JP2003062849A - Method for molding thermoplastic resin foamed molded object and molded object - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a means for obtaining a thermoplastic resin foamed molded object of good quality having a thin-walled part in a short molding cycle. SOLUTION: In a foam molding mold comprising a pair of a core mold and a cavity mold, the steam orifice opening ratio of the leading end part of the thin-walled part of the thermoplastic resin foamed molded object is largely set to 3-12% and the steam orifice opening ratio of a portion other than the leading end part is set as small as 0.6-1%.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and a mold for producing a thermoplastic resin foam molding having a thin portion, and more specifically, a thin portion such as a box, for example, a rising portion of a side wall or a partition wall. A method and a method for manufacturing a thermoplastic resin foam molded article having a thin wall portion of good quality that can easily fill pre-expanded particles in a narrow molding space that forms a fitting portion of a box lid, etc., and has a short molding cycle. Regarding the type.

[0002]

2. Description of the Related Art Thermoplastic resin in-mold foam moldings using thermoplastic resin foam particles typified by styrene resin are excellent in lightness, heat insulation and cushioning property. Widely used in cushion packaging for home appliances and building materials. For example, in the case of these containers, there is a need for a design design in consideration of economic efficiency such as improvement of storage efficiency and reduction of the amount of resin used, or for adding a mechanism for fitting a box body and a lid body, for example. In many cases, a thin portion or a narrow rising portion is provided.

However, it is not easy to uniformly fill pre-expanded particles in such a narrow rising portion and obtain a foamed molded product of good quality in a short molding cycle. For example, in Japanese Examined Patent Publication No. 7-4826, a molding space in which a plurality of pre-expanded particles are arranged in a narrow space is formed in order to prevent the pre-expanded particles from accumulating and accumulating in the molding space when molding a polyolefin resin in-mold molded article. In addition, the pre-expanded particles are compressed and filled in every corner so as to be smaller than the gap size of the narrow molding space, and at the time of heat molding, the expansion of the pre-expanded particles is performed until the water vapor reaches the inner particles of the entire molding space. A method of suppressing and molding is disclosed.
However, this method is mechanically complicated as compared with the above-mentioned molding method which is generally performed without compression, such as the need to compress the particles to be filled, and there are still problems in actual use. There is.

Further, in Japanese Unexamined Patent Publication (Kokai) No. 10-643, pre-foaming is performed with steam holes provided only on a surface substantially perpendicular to the mold opening direction, and the drain valve on the mold side to which the feeder is attached being closed. A method is disclosed in which pre-expanded particles are packed while being rectified by packing the particles only in the packing direction. This method allows the pre-expanded particles to be skillfully introduced into the narrow gaps of the target pre-expanded particles having a particularly narrow gap of 1 or more and less than 2 grains, but the pre-expanded particles may be introduced into the mold opening direction. Since steam holes are present only in substantially vertical planes, steam heating tends to be insufficient in thin-walled portions such as rising portions and the surface property of the molded body tends to deteriorate. Therefore, in order to improve the surface property, it is necessary to take a long time for steam heating, and as a result, there is a big problem that the molding cycle is significantly extended, and therefore further improvement is desired. It was a thing.

[0005]

SUMMARY OF THE INVENTION The present invention does not use the complicated method as described above but uses a normal molding method to form a thin wall portion such as a narrow rising portion of a molded body space, for example, pre-foaming. Even in the thin portion of a comparatively thick general molded product having more than 2 particles, the thermoplastic resin pre-expanded particles are uniformly filled and a thermoplastic resin expanded molded product of good quality is obtained in a short molding cycle. It provides a method.

[0006]

As a result of earnest research to solve the above problems, the present inventor can easily solve the above problems by using a mold in which steam holes of the mold are unevenly distributed depending on parts. That is, the present invention has been achieved.

That is, according to the present invention, 1) thermoplastic resin pre-expanded particles are filled in a molding space formed by at least a pair of molds having steam holes on substantially the entire surface, and steam is injected into the molding space through the steam holes. Of the thermoplastic resin pre-expanded particles by heat-sealing the thermoplastic resin pre-expanded particles to obtain a thermoplastic resin foam molded article, and with respect to the vapor hole opening ratio of the mold, a thin wall of the thermoplastic resin foam molded article is obtained. For increasing the steam hole opening ratio of the tip portion of the portion and reducing the steam hole opening ratio of the portion other than the thin portion tip portion, the steam hole opening ratio per 100 cm ² of the former is 3% to 12%, Area of the latter 100 cm
^{The present} invention relates to a method for molding a thermoplastic resin foam molded article, wherein the opening ratio of steam holes per ² is 0.6% to 1%.

2) Thermoplastic resin pre-expanded particles are filled in a molding space formed by at least a pair of molds having steam holes on substantially the entire surface thereof, and steam is introduced into the molding space through the steam holes. A mold for heat-sealing thermoplastic resin pre-expanded particles to obtain a thermoplastic resin foam molded article, and
Regarding the steam hole opening ratio of the mold, regarding the steam hole opening ratio of the thin-walled end portion of the thermoplastic resin foam molded article to be increased and the steam hole opening ratio other than the thin-walled end portion thereof to be small, the former Has an opening ratio of 3 per 100 cm ^{2 of}
% To 12%, and the latter has a steam hole opening ratio per area of 100 cm ² of 0.6% to 1%, and relates to a thermoplastic resin foam molding die.

Further, the present invention relates to 3) a foamed thermoplastic resin molded article characterized by being molded by the method described in 1) above.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION As the thermoplastic resin used in the present invention, any thermoplastic resin used for in-mold foam molding can be used. For example, polystyrene resin, polyolefin resin, polymethylmethacrylate resin are preferable. .

The polystyrene-based resin which can be used in the present invention is not only a general expandable polystyrene resin but also styrene or methylstyrene in an amount of 50%.
Examples thereof include polystyrene resins, high-impact polystyrene resins, copolymer resins of styrene and butadiene, methyl methacrylate, maleic anhydride, etc., which are used alone or in combination of two or more. .

Examples of the polyolefin resin that can be used in the present invention include low-, medium-, high-density polyethylene, linear low-, ultra-low-density polyethylene, ethylene resins represented by ethylene-vinyl acetate copolymer, polypropylene, Propylene resins represented by ethylene / propylene random copolymers and ethylene / propylene block copolymers are mentioned. These are used alone or as a mixture of two or more. Further, these may be crosslinked or non-crosslinked. Among these, as the polyolefin-based resin, a mixed resin of two or more kinds of low, medium, high density polyethylene, linear low, and ultra low density polyethylene is preferable in terms of excellent foamability and moldability.

As the thermoplastic resin which can be used in the present invention, a polystyrene resin is particularly preferable from the viewpoints of economy and appearance. As the polystyrene resin, a polystyrene resin is easily available and inexpensive. It can be used most preferably in terms of economy.

As the mold used in the present invention, a mold which is generally used for molding thermoplastic resin pre-expanded particles can be used. Then, the steam holes of the mold can be unevenly distributed depending on the site. That is, the mold of the present invention increases the steam hole opening ratio at the tip of the thin-walled portion of the thermoplastic resin foam molding, and reduces the steam hole opening ratio at the side other than the tip of the thin-walled portion, the bottom surface, and the like.

The thin portion of the present invention is a portion having a smaller thickness than the average thickness of the foamed plastic resin product. For example, in the case of a box-shaped foam molded article, the wall thickness is thinner than the bottom wall thickness, or the opening of the box-formed article or the outer peripheral portion of the lid molded article for fitting the box body and the lid together. An uneven fitting portion (generally, a box is provided with a convex portion and a lid is provided with a concave portion is often fitted).

In the present invention, the thin-walled tip portion is a thin-walled portion of a molded product, which is normally formed near the downstream end as seen from the flow of the expandable particles which are the molding raw material. Is. In the present invention, the plane parallel to the box bottom in the peripheral portion of this thin portion is called the PL plane. The PL surface is the mold opening / closing surface of the mold at or near the thin-walled portion, and is a portion other than the thin-walled portion such as the fitting irregularities, for example, the bottom surface of the box molded body. It is formed on the surface parallel to.
From the thin-walled tip and the PL surface to the upstream side of the particle flow, P
A region including a region traced back by a distance corresponding to the wall thickness of the L-plane,
In the present invention, it is referred to as the thin portion front end portion.

This will be described with reference to the drawings. For example, FIG. 3 shows a schematic cross section of a molded product and displays the parts. Figure 1 (1)
Is an example having a fitting portion between the box body and the lid at the tip, (2) in FIG. 3 is an example in which the tip of the wall surface is partly thinner than the bottom thickness, and (3) in FIG. In this example, the entire side wall is thinner than the thickness. In each example, P
The L plane is defined as the indicated position in the figure. Here, as shown by the thick solid line in the figure, the thin-walled tip portion is located on the upstream side of the flow of particles from the PL surface (in the direction opposite to the thin-walled portion tip and in the downward direction in the figure). It is the region from the point that traces back the length of the thickness a to the tip of the thin portion.

The mold of the present invention has a steam hole opening ratio of 3% to 12% per 100 cm ^{2 of the} tip of the thin-walled portion of the thermoplastic resin foam molded article, and an area of 100 c other than the peripheral portion.
It is preferable that the vapor hole opening ratio per m ² is 0.6% to 1%. Further, from the viewpoint of mold strength and the like, the steam hole opening ratio per 100 cm ² of the thin-walled tip portion of the thermoplastic resin foamed molded product is 3.5% to 9%, and the area other than the tip portion per 100 cm ² area is 100% ² . Vapor hole opening ratio of 0.7% to 1%
It is more preferable that the opening ratio of the steam holes per 100 cm ^{2 of the} tip portion of the thin portion of the thermoplastic resin foam-molded article is 3.5% to 5.5%, and the area 1 other than the tip portion is 1%.
Most preferably, the vapor hole opening ratio per 00 cm ² is 0.8% to 1%.

When the vapor hole opening ratio of the present invention is expressed by a ratio, the thin-walled tip portion has a ratio of 20: 1 to other than the tip portion.
The ratio is 3: 1, more preferably 90: 7 to 7: 2, and most preferably 55: 8 to 7: 2.

In the present invention, the steam hole opening ratio is set to 10
The reason for expressing it as 0 cm ² is that it is considered that the number of core vents or slits arranged as shown in the example below falls within a region where it is easy to numerically grasp, considering the area.
For example, it can be converted into per unit area such as per cm ² . The mold of the present invention is not practical when the vapor hole opening ratio of the thin-walled end portion of the thermoplastic resin foam molded article is 12% or more, which is not practical, and when it is 3% or less, filling is performed. It is difficult for air to escape, and it tends to be difficult to fill the thermoplastic resin pre-expanded particles to the tip. Further, if the opening ratio of the steam holes at the tip of the thin portion of the thermoplastic resin foam molding is adjusted to the above range and the opening ratio of the steam holes other than the peripheral portion is set to 1% or more, the thermoplastic resin pre-expanded particles are filled. Air tends to escape by the time it reaches the tip, and it tends to be difficult to fill up to the tip. Also,
If it is 0.6% or less, it becomes difficult for steam to flow during heating, and the appearance of the foamed molded product tends to deteriorate. As the steam holes of the mold of the present invention, core vents, pinholes, slits and the like which are generally used as steam holes can be used. Among them, the core vent can be preferably used because it is easy to adjust the number of steam holes and easy to replace. As the core vent used in the present invention, a core vent generally used for a molding die of a thermoplastic resin foam can be appropriately selected, such as a slit core vent having a slit formed in the core vent itself and a lotus root core vent having a perforation hole. Among these core vents, a slit core vent having a diameter of 10 mm and a slit width of 0.2 to 0.4 mm can be preferably used. In order to adjust the steam hole opening ratio of the present invention to a predetermined value, it is sufficient to appropriately adjust the drill hole diameter, the drill hole number, the slit width, the number of slits, and the steam hole number. That is, the aperture ratio can be increased by increasing or increasing the drill hole diameter, the drill hole number, the slit width, the number of slits, and the number of steam holes. If the number is small or small, the aperture ratio can be lowered.

Regarding the installation of the core vent, for example, in the past, "Plastic mold handbook" edited by the Japan Synthetic Resin Technology Association (published June 30, 1989, Nikkan Kogyo Shimbun), page 414, the tip portion was 20 mm, and the other portion was 35 mm. There is a technical disclosure that it will be installed on the pitch. For the tip, place 5 pieces per 10 cm in length,
Except for the tip part, about 2.86 pieces are arranged per 10 cm in length, so 25 steam holes and about 8.2 steam holes are provided per 100 cm ² area (a rectangle of 10 cm in length and width is virtually considered). Become. Also disclosed to the public,
Most of the molds on the market that are sold have a tip pitch of 2
The pitch is 0 to 25 mm, and the pitch is about 25 to 35 mm except the tip portion, and 16 to 25 to 8.2 to 16 steam holes are provided per 100 cm ² area (according to the same calculation).

The steam hole opening ratio in such a mold for a molded body is, for example, in the case of using a standard slit core vent having a diameter of 10 mm (opening area 18 mm ² ) in the mold, the former is 100 cm in area at the tip. ^The average steam hole opening ratio per ² is about 3%, and the average except the tip is about 1.5%. In the latter, the steam hole opening ratio per tip 100 cm ² is about 2.2 to 3.7%. Other than that, it is 1.5 to 2.9%.

On the other hand, the steam hole opening ratio of the present invention is 12.3 to 24.5 m when the tips of the thin portions are evenly arranged.
The m pitch is equal to or slightly narrower than the above example, and about 16.7 to 66.1 steam holes are installed per 100 cm ^{2 of} area, but other than the tip portion, compared to the steam holes shown in the above-mentioned known art. Less than half 42.5 ~ 55m
Almost uniformly arranged at m pitches. This is an area of 100 cm ²
This is equivalent to setting the number of vapor holes per 3.3 to 5.5. That is, it is intended to increase the difference in the steam hole opening ratio between the thin-walled tip portion and other parts, and it is achieved by making the steam hole opening ratio of the other parts smaller than that of the mold used for normal molding. .

According to this method, since many steam holes are arranged at the tip of the thin portion, the effect of stealing the meat from the mold can be expected, the heat capacity can be reduced, and a favorable effect can be expected on the heat balance of heating and cooling.

FIG. 1 is a schematic cross-sectional view showing an example of a mold for in-mold foam molding used in the present invention, which comprises a core mold 1 and a cavity mold 2, and a molding space 3 is formed by the inner surfaces of both molds.
Are formed. 4a and 4b are steam holes (the core vent is conceptually shown in the figure), 5 is a feeder, 6
Is a core mold side steam valve, 7 is a cavity mold side steam valve, 8
Is a core mold side drain valve, and 9 is a cavity mold side drain valve. In the figure, the extrusion pin, the cooling water pipe, etc. are omitted.

Reference numeral 4a in FIG. 1 denotes a steam hole existing at the tip of the thin portion, and reference numeral 4b denotes a steam hole existing at other portions. The aperture ratio of the steam holes 4a is 100 cm
² % 3% to 12%, 4b aperture ratio area 100 cm ²
With a structure of 0.6% to 1%, the pre-expanded particles can be uniformly filled in the molding space corresponding to the thin-walled end portion of the thermoplastic resin foam, and the thermoplastic resin molding Since the tip of the thin portion and the other portion can be uniformly cooled in a well-balanced manner, the molding cycle can be shortened.

[0027]

The present invention will be described in more detail with reference to the following examples, but it goes without saying that the present invention is not limited to these examples. (Example 1) Molding was performed using a molding die as shown in FIG.

In this mold, core vents 4a (slit core vents having an opening area of 18 mm ² / piece) were installed at the tip of the thin portion at an average pitch of about 20 mm (vapor hole opening rate per 100 cm ^{2 of} 4.5%), The other parts have the same outer diameter,
Core vents 4b with the same opening area have an average pitch of about 45m
It is installed at m (steam hole opening ratio: 0.9%), and two feeders are provided.

FIG. 2 is a schematic perspective view of the mold forming space for showing the distribution of the steam hole opening ratio in this embodiment. With this mold, polystyrene pre-expanded particles [Kanepearl NSGMB (registered trademark) manufactured by Kanegafuchi Chemical Industry Co., Ltd., expansion ratio 55]
2 times] under the conditions shown in Table 1, similarly, as shown in the item of molded product quality in Table 1, a molded product having good appearance and internal fusion was obtained in a short molding cycle of 90 seconds.

The molding quality in Table 1 is defined as follows. (Appearance of tip) and (Other appearance) ⊚: There is no defective fusion and the surface is almost smooth and beautiful.

◯: The defective portion for fusion bonding is about 5% or less of the entire length, and the surface is almost smooth and beautiful.

Δ: Poor fusion bonding is about 20% or less of the entire length, and the surface is almost smooth and beautiful.

X: 50% or more of the defective fusion portion is present in the entire length, or the appearance is not entirely smooth. (Internal fusion) A cut with a depth of about 1 mm is made using a razor at the center, which divides the longitudinal direction of the molded body into two equal parts. The molded body is divided into two parts by hand around this. For the resulting cross section, the foamed particles of the original substantially spherical shape are painted black with black ink on the observable particle portion on the ruptured surface to carry out the primary treatment (the fused particles rupture the particles themselves, The unfused particles do not break themselves, and the particle shape can be observed on the fracture surface). Image processing device (Corporation)
The area of the black portion with respect to the entire area of the fracture surface was calculated by treating with Pierce, product number: PIAS-II), and the internal fusion rate was calculated by the following formula, and evaluated by the following evaluation criteria.

Internal fusion rate = (total area-black area) /
Overall area × 100 (%) ◎: 90% or more ○: 85% or more and less than 90% △: 80% or more and less than 85% ×: Less than 80% (Batch weight) After molding, store at 25 ° C 50% RH for 48 hours average mass of the measured molded article (example 2) as in example 1 of the mold, placed at an average pitch of about 13mm to Koabento 4a around the thin tip portion in Koabento (100 cm ² per steam aperture ratio:
10.7%) and other than that, except that core vents 4b having the same outer diameter and the same opening area were installed at an average pitch of about 45 mm (steam hole opening ratio: 0.9%), the same as Example 1. Molding was performed by the same method to obtain a molded body. The evaluation results are shown in Table 1. As a result of molding, a molded product having good appearance and internal fusion was obtained in a short molding cycle of 90 seconds. (Example 3) As in Example 1 of the mold, placed at an average pitch of about 20mm to Koabento 4a around the thin tip portion in Koabento (100 cm ² per steam aperture ratio:
4.5%) and other than that, except that core vents 4b having the same outer diameter and the same opening area were installed at an average pitch of about 52 mm (steam hole opening ratio: 0.7%), the same as Example 1. Molding was performed by the same method to obtain a molded body. The evaluation results are shown in Table 1. As a result of molding, a molded product having good appearance and internal fusion was obtained in a short molding cycle of 91 seconds. (Comparative Example 1) Example 1 The same mold, placed at an average pitch of about 20mm to Koabento 4a around the thin tip portion in Koabento (100 cm ² per steam aperture ratio:
Other than that, the core vents 4b having the same outer diameter and the same opening area were installed at an average pitch of about 25 mm that is adopted in a conventional general mold (steam hole opening ratio: 2%), and the molding was carried out under the same conditions as in Example 1 except that the steam hole opening ratio was made larger than that in Example 1. The evaluation results are shown in Table 1.

As a result of the molding, as shown in the result item, the outer appearance of the tip portion was beautiful, but the outer appearances of the other parts were swollen and not smooth.

Further, on the other hand, molding was performed by searching for conditions that make the appearance as smooth and beautiful as possible. As a result, the appearance of the other parts was improved, but the molding cycle was 105 seconds, which was considerably longer than that of Example 1. (Comparative Example 2) As in Example 1 of the mold, placed at an average pitch of about 20mm to Koabento 4a around the thin tip portion in Koabento (100 cm ² per steam aperture ratio:
4.5%), but for other parts, core vents 4b having the same outer diameter and the same opening area were installed at an average pitch of about 80 mm (steam hole opening ratio: 0.3%) to implement the steam hole opening ratio. Molding was performed under the same conditions as in Example 1 except that the size was made smaller than in Example 1. The evaluation results are shown in Table 1.

As a result, a molded product having a level of ∘ level was obtained in the external appearance of the tip, but in the external appearance of the other parts, unevenness was caused due to poor surface fusion, and internal fusion was also poor, resulting in good molding. I couldn't get a body.

On the other hand, in the same manner as in Comparative Example 1, a condition was searched for that the appearance was as smooth and beautiful as possible, and molding was performed. As a result, the overall appearance was improved, but the molding cycle was 113 seconds, which was considerably longer than in Example 1. (Comparative Example 3) As in Example 1 of the mold, placed at an average pitch of about 30mm to Koabento 4a around the thin tip portion in Koabento (100 cm ² per steam aperture ratio:
2%), and the vapor hole opening ratio was made smaller than that in Example 1.
The core vents 4b having the same outer diameter and the same opening area are installed at an average pitch of about 45 mm in other portions (same hole opening rate:
(0.9%) except that the molding was performed under the same conditions as in Example 1.
The evaluation results are shown in Table 1.

As a result, the outer appearance of the tip portion is markedly defective in fusion bonding both inside and outside of the surface, and also in other parts, defective fusion bonding is caused in the surface as a whole, and a good molded product can be obtained. There wasn't.

On the other hand, in the same manner as in Comparative Example 1, conditions were searched for such that the appearance was as smooth and beautiful as possible, and molding was performed. However, the tip can only be improved to the △ level, and the molding cycle is 1
It was 08 seconds, which was considerably longer than that in Example 1. (Comparative Example 4) As in Example 1 of the mold, placed at an average pitch of about 12mm to Koabento 4a around the thin tip portion in Koabento (100 cm ² per steam aperture ratio:
12.5%) and the vapor hole opening ratio was made smaller than that in Example 1. Other parts were molded under the same conditions as in Example 1 except that core vents 4b having the same outer diameter and the same opening area were installed at an average pitch of about 45 mm (steam hole opening ratio: 0.9%). The evaluation results are shown in Table 1.

As shown in the results item, a molded product having good appearance and internal fusion was obtained. However, the tip was slightly overheated and the appearance was evaluated as ◯. Further, when the molding was repeated 140 times, cracks were formed between the core vents of the mold and the mold was damaged, so the molding was terminated.

On the other hand, in the same manner as in Comparative Example 1, a condition was searched for such that the appearance was as smooth and beautiful as possible, and molding was performed. However, as the tip portion is improved, the appearance level of the other parts is decreased, and the other parts are not improved as a whole. Further, also in this case, when the molding was repeated 122 times, cracks were formed between the core vents of the mold, and the mold was broken, so the molding was terminated.

In this comparative example, in any of the cases as described above, the mold was damaged early, and stable continuous molding could not be performed.

[0044]

[Table 1]

[0045]

As described above, according to the present invention, it is possible to efficiently produce a thermoplastic resin foam molded article having a thin portion of good quality in a short molding cycle.

[Brief description of drawings]

FIG. 1 is a schematic sectional view showing an example of an in-mold foam molding die of the present invention.

FIG. 2 is a schematic perspective view schematically showing a molding space of a mold for showing an example of distribution of a steam hole opening ratio according to the present invention.

FIG. 3 is a schematic cross-sectional view showing an example of the thin tip portion of the present invention.

[Explanation of symbols]

1. Core mold 2. Cavity mold 3. Molding die 4. Steam holes (core vent in this case) 5. Feeder 6. Core mold side steam valve 7. Cavity mold side steam valve 8. Core mold side drain valve 9. Cavity mold side drain valve

Claims (3)

[Claims] 1. A thermoplastic resin pre-expanded particle is filled in a molding space formed by at least a pair of molds having steam holes on substantially the entire surface thereof, and steam is introduced into the molding space through the steam hole. A method for forming a thermoplastic resin foam-molded article by heat-sealing thermoplastic resin pre-expanded particles, and with respect to the steam hole opening ratio of the mold, the steam at the tip of the thin-walled part of the thermoplastic resin foam-molded article. With respect to increasing the hole opening ratio and decreasing the steam hole opening ratio other than the tip portion of the thin-walled portion, the former has a steam hole opening ratio of 3% to 1 per 100 cm ² of area.
2%, and the latter has a pore opening ratio of steam per 100 cm ² of 0.6% to 1%, which is a method for molding a thermoplastic resin foam molded article. 2. A thermoplastic resin pre-expanded particle is filled in a molding space formed by at least a pair of molds having steam holes on substantially the entire surface thereof, and steam is introduced into the molding space through the steam hole, A mold for heat-sealing pre-expanded thermoplastic resin particles to obtain a thermoplastic resin foam molded product, and with respect to a steam hole opening ratio of the mold, a thin-walled end portion of the thermoplastic resin foam molded product. To increase the steam hole opening ratio of, and to reduce the steam hole opening ratio other than the thin-walled tip portion,
The former has a pore opening ratio of 3% per 100 cm ²
It is 12%, and the latter has a steam hole opening ratio per area of 100 cm ² of 0.6% to 1%, and a thermoplastic resin foam molding die. 3. A thermoplastic resin foam-molded article obtained by molding according to the method of claim 1.