Application of hollow glass beads and adhesive for automobile welding

Abstract

The invention discloses application of hollow glass beads as an additive for improving the shear strength of an adhesive for automobile welding, and belongs to the technical field of adhesives. According to the application of the hollow glass beads as the additive for improving the shear strength of the adhesive for automobile welding, the adhesive for automobile welding comprises an inorganic filler, the inorganic filler comprises the hollow glass beads, the weight percentage of the inorganic filler in the adhesive is 25-55%, and the weight percentage of the hollow glass beads in the adhesive is 10-30%. The weight percentage of the hollow glass beads in the adhesive is 5-10%, and the compressive strength of the hollow glass beads is greater than or equal to 6000 psi. According to the application of the hollow glass beads as the additive for improving the shear strength of the adhesive for automobile welding, the situation that the shear strength is greatly reduced due to the fact that the content of inorganic filler is high can be prevented through the hollow glass beads with the specific content and the specific compressive strength.

Description

Technical Field

[0001] The invention relates to the technical field of adhesives, and more specifically to the application of hollow glass microspheres and adhesives for automobile welding. Background Art

[0002] Body welding is an important process in body manufacturing. In order to improve the sealing and corrosion resistance of the body and reduce vibration, sealant needs to be applied to the overlap of the body sheet metal. Recently, the development of body assembly technology that uses bonding to replace spot welding or partially replace spot welding has given adhesives new applications in body assembly.

[0003] The adhesives and sealants used in the welding line, in addition to having the general properties of automotive adhesives, the most important thing is that they will not have adverse effects on the coating process, can withstand the washing of the coating pre-treatment process, and will not pollute the electrophoretic fluid and coating quality. At present, there are three types of adhesives and sealants mainly used in the welding process: automotive hemming adhesive, automotive spot welding adhesive and expansion type shockproof adhesive.

[0004] The automobile body is welded from several steel plates. The existence of welds is inevitable. The sealing quality of the welds is directly related to the quality and corrosion resistance of the car body, and is a very important indicator of the technical performance of the whole vehicle. In automobile manufacturing, if the gaps at the joints of the sheet metal parts are not sealed with effective measures, the car will inevitably leak water, air and dust during driving. In severe cases, it may cause the steel plate at the weld to rust, causing the steel plate to perforate prematurely and accelerate the scrapping of the vehicle. The common weld sealing method in the automobile manufacturing industry is to apply spot welding sealant. Spot welding sealant is a solvent-free reactive adhesive with rubber as the base material. It has high viscosity at room temperature. After heating and curing, it becomes a rubber elastomer with excellent sealing and waterproof leakage performance. It is pumped at room temperature through high pressure, and has good adhesion to oily steel plates and good anti-sagging properties. The curing temperature ranges from 140℃ to 210℃. The cured product is flexible, has good sealing properties when vibrating, and is not easy to be peeled off under low temperature conditions. Spot welding sealant is mainly used in the front wall, side wall, floor, etc. Its main function is to prevent water and gas from penetrating into the cab from below the floor or the engine compartment. It can be divided into two categories based on performance: expansion type and non-expansion type. The use process is as follows: before welding the stamping parts, apply the glue on the single plate at the joint of the stamping parts, then close the two plates and spot weld them, and cure them together with the baking process such as electrophoretic paint, midcoat and topcoat. The spot welding sealant used in automobile production is required to have good construction processability and thixotropy, and can ensure the sealing performance. It will not be washed away during the pre-treatment of the subsequent coating process, and it can pollute the electrophoretic liquid. The spot welding sealant cannot contain silicon substances. A trace of silicone resin may cause harm to the quality of electrophoretic paint and topcoat. It cannot affect the strength of spot welding. During welding, the spot welding sealant does not decompose toxic gases or substances that can cause metal corrosion. It does not flow during the heating process. After the glue film is cured, it has sufficient elasticity and adhesion, and is resistant to media and aging.

[0005] The car doors, engine hoods and trunk lids of automobiles are usually connected by spot welding after the inner and outer covers are folded. However, this process adds many pits on the surface of the car body caused by welding, which seriously affects the appearance quality of the car body. In order to solve this problem, the method of bonding instead of spot welding is used to produce the folding structure of car doors, engine hoods and trunk lids. The adhesive used is called folding glue. The use of bonding instead of welding to manufacture automobile folding parts has a very broad application prospect and is the development direction of automobile manufacturing technology. In addition to car doors, engine hoods and trunk lids, it can also be used for other parts such as side panels. Folding glue is a heat-cured, flexible single-component paste adhesive based on epoxy resin. It has good flow resistance, no corrosive gas is released when heated, and it has good corrosion resistance. It does not contain solvents and PVC, and has good adhesion to oil-surface steel plates and galvanized layers. Hemming glue is mainly used for the hemming of the outer panels of car doors, engine hoods and trunk lids. Its main function is to increase the connection force between the hemming and the connecting sheet metal, improve the overall rigidity, and prevent water, dust, rust, and dust from entering the joints.

[0006] Inorganic fillers such as wollastonite, mica powder or talcum powder are usually added to adhesives used for automotive welding to reduce the rubber content, reduce the elastic deformation of the sealant, and reduce the extrusion expansion rate. However, in general, increasing the amount of inorganic fillers added will significantly reduce the shear strength of the adhesive.

[0007] Existing hollow glass microspheres with high compressive strength of 7000 to 9000 psi are generally used in preparing liquid crystal polyester composition (LCP) materials for acoustic diaphragms.

[0008] Existing hollow glass microspheres with high compressive strength of more than 11,000 psi are used in the preparation of polypropylene materials for automotive interior and exterior parts.

[0009] However, the use of hollow glass microspheres with high compressive strength as an additive for improving the shear strength of adhesives for automotive welding has not been reported. Summary of the invention

[0010] The technical problem to be solved by the present invention is to overcome the defects and shortcomings of existing adhesives for automobile welding, that is, the high content of inorganic fillers leads to a significant reduction in shear strength, and to provide the use of hollow glass microspheres as an additive for improving the shear strength of adhesives for automobile welding. By controlling the specific content of hollow glass microspheres with greater compressive strength, the shear strength of the adhesive is prevented from being significantly reduced, and the shear strength of the adhesive is also improved.

[0011] The above-mentioned purpose of the present invention is achieved through the following technical solutions:

[0012] The hollow glass microspheres are used as an additive for improving the shear strength of an adhesive for automobile welding. The adhesive for automobile welding comprises an inorganic filler, the inorganic filler comprises hollow glass microspheres, the weight percentage of the inorganic filler in the adhesive is 25-55%, the weight percentage of the hollow glass microspheres in the adhesive is 5-10%, and the compressive strength of the hollow glass microspheres is greater than or equal to 6000psi.

[0013] The test standard for the compressive strength of hollow glass microspheres is tested using the MAXIMATOR hollow microsphere pressure testing system.

[0014] The automobile welding adhesive of the present invention includes hollow glass microbeads with a specific content and a specific compressive strength, which can prevent the shear strength from being greatly reduced due to a high content of inorganic fillers. The mechanism of action may be as follows: at a microscopic level, the surface of the substrate to be bonded to the automobile has unevenness such as pits, and the hollow glass microbeads can play an anchoring role and fill in the pits on the substrate plate surfaces on both sides, thereby fixing the substrates on both sides and increasing the friction of the substrates on both sides. Therefore, even if a large amount of inorganic fillers is contained, the shear strength of the cured adhesive will not be greatly reduced, and the shear strength of the adhesive can even be improved, and the T peel strength of the adhesive can also be improved.

[0015] However, the compressive strength of hollow glass microspheres is too low. When the two substrates to be bonded are displaced, the hollow glass microspheres are easily broken, and therefore cannot be anchored in the two substrates, and thus cannot play a role in improving the shear strength.

[0016] Preferably, the compressive strength of the hollow glass microspheres is 6000-8000 psi.

[0017] Hollow glass beads have high compressive strength, which is more conducive to improving the shear strength and T-peel strength of adhesives used for automotive welding. However, a certain amount of glass beads will inevitably be damaged during production and construction. The damaged glass beads will increase the wear of construction equipment and reduce the service life of construction equipment. The higher the compressive strength of the glass beads, the lower the breakage rate will be, and the lower the wear on construction equipment will be.

[0018] In a specific embodiment, the compressive strength of the hollow glass microspheres is 6000psi, 6500psi, 7000psi, 7500psi, or 8000psi.

[0019] Preferably, the true density of the hollow glass microspheres is 0.36-0.4 g / cm 3 .

[0020] The detection standard for the true density of hollow glass beads is tested using the Quantachrome5200e true density tester.

[0021] Automotive welding adhesives are produced using kneading machines with large torque. Hollow glass beads may be damaged during production. High compressive strength is beneficial to reduce the breakage rate. Therefore, in order to make the finished product density the same, the amount of glass beads added is inversely proportional to the compressive strength of the glass beads. The higher the compressive strength of the glass beads, the higher the mechanical strength of the finished product under the same test conditions.

[0022] Preferably, the automobile welding adhesive is automobile spot welding adhesive or automobile hemming adhesive.

[0023] The present invention also protects an automotive spot welding adhesive, which comprises the following components by weight: 15-25 parts of a diluent; 5-10 parts of solid styrene-butadiene rubber; 10-15 parts of solid butadiene rubber; 10-20 parts of a bisphenol A epoxy resin; 1-5 parts of a curing agent; 1-5 parts of a curing accelerator; 5-15 parts of a flame retardant; 2-5 parts of a moisture absorbent; 0.1-1 parts of a silane coupling agent; 25-40 parts of an inorganic filler;

[0024] The inorganic filler includes hollow glass microspheres;

[0025] The weight percentage of the inorganic filler in the adhesive is 25-40%;

[0026] The weight percentage of the hollow glass microspheres in the adhesive is 5 to 10%;

[0027] The compressive strength of the hollow glass microspheres is greater than or equal to 6000 psi.

[0028] The automobile spot welding adhesive of the present invention prevents the shear strength of the adhesive from being greatly reduced by controlling the specific content of hollow glass microspheres with greater compressive strength, and also improves the shear strength of the adhesive.

[0029] Moreover, hollow glass microspheres have the advantages of large volume and light weight. Therefore, the specific content of hollow glass microspheres in the present invention can also reduce the density of the adhesive, which is beneficial to the weight reduction of the whole vehicle, especially the improvement of the cruising range of new energy vehicles, and has a promoting effect on improving the vehicle mileage and service life.

[0030] In addition, the VOC content of the adhesive material mainly depends on the content of the diluent. The hollow glass microspheres of the present invention have a low oil absorption value, which can reduce the amount of diluent added for later viscosity adjustment of the material. Therefore, the present invention is conducive to reducing VOC emissions and improving the environmental friendliness of the product.

[0031] Finally, hollow glass microspheres can also help improve the dispersibility of adhesives, making the product appearance more delicate.

[0032] The automobile welding adhesive of the present invention has excellent compatibility with cold-rolled steel plates, galvanized plates and aluminum plates, and can be constructed manually or by robots; it has excellent effects of corrosion protection and noise reduction for the entire vehicle and prolonging the service life of the vehicle.

[0033] The automotive spot welding adhesive composition of the present invention does not contain polyvinyl chloride resin, thereby avoiding the disadvantages of polyvinyl chloride decomposing and generating hydrogen chloride to corrode vehicle sheet metal due to high temperature during construction at the welding point, causing local corrosion of the vehicle and shortening the service life of the vehicle.

[0034] In a specific embodiment, the diluent is an inert, environmentally friendly, low-volatile phthalate plasticizer, preferably DINP, DPHP, DIDP, etc.

[0035] Preferably, the number average molecular weight of the solid styrene butadiene rubber is 250,000 to 300,000. The physical properties and mechanical processing properties of the styrene butadiene rubber with this molecular weight distribution are close to those of natural rubber, and its wear resistance, heat resistance, aging resistance and vulcanization speed are better than those of natural rubber. Dynasol Group's E1009L and Kunshan Chemical's SBR1502 are preferred.

[0036] Preferably, the number average molecular weight of the solid butadiene rubber is 50,000 to 70,000. The solid butadiene rubber with this molecular weight distribution has excellent cold resistance, wear resistance and toughness after vulcanization, and BR9000 of Yanshan Chemical and BR9000 of Shanghai Zhengshang Chemical are preferred.

[0037] Preferably, the number average molecular weight distribution of the bisphenol A epoxy resin is 300,000 to 350,000. The bisphenol A epoxy resin is a thermosetting bisphenol A epoxy resin mixture with a narrow molecular weight distribution, preferably Dow DER732P, Kunshan Guodu YD-128, etc.

[0038] In a specific embodiment, the curing agent is a modified polyamine compound, which has excellent functions such as low price and high reaction activity. Preferably, the dicyandiamide curing agent of Guangzhou Changhao Chemical and Shanghai Merman Chemical is used.

[0039] In a specific embodiment, the curing accelerator is dicumyl peroxide and polyurea, preferably DCP of Nouryon Chemical and E-20 of Shanghai Moman Chemical.

[0040] In a specific embodiment, the flame retardant is high white aluminum hydroxide, preferably high white aluminum hydroxide from Jiaqi Chemical and Jinan Jiuding.

[0041] In a specific implementation, the calcium oxide content of the calcium oxide produced by Shanghai Fanhua or Liaoning Benxi Calcium Industry is greater than 90%.

[0042] In a specific implementation manner, the silane coupling agent is preferably Yantai Wanhua's Yantai Wanhua, Nanjing University's A186, A160, etc.

[0043] In a specific embodiment, the inorganic filler includes wollastonite, stearic acid coated calcium carbonate and hollow glass microspheres. WDP wollastonite from Lishu Dadingshan Wollastonite Co., Ltd. and WN502 from Changzhou Calcium Carbonate are preferred. The weight percentage of the wollastonite in the adhesive is 0.5-5%.

[0044] In a specific implementation manner, the viscosity, shear strength and density of the automotive spot welding adhesive can be adjusted by adjusting the content of the diluent, bisphenol A epoxy resin and hollow glass microspheres.

[0045] The present invention also protects an automobile hemming adhesive, which comprises the following components by weight: 3-10 parts of a diluent; 35-45 parts of a bisphenol A epoxy resin; 1-5 parts of a curing agent; 0.5-2 parts of a thixotropic agent; 0.5-2 parts of a curing accelerator; 1-5 parts of a moisture absorbent; 5-15 parts of a PVC paste resin; and 35-55 parts of an inorganic filler.

[0046] The inorganic filler includes hollow glass microspheres.

[0047] The weight percentage of the inorganic filler in the adhesive is 35-55%,

[0048] The weight percentage of the hollow glass microspheres in the adhesive is 5 to 10%.

[0049] The compressive strength of the hollow glass microspheres is greater than or equal to 6000 psi.

[0050] The automobile hem glue of the present invention prevents the shear strength of the adhesive from being greatly reduced by controlling the specific content of hollow glass microspheres with greater compressive strength, and also improves the shear strength of the adhesive.

[0051] Moreover, hollow glass microspheres have the advantages of large volume and light weight. Therefore, the specific content of hollow glass microspheres in the present invention can also reduce the density of the adhesive, which is beneficial to the weight reduction of the whole vehicle, especially the improvement of the cruising range of new energy vehicles, and has a promoting effect on improving the vehicle mileage and service life.

[0052] In addition, the VOC content of the adhesive material mainly depends on the content of the diluent. The hollow glass microspheres of the present invention have a low oil absorption value, which can reduce the amount of diluent added for later viscosity adjustment of the material. Therefore, the present invention is conducive to reducing VOC emissions and improving the environmental friendliness of the product.

[0053] Finally, hollow glass microspheres can also help improve the dispersibility of adhesives, making the product appearance more delicate.

[0054] The automobile welding adhesive of the present invention has excellent compatibility with cold-rolled steel plates, galvanized plates and aluminum plates, and can be constructed manually or by robots; it has excellent effects of corrosion protection and noise reduction for the entire vehicle and prolonging the service life of the vehicle.

[0055] In a specific embodiment, the diluent is an inert, environmentally friendly, low-volatile phthalate plasticizer, preferably DINP, DPHP, DIDP, etc.

[0056] In a specific embodiment, the bisphenol A epoxy resin is a thermosetting bisphenol A epoxy resin mixture with a narrow molecular weight distribution, and the molecular weight distribution is 300,000 to 350,000, preferably Dow DER732P, Kunshan Guodu YD-128, etc.

[0057] In a specific embodiment, the curing agent is a modified polyamine compound, which has excellent functions such as low price and high reaction activity. Preferably, the dicyandiamide curing agent of Guangzhou Changhao Chemical and Shanghai Merman Chemical is used.

[0058] In a specific embodiment, the thixotropic agent is preferably an inorganic thixotropic agent, which provides high-quality thixotropic properties, anti-sagging, and easy spraying properties.

[0059] In a specific embodiment, the curing accelerator is dicumyl peroxide and polyurea, preferably DCP of Nouryon Chemical and E-20 of Shanghai Moman Chemical.

[0060] In a specific implementation manner, the moisture absorbent can be calcium oxide from Shanghai Fanhua or Liaoning Benxi Calcium Industry, with a calcium oxide content greater than 90%.

[0061] In a specific embodiment, the PVC paste resin is a homopolymer resin with a high oil absorption value, preferably 370HD from Thailand, P1353K from France, etc.

[0062] In a specific embodiment, the inorganic filler includes silicate, mica powder and hollow glass microspheres, preferably wollastonite and mica powder from Jiangxi Aote Materials. Preferably, WDP wollastonite from Lishu Dadingshan Wollastonite Co., Ltd. and GB-2 mica powder from Anhui Ge Rui New Materials Co., Ltd. The weight percentage of the wollastonite in the automotive hemming glue is 0.5-5%.

[0063] In a specific implementation manner, the viscosity, shear strength and density of the automotive hemming adhesive can be adjusted by adjusting the content of the diluent, bisphenol A epoxy resin and hollow glass microspheres.

[0064] The method for preparing any of the above-mentioned adhesives for automobile welding comprises the following steps: mixing the components uniformly in a kneader to obtain the adhesive for automobile welding.

[0065] Compared with the prior art, the present invention has the following beneficial effects:

[0066] The invention discloses the use of hollow glass microspheres as an additive for improving the shear strength of an adhesive for automobile welding. The hollow glass microspheres with a specific content and a specific compressive strength can prevent the shear strength from being greatly reduced due to a high content of inorganic fillers.

[0067] The automotive spot welding adhesive of the present invention can achieve a shear strength of more than 0.71 MPa after being baked and cured.

[0068] After being baked and cured, the automotive hemming adhesive of the present invention has an oil surface shear strength of more than 15.7 MPa, a non-oil surface shear strength of more than 17.7 MPa, and a T peel strength of more than 2.4 N / mm. BRIEF DESCRIPTION OF THE DRAWINGS

[0069] Figure 1 This is the appearance diagram of the adhesive of Example 1 of the present invention. DETAILED DESCRIPTION

[0070] The present invention is further described below in conjunction with specific embodiments, but the embodiments do not limit the present invention in any form. Unless otherwise specified, the raw materials and reagents used in the embodiments of the present invention are conventionally purchased raw materials and reagents.

[0071] The test standard for the compressive strength of hollow glass microspheres is tested using the MAXIMATOR hollow microsphere pressure testing system.

[0072] The detection standard for the true density of hollow glass beads is tested using the Quantachrome5200e true density tester.

[0073] Hollow glass microsphere 1, manufacturer is Zhongke Yali Technology Co., Ltd., brand is H38HS, compressive strength is 6000Psi, true density is 0.36~0.4g / cm 3 .

[0074] Hollow glass microspheres 2, manufactured by 3M, brand VS7000, compressive strength 7000Psi, true density 0.38g / cm 3 .

[0075] Hollow glass microsphere 3, manufacturer is Zhongke Yali, brand is H38HH, compressive strength is 8000Psi, true density is 0.38g / cm 3 .

[0076] Hollow glass microspheres 4, manufactured by Zhengzhou Saint-Laite, brand 38P5500, compressive strength 5500Psi, true density 0.38g / cm 3 .

[0077] The raw materials of automotive spot welding glue are shown in Table 1 below:

[0078] Table 1

[0079]

[0080]

[0081] The raw materials of automobile hemming adhesive are shown in Table 2 below:

[0082] Table 2

[0083]

[0084]

[0085] Examples 1 to 9

[0086] A spot welding adhesive for automobiles comprises the following components by weight: a diluent; solid styrene-butadiene rubber; solid butadiene rubber; bisphenol A epoxy resin; a curing agent; a curing accelerator; a flame retardant; a moisture absorbent; a silane coupling agent; and an inorganic filler; the inorganic filler comprises hollow glass microspheres, wollastonite and stearic acid-coated calcium carbonate.

[0087] The specific content of each component is shown in Table 3 below.

[0088] Table 3

[0089]

[0090] The preparation method of the above-mentioned automotive spot welding adhesive is specifically as follows:

[0091] S1. Add the styrene-butadiene rubber and butadiene rubber after refining to the kneader and stir evenly;

[0092] S2. Add appropriate amount of diluent while stirring to control material viscosity and temperature;

[0093] S3. Sequentially add inorganic filler wollastonite, stearic acid-coated calcium carbonate and hollow glass microspheres and stir until uniform;

[0094] S4. Add curing agent, curing accelerator and other raw materials in sequence, control the mixture temperature below 40 ° C, and stir evenly;

[0095] S5. Add the flame retardant, stir until uniform, then add the bisphenol A epoxy resin and stir until uniform;

[0096] S6. Add the diluted silane coupling agent and stir until uniform;

[0097] S7. After vacuum degassing, filter through a 40-mesh filter bag and fill.

[0098] Embodiments 10 to 18

[0099] A car hemming adhesive comprises the following components by weight: a diluent; bisphenol A epoxy resin; a curing agent; a thixotropic agent; a curing accelerator; a moisture absorbent; a PVC paste resin; and an inorganic filler; the inorganic filler comprises hollow glass microspheres, wollastonite and mica powder.

[0100] The specific content of each component is shown in Table 4 below.

[0101] Table 4

[0102]

[0103]

[0104] The preparation method of the above-mentioned automobile hemming adhesive is specifically as follows:

[0105] S1. Add bisphenol A epoxy resin to the kneader;

[0106] S2. Add diluent, hygroscopic agent and PVC paste resin while stirring the epoxy resin, and stir the mixture evenly;

[0107] S3. Inorganic filler wollastonite, mica powder, stearic acid-coated calcium carbonate were added sequentially and stirred until uniform;

[0108] S4. Add curing agent, curing accelerator and other raw materials in sequence, control the mixture temperature below 40 ° C, and stir evenly;

[0109] S5. Add the thixotropic agent to the mixture, stir until uniform, and control the mixture temperature below 40°C;

[0110] S6. After vacuum degassing, filter through a 40-mesh filter bag and fill.

[0111] Comparative Examples 1 to 5

[0112] A spot welding adhesive for automobiles comprises the following components by weight: a diluent; solid styrene-butadiene rubber; solid butadiene rubber; bisphenol A epoxy resin; a curing agent; a curing accelerator; a flame retardant; a moisture absorbent; a silane coupling agent; and an inorganic filler; the inorganic filler comprises hollow glass microspheres (if any), wollastonite, and stearic acid-coated calcium carbonate.

[0113] The specific content of each component is shown in Table 5 below.

[0114] Table 5

[0115]

[0116]

[0117] The preparation method of the above-mentioned automotive spot welding adhesive is the same as that in the embodiment, and will not be repeated here.

[0118] Comparative Examples 6 to 10

[0119] A car hemming adhesive comprises the following components by weight: a diluent; a bisphenol A epoxy resin; a curing agent; a thixotropic agent; a curing accelerator; a moisture absorbent; a PVC paste resin; and an inorganic filler; the inorganic filler comprises hollow glass microspheres (if any), wollastonite and mica powder.

[0120] The specific content of each component is shown in Table 6 below.

[0121] Table 6

[0122]

[0123] The preparation method of the above-mentioned automobile hem glue is the same as that in the embodiment, and will not be repeated here.

[0124] Results

[0125] The spot welding adhesive and hemming adhesive of the above embodiments and comparative examples were tested for relevant properties:

[0126] (1) Density: g / cm 3 The test standard is GB / T13354-1992, the test conditions are 23℃, 37ml density cup.

[0127] (2) Viscosity: The unit is seconds. Test conditions: 23°C, pore size 2.64 mm, pressure 5.5 bar, time required to extrude 20 g.

[0128] (3) Curing conditions: 160°C, 30 min.

[0129] (4) Storage period: in months. The product viscosity change rate is less than 30%.

[0130] (5) Shear strength: The unit is MPa. The specimens are made into 3 groups of samples according to the oil surface cold-rolled steel plate and galvanized plate, with a coating area of ​​12.5mm*25mm. A 2mm thick tetrafluoroethylene gasket is used to control the film thickness to 2mm. The specimens are clamped with a long tail clip and baked at 160℃ for 30min. After being taken out and placed at room temperature for 24 hours, they are tested using a universal testing machine at a tensile speed of 50mm / min. The specimens should be cohesively broken.

[0131] (6) Sagging limit: in mm. Prepare a 100 mm*80 mm*5 mm wet film on a cold-rolled steel plate or galvanized plate, place it vertically, and use a marker to record the position of the bottom of the film. Place it at room temperature for 10 min and record the distance the film moves downward. Place it vertically at 160°C for 20 min and record the distance the film moves downward. The sum of the distances the film moves downward under the two conditions is the product sag distance.

[0132] (7) Tensile strength: The unit is MPa. A film of corresponding size was prepared using a mold of 200 mm*100 mm*2 mm, and baked at 160°C for 30 min. After being taken out and placed at room temperature for 24 hours, a type II cutter was used to cut the sample, and the film was tested using a universal testing machine at a tensile speed of 50 mm / min.

[0133] (8) T peel strength: The unit is N / mm. Take cold-rolled steel sheets or galvanized sheets with a size of 150 mm*25 mm, make 3 sets of samples, make them into L shape, stick 0.1 mm thick high temperature tape on the cold-rolled steel sheets or galvanized sheets, apply 100 mm thick glue on the cold-rolled steel sheets or galvanized sheets, overlap the two sheets in a T shape, clamp them with a long tail clip, bake them at 160°C for 30 min, take them out and leave them at room temperature for 24 hours, and then use a universal testing machine to test them at a tensile speed of 50 mm / min.

[0134] (9) VOC: unit: g / kg. Test standard: GB 33372-2020.

[0135] (10) Appearance: Use a scraper to evenly apply the finished product on a transparent glass plate. The film thickness should be 1mm-2mm. Observe the appearance of the film. The surface should be fine and free of particles and raw powder.

[0136] Figure 1 This is the appearance of the adhesive of Example 1 of the present invention. It can be seen that the surface is fine and smooth, without particles or raw powder.

[0137] The test results of various embodiments of automotive spot welding adhesive are shown in Table 7 below:

[0138] Table 7

[0139]

[0140]

[0141] The test results of various embodiments of automobile hemming adhesive are shown in Table 8 below:

[0142] Table 8

[0143]

[0144] The test results of various comparative examples of automotive spot welding adhesives are shown in Table 9 below:

[0145] Table 9

[0146] performance Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Comparative Example 5 density 1.27 1.45 1.37 0.84 1.52 Viscosity 98 122 116 77 134 Curing conditions 160℃,20mins 160℃,20mins 160℃,20mins 160℃,20mins 160℃,20mins Storage period 3 3 3 3 3 Shear Strength 0.67 0.57 0.63 0.53 0.55 Sagging limit 0 0 0 0 2 Tensile Strength 0.64 0.55 0.58 0.51 0.53 VOC 13 19 17 9 22 Appearance exquisite exquisite exquisite exquisite exquisite T peel strength 0.2 0.16 0.18 0.11 0.13

[0147] The test results of various comparative examples of automotive hemming adhesive are shown in Table 10 below:

[0148] Table 10

[0149] performance Comparative Example 6 Comparative Example 7 Comparative Example 8 Comparative Example 9 Comparative Example 10 density 1.07 1.47 1.38 0.85 1.51 Viscosity 97 125 116 79 134 Curing conditions 160℃,20mins 160℃,20mins 160℃,20mins 160℃,20mins 160℃,20mins Storage period 3 3 3 3 3 T peel strength 2.23 1.92 2.05 1.67 1.77 Shear strength (oil surface) 14.8 13.6 14.2 12.2 12.8 Shear strength (non-oil surface) 16.9 15.6 16.3 13.5 14.4 Sagging limit 0 0 0 0 2 VOC 14 19 16 5 23 Appearance exquisite exquisite exquisite exquisite exquisite

[0150] From the above results, it can be seen that

[0151] The automotive spot welding adhesive of the present invention has a shear strength of more than 0.71 MPa and up to 2.24 MPa after baking and curing. The density can be as low as 1.28 g / cm 3 Below, can be as low as 0.92g / cm 3 . VOC can be as low as below 22g / kg, and as low as 12g / kg.

[0152] The automotive hem glue of the present invention has an oil surface shear strength of more than 15.7 MPa and up to 30.4 MPa after baking and curing. The non-oil surface shear strength can reach more than 17.7 MPa and up to 32.2 MPa. The T peel strength can reach more than 2.4 N / mm and up to 4.9 MPa. The density can be as low as 1.2 g / cm 3 Below, can be as low as 0.87g / cm 3 . VOC can be as low as below 13g / kg, and can be as low as 5g / kg.

[0153] It can be seen from the embodiments and comparative examples that when hollow glass microspheres are not included, the density is too large, and the shear strength decreases with the increase of the inorganic filler content. The addition of a small amount of hollow glass microspheres has no obvious effect on reducing the density and improving the shear strength. However, when the content of hollow glass microspheres is too high, although its density is low, its shear strength is obviously too low to meet the requirements.

[0154] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the embodiments of the present invention. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the embodiments here. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the claims of the present invention.

Claims

1. Use of hollow glass microspheres as an additive for improving the shear strength of adhesives for automobile welding, characterized in that: The adhesive for automobile welding includes an inorganic filler, which includes hollow glass microspheres. The weight percentage of the inorganic filler in the adhesive is 25-55%, the weight percentage of the hollow glass microspheres in the adhesive is 5-10%, and the compressive strength of the hollow glass microspheres is greater than or equal to 6000psi.

2. The use according to claim 1, characterized in that: The compressive strength of the hollow glass microspheres is 6000-8000 psi.

3. The use according to claim 1, characterized in that: The true density of the hollow glass microspheres is 0.36-0.4 g / cm 3 .

4. The use according to claim 1, characterized in that: The adhesive for automobile welding is automobile spot welding adhesive or automobile hemming adhesive.

5. A spot welding adhesive for automobiles, characterized in that: The composition comprises the following components by weight: 15-25 parts of diluent; 5-10 parts of solid styrene-butadiene rubber; 10-15 parts of solid butadiene rubber; 10-20 parts of bisphenol A epoxy resin; 1-5 parts of curing agent; 1-5 parts of curing accelerator; 5-15 parts of flame retardant; 2-5 parts of moisture absorbent; 0.1-1 parts of silane coupling agent; 25-40 parts of inorganic filler; The inorganic filler includes hollow glass microspheres; The weight percentage of the inorganic filler in the adhesive is 25-40%; The weight percentage of the hollow glass microspheres in the adhesive is 5 to 10%; The compressive strength of the hollow glass microspheres is greater than or equal to 6000 psi.

6. The automotive spot welding adhesive as claimed in claim 5, characterized in that: The number average molecular weight of the solid styrene-butadiene rubber is 250,000 to 300,000.

7. The automotive spot welding adhesive as claimed in claim 5, characterized in that: The number average molecular weight of the solid butadiene rubber is 50,000 to 70,000.

8. The automotive spot welding adhesive as claimed in claim 5, characterized in that: The number average molecular weight distribution of the bisphenol A epoxy resin is 300,000 to 350,000.

9. A hem glue for automobile, characterized in that: The composition includes the following components by weight: 3-10 parts of diluent; 35-45 parts of bisphenol A epoxy resin; 1-5 parts of curing agent; 0.5-2 parts of thixotropic agent; 0.5-2 parts of curing accelerator; 1-5 parts of moisture absorbent; 5-15 parts of PVC paste resin; and 35-55 parts of inorganic filler. The inorganic filler includes hollow glass microspheres. The weight percentage of the inorganic filler in the adhesive is 35-55%, The weight percentage of the hollow glass microspheres in the adhesive is 5 to 10%. The compressive strength of the hollow glass microspheres is greater than or equal to 6000 psi.

10. The automotive hem glue as claimed in claim 9, characterized in that: The inorganic filler comprises silicate, mica powder and hollow glass microspheres, and the weight percentage of the wollastonite in the automotive hemming glue is 0.5-5%.

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