Stock material or miscellaneous articles – Coated or structually defined flake – particle – cell – strand,... – Particulate matter
Reexamination Certificate
2000-08-04
2002-07-02
Le, Hoa T. (Department: 1773)
Stock material or miscellaneous articles
Coated or structually defined flake, particle, cell, strand,...
Particulate matter
C427S220000, C427S221000, C427S242000, C428S407000
Reexamination Certificate
active
06413639
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to Mg—Al-based hydrotalcite-type particles, a chlorine-containing resin stabilizer, and a process for producing the Mg—Al-based hydrotalcite-type particles. More particularly, the present invention relates to Mg—Al-based hydrotalcite-type particles having a large plate surface diameter and an adequate thickness which are suitable as a stabilizer for chlorine-containing resins; the chlorine-containing resin stabilizer; and a process for producing such Mg—Al-based hydrotalcite-type particles.
As layered compounds, there are known various compounds as well as clay minerals or the like. Among these layered compounds, layered double hydroxides such as hydrotalcite have such a structure capable of inserting various ions or molecules into spacings between respective layers thereof and, therefore, can exhibit an anion-exchanging property.
In general, as described in Journal of the Chemical Society of Japan, 1995, No. 8, pp. 622 to 628, the hydrotalcite is represented by the formula:
[M
2+
1-x
M
3+
x
(OH)
2
]
x
+
[An
−
x
.yH
2
O]
x
−
(wherein M
2+
is a divalent metal ion such as Mg
2+
, Co
2+
, Ni
2+
or Zn
2+
; M
3+
is a trivalent metal ion such as Al
3+
, Fe
3+
or Cr
3+
; An
−
is an n-valent anion such as OH
−
, Cl
−
, CO
3
2−
or SO
4
2−
; and x is usually 0.2 to 0.33,)
and such hydrotalcite has a laminated crystal structure which comprises two-dimensional main layers composed of regular octahedral brucite units each having a positive charge, and interlayers each having a negative charge.
The hydrotalcite has been used in various applications because of good anion-exchanging property thereof, for example, as ion exchange materials, adsorbents, deodorants or the like. Also, the hydrotalcite has been used in various other applications such as stabilizers for resins or rubbers, e.g., polyethylene, polypropylene and chlorine-containing resins (typically, vinyl chloride resins), as well as paints, various catalysts, agricultural films, inks or the like.
In particular, as gasket materials the chlorine-containing resins have been widely used because the chlorine-containing resins are more excellent in flexibility and adhesion property than those of rubbers, thermoplastic elastomers or the like.
However, the chlorine-containing resins are susceptible to heat deterioration and oxidation degradation and, therefore, suffer from deteriorated properties such as low elongation when used for a long period of time, thereby causing such a problem that the resins are no longer usable as gasket materials.
In recent years, as to catalysts or the like, it has also been required to use those containing no harmful metals from the standpoint of environmental protection. The hydrotalcite-type particles have been expected to satisfy these requirements because the hydrotalcite-type particles have almost no toxicity and exhibit an excellent catalytic property or the like.
In particular, among the hydrotalcite-type particles, Mg—Al-based hydrotalcite-type particles containing Mg
2+
as a divalent metal ion and Al
3+
as a trivalent metal ion, are most noticeable owing to its good stability. There have also been known iron-based hydrotalcite-type particles (Japanese Patent Application Laid-Open (KOKAI) No. 9-227127(1997)). However, when the iron-based hydrotalcite-type particles are kneaded with resins, the obtained kneaded material is disadvantageously colored due to inclusion of the iron. Further, when used as a stabilizer for chlorine-containing resins, the iron-based hydrotalcite-type particles cannot exhibit a sufficient heat resistance as compared to the Mg—Al-based hydrotalcite-type particles.
As the general production method of hydrotalcite, there is known a method of mixing an aqueous metal salt solution containing divalent metal ions and trivalent metal ions which constitute main layers thereof, with an aqueous carbonate solution containing carbonate ions which constitute interlayers thereof, and then subjecting the obtained mixture to coprecipitation reaction while controlling the temperature, the pH value and the like (Eiichi NARITA, “Chemistry of Layered Double Hydroxides as a Fixing Agent of Anions” in “Surface Techniques”, pages 722-727, 1993). In addition to the above method of conducting the reaction under ordinary pressure, there is also known a method of producing hydrotalcite under pressure by hydrothermal reaction using an autoclave.
Hitherto, hydrotalcite-type particles to be kneaded into resins, have been required to possess a large plate surface diameter and an adequate thickness in the consideration of dispersibility in resins upon kneading. For example, it has been required to provide such hydrotalcite-type particles having a plate surface diameter of 0.2 to 1 &mgr;m and a thickness of 0.05 to 0.2 &mgr;m. However, the hydrotalcite-type particles obtained by the coprecipitation reaction have a plate surface diameter as small as 0.05 to 0.25 &mgr;m and a thickness of 0.05 to 0.2 &mgr;m. Therefore, in order to obtain hydrotalcite-type particles having a large plate surface diameter, it is necessary to use specific reaction conditions such as hydrothermal synthesis or the like.
Further, in the case where the hydrotalcite-type particles are used as a stabilizer for chlorine-containing resins or rubbers such as vinyl chloride resins or the like, it is required that the particles are not only sufficiently dispersed in the resins or rubbers to obtain resin or rubber products having an excellent heat resistance, but also have a higher chlorine ion-capturing ability.
In addition, as non- or low-toxic lead-free stabilizers for chlorine-containing resins, carboxylate, for example, zinc stearate are used as an essential component. However, when such carboxylates added as a stabilizer captures a chlorine gas released from the chlorine-containing resins, zinc chloride is produced by the reaction therebetween. As is known to those skilled in the arts, the thus produced zinc chloride acts as a decomposition catalyst for the chlorine-containing resins, so that carbon-carbon bonds constituting a skeleton of the resins are broken continuously, resulting in undesirable carbonization of the resins (so-called zinc burning). Accordingly, when used as a stabilizer for the chlorine-containing resins, the hydrotalcite-type particles are required to have a high ability of preventing the zinc burning.
At the present time, it has been strongly demanded to provide Mg—Al-based hydrotalcite-type particles which have a large plate surface diameter, an adequate thickness and a high zinc burning-preventing ability, and is suitable as a stabilizer for chlorine-containing resins. However, such Mg—Al-based hydrotalcite-type particles capable of satisfying the above properties have not been obtained yet.
Specifically, in the conventional coprecipitation method, it is not possible to obtain hydrotalcite-type particles having a large plate surface diameter. Under specific reaction conditions such as hydrothermal synthesis using the autoclave, it is possible to produce hydrotalcite-type particles having a large plate surface diameter. However, when the thus produced hydrotalcite-type particles are use as a stabilizer of chlorine-containing resins, the obtained chlorine-containing resin composition cannot show a sufficient heat resistance.
In particular, the chlorine-containing resin Compositions used as gasket materials are required to have an excellent heat stability and an adequate hardness. Especially, in the case of white or light-colored gasket materials, it is necessary that these materials are free from discoloration due to heat upon processing, i.e., have a good tinting property. As a stabilizer for such chlorine-containing resins satisfying these requirements, the hydrotalcite-type particles are required to exhibit a large plate surface diameter, an adequate thickness and a higher chlorine ion-capturing ability.
Further,
Honmyo Torayuki
Katamoto Tsutomu
Kobayashi Naoya
Yamamoto Akinori
Le Hoa T.
Nixon & Vanderhye
Toda Kogyo Corporation
LandOfFree
Mg-Al based hydrotalcite-type particles, chlorine-containing... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Mg-Al based hydrotalcite-type particles, chlorine-containing..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Mg-Al based hydrotalcite-type particles, chlorine-containing... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2881420