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...
Patent
1999-06-25
2000-10-10
Acquah, Samuel A.
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...
524402, 524442, 524449, 524451, 428402, C08K 338
Patent
active
061302805
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an oxymethylene polymer resin shaped article having high flexural modulus. More particularly, the present invention is concerned with an oxymethylene polymer resin shaped article which is produced by molding an oxymethylene polymer resin, wherein the oxymethylene polymer resin is selected from the group consisting of an oxymethylene homopolymer resin, an oxymethylene copolymer resin and a mixture thereof. The oxymethylene copolymer resin comprises a copolymer of an oxymethylene monomer and a comonomer copolymerizable therewith, wherein the amount of the comonomer is extremely limited. The shaped article has an improved crystal structure, wherein the crystallinity is 72% or more, the average crystallite size is 150 .ANG. or more, and 70% by volume or more of the whole volume of the shaped article is comprised of spherulites each having a diameter of 60 .mu.m or less. The shaped article also has a thickness of 1 mm or more. The oxymethylene polymer resin shaped article of the present invention exhibits excellent mechanical properties including especially high flexural modulus.
The oxymethylene polymer resin shaped article of the present invention can be advantageously used as a material for a sliding part and a precision part. Further, the oxymethylene polymer resin shaped article of the present invention exhibits high flexural modulus and high heat conductivity both at high temperatures, and, hence, can be advantageously used in the field of parts for electric and electronic apparatuses.
2. Prior Art
A shaped article of an oxymethylene polymer resin has various excellent properties, such as excellent mechanical properties, excellent fatigue resistance, excellent self-lubricating properties, and excellent heat resistance. Therefore, oxymethylene polymer resin shaped articles have been used in a wide variety of commercial applications, such as various parts for use in various machines, for example, automobiles, electric apparatuses, electronic apparatuses and office automation machines.
These commercial applications include those applications in which an oxymethylene polymer resin shaped article is required to exhibit especially high mechanical properties while maintaining the other excellent properties inherent in an oxymethylene polymer resin shaped article. In such applications, the mechanical properties of an oxymethylene polymer resin shaped article are improved by a method in which, before the molding of an oxymethylene polymer resin, a large amount of a reinforcement (filler), such as a glass fiber or a carbon fiber, is incorporated into the oxymethylene polymer resin. However, with respect to the resultant composite shaped article having incorporated thereinto a large amount of a reinforcement, there have been problems in that the shaped article has a large specific gravity, a poor sliding property and a poor surface appearance.
Therefore, various attempts have been made to improve the mechanical properties of the oxymethylene polymer resin shaped article by a method using very little or no reinforcement. Among these attempts, there have been attempts to achieve the above object by improving the crystal structure of the oxymethylene polymer resin. As examples of known methods for improving the crystal structure of the oxymethylene polymer resin in an attempt to obtain a shaped article having improved mechanical properties, there can be mentioned a method in which an oxymethylene polymer resin to be molded is subjected to isothermal crystallization at a relatively high temperature, and a method in which an oxymethylene polymer resin to be molded is subjected to annealing (see, for example, J. of Appl. Polym. Sci. vol. 1, p. 169 (1959); J. Macromol. Sci. Phys. B13(3), p. 323 (1977); Polymer vol. 19, p. 1163 (1978); and J. of Appl. Polym. Sci. vol. 55, p. 489 (1995)). The oxymethylene polymer resin shaped articles obtained by these methods are remarkably improved in crystallinity; however, these shaped articles are di
REFERENCES:
Hammer et al., Journal of Applied Polymer Science, vol. 1, No. 2, pp. 169-177, 1959.
Hojfors et al., J. Macromol. Sci.-Phys., B13(3), pp. 323-348, 1977.
Salaris et al., Polymer, vol. 19, pp. 1163-1170, 1978.
Plummer et al., Journal of Applied Polymer Science, vol. 55, pp. 489-500, 1995.
Cutler et al., Polymer, vol. 20, pp. 1470-1472, 1979.
Franbourg et al., Polymer Bulletin, vol. 24, pp. 445-450, 1990.
Wright et al., Polymer, vol. 29, pp. 793-796, 1988.
Runt, Journal of Materials Science, vol. 26, pp. 792-798, 1991.
Harada et al., Kagaku to Kogyo (Science and Industry), vol. 64, No. 9, pp. 454-460, 1990.
Nagahara Hajime
Yokoyama Hiroshi
Acquah Samuel A.
Asahi Kasei Kogyo Kabushiki Kaisha
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