Polyurethane foaming molding method based on long and short glass fiber reinforcement

Abstract

The present invention provides a polyurethane foaming molding method based on long and short glass fiber reinforcement, and relates to the field of polyurethane composite material preparation. The polyurethane foaming molding method based on long and short glass fiber reinforcement specifically includes the following steps: mold pretreatment - skin laying and fixing - glass fiber cloth and long glass fiber strip laying - short glass fiber strip polyurethane mixed spraying - surface spraying - mold closing and curing - demoulding and shaping - trimming; Step 1. Mold pretreatment: select the required molding mold, spray demoulding wax on the inner wall of the mold, and lay a layer of waterproof surface felt on the inner side of the upper mold after the wax layer is dried; Step 2. Skin laying and fixing. The foaming molding method can reduce the use of polyurethane materials, reduce costs, and enhance the overall strength of the product. At the same time, short glass fibers are synchronously mixed in the polyurethane foam material to increase local strength, reduce the use of embedded parts, and avoid the labor intensity of subsequent processes.

Description

Technical Field

[0001] The invention relates to the field of preparation of polyurethane composite materials, in particular to a polyurethane foaming molding method based on long and short glass fiber reinforcement. Background Art

[0002] At present, the bus air duct includes the air duct body, luggage racks, profiles, advertising light boxes, reading lights, hangers, inspection covers, etc. With the advancement of science and technology, in addition to the air-conditioning system, multimedia, disinfection and sterilization device assemblies have been added to the air duct. For this reason, the air duct body needs to improve its mechanical properties and increase its load-bearing capacity, while meeting the trend of lightweight components in new energy vehicles.

[0003] And rigid polyurethane foam (polyurethane rigid foam) has excellent properties such as light weight, heat preservation, moisture-proof, sound insulation, heat resistance, shock resistance, corrosion resistance, etc., and is widely used in the fields of construction, refrigeration, transportation, packaging, etc. However, compared with other materials, the mechanical performance indicators such as bending strength and compression strength of polyurethane rigid foam are relatively low, thereby limiting its widespread use. In recent years, the research on the enhancement of polyurethane rigid foam has become a major focus. Traditionally, polyurethane foam is used to prepare a mold with a predetermined shape, which is to spray a release agent on the mold, then spray the mold paint, pour the polyurethane raw material for foaming into the mold, close the mold, shake the mold to carry out the foaming reaction, so that the polyurethane raw material foams fill the entire mold cavity, and then take out the product after the mold is opened. But the method for manufacturing polyurethane foam has the disadvantages of large polyurethane raw material consumption, high production cost, and insufficient strength of the finished product obtained. Summary of the invention

[0004] 1. Technical issues to be resolved

[0005] In view of the deficiencies in the prior art, the present invention provides a polyurethane foaming molding method based on long and short glass fiber reinforcement, which solves the problems of large amount of polyurethane raw materials used, high production cost, and insufficient strength of the finished product in the traditional polyurethane foaming preparation molding method.

[0006] (II) Technical solution

[0007] To achieve the above objectives, the present invention is implemented through the following technical scheme: a polyurethane foaming molding method based on long and short glass fiber reinforcement, specifically comprising the following steps: mold pretreatment - surface laying and fixing - glass fiber cloth and long glass fiber strip laying - short glass fiber strip polyurethane mixed spraying - surface spraying - mold closing and curing - demoulding and curing - trimming;

[0008] Step 1. Mold pre-treatment:

[0009] Select the required molding mold, spray the demoulding wax on the inner wall of the mold, and lay a layer of waterproof surface felt on the inner side of the upper mold after the wax layer dries;

[0010] Step 2. Laying and fixing the skin:

[0011] Prepare a micro-foam material, cut it and lay it flat on the mold surface to form a skin, then fix it on the lower mold with a clip, and apply ultrasonic vibration to the skin with an ultrasonic device to obtain a uniformly infiltrated skin;

[0012] Step 3. Laying of fiberglass cloth and long fiberglass strips:

[0013] Prepare a whole sheet of fiberglass cloth and several long fiberglass strips, lay the whole sheet of fiberglass cloth on the surface, then lay three fiberglass strips at equal intervals at the load-bearing point, and then lay the remaining long fiberglass strips vertically;

[0014] Step 4. Spray short glass fiber strips and polyurethane mixture:

[0015] After cutting the long glass fiber strips into a plurality of short glass fiber strips, the polyurethane and the short glass fiber strips are evenly mixed to form a mixture, and the mixture is put into a dry container in proportion using isocyanate and polyether, and fully stirred to obtain a mixed raw material, and then the mixture is placed in the mixed raw material to be fully wetted, and then a catalyst and a foaming agent are added in sequence, and the stirring is continued to be fully stirred to make the solution mixed evenly without stratification to obtain a mixed material; and then the mixed material is sprayed on the upper end of the glass fiber cloth to cover all the glass fiber strips;

[0016] Step 5. Surface spraying

[0017] An interface layer is set on the mixture that completely covers the glass fiber strips. After foaming and shaping, the base resin and hardener are mixed evenly and then applied to the interface layer, and then the glass fiber layer is attached, and the surface resin and hardener are mixed evenly and then applied to the glass fiber layer.

[0018] Preferably, the waterproof surface felt laid in step 1 needs to ensure that the felt layer fits tightly with the mold surface.

[0019] Preferably, the temperature of the micro-foam material in step 2 is 20-25° C., wherein the size of the micro-foam material is larger than the surface of the mold, and the number of the card strips is multiple and evenly distributed.

[0020] Preferably, the length of the short glass fiber strips in step 4 is a short segment of 20-30 mm.

[0021] Preferably, the mixing ratio of the short glass fiber strips and the polyurethane in step 4 is 1:1, and the interface layer is made of calcium carbonate particles.

[0022] Preferably, the mold closing time for the mold closing and curing is 6-8 minutes.

[0023] Preferably, the trimming includes trimming excess material and burrs on the edge and grinding the burrs.

[0024] (III) Beneficial effects

[0025] The present invention provides a polyurethane foaming molding method based on long and short glass fiber reinforcement. It has the following beneficial effects:

[0026] The present invention provides a polyurethane foaming molding method based on long and short glass fiber reinforcement. The foaming molding method can reduce the use of polyurethane materials, reduce costs, enhance the overall strength of products, and facilitate product lightweighting. By adding an interface layer on the outermost side to cooperate with glass fiber covering, the surface strength can be effectively increased, and ultrasonic vibration is used to promote the foaming material to better infiltrate into the epidermis, thereby ensuring the foaming quality; and laying a micro-foamed epidermis can enhance the smoothness and aesthetics of the product surface and provide good thermal insulation performance. At the same time, short glass fibers are synchronously mixed in the polyurethane foam material, and glass fiber cloth and glass fiber strips are reasonably laid, which can significantly improve the mechanical strength and durability of the finished product, increase local strength, reduce the use of embedded parts, and avoid the labor intensity of subsequent processes. DETAILED DESCRIPTION

[0027] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0028] Embodiment 1:

[0029] The embodiment of the present invention provides a polyurethane foaming molding method based on long and short glass fiber reinforcement, which specifically includes the following steps: mold pretreatment - surface laying and fixing - glass fiber cloth and long glass fiber strip laying - short glass fiber strip polyurethane mixed spraying - surface spraying - mold closing and curing - demoulding and curing - trimming;

[0030] Step 1. Mold pre-treatment:

[0031] Select the required molding mold, spray the release wax on the inner wall of the mold, use a spray gun to evenly spray the release wax, and ensure that every corner of the mold surface is covered. After spraying, let it stand for 10 to 15 minutes to wait for the wax layer to dry and form a smooth protective film;

[0032] After the wax layer is dry, a layer of waterproof surface felt is laid on the inner side of the upper mold. The waterproof felt is cut into a size suitable for the mold, and then the felt layer is laid flatly from one end to avoid bubbles and wrinkles. The felt layer is gently compacted with a pressure roller to ensure that the felt layer is tightly combined with the mold surface.

[0033] Step 2. Laying and fixing the skin:

[0034] Prepare the micro-foam material according to the product requirements, ensure that it reaches an ambient temperature of 20-25°C before use, and lay it flat on the mold surface to form a skin after cutting, and then fix it on the lower mold with a clip strip;

[0035] That is, the micro-foam material is cut into a suitable size, usually slightly larger than the surface of the mold. Starting from one end of the mold, the micro-foam material is spread flat on the surface of the mold to ensure that there are no bubbles. The micro-foam material is fixed with multiple clips to form a skin. The clips should be evenly distributed to prevent the material from moving during the curing process.

[0036] Step 3. Laying of fiberglass cloth and long fiberglass strips:

[0037] Prepare a whole sheet of fiberglass cloth and several long fiberglass strips. First, lay the whole sheet of fiberglass cloth on the micro-foam skin to ensure that the cloth is flat and wrinkles are avoided. Then, lay three fiberglass strips at equal intervals at the bearing point, and then lay the remaining long fiberglass strips vertically. The remaining long fiberglass strips are laid at intervals to enhance the strength of the overall structure.

[0038] Step 4. Spray short glass fiber strips and polyurethane mixture:

[0039] After cutting the long glass fiber strips into multiple short glass fiber strips, the long glass fiber filaments are cut into short segments of 20-30 mm to obtain short glass fiber strips, ensuring that the length is consistent, and the polyurethane and the short glass fiber strips are evenly mixed in a mixing ratio of 1:1 to form a mixture, and isocyanate and polyether are charged into a dry container in proportion, and fully stirred to obtain a mixed raw material, and then the mixture is placed in the mixed raw material to fully wet it, and then the catalyst and foaming agent are added in turn, and continued to be fully stirred to make the solution mixed evenly without stratification to obtain a mixture; then use a spray gun to evenly spray the mixture to ensure that all laid glass fiber cloths are covered, and a uniform speed and distance should be maintained during spraying.

[0040] Step 5. Surface spraying:

[0041] An interface layer is set on the mixture that completely covers the glass fiber strips. After the foaming is fixed, the base resin and hardener are mixed evenly and then applied to the interface layer, and then the glass fiber layer is attached. The surface resin and hardener are mixed evenly and then applied to the glass fiber layer.

[0042] Step 6. Mold closing and curing:

[0043] Close the mold carefully to ensure that it is aligned and tight, and check the sealing of the mold to prevent material leakage. Maintain the mold closed for 6 minutes and avoid moving the mold during this period to ensure that the polyurethane is fully cured.

[0044] Step 7. Demolding and curing:

[0045] After curing is completed, gently open the mold to ensure that the finished product is not damaged. If the finished product adheres to the mold, you can gently tap the edge of the mold to help demolding. Then place the demolded finished product at room temperature for curing for 24 hours to ensure that the material is fully cured and stable.

[0046] Step 8. Trimming

[0047] Fix the finished product on the workbench to ensure safety, use a manual tool to carefully trim excess material and burrs, and trim along the edge of the product to ensure smooth edges; after trimming, use sandpaper to polish to improve surface finish and aesthetics.

[0048] Embodiment 2:

[0049] The polyurethane foaming molding method based on long and short glass fiber reinforcement specifically comprises the following steps:

[0050] Step 1. Mold pre-treatment:

[0051] Select the required molding mold, spray the release wax on the inner wall of the mold, use a spray gun to evenly spray the release wax, and ensure that every corner of the mold surface is covered. After spraying, let it stand for 10 minutes to wait for the wax layer to dry and form a smooth protective film;

[0052] After the wax layer is dry, a layer of waterproof surface felt is laid on the inner side of the upper mold. The waterproof felt is cut into a size suitable for the mold, and then the felt layer is laid flatly from one end to avoid bubbles and wrinkles. The felt layer is gently compacted with a pressure roller to ensure that the felt layer is tightly combined with the mold surface.

[0053] Step 2. Laying and fixing the skin:

[0054] Prepare the micro-foam material according to the product requirements, ensure that it reaches an ambient temperature of 25°C before use, and lay it flat on the mold surface to form a skin after cutting, and then fix it on the lower mold with a clip strip;

[0055] That is, the micro-foam material is cut into a suitable size, usually slightly larger than the surface of the mold. Starting from one end of the mold, the micro-foam material is spread flat on the surface of the mold to ensure that there are no bubbles. The micro-foam material is fixed with multiple clips to form a skin. The clips should be evenly distributed to prevent the material from moving during the curing process.

[0056] Step 3. Laying of fiberglass cloth and long fiberglass strips:

[0057] Prepare a whole sheet of fiberglass cloth and several long fiberglass strips. First, lay the whole sheet of fiberglass cloth on the micro-foam skin to ensure that the cloth is flat and wrinkles are avoided. Then, lay three fiberglass strips at equal intervals at the bearing point, and then lay the remaining long fiberglass strips vertically. The remaining long fiberglass strips are laid at intervals to enhance the strength of the overall structure.

[0058] Step 4. Spray short glass fiber strips and polyurethane mixture:

[0059] After cutting the long glass fiber strips into multiple short glass fiber strips, cut the long glass fiber filaments into 30 mm short segments to obtain short glass fiber strips, ensuring that the length is consistent, and mix the polyurethane and short glass fiber strips in a mixing ratio of 1:1 to form a mixture. Use a spray gun to evenly spray the mixture to ensure that all laid glass fiber cloths are covered. Maintain a uniform speed and distance during spraying.

[0060] Step 5. Mold closing and curing:

[0061] Close the mold, ensure that it is aligned and tight, and check the sealing of the mold. Maintain the mold closed for 6 minutes and avoid moving the mold during this period to ensure that the polyurethane is fully cured.

[0062] Step 6. Demolding and curing:

[0063] After curing is completed, gently open the mold to ensure that the finished product is not damaged. If the finished product adheres to the mold, you can gently tap the edge of the mold to help demolding. Then place the demolded finished product at room temperature for curing for 24 hours to ensure that the material is fully cured and stable.

[0064] Step 7. Trimming

[0065] Fix the finished product on the workbench to ensure safety, use an electric trimmer to trim excess material and burrs, and trim along the edge of the product to ensure a smooth edge; after trimming, use sandpaper to polish.

[0066] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A polyurethane foaming molding method based on long and short glass fiber reinforcement, characterized in that: The specific steps include: Mould pre-treatment - surface laying and fixing - glass fiber cloth and long glass fiber strip laying - short glass fiber strip polyurethane mixed spraying - surface spraying - mould closing and curing - demoulding and curing - trimming; Step 1. Mold pre-treatment: Select the required molding mold, spray the demoulding wax on the inner wall of the mold, and lay a layer of waterproof surface felt on the inner side of the upper mold after the wax layer dries; Step 2. Laying and fixing the skin: Prepare a micro-foam material, cut it and lay it flat on the mold surface to form a skin, then fix it on the lower mold with a clip, and apply ultrasonic vibration to the skin with an ultrasonic device to obtain a uniformly infiltrated skin; Step 3. Laying of fiberglass cloth and long fiberglass strips: Prepare a whole sheet of fiberglass cloth and several long fiberglass strips, lay the whole sheet of fiberglass cloth on the surface, then lay three fiberglass strips at equal intervals at the load-bearing point, and then lay the remaining long fiberglass strips vertically; Step 4. Spray short glass fiber strips and polyurethane mixture: After cutting the long glass fiber strips into a plurality of short glass fiber strips, the polyurethane and the short glass fiber strips are evenly mixed to form a mixture, and the mixture is put into a dry container in proportion using isocyanate and polyether, and fully stirred to obtain a mixed raw material, and then the mixture is placed in the mixed raw material to be fully wetted, and then a catalyst and a foaming agent are added in sequence, and the stirring is continued to be fully stirred to make the solution mixed evenly without stratification to obtain a mixed material; and then the mixed material is sprayed on the upper end of the glass fiber cloth to cover all the glass fiber strips; Step 5. Surface spraying: An interface layer is set on the mixture that completely covers the glass fiber strips. After foaming and shaping, the base resin and hardener are mixed evenly and then applied to the interface layer, and then the glass fiber layer is attached, and the surface resin and hardener are mixed evenly and then applied to the glass fiber layer.

2. The polyurethane foaming molding method based on long and short glass fiber reinforcement according to claim 1, characterized in that: The waterproof surface felt laid in step 1 needs to ensure that the felt layer is in close contact with the mold surface.

3. The polyurethane foaming molding method based on long and short glass fiber reinforcement according to claim 1, characterized in that: The temperature of the micro-foam material in step 2 is 20-25° C., wherein the size of the micro-foam material is larger than the surface of the mold, and the number of the card strips is multiple and evenly distributed.

4. The polyurethane foaming molding method based on long and short glass fiber reinforcement according to claim 1, characterized in that: The length of the short glass fiber strips in step 4 is a short segment of 20-30 mm.

5. The polyurethane foaming molding method based on long and short glass fiber reinforcement according to claim 1, characterized in that: The mixing ratio of the short glass fiber strips and the polyurethane in step 4 is 1:1, and the interface layer is made of calcium carbonate particles.

6. The polyurethane foaming molding method based on long and short glass fiber reinforcement according to claim 1, characterized in that: The mold closing time for the mold closing and curing is 6-8 minutes.

7. The polyurethane foaming molding method based on long and short glass fiber reinforcement according to claim 1, characterized in that: The trimming includes trimming excess material and burrs on the edge and grinding the burrs.