A preparation method of unbleached impregnated insulating paper

Abstract

The present invention provides a method for preparing unbleached impregnated insulating paper, belonging to the technical field of insulating paper preparation. The method uses a mixture of unbleached softwood sulfate pulp and unbleached hardwood sulfate pulp as raw materials, adds a bulking agent, gelatinized cationic starch, and a wet strength agent, and adjusts the preparation process to produce unbleached impregnated insulating paper with high dry and wet strength and good liquid absorption properties.

Description

Technical Field

[0001] The present invention relates to the technical field of insulating paper preparation, and in particular to a method for preparing unbleached impregnated insulating paper. Background Art

[0002] As the primary reinforcement material for paper-based copper-clad laminates, impregnated insulating paper requires not only excellent insulating properties from the impregnating resin but also stringent requirements for the base paper used. The fiber structure must be uniform, with stable thickness and basis weight, high tensile strength and wet strength, and good liquid absorption. Currently, there are two types of impregnated base paper: cotton pulp and wood pulp. Cotton pulp has excellent water absorption, but the fibers are prone to deflection after forming, which can affect performance. Wood pulp, on the other hand, has short, dense fibers and poor liquid absorption, making it difficult to meet user requirements.

[0003] Therefore, the problem to be solved by the present invention is to provide a high-quality unbleached impregnated insulating paper with high dry and wet strength and good liquid absorption performance. Summary of the Invention

[0004] In view of this, the present invention provides a method for preparing unbleached impregnated insulating paper, which adopts a simple process and reasonable raw materials, and adds chemical additives to prepare high-quality unbleached impregnated insulating paper with high dry and wet strength and good liquid absorption performance.

[0005] The method for preparing the unbleached impregnated insulating paper of the present invention comprises the following steps:

[0006] (1) mixing unbleached kraft softwood pulp and unbleached kraft hardwood pulp to obtain a mixed pulp, adding purified water to the mixed pulp and performing hydraulic pulping until the pulp is dispersed;

[0007] (2) After hydraulic pulping, the pulp is concentrated and dehydrated using an inclined screen, then placed in a forewater tank, and then into a pulping machine for refining to obtain the finished pulp;

[0008] (3) Place the finished pulp into a pulping tank, add a leavening agent and gelatinized cationic starch into the pulping tank, stir for 60 minutes, and then adjust the pulp concentration;

[0009] (4) The slurry enters the pulping tank, where a wet strength agent is added and diluted with water to form a 0.6±0.2% slurry-water mixture. The water is filtered and formed into a wet paper blank, which is further dehydrated by pressing to form a wet paper sheet with a certain wet strength.

[0010] (5) The wet paper is placed in a drying cylinder for the first drying and dehydration. When the moisture content is 8-11%, it enters the three-roll calender and enters the drying cylinder again for the second dehydration to reduce the moisture content to 5.0-8.0%. It is then wound to a moisture content of 0.6-0.7 g / cm 3 Tightness;

[0011] (6) After being rolled, cut and inspected, the paper is packed and put into storage.

[0012] Preferably, the mass ratio of unbleached kraft softwood pulp to unbleached kraft hardwood pulp in the mixed pulp of step (1) is 8:2; the beating degree of the mixed pulp is 15 to 18 0 SR, fiber wet weight 14-22 g;

[0013] Preferably, the conductivity of the purified water in step (1) is 20±5 us / mm.

[0014] Preferably, the slurry concentration in the forewater tank in step (2) is 3.6-4.0%, and the pH value is 5.0-8.0.

[0015] Preferably, the beating degree of the finished pulp in step (2) is 18 to 20 0 SR, wet weight is 14-16 g.

[0016] Preferably, the amount of the leavening agent added in step (3) is 0.5% to 0.8% of the finished pulp, and the leavening agent is dissolved in 60-80° C. purified water before addition. In a specific embodiment of the present invention, the leavening agent is a powdered non-ionic leavening agent purchased from Guangzhou Mingri Chemical Co., Ltd.

[0017] Preferably, the amount of gelatinized cationic starch added in step (3) is 0.5% to 1.0% of the finished slurry, and the gelatinized cationic starch is dissolved in purified water at 85-92° C. before addition. In a specific embodiment of the present invention, the modified cassava starch is gelatinized cationic starch purchased from Guangdong Huimei Starch Technology Co., Ltd., model HM-633.

[0018] Preferably, the slurry concentration is adjusted to 2.6±0.1% in step (3).

[0019] Preferably, the pulp in step (4) needs to pass through the fore tank before entering the pulping tank, and be pumped to the discharge box, and then flow into the pulping tank.

[0020] Preferably, the wet strength agent in step (4) is PPE (polyamide polyepichlorohydrin), and the amount of the wet strength agent added is 0.3% to 0.6% of the slurry.

[0021] Preferably, the pressing in step (4) includes compound K pressing, main pressing and light pressing.

[0022] Preferably, the temperature of the first drying and dehydration in step (5) is 70°C to 108°C; the temperature of the second drying and dehydration is 30°C to 80°C.

[0023] Compared with the prior art, the present invention has the following beneficial effects: the present invention provides a method for preparing unbleached impregnated insulating paper, which uses a mixed pulp of unbleached kraft softwood pulp and unbleached kraft hardwood pulp as a raw material, adds a leavening agent, gelatinized cationic starch and a wet strength agent, and adjusts the preparation process to obtain unbleached impregnated insulating paper, which has the characteristics of high dry and wet strength and good liquid absorption performance. DETAILED DESCRIPTION

[0024] The present invention will be further described below with reference to the embodiments.

[0025] Example 1

[0026] A method for preparing unbleached impregnated insulating paper, comprising the following steps:

[0027] (1) Unbleached kraft softwood pulp and unbleached kraft broadleaf pulp were mixed in a mass ratio of 8:2 to obtain a mixed pulp, and purified water with an electrical conductivity of 15 μs / mm was added to the mixed pulp for hydraulic pulping; the mixed pulp had a beating degree of 16 0 SR, fiber wet weight 22 g;

[0028] (2) After hydraulic pulping, the pulp is concentrated and dehydrated using an inclined screen, and then placed in a fore-beating tank. At this time, the pulp concentration is 3.6% and the pH value is 6.5. It is then put into a pulping machine for refining to obtain a beating degree of 19. 0 SR, finished pulp with a wet weight of 14.6 g;

[0029] (3) The finished pulp is placed in a pulping tank, and 0.8% of a leavening agent and 0.5% of gelatinized cationic starch (Guangdong Huimei Starch Technology HM-633) are added to the pulping tank. After stirring for 60 minutes, the pulp concentration is adjusted to 2.52%; the leavening agent is dissolved in 76°C pure water before being added, and the gelatinized cationic starch is dissolved in 90°C pure water before being added.

[0030] (4) The pulp enters the pre-papermaking pool and is pumped to the discharge box and then flows into the pulping pool. 0.5% wet strength agent PPE is added to the pulp and diluted with water to form a 0.56% pulp-water mixture. The pulp-water mixture is pumped to the cleaner through the pulping pump and distributed to two circular screens for water filtration through a pressure screen (0.012 MPa) to obtain 82.7% wet paper blanks. The wet paper blanks are further squeezed and dehydrated through a composite K pressure (0.25 MPa), a main pressure (0.28 MPa) and a light pressure (0.22 MPa) to form a wet paper sheet with a certain wet strength (until the wet paper sheet is wrinkled);

[0031] (5) Place the wet paper sheets into the drying cylinders at 1#: 70℃, 2#: 75℃, 3#: 80℃, 4#: 90℃

[0032] The first drying and dehydration is carried out at 5#: 90℃, 6#: 95℃, 7#: 105℃, 8#: 105℃, 9#: 105℃, and 10#: 90℃ (the first drying is composed of 10 drying cylinders). When the moisture content is 10.8%, it enters the three-roll calender and enters the drying cylinder again for the second drying and dehydration (the second drying is composed of 4 drying cylinders). The temperature is 11#: 80℃, 12#: 70℃, 13#: 50℃, and 14#: 30℃. The second dehydration reduces the moisture content to 6.6%, and then enters the winding to make it reach 0.65g / cm 3 Tightness;

[0033] (6) After being rolled, cut and inspected, the paper is packed and put into storage.

[0034] The paper prepared in Example 1 was tested, and the results are shown in Table 1:

[0035] Table 1

[0036]

[0037] As can be seen from Table 1, the unbleached impregnated insulating paper prepared by the present invention has uniform basis weight, and the relevant indicators meet or exceed the requirements of the national standard GB1913.1-2005. That is, the basis weight difference of the whole paper is ±4g / m 2 , uniform thickness, thickness tolerance ±0.01mm, high tensile index, longitudinal ≥62N.m / g, transverse ≥35N.m / g, high capillary water absorption, longitudinal ≥45mm / 10min, transverse ≥40mm / 10mm, high power frequency breakdown voltage >600V / layer.

[0038] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. A method for preparing unbleached impregnated insulating paper, characterized in that: The following steps are involved: (1) unbleached kraft softwood pulp and unbleached kraft hardwood pulp are mixed to obtain a mixed pulp, purified water is added to the mixed pulp, and the pulp is hydraulically crushed until the pulp is dispersed; (2) After hydraulic pulping, the pulp is concentrated and dehydrated using an inclined screen, then placed in a forewater tank, and then into a pulping machine for refining to obtain the finished pulp; (3) Put the finished pulp into the pulping tank, add the leavening agent and gelatinized cationic starch into the pulping tank, stir for 60 minutes, and then adjust the pulp concentration; (4) The pulp enters the pulping tank, a wet strength agent is added, and water is added to dilute it to form a 0.6±0.2% pulp-water mixture. The water is filtered and formed into a wet paper blank, which is further dehydrated by pressing to form a wet paper sheet with a certain wet strength; (5) The wet paper is placed in the drying cylinder for the first drying and dehydration. When the moisture content is 8-11%, it enters the three-roll calender and enters the drying cylinder again for the second dehydration to reduce the moisture content to 5.0-8.0%. It is then wound and rewound to a moisture content of 0.6-0.7 g / cm 3 Tightness; (6) After being rolled, cut and inspected, the paper is packed and put into storage; The amount of the leavening agent added in step (3) is 0.5% to 0.8% of the finished pulp, and the leavening agent is dissolved in 60-80°C pure water before addition; The temperature of the first drying and dehydration in step (5) is 70°C to 108°C; the temperature of the second drying and dehydration is 30°C to 80°C.

2. The method for preparing unbleached impregnated insulating paper according to claim 1, characterized in that: The mass ratio of unbleached kraft softwood pulp to unbleached kraft hardwood pulp in the mixed pulp of step (1) is 8:2; the beating degree of the mixed pulp is 15 to 18 0 SR, fiber wet weight is 14-22 g; the conductivity of the purified water is 20±5 us / mm.

3. The method for preparing unbleached impregnated insulating paper according to claim 1, characterized in that: The slurry concentration in the pre-beating tank in step (2) is 3.6-4.0%, and the pH value is 5.0-8.

0.

4. The method for preparing unbleached impregnated insulating paper according to claim 1, characterized in that: The beating degree of the finished pulp in step (2) is 18 to 20 0 SR, wet weight is 14~16 grams.

5. The method for preparing unbleached impregnated insulating paper according to claim 1, characterized in that: The gelatinized cationic starch in step (3) is added in an amount of 0.5% to 1.0% of the finished slurry, and is dissolved in purified water at 85-92° C. before being added.

6. The method for preparing unbleached impregnated insulating paper according to claim 1, characterized in that: In step (3), the slurry concentration is adjusted to 2.6±0.1%.

7. The method for preparing unbleached impregnated insulating paper according to claim 1, characterized in that: Before entering the pulping tank in step (4), the pulp needs to pass through the fore-cutting tank and be pumped to the discharge box, and then flow into the pulping tank.

8. The method for preparing unbleached impregnated insulating paper according to claim 1, characterized in that: The wet strength agent in step (4) is PPE, and the amount of the wet strength agent added is 0.3% to 0.6% of the slurry.

9. The method for preparing unbleached impregnated insulating paper according to claim 1, characterized in that: The pressing in step (4) includes compound K pressing, main pressing and light pressing.

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