JPH11239546A - Thermoplastic resin-made bathtub - Google Patents

Abstract

PROBLEM TO BE SOLVED: To facilitate recycling without surface defect owing to a shrink by integrally molding a reinforcing rib over from the rear surface of a bathtub main body to the rear surface of an apron which is protruded in the edge part of a main body and permitting shrink amounts at the front surface sides of the bathtub main body and the apron corresponding to the reinforcing rib to <=a specified value. SOLUTION: A thermoplastic resin-made bathtub is constituted of the bathtub main body 1, the apron 2 protruded in the edge part of the main body 1 and the reinforcing rib 3 which is integrally arranged over from the rear surface of the main body 1 to the rear surface of the apron 2. Polyethylene, polystyrene, an ABC resin and polyamide, etc., are exemplified as the thermoplastic resin. The thermoplastic resin-made bathtub is formed by gas pressurizing injection molding or gas common usage injecting compression molding. The shrink amount (the depth of a recession) occurring on the surfaces of the main body 1 and the apron 2 corresponding to the position of the reinforcing rib 3 in the thermoplastic resin-made bath tub is required to be <=5 μm in consideration of obtaining marketability.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a bathtub for integrally molding a thermoplastic resin.

[0002]

2. Description of the Related Art Conventionally, as a synthetic resin bathtub, a reinforced base material impregnated with a resin is attached one by one to a male mold and stacked to a required thickness. A fiber reinforced plastic (FRP) manufactured by attaching a reinforcing piece separately to the rear surface of the apron that protrudes from the portion is known (Japanese Patent Laid-Open No. 4-135).
522).

[0003] Further, a lower mold having a gel coat layer formed by spray coating and an upper mold having a reinforcing layer in which reinforcing fibers are mixed with an unsaturated polyester resin are combined to form an unsaturated mold between the gel coat layer and the reinforcing layer. There is also known an unsaturated polyester resin mainly formed by injecting and molding a polyester resin (JP-A-5-130947).

[0004]

However, all synthetic resin bathtubs have many manufacturing steps, and have a problem of poor productivity. In addition, it is usual to attach reinforcing pieces to the back of the bathtub body or the apron, but this installation requires a lot of trouble, especially when the shape of the reinforcing piece becomes complicated or the number of mounting points increases It takes more time and effort and increases the processing cost. Furthermore, it is desirable that a large product such as a bathtub can be recycled, but it is difficult to do so because it is made of a thermosetting resin, and there is a problem that a used bathtub must be discarded.

The above problem can be solved if the bathtub can be formed as an integral molded product of a thermoplastic resin. However, instead of the reinforcing piece separately attached, a reinforcing rib is integrally provided on the back surface of the bathtub body and the apron. If it is formed, sink marks will be generated on the surface side corresponding to the reinforcing ribs, and sufficient marketability cannot be obtained. Especially for products that are large and subject to heat load, such as bathtubs, the reinforcing ribs are also large, so the sink marks generated on the surface side corresponding to the reinforcing ribs are also large, which is a major obstacle to making the bathtub a thermoplastic resin molded product. Has become.

The present invention has been made in view of the above-mentioned conventional problems, and has as its object to provide a bathtub of a thermoplastic resin molded product having sufficient marketability.

[0007]

For this purpose, the present invention provides a gas pressure injection molding in which reinforcing ribs are formed integrally from the back surface of the bathtub body to the back surface of the apron projecting from the edge of the bathtub body. Alternatively, the present invention provides a thermoplastic resin bathtub, which is a thermoplastic resin integrally molded product by injection compression molding using a gas and has a sink amount of 5 μm or less on the surface side of the bathtub body and apron corresponding to the reinforcing rib. Is what you do.

[0008]

FIG. 1 is a perspective view from the bottom side showing an example of a thermoplastic resin bathtub according to the present invention. The present thermoplastic resin bathtub has a bathtub body 1 and an edge of the bathtub body 1. Apron 2 which overhangs the apron 2 from the back of the bathtub body 1
And the reinforcing ribs 3 are integrally formed over the back surface.

The present thermoplastic resin bathtub is an integrally molded product of a thermoplastic resin. As the thermoplastic resin, for example, polyethylene, polystyrene, impact-resistant polystyrene, AS
Resin, ABS resin, modified polyphenylene ether, polyamide, polymethyl methacrylate, and the like can be used. Those obtained by filling these thermoplastic resins with an inorganic filler such as glass fiber, carbon fiber, calcium carbonate, talc, and mica can also be used.

Since the present thermoplastic resin bathtub is made of the above-mentioned thermoplastic resin, in order to obtain the necessary structural strength particularly at the time of heat load when hot water is placed in the bathtub body 1,
The reinforcing rib 3 is essential. This reinforcing rib 3 is shown in FIG.
, The thickness of the bathtub body 1 is T,
Where w is the width of the base and h is the height of the reinforcing rib,
= (1.0 to 5) × T, and h = (1.1 to 1)
1) It is preferably within the range of xw. If w and h are too small, the strength under heat load tends to be insufficient, and if w and h are excessively large, a noticeable sink mark tends to occur on the surface side corresponding to the reinforcing rib 3.

Further, in order to increase the surface hardness of the thermoplastic resin bathtub so as to make it hard to be damaged, at least the bathtub body 1
Preferably, a hard surface layer having a pencil hardness of H or more is formed on the surface of the apron 2. This surface layer can be formed, for example, by applying a gel coat composition by spraying or brushing. As a gel coat composition,
An unsaturated polyester resin, a vinyl ester resin, an acrylic syrup, or a mixture thereof can be used. In addition, for example, by in-mold molding using a hard coat film such as a polyester resin base film provided with a hard coat layer of a thermosetting acrylic resin or the like, or a color film or an adhesive layer interposed therebetween. A hard surface layer can also be formed by molding the present thermoplastic resin bathtub and integrally attaching the hard coat layer to the surface.

Incidentally, the large reinforcing ribs 3 as described above are used.
Is integrally formed, the bathtub body 1 corresponding to the reinforcing rib 3 is formed.
Further, on the surface of the apron 2, remarkable sinks (dents) are generated due to the heat shrinkage of the resin. When significant sink marks occur, marketability in appearance cannot be obtained.

Therefore, in the present invention, a thermoplastic resin integrally molded article is formed by gas pressure injection molding or gas combined injection compression molding. Hereinafter, an example of the gas pressure injection molding and the gas combined injection compression molding will be described.

(1) Gas Pressure Injection Molding First, the mold used will be described.

As shown in FIG. 3, the mold 4 comprises a fixed mold 5 and a movable mold 6, and a cavity 7 is formed between the two.

A groove is formed in the parting part of the mold 4 and constitutes a path 8 for opening to the atmosphere. The open-to-atmosphere path 8 serves as an exhaust path at the time of thermoplastic resin injection.
This is a gap in which the cavity 7 can be evacuated without invading the molten resin. Although the gap left in the parting portion may be used as it is as the open-to-atmosphere path 8, it is preferable to form the above-mentioned groove for smooth exhaust.

On the other hand, on the side of the cavity surface 7a corresponding to the back surface of the bathtub, which is a molded product, a gap for communicating the cavity 7 outside the mold 4 is sealed. For example, the gap around the ejector pin 9 is sealed with an O-ring 10a,
The gap between the other mold components is also sealed by the O-ring 10b.

A gas injection pin 11 is provided on the side of the cavity surface 7a corresponding to the back surface of the bathtub. The gas injection pin 11 is embedded in the movable mold 6 with its front end face facing the cavity 7. The gas supply pin 11 is connected to a pressurized gas source (not shown) via a valve 12. The pressurized gas sent from the discharge path 13 is supplied to the cavity 7 through a gap left between the movable mold 6 and the pressurized gas. Although only one gas injection pin 11 is shown in the drawing, the gas injection pin 11 can be provided at a plurality of positions, and the supply of the pressurized gas is performed by using a gap around the ejector pin 9 instead of the gas injection pin 11. It is also possible to do.

The bathtub is formed by gas pressure injection molding by injecting the molten thermoplastic resin into the cavity 7 of the mold 4 as described above. The injection amount of the thermoplastic resin may be equal to the volume of the cavity 7, but is preferably slightly larger than that. At the time of injection of the thermoplastic resin, the air in the cavity 7 and the volatile components from the thermoplastic resin are discharged from the atmosphere opening path 8.

On the other hand, pressurized gas is supplied into the cavity 7 through the gas supply / discharge path 13. The supply of the pressurized gas may be started at any time before, during, or immediately after the injection of the thermoplastic resin. The pressurized gas may be, for example, air or carbon dioxide gas, but is preferably an inert gas such as nitrogen. The pressure of the pressurized gas is usually 10 to 250 kgf / c
m ² , preferably 40 to 200 kgf / cm ² .

The pressurized gas supplied into the cavity 7 is
The resin is injected while being sandwiched between the thermoplastic resin in the cavity 7 and the cavity surface 7a, and the surface of the bathtub, which is a molded product obtained, is pressed against the corresponding cavity surface 7b. The pressing by the pressurized gas suppresses the occurrence of sink marks on the surface of the bathtub, improves the transferability on the cavity surface 7b side, and prevents poor appearance such as sink marks and uneven gloss.

After injection of the thermoplastic resin and pressurization of the pressurized gas as described above to cool the thermoplastic resin in the cavity 7, the pressurized gas in the cavity 7 is discharged if necessary. Remove the bathtub.

(2) Combined Injection Compression Molding Using the mold 4 described with reference to FIG. 3, the molten thermoplastic resin is injected with the mold 4 slightly opened. A pressurized gas is supplied to the cavity 7 before or during the injection of the thermoplastic resin. The injection amount of the thermoplastic resin may be an amount that just fills the cavity 7 at the time of mold clamping, but is preferably slightly larger than that.

The type of pressurized gas used is the same as that used in the gas pressure injection molding, but the pressure can be lower than that in the gas pressure injection molding.

Next, immediately before or after the injection of the thermoplastic resin is completed, the mold is clamped while the supply of the pressurized gas is maintained, and the thermoplastic resin in the cavity 7 is compressed. At this time, some surplus thermoplastic resin can be made to flow back from the gate.

By the compression accompanying the mold clamping, the cavity 7
The pressurized gas sandwiched between the thermoplastic resin in the inside and the cavity surface 7a is further pressurized, and strongly presses the surface side of the bathtub, which is the obtained molded product, to the corresponding cavity surface 7b. The pressing by the pressurized gas suppresses the occurrence of sink marks on the surface of the bathtub, improves the transferability on the cavity surface 7b side, and prevents poor appearance such as sink marks and uneven gloss.

The thermoplastic resin bathtub of the present invention can be obtained by gas pressure injection molding or gas combined injection compression molding as described above. The reinforcing rib 3 of the thermoplastic resin bathtub thus obtained is obtained. The sinkage (depth of the depression) generated on the surface of the bathtub body 1 and the apron 2 corresponding to the position is
In order to obtain marketability, the thickness needs to be 5 μm or less.

Further, the hard surface layer is formed by molding a bath by gas pressure injection molding using a mold 4 as shown in FIG. It can also be carried out by slightly opening the mold 4 to loosen the mold clamping force and injecting the gel coat composition into the surface of the bathtub.

[0029]

EXAMPLE 1 Using a mold as shown in FIG.
A bathtub as shown in FIG. 1 having an inner length of 1200 mm, an inner depth of 550 mm, and a 100 mm wide apron projecting from the periphery was integrally formed by gas combined injection compression molding. The thickness of the bathtub body and the apron was 2 mm, the root width of the reinforcing rib was 6 mm, and the height of the reinforcing rib was 60 mm.

The molten ABS resin was injected with the mold opened 10 mm from the mold clamping position, and when 80% by volume of the amount of the molten resin required for molding was injected, nitrogen gas at a pressure of 50 kgf / cm ² was injected into the cavity. Immediately after the injection was completed, and the mold was clamped at a pressure of 150 kg / cm ² . A obtained
With respect to the bathtub made of BS, the occurrence of sink marks on the front surface side corresponding to the positions of the reinforcing ribs on the back surface could hardly be observed with the naked eye. When the amount of sink was measured with a surface roughness meter,
m or less.

[0031]

The present invention is as described above, and is a marketable bathtub made of a thermoplastic resin and having almost no surface defects due to sink marks. Is also easy.

[Brief description of the drawings]

FIG. 1 is a perspective view from the bottom side showing an example of a thermoplastic resin bathtub according to the present invention.

FIG. 2 is an explanatory diagram of a reinforcing rib.

FIG. 3 is a view showing an example of a mold used for gas pressure injection molding and gas combined injection compression molding.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Bathtub main body 2 Apron 3 Reinforcement rib 4 Die 5 Fixed type 6 Movable type 7 Cavity 7a, 7b Cavity surface 8 Atmospheric release path 9 Ejector pin 10a, 10b O-ring 11 Gas injection pin 12 Valve 13 Gas supply / exhaust path

Claims (2)

[Claims] 1. A thermoplastic resin integrated by gas pressure injection molding or gas compression injection molding in which reinforcing ribs are integrally formed from the back surface of the bathtub body to the back surface of the apron projecting from the edge of the bathtub body. A thermoplastic resin bathtub, which is a molded product, and has a sink amount of 5 μm or less on the surface side of the bathtub body and the apron corresponding to the reinforcing rib. 2. The thermoplastic resin bathtub according to claim 1, wherein a hard surface layer having a pencil hardness of H or more is formed on the surfaces of the bathtub body and the apron.