Recycling method of piezoelectric thick film cleaning solvent

Abstract

The invention relates to a recovery method of a piezoelectric thick film cleaning solvent, which comprises the following steps: S1, reducing the pressure of a hydrofluoroether mixed solution containing a small amount of silicone oil to 0.03 MPa or below, and heating to 10 DEG C or below higher than the boiling point of hydrofluoroether under the condition of stirring; s2, after hydrofluoroether is boiled to generate steam, the steam reaches a condensing device through a pipeline, and a condensed hydrofluoroether solvent is conveyed to a recovery device; and S3, filtering the solvent obtained by the recovery device to obtain the hydrofluoroether solvent which is recovered after silicone oil is removed. According to the method, silicone oil in the solvent can be removed, recycling of hydrofluoroether is achieved, the process is easy to implement and operate, and the hydrofluoroether recycling cost is low.

Description

Technical Field

[0001] The invention belongs to the technical field of piezoelectric films, and in particular relates to a method for recovering a cleaning solvent for a piezoelectric thick film. Background Art

[0002] Piezoelectric thick film is a planar element made of fluorinated copolymer P (VDF-TrFE) material. Due to the molecular structure of P (VDF-TrFE) and the β piezoelectric phase formed by crystallization, the piezoelectric thick film element has a high piezoelectric voltage coefficient and has technical advantages in receiving acoustic sensors and hydrophones. In the process of preparing piezoelectric thick film, high electric field strength polarization is an indispensable step, which is used to adjust the orientation of the crystal domains in the element and improve and stabilize its piezoelectric performance. In order to reduce the probability of component breakdown failure in a high field strength environment and increase the success rate of polarization, the component needs to be placed in a highly insulating viscous silicone oil before polarization. Therefore, the polarized component is wrapped in silicone oil. Although the piezoelectric thick film has good performance at this time, its surface is severely contaminated, affecting its next use. Therefore, the piezoelectric thick film needs to be cleaned to remove silicone oil contamination.

[0003] Hydrofluoroether is a class of organic ether compounds containing fluorine, which is considered to be an effective silicone oil cleaning agent. It can remove the silicone oil on the surface of the piezoelectric thick film by wiping, soaking or ultrasound, ensuring the cleanliness of the piezoelectric thick film for subsequent process flow. The removed silicone oil is mixed with hydrofluorocarbon, so the separation of the two and the recovery of hydrofluorocarbon are crucial to the economy of the cleaning step. However, it is very necessary to remove the small amount of silicone oil mixed in the hydrofluoroether in order to achieve the recovery and reuse of the hydrofluoroether (i.e., repeated cleaning).

[0004] However, hydrofluoroethers have a certain solubility in silicone oil, and separation and recovery are difficult or too costly. Currently, there are few reports on similar technologies for separating large amounts of volatile solvents from silicone oil and recovering solvents. Most of them are aimed at the purification and collection of silicone oil containing a small amount of volatile components. For example, a patent application with Chinese patent publication number CN104530432A proposes a method for separating volatile components from polysiloxane (i.e., silicone oil) by pressurized fluid extraction. This method is not designed for volatile component recovery and requires the use of pressurized fluid extraction equipment. Such equipment is expensive, which limits the application of the technology. Summary of the invention

[0005] The technical problem to be solved by the present invention is to provide a method for recovering a piezoelectric thick film cleaning solvent, which can remove silicone oil in the solvent and realize the recovery and reuse of hydrofluoroether.

[0006] The technical solution of the present invention is to provide a method for recovering a piezoelectric thick film cleaning solvent, comprising the following steps: S1, decompressing the hydrofluoroether mixed liquid containing a small amount of silicone oil to below 0.03 MPa, and heating it to within 10°C above the boiling point of the hydrofluoroether under stirring; S2, wait for the hydrofluoroether to boil and generate steam, which reaches the condensing device through the pipeline, and send the condensed hydrofluoroether solvent to the recovery device; S3, filtering the solvent obtained by the recovery device to obtain the hydrofluoroether solvent recovered by removing the silicone oil.

[0007] Preferably, in step S1, the temperature is raised to 60-65° C. under stirring.

[0008] Preferably, in step S2, a desiccant is placed in the recovery device to absorb trace moisture in the solvent.

[0009] Preferably, in step S2, the condensation temperature is -20-0°C.

[0010] Preferably, in step S2, a desiccant is placed in the recovery device, and the desiccant is any one of anhydrous calcium chloride, anhydrous magnesium sulfate or molecular sieve or a combination thereof.

[0011] Preferably, in step S2, a material for absorbing silicone oil is provided on the pipeline through which the steam passes, and the material used is any one of a filter screen, absorbent cotton or silica gel microspheres or a combination thereof.

[0012] Compared with the prior art, the present invention has the following advantages: (1) The method only requires conventional devices in the prior art such as heating, decompression, and condensation, which has low cost and high recovery efficiency; (2) The adsorption material arranged in the pipeline has the function of silicone oil filtration and adsorption, which improves the purity of the recovered solvent. The recovered solvent can meet the needs of cleaning the piezoelectric thick film; (3) The method has quasi-continuous working capabilities and can also work in batches. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 It is a schematic diagram of the recovery device of the present invention. DETAILED DESCRIPTION

[0014] The present invention will be further described below with regard to specific embodiments: A method for recovering a piezoelectric thick film cleaning solvent comprises the following steps: (1) After the hydrofluoroether mixed liquid containing a small amount of silicone oil is depressurized to 0.03 MPa, the temperature is raised to 60-65° C. while stirring; in this embodiment, the temperature is raised to 62° C.; (2) When the hydrofluoroether boils and generates steam, the steam reaches the condensing device through the pipeline, and the condensed hydrofluoroether solvent is sent to the recovery device. A desiccant is placed in the recovery device to absorb trace moisture in the solvent. In this embodiment, the condensation temperature is -10°C, and the desiccant placed in the recovery device is anhydrous magnesium sulfate; (3) Filtering the solvent obtained by the recovery device to obtain a hydrofluoroether solvent recovered by removing the silicone oil.

[0015] As a preferred method, in step (2), a material for absorbing silicone oil is arranged on the pipeline through which the steam passes, and the material used is silica gel microspheres. In order to improve the adsorption efficiency, a filter screen can be superimposed on the silica gel microspheres.

[0016] In order to prevent silicone oil from mixing into the recovered hydrofluoroether solvent, the present invention mainly adopts three measures: (1) the boiling point of silicone oil is higher than 100°C. In order to avoid excessive volatilization of silicone oil, the heating temperature should not be too high, but within 10°C higher than the boiling point of hydrofluoroether (the boiling point of hydrofluoroether is 56°C); (2) the heating device is used for stirring to avoid boiling; (3) a material for absorbing silicone oil is arranged on the pipeline through which the steam passes so as to filter the steam and reduce the passing rate of high-viscosity silicone oil.

[0017] To realize this recovery method, the present invention uses conventional devices including a heating device 1, a condensing device 2, a decompression device 3, a recovery device 4, a liquid adding device 5, etc., and each device is sealed. The interconnection relationship is as follows: Figure 1 As shown, the pressure reducing device 3, the condensing device 2 and the recovery device 4 are connected in sequence through the pipeline 6, the condensing device 2 is also connected to the heating device 1 through the pipeline 6, and the heating device 1 is also connected to the liquid adding device 5 through the pipeline 6, and a stop valve 7 is arranged on the connecting pipeline between the pressure reducing device 3 and the condensing device 2 and the connecting pipeline between the heating device 1 and the liquid adding device 5, and a stop valve 7 is arranged on the external pipeline between the recovery device 4 and the heating device 1.

[0018] The piezoelectric thick film cleaning solvent recovery method is suitable for laboratory and pilot-scale solvent recovery, and can realize quasi-continuous hydrofluoroether recovery operation. The recovered hydrofluoroether cleaning solvent can continue to be used for cleaning the piezoelectric thick film.

[0019] The devices required by the present invention are all conventional devices, and the process is simple, easy to implement, and has low recycling cost.

[0020] The above is only an explanation of the preferred embodiments of the present invention, which should not be construed as a limitation on the claims. Any equivalent process changes made using the present invention specification are included in the patent protection scope of the present invention.

Claims

1. A method for recovering a piezoelectric thick film cleaning solvent, characterized in that: The following steps are included: S1, decompressing the hydrofluoroether mixed liquid containing silicone oil to below 0.03 MPa, and heating it to within 10° C. above the boiling point of the hydrofluoroether while stirring; S2, wait for the hydrofluoroether to boil and generate steam, which reaches the condensing device through the pipeline, and send the condensed hydrofluoroether solvent to the recovery device; S3, filtering the solvent obtained by the recovery device to obtain the hydrofluoroether solvent recovered by removing the silicone oil.

2. The method for recovering a piezoelectric thick film cleaning solvent according to claim 1, characterized in that: In step S1, the temperature is raised to 60-65° C. under stirring.

3. The method for recovering a piezoelectric thick film cleaning solvent according to claim 1, characterized in that: In step S2, a desiccant is placed in the recovery device to absorb the residual moisture in the solvent.

4. The method for recovering a piezoelectric thick film cleaning solvent according to claim 1, characterized in that: In step S2, the condensation temperature is -20-0°C.

5. The method for recovering a piezoelectric thick film cleaning solvent according to claim 1, characterized in that: In step S2, a desiccant is placed in the recovery device, and the desiccant is any one of anhydrous calcium chloride, anhydrous magnesium sulfate or molecular sieve or a combination thereof.

6. The method for recovering a piezoelectric thick film cleaning solvent according to claim 1, characterized in that: In step S2, a material for absorbing silicone oil is arranged on the pipeline through which the steam passes, and the material used is any one of a filter screen, absorbent cotton or silica gel microspheres or a combination thereof.

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