JPH11320605A - Composite molded product and manufacture thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To readily obtain high interfacial bonding strength, high rigidity, good slidability, chemical resistance, fatigue resistance or the like by avoiding a skin layer on a surface of a primary molding in the contact surface of the primary and secondary moldings. SOLUTION: A crystalline resin material A is pre-molded to form a primary molding, to which a thermoplastic resin material B is secondarily injection- molded and fused therewith, so as to integrate both of them. The joining surface of the primary-side resin material is subjected to a flame treatment or a hot air treatment, and a portion or all of the surface layer of the joining surface is melt-treated, e.g. by being re-melted, gradually cooled and solidified, thereby substantially avoiding the skin layer of the surface. The flame treatment or hot air treatment is readily applied to only the joining surface of the primary molding, e.g. by applying the hot air at a high temperature to a cavity after the primary molding is provided in the secondary mold which is then closed. The molding method is most preferably an injection molding.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a composite molded product having a high rigidity portion and a flexible portion and a method of manufacturing the same. An object of the present invention is to provide a composite molded product suitable for various equipment parts that require a rigid part and a flexible part.

[0002]

2. Description of the Related Art A crystalline resin, especially a polyacetal resin, is a typical engineering plastic because of its excellent mechanical strength, chemical resistance, slidability, etc., and its relatively low cost. Although used for a wide range of applications such as automobiles and electric / electronic parts, in recent years, automobiles and electric / electronic parts have been required to have various characteristics. However, such a polyacetal resin generally has high rigidity, and it is possible to impart flexibility by modifying the polyacetal resin, but in any case, a part of the molded article requires high rigidity as it is, and the other part requires high rigidity. It is not possible to obtain an integrally molded product that requires flexibility.
As one of the characteristics imparting methods, a composite molded part combining different materials has been developed. Generally, as a method of integrally molding two kinds of materials, partially different characteristics are obtained by a dual molding method in which a dissimilar resin is secondarily molded on a primary molded article of the resin and the interface is fused and fixed. Although it is known to obtain a composite molded product having a polyacetal resin having high crystallinity as a primary molded product, fusion at the interface between the primary resin and the secondary resin is not known. Sufficiently, it is easily peeled off by external force, and often does not satisfy the function as an integrally molded product in use. In order to supplement the fusion strength at the interface between the two resins, the primary molded product must be provided with a mechanical structure such as an undercut or through hole to provide a mechanical anchor effect, or an adhesive must be applied to the primary molded product. As can be seen, the shape becomes complicated and the process becomes complicated, which is economically disadvantageous, and is also undesirable in terms of production efficiency. In particular, since polyacetal resin has high crystallinity, the composite molded product is not provided with a mechanical structure having a mechanical anchor effect in the bonding strength between different materials,
It was very difficult to obtain high bonding strength only by the fusion strength at the interface.

[0003]

Means for Solving the Problems The present inventor has developed a high rigidity, good sliding property, chemical resistance, fatigue resistance and low cost properties of a resin material (A) mainly composed of a crystalline resin. Plastic resin
When (B) is a thermoplastic elastomer, a composite molded product that combines flexibility, soft touch feeling, and transparency, especially a mechanical structure with a mechanical anchor effect such as providing an undercut or through hole in the primary molded product Without applying a process such as applying an adhesive to the primary molded product,
As a result of intensive studies to economically and efficiently obtain a composite molded product having a high fusion strength at the joint, the present invention has been achieved. That is,
The present invention is a composite molded article obtained by integrally molding a thermoplastic resin (B) into a primary molded article made of a crystalline resin (A), and a contact surface between the primary molded article and the secondary molded article. A composite molded article characterized in that substantially no skin layer is observed on the surface of the primary molded article, and a method for producing the composite molded article.

[0004]

BEST MODE FOR CARRYING OUT THE INVENTION The constituent materials of the composite molded article of the present invention and the method for producing the same will be described in detail below. In producing the composite molded article of the present invention by the multiple molding method, a molded article made of the crystalline resin (A) is used as a primary molded article. Such a primary molded product can be easily obtained by molding by a known molding means, generally using a non-reinforced type of a crystalline resin. Further, an elastomer-filled type based on such a crystalline resin can also be used as the primary molded article in the present invention. The resin used as the crystalline resin material (A) that can be used for forming the primary molded article has a relatively low melting point, excellent thermal stability, and preferably a copolymer type having a low crystallinity. Examples of the resin material (A) include polypropylene, polyethylene, polyacetal, polyamide, polybutylene terephthalate, polyethylene terephthalate, and copolymers containing these as main components.

Next, in order to obtain the composite molded article of the present invention, the thermoplastic resin (B) which is secondarily injection-molded with respect to the primary molded article is not particularly limited, but a thermoplastic elastomer is preferred. Used. Among them, polyurethane-based, polyester-based, and polyamide-based thermoplastic elastomers are particularly preferable. The hardness of the thermoplastic elastomer is preferably 90 A or less in A hardness of JIS.

Also, a resin material constituting the molded article of the present invention
(A) and (B) may contain an inorganic filler. Such a filler is preferably blended in order to obtain excellent properties such as mechanical strength, heat resistance, dimensional stability, and electrical properties, and is particularly effective for increasing rigidity. For this purpose, a fibrous, powdery or plate-like filler is used depending on the purpose. Examples of the fibrous filler include glass fiber, asbestos fiber, carbon fiber, silica fiber, silica / alumina fiber, zirconia fiber, boron nitride fiber, silicon nitride fiber, boron fiber, potassium titanate fiber, stainless steel, aluminum, titanium, Inorganic fibrous substances such as fibrous materials of metals such as copper and brass can be used. Particularly typical fibrous fillers are glass fibers. In addition, a high melting point organic fibrous substance such as polyamide, fluororesin, and acrylic resin can also be used. On the other hand, as the particulate filler, carbon black, graphite, silica, quartz powder, glass beads,
Glass balloon, glass powder, calcium silicate, aluminum silicate, kaolin, talc, clay, diatomaceous earth, silicates such as wollastonite, oxides of metals such as iron oxide, titanium oxide, alumina, calcium carbonate, Examples thereof include metal carbonates such as magnesium carbonate, metal sulfates such as calcium sulfate and barium sulfate, and other metal powders such as silicon carbide, silicon nitride, boron nitride. Examples of the plate-like filler include mica, glass flake, various metal foils, and the like. These inorganic fillers can be used alone or in combination of two or more. The combined use of a fibrous filler, especially a glass fiber or a carbon fiber, and a granular or plate-like filler is a preferable combination, particularly in terms of having both mechanical strength, dimensional accuracy, electrical properties and the like. The amount of inorganic filler added is resin material
(A) and (B) are each 40% by weight or less based on the total amount. If it is more than this, the moldability and toughness are impaired, which is not preferable. Particularly preferably, it is at most 30% by weight.

The resin material (A) used in the present invention
And (B) is a known substance other than the above, which is generally added to a thermoplastic resin within a range that does not affect the fusing property of both or one or both of them to impart desired properties according to the purpose. That is, various stabilizers such as antioxidants and ultraviolet absorbers, antistatic agents, flame retardants, flame retardant aids, coloring agents such as dyes and pigments, lubricants, plasticizers and crystallization accelerators, and crystal nucleating agents , A release agent, a surfactant, an antistatic agent and the like can be of course blended in any combination.

The composite molded article of the present invention is molded by a so-called multiple molding method using at least two types of resin materials (A) and (B). As a molding method, injection molding, compression molding and other molding methods are applied, but injection molding is generally preferred.

In the present invention, the crystalline resin material (A) is molded in advance to form a primary molded article, and then the thermoplastic resin material (B) is secondarily injection molded, fused and integrated. A flame (flame) treatment or a hot air treatment is performed on the joint surface of the primary resin material, and the surface of the surface is formed by a melting process such as re-melting gradually cooling and solidifying a part or the entire surface layer of the joint surface. A composite molded article having a high fusion strength can be obtained only when the layer is not substantially recognized.

Here, the skin layer is a layered region seen near the surface of the crystalline resin molded product. The skin layer
It can be confirmed by making a thin sample in a vertical direction from the surface with a microtome or the like and observing this with a polarizing microscope. In FIG. 4, which will be described later, there is a layered region in which spherulites are difficult to distinguish from the surface toward the center, and this region is a skin layer. Further, the melting treatment is a treatment in which the surface of the crystalline resin molded article is heated to partially melt or soften the resin so that the skin layer is not observed when the resin is solidified. After the resin is partially melted, the secondary molding may be performed immediately, or after the resin is solidified, the secondary molding may be performed. In short, it is necessary that the skin layer is not substantially recognized on the surface of the primary molded product in the secondary molded product.

The flame (flame) treatment or the hot air treatment of the primary molded product of the composite molded product of the present invention is performed, for example, by mounting the primary molded product on a secondary molding die, closing the die, and then applying high-temperature hot air to the cavity. For example, only the joining surface of the primary molded product can be easily performed by feeding the product into the inside.

When the secondary resin is injection-molded, the surface of the heat-treated primary molded product may be in a molten state, kept at a high temperature, or cooled and solidified.

[0013]

EXAMPLES Examples of the present invention will be described below, but the present invention is not limited to these examples. Example 1, Comparative Examples 1 to 3 Using the following resin materials (A) and (B), a primary molded product was subjected to the treatment shown in Table 3, and then subjected to secondary molding to produce a composite molded product. The adhesion strength was evaluated.
The results are shown in Table 3. Resin material (A) POM: polyacetal resin (manufactured by Polyplastics Co., Ltd., Duracon M90) Resin material (B) PUR: thermoplastic polyurethane resin (adipate, hardness JIS A80) Adhesion strength was evaluated as follows. [Adhesion strength evaluation method] A 1/8 inch thick combustion test piece was molded as a primary molded product. Next, after mounting this molded piece in the mold cavity of the 1/4 inch combustion test piece, secondary molding was performed using the resin shown as the secondary resin material as a secondary material,
As shown in FIG. 1 (a), a composite molded article having two layers was obtained.
The adhesion strength (tensile strength, tensile elongation) of the composite molded product is
Evaluation was made by measuring the 90 ° peel strength (FIG. 1 (b)) using a tensile tester. Table 1 shows the test results. <Molding conditions> Molding machine: Nikko J75 SS II-A Primary molding conditions

[0014]

[Table 1]

Secondary molding conditions

[0016]

[Table 2]

[0017]

[Table 3]

Examples 2 and 3, Comparative Examples 4 and 5 Using the resin materials (A) and (B), a primary molded product was subjected to the treatment shown in Table 6 and then subjected to secondary molding to form a composite molded product. Was prepared, and its adhesion strength was evaluated. The results are shown in Table 6. [Adhesion strength evaluation method] A 1/8 inch thick combustion test piece was molded as a primary molded product. Next, this molded piece is cut in half from the center, and again 1/8 so that the flow end surface becomes the joining surface.
After mounting in the mold cavity of the inch combustion test specimen, secondary molding is performed using the resin shown as the secondary resin material as a secondary material, and a composite molded product having a joint at the center shown in FIG. 2 is obtained. Was. The adhesion strength (tensile strength, tensile elongation) of the composite molded product was measured using a tensile tester. The tensile test was performed at a speed of 20 mm / min. <Molding conditions> Molding machine: FANUC AUTOSHOT MODEL
50B Primary molding conditions

[0019]

[Table 4]

[0020] Secondary molding conditions

[0021]

[Table 5]

[0022]

[Table 6]

FIG. 3 is a photograph showing a structure observation result of a cross section of the primary molded article by a polarizing microscope after the test of Example 3.
As shown. Compared to the photograph of FIG. 4 in the case of no treatment (Comparative Example 4), it can be confirmed that the skin layer disappeared and a fine crystal layer was formed up to the surface.

[0024]

According to the present invention, the surface layer of the joint portion of the primary molded article is once melted and then gradually cooled to make a state in which the skin layer is not substantially recognized, so that the normal molding temperature condition can be obtained. It is possible to easily and economically efficiently produce a composite molded product having a strong interfacial adhesion strength, which cannot be obtained by the conventional double molding method, without providing an anchor shape or using an adhesive. Moreover, the composite molded product of the present invention has the high rigidity, good sliding property, chemical resistance, and fatigue resistance of the crystalline resin and the flexibility, soft touch feeling, and transparency of the thermoplastic elastomer. It is suitable for many uses in the automotive field and electric / electronic field where such properties are required as a molded article.

[Brief description of the drawings]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a view showing a molded article for measuring adhesion strength used in Example 1, and (a) a composite molded article in the form of a combustion test piece having a joint at the center where a primary molded article and a secondary molded article are joined. Perspective view of the
(b) is a diagram illustrating a test situation of 90 ° peel strength.

FIG. 2 is a view showing a molded product for measuring adhesion strength used in Examples 2 to 3, which is a combustion test piece type composite molded product having a joint at the center where a primary molded product and a secondary molded product are joined. is there.

FIG. 3 is a photograph showing a structure observation result by a polarizing microscope of a cross section of a joined part of a primary molded article after a test of Example 3.

FIG. 4 is a photograph showing a structure observation result by a polarizing microscope of a cross section of a joined part of a primary molded article after a test of Comparative Example 4.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Primary molded article 2 Secondary molded article 3 Joint 4 Gate

Claims (11)

[Claims] 1. A composite molded article obtained by secondary molding of a thermoplastic resin (B) on a primary molded article of a crystalline resin (A) and integrally molding the same, wherein contact between the primary molded article and the secondary molded article is carried out. A composite molded article characterized in that substantially no skin layer is observed on the surface of the primary molded article. 2. The composite molded article according to claim 1, wherein the crystalline resin (A) is a polyacetal resin. 3. The composite molded article according to claim 1, wherein the thermoplastic resin (B) is a thermoplastic elastomer. 4. The composite molded article according to claim 1, wherein the thermoplastic resin (B) is a thermoplastic polyurethane. 5. A thermoplastic resin obtained by subjecting a whole or part of the surface of a primary molded article made of a crystalline resin (A) to a melting treatment.
A method for producing a composite molded article integrally molded by a double molding or a two-color molding method, wherein (B) is subjected to secondary molding. 6. The method for producing a composite molded article according to claim 5, wherein the secondary molding is performed while the joining surface of the primary molded article is in a molten state or a high temperature state. 7. The method for producing a composite molded product according to claim 5, wherein the melting treatment is a flame (flame) treatment. 8. The composite molded product according to claim 5, wherein the melting process is performed by mounting the primary molded product on the secondary molding die, closing the die, and then sending high-temperature hot air into the cavity. Manufacturing method. 9. The method for producing a composite molded article according to claim 5, wherein the crystalline resin (A) is a polyacetal resin. 10. The method for producing a composite molded article according to claim 5, wherein the thermoplastic resin (B) is a thermoplastic elastomer. 11. The method for producing a composite molded article according to claim 5, wherein the thermoplastic resin (B) is a thermoplastic polyurethane.