JPH07124997A - Outsert molded article - Google Patents

Abstract

PURPOSE:To prevent cracks and breakages from occurring on a molded resin- made functional part or a runner part connecting it even in a high temp. or low temp. atmosphere by performing, outsert molding of a functional part on a base sheet with a cut or a perforated hole by using a polyacetal copolymer resin with a crystallization time of at least a specified time. CONSTITUTION:As a resin used for outsert molding, a polyacetal copolymer resin with a crystallization time of at least 5min. is used. This copolymer resin is pref. a polymer wherein 3-30wt.% oxyalkylene unit with the carbon number of at least 2 are incorporated in a polymer wherein oxymethylene unit is a main constitutional unit and the melt index is pref. 1.0-60g/10min.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an outsert molded product, and more particularly to an outsert molded product suitable for use in applications requiring precision and excellent dimensional stability.

[0002]

2. Description of the Related Art Various chassis such as tape recorders and video tape recorder (VTR) chassis, switch boards, and the like have a large degree of freedom in designing, post-processing can be reduced, and weight can be reduced. Outsert moldings in which a hard substrate made of metal or the like and a thermoplastic resin are integrated are widely used because of their advantages such as low cost. As these thermoplastic resins for outsert molding, various resins such as polyolefin resins such as polyethylene and polypropylene as well as engineering plastics such as polyester resins, polyacetal resins, polyamide resins and polycarbonate resins are used. The engineering plastics mentioned above are used for applications that require particularly high precision and dimensional stability. Especially for chassis such as tape recorders and VTRs, polyacetal resin with excellent rigidity, creep properties and sliding properties is widely used. It is used.

[0003]

However, although the polyacetal resin has excellent mechanical properties such as creep properties, electrical properties, and sliding properties, it has a large shrinkage at the time of molding, and it is hard to cure with metal or heat. There is a problem in that the airtightness and adhesion to a hard substrate made of a flexible resin deteriorates. Also,
If the molded product is placed in a high temperature atmosphere, the airtightness and adhesion will deteriorate due to the post-shrinkage of the polyacetal resin, cracks will occur in the resin functional parts and the runners connecting the resin functional parts, and There is a problem that the functional part is also cracked. As a method of preventing cracking of the runner part, a method of providing an S-shaped part on the runner part and adding a mechanism for absorbing and dispersing stress is used, but there is a problem in designing the molded product. There is.

[0004]

DISCLOSURE OF THE INVENTION The inventors of the present invention have solved the problems of the prior art, improved the airtightness and adhesion between the hard substrate and the resin parts, and placed them in a high temperature or low temperature atmosphere. Also in the case, as a result of diligent study to prevent the occurrence of cracks and cracks in resin parts and resin runners and to provide good outsert molded products, it is extremely effective to use a specific polyacetal copolymer resin. Therefore, the present invention has been completed.

That is, the present invention is an outsert molded article in which a functional portion of a polyacetal copolymer resin having a crystallization time of 5 minutes or more is formed on a hard substrate having at least one notch or hole by an outsert molding method. is there.

The crystallization time referred to in the present invention means that the polyacetal resin is held at 200 ° C. for 5 minutes by using a differential scanning calorimeter (hereinafter referred to as DSC), and then the temperature is lowered to 152 ° C. at 10 ° C./minute. It means the time from the start of holding when kept at ℃ to the exothermic peak due to crystallization, and the shorter the time, the faster the crystallization rate.

In the present invention, the polyacetal copolymer resin having the crystallization time of 5 minutes or more is selectively used.
In order to obtain an excellent outsert molded product, the crystallization time of the resin material used is important. If the crystallization time is shorter than 5 minutes, the shrinkage during molding and the post-shrinkage when the molded product is heated are large. Therefore, the intended effect of the present invention cannot be obtained. On the contrary, if the crystallization time is too long, not only the solidification time of the injected resin becomes long and the productivity is lowered, but also the mechanical strength of the obtained molded article is lowered, which is not preferable and practically 5 A range of up to 200 minutes is preferred.

The polyacetal resin of the present invention means a copolymer containing a oxymethylene unit (-OCH _2- ) as a main constituent unit and a copolymer or terpolymer obtained by copolymerizing the following cyclic ether or cyclic formal. It is united. Further, the skeleton of the polymer is not particularly limited, and there is no problem even if it has not only a linear structure but also a branched structure or a crosslinked structure.

The melt index (hereinafter referred to as MI) of the polyacetal resin is not particularly limited, but is preferably 1.0 to 60 g / 10 minutes from the viewpoint of moldability. When the MI is less than 1.0, the resin does not flow well during injection molding, and it becomes difficult to obtain a molded product having a desired shape.
On the other hand, if the MI is too large, the molded product becomes brittle, which is not preferable. The melt index referred to in the present invention is AST.
According to MD-1238, the value measured at a temperature of 190 ° C. and a load of 2160 g is expressed in units of g / 10 minutes.

The comonomer component used for producing the polyacetal copolymer is not particularly limited, but it is generally preferable to be at least one selected from those having a structure of the following general formula.

[0011]

[Chemical 1]

(Wherein R ₁ , R ₂ , R ₃ and R ₄ are the same or different substituents, and are a hydrogen atom, an alkyl group (having 1 to 5 carbons and 0 to 3 hydrogens being halogens). Atom-substituted, the same shall apply hereinafter) or a halogen-substituted alkyl group, and R ₅ represents a methylene group, an oxymethylene group, a methylene group or an oxymethylene group substituted by an alkyl group or an alkyl halide, respectively. Group (in this case p =
Integer of 0 to _{3), - (CH 2) q} -OCH 2 - (q = 1~4 integer)
Or - a divalent group represented by (q = 1 to 4 integer) (in this case p = 1) - (O- CH 2 -CH 2) q -OCH 2. ) Further, in order to obtain a copolymer having a crystallization time of 5 minutes or more as described above, 3 oxyalkylene units having 2 or more carbon atoms are added to a polymer having an oxymethylene unit as a main constituent unit.
To 30 mol%, preferably 3 to 15 mol%, in particular, the monomer component constituting the oxyalkylene unit having 2 or more carbon atoms is 1,3-dioxolane, diethylene glycol formal, 1,3-propanediol formal, 1,4 It is desirable to use at least one of butanediol formal, 1,5-pentanediol formal, and 1,6-hexanediol formal.

The present invention is based on conventionally known additives such as various stabilizers including antioxidants, nucleating agents, pigments, antistatic agents, light stabilizers and reinforcing materials such as
Glass fiber, glass flakes, talc, mica,
Potassium titanate whiskers can be added and blended. In addition, polymer blends with polyurethane resins, acrylic resins, polyolefin resins, etc., and polymer alloys are also possible.

[0014]

[Function] The polyacetal copolymer resin having a crystallization time of 5 minutes or more has not only excellent mechanical strength, heat resistance and slidability, but also small shrinkage during molding and shrinkage due to post-heating and excellent dimensional stability. Since it exhibits excellent properties, it becomes an optimal resin material for outsert molding of chassis that requires particularly precise and dimensional stability, and airtightness between metal parts or thermosetting resin parts and polyacetal copolymer resin parts In addition, it is possible to obtain an excellent outsert molded product which is excellent in adhesion and has few cracks and cracks over a long period of time.

[0015]

EXAMPLES The present invention will now be described in detail with reference to Examples, but it goes without saying that the present invention is not limited to these.

Example 1 As a copolymer component, a polyacetal copolymer resin containing 3% by weight of an oxyalkylene unit composed of 1,3-dioxolane was used to mold a molded product shown in FIG. 1 with an injection molding machine. The molded product obtained is at a temperature of 23 ° C and a relative humidity of 50.
After being left for 24 hours in a room adjusted to 100%, the degree of sticking (degree of rattling) between the outsert metal member and the resin boss portion and the presence or absence of cracks or breaks in the resin portion were examined.
Further, after performing a heat shock test on this molded product, the degree of fixation (the degree of rattling) between the metal part and the resin boss portion and the presence or absence of cracks or cracks in the resin portion were examined. The results are shown in Table 1.

The heat shock test is a test in which a molded product is heated at 120 ° C. for 1 hour and then immediately transferred to an atmosphere of −40 ° C. and cooled for 1 hour. The cycle was tested.

Example 2 A polymer having 5% by weight of oxyethylene units was prepared in the same manner as in Example 1 except that the mixing ratio of trioxane and 1,3-dioxolane was changed. The same test as in Example 1 was carried out also when this polymer was used. The results are shown in Table 1.

Example 3 A polymer having an oxybutylene unit of 4% by weight was prepared in the same manner as in Example 1 except that 1,3-dioxolane was changed to 1,4-butanediol formal. The same test as in Example 1 was carried out also when this polymer was used. The results are shown in Table 1.

Comparative Example 1 A polymer having 2.5% by weight of oxyethylene units was obtained by the same procedure as in Example 1 except that trioxane and ethylene oxide were mixed at a constant mixing ratio. The same test as in Example 1 was carried out also when this polymer was used. The results are shown in Table 1.

The degree of adhesion between the outsert part (metal part) and the resin part was evaluated according to the following criteria.

○: There is almost no gap between the metal part and the resin part, and there is no rattling of the resin part. ×: There is a gap between the metal substrate and the resin part, and there is rattling of the resin part. The presence or absence of warpage, deformation, cracks and cracks of the resin part was evaluated according to the following criteria.

○: No warpage, deformation, cracks, or cracks in resin parts ×: Significant warpage, deformation, or cracks, cracks in resin parts

[0024]

[Table 1]

[0025]

The polyacetal resin of the present invention not only has excellent mechanical strength, heat resistance, and slidability, but also exhibits excellent dimensional stability with little shrinkage during molding and shrinkage due to post-heating. It is used for parts such as outsert molding parts that require precision and dimensional stability. Further, by using this polyacetal resin, it is possible to obtain an outsert molded product which is excellent in fixing the outsert component and the resin component, has no rattling of the resin component, and has very few cracks or cracks of the resin component.

[Brief description of drawings]

FIG. 1 is a schematic view of an outsert molded product manufactured in an example.

[Explanation of symbols]

 1 Hard substrate (metal part) 2 Polyacetal copolymer resin 3 Runner part

Claims (4)

[Claims] 1. An outsert molded article obtained by forming a functional part of a polyacetal copolymer resin having a crystallization time of 5 minutes or more by an outsert molding method on a substrate having at least one notch or hole. 2. A polyacetal copolymer resin having a crystallization time of 5 minutes or more containing 3 to 30% by weight of an oxyalkylene unit having 2 or more carbon atoms in a polymer having an oxymethylene unit as a main constituent unit. The outsert molded article according to claim 1. 3. The monomer component constituting the oxyalkylene unit having 2 or more carbon atoms is ethylene oxide, 1,3
-Dioxolane, diethylene glycol formal, 1,
3-propanediol formal, 1,4-butanediol formal, 1,5-pentanediol formal and
The outsert molded article according to claim 2, which is any one or more of 1,6-hexanediol formal. 4. The outsert molded article according to claim 1, wherein the polyacetal copolymer resin has a melt index of 1.0 to 60 g / 10 minutes.