High-transparency modified unsaturated polyester and preparation method thereof

Abstract

The preparation method specifically comprises the following steps: (1) first-step material feeding: adding isophthalic acid, propylene glycol, ethylene glycol and diethylene glycol into a reaction kettle, starting stirring and heating, after the materials are molten, gradually heating and reacting, taking reactants and measuring the acid value, and then adding a catalyst and a catalyst into the reaction kettle; when the measured acid value meets the condition, cooling to obtain primary ester; (2) second-step feeding: adding epoxy resin, PCDL, adipic acid, maleic anhydride and methylpropanediol into the primary ester obtained in the step (1), continuously heating and reacting, measuring the acid value of a reactant after the reaction is completed, and respectively vacuumizing and cooling when the measured acid value meets the condition; and (3) adding a polymerization inhibitor, continuously carrying out cooling reaction, mixing the reactant in the reaction kettle with an active monomer, controlling the temperature, stirring, cooling, and discharging. The invention has the advantages that the compatibility of the system is improved, and the light transmittance of the cured resin is improved on the premise of not influencing the mechanical properties.

Description

Technical Field

[0001] The invention relates to the technical field of polymer synthetic resin modification, in particular to a highly transparent modified unsaturated polyester and a preparation method thereof. Background Art

[0002] Unsaturated polyester (UPR) is one of the most widely used coating resins. It is usually a linear polymer compound with unsaturated double bonds obtained by heating and polycondensing saturated / unsaturated diol acids. It has a fast curing rate, easy-to-obtain raw materials, low price, good chemical corrosion resistance, excellent mechanical properties and a wide processing temperature range. However, when it is cured, the shrinkage rate of the paint film is large, the hardness and adhesion are poor, and the transparency of the coating film is general, which limits its further application. The performance control of the cured product is usually achieved by adjusting the monomer type and introducing a variety of oligomers, but the transparency is slightly improved.

[0003] Photovoltaic power generation technology realizes the conversion of light energy into electrical energy, improves energy utilization efficiency, and has great application value. Therefore, improving the light utilization rate of photovoltaic panels and extending their service life naturally become the focus of research and are also the application goals of this modification.

[0004] Zhao Chenjing et al. used diphenyl hexafluorophosphate as an initiator and introduced the F element to mix epoxy resin and unsaturated polyester in different proportions to prepare a free radical-cationic photocuring system. The mechanical properties of the product were indeed improved, but the transparency of the coating was not analyzed in depth, and the coating was cured by ultraviolet light, which is slightly different from the room temperature curing method.

[0005] Shi Yongfang and others also constructed a series of UPR-EP interconducting polymer networks (IPNs) to study the compatibility and interaction between the two. As for the study of its high transparency, the commonly used method is to add nanomaterials or construct organic-inorganic hybrid networks, but this undoubtedly increases the complexity of the preparation process and increases the cost.

[0006] The above methods all introduce epoxy resin structure into the unsaturated polyester molecular chain, but the focus of investigation is different. They neither focus on the exploration of the transparency of resin curing nor have economic benefits, etc. Summary of the invention

[0007] The purpose of the present invention is to provide a highly transparent modified unsaturated polyester and a preparation method thereof, by introducing epoxy resin and PCDL into a macromolecular chain to form an organic interpenetrating network system, thereby improving the compatibility of the system, and increasing the light transmittance of the resin cured product without affecting the mechanical properties, thereby meeting the application requirements of highly transparent photovoltaic protective resins.

[0008] The above technical objectives of the present invention are achieved through the following technical solutions:

[0009] A highly transparent modified unsaturated polyester, characterized in that the general structural formula of the highly transparent modified unsaturated polyester is:

[0010]

[0011] In the general formula, R 1 for R 2 for The range of x is 482 to 530.

[0012] A method for preparing highly transparent modified unsaturated polyester, characterized in that it specifically comprises the following steps:

[0013] (1) In the first step, isophthalic acid, propylene glycol, ethylene glycol and diethylene glycol are added to a reaction kettle, stirring is started and the temperature is increased. After the materials are melted, the temperature is gradually increased and then reacted. The reactants are taken to measure the acid value. When the measured acid value meets the conditions, the temperature is lowered to obtain a primary ester.

[0014] (2) In the second step, epoxy resin, PCDL, adipic acid, maleic anhydride and methyl propylene glycol are added to the primary ester obtained in step (1), and the temperature is continued to be raised to react. After the reaction is completed, the acid value of the reactant is measured. When the acid value meets the conditions, vacuum is evacuated and the temperature is lowered;

[0015] (3) After adding the polymerization inhibitor, the temperature is continued to decrease and the reaction is continued, and then the reactants in the reactor are mixed with the active monomers, the temperature is controlled and stirred, and then the material is discharged after the temperature is decreased to obtain a highly transparent modified unsaturated polyester.

[0016] Preferably, the added raw materials of the highly transparent modified unsaturated polyester are as follows in parts by mass: 222.5 parts of isophthalic acid, 146.25 parts of maleic anhydride, 144-149 parts of propylene glycol, 36.5-38 parts of ethylene glycol, 23-24 parts of diethylene glycol, 35.5-37 parts of methyl propanediol, 18.51 parts of adipic acid, 18.51 parts of PCDL, 18.5-43 parts of epoxy resin, 260 parts of active monomers, and 0.1 parts of inhibitor.

[0017] Preferably, the active monomer is styrene.

[0018] Preferably, the polymerization inhibitor is hydroquinone.

[0019] Preferably, the gradual heating in step (1) is specifically as follows: heating to 175-185°C for 1 hour of heat preservation, and then slowly heating to 200-210°C, during which the distillation temperature is maintained at ≤105°C, and after the material is completely transparent, the temperature is continued to be kept for 1 hour.

[0020] Preferably, in step (1), the acid value satisfies the condition of ≤5 mgKOH / g, and the temperature is cooled to 100°C.

[0021] Preferably, the temperature-raising reaction in step (2) is specifically to raise the temperature to 200-210° C. and keep the temperature for 2-3 hours.

[0022] Preferably, in the step (2), the acid value during vacuuming satisfies the condition of ≤60 mgKOH / g, the acid value during cooling satisfies the condition of ≤40 mgKOH / g, and the temperature is cooled to 150°C.

[0023] Preferably, after adding the polymerization inhibitor in step (3), the temperature is reduced to 100°C, the stirring temperature is 70-80°C, the stirring time is 30 minutes, and the discharge temperature is reduced to below 60°C.

[0024] In summary, the present invention has the following beneficial effects:

[0025] 1. The present invention adopts a two-step method to feed materials, utilizes PCDL to improve the flexibility of its molecular chain and grafts epoxy resin onto the long chain of unsaturated polyester, so that the heat resistance, weather resistance and mechanical properties of the prepared unsaturated polyester-epoxy resin composite network system are significantly improved. The introduction of epoxy resin makes the system cross-linking density larger, so it has better thermal stability and weather resistance. At the same time, hydroxyl, epoxy group and ether bond act on the molecular chain and free radicals, thereby improving the mechanical properties of the resin cured product.

[0026] 2. The present invention controls the molar ratio of alcohol to acid in the system to make the esterification reaction of alcohol hydroxyl more complete, and then uses a two-step method to introduce PCDL into the polyester chain. The PCDL structure acts as a soft block, which changes the structure and arrangement of the molecular chain, thereby significantly improving the flexibility of the polyester molecular chain, reducing the viscosity of the system, and solving the problem of high viscosity of the unsaturated polyester system.

[0027] 3. Compared with the single-component unsaturated polyester, the unsaturated polyester-epoxy resin composite network system prepared by the present invention improves the transparency of the resin cured product by the introduction of epoxy resin. The tightly connected molecular chains and double cross-linked structure of the UPR-EP system make the surface of the cured product smooth and the texture clear and regular, reducing the scattering of the incident light. The surface of the unsaturated polyester-epoxy resin cured product is smoother and smoother, and the transmittance at the same wavelength is better than that of UPR resin, which meets the application requirements of photovoltaic protective resin. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 The infrared spectra of the unsaturated polyester resins of Example 3 and Comparative Example 1 are shown;

[0029] Figure 2The SEM images of the unsaturated polyester resin cured products of Example 3 and Comparative Example 1;

[0030] Figure 3 Graph showing the transmittance of the unsaturated polyester resins of Example 3 and Comparative Example 1. DETAILED DESCRIPTION

[0031] The specific implementation manner of the present invention is further described below in conjunction with the accompanying drawings, and this embodiment does not constitute a limitation of the present invention.

[0032] A highly transparent modified unsaturated polyester, the general structural formula is:

[0033]

[0034] In the general formula, R 1 for R 2 for The range of x is 482 to 530.

[0035] A method for preparing a highly transparent modified unsaturated polyester comprises the following steps:

[0036] (1) The first step is to add isophthalic acid, propylene glycol, ethylene glycol and diethylene glycol into a reaction kettle, start stirring and heat up. After the materials are melted, the temperature is gradually raised to 175-185°C for insulation reaction for 1 hour, and then slowly raised to 200-210°C. During this period, the distillation temperature is maintained at ≤105°C. After the materials are completely transparent, they are kept warm for 1 hour. The reactants are taken to determine the acid value. When the acid value meets the condition of ≤5 mgKOH / g, the temperature is lowered to 100°C to obtain the primary ester.

[0037] (2) In the second step, epoxy resin, PCDL, adipic acid, maleic anhydride and methyl propylene glycol are added to the primary ester obtained in step (1), and the temperature is continuously raised to 200-210° C. and kept at this temperature for 2-3 hours. After the reaction is completed, the acid value of the reactant is measured. When the acid value is ≤60 mgKOH / g, vacuum operation is performed. When the acid value is ≤40 mgKOH / g, the temperature is lowered to 150° C.

[0038] (3) After adding the polymerization inhibitor, the temperature is continued to be lowered to 100°C for reaction, and then the reactants in the reactor are mixed and stirred with the active monomers, and the stirring temperature is controlled to be 70-80°C for 30 minutes. The temperature is then lowered to below 60°C and the material is discharged to obtain a highly transparent modified unsaturated polyester.

[0039] The added raw materials are in parts by mass: 222.5 parts of isophthalic acid, 146.25 parts of maleic anhydride, 144-149 parts of propylene glycol, 36.5-38 parts of ethylene glycol, 23-24 parts of diethylene glycol, 35.5-37 parts of methyl propanediol, 18.51 parts of adipic acid, 18.51 parts of PCDL, 18.5-43 parts of epoxy resin, 260 parts of active monomer styrene, and 0.1 part of inhibitor hydroquinone.

[0040] Example 1

[0041] The raw materials for preparing highly transparent modified unsaturated polyester resin include the following components by mass: 222.5 parts of isophthalic acid, 146.25 parts of maleic anhydride, 144 parts of propylene glycol, 36.5 parts of ethylene glycol, 23 parts of diethylene glycol, 35.5 parts of methyl propanediol, 18.51 parts of adipic acid, 18.51 parts of PCDL, 30.5 parts of epoxy resin, 260 parts of active monomers, and 0.1 parts of inhibitor.

[0042] Embodiment 2:

[0043] The raw materials for preparing highly transparent modified unsaturated polyester resin include the following components by mass: 222.5 parts of isophthalic acid, 146.25 parts of maleic anhydride, 147 parts of propylene glycol, 37.5 parts of ethylene glycol, 23.5 parts of diethylene glycol, 36 parts of methyl propanediol, 18.51 parts of adipic acid, 18.51 parts of PCDL, 30.5 parts of epoxy resin, 260 parts of active monomers, and 0.1 parts of inhibitor.

[0044] Embodiment 3:

[0045] The raw materials for preparing highly transparent modified unsaturated polyester resin include the following components by mass: 222.5 parts of isophthalic acid, 146.25 parts of maleic anhydride, 149 parts of propylene glycol, 38 parts of ethylene glycol, 24 parts of diethylene glycol, 37 parts of methyl propanediol, 18.51 parts of adipic acid, 18.51 parts of PCDL, 30.5 parts of epoxy resin, 260 parts of active monomers, and 0.1 parts of inhibitor.

[0046] Embodiment 4:

[0047] The raw materials for preparing highly transparent modified unsaturated polyester resin include the following components by mass: 222.5 parts of isophthalic acid, 146.25 parts of maleic anhydride, 149.36 parts of propylene glycol, 38 parts of ethylene glycol, 23.6 parts of diethylene glycol, 36.25 parts of methyl propanediol, 18.51 parts of adipic acid, 18.51 parts of PCDL, 30 parts of epoxy resin, 260 parts of active monomers, and 0.1 parts of inhibitor.

[0048] Embodiment 5:

[0049] The raw materials for preparing highly transparent modified unsaturated polyester resin include the following components by mass: 222.5 parts of isophthalic acid, 146.25 parts of maleic anhydride, 149.36 parts of propylene glycol, 38 parts of ethylene glycol, 23.6 parts of diethylene glycol, 36.25 parts of methyl propanediol, 18.51 parts of adipic acid, 18.51 parts of PCDL, 43 parts of epoxy resin, 260 parts of active monomers, and 0.1 parts of inhibitor.

[0050] Comparative Example 1:

[0051] No epoxy resin or PCDL was added, and the amounts of other substances added and the operating steps were the same as in Example 3.

[0052] The unsaturated polyester resins prepared in Example 3 and Comparative Example 1 were subjected to infrared testing and analysis. The infrared spectra are shown in FIG. Figure 1 shown.

[0053] Depend on Figure 1 It can be seen that 3030cm -1 The stretching vibration peak of the OH bond in the hydroxyl group is 1641 cm -1 It is the characteristic absorption peak of carbon-carbon double bond, indicating that the double bond has been successfully introduced into the resin molecular chain. -1 The stretching vibration peak of the CH bond is 1735 cm -1 The stretching vibration peak of -CO- is strong and sharp. -1 The stretching vibration absorption peak of COC after esterification is 701cm. At this time, the acid and alcohol in the reaction system have reacted and introduced the ester group into the resin molecular chain. -1 It is the stretching vibration absorption peak of the CH bond on the benzene ring, which is the isophthalic substitution on the unsaturated hydrocarbon. In summary, the reaction has synthesized isophthalic unsaturated polyester, and the unsaturated polyester-epoxy resin has two special absorption peaks compared with the unsaturated polyester, 916cm -1 、1247cm -1 The peaks are the asymmetric stretching vibration peak of the epoxy group and the symmetric stretching absorption peak of the epoxy group. Therefore, it is proved that the epoxy resin has also been successfully introduced into the unsaturated polyester molecular chain to obtain the final product.

[0054] Performance Testing:

[0055] The preparation route of the unsaturated polyester resin cured sample is as follows:

[0056] (1) Weigh the unsaturated polyester resins prepared in Examples 1 to 5 and Comparative Example 1 into a measuring cylinder, add 2% cobalt isooctanoate-cyclohexanone peroxide curing agent in order, stir mechanically for 1 minute, and then put into a vacuum barrel to drain bubbles for 30 minutes;

[0057] (2) The mixture from which bubbles have been removed by vacuuming is poured into a glass mold, cured at room temperature for 3 hours, and then cured in an oven at 80° C. for 6 to 10 hours to form a mold.

[0058] Figure 2 The SEM images of the unsaturated polyester resin cured products prepared in Example 3 and Comparative Example 1 are shown in FIG. Figure 2 It can be seen that the surface of the epoxy-modified cured product is smooth and has a clear and regular texture, while the surface of the pure unsaturated polyester is rough and the particle clusters are disordered. This is attributed to the tightly connected molecular chains and double cross-linked structure of the unsaturated polyester-epoxy resin system, and the presence of free small molecules in the single-component unsaturated polyester. Therefore, when the incident light enters the surface of the cured coating, the smooth structure reduces the scattering of light inside and enhances the light transmittance.

[0059] like Figure 3 As shown, Figure 3 The light transmittance curves of the unsaturated polyester resin cured products prepared in Example 3 and Comparative Example 1 are shown. The transmittance data of the two samples at the same wavelength were tested by an ultraviolet spectrophotometer. The transmittance of the unsaturated polyester-epoxy resin (UPR-EP) system cured product is significantly better than that of the single-component unsaturated polyester (UPR), and the overall transmittance is maintained above 80%, and can reach up to 90%, which is sufficient to prove its excellent transparency.

[0060] The transmittance test results of the cured products of Example 3 and Comparative Example 1 are shown in Table 1 below.

[0061] Table 1 Transmittance of cured products of Example 3 and Comparative Example 1

[0062] Sample Example 3 Comparative Example 1 Transmittance % 90.3 86.3

[0063] It can be seen from Table 1 that the transmittance of Example 3 after high transparency modification is much higher than that of the unmodified Comparative Example 1, which meets the application requirements of photovoltaic panel coatings and has high economic benefits.

[0064] The performance results of the resins and their cured products of each embodiment and comparative embodiment 1 are shown in Table 2 below:

[0065] Table 2 Performance test data of resin and its cured product in each embodiment and comparative example 1

[0066]

[0067] It can be seen from Table 2 that, compared with the performance of the cured product of Comparative Example 1, the highly transparent modified unsaturated polyester prepared in each embodiment of the present invention has better mechanical properties than that of Comparative Example 1, and the liquid resin parameters also meet the market application standards.

[0068] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art may make various modifications or equivalent substitutions to the present invention within the essence and protection scope of the present invention, and such modifications or equivalent substitutions should also be deemed to fall within the protection scope of the technical solution of the present invention.

Claims

1. A highly transparent modified unsaturated polyester, characterized in that: The general structural formula of the highly transparent modified unsaturated polyester is: In the general formula, R1 is R2 is The range of x is 482 to 530.

2. A method for preparing a highly transparent modified unsaturated polyester, characterized in that: The specific steps include: (1) In the first step, isophthalic acid, propylene glycol, ethylene glycol and diethylene glycol are added to a reaction kettle, stirring is started and the temperature is increased. After the materials are melted, the temperature is gradually increased and then reacted. The reactants are taken to measure the acid value. When the measured acid value meets the conditions, the temperature is lowered to obtain a primary ester. (2) In the second step, epoxy resin, PCDL, adipic acid, maleic anhydride and methyl propylene glycol are added to the primary ester obtained in step (1), and the temperature is continued to be raised to react. After the reaction is completed, the acid value of the reactant is measured. When the acid value meets the conditions, vacuum is evacuated and the temperature is lowered; (3) After adding the polymerization inhibitor, the temperature is continued to decrease and the reaction is continued, and then the reactants in the reactor are mixed with the active monomers, the temperature is controlled and stirred, and then the material is discharged after the temperature is decreased to obtain a highly transparent modified unsaturated polyester.

3. The method for preparing a highly transparent modified unsaturated polyester according to claim 2, characterized in that: The added raw materials of the highly transparent modified unsaturated polyester are as follows in parts by mass: 222.5 parts of isophthalic acid, 146.25 parts of maleic anhydride, 144-149 parts of propylene glycol, 36.5-38 parts of ethylene glycol, 23-24 parts of diethylene glycol, 35.5-37 parts of methyl propanediol, 18.51 parts of adipic acid, 18.51 parts of PCDL, 18.5-43 parts of epoxy resin, 260 parts of active monomers, and 0.1 part of polymerization inhibitor.

4. The method for preparing a highly transparent modified unsaturated polyester according to claim 2, characterized in that: The active monomer is styrene.

5. The method for preparing a highly transparent modified unsaturated polyester according to claim 2, characterized in that: The polymerization inhibitor is hydroquinone.

6. The method for preparing a highly transparent modified unsaturated polyester according to claim 2, characterized in that: The gradual heating in step (1) is specifically as follows: heating to 175-185° C. and keeping the temperature for 1 hour, then slowly heating to 200-210° C., during which the distillation temperature is kept ≤105° C., and after the material is completely transparent, keeping the temperature for 1 hour.

7. The method for preparing a highly transparent modified unsaturated polyester according to claim 2, characterized in that: In the step (1), the acid value satisfies the condition of ≤5 mgKOH / g, and the temperature is lowered to 100°C.

8. The method for preparing a highly transparent modified unsaturated polyester according to claim 2, characterized in that: The temperature-raising reaction in step (2) is specifically to raise the temperature to 200-210° C. and keep the temperature for 2-3 hours.

9. The method for preparing a highly transparent modified unsaturated polyester according to claim 2, characterized in that: In the step (2), the acid value during vacuuming satisfies the condition of ≤60 mgKOH / g, the acid value during cooling satisfies the condition of ≤40 mgKOH / g, and the temperature is cooled to 150°C.

10. The method for preparing a highly transparent modified unsaturated polyester according to claim 2, characterized in that: After adding the polymerization inhibitor in step (3), the temperature is reduced to 100° C., the stirring temperature is 70-80° C., the stirring time is 30 min, and the discharge temperature is reduced to below 60° C.

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