JPH04212838A - Thermoplastic-resin sandwich-shaped molded form and manufacture thereof - Google Patents

Abstract

PURPOSE:To provide a sandwich-shaped light-weight molded form composed of a low-cost thermoplastic resin, which is manufactured easily, and manufacture thereof. CONSTITUTION:A sandwich-shaped molded form is manufactured in such a manner that a core consisting of the foam of an ABS resin is positioned at a central section in the thickness direction, surface layers made up of a polycarbonate resin are formed on both sides of the core and these core and surface layers are monolithic-molded. A foamable ABS resin sheet and a polycarbonate resin sheet are laminated so that the former is held by the latter, and introduced into a mold and heated at the foaming temperature or higher of the ABS resin under pressure and both resins are melted, and pressure is lowered and the ABS resin is foamed in the mold, thus acquiring said sandwich-shaped molded form.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sandwich-like molded article (sandwich material) made of a thermoplastic resin and a method for efficiently producing the molded article.

0002

[Prior art] Foam-molded core part and fiber reinforced resin (F
A sandwich material consisting of a surface layer of FRP (RP) is usually produced by bonding the core and FRP, or by applying FRP to the surface of the core.
A method of molding the outer skin of RP, a method of molding the FRP outer shell in advance and injecting foamable resin into it, a method of installing reinforcing fibers on the inner surface of a mold, and injecting foamable resin into the mold. Epidermis F
It is manufactured by a method of simultaneously molding RP.

[0003] Among the above methods, the foam core and the skin F
The method of making RP and gluing them together yields a good product, but the process is complicated and requires skill, as it involves molding individual molded products into a predetermined shape, combining them in a predetermined manner, and gluing them together. Requires skill. Various practical methods have been proposed for foam-molding a core in advance and molding FRP on the outside, but the basic method is to mold a predetermined foam core and place it in a mold to form a skin FRP. If the core does not have a predetermined shape, it will not fit into the mold, or there will be a gap that will prevent the core from being placed in the desired position of the desired molded product, making it impossible to make a good sandwich material.

[0004] In addition, in the method called foam RTM, reinforcing material is wrapped around the outside of the foam core and resin is injected, but unless the core is precisely made and the gap between it and the mold is small, the position of the core cannot be determined. In the method called Foam RTM, this drawback is compensated for by wrapping the foam, which retains its expansion force, in a reinforcing material soaked in resin and expanding it by heating in a mold, but the expansion temperature and the curing temperature of the resin are approximately the same. must match. In addition, the core is also hard and the amount of expansion is limited, so a core that differs from the predetermined shape cannot be put to practical use.

Furthermore, the method of pre-molding the outer shell FRP and injecting foamed resin into it is based on
The first task is to mold the RP. In the method of placing reinforcing fibers on the wall of a mold and injecting foamed resin, the primary problem is fixing the reinforcing fibers, and another problem is that the foamed air bubbles infiltrate the reinforcing material. In any case, although pre-forming the core reduces the problem, making this core is also a challenge in itself and is unlikely to lead to a method of obtaining a cheap sandwich material.

[0006]

SUMMARY OF THE INVENTION One object of the present invention is to provide a sandwich-like molded product (sandwich material) that is easy to manufacture and inexpensive. The object is to provide a method that can be manufactured by high-speed molding.

[0007]

[Means for Solving the Problems] The above-mentioned first object has a core layer made of ABS resin foam in the center, a surface layer made of polycarbonate resin on both sides, and these are integrally molded. This is achieved by the sandwich-shaped molded product of the present invention made of a thermoplastic resin characterized by the following.

Another object is to laminate a sheet of foamable ABS resin and a sheet of non-foamable polycarbonate resin that may or may not contain reinforcing fibers, and to mold this laminate into a mold. This book is characterized in that the ABS resin is heated under pressure and heated to a temperature above which both of the above resins melt and foam under normal pressure, and then the pressure is released and the ABS resin is foamed in a mold to form the mold. This is achieved by the method of manufacturing a sandwich-like molded article of the invention.

The main purpose of the present invention is to form a foamable sheet by mixing a foaming agent and a resin that melts at a temperature below the foaming temperature in an unfoamed state, and then laminating it with a sheet of a resin having a higher melting point than the resin. The foamed resin is then placed in a mold and heated under pressure to melt and integrate both resins without mixing, without substantially transferring the foamed air bubbles of the foamed resin to the non-foamed resin phase. The object of the present invention is to obtain at once a molded product in which a foamed resin layer and a non-foamed resin layer are separated but integrated. This is based on the discovery that the combination of foamable polycarbonate resins is optimal.

[0010] That is, ABS resin and polycarbonate resin are compatible with each other, and the melting points, melt viscosities, etc. of ABS resin and polycarbonate resin are respectively within suitable ranges for carrying out the above molding. is the optimal combination among practical resins.

In the present invention, a foamable ABS sheet and a non-foamable polycarbonate sheet are laminated and molded.
BS sheets are produced by forming ABS resin with a foaming agent into a sheet at a temperature below the foaming temperature.

The composition of the ABS resin is determined depending on the type of polycarbonate resin used. The blowing agent is not particularly limited as long as it is suitable for this purpose, but examples include azo compounds such as azodicarbonamide, hydrazide compounds such as paratoluenesulfonyl hydrazide, nitroso and nitro compounds such as dinitrosopentamethylenetetramine, etc. A foaming aid may be added if necessary. Polycarbonate (PC) resin does not contain foaming agents and is ABS
A material with a higher melting point and higher melt viscosity than resin is used in the form of a sheet. Therefore, as mentioned above, when PC resin and ABS resin are laminated with the former sandwiching the latter and placed in a mold and molded at a temperature where the PC resin melts, the ABS resin will completely melt and the foam inside will form. Even if the agent foams, air bubbles are difficult to mix into the surface layer of the PC resin.

[0013] In many cases, it is preferable for the above-mentioned PC resin sheet to be made into a fiber reinforced sheet (FRP) in advance as a sandwich material. In other words, a sheet made of only PC resin may be used, but depending on the purpose, a fiber-reinforced PC resin sheet may be used. Such sheets are made of PC resin, glass fiber,
A sheet made by mixing milled fibers such as carbon fibers, or short fibers such as silicon carbide whiskers, or by impregnating a woven fabric or web of glass fibers, carbon fibers, etc. with melted or dissolved PC resin. Examples include things.

[0014] In the present invention, during molding, foamable AB
Taking advantage of their flexibility, S resin sheet and non-foaming polycarbonate (PC) resin (PC) sheet are bent and molded into a mold rather than a flat plate, and these are laminated and bonded with separate reinforcing fiber materials. The advantage of implementing the present invention is that the sheet and/or the reinforcing fiber material can be sandwiched and fixed between the molds. In practice, in the present invention, it is possible to laminate one foamable ABS resin sheet with a non-foamable PC resin sheet, but it is also possible to stack multiple sheets (for example, P
C/ABS/PC/ABS/PC) stacking, etc.
It is also possible to add different types of sheets between the sheets. The latter is preferable because it can also serve as reinforcement for the core portion. Further, it is also preferable to use a substantially integral sheet obtained by laminating these sheets, for example, a molded product using a multicolor extruder or the like.

[0015]

[Effects of the Invention] According to the present invention, a lightweight and inexpensive sandwich material can be obtained. The advantages of the present invention are particularly apparent when producing thin sandwich materials.

In other words, putting a sheet of foamable ABS resin into a mold means that there is no need to precisely make a foam core, and at the same time, utilizing the expansion force is internal pressure molding, which allows the foam core to be molded. It is free from the problems of preforming when used, especially the molding of a foam core that closely matches the shape of the molded object, and the problem of resin injection into the fiber layer packed between the mold and the core in a method called foam RTM. It means to do something. In addition, even if a sheet of polycarbonate (PC) resin with a high melting point is raised to a temperature above the Tg or the flow start point, it can be integrated with ABS resin with a low melting point in the mold, and the ABS resin can be foamed. There is no problem of the foamed resin penetrating into the reinforcing material.

[0017]

EXAMPLES Next, examples of the present invention will be described, but the present invention is not limited thereto.

[0018]

Example 1 A commercially available ABS resin containing a blowing agent (trade name "Polysrene"; manufactured by Kyowa Kasei Co., Ltd.) was obtained. This was molded at 150°C to form a sheet with a thickness of 0.3 mm. On the other hand, a commercially available polycarbonate sheet (trade name "Panlite"film; manufactured by Teijin Kasei) was obtained. This sheet had a thickness of 0.1 mm.

[0019] The above two polycarbonate sheets/one "polysrene" sheet/one polycarbonate sheet were laminated in the order, placed in a mold, heated to 240°C in a pressed state, and the mold interval was opened to 2 mm. . After cooling, the molded product was taken out to obtain a sandwich material having a thickness of 2 mm and having a foam core of ABS resin between the polycarbonate resin layers.

[0020]

[Example 2] A commercially available carbon fiber fabric (manufactured by Toray) was sandwiched between the polycarbonate sheet of Example 1, and heated at 320°C and 200k.
A carbon fiber reinforced polycarbonate sheet was obtained by hot pressing at g/cm2. A sheet of "polysrene" used in Example 1 was sandwiched between these two sheets. This laminated part was placed in a mold, pressurized to 200 kg/cm2, and heated to 260°C. Next, the mold interval was opened to 2 mm, and after cooling, the molded product was taken out. A sandwich material was obtained whose surface was carbon fiber reinforced polycarbonate and whose center was foamed ABS. As a result of a bending test, this sandwich material had a strength of 6.7 kg/
mm2, and the elastic modulus was 780 kg/mm2.

Claims (3)

[Claims] [Claim 1] A thermal device characterized by having a core layer made of an ABS resin foam at the center in the thickness direction, and a surface layer made of a polycarbonate resin on both sides, and these are integrally molded. A sandwich-shaped molded product made of plastic resin. 2. The sandwich-shaped molded product according to claim 1, wherein the surface layer made of polycarbonate resin contains reinforcing fibers. 3. A sheet of foamable ABS resin and a sheet of non-foamable polycarbonate resin are laminated, and this laminate is placed in a mold and heated under pressure to melt both resins. 2. The method for producing a sandwich-shaped molded product according to claim 1, further comprising raising the temperature to a temperature at which it foams under normal pressure, and then relaxing the pressure to foam the ABS resin in a mold.