Coated composite rubber sealing strip material for transformer tank edge and preparation method

Abstract

The invention relates to a coated composite rubber sealing strip material for a transformer tank edge and a preparation method thereof, and the preparation method comprises the following steps: respectively mixing an inner layer material and an outer layer material according to the raw material mass part ratio, then batching out, respectively obtaining an inner layer rubber sheet and an outer layer rubber sheet, and extruding by a composite extrusion head to form a coated composite rubber strip; the composite rubber strip is vulcanized to prepare the composite rubber sealing strip; according to the coated composite rubber sealing strip for the transformer tank edge and the preparation method of the coated composite rubber sealing strip, a low-compression permanent deformation rubber material is adopted as an inner layer material, a rubber material with transformer oil resistance, thermal oxidation resistance and ozone aging resistance is adopted as an outer layer material to wrap the inner layer material, and the two materials complement each other; the sealing material has lower compression set, is not easy to crack, and can effectively ensure the sealing effect and the service life of the transformer box edge.

Description

Technical Field

[0001] This invention belongs to the field of sealing technology, specifically relating to a wrap-around composite rubber sealing strip for transformer tank edges and its preparation method. Background Technology

[0002] Currently, transformer enclosure sealing strips are mainly made of single types of rubber, often nitrile rubber or acrylate rubber. Each material has its advantages and disadvantages. Nitrile rubber has good resistance to transformer oil and low compression set, but poor resistance to heat, oxygen, and ozone aging, making it prone to cracking when exposed to air, leading to seal failure. Acrylic rubber has better resistance to transformer oil, heat, oxygen, and ozone aging than nitrile rubber, but it has high internal stress, poor low-temperature performance and mechanical properties, and high compression set, making it difficult for the material to spring back after prolonged compression, thus causing seal failure. With the continuous development of rubber materials, fluororubber, chlorohydrin rubber, fluorosilicone rubber, and hydrogenated nitrile rubber, due to their better resistance to transformer oil, heat, oxygen, and ozone aging, are also potential alternative materials for transformer enclosure sealing strips.

[0003] Patent CN101728064B discloses a composite sealing strip for transformer tanks and its preparation method. An inner sealing strip is provided on the vertical inner side of the intermediate sealing strip, and an outer sealing strip is provided on the vertical outer side. The intermediate sealing strip is made of nitrile rubber, while the inner and outer sealing strips are made of acrylic rubber or chlorohydrin rubber. Utilizing the properties of different rubber materials, the composite sealing strip exhibits low compression set and good resistance to cracking and aging, thus achieving a longer service life and better sealing performance. However, this method can only be used for rectangular sealing strips and cannot be used for O-ring sealing strips. Furthermore, since the sealing strip is only provided on the vertical outer side, the adhesion between the outer and inner sealing strips cannot be guaranteed, potentially causing the outer sealing strip to detach during compression, thus affecting the protective effect.

[0004] In view of this, it is necessary to propose an O-ring seal that uses composite materials and has better stability and service life. Summary of the Invention

[0005] The purpose of this invention is to provide a transformer-type encapsulated composite rubber sealing strip with long service life and excellent sealing performance, as well as its preparation method.

[0006] To achieve the above objectives, this invention discloses a method for preparing a wrapped composite rubber sealing strip for transformer tank edges. The wrapped composite rubber sealing strip includes an inner layer material and an outer layer material wrapping the inner layer material. The inner layer material is a rubber material with low compression set, and the outer layer material is a rubber material with resistance to transformer oil and resistance to heat, oxygen, and ozone aging. The method for preparing the wrapped composite rubber sealing strip includes:

[0007] S1. The inner and outer layer materials are mixed according to the raw material mass ratio and then sheeted to obtain inner and outer layer films respectively;

[0008] S2. Load the inner and outer film into the corresponding inner and outer extruders respectively. The inner and outer film are extruded into a wrap-around composite strip through the composite extrusion head connected to the two extruders.

[0009] S3. The composite rubber strip is vulcanized by a microwave continuous vulcanization device to prepare a composite rubber sealing strip.

[0010] Preferably, the composite extrusion head includes a first extrusion head and a second extrusion head that pass through the middle, the second extrusion head is disposed inside the first extrusion head, the second extrusion head is provided with a second channel for the inner layer film to pass through, and a first channel for the outer layer film to pass through is formed between the first extrusion head and the second extrusion head; the composite material is extruded through a third channel at the front of the first extrusion head.

[0011] Preferably, the front end of the second extrusion head is provided with a shaping ring, and the front edge of the shaping ring is wavy.

[0012] The inner area of ​​the shaping ring is not greater than the cross-sectional area of ​​the second channel.

[0013] Preferably, the shaping ring has an annular cooling chamber inside, through which the surface of the rubber material passing through the inner and outer sides of the shaping ring is simultaneously and briefly cooled by the coolant, so that the surface hardness of the rubber material at the contact position between the inner and outer layers of the rubber sheet is greater than that at other positions for a short period of time.

[0014] Preferably, the rear side of the shaping ring is provided with an inlet pipe and an outlet pipe that communicate with the cooling chamber.

[0015] Preferably, the inlet pipe and outlet pipe are provided with a heat insulation layer or are made of heat insulation material.

[0016] Preferably, the sidewall of the second extruder head is provided with an inlet pipe channel and an outlet pipe channel, with the inlet pipe located inside the inlet pipe channel and the outlet pipe located inside the outlet pipe channel.

[0017] Preferably, the temperature of the coolant flowing out of the cooling chamber does not exceed 95°C.

[0018] An inner and outer layer material for an encapsulated composite rubber sealing strip, characterized in that:

[0019] The inner layer material is prepared from the following materials in the following mass ratio:

[0020] ,

[0021] The outer layer material may be acrylate rubber, fluororubber, chlorohydrin rubber, fluorosilicone rubber or hydrogenated nitrile rubber, wherein the acrylate rubber includes reactive acrylate rubber or carboxylic acid acrylate rubber.

[0022] The active acrylic rubber material is prepared from the following materials in the indicated mass ratios:

[0023]

[0024] or

[0025] ,

[0026] The carboxylic acid type acrylate rubber material is prepared from the following materials in the indicated mass ratios:

[0027] ,

[0028] The fluororubber material is prepared from the following materials in the indicated mass ratios:

[0029]

[0030] or

[0031] .

[0032] The wrap-around composite rubber sealing strip for transformer tank lining and its preparation method of the present invention have at least the following advantages:

[0033] 1. The composite sealing strip of the present invention uses nitrile rubber as the inner layer material and acrylate rubber, fluororubber, chlorohydrin rubber, fluorosilicone rubber or hydrogenated nitrile rubber as the outer layer material to wrap the nitrile rubber material. The two materials complement each other, resulting in lower compression set and less cracking, which can effectively ensure the sealing effect and service life of the transformer box edge.

[0034] 2. When the composite rubber compound is extruded through the composite extruder, the wavy edge of the forming ring creates a wavy bonding surface at the boundary between the inner and outer layers of the composite rubber compound. This not only makes the bonding between the inner and outer layers of the rubber compound tighter, but also further alleviates problems such as high compression set of acrylic rubber materials from the perspective of force distribution. Attached Figure Description

[0035] Figure 1 This is a schematic diagram of a composite extrusion head.

[0036] The numbers in the diagram are: first extruder 1, second extruder 2, first channel 3, second channel 4, third channel 5, shaping ring 6, cooling chamber 7, liquid inlet pipe 8, liquid outlet pipe 9. Detailed Implementation

[0037] The present invention will be further described in detail below through embodiments, so that those skilled in the art can implement it based on the description.

[0038] It should be understood that terms such as “having,” “comprising,” and “including” as used herein do not exclude the presence or addition of one or more other elements or combinations thereof.

[0039] A type of encapsulated composite rubber sealing strip for transformer tank lining, comprising an inner layer material and an outer layer material wrapping the inner layer material. The inner layer material is made of rubber with low compression set, and the outer layer material is made of rubber with resistance to transformer oil and resistance to heat, oxygen, and ozone aging. The cross-section of the encapsulated composite rubber sealing strip can be designed as circular, elliptical, trapezoidal, or semi-circular, etc., as needed. Generally, the thickness of the outer layer material can be controlled between 0.5-1.5 mm. If it is too thin, it is easy to break, and if it is too thick, it will increase the cost and cause the overall compression set of the sealing strip to increase.

[0040] The nitrile rubber material is prepared from the following materials in the indicated mass ratios: 100 parts nitrile rubber, 80 parts carbon black N550, 9 parts plasticizer DOP, 2 parts antioxidant 445, 1 part antioxidant RD, 3 parts stearic acid, 4 parts zinc oxide, 0.5 parts sulfur, 0.8 parts accelerator TMTD, 0.5 parts accelerator M, and 0.6 parts accelerator TMTM.

[0041] The outer acrylic rubber material is prepared from the following materials in the indicated mass ratios: 100 parts of active chlorine-type acrylic rubber, 45 parts of silica, 0.5 parts of anti-scorching agent CTP, 10 parts of plasticizer TP-95, 1.2 parts of vulcanizing agent TCY, and 1 part of accelerator BZ.

[0042] It is worth noting that there is a wide variety of choices for the outer layer material. This invention discloses several optional outer layer material formulations, which, in addition to having resistance to transformer oil and resistance to heat, oxygen, and ozone aging, also have good cost control and processability. Regarding the color of the outer layer material, adding silica makes the outer layer material gray, and this color may be more popular with customers in practical applications (other color masterbatches can be added if other colors are required). However, using carbon black, although it will make the outer layer material black, the overall performance (toughness, service life, etc.) of the outer layer material is slightly better than that of the outer layer material using silica.

[0043] A method for preparing a wrapped composite rubber sealing strip for transformer tank lining includes the following steps:

[0044] S1. The inner and outer layer materials are mixed according to the raw material mass ratio and then sheeted to obtain inner and outer layer films respectively;

[0045] S2. Load the inner and outer film into the corresponding inner and outer extruders respectively. The inner and outer film are extruded into a wrap-around composite strip through the composite extrusion head connected to the two extruders.

[0046] S3. The composite rubber strip is vulcanized in a microwave continuous vulcanization device at a temperature of 240℃ to prepare a composite rubber sealing strip.

[0047] like Figure 1 As shown, a method for preparing an encapsulated composite rubber sealing strip is disclosed. The composite extrusion head includes a first extrusion head 1 and a second extrusion head 2 that pass through the center. The second extrusion head is disposed inside the first extrusion head. The second extrusion head is provided with a second channel 4 for the inner layer of rubber to pass through. A first channel 3 for the outer layer of rubber to pass through is formed between the first extrusion head and the second extrusion head. The composite rubber material is extruded through a third channel 5 at the front of the first extrusion head.

[0048] The second extrusion head has a shaping ring 6 at its front end. The edge of the front end of the shaping ring 6 is a wavy line with a wave height of no more than 0.2 mm (preferably with a wavelength of no less than 2 mm).

[0049] The inner area of ​​the shaping ring is not greater than the cross-sectional area of ​​the second channel.

[0050] The shaping ring has an annular cooling chamber 7 inside, which uses coolant to simultaneously and briefly cool the surfaces of the rubber material passing through the inner and outer sides of the shaping ring. This causes the surface hardness of the rubber material at the contact point between the inner and outer rubber layers to be greater than that of other locations for a short period of time. As the inner and outer rubber layers are extruded into the third channel, the wavy shape is preserved more at the interface between the inner and outer rubber layers, thus better distributing external pressure and exhibiting better low compression set at thinner sections. This results in a slight improvement in the overall compression set of the sealing strip. The cooling of the shaping ring is limited to the surfaces of the inner and outer rubber layers. Subsequently, the surface temperature of the inner and outer rubber layers rapidly rises to the overall temperature of the rubber material. By this time, the composite rubber strip has already been extruded from the third channel, and the shape of the interface between the inner and outer rubber layers is roughly finalized.

[0051] The rear side of the shaping ring is provided with an inlet pipe 8 and an outlet pipe 9 that communicate with the cooling chamber. The inlet pipe and the outlet pipe are provided with a heat insulation layer or are made of heat insulation material. The side wall of the second extruder head is machined with an inlet pipe channel and an outlet pipe channel, with the inlet pipe located in the inlet pipe channel and the outlet pipe located in the outlet pipe channel.

[0052] When the coolant flows out of the cooling chamber, its temperature does not exceed 95℃. This means that the surface temperature of the cooled rubber material will, in most cases, not exceed 95℃ (in actual production extrusion, the nozzle temperature of the composite extruder is around 105℃, and because the forming ring is relatively thin, the flow rate of the cooling chamber is not very large; generally, a coolant outlet temperature of 80-95℃ is sufficient). At this temperature, the wavy bonding surface maintains its shape better during extrusion through the third channel, and the toughness of the inner surface of the acrylate rubber material after cooling treatment is also slightly enhanced, making it less prone to breakage due to extrusion. Furthermore, the surface of the nitrile rubber material after cooling treatment can effectively reduce surface cracks caused by pre-crosslinking, and to a certain extent, reduce the occurrence of surface cracking; all of these contribute to extending the service life of the sealing strip.

[0053] In a series of tests, taking the cylindrical composite sealing strip (with an average outer layer material thickness of 1 mm and an inner layer material diameter of 6 mm) prepared using the above method and ingredients as an example, the compression set of the composite sealing strip of the present invention (compression 25%, 125°C, 24h) is only 27% (the compression set of some sealing strips treated with shaping rings can approach 26.5%), while the compression set of nitrile rubber sealing strip is 34% and that of acrylic rubber sealing strip is 50%. It can be seen that the composite sealing strip of the present invention has a low compression set, which can effectively ensure the sealing effect and service life of the transformer box edge.

[0054] In another set of tests, we bent the sealing strip (same specifications as above) 90° and simultaneously compressed it by 40% using a tooling fixture. The fixture was then placed in a 125°C oven to observe the cracking of the strip. The nitrile rubber strip cracked after only 7 days, while the composite strip and acrylic strip showed no cracking after 30 days. This demonstrates that the composite strip of this invention has superior aging resistance compared to the nitrile rubber strip, implying a longer service life.

[0055] Although embodiments of the present invention have been disclosed above, they are not limited to the applications listed in the specification and embodiments. They can be applied to various fields suitable for the present invention. For those skilled in the art, other modifications can be easily made. Therefore, without departing from the general concept defined by the claims and their equivalents, the present invention is not limited to the specific details and embodiments shown and described herein.

Claims

1. A method for preparing a wrapped composite rubber sealing strip for transformer tank rims, characterized in that, The encapsulated composite rubber sealing strip includes an inner layer material and an outer layer material that wraps around the inner layer material. The inner layer material is a rubber material with low compression set, and the outer layer material is a rubber material with resistance to transformer oil and resistance to heat, oxygen, and ozone aging. The preparation method of the encapsulated composite rubber sealing strip includes: S1. The inner and outer layer materials are mixed according to the raw material mass ratio and then sheeted to obtain inner and outer layer films respectively; S2. Load the inner and outer film into the corresponding inner and outer extruders respectively. The inner and outer film are extruded into a wrap-around composite strip through the composite extrusion head connected to the two extruders. S3. The composite rubber strip is vulcanized by a microwave continuous vulcanization device to prepare a composite rubber sealing strip.

2. The method for preparing the encapsulated composite rubber sealing strip according to claim 1, characterized in that: The composite extrusion head includes a first extrusion head and a second extrusion head that pass through the middle. The second extrusion head is located inside the first extrusion head. The second extrusion head has a second channel for the inner layer film to pass through. A first channel for the outer layer film to pass through is formed between the first extrusion head and the second extrusion head. The composite material is extruded through a third channel at the front of the first extrusion head.

3. The method for preparing the encapsulated composite rubber sealing strip according to claim 2, characterized in that: The second extrusion head has a shaping ring at its front end, and the edge of the front end of the shaping ring is a wavy line with a wave height of no more than 0.2 mm.

4. The method for preparing the encapsulated composite rubber sealing strip according to claim 3, characterized in that: The inner area of ​​the shaping ring is not greater than the cross-sectional area of ​​the second channel.

5. The method for preparing the encapsulated composite rubber sealing strip according to claim 2, characterized in that: The shaping ring has an annular cooling chamber inside, which uses coolant to simultaneously and briefly cool the surface of the rubber material passing through the inner and outer sides of the shaping ring, so that the surface hardness of the rubber material at the contact point between the inner and outer layers of the rubber sheet is greater than that at other locations for a short period of time.

6. The method for preparing the encapsulated composite rubber sealing strip according to claim 5, characterized in that: The rear side of the shaping ring is provided with an inlet pipe and an outlet pipe that communicate with the cooling chamber.

7. The method for preparing the encapsulated composite rubber sealing strip according to claim 6, characterized in that: The inlet and outlet pipes are equipped with insulation layers or are made of insulation materials.

8. The method for preparing the encapsulated composite rubber sealing strip according to claim 6, characterized in that: The second extruder head has an inlet pipe channel and an outlet pipe channel machined on its side wall. The inlet pipe is located in the inlet pipe channel and the outlet pipe is located in the outlet pipe channel.

9. The method for preparing the encapsulated composite rubber sealing strip according to claim 5, characterized in that: When the coolant flows out of the cooling chamber, the temperature does not exceed 95°C.

10. An inner and outer layer material for the encapsulated composite rubber sealing strip as described in claim 1, characterized in that: The inner layer material is prepared from the following materials in the following mass ratio: ， The outer layer material is made of acrylate rubber, fluororubber, chlorohydrin rubber, fluorosilicone rubber or hydrogenated nitrile rubber, wherein the acrylate rubber includes reactive acrylate rubber or carboxylic acid acrylate rubber. The active acrylic rubber material is prepared from the following materials in the indicated mass ratios: or , The carboxylic acid type acrylate rubber material is prepared from the following materials in the indicated mass ratios: ， The fluororubber material is prepared from the following materials in the indicated mass ratios: or .

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