Modified PC material with good weather resistance and preparation method thereof

Abstract

The invention discloses a modified PC material with good weather resistance and a preparation method thereof. The modified PC material with good weather resistance is composed of PC resin, a flexibilizer and modified diatomite, and the modified diatomite is prepared from 2, 3-dimethyl-1, 3-butadiene, a modifier and a chain control agent. The preparation method comprises the following steps: mixing the modified diatomite with other PC raw materials, and carrying out melt mixing and extrusion granulation to obtain the modified PC material. Compared with the prior art, the prepared modified PC material has excellent weather resistance, mechanical strength and processability, the compatibility of the inorganic filler and a PC matrix is improved through chemical modification, the overall performance of the material is effectively improved, and the problems that a traditional PC material is prone to aging and strength is reduced when used outdoors are solved.

Description

Technical Field

[0001] The present invention relates to the technical field of PC materials, and in particular to a modified PC material with good weather resistance and a preparation method thereof. Background Art

[0002] Polycarbonate (PC) is a thermoplastic engineering plastic with excellent performance. It is widely used in the fields of automobiles, electronic appliances, construction, and medical treatment due to its excellent transparency, impact resistance, heat resistance, and mechanical strength. However, when used in natural environments, PC materials are easily affected by factors such as ultraviolet rays, temperature changes, and humidity, which leads to a decrease in material performance, such as yellowing and reduced strength, which limits its wide application in outdoor applications.

[0003] At present, in order to improve the weather resistance of PC materials, researchers have adopted a variety of methods, including adding chemical additives such as UV absorbers, light stabilizers, antioxidants, and surface treatment of PC materials by physical or chemical methods. Although these methods have improved the weather resistance of PC materials to a certain extent, there are still some problems, such as the migration and seepage of chemical additives may lead to unstable material performance, and the effect will gradually weaken after long-term use; while physical or chemical surface treatment methods may increase production costs, and the treatment effect is difficult to maintain for a long time.

[0004] In addition, in order to further improve the mechanical properties of PC materials and reduce costs, inorganic fillers are usually added to PC materials. However, the addition of inorganic fillers may affect the processing performance of the material and the surface quality of the final product, and the unmodified inorganic fillers have poor compatibility with the PC matrix, resulting in uneven dispersion, thus affecting the overall performance of the material.

[0005] CN104962056A discloses a high light-shielding PC material and a preparation method thereof, wherein the material formula is composed of the following ingredients: polycarbonate accounts for 65-85%, treated titanium dioxide accounts for 15-35%, silicone oil accounts for 1-3%, toughening agent accounts for 2-5%, lubricant accounts for 0.2-1%, and antioxidant accounts for 0.2-1%. This high light-shielding PC material has a notched impact strength of more than 50KJ / ㎡, a surface hardness (measured by R scale) of more than 110, a light transmittance of 1.0mm thick material is less than 15%, and a heat deformation temperature under a pressure of 1.8MPa is higher than 120°C. This material is considered to be suitable for a variety of applications, including reflective plates of liquid crystal displays and bases of LED lamps, due to its excellent mechanical properties, high impact strength, and excellent light reflection and shielding effects. However, the poor dispersion of titanium dioxide in the PC material prepared by the invention in the resin will still affect the performance of the PC material.

[0006] CN112812517A discloses a chemical-resistant transparent PC material for NCL process and its preparation method. The material is formulated as follows by weight: 15-30 parts of polycarbonate, 10-20 parts of silicon PC powder, 50-60 parts of poly(1,4-cyclohexane dimethanol terephthalate), 0.1-1 parts of ester exchange inhibitor, 0.1-1 parts of anti-yellowing agent, 0.2-1 parts of cross-linking agent, 0.1-0.5 parts of antioxidant, and 0.1-1 parts of lubricant. This material effectively solves the problem of traditional PC materials being chemical-resistant and easy to crack, while improving transparency. However, the mechanical properties of the PC material prepared by this invention are poor. Summary of the invention

[0007] In view of the above-mentioned defects of the prior art, the technical problem to be solved by the present invention is to improve the mechanical properties of the modified PC material with good weather resistance and the service life of the PC material.

[0008] To achieve the above object, the present invention provides a modified PC material with good weather resistance, comprising the following components in parts by weight: 70-90 parts of PC resin, 5-10 parts of toughening agent and 10-30 parts of modified diatomaceous earth, wherein the modified diatomaceous earth is prepared from 2,3-dimethyl-1,3-butadiene, modifier, chain control agent and diatomaceous earth.

[0009] Preferably, the method for preparing the modified diatomite comprises the following steps: S1, mixing 2,3-dimethyl-1,3-butadiene, a chain control agent and a solvent, adding a modifier and an initiator, and heating in an inert gas to obtain a mixture; S2, adding a precipitant to the mixture in step S1, filtering with suction, and drying to obtain a composite; S3, adding the complex in step S2 into a solvent, adding diatomaceous earth, stirring evenly, and drying to obtain modified diatomaceous earth.

[0010] More preferably, the preparation method of the modified diatomite comprises the following steps, in parts by weight: S1. Mix 5-15 parts of 2,3-methyldi-1,3-butadiene, 10-30 parts of chain control agent and 20-50 parts of solvent, add 5-15 parts of modifier and 0.05-2 parts of initiator, and heat in an inert gas to obtain a mixture; S2, adding a precipitant to the mixture in step S1, filtering with suction, and drying to obtain a composite; S3, adding the complex in step S2 to 5-15 parts of solvent, adding 8-15 parts of diatomaceous earth, stirring at 200-500 rpm for 30-50 min, drying at 65-80° C. for 24-30 h, and finally vacuum drying at 50-65° C. for 24-30 h to obtain modified diatomaceous earth.

[0011] Preferably, the modifier is any one of bis(3-trimethoxysilylpropyl)fumarate, 2-acrylic acid, 2-methyl, 2-[(trimethoxysilyl)methyl]-1,3-propylene glycol ester, and nitrogen-(3-methacryloyloxy-2-hydroxypropyl)-3-aminopropyltriethoxysilane.

[0012] More preferably, the modifier is N-(3-methacryloyloxy-2-hydroxypropyl)-3-aminopropyltriethoxysilane.

[0013] Preferably, the chain control agent is 4-cyano-4-[(2-phenylethyl)thio]thioxomethyl]thio]-pentanoic acid.

[0014] Preferably, the precipitant is petroleum ether or cyclopentane.

[0015] Preferably, the initiator is di-tert-butyl peroxide.

[0016] Preferably, the toughening agent is ethylene-vinyl acetate-vinyl trimethoxysilane terpolymer.

[0017] The invention also discloses a method for preparing the modified PC material with good weather resistance.

[0018] The present invention also discloses a method for preparing the modified PC material with good weather resistance, comprising the following steps, calculated in parts by weight: After mixing 70-90 parts of PC resin, 5-10 parts of toughening agent and 10-30 parts of modified diatomaceous earth, the mixture is added to an extruder, and subjected to melt mixing, extrusion and granulation to obtain a modified PC material with good weather resistance.

[0019] In the present invention, when preparing a modified PC material with good weather resistance, diatomaceous earth is added mainly to improve the mechanical strength of the modified PC material, reduce production costs, improve processing performance, and enhance stability. Diatomaceous earth, as a relatively cheap filler, can effectively improve the physical properties of the modified PC material. However, in the process of adding diatomaceous earth, dispersibility problems may be encountered, resulting in inconsistent product performance. The surface of diatomaceous earth is modified by chemical methods to improve compatibility with PC materials, thereby improving the mechanical properties of the modified PC material.

[0020] In the preparation of modified diatomaceous earth, the raw materials and their functions are as follows: The functional groups contained in the modifier include vinyl (C=C) and silane (Si-OR). Vinyl participates in the polymerization reaction to form polymer chains, while silane can react chemically with the surface of diatomaceous earth to form chemical bonds, thereby enhancing the interfacial bonding between the polymer and the filler. These silane groups in the modifier play a role in bridging the rubber matrix and the inorganic filler, thus improving the performance of the composite material.

[0021] The functional groups contained in the chain controller mainly include a thiocarbonylsulfide (C=S) group and a leaving group. In polymerization, the thiocarbonylsulfide group of the chain controller reacts reversibly with the growing free radical chain to form a dormant chain. The leaving group must be able to effectively reinitiate the polymerization reaction and be a good homolytic leaving group. During the polymerization process, the chain controller controls the molecular weight and molecular weight distribution of the polymer through the thiocarbonylsulfide group and the growing polymer chain. The chain controller affects the molecular weight of the polymer, which in turn can affect the mechanical properties of the PC material polymer.

[0022] Beneficial effects of the present invention: 1. Compared with the prior art, the present invention significantly improves the weather resistance of PC materials by introducing specific modified diatomaceous earth. This modified filler not only enhances the mechanical capacity of the material, but also effectively prolongs the service life of the material in outdoor applications, solving the problem of easy aging and performance degradation of traditional PC materials.

[0023] 2. Compared with the prior art, the modifier and chain control agent used in the present invention improve the compatibility and dispersibility of the inorganic filler and the PC matrix, thereby improving the mechanical strength and toughness of the composite material. This improvement not only enhances the tensile and tear resistance of the material, but also improves the overall durability of the material, so that it can maintain stable performance in various application environments. DETAILED DESCRIPTION

[0024] Parameters for specific chemical substances used, sources.

[0025] 4-Cyano-4-[(2-phenylethyl)thio]thioxomethyl]thio]-pentanoic acid, CAS No.: 1351859-46-5.

[0026]

[0027] 2-Propenoic acid,2-methyl-, 2-[(trimethoxysilyl)methyl]-1,3-propanediyl ester (9CI), CAS No.: 138966-64-0.

[0028]

[0029] N-(3-methacryloyloxy-2-hydroxypropyl)-3-aminopropyltriethoxysilane, CAS number: 96132-98-8.

[0030]

[0031] PC resin, model: LS-2020, from Mitsubishi, Japan.

[0032] Diatomaceous earth, 350 mesh.

[0033] Ethylene-vinyl acetate-vinyl trimethoxysilane terpolymer, model: KH-151, is from Hangzhou Jessica Chemical Co., Ltd.

[0034] Example 1 A method for preparing a modified PC material with good weather resistance comprises the following steps: 80 kg PC resin, 8 kg ethylene-vinyl acetate-vinyl trimethoxysilane terpolymer and 20 kg modified diatomaceous earth were mixed at 2000 rpm for 30 min, added to an extruder, melt-mixed, extruded and granulated at 230° C. to obtain the modified PC material with good weather resistance.

[0035] The preparation method of the modified diatomite comprises the following steps: S1, 10 kg of 2,3-methyldi-1,3-butadiene, 20 kg of 4-cyano-4-[(2-phenylethyl)thio]thioxomethyl]thio]-pentanoic acid and 45 kg of dichloromethane were mixed at 300 rpm for 20 min, and then 8 kg of nitrogen-(3-methacryloyloxy-2-hydroxypropyl)-3-aminopropyltriethoxysilane and 0.05 kg of di-tert-butyl peroxide were added, nitrogen was introduced for 25 min, and the mixture was heated to 135 ° C and kept warm for 24 h to obtain a mixture; S2, adding 10 kg of cyclopentane to the mixture in step S1, then precipitating, filtering, and drying at 120° C. for 24 h to obtain a composite; S3, adding the complex in step S2 into 10 kg of dichloromethane, adding 10 kg of diatomaceous earth, stirring at 200 rpm for 30 min, drying at 65° C. for 24 h, and finally vacuum drying at 50° C. for 24 h to obtain modified diatomaceous earth.

[0036] Example 2 The difference between Example 2 of the present application and Example 1 is that the nitrogen-(3-methacryloyloxy-2-hydroxypropyl)-3-aminopropyltriethoxysilane in Example 1 is replaced by bis(3-trimethoxysilylpropyl) fumarate.

[0037] Example 3 The difference between Example 3 of the present application and Example 1 is that the nitrogen-(3-methacryloyloxy-2-hydroxypropyl)-3-aminopropyltriethoxysilane in Example 1 is replaced by 2-acrylic acid, 2-methyl, 2-[(trimethoxysilyl)methyl]-1,3-propanediol ester.

[0038] Comparative Example 1 The difference between Comparative Example 1 of the present application and Example 1 is that the nitrogen-(3-methacryloxy-2-hydroxypropyl)-3-aminopropyltriethoxysilane in Example 1 is replaced by γ-methacryloxypropyltrimethoxysilane.

[0039] Comparative Example 2 The difference between Comparative Example 2 of the present application and Example 1 is that the 4-cyano-4-[(2-phenylethyl)thio]thioxomethyl]thio]-pentanoic acid in Example 1 is replaced by 2-(dodecyl trithiocarbonate)-2-methylpropanoic acid.

[0040] Comparative Example 3 A method for preparing a modified PC material with good weather resistance comprises the following steps: 80 kg PC resin, 8 kg ethylene-vinyl acetate-vinyl trimethoxysilane terpolymer and 20 kg diatomaceous earth were mixed at 2000 rpm for 30 minutes, added to an extruder, melt-mixed, extruded and granulated to obtain the modified PC material with good weather resistance.

[0041] Test Example 1 Test tensile strength: GB / T 528-2009 "Determination of tensile stress-strain properties of vulcanized rubber or thermoplastic rubber" was used to test on a universal material tensile machine at 30°C and a tensile rate of 60mm / min. Five specimens were tested for each sample and the average value was taken.

[0042] Test elongation at break: The test is carried out using the method in GB / T 1040.3-2006 "Determination of tensile properties of plastics Part 3: Test conditions for films and sheets".

[0043] The tear strength refers to the test method of GB / T 16578.1-2008 "Determination of tear resistance of plastic film and sheeting Part 1: Trouser tear method".

[0044] Weather resistance is tested according to GB / T 16422.1-2019 "Plastics Laboratory Light Source Exposure Test Methods Part 1: General Principles", test conditions: 60°C, 90% relative humidity; illumination, 550w / m 2; Time, 120min (102min light exposure, 18min spraying). The evaluation method is to observe the color change of the color plate surface: small color change, good weather resistance; large color change, poor weather resistance. Level 1 means that the color change is very small and has almost no effect on the appearance; Level 2 means that the color change is small and the appearance is slightly affected; Level 3 means that the color change is obvious and the appearance is greatly affected; Level 4 means that the color change is serious and the appearance is greatly affected.

[0045] Table 1 Compared with the test results in Examples 1-3 and Comparative Example 1, it is found that the mechanical properties of the modified PC material with good weather resistance in Example 1 are the best. The possible reason is that different modifiers are used. The modifier can provide functional groups that interact with inorganic fillers, and is introduced into the PC polymer chain through copolymerization, thereby enhancing the interfacial bonding between the PC polymer chain and the inorganic filler. The addition of the modifier can improve the dispersibility and compatibility of the inorganic filler in the rubber matrix, thereby improving the mechanical properties and durability of the composite material. Compared with the modifiers in Examples 1-3 and Comparative Example 1, the modifier in Example 1 contains amino and hydroxyl groups in addition to vinyl monomers and silane groups that react with chain control agents and dienes. The amino and hydroxyl groups can further react with the acid groups contained in the chain control agent or the hydroxyl groups contained in the inorganic filler, thereby increasing the crosslinking degree of the polymer, further enhancing the interfacial bonding between the modified inorganic filler and the PC polymer, and thus improving the mechanical properties of the modified PC material.

[0046] Compared with the test results in Example 1 and Comparative Example 2, it is found that the mechanical properties of the modified PC material in Example 1 are the best. The possible reason is that different chain controllers are used. The role of the chain controller is to act as a chain transfer agent in the polymerization process, control the molecular weight and molecular weight distribution of the PC polymer, and realize active free radical polymerization. The chain controller is reversibly added to the growing polymer chain and then broken, so that the free radical lifetime in the polymerization process is extended, thereby controlling the growth of the polymer chain. The chain controller contains a dithioester and an active group and a leaving group, wherein the active group is responsible for the reactivity of the carbon-sulfur bond to the free radical addition and controls the stability of the intermediate free radical; and the ability to promote active free radical polymerization in the chain controller depends largely on the leaving ability of the leaving group, which is usually related to the pKa value of its conjugate acid. The leaving tendency of the leaving group is inversely proportional to the pKa value, that is, the smaller the pKa value, the easier it is for the leaving group to leave. The leaving ability of the leaving group in the chain control agent in embodiment 1 is very different from the leaving group in comparative example 2, and for 4-cyano-4-[(2-phenylethyl) thio] thiooxymethyl] thio]-pentanoic acid, the leaving group may be a thiocarbonate group (-S-COO-).Thiocarbonates have a good leaving tendency, because the pKa value of their conjugated acid (thiocarbonic acid) is relatively low, so that the thiocarbonate group is easy to leave.And for 2-(dodecyl trithiocarbonate group)-2-methylpropionic acid, the leaving group is a trithiocarbonate group (-S3-COO-).The leaving tendency of trithiocarbonate groups may be similar to thiocarbonates, but due to additional sulfur atoms, may affect its electron density and leaving tendency.The pKa value of the conjugated acid (trithiocarbonic acid) of trithiocarbonates may be different from thiocarbonic acid, and this may affect the leaving tendency of leaving group. Therefore, the modified inorganic filler prepared in Example 1 has better reactivity and higher compatibility with the PC polymer, thus showing better mechanical properties.

[0047] Compared with the test results in the table of Example 1 and Comparative Example 3, it is found that the mechanical properties of the modified PC material in Example 1 are better. The possible reason is that the modified diatomaceous earth has good compatibility with the PC matrix material and can be co-vulcanized, and the silane can form a chemical bond with the inorganic particles. The macromolecular modifier can improve the blending effect of PC material and diatomaceous earth, and provide a better basis for more effectively exerting the synergistic properties of different components. Therefore, the mechanical properties of the modified PC material in Example 1 are better.

[0048] Comparing the weather resistance test results of Examples 1-3, Comparative Examples 1-2 and Comparative Example 3, it is found that the weather resistance of the PC material in Comparative Example 3 is the worst. The possible reason is that the cross-linking degree of the polymer formed by the modified diatomaceous earth and the PC material is increased, the mechanical properties are enhanced, and the stabilizer is good, which can prevent the PC material from decomposing during processing or heating, thereby better maintaining its performance stability and reducing the impact of thermal aging on the weather resistance of the material.

Claims

1. A modified PC material with good weather resistance, characterized in that: The invention comprises the following components in parts by weight: 70-90 parts of PC resin, 5-10 parts of toughening agent and 10-30 parts of modified diatomaceous earth; the modified diatomaceous earth is prepared from 2,3-dimethyl-1,3-butadiene, modifier, chain control agent and diatomaceous earth.

2. The modified PC material with good weather resistance as claimed in claim 1, characterized in that: The preparation method of the modified diatomite comprises the following steps: S1, mixing 2,3-dimethyl-1,3-butadiene, a chain control agent and a solvent, adding a modifier and an initiator, and heating in an inert gas to obtain a mixture; S2, adding a precipitant to the mixture in step S1, filtering with suction, and drying to obtain a composite; S3, adding the complex in step S2 into a solvent, adding diatomaceous earth, stirring evenly, and drying to obtain modified diatomaceous earth.

3. The modified PC material with good weather resistance as claimed in claim 2, characterized in that: The preparation method of the modified diatomite comprises the following steps, measured in parts by weight: S1. Mix 5-15 parts of 2,3-methyldi-1,3-butadiene, 10-30 parts of chain control agent and 20-50 parts of solvent, add 5-15 parts of modifier and 0.05-2 parts of initiator, and heat in an inert gas to obtain a mixture; S2, adding a precipitant to the mixture in step S1, filtering with suction, and drying to obtain a composite; S3, adding the complex in step S2 to 5-15 parts of solvent; adding 8-15 parts of diatomaceous earth, stirring at 200-500 rpm for 30-50 min, drying at 65-80° C. for 24-30 h, and finally vacuum drying at 50-65° C. for 24-30 h to obtain modified diatomaceous earth.

4. The modified PC material with good weather resistance as claimed in claim 1, characterized in that: The modifier is any one of bis(3-trimethoxysilylpropyl)fumarate, 2-acrylic acid, 2-methyl, 2-[(trimethoxysilyl)methyl]-1,3-propylene glycol ester, and nitrogen-(3-methacryloyloxy-2-hydroxypropyl)-3-aminopropyltriethoxysilane.

5. The modified PC material with good weather resistance as claimed in claim 4, characterized in that: The modifier is nitrogen-(3-methacryloyloxy-2-hydroxypropyl)-3-aminopropyltriethoxysilane.

6. The modified PC material with good weather resistance as claimed in claim 1, characterized in that: The chain control agent is 4-cyano-4-[(2-phenylethyl)thio]thioxomethyl]thio]-pentanoic acid.

7. The modified PC material with good weather resistance as claimed in claim 2, characterized in that: The precipitant is petroleum ether or cyclopentane.

8. The modified PC material with good weather resistance as claimed in claim 2, characterized in that: The initiator is di-tert-butyl peroxide.

9. The modified PC material with good weather resistance as claimed in claim 1, characterized in that: The toughening agent is ethylene-vinyl acetate-vinyl trimethoxysilane terpolymer.

10. The method for preparing a modified PC material with good weather resistance according to any one of claims 1 to 9, characterized in that: The method comprises the following steps, in parts by weight: 70-90 parts of PC resin, 5-10 parts of toughening agent and 10-30 parts of modified diatomaceous earth are mixed and added to an extruder, and melt-mixed, extruded and granulated to obtain the modified PC material with good weather resistance.

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