JP7733510B2 - Method for applying a two-part addition-curable silicone composition and apparatus therefor - Google Patents

Description

The present invention relates to a method for applying a two-component addition-curable silicone composition and an apparatus for doing so.

In recent years, the miniaturization and high precision of electrical and electronic components has created a demand for intermittent application of small amounts of curable silicone composition, on the order of a few microliters, onto electrical and electronic components and substrates. Generally, two-part addition-curable silicone compositions are used because they have a fast curing reaction and do not produce by-products during curing, and a static mixer is used to mix the two parts.

With two-component addition-curable silicone compositions, the addition reaction begins immediately after the two components come into contact. Therefore, when a small amount is applied, the viscosity increases inside the static mixer, and the rate of decrease in the amount applied from the start of application can exceed 30% after one hour. In severe cases, clogging can occur inside the static mixer or at the discharge section.

To solve these problems, it has been proposed to reduce the room temperature curing property of two-component addition-curable silicone compositions, and Patent Documents 1 to 3 propose achieving both coating ease and curing properties by laminating substrates to which each component of the two-component addition-curable silicone composition has been applied separately from two different nozzles.

Meanwhile, Patent Documents 4 to 7 propose a method of mixing a two-component addition-curable silicone composition in a static mixer cooled to -60°C to +5°C, and then discharging the mixture into a mold at +25°C to +100°C, or into water at +25°C or higher, to form a cured product. Furthermore, Patent Document 8 proposes providing a cooling device to the static mixer in order to cool the liquid inside the static mixer.

However, Patent Documents 4 to 8 are indifferent to the application of small amounts of two-component addition-curable silicone compositions.

Japanese Patent Application Laid-Open No. 2015-091576 Japanese Patent Application Laid-Open No. 2015-091948 Japanese Patent Application Laid-Open No. 2015-214703 Japanese Unexamined Patent Publication No. 62-207611 Japanese Unexamined Patent Publication No. 62-264920 Japanese Patent Application Publication No. 63-046230 Japanese Patent Application Publication No. 05-005063 JP 2011-036788 A

The object of the present invention is to provide a method and apparatus for applying small amounts of a two-component addition-curable silicone composition with good workability without impairing its room-temperature curing properties.

This device is characterized by comprising a static mixer with inlets for introducing each part of the two-part addition-curable silicone composition, multiple elements for mixing the parts, a cooler for cooling the mixer, and a nozzle for discharging the mixed addition-curable silicone composition in small amounts.

In this device, the static agitator preferably has an internal volume of 1 to 5 ml, and the static agitator preferably has 7 to 40 elements. Furthermore, in this device, it is preferable that the static agitator and the cooler are separable.

This method is also characterized by introducing each part of the two-part addition-curable silicone composition into a static mixer, mixing the parts while cooling them to prepare the addition-curable silicone composition, and then extruding the composition in small amounts from a nozzle.

In this method, it is preferable to eject the curable silicone composition intermittently, with the ejection amount preferably being 0.5 to 5 μl per shot.

Furthermore, in this method, it is preferable that the pot life of the two-component addition-curable silicone composition at 25°C as specified in JIS K 6870:2008 is 10 to 60 minutes, and the cooling temperature is 20°C or lower.

The coating method and device of the present invention are characterized by their ease of use and the ability to apply small amounts without impairing the room-temperature curing properties of two-component addition-curable silicone compositions.

FIG. 1 is a perspective view of the device with a partial cutaway. FIG. 2 is a perspective view, partially cut away, of another embodiment of the device. FIG. 3 is a perspective view showing that the device can be separated into a static agitator and a cooler. FIG. 4 is a perspective view of the device, partially cut away, showing the syringe for dispensing the two-part addition-curable silicone composition attached. FIG. 5 is a perspective view showing a coating operation using this device. FIG. 6 is a perspective view showing another coating operation using the present device. FIG. 7 is a perspective view showing another coating operation using the present device. FIG. 8 is a perspective view showing another coating operation using the present device. FIG. 9 is a semi-logarithmic graph showing the relationship between the temperature and the pot life of the curable silicone composition used in Example 1. FIG. 10 is a semi-logarithmic graph showing the relationship between the temperature and the pot life of the curable silicone composition used in Example 2.

<Definition of terms>
The term "viscosity" as used herein means the value at 25°C (unit: mPa s or Pa s) measured using a B-type rotational viscometer in accordance with JIS K 7117-1:1999 "Plastics - Liquid, emulsion or dispersion resins - Measurement of apparent viscosity using a Brookfield rotational viscometer."

As used herein, the term "pot life" refers to the time it takes for the viscosity to double from the viscosity immediately after mixing the two components at a specified temperature, as determined by the method specified in JIS K 6870:2008 "Adhesives - Determination of pot life (usable time) of multi-component adhesives."

<Method of applying a two-component addition-curable silicone composition and apparatus therefor>
The coating method and the apparatus therefor of the present invention will be described in detail with reference to the drawings.
1 is a partially cutaway perspective view showing an example of the apparatus. The apparatus comprises a static stirrer 1, a cooler 2 provided to cover the stirrer 1, and a nozzle 3 connected to the stirrer 1.

The static mixer 1 is provided with inlets 11 and 11' for introducing each component of the two-component addition-curable silicone composition. These inlets are connected to containers (not shown) for storing the two components, or to pipes or tubes (not shown) for transferring the two components from the containers. Syringes or cartridges can be used as these containers. The two components are transferred to the inlets 11 and 11' in fixed amounts. The two components may be pre-cooled before transfer. The internal volume of the static mixer 1 is not limited, but a volume of 1 to 5 ml is preferred, given the need for intermittent application of small amounts. The static mixer 1 is also provided with multiple elements 12 for mixing the two components. The elements 12 are made of metals such as stainless steel or titanium, or plastics such as polyethylene, polypropylene, nylon, and polyvinylidene chloride. Their shape is not limited, but a rectangular plate twisted 180 degrees is commonly used to separate and mix the two components. By arranging multiple right elements, each made of a square plate twisted 180 degrees to the right, and multiple left elements twisted 180 degrees to the left, alternately inside the cylinder of the static agitator 1, it is possible to effectively suppress drift while minimizing shearing.

The two liquids are introduced into one end of the static mixer 1 and, as they flow to the other end, are divided and mixed by the elements 12, eventually forming a uniform composition. If there is a significant difference in the viscosities of the two liquids, one liquid may easily pass through the elements 12, preventing a uniform composition from being obtained. Therefore, it is preferable to match the viscosities of the two liquids in advance. Furthermore, if the viscosity of the two liquids is low, each liquid may easily pass through the elements 12, preventing a uniform composition from being obtained. In such cases, it is preferable to either appropriately shape the elements or increase the number of elements. While increasing the number of elements improves the uniformity of the resulting composition, it also increases the length of time the composition remains in the static mixer 1, potentially resulting in thickening or gelation of the composition. Therefore, it is preferable to minimize the number of elements to match the application speed. Specifically, the number of elements is preferably within the range of 7 to 40, or 7 to 30. Furthermore, to facilitate easy internal cleaning of the static mixer 1, it is preferable that the elements 12 be detachable from the static mixer 1.

The static agitator 1 is equipped with a cooler 2. The cooler 2 is equipped with inlet and outlet ports 11, 11' for introducing and discharging a refrigerant. The cooler 2 cools the two liquids, preventing thickening and gelation of the composition obtained by mixing them. The cooling temperature of the cooler 2 is not limited, but is generally preferably 20°C or lower, 15°C or lower, or 5°C or lower. On the other hand, a temperature of -5°C or higher, 0°C or higher, or 5°C or higher is preferred to prevent thickening of the curable silicone composition due to cooling and to prevent condensation on the composition or its surroundings after application. This cooling temperature can be easily estimated from the residence time (the time from when the curable silicone composition is introduced into the static agitator until it is discharged), which is determined from the internal volume and discharge rate of the static agitator, and the pot life of the composition. For example, if the viscosity of the curable silicone composition at 25°C is relatively low, such as 100 Pa·s or less, the composition can be cooled to a temperature that provides a pot life of at least 0.5, at least 0.6, at least 0.8, or at least 1 time the residence time. Alternatively, if the viscosity of the curable silicone composition at 25°C exceeds 100 Pa·s, the composition can be cooled to a temperature that provides a pot life of at least 1.5, or at least 2 times the residence time. Cooling the composition to a predetermined temperature or below can prevent changes in the coating amount due to thickening of the composition and clogging in the static mixer or discharge section. The refrigerant used in the cooler 2 is not limited, and examples include liquids such as water, an aqueous solution of alcohol, an aqueous solution of diethylene glycol, and oil; and gases such as air and nitrogen. It is preferable to select an appropriate refrigerant depending on the cooling temperature. In FIG. 1, the refrigerant flows freely within the cooler 2, but it is preferable to control the flow of the refrigerant to avoid localized cooling of the static mixer 1. For example, in Figure 2, the refrigerant flows through a conduit 22 connected to the inlet and outlet. This allows the static agitator 1 to be cooled uniformly. Also, as shown in Figure 3, in this device, the static agitator 1 and the cooler 2 may be separable.

Figure 4 is a partially cutaway perspective view of the device fitted with a syringe 4 for supplying a two-component addition-curable silicone composition. As shown in Figure 4, by fitting a container such as a syringe or cartridge to the device, the device itself can be minimized. Also, in Figure 4, a fixed amount of two components can be supplied to the static mixer 1 using an air supply mechanism (not shown) connected to the syringe 4.

The addition-curable silicone composition mixed in the static agitator 1 is dispensed in small amounts from nozzle 3. There are no restrictions on the amount dispensed, but to achieve intermittent small-volume application, a dose of 0.5 to 5 μl per shot is preferred. Also, while Figures 1 to 4 show the addition-curable silicone composition being dispensed from nozzle 3, it is possible to dispense the addition-curable silicone composition in even smaller amounts by replacing nozzle 3 with a jet nozzle.

Although there are no limitations on the two-component addition-curable silicone composition to which the present invention is applicable, it is preferable that the viscosity at 25°C specified in JIS K 7117-1:1999 "Plastics - Liquid, emulsion, or dispersion resins - Method for measuring apparent viscosity using a Brookfield rotational viscometer" is in the range of 100 to 1,000,000 mPas, or in the range of 500 to 500,000 mPas. Furthermore, fast-curing silicone compositions having a pot life at 25°C (the time it takes for the viscosity to double compared to the viscosity immediately after mixing the two components) of 10 to 60 minutes specified in JIS K 6870:2008 "Adhesives - Determination of pot life (usable life) of multi-component adhesives" can also be used. In this case, the cooling temperature of the static stirrer 1 is preferably 20°C or less, 15°C or less, or 5°C or less, while a temperature of -5°C or more, 0°C or more, or 5°C or more is preferred, as this reduces the risk of thickening of the curable silicone composition due to cooling and condensation on the composition or its surroundings after application. The pot life of this two-part addition-curable silicone composition at each cooling temperature can be estimated from a semi-logarithmic graph created using temperatures at at least three different points and the measured pot life values at those points. When a two-part addition-curable silicone composition with such a pot life is applied intermittently at a discharge rate of 5 μl/shot, the rate of decrease in the applied amount from the start of application can be kept to less than 30% even after one hour. Examples of such two-component addition-curable silicone compositions include DOWSIL ^™ EA-4700 CV ADHESIVE A&B manufactured by Dow-Toray Industries, Inc. and DOWSIL ^™ TC-4525 CV GAPFILLER A&B manufactured by Dow-Toray Industries, Inc.

Figures 5 to 8 show the application process using this device. In Figure 5, the device is fixed in place and small amounts of addition-curable silicone composition 6 are applied to substrate 5 in dots. To apply small amounts intermittently, the substrate 5 itself can be moved in the X and Y directions by an XY stage mechanism 7. This XY stage mechanism has two slide members that are slidably mounted on parallel guide axes along the X direction on a horizontal plane, and two slide members that are slidably mounted on parallel guide axes along the Y direction, which is perpendicular to the X direction on a horizontal plane. This XY stage mechanism moves the substrate 5 on the stage to any desired position. This XY stage mechanism allows small amounts of addition-curable silicone composition to be applied intermittently to substrate 5 without moving the device.

In Figure 6, the substrate 5 is fixed, and the device can be moved in the X and Y directions by an XY slide mechanism. This XY slide mechanism is a mechanism that moves the device to any position using a slide member that is mounted on a horizontal plane so that it can slide on guide axes that are parallel to each other along the X axis, and a stand for the device that is mounted on a slide member that is mounted on a horizontal plane so that it can slide in the Y axis direction, which is perpendicular to the X axis. This XY slide mechanism makes it possible to intermittently apply small amounts of addition-curable silicone composition to the substrate 5 without having to move the large substrate.

Furthermore, in Figure 7, the combined use of an XY slide mechanism and an XY stage mechanism allows both the device and the substrate to be moved, enabling small amounts of addition-curable silicone composition to be applied intermittently at higher speeds. Also, in Figure 8, small amounts of addition-curable silicone composition are applied intermittently in a bead shape. The addition-curable silicone composition 6 applied to the substrate 5 in this way can be cured at room temperature or by heating as needed.

The coating method and apparatus of the present invention will be described in detail using examples, but the present invention is not limited to these examples.

[Example 1]
A two-part addition-curable silicone composition consisting of the following parts A and B was prepared, and this was cooled to a predetermined temperature. The applicator was then used to apply the composition at the initial discharge pressure, and the applicability was evaluated. The viscosity was measured at 25°C using a rotational viscometer at a shear rate of 10 (1/s) in accordance with JIS K 7117-1:1999.

(Preparation of Solution A)
Solution A, with a viscosity of 1,080 mPa s, was prepared by uniformly mixing 50 parts by mass of a dimethylpolysiloxane endcapped at both molecular chain terminals with dimethylvinylsiloxy groups and having a viscosity of 360 mPa s, 50 parts by mass of a dimethylpolysiloxane endcapped at both molecular chain terminals with dimethylvinylsiloxy groups and having a viscosity of 2,000 mPa s, and a 1,3-divinyl-tetramethyldisiloxane platinum complex (in an amount such that the platinum metal content in the composition was 25 ppm by mass).

(Preparation of Solution B)
Solution B having a viscosity of 850 mPa s was prepared by uniformly mixing 50 parts by mass of a dimethylpolysiloxane end-capped at both molecular chain terminals with dimethylvinylsiloxy groups and having a viscosity of 360 mPa s, 50 parts by mass of a dimethylpolysiloxane end-capped at both molecular chain terminals with dimethylvinylsiloxy groups and having a viscosity of 2,000 mPa s, 10 parts by mass of a dimethylsiloxane-methylhydrogensiloxane copolymer end-capped at both molecular chain terminals with trimethylsiloxy groups and having a viscosity of 5 mPa s, 1 part by mass of a dimethylpolysiloxane end-capped at both molecular chain terminals with dimethylhydrogensiloxy groups and having a viscosity of 10 mPa s, and 2-phenyl-3-butyn-2-ol (in an amount that would result in 100 ppm by mass in the composition).

Table 1 lists the viscosity at 25°C of the curable silicone composition obtained immediately after mixing the above-mentioned components A and B in a 1:1 volume ratio, as well as the pot life at specified temperatures specified in JIS K 6870:2008. Additionally, temperatures other than 25°C and the pot life at those temperatures were estimated using a semi-logarithmic graph (Figure 9) created from actual measurements, and are also listed in Table 1.

The above-mentioned solutions A and B were filled into a MIXPAC dual syringe (CD050-01-PP) and introduced into a static mixer (MIXPAC static mixer MA0517-0413; 30 elements; internal volume 2.0 ml) so that the volume ratio of solutions A to B was 1:1. The static mixer was cooled to a predetermined temperature using a cooler while mixing, and the solution was applied to the substrate from the nozzle at a rate of 1.0 μl/shot every 2 seconds. The initial amount applied was compared with the amount applied after 30 minutes to determine the reduction in the amount applied. A reduction in the amount applied of 10% or less was rated as "good," a reduction in the amount between 10% and 30% was rated as "fair," and a reduction in the amount applied of more than 30% was rated as "poor." The results are shown in Table 2.

The above-mentioned solutions A and B were filled into a MIXPAC dual syringe (CD050-01-PP) and introduced into a static mixer (MIXPAC static mixer MA0517-0413 (number of elements: 30; internal volume: 2.0 ml) so that the volume ratio of solution A to solution B was 1:1. The static mixer was cooled to a predetermined temperature using a cooler while mixing, and the solution was applied to the substrate from the nozzle at a rate of 1.0 μl/shot every 2 seconds. The application process was then stopped for 60 minutes and then restarted. The initial application amount was compared with the application amount after 60 minutes to determine the reduction in application amount. Note that application quality was rated as "good" when the reduction in application amount was 10% or less, "fair" when it was between 10% and 30%, and "poor" when it was more than 30%. The results are shown in Table 3.

[Example 2]
DOWSIL ^™ EA-4700 CV ADHESIVE A&B manufactured by Dow Toray Industries, Inc. was used as the two-component addition-curable silicone composition. Its properties are shown in Table 4. In addition, temperatures other than 25°C and the pot life at those temperatures were estimated using a semi-logarithmic graph (FIG. 10) created from actual measurements, and these results are also shown in Table 4.

DOWSIL ^™ EA-4700 CV ADHESIVE A&B was filled into a MIXPAC dual syringe (CD050-01-PP) and introduced into a static mixer (MIXPAC static mixer MA0517-0413; 30 elements; internal volume 2.0 ml) so that the volume ratio of solution A to solution B was 1:1. The static mixer was cooled to a predetermined temperature using a cooler while mixing, and the solution was applied to the substrate from the nozzle at a rate of 1.2 μl/shot every 2 seconds. The initial amount applied was compared with the amount applied after 30 minutes to determine the reduction in the amount applied. A reduction in the amount applied of 10% or less was evaluated as "good," a reduction in the amount between 10% and 30% was evaluated as "fair," and a reduction in the amount applied of more than 30% was evaluated as "poor." The results are shown in Table 5.

[Example 3]
The two-component addition-curable silicone composition used was DOWSIL ^™ TC-4525 CV GAPFILLER A&B manufactured by Dow Toray Co., Ltd. The properties of this composition are shown in Table 6.

DOWSIL ^™ TC-4525 CV GAPFILLER A&B was filled into a MIXPAC dual syringe (CD050-01-PP) and introduced into a static mixer (MIXPAC static mixer MA6.3-12-S; 12 elements; internal volume 1.9 ml) so that the volume ratio of solution A to solution B was 1:1. The static mixer was cooled to a predetermined temperature using a cooler while mixing, and the solution was applied to the substrate from the nozzle at a rate of 1.5 μl/shot every 2 seconds. The initial amount applied was compared with the amount applied after 30 minutes to determine the reduction in the amount applied. A reduction in the amount applied of 10% or less was evaluated as "good," a reduction in the amount between 10% and 30% was evaluated as "fair," and a reduction in the amount applied of more than 30% was evaluated as "poor." The results are shown in Table 7.

The above evaluation of application properties shows that by cooling the static mixer to below 20°C, below 15°C, or below 5°C using a cooler, it is possible to apply small amounts with good workability. Furthermore, even if application work is interrupted, by continuing to cool the static mixer, it was found that small amounts can be applied smoothly even after application work is resumed.

The coating method and apparatus of the present invention are easy to use and allow for small amounts of coating to be applied without impairing the room-temperature curing properties of the two-component addition-curable silicone composition. Therefore, they are suitable, for example, as a method and apparatus for intermittently applying small amounts of addition-curable silicone composition to electrical and electronic components or their substrates.

REFERENCE SIGNS LIST 1 static stirrer 2 cooler 3 nozzle 4 syringe for supplying two-component addition-curable silicone composition 5 substrate 6, 6' addition-curable silicone composition 7 XY stage mechanism 8 XY slide mechanism 11, 11' inlet ports for each component of two-component addition-curable silicone composition 12 element 21, 21' refrigerant inlet/outlet ports 22 refrigerant conduit

Claims (1)

A method for applying a two-part addition-curable silicone composition, comprising: introducing each part of the two-part addition-curable silicone composition into a static mixer, mixing the parts while cooling them to prepare an addition-curable silicone composition, and then extruding the composition little by little from a nozzle ;
The curable silicone composition is intermittently ejected in an amount of 0.5 to 5 μl per shot;
A coating method in which the pot life of the two-component addition-curable silicone composition at 25°C as specified in JIS K 6870:2008 is 10 to 60 minutes, the cooling temperature is 20°C or lower, and the pot life is the time it takes for the viscosity to double from the viscosity immediately after mixing the two components .