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
2001-06-15
2003-05-20
Wu, David W. (Department: 1713)
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...
C524S378000, C524S366000, C524S385000, C524S391000, C524S570000, C524S585000, C523S333000, C523S334000, C523S339000
Reexamination Certificate
active
06566432
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a coloring resin composition. More specifically, the present invention relates to a coloring resin composition for use in coloring molded articles of thermoplastic resin, and a colored resin molded article obtained by using the coloring resin composition.
2. Description of the Related Art
Conventional coloring resin compositions for use in coloring molded articles of thermoplastic resin or manufacturing colored resin molded articles, include powdered dry color in which pigment and a dispersing agent are mixed; liquid color or paste color in which pigment is dispersed in a dispersing agent that is in liquid state at room temperature; and pellet-, flake- or bead-shape coloring pellets (also termed coloring compound) or master batches in which pigment is dispersed in resin that is in solid state at room temperature. The master batches are the same as the coloring pellets in that pigment is dispersed in resin that is solid at room temperature. However, the coloring pellets are different from the master batch in that the coloring pellets are molded as they are while the master batches are diluted first with appropriate thermoplastic resin (resin for dilution or resin to be colored) before being molded, since the pigment concentration is high.
The coloring resin compositions are selected for application on the basis of their characteristics. Among them, master batches are preferably used due to ease of handling and in consideration of the working environment during the application. Master batches are high in pigment concentration and have little effect on various properties such as heat resistance and strength of thermoplastic resin to be colored. Additionally, pigment dispersibility is required to be higher than previously, as polyolefin resin has been molded with improved precision and accelerated speed.
Generally, the following dispersing agents are used in order to add pigment dispersibility in a master batch. The agents include stearic acid; metallic soap such as zinc stearate, magnesium stearate, aluminum stearate and calcium stearate; ethylene bisamide; hydrocarbon wax such as polyethylene wax and polypropylene wax; and derivatives thereof such as wax consisting of an acid modified product or a hydroxyl group modified product.
However, when high pigment dispersibility is required in order to mold articles by high-speed spinning at a diameter of 10 and several microns, or by forming into films, the above-noted dispersing agents have not provided sufficient dispersibility.
In Japanese Unexamined Patent Application Publication No. 7-53772, a compound expressed by the following chemical formula is used as a dispersing agent of a coloring resin composition:
(CH
3
—(CH
2
)
x
—CH
2
—O(CH
2
CH
2
O)
n
H
wherein x is 28 to 48 on average, and n is 1 to 16.
This dispersing agent provides more preferable results than does a conventional agent. However, such problems due to lack of pigment dispersion are still found as thread breakage during spinning, clogging filters of melt spinning apparatus, and the development of lumps on a film surface. Moreover, although the composition may be spun at high speed or formed into a film, a molded article thereof is not often practically strong enough when higher mechanical physical strength is required for the molded article.
In order to solve the above-noted problems and enhance pigment dispersibility, attempts to improve the processing methods of master batches, to use a high-powered kneading machine, and so forth have been made. However, sufficient pigment dispersibility has not yet been achieved therefrom.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to provide a coloring resin composition having excellent pigment dispersibility and high coloring properties. The coloring resin composition can be used as a master batch without giving physical inhibitions of 5% or higher to each mechanical strength of resin to be colored, such as tensile strength, flexural modulus and impact strength. It is another object of the present invention to provide a colored resin molded article by using the coloring resin composition.
In order to achieve the above-noted objects, a coloring resin composition according to a first aspect of the invention includes a dispersing agent, a pigment and a thermoplastic resin. The following Formula 1 expresses the dispersing agent, and the thermoplastic resin is a metallocene polyolefin:
C
n
H
2n+1
(OCH
2
CH
2
)
m
OH Formula 1
wherein n is an integer of 1 to 100, and m is an integer of 1 to 100.
A coloring resin composition according to a second aspect of the invention is provided by removing water from a mixture of a dispersing agent expressed by the same Formula 1 as above, a pigment, water and a metallocene polyolefin.
Subsequently, the coloring resin composition of the present invention is used to provide a colored resin molded article according to the present invention. The coloring resin composition of the present invention has excellent pigment dispersibility and good coloring properties, so that colored resin molded products having excellent mechanical strength and high coloring properties can be manufactured therefrom.
The coloring resin composition according to the present invention can be used as a master batch or coloring pellets not only for colored resin molded articles but also for others such as ink, coating paint and adhesive.
DESCRIPTION OF THE PREFERRED EMBODIMENT
The embodiments of the present invention will be explained in detail below.
The metallocene polyolefin is a general term of polyolefin in which metallocene is used as a catalyst for polymerization. This polymer is a high molecular weight polymer having higher monodispersibility and a narrower molecular weight distribution (for instance, Mw/Mn<2 in case of metallocene polyethylene) than a polymer in which conventional Ziegler catalyst, Ziegler-Natta catalyst or the like is used. The polymer obtained thereby has low crystallinity and is nearly amorphous. The density and melting point thereof are significantly lower than those of general polyolefin consisting of the same monomer that is polymerized by a non-metallocene catalyst.
Such polymer and the dispersing agent of the above-noted Formula 1 are used for the coloring resin composition, so that a large amount of pigment can be dispersed quite evenly. Accordingly, the composition can provide molded articles having excellent mechanical strength without such problems as breakage of films due to lack of pigment dispersibility, and is also suitable for spinning and forming into films. Moreover, since pigment dispersibility is preferable, the coloring resin composition also has excellent coloring properties.
According to the knowledge of the present inventors, the water with which the pigment particles are wetted evaporates during a melting and kneading process when a mixture of a dispersing agent, pigment and resin contains water, and the surface of the pigment particles which are refined by shearing during kneading is coated with molten thermoplastic resin, thus preventing the re-agglomeration of pigment particles and providing a resin composition having excellent pigment dispersibility. The present inventors also found that the dispersibility of pigment improves by carrying out the flushing of pigment from the aqueous phase to a resin phase slowly at the temperatures near the boiling point of water. The use of metallocene polyolefin having a lower melting point than general polyolefin has also the advantage of carrying out such flushing easily and effectively.
The dispersing agent used in the coloring resin composition of the present invention containing a dispersing agent, a pigment and a thermoplastic resin is expressed in the following Formula 1:
C
n
H
2n+1
(OCH
2
CH
2
)
m
OH Formula 1
wherein n is an integer of 1 to 100, and m is an integer of 1 to 100.
When n exceeds 100 in the formula above, pigment dispersibility may decline. At the same time,
Kawamura Masayasu
Koide Masashi
Lee Rip A.
Toyo Ink Mfg. Co. Ltd.
Wu David W.
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