KR100346078B1 - Rubber-polysulfone copolymer as toughener and the preparation thereof, and epoxy resin containing the copolymer - Google Patents

Abstract

The present invention relates to a rubber-polysulfone copolymer useful as a toughening agent, a method for preparing the same, and an epoxy resin composition containing the same, wherein the carboxyl-terminated poly (butadiene co-acrylonitrile) (CTBN) and poly The toughening agents of the present invention, copolymerized with amine-terminated poly (arylene ether sulfone) (PES-NH ₂ ) as sulfone components, provide improved toughness with excellent thermal stability, mechanical properties and corrosion resistance when used in epoxy resin compositions. can do.

Description

RUBBER-POLYSULFONE COPOLYMER AS TOUGHENER AND THE PREPARATION THEREOF, AND EPOXY RESIN CONTAINING THE COPOLYMER}

The present invention relates to a rubber-polysulfone copolymer as a toughening agent, a preparation method thereof, and an epoxy resin composition containing the same as a toughening agent, and specifically, a carboxyl-terminated poly (butadiene co-acrylonitrile) ( CTBN) and a copolymer of amine-terminated poly (arylene ether sulfone) (PES-NH ₂ ), a thermoplastic polymer, a method for preparing the same, and including the same as a toughening agent, thereby improving the toughness without reducing thermal stability, mechanical properties and corrosion resistance. An epoxy resin composition improved to an optimum level.

Epoxy resins generally have excellent thermal stability, dimensional stability, elastic modulus and mechanical properties, and thus are widely used as high performance adhesives and composite materials for aircraft materials or the electrical and electronics industries.

However, epoxy resins themselves are too brittle and are somewhat limited in their scope of application. Thus, rubber components such as carboxyl-terminated poly (butadiene co-acrylonitrile) (CTBN), amine-terminated poly (butadiene co-acrylonitrile) (ATBN to improve the fracture toughness of epoxy resins ), Inorganic hard particles (e.g. aluminum trihydrate, glass beads), and high performance thermoplastic polymers (e.g. polyethersulfone (PES), polyetherimide (PEI), polyetherketone (PEK), polyphenylene oxide ( Research into introducing PPO)) and the like as an additive of an epoxy resin has been conducted.

However, the rubber additive improves the toughness of the epoxy resin, but has a low glass transition temperature, thereby limiting the use of the epoxy resin at high temperatures and causing a decrease in mechanical properties. In addition, high-performance thermoplastic polymer additives improve the thermal stability and mechanical properties of epoxy resins, but they are less robust than rubber additives, are difficult to dissolve due to their high molecular weight, and do not form chemical bonds with epoxy resins. have.

Accordingly, the present inventors conducted intensive studies, and added a copolymer synthesized by copolymerizing CTBN, a commercial liquid rubber, and PES-NH ₂ , a high performance thermoplastic polymer having high glass transition temperature and excellent mechanical properties, to the epoxy resin as a toughening agent. The present invention has been accomplished by discovering that an epoxy resin composition having improved toughness to an optimal level can be produced without reducing thermal stability, mechanical properties and corrosion resistance.

It is an object of the present invention to provide novel rubber-polysulfone copolymers and methods for their preparation that can be usefully used as toughening agents.

It is another object of the present invention to provide an epoxy resin composition containing the rubber-polysulfone copolymer, wherein the toughness is improved to an optimum level without a decrease in thermal stability, mechanical properties and corrosion resistance.

1 and 2 show carboxyl-terminated poly (butadiene co-acrylonitrile) (CTBN), amine-terminated poly (arylene ether sulfone) (PES-NH ₂ ) and CTBN according to the invention, respectively. a graph showing the GPC and FT-IR measurements of the copolymer of PES-NH _2,

3 is compared to the CTBN, PES-NH _2, CTBN and blend and thermal analysis (TGA) results of the CTBN and the epoxy resin containing 20% by weight of the copolymer of PES-NH ₂ The composition according to the present invention of the PES-NH ₂ Is a graph

4A to 4D show SEM images of fracture surfaces of specimens made of an epoxy resin composition containing 10, 20, 30, and 40 wt% of a copolymer of CTBN and PES-NH ₂ prepared according to the present invention, respectively.

In order to achieve the above object, the present invention provides a copolymer of Formula 1 useful as a toughening agent:

Where

BN is Where 0 <x <1, y = 1-x, and m is an integer of 1 or more;

PES Where n is an integer greater than or equal to 1.

Also, in the present invention, (a) a carboxyl-terminated poly (butadiene co-acrylonitrile) (CTBN) of formula (2) is dicyclohexylcarbodiimide (DCC) of formula (3) and N- of formula (4) After reacting with hydroxysuccinimide (NHS) to obtain a compound of formula (5), (b) the obtained compound of formula (5) is amine-terminated poly (arylene ether sulfone) of formula (6) (PES-NH ₂ The present invention provides a process for preparing a copolymer of formula (I) comprising reacting:

Where

BN is Where 0 <x <1, y = 1-x, and m is an integer of 1 or more;

PES Where n is an integer greater than or equal to 1.

In addition, the present invention provides an epoxy resin composition containing the copolymer of Formula 1 as a toughening agent.

Hereinafter, the present invention will be described in more detail.

According to the present invention, a toughening agent capable of imparting excellent toughness to an epoxy resin may be prepared by copolymerizing CTBN, which is a commercial liquid rubber, and PES-NH ₂ , which is a high performance thermoplastic polymer having high glass transition temperature and excellent mechanical properties.

The target molecular weight of the triblock copolymer of Chemical Formula 1 according to the present invention is 15,000 to 20,000 g / mol, experimental measurement molecular weight is 17,000 to 23,100 g / mol, mainly by changing the molecular weight of PES-NH ₂ molecular weight of the copolymer Adjust E.g., 5,500 g / mol PES-NH 2 with a 3,200 g / mol using CTBN, and 5,500 or 8,000 g / mol PES-NH ₂ of the - to _{5,500 g / mol PES-NH 2} - 3,200 g / mol CTBN can be synthesized in a 8,000 g / mol PES-NH ₂ molecular weight 20,000 g / mol consisting of a copolymer composed of a molecular weight 15,000 g / mol of copolymer or a _{8,000 g / mol PES-NH 2} - 3,200 g / mol CTBN.

According to the present invention, in the preparation of these copolymers using CTBN and PES-NH ₂ , since the terminal COOH functional group of CTBN has low reactivity with amine, the terminal of CTBN is activated to activate the amine as shown in Scheme 1 below. It should increase the responsiveness to.

Where

BN is Where 0 <x <1, y = 1-x, and m is an integer of 1 or more;

PES Where n is an integer greater than or equal to 1.

Specifically, first, the CTBN of Chemical Formula 2 is reacted with dicyclohexylcarbodiimide (DCC) of Chemical Formula 3 and N-hydroxysuccinimide (NHS) of Chemical Formula 4 to produce a compound of Chemical Formula 5. In this case, DCC and NHS may be used in amounts of 2 to 4 mol and 4 to 8 mol with respect to 1 mol of CTBN, and for 1 to 2 hours in an organic solvent such as CH ₂ Cl ₂ under low temperature of about 0 ° C. React.

Subsequently, the obtained compound of Formula 5 is reacted with PES-NH ₂ of Formula 6 to obtain a copolymer of Formula 1. In this case, PES-NH ₂ may be used in an amount of 2 moles per 1 mole of CTBN, and reacted for 10 to 14 hours in an organic solvent such as CH ₂ Cl ₂ under normal temperature conditions. In this step, the N, N-dicyclohexylurea (DCU) of Formula 7 is produced as a by-product together with the copolymer of Formula 1, followed by repeated filtration and drying of the product, DCU, and unreacted DCC. And NHS can be completely removed to recover the desired copolymer.

The copolymer of Formula 1 produced according to the present invention can be added to the epoxy resin composition in 5 to 40% by weight when used as a toughening agent, homogeneous epoxy resin composition containing a toughening agent by dissolving at 120 to 140 ℃ after addition Can be obtained.

The epoxy resin composition according to the present invention may be molded into a cured epoxy resin composition by adding a curing agent such as p-dichlorodiphenylsulfone (p-DDS) to the mold and curing in a conventional manner.

Epoxy resin composition prepared according to the present invention is excellent in thermal stability, mechanical properties and corrosion resistance as well as toughness can be used as materials and adhesives for aerospace, automotive industry and electrical, electronics industry.

Hereinafter, the present invention will be described in more detail based on the following examples. However, the following examples are only for illustrating the present invention, and the scope of the present invention is not limited thereto.

Example 1 Synthesis of Copolymer

A commercially available Hycar CTBN1300 × 13 (AN (acrylonitrile) = 26%) having a molecular weight of 3,200 g / mol was obtained, and PES-NH ₂ having a molecular weight of 5,500 and 8,000 g / mol was synthesized. Used for preparation.

A three-necked flask was equipped with a stirrer, a thermometer, and a nitrogen inlet tube, and a flame was added to the reactor using a Bunsen burner to remove moisture remaining in the reactor under a nitrogen atmosphere. The reactor was left in an ice container cooled to 0 ° C. in advance, and CTBN was dissolved in CH ₂ Cl _{2 and placed} in the reactor. Subsequently, DCC and NHS corresponding to 4 and 8 times the number of moles of CTBN usage were dissolved in CH ₂ Cl ₂ under a temperature condition of 0 ° C. and added to the reactor.

After 1 hour of reaction, when colloidal white precipitates were generated, PES-NH ₂ corresponding to 2 times the number of moles of CTBN was dissolved in CH ₂ Cl ₂ and added to the reactor. The reaction was carried out at room temperature for 12 hours, and the resultant brown viscous solution was filtered and then precipitated in a methanol / water (3: 1) mixed solution. The precipitate was filtered and dried first at room temperature and then dried at 80 ° C. in a vacuum oven. Warmed slowly to 2 nd drying. This recovery process was performed once more to remove by-products DCU, and unreacted DCC and NHS, and to recover the fully dried copolymer powder.

The recovered copolymer powder was analyzed through thermal analysis (DSC and TGA), end group analysis, molecular weight measurement, viscosity measurement, GPC and FT-IR, and the results are shown in Table 1 and FIGS. 1 and 2 below. .

As can be seen from Table 1, the resulting copolymer has two glass transition temperatures (Tg) as one of typical properties of the block copolymer, and in terms of thermal stability, rubber (CTBN) and polysulfone (PES-NH ₂ ) The intermediate nature of each pyrolysis curve is shown. In addition, the results of the GPC measurement, as shown in Figure 1, the curve of the single peak of the copolymer is eluted earlier than in the case of rubber (CTBN) and polysulfone (PES-NH ₂ ), respectively, the molecular weight through the reaction It can be seen that this increased copolymer was produced. In addition, FT-IR measurement results, Fig. C = O peak at 1,650 cm ^-1 a wide range of the OH peak (2,800 to 3,000 cm ^-1) of the terminal functional groups of the CTBN COOH is not being shown in the amide bond as shown in It can be seen in. These analysis results confirm that the copolymer of CTBN and PES-NH ₂ was successfully synthesized.

Target molecular weight [Mn] Terminal group Measured molecular weight [Mn] ¹ Viscosity [η] (dl / g) ² Glass transition temperature (Tg) (℃) ³ Thermal decomposition temperature (Td) (℃) ⁴ Copolymer 15,000 NH ₂ 17,072 0.17 -24, 160 423 20,000 NH ₂ 23,037 0.20 -34, 165 413 PES-NH ₂ 5,500 NH ₂ 5,929 0.17 167 447 8,000 NH ₂ 8,822 0.19 174 481 CTBN - COOH 3,200 0.17 -36 330 Auto-titrator, metrohm 2. Viscosity measured at 25 ° C. in CHCl ₃ ; Glass transition temperature by DSC (secondary heating in DSC-2910, N ₂ ) 4. Pyrolysis temperature by TGA (TGA-2950, 5 wt% loss in air)

Example 2 Preparation of Epoxy Resin Composition

In Example 1, the copolymer prepared from PES-NH ₂ having a molecular weight of 5,929 g / mol was added to 5, 10, 15, 20, 25, 30, 35, and 40% by weight in an epoxy resin (Epikote 828). Each added. The mixture was heated to 130 ° C. to completely dissolve the copolymer in an epoxy resin, and then, 1 mole of p-DDS was added per 2 moles of epoxy resin as a curing agent and dissolved to prepare an epoxy resin composition.

In addition, the epoxy resin composition which does not contain the said copolymer was produced, and it was set as the control.

Comparative Example 1

Only the high molecular weight 3,200 g / mol commercially available Haika CTBN1300 × 13 was added to the epoxy resin (Epikote 828) at 5, 10, 15, 20, 25, 30, 35 and 40% by weight, respectively. An epoxy resin composition was prepared in the same manner as in Example 2.

Comparative Example 2

PES-NH ₂ having a molecular weight of 5,929 g / mol was synthesized and added to the epoxy resin (Epikote 828) at 5, 10, 15, 20, 25, 30, 35 and 40% by weight, respectively. An epoxy resin composition was prepared in the same manner.

Comparative Example 3

Commercially available Haika CTBN1300 × 13 with a molecular weight of 3,200 g / mol and PES-NH ₂ with a molecular weight of 5,929 g / mol were simply mixed to form their blends (CTBN: PES = 1: 2). The resulting blend of CTBN and PES was added to the epoxy resin (Epikote 828) at 5, 10, 15, 20, 25, 30, 35 and 40% by weight, respectively, in the same manner as in Example 2 The composition was prepared.

Physical property analysis of the composition

The compositions prepared in Examples 2 and Comparative Examples 1 to 3 were poured into a preheated silicone rubber mold, and then cured by treatment at 130 ° C. for 5 hours, and at 220 ° C. for 2 hours. toughness, K _IC ), flexural test (mechanical characteristics), thermal analysis (TGA) and solvent resistance (corrosion resistance) measurement to analyze the physical properties of the epoxy resin composition.

Toughness: The resin composition was molded into single-edge-notched bending (SENB) specimens. Prior to testing, SENB specimens were preliminarily smoothed with sandpaper to form a square (3 × 6 × 40 mm), and then sharp initial gaps were formed in the specimens using razor blades soaked in liquid nitrogen in the previously dug grooves. The toughness was measured at 12.5 mm / min using Instron 5567 according to ASTM D-5045. The tenacity of ten specimens was measured to obtain an average value, and the results are shown in Table 2 below.

Mechanical properties: The resin composition was molded into SENB specimens (60 × 10 × 3 mm) and flexural tests were performed. The flexural test was carried out at a speed of 1.2 mm / min according to ASTM D-790, and the average value was obtained by measuring the flexural strength and flexural modulus of the ten specimens and the results are shown in Table 3 below.

Thermal Analysis: An epoxy resin composition containing 20 wt% of the toughening agent was analyzed by a thermal analyzer (TGA, 10 ° C./min in air), and the results are shown in FIG. 3.

Corrosion resistance: In order to confirm the progress of chemical bonding between the toughening agent component and the epoxy resin, the cured epoxy resin was added to a solvent of CHCl ₃ at 25 ° C. to measure the resistance to the solvent, and the results are shown in Table 4 below. It was.

Toughness Test Results (Unit: MPa · m ^1/2 ) weight% Example 2 Comparative Example 1 Comparative Example 2 Comparative Example 3 0 (control) 0.59 ± 0.02 5 0.87 ± 0.02 0.85 ± 0.03 0.71 ± 0.02 0.91 ± 0.02 10 1.03 ± 0.04 0.92 ± 0.01 0.85 ± 0.05 1.00 ± 0.04 15 1.11 ± 0.05 0.97 ± 0.02 0.90 ± 0.05 1.11 ± 0.05 20 1.23 ± 0.02 1.07 ± 0.04 0.97 ± 0.02 1.20 ± 0.05 25 1.41 ± 0.05 - 0.99 ± 0.03 1.35 ± 0.06 30 1.66 ± 0.03 - 1.06 ± 0.04 1.46 ± 0.05 35 1.85 ± 0.03 - 1.10 ± 0.05 1.50 ± 0.03 40 2.18 ± 0.03 - 1.13 ± 0.03 1.63 ± 0.05

Mechanical property test result (unit: MPa) weight% Example 2 Comparative Example 1 Comparative Example 2 Comparative Example 3 0 (control) σ 127 ± 1.9 Ε 2164 ± 42 5 σ 126 ± 1.3 118 ± 3.7 127 ± 3.3 124 ± 2.2 Ε 2056 ± 10 2109 ± 39 2143 ± 43 2118 ± 37 10 σ 121 ± 5.1 113 ± 1.6 128 ± 3.4 123 ± 3.7 Ε 2038 ± 17 1984 ± 42 2143 ± 19 2076 ± 16 15 σ 118 ± 4.5 94 ± 2.3 131 ± 7.1 115 ± 3.0 Ε 2032 ± 36 1750 ± 34 2149 ± 93 2047 ± 45 20 σ 116 ± 0.8 63 ± 6.4 131 ± 1.1 112 ± 3.8 Ε 2030 ± 8 1441 ± 22 2208 ± 67 2010 ± 53 25 σ 114 ± 2.0 - 126 ± 1.9 103 ± 2.1 Ε 2126 ± 15 - 2220 ± 35 1956 ± 26 30 σ 114 ± 5.1 - 127 ± 2.2 101 ± 4.3 Ε 2129 ± 7 - 2260 ± 46 1913 ± 30 35 σ 113 ± 2.7 - 124 ± 5.4 96 ± 1.0 Ε 2139 ± 19 - 2263 ± 47 1848 ± 38 40 σ 111 ± 7.1 - 123 ± 4.2 94 ± 1.4 Ε 2168 ± 8 - 2356 ± 32 1829 ± 24 σ: flexural strength, Ε: flexural modulus

Corrosion Resistance Test Results weight% Example 2 Comparative Example 1 Comparative Example 2 Comparative Example 3 10 IS PS IS IS 20 IS SS IS IS 30 IS - IS PS 40 IS - IS PS IS: insoluble, PS: partially dissolved, SS: dissolved

In Tables 2 and 3, the epoxy resin prepared in Example 2 according to the present invention showed excellent toughness up to 2.2 MPa · m ^1/2 , and the flexural strength and the flexural modulus of the mechanical properties were 111 to 126 MPa, respectively. , And 2030 to 2168 MPa, which is similar to the value of the epoxy resin itself and showed a higher value than Comparative Examples 1 to 3. In addition, it can be seen from Table 4 that the epoxy resin prepared in Example 2 also has no decrease in corrosion resistance.

In addition, as shown in FIG. 3, the epoxy resin prepared in Example 2 exhibited higher thermal stability than that of Comparative Examples 1 to 3, and showed similar thermal characteristics as the epoxy resin itself.

In addition, by analyzing the fracture surface of the specimen prepared by SEM (Jeol-JSM 5600) to investigate the toughness improvement mechanism of the epoxy resin containing the copolymer toughening agent according to the present invention, the phase separation behavior was investigated and the result is shown in Figure 4a. To 4d (FIG. 4a: 10 wt% copolymer, FIG. 4b: 20 wt% copolymer, FIG. 4c: 30 wt% copolymer, and FIG. 4d: 40 wt% copolymer). From FIG. 4, it can be observed that as the addition amount of the copolymer according to the present invention increases to 40 wt%, the size of the secondary phase of the copolymer increases from 0.5 μm to 5 μm. It is considered that the toughness of the epoxy resin is improved by the co-effect of the two because the soft rubber and the polysulfone, which is a hard thermoplastic resin, coexist in the secondary phase of the copolymer.

The rubber-polysulfone copolymer according to the present invention gives the composition excellent thermal stability, mechanical properties and corrosion resistance as well as excellent toughness when used as a toughening agent in the epoxy resin composition, and thus the epoxy resin composition according to the present invention is used for aerospace applications. It can be widely used as a material and adhesive for automotive, electric and electronic industry.

Claims (5)

A copolymer represented by the following Chemical Formula 1 having a molecular weight of 15,000 to 25,000 g / mol: Formula 1 Where BN is Where 0 <x <1, y = 1-x, and m is an integer of 1 or more; PES Where n is an integer greater than or equal to 1. (a) The carboxyl-terminated poly (butadiene co-acrylonitrile) (CTBN) of formula (2) is converted to dicyclohexylcarbodiimide (DCC) of formula (3) and N-hydroxysuccinimide of formula (4) After reacting with (NHS) to obtain a compound of formula (b) reacting the obtained compound of formula 5 with an amine-terminated poly (arylene ether sulfone) (PES-NH ₂ ) of formula Method for producing a copolymer according to claim 1 Formula 2 Formula 3 Formula 4 Formula 5 Formula 6 Where BN is Where 0 <x <1, y = 1-x, and m is an integer of 1 or more; PES Where n is an integer greater than or equal to 1. The method of claim 2, In step (a), DCC and NHS are each used in amounts of 2 to 4 and 4 to 8 moles per mole of CTBN, and the reaction is carried out for 1 to 2 hours in an organic solvent under low temperature conditions of about 0 ° C. Characterized in that the method. The method of claim 2, In step (b), PES-NH ₂ is used in an amount of 2 moles per mole of CTBN, and the reaction is carried out for 10 to 14 hours in an organic solvent under normal temperature conditions. An epoxy resin composition containing 5 to 40% by weight of the copolymer according to claim 1 as a toughening agent.