Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Reexamination Certificate
1999-08-13
2001-02-06
Hoke, Veronica P. (Department: 1714)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Processes of preparing a desired or intentional composition...
C558S073000, C558S092000
Reexamination Certificate
active
06184275
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a crystalline polymer composition and more particularly to a crystalline polymer composition containing 100 parts by weight of a crystalline polymer and 0.005 to 5 parts by weight of a compound represented by formula (I) hereinafter described having a chlorine content of 500 ppm or less.
2. Description of the Related Art
Crystalline polymers, such as polyethylene, polypropylene, polybutene-1, polyethylene terephthalate, polybutylene terephthalate, and polyamide, are slow in crystallization after heat molding and therefore have a low molding efficiency and need mold cooling. Further, they undergo mold shrinkage on crystallization. Furthermore, moldings of these crystalline polymers tend to have insufficient strength or poor transparency due to large crystals formed.
It is known that all these drawbacks are attributed to the crystallinity of the polymers and could be eliminated by increasing the crystallizing temperature of the polymers so as to produce fine crystals rapidly.
Addition of a nucleating agent or a nucleation accelerator is known effective for this purpose. Conventionally used nucleating agents or nucleation accelerators include carboxylic acid metal salts, such as aluminum 4-t-butylbenzoate and sodium adipate, acid phosphoric esters, such as sodium bis(4-t-butylphenyl)phosphate and sodium 2,2′-methylenebis(4,6-di-t-butylphenyl)phosphate, and polyhydric alcohol derivatives, such as dibenzylidene sorbitol and bis(methylbenzylidene) sorbitol.
Of these known compounds, metal salts of a cyclic phosphate of an alkylidenebisphenol disclosed in Japanese Patent Laid-Open Nos. 1736/83 and 184252/84, etc. are particularly effective and have been used widely. However, their effects are still sometimes insufficient, and cases are met with in which an alkali metal chloride is dissolved out in the polymer to cause surface roughness or voids, which are problematical in the practice.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a crystalline polymer composition which is free from surface roughness or voids and excellent in strength and transparency.
In order to remove the above-described disadvantage of the metal salt of the alkylidenebisphenol cyclic phosphate, the inventors have conducted extensive investigation and found that the disadvantage is closely related to the chlorine content of the metal salt of the alkylidenebisphenol cyclic phosphate.
The metal salt of an alkylidenebisphenol cyclic phosphate which can be used in the present invention is usually prepared by allowing phosphorus trichloride (or phosphorus oxychloride) and a 2,2′-alkylidenephenol to react, followed by, if necessary, hydrolysis to obtain a cyclic acid phosphoric ester, which is then allowed to react with an alkali metal hydroxide, e.g., sodium hydroxide. The product is collected by filtration, dried, and, if desired, ground for use as a nucleating agent.
The compound thus prepared usually has a chlorine content exceeding 500 ppm. Therefore, where it is used in contact with water or under a high humidity condition, an alkali metal chloride dissolves out to cause surface roughness or voids.
Since it is extremely difficult to completely remove the chlorine content from the compound, the inventors aimed to find an acceptable range of the chlorine content for practical use. As a result, they have found that the outstanding problems are all settled by controlling the chlorine content in the alkylidenebisphenol cyclic phosphate to 500 ppm or less.
The present invention provides a crystalline polymer composition comprising 100 parts by weight of a crystalline polymer and 0.005 to 5 parts by weight of a compound represented by formula (I):
wherein R
1
and R
2
each independently represent an alkyl group having 1 to 9 carbon atoms; R
3
represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms; and M represents an alkali metal,
the compound having a chlorine content of 500 ppm or less.
The crystalline polymer composition according to the present invention is free from surface roughness or voids and excellent in strength and transparency.
DETAILED DESCRIPTION OF THE INVENTION
The compound of formula (I) which is used in the present invention is useful as a nucleating agent.
In formula (I), the alkyl group having 1 to 9 carbon atoms as represented by R
1
or R
2
includes methyl, ethyl, propyl, isopropyl, butyl, sec-butyl, t-butyl, isobutyl, amyl, t-amyl, hexyl, heptyl, octyl, isooctyl, 2-ethylhexyl, t-octyl, nonyl, and t-nonyl groups. The alkyl group having 1 to 4 carbon atoms as represented by R
3
includes methyl, ethyl, propyl, isopropyl, butyl, sec-butyl, t-butyl, and isobutyl groups. The alkali metal as represented by M includes sodium, potassium, and lithium.
Of the compounds represented by formula (I), preferred are those in which R
1
is a tertiary alkyl group, such as a t-butyl group or a t-amyl group; R
2
is an alkyl group having 1 to 4 carbon atoms; and R
3
is a hydrogen atom or a methyl group.
It is still preferred that both R
1
and R
2
be t-butyl groups. In this case, R
3
is preferably a hydrogen atom, and M is preferably sodium or lithium. It is particularly preferred that both R
1
and R
2
be t-butyl groups; R
3
be a hydrogen atom; and M be sodium.
Accordingly, compounds shown below are preferred of the compounds represented by formula (I).
The compounds of formula (I) are usually prepared by allowing phosphorus trichloride (or phosphorus oxychloride) and a 2,2′-alkylidenephenol to react, followed by, if necessary, hydrolysis to obtain a cyclic acid phosphoric ester and allowing the cyclic acid phosphoric ester to react with an alkali metal hydroxide, e.g., sodium hydroxide. The product is collected by filtration, dried, and, if desired, ground for use as a nucleating agent.
The compound thus prepared contains a large amount of chlorine, which is mainly derived from an alkali metal chloride, and usually has a chlorine content exceeding 500 ppm. Where it is used as such in contact with moisture, for example, in contact with water or under a high humidity condition, an alkali metal chloride, e.g., NaCl dissolves out to cause surface roughness or voids.
The present invention consists in using the compound of formula (I) having its chlorine content reduced to 500 ppm or less, preferably 300 ppm or less, still preferably 200 ppm or less, as a nucleating agent thereby to eliminate the above-mentioned disadvantage. Reduction of the chlorine content to 500 ppm or less can be achieved by, for example, proper selection of washing conditions, i.e., the number of times of washing, the amount of wash water, the temperature of wash water, the stirring time, and the washing time, or a method comprising dissolving the compound in an organic solvent followed by filtration to remove any insoluble inorganic salt. While the lower limit of the chlorine content is not particularly limited, it is practically impossible to reduce the chlorine content of 1 ppm or less.
The compound of formula (I) having a chlorine content of 500 ppm or less is used in an amount of 0.005 to 5 parts by weight, preferably 0.01 to 3 parts by weight, per 100 parts by weight of a crystalline polymer. When added in an amount less than 0.005 part by weight, the compound hardly serves as a nucleating agent. Even if the compound is added in amounts exceeding 5 parts, no further effects is expected for amount, but adverse effects on other various physical properties and bad economy result.
The crystalline polymers which can be used in the crystalline polymer composition of the present invention include &agr;-olefin polymers, such as low-density polyethylene, linear low-density polyethylene, high-density polyethylene, polypropylene, polybutene-1, poly-3-methylbutene, ethylene-propylene block or random copolymers; thermoplastic linear polyesters, such as polyethylene terephthalate, polybutylene terephthalate, and polyhexamethylene terephthalate; linear polyamides, such as polycaprolactam and polyhexamethyl
Takahashi Masayuki
Tobita Etsuo
Asahi Denka Kogyo Kabushiki Kaisha
Hoke Veronica P.
Young & Thompson
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