Adhesive Composition

Abstract

The present application relates to an epoxy-based adhesive composition, which may include (a) one or more epoxy resins, (b) a urethane resin having a weight average molecular weight (Mw) of 30,000 or less, and having a polytetrahydrofuran unit, (c) a core-shell rubber in the form of secondary particles in which two or more core-shell rubbers in the form of primary particles are aggregated and (d) one or more epoxy curing agents. The adhesive composition of the present application can provide excellent adhesion strength, peel strength and impact-resistant strength uniformly over a wide temperature range.

Claims

1. An adhesive composition comprising: (a) one or more epoxy resins; (b) a urethane resin having a weight average molecular weight (Mw) of 30,000 or less, and having a polytetrahydrofuran unit; (c) a core-shell rubber in the form of secondary particles in which two or more core-shell rubbers in the form of primary particles are aggregated; and (d) one or more epoxy curing agents.

2. The adhesive composition according to claim 1, comprising a bisphenol A-based epoxy resin.

3. The adhesive composition according to claim 2, wherein the bisphenol A-based epoxy resin has an epoxy equivalent in a range of 180 to 500.

4. The adhesive composition according to claim 2, further comprising a bisphenol F-based epoxy resin.

5. The adhesive composition according to claim 4, wherein the bisphenol F-based epoxy resin has an epoxy equivalent of less than 180.

6. The adhesive composition according to claim 1, wherein the polytetrahydrofuran unit has an OH equivalent in a range of 400 to 2,200.

7. The adhesive composition according to claim 6, wherein the polytetrahydrofuran unit has an OH equivalent of 1,100 or less.

8. The adhesive composition according to claim 1, wherein the urethane resin (b) has a non-aromatic isocyanate unit, a polyol unit and the polytetrahydrofuran unit.

9. The adhesive composition according to claim 8, wherein the urethane resin (b) has at least one of isocyanate ends terminated with an amine-based compound, a phenol-based compound, an oxime-based compound, or a bisphenol-based compound.

10. The adhesive composition according to claim 8, wherein the urethane resin (b) comprises a unit in which an isocyanate end is terminated by polytetrahydrofuran.

11. The adhesive composition according to claim 1, comprising 5 to 25 parts by weight of the urethane resin (b) based on a total content of the adhesive composition.

12. The adhesive composition according to claim 1, wherein the core-shell rubber in the form of primary particles has an average particle diameter of 250 nm to 500 nm.

13. The adhesive composition according to claim 12, wherein cores in the core-shell rubber in the form of primary particles have an average particle diameter of 180 to 495 nm.

14. The adhesive composition according to claim 12, wherein cores in the core-shell rubber in the form of primary particles have an average particle diameter of 280 to 490 nm.

15. The adhesive composition according to claim 12, wherein the core-shell rubber in the form of primary particles has a ratio of a core particle diameter to a total particle diameter of the core-shell satisfying 0.8 to 0.99.

16. The adhesive composition according to claim 1, wherein the core-shell rubber has butadiene-based cores.

17. The adhesive composition according to claim 1, comprising 5 to 35 parts by weight of the core-shell rubber (c) based on a total content of the adhesive composition.

18. The adhesive composition according to claim 16, further comprising a liquid rubber, wherein a total rubber content is 10 parts by weight or more based on a total content of the adhesive composition.

19. A structure comprising a cured product of the adhesive composition according to claim 1; and a base material in contact with the cured product.

20. A method for producing a structure, comprising: applying the composition according to claim 1 to a surface of a base material; and curing the composition applied to the surface of the base material.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0086] FIG. 1 shows the particle size distribution of the core-shell rubbers (in the form of primary particles) prepared according to one embodiment of the present application. The horizontal axis means particle diameters, and the vertical axis means relative numbers of rubbers.

[0087] FIG. 2 is an image taken to the appearance that the core-shell rubbers prepared according to one embodiment of the present application are dispersed in an epoxy resin.

MODE FOR INVENTION

[0088] Hereinafter, the present application will be described through examples and comparative examples. However, the scope of the present application is not limited by the scope set forth below.

PRODUCTION EXAMPLES

Production Example 1: Production of Core-Shell Rubber Assembly

[0089] First step (production of core): 70 parts by weight of ion-exchanged water, 60 parts by weight of 1,3-butadiene as a monomer, 1.0 part by weight of sodium dodecylbenzene sulfonate as an emulsifier, 0.85 parts by weight of calcium carbonate, 0.28 parts by weight of tertiary dodecyl mercaptan and 0.28 parts by weight of persulfate potassium as an initiator were introduced into a nitrogen-substituted polymerization reactor, and reacted at 75° C. until a polymerization conversion ratio was 30 to 40%. Thereafter, 0.3 parts by weight of sodium dodecylbenzene sulfonate was introduced thereto, 20 parts by weight of 1.3-butadiene was further introduced thereto, and the temperature was raised to 80° C. to terminate the reaction at the time when the polymerization conversion ratio was 95%. The produced polymer had a latex gel content of 73%. At this time, the rubber latex was coagulated with a dilute acid or a metal salt, and then washed, dried in a vacuum oven at 60° C. for 24 hours, and 1 g of the resulting rubber was placed in 100 g of toluene and stored in a dark room at room temperature for 48 hours, and then the latex gel content was measured by separating the sol and the gel.

[0090] Second step: 70 parts by weight of the produced rubber latex was put into a closed reactor, and the temperature of the reactor filled with nitrogen was raised to 75° C. Thereafter, 0.1 parts by weight of sodium pyrophosphate, 0.2 parts by weight of dextrose and 0.002 parts by weight of ferrous sulfide were introduced into the reactor in a lump.

[0091] In a separate mixing device, 25.5 parts by weight of methyl methacrylate, 4.5 parts by weight of styrene, 0.5 parts by weight of sodium dodecylbenzene sulfonate as an emulsifier, 0.1 parts by weight of cumene hydroperoxide and 20 parts by weight of ion-exchanged water were mixed to prepare a monomer emulsion.

[0092] To the reactor to which the rubber latex had been introduced, the emulsion was continuously added over 3 hours, and then, after 30 minutes, 0.03 parts by weight of hydroperoxide was added and aged at the same temperature for 1 hour to terminate the reaction at the time when the polymerization conversion ratio was 98%.

[0093] At an appropriate time in the process, the average particle diameter of the core measured by Nicomp N300 dynamic light scattering equipment was 320 nm, and the average particle diameter of the core-shell rubber resin latex was 345 nm.

[0094] In addition, the particle size distribution of the produced core-shell rubber in the form of primary particles was measured, and the results were described in FIG. 1.

[0095] Thereafter, an antioxidant was added to the reactant, aggregated with magnesium sulfate, and then dehydrated and dried to produce a core-shell rubber in an aggregated form.

Production Example 2: Production of Modified Urethane Resin

[0096] 109.76 g of polytetrahydrofuran having an OH equivalent of 500, 36.92 g of hexamethylene diisocyanate, 2.51 g of propylene glycol, 22.75 g of t-butylphenol and 0.1 g of a tin catalyst were introduced into a nitrogen-substituted polymerization reactor and mixed, and reacted at 75° C. to produce a urethane resin.

Production Example 3: Production of Modified Urethane Resin

[0097] 493.92 g of polytetrahydrofuran having an OH equivalent of 2,250, 36.92 g of hexamethylene diisocyanate, 2.51 g of propylene glycol, 22.75 g of t-butylphenol and 0.1 g of a tin catalyst were introduced into a nitrogen-substituted polymerization reactor and mixed, and reacted at 75° C. to produce a urethane resin.

Production Example 4: Production of Structural Adhesive

[0098] The compositions of Examples and Comparative Examples containing the components shown in Table 1 below in predetermined contents (weight ratio: parts by weight) were prepared as adhesive materials. Specifically, the core-shell rubber conglomerates and the epoxy resins were placed in a planetary mixer and mixed at 80° C. for 5 hours. The appearance that the core-shell rubbers are dispersed in the epoxy resin is as shown in FIG. 2. Thereafter, the remaining components excluding ‘the urethane resin, the curing agent and the catalyst’ were placed in the planetary mixer and stirred at 80° C. for 3 hours. Finally, the temperature was lowered to 40° C., ‘the urethane resin, the curing agent and the catalyst’ were put in the planetary mixer and mixed for 1 hour, and then the temperature was lowered to room temperature (about 23° C.) to terminate the kneading.

[0099] Method of Measuring Physical Properties

[0100] Impact Peel Strength

[0101] Five specimens were manufactured for each of Examples and Comparative Examples, and an object weighing 45 kg was dropped freely at a rate of 2 m/s at a height of 1.5 m in accordance with DIN ISO 11343, and the impact peel strength (unit: N/mm) was measured at each of 80° C., 23° C. and −40° C. and the average value was taken.

[0102] In the case of the specimen, two cold rolled steel having a size of 90 mm×25 mm×1.6 mm (length×width×thickness) and a strength of 440 MPa were prepared, and the adhesive was applied to a predetermined area of the cold rolled steel so that the adhesive area of the cold rolled steel was 25 mm×30 mm, and cured at 180° C. for 20 minutes. Using glass beads, the thickness of the adhesive layer was kept uniform at 0.2 mm. The measurement results were described in Table 2.

[0103] Shear Strength Experiment

[0104] For the specimens prepared in connection with Examples and Comparative Examples, five shear strength measurements were performed in accordance with DIN EN 1465 and the average value was taken. At this time, the shear strength (unit: Mpa) measurement was made under conditions of 10 mm/min and 23° C.

[0105] In the case of the specimen, two cold rolled steel sheets having a size of 100 mm×25 mm×1.6 mm (length×width×thickness) and a strength of 440 MPa were prepared, and the adhesive was applied to a predetermined area of the cold rolled steel so that the adhesive area of the cold rolled steel was 25 mm×10 mm, and cured at 180° C. for 20 minutes. Using glass beads, the thickness of the adhesive layer was kept uniform at 0.2 mm. The measurement results were described in Table 2.

[0106] Experiment Results

TABLE-US-00001 TABLE 1 Example Comparative Example 1 2 1 2 3 4 First epoxy resin.sup.1) 30 20 30 30 30 10 Second epoxy resin.sup.2) 25 28 25 25 25 30 Core-shell rubber.sup.3) 15 12 — 15 15 — Core-shell rubber.sup.4) — — 15 — — — Liquid rubber.sup.5) — 10 — — — 30 Modified urethane resin.sup.6) 10 10 10 — — 10 Modified urethane resin.sup.7) — — — 10 — — Modified urethane resin.sup.8) — — — — 10 — Mono epoxy resin.sup.9) 1.6 1.6 1.6 1.6 1.6 1.6 Colorant.sup.10) 0.05 0.05 0.05 0.05 0.05 0.05 Curing agent.sup.11) 6 6 6 6 6 6 Catalyst.sup.12) 1 1 1 1 1 1 CaCO.sub.3 7 7 7 7 7 7 CaO 1 1 1 1 1 1 Fumed silica.sup.13) 3 3 3 3 3 3 Silane coupling agent.sup.14) 0.35 0.35 0.35 0.35 0.35 0.35 1. First epoxy resin.sup.1): Bisphenol A-based epoxy resin having an epoxy equivalent of about 180 or more 2. Second epoxy resin.sup.2): Bisphenol F-based epoxy resin having an epoxy equivalent of less than about 180 3. Core-shell rubber.sup.3): Core-shell rubber of Production Example 1 4. Core-shell Rubber.sup.4): Paralloid EXL2600 from DOW 5. Liquid rubber.sup.5): Struktol Polydis6401 6. Modified urethane resin.sup.6): Urethane resin of Production Example 2 7. Modified urethane resin.sup.7): Huntzman DY965 8. Modified urethane resin.sup.8): Urethane resin of Production Example 3 9. Mono epoxy resin.sup.9): NC513 from Cardolite 10. Colorant.sup.10): Pigment violet 23 11: Curing agent.sup.11): Airproduct 1200G 12: Catalyst.sup.12): Evonik Amicure UR7/10 13: Fumed silica.sup.13): Cabo TS720 14: Silane coupling agent.sup.14): GE Advanced material A-187

TABLE-US-00002 TABLE 2 Example Comparative Example 1 2 1 2 3 4 Impact strength (−40° C.) 40 36 28 X 10 6 Impact strength (23° C.) 45 42 30 44 32 32 Impact strength (80° C.) 40 39 28 38 30 28 Shear strength (23° C.) 35 34 24 34 29 28 X: the case where the stably measured value is not obtained because the measured value is very low