Recovery method of PMMA thermoplastic resin / fiber reinforced composite material

Abstract

The invention provides a method for recovering a PMMA (polymethyl methacrylate) thermoplastic resin / fiber reinforced composite material, which comprises the following steps of: mixing and dissolving the PMMA thermoplastic resin / fiber reinforced composite material and a solvent methyl methacrylate (MMA); and separating the dissolved solid-phase product from the liquid-phase product, and carrying out polymerization reaction on the liquid-phase product to obtain the PMMA thermoplastic resin or the composite material thereof. According to the method, the resin and the fibers are integrally recycled in a closed-loop mode, so that emission of the waste PMMA thermoplastic resin / fiber reinforced composite material is reduced, the recycling rate of the PMMA thermoplastic resin is increased, and environmental protection is facilitated; efficient separation can be realized at normal pressure and lower temperature, energy is saved, the device is simple, a large reaction device or equipment is not needed, and the cost is low; and the method has relatively high economic benefits and environmental benefits. The PMMA thermoplastic resin and the composite material prepared by processing the PMMA thermoplastic resin and the fiber recovered by the method still show excellent mechanical properties, and have wide application prospects.

Description

Technical Field

[0001] The invention belongs to the technical field of resin composite material recycling, and particularly relates to a method for recycling PMMA thermoplastic resin / fiber reinforced composite material. Background Art

[0002] Fiber-reinforced thermoplastics are widely used in various engineering fields due to their advantages, such as light weight, high strength, corrosion resistance, acid and alkali resistance, and excellent mechanical and durability properties. Separating composite materials into their component parts is one of the main features that makes thermoplastic resins and composite materials attractive, and recycling offers real economic and environmental benefits. However, the diversity and complexity of composite materials make recycling and reuse very challenging.

[0003] Currently, common recycling technologies for thermoplastic resins and composites include mechanical grinding, thermal decomposition of the polymer matrix, and chemical dissolution. Mechanical recycling primarily involves crushing or grinding waste resin into small particles, which are then roughly processed and reused as fillers. This method destroys valuable components in the composite, such as carbon fiber and glass fiber, resulting in lower performance and a low added value for the recycled material.

[0004] Thermal decomposition of polymers separates the resin from the fiber material at higher temperatures. Chinese invention patent CN115534259 A describes a recycling system for continuous fiber-reinforced thermoplastic composites. This system produces no secondary waste, enabling composite material recycling and reducing costs. However, the system requires a temperature of 400°C for insulation, resulting in high energy consumption. H. Bel Haj Frej et al. used a pyrolysis method to recycle acrylic-based carbon fiber-reinforced laminated composites (CF / Elium 188-O) (Resources, Conservation & Recycling, 2021, 173, 105705). The composite material was depolymerized at various temperatures, ranging from 350°C to 450°C, for over four hours. This yielded purified resin and fiber, which can be reused. While thermal decomposition can recycle composite materials, it requires high temperatures and equipment requirements. The resin produced by pyrolysis requires further purification, increasing costs.

[0005] Chemical recycling uses chemical solvents to degrade and dissolve the polymer matrix, then recover the reinforcing material. These methods primarily include direct dissolution and supercritical fluid recovery. While chemical recycling can yield higher-quality fibers than mechanical or thermal recycling methods, the use of organic solvents is costly and carries the risk of environmental pollution.

[0006] PMMA (polymethyl methacrylate) / fiber-reinforced composites maintain the strength of PMMA while further enhancing it through fiber reinforcement, significantly increasing PMMA's tensile, flexural, and impact strengths. They are typically lighter than traditional metal and plastic materials, a key advantage for applications requiring weight reduction, such as automotive and aerospace. The green recycling of PMMA (polymethyl methacrylate) / fiber-reinforced composites has significant economic significance.

[0007] In summary, there is an urgent need for a simple, environmentally friendly solvent and method to recycle PMMA and fiber-reinforced composites to further expand the application range of PMMA. This invention proposes a method for recycling PMMA thermoplastic resin / fiber-reinforced composites, which can recover the PMMA resin matrix and fibers and reuse them in the preparation of resin and fiber-reinforced composites. Summary of the Invention

[0008] In response to the technical problems of high energy consumption or strong pollution in the composite material recycling process in the existing technology, the present invention provides a method for recycling PMMA thermoplastic resin / fiber-reinforced composite materials, which does not require post-processing of the solvent, solves the problem of inconvenient recycling of fiber-reinforced composite materials, and broadens their application fields.

[0009] The technical solution adopted in the present invention is as follows: A method for recycling PMMA thermoplastic resin / fiber reinforced composite material comprises the following steps: (1) Mix and dissolve the PMMA thermoplastic resin / fiber reinforced composite material with the solvent MMA; (2) Separating the dissolved solid phase product from the liquid phase product, and using the liquid phase product to prepare thermoplastic acrylic resin or its composite material.

[0010] Preferably, the fibers in the PMMA thermoplastic resin / fiber reinforced composite material in step (1) include one or more of basalt fiber, glass fiber, carbon fiber and aramid.

[0011] Preferably, in step (1), the mass ratio of PMMA thermoplastic resin / fiber reinforced composite material to solvent MMA is 1:10-100.

[0012] Preferably, the dissolution temperature in step (1) is 30-80°C and the dissolution time is 3-60h.

[0013] Preferably, the dissolving is carried out with stirring and / or shaking.

[0014] Preferably, an initiator is added to the liquid phase product in step (2) for polymerization to obtain a thermoplastic acrylic resin or a composite material thereof.

[0015] Preferably, the initiator is at least one of an azo initiator, a peroxide initiator or a reduction initiator, and the amount of the initiator added is 0.1-3 wt % of the MMA.

[0016] The azo initiator includes azobisisobutyronitrile (AIBN) or azobisisoheptanenitrile (ABVN). The peroxide initiator includes inorganic peroxide initiators and organic peroxide initiators. Inorganic peroxide initiators include hydrogen peroxide, ammonium persulfate, or potassium persulfate. Organic peroxide initiators include benzoyl peroxide (BPO), lauroyl peroxide (LPO), tert-butyl benzoyl peroxide, or methyl ethyl ketone peroxide. Reducing initiators include N,N-dimethylaniline (DMT) or N,N-dimethyl-p-toluidine (DMA).

[0017] Preferably, fillers are added to the liquid phase product to prepare a corresponding PMMA thermoplastic resin composite material.

[0018] Preferably, the filler includes reinforcing fibers or nano inorganic particles, the reinforcing fibers include carbon fibers, basalt fibers, glass fibers or aramid fibers, and the inorganic nano particles include nano silicon dioxide, nano titanium dioxide or nano zinc oxide.

[0019] Preferably, the thermoplastic acrylic acid or its composite material prepared by the above method is used in the fields of aviation materials, wind power manufacturing, building materials, furniture decoration, agricultural materials, liquid crystal materials, electronic and electrical materials, optical materials, transportation, medical materials, military materials or paint coatings.

[0020] The beneficial effects of the present invention are as follows: 1. The present invention adopts a closed-loop approach to achieve the overall recycling of resin and fiber, which not only reduces the emission of waste PMMA thermoplastic resin / fiber-reinforced composite materials and improves the recycling rate of PMMA thermoplastic resin, which is beneficial to environmental protection; but also can achieve efficient separation at normal pressure and low temperature, saving energy, simple device, no need for large-scale reaction devices or equipment, and low cost.

[0021] 2. Since the solvent used in the present invention is an MMA reactive solvent, MMA can be directly polymerized for the preparation of resins and composite materials without further solvent removal, thus having high economic and environmental benefits.

[0022] 3. The PMMA thermoplastic resin and fiber recovered by the present invention still exhibit excellent mechanical properties when processed to prepare PMMA thermoplastic resin and composite materials thereof. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0024] Figure 1 This is a photo of the resin and glass fiber after recycling of the glass fiber reinforced / PMMA composite material in Example 2.

[0025] Figure 2 This is a picture of the basalt fiber reinforced PMMA composite material of Example 3 ( Figure 2 a), and recycled basalt fiber ( Figure 2 b). DETAILED DESCRIPTION

[0026] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without creative work are within the scope of protection of the present invention.

[0027] Unless otherwise specified, the experimental methods used in the examples of the present invention are conventional methods.

[0028] Unless otherwise specified, the materials, reagents, etc. used in the examples of the present invention can be obtained from commercial sources.

[0029] In the present embodiment, "parts" means "parts by weight".

[0030] Example 1 This embodiment provides a method for recycling PMMA / glass fiber composite materials, comprising the following steps: 2 parts of glass fiber reinforced PMMA composite material was dissolved in 40 parts of methyl methacrylate and mixed evenly. The mixture was placed in a constant temperature oscillator and shaken and dissolved at 60°C and 180 rpm for 16 hours. The composite material first swelled and then dissolved. The glass fiber and the liquid resin solution are separated by filtration, and the glass fiber is washed with MMA and dried to obtain the recycled glass fiber and PMMA+MMA binary resin solution. Figure 1 As shown in the figure, MMA can dissolve waste glass fiber / PMMA composite materials very well and can separate and recycle glass fibers.

[0031] To the recovered binary resin solution, redox initiators lauroyl peroxide and N,N-dimethylaniline were added at a rate of 2.0 wt% of MMA, with the mass ratio of oxidant to reductant being 4:1. The solution was then vacuum infused with continuous glass fiber cloth at a mass ratio of glass fiber cloth to binary resin solution of 7:3. A PMMA / glass fiber composite was prepared, and the tensile strength of the composite material in the 0° direction was 1121.2 MPa.

[0032] Example 2 This embodiment provides a method for recycling a PMMA resin / basalt fiber composite material, comprising the following steps: 5 parts of waste PMMA resin / basalt fiber composite material were added to 200 parts of methyl methacrylate solvent and mixed evenly, then placed in a constant temperature oscillator, heated to 40°C, and shaken at 180 rpm for 20 hours to dissolve; The dissolved mixture is filtered to obtain a solid phase product and a liquid phase product. The solid phase product is washed with methyl methacrylate, dried and recovered to obtain basalt fiber; the washing liquid is combined with the liquid phase product to be used as a recycled resin for secondary use, such as Figure 2 As shown in the picture, the waste raw material basalt fiber reinforced PMMA composite material is as follows Figure 2 As shown in a, the recycled basalt fibers are Figure 2 As shown in b, MMA can dissolve waste PMMA resin / basalt fiber composites very well and can separate and recycle basalt fibers.

[0033] The initiator benzoyl peroxide was added to the recovered binary resin solution in an amount of 1.0 wt% of MMA. The initiator was mixed with carbon fiber through a vacuum infusion process to prepare a PMMA resin / carbon fiber composite material. The mass fraction of carbon fiber in the composite material was 60 wt%.

[0034] Example 3 This embodiment provides a method for recycling PMMA resin / carbon fiber composite materials, comprising the following steps: 5 parts of waste PMMA / carbon fiber composite material were added to 250 parts of methyl methacrylate solvent and mixed evenly. Then, the mixture was placed in a constant temperature oscillator, heated to 65 °C and shaken for 18 h. The composite material first swelled and then dissolved.

[0035] The dissolved mixture is filtered to obtain a solid phase product and a liquid phase product. The solid phase product is washed with methyl methacrylate, dried and recovered to obtain carbon fiber; the washing liquid is combined with the liquid phase product to be reused as recovered resin.

[0036] To the recovered binary resin solution, lauroyl peroxide as an initiator was added in an amount of 1.5 wt % of MMA, and PMMA resin was prepared by a vacuum infusion process.

[0037] Example 4 This embodiment provides a method for recycling PMMA resin / carbon fiber composite materials, comprising the following steps: 5 parts of waste PMMA / carbon fiber composite material were added to 250 parts of methyl methacrylate solvent and mixed evenly. Then, the mixture was placed in a constant temperature oscillator, heated to 65°C and shaken for 20 hours. The composite material first swelled and then dissolved.

[0038] The dissolved mixture is filtered to obtain a solid phase product and a liquid phase product. The solid phase product is washed with methyl methacrylate, dried and recovered to obtain carbon fiber; the washing liquid is combined with the liquid phase product to be reused as recovered resin.

[0039] To the recovered binary resin solution, tert-butyl benzoyl peroxide (0.8 wt% of MMA) was added as initiator. The resin and aramid were vacuum infused to obtain a PMMA resin / aramid composite material. The mass fraction of aramid in the composite material was 40 wt%.

[0040] Example 5 This embodiment provides a method for recycling PMMA / basalt fiber composite materials, comprising the following steps: 2 parts of waste polymethyl methacrylate / basalt fiber composite material were added to 200 parts of methyl methacrylate solvent and mixed evenly, then placed in a constant temperature oscillator, heated to 80°C, and shaken at 180 rpm for 3 hours to dissolve; The dissolved mixture is filtered to obtain a solid phase product and a liquid phase product. The solid phase product is washed with methyl methacrylate, dried and recovered to obtain basalt fiber; the washing liquid and the liquid phase product are combined and reused as a recovered resin.

[0041] To the recovered binary resin solution, initiator ammonium persulfate and nano-titanium dioxide were added, with the amount of the initiator added being 0.1 wt % of the MMA, and a titanium dioxide-modified PMMA resin composite material was prepared by vacuum infusion process.

[0042] Example 6 This embodiment provides a method for recycling PMMA / carbon fiber composite materials, comprising the following steps: 2 parts of waste PMMA / carbon fiber composite material were added to 20 parts of methyl methacrylate solvent and mixed evenly. Then, the mixture was placed in a constant temperature oscillator, heated to 30°C, and shaken at 180 rpm for 60 hours to dissolve. The dissolved mixture is filtered to obtain a solid phase product and a liquid phase product. The solid phase product is washed with methyl methacrylate (MMA), dried and recovered to obtain carbon fiber; the washing liquid and the liquid phase product are combined and reused as a recovered resin.

[0043] To the recovered binary resin solution, initiator azobisisoheptanonitrile and nano-zinc oxide were added, with the amount of the initiator added being 3 wt % of the MMA, and a nano-zinc oxide-modified PMMA resin composite material was prepared by vacuum infusion process.

[0044] Example 7 This embodiment provides a method for recycling PMMA / carbon fiber composite materials, comprising the following steps: 1 part of waste PMMA / carbon fiber composite material was added to 80 parts of methyl methacrylate solvent and mixed evenly. Then, the mixture was placed in a constant temperature oscillator, heated to 50°C, and shaken at 180 rpm for 20 hours to dissolve. The dissolved mixture is filtered to obtain a solid phase product and a liquid phase product. The solid phase product is washed with methyl methacrylate (MMA), dried and recovered to obtain carbon fiber; the washing liquid and the liquid phase product are combined and reused as a recovered resin.

[0045] To the recovered binary resin solution, initiators potassium persulfate, benzoyl peroxide and nano-silica were added, with the amount of the initiator added being 0.5 wt % of MMA, to prepare a nano-silica-modified PMMA resin composite material through a vacuum infusion process.

[0046] Example 8 This embodiment provides a method for recycling a PMMA resin / aramid composite material, comprising the following steps: 5 parts of waste PMMA / aramid composite material were added to 300 parts of methyl methacrylate solvent and mixed evenly. Then, the mixture was placed in a constant temperature oscillator, heated to 60°C and shaken for 20 hours. The composite material first swelled and then dissolved.

[0047] The dissolved mixture is filtered to obtain a solid phase product and a liquid phase product. The solid phase product is washed with methyl methacrylate, dried and recovered to obtain aramid; the washing liquid is combined with the liquid phase product to be reused as a recovered resin.

[0048] To the recovered binary resin solution, tert-butyl benzoyl peroxide (TBTB) was added as an initiator in an amount of 0.8 wt% of MMA. The resin and carbon fiber were vacuum infused to obtain a PMMA resin / carbon fiber composite material. The mass fraction of carbon fiber in the composite material was 50 wt%.

[0049] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for recycling PMMA thermoplastic resin / fiber reinforced composite materials, characterized in that: The steps include: (1) Mix and dissolve the PMMA thermoplastic resin / fiber reinforced composite material with the solvent MMA; (2) The dissolved solid phase product is separated from the liquid phase product, and the liquid phase product is polymerized to obtain PMMA thermoplastic resin or its composite material.

2. The method for recycling PMMA thermoplastic resin / fiber reinforced composite material according to claim 1, characterized in that: The fibers in the PMMA thermoplastic resin / fiber reinforced composite material in step (1) include one or more of basalt fiber, glass fiber, carbon fiber and aramid.

3. The method for recycling PMMA thermoplastic resin / fiber reinforced composite material according to claim 1, characterized in that: In the step (1), the mass ratio of PMMA thermoplastic resin / fiber reinforced composite material to solvent is 1:10-100.

4. The method for recycling PMMA thermoplastic resin / fiber reinforced composite material according to claim 1, characterized in that: The dissolution temperature in step (1) is 30-80°C and the dissolution time is 3-60h.

5. The method for recycling PMMA thermoplastic resin / fiber reinforced composite material according to claim 4, characterized in that: The dissolution is carried out with stirring and / or shaking.

6. The method for recycling PMMA thermoplastic resin / fiber reinforced composite material according to claim 1, characterized in that: In the step (2), an initiator is added to the liquid phase product to carry out a polymerization reaction.

7. The method for recycling PMMA thermoplastic resin / fiber reinforced composite material according to claim 6, characterized in that: The initiator is one or more of an azo initiator, a peroxide initiator and a reduction initiator, and the added amount is 0.1-3wt% of MMA.

8. The method for recycling PMMA thermoplastic resin / fiber reinforced composite material according to any one of claims 1 to 7, characterized in that: The liquid phase product is added with fillers to prepare a corresponding PMMA thermoplastic resin composite material.

9. The method for recycling PMMA thermoplastic resin / fiber reinforced composite material according to claim 8, characterized in that: The filler includes reinforcing fibers or inorganic nanoparticles; the reinforcing fibers include carbon fibers, basalt fibers, glass fibers or aramid fibers; and the inorganic nanoparticles include nano-silicon dioxide, nano-titanium dioxide or nano-zinc oxide.

10. Use of the PMMA thermoplastic resin or its composite material prepared by the method according to any one of claims 1 to 9 in the fields of aviation materials, wind power manufacturing, building materials, furniture decoration, agricultural materials, liquid crystal materials, electronic and electrical materials, optical materials, transportation, medical materials, military materials or paint coatings.

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