JP6103602B2 - Chitin nanofiber dispersion plasticizer and method for producing polyolefin microporous stretch film containing chitin nanofiber - Google Patents

Description

The present invention relates to chitin nanofibers dispersed plasticizer and preparation how chitin nanofibers containing polyolefin microporous stretched film, in particular, relates to a novel improvement for obtaining a high pin puncture strength and safety separator.

  In general, chitin nanofiber is one of the nanomaterials. The shell of shrimp and shrimp is deacetylated by chemical treatment and then converted to nanofiber by grinder treatment. The diameter is tens to hundreds of nanometers. Is an ultrafine fiber. Therefore, it has been attracting attention as having a large surface area compared with conventional fibers and exhibiting a new and special function. Polymer materials such as nylon and polyester are mainly used as raw materials for nanofibers. Recently, in consideration of the environment, nanofibers are obtained from biological materials and used actively. Research has been done.

  For example, a hard coat film that has a hard surface with excellent scratch resistance and abrasion resistance has been developed by forming a hard coat layer containing chitin nanofibers based on a curable resin on the base plastic film. (Patent Document 1). A composite material in which chitin nanofibers are impregnated with a curable silicon resin mixture to have a reinforcing effect by nanofibers has also been developed (Patent Document 2).

  In general, chitin nanofibers have a structure having a hydroxyl group, and thus have high hydrophilicity. Once dried, the chitin nanofibers are strongly aggregated by hydrogen bonds between the nanofibers, making it difficult to defibrate again. Therefore, it is common to produce a nano-fibre water slurry by subjecting deacetylated chitin to mechanical treatment in an aqueous medium. Therefore, when mixing with polyolefin, since this water slurry is added in a kneader, it is necessary to perform a dehydration treatment in the extruder. When mixing with polyolefin, chitin nanofibers and polyolefin are kneaded with a super mixer, then extruded onto strands with a twin screw extruder to produce pellets combined with chitin nanofibers. A film was manufactured (Patent Document 3).

  The polyolefin sheet microporous by adding chitin nanofibers in the present invention described later is considered to be used as a separator for non-aqueous secondary batteries, but the manufacturing method of this separator corresponds to a general wet method. To do. In the wet method, a general polyolefin raw material and a plasticizer such as paraffin are kneaded at a temperature equal to or higher than the melting point of both and extruded into a sheet form from a T-die to form a sheet. Furthermore, after stretching the sheet with a stretching machine at a predetermined magnification, the phase-separated plasticizer was removed with an extractant such as methylene chloride to produce a microporous film.

  Next, a method for producing a microporous sheet by dispersing and mixing chitin nanofibers in polyolefin will be described. Conventionally, when a chitin nanofiber and a polyolefin are compounded, the polyolefin material and the chitin nanofiber are kneaded in an extruder, extruded into a strand shape, pelletized, and extruded from a hollow fiber production nozzle. A method for producing a porous hollow fiber membrane has been taken (Patent Document 3).

JP 2012-131201 A JP 2012-62457 A Japanese Patent Laid-Open No. 8-10592 JP-A-4-126352 JP 2004-269579 A

Since the conventional separator for a non-aqueous secondary battery and the manufacturing method thereof are configured as described above, the following problems exist.
Conventionally, lithium dendrite deposited on the negative electrode is the main cause of film breakage of the separator. If the separator breaks, the insulation state cannot be maintained, and abnormal heat generation of the battery due to a short circuit occurs. Therefore, a high puncture strength is required for the separator. In addition, the lithium ion battery for electric vehicles is required to have a high output, and in order to realize this, it is necessary to enlarge the fine pore diameter formed in the separator. However, since the film breakage of the separator occurs starting from the micropores, the piercing strength decreases when the micropore diameter is increased. Because of the abnormality, the fine pore diameter and the puncture strength are in a trade-off relationship, and it has been usually difficult to achieve both.

  Conventionally, in order to improve the heat resistance and strength of the separator, a method of bonding polyethylene and polypropylene (Patent Document 4) and a composite with a reinforcing fiber such as glass fiber or aramid fiber (Patent Document 5) have been proposed. Has been. However, when a blend of polyethylene and polypropylene is used as a raw material, it is difficult to uniformly knead them, and in particular, the molecular weight of polyethylene cannot be increased. Moreover, the laminated porous film is not practical because of its high cost. While glass fibers and aramid fibers have a fiber diameter of 5 μm or more, the thickness of the lithium ion battery separator is only about 5 to 20 μm, so these fibers may cause breakage or film surface irregularities in the film manufacturing process. Therefore, it was difficult to use a conventional reinforcing fiber because the porous film could not be formed well. In addition, the separator must have insulating properties, and there is a problem that carbon fibers cannot be used for strength improvement.

  In order to solve the above-mentioned problems, it has already been confirmed in Patent Document 3 that it is effective to make chitin nanofibers composite with a polyolefin material. In this method, chitin nanofibers and polyolefin are put into a twin-screw extruder and kneaded, and then extruded into strands to produce pellets. Next, using the obtained pellets, extruded from a hollow fiber production nozzle having a double-pipe structure at 220 ° C., poured into a water tank in which water at about 20 ° C. circulates, cooled, and an unstretched hollow fiber product was obtained. obtain. This unstretched hollow fiber-like material is uniaxially stretched between two pairs of Nelson rolls having different rotational speeds at 120 ° C. at a stretch ratio of 5 to obtain a microporous hollow fiber membrane. In order to obtain a microporous membrane by this method, it is necessary to manufacture a raw material in which chitin nanofibers and polyolefin are mixed, but the above-mentioned raw material manufacturing process is added to the conventional wet method, leading to an increase in cost. It was a big barrier to practical use.

  The present invention has been made to solve the above-described problems. Particularly, among the mechanical and thermal characteristics required as a separator for a non-aqueous secondary battery, in particular, the puncture strength and heat resistance are improved. The purpose of the present invention is to provide a high-quality and low-cost chitin nanofiber composite separator.

The chitin nanofiber-dispersed plasticizer according to the present invention is a plasticizer having a molecular weight of 100 to 1000, which is a chitin nanofiber having a fiber diameter of 5 nm to 1 μm after acetylation treatment of at least crab or shrimp chitin. The plasticizer according to claim 1, wherein the plasticizer according to claim 1 is a liquid paraffin, nonane, decane, decalin, paraxylene, undecane, a linear or cyclic aliphatic hydrocarbon of dodecane, and Mineral oil fractions corresponding to these boiling points, and dibutyl phthalate, dioctyl phthalate are composed of one or several kinds of phthalates that are liquid at room temperature, and are described in claim 1 or 2 The chitin nanofiber powder in the plasticizer is composed of 0.01 to 30 weight percent, The chitin nanofibers described in 1) have a structure in which water after defibration is removed by hydroxyl substitution by solvent replacement with ethanol, ethyl acetate, normal hexane, or ethyl acetate multiple times, and the chitin according to the present invention A process for producing a polyolefin microporous stretched film containing nanofibers is a process of obtaining a polyolefin resin composition by melt-kneading with polyolefin using the chitin nanofiber-dispersed plasticizer according to any one of claims 1 to 4, The process of extruding a polyolefin resin composition, the process of stretching the resulting extruded product to form a film, the process of extracting a plasticizer from the film, and after stretching the plasticizer, stretch the sheet at a temperature below the melting point of the polyolefin raw material Ru method der comprising the step of performing heat for suppressing the contractile while.

Producing how chitin nanofibers dispersed plasticizer and chitin nanofibers containing polyolefin microporous stretched film according to the present invention, since it is constructed as described above, it is possible to obtain the following effects.
In other words, by using a plasticizer in which chitin nanofibers are dispersed in paraffin, it is combined with polyolefin by the same method as the conventional wet method, so that the puncture strength is particularly high compared to the separator manufactured by the conventional method. A separator can be obtained and a highly safe separator can be obtained. In addition, since chitin nanofibers and polyolefin can be combined with only one twin-screw kneader, the yield of chitin in the composite separator can be easily controlled, and uniform dispersion in polyolefin is possible. It becomes.

It is a general-view figure of the small neater used for the manufacturing method of the polyolefin microporous stretched film containing chitin nanofiber of this invention. It is a general-view figure which shows the sheet forming apparatus used for the sheet | seat shaping | molding in this invention. It is a general-view figure which shows the extending | stretching apparatus used for film stretching in this invention. It is a composition figure which shows the SEM image of the microporous film manufactured in Example 1 of this invention. It is a composition figure which shows the SEM image of the microporous film manufactured in Example 2 of this invention. FIG. 3 is a composition diagram showing an SEM image of a microporous film made of only the polyolefin of Comparative Example 1. 4 is a composition diagram showing an SEM image of a commercially available PE microporous film of Comparative Example 2. FIG. 4 is a composition diagram showing an SEM image of a commercially available PP microporous film of Comparative Example 3. FIG.

The present invention has made it possible to make a chitin nanofiber composite separator with improved puncture strength and heat resistance, among mechanical and thermal properties required as a separator for a non-aqueous secondary battery, with high quality and low cost. and to provide a manufacturing how chitin nanofibers dispersed plasticizer and chitin nanofibers containing polyolefin microporous stretched film.

Hereinafter, chitin nanofibers dispersed plasticizers of the present invention and the preferred embodiment of the manufacturing how chitin nanofibers containing polyolefin microporous stretched film is described in conjunction with the drawings.
In the present invention, in order to produce a chitin nanofiber composite separator, by dispersing chitin nanofibers in a plasticizer such as paraffin used in a general wet method, without changing the conventional apparatus configuration, This makes it possible to supply a separator for a non-aqueous secondary battery having high strength and high heat resistance.
In the present invention, the chitin substance contained in crab and shrimp shells is deacetylated by chemical treatment, and then subjected to defibration treatment by facing collision treatment, high pressure homogenizer treatment, etc., and chitin nanofibers are highly dispersed. A slurry is produced. In this slurry state, it is impossible to add to a plasticizer such as liquid paraffin. Therefore, after replacing the solvent with a chemical, liquid paraffin-dispersed chitin nanofibers were obtained.
First, the slurry after the defibration process is put in ethanol and centrifuged for 20 minutes. A. After the solid content of the solution is allowed to settle, the supernatant is removed. B. Add the same amount of ethanol as the removed amount and stir to make a uniform solution. C. This is centrifuged for 20 minutes. As described above, A. B. C. Repeat step 3 or more times. Thereafter, the solid content of the solution was again settled, and a liquid paraffin-dispersed chitin nanofiber was obtained by adding a plasticizer such as liquid paraffin.

  The liquid paraffin-dispersed chitin nanofibers and polyolefin obtained as described above are put into a twin screw extruder or a pressure kneader 10 in FIG. 1 and melted and kneaded, and then the T die of the sheet forming apparatus 20 in FIG. A sheet in which paraffin and polyolefin are phase-separated is produced by further extruding into a sheet and cooling and forming with a cast roll. The sheet was stretched simultaneously or sequentially with the stretching machine 30 of FIG. 3 and stretched to a predetermined magnification, and then the plasticizer was removed with an extractant such as methylene chloride, and after heat setting to remove residual stress, micropores were formed. Get a film. This film can be used as a separator for non-aqueous secondary batteries.

By carrying out the above-mentioned adjustment, a large amount of amino groups can be retained, so that dispersibility in the plasticizer is increased. In addition, the polyolefin resin in this invention uses the polyolefin resin used for normal extrusion, injection, inflation, blow molding, etc., ethylene, propylene, 1-butene, 4-methyl-1-pentene, 1-hexene, and Homopolymers and copolymers such as 1-octene, multistage polymers and the like can be used.
In addition, polyolefins selected from the group of these homopolymers, copolymers, and multistage polymers can be used alone or in combination. Representative examples of the polymer include low density polyethylene, linear low density polyethylene, medium density polyethylene, high density polyethylene, ultrahigh molecular weight polyethylene, isotactic polypropylene, atactic polypropylene, ethylene-propylene random copolymer, polybutene. And ethylene propylene rubber. When using the microporous membrane of the present invention as a separator for a non-aqueous secondary battery, it is preferable to use a resin mainly composed of high-density polyethylene because of its low melting point and high strength required performance. From the viewpoint of properties, the polyethylene resin preferably occupies 50% by weight or more of the resin component. Further, when the amount of the ultra-high-molecular-weight polyolefin having a molecular weight of 1 million or more exceeds 10 parts by weight, it becomes difficult to uniformly knead, and therefore the amount is preferably 10 parts by weight or less.

The chitin nanofiber used in the present invention has a fiber diameter on the nano order and has an amino group on the fiber surface. By having an amino group, uniform dispersibility in the plasticizer and polyolefin is increased, and kneading and sheeting are facilitated. Thereby, it becomes possible to express the puncture strength superior to the conventional separator characteristics.
In addition to liquid paraffin and the like, the plasticizer used in the present invention is nonane, decane, decalin, paraxylene, undecane, a linear or cyclic aliphatic hydrocarbon of dodecane, and a mineral oil fraction having a boiling point corresponding to these, In addition, phthalic acid esters which are liquid at room temperature such as dibutyl phthalate and dioctyl phthalate can be used.

The film formed by combining the chitin nanofibers of the present invention may be a single layer or a multilayer. In the case of using multiple layers, the chitin nanofiber composite film may be contained in at least one of the films to be formed. The film thickness after stretching is preferably in the range of 5 μm to 50 μm. If the film thickness is 5 μm or more, the mechanical strength is sufficient, and if it is 50 μm or less, the occupied volume of the separator is reduced, which is advantageous from the viewpoint of increasing the capacity of the battery. The Gurley value is preferably in the range of 50 seconds / 100 cc or more and 1000 seconds / 100 cc or less.
Therefore, the present invention uniformly disperses chitin having an amino group in a plasticizer and kneads it with a polyolefin, thereby converting the chitin lump into a nanofiber and a composite with the polyolefin. A microporous sheet for a non-aqueous secondary battery can be manufactured without changing the configuration and the process.

Next, Example 1 and Example 2 in the present invention will be described with reference to the drawings. In addition, each physical property value obtained by the present invention is a value obtained by the following method.
Puncture strength: The produced sheet was cut into a 50 mm × 50 mm square, and the maximum load when the needle penetrated was measured using an automatic puncture strength meter (KES-FB3-AUTO). In addition, 10 points | pieces were measured with the same sheet | seat, and the average value was computed.
Gurley value: The prepared sheet was cut into a 50 mm × 50 mm square, and measurement was performed using a Gurley automatic measuring machine (manufactured by TESTING MACHINES INC). In this measurement, the time required for 100 cc of air stipulated by JIS P8177 to pass through the sheet was taken as the Gurley value.
Surface observation: The produced sheet was subjected to platinum deposition with a thickness of 0.3 nm using a vacuum deposition apparatus (E-1045 manufactured by Hitachi High-Tech). The surface of this sheet was observed using FE-SEM (SUPRA55VP manufactured by Carl Zeiss).
Porosity and film thickness: As for the film thickness, a sample was cut into a 50 × 50 mm square, 10 points on each part of the sheet were measured using a micrometer, and the average value was taken as the film thickness. The porosity was calculated from the actual weight of the sheet and the theoretical weight calculated from the density and volume.

Example 1
As raw materials, paraffin in which chitin nanofibers of 5 nm to 1 μm shown in Table 1 are highly dispersed in liquid paraffin P-350P (Molesco) and ultra high molecular weight polyethylene Mitsui Hi-Z Million 030S (Mitsui Chemicals) are used. It was. 30 parts by weight of the polyethylene was mixed with 70 parts by weight of the paraffin and swelled at room temperature for 1 hour. These were kneaded by a kneader 10 shown in FIG. 1, and then a sheet having a thickness of 1 mm was formed by a sheet forming apparatus 20 comprising a press machine shown in FIG. This sheet was simultaneously biaxially stretched by a stretching machine 30 shown in FIG. Tables 2 and 3 show the kneading conditions and stretching conditions. The film produced by simultaneous biaxial stretching was degreased with liquid paraffin with methylene chloride and subjected to heat setting at 120 ° C. for 5 minutes to remove residual stress in the film.

(Example 2)
In the method of Example 1, a solution in which chitin nanofibers were dispersed in methanol was used. The rest is the same as in the first embodiment.
(Comparative Example 1)
A sheet was produced from the raw material not using chitin nanofibers by the method of Example 1. The raw material composition is shown in Comparative Example 1 in Table 1. The rest is the same as in the first embodiment.
(Comparative Example 2)
The obtained commercially available wet separator A was designated as Comparative Example 2.
(Comparative Example 3)
The commercially available dry separator B was used as Comparative Example 3.

Results Comparison FIGS. 4 and 5 show SEM images of separators produced under the conditions of Examples 1 and 2. FIG. FIG. 5 shows a sample using a solution in which chitin nanofibers are dispersed in methanol, and there are many lumps that form nodes in each part. It seems that chitin nanofibers are aggregated in this part, and it is estimated that the dispersibility in polyolefin is bad.
FIG. 4 uses a dispersion obtained by adding chitin nanofibers to paraffin in advance. Compared to FIG. 5, FIG. 4 does not show almost bulky crystals, and it is presumed that the dispersion state is good.
Table 4 shows the separator characteristics of Examples 1 and 2 and Comparative Examples 1 to 3. When the results of Examples 1 and 2 are compared, the Gurley value that affects the battery characteristics of the lithium ion battery is lower in Example 1. This indicates that lithium ions easily pass through. Next, when comparing the porosity, the value of Example 1 is large, indicating that many fine holes are formed. On the other hand, the separator of Example 2 has a porosity of only about 10% as compared with Example 1, but the Gurley value is about twice as large. This indicates that the fine holes formed in the separator are not through holes. This is presumed to be because the lump crystals confirmed in the SEM observation results of Example 2 are the resistance.
The puncture strength indicates the strength at the time of film breakage due to contamination of lithium ion dendrites caused by deterioration with time or foreign matters during battery production. In Example 1, the puncture strength is greatly increased as compared with Example 2, which is considered to be an effect due to the high dispersion state of chitin nanofibers.

Comparative Example 1 is a microporous film formed only of polyolefin. Compared with Example 1, all the characteristic values of the Gurley value, the puncture strength, and the porosity are improved. Next, when Example 2 and a comparative example are compared, characteristics other than the porosity are deteriorated. This is thought to be due to the fact that the chitin nanofibers are not well dispersed and the microporous formation is not uniformly formed. FIG. 6 shows an SEM image of Comparative Example 1. Bulky crystals are observed in each part, which is considered to be the cause of the high Gurley value. Furthermore, the separator made only of polyolefin could not be stretched at the stretch ratio performed in Example 1.
The comparative example 2 is a characteristic value of the PE separator manufactured by the obtained general wet method. Compared with Example 1, the characteristic values other than the Gurley value are bad. Since a general wet PE separator is continuously manufactured using an extruder, the characteristic value is higher than that of a separator manufactured by a kneader as in Example 1. In particular, the phase separation between paraffin and polyolefin greatly affects the formation of micropores, so that it is difficult to form through holes. This is considered to be the reason why the Gurley value of Example 1 is worse than that of Comparative Example 2. The characteristic value of Comparative Example 2 is lower in puncture strength than that of Example 1. It shows that higher strength can be obtained than commercially available PE separators by highly dispersing chitin nanofibers. FIG. 7 shows an SEM image of Comparative Example 2. A thick crystal structure is seen from the figure, and it can be confirmed that the pore shape is non-uniform.
The comparative example 3 shows the characteristic value of PP separator manufactured by the obtained general dry method. Compared to Example 1, the Gurley value is low and lithium ions easily pass through, but the puncture strength is accordingly low, and it is easy to break. Compared with Example 1, the characteristic values shown in Comparative Examples 2 and 3 showed a large difference particularly in the value of piercing strength. This indicates that the characteristics are improved by highly dispersing chitin nanofibers. The SEM image of the comparative example 3 of FIG. 8 is shown. From FIG. 8, it can confirm that the site | part which is not partially opened, and it can confirm that a shape is nonuniform.

The gist of the present invention described above is as follows.
That is, after chitin of at least crab or shrimp is acetylated, chitin nanofibers having a fiber diameter of 5 nm to 1 μm are uniformly dispersed in a plasticizer having a molecular weight of 100 to 1000 by a fibrillation means. Chitin nanofiber dispersed plasticizers, and the above-mentioned plasticizers include liquid paraffin, nonane, decane, decalin, paraxylene, undecane, linear or cyclic aliphatic hydrocarbons of dodecane, and boiling point. A chitin nanofiber dispersion plasticizer characterized by using one or several kinds of liquid phthalate esters at room temperature of mineral oil fractions corresponding to the above and dibutyl phthalate and dioctyl phthalate, The chitin nanofiber powder in the preparation is 0.01 to 30 weight percent Chitin nanofiber dispersion plasticizer, and as the chitin nanofiber described above, the water after defibration treatment was hydroxyl-removed by solvent replacement multiple times with ethanol, ethyl acetate, normal hexane, or ethyl acetate. A step of obtaining a polyolefin resin composition by melt-kneading with polyolefin using the chitin nanofiber dispersion plasticizer described above, and extruding the polyolefin resin composition A process, a process of stretching the obtained extrusion-molded body to form a film, a process of extracting a plasticizer from the film, and after extracting the plasticizer, for stretching the sheet at a temperature below the melting point of the polyolefin raw material to suppress shrinkage Polyolefin fine particles containing chitin nanofibers, characterized by comprising a process of heat setting Ru manufacturing method der porous stretched film.

  Therefore, in the above-mentioned present invention, the conventional pellet manufacturing process can be shortened by previously mixing and swelling chitin nanofibers with a plasticizer such as liquid paraffin. In addition, since chitin nanofibers are highly dispersed in paraffin, it is possible to apply the conventional wet manufacturing method as it is. In the wet process, paraffin and polyolefin are melted and kneaded with a pressure kneader or an extruder, then extruded into a sheet shape from the T-die of the sheet forming apparatus 20 in FIG. 2, and cooled by a cast roll. A sheet in which paraffin and polyolefin are phase separated is produced. The sheet is stretched simultaneously or sequentially with a stretching machine 30 in FIG. 3 and stretched to a predetermined magnification, and then the plasticizer is removed with an extractant such as methylene chloride, and further heat setting is performed to remove residual stress, thereby forming micropores. Film is obtained. This film can be used as a separator for non-aqueous secondary batteries.

Producing how chitin nanofibers dispersed plasticizer and chitin nanofibers containing polyolefin microporous stretched film according to the present invention, after the acetylation process at least crab or chitin shrimp in fibrillation treatment method, the fiber diameter 5nm~1μm Because the chitin nanofiber dispersed plasticizer in which the chitin nanofiber is uniformly dispersed in a plasticizer having a molecular weight of 100 to 1000 is used, the mechanical properties required as a separator for a lithium ion battery (non-aqueous secondary battery) In addition, among the thermal characteristics, in particular, a chitin nanofiber composite separator with improved puncture strength and heat resistance can be provided at high quality and at low cost.

10 Pressure Kneader 20 Sheet Forming Device 30 Stretching Machine

Claims (5)

  After chitin of at least crab or shrimp is acetylated, chitin nanofibers having a fiber diameter of 5 nm to 1 μm are uniformly dispersed in a plasticizer having a molecular weight of 100 to 1000 by defibrating treatment means. Chitin nanofiber dispersion plasticizer.   The plasticizer according to claim 1 includes liquid paraffin, nonane, decane, decalin, paraxylene, undecane, a linear or cyclic aliphatic hydrocarbon of dodecane, a mineral oil fraction having a boiling point corresponding to these, and dibutyl A chitin nanofiber-dispersed plasticizer characterized by using one kind or a mixture of several kinds of phthalates that are liquid at room temperature of phthalate or dioctyl phthalate.   A chitin nanofiber dispersion plasticizer, wherein the chitin nanofiber powder in the plasticizer according to claim 1 or 2 is 0.01 to 30 weight percent.   The chitin nanofiber according to claim 1, wherein the water after fibrillation is subjected to solvent removal with ethanol, ethyl acetate, normal hexane, or ethyl acetate multiple times to remove hydroxyl groups. Fiber dispersion plasticizer.   A step of obtaining a polyolefin resin composition by melt-kneading with polyolefin using the chitin nanofiber-dispersed plasticizer according to any one of claims 1 to 4, and a step of extruding the polyolefin resin composition. A process of stretching an extruded product to form a film, a process of extracting a plasticizer from the film, and a process of heat setting to suppress shrinkage while stretching the sheet at a temperature below the melting point of the polyolefin raw material after extracting the plasticizer A process for producing a polyolefin microporous stretched film containing chitin nanofibers, comprising:

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