Low-odor unsaturated polyester resin and preparation method thereof

Abstract

The invention discloses a low-odor unsaturated polyester resin and a preparation method thereof, and the low-odor unsaturated polyester resin comprises the following components in parts by weight: 45-55 parts of an unsaturated polyester resin base polymer, 10-30 parts of low-viscosity resin, 1-5 parts of a diluent monomer styrene or 10-30 parts of an acrylate active diluent monomer, 0.5-0.7 part of a polymerization inhibitor p-hydroxyanisole, 0.4-0.6 part of an accelerant and 1-2 parts of an initiator, wherein the low-viscosity resin is selected from at least one of amino acrylate resin or polyester acrylate resin. The method has the advantages that by introducing the low-viscosity resin, the use amount and volatilization of styrene can be reduced, and the mechanical property of the resin can be maintained or improved.

Description

Technical Field

[0001] This invention relates to the field of polymer materials technology, and in particular to a low-odor unsaturated polyester resin and its preparation method. Background Technology

[0002] Unsaturated polyester resins (UPR) possess excellent mechanical, electrical, and chemical resistance properties, and are easy to process, making them one of the most widely used coating resins. They are typically linear polymers with unsaturated double bonds, obtained through the thermal polycondensation of saturated / unsaturated diol acids. They exhibit rapid curing, readily available and inexpensive raw materials, excellent mechanical properties, and a wide processing temperature range. Currently, considering material cost, resin storage, molding operations, curing characteristics, and final performance, styrene is the most suitable monomer for unsaturated polyester resins, typically accounting for 40%–50% of the total resin volume. However, styrene has strong volatility and a pungent odor, which can harm human health and the environment, limiting its application in enclosed spaces or environments with high environmental requirements. Furthermore, the volatilization of styrene can lead to a decrease in the mechanical properties of the resin, such as increased brittleness and reduced tensile strength.

[0003] Huang Xinhui et al. addressed the issue of styrene volatility in unsaturated polyester resins (UPRs) by adding organomontmorillonite (OMMT) to UPRs to suppress styrene volatilization, thereby preparing UPRs with low styrene volatilization. However, this method only suppresses styrene volatilization and does not reduce the amount of styrene used.

[0004] Liu Qingguo et al. designed and synthesized two low-volatility, low-toxicity macromonomers, namely acrylated epoxidized soybean oil (HAESO) and urethane acrylate (HEA-MDI), to replace styrene as a crosslinking component. However, the macromonomers used in this method have high viscosity, and some of their mechanical properties are slightly lower than those of traditional UPE / St resins.

[0005] Chinese patent CN105566577A, entitled "A Method for Preparing a Styrene-Free, Low-Volatile Unsaturated Polyester Resin," describes a method for preparing an unsaturated polyester by adding acrylate monomers to replace styrene. This method effectively reduces the use of styrene, but it does not offer significant advantages in mechanical properties.

[0006] These methods often fail to maintain or improve the mechanical properties of the resin while reducing the amount of styrene used. Summary of the Invention

[0007] The purpose of this invention is to provide a low-odor unsaturated polyester resin and its preparation method. By introducing a low-viscosity resin, the amount of styrene used and its volatility can be reduced, while maintaining or improving the mechanical properties of the resin.

[0008] The above-mentioned technical objective of the present invention is achieved through the following technical solution: A low-odor unsaturated polyester resin, by weight, comprises the following components: 45-55 parts of unsaturated polyester resin base polymer, 10-30 parts of low-viscosity resin, 1-5 parts of styrene or 10-30 parts of acrylate reactive diluent monomer, 0.5-0.7 parts of polymerization inhibitor p-hydroxyanisole, 0.4-0.6 parts of accelerator, and 1-2 parts of initiator, wherein the low-viscosity resin is selected from at least one of amino acrylate resin or polyester acrylate resin.

[0009] Preferably, the unsaturated polyester resin base polymer comprises, by weight, the following components: 150 parts of diacid, 80 parts of diol, 1 part of p-toluenesulfonic acid catalyst, and 0.5 parts of BHT antioxidant.

[0010] Preferably, the dicarboxylic acid includes unsaturated dicarboxylic acids and saturated dicarboxylic acids. The unsaturated dicarboxylic acid is selected from maleic anhydride or fumaric acid, and the unsaturated dicarboxylic acid accounts for 30% to 60% of the total weight of the dicarboxylic acids. The saturated dicarboxylic acid is selected from picric acid, phthalic anhydride, or isophthalic acid. The diol is selected from neopentyl glycol, ethylene glycol, diethylene glycol, or methylpropanediol.

[0011] Preferably, the accelerator is selected from cobalt naphthenate or cobalt isooctanoate.

[0012] Preferably, the initiator is selected from benzoyl peroxide or methyl ethyl ketone peroxide.

[0013] Preferably, the amino acrylate resin is a modified amino resin of HEA, HPA, HEMA or HPMA, with a viscosity of 200~400 mPa·s.

[0014] Preferably, the viscosity of the polyester acrylate resin is 200~450 mPa·s, and the functionality is 2~4.

[0015] Preferably, the acrylate reactive diluent monomer is selected from isobornyl methacrylate or hexanediol diacrylate.

[0016] A method for preparing a low-odor unsaturated polyester resin includes the following steps: S1, add dicarboxylic acid, diol, catalyst and antioxidant to the reactor, gradually raise the temperature to 175~185℃ under nitrogen protection and hold for 1 hour, then slowly raise the temperature to 210~230℃ and hold for 2~3 hours, during which the distillation temperature is kept ≤105℃. After the material is completely transparent, continue to hold for 1 hour. After the esterification reaction is completed, the acid value of the reactants is measured. When the measured acid value meets the conditions, vacuum and cooling are performed respectively to obtain unsaturated polyester resin base polymer. S2, cool the unsaturated polyester resin base polymer to 70~90℃, then add low viscosity resin and stir evenly; S3, add styrene or other acrylate reactive diluent monomers to adjust the viscosity of the resin to a suitable range; S4, after adding the polymerization inhibitor, the temperature is reduced to 70~80℃, and after stirring evenly for 30 minutes, the material is discharged to obtain liquid low-odor unsaturated polyester resin. S5, mix liquid low-odor unsaturated polyester resin with accelerator and initiator, and cure at 70~90℃ for 6~10h to obtain low-odor unsaturated polyester resin cured product.

[0017] Preferably, in step S1, the acid value during vacuuming is ≤60mg / g, the acid value during cooling is ≤30mg / g, and the temperature is cooled to 150℃.

[0018] In summary, the present invention has the following beneficial effects: 1. This invention effectively replaces part of the styrene by introducing low-viscosity amino acrylate resin or polyester acrylate resin, significantly reducing the VOC content and irritating odor of the resin; at the same time, by reducing the use of styrene, it reduces the harm to the environment and operators during production and use, and complies with the requirements of current environmental protection regulations.

[0019] 2. Low-viscosity amino acrylate resins and polyester acrylate resins have good compatibility and reactivity, and can form a dense cross-linked network with unsaturated polyesters, thereby maintaining or even improving the mechanical properties of the product; at the same time, they help to reduce the overall viscosity of the resin system, improve its flowability and processing performance, and are suitable for a variety of molding processes. Detailed Implementation

[0020] The specific embodiments of the present invention will be further described below. These embodiments do not constitute a limitation on the present invention.

[0021] A low-odor unsaturated polyester resin, comprising the following components by weight: The composition includes 45-55 parts of unsaturated polyester resin base polymer, 10-30 parts of low viscosity resin, 1-5 parts of styrene or 10-30 parts of acrylate reactive diluent monomer, 0.5-0.7 parts of polymerization inhibitor p-hydroxyanisole, 0.4-0.6 parts of accelerator, and 1-2 parts of initiator, wherein the low viscosity resin is selected from at least one of amino acrylate resin or polyester acrylate resin.

[0022] The unsaturated polyester resin base polymer comprises, by weight, the following components: 150 parts of diacid, 80 parts of diol, 1 part of catalyst p-toluenesulfonic acid, and 0.5 parts of antioxidant BHT.

[0023] Dicarboxylic acids include unsaturated and saturated dicarboxylic acids. The unsaturated dicarboxylic acid is selected from maleic anhydride or fumaric acid, and the unsaturated dicarboxylic acid accounts for 30% to 60% of the total weight of the dicarboxylic acid. The saturated dicarboxylic acid is selected from picric acid, phthalic anhydride, or isophthalic acid. The diol is selected from neopentyl glycol, ethylene glycol, diethylene glycol, or methylpropanediol.

[0024] The accelerator is selected from cobalt naphthenate or cobalt isooctanoate.

[0025] The initiator is selected from benzoyl peroxide or methyl ethyl ketone peroxide.

[0026] The amino acrylate resin is a modified amino resin of HEA, HPA, HEMA or HPMA, with a viscosity of 200~400 mPa·s.

[0027] The viscosity of polyester acrylate resin is 200~450 mPa·s, and the functionality is 2~4.

[0028] The acrylate reactive diluent monomer is selected from either isobornyl methacrylate or hexanediol diacrylate.

[0029] A method for preparing a low-odor unsaturated polyester resin includes the following steps: S1, add dicarboxylic acid, diol, catalyst and antioxidant to the reactor, gradually raise the temperature to 175~185℃ under nitrogen protection and hold for 1 hour, then slowly raise the temperature to 210~230℃ and hold for 2~3 hours, during which the distillation temperature is kept ≤105℃. After the material is completely transparent, continue to hold for 1 hour. After the esterification reaction is completed, the acid value of the reactants is measured. When the measured acid value meets the conditions, vacuum and cooling are performed respectively to obtain unsaturated polyester resin base polymer. S2, cool the unsaturated polyester resin base polymer to 70~90℃, then add low viscosity resin and stir evenly; S3, add styrene or other acrylate reactive diluent monomers to adjust the viscosity of the resin to a suitable range; S4, after adding the polymerization inhibitor, the temperature is reduced to 70~80℃, and after stirring evenly for 30 minutes, the material is discharged to obtain liquid low-odor unsaturated polyester resin. S5, mix liquid low-odor unsaturated polyester resin with accelerator and initiator, and cure at 70~90℃ for 6~10h to obtain low-odor unsaturated polyester resin cured product.

[0030] In step S1, the acid value during vacuuming must be ≤60mg / g, the acid value during cooling must be ≤30mg / g, and the temperature must be lowered to 150℃.

[0031] Synthesis of low-viscosity amino acrylate resin: 40 parts HEMA, 60 parts amino resin and 0.1 parts of polymerization inhibitor p-hydroxyanisole were added to a reactor, heated to 80~100℃ under nitrogen protection, reacted for 6h, and when the viscosity was measured to be 100~150mPa·s, the temperature was reduced to 60℃ and the material was discharged.

[0032] Synthesis of low-viscosity polyester acrylate resin: 70 parts of trimethylolpropane, 30 parts of hexamethylenetetramol, and 60 parts of maleic anhydride were added to a reactor. Under nitrogen protection, the temperature was gradually increased to 210~230℃ for esterification until the acid value was ≤10mg / g. After cooling to 80℃, acrylic acid was added, and the temperature was increased to 120℃ under nitrogen protection for reflux dehydration to carry out the esterification reaction until the acid value was ≤5mg / g. After cooling, a pale yellow resin with a viscosity of 200~450mPa·s was obtained.

[0033] Example 1 Unsaturated polyester resin base polymer: 100 parts adipic acid, 50 parts maleic anhydride, 80 parts ethylene glycol, 1 part p-toluenesulfonic acid and 0.5 parts BHT are added to a reaction vessel, heated to 140℃ under nitrogen protection, and esterification reaction is carried out until the acid value drops to ≤30mg / g.

[0034] Low-odor unsaturated polyester resin: Cool the unsaturated polyester resin base polymer to 80°C, add 35 parts of low-viscosity amino acrylate resin, add 0.53 parts of polymerization inhibitor p-hydroxyanisole (MEHQ), add 5 parts of styrene, stir evenly and discharge to obtain liquid low-odor unsaturated polyester resin.

[0035] Example 2 Unsaturated polyester resin base polymer: 100 parts adipic acid, 50 parts maleic anhydride, 80 parts ethylene glycol, 1 part p-toluenesulfonic acid and 0.5 parts BHT are added to a reaction vessel, and the mixture is heated to 140℃ under nitrogen protection to carry out esterification reaction until the acid value drops to ≤30mg / g.

[0036] Low-odor unsaturated polyester resin: Cool the unsaturated polyester resin base polymer to 80°C, add 35 parts of low-viscosity polyester acrylate resin, add 0.53 parts of polymerization inhibitor p-hydroxyanisole (MEHQ), add 5 parts of styrene, stir evenly and discharge to obtain liquid low-odor unsaturated polyester resin.

[0037] Example 3 Unsaturated polyester resin base polymer: Preparation of unsaturated polyester resin: 100 parts isophthalic acid, 50 parts maleic anhydride, 80 parts ethylene glycol, 1 part p-toluenesulfonic acid and 0.5 parts BHT are added to a reaction vessel, and the temperature is raised to 140℃ under nitrogen protection to carry out esterification reaction until the acid value drops to ≤30mg / g.

[0038] Low-odor unsaturated polyester resin: The unsaturated polyester resin base polymer is cooled to 80°C, 40 parts of low-viscosity amino acrylate resin are added, 0.6 parts of polymerization inhibitor p-hydroxyanisole (MEHQ) are added, and 25 parts of isobornyl methacrylate (IBOMA) are added. After stirring evenly, the product is discharged to obtain liquid low-odor unsaturated polyester resin.

[0039] Example 4 Unsaturated polyester resin base polymer: Preparation of unsaturated polyester resin: 100 parts isophthalic acid, 50 parts maleic anhydride, 80 parts ethylene glycol, 1 part p-toluenesulfonic acid and 0.5 parts BHT are added to a reaction vessel, and the temperature is raised to 140℃ under nitrogen protection to carry out esterification reaction until the acid value drops to ≤30mg / g.

[0040] Low-odor unsaturated polyester resin: The unsaturated polyester resin base polymer is cooled to 80°C, 40 parts of low-viscosity polyester acrylate resin are added, 0.6 parts of polymerization inhibitor p-hydroxyanisole (MEHQ) are added, and 25 parts of isobornyl methacrylate (IBOMA) are added. After stirring evenly, the product is discharged to obtain liquid low-odor unsaturated polyester resin.

[0041] Comparative Example 1 Weigh 100 parts of the unsaturated polyester resin base polymer prepared by the method of Example 1, add 60 parts of styrene as a diluent, 0.3 parts of cobalt naphthenate as a promoter, and 0.1 parts of p-hydroxyanisole (MEHQ) as a polymerization inhibitor, and mechanically stir at room temperature to mix evenly to obtain a conventional unsaturated polyester resin sample.

[0042] Preparation of unsaturated polyester resin cured samples: Take the liquid low-odor unsaturated polyester resins prepared in quantitative Examples 1-4 and Comparative Example 1 into a graduated cylinder, add 0.5 parts of cobalt isooctanoate and 2 parts of methyl ethyl ketone peroxide in sequence, stir mechanically for 1 min, and then put it into a vacuum tank to remove bubbles for 30 min. Pour the mixture after removing bubbles by vacuuming into a glass mold, cure at room temperature for 3 h, and then cure in an oven at 80℃ for 8 h to form the product.

[0043] The obtained mold was tested, and the relevant performance data are shown in Table 1 below. Table 1: Comparison of relevant performance data between Examples 1-2 with added styrene, Examples 3-4 without styrene, and comparative examples.

[0044] As shown in Table 1, the mechanical properties (tensile / flexural / impact strength) of all low-odor resins are superior to those of the traditional formulations, demonstrating that low-viscosity amino / polyester acrylate resins can effectively replace styrene and enhance crosslinking density. Examples 1-2 containing styrene exhibit the best performance, while Examples 3-4 without styrene show higher strength than the traditional resins.

[0045] To investigate whether the amount of volatile organic compounds (VOCs) in the synthesized low-odor unsaturated polyester resin was significantly reduced, Table 2 was obtained by monitoring the curing process of the synthetic resin.

[0046] Table 2: Detection Results of Volatile Organic Compounds (VOCs) in Resin

[0047] Table 2 shows that the VOC emission reduction effect is significant, with the total VOC of the styrene-free formulation (Examples 3-4) as low as 35-38 mg / m³. 3 It is only 6.7% to 7.3% of that of traditional resins. The total VOC of the formulation containing 5% styrene (Examples 1-2) is controlled at 70-76 mg / m³. 3 Compared to traditional resins, the odor level is reduced by more than 85%. All low-odor resins are rated at 1.0 to 1.2 (nearly odorless), which is far superior to the 3.5 rating of traditional resins (significantly irritating).

[0048] In summary, the low-odor modified unsaturated polyesters prepared in the various embodiments of the present invention exhibit better mechanical properties than those in Comparative Example 1. While maintaining or enhancing mechanical properties, they reduce VOC emissions, and the liquid resin parameters also meet market application standards.

[0049] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art can make various modifications or equivalent substitutions to the present invention within the scope of its essence and protection. Such modifications or equivalent substitutions should also be considered to fall within the protection scope of the present invention.

Claims

1. A low odor unsaturated polyester resin characterized in that, By weight parts, including the following components: unsaturated polyester resin base polymer 45~55 parts, low viscosity resin 10~30 parts, dilute monomer is styrene 1~5 parts or acrylate active diluent monomer 10~30 parts, polymerization inhibitor p-hydroxyanisole 0.5~0.7 parts, promoter 0.4~0.6 parts, initiator 1~2 parts, wherein the low viscosity resin is selected from at least one of amino acrylate resin or polyester acrylate resin.

2. A low odor unsaturated polyester resin according to claim 1, characterized in that: The unsaturated polyester resin base polymer includes the following components by weight parts: diacid 150 parts, diol 80 parts, catalyst p-toluenesulfonic acid 1 part, antioxidant BHT 0.5 parts.

3. A low odor unsaturated polyester resin according to claim 2, characterized in that: The diacid includes unsaturated diacid and saturated diacid, the unsaturated diacid is selected from one of maleic anhydride or fumaric acid, the unsaturated diacid accounts for 30%~60% of the total weight of diacid, the saturated diacid is selected from one of adipic acid, phthalic anhydride, isophthalic acid, and the diol is selected from one of neopentyl glycol, ethylene glycol, diethylene glycol or methyl propylene glycol.

4. The low odor unsaturated polyester resin of claim 1, wherein: The promoter is selected from one of cobalt naphthenate or isooctanoic acid.

5. The low odor unsaturated polyester resin according to claim 1, wherein: The initiator is selected from one of benzoyl peroxide or methyl ethyl ketone peroxide.

6. A low odor unsaturated polyester resin according to claim 1, characterized in that: The amino acrylate resin is a modified amino resin of HEA, HPA, HEMA or HPMA, and the viscosity is 200~400 mPa·s.

7. A low odor unsaturated polyester resin according to claim 1, characterized in that: The viscosity of the polyester acrylate resin is 200~450 mPa·s, and the functionality is 2~4.

8. A low odor unsaturated polyester resin according to claim 1, characterized in that: The acrylate active diluent monomer is selected from one of isobornyl methacrylate or hexanediol diacrylate.

9. A method for preparing a low-odor unsaturated polyester resin according to any one of claims 1 to 8, characterized in that: The method comprises the following steps: S1, the diacid, diol, catalyst and antioxidant are added to the reaction kettle, and gradually heated to 175~185℃ under nitrogen protection for 1h, then slowly heated to 210~230℃, and kept for 2~3h, during which the distillation temperature is kept ≤105℃, after the material is completely transparent, continue to keep for 1h, and then measure the acid value of the reaction product after the esterification reaction is completed, when the acid value meets the condition, vacuum and cooling are carried out respectively to obtain the unsaturated polyester resin base polymer; S2, the unsaturated polyester resin base polymer is cooled to 70~90℃, then the low viscosity resin is added, and stirred uniformly; S3, the styrene or other acrylate active diluent monomer is added, and the viscosity of the resin is adjusted to the appropriate range; S4, after the polymerization inhibitor is added, the temperature is reduced to 70~80℃, stirred uniformly for 30min, and then discharged to obtain the liquid low odor unsaturated polyester resin; S5, the liquid low odor unsaturated polyester resin is mixed with the promoter and initiator, and cured at 70~90℃ for 6~10h to obtain the low odor unsaturated polyester resin cured product.

10. The method for preparing a low-odor unsaturated polyester resin according to claim 1, characterized in that: The acid value of the step S1 vacuum meets the condition of ≤60mg / g, and the acid value of the cooling meets the condition of ≤30mg / g, and the temperature is cooled to 150℃.

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