A heat-curing adhesive and its preparation method

Abstract

The present invention relates to the technical field of adhesives, with the classification number IPC C09J123 / 26, and discloses a heat-curable adhesive and a preparation method thereof. By mass fraction, the raw material composition includes: 5-20 parts of functional rubber, 1-15 parts of modified phenolic resin, 1-15 parts of special vulcanizing agent, 1-15 parts of metal salt, 1-15 parts of metal oxide, 1-15 parts of filler, and 70-75 parts of solvent. The present invention prepares a heat-curable adhesive with excellent bonding performance, aging resistance, impact resistance and stability by carrying out phenol red modification on phenolic resin, controlling the phenol content in the phenol red-modified phenolic resin, compounding the special vulcanizing agent, functional rubber and phenol red-modified phenolic resin, and compounding the filler carbon black N642 with the functional rubber.

Description

Technical Field

[0001] The present invention relates to the technical field of adhesives, in particular to the field of IPC C09J123 / 26, and more specifically, to a heat-curable adhesive and a preparation method thereof. Background Art

[0002] A heat-curable adhesive is an adhesive used in the process of bonding rubber to rigid substrates such as steel, iron, ceramics, and nylon, and is widely used in application scenarios such as construction, transportation, and vibration isolation, especially in high-standard environments such as aerospace, automotive, and military industries, where high performance requirements are imposed on the heat-curable adhesive. A heat-curable adhesive with thermosetting phenolic resin as an important raw material has excellent mechanical properties and coating properties and a wide range of applications. In some cases, the heat-curable adhesive is used in high-temperature and high-pressure environments (usually 145°C - 195°C). Due to the large thermal stress of thermosetting phenolic resin, it is easy to cause thermal stress concentration damage, resulting in poor stability and adhesiveness, and reducing the service life of the adhesive.

[0003] To solve the above problems, application document CN201810758896.8 discloses a natural rubber single-coated heat-curable adhesive, the raw materials of which include: halogenated polyolefin, tert-butyl phenolic resin, metal oxide, silane coupling agent, adhesive assistant, sulfur, carbon black, white carbon black, chloroprene rubber, highly catalytic active titanium dioxide, carbon black and solvent. The prepared adhesive has good bonding performance and weather resistance. However, the adhesive effect of the adhesive is not significantly improved.

[0004] Application document CN201310443270.5 discloses a heat-curable adhesive and a preparation method thereof. The raw materials include: phenolic / epoxy component, first accelerator, halogenated polyolefin, co-vulcanization component, metal oxide, adhesion promoter, wetting agent, dispersant and inert filler. The prepared adhesive can enhance the bonding strength and peeling strength between the rubber and metal phases, but its bonding performance for non-polar rubber is not good. Summary of the Invention

[0005] To solve the above technical problems, the first aspect of the present invention provides a heat-curable adhesive. By mass, the raw materials include: 5 - 20 parts of functional rubber, 1 - 15 parts of modified phenolic resin, 1 - 15 parts of special vulcanizing agent, 1 - 15 parts of metal salt, 1 - 15 parts of metal oxide, 1 - 15 parts of filler, and 70 - 75 parts of solvent.

[0006] Preferably, for the heat-curable adhesive, by mass, the raw materials include: 7 - 15 parts of functional rubber, 5 - 10 parts of modified phenolic resin, 1 - 5 parts of special vulcanizing agent, 1 - 3 parts of metal salt, 1 - 3 parts of metal oxide, 3 - 10 parts of filler, and 70 - 75 parts of solvent.

[0007] Preferably, the solvent includes one or more of methyl isobutyl ketone and xylene.

[0008] More preferably, the solvent is methyl isobutyl ketone (CAS No.: 108-10-1), purchased from Shandong Wenshao Chemical Co., Ltd.

[0009] Preferably, the functional rubber includes one or more of chlorinated natural rubber, chlorinated butyl rubber, chlorinated polyethylene, and chlorinated polypropylene.

[0010] Preferably, the modified phenolic resin includes one or more of phenol red modified phenolic resin and phenol red derivative modified phenolic resin.

[0011] More preferably, the functional rubber is chlorinated natural rubber.

[0012] More preferably, the modified phenolic resin is phenol red modified phenolic resin.

[0013] More preferably, the mass ratio of the chlorinated natural rubber to the phenol red modified phenolic resin is (0.4 - 0.5):1.

[0014] More preferably, by mass parts, the addition amount of phenol in the phenol red modified phenolic resin is 18 - 22 parts.

[0015] Because the adsorption performance of phenolic resin is superior to other synthetic resins, more and more adhesive formulations choose to add phenolic resin. However, the presence of phenolic resin will reduce the initial adhesion of the adhesive, and the phenolic resin itself has insufficient toughness and poor impact resistance, and is prone to cracking when subjected to external forces. In addition, the system of phenolic resin becomes unstable at high temperatures (200 - 340°C). To solve these problems, the present application modifies the phenolic resin to obtain phenol red modified phenolic resin, which effectively improves the bonding performance and impact resistance of the adhesive while ensuring a certain heat resistance. The applicant speculates that by synthesizing phenolic resin with a specific amount of sulfonate group-containing phenol red replacing part of phenol, the phenol content is reduced to a certain extent, effectively inhibiting the migration of free phenol, and after introducing phenol red, the chain segment flexibility is increased, the structure is stable and not easy to break, and the hydroxyl group and active groups such as terminal amino groups on the fiber surface generate chemical bond binding or hydrogen bond interaction, which can enhance the stability, adhesiveness and heat resistance of the adhesive against thermal shock.

[0016] To further improve the toughness of the adhesive, elastomers such as chlorinated natural rubber can be added to the phenol red modified phenolic resin. In this application, the mass ratio of chlorinated natural rubber to phenol red modified phenolic resin is controlled to be (0.4 - 0.5):1, effectively improving the toughness and mechanical strength of the adhesive. The applicant speculates that a specific amount of chlorinated natural rubber has good compatibility with the phenol red modified phenolic resin, and the chlorinated natural rubber is uniformly dispersed in the phenol red modified phenolic resin, enhancing the toughness and mechanical strength of the phenolic resin.

[0017] Further preferably, the mass ratio of the chlorinated natural rubber to the phenol red modified phenolic resin is 0.5:1.

[0018] Further preferably, the chlorinated natural rubber (CAS No.: 68649 - 03 - 6) is purchased from Shandong Haoyao New Materials Co., Ltd.

[0019] Further preferably, for the phenol red modified phenolic resin, by mass fraction, the raw materials include: 25 - 30 parts of phenol red, 15 - 25 parts of phenol, 42 parts of formaldehyde solution, and 3 parts of barium hydroxide monohydrate.

[0020] Further preferably, for the preparation method of the phenol red modified phenolic resin:

[0021] Add phenol red, phenol, and barium hydroxide monohydrate into the formaldehyde solution according to the ratio, and stir at 60°C for 30 min. Then raise the temperature to 70°C and keep for 2 h, then raise the temperature to 80°C and keep for 3 h. After vacuum dehydration, the above-mentioned phenol red modified phenolic resin is obtained.

[0022] Further preferably, by mass fraction, 25 parts of phenol red, 25 parts of phenol, 42 parts of formaldehyde solution, and 3 parts of barium hydroxide monohydrate are used to obtain the 1# phenol red modified phenolic resin.

[0023] Further preferably, by mass fraction, 30 parts of phenol red, 20 parts of phenol, 42 parts of formaldehyde solution, and 3 parts of barium hydroxide monohydrate are used to obtain the 2# phenol red modified phenolic resin.

[0024] Further preferably, by mass fraction, 35 parts of phenol red, 15 parts of phenol, 42 parts of formaldehyde solution, and 3 parts of barium hydroxide monohydrate are used to obtain the 3# phenol red modified phenolic resin.

[0025] Further preferably, the phenol red modified phenolic resin is the 2# phenol red modified phenolic resin, and by mass fraction, there are 20 parts of phenol.

[0026] Further preferably, the phenol red (CAS No.: 143-74-8) is purchased from Hubei Dongcao Chemical Technology Co., Ltd.; the phenol (CAS No.: 108-95-2) is purchased from Shandong Shengxu Energy Co., Ltd.; the formaldehyde (CAS No.: 50-00-0) is purchased from Jinan Mingchuan Chemical Co., Ltd.; the barium hydroxide monohydrate (CAS No.: 22326-55-2) is purchased from Jinan Baite New Materials Co., Ltd.

[0027] Preferably, the special vulcanizing agent includes one or more of nitrobenzene, p-nitrosotoluene, p-dinitrobenzene, m-dinitrobenzene, and o-dinitrobenzene.

[0028] Further preferably, the special vulcanizing agent is p-dinitrobenzene.

[0029] Further preferably, the mass ratio of p-dinitrobenzene, chlorinated natural rubber, and phenol red modified phenolic resin is (4-5):(4-6):(9-10).

[0030] Toughening the phenolic resin by adding a rubber-like elastomer will reduce its crosslinking degree to a certain extent. However, when the crosslinking density is too low, the three-dimensional network structure in the system is insufficient and the stability of the adhesive is poor. In this application, controlling the mass ratio of p-dinitrobenzene, chlorinated natural rubber, and phenol red modified phenolic resin to be (4-5):(4-6):(9-10) effectively improves the stability and bonding performance of the adhesive. The applicant speculates that the combined action of a specific amount of special vulcanizing agent, chlorinated natural rubber, and phenol red modified phenolic resin results in better diffusion of rubber molecules and special vulcanizing agent into the resin network; when combined with a rubber substrate, local chain segment diffusion of macromolecules is likely to occur, and there is also a strong bonding strength to the non-polar rubber substrate, improving the stability and bonding performance of the adhesive while ensuring good toughness of the adhesive.

[0031] Further preferably, the mass ratio of p-dinitrobenzene, chlorinated natural rubber, and phenol red modified phenolic resin is 4:5:10.

[0032] Further preferably, the p-dinitrobenzene (CAS No.: 105-12-4) is purchased from Hubei Xinrunde Chemical Industry Co., Ltd.

[0033] Preferably, the metal oxide includes one or more of magnesium oxide, titanium oxide, zinc oxide, and iron(III) oxide.

[0034] Further preferably, the metal oxide is magnesium oxide (CAS No.: 1309-48-4), purchased from Guangzhou Baochu Chemical Co., Ltd.

[0035] Preferably, the metal salt includes metal chlorides.

[0036] Further preferably, the metal chloride includes one or more of zinc chloride, calcium chloride, magnesium chloride, iron chloride, and copper chloride.

[0037] Further preferably, the metal chloride is zinc chloride.

[0038] Further preferably, the mass ratio of the zinc chloride, magnesium oxide, and phenol red-modified phenolic resin is (1.8 - 2.2):1:(4.8 - 5.2).

[0039] Magnesium oxide can be used as a vulcanizing agent to improve the mechanical properties of the adhesive and prevent premature vulcanization of the rubber during mixing. Therefore, when the amount of magnesium oxide is too large, the curing efficiency will be reduced, affecting the interfacial co-crosslinking and interfacial adhesion properties. In this application, controlling the mass ratio of zinc chloride, magnesium oxide, and phenol red-modified phenolic resin to be (1.8 - 2.2):1:(4.8 - 5.2) can effectively improve the mechanical properties and curing efficiency of the adhesive. The applicant speculates that a specific amount of zinc chloride, magnesium oxide, and phenol red-modified phenolic resin act together to complex and form a network structure, enhancing the mechanical properties and curing efficiency of the adhesive, facilitating interfacial bonding. The obtained adhesive can be cured in 15 minutes to obtain a high bonding strength.

[0040] Further preferably, the mass ratio of the zinc chloride, magnesium oxide, and phenol red-modified phenolic resin is 2:1:5.

[0041] Further preferably, the metal chloride is zinc chloride (7646 - 85 - 7), purchased from Jinan Huijinchuan Chemical Co., Ltd.

[0042] Preferably, the filler includes one or more of carbon black, sepiolite, talcum powder, and kaolin.

[0043] Further preferably, the filler is carbon black, including one or more of carbon black N660, carbon black N642, carbon black N762, and carbon black N990.

[0044] Further preferably, the carbon black is carbon black N642.

[0045] Further preferably, the mass ratio of the carbon black N642 to the chlorinated natural rubber is (2.8 - 3.2):10.

[0046] Generally, rubber aging is mainly promoted by factors such as light and heat to form photo-oxidative and thermo-oxidative aging. Carbon black has good stability to light and heat, can also improve the heat-resistant deformation performance, and endows products with properties such as tear resistance, abrasion resistance, and cold resistance, extending the service life. However, the dispersibility of carbon black in the system has a great impact on the performance exertion. In this application, controlling the mass ratio of carbon black N642 to chlorinated natural rubber to be (2.8 - 3.2):10 can effectively improve the aging resistance and abrasion resistance of the adhesive. The applicant speculates that carbon black N642 has a relatively low structure and poor dispersibility at the same particle size. However, when the mass ratio of carbon black N642 to chlorinated natural rubber is (2.8 - 3.2):10, under their combined action, carbon black N642 has better dispersibility in the system, forming a relatively tight and firm network structure, effectively improving the aging resistance and abrasion resistance of the adhesive.

[0047] Further preferably, the mass ratio of the carbon black N642 to the chlorinated natural rubber is 3:10.

[0048] Further preferably, the carbon black N642 (CAS No.: 1333 - 86 - 4) is purchased from Tianjin Yihuachang New Material Technology Co., Ltd.

[0049] The second part of the present invention provides a preparation method of a heat-curable adhesive, comprising the following steps:

[0050] S1. Mix the formula amounts of functional rubber, metal salt, metal oxide, filler, special vulcanizing agent and solvent, and stir at 45 - 55 °C and 400 - 800 rpm for 20 - 30 min to obtain a mixed liquid A;

[0051] S2. Add the formula amount of modified phenolic resin to the mixed liquid A, and stir at 300 - 600 rpm for 1 - 2 h to obtain the heat-curable adhesive.

[0052] Beneficial effects

[0053] (1) Using phenol red-modified phenolic resin and controlling the addition amount of phenol in the phenol red-modified phenolic resin to be 20 parts by mass can enhance the stability, adhesion and heat resistance of the adhesive to resist thermal shock.

[0054] (2) By controlling the mass ratio of chlorinated natural rubber to phenol red-modified phenolic resin to be (0.4 - 0.5):1, the toughness and mechanical strength of the adhesive can be effectively improved.

[0055] (3) By controlling the mass ratio of p-dinitrosobenzene, chlorinated natural rubber, and phenol red-modified phenolic resin to be (4 - 5):(4 - 6):(9 - 10), the stability and adhesion performance of the adhesive can be effectively improved.

[0056] (4) By controlling the mass ratio of zinc chloride, magnesium oxide, and phenol red-modified phenolic resin to be (1.8 - 2.2):1:(4.8 - 5.2), the mechanical properties and curing efficiency of the adhesive are effectively improved.

[0057] (5) By controlling the mass ratio of carbon black N642 to chlorinated natural rubber to be (2.8 - 3.2):10, the aging resistance and wear resistance of the adhesive are effectively improved. Detailed implementation manners

[0058] Example 1

[0059] In the first aspect of this example, a heat-curable adhesive is provided. By mass, the raw materials include: 10 parts of functional rubber, 5 parts of modified phenolic resin, 4 parts of special vulcanizing agent, 2 parts of metal salt, 1 part of metal oxide, 3 parts of filler, and 75 parts of solvent.

[0060] The solvent is methyl isobutyl ketone (CAS No.: 108 - 10 - 1), purchased from Shandong Wenshao Chemical Co., Ltd.

[0061] The functional rubber is chlorinated natural rubber.

[0062] The modified phenolic resin is phenol red-modified resin.

[0063] The chlorinated natural rubber (CAS No.: 68649 - 03 - 6) is purchased from Shandong Haoyao New Materials Co., Ltd.

[0064] The phenol red-modified phenolic resin is 2# phenol red-modified phenolic resin. By mass, the raw materials include: 30 parts of phenol red, 25 parts of phenol, 42 parts of formaldehyde solution, and 3 parts of barium hydroxide monohydrate.

[0065] The preparation method of the phenol red-modified phenolic resin includes the following steps:

[0066] Add phenol red, phenol, and barium hydroxide monohydrate into the formaldehyde solution according to the ratio, and stir at 60 °C for 30 min. Then raise the temperature to 70 °C and keep it for 2 h, and then raise the temperature to 80 °C and keep it for 3 h. After vacuum dehydration, the phenol red-modified phenolic resin is obtained.

[0067] The phenol red (CAS No.: 143 - 74 - 8) is purchased from Hubei Dongcao Chemical Technology Co., Ltd.; the phenol (CAS No.: 108 - 95 - 2) is purchased from Shandong Shengxu Energy Co., Ltd.; the formaldehyde (CAS No.: 50 - 00 - 0) is purchased from Jinan Mingchuan Chemical Co., Ltd.; the barium hydroxide monohydrate (CAS No.: 22326 - 55 - 2) is purchased from Jinan Baite New Materials Co., Ltd.

[0068] The special vulcanizing agent is p-dinitrosobenzene.

[0069] The p-dinitrosobenzene (CAS No.: 105-12-4) was purchased from Hubei Xinrunde Chemical Co., Ltd.

[0070] The metal oxide is magnesium oxide (CAS No.: 1309-48-4), which was purchased from Guangzhou Baochu Chemical Co., Ltd.

[0071] The metal chloride is zinc chloride.

[0072] The zinc chloride (7646-85-7) was purchased from Jinan Huijinchuan Chemical Co., Ltd.

[0073] The carbon black is carbon black N642.

[0074] The carbon black N642 (CAS No.: 1333-86-4) was purchased from Tianjin Yihuachang New Material Technology Co., Ltd.

[0075] In the second aspect of this embodiment, a preparation method of a heat-curable adhesive is provided, including the following steps:

[0076] S1. Mix the functional rubber, metal salt, metal oxide, filler, special vulcanizing agent and solvent in the formula amounts, and stir at 50 °C and 600 rpm for 25 min to obtain a mixed solution A;

[0077] S2. Add the formula amount of modified phenolic resin to the mixed solution A and stir at 400 rpm for 1 h to obtain the heat-curable adhesive.

[0078] Example 2

[0079] The difference from Example 1 is that the phenol red modified phenolic resin is 1# phenol red modified phenolic resin, and the phenol is 25 parts by mass.

[0080] Example 3

[0081] The difference from Example 1 is that the phenol red modified phenolic resin is 3# phenol red modified phenolic resin, and the phenol is 15 parts by mass.

[0082] Example 4

[0083] The difference from Example 1 is that by mass, the raw materials of the heat-curable adhesive include: 10 parts of functional rubber, 5 parts of modified phenolic resin, 3 parts of special vulcanizing agent, 2 parts of metal salt, 1 part of metal oxide, 3 parts of filler, and 75 parts of solvent.

[0084] Example 5

[0085] The difference from Example 1 is that by mass, the raw materials of the heat-curable adhesive include: 8 parts of functional rubber, 6 parts of modified phenolic resin, 3 parts of special vulcanizing agent, 2 parts of metal salt, 2 parts of metal oxide, 4 parts of filler, and 75 parts of solvent.

[0086] Example 6

[0087] The difference from Example 1 is that, by mass parts, the raw materials of the heat vulcanization adhesive include: 7 parts of functional rubber, 7 parts of modified phenolic resin, 3 parts of special vulcanizing agent, 3 parts of metal salt, 2 parts of metal oxide, 4 parts of filler, and 75 parts of solvent.

[0088] Example 7

[0089] The difference from Example 1 is that, by mass parts, the raw materials of the heat vulcanization adhesive include: 11 parts of functional rubber, 6 parts of modified phenolic resin, 1 part of special vulcanizing agent, 2 parts of metal salt, 1 part of metal oxide, 4 parts of filler, and 75 parts of solvent.

[0090] Example 8

[0091] The difference from Example 1 is that, by mass parts, the raw materials of the heat vulcanization adhesive include: 10 parts of functional rubber, 6 parts of modified phenolic resin, 3 parts of special vulcanizing agent, 1 part of metal salt, 1 part of metal oxide, 3 parts of filler, and 75 parts of solvent.

[0092] Example 9

[0093] The difference from Example 1 is that, by mass parts, the raw materials of the heat vulcanization adhesive include: 10 parts of functional rubber, 5 parts of modified phenolic resin, 3 parts of special vulcanizing agent, 3 parts of metal salt, 1 part of metal oxide, 3 parts of filler, and 75 parts of solvent.

[0094] Performance Test

[0095] (1) Bonding Strength

[0096] The polished galvanized iron sheet is dip-coated in the adhesives of Examples 1 - 9 and then air-dried naturally. Using natural rubber, vulcanize at 165°C under a pressure of 10 Mpa for 15 min. Then, conduct a thermal shock test on the samples according to the national standard IEC60068 - 2 - 14, from -60°C to 110°C, with a temperature transition time of 10 min, a temperature holding time of 30 min, and 150 cycles, and conduct a peel strength test. The peel strength test is carried out according to GB / T 7760 - 2003, and the results are recorded in Table 1.

[0097] (2) Adhesive Attachment Rate

[0098] The adhesive attachment rate refers to the percentage of rubber remaining on the bonded galvanized iron sheet after the peel strength test in (1), and the results are recorded in Table 1.

[0099] (3) Aging Resistance

[0100] The polished galvanized iron sheet was dip-coated in the adhesives of Examples 1-9 and then air-dried naturally. Using natural rubber, it was vulcanized at 165 °C under a pressure of 10 MPa for 15 min. Then the sample was placed under a UV lamp with a light wave wavelength in the range of 280-385 nm and a radiation intensity of 15 KWh / m 2 , and the radiation time was 168 h. The cracks, warping, and peeling phenomena that occurred in the sample were observed, and the results were recorded in Table 1.

[0101] The percentage of the area with cracks, warping, and peeling phenomena in the total area of the iron sheet was denoted as S. 0 < S ≤ 2% was considered none; 2 < S ≤ 5% was considered slight; 5 < S ≤ 10% was considered medium; and S > 10 was considered severe.

[0102] Table 1

[0103] Bonding strength (N / mm) Adhesive rate (%) Aging resistance Example 1 22.50 98 None Example 2 18.92 80 Medium Example 3 16.44 70 Medium Example 4 20.33 95 None Example 5 17.66 75 Severe Example 6 19.32 90 Medium Example 7 18.42 80 Medium Example 8 19.12 80 Medium Example 9 15.44 60 Medium

Claims

1. A heat-curing adhesive, characterized in that, By mass parts, the raw materials include: 5-20 parts of functional rubber, 1-15 parts of modified phenolic resin, 1-15 parts of special vulcanizing agent, 1-15 parts of metal salt, 1-15 parts of metal oxide, 1-15 parts of filler, and 70-75 parts of solvent; The functional rubber is chlorinated natural rubber; The modified phenolic resin is phenol red modified phenolic resin; For the phenol red modified phenolic resin, by mass parts, the raw materials include: 25-30 parts of phenol red, 15-25 parts of phenol, 42 parts of formaldehyde solution, and 3 parts of barium hydroxide monohydrate; The filler is carbon black N642, and the mass ratio of carbon black N642 to chlorinated natural rubber is (2.8-3.2):10; The special vulcanizing agent is p-dinitrosobenzene; The mass ratio of p-dinitrosobenzene, chlorinated natural rubber, and phenol red modified phenolic resin is 4:10:5; The metal oxide is magnesium oxide; The metal salt is zinc chloride; The mass ratio of zinc chloride, magnesium oxide, and phenol red modified phenolic resin is (1.8-2.2):1:(4.8-5.2).

2. The heat-curing adhesive according to claim 1, wherein By mass parts, the addition amount of phenol in the phenol red modified phenolic resin is 18-22 parts.

3. A method for preparing the heat vulcanizing adhesive according to claim 1, characterized in that, It includes the following steps: S1. Mix the formula amounts of functional rubber, metal salt, metal oxide, filler, special vulcanizing agent and solvent, and stir at 45-55 °C and 400-800 rpm for 20-30 min to obtain a mixed solution A; S2. Add the formula amount of modified phenolic resin to the mixed solution A and stir at 300-600 rpm for 1-2 h to obtain a heat vulcanizing adhesive.