Process for producing polyimide resin

Details Process for producing polyimide resin Process for producing polyimide resin

2002-04-04

2004-09-14

Hightower, P. Hampton (Department: 1711)

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

Synthetic resins

From carboxylic acid or derivative thereof

C528S125000, C528S126000, C528S128000, C528S170000, C528S171000, C528S172000, C528S173000, C528S174000, C528S176000, C528S185000, C528S188000, C528S220000, C528S228000, C528S350000

Reexamination Certificate

active

06790930

ABSTRACT:

TECHNICAL FED
The present invention relates to a method for producing polyimide resins. More particularly, the invention relates to a method for producing polyimide resins for forming polyimides by mixing material polymers for polyimides and drying this by heating under reduced pressure.
BACKGROUND ART
Among a variety of organic polymers, polyimides have been widely used in various fields ranging from the aerospace field to the electronic communications field because of their superior heat resistance.
Generally, a polyimide is obtained by reacting diamine with acid dianhydride in organic solvent to afford a polyamic acid, which is cyclopolymerized for imidization.
In the reaction of imidization of a polyamic acid, water is produced. Generally, to imidize while removing water, a method for azeotropic removal of produced water is used. For instance, JP 63-297427 discloses a method for forming polyimides by forming amide acid in an organic solvent such as N-methyl pyrrolidone, heating after adding an azeotropic solvent such as toluene or xylene to remove water azeotropically out of the reaction system. With the use of this method, however, it is impossible to keep a polyamic acid away from its hydrolysis by the produced water which exists in a solution. This makes it difficult to obtain high-molecular weight polyimides.
In another method, there is a method for chemically removing the produced water. More particularly, there is a method for adding a basic catalyst included in tertiary amines such as triethyl amine, pyridine, picoline (e.g. &bgr;-picoline), and isoquinoline, or a combination of a basic catalyst and an anhydride such as acetic anhydride. Water produced in the imidization is chemically removed by the reaction with acid anhydride. This method, however, requires a process for purification of a reaction mixture to remove the residue such as tertiary amines and acetic anhydrides out of the system.
When highly basic diamines, for instance, alicyclic diamines with basicity higher than aromatic diamines are used as a diamine monomer, a salt is produced by the neutralization reaction before forming a polyamic acid at the point that the alicyclic diamines are mixed with acid dianhydrides and precipitated. Since this salt is in a stable state, it is neither possible to form a polyamic acid by polymerization reaction nor to imidize polyamic acid by the reaction with a hydrating reagent. It was, therefore, difficult to obtain polyimides using alicyclic diamines.
A method for reacting acid dianhydrides and diisocyanates is used as a method to obtain polyimides without a step of producing an intermediate. This method usually requires heating at least 250° C. under ordinary pressure to complete imidization because of low reactivity of acid dianhydride and diisocyanate, eared with the case of using diamine and acid dianhydride. Consequently, the kinds of the usable organic solvents at the time of reaction are limited. There were problems that required synthesis of polyimides was not realized depending on the structure of diisocyanate and/or acid dianhydride which is a starting material because of poor solubility in a high-boiling organic solvent.
In order to solve the above-mentioned problems, the present invention provides a method for easily producing high-molecular weight polyimides at high yield.
DISCLOSURE OF THE INVENTION
A method for producing a polyimide resin according to the present invention comprises the processes for: (a) mixing material monomers for polyimides; and (b) drying the mixture by heating under reduced pressure after the process (a).
Another method for producing a polyimide resin according to the present invention comprises the processes for: (c) producing a polyamic acid by mixing an acid dianhydride and a diamine in an organic solvent and reacting between them, wherein the material monomers are an acid dianhydride and a diamine; and (d) drying the polyamic acid by heating under reduced pressure after the process (c).
In still another method for producing a polyimide resin according to the present invention, the process (d) may be a process for drying the polyamic acid by heating under reduced pressure until its imidization reaction is completed in the absence of an azeotropic solvent and/or a hydration condensing reagent.
A further method for producing a polyimide resin is to produce a salt in the process (a).
In a still further method for producing a polyimide resin, material monomers for polyimides may be an acid dianhydride and A diisocyanate in the process (a).
The may contain an organic solvent.
In the drying process, the ambient temperature may be adjusted within the range of 80° C. to 400° C., and/or the pressure may be adjusted within the range of 0.001×10
5
to 0.9×10
5
Pa and the pressure may be adjusted within the range of 0.001×10
5
to 0.6×10
5
Pa.
The drying process may include drying the polyamic acid by heating under reduced pressure until its imidization reaction is completed in the absence of the azeotropic solvent and/or the hydration condensing reagent.
The polyimide resin preferably has a glass transition temperature of 350° C. or lower and/or a weight-average molecular weight of 5,000 to 1,000,000.
The molecular weight of the polyimide formed in the process (d) is substantially identical with the theoretical molecular weight of the polyimide obtained from the weight-average molecular weight of the polyamic acid, or the molecular weight of the polyimide increases before the drying process.
The polyimide resin may be soluble in the organic solvent.
The acid dianhydride according to the present invention may include one kind or a combination of at least two kinds of combination selected from the acid dianhydride represented by the following formulae (1) to (3) in a proportion of not smaller than 10 mole % (wherein X is a divalent organic group, and Y and Z are each a single bond or a divalent organic group):
In the formula (1), X represents —C(CH
3
)
2
—, —C(CF
3
)
2
—, —CH
2
C(CH
3
)
2
CH
2
—, —(CH
2
)
q
— (q is an integer from 1 to 10) and may be a divalent organic group selected from the following I group (wherein T is any one of Cl, F, Br, CH
3
—, CH
3
O—):
In the formula (1), Z may be a divalent organic group selected from a single bond, —O—, —C(═O)—, —C(O)O—, and —SO
2
—.
In the formula (2), Y may be a divalent organic group selected from the group consisting of a single bond, —O—, —C(═O)—, or —SO
2
—.
The diamine according to the present invention may be an aliphatic diamine and/or an alicyclic diamine.
In addition, the diamine may contain at least one kind of diamine represented by the following formulae (4) and (5) in a proportion of not smaller than 10 mole % based on the total amount of diamine monomer:
(wherein R is independently selected from the group consisting of Cl, F, Br, a hydroxy group, a carboxy group, an alkyl group having 1 to 4 carbons, or an alkoxyl group, and A is an independent divalent organic group selected from a single bond, —C(CH
3
)
2
—, —(CH
2
)
p
— (p is an integer not smaller than 1), —C(CF
3
)
2
—, —O—, —S—, SO
2
—, —C(═O)—, —C(═O)O—, or —NHCO—, n=0, 1, and 2. j is an integer not smaller than 0.)
The diamine of the present invention may contain a combination of one kind or a combination of at least two kinds of diamines selected from the following formulae in a proportion of not smaller than 10 mole % based on the total amount of diamine monomers:
(wherein R
1
is Cl, F, Br or CH
3
— or CH
3
O—, R
2
is hydrogen, an alkyl group having 1 to 4 carbons or an alkoxy group having 1 to 4 carbons, and A is a divalent organic group selected from a single bond, —C(CH
3
)
2
—, —S—, —O—, —SO—, —SO
2
—, —C(═O)—, —C(═O)O—, and —(CH
2
) p— (p is an integer from 1 to 10), —C(CF
3
)
2
—, —C(═O)O—, —NHCO—. m=0, 1, and 2. n=1, 2. k is an integer of not smaller than 0).
The acid dianhydride may contain an ester acid dianhydride of the following formula (6) in a proportion of not smaller than 50 mole % based on the total amount of acid d

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