JPH0225315A - Insert blow molded body - Google Patents

Abstract

PURPOSE:To shorten the cooling time and improve the bond strength of a molded body by a method wherein the surface of a part, to the portion of which a main body bonds, is covered with thermoplastic resin, which is weldable to the main body and the melting point of which is lower than that of the main body. CONSTITUTION:When a headrest main body 1, for example, is intended to be molded, the portion, to which the main body is bonded, at the tip of a stay 2 is covered in advance with resin, the melting point of which is lower than that of the resin consisting of the main body by 5 deg.C or more and which is weldable to the main body, by the thickness of 0.2mm and thicker or 0.5mm. The resultant stays are arranged just below and near the center of a parison 7 extruded from a die 6. When the molten parison hangs down by the predetermined length so long as to cover the tips of the stays, a mold 10 is closed so as to pinch the parison and the stays by the mold. At this time, the parison is welded together and the resins covering the stays are simultaneously compressed so as to be fixed to the resin of the main body by pressure with compression parts provided on the mold 10. The surface of the resin, with which the stay is covered, melts by the heat of the resin of the main body, resulting in fusion-bonding 5 said resin to the resin of the main body.

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention is a blow-molded article made of thermoplastic resin having an insert portion, and is used, for example, in a headrest attached to the upper part of an automobile seat or attached to a seat. This invention relates to a blow-molded object formed by inserting parts used for the core of an armrest, etc.

<Prior art> In blow molding, the parts to be attached to the molded product are inserted in advance into a cylindrical molten parison extruded from an extruder (for example, a stick when molding a headrest core). Insert blow molding, in which parts in various shapes such as plates (for example, screws) are attached inside a mold and the parts are integrally molded each time it is blow molded, is widely used for automobile parts, etc. .

However, it is difficult to obtain sufficient joint strength when joining metal parts and the molded product body, and even if high strength is obtained, there are problems such as high cost. It is hoped that the technology that can be obtained will be developed.

For example, in the case of Japanese Patent Publication No. 62-4209, the conventional technology is to provide a separate resin outlet outside the cylindrical parison extruded from the die in the vicinity of the parison outlet, and extrude a sheet-shaped molten resin from this outlet to form the parison. The headrest core is manufactured by inserting a stay between the seats and blow molding.

According to this method, the stay is cooled and solidified while being sandwiched between the parison and the sheet, so the stay is fixed by the resin.

However, this method not only requires a complicated special die to extrude the resin, but also the fused sheet and parison overlap (approximately twice the thickness of the parison), making it difficult to cool this area. Therefore, it is necessary to significantly lengthen the cooling time.

Furthermore, since the insert part and the resin are not bonded, it is difficult to obtain high strength even if measures are taken to prevent removal.

Furthermore, JP-A No. 60-217117 discloses a method of molding by inserting parts that have been heated in advance; For example, when a metal stay is heated and inserted, only a small portion enters the mold, and most of the stay is cooled in the air, so it is difficult to cool down (the temperature of the stay part decreases). As a result, the cooling of the joint with the inserted part is significantly delayed, requiring a long period of time to cool down.

As mentioned above, conventional methods have problems in terms of strength because the cooling time is long and the adhesive strength with the insert parts is low.

<Problem to be solved by the invention> In the conventional method, the molten resin layers overlap, resulting in separation of cooling.When molding an insert part by heating, it takes time to remove heat from the insert part, and cooling The present invention requires a long time, and in addition, the strength of the bond between the insert part and the main body is insufficient, making it particularly unsatisfactory for applications that require high strength, such as headrests and armrests. This was done in an attempt to solve this problem.

<Means for Solving the Problems> The present invention provides an insert blow molded article in which a metal part is inserted into a main body made of thermoplastic resin, and the surface of the part where the part joins the main body has weldability to the main body. , and a thermoplastic resin whose melting point is 5°C or more lower than that of the main body.
．． To provide an insert blow molded article characterized by being coated with a thickness of 2 mm or more.

Next, the present invention will be explained in detail with reference to the drawings. FIG. 1 is a schematic diagram of the layers of a hendrest core for an automobile according to an embodiment of the present invention, and FIG. 2 is a partial sectional view of FIG. 1. However, this example is given as an example of the application and is not intended to limit the application.

In Fig. 1, 1 is a blow-molded core or main body, 2
3 is a stay or part made of metal, and 3 is a compression part in which the resin of the main body is compression molded using a mold. Next, in Fig. 2, which is a cross-sectional view, 4 is a coating layer of a resin that is weldable to the main body on which the stay is coated and has a melting point lower than that of the main body by 5°C or more, and 5 is a coating layer between the core (main body) and the stay (main body). This is the joint part with the resin coating layer coated on the parts).

When forming the core (main body), the stay (
Part) 2 is a thermoplastic resin that constitutes the main body, such as a high-density polyethylene resin with a melting point of 131°C (in the present invention,
Melting point measurement method is PERKIN-ELMER DSC
This value was measured using a measuring device under the following conditions.

The amount of sample 8.0~ is heated from room temperature to 160°C at a rate of 200°C/min to melt the sample, and then heated at 8°C/min.
After lowering the temperature to 50℃ with n and holding 1mln at 50℃, 8-
1? This is the peak temperature of the melting energy when the temperature is raised again at ℃/min. ), the insert stay should be made of low-density polyethylene resin with a melting point of 110°C, which has a melting point of 5°C or more lower than the resin of the main body and has a weldability to the main body resin. 0
．． The tip of the stay is coated with a thickness of 2B or more, for example, 0.5 m, at the point where it joins with the main body, and this is placed near the center directly below the parison 7 extruded from the die 6 as shown in Fig. 3. When this stay is placed and the molten parison hangs down to a predetermined length and covers the tip of the stay, the mold 10 is closed and the parison and stay are sandwiched between the molds. 9, the parisons are fused to each other, and the resin coated on the stay is also press-bonded to the compressed resin of the main body at the same time. At this time, the surface of the resin coated on the stay and which has a weldability to the main body is melted by the heat of the main body resin and is fused and bonded to the main body resin. Next, by blowing fluid into the hollow body and performing blow molding, a blow molded body in which the part into which the stay is inserted and the main body are integrated can be obtained.

In addition, the necessary parts of the Sudei, that is, the parts that will be joined to the main body, are coated with a resin that has a melting point 5 degrees Celsius or more lower than the resin used to mold the main body and is weldable to the main body. The reason for this is as shown in Figure 7. (As the melting point of the resin coating the main body molding resin approaches, the bonding strength decreases significantly. If the limit value of the bonding strength is set to, for example, 80, the melting point of the resin coating the main body molding resin is 5°C or more lower.) In addition, the lower limit for the thickness of the coating is the minimum thickness that can obtain the bonding strength limit of 0.2X, and preferably 0.4X or more.The bonding strength increases by increasing the thickness of the coating. Although there is a tendency to make it thicker than necessary, there is a limit to it because it takes effort during coating, increases cooling time, increases material cost, etc., and it is practical to keep the thickness within 5 mm.

The reason for regulating the melting point and coating thickness of the coating resin is that the inserted parts are metal and have high thermal conductivity, so they can be heated to room temperature (
For example, if the part is inserted and molded at 25° C., the molten resin that comes into contact with the part will solidify, and a solidified film-like layer will be formed on the surface of the part in the initial stage of contact. Subsequently, other parts gradually cool and solidify, but at this time, volume shrinkage occurs due to solidification (especially resins such as polyethylene and polypropylene have a high yield rate, so resins initially form on the surface of the inserted part. The part that has solidified into a film is pulled and lifts up from the insert part, creating a gap between the part and the resin, resulting in insufficient fixation.

As a countermeasure to this, the parts are heated in advance to a temperature close to their melting point to prevent the lettuce from solidifying immediately upon contact with the molten resin.

This heating can prevent the creation of gaps between the part and the resin, but since the part is heated, the resin around the part becomes difficult to cool down, and it takes quite a long time to maintain the dimensional accuracy of the molded part. It has to be cooled, which reduces productivity.

As a countermeasure for this, in the present invention, a resin layer of 0.2 MIII or more, preferably 1, <&t0.4 m or more is provided at the part where the inserted part is joined to the molded product body, and this resin layer serves as a heat insulating layer and prevents the molten resin from coming into contact with it. In addition, since this heat insulating layer uses a resin whose melting point is 5°C or more lower than the resin used to mold the main body, it should be inserted at room temperature (e.g. 258°C) without being heated in advance. However, since the parts that come into contact with the molten resin used to form the main body are heated by the molten resin, the temperature of the contact surface rises, and the surface of the resin coated on the inserted part melts, causing the parts that come into contact with the molten resin that forms the main body to melt. The contact surfaces are fused.

In other words, by creating a heat insulating layer using a resin whose melting point is at least 5°C lower than the main body resin, the molten resin melts the contact surface of the resin of the insert part with the main body resin and fuses it with the main body resin, resulting in high bonding strength. Become. If the heat insulating layer is made of a resin with a melting point that is the same as or close to that of the main body, if the temperature of the insert parts remains at room temperature, the temperature of the joint surface will not rise above the melting point and fusion will not occur, resulting in low joint strength (sufficient strength will not be achieved). However, if the temperature of the resin used to mold the main body is raised significantly (for example, in the case of high-density polyethylene, it is usually
If it was set to 250°C. ) If the insert parts are heated to a temperature of 100℃ or higher, they will fuse together and provide sufficient strength, but if the resin temperature is high, the drawdown will be large and the wall thickness will be large in blow molding. Problems such as non-uniformity, severe oxidation deterioration of the resin, and burning of the resin occur, and when regenerating the resin, the strength decreases due to the deterioration of the resin, and the cooling time must also be extended. On the other hand, when a part is heated and inserted, the area around the part is cooled down to K There are problems such as control of heat, handling of hot parts is dangerous, time-consuming, and troublesome in terms of work.

The resin used in the present invention may be a thermoplastic resin for both the resin for molding the main body and the resin for coating the insert part, and a wide variety of generally known resins can be used.

The resin for the main body is not particularly limited as long as it can be blow-molded. Representative examples include polyolefin resins (e.g. polyethylene, polypropylene resins and copolymers containing these), polyamide resins (e.g. nylon 6),
, nylon 11, nylon 12, or copolymers thereof), as well as blends containing these resins with other polymers, etc. are used.

Examples of the shape of the parts to be inserted include metal rods partially or fully covered with resin, screws and metal fittings covered with resin, and shapes such as plate or block shapes. It is not limited to the shape shown in FIG. 2, but any shape can be used.

In order to increase the adhesive strength between metal and resin, it is preferable to use a resin that is adhesive to metal. For example, when the main body of the molded article is polyolefin, polyethylene, polypropylene copolymerized or graft-polymerized with acrylic acid or methacrylic acid, carboxyl groups, ionomer resin, and nylon 11.12 are preferably used.

The inner metal parts are preferably iron and iron alloys, aluminum and its alloys, or metals whose surfaces are plated with nickel, chromium, zinc, etc. from the viewpoint of adhesion to the resin.

However, the metal used is not limited to the above.

The lower limit of the melting point of the coating resin is determined depending on the material used and the application. For example, in the case of automobile parts that require heat resistance and high strength, those with a melting point of 100℃ or higher are ≠+411L
<, - It is preferable to use a resin having a melting point of 80°C or higher in the film.

Next, typical examples of combinations of resin for molding the main body and resin for coating the insert parts are shown below.

Table 1] Note) * indicates a product made by graft polymerization of maleic anhydride. Molded products molded in this way have a high bonding strength between the parts and the main body. It is suitable for use in applications that require high reliability because there is no unevenness in adhesive strength due to temperature variations, which is often seen in
Examples of applications include headrests, armrests, bumpers,
These include automobile parts such as spoilers, ducts, and tanks, chair seats, photocopier panels, electronic equipment, and musical instrument cases.

The method for coating the parts to be inserted may be any general method such as fluidized dipping using resin powder or injection molding press molding (the method is not limited to this method).

The present invention will be described in more detail below with reference to the drawings regarding a headrest core of an automobile as an example, but the present invention is not limited thereto.

Embodiment 1 Figure 3 shows insert blow molding of an automobile headrest core according to an embodiment of the present invention. 2 is a metal stay to be inserted, and 4 is a metal stay with a density of 0 at the part where this stay joins with the main body. A low density polyethylene resin powder graft-polymerized with maleic anhydride having a melt index of 4 and a melting point of 110°C was molded to a thickness of 0.926 by a fluidized dipping method.
After the other end of this stay is fixed to the holder 8, the ballin is extruded from the die 6 to a predetermined length, the mold 10 is closed, and pressurized fluid (air) is applied inside. was blown and cooled to form a headrest core material.

At this time, the resin used to mold the main body has a density of 0.958. Mel)・
High-density polyethylene with an index of 0.4 and a melting point of 131°C was used.

The temperature of the high-density polyethylene resin extruded from the die was 200°C, the thickness of the parison was 4 m, the temperature of the mold for molding was 25°C, and the cooling time was 35 seconds. If the cooling time is 30 seconds or less, the cooling is insufficient and the shrinkage after removal from the mold is large (the problem of stays was uneven and the dimensions were out of the allowable range).

Two days after molding, the rotational torque was measured using a torque wrench to determine the joint strength between the stay and the molded product body.

As shown in Table 2, the torque was 190 &-am, and the strength of the joint was sufficient to the extent that the blow-molded main body was greatly deformed before the joint came off.

Example 2 Molding was carried out under the same conditions as in Example 1, except that the resin covering the stay was a low-density polyethylene resin with a density of 0.922, a melt index of 2, and a melting point of 123°C. As shown in Table 1, the strength of the joint of the insert was 14okg.
The joint peeled off at -cm.

This strength is sufficient for practical use.

Example 3 Example 2 except that the coating thickness was changed to 0.2 in Example 2.
It was molded under the same conditions. As a result, as shown in Table 2, the strength of the joint was 80 to 9 cm, which was inferior to the previous one, but strong enough for practical use.

Comparative Example 1 In Example 2, only the thickness of the coating part was changed to 0. Molding was carried out under the same conditions except that In was used. The results are shown in Table 2, and the bonding strength is 1.
Low at 5kC1l-cm (the stay moved with a small amount of force).

Comparative Example 2 High-density polyethylene with a density of 0.952, a melt index of 7, and a melting point of 128°C was used as the resin to coat the stay.
．． Molding was carried out under the same conditions as in Example 1, except that the coating was coated by the fluidized dipping method to a thickness of 5B.

As shown in Table 2, the bonding strength of the stay to this molded product was <8 kl/-cpn, meaning that there was almost no fusion.

Comparative Example 3 Molding was carried out under the same conditions as in Comparative Example 2, except that in Comparative Example 2, the steel was heated to ioo°C in advance. The bonding strength of the stay to this molded product is 80
Although the bonding strength was somewhat low with 9-crn, it was possible to withstand practical use. However, the time required for cooling to obtain a product with predetermined dimensional accuracy was 90 seconds, which required a significantly longer cooling time.

Comparative Example 4 In Comparative Example 2, molding was carried out under the same conditions as in Comparative Example 2, except that the temperature of the parison during molding was as high as 230°C.

The bonding strength at this time is as shown in Shishi 2, and the bonding strength with the insert is 4 ok6! - The sieve was too low to be practical, and cooling required 50 seconds, requiring a longer cooling time.

Comparative Example 5 The conditions were the same as Comparative Example 2, except that the resin temperature of the parison during molding was 250°C. As shown in Table 2, the bonding strength at this time was excellent at 130 knees, but the time required for cooling had to be longer, 60 seconds.

Comparative Example 6 The same conditions as in Example 1 except that high-density polyethylene (resin A) was used as the resin for molding the main body and the stay was only degreased without coating the surface. In the case of this molded product and the stay, the strength was so weak that the stay could come off when the molded product was taken out, and a gap was created between the stay and the resin.

Comparative Example 7 Molding was carried out under the same conditions as Comparative Example 6, except that the stay was heated to 100°C. Although there is no gap between the molded stay and the resin, the joint strength is less than 5K in Table 2.
g-cm, which was very low and far from a practical level.

<Effects of the Invention> The present invention has been made in order to efficiently increase the bonding strength between the insert part and the molded body body, and there is no need to preheat the insert part, and the time required for cooling is short. It is possible to obtain an insert blow-molded body with high bonding strength by a very simple method that does not require any special processing to prevent insert parts from falling out or rotating, and does not require overlapping parisons. In particular, the conventional method of heating and inserting parts was unreliable due to poor strength due to temperature variations.Moreover, it took time to attach many parts to one main body at the same time, and the temperature of the parts increased. I couldn't do it because it would fall. However, according to the present invention, all of these problems can be solved.

[Brief explanation of the drawing]

Figure jI1 is a front view of a headrest core that is an example of the present invention,
Figure 2 is a sectional view of this, Figures 3 and 4 are schematic diagrams showing the method of molding the headrest, Figure 5 is an example in which the tip of the stay 2 is coated with resin, and Figure 6 is an example in which the stay has a notch. For example, FIG. 7 is an explanatory diagram of the limit of bonding strength. 1...Headrest core body, 2...Stay, 3...
・Compression molding part, 4...Resin coating part, 5...Joint part between core wood body and coating resin, 6...Gui, 7...Parison, 8...Stay holder 9... Molten resin compression section,
10... Venus for blow molding, 11... Internal space of headrest core, 12, 13... Notch of stay.
-Shired Fu Asahi Kasei Kogyo Co., Ltd. Figure 3 Figure 5 Sanction 4 Figure 4 Figure 6 L'' Procedural amendment (voluntary) September 73, 1988

Claims (1)

[Claims] In an insert blow-molded body in which a metal part is inserted into a body made of thermoplastic resin, the surface of the part where the part joins the body is a thermoplastic resin that has weldability to the body and has a melting point 5°C or more lower than that of the body. An insert blow molded article characterized by being coated with a thickness of 0.2 mm or more.