JP2010229381A - Urethane modified epoxy resin, urethane modified epoxy resin cured product, process for production of urethane modified epoxy resin and process for production of urethane modified epoxy resin cured product - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a urethane modified epoxy resin and a cured product of the same excellent in heat resistance without causing increased viscosity and solidification caused by an increased molecular weight or decline of glass transition temperature (Tg). <P>SOLUTION: The urethane modified epoxy resin is produced in-situ by the reaction of a bisphenol S type epoxy resin with a polyol compound and a polyisocyanate compound in the bisphenol S type epoxy resin. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a urethane-modified epoxy resin, a urethane-modified epoxy resin cured product, a method for producing a urethane-modified epoxy resin, and a method for producing a urethane-modified epoxy resin cured product.

  Epoxy resins can be used in various applications because various curing agents can be used and various physical properties of the cured product can be brought out. In particular, the field utilizing high-performance adhesiveness, which is one of the basic characteristics of epoxy resins, occupies an industrially important position. Specific examples include electrical insulating materials (casting, impregnation, laminates, sealing materials), matrix resins of structural materials such as CFRP, sheet adhesives for honeycomb structures, structural adhesives, etc. it can.

  On the other hand, in Non-Patent Document 1, a polyisocyanate compound and a polyol compound are reacted to synthesize a urethane prepolymer having isocyanate groups at both ends, and then mixed with an epoxy resin, and the terminal isocyanate group in the urethane prepolymer and an epoxy are mixed. It is disclosed that a urethane-modified epoxy resin is produced by reacting with a hydroxyl group in a resin. According to such a urethane-modified epoxy resin, it is possible to improve the peel strength while maintaining the tensile shear force with respect to the above-described epoxy resin.

  However, since the urethane-modified epoxy resin is synthesized by reacting a urethane prepolymer and an epoxy resin, the molecular weight of the epoxy resin increases, resulting in thickening or solidification. It becomes difficult. For this reason, it is generally dissolved in an organic solvent and used as a varnish. For this reason, it is not suitable for use as an epoxy resin, an electrically insulating material, a matrix resin of a structural material such as CFRP, a sheet-like adhesive for a honeycomb structure, or a structural adhesive.

  Non-Patent Document 2 discloses an in-situ reaction of a polyisocyanate compound and a polyol compound in a liquid bisphenol A type epoxy resin, that is, a reaction between a polyisocyanate compound and a polyol compound in a bisphenol A type epoxy resin. It is disclosed to obtain a modified epoxy resin.

  However, the urethane-modified epoxy resin thus obtained has a problem that the glass transition temperature (Tg) of a cured product to be actually used is lowered, and heat resistance and reliability are insufficient. As a result, there has been a problem that it cannot be applied to the above structural materials that require heat resistance.

Tokisawa Makoto, Wakabayashi Nobuyoshi, Sato Shoichi; Journal of the Adhesion Society of Japan, 28, [3], 86-91 (1992) Yuya Sugiki, Eisuke Yamada, Shinji Inagaki; Proceedings of the 46th Annual Meeting of the Adhesion Society of Japan, p91-92 (2008)

  The present invention provides a urethane-modified epoxy resin excellent in heat resistance and a cured product thereof without causing thickening and solidification due to an increase in molecular weight, and without causing a decrease in glass transition temperature (Tg). With the goal.

  In order to achieve the above object, the present invention is characterized in that in the bisphenol S type epoxy resin, the bisphenol S type epoxy resin is reacted with a polyol compound and a polyisocyanate compound and produced in-situ. , Relates to urethane-modified epoxy resin.

  Further, in the present invention, in the bisphenol S-type epoxy resin, a polyol compound and a polyisocyanate compound are reacted with the bisphenol S-type epoxy resin to produce a urethane-modified epoxy resin in-situ and then cured. It is related with the urethane-modified epoxy resin hardened | cured material characterized by the above-mentioned.

  The inventors of the present invention have intensively studied to solve the above problems. As a result, it is surprising to react a polyol compound and a polyisocyanate compound in a bisphenol S-type epoxy resin to synthesize a urethane-modified epoxy resin, specifically, a urethane-modified bisphenol S-type epoxy resin in-situ. In addition, the inherent advantages of urethane-modified epoxy resins such as high peel strength and fracture toughness are lost without causing problems such as solidification due to high viscosity of the urethane-modified epoxy resin and a decrease in glass transition temperature (Tg) of the cured product. As a result, the inventors have found that the present invention has not been completed.

  Epoxy resins include bisphenol A type epoxy resin, bisphenol F type epoxy resin, bisphenol S type epoxy resin, dimer acid glycidyl ester type epoxy resin, polyalkylene ether type epoxy resin, phenol novolac type epoxy resin, orthocresol novolac type. Epoxy resin, biphenyl type epoxy resin, dicyclopentadiene type epoxy resin, naphthol type epoxy resin, naphthalene type epoxy resin, alicyclic epoxy resin, heterocyclic ring containing epoxy resin, diglycidyl epoxy resin, glycidyl amine type epoxy resin, etc. There are different types.

  Therefore, it is difficult to select the bisphenol A-type epoxy resin described in Non-Patent Document 2 as described above from a large number of the epoxy resins as described above and replace it with the bisphenol S-type epoxy resin of the present invention. In addition, as described above, when a bisphenol A type epoxy resin is used, the glass transition temperature (Tg) of the cured product is lowered. Therefore, even when the same series of bisphenol S type epoxy resins are used. It is thought that a similar phenomenon occurs. As a result, it is difficult for those skilled in the art to replace the bisphenol A type epoxy resin described in Non-Patent Document 2 with the bisphenol S type epoxy resin defined in the present invention.

  In the present invention, the reason why the glass transition temperature (Tg) of the cured urethane-modified epoxy resin is improved by reacting the polyol compound and the polyisocyanate compound in the bisphenol S-type epoxy resin and producing it in-situ. Is not clear, but can be thought of as follows.

As will be described in the following examples, solid ¹³ C-NMR of in-situ urethane-modified bisphenol S-type epoxy resin cured product was measured and attributed to urethane-bonded (—NH—CO—O—) carbon appearing at 157 ppm. When the relaxation time T ₁ was measured from the spectrum, it was found that the relaxation time T ₁ becomes longer as the in-situ urethane modification amount increases. Since T ₁ is a measure of molecular mobility, it indicates that as T ₁ increases, the molecular mobility decreases. Therefore, it is shown that the molecular mobility of the urethane bond of the in-situ urethane-modified bisphenol S-type epoxy resin cured product decreases as the amount of urethane modification increases. Since the urethane bond in polyurethane is a crystalline hard segment, the crystallinity increases in proportion to the amount of urethane modification, which decreases the molecular mobility of the urethane bond and increases the glass transition temperature (Tg). thinking.

  As described above, according to the present invention, a urethane-modified epoxy resin excellent in heat resistance without causing thickening and solidification due to an increase in molecular weight and without causing a decrease in glass transition temperature (Tg). And a cured product thereof.

It is an external view which shows the sample shape of a compact tension type for evaluating fracture toughness. It is a figure which shows the outline of the sample shape at the time of evaluating bending strength and a bending elastic modulus, and an evaluation aspect.

  Hereinafter, details of the present invention and other features and advantages will be described in detail based on embodiments.

  The urethane-modified epoxy resin and its cured product of the present invention are required to contain a bisphenol S type epoxy resin in the skeleton. The bisphenol S-type epoxy resin is not particularly limited as long as the target urethane-modified epoxy resin can be produced in-situ by reacting a polyol compound and an isocyanate compound described below in the resin. However, it is preferably liquid at normal temperature, and from this viewpoint, the epoxy equivalent is preferably 300 (g / eq) or less.

  By using such a liquid bisphenol S-type epoxy resin, a polyol compound and an isocyanate compound can be reacted in the absence of a solvent as described below. A separate solvent is prepared, and the reaction is carried out under such a solvent. There is no need to do it. Therefore, the reaction system for synthesizing the urethane-modified epoxy resin can be simplified, and the operation required for the reaction can be simplified. Further, since the target urethane-modified epoxy resin is not affected by a separately prepared solvent, heat resistance and the like can be further improved while maintaining high peel strength and fracture toughness.

  The lower limit of the epoxy equivalent is not particularly limited, but is preferably 165 (g / eq). When the lower limit of the epoxy equivalent is less than 165 (g / eq), the molecular weight of the finally obtained urethane-modified epoxy resin and its cured product is not sufficient, not only its heat resistance, but also peel strength and fracture toughness, etc. The original properties of the urethane-modified epoxy resin will deteriorate.

  As described above, by using a bisphenol S-type epoxy resin that is liquid at room temperature, the target urethane-modified epoxy resin is produced in-situ in the absence of a solvent as will be described below. be able to. In addition, normal temperature here means room temperature, for example, and specifically means about 25 ° C.

  Moreover, in order to synthesize the urethane-modified epoxy resin, the polyol compound to be reacted with the bisphenol S-type epoxy resin is preferably one having excellent compatibility with the epoxy resin, for example, a polyhydric alcohol such as ethylene glycol or glycerin, Polyether polyols obtained by ring-opening polyaddition of ethylene oxide or propylene oxide to polyhydric phenols such as bisphenol A, castor oil polyols obtained by esterifying castor oil with polyhydric alcohols such as ethylene glycol and glycerin, 1,3- Polyester polyols obtained by polycondensation of polyhydric alcohols such as pentanediol and polycarboxylic acids such as adipic acid, and epoxy polyols obtained by adding alkanolamines such as diisopropanolamine to epoxy resins such as bisphenol A type epoxy resins. , Dimer alcohols such as oleyl alcohol dimer, hydroxyl group-containing elastomers such as hydroxyl group-containing liquid polybutadiene, polyhydric alcohols such as 1,4-butanediol, adipic acid esters of 3-methyl-1,5-pentanediol, etc. Is mentioned.

  From the viewpoint of abundant molecular weight grade and low cost, it is preferable to use a polyether polyol obtained by polyaddition of propylene oxide to ethylene glycol or a polyhydric alcohol such as 1,4-butanediol.

  In addition, in order to synthesize the urethane-modified epoxy resin, the polyisocyanate to be reacted with the bisphenol S-type epoxy resin is preferably one having excellent compatibility with the epoxy resin, for example, toluene diisocyanate, trimethylolpropane adduct of toluene diisocyanate. , 4,4'-diphenylmethane diisocyanate (MDI), polymeric MDI, urethane prepolymers (polyol-modified MDI) obtained by reacting various polyols with MDI, etc. MDI is preferable from the viewpoint of low price and the like.

  In addition, inorganic fillers, such as calcium carbonate, talc, and titanium dioxide, can be used for the urethane-modified epoxy resin and its cured product as an extender and a reinforcing material, if necessary.

  The urethane-modified epoxy resin can be produced, for example, as follows. First, a bisphenol S-type epoxy resin is prepared, a polyol compound and a polyisocyanate compound are added to the resin, heated to 80 ° C. to 100 ° C. with stirring, and held for several hours to achieve the desired urethane modification. An epoxy resin is obtained. At this time, when the bisphenol S-type epoxy resin is in a liquid state, the reaction can be performed without a solvent. However, when the bisphenol S-type epoxy resin is a solid, an applicable solvent such as toluene is used.

  However, by using a liquid bisphenol S-type epoxy resin and performing the reaction in the absence of a solvent, it is not necessary to prepare a separate solvent and perform the reaction under such a solvent as described above. Therefore, the reaction system for synthesizing the urethane-modified epoxy resin can be simplified, and the operation required for the reaction can be simplified. Further, since the target urethane-modified epoxy resin is not affected by a separately prepared solvent, heat resistance and the like can be further improved while maintaining high peel strength and fracture toughness.

  In the synthesis process, a chain extender, a catalyst, or the like can be used as necessary. This catalyst is used for the purpose of sufficiently completing the formation of urethane bonds.

  In addition, when hardening the obtained urethane-modified epoxy resin, it can carry out by heating to the temperature of 80 to 160 degreeC, and hold | maintaining for several hours, for example. In addition, it can also be cured using an amino curing agent or the like. Examples of amino curing agents include polyalkylene polyamines, aminoethylpiperazines, metaxylene diamines, isophorone diamines, polyoxyalkylene diamines, reaction products of these amines with monomer acids and dimer acids, modified polyamines, and the like. Can do. Furthermore, a general-purpose curing accelerator such as an imidazole compound can be used as necessary.

  Next, the present invention will be specifically described based on examples. The evaluation method of the characteristics shown in the examples is as follows.

(1) Glass transition temperature (Tg) [° C.]: Peak temperature of the temperature dispersion loss tangent curve of the cured product measured using a dynamic viscoelasticity measuring device under conditions of a frequency of 1 Hz and a heating rate of 5 ° C./min. Derived from

(2) Fracture toughness [MN / m ^2/3 ]: The shape of the test piece was a compact tension type as shown in FIG. The pre-crack was introduced using a razor. The measurement was carried out by pulling both sides of the precrack at room temperature at a crosshead speed of 0.5 mm / min using a tensile tester, and the fracture toughness value K _IC was calculated from equation (1).
K _IC = (P _c / ca ^1/2 ) × F (1)
F = {(2 + b / a) × (0.866 + 4.64b ² / a ² + 14.72b ³ / a ³ -5.6b ⁴ / a ⁴ )} / (1-b / a) ^3/2
P _c : Load [kgf]
c: Test piece thickness [mm]

(3) T-type peel strength and shear strength: T-type peel strength was measured according to JIS K 6854, and shear strength was measured according to JIS K 6850. As the adherend, a steel plate (SPCC) that had been sufficiently degreased by immersion in toluene for a whole day and night was processed into the shape described in JIS. A urethane-modified epoxy resin composition synthesized by the method as described below was applied to this adherend, a 0.2 mm spacer was adhered, and a curing reaction as shown below was performed to prepare a test piece. The measurement was performed using a tensile tester at room temperature, and the crosshead speed was 50 mm / min for T-type peel strength and 5 mm / min for shear strength.

(4) Bending strength and flexural modulus: A plate-like cured product as shown in FIG. 2 was used for the test piece. The measurement was carried out by applying a load to the bending elastic jig at a crosshead speed of 1 mm / min at room temperature using a tensile tester. The distance between the fulcrums was 30 mm. The bending strength was calculated from the formula (2) using the maximum load Pc from the load-time curve. The flexural modulus was calculated from equation (3) using the initial slope m of the load-time curve.
σ _fb = (3PcLν / 2Wh ² ) × 9.80665 Equation (2)
σ _fb : Bending strength [MPa]
Pc: Maximum bending stress [kgf]
Lv: Distance between fulcrums [mm]
W: Specimen width [mm]
h: Test piece thickness [mm]
E _f = (Lν ³ /4Wh)×m×9.80665×10 ^-3 Formula (3)
E _f : Flexural modulus [GPa]
Lv: Distance between fulcrums [mm]
W: Specimen width [mm]
m: slope of load-time curve

(5) Viscosity: The viscosity after storing the urethane-modified epoxy resin composition synthesized by the method as described below at 60 ° C. for 2 hours was measured with a B-type viscometer.

(6) Relaxation time T ₁ of urethane-bonded carbon by solid ¹³ C-NMR: The cured product was cut into fine particles with a nipper and sealed in a zirconia sample tube having a diameter of 6 mm and a length of 21 mm. This was set in a solid state NMR apparatus (JNN-ECA400 manufactured by JEOL Ltd.), rotated at a rotation speed of 9 kHz, and ¹³ C (observation frequency: 100.5 MHz) -NMR measurement was performed at room temperature. Using the Torchia method, the relaxation time T ₁ of urethane-bonded carbon appearing at 157 ppm was measured.

(Synthesis example)
A 1000 ml four-necked separable flask equipped with a nitrogen gas inlet tube, a drying tube, and a stirrer was added to a bisphenol S-type liquid epoxy resin having an epoxy equivalent of 201 g / eq (TX-0710 manufactured by Toto Kasei Co., Ltd.) 207.2 g of abbreviated))) and 48.01 g of a bifunctional polyether polyol (P-2000 manufactured by ADEKA Co., Ltd. (hereinafter abbreviated as PPG2000)) having a hydroxyl value of 55.4 mgKOH / g as a polyol, respectively, at 80 ° C. for 2 hours After stirring, 11.9 g of a commercially available reagent, MDI, was added as a polyisocyanate, and the mixture was further stirred for 2 hours to synthesize a both-end isocyanate group urethane prepolymer. Next, 2.2 g of commercially available reagent 1,4-butanediol (hereinafter abbreviated as BD) was used as a chain extender, and di-n-butyltin dilaurate (hereinafter abbreviated as DBTDL) was used as a catalyst. After adding 0.1 g of a 20-fold diluted solution of tetrahydrofuran (hereinafter abbreviated as THF), the temperature was raised to 100 ° C., and the absorption spectrum of the isocyanate group (hereinafter abbreviated as NCO group) disappeared. This was confirmed by measurement and the synthesis of in-situ urethane-modified BPSEp was completed.

  At this time, the molar ratio of PPG2000 / MDI / BD was 1/2/1, and the urethane modification rate was 30 parts by weight with respect to 100 parts by weight of BPSEP. This urethane-modified BPSEp having a modification rate of 30 parts by weight is hereinafter abbreviated as in-situ urethane-modified BPSEp (30 phr).

  Next, after collecting 52 g and 78 g of the above-synthesized in-situ urethane-modified BPSEp (30 phr), add 80 g and 30 g of BPSep to each and stir and dilute them, thereby in-situ urethane-modified BPSEp (10 phr) and in-situ urethane modified BPSEp (20 phr) were prepared.

(Examples 1 to 3 and Comparative Example 1)
The in-situ urethane-modified BPSEp (10 phr), in-situ urethane-modified BPSEp (20 phr) and in-situ urethane-modified BPSEp (30 phr) synthesized in Synthesis Example 1 were used as curing agents with 3,5-diethyltoluene-2,4- Diamine (Etacure 100 manufactured by Albemarle Japan Co., Ltd. (hereinafter abbreviated as DETDA)), 2-ethyl-4-methylimidazole (Curesol 2E4MZ (hereinafter abbreviated as 2E4MZ) manufactured by Shikoku Chemicals Co., Ltd.) as a curing accelerator. Each was blended with the composition shown in Table 1 and stirred at 60 ° C. for 5 minutes or more using a Lamond stirrer and then vacuum degassed at 60 ° C. for 30 minutes or more.

  Next, the resin compositions shown in Table 1 are poured into the molds for the above characteristic tests (1), (2), and (4) preheated to 120 ° C., and the curing reaction is performed using a heated hydraulic press. To remove each mold and obtain each test piece.

  Subsequently, each resin composition shown in Table 1 was applied to each of the two adherend steels for the characteristic test (3) and bonded together, and then fixed with clips to perform a heat curing reaction. The curing conditions were 80 ° C / 2h + 120 ° C / 2h + 160 ° C / 1h + 180 ° C / 1h for all.

  When Comparative Example 1 that was not modified with in-situ urethane was compared as a blank, both the Tg and T-type peel strength improved as the amount of modified in-situ urethane increased. Fracture toughness was improved in Example 1 using in-situ urethane-modified BPSEp (10 phr) and decreased in Examples 2 and 3, but was within an acceptable range. Therefore, it was possible to achieve the intended purpose of improving the peel strength and fracture toughness without lowering the Tg. Further, the viscosity at 60 ° C. for 2 hours was higher in Example 1 than in Comparative Example 1, but was within an allowable range.

  In the examples, the relaxation time T1 of urethane-bonded carbon measured by solid state 13C-NMR increased with the amount of modification, indicating that the molecular mobility of urethane-bonded carbon decreased in inverse proportion to the amount of urethane modification, The decrease in molecular mobility confirmed the increase in glass transition temperature (Tg). This decrease in molecular mobility is believed to be due to an increase in crystalline urethane bonds.

  While the present invention has been described in detail based on the above specific examples, the present invention is not limited to the above specific examples, and various modifications and changes can be made without departing from the scope of the present invention.

Claims (9)

  A urethane-modified epoxy resin produced in-situ by reacting a polyol compound and a polyisocyanate compound with the bisphenol S-type epoxy resin in a bisphenol S-type epoxy resin.   The urethane-modified epoxy resin according to claim 1, wherein the bisphenol S-type epoxy resin has an epoxy equivalent of 300 (g / eq) and is liquid at normal temperature.   The polyol compound according to claim 1 or 2, wherein the polyol compound is at least one of a polyether polyol and 1,4-butanediol, and the polyisocyanate compound is 4,4'-diphenylmethane diisocyanate. Urethane modified epoxy resin.   In the bisphenol S-type epoxy resin, the bisphenol S-type epoxy resin is reacted with a polyol compound and a polyisocyanate compound to produce a urethane-modified epoxy resin in-situ, and then cured, Urethane-modified epoxy resin cured product. The urethane-modified epoxy resin cured product according to claim 4, wherein the bisphenol S-type epoxy resin has an epoxy equivalent of 300 (g / eq) and is liquid at normal temperature.   The polyol compound according to claim 4 or 5, wherein the polyol compound is at least one of a polyether polyol and 1,4-butanediol, and the polyisocyanate compound is 4,4'-diphenylmethane diisocyanate. Urethane-modified epoxy resin cured product.   The urethane-modified epoxy resin cured product according to any one of claims 4 to 6, wherein a relaxation time T1 of the urethane-bonded carbon measured by solid-state 13C-NMR is 20 seconds or more.   In the bisphenol S type epoxy resin, a polyol compound and a polyisocyanate compound are reacted with the bisphenol S type epoxy resin to produce a urethane modified epoxy resin in-situ. Production method.   A urethane characterized by reacting a polyol compound and a polyisocyanate compound with the bisphenol S-type epoxy resin in a bisphenol S-type epoxy resin to produce a urethane-modified epoxy resin in-situ and then curing. Manufacturing method of modified epoxy resin cured product.

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