Microcapsules for improving the support performance of filter rod outer tube, a preparation method thereof and a cigarette filter rod comprising the same

Abstract

The application discloses a kind of microcapsules for improving the support performance of filter rod outer tube and its preparation method and cigarette filter rod comprising it, the capsule wall of microcapsule is modified silica, the capsule core of microcapsule is poly-N-isopropyl acrylamide (PNIPAM).During the process of filter rod smoking, the capsule wall of microcapsule is softened, SiO2 is broken, so that the capsule core poly-N-isopropyl acrylamide is released, and the phase change of poly-N-isopropyl acrylamide material is generated by heating, the high molecular polymer network shrinks to compact colloidal structure, so that the filter rod is hardened, thereby supporting the groove layer and outer tube and preventing soft collapse.The urethane bond and azo bond of the capsule wall silica are modified, or the capsule wall silica is modified by γ-(methacryloyloxy) propyl trimethoxysilane, so that the capsule wall is more easily broken after heating, thereby facilitating the release of internal poly-N-isopropyl acrylamide, and supporting the outer tube while also carrying the release of flavor.

Description

Technical Field

[0001] This invention relates to the field of heated non-combustible cigarette technology, specifically to a microcapsule for improving the support performance of the outer tube of a filter rod, a method for preparing the same, and a cigarette filter rod containing the same. Background Technology

[0002] Cigarette filters are typically made of cellulose acetate or polylactic acid (PLA) tow. During smoking, due to increased heat and moisture, these filters soften and collapse. A large thermal collapse value can affect the filter's stability and smoking quality. The standard YC / T 354-2010, "Determination of Physical Properties of Cigarettes and Filters: Thermal Collapse," specifies the test method for thermal collapse of filter rods.

[0003] Currently, researchers point out that temperature is a major factor affecting thermal collapse value. During combustion, the higher the temperature and the closer the combustion cone is to the pressure application point, the greater the thermal collapse value. Secondly, moisture has a significant impact on thermal collapse; the higher the water content at the pressure application point, the greater the thermal collapse value. To prevent the filter rod from softening and collapsing due to heat during suction, researchers typically reduce the temperature of the smoke reaching the mouthpiece or install a separate support element inside the filter rod. Furthermore, to address the issue of the filter rod softening due to moisture on the contact surface between the filter rod and the lip, a waterproof layer is applied to the filter rod forming paper, or a smooth, waterproof material is used.

[0004] Therefore, improving the support performance and hydrophobicity of the filter rod is an effective means to prevent the filter rod from softening and collapsing during the suction process, and it is also a problem that people hope to solve.

[0005] To address the above problems, this invention is proposed. Summary of the Invention

[0006] The first aspect of the present invention provides a microcapsule for improving the support performance of the outer tube of a filter rod, wherein the capsule wall is silica containing urethane bonds and azo bonds or silica modified with γ-(methacryloyloxy)propyltrimethoxysilane, and the capsule core is poly(N-isopropylacrylamide) (PNIPAM).

[0007] A second aspect of the present invention provides a method for preparing the microcapsules described in the first aspect of the present invention, wherein when the capsule wall of the microcapsule is silicon dioxide containing urethane bonds and azo bonds, the method includes the following steps:

[0008] (a1) Take 1.1g-1.3g polyethyleneimine (PEI), 0.8-1.0g poly(N-isopropylacrylamide), 1.1g-1.3g glycerol, 530mg-540mg CTAB (hexadecyltrimethylammonium bromide), and 7-10g deionized water, stir them evenly in a beaker, and the product is aqueous solution A.

[0009] (a2) Dissolve 1.2-1.3g of surfactant in 50-60mL of cyclohexane and add a lipophilic water-in-oil (W / O) type nonionic surfactant. Stir well in a beaker. The product is an oil phase B solution.

[0010] (a3) Take 1 mL-1.2 mL of this cyclohexane solution, add 500 μL-520 μL of TEOS (tetraethoxysilane) and 25-35 μL of hexamethylene diisocyanate, mix well, and the product is monomer phase solution C;

[0011] (a4) Take a 100ml beaker, add 650μL-680μL of aqueous solution A and 6.2g-6.3g of oil solution B, mix, stir, and then ultrasonically emulsify to form a homogeneous reverse emulsion;

[0012] (a5) Under magnetic stirring, the product monomer phase solution C from step (a3) ​​is added dropwise to the product from step (a4) at a rate of one drop every 5 to 10 seconds, and stirring is continued for 10 to 30 minutes. The mixture is then stirred continuously at room temperature with a humidity of 25% to 30% for 24 to 48 hours.

[0013] Because TEOS tetraethoxysilane hydrolyzes at the oil-water interface to produce silanol groups, these silanol groups, besides condensing to form SiO2, can also react with one end of the diisocyanate to form urethane, while the other end of the diisocyanate can react with polyethyleneimine. During the condensation process, an aqueous solution of poly(N-isopropylacrylamide) is slowly added dropwise to the system, allowing the SiO2 / PEI to encapsulate the poly(N-isopropylacrylamide) molecules during the condensation. This forms SiO2 / PEI composite microcapsules.

[0014] (a6) Centrifuge the product from step (a5) and wash it with 95% ethanol. Repeat this process three times.

[0015] (a7) Drying yields white solid PNIPAM / PEI-SiO2 microcapsules.

[0016] Preferably, in step (a1), the stirring time is 10 min-15 min; in step (a2), the lipophilic water-in-oil (W / O) nonionic surfactant is selected from sorbitan monooleate Span80, and the stirring time is 10 min-15 min; in step (a3), the stirring time is 10 min-30 min; in step (a4), the magnetic stirring time is 10 min-30 min, the rotation speed is 600 rpm-800 rpm, the ultrasonic emulsification time is 30 min-1 h, and the ultrasonic frequency is 80 kHz-120 kHz; in step (a6), the centrifugation conditions are: centrifugation at a speed of 8000 r / min-10000 r / min for 30 min-40 min; in step (a7), the drying conditions are: vacuum drying at 25°C for 1.5 h-3 h.

[0017] A third aspect of the present invention provides a method for preparing the microcapsules described in the first aspect of the present invention, wherein when the capsule wall of the microcapsule is γ-(methacryloyloxy)propyltrimethoxysilane modified silica, the method includes the following steps:

[0018] (b1) Take 1.1g-1.3g of poly(N-isopropylacrylamide), 1.1g-1.3g of glycerol, 530mg-540mg of CTAB (hexadecyltrimethylammonium bromide), and 7-10g of deionized water, stir them evenly in a beaker, and the product is aqueous solution A.

[0019] (b2) Dissolve 1.2-1.3g of surfactant in 50-60ml of cyclohexane, add a lipophilic water-in-oil (W / O) type nonionic surfactant, stir evenly in a beaker, and the product is the oil phase B solution;

[0020] (b3) Take 1 mL-1.2 mL of this cyclohexane solution, add 500 μL-520 μL of TEOS (tetraethoxysilane) and 25-35 μL of hexamethylene diisocyanate, mix well, and the product is monomer phase solution C;

[0021] (b4) Take a 100ml beaker, add 650μL-680μL of aqueous solution A and 6.2g-6.3g of oil solution B, mix, stir magnetically for 10min-30min at 600rpm-800rpm, and then sonicate for 30min at 80kHz-120kHz to form a homogeneous reverse emulsion;

[0022] (b5) Under magnetic stirring, the monomeric phase solution C of the product from step (b3) is added dropwise to the product from step (b4) at a rate of one drop every 5-10 seconds. Stirring is continued for 10-30 minutes. Stirring is continued for 24-48 hours at room temperature of 25%-30% and a speed of 250-300 rpm.

[0023] At this point, TEOS tetraethoxysilane hydrolyzes at the oil-water interface to generate silanol groups. Besides self-condensing to form SiO2, these silanol groups also undergo condensation. During this process, 1.65g (1.6g-1.7g) of KH570 and 2.01g (2.0g-2.1g) of a highly flexible resin, preferably ethyl acrylate monomer, are added during stirring. In this process, KH570 modifies the double bonds on the microsphere surface, and then the addition of monomers such as ethyl acrylate allows polymerization to form on the SiO2 double bond surface, thus creating a microcapsule protective film.

[0024] (b6) Centrifuge the product from step (b5) and wash it with 95% ethanol. Repeat this process three times.

[0025] (b7) Drying yields white solid PNIPAM / KH570-SiO2 microcapsules.

[0026] Preferably, in step (b1), the stirring time is 10 min-15 min; in step (b2), the lipophilic water-in-oil (W / O) type nonionic surfactant is selected from sorbitan monooleate Span80, and the stirring time is 10 min-15 min; in step (b3), the stirring time is 10 min-30 min; in step (b4), the magnetic stirring time is 10 min-30 min, the rotation speed is 600 rpm-800 rpm, the ultrasonic emulsification time is 30 min-1 h, and the ultrasonic frequency is 80 kHz-120 kHz; in step (b6), the centrifugation conditions are: centrifugation at a speed of 8000 r / min-10000 r / min for 30 min-40 min; in step (b7), the drying conditions are: vacuum drying at 25°C for 1.5 h-3 h.

[0027] A fourth aspect of the present invention provides a cigarette filter rod comprising the microcapsules described in the first aspect of the present invention, comprising an outer tube (1) and a support member (4) within the outer tube (1), the support member (4) comprising a filler and microcapsules dispersed in the filler.

[0028] Preferably, the cigarette filter rod further includes an inner tube (2) and a groove layer (3) located between the outer tube (1) and the inner tube (2), wherein the groove layer (3) has a support member (4) in the cavity on the side near the inner tube (2);

[0029] Preferably, the inner tube (2) has a filter rod core (5) inside its cavity;

[0030] The cross-sectional shape of the trench layer (3) is "U-shaped", "V-shaped" or "trapezoidal".

[0031] Preferably, the filler is a diacetate cellulose bundle or a polylactic acid cellulose bundle, wherein the amount of microcapsules added to the filler is 0.5 mg microcapsules / 1 mm cellulose bundle.

[0032] Preferably, the inner tube (2) is selected from 8000CU-10000CU high-transparency forming paper, the outer tube (1) is selected from forming paper, and the groove layer (3) is selected from non-woven fabric or forming paper.

[0033] The filter rod containing the supporting component of this invention can be used as a standalone cigarette filter rod, or as a segment of a binary composite filter rod or a ternary composite filter rod. Preferably, the filter rod containing the supporting component is combined with a segment of a filter rod without microcapsule bundles. The filter rod without microcapsule bundles includes an outer tube (1), an inner tube (2), and a grooved layer (3) located between the two. The cavity of the grooved layer (3) near the inner tube (2) does not have a supporting component. The axial length ratio of the filter rod containing the supporting component to the filter rod without microcapsule bundles is 1.39:1-1.46:1. In actual production, the ratio of the axial lengths of the two components can be adjusted according to different specifications and machine models.

[0034] The fifth aspect of the present invention provides a cigarette comprising the cigarette filter rod described in the fourth aspect of the present invention.

[0035] Compared with the prior art, the present invention has the following beneficial effects:

[0036] 1. This invention first proposes adding a support component inside the outer tube of the filter rod. The support component (4) includes a filler and microcapsules dispersed in the filler. This invention is the first to conceive of adding a material that hardens when heated inside the outer tube. The capsule wall of the microcapsule is silicon dioxide, and the core of the microcapsule is poly(N-isopropylacrylamide). During the filter rod suction process, the filter rod temperature rises, causing the capsule wall of the microcapsule to soften and SiO2 to rupture, thereby releasing the poly(N-isopropylacrylamide) core. The PNIPAM material undergoes a phase change when heated, and the polymer network shrinks into a tight colloidal structure, making the filter rod harden. This provides support for the trench layer (3) and the outer tube (1) and prevents the outer tube (1) from softening and collapsing.

[0037] 2. The present invention further proposes a filter rod structure containing a support component. The filter rod includes an outer tube, an inner tube, and a grooved layer located between the two. The grooved layer has a support component in the cavity near the inner tube. The support component includes a filler and microcapsules dispersed in the filler. This structure can enable the support component 4 to provide stronger support to the outer tube 1.

[0038] 3. PNIPAM, which hardens after agglomeration due to heat, is hydrophobic, which also prevents surface moisture from the filter rod in contact with the lips from entering the filter rod core and causing the filter rod to soften, thus avoiding thermal collapse caused by increased moisture.

[0039] 4. At low temperatures, PNIPAM is in a stretched state in water. As the temperature rises, PNIPAM contracts, and its loose coil structure aggregates into a dense, granular structure, thus hardening and providing support. This invention utilizes this characteristic. At low temperatures, PNIPAM is first placed in a fragrance solution to swell and adsorb fragrance, and then encapsulated to form microcapsules. As the temperature rises, the silica capsule wall ruptures, releasing the PNIPAM core and the adsorbed fragrance slowly. In other words, PNIPAM can swell and adsorb fragrance in a fragrance solution at low temperatures, and shrink at high temperatures to release the fragrance substances. This not only provides better storage conditions for fragrances but also enhances the aroma during aspiration. The microcapsules of this invention not only achieve slow release of fragrance after heating but also support the outer tube after heating.

[0040] 5. The present invention further modifies the silica of the capsule wall with urethane and azo bonds. Both urethane and azo bonds are easily decomposed at high temperatures, making the capsule wall of the microcapsule of the present invention easier to rupture after being heated, thereby facilitating the release of fragrance carried by the internal PNIPAM.

[0041] 6. The present invention further modifies the silica of the capsule wall with γ-(methacryloyloxy)propyltrimethoxysilane. γ-(methacryloyloxy)propyltrimethoxysilane (KH570) can improve the adhesion of silica, increase water resistance, and reduce curing temperature, thereby making the microcapsules easy to decompose at high temperature, and thus allowing the PNIPAM encapsulated in the microcapsules to release fragrance.

[0042] 7. The filter rod containing the supporting component of this invention can be used as a standalone cigarette filter rod, or as a segment of a binary composite filter rod or a ternary composite filter rod. When the cigarette is smoked to a certain temperature, the outer ring of the filter rod hardens, making the outer layer of the filter rod, which would normally soften after smoking, harder, thus supporting the cylindrical structure of the filter rod and improving the thermal collapse of the filter rod during smoking. Attached Figure Description

[0043] Figure 1 Electron micrograph of hollow silica;

[0044] Figure 2 This is a cross-sectional view of a filter rod containing supporting components;

[0045] Figure 3 This is a composite diagram of filter rods;

[0046] Figure 4This is a cross-sectional view of another filter rod containing a support component.

[0047] The names of the reference numerals in the accompanying drawings are as follows: 1-outer tube, 2-inner tube, 3-groove layer, 4-support component, 5-filter rod core, 11-filter rod containing support component, 12-filter rod without support component. Detailed Implementation

[0048] The present invention will now be described in further detail with reference to the embodiments.

[0049] Those skilled in the art will understand that the following embodiments are for illustrative purposes only and should not be construed as limiting the scope of the invention. Where specific techniques or conditions are not specified in the embodiments, they are performed in accordance with the techniques or conditions described in the literature in the field or according to the product instructions. Materials or equipment whose manufacturers are not specified are all conventional products that can be obtained by purchase.

[0050] Those skilled in the art will understand that, unless specifically stated otherwise, the singular forms “a,” “an,” “the,” and “the” used herein may also include the plural forms. It should be further understood that the term “comprising” as used in this specification means the presence of the stated features, integers, steps, operations, elements, and / or components, but does not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof. It should be understood that when we say an element is “connected” to another element, it can be directly connected to the other element, or there may be an intermediate element. Furthermore, the term “connected” as used herein can include wireless connections.

[0051] In the description of this invention, unless otherwise stated, "a plurality of" means two or more. The terms "inner," "upper," "lower," etc., indicate the orientation or state relationship based on the orientation or state relationship shown in the drawings, and are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention.

[0052] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installed," "connected," and "equipped with" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium. Those skilled in the art will understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0053] It will be understood by those skilled in the art that, unless otherwise defined, all terms used herein, including technical and scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. It should also be understood that terms such as those defined in general dictionaries should be understood to have the meaning consistent with their meaning in the context of the prior art, and should not be interpreted in an idealized or overly formal sense unless defined as herein.

[0054] Example 1

[0055] I. Preparation of Poly-N-Isopropylacrylamide

[0056] Add 98% concentrated sulfuric acid to a 250ml three-necked flask, stir and add 15ml isopropanol dropwise. Use the heat of dilution reaction to raise the temperature to 50-60℃, add 1% copper chloride dihydrate, and slowly add 13ml (0.2mol) acrylonitrile. Maintain the temperature at 50-60℃ throughout this process.

[0057] After the addition was complete, the reaction was carried out at 60-70℃ for 1 hour. The mixture was then cooled to room temperature, neutralized in filtered water to pH 2, and extracted with 50 ml of diethyl ether until the solution separated into layers. The lower organic layer was dried over anhydrous magnesium sulfate for 12 hours, and the solvent was evaporated at 100℃ to obtain the crude synthesized N-isopropylacrylamide (NIPAM).

[0058] Mix 1 part hexane and 1 part toluene (1:1) in a solvent mixture and heat to 80°C. Stir magnetically at 200 rpm, and add 10 g of crudely synthesized N-isopropylacrylamide (NIPAM) and 0.6 g of photoinitiator Irgacure 184. Irgacure 184 is a photoinitiator with excellent resistance to yellowing and high activity, which helps the polymerization of N-isopropylacrylamide monomers and does not easily change color, thus affecting product quality. Stir manually until completely dissolved, filter the precipitate and insoluble matter with filter paper, and place the remaining solution in an open bottle and seal it. Let it stand in a refrigerator at 4°C for 2 hours to allow crystallization. After crystallization, filter again. After filtering twice, dry under vacuum at 45°C to obtain pure N-isopropylacrylamide.

[0059] Pure N-isopropylacrylamide was mixed with cigarette flavorings. The N-isopropylacrylamide mixture was then placed on a polytetrafluoroethylene (PTFE) plate and placed in a shaker at 100 rpm, continuously irradiated with a 365 nm LED light source for 1 minute. This process allows the N-isopropylacrylamide to be loaded with flavorings during the polymerization of poly(N-isopropylacrylamide). Compared to polymerization using a catalyst, this method produces pure poly(N-isopropylacrylamide) free from other chemical contamination.

[0060] In addition to loading fragrances and flavorings onto N-isopropylacrylamide during its polymerization into polyN-isopropylacrylamide, N-isopropylacrylamide can also be polymerized into polyN-isopropylacrylamide first, and then fragrances and flavorings can be adsorbed onto it. The specific steps are as follows:

[0061] Pure N-isopropylacrylamide was placed on a polytetrafluoroethylene plate and placed in a shaker at 100 rpm, continuously irradiated with a 365 nm LED light source for 1 minute. This allowed the N-isopropylacrylamide to polymerize into polyN-isopropylacrylamide. The prepared polyN-isopropylacrylamide was then immersed in cigarette flavoring and fragrance for 2-3 hours. After removal, polyN-isopropylacrylamide containing the flavoring and fragrance was obtained.

[0062] Compared to polymerizing N-isopropylacrylamide and then adsorbing fragrance, loading fragrance during the polymerization of N-isopropylacrylamide can ensure a larger fragrance loading capacity. Therefore, this embodiment adopts the method of loading fragrance during the polymerization of N-isopropylacrylamide.

[0063] Then it is used as the core material for subsequent steps.

[0064] II. Preparation of PNIPAM / SiO2 microcapsules containing urethane and azo bonds

[0065] Step 1: Take 1.1g polyethyleneimine (PEI), 1.1g poly(N-isopropylacrylamide), 1.1g glycerol, 535mg CTAB (hexadecyltrimethylammonium bromide), and 7.3g deionized water, and stir them evenly in a beaker. The product is aqueous phase A solution.

[0066] Step 2: Dissolve 1.285g of surfactant in 50mL of cyclohexane and add a lipophilic water-in-oil (W / O) nonionic surfactant, preferably sorbitan monooleate Span80. Stir well in a beaker; the product is an oil phase solution B.

[0067] Step 3: Take 1.2 mL of this cyclohexane solution, add 500 μL of TEOS (tetraethoxysilane) and 30 μL of hexamethylene diisocyanate, mix well, and the product is monomer phase solution C.

[0068] Step 4: Take a 100ml beaker, add 650μL of aqueous solution A and 6.25g of oil solution B, mix, stir magnetically for 10min at 600rpm, and then sonicate for 30min at 80kHz to form a homogeneous reverse emulsion.

[0069] Step 5: Under magnetic stirring, the monomer phase solution C of the product from Step 3 is added dropwise to the product from Step 4 at a rate of one drop every 5 seconds. Stirring continues for 10 minutes, and then continuously for 24 hours at 25% room temperature. Because TEOS tetraethoxysilane hydrolyzes at the oil-water interface to produce silanol groups, these silanol groups, in addition to condensing to form SiO2, can also react with one end of the diisocyanate to form a urethane, while the other end of the diisocyanate can react with polyethyleneimine. During the condensation process, an aqueous solution of poly(N-isopropylacrylamide) is slowly added dropwise to the system, allowing the SiO2 / PEI to encapsulate the poly(N-isopropylacrylamide) molecules during the condensation process. This forms SiO2 / PEI composite microcapsules.

[0070] Step 6: Centrifuge the product from Step 5 at 8000 r / min for 30 min and wash with 95% ethanol. Repeat this process three times.

[0071] Step 7: Vacuum drying is performed at 25 degrees Celsius, and the product is white solid PNIPAM / PEI-SiO2 microcapsules.

[0072] III. Composite of PNIPAM / SiO2 microcapsules and filter rods

[0073] See the schematic diagram of the filter rod structure containing the supporting components. Figure 2 .

[0074] Step 1: First, make the core, i.e. the inner tube. The forming paper is 8000CU high transparency forming paper with a circumference of 15.3mm ± 0.1.

[0075] Step 2: First, the grooved paper made of non-woven fabric is pressed using a square gear roller with a width of 1mm, a depth of 1mm, and a spacing of 1mm. That is to say, the cross-sectional shape of the groove in the groove layer (3) is "trapezoidal".

[0076] Step 3: The microcapsules from Examples 1, 2, and 3 are uniformly added to the fiber bundle (filter rod) at a dosage of 0.5 mg / mm cellulose acetate. After the fiber bundle has cured for 2 hours, it can uniformly fill the 1 mm groove, serving as the outer filter rod. The grooves formed during the lamination process increase the air permeability of the filter rod after it hardens.

[0077] Step 4: The square groove has a larger contact area with the outermost tipping paper, and is more closely bonded to the normal forming paper. Hot melt adhesive with a viscosity of 6000±500mPa.s is used to form a cigarette filter rod unit with the normal rod core, i.e., the outer tube, with a circumference of 22.1mm±0.1.

[0078] Step 5: The filter rod 11 containing the support component from Step 3 is combined with the filter rod 12 without microcapsule tow, with a combined length of 23mm + 7mm. See Figure 3 .

[0079] The cross-sectional shape of the trench layer (3) can also be "V-shaped", see Figure 4 In addition, the cross-sectional shape of the trench layer (3) can also be "U-shaped".

[0080] In this embodiment, the cigarette sample formed by combining the microcapsules and grooved filter rods prepared in this embodiment with other units is named Example 1 - Grooved Filter Rod. For comparison, the cigarette sample formed by combining the microcapsules and ordinary filter rods (that is, the outer tube has cellulose acetate bundles inside and does not have a groove structure) prepared in this embodiment with other units is named Example 1 - Ordinary Filter Rod.

[0081] Comparative Example

[0082] The comparative example is a filter rod without internal support components, which differs from Example 1 only in that the filter rod does not contain support components.

[0083] Among them, the cigarette sample composed of a filter rod with a grooved structure and other units was named the comparative example - grooved filter rod, and the cigarette sample composed of a regular filter rod (that is, the outer tube has cellulose acetate bundles and does not have a grooved structure) and other units was named the comparative example - regular filter rod.

[0084] Example 2

[0085] Preparation of PNIPAM / SiO2 microcapsules without urethane and azo bonds

[0086] Hollow silica microspheres were first prepared, and then poly(N-isopropylacrylamide) was dispersed in the hollow silica microspheres using ultrasound to obtain silica microspheres PNIPAM / SiO2 containing poly(N-isopropylacrylamide).

[0087] (1) Preparation of hollow silica microspheres:

[0088] Step 1: Measure 24.0 mL of a 10 mmol / L hexadecyltrimethylammonium bromide (CTAB) aqueous solution and pour it into a three-necked flask, then fix the apparatus.

[0089] Step 2: Add 0.48g of urea and mechanically stir (250rpm) at room temperature to dissolve the urea and form an aqueous solution A.

[0090] Step 4: Add 1.3 mL (1.0 g) of cyclohexane, 216 μL of n-hexadecane (HD), and 3.2 mL (3.0 g) of tetraethyl orthosilicate (TEOS) to the product from Step 3 in sequence.

[0091] Step 3: Pre-emulsify at room temperature (250 rpm) for 30 min, then transfer to a colorimetric tube and sonicate at 80 kHz for 30 min.

[0092] Step 4: After aging at room temperature for 12 hours, place the mixture in an oil bath heated to 70°C and react for 24 hours. After centrifugation with anhydrous ethanol at a 1:1 (v:v) ratio, a white solid is obtained.

[0093] Step 5: The product is dried in a 50℃ forced-air drying oven to obtain hollow SiO2 microspheres.

[0094] from Figure 1 SEM showed that the hollow silica microspheres in Example 2 were not completely sealed. In this example, poly-N-isopropylacrylamide was further injected into the hollow interior by ultrasonic dispersion.

[0095] (2) Preparation by ultrasonic dispersion (PNIPAM / SiO2)

[0096] Step 6: At 20°C, weigh 100 mg of hollow silica microspheres and place them in a centrifuge tube. Add 0.5 mL of 10 wt% poly(N-isopropylacrylamide) aqueous solution.

[0097] Step 7: After ultrasonic dispersion at a frequency of 20 kHz, poly-N-isopropylacrylamide enters the interior of the hollow silica microspheres through the surface pores to form microcapsules. Let stand for 30 minutes and then evacuate for 10 minutes.

[0098] Step 8: Then, the product (PNIPAM / SiO2) from Step 7 is centrifuged, the sample is ultrasonically washed three times with ethanol, and then dried in a vacuum drying oven at 20°C for 24 hours. The ambient temperature is 20°C.

[0099] In this embodiment, the cigarette sample formed by combining the microcapsules and grooved filter rods prepared in this embodiment with other units is named Example 2 - Grooved Filter Rod. For comparison, the cigarette sample formed by combining the microcapsules and ordinary filter rods (that is, the outer tube has cellulose acetate bundles inside and does not have a groove structure) prepared in this embodiment with other units is named Example 2 - Ordinary Filter Rod.

[0100] Example 3

[0101] I. Preparation of Poly-N-Isopropylacrylamide

[0102] Same as Example 1.

[0103] II. Preparation of γ-(methacryloyloxy)propyltrimethoxysilane modified PNIPAM / SiO2 microcapsules

[0104] Step 1: Take 1.1g of poly(N-isopropylacrylamide), 1.1g of glycerol, 535mg of CTAB (hexadecyltrimethylammonium bromide), and 7.3g of deionized water, and stir them evenly in a beaker. The product is an aqueous phase A solution.

[0105] Step 2: Dissolve 1.285g of surfactant in 50mL of cyclohexane and add a lipophilic water-in-oil (W / O) nonionic surfactant, preferably sorbitan monooleate Span80. Stir well in a beaker; the product is an oil phase solution B.

[0106] Step 3: Take 1.2 mL of this cyclohexane solution, add 500 μL of TEOS (tetraethoxysilane) and 30 μL of hexamethylene diisocyanate, mix well, and the product is monomer phase solution C.

[0107] Step 4: Take a 100ml beaker, add 650μL of aqueous solution A and 6.25g of oil solution B, mix, stir magnetically for 10min at 600rpm, then sonicate for 30min at 80kHz to form a homogeneous reverse emulsion.

[0108] Step 5: Under magnetic stirring, the monomer phase solution C of the product from Step 3 is added dropwise to the product from Step 4 at a rate of one drop every 5 seconds. Stirring continues for 10 minutes. At this point, TEOS tetraethoxysilane hydrolyzes at the oil-water interface to produce silanol groups. Besides self-condensing to form SiO2, these silanol groups also contribute to the formation of SiO2. During this condensation process, 1.65 g of KH570 and 2.01 g of a highly flexible resin, preferably ethyl acrylate monomer, are added. KH570 modifies the double bonds on the surface of the microspheres, and the addition of monomers such as ethyl acrylate allows polymerization to form on the SiO2 double bond surface, thus creating a microcapsule protective film. The mixture is continuously stirred at 250 rpm for 24 hours at 25% room temperature.

[0109] Step 6: Centrifuge the product from Step 5 at 8000 r / min for 30 min and wash with 95% ethanol. Repeat this process three times.

[0110] Step 7: Vacuum drying is performed at 25 degrees Celsius, and the product is white solid PNIPAM / KH570-SiO2 microcapsules.

[0111] In this embodiment, the cigarette sample formed by combining the microcapsules and grooved filter rods prepared in this embodiment with other units is named Example 3 - Grooved Filter Rod. For comparison, the cigarette sample formed by combining the microcapsules and ordinary filter rods (that is, the outer tube has cellulose acetate bundles and does not have a groove structure) prepared in this embodiment with other units is named Example 3 - Ordinary Filter Rod.

[0112] III. Composite of PNIPAM / SiO2 microcapsules and filter rods

[0113] Same as Example 1.

[0114] The composite filter rods from Comparative Example, Example 1, Example 2, and Example 3 were rolled into cigarettes to obtain Sample 1 - Grooved Filter Rod, Sample 1 - Ordinary Filter Rod, Sample 2 - Grooved Filter Rod, Sample 2 - Ordinary Filter Rod, Sample 3 - Grooved Filter Rod, Sample 3 - Ordinary Filter Rod, Comparative Example - Grooved Filter Rod, and Comparative Example - Ordinary Filter Rod. All samples were equilibrated in a constant temperature and humidity chamber for 48 hours, and five cigarettes were selected as test samples according to an average mass ±0.02g. Ordinary cigarettes were used as blank samples. The thermal collapse test of the filter rods was performed using the method of the standard "YC / T 354-2010 Determination of Physical Properties of Cigarettes and Filter Rods - Thermal Collapse".

[0115] Table 1. Ordinary filter rods with microcapsules directly added according to Examples 1, 2, and 3.

[0116]

[0117] Table 2 shows the grooved filter rods with microcapsules added in the form of grooved fasteners according to Examples 1, 2, and 3.

[0118]

[0119] The outer groove (external groove) refers to the groove on the side of the outer pipe within the main groove, while the inner groove (internal groove) refers to the groove on the side of the inner pipe within the main groove (i.e., the filling groove). Figure 2 and Figure 4 (The groove for filling support components).

[0120] As can be seen from the implementation data table, comparing the comparative examples and Examples 1-3, it is evident that the thermal collapse values ​​of the microcapsule filter rods containing PNIPAM are all reduced, and the range is smaller compared to the blank sample. Furthermore, when measuring the outer and inner grooves, the thermal collapse at the inner groove location is larger, which also indirectly indicates that filter rods with more microcapsule-filled portions can reduce the thermal collapse value during aspiration.

[0121] A comparison of Examples 1 and 2 reveals that the silica in the capsule wall contains urethane and azo bonds, which facilitates the decomposition of the capsule wall at high temperatures. Example 1 exhibits better PNIPAM release, resulting in a lower thermal collapse value. Furthermore, sensory evaluation shows that the smoke from Example 1 has a richer aroma.

[0122] A comparison of Examples 3 and 2 reveals that γ-(methacryloyloxy)propyltrimethoxysilane (KH570) can improve the adhesion of silica, increase water resistance, and lower the curing temperature, thereby making the microcapsules easier to decompose at high temperatures, and thus allowing the PNIPAM encapsulated in the microcapsules to release fragrance. Example 3 exhibits better PNIPAM release, resulting in a lower thermal collapse value, and sensory evaluation shows that the smoke from Example 3 has a richer aroma.

Claims

1. A microcapsule for improving the support performance of the outer tube of a filter rod, characterized in that, The capsule wall is made of silica containing urethane and azo bonds or γ-(methacryloyloxy)propyltrimethoxysilane modified silica, and the capsule core is made of poly(N-isopropylacrylamide).

2. A method for preparing the microcapsules according to claim 1, characterized in that, When the capsule wall of the microcapsule is silica containing urethane bonds and azo bonds, it includes the following steps: (a1) Take polyethyleneimine (PEI), poly(N-isopropylacrylamide), glycerol, hexadecyltrimethylammonium bromide (CTAB), and deionized water, stir them in a beaker, and the product is an aqueous solution A. (a2) Dissolve the surfactant in cyclohexane and add a lipophilic water-in-oil nonionic surfactant. Stir in a beaker. The product is an oil phase solution B. (a3) Take this cyclohexane solution, add tetraethoxysilane (TEOS) and hexamethylene diisocyanate and mix. The product is a monomer phase solution C. (a4) Take a beaker, add aqueous solution A and oil solution B, mix, stir, and then ultrasonically emulsify to form a homogeneous reverse emulsion; (a5) Add the monomeric phase solution C of the product from step (a3) ​​dropwise into the product from step (a4) under magnetic stirring, and continue stirring at room temperature with a humidity of 25%. (a6) Centrifuge the product from step (a5) and wash it with ethanol. Repeat this process three times. (a7) Drying yields white solid PNIPAM / PEI-SiO2 microcapsules.

3. The preparation method according to claim 2, characterized in that, In step (a1), the stirring time is 10 min - 15 min; in step (a2), the lipophilic water-in-oil (W / O) type nonionic surfactant is selected from sorbitan monooleate Span80, and the stirring time is 10 min - 15 min; in step (a3), the stirring time is 10 min - 30 min; in step (a4), the magnetic stirring time is 10 min - 30 min, the rotation speed is 600 rpm - 800 rpm, the ultrasonic emulsification time is 30 min - 1 h, and the ultrasonic frequency is 80 kHz - 120 kHz; in step (a6), the centrifugation conditions are: centrifugation at a speed of 8000 r / min - 10000 r / min for 30 min - 40 min; in step (a7), the drying conditions are: vacuum drying at 25℃ for 1.5 h - 3 h.

4. A method for preparing the microcapsules according to claim 1, characterized in that, When the capsule wall is γ-(methacryloyloxy)propyltrimethoxysilane-modified silica, it includes the following steps: (b1) Take poly(N-isopropylacrylamide), glycerol, hexadecyltrimethylammonium bromide (CTAB), and deionized water, stir them in a beaker, and the product is an aqueous solution A. (b2) Dissolve the surfactant in cyclohexane and add a lipophilic water-in-oil nonionic surfactant. Stir in a beaker. The product is an oil phase solution B. (b3) Take this cyclohexane solution, add tetraethoxysilane (TEOS) and hexamethylene diisocyanate and mix. The product is a monomer phase solution C. (b4) Take a beaker, add aqueous solution A and oil solution B, mix, stir, and then ultrasonically emulsify to form a homogeneous reverse emulsion; (b5) Add the monomeric phase solution C of the product from step (b3) dropwise into the product from step (a4) under magnetic stirring, and continue stirring at room temperature with a humidity of 25%. (b6) Centrifuge the product from step (b5) and wash it with ethanol. Repeat this process three times. (b7) Drying yields white solid PNIPAM / KH570-SiO2 microcapsules.

5. The preparation method according to claim 4, characterized in that, In step (b1), the stirring time is 10 min - 15 min; in step (b2), the lipophilic water-in-oil (W / O) type nonionic surfactant is selected from sorbitan monooleate Span80, and the stirring time is 10 min - 15 min; in step (b3), the stirring time is 10 min - 30 min; in step (b4), the magnetic stirring time is 10 min - 30 min, the rotation speed is 600 rpm - 800 rpm, the ultrasonic emulsification time is 30 min - 1 h, and the ultrasonic frequency is 80 kHz - 120 kHz; in step (b6), the centrifugation conditions are: centrifugation at a speed of 8000 r / min - 10000 r / min for 30 min - 40 min; in step (b7), the drying conditions are: vacuum drying at 25℃ for 1.5 h - 3 h.

6. A cigarette filter rod comprising the microcapsules of claim 1, characterized in that, It includes an outer tube (1) and a support component (4) inside the outer tube (1), the support component (4) including a filler and microcapsules dispersed in the filler.

7. The cigarette filter rod according to claim 6, characterized in that, The cigarette filter rod also includes an inner tube (2) and a groove layer (3) located between the outer tube (1) and the inner tube (2), wherein the groove layer (3) has a support member (4) in the cavity on the side near the inner tube (2); The inner tube (2) has a filter rod core (5) inside its cavity; The cross-sectional shape of the trench layer (3) is "U-shaped", "V-shaped" or "trapezoidal".

8. The cigarette filter rod according to claim 6, characterized in that, The filler is a diacetate fiber bundle or a polylactic acid fiber bundle, wherein the amount of microcapsules added to the filler is 0.5 mg microcapsules / 1 mm fiber bundle.

9. The cigarette filter rod according to claim 7, characterized in that, The inner tube (2) is selected from 8000CU-10000CU high-transparency forming paper, the outer tube (1) is selected from forming paper, and the groove layer (3) is selected from non-woven fabric or forming paper.

10. A cigarette comprising a cigarette filter rod according to any one of claims 6-9.

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