Preparation method of high-thickness L-shaped paperboard for transformer

Abstract

The invention belongs to the technical field of insulation product production, and discloses a preparation method of a high-thickness L-shaped paperboard for a transformer, which comprises the following steps: cutting, humidifying and moisturizing a raw material paperboard with high paperboard thickness, uniformly coating casein glue on the raw material paperboard by using a casein glue rolling machine, then paving and stacking the paperboards on a clean thin paperboard in sequence, and drying to obtain the high-thickness L-shaped paperboard for the transformer. And performing hot pressing at 135-145 DEG C, demolding and cooling after hot pressing is finished, and cutting to obtain a finished product. The product quality is good, the electrical strength is increased, and the electrical strength requirement of the high-voltage transformer can be met.

Description

Technical Field

[0001] The invention belongs to the technical field of insulating product production, and particularly relates to a method for preparing a high-thickness L-shaped paperboard for a transformer. Background Art

[0002] High-thickness L-shaped paperboard is an important component of the high-voltage transformer lead wire. The L-shaped wire clip made of it can fix and connect the wires in the transformer, ensure electrical safety, facilitate maintenance and repair, carry and distribute current, etc. Therefore, it is a very important component in the transformer. Accordingly, the quality of high-thickness L-shaped paperboard is particularly important in high-voltage transformers.

[0003] In the preparation of L-shaped paperboard, the thickness of the single-layer paperboard and the number of glue layers have a great influence on its electrical strength. The thicker the single-layer paperboard is and the fewer the glue layers are, the greater the electrical strength of the product is and the better the product performance is. At present, the manufacturing process of L-shaped paperboard is to bond multiple layers of thin raw paperboard with phenolic glue paper. The thicker the prepared paperboard is, the more phenolic glue paper is required. When the L-shaped paperboard product reaches a certain thickness, it is impossible to use thin raw paperboard and phenolic glue paper to bond to produce products that meet customer requirements because the dry paperboard is easy to crack when bent and the paperboard is tough. The existing process products can only bond single-layer cardboard with a maximum thickness of 2mm (cardboard with a thickness above 2mm is easy to crack when bent without humidification. The bonding strength of the cardboard with phenolic adhesive paper is poor after humidification. The moisture escape from the cardboard will cause the adhesive layer to crack, so phenolic adhesive paper is not used as an adhesive after humidification of thick cardboard). The products produced by this process have serious limitations when used in transformers with voltage levels of 500KV and above, and cannot meet customers' requirements for high-voltage products. Therefore, a new production process is urgently needed to solve the above problems. Summary of the invention

[0004] The technical problem to be solved by the present invention is: to provide a method for preparing high-thickness L-shaped paperboard for transformers, which overcomes the defects in the prior art. The raw material uses high-thickness paperboard, which is bonded with casein glue. Because the thickness of the paperboard of the single-layer raw material is increased, the number of glue layers is reduced, and the electrical strength of the product is increased, and the electrical strength can meet the electrical strength requirements of the high-voltage transformer.

[0005] In order to solve the above technical problems, the technical solution of the present invention is:

[0006] A method for preparing a high-thickness L-shaped paperboard for a transformer comprises the following steps:

[0007] a. Cardboard cutting: select the thickness of the cardboard to be processed according to product requirements, calculate the length and width of the cardboard according to the size, and implement cutting;

[0008] b. Cardboard humidification: Place the cut cardboard into the spray room, turn on the spray equipment, and adjust the humidification water volume per unit area according to the thickness of the cardboard to make the cardboard evenly humidified;

[0009] c. Cardboard moisturizing: After humidification, wrap the wet cardboard with plastic film and determine the moisturizing time based on the cardboard thickness and the formula "moisturizing time = 4h / mm";

[0010] d. Bonding: Use casein glue roller to evenly glue the moisturized cardboard. The glue is casein glue. The first and last cardboards are glued on one side, and the other cardboards are glued on both sides to ensure that the glue amount of each layer of cardboard is even. After gluing, lay the cardboards flat and stack them on clean thin cardboards in order.

[0011] e. Upper mold: Turn on the heating switch of the L-shaped cardboard hot press 30 minutes in advance, heat it to 135℃~145℃, place the glue-coated cardboard on the L-shaped cardboard hot press mold, turn on the mold closing switch, maintain the temperature and make the cardboard and mold fit together, and release the mold closing switch after the pressure gauge pointer turns to the set pressure;

[0012] f. Demolding: After the hot pressing time is over, stop heating, turn on the mold opening switch, take out the pressed L-shaped cardboard, and dissipate heat for 2 hours;

[0013] g. Bracket processing: The L-shaped cardboard after cooling in step g is cut to the finished size according to customer requirements, and trimmed and cleaned to obtain a high-thickness L-shaped cardboard product.

[0014] Preferably, in step a, the thickness of the cardboard is 3 mm to 5 mm.

[0015] Furthermore, in the step a, the thickness of the cardboard is 4 mm.

[0016] Preferably, in step b, a spray method is used for humidification, and the humidification amount is 0.9 kg / ㎡.

[0017] Preferably, the moisturizing time of the 4 mm cardboard in step c is 16 hours.

[0018] Preferably, the casein glue rolling machine in step d is a 600 type glue coating machine produced by Renxian Aofei Machinery Factory.

[0019] Preferably, in the step e, the L-shaped cardboard with a thickness of 12 mm is heated to a temperature of 135° C., the L-shaped cardboard with a thickness of 16 mm is heated to a temperature of 140° C., and the L-shaped cardboard with a thickness of 20 mm is heated to a temperature of 145° C.; the clamping pressure varies with the thickness of the L-shaped cardboard, wherein the clamping pressure of the L-shaped cardboard with a thickness of 12 mm is 12 MPa / ㎡, the clamping pressure of the L-shaped cardboard with a thickness of 16 mm is 14 MPa / ㎡, and the clamping pressure of the L-shaped cardboard with a thickness of 20 mm is 15 MPa / ㎡.

[0020] Preferably, in step f, a blower is used to dissipate heat and cool down.

[0021] Due to the adoption of the above technical solution, the beneficial effects of the present invention are:

[0022] The present invention adopts raw paperboard with high thickness and uses casein glue instead of phenolic sizing paper for bonding, thereby reducing the number of bonding layers, and overcomes the defects caused by using phenolic sizing paper for bonding, such as the adhesive layer is prone to bulging and cracking when bonding with wet raw paperboard with high thickness, the paperboard is prone to cracking when bonding with dry raw paperboard with high thickness, and cracks are prone to occur when bonding with dry raw paperboard with low thickness to produce products with high total thickness, resulting in electrical strength not meeting the standard. The quality of the produced products is significantly better than that of products of the same thickness produced by the prior art, and the high voltage electrical strength requirements of customers are met.

[0023] In short, the electrical strength of the product made by the present invention is significantly improved, meeting the customer's requirements for high voltage grade electrical strength. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 The L-shaped paperboard is obtained according to the first embodiment of the present invention;

[0025] Figure 2 The L-shaped paperboard is obtained in Example 2 of the present invention;

[0026] Figure 3 The L-shaped paperboard is obtained according to the third embodiment of the present invention;

[0027] Figure 4 The L-shaped paperboard is obtained according to the fourth embodiment of the present invention;

[0028] Figure 5 The L-shaped paperboard is obtained in Example 5 of the present invention;

[0029] Figure 6 This is the L-shaped paperboard prepared in Example 6 of the present invention. DETAILED DESCRIPTION

[0030] The technical solution of the present invention is further described below in conjunction with embodiments:

[0031] Example 1: A method for preparing a 500KV voltage 12mm thick L-shaped paperboard (t12×300×2000 (total thickness×width×length)) using a 2mm thick raw paperboard in the prior art:

[0032] 1. Cutting: Calculate the length and width of the cardboard according to the drawing size. The thickness of the material is t2 (t is the thickness of the cardboard). The specific dimensions are as follows:

[0033] t2×300×2000 6 pieces

[0034] 2. Cut the phenolic glue paper of appropriate size according to the size of the prepared cardboard;

[0035] 3. After the cardboard and phenolic adhesive tape are fully prepared, start to stack them. Lay a piece of cardboard on the bottom in advance, lay the adhesive tape on the cardboard, and then lay the cardboard on the phenolic adhesive tape. Repeat this process until the laying thickness reaches the required thickness of the product;

[0036] 4. Put the laid cardboard into the L-shaped cardboard hot press, and make sure the cardboard is flat and placed in the right position;

[0037] 5. Upper mold: Turn on the heating switch of the L-shaped cardboard hot press 30 minutes in advance, set the temperature to 135℃, maintain the temperature after preheating and place the laid cardboard on the L-shaped cardboard hot press mold, turn on the mold closing switch to make the cardboard and mold fit together, and release the mold closing switch after the pressure gauge pointer turns to a pressure of 12MPa / ㎡;

[0038] 6. According to the preset program, the hot press automatically opens the mold after the hot pressing time is over. The operator takes out the L-shaped cardboard and cools it for 2 hours, then cuts it to the finished size as required, trims and cleans it, and obtains a 12mm thick L-shaped cardboard product.

[0039] Embodiment 2: The present invention uses 4mm thick raw material paperboard to prepare 500KV voltage 12mm thick L-shaped paperboard (t12×300×2000 (total thickness×width×length)):

[0040] 1. Cutting: Calculate the length and width of the cardboard according to the drawing size. The thickness of the material is t4 (t is the thickness of the cardboard). The specific dimensions are as follows:

[0041] t4×300×2000 3 pieces

[0042] 2. Place the cardboard in the spray room, turn on the spray equipment, and humidify the cardboard evenly with a water volume of 0.9kg / ㎡ based on the 4mm thickness of the cardboard;

[0043] 3. After humidification, wrap the wet cardboard with plastic film and keep it moist for 16 hours;

[0044] 4. Use the casein glue roller to evenly apply glue to the moisturized cardboard. Pay attention to applying glue on one side of the first and last cardboard to ensure that the glue amount of each layer of cardboard is uniform. After the gluing is completed, lay the cardboards flat in order and stack them on the clean cardboard;

[0045] 5. Turn on the heating switch of the L-shaped cardboard hot press 30 minutes in advance, set the temperature to 135℃, maintain the temperature after preheating, place the glue-coated cardboard on the L-shaped cardboard hot press mold, turn on the mold closing switch, and make the cardboard and mold fit together. After the pressure gauge pointer turns to a pressure of 12MPa / ㎡, release the mold closing switch;

[0046] 6. According to the preset program, the press automatically opens the mold after the hot pressing time is over. The operator takes out the L-shaped cardboard and cools it for 2 hours, then cuts it to the finished size as required, trims and cleans it, and obtains a 12mm thick L-shaped cardboard product.

[0047] Example 3: A method for preparing a 500KV voltage 16mm thick L-shaped paperboard (t16×300×2000 (total thickness×width×length)) using a 2mm thick raw paperboard in the prior art:

[0048] 1. Cutting: Calculate the length and width of the cardboard according to the drawing size. The thickness of the material is t2 (t is the thickness of the cardboard). The specific dimensions are as follows:

[0049] t2×300×2000 8 pieces

[0050] 2. Cut the phenolic glue paper of appropriate size according to the size of the prepared cardboard;

[0051] 3. After the cardboard and phenolic adhesive tape are fully prepared, start to stack them. Lay a piece of cardboard on the bottom in advance, lay the adhesive tape on the cardboard, and then lay the cardboard on the phenolic adhesive tape. Repeat this process until the laying thickness reaches the required thickness of the product;

[0052] 4. Put the laid cardboard into the L-shaped cardboard hot press, and make sure the cardboard is flat and placed in the right position;

[0053] 5. Upper mold: Turn on the heating switch of the L-shaped cardboard hot press 30 minutes in advance, set the temperature to 140℃, maintain the temperature after preheating, place the laid cardboard on the L-shaped cardboard hot press mold, turn on the mold closing switch, and make the cardboard and mold fit together. After the pressure gauge pointer turns to a pressure of 14MPa / ㎡, release the mold closing switch;

[0054] 6. According to the preset program, the hot press automatically opens the mold after the hot pressing time is over. The operator takes out the L-shaped cardboard and cools it for 2 hours, then cuts it to the finished size as required, trims and cleans it, and obtains a 16mm thick L-shaped cardboard product.

[0055] Example 4: The present invention uses 4mm thick raw paperboard to prepare 500KV voltage 16mm thick L-shaped paperboard (t16×300×2000 (total thickness×width×length)):

[0056] 1. Cutting: Calculate the length and width of the cardboard according to the drawing size. The thickness of the material is t4 (t is the thickness of the cardboard). The specific dimensions are as follows:

[0057] t4×300×2000 4 pieces

[0058] 2. Place the cardboard in the spray room, turn on the spray equipment, and humidify the cardboard with a water volume of 0.9kg / ㎡ for a 4mm thick cardboard to make the cardboard evenly humidified;

[0059] 3. After humidification, wrap the wet cardboard with plastic film and keep it moist for 16 hours;

[0060] 4. Use the casein glue roller to evenly apply glue to the moisturized cardboard. Pay attention to applying glue on one side of the first and last cardboard to ensure that the glue amount of each layer of cardboard is uniform. After the gluing is completed, lay the cardboards flat in order and stack them on the clean cardboard;

[0061] 5. Turn on the heating switch of the L-shaped cardboard hot press 30 minutes in advance, set the temperature to 140℃, maintain the temperature after preheating, place the glue-coated cardboard on the L-shaped cardboard hot press mold, turn on the mold closing switch, and make the cardboard and mold fit together. After the pressure gauge pointer turns to a pressure of 14MPa / ㎡, release the mold closing switch;

[0062] 6. According to the preset program, the press automatically opens the mold after the hot pressing time is over. The operator takes out the L-shaped cardboard and cools it for 2 hours, then cuts it to the finished size as required, trims and cleans it, and obtains a 16mm thick L-shaped cardboard product.

[0063] Example 5: A method for preparing a 500KV voltage 20mm thick L-shaped paperboard (t20×300×2000 (total thickness×width×length)) using a 2mm thick raw paperboard in the prior art:

[0064] 1. Cutting: Calculate the length and width of the cardboard according to the drawing size. The thickness of the material is t2 (t is the thickness of the cardboard). The specific dimensions are as follows:

[0065] t2×300×2000 10 pieces

[0066] 2. Cut the phenolic glue paper of appropriate size according to the size of the prepared cardboard;

[0067] 3. After the cardboard and phenolic adhesive tape are fully prepared, start to stack them. Lay a piece of cardboard on the bottom in advance, lay the adhesive tape on the cardboard, and then lay the cardboard on the phenolic adhesive tape. Repeat this process until the laying thickness reaches the required thickness of the product;

[0068] 4. Put the laid cardboard into the L-shaped cardboard hot press, and make sure the cardboard is flat and placed in the right position;

[0069] 5. Upper mold: Turn on the heating switch of the L-shaped cardboard hot press 30 minutes in advance, set the temperature to 145℃, maintain the temperature after preheating, place the laid cardboard on the L-shaped cardboard hot press mold, turn on the mold closing switch, and make the cardboard and mold fit together. After the pressure gauge pointer turns to a pressure of 15MPa / ㎡, release the mold closing switch;

[0070] 6. According to the preset program, the hot press automatically opens the mold after the hot pressing time is over. The operator takes out the L-shaped cardboard and cools it for 2 hours, then cuts it to the finished size as required, trims and cleans it, and obtains a 20mm thick L-shaped cardboard product.

[0071] Example 6: The present invention uses 4mm thick raw paperboard to prepare 500KV voltage 20mm thick L-shaped paperboard (t20×300×2000 (total thickness×width×length)):

[0072] 1. Cutting: Calculate the length and width of the cardboard according to the drawing size. The thickness of the material is t4 (t is the thickness of the cardboard). The specific dimensions are as follows:

[0073] t4×300×2000 5 pieces

[0074] 2. Place the cardboard in the spray room, turn on the spray equipment, and humidify the cardboard with a water volume of 0.9kg / ㎡ for a 4mm thick cardboard to make the cardboard evenly humidified;

[0075] 3. After humidification, wrap the wet cardboard with plastic film and keep it moist for 16 hours;

[0076] 4. Use the casein glue roller to evenly apply glue to the moisturized cardboard. Pay attention to applying glue on one side of the first and last cardboard to ensure that the glue amount of each layer of cardboard is uniform. After the gluing is completed, lay the cardboards flat in order and stack them on the clean cardboard;

[0077] 5. Turn on the heating switch of the L-shaped cardboard hot press 30 minutes in advance, set the temperature to 145℃, maintain the temperature after preheating, place the glue-coated cardboard on the L-shaped cardboard hot press mold, turn on the mold closing switch, and make the cardboard and mold fit together. After the pressure gauge pointer turns to a pressure of 15MPa / ㎡, release the mold closing switch;

[0078] 6. According to the preset program, the press automatically opens the mold after the hot pressing time is over. The operator takes out the L-shaped cardboard and cools it for 2 hours, then cuts it to the finished size as required, trims and cleans it, and obtains a 20mm thick L-shaped cardboard product.

[0079] Product test results and analysis:

[0080] The performance of L-shaped paperboard products with a thickness of 12 mm, 16 mm, and 20 mm made by the prior art of Examples 1, 3, and 5 and the present invention of Examples 2, 4, and 6 was analyzed, and the obtained data is shown in Table 1:

[0081] Table 1 Test results of products produced by the present invention and prior art

[0082]

[0083]

[0084] Note: Thickness measurement refers to the condition where the weight does not change after drying; interlayer adhesion refers to the bonding of cardboard pieces and whether there are obvious cracks; sample moisture refers to the data obtained by sampling from the same position on the cut edge material and thoroughly drying it again for moisture testing; oil absorption rate is the data measured after the sample is completely soaked, and electrical strength is the result of testing in transformer oil after the sample is completely soaked.

[0085] Conclusion: Through the comparative analysis of the above data, it can be seen that the products prepared by the present invention and the products of the prior art are in terms of low thickness (product thickness 12mm) and low voltage products. The existing production process and the present invention can meet the customer's demand for products. However, under high thickness and high voltage conditions, since the bonding performance of the existing phenolic glue paper cannot meet the standard, it will cause the product to crack, and the electrical strength cannot meet the standard requirements; while the high thickness (product thickness 16mm and 20mm) L-shaped cardboard produced by the present invention has an increased single-layer cardboard thickness, a reduced number of glue layers, a significantly increased electrical strength of the product, and a significantly better interlayer bonding effect. Therefore, the product of the present invention shows unique advantages and can meet customers' electrical strength requirements for high thickness and high voltage grade products.

[0086] In addition, the present invention adopts a method of directly spraying casein glue with a glue coating machine, replacing the phenolic glue paper in the existing process. This improvement not only reduces the production cost, but also makes the processing process more convenient, the product performance is more stable, and can meet the quality requirements of high-thickness L-shaped paperboards for transformers of various voltage levels, and has a high promotion value in practical applications.

[0087] It should be understood that these embodiments are only used to illustrate the present invention and are not used to limit the scope of the present invention. In addition, it should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms also fall within the scope limited by the appended claims of the application.

Claims

1. A method for preparing a high-thickness L-shaped paperboard for a transformer, characterized in that: The following steps are involved: a. Cardboard cutting: select the thickness of the cardboard to be processed according to product requirements, calculate the length and width of the cardboard according to the size, and implement cutting; b. Cardboard humidification: Place the cut cardboard into the spray room, turn on the spray equipment, and adjust the humidification water volume per unit area according to the thickness of the cardboard to make the cardboard evenly humidified; c. Cardboard moisturizing: After humidification, wrap the wet cardboard with plastic film and determine the moisturizing time based on the cardboard thickness and the formula "moisturizing time = 4h / mm"; d. Bonding: Use casein glue roller to evenly glue the moisturized cardboard. The glue is casein glue. The first and last cardboards are glued on one side, and the other cardboards are glued on both sides to ensure that the glue amount of each layer of cardboard is even. After gluing, lay the cardboards flat and stack them on clean thin cardboards in order. e. Upper mold: Turn on the heating switch of the L-shaped cardboard hot press 30 minutes in advance, heat it to 135℃~145℃, place the glue-coated cardboard on the L-shaped cardboard hot press mold, turn on the mold closing switch, maintain the temperature and make the cardboard and mold fit together, and release the mold closing switch after the pressure gauge pointer turns to the set pressure; f. Demolding: After the hot pressing time is over, stop heating, turn on the mold opening switch, take out the pressed L-shaped cardboard, and dissipate heat for 2 hours; g. Bracket processing: The L-shaped cardboard after cooling in step g is cut to the finished size according to customer requirements, and trimmed and cleaned to obtain a high-thickness L-shaped cardboard product.

2. The method for preparing the high-thickness L-shaped paperboard for transformer according to claim 1, characterized in that: In step a, the thickness of the cardboard is 4 mm.

3. The method for preparing the high-thickness L-shaped paperboard for transformer according to claim 1, characterized in that: In the step b, a spray method is used for humidification, and the humidification amount is 0.9 kg / ㎡.

4. The method for preparing the high-thickness L-shaped paperboard for transformer according to claim 1, characterized in that: The moisturizing time of the 4 mm cardboard in step c is 16 hours.

5. The method for preparing the high-thickness L-shaped paperboard for transformer according to claim 1, characterized in that: In the step e, the 12 mm thick L-shaped cardboard is heated to a temperature of 135° C., the 16 mm thick L-shaped cardboard is heated to a temperature of 140° C., and the 20 mm thick L-shaped cardboard is heated to a temperature of 145° C.; the mold clamping pressure varies with the thickness of the L-shaped cardboard, wherein the mold clamping pressure of the 12 mm thick L-shaped cardboard is 12 MPa / ㎡, the mold clamping pressure of the 16 mm thick L-shaped cardboard is 14 MPa / ㎡, and the mold clamping pressure of the 20 mm thick L-shaped cardboard is 15 MPa / ㎡.

6. The method for preparing the high-thickness L-shaped paperboard for transformer according to claim 1, characterized in that: In step f, a blower is used to dissipate heat and cool down the temperature.

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