JP5798912B2 - Polyimide resin - Google Patents

Description

  The present invention relates to a polyimide resin in which stress relaxation hardly changes and is excellent in flexibility and durability.

Polyimide resins are generally highly elastic and stress relaxation is unlikely to change, so they are molded into various molded articles such as belts.
However, since the resin structure of the polyimide resin is rigid, the flexibility is low and the durability is poor. For example, a belt made of polyimide resin is easily subjected to bending fatigue at a bending portion such as a pulley, and is easily cracked or broken. Recently, with the downsizing and speeding up of equipment, many small-diameter pulleys are used, and the above-mentioned problems are remarkable.

  The present applicant has previously developed a polyimide resin as described in Patent Document 1 as a polyimide resin excellent in flexibility and durability. In this polyimide resin, urethane prepolymers with isocyanate groups at both molecular ends and diisocyanates are chain-extended with urea bonds with diamine compounds, and imide units are introduced into the urea bond with tetracarboxylic dianhydrides. It shows flexibility and durability by the urethane component derived from the urethane prepolymer. As the polyimide resin having such physical properties, those capable of efficiently introducing an imide unit into the main chain are desirable.

  On the other hand, the present applicant has developed an imide-modified elastomer as described in Patent Document 2 as an elastomer having an imide component. Although this imide-modified elastomer exhibits high strength by a continuous imide unit and flexibility by a urethane component, since it is an elastomer, it has not been possible to suppress changes in stress relaxation in the same manner as a polyimide resin.

JP 2008-106095 A JP 2008-101195 A

  The subject of this invention is providing the polyimide resin which can suppress the change of stress relaxation, is excellent in a softness | flexibility and durability, and is easy to manufacture.

［式中、Ｒ₁は、芳香族環または脂肪族環を含む２価の有機基を示す。Ｒ₂は、重量平均分子量１００〜１０，０００の２価の有機基を示す。Ｒ₃は、芳香族環、脂肪族環または脂肪族鎖を含む２価の有機基を示す。Ｒ₄は、４個以上の炭素を含む４価の有機基を示す。ｎは１〜１００の整数を示す。ｍは２〜１，０００の整数を示す。ｌは１〜１００の整数を示す。］で表されることを特徴とするポリイミド樹脂。
（２）ジイソシアナートとポリオールから得た分子両末端にイソシアナト基を有するウレタンプレポリマーと、ジアミン化合物とテトラカルボン酸二無水物から得た分子両末端にアミノ基を有するポリアミック酸プレポリマーと、を混合して反応させた後、前記ポリアミック酸プレポリマーをイミド化した共重合体である前記（１）記載のポリイミド樹脂。
（３）前記ウレタンプレポリマーおよび前記ポリアミック酸プレポリマーの割合が、重量比で、ウレタンプレポリマー：ポリアミック酸プレポリマー＝１：０．５〜９．５である前記（２）記載のポリイミド樹脂。
（４）イミド分率が３０〜９５重量％である前記（１）〜（３）のいずれかに記載のポリイミド樹脂。
（５）イミド分率が５５〜９５重量％である前記（１）〜（４）のいずれかに記載のポリイミド樹脂。
（６）前記（１）〜（５）のいずれかに記載のポリイミド樹脂からなる成形品。
（７）ベルトである前記（６）記載の成形品。 As a result of intensive studies to solve the above-described problems, the present inventors have found a solution means having the following configuration and have completed the present invention.
(1) General formula (I):

[Wherein, R ₁ represents a divalent organic group containing an aromatic ring or an aliphatic ring. R ₂ represents a divalent organic group having a weight average molecular weight of 100 to 10,000. R ₃ represents a divalent organic group containing an aromatic ring, an aliphatic ring or an aliphatic chain. R ₄ represents a tetravalent organic group containing 4 or more carbon atoms. n shows the integer of 1-100. m represents an integer of 2 to 1,000. l represents an integer of 1 to 100. ] The polyimide resin characterized by the above-mentioned.
(2) a urethane prepolymer having an isocyanate group at both molecular ends obtained from a diisocyanate and a polyol, a polyamic acid prepolymer having an amino group at both molecular ends obtained from a diamine compound and tetracarboxylic dianhydride, After mixing and reacting, the polyimide resin according to the above (1), which is a copolymer obtained by imidizing the polyamic acid prepolymer.
(3) The polyimide resin according to (2) above, wherein the urethane prepolymer and the polyamic acid prepolymer have a weight ratio of urethane prepolymer: polyamic acid prepolymer = 1: 0.5 to 9.5.
(4) The polyimide resin according to any one of (1) to (3), wherein the imide fraction is 30 to 95% by weight.
(5) The polyimide resin according to any one of (1) to (4), wherein the imide fraction is 55 to 95% by weight.
(6) A molded article comprising the polyimide resin according to any one of (1) to (5).
(7) The molded product according to (6), which is a belt.

  According to the present invention, it is possible to introduce two or more imide units that are efficiently continuous to the main chain, and therefore, the production is easy, and the introduced imide unit impairs the high elasticity derived from the imide component. There is an effect that the stress relaxation change can be suppressed and flexibility and durability can be improved by the urethane component introduced into the main chain.

  The polyimide resin of the present invention may be referred to as a polyimide resin represented by the above general formula (I) (hereinafter referred to as “polyimide resin (I)”) in which two or more imide units continuous in the main chain are introduced. .)

In the general formula (I), R ₁ represents a divalent organic group containing an aromatic ring or an aliphatic ring. For example, the urethane prepolymer (c) is combined with the polyol (b) according to the reaction process formula (A) described later. Examples of the diisocyanate (a) that can be formed include residues other than the isocyanato group (-NCO).

R ₂ represents a divalent organic group having a weight average molecular weight of 100 to 10,000, preferably 300 to 5,000. For example, the urethane prepolymer (c) together with the diisocyanate (a) according to the reaction process formula (A) In the polyol (b) capable of forming, a residue other than two hydroxyl groups (—OH) is exemplified.

R ₃ represents a divalent organic group containing an aromatic ring, an aliphatic ring, or an aliphatic chain. For example, according to the reaction process formula (B) described later, a polyamic acid prepolymer ( f) at least one diamine compound selected from an aromatic diamine compound having 6 to 27 carbon atoms, an aliphatic diamine compound having 6 to 24 carbon atoms and an alicyclic diamine compound having 6 to 24 carbon atoms (d) ) And the like other than the amino group (—NH ₂ ). The above-mentioned aliphatic chain includes one having 1 carbon.

R ₄ represents a tetravalent organic group containing 4 or more carbon atoms, and has, for example, 6 to 18 carbon atoms capable of forming a polyamic acid prepolymer (f) together with the diamine compound (d) according to the reaction process formula (B). Examples include a residue of at least one tetracarboxylic dianhydride (e) selected from an aromatic tetracarboxylic dianhydride and an alicyclic tetracarboxylic dianhydride having 4 to 6 carbon atoms.

  n represents an integer of 1 to 100, preferably 2 to 50. m represents an integer of 2 to 1,000, preferably 5 to 500. l represents an integer of 1 to 100, preferably 2 to 80.

  Polyimide resin (I) is a polyamic acid having an amino group at both molecular terminals obtained from a urethane prepolymer having an isocyanate group at both molecular terminals obtained from diisocyanate and polyol, and a diamine compound and tetracarboxylic dianhydride. After mixing and reacting with a prepolymer, a copolymer obtained by imidizing a polyamic acid prepolymer is preferable. The polyimide resin (I) can be produced through, for example, reaction process formulas (A) to (C) as shown below.

［式中、Ｒ₁，Ｒ₂，ｎは、上述したものと同じである。］ [Reaction process formula (A)]

[Wherein R ₁ , R ₂ and n are the same as described above. ]

(Synthesis of urethane prepolymer (c))
First, in accordance with the reaction process formula (A), a urethane prepolymer (c) having an isocyanate group at both molecular ends is obtained from the diisocyanate (a) and the polyol (b). The polyimide resin (I) can exhibit excellent flexibility and durability due to the urethane component derived from the urethane prepolymer (c).

  Examples of the diisocyanate (a) include 2,4-tolylene diisocyanate (TDI), 2,6-tolylene diisocyanate (TDI), 4,4′-diphenylmethane diisocyanate (MDI), polymeric MDI ( Cr.MDI), dianisidine diisocyanate (DADL), diphenyl ether diisocyanate (PEDI), pitirylene diisocyanate (TODI), naphthalene diisocyanate (NDI), hexamethylene diisocyanate (HMDI), isophorone diisocyanate Nart (IPDI), lysine diisocyanate methyl ester (LDI), metaxylylene diisocyanate (MXDI), 2,2,4-trimethylhexamethylene diisocyanate (TMDI), 2,4,4-trimethylhexamethylenedi Cyanate (TMDI), dimer acid diisocyanate (DDI), isopropylidenebis (4-cyclohexyl isocyanate) (IPCI), cyclohexylmethane diisocyanate (hydrogenated MDI), methylcyclohexane diisocyanate (hydrogenated TDI), TDI dimer (TT) etc. are mentioned, These may mix and use 1 type, or 2 or more types, It is preferable to use what was distilled under reduced pressure.

  Examples of the polyol (b) include polyether polyols such as polypropylene glycol (PPG), polyoxytetramethylene glycol (PTMG), and polymer polyols; polycarbonate polyols; polyesters such as adipate polyols (condensed polyester polyols) and polycaprolactone polyols Polybutadiene polyol; acrylic polyol and the like may be mentioned, and these may be used alone or in combination of two or more.

  The polyol (b) is preferably used after being dried under reduced pressure under conditions of 70 to 90 ° C., 1 to 5 mmHg, and 10 to 30 hours. Moreover, as a weight average molecular weight of a polyol (b), it is preferable that it is 100-10,000, and it is more preferable that it is 300-5,000. The weight average molecular weight is a value obtained by measuring the polyol (b) by gel permeation chromatography (GPC) and converting the obtained measurement value into polystyrene.

  The reaction is preferably carried out in an inert gas atmosphere such as argon gas or nitrogen gas after the diisocyanate (a) and the polyol (b) are mixed at a predetermined ratio. The mixing ratio (mole) of diisocyanate (a) to polyol (b) is preferably diisocyanate (a): polyol (b) = 1.01: 1 to 2: 1. The reaction temperature is suitably from room temperature (23 ° C.) to 90 ° C., and the reaction time is suitably from 1 hour to 5 hours.

  The reaction may be performed in a solvent or without a solvent. Examples of a solvent that can be used when the reaction is carried out in a solvent include N, N-dimethylacetamide, N-methyl-2-pyrrolidone (NMP), N-hexyl-2-pyrrolidone, and 1,3-dimethyl-2-imidazolidone. These may be used singly or in combination of two or more, and it is preferable to use a dehydrated one.

  As a weight average molecular weight of the urethane prepolymer (c) obtained, it is preferable that it is 300-50,000, and it is more preferable that it is 500-45,000. If the weight average molecular weight of the urethane prepolymer (c) is too small, the polyimide resin (I) becomes too hard, and the flexibility and durability may be reduced. Moreover, since the polyimide resin (I) becomes too soft when the weight average molecular weight of the urethane prepolymer (c) is too large, it may be difficult to suppress changes in stress relaxation. The weight average molecular weight is a value obtained by measuring the urethane prepolymer (c) by GPC and converting the obtained measurement value into polystyrene.

［式中、Ｒ₃，Ｒ₄，ｍは、上述したものと同じである。］ [Reaction process formula (B)]

[Wherein R ₃ , R ₄ and m are the same as described above. ]

(Synthesis of polyamic acid prepolymer (f))
Next, according to the reaction process formula (B), a polyamic acid prepolymer (f) having amino groups at both molecular ends is obtained from the diamine compound (d) and the tetracarboxylic dianhydride (e). When this polyamic acid prepolymer (f) is imidized, two or more continuous imide units are obtained. Since the polyimide resin (I) is imidized after reacting the polyamic acid prepolymer (f) with the urethane prepolymer (c) described above, two or more imide units continuous to the main chain are efficiently introduced. can do.

  Examples of the diamine compound (d) include 1,4-diaminobenzene (alias: p-phenylenediamine, abbreviation: PPD), 1,3-diaminobenzene (alias: m-phenylenediamine, abbreviation: MPD), 2,4. -Diaminotoluene (alias: 2,4-toluenediamine, abbreviation: 2,4-TDA), 4,4'-diaminodiphenylmethane (alias: 4,4'-methylenedianiline, abbreviation: MDA), 4,4 ' -Diaminodiphenyl ether (alias: 4,4'-oxydianiline, abbreviation: ODA, DPE), 3,4'-diaminodiphenyl ether (alias: 3,4'-oxydianiline, abbreviation: 3,4'-DPE) 3,3′-dimethyl-4,4′-diaminobiphenyl (also known as o-tolidine, abbreviation: TB), 2,2′-dimethyl-4,4′-diamino Phenyl (alias: m-tolidine, abbreviation: m-TB), 2,2'-bis (trifluoromethyl) -4,4'-diaminobiphenyl (abbreviation: TFMB), 3,7-diamino-dimethyldibenzothiophene- 5,5-dioxide (alias: o-tolidine sulfone, abbreviation: TSN), 4,4′-diaminobenzophenone, 3,3′-diaminobenzophenone, 4,4′-bis (4-aminophenyl) sulfide (alias: 4,4′-thiodianiline (abbreviation: ASD), 4,4′-diaminodiphenylsulfone (also known as 4,4′-sulfonyldianiline, abbreviation: ASN), 4,4′-diaminobenzanilide (abbreviation: DABA) 1, n-bis (4-aminophenoxy) alkane (n = 3,4,5, abbreviation: DAnMG), 1,3-bis (4-aminopheno) Ii) -2,2-dimethylpropane (abbreviation: DANPG), 1,2-bis [2- (4-aminophenoxy) ethoxy] ethane (abbreviation: DA3EG), 9,9-bis (4-aminophenyl) fluorene (Abbreviation: FDA), 5 (6) -amino-1- (4-aminomethyl) -1,3,3-trimethylindane, 1,4-bis (4-aminophenoxy) benzene (abbreviation: TPE-Q) 1,3-bis (4-aminophenoxy) benzene (alias: resorcinoxydianiline, abbreviation: TPE-R), 1,3-bis (3-aminophenoxy) benzene (abbreviation: APB), 4,4 ′ -Bis (4-aminophenoxy) biphenyl (abbreviation: BAPB), 4,4'-bis (3-aminophenoxy) biphenyl, 2,2-bis (4-aminophenoxyphenyl) propa (Abbreviation: BAPP), bis [4- (4-aminophenoxy) phenyl] sulfone (abbreviation: BAPS), bis [4- (3-aminophenoxy) phenyl] sulfone (abbreviation: BAPS-M), 2,2 -Bis [4- (4-aminophenoxy) phenyl] hexafluoropropane (abbreviation: HFBAPP), 3,3′-dicarboxy-4,4′-diaminodiphenylmethane (abbreviation: MBAA), 4,6-dihydroxy-1 , 3-phenylenediamine (also known as 4,6-diaminoresorcin), 3,3′-dihydroxy-4,4′-diaminobiphenyl (also known as 3,3′-dihydroxybenzidine, abbreviated as HAB), 3,3 ′ , 4,4′-tetraaminobiphenyl (also known as 3,3′-diaminobenzidine, abbreviated as TAB) and the like. 1,6-hexamethylenediamine (HMDA), 1,8-octamethylenediamine (OMDA), 1,9-nonamethylenediamine, 1,12-dodecamethylenediamine (DMDA), 1-amino-3- C6-C24 aliphatic or cycloaliphatic diamine compounds such as aminomethyl-3,5,5-trimethylcyclohexane (also known as isophoronediamine), 4,4'-dicyclohexylmethanediamine, cyclohexanediamine; Examples thereof include silicone diamine compounds such as bis (3-aminopropyl) -1,1,3,3-tetramethyldisiloxane, and these may be used alone or in combination of two or more.

  Examples of the tetracarboxylic dianhydride (e) include pyromellitic anhydride (PMDA), oxydiphthalic dianhydride (ODPA), biphenyl-3,4,3 ′, 4′-tetracarboxylic dianhydride (BPDA). ), Benzophenone-3,4,3 ′, 4′-tetracarboxylic dianhydride (BTDA), diphenylsulfone-3,4,3 ′, 4′-tetracarboxylic dianhydride (DSDA), 4,4 6 carbon atoms such as '-(2,2-hexafluoroisopropylidene) diphthalic dianhydride (6FDA), m (p) -terphenyl-3,4,3', 4'-tetracarboxylic dianhydride To 18 aromatic tetracarboxylic dianhydrides; cyclobutane-1,2,3,4-tetracarboxylic dianhydride, 1-carboxymethyl-2,3,5-cyclopentanetricarboxylic acid-2, : 3,5 dianhydride alicyclic tetracarboxylic dianhydride of 4-6 carbon atoms such as, and the like. These may be used alone or in combination.

  The reaction is preferably carried out in an inert gas atmosphere such as argon gas or nitrogen gas after the diamine compound (d) and the tetracarboxylic dianhydride (e) are mixed at a predetermined ratio. The mixing ratio (mole) of the diamine compound (d) to the tetracarboxylic dianhydride (e) is such that the diamine compound (d): tetracarboxylic dianhydride (e) = 1.01: 1 to 2: 1. It is preferable to do this. The reaction temperature is suitably from room temperature (23 ° C.) to 90 ° C., and the reaction time is suitably from 1 hour to 5 hours. The reaction may be performed in a solvent or without a solvent. Examples of the solvent that can be used when the reaction is carried out under a solvent include the same solvents as those exemplified in the reaction process formula (A).

  The weight average molecular weight of the resulting polyamic acid prepolymer (f) is preferably 10,000 to 1,000,000, and more preferably 20,000 to 500,000. If the weight average molecular weight of the polyamic acid prepolymer (f) is too small, the polyimide resin (I) becomes too soft and it may be difficult to suppress changes in stress relaxation. Further, if the weight average molecular weight of the polyamic acid prepolymer (f) is too large, the polyimide resin (I) becomes too hard, and the flexibility and durability may be reduced. The weight average molecular weight is a value obtained by measuring the polyamic acid prepolymer (f) by GPC and converting the obtained measurement value into polystyrene.

［式中、Ｒ₁〜Ｒ₄，ｎ，ｍ，ｌは、上述したものと同じである。］ [Reaction process formula (C)]

[Wherein R _{1 to} R ₄ , n, m, and l are the same as those described above. ]

(Synthesis of polyimide resin (I))
Finally, the urethane prepolymer (c) and the polyamic acid prepolymer (f) are mixed and reacted to thereby react with the polyurethane amic acid (hereinafter referred to as “PUA”) which is a precursor of the polyimide resin (I). .) (G) is obtained, and the resulting PUA (g) is imidized to obtain a polyimide resin (I).

  The reaction of the urethane prepolymer (c) and the polyamic acid prepolymer (f) may be performed either in a solvent or without a solvent. When the reaction is performed in a solvent, the urethane prepolymer (c) and the polyamic acid prepolymer (f) are added to the solvent in a predetermined ratio and mixed, and the reaction is performed under an inert gas atmosphere such as argon gas or nitrogen gas. It is preferable to carry out the reaction.

The mixing ratio of the urethane prepolymer (c) and the polyamic acid prepolymer (f) is a weight ratio in terms of solid content, and the urethane prepolymer (c): polyamic acid prepolymer (f) = 1: 0.5-9. Is preferably in the range of .5. Moreover, it is preferable to mix the urethane prepolymer (c) and the polyamic acid prepolymer (f) so that the NCO / NH ₂ ratio is about 1.0. Thereby, the ratio of the imide component in polyimide resin (I) can be raised moderately, As a result, the change of stress relaxation can be suppressed, maintaining a softness | flexibility and obtaining high durability.

  Examples of the solvent that can be used include the same solvents as those exemplified in the reaction process formula (A). As reaction temperature, it is preferable that it is 100-300 degreeC, It is more preferable that it is 135-200 degreeC, It is further more preferable that it is 140-160 degreeC. The reaction time is suitably about 1 hour to 10 hours.

  The imidation (dehydration condensation reaction) of PUA (g) may be performed under the condition that PUA (g) is not thermally decomposed. The reaction temperature is about 150 to 250 ° C., and the reaction time is about 90 to 150 minutes. Is appropriate. Prior to imidization, the solvent may be volatilized by heat-treating PUA (g) under conditions of about 70 to 200 ° C. and about 20 minutes to 3 hours.

  On the other hand, when the reaction is carried out in the absence of a solvent, since it can be carried out in an extruder equipped with a heating means having an exhaust system in addition to a normal stirred tank reactor, the resulting polyimide resin (I) It can be extruded and formed into a film or sheet as it is.

  The weight average molecular weight of the polyimide resin (I) is preferably 10,000 to 1,000,000, more preferably 15,000 to 150,000, and 20,000 to 100,000. Is more preferable. If the weight average molecular weight of the polyimide resin (I) is too small, it is difficult to suppress changes in stress relaxation, which is not preferable. Moreover, when the weight average molecular weight of polyimide resin (I) is too large, there exists a possibility that a softness | flexibility and durability may fall. The weight average molecular weight is a value derived from a value obtained by measuring PUA (g) by GPC and converting the obtained measurement value into polystyrene. The reason why PUA (g), not polyimide resin (I), is measured by GPC is that polyimide resin (I) is insoluble in the GPC measurement solvent.

  The ratio of the imide component in the polyimide resin (I), that is, the imide fraction, is preferably 30 to 95% by weight, and more preferably 55 to 95% by weight. If the imide fraction is too small, it is difficult to suppress changes in stress relaxation, which is not preferable. Further, if the imide fraction is too large, flexibility and durability may be reduced.

  The imide fraction is a value calculated from the charged amounts of the urethane prepolymer (c) and the polyamic acid prepolymer (f), and is a value calculated from the following formula (α).

  The elastic modulus of the polyimide resin (I) is preferably 0.1 to 2.5 GPa, more preferably 1 to 2 GPa. If the elastic modulus is too small, it is difficult to suppress changes in stress relaxation, which is not preferable. Further, if the elastic modulus is too large, flexibility and durability may be reduced. The elastic modulus can be adjusted to a desired value by adjusting the imide fraction described above. As will be described later, the elastic modulus is a value calculated from a stress at an elongation rate of 1% in a predetermined tensile test.

  The polyimide resin (I) described above can be used after being molded into a desired molded product. Molded products include, for example, sheets, films, tubes, hoses, roll gears, diaphragms, packing materials, soundproof materials, vibration proof materials, boots, gaskets, belts, belt laminate products, coating materials, pervaporation separation membranes, optics Non-linear materials, elastic fibers, piezoelectric elements, actuators, other various automobile parts, industrial machine parts, sporting goods and the like can be mentioned.

  Among the exemplified molded articles, a belt will be described. Examples of the belt include a transport belt such as a food transport belt and a substrate transport belt; a drive belt; a suction (perforated) belt and the like. When the polyimide resin (I) is molded into the above-described molded product, it is preferable that the polyimide resin (I) is imidized after being molded in the state of PUA (g) for efficient molding. As a specific example, if a solution containing PUA (g) is subjected to centrifugal molding and imidized, a seamless belt without a core made of polyimide resin (I) can be obtained. In addition, polyimide resin (I) is not limited to the illustrated use, It can use suitably in the field | area where the change suppression of stress relaxation, a softness | flexibility, and durability are requested | required.

  EXAMPLES Hereinafter, although a synthesis example and an Example are given and this invention is demonstrated in detail, this invention is not limited only to the following synthesis examples and Examples.

The polyimide resins used in the following examples are the following four types.
<Synthesis Example 1>
A polyimide resin (1) was synthesized according to the reaction process formulas (A) to (C) described above.
(Synthesis of urethane prepolymer)
First, 4,4′-diphenylmethane diisocyanate (MDI) [manufactured by Nippon Polyurethane Industry Co., Ltd.] was distilled under reduced pressure. Also, polyoxytetramethylene glycol (PTMG) (i) [trade name “PTMG1000” manufactured by Hodogaya Chemical Co., Ltd., weight average molecular weight: 1,000] under the conditions of 80 ° C., 2-3 mmHg, 24 hours. It was dried under reduced pressure.

  Next, 10.13 g of MDI described above and 20.24 g of PTMG were respectively added to a 500 ml four-necked separable flask equipped with a stirrer and a gas introduction tube, and stirred at 80 ° C. for 2 hours under an argon atmosphere. A urethane prepolymer having an isocyanato group at both ends was obtained. As a result of measuring the obtained urethane prepolymer by GPC, the weight average molecular weight was 15,000 in terms of polystyrene.

(Synthesis of polyamic acid prepolymer)
9.75 g of 4,4′-diaminodiphenylmethane (MDA) and 6.31 g of pyromellitic anhydride (PMDA) were respectively added to a 500 ml four-necked separable flask equipped with a stirrer and a gas introduction tube, and an argon atmosphere was added. Under stirring at 80 ° C. for 2 hours, a polyamic acid prepolymer having amino groups at both molecular ends was obtained.

(Synthesis of polyimide resin (1))
30 g of urethane prepolymer and polyamic so that the mixing ratio of the obtained urethane prepolymer and polyamic acid prepolymer is urethane prepolymer: polyamic acid prepolymer 1: 0.54 by weight ratio in terms of solid content. 16 g of acid prepolymer was added to each 500 ml four-necked separable flask equipped with a stirrer and a gas introduction tube, and 200 ml of dehydrated N-methyl-2-pyrrolidone (NMP) was further added.

Next, it stirred at 150 degreeC under argon gas atmosphere for 2 hours, and obtained the solution containing PUA. The obtained PUA solution was poured into a mold of a centrifugal molding machine and subjected to centrifugal molding under conditions of a mold temperature of 120 ° C. and a rotation speed of 300 rpm for 2 hours to obtain a PUA sheet. This PUA sheet is heated at 200 ° C. for 2 hours in a vacuum desiccator together with the mold (dehydration condensation reaction), whereby n in the general formula (I) is 1 to 100, m is 2 to 1,000, and l is A polyimide resin (1) of 1 to 100 was obtained as a seamless belt without a core and having a circumferential length of 300 mm and a thickness of 100 μm. The obtained polyimide resin (1), a result of measuring the IR spectrum at ATR method, 1780 cm ^-1, absorption derived from the imide ring to 1720 cm ^-1 and 1380 cm ^-1 were observed.

<Synthesis Example 2>
First, a urethane prepolymer having a weight average molecular weight of 15,000 was obtained in the same manner as in Synthesis Example 1 except that MDI was changed to 5.53 g and PTMG was changed to 11.06 g.

  Next, a polyamic acid prepolymer was obtained in the same manner as in Synthesis Example 1 except that MDA was changed to 13.13 g and PMDA was changed to 12.06 g.

  16. The urethane prepolymer was 16. so that the mixing ratio of the obtained urethane prepolymer and the polyamic acid prepolymer was urethane prepolymer: polyamic acid prepolymer = 1: 1.5 by weight ratio in terms of solid content. A solution containing PUA was obtained in the same manner as in Synthesis Example 1 except that 59 g and the polyamic acid prepolymer were changed to 25.2 g.

Then, in the same manner as in Synthesis Example 1, a PUA sheet was obtained from this PUA solution, and a polyimide resin (2) was obtained from this PUA sheet as a seamless belt without a core and having a peripheral length of 300 mm and a thickness of 100 μm. The obtained polyimide resin (2), a result of measuring the IR spectrum at ATR method, 1780 cm ^-1, absorption derived from the imide ring to 1720 cm ^-1 and 1380 cm ^-1 were observed.

<Synthesis Example 3>
First, a urethane prepolymer having a weight average molecular weight of 15,000 was obtained in the same manner as in Synthesis Example 1 except that MDI was 4.4 g and PTMG was 8.7 g.

  Next, a polyamic acid prepolymer was obtained in the same manner as in Synthesis Example 1 except that MDA was changed to 26.4 g and PMDA was changed to 27.1 g.

  13.1 g of urethane prepolymer so that the mixing ratio of the obtained urethane prepolymer and polyamic acid prepolymer is urethane prepolymer: polyamic acid prepolymer = 1: 4 in terms of weight ratio in terms of solid content. A solution containing PUA was obtained in the same manner as in Synthesis Example 1 except that the polyamic acid prepolymer was changed to 53.5 g.

And it carried out similarly to the synthesis example 1, and obtained the PUA sheet | seat from this PUA solution, and obtained the polyimide resin (3) from this PUA sheet | seat as a seamless belt with a peripheral length of 300 mm and thickness of 100 micrometers. The obtained polyimide resin (3), a result of measuring an IR spectrum by ATR method, 1780 cm ^-1, absorption derived from the imide ring to 1720 cm ^-1 and 1380 cm ^-1 were observed.

<Synthesis Example 4>
First, a urethane prepolymer having a weight average molecular weight of 15,000 was obtained in the same manner as in Synthesis Example 1, except that MDI was 1.7 g and PTMG was 3.3 g.

  Next, a polyamic acid prepolymer was obtained in the same manner as in Synthesis Example 1 except that MDA was changed to 22.6 g and PMDA was changed to 24.1 g.

  5 g of urethane prepolymer and polyamic acid were used so that the mixing ratio of the obtained urethane prepolymer and polyamic acid prepolymer was urethane prepolymer: polyamic acid prepolymer = 1: 9 in terms of weight ratio in terms of solid content. A solution containing PUA was obtained in the same manner as in Synthesis Example 1 except that the prepolymer was changed to 46.7 g.

And it carried out similarly to the synthesis example 1, and obtained the PUA sheet | seat from this PUA solution, and obtained the polyimide resin (4) from this PUA sheet | seat as a seamless belt with the circumference of 300 mm and thickness of 100 micrometers without a core. The obtained polyimide resin (4), a result of measuring the IR spectrum at ATR method, 1780 cm ^-1, absorption derived from the imide ring to 1720 cm ^-1 and 1380 cm ^-1 were observed.

[Examples 1 to 4]
About the polyimide resin (1)-(4) obtained by the synthesis examples 1-4 mentioned above, the weight average molecular weight, the imide fraction, the elasticity modulus, the stress relaxation retention rate, and durability were evaluated. Each evaluation method is shown below, and the results are shown in Table 1.

(Weight average molecular weight)
The PUA solution was measured by GPC, and the obtained measurement value was derived from the value in terms of polystyrene.

(Imide fraction)
It calculated from the formula (α) described above.

(Elastic modulus)
A No. 3 dumbbell test piece is punched out of a seamless belt made of polyimide resins (1) to (4), and using an autograph “AGS-G” manufactured by Shimadzu Corporation, under conditions of 20 mm between marked lines and a pulling speed of 50 mm / min. A tensile test was performed, and the elastic modulus was calculated from the stress at an elongation rate of 1%.

(Stress relaxation retention)
First, a seamless belt made of polyimide resins (1) to (4) was processed into a belt shape having a width of 10 mm and a circumferential length of 300 mm to obtain a test belt. Next, the initial stress (S1) when this test belt was set between two-shaft pulleys and stretched by 0.5% was measured by a load cell. Next, this test belt was run at a running speed of 300 m / min with the stretched state 0.5%, and the stress (S2) after running for 200 hours was measured with a load cell. The initial stress (S1) and the stress after running for 200 hours (S2) were applied to the formula: (S2 / S1) × 100 to calculate the stress relaxation retention rate (%).

(durability)
First, a seamless belt made of polyimide resins (1) to (4) was processed into a belt shape having a width of 10 mm and a circumferential length of 300 mm to obtain a test belt. Next, this test belt was set between two-shaft pulleys, and was run under conditions of a running speed of 300 m / min with the stretched 0.5%, and durability was evaluated from the number of revolutions until belt breakage. Judgment criteria were set as follows.
◎: 5 × 10 ⁷ rotations or more ○: 1 × 10 ⁷ rotations or more and less than 5 × 10 ⁷ rotations △: 5 × 10 ⁶ rotations or more and less than 1 × 10 ⁷ rotations X: Less than 5 × 10 ⁶ rotations

[Comparative Example 1]
A PUA sheet is obtained in the same manner as in Synthesis Example 1 except that the product name “U-Varnish-A” manufactured by Ube Industries, Ltd. is used as the PUA solution, and the polyimide resin is removed from the PUA sheet without the core. A seamless belt having a circumference of 300 mm and a thickness of 100 μm was obtained.

  About the obtained polyimide resin, it carried out similarly to Examples 1-4, and evaluated the weight average molecular weight, the imide fraction, the elasticity modulus, the stress relaxation retention, and durability. The results are shown in Table 1.

  As is apparent from Table 1, Examples 1 to 4 are excellent in stress relaxation retention and excellent in durability. On the other hand, Comparative Example 1, which is a general polyimide resin, showed an inferior durability although it was excellent in stress relaxation retention.

Claims (4)

A urethane prepolymer having an isocyanate group at both molecular ends obtained from diisocyanate and polyol, and a polyamic acid prepolymer having an amino group at both molecular ends obtained from a diamine compound and tetracarboxylic dianhydride are mixed. Is a copolymer imidized with the polyamic acid prepolymer,
The imide fraction is 55 to 95% by weight,
While the elastic modulus is 1 to 2 GPa,
Formula (I):

[Wherein, R ₁ represents a divalent organic group containing an aromatic ring or an aliphatic ring. R ₂ represents a divalent organic group having a weight average molecular weight of 100 to 10,000. R ₃ represents a divalent organic group containing an aromatic ring, an aliphatic ring or an aliphatic chain. R ₄ represents a tetravalent organic group containing 4 or more carbon atoms. n shows the integer of 1-100. m represents an integer of 2 to 1,000. l represents an integer of 1 to 100. ] The polyimide resin characterized by the above-mentioned. The proportion of the urethane prepolymer and the polyamic acid prepolymer, by weight, the urethane prepolymer polyamic acid prepolymer = 1: 0.5 to 9.5 in a claim 1, wherein the polyimide resin. Molded article comprising a polyimide resin according to claim 1 or 2. The molded article according to claim 3, which is a belt.