Nano-material-based high-temperature-yellowing-resistant unsaturated polyester resin molding compound and preparation method thereof

Abstract

The invention relates to the field of household appliance plastic packaging materials, in particular to a high-temperature-yellowing-resistant unsaturated polyester resin molding compound based on a nano material and a preparation method of the high-temperature-yellowing-resistant unsaturated polyester resin molding compound. The composition comprises the following components in parts by weight: 60-75 parts of unsaturated polyester resin; 25-40 parts of a low shrinkage agent; 1-3 parts of a nano material; 1-3 parts of an organic antioxidant; 3-5 parts of an internal release agent; 1-2 parts of a curing agent; 280 to 300 parts of a filler; 55 to 65 parts of chopped glass fiber; the high-temperature-yellowing-resistant unsaturated polyester resin molding compound has long-acting high-temperature-yellowing-resistant performance, cerium oxide reacts with phosphite ester at high temperature, P (I) in the phosphite ester has strong reducibility, tetravalent cerium ions in CeO2 have strong oxidizability, a complex containing Ce-P-O bonds is generated, and therefore the molding compound can be used for preparing the high-temperature-yellowing-resistant unsaturated polyester resin molding compound. Compared with single CeO2 or phosphite ester, the compound shows stronger free radical capturing capacity, and alkyl free radicals and alkoxy free radicals can be more effectively quenched; and the capability of decomposing hydroperoxide is far better than that of independent phosphite ester and cerium oxide.

Description

Technical Field

[0001] This invention relates to the field of molding compounds for home appliances, and more particularly to a high-temperature resistant, yellowing-resistant unsaturated polyester resin molding compound based on nanomaterials and its preparation method. Background Technology

[0002] With the continuous development of materials science, new composite materials are constantly emerging. Bulk Molding Compound (BMC), as a high-performance composite material, has demonstrated unique advantages in many fields. Especially in the home appliance industry, BMC possesses excellent processing properties, perfectly meeting the manufacturing needs of home appliance shells of various shapes. Commonly available home appliance shells are made of unsaturated polyester composite materials. This composite material has excellent electrical insulation, high strength, and dimensional stability, but it is extremely prone to oxidation and yellowing, especially at high temperatures, where the oxidation rate is faster and the yellowing edges are more pronounced, severely affecting the appearance of the appliance. Therefore, high standards are required for the performance of its shell materials.

[0003] Early technologies for addressing the problem of oxidative yellowing in molded products typically involved adding antioxidants. These antioxidants often had low molecular weights, strong migration capabilities, and weak solvent extraction resistance, resulting in poor long-term effectiveness. In recent years, medium- to high molecular weight antioxidants have become more prevalent in the market, but their antioxidant performance remains unsatisfactory under prolonged high-temperature conditions. This is because antioxidant migration still affects the antioxidant effect of the molding compound.

[0004] Chinese Patent Publication No. CN102993660B discloses a method for preparing a high-temperature resistant, flame-retardant unsaturated polyester molding compound. This unsaturated polyester molding compound is composed of phthalic unsaturated polyester, a compounded low-shrinkage agent, a curing agent, a polymerization inhibitor, inorganic fillers, a thickener, a flame retardant, a release agent, ground glass fibers, and reinforcing fibers. The resulting unsaturated polyester molding compound has the advantages of high strength, low shrinkage, excellent electrical insulation, and high-temperature resistance. However, its preparation exhibits significant yellowing during high-temperature testing, which does not yet meet the aesthetic requirements for appliance casing materials. Chinese Patent Application Publication No. CN112831169B discloses a high thermal conductivity, high flame-retardant thermosetting bulk molding compound, its preparation method, and applications. This thermosetting bulk molding compound is composed of phthalic unsaturated polyester resin, a low-shrinkage agent, thermally conductive fillers, and reinforcing fibers. Its products possess excellent electrical insulation, low dimensional stability, high thermal conductivity, and flame retardancy. However, its products cannot guarantee long-term resistance to yellowing under prolonged high temperatures, nor can they meet the market's aesthetic requirements for appliance casing materials.

[0005] Therefore, inventing a long-lasting, high-temperature resistant, yellowing-resistant, electrically insulating, and mechanically strong unsaturated polyester molding compound has become an urgent technical problem to be solved. Summary of the Invention

[0006] The purpose of this invention is to address the shortcomings of existing technologies by providing a high-temperature resistant, yellowing-resistant unsaturated polyester resin molding compound based on nanomaterials and its preparation method.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0008] The first aspect of the present invention is to provide a high-temperature resistant, yellowing-resistant unsaturated polyester resin molding compound based on nanomaterials, comprising, by weight:

[0009]

[0010] Preferably, the unsaturated polyester resin is a terephthalic unsaturated polyester resin.

[0011] Preferably, the low-shrinkage agent is a saturated polyester resin type low-shrinkage agent.

[0012] Preferably, the nanomaterial is nano-cerium oxide.

[0013] Preferably, the organic antioxidant is triphenyl phosphite.

[0014] Preferably, the internal release agent is stearate.

[0015] More preferably, the stearate is zinc stearate.

[0016] Preferably, the curing agent is tert-butyl peroxide.

[0017] Preferably, the filler comprises at least one of calcium carbonate, aluminum hydroxide, calcium sulfate, and talc.

[0018] Preferably, the chopped glass fiber is 3mm chopped glass fiber or 6mm chopped glass fiber.

[0019] A second aspect of the present invention is to provide a method for preparing the above-mentioned high-temperature resistant yellowing unsaturated polyester resin molding compound, the steps of which include:

[0020] S1. Weigh out unsaturated polyester resin, low shrinkage agent, nanomaterials, organic antioxidant, internal release agent and curing agent according to the weight parts, add them to the mixing tank in sequence and stir evenly to obtain the first mixture;

[0021] S2. Weigh the filler and chopped glass fiber according to the weight proportions, place the filler in a two-roller kneader, add the first mixture and knead, then add the chopped glass fiber and continue kneading to obtain the second mixture.

[0022] S3. The second mixture is cured and molded using a molding machine to obtain the high-temperature resistant yellowing unsaturated polyester resin molding compound; wherein the molding temperature is 135-145℃ and the molding time is 200s.

[0023] The present invention adopts the above technical solution and has the following technical effects compared with the prior art:

[0024] The high-temperature yellowing resistant unsaturated polyester resin molding compound of this invention possesses long-lasting high-temperature yellowing resistance. This invention imparts thermal oxidation resistance to the unsaturated polyester resin molding compound by selecting a suitable nanomaterial—nano-cerium oxide. The cerium ions on the surface of nano-cerium oxide (CeO2) can reversibly switch between +3 and +4 valence states, forming oxygen vacancy defects, enabling dynamic capture of free radicals and further converting hydroperoxides into stable products such as alcohols / ketones. Simultaneously, nano-cerium oxide can catalyze the decomposition of superoxide anions and singlet oxygen, blocking the initiation of oxidation chain reactions and providing long-lasting thermal oxidation protection for the unsaturated polyester composite material. Nano-sized cerium oxide has a very large specific surface area, exposing more active sites and further enhancing the reversible switching capability between +3 and +4 valence ions.

[0025] When cerium oxide reacts with phosphite at high temperatures, the P(I) in the phosphite has strong reducing properties, while the tetravalent cerium ion in CeO2 has strong oxidizing properties, forming a complex containing Ce-PO bonds. This complex exhibits a stronger free radical scavenging ability than CeO2 or phosphite alone, and can more effectively quench alkyl and alkoxy radicals. Its ability to decompose hydroperoxides also far exceeds that of phosphite and cerium oxide alone. At the same time, the strong coordination between Ce(III) and phosphite can stabilize the active component, preventing its deactivation or migration, and providing long-term antioxidant protection for the product.

[0026] Under high-temperature conditions, the products containing nano-cerium oxide and phosphite exhibit significantly improved resistance to thermal oxidation and yellowing, ensuring that no obvious yellowing occurs on the surface after 168 hours of continuous high-temperature aging in a 160℃ oven. Simultaneously, this molding compound also possesses good electrical insulation and excellent mechanical properties, meeting the performance requirements for appliance casing materials. Detailed Implementation

[0027] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0028] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other.

[0029] The present invention will be further described below with reference to embodiments, but these are not intended to limit the scope of the invention.

[0030] Example 1

[0031] This embodiment provides a method for preparing a high-temperature resistant, yellowing-resistant unsaturated polyester resin molding compound, the steps of which include:

[0032] S1. Weigh 60 parts of terephthalic unsaturated polyester resin, 40 parts of saturated polyester resin low shrinkage agent, 1 part of nano cerium oxide, 1 part of triphenyl phosphite, 3 parts of stearate and 1 part of tert-butyl peroxide according to the weight ratio, add them to the mixing tank in sequence, and stir at 300-500 rpm / min for 10 min to obtain the first mixture.

[0033] S2. Weigh 280 parts of aluminum hydroxide and 55 parts of chopped glass fiber according to the weight ratio. Place the aluminum hydroxide in a two-roller kneader, add the first mixture, knead in the forward direction for 10 minutes, then add the chopped glass fiber, and continue kneading in the forward direction for 10 minutes to obtain the second mixture.

[0034] S3. The second mixture is cured and molded using a molding machine to obtain the high-temperature resistant yellowing unsaturated polyester resin molding compound; wherein the molding temperature is 140℃ and the time is 200s.

[0035] Comparative Example 1

[0036] This comparative example provides a method for preparing unsaturated polyester resin molding compound, the steps of which include:

[0037] (1) By mass: Add 60 parts of terephthalic unsaturated polyester resin, 40 parts of saturated low shrinkage agent, 0.4 parts of triphenyl phosphite, 3 parts of internal release agent and 1 part of curing agent to a dry and clean mixing container, and stir at a speed of 300-500 rpm / min for 10 min to obtain mixture 1;

[0038] (2) Add 280 parts of inorganic filler to a dry and clean double roller kneader. Add the mixture 1 obtained in step (1) to the double roller kneader, turn on the forward rotation and knead for 10 minutes to ensure uniform kneading and obtain mixture 2.

[0039] (3) Add 55 parts of chopped glass fiber to a two-roller kneader containing mixture 2, and continue kneading for 10 minutes to obtain mixture 3;

[0040] (4) The mixture 3 obtained in step (3) is molded in a molding press at 140°C for 200s and cured to obtain an unsaturated polyester molding compound.

[0041] Comparative Example 2

[0042] This comparative example provides a method for preparing unsaturated polyester resin molding compound, the steps of which include:

[0043] (1) By mass: Add 60 parts of terephthalic unsaturated polyester resin, 40 parts of saturated low shrinkage agent, 3 parts of internal release agent and 1 part of curing agent to a dry and clean mixing container, and stir at a speed of 300-500 rpm / min for 10 min to obtain mixture 1;

[0044] (2) Add 280 parts of inorganic filler to a dry and clean double roller kneader. Add the mixture 1 obtained in step (1) to the double roller kneader, turn on the forward rotation and knead for 10 minutes to ensure uniform kneading and obtain mixture 2.

[0045] (3) Add 55 parts of chopped glass fiber to a two-roller kneader containing mixture 2, and continue kneading for 10 minutes to obtain mixture 3;

[0046] (4) The mixture 3 obtained in step (3) is molded in a molding press at 140°C for 200s and cured to obtain an unsaturated polyester molding compound.

[0047] Detection Examples

[0048] The plastics of Example 1 and Comparative Examples 1-2 were subjected to performance tests, including tensile strength test, flexural strength test, impact toughness test, yellowing performance test and insulation resistance test. The results are shown in Table 1.

[0049] Table 1

[0050] Example 1 Comparative Example 1 Comparative Example 2 Tensile strength / MPa ＞30 ＞30 ＞30 Bending strength / MPa ＞90 ＞90 ＞90 Impact toughness / KJ / ㎡ ＞25 ＞25 ＞25 Insulation resistance / Ω <![CDATA[1*10 13 ]]> <![CDATA[1*10 13 ]]> <![CDATA[1*10 13 ]]> Initial yellowing value 0.95 1.16 1.23 24-hour yellowing value 1.09 1.45 6.78 48h yellowing value 1.34 1.50 7.14 72h yellowing value 1.51 5.32 9.47 96h yellowing value 1.57 8.21 10.31 120h yellowing value 1.69 8.74 11.08 144h yellowing value 1.76 9.69 11.72 168h yellowing value 1.85 10.43 12.45

[0051] The above test results show that the long-lasting high-temperature resistant unsaturated polyester molding compound prepared in Example 1 exhibits excellent high-temperature yellowing resistance. Compared with Comparative Examples 1-2, in the 160℃ high-temperature aging test, the yellowing value of the Example 1 sample with added nano-cerium oxide increased slowly, and there was no obvious color change in appearance; the yellowing value of the Comparative Example 1 sample with only added triphenyl phosphite began to increase sharply after 48 hours. At 72 hours, the sample already showed obvious yellowing; while the blank Comparative Example 2 sample easily showed obvious yellowing after 24 hours, and finally became severely yellowed after 168 hours, with a yellowing value as high as 12.45. These experimental data indicate that the present invention effectively solves the problem of yellowing of the outer shell of some household appliances that need to operate at high temperatures for extended periods, affecting the aesthetics of the product. Furthermore, within the reasonable formulation range of the present invention, the prepared unsaturated polyester resin molding compound also possesses good mechanical properties and electrical insulation, making it suitable for manufacturing molding compound components for household appliances.

[0052] The above description is merely a preferred embodiment of the present invention and does not limit the implementation and protection scope of the present invention. Those skilled in the art should realize that any equivalent substitutions and obvious changes made based on the content of this specification should be included within the protection scope of the present invention.

Claims

1. A high-temperature resistant, yellowing-resistant unsaturated polyester resin molding compound based on nanomaterials, characterized in that, By weight, the components include:

2. The high-temperature resistant, yellowing-resistant unsaturated polyester resin molding compound according to claim 1, characterized in that, The unsaturated polyester resin is a terephthalic unsaturated polyester resin.

3. The high-temperature resistant, yellowing-resistant unsaturated polyester resin molding compound according to claim 1, characterized in that, The low-shrinkage agent is a saturated polyester resin type low-shrinkage agent.

4. The high-temperature resistant, yellowing-resistant unsaturated polyester resin molding compound according to claim 1, characterized in that, The nanomaterial is nano-cerium oxide.

5. The high-temperature resistant, yellowing-resistant unsaturated polyester resin molding compound according to claim 1, characterized in that, The organic antioxidant is triphenyl phosphite.

6. The high-temperature resistant, yellowing-resistant unsaturated polyester resin molding compound according to claim 1, characterized in that, The internal release agent is stearate.

7. The high-temperature resistant, yellowing-resistant unsaturated polyester resin molding compound according to claim 1, characterized in that, The curing agent is tert-butyl peroxide.

8. The high-temperature resistant, yellowing-resistant unsaturated polyester resin molding compound according to claim 1, characterized in that, The filler includes at least one of calcium carbonate, aluminum hydroxide, calcium sulfate, and talc.

9. The high-temperature resistant, yellowing-resistant unsaturated polyester resin molding compound according to claim 1, characterized in that, The chopped glass fiber is either 3mm or 6mm chopped glass fiber.

10. A method for preparing a high-temperature resistant, yellowing-resistant unsaturated polyester resin molding compound as described in any one of claims 1-9, characterized in that the step... include: S1. Weigh out unsaturated polyester resin, low shrinkage agent, nanomaterials, organic antioxidant, internal release agent and curing agent according to the weight parts, add them to the mixing tank in sequence and stir evenly to obtain the first mixture; S2. Weigh the filler and chopped glass fiber according to the weight proportions, place the filler in a two-roller kneader, add the first mixture and knead, then add the chopped glass fiber and continue kneading to obtain the second mixture. S3. The second mixture is cured and molded using a molding machine to obtain the high-temperature resistant yellowing unsaturated polyester resin molding compound; wherein the molding temperature is 135-145℃ and the molding time is 200s.

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