Classifications

• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
  • C08J5/00—Manufacture of articles or shaped materials containing macromolecular substances
  • C08J5/04—Reinforcing macromolecular compounds with loose or coherent fibrous material

Definitions

• the present invention relates to a method for manufacturing a resin molded product.
• cellulose nanofibers which are obtained by defibrating cellulose fibers to nano-size, have been attracting attention.
• Cellulose fibers are biomass made from pulp derived from plants such as wood, and it is hoped that their effective use will help reduce environmental impact.
• cellulose nanofibers that has been proposed is to disperse cellulose nanofibers in resin to improve the strength of the resin material.
• a resin composition containing cellulose nanofibers is disclosed in Patent Document 1, for example.
• the embodiment of the present invention was made in consideration of the above problems, and its purpose is to suppress the occurrence of silver streaks in a method for producing a resin molded product using a resin composition containing cellulose nanofibers.
• This specification discloses a method for producing a resin molded product as described below.
• the manufacturing method according to an embodiment of the present invention includes a step (C) of drying the resin composition prior to the step (B) of molding the resin composition into a resin molded product, so that the moisture content of the resin composition can be reduced before step (B) can be carried out. This makes it possible to suppress the occurrence of silver streaks caused by moisture contained in the resin composition.
• step (C) be carried out so that the moisture content of the resin composition is 400 ppm by mass or less.
• step (C) be carried out so that the moisture content of the resin composition is 240 ppm by mass or less.
• step (C) is carried out at a certain temperature or higher, specifically, at a temperature of 100°C or higher.
• step (C) is carried out for a certain period of time or more, specifically, for one hour or more.
• thermoplastic resin contained in the resin composition for example, polypropylene can be suitably used.
• Item 7 The method for producing a resin molded article according to any one of items 1 to 6, wherein the cellulose nanofibers have an average fiber diameter of 10 nm or more and 100 nm or less.
• the average fiber diameter of the cellulose nanofibers contained in the resin composition is preferably 10 nm or more and 100 nm or less.
• the average fiber length of the cellulose nanofibers contained in the resin composition is preferably 10 ⁇ m or more and 100 ⁇ m or less.
• the occurrence of silver streaks can be suppressed in a method for producing a resin molded product using a resin composition containing cellulose nanofibers.
• FIG. 1 is a flowchart showing a method for manufacturing a resin molded product according to an embodiment of the present invention.
• FIG. 1 shows the results of checking the presence or absence of silver streaks for samples #1-1, #1-2, #1-3, #5-1, #5-2, #5-3, #8-1, and #8-2 together with external photographs.
• 1 is a graph showing the relationship between drying time and moisture content.
• FIG. 12 shows the results of confirmation of the presence or absence of silver streaks for Samples #12-1 to #12-10 together with appearance photographs.
• 1 is a graph showing the relationship between drying time and moisture content.
• 1 is a flowchart showing an example of a method for producing a resin composition.
• FIG. 1 shows an engine cover 1 and a crossbar member 10 for a jet ski.
• Figure 1 is a flowchart showing the method for manufacturing a resin molded product.
• thermoplastic resin for example, polypropylene can be suitably used, but a thermoplastic resin other than polypropylene (for example, nylon) may also be used.
• the resin composition may also contain components other than the thermoplastic resin and cellulose nanofibers (for example, a dispersant).
• Cellulose nanofibers are fibers with nano-sized diameters obtained by defibrating cellulose fibers.
• the average fiber diameter of the cellulose nanofibers contained in the resin composition is preferably 10 nm or more and 100 nm or less.
• the average fiber length of the cellulose nanofibers contained in the resin composition is preferably 10 ⁇ m or more and 100 ⁇ m or less.
• the "average fiber diameter” and “average fiber length” of cellulose nanofibers refer to the “number average fiber diameter” and “number average fiber length,” respectively.
• the number average fiber diameter and number average fiber length of cellulose nanofibers can be measured, for example, by observing the cellulose nanofibers with a microscope such as an electron microscope or an atomic force microscope.
• cellulose nanofiber content of the resin composition can be, for example, 5% by mass or more and 30% by mass or less.
• the resin composition prepared in step s1 is, for example, in the form of pellets, but may be in other forms.
• the resin composition containing the thermoplastic resin and the cellulose nanofibers can be produced, for example, by the method described below.
• step s2 drying step
• the resin composition is dried, for example, using a dryer.
• a dryer for example, a hot air dryer, a dehumidifying dryer (sometimes called a "dehumidifying hot air dryer"), or a vacuum dryer can be used.
• step s3 molding step.
• This step s3 can be suitably carried out by, for example, injection molding.
• the molding temperature and filling pressure when molding by injection molding can be appropriately set depending on the thermoplastic resin used, the cellulose nanofiber content, etc.
• the manufacturing method according to an embodiment of the present invention includes step s2 (drying step) of drying the resin composition prior to step s3 (molding step) of molding the resin composition into a resin molded product. Therefore, the moisture content of the resin composition can be reduced before the molding step, thereby suppressing the occurrence of silver streaks caused by moisture contained in the resin composition.
• the drying process be carried out so that the moisture content of the resin composition is sufficiently reduced. Specifically, it is preferable that the drying process be carried out so that the moisture content of the resin composition is 400 ppm by mass or less, and it is more preferable that the drying process be carried out so that the moisture content of the resin composition is 240 ppm by mass or less.
• the drying process be carried out at a certain temperature or higher, specifically, at a temperature of 100°C or higher.
• the drying process be carried out at a temperature lower than the melting point of the thermoplastic resin contained in the resin composition.
• the thermoplastic resin is polypropylene, it is preferable that the drying process be carried out at a temperature of 150°C or lower.
• the drying process be carried out for a certain period of time or more; specifically, it is preferable that it be carried out for one hour or more, and more preferably for two hours or more.
• pellet-shaped resin composition in which cellulose nanofibers were dispersed in commercially available polypropylene (J-466HP manufactured by Prime Polymer) were prepared as the resin composition.
• the cellulose nanofiber content in the resin composition was 5% by mass.
• the average fiber diameter and average fiber length of the cellulose nanofibers were approximately 100 nm and approximately 100 ⁇ m, respectively.
• the prepared resin composition was dried under different drying conditions (temperature and time) or without drying, and the moisture content was measured. Drying was performed using a 50 kg capacity box-type hot air dryer. The moisture content was measured using a precision moisture meter CZA3100 manufactured by CHINO, and the mass measurement required for the moisture content measurement was performed using a precision mass measuring instrument. These measurements were performed on four samples (samples #1 to #4) extracted from lot A, three samples (samples #5 to #7) extracted from lot B, and four samples (samples #8 to #11) extracted from lot C.
• each sample was injection molded to obtain a resin molded product.
• the mold used in the molding process was a flat mold measuring 150 mm in length, 120 mm in width, and 3 mm in thickness (gate cross-section size: 2 mm x 3 mm).
• the molding machine used was a Kawaguchi Iron Works injection molding machine KB80B2.
• the injection molding conditions were as shown in Table 1 below. The obtained resin molded products were visually observed to check for the presence or absence of silver streaks.
• Tables 2, 3, and 4 below show the results of moisture content measurements for each sample.
• Figure 2 also shows the results of checking for the presence or absence of silver streaks for eight samples (samples #1-1, #1-2, #1-3, #5-1, #5-2, #5-3, #8-1, and #8-2) along with external photographs.
• Figure 3 shows a graph with drying time on the horizontal axis and moisture content on the vertical axis.
• Figure 3 plots the average values of samples #1-1, #2-1, and #3-1 for Lot A; the average values of samples #1-2, #2-2, and #3-2; and the average values of samples #1-3, #2-3, #3-3, and #4.
• samples #6-2, #6-3, #7-2, #7-3, #9-2, #10-2 and #11-2 had almost no silver streaks.
• a drying temperature of 100°C or higher can sufficiently reduce the moisture content even when the moisture content of the resin composition in the undried state is relatively high (in other words, it can reduce the need to strictly control the moisture content at the stage of preparing the resin composition). If the drying temperature is less than 100°C (for example, 80°C), it may be difficult to sufficiently reduce the moisture content if the moisture content of the resin composition is relatively high, as in lot A.
• Lid D a pellet-shaped resin composition (CellenpiaPlas (registered trademark) manufactured by Nippon Paper Industries Co., Ltd.) in which cellulose nanofibers are dispersed in polypropylene was prepared as the resin composition.
• the cellulose nanofiber content of the resin composition was 5 mass%.
• the average fiber diameter of the cellulose nanofibers was 100 nm or less.
• the moisture content of the prepared resin composition was measured after drying under different drying conditions (temperature and time), or without drying. Drying was performed using a 50 kg capacity box-type hot air dryer. Moisture content was measured using a VaporProXL precision moisture meter manufactured by Eiko Seiki Co., Ltd., and mass measurements required for moisture content measurement were performed using a precision mass measuring instrument. These measurements were performed on one sample (sample #12) extracted from Lot D.
• sample #12 that was not dried is indicated as sample #12-1, and samples that were dried at 110°C for 0.5 hours, 1 hour, 1.5 hours, 2 hours, 2.5 hours, 3 hours, 3.5 hours, 4 hours, and 4.5 hours are indicated as samples #12-2, #12-3, #12-4, #12-5, #12-6, #12-7, #12-8, #12-9, and #12-10, respectively.
• the mold used in the molding process was a flat mold measuring 150 mm in length, 120 mm in width, and 3 mm in thickness (gate cross-section size: 2 mm x 3 mm).
• the molding machine used was an electric injection molding machine J80ADS-110U manufactured by Japan Steel Works.
• the injection molding conditions were as shown in Table 5 below.
• the obtained resin molded products were visually observed to check for the presence or absence of silver streaks.
• Table 6 below shows the results of moisture content measurements for each sample.
• Figure 4 shows the results of checking for the presence or absence of silver streaks for each sample, along with external photographs.
• Figure 5 shows a graph with drying time on the horizontal axis and moisture content on the vertical axis.
• the marker " ⁇ ” in Figure 5 means that there were almost no silver streaks, the marker “ ⁇ ” means that there were sufficiently few silver streaks, and the marker " ⁇ ” means that silver streaks were present.
• Method of producing resin composition There are no particular limitations on the method for producing the resin composition prepared in step s1, and various methods known in the art for producing resin compositions containing cellulose nanofibers can be used.
• FIG. 6 is a flow chart showing an example of a method for producing a resin composition.
• pulp is prepared (step s11).
• the pulp can be derived from wood, for example. There are no particular limitations on the type of tree. Various known methods can be used to convert wood into pulp.
• the pulp is subjected to a hydrophobization treatment (step s12).
• the hydrophobization treatment can increase the compatibility between the cellulose nanofibers and the resin. There are no particular limitations on the method of the hydrophobization treatment.
• step s13 the hydrophobized pulp and the thermoplastic resin are kneaded to form a master batch.
• kneading method There are no particular limitations on the kneading method, and kneading can be performed using a kneader.
• the pulp is defibrated, and the cellulose nanofibers are dispersed in the resin.
• step s14 the master batch and the thermoplastic resin are kneaded to form a resin composition.
• a resin composition There are no particular limitations on the kneading method used in step s14, and kneading can be performed using a kneader.
• the cellulose nanofiber content of the master batch can be, for example, about 30% to 45% by mass, and the cellulose nanofiber content of the resin composition obtained by step s14 can be about 5% to 15% by mass.
• the manufacturing method illustrated in FIG. 6 allows pulp defibration and dispersion of cellulose nanofibers in resin to be performed simultaneously, which reduces manufacturing costs.
• the manufacturing method for the resin composition is not limited to the one illustrated in FIG. 6.
• the resin molded article obtained by the manufacturing method according to the embodiment of the present invention can be used in various applications because the occurrence of silver streaks is suppressed.
• the resin molded article obtained by the manufacturing method according to the embodiment of the present invention is excellent in strength because it is formed from a resin composition containing cellulose nanofibers, and can be suitably used as a member of various transport equipment (particularly, as a replacement for members conventionally formed from resin compositions containing reinforcing fillers such as talc or glass fiber).
• the resin molded product obtained by the manufacturing method of the embodiment of the present invention can be, for example, a crossbar member 10 for a jet ski, as shown in FIG. 7.
• FIG. 7 also shows an engine cover 1 that is placed on top of the engine.
• the crossbar member 10 is attached to the back side of the engine cover 1, and is a member that supports and reinforces the engine cover 1.
• resin molded products obtainable by the manufacturing method of the embodiment of the present invention can be, for example, inner engine hatches and base seats for jet skis, assist grips and helmet boxes for motorcycles, lower covers and leg shields for scooter-type motorcycles, engine covers for outboard motors, etc.
• the method for producing a resin molded product includes a step (A) of preparing a resin composition containing a thermoplastic resin and cellulose nanofibers, and a step (B) of molding the resin composition into a resin molded product, and further includes a step (C) of drying the resin composition prior to the step (B).
• the manufacturing method according to an embodiment of the present invention includes a step (C) of drying the resin composition prior to the step (B) of molding the resin composition into a resin molded product, so that the moisture content of the resin composition can be reduced before step (B) can be carried out. This makes it possible to suppress the occurrence of silver streaks caused by moisture contained in the resin composition.
• step (C) is carried out so that the moisture content of the resin composition is 400 ppm by mass or less.
• step (C) be carried out so that the moisture content of the resin composition is 400 ppm by mass or less.
• step (C) is carried out so that the moisture content of the resin composition is 240 ppm by mass or less.
• step (C) be carried out so that the moisture content of the resin composition is 240 ppm by mass or less.
• step (C) is carried out at a temperature of 100°C or higher.
• step (C) is carried out at a certain temperature or higher, specifically, at a temperature of 100°C or higher.
• step (C) is carried out for 4 hours or more.
• step (C) is carried out for a certain period of time or more, specifically, for 4 hours or more.
• thermoplastic resin is polypropylene.
• thermoplastic resin contained in the resin composition for example, polypropylene can be suitably used.
• the average fiber diameter of the cellulose nanofibers is 10 nm or more and 100 nm or less.
• the average fiber diameter of the cellulose nanofibers contained in the resin composition is preferably 10 nm or more and 100 nm or less.
• the average fiber length of the cellulose nanofiber is 10 ⁇ m or more and 100 ⁇ m or less.
• the average fiber length of the cellulose nanofibers contained in the resin composition is preferably 10 ⁇ m or more and 100 ⁇ m or less.
• the occurrence of silver streaks can be suppressed.
• the resin molded article produced using the production method according to the embodiment of the present invention is suitable for use as a component for various types of transportation equipment, for example.

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• Health & Medical Sciences (AREA)
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• Manufacture Of Macromolecular Shaped Articles (AREA)
• Processing And Handling Of Plastics And Other Materials For Molding In General (AREA)
• Reinforced Plastic Materials (AREA)

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Citations (8)

• 2023
  • 2023-11-10 JP JP2024558834A patent/JPWO2024106340A1/ja active Pending
  • 2023-11-10 WO PCT/JP2023/040592 patent/WO2024106340A1/ja not_active Ceased
  • 2023-11-14 TW TW112143782A patent/TW202428746A/zh unknown

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