Stock material or miscellaneous articles – Coated or structually defined flake – particle – cell – strand,... – Particulate matter
Reexamination Certificate
1999-04-06
2002-04-23
Le, Hoa T. (Department: 1773)
Stock material or miscellaneous articles
Coated or structually defined flake, particle, cell, strand,...
Particulate matter
C427S215000, C427S220000, C427S372200, C427S377000, C427S384000, C428S404000
Reexamination Certificate
active
06376077
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a process for the production of coupling agent-treated inorganic particles suitable for use as an additive or a filler for a synthetic resin. Further, the present invention relates to a synthetic resin composition containing the above inorganic particles and a molded article obtained from the above synthetic resin composition. More specifically, the present invention relates to a process for the production of coupling agent-treated inorganic particles, which process is excellent in surface-treatment uniformity, uses an expensive coupling agent at high coefficient of utilization and further satisfies the fundamental requirements for forming a bond between a coupling agent and an inorganic particle surface, and relates to a synthetic resin composition containing the above inorganic particles and a molded article obtained from the above synthetic resin composition.
PRIOR ART OF THE INVENTION
Inorganic particles used as an additive or a filler for a synthetic resin are usually surface-treated with an organic agent such as a surfactant or a higher fatty acid in order to increase the compatibility with a polymer and improve the processability and the moldability of an obtained synthetic resin composition or improve the physical properties and the appearance of a molded article. Further, there are many proposals of incorporating inorganic particles treated with a variety of coupling agents into a synthetic resin. However, coupling agents are generally expensive. Further, a synthetic resin composition into which coupling agent-treated inorganic particles are incorporated is poor in processability. From these reasons, there has been hardly used inorganic particles treated with a coupling agent. Instead, in most cases, coupling agents have been used in a so-called integral blend method wherein higher fatty acid-treated inorganic particles are mainly used and a coupling agent is added, as required, at kneading for molding.
Recently, inorganic particles surface-treated with a coupling agent are required since it is desired to exploit and use the full performances of a coupling agent instead of the use of the coupling agent in the integral blend method.
As a method of surface-treating inorganic particles with a coupling agent, there is known a dryprocess. For example, the dry process is carried out as follows. While the dry powder of inorganic particles is heavily stirred in a Henschel mixer, an aqueous solution of a coupling agent is dropwise added or spray-injected with a spray or the like. And, the stirring is continued. Then, heat-drying is carried out in the mixer to obtain a treated product. This process is ordinarily used. In this dry process, the whole amount of the coupling agent aqueous solution is absorbed into the dry powder of the inorganic particles and the heat drying is carried out. Thereby, this dry process satisfies the treatment requirements for forming a chemical bond between the coupling agent and the inorganic particle surface along the chemical properties of the coupling agent. Due to this method, the coefficient of utilization of the coupling agent used for the treatment is naturally increased to the utmost. In this point, it can be said that a coupling agent is an optimum surface-treating agent for the dry treatment process.
There can be found proposals of methods comprising treating inorganic particles with a coupling agent by a wet surface-treatment process. However, these methods require using an organic solution such as alcohol so that the methods have too many problems for an industrial production.
When coupling agent-treated inorganic particles obtained by a conventional dry treatment process are incorporated into a synthetic resin, in many cases, the effect of improving properties can not be obtained as expected. The reason is considered to be as follows. In the conventional dry treatment, surface-treatment is nonuniform and part of the coupling agent works as a binder to strongly coagulate the inorganic particles each other, which deteriorate the dispersibility of the inorganic particles in the resin. When uniform surface-treatment can be obtained, the ubiquity of a coupling agent in inorganic particles is prevented. Therefore, the coupling agent does not work as a binder and good dispersibility is maintained. The effect of the coupling agent treatment is fully exerted. That is, it is supposed that the synthetic resin composition incorporated with a coupling agent is improved in physical properties.
The wet surface-treatment process is most recommended for attaining the uniform surface-treatment of inorganic particles with a coupling agent. However, when inorganic particles are wet-surface-treated with a coupling agent and then, as in a conventional method of obtaining a higher fatty acid-treated product, dehydrated by filtration before a drying step, the major part of the coupling agent used is lost due to its leak together with a filtrate. Furthermore, COD (chemical oxygen demand) in wastewater becomes high and it requires a high cost to treat the wastewater. The present inventors have studied the factors of the above problems and, as a result, reached the present invention.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a process for the production of coupling agent-treated inorganic particles, wherein the uniformity of surface-treatment by a wet treatment method and the high coefficient of a coupling agent by a dry treatment method are compatible.
It is another object of the present invention to provide a synthetic resin composition which can give a molded article excellent in physical properties when the coupling agent-treated inorganic particles are incorporated into a synthetic resin.
It is further another object of the present invention to provide a molded article obtained from the above synthetic resin composition.
According to the present invention, there is provided a process for the production of coupling agent-treated inorganic particles, which comprises adding a solution of a coupling agent into an aqueous suspension of inorganic particles with stirring and, after the mixing with stirring, heat-drying the resultant suspension without dehydration by filtration and concentration. Further, there is provided a synthetic resin composition containing 100 parts by weight of a synthetic resin and 1 to 300 parts by weight of the coupling agent-treated inorganic particles obtained by the above process. Furthermore, there is provided a molded article obtained from the above synthetic resin composition. Still further, there is provided coupling-agent treated inorganic particles obtained by the above production process.
DETAILED DESCRIPTION OF THE INVENTION
The inorganic particles used in the production process of the present invention are metal compounds such as a hydroxide, a carbonate, a basic carbonate, a basic sulfate, a phosphate, a silicate and an oxide of a metal. The specific examples of the metal compounds suited for use in the present invention include aluminum hydroxide, magnesium hydroxide, solid solution hydroxide: Mg
1−x
M
x
(OH)
2
, wherein M is a divalent metal such as Mn, Co, Fe, Ni or Zn and X<1, a hydrotalcite compound, LiAl
2
(OH)
6
A
n−
1
.mH
2
O, wherein A is an anion having a valence of n and m>3, a chalcoalumite type compound, magnesium carbonate, calcium carbonate, basic calcium carbonate, dawsonite, basic magnesium sulfate: Mg
6
(OH)
10
SO
4
3.H
2
O, calcium phosphate, talc, mica, kaolin, alumina, titania, magnesia, hydrozincite and spinel type oxides [MgAl
2
O
4
and ZnAl
2
O
4
]. The production process of the present invention is suited for surface-treating inorganic particles such as a magnesium hydroxide which serves a useful function as a flame-retardant for synthetic resins and which has a BET specific surface area of 15 m
2
/g or less and an average secondary particle diameter of 2 &mgr;m or less and whose primary crystal particle has a shape of hexagonal platelet, and a hydrotalcite compound which serves a
Hiraishi Wataru
Ohishi Shunji
Kyowa Chemical Industry Co. Ltd.
Le Hoa T.
Wenderoth Lind & Ponack LLP
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