KR102236968B1 - Alkali silicate adhesive composition and method of curing using the same - Google Patents

Abstract

The alkali silicate adhesive composition of the present invention includes sodium silicate, potassium silicate and lithium silicate, and the mass ratio of the sodium silicate, potassium silicate and lithium silicate is 50 to 80: 50 to 80: 20 to 50.
The curing method of the alkali-based silicate adhesive composition of the present invention comprises the steps of preparing an alkali-based silicate adhesive composition; Applying the adhesive composition to an adherend; And high-speed curing of the adhesive composition at a torque of 50 to 170 kgf and a temperature of 25 to 180° C. for 0.5 to 36 hours.

Description

Alkali silicate adhesive composition and method of curing using the same}

The present invention relates to an alkali silicate adhesive composition and a curing method using the same.

As the polymer adhesive market increases, the demand for various functional adhesives is also increasing. On the other hand, as the demand for eco-friendly products has increased rapidly due to the recent reinforcement of environmental regulations, it is necessary to develop eco-friendly and various functional adhesives.

Organic substance-based adhesives, which are widely used in the past, have a problem that they are harmful to the human body and cause environmental pollution. Therefore, active research has been conducted on an environmentally friendly and harmless inorganic material-based adhesive. However, the inorganic material-based adhesive has disadvantages such as poor water resistance and poor adhesive properties compared to the organic material-based adhesive.

Meanwhile, as a representative example of an inorganic material-based adhesive, an alkali silicate-based adhesive has been developed to be used for fibrous adherends such as paper, but there is a problem that the adherend is discolored and adhesive strength is weakened over time. In addition, there is a problem that it is difficult to apply to an adherend made of various materials such as stainless steel, metal, or ceramic.

An object of the present invention is to provide an eco-friendly adhesive composition that can replace an organic material-based adhesive that has been used in the past, and has improved water resistance and high adhesive strength. In addition, an object of the present invention is to provide a method for curing at high speed using such an eco-friendly adhesive composition.

The alkali silicate adhesive composition of the present invention includes sodium silicate, potassium silicate and lithium silicate, and the mass ratio of the sodium silicate, potassium silicate and lithium silicate is 50 to 80: 50 to 80: 20 to 50.

The curing method of the alkali-based silicate adhesive composition of the present invention comprises the steps of preparing an alkali-based silicate adhesive composition; Applying the adhesive composition to an adherend; And high-speed curing of the adhesive composition at a torque of 50 to 170 kgf and a temperature of 25 to 180° C. for 0.5 to 36 hours.

The alkali-based silicate adhesive composition according to an embodiment of the present invention can replace the existing organic material-based adhesive having problems of human body hazard and low heat resistance. In addition, it is possible to improve the adhesive strength and improve the polymerization properties than the conventional inorganic material-based adhesive having a low adhesive strength. In addition, it is possible to improve the low water resistance of the existing silicate-based adhesive. In addition, heat resistance and flame retardancy can be improved, and since it can be applied to an adherend made of stainless steel, metal, or ceramic, it can be applied to various fields such as aviation, transportation equipment, vehicles, or construction industries.

Since the alkali-based silicate adhesive composition of the present invention is an inorganic material-based adhesive composition, it is harmless to the human body and is environmentally friendly, and the manufacturing cost is low, so it can be used in various industries.

By adding an additional filler to the alkali-based silicate adhesive composition of the present invention, it can be utilized for various purposes.

1A is a photograph of an adherend prepared in an embodiment of the present invention, and (b) is a photo of a curing mold for applying compression pressure to the adherend.
2 is a graph of shear strength according to SS ratio in an embodiment of the present invention.
3 is a schematic diagram of a method for evaluating water resistance in an experimental example of the present invention.
4 is a result of measuring the residual mass ratio according to exemplary embodiments of the present invention.
5 is a result of measuring shear strength according to compression pressure in an embodiment of the present invention.
6 is a result of measuring shear strength according to curing time at each curing temperature in an embodiment of the present invention.
7 is a result of measuring the residual mass ratio and Vickers hardness according to the curing time.

Hereinafter, various embodiments of the present document will be described with reference to the accompanying drawings. The examples and terms used therein are not intended to limit the technology described in this document to a specific embodiment, and should be understood to include various changes, equivalents, and/or substitutes for the corresponding embodiment.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

An alkali-based silicate adhesive composition according to various embodiments of the present invention may include sodium silicate, potassium silicate, and lithium silicate. At this time, the mass ratio of sodium silicate, potassium silicate, and lithium silicate may be 50 to 80:50 to 80: 20 to 50. In the present invention, when the mass ratio of sodium silicate, potassium silicate, and lithium silicate satisfies the above value, it is possible to improve adhesion strength compared to an organic material-based adhesive having a low adhesion strength. Therefore, it is possible to replace the organic material-based adhesive that is harmful to the human body. In addition, it is possible to improve the low water resistance of the existing silicate-based adhesive. In addition, heat resistance and flame retardancy can be improved, and since it can be applied to an adherend made of stainless steel, metal, or ceramic, it can be applied to various fields such as aviation, transportation equipment, vehicles, or construction industries.

Preferably, the mass ratio of sodium silicate, potassium silicate and lithium silicate may be 7:7:3.

In sodium silicate, the molar ratio of silicic acid and sodium (SiO ₂ /Na ₂ O) may be 2 to 3. Preferably, the molar ratio of silicic acid and sodium (SiO ₂ /Na ₂ O) may be from 2.4 to 2.6.

In potassium silicate, the molar ratio of silicic acid and potassium (SiO ₂ /K ₂ O) may be 3 to 4. Preferably, the molar ratio of silicic acid and potassium (SiO ₂ /K ₂ O) may be 3.2 to 3.4.

In lithium silicate, the molar ratio of silicic acid and lithium (SiO ₂ /Li ₂ O) may be 4 to 5. Preferably, the molar ratio of silicic acid and potassium (SiO ₂ /K ₂ O) may be 4.6 to 4.8.

The molar ratio is an important factor because it affects the structural ratio of a single molecule. In the present invention, by controlling the molar ratio of silicic acid and alkali elements in sodium silicate, potassium silicate, and lithium silicate as described above, the adhesive strength can be improved compared to the organic material-based adhesive having low adhesive strength, and polymerization properties can be improved. I can. Therefore, it is possible to replace the organic material-based adhesive that is harmful to the human body. In addition, it is possible to improve the low water resistance of the existing silicate-based adhesive. In addition, heat resistance and flame retardancy can be improved, and since it can be applied to an adherend made of stainless steel, metal, or ceramic, it can be applied to various fields such as aviation, transportation equipment, vehicles, or construction industries.

Since the alkali-based silicate adhesive composition of the present invention is an inorganic material-based adhesive composition, it is harmless to the human body and is environmentally friendly, and the manufacturing cost is low, so it can be used in various industries.

On the other hand, by adding an additional filler to the alkali-based silicate adhesive composition of the present invention, it can be utilized for various purposes.

A method of curing an alkali-based silicate adhesive composition according to various embodiments of the present invention includes: preparing an alkali-based silicate adhesive composition; Applying the adhesive composition to the adherend; And high-speed curing of the adhesive composition at a torque of 50 to 170 kgf and a temperature of 25 to 180° C. for 0.5 to 36 hours. At this time, the alkaline silicate adhesive composition is as described above.

On the other hand, in the high-speed curing step, it may be preferably cured at a compression pressure of 150 kgf. In addition, in the high-speed curing step, the curing time may be adjusted according to the curing temperature. For example, the curing time can be shortened at a high curing temperature. Preferably, it can be cured for 36 hours at a curing temperature of 80°C. Alternatively, it may be cured for 12 hours at a curing temperature of 120°C. At a curing temperature of 140° C., it can be cured for 2 hours.

Through the curing method of the present invention, the adhesive composition can be applied to an adherend made of stainless steel or metal, and high water resistance and shear strength of the adhesive can be secured.

Hereinafter, the present invention will be described in detail by examples. However, the following examples are for illustrative purposes only, and the present invention is not limited by the following examples.

Example

Sodium silicate, potassium silicate, and lithium silicate having the characteristics of Table 1 were mixed in a mass ratio of 70:70:30 to prepare an alkaline silicate adhesive composition.

Property Sodium silicate Potassium silicate Lithium silicate pH 12 to 13 11 to 12 11 to 12 Density(g cm ^-3 ) 1.55 to 1.57 1.38 to 1.40 1.19 ~ 1.21 Na₂O, K₂O, Li₂O (%) 13 to 14 13 to 14 2 ~ 2.2 SiO₂(%) 33 to 35 27.5 ~ 28.5 19.5 ~ 20.5 Molar ratio 2.4 ~ 2.6 3.2 ~ 3.4 4.6 ~ 4.8 Viscosity(cps, 20℃) Max. 1,500 Max. 50 Max. 50

SUS304, which is an adherend, was prepared as shown in (a) of FIG. 1 according to the standard size of ASTM D 3165. The bonding line to which the adhesive composition is applied is located in the center of the adherend and has an interval of 10 mm. On the other hand, the surface of the adherend was ground before measuring the shear strength. Grinding was performed at a rotation speed of 80 rpm for 1 minute using 800 P (400 grit) of SIC paper. After grinding, the surface of the adherend was washed with ethanol and distilled water, and dried in a convection oven.

Compression pressure was applied to the adherend using a hardening mold. Referring to (b) of Figure 1, the mold was made of SM45C steel. Compression pressure was applied by means of a torque wrench. 16 bolts were joined at regular intervals. Compression pressure was applied by varying the torque values to 50, 100 and 150 kgf. The adherend was fixed to the mould, and the adhesive composition was applied on the bonding line of the adherend. Thermal curing was performed at different temperatures of 80, 120 and 140° C. using a convection oven, and curing time was performed for 2 to 36 hours.

Experimental Example 1- Shear strength measurement

Shear strength measurement was performed according to ASTM D 3165 standard, and was measured using a universal material tester (UTM, INSTRON, 8801). Shear strength was measured by mixing potassium silicate (hereinafter “PS”) and lithium silicate (hereinafter “LS”) in sodium silicate (hereinafter “SS”) at different weight ratios of 10 to 90 wt %. The results are shown in FIG. 3. Each specimen was heat cured at 120° C. for 12 hours.

Referring to FIG. 2, the shear strength of SS was measured to be 6.66 MPa. On the other hand, when SS and PS were mixed at a weight ratio of 50:50, the maximum shear strength was shown, and the shear strength was 8.86 MPa. After that, when the ratio of SS was increased to 60% and 70%, the shear strength decreased. When SS and PS were mixed at 70:30, the maximum shear strength was shown, and the shear strength was 3.79 MPa. Through this, it was confirmed that the addition of LS reduced the adhesive shear strength.

Experimental Example 2- Evaluation of water resistance according to the composition of the adhesive composition

Referring to FIG. 3, water resistance is obtained by immersing the adhesive composition cured at 120° C. for 12 hours in distilled water for 24 hours, and then measuring the initial mass (m _i ) and the residual mass ( m _r ) of the adhesive. It was evaluated through (m _r / m _{i ).}

On the other hand, in Experimental Example 1 above, it was confirmed that the SS exhibited a shear strength of 6.66 MPa, but showed low water resistance due to its water-soluble property. Therefore, an attempt was made to improve water resistance by mixing SS, PS and LS.

The adhesive and LS mixed at the mass ratio of SS:PS=50:50 (hereinafter referred to as'SS@PS') and SS:LS=70:30 (hereinafter referred to as'SS@LS') showed the highest shear strength in Experimental Example 1 The water resistance was evaluated by measuring the residual mass ratio of the adhesive mixed with SS:PS:LS=7:7:3 (hereinafter referred to as'MS773') in which a small amount of was added.

The results are shown in Fig. 4 and Table 2 below.

Case
(Unit) Mass of the substrate
(g) Initial mass of
MS, m _i
(g) Remaining mass of MS, m _r
(g) Residual ratio,
m _r / m _i
(%) SS:PS #1 ¹⁾ 42.431 0.127 0.041 32.28 SS:PS #2 42.366 0.11 0.034 30.91 SS:PS #3 42.3 0.082 0.024 29.27 Average residual ratio (%) 30.82 SS:LS #1 ²⁾ 42.271 0.15 0.136 90.67 SS:LS #2 42.451 0.087 0.074 85.06 SS:LS #3 42.512 0.093 0.082 88.17 Average residual ratio (%) 87.97 MS773 #1 ³⁾ 42.677 0.149 0.095 63.76 MS773 #2 42.522 0.091 0.046 50.55 MS773 #3 42.605 0.073 0.033 45.21 Average residual ratio (%) 53.17

SS: Sodium silicate; PS: potassium silicate; LS: lithium silicate.

Mass ratios: 1) SS:PS = 50:50; 2) SS:LS = 70:30; 3) MS = SS:PS:LS = 7:7:3

4 and Table 2, the residual mass ratio of SS@PS was 30.8%, and the residual mass ratio of SS@LS was 88.0%. That is, it was confirmed that the shear strength of SS@PS was higher than that of SS@LS, but the water resistance was much lower. On the other hand, in the case of MS773 with a small amount of LS added, it was confirmed that the residual mass ratio was 53.2%, which was 172.7% higher than that of SS@PS.

Experimental Example 3- Shear strength measurement according to curing conditions

Shear strength according to curing compression pressure was measured for MS773. Shear strength was tested three times at each compression pressure, and the average was calculated and compared. Each specimen was cured at 120° C. for 12 hours. Referring to FIG. 5, when compressive pressures of 50, 100 and 150 kgf were applied, average shear strengths were 6.17, 5.49 and 8.06 MPa, respectively. That is, the shear strength was highest when the curing pressure was 150 kgf.

After establishing the optimum curing pressure, the shear strength was measured by curing at various temperatures. After curing for 2 to 36 hours at each temperature of 80, 120 and 140 °C, the shear strength was measured. Referring to FIG. 6A, when curing at a temperature of 80° C., the shear strength was the highest at 7.4 MPa at 36 hours. That is, it can be seen that in mild conditions, as the curing time increases, the shear strength increases.

Referring to (b) of FIG. 6, when curing at a temperature of 120° C., the shear strength was the highest at 9.29 MPa at 12 hours. However, the shear strength decreased after 12 hours.

Referring to FIG. 6C, when curing at a temperature of 140° C., the adhesive strength was very low, and the shear strength could not be measured in 6 to 24 hours. Shear strength decreased with increasing curing time. That is, the shear strength was the highest at 7.3 MPa at 2 hours.

That is, it can be seen that as the curing temperature increases, the curing time providing the maximum shear strength point decreases.

Experimental Example 4-Observation of adhesion properties of Examples

Residual tests confirmed the relationship between the evaporation and shear strength of water in the adhesive. The residual test is similar to the previously conducted water resistance evaluation. MS773 was coated on the SUS304 specimen and then thermally cured. The residual mass ratio ( m _ac / m _bc ) was calculated by measuring the mass before thermal curing ( m _bc ) and the mass after thermal curing ( m _{ac) using an electronic balance.} Each experiment was performed 3 times and the average was calculated.

7A is a result of measuring the residual mass ratio according to the curing time at different curing temperatures. Referring to FIG. 7A, when curing was performed at 80° C., the residual mass ratio was 49.67% at 2 hours and decreased to 46.10% at 36 hours. On the other hand, when curing proceeded at 120° C., the residual mass ratio was 48.59% at 2 hours and rapidly decreased to 45.02% at 24 hours. When curing proceeded at 140° C., the residual mass ratio was 46.87% at 2 hours and rapidly decreased to 44.71% at 24 hours. Based on these results, it was confirmed that the residual mass ratio tended to decrease as the curing time increased. On the other hand, in terms of maximum shear strength, the residual mass ratio was 46.10% after curing at 80°C for 36 hours, 45.96% after curing at 120°C for 12 hours, and 46.87% after curing at 140°C for 2 hours. The MS773 adhesive composition contained 61.05 wt% water. The maximum shear strength was achieved when 88.44% of water was evaporated.

On the other hand, it was observed why the shear strength was different through the Vickers hardness test. Vickers hardness according to the curing time was measured, and the data are averaged by measuring six times.

Referring to (b) of FIG. 7, the hardness also increased as the curing time increased. Specifically, when curing proceeded at 80° C., the hardness was 203.2 HV at 2 hours, and the hardness at 36 hours was 310 HV. When curing proceeded at 120° C., the hardness showed 263 HV at 2 hours, and 340.85 HV at 24 hours. When curing proceeded at 140° C., the hardness showed 332 HV at 2 hours, and 392 HV at 24 hours. From the viewpoint of maximum shear strength, the hardness was 310 HV when cured at 80° C. for 36 hours, the hardness was 313.75 HV when cured at 120° C. for 12 hours, and the hardness was 332 HV when cured at 140° C. for 2 hours. In general, the hardness also increased with increasing curing time regardless of temperature, and the maximum shear strength showed a hardness of 310 HV or more. The hardness increases with the curing time, but the shear strength decreases in some cases.

This reduction in shear strength can be explained by evaporation. In other words, when the curing time is longer than 12 hours at a curing temperature of 120°C, or when the curing time is longer than 2 hours at 140°C, the trapped moisture is evaporated, thereby promoting gas discharge from the adhesive layer. As it occurs, the shear strength decreases.

So far, the present invention has been looked at around its preferred embodiments. Those of ordinary skill in the art to which the present invention pertains will be able to understand that the present invention may be implemented in a modified form without departing from the essential characteristics of the present invention. Therefore, the disclosed embodiments should be considered from an illustrative point of view rather than a limiting point of view. The scope of the present invention is shown in the claims rather than the above description, and all differences within the scope equivalent thereto should be construed as being included in the present invention.

Claims (5)

Sodium silicate, potassium silicate and lithium silicate,
The mass ratio of the sodium silicate, potassium silicate and lithium silicate is 50 to 80: 50 to 80: 20 to 50,
The molar ratio of silicic acid and sodium in the sodium silicate (SiO ₂ /Na ₂ O) is 2.4 to 2.6,
In the potassium silicate, the molar ratio of silicic acid and potassium (SiO ₂ /K ₂ O) is 3.2 to 3.4,
In the lithium silicate, the molar ratio of silicic acid and lithium (SiO ₂ /Li ₂ O) is an alkali silicate adhesive composition of 4.6 to 4.8. delete Preparing an alkaline silicate adhesive composition;
Applying the adhesive composition to an adherend; And
High-speed curing of the adhesive composition for 0.5 to 36 hours at a compression pressure of 50 to 170 kgf, a temperature of 25 to 180 °C,
The alkali-based silicate adhesive composition includes sodium silicate, potassium silicate, and lithium silicate,
The mass ratio of the sodium silicate, potassium silicate and lithium silicate is 50 to 80: 50 to 80: 20 to 50,
The molar ratio of silicic acid and sodium in the sodium silicate (SiO ₂ /Na ₂ O) is 2.4 to 2.6,
In the potassium silicate, the molar ratio of silicic acid and potassium (SiO ₂ /K ₂ O) is 3.2 to 3.4,
In the lithium silicate, the molar ratio of silicic acid and lithium (SiO ₂ /Li ₂ O) is 4.6 to 4.8, the curing method of the alkali-based silicate adhesive composition.

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