Chemistry of inorganic compounds – Oxygen or compound thereof – Metal containing
Patent
1998-08-26
2000-10-03
Cain, Edward J.
Chemistry of inorganic compounds
Oxygen or compound thereof
Metal containing
523210, 523212, 523216, 524497, C01G 2502, C08K 910, C08K 322
Patent
active
061269158
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to titanium dioxide powder which has a low volatile moisture content and hence is free of the possibility that the quality is deteriorated due to generation of foams upon kneading processing into synthetic resin articles and the like, and to a method for manufacturing the same. Further, the present invention relates to a masterbatch which contains the titanium dioxide powder in a thermoplastic resin. The masterbatch is used when coloring and molding thermoplastic resins, is excellent in high speed and high temperature processability, and can be used for resin molded articles which are uniform and have excellent opacifying properties, particularly those for melt extruded laminate films.
BACKGROUND ART
Titanium dioxide (TiO.sub.2 : hereafter, sometimes referred to as titanium oxide for brevity) is known as a white pigment, ultraviolet light screening agent or the like, and is utilized widely as a coloring agent or an opacifying agent for plastics articles. Additives such as titanium dioxide and fillers are kneaded into plastics in heated and molten state. Hitherto, polyolefin-based plastics used as a plastic film, sheet or the like are kneaded at a temperature around 200.degree. C., which temperature is lower than the temperature at which engineering plastics are processed. Recently, however, there is a tendency that in order to increase productivity, height temperatures elevated to about 300.degree. C. are used for mixing, kneading and molding so that process time can be reduced. Also, the requirement for the precision of the trimmed shape of articles is becoming stricter. This leads to severer requirement for the physical properties of titanium dioxide powder to be mixed in plastics.
More specifically, titanium dioxide powder is demanded which is easy to disperse in plastics, has high opacifying power, is excellent in weatherability and light resistance, and generates less amount of a gas or gases upon processing. Although titanium dioxide powders are not influenced remarkably by gas generation at kneading temperatures around 200.degree. C., above which temperature the organic components in the surface treating agent used for surface modification of titanium dioxide will decompose or gaseous components will vaporize such as liberation of water of crystallization to form foams, so that there occur frequently problems of causing failure of quality.
When thermoplastic resins are pigmented with the above-mentioned titanium oxide, there is used a pigmenting composition. As the pigmenting composition, there have heretofore been used dry colors in the form of powder which comprise a pigment and a dispersant, liquid colors or paste colors which comprise a pigment dispersed in a dispersant that is liquid at ambient temperature, masterbatches which comprise a resin that is solid at ambient temperature and a pigment dispersed therein in high concentrations, the mixture being shaped into pellets or flakes. Of these, frequently used are masterbatches because they are easy to handle and are excellent in maintaining operational environment upon use.
As described above, titanium oxide is used in large amounts as a white pigment for pigmenting resins because of its excellent whiteness, high opacifying properties, and high pigmenting power. However, titanium oxide by nature is hydrophilic and therefore is subjected to surface treatment with inorganic or organic substances in order to improve weatherability, hydrophobicity and dispersibility.
For example, there are known titanium oxides treated with polyol- and polysiloxane-based surface treating agents, respectively. The titanium oxide whose surface is treated with a polyol-based surface treating agent is highly dispersible but it receives less effect of hydrophobic treatment so that it adsorbs much water. Masterbatches which contain such a surface-treated titanium oxide and a thermoplastic resin also are less hydrophobic so that they tend to contain much water.
On the other hand, titanium oxide whose surface is treated with
Hosokawa Masaru
Miyasita Susumu
Muraoka Kazuyoshi
Sakuma Noburu
Tunashima Makoto
Cain Edward J.
Tohkem Products Corporation
Toyo Ink Manufacturing Co. Ltd.
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