JP2009057410A - Production method for methacrylic resin molding material - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing a methacrylic resin molding material having high uniformity of a repose angle. <P>SOLUTION: By attaching an amide compound on the surfaces of methacrylic resin pellets at a temperature ≥35°C, the methacrylic resin molding material is produced. Preferably, a use amount of the amide compound is 0.003-0.05 pts.wt. to 100 pts.wt. methacrylic resin pellets. Preferably, the amide compound is a bisamide compound, and preferably, its melting point is 30-200°C. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a method for producing a methacrylic resin molding material.

  Methacrylic resins have been used for vehicle lamp covers, lighting covers, signboards, optical lenses, light guides, transparent tableware and the like, taking advantage of their excellent transparency and weather resistance. Moreover, recently, taking advantage of its transparency, it is also used for relatively thick figurines, containers and accessories. Production of these methacrylic resin molded bodies is often performed by an injection molding method, and methacrylic resin is processed into pellets and supplied as a molding material.

  Here, an outline of a typical injection molding method will be described. An injection molding apparatus used for this purpose is a mold, a mold clamping device that drives the mold in a mold closing direction or a mold opening direction, and a mold clamping. And an injection device for injecting molten resin into the mold. The mold is composed of a movable side mold plate and a fixed side mold plate. The fixed side mold plate is formed with a sprue for allowing molten resin to pass through. The parting of the movable side mold plate and the fixed side mold plate is performed. A runner and a gate are formed along the line, and a cavity for forming a product is formed between the two mold plates. In addition, a hot runner for allowing the molten resin to pass through while maintaining the temperature is installed in the fixed side template, and further, the molten resin reaches the gate formed along the parting line through the hot tip. There is also. The movable mold plate is provided with a protruding means for taking out the formed product. The injection device is for plasticizing and melting the molding material and injection filling it into the cavity of the mold. The injection device is attached to the cylinder, the screw provided to rotate in it, and the tip of the cylinder. The injection nozzle, the hopper for supplying the molding material to the cylinder, the motor for rotationally driving the screw, the ram mechanism for driving the screw forward, and the like. A heater is provided on the outer periphery of the cylinder to melt the molding material inside.

  The molding material is supplied into the cylinder by the rotational drive of the screw, heated by an energized heater, melted and kneaded under shear frictional heat and pressure action due to the rotation of the screw, and sent to the tip of the screw. Accumulated. At that time, the screw gradually descends backward due to the resin pressure accumulated in the tip of the molten resin, and stops when the desired position is reached. When the screw descends while gradually rotating, an appropriate back pressure is applied from the rear of the screw to exhaust the molten resin decomposition gas, entrained air, water vapor, and the like to the rear and deaerate it from the hopper. Next, the screw is driven forward by the ram mechanism, the molten resin is injected and filled from the nozzle into the cavity of the mold, and a holding pressure for compensating the volume shrinkage accompanying cooling and solidification of the molten resin is applied. Subsequently, the cooling of the molded product in the mold and the measurement of the molten resin for the next molding are performed simultaneously. After completion of cooling, the movable side mold plate is moved, the mold is opened, and the molded product is taken out.

  In such an injection molding method, when a molded product having a relatively large thickness or a large product volume is produced, a large amount of the molding material is sent to the tip of the screw and accumulated as described above (plasticization step). It is necessary to accumulate in the cylinder as a molten resin, and it takes a long time to measure. Also, when the molten resin filled in the mold is cooled by heat exchange with the mold surface, if the molten resin is taken out to the center layer of the molded body without sufficiently cooling and solidifying, a predetermined dimension can be obtained by molding shrinkage of the methacrylic resin. Since it may not be possible, a long cooling time is required and the time for one cycle becomes long.

  If the molding material is accumulated in the cylinder for a long time in a molten state in this way, the molding material will melt more than necessary, and the adhesion between the semi-molten molding material (solid) staying in the screw groove and the cylinder inner wall will increase. It becomes difficult to transfer the molten resin forward. Further, since the molding material is melted at an early stage in the screw supply zone, a molten coating is easily formed on the outer periphery of the screw, and it is difficult to degas the cracked gas and water vapor during measurement. Then, the decomposition of the molding material is accelerated by delaying the transfer, and the generation of gas is remarkably increased, and the molten resin is accumulated at the tip of the screw while containing the decomposition gas and air due to insufficient degassing. Become. And when such a molten resin is filled in the mold, bubbles may be generated inside the molded body, or defects that appear to shine on the silver strip called silver derived from the bubbles may be generated on the surface of the molded body. There is.

  In order to solve such problems, for example, in JP-A-8-217945 (Patent Document 1), an amide compound is attached to the surface of a methacrylic resin pellet, and the angle of repose after the attachment is adjusted to a predetermined range. It has been proposed to use those as molding materials. However, the angle of repose of the obtained methacrylic resin molding material is difficult to be uniform, and there is a problem that when the molding material is applied to injection molding, it is difficult to stably obtain the effect of suppressing the generation of bubbles and silver. .

JP-A-8-217945

  Accordingly, an object of the present invention is to provide a method capable of producing a methacrylic resin molding material having high repose angle uniformity.

  As a result of intensive studies, the present inventors have found that the above object can be achieved by attaching an amide compound to the surface of a methacrylic resin pellet at a predetermined temperature or higher, and have completed the present invention.

  That is, the present invention provides a method for producing a methacrylic resin molding material, characterized in that an amide compound is attached to the surface of a methacrylic resin pellet at 35 ° C. or higher.

  According to the present invention, a methacrylic resin molding material with high repose angle uniformity can be manufactured.

  Hereinafter, the present invention will be described in detail. The methacrylic resin pellet used as a raw material in the present invention is a methacrylic resin or a pellet (granular material) of a methacrylic resin composition in which a release agent, an ultraviolet absorber, a pigment, an antioxidant, a flame retardant, and the like are blended. .

  A methacrylic resin is a polymer obtained by polymerizing a monomer containing methyl methacrylate as a main component, specifically, a monomer containing 50% by weight or more of methyl methacrylate. It may be a coalescence or a copolymer of 50% by weight or more of methyl methacrylate and 50% by weight or less of other monomers. Examples of monomers other than methyl methacrylate include, for example, ethyl methacrylate, propyl methacrylate, butyl methacrylate, benzyl methacrylate, 2-ethylhexyl methacrylate, cyclohexyl methacrylate, bornyl methacrylate, adamantyl methacrylate, and cyclohexane methacrylate. Methacrylic acid esters such as pentadienyl; methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, benzyl acrylate, 2-ethylhexyl acrylate, cyclohexyl acrylate, bornyl acrylate, adamantyl acrylate, acrylic Acrylic esters such as cyclopentadienyl; unsaturated carboxylic acids such as acrylic acid, methacrylic acid, maleic acid, itaconic acid, maleic anhydride, itaconic anhydride, Acid anhydrides; hydroxyl group-containing monomers such as 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, monoglycerol acrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, monoglycerol methacrylate Nitrogen-containing monomers such as acrylamide, methacrylamide, acrylonitrile, methacrylonitrile, diacetone acrylamide, and dimethylaminoethyl methacrylate; Epoxy group-containing monomers such as allyl glycidyl ether, glycidyl acrylate, and glycidyl methacrylate Body; styrene-based monomers such as styrene and α-methylstyrene.

  The production of the methacrylic resin can be performed, for example, by a bulk polymerization method, and among them, it is preferably performed by a continuous bulk polymerization method. According to the continuous mixed polymerization method, it is possible to produce a methacrylic resin having as few impurities as possible and improving the transparency, and it is possible to produce a methacrylic resin pellet by cutting a strand obtained by molding this. The molding in this case is a die having a plurality of holes at the outlet of an extruder having a heatable cylinder and a screw rotating in the same, such as a single screw extruder, a twin screw extruder or a degassing extruder. Can be carried out using an apparatus in which

  The melted strand thus obtained is cooled and cut by, for example, a water stream strand cutting method to form pellets (molding material) having a diameter of 2 to 4 mm and a length of 2 to 5 mm. The water stream strand cutting method used here is a method in which a melted strand is cooled by flowing down a flowing chute on which a water film is formed with cooling water, and then cut into pellets.

  Alternatively, the methacrylic resin pellets may be produced by a method in which the methacrylic resin is melt-kneaded with an extruder and then extruded from a die hole and cut when the extrudate reaches a predetermined length.

  A methacrylic resin molding material is produced by adhering an amide compound to the surface of the methacrylic resin pellet thus obtained. In the present invention, the adhering temperature is set to 35 ° C. or higher. By attaching an amide compound to the surface of the methacrylic resin pellets at a predetermined temperature or more in this way, the uniformity of the angle of repose of the resulting methacrylic resin molding material can be improved, and as a result, when the molding material is applied to injection molding The effect of suppressing the generation of bubbles and silver can be stably obtained. The adhesion temperature is preferably 40 to 100 ° C, more preferably 40 to 80 ° C.

The amide compound may be, for example, a monoamide compound or a bisamide compound, but a bisamide compound is preferably used. As the monoamide compound, an aliphatic monoamide compound represented by RCONH ₂ (R represents a monovalent aliphatic hydrocarbon group) is preferably used. Examples thereof include stearic acid amide, palmitic acid amide, oleic acid amide, And erucic acid amide. The bisamide compound is R ¹ CONH—R ² —NHCOR ³ (R ¹ and R ³ each represent a monovalent aliphatic hydrocarbon group, and R ² represents a divalent aliphatic hydrocarbon group). The aliphatic bisamide compounds shown are preferably used, and examples thereof include methylene bis stearamide, ethylene bis stearamide, ethylene bis oleate amide, hexamethylene bis stearamide, methylene bis stearamide, ethylene bis stearamide. Examples include acid amides.

  The amount of the amide compound used is usually 0.003 to 0.5 parts by weight, preferably 0.008 to 0.015 parts by weight, based on 100 parts by weight of the methacrylic resin pellets. If the amount of the amide compound used is too small, when the resulting methacrylic resin molding material is applied to injection molding, it is difficult to obtain the effect of suppressing the generation of bubbles and silver. If the amount of the amide compound used is too large, when the resulting methacrylic resin molding material is applied to injection molding, it is too slippery to measure.

  Moreover, it is preferable that the melting point of an amide compound is 30-200 degreeC, and it is more preferable that it is 70-170 degreeC. If this melting point is too low, the resulting methacrylic resin molding material will be sticky. Moreover, when this melting | fusing point is too high, it will become difficult to attach to a methacryl resin pellet.

  Examples of the method of attaching the amide compound to the surface of the methacrylic resin pellet include a method of mixing the methacrylic resin pellet and the amide compound by stirring, a method of spraying the amide compound on the methacrylic resin pellet, and the like. At that time, as the amide compound, an aqueous solution thereof may be used. Further, the attachment may be performed before the methacrylic resin is accumulated in the hopper of the injection molding machine or after the accumulation.

  The adhesion temperature may be adjusted, for example, by heating the methacrylic resin pellets and / or the amide compound before the adhesion, or may be adjusted by heating the atmospheric gas in the adhesion system. The pellet temperature at the time of attachment, specifically, the surface temperature of the pellet may be set to the predetermined attachment temperature. The attaching time is appropriately adjusted, but is usually about 10 seconds to 10 minutes.

  The methacrylic resin molding material thus obtained can be suitably used as a material for melt molding including injection molding after being subjected to pretreatment such as preliminary drying as necessary. In particular, it can be suitably used as a material for injection molding for producing a molded product having a relatively large thickness (for example, 3 mm or more) or a large product volume.

  Examples of the present invention will be described below, but the present invention is not limited thereto.

Examples 1-3, Comparative Example 1
As a methacrylic resin pellet, “SUMIPEX LG2” (transparent) manufactured by Sumitomo Chemical Co., Ltd. was used. As the amide compound, “Kao wax EB-FF” (ethylene bis stearamide, melting point: 141.5 to 146.5 ° C.) manufactured by Kao Corporation was used.

  After 3000 g of methacrylic resin pellets were heated in an oven to the temperature shown in Table 1, they were put in a plastic bag, 0.36 g of an amide compound was added, and the mouth of the plastic bag was closed and shaken for 30 seconds. The temperature of the pellet in the plastic bag at this time was measured and shown in Table 1 as the attaching temperature.

  Collect 300g of pellets each containing amide compound from a plastic bag 8 times, leave each sample overnight at room temperature (about 15 hours), then collect 200g from each sample and rotate its angle of repose It measured using the type | formula repose angle measuring device. The angle of repose of each sample is shown in Table 1 together with its average value and standard deviation. The angle of repose of the pellets not attached with the amide compound was 36 °.

Claims (3)

  A method for producing a methacrylic resin molding material, comprising attaching an amide compound to a surface of a methacrylic resin pellet at 35 ° C. or higher.   The production method according to claim 1, wherein the amount of the amide compound used is 0.003 to 0.05 parts by weight with respect to 100 parts by weight of the methacrylic resin pellets.   The production method according to claim 1 or 2, wherein the amide compound is a bisamide compound.