Automotive Adhesives

Abstract

To provide an adhesive for automobile capable of being hardened even in a low input thermal energy condition, and allowing a hardened product to exhibit excellent bond performance at a low temperature, and have excellent damping performance.SOLUTION: An adhesive for automobile comprises the following composition: (a) a bisphenol A type epoxy resin and / or a bisphenol F type epoxy resin; (b) a polypropylene glycol diglycidyl ether with an epoxy equivalent of 290-330 g / eq; (c) a core-shell type acrylic resin particle; (d) dicyandiamide; and (e) a hardening accelerator. A mixing ratio of (a)-(e) is as follows: a mass ratio of the (a) component to the (b) component is (a):(b)=1:1.8-2.5; and based on 100 pts.mass of the total amount of the (a) component and the (b) component, the content of the (c) component is 50-80 pts.mass, the content of the (d) component is 8-12 pts.mass, and the content of the (e) component is 6-10 pts.mass.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an automotive adhesive used on automobile assembly lines, and in particular to an automotive adhesive that can be cured even under low heat input energy conditions and that provides excellent adhesive performance and vibration damping properties of the cured product at low temperatures. [Background technology]

[0002] Conventionally, adhesives primarily composed of epoxy resins have been used as automotive adhesives. For example, Patent Document 1 describes an automotive adhesive with excellent vibration-damping properties that combines a rubber-modified epoxy resin, a urethane-modified epoxy resin, a composition in which fine powder-coated rubber particles are dispersed in an epoxy resin, and a dimer acid glycidyl ester-type epoxy resin. The automotive adhesive described in Patent Document 1 has excellent vibration-damping properties. However, there are problems with the curing conditions being high temperature and long time, and with the cured product having insufficient adhesive performance at low temperatures.

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2-150484 DISCLOSURE OF THE INVENTION [Problem to be solved by the invention]

[0004] An object of the present invention is to provide an automotive adhesive that can be cured even under low heat input energy conditions, and that produces a cured product that exhibits excellent adhesive performance at low temperatures and has excellent vibration damping properties. [Means for solving the problem]

[0005] The present invention solves the above-mentioned problems by blending two specific epoxy resins in a specific ratio and blending a specific amount of core-shell acrylic resin particles. Specifically, the present invention relates to an automotive adhesive comprising (a) a bisphenol A epoxy resin and / or a bisphenol F epoxy resin, (b) a polypropylene glycol diglycidyl ether having an epoxy equivalent of 290 to 330 g / eq, (c) core-shell acrylic resin particles, (d) dicyandiamide, and (e) a curing accelerator, wherein the mass ratio of component (a) to component (b) is (a):(b)=1:1.8 to 2.5, and the amounts of component (c), component (d), component (e), and component (e) are 50 to 80 parts by mass, 8 to 12 parts by mass, and 6 to 10 parts by mass, respectively, per 100 parts by mass of the total amount of components (a) and (b).

[0006] Component (a) is a bisphenol A epoxy resin and / or bisphenol F epoxy resin that have traditionally been used in automotive adhesives. Component (b) is a polypropylene glycol diglycidyl ether with an epoxy equivalent of 290 to 330 g / eq. The mass ratio of component (a) to component (b) is (a):(b) = 1:1.8 to 2.5. A ratio of less than 1:1.8 is undesirable because the vibration damping properties of the cured product decrease. A ratio of more than 1:2.5 is undesirable because the adhesive performance of the cured product at low temperatures decreases.

[0007] Component (c) is a core-shell type acrylic resin particle. The core-shell type acrylic resin particle has a core primarily composed of synthetic rubber and a shell primarily composed of an acrylic copolymer. Examples of synthetic rubbers used for the core include polybutadiene rubber, acrylic rubber, acrylic-silicone composite rubber, and silicone rubber. The core-shell type acrylic resin particles have a primary particle diameter of approximately 1.0 to several μm and a secondary particle diameter of approximately 20 to 2000 μm. Specifically, commercially available products such as the "Dianal LP Series" manufactured by Mitsubishi Chemical Corporation, the "Kane Ace Series" manufactured by Kaneka Corporation, and the "Staphyloid Series" manufactured by Aica Kogyo Co., Ltd. can be used alone or in combination. The blending ratio of component (c) is 50 to 80 parts by mass per 100 parts by mass of the total amount of components (a) and (b). A blending ratio of less than 50 parts by mass of component (c) is undesirable because it reduces the adhesive performance of the cured product at low temperatures. If the blending ratio of component (c) exceeds 80 parts by mass, the fluidity of the automotive adhesive decreases, making application difficult, which is undesirable.

[0008] Component (d) is dicyandiamide, a latent curing agent for crosslinking the epoxy compounds (component (a)) and (component (b)). Therefore, the automotive adhesive of the present invention can be prepared as a one-component adhesive. The blending ratio of component (d) is 8 to 12 parts by mass per 100 parts by mass of the total of components (a) and (b). A blending ratio of component (d) less than 8 parts by mass is undesirable because the crosslink density of the cured product is low and the strength is insufficient. A blending ratio of component (d) greater than 12 parts by mass is undesirable because the crosslink density of the cured product is high, making it brittle and reducing the adhesive performance of the cured product at low temperatures.

[0009] Component (e) is a curing accelerator, and conventionally known epoxy resin curing accelerators can be used. Specifically, polyamine compounds and urea compounds such as 4,4'-methylenebis(phenyldimethylurea) can be used alone or in combination. The blending ratio of component (e) is 6 to 10 parts by mass per 100 parts by mass of the total of components (a) and (b). By using components (d) and (e) in combination and at their blending ratios, a cured product can be obtained under low heat input curing conditions of 130°C for 15 minutes.

[0010] In addition to the above components (a) to (e), the automotive adhesive of the present invention can contain other conventionally known compounds or substances. In many cases, a filler (f) is also included. Examples of fillers include calcium carbonate, surface-treated calcium carbonate, clay, talc, silica powder, cellulose powder, resin powder, and metal powder, which are used alone or in combination. The filler is added in an amount of approximately 50 to 150 parts by mass per 100 parts by mass of the total of components (a) and (b). Other compounds or substances that can be added include antioxidants, adhesion promoters, moisture-wicking agents, and plasticizers.

[0011] The automotive adhesive according to the present invention has good fluidity. Specifically, the rheometer viscosity at 20°C is preferably about 50 to 900 Pa·s, and a rheometer viscosity of this order results in excellent application workability. The rheometer viscosity was measured using a parallel plate rheometer under the following conditions and method: the diameter of the parallel plates was 15 mm, the gap between the plates was 0.15 mm, the measurement temperature was 20°C, and the shear rate was 15 s -1 The measurement was carried out for 180 seconds, and the average value of the measurements taken over 20 seconds from 160 seconds to 180 seconds after the start of the measurement was taken as the rheometer viscosity.

[0012] Furthermore, the automotive adhesive of the present invention is preferably prepared so that when cured at 130°C for 15 minutes and bonded to an adherend such as a steel plate, the peel displacement of the adherend at -30°C is 0.4 mm or more. A peel displacement of this magnitude ensures excellent adhesive performance at low temperatures. The peel displacement is measured using the following procedure: (1) Two cold-rolled steel plates measuring 85 mm in length, 25 mm in width, and 1.6 mm in thickness are prepared. (2) Each cold-rolled steel plate is bent lengthwise into an L-shape, with the height of the upright portion (reference numeral 1 in Figure 1) set to 20 mm. Note that Figure 1 is a side view. (3) The automotive adhesive 3 is applied to the upright portion 1 in the manner shown in Figure 1. At this time, the automotive adhesive 3 is not applied to the upper 2.5 mm of the upright portion 1 or the lower 2.5 mm of the upright portion 1. The adhesive is also applied to the entire width. Therefore, the application area of ​​the automotive adhesive 3 is 15 mm x 25 mm = 375 mm. 2 (4) The upright portions 1, 1 of two cold-rolled steel plates bent into an L-shape are bonded together using an applied automotive adhesive 3 in the manner shown in Figure 1. (5) The automotive adhesive 3 is then heated and cured at 130°C for 15 minutes to prepare a test specimen. (6) Both ends of the horizontal portions 2, 2 of the test specimen are gripped and placed in a tensile tester, and the specimen is pulled at a pulling rate of 50 mm / min in an atmosphere of -30°C, and the elongation (mm) at break is measured. (7) The elongation at break is called the peel displacement, and if this value is 0.4 mm or more, it is determined to have excellent adhesive performance at low temperatures.

[0013] The automotive adhesive of the present invention is preferably prepared so that when a cured product is obtained by curing at 130°C for 15 minutes, the cured product has a loss tangent (tanδ) at 23°C of 0.35 or more. A loss tangent (tanδ) of this level exhibits good vibration-damping properties. The loss tangent (tanδ) is measured by the following procedure: (1) The automotive adhesive of the present invention is cured at 130°C for 15 minutes to prepare a test piece measuring 30 mm in length, 5 mm in width, and 2 mm in thickness. (2) The test piece is placed in a dynamic viscoelasticity analyzer (DMA) and heated from -30°C to 80°C at a temperature of 20 Hz and a heating rate of 5°C / min in tension mode, and the loss tangent (tanδ) at 23°C is measured. (3) A loss tangent (tanδ) of 0.35 or more is considered to have excellent vibration-damping properties. [Effects of the Invention]

[0014] The automotive adhesive according to the present invention can be cured even under low heat input energy conditions, and exhibits excellent adhesive performance at low temperatures and excellent vibration damping properties. [Example]

[0015] Example 1 The following compounds or substances were uniformly mixed in the following amounts to obtain an automotive adhesive. Bisphenol A epoxy resin 8.0 parts by mass (DIC Corporation's "Epicron 850") Bisphenol A epoxy resin *1) 21.0 parts by mass Core-shell acrylic resin particles *1) 14.0 parts by mass Polypropylene glycol diglycidyl ether 52.0 parts by mass (epoxy equivalent weight 300g / eq) Core-shell acrylic resin particles 35.0 parts by mass (Mitsubishi Chemical Corporation's "Dianal LP-4200") Dicyandiamide 8.0 parts by mass (Eponic Japan Co., Ltd. "Dicianex 1400F") 4,4'-methylenebis(phenyldimethylurea) 6.5 parts by mass Calcium carbonate 75.0 parts by mass ("Heavy calcium carbonate" manufactured by Takehara Chemical Industry Co., Ltd.) Surface-treated calcium carbonate 7.5 parts by mass (Shiraishi Kogyo Co., Ltd. "Hakuenka CCR") Surface-treated silica 3.0 parts by mass (Aerosil RY200S manufactured by Nippon Aerosil Co., Ltd.) Surface-treated quicklime 3.0 parts by mass ("CML31" manufactured by Ohmi Chemical Industry Co., Ltd.) *1) Kane Ace MX-154 manufactured by Kaneka Corporation was used, which consists of 60% by mass of bisphenol A type epoxy resin and 40% by mass of core-shell type acrylic resin particles.

[0016] Example 2 An automotive adhesive was obtained in the same manner as in Example 1, except that the masses of the following compounds were changed. Bisphenol A epoxy resin 7.0 parts by mass (DIC Corporation's "Epicron 850") Polypropylene glycol diglycidyl ether 53.0 parts by mass (epoxy equivalent weight 300g / eq)

[0017] Example 3 An automotive adhesive was obtained in the same manner as in Example 1, except that the masses of the following compounds were changed. Bisphenol A epoxy resin 6.0 parts by mass (DIC Corporation's "Epicron 850") Polypropylene glycol diglycidyl ether 54.0 parts by mass (epoxy equivalent weight 300g / eq)

[0018] Example 4 An automotive adhesive was obtained in the same manner as in Example 1, except that the masses of the following compounds were changed. Bisphenol A epoxy resin 4.0 parts by mass (DIC Corporation's "Epicron 850") Polypropylene glycol diglycidyl ether 56.0 parts by mass (epoxy equivalent weight 300g / eq)

[0019] Example 5 An automotive adhesive was obtained in the same manner as in Example 1, except that the masses of the following compounds were changed. Bisphenol A epoxy resin 2.0 parts by mass (DIC Corporation's "Epicron 850") Polypropylene glycol diglycidyl ether 58.0 parts by mass (epoxy equivalent weight 300g / eq)

[0020] Comparative Example 1 An automotive adhesive was obtained in the same manner as in Example 1, except that the masses of the following compounds were changed. Bisphenol A epoxy resin 10.0 parts by mass (DIC Corporation's "Epicron 850") Polypropylene glycol diglycidyl ether 50.0 parts by mass (epoxy equivalent weight 300g / eq)

[0021] Comparative Example 2 An automotive adhesive was obtained in the same manner as in Example 1, except that the masses of the following compounds were changed. Bisphenol A epoxy resin 9.0 parts by mass (DIC Corporation's "Epicron 850") Polypropylene glycol diglycidyl ether 51.0 parts by mass (epoxy equivalent weight 300g / eq)

[0022] Comparative Example 3 An automotive adhesive was obtained in the same manner as in Example 1, except that the masses of the following compounds were changed. Bisphenol A epoxy resin 0.0 parts by mass (DIC Corporation's "Epicron 850") Polypropylene glycol diglycidyl ether 60.0 parts by mass (epoxy equivalent weight 300g / eq)

[0023] The rheometer viscosity (Pa·s), peel displacement (mm), and loss tangent (tanδ) of the automotive adhesives of Examples 1 to 5 and Comparative Examples 1 to 3 were measured using the methods described in paragraphs 0011, 0012, and 0013, and the results are shown in Table 1.

[0024] [Table 1] ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ Rheometer viscosity Peel displacement Loss tangent (tanδ) ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ Example 1 320 0.58 0.36 Example 2 394 0.70 0.37 Example 3 362 0.60 0.41 Example 4 365 0.53 0.49 Example 5 358 0.56 0.57 Comparative Example 1 253 0.52 0.29 Comparative Example 2 393 0.52 0.31 Comparative Example 3 334 0.37 0.65 ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━

[0025] The automotive adhesives according to Examples 1 to 5 were prepared by mixing a bisphenol A type epoxy resin ("Epicron 850" manufactured by DIC Corporation) and a bisphenol A type epoxy resin *1) [total mass of components]:[polypropylene glycol diglycidyl ether (epoxy equivalent 300 g / eq)]=1:1.8-2.5. On the other hand, the automotive adhesives of Comparative Examples 1 and 2 have this ratio of 1:1.6-1.7. Therefore, the loss tangent (tanδ) of Comparative Examples 1 and 2 is less than 0.35, and vibration damping properties are unsatisfactory. Furthermore, the adhesive of Comparative Example 3 has this ratio of 1:2.9, and the peel displacement is less than 0.4 mm, and adhesive performance at low temperatures is unsatisfactory.

[0026] Example 6 The following compounds or substances were uniformly mixed in the following amounts to obtain an automotive adhesive. Bisphenol A epoxy resin 6.0 parts by mass (DIC Corporation's "Epicron 850") Bisphenol A epoxy resin *1) 21.0 parts by mass Core-shell acrylic resin particles *1) 14.0 parts by mass Polypropylene glycol diglycidyl ether 54.0 parts by mass (epoxy equivalent weight 300g / eq) Core-shell acrylic resin particles 28.0 parts by mass (Mitsubishi Chemical Corporation's "Dianal LP-4200") Dicyandiamide 8.0 parts by mass (Eponic Japan Co., Ltd. "Dicianex 1400F") 4,4'-methylenebis(phenyldimethylurea) 6.5 parts by mass Calcium carbonate 75.0 parts by mass ("Heavy calcium carbonate" manufactured by Takehara Chemical Industry Co., Ltd.) Surface-treated calcium carbonate 7.5 parts by mass (Shiraishi Kogyo Co., Ltd. "Hakuenka CCR") Surface-treated silica 3.0 parts by mass (Aerosil RY200S manufactured by Nippon Aerosil Co., Ltd.) Surface-treated quicklime 3.0 parts by mass ("CML31" manufactured by Ohmi Chemical Industry Co., Ltd.) *1) This has the same meaning as in Example 1.

[0027] Example 7 An automotive adhesive was obtained in the same manner as in Example 6, except that the masses of the following substances were changed. Core-shell acrylic resin particles 42.0 parts by mass (Mitsubishi Chemical Corporation's "Dianal LP-4200")

[0028] Example 8 An automotive adhesive was obtained in the same manner as in Example 6, except that the masses of the following substances were changed. Core-shell acrylic resin particles 49.0 parts by mass (Mitsubishi Chemical Corporation's "Dianal LP-4200")

[0029] Comparative Example 4 An automotive adhesive was obtained in the same manner as in Example 6, except that the masses of the following substances were changed. Core-shell acrylic resin particles 14.0 parts by mass (Mitsubishi Chemical Corporation's "Dianal LP-4200")

[0030] Comparative Example 5 An automotive adhesive was obtained in the same manner as in Example 6, except that the masses of the following substances were changed. Core-shell acrylic resin particles 63.0 parts by mass (Mitsubishi Chemical Corporation's "Dianal LP-4200")

[0031] The rheometer viscosity (Pa·s), peel displacement (mm), and loss tangent (tanδ) of the automotive adhesives of Examples 6 to 8 and Comparative Examples 4 and 5 were measured using the methods described in paragraphs 0011, 0012, and 0013, and the results are shown in Table 2.

[0032] [Table 2] ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ Rheometer viscosity Peel displacement Loss tangent (tanδ) ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ Example 6 158 0.50 0.42 Example 7 621 0.60 0.40 Example 8 872 0.58 0.39 Comparative Example 4 75 0.32 0.40 Comparative Example 5 Unmeasurable 0.50 0.42 ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━

[0033] The automotive adhesives according to Examples 6 to 8 were prepared by mixing a bisphenol A type epoxy resin ("Epicron 850" manufactured by DIC Corporation) and a bisphenol A type epoxy resin *1) and polypropylene glycol diglycidyl ether (epoxy equivalent 300g / eq) for a total of 100 parts by mass, core-shell type acrylic resin particles *1) and core-shell acrylic resin particles ("Dianal LP-4200" manufactured by Mitsubishi Chemical Corporation) in a total mass of 52 to 78 parts by mass. On the other hand, the automotive adhesive of Comparative Example 4 has this amount at 35 parts by mass. As a result, the peel displacement of Comparative Example 4 is less than 0.4 mm, and the adhesive performance at low temperatures is not satisfactory. Furthermore, the automotive adhesive of Comparative Example 5 has this amount at 95 parts by mass, and the rheometer viscosity cannot be measured, there is almost no fluidity, and the application process is difficult and impractical.

[0034] Example 9 An automotive adhesive was obtained in the same manner as in Example 3, except that the masses of the following substances were changed. 4,4'-methylenebis(phenyldimethylurea) 5.5 parts by mass

[0035] Example 10 An automotive adhesive was obtained in the same manner as in Example 3, except that the masses of the following substances were changed. 4,4'-methylenebis(phenyldimethylurea) 8.0 parts by mass

[0036] Example 11 An automotive adhesive was obtained in the same manner as in Example 10, except that a polyamine-based curing accelerator (Amicure MY-24, manufactured by Ajinomoto Fine-Techno Co., Ltd.) was used instead of 4,4'-methylenebis(phenyldimethylurea).

[0037] Example 12 The following compounds or substances were uniformly mixed in the following amounts to obtain an automotive adhesive. Bisphenol F epoxy resin *2) 27.0 parts by mass Core-shell acrylic resin particles *2) 9.0 parts by mass Polypropylene glycol diglycidyl ether 54.0 parts by mass (epoxy equivalent weight 300g / eq) Core-shell type acrylic resin particles 40.0 parts by mass (Mitsubishi Chemical Corporation's "Dianal LP-4200") Dicyandiamide 8.0 parts by mass (Eponic Japan Co., Ltd. "Dicianex 1400F") 4,4'-methylenebis(phenyldimethylurea) 6.5 parts by mass Calcium carbonate 75.0 parts by mass ("Heavy calcium carbonate" manufactured by Takehara Chemical Industry Co., Ltd.) Surface-treated calcium carbonate 7.5 parts by mass (Shiraishi Kogyo Co., Ltd. "Hakuenka CCR") Surface-treated silica 3.0 parts by mass (Aerosil RY200S manufactured by Nippon Aerosil Co., Ltd.) Surface-treated quicklime 3.0 parts by mass ("CML31" manufactured by Ohmi Chemical Industry Co., Ltd.) *2) Kane Ace MX-136 manufactured by Kaneka Corporation was used, which consists of 75% by mass of bisphenol F type epoxy resin and 25% by mass of core-shell type acrylic resin particles.

[0038] The rheometer viscosity (Pa·s), peel displacement (mm), and loss tangent (tanδ) of the automotive adhesives of Examples 9 to 12 were measured using the methods described in paragraphs 0011, 0012, and 0013, and the results are shown in Table 3.

[0039] [Table 3] ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ Rheometer viscosity Peel displacement Loss tangent (tanδ) ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ Example 9 234 0.56 0.48 Example 10 293 0.57 0.35 Example 11 404 0.54 0.47 Example 12 259 0.55 0.36 ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━

[0040] The automotive adhesives of Examples 9 to 12 all had peel displacements of 0.4 mm or more and loss tangents (tanδ) of 0.35 or more, thus satisfying the adhesive performance requirements at low temperatures and also exhibiting excellent vibration damping properties. [Brief explanation of the drawings]

[0041] [Figure 1] FIG. 2 is a side view of a test piece when measuring peel displacement. [Explanation of symbols]

[0042] 1 Upright part 2 horizontal part 3 Applied and cured automotive adhesive

Claims

1. (a) bisphenol A type epoxy resin and / or bisphenol F type epoxy resin, (b) polypropylene glycol diglycidyl ether having an epoxy equivalent of 290 to 330 g / eq; (c) core-shell type acrylic resin particles, (d) dicyandiamide and (e) Curing accelerator Including, the mass ratio of component (a) to component (b) is (a):(b)=1:1.8 to 2.5; An automotive adhesive, wherein the amount of the component (c) is 50 to 80 parts by mass, the amount of the component (d) is 8 to 12 parts by mass, and the amount of the component (e) is 6 to 10 parts by mass, relative to 100 parts by mass of the total amount of the component (a) and the component (b).

2. The automotive adhesive of claim 1, further comprising (f) a filler.

3. 2. The automotive adhesive according to claim 1, which can be cured at 130°C for 15 minutes.

4. 4. The automotive adhesive according to claim 3, wherein when cured under the conditions described in claim 3, the loss tangent (tan δ) of the cured product is 0.35 or more.

5. The automotive adhesive according to claim 3, which, when cured under the conditions described in claim 3 to bond adherends, exhibits a peel displacement of 0.4 mm or more at -30°C.

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