Preparation method of lightweight epoxy resin substitute wood

Abstract

The present invention provides a method for preparing a lightweight epoxy resin substitute, comprising the following steps: providing raw materials and curing treatment steps, wherein the curing treatment step comprises first mixing and stirring the epoxy resin, thermal initiator, defoamer and hollow glass microspheres under normal temperature and vacuum conditions to form a resin mixture; then dripping the photoinitiator at the front end of the resin mixture, and irradiating the photoinitiator with an ultraviolet light source to initiate a front polymerization reaction, causing the thermal initiator to decompose through the reaction heat release, and continuously promoting the front polymerization reaction until the resin mixture is completely cured, thereby obtaining a lightweight epoxy resin substitute. During the curing process, the thermal initiator cooperates with the photoinitiator to initiate the front polymerization reaction, which greatly shortens the curing cycle of the substitute, and the highest temperature of the curing process is low, and the residual stress is small.

Description

Technical Field

[0001] The invention relates to the field of wood substitutes, and in particular to a method for preparing a lightweight epoxy resin wood substitute. Background Art

[0002] Epoxy resin wood substitute is one of the important wood substitute materials at present. Due to its advantages such as good dimensional stability, good storage stability of raw materials used in its preparation, and low environmental pollution, it is gradually used in actual industrial production, especially in mold industries such as automobiles and space shuttles.

[0003] However, existing epoxy resin substitutes have problems such as easy deformation during the processing of finished products, large shrinkage in curing volume, long curing time, easy cracking, more pores in the finished products, and uneven density, resulting in a relatively low qualified rate of finished products. In order to solve the above problems, Chinese invention patent application CN106433030A discloses an epoxy resin substitute, which is obtained by reacting a resin component and a curing component; the resin component is obtained by reacting an epoxy resin and a toughening agent under the action of a catalyst; the toughening agent is selected from one or more of nitrile rubber, monopolymer acid, dimer acid, trimer acid and polyethylene; the catalyst is composed of dimethylaminomethylphenol and imidazole and its derivatives; the curing component includes C 3 ~C 20 Fatty acid anhydride, catalyst and hollow glass microspheres.

[0004] The above invention patent application is obtained through the above nitrile rubber, polyacid, epoxy resin, C 3 ~C 20 The combined effects of fatty acid anhydride, catalyst and hollow glass microspheres make the epoxy resin substitute wood prepared by the present invention have good toughness, few pores, and are not easy to crack and deform. However, the curing temperature of the invention patent application is 100-150°C, and the curing is performed in two times, and the curing time is more than ten hours; especially in the process of processing thick and lightweight epoxy resin substitute wood with a thickness of more than 5 mm, there is even a situation where the substitute wood board is heartburned. In addition, the residual internal stress of the newly prepared substitute wood is relatively large. The common method of releasing the residual stress is to store the cured epoxy substitute wood for a period of time, or reheat it, and wait for the residual stress to be released. In this way, the production cycle of the epoxy resin substitute wood is extended in disguise. Summary of the invention

[0005] In view of this, the present invention is indeed necessary to provide a method for preparing a lightweight epoxy resin substitute for wood to solve the above problems.

[0006] Specifically, the present invention provides a method for preparing a lightweight epoxy resin substitute wood, comprising the following steps:

[0007] Providing raw materials and providing a component of an epoxy resin composite material, which includes, by weight, 100 parts of epoxy resin, 0.05-5 parts of photoinitiator, 5-10 parts of thermal initiator, 1-3 parts of defoamer and 5-20 parts of hollow glass microspheres;

[0008] Curing treatment: first, under normal temperature and vacuum conditions, mix and stir the epoxy resin, thermal initiator, defoamer and hollow glass microspheres to form a resin mixture; then drop the photoinitiator to the front end of the resin mixture, and use a light source to irradiate the photoinitiator to initiate a front polymerization reaction, prompting the thermal initiator to continuously promote the front polymerization reaction until the resin mixture is completely cured, so as to obtain a lightweight epoxy resin substitute. Preferably, the thickness of the lightweight epoxy resin substitute is greater than 5 mm; more preferably, the thickness of the lightweight epoxy resin substitute is 5 to 50 mm.

[0009] Based on the above, the curing treatment step includes: first adding the thermal initiator, defoamer and hollow glass microspheres to the epoxy resin, and vacuum stirring for 5 to 10 minutes at room temperature to form a resin mixture; then quickly placing the resin mixture in a curing mold, dripping the photoinitiator at one end of the curing mold, and irradiating the photoinitiator with an ultraviolet light source to cause the resin mixture in which it is located to undergo a curing reaction and release heat, and the released heat triggers the thermal initiator to continue to undergo a front polymerization reaction until the resin mixture is completely cured to obtain a lightweight epoxy resin substitute. Preferably, the ultraviolet light source irradiates the photoinitiator for 20 to 30 seconds; the thickness of the curing mold is 5 to 50 mm.

[0010] In the curing process, the photoinitiator is arranged at one end irradiated by the cold light source, so that the cold light source irradiates the photoinitiator, so that the epoxy resin at the front end is cured under the action of the photoinitiator and releases a large amount of heat; the released heat is consumed by the thermal initiator at the rear end, promoting the continuous curing reaction of the epoxy resin at the rear end, and the curing cycle is short. In addition, no additional heat source is required for heating in the entire curing process, so that the maximum temperature of the epoxy resin with a thickness greater than or equal to 5 mm during the curing process does not exceed 200°C, thereby avoiding the phenomenon of heartburn due to excessively high temperature of the cured product.

[0011] In addition, in the above-mentioned curing treatment step, since the photoinitiator is arranged at one end of the curing mold, the epoxy resin undergoes a front polymerization reaction under the action of the photoinitiator and the thermal initiator, so that the epoxy resin is gradually cured from one end to the other end. During the curing process, the front end is a cured resin solid, and the residual stress existing in the resin curing section can be quickly released through the uncured epoxy resin liquid section, so that there is no or less residual stress inside and outside the epoxy resin cured product, and the mechanical properties of the cured product are not affected.

[0012] Based on the above, the ultraviolet light source is preferably an ultraviolet cold light source.

[0013] Based on the above, the photoinitiator is one or more of diaryliodonium salts, triaryliodonium salts, triarylsulfonium salts and ferrocenium salts.

[0014] Based on the above, the thermal initiator is at least one of aliphatic amines, aromatic amine polyamines, modified aliphatic amines and boron trifluoride complex thermal initiators; for example, boron trifluoride-ethylamine complex, boron trifluoride-piperidine complex, boron trifluoride-triethanolamine complex, polyamide 651, Epicure 3371, etc. As long as the thermal initiator used in the present invention is not limited to the above-mentioned substances, as long as it can initiate the curing of the resin mixture under the action of heat, it is within the protection scope of the present invention.

[0015] Based on the above, the epoxy resin is an epoxy resin containing two or more epoxy groups and having a viscosity less than 100000 mPa.s; for example, 221 resin, bisphenol A epoxy resin, double F epoxy resin, etc.

[0016] Based on the above, the defoaming agent is at least one of silicone, polyether and polyether-modified silicone defoaming agents; for example, BYK-065, BYK-022, BYK-052, etc.

[0017] Based on the above, the true density of the hollow glass microspheres is 0.1-0.75 g / cm 3 ; For example, HL20, HL15, HL25, HL30, HL32, HL38, HL42, HL60, HS75, etc.

[0018] Therefore, the preparation method of the above-mentioned lightweight epoxy resin substitute wood provided by the present invention has the following advantages:

[0019] First, the preparation method provided by the present invention uses a thermal initiator in combination with a photoinitiator during the curing process, and the photoinitiator is added at one end irradiated by the light source, so that the epoxy resin undergoes a rapid front polymerization reaction, and the epoxy resin is rapidly cured and completely, which greatly shortens the curing cycle;

[0020] Second, the preparation method provided by the present invention adopts a front-line polymerization reaction during the curing process, and does not need to add an additional heat source for heating, thereby avoiding the maximum temperature being too high during the curing process. In particular, the use of an ultraviolet cold light source can reduce or avoid the heartburn phenomenon during the preparation of thick-sized lightweight epoxy resin substitute wood, thereby improving the preparation yield of thick-sized lightweight epoxy resin substitute wood;

[0021] Third, due to the front-line polymerization reaction in the preparation of lightweight epoxy resin substitute wood, the residual stress in the epoxy resin that has been cured at the front end can be released through the uncured epoxy resin liquid at the rear end, so that the prepared lightweight epoxy resin substitute wood has less residual stress or even no residual stress, and can basically be used directly without removing residual stress through secondary heating or storage.

[0022] Fourthly, the present invention only needs to add a small amount of photoinitiator to one end irradiated by the light source to initiate the curing of the epoxy resin system, thereby reducing the residual photoinitiator and preventing the residual photoinitiator from migrating into food through human contact. Therefore, the lightweight epoxy resin substitute prepared by the method provided by the present invention has good safety and basically does not cause harm to the human body.

[0023] Therefore, the preparation method of the above-mentioned lightweight epoxy resin substitute wood provided by the present invention has the characteristics of simple curing process, short curing cycle, no need to add additional curing heating heat source, low maximum temperature in the curing process, basically no need for warehousing and the prepared substitute wood product can be directly used, and the substitute wood product has good safety. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 Schematic diagram of the curing process of the lightweight epoxy resin substitute wood provided in an embodiment of the present invention.

[0025] Among them, the symbols in the figure are: 1 resin mixture, 2 curing mold, 3 photoinitiator, 4 UV cold light source, 5 thermal initiator. DETAILED DESCRIPTION

[0026] The technical solution of the present invention is further described in detail below through specific implementation methods.

[0027] Embodiments 1 to 5 of the present invention each provide a method for preparing a lightweight epoxy resin substitute wood, comprising the steps of:

[0028] The raw materials and components of the epoxy resin composite materials provided in each embodiment are shown in Table 1;

[0029] curing treatment, adding the thermal initiator, defoamer and hollow glass microspheres to the epoxy resin, and vacuum stirring for about 5 to 10 minutes at room temperature to form a resin mixture; then quickly transferring the resin mixture to a Figure 1The curing is performed in the curing device shown. Specifically, the resin mixture 1 is quickly loaded into the curing mold 2, and the photoinitiator 3 is dripped at the front end of the resin mixture 1 in the curing mold 2. The ultraviolet cold light source 3 located in front of the curing mold 1 is used to irradiate the photoinitiator 2 for about 20 to 30 seconds, so that the photoinitiator 2 triggers the front end of the resin mixture 1 in the curing mold 2 to cure and release heat. The released heat is consumed and decomposed by the thermal initiator 5 evenly dispersed in the resin mixture 1, so that the resin mixture 1 located in the rear end of the curing mold 2 is continuously cured, and the front polymerization reaction is continuously promoted until the resin mixture 1 in the entire curing mold 2 is completely cured. Wherein, the size of the curing mold 2 is 5 cm×5 cm×20 cm.

[0030] Table 1 Epoxy resin wood substitute raw material mass ratio table

[0031] raw material Epoxy resin Photoinitiator Thermal initiator Defoaming agent Hollow glass microspheres Example 1 221 resin 100 parts 0.05 parts of triaryl hexafluoroantimonate sulfonium salt 6 parts of Boron trifluoride-ethylamine complex BYK-065 1 copy HL20 15 copies Example 2 221 resin 100 parts 0.10 parts of triaryl hexafluoroantimonate sulfonium salt 6 parts of Boron trifluoride-ethylamine complex BYK-065 1 HL20 15 copies Example 3 221 resin 100 parts 0.05 parts of ferrocenium salt Polyamide 651 8 parts BYK-065 1 copy HL20 15 copies Example 4 100 parts of bisphenol A epoxy resin 2.5 parts of diaryliodonium salt Boron trifluoride-piperidine complex 5 parts BYK-0222 copies HL1520 copies Example 5 Double F type epoxy resin 100 parts 5 parts of triaryl iodonium salt Boron trifluoride-triethanolamine complex 10 parts BYK-0523 copies HL605 copies Comparative Example 1 221 resin 100 parts 3 parts of triaryl hexafluoroantimonate sulfonium salt 6 parts of Boron trifluoride-ethylamine complex BYK-065 1 copy HL2015 Comparative Example 2 221 resin 100 parts 0 6 parts of Boron trifluoride-ethylamine complex BYK-065 1 copy HL2015 Comparative Example 3 221 resin 100 parts 0 6 parts of Boron trifluoride-ethylamine complex BYK-065 1 copy HL2015 Comparative Example 4 221 resin 100 parts 0 8 parts of Boron trifluoride-ethylamine complex BYK-065 1 copy HL2015

[0032] Comparative Example 1 provides a method for preparing a lightweight epoxy resin substitute for wood, which is basically the same as the method for preparing a lightweight epoxy resin substitute for wood provided in Example 1, with the main difference being that in this comparative example, the mass portion of the photoinitiator is increased, and after the photoinitiator is evenly mixed with other raw materials, a cold light source is used for irradiation, instead of adding the photoinitiator to one end of the curing mold in Example 1; other processes remain unchanged.

[0033] Comparative Example 2 provides a method for preparing a lightweight epoxy resin substitute for wood, which is basically the same as the method for preparing a lightweight epoxy resin substitute for wood provided in Example 1, with the main difference being that: in this comparative example, no photoinitiator is used, only a thermal initiator is used, and the curing mold is heated to 60°C for curing until the resin in the entire curing mold is completely cured; other processes remain unchanged.

[0034] Comparative Example 3 provides a method for preparing a lightweight epoxy resin substitute for wood, which is basically the same as the method for preparing a lightweight epoxy resin substitute for wood provided in Comparative Example 2, with the main difference being that the resin of the curing mold is cured at room temperature until the entire curing mold is completely cured; other processes remain unchanged.

[0035] Comparative Example 4 provides a method for preparing a lightweight epoxy resin substitute for wood, which is basically the same as the method for preparing a lightweight epoxy resin substitute for wood provided in Comparative Example 3, the main difference being that the weight fraction of the thermal initiator is increased.

[0036] Performance Testing

[0037] The preparation methods of the lightweight epoxy resin substitute wood provided in Examples 1 to 5 and Comparative Examples 1 to 4 were tested by observing the curing condition, curing time, maximum temperature of the curing process, degree of curing, surface residual stress of the new substitute wood before storage, and residual stress after storage for 1 month. The results are shown in Table 2.

[0038] Testing method for the maximum temperature of the cured product: insert a thermocouple in the middle of the curing mold to test the maximum temperature during the curing reaction.

[0039] Test method for the reaction degree of the cured product: Use a differential scanning calorimeter to test whether the cured products provided in each embodiment and comparative example are completely cured.

[0040] Residual stress test method: Use resistance stress gauge for measurement.

[0041] Table 2 Evaluation table of epoxy resin wood substitute curing performance results

[0042] sample Curing time / min Condition of solidified material Maximum temperature during curing process / ℃ Degree of curing Surface residual stress / MPa Residual stress after 1 month storage / MPa Example 1 5 normal 180 Fully cured 0.4 0 Example 2 4 normal 186 Fully cured 0.5 0 Example 3 4 normal 189 Fully cured 0.5 0 Example 4 3 normal 194 Fully cured 0.6 0 Example 5 3 normal 197 Fully cured 0.7 0 Comparative Example 1 3 normal 212 Fully cured 0.6 0 Comparative Example 2 30 Burnt inside 297 / 5.2 / Comparative Example 3 120 normal 147 Post-curing required 3.6 1.1 Comparative Example 4 90 normal 162 Post-curing required 4.4 1.5

[0043] It can be seen from Table 2 that compared with Comparative Example 1, in Example 1, the photoinitiator is dripped at one end of the curing mold. Although the curing time is slightly increased, the maximum temperature and surface residual stress during the curing process are relatively small. The residual stress can be basically eliminated within 1 month, which is beneficial to shorten the storage time and reduce the cost; and the amount of photoinitiator added is relatively small, which increases the safety of the wood substitute product.

[0044] Compared with Example 1, Comparative Example 2 uses only thermal initiators and heats to 60°C for curing to prepare thick-sized lightweight epoxy resin substitute wood. Not only does it take a long curing time, but it is also prone to heartburn, thereby reducing the product yield. Comparative Example 3 uses only thermal initiators and room temperature curing to prepare thick-sized lightweight epoxy resin substitute wood. The curing time is long and it cannot be completely cured in one time, requiring secondary curing treatment. In addition, the residual stress of the product is relatively large, and the residual stress cannot be completely eliminated even if it is stored for 1 month. Compared with Comparative Example 3, Comparative Example 4 increases the amount of thermal initiator used and shortens the curing time, but the maximum temperature and residual stress in the curing process are increased, and secondary curing is also required.

[0045] It can be seen that compared with using only a thermal initiator as an initiator for preparing epoxy resin substitute wood, the embodiment of the present invention uses a thermal initiator in combination with a photoinitiator to initiate epoxy resin curing, which not only shortens the curing time, but also simplifies the curing process (no need for secondary curing or secondary heating to remove residual stress), improves product yield, and at the same time, the residual stress of the prepared substitute wood product is relatively small, thereby reducing costs.

[0046] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, ordinary technicians in the field should understand that the specific implementation methods of the present invention can still be modified or some technical features can be replaced by equivalents without departing from the spirit of the technical solution of the present invention, which should be included in the scope of the technical solution for protection of the present invention.

Claims

1. A method for preparing a lightweight epoxy resin substitute wood, comprising the following steps: Providing raw materials and components of an epoxy resin composite material, including, by weight, 100 parts of epoxy resin, 0.05-5 parts of photoinitiator, 5-10 parts of thermal initiator, 1-3 parts of defoamer and 5-20 parts of hollow glass microspheres, wherein the photoinitiator is one or more of diaryliodonium salts, triaryliodonium salts, triarylsulfonium salts and aromatic ferrocenium salts, and the thermal initiator is at least one of aliphatic amines, aromatic amine polyamines, modified aliphatic amines and boron trifluoride complex thermal initiators; Curing treatment: first, under normal temperature and vacuum conditions, the epoxy resin, thermal initiator, defoamer and hollow glass microspheres are mixed and stirred evenly to form a resin mixture, and the resin mixture is placed in a curing mold; then the photoinitiator is dripped onto the front end of the resin mixture in the curing mold, and the photoinitiator is irradiated with a light source to initiate a front polymerization reaction, and the thermal initiator is prompted to continuously promote the front polymerization reaction until the resin mixture is completely cured, so as to obtain a lightweight epoxy resin substitute with a thickness greater than or equal to 5 mm.

2. The preparation method according to claim 1, characterized in that: The curing treatment step comprises firstly adding the thermal initiator, defoamer and hollow glass microspheres into the epoxy resin, and vacuum stirring for 5 to 10 minutes at room temperature to form the resin mixture; then placing the resin mixture in the curing mold, dripping the photoinitiator at one end of the resin mixture in the curing mold, and irradiating the photoinitiator with an ultraviolet light source to cause the resin mixture in which the photoinitiator is located to undergo a curing reaction and release heat, and the released heat triggers the thermal initiator to continuously perform a front polymerization reaction until the resin mixture is completely cured, thereby obtaining a lightweight epoxy resin substitute.

3. The preparation method according to claim 2, characterized in that: The ultraviolet light source irradiates the photoinitiator for 20 to 30 seconds.

4. The preparation method according to claim 2 or 3, characterized in that: The ultraviolet light source is an ultraviolet cold light source.

5. The preparation method according to claim 4, characterized in that: The thickness of the lightweight epoxy resin substitute wood is 5 to 50 mm.

6. The preparation method according to any one of claims 1 to 3, characterized in that: The epoxy resin is an epoxy resin containing two or more epoxy groups, and has a viscosity of less than 100000 mPa.s.

7. The preparation method according to any one of claims 1 to 3, characterized in that: The defoaming agent is at least one of silicone, polyether and polyether-modified silicone defoaming agents.

8. The preparation method according to any one of claims 1 to 3, characterized in that: The true density of the hollow glass microspheres is 0.1 to 0.75 g / cm 3 .

Images