A production method of vinyl chloride-based blended resin

Abstract

The present invention provides a production method of vinyl chloride-based blended resin, belonging to the technical field of preparation of polymer materials. The present invention adopts a two-stage temperature-rising reaction method to improve the conversion rate of vinyl chloride, reduce the vinyl chloride residue inside the vinyl chloride-based blended resin particles and reduce the abnormal particles generated by hollow particles; at the same time, by sieving the polymerization emulsion twice to further adjust the product particle size, the prepared vinyl chloride-based blended resin has the advantages of few abnormal particles, low oil absorption value, and small plasticizer swelling rate.

Description

Technical Field

[0001] The present invention relates to the technical field of polymer material preparation, and specifically relates to a production method of vinyl chloride-based blended resin. Background Art

[0002] Products such as plastisol, automotive sealant, automotive primer, and tarpaulin coating are generally prepared by baking a polyvinyl chloride paste coating. The polyvinyl chloride paste mainly consists of paste resin with a diameter of 1.0 μm, blended resin with a diameter of 20 - 60 μm, plasticizer, filler, pigment, heat stabilizer, etc. The polyvinyl chloride paste generally has problems such as high paste viscosity and large time-dependent fluctuations in paste viscosity during storage. Therefore, it is necessary to add blended resin to reduce the viscosity of the resin paste and improve the stability of the paste viscosity during storage of the resin paste. The blended resin is prepared by a suspension polymerization process, and the main process is as follows: auxiliaries such as monomers, dispersants, and initiators are added to a reaction kettle. After stirring, the monomers are dispersed into suitable droplets for polymerization reaction. After discharging under the condition of reaching the reaction pressure drop, it is dehydrated by a centrifuge and dried to obtain the finished product. For example, the preparation methods of polyvinyl chloride blended resin disclosed in patents CN1259368C, CN1122340A, CN1241580A, CN101263166A, CN1796424A, CN101200512A, and CN102432718A.

[0003] As is well known, in the suspension polymerization process, due to reasons such as insufficient conversion rate and thick film, the monomers in the droplets cannot react completely and cannot be removed completely, resulting in resin particles with empty shells or semi-empty shells. These particles will form abnormal-shaped particles during the stirring process. These abnormal-shaped particles cannot be intercepted by the sieve mesh due to their small cross-sectional diameter and are carried into the resin paste with the product, resulting in difficulties in filtration during the production and use of the resin paste; problems such as scratches during scraping coating, blockage of the spray gun during spraying, and surface defects of the product during application; in addition, due to the thick film of the blended resin, the vinyl chloride monomer in the directly discharged blended resin product after polymerization usually remains in the resin powder particles because it is difficult to be removed from the resin particles. When such a blended resin product is added to the resin paste, the plasticizer softens the film of the blended resin, and the vinyl chloride monomer expands, resulting in a large swelling rate of the blended resin, and thus a high problem of the increase rate of the particle size when the blended resin is added to the resin paste. Summary of the Invention

[0004] In view of the above deficiencies of the prior art, the present invention provides a production method of vinyl chloride-based blended resin to improve the performance of the blended resin, reduce the content of abnormal-shaped particles in the blended resin, reduce the ratio of swelling of the blended resin by the plasticizer after being added to the resin paste, and improve the quality of the blended resin.

[0005] To achieve the above object, the specific technical solution of the present invention is as follows:

[0006] A production method of vinyl chloride-based blended resin, comprising the following steps:

[0007] (a) Mix water, 70% - 100% of the feeding amount of vinyl chloride, comonomer, initiator, dispersant, and buffer evenly;

[0008] (b) Strongly disperse the mixture obtained in step (a);

[0009] (c) Raise the temperature to the first-stage reaction temperature for reaction; the first-stage reaction temperature is: 35 - 65 °C;

[0010] (d) Dropwise add the remaining 0% - 30% of the feeding amount of vinyl chloride;

[0011] (e) When the pressure reaches the first-stage pressure drop, raise the temperature to the second-stage reaction temperature and continue the reaction until the pressure reaches the second pressure drop; the second-stage reaction temperature is: 5 - 15 °C higher than the first-stage reaction temperature;

[0012] (f) Add terminator and emulsifier, stir for a period of time, and then discharge to a primary vibrating screen;

[0013] (g) The slurry passed through the primary vibrating screen is then passed through a secondary vibrating screen and then centrifugally dewatered;

[0014] (h) After drying, pass through a dry powder vibrating screen to obtain the finished product of vinyl chloride-based blended resin.

[0015] In the present invention, after strongly dispersing the reaction mixture, a two-stage temperature-raising reaction method is adopted to improve the conversion rate of vinyl chloride, reduce the vinyl chloride residue inside the vinyl chloride-based blended resin particles, and reduce the abnormal particles generated by hollow particles; at the same time, the product particle size is further adjusted by sieving the polymerization emulsion twice. The vinyl chloride-based blended resin prepared by the present invention has an extremely low monomer residue (less than 50 ppm), and the particle morphology is spherical with few abnormal particles. At the same time, the vinyl chloride-based blended resin of the present invention also has the advantages of low oil absorption value and small plasticizer swelling rate.

[0016] Preferably, the weight ratio of vinyl chloride, comonomer, water, initiator, dispersant, buffer, terminator, and emulsifier is 100:(0 - 15):(120 - 150):(0.02 - 0.15):(0.1 - 0.5):(0.01 - 0.05):(0.05 - 0.5):(0.1 - 1.5); when the weight of the comonomer is zero, the prepared product is a homopolymer blended resin.

[0017] Preferably, the first-stage pressure drop is 0.05 - 0.2 MPa.

[0018] Preferably, the pressure drop in the second stage is 0.01~0.5 MPa.

[0019] Preferably, the mixing time in step (a) does not exceed 30 min.

[0020] Preferably, in step (b), a high-speed homogenizing pump is used for strong dispersion. The high-speed homogenizing pump is a single-stage or multi-stage homogenizing pump with a shear line speed of 5~30 m / s, and the circulating homogenizing amount is 1~6 times the total feeding amount of the raw materials.

[0021] The total feeding amount of the raw materials is the sum of the weights of vinyl chloride, comonomer, water, initiator, dispersant, buffer, terminator, and emulsifier.

[0022] Preferably, the order of adding materials in step (a) can be arbitrarily combined.

[0023] Preferably, step (b) is carried out under the condition of ≤30 °C.

[0024] Preferably, the first-stage vibrating screen is 30~140 mesh.

[0025] Preferably, the second-stage vibrating screen is 60~160 mesh.

[0026] Preferably, the comonomer is selected from one or more of mono-ene ester monomers, vinyl ether monomers, aryl vinyl monomers, maleic acid and its anhydride / ester monomers, and vinyl halide monomers.

[0027] More preferably, the mono-ene ester monomers are mono-ene esters in which the alkyl chain of the linear, branched, or cyclic alcohol of the esterification group R-COO-R' contains 1~12 carbon atoms, including but not limited to vinyl acetate, methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, tert-butyl acrylate, pentyl acrylate, isopentyl acrylate, cyclohexyl acrylate, 2-ethylhexyl acrylate, methyl methacrylate, ethyl methacrylate, propyl methacrylate, butyl methacrylate, tert-butyl methacrylate, pentyl methacrylate, isopentyl methacrylate, 2-ethylhexyl methacrylate, and cyclohexyl methacrylate.

[0028] More preferably, the maleic acid and its anhydride / ester monomers include but not limited to diethyl fumarate, dimethyl itaconate, diethyl itaconate, diisopropyl itaconate, and dioctyl itaconate.

[0029] Preferably, the reaction is carried out in a reaction kettle, and the reaction kettle is a polymerization reaction kettle with an operating pressure ≥1.0 MPa and temperature control.

[0030] Preferably, in the method, steps (a) and (b) are carried out separately using a reactor and then transferred to a reaction kettle; alternatively, steps (a) and (b) are carried out using the same reaction kettle for strong dispersion and then directly heated for reaction.

[0031] Preferably, the initiator is selected from one or more of organic peroxides and azo compounds. The organic peroxides include diacetyl peroxide, didecanoyl peroxide, acetylbenzoyl peroxide, dilauroyl peroxide, dibenzoyl peroxide, di-tert-butyl peroxide, diisobutyryl peroxide, bis-(3,5,5-trimethylhexanoyl) peroxide, bis-2,4-dichlorobenzoyl peroxide, diisopropyl percarbonate, bis-(3-methoxybutyl) peroxydicarbonate, bis-(4-tert-butylcyclohexyl) peroxydicarbonate, di-sec-butyl peroxydicarbonate, dicetyl peroxydicarbonate, dimyristyl peroxydicarbonate, diethylhexyl peroxydicarbonate, cumyl peroxyneodecanoate, 1,1,3,3-tetramethylbutyl peroxyneodecanoate, tert-amyl peroxyneodecanoate, tert-butyl peroxyneodecanoate, 1,1-dimethyl-3-hydroxybutyl peroxyneodecanoate, tert-butyl peroxyneoheptanoate, cumyl peroxyneoheptanoate, tert-amyl peroxypivalate, tert-butyl peroxypivalate; the azo compounds include azobisisobutyronitrile, azobisisoheptonitrile, tert-butyl hydroperoxide.

[0032] Preferably, the dispersant is selected from one or more of polyvinyl alcohol, gelatin, cellulose, and polyethylene oxide.

[0033] Preferably, the buffer is selected from one or more of ammonia water and alkali metal salt compounds. The alkali metal salt compounds include sodium bicarbonate, sodium carbonate, disodium hydrogen phosphate, sodium dihydrogen phosphate, and citric acid.

[0034] Preferably, the dispersant (also known as protective colloid) is selected from one or more of polyvinyl alcohol, gelatin, cellulose derivatives, and polyethylene oxide.

[0035] More preferably, the dispersant is one or more of polyvinyl alcohol with an alcoholysis degree of 5-30 mol%, gelatin with a kinematic viscosity ≥ 2 mPa·s at a concentration of 6.67%, and cellulose ether with a viscosity ≤ 400 mPa·s at a concentration of 2%.

[0036] Preferably, the terminator is selected from one or more of hindered phenols, phosphites, aromatic amines, thioesters, thiophenols, hydroxylamines, and semicarbazides.

[0037] Preferably, the emulsifier is selected from one or more of aliphatic hydrocarbon / carboxylic acid derivatives and polyoxyethylene ethers.

[0038] The present invention also provides a polyvinyl chloride blended resin prepared by the described method.

[0039] Compared with the prior art, the advantages of the present invention are as follows:

[0040] (1) For the vinyl chloride-based blended resin prepared by the method of the present invention, the residual monomer content is less than 50 ppm; the oil absorption value is less than 10%; when blended into polyvinyl chloride paste resin, it can significantly reduce the paste viscosity, increase the fluidity, improve the coating working conditions of the resin, and reduce the cost.

[0041] (2) The present invention adopts a two-stage temperature-rising reaction mode to improve the conversion rate of vinyl chloride, reduce the vinyl chloride residue inside the vinyl chloride-based blended resin particles and reduce the abnormal particles generated by hollow particles; at the same time, by sieving the polymerization emulsion twice, the product particle size and particle size distribution are further adjusted, and the product particle size and particle size distribution are easy to control. The method of the present invention is simple to operate and is conducive to large-scale production. Description of the Drawings

[0042] Figure 1 It is a photograph of the vinyl chloride-based blended resin under a microscope; among them, Figure 1 a is a photograph of the vinyl chloride-based blended resin prepared in Example 1 under a microscope; Figure 1 b is a photograph of the vinyl chloride-based blended resin prepared in Example 2 under a microscope; Figure 1 c is a photograph of the vinyl chloride-based blended resin prepared in Comparative Example 1 under a microscope; Figure 1 d is a photograph of the vinyl chloride-based blended resin prepared in Comparative Example 2 under a microscope. Detailed Embodiments

[0043] The technical solutions of the present invention will be described clearly and completely below. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts fall within the scope of protection of the present invention.

[0044] The present invention provides a production method of a vinyl chloride-based blended resin, including the following steps:

[0045] (a) Mix water, 70% - 100% of the feeding amount of vinyl chloride, comonomer, initiator, dispersant, and buffer evenly;

[0046] (b) Strongly disperse the mixture obtained in step (a);

[0047] (c) Raise the temperature to the first-stage reaction temperature for reaction; the first-stage reaction temperature is: 35 - 65 °C;

[0048] (d) Add vinyl chloride with the remaining 0% - 30% of the feeding amount dropwise;

[0049] (e) When the pressure reaches the first-stage pressure drop, raise the temperature to the second-stage reaction temperature and continue the reaction until the pressure reaches the second pressure drop; the second-stage reaction temperature is: 5 - 15 °C higher than the first-stage reaction temperature;

[0050] (f) Add a terminator and an emulsifier, stir for a period of time, and then discharge the material to a primary vibrating screen;

[0051] (g) The slurry passed through the primary vibrating screen is then passed through a secondary vibrating screen and then centrifuged for dehydration;

[0052] (h) After drying, pass through a dry powder vibrating screen to obtain the finished product of vinyl chloride-based blended resin.

[0053] In some examples, the weight ratio of the vinyl chloride, comonomer, water, initiator, dispersant, buffer, terminator, and emulsifier is 100:(0 - 15):(120 - 150):(0.02 - 0.15):(0.1 - 0.5):(0.01 - 0.05):(0.05 - 0.5):(0.1 - 1.5).

[0054] In some examples, the first-stage pressure drop is 0.05 - 0.2 MPa; the second-stage pressure drop is 0.01 - 0.5 MPa.

[0055] In some examples, the mixing time in step (a) does not exceed 30 min.

[0056] In some examples, in step (b), a high-speed homogenizing pump is used for strong dispersion. The high-speed homogenizing pump is a single-stage or multi-stage homogenizing pump with a shear line speed of 5 - 30 m / s, and the circulating homogenizing amount is 1 - 6 times the total feeding amount of the raw materials.

[0057] In some examples, step (b) is carried out under the condition of ≤30 °C.

[0058] In some examples, the primary vibrating screen is 30 - 140 mesh; the secondary vibrating screen is 60 - 160 mesh.

[0059] In some examples, the comonomer is selected from one or more of mono-ene ester monomers, vinyl ether monomers, aryl vinyl monomers, maleic acid and its anhydride / ester monomers, and vinyl halide monomers.

[0060] In some examples, the initiator is selected from one or more of organic peroxides and azo compounds. The organic peroxides include diacetyl peroxide, didecanoyl peroxide, acetyl benzoyl peroxide, dilauroyl peroxide, dibenzoyl peroxide, di-tert-butyl peroxide, diisobutyryl peroxide, bis-(3,5,5-trimethylhexanoyl) peroxide, bis-2,4-dichlorobenzoyl peroxide, diisopropyl peroxycarbonate, bis-(3-methoxybutyl) peroxydicarbonate, bis-(4-tert-butylcyclohexyl) peroxydicarbonate, di-sec-butyl peroxydicarbonate, dicetyl peroxydicarbonate, dimyristyl peroxydicarbonate, diethylhexyl peroxydicarbonate, cumyl peroxyneodecanoate, 1,1,3,3-tetramethylbutyl peroxyneodecanoate, tert-amyl peroxyneodecanoate, tert-butyl peroxyneodecanoate, 1,1-dimethyl-3-hydroxybutyl peroxyneodecanoate, tert-butyl peroxyneoheptanoate, cumyl peroxyneoheptanoate, tert-amyl peroxypivalate, tert-butyl peroxypivalate; the azo compounds include azodiisobutyronitrile, azodiisoheptonitrile, tert-butyl hydroperoxide.

[0061] In some examples, the dispersant is selected from one or more of polyvinyl alcohol, gelatin, cellulose, and polyethylene oxide.

[0062] In some examples, the buffer is selected from one or more of ammonia water and alkali metal salt compounds. The alkali metal salt compounds include sodium bicarbonate, sodium carbonate, disodium hydrogen phosphate, sodium dihydrogen phosphate, and citric acid.

[0063] In some examples, the dispersant (also known as protective colloid) is selected from one or more of polyvinyl alcohol, gelatin, cellulose derivatives, and polyethylene oxide.

[0064] In the following specific examples, the polyvinyl alcohol as the dispersant is polyvinyl alcohol with an alcoholysis degree of 15 mol%; the gelatin is gelatin with a kinematic viscosity of 3 mPa·s at a concentration of 6.67%.

[0065] In some examples, the terminator is selected from one or more of hindered phenols, phosphites, aromatic amines, thioesters, thiophenols, hydroxylamines, and thiosemicarbazides.

[0066] In the following specific examples, the terminator is antioxidant 1010.

[0067] In some examples, the emulsifier is selected from one or more of aliphatic hydrocarbon / carboxylic acid derivatives and polyoxyethylene ethers.

[0068] Example 1

[0069] A polyvinyl chloride blended resin is prepared as follows:

[0070] Add 4000 kg of pure water, 3000 kg of vinyl chloride monomer, 240 kg of vinyl acetate, 0.27 kg of azobisisobutyronitrile, 1.80 kg of tert-butyl peroxyneodecanoate, 1.50 kg of tert-butyl peroxypivalate, 13 kg of polyvinyl alcohol, and 0.70 kg of ammonium bicarbonate into a 10000 L high-pressure reactor. After stirring for 20 min, perform strong dispersion with a single-stage homogenization pump at 14 m / s, and the circulation homogenization amount is 35000 kg. During the homogenization process, control the material temperature in the reactor ≤ 20 °C with cooling water. After the homogenization is completed, directly raise the temperature to 60 °C for reaction. When the pressure drop reaches 0.2 MPa (after reacting for 240 min), raise the material temperature to 65 °C through the reactor jacket and continue the reaction. When the pressure drop reaches 0.5 MPa (after continuing to react for 60 min), add 2 kg of terminator and 20 kg of alkylphenol polyoxyethylene ether, stir for 20 min, discharge the material to a first-stage vibrating screen with 80 meshes and a second-stage vibrating screen with 110 meshes, sieve, and then dry. After sieving the dry powder, obtain the finished product of polyvinyl chloride blended resin. The particle morphology of the polyvinyl chloride blended resin is shown in Figure 1 a, and the performance test results are shown in Table 1.

[0071] Example 2

[0072] A polyvinyl chloride blended resin is prepared as follows:

[0073] Add 4000 kg of pure water, 2100 kg of vinyl chloride, 360 kg of vinyl acetate, 0.25 kg of azobisisobutyronitrile, 1.50 kg of tert-butyl peroxyneodecanoate, 1.20 kg of tert-butyl peroxypivalate, 13 kg of gelatin, and 0.70 kg of ammonium bicarbonate into a 10000 L high-pressure reactor. After stirring for 20 min, perform strong dispersion with a single-stage homogenization pump at 14 m / s, and the circulation homogenization amount is 35000 kg. During the homogenization process, control the material temperature in the reactor ≤ 20 °C with cooling water. After the homogenization is completed, directly raise the temperature to 50 °C for reaction, and start to uniformly dropwise add 900 kg of vinyl chloride. Finish the dropwise addition when the pressure drop reaches 0.2 MPa. After the pressure drop reaches 0.2 MPa (after reacting for 240 min), raise the material temperature to 65 °C through the reactor jacket and continue the reaction. When the pressure drop reaches 0.5 MPa (after continuing to react for 60 min), add 2 kg of terminator and 20 kg of BYK-1162, stir for 20 min, discharge the material to a first-stage vibrating screen with 80 meshes and a second-stage vibrating screen with 120 meshes, sieve, and then dry. After sieving the dry powder, obtain the finished product of polyvinyl chloride blended resin. The particle morphology of the polyvinyl chloride blended resin is shown in Figure 1 b, and the performance test results are shown in Table 1.

[0074] Example 3

[0075] A polyvinyl chloride blended resin is prepared as follows:

[0076] Add 4000 kg of pure water, 2100 kg of vinyl chloride, 150 kg of vinyl acetate, 150 kg of butyl acrylate, 0.27 kg of azobisisobutyronitrile, 1.80 kg of tert-butyl peroxyneodecanoate, 1.50 kg of tert-butyl peroxypivalate, 11 kg of gelatin, and 0.70 kg of ammonium bicarbonate into a 10000 L high-pressure reactor. After stirring for 20 min, perform strong dispersion with a single-stage homogenizing pump at 14 m / s, with a circulating homogenization amount of 35000 kg. During the homogenization process, control the material temperature in the reactor with cooling water to ≤20 °C. After the homogenization is completed, directly raise the temperature to 55 °C for reaction, and start to uniformly add 900 kg of vinyl chloride dropwise. Finish the dropping when the pressure drop reaches 0.2 MPa. After the pressure drop reaches 0.2 MPa (after reacting for 240 min), raise the material temperature to 63 °C through the jacket of the reactor and continue the reaction. When the pressure drop reaches 0.5 MPa (after reacting for another 60 min), add 2 kg of terminator and 20 kg of BYK-1162, stir for 20 min, discharge the material to a first-stage vibrating screen with 100 meshes and a second-stage vibrating screen with 120 meshes, sieve, and then dry. After sieving the dry powder, obtain the finished product of polyvinyl chloride blended resin. The performance test results of the polyvinyl chloride blended resin are shown in Table 1.

[0077] Comparative Example 1

[0078] A polyvinyl chloride blended resin is prepared according to the following steps:

[0079] Add 4000 kg of pure water, 3000 kg of vinyl chloride, 240 kg of vinyl acetate, 0.27 kg of azobisisobutyronitrile, 1.80 kg of tert-butyl peroxyneodecanoate, 1.50 kg of tert-butyl peroxypivalate, 13 kg of polyvinyl alcohol, and 0.70 kg of sodium bicarbonate into a 10000 L high-pressure reactor at one time. After stirring for 20 min, raise the temperature to 60 °C for reaction. When the pressure drop reaches 0.2 MPa (after reacting for 240 min), raise the material temperature to 65 °C through the jacket of the reactor and continue the reaction. When the pressure drop reaches 0.5 MPa (after reacting for another 60 min), add 2 kg of terminator and 20 kg of alkylphenol polyoxyethylene ether, stir for 20 min, discharge the material to a first-stage vibrating screen with 80 meshes and a second-stage vibrating screen with 110 meshes, sieve, and then dry. After sieving the dry powder, obtain the finished product of polyvinyl chloride blended resin. The particle morphology of the polyvinyl chloride blended resin is shown in Figure 1 c, and the performance test results are shown in Table 1.

[0080] Comparative Example 2

[0081] A polyvinyl chloride blended resin is prepared according to the following steps:

[0082] Add 4000 kg of pure water, 3000 kg of vinyl chloride, 240 kg of vinyl acetate, 0.27 kg of azobisisobutyronitrile, 1.80 kg of tert-butyl peroxyneodecanoate, 1.50 kg of tert-butyl peroxypivalate, 13 kg of polyvinyl alcohol, and 0.70 kg of sodium bicarbonate into a 10000 L high-pressure reactor. After stirring for 20 min, perform strong dispersion with a single-stage homogenizing pump at 14 m / s, and the circulating homogenization amount is 35000 kg. During the homogenization process, control the material temperature in the reactor ≤ 20 °C with cooling water. After the homogenization is completed, directly raise the temperature to 60 °C for reaction. When the pressure drop reaches 0.2 MPa, add 2 kg of terminator and 20 kg of alkylphenol polyoxyethylene ether, stir for 20 min, discharge to a first-stage vibrating screen with 80 meshes and a second-stage vibrating screen with 110 meshes, and obtain the finished product of polyvinyl chloride blended resin after screening, drying, and dry powder screening. The particle morphology of the polyvinyl chloride blended resin is shown in Figure 1 d, and the performance test results are shown in Table 1.

[0083] Comparative Example 3

[0084] A polyvinyl chloride blended resin is prepared as follows:

[0085] Add 4000 kg of pure water, 3000 kg of vinyl chloride monomer, 240 kg of vinyl acetate, 0.27 kg of azobisisobutyronitrile, 1.80 kg of tert-butyl peroxyneodecanoate, 1.50 kg of tert-butyl peroxypivalate, 13 kg of polyvinyl alcohol, and 0.70 kg of ammonium bicarbonate into a 10000 L high-pressure reactor. After stirring for 20 min, perform strong dispersion with a single-stage homogenizing pump at 14 m / s, and the circulating homogenization amount is 35000 kg. During the homogenization process, control the material temperature in the reactor ≤ 20 °C with cooling water. After the homogenization is completed, directly raise the temperature to 60 °C for reaction for 300 min (the pressure drop is 0.4 MPa), add 2 kg of terminator and 20 kg of alkylphenol polyoxyethylene ether, stir for 20 min, discharge to a first-stage vibrating screen with 80 meshes and a second-stage vibrating screen with 110 meshes, and obtain the finished product of polyvinyl chloride blended resin after screening and drying. The performance test results of the polyvinyl chloride blended resin are shown in Table 1.

[0086] Paste viscosity, fineness of the doctor blade, and for 100 g of resin paste filtered through a 100-mesh sieve. The paste resin was prepared according to the paste preparation process in GB / T 12004.2-1996 "Preparation of Polyvinyl Chloride Paste Resin Paste". The formulation used plasticizer DINP: paste resin P-450: blending resin in a ratio of 60:60:40. The test conditions for the paste viscosity of the resin paste were a constant temperature of 25 °C and Brookfield LV-04 (#64) - 1 min. The apparent density was tested according to GB / T 20022 "Plastics - Homopolymer and Copolymer Resins of Vinyl Chloride - Determination of Apparent Density". The oil absorption value was tested according to GB / T 3400 "Plastics - General Purpose Homopolymer and Copolymer Resins of Vinyl Chloride - Determination of Plasticizer Absorption at Room Temperature". The residual monomer was tested according to GB / T 29874 "Plastics - Homopolymer and Copolymer Resins of Vinyl Chloride - Determination of Residual Vinyl Chloride Monomer in Dry Powder by Gas Chromatography". The sieve residue was tested according to the method in GB / T 21843 "Plastics - Homopolymer and Copolymer Resins of Vinyl Chloride - Determination of Particle Size by Mechanical Sieve".

[0087] Table 1: Performance Test Results of Polyvinyl Chloride Blending Resin

[0088]

[0089] From Figure 1 It can be seen that the polyvinyl chloride blending resin prepared by the method of the present invention is spherical, has a uniform particle size distribution, and few abnormal particles. Without subjecting the reaction mixture to high-speed homogenization (Comparative Example 1) or only performing a one-step temperature-raising polymerization reaction (Comparative Example 2), it will directly affect the particle morphology of the product. As can be seen from Table 1, for the polyvinyl chloride blending resin prepared by the present invention, the residual monomer content is less than 50 ppm; the oil absorption value is less than 10%; when blended into polyvinyl chloride paste resin, it can significantly reduce the paste viscosity, increase the fluidity, improve the coating working conditions of the resin, and reduce costs. Without subjecting the reaction mixture to high-speed homogenization (Comparative Example 1) or only performing a one-step temperature-raising polymerization reaction (Comparative Example 2) or simply prolonging the reaction time (Comparative Example 3), it will not improve the oil absorption value and mixing viscosity of the polyvinyl chloride blending resin. Moreover, if the reaction time is further prolonged, the polymerization emulsion will show slight demulsification or caking phenomena, resulting in an increase in the frequency of kettle cleaning and a reduction in production efficiency.

[0090] The above specific embodiments have described the implementation of the present invention in detail. However, the present invention is not limited to the specific details in the above embodiments. Within the scope of the claims and technical concept of the present invention, various simple modifications and changes can be made to the technical solutions of the present invention, and these simple variations all belong to the protection scope of the present invention.

Claims

1. A method for producing a vinyl chloride-based blended resin, characterized in that: The following steps are involved: (a) mixing water, 70% to 100% of the feed amount of vinyl chloride, comonomer, initiator, dispersant and buffer uniformly; (b) performing strong dispersion on the mixture obtained in step (a); the strong dispersion is performed using a high-speed homogenizing pump, the high-speed homogenizing pump is a single-stage or multi-stage homogenizing pump with a shear linear velocity of 5 to 30 m / s, and the circulating homogenization amount is 1 to 6 times the total amount of raw materials fed; the strong dispersion is performed at a temperature of ≤30°C; (c) heating to the first stage reaction temperature for reaction; the first stage reaction temperature is: 35-65°C; (d) adding dropwise the remaining 0% to 30% of the amount of vinyl chloride fed; (e) When the pressure reaches the first stage pressure drop, the temperature is raised to the second stage reaction temperature and the reaction is continued until the pressure reaches the second pressure drop; the second stage reaction temperature is: based on the first stage reaction temperature plus 5 to 15°C; (f) adding terminator and emulsifier, stirring for a period of time, and then discharging the material onto a first-stage vibrating screen; (g) the slurry after being screened by the primary vibrating screen is screened by the secondary vibrating screen and then centrifuged for dehydration; (h) After drying, the powder is sieved through a dry powder vibration screen to obtain a finished product of a vinyl chloride blended resin.

2. The method for producing a vinyl chloride-based blended resin according to claim 1, characterized in that: The weight ratio of the vinyl chloride, comonomer, water, initiator, dispersant, buffer, terminator and emulsifier is 100:(0-15):(120-150):(0.02-0.15):(0.1-0.5):(0.01-0.05):(0.05-0.5):(0.1-1.5).

3. The method for producing a vinyl chloride based blended resin according to claim 1, characterized in that: The pressure drop in the first stage is 0.05-0.2 MPa; the pressure drop in the second stage is 0.01-0.5 MPa.

4. The method for producing a vinyl chloride based blended resin according to claim 1, characterized in that: The mesh size of the first-stage vibrating screen is 30-140; the mesh size of the second-stage vibrating screen is 60-160.

5. The method for producing a vinyl chloride-based blended resin according to claim 1, characterized in that: Preferably, the mixing time in step (a) is no longer than 30 min.

6. The method for producing a vinyl chloride-based blended resin according to claim 1, characterized in that: The comonomer is selected from one or more of monoolefin ester monomers, vinyl ether monomers, aromatic vinyl monomers, maleic acid and its anhydride / ester monomers, and vinyl halide monomers.

7. The method for producing a vinyl chloride-based blended resin according to claim 6, characterized in that: The monoolefin monomers include, but are not limited to, vinyl acetate, methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, tert-butyl acrylate, amyl acrylate, isoamyl acrylate, cyclohexyl acrylate, ethylhexyl acrylate, methyl methacrylate, ethyl methacrylate, propyl methacrylate, butyl methacrylate, tert-butyl methacrylate, amyl methacrylate, isoamyl methacrylate, ethylhexyl methacrylate, and cyclohexyl methacrylate.

8. The method for producing a vinyl chloride-based blended resin according to claim 6, characterized in that: The maleic acid and its anhydride / ester monomers include but are not limited to diethyl fumarate, dimethyl itaconate, diethyl itaconate, diisopropyl itaconate, and dioctyl itaconate.

9. A vinyl chloride based blended resin prepared by the method according to any one of claims 1 to 8.

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