Natural aromatic polyhydroxy acid assembly, heat insulation molding compound and preparation method

Abstract

The invention relates to the field of unsaturated polyester resin molding compounds, in particular to a natural aromatic polyhydroxy acid assembly, a heat insulation molding compound and a preparation method. In order to solve the problems that in the prior art, an unsaturated polyester resin heat insulation molding compound adopts flour as a foaming agent, and the foaming heat insulation effect on an oily curing system which cannot contain water is poor, an assembly formed by performing water bath ultrasonic treatment on natural aromatic polyhydroxy acid is adopted as the foaming agent. The foaming agent can generate water and carbon dioxide gas through high-temperature decarboxylation in an oily curing system to realize in-situ foaming of unsaturated polyester resin, so that the density of a molding compound is reduced, and the heat insulation performance of a material is enhanced; a product obtained after high-temperature decarboxylation of the foaming agent generally has strong reducibility and can endow a material with a good anti-aging effect, so that the service life of the material is prolonged; in addition, the foaming agent also has the advantages of high degradation speed and no long-term accumulation in the environment, so that the potential harm to an ecological system is reduced, and the requirement of sustainable development is met.

Description

Technical Field

[0001] The present application relates to the field of unsaturated polyester resin molding materials, and in particular to natural aromatic polyhydroxy acid assemblies, thermal insulation molding materials and preparation methods. Background Art

[0002] Unsaturated polyester resin, as a thermosetting resin, is widely used due to its excellent physical and chemical properties. By mixing with fillers, pigments and crosslinking agents, unsaturated polyester can be made into products with specific colors and shapes to meet diverse design and usage requirements. Under the influence of the greenhouse effect, global temperatures are rising sharply, and thermal insulation unsaturated polyester resin sheet molding compounds will have broad market application potential.

[0003] Existing high temperature resistant heat insulation molding materials usually achieve intrinsic heat insulation and high temperature resistance of the matrix by adding heat insulation fillers such as inorganic substances such as aluminum oxide and zirconium oxide, and achieve intrinsic halogen-free flame retardancy of the material by adding flame retardant fillers such as aluminum hydroxide and borates. For example, the patent with application number CN 115519854A discloses a heat insulating unsaturated polyester glass fiber laminate and its preparation method, which achieves material flame retardancy by adding aluminum hydroxide / calcium carbonate, and achieves heat insulation effect by foaming after flour absorbs water. However, for oily curing systems that cannot contain water, flour cannot absorb water, and the foaming and heat insulation effect of this method is not good. Summary of the invention

[0004] Based on the above purpose, the purpose of the present invention is to overcome the shortcomings of the prior art and provide a natural aromatic polyhydroxy acid assembly and a thermal insulation molding material containing the assembly and a preparation method. The natural aromatic polyhydroxy acid assembly is used as a bio-based foaming agent, which undergoes a decarboxylation reaction when heated (above 200°C) to generate water and carbon dioxide gas, thereby achieving in-situ foaming of unsaturated polyester, reducing the density of the film plastic, and enhancing the thermal insulation performance of the material.

[0005] To this end, the first technical solution of the present application discloses a method for preparing a natural aromatic polyhydroxy acid assembly, comprising the following steps:

[0006] The natural aromatic polyhydroxy acid solution is treated by ultrasonic treatment in a water bath and then cooled until nanoparticles are crystallized and precipitated;

[0007] The nanoparticle crystals are filtered and dried to obtain the natural aromatic polyhydroxy acid assembly.

[0008] Preferably, the natural aromatic polyhydroxy acid is at least one of p-hydroxycinnamic acid, salicylic acid, tannic acid, gallic acid, vanillic acid and caffeic acid.

[0009] Preferably, the water bath ultrasonic conditions are 100-400w, 10-60Hz, 30-60℃ water bath treatment for 1-2h.

[0010] Preferably, the drying temperature is 40-60° C. for 4-8 hours.

[0011] Also, the natural aromatic polycarboxylic acid assembly prepared according to the above preparation method and the use of the assembly as a foaming agent in the preparation of unsaturated polyester resin molding materials.

[0012] The second technical scheme of the present application discloses a method for preparing an unsaturated polyester resin thermal insulation molding material, comprising the following steps: mixing and kneading the above-mentioned natural aromatic polycarboxylic acid assembly and a resin matrix containing an unsaturated polyester resin to obtain an unsaturated polyester resin molding material prefabricated sheet, and then making the unsaturated polyester resin thermal insulation molding material through a hot pressing process.

[0013] Preferably, the mass ratio of the natural aromatic polycarboxylic acid assembly to the resin matrix comprising the unsaturated polyester resin is (0.5-2):1.

[0014] Preferably, the resin matrix containing unsaturated polyester resin includes: unsaturated polyester resin, inorganic filler, initiator, thickener, low shrinkage agent.

[0015] Preferably, the hot pressing process is 220-260° C., 10-20 MPa, and pressing for 5-20 min.

[0016] And, the unsaturated polyester resin thermal insulation molding material prepared according to the above preparation method.

[0017] Beneficial effects: This application aims at the problem that flour is used as a foaming agent in the prior art unsaturated polyester resin thermal insulation molding materials. For the oily curing system that cannot contain water, the flour cannot absorb water, resulting in poor foaming and thermal insulation effect. The natural aromatic polyhydroxy acid assembly formed by water bath ultrasound of natural aromatic polyhydroxy acid is used as a foaming agent. On the one hand, the foaming agent can simultaneously produce water and carbon dioxide gas through high-temperature decarboxylation in oily and non-oily curing systems, thereby realizing in-situ foaming of unsaturated polyester resin, thereby reducing the density of the molding material and enhancing the thermal insulation performance of the material; on the other hand, the product of the foaming agent after high-temperature decarboxylation generally has strong reducing properties, which can give the material a good anti-aging effect, thereby extending the service life of the material; finally, the foaming agent also has the advantages of fast degradation and no long-term accumulation in the environment, thereby reducing the potential harm to the ecosystem and meeting the requirements of "sustainable development".

[0018] The unsaturated polyester resin thermal insulation molding material prepared by using the prepared natural aromatic polycarboxylic acid assembly as a foaming agent in the present application has the characteristics of uniform pore distribution, low density, good thermal insulation performance, high mechanical properties, etc. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is a SEM image of the cross section of the thermal insulation molding material of Example 1;

[0020] Figure 2 is a SEM image of the cross section of the thermal insulation molding material of Example 4;

[0021] Figure 3 This is the SEM image of the cross section of the thermal insulation molding compound. DETAILED DESCRIPTION

[0022] The following will be combined with the drawings in 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 those skilled in the art without creative work are within the scope of protection of the present invention.

[0023] Unless otherwise specifically stated, the relative arrangement, numerical expressions and numerical values ​​of the parts and steps set forth in these embodiments do not limit the scope of the present application. At the same time, it should be understood that, for ease of description, the sizes of the various parts shown in the accompanying drawings are not drawn according to the actual proportional relationship. The technology, method and equipment known to those of ordinary skill in the relevant field may not be discussed in detail, but in appropriate cases, the technology, method and equipment should be considered as a part of the authorization specification. In all examples shown and discussed here, any specific value should be interpreted as being merely exemplary, rather than as a limitation. Therefore, other examples of exemplary embodiments may have different values. It should be noted that similar reference numerals and letters represent similar items in the following drawings, so that once a certain item is defined in an accompanying drawing, it does not need to be further discussed in subsequent drawings.

[0024] Unless otherwise specified, the meanings of the technical terms in this specification are the same as those generally understood by those skilled in the art. However, if there is any conflict, the definitions in this specification shall prevail.

[0025] The term "oily curing system" in this application specifically refers to unsaturated polyester resin molding oily curing systems such as thermal reorganization curing systems, drying curing systems, etc., whose components are all organic matter and the curing process is sensitive to water. Non-oily curing systems such as water-based emulsion curing systems use water as a solvent and dispersant and are not sensitive to water.

[0026] The first embodiment of the present application provides a method for preparing a natural aromatic polyhydroxy acid assembly, comprising the following steps:

[0027] The natural aromatic polyhydroxy acid solution is treated in an ultrasonic water bath and then cooled until nanoparticles are crystallized and precipitated;

[0028] The nanoparticle crystals are filtered and dried to obtain the natural aromatic polyhydroxy acid assembly.

[0029] In this embodiment, the natural aromatic polyhydroxy acid refers to an aromatic substance with multiple hydroxyl groups and carboxyl groups on the benzene ring of a non-petroleum-based material, and the present application preferably refers to at least one of p-hydroxycinnamic acid, salicylic acid, tannic acid, gallic acid, vanillic acid, and caffeic acid. These natural aromatic polyhydroxy acids can undergo hydrolysis, coupling, and other reactions under water bath ultrasound conditions to form nanoparticles with a large number of terminal carboxyl groups. These nanoparticles are cooled and crystallized to form natural aromatic polyhydroxy acid assemblies. These assemblies will decarboxylate to produce water and carbon dioxide gas under high temperature conditions, and the reaction products are usually highly reducing.

[0030] It can be understood that during the ultrasonic water bath process, the natural aromatic polyhydroxy acid exists in the form of a solution, and the solvent for dissolving it is a solvent conventionally known to those skilled in the art, and the present application is preferably at least one of deionized water, ethanol, dimethyl carbonate, n-butanol, ethyl acetate, ethylene glycol, diethylene glycol, and glycerol.

[0031] In this embodiment, the ultrasonic water bath is to perform ultrasonic treatment under water bath conditions, the purpose of which is to promote the hydrolysis and coupling reaction of natural aromatic polyhydroxy acids to form nanoparticles with a large number of terminal carboxyl groups. In this process, the conditions of the ultrasonic water bath are preferably 100-400w, 10-60Hz, and 30-60℃ water bath treatment for 1-2h. Below the range of 100w, 10Hz, the hydrolysis and coupling reaction of natural aromatic polyhydroxy acids cannot be achieved. Above this range, it is easy to over-hydrolyze them and nanoparticles cannot be formed. At the same time, long-term ultrasonic treatment will cause a sharp rise in the temperature of the solution, so the temperature needs to be maintained by water bath treatment.

[0032] In this embodiment, the purpose of drying is to remove water or solvent on the surface of the nanoparticles, and the preferred drying condition is 40-60°C for 4-8 hours. Below this temperature / time, the nanoparticles are not completely dried; above this temperature, the nanoparticles will partially volatilize and oxidize; above this time, the production efficiency is low.

[0033] In a further embodiment, the natural aromatic polycarboxylic acid assembly prepared according to the above preparation method can be used as a foaming agent to prepare unsaturated polyester resin molding material.

[0034] Since the natural aromatic polycarboxylic acid assembly of the present application can undergo a decarboxylation reaction at a high temperature of more than 200°C to generate carbon dioxide and water, it can realize in-situ foaming of the unsaturated polyester resin, thereby reducing the density of the unsaturated polyester resin plastic mold and enhancing the thermal insulation performance of the material; at the same time, since the product of the decarboxylation of the natural aromatic polyhydroxy acid generally has strong reducing properties, it can also give the material a good anti-aging effect, thereby extending the service life of the material.

[0035] The second embodiment of the present application provides a method for preparing an unsaturated polyester resin thermal insulation molding material, comprising the following steps: mixing and kneading the above-mentioned natural aromatic polycarboxylic acid assembly and a resin matrix containing an unsaturated polyester resin to obtain an unsaturated polyester resin molding material prefabricated sheet, and then making the unsaturated polyester resin thermal insulation molding material through a hot pressing process.

[0036] In this embodiment, the mass ratio of the natural aromatic polycarboxylic acid assembly to the resin matrix comprising the unsaturated polyester resin is (0.5-2):1.

[0037] It can be understood that the resin matrix containing unsaturated polyester resin described in the present application needs to contain at least unsaturated polyester resin, such as bisphenol A type unsaturated polyester resin, and in order to improve its performance, it may also contain inorganic fillers such as calcium hydroxide, aluminum oxide, etc.; initiators such as TBPB (tert-butyl perbenzoate), TBPO (tributyl phosphorus oxide), BPO (benzoyl peroxide), etc.; thickeners such as magnesium oxide, etc.; low shrinkage agents such as polystyrene, polyvinyl acetate, polymethyl methacrylate; in addition, it may also include assembly agents such as hydroquinone, para-benzoquinone; release agents such as zinc stearate, etc., all of which are within the conventional knowledge of those skilled in the art.

[0038] And it is understandable that the addition amount of the above materials does not exceed the conventional knowledge of those skilled in the art. This application only provides preferred addition amounts. For example, in some preferred embodiments, the resin matrix comprises unsaturated polyester resin, inorganic filler, initiator, thickener, low shrinkage agent, release agent, and reinforcing fiber. The amount used is 50-80 parts by weight of unsaturated polyester resin, 50-100 parts by weight of inorganic filler, 0.1-5 parts by weight of initiator, 0.1-5 parts by weight of thickener, 20-50 parts by weight of low shrinkage agent, 0.1-5 parts by weight of release agent, and 1-30 parts by weight of reinforcing fiber.

[0039] In this embodiment, the hot pressing process is 220-260°C, 10-20MPa, and pressing for 5-10min. Since the natural aromatic polycarboxylic acid assembly prepared in this application can undergo a decarboxylation reaction at above 200°C, the hot pressing process can be used to foam the unsaturated polyester resin in situ to form uniformly distributed pores, thereby obtaining an unsaturated polyester resin thermal insulation molding material with low density, good thermal insulation performance, and high mechanical properties.

[0040] The properties of the unsaturated polyester resin thermal insulation molding material prepared in the present application will be described below through specific examples.

[0041] Since the unsaturated polyester resin described in the present application has similar performance in modeling, and the natural aromatic polyhydroxy acid also has similar performance in hydrolysis and coupling, therefore, the unsaturated polyester resin in the embodiments of the present application is bisphenol A type unsaturated polyester resin, and the natural aromatic polyhydroxy acid is gallic acid.

[0042] The natural aromatic polyhydroxy acids described in Examples 1-3 below were pretreated using the following steps before being mixed with other components:

[0043] 100g of natural aromatic polyhydroxy acid is dissolved in 500ml of deionized water, and ultrasonically treated for 1h in a constant temperature water area at 400W, 30Hz, and 30℃ to cause hydrolysis, coupling, and other reactions to form nanoparticles with a large number of terminal carboxyl groups. When the solution is cooled to room temperature, the nanoparticles are crystallized, filtered, and dried at 50℃ for 4h to obtain natural aromatic polyhydroxy acid crystals, such as gallic acid crystals, tannic acid crystals, or caffeic acid crystals.

[0044] Example 1 Preparation of thermal insulation molding compound

[0045] Weigh 50 parts of bisphenol A type unsaturated polyester resin, 38 parts of polymethyl methacrylate, 30 parts of aluminum hydroxide, 0.1 parts of tert-butyl perbenzoate, and 0.1 parts of calcium hydroxide by mass and put them into a blender and stir for 30 minutes. Then transfer the material to a kneader, and add 50 parts of pretreated gallic acid crystals, 2 parts of zinc stearate, and 20 parts of aluminum hydroxide by mass, and continue kneading for 20 minutes to obtain an unsaturated polyester resin molding material preform. The unsaturated polyester resin molding material preform was hot-pressed at 220°C and 20MPa for 10 minutes to form a thermal insulation molding material, and its cross-sectional microscopic SEM image is shown as follows: Figure 1 As shown: its pore structure is uniform in size and densely distributed.

[0046] Example 2 Preparation of thermal insulation molding compound

[0047] Weigh 50 parts of bisphenol A type unsaturated polyester resin, 38 parts of polymethyl methacrylate, 30 parts of aluminum hydroxide, 0.1 parts of tert-butyl peroxybenzoate, and 0.1 parts of calcium hydroxide by mass and put them into a mixer and stir for 30 minutes. Then transfer the materials to a kneader, and add 80 parts of pretreated gallic acid crystals, 2 parts of zinc stearate, and 20 parts of aluminum hydroxide by mass, and continue kneading for 20 minutes to obtain an unsaturated polyester resin molding material preform. The unsaturated polyester resin molding material preform is hot-pressed at 260°C and 10MPa for 5 minutes to form a thermal insulation molding material.

[0048] Example 3 Preparation of thermal insulation molding compound

[0049] Weigh 50 parts of bisphenol A type unsaturated polyester resin, 38 parts of polymethyl methacrylate, 30 parts of aluminum hydroxide, 0.1 parts of tert-butyl perbenzoate, and 0.1 parts of calcium hydroxide by mass and put them into a mixer and stir for 30 minutes. Then transfer the materials to a kneader, and add 110 parts of pretreated gallic acid crystals, 2 parts of zinc stearate, and 20 parts of aluminum hydroxide by mass, and continue kneading for 20 minutes to obtain an unsaturated polyester resin molding material preform. The unsaturated polyester resin molding material preform is hot-pressed at 240°C and 15MPa for 20 minutes to form a thermal insulation molding material.

[0050] Example 4 Preparation of thermal insulation molding compound

[0051] Weigh 50 parts of bisphenol A type unsaturated polyester resin, 38 parts of polymethyl methacrylate, 30 parts of aluminum hydroxide, 0.1 parts of tert-butyl perbenzoate, and 0.1 parts of calcium hydroxide by mass and put them into a blender and stir for 30 minutes. Then transfer the material to a kneader, and add 50 parts of pretreated tannic acid crystals, 2 parts of zinc stearate, and 20 parts of aluminum hydroxide by mass, and continue kneading for 20 minutes to obtain an unsaturated polyester resin molding material preform. The unsaturated polyester resin molding material preform is hot-pressed at 220°C and 20MPa for 10 minutes to form a thermal insulation molding material, and its SEM image is as follows Figure 2 As shown in the figure, compared with Example 1, the pore size is larger and unevenly distributed. This is because tannic acid is gradually decomposed into gallic acid during the ultrasonic treatment process, and the final product contains both tannic acid and gallic acid.

[0052] Example 5 Preparation of thermal insulation molding compound

[0053] Weigh 50 parts of bisphenol A type unsaturated polyester resin, 38 parts of polymethyl methacrylate, 30 parts of aluminum hydroxide, 0.1 parts of tert-butyl perbenzoate, and 0.1 parts of calcium hydroxide by mass and put them into a blender and stir for 30 minutes. Then transfer the material to a kneader, and add 50 parts of pretreated caffeic acid, 2 parts of zinc stearate, and 20 parts of aluminum hydroxide by mass, and continue kneading for 20 minutes to obtain an unsaturated polyester resin molding material preform. The unsaturated polyester resin molding material preform is hot-pressed at 220°C and 20MPa for 10 minutes to form a thermal insulation molding material, and its SEM picture is as follows Figure 3 As shown: compared with Example 1, the bubbles are larger, uneven in size and uneven in distribution.

[0054] It should be noted that the enlarged pore size and uneven size distribution of the pores in Example 4 and Example 5 are caused by the physical and chemical properties of tannic acid and caffeic acid themselves, which do not affect the technical effects of reducing density and heat insulation achieved by the present application. As shown in Table 1, Example 4 and Example 5 can actually achieve the technical effects of reducing density and heat insulation.

[0055] Comparative Example 1 Preparation of thermal insulation molding material

[0056] Weigh 50 parts of bisphenol A type unsaturated polyester resin, 38 parts of polymethyl methacrylate, 30 parts of aluminum hydroxide, 0.1 parts of tert-butyl perbenzoate, and 0.1 parts of calcium hydroxide by mass and put them into a mixer and stir for 30 minutes. Then transfer the material to a kneader, add 2 parts of zinc stearate and 20 parts of aluminum hydroxide by mass, and continue kneading for 20 minutes. Subsequently, an unsaturated polyester resin molding material preform is obtained. The unsaturated polyester resin molding material preform is hot-pressed at 220°C and 20MPa for 10 minutes to form an insulating bio-based unsaturated polyester resin sheet molding material.

[0057] The preparation process is the same as that of Example 1.

[0058] The products obtained in the above Examples 1-5 and Comparative Example 1 were subjected to relevant performance tests:

[0059] Among them, the tensile strength is tested in accordance with "GB / T 1040-2018"; the volume resistivity is obtained by ZC36 high insulation resistance measuring instrument in accordance with "GB / T31838.2-2019"; the thermal conductivity is tested by using the German NETZSCH LFA467 instrument to measure the thermal diffusion coefficient of the material, and then the DSC instrument is used to measure the specific heat capacity of the material, and then the material density is obtained according to the volume and weight of the material, and finally the thermal conductivity of the material is obtained according to the formula: thermal conductivity = thermal diffusion coefficient * specific heat capacity * density; the flammability is tested in accordance with "UL 94-2013"; the load deformation temperature is tested in accordance with "GB / T1634.2-2019".

[0060] The test results are shown in Table 1:

[0061] Table 1 Performance test results

[0062]

[0063] It can be seen that compared with the unsaturated polyester molding compound made of the traditional formula in Example 1, the composite material obtained in the examples of the present application is in situ micro-foamed by the natural aromatic polyhydroxy acid, and the density of the obtained product is lower than that of the unfoamed comparative example 1. At the same time, due to the presence of foaming products carbon dioxide, water, and unreacted natural aromatic polyhydroxy acid in the pores, the flame retardant performance of the examples is better, and its flame retardant grade (vertical burning) is V-0 (after two 10-second combustion tests on the sample, the flame is extinguished within 30 seconds. No burning objects can fall), while the flame retardant grade of comparative example 1 is v-1 (after two 10-second combustion tests on the sample, the flame is extinguished within 60 seconds. No burning objects can fall). Therefore, the technical solution of the present application has the characteristics of low density and good heat insulation and flame retardancy while ensuring tensile strength, insulation performance and heat resistance.

[0064] The above is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed by the present invention should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims

1. A method for preparing a natural aromatic polyhydroxy acid assembly, characterized in that: The steps include: The natural aromatic polyhydroxy acid solution is treated by ultrasonic treatment in a water bath and then cooled until nanoparticles are crystallized and precipitated; The nanoparticle crystals are filtered and dried to obtain the natural aromatic polyhydroxy acid assembly.

2. The preparation method according to claim 1, characterized in that: The natural aromatic polyhydroxy acid is at least one of p-hydroxycinnamic acid, salicylic acid, tannic acid, gallic acid, vanillic acid and caffeic acid.

3. The preparation method according to claim 1, characterized in that: The water bath ultrasonic conditions are 100-400w, 10-60Hz, 30-60℃ water bath treatment for 1-2h.

4. The preparation method according to claim 1, characterized in that: The drying temperature is 40-60° C. for 4-8 hours.

5. A natural aromatic polycarboxylic acid assembly prepared according to any one of the preparation methods of claims 1-4.

6. Use of the natural aromatic polycarboxylic acid assembly according to claim 5 as a foaming agent in the preparation of unsaturated polyester resin molding materials.

7. A method for preparing an unsaturated polyester resin thermal insulation molding material, characterized in that: The method comprises the following steps: mixing and kneading the natural aromatic polycarboxylic acid assembly as claimed in claim 5 and a resin matrix containing unsaturated polyester resin to obtain an unsaturated polyester resin molding material preform, and then subjecting the preform to a hot pressing process to prepare an unsaturated polyester resin thermal insulation molding material.

8. The preparation method according to claim 7, characterized in that: The mass ratio of the natural aromatic polycarboxylic acid assembly to the resin matrix containing the unsaturated polyester resin is (0.5-2):

1.

9. The preparation method according to claim 7, characterized in that: The hot pressing process is 220-260° C., 10-20 MPa, and pressing for 5-20 minutes.

10. An unsaturated polyester resin thermal insulation molding material prepared according to the preparation method according to any one of claims 7 to 9.

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