JPH0122143B2 - - Google Patents

Description

[Detailed description of the invention]

[Technical Field] The present invention relates to a method for manufacturing molded products such as bathtubs, counters, wall materials, etc. whose surfaces are formed with high hardness. [Background Art] In the case of bathtubs and the like, it is necessary to form a gel coat layer with high hardness on the surface of the bathtub in order to improve the scratch resistance.The production of this molded article will be explained using a bathtub as an example. That is, first, a core layer 6 that looks like artificial marble is created, for example, by hand-laying up FRP or casting resin on a mold, and then the surface of this core layer 6 is coated as shown in Figure 1. A polyfunctional acrylate resin 7 mixed with a photosensitizer is coated, and the polyfunctional acrylate resin 7 is photocured by irradiation with ultraviolet rays or electron beams, and the polyfunctional acrylate resin 7 forms a highly hard gel coat. Thus, layer 8 is formed. This polyfunctional acrylate resin 7 gives significantly higher hardness than other resins upon curing, and as is well known, is generally used as an ultraviolet curable type or an electron beam curable type. However, when polyfunctional acrylate resin is used as an ultraviolet curing type or an electron beam curing type, special equipment for ultraviolet ray irradiation or electron beam irradiation is required, which increases the equipment cost. In the case of multifunctional acrylate resins, it is necessary to devise ways to irradiate the polyfunctional acrylate resin with ultraviolet rays or electron beams, resulting in complicated equipment, which also poses the problem of high equipment costs. If further UV irradiation or electron beam irradiation is performed,
Another problem is the risk of explosion when using solvents. On the other hand, polyfunctional acrylate resins are anaerobic, and due to the polymerization inhibiting effect of oxygen, radical polymerization may not proceed, gel time may become long, or crosslinking density may not increase. It is well known that this is a big problem. Conversely, it is also known that polyfunctional acrylate resins can be thermally polymerized in a state where air is completely blocked. However, when applying this polyfunctional acrylate resin as a gel coat layer to the surface of a molded product, it is not possible to cure it while completely blocking air, and it is necessary to rely on ultraviolet curing or electron beam curing methods. It was designed to cure a functional acrylate resin. [Object of the Invention] The present invention has been made in view of the above points, and is capable of curing a polyfunctional acrylate resin while completely blocking air, and eliminates the need for ultraviolet irradiation or electron beam irradiation. It is an object of the present invention to provide a method for manufacturing a molded article with a high surface hardness, which can form a gel coat layer made of a polyfunctional acrylate resin without any problems. [Disclosure of the Invention] However, the method for producing a molded product with a high surface hardness according to the present invention involves coating the surface of a mold 1 with a polyfunctional acrylate resin 2, and then coating the surface of the polyfunctional acrylate resin 2 with a heat-curing mold. A resin 3 is applied and heated to harden the polyfunctional acrylate resin 2 and thermosetting resin 3 to form a gel coat layer 4, and then a core molding material 5 is laminated on the surface of the gel coat layer 4. The polyfunctional acrylate resin 2 is sandwiched between the mold 1 and the heat-curable resin 3, so that it is cured while completely blocking air. The present invention will now be described in detail with reference to Examples. First, a mold release agent such as wax or poval is thinly and uniformly applied to the surface of the mold 1, and then a polyfunctional acrylate resin 2 is thinly and uniformly applied to the surface of the mold 1 by using a brush, spray, or the like. As the polyfunctional acrylate resin 2, any resin commonly used for ultraviolet curing can be used. Further, the polyfunctional acrylate resin 2 contains an appropriate amount of a known curing agent or curing accelerator for heat curing. If the coating thickness of the polyfunctional acrylate resin 2 is too thick, cracks will occur, so it is preferable to suppress the coating thickness to 100 μm or less. Immediately after applying the polyfunctional acrylate resin 2 in this way, a heat-curable resin 3 is further applied to the surface.
Apply evenly over the entire surface. As this thermosetting resin 3, those used as gel coat resins such as general-purpose unsaturated polyester resins can be used. The coating amount of heat-curing resin 3 is based on the total thickness of polyfunctional acrylate resin 2.
It is best to set it so that it is 300μ or less. By applying the thermosetting resin 3 in this manner, the polyfunctional acrylate resin 2 is sandwiched between the mold 1 and the thermosetting resin 3 and is completely shielded from air. Next, the polyfunctional acrylate resin 2 and the thermosetting resin 3 are cured by heating. Since the polyfunctional acrylate resin 2 is completely shielded from air, the gelation reaction progresses by heating and it is cured. When the polyfunctional acrylate resin 2 is thermally cured in this manner, a cured layer having a hardness level equivalent to that obtained by ultraviolet curing is provided. In this way, the gel coat layer 4 is composed of two hardened layers of the polyfunctional acrylate resin 2 and the thermosetting resin 3.
is formed on the surface of the mold 1, and is then formed on the surface of the gel coat layer 4 as shown in FIGS. 2 and 3 a by conventional methods such as hand lay-up of FRP or resin casting. The core molding material 5 is laminated and cured, and at the same time, the core molding material 5 and the gel coat layer 4 are bonded together. Then, by removing this from the mold 1, the polyfunctional acrylate resin 2 is applied to the surface of the core layer 6, such as an artificial marble-like material obtained by hardening the core molding material 5 as shown in FIG. 3b. A molded article having a high hardness surface on which a two-layer gel coat layer 4 with a heat-curable resin 3 is laminated is obtained. Here, the polyfunctional acrylate resin 2 does not have good adhesion to the core layer 6, and if the polyfunctional acrylate resin 2 is directly laminated on the core layer 6, the polyfunctional acrylate resin 2
However, the polyfunctional acrylate resin 2 is bonded to the core layer 6 through the thermosetting resin 3.
Since the polyfunctional acrylate resin 2 is laminated on the core layer 6, the adhesion of the polyfunctional acrylate resin 2 to the core layer 6 can be improved. Next, specific examples of the polyfunctional acrylate resin in the present invention will be given to illustrate its effects. That is, the polyfunctional acrylate resins in Specific Examples 1 to 7 shown in the following table were applied to the surface of the mold to a coating thickness of 80μ, and the isophthalic acid-based polyester acrylate resin was further applied as a heat-curable resin to this surface. The hardness, scratch resistance, and stain resistance of the surface of the cured layer of the polyfunctional acrylate resin were measured, and the results are shown in the table below.

〔Effect of the invention〕

As described above, in the present invention, a polyfunctional acrylate resin is applied to the surface of the mold, a heat-curable resin is applied to the surface of the polyfunctional acrylate resin, and the polyfunctional acrylate resin is heated. The polyfunctional acrylate resin is sandwiched between the mold and the heat-curable resin and is completely shielded from air. It is now possible to cure by heating, which eliminates the need for irradiation with ultraviolet rays, which reduces equipment costs, and allows uniform heating even for irregularly shaped molded products, making it possible to cure irregularly shaped products. The surface hardness of the material can be easily improved, and there is less risk of explosion due to solvents, which occurs when UV irradiation is performed. Moreover, the polyfunctional acrylate resin is laminated on the core layer via the heat-curable resin, so that the adhesion of the polyfunctional acrylate resin to the core layer can be improved.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a conventional example, FIG. 2 is a sectional view of an embodiment of the present invention, and FIGS. 3a and 3b are an enlarged sectional view and a perspective view of a portion of the same. 1 is a mold, 2 is a polyfunctional acrylate resin,
3 is a thermosetting resin, 4 is a gel coat layer, 5 is a core molding material, and 6 is a core layer.

Claims (1)

[Claims] 1. After applying a polyfunctional acrylate resin to the surface of the mold, a heat-curing resin is applied to the surface of the polyfunctional acrylate resin, and the polyfunctional acrylate resin and the heat-curing resin are cured by heating. A method for producing a molded article with a high surface hardness, which comprises forming a gel coat layer, and then laminating a core molding material on the surface of the gel coat layer and curing it.