Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – From carboxylic acid or derivative thereof
Reexamination Certificate
2001-02-23
2003-07-15
Acquah, Samuel A. (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
From carboxylic acid or derivative thereof
C528S286000, C528S298000, C528S302000, C528S308000, C528S308600, C524S706000, C524S709000, C524S711000, C524S783000, C502S208000, C502S227000
Reexamination Certificate
active
06593447
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a catalyst for producing a polyester and a process for producing the polyester by using the same. More particularly, the present invention relates to a catalyst for producing a polyester, comprising a specific titanium compound and a phosphorus compound, and a process for producing the polyester having a good color tone (b value), and thus not needing an addition of a cobalt compound to regulate the color tone, by using the catalyst.
BACKGROUND ART
The polyesters, particularly, polyethylene terephthalate, polyethylene naphthalate, polytrimethylene terephthalate and polytetramethylene terephthalate, have excellent mechanical, physical and chemical performances and thus are widely utilized for various fibers, films and other shaped articles.
For example, polyethylene terephthalate is usually produced by preparing an ethyleneglycol ester of terephthalic acid and/or oligomers of the ester by a direct esterification reaction of terephthalic acid with ethyleneglycol, or an interesterification reaction of a lower dialkyl ester of terephthalic acid, for example, dimethyl terephthalate, with ethyleneglycol, or a reaction of terephthalic acid with ethyleneoxide, and then by polymerizing ethyleneglycol ester of terephthalic acid and/or oligomer of the ester in the presence of a polymerization catalyst under a reduced pressure at an elevated temperature, until the polymerization product obtains a target degree of polymerization. Also, the polyethylene naphthalate, polytrimethylene terephthalate and polytetramethylene terephthalate can be produced by a process similar to that mentioned above.
It is well known that the reaction rate of the polymerization reaction and the quality of the resultant polyester are greatly influenced by the type of the catalyst for the polymerization reaction step. As a polymerization catalyst for the polyethylene terephthalate, antimony compounds are most widely employed, because they exhibit excellent catalytic property for polymerization, and the resultant polyester has a good color tone.
However, when the animony compounds are employed as a polymerization catalyst, the resultant polyester is disadvantageous in that when a melt-spinning procedure of the resultant polyester is continuously carried out for a long period, a foreign substance is cohered and accumulated around the melt-spinning orifice (which foreign substance will be referred to as an orifice foreign substance hereinafter), and causes the stream of the polymer melt extruded through the orifice to be bent (which will be referred to as a bending phenomenon of polymer melt stream hereinafter), and the bending phenomenon causes formation of fluffs and breakage of melt spun filaments to occur during the melt-spinning and drawing procedures. Namely, the shaping property of the polyester is degraded by the antimony compound catalyst.
As a polymerization catalyst other than the antimony compounds, the utilization of titanium compounds, for example, titanium tetrabutoxide is suggested. When the titanium compound as mentioned above is employed, the problem of accumulation of the orifice foreign substance can be solved. However, this catalyst causes a new disadvantage in that the resultant polyester per se is colored yellowish and exhibits a poor stability to heat-melting.
To solve the above-mentioned coloring problem, generally, a cobalt compound is mixed into the polyester to erase the yellowish color. It is true that the color tone (apparent whiteness) of the polyester can be improved by mixing the cobalt compound into the polyester. However, the mixed cobalt compound causes the stability of the polyester to heat melting to be decreased and thus the resultant polyester to be easily decomposed.
As a titanium compound for catalyst for the production of the polyester, it is known to employ titanium hydroxide in Japanese Examined Patent Publication No. 48-2,229, &agr;-titanic acid in Japanese Examined Patent Publication No. 47-26,597.
However, in the former catalyst the titanium hydroxide is difficult to pulverize and in the latter catalyst, &agr;-titanic acid is easily modified and is difficult to store and handle. Thus, both the catalysts are not suitable for practical industrial use, and also the catalysts are seldom produce a polyester having a good color tone (b value).
Also, Japanese Examined Patent Publication No. 59-46,258 discloses that a product obtained by a reaction of a titanium compound with trimellitic acid is used as a catalyst for producing the polyester, and Japanese Unexamined Patent Publication No. 58-38,722 discloses that a product of titanium compound with a phosphite ester is usable as a catalyst for producing the polyester. It is true that both the processes enable the stability of the polyester for melting heat to be enhanced to some extent. However, the color tone (colorlessness) of the resultant polyester is unsatisfactory. Thus, the color tone (b value) of the polyester must be further improved.
Further, Japanese Unexamined Patent Publication No. 7-138,354 discloses employment of a complex of a titanium compound with a phosphorus compound as a catalyst for producing the polyester. This process enables the stability of the resultant polyester to melting heat to some extent. However, the color tone of the resultant polyester is unsatisfactory.
Furthermore, when the phosphorus-containing catalyst as mentioned above is employed, the catalyst per se is usually retained, as a foreign substance, in the resultant polyester polymer. Thus, this problem must be solved.
DISCLOSURE OF THE INVENTION
An object of the present invention to provide a catalyst for producing a polyester having a good color tone (b value), a low content of a foreign substance and an excellent melting heat stability, and a process for producing a polyester by using the same.
The above-mentioned object can be attained by the catalyst of the present invention for producing a polyester and the process of the present invention for producing a polyester by using the catalyst. The catalyst of the present invention for producing the polyester comprises a reaction product of
(A) a titanium compound component comprising at least one member selected from the group consisting of:
titanium compounds (1) represented by the general formula (I):
in which formula (I), R
1
represents an alkyl group having 1 to 10 carbon atoms and p represents an integer of 1 to 3, and
titanium compounds (2) produced by reacting the titanium compounds (1) of the formula (I) with aromatic polycarboxylic acids represented by the general formula (II):
in which formula (II), n represents an integer of 2 to 4, or anhydrides of the aromatic polycarboxylic acids of the formula (II), with
(B) a phosphorus compound component comprising at least one member selected from the phosphorus compounds (3) of the general formula (III):
in which formula (III), m represents an integer of 1 or 2, q represents an integer of 0 or 1, the sum of m and q, (m+q), is 1 or 2, R
2
represents an unsubstituted or substituted aryl group having 6 to 20 carbon atoms or alkyl group having 1 to 20 carbon atoms and when m represents 2, the two R
2
groups are the same as each other or different from each other.
The process of the present invention for producing a polyester comprises polymerizing a polymerization-starting material comprising at least one member selected from the group consisting of alkyleneglycol esters of aromatic difunctional carboxylic acids and oligomers thereof in the presence of a catalyst, wherein the catalyst comprises a reaction product of
(A) a titanium compound component comprising at least one member selected from the group consisting of:
titanium compounds (1) represented by the general formula (I):
in which formula (I), R
1
represents an alkyl group having 1 to 10 carbon atoms and p represents an integer of 1 to 3, and
titanium compounds (2) produced by reacting the titanium compounds (1) of the formula (I) with aromatic polycarboxylic acids represented by the general formula (
Acquah Samuel A.
Sughrue & Mion, PLLC
Teijin Limited
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