JP3774416B2 - Method for molding multilayer hollow body made of synthetic resin having blow molded inner layer - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to primary molding in which a pair of semi-hollow bodies are injection-molded using a fixed mold and a slide mold, and a molten resin is applied to the abutting portions of the pair of semi-hollow bodies obtained by the primary molding. Blow molding, in which a hollow body is formed from a secondary molding that forms a hollow body from a pair of semi-hollow bodies by injection and a tertiary molding that forms an inner layer inside the hollow body obtained by the secondary molding. The present invention also relates to a method for forming a multilayer hollow body made of a synthetic resin having an inner layer.
[0002]
[Prior art]
Synthetic resin hollow bodies such as tanks are widely used in various fields for liquids, gases, and powders. Such tanks, such as automobile fuel tanks, oil tanks, steering oil tanks, brake oil tanks, etc., were formed from sheet metal by bending, drawing, welding, rust-proof coating, etc. A lighter synthetic resin tank has been proposed along with the weight reduction.
[0003]
Such a synthetic resin tank can be molded by an injection molding method proposed by the present applicant, for example, in JP-A 2000-43100 and JP-A 2000-167885. A fixed mold and a slide mold are used for carrying out this molding method. This fixed mold is formed with a core protruding outward from the parting line and a recess recessed inward, and the slide mold has a recess cooperating with the core of the fixed mold and a fixed mold. A core cooperating with the recess of the mold is provided. Therefore, when the slide mold is clamped with respect to the fixed mold at a predetermined position, the first cavity is formed by the core of the fixed mold and the recess of the slide mold, and the concave of the fixed mold and the core of the slide mold And the second cavity is formed. When the molten resin is injected into the first and second cavities in the primary molding, a pair of semi-hollow bodies are molded. With the primary molded product remaining in the slide mold, the slide mold is slid to the second position and clamped. If it does so, a pair of semi-hollow bodies will face | match at a junction part. Molten resin is injected into the joint by secondary molding. Then, a hollow body in which a pair of semi-hollow bodies is integrated is obtained.
[0004]
According to the above injection molding method proposed by the present applicant, a sealed hollow body can be manufactured or molded, a hollow body with a uniform wall thickness can be made, and even complicated shapes can be dealt with. There are also advantages such as being able to. Further, when molded from ABS resin, AS resin, polyamide, or the like, an impact-resistant hollow body can be obtained, and when molded from polypropylene or the like, a number of advantages such as a chemical-resistant hollow body can be obtained. However, placing a heavy emphasis on impact resistance results in inferior chemical resistance. On the other hand, placing emphasis on chemical resistance results in a hollow body that is vulnerable to impact. Further, a conventional hollow body made of a single layer is not always perfect in terms of evaporation of contents. Therefore, a hollow body composed of two layers in which the outer layer and the inner layer have their respective functions is also desired. Such a two-layer synthetic resin tank can be molded by blow molding. The head of the blow molding machine for two-layer molding includes a main nozzle that pushes out the main material layer, a first sub nozzle that pushes out the adhesive layer, a second sub nozzle that pushes out the inner layer, and the like. Therefore, by extruding the respective resin materials from these nozzles, a semi-molded product having two layers in which the outer layer and the inner layer are bonded can be obtained. By appropriately finishing the semi-molded product, a synthetic resin tank having an inner layer can be obtained.
[0005]
[Problems to be solved by the invention]
As described above, a synthetic resin tank consisting of an inner layer and an outer layer, that is, a hollow body can also be formed by blow molding. However, since the head has a multi-layer structure as described above, there is a disadvantage that the blow molding apparatus is expensive, and therefore the synthetic resin hollow body obtained by blow molding is expensive. Moreover, the process of finishing into a hollow body is specially required, resulting in high costs. Furthermore, the trace of finishing remains and the appearance shape is also damaged.
The present invention is intended to provide a method for forming a hollow body made of a synthetic resin that eliminates the above-described conventional drawbacks. Specifically, the present invention is capable of airtightly containing a fluid such as a liquid contained therein. of course is also the wall thickness is uniform qualitative and excellent in external shape, moreover made of inexpensive synthetic resin hollow body is made of synthetic resin having an inner layer that is blow molded Chi molding method Sunawa obtained It aims at providing the shaping | molding method of a multilayer hollow body.
[0006]
[Means for Solving the Problems]
In the present invention, an injection molding method is applied to achieve the above object. According to the injection molding method, since it is shaped by the mold, the wall thickness becomes uniform and the appearance shape does not fall. Furthermore, a blow molding method is also applied. At this time, according to the present invention, a blow molding machine having a single-layer head structure can be applied. Therefore, it becomes possible to form a hollow body having a multilayer structure at low cost. Thus, the invention described in claim 1 is obtained by primary molding in which a pair of semi-hollow bodies are injection-molded so as to have a butt portion using a fixed mold and a slide mold, and the primary molding. Secondary molding in which the butted portions of the pair of semi-hollow bodies are joined by a molten resin to form a hollow body from the pair of semi-hollow bodies, and an adhesive is applied to the inner surface of the hollow body obtained by the secondary molding Alternatively, spraying and extruding a parison whose tip is sealed into the inside of the parison, while blowing compressed air into the parison, the blown parison is blown into a shape in close contact with the inner surface of the hollow body. And tertiary molding. The invention according to claim 2 is a primary molding in which a pair of semi-hollow bodies are molded so as to have an abutting portion using a fixed mold and a slide mold, and a pair of obtained by the primary molding. Secondary molding in which the butted portions of the semi-hollow bodies are joined with a molten resin to form a hollow body from a pair of semi-hollow bodies, and an adhesive is applied or sprayed on the inner surface of the hollow body obtained by the secondary molding. Then , a blow molding nozzle is inserted therein to push out the parison whose tip is sealed, and while the blow molding nozzle is pulled out, compressed air is blown into the parison, and the parison extruded thereby is a hollow body. And tertiary molding that is blow-molded into a shape that is in close contact with the inner surface. According to a third aspect of the present invention, in the molding method according to the first or second aspect, at the time of the primary molding, a blow molding through-hole is formed in one of the semi-hollow bodies.
[0007]
DETAILED DESCRIPTION OF THE INVENTION
First, an embodiment of a mold used for carrying out the primary molding and the secondary molding of the present invention will be described, then an embodiment of a nozzle for blow molding will be described, and these mold and blow A molding example using a molding nozzle will be described. 1A is a cross-sectional view showing the slide mold 20 closed at the first position. As shown in FIG. 1, the mold according to the present embodiment is The fixed mold 1 located on the right side in FIG. 1 (a), the mold is opened and closed, and the fixed mold 1 is slidably driven in the vertical direction in FIG. 1 (a). The slide mold 20 is schematically configured. In addition, a fixed plate to which the fixed mold 1 is fixedly attached, a movable plate for driving the slide mold 20 in the mold opening / closing direction, and a slide mold 20 are slidably driven in the vertical direction in FIG. The drive device, the ejector device provided in the slide mold 20, the mold clamping device, etc. are not shown in FIG.
[0008]
As shown in FIG. 1A, a first sprue 2 for primary molding is provided at a substantially central portion of the fixed mold 1 so as to cross the fixed mold 1. . The primary sprue 2 for primary molding extends in the vertical direction by a runner 3 and is connected to second and third sprues 4 and 5 for primary molding. The second sprue 4 opens at the top of the fixed-side core of the fixed mold 1 described later, and the third spru 5 opens at the fixed-side recess. A secondary forming spru 6 is provided below the primary forming spru 2 at a predetermined distance from the primary forming spru 2. The secondary forming spru 6 is open to the parting line P side and communicates with a concave groove 7 formed on the parting line P side of the slide mold 20. The concave groove 7 reaches the side surface of the slide-side annular core 27 of the slide mold 20 described later.
[0009]
At a position above the first sprue 2 for primary molding of the fixed mold 1, a fixed-side core 11 having a predetermined size in which a side surface shape protruding outward from the parting line P has a square shape is formed. ing. A small fixed-side annular core 12 is formed around the fixed-side core 11 at a predetermined interval from the fixed-side core 11. The fixed side core 11 constitutes a second cavity Cb for forming a second semi-hollow body in cooperation with a slide side recess 21 of the slide mold 20 to be described later. Is also small by the thickness of the semi-hollow body.
[0010]
A fixed-side recess 15 having a predetermined depth in which the side surface shape recessed from the parting line P side has a substantially square shape is formed at a position below the fixed mold 1. The fixed recess 15 includes a circular first bottom wall 16 or recess having a relatively small area, and a second bottom wall 17 rising from the periphery of the first bottom wall 16 and extending outward. , And a peripheral wall 18 rising from the periphery of the second bottom wall 17. A step portion 19 having a predetermined depth from the parting line P side is formed outside the peripheral wall 18. Further, the third sprue 5 for primary molding is opened in the second bottom wall 17. The fixed cavity 15 formed in this way constitutes a first cavity Ca for forming a first semi-hollow body in cooperation with a slide core 25 of the slide mold 20 described later.
[0011]
At the upper position of the slide mold 20, a slide side recess 21 having a substantially square side surface opened to the parting line P side is formed. The slide-side recess 21 includes a bottom wall 22 and a peripheral wall 23 rising from the periphery of the bottom wall 22, and a stepped portion 24 having a predetermined depth from the parting line P side is provided outside the peripheral wall 23. Is formed. The slide-side recess 21 is larger than the fixed-side core 11 of the fixed mold 1 described above by the thickness of the second semi-hollow body. Thereby, the second cavity Cb for forming the second semi-hollow body having a predetermined thickness is formed. Further, the step 24 and the fixed-side annular core 12 of the fixed mold 1 constitute a cavity Cs in which a half of the joining space is formed in the second semi-hollow body during the primary molding.
[0012]
A slide-side core 25 protruding outward from the parting line P is formed at a predetermined position below the slide mold 20. The slide-side core 25 constitutes a first cavity Ca for forming the first semi-hollow body in cooperation with the fixed-side recess 15 of the fixed mold 1. It is small by the thickness of one semi-hollow body. A relatively small-diameter columnar protrusion 26 is formed on the top of the slide-side core 25. The cylindrical projection 26 constitutes a cavity for forming a blow-molding through hole in the first semi-hollow body in cooperation with the first bottom wall 16 of the fixed mold 10, that is, the recess. Thus, it is smaller than the second bottom wall 16. A slide-side annular core 27 is formed around the base of the slide-side core 25 so as to surround the slide-side core 25 at a predetermined interval from the slide-side core 25. The slide-side annular core 27 cooperates with the fixed-side step portion 19 of the fixed mold 1 to form a half of the joint space portion in the first semi-hollow body.
[0013]
The blow molding nozzle 30 includes a vertically long head die 31 as shown in FIG. An external die 32 and an internal die 33 are concentrically provided in the head die 31. A resin passage is formed between the outer die 32 and the inner die 33, and a mandrel 34 is provided at the lower end thereof so that the height can be adjusted. An air pipe 35 extending to the lower side of the mandrel 34 is provided inside the internal die 33 thus configured. Note that reference numeral 36 in FIG. 2A indicates an extruder.
[0014]
Next, a pair of semi-hollow bodies are formed by primary molding using the fixed mold 1 and the slide mold 20, and then a pair of semi-hollow bodies are joined by secondary molding to form a hollow body. Then, a molding method for blow molding the inner layer on the inner surface of the hollow body by tertiary molding using the blow molding nozzle 30 will be described.
[0015]
The slide mold 20 is clamped with respect to the fixed mold 1 at the first position shown in FIG. Then, the second cavity Cb for forming the second semi-hollow body is constituted by the fixed-side core 11 of the fixed mold 1 and the slide-side recess 21 of the slide mold 20. Further, the fixed cavity 15 of the fixed mold 1 and the slide core 25 of the slide mold 20 constitute a first cavity Ca for forming the first semi-hollow body. At this time, the cavity Cs for forming the joint space in the opening of the second semi-hollow body by the fixed-side annular core 12 of the fixed mold 1 and the slide-side step portion 24 of the slide mold 20 The fixed side step portion 19 of the fixed mold 1 and the slide side annular core 27 of the slide mold 20 constitute a cavity Cs ′ for forming a joint space in the opening of the first semi-hollow body. Further, a cavity Ct for forming a blow molding through-hole in the first semi-hollow body by the first bottom wall 16 of the fixed mold 1, that is, the concave portion and the columnar protrusion 26 of the slide mold 20. Is configured.
[0016]
The primary molding molten resin is injected from the primary molding sprue 2 of the fixed mold 1 in a known manner. The molten resin is injected and filled into the second and first cavities Cb and Ca from the primary molding spru 2 through the runner 3 and the second and third sprues 4 and 5 for primary molding. By this primary molding, a pair of first and second semi-hollow bodies A and B are simultaneously molded. At this time, as shown in FIG. 1 (b), the abutting portions of the first and second semi-hollow bodies A and B constitute half of the joining space portion S having a substantially trapezoidal cross-sectional shape. Half-joint spaces Sa and Sb are formed. Further, the first semi-hollow body A is formed with a blow-molding through hole Bs protruding outward.
[0017]
Waiting for a certain amount of cooling and solidification, the slide mold 20 is opened by a predetermined interval. Then, with the slide mold 20 in a state where the second semi-hollow body B is attached to the slide mold 20, the opening of the second semi-hollow body B is formed in the opening of the first semi-hollow body A. Slide to the second position where they are aligned. Then, mold clamping is performed. If it does so, the opening part of the 1st, 2nd semi-hollow bodies A and B will contact | abut, and the cyclic | annular joining space part S closed by the semi-joining space parts Sa and Sb will be comprised. The state in which the mold is clamped in this way and the joining space portion S is configured is shown in FIG.
[0018]
A molten resin for secondary molding is injected from the injection machine. The molten resin is injected from the secondary molding sprue 6 of the fixed mold 1 through the concave groove 7 into the bonding space S. As a result, the first and second semi-hollow bodies A and B are integrated to obtain a synthetic resin hollow body S ′. The slide mold 20 is opened after cooling and solidification. The hollow body S ′ is protruded by the ejector pin. Thereafter, the above operation is repeated to form the hollow body S ′.
[0019]
Next, tertiary molding is performed. That is, as shown in FIG. 2B, the hollow body S ′ is set in a separately prepared holder H with the blow molding through hole Bs on the upper side. The molten resin is injected from the extruder 36 to the blow molding nozzle 30 (having a function of making the molten resin into a pipe shape and a function of blowing compressed air). The front end of the parison PR extruded from the blow molding nozzle 30 is sealed, the parison PR is inserted into the hollow body S ′ from the blow molding through hole Bs, and the lower end of the blow molding nozzle 30 is blow molded. It is seated on the upper end of the through hole Bs. Parison state the tip and blockade of PR is shown in the (b) 2, while being seated the lower end of the blow molding nozzle 30 to the upper end of the through hole Bs for blow molding of FIG. 2 (c) Is shown in While extruding the parison PR, compressed air is blown from the air pipe 35. Thereby, the parison PR to be extruded expands and is brought into close contact with the inner surface of the hollow body S ′. As shown in FIG. 2 (d), the blow molding nozzle 30 is pulled up to a predetermined height, and the parison cutter / pinch 37, 37 (having the function of cutting the parison and the function of joining the cut portions). Cut the parison PR. As a result, a synthetic resin multilayer hollow body SH having an inner layer blow-molded therein is obtained. When cutting, the lower end of the parison PR is joined or sealed. The adhesive multilayer hollow bodies SH outer surface of the blow molding hole Bs inner surface and the parison PR of joining by fusion or the like, the parison PR which protrudes after cutting from the hole Bs for blow molding an end face machining with deburring process Remove. The hole Bk shown in (d) of FIG. 2 is a portion that becomes an injection port when used as a tank, and a primary semi-hollow body is formed so that a cap or the like can be attached to the outer portion Sk of this portion. It is also possible to provide screws, grooves, etc. at the time of the deburring process of the parison. The multilayer hollow body SH is taken out. Thereafter, a multilayer hollow body SH made of synthetic resin having an inner layer blow-molded in the same manner is formed.
[0020]
The present invention is not limited to the above embodiment and can be implemented in various forms. For example, in the above embodiment, the example in which the blow-molded inner layer is one layer has been described. However, it is obvious that a multilayer hollow body SH having a multilayer inner layer can be molded by using a multilayer blow molding nozzle. is there. Further, the inner layer, that is, the parison PR can be blow-molded as described above while inserting the blow-molding nozzle 30 into the hollow body S ′ and pulling up the blow-molding nozzle 30. Furthermore, an adhesive may be applied or sprayed on the inner surface of the hollow body S ′ before the tertiary molding. For example, the adhesive can be applied to the inner surface by putting an adhesive in the hollow body S ′, temporarily sealing the blow-molding through holes Bs, and shaking the hollow body S ′. As described above, when the adhesive is applied or sprayed on the inner surface of the hollow body S ′, a multilayer hollow body SH having a high adhesive strength is obtained. In the above embodiment, the blow molding nozzle 30 is driven in the vertical direction. However, since the movement of the blow molding nozzle 30 and the holder H is relative, the holder H is driven. It is clear that this can be implemented. Accordingly, the description of raising the “blow molding nozzle” in the claims includes driving the “holder”. Furthermore, it is clear that a hollow body having a multilayer structure can be formed by repeating the tertiary forming.
[0021]
In the above embodiment, the blow-molding through hole Bs is formed at the time of primary molding. The blow-molded through hole is set in the holder H after the hollow body is molded, and then opened with a drill or the like. You can also. Further, the pair of first and second semi-hollow bodies A and B are joined by injection molten resin at the time of secondary molding, but as described in Japanese Patent No. 2729900 (Japanese Patent Laid-Open No. 7-16945). It is also clear that a secondary molding can be fused using a heater.
[0022]
【The invention's effect】
As described above, according to the present invention, the hollow body is formed by the primary molding and the secondary molding, and the adhesive is applied or sprayed on the inner surface of the hollow body by the tertiary molding. While extruding the sealed parison, blow compressed air into the parison to form the inner layer, or insert a blow molding nozzle to push out the parison whose tip is blocked and pull out the blow molding nozzle However, since compressed air is blown into the parison to mold the inner layer, that is, the outer layer and the inner layer are molded by different molding methods, the outer layer and the inner layer are molded with synthetic resin hollow bodies having different functions. can do. For example, it has a uniform wall thickness, quality, impact resistance, and appearance, and a composition that can hold fluids such as liquids contained inside in a liquid-tight or chemically stable manner. An effect peculiar to the present invention is obtained that a multilayer hollow body made of resin can be formed. Further, since the adhesive is applied or sprayed on the inner surface of the hollow body, the effect of adhering the blow molded inner layer to the inner surface of the hollow body can be further obtained. Furthermore, since the parison for tertiary molding can be molded with a single-layer blow molding nozzle, tertiary molding can be performed at low cost. Therefore, the effect that the synthetic resin multilayer hollow body can be molded at low cost is also obtained. Although it is slightly more costly than that, it can be molded with a multilayer blow molding nozzle if necessary, and it is possible to improve the strength, and multilayer molding of different materials can be performed. It is possible to provide a molded product.
According to the invention described in claim 3, since the blow-molding through-hole is formed in one of the semi-hollow bodies during the primary molding, in addition to the above effects, the cost of the tertiary molding can be further reduced.
[Brief description of the drawings]
FIG. 1 is a view showing an embodiment of a mold used for primary and secondary molding according to the present invention, in which (a) shows the mold with the slide mold closed at a first position. Sectional drawing, (b) is a sectional view showing only the main part in a state where secondary molding is performed.
FIG. 2 is a diagram showing a state of tertiary molding according to the present invention, in which (a) is a sectional view showing an embodiment of a blow molding nozzle, and (b) is a state in which a hollow body is set in a holder. Sectional view showing, (C) is a sectional view schematically showing a state in the middle of blow molding, (D) is a sectional view showing a state in which blow molding is finished and the blow molding nozzle is pulled up is there.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Fixed mold 11 Fixed side core 15 Fixed side recessed part 20 Slide mold 21 Slide side recessed part 25 Slide side core 30 Blow molding nozzle A 1st semi-hollow body B 2nd semi-hollow body Bs Blow molding through-hole S '' Hollow body SH Multi-layer hollow body

Claims (3)

Primary molding that uses a fixed mold and a slide mold to injection-mold a pair of semi-hollow bodies so as to have a mating part, and melts the mating parts of the pair of semi-hollow bodies obtained by the primary molding Secondary molding in which a hollow body is molded from a pair of semi-hollow bodies by bonding with a resin;
Applying or spraying an adhesive on the inner surface of the hollow body obtained by the secondary molding, while extruding a parison whose tip is sealed inside, blows compressed air into the parison, thereby A method for forming a multilayer hollow body made of a synthetic resin having a blow-molded inner layer, wherein the extruded parison is molded from a tertiary molding in which the parison to be extruded is blow-molded into a shape in close contact with the inner surface of the hollow body. Primary molding that forms a pair of semi-hollow bodies using a fixed mold and a slide mold so as to have a mating portion, and a mating portion of the pair of semi-hollow bodies obtained by the primary molding is a molten resin. Secondary molding in which a hollow body is formed from a pair of semi-hollow bodies by joining together,
An adhesive is applied or sprayed on the inner surface of the hollow body obtained by the secondary molding, and a blow molding nozzle is inserted into the hollow body to extrude a parison whose tip is sealed and the blow molding nozzle. The blow molding is characterized in that compressed air is blown into the parison while pulling out, and the parison to be extruded is molded from a tertiary molding in which the parison is in close contact with the inner surface of the hollow body. A method for forming a multilayer hollow body made of a synthetic resin having an inner layer. 3. The molding method according to claim 1 or 2, wherein, during the primary molding, a blow hole is formed in one half-hollow body and a multilayer hollow body made of a synthetic resin having a blow molded inner layer is formed. .

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