Production method for thermoplastic resin composition, and kneader

Abstract

To provide a production method for a thermoplastic resin composition in which solid contents are appropriately pulverized by performing high-level pulverization simultaneously with kneading while eliminating a need for a filter or a separate pulverization step, and a kneader used in the production method.SOLUTION: There is provided a production method for a thermoplastic resin composition by supplying a thermoplastic resin raw material and solid contents having an average particle size of 50 μm or more to a kneading device kneader having at least one screw 103 and 104 and a casing 105 accommodating the screw. The method comprises a kneading and pulverizing step of kneading the thermoplastic resin composition containing the solid contents and pulverizing the solid contents, wherein the kneading device kneader has clearance regions C1 to C3 of 500 μm or less formed by the screw inside the kneading device kneader.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a method for producing a thermoplastic resin composition and a kneader. [Background technology]

[0002] In recent years, waste recycling has been actively promoted in order to reduce environmental pollution caused by plastic waste (see, for example, Patent Document 1). In particular, resins produced from plastics that have been purchased, used, and then discarded by consumers are called PCR (post-consumer resin), and with the growing demand for reducing environmental pollution, there is a strong demand for technologies to promote their use. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2004-136578 Summary of the Invention [Problem to be solved by the invention]

[0004] Recycled resins such as PCR usually contain relatively large solid particles such as inorganic fillers and incompatible resin lumps, and depending on the application, these solid particles must be removed or crushed. Conventional techniques for removing solid particles include melting the resin and filtering it through a filter, or providing an additional crushing process, but these methods have issues such as the significant effort required for filter replacement and the additional crushing process.

[0005] Therefore, an object of the present invention is to provide a method for producing a thermoplastic resin composition in which the solid content is appropriately pulverized by performing high-level pulverization simultaneously with kneading while eliminating the steps of using a filter or a separate pulverization process, and a kneader to be used in the production method. [Means for solving the problem]

[0006] As a result of intensive research conducted by the present inventors to solve the above-mentioned problems, they found that the above-mentioned problems can be solved by kneading using a kneader having a clearance of a specific value or less, and specifically, they completed the present invention as described below.

[0007] That is, the present invention is as follows. [1] A method for producing a thermoplastic resin composition by supplying a thermoplastic resin and a solid component having an average particle size of 50 μm or more to a kneader having at least one screw and a casing accommodating the screw, A method for producing a thermoplastic resin composition, characterized in that the kneader has a clearance area of ​​500 μm or less formed by the screw. [2] The manufacturing method described in [1] above, wherein the average particle size of the solid content upstream of the casing is 50 μm to 1000 μm. [3] The manufacturing method described in [1] above, wherein the average particle size of the solid content downstream of the casing is 1 μm to 30 μm. [4] The method according to [1] above, wherein the kneader is a multi-screw kneader having a plurality of screws. [5] The manufacturing method described in [1] above, wherein the screw has a spiral concave and convex portion, and a clearance area of ​​500 μm or less is formed between the convex portion of the screw and the inner wall of the casing. [6] The manufacturing method according to [1] above, wherein the screw has spiral projections and recesses, and the clearance area of ​​500 μm or less is formed between adjacent projections. [7] The manufacturing method described in [4] above, wherein a clearance area of ​​500 μm or less is formed between the plurality of screws. [8] A kneader comprising at least one screw and a casing that accommodates the screw, A kneader characterized by having a clearance area of ​​500 μm or less formed by the screw inside the kneader. [Effects of the Invention]

[0008] According to the present invention, it is possible to provide a method for producing a thermoplastic resin composition in which the solid content is appropriately pulverized by performing high-level pulverization simultaneously with kneading while eliminating the steps of using a filter or a separate pulverization step, and a kneader used in the production method. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is an example of a kneader casing and at least one screw. DETAILED DESCRIPTION OF THE INVENTION

[0010] The method for producing a thermoplastic resin composition of the present invention will be described in detail below, but the explanation of the constituent elements described below is an example (typical example) of the present invention, and the present invention is not limited thereto.

[0011] (Kneading machine) The kneader used in the present invention will be described with reference to FIG. 1. The kneader in FIG. 1 has at least one screw and a casing that houses the screw. The kneader uses a thermoplastic resin and solid matter with a particle size of 50 μm or more as raw materials, kneads them, and is equipped with a kneading / pulverizing means that pulverizes the solid matter. The kneader also has a clearance area of ​​500 μm or less formed by the screw. The solid matter may be particles contained in a thermoplastic resin, or may be a filler or other bulking agent, so long as the solid matter has a particle size of 50 μm or more. The thermoplastic resin composition may be cooled in a cooler after being extruded from the kneader. The kneader is preferably equipped with a heater for heating the materials in the casing. It is also preferable that the kneader has a function of extruding the resin. It may also be equipped with an inlet for the materials on the upstream side and a die for extruding the thermoplastic resin composition on the downstream side. The clearance area is configured to melt and knead the thermoplastic resin and filler, thereby applying shear stress to the solids contained in the material being kneaded (referred to as the thermoplastic resin composition being kneaded), thereby finely pulverizing and pulverizing the solids. The kneader is preferably a multi-screw kneader, and more preferably a twin-screw kneader. The screw preferably has helical irregularities. Areas of clearance of 500 μm or less formed by the screws in the kneader include the screw-casing clearance (C1), the screw-to-screw clearance (C2), and the clearance between the convex portions of the screws (C3). When the kneader is a multi-screw kneader, it is preferable that a clearance region of 500 μm or less is formed between the screws. It is also preferable that a clearance area of ​​500 μm or less is formed between the convex portion of the screw and the inner wall of the casing. It is also preferable that a clearance region of 500 μm or less is formed between the convex portions of the spiral irregularities provided on the screw in the longitudinal direction of the screw. Furthermore, since the temperature increases and the viscosity of the resin decreases toward the latter half of the kneader, it is preferable that the clearance between the convex portions of the screw be narrower downstream of the casing than upstream of the casing in order to increase the shear stress accordingly. The screw may also be tapered from the upstream to the downstream. The clearance referred to in this application refers to the shortest distance between components.

[0012] (Method of producing thermoplastic resin composition) The method for producing the thermoplastic resin composition will be described below: First, a thermoplastic resin and solid matter having a particle size of 50 μm or more are fed into a raw material inlet of a kneader. The solid content may be particles contained in a thermoplastic resin or a filler, etc., as long as the solid content has a particle size of 50 μm or more. Note that the particle size in this application refers to the volume average particle size. In the kneader, a thermoplastic resin containing solids is melted by a heater and kneaded by a screw, and the solids of the thermoplastic resin composition are pulverized by applying shear stress to the thermoplastic resin composition as it passes through a clearance area of ​​500 μm or less formed by the screw, and then the thermoplastic resin composition is extruded from an outlet, completing the operation. It is preferable that the kneading time be short while still allowing good pulverization. A short kneading time can save energy and also minimize thermal degradation of the resin. The melting temperature varies depending on the type of resin, but is preferably equal to or higher than the melting point of the resin, and more preferably 20°C or higher than the melting point. On the other hand, if the temperature is too high, it is not desirable from the viewpoints of energy loss, reduction in grinding ability, and thermal degradation of the resin, so the upper limit is preferably within 100°C of the melting point, and more preferably within 50°C.

[0013] (Molding of thermoplastic resin composition) The thermoplastic resin composition of the present invention may then be cut into pellets, or may be directly extruded into a die to form a sheet, or may be stretched after being formed into a sheet to form a stretched sheet, or may be stacked to form a laminate.

[0014] Examples of thermoplastic resin raw materials include polyolefin resins, polystyrene resins, polyamide resins, polyester resins, and polycarbonate resins. From the viewpoint of moldability and strength, the thermoplastic resin is preferably a polyolefin resin, more preferably a polypropylene resin. Furthermore, the thermoplastic resin raw material is preferably a recycled resin (so-called PCR). The thermoplastic resin raw material itself may contain solid matter with a particle size of 50 μm or more.

[0015] The solid content may be particles contained in the thermoplastic raw material or a filler, etc., as long as the solid content has a particle size of 50 μm or more. The filler is preferably an inorganic filler or an organic filler, and more preferably an inorganic filler. Examples of inorganic fillers include calcium carbonate, talc, titanium oxide, metallic aluminum, silica, etc. Among these, calcium carbonate is more preferred from the viewpoint of economy.

[0016] Examples of the organic filler include polyester, nylon, etc. The organic filler is preferably particles that exist in a solid state during stretching.

[0017] When the filler is dropped into the kneader, the particle size of the filler is preferably 1000 μm or less, more preferably 500 μm, and even more preferably 300 μm, from the viewpoint of ensuring good meshing with the screw and supplying the filler. Furthermore, when the filler is added to the kneader, the particle size of the filler is preferably 50 μm or more, more preferably 100 μm or more, from the viewpoint of exhibiting the filler function after stretching.

[0018] The particle size of the filler downstream of the kneader is preferably 30 μm or less, more preferably 20 μm or less, from the viewpoint of preventing poor appearance and excessive surface roughening, and is preferably 1 μm or more from the viewpoint of exhibiting the function as a filler. [Example]

[0019] The present invention will be explained in more detail below with reference to examples. The materials, amounts used, ratios, processing details, processing procedures, etc. can be changed as appropriate without departing from the scope of the present invention. Therefore, the scope of the present invention should not be interpreted as being limited by the specific examples shown below. In the examples, the terms "parts", "%", etc. are based on mass unless otherwise specified.

[0020] Example 1 A resin sheet was produced according to the following procedure. Details of the materials used are as follows (see Table 1 below).

[0021] [Material Details] Pellets: Propylene polymer with a melting point of 162°C (DSC peak temperature) Filler: Calcium carbonate with an average particle size of 100 μm

[0022] The types and amounts (mass%) of materials used in producing the resin sheet, the production conditions, and the evaluation results are shown in Table 2 below. The material symbols shown in Table 2 correspond to the material symbols shown in Table 1.

[0023] [procedure] The pellets (PP) and calcium carbonate (CaCO3) listed in Table 2 were melt-kneaded in a kneader set at 230°C, extrusion-molded, and cooled to 70°C in a cooling device to obtain a single-layer unstretched sheet. This unstretched sheet was heated to 160°C and then stretched 5 times by 5 times in both the machine and cross directions to obtain a biaxially oriented sheet.

[0024] [evaluation] The stretched sheets produced in the examples were measured for smoothness, and the number and size of spots on the stretched sheets were visually inspected. Details of each test are as follows:

[0025] Smoothness Smoothness is a measure of the flatness of paper and is determined based on JIS P 8155:2010 "Paper and paperboard - Smoothness test method - Oken method." The smoothness value was measured using a "Digital Oken-type Air Permeability Smoothness Tester" manufactured by Asahi Seiko Co., Ltd. under conditions of 23°C and humidity of 50%, and was evaluated as follows. ◎ 1500 seconds or more 〇 900 seconds or more △ 500 seconds or more × Less than 500 seconds

[0026] [spots] The number of spots was measured by counting the number of spots that could be identified in a randomly selected area of ​​2 mm x 2 mm using an optical microscope, and was evaluated as follows: 〇 25 or less △ 50 or less × Over 50 pieces

[0027] The size of the spots was evaluated by visually observing the produced stretched sheet as follows. ◎ Barely visible to the naked eye or not visible at all ○ Slightly visible to the naked eye △ Can be seen with the naked eye × Many visible to the naked eye

[0028] The stretched sheet of Example 1 was subjected to the above evaluations, and the results are shown in Table 2 below.

[0029] (Example 2), (Example 3) Stretched sheets of Examples 2 and 3 were obtained in the same manner as in Example 1, except that the screw rotation speed and kneading time were changed to the conditions shown in Table 2. The stretched sheets of Examples 2 and 3 were evaluated in the same manner as in Example 1. The results are shown in Table 2 below.

[0030] (Comparative Example 1) A stretched sheet of Comparative Example 1 was obtained in the same manner as in Example 1, except that the clearance of the kneader in producing the stretched sheet was changed to the conditions shown in Table 2. The stretched sheet of the comparative example was evaluated in the same manner as in Example 1. The results are shown in Table 2 below.

[0031] [Table 1]

[0032] [Table 2]

[0033] The results of the examples show that the stretched sheets obtained by stretching the thermoplastic resin compositions produced by the production method of the present invention have good smoothness and good numbers and sizes of spots, and that the solid content is appropriately pulverized while reducing the number of steps. Therefore, it has become clear that the thermoplastic resin compositions produced by the production method of the present invention are sufficiently durable for use as stretched sheets. [Explanation of symbols]

[0034] 101....Upstream of casing, 102....Downstream of casing, 103, 104....Screw, 105....Casing, C1 to C3...Clearance

Claims

1. A method for producing a thermoplastic resin composition by supplying a thermoplastic resin and a solid component having an average particle size of 50 μm or more to a kneader having at least one screw and a casing accommodating the screw, comprising: A method for producing a thermoplastic resin composition, characterized in that the kneader has a clearance area of ​​500 μm or less formed by the screw.

2. The method according to claim 1, wherein the solid content upstream of the casing has an average particle size of 50 μm to 1000 μm.

3. 2. The method of claim 1, wherein the solids downstream of the casing have an average particle size of 1 μm to 30 μm.

4. The method according to claim 1, wherein the kneader is a multi-screw kneader having a plurality of screws.

5. The manufacturing method according to claim 1 , wherein the screw has a spiral concave and convex portion, and the clearance area of ​​500 μm or less is formed between the convex portion of the screw and the inner wall of the casing.

6. The manufacturing method according to claim 1 , wherein the screw has helical projections and recesses, and the clearance area of ​​500 μm or less is formed between adjacent projections.

7. The manufacturing method according to claim 4 , wherein the clearance area of ​​500 μm or less is formed between the plurality of screws.

8. A kneader comprising at least one screw and a casing that houses the screw, A kneader characterized in that the kneader has a clearance area of ​​500 μm or less formed by the screw.

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