Liquid glue and method for preparing the same

Abstract

The application belongs to the technical field of liquid glue and specifically relates to a liquid glue and a preparation method thereof. The liquid glue provided by the application is obtained by polymerization of monomer I, monomer II, monomer III and monomer IV. The application adopts four different types of monomers to obtain a liquid glue polymer through a free radical polymerization reaction, and a crosslinking agent is added in the polymerization process, so that not only polar groups such as amino groups, hydroxyl groups, ester groups and epoxy groups are introduced into the side chains of the liquid glue molecules, but also a three-dimensional network structure is formed between the liquid glue molecules through crosslinking, and the bonding performance and temperature resistance of the liquid glue are effectively improved.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of liquid silicone glue, and particularly relates to a liquid glue and a preparation method thereof. BACKGROUND

[0002] As a core category of connecting materials, liquid glue is applied to the fields of automobile manufacturing, electronic product production, medical equipment manufacturing, handcraft manufacturing industry, repair and repair industry, and building engineering, and its importance is not only reflected in the basic function of bonding, but also deeply penetrates into multiple dimensions such as industrial upgrading, life convenience, technological breakthrough and sustainable development, and is one of the important materials indispensable to modern social production and life.

[0003] Common liquid glue is mainly liquid silicone rubber, which has the characteristics of no deformation, high temperature resistance, acid and alkali resistance, low shrinkage, good tensile and elastic force, etc. It uses water as a solvent or dispersion medium, and the main component is a polymer emulsion such as an acrylate emulsion. In addition, thickening agents, preservatives, defoaming agents and other additives are added. It has the characteristics of good environmental protection, no release of volatile organic compounds, non-flammability, easy to use, and water washability. However, its drying speed is slow, it is easy to warp after drying, and its light transmittance is also poor, which limits its application field.

[0004] The Chinese patent application file with the publication number CN110283460A discloses a liquid silicone rubber formula, which includes 20%-50% of silicon dioxide, 45%-75% of oligomeric siloxane, 1%-10% of polymethyl hydrogen-containing siloxane, 2%-10% of vulcanizing agent, 0.1%-5% of chain extender, and 1%-15% of anti-sticking agent. The flowability of the glue can be improved by the vulcanizing agent, the reaction can be accelerated with increasing temperature by the chain extender, and the solution can be prevented from sticking to the inside of the device by the anti-sticking agent due to too high consistency. However, the liquid silicone rubber can hardly achieve high-strength bonding to polar substrates only by the reactivity of polymethyl hydrogen-containing siloxane, and the anti-sticking agent in the formula can interfere with the chemical bonding of the glue layer and the substrate surface, resulting in a decrease in initial adhesion. A high content of silicon dioxide in the formula or a wide particle size distribution can cause light scattering inside the glue layer, resulting in a decrease in the light transmittance of the glue film. SUMMARY

[0005] In order to solve the technical problems of glue film warping and low adhesion in the prior art, the purpose of the present application is to provide a liquid glue and a preparation method thereof.

[0006] In order to achieve the above-mentioned purpose, the technical scheme of the present application is as follows:

[0007] A liquid adhesive is obtained by polymerization of monomer I, monomer II, monomer III and monomer IV; the monomer III is composed of N-hydroxymethyl acrylamide and glycidyl methacrylate in a mass ratio of 8-11:3-6; the monomer IV is composed of vinyl triethoxysilane and vinyl tri(2-methoxyethoxy)silane in a mass ratio of 3-5:1-2.

[0008] By the above technical solution, the monomer I, monomer II and monomer III are polymerized under the initiation of potassium persulfate to obtain a liquid adhesive polymer, the monomer III is N-hydroxymethyl acrylamide and glycidyl methacrylate, wherein the N-hydroxymethyl acrylamide can introduce amino and hydroxyl groups in the side chain of the liquid adhesive molecule, and the glycidyl methacrylate can introduce ester groups and epoxy groups in the side chain of the liquid adhesive molecule, the introduction of these polar groups can improve the adsorption effect of the liquid adhesive on the surface of the adherend, and can also serve as crosslinking sites to improve the cohesive strength of the polymer, thereby improving the wear resistance and thermal stability of the liquid adhesive. It is found that the mass ratio of N-hydroxymethyl acrylamide and glycidyl methacrylate will affect the initial tack and holding power of the liquid adhesive, when the mass ratio is within the range defined in the application, the initial tack and holding power of the liquid adhesive are optimal, which is caused by the change of adsorption sites in the side chain of the liquid adhesive molecule and / or crosslinking degree. The monomer IV is an organosilane, by introducing organosilane side chains containing silicon-oxygen bonds into the molecular structure of the liquid adhesive, the heat resistance of the liquid adhesive molecule is effectively improved, the viscosity of the liquid adhesive at high temperature is improved, thereby effectively avoiding the warping of the adhesive film.

[0009] Further, the monomer I is one of ethyl acrylate, n-butyl acrylate, lauryl acrylate, 2-ethylhexyl acrylate, and n-octyl methacrylate; the monomer II is one of methyl methacrylate, ethyl methacrylate, and styrene.

[0010] In the above technical solution, the steric hindrance effect caused by the side chain of the monomer I can weaken the interaction between the polymer main chains, forming an internal plasticizing effect, and its side chain can also absorb and disperse stress, reducing stress concentration in the polymer, improving the flexibility and adhesion of the liquid adhesive after film formation, and avoiding warping of the adhesive film; the molecular side chain of the monomer II is short, and the polymer formed after polymerization has high crosslinking density and tight molecular structure, improving the cohesive strength of the polymer, and thus the hardness, wear resistance and thermal stability of the liquid adhesive film layer can be improved.

[0011] Further, the preparation method of the liquid adhesive is as follows: mixing monomer I, monomer II, monomer III and monomer IV with emulsifier, sodium bicarbonate and 2 / 3 water, stirring for 1-1.5 h to obtain a pre-emulsion; mixing 1 / 2 sodium persulfate with 1 / 3 water, adding 1 / 3 of the pre-emulsion under stirring, heating to 85-90℃, passing N2, keeping the temperature for 0.5-1 h, continuously heating to 100-105℃, adding the remaining pre-emulsion under stirring, controlling the dropping time within 2.5 h, adding the remaining 1 / 2 sodium persulfate after the dropping is completed, adding a crosslinking agent, keeping the temperature for 5-5.5 h, continuously stirring for 1-1.5 h, stopping the stirring, cooling, and obtaining the liquid adhesive.

[0012] By the above technical solution, the preparation of the pre-emulsion is conducive to forming latex particles with a narrower and more uniform particle size distribution in the polymerization process, effectively preventing demulsification and layering in the polymerization process; the stepwise addition of sodium persulfate can control the free radical generation rate, reduce the excessive local reaction, and reduce the probability of side reactions; the second addition of sodium persulfate helps to further promote the reaction of residual monomers, improve the monomer conversion rate and the molecular weight of the polymer; by controlling the dropping time of the pre-emulsion, the release of reaction heat is controlled, avoiding the instability of the emulsion caused by high local heat concentration, and making the prepared liquid adhesive more uniform; the addition of the crosslinking agent in the polymerization process can form crosslinking between the molecules and the side chains of the polymer, form a three-dimensional network structure, and improve the thermal stability and bonding performance of the liquid adhesive.

[0013] Further, the weight fractions of the components in the preparation method of the liquid adhesive are as follows: monomer I 35-45 parts, monomer II 40-50 parts, monomer III 8-11 parts, monomer IV 5-8 parts, sodium persulfate 5-8 parts, emulsifier 10-15 parts, sodium bicarbonate 2-5 parts, crosslinking agent 8-12 parts, and water 50-60 parts.

[0014] Further, the crosslinking agent is ethylene glycol dimethacrylate.

[0015] Ethylene glycol dimethacrylate contains two methacrylate functional groups, which can participate in free radical polymerization, and can form chemical bonds between polymer chains during polymerization, thereby forming a three-dimensional network structure for the prepared liquid adhesive and improving the bonding performance of the liquid adhesive.

[0016] Further, the emulsifier is one of sodium dodecyl sulfate, sodium dodecyl benzene sulfonate, and dioctyl sodium sulfosuccinate.

[0017] Compared with the prior art, the liquid adhesive and the preparation method thereof have the following technical advantages: the liquid adhesive polymer is obtained by free radical polymerization reaction of four different types of monomers, and a crosslinking agent is added in the polymerization process, so that polar groups such as amino groups, hydroxyl groups, ester groups and epoxy groups are introduced into the side chains of the liquid adhesive molecules, and a three-dimensional network structure is formed between the liquid adhesive molecules through crosslinking, thereby effectively improving the bonding performance and temperature resistance of the liquid adhesive; the liquid adhesive has good bonding performance and holding performance, good exhaust performance and wear resistance, is not easy to warp, has high light transmittance, and the preparation method is simple, raw materials are easy to obtain, and industrial production can be realized. BRIEF DESCRIPTION OF DRAWINGS

[0018] Figure 1 The infrared spectrum of the liquid adhesive prepared in Example 4. DETAILED DESCRIPTION

[0019] The following will be further described in combination with specific examples, but the present application is not limited to the following examples. Those skilled in the art can make various modifications according to the basic idea of the present application, as long as the modifications do not deviate from the basic idea of the present application, and are within the scope of the present application.

[0020] Example 1

[0021] A liquid adhesive is obtained by polymerization of n-butyl acrylate, methyl methacrylate, monomer III and monomer IV; the monomer III is composed of N-hydroxymethyl acrylamide and glycidyl methacrylate in a mass ratio of 8:3; and the monomer IV is composed of vinyl triethoxysilane and vinyl tri(2-methoxyethoxy)silane in a mass ratio of 3:1.

[0022] The preparation method of the liquid adhesive is as follows: 35 g of monomer I, 40 g of monomer II, 11 g of monomer III and 8 g of monomer IV are mixed with 10 g of sodium dodecyl sulfate, 2 g of sodium bicarbonate and 33 g of water, and stirred for 1 h to obtain a pre-emulsion; 2.5 g of sodium persulfate is uniformly mixed with 17 g of water, and then 1 / 3 of the pre-emulsion is added under stirring, and then heated to 85℃, and N2 is introduced, and the reaction is kept for 0.5 h, and then heated to 100℃, and the remaining pre-emulsion is added dropwise under stirring, and the dropwise adding time is controlled to be within 2.5 h, and then 2.5 g of sodium persulfate and 8 g of ethylene glycol dimethacrylate are added after the dropwise adding is completed, and the reaction is kept for 5 h, and then stirred for 1 h, and then the stirring is stopped, and then cooled to obtain the liquid adhesive.

[0023] Example 2

[0024] A liquid adhesive is prepared by polymerization of lauryl acrylate, styrene, monomer III and monomer IV; the monomer III is composed of N-hydroxymethyl acrylamide and glycidyl methacrylate in a mass ratio of 11:6; the monomer IV is composed of vinyl triethoxysilane and vinyl tri(2-methoxyethoxy)silane in a mass ratio of 5:2.

[0025] The preparation method of the liquid adhesive is as follows: 45 g of monomer I, 50 g of monomer II, 8 g of monomer III and 5 g of monomer IV are mixed with 15 g of sodium dodecyl benzene sulfonate, 5 g of sodium bicarbonate and 40 g of water, stirred for 1.5 h to obtain a pre-emulsion; 4 g of sodium persulfate is uniformly mixed with 20 g of water, and 1 / 3 of the pre-emulsion is added under stirring, then heated to 90℃, N2 is introduced, and the reaction is kept for 1 h; the temperature is continuously increased to 105℃, the remaining pre-emulsion is added dropwise under stirring, the dropwise adding time is controlled within 2.5 h, 4 g of sodium persulfate is added after the dropwise adding is completed, 12 g of ethylene glycol dimethacrylate is added, the reaction is kept for 5.5 h, the stirring is continuously kept for 1.5 h, the stirring is stopped, and the liquid adhesive is obtained after cooling.

[0026] Example 3

[0027] A liquid adhesive is prepared by polymerization of lauryl acrylate, styrene, monomer III and monomer IV; the monomer III is composed of N-hydroxymethyl acrylamide and glycidyl methacrylate in a mass ratio of 11:6; the monomer IV is composed of vinyl triethoxysilane and vinyl tri(2-methoxyethoxy)silane in a mass ratio of 5:2.

[0028] The preparation method of the liquid adhesive is as follows: 45 g of monomer I, 50 g of monomer II, 8 g of monomer III and 5 g of monomer IV are mixed with 15 g of sodium dodecyl benzene sulfonate, 5 g of sodium bicarbonate and 40 g of water, stirred for 1.5 h to obtain a pre-emulsion; 4 g of sodium persulfate is uniformly mixed with 20 g of water, and 1 / 3 of the pre-emulsion is added under stirring, then heated to 90℃, N2 is introduced, and the reaction is kept for 1 h; the temperature is continuously increased to 105℃, the remaining pre-emulsion is added dropwise under stirring, the dropwise adding time is controlled within 2.5 h, 4 g of sodium persulfate is added after the dropwise adding is completed, 12 g of ethylene glycol dimethacrylate is added, the reaction is kept for 5.5 h, the stirring is continuously kept for 1.5 h, the stirring is stopped, and the liquid adhesive is obtained after cooling.

[0029] Example 4

[0030] The difference between this example and Example 3 is that the monomer III is composed of N-hydroxymethyl acrylamide and glycidyl methacrylate in a mass ratio of 9:4; the monomer IV is composed of vinyl triethoxysilane and vinyl tri(2-methoxyethoxy)silane in a mass ratio of 5:1.

[0031] The other is the same as Example 3.

[0032] Comparative Example 1

[0033] This comparative example is similar to Example 3, and the difference between this comparative example and Example 3 is that the monomer III in the liquid adhesive of this comparative example is N-hydroxymethyl acrylamide.

[0034] Comparative Example 2

[0035] This comparative example is similar to Example 3, and the difference between this comparative example and Example 3 is that the monomer III in the liquid adhesive of this comparative example is composed of N-hydroxymethyl acrylamide and glycidyl methacrylate according to a mass ratio of 2:11.

[0036] Comparative Example 3

[0037] This comparative example is similar to Example 3, and the difference between this comparative example and Example 3 is that the monomer IV in the liquid adhesive of this comparative example is composed of vinyl triethoxysilane and vinyl tri(2-methoxyethoxy)silane according to a mass ratio of 1:5.

[0038] Comparative Example 4

[0039] This comparative example is similar to Example 4, and the difference between this comparative example and Example 4 is that the monomer IV in the liquid adhesive of this comparative example is vinyl triethoxysilane.

[0040] Comparative Example 5

[0041] This comparative example is similar to Example 4, and the difference between this comparative example and Example 4 is that the crosslinking agent in the preparation method of the liquid adhesive of this comparative example is divinylbenzene.

[0042] Test Example

[0043] Adhesion test: The liquid adhesives prepared in Examples 1-4 and Comparative Examples 1-5 were tested for initial adhesion according to GB / T 31125-2014, and for holding adhesion according to GB / T 4851-2014; the liquid adhesives prepared in Examples 1-4 and Comparative Examples 1-5 were tested for AF screen peeling force according to GB / T 2792-81; curling test: the liquid adhesives prepared in Examples 1-4 and Comparative Examples 1-5 were attached to a curved AF screen, and then placed in an oven at 75°C for 10h to confirm whether the edge part was curled, 10 test pieces were tested for each group, and the number of test pieces with edge curling of more than 2mm was recorded; the test results are shown in Table 1.

[0044] Transmittance test: the liquid glue prepared in Example 1-Example 4 was placed under the irradiation of ultraviolet lamp (ultraviolet light wavelength is 365nm) for 24h, and the liquid glue before irradiation and the liquid glue after irradiation were respectively placed in the transmittance haze test window at room temperature, the test was repeated three times, and the average value was recorded; the test results are shown in Table 2.

[0045] Infrared spectrum test: the liquid glue prepared in Example 4 was tested by using Fourier infrared spectrometer (FT-IR, Nicolet 5700, Nicolet company), the sample preparation method was that the liquid glue was coated on KBr tablet, dried, and after the dry treatment of the cured film, the crushed tablet was mixed with KBr powder uniformly, and then pressed. The test method was that the resolution was 4cm -1 -500cm -1 , the scanning times were 32 times, and the scanning range was 4000cm -1 -500cm -1 , the scanning times were 32 times, and the scanning range was 4000cm Figure 1

[0046] Table 1 adhesion test results

[0047]

[0048] As shown in Table 1, the liquid glue provided by the application has good initial adhesion and adhesion, high peeling strength and is not easy to warp, and has excellent performance and good protection effect on the screen.

[0049] Compared with Example 3, the component and the amount ratio of monomer III in the liquid glue of Comparative Example 1 and Comparative Example 2 are changed, but the initial adhesion and adhesion of the prepared protective film are reduced, which shows that the component and the amount ratio of monomer III can adjust the initial adhesion and adhesion of the liquid glue; the amount ratio of monomer IV is changed in Comparative Example 3, but the adhesion of the prepared protective film is reduced, and the number of warping increases, which shows that monomer IV can effectively improve the adhesion and high temperature stability of the liquid glue. Compared with Example 4, the component of monomer IV is changed in Comparative Example 4, but the adhesion of the prepared protective film is reduced, and the number of warping increases, and Comparative Example 5 uses the same multi-functional crosslinking agent instead of ethylene glycol dimethacrylate, but the adhesion of the prepared liquid glue is reduced, which shows that not all crosslinking agents can have the technical effect of ethylene glycol dimethacrylate.

[0050] Table 2 transmittance test results

[0051]

[0052] As shown in Table 2, the liquid glue provided by the application has high transmittance, and the transmittance decreases slowly.

[0053] From Figure 1It can be seen that the stretching vibration peak of -OH appears at 3440 cm -1 The stretching vibration peak of C-H appears at 2884 cm -1 The characteristic absorption peak of ester group appears at 1736 cm -1 The bending vibration peak of secondary amine group appears at 1596 cm -1 The characteristic absorption peak of C-Si appears at 1344 cm -1 The characteristic absorption peak of Si-O-C appears at 1280 cm -1 The characteristic absorption peak of Si-O-C appears at 1243 cm -1 The characteristic absorption peak of ether group appears at 940 cm -1 The characteristic absorption peak of epoxy group appears at 940 cm, which indicates that monomer I, monomer II, monomer III and monomer IV all participate in the polymerization reaction, and good polymerization effect is achieved.

[0054] The above examples are merely illustrative of the present application and are not intended to limit the present application. Those skilled in the art cannot modify the above examples without departing from the spirit and scope of the present application. All equivalent modifications or changes made by those skilled in the art without departing from the technical idea of the present application still belong to the protection scope of the present application.

Claims

1. A liquid adhesive, characterized by, Polymerized from monomer I, monomer II, monomer III and monomer IV; the monomer III is composed of N-hydroxymethyl acrylamide and glycidyl methacrylate in a mass ratio of 8-11:3-6; the monomer IV is composed of vinyl triethoxysilane and vinyl tri(2-methoxyethoxy)silane in a mass ratio of 3-5:1-2; The monomer I is one of ethyl acrylate, n-butyl acrylate, lauryl acrylate, 2-ethylhexyl acrylate and n-octyl methacrylate; the monomer II is one of methyl methacrylate, ethyl methacrylate and styrene; The weight fractions of the components in the preparation method of the liquid glue are: monomer I 35-45 parts, monomer II 40-50 parts, monomer III 8-11 parts, monomer IV 5-8 parts, sodium persulfate 5-8 parts, emulsifier 10-15 parts, sodium bicarbonate 2-5 parts, crosslinking agent 8-12 parts, and water 50-60 parts. The crosslinking agent is ethylene glycol dimethacrylate. Specifically, monomer I, monomer II, monomer III and monomer IV are mixed with emulsifier, sodium bicarbonate and 2 / 3 water, stirred for 1-1.5h to obtain a pre-emulsion; 1 / 2 sodium persulfate is uniformly mixed with 1 / 3 water, and under stirring, 1 / 3 of the pre-emulsion is added, then heated to 85-90℃, N2 is introduced, and the reaction is kept for 0.5-1h, then heated to 100-105℃, the remaining pre-emulsion is added dropwise under stirring, the dropwise time is controlled within 2.5h, after the dropwise addition is completed, the remaining 1 / 2 sodium persulfate is added, the crosslinking agent is added, and the reaction is kept for 5-5.5h, then stirred for 1-1.5h, stopped stirring, cooled, and the liquid glue is obtained.

2. The method of claim 1, wherein The emulsifier is one of sodium dodecyl sulfate, sodium dodecylbenzenesulfonate and dioctyl sodium sulfosuccinate.

3. The method of claim 2, wherein ​

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