PVC composition and preparation method thereof

Abstract

The invention discloses a PVC (polyvinyl chloride) composition and a preparation method thereof, and belongs to the technical field of high polymer materials, the product takes an organic maleimide derivative and methyltin mercaptide compounded inorganic titanium dioxide as a heat stable component, so that the heat stability of the product can be remarkably improved, and the heat stability of the product is improved; the low discoloration performance can still be maintained in the processing environment of 190 DEG C, meanwhile, the vicat softening point of the product can also be maintained at a high level, the torque rheology reaches the standard, and the comprehensive processing performance is excellent.

Description

Technical Field

[0001] The invention relates to the technical field of polymer materials, and in particular to a PVC composition and a preparation method thereof. Background Art

[0002] Although PVC (polyvinyl chloride) has many properties such as light weight, high strength, and low price, its thermal stability is poor. Its decomposition efficiency will be significantly improved at processing temperatures above 100°C. In addition to affecting the mechanical properties, the biggest impact is the obvious irreversible discoloration phenomenon, which greatly affects the expansion of the product's application range. For this reason, people will add a certain amount of heat stabilizing additives to the PVC matrix resin to compound composite materials, such as silicone heat stabilizers, etc. However, these heat stabilizers have a very limited effect on improving the appearance stability of the product, especially when used or processed in an environment above 150°C. The heat retention discoloration is very serious, and due to compatibility issues, the Vicat softening point of these composite materials will also be significantly reduced, the suitable processing temperature will be reduced, and even the torque rheology cannot meet the standard (generally required to be within 15%), and the processing difficulty will increase or even be difficult to process. Summary of the invention

[0003] Based on the defects of the prior art, the purpose of the present invention is to provide a PVC composition, which uses an organic maleimide derivative and methyltin mercaptan combined with inorganic titanium dioxide as a thermal stabilizing component, which can not only significantly improve the thermal stability of the product, but also maintain low discoloration under a processing environment of up to 190°C, and at the same time, the Vicat softening point of the product can also be maintained at a high level, and the comprehensive processing performance is excellent.

[0004] In order to achieve the above object, the technical solution adopted by the present invention is:

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

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

[0007] In order to improve the thermal stability of the products, some organic heat stabilizers that react with PVC resin and passivate active groups, or inorganic particles with good intrinsic thermal stability are introduced as heat stabilizers as functional compound components in existing plastic composite materials. However, such an approach has very limited effect in PVC resin products. The main reason is that the number of defect structures (tert-butyl chloride, allyl chloride, etc.) in PVC resin molecules is greater than that of other plastic molecules such as polypropylene, and the thermal decomposition temperature is low. Injection molding at a processing temperature above 150°C will cause obvious color change, not to mention the subsequent use effect. In addition, 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 makes the product significantly more difficult to process when used in processing some electronic and electrical housings or packaging boxes. For this reason, in the technical solution of the present invention, in order to maintain good appearance color stability for PVC resin processing or retention at a temperature of at least 150°C and ensure a high level of mechanical properties, methyl tin mercaptan is used as the main thermal stabilizer. Compared with other types of thermal stabilizers, this component can effectively inhibit the decomposition behavior of PVC resin under high temperature conditions, quickly capture free radicals and peroxides in the matrix component, and this component will not weaken the mechanical properties of the product, so that the product takes into account both thermal processing stability and performance; however, the improvement of the thermal stability of the product by methyl tin mercaptan alone is very limited. In the product of the present invention, a certain amount of maleimide derivatives and titanium dioxide need to be assisted to work synergistically. The two can cooperate with methyl tin mercaptan to significantly improve the ability of the thermal stabilizing additive component to capture easily oxidized / decomposed structural groups in the resin in two dimensions of physical adsorption and chemical reaction, and the latter can also improve the whiteness of the product to a certain extent, masking the yellowing effect of the product. At the same time, under the coordination of the three, the compatibility between the component and the resin is good, and the Vicat softening point of the product will not be 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 fail to be 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, in the PVC composition, the mass percentage of PVC resin is ≥85%.

[0009] Further preferably, in the PVC composition, the mass percentage of PVC resin is ≥90%.

[0010] In the technical solution of the present invention, the product can achieve excellent thermal stability and processing performance when the base resin content is as high as 90% or more, without considering the application limitations of existing products based on high-dose functional additives, and has strong practicality.

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

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

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

[0014] Preferably, the methyltin mercaptan includes (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 based on whether or not 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 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 polymerization degree of the PVC resin is 400-1050.

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

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

[0020] Based on the different average polymerization degrees of the PVC resin matrix, the compatibility and processing dispersibility of the product with the heat stabilizing functional additive are also different. When the PVC resin within the above range is preferred, the product can not only ensure a higher Vicat softening point, but also have better thermal stability.

[0021] Preferably, the average degree of polymerization of the PVC resin is determined using 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 comprises N-maleimide containing a phenyl substituent.

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

[0025] In the product described in the present invention, the maleimide derivative needs to be used in combination with thiol-type organic tin and titanium dioxide. In this system, the maleimide derivative substituted with N-phenyl substituents has better effects and the prepared product has better comprehensive performance.

[0026] Preferably, the average particle size of the titanium dioxide is 2 to 5 μm.

[0027] The average particle size of the titanium dioxide is directly tested and confirmed by 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 needs of mechanical properties, technicians in this field can select a suitable toughening agent for use according to actual conditions, as long as it does not affect the normal effect of the key components with the function of improving thermal stability in the product of the present invention.

[0030] Preferably, the components of the PVC composition further include 1 to 2 parts of a processing aid.

[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 impairing the technical effects of the products described in the present invention, those skilled in the art can introduce suitable processing aids into the products according to actual needs. In addition to the above-mentioned types described in the present invention, other components such as dispersants and preservatives can also be introduced to enhance the product's antistatic, anti-corrosion, flame retardant and other additional effects. The technical solution of the present invention does not make exclusive limitations on processing aids.

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

[0034] More preferably, the antioxidant is a mixture of a hindered phenol antioxidant and a phosphite antioxidant 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 types of antioxidants and lubricants described in the present invention are only preferred choices. In actual production and use, the PVC composition described in the present invention can select more suitable types of antioxidants and lubricants according to actual needs, and is not limited to the preferred types described in the present invention.

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

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

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

[0040] The preparation method of the PVC composition of the present invention has simple operation steps and can realize industrial-scale production.

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

[0042] Another object of the present invention is to provide an electronic appliance housing comprising the PVC composition of the present invention.

[0043] The PVC composition of the present invention has extremely high thermal stability and can maintain good appearance color stability after injection molding and other processing activities at a processing temperature 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 a high temperature environment and have high requirements for appearance stability.

[0044] The beneficial effect of the present invention is that the present invention provides a PVC composition, which uses an organic maleimide derivative and methyltin mercaptan combined with inorganic titanium dioxide as a thermal stabilizing component, which can not only significantly improve the thermal stability of the product, but also maintain low discoloration under a processing environment of up to 190°C. At the same time, the Vicat softening point of the product can also be maintained at a high level, the torque rheology meets the standard, and the comprehensive processing performance is excellent. DETAILED DESCRIPTION

[0045] In order to better illustrate the purpose, technical solutions and advantages of the present invention, the present invention will be further described below in conjunction with specific embodiments and comparative examples, the purpose of which is to understand the content of the present invention in detail, rather than to limit the present invention. All other embodiments obtained by those of ordinary skill in the art without making creative work premise belong to the protection scope of the present invention. The experimental reagents and instruments involved in the implementation of the present invention, unless otherwise specified, are all commonly used common reagents and instruments.

[0046] Examples 1 to 12

[0047] An embodiment of a PVC composition and a preparation method thereof according to the present invention, the components of the PVC composition are shown in Table 1.

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

[0049] When the components are melt-blended and extruded, the temperature zones of the twin-screw extruder are set to 100°C for zone one, 150°C for zone two, 165°C for zone three, 165°C for zone four, 165°C for zone five, 165°C for zone six, 165°C for zone seven, 165°C for zone eight, and 160°C for zone nine, the screw speed is 150rpm, and the screw aspect ratio is 40:1.

[0050] Comparative Examples 1 to 11

[0051] The difference between the comparative examples and the embodiments is only in the types and proportions of components, as shown in Table 2.

[0052] Among 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 produced by Rohm and Haas Chemical, a methyl methacrylate-acrylate copolymer;

[0058] The toughening agent 2 is Kane Ace B-564 produced by Kanebuchi, Japan, a methyl methacrylate-butadiene-styrene terpolymer;

[0059] The methyl tin mercaptan 1 is a coordination type methyl tin mercaptan prepared according to Example 1 of the specification of CN101768184B, (CH3)3Sn2(SCH2COOC8H 17 )5;

[0060] The methyl tin mercaptanate 2 is SW977 produced by Hubei Benxing, a non-coordinating methyl tin mercaptanate, CH3Sn(SCH2COOC8H 17 )3;

[0061] The methyl tin mercaptan 3 is YT181 produced by Yunnan Tin Industry, a non-coordinating methyl tin mercaptan, CH3Sn(SCH2COOC8H 17 )3 and (CH3)2Sn(SCH2COOC8H 17 )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 produced 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 mixture of commercially available hindered phenol antioxidant and phosphite antioxidant: antioxidant 1010 and antioxidant 627A in a mass ratio of 2:1;

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

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

[0073] Table 1

[0074]

[0075]

[0076] Table 2

[0077]

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

[0079] (1) Thermal retention color difference test: Each product is normally injected with a standard color plate at 190°C, and the L1, a1, and b1 values ​​are tested using a colorimeter. At the same time, parallel samples are plasticized in an injection molding machine, and heat retention is performed at 190°C for 5 minutes. Three mold color plates are continuously injected, and the third color plate is taken to test the L2, a2, and b2 values, and the color difference is calculated with the color plate injected normally: DE = [(L2-L1) 2 +(a2-a1) 2 +(b2-b1) 2 ] 1 / 2

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

[0081] (3) Torque rheological properties: Each product was added to the HAAKE Polylab OS torque rheometer for mixing, the mixing temperature was 190°C, the rotation speed was 60 rpm, and the mixing time was 30 min. The lowest torque value during the mixing process was recorded as M0, and the torque at the end of the mixing was recorded as M1. The change in torque was calculated by the following formula: DM = (M1-M0) / M0*100%. The greater the torque change, the more crosslinking was generated in the later stage, and the more obvious the deterioration of 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] It can be seen from Tables 3 and 4 that the product of the present invention has excellent processing performance. After the heat retention test, the front and back color difference value of 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%, the torque rheology meets the standard, and the comprehensive processing performance is excellent. This is mainly attributed to the organic maleimide derivatives and methyl tin mercaptan compounded with inorganic titanium dioxide in the product as heat stabilizing components to achieve a synergistic effect.

[0088] In contrast, the products of Comparative Example 1 and Comparative Example 2 lack maleimide derivatives and methyltin mercaptide, respectively. It can be seen that the color difference values ​​of both after the heat retention test are greater than those of the example product, and the Vicat softening point of the product of Comparative Example 2 is less than 70°C. On the other hand, if these two substances are replaced with conventional heat stabilizers for PVC, as shown in Comparative Examples 4 and 5 and Comparative Examples 8 and 9, although the Vicat softening point of the product is higher, it still cannot meet the appearance stability effect and torque rheological properties of the product itself. In addition, titanium dioxide in the product is also indispensable. As shown in Comparative Example 7, in the absence of the masking effect and synergistic effect of titanium dioxide, the color difference of the product after heat retention still cannot meet the standard.

[0089] According to the product performance of Example 1, Examples 4-5 and Comparative Example 3, it can be seen that as the introduction content of methyl tin mercaptan increases, the appearance stability of the product is significantly improved, but relatively, the Vicat softening point of the product decreases. If too much is added, as shown in Comparative Example 3, the Vicat softening point of the product decreases to 70.3°C, which cannot meet the passing requirements. According to Examples 11-12, it can be seen that when the addition amount is certain, the selection of coordinated methyl tin mercaptan can achieve better thermal retention stability, the color difference value of the product is lower, and the torque change DM can be maintained at a lower level.

[0090] On the other hand, it can be seen from Examples 1, 13 and 14 that when selecting maleimide derivatives, N-phenyl-substituted maleimide is preferred, which can further improve the appearance stability of the product under a hot processing environment while maintaining a relatively stable Vicat softening point; however, too much maleimide derivative should not be introduced. 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 processing is difficult.

[0091] It can be seen from the products of Examples 1 and 8 to 10 that the degree of polymerization of the base resin PVC in the product also affects the processing properties of the product. When a PVC resin with a moderate degree of polymerization is selected, the heat retention stability and Vicat softening point of the product can be made higher.

[0092] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the essence and scope of the technical solution of the present invention.

Claims

1. A PVC composition, characterized in that: The composition comprises the following components in parts by weight: 100 parts of PVC resin, 3-5 parts of toughening agent, 1-3 parts of methyl tin mercaptan, 0.05-0.3 parts of maleimide derivative, 0.2-0.5 parts of titanium dioxide, and 0.4-1 parts of antioxidant.

2. The PVC composition according to claim 1, characterized in that: The methyl tin mercaptan includes at least one of a coordinated methyl tin mercaptan and a non-coordinated methyl tin mercaptan.

3. The PVC composition according to claim 1, characterized in that: The methyltin mercaptide includes (CH3)3Sn2(SCH2COOC8H 17 )5. CH3Sn(SCH2COOC8H 17 )3、(CH3)2Sn(SCH2COOC8H 17 )At least one of 2.

4. The PVC composition according to claim 1, characterized in that: The average polymerization degree of the PVC resin is 400-1050.

5. The PVC composition according to claim 1, characterized in that: The maleimide derivative includes at least one of N-substituted maleimide, alkyl-substituted maleimide and phenyl-substituted maleimide.

6. The PVC composition according to claim 1, characterized in that: The average particle size of the titanium dioxide is 2 to 5 μm.

7. The PVC composition according to claim 1, characterized in that: The toughening agent includes at least one of methyl methacrylate-acrylate copolymer, acrylonitrile-butyl acrylate-styrene terpolymer, and chlorinated polyethylene.

8. The PVC composition according to claim 1, characterized in that: The components of the PVC composition also include 1 to 2 parts of a processing aid; preferably, the processing aid includes at least one of a lubricant, an antistatic agent, and a flame retardant.

9. The method for preparing the PVC composition according to claim 1, characterized in that: The following steps are involved: The other components except the toughening agent are heated to 90-100° C. and mixed evenly, then the toughening agent is added and mixed evenly, cooled to 75-80° C. and placed in a screw extruder for melt extrusion and granulation to obtain the PVC composition.

10. An electronic appliance housing, characterized in that: The invention comprises the PVC composition according to any one of claims 1 to 9.

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