WO1996027629A1

WO1996027629A1 - Isotropic poly(ester-imides) copolymers

Info

Publication number: WO1996027629A1
Application number: PCT/US1996/003001
Authority: WO
Inventors: Joel David Citron
Original assignee: E.I. Du Pont De Nemours And Company
Priority date: 1995-03-06
Filing date: 1996-03-05
Publication date: 1996-09-12

Abstract

Poly(imide-esters) derived from trimellitic anhydride, 4,4'-oxydianiline and/or p-aminobenzoic acid, and a bisphenol are disclosed. Other repeat units derived from p-hydroxybenzoic acid, terephthalic acid and/or 2,6-napththalene dicarboxylic acid may optionally be present. The polymers can be used in making moldings or films.

Description

XΠ E

ISOTROPIC POLY(ESTER-IMIDES) COPOLYMERS FIELD OF THE INVENTION Poly(ester-imides) copolymers made from trimellitic anhydride, 4,4'-oxydianiline or p-aminobenzoic acid, and a bisphenol, are useful as molding resins for parts which require high temperature resistance. Such copolymers may optionally include repeat units derived from 4-hydroxybenzoic acid, terephthalic acid and/or 2,6-naphthalene dicarboxylic acid.

TECHNICAL P AC QRQU P Japanese Patent Application 4-66259 describes a poly(ester-imide) made from Bisphenol-A and an imide-containing dicarboxylic acid. This dicarboxylic acid was made from 3,4'-oxydianiline and trimellitic anhydride.

Polymers which are useful as molding resins, which possess good thermal stability, and which are made from readily available monomers are comparatively desirable. Accordingly, Applicants have found novel poly(ester-imides) copolymers which are made from readily available starting materials and which exhibit high glass transition temperatures.

SUMMARY OF THE INVENTION This invention concerns an isotrσpic poly(ester-imide) consisting essentially of repeat units of the formula:

(a) about 30 to 100 mole percent, total, of one or both of

(D

and

(ID (b) 0 to about 70 mole percent, total, of one or more of

(in)

(TV), and

(V)

wherein Z is independently -O-, -C(=O)-, -S-, -SO2-, or an alkylene or alkylidene containing 1 to 8 carbon atoms.

DETAILS OF THE INVENTION As indicated above, the present invention is directed to poly(ester-imides) copolymers made from trimellitic anhydride, 4,4'-oxydian-line or p-aminobenzoic acid, and a bisphenol, are useful as molding resins for parts which require high temperature resistance. Such polymers may be suitably made, for example, by a "three-step" procedure, although not necessarily in three physically separated steps. Such a procedure may be generally described as follows. First, a molar portion of trimellitic anhydride may be reacted with a molar portion of p-aminobenzoic acid to form an "amic-acid" which is also a dicarboxylic acid. Second, the resulting amic-acid can be cyclized by conventional means (using heat or dehydrating catalysts) to form an i ide containing dicarboxylic acid. Alternatively , two molar portions of trimellitic anhydride may be reacted with one molar portion of 4,4'-oxydianiline, also referred to as bis(4~a-ninophenyl) ether, to form a "bis amic-acid." The resulting bis amic-acid can then be cyclized to form a dicarboxylic acid containing two imide groups. Third, in a subsequent step in the procedure, one or both of the above imide-containing dicarboxylic acids may then be polymerized with a bisphenol to form the desired poly(imide-ester). By the term "bisphenol" is meant a compound of the formula

wherein Z is as defined above. In a preferred bisphenol, and poly(imide-ester), Z is -O-, -CH₂-, or -C(CH₃)₂-. It is especially preferred if Z is -C(CH₃)₂-. At this time, other monomers which form repeat units (UI), (TV) and (V) shown above, namely the monomers by the name of 4-hydroxybenzoic acid, terephthalic acid, and 2,6-naphthalene dicarboxylic acid, respectively, if desired in the polymer, may also be present when forming the poly(imide-ester) copolymer. Additional bisphenol, preferably equimolar with the total amount of monomers (IV) and or (V) added should also be present.

Since carboxylic acids and phenolic hydroxyl groups do not readily react with one another, "reactive equivalents" ofthe carboxylic acid groups and/or hydroxyl groups are usually employed in the polymerization. Thus, for example, the hydroxyl groups on the bisphenol may be present as esters of alkyl carboxylic acids, particularly the lower carboxylic acids, and most preferably acetic acid. These esters may be formed beforehand, or in the same vessel used for the polymerization. A byproduct of such a polymerization is acetic acid. Alternatively, the carboxylic acids on the imide-containing dicarboxylic acids may be converted to aryl esters, particularly their phenyl esters, and then polymerized with the bisphenol. The byproduct of such a polymerization is phenol. Methods for the formation of aromatic esters are well known to the skilled artisan, who may alternatively employ other well-known techniques, such as the use of polymerization catalysts, for instance, potassium acetate.

In preferred poly(imide-esters) copolymers according to the present invention, the repeat units (I) and/or (II) above are about 50 to 100 mole percent of the polymer, more preferably about 100 mole percent. It is also preferred if only one of repeat units (I) or (II), not both, is present. In other preferred poly(imide- esters), only one of repeat units (IH), (IV) or (V) is present, and/or Z is the same in all repeat units. The polymers disclosed herein are isotropic as compared to anisotropic. By isotropic is meant that the properties of the polymers are essentially the same in any direction, and, in the absence of a shear field, the polymer has a random conformation. This can be determined by the so-called TOT test (or a variation thereof), which is described in U.S. Patent 4,188,372, which is hereby incorporated by reference in its entirety.

The poly(imide-esters) disclosed herein are useful as molding resins and in making films. They are particularly useful for making moldings which require good thermal resistance (glass transition temperatures of about 200°C) and chemical resistance. Such parts are useful in electronics and automobiles.

In the following examples, the glass transition temperatures (Tg) were measured by Differential Scanning Calorimetry (DSC) at a heating rate of 25°C/min, and the midpoint of the transition was taken as the Tg.

EXAMPLE 1 This example illustrates the preparation of a dicarboxylic acid containing two imide groups. Trimellitic anhydride (299.0 g, 1.556 moles) was dissolved in N,N-dimethylfoιmamide (DMF) (500 mL) in a 4-neck round-bottomed flask equipped with a Drierite® drying tower, mechanical stirrer, thermometer, reflux condenser and graduated addition funnel. The solution was heated to 50°C by a heating mantle. A solution of 4,4'-oxydianiline (150 g, 0.749 mole) in DMF (350 mL) was added dropwise over ca. 1 h to the anhydride solution via the addition funnel. The solution was heated to reflux for 3 h and then allowed to cool to room temperature. Methanol (1 L) was added to the reaction mixture (which usually crystallized after cooling to room temperature) and the product was recovered by filtration at reduced pressure. The yellow solid was stirred in boiling water (2 L) for several minutes, filtered under reduced pressure, and washed with methanol (1 L). The product, whose formula is shown below, was recovered (70% yield) as a yellow powder after drying at ca. 100°C under a nitrogen purge for 24 h. The product had a DSC melting point of 380°C, and no unreacted anhydride or partially reacted amic-acid was detected. O O U υ

o

EXAMPLE 2 This example illustrates the preparation of a dicarboxylic acid containing one imide group. Trimellitic anhydride (200 g), p-aminobenzoic acid (145 g) and 1 L of DMF were added to a 2 L four-necked round bottomed flask. A condenser, mechanical stirrer and thermometer were attached to the flask and the flask contents were stirred and heated by an electric heating mantle. After 4.5 h the solution was allowed to cool to room temperature. Then 1 L of methanol was added with stirring, which continued for 5 min. The mixture of solid and liquid was then filtered using a Buchner funnel, and the solid washed with 1 L of methanol. Two liters of distilled water were then heated to boiling in a 4 L beaker and the solid was added with stirring, which was continued for 5 min. This mixture was then filtered using a Buchner funnel, and the solid was washed with 1 L of methanol. The solid was dried in a vacuum oven with a nitrogen bleed at about 170°C for about 18 h. The product was as shown below.

EXAMPLE 3

This example illustrates the preparation of a poly(ester-imide) copolymer according to the present invention. A 3 L glass kettle which was heated by an electrically heated liquid metal bath was used as the polymerization vessel. The kettle contents were agitated by a Cole-Paimer® Servodyne Unit equipped with a 50: 1 gear reducer, a millivoltmeter which indicated relative torque, and a meter which indicated RPM. The agitator was a Hastalloy® paddle, which was mounted onto the kettle through a Teflon® bushing. At the top of the ketde was a 2.5 cm OD glass Vigreaux column and a water cooled condenser equipped witii a splitter to remove distillate. The kettle was also equipped with a nitrogen bleed valve so the kettle contents could be kept under an N₂ atmosphere. An additional nitrogen bleed valve was used during the vacuum part of the cycle to help control pressure. To the kettle was added 437.4 g (0.798 moles) of the dicarboxylic acid prepared in Example 1, 56.7 g (0.342 moles) of terephthalic acid, 157.4 g (1.14 moles) of 4-hydroxy benzoic acid, 260.2 g (1.14 moles) of 2,2-bis(4-hydroxy- phenyl)propane (Bisphenol A), and 359.5 g of acetic anhydride. The apparatus was closed, swept with nitrogen, and then lowered into the metal bath, which was at 170°C. The bath temperature was raised to 210°C and the agitator slowly started up to 5 rpm to help melt the contents. Refluxing started and the agitator speed was increased to 50 rpm. After refluxing 40 min to assure complete acetylation, takeoff of the byproduct acetic acid commenced. The bath set temperature was increased 20°C every 20 min until it reached 310°C. After 20 min at 310°C, the set temperature was raised to 340°C.

After greater than 93% of the theoretical amount of acetic acid had been removed, the column, condenser and splitter were removed, and a vacuum source which had means for measuring and controlling the pressure was attached. The pressure was lowered to 84 kPa, lowered to 67 kPA after 10 minutes, and subsequently reduced about 17 kPa every 10 min until 17 kPa (absolute) was reached. After another 10 min, the pressure was reduced to 6.7 kPa. The torque rose to 69 mv, at which point the stirrer speed was reduced to 30 rpm and the torque allowed to rise above 90 mv. The agitator was stopped, the kettle pressurized to atmospheric pressure with nitrogen, and removed from the metal bath. The system was dismantled and the hot soft polymer removed by cutting away with a shears or by using a putty knife. The kettle was then placed back into the hot metal bath and the sides scraped to remove as much polymer as possible. About 792 g of polymer (850 g theoretical) was recovered.

The polymer recovered was orange-brown and transparent, indicative of an amorphous isotropic resin. It had a Tg of 195°C.

EXAMPLE 4 This example illustrates the preparation of another poly(ester-imide) copolymer according to the present invention. The same apparatus used in Example 3 was used. Into the kettle was added 294.7 g (1.292 moles) of Bisphenol A, 401.8 g (1.291 moles) ofthe dicarboxylic acid made in Example 2, and 271.5 g of acetic anhydride. The apparatus was closed, swept with nitrogen, and then lowered into the metal bath, which was at 170°C. The bath temperature was raised to 210°C and the agitator slowly started up to 5 rpm to melt the contents. Refluxing started and the agitator speed was increased to 50 rpm. After refluxing 20 min to assure complete acetylation, takeoff of the byproduct acetic acid commenced, and the bath set point was raised to 230°C. As the bath temperature reached about 220°C the mixture became pasty. The stirrer was stopped and the bath set point raised consecutively to 250°C, 270°C, 290°C, and finally to 310°C. At 310°C the mixture became stirrable, so the stirrer was set to 30 rpm and the bath set point was raised again to 340°C to distill of the remaining acetic acid and keep the contents molten. As the bath temperature actually reached 330°C distillation began and the stirrer was set at 50 rpm.

After greater than 92% of the theoretical amount of acetic acid had been removed, the column, condenser and splitter were removed, and a vacuum source which had means for measuring and controlling the pressure was attached. The pressure was lowered to 84 kPa, the after 10 minutes lowered to 67 kPa, then reduced about 17 kPa every 10 min until 17 kPa (absolute) was reached. After another 10 min the pressure was reduced to 6.7 kPa, then 2.7 kPa after another 10 min, and finally to 133 Pa. The torque rose to 69 mv, at which point the stirrer speed was reduced to 30 rpm and the torque allowed to rise to 150 mv. The agitator was stopped, the kettle pressurized to atmospheric pressure with nitrogen, and removed from the metal bath. The system was dismantled and the soft polymer removed by cutting away with a shears or with a putty knife. The kettle was then placed back into the bath and the sides scraped to remove as much polymer as possible. About 609 g of polymer (650 g theoretical) was recovered. The polymer recovered was amber and transparent, indicative of an amorphous isotropic resin. It had a Tg of 207°C.

Claims

What is claimed is:

1. An isotropic poly(ester-imide) copolymer consisting essentially of repeat units of the formula:

(a) about 30 to 100 mole percent of

(D

(b) 0 to about 70 mole percent, total, of one or more of

(IH)

(IV), and

(V)

wherein Z is independently -O-, -C(=O)-, -S-, -SO₂-, or an alkylene or alkylidene containing 1 to 8 carbon atoms.—

2. The isotropic poly(imide-ester) copolymer as recited in Claim 1 wherein Z is independently -O-, -C(=O)-, -CH₂-, or -C(CH₃)₂-.

3. The isotropic poly(imide-ester) copolymer as recited in Qaim 1 wherein (a) is about 50 to 100 mole percent of said repeat units.

4. The isotropic poly(imide -ester) copolymer as recited in Qaim 1 wherein (a) is essentially 100 mole percent of said repeat units.

5. The isotropic poly(imide-ester) copolymer as recited in Qaim 1 wherein said alkylene is -CH₂- or -C(CH3)₂-.

6. The isotropic poly(imide-ester) copolymer as recited in Claim 1 wherein

Z is -C(CH₃)₂-.

7. The isotropic poly(imide-ester) copolymer as recited in Qaim 5 wherein Z is -C(CH₃)₂-.

8. The isotropic poly(imide-ester) copolymer as recited in Qaim 3 wherein Z is independently -O-, -C(=O)-, -CH₂-, or -C(CH₃)₂-.