Production method of vinyl chloride-based blended resin

Abstract

The invention provides a production method of vinyl chloride-based blended resin, and belongs to the technical field of high polymer material preparation. According to the invention, a two-stage heating reaction mode is adopted to improve the conversion rate of vinyl chloride, reduce the residual quantity of vinyl chloride in vinyl chloride-based blended resin particles and reduce special-shaped particles generated by empty-shell particles; meanwhile, the size fraction of the product is further adjusted by sieving the polymerized emulsion twice, so that the prepared vinyl chloride-based blended resin has the advantages of few special-shaped particles, low oil absorption value, small plasticizer swelling rate and the like.

Description

Technical Field

[0001] The invention relates to the technical field of polymer material preparation, and in particular to a method for producing a vinyl chloride blended resin. Background Art

[0002] Products such as varnish, automotive sealant, automotive primer, and tarpaulin coating are generally prepared by baking polyvinyl chloride paste coating. Polyvinyl chloride paste is mainly composed of paste resin with a diameter of 1.0 μm, blended resin with a diameter of 20-60 μm, plasticizer, filler, pigment, thermal stabilizer, etc. Polyvinyl chloride paste generally has problems such as high paste viscosity and large fluctuations in paste viscosity over time during paste 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 the storage process of the resin paste. The blended resin is prepared by a suspension polymerization process, and the main process is as follows: monomers, dispersants, initiators and other additives are added to a reactor, and after stirring, the monomers are dispersed into suitable droplets for polymerization reaction. After reaching the reaction pressure drop conditions, the material is discharged and dehydrated and dried by a centrifuge to obtain a finished product, such as the preparation method of polyvinyl chloride blended resin disclosed in patents CN1259368C, CN1122340A, CN1241580A, CN101263166A, CN1796424A, CN101200512A, and CN102432718A.

[0003] As we all know, the suspension polymerization process will lead to incomplete monomer reaction and removal in the droplets due to insufficient conversion rate and thick film, and finally form empty shell or half-empty shell resin particles. Such particles will form irregular particles during the stirring process. These irregular particles cannot be intercepted by the screen due to their small cross-sectional diameter. They are brought into the resin paste along with the product, resulting in difficulty in filtering the resin paste during production and use; problems such as scratches during scraping, blockage of spray guns during spraying, and surface defects of products; in addition, because the blended resin film is thick, the blended resin product that is usually discharged directly after the polymerization is completed remains in the resin powder particles because the vinyl chloride monomer is difficult to remove from the resin particles. When such a blended resin product is added to the resin paste, the plasticizer softens the blended resin film and the vinyl chloride monomer expands, resulting in a large swelling rate of the blended resin, resulting in a high rate of increase in the particle size of the blended resin added to the resin paste. Summary of the invention

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

[0005] To achieve the above purpose, the specific technical solutions of the present invention are as follows:

[0006] A method for producing a vinyl chloride blended resin comprises the following steps:

[0007] (a) Mix water, 70% to 100% of the feed amount of vinyl chloride, comonomer, initiator, dispersant and buffer uniformly;

[0008] (b) strongly dispersing the mixture obtained in step (a);

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

[0010] (d) adding dropwise the remaining 0% to 30% of the feed amount of vinyl chloride;

[0011] (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 5~15℃;

[0012] (f) Add terminator and emulsifier, stir for a period of time, and then discharge the material to the first-stage vibrating screen;

[0013] (g) the slurry after being screened by the primary vibrating screen is screened by the secondary vibrating screen and then centrifuged for dehydration;

[0014] (h) After drying, the powder is sieved through a dry powder vibration screen to obtain a finished product of vinyl chloride blended resin.

[0015] The present invention improves the conversion rate of vinyl chloride by strongly dispersing the reaction mixture and adopts a two-stage temperature-raising reaction method, reduces the residual amount of vinyl chloride inside the vinyl chloride-based blended resin particles and reduces the irregular particles generated by the empty shell particles; at the same time, the product particle size is further adjusted by screening the polymer emulsion twice. The vinyl chloride-based blended resin prepared by the present invention has an extremely low monomer residual amount (less than 50 ppm), and the particle morphology is spherical with few irregular 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 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); when the weight of the comonomer is zero, the prepared product is a homopolymer blended resin.

[0017] Preferably, the pressure drop in the first stage 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, and the high-speed homogenizing pump is a single-stage or multi-stage homogenizing pump with a shear linear speed of 5 to 30 m / s, and the circulating homogenization amount is 1 to 6 times the total raw material feed amount.

[0021] The total amount of raw materials is the sum of the weight 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, the step (b) is carried out at a temperature of ≤30°C.

[0024] Preferably, the first-stage vibrating screen has a mesh size of 30 to 140.

[0025] Preferably, the secondary vibrating screen has a mesh size of 60 to 160.

[0026] Preferably, 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.

[0027] More preferably, the monoolefin ester monomer is a monoolefin ester containing 1 to 12 carbon atoms in the alkyl chain of a straight, branched or cyclic alcohol of the esterification group R-COO-R', including but not limited to vinyl acetate, methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, tert-butyl acrylate, pentyl acrylate, isopentyl acrylate, cyclohexyl acrylate, ethylhexyl acrylate, methyl methacrylate, ethyl methacrylate, propyl methacrylate, butyl methacrylate, tert-butyl methacrylate, pentyl methacrylate, isopentyl methacrylate, ethylhexyl methacrylate, and cyclohexyl methacrylate.

[0028] More preferably, 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.

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

[0030] Preferably, in the method, steps (a) and (b) are carried out in separate reactors and then transferred to a reactor; or, steps (a) and (b) are carried out in the same reactor and then directly heated to react after strong dispersion.

[0031] Preferably, the initiator is selected from one or more of organic peroxides and azo compounds, and the organic peroxides include diacetyl peroxide, didecanoyl peroxide, acetylbenzoyl peroxide, dilauroyl peroxide, dibenzoyl peroxide, di-tert-butyl peroxide, diisobutyryl peroxide, di-(3,5,5-trimethylhexanoyl) peroxide, bis-2,4-dichlorobenzoyl peroxide, diisopropyl percarbonate, di-(3-methoxybutyl) peroxydicarbonate, di-(4-tert-butylcyclohexyl) peroxydicarbonate, di-sec-butyl peroxide dicarbonate, di-tert ... Carbonate, dicetyl peroxydicarbonate, dimyristyl peroxydicarbonate, diethylhexyl peroxydicarbonate, isopropyl peroxyneodecanoate, 1,1,3,3-tetramethylbutyl peroxyneodecanoate, tert-amyl peroxyneodecanoate, tert-butyl peroxyneodecanoate, 1,1-dimethyl-3-hydroxybutyl peroxyneodecanoate, tert-butyl peroxyneodecanoate, isopropyl peroxyneodecanoate, tert-amyl peroxypivalate, tert-butyl peroxypivalate; the azo compound includes azobisisobutyronitrile, azobisisoheptanenitrile, and 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, and the alkali metal salt compounds include sodium bicarbonate, sodium carbonate, disodium hydrogen phosphate, sodium dihydrogen phosphate, and citric acid.

[0034] Preferably, the dispersant (also called 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 to 30 mol%, gelatin with a kinematic viscosity of ≥2 mPa·s at a concentration of 6.67%, and cellulose ether with a viscosity of ≤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 thiosemicarbazides.

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

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

[0039] Compared with the prior art, the present invention is beneficial in that:

[0040] (1) The vinyl chloride based blended resin prepared by the method of the present invention has a residual monomer content of less than 50 ppm and an oil absorption value of less than 10%. When blended into polyvinyl chloride paste resin, the paste viscosity can be greatly reduced, the flowability can be increased, the coating conditions of the resin can be improved, and the cost can be reduced.

[0041] (2) The present invention adopts a two-stage temperature-raising reaction method to improve the conversion rate of vinyl chloride, reduce the residual amount of vinyl chloride in the vinyl chloride-blended resin particles, and reduce the irregular particles generated by the empty shell particles; at the same time, the product particle size and particle size distribution are further adjusted by screening the polymer emulsion twice, and the size and particle size distribution of the product particle size are easy to control. The method of the present invention is simple to operate and is conducive to large-scale production. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 This is a photo of vinyl chloride blended resin under a microscope; among them, Figure 1 a is a photo of the vinyl chloride blended resin prepared in Example 1 under a microscope; Figure 1 b is a photo of the vinyl chloride blended resin prepared in Example 2 under a microscope; Figure 1 c is a photo of the vinyl chloride blended resin prepared in Comparative Example 1 under a microscope; Figure 1 d is a photo of the vinyl chloride-based blended resin prepared in Comparative Example 2 under a microscope. DETAILED DESCRIPTION

[0043] The technical solution of the present invention will be described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0044] The present invention provides a method for producing a vinyl chloride blended resin, comprising the following steps:

[0045] (a) Mix water, 70% to 100% of the feed amount of vinyl chloride, comonomer, initiator, dispersant and buffer uniformly;

[0046] (b) strongly dispersing the mixture obtained in step (a);

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

[0048] (d) adding dropwise the remaining 0% to 30% of the feed amount of vinyl chloride;

[0049] (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 5~15℃;

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

[0051] (g) the slurry after being screened by the primary vibrating screen is screened by the secondary vibrating screen and then centrifuged for dehydration;

[0052] (h) After drying, the powder is sieved through a dry powder vibration screen to obtain a finished product of vinyl chloride 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) is no longer than 30 min.

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

[0057] In some examples, the step (b) is performed at a temperature of ≤ 30 °C.

[0058] In some examples, the first-stage vibrating screen has a mesh size of 30 to 140; the second-stage vibrating screen has a mesh size of 60 to 160.

[0059] In some examples, 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.

[0060] In some examples, the initiator is selected from one or more of organic peroxides and azo compounds, and the organic peroxides include diacetyl peroxide, didecanoyl peroxide, acetylbenzoyl peroxide, dilauroyl peroxide, dibenzoyl peroxide, di-tert-butyl peroxide, diisobutyryl peroxide, di-(3,5,5-trimethylhexanoyl) peroxide, bis-2,4-dichlorobenzoyl peroxide, diisopropyl percarbonate, di-(3-methoxybutyl) peroxydicarbonate, di-(4-tert-butylcyclohexyl) peroxydicarbonate, di-sec-butyl peroxide, di-tert-butyl peroxide, di-(3,5,5-trimethylhexanoyl) peroxide, di-2,4-dichlorobenzoyl peroxide, diisopropyl percarbonate, di-(3-methoxybutyl) peroxydicarbonate, di-(4-tert-butylcyclohexyl) peroxydicarbonate, di-sec-butyl peroxide, di-tert ... The invention relates to dicarbonates, dicetyl peroxydicarbonate, dimyristyl peroxydicarbonate, diethylhexyl peroxydicarbonate, isopropyl peroxyneodecanoate, 1,1,3,3-tetramethylbutyl peroxyneodecanoate, tert-amyl peroxyneodecanoate, tert-butyl peroxyneodecanoate, 1,1-dimethyl-3-hydroxybutyl peroxyneodecanoate, tert-butyl peroxyneodecanoate, isopropyl peroxyneodecanoate, tert-amyl peroxypivalate, and tert-butyl peroxypivalate; the azo compounds include azobisisobutyronitrile, azobisisoheptanenitrile, and 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, and 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 called protective colloid) is selected from one or more of polyvinyl alcohol, gelatin, cellulose derivatives, and polyethylene oxide.

[0064] In the following specific examples, the dispersant polyvinyl alcohol is polyvinyl alcohol with an alcoholysis degree of 15 mol %; the gelatin is gelatin with a kinematic viscosity of 3 m Pa·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 hydrocarbons / carboxylic acid derivatives and polyoxyethylene ethers.

[0068] Example 1

[0069] A polyvinyl chloride blended resin, the preparation steps are as follows:

[0070] 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 were added to a 10000 L high-pressure reactor. After stirring for 20 min, strong dispersion was carried out in a 14 m / s single-stage homogenizing pump. The circulating homogenization amount was 35000 kg. During the homogenization process, the reactor was controlled to have a material temperature of ≤20 °C with cooling water. After the homogenization was completed, the temperature was directly raised to 60 °C for reaction. When the pressure drop reached 0.2 MPa (reaction for 240 min), the material temperature was raised to 65 °C through the reactor jacket to continue the reaction. When the pressure drop reached 0.5 MPa (reaction continued for 60 min), 2 kg of terminator and 20 kg of alkylphenol polyoxyethylene ether were added and stirred for 20 min. min, discharge the material to the first-level vibration screen with 80 mesh and the second-level vibration screen with 110 mesh, and then dry it. The dry powder is sieved to obtain the finished product of polyvinyl chloride blended resin. The particle morphology of polyvinyl chloride blended resin can be seen in Figure 1 a. The performance test results are shown in Table 1.

[0071] Example 2

[0072] A polyvinyl chloride blended resin, the preparation steps are as follows:

[0073] 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 were added to a 10000 L high-pressure reactor. After stirring for 20 min, strong dispersion was carried out in a 14 m / s single-stage homogenizing pump. The circulating homogenization amount was 35000 kg. During the homogenization process, the reactor was controlled to have a material temperature of ≤20 °C with cooling water. After the homogenization was completed, the temperature was directly raised to 50 °C for reaction, and 900 kg of vinyl chloride was uniformly added. The addition was completed when the pressure drop reached 0.2 MPa. After the pressure drop reached 0.2 MPa (reaction for 240 min), the material temperature was raised to 65 °C through the reactor jacket to continue the reaction. When the pressure drop reached 0.5 MPa (reaction continued for 60 min), 2 kg of terminator and 20 kg of BYK-1162, stir for 20 min, discharge to the first-level vibrating screen with 80 mesh, the second-level vibrating screen with 120 mesh, and then dry, and the dry powder is sieved to obtain the finished product of polyvinyl chloride blended resin. The particle morphology of polyvinyl chloride blended resin can be seen in Figure 1 b. The performance test results are shown in Table 1.

[0074] Example 3

[0075] A polyvinyl chloride blended resin, the preparation steps are as follows:

[0076] 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 were added to a 10000 L high-pressure reactor. After stirring for 20 min, the reactor was strongly dispersed by a 14 m / s single-stage homogenizing pump. The circulating homogenization amount was 35000 kg. During the homogenization process, the reactor was controlled to have a material temperature of ≤20 °C with cooling water. After the homogenization was completed, the temperature was directly raised to 55 °C for reaction, and 900 kg of vinyl chloride was uniformly added. The addition was completed when the pressure drop reached 0.2 MPa. After the pressure drop reached 0.2 MPa (reaction for 240 min), the material temperature was raised to 63 °C through the reactor jacket to continue the reaction. When the pressure drop reached 0.5 MPa (reaction continued for 60 min), 2 kg terminator, 20 kg BYK-1162, stirred for 20 min, put the material on the first-level vibrating screen with 100 mesh and the second-level vibrating screen with 120 mesh, sieved and dried, the dry powder was sieved to obtain the finished product of polyvinyl chloride blended resin. The performance test results of polyvinyl chloride blended resin are shown in Table 1.

[0077] Comparative Example 1

[0078] A polyvinyl chloride blended resin, the preparation steps are as follows:

[0079] 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 peroxy neodecanoate, 1.50 kg of tert-butyl peroxy pivalate, 13 kg of polyvinyl alcohol, and 0.70 kg of sodium bicarbonate were added to a 10000 L high-pressure reactor at one time. After stirring for 20 minutes, the temperature was raised to 60 °C for reaction. When the pressure drop reached 0.2 MPa (reaction for 240 minutes), the material temperature was raised to 65 °C through the reactor jacket to continue the reaction. When the pressure drop reached 0.5 MPa (reaction continued for 60 minutes), 2 kg of terminator and 20 kg of alkylphenol polyoxyethylene ether were added and stirred for 20 minutes. The material was discharged to the first-level vibrating screen with 80 mesh and the second-level vibrating screen with 110 mesh, and then dried. After the dry powder was sieved, the polyvinyl chloride blended resin product was obtained. The particle morphology of the polyvinyl chloride blended resin is shown in Figure 1 c. The performance test results are shown in Table 1.

[0080] Comparative Example 2

[0081] A polyvinyl chloride blended resin, the preparation steps are as follows:

[0082] 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 peroxy neodecanoate, 1.50 kg of tert-butyl peroxy pivalate, 13 kg of polyvinyl alcohol, and 0.70 kg of sodium bicarbonate were added to a 10000 L high-pressure reactor. After stirring for 20 minutes, the mixture was strongly dispersed in a 14 m / s single-stage homogenizing pump. The circulating homogenization amount was 35000 kg. During the homogenization process, the reactor was controlled to have a material temperature of ≤20 °C with cooling water. After homogenization, the temperature was directly raised to 60 °C for reaction. When the pressure drop reached 0.2 MPa, 2 kg of terminator and 20 kg of alkylphenol polyoxyethylene ether were added and stirred for 20 minutes. The mixture was discharged to a first-level vibrating screen with 80 mesh and a second-level vibrating screen with 110 mesh, and then dried and sieved with dry powder to obtain the finished polyvinyl chloride blended resin. The particle morphology of polyvinyl chloride blended resin can be seen in Figure 1 d. The performance test results are shown in Table 1.

[0083] Comparative Example 3

[0084] A polyvinyl chloride blended resin, the preparation steps are as follows:

[0085] 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 were added to a 10000 L high-pressure reactor. After stirring for 20 min, the mixture was strongly dispersed in a 14 m / s single-stage homogenizing pump. The circulating homogenization amount was 35000 kg. During the homogenization process, the reactor was controlled to have a material temperature of ≤20 °C with cooling water. After homogenization, the temperature was directly raised to 60 °C for reaction for 300 min (pressure drop of 0.4 MPa). 2 kg of terminator and 20 kg of alkylphenol polyoxyethylene ether were added and stirred for 20 min. The mixture was discharged to a first-level vibrating screen with 80 mesh and a second-level vibrating screen with 110 mesh, and then dried. The dry powder was sieved to obtain the finished polyvinyl chloride blended resin. The performance test results of the polyvinyl chloride blended resin are shown in Table 1.

[0086] Paste viscosity, scraper fineness, 100g resin paste 100 mesh filtration The paste resin is prepared according to the paste making process in GB / T 12004.2-1996 "Preparation of polyvinyl chloride paste resin paste", and the formula uses plasticizer DINP: paste resin P-450: blended resin ratio of 60:60:40. The paste viscosity test conditions of the resin paste are 25 ℃ constant temperature, Bruker LV-04 (#64) -1 min. The apparent density is tested according to GB / T 20022 "Determination of apparent density of plastic vinyl chloride homopolymer and copolymer resin". The oil absorption value is tested according to GB / T3400 "Determination of plasticizer absorption at room temperature for general-purpose vinyl chloride homopolymer and copolymer resin". The residual monomer is tested according to GB / T 29874 "Determination of residual vinyl chloride monomer in dry powder by gas chromatography for plastic vinyl chloride homopolymer and copolymer resin". The residue on the sieve is tested according to the method of GB / T 21843 "Determination of particle size of plastic vinyl chloride homopolymer and copolymer resins by mechanical sieving".

[0087] Table 1: Performance test results of polyvinyl chloride blended resin

[0088]

[0089] from Figure 1 It can be seen that the polyvinyl chloride blended resin prepared by the method of the present invention is spherical, has a uniform particle size distribution, and has few irregular particles. If the reaction mixture is not homogenized at high speed (Comparative Example 1) or only subjected to a single temperature-raising polymerization reaction (Comparative Example 2), the particle morphology of the product will be directly affected. As can be seen from Table 1, the polyvinyl chloride blended resin prepared by the present invention has a residual monomer content of less than 50 ppm and an oil absorption value of less than 10%. When blended into polyvinyl chloride paste resin, the paste viscosity can be greatly reduced, the flowability can be increased, the coating conditions of the resin can be improved, and the cost can be reduced. If the reaction mixture is not homogenized at high speed (Comparative Example 1) or only subjected to a single temperature-raising polymerization reaction (Comparative Example 2) or the reaction time is simply extended (Comparative Example 3), the oil absorption value and the viscosity of the polyvinyl chloride blended resin will not be improved. Moreover, if the reaction time continues to be extended, the polymer emulsion will show slight demulsification or agglomeration, resulting in an increase in the frequency of kettle cleaning and reduced production efficiency.

[0090] The above specific embodiments describe the implementation of the present invention in detail, but 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, the technical solution of the present invention can be modified and changed in many simple ways, and these simple modifications 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) Mix water, 70% to 100% of the feed amount of vinyl chloride, comonomer, initiator, dispersant and buffer uniformly; (b) strongly dispersing the mixture obtained in step (a); (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 feed amount of vinyl chloride; (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 5~15℃; (f) Add terminator and emulsifier, stir for a period of time and then discharge the material to the 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 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 strong dispersion in step (b) is performed using a high-speed homogenizing pump, which is a single-stage or multi-stage homogenizing pump with a shear line speed of 5 to 30 m / s, and the circulating homogenization amount is 1 to 6 times the total raw material feed amount.

5. 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.

6. The method for producing a vinyl chloride-based blended resin according to claim 1, characterized in that: Preferably, the mixing time in step (a) does not exceed 30 min.

7. 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.

8. The method for producing a vinyl chloride-based blended resin according to claim 7, 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.

9. The method for producing a vinyl chloride-based blended resin according to claim 7, 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.

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

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