Recovery method and application of fiber reinforced thermoplastic composite material

Abstract

The invention discloses a recycling method and application of a fiber-reinforced thermoplastic composite.The recycling method comprises the steps that the waste fiber-reinforced thermoplastic composite is crushed and ground into recycled powder, the particle size of the recycled powder is controlled to be 18-45 micrometers, and the particle size of the recycled powder is controlled to be 330-750 meshes, so that the recycled powder is used as filler; the filler is used for an SMC (Sheet Molding Compound) of a fiber-reinforced thermoplastic resin matrix. The recycling method provides a brand-new thermoplastic composite material recycling thought, and compared with the prior art that the fibers and the resin are separated and then reutilized, or remelting and remodeling are carried out to achieve recycling, the whole recycling process is easy to operate, industrialization is easier to achieve, and the recycling method is suitable for industrial production. And the production cost of the existing thermoplastic resin matrix SMC sheet molding compound can be reduced.

Description

Technical Field

[0001] The present invention belongs to the technical field of thermoplastic composite materials, and particularly relates to a recycling method and application of thermoplastic composite materials. Background Art

[0002] Fiber-reinforced resin matrix composites, due to their high strength, lightweight, corrosion resistance, wear resistance, and designability, are widely used in the automotive, aerospace, wind power, military, and construction industries. With the expansion of composite applications and the approaching retirement of composite industrial products, the recycling and reuse of waste composite materials is a current challenge.

[0003] At present, the main methods for recycling thermoplastic composites are: (1) chemical method, which separates the fibers from the resin matrix in the discarded thermoplastic composites by introducing chemical reagents. This method is still limited to the laboratory stage and is time-consuming. It may also produce waste solutions that require subsequent treatment, increasing the overall process cost, and is still a long way from industrialization; (2) remelting and reshaping method, which crushes the discarded thermoplastic composites and then re-moldes them. The secondary molding requires a higher temperature and the material has poor fluidity. It can only be used to form structural parts with low strength and surface requirements. Summary of the Invention

[0004] In view of the defects in the prior art, the object of the present invention is to provide a method for recycling fiber-reinforced thermoplastic composite materials.

[0005] In a first aspect, the present invention provides a method for recycling fiber-reinforced thermoplastic composite materials, comprising: Waste fiber-reinforced thermoplastic composite materials are crushed and ground into recycled powder with a particle size of 18-45 microns and 330-750 mesh, which is used as a filler. The powder is used as a filler in the preparation of fiber-reinforced thermoplastic resin matrix SMC sheet molding compound.

[0006] In another embodiment, the waste fiber-reinforced thermoplastic composite material comprises a mixture of any one or more of a fiber-reinforced polyethylene composite material, a fiber-reinforced polypropylene composite material, and a fiber-reinforced polyamide composite material.

[0007] In another embodiment, the crushing comprises: feeding the discarded fiber reinforced thermoplastic composite material into a crusher, and crushing it into small-sized waste materials after one or more crushing steps, with the size controlled within 5 cm.

[0008] In another embodiment, the grinding comprises: feeding the small-sized waste into a grinding mill, and generating a recycled powder through one or more grindings, wherein the particle size of the final recycled powder is controlled to be 18-45 microns and 330-750 mesh.

[0009] In the field of composite materials, various fillers are added to the resin matrix to reduce costs, improve material performance, or impart special functions. For example, the unit volume cost of the composite material can be significantly reduced by adding calcium carbonate and talc, and the combustion of the composite material can be suppressed or delayed by adding flame retardant fillers such as aluminum hydroxide (ATH), magnesium hydroxide, phosphorus-based, and intumescent fillers. In this technical solution, discarded fiber-reinforced thermoplastic composites are crushed and ground into recycled powder, which can be used as fillers, providing a new technical route for the recycling and reuse of composite materials. In this recycling method, mechanical crushing and grinding are easier to operate and implement than the existing chemical recycling method, and can also avoid the performance defects and appearance defects that occur in the remelting and reshaping methods.

[0010] In a second aspect, a filler is provided, comprising the recycled powder, for use in a fiber-reinforced thermoplastic resin matrix SMC sheet molding compound.

[0011] In another embodiment, the filler includes: recycled powder, and other fillers; the other fillers are a mixture of any one or more of aluminum hydroxide and magnesium hydroxide.

[0012] In a third aspect, a fiber-reinforced thermoplastic resin matrix SMC sheet molding compound is provided, wherein the fiber-reinforced thermoplastic resin matrix SMC sheet molding compound comprises the above-mentioned filler.

[0013] In another embodiment, the fiber-reinforced thermoplastic resin matrix SMC sheet molding compound comprises, by weight of raw materials: chopped fibers, 20-40 parts; Thermoplastic resin matrix, 60-80 parts; The thermoplastic resin matrix comprises, by weight of raw materials: Thermoplastic resin, 70-80 parts; Release agent: 3-4 parts; Curing agent: 1-2 parts; Thickener: 2.5-3.5 parts; Filler, including 3-35 parts of recycled powder and 0-70 parts of other fillers; Viscosity reducer: 1-4 parts.

[0014] In another embodiment, the viscosity of the thermoplastic resin matrix at 30° C. is controlled within the range of 6000-15000 cp.

[0015] In the present invention, due to the effect of fibers in the recycled powder and the presence of larger particles in the recycled powder, the viscosity of the resin matrix increases. Therefore, it is necessary to add a viscosity reducer to control the viscosity of the thermoplastic resin matrix at 30°C within the range of 6000-15000cp.

[0016] Compared with the prior art, the advantages of the present invention are: (1) It provides a new recycling idea for thermoplastic composite materials. Compared with the existing technology of separating fibers and resins and reusing them separately, or remelting and reshaping them for reuse, the present invention crushes and grinds the discarded thermoplastic composite materials into recycled powder, which is then used as filler in thermoplastic resin matrix SMC sheet molding compound to form a recycling system. The whole process is simple to operate and easier to industrialize. (2) Reducing the production cost of existing thermoplastic resin matrix SMC sheet molding compounds. When preparing thermoplastic resin matrix SMC sheet molding compounds, the recycled powder obtained by the present invention is used as a filler to reduce or replace the number of traditional fillers added in the existing thermoplastic resin system. In addition, since the recycled powder contains short fibers, the mechanical properties of the product can be improved. Therefore, under the premise of meeting the same mechanical properties, the number of existing short-cut fibers can be reduced by adding recycled powder, thereby reducing the raw material cost of the SMC sheet. (3) Improve the mechanical properties of SMC products. In the fiber-reinforced thermoplastic resin matrix SMC sheet molding compound according to the present invention, the mechanical properties of subsequent products are significantly improved due to the presence of short fibers in the recycled powder; (4) Improvement of other properties of SMC products. For example, when the recycled powder contains components with flame retardant function, the flame retardant function will continue to be reflected and maintained in subsequent products. DETAILED DESCRIPTION

[0017] To make the purpose, technical solutions and advantages of the present invention clearer, the present invention will be described in detail below with reference to specific embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0018] Example 1 Step 1: Crushing the discarded fiber-reinforced thermoplastic composite material. Specifically, the discarded fiber-reinforced thermoplastic composite material is fed into a double-shaft crusher, and after one or more crushings, is finally crushed into small-sized waste materials with a size controlled within 5 cm. The fiber-reinforced thermoplastic composite material can be a composite material with the same resin matrix or a mixture of composite materials with different resin matrices. Specifically, the discarded fiber-reinforced thermoplastic composite material includes a thermoplastic glass fiber composite material and a thermoplastic carbon fiber composite material, and can be recycled as a single type or mixed, and the waste material can have special functions, such as flame retardant properties. Step 2: Grind the small-sized waste into recycled powder once or multiple times. Specifically, the small-sized waste is fed into a grinder and ground into powder in a grinding chamber. The powder is then blown up by a fan and fed into an analyzer system. Powder that meets the fineness requirements enters a cyclone separator for collection to obtain recycled powder. Powder that does not meet the fineness requirements is returned to the grinding chamber for re-grinding. The particle size of the recycled powder is controlled at 18-45 microns and 330-750 mesh. The recycled powder is used as a filler.

[0019] In this embodiment, waste fiber-reinforced thermoplastic composite materials are crushed and ground into recycled powder. This recycling process is simple and easily industrialized. The resulting recycled powder can be used alone or mixed with other traditional fillers as a filler in the composite resin matrix, and then recycled into fiber-reinforced composite products. This recycling method adds a new filler option to existing traditional fillers, which helps reduce raw material costs. Furthermore, any traditional fillers present in the original waste fiber-reinforced thermoplastic composite material will remain in the recycled powder, and their functions will continue to be reflected and maintained in subsequent products.

[0020] Example 2 This embodiment provides a filler, including the recycled powder obtained in Example 1.

[0021] Example 3

[0022] This embodiment provides a filler, which includes the recycled powder recovered in Example 1 and other fillers, the weight proportion of the recycled powder is 3-35 parts, and the weight proportion of the other fillers is 0-70 parts; the other fillers include aluminum hydroxide.

[0023] In this embodiment, by adding recycled powder, the amount of other fillers added can be replaced or greatly reduced, thereby saving raw material costs.

[0024] Example 4 This embodiment provides a chopped glass fiber reinforced thermoplastic resin matrix SMC sheet molding compound, which comprises, by weight of raw materials: Chopped glass fiber, specifically Taishan glass fiber, 25 parts; Thermoplastic resin matrix, 75 parts; The thermoplastic resin matrix, calculated by weight of raw materials, specifically comprises: Acrylic resin MC590, 75 parts; Curing agent, specifically LUPEROX POP2, 1.5 parts; Release agent, specifically BYK 9912, 3.75 parts; Viscosity reducer, specifically BYK 9010, 1.5 parts; Thickener, specifically MK35, 3 parts; The filler specifically includes: 52.5 parts of 800-mesh ON921 ATH; and 6 parts of recycled powder, wherein the recycled powder is obtained by crushing and grinding discarded thermoplastic glass fiber composite materials. The thermoplastic glass fiber composite materials have flame retardant properties and a flame retardant grade of UL94 FV0.

[0025] The viscosity of the thermoplastic resin matrix at 30° C. is 6700 cP.

[0026] Example 5 The difference from Example 4 is that the thermoplastic resin matrix comprises the following components in parts by weight of raw materials: Acrylic resin MC590, 75 parts; Curing agent, specifically LUPEROX POP2, 1.5 parts; Release agent, specifically BYK 9912, 3.75 parts; Viscosity reducer, specifically BYK 9010, 1.5 parts; Thickener, specifically MK35, 3 parts; The filler specifically includes: 18 parts of 800-mesh ON921 ATH; and 12 parts of recycled powder, which is obtained by crushing and grinding discarded thermoplastic glass fiber composite materials. The thermoplastic glass fiber composite materials have flame retardant properties and a flame retardant grade of UL94 FV0.

[0027] The viscosity of the thermoplastic resin matrix at 30° C. is 13200 cP.

[0028] Example 6 The difference from Example 4 is that the thermoplastic resin matrix comprises the following components in parts by weight of raw materials: Acrylic resin MC590, 75 parts by weight; Curing agent, specifically LUPEROX POP2, 1.5 parts; Release agent, specifically BYK 9912, 3.75 parts; Viscosity reducer, specifically BYK 9010, 1.5 parts; Thickener, specifically MK35, 3 parts; Filler, including: 9.8 parts of 800-mesh ON921 ATH; 18 parts of recycled powder, wherein the recycled powder is obtained by crushing and grinding discarded thermoplastic glass fiber composite material, wherein the thermoplastic glass fiber composite material has flame retardant properties and a flame retardant grade of UL94FV0; The viscosity of the thermoplastic resin matrix at 30° C. is 13150 cP.

[0029] Example 7 The difference from Example 4 is that the thermoplastic resin matrix comprises, based on parts by weight of raw materials: Acrylic resin, specific model MC590, 75 parts; The curing agent is LUPEROX POP2, which is 1.5 parts by weight. The release agent is BYK 9912, with a weight of 3.75 parts. Viscosity reducer, specifically BYK 9010, 3 parts by weight, Thickener, specifically MK35, 3 parts by weight, The filler comprises: 8 parts of 800-mesh ON921 ATH; and 32 parts of recycled powder, wherein the recycled powder is obtained by crushing and grinding discarded thermoplastic glass fiber composite material, and the thermoplastic glass fiber composite material has flame retardant properties and a flame retardant grade of UL94FV0.

[0030] The viscosity of the thermoplastic resin matrix at 30° C. is 14100 cP.

[0031] Example 8 This embodiment provides a chopped carbon fiber reinforced thermoplastic resin matrix SMC sheet molding compound, which comprises, by weight of raw materials: Chopped carbon fiber, specifically Hengshen carbon fiber, 25 parts; Thermoplastic resin matrix, 75 parts; The thermoplastic resin matrix, calculated by weight of raw materials, specifically comprises: Acrylic resin MC590, 75 parts; Curing agent, specifically LUPEROX POP2, 1.5 parts; Release agent, specifically BYK 9912, 3.75 parts; Viscosity reducer, specifically BYK 9010, 1.5 parts; Thickener, specifically MK35, 3 parts; The filler comprises: 52.5 parts of 800-mesh ON921 ATH; and 6 parts of recycled powder, wherein the recycled powder is obtained by crushing and grinding discarded thermoplastic carbon fiber composite materials, and the thermoplastic carbon fiber composite materials have flame retardant properties and a flame retardant grade of UL94 FV0.

[0032] The viscosity of the thermoplastic resin matrix at 30° C. is 6700 cP.

[0033] Example 9 The difference from Example 8 is that the thermoplastic resin matrix comprises, in parts by weight of raw materials: Acrylic resin MC590, 75 parts; Curing agent, specifically LUPEROX POP2, 1.5 parts, Release agent, specifically BYK 9912, 3.75 parts, Viscosity reducer, specifically BYK 9010, 1.5 parts, Thickener, specifically MK35, 3 parts, The filler described in Example 3 specifically includes: 18 parts of 800-mesh ON921 ATH; and 12 parts of recycled powder, which is obtained by crushing and grinding discarded thermoplastic carbon fiber composite materials. The thermoplastic carbon fiber composite material has flame retardant properties and a flame retardant grade of UL94 FV0.

[0034] The viscosity of the thermoplastic resin matrix at 30° C. is 13200 cP.

[0035] Example 10 The difference from Example 8 is that the thermoplastic resin matrix comprises, in parts by weight of raw materials: Acrylic resin MC590, 75 parts; Curing agent, specifically LUPEROX POP2, 1.5 parts, Release agent, specifically BYK 9912, 3.75 parts, Viscosity reducer, specifically BYK 9010, 1.5 parts, Thickener, specifically MK35, 3 parts, The filler specifically includes: 9.8 parts of 800-mesh ON921 ATH; and 18 parts of recycled powder, which is obtained by crushing and grinding discarded thermoplastic carbon fiber composite materials. The thermoplastic carbon fiber composite materials have flame retardant properties and a flame retardant grade of UL94 FV0.

[0036] The viscosity of the thermoplastic resin matrix at 30° C. is 13150 cP.

[0037] Example 11 The difference from Example 8 is that the thermoplastic resin matrix comprises, in parts by weight of raw materials: Acrylic resin MC590, 75 parts; Curing agent, specifically LUPEROX POP2, 1.5 parts, Release agent, specifically BYK 9912, 3.75 parts, Viscosity reducer, specifically BYK 9010, 3 parts, Thickener, specifically MK35, 3 parts, The filler specifically includes: 800-mesh ON921 ATH, 8 parts; and recycled powder, 32 parts. The recycled powder is obtained by crushing and grinding discarded thermoplastic carbon fiber composite materials. The thermoplastic carbon fiber composite materials have flame retardant properties and a flame retardant grade of UL94 FV0.

[0038] The viscosity of the thermoplastic resin matrix at 30° C. is 14100 cP.

[0039] Comparative Example 1 As a comparative example of Example 4.

[0040] A short glass fiber reinforced thermoplastic resin matrix SMC sheet film plastic, comprising, by weight, 25 parts of 25% short glass fibers and 75 parts of a thermoplastic resin matrix; the thermoplastic resin matrix comprises: Thermoplastic resin, specifically acrylic resin MC590, 75 parts; Curing agent, specifically LUPEROX POP2, 1.5 parts, Release agent, specifically BYK 9912, 3.75 parts, Viscosity reducer, specifically BYK 9010, 1.5 parts, Thickener, specifically MK35, 3 parts, As filler, 120 parts of 800-mesh ON921 ATH was selected.

[0041] The viscosity of the thermoplastic resin matrix at 30° C. is 14500 cP.

[0042] In this comparative example, the amount of ATH added is the minimum amount required for the flame retardancy of the corresponding SMC sheet molding compound product to reach UL94 FV0 level.

[0043] Comparative Example 2 As a comparative example of Example 8.

[0044] A short carbon fiber reinforced thermoplastic resin matrix SMC sheet film plastic, comprising, by weight, 25 parts of short carbon fibers and 75 parts of thermoplastic resin matrix; The thermoplastic resin matrix comprises: Acrylic resin MC590, 75 parts; Curing agent, specifically LUPEROX POP2, 1.5 parts, Release agent, specifically BYK 9912, 3.75 parts, Viscosity reducer, specifically BYK 9010, 1.5 parts, Thickener, specifically MK35, 3 parts, As filler, 120 parts of 800-mesh ON921 ATH was selected.

[0045] The viscosity of the thermoplastic resin matrix at 30° C. is 14500 cP.

[0046] In this comparative example, the amount of ATH added is the minimum amount required for the flame retardancy of the corresponding SMC sheet molding compound product to reach UL94 FV0 level.

[0047] The sheet molding compounds of each embodiment of the present invention have a curing time of about 24 hours at 30°C and are well cured. Under the condition of the same feed mass, the fluidity is verified according to three feed areas of 50%, 35%, and 25%. The results show that all three feed areas can be molded.

[0048] Mechanical property verification: The fiber-reinforced thermoplastic resin matrix SMC sheets of Examples 4-11 and Comparative Examples 1-2 were compression molded, and specimens were prepared and tested according to ASTM D3039 and ASTM D7264. The test items included tensile strength, tensile modulus, flexural strength, and flexural modulus. The test results are detailed in Table 1.

[0049] Table 1 performance Tensile strength / MPa Tensile modulus / GPa Bending strength / MPa Flexural modulus / GPa Example 4 110 9.0 208 11.0 Example 5 84 7.1 152 7.3 Example 6 87 6.9 140 7.3 Example 7 79 6.5 132 7.2 Example 8 189 19.9 341 17.0 Example 9 153 15.6 249 11.2 Example 10 150 15.2 229 10.7 Example 11 135 14.7 212 10.3 Comparative Example 1 72 6.4 127 8.3 Comparative Example 2 124 14.1 208 12.8 As can be seen from Table 1; (1) The content of chopped glass fiber in Examples 4-7 is the same as that in Comparative Example 1. When 1-32 parts of recycled powder are added to the resin matrix, the composite parts subsequently molded have improved tensile strength, tensile modulus, and flexural strength compared to the SMC sheet molding compound without recycled powder. The content of chopped carbon fiber in Examples 8-11 is the same as that in Comparative Example 2. When 1-32 parts of recycled powder are added to the resin matrix, the composite parts subsequently molded have improved tensile strength, tensile modulus, and flexural strength compared to the SMC sheet molding compound without recycled powder. The improvement in relevant properties is due to the positive effect of the chopped fibers in the recycled powder. (2) As the amount of recycled powder added gradually increases, the advantages of improving the tensile strength, tensile modulus, and flexural strength of composite parts subsequently molded from SMC sheet molding compounds gradually decrease. This may be because as the recycled powder content increases, the effect on the viscosity of the resin matrix increases (the viscosity increases), the wettability of the resin matrix to the fiber decreases, resulting in a decrease in mechanical properties; (3) Compared with the SMC sheet molding compound without recycled powder added, the composite material molded by SMC sheet molding compound with recycled powder added to the resin matrix has a lower flexural modulus in the subsequent compression molding, but it still meets the flexural modulus requirements of most composite parts.

[0050] In addition, the flame retardancy of composite materials molded from SMC sheet molding compounds was tested. Comparative Examples 1 and 2 required 120 parts of aluminum hydroxide for the corresponding composite products to meet the UL94 FV0 flame retardancy rating. However, in Examples 4 and 8, when the recycled powder addition amount was reduced to 6 parts and the aluminum hydroxide addition amount was reduced to 52.5 parts, the corresponding composite products still met the UL94 FV0 flame retardancy rating. The corresponding composite products of Examples 5-7 and 9-11 did not achieve the FV0 level, but still had good flame retardancy.

[0051] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for recycling fiber-reinforced thermoplastic composite materials, characterized in that: include: The discarded fiber-reinforced thermoplastic composite material is crushed and ground into recycled powder, wherein the particle size of the recycled powder is controlled to be 18-45 microns and 330-750 meshes.

2. The method for recycling fiber-reinforced thermoplastic composite materials according to claim 1, characterized in that: The waste fiber-reinforced thermoplastic composite material includes any one or more combinations of fiber-reinforced polyethylene composite material, fiber-reinforced polypropylene composite material, and fiber-reinforced polyamide composite material.

3. The method for recycling fiber-reinforced thermoplastic composite materials according to claim 1, characterized in that: The crushing includes: The discarded fiber reinforced thermoplastic composites are fed into the crusher and crushed into small-sized waste materials after one or more crushing operations, with the size controlled within 5 cm.

4. The method for recycling fiber-reinforced thermoplastic composite materials according to claim 3, characterized in that: The small-sized waste is fed into a grinding mill and is ground once or multiple times to generate recycled powder. The particle size of the recycled powder is controlled at 18-45 microns and 330-750 mesh.

5. A filler, characterized in that: The invention comprises any one of the recycled powders according to claims 1 to 4.

6. A filler according to claim 5, characterized in that: Other fillers are also included.

7. A filler according to claim 6, characterized in that: The other fillers are a mixture of any one or more of aluminum hydroxide and magnesium hydroxide.

8. A fiber-reinforced thermoplastic resin matrix SMC sheet film plastic, characterized in that: The invention comprises any one of the fillers according to claims 5 to 7.

9. The fiber-reinforced thermoplastic resin matrix SMC sheet film plastic according to claim 8, characterized in that: Calculated by weight of raw materials, including: chopped fibers, 20-30 parts; Thermoplastic resin matrix, 70-80 parts; The thermoplastic resin matrix, calculated by weight of raw materials, comprises: Thermoplastic resin, 70-80 parts; Release agent, 3-4 parts; Curing agent: 1-2 parts; Thickener: 2.5-3.5 parts; Filler, including 3-35 parts of recycled powder and 0-70 parts of other fillers; Viscosity reducer, 1-4 parts.

10. The method for recycling fiber-reinforced thermoplastic composite materials according to claim 5, characterized in that: The viscosity of the thermoplastic resin matrix at 30° C. is 6000-15000 cP.