Post-heat treatment of cellulose-based expandable microspheres

Abstract

The present invention relates to a storage-stable, thermally expandable microsphere comprising a polymer shell surrounding a hollow core, wherein the hollow core contains a blowing agent, and the polymer shell comprises a carboxylate-functionalized cellulose, and the microsphere retains at least 80% of the original weight of the blowing agent encapsulated within the microsphere even after storage for 6 months under atmospheric conditions. The present invention relates to a method for preparing storage-stable, thermally expandable microspheres, wherein the storage-stable, thermally expandable microspheres comprise a polymer shell surrounding a hollow core, the hollow core containing a blowing agent, and the polymer shell containing carboxylate-functionalized cellulose, and the method comprises (i) preparing thermally expandable microspheres comprising a polymer shell surrounding a hollow core, the hollow core containing a blowing agent, and the polymer shell containing carboxylate-functionalized cellulose, and (ii) subjecting the thermally expandable microspheres obtained in step (i) to post-heat treatment by heating the thermally expandable microspheres to a temperature of at least 40°C.

Description

[Technical Field]

[0001] The present invention relates to thermally expandable microspheres made from a cellulosic biopolymer that retains at least 80% of the original weight of the foaming agent encapsulated in the microspheres after storage for six months under atmospheric conditions, as well as to a method for producing such expandable microspheres. [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 Patent Publication No. 00 / 37547, and International Patent 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, foamed materials for protective helmet liners, and automotive weatherstrips.

[0003] Thermally expandable polymer microspheres typically contain a thermoplastic polymer 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 polymer 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. Thus, expandable microspheres are described, and at least a portion of the monomers making up the thermoplastic shells here are bio-based and derived from renewable resources. For example, International Patent Publication 2019 / 043235 describes a polymer containing a lactone monomer, International Patent Publication 2019 / 101749 describes a copolymer containing a dialkyl itaconate monomer, and International Patent Publication 2020 / 099440 and International Patent Publication 2021 / 234010 disclose thermally expandable microspheres made from cellulosic biopolymers.

[0005] Expandable microspheres made from cellulosic biopolymers have been found to be particularly desirable in terms of biodegradability, the availability of monomers from sustainable sources, and the expandability and performance characteristics of the microspheres. However, some issues remain regarding the long-term storage of unexpanded cellulosic microspheres, as it has been found that the expandability of unexpanded microspheres deteriorates to some extent over time, likely due to the tendency for the encapsulated foaming agent to be lost from the unexpanded microspheres by diffusion through the polymer network of the microsphere shell. It is undesirable that some issues remain, as unexpanded microspheres are typically manufactured at the manufacturer's facility and then shipped to the customer in larger batches, which are then expanded incrementally by the customer in smaller quantities according to their needs. However, this means that a portion of the larger batch of unexpanded microspheres originally shipped may be stored at the customer's facility for unpredictable periods, often such as three months, six months, or even longer.

[0006] Therefore, there remains a need for expandable microspheres made from cellulosic biopolymers with improved storage stability. For example, it would be desirable if expandable microspheres made from cellulosic biopolymers could be stored for up to 3 months, preferably up to 6 months, or even longer, without significant impairment of expandability. It would be even more desirable if expandable microspheres made from cellulosic biopolymers could retain at least 80% of the original weight of the foaming agent encapsulated in the microspheres even after being stored for up to 3 months, preferably up to 6 months, or even longer. It would be even more desirable if the cellulosic biopolymer could retain at least 85%, e.g., at least 90%, at least 95%, or even at least 98% of the original weight of the foaming agent encapsulated in the microspheres when stored under atmospheric conditions for 6 months or more.

[0007] Accordingly, the present invention relates to finding such expandable polymer microspheres made from cellulosic biopolymers that retain at least 80% of the original weight of the foaming agent encapsulated in the microspheres after storage for 6 months under atmospheric conditions, and to a method for producing them. It has been found that the microspheres of the present invention can be efficiently produced by subjecting expandable microspheres made from cellulosic biopolymers to post-heat treatment after their formation. [Overview of the Initiative]

[0008] In a first aspect, the present invention relates to a storage-stable, thermally expandable microsphere comprising a polymer shell surrounding a hollow core, wherein the hollow core contains a blowing agent, and the polymer shell comprises a carboxylate-functionalized cellulose, and the microsphere retains at least 80% of the original weight of the blowing agent encapsulated within the microsphere even after storage for six months under atmospheric conditions.

[0009] The present invention further relates to a method for preparing storage-stable, thermally expandable microspheres comprising a polymer shell surrounding a hollow core, wherein the hollow core contains a blowing agent, and the polymer shell contains carboxylate-functionalized cellulose, comprising: (i) preparing thermally expandable microspheres comprising a polymer shell surrounding a hollow core, wherein the hollow core contains a blowing agent, and the polymer shell contains carboxylate-functionalized cellulose; and (ii) subjecting the thermally expandable microspheres obtained in step (i) to post-heat treatment by heating the thermally expandable microspheres to a temperature of at least 40°C.

[0010] The present invention further relates to storage-stable, thermally expandable microspheres obtained by the above method. [Brief explanation of the drawing]

[0011] [Figure 1] Figure 1 illustrates the differences in microspheres between a single-core (Figure 1A) and a multi-core (Figure 1B) architecture. [Figure 2] Figure 2 shows the effect of pyromelittic dianhydride (PMDA) or pyromelittic acid (PMA) on storage stability after post-heat treatment. [Figure 3] Figure 3 shows an exemplary thermogram for measuring the amount of foaming agent encapsulated in exemplary microspheres. [Modes for carrying out the invention]

[0012] The present invention discloses a storage-stable, thermally expandable microsphere comprising a polymer shell surrounding a hollow core, the hollow core containing a blowing agent, and the polymer shell comprising a carboxylate-functionalized cellulose, wherein the microsphere retains at least 80% of the original weight of the blowing agent encapsulated within the microsphere even after storage for 6 months under atmospheric conditions.

[0013] Expandable microspheres are based on a polymer shell containing carboxylate-functionalized cellulose. The functional group is a carboxylate group, or two or more carboxylate groups, which are typically C1-C1. 12 The carboxylates are selected from carboxylates. Therefore, the term "carboxylate-functionalized cellulose" means that the cellulose contains at least one carboxylate group. The carboxylate portion forms part of the link between the carboxylate functional group and the cellulose, i.e., the cellulose is linked to the carboxylate functional group via an ester bond.

[0014] The polymer shell can comprise one or more polymer components or can consist of one or more polymer components, where at least one component, two or more components, or all of the polymer components are selected from such carboxylate-functionalized cellulose. If the shell contains polymers other than those described in this disclosure (i.e., carboxylate-functionalized cellulose), their content is typically less than 50% by weight, for example, less than 30% by weight, or less than 10% by weight, for example, 9% by weight or less, 5% by weight or less, and even 2% by weight or less. These ratios are based on the total polymer content of the shell.

[0015] In multiple embodiments, the carboxylate functional groups on the carboxylate-functionalized cellulose can be represented by formula (1).

[0016]

Chemical formula

[0017] In formula (1), A is selected from -H, -OH, -OR b , -C(O)OH, and -C(O)OR b . In multiple embodiments, A is selected from -H and -C(O)OH.

[0018] R a may not be present, that is, it is possible to attach A directly to the C=O group. However, if present, R a can be selected from saturated aliphatic groups or unsaturated aliphatic groups having 1 to 11 carbon atoms, and can be linear, branched, or cyclic.

[0019] R a can also be selected from 5-membered and 6-membered aromatic rings.

[0020] R a is -OH, a halide, C 1~4 alkyl, and C 1~4It may optionally contain one or more substituents selected from alkoxys, where C 1~4 Alkyl and C 1~4 The alkoxy group may optionally be substituted with one or more groups selected from halides and -OH groups.

[0021] In multiple embodiments, R a It contains 1 to 7 carbon atoms, for example, 1 to 5 or 1 to 3 carbon atoms.

[0022] In each being, R b C 1~4 Alkyl (e.g., C 1~2 It has one or more substituents selected from alkyl groups and optionally selected from halides and -OH groups. In some embodiments, C 1~4 Alkyl or C 1~2 Alkyl groups are unsubstituted.

[0023] In multiple embodiments, R a This may be a saturated linear or branched aliphatic group or a cyclic aliphatic group. [ka] v is an integer in the range of 1 to 11, for example, in the range of 1 to 8 (1 to 6 or 1 to 4, etc.). w is an integer in the range of 3 to 11, for example, in the range of 4 to 6.

[0024] In each being, R c These are independently H, -OH, halide, and C 1~4 Alkyl, and C 1~4 Selected from alkoxy, C 1~4 Alkyl and C 1~4 The alkoxy group may be substituted with one or more groups selected from halides and -OH groups.

[0025] In other embodiments, R a It is an unsaturated linear or branched chain containing "y" double bonds. [ka] However, this is also acceptable. x is an integer in the range of 2 to 11, for example, 2 to 6 or 2 to 4. y represents the number of double bonds, which is typically 1 or 2.

[0026] In further embodiments, R a It contains "y" double bonds. [ka] This may also be the case, where y is typically 1 or 2.

[0027] In further embodiments, R a teeth [ka] This is also acceptable. z is an integer selected from 5 and 6.

[0028] In further embodiments, R a R may be a linear or branched aliphatic group containing a cyclic or aromatic ring. a It has 11 or fewer carbon atoms. [ka] This may also be the case, where E is as defined above. [ka] p and r are each independently integers between 0 and 8, and p+r is at least 1. q and s are each the number of double bonds in each acyclic aliphatic component. In some embodiments, q and s are each independently selected from 0, 1, and 2.

[0029] The halides are typically selected from F and Cl. However, in several embodiments, the functional group does not contain a halide, thereby using groups A and R a , R band R c No halides are present inside.

[0030] In some embodiments, at least one R c The base is H. In other embodiments, there are two or fewer R c The group is anything other than H, and in further embodiments, one or fewer R groups. c The group is something other than H. In a further embodiment, all R c The base is H.

[0031] R a , R b , and R c In the above definition, when there are two or more -OH substituents, typically there is one or fewer -OH substituents per carbon atom.

[0032] In a particular embodiment, R a R is a C1-C8 aliphatic (alkylene) group which may be substituted. In other embodiments, R a R is an optional C6 aromatic ring. In further embodiments, R a It is a non-substitutional type.

[0033] In several embodiments, the functional group on the cellulose substituent is selected from acetate, propionate, butyrate, pentanoate, hexanoate, heptanoate, octanoate, and phthalate. In further embodiments, it is selected from acetate, propionate, and butyrate, and preferably from acetate. Therefore, the carboxylate-functionalized cellulose is preferably acetate-functionalized cellulose, propionic acid-functionalized cellulose, or butyrate-functionalized cellulose, and more preferably acetate-functionalized cellulose.

[0034] The degree of substitution (DS) of the hydroxyl group of cellulose by one or more carboxylic acid bases may be in the range of 0.9 to 3.5, and in some embodiments, it is in the range of 1.5 to 3.5, for example, in the range of 2.0 to 3.3.

[0035] Optionally, other functional groups may be present in the functionalized cellulose. For example, -OH groups on cellulose molecules that have not yet been substituted with carboxylate functionalities can be substituted with alkoxy groups, or two or more alkoxy groups selected from, for example, C1-C6 alkoxy groups. In other embodiments, less preferably, -OH groups can be substituted with halide groups, for example, F or Cl. If such other functional groups are present, their molar amounts are lower than those of one or more carboxylic acid bases. In several embodiments, the degree of substitution of cellulose by other functional groups is 1 or less, for example, 0.5 or less or 0.2 or less. In further embodiments, the degree of substitution by groups other than carboxylic acid bases is 0.1 or less.

[0036] In several embodiments, the carboxylate-functionalized cellulose comprises an acetate group, a propionate group, or a butyrate group, preferably a plurality of acetate groups.

[0037] In several embodiments, cellulose may be functionalized with two or more different carboxylate bases. In some embodiments, the carboxylate-functionalized cellulose is functionalized with at least two of the carboxylate functionalities described above, for example, exactly two different carboxylate functionalities. For example, the carboxylate-functionalized cellulose may be configured to be functionalized with at least an acetate group and at least an additional group selected from propionate, butyrate, pentanoate, hexanoate, heptanoate, octanoate, and phthalate groups. In some embodiments, the carboxylate-functionalized cellulose is functionalized with at least an acetate group and at least one additional group selected from butyrate and propionate groups (i.e., an additional carboxylate base, R a (where A is an aliphatic and unsubstituted C2 or C3 group, and A is H) and are functionalized with. For example, carboxylate-functionalized cellulose may be functionalized with acetate and butyrate groups, or carboxylate-functionalized cellulose may be functionalized with acetate and propionate groups.

[0038] In several embodiments, the glass transition temperature (T) of the functionalized cellulose forming the shell of the microsphere or at least a portion of the shell of the microsphere is specified. g ) is at least 80°C. g This can be measured using differential scanning calorimetry (DSC), for example, using the method described by Nishio et al; Cellulose, 2006(13), 245-259, where a 5 mg sample is first heated from ambient temperature (25°C) to 240°C at a rate of 20°C / min under a nitrogen atmosphere, then immediately quenched to -50°C, and then secondly heated from -50°C to 240°C at a rate of 20°C / min under a nitrogen atmosphere. g The calculation is based on the second heating cycle.

[0039] In further embodiments, the T of carboxylate-functionalized cellulose g The temperature is at least 90°C, for example, at least 100°C, at least 110°C, or at least 120°C. In some embodiments, the temperature of the carboxylate-functionalized cellulose is T g This is 250°C or less, for example, 220°C or less, or 200°C or less, or 190°C or less, for example, about 180°C. In some embodiments, T g This range is 80 to 250°C, for example, 90 to 220°C, 100 to 200°C, or 110 to 190°C. In a further embodiment, T g This is within the range of 120-190°C, for example, 150-190°C or 170-190°C.

[0040] The melting point of functionalized cellulose is typically T g The melting point is greater than or equal to the value, and in embodiments, it is higher than 125°C. In further embodiments, the melting point is greater than 150°C. The melting point is typically 270°C or less, for example, 250°C or less.

[0041] T of carboxylate-functionalized cellulose gThe melting point and other properties can be altered or controlled by changing the functional groups on the functionalized cellulose or by changing the molecular weight.

[0042] Thermally expandable microspheres are hollow, with a shell containing carboxylate-functionalized cellulose, and a hollow center or core containing one or more foaming agents. The carboxylate-functionalized cellulose used to prepare the microspheres is typically 1.1–1.35 g / cm³. 3 It has a density of 1 g / cm³. In expandable microspheres, the density is typically 1 g / cm³. 3 It is less than 0.005 to 0.8 g / cm³, preferably 0.005 to 0.8 g / cm³. 3 , or 0.01~0.6 g / cm³ 3 This range is used. In preferred embodiments, the density of the expandable microspheres is 0.01 to 0.4 g / cm³. 3 It is within the range of higher densities, especially 1 g / cm³. 3 The densities mentioned above generally mean that the microsphere sample is not suitable for use.

[0043] In several embodiments, the number-average molecular weight (M) of the functionalized cellulose used to form microspheres is n The range is 1,000 to 700,000 Da, for example, 2,000 to 500,000 Da or 2,000 to 100,000 Da. In some embodiments, it is, for example, 10,000 to 100,000 Da, for example, 10,000 to 50,000 Da.

[0044] Thermally expandable microspheres have an expansion initiation temperature T Start The temperature may be 80°C or higher and less than 250°C. The expansion start temperature is T Start It is called the temperature at which maximum expansion is reached, and the temperature at which it is reached is T max It is called T Start and T Max This may be measured using standard measurement techniques that are generally known to those skilled in the art. For example, T Start and T MaxThis can be measured in 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 expansion of the thermally expandable microspheres begins, 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 measured from this inflation thermogram, for example, using STARe software from Mettler-Toledo.

[0045] In several embodiments, the thermally expandable microspheres are sized to be Start It may have the following characteristics. In a preferred embodiment, the thermally expandable microspheres are heated in the range of 120 to 185°C. Start It has.

[0046] To further enhance the properties of the polymer shell, the polymer shell of the thermally expandable microsphere may contain a hydrogen bonding donor selected from the group consisting of an anhydride-containing compound or alcohols, ureas, and carboxylic acids, preferably an anhydride-containing compound or a hydrogen bonding donor in the form of a carboxylic acid. For example, the hydrogen bonding donor may interact with groups on the carboxylate-functionalized cellulose via hydrogen bonding. By adding an anhydride-containing compound or a hydrogen bonding donor selected from the group consisting of alcohols, ureas, and carboxylic acids, preferably an anhydride-containing compound or a hydrogen bonding donor in the form of a carboxylic acid, the barrier properties of the polymer shell can be further improved, and the mechanical properties of the polymer shell, and consequently the expansion properties of the microsphere, can be enhanced. Therefore, the hydrogen bonding donor functions as a polymer shell enhancer.

[0047] The anhydride-containing compound or hydrogen bond donor may be a polymer having an average molecular weight of, for example, 10,000 g / mol, an average molecular weight of, for example, 1,000 g / mol to 5,000 g / mol, or an average molecular weight of, for example, 1,500 g / mol to 3,000 g / mol. Alternatively, the anhydride-containing compound or hydrogen bond donor may be a low molecular weight compound, and is typically or preferably a low molecular weight compound having a molecular weight of, for example, less than 2,000 g / mol, preferably less than 1,500 g / mol, more preferably less than 1,000 g / mol, and even more preferably less than 500 g / mol. For example, the anhydride-containing compound or hydrogen bond donor may have a molecular weight in the range of 20 to 500 g / mol, preferably 30 to 400 g / mol, and more preferably 40 to 300 g / mol.

[0048] An anhydride-containing compound is a compound containing at least one anhydride group, such as at least two anhydride groups or at least three anhydride groups. However, a compound containing exactly two anhydride groups (dianhydride) is preferred.

[0049] In some embodiments, the anhydride-containing compound is preferably selected from the group consisting of 1,2,4,5-benzenetetracarboxylic acid dianhydride, benzophenonetetracarboxylic acid dianhydride, ethylenetetraacetic acid dianhydride, butanetetracarboxylic acid dianhydride, ethylenediaminetetraacetic acid anhydride, 3,3′,4,4′-biphenyltetracarboxylic acid dianhydride, bicyclo[2.2.2]octo-7-ene-2,3,5,6-tetracarboxylic acid dianhydride, cyclobutane-1,2,3,4-tetracarboxylic acid dianhydride, 4,4′-oxydiphthalic acid anhydride, and tetrahydrofuran-2,3,4,5-tetracarboxylic acid dianhydride. More preferably, the anhydride-containing compound is selected from the group consisting of 1,2,4,5-benzenetetracarboxylic acid dianhydride, benzophenonetetracarboxylic acid dianhydride, and ethylenetetraacetic acid dianhydride, and even more preferably from the group consisting of 1,2,4,5-benzenetetracarboxylic acid dianhydride or benzophenonetetracarboxylic acid dianhydride. Particularly preferred is that the anhydride-containing compound is pyromellitic anhydride (1,2,4,5-benzenetetracarboxylic dianhydride). 1,2,4,5-benzenetetracarboxylic dianhydride is also known as pyromellitic anhydride, and will be referred to as such in this disclosure.

[0050] The hydrogen bond donors, selected from the group of alcohols, ureas, and carboxylic acids, are compounds having hydrogen atoms covalently bonded to a more electronegative atom, namely oxygen (if the hydrogen bond donor is an alcohol or a carboxylic acid) or nitrogen (if the hydrogen bond donor is urea). Here, these hydrogen atoms form intermolecular hydrogen bonds with the functional groups (hydrogen bond acceptors) of the carboxylate-functionalized cellulose, e.g., the carboxylate functional group, or, if present, one or more further, arbitrary hydroxyl and ether groups.

[0051] The hydrogen bond donor is selected from the group consisting of alcohols, urea, and carboxylic acids. Preferably, the hydrogen bond donor is selected from the group consisting of alcohols and carboxylic acids. In a more preferred embodiment, the hydrogen bond donor is a carboxylic acid. In another more preferred embodiment, the hydrogen bond donor is an alcohol.

[0052] A hydrogen bonding donor selected from the group consisting of alcohols, ureas, and carboxylic acids, preferably in the form of a carboxylic acid, may have a molecular weight in the range of 20 to 2000 g / mol, preferably in the range of 20 to 500 g / mol, more preferably in the range of 30 to 400 g / mol, and even more preferably in the range of 40 to 300 g / mol.

[0053] When the hydrogen bond donor is an alcohol, it can be selected from compounds containing at least one alcohol group, for example, 1, 2, 3, 4, 5, or 6 alcohol groups, and preferably has a molecular weight in the range of 20 to 2000 g / mol. When the hydrogen bond donor is an alcohol, it is preferably a diol, triol, tetraol, pentaol, or hexaol.

[0054] Suitable diols include, for example, 1,2-ethanediol, 1,2-propanediol, 1,3-propanediol, 1,2-butanediol, 1,3-butanediol, 2,3-butanediol, 1,4-butanediol, 1,2-pentanediol, 1,3-pentanediol, 1,4-pentanediol, 1,5-pentanediol, 1,2-hexanediol, 1,3-hexanediol, 1,4-hexanediol, 1,5-hexanediol, 1,6-hexanediol, 1,2-cyclohexanediol, 1,3-cyclohexanediol, and 1,4-cyclohexanediol, with 1,3-butanediol being preferred.

[0055] Suitable triols include, for example, glycerol, 1,2,3-butanetriol, 1,2,4-butanetriol, 1,1,1-tris(hydroxymethyl)propane, pentanetriol, and hexanetriol. Glycerol is a preferred triol.

[0056] Suitable tetraols include, for example, ascorbic acid (vitamin C), erythritol, slaytol, or pentaerythritol. Preferred tetraols are ascorbic acid (vitamin C) and pentaerythritol.

[0057] Suitable pentaols are xylitol, arabitol, ribitol, glucose, fructose, galactose, and mannose.

[0058] Suitable hexaols include, for example, sorbitol, mannitol, and cyclohexanehexol. A preferred hexaol is sorbitol.

[0059] When the hydrogen bond donor is an alcohol, it is preferable to select from 1,3-butanediol, glycerol, ascorbic acid (vitamin C), or sorbitol.

[0060] The hydrogen bond donor is particularly preferably a carboxylic acid, i.e., a compound containing at least one carboxylic acid group of a monocarboxylic acid, dicarboxylic acid, tricarboxylic acid, tetracarboxylic acid, or polycarboxylic acid (e.g., a polycarboxylic acid polymer). More specifically, the hydrogen bond donor is a carboxylic acid having a molecular weight in the range of 20 to 2000 g / mol. Preferably, the hydrogen bond donor is a carboxylic acid containing at least two carboxylic acid groups (-COOH), particularly a dicarboxylic acid, tricarboxylic acid, or tetracarboxylic acid.

[0061] Examples of monocarboxylic acids include formic acid, acetic acid, propionic acid, butyric acid, valeric acid, caproic acid, and lactic acid.

[0062] Examples of dicarboxylic acids include adipic acid, maleic acid, succinic acid, tartaric acid, and aldaric acid.

[0063] Examples of tricarboxylic acids include citric acid and isocitric acid.

[0064] Examples of tetracarboxylic acids include pyromellitic acid (1,2,4,5-benzenetetracarboxylic acid), ethylenediaminetetraacetic acid (EDTA), and butanetetracarboxylic acids, such as 1,2,3,4-butanetetracarboxylic acid (BTCA).

[0065] Preferred examples of suitable hydrogen bond donors for carboxylic acid forms are citric acid, maleic acid, succinic acid, pyromellitic acid (1,2,4,5-benzenetetracarboxylic acid), lactic acid, tartaric acid, ethylenediaminetetraacetic acid (EDTA), and butanetetracarboxylic acid, e.g., 1,2,3,4-butanetetracarboxylic acid (BTCA). More preferred examples of suitable hydrogen bond donors for carboxylic acid forms are pyromellitic acid (1,2,4,5-benzenetetracarboxylic acid), citric acid, tartaric acid, 1,2,3,4-butanetetracarboxylic acid (BTCA), and maleic acid.

[0066] In particular, when the hydrogen bond donor is in the form of a carboxylic acid according to a preferred embodiment, it is selected from the group consisting of pyromellitic acid (1,2,4,5-benzenetetracarboxylic acid), citric acid, tartaric acid, 1,2,3,4-butanetetracarboxylic acid (BTCA), and maleic acid.

[0067] More specifically, when the hydrogen bond donor is in the form of a carboxylic acid according to a preferred embodiment, it is selected from the group consisting of pyromellitic acid (1,2,4,5-benzenetetracarboxylic acid), citric acid, tartaric acid, and 1,2,3,4-butanetetracarboxylic acid (BTCA).

[0068] Preferably, when the hydrogen bond donor is in the form of a carboxylic acid according to a preferred embodiment, it is a tricarboxylic acid or tetracarboxylic acid such as citric acid, pyromellitic acid (1,2,4,5-benzenetetracarboxylic acid), or 1,2,3,4-butanetetracarboxylic acid (BTCA).

[0069] In certain embodiments, if the hydrogen bond donor is in the form of a carboxylic acid according to a preferred embodiment, it is a tetracarboxylic acid such as pyromellitic acid (1,2,4,5-benzenetetracarboxylic acid) or 1,2,3,4-butanetetracarboxylic acid (BTCA). Most preferably, the hydrogen bond donor is in the form of a carboxylic acid, which is pyromellitic acid (1,2,4,5-benzenetetracarboxylic acid).

[0070] The amount of anhydride-containing compound or hydrogen bond donor selected from the group consisting of alcohols, ureas, and carboxylic acids, which can be used to prepare the expandable microspheres of the present invention, is not particularly limited, preferably the amount of anhydride-containing compound or hydrogen bond donor in the form of a carboxylic acid.

[0071] However, the amount of anhydride-containing compound or hydrogen bond donor selected from the group of alcohols, urea, and carboxylic acids, preferably the amount of hydrogen bond donor in the form of anhydride-containing compound or carboxylic acid, may be 0.01 to 50% by weight based on the total weight of each anhydride-containing compound or hydrogen bond donor and the carboxylate-functionalized cellulose. In some embodiments, it may be in the range of 0.01 to 40% by weight, for example, in the range of 0.05 to 35% by weight, in the range of 0.1 to 30% by weight, or in the range of 0.5 to 25% by weight, for example, in the range of 0.5 to 20% by weight, in the range of 1.0 to 20% by weight, or in the range of 1.2 to 17% by weight, or in the range of 1.5% to 15% by weight, where the weight percentage is based on the total weight of each anhydride-containing compound or hydrogen bond donor and the carboxylate-functionalized cellulose.

[0072] In some embodiments, when the carboxylate-functionalized cellulose is acetate-functionalized cellulose, the amount of the anhydride-containing compound or selected from the group consisting of alcohols, urea, and carboxylic acids or the hydrogen bond donor, preferably in the form of the anhydride-containing compound or carboxylic acid or the amount of the hydrogen bond donor, may be 0.01 to 50% by weight. For example, it may be in the range of 0.01 to 40% by weight, 0.05 to 30% by weight, 0.1 to 20% by weight, or 0.5 to 15% by weight, for example, in the range of 0.5 to 10% by weight, 1.0 to 5.0% by weight, or further 1.2 to 5% by weight, or 1.5 to 5% by weight, where the weight percentage is based on the total weight of each of the anhydride-containing compound or the hydrogen bond donor and the acetate-functionalized cellulose.

[0073] In some embodiments, when the carboxylate-functionalized cellulose is butyric acid-functionalized cellulose or propionic acid-functionalized cellulose, for example preferably cellulose butyrate acetate (CAB) or cellulose propionate acetate (CAP), the amount of the anhydride-containing compound or the hydrogen bond donor selected from the group consisting of alcohols, urea, and carboxylic acids, preferably the amount of the anhydride-containing compound or the hydrogen bond donor in the form of a carboxylic acid, may be 0.01 to 50% by weight, for example, in the range of 0.01 to 40% by weight, 0.05 to 35% by weight, 0.1 to 30% by weight, or 0.5 to 25% by weight, for example, in the range of 1.0 to 20% by weight, 3.0 to 20% by weight, or further 5.0 to 18% by weight, or 10 to 15% by weight, where the weight percentage is based on the total weight of the anhydride-containing compound or the hydrogen bond donor and the butyric acid-functionalized cellulose or propionic acid-functionalized cellulose, respectively.

[0074] In further embodiments, the polymer shell may be configured to include particles for improving the mechanical properties and gas barrier properties of the polymer shell, and thus also act as a polymer shell enhancer. Examples of such particles include talc, montmorillonite, nanocrystalline cellulose, and various types of clay (such as bentonite).

[0075] Numerous factors can result in high density. For example, high density can be caused by a low microsphere yield, i.e., a low proportion of microspheres in the polymer material that prevents the overall density from being reduced to an acceptable level. Another problem is poor expansion properties, which can occur when there are too many microspheres and they contain insufficient blowing agent to allow for proper expansion. This can result from the polymer shell being too permeable to the blowing agent, or from the formation of so-called "multicore" microspheres, i.e., multiple blowing agent-containing cores within the shell instead of a single blowing agent-containing core (e.g., like a microspherical foam or sponge). In such multicore microspheres, the concentration of blowing agent is typically too low to adequately reduce the density. Another cause is polymer aggregation or cohesiveness, resulting in poor microsphere production and higher density material. Too high a proportion of aggregated material, or microspheres that do not expand sufficiently, can also lead to significant heterogeneity in the expansion properties of the resulting microsphere product. This is particularly undesirable for surface-sensitive applications such as coatings where a smooth finish is desired.

[0076] Exemplary cross-sections of single-core and multi-core microspheres are provided in Figures 1A and 1B, respectively, where polymer region 1 is represented by a mesh-like area and foaming agent-containing region 2 is represented by a blank area.

[0077] The thermally expandable microspheres comprise at least one blowing agent. These 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 several 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 do not react with the functionalized cellulose shell. The boiling point at high pressure can be calculated using the Clausius-Clapeyron equation.

[0078] Examples of foaming agents include dialkyl ethers, alkanes, and halocarbons (e.g., chlorocarbons, fluorocarbons, or chlorofluorocarbons). In some embodiments, the dialkyl ether comprises two alkyl groups selected from C2-C5 alkyl groups. In some embodiments, the alkane comprises 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 dialkyl ether, alkane, and haloalkane may be linear, branched, or cyclic. One or more blowing agents or a mixture thereof may be used.

[0079] In several embodiments, for environmental reasons, one or more blowing agents are selected from alkyl ethers and alkanes, and in further embodiments, one or more blowing agents are selected from alkanes. Haloalkanes are preferably avoided due to their potential ozone-depleting properties and their generally higher global warming potential.

[0080] Examples of suitable blowing agents that can be used include n-pentane, isopentane, neopentane, cyclopentane, cyclohexane, n-butane, isobutane, isohexane, neohexane, heptane, isoheptane, octane, isooctane, isodecane, and isododecane. In a preferred embodiment, the blowing agent is C4-C 12 It is selected from isoalkanes.

[0081] In these expandable microspheres, the one or more blowing agents are typically present in an amount of 5 to 50% by weight, based on the total weight of the functionalized cellulose, one or more blowing agents, and, if present, one or more additives, such as anhydrous compounds or hydrogen bond donors selected from the group consisting of alcohols, urea, and carboxylic acids, for example, in an amount ranging from 5 to 45% by weight, or 10 to 40% by weight.

[0082] Carboxylate-functionalized cellulose materials can be purchased commercially, or they can be prepared by known means, for example, by mixing cellulose with a suitable carboxylic acid (e.g., acetic acid, propionic acid, or butyric acid, and optionally additional carboxylic acids) in the presence of a strong acid such as sulfuric acid, or by a base-catalyzed reaction of cellulose with acyl chloride, as described, for example, in Nishio et al.; Cellulose, 2006(13), 245-259.

[0083] Suitable examples of carboxylate-functionalized celluloses include cellulose acetate (CA) (i.e., carboxylate-functionalized cellulose that does not contain further carboxylate functional groups other than acetic acid), cellulose propionate acetate (CAP), and cellulose butyrate acetate (CAB), in particular, with average molecular weights (M) in the range of 2,000 to 100,000 Da, e.g., 2,000 to 80,000 Da, 10,000 to 50,000 Da, or 20,000 to 50,000 Da. n These are cellulose acetate (CA), cellulose propionate acetate (CAP), and cellulose butyrate acetate (CAB), which have the properties of ).

[0084] Preferred acetate-functionalized cellulose has a number-average molecular weight (M) in the range of 10,000 to 100,000 Da, for example, in the range of 10,000 to 80,000 Da, preferably in the range of 10,000 to 50,000 Da, and more preferably in the range of 20,000 to 50,000 Da. n The present invention relates to cellulose acetate (CA) having (i.e., acetate-functionalized cellulose that does not contain further carboxylate functional groups different from acetic acid) and butyric acid cellulose acetate. More preferably, the number average molecular weight (M) is in the range of 10,000 to 100,000 Da, for example, in the range of 10,000 to 80,000 Da, preferably in the range of 10,000 to 50,000 Da, and more preferably in the range of 20,000 to 50,000 Da. n It is cellulose (CA) having ).

[0085] For example, if the polymer shell contains cellulose propionate acetate (CAP) or cellulose acetate butyrate (CAB), the amount of hydrogen bond donor in the form of carboxylic acid used may be 0.01 to 50% by weight, based on the total weight of the hydrogen bond donor and the carboxylate-functionalized cellulose. In some embodiments, the range can be 0.01 to 40% by weight, for example, 0.05 to 35% by weight, 0.1 to 30% by weight, or 0.5 to 25% by weight, for example, 1.0 to 20% by weight, 3.0 to 20% by weight, or 5.0 to 18% by weight, or 10% to 15% by weight, where the weight percentage is based on the total weight of the hydrogen bond donor and the carboxylate-functionalized cellulose.

[0086] For example, if the polymer shell contains cellulose acetate (CA) (i.e., acetate-functionalized cellulose that does not contain further carboxylate functional groups other than acetic acid), the amount of hydrogen bond donor in the form of carboxylic acid used may be 0.01 to 50% by weight, based on the total weight of the hydrogen bond donor and the carboxylate-functionalized cellulose. In some embodiments, this can be in the range of 0.01 to 40% by weight, for example, 0.05 to 30% by weight, 0.1 to 20% by weight, or 0.5 to 15% by weight, for example, 0.5 to 10% by weight, 1.0 to 5.0% by weight, or 1.2 to 5% by weight, or 1.5% to 5% by weight, where the weight percentage is based on the total weight of the hydrogen bond donor and the carboxylate-functionalized cellulose.

[0087] The storage-stable, thermally expandable microspheres of the present invention retain at least 80% of the original weight of the foaming agent encapsulated within the microspheres after 6 months of storage under atmospheric conditions.

[0088] Preferably, the storage-stable, thermally expandable microspheres of the present invention retain at least 85%, preferably at least 90%, more preferably at least 95%, and most preferably at least 98% of the original weight of the foaming agent encapsulated in the microspheres after 6 months of storage under atmospheric conditions.

[0089] The weight of the blowing agent in microspheres can be determined by measuring the volatility content of the microspheres (i.e., the weight of the volatile substance encapsulated within the microspheres). Therefore, as used in this disclosure in the context of microspheres, the terms “weight of the blowing agent,” “weight percentage of the blowing agent,” and “volatility content” are considered equivalent and interchangeable. The measurement of the volatility content of microspheres is well known to those skilled in the art, and in principle, any suitable method for measuring the volatility content of microspheres can be used.

[0090] For example, the volatility content can be measured using a Mettler Toledo TGA / DSC1 TGA instrument. In an exemplary and preferred experimental setup, the volatility content of microspheres according to the present invention is measured as follows: The sample to be analyzed is prepared from 1.7 mg (+ / - 0.2 mg) of thermally expandable microspheres contained in pulverizable aluminum oxide in a volume of 600 μl. The temperature of the sample is raised from 30°C to 650°C in a nitrogen atmosphere at a heating rate of 20°C / min. The sample is held at 650°C in a nitrogen atmosphere for a further 2 minutes, then the nitrogen is replaced with air, and the sample is held at 650°C for a further 15 minutes. The weight of the sample is continuously monitored during the heating procedure. An exemplary thermogram thus obtained is shown in Figure 3, with sample weight (mg) on ​​the y-axis and heating temperature (°C) (correlated with heating time (t) to 650°C) on the x-axis. The volatile content (VC, %) of the microspheres can be obtained from such a thermogram by subtracting the weight of the sample measured at the second inflection point (IP2) of the thermogram curve (i.e., the point at which the weight of the sample reaches a first essentially stable plateau after the evaporation of the blowing agent (typically 170°C to 300°C, depending on the actual blowing agent and polymer used)) from the starting weight of the sample (SW; weight at 30°C and t=0), dividing this difference by the starting weight of the sample, and multiplying the result by 100 (see also equation (2) below).

[0091]

number

[0092] Percentage of foaming agent retained within microspheres after storage (VC 貯蔵後保持 The unit %) represents the volatile content (VC) after storage. 貯蔵後 This can be calculated by dividing the volatile content (VC0) by the volatile content before storage and multiplying by 100 (see also equation (3) below).

[0093]

number

[0094] As used in this disclosure, the term “atmospheric conditions” means standard room temperature in the range of 20 to 25°C, such as 22.5 ± 2.5°C, or 22 ± 2°C, or 22 ± 1°C, and normal storage conditions at atmospheric pressure (i.e., 10¹³ ± 50 mbar, e.g., 10¹³ ± 20 mbar, or 10¹³ ± 10 mbar).

[0095] The expandable microspheres of the present invention can be prepared according to the following method, i.e., the expandable microspheres of the present invention can be obtained according to the following method. Thus, in a further embodiment, the present invention relates to a method for preparing storage-stable, thermally expandable microspheres comprising a polymer shell surrounding a hollow core, wherein the hollow core contains a foaming agent, and the polymer shell comprises a carboxylate-functionalized cellulose, i.e., the expandable microspheres described above, and the method for production comprises the following steps.

[0096] (i) To prepare a thermally expandable microsphere comprising a polymer shell surrounding a hollow core, wherein the hollow core contains a foaming agent, and the polymer shell contains carboxylate-functionalized cellulose, (ii) The process includes subjecting the thermally expandable microspheres obtained in step (i) to a post-heat treatment by heating the thermally expandable microspheres to a temperature of at least 40°C.

[0097] A further aspect of the present invention provides an expandable microsphere, i.e., a microsphere that retains at least 80% of the original weight of the foaming agent encapsulated within it after storage for six months under atmospheric conditions. Therefore, all configurations relating to the polymer shell of the expandable microsphere, any further components such as the anhydride-containing compound or the hydrogen bond donor selected from the group of alcohols, ureas, and carboxylic acids, the foaming agent, and all configurations relating to the components used to prepare the expandable microsphere, including any further optional components, may be the same as those described above for the expandable microsphere according to the first aspect of the present invention.

[0098] In a first step (i) of a method according to a further aspect of the present invention, a thermally expandable microsphere is prepared, comprising a polymer shell surrounding a hollow core, the hollow core containing a foaming agent, and the polymer shell comprising carboxylate-functionalized cellulose.

[0099] In principle, any known method can be used to prepare such expandable microspheres. Suitable methods include, for example, solvent extraction, or alternatively, spray drying, preferably spray drying.

[0100] A solvent extraction method can be used to prepare expandable microspheres by dissolving a component, which may optionally contain an anhydride-containing compound or a hydrogen bond donor selected from the group consisting of alcohols, urea, and carboxylic acids, in a suitable organic solvent or mixture of solvents, adding one or more foaming agents, and mixing with an aqueous phase which may contain one or more emulsifiers. After a certain period of time (e.g., between 1 minute and 20 hours, e.g., within the range of 5 minutes and 10 hours), unexpanded microspheres are optionally formed under active mixing (e.g., by stirring) and can be separated as a solid using conventional techniques such as decanting or filtration.

[0101] This mixing can be carried out at ambient temperature, but temperatures in the range of 5 to 75°C can be used.

[0102] In some embodiments, the aqueous phase may be pre-saturated with one or more organic solvents to which the carboxylate-functionalized cellulose is soluble before being mixed with the organic phase containing the carboxylate-functionalized cellulose. In further embodiments, the mixture may be allowed to stand or be stirred for a period of time, for example, 1 to 100 hours or 2 to 50 hours, to allow at least a portion of the solvent / aqueous mixture to evaporate. This can be done at a temperature in the range of 10 to 95°C, for example, 20 to 90°C.

[0103] The emulsifier helps stabilize droplets of the carboxylate-functionalized cellulose-containing organic phase in the aqueous phase, and in several embodiments, assists in forming an emulsion of the organic phase (i.e., an oil-in-water emulsion) in the aqueous phase.

[0104] Stabilization of droplets or emulsion droplets is preferable for several reasons. If they are not stabilized, droplets containing carboxylic acid-modified cellulose may coalesce with the foaming agent. Coalitioning can have adverse effects, such as uneven droplet size, insufficient microsphere yield, and can increase microsphere aggregation.

[0105] The emulsifier is typically present in the aqueous phase in an amount of 0 to 20% by weight, for example, 0.01 to 20% by weight, 0.05 to 10% by weight, or 0.1 to 5% by weight. In further embodiments, the emulsifier is present in the aqueous phase in an amount of 0.1 to 1% by weight.

[0106] The choice of emulsifier is not particularly limited and can be selected from inorganic or organic emulsifiers.

[0107] Examples of inorganic materials that can act as emulsifiers include silica, particularly colloidal silica that can be used in its unmodified "naked" form or optionally surface modified, for example, with organosilane-modified silica or colloidal silica, to adjust its hydrophobic / hydrophilic properties.

[0108] In a plurality of embodiments, the "organic" group in the organosilane may be selected from C 1~20 alkyl, C 1~20 alkenyl, C 5~6 aryl, and C having one or more (e.g., 1 to 3) heteroatoms selected from O, S, and N 5-6 heteroaryl. Each of these groups may optionally be substituted with one or more groups selected from halide, hydroxy, epoxy, thiol, amino, C 1~20 alkylamino, di-C 1~20 alkylamino, hydroxyamino, hydroxy-C 1~20 alkylamino, (hydroxy-C 1~20 alkyl)(C 1~20 alkyl)amino, di(hydroxy-C 1~20 alkyl)amino C 1-20 alkoxy, C 1~20 amide, C 1~20 ureido, C 1~20 mercapto, C 3~20 epoxyalkoxy, C 1~20 alkyl acrylate, ethylene glycol having 1 to 20 ethylene glycol groups or its oligomer, and propylene glycol having 1 to 20 propylene glycol groups or its oligomer. Any aliphatic group may be linear, branched, or cyclic.

[0109] Organosilane-modified silica or colloidal silica can be produced by reacting silica (or colloidal silica) typically with an organosilane compound having the formula, R n SiX 4-n where R is one of the organic groups specified above and X is halide, hydroxy, or C1~6 It is an alkoxy, where n is an integer in the range of 1 to 3, typically 1 or 2.

[0110] Suitable silane compounds include tris-(trimethoxy)silane, octyltriethoxysilane, methyltriethoxysilane, methyltrimethoxysilane, gamma-mercaptopropyltrimethoxysilane, beta-(3,4-epoxycyclohexyl)-ethyltrimethoxysilane, epoxy groups (epoxysilanes), glycidoxy groups and / or glycidoxypropyl groups, such as gamma-glycidoxypropyltrimethoxysilane, gamma-glycidoxypropylmethyldiethoxysilane, (3-glycidoxypropyl)trimethoxysilane, (3-glycidoxypropyl)hexyltrimethoxysilane, beta-(3,4-epoxycyclohexyl)-ethyltriethoxysilane, and vinyl groups containing glycidoxypropyl groups, such as vinyltriethoxysilane, vinyltrimethoxysilane, vinyltris-(2-methoxyethoxy)silane, vinylmethyldiethoxysilane, etc. Examples include silanes containing vinyl groups, such as toxysilane and vinyltriisopropoxysilane; gamma-methacrylateoxypropyltrimethoxysilane, gamma-methacrylateoxypropyltriisopropoxysilane, gamma-methacrylateoxypropyltriethoxysilane, octyltrimethyloxysilane, ethyltrimethoxysilane, propyltriethoxysilane, phenyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, cyclohexyltrimethoxysilane, cyclohexyltriethoxysilane, dimethyldiethoxysilane, 3-chloropropyltriethoxysilane, 3-methacrylateoxypropyltrimethoxysilane, i-butyltriethoxysilane, trimethylethoxysilane, phenyldimethylethoxysilane, hexamethyldisilozane, trimethylsilyl chloride, vinyltriethoxysilane, hexamethyldisilizane, and mixtures thereof. U.S. Patent No. 4,927,749 discloses more suitable silanes that may be used.

[0111] Examples of silica that can be used include silica sold under the trademark names Levasil®, Bindzil®, and Ludox®, which are related to colloidal silica. As for the solid form of silica, fumed silica is an option, and precipitated silica may also be used, which can be dispersed in water to form a fine suspension. Sources of fumed silica include silica sold under the trademark names Cab-o-Sil® and Aerosil®.

[0112] Other inorganic emulsifiers include colloidal clays (e.g., chalk and bentonite), as well as salts, oxides, and hydroxides of Al, Ca, Mg, Ba, Fe, Zn, Ti, Ni, and Mn (e.g., calcium phosphate, calcium carbonate, magnesium hydroxide, barium sulfate, calcium oxalate, titanium dioxide, and hydroxides of aluminum, iron, zinc, nickel, or manganese).

[0113] Using solid inorganic emulsifiers, solid inorganic particles can create a so-called "Pickering" emulsion at the interface between the aqueous and organic phases.

[0114] Examples of organic emulsifiers include anionic, cationic, amphoteric, amphoteric, and nonionic surfactants, which are generally known and commercially available.

[0115] Examples include sorbitan esters (such as those sold under the trade name Span™), for example, sorbitan monolaurate (e.g., Span™ 20) and sorbitan monooleate (e.g., Span™ 80). Further examples include polyethoxylated sorbitan esters (such as those sold under the trade name Tween™), for example, PEG-20 sorbitan monolaurate (Tween™ 20), PEG-20 sorbitan monooleate (Tween™ 80), and polyoxyethylene (PEG-20) sorbitan trioleate (Tween™ 85). Other examples include C6-C 22 alkyl sulfates; of the formula C n H 2n+1 (OC m H 2m ) p -OSO3 - having an anion of (where n is from 6 to 22, m is from 2 to 3, p is from 2 to 4, for example sodium lauryl ether sulfate and C 12-14 sodium pareth-3 sulfate); C 6-22 alkyl glucosides, for example lauryl glucoside; of the formula C n H 2n+1 C(O)N(X)CH2(C4H4[OH]4)CH2OH glucamides (where n is from 6 to 22, X is H or C 1-4 alkyl, for example, caprylyl methyl glucamide, lauryl methyl glucamide, and dodecyl glucamide); C 2-16 amino acids substituted with carboxylate groups, and their salts, for example, sodium cocoyl glutamate or disodium and sodium lauroyl sarcosinate; C 6-22 fatty acids and their salts such as sodium oleate and potassium oleate; polyethylene glycol-substituted phenols having 5 to 25 glycol units, for example, polyethylene glycol p-(1,1,3,3-tetramethylbutyl)-phenyl ether (available as Triton™ X-100); C 6~22 alkylamine oxides, for example lauramine oxide, and C6~22 Examples include alkyl alcohols, such as cetyl alcohol and stearyl alcohol. Further examples include polymer emulsifiers, such as (meth)acrylate and (meth)acrylic acid polymers (e.g., polymethyl methacrylic acid), and at least one C 3-10 Alkenyl group and at least one C 1-4 Polymers based on organic ammonium salts having alkyl groups, for example, Polydiallyldimethylammonium chloride (polyDADMAC) is one example.

[0116] Consumer cleaning liquids are sources of emulsifiers, such as sodium dodecyl sulfate, C 12-14 It may be used as a product sold under the trade names Yes® and Fairy®, containing sodium pareth-3-sulfate and lauramine oxide.

[0117] Other examples of emulsifiers include polyvinyl alcohol, which is optionally partially or completely saponified. In several embodiments, the polyvinyl alcohol has a degree of hydrolysis in the range of 70–100 mol%, e.g., 80–100 mol%, or 80–98 mol%. The Hopler viscosity in a 4% aqueous solution may be in the range of 1–70 mPas, or in other embodiments, 3–40 mPas (measured at 20°C according to DIN 53015).

[0118] One or more emulsifiers may be used. A mixture of organic and inorganic emulsifiers may also be used.

[0119] The organic solvent can be selected from organic solvents having one or more functional groups selected from, for example, esters, amides, aldehydes, ketones, alcohols (including glycols), and ethers having 3 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 halocarboxylic acids having 1 to 6 carbon atoms, where the halogen is selected from fluorine, chlorine, bromine, and iodine. In some embodiments, all alcohols used are glycols.

[0120] 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 (examples) Examples of solvents include propylene 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 monoethyl ether acetate, ethylene glycol monobutyl ether acetate, ethylene glycol diacetate), 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, methyl chloride, chloroform, carbon tetrachloride, trichloroacetic acid, methyl bromide, methyl iodide, trichloroethylene, and tetrachloroethylene. The organic solvent may be a mixture of two or more solvents.The organic solvent may contain water, but typically the water content of the organic solvent(s) before mixing with the aqueous phase is less than 5% by weight, i.e., 0–5% by weight of water, for example, 0–1% by weight of water.

[0121] In some embodiments, the solvent is selected from one or more of ethyl acetate, methyl acetate, ethyl formate, and acetone.

[0122] Typically, the carboxylate-functionalized cellulose content in the organic phase is in the range of 0.1 to 50% by weight. In some embodiments, the carboxylate-functionalized cellulose content in the organic phase may be in the range of 0.5 to 25% by weight, for example, 1 to 15% by weight.

[0123] The amount of blowing agent(s) in the organic phase is typically in the range of 0.5 to 20% by weight, for example, in the range of 1 to 15% by weight. In some embodiments, the weight of the blowing agent in the organic phase is less than or equal to the weight of the carboxylate-functionalized cellulose, and for example, the weight ratio of the blowing agent to the carboxylate-functionalized cellulose may be 1.0 or less, for example, 0.8 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 carboxylate-functionalized cellulose in the organic phase is in the range of 0.1 to 1.0, for example, in the range of 0.2 to 0.8.

[0124] The weight percentage of the organic phase in the total water / organic phase emulsion may be in the range of 0.1 to 45% by weight, based on the total weight of the water / organic phase emulsion, for example, 1 to 30% by weight, or 3 to 25% by weight, or 4 to 15% by weight.

[0125] When adding substances that react with the carboxylate-functionalized cellulose and / or particles to further improve the polymer shell properties, these substances and / or particles are typically added to the organic phase (i.e., the phase containing the carboxylate-functionalized cellulose, solvent, and blowing agent).

[0126] As an alternative and preferred configuration, the preparation of the thermally expandable microspheres may be carried out by a spray drying process comprising: mixing the carboxylate-functionalized cellulose, an organic solvent, the blowing agent, and optionally an anhydride-containing compound or a hydrogen bond donor selected from the group consisting of alcohol, urea, and carboxylic acid; and then spraying the mixture thus obtained into a drying apparatus to produce thermally expandable microspheres having a polymer shell surrounding a hollow core, wherein the polymer shell contains the acetate-functionalized cellulose and the hollow core contains the blowing agent.

[0127] 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.

[0128] A suitable spray dryer for carrying out the spray drying process is the Buechi B-290 mini spray dryer, commercially available from Buechi / Switzerland.

[0129] The order in which carboxylate-functionalized cellulose, organic solvents, foaming agents, and optionally, anhydrous compounds or hydrogen bond donors selected from the group consisting of alcohols, urea, and carboxylic acids are added for mixing is not limited, and any order can be chosen.

[0130] However, in a preferred embodiment, in a method for producing expandable microspheres, carboxylate-functionalized cellulose is first mixed with an organic solvent, and then, in a further step, a blowing agent and optionally, a hydrogen bond donor selected from the group consisting of an anhydride-containing compound or alcohol, urea, and carboxylic acid are added to this mixture.

[0131] The mixing of carboxylate-functionalized cellulose may be carried out at ambient temperature, but temperatures in the range of 5 to 75°C can be used. The mixing is usually carried out until the carboxylate-functionalized cellulose is completely dissolved in the organic solvent.

[0132] In several embodiments, a mixture of carboxylate-functionalized cellulose and an organic solvent can be left standing or stirred for a period of time, for example, 1 to 100 hours or 2 to 50 hours, to evaporate at least a portion of the solvent. This can be done at a temperature in the range of 10 to 95°C, for example, 20 to 90°C.

[0133] In a further step, a blowing agent and, optionally, a hydrogen bond donor selected from the group consisting of anhydrous compounds or alcohols, urea, and carboxylic acids, are added to the mixture of carboxylate-functionalized cellulose and organic solvent. When adding the hydrogen bond donor selected from the group consisting of anhydrous compounds or alcohols, urea, and carboxylic acids to the mixture of carboxylate-functionalized cellulose and organic solvent, the order in which the blowing agent and the hydrogen bond donor selected from the group consisting of anhydrous compounds or alcohols, urea, and carboxylic acids are added is not important; that is, the blowing agent may be added first, followed by the hydrogen bond donor selected from the group consisting of anhydrous compounds or alcohols, urea, and carboxylic acids, or the hydrogen bond donor selected from the group consisting of anhydrous compounds or alcohols, urea, and carboxylic acids may be added first, followed by the blowing agent. Furthermore, this mixing step can be carried out at ambient temperature, but temperatures in the range of 5 to 75°C can be used. Furthermore, this mixing process is typically carried out until the foaming agent and, optionally, a hydrogen bond donor selected from the group consisting of anhydrous compounds, alcohols, urea, and carboxylic acids, are completely dissolved in the organic solvent.

[0134] After adding a foaming agent and optionally a hydrogen bond donor selected from the group consisting of anhydrous compounds or alcohols, urea, and carboxylic acids to a mixture of carboxylate-functionalized cellulose and an organic solvent, the resulting mixture may be further stirred for, for example, 1 minute to 100 hours, 10 minutes to 80 hours, or 1 hour 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.

[0135] A mixture comprising carboxylate-functionalized cellulose, an organic solvent, a blowing agent, and optionally an anhydride-containing compound or a hydrogen bond donor selected from the group consisting of alcohol, urea, and carboxylic acid, 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.

[0136] 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, or noble gases (such as argon). Preferably, in the method for producing expandable microspheres as described herein, a spray gas is used, and more preferably, this spray gas is nitrogen.

[0137] 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 spray gas may also be selected from nitrogen, carbon dioxide, (pressurized) air, and noble gases (such as argon). Nitrogen is preferred as the drying gas.

[0138] 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.

[0139] It has been found that by the method described above, an expandable microsphere comprising a polymer shell surrounding a hollow core can be obtained, wherein the hollow core contains a foaming agent and the polymer shell contains carboxylate-functionalized cellulose. It has been further found that this method is particularly suitable for obtaining such expandable microspheres in which the polymer shell further comprises an anhydride-containing compound or a hydrogen bond donor selected from the group consisting of alcohols, urea, and carboxylic acids.

[0140] The organic solvent can be selected from the same solvents described above for solvent extraction methods for preparing expandable microspheres.

[0141] Typically, the carboxylate-functionalized cellulose content in the spray-drying mixture is in the range of 0.1 to 50% by weight. In some embodiments, it may be in the range of 1 to 40% by weight, for example, 5 to 35% by weight, or even 7.5 to 30% by weight. The weight percentage is based on the total weight of the spray-drying mixture.

[0142] The amount of blowing agent(s) in the spray-drying mixture is typically in the range of 0.5 to 50% by weight. In some embodiments, it may be in the range of 0.5 to 40% by weight, for example, 1 to 30% by weight, or even 3 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 carboxylate-functionalized cellulose. For example, the weight ratio of the blowing agent to the carboxylate-functionalized cellulose 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 carboxylate-functionalized cellulose in the organic 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.

[0143] The amount of anhydrous compound or hydrogen bond donor selected from the group consisting of alcohols, urea, and carboxylic acids in the mixture for spray drying is typically in the range of 0 to 15% by weight. In some embodiments, the amount is in the range of 0.01 to 15% by weight, and may be, for example, in the range of 0.05 to 10% by weight, 0.1 to 5% by weight, or 0.2 to 5% by weight. The weight percentage is based on the total weight of the mixture for spray drying.

[0144] The amount of organic solvent totals 100% by weight. Preferably, the amount of organic 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.

[0145] Unexpanded microspheres obtained by solvent extraction or spray drying typically have a volume-average particle size (diameter) (D(0.5) value) 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, or even in the range of 30 to 80 μm.

[0146] In a second step (ii) of a method according to a further aspect of the present invention, the thermally expandable microspheres obtained in step (i) are subjected to a post-heat treatment by heating the thermally expandable microspheres to a temperature of at least 40°C.

[0147] Surprisingly, expandable microspheres post-heat-treated according to the second step (ii) of the method according to a further aspect of the present invention were found to have significantly improved storage stability. That is, such post-heat-treated expandable microspheres retain at least 80% of the original weight of the foaming agent encapsulated in the microspheres after 6 months of storage under atmospheric conditions. For example, at least 85%, at least 90%, at least 95%, and even more than 98%.

[0148] Heating can be carried out by any known method for heating a substance, such as placing expandable microspheres in a heat chamber or setting an oven to a suitable temperature. Heating can also be carried out by tumbling the material in a stirred container, where heating is achieved either by introducing heated gas into the container or by heating the walls of a jacketed container. Tumbling can be achieved by any means, such as setting up a ribbon blender, or by stirring with a rotating paddle.

[0149] There is no particular upper limit to the temperature used for post-heat treatment. However, these temperatures must be lower than the expansion temperature of each expandable microsphere, otherwise they would already begin to expand. Therefore, in some embodiments, post-heat treatment may be carried out at temperatures of 50°C to 150°C, preferably 60°C to 140°C, more preferably 70°C to 130°C, and most preferably 75°C to 125°C.

[0150] There is no particular required length of time for post-heat treatment. However, in some embodiments, post-heat treatment is carried out for at least 5 minutes, preferably at least 10 minutes, more preferably at least 30 minutes, and even more preferably at least 50 minutes. In some embodiments, post-heat treatment is carried out for 10 hours or less, such as 5 hours or less, 2 hours or less, or 1 hour or less. However, the temperature used for post-heat treatment and the length of time for post-heat treatment may be dependent on each other, and those skilled in the art can adjust the appropriate length of post-heat treatment for a particular treatment temperature, and vice versa. For example, a preferred method according to a further embodiment of the present invention includes heating the expandable microsphere obtained in step (i) at 75°C to 125°C, for example 100°C, for 5 minutes to 2 hours, for example 10 minutes to 1 hour, for example 1 hour.

[0151] In a preferred embodiment, the post-heat treatment is carried out at a temperature of 70°C to 130°C, such as 75°C to 125°C or 80°C to 120°C, for at least 20 minutes, such as at least 30 minutes or at least 50 minutes.

[0152] In a particularly preferred embodiment, the temperature during post-heat treatment is maintained at a predetermined temperature for at least 1 minute, such as at least 2 minutes, at least 3 minutes, at least 5 minutes, at least 10 minutes, at least 20 minutes, at least 30 minutes, or at least 50 minutes. As used in this disclosure, the term “maintain a predetermined temperature” means that the temperature does not change significantly over a particular period of time, i.e., the temperature is kept constant. A temperature is considered constant if the predetermined temperature (such as the temperature described above for post-heat treatment) does not change by more than ±5°C over the indicated period, such as ±3°C, ±2°C, or ±1°C. In other words, as used in this disclosure, maintaining a predetermined temperature means that there is no continuous increase in temperature, i.e., no continuous rise in temperature, but the temperature is kept at the predetermined temperature for at least a certain period of time.

[0153] The post-heat treatment in step (ii) may be supported by using ventilation and / or tumbling during the treatment. This ensures uniform post-heat treatment of all thermally expandable microspheres in a batch of microspheres. If implemented, ventilation is preferably carried out using air. In some embodiments, ventilation is not carried out under an inert gas atmosphere such as a nitrogen atmosphere.

[0154] In some embodiments, the post-heat treatment of step (ii) is carried out at standard atmospheric pressure, such as 101.3 kPa ± 5 kPa (10¹³ ± 50 mbar). In other words, in some embodiments, no additional external pressure other than standard atmospheric pressure is applied during the post-heat treatment of step (ii).

[0155] Post-heat treatment of expandable microspheres has the effect of improving the storage stability of the expandable microspheres. Therefore, in some embodiments, after the first step (i) and the second step (ii), in a further step (iv), the thermally expandable microspheres obtained in step (ii) are stored for at least 5 minutes, e.g., at least 10 minutes, at least 30 minutes, at least 1 hour, at least 12 hours, at least 1 day, preferably at least 10 days, e.g., at least 20 days, at least 1 month, at least 2 months, at least 3 months, or further at least 6 months. The storage conditions are not limited in principle and are, for example, any temperature at which the expandable microspheres have not yet expanded, but are usually below the temperature used to carry out the post-heat treatment in step (ii), in particular ambient temperature such as 25°C ± 5°C or 22.5°C ± 2.5°C, and / or standard atmospheric pressure such as 101.3 kPa ± 5 kPa (10¹³ ± 50 mbar).

[0156] Therefore, in a preferred embodiment, the manufacturing method of the present invention is (iv) which, if carried out in step (ii), includes storing the thermally expandable microspheres obtained in step (iii) (described below) for at least 10 minutes, preferably at least 30 minutes, more preferably at least 1 hour, most preferably at least 1 day, for example at least 10 days, at least 20 days, or at least 1 month.

[0157] In further embodiments, the thermally expandable microspheres obtained in step (ii) are cooled in step (iii). Cooling in step (iii) means that the temperature of the thermally expandable microspheres is reduced to a temperature below the temperature used in step (ii) to carry out post-heat treatment. In step (iii), the still thermally expandable microspheres, i.e., the microspheres that have not yet expanded, are cooled. If step (iv) is applicable, step (iii) may be carried out before this step (iv). In step (iii), active cooling may be used by using any type of cooling device, such as a refrigerator. However, it is preferable that the cooling is carried out only by allowing the post-heat-treated thermally expandable microspheres to cool to ambient temperature, i.e., without using any specific cooling device. Therefore, in a preferred embodiment, in step (iii), the thermally expandable microspheres obtained from step (ii) are cooled to below 40°C, for example below 30°C, preferably to ambient temperature, for example 25°C ± 5°C, or even further to 22.5°C ± 2.5°C.

[0158] Therefore, in a more preferred embodiment, the manufacturing method of the present invention further, (iii) A step of cooling the thermally expandable microspheres obtained in step (ii) to a temperature below the temperature used in step (ii), preferably to ambient temperature.

[0159] In certain preferred embodiments, the manufacturing method of the present invention includes both of the further steps (iii) and (iv).

[0160] Furthermore, the present invention relates to expandable microspheres with storage stability obtained by a method including the post-heat treatment described above. [Examples]

[0161] The following examples are intended to illustrate the present invention.

[0162] The volatile content in microspheres was measured using a Mettler Toledo TGA / DSC1 TGA instrument with the following procedure: The sample to be analyzed was prepared from 1.7 mg (±0.2 mg) of thermally expandable microspheres contained in pulverizable aluminum oxide in a volume of 600 μl. The sample temperature was increased from 30°C to 650°C in a nitrogen atmosphere at a heating rate of 20°C / min. The sample was held at 650°C in a nitrogen atmosphere for a further 2 minutes, then the nitrogen was replaced with air, and the sample was held at 650°C for a further 15 minutes or more. The weight of the sample was continuously monitored during the heating procedure, and a thermogram was obtained with the sample weight (mg) on ​​the y axis and the heating temperature (°C correlated with heating time (t) up to a maximum of 650°C) on the x-axis. The volatile content (VC, %) of the microspheres was obtained by subtracting the weight of the sample measured at the second inflection point (IP2) of the thermogram curve (i.e., the point at which the weight of the sample reaches a first essentially stable plateau after evaporation of the blowing agent (170°C to 300°C, depending on the actual blowing agent and polymer used)) from the initial weight of the sample (SW; weight at 30°C and t=0), dividing this difference by the initial weight of the sample, and multiplying the result by 100 (see also equation (2) below). The percentage of blowing agent retained in the microspheres after storage (VC) 貯蔵後保持 The volatile content (VC) is expressed in %) after storage. 貯蔵後 This was calculated by multiplying the volatile content (VC0) and 100 before storage (see also equation (3) defined above).

[0163] Expansion characteristics were evaluated using a Mettler TMA / SDTA 841e thermomechanical analyzer interfaced to a PC running STARe software. Samples were prepared from 0.5 mg (+ / -0.02 mg) of thermally expandable microspheres contained in an aluminum oxide crucible with a diameter of 6.8 mm and a depth of 4.0 mm. The crucible was sealed with an aluminum oxide lid with a diameter of 6.1 mm. Using a TMA expansion probe, the sample temperature was increased from approximately 30°C to 240°C at a heating rate of 20°C / min while applying a load (net) of 0.06 N to the probe. Expansion characteristics were analyzed by measuring the vertical displacement of the probe. The initial temperature of expansion (T start ): The temperature (°C) at which the probe displacement began. Maximum expansion temperature (T max ) is the temperature (°C) when the probe displacement reaches its maximum. The TMA density is calculated by multiplying the sample weight (d) by the volume increase (dm) of the sample when the probe displacement reaches its maximum value. 3 This is the result of dividing by ).

[0164] Common synthesis method: A solution of carboxylate-functionalized cellulose polymer in a suitable organic solvent was prepared by dissolving the polymer overnight using a magnetic stirrer.

[0165] A foaming agent was added to the solution, and the mixture was stirred for 5 minutes to redissolve any precipitated polymers.

[0166] Where applicable, an anhydrous compound or a hydrogen bond donor selected from the group consisting of alcohols, urea, and carboxylic acids was further added to the solution, and the mixture was stirred for a further 10 minutes to dissolve the anhydrous compound or the hydrogen bond donor selected from the group consisting of alcohols, urea, and carboxylic acids.

[0167] Next, the resulting mixture was spray-dried using a Buechi Mini Spray Dryer B-290. Nitrogen was used as the spray gas at a supply rate of 238 l / hour for the examples containing cellulose acetate (CAB) and at a supply rate of 307 l / hour for the examples containing cellulose acetate (CA). The supply rate of the mixture to be spray-dried was 13 ml / min. The temperature of the drying gas was 105°C at the inlet (for all examples using cellulose acetate 1 (CA1)) or 70°C (for all examples using cellulose acetate butyrate 1 (CAB1)), and the suction speed was 38 m 3 It was / time.

[0168] The dried solid was collected from the bottom of the cyclone, analyzed, and subjected to further post-heat treatment where applicable.

[0169] Table 1 lists the carboxylate-functionalized cellulose polymers used to prepare the microspheres. They were either cellulose acetate (CA) or cellulose acetate butyrate (CAB).

[0170] [Table 1]

[0171] Example 1 The effect of a 1-hour post-heat treatment at 125°C on expandable microspheres fabricated from CA1 was determined.

[0172] A mixture containing 13.5 g of CA1, 159.0 g of acetone, and 7.2 g of isooctane was prepared and spray-dried as described above to prepare expandable microspheres. Start , T Max The TMA density and the volatile content of the resulting expandable microspheres were measured and are shown in Table 2.

[0173] [Table 2]

[0174] The resulting microspheres were divided into two portions of the same size. One portion was subjected to a post-heat treatment at 125°C for 1 hour by placing approximately 1 g of the material in an oven set to 125°C, while the other portion was left untreated. The post-heat treated portion was then cooled to ambient temperature (22.5 ± 2.5°C). Both portions of the expandable microspheres were then stored at 22.5 ± 2.5°C and standard pressure (10¹³ ± 50 mbar), and the volatile content of the expandable microspheres was measured after 1 month, 2 months, and 6 months. Furthermore, the volatile content of the post-heat treated expandable microspheres was also measured immediately after the post-heat treatment. The results are shown in Table 3 below.

[0175] [Table 3]

[0176] As can be seen from Table 3, post-heat treatment significantly improves the volatile content of expandable microspheres. With post-heat treatment, a retention of 97.3% by weight of volatile substances can be achieved even after 6 months of storage, whereas the same untreated expandable microspheres have only 22.8% by weight of remaining volatile content.

[0177] Example 2 The effect of post-heat treatment at 100°C for 1 hour on expandable microspheres prepared from CAB1 using 1,2,4,5-benzenetetracarboxylic acid dianhydride (pyromellitic acid dianhydride; PMDA) or 1,2,4,5-benzenetetracarboxylic acid (pyromellitic acid; PMA) was determined.

[0178] A mixture containing CAB1, acetone, isooctane, and PMA or PMDA in the amounts specified in Table 4 was prepared and spray-dried as described above to prepare expandable microspheres. Start , T MaxThe TMA density and the volatile content of the resulting expandable microspheres were measured and are shown in Table 5.

[0179] [Table 4]

[0180] [Table 5]

[0181] Each of the obtained microspheres was divided into two equal-sized portions. For each experiment, one portion was subjected to a post-heat treatment at 100°C for 1 hour by placing approximately 1 g of the material in an oven set to 100°C, while the other portion was left untreated. The post-heat treated portion was then cooled to ambient temperature (22.5 ± 2.5°C). All portions of the expandable microspheres were then stored at 22.5 ± 2.5°C and standard pressure (10¹³ ± 50 mbar), and the volatile content of the expandable microspheres was measured after 1 month, 3 months, and 6 months. Furthermore, the volatile content of the post-heat treated expandable microspheres was also measured immediately after the post-heat treatment. The results are shown in Table 6 below.

[0182] [Table 6]

[0183] As can be seen from Table 6, post-heat treatment significantly improves the volatile content of expandable microspheres. With post-heat treatment, retention of up to 93.5% by weight of volatile substances can be achieved even after 6 months of storage, whereas the same untreated expandable microspheres have a significantly lower remaining volatile content of less than 80% by weight.

[0184] Example 3 The effects of different temperatures on post-heat treatment were measured using expandable microspheres prepared from CA1 with 1,2,4,5-benzenetetracarboxylic dianhydride (pyromellitic dianhydride; PMDA).

[0185] A mixture containing 13.5 g of CA1, 159.0 g of acetone, 7.2 g of isooctane, and 0.36 g of PMDA was prepared and spray-dried as described above to prepare expandable microspheres. Start , T Max The TMA density and the volatile content of the resulting expandable microspheres were measured and are shown in Table 7.

[0186] [Table 7]

[0187] The charge of the obtained microspheres was divided into four parts of the same size. Three parts were individually subjected to post-heat treatment at 75°C, 100°C, or 125°C for 1 hour by placing approximately 1g in an oven set to the respective temperature, while one part was left untreated. The parts that underwent post-heat treatment were then cooled to ambient temperature (22.5±2.5°C). All parts of the expandable microspheres were then stored at 22.5±2.5°C and standard pressure (10¹³±50 mbar), and the volatile content of the expandable microspheres was measured after 1 month, 2 months, and 6 months. Furthermore, the volatile content of the post-heat treated expandable microspheres was also measured immediately after post-heat treatment. The results are shown in Table 8 below.

[0188] [Table 8]

[0189] As can be seen from Table 8, post-heat treatment can be carried out over a wide temperature range and still significantly improves the volatile content of the microspheres, which can be expanded.

[0190] Example 4 The effects of different post-heat treatment periods were measured using expandable microspheres prepared from CA1 with 1,2,4,5-benzenetetracarboxylic acid (pyromellitic acid, PMA).

[0191] A mixture containing 13.5 g of CA1, 159.0 g of acetone, 7.2 g of isooctane, and 0.42 g of PMA was prepared and spray-dried as described above to prepare expandable microspheres. Start , T Max The TMA density and the volatile content of the resulting expandable microspheres were measured and are shown in Table 9.

[0192] [Table 9]

[0193] The charge of the obtained microspheres was divided into six parts of the same size. Five parts were individually subjected to a post-heat treatment at 100°C for 5 minutes, 15 minutes, 30 minutes, 1 hour, or 2 hours by placing approximately 1 g in an oven set to 100°C, while one part was left untreated. The post-heat treated part was then cooled to ambient temperature (22.5 ± 2.5°C). All parts of the expandable microspheres were then stored at 22.5 ± 2.5°C and standard pressure (10¹³ ± 50 mbar), and the volatile content of the expandable microspheres was measured after 1 month, 2 months, and 3 months. Furthermore, the volatile content of the post-heat treated expandable microspheres was also measured immediately after the post-heat treatment. The results are shown in Table 10 below.

[0194] [Table 10]

[0195] As can be seen from Table 10, post-heat treatment can be carried out over a wide range of time periods and still significantly improves the volatile content of the expandable microspheres.

[0196] Example 5 The effect of adding an anhydride-containing compound (i.e., 1,2,4,5-benzenetetracarboxylic acid dianhydride (pyromellitic acid dianhydride; PMDA)) or a hydrogen bond donor (i.e., 1,2,4,5-benzenetetracarboxylic acid (pyromellitic acid; PMA)) on storage stability after post-heat treatment was measured.

[0197] A mixture containing CA1, acetone, isooctane, and, where applicable, the amounts of PMDA or PMA specified in Table 11 was prepared and spray-dried as described above to prepare expandable microspheres. Start , T Max The TMA density and the volatile content of the resulting expandable microspheres were measured and are shown in Table 12.

[0198] [Table 11]

[0199] [Table 12]

[0200] For each experiment, the charge of each microsphere obtained was divided into two parts of the same size. For each experiment, one part was subjected to a post-heat treatment at 100°C for 1 hour by placing approximately 1 g of the material in an oven set to 100°C, while the other part was left untreated. The part subjected to post-heat treatment was then cooled to ambient temperature (22.5 ± 2.5°C). All parts of the expandable microsphere were then stored at 22.5 ± 2.5°C and standard pressure (10¹³ ± 50 mbar), and the volatile content of the expandable microspheres was measured after 1 month, 3 months, and 6 months. Furthermore, the volatile content of the post-heat treated expandable microspheres was also measured immediately after the post-heat treatment. The results are shown in Table 13 below.

[0201] [Table 13]

[0202] As can be seen from Table 13, post-heat treatment significantly improves the volatile content of expandable microspheres. With post-heat treatment, retention of up to essentially 100% by weight of volatile substances can be achieved even after 6 months of storage, while the same untreated expandable microspheres have significantly less remaining volatile content than 80% by weight. The results are also illustrated in Figure 2. In Figure 2, (Δ) means that each sample underwent post-heat treatment. For each experiment, the first column shows the volatile content before storage, the second column shows the volatile content after 1 month (1 m) of storage, the third column shows the volatile content after 3 months (3 m) of storage, and the fourth column shows the volatile content after 6 months (6 m) of storage.

Claims

1. A storage-stable, thermally expandable microsphere comprising a polymer shell surrounding a hollow core, wherein the hollow core contains a blowing agent, and the polymer shell comprises a carboxylate-functionalized cellulose, wherein the microsphere retains at least 80% of the original weight of the blowing agent encapsulated within the microsphere even after 6 months of storage under atmospheric conditions.

2. A thermally expandable microsphere with storage stability according to claim 1, which retains at least 85%, preferably at least 90%, more preferably at least 95%, and most preferably at least 98% of the original weight of the foaming agent encapsulated in the microsphere after storage for six months under atmospheric conditions.

3. The storage-stable, thermally expandable microsphere according to claim 1 or 2, wherein the polymer shell further comprises an anhydride-containing compound, or a hydrogen bond donor selected from the group consisting of an anhydride-containing compound or a carboxylic acid.

4. The storage-stable, thermally expandable microsphere according to claim 3, wherein the hydrogen bond donor is selected from the group consisting of pyromelittic acid dianhydride (1,2,4,5-benzenetetracarboxylic acid dianhydride), benzophenonetetracarboxylic acid dianhydride, pyromelittic acid (1,2,4,5-benzenetetracarboxylic acid), citric acid, tartaric acid, butanetetracarboxylic acid, succinic acid, lactic acid, maleic acid, and any combination thereof, preferably from the group consisting of pyromelittic acid dianhydride (1,2,4,5-benzenetetracarboxylic acid dianhydride), citric acid, pyromelittic acid (1,2,4,5-benzenetetracarboxylic acid), and 1,2,3,4-butanetetracarboxylic acid.

5. The carboxylate-functionalized cellulose contains a carboxylate group of formula (1), 【Chemistry 1】 During the ceremony, A is -H, -OH, -OR ｂ -C(O)OH, and -C(O)OR ｂ Selected from, R ａ is absent, whereby A is directly bonded to the C=O group, or R ａ is a saturated aliphatic group or an unsaturated aliphatic group having 1 to 11 carbon atoms, which may be linear, branched or cyclic, and is selected from 5- and 6-membered aromatic rings, wherein R ａ is optionally substituted with one or more substituents selected from -OH, halides, C １～４ alkyl, and C １～４ alkoxy, and the C １～４ alkyl and C １～４ alkoxy groups may be optionally substituted with one or more groups selected from halides and -OH, and In each existence, R ｂ However, C １～４ A storage-stable, thermally expandable microsphere according to any one of claims 1 to 4, having one or more substituents selected from alkyl groups and optionally selected from halide groups and -OH groups.

6. The following conditions, namely, (a) A is selected from H and C(O)OH, (b) R ａ It contains 1 to 7 carbon atoms. (c) R ａ teeth, 【Chemistry 2】 【Transformation 3】 【Chemistry 4】 【Transformation 5】 and 【Transformation 6】 Selected from, in the formula, v is an integer in the range of 1 to 11. w is an integer in the range of 3 to 11. x is an integer in the range of 2 to 11. y is either 1 or 2. z is 5 or 6, in each existence R ｃ These are independently H, -OH, and halide. C １～４ Alkyl and C １～４ Selected from alkoxy, C １～４ Alkyl and C １～４ The alkoxy group may be substituted with one or more groups selected from halides and -OH groups. (d) R ａ It has 11 or fewer carbon atoms. 【Transformation 7】 Selected from, in the formula, E is defined as in (c) above. 【Transformation 8】 And, p and r are each independent integers between 0 and 8, and p + r is at least 1. A storage-stable, thermally expandable microsphere according to any one of claims 1 to 5, wherein q and s are the number of double bonds in each acyclic aliphatic component, and one or more of these are independently selected from 0, 1, and 2.

7. The carboxylate-functionalized cellulose may be substituted with C １ ~C ８ Aliphatic carboxylic acid bases, and optionally substituted C ６ A storage-stable, thermally expandable microsphere according to any one of claims 1 to 6, comprising carboxylate functionalization selected from carboxylic acid bases containing aromatic rings, preferably selected from acetate, propionate, butyrate, pentanoate, hexanoate, heptanoate, octanoate, and phthalate salts.

8. The storage-stable, thermally expandable microsphere according to any one of claims 1 to 7, wherein the carboxylate-functionalized cellulose is acetic acid-functionalized cellulose, propionic acid-functionalized cellulose, or butyric acid-functionalized cellulose, preferably acetic acid-functionalized cellulose or butyric acid-functionalized cellulose, most preferably acetic acid-functionalized cellulose.

9. The carboxylate-functionalized cellulose has a number average molecular weight (M) in the range of 2,000 to 100,000 Da, and preferably in the range of 10,000 to 50,000 Da. ｎ A thermally expandable microsphere with storage stability according to claim 8, having the following characteristics:

10. A method for preparing storage-stable, thermally expandable microspheres comprising a polymer shell surrounding a hollow core, wherein the hollow core contains a blowing agent, and the polymer shell comprises a carboxylate-functionalized cellulose, and the method is (i) To prepare a thermally expandable microsphere comprising a polymer shell surrounding a hollow core, wherein the hollow core contains a foaming agent, and the polymer shell contains carboxylate-functionalized cellulose, (ii) A manufacturing method comprising the step of subjecting the thermally expandable microspheres obtained in step (i) to a post-heat treatment by heating the thermally expandable microspheres to a temperature of at least 40°C.

11. The manufacturing method according to claim 10, wherein the post-heat treatment is carried out at a temperature of 50°C to 150°C, preferably 60°C to 140°C, more preferably 70°C to 130°C, and most preferably 75°C to 125°C.

12. The manufacturing method according to claim 10 or 11, wherein the post-heat treatment is carried out for at least 5 minutes, preferably at least 10 minutes, more preferably at least 30 minutes, and even more preferably at least 50 minutes.

13. (iii) A manufacturing method according to any one of claims 10 to 12, comprising the step of cooling the thermally expandable microspheres obtained in step (ii) to a temperature below the temperature used in step (ii), preferably to ambient temperature.

14. A manufacturing method according to any one of claims 10 to 13, comprising (iv) storing the thermally expandable microspheres obtained in step (ii), or, if carried out, the thermally expandable microspheres obtained in step (iii), for at least 10 minutes, preferably at least 30 minutes, more preferably at least 1 hour, and most preferably at least 1 day.

15. Storage-stable, thermally expandable microspheres obtained by a manufacturing method according to any one of claims 10 to 14.

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