Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Reexamination Certificate
2001-01-02
2002-08-27
Yoon, Tae H. (Department: 1714)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Processes of preparing a desired or intentional composition...
C523S206000, C523S209000, C523S212000, C524S493000, C428S304400, C428S312600, C428S315500
Reexamination Certificate
active
06441063
ABSTRACT:
DETAILED DESCRIPTION OF THE INVENTION
1. Field of the Invention
The present invention relates to a thermoplastic resin composition, a process for production thereof, and a film produced from said composition. More particularly, the present invention relates to a thermoplastic resin composition obtained by kneading a thermoplastic resin and particular inorganic particles using a vented double-screw kneader and extruder, a process for production thereof, and a biaxially oriented film produced from said composition.
2. Prior Art
Thermoplastic resins, particularly aromatic polyesters have excellent physical and chemical properties and are therefore used in a large amount in the fields of fiber, film, resin, etc. Meanwhile, they are known to arouse, in producing a molded product therefrom or in handling the molded product, a problem of reduction in workability, productivity or product value, caused by inferior slipperiness.
For such a problem, it was proposed to add fine particles to a thermoplastic resin to produce a molded product having appropriate surface unevenness and improved slipperiness. As the fine particles, there are being used inorganic particles of, for example, silica, titanium dioxide, calcium carbonate, talc or kaolinite. In adding inorganic particles, however, the presence of large particles therein poses a problem. The presence of large particles causes, in the case of, for example, a film for magnetic tape, reduction in electromagnetic transduction property or drop out and impairs important film qualities. To remove such large particles, it is generally conducted, in adding inorganic particles during polymer synthesis, to convert the inorganic particles into a slurry or solution, subject the slurry or solution to grinding and sifting, and then add the resulting material. This operation, however, requires a large cost and a long time for slurry formation, grinding and sifting; moreover, when the particles after the above operation are added during polymer synthesis, the particles cause reagglomeration and it is impossible to completely prevent the incoming of large particles. In recent years, it has been conducted to produce various kinds of value-added polymers from a single master polymer. In this case, addition of particles during polymer synthesis incurs a big operational loss when the kind of particles used is changed.
Hence, there were proposed, for example, a method which comprises kneading powdery particles into a polyester using a single-screw extruder or a double-screw kneader and extruder (JP-A-1-157806), or a method which comprises adding, to a polyester, a liquid slurry of particles dispersed in a medium (JP-A-6-91635). When these methods are applied to inorganic particles, however, insufficient disintegration of agglomerated particles or large particles takes place if the shear stress applied is insufficient, resulting in inferior dispersion of particles in resin; if the shear stress is too high, excessive disintegration of particles takes place, resulting in decreased particle sizes, and the intended slipperiness, etc. are not achieved.
When the inorganic particles are, in particular, silica particles, the silica particles agglomerate easily because they have a large number of silanol groups on the surfaces. When the above-mentioned methods are applied to silica particles, insufficient disintegration of agglomerated particles or large particles takes place if the shear stress applied is insufficient, resulting in inferior dispersion of particles in resin; if the shear stress is too high, excessive disintegration of particles takes place, resulting in decreased particle sizes, the intended slipperiness, etc. are not achieved, and excessive disintegration further incurs reagglomeration and formation of large particles.
To prevent the agglomeration of silica particles, it is generally conducted to treat a silica powder with a silicon-containing organic compound. The silica powder treated with a silicon-containing organic compound is already in commercial production and is in use in various applications.
When the above-mentioned methods are applied to the silica powder treated with a silicon-containing organic compound, the silica powder is easily dispersed in non-polar solvents for its hydrophobicity but is very difficult to disperse in polar solvents.
Problems to Be Solved by the Invention
The present inventors made a study in order to alleviate the above-mentioned drawbacks of the conventional method for addition of particles and produce a thermoplastic resin film superior particularly in slipperiness and surface uniformity. As a result, the present invention has been completed.
An object of the present invention is to provide a thermoplastic resin composition wherein inorganic particles are easily synthesized in a thermoplastic resin, whereby particles in the obtained thermoplastic resin have good dispersibility, and a process for production of such a composition.
Other object of the present invention is to provide a biaxially oriented film produced, by the above process, from a thermoplastic resin composition wherein inorganic particles are contained in good dispersibility.
Means for Solving the Problems
According to the study made by the present inventors, the above object of the present invention is achieved by a thermoplastic resin composition containing inorganic particles, wherein (i) the inorganic particles have pore volume of 0.1 to 3 ml/g and (ii) the inorganic particles are treated at the surfaces with a hydrophilic polyester of 0.05 to 10 times the weight of the inorganic particles or with a silicon-containing organic compound.
The above thermoplastic resin composition of the present invention is classified into the following compositions (a) and (b), based on the kind of the compound used for surface treatment of inorganic particles.
(a) A thermoplastic resin composition containing inorganic particles, wherein (i) the inorganic particles have pore volume of 0.1 to 3 ml/g and (ii) the inorganic particles are treated at the surfaces with a hydrophilic polyester of 0.05 to 10 times the weight of the inorganic particles.
(b) A thermoplastic resin composition containing silica particles, wherein (i) the silica particles have pore volume of 0.1 to 3 ml/g and (ii) the inorganic particles are treated at the surfaces with a silicon-containing organic compound.
The study by the present inventors further found out that the above thermoplastic resin composition can be produced by a process for producing a thermoplastic resin composition by kneading a thermoplastic resin and inorganic particles using a vented double-screw kneader and extruder, in which process (i) the inorganic particles have pore volume of 0.1 to 3 ml/g, (ii) the inorganic particles are treated at the surfaces with a hydrophilic polyester of 0.05 to 10 times the weight of the inorganic particles or with a silicon-containing organic compound, and the inorganic particles are fed into the vented double-screw kneader and extruder in the form of their dispersion in water and/or an inert organic solvent.
The present invention is described below in more detail.
As the thermoplastic resin constituting the composition of the present invention, there are mentioned a polyethylene, a polypropylene, polyamides, polyesters, and the like. Of these, an aromatic polyester is preferred.
As the aromatic polyester, an aromatic polyester composed of an aromatic dicarboxylic acid as a main acid component and an aliphatic glycol as a main glycol component is particularly preferred. The aromatic dicarboxylic acid can be exemplified by terephthalic acid, 2,6-naphthalenedicarboxylic acid and 4,4′-diphenyldicarboxylic acid. Of these, terephthalic acid or 2,6-naphthalenedicarboxylic acid is preferred. The aliphatic glycol can be exemplified by ethylene glycol, propylene glycol, 1,4-butanediol and 1,4-cyclohexanedimethanol. Of these, ethylene glycol is preferred.
The polyester is preferably a homopolymer composed of the above aromatic dicarboxylic acid component and the above aliphatic glycol component,
Kameoka Akira
Kosuge Masahiko
Kudo Takafumi
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