Cellulose acetate composition, method for producing the same, and molded product

Abstract

To provide a technique for plasticizer-filled cellulose acetate compositions that exhibit excellent functionality and comply with standards and regulations for food, additives and the like.SOLUTION: A cellulose acetate composition comprises cellulose acetate as a main component and comprises, as a plasticizer, a benzoic acid ester compound.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to plasticizer-filled cellulose acetate compositions and related art. [Background technology]

[0002] Cellulose acetate is a semi-synthetic polymer made by esterifying cellulose with acetic anhydride, and is broadly classified into two types based on the degree of acetylation: the first is cellulose triacetate (CTA), which has an acetylation degree of 59% or more, and the second is cellulose diacetate (CDA), which has an acetylation degree of about 50-59%.

[0003] Cellulose acetate has excellent physical properties, particularly ease of processability and high optical properties, and has therefore been used for many years in the fields of plastics, fibers, films (e.g., photographic films, etc.) In addition, cellulose acetate has been attracting attention in recent years from the viewpoint of the global environment, because it is biodegradable.

[0004] Usually, molded products of cellulose acetate are obtained by flowing a solution of cellulose acetate dissolved in a solvent into a desired shape and then removing the solvent by evaporation or the like. On the other hand, development of cellulose acetate that can be molded by a general method by imparting heat moldability to the cellulose acetate by a compound method in which a plasticizer is filled, instead of the solvent method, is also being considered. Specifically, a composition and molded product in which a glycerin ester plasticizer (triacetin) is contained in cellulose acetate have been proposed (for example, Patent Document 1). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2019-44102 A Summary of the Invention [Problem to be solved by the invention]

[0006] However, when highly volatile triacetin is used as a plasticizer, triacetin volatilizes from the cellulose acetate composition when heated during molding or drying, adversely affecting drying equipment, molding equipment, etc. Furthermore, the volatilization of triacetin during molding causes compositional fluctuations in the cellulose acetate composition, resulting in problems with the productivity and quality stability of molded products.

[0007] In addition, since triacetin is water-soluble, it easily dissolves out of the cellulose acetate composition when immersed in warm water, etc. Therefore, if it is to comply with the standards for warm water dissolution tests in the Ministry of Health, Labor and Welfare's No. 370 test for foods, additives, etc., the amount of triacetin to be contained in the molded product is limited.

[0008] The present invention has been made in consideration of the above circumstances, and an object of the present invention is to provide a technology for a cellulose acetate composition filled with a plasticizer that has excellent functionality while also complying with standards and regulations for foods, additives, etc. [Means for solving the problem]

[0009] The cellulose acetate composition of the present invention contains cellulose acetate as a main component and a benzoate compound as a plasticizer. The method for producing the cellulose acetate composition further comprises the steps of: feeding the plasticizer to the cellulose acetate granules while stirring them to prepare a mixture; and kneading the mixture at a temperature at which the mixture becomes viscous and flowable. Effect of the Invention

[0010] INDUSTRIAL APPLICABILITY The present invention provides a technology for providing a cellulose acetate composition filled with a plasticizer that has excellent functionality while also complying with standards for foods, additives, etc. [Brief description of the drawings]

[0011] [Figure 1] 1 is a schematic diagram of a system illustrating an embodiment of a method for producing a cellulose acetate composition according to the present invention. [Diagram 2]1 is a flowchart showing an embodiment of a method for producing a cellulose acetate composition according to the present invention. [Diagram 3] 11 is a table showing comparative examples and examples in which the effects of the present embodiment are confirmed. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings. Fig. 1 is a schematic diagram of a system 10 showing an embodiment of a method for producing a cellulose acetate composition according to the present invention. Thus, the system 10 comprises a mixing vessel 11 in which a plasticizer 26 is supplied to cellulose acetate granules 25 while stirring them to produce a mixture 27, and a kneader 30 which sets the mixture 27 at a temperature at which it becomes viscous and flows, and kneads the mixture.

[0013] The cellulose acetate may be cellulose acetate (CA) in which the hydroxyl groups of cellulose are esterified with acetic acid. In the present embodiment, the cellulose acetate may be cellulose acetate propionate (CAP) in which the hydroxyl groups of cellulose are esterified with not only acetic acid but also propionic acid. Furthermore, the cellulose acetate may be cellulose acetate butyrate (CAB) in which the hydroxyl groups of cellulose are esterified with not only acetic acid but also butyric acid.

[0014] The average molecular weight of cellulose acetate is 1×10 4 ~100×10 4 , preferably 5 x 10 4 ~75×10 4 , and more preferably 10×10 4 ~50×10 4 However, there is no particular limitation and it can be selected according to the application. The acetylation degree of cellulose acetate (% of bound acetic acid) can be selected from the range of 52.0 to 62.5%. The acetylation degree of cellulose acetate is preferably 59% or less (e.g., 52.0 to 58.0%), particularly 54 to 56% (e.g., about 55%).

[0015] Cellulose acetate granules 25 are fed from a feed vessel 15 to the mixing vessel 11. It is preferable that the average particle size of the cellulose acetate granules 25 is in the range of 0.1 mm to 1.0 mm. If the average particle size is less than 0.1 mm, the granules are difficult to handle and tend to fly up, reducing workability.

[0016] Furthermore, if the maximum particle size is greater than 1 mm, the specific surface area of ​​the cellulose acetate granules 25 supplied to the mixing vessel 11 will be small, and the surfaces of the granules 25 will not be wetted, which may result in separation of the plasticizer 26. However, the average particle size of the cellulose acetate granules 25 applied to the present invention is not limited to the above-mentioned range.

[0017] In order to more preferably adjust the basic physical properties and moldability of the cellulose acetate composition, a mixture of multiple varieties of cellulose acetate granules 25 may be used. Specifically, the cellulose acetate granules 25 may be compounded with granules 25 of other cellulose esters (e.g., organic acid esters such as cellulose propionate and cellulose butyrate, and inorganic acid esters such as cellulose nitrate, cellulose sulfate, and cellulose phosphate).

[0018] The ratio of cellulose acetate granules 25 and plasticizer 26 in mixture 27 is 10 to 100 parts by weight of plasticizer 26 for 100 parts by weight of cellulose acetate granules 25. If the amount of plasticizer 26 is less than 10 parts by weight, the degree of penetration of plasticizer 26 into granules 25 is likely to vary, and if the ratio exceeds 100 parts by weight, granules 25 and plasticizer 26 may separate due to gravity during the standing period in standing space 20.

[0019] Examples of the plasticizer 26 include an adipic acid ester-containing compound, an adipic acid polyester-containing compound, a polyether ester compound, a polyether ester-containing compound, a sebacic acid ester compound, an epoxy ester, a benzoic acid ester, a trimellitic acid ester, a glycol ester compound, an acetate ester, a dibasic acid ester compound, a phosphate ester compound, a phthalic acid ester compound, camphor, a citrate ester, a stearic acid ester, a metal soap, a polyol, a polyalkylene oxide, etc. Among these, a benzoic acid ester is more preferable.

[0020] In addition, organic powders such as cellulose fiber, cellulose powder, CNF (cellulose nanofiber), wood flour, coffee grounds powder, and starch, or inorganic powders such as kaolin, talc, diatomaceous earth, quartz, calcium carbonate, barium sulfate, titanium oxide, and alumina may be used as fillers depending on the performance required of the final product.

[0021] Further additives include heat stabilizers such as hindered phenol-based antioxidants, phosphorus-based heat stabilizers, metal deactivators, and sulfur-based heat stabilizers; weather resistance additives such as liquid and powder triazine-based ultraviolet absorbers, benzophenone-based ultraviolet absorbers, benzoate-based ultraviolet absorbers, and hindered amine-based light stabilizers; dispersants and lubricants such as hydrocarbon-based, fatty acid-based, higher alcohol-based, fatty acid amide-based, metal soap-based, paraffin-based, and ester-based; anti-blocking agents such as silica; and pigments and colorants.

[0022] Examples of fatty acid amide lubricants include stearic acid amide, oleic acid amide, and erucic acid amide. Examples of metal soap lubricants include zinc stearate, magnesium stearate, calcium stearate, and sodium stearate. These lubricants are preferably mixed in an amount of 0.05 to 2.0 parts by weight, and more preferably 0.1 to 0.9 parts by weight, per 100 parts by weight of the total of cellulose acetate and plasticizer.

[0023] The mixing vessel 11 has a rotor 12 that stirs the cellulose acetate granules 25 supplied from a supply vessel 15, and a sprayer 16 that sprays a plasticizer 26 onto the stirred granules 25. By spraying while stirring in this manner, the surfaces of the cellulose acetate granules 25 can be uniformly wetted with the plasticizer 26, and a uniform mixture 27 can be produced.

[0024] As a method of supplying the plasticizer 26 to the cellulose acetate granules 25, the plasticizer 26 may be successively supplied from the supply container 15 while being sprayed, or the repetition of the movement and rest of the rotor 12 may be time-controlled. Although the plasticizer 26 is supplied by spraying as an example, the supply method is not limited as long as it is continuously supplied to the stirred granules 25. For example, the plasticizer 26 may be mixed by flowing it down from a pipe (not shown) instead of being sprayed.

[0025] The mixing vessel 11 is not particularly limited, and a mixer such as a tumbler mixer, a Henschel mixer, a ribbon mixer, a kneader, etc. can be used. The rotation speed of the stirring blade in the mixing vessel 11 is preferably 200 rpm or more, preferably 400 rpm or more, and more preferably 500 rpm or more.

[0026] By realizing such high speed rotation, the temperature of the cellulose acetate granules 25 can be raised by frictional heat of kinetic energy even without providing a heating means in the mixing vessel 11 (although a heating means may be provided). The temperature at this time is adjusted to a range of 40°C to 70°C, preferably 50°C to 60°C. This reduces the viscosity of the plasticizer 26 and improves the wettability, allowing the plasticizer to be mixed evenly and uniformly into the cellulose acetate granules 25.

[0027] The mixture 27 discharged from the mixing container 11 is divided into portions and stored in a plurality of trays 28, and is transported to the still space 20. The still space 20 is preferably an airtight cabinet in order to suppress the volatilization of the plasticizer 26 from the mixture 27. The mixture 27 that has been left still for a specified time in the still space 20 is transported to the kneader 30 while still stored in the trays 28.

[0028] The conveying devices 21, 22 for the trays 28 containing the mixture 27 are exemplified by belt conveyors, but are not particularly limited thereto. The work of conveying the trays 28 containing the mixture 27 may be performed by personnel. In order to reduce the variation in product quality, it is preferable that the standing time from when the mixture 27 is produced until when it is fed into the kneader 30 is set to a constant time.

[0029] In this embodiment, by leaving the mixture 27 at room temperature for 8 hours or more (more preferably 12 hours), the plasticizer 26 in powder form, liquid form, or a mixture thereof can be permeated deep into the cellulose acetate granules 25. As a result, when the mixture 27 is heated and kneaded, the plasticizer 26 can be uniformly dispersed in the cellulose acetate matrix without separation. As a result, the fluidity and tensile elongation can be optimized according to the molding method, and a molded body of cellulose acetate with excellent stability and uniformity can be produced.

[0030] The standing time of the mixture 27 in the standing space 20 is preferably 12 hours or more, but if it is 8 hours or more, it can be said that the penetration of the plasticizer 26 into the granular material 25 approaches an equilibrium state. The upper limit of the standing time is set to 48 hours to avoid the influence of deterioration such as oxidation of the plasticizer 26. The mixture 27 in the standing space 20 is managed in a first-in first-out (FIFO) manner in accordance with the operation schedule of the kneader 30 so that the residence time is constant.

[0031] In the system 10, the stationary space 20 for the tray 28 containing the mixture 27 is not an essential component. The tray 28 containing the mixture 27 may be directly transported from the mixing container 11 to the kneader 30 by the transport device 21.

[0032] The kneader 30 is composed of an input means 31, a drive means 32, a kneading means 33, and a granulating means 35. Here, the kneading means 33 is composed of a cylinder constituting the outside, and a screw (not shown) that rotates inside the cylinder by the driving force of the drive means 32. Here, the cylinder and the screw are set to a temperature in the range of 120°C to 250°C where the mixture 27 viscously flows, or 230°C or lower from the viewpoint of preventing decomposition.

[0033] The mixture 27 transported from the still space 20 is fed into the feeding means 31. The fed mixture 27 is heated and kneaded by a screw rotating around its axis inside a cylinder, and discharged from the most downstream of the kneading means 33. The discharged kneaded mixture 27 is branched into bundles in the granulating means 35, cooled and solidified, and then cut into pellet-shaped cellulose acetate compositions.

[0034] This pellet-like cellulose acetate composition is reheated and melted in a molding machine (not shown) and then injected into a mold to form a bulk molded product, or stretched (e.g., inflation method, calendar processing method, T-die method, blowing method, etc.) to form a film-like molded product, or foamed to form a foamed molded product, thereby serving as a raw material for producing general polymer molded products.

[0035] 1, a continuous type kneader such as a single-screw or multi-screw extruder is shown as an example of the kneader 30, but a batch type kneader or Banbury mixer can also be used. Any kneader 30 can be used as long as it can adjust the temperature of the enclosed space to a temperature at which the mixture 27 becomes viscous and flow and perform stirring (kneading).

[0036] A method for producing a cellulose acetate composition according to an embodiment of the present invention will be described with reference to the flow chart in FIG. 2 (see FIG. 1 as appropriate). First, a plasticizer 26 is supplied to a mixing vessel 11 while stirring cellulose acetate granules 25 to produce a mixture 27 (S11). Next, the mixture 27 is left to stand at room temperature for 8 hours or more in a standing space 20 (S12). Then, the mixture 27 is fed into a kneader 30 and kneaded at a temperature set to cause viscous flow (S13). The kneaded mixture is cooled and solidified to produce a cellulose acetate composition cut into pellets (S14). The pellets are then reheated and melted in a molding machine, and then injected into a mold or the like to produce a molded product (S15). EXAMPLES

[0037] Fig. 3 is a table showing Comparative Examples and Examples 1-5 in which the effects of this embodiment were confirmed. As Comparative Examples, a single use of triacetin, which is widely used as a plasticizer, is used. In Examples 1-5, a benzoic acid ester compound that is likely to comply with standards for foods, additives, etc. is used. In Fig. 3, the basic physical properties of the cellulose acetate composition are measured in accordance with JIS standards applied to ordinary petroleum-based plastics using test pieces prepared in accordance with industrial standards.

[0038] Figure 3 shows the test results indicating that the use of the plasticizers of Examples 1-5 in cellulose acetate compositions provides sufficient functionality for practical use. Note that Figure 3 shows only a portion of the data extracted from a series of extensive test results in which multiple parameters that affect the basic physical properties of cellulose acetate compositions were simultaneously varied to search for optimal conditions.

[0039] Benzoic acid ester compounds that are commercially available as plasticizers 26 include the following. The product names (chemical names) listed in each company's product catalog are transcribed below. Examples include JP120 (benzoic acid glycol ester) from J-Plus Corporation and PB-3A (benzoic acid type) from DIC Corporation.

[0040] (Production of test specimens) The cellulose acetate granules 25 used are a commercially available product with an acetylation rate of 55%. As shown in Fig. 3, in the comparative example and Examples 1-5, the ratio of the plasticizer 26 in the mixture 27 with the cellulose acetate granules 25 is 25% by weight. Furthermore, for a total of 100 parts by weight of the cellulose acetate granules 25 and the plasticizer 26, the blending amounts of the additives are 0.5 parts by weight of the phenol-based antioxidant-1, 0.5 parts by weight of the phosphite-based antioxidant-2, and 0.5 to 0.9 parts by weight of fatty acid amide or metal soap as a dispersant and lubricant.

[0041] Specifically, the mixture 27 was produced by stirring and mixing the cellulose acetate granules 25 while spraying the plasticizer 26 in a high-speed mixer set at 500 rpm / min as the mixing vessel 11. Furthermore, additives (antioxidants, etc.) were mixed into the mixture 27 using a ribbon blender, which is a low-speed mixer set at 120 rpm / min. The mixture 27 was then placed on a tray 28 and allowed to stand at room temperature (25°C) for 8 hours in an airtight state, and then introduced into the kneader 30.

[0042] A CK70HT (screw diameter 70 mm, L / D=44) manufactured by Taiwanese manufacturer CKF was used as the kneading machine 30. The screw rotation speed was set to 300-600 rpm, and the molding temperature was set to 200-220°C.

[0043] The kneaded material discharged from the kneader 30 was formed into pellets and cooled, and then reheated and melted in an injection molding machine and injected into a mold to prepare test pieces for testing various basic performances (MFR, flexural modulus, tensile strength, impact strength). When the prepared test pieces were observed, the transparency was excellent in both the comparative example and Examples 1-5.

[0044] The cellulose acetate composition using the plasticizer of Example 1-5 showed improved bending strength, tensile strength, tensile elongation, and Charpy impact strength compared to the cellulose acetate composition using the plasticizer of Comparative Example. On the other hand, the flexural modulus of Example 1-5 showed a decrease compared to the Comparative Example. Nevertheless, the basic physical properties obtained in Example 1-5 were almost equivalent to those of general-purpose petroleum-based plastics such as PP, PE, and PS.

[0045] (Seat molding) The pellets formed from the mixture 27 of the comparative example and the example were further molded into a sheet, and the results are described below. The molding machine into which the pellets were fed was a single-layer sheet film molding machine manufactured by Tanabe Plastic Machinery Co., Ltd., and was set to a screw diameter of 55 mm, a die width of 500 mm, and a coat hanger die shape. The molding conditions were a molding temperature of 220 to 225°C, a discharge rate of 30 kg / Hr, a film width of 350 mm, a sheet shape of 300 μm in thickness, and a winding speed of 1 to 2 m / min.

[0046] The sheets molded from the pellets of the comparative example and the examples 1-5 all had stable moldability and could be molded continuously. Furthermore, there was no significant difference in the uniformity of the thickness of the sheets, and the film thickness could be arbitrarily set within the range of 100 to 500 μm, and the transparency was excellent and roll winding was possible. When the pellets were fed into the molding machine, weather resistance additives, heat resistance additives, antiblocking agents, and coloring pigments were also fed at the same time, and it was confirmed that this did not cause any problems in the moldability of the sheets.

[0047] (Blown film processing) The pellets formed from the mixture 27 of the comparative example and the example were further molded into an inflation film, and the results are described below. The molding machine into which the pellets were fed was a single-layer inflation film molding machine manufactured by Placo Co., Ltd., and the screw diameter and circular die width were set to 50 mm and 100 mm, respectively. The molding conditions were a molding temperature of 220 to 225°C, a blow ratio of 1.5 to 2.0, a film width of 400 mm, a film thickness of 100 μm, and a winding speed of 2 to 5 m / min.

[0048] The blown films molded from the pellets of the comparative example and Examples 1-5 all had stable bubble shapes, allowing for stable continuous molding. Furthermore, there was no significant difference in the uniformity of the film thickness. The film thickness could be set arbitrarily within the range of 30 to 150 μm, had excellent transparency, and could be rolled up. When the pellets were fed into the molding machine, weather resistance additives, heat resistance additives, antiblocking agents, and coloring pigments were also added at the same time, and it was confirmed that this did not cause any problems in the moldability of the blown film.

[0049] (Blow molding processing) The pellets molded from the mixture 27 of the comparative example and the examples 1-5 were further subjected to a blow molding process. The molding machine into which the pellets were fed was an accumulation type single layer blow molding machine manufactured by Placo Co., Ltd., with a screw diameter of 75 mm, an electric / hydraulic hybrid type, and a product mold set to a 250 ml chemical bottle. The molding conditions were a molding temperature of 220 to 225°C, and a discharge rate of 30 kg / Hr. In the blow molding, the molten pellets are extruded toward the head by the extrusion screw, and are expanded into a cylindrical shape through the ring-shaped outlet of the head, and are inserted into the mold. This pre-molded state before expansion is called a parison.

[0050] The blown molded products made from the pellets of the comparative example and examples 1-5 all had stable melt discharge from the blow molding machine and parison formation, and there was no significant difference in bottle moldability by air injection into the mold, allowing stable continuous molding and excellent transparency. As for the small blown products, there was no significant difference in the smoothness of the appearance and the uniformity of the product thickness between the comparative example and examples 1-5.

[0051] In addition, in all blow molding methods, extrusion blow molding, injection blow molding, and multilayer blow molding, the results are similar in both Comparative Example and Examples 1 to 5. Furthermore, when a 5-liter large bottle was prototyped using another blow molding machine manufactured by Placo Co., Ltd., it was confirmed that it could be molded without any problems in both Comparative Example and Examples 1 to 5. It was also confirmed that adding a color pigment at the same time as adding pellets to the blow molding machine did not cause any problems in moldability.

[0052] (Injection molding processing) The pellets molded from the mixture 27 of the comparative example and the examples 1-5 were further injection molded. The molding machine for feeding the pellets was an electric injection molding machine manufactured by Sodick Co., Ltd., with a screw diameter of 50 mm and a tray-shaped product (200W x 400L x 12mmH, thickness 1.5mm) as the product mold. The molding temperature was set to 220-225°C as the molding condition.

[0053] In the injection molded products molded from the pellets of the comparative example and examples 1-5, the molten material was discharged stably from the nozzle at the tip of the injection molding machine, continuous molding was possible, there was no significant difference in the smoothness of the appearance and the uniformity of the product thickness, and the transparency was also excellent.

[0054] (3D Printing) The results of further 3D printing the pellets formed from the mixture 27 of the comparative example and the examples 1-5 will be described. The molding machine into which the pellets are fed is a 3D molding machine manufactured by Canon Inc., and a fused direct deposition modeling method is adopted. Also, 3D printing molding is possible by the filament molding method as follows. First, a filament with a diameter of 1.75 mm was created using a filament molding machine. Then, as molding conditions, the molding temperature was set to 220 to 225°C, the print head temperature was set to 80 to 105°C, and the print speed was set to 50 mm / s.

[0055] In both the comparative example and the pellets of Examples 1-5, there were no problems with filament molding and 3D printing molding, and the transparency was also excellent. [Explanation of symbols]

[0056] 10... manufacturing system, 11... mixing container, 12... rotating body, 15... supply container, 16... sprayer, 20... stationary space, 21, 22... conveying equipment, 25... cellulose acetate granules (granules), 26... plasticizer, 27... mixture, 28... tray, 30... kneader, 31... feeding means, 32... driving means, 33... kneading means, 35... granulation means.

Claims

1. The main component is cellulose acetate. A cellulose acetate composition comprising a benzoate compound as a plasticizer.

2. The cellulose acetate composition of claim 1, A cellulose acetate composition comprising 10 to 100 parts by weight of the plasticizer based on 100 parts by weight of the cellulose acetate.

3. A method for producing the cellulose acetate composition according to claim 1 or claim 2, comprising the steps of: a step of supplying the plasticizer to the cellulose acetate granules while stirring the granules to form a mixture; and kneading the mixture at a temperature at which the mixture viscously flows.

4. The method for producing a cellulose acetate composition according to claim 3, A method for producing a cellulose acetate composition, wherein the supply of the plasticizer is by spraying.

5. The method for producing a cellulose acetate composition according to claim 3, The method for producing a cellulose acetate composition further comprises a step of allowing the mixture to stand at room temperature for 8 hours or more.

6. A molded product obtained by molding the cellulose acetate composition according to claim 1 or 2.

7. The molded product according to claim 6, which is molded by 3D printing.

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