Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – At least one aryl ring which is part of a fused or bridged...
Reexamination Certificate
2002-03-28
2004-04-13
Sanders, Kriellion A. (Department: 1714)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
At least one aryl ring which is part of a fused or bridged...
C524S439000, C524S492000, C524S493000, C524S494000, C525S439000, C525S444000
Reexamination Certificate
active
06720377
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a color pigment master batch for obtaining a blow-molded article having a grain-tone appearance and a blow molding method using the same. The color pigment master batch of the present invention can produce a clear grain tone without particularly adjusting blow molding conditions by using a specific thermoplastic elastomer and can make it easy to recycle molding burrs generated in producing blow molded articles.
BACKGROUND ART
In recent years, products such as interior household articles having appearances of a grain tone and a marble tone are prevailing, and particularly a lot of products on which films printed with a grain pattern and a marble pattern are stuck are available in the market as such products. These patterns are artificially produced as imitations of natural matters, but they are abstract and have natural feelings, so that they are in a boom as a pattern having a “healing” effect. In addition to products using films printed with these patterns, products having appearances of a grain tone and a marble tone have come to be produced as well by an injection molding method and an extrusion molding method, and in order to obtain products having a thick feeling, it has been started to be investigated to produce them by a blow molding method.
In producing products having appearances of a grain tone and a marble tone, resin pellets which are dry-blended with a pigment master batch having a relatively inferior dispersibility are molten and extruded to produce flow stripes of the pigment by virtue of flowing and drawing effects of the resin in extruding, whereby specific stripe patters are produced. Wooden members in which a grain tone is revealed by adding wooden powder and a foaming agent are produced by a heterogeneous extrusion method, and these wooden members are prevailingly used for housing products. Further, pigments which have been developed for use in such wooden members have come to be used as well in a blow molding method to develop products, but the existing state is that they are not prevailing so much because of a low blow-molding aptitude of the pigments.
Resin-molded articles having appearances of stripe patterns such as a grain tone and a marble tone are produced basically by dry-blending and molding a colored master batch in which dispersion of a pigment for a stripe pattern into a molding base resin is not caused over a fixed level through a plasticizing step and an extruding step of a molding material and using a pigment-dispersed pattern for an appearance design. The appearance of a marble tone is expressed by thick and thin stripes of a pigment for a stripe pattern including an inside of the product, and the appearance of a grain tone is expressed by stripe patterns produced on a surface of the product. In a step of producing a grain pattern by a stripe pattern on a surface of the product, (1) a molding base resin is dry-blended with a pigment master batch for a grain tone and a base color pigment master batch which presents a ground color to be plasticized and extruded; (2) the pigment master batch for a grain tone molten in an extruding step is turned into islands and extruded while gradually pulled to a wall face side of an extruding passage; (3) when reaching the vicinity of the wall face having a large shearing stress, the islands of the molten pigment master batch for a grain tone are stretched to produce continuous long stripes; (4) the pigment appears in the form of stripes on the surface of the molded article extruded; and (5) the pigment for a grain tone short of stretching which remains in the inside in a depth of over a fixed level from the molded article is masked by the pigment of a base color and can not be observed from the outside, and only the stripe patterns on the surface come to be resultingly observed.
The situation is the same also in a blow molding method. In the case of the blow molding method, an extruding speed is slow as compared with those of other molding methods, and an extruding viscosity of a molding material is high. Accordingly, there is the problem that it is difficult to deform the pigment master batch for a grain tone and draw it out to the outside. High melting-point resins of an engineering plastic base such as a polyester base, a polyamide base and an acryl base and partially cross-linked olefin base resins have so far been used as a carrier resin used for a pigment master batch for a grain tone. Those prepared by using the above resins are used as a pigment master batch for a grain tone in a blow molding method as is the case with the other processing methods. However, it is difficult to obtain distinct stripe patterns, and they are used at the sacrifice of the molding conditions in many cases in order to produce the stripe patterns.
However, even if the molding conditions are sacrificed, the pigment resultingly settles down into the inside, so that a stripe feeling is not revealed, or the pigment separates from the carrier resin to be turned into mere blurs. In order to solve this, a master batch containing a mutable carrier resin is used in a certain case, but the carrier resin is dispersed in an extruding step, and stripe patterns are not resultingly obtained. Further, a large problem observed in using these conventional pigment master batches for a grain tone resides in that if molding burrs are mixed in as a recycling material, the ground color of the grain pattern changes and is not stabilized. This is considered attributable to that the pigment remaining in the inside of the carrier resin which has once been molded and molten does not separate from the carrier resin when molten again, so that the grain color is overlapped on the ground color while accumulated whenever recycled. Such inconvenience leads to an increase in a production cost including a material cost and a recycling cost. Further, a reduction in the impact property and the pinch-off strength affected by the carrier resin which is incompatible with the molding base resin is not yet solved, and a totally satisfactory grain-tone article has not been able to be obtained in blow molding, particularly blow molding in which a polyolefin base resin is used as a molding base resin.
DISCLOSURE OF THE INVENTION
An object of the present invention is to provide a color pigment master batch which is suited to blow molding conditions and mechanical characteristics of a blow molding machine in blow molding in which used is a polyolefin resin, particularly polypropylene delayed in development and spread for grain-tone household articles and which has a high recycling property and a process for producing a blow-molded article having a grain-tone appearance using this color pigment master batch.
Intensive researches were repeated by the present inventors from the viewpoints that suited to blow-molding characteristics as a color pigment master batch for obtaining grain patterns are those having the characteristics that (1) stripes having a grain tone are produced without changing the molding conditions to a large extent, that is, the stripes are distinctly revealed on the surface of the article under general molding conditions, (2) molding burrs have a good recycling property, that is, when a recycled material is mixed in, a residual grain color of the recycled material is quickly redispersed, and a change in the color is not caused in every molding and (3) a reduction in the physical properties is not caused, that is, a reduction in the pinch-off strength is less liable to be caused, and the impact performance is not lowered. As a result thereof, they have found that the object described above can be achieved by using as a carrier resin in a color pigment master batch, a thermoplastic elastomer which is a crystalline thermoplastic elastomer having a specific Vicat softening point and a specific crystal melting point and in which an MFR (melt flow rate) ratio to a molding base resin is not less than a specific value or using as a carrier resin in a color pigment master batch for blow molding, a thermoplastic el
Miyaoka Toshihisa
Takimoto Masami
Watanabe Takeshi
Idemitsu Petrochemical Co. Ltd.
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
Sanders Kriellion A.
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