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CN-121975344-A - Modified lignin-based additive and application thereof in high-toughness epoxy resin adhesive

CN121975344ACN 121975344 ACN121975344 ACN 121975344ACN-121975344-A

Abstract

The invention provides a modified lignin-based additive and application thereof in a high-toughness epoxy resin adhesive, and belongs to the technical field of environment-friendly adhesives. The modified lignin-based additive and the application thereof provided by the invention can obviously improve the comprehensive performance of the epoxy resin adhesive without obviously changing the original curing process of the epoxy resin adhesive, and can also improve the wetting and spreading capacities of resin components on substrates made of different materials, thereby enhancing the reliability of interface adhesion. By adopting the lignin which is widely available and renewable as the core raw material, the invention not only provides a high-efficiency functional auxiliary agent for preparing the high-performance epoxy resin structural adhesive, but also expands the high-added-value application path of the lignin, thereby being beneficial to promoting the development of adhesive products to a more environment-friendly and sustainable direction.

Inventors

  • SHEN YUHONG
  • SHEN SHENG

Assignees

  • 廊坊天辰化工有限公司

Dates

Publication Date
20260505
Application Date
20260205

Claims (10)

  1. 1. The preparation method of the modified lignin-based additive is characterized by comprising the following steps of: S1, mixing dry polyethylene glycol, citric acid monohydrate and p-toluenesulfonic acid serving as a catalyst, heating and stirring to react to form a pre-reaction system, and then adding dry high-purity lignin powder into the pre-reaction system and continuously stirring to react to obtain a semi-crosslinked lignin functional element; S2, carrying out high-speed dry mixing pretreatment on hydrophobic fumed silica and a silane coupling agent to obtain pretreated silica, premixing the semi-crosslinked lignin functional element, polyvinyl butyral and the pretreated silica, carrying out melt blending, and then carrying out molding and crushing to obtain the modified lignin-based additive.
  2. 2. The preparation method according to claim 1, wherein the polyethylene glycol is used in the amount of 55 to 65 parts by weight, the citric acid monohydrate is used in the amount of 10 to 30 parts by weight, the p-toluenesulfonic acid catalyst is used in the amount of 0.3 to 1.0 part by weight, and the high purity lignin powder is used in the amount of 10 to 30 parts by weight in the step S1.
  3. 3. The method according to claim 1, wherein the heating and stirring reaction to form the pre-reaction system in step S1 is performed at a temperature of 110 to 140 degrees celsius for 10 to 30 minutes; the step S1 is to add high-purity lignin powder and then to continue stirring reaction for 60 to 150 minutes at the temperature of 110 to 140 ℃; the amount of the hydrophobic fumed silica used in the preparation of the pretreated silica in the step S2 is 8 to 16 parts by weight, and the amount of the silane coupling agent is 0.8 to 3.2 parts by weight; The material for melt blending in step S2 comprises 100 parts by weight of semi-crosslinked lignin functional motifs and 10 to 28 parts by weight of polyvinyl butyral; The melt blending in step S2 is performed at a temperature of 95 to 125 degrees celsius for 10 to 30 minutes.
  4. 4. The preparation method according to claim 1, wherein the high-purity lignin powder and citric acid monohydrate in step S1 are dried in vacuum at a temperature of 100 to 110 ℃ for 3 to 5 hours before mixing, and the polyethylene glycol in step S1 is dried before mixing.
  5. 5. The preparation method according to claim 1, wherein the heating and stirring reaction in the step S1 is performed by heating in an oil bath; The stirring speed of the stirring reaction in the step S1 is 250 to 350 revolutions per minute; The rotating speed of the high-speed dry mixing pretreatment in the step S2 is 1400 to 1600 revolutions per minute, and the treatment time is 8 to 12 minutes; the premixing speed in the step S2 is 700 to 900 revolutions per minute, the mixing time is 6 to 10 minutes, the melt blending in the step S2 is carried out by a torque rheometer, and the rotor speed of the melt blending is 40 to 60 revolutions per minute.
  6. 6. The method of claim 1, wherein the shaping in step S2 comprises pressing the melt blended materials into a sheet and cooling; The crushing in the step S2 comprises crushing, grinding and sieving the cooled material, wherein the mesh number of the sieve is 180-220 mesh.
  7. 7. A modified lignin-based additive prepared by the preparation method according to any one of claims 1 to 6.
  8. 8. Use of the modified lignin-based additive of claim 7 in the preparation of a high toughness epoxy resin adhesive.
  9. 9. The use according to claim 8, wherein the raw materials for preparing the high toughness epoxy resin adhesive comprise bisphenol a type liquid epoxy resin and polyamide curing agent; The preparation raw materials comprise, by weight, 100 parts of bisphenol A type liquid epoxy resin, 1.0 to 8.0 parts of modified lignin-based additive, 40 to 50 parts of polyamide curing agent, 20 to 60 parts of precipitated barium sulfate, 0.5 to 4.0 parts of fumed silica and 0.5 to 2.0 parts of gamma-aminopropyl triethoxysilane.
  10. 10. The use according to claim 9, wherein the high toughness epoxy resin adhesive is prepared by mixing and dispersing bisphenol a liquid epoxy resin and modified lignin-based additive at a temperature of 60 to 70 degrees celsius, then adding filler and mixing and vacuum debubbling to obtain a resin component; The step of mixing and dispersing uniformly comprises stirring at 400-600 rpm for 5-15 min, and dispersing at 1000-1400 rpm for 25-35 min; Vacuum defoaming is carried out under the condition that the vacuum degree is not lower than-0.09 MPa, and the stirring defoaming time is 10 to 20 minutes; the mixing weight ratio of the resin component to the curing agent component is 3.0:1.0 to 3.2:1.0; After mixing the resin component and the hardener component, the pot life in an environment of 25 degrees celsius is 45 to 55 minutes.

Description

Modified lignin-based additive and application thereof in high-toughness epoxy resin adhesive Technical Field The invention relates to the technical field of environment-friendly adhesives, in particular to a modified lignin-based additive and application thereof in a high-toughness epoxy resin adhesive. Background Epoxy resin adhesives are widely used in various industrial fields such as aerospace, automobile manufacturing, electronic and electrical appliances, construction engineering and composite materials due to excellent adhesive strength, chemical resistance, electrical insulation and good process adaptability. In particular to a bi-component epoxy structural adhesive which is a key material for structural connection of metals, ceramics, glass and various engineering plastics. However, the traditional epoxy resin has high crosslinking density and poor molecular chain segment movement capability after being cured, so that the inherent brittleness is high, the impact toughness and the elongation at break are often insufficient, and brittle fracture is easy to occur at the part bearing dynamic load or having stress concentration, so that the application reliability of the epoxy resin under severe working conditions is limited. In order to improve the toughness of epoxy resins, common technical means include the addition of toughening agents such as liquid rubber, thermoplastic resins, core-shell particles or rigid particles. Although these methods can bring about a certain improvement in toughness, they often involve problems such as a decrease in modulus, heat resistance, or a significant increase in processing viscosity, and the compatibility of a part of the toughening agent with the epoxy resin is limited, and there is a risk of phase separation during long-term use. On the other hand, good workability is critical to the practical application of the adhesive. Thixotropic properties are one of the key indicators for evaluating the workability of adhesives, and ideal thixotropic properties require that the adhesive maintain a high viscosity at rest or low shear rates to prevent filler settling and sagging during storage, while rapidly decreasing in viscosity at high shear rates of construction agitation or coating to facilitate handling, yet rapidly regain high viscosity after construction to maintain the shape of the adhesive. Many conventional thickeners or thixotropic agents, while capable of adjusting viscosity, tend to have difficulty achieving a desirable balance between high and low shear viscosity and recovery rate, or negatively impacting the final mechanical properties of the adhesive. At the same time, with increasing emphasis on sustainable development and efficient utilization of resources, the development of high performance chemicals and materials using renewable biomass resources is an important research direction. Lignin is a natural aromatic polymer with the content inferior to that of cellulose in nature, mainly comes from byproducts of the paper industry, and has huge yield and low utilization rate. The lignin molecular structure contains rich active functional groups such as phenolic hydroxyl groups, alcoholic hydroxyl groups and the like, and has the potential of being used as a polymer material modifier or filler. However, unmodified lignin has problems of complex structure, high polarity, poor compatibility with most synthetic resins, easy occurrence of heat aggregation in the heating process and the like, and is often added into a system such as epoxy resin and the like to cause uneven dispersion and weak interface bonding, so that the unmodified lignin is difficult to play a reinforcing role, can become a defect point and deteriorate the mechanical property of a material. Therefore, how to effectively perform functional modification on lignin, breaks the application bottleneck of lignin, enables lignin to be used as a high-performance auxiliary agent to be applied to synthetic materials such as epoxy resin and the like, and realizes high-value utilization of biomass resources, which is a challenging subject in the field. Disclosure of Invention The invention aims to provide a modified lignin-based additive and application thereof in high-toughness epoxy resin adhesive, and solves the problems that the existing epoxy resin adhesive, in particular structural adhesive, is difficult to consider in toughness, thixotropy, wettability to a substrate and the like, and is difficult to realize high performance by effectively utilizing biomass resources. In order to achieve the above object, the present invention provides the following technical solutions: The invention provides a preparation method of a modified lignin-based additive, which comprises the following steps: S1, mixing dry polyethylene glycol, citric acid monohydrate and p-toluenesulfonic acid serving as a catalyst, heating and stirring to react to form a pre-reaction system, and then adding dry high-purity lignin powder i