A PVC composition and a method for producing the same

Abstract

The application discloses a PVC composition and a preparation method thereof, and belongs to the technical field of high polymer materials. The product uses organic maleimide derivatives and thiol methyl tin to be compounded with inorganic titanium white powder as a thermal stability component. The product can significantly improve the thermal stability, can still maintain low discoloration under a processing environment of up to 190 DEG C, and can maintain a high level of the Vicat softening point. The torque rheology reaches a standard, and the comprehensive processing performance is excellent.

Description

Technical Field

[0001] This invention relates to the field of polymer materials technology, specifically to a PVC composition and its preparation method. Background Technology

[0002] While PVC (polyvinyl chloride) possesses numerous advantages such as lightweight, high strength, and low price, its thermal stability is poor. At processing temperatures above 100°C, its decomposition efficiency significantly increases. Besides affecting mechanical properties, the most significant impact is the occurrence of noticeable irreversible discoloration, severely limiting the application range of the product. To address this, heat-stabilizing additives, such as silicone heat stabilizers, are added to the PVC matrix resin to create composite materials. However, these heat stabilizers offer limited improvement in the product's appearance stability, especially when used or processed at temperatures above 150°C, where heat retention discoloration becomes severe. Furthermore, due to compatibility issues, the Vicat softening point of these composite materials is significantly reduced, lowering the suitable processing temperature and even leading to failure to meet torque rheological standards (generally required to be within 15%), increasing processing difficulty and even making processing impossible. Summary of the Invention

[0003] Based on the deficiencies of the existing technology, the purpose of this invention is to provide a PVC composition in which an organic maleimide derivative and a methyltin mercaptan compounded with inorganic titanium dioxide are used as heat-stabilizing components. This not only significantly improves the thermal stability of the product, but also maintains low discoloration even in processing environments up to 190°C. At the same time, the Vicat softening point of the product can also be maintained at a high level, resulting in excellent overall processing performance.

[0004] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0005] A PVC composition comprising the following components in parts by weight:

[0006] 100 parts PVC resin, 3-5 parts toughening agent, 1-3 parts methyltin mercaptan, 0.051-0.3 parts maleimide derivative, 0.2-0.5 parts titanium dioxide, and 0.4-1 parts antioxidant.

[0007] In existing plastic composite materials, to improve the thermal stability of products, some organic heat stabilizers that react with PVC resin and passivate active groups are introduced, or inorganic particles with good intrinsic thermal stability are used as heat stabilizers as functional compound components. However, this approach has very limited effect on PVC resin products. The main reason is that the number of defective structures (tert-butyl chloride, allyl chloride, etc.) in PVC resin molecules is greater than that in other plastic molecules such as polypropylene, and the thermal decomposition temperature is low. At processing temperatures above 150°C, injection molding will cause obvious color changes, not to mention the subsequent use effect. Furthermore, due to compatibility issues, many heat stabilizers will significantly weaken the processing performance of the product, especially the Vicat softening point and torque rheology, which significantly increases the processing difficulty when the product is used to process some such as electronic appliance shells or packaging boxes. Therefore, in this invention, to ensure that PVC resin maintains good appearance and color stability during processing or residence at at least 150°C while guaranteeing high mechanical properties, methyl tin mercaptan is used as the main heat stabilizer. Compared to other types of heat stabilizers, this component can effectively inhibit the decomposition of PVC resin under high-temperature conditions, quickly capture free radicals and peroxides in the matrix components, and does not weaken the mechanical properties of the product, thus ensuring both heat processing stability and performance. However, methyl tin mercaptan alone has very limited effect on improving the thermal stability of the product. In this invention, it is necessary to combine it with a certain amount of maleimide derivatives and titanium dioxide for synergistic effect. The two can work together with methyl tin mercaptan to significantly enhance the ability of the heat stabilizing agent to capture easily oxidized / decomposed structural groups in the resin in both physical adsorption and chemical reaction dimensions. Furthermore, the latter can also improve the whiteness of the product to a certain extent and mask the yellowing effect. At the same time, with the combination of the three, the compatibility between the components and the resin is good, and the Vicat softening point of the product is not reduced. If the three components are missing or arbitrarily replaced with other common heat stabilizers for plastic products, or if too many components are added, not only will the color stability of the product be not guaranteed, but the Vicat softening point of the product will also be lowered, the torque rheology will not meet the standards, and the processing difficulty will increase.

[0008] Preferably, the PVC composition contains ≥85% by mass of PVC resin.

[0009] More preferably, the PVC composition contains ≥90% by mass of PVC resin.

[0010] In the technical solution of this invention, the product can achieve excellent thermal stability and processing performance when the matrix resin content is as high as 90% or more, without having to consider the application limitations of existing products based on high doses of functional additives, and is highly practical.

[0011] Preferably, in the PVC composition, the toughening agent is in the range of 3 parts, 4 parts, 4.5 parts, 5 parts by weight, or any two of these; the methyltin mercaptan is in the range of 1 part, 1.5 parts, 2 parts, 2.5 parts, 3 parts by weight, or any two of these; the maleimide derivative is in the range of 0.05 parts, 0.1 parts, 0.2 parts, 0.25 parts, 0.3 parts by weight, or any two of these; the titanium dioxide is in the range of 0.2 parts, 0.25 parts, 0.3 parts, 0.4 parts, 0.5 parts by weight, or any two of these; and the antioxidant is in the range of 0.4 parts, 0.6 parts, 0.7 parts, 0.8 parts, 1 part by weight, or any two of these.

[0012] Preferably, the thiol methyltin includes at least one of coordinated thiol methyltin and non-coordinated thiol methyltin.

[0013] Preferably, the thiol methyltin is a coordinated thiol methyltin.

[0014] Preferably, the thiol methyltin comprises (CH3)3Sn2(SCH2COOC8H 17 5. CH3Sn(SCH2COOC8H) 17 3、(CH3)2Sn(SCH2COOC8H 17 At least one of 2.

[0015] The molecular weight of methyl tin mercaptan varies depending on whether it has a coordination configuration. In the PVC composition of the present invention, when a coordination methyl tin mercaptan with a larger molecular weight is selected, the product has better appearance and color stability under heat retention conditions.

[0016] Preferably, the apparent density of the PVC resin according to GB / T20022-2005 is 0.47 to 0.54 g / mL.

[0017] Preferably, the average degree of polymerization of the PVC resin is 400 to 1050.

[0018] More preferably, the average degree of polymerization of the PVC resin is a range of one or both of 400, 500, 600, 700, 800, and 1050.

[0019] More preferably, the average degree of polymerization of the PVC resin is 500 to 800.

[0020] Due to the different average degree of polymerization of PVC resin matrix, the compatibility and processing dispersibility of the product with heat-stabilizing functional additives also vary. When PVC resin within the above range is preferred, the product can not only ensure a higher Vicat softening point, but also has better thermal stability.

[0021] Preferably, the average degree of polymerization of the PVC resin is determined according to the GB / T 5761-2018 standard.

[0022] Preferably, the maleimide derivative includes at least one of N-substituted maleimide, alkyl-substituted maleimide, and phenyl-substituted maleimide.

[0023] More preferably, the maleimide derivative includes N-phenyl-substituted maleimides.

[0024] More preferably, the N-phenyl-substituted maleimide includes at least one of N-phenylmaleimide and N,N'-(4,4'-methylenediphenyl)bismaleimide.

[0025] In the product described in this invention, the maleimide derivative needs to be used in combination with thiol-type organotin and titanium dioxide. In this system, maleimide derivatives with N-phenyl substituents have better effects and the prepared product has better overall performance.

[0026] Preferably, the titanium dioxide has an average particle size of 2–5 μm.

[0027] The average particle size of the titanium dioxide was confirmed by direct testing with a laser particle size analyzer.

[0028] Preferably, the toughening agent includes at least one of methyl methacrylate-acrylate copolymer, acrylonitrile-butyl acrylate-styrene terpolymer, and chlorinated polyethylene.

[0029] Based on the requirements of mechanical properties, those skilled in the art can select appropriate toughening agents for use according to the actual situation. As long as it does not affect the normal function of the key components with thermal stability improvement function in the product of the present invention, it will not be significantly affected.

[0030] Preferably, the PVC composition further includes 1 to 2 parts of processing aids.

[0031] Preferably, the processing aid includes at least one of a lubricant, an antistatic agent, and a flame retardant.

[0032] It should be noted that, without compromising the technical effect of the product described in this invention, those skilled in the art may introduce suitable processing aids into the product according to actual needs. In addition to the types described above in this invention, other components such as dispersants and preservatives may also be introduced to enhance the product's antistatic, anti-corrosion, and flame-retardant effects. The technical solution of this invention does not impose exclusive restrictions on processing aids.

[0033] Preferably, the antioxidant is at least one of hindered phenolic antioxidants and phosphite antioxidants.

[0034] More preferably, the antioxidant is a mixture of hindered phenolic antioxidants and phosphite antioxidants in a mass ratio of (1-2):1.

[0035] Preferably, the lubricant is at least one of polyethylene wax and stearic acid.

[0036] It should be noted that the selection of antioxidants and lubricants described in this invention is only a preferred choice. In actual production and use, the PVC composition of this invention may select more suitable antioxidants and lubricants according to actual needs, and is not limited to the preferred types described in this invention.

[0037] Another object of the present invention is to provide a method for preparing the PVC composition, comprising the following steps:

[0038] The components other than the toughening agent are heated to 90-100°C and mixed evenly. Then the toughening agent is added and mixed evenly. After cooling to 75-80°C, the mixture is placed in a screw extruder for melt extrusion and granulation to obtain the PVC composition.

[0039] Preferably, the temperature during melt extrusion granulation is 100–180°C.

[0040] The preparation method of the PVC composition described in this invention has simple operation steps and can achieve industrial-scale production.

[0041] Another object of the present invention is to provide the use of the PVC composition in the manufacture of electronic and electrical appliance housings.

[0042] Another object of the present invention is to provide an electronic or electrical enclosure comprising the PVC composition described herein.

[0043] The PVC composition of this invention has extremely high thermal stability. It can maintain good appearance and color stability even after processing activities such as injection molding at temperatures above 150°C. At the same time, the Vicat softening point of the product can reach a high level, and the torque rheology is suitable. It is very suitable for electronic and electrical housings that need to be processed in high-temperature environments and have high requirements for appearance stability.

[0044] The beneficial effects of the present invention are that it provides a PVC composition in which an organic maleimide derivative and a thiol methyltin compounded with inorganic titanium dioxide are used as heat-stabilizing components. This not only significantly improves the thermal stability of the product, but also maintains low discoloration even in processing environments up to 190°C. At the same time, the Vicat softening point of the product can be maintained at a high level, the torque rheology meets the standards, and the overall processing performance is excellent. Detailed Implementation

[0045] To better illustrate the purpose, technical solution, and advantages of this invention, the invention will be further described below with reference to specific embodiments and comparative examples. The purpose of this description is to provide a detailed understanding of the invention, not to limit its scope. All other embodiments obtained by those skilled in the art without inventive effort are within the protection scope of this invention. Unless otherwise specified, the experimental reagents and instruments involved in the implementation of this invention are commonly used reagents and instruments.

[0046] Examples 1-12

[0047] An embodiment of the PVC composition and its preparation method described in this invention is shown in Table 1.

[0048] The components other than the toughening agent are heated to 90-100°C and mixed evenly. Then the toughening agent is added and mixed evenly. After cooling to 75-80°C, the mixture is placed in a twin-screw extruder for melt extrusion granulation to obtain the PVC composition.

[0049] During the melt blending extrusion of the components, the temperature zones of the twin-screw extruder are set as follows: Zone 1: 100℃, Zone 2: 150℃, Zone 3: 165℃, Zone 4: 165℃, Zone 5: 165℃, Zone 6: 165℃, Zone 7: 165℃, Zone 8: 165℃, Zone 9: 160℃. The screw speed is 150 rpm, and the screw length-to-diameter ratio is 40:1.

[0050] Comparative Examples 1-11

[0051] The only difference between each comparative example and the embodiment is the type and ratio of components, as shown in Table 2.

[0052] In the components described in each embodiment and comparative example,

[0053] The PVC resin 1 is PVC S-50 produced by Formosa Plastics, with an average degree of polymerization of 500.

[0054] The PVC resin 2 is PVC S-60 produced by Formosa Plastics, with an average degree of polymerization of 800.

[0055] The PVC resin 3 is PVC P400 produced by Xinjiang Zhongtai Chemical, with an average degree of polymerization of 400.

[0056] The PVC resin 4 is PVC S-65M produced by Formosa Plastics, with an average degree of polymerization of 1050.

[0057] The toughening agent 1 is PARALOID KM-355P, a methyl methacrylate-acrylate copolymer, produced by Rohm and Haas Chemical.

[0058] The toughening agent 2 is Kane Ace B-564, a methyl methacrylate-butadiene-styrene terpolymer manufactured by Kaneka Corporation of Japan.

[0059] The thiol methyltin 1 is a coordinated thiol methyltin prepared according to Example 1 of CN101768184B specification, (CH3)3Sn2(SCH2COOC8H 17 5;

[0060] The methyltin thiol 2 is SW977 produced by Hubei Benxing, a non-coordinated methyltin thiol, CH3Sn(SCH2COOC8H 17 )3;

[0061] The thiol methyltin 3 is YT181 produced by Yunnan Tin Industry, a non-coordinated thiol methyltin, CH3Sn(SCH2COOC8H 17 )3 and (CH3)2Sn(SCH2COOC8H 17 A mixture of 2;

[0062] The maleic acid-type methyltin is DX-650 produced by Jianhua Dongxu.

[0063] The calcium-zinc stabilizer is QY-307K5 produced by Guangdong Xinda.

[0064] The maleimide derivative 1 is N-phenylmaleimide produced by Suzhou Haofan Biotechnology Co., Ltd.

[0065] The maleimide derivative 2 is N,N'-(4,4'-methylenediphenyl)bismaleimide produced by Suzhou Haofan Biotechnology Co., Ltd.

[0066] The maleimide derivative 3 is cyclohexylmaleimide produced by Suzhou Haofan Biotechnology Co., Ltd.

[0067] The silicone resin is MB50-002 manufactured by Dow Corning.

[0068] The maleic anhydride-type polymer heat-resistant modifier is SMA725 produced by Jiaxing Huawen Chemical.

[0069] The titanium dioxide is TIKON 33 produced by TRONOX, with an average particle size of 2.7 μm;

[0070] The antioxidant is a commercially available hindered phenolic antioxidant and phosphite antioxidant: antioxidant 1010 and antioxidant 627A are compounded in a mass ratio of 2:1;

[0071] The lubricant is commercially available oxidized polyethylene wax.

[0072] Unless otherwise specified, all components and raw materials used in the embodiments and comparative examples of this invention are commercially available, and the same type of components and raw materials are used in each parallel experiment.

[0073] Table 1

[0074]

[0075]

[0076] Table 2

[0077]

[0078] To verify the performance of the product described in this invention, the products prepared in each embodiment and comparative example were subjected to the following performance tests, the specific steps of which are as follows:

[0079] (1) Heat retention color difference test: Standard color swatches of each product were injection molded at 190℃. The L1, a1, and b1 values ​​were measured using a colorimeter. Simultaneously, parallel samples were plasticized in the injection molding machine and heat-retained at 190℃ for 5 minutes. Three color swatches were continuously injection molded. The L2, a2, and b2 values ​​of the third color swatch were measured, and the color difference was calculated with the normally injection molded color swatches: DE=[(L2-L1)] 2 +(a2-a1) 2 +(b2-b1) 2 ] 1 / 2

[0080] (2) Vicat softening point: according to GB / T 1633-2000B 120 Legal test.

[0081] (3) Torque rheological properties: Each product was added to a HAAKE Polylab OS torque rheometer for mixing at a temperature of 190℃, a speed of 60 rpm, and a mixing time of 30 min. The minimum torque during the mixing process was recorded as M0, and the torque at the end of the mixing process was recorded as M1. The change in torque was calculated using the following formula: DM = (M1 - M0) / M0 * 100%. A larger change in torque indicates more cross-linking in the later stages, which leads to a more significant deterioration in the processing performance of the system.

[0082] The test results are shown in Tables 3 and 4.

[0083] Table 3

[0084]

[0085] Table 4

[0086]

[0087] As shown in Tables 3 and 4, the product of this invention has excellent processing performance. After the heat retention test, the color difference value before and after the product can be maintained within 5.5, and the Vicat softening point can reach above 72°C. The torque change DM can be maintained within 15%, and the torque rheology meets the standard. The overall processing performance is excellent. This is mainly due to the synergistic effect of the organic maleimide derivative and the inorganic titanium dioxide compounded with thiol methyl tin in the product as heat-stabilizing components.

[0088] In contrast, Comparative Example 1 and Comparative Example 2 lacked maleimide derivative and methyltin mercaptan, respectively. It can be seen that the color difference values ​​of both after the heat retention test were greater than those of the example products, and the Vicat softening point of Comparative Example 2 was less than 70°C. On the other hand, if these two substances were replaced with conventional PVC heat stabilizers, as shown in Comparative Examples 4 and 5 and Comparative Examples 8 and 9, although the Vicat softening points of the products were higher, they still could not meet the requirements for appearance stability and torque rheological properties. Furthermore, titanium dioxide is also indispensable in the products. As shown in Comparative Example 7, without the masking effect and synergistic effect of titanium dioxide, the color difference of the product after heat retention still failed to meet the standards.

[0089] Based on the product performance data from Examples 1, 4-5, and Comparative Example 3, it can be seen that as the content of methyltin thiol increases, the appearance stability of the product significantly improves. However, the Vicat softening point of the product decreases accordingly. If too much is added, as shown in Comparative Example 3, the Vicat softening point of the product drops to 70.3℃, failing to meet the acceptable requirements. Furthermore, as shown in Examples 11-12, when the addition amount is constant, selecting coordinated methyltin thiol can achieve better thermal retention stability, resulting in lower color difference values ​​and a lower torque variation (DM).

[0090] On the other hand, as can be seen from Examples 1, 13 and 14, when selecting maleimide derivatives, N-phenyl-substituted maleimides are preferred, which can further improve the appearance stability of the product under hot working conditions when the Vicat softening point is relatively stable. However, maleimide derivatives cannot be introduced in large quantities. As shown in Comparative Example 6, even if the final addition amount is only 1 part, the torque change DM of the product reaches 38.7%, the torque rheology does not meet the standard, and the processing is difficult.

[0091] As can be seen from the products in Examples 1 and 8-10, the degree of polymerization of the matrix resin PVC in the product also affects the processing performance of the product. When a PVC resin with a moderate degree of polymerization is selected, the thermal retention stability and Vicat softening point of the product can be higher.

[0092] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A PVC composition, characterized in that, The PVC composition comprises the following components by weight: PVC resin 100 parts, toughening agent 3-5 parts, thiol methyl tin 1-3 parts, maleimide derivative 0.05-0.3 parts, titanium white powder 0.2-0.5 parts, antioxidant 0.4-1 part; the average polymerization degree of the PVC resin is 500-800.

2. The PVC composition according to claim 1, wherein, The thiol methyl tin comprises at least one of coordination type thiol methyl tin and non-coordination type thiol methyl tin.

3. The PVC composition according to claim 1, wherein, at least one of (CH3)3Sn2(SCH2COOC8H 17 )5, CH3Sn(SCH2COOC8H 17 )3, and (CH3)2Sn(SCH2COOC8H 17 )2.

4. The PVC composition according to claim 1, wherein, The maleimide derivative comprises at least one of N-substituted maleimide, alkyl-substituted maleimide and phenyl-substituted maleimide.

5. The PVC composition according to claim 1, wherein, The average particle size of the titanium white powder is 2-5 μm.

6. The PVC composition according to claim 1, wherein, The toughening agent comprises at least one of methyl methacrylate-acrylic ester copolymer, acrylonitrile-butyl acrylate-styrene terpolymer and chlorinated polyethylene.

7. The PVC composition according to claim 1, wherein, The components of the PVC composition further comprise processing aid 1-2 parts.

8. The PVC composition according to claim 7, wherein, The processing aid comprises at least one of lubricant, antistatic agent and flame retardant.

9. The process for the preparation of PVC composition as claimed in claim 1, wherein, The method comprises the following steps: other components except the toughening agent are heated to 90-100 ℃ and mixed uniformly, then the toughening agent is added and mixed uniformly, and after cooling to 75-80 ℃, it is put into a screw extruder for melt extrusion granulation, thus obtaining the PVC composition.

10. An electronic appliance housing, characterized by comprising: The PVC composition comprises the PVC composition according to any one of claims 1-8.

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