A reactive vinyl chloride polymer and its preparation method

Abstract

The present invention belongs to the technical field of polymer materials, and specifically relates to a reactive vinyl chloride polymer and a preparation method thereof. Conventional toughening modifiers such as MBS, EVA, and CPE can all toughen and modify PVC, but the resulting PVC products have a relatively low Vicat softening point and hardness, and are prone to deformation after long-term use. In response to the above problems, the present invention provides a reactive vinyl chloride polymer, which uses vinyl chloride as a main monomer and vinyl acetate, a silane coupling agent, and an acrylate with a low glass transition temperature as auxiliary monomers. A vinyl chloride polymer with a low glass transition temperature, a wide molecular weight distribution range, and a reactive group alkoxysilane is obtained through suspension polymerization, which takes into account the performance requirements of impact resistance, tensile yield strength, Vicat softening point, and flexural modulus. It can not only be used as a processing aid modifier to achieve a better plasticizing effect, but also make the cost advantage of the resulting PVC products more prominent.

Description

Technical Field

[0001] The invention belongs to the technical field of polymer materials, and particularly relates to a reactive vinyl chloride polymer and a preparation method thereof. Background Art

[0002] Polyvinyl chloride (PVC), a versatile resin, is inexpensive, possesses excellent dielectric properties and chemical stability, and is one of the world's most mass-produced plastics, widely used in construction, chemical engineering, agriculture, and transportation. However, rigid PVC suffers from limitations such as brittleness, poor heat deformation resistance, and thermal stability, which, to a certain extent, limit its application in many areas. To address these shortcomings, research on toughening and modifying PVC has begun both domestically and internationally. Currently, a wide variety of PVC modifiers are available, including MBS, EVA, and CPE.

[0003] Studies have shown that modifiers such as MBS, EVA, and CPE can all be used as toughening modifiers for PVC, but the Vicat softening point and hardness of the resulting PVC products are relatively low (taking PVC profile products as an example, the Vicat softening point of PVC profile products that meet the requirements of GB / T8814-2017 has long been difficult to exceed 80°C), and the weather resistance of PVC products has hardly been improved, and the overall performance needs to be further improved.

[0004] In order to solve the above problems, the present invention provides a reactive vinyl chloride polymer, which uses vinyl chloride as a main monomer and vinyl acetate, a silane coupling agent, and an acrylate with a low glass transition temperature as auxiliary monomers. A vinyl chloride polymer with a low glass transition temperature, a wide molecular weight distribution range, and a reactive group alkoxysilane is obtained by suspension polymerization.

[0005] The vinyl chloride polymer contains vinyl chloride segments in its molecular structure, which solves the problem of its compatibility with PVC;

[0006] The vinyl chloride polymer contains vinyl acetate structural segments in its molecular structure, which gives it good internal plasticity and improves the thermal processing plasticity of PVC.

[0007] The vinyl chloride polymer contains a low glass transition temperature acrylic acid ester structure segment in its molecular structure, which, on the one hand, promotes the gelation of polyvinyl chloride and improves the processing and plasticizing properties of PVC. On the other hand, as a soft monomer with a low glass transition temperature, it improves the impact resistance of PVC.

[0008] The molecular structure of the vinyl chloride polymer contains silane coupling agent structural segments and incompletely polymerized double bonds of the cross-linking agent, which makes the obtained vinyl chloride polymer have good reactivity. The silane coupling agent structural segments themselves have good water resistance, weather resistance and impact resistance. More importantly, the obtained vinyl chloride polymer has better compatibility with the inorganic filler, and the inorganic filler can be better dispersed in the material system composed of PVC, vinyl chloride polymer, etc., which is conducive to further improving the comprehensive properties of PVC, such as mechanical properties, thermal stability, and weather resistance.

[0009] The incompletely polymerized double bonds of the cross-linking agent and the reactive alkylsiloxy groups introduced into the structural fragments of the silane coupling agent not only undergo self-cross-linking during the thermal initiation process of high-temperature melt shearing of PVC into products, but can also undergo silane hydrolysis in the presence of water (both the hydrotalcite and zeolite structures in the PVC composite stabilizer contain water) and organic acids (such as stearic acid in the PVC composite stabilizer), forming silanol grafted products with vinyl polymers and CPE, and further undergoing a cross-linking reaction of silanol condensation, thereby forming a three-dimensional cross-linked structure, which can not only improve the Vicat softening point and hardness of PVC products, but also improve their tensile yield strength and flexural modulus. At the same time, the reaction consumes the free radicals generated by the high-temperature de-Cl of PVC, inhibits the color-developing zipper reaction, and thus improves the thermal stability of PVC and the weather resistance of PVC products.

[0010] The vinyl chloride polymer obtained by the present invention can not only be used as a processing aid modifier to achieve a good plasticizing effect, but also, when used together with a traditional impact modifier, can effectively reduce the amount of the traditional impact modifier used, while taking into account the performance requirements of impact resistance, tensile yield strength, Vicat softening point and flexural modulus, making the cost advantage of the obtained PVC products more prominent. Summary of the Invention

[0011] A problem with the prior art is that conventional toughening modifiers such as MBS, EVA, and CPE can toughen PVC, but the resulting PVC products have a low Vicat softening point and low hardness. To address this problem, the present invention provides a reactive vinyl chloride polymer comprising the following raw materials, calculated by weight:

[0012] 49-63 parts of vinyl chloride;

[0013] 3.5-10.5 parts of vinyl acetate;

[0014] Acrylate 3.5-10.5 parts;

[0015] Silane coupling agent 0.42-1.05 parts;

[0016] Cross-linking agent 0.14-0.42 parts;

[0017] Initiator 0.28-0.42 parts;

[0018] Chain transfer agent 0.15-0.21 parts;

[0019] Thermal stabilizer 0.14-0.42 parts;

[0020] Terminator 0.006-0.014 parts;

[0021] Dispersant 2.45-4.2 parts;

[0022] 100-130 parts of deionized water.

[0023] Specifically, the acrylic acid ester is a blend of butyl acrylate and isooctyl acrylate.

[0024] Specifically, the weight ratio of butyl acrylate to isooctyl acrylate in the blend is 3:1.

[0025] Specifically, the silane coupling agent is a blend of vinyltriethoxysilane and γ-methacryloxypropyltrimethoxysilane.

[0026] Specifically, the weight ratio of vinyltriethoxysilane to γ-methacryloxypropyltrimethoxysilane in the blend is 5:2.

[0027] Specifically, the cross-linking agent is a blend of diallyl phthalate and triallyl isocyanurate.

[0028] Specifically, the weight ratio of diallyl phthalate to triallyl isocyanurate in the blend is 1:3.

[0029] Specifically, the initiator is azobisisobutyronitrile.

[0030] Specifically, the chain transfer agent is mercaptoethanol.

[0031] Specifically, the heat stabilizer is a blend of zinc carboxylate and epoxidized soybean oil.

[0032] Specifically, the weight ratio of zinc carboxylate to epoxidized soybean oil in the blend is 1:2.

[0033] Specifically, the terminator is acetone thiosemicarbazone.

[0034] Specifically, the dispersant is a blend of polyvinyl alcohol KH-20, hydroxypropyl methylcellulose E50 and polyvinyl alcohol LL-02.

[0035] Specifically, the weight ratio of polyvinyl alcohol KH-20, hydroxypropyl methylcellulose E50, and polyvinyl alcohol LL-02 in the blend is 5:1:2.

[0036] Specifically, the preparation method of the reactive vinyl chloride polymer comprises the following steps:

[0037] (1) adding the formulated amount of vinyl acetate, silane coupling agent, crosslinking agent, initiator, chain transfer agent, heat stabilizer, 6 / 7 formulated amount of dispersant, and 6 / 7 formulated amount of deionized water into a reactor in sequence, stirring evenly, and then adding 2 / 5-1 / 2 formulated amount of vinyl chloride into the reactor, stirring evenly, to obtain a pre-dispersed mixture;

[0038] (2) adding the remaining amount of dispersant, deionized water and the amount of acrylate in the formula to a dispersion kettle with stirring, stirring thoroughly to obtain a uniform dispersion;

[0039] (3) raising the temperature of the pre-dispersed mixture in the reactor in step (1) to 64-68° C. and reacting until the pressure in the reactor drops by 0.2 MPa, then continuously and evenly adding the uniform dispersion obtained in step (2) and the remaining amount of vinyl chloride within 3.5 hours, stirring and reacting at a constant temperature until the pressure in the reactor drops to 0.4 MPa, and then adding the terminator in the amount of the formula to terminate the reaction;

[0040] (4) then stripping the reaction product in the reactor to remove unreacted vinyl chloride;

[0041] (5) After the stripping is completed, the remaining product in the reactor is collected, and then the product collected in the reactor is subjected to multiple centrifugation-water washing-centrifugal dehydration treatments to make the moisture content of the product lower than 25%. The product is then dried to make the moisture content of the product lower than 2%. The dried product is then sieved with a 40-mesh sieve to obtain a reactive vinyl chloride polymer.

[0042] Specifically, the drying method in step (6) is to place the dehydrated product in a forced air drying oven at 60-65°C for drying.

[0043] The present invention has the following beneficial effects:

[0044] (1) The present invention provides a reactive vinyl chloride polymer, which uses vinyl chloride as a main monomer and vinyl acetate, a silane coupling agent, and an acrylate with a low glass transition temperature as auxiliary monomers, and obtains a vinyl chloride polymer with a low glass transition temperature, a wide molecular weight distribution range, and a reactive group alkoxysilane through low-temperature emulsion polymerization.

[0045] The vinyl chloride polymer contains vinyl chloride segments in its molecular structure, which solves the problem of its compatibility with PVC;

[0046] The vinyl chloride polymer contains vinyl acetate structural segments in its molecular structure, which gives it good internal plasticity and improves the thermal processing plasticity of polyvinyl chloride;

[0047] The vinyl chloride polymer contains a low glass transition temperature acrylic acid ester structure segment in its molecular structure, which, on the one hand, promotes the gelation of polyvinyl chloride and improves the processing and plasticizing properties of PVC. On the other hand, as a soft monomer with a low glass transition temperature, it improves the impact resistance of PVC.

[0048] The vinyl chloride polymer molecular structure contains a silane coupling agent structural segment, which itself has good water resistance, weather resistance and impact resistance. More importantly, it makes the obtained vinyl chloride polymer have better compatibility with the inorganic filler. The inorganic filler can be better dispersed in the material system composed of PVC, vinyl chloride polymer, etc., which is conducive to further improving the comprehensive properties of PVC, such as mechanical properties, thermal stability, and weather resistance.

[0049] The molecular structure of the vinyl chloride polymer contains silane coupling agent structural fragments and incompletely polymerized double bonds of the cross-linking agent, which endows the obtained vinyl chloride polymer with good reactivity. Not only does it undergo self-crosslinking during the thermal initiation process of high-temperature melt shearing of PVC into products, but it can also undergo silane hydrolysis in the presence of water (both the hydrotalcite and zeolite structures in the PVC composite stabilizer contain water) and an organic acid (such as stearic acid in the PVC composite stabilizer), forming a silanol grafted product with the vinyl polymer and CPE, and further undergoing a silanol condensation cross-linking reaction to form a three-dimensional cross-linked structure. This not only improves the Vicat softening point and hardness of the PVC product, but also improves its tensile yield strength and flexural modulus. At the same time, the reaction consumes free radicals generated by the high-temperature de-Cl in the PVC, inhibiting the color-developing zipper reaction, thereby improving the thermal stability of the PVC and enhancing the weather resistance of the PVC product.

[0050] (2) The vinyl chloride polymer obtained by the present invention can not only be used as a processing modifier to achieve a good plasticizing effect, but also, when used together with a traditional impact modifier, can effectively reduce the amount of the traditional impact modifier used, while taking into account the performance requirements of impact resistance, tensile yield strength, Vicat softening point and flexural modulus, making the cost advantage of the obtained PVC products more prominent. DETAILED DESCRIPTION

[0051] The present invention will be described in detail below with reference to the following examples. However, it should be understood that the following examples are merely illustrative of the embodiments of the present invention and are not intended to limit the scope of the present invention.

[0052] The reactive vinyl chloride polymers in the following examples and comparative examples of the present invention were prepared according to the following steps. The only difference between Comparative Examples 1-8 and Example 1 is the amount of raw materials used. The specific amounts of raw materials used in the examples and comparative examples are shown in Table 1:

[0053] (1) adding the formulated amount of vinyl acetate, silane coupling agent, crosslinking agent, initiator, chain transfer agent, heat stabilizer, 6 / 7 formulated amount of dispersant, and 6 / 7 formulated amount of deionized water into a reactor in sequence, stirring evenly, and then adding 2 / 5-1 / 2 formulated amount of vinyl chloride into the reactor, stirring evenly, to obtain a pre-dispersed mixture;

[0054] (2) adding the remaining amount of dispersant, deionized water and the amount of acrylate in the formula to a dispersion kettle with stirring, stirring thoroughly to obtain a uniform dispersion;

[0055] (3) raising the temperature of the pre-dispersed mixture in the reactor in step (1) to 64-68° C. and reacting until the pressure in the reactor drops by 0.2 MPa, then continuously and evenly adding the uniform dispersion obtained in step (2) and the remaining amount of vinyl chloride within 3.5 hours, stirring and reacting at a constant temperature until the pressure in the reactor drops to 0.4 MPa, and then adding the terminator in the amount of the formula to terminate the reaction;

[0056] (4) then stripping the reaction product in the reactor to remove unreacted vinyl chloride;

[0057] (5) After the stripping is completed, the remaining product in the reactor is collected, and then the product collected in the reactor is subjected to multiple centrifugation-water washing-centrifugal dehydration treatments, with the centrifuge speed being 2100-2400 rpm. After the dehydration treatment, the moisture content of the product is 19-25%. The product is then placed in a blast drying oven at 60-65°C for drying, so that the moisture content of the product does not exceed 2%. The dried product is then sieved with a 40-mesh sieve to obtain a reactive vinyl chloride polymer.

[0058] Table 1

[0059]

[0060] Comparative Example 9 is the same as Example 1, except that no silane coupling agent is added in Comparative Example 9.

[0061] The reactive vinyl chloride polymers prepared in Examples 1-3 and Comparative Examples 1-9 of the present invention were processed into 2.5 mm thick sheets and subjected to relevant performance tests. The test results of various properties of the sheets obtained in Examples 1-3 and Comparative Examples 1-9 are shown in Table 2. The sheets in Examples 1-3 and Comparative Examples 1-9 were composed of the following raw materials in parts by weight:

[0062] 100 parts of polyvinyl chloride;

[0063] 4 parts of calcium zinc composite stabilizer;

[0064] 25 parts of calcium carbonate;

[0065] 5 parts of titanium dioxide;

[0066] 2 parts of reactive vinyl chloride polymer;

[0067] 4 copies of CPE.

[0068] Table 2

[0069]

[0070] Weather resistance: Test standard ASTM G154, UV aging for 500h according to the weather resistance test standard, the △E change cannot exceed 5.

[0071] Impact resistance: Test standard ASTM D4226-16.

[0072] With the above-described preferred embodiments of the present invention as a guide, and with reference to the above description, relevant personnel are fully capable of making various changes and modifications without departing from the technical scope of this invention. The technical scope of this invention is not limited to the contents of the specification and must be determined according to the scope of the claims.

Claims

1. A reactive vinyl chloride polymer, characterized in that: The preparation comprises the following raw materials in parts by weight: 49-63 parts of vinyl chloride; 3.5-10.5 parts of vinyl acetate; Acrylate 3.5-10.5 parts; Silane coupling agent 0.42-1.05 parts; Cross-linking agent 0.14-0.42 parts; Initiator 0.28-0.42 parts; Chain transfer agent 0.15-0.21 parts; Thermal stabilizer 0.14-0.42 parts; Terminator 0.006-0.014 parts; Dispersant 2.45-4.2 parts; 100-130 parts of deionized water; The silane coupling agent is a blend of vinyl triethoxysilane and γ-methacryloxypropyl trimethoxysilane; wherein the weight ratio of vinyl triethoxysilane to γ-methacryloxypropyl trimethoxysilane is 5:2; The cross-linking agent is a blend of diallyl phthalate and triallyl isocyanurate, wherein the weight ratio of diallyl phthalate to triallyl isocyanurate is 1:

3.

2. A reactive vinyl chloride polymer according to claim 1, characterized in that: The acrylic acid ester is a blend of butyl acrylate and isooctyl acrylate.

3. The reactive vinyl chloride polymer according to claim 1, characterized in that: The chain transfer agent is mercaptoethanol.

4. The reactive vinyl chloride polymer according to claim 1, characterized in that: The heat stabilizer is a blend of zinc carboxylate and epoxidized soybean oil.

5. The reactive vinyl chloride polymer according to claim 1, characterized in that: The dispersant is a blend of polyvinyl alcohol KH-20, hydroxypropyl methylcellulose E50 and polyvinyl alcohol LL-02.

6. A reactive vinyl chloride polymer according to any one of claims 1 to 5, characterized in that: The preparation method comprises the following steps: (1) adding the formulated amount of vinyl acetate, silane coupling agent, crosslinking agent, initiator, chain transfer agent, heat stabilizer, 6 / 7 formulated amount of dispersant, and 6 / 7 formulated amount of deionized water into a reactor in sequence, stirring evenly, and then adding 2 / 5-1 / 2 formulated amount of vinyl chloride into the reactor, stirring evenly, to obtain a pre-dispersed mixture; (2) adding the remaining amount of dispersant, deionized water and the amount of acrylate in the formula to a dispersion kettle with stirring, stirring thoroughly to obtain a uniform dispersion; (3) raising the temperature of the pre-dispersed mixture in the reactor in step (1) to 64-68° C. and reacting until the pressure in the reactor drops by 0.2 MPa, then continuously and evenly adding the uniform dispersion obtained in step (2) and the remaining amount of vinyl chloride within 3.5 hours, stirring and reacting at a constant temperature until the pressure in the reactor drops to 0.4 MPa, and then adding the terminator in the amount of the formula to terminate the reaction; (4) then stripping the reaction product in the reactor to remove unreacted vinyl chloride; (5) After the stripping is completed, the remaining product in the reactor is collected, and then the product collected in the reactor is subjected to multiple centrifugation-water washing-centrifugal dehydration treatments to make the moisture content of the product lower than 25%, and then the product is dried to make the moisture content of the product lower than 2%. The dried product is then sieved with a 40-mesh sieve to obtain a reactive vinyl chloride polymer.

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