Salt-fog-resistant high-damping epoxy-rubber damping adhesive for automobiles

Abstract

The application belongs to the field of epoxy resin, and particularly relates to a salt-fog-resistant high-damping epoxy-rubber damping glue for automobiles. The damping glue comprises rubber, epoxy resin and rosin-modified phenolic resin, etc. The rosin-modified phenolic resin is added in the matrix of the rubber and the epoxy resin, so that the peeling strength and the salt-fog-resistant performance of the damping glue can be significantly improved, and a curing agent does not need to be additionally added. The damping glue also has the technical effects of wide temperature range, moisture and heat resistance, etc.

Description

Technical Field

[0001] This invention belongs to the field of epoxy resin, specifically relating to a salt spray resistant, high-damping epoxy-rubber damping adhesive for automobiles. Background Technology

[0002] As the automotive industry moves towards lightweighting and comfort, in-vehicle vibration and noise control have become important indicators for evaluating the driving experience. Damping materials, by dissipating vibrational mechanical energy into heat energy, are an effective means of reducing structural noise. Currently, automotive damping adhesives are mainly divided into three categories: asphalt-based damping plates, butyl rubber sheets, and epoxy resin-based damping adhesives.

[0003] Traditional asphalt-based damping materials, while low in cost, suffer from strong odor, poor environmental performance, and a tendency to harden and become brittle at low temperatures and flow at high temperatures, resulting in a narrow effective damping temperature range. Epoxy resin damping adhesives, although exhibiting high bonding strength and good corrosion resistance, suffer from high cross-linking density after curing, restricting molecular chain movement and leading to a narrow damping temperature range near the glass transition temperature (Tg) (typically below 30°C). The loss factor greater than 0.3 in this temperature range fails to cover the all-weather environment (-20°C to 80°C) required for automotive use. While rubber systems offer good flexibility, their low modulus results in insufficient adhesion to steel plates, and the need for vulcanization complicates the construction process. Therefore, using composite materials of rubber and epoxy resin to prepare damping adhesives can effectively improve both the damping temperature range and toughness. For example, CN101914230A discloses a weldable damping adhesive for automotive damping plates, including nitrile rubber, phenolic epoxy resin, curing agent, etc.; CN100506940A discloses a damping potting compound, including rigid epoxy, flexible epoxy, reactive diluent, liquid nitrile rubber, etc., with a temperature range of tanδ>0.3 of 45℃.

[0004] However, the existing rubber / epoxy resin composite damping adhesives, with a tanδ greater than 0.3, still cannot cover all-weather environments. Furthermore, their peel strength is low, especially after high-temperature treatment where it significantly decreases. Therefore, developing a damping adhesive that can both firmly bond to the vehicle body steel panels and maintain a loss factor greater than 0.3 over a wide temperature range (especially from -20°C to 80°C) is a pressing technical problem to be solved in this field. Summary of the Invention

[0005] To solve the above-mentioned technical problems, when preparing damping adhesive using rubber and epoxy resin as the base materials, this invention found that adding rosin-modified phenolic resin can significantly improve the peel strength and salt spray resistance of the damping adhesive, thereby obtaining a damping adhesive with excellent performance.

[0006] The present invention first provides a salt spray resistant and high-damping epoxy-rubber damping adhesive for automobiles, comprising: 10-50 parts by weight of rubber, 20-60 parts by weight of epoxy resin, and 1-20 parts by weight of rosin-modified phenolic resin.

[0007] In some embodiments, the rubber is selected from at least one of carboxyl-terminated nitrile butadiene rubber (CTBN), epoxy-terminated nitrile butadiene rubber (ETBN), or hydroxyl-terminated polybutadiene rubber (HTPB). These rubbers have moderate compatibility with epoxy resins and can form an "island structure" during curing, effectively absorbing vibrational energy.

[0008] In some embodiments, the epoxy resin is selected from polyurethane-modified epoxy resins. For example, Lepmod EU6001, Lepmod EU6003, Lepmod EU6004, and Lepmod EU6018 epoxy resins from Complex High-Tech Materials (Shanghai) Co., Ltd. Polyurethane-modified epoxy resins have a large number of polar groups such as urethane, urea, and ether groups, which, when used to prepare damping adhesives, can form hydrogen bonds, van der Waals forces, and dipole interactions with metals, significantly improving interfacial adhesion. Compared to the drawbacks of pure epoxy resins, such as high rigidity, brittleness, and high internal stress, polyurethane-modified epoxy resins can form a separation of hard and soft phases. The internal stress generated by curing shrinkage, external impact, and thermal cycling is absorbed and dispersed by the soft phase, reducing interfacial stress concentration, improving fracture toughness, and thus significantly improving bond strength.

[0009] In some embodiments, the rosin-modified phenolic resin is a commercially available product, such as 210 rosin-modified phenolic resin. Rosin-modified phenolic resin is mainly used in the ink industry and has a low viscosity. To better meet the performance requirements of damping adhesives, in some embodiments, a high-viscosity rosin-modified phenolic resin improved by this invention is used. This high-viscosity rosin-modified phenolic resin is prepared by reacting cashew phenol with furfural to form a phenolic resin, which is then reacted with rosin and pentaerythritol. Compared to commercially available rosin-modified phenolic resins, the newly synthesized rosin-modified phenolic resin has a higher molecular weight, which can further improve peel strength.

[0010] In some embodiments, the high-viscosity rosin-modified phenolic resin is prepared using the following steps:

[0011] (a) Cashew phenol, furfural and acid catalyst are added to a reaction vessel in a mass ratio of 100:(20~30):(1~5), and condensed at 60~90℃ for 2~4h under acid catalysis, and phenolic resin is obtained by discharging the material.

[0012] (b) 100 parts by mass of rosin are heated to 140~160°C to melt, a metal oxide catalyst is added, and the phenolic resin prepared in step (a) is slowly added to the molten rosin at 160~200°C to carry out a Diels-Alder addition reaction. The mass ratio of rosin, phenolic resin and metal oxide catalyst is 100:(40~100):(1~3).

[0013] (c) After the addition is complete, add 15-20 parts by weight of pentaerythritol, and heat to 250-270°C for esterification reaction within 3.5-4 hours, and then discharge under reduced pressure.

[0014] In some embodiments, the acid catalyst is selected from hydrochloric acid, sulfuric acid, or toluenesulfonic acid; and the metal oxide catalyst is selected from lithium oxide, magnesium oxide, calcium oxide, or zinc oxide.

[0015] In some embodiments, the components also include other additives, such as vulcanizing agents, low-temperature damping modifiers, fillers, etc.

[0016] In some embodiments, the vulcanizing agent is selected from sulfur, peroxide, metal oxide, etc., and the amount used is 0.5 to 4 parts by weight.

[0017] To further enhance the low-temperature damping performance, the component also contains 1 to 8 parts by weight of a low-temperature damping modifier, which is selected from acrylate rubber and / or silicone rubber microspheres.

[0018] In some embodiments, the component further comprises 1 to 10 parts by weight of filler selected from mica powder or talc powder. For example, Muscovite Mica SX-300, with its mica sheet-like structure, helps to increase interfacial friction and improve the damping factor.

[0019] The present invention also provides a method for preparing the aforementioned epoxy-rubber damping adhesive for automobiles, comprising the following steps:

[0020] (1) Preparation of damping adhesive components

[0021] Rubber is dissolved in an ester solvent (such as ethyl acetate) to form a dispersion of 10-30 wt%; epoxy resin is dissolved in a ketone solvent (such as methyl ethyl ketone) at 50-80℃ to prepare an epoxy resin solution of 20-60 wt%; rosin-modified phenolic resin is dissolved in an ester solvent (such as ethyl acetate) to form a solution of 20-50%; according to the formula ratio, the epoxy resin solution, rubber solution and rosin-modified phenolic resin solution are mixed, and other optional additives are added. The mixture is stirred evenly to obtain a damping adhesive solution, which is then cooled to room temperature and packaged.

[0022] (2) Preparation of the adhesive film:

[0023] During construction, the damping adhesive is coated onto the release film with a thickness of 450~600μm using an intelligent coating tester. After the diluent evaporates at room temperature for 0.5~2 hours, it is placed in an 80℃ oven for 1~4 hours to further evaporate the diluent.

[0024] (3) Curing of damping adhesive

[0025] The adhesive film is transferred to a passivated steel plate and held at 180-220℃ for 1-5 minutes. It is then pressed using rollers at 120-170℃ with a pressure of 50-80 kg / cm². 2 The pressing time is 2-5 minutes.

[0026] Compared with the prior art, the beneficial effects of the present invention include at least the following:

[0027] 1. This invention synthesizes a novel high-viscosity rosin-modified phenolic resin, which can significantly improve salt spray resistance and peel strength (especially peel strength after high-temperature treatment) in epoxy-rubber damping adhesives; the rosin-modified phenolic resin also has the curing function of epoxy resin, without the need for additional curing agents.

[0028] 2. The damping adhesive of the present invention constructs an interpenetrating polymer network structure by combining epoxy resin and rubber, so that the loss factor (tanδ) can reach above 0.3 in a wide temperature range of -20℃ to 80℃, effectively solving the problem of narrow temperature range of single materials; the addition of rosin-modified phenolic resin significantly improves the resistance to damp heat, salt spray resistance and adhesion.

[0029] 3. The damping adhesive of the present invention has outstanding temperature resistance. After being kept at 200°C for 2 hours, the peel strength retention rate is greater than 80%, which not only overcomes the shortcomings of insufficient adhesion of damping adhesive, but also avoids the reduction of adhesion of damping adhesive caused by high temperature in summer. Detailed Implementation

[0030] To make the objectives, technical solutions, and beneficial effects of this invention clearer, the invention will be further described in detail below with reference to specific embodiments. It should be understood that the specific embodiments described in the following description are merely illustrative examples of specific implementations of this invention and are intended to explain the invention, but do not constitute a limitation thereof.

[0031] The endpoints of the ranges and any values ​​disclosed herein are not limited to the exact ranges or values, which should be understood to include those close to them.

[0032] Example 1

[0033] High-viscosity rosin-modified phenolic resin was prepared using the following method:

[0034] Preparation of phenolic resin: The mixture was purged with nitrogen three times in a flask, and 100g of cashew phenol was added. The mixture was heated to 60℃ to melt. 3g of 10% HCl solution was added dropwise and stirred until homogeneous. Then, 20g of furfural was added (in three portions, maintaining a temperature ≤80℃), and stirred until homogeneous. The mixture was condensed at 80℃ for 3 hours until the furfural reaction was essentially complete. The pH was adjusted to neutral with 10% NaOH aqueous solution, and the mixture was washed three times with 50℃ warm water to remove salts and free phenols, yielding the phenolic resin.

[0035] Rosin addition and esterification: 100g of rosin was added to the reactor under nitrogen protection and heated to 140-160℃ until completely melted. The temperature was then lowered to 110℃, and 100g of the above-mentioned phenolic resin and 2g of zinc oxide were added. The temperature was then raised to 170℃ and held for 3 hours to complete the addition reaction. 20g of pentaerythritol was added for esterification to adjust the acid value. The temperature was increased in stages (holding at 220℃ for 1 hour, 250℃ for 1 hour, and 270-275℃ for 2 hours) until the acid value was ≤20mg KOH / g and the softening point was 135-150℃.

[0036] Post-processing: Vacuum for 1-2 hours to remove residual moisture and small molecules, cool to below 180℃ before discharge, cool and slice, then pulverize.

[0037] Performance parameters of rosin-modified phenolic resin: appearance is yellowish-brown solid, melting point is 136℃, and acid value is 19.

[0038] Example 2

[0039] In this embodiment, five kinds of salt spray resistant high damping epoxy-rubber damping adhesives for automobiles were prepared (parts by weight). Except for the rosin-modified phenolic resin prepared in Example 1, the other components were all commercially available products.

[0040] The damping adhesive is prepared using the following steps:

[0041] (1) Dissolve the rubber component in ethyl acetate to form a 25% dispersion. Dissolve the epoxy resin in methyl ethyl ketone at 60°C to prepare a 50% epoxy resin solution. Dissolve the rosin-modified phenolic resin in ethyl acetate to form a 30% solution. Mix the epoxy resin solution, rubber solution, and rosin-modified phenolic resin solution according to the formula ratio, stir evenly, and then add other additives (vulcanizing agents, fillers, etc.) to obtain the adhesive solution. After cooling to room temperature, package it.

[0042] (2) Preparation of adhesive film

[0043] Pour the adhesive onto the PET release film and coat it with a special intelligent coating machine to a thickness of 500 micrometers. After leaving it at room temperature for 1 hour, place it in an oven at 80°C for 2 hours.

[0044] (3) Adhesive film transfer: Cut the adhesive film to size and transfer it to the passivated steel plate while tearing. Incubate the adhesive film on the substrate at 200℃ for 2-3 minutes, then at 150℃ and 60 kg / cm². 2 Perform hot pressing for 3 minutes.

[0045] The compositions of the preparation examples and comparative examples are as follows:

[0046] Preparation Example 1

[0047] 30 parts of DN631 carboxyl-terminated nitrile butadiene rubber, 10 parts of NX775 carboxyl-terminated nitrile butadiene rubber, 50 parts of Lepmod EU6001 epoxy resin, 10 parts of rosin-modified phenolic resin prepared in Example 1, 0.5 parts of dicumyl peroxide, and 2 parts of SX-300 muscovite.

[0048] Preparation Example 2

[0049] DN631 carboxyl-terminated nitrile butadiene rubber 30 parts, NX775 carboxyl-terminated nitrile butadiene rubber 10 parts, Lepmod EU6001 epoxy resin 50 parts, 210 rosin-modified phenolic resin 10 parts, dicumyl peroxide 0.5 parts, SX-300 muscovite 2 parts.

[0050] Preparation Example 3

[0051] 40 parts of 1072CGA carboxyl-terminated nitrile butadiene rubber, 50 parts of Lepmod EU6004 epoxy resin, 10 parts of rosin-modified phenolic resin prepared in Example 1, 1 part of zinc oxide, and 1 part of aluminum oxide.

[0052] Preparation Example 4

[0053] 20 parts of DN631 carboxyl-terminated nitrile butadiene rubber, 10 parts of NX775 carboxyl-terminated nitrile butadiene rubber, 60 parts of Lepmod EU6003 epoxy resin, 5 parts of rosin-modified phenolic resin prepared in Example 1, 0.5 parts of dicumyl peroxide, and 3 parts of SX-300 muscovite.

[0054] Preparation Example 5

[0055] 50 parts of 1072CGA carboxyl-terminated butadiene-acrylonitrile rubber, 40 parts of Lepmod EU6018 epoxy resin, 10 parts of rosin-modified phenolic resin prepared in Example 1, 1 part of sulfur, and 2 parts of SX-300 muscovite.

[0056] Comparative Example 1

[0057] The commercially available damping adhesive product is Santoprene 201-87.

[0058] Comparative Example 2

[0059] Compared to Preparation Example 1, this preparation was identical except for the absence of phenolic resin.

[0060] Comparative Example 3

[0061] Compared with Preparation Example 1, commercially available methyl phenolic resin was used instead of rosin-modified phenolic resin, and formaldehyde and phenol were synthesized in a 1:1 ratio, with the rest being the same.

[0062] Performance testing

[0063] 1. Testing Methods

[0064] (1) Loss factor test method: Dynamic mechanical analysis (DMA) method, apply small-amplitude oscillating stress / strain to the sample, measure the storage modulus E' and loss modulus E'', and obtain the loss factor from tanδ=E' / E''.

[0065] (2) Peel strength: T peel strength GB / T2791-1995.

[0066] (3) Salt spray performance: GB / T1771-2007.

[0067] (4) Tg: Measured using the DSC method.

[0068] 2. Test Results

[0069] The experimental results are shown in Table 1. The results indicate that the damping adhesives prepared in Examples 1-3 all exhibit a wide temperature range and high damping properties. Specifically, Examples 1 and 3, using the rosin-modified phenolic resin of this invention, showed significantly better peel strength after salt spray resistance and high-temperature treatment than Comparative Example 1. Example 2, using commercially available rosin-modified phenolic resin, performed similarly to Comparative Example 1, but still outperformed Comparative Examples 2-3. However, compared to Comparative Examples 2-3 using phenolic resin-free resin and ordinary phenolic resin, the performance was poorer, significantly lower than that of Examples 1-3. Therefore, adding rosin-modified phenolic resin to rubber and epoxy resin-based damping adhesives can effectively improve salt spray resistance and peel strength, resulting in high-performance damping adhesives.

[0070]

[0071] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and do not constitute a limitation on the content of the present invention. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solutions of the present invention, including combining various technical features in any other suitable manner. These simple modifications and combinations should also be regarded as the content disclosed in the present invention and all fall within the protection scope of the present invention.

Claims

1. A salt spray resistant, high-damping epoxy-rubber damping adhesive for automobiles, comprising: 10-50 parts by weight of rubber, 20-60 parts by weight of epoxy resin, and 1-20 parts by weight of rosin-modified phenolic resin; The rosin-modified phenolic resin is a high-viscosity rosin-modified phenolic resin, which is prepared by reacting cashew phenol with furfural to form phenolic resin, and then reacting it with rosin and pentaerythritol.

2. The epoxy-rubber damping adhesive for automobiles as described in claim 1, characterized in that, The rubber is selected from at least one of carboxyl-terminated butadiene nitrile rubber, epoxy-terminated butadiene nitrile rubber, or hydroxyl-terminated polybutadiene rubber.

3. The epoxy-rubber damping adhesive for automobiles as described in claim 1, characterized in that, The epoxy resin is a polyurethane-modified epoxy resin.

4. The epoxy-rubber damping adhesive for automobiles as described in claim 1, characterized in that, The high-viscosity rosin-modified phenolic resin is prepared using the following steps: (a) Cashew phenol, furfural and acid catalyst are added to a reaction vessel in a mass ratio of 100:(20~30):(1~5), and condensed at 60~90℃ for 2~4h under acid catalysis, and phenolic resin is obtained by discharging the material. (b) 100 parts by mass of rosin are heated to 140~160°C to melt, a metal oxide catalyst is added, and the phenolic resin prepared in step (a) is slowly added to the molten rosin at 160~200°C to carry out a Diels-Alder addition reaction. The mass ratio of rosin, phenolic resin and metal oxide catalyst is 100:(40~100):(1~3). (c) After the addition is complete, add 15-20 parts by weight of pentaerythritol, and heat to 250-270°C for esterification reaction within 3.5-4 hours, and then discharge under reduced pressure.

5. The epoxy-rubber damping adhesive for automobiles as described in claim 4, characterized in that, The acid catalyst is selected from hydrochloric acid, sulfuric acid, or methylbenzenesulfonic acid; the metal oxide catalyst is selected from lithium oxide, magnesium oxide, calcium oxide, or zinc oxide.

6. The epoxy-rubber damping adhesive for automobiles as described in any one of claims 1-5, characterized in that, The epoxy-rubber damping adhesive for automobiles also includes one or more of the following: vulcanizing agent, low-temperature damping modifier, and filler.

7. The epoxy-rubber damping adhesive for automobiles as described in claim 6, characterized in that, The vulcanizing agent is 0.5 to 4 parts by weight, and the vulcanizing agent is selected from sulfur, peroxide or metal oxide.

8. The epoxy-rubber damping adhesive for automobiles as described in claim 6, characterized in that, The low-temperature damping modifier is 1 to 8 parts by weight, and the low-temperature damping modifier is selected from acrylate rubber and / or silicone rubber microspheres.

9. The epoxy-rubber damping adhesive for automobiles as described in claim 6, characterized in that, The filler is 1 to 10 parts by weight, and the filler is selected from mica powder or talc powder.

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