JP4356608B2 - Two-layer injection molded product and resin filler neck - Google Patents

Description

  The present invention relates to a two-layer injection-molded article and a resin filler neck, and more specifically, a two-layer injection-molded article having a two-layer structure made of different resin materials that have different molding temperatures and can be bonded to each other by a thermochemical reaction, and The present invention relates to a resin filler neck provided with this two-layer injection molded product.

  Conventionally, as a resin joint used for a resin fuel tank for vehicles, it has a first resin layer made of a first resin material such as modified polyethylene that can be welded to the resin fuel tank, and a fuel barrier property (fuel permeation resistance). There is known one using a two-layer injection molded product having a two-layer structure with a second resin layer made of a second resin material such as polyamide (for example, see Patent Document 1 and Patent Document 2).

  In this two-layer injection molded product, the molding temperature of the polyamide as the second resin material constituting the second resin layer is higher than the molding temperature of the modified polyethylene as the first resin material constituting the first resin layer, Both resin materials can be bonded by thermochemical reaction at the molding temperature of the second resin material.

Such a two-layer injection molded product is manufactured as follows, for example. First, a first resin material is injected into a predetermined cavity of an injection mold having a slide core mold to form a tubular first resin layer. Thereafter, the slide core mold is replaced with a predetermined shape having a small outer diameter, and a cavity corresponding to the shape of the second resin layer is formed in the mold. Then, with the first resin layer arranged in the injection mold in this way, the second resin material is injected into the cavity, and the tubular second resin layer is molded inside the first resin layer. . At this time, the first resin layer and the second resin layer are integrally bonded to each other by causing a thermochemical reaction between the first resin material and the second resin material using the amount of heat of the second resin material.
JP 2002-254938 A JP 2004-11419 A

  By the way, fuel such as gasoline is injected from a fuel inlet formed in the rear fender or the like of the vehicle and guided to a fuel tank through a filler tube. The filler tube and the fuel inlet are formed of a resin filler neck. Are connected through.

  As such a resin filler neck, conventionally, an injection molded product made of polyacetal or polyethylene has been used. However, the filler neck made of polyacetal has low impact resistance, while the filler neck made of polyethylene has a drawback of low fuel barrier property (fuel permeation resistance).

  Therefore, it is conceivable to apply the above-described conventional two-layer injection molding technique to a resin filler neck. However, since the filler neck has a large shape for a relatively thin product thickness, there are the following problems in applying the two-layer injection molding technique to the filler neck.

  That is, in the two-layer injection molding technology, the first resin is obtained by causing a thermochemical reaction between the two resin materials using the amount of heat of the second resin material injected after molding the first resin layer from the first resin material. The layer and the second resin layer are adhered. If such a two-layer injection molding technique is applied to a large product, the amount of heat of the second resin material decreases as the second resin material flowing in the cavity advances from the gate to the end of the cavity. The amount of heat of the second resin material is insufficient, and adhesion failure between the first resin layer and the second resin layer is likely to occur.

  The present invention has been made in view of the above circumstances, and even if the product thickness is relatively thin, the adhesive strength between the first resin layer and the second resin layer even when applied to a large-sized product. It is a technical problem to be solved to provide a two-layer injection-molded article that is advantageous for sufficiently securing the resin filler neck provided with the two-layer injection-molded article.

  The two-layer injection molded product of the present invention that solves the above problems can be bonded to the first resin material by a thermochemical reaction in a state where the first resin layer made of the first resin material is disposed in the injection mold. The second resin material is injected from the gate into the cavity of the injection mold in which the first resin layer is disposed by molding a second resin material molded at a molding temperature higher than the molding temperature of the first resin material. A two-layer injection molded product obtained by molding a layer and adhering the first resin layer and the second resin layer, wherein the second resin layer is molded at a cavity portion near the gate. It is characterized in that it has at least a part of a thickness gradient portion in which the thickness is gradually increased from the end portion toward the end forming portion formed at the cavity portion near the end.

  Here, “the wall thickness is gradually increased” means that the wall thickness is gradually increased in addition to the wall thickness being gradually increased gradually. It is.

  In this two-layer injection-molded product, the thickness gradually increases from the gate molded part molded at the cavity part near the gate where the second resin material is injected toward the terminal molded part molded at the cavity part near the terminal. The wall thickness gradient portion is provided at least in part. For this reason, during the two-layer injection molding, the second resin material injected from the gate into the cavity of the injection mold in which the first resin layer is disposed is moved from the cavity portion near the gate to the end (cavity end) near the cavity. When flowing toward the part, it flows in the cavity where the flow path cross-sectional area gradually increases. That is, when the second resin material flows from the cavity portion near the gate toward the cavity portion near the end, the flow resistance gradually decreases. Therefore, the second resin material flows to the end of the cavity while maintaining a considerable amount of heat immediately after being injected into the cavity from the gate. Therefore, even in the vicinity of the end of the cavity, the thermochemical reaction between the first resin material and the second resin material can be satisfactorily performed using the amount of heat of the second resin material, and the first due to this thermochemical reaction. It becomes possible to maintain high adhesiveness between the resin layer and the second resin layer.

  Therefore, according to the two-layer injection-molded product of the present invention, the adhesive strength between the first resin layer and the second resin layer can be applied to a large-sized product even though the product thickness is relatively thin. It is advantageous to ensure sufficient.

  In a preferred aspect, the thickness gradient portion gradually increases in thickness continuously from the gate molding portion toward the terminal molding portion. When the thickness of the thickness gradient portion gradually increases stepwise, there is a concern that cracks due to stress concentration are likely to occur at the concave corners or the like in each step portion. In this respect, if the thickness of the thickness gradient portion is gradually and gradually increased, there is no portion that becomes a starting point of cracking due to stress concentration, which is advantageous in terms of strength.

  In a preferred aspect, the maximum thickness of the second resin layer on the end molding portion side in the thickness gradient portion is the minimum thickness on the gate molding portion side of the second resin layer in the thickness gradient portion. It is set to 1.5 to 3 times. According to this aspect, while maintaining the product thickness within an appropriate range, the fluidity of the second resin material at the time of injection molding of the second resin layer is ensured, and the first resin layer and the first resin by the thermochemical reaction are secured. It becomes possible to maintain high adhesiveness with two resin layers.

  The resin filler neck of the present invention that solves the above-mentioned problems comprises the two-layer injection molded product according to claim 1, 2, or 3, wherein the first resin material is maleic acid-modified polyethylene, and the second resin material Is a polyamide or ethylene vinyl alcohol.

  The two-layer injection molded product of the present invention has a two-layer structure including a first resin layer made of a first resin material and a second resin layer made of a second resin material. The overall shape of the two-layer injection-molded product is not particularly limited, and can be, for example, tubular or plate-shaped.

  The first resin material and the second resin material are different kinds of resin materials having different molding temperatures, and both resin materials can be bonded by a thermochemical reaction at the molding temperature of the second resin material.

  As such a combination of resin materials, for example, maleic acid-modified polyethylene (modified PE, molding temperature: about 200 ° C.) as the first resin material and polyamide (PA, molding temperature: about 230) as the second resin material. And a combination of modified PE as the first resin material and ethylene vinyl alcohol (EVOH, molding temperature: about 220 ° C.) as the second resin material. As the polyamide at this time, 12 nylon, 6 nylon or the like can be suitably used.

  Here, when the modified PE is adopted as the first resin material and PA is adopted as the second resin material, at the molding temperature (about 230 ° C.) of the PA as the second resin material, the carboxyl group in the modified PE and Both resin materials are bonded together by bonding with an amino group in PA by a thermochemical reaction to form an amide bond.

  Moreover, when modified PE is employ | adopted as a 1st resin material, the 1st resin layer which consists of this modified PE functions as an impact-resistant protective layer, and can contribute to the improvement of the intensity | strength and rigidity of this two-layer injection molded product. On the other hand, when PA or EVOH is adopted as the second resin material, the second resin layer made of PA or EVOH functions as a fuel barrier layer, and can contribute to the improvement of the fuel permeation resistance of the two-layer injection molded product. .

  The two-layer injection-molded product of the present invention has a first resin layer made of the first resin material disposed in the injection mold, and the cavity of the injection mold (cavity for molding the second resin layer). The second resin material is manufactured by injecting the second resin material from a gate (second resin material injection gate) and molding the second resin layer and bonding the first resin layer and the second resin layer.

  Here, the first resin layer may be molded into a predetermined shape by using, for example, a predetermined slide core mold in the injection mold for molding the second resin layer, or another first first resin layer. Alternatively, the resin layer injection mold may be separately molded and then disposed at a predetermined position in the second resin layer injection mold. However, when the first resin layer is molded separately, there is a risk of poor adhesion with the second resin layer due to the cooling of the first resin layer, and the first resin layer or the like is heated to prevent this. In some cases, it may be necessary to place in the injection mold or to heat the injection mold.

  For example, when the overall shape is a tubular two-layer injection molded product and the first resin layer is injection molded in the injection mold for the second resin layer, the inner peripheral surface of the molded product is molded. After forming the tubular first resin layer in the injection mold for the second resin layer using the predetermined first slide core mold, the outer diameter is different from the first slide core mold by a predetermined amount. By exchanging with the second slide core mold, a cavity having a predetermined shape (cavity for molding the second resin layer) is formed in the injection mold in which the first resin layer is disposed, and a gate ( The second resin material may be injected from the second resin material injection gate).

  Further, when the overall shape is a tubular two-layer injection molded product, and when the first resin layer is separately molded using another injection mold (first resin layer mold), a predetermined first After forming the tubular first resin layer using the molding die for one resin layer, the first resin layer is removed, and a gap corresponding to the outer shape of the first resin layer and a predetermined shape continuous to the gap In the state where the heated first resin layer is disposed in the gap of the injection mold (second resin layer molding mold) having a cavity (second resin layer molding cavity), as necessary. The second resin material may be injected from the gate (the second resin material injection gate).

  In the two-layer injection molded product of the present invention, the second resin layer has a wall thickness from a gate molded part molded at a cavity part near the gate toward a terminal molded part molded at a cavity part near the terminal. It has at least part of the thickness gradient portion that is gradually thickened.

  The two-layer injection-molded product has a processed part obtained by cutting or processing a gate mark for injecting the second resin material or an unnecessary formed part in the vicinity of the gate mark at the gate molded part or the vicinity thereof.

  The said thickness gradient part may be formed in the whole 2nd resin layer, and may be partially formed in one part or multiple pieces in a part of 2nd resin layer.

  That is, the end portion of the two-layer injection molded product of the present invention may be constituted by a single layer portion of the first resin layer or the second resin layer. The end portion is composed of a first single layer portion made of a first resin layer, and the end portion of the two-layer injection molded product on the end molding portion side is composed of a second single layer portion made of a second resin layer. A thickness gradient portion may be continuously formed between the layer portion and the second single layer portion. By carrying out like this, the individual characteristic of the 1st resin material or the 2nd resin material which constitutes the 1st single layer part or the 2nd single layer part can be given at each end part of a 2 layer injection-molded product, and a product characteristic Can be diversified.

  Further, as the thickness gradient portion, the thickness may gradually increase gradually from the gate molded portion toward the terminal molded portion, or from the gate molded portion toward the terminal molded portion. The wall thickness may be gradually increased gradually. However, as described above, considering the strength, it is preferable that the wall thickness is gradually increased gradually. Further, the thickness gradient portion may be formed by a combination of a step portion whose thickness changes stepwise and an inclined portion (taper portion) whose thickness changes continuously.

  The change in the thickness of the second resin layer in the thickness gradient portion is, for example, such that the maximum thickness on the end molding portion side is about 1.5 to 3 times the minimum thickness on the gate molding portion side. Can be. In addition, it is preferable that the thickness of the second resin layer in the gate molding portion (minimum thickness on the gate molding portion side) is about 0.5 mm or more. If it is thinner than this, it is difficult to ensure the fluidity of the second resin material in the cavity when the second resin layer is molded.

  The thickness of the first resin layer is not particularly limited, and may be uniform throughout. For example, the total thickness of the first resin layer and the second resin layer is uniform throughout. As described above, the thickness of the first resin layer may be changed so as to correspond to the thickness gradient portion of the second resin layer.

  Further, the thickness of the second resin layer and the thickness of the first resin layer in the thickness gradient portion are, for example, (the thickness of the second resin layer) in the gate molding portion: (the thickness of the first resin layer) ) = 1: 2, and it can be changed so that (the thickness of the second resin layer) :( the thickness of the first resin layer) = 2: 1 at the terminal molded portion. In addition, as total thickness of the 1st resin layer and 2nd resin layer in a thickness gradient part, it can be set as about 2.5-5.0 mm.

  The two-layer injection molded product of the present invention can be suitably used for a resin filler neck connected to a filler tube for a vehicle fuel tank. In this case, as described above, as the first resin material, modified PE that can function as an impact-resistant protective layer and contribute to improvement in strength and rigidity is employed, and as the second resin material, it functions as a fuel barrier layer. It is preferable to employ PA or EVOH that can contribute to improvement of fuel permeation resistance, and a tubular two-layer structure in which the first resin layer forms an outer layer and the second resin layer forms an inner layer is preferable. preferable.

  When the two-layer injection molded product of the present invention is applied to a resin filler neck, the one end portion on the gate molding portion side may constitute a joining end portion made of the first single layer portion of the first resin layer. preferable. In this way, one end portion of the filler neck is a joining end portion made of the first single layer portion of the first resin (modified PE) layer, so that the joining end portion is hot-plate welded to the filler tube made of PE or the like. Can be bonded more favorably.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited to these.

  In this embodiment, the two-layer injection molded product of the present invention is applied to a resin filler neck connected to a filler tube for an automobile fuel tank.

  As shown in the cross-sectional view of FIG. 1, the filler neck 1 has a tubular shape as a whole. The first resin layer 2 is a tubular outer layer, and the second resin layer 3 is a tubular inner layer. The main component is a tubular metal retainer 4. Then, the first resin layer 2 and the second resin layer 3 are integrally bonded by two-layer injection molding, and the two-layer injection molded product of the present invention is applied to this integrated product A.

  That is, in the integrated product A of the first resin layer 2 and the second resin layer 3, the first resin layer 2 made of modified PE (maleic acid modified polyethylene) as the first resin material is disposed in the injection mold. In this state, PA as a second resin material that can be bonded to the first resin material by a thermochemical reaction and is molded at a molding temperature higher than the molding temperature of the first resin material is used as the first resin layer 2. The second resin layer 3 is molded and injected into the cavity of the injection mold (second resin layer molding cavity) in which the second resin layer 3 is injected from the gate (second resin material injection gate). The resin layer 2 and the second resin layer 3 are bonded together.

  The second resin layer 3 in the integrated product A is firstly formed from the gate molding portion 5 molded at a cavity (second resin layer molding cavity) near the gate (second resin material injection gate). A first tapered wall thickness gradient in which the wall thickness gradually and gradually increases toward the first terminal molding portion 6 molded at the cavity portion in the vicinity of the terminal (the first terminal of the second resin layer molding cavity). Similarly, the thickness continuously increases from the gate molding portion 5 toward the second end molding portion 8 molded at the cavity portion in the vicinity of the second end (second end of the second resin layer molding cavity). And a second tapered thickness gradient portion 9 which is gradually thickened.

  On the other hand, the first resin layer 2 in the integrated product A is directed from the gate molding portion 5 side to the first terminal molding portion 6 side of the second resin layer 3 so as to correspond to the first tapered thickness gradient portion 7. From the side of the gate molding portion 5 of the second resin layer 3 so as to correspond to the first tapered thickness inclined portion 10 and the second tapered thickness gradient portion 9 whose thickness is continuously and gradually reduced. And a second tapered thickness inclined portion 11 whose thickness is continuously and gradually reduced toward the second end molding portion 8 side.

  The total thickness of the first resin layer 2 and the second resin layer 3 in the first tapered thickness gradient portion 7 and the first tapered thickness gradient portion 10 is about 3 mm, which is a uniform thickness as a whole. It is said that. Further, the thickness of the second resin layer 3 in the gate molding portion 5 is about 1 mm, and the change in the thickness of the second resin layer 3 in the first tapered thickness gradient portion 7 is caused by the gate molding portion 5 side. The maximum thickness on the first end molding portion 6 side is about twice the minimum thickness. Furthermore, the thickness of the second resin layer 3 and the thickness of the first resin layer 2 in the first tapered thickness gradient portion 7 and the second tapered thickness gradient portion 10 are the second on the gate molding portion 5 side. The minimum thickness portion of the resin layer 3 (thickness of the second resin layer 3) :( thickness of the first resin layer 2) = 1: 2, and the second resin layer 3 on the first end molding portion 6 side. The thickness is changed so that (thickness of the second resin layer 3) :( thickness of the first resin layer 2) = 2: 1. In addition, also in the 2nd taper thickness gradient part 9 and the 2nd taper thickness gradient part 11, the thickness of the 2nd resin layer 3 and the thickness of the 1st resin layer 2 are the gate shaping | molding part 5 side. The minimum thickness portion of the second resin layer 3 (thickness of the second resin layer 3) :( thickness of the first resin layer 2) = 1: 2, and the second resin on the second end molding portion 8 side. The maximum thickness of the layer 3 is changed so that (thickness of the second resin layer 3) :( thickness of the first resin layer 2) = 2: 1.

  The filler neck 1 has a bulging joint end portion 12 which is thicker than other portions on one end side (the lower end side in FIG. 1; hereinafter the same) of the integrated product A. The end surface 13 side portion of the bulging joint end portion 12 is constituted by a first single layer portion of the first resin layer 2 made of modified PE as the first resin material. A second resin layer 3 is disposed on the other end side (the upper end side in FIG. 1; the same applies hereinafter) of the integrated product A on the inner surface of the bulging joint end portion 12. The two resin layers 3 constitute the gate molding part 5.

  Further, the filler neck 1 has a mounting end portion 14 on which the metal retainer 4 is mounted on the other end side of the integrated product A. The second resin layer 3 at the mounting end 14 is a large-diameter portion 15 so as to bulge one step outward in the radial direction, and a concave step portion 16 on the inner peripheral side of the large-diameter portion 15 An O-ring 17 for securing a sealing property between the two resin layers 3 and the metal retainer 4 and an annular member 18 for restricting the position of the O-ring 17 and preventing the o-ring 17 from being removed are disposed. Further, the first resin layer 2 at the mounting end portion 14 is formed as a large diameter portion 19 so as to bulge one step radially outward, and the metal retainer 4 is formed at the outer peripheral side tip of the large diameter portion 19. Has an annular projection 20 for snap-coupling. A metal retainer 4 is mounted on the mounting end 14. Note that the vicinity of the tip of the large-diameter portion 15 of the second resin layer 3 at the mounting end portion 14 constitutes the first end molding portion 6.

  Furthermore, the filler neck 1 has an escape pipe portion 21 for releasing a gas pressure in a fuel tank (not shown) to the outside on one end side of the integrated product A. In addition, on the outer peripheral surface of the first resin layer 2 in the escape pipe part 21, three annular protrusions 22 are formed for increasing the coupling force with a gas escape tube (not shown) attached to the escape pipe part 21. Has been. In addition, the second resin layer 3 in the distal end side (the lower end side in FIG. 1, hereinafter the same) portion of the escape pipe portion 21 constitutes the second end molding portion 8.

  Here, on the inner peripheral surface of the first resin layer 2 on one end side of the integral product A on the inner peripheral surface of the bulging joint end portion 12, the first resin layer 2 is provided as an unnecessary portion when injection molding is performed. There is a first gate mark A that is a mark obtained by cutting one runner portion. In addition, the second resin layer 3 that is unnecessary when the second resin layer 3 is injection-molded on the inner peripheral surface of the second resin layer 3 on the other end side of the integral product A on the inner peripheral surface of the bulging joint end portion 12. There is a second gate mark B which is a mark obtained by cutting the runner portion.

  The filler neck 1 has a hot plate on a filler tube (a three-layer structure in which a fuel barrier layer made of EVOH is used as an intermediate layer and PE layers are disposed on both sides thereof) with the end face 13 of the bulging joint end 12 not shown. They are bonded together by welding and used. At this time, since the end surface 13 of the bulging joint end portion 12 is constituted by the first single layer portion of the first resin layer 2 made of the modified PE, the end surface 13 of the bulging joint end portion 12 and the filler tube are excellent. Can be adhered to.

  Further, the vicinity of the bulging joint end portion 12 is a portion where stress is likely to concentrate when the filler neck 1 is used, and the bulging joint end portion 12 has a large elongation at break (it is difficult to break even if stretched). Since it is mainly comprised by the 1st resin layer 2 which consists of this, and it is made thicker than another site | part, impact resistance improves. For this reason, even if the second resin layer 3 as the fuel barrier layer breaks, it is possible to prevent the fuel from permeating through the portion of the first resin layer 3 at the bulging joint end portion 12.

  The integrated product A as a two-layer injection molded product in the filler neck 1 having the above-described configuration can be manufactured as follows. In addition, the following mold structures such as a movable mold, a fixed mold, and a slide mold are merely examples, and can be appropriately changed depending on functions required for products.

  First, as shown in FIG. 2, a first main mold 30 including a first fixed mold 31 and a first movable mold 32 having a first gate (first resin material injection gate) 42, and the first main mold 30. An injection mold having a mold configuration including a slide core 33 slidably disposed in the mold 30 is prepared. Note that the slide core 33 is divided into two parts with the paper surface of FIG. 2 as a boundary surface, and each divided type is slidable in the front and back direction of the paper surface.

  Then, the first movable mold 32 with the slide core 33 set at a predetermined position is moved in the direction approaching the first fixed mold 31, and the first fixed mold 31, the first movable mold 32, and the slide core 33 are moved. Thus, a first cavity 41 having a predetermined shape (a first resin layer forming cavity having a shape corresponding to the shape of the first resin layer 2) 41 is formed (see FIG. 2). Then, the modified PE as the first resin material is injected into the first cavity 41 from the first gate (first resin material injection gate) 42 at a molding temperature of about 200 ° C. to mold the first resin layer 2. To do.

  Thereafter, the first movable mold 32 is moved away from the first fixed mold 31 and the slide core 33 is removed from the first movable mold 32 together with the first resin layer 2. The 1st runner (part formed in the site | part shown with a dotted pattern in FIG. 2 after the injection molding of the 1st resin layer 2) as an unnecessary part is cut | disconnected. A first gate mark A is formed on the inner peripheral surface of the first resin layer 2 by cutting the first runner.

  Thereafter, the slide core 33 holding the first resin layer 2 is set at a predetermined position of the second movable mold 52 different from the first movable mold 32. Then, the second movable mold 52 in which the slide core 33 is set together with the first resin layer 2 is moved in the direction approaching the second fixed mold 51 different from the first fixed mold 31, so that the second The fixed cavity 51, the second movable mold 52, the slide core 33, and the first resin layer 2 form a second cavity (second resin layer molding cavity having a shape corresponding to the shape of the second resin layer 3) 61. (See FIG. 3). Then, PA as the second resin material is injected at a molding temperature of about 2230 ° C. from the second gate (gate for second resin material injection) 62 provided in the second fixed mold 52 in the second cavity 61. The second resin layer 2 was molded, and the first resin layer 2 and the second resin layer 3 were integrally bonded by a thermochemical reaction to mold the integrally molded product A.

  Thereafter, the second movable mold 52 is moved away from the second fixed mold 51, and the slide core 33 is removed together with the integrally molded product A from the second movable mold 52. The body is separated from each other and the integrally molded product A is removed. And the 2nd runner (The part formed in the site | part shown with a dotted pattern in FIG. 3 after the injection molding of the 2nd resin layer 3) as an unnecessary part is cut | disconnected from the 2nd resin layer 3. FIG. A second gate mark A is formed on the inner peripheral surface of the second resin layer 3 by cutting the second runner.

  In the integrally molded product A obtained in this way, the second resin layer 3 has a first end (from the gate molding portion 5 molded at the site of the second cavity 61 in the vicinity of the second gate 62 from which the second resin material is injected ( The first taper-like thickness in which the thickness is gradually and gradually increased toward the first end molding portion 6 molded at the cavity portion in the vicinity of the first end of the second cavity 61 for molding the second resin layer). Thickness toward the second end molding portion 8 molded at the cavity portion near the second end (second end of the second cavity 61 for molding the second resin layer) from the gradient portion 7 and the gate molding portion 5. Has a second tapered thickness gradient portion 9 that is gradually and gradually increased. For this reason, the second resin material injected from the second gate 62 into the second cavity 61 of the injection mold 30 in which the first resin layer 2 is disposed is transferred from the second cavity 61 in the vicinity of the second gate 62. When flowing toward the second cavity 61 near the first end or the second end, it flows in the second cavity 61 in which the flow path cross-sectional area gradually increases. That is, when the second resin material flows from the portion of the second cavity 61 near the second gate 62 toward the first end or the portion of the second cavity 61 near the second end, the flow resistance gradually decreases. Accordingly, the second resin material flows to the first end and the second end of the second cavity while maintaining a considerable amount of heat immediately after being injected into the second cavity 61 from the second gate 62. Therefore, the thermochemical reaction between the first resin material and the second resin material can be satisfactorily caused by using the amount of heat of the second resin material also at the first end of the second cavity 61 and in the vicinity of the second end. It is possible to maintain high adhesion between the first resin layer 2 and the second resin layer 3 due to this thermochemical reaction.

  Therefore, even when the filler neck 1 which is a product having a large shape (about 50 to 150 mm) is manufactured as compared with the comparatively thin product thickness as in this embodiment, the first resin layer 2 and Adhesive strength with the second resin layer 3 can be sufficiently ensured.

  In the present embodiment, the first tapered thickness gradient portion 7 and the second tapered thickness gradient portion 9 are formed from the gate forming portion 5 toward the first end forming portion 6 and the second end forming portion 8. The thickness gradually increases gradually. For this reason, there is no portion that becomes a starting point of cracking due to stress concentration, which is advantageous in terms of strength.

It is sectional drawing which shows the whole filler neck which concerns on a present Example which has the integrated product A to which the two-layer injection molded product of this invention is applied. It is a mold structure sectional view for explaining signs that the 1st resin layer of the above-mentioned integrated product A is fabricated. It is a mold structure sectional view for explaining signs that the 2nd resin layer of the above-mentioned integrated product A is fabricated.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Filler neck 2 ... 1st resin layer 3 ... 2nd resin layer 5 ... Gate shaping | molding part 6 ... 1st terminal shaping | molding part 7 ... 1st thickness gradient part 8 ... 2nd terminal shaping | molding part 9 ... 2nd thickness gradient Part 10: 1st thickness inclination part 11 ... 2nd thickness inclination part 12 ... Bulging junction end part 14 ... Mounting end part

Claims (4)

In a state where the first resin layer made of the first resin material is disposed in the injection mold, it can be bonded to the first resin material by a thermochemical reaction and at a molding temperature higher than the molding temperature of the first resin material. The second resin layer is molded by injecting the second resin material to be molded from the gate into the cavity of the injection mold in which the first resin layer is disposed, and the first resin layer and the second resin. A two-layer injection-molded product obtained by adhering layers,
The second resin layer has at least a thickness gradient portion that is gradually increased in thickness from a gate molded portion molded at a cavity portion near the gate toward a terminal molded portion molded at a cavity portion near the end. A two-layer injection-molded product characterized by having a part.   2. The two-layer injection molded product according to claim 1, wherein the thickness gradient portion has a thickness that gradually increases gradually from the gate molding portion toward the terminal molding portion.   The maximum thickness of the second resin layer on the end molding portion side in the thickness gradient portion is 1.5 to 3 of the minimum thickness on the gate molding portion side of the second resin layer in the thickness gradient portion. The double-layer injection-molded product according to claim 1 or 2, wherein the double-layer injection-molded product is set to be double.   A resin comprising the two-layer injection-molded product according to claim 1, 2, or 3, wherein the first resin material is maleic acid-modified polyethylene, and the second resin material is polyamide or ethylene vinyl alcohol. Made filler neck.

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