferably tannic acid. These percentages are based on the total weight of the thermoplastic shell. In some embodiments, the thermoplastic shell is configured to contain 98% by weight or less of tannins, for example, 95% by weight or less, 90% by weight or less, 80% by weight or less, 70% by weight or less, 60% by weight or less, 50% by weight or less, 30% by weight or less, 20% by weight or less, 10% by weight or less, 5% by weight or less, 3% by weight or less, 2% by weight or less, or further 1% by weight or less, preferably hydrolyzable tannins, fluorotannins, and condensed tannins, more preferably hydrolyzable tannins and condensed tannins, even more preferably hydrolyzable tannins, most preferably tannic acid.

[0027] Further polymeric components are not limited, and therefore, if present, any polymeric components known to those skilled in the art can be used as polymeric components. In some embodiments, the thermoplastic shell further comprises at least one polymeric component selected from the group consisting of polysaccharides, polysaccharide derivatives, polyesters, polyethers, polyacids, polyols, polyalkenes, lignin, polyvinyl, or any combination thereof. In some embodiments, the polysaccharides and polysaccharide derivatives may be selected from the group consisting of cellulose, cellulose derivatives, chitosan, hemicellulose, and alginates, and are preferably selected from cellulose, cellulose derivatives, and chitosan. The cellulose derivative may be a cellulose ester or carboxycellulose. In some embodiments, the lignin may be selected from kraft lignin, sulfonated lignin (also called lignosulfonate), organosole v-lignin, hydrolyzed lignin, vapor explosion lignin, crushed wood lignin, acetylated lignin, and soda lignin. The polyvinyl may be a polyvinyl acetate such as poly(1-vinylpyrrolidone-co-vinyl acetate), or a polyvinyl alcohol such as polyvinyl alcohol having a degree of hydrolysis of at least 20 mol%, such as about 30 to >99 mol%. In some embodiments, the polymer components may be selected from alkylcellulose, carboxycellulose, vinyl acetate copolymers, polylactic acid, polyethylene glycol, polyvinyl alcohol, polyacrylic acid, nanocrystalline cellulose, or combinations thereof.

[0028] In preferred embodiments, the polymeric components are selected from cellulose, cellulose derivatives, chitosan, lignin, and any combination thereof. In even more preferred embodiments, the polymeric components are selected from cellulose derivatives, lignin, and any combination thereof, most preferably from alkylcellulose, cellulose esters, carboxycellulose, lignosulfonates, kraft lignin such as acetylated kraft lignin, and any combination thereof.

[0029] In some embodiments, if the shell comprises two or more different polymer components, the first polymer component may be selected from any of the polymer components described above, and the second component (different from the first polymer component) may be selected from cellulose, cellulose derivatives, chitosan, lignin, and polyvinyl, preferably cellulose derivatives, lignin, and polyvinyl, for example, polyvinyl acetate and polyvinyl alcohol, most preferably carboxycellulose, kraft lignin, for example acetylated kraft lignin, polyvinyl acetate, for example poly(1-vinylpyrrolidone-co-vinyl acetate), and polyvinyl alcohol, for example, polyvinyl alcohol having a degree of hydrolysis of at least 20 mol%, for example, about 30 to >99 mol%.

[0030] In one embodiment, the thermoplastic shell contains or consists of tannin and polyvinyl alcohol. The tannin preferably contains or consists of tannic acid. The weight ratio of tannin to polyvinyl alcohol in the thermoplastic shell is preferably in the range of about 10:90 to about 90:10, preferably about 15:85 to about 85:15, and more preferably about 80:20 to about 20:80. The polyvinyl alcohol preferably has a degree of hydrolysis of at least 20 mol%, such as about 30 to >99 mol%. Polyvinyl alcohol having a specific degree of hydrolysis is typically obtained by controllably hydrolyzing polyvinyl acetate, and therefore, a polyvinyl alcohol polymer obtained in this way and having a degree of hydrolysis of less than 100% is strictly speaking a poly(vinyl acetate-co-vinyl alcohol) polymer, but more generally referred to as polyvinyl alcohol having a degree of hydrolysis of x mol%. The polyvinyl alcohol polymer preferably has a weight-average molecular weight (GPC) in the range of about 5,000 to about 200,000 Da, for example, about 10,000 to about 150,000 Da, for example, about 10,000 to about 50,000 Da, for example, about 13,000 to about 23,000 Da. For those skilled in the art, it would be routine to prepare polyvinyl alcohol having a specific degree of hydrolysis and / or a specific molecular weight.

[0031] In an embodiment, the thermoplastic shell includes one or more non-polymer additives. The thermoplastic shell may include any such non-polymer additives in addition to any of the above-described polymeric component(s) or any combination thereof. The non-polymer additives, per se, are not limited. However, in some embodiments, the thermoplastic shell includes a non-polymer additive selected from the group consisting of carboxylic acids, anhydrides, esters, carbohydrates, alcohols, epoxides, and ureas. In some embodiments, the non-polymer additive is selected from citric acid, pyromellitic dianhydride (PMDA), pyromellitic acid (PMA), pyromellitic dianhydride (PMDA), tartaric acid, 1,2,3,4-butanetetracarboxylic acid (BTCA), succinic acid, maleic acid, lactic acid, polyacrylic acid (PAA), urea, sorbitol, glucose, fructose, vitamin C (ascorbic acid), glycerol, and 1,3-butanediol.

[0032] The thermally expandable microspheres are hollow, the shell contains tannin, and the hollow center or core contains one or more blowing agents. The tannin used in the preparation of the microspheres typically has a density of 1.0 to 1.35 g / cm 3 In the expandable microspheres, the density is typically less than 1 g / cm 3 and preferably ranges from 0.005 to 0.8 g / cm 3 or from 0.01 to 0.75 g / cm 3 In a further embodiment, the density of the expandable microspheres ranges from 0.01 to 0.5 g / cm 3 Higher densities, particularly densities of 1 g / cm 3 or greater, indicate that a sample of the microspheres is not suitable for use.

[0033] The thermally expandable microspheres preferably have a temperature T Start at which expansion begins in the range of 90 °C to 210 °C, such as 100 °C to 210 °C. The temperature at which expansion begins is referred to as T Start and the temperature at which maximum expansion is reached is referred to as T max T start and Tmax This may be determined using standard measurement techniques that are generally known to those skilled in the art. For example, T start and T max This can be determined by a heating experiment using a Mettler-Toledo thermomechanical analyzer, such as the Mettler-Toledo TMA / SDTA 841e, with a heating rate of 20°C / min and a load (net) of 0.06 N. In such a heating experiment, a sample of a known weight of thermally expandable microspheres is heated at a constant heating rate of 20°C / min under a load (net) of 0.06 N. As the thermally expandable microspheres begin to expand, the volume of the sample increases and the load moves upward. From these measurements, an expansion thermogram is obtained, where the vertical axis indicates the height to which the load moves upward and the horizontal axis indicates temperature. start and T max This can be determined from this inflation thermogram, for example, using STARe software from Mettler-Toledo.

[0034] In several embodiments, the thermally expandable microspheres are heated in a range of 90°C to 190°C, such as 110°C to 190°C. start The thermally expandable microspheres have a temperature range of 120°C to 185°C, most preferably 125°C to 185°C. start It is even more preferable to have it.

[0035] Many factors can contribute to high density, including poor expansion characteristics that can occur when there are too many microspheres and they contain insufficient foaming agent to allow for proper expansion. This can result from the polymer shell being too permeable to the foaming agent, or from the formation of so-called "multicore" microspheres, i.e., having multiple foaming agent-containing cores within the shell instead of a single foaming agent-containing core (e.g., like a microspherical foam or sponge). In such multicore microspheres, the concentration of foaming agent is typically too low to adequately reduce density. Another cause is polymer aggregation or cohesiveness, resulting in poor microsphere production and higher density material. Microspheres with too high a proportion of aggregated material or that do not expand sufficiently can also lead to significant heterogeneity in the expansion characteristics of the resulting microsphere product. This is particularly undesirable for surface-sensitive applications such as coatings where a smooth finish is desired.

[0036] Exemplary cross-sections of single-core and multi-core microspheres are provided in Figures 1A and 1B, respectively, where the shell material region 1 is represented by a mesh-like area and the foaming agent-containing region 2 is represented by a blank area.

[0037] In further embodiments, the thermoplastic shell may include particles to improve the mechanical properties and gas barrier properties of the thermoplastic shell. Examples of such particles include various types of clay such as talc, montmorillonite, and bentonite.

[0038] The hollow core of the thermally expandable microsphere of the present invention contains a blowing agent. The blowing agent may include one or more different blowing agents. The one or more blowing agents generally have a boiling point above 25°C at a pressure of 5.0 bara, or above 25°C at a pressure of 3.0 bara, where "bara" is an abbreviation for "bar (absolute) pressure". In some embodiments, they have a boiling point above 25°C at atmospheric pressure (1.013 bara). Typically, they have a boiling point of 250°C or less at atmospheric pressure (e.g., 220°C or less, or 200°C or less). They are preferably inert and preferably do not react with the tannin shell. The boiling point at high pressure can be calculated using the Clausius-Clapeyron equation.

[0039] Examples of foaming agents include alcohols, esters, dialkyl ethers, alkanes, and halocarbons (e.g., chlorocarbons, fluorocarbons, or chlorofluorocarbons). In some embodiments, the alcohol comprises at least one C2-C8 alcohol, such as a C2-C6 alcohol or a C2-C4 alcohol. In some embodiments, the ester comprises two alkyl groups, each independently selected from C2-C5 alkyl groups. In some embodiments, the dialkyl ether comprises two alkyl groups, each independently selected from C2-C5 alkyl groups. In some embodiments, the alkane comprises at least one C4-C 12 It is an alkane. In some embodiments, the haloalkane is C2-C 10 Selected from haloalkanes. The haloalkane may contain one or more halogen atoms selected from chlorine and fluorine. The alkyl or haloalkyl group in the alcohols, dialkyl ethers, alkanes, and haloalkanes can be linear, branched, or cyclic. One or more blowing agents or a mixture thereof may be used.

[0040] In several embodiments, for environmental reasons, one or more blowing agents are selected from alcohols, esters, alkyl ethers, and alkanes, and in further embodiments, one or more blowing agents are selected from alcohols and alkanes, preferably from alcohols. Haloalkanes are preferably avoided due to their potential ozone-depleting properties and their generally higher global warming potential.

[0041] Examples of suitable foaming agents that can be used include ethanol, n-propanol, isopropanol, n-butanol, tert-butyl alcohol, n-pentanol, isopentanol, n-hexanol, isohexanol, heptanol, isoheptanol, octanol, isooctanool, tert-butyl acetate, butyl acetate, methyl tert-butyl ether, n-pentane, isopentane, neopentane, cyclopentane, cyclohexane, n-butane, isobutane, isohexane, neohexane, heptane, isoheptane, octane, isooctane, isodecane, and isododecane. In preferred embodiments, the foaming agent is selected from C2-C8 alcohols, e.g., C2-C6 alcohols or C2-C4 alcohols. In more preferred embodiments, the foaming agent includes a foaming agent selected from isooctane, isohexane, tert-butyl acetate, butyl acetate, methyl tert-butyl ether, tert-butyl alcohol, and combinations thereof. In a particularly preferred embodiment, the foaming agent includes tert-butyl alcohol, isooctane, or a combination thereof.

[0042] In expandable microspheres, one or more foaming agents are typically present in amounts ranging from 0.5 to 50% by weight, based on the total weight of the shell material and the one or more foaming agents, for example, in amounts ranging from 1 to 40% by weight or 2 to 30% by weight.

[0043] The expandable microspheres of the present invention can be obtained by a spray-drying process comprising mixing tannin, a solvent, a blowing agent, and optionally any further components such as polymeric or non-polymeric components, and then spraying the mixture thus obtained into a drying apparatus to produce thermally expandable microspheres having a thermoplastic shell surrounding a hollow core, wherein the thermoplastic shell contains tannin and the hollow core contains the blowing agent.

[0044] In principle, the spray drying apparatus for carrying out the spray drying process is not limited, and any conventional and commercially available spray drying apparatus can be used for the spray drying process. A typical spray drying apparatus suitable for the process described herein comprises a drying chamber equipped with a nozzle, a drying gas inlet, and an outlet connecting the drying chamber to a cyclone. The liquid to be atomized, usually combined with a spray gas, is sprayed into the drying chamber through a nozzle, usually located at the top of the spray chamber (but may be located at any other part of the spray dryer). In the drying chamber, the atomized liquid is dried by the drying gas supplied into the spray chamber through the drying gas inlet. The drying gas inlet may be located, for example, immediately next to the nozzle. The atomized liquid dries and forms particles. The resulting particles are then supplied into the cyclone together with the drying gas through the drying chamber outlet, usually located in the bottom area of ​​the drying chamber. In the cyclone, the particles are separated from the dry air. The dry air may be further filtered to remove any residual particles from the dry air.

[0045] One suitable spray drying apparatus for carrying out the spray drying process is the Buchi Mini Spray Dryer B-290, commercially available from Buchi / Switzerland.

[0046] The order in which tannins, solvents, foaming agents, and optionally further components such as polymer or non-polymer components are added is not restricted, and any order can be chosen.

[0047] However, in a preferred embodiment, in the process for generating expandable microspheres, tannin is first mixed with a solvent and optionally with further components such as polymeric or non-polymeric components, and then in a further step, a foaming agent is added to the mixture.

[0048] Tannin mixing can be carried out at ambient temperature, but temperatures in the range of 5 to 75°C can be used. Mixing is usually continued until the tannin is completely dissolved in the solvent.

[0049] In some embodiments, the mixture of tannin, a solvent, and optionally further components such as polymeric or non-polymeric components may be left to stand or stirred for a period of time such as 1 to 100 hours or 2 to 50 hours. This may be carried out at a temperature in the range of 10 to 95°C, for example, 20 to 90°C.

[0050] In a further step, the blowing agent is added to a mixture of tannin, solvent, and optionally, other components such as polymeric or non-polymeric components. This mixing step can be carried out at ambient temperature, but temperatures in the range of 5 to 75°C can be used. This mixing step is usually carried out until the blowing agent is completely dissolved in the solvent.

[0051] The foaming agent may be added to a mixture of tannin, solvent, and optionally further components such as polymeric or non-polymeric components, and the resulting mixture may be further stirred for a period of time, for example, 1 to 100 hours or 2 to 50 hours. This stirring may also be carried out at a temperature in the range of 10 to 95°C, for example, 20 to 90°C.

[0052] A mixture comprising tannin, a solvent, a blowing agent, and optionally further components such as polymeric or non-polymeric components is then sprayed into a drying apparatus to produce the thermally expandable microspheres described herein. The drying apparatus may be a spray dryer as described above.

[0053] The spray gas that is atomized along with the liquid through the nozzle is not particularly limited and may be any suitable spray gas known to those skilled in the art. For example, the spray gas may be selected from nitrogen, carbon dioxide, (pressurized) air, noble gases (such as argon), etc. Preferably, in the method for generating expandable microspheres as described herein, a spray gas is used, and more preferably, this spray gas is nitrogen.

[0054] Furthermore, the drying gas is not particularly limited and may be any suitable drying gas known to those skilled in the art. For example, the drying gas may also be selected from nitrogen, carbon dioxide, (pressurized) air, noble gases (such as argon), etc. Nitrogen is preferred as the drying gas.

[0055] Further process parameters for operating the spray dryer, such as the spray gas flow rate, the inlet temperature of the drying gas entering the drying chamber, the supply rate of the liquid to be atomized, and the inhaler speed and sprayer speed for circulating the drying gas within the spray dryer, can be easily selected by those skilled in the art.

[0056] The method described above makes it possible to obtain an expandable microsphere comprising a thermoplastic shell surrounding a hollow core, wherein the hollow core contains a foaming agent and the thermoplastic shell contains tannin.

[0057] The solvent may be water, or an organic solvent selected from those having one or more functional groups selected from esters, amides, aldehydes, ketones, alcohols (including glycols), and ethers, such as those having 1 to 12 carbon atoms. In some embodiments, the esters, ketones, and ethers may be part of a cyclic structure. Further examples include haloalkanes having 1 to 6 carbon atoms and halo-carboxylic acids having 1 to 6 carbon atoms, where the halogen is selected from fluorine, chlorine, bromine, and iodine. The solvent may also be a mixture of water and an organic solvent, such as any of the organic solvents described above.

[0058] Examples of organic solvents that can be used include ethyl acetate, ethyl formate, methyl acetate, n-propyl formate, isopropyl formate, n-propyl acetate, isopropyl acetate, isobutyl acetate, n-butyl acetate, n-pentyl formate, isopentyl formate, n-pentyl acetate, isopentyl acetate, ethyl propionate, isobutyl isobutyrate, n-butyl propionate, ethyl 3-ethoxypropionate, 2-ethylhexyl acetate, acetone, methyl ethyl ketone, diethyl ketone, methyl isobutyl ketone, methyl isoamyl ketone, methyl n-amyl ketone, mesityl oxide, acetophenone, cyclohexanone, diethyl phthalate, ethyl lactate, benzyl acetate, butyrolactone, acetylacetone, methylcyclohexanone, benzaldehyde, diisobutyl ketone, diacetone alcohol, ethylene glycol, glyceryl-α-monochlorohydrin, propylene glycol, glycol ether (e.g., propylene glycol Examples of solvents include glycol monomethyl ether, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol mono-n-butyl ether, propylene glycol mono-tert-butyl ether, propylene glycol monopropyl ether, propylene glycol monobutyl ether), glycol ether esters (e.g., ethylene glycol monomethyl ether acetate, ethylene glycol acetate monoethyl ether, ethylene glycol acetate monobutyl ether, ethylene glycol diacetate), methanol, ethanol, n-propyl alcohol, isopropyl alcohol, n-butanol, sec-butanol, isobutanol, benzyl alcohol, diisopropyl ether, dimethoxymethane, dimethoxyethane, 1,4-dioxane, 1,3-dioxolane, tetrahydrofuran, anisole, phenethole, and dimethylformamide. Other examples of solvents include dimethyl sulfoxide, toluene, xylene, n-methyl-2-pyrrolidone, methylene chloride, chloroform, carbon tetrachloride, trichloroacetic acid, methylene bromide, methylene iodide, trichloroethylene, and tetrachloroethylene. The organic solvent may be a mixture of two or more solvents.If the solvent is a mixture of two or more organic solvents, one of the solvents is preferably acetone. In some embodiments, acetone is mixed with an alcohol such as methanol or ethanol.

[0059] In some embodiments, the solvent is a mixture of water and an organic solvent. In such embodiments, the mixture preferably contains water in an amount of 50% by weight or less, for example, 40% by weight or less, 30% by weight or less, or 20% by weight or less. In such embodiments, it is even more preferable that the mixture contains water in an amount of at least 1% by weight, such as at least 2% by weight or at least 4% by weight based on the total weight of the solvent.

[0060] In particularly preferred embodiments, the solvent is selected from one or more of water, methanol, ethanol, and acetone. More preferably, the solvent comprises water, methanol, ethanol, or acetone. In some specific preferred embodiments, the solvent comprises acetone. In some embodiments, the solvent comprises a mixture of at least two solvents, which is preferably selected from the group consisting of water, methanol, ethanol, acetone, and combinations thereof. In some embodiments, the solvent comprises acetone and water, or acetone and ethanol.

[0061] Typically, the content of shell components in the spray-drying mixture ranges from 0.1 to 50% by weight. In some embodiments, the amount can range from 1 to 40% by weight, for example, from 5 to 35% by weight, or even from 10 to 30% by weight. The weight percentage is based on the total weight of the spray-drying mixture.

[0062] In some embodiments, the tannin content in the spray-drying mixture is typically in the range of 0.1 to 50% by weight. In some embodiments, the amount can be in the range of 1 to 40% by weight, for example, 5 to 35% by weight, or even 10 to 30% by weight. The weight percentage is based on the total weight of the spray-drying mixture.

[0063] The amount of one or more blowing agents in the spray-drying mixture is typically in the range of 0.5 to 50% by weight. In some embodiments, it can be in the range of 0.5 to 40% by weight, for example, 1 to 30% by weight, 3 to 25% by weight, or even 5 to 25% by weight. In some embodiments, the weight of the blowing agent in the spray-drying mixture is less than or equal to the weight of the shell components, such as tannins. For example, the weight ratio of the blowing agent to the tannins may be 1.5 or less, for example, 1.3 or less, or 1.1 or less. In some embodiments, the minimum weight ratio is 0.1, or in further embodiments, 0.2. In some embodiments, the weight ratio of the blowing agent to the tannins in the solvent phase is in the range of 0.1 to 1.5, for example, 0.2 to 1.3, or even 0.3 to 1.1.

[0064] The amount of solvent totals 100% by weight. Preferably, the amount of solvent is at least 30% by weight, more preferably at least 40% by weight, and even more preferably at least 50% by weight. The weight percentage is based on the total weight of the spray-drying mixture.

[0065] The volume-average particle size (diameter) of unexpanded microspheres, i.e., the D(0.5) value, is typically in the range of 1 to 500 μm (e.g., 5 to 200 μm), or in some embodiments, in the range of 10 to 100 μm, and even further in the range of 30 to 80 μm.

[0066] The diameter of an expanded microsphere is typically in the range of 1.5 to 8 times larger than that of an unexpanded microsphere, for example, 2 to 7 times or 3 to 6 times its original diameter.

[0067] Particle size is preferably measured using light scattering techniques, such as laser diffraction including low-angle laser scattering (LALLS). They can also be measured by image analysis from photographs or electron microscope images of microspheres before or after expansion.

[0068] To expand the expandable microspheres, they require the boiling point of the foaming agent and the T of tannin. g It can be heated to temperatures above the melting point of the microspheres, and also to temperatures below the melting point of the microspheres. To interrupt the expansion, the microspheres are heated to the tannin T g And / or it can be cooled down to below the boiling point of the foaming agent.

[0069] Methods for heating expandable microspheres include, for example, direct or indirect contact with a heat transfer medium such as steam or pressurized steam, as described in International Publication Nos. 2004 / 056549, 2014 / 198532, and 2016 / 091847. In further embodiments, direct or indirect contact with another heated gas (e.g., air or nitrogen) optionally mixed with steam can be used. In further embodiments where indirect heating is used, a liquid heat transfer medium (e.g., heated oil) may be used. In another embodiment, IR radiation can be used to heat the microspheres.

[0070] The expansion properties of thermally expandable thermoplastic microspheres can be evaluated using a thermomechanical analyzer (e.g., Mettler TMA 841), and quantitative data can be obtained from images using suitable software such as STARe software.

[0071] Expandable thermoplastic microspheres may be supplied in an unexpanded form, for example, for local expansion to their intended use, or they may be pre-expanded before shipment to their final use location.

[0072] Microspheres can be found in numerous applications in the manufacture of, for example, paper (e.g., embossed paper, paper fillers, adhesives), inks, cork, cement-based compositions, adhesives, foams, insulating materials, coatings, rubber-based products, thermoplastics, thermosetting resins, ceramics, nonwoven composite materials, and fillers, and can provide lightweight fillers in such applications.

[0073] Microsphere expansion is typically irreversible; that is, cooling the microspheres after thermal expansion does not cause them to contract back to their pre-expansion size.

[0074] Another aspect of the present invention is a process for preparing a thermally expandable microsphere, comprising mixing tannin, a solvent, a blowing agent, and optionally further components such as polymeric or non-polymeric components, and then spraying the mixture thus obtained into a drying apparatus to produce a thermally expandable microsphere having a thermoplastic shell surrounding a hollow core, wherein the thermoplastic shell comprises tannin and optionally further components such as polymeric or non-polymeric components, and the hollow core comprises a blowing agent.

[0075] Process parameters, spray drying apparatus, tannin, solvent, blowing agent, optional further components such as polymeric or non-polymeric components, and their amounts are the same as those already described above and apply equally to the process according to the second aspect of the present invention.

[0076] In a further embodiment, the present invention also covers thermally expandable microspheres obtained by a process for preparing thermally expandable microspheres as described above.

[0077] Examples

[0078] The following examples are intended to illustrate the present invention.

[0079] Microscopic evaluation of expansion characteristics was performed using a Linkam LTS420 heating stage in combination with a Leica DM1000 microscope. The heating rate was 40°C / min.

[0080] Expansion characteristics were evaluated using a Mettler TMA 841 thermomechanical analyzer interfaced to a PC running STARe software. The heating rate was 20°C / min using a 0.06 N (net) load.

[0081] Gas chromatography-flame ionization detection (GC-FID) analysis was performed using an Agilent 7697A Headspace in combination with an Agilent 7890A GC.

[0082] General synthesis method:

[0083] Solutions of tannic acid, a foaming agent, and, where applicable, further components in a suitable solvent were prepared by dissolving the tannic acid, foaming agent, and, where applicable, further components overnight using a magnetic stirrer.

[0084] Further components are, Citric acid (obtained from Fischer); PMDA (obtained from Merck); Chitosan (obtained from Chitolytic, (CO-101211, 3kDa, degree of deacetylation >86.5%)); Carboxymethylcellulose (CMC) (obtained from Nouryon (8-10kDa, DS 0.7)); First lignin (Lignin 1) (obtained from Domsjo (lignosulfonate, DP20, 12kDa)); Second lignin (Lignin 2) (obtained from Borregaard (lignosulfonate, DP-35512)); Third lignin (Lignin 3) (obtained from UPM Biochemicals (Kraft lignin, BioPiva 100)); Fourth lignin (Lignin 4) (obtained from UPM Biochemicals and then acetylated in-house (Kraft lignin, BioPiva 100)); Fifth lignin (Lignin 5) (obtained from Sodra (Kraft lignin, Lignin)); Sixth lignin (Lignin 6) (obtained from Bloom (organosolv lignin, Beechwood AAF Lignin)); First cellulose acetate (CA1) (obtained from Eastman (CA-398-3, 30kDa, DS 2.45)); Second cellulose acetate (CA2) (obtained from Cerdia (17kDa, DS 2.1)); Cellulose acetate propionate (CAP) (obtained from Eastman (CAP-482-0.5, 25kDa, DS(Ac) 0.1, DS(Pr) 2.35); Cellulose acetate butyrate (CAB) (obtained from Eastman); The materials were poly(1-vinylpyrrolidone-co-vinyl acetate) (PVPVA) (obtained from Merck (190837)); first polyvinyl alcohol (PVA1) (obtained from Kuraray (Kuraray Poval LM-20, 40 mol.% hydrolysis degree)); and second polyvinyl alcohol (PVA2) (obtained from Sigma-Aldrich (Mw 13,000~23,000, 98 mol.% hydrolysis degree)).

[0085] Next, the resulting mixture was spray-dried using a Buchi Mini Spray Dryer B-290. Nitrogen was used as the spray gas at a supply rate of 238–307 L / hour. The supply rate of the mixture being spray-dried was 4–13 ml / min (depending on the solvent). The temperature of the drying gas at the inlet was 70–150°C (depending on the solvent), and the inhaler speed was 38 m / min. 3 It was [time].

[0086] Dry solids were collected from the bottom of the cyclone and analyzed.

[0087] Details of the prepared samples are shown in Table 1, and data on the obtained microspheres are shown in Table 2.

[0088] [Table 1-1]

[0089] [Table 1-2]

[0090] [Table 1-3]

[0091] [Table 1-4]

[0092] [Table 1-5]

[0093] [Table 1-6]

[0094] [Table 1-7]

[0095] [Table 1-8]

[0096] [Table 1-9]

[0097] [Table 1-10]

[0098] [Table 2-1]

[0099] [Table 2-2]

[0100] [Table 2-3]

[0101] These data demonstrate that bio-based microspheres can be fabricated using tannin-containing compositions that exhibit at least good expansion under microscopic evaluation and high versatility regarding an adjustable temperature over a wide range for initiating expansion. Furthermore, the microspheres of the present invention have a suitable expansion density for use in a wide range of applications and therefore possess desirable expansion performance.

[0102] Water resistance test: The microspheres from samples 24 and 29 described above were individually subjected to water resistance tests. In this test, approximately 1 g of microspheres were immersed in approximately 10 ml of water, thoroughly mixed, and then the water-microsphere mixture was stored at ambient temperature (20-25°C) for 7 days with shaking once a day. After storage, the microspheres were filtered, dried, and their properties were evaluated.

[0103] For comparative purposes, two comparative microspheres were prepared (Samples 52 and 53). The microspheres of Sample 52 contained CAP and pyromelittic acid (PMA), and the microspheres of Sample 53 contained CAB and pyromelittic acid (PMA). The microspheres of Samples 52 and 53 were also subjected to water resistance testing. However, due to the obvious and rapid degradation of the comparative microspheres as determined by visual inspection, the microsphere properties were already evaluated after only one day of storage.

[0104] Table 3 summarizes the details of the synthesis, and Table 4 summarizes the microsphere properties of the microspheres immediately after preparation and after water resistance testing.

[0105] [Table 3]

[0106] [Table 4]

[0107] One important property for evaluating the water resistance of microspheres is the density of the microspheres before and after storage in water. An increase in density usually indicates the decomposition of microspheres, resulting from some microspheres completely disintegrating and / or some microspheres losing at least partially their foaming agent and / or water entering the microspheres. The microspheres of samples 24 and 29 of the present invention showed no increase in density even after being stored in water for 7 days. Rather, the density further decreases, which is thought to be caused by the rearrangement of polymer chains when the shell partially swells in water, resulting in a shell with improved properties after drying. In contrast, the comparative microspheres of samples 52 and 53 showed a significant increase in density after being stored in water for only 1 day, indicating that they have much lower water resistance than those observed in the samples of the present invention.

[0108] Storage stability test: The microspheres from samples 24 and 29, as well as comparative sample 52, were individually subjected to storage stability tests. In this test, approximately 2-3 grams of microspheres were stored for 6 months in plastic cups with lids on top at ambient temperature (20-25°C) on a shelf. After storage, the properties of the microspheres were evaluated. The microsphere properties of the microspheres immediately after preparation and after the storage stability test are summarized in Table 5.

[0109] [Table 5]

[0110] One important property for evaluating the storage stability of microspheres is the density of the microspheres before and after storage. An increase in density typically indicates the degradation of microspheres, resulting from some microspheres completely collapsing and / or some microspheres loosening their foaming agents at least partially. The microspheres of samples 24 and 29 of the present invention did not show an increase in density even after 6 months of storage. Rather, the density is further reduced, which is thought to be caused by the rearrangement of polymer chains over time, giving the shell improved properties after storage. In contrast, the comparative microsphere of sample 52 showed a significant increase in density after 6 months of storage, indicating that the comparative example has much lower storage stability than that observed in the samples of the present invention.

Claims

1. A thermally expandable microsphere comprising a thermoplastic shell surrounding a hollow core, wherein the hollow core contains a foaming agent and the thermoplastic shell contains tannin.

2. The thermally expandable microsphere according to claim 1, wherein the tannin comprises a condensed tannin, a hydrolyzable tannin, or a mixture thereof.

3. The thermally expandable microsphere according to claim 1 or 2, wherein the tannin contains tannic acid.

4. The thermally expandable microsphere according to any one of claims 1 to 3, wherein the thermoplastic shell further comprises a first polymer component.

5. The thermally expandable microsphere according to claim 4, wherein the thermoplastic shell further comprises a further second polymer component different from the first polymer component.

6. The thermally expandable microsphere according to claim 4 or 5, wherein the thermoplastic shell comprises up to 50% by weight, preferably 1 to 45% by weight, and more preferably 5 to 40% by weight of the polymer component, the weight percentage being based on the total weight of the thermoplastic shell.

7. The thermally expandable microsphere according to claim 4 or 5, wherein the thermoplastic shell comprises 50 to 99.9% by weight, preferably 55 to 99% by weight, more preferably 60 to 98% by weight, and more preferably 70 to 95% by weight of the polymer component, and the weight percentage is based on the total weight of the thermoplastic shell.

8. The thermally expandable microsphere according to any one of claims 4 to 7, wherein the first polymer component is selected from the group consisting of cellulose, cellulose derivatives, chitosan, lignin, or polyvinyl.

9. The thermally expandable microsphere according to claim 8, wherein the first polymer component is selected from cellulose derivatives, lignin, and polyvinyl, and preferably from alkylcellulose, cellulose esters, carboxycellulose, lignosulfonates, kraft lignin, and polyvinyl alcohol.

10. The thermally expandable microsphere according to any one of claims 5 to 9, wherein the further second polymer component is selected from the group consisting of cellulose, cellulose derivatives, lignin, and polyvinyl.

11. The thermally expandable microsphere according to claim 10, wherein the further second polymer component is selected from cellulose derivatives, lignin, and polyvinyl, preferably from carboxycellulose, kraft lignin, poly(1-vinylpyrrolidone-co-vinyl acetate), and polyvinyl alcohol.

12. The thermally expandable microsphere according to any one of claims 1 to 11, wherein the blowing agent comprises an alcohol, ether, ester, or hydrocarbon, preferably an alcohol or hydrocarbon, and preferably a compound selected from the group consisting of isooctane, isohexane, tert-butyl acetate, butyl acetate, methyl tert-butyl ether, tert-butyl alcohol, and combinations thereof, and preferably tert-butyl alcohol or isooctane.

13. A method for preparing a thermally expandable microsphere comprising a thermoplastic shell surrounding a hollow core, wherein the hollow core comprises a foaming agent, the thermoplastic shell comprises tannin, and the method of preparation is (i) A step of preparing a mixture containing the tannin and the foaming agent in a solvent, A method for producing a product, comprising: (ii) spray-drying the mixture obtained in step (i) to obtain thermally expandable microspheres.

14. The manufacturing method according to claim 13, wherein the solvent is selected from the group consisting of water, alcohol, ketone, ether, ester, and combinations thereof.

15. The manufacturing method according to claim 13 or 14, wherein the solvent comprises a mixture of at least two solvents selected from the group consisting of water, methanol, ethanol, acetone, and combinations thereof.

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