Stock material or miscellaneous articles – Web or sheet containing structurally defined element or... – Including a second component containing structurally defined...
Reexamination Certificate
1997-09-30
2001-08-28
Thibodeau, Paul (Department: 1773)
Stock material or miscellaneous articles
Web or sheet containing structurally defined element or...
Including a second component containing structurally defined...
C428S031000, C428S324000, C264S108000, C264S328120, C264S328180
Reexamination Certificate
active
06280837
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a resin molded article which can prevent formation of a flow mark also known as a flow pattern.
2. Background Information
Previously, painting was used in order to give a resin molded article, such as thermoplastic resin, a uniform and aesthetically pleasing appearance like metallic tone and pearl tone having a deep feeling.
However, such painting required cumbersome and complicated steps, such as degreasing and washing; prime-coating, intercoating and overcoating; and dust removing, drying and stoving of the surface of the molded article. Further, painting required facilities and paints, and the steps required a longer cycle time. Thus, painting was mainly responsible for higher costs.
To avoid such problems, molding has been carried out using a thermoplastic resin composition. In this thermoplastic resin composition, a metallic piece, glitter material and a colorant are directly mixed into a synthetic resin. The metallic piece, such as scaly-aluminum powders, acts as an agent which imparts metallic or pearl tone. An example of the glitter material is pearlescent pigment made of mica. A molded article using such a thermoplastic resin composition is referred to as a resin molded article.
As shown in
FIG. 2
however, at the molding of the resin molded article
9
, a flow mark
8
can occur in some cases at a downstream side of the resin flow, where the downstream side is near a molded article end
92
remote from a gate position
91
at molding. Such a flow mark
8
occurs along with the resin flow in a shape substantially similar to the letter “U”, as shown in
FIGS. 2 and 3
.
Since the flow mark
8
deteriorates the decorative effect of the molded article, the present inventors have studied extensively to prevent the formation of such a flow mark. The present inventors have found that the flow mark is primarily composed of relatively dark portions and relatively light portions, alternating from one to another at a remote location from the gate position, as shown in FIG.
3
. The present inventors have further discovered that the flow mark generally is not easily formed in a case where the color of the molded article is concentrated, whereas the flow mark is easily formed where the color of the molded article is pale color or colorless. Moreover, as the amount of the glitter material added increases, the likelihood of the flow mark formation increases also, as conceptionally illustrated in FIG.
4
.
The present inventor's study of the mechanism of the formation of the flow mark has revealed that the flowing state at the front portion of the flow becomes unstable due to the fact that the rate of the resin flow is reduced at the downstream side in a cavity near an end of the molded article in the flow direction N, as shown in FIG.
5
(A). For this reason, flow distortion
81
occurs causing the breakage
82
at the front portion of the flow. The “dark portion” is formed in the breakage portion
82
where adhesion to the cavity surface is lowered which generates a concave and convex portion on the surface.
As shown in FIG.
5
(B), on the surface of the molded article having the flow mark, multiple linear grooves
72
can be observed at the dark portion. On the other hand, at the light portion, such linear groove
72
is not formed. Glitter material
71
is in the interior of the molded article. Also shown in FIG.
5
(B) are the flow distortion and breakage at the front portion of the flow, which are formed at the downstream side in the resin flow direction N.
Subsequently, the present inventors have studied adjustment of injection pressure for a thermoplastic resin composition, adjustment of a rate of the resin flow, and other factors in order to prevent the flow mark from occurring. However, the molding conditions were difficult, and thus obtained no sufficient results.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a resin molded article having a uniform glitter feel, which can prevent formation of a flow mark.
The invention provides a resin molded article obtainable by molding using a thermoplastic resin composition in which glitter material is mixed into a synthetic resin. The resin molded article has a molding ratio L/T of not less than 100, wherein T is the thickness of the molded article and L is the distance from a gate position at molding to the remotest position on the molded article. The glitter material has an average particle size d of about 10 &mgr;m<d≦200 &mgr;m.
According to the present invention, in a resin molded article having the molding ratio L/T of not less than 100, the average particle size d of the glitter material to be added to a synthetic resin, is greater than 10 &mgr;m and not less than equal to 200 &mgr;m. For this reason, the glitter does not cause deviation in a molded article at molding, and the distortion and breakage of flow at the front portion of the flow are prevented. Therefore, the flow mark is not formed, thereby giving a uniform glittering feel.
The present invention's objects, features and advantages are elucidated by the following detailed description and drawings.
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Isomichi Mitsuhiro
Ito Katsushi
Kobayashi Masato
Koizumi Junji
Mitzutani Haruyasu
Pillsbury & Winthrop LLP
Thibodeau Paul
Toyoda Gosei Co,., Ltd.
Zacharia Ramsey
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