Method for producing sheet-like extrusion molded product

Abstract

An object of the present disclosure is to provide a method for producing a sheet-like extrusion-molded product configured to suppress wear of an extrusion molding machine, improve moldability of a thermoplastic resin composition, and produce a sheet-like extrusion-molded product having a small linear expansion coefficient. A method for producing a sheet-like extrusion molded product includes: kneading a thermoplastic resin composition; and carrying out extrusion molding on the thermoplastic resin composition through a mold. The thermoplastic resin composition includes a thermoplastic resin and a filler. The thermoplastic resin contains a polypropylene having an MFR of 20 g / 10 min or more and 60 g / 10 min or less at a temperature of 230 DEG C and a load of 2.16 kgf. The filler comprises wood flour and talc. The content of the filler is 60 parts by mass or more and 72 parts by mass or less per 100 parts by mass of the total of the thermoplastic resin and the filler. The content of the wood flour is 20 parts by mass or more and 70 parts by mass or less with respect to 100 parts by mass of the total filler.

Description

Technical Field

[0001] This disclosure relates to a method for producing sheet extruded products. Background Technology

[0002] Patent Document 1 discloses a resin composition containing inorganic fillers. This resin composition containing inorganic fillers comprises a thermoplastic resin and inorganic fillers. Furthermore, wood flour is mixed with the resin composition containing inorganic fillers. Based on the total mass of the resin composition containing inorganic fillers, the content of inorganic fillers is 40% by mass or greater.

[0003] The following problems exist: When using the resin composition containing inorganic fillers as described in Patent Document 1 in an extrusion molding process, the extruder is prone to wear. Furthermore, when adjusting the composition of the resin composition containing inorganic fillers in an attempt to suppress extruder wear, the molding properties of the resin composition may decrease, or the coefficient of linear expansion of the molded product may increase. Reference List Patent documents

[0004] Patent Document 1: JP 2004-203982 A Invention Summary

[0005] The purpose of this disclosure is to provide a method for producing sheet extruded products, the method being configured to suppress wear on the extruder, improve the molding properties of the thermoplastic resin composition, and produce sheet extruded products with a small coefficient of thermal expansion.

[0006] A method for producing sheet-like extruded products according to one aspect of this disclosure includes: kneading a thermoplastic resin composition; and then extruding the thermoplastic resin composition through a die. The thermoplastic resin composition comprises a thermoplastic resin and fillers. The thermoplastic resin comprises polypropylene having an MFR of greater than or equal to 20 g / 10 min and less than or equal to 60 g / 10 min at a temperature of 230°C and a load of 2.16 kgf. The fillers include wood flour and talc. The filler content is greater than or equal to 60 parts by mass and less than or equal to 72 parts by mass relative to a total of 100 parts by mass of thermoplastic resin and fillers. The wood flour content is greater than or equal to 20 parts by mass and less than or equal to 70 parts by mass relative to 100 parts by mass of all fillers. Description of the implementation plan

[0007] 1. Overview Typically, an extrusion molding machine is used for extrusion molding. An extrusion molding machine includes, for example, an extruder, a gear pump, a die, a cooler, a traction machine, and a cutter.

[0008] Examples of extruders here include single-screw extruders containing one screw and twin-screw extruders containing two screws. The twin-screw extruders include co-rotating twin-screw extruders and counter-rotating twin-screw extruders.

[0009] A gear pump is positioned between the extruder and the die. A gear pump is a pump that uses the engaging parts of gears to transport molten resin from the extruder to the die.

[0010] The mold, particularly the die, is a cover attached to the gear pump. In this embodiment, for example, a T-die (hanger die) is used. This allows the molten resin to be extruded in sheet form.

[0011] A cooling machine cools and cures the resin extruded in sheet form. In this embodiment, for example, a three-roll cooling roller is used.

[0012] A traction machine pulls out a solidified, elongated sheet-like extruded product. Here, the surface of the sheet-like extruded product can be corona-treated, and then decorative sheets can be attached to that surface. Examples of decorative sheets include sheets with textured or stone patterns already screen-printed on them.

[0013] The cutter cuts the elongated sheet extruded product (including products with decorative pieces already attached) to a predetermined length. The resulting sheet extruded product is used, for example, as flooring material.

[0014] Here, when the resin composition containing inorganic fillers of Patent Document 1 is used to produce sheet extrusion products, the screw of the extruder or the gears of the gear pump will wear. As mentioned above, when the extruder wears out, it is difficult to produce sheet extrusion products stably, and therefore, components such as the screw and gears must be replaced periodically every few months to every six months. As a result, operating costs such as maintenance costs increase.

[0015] Therefore, the inventors sought to identify the causes of wear in extrusion molding machines in order to suppress wear. Therefore, regarding the resin composition containing inorganic fillers in Patent Document 1, the inventors believe that a high content of inorganic fillers (especially mica) is one of the causes of wear.

[0016] However, inorganic fillers are necessary, for example, to ensure the strength of sheet extruded products. Therefore, simply reducing the content of inorganic fillers is not a solution. Reduced inorganic filler content can affect the moldability and / or coefficient of linear expansion of sheet extruded products.

[0017] In view of the foregoing, the inventors have developed a method for producing sheet extruded products as described below. Specifically, the method for producing sheet extruded products according to this embodiment includes kneading a thermoplastic resin composition; and then extruding the thermoplastic resin composition through a die. The thermoplastic resin composition comprises a thermoplastic resin and fillers.

[0018] Here, the thermoplastic resin comprises polypropylene having an MFR of greater than or equal to 20 g / 10 min and less than or equal to 60 g / 10 min at a temperature of 230°C and a load of 2.16 kgf.

[0019] The filler comprises wood flour and talc. Relative to 100 parts by weight of the total thermoplastic resin and filler, the filler content is greater than or equal to 60 parts by weight and less than or equal to 72 parts by weight. Relative to 100 parts by weight of all filler, the wood flour content is greater than or equal to 20 parts by weight and less than or equal to 70 parts by weight.

[0020] When the above conditions are met, wear on the extrusion molding machine can be suppressed, the details of which will be described later. The molding properties of thermoplastic resin compositions can be improved. Sheet extruded products with a low coefficient of thermal expansion can be produced on a production line.

[0021] 2. Details The method for producing sheet extruded products according to this embodiment will now be described.

[0022] The sheet-like extruded product according to this embodiment is produced by an extrusion molding method. A known extrusion molding machine can be used for this purpose.

[0023] That is, the method for producing sheet extruded products according to this embodiment includes: kneading a thermoplastic resin composition by, for example, the above-described extrusion molding machine, and then extruding the thermoplastic resin composition through a die (die head).

[0024] The thermoplastic resin composition according to this embodiment comprises a thermoplastic resin and a filler.

[0025] The thermoplastic resin comprises polypropylene having a melt flow rate (MFR) greater than or equal to 20 g / 10 min and less than or equal to 60 g / 10 min at a temperature of 230°C and a load of 2.16 kgf. Here, MFR is the melt mass flow rate and can be measured based on, for example, JIS K7210. The MFR of polypropylene is preferably greater than or equal to 25 g / 10 min. The MFR of polypropylene is preferably less than or equal to 50 g / 10 min.

[0026] When the MFR of polypropylene is less than 20 g / 10 min, the molten resin is not easily extruded from the mold, and the extrusion speed decreases, which reduces the productivity of sheet extrusion products. When polypropylene with an MFR greater than 60 g / 10 min is used, the fluidity is too high, which leads to large deviations in the thickness of sheet extrusion products. In addition, this type of polypropylene is not easy to obtain. Therefore, the upper limit of the MFR of polypropylene is set at 60 g / 10 min.

[0027] Thermoplastic resins may include thermoplastic resins other than polypropylene, provided that the flowability of the thermoplastic resin composition is not impaired. Examples of thermoplastic resins other than polypropylene include, but are not particularly limited to, polyethylene, polybutene, polystyrene, polyvinyl chloride, polycarbonate, polyethylene terephthalate, polyamide 66, and polyamide 6.

[0028] The fillers include wood flour and talc. As mentioned above, the wood flour is included in the thermoplastic resin composition, which allows for a reduction in the coefficient of linear expansion of the sheet extruded product. Furthermore, talc has a Mohs hardness of 1, which is low among standard minerals; therefore, when talc is included in the thermoplastic resin composition, it ensures the strength of the sheet extruded product while inhibiting wear on the extruder (especially the screw and / or gears).

[0029] Examples of wood flour include, but are not limited to, sawdust from coniferous and / or broadleaf wood. Examples of coniferous wood include, but are not particularly limited to, *Tsuga heterophylla* (Western hemlock).

[0030] The wood flour includes wood flour that passes through a preferably 30-mesh sieve (sieve aperture size: 500 μm), more preferably a 36-mesh sieve (sieve aperture size: 425 μm), and even more preferably a 60-mesh sieve (sieve aperture size: 250 μm). As described above, the wood flour with a small particle size is included in the thermoplastic resin composition, which allows for a reduction in the coefficient of linear expansion of the sheet extruded product.

[0031] The wood flour content is greater than or equal to 20 parts by weight, preferably greater than or equal to 40 parts by weight and less than or equal to 70 parts by weight, relative to 100 parts by weight of all fillers. When the wood flour content is less than 20 parts by weight, the coefficient of linear expansion of the sheet extruded product can be increased. In particular, a wood flour content greater than or equal to 40 parts by weight allows for a decrease in the coefficient of linear expansion of the sheet extruded product. In contrast, when the wood flour content is greater than 70 parts by weight, the thermoplastic resin composition becomes difficult to mold.

[0032] The wood flour content is preferably greater than or equal to 35 parts by weight and less than or equal to 45 parts by weight relative to a total of 100 parts by weight of thermoplastic resin and filler. This is beneficial for the molding of the thermoplastic resin composition and can also reduce the coefficient of linear expansion of sheet extruded products.

[0033] The average particle size of talc is preferably greater than or equal to 12 μm, more preferably greater than or equal to 14 μm. Here, average particle size refers to the volume-based median diameter (D50) obtained by particle size distribution measurement using laser diffraction. The average particle size of talc is preferably less than or equal to 50 μm, more preferably less than or equal to 30 μm. This allows for a reduction in the coefficient of linear expansion of the sheet extruded product.

[0034] The filler may also include mica. Mica has a Mohs hardness of 2.5 to 3. In contrast, talc has a Mohs hardness of 1. As mentioned above, the Mohs hardness of mica is higher than that of talc. Therefore, further inclusion of mica in the filler can enhance the strength of sheet extruded products.

[0035] When the filler further includes mica, the mica content is preferably greater than or equal to 1 part by weight and less than or equal to 10 parts by weight relative to a total of 100 parts by weight of thermoplastic resin and filler. As mentioned above, when the mica content is less than or equal to 10 parts by weight, wear on the extrusion molding machine can be suppressed. Furthermore, when the mica content is greater than or equal to 1 part by weight, the strength of the sheet extruded product can be improved.

[0036] The filler content is greater than or equal to 60 parts by weight and less than or equal to 72 parts by weight relative to a total of 100 parts by weight of thermoplastic resin and filler. When the filler content is less than 60 parts by weight, the thermoplastic resin composition has too high a flowability during extrusion molding, which leads to difficulty in molding. In contrast, when the filler content is greater than 72 parts by weight, the thermoplastic resin composition has too low a flowability during extrusion molding, which also leads to difficulty in molding.

[0037] Therefore, thermoplastic resin compositions can be obtained by mixing and kneading thermoplastic resins and fillers, for example, by using a mixer such as a Henschel mixer. In this case, the thermoplastic resin composition has an MFR preferably greater than or equal to 2.0 g / 10 min and less than or equal to 6.0 g / 10 min at a temperature of 230°C and a load of 2.16 kgf.

[0038] Next, the thermoplastic resin composition is kneaded, for example, using an extruder, and then extruded through a die (die). This yields a sheet-like extruded product. The thickness of the sheet-like extruded product is greater than or equal to 0.5 mm and less than or equal to 3 mm, but is not limited thereto. As described above, decorative sheets can be attached to the surface of the sheet-like extruded product.

[0039] 3. Aspects As can be seen from the above implementation plan, this disclosure includes the following aspects.

[0040] The first aspect is a method for producing sheet-like extruded products, the method comprising: kneading a thermoplastic resin composition; and then extruding the thermoplastic resin composition through a die. The thermoplastic resin composition comprises a thermoplastic resin and fillers. The thermoplastic resin comprises polypropylene having an MFR of greater than or equal to 20 g / 10 min and less than or equal to 60 g / 10 min at a temperature of 230°C and a load of 2.16 kgf. The fillers comprise wood flour and talc. The filler content is greater than or equal to 60 parts by mass and less than or equal to 72 parts by mass relative to a total of 100 parts by mass of the thermoplastic resin and fillers. The wood flour content is greater than or equal to 20 parts by mass and less than or equal to 70 parts by mass relative to 100 parts by mass of all fillers.

[0041] This aspect enables extrusion molding machines to suppress wear. It can improve the molding properties of thermoplastic resin compositions. It can produce sheet extruded products with a small coefficient of linear expansion.

[0042] The second aspect is a method for producing sheet-like extruded products based on the first aspect. In the second aspect, the filler also includes mica. The mica content is less than 10 parts by weight relative to 100 parts by weight of the total thermoplastic resin and filler.

[0043] In this regard, further inclusion of mica in the filler enhances the strength of the sheet extruded product. Furthermore, when the mica content is less than or equal to 10 parts by weight, wear on the extruder can be suppressed.

[0044] The third aspect is a method for producing sheet-like extruded products based on the first or second aspect. In the third aspect, the content of wood flour is greater than or equal to 40 parts by mass and less than or equal to 70 parts by mass relative to 100 parts by mass of all fillers.

[0045] In this respect, a wood flour content of 40 parts by weight or more reduces the coefficient of linear expansion of the sheet extruded product. A wood flour content of 70 parts by weight or less suppresses the reduction in the molding properties of the thermoplastic resin composition.

[0046] The fourth aspect is a method for producing sheet-like extruded products based on any one of the first to third aspects. In the fourth aspect, the wood flour comprises wood flour that has passed through a 60-mesh sieve.

[0047] This can reduce the coefficient of linear expansion of sheet extrusion products. Example

[0048] The present disclosure will now be described in detail with reference to the embodiments. The present disclosure is not limited to the following embodiments.

[0049] 1. Sample (1) Materials The following materials were mixed in the proportions shown in Table 1 using a Henschel mixer. This yielded a thermoplastic resin composition.

[0050] <Thermoplastic Resins> Polypropylene 1: Product name "BC03B" (MFR: 30g / 10min) manufactured by Polypropylene Corporation of Japan. Polypropylene 2: Product name "BC3AD" (MFR: 10g / 10min) manufactured by Polypropylene Corporation of Japan. <packing> <<Wood Powder>> Wood flour 1: Western Hemlock sawdust (passed through a 40-mesh sieve) Wood flour 2: Western Hemlock sawdust (which passes through a 60-mesh sieve). Talc Talc 1: Product name "sss" (average particle size: 12μm) manufactured by Nippon Talc Co., Ltd. Talc 2: Product name “MS-T” (average particle size: 20 μm) manufactured by Nippon Talc Co., Ltd. <<Mica>> Mica: Manufactured by Kuraray Co., Ltd. under the product name "60-C". (2) Production methods The thermoplastic resin composition is kneaded using the extruder described above and then extruded through a die (die head). This yields a sheet-like extruded product. Specifically, after loading the thermoplastic resin composition into the extruder (co-rotating twin-screw extruder) and kneading it, the thermoplastic resin composition is extruded from a T-die through a gear pump, wound onto cooling rollers (3-roll method), and continuously molded. Thus, a sheet-like extruded product with a thickness of 1.3 mm and a width of 20 cm is obtained. Note that the extrusion speed is approximately 5 to 15 m / min.

[0051] 2. Testing (1) Molding performance The molding performance is evaluated by observing the condition of the resin discharged from the T-die and classifying the observations based on the following evaluation criteria.

[0052] <Evaluation Criteria> A: The discharge from the T-die head is stable and molding is easy. B: Discharge from the T-die is unstable and molding is difficult (narrow range of discharge pressure and / or discharge temperature, and strict control conditions). C: Molding is not possible (there is no favorable range for discharge pressure and / or discharge temperature, and discharge is not possible, or the favorable range is very narrow and not suitable for continuous production).

[0053] (2) Coefficient of linear expansion The coefficient of linear expansion of sheet extruded products was measured using the thermomechanical analysis (TMA) method listed in JIS K7197. Note that Comparative Examples 6, 7, 16, and 17, whose molding performance was rated "C", were not evaluated in terms of the following properties.

[0054] (3) MFR The MFR of thermoplastic resin compositions at a temperature of 230°C and a load of 2.16 kgf was measured based on JIS K7210.

[0055] (4) Wear properties The interior of the extrusion molding machine was observed before and after the production of sheet extruded products for a predetermined period of time, and the wear characteristics were assessed by classifying the observations of the differences before and after production based on the following evaluation criteria.

[0056] <Evaluation Criteria> A: Almost no wear was observed in the screw, gears, etc. of the extrusion molding machine. B: Slight wear was observed in the screw, gears, etc. of the extrusion molding machine. C: Wear was clearly observed in the screw, gears, etc. of the extrusion molding machine.

[0057] [Table 1]

[0058] Table 1 confirms that Examples 1 to 9 suppressed wear on the extruder, improved the molding performance of the thermoplastic resin composition, and could produce sheet extruded products with a smaller coefficient of linear expansion compared to Comparative Examples 1 to 17.

[0059] Examples 1 and 2 confirm that including wood flour that passes through a 60-mesh sieve in the wood flour can further reduce the coefficient of linear expansion of sheet extruded products.

[0060] Comparative Examples 16 and 17 confirmed that when the MFR of polypropylene is less than 20 g / 10 min at a temperature of 230°C and a load of 2.16 kgf, the molding performance decreases.

[0061] Comparative Examples 1 to 7 and Comparative Example 14 confirmed that when the filler content is greater than or equal to 60 parts by mass and less than or equal to 72 parts by mass relative to the total 100 parts by mass of thermoplastic resin and filler, the molding performance decreases.

[0062] Comparative Examples 5 and 8 to 10 confirmed that when the wood flour content is less than 20 parts by weight relative to 100 parts by weight of all fillers, the coefficient of linear expansion is large. Note that, similarly in Comparative Example 15, the wood flour content is less than 20 parts by weight relative to 100 parts by weight of all fillers, but the coefficient of linear expansion is small. A comparison between Comparative Examples 9 and 15 suggests that the reason lies in the mica.

[0063] Comparative Examples 3 and 11 to 14 confirmed that when the content of wood flour is greater than 70 parts by weight relative to 100 parts by weight of all fillers, the molding performance decreases.

[0064] Comparative Example 15 confirmed that when the mica content was greater than 10 parts by mass relative to the total 100 parts by mass of thermoplastic resin and filler, the extruder experienced wear.

Claims

1. A method for producing sheet extruded products, the method comprising: Kneading thermoplastic resin compositions; Then The thermoplastic resin composition is extruded through a mold. The thermoplastic resin composition comprises a thermoplastic resin and fillers. The thermoplastic resin comprises polypropylene having an MFR greater than or equal to 20 g / 10 min and less than or equal to 60 g / 10 min at a temperature of 230°C and a load of 2.16 kgf. The filler comprises wood flour and talc. Of a total of 100 parts by weight of the thermoplastic resin and the filler, the content of the filler is greater than or equal to 60 parts by weight and less than or equal to 72 parts by weight. The wood flour content is greater than or equal to 20 parts by weight and less than or equal to 70 parts by weight relative to 100 parts by weight of all the filler.

2. The method of claim 1, wherein The filler also contains mica, and The content of mica is less than or equal to 10 parts by mass relative to a total of 100 parts by mass of the thermoplastic resin and the filler.

3. The method of claim 1, wherein The wood flour content is greater than or equal to 40 parts by weight and less than or equal to 70 parts by weight relative to 100 parts by weight of all the filler.

4. The method according to any one of claims 1 to 3, wherein The wood flour comprises wood flour that has passed through a 60-mesh sieve.

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