Aromatic polyester and molded article using the same

Details Aromatic polyester and molded article using the same Aromatic polyester and molded article using the same

2000-04-19

2001-09-25

Boykin, Terressa M. (Department: 1711)

Synthetic resins or natural rubbers -- part of the class 520 ser

Synthetic resins

From phenol, phenol ether, or inorganic phenolate

C528S198000, C528S271000, C528S272000

Reexamination Certificate

active

06294643

ABSTRACT:

BACKGROUND OF THE INVENTION
The present invention relates to an aromatic polyester having the following structural units (1) to (5) and a molded article using the aromatic polyester.
wherein Ra, Rb, Rc, Rd, Re and Rf each independently represents a lower alkyl group, lower alkoxy group, phenyl group or halogen atom, and n represents an integer from 0 to 3.
Conventionally, aromatic polyesters having the above-described structural units (1), (2), (4) and (5) have been known. Recently, aromatic polyester also having the structural unit (3) have been suggested. For example, an aromatic polyester has been disclosed in which the ratio of (2) to (3) (=molar ratio of (2) to (3), that is, ratio of number of unit (2) to number of unit (3) in the aromatic polyester. Hereinafter in this specification, the molar ratio of a unit to another unit is indicated by using “/”. For example, the molar ratio of (2) to (3) is indicated by as (2)/(3)) is 1.0 and (4)/(5) is 2.33 (JP-A-63-57633).
However, the above-described aromatic polyester has problems that, when molded, the ratio of the molding contraction coefficient along the vertical direction (TD direction) to the flow to the molding contraction coefficient along the flow direction (MD direction), that is TD/MD ratio, is remarkably large, and deformations such as warping of molded articles and the like occur.
On the other hand, an aromatic polyester having excellent molding property at lower temperature is also disclosed in which 1≦(2)/(3)≦9 and 1.86≦(4)/(5)≦4 (JP-B-7-98859). In this publication, it is also disclosed that, when (2)/(3)<1, namely, (3) is surplus as compared with (2), molding property of the aromatic polyester at lower temperature has remarkably lowered.
Further, an aromatic polyester having excellent molding property at lower temperature is also disclosed in which 1≦(2)/(3)≦9 and 0.3≦(4)/(5)≦1. It is also disclosed that, when (2)/(3)<1, namely, (3) is surplus as compared with (2), molding property of the aromatic polyester at lower temperature has remarkably lowered (JP-A No. 10-95839).
SUMMARY OF THE INVENTION
Under such conditions, the present inventors have intensively studied to find an aromatic polyester having excellent molding property at lower temperature and giving excellent TD/MD ratio to the molded article. As the result, they have found that, even if (3) is surplus as compared with (2), a polyester in which (2)/(3) and (4)/(5) are in the specific ranges has unexpectedly excellent molding property, and TD/MD ratio of the molded article is remarkably excellent. The present invention has thus been completed.
The present invention provides an aromatic polyester having the following structural units (1) to (5) wherein the amount of the structural unit (1) is 40 to 70% based on the total of the all structural units, (2)/(3) is from 0.7 to 0.95, (4)/(5) is from 1.1 to 2.4, and {(2)+(3)}/{(4)+(5)} is from 0.9 to 1.1.
wherein Ra, Rb, Rc, Rd, Re and Rf each independently represents a lower alkyl group, lower alkoxy group, phenyl group or halogen atom, and n represents an integer from 0 to 3.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
In the aromatic polyester of the present invention, the structural unit (1) is usually derived from p-hydroxybenzoic acids represented by the following general formula (6)
wherein, each Ra independently represents a lower alkyl group, lower alkoxy group, phenyl group or halogen atom; n represents an integer from 0 to 3; R
1
represents a hydrogen atom or lower acyl group; and R
2
represents a hydroxyl group, lower alkoxy group or halogen atom.
Examples of the lower alkyl group include a methyl group, ethyl group and propyl group. Examples of the lower alkoxy group include a methoxy group, ethoxy group, t-butoxy group and phenoxy group. Examples of the halogen atom include chlorine and bromine. n represents an integer from 0 to 3, and an unsubstituted group in which n is 0 is preferable.
Examples of the lower acyl group include an acetyl group, propionyl group and benzoyl group.
Typical examples of the p-hydroxybenzoic acids include p-hydroxybenzoic acid, methyl p-hydroxybenzoate, ethyl p-hydroxybenzoate. p-acetoxybenzoic acid, methyl p-acetoxybenzoate, ethyl p-acetoxybenzoate, propyl p-hydroxybenzoate, phenyl p-hydroxybenzoate and benzyl p-hydroxybenzoate. Among other, p-hydroxybenzoic acid and p-acetoxybenzoic acid are preferred.
The structural unit (2) is usually derived from 4,4′-dihydroxybiphenyls represented by the following general formula (7):
wherein Rb and Rc each independently represents a lower alkyl group, lower alkoxy group, phenyl group or halogen atom; n represents an integer from 0 to 3; and R
3
and R
4
each independently represents a hydrogen atom or lower acyl group.
Examples of the 4,4′-dihydroxybiphenyls include 4,4′-dihydroxybiphenyl and 4,4′-diacetoxybiphenyl.
The structural unit (3) is usually derived from 1,4-hydroquinones represented by the following general formula (8):
wherein each Rd independently represents a lower alkyl group, lower alkoxy group, phenyl group or halogen atom; n represents an integer from 0 to 3; and R
5
and R
6
each independently represents a hydrogen atom or lower acyl group. Typical examples of the 1,4-hydroquinones include 1,4-hydroquinone and 1,4-diacetoxybenzene.
The structural unit (4) is usually derived from terephthalic acids represented by the following general formula (9):
wherein each Re independently represents a lower alkyl group, lower alkoxy group, phenyl group or halogen atom; n represents an integer from 0 to 3; and R
7
and R
8
each independently represents a hydroxyl group, lower alkoxy group or halogen atom.
Typical examples of the terephthalic acids include terephthalic acid and dimethyl terephthalate.
The structural unit (5) is usually derived from isophthalic acids represented by the following general formula (10):
wherein, each Rf independently represents a lower alkyl group, lower alkoxy group, phenyl group or halogen atom; n represents an integer from 0 to 3; and R
9
and R
10
each independently represents a hydroxyl group, lower alkoxy group or halogen atom.
Typical examples of the isophthalic acids include isophthalic acid and dimethyl isophthalate.
In the aromatic polyester of the present invention, the content of the structural unit (1) is usually from about 40 to 70%, preferably from about 55 to 65% based on the total of the all structural units. In this specification, “%” indicating the content of a structural unit is molar basis, that is, based on the number of the structural unit, not based on the weight of the structural unit, unless otherwise mentioned.
When the content of the structural unit (1) is less than 40%, the molding property of the aromatic polyester tends to deteriorate, or the heat resistance of a molded article made of the polyester tends to deteriorate. When the content of the structural unit (1) exceeds 70%, the molding property of the aromatic polyester tends to deteriorate. Hence, the content of the structural unit (1) less than 40% and that over 70% are undesirable.
In the aromatic polyester of the present invention, (2)/(3) is usually about 0.7 to 0.95, preferably about 0.75 to 0.95, particularly preferably about 0.8 to 0.9.
When (2)/(3) is less than 0.7, the deflection temperature under load of a molded article made of the aromatic polyester tends to drop. When it exceeds 0.95, the heat resistance of the molded article tends to deteriorate. Hence, (2)/(3) less than 0.7 and that over 0.95 are undesirable.
In the aromatic polyester of the present invention, (4)/(5) is usually about 1.1 to 2.4, preferably about 1.1 to 2.0, particularly preferably about 1.2 to 1.8.
When (4)/(5) is less than 1.1, the heat resistance of a molded article made of the aromatic polyester tends to deteriorate, hence undesirable. When it exceeds 2.4, TD/MD ratio of the molding contraction coefficient of a molded article made of the aromatic polyester tends to increase, undesirably.
Herein, MD represents the moldin

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