JP2006272786A - Injection molding method and injection mold of hollow molded product - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a molding method for a cylindrical hollow molded product with a bellows portion such as a boot for a constant velocity joint, which allows manufacturing the hollow molded product by which the flow nonuniformity of a resin in molding does not occur, good appearance can be obtained, deformation in demolding by high pressure air is reduced, dimensional accuracy and dimensional stability is good, and which can be recycled by injection molding in good productivity. <P>SOLUTION: A molten thermoplastic resin is injected from one point of a top portion of a dome-shaped 40 arranged so as to project from one opening end of the hollow molded product molded in a molding space 30 to the out side in an axial direction of the molded product to fill the molding space with the molten thermoplastic resin, thereby the hollow molded product whose one end is closed is molded, a cavity mold 10 is opened, and the molded product is taken out by blowing the high pressure air to the inner face of the part which becomes the lid formed in the dome-shaped gate 40 portion of the hollow molded product outwardly fitted on the core mold 20 from the core mold 20 after molding. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an injection molding method for a hollow molded article and an injection mold. More specifically, it is used as a cylindrical hollow molded product having both ends opened, for example, a constant velocity joint boot mounted on an automobile axle, a rack and pinion boot, a boot mounted on a shift lever, a shaft boot of a motorcycle, and the like. The present invention relates to a method for injection-molding a hollow molded article such as a resin boot having a bellows portion and a mold used therefor, and more particularly to an injection molding method and an injection mold for the hollow molded article using a thermoplastic resin. .

  Conventionally, various boots as described above are generally manufactured by injection molding of chloroprene rubber. However, chloroprene rubber is a vulcanized rubber and cannot be recycled. Therefore, boots made by blow molding of a recyclable polyester resin have been used. However, polyester resin boots are hard and brittle and lack flexibility, so they are durable especially in applications such as constant velocity joint boots that are used under harsh conditions where they are repeatedly bent while rotating at high speed. There is a problem with sex.

  A resin boot manufactured by injection molding of a thermoplastic resin is also known. As a method of molding a hollow molded article having a bellows part such as a constant velocity joint boot by injection molding of a thermoplastic resin, for example, a cavity mold divided so as to be openable and closable and disposed in the cavity mold There is a method of injecting and filling a molten thermoplastic resin into a molding space formed between the cavity mold and the core mold of a molding mold including a core mold. In this injection molding method, for example, as shown in FIG. 12A, an injection nozzle 104 is provided in a molding space 103 formed by a cavity mold 101 composed of a pair of split molds 101a and 101b and a core mold 102. A hollow molded product P with one end closed is injected by injecting a molten thermoplastic resin. After molding, the cavity mold 101 (101a, 101b) is opened and the core is opened as shown in FIG. By blowing high-pressure air from the air holes 105 provided in the core mold 102 into the hollow molded product P that is externally fitted to the mold 102, the hollow molded product P is hollow using the elastic deformation of the bellows portion. The molded product P is expanded and removed from the core mold 102 by high-pressure air. However, in this method, since the hollow molded product P is forcibly pulled out from the core mold 102 so that the hollow molded product P is expanded and the bellows part climbs over the peak portion in the core mold 101, the mold is removed. There is a problem that elongation or distortion occurs in the hollow molded product P, and the design dimensions of the mold do not match the dimensions of the product. Therefore, a method is known in which the core mold is divided and pulled out from the molded product so that the mold can be released without being forcibly removed. However, this method complicates the structure of the molding die and makes the molding operation complicated. In addition, the outer mold (cavity mold) and the core mold are preliminarily set to dimensions that are compressed by an amount corresponding to the extension of the final molded product, based on the height direction of the molded product. Thereafter, a method for enlarging a molded product to a predetermined size (for example, see Patent Document 1) is known. However, in this way, it is difficult to set the dimensions corresponding to the extension by the method of forming the dimensions corresponding to the extension corresponding to the time of demolding, and it is not easy to mold the final product to the dimensions as designed. Absent. Also, a boot manufacturing method having mounting portions at both ends of the bellows portion, the first step of forming a preform that is longer in the axial direction than the intended boot using a thermoplastic tree material, and mounting A second step of hermetically closing the opening of the part with a closing member, and when the temperature of the bellows part is equal to or higher than a predetermined temperature, the length of the preformed body in the axial direction is shortened. And a third step of obtaining a target boot by sucking existing gas from the inside of the preformed body via a communication port formed in the closing member and holding it in this state for a predetermined time. (See, for example, Patent Document 2). However, in this way, in the method of adjusting the dimensions by applying an external force to the molded product after molding, not only the strain due to stress remains in the molded product and the size may change after production, but also the manufacturing process Becomes complicated. Also known is a method in which the bellows portion is formed in a spiral shape, and the molded product is rotated and released from the core mold (see, for example, Patent Document 3). In this method, the bellows portion is formed in a spiral shape. Only goods can be manufactured.

  Further, conventionally, when manufacturing a cylindrical hollow molded product having a bellows portion such as a resin boot, a molten thermoplastic resin is injected into the molding space 103 formed from the cavity mold 101 and the core mold 102. For example, a thermoplastic resin melted from the injection nozzle 104 into the molding space 103 via planar gates 106A and 106B called direct or disk gates as shown in FIGS. 13 (a) and 13 (b), for example. Had been injected. However, as shown in FIGS. 13A and 13B, the planar gates 106A and 106B include a portion Y where the corner portion X and the injected resin material M collide with the inner surface of the mold as shown in FIGS. Therefore, the injected resin material M becomes turbulent (disturbed) at these portions X and Y, and flow irregularities and weld lines are likely to occur on the appearance of the molded product. Furthermore, after molding, when high-pressure air is blown from the core mold 102 into the molded product P, the high-pressure air is blown onto the planar portion Pc that serves as a lid of the hollow molded product P. There is a possibility that the pressure is not uniformly applied to the inside, and the portion Pc serving as the lid is torn due to the edge effect, and high-pressure air leaks from the torn portion, making it impossible to remove the mold. In order to prevent this, the thickness of the portion Pc (that is, the portion of the gates 106A and 106B) that becomes the lid is increased, and even if the tear is prevented, it is sprayed onto the inner surface of the flat lid portion and press-fitted into the molded product P. There is a possibility that the air to be released does not uniformly spread between the core mold 102 and the molded product P, and a demolding failure occurs in which only one side of the molded product is demolded from the core mold 102.

For this reason, although various proposals as described above have been made, a cylindrical hollow molded article having a bellows portion is excellent in flexibility, like a thermoplastic resin, particularly a thermoplastic elastomer, and has a joint boot. As described above, chloroprene rubber, which is a vulcanized rubber that cannot be recycled in the past, has been mainly used.
JP-A-6-190878 JP 11-257490 A Japanese Patent Laid-Open No. 10-73162

  In view of the above points, the present invention provides a cylindrical hollow molded article, particularly a hollow molding article having a bellows portion, for example, a hollow molded article such as a constant velocity joint boot, produced by injection molding of a thermoplastic resin. It has a good appearance without causing unevenness of flow, has little deformation when demolded by high-pressure air, has excellent dimensional accuracy and dimensional stability, and can be recycled with high productivity. It is intended to do.

  As a result of intensive research to achieve the above object, the present inventor has melted into a molding space of a molding die when manufacturing a cylindrical hollow molded article having a bellows portion by injection molding of a thermoplastic resin. By adopting a dome-shaped gate as the gate when injecting the thermoplastic resin, the flow of the resin during molding does not occur, and the dome-shaped lid is molded on the dome-shaped gate portion at the time of demolding Obtaining knowledge that high-pressure air is blown into the part that becomes the pressure, and the pressure of the high-pressure air blown into the molded product acts uniformly inside the molded product, so that the molded product can be easily removed from the core mold. The present invention has been completed.

  That is, the method for injection molding of a hollow molded product according to the present invention includes a cavity mold divided into an openable and closable shape and a cavity mold of the molding mold including a core mold disposed in the cavity mold. An injection molding method for producing a cylindrical hollow molded product having an opening at both ends by injecting and filling a molten thermoplastic resin into a molding space formed with a core mold, One point of the apex portion of the dome-shaped gate provided in communication with the molding space of the mold so as to protrude outwardly in the axial direction of the molded product from one opening edge of the hollow molded product molded in the molding space A hollow thermoplastic resin is injected into the molding space through the dome-shaped gate and filled with a thermoplastic resin melted in the axial direction of the hollow molded product to be molded. Mold the molded product, and after molding, the cavity mold Opening and blowing high-pressure air from the apex of the dome-shaped gate in the core mold toward the axial direction of the molded article into the inside of the hollow molded article externally fitted to the core mold. The molded product is taken out.

  As a preferred embodiment, the longitudinal cross-sectional shape of the dome-shaped gate is substantially hemispherical, and molten thermoplastic resin is injected from an injection hole provided at the apex portion of the approximately hemispherical gate.

  In a preferred embodiment, the molten thermoplastic resin is injected and filled into the molding space from the dome-shaped gate toward the axial direction of the molded product molded in the molding space.

  As a preferred embodiment, the hollow molded article includes a pair of annular attachment portions that are open at both ends, and a bellows portion that integrally connects the two.

  As a preferred embodiment, the hollow molded product has one mounting portion having a larger diameter than the other, and is formed in a molding space via a dome-shaped gate provided at the opening edge of the small-diameter side mounting portion in the molding die. It is made by injecting and filling a molten thermoplastic resin.

  As a preferred embodiment, the hollow molded article includes a large-diameter side attachment portion attached to the outer case, a small-diameter side attachment portion attached to the shaft, and a bellows portion integrally connecting both of them. It is.

  In a preferred embodiment, the thermoplastic resin is a thermoplastic elastomer.

  In a preferred embodiment, the thermoplastic elastomer resin contains an acrylic block copolymer (A).

  In a preferred embodiment, the thermoplastic elastomer resin is a thermoplastic elastomer composition containing an acrylic block copolymer (A) and an olefinic thermoplastic elastomer (B).

  As a preferred embodiment, the thermoplastic elastomer composition comprises 50 to 600 parts by weight of the olefinic thermoplastic elastomer (B) and 5 to 5 parts of the compatibilizer (C) with respect to 100 parts by weight of the acrylic block copolymer (A). Contains 50 parts by weight.

  As a preferred embodiment, the acrylic block copolymer (A) contains 50 to 90% by weight of the acrylic polymer block (a) and 50 to 10% by weight of the methacrylic polymer block (b). To do.

  As a preferred embodiment, at least one of the acrylic polymer block (a) and the methacrylic polymer block (b) has a reactive functional group (c).

  In a preferred embodiment, the olefinic thermoplastic elastomer (B) is obtained by dynamically crosslinking an EPDM rubber or an acrylonitrile-butadiene rubber in an olefin resin.

  In a preferred embodiment, the compatibilizer (C) is an olefin thermoplastic resin containing an epoxy group.

  An injection mold for a hollow molded product according to the present invention includes a cavity mold divided so as to be openable and closable, and a core mold disposed in the cavity mold, and the cavity mold and the core mold are provided. An injection mold for producing a cylindrical hollow molded product having an opening at both ends by injecting and filling a molten thermoplastic resin into a molding space formed between the mold and the molding A dome-shaped gate is provided so as to protrude outward in the axial direction of a molded product molded in the molding space, and a single injection hole is provided in a cavity mold located at the apex of the dome-shaped gate. An openable and closable air hole communicating with the high-pressure air supply means is provided on the inner surface of the apex portion of the dome-shaped gate in the core mold, and a molten thermoplastic resin is molded from the injection hole through the dome-shaped gate. In space After filling and filling to form a hollow molded product, the cavity mold is opened, the air hole is opened, and high pressure air is blown from the high pressure air supply means into the hollow molded product through the air hole. The molded product is taken out from the core mold.

  In a preferred embodiment, the longitudinal cross-sectional shape of the dome-shaped gate is substantially hemispherical, and an injection hole extending in the axial direction of the hollow molded article to be molded is provided at the apex of the substantially hemispherical gate.

  As a preferred embodiment, the opening edge to the molding space in the dome-shaped gate is formed so as to be in the same direction as the axial direction of the molded product molded in the molding space.

  As a preferred embodiment, a vent hole penetrating in the axial direction in the axial center portion of the core mold and connected to the high-pressure air supply means is provided, and a tip end portion of the vent hole is used as the air hole. An opening / closing shaft that slides in the axial direction of the core mold is provided in the air hole with the tip facing the dome-shaped gate, and the air hole can be opened / closed by the opening / closing shaft.

  As a preferred embodiment, a single or a plurality of ventilation grooves extending in the axial direction are provided on the inner peripheral surface inside the ventilation hole, and the opening and closing shaft is retracted to a position where the tip is provided with the ventilation groove. The air hole can be opened and high-pressure air can be blown into the molded product from the air hole through the air groove and the air hole.

  A preferable embodiment is a molding die for molding a hollow molded product including a pair of annular mounting portions opened at both ends and a bellows portion integrally connecting the two.

  A preferred embodiment is a molding die for molding a hollow molded product in which one attachment portion has a larger diameter than the other, and the dome-shaped gate is provided at the opening edge of the small-diameter side attachment portion in the molding space. It is provided.

  As a preferred embodiment, molding for molding a constant velocity joint boot including a large-diameter side attachment portion attached to the outer case, a small-diameter side attachment portion attached to the shaft, and a bellows portion integrally connecting the two. It is a mold.

  In the present invention, a molding formed between the cavity mold and the core mold of a molding mold comprising a cavity mold divided so as to be openable and closable and a core mold disposed in the cavity mold. Injecting and filling the molten thermoplastic resin into the space to obtain a cylindrical hollow molded product opened at both ends, the molten thermoplastic resin is injected from one of the apex portions of the dome-shaped gate, By injecting and filling the thermoplastic resin into the molding space through the dome-shaped gate and forming a hollow molded product with one end closed, the molten thermoplastic resin injected into the molding space is The dome-shaped gate is smoothly filled into the molding space, and the flow of the resin is not disturbed and the appearance of the molded product is not impaired. In addition, after molding, it was press-fitted by blowing high pressure air from the apex portion of the dome-shaped gate in the core mold to the inside of the hollow molded product that is externally fitted to the core mold. After air is blown onto the dome-shaped lid portion formed by the dome-shaped gate portion, the air is smoothly blown along the inner surface of the dome-shaped lid portion and enters between the core mold and the hollow molded product, The pressure of high-pressure air acts uniformly inside the molded product, and it can be easily removed from the core mold, causing the molded product to be deformed or causing excessive stress to remain in the molded product and causing distortion. Therefore, it is possible to obtain a molded product having high dimensional stability of the molded product and little dimensional change. In addition, it is possible to manufacture a good hollow molded product with high productivity without complicating the mold structure and making the operation complicated as in the case of employing a split-type core mold. In addition, the hollow molded product molded in a state with a dome-shaped lid as described above is used to cut off the dome-shaped lid portion and the runner portion that is molded in a connected state after the molding. Product.

  Also, the longitudinal cross-sectional shape of the dome-shaped gate is approximately hemispherical, and the molten thermoplastic resin is injected from the injection hole provided at the apex of the approximately hemispherical gate, so that the turbulence generated in the injected resin flow Flow (disturbance) can be suppressed.

  The opening edge to the molding space in the dome-shaped gate is formed so as to be in the same direction as the axial direction of the molded product molded in the molding space, and the molten thermoplastic resin is fed from the dome-shaped gate into the molding space. By injecting and filling the molding space in the molding space in the axial direction of the molded product, resin is injected linearly from the dome-shaped gate into the molding space, and the turbulent flow (disturbance) generated in the resin flow Can be suppressed.

  A vent hole that penetrates in the axial direction of the core die of the core mold and is connected to the high-pressure air supply means is provided, and the tip of the vent hole serves as the air hole, and the tip is inserted into the vent hole. An opening / closing shaft that slides in the axial direction of the core mold is provided facing the dome-shaped gate, and the air hole can be opened / closed by the opening / closing shaft, so that the molten thermoplastic resin into the molding space can be opened and closed. It is possible to reliably prevent the resin from entering the air holes during injection, and at the time of mold release after molding, the high pressure air is quickly blown into the molded product at the same time as the cavity mold is opened. It is possible to remove the mold, and molding with high productivity becomes possible.

  One or more ventilation grooves extending in the axial direction are provided on the inner peripheral surface of the ventilation hole, and the opening and closing shaft is retracted to a position where the tip is provided with the ventilation groove, thereby opening an air hole. By allowing high-pressure air to be blown into the molded product from the ventilation hole through the ventilation groove and the air hole, the resin can surely enter the air hole when the molten thermoplastic resin is injected into the molding space. Can be prevented.

  In the present invention, a hollow molded product having a bellows part can be easily removed from the core mold, and therefore, a pair of annular mounting portions opened at both ends and a bellows integrally connecting the two It is suitable for molding of a hollow molded product having a portion.

  In addition, in a molded product in which one mounting portion has a larger diameter than the other, the heat melted into the molding space via a dome-shaped gate provided at the opening edge of the small-diameter side mounting portion in the molding die. By injecting and filling the plastic resin, the molten thermoplastic resin injected from the dome-shaped gate is smoothly filled into the molding space, and a good molded product in which no weld line is generated can be obtained.

  In particular, the present invention relates to a constant velocity joint boot comprising a large-diameter side attachment portion attached to an outer case, a small-diameter side attachment portion attached to a shaft, and a bellows portion integrally connecting the two. It is suitable for manufacturing by molding.

  The thermoplastic resin is a thermoplastic elastomer, and further the thermoplastic elastomer resin includes an acrylic block copolymer (A). In particular, the thermoplastic elastomer resin is an acrylic block copolymer (A). In the case of the thermoplastic elastomer composition containing the olefin-based thermoplastic elastomer (B), it is excellent in flexibility and durability, and an optimal molded article for a constant velocity joint boot or the like can be obtained.

  The thermoplastic elastomer composition contains 50 to 600 parts by weight of an olefinic thermoplastic elastomer (B) and 5 to 50 parts by weight of a compatibilizer (C) with respect to 100 parts by weight of the acrylic block copolymer (A). Further, the acrylic block copolymer (A) contains 50 to 90% by weight of the acrylic polymer block (a) and 50 to 10% by weight of the methacrylic polymer block (b). Thus, a hollow molded article excellent in flexibility and durability can be obtained.

  Moreover, when the reactive functional group (c) is contained in at least one polymer block of the acrylic polymer block (a) and the methacrylic polymer block (b), a molded product having excellent heat resistance is obtained. Obtainable.

  When the olefinic thermoplastic elastomer (B) is a dynamically crosslinked EPDM rubber or acrylonitrile-butadiene rubber in an olefin resin, it has a compression set excellent in rubber properties while having thermoplasticity, A molded product having a small elasticity change at a high temperature can be obtained.

  Further, when the compatibilizing agent (C) is an olefinic thermoplastic resin containing an epoxy group, the epoxy group of the olefinic thermoplastic resin is an acrylic block copolymer (A) polymethacrylic anhydride. It is preferable that the acrylic block copolymer (A) and the olefinic thermoplastic elastomer (B) can be made better compatible by reacting with the unit (c) such as a product.

  Embodiments of the present invention will be described in detail with reference to the drawings based on examples, but the present invention is not limited thereto.

  The injection molding method and injection mold according to the present invention are used when, for example, a resin boot having a bellows portion such as a constant velocity joint boot is molded by injection molding of a thermoplastic elastomer resin.

  An injection mold according to the present invention includes, for example, a cavity mold 10 including divided molds 10A and 10B, which is divided into two to be opened and closed, and one divided mold 10A of the cavity mold 10 as shown in FIG. 10B, a hollow core molding 20 such as a joint boot is injected and filled with a thermoplastic elastomer resin in a cylindrical molding space 30 formed between them. The product is molded. The split molds 10A and 10B of the cavity mold 10 are fixed to a base plate (not shown) located on the back side of the cavity mold 10 and are provided so as to be movable to the left and right together with the base plate so as to be freely opened and closed. It is fixed to a base plate (not shown) located on the upper side.

  The injection mold shown in the figure is, for example, an annular large-diameter side attachment portion 3 attached to an outer case and an annular small-diameter side attachment portion 2 attached to a shaft, as shown in FIG. The constant velocity joint boot 1 including the bellows portion 4 is used for injection molding. As shown in FIGS. 2 and 3, the pair of split molds 10A and 10B constituting the cavity mold 10 have a substantially bilaterally symmetric shape, and the boots 1 formed on the respective split surfaces 11A and 11B facing each other. Depending on the shape, molding recesses 30 </ b> A and 30 </ b> B constituting the outer peripheral surface of the molding space 30 are formed. The concave portions 30A and 30B are formed in a shape in which the small-diameter side mounting portion 2 of the boot 1 is positioned below the dividing surfaces 11A and 11B and expands upward in a bellows shape. Moreover, in order to form a dome-shaped lid from the opening end of the small-diameter side mounting portion 2 of the boot 1 at the lower portion of each recess 30A, 30B, approximately 1/4 spherical gate recesses 31A, 31B are formed. When the split molds 10A and 10B are formed and closed, the pair of gate recesses 31A and 31B constitute the outer peripheral surface of the dome-shaped gate. Furthermore, a pair of grooves 41A forming a resin injection port 41 extending in the axial direction of the boot 1 molded in the molding space 30 (molding recesses 30A, 30B) downward from the lower end central part of each of the gate recesses 31A, 31B, 41B is provided, and the lower end portions of the grooves 41A and 41B form a resin injection path 42 communicating with a nozzle mounting portion (reference numeral 43 in the split mold 10B) connected to a resin injection nozzle of an injection molding machine (not shown). The grooves 42A and 42B communicate with each other. Thus, the dome-shaped gate 40 for injecting resin is preferably provided on the small-diameter side mounting portion 2 side in order to reduce the distortion of the boot shape after molding.

  On the other hand, as shown in FIG. 1, the core mold 20 includes a hollow outer mold 20 </ b> A that forms the inner peripheral surface of the molding space 30 according to the inner surface shape of the boot 1, and a downward facing that is fitted into the outer mold 20 </ b> A. Are substantially fixed to the lower surface of the substrate 20C with bolts or the like (not shown). A dome-shaped convex portion 23 that forms the inner peripheral surface of the dome-shaped gate is formed at the lower end portion of the outer mold 20A, and the outer molds 20A and 20B of the core mold 20 are formed from the center end of the dome-shaped convex portion 23. A vent hole 24 is formed so as to penetrate through the substrate 20C, and a lower end opening of the vent hole 24 opens to the dome-shaped gate 40, and serves as an air hole 21 that ejects air toward the inside of the molded product P. The vent hole 24 is provided with an opening / closing shaft 22 provided so as to be slidable instantaneously by a solenoid or the like. The air hole 21 is closed so that the molten thermoplastic resin injected from the injection port 41 does not enter and is removed. At the time of molding, the pair of split molds 10A and 10B of the cavity mold 10 are opened, and at the same time, the opening / closing shaft 22 slides up in the vent hole 24, and high-pressure air from an air compressor (not shown) is air. 21 blown toward an inner surface of the molded article from, and is a core metal mold 20 and the structure in which the molded article is demolded.

  The shape of the dome-shaped gate 40 is not limited to that shown in the figure, and the flow of the injected resin is not disturbed, and from the air hole 21 to the inside of the molded product, specifically, the boot-shaped gate 40 portion. As long as the shape is such that the high-pressure air blown toward the inner surface of the portion that becomes the lid of the molded product formed on the molded product acts uniformly on the inner surface of the molded product, as shown in FIG. By making the shape substantially hemispherical and injecting the molten thermoplastic resin M from the injection hole 41 provided at the apex portion of the substantially hemispherical gate, the flow of the resin M to be injected (indicated by arrows in the figure) Occurrence of turbulent flow (turbulence) can be effectively suppressed, and flow molding and weld lines do not occur, and a molded product excellent in appearance and mechanical properties can be obtained.

  Furthermore, the opening edge 40a to the molding space 30 in the dome-shaped gate 40 is formed in a substantially cylindrical shape so as to be in the same direction as the axial direction of the boot 1 molded in the molding space 30, and is melted thermoplastic resin. Is injected into the molding space 30 from the dome-shaped gate 40 in the axial direction of the boot molded in the molding space 30, and the resin is injected linearly from the dome-shaped gate 40 into the molding space 30. Therefore, the turbulence (turbulence) generated in the resin flow can be more effectively suppressed.

  Further, as shown in the figure, the axial center portion of the core mold 20 is provided with a vent hole 24 penetrating in the axial direction and connected to a high-pressure air supply means such as a compressor (not shown). Is provided with an opening / closing shaft 22 that slides in the axial direction of the core mold 20 with the tip 22a facing the dome-shaped gate 40 in the ventilation hole 24. By making the air hole 21 openable and closable by 22, it is possible to reliably prevent the resin from entering the air hole 30 when the molten thermoplastic resin is injected into the molding space 30, and after molding. When the boot molded product P is released from the core mold 20, the boot 1 molded from the core mold 20 is blown by blowing high-pressure air into the boot molded product P that is quickly molded simultaneously with the opening of the cavity mold 10. Demolding Rukoto can, it becomes possible to high productivity of the molding.

  Furthermore, as shown in FIG. 4, the diameter of the portion 24a near the tip of the vent hole 24 of the core mold 20 is reduced, and one or a plurality of vent grooves extending in the axial direction are provided on the inner peripheral surface thereof, as shown in the figure. Then, four vent grooves 25 are provided, and as shown in FIG. 8, the opening / closing shaft 22 is retracted until the end of the opening 22a comes to the position where the ventilation grooves 25 are provided, and the air holes 21 are opened. By allowing high-pressure air to be blown from the vent hole 24 through the vent groove 25 and the air hole 21 into the molded boot molded product P, air is injected when the molten thermoplastic resin is injected into the molding space 30. Intrusion of the resin into the hole 21 can be reliably prevented.

  In order to injection-mold a hollow molded article, for example, a constant velocity joint boot from a thermoplastic resin such as a thermoplastic elastomer, by using the injection mold as described above, as shown in FIG. The split molds 10A and 10B of the mold 10 are joined together, and a core mold 20 is disposed in the cavity mold 10 so that a molding space corresponding to a predetermined boot shape is formed between the cavity mold 10 and the core mold 20. 30 forms. Next, from an injection molding machine (not shown) connected to the nozzle mounting portion 43 of the mold, as shown in FIGS. 5 and 6, the mold resin injection path 42, the injection port 41, the dome-shaped gate 40, and further in the molding space 30 Then, a molten thermoplastic resin is injected and filled, and a hollow molded product having one end closed, for example, a molded product P of a boot, is formed by a portion c serving as a lid formed on the dome-shaped gate 40 portion.

  After the molding as described above, as shown in FIG. 8, the split molds 10A and 10B of the cavity mold 10 are opened to the left and right, and the hollow molding that is externally fitted to the core mold 20 as shown in FIG. The inside of the product P is in close contact with the core die 20 by blowing high-pressure air in the axial direction from the apex portion of the dome-shaped gate 40 in the core die 20 to the inner surface of the portion c serving as a lid of the molded product P. A pressure is applied uniformly to the inner surface of the molded product P to form a gap between the outer peripheral surface of the core mold 20 and the inner peripheral surface of the molded product P, and the molded product P is instantaneously expanded. The molded product P is removed from the mold 20 by pushing it downward.

  In the molded product P removed from the core mold 20, as shown in FIG. 9, excess resin portions such as the runner portion and the sprue portion from the portion c serving as a lid are cut off from the portion indicated by L in the drawing. Thus, a product such as a resin boot 1 as shown in FIG. 10 is obtained.

  Next, description will be made regarding the use in the injection molding method of the present invention. The resin to be used is not particularly limited, but a thermoplastic resin is preferable, and when a resin boot such as a joint boot is molded, it is preferable to use a thermoplastic elastomer.

The thermoplastic elastomer resin is not particularly limited, but is preferably an acrylic block copolymer that is excellent in moldability, heat resistance, oil resistance, compression set and small tensile set. In particular, an olefin / acrylic composite thermoplastic elastomer resin is preferably used.

  Also, thermoplastic polyurethane (TPU), chlorine-containing polymers such as polyvinylidene chloride (PVDC), polyvinyl chloride (PVC), chlorinated polyethylene (CPE), fluorine-containing polymers such as polyvinylidene fluoride (PDVF), polyester It is also possible to use thermoplastic polymers such as acrylonitrile-butadiene-styrene copolymer (ABS), styrene-acrylonitrile copolymer (SAN), styrene-maleic anhydride copolymer (SMA), polyacetals, polycarbonates, polyphenylene oxide.

  Examples of the acrylic block copolymer include those described in JP-A No. 2004-300164 and JP-A No. 2004-315803. The olefin / acrylic composite thermoplastic elastomer resin includes (A) an acrylic block copolymer, (B) an olefinic thermoplastic elastomer, and (C) a compatibilizer. Preferably used.

  The olefin / acrylic composite thermoplastic elastomer resin will be described. The olefin / acrylic composite thermoplastic elastomer resin suitably used in the present invention is a thermoplastic elastomer composition comprising (A) an acrylic block copolymer and (B) an olefinic thermoplastic elastomer, A thermoplastic elastomer composition containing (C) a compatibilizer in addition to (A) and (B) is preferred.

  The acrylic block copolymer (A) that is preferably used as the thermoplastic elastomer in the present invention will be described in more detail.

  As the acrylic block copolymer (A), an acrylic polymer block (a) and a methacrylic polymer block (b) are preferable. The structure of the acrylic block copolymer (A) may be a linear block copolymer, a branched (star) block copolymer, or a mixture thereof. . The structure of the acrylic block copolymer (A) may be used depending on the processing characteristics and mechanical characteristics, but is preferably a linear block copolymer from the viewpoint of cost and ease of polymerization. .

The linear block copolymer may have any structure, but the acrylic polymer block constituting the acrylic block copolymer (A) from the viewpoint of its physical properties or physical properties when made into a composition. (A) and the methacrylic polymer block (b) have the general formula: (ab) _n , general formula: b- (ab) _n , general formula: (ab) _n -a (n Is preferably at least one block copolymer selected from the group consisting of block copolymers represented by 1 to 3). Among these, an ab type diblock copolymer, a bab type triblock copolymer, or a mixture thereof from the viewpoint of easy handling during processing and physical properties in the case of a composition. Is preferred.

  The acrylic block copolymer (A) preferably has a reactive functional group (c) in at least one of the blocks (a) and (b).

  Further, as the reactive functional group (c), the general formula (1):

(Wherein R ¹ is a hydrogen atom or a methyl group, and may be the same or different, p is an integer of 0 or 1, q is an integer of 0 to 3) Unit (c) consisting of (c1) and / or a unit (c2) containing a carboxyl group is present per at least one polymer block of acrylic polymer block (a) and methacrylic polymer block (b). One or more are preferable, and when the number is two or more, the mode in which the unit (c) is polymerized may be random copolymerization or block copolymerization. .

  The manner in which the unit (c) is contained in the block copolymer is represented by taking a b-a-b type triblock copolymer as an example, and (b / c) -ab type, (b / c)- a- (b / c) type, cb-a-b type, c-b-a-b-c type, b- (a / c) -b-type, b-a-c-b type, b -C-ab type and the like may be used. Here, (a / c) means that the unit (c) is contained in the block (a), and (b / c) means that the unit (c) is contained in the block (b). C−a− and a−c− indicate that the unit (c) is bonded to the end of the block (a). Expressions are (a / c), (b / c), c-a-, a-c-, etc., all of which belong to block (a) or block (b).

  The number average molecular weight of the acrylic block copolymer (A) is preferably 30000 to 500000, more preferably 40000 to 400000, and further preferably 50000 to 300000. If the molecular weight is less than 30,000, sufficient mechanical properties as an elastomer may not be exhibited, and if it exceeds 500,000, processing properties may be deteriorated.

  The ratio (Mw / Mn) of the weight average molecular weight (Mw) and the number average molecular weight (Mn) of the acrylic block copolymer (A) is preferably 1 to 2, and preferably 1 to 1.8. Is more preferable. If Mw / Mn exceeds 2, the compression set of the acrylic block copolymer (A) may deteriorate. In the present invention, the number average molecular weight (Mn) and the weight average molecular weight (Mw) are obtained by using gel permeation chromatography and using chloroform as a mobile phase to obtain a molecular weight in terms of polystyrene.

  The composition ratio between the acrylic polymer block (a) and the methacrylic polymer block (b) constituting the acrylic block copolymer (A) is the required physical properties and molding required during processing of the composition. And the molecular weight required for each of the acrylic polymer block (a) and the methacrylic polymer block (b). When the range of the composition ratio of a preferable acrylic polymer block (a) and a methacrylic polymer block (b) is illustrated, the acrylic polymer block (a) is 50 to 90% by weight, and further 50 to 80% by weight. In particular, it is 50 to 70% by weight, the methacrylic polymer block (b) is 50 to 10% by weight, further 50 to 20% by weight, particularly 50 to 30% by weight. When the proportion of the acrylic polymer block (a) is less than 50% by weight, the mechanical properties as an elastomer, particularly the elongation at break may be lowered, or the flexibility may be lowered. In some cases, rubber elasticity at high temperatures may be reduced.

The relationship between the glass transition temperatures of the acrylic polymer block (a) and the methacrylic polymer block (b) constituting the acrylic block copolymer (A) is the glass transition of the acrylic polymer block (a). When the temperature is Tg _a and that of the methacrylic polymer block (b) is Tg _b , the relationship of the following formula is preferably satisfied.
Tg _a <Tg _b

The glass transition temperature (Tg) of the acrylic polymer block (a) or the methacrylic polymer block (b) is roughly based on the following Fox formula, and the weight ratio of the monomer in each polymer block is used. Can be obtained.
_{1 / Tg = (W 1 /} Tg 1) + (W 2 / Tg 2) + ... + (W m / Tg m)
W ₁ + W ₂ + ... + W _m = 1
(In the formula, Tg represents the glass transition temperature of the polymer block, and Tg ₁ , Tg ₂ ,..., Tg _m represent the glass transition temperatures of the polymerized monomers (homopolymers), and W ₁ , W ₂ ,..., W _m represent the weight ratio of the polymerized monomers.

  The glass transition temperature of each polymerized monomer in the Fox formula is described, for example, in Polymer Handbook Third Edition (Wiley-Interscience, 1989). So this value is used.

Acrylic polymer block (a) is preferably a relation of the glass transition temperature of the methacrylic polymer block (b), satisfies the Tg _a <Tg _b. The acrylic polymer block (a) contains 50 to 100% by weight, preferably 60 to 100% by weight of a unit containing an acrylate ester, and has a functional group serving as a precursor of the unit (c). 0 to 50% by weight, preferably 0 to 40% by weight of the monomer, and 0 to 50% by weight, preferably 0 to 25% by weight, of other vinyl monomers copolymerizable therewith. It is preferable to contain. If the proportion of the unit containing the acrylate ester is less than 50% by weight, the physical properties, particularly the elongation of the tensile properties, which are characteristics when using the acrylate ester may be reduced.

The molecular weight of the acrylic polymer block (a) may be determined from the required elastic modulus and rubber elasticity, the time required for the polymerization, and the like. When the number average molecular weight of the acrylic polymer block (a) is M _A , the range is exemplified. Preferably, M _A > 3000, more preferably M _A > 5000, still more preferably M _A > 10000, and particularly preferably M _A. If the number average molecular weight M _A of the acrylic polymer block (a) which is> 20000, most preferably M _A > 40000 is smaller than the above range, the tensile elongation is lowered. However, since the polymerization time tends to be longer when the number average molecular weight is large, the polymerization time may be set according to the required productivity, but is preferably 500,000 or less, more preferably 300,000 or less.

  Examples of the acrylic acid ester constituting the acrylic polymer block (a) include methyl acrylate, ethyl acrylate, n-propyl acrylate, n-butyl acrylate, isobutyl acrylate, n-pentyl acrylate, and acrylic acid. Acrylic aliphatic hydrocarbons such as n-hexyl, n-heptyl acrylate, n-octyl acrylate, 2-ethylhexyl acrylate, nonyl acrylate, decyl acrylate, dodecyl acrylate, stearyl acrylate, etc. ~ 18 alkyl) esters; acrylic acid cycloaliphatic hydrocarbon esters such as cyclohexyl acrylate and isobornyl acrylate; aromatic aromatic hydrocarbon esters such as phenyl acrylate and toluyl acrylate; aralkyl esters of acrylic acid such as benzyl acrylate Ester, ester of acrylic acid such as 2-methoxyethyl acrylate and 3-methoxybutyl acrylate and functional group-containing alcohol having etheric oxygen; trifluoromethyl methyl acrylate, 2-trifluoromethyl ethyl acrylate, acrylic 2-perfluoroethylethyl acid, 2-perfluoroethyl-2-perfluorobutylethyl acrylate, 2-perfluoroethyl acrylate, perfluoromethyl acrylate, diperfluoromethyl methyl acrylate, 2-peracrylate Fluorinated alkyl esters such as fluoromethyl-2-perfluoroethylmethyl, 2-perfluorohexylethyl acrylate, 2-perfluorodecylethyl acrylate, 2-perfluorohexadecylethyl acrylate, etc.These may be used alone or in combination of two or more. Among these acrylate esters, n-butyl acrylate is preferable from the viewpoint of low-temperature characteristics, compression set, cost, and availability. If oil resistance and mechanical properties are required, ethyl acrylate is preferred. When low temperature characteristics, mechanical characteristics, and compression set are required, 2-ethylhexyl acrylate is preferred. From the standpoints of mechanical properties, oil resistance and low temperature properties, 2-methoxyethyl acrylate 10-90% by weight, n-butyl acrylate 10-90% by weight, ethyl acrylate 0% in the whole acrylic polymer block (a) A mixture of ˜80 wt% is preferable, and a mixture of 2-methoxyethyl acrylate 15 to 85 wt%, n-butyl acrylate 15 to 85 wt%, and n-ethyl acrylate 0 to 70 wt% is more preferable.

  Examples of the functional group serving as a precursor of the unit (c) include t-butyl acrylate, isopropyl acrylate, α, α-dimethylbenzyl acrylate, α-methylbenzyl acrylate, and t-butyl methacrylate. , Isopropyl methacrylate, α, α-dimethylbenzyl methacrylate, α-methylbenzyl methacrylate, and the like, but are not limited thereto. A method for introducing the unit (c) into the acrylic block copolymer (A) will be described later.

  Furthermore, examples of the vinyl monomer copolymerizable with the acrylate ester constituting the acrylic polymer block (a) include a methacrylic acid ester, an aromatic alkenyl compound, a vinyl cyanide compound, and a conjugated diene compound. , Halogenated unsaturated compounds, unsaturated dicarboxylic acid compounds, vinyl ester compounds, maleimide compounds, and the like.

  Examples of the methacrylic acid ester include methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, n-pentyl methacrylate, and n-methacrylate. Methacrylic acid aliphatic carbonization such as hexyl, n-heptyl methacrylate, n-octyl methacrylate, 2-ethylhexyl methacrylate, nonyl methacrylate, decyl methacrylate, dodecyl methacrylate, stearyl methacrylate Hydrogen (for example, alkyl having 1 to 18 carbon atoms) ester; methacrylic acid alicyclic hydrocarbon ester such as cyclohexyl methacrylate and isobornyl methacrylate; aralkyl methacrylic acid aralkyl ester such as benzyl methacrylate; phenyl methacrylate Methacrylic acid aromatic hydrocarbon esters such as toluyl methacrylate; Esters of methacrylic acid such as 2-methoxyethyl methacrylate and 3-methoxybutyl methacrylate and functional group-containing alcohols having etheric oxygen; Trifluoromethyl methyl acrylate, 2-trifluoromethyl ethyl methacrylate, 2-perfluoroethyl ethyl methacrylate, 2-perfluoroethyl-2-perfluorobutyl ethyl methacrylate, 2-perfluoro methacrylate Ethyl, perfluoromethyl methacrylate, diperfluoromethyl methyl methacrylate, 2-perfluoromethyl-2-perfluoroethyl methyl methacrylate, 2-perfluorohexyl methacrylate, 2-par methacrylate Fluoro Shiruechiru, such as methacrylic acid fluorinated alkyl esters such as meta 2-perfluoro-hexadecyl acrylate and the like.

  Examples of the aromatic alkenyl compound include styrene, α-methylstyrene, p-methylstyrene, and p-methoxystyrene.

  Examples of the vinyl cyanide compound include acrylonitrile and methacrylonitrile.

  Examples of the conjugated diene compound include butadiene and isoprene.

  Examples of the halogen-containing unsaturated compound include vinyl chloride, vinylidene chloride, perfluoroethylene, perfluoropropylene, and vinylidene fluoride.

  Examples of the unsaturated dicarboxylic acid compound include maleic anhydride, maleic acid, monoalkyl esters and dialkyl esters of maleic acid, fumaric acid, monoalkyl esters and dialkyl esters of fumaric acid, and the like.

  Examples of the vinyl ester compound include vinyl acetate, vinyl propionate, vinyl pivalate, vinyl benzoate, and vinyl cinnamate.

  Examples of the maleimide compound include maleimide, methylmaleimide, ethylmaleimide, propylmaleimide, butylmaleimide, hexylmaleimide, octylmaleimide, dodecylmaleimide, stearylmaleimide, phenylmaleimide, cyclohexylmaleimide and the like.

  The copolymerizable vinyl monomers may be used alone or in combination of two or more. The vinyl monomer is required when the acrylic polymer block (a) is used as a composition, and the glass transition temperature, elastic modulus, and polarity required for the acrylic polymer block (a). The preferred one can be selected depending on the properties to be used, compatibility with the olefin-based thermoplastic elastomer (B) and the polyorganosiloxane-based graft polymer (D), and the like. For example, acrylonitrile can be copolymerized for the purpose of improving oil resistance.

The glass transition temperature of the acrylic polymer block (a) is preferably 50 ° C. or lower, more preferably 0 ° C. or lower. When the glass transition temperature is higher than 50 ° C., the rubber elasticity of the acrylic block copolymer (A) may be lowered. Setting the glass transition temperature of the acrylic polymer block _(a) (Tg a) uses the values described in Polymer Handbook Third Edition of the foregoing as the glass transition temperature of the homopolymer of each monomer constituting the polymer block From the polymerization ratio of each monomer, the weight ratio of the monomer constituting the polymer block can be adjusted according to the Fox formula.

Methacrylic polymer block (b) is preferably a relation of the glass transition temperature of the acrylic polymer block (a), satisfies the Tg _a <Tg _b. From the viewpoint of easily obtaining an acrylic block copolymer (A) having desired physical properties, cost and availability, a unit containing a methacrylic acid ester is contained in the entire methacrylic polymer block (b). 10 to 99.5% by weight, preferably 20 to 99.5% by weight of a monomer containing 50 to 100% by weight, preferably 50 to 85% by weight and having a functional group as a precursor of the unit (c) It is preferable to contain 0.1 to 50% by weight, and preferably 0.1 to 25% by weight, of other vinyl monomers that can be copolymerized therewith.

  The molecular weight of the methacrylic polymer block (b) may be determined from the required cohesive force and the time required for the polymerization.

The cohesive force is said to depend on the interaction between molecules (in other words, polarity) and the degree of entanglement, and as the number average molecular weight increases, the entanglement point increases and the cohesive force increases. That is, the number-average molecular weight required for the methacrylic polymer block (b) and M _B, the the entanglement molecular weight of the polymer constituting the methacrylic polymer block (b) of M _B as Mc _B Exemplifying the range, when cohesive force is required, preferably M _B > Mc _B. As a further example, when a further cohesive force is required, preferably M _B > 2 × Mc _B. Conversely, when it is desired to achieve both a certain cohesive force and creep property, Mc _B <M _B <2 × Mc _B is preferred. The molecular weight between the entanglement points may be referred to Wu et al. (Polym. Eng. And Sci., 1990, Vol. 30, p. 753). For example, the range of the number average molecular weight of the methacrylic polymer block (b) when the cohesive force is required assuming that the methacrylic polymer block (b) is entirely composed of methyl methacrylate. Then, it is preferable that it is 9200 or more. However, when the unit (c) is contained in the methacrylic polymer block (b), the cohesive force by the unit (c) is imparted, so the number average molecular weight can be set lower than this. When the number average molecular weight is increased, the polymerization time tends to be longer, so it may be set according to the required productivity, but is preferably 200000 or less, more preferably 100000 or less.

  Examples of the methacrylic acid ester constituting the methacrylic polymer block (b) include those exemplified as vinyl monomers copolymerizable with the acrylate ester constituting the acrylic polymer block (a). It is done. These methacrylic acid esters may be used alone or in combination of two or more. Among these, methyl methacrylate is preferable from the viewpoints of cost and availability.

  Examples of the monomer having a functional group serving as a precursor of the unit (c) include monomers similar to the constituent monomers exemplified in the description of the acrylic polymer block (a).

  Examples of vinyl monomers copolymerizable with the methacrylic acid ester constituting the methacrylic polymer block (b) include acrylic acid esters, aromatic alkenyl compounds, vinyl cyanide compounds, conjugated diene compounds, halogens. Examples thereof include an unsaturated compound, an unsaturated dicarboxylic acid compound, a vinyl ester compound, and a maleimide compound.

  As said acrylic ester, the monomer similar to the structural monomer illustrated by description of the said acrylic polymer block (a) is mentioned.

  The aromatic alkenyl compound, vinyl cyanide compound, conjugated diene compound, halogen-containing unsaturated compound, unsaturated dicarboxylic acid compound, vinyl ester compound and maleimide compound are the same in the description of the acrylic polymer block (a). Examples thereof include the same monomers as the constituent monomers exemplified as the polymerizable vinyl monomer. As the copolymerizable vinyl monomer, at least one of the above constituent monomers is used.

  The polymer of methyl methacrylate is almost quantitatively depolymerized by thermal decomposition, but in order to suppress this, when the methacrylic polymer block (b) is composed of a polymer of methyl methacrylate polymer. Can be copolymerized with acrylate esters such as methyl acrylate, ethyl acrylate, butyl acrylate, 2-methoxyethyl acrylate or mixtures thereof or styrene. Furthermore, acrylonitrile can be copolymerized with the methacrylic polymer block (b) for the purpose of improving oil resistance.

The glass transition temperature (Tg _b ) of the methacrylic polymer block (b) is preferably 100 ° C. or higher, more preferably 110 ° C. or higher. When the glass transition temperature is less than 100 ° C., rubber elasticity at a high temperature may be lowered from a desired value. The glass transition temperature (Tg _b ) of the methacrylic polymer block (b) is set by the value described in the above-mentioned Polymer Handbook 3rd edition as the glass transition temperature of the homopolymer of each monomer constituting the polymer block. It can be carried out by adjusting the weight ratio of the monomer constituting the polymer block according to the Fox formula from the polymerization ratio of each monomer.

  The reactive functional group (unit (c)) in the acrylic polymer block (a) and / or the methacrylic polymer block (b) has reactivity with a compound having an amino group, a hydroxyl group, an epoxy group, or the like. Thus, the acrylic block copolymer (A) can be used as a crosslinking site with the compatibilizer (C) when blended with the thermoplastic elastomer (B). Moreover, since the unit (c) has a high glass transition temperature (Tg), when introduced into the methacrylic polymer block (b), which is a hard segment, the heat resistance of the acrylic block copolymer (A). Can be improved. The glass transition temperature of the polymer containing the unit (c) is, for example, as high as 159 ° C. in the case of polymethacrylic anhydride, and by introducing the unit (c), the acrylic block copolymer (A) Heat resistance can be improved, which is preferable.

  The unit (c) is represented by the general formula (1):

(Wherein R ¹ is a hydrogen atom or a methyl group, and may be the same or different, p is an integer of 0 or 1, q is an integer of 0 to 3) It consists of (c1) and a unit (c2) containing a carboxyl group.
Q in the general formula (1) is an integer of 0 to 3, preferably 0 or 1, and more preferably 1. When q exceeds 3, polymerization may become complicated or cyclization to an acid anhydride group may be difficult.
In general formula (1), p is an integer of 0 or 1. When q is 0, p is also 0. When q is 1 to 3, p is preferably 1.

The unit (c) is contained in the acrylic polymer block (a) and / or the methacrylic polymer block (b). The introduction site of the unit (c) is required for the reaction point of the acrylic block copolymer (A), the cohesive force and glass transition temperature of the block constituting the acrylic block copolymer (A), and further. Depending on the physical properties of the acrylic block copolymer (A), it can be used properly. From the viewpoint of improving the heat resistance and heat decomposability of the acrylic block copolymer (A), the unit (c) may be introduced into the methacrylic polymer block (b). From the viewpoint of imparting rubber elasticity to the coalescence (A), the unit (c) may be introduced into the acrylic polymer block (a) as a crosslinkable reaction site (crosslinking point). From the viewpoint of control of the reaction point, heat resistance, rubber elasticity, etc., it is preferable to have the unit (c) in either the acrylic polymer block (a) or the methacrylic polymer block (b). When the unit (c) is contained in the methacrylic polymer block (b), R ^{1 in the} general formula (1) is preferably a methyl group, and is contained in the acrylic polymer block (a). In this case, R ¹ in the general formula (1) is preferably a hydrogen atom. When R ¹ is a hydrogen atom when the unit (c) is contained in the methacrylic polymer block (b), or when R ¹ is a methyl group when contained in the acrylic polymer block (a) The difference in glass transition temperature between the acrylic polymer block (a) and the methacrylic polymer block (b) is reduced, and the rubber elasticity of the acrylic block copolymer (A) tends to be lowered.

  The preferred range of the content of the unit (c) is the cohesive strength of the unit (c), the reactivity with the compatibilizer (C), the structure and composition of the acrylic block copolymer (A), the acrylic block copolymer It varies depending on the number of blocks constituting the coalescence (A), the glass transition temperature, and the site and manner in which the acid anhydride group-containing unit (c1) and carboxyl group-containing unit (c2) are contained. 0.1-99.9 weight% is preferable in the whole acrylic block copolymer (A), 0.1-80 weight% is more preferable, 0.1-50 weight% is further more preferable. When the content of the unit (c) is less than 0.1% by weight, the compatibility between the acrylic block copolymer (A) and the compatibilizer (C) may be insufficient. Further, when the unit (c) having a high Tg is introduced into the methacrylic polymer block (b), which is a hard segment, for the purpose of improving the heat resistance of the methacrylic polymer block (b), 0.1% by weight. If it is less, the improvement in heat resistance is insufficient and the expression of rubber elasticity at high temperatures may be reduced. On the other hand, if it exceeds 99.9% by weight, the cohesive force becomes too strong and the productivity may be lowered.

  When the acrylic block copolymer (A) contains a unit (c2) containing a carboxyl group, heat resistance and cohesive force are improved. The unit (c2) containing a carboxyl group has a strong cohesive force, and the polymer of a monomer containing a carboxyl group has a high glass transition temperature (Tg). For example, the glass transition temperature (Tg) of polymethacrylic acid is As high as 228 ° C., the heat resistance of the block copolymer is improved. A functional group such as a hydroxyl group also has hydrogen bonding ability, but has a lower Tg and a smaller effect of improving heat resistance than the unit (c2) containing a carboxyl group. Therefore, if it contains the unit (c2) containing a carboxyl group, the heat resistance and cohesion of the acrylic block copolymer (A) can be further improved, which is preferable.

  The content of the carboxyl group-containing unit (c2) can be 1 or 2 or more per polymer block. When the number is 2 or more, the unit (c2) is The mode of polymerization may be random copolymerization or block copolymerization.

  The preferred range of the content of the carboxyl group-containing unit (c2) is the cohesive strength of the carboxyl group-containing unit (c2), the structure and composition of the block copolymer, the number of blocks constituting the block copolymer, In addition, it varies depending on the site and mode of the unit (c2) containing a carboxyl group.

  The content of the carboxyl group-containing unit (c2) is preferably from 0.1 to 50% by weight, more preferably from 0.5 to 50% by weight, and more preferably from 1 to 40% by weight in the entire acrylic block copolymer (A). % Is more preferable. If the amount exceeds 50% by weight, the carboxyl group-containing unit (c2) tends to cyclize with the adjacent ester unit at high temperature, so that the physical properties after molding change, and stable physical properties are obtained. It may be difficult to make a product. In addition, when producing | generating the unit (c2) containing a carboxyl group in the introduction process of a unit (c), 0.1 weight% or more is normally produced | generated. When the production amount is less than 0.1% by weight, the heat resistance and cohesion can be improved even if the carboxyl group-containing unit (c2) is introduced into the methacrylic polymer block (b) which is a hard segment. It may be insufficient.

  Although it does not specifically limit as a manufacturing method of an acryl-type block copolymer (A), It is preferable to use controlled polymerization. Examples of the controlled polymerization include living anion polymerization, radical polymerization using a chain transfer agent, and recently developed living radical polymerization. Living radical polymerization is preferable from the viewpoint of controlling the molecular weight and structure of the block copolymer and copolymerizing a monomer having a crosslinkable functional group. Furthermore, atom transfer radical polymerization is preferable from the viewpoint of ease of control.

  In the atom transfer radical polymerization, an organic halide or a sulfonyl halide compound is used as an initiator, and a metal complex having a group metal of group 8, 9, 10, or 11 as a central metal in the periodic table is used as a catalyst ( For example, Matyjaszewski et al., Journal of American Chemical Society, 1995, 117, 5614, Macromolecules, 1995, 28, 7901, Science, 1996, 272, 866, or Sawamoto et al., 28, 17).

  According to these methods, in general, the polymerization rate is very high, and the radical polymerization is likely to cause a termination reaction such as coupling between radicals, but the polymerization proceeds in a living manner and Mw / Mn = 1 having a narrow molecular weight distribution. A polymer having a molecular weight of about 1 to 1.5 is obtained, and the molecular weight can be freely controlled by the ratio of the monomer and the initiator when charged.

  In the atom transfer radical polymerization method, as the organic halide or sulfonyl halide compound used as an initiator, a monofunctional, difunctional, or polyfunctional compound can be used. These can be used properly according to the purpose. When producing a diblock copolymer, a monofunctional compound is preferable. In the case of producing an aba type triblock copolymer or a babb type triblock copolymer, it is preferable to use a bifunctional compound. In the case of producing a branched block copolymer, it is preferable to use a polyfunctional compound.

Examples of the monofunctional compound include compounds represented by the following chemical formulas.
C ₆ H ₅ —CH ₂ X
C ₆ H ₅ -CHX-CH _{3
C 6 H 5 -C (CH 3} ) 2 X
R ¹ —CHX—COOR ^{2
_{R 1 -C (CH 3) X}} -COOR 2
R ¹ —CHX—CO—R ²
R ¹ —C (CH ₃ ) X—CO—R ²
R ¹ —C ₆ H ₄ —SO ₂ X
(In the formula, C ₆ H ₄ represents a phenylene group. The phenylene group may be ortho-substituted, meta-substituted, or para-substituted. R ¹ is a hydrogen atom or an alkyl group having 1 to 20 carbon atoms, and 6 to 6 carbon atoms. 20 represents an aryl group or an aralkyl group having 7 to 20 carbon atoms, X represents chlorine, bromine or iodine, and R ² represents a monovalent organic group having 1 to 20 carbon atoms.)

Examples of the bifunctional compound include compounds represented by the following chemical formulas.
X—CH ₂ —C ₆ H ₄ —CH ₂ —X
_{X-CH (CH 3) -C} 6 H 4 -CH (CH 3) -X
_{X-C (CH 3) 2} -C 6 H 4 -C (CH 3) 2 -X
X—CH (COOR ³ ) — (CH ₂ ) _n —CH (COOR ³ ) —X
_{X-C (CH 3) (} COOR 3) - (CH 2) n -C (CH 3) (COOR 3) -X
X—CH (COR ³ ) — (CH ₂ ) _n —CH (COR ³ ) —X
_{X-C (CH 3) (} COR 3) - (CH 2) n -C (CH 3) (COR 3) -X
_{X-CH 2 -CO-CH 2} -X
_{X-CH (CH 3) -CO} -CH (CH 3) -X
_{X-C (CH 3) 2} -CO-C (CH 3) 2 X
_{X-CH (C 6 H 5} ) -CO-CH (C 6 H 5) -X
X—CH ₂ —COO— (CH ₂ ) _n —OCO—CH ₂ —X
_{X-CH (CH 3) -COO-} (CH 2) n -OCO-CH (CH 3) -X
_{X-C (CH 3) 2} -COO- (CH 2) n -OCO-C (CH 3) 2 -X
_{X-CH 2 -CO-CO-} CH 2 -X
_{X-CH (CH 3) -CO} -CO-CH (CH 3) -X
_{X-C (CH 3) 2} -CO-CO-C (CH 3) 2 -X
X—CH ₂ —COO—C ₆ H ₄ —OCO—CH ₂ —X
X—CH (CH ₃ ) —COO—C ₆ H ₄ —OCO—CH (CH ₃ ) —X
_{X-C (CH 3) 2} -COO-C 6 H 4 -OCO-C (CH 3) 2 -X
_{X-SO 2 -C 6 H 4} -SO 2 -X
(In the formula, R ³ represents an alkyl group having 1 to 20 carbon atoms, an aryl group having 6 to 20 carbon atoms, or an aralkyl group having 7 to 20 carbon atoms. C ₆ H ₄ represents a phenylene group. The phenylene group is ortho-substituted. C ₆ H ₅ represents a phenyl group, n represents an integer of 0 to 20, and X represents chlorine, bromine or iodine.

Examples of the polyfunctional compound include compounds represented by the following chemical formulas.
C ₆ H ₃ (CH ₂ X) _{3
C 6 H 3 (CH (CH} 3) -X) 3
_{C 6 H 3 (C (CH} 3) 2 -X) 3
_{C 6 H 3 (OCO-CH} 2 X) 3
_{C 6 H 3 (OCO-CH} (CH 3) -X) 3
_{C 6 H 3 (OCO-C} (CH 3) 2 -X) 3
C ₆ H ₃ (SO ₂ X) ₃
(In the formula, C ₆ H ₃ represents a trisubstituted phenyl group. The position of the substituent of the trisubstituted phenyl group may be any of the 1st to 6th positions. X represents chlorine, bromine or iodine.)

  In these organic halides or sulfonyl halide compounds that can be used as initiators, the carbon to which the halogen is bonded is bonded to the carbonyl group, phenyl group, etc., and the carbon-halogen bond is activated to initiate polymerization. To do. The amount of the initiator to be used may be determined from the ratio with the monomer in accordance with the required molecular weight of the block copolymer. That is, the molecular weight of the block copolymer can be controlled by the number of monomers used per molecule of the initiator.

  The transition metal complex used as the catalyst for the atom transfer radical polymerization is not particularly limited, but as a preferred one, a complex of monovalent and zerovalent copper, divalent ruthenium, divalent iron or divalent nickel is preferable. I can give you. Among these, a copper complex is preferable from the viewpoint of cost and reaction control.

Examples of the monovalent copper compound include cuprous chloride, cuprous bromide, cuprous iodide, cuprous cyanide, cuprous oxide, cuprous perchlorate and the like. . In the case of using a copper compound, 2,2′-bipyridyl and its derivative, 1,10-phenanthroline and its derivative, tetramethylethylenediamine (TMEDA), pentamethyldiethylenetriamine, hexamethyl (2-aminoethyl) Polyamines such as amines can also be added as ligands. A tristriphenylphosphine complex of divalent ruthenium chloride (RuCl ₂ (PPh ₃ ) ₃ ) can also be used as a catalyst.

When a ruthenium compound is used as a catalyst, aluminum alkoxides can also be added as an activator. Further, a divalent iron bistriphenylphosphine complex (FeCl ₂ (PPh ₃ ) ₂ ), a divalent nickel bistriphenylphosphine complex (NiCl ₂ (PPh ₃ ) ₂ ), and a divalent nickel bistributylphosphine A complex (NiBr ₂ (PBu ₃ ) ₂ ) can also be used as a catalyst. The amount of the catalyst, ligand and activator used is not particularly limited, but can be appropriately determined from the relationship between the amount of initiator, monomer and solvent used and the required reaction rate.

  The atom transfer radical polymerization can be carried out without solvent (bulk polymerization) or in various solvents. Examples of the solvent include hydrocarbon solvents such as benzene and toluene, halogenated hydrocarbon solvents such as methylene chloride and chloroform, ketone solvents such as acetone, methyl ethyl ketone, and methyl isobutyl ketone, methanol, ethanol, propanol, and isopropanol. Alcohol solvents such as n-butanol and t-butanol, nitrile solvents such as acetonitrile, propionitrile, benzonitrile, ester solvents such as ethyl acetate and butyl acetate, carbonate solvents such as ethylene carbonate and propylene carbonate, etc. These can be used by mixing at least one of them. Moreover, when using a solvent, the usage-amount can be suitably determined from the relationship between the viscosity of the whole system, and the required reaction rate (namely, stirring efficiency).

  The atom transfer radical polymerization can be performed preferably in the range of room temperature to 200 ° C, more preferably 50 to 150 ° C. If the atom transfer radical polymerization temperature is lower than room temperature, the viscosity may be too high and the reaction rate may be slow, and if it exceeds 200 ° C., an inexpensive polymerization solvent may not be used.

  As a method for producing the acrylic block copolymer (A) by the atom transfer radical polymerization, a method of sequentially adding monomers, a method of polymerizing the next block using a polymer synthesized in advance as a polymer initiator And a method of bonding separately polymerized polymers by reaction. These methods can be used properly according to the purpose. From the viewpoint of simplicity of the production process, a method by sequential addition of monomers is preferred.

  Furthermore, a method for introducing a unit (c) composed of a unit (c1) containing an acid anhydride group and / or a unit (c2) containing a carboxyl group into the acrylic block copolymer (A) is shown below. .

  The method for introducing the acid anhydride group-containing unit (c1) is not particularly limited, but a unit containing a group that serves as a precursor of the acid anhydride group is introduced into the block copolymer, and then the ring. It is preferable to make it. Details of the method will be described below.

  General formula (2):

(Wherein R ² represents a hydrogen atom or a methyl group, R ³ represents a hydrogen atom, a methyl group or a phenyl group, and may be the same as or different from each other except that it contains at least one methyl group). A block copolymer composition using the monomer exemplified below as a block copolymer having at least one unit, that is, an acrylic ester constituting the acrylic polymer block (a), preferably 180 to 300 It can be introduced by melt-kneading and cyclization at a temperature of ° C. When the temperature is lower than 180 ° C., the acid anhydride group may be insufficiently formed. When the temperature is higher than 300 ° C., the monomers exemplified below as the acrylic acid ester constituting the acrylic polymer block (a) are used. The used acrylic block copolymer itself may be decomposed.

  The unit represented by the general formula (2) is eliminated and cyclized with an adjacent ester unit at a high temperature to generate, for example, a 6-membered cyclic acid anhydride group (for example, Hatada et al., J.M. Chemistry (JMS PURE APPL. CHEM.), A30 (9 & 10), PP.645-667 (1993)). According to these, in general, a polymer having a bulky ester unit and having β-hydrogen is decomposed at a high temperature to produce a carboxyl group, followed by cyclization, such as a 6-membered ring. An acid anhydride group is formed. By utilizing these methods, an acid anhydride group can be easily introduced into the acrylic block copolymer (A). Specific examples of the monomer constituting the unit represented by the general formula (2) include t-butyl acrylate, isopropyl acrylate, α, α-dimethylbenzyl acrylate, α-methylbenzyl acrylate, meta Examples include, but are not limited to, t-butyl acrylate, isopropyl methacrylate, α, α-dimethylbenzyl methacrylate, and α-methylbenzyl methacrylate. Among these, t-butyl acrylate and t-butyl methacrylate are preferable from the viewpoint of availability, ease of polymerization, and ease of formation of acid anhydride groups.

  Various methods can be applied to the introduction of the carboxyl group-containing unit (c2), and there is no particular limitation. However, in the process of introducing the acid anhydride group-containing unit (c1) into the acrylic block copolymer. It is preferable to generate a unit (c2) containing a carboxyl group by appropriately adjusting the heating temperature and time according to the type and content of the unit represented by the general formula (2). This is because it is easy to control the reaction point of the acrylic block copolymer (B) and to introduce the carboxyl group-containing unit (c2) into the acrylic block copolymer (A).

  Therefore, from the viewpoint of the introduction method, the carboxyl group-containing unit (c2) is preferably contained in the same block as the block containing the acid anhydride group-containing unit (c1). From the point of cohesive strength, it is more preferable that it is contained in the methacrylic polymer block (b). That is, by introducing a unit (c2) having a carboxyl group with high Tg and cohesive force into the methacrylic polymer block (b) which is a hard segment, it becomes possible to express rubber elasticity more at high temperatures. It is. Moreover, when the unit (c2) which has a carboxyl group is contained in an acrylic polymer block (a), it is preferable from a compatible point with a compatibilizing agent (C).

  Next, (B) the olefinic thermoplastic elastomer in the thermoplastic elastomer composition will be described. The olefinic thermoplastic elastomer (B) is not particularly limited, but is a polyolefin composed of a thermoplastic polyolefin homopolymer or copolymer, and an olefinic rubber or acrylonitrile butadiene that is completely crosslinked or partially crosslinked. What consists of a combination with rubber | gum (NBR) can be used preferably.

  The polyolefins include thermoplastic and crystalline polyolefin homopolymers and copolymers. Among them, a polypropylene-based component is preferable, and a copolymer containing ethylene in polypropylene is more preferable in order to improve low temperature characteristics.

  As the olefin rubber, ethylene / propylene rubber having excellent low-temperature characteristics and EPDM rubber which is a terpolymer of non-conjugated diene are preferable, and those obtained by dynamically crosslinking EPDM rubber in an olefin resin are particularly preferable. Since EPDM rubber can be uniformly dispersed in a small amount of olefin resin by dynamically cross-linking EPDM rubber in olefin resin, it has excellent rubber properties such as compression durability strain while having thermoplasticity. Can be expressed.

  Moreover, as an olefin type thermoplastic elastomer (B), it is preferable to use a 23-degree C Shore A hardness of 50-90, especially 65-85. Such olefin-based thermoplastic elastomers are commercially available under trade names such as Santoprene and GEOLLAST (both manufactured by Advanced Elastomers), and can be easily obtained from the market.

  Furthermore, the compatibilizing agent (C) in the thermoplastic elastomer composition is not particularly limited, but in order to better compatibilize the acrylic block copolymer (A) and the olefinic thermoplastic elastomer (B), An olefinic thermoplastic resin (modified polyolefin) containing an epoxy group that reacts with the unit (c) such as polymethacrylic anhydride of the acrylic block copolymer (A) is preferred. Examples thereof include commercially available copolymers of ethylene and glycidyl methacrylate, or ethylene and glycidyl methacrylate having methyl acrylate, polypropylene grafted with glycidyl methacrylate, and the like. The content of glycidyl methacrylate in these modified polyolefin resins is preferably 0.05 wt% to 50 wt%, more preferably 0.1 wt% to 20 wt%. If the glycidyl methacrylate content is less than 0.05% by weight, the compatibility between the acrylic block copolymer (A) and the olefinic thermoplastic elastomer (B) may be insufficient, and the tensile strength may deteriorate. . When the content of glycidyl methacrylate is more than 50% by weight, the cohesiveness of the acrylic block copolymer (A) and the olefinic thermoplastic elastomer (B) becomes too strong, and the tensile elongation may be lowered. These modified polyolefin resins are, for example, commercially available product names such as Bond First (manufactured by Sumitomo Chemical Co., Ltd.), Modiper (manufactured by Nippon Oil & Fats Co., Ltd.), and can be easily obtained from the market.

  The thermoplastic elastomer composition used in the present invention includes (A) an acrylic block copolymer and (B) an olefin thermoplastic elastomer, and in addition to (A) and (B) (C ) Containing a compatibilizing agent is suitable. For example, 50 to 600 parts by weight of the olefinic thermoplastic elastomer (B), more preferably 200 to 100 parts by weight with respect to 100 parts by weight of the acrylic block copolymer (A). It is preferable that it consists of 600 parts by weight, more preferably 400 parts by weight, and (C) 5 to 50 parts by weight of a compatibilizer. When the respective contents are within the above ranges, a molded article having good heat resistance, oil resistance, and injection molding can be obtained, which is particularly preferable in the case of a boot for a constant velocity joint for automobiles.

  This thermoplastic elastomer composition measures the acrylic block copolymer (A), olefinic thermoplastic elastomer (B), and compatibilizer (C) before being actually molded and put them into a molding machine. However, from the viewpoint of handling, uniformity of kneading, etc., it is preferable to pelletize before molding. Below, the pelletization is demonstrated.

  The method for pelletizing the thermoplastic elastomer composition is not particularly limited, but mechanically while heating at an appropriate temperature using a known apparatus such as a Banbury mixer, roll mill, kneader, single-screw or multi-screw extruder. Can be shaped into pellets. What is necessary is just to adjust the temperature at the time of kneading | mixing according to the melting temperature of the acrylic block copolymer (A), olefin type thermoplastic elastomer (B), and compatibilizer (C) to be used, for example, 180-300 degreeC. It can be pelletized by melt kneading.

  Moreover, when the low temperature characteristic is requested | required as a thermoplastic elastomer resin used for this invention, it is a composition which consists of an acrylic type block copolymer (A) and a polyorganosiloxane type graft polymer (D). Is preferred. Furthermore, when the elastic modulus at a high temperature is required, it is preferably a composition comprising an acrylic block copolymer, a polyorganosiloxane graft polymer (D), a thermoplastic resin, a lubricant and an inorganic filler.

  The composition of the polyorganosiloxane-based graft polymer (D) in the thermoplastic elastomer resin is not particularly limited, but the monomer (d2) is present in the presence of 40 to 95% by weight of the polyorganosiloxane (d1). ) Is polymerized in an amount of 0 to 10% by weight, and further a vinyl monomer (d3) is polymerized in an amount of 5 to 60% by weight [(d1), (d2) and (d3) in total 100% by weight]. It is preferably a coalescence. The monomer (d2) is composed of 50 to 100% by weight of a polyfunctional monomer (x) containing two or more polymerizable unsaturated bonds in the molecule, and other copolymerizable vinyl monomers ( y) A monomer composed of 0 to 50% by weight. Furthermore, it is preferable that the content of the graft component combining the monomer (d2) and the vinyl monomer (d3) is 5 to 40% by weight and the polyorganosiloxane content is 95 to 60% by weight.

  The thermoplastic elastomer resin can be blended with a lubricant, an inorganic filler, and a thermoplastic resin in order to increase the elastic modulus at a high temperature. Regarding the blending amount, the polyorganosiloxane graft polymer (D) 10 to 100 parts by weight, the lubricant 0.1 to 10 parts by weight, and the inorganic filler 0 to 100 parts by weight of the acrylic block copolymer (A). 0.1 to 100 parts by weight and 0.1 to 100 parts by weight of a thermoplastic resin can be exemplified as preferable ranges.

  The thermoplastic elastomer resin used in the present invention includes a stabilizer (anti-aging agent, light stabilizer, UV absorber, etc.), flexibility imparting agent, flame retardant, release agent, You may add an antistatic agent, an antibacterial antifungal agent, etc. These additives may be appropriately selected and used in accordance with required physical properties, processability, and the like.

  The hollow molded article of the present invention is manufactured by injection molding a thermoplastic resin such as the thermoplastic elastomer resin as described above. For example, the conditions for injection molding of a hollow molded article from a thermoplastic elastomer resin by the method of the present invention are generally as follows: cylinder temperature: 150 to 230 ° C., nozzle temperature: 180 to 240 ° C., injection speed: low speed, cooling time: 30 Second, mold temperature: molding conditions such as 30 to 80 ° C.

  The hollow molded article produced by the method of the present invention as described above has excellent low-temperature characteristics, oil resistance, heat resistance, weather resistance, mechanical characteristics, fatigue strength, and the like. In addition, it is excellent in simplification of the molding process and recyclability as compared with conventional vulcanized rubber systems.

  Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to these examples.

  In the following, BA, MEA, MMA, and TBMA mean n-butyl acrylate, 2-methoxyethyl acrylate, methyl methacrylate, and t-butyl methacrylate, respectively.

(Molecular weight)
The molecular weight of the acrylic block copolymer was measured with a GPC analyzer (system: GPC system manufactured by Waters, column: Shodex K-804 (polystyrene gel) manufactured by Showa Denko KK). The molecular weight in terms of polystyrene was determined using chloroform as the mobile phase.

(6-membered cyclic acid anhydride group conversion analysis)
Confirmation of the 6-membered cyclic acid anhydride group conversion reaction of the acrylic block copolymer was performed by infrared spectrum analysis (manufactured by Shimadzu Corporation, using FTIR-8100) and nuclear magnetic resonance analysis (manufactured by BRUKER, AM400). Use).
As a nuclear magnetic resonance analysis solvent, a block body having a carboxylic acid ester structure was analyzed using deuterated chloroform as a measurement solvent together with a block body having a 6-membered cyclic acid anhydride structure.

<Production example of acrylic block copolymer>
After the inside of the polymerization vessel of a 500 L reactor equipped with a stirrer capable of heating and cooling was purged with nitrogen, 840.1 g (5.9 mol) of copper bromide was weighed and 12 L of acetonitrile (nitrogen bubbling) was added. After heating and stirring at 70 ° C. for 30 minutes, 421.7 g (1.17 mol) of diethyl 2,5-dibromoadipate initiator, 41.4 L (288.9 mol) BA, and 18.6 L (144.5 mol) MEA were added. It was. The mixture was heated and stirred at 85 ° C., and 0.1 L (0.59 mol) of ligand diethylenetriamine was added to initiate polymerization.

  About 0.2 ml of the polymerization solution was sampled from the polymerization solution at regular intervals from the start of polymerization, and the conversion rate of BA was determined by gas chromatogram analysis of the sampling solution. The polymerization rate was controlled by adding diethylenetriamine as needed. When the conversion rate of BA was 94% and the conversion rate of MEA was 96%, TBMA 24.9L (153.8 mol), MMA 24.7L (230.8 mol), copper chloride 580 g (5.9 mol), butyl acetate 1.2 L (9.1 mol) and 122.8 L of toluene (nitrogen bubbled) were added. Similarly, conversion rates of TBMA and MMA were determined. When the conversion rate of TBMA was 61% and the conversion rate of MMA was 56%, 80 L of toluene was added and the reactor was cooled in a water bath to complete the reaction.

The reaction solution was diluted with 115 L of toluene, 1337 g of p-toluenesulfonic acid monohydrate was added and stirred at room temperature for 3 hours, and then the solid was removed using a bag filter (HAYWARD). To the polymer solution obtained, 1642 g of an adsorbent (trade name KYOWARD 500SH, manufactured by Kyowa Chemical Co., Ltd.) was added and stirred for another 3 hours at room temperature. The adsorbent was filtered using a bag filter to obtain a colorless and transparent polymer solution. Obtained. This solution was dried using a horizontal evaporator (heat transfer area: 1 m ² ) to remove the solvent and residual monomer, thereby obtaining the target block copolymer. When the GPC analysis of the obtained block copolymer was conducted, the number average molecular weight (Mn) was 93700, and molecular weight distribution (Mw / Mn) was 1.36.

  A pressure kneader (((1A40T6.5) 700 g) and a phenolic antioxidant (trade name: Irganox 1010, manufactured by Ciba Specialty Chemicals Co., Ltd.) A target 6-membered cyclic acid anhydride group-containing block copolymer was obtained by melting and kneading at 70 rpm for 20 minutes using a Moriyama Corporation DS1-5MHB-E type kneader. The block of the polymer obtained by the pressure kneader was freeze-pulverized with liquid nitrogen and a pulverizer to obtain the block copolymer pellets.

The conversion of the t-butyl ester moiety to a 6-membered cyclic acid anhydride group could be confirmed by IR (infrared absorption spectrum) analysis and ¹³ C-NMR (nuclear magnetic resonance spectrum) analysis.
That is, in the IR analysis, it was confirmed that an absorption spectrum derived from an acid anhydride group was observed around 1800 cm ⁻¹ after conversion. ^{In the 13} C-NMR analysis, it was confirmed that the 82 ppm signal derived from the methine carbon of the t-butyl group and the 28 ppm signal derived from the methyl carbon disappeared after the conversion.

(Examples 1 and 2)
(Thermoplastic elastomer composition)
1076.9 g of the acrylic block copolymer obtained in the production example, 2153.8 g of an olefinic thermoplastic elastomer (trade name Santoprene 111-80, manufactured by Advanced Elastomer Systems), and a compatibilizing agent (ethylene-glycidyl methacrylate- (Methacrylate) 269.2 g was thoroughly mixed by hand blending so as to be uniformly dispersed. Kneading conditions are C1 to C3: 100 ° C., C4: 180 ° C., C5: 180 ° C., C6: 200 ° C., C7: 220 ° C., die head: 220 ° C., rotation speed: 150 rpm, vented twin screw extruder “TEX30HSS-25” .5PW-2V "(manufactured by Nippon Steel Works). The extruded strand was pelletized with a pelletizer “SCF-100” (manufactured by Isuzu Chemical Industries, Ltd.) so as to facilitate injection molding. The obtained pellets were dried at 80 ° C. for 3 hours or more.

(Injection mold)
The injection mold having the structure shown in FIGS. 1 to 4, the height shown in FIGS. 10 (Example 1) and 11 (Example 2) is 105 mm, and the bellows is shown in FIGS. 10 and 11. An inner diameter of the portion 4 (distance from the central axis 0 to the apex of the valley portion 5) and a wall thickness of the die comprising the cavity die 10 and the core die 20 which are joint boots shown in Table 1, FIG. 4 and FIG. And an injection molding machine “J150E-P” (manufactured by Nippon Steel Works) with a clamping pressure of 150 TON.

  The resin boot 1 shown in FIG. 10 is attached to a small-diameter side attachment portion 2 attached to the shaft of an automobile and a non-circular outer shape outer case having three recesses such as a triport type constant velocity joint. It is a constant velocity joint boot provided with the large diameter side attaching part 3 and the bellows part 4 which connect both together. The constant velocity joint boot 1 has a substantially truncated cone shape as a whole, in which a small diameter side mounting portion 2 and a large diameter side mounting portion 3 are integrally connected by a bellows portion 4. Like the shaft boot of a two-wheeled vehicle, it is possible to perform injection molding of a substantially cylindrical boot having the same mounting diameters 2 and 3 at both ends. In addition, the bellows portion 4 may be formed by alternately forming a plurality of independent ridges and recesses as shown in the figure, or each ridge and recess may be It may be formed in a spiral shape. Furthermore, the planar shape (transverse cross-sectional shape) of the attachment portions 2 and 3 and the bellows portion 4 at both ends may not be circular, but may be rectangular or elliptical, and the overall shape is not particularly limited. In the illustrated constant velocity joint boot 1, four peak portions 6 a to 6 d are formed in the bellows portion 4. The number of the ridges 6 of the bellows part 4 is not particularly limited, but is preferably 3 to 5 from the viewpoint of the processability of injection molding and the expandability of the bellows part 4 during rotation. When the number of bellows ridges 6 is less than 3, it may be difficult to remove the mold after injection molding. On the other hand, when the number of the peak parts 6 of the bellows part 4 is more than five, the thickness of the bellows part 4 becomes thin, and the bellows part 4 may expand and break during rotation.

(injection molding)
The pellets of the thermoplastic elastomer composition obtained as described above were injection molded at a cylinder temperature of 180 ° C., a nozzle temperature of 230 ° C., an injection speed of 10%, a cooling time of 30 seconds, and a mold temperature of 40 ° C. At the same time that 10 is opened, the mold is removed from the core mold 20 with an air pressure of 5 kg / cm ² (0.49 MPa) emitted from the air hole 21 of the core mold 20, and from the gate portion of the molded product (part of line L in FIG. 1). The tip was excised to obtain a constant velocity joint boot 1.

(Comparative Example 1)
A substantially same injection mold is used as the gate for injecting the thermoplastic elastomer into the molding space 30 except that the gate is not a dome-shaped gate but a planar gate shown in FIG. 1 to produce a constant velocity joint boot 1.

  In Examples 1 and 2, the mold release from the core mold after molding is very good, the productivity is good, the resin flow is not uneven during molding, and it has a good appearance, and it is removed by compressed air. It was possible to manufacture a hollow molded product that was small in deformation at the time of molding, excellent in dimensional accuracy and dimensional stability, and recyclable. On the other hand, in Comparative Example 1, the air that is press-fitted into the molded product P is not uniformly distributed between the core mold 102 and the molded product P, and is removed from the core mold 102 only on one side of the molded product. A defect occurred.

It is sectional drawing of an injection mold. It is a front view of the division surface of one division type of a cavity metal mold | die. It is a front view of the division surface of the other division type | mold of a cavity metal mold | die. It is sectional drawing of the outer mold | type of a core metal mold | die. It is sectional drawing of the metal mold | die in the state which inject | poured resin. It is sectional drawing of a different angle of the metal mold | die in the state which inject | emitted resin. It is sectional drawing explaining the flow of the resin in a dome shaped gate. It is sectional drawing of the state which opened the metal mold | die after shaping | molding. It is sectional drawing which shows a mode that a molded article is demolded from a core metal mold | die by high pressure air. 1 is a cross-sectional view of a constant velocity joint boot formed in Example 1. FIG. 6 is a cross-sectional view of a constant velocity joint boot formed in Example 2. FIG. The conventional injection molding method and injection mold are shown, (a) is sectional drawing which shows a mode that it demolds after shaping | molding, (b) after shaping | molding. The conventional injection molding method and the injection mold are shown, (a) and (b) are enlarged sectional views of the injection gate portion showing the flow of the resin, and (b) is the state when the molded product is demolded with high-pressure air. It is an expanded sectional view shown.

Explanation of symbols

1 Resin boots (Constant velocity joint boots)
2 Small diameter side mounting part 3 Large diameter side mounting part 4 Bellows part 5 Valley part 6 Mountain part 10 Cavity mold 10A, 10B Split mold 20 Core mold 20A Outer mold 20B Medium mold 20C Substrate 21 Air hole 22 Opening / closing axis 23 Dome-shaped convex Portion 24 Ventilation hole 30 Molding space 30A, 30B Molding recess 31A, 31B Gate recess 40 Gate 41 Inlet 41A, 41B Groove 42 Resin injection path 42A, 42B Groove L Cut part M Resin P Molded product

Claims (22)

  In a molding space formed between the cavity mold and the core mold of a molding mold composed of a cavity mold divided so as to be openable and closable and a core mold disposed in the cavity mold, An injection molding method for injecting and filling a molten thermoplastic resin to produce a cylindrical hollow molded product opened at both ends, wherein one open end of a hollow molded product molded in the molding space Melted from one point of the apex of the dome-shaped gate provided in communication with the molding space of the mold so as to protrude from the edge outward in the axial direction of the molded product toward the axial direction of the hollow molded product to be molded The molded thermoplastic resin is injected, the thermoplastic resin is injected and filled into the molding space through the dome-shaped gate, and a hollow molded product with one end closed is molded. After molding, the cavity mold is opened. In addition, hollow molding that is externally fitted to the core mold Injecting a molded product from the core mold by blowing high-pressure air from the apex portion of the dome-shaped gate in the core mold toward the axial direction of the molded product. Molding method.   The injection molding method according to claim 1, wherein the longitudinal cross-sectional shape of the dome-shaped gate is substantially hemispherical, and the molten thermoplastic resin is injected from an injection hole provided at a vertex of the substantially hemispherical gate.   The injection molding method according to claim 1 or 2, wherein a molten thermoplastic resin is injected and filled into the molding space from the dome-shaped gate toward an axial direction of a molded product molded in the molding space.   The injection molding method according to any one of claims 1 to 3, wherein the hollow molded article includes a pair of annular mounting portions that are open at both ends, and a bellows portion that integrally connects the two.   The hollow molded product is a thermoplastic product in which one mounting portion has a larger diameter than the other, and is melted into the molding space via a dome-shaped gate provided at the opening edge of the small-diameter side mounting portion in the molding die. The injection molding method according to any one of claims 1 to 4, wherein the resin is injected and filled.   6. The constant velocity joint boot according to claim 5, wherein the hollow molded product is a constant velocity joint boot including a large-diameter side attachment portion attached to the outer case, a small-diameter side attachment portion attached to the shaft, and a bellows portion integrally connecting the two. The injection molding method described.   The injection molding method according to claim 1, wherein the thermoplastic resin is a thermoplastic elastomer.   The injection molding method according to claim 7, wherein the thermoplastic elastomer resin contains an acrylic block copolymer (A).   The injection molding method according to claim 8, wherein the thermoplastic elastomer resin is a thermoplastic elastomer composition comprising an acrylic block copolymer (A) and an olefinic thermoplastic elastomer (B).   The thermoplastic elastomer composition contains 50 to 600 parts by weight of the olefinic thermoplastic elastomer (B) and 5 to 50 parts by weight of the compatibilizer (C) with respect to 100 parts by weight of the acrylic block copolymer (A). Item 10. The injection molding method according to Item 9.   The acrylic block copolymer (A) contains 50 to 90% by weight of the acrylic polymer block (a) and 50 to 10% by weight of the methacrylic polymer block (b). The injection molding method according to any one of the above.   The resin boot according to claim 11, wherein at least one of the acrylic polymer block (a) and the methacrylic polymer block (b) has a reactive functional group (c).   The injection molding method according to any one of claims 9 to 12, wherein the olefinic thermoplastic elastomer (B) is obtained by dynamically crosslinking an EPDM rubber or an acrylonitrile-butadiene rubber in an olefin resin.   The injection molding method according to any one of claims 10 to 13, wherein the compatibilizing agent (C) is an olefin-based thermoplastic resin containing an epoxy group.   A cavity mold divided so as to be openable and closable, and a core mold disposed in the cavity mold, and in the molding space formed between the cavity mold and the core mold, molten heat An injection mold for producing a cylindrical hollow molded product that is injected and filled with a plastic resin and that is open at both ends, the axial direction of the molded product molded in the molding space from the molding space A dome-shaped gate is provided so as to protrude outward, a single injection hole is provided in the cavity mold located at the apex of the dome-shaped gate, and a high pressure is applied to the inner surface of the apex of the dome-shaped gate in the core mold. After opening and closing air holes communicating with the air supply means, the molten thermoplastic resin is injected into the molding space from the injection hole through the dome-shaped gate and filled to form a hollow molded product , The tee mold is opened and the air hole is opened, and high pressure air is blown from the high pressure air supply means to the inside of the hollow molded article through the air hole, whereby the molded article is taken out from the core mold. An injection mold for a hollow molded product, characterized in that   The injection mold according to claim 15, wherein the longitudinal cross-sectional shape of the dome-shaped gate is substantially hemispherical, and an injection hole extending in the axial direction of a hollow molded article to be molded is provided at the apex of the substantially hemispherical gate. Type.   The injection molding metal according to claim 15 or 16, wherein an opening edge to the molding space in the dome-shaped gate is formed so as to be in the same direction as an axial direction of a hollow molded product molded in the molding space. Type.   A vent hole penetrating in the axial direction of the core mold and connected to the high-pressure air supply means is provided in the axial center portion of the core mold, and the tip end portion of the vent hole is used as the air hole. The injection mold according to any one of claims 15 to 17, wherein an opening / closing shaft that slides in an axial direction of the core mold is provided facing the dome-shaped gate, and the air hole can be opened / closed by the opening / closing shaft. Type.   One or more ventilation grooves extending in the axial direction are provided on the inner peripheral surface of the ventilation hole, and the opening and closing shaft is retracted to a position where the tip is provided with the ventilation groove, thereby opening an air hole. The injection mold according to claim 18, wherein high-pressure air can be blown from the ventilation hole into the hollow molded product through the ventilation groove and the air hole.   The injection mold according to any one of claims 15 to 19, which is a molding die for molding a hollow molded product including a pair of annular mounting portions opened at both ends and a bellows portion integrally connecting the two. .   16. A molding die for molding a hollow molded product in which one attachment portion has a larger diameter than the other, and the dome-shaped gate is provided at the opening edge of the small-diameter side attachment portion in the molding space. The injection mold according to any one of -20. A molding die for molding a constant velocity joint boot comprising a large-diameter side attachment portion attached to an outer case, a small-diameter side attachment portion attached to a shaft, and a bellows portion integrally connecting the two. 21. An injection mold according to item 21.

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