JPH06270201A - Resin multi-layer structure - Google Patents

Abstract

PURPOSE:To provide a resin multi-layer structure generating no remarkable lowering of mechanical strength in a welding section. CONSTITUTION:A multi-layer structure is a molded body consisting of a resin section (A) containing a reinforcing filler of 5-70wt.% and another resin section (B) containing no reinforcing filler substantially, and its surface layer section except the neighborhood of a weld section is coated with the resin section (A), while the surfaces of a central section and the weld section of the molded body is coated with the resin section (B).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a resin multi-layer structure, and more specifically, it is molded by an injection molding method, the surface layer of the molded body is covered with a resin containing a reinforcing filler, and the central portion is unreinforced. The present invention relates to a resin multilayer structure made of resin.

[0002]

BACKGROUND OF THE INVENTION A variety of resins, whether thermoplastic or thermosetting, are used instead of metallic materials for household products, generally because of their lightness, corrosion resistance, and good workability. Widely used in industrial materials. Although there are various methods of molding and processing these resins, the injection molding method is widely adopted in terms of high production efficiency, that is, low molding cost when mass-produced. The resin used for injection molding is generally blended with a filler suitable for the purpose in order to improve mechanical and thermal performances.

When injection molding is performed using a resin containing a filler, the orientation of the filler varies depending on the flow of the resin. For example, when a rod-shaped filler is used, in the surface layer portion of the molded product, the length direction is mainly oriented so as to match the flow direction of the resin, while the central portion has no directionality. When a scale-like filler is used, the filler is oriented in the surface layer portion so as to be parallel to the surface, and its tendency is alleviated toward the center and has no particular directionality in the center portion. In the case of a molded product obtained by the injection molding method, the mechanical strength of the portion where the resin collides during molding, that is, the weld part, decreases regardless of the presence or absence of the filler, but when the filler is contained, the filler collides. Since it cannot penetrate through the mutually matching resins, it is unavoidable that the mechanical strength of the portion is relatively greatly reduced as compared with the portion other than the weld portion. Also,
Blending a filler with a resin generally improves the elastic modulus, mechanical strength, heat resistance, etc., but reduces the elongation. Unlike rod-shaped or scale-shaped fillers that are oriented in the resin flow direction in the surface layer of the molded product, a resin that contains an amorphous filler such as a fine powder that is isotropic in two dimensions is The molding shrinkage is isotropic and the dimensional stability is excellent, but the reinforcing effect is smaller than that of a resin containing a filler such as a rod-shaped or scale-shaped filler, and the impact strength is lowered. The above-mentioned deterioration in performance is observed in ordinary molded products, but is particularly remarkable in the multilayer structure.

Therefore, an object of the present invention is to provide a resin multi-layer structure in which the mechanical strength is not significantly reduced even in the welded portion.

[0005]

According to the present invention, the above object is to achieve a resin part A containing 5 to 70% by weight of a reinforcing filler.
And a resin part B substantially containing no reinforcing filler, wherein the surface layer part of the molded product except for the vicinity of the weld part is covered with the resin part A, and the surface of the center part and the vicinity of the weld part of the molded product Can be achieved by the resin multilayer structure including the resin portion B.

The present invention will be described in detail below.

The resin multi-layer structure of the present invention is a molded article comprising a resin portion A containing 5 to 70% by weight of a reinforcing filler and a resin portion B containing substantially no reinforcing filler. The surface layer portion of the molded body excluding the vicinity is covered with the resin portion A, and the other portion is the resin portion B.
More specifically, an injection-molded product having a complicated shape in which the occurrence of welds is inevitable, such as a shelf-shaped molded product having crosspieces shown in the examples, can be mentioned.

As the resin used for the resin portion A and the resin portion B of the above resin multilayer structure, either a thermoplastic resin or a thermosetting resin can be used, but from the viewpoint of ease of molding, it is a thermoplastic resin. It is preferably used. Specific examples of the thermoplastic resin include polyolefin such as polyethylene and polypropylene, polyester such as polyethylene terephthalate and polybutylene terephthalate, polystyrene, polycarbonate, ABS resin and the like, and among these, polyolefin, particularly polypropylene is preferably used. The resins of the resin part A and the resin part B may be the same kind or different kinds, but are not particularly limited.
From the viewpoint of improving the adhesiveness between the resin portion A and the resin portion B, the same kind of thermoplastic resin is preferably used.

The reinforcing filler contained in the resin portion A is not particularly limited, but scale-like, fibrous or flake-like inorganic fillers such as mica, talc, glass fibers and glass flakes are preferably used. Among these inorganic fillers, scale inorganic fillers, especially mica are suitable. The content of the reinforcing filler in the resin portion A is 5 to 70% by weight, preferably 20 to 50% by weight. Content ratio is 5
If it is less than wt%, the filling effect is not sufficient, and the rigidity and heat resistance of the resin multilayer structure cannot be sufficiently improved. On the other hand, when the content ratio exceeds 70% by weight, the fluidity of the resin deteriorates, and the molding process by injection molding becomes difficult. The resin portion B does not substantially contain the reinforcing filler. Here, "substantially" means that the reinforcing filler is not contained at all, or even if it is contained, it is contained in a very small amount of 1% or less.

The rigidity, which indicates the degree of deformation when the molded body receives an external force, is mainly determined by the rigidity of the surface layer portion of the molded body, which is more deformed than the central portion of the molded body, and the influence of the central portion where the deformation is small is small. . For the same reason, the heat resistance representing the rigidity of the molded product at high temperature is mainly determined by the heat resistance of the surface layer portion of the molded product. In addition, the strength of the weld portion of the molded body that the resin that flows in from two directions collides during molding depends on the joint strength of the interface of the resin that flows in from two directions, and the joint strength of this weld portion depends on the shape of the filler. Regardless, the case of no filling is the strongest, and it decreases as the compounding amount of the filler increases. The present invention has been made by paying attention to the above points, and in the resin multilayer structure of the present invention, the surface layer portion except the weld portion is covered with the resin containing the reinforcing filler, and the weld portion is reinforced and filled. Since the materials are joined with a resin that is not substantially mixed, the rigidity and heat resistance are high, and the weld strength is high. The thickness of the resin portion A is appropriately selected according to the required strength, but from the viewpoint of moldability, it is 0.
It is preferably 5 mm or more.

An injection molding method is adopted as a method for producing the above resin multilayer structure. In the injection molding method, when different resins are injected into the same cavity, the first resin injected into the mold for the first time begins to solidify the part in contact with the mold when it contacts the mold whose melting temperature is lower than the surface layer. To form a part. Then, the second resin injected into the mold is
First shot in the center, not yet solidified
The second resin forms the central portion while pushing the resin of (1) further away. The first resin that has been pushed away and has not solidified comes into contact with a new mold surface, and forms a surface layer portion at a distant portion. That is, the first resin injected first mainly forms the surface layer portion, and the second resin injected subsequently mainly forms the central portion. In the present invention,
Utilizing this phenomenon, the reinforcing filler-containing resin that forms the resin portion A is first injected, and subsequently, the resin that does not substantially contain the reinforcing filler that forms the resin portion B is injected. The surface layer of the body is covered with a resin containing a reinforcing filler, the center part is made of a resin containing substantially no reinforcing filler, and the weld part is joined with a resin containing substantially no reinforcing filler. A resin multilayer structure is obtained.

The injection molding machine used in the above injection molding method plasticizes two different kinds of resins without being mixed with each other, and after injecting one resin, while the resin in the inflow path is in a molten state, Next, as long as it has a structure capable of injecting another resin, it is not particularly limited, but for example, a two-color injection molding machine having two plasticizing cylinders is used. Further, in order to prevent rapid solidification of the resin in the vicinity of the resin inflow path, a structure may be used in which a heating device is installed in the relevant part of the mold.

[0013]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited thereto.

Example 1 A mica-reinforced polypropylene resin (a mica content of 40% by weight, sometimes referred to as PP / MC hereinafter) corresponding to 45% of the total cavity volume was first injected using a two-color molding injection molding machine. Then, a non-reinforced polypropylene resin containing no reinforcing filler (hereinafter sometimes referred to as PP) was injected to obtain a molded body shown in FIG. The obtained molded body has a structure in which the surface layer portion is made of mica reinforced polypropylene resin and the central portion is made of non-reinforced polypropylene resin, except for the so-called weld vicinity where the resin is finally filled. In the vicinity of the so-called weld portion where the resin in the central portion is finally filled, the resin multilayer structure has a structure in which both the surface layer portion and the central portion are made of non-reinforced polypropylene resin. 2 and 3 show cross-sectional views of the obtained molded body near the crosspiece side a and near the weld b, respectively. Using a universal mechanical strength tester, a wedge having a tip angle of 60 ° shown in FIG. 4 was pushed into the crosspiece center of the molded product, and the expansion rigidity and the expansion breaking load were measured. The load at the time of a stroke in which the distance between the crosspieces was expanded from 12 mm to 15 mm was defined as the expansion rigidity, and the load when the crosspiece was broken was defined as the expanded fracture load. The obtained measurement results are shown in Table 1.

Comparative Example 1 A molded product was obtained in the same manner as in Example 1 except that mica-reinforced polypropylene resin (PP / MC) corresponding to the entire cavity volume was injected in one step. The expanded rigidity and the expanded breaking load of the cross member of the obtained molded product were measured in the same manner as in Example 1, and the results are shown in Table 1.

Comparative Example 2 A molded product was obtained in the same manner as in Example 1 except that the non-reinforced polypropylene resin (PP) corresponding to the total volume of the cavity was injected in one step. The expanded rigidity and the expanded breaking load of the cross member of the obtained molded product were measured in the same manner as in Example 1, and the results are shown in Table 1.

[0017]

[Table 1]

[0018]

As described above, in the resin multilayer structure of the present invention, the surface layer except the weld portion is covered with the resin containing the reinforcing filler, and the weld portion does not substantially contain the reinforcing filler. Since they are joined with resin, they are characterized by high rigidity and heat resistance, and high weld strength.
Such a structure is suitable as one having a complicated shape such as a shelf-shaped molded body having a crosspiece.

[Brief description of drawings]

FIG. 1 is a perspective view of a preferred embodiment of a resin multilayer structure of the present invention.

2 is a cross-sectional view of the cross-section a near the crosspiece in FIG.

FIG. 3 is a cross-sectional view near the weld portion b of the crosspiece in FIG.

FIG. 4 is a diagram showing an outline of a method for measuring expansion strength of a crosspiece.

[Explanation of symbols]

 A: Resin part made of a resin containing a reinforcing filler B: Resin part made of a resin substantially not containing a reinforcing filler C: Crosspiece D: Wedge

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Claims (3)

[Claims] 1. A molded article comprising a resin part (A) containing 5 to 70% by weight of a reinforcing filler and a resin part (B) containing substantially no reinforcing filler, excluding the vicinity of the weld part. The surface layer portion of the molded body is covered with the resin portion (A),
The surface of the molded body in the center and near the weld is the resin (B)
A resin multi-layer structure comprising: 2. The resin multilayer structure according to claim 1, wherein the reinforcing filler is a scale-like inorganic filler. 3. The resin multilayer structure according to claim 1, wherein the resin used in the resin portion (A) and the resin portion (B) is polyolefin.