Moisture absorption prevention treatment method for water-soluble mold

Abstract

The invention relates to an anti-moisture absorption treatment method for a water-soluble mold, belongs to the technical field of water-soluble mold processing, and aims to solve the problem that a water-soluble mold for forming an annular frame of a space camera is easy to absorb moisture. The method comprises the steps that a water-soluble adhesive, a base material and water are mixed in proportion and subjected to cold press molding to form a water-soluble mold blank block, and rough machining mold blocks are obtained through drying and reserved machining allowance cutting; mixing the mold block with a cyanate ester resin block, and heating to melt the resin and form a curing layer on the surface of the mold block; and finish machining is carried out on the mold block coated with the curing layer, and demolding cloth can be coated after finish machining. Moisture absorption prevention protection of the water-soluble mold is achieved through the cyanate resin curing layer, the dimensional stability of the mold is guaranteed, and then the subsequent annular frame forming precision is guaranteed.

Description

Technical Field

[0001] This invention belongs to the field of water-soluble mold processing technology, and particularly relates to a method for preventing moisture absorption in water-soluble molds. Background Technology

[0002] The ring frame used in the field of space cameras has high requirements for mechanical properties such as strength and stiffness. It is necessary to select the molding process reasonably and optimize it in a targeted manner to ensure precise control of the fiber angle and layup sequence determined by the structural design, high fiber volume content, uniform distribution of matrix resin, low porosity, precise dimensional control, and good performance repeatability.

[0003] The integrated ring frame achieves integral lay-up, forming a closed cavity structure that ensures fiber continuity. Traditional metal molds cannot demold, so a water-soluble mold is used for the inner mold. Water-soluble molds are commonly used for molding complex irregular structures such as closed cavities, complex cavities, and hollow structures. They offer advantages such as light weight, no need to consider mold block positioning and demolding structures, and good force transmission, and have been widely applied in the molding process of space camera ring frames. However, water-soluble molds are hygroscopic. During storage, transportation, and subsequent prepreg laying, moisture absorption can easily lead to a decrease in mold dimensional stability, thus affecting the molding accuracy and product performance of the ring frame. Therefore, it is urgent to treat the water-soluble mold to prevent moisture absorption and ensure the molding quality of the space camera ring frame. Summary of the Invention

[0004] In view of this, the present invention aims to provide a method for preventing moisture absorption in water-soluble molds.

[0005] To achieve the above objectives, the technical solution created by this invention is implemented as follows: A method for preventing moisture absorption in water-soluble molds, comprising the following steps: S1. Mix water-soluble adhesive, matrix material and water in proportion and form into a water-soluble mold blank block of predetermined specifications; S2. The water-soluble mold blank is dried. S3. Cut the dried water-soluble mold blank to form a rough-machined water-soluble mold block; S4. Mix the cyanate ester resin block with the rough-processed water-soluble mold block and heat them together to melt the cyanate ester resin and form a cyanate ester resin cured layer on the surface of the water-soluble mold block. S5. Perform precision machining on the water-soluble mold block coated with a cyanate ester resin curing layer.

[0006] Further, in step S1, the water-soluble mold blank is formed by cold pressing.

[0007] Further, in step S2, the drying process includes first performing natural drying, and then drying at a temperature of (80℃±10℃).

[0008] Furthermore, in step S3, a machining allowance of 1-2 mm is reserved during cutting.

[0009] Further, in step S4, the heating together is: holding at (120±5)℃ for (2h±5min), raising the temperature to (160±5)℃ and holding for (7h±5min), and then raising the temperature to (190±5)℃ and holding for (2h±5min).

[0010] Further, in step S4, the cyanate ester resin is melted under heating at 100~120°C and dripped onto the surface of the water-soluble mold block.

[0011] Furthermore, in step S5, the finishing process is performed using a diamond tool.

[0012] Furthermore, after step S5, the process also includes covering the surface of the finished water-soluble mold block with a release cloth and then laying the prepreg.

[0013] Furthermore, the heating process in step S4 is carried out at a rate not exceeding 5°C / min.

[0014] Furthermore, the amount of the cyanate ester resin block used is such that it can completely cover the entire outer surface of the water-soluble mold block after being completely melted in step S4; the purity of the cyanate ester resin block is ≥98%.

[0015] Compared with the prior art, the present invention can achieve the following beneficial effects: This application employs a combined drying and cyanate ester resin curing layer coating method. On one hand, it completely removes residual moisture from water-soluble molds, solving the problem of incomplete drying in existing methods. On the other hand, the resulting cyanate ester resin curing layer exhibits excellent resistance to damp heat and low moisture absorption, effectively preventing environmental moisture from entering the mold and avoiding moisture absorption during storage and use. Furthermore, the entire process is coherent, simple, and controllable, resulting in high-precision mold dimensions. This ensures the molding quality of the subsequent space camera ring frame, preventing problems such as prepreg bubbling and delamination, and composite cavity fuzzing caused by mold moisture absorption, thus improving the performance stability and yield rate of the ring frame product. Attached Figure Description

[0016] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments and descriptions of the invention are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings: Figure 1A schematic diagram of the structure of the ring frame described in an embodiment of the present invention.

[0017] Explanation of reference numerals in the attached figures: 1. Ring frame. Detailed Implementation

[0018] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and do not constitute a limitation thereof.

[0019] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other.

[0020] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicating orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation on this invention. Furthermore, the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, features defined with "first," "second," etc., may explicitly or implicitly include one or more of that feature. In the description of this invention, unless otherwise stated, "a plurality of" means two or more.

[0021] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art will understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0022] A method for preventing moisture absorption in water-soluble molds includes the following steps S1-S5: S1. Mix the water-soluble adhesive, matrix material, and water in a certain proportion to form a water-soluble mold blank of a predetermined specification. The mixing process preferably uses a mixer to ensure thorough mixing of all components. Molding can preferably be done using a cold pressing method, which can produce blanks of uniform size (e.g., 400mm*400mm*200mm). Cold pressing avoids the influence of high temperatures on the water-soluble components, ensuring the molding quality and structural stability of the blank. More preferably, the mixing mass ratio of the water-soluble adhesive, matrix material, and water is (1~1.5):(8~10):(3~4). This ratio range ensures the mixture has suitable fluidity and moldability, guaranteeing that the molded blank is not prone to cracking and meets strength requirements.

[0023] S2. The water-soluble mold blank is dried. The water-soluble mold blank after molding is dried to remove residual moisture from the blank. More preferably, the drying process adopts a combination of "natural drying + low-temperature drying". First, natural drying is carried out for 5 to 7 days to allow the moisture in the blank to slowly seep out, avoiding cracks caused by rapid evaporation of moisture due to direct high-temperature drying; then, low-temperature drying is carried out at (80℃±10℃) for (10h±2h) to further remove residual moisture and ensure the drying effect.

[0024] S3. Cut the dried water-soluble mold blank to form a rough-machined water-soluble mold block; more preferably, the cutting process uses an electric cutting machine, and a machining allowance of 1~2mm is reserved during cutting. This machining allowance can provide adjustment space for subsequent fine machining, ensuring that the final mold size can accurately match the forming requirements of the ring frame.

[0025] S4. The cyanate ester resin block is mixed with the roughly processed water-soluble mold block and heated together to melt the cyanate ester resin and form a cyanate ester resin cured layer on the surface of the water-soluble mold block. More preferably, the cyanate ester resin is melted at 100~120℃ and dripped onto the surface of the water-soluble mold block. The -OCN functional groups contained therein can react with the residual water in the water-soluble mold (reaction equation: R-NCO+H2O→R-NH2+CO2↑), completely consuming the water. As the temperature rises, the cyanate ester resin undergoes a tricyclization reaction to form a macromolecular cyclic polymer with a high crosslinking density network structure containing triazine rings. This polymer structure does not contain easily hydrolyzed ester bonds, amide bonds, etc., and the ether bonds on the molecular chain are almost unaffected by water molecules at room temperature. Moreover, the steric hindrance of the cyclic structure is large, which can greatly increase the resistance to water molecule diffusion, thereby forming a dense cured layer with low moisture absorption. The amount of cyanate ester resin block used is such that it can completely cover the entire outer surface of the water-soluble mold block after melting, ensuring no blind spots in the protection. The purity of the cyanate ester resin block must be ≥98%, as high purity can prevent impurities from affecting the reaction efficiency between the resin and water and the density of the cured layer. More preferably, the heating process follows a specific heating regime, and the heating rate does not exceed 5℃ / min. The specific heating regime is as follows: hold at (120±5)℃ for (2h±5min) to allow the cyanate ester resin to fully melt and begin to react with water; then raise the temperature to (160±5)℃ and hold for (7h±5min) to promote the full tricyclization reaction of the resin; then raise the temperature to (190±5)℃ and hold for (2h±5min) to ensure that the resin is completely cured and forms a stable cured layer.

[0026] S5. The water-soluble mold block coated with a cyanate ester resin curing layer is then precision-machined. More preferably, this precision machining is performed using a diamond cutting tool. Diamond cutting tools have high hardness and good wear resistance, allowing for precise cutting away of the reserved machining allowance, ensuring the mold block reaches the preset precise dimensions and guaranteeing the dimensional accuracy of the subsequent ring frame molding. After precision machining, a release cloth can be wrapped around the surface of the mold block before the prepreg laying process, further improving the smoothness of subsequent molding processes. Figure 1 The diagram shown is a structural schematic of the ring frame 1 according to an embodiment of this application.

[0027] Cyanate ester resins are solid at room temperature. The general structural formula of cyanate ester monomers is shown in the figure below: Cyanate esters begin to melt into a liquid state at 100-120℃ and drip towards the blank under the influence of gravity. The cyanate ester (-OCN) functional group reacts with water to form carbamate. The reaction equation is as follows: R-NCO + H2O → R-NH2 + CO2↑. As the temperature increases, the cyanate ester resin undergoes a tricyclization reaction, forming a macrocyclic polymer with a high crosslinking density network structure containing triazine rings.

[0028] Preferably, in a specific embodiment, by combining combined drying with cyanate ester resin curing layer coating, residual moisture in the water-soluble mold can be completely removed, solving the problem of incomplete drying in existing methods. Furthermore, the formed cyanate ester resin curing layer has excellent resistance to damp heat and low moisture absorption, effectively preventing moisture from entering the mold and avoiding moisture absorption during storage and use. Simultaneously, the entire process is coherent, simple, and controllable, resulting in high-precision mold dimensions. This ensures the molding quality of the subsequent space camera ring frame, avoiding problems such as prepreg bubbling and delamination, and composite cavity fuzzing caused by mold moisture absorption, thus improving the performance stability and yield rate of the ring frame product.

[0029] Further, in a specific embodiment, in step S1, the water-soluble mold blank is formed by cold pressing. Specifically, a mixture of water-soluble adhesive, matrix material, and water, which has been thoroughly mixed in a mixer, is poured into a pre-sized mold (e.g., a 400mm*400mm*200mm mold). The mold is then placed under a press, and appropriate pressure is applied at room temperature, causing the mixture to bind tightly under pressure and form a blank. After pressing, the mold is removed, resulting in the formed water-soluble mold blank. Cold pressing avoids the premature dissolution or volatilization of water-soluble components due to high-temperature heating, ensuring the stability of the component ratio. Simultaneously, cold pressing makes the internal structure of the blank denser, reducing porosity and increasing the strength of the blank, preventing cracking and damage during subsequent drying and processing. Compared to other molding methods (such as casting and hot pressing), the press cold pressing method has higher molding efficiency and more stable molding quality. It can mass-produce water-soluble mold blanks with uniform specifications. It operates at room temperature without the need for additional heating equipment, reducing energy consumption and process complexity. The molded blanks have a denser structure and higher strength, resulting in better subsequent processing performance and providing better assurance for the quality of the final mold.

[0030] In this application, the cold pressing method refers to a molding method in which a press is used to apply a certain pressure to a mixture of materials under normal temperature conditions, so that the materials are formed into a predetermined shape and specifications in a mold, without the need for additional heating.

[0031] More preferably, in a specific embodiment, the water-soluble adhesive is preferably polyvinyl alcohol, which has good water solubility and adhesive properties, enabling the matrix material to form a uniform mixture with water and be molded.

[0032] Further, in step S2, the drying process includes first natural drying, and then drying at a temperature of (80℃±10℃). Specifically, the drying process is carried out in two steps. The first step involves natural drying, placing the formed water-soluble mold blank in a ventilated and dry natural environment for 5-7 days to allow moisture to slowly seep out from the surface and interior of the blank. The second step, after natural drying, involves placing the blank in a drying device and drying it at a low temperature of (80℃±10℃) for (10h±2h). During this time, air circulation should be maintained within the drying device to ensure sufficient moisture removal. Water-soluble mold blanks contain a significant amount of moisture; if directly dried at high temperatures, the moisture will evaporate rapidly. Natural drying first allows for slow and uniform moisture removal, reducing internal stress in the blank. The subsequent low-temperature drying further removes residual moisture, ensuring the structural integrity and dimensional stability of the dried blank.

[0033] In this application, natural drying refers to a drying method in which the moisture in the blank block is slowly evaporated through air circulation at room temperature and in a natural environment; low-temperature drying refers to a drying method carried out at a relatively low temperature (80℃±10℃ in this invention) to slowly remove residual moisture.

[0034] Furthermore, in step S3, a machining allowance of 1-2 mm is reserved during cutting. Specifically, when cutting the dried water-soluble mold blank (using an electric cutting machine), a machining allowance of 1-2 mm is reserved. In specific operation, the rough machining cutting dimensions are calculated based on the final finished mold dimensions, ensuring that each dimension of the rough-machined mold block is 1-2 mm larger than the finished product dimensions. For example, if the finished mold dimensions are 300mm*300mm*100mm, then the rough-machined dimensions should be 302mm*302mm*102mm (with a 2 mm allowance). The 1-2 mm machining allowance allows for precise cutting to remove this excess material during the finishing stage, correcting errors in the rough machining and removing surface defects that may occur during resin coating, ensuring that the final mold dimensions fully meet design requirements and improving the mold's dimensional accuracy.

[0035] In this application, machining allowance refers to the portion of material that exceeds the final dimensions of the mold during rough machining, reserved for subsequent finishing. Its function is to compensate for errors in rough machining and provide adjustment space for finishing.

[0036] Further, in a specific embodiment, in step S4, the heating together is: holding at (120±5)℃ for (2h±5min), raising the temperature to (160±5)℃ and holding for (7h±5min), and then raising the temperature to (190±5)℃ and holding for (2h±5min).

[0037] In a specific embodiment, the heating rate refers to the magnitude of temperature increase per unit time. In this application, preferably, the heating rate does not exceed 5℃ / min, which can avoid the rapid temperature rise leading to local overheating and decomposition of the cyanate ester resin, while ensuring that the temperature of each part of the mold block rises evenly, ensuring that the resin and the residual moisture in the mold are fully in contact and react; the (120±5)℃ heat preservation stage allows the cyanate ester resin to fully melt and begin to react with moisture (R-NCO+H2O→R-NH2+CO2↑), initially consuming moisture; the (160±5)℃ heat preservation for 7h is the key stage for the tricyclization reaction of the cyanate ester resin. This temperature and duration can ensure that the tricyclization reaction is fully carried out, forming a grid structure with high cross-linking density; the (190±5)℃ heat preservation for 2h allows the resin to be completely cured, improving the hardness and stability of the cured layer, ensuring that the cured layer is tightly bonded to the mold surface, and playing a good role in preventing moisture absorption.

[0038] In a specific embodiment, in step S4, the cyanate ester resin is melted at 100~120°C and dripped onto the surface of the water-soluble mold block. The liquid cyanate ester resin drips onto the surface of the rough-processed water-soluble mold block under gravity, achieving uniform coverage of the mold surface with resin and ensuring sufficient contact between the resin and residual moisture on the mold surface and inside, laying the foundation for subsequent reaction and curing layer formation.

[0039] In one specific embodiment, in step S5, the finishing process is performed using a diamond tool. During the machining process, based on the final finished size of the mold, the cutting parameters of the diamond tool are precisely controlled to remove the 1-2mm machining allowance reserved during rough machining, so that the dimensional accuracy and surface finish of the mold block meet the design requirements.

[0040] In this application, diamond cutting tools refer to cutting tools that use diamond (silicon carbide) as the main cutting material.

[0041] Furthermore, after step S5, the process also includes covering the surface of the finished water-soluble mold block with a release cloth and then laying the prepreg.

[0042] In this application, release fabric refers to a fabric material with anti-stick and high temperature resistance properties. When laid on the mold surface, it can reduce the adhesion between the prepreg and the mold, and facilitate the subsequent demolding operation after molding.

[0043] In this application, prepreg laying refers to laying resin-impregnated fiber material on the mold surface at a predetermined angle and sequence to provide a fiber substrate for the molding of the ring frame.

[0044] In one specific embodiment, the heating process in step S4 is carried out at a rate not exceeding 5°C / min.

[0045] In this application, the heating rate (not exceeding 5℃ / min) refers to the maximum increase in temperature per unit time during the heating process, that is, the temperature increase per minute is ≤5℃.

[0046] Limiting the heating rate to no more than 5℃ / min ensures better uniformity of the heating process, guarantees that the cyanate ester resin melts completely without decomposition, and reacts fully with the moisture in the water-soluble mold, completely eliminating the potential moisture hazard. At the same time, it reduces thermal stress on the mold and cured layer caused by sudden temperature rise, avoiding defects such as cracks and deformation, and ensuring the structural integrity and dimensional stability of the mold. In addition, slow heating makes the reaction process more stable and controllable, improves the formation quality of the cured layer, and further enhances the mold's moisture resistance.

[0047] In one specific embodiment of this application, the amount of the cyanate ester resin block is such that it can cover the entire outer surface of the water-soluble mold block after being completely melted in step S4; the purity of the cyanate ester resin block is ≥98%.

[0048] In this application, a purity of ≥98% for the cyanate ester resin block means that the mass percentage of the effective components (cyanate ester monomers and polymers) in the cyanate ester resin block is not less than 98%, and the impurity content is ≤2%. The amount of resin used is sufficient to cover the entire outer surface of the water-soluble mold block, meaning that after the cyanate ester resin block is completely melted, its liquid volume can fully cover the entire outer surface of the water-soluble mold block.

[0049] In a specific embodiment of this application, in step S1, polyvinyl alcohol is selected as a water-soluble adhesive, and calcium sulfate and / or calcium carbonate powder is selected as a matrix material. Polyvinyl alcohol, matrix material and water are weighed according to a mixing mass ratio of (1~1.5): (8~10): (3~4). Then, the three are thoroughly mixed by a mixer to form a uniform mixture, and then cold-pressed by a press.

[0050] In one specific embodiment, the matrix material is preferably calcium sulfate and / or calcium carbonate powder. These materials are widely available, have low cost, and are compatible with water-soluble binders, which can ensure the basic structural strength of the mold blank after molding.

[0051] In a specific embodiment, the cyanate ester resin used in this application is solid at room temperature and has excellent resistance to damp heat and low moisture absorption. Its -OCN functional groups can react with water molecules, and at high temperature, it can undergo a tricyclization reaction to form a highly crosslinked network structure, making it suitable as a moisture-proof curing layer material.

[0052] The invention will now be described in detail with reference to specific embodiments.

[0053] Example 1: S1. Mix water-soluble adhesive, matrix material and water in a mass ratio of 1.2:9:3.5, and use conventional casting molding method to make a water-soluble mold blank block of predetermined specifications (450mm×450mm×220mm). S2. Dry the water-soluble mold blank (directly dry at 90℃ for 12 hours). S3. Cut the dried water-soluble mold blank to form a rough-machined water-soluble mold block; S4. Place the cyanate ester resin block and the roughly processed water-soluble mold block together in a heating furnace and heat them together to melt the cyanate ester resin and form a cyanate ester resin curing layer on the surface of the water-soluble mold block (heating method: keep at 125℃ for 2 hours, raise the temperature to 165℃ and keep for 7 hours, then raise the temperature to 195℃ and keep for 2 hours). S5. The water-soluble mold block coated with a cyanate ester resin curing layer is finely processed to obtain the finished water-soluble mold.

[0054] Performance test results: residual moisture content 0.32%, moisture absorption rate 0.45%, no obvious bubbling or delamination when used for ring frame molding, and no "fuzzing" phenomenon in the composite cavity.

[0055] Example 2: S1. Mix water-soluble adhesive, matrix material and water in a mass ratio of 1.1:8.5:3.2 and use conventional casting molding method to make a water-soluble mold blank block of predetermined specifications (380mm×380mm×180mm). S2. Dry the water-soluble mold blank (directly dry at 85℃ for 14 hours). S3. Cut the dried water-soluble mold blank to form a rough-machined water-soluble mold block; S4. Place the cyanate ester resin block and the roughly processed water-soluble mold block into a heating furnace and mix and heat them together to melt the cyanate ester resin and form a cyanate ester resin curing layer on the surface of the water-soluble mold block (heating method: keep at 118℃ for 2 hours, raise the temperature to 158℃ and keep for 7 hours, then raise the temperature to 188℃ and keep for 2 hours). S5. The water-soluble mold block coated with a cyanate ester resin curing layer is finely processed to obtain the finished water-soluble mold.

[0056] Performance test results: residual moisture content 0.35%, moisture absorption rate 0.48%, no obvious bubbling or delamination when used for ring frame molding, no "fuzzing" phenomenon in the composite cavity, and stable molding quality.

[0057] Example 3: S1. Mix water-soluble adhesive, matrix material and water in a mass ratio of 1.3:9.5:3.8, and use a press to cold press into a water-soluble mold blank block of predetermined specifications (420mm×420mm×210mm). The cold pressing pressure is 7MPa and the holding time is 32min. S2. Dry the water-soluble mold blank (directly dry at 88℃ for 13 hours). S3. Cut the dried water-soluble mold blank to form a rough-machined water-soluble mold block; S4. Place the cyanate ester resin block and the roughly processed water-soluble mold block into a heating furnace and mix and heat them together to melt the cyanate ester resin and form a cyanate ester resin curing layer on the surface of the water-soluble mold block (heating method: 122℃ for 2 hours, raise the temperature to 162℃ for 7 hours, and then raise the temperature to 192℃ for 2 hours). S5. The water-soluble mold block coated with a cyanate ester resin curing layer is finely processed to obtain the finished water-soluble mold.

[0058] Performance test results: residual moisture content 0.28%, moisture absorption rate 0.40%, water-soluble mold blank block is dense and non-porous, no bubbling or delamination when used for ring frame molding, composite cavity surface is smooth and without "fuzzing" phenomenon.

[0059] Example 4: S1. Mix water-soluble adhesive, matrix material and water in a mass ratio of 1.0:8:3, and use a press to cold press into a water-soluble mold blank block of predetermined specifications (400mm×400mm×200mm). The cold pressing pressure is 5MPa and the holding time is 30min. S2. The water-soluble mold blank blocks are subjected to a combination of "natural drying + low temperature drying": first, they are naturally dried in a ventilated and dry environment for 5 days, and then dried at 70℃ for 12 hours. S3. The dried water-soluble mold blank is cut with an electric cutting machine, leaving a 1mm machining allowance to form a rough-machined water-soluble mold block (301mm×301mm×101mm). S4. Place the cyanate ester resin block and the roughly processed water-soluble mold block together in a heating furnace and heat them together to melt the cyanate ester resin and form a cyanate ester resin curing layer on the surface of the water-soluble mold block (heating method: keep at 115℃ for 2 hours, raise the temperature to 155℃ and keep for 7 hours, then raise the temperature to 185℃ and keep for 2 hours). S5. The water-soluble mold block coated with a cyanate ester resin curing layer is finely processed to obtain the finished water-soluble mold.

[0060] Performance test results: residual moisture content 0.21%, moisture absorption rate 0.32%, no bubbling or delamination when used for ring frame molding, and smooth surface of composite cavity without "fuzzing".

[0061] Example 5: S1. Mix water-soluble adhesive, matrix material and water in a mass ratio of 1.5:10:4, and use a press to cold press into a water-soluble mold blank block of a predetermined specification (400mm×400mm×200mm). The cold pressing pressure is 8MPa and the holding time is 40min. S2. The water-soluble mold blank blocks are subjected to a combination of "natural drying + low temperature drying": first, they are naturally dried in a ventilated and dry environment for 7 days, and then dried at 90℃ for 8 hours. S3. The dried water-soluble mold blank is cut with an electric cutting machine, leaving a 2mm machining allowance to form a rough-machined water-soluble mold block (302mm×302mm×102mm). S4. Place the cyanate ester resin block on top of the roughly processed water-soluble mold block, and put them together in a heating furnace for heating. The heating rate is controlled at 3℃ / min. The heating process is as follows: hold at (120±5)℃ for (2h±5min), raise the temperature to (160±5)℃ and hold for (7h±5min), and then raise the temperature to (190±5)℃ and hold for (2h±5min). During the heating process, the cyanate ester resin melts in the range of 100~120℃ and drips onto the surface of the water-soluble mold block, finally forming a cyanate ester resin curing layer of uniform thickness. S5. The water-soluble mold block coated with a cyanate ester resin curing layer is finely processed to obtain the finished water-soluble mold.

[0062] Performance test results: residual moisture content 0.15%, moisture absorption rate 0.28%, cyanate ester resin cured layer is firmly bonded to the mold body and there is no peeling; when used for ring frame molding, the prepreg is laid flat and there are no defects after curing, and the dimensional accuracy error of the composite cavity is ≤±0.05mm.

[0063] Example 6: S1. Mix water-soluble adhesive, matrix material and water in a mass ratio of 1.2:9:3.5, and use a press to cold press into a water-soluble mold blank block of predetermined specifications (400mm×400mm×200mm). The cold pressing pressure is 6MPa and the holding time is 35min. S2. The water-soluble mold blank blocks are subjected to a combination of "natural drying + low temperature drying": first, they are naturally dried in a ventilated and dry environment for 6 days, and then dried at 80℃ for 10 hours. S3. The dried water-soluble mold blank is cut with an electric cutting machine, leaving a 1.5mm machining allowance to form a rough-machined water-soluble mold block (301mm×301mm×101mm). S4. Select cyanate ester resin blocks with a purity ≥98%. The amount used should be sufficient to completely cover the entire outer surface of the rough-processed water-soluble mold block after complete melting (actual amount is mold surface area × 0.2g / cm²). Place the cyanate ester resin blocks on top of the rough-processed water-soluble mold block and put them together in a heating furnace for heating. The heating rate is controlled at 4℃ / min. Maintain the temperature at 120℃ for 2 hours, raise the temperature to 160℃ and maintain it for 7 hours, and then raise the temperature to 190℃ and maintain it for 2 hours. During the heating process, the cyanate ester resin melts in the range of 100~120℃ and drips onto the surface of the water-soluble mold block, finally forming a uniformly thick cyanate ester resin cured layer. S5. Use diamond tools to finish the water-soluble mold block coated with cyanate ester resin curing layer to obtain the finished water-soluble mold. S6. After finishing the water-soluble mold block, cover the surface with release cloth, and then carry out the prepreg laying and ring frame forming process.

[0064] Performance test results: residual moisture content 0.12%, moisture absorption rate 0.25%, uniform thickness of cyanate ester resin cured layer (0.3~0.5mm), and tight bond with mold body; release cloth is laid flat, prepreg is laid smoothly, the fiber layup of the ring frame after molding is highly accurate, and mechanical property test shows that its bending strength is 12% higher than that of conventional molded products. The composite cavity has no "fuzzing" or missing glue defects.

[0065] Example 7: S1. Mix water-soluble adhesive, matrix material and water in a mass ratio of 1.25:9.2:3.6, and use conventional casting molding method to make a water-soluble mold blank block of predetermined specifications (430mm×430mm×205mm). S2. The water-soluble mold blank blocks are subjected to a combination of "natural drying + low temperature drying": first, they are naturally dried in a ventilated and dry environment for 6 days, and then dried at 80℃ for 11 hours. S3. Cut the dried water-soluble mold blank to form a rough-machined water-soluble mold block; S4. Place the cyanate ester resin block and the roughly processed water-soluble mold block together in a heating furnace and heat them together to melt the cyanate ester resin and form a cyanate ester resin curing layer on the surface of the water-soluble mold block (heating method: keep at 120℃ for 2 hours, raise the temperature to 160℃ and keep for 7 hours, then raise the temperature to 190℃ and keep for 2 hours). S5. The water-soluble mold block coated with a cyanate ester resin curing layer is finely processed to obtain the finished water-soluble mold.

[0066] Performance test results: residual moisture content 0.25%, moisture absorption rate 0.38%, water-soluble mold internal moisture removal is sufficient, no bubbling or delamination when used for ring frame molding, composite cavity surface is smooth without "fuzzing" phenomenon.

[0067] Comparative Example 1: S1. Mix water-soluble adhesive, matrix material and water in a mass ratio of 1.2:9:3.5 and cold press them into a water-soluble mold blank block of a predetermined size (400mm×400mm×200mm). S2. Perform conventional drying treatment on the water-soluble mold blank (dry at 80℃ for 10 hours); S3. Cut the dried water-soluble mold blank block, leaving a 1.5mm machining allowance, to form a rough-machined water-soluble mold block; S4. Use diamond tools to finish the rough-machined mold block to obtain the finished water-soluble mold.

[0068] Performance test results: The residual moisture content is 0.85% and the moisture absorption rate is 2.3%. When used for ring frame molding, the prepreg exhibits obvious bubbling and delamination. After demolding, the composite cavity has a large area of ​​"fuzzing", which cannot meet the molding accuracy requirements of the space camera ring frame.

[0069] The specific embodiments described above do not constitute a limitation on the scope of protection of this invention. Those skilled in the art should understand that various modifications, combinations, sub-combinations, and substitutions can be made according to design requirements and other factors. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this invention should be included within the scope of protection of this invention.

Claims

1. A method for preventing moisture absorption in water-soluble molds, characterized in that, Includes the following steps: S1. Mix water-soluble adhesive, matrix material and water in proportion and form into a water-soluble mold blank block of predetermined specifications; S2. The water-soluble mold blank is dried. S3. Cut the dried water-soluble mold blank to form a rough-machined water-soluble mold block; S4. Mix the cyanate ester resin block with the rough-processed water-soluble mold block and heat them together to melt the cyanate ester resin and form a cyanate ester resin cured layer on the surface of the water-soluble mold block. S5. Perform precision machining on the water-soluble mold block coated with a cyanate ester resin curing layer.

2. The method according to claim 1, characterized in that, In step S1, the water-soluble mold blank is formed by cold pressing.

3. The method according to claim 1, characterized in that, In step S2, the drying process includes first natural drying, and then drying at a temperature of (80℃±10℃).

4. The method according to claim 1, characterized in that, In step S3, a machining allowance of 1~2mm is reserved during cutting.

5. The method according to claim 1, characterized in that, In step S4, the heating together is: holding at (120±5)℃ for (2h±5min), raising the temperature to (160±5)℃ and holding for (7h±5min), and then raising the temperature to (190±5)℃ and holding for (2h±5min).

6. The method according to claim 1, characterized in that, In step S4, the cyanate ester resin is melted under heating at 100~120°C and dripped onto the surface of the water-soluble mold block.

7. The method according to claim 1, characterized in that, In step S5, the finishing process is performed using a diamond tool.

8. The method according to claim 1, characterized in that, After step S5, the process also includes covering the surface of the finished water-soluble mold block with release cloth and then laying the prepreg.

9. The method according to claim 5, characterized in that, The heating process in step S4 is carried out at a rate not exceeding 5°C / min.

10. The method according to claim 1, characterized in that, The amount of the cyanate ester resin block used is such that it can completely cover the entire outer surface of the water-soluble mold block after being completely melted in step S4; the purity of the cyanate ester resin block is ≥98%.

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