DE2223819A1 - Composite body made from melt-fusible linear polyimides of 2,2-bis- (3,4-dicarboxyphenyl) -hexafluoropropane dianhydride - Google Patents

Description

Composite body made of linear polyimides of 2,2-bis ~ (3,4-dicarboxyphenyl) -hexafluoropropane dianhydride that can be melted in the melt

The invention relates to composite structures with a laminar structure and a manufacturing method therefor. It relates in particular to composite structures of melt-fusible ones aromatic linear polyimides and a production method therefor.

Polyimides are known polymeric materials, for example, they are described in U.S. Patents 3,179,631, 3,179,634, and 3,356 described. Certain melt processable polyimides are also described in US Pat. No. 3,234,181. As described in the aforementioned patents, the polyimides are obtained by treating certain tetracarboxylic acid dianhydrides reacts with certain di-primary diamines, so-

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that polyamic acids are obtained as intermediates which are converted into the corresponding polyimides in a suitable manner, for example by chemical treatment or by heat treatment. The polyimides thus obtained are generally difficult to process materials; however, US Pat. No. 3,234,181 discloses that melt-processable polyimides can be obtained from special letracarboxylic acid dianhydrides and special primary diamines. hexafluoropropane dianhydride derived, and which are characterized by a G-read transition temperature between about 22O ⁰ C and about 385 ⁰ C, aRT such polyimides are not disclosed by the prior. are by completely surprising and unexpected properties, such as by fusibility in of the melt ("melt fusibility").

The object of the present invention is therefore to create shaped structures with a preferably laminar structure special polymeric polyimide material that has unique and unexpected properties.

According to the invention, a composite structure is created that has a Reinforcing agent and a melt-fusible aromatic linear polymeric polyimide material to the following repeating structural unit on v / eist:

NO-

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AD-4536-B «3 22.238 » 9

in which R means one of the following radicals:

or

where R 'is a divalent bridging radical: -0-, -S-? or "0-R" -0-, where R "is a divalent aromatic radical, such as phenylene, and η is a number which is so large that a polymer with an inherent viscosity of at least about 0.15, preferably of at least about 0.30, measured as a solution of the polymer in sulfuric acid of 3O ⁰ Gj, and the polyamide has a glass transition temperature between about 220 ⁰ C and about 385 ° C,

A preferred embodiment of the present invention comprises a molded structure of laminar construction comprising a plurality of layers of the above-mentioned composite structure Has. This type of structure is suitable for high-temperature applications, for example for building boards or for Manufacture of parts to be used at high temperature. The composite structures of the present invention have excellent physical properties.

The composite structures of the present invention are characterized by a reinforcing agent. To those in the composite structure reinforcing agents used include fibers such as carbon fibers, glass fibers, boron fibers, metal fibers, etc. and particulate filler materials, such as asbestos, mica, graphite, silicon carbide whiskers, fluorocarbon resins, such as polytetrafluoroethylene, etc. The reinforcement

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Medium is used in amounts up to about 70 vol .- ^, preferably 40 to 60 vol .- $, based on the total volume of the composite structure, used in composite structures made by compression molding.

The composite structure of the present invention is further characterized by an aromatic I which can be melted in the melt linear polymeric polyimide material characterized with the following repeating structural unit:

,NO

wherein R represents one of the following radicals:

or

wherein R ^{1 is} a divalent bridging radical: -0-, -S- or. -O-R '' - Ο-, where R "is a divalerite aromatic radical, such as phenyls, and η is a number which is so large that a polymer with an inherent viscosity of at least about 0.15» preferably at least about 0.30, measured as a solution of the polymer in sulfuric acid at 30 ⁰ C, is formed, wherein the Polyiraid has a glass transition temperature between about 220 ⁰ C and 385 ⁰ C.

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The polyimide described above is obtained by reaction of 2,2-bis (3,4-dicarboxyphenyl) hexafluoropropane dianhydride the formula: ■ - '

with at least one aromatic primary diamine of the formula;

and'

wherein R ^{1 is} a divalent bridging group: -0-, -S- or -0-R "-0-, wherein R" is phenylene, in a suitable solvent at a temperature below about 75 ⁰ O, whereby as an intermediate one Polyamic acid obtained. Thereafter, the polyamic acid is converted into

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the corresponding polyimide is converted, this conversion treatment For example, it may consist of adding a chemical converting agent such as acetic anhydride to the reaction system, which causes the polyamic acid to form the imide bonds characteristic of the polyimide described above cyclized.

The 2,2-bis- (3,4-dicarboxyphenyl) hexafluoropropane dianhydride used in the process described above can be made according to US Pat. No. 3,310,573.

Suitable aromatic primary diamines of the above formula include:

4,4'-diamino-diphenyl ether, (ODA); 4,4'-diamino-diphenyl sulfide, (EDA) j 1,3-bis ~ [4-arainophenoxy] benzene, (EBA); 1,4-bis [4-aminophenoxy] benzene,

and any of the above diamines in combination with one another or in combination with m-phenylenediamine; p-phenylenediamine; 1,5-Diauiinonaphthalin “The diamines can in themselves be produced in a known manner.

In the present invention, a modified method for implementing the 2 _; 2 «bis ~ (3,4« ~ oicarbo3typhenyl) -hexafluoropropane dianhydride with the masin or the mixture of diamines used, which ex * s for the production of a binder solution with at least one of the diamino defined above in a suitable solvent, preferably in a highly polar solvent, such as, for example, J, H-Dimethylacet.amid, H, U ~ diru3thylforiflamid, N-methyl pyrrolidone, etc. In the preparation of the .Oindmittel solution looked like a wish-

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vert highlighted at least one of the dianhydride rings with React water or alcohol beforehand before adding the diamine in order to increase the viscosity of the binder solution so far lessen that you get a good-wetting of the reinforcing Easer achieved when the latter is passed through the binder solution.

The composite structures described above can be made by combining the reinforcing agent and the precursor of the above polyimide to form an intermediate structure which can then be treated to convert the precursor to the polyimide. For example, “prepregs” (= pre-impregnated structures) can be produced from carbon fibers by passing carbon fibers through a binder solution and then aligning the “wetted” lasers, arranged side by side}. The structure obtained is preferably partially cured or partially converted into the polyimide by the application of heat, which is done, for example, by ^{directing an air stream of about 150 °} C. thereon in order to increase the viscosity of the binder solution and thereby fix the fibers. The “prepreg” can be cured by heating in an oven at about at least 200 ^° C., preferably at 200 to 400 ^° C., in the course of a suitable period of time, for example in half an hour to 25 hours.

Laminate structures can be made from the cured "prepregs" described above by stacking "prepregs" into a stack of at least several layers, which are then pressed together using a suitable pressure of, for example, 7.03 to 352 kg / cm ² (100 to 5000 psi ) at temperatures between about 275 ° C and 525 ⁰ C for a suitable time, for example, be from 1 minute to 60 minutes, pressed. The laminate is then left under pressure to a temperature below the glass transition temperature of the polyimide of the laminate

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cool, then ^ it is taken out of the press,

The following examples are intended to explain the invention further. but without restricting them. All in the following Examples of parts and percentages given represent parts by weight and percentages by weight, respectively, if nothing other is indicated. . '

The polymers produced in the following examples and the shaped structures produced therefrom were according to the assessed using the following procedure:

INHERENT VISCOSITY: The inherent viscosity of the polymer samples is obtained by measuring the viscosity of the polymer solution and the solvent, it is after calculated using the following equation:

Viscosity of the poly

a ... -,. -L. τ -O.-U ι merisate solution natural logarithm '

Viscosity of the inherent solvent. "

Viscosity ~ ■ -—— ~

where C is the concentration, expressed in grams of polymer per 100 ml of solution. The polymer solution is obtained by dissolving 0.5 g of the polymeric polyimide in an initial amount of solvent of less than 100 ml at 30 ^° C. and then adjusting the total solution to 100 ml by adding further solvent at 30 ^° C. The solvents used are either Pyridine or sulfuric acid, which is given here along with the inherent viscosity values. It is known that the inherent viscosity and the molecular weight of the polymer are related to each other »

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GLASS ENVIRONMENTAL TEMPERATURE, Tg: The glass transition temperature the polymer samples are obtained either by differential scanning calorimetry ("differential scanning calorimetry") or differential thermal analysis techniques at 30 ° C / min. under use a DuPont Model 900 DTA Analyzer. The glass transition temperature is used as the intersection of the intersecting tangent lines at the first turning point of the heating curve of the polymer defined, ■

ia HOHIiIAUMVOLUIiE] J: The volume percentage of voids in the composite structure is calculated as follows: -

T. The weight percentage of polymeric resin is first made calculated from a Kjeldahl nitrogen analysis of the composite structure;

2. The percentage by volume of polymeric resin in the composite is calculated from the following relationship:

^{Percentage by} volume _ weight * ~ * ^resin _x density of the offset resin ~ density of the resin body

3. The volume percentage of reinforcing agent (RA) in the composite is calculated from the following relationship:

Volume percent RA - ^ ± ^ t _x

Density of RA

4. Finally, the volume percentage of voids in the composite is calculated:

Volume percent voids = 100 - (volume percent resin

+ Volume percent RA)

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BENDING MODULE AND BENDING STRENGTH: According to ASTM-D-790 when applied a span to depth ratio between 30: 1 and 50: 1 and a crosshead speed of 0.5 cm / min. (0.20 inches / min).

IZOD IMPACT STRENGTH: According to ASTMtD-256.

FLOW INDEX UNDER PRESSURE: A 1 g sample of polyimide polymer, sized to pass through a 0.84 mm (20 mesh - U.S. Sieve Size) sieve one on a piece of aluminum foil, which is coated with a dry film lubricant Graphokote No.220, so that it

2 2
covered an area of 4.13 cm (0.64 in.). Another piece of aluminum foil, also coated with the dry film lubricant Graphokote No.220, is placed over the polyimide and the whole assembly is placed between two steel plates in a press and subjected to a force of 2270 kg (which is a pressure of 548 kg / cm (7800 psi), based on the initial cross-sectional area of the polyimide) and held for 5 minutes at a temperature of 375 ^° C., unless otherwise stated. The press is then cooled and the polyimide polymer is removed. The pressure flow index is calculated as follows:

Area at the end of the experiment

Pressure Ilast index = ——— "-" "" TTT

initial flat

HORIZONTAL SHORT BEAM SHEAS STRENGTH: This test is performed in accordance with ASTM-2344 performed using a ratio of span. to depth

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of 5: 1 and a crosshead speed of 0.5 cm / min. (0.2 inch / min) applies, -

I ¹ EFFICIENCY EQUIPMENT a) EIi: The strength properties, such as tensile strength, tensile modulus and elongation, are measured in accordance with ASTM-D 1708. · ■ · -

example 1

To a 1 liter resin flask equipped with a mechanical stirrer, nitrogen purge and thermometer are added 111 g (0.25 mol) of 2,2-bis- (3,4-hiicarboxyphenyl) -hexafluoropropane dianhydride, 323 ml of dimethylformamide and 29 , 2 ml (0.5 mol) of absolute ethyl alcohol. The dianhydride goes into solution quickly. The resin flask is then immersed in a heated oil bath to about 110 ⁰ C. After about 10 minutes of stirring, the contents of the flask reaches 100 ⁰ C and is kept at this temperature for a further hour to allow the complete reaction of the dianhydride is ensured with the alcohol. The solution is then cooled to room temperature with a wet ice bath and. a dry powder mixture of 25 g (0.125 mol) 4,4'-oxydianiline and 13.5 g (0.125 mol) m-phenylenediamine is added and washed with 23 ml of dimethylformamide. Due to the exothermic reaction, the temperature is 10 to 20 ^° C. The solution is stirred for at least 20 minutes so that complete equilibration is ensured. The binder solution so prepared has a pesticide concentration of 30 (based on cured polyimide solids).

"Prepregs" oriented in one direction are produced by carbon fiber roving with a high modulus is passed through the binder solution and then the moist, impregnated one

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Wraps yarn on a flat rotating mandrel. A machine steered yarn guide is used to lay the strands side by side with minimal overlap. Between 6 and 12 layers can be applied, depending on the type of yarn used and the thickness required for the finished, shaped laminate. Hot air heat guns are used to partially cure the polyimide binder applied to the fibers as the mandrel rotates. The purpose of this is to increase the viscosity of the binder and thereby fix it and to prevent dripping from the fibers during winding. The still located on the mandrel "prepreg" is brought into a vacuum oven at room temperature and heated under vacuum at a nitrogen purge at 200 ° to 210 ⁰ C in the course of a period of 2 hours. The sample is a further hour »heated at this temperature for then is post-cured by heating in a forced air oven at 300-310 ⁰ C 160 min.

A sample of the cured "prepreg" is cut with a saw and mm in a molding frame of about 3 _f 18 (0.125 inch) thickness down. This results in an even pressure for all parts of the compact. During the compression molding operation, the sample is placed in the hot press and held at contact pressure for 1 to 2 minutes. Then it becomes full

Pressure applied (about 176 kg / cm (2500 psi)) maintained for 20 minutes and 2 * Then, the press under pressure to a temperature below the glass transition temperature is, that is 28O ⁰ C cooled, and the laminate of the frame removed. The resulting flat laminate is then machined to take the appropriate shape. The polyimide of this example has a glass transition temperature of about 280 ⁰ C and a pressure flow index of 13,

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Examples 2-5

The method described in Example 1 is used to prepare the binder solutions from the dianhydride and the diamines given in Table I below; the properties of the polyimide of these solutions are also listed in Table I. The binder solution is hardened by heating the binder solution in an open dish from room temperature to 20O ⁰ C over a period of 2 1/2 hours in a vacuum oven, holding it for 1 hour at 200 ° C and then in an air circulation oven at 300 ⁰ C post-treated for 1 hour. -

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at
game 2 TiiBJBECE I mole
Ethanol '
.per mole
Dianhydric Inherent fflasum-
Viscosity wall
lung
i temp.,
⁰ C 290 Pressure-
Puddle
.index Roentgen-
diffractive
Results - 3 283 4th 2 0.64 368 5 ' amorphous O 5 Characterization of the binder solutions 2 0.67 321-325 ' 6th • KIM (O
co β? « Dianhydride diamine ■ HM 0.38. 3 amorphous αϊ
O ' OM = 1 . ■ 0.34 ' 7th • BIM ο MPD = 61 ■ ODA 2,2-bis- (3,4-dicarboxyphenyl) hexafIttorpropane dianhydride PPD s 61 ODA / MED
(1: 1) 4,4 '-diajaino-diphenyl ether 1.5 s
-ND 6P 1,5-.ND m-phenylenediamine 6Γ PPD p-phenylenediamine 1,5-diaminonaphthalene

CaJ OO

"B e i s.p i e 1 e-. 6-12

The method of preparation described in Example 1 is used of "prepregs" and laminate structures from the binder solutions and the reinforcing fibers listed in Table II below. The conditions of compression molding and the Laminate properties are also included in Table II.

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Case- binder ^{game l0} ' ^s ^ g *

TABLE II Unidirectional laminates

Properties of the laminate

Kr. At- mol % mol

play phthalic acid nol anhydride mol

Dianhydride

Reinforcement conditions of the P-orm-

kungspressens .

fibers pre-time pressure temp. ^ ¹ * Z <* rf $ ^ie g? "Siege- horizontal- under _{k &} / _C m ² o _Q ⁶ ^ strength- modul shear strength-

he

hit bridge

10

11 ** 12th

3 4th

O O O O

O
6th
O

2 2

2 2

Carbon***

Glass

Carbon***

carbon

carbon

Min.

■ MM

1 1

Min.

MMMM

6 6 6

(psi) spaces

190
(2700) 375 57 2.5 176
(2500) 375 65 3.1 281
(4000) 380 72 <2 176
(2500) 375 41 <2

W.
(psi)

7.03
(100)

X1 (T ^O , kg / cm '

1.69 (24)

speed.

6,176 (2,500)

6,176 (2,500)

6 (2500) 37-44 <2
<2

34-43 <2

8.93-9.28 1.97

(127-132) (28)

15.8 0.59

(225). (8.4)

5.77-6.47 1.20

(82-92) (17)

6.54-7.1 1.27

(93-101) (18)

6.82-7.31 1.41 0.26-0.295

(97-104) (20) (3.7-4.2)

5.77-6.61 1.05-1 ^ 4 0.534-0.626

(82-94) 05-19) (7.6-8.9)

* $ 30 pesticide binder solution

** Binder solution of Example 11 modified by using the specified amounts of phthalic anhydride and alcohol

*** Graphitic carbon high modulus piping

0.436 (6.2)

0.56 (8.0)

0.977 (13.9) ₍

0.485-0.555 (6.9-7.9)

0.541-0.612 (7.7-8.7)

N) Ca) OO

Claims (11)

May 16, 1972 CASE: AD-4536-B E.I. DU PONT- DE EEMOUES AND COMPANY PATENT CLAIMS: 1. Composite structure, characterized by a reinforcing agent and a melt-fusible aromatic linear polymeric polyimide material having the following repeating structural unit: NO wherein R represents one of the following radicals: ~ 17 - 209850/1201 AD-4536-B or - where E ^{1 is} a divalent bridging radical: -0-, -S- or -0-R "-0-, where R" is phenylene and η is a number which is so large that a polymer with an inherent viscosity of at least about 0.15, measured as a solution of the polymer in sulfuric acid at 30 ⁰ C, is produced, and the polyimide has a glass transition temperature between about 22O ⁰ C and about 385 ⁰ C. 2. composite structure according to claim 1, characterized in that the reinforcing agent up to about 70 vol .- $ des Structure " 3 »composite structure according to claim 1, characterized in that that the reinforcing agent consists of fibers. 4. composite structure according to claim 3, characterized in that that the fibers are carbon fibers, glass fibers or metal fibers «, 5. composite structure according to claim 4ι characterized in that that the pasers make up to about 70 yoles of the structure. 6, composite structure according to claim 1 with a laminar structure, characterized by a plurality of layers bonded together. α ':, IAi. «W-ν- ν - ... -»; - .. v- ^; -> ■ - ... ■■■■ ■■ - 18 - 209850/1201 AD-4536-B * 3 7. composite structure according to claim 6, characterized in that that! fibers represent the reinforcing agent. 8. composite structure according to claim 7 »characterized in that that the fibers are carbon fibers, glass fibers or metal fibers ·. 9. composite structure according to claim 8, characterized in that that the pasers make up to about 70 vol. ~ $ of the structure. - 10. A method for producing composite structures from a reinforcing agent and an aromatic linear polyimide fusible in the melt, characterized in that the reinforcing agent is brought into contact with a binder solution of a precursor of the polyimide and then the reinforcing agent is heated ^{to a temperature of at least 200 ° C} , 11. The method according to claim 10, characterized in that fibers are used as a reinforcing agent and the coated fibers are aligned in a juxtaposed arrangement and then ^{preheated to about 150 0} G, so that pre-impregnated structures ("prepregs") are formed and then a large number of these " Prepregs "are connected to one another at a temperature above about 200 ^{0 C, so.} that a laminar structure is created. - 19th 209850/1201 CiRIGINAL IMSPSCTED