PVC (polyvinyl chloride) resin as well as polymerization method and application thereof

Abstract

The invention discloses PVC (polyvinyl chloride) resin as well as a polymerization method and application thereof, and belongs to the technical field of PVC polymerization. The PVC resin is prepared from the following raw materials in parts by weight: 40 to 90 parts of vinyl chloride, 125 to 240 parts of desalted water, 0.05 to 0.15 part of dispersing agent, 0.04 to 0.10 part of initiator emulsion, 5 to 10 parts of terminating agent and 1 to 5 parts of modified MBS emulsion. The preparation method comprises the following steps: by taking vinyl chloride as a monomer, adding desalted water, a dispersing agent and an initiator emulsion, stirring and mixing for 10-20 minutes at normal temperature, raising the temperature of a kettle to 57-60 DEG C, when the reaction begins and the pressure drop value in the kettle reaches 0.10-0.30 MPa, filling a terminating agent into the kettle, adding the modified MBS emulsion, stirring for 20-30 minutes, and carrying out centrifugal dewatering, drying and screening operation on a polymer material obtained by the reaction to obtain PVC resin powder. The PVC resin disclosed by the invention is low in odor and resistant to yellowing, and meets the processing requirements of medical plastic products.

Description

Technical Field

[0001] The invention discloses a PVC resin and a polymerization method and application thereof, belonging to the technical field of PVC polymerization. Background Art

[0002] Polyvinyl chloride (PVC) has excellent chemical and physical properties. Its processed products are highly transparent, wear-resistant, cold-resistant, oil-resistant, heat-resistant and aging-resistant, and can be highly filled. In addition to being used as synthetic leather, canvas, sheath materials, films, sheets, and special-shaped products of hoses, after optimizing the processing formula and process conditions, it can also be used in medical materials (hospital emergency auxiliary equipment, medical containers, surgical instruments, blood tubes, implant tubes, and drug transport containers) and food packaging in various occasions. It has a wide range of uses and application prospects.

[0003] During the polymerization of polyvinyl chloride, due to the use of initiators, dispersants, terminators and related solvents, the polyvinyl chloride resin itself has a strong odor at a certain temperature. Although it undergoes the subsequent drying and gas stripping process, it is mainly to evaporate the moisture in the resin, and there are still more or less various additives, solvents and small molecules with high volatility in the resin. Therefore, these residual additives will completely evaporate during the heating process of the resin processing, causing the material to have a strong odor. When polyvinyl chloride resin is placed at a temperature of 60-80℃ for half an hour, it can volatilize gases with a strong odor, such as olefins, alkanes, acetic acid, 2-ethylhexanol, 2-methylbutanol, especially 2-ethylhexanol and 2-methylbutanol, which have a strong pungent odor, which has an adverse effect on the odor of medical products and processing.

[0004] In the prior art, the means to reduce the odor of PVC resin are: 1. After the PVC resin is obtained by polymerization, when the PVC resin is heated and blended with various additives, an odor absorbent is added to reduce the odor. CN201710206562.5 A low-odor medical PVC composition and preparation method, but the PVC composition obtained by this method has an unsatisfactory effect in reducing the odor. If the use temperature is increased, the PVC composition will still emit an odor, and the odor level is poor in a high temperature environment. Moreover, although this method can reduce the odor of the PVC composition, the PVC resin itself still has a strong odor, and it will still emit a strong odor during the process of heating and blending to prepare the PVC composition.

[0005] 2. After the PVC resin is obtained by polymerization, the PVC resin is modified again to reduce the odor. The existing technology is to carry out graft copolymerization and remove the monomers that produce odor in the PVC resin. CN202011580543.7 A suspension swelling graft modification method for PVC resin and CN202110532247.8 A method for removing residual monomers in modified PVC resin by chemical conversion both adopt this type of method. This type of method requires copolymerization again. This method requires the re-addition of copolymer monomers, the re-addition of initiators, and the re-polymerization. The process is cumbersome and undoubtedly increases the production cost of low-odor PVC resin.

[0006] 3. At present, the odor level of PVC resin and PVC composition is usually only studied at room temperature of 18-28℃, but the odor level at high temperature of 60℃ or even 90℃ is not involved. PVC resin for medical plastic products is usually used to produce medical devices and drug packaging, such as instrument accessories, syringes, catheters, drug packaging bags, medicine bottles, tablets or capsules. PVC sheets are often heated and sealed or heated to engrave the production date, or added with additives for secondary processing into PVC compositions; therefore, PVC resin for medical plastic products is often used in an environment of 60℃ or even 90℃. It is more difficult for PVC resin to achieve a low odor level in an environment higher than room temperature. In addition, medical device production workshops and drug packaging workshops have high requirements for low odor levels. Therefore, there is an urgent need for a low-odor PVC resin suitable for the preparation of medical plastic products. Summary of the invention

[0007] The technical problem to be solved by the present invention is to overcome the deficiencies of the prior art and provide a PVC resin and a polymerization method and application thereof. The PVC resin has low odor and is resistant to yellowing, and can meet the processing requirements of medical plastic products.

[0008] The technical scheme of the method adopted by the present invention to solve the technical problem is: the PVC resin is prepared from the following raw materials in parts by weight: 40-90 parts of vinyl chloride, 125-240 parts of desalted water, 0.05-0.15 parts of dispersant, 0.04-0.10 parts of initiator emulsion, 5-10 parts of terminator and 1-5 parts of modified MBS emulsion.

[0009] The PVC resin is prepared from the following raw materials in parts by weight: 55-65 parts of vinyl chloride, 170-190 parts of desalted water, 0.06-0.11 parts of dispersant, 0.05-0.07 parts of initiator emulsion, 6-9 parts of terminator and 2-4 parts of modified MBS emulsion.

[0010] The terminator is a 2-5% by mass solution of N,N-diethylhydroxylamine (DEHA for short).

[0011] The dispersant is a compound of high alcoholysis degree polyvinyl alcohol and low alcoholysis degree polyvinyl alcohol in a weight ratio of 1:1-5; the high alcoholysis degree polyvinyl alcohol is a polyvinyl alcohol with a polymerization degree of 800-2000 and an alcoholysis degree of 70-90%; the low alcoholysis degree polyvinyl alcohol is a polyvinyl alcohol with a polymerization degree of 200-500 and an alcoholysis degree of 30-55%. Preferably, the dispersant is a compound of high alcoholysis degree polyvinyl alcohol and low alcoholysis degree polyvinyl alcohol in a weight ratio of 1:1.5-2; The initiator emulsion is a uniform emulsion in which the emulsifier, initiator and deionized water are homogenized to form an initiator content of 5-40%, wherein the weight ratio of the emulsifier to the initiator is 1:1-5. Preferably, the weight ratio of the emulsifier to the initiator is 1:2-3.

[0012] The emulsifier is polyvinyl alcohol with a polymerization degree of 800-2000 and an alcoholysis degree of 70-90%; the initiator is a mixture of tert-amyl peroxypivalate (abbreviated as TAPP) and di(2-ethylhexyl) peroxydicarbonate (abbreviated as EHP) in a weight ratio of 1-2:1.

[0013] The preparation method of the modified MBS emulsion comprises the following steps: 1) Mix stearic acid and water, heat to 70-90°C to dissolve and obtain a stearic acid aqueous solution; 2) Add stearic acid aqueous solution into MBS latex and stir evenly.

[0014] In step 1), the weight ratio of stearic acid to water is 1:5-15; in step 2), the weight ratio of stearic acid aqueous solution to MBS latex is 1:3-5. If the amount of stearic acid aqueous solution is too large, the solution will cause MBS latex to demulsify and precipitate, which is not conducive to subsequent uniform mixing with PVC. If the amount is too small, it will not play a corresponding role.

[0015] The polymerization method of the PVC resin comprises the following steps: Take vinyl chloride as the monomer, in the presence of desalted water, dispersant and initiator emulsion, stir and mix at room temperature for 10-20 minutes, then raise the kettle temperature to 57-60°C to start the reaction, when the pressure drop in the kettle reaches 0.10-0.30MPa, add terminator into the kettle, then add modified MBS emulsion, continue stirring for 20-30 minutes, centrifuge dehydrate, dry and sieve the polymer material obtained by the reaction to obtain PVC resin powder.

[0016] The application of the PVC resin is characterized by being used in the field of medical plastic products.

[0017] The present invention is described as follows: The applicant found in the research that adding modified MBS emulsion during the polymerization reaction of preparing PVC resin can not only improve the processing performance of PVC resin itself, but also significantly reduce the odor of PVC resin. Even the obtained PVC resin still maintains good low odor performance when heated from 23°C to 90°C. The modified MBS emulsion is liquid and has better dispersibility. It can condense and settle during the polymerization process. As the polymerization reaction continues, the particles condensed by the liquid modified MBS emulsion are dispersed on the PVC microparticles generated by the polymerization, thereby blocking the odor emission.

[0018] In addition, the applicant found that if modified MBS resin is added during the heating and blending process after the PVC resin is obtained by polymerization, the two resins are completely physically blended, and the MBS resin cannot enter the interior of the PVC sub-particles and is effectively distributed on the surface of the PVC particles. In this case, the modified MBS resin only has a toughening effect and almost no deodorizing effect.

[0019] Preferably, MBS latex is made of the following raw materials in parts by weight: 70-85 parts of styrene-butadiene latex, 15-35 parts of methyl methacrylate, 0.1-0.5 parts of initiator, and 200-300 parts of deionized water, wherein the styrene-butadiene latex is made of the following raw materials in parts by weight: 60-65 parts of butadiene, 35-40 parts of styrene, 0.1-0.5 parts of initiator, 1-3.5 parts of composite emulsifier, 0.2-0.5 parts of electrolyte salt, and 200-300 parts of deionized water; The composite emulsifier is a mixture of fatty acid soap and sodium dodecylbenzene sulfonate in a weight ratio of 1:2-3. The fatty acid soap is one of potassium laurate soap and potassium coconut oil soap.

[0020] The initiator is one of potassium persulfate, ammonium persulfate or cumene hydroperoxide.

[0021] The electrolyte salt is an organic acid metal salt; preferably, the organic acid metal salt is potassium tartrate.

[0022] Preferably, the preparation method of the MBS latex is as follows: 1) Synthesis of styrene-butadiene latex: deionized water, composite emulsifier, initiator are added to the reactor in sequence, nitrogen is passed, butadiene and styrene are added, the temperature is raised to 50-80°C for reaction, the pressure is controlled below 1Mpa, stirring and reaction is stopped when the pressure is less than 0.2Mpa, and electrolyte salt is added to remove excess composite emulsifier to obtain styrene-butadiene latex; 2) MBS synthesis: Deionized water, styrene-butadiene latex, methyl methacrylate and initiator are added into a reaction kettle for graft polymerization at a polymerization temperature of 50-80°C and a reaction time of 4-7 hours to obtain MBS latex.

[0023] Compared with the prior art, the present invention has the following beneficial effects: 1. The PVC resin of the present invention has low odor and yellowing resistance, and can meet the processing requirements of medical plastic products.

[0024] The PVC resin of the present invention has low odor and can be used for medical products. MBS has been added, so when producing relatively high impact-resistant products, no impact modification is required. Stearic acid has been added, so the processing performance is good, and no or less lubricant can be added when producing products. In addition, the applicant has found that adding modified MBS emulsion in the polymerization reaction can significantly reduce the odor of PVC; the applicant has also found that blending the same amount of PVC resin, MBS resin and stearic acid does not have the effect of reducing odor. The PVC resin of the present invention not only has low odor at room temperature, but also has a good odor level as the temperature rises. The odor level at 23°C is level 1, the odor level at 60°C is level 2, and the odor level at 90°C is level 2.5-3, and it can still maintain low odor in a hot environment.

[0025] The PVC resin of the present invention has high whiteness and good aging resistance, the whiteness of the PVC resin can reach 97.6-98.5%, and the aging whiteness of the PVC resin (160°C, 10 minutes) can reach 88.0-90.7%. In addition, the PVC resin of the present invention has good thermal stability, and the 160°C Congo red thermal stability time is 4.61-5.10 minutes.

[0026] 2. The preparation method of the PVC resin of the present invention is simple, easy and low-cost. It can reduce the odor of the PVC resin and increase the yellowing resistance of the PVC resin without any modification or increase in equipment cost.

[0027] 3. The PVC resin of the present invention can be applied to the field of medical plastic products and meet the requirements of medical PVC. DETAILED DESCRIPTION

[0028] The present invention is further described below in conjunction with specific examples, wherein Example 1 is the best example. The comparative examples are designed to demonstrate the effects of the present invention. The raw materials and additives used are as follows: MBS latex is made of the following raw materials in parts by weight: 75 parts of styrene-butadiene latex, 20 parts of methyl methacrylate, 0.3 parts of initiator (potassium persulfate), and 250 parts of deionized water, wherein the styrene-butadiene latex is made of the following raw materials in parts by weight: 60 parts of butadiene, 40 parts of styrene, 0.4 parts of initiator (potassium persulfate), 2 parts of composite emulsifier (potassium laurate soap and sodium dodecylbenzene sulfonate in a weight ratio of 1:3), 0.3 parts of potassium tartrate, and 270 parts of deionized water; The preparation method of MBS latex is as follows: 1) Synthesis of styrene-butadiene latex: deionized water, composite emulsifier, initiator were added to the reactor in sequence, nitrogen was passed through, butadiene and styrene were added, the temperature was raised to 70°C for reaction, the pressure was controlled below 1 MPa, stirring and reaction was stopped when the pressure was less than 0.2 MPa, potassium tartrate was added to remove the excess composite emulsifier to obtain styrene-butadiene latex; 2) MBS synthesis: Deionized water, styrene butadiene latex, methyl methacrylate and initiator were added into a reaction kettle for graft polymerization at a polymerization temperature of 70°C and a reaction time of 5 hours to obtain MBS latex.

[0029] Example 1 The PVC resin of this embodiment is made from the following raw materials in parts by weight: 60 parts of vinyl chloride, 180 parts of desalted water, 0.07 parts of dispersant, 0.06 parts of initiator emulsion, 7 parts of terminator and 3 parts of modified MBS emulsion; The dispersant is a compound of high alcoholysis degree polyvinyl alcohol and low alcoholysis degree polyvinyl alcohol in a weight ratio of 1:1.5. The high alcoholysis degree polyvinyl alcohol has a polymerization degree of 1000 and an alcoholysis degree of 80%; the low alcoholysis degree polyvinyl alcohol has a polymerization degree of 300 and an alcoholysis degree of 45%.

[0030] The initiator emulsion is a uniform emulsion in which the emulsifier, initiator and deionized water are homogenized to form an initiator content of 30%, wherein the weight ratio of the emulsifier to the initiator is 1:3; the emulsifier is polyvinyl alcohol with a polymerization degree of 1000 and an alcoholysis degree of 80%. The initiator is a mixture of TAPP and EHP at a weight ratio of 2:1.

[0031] Wherein, the preparation method of modified MBS emulsion is as follows: 1) Mix stearic acid and water in a weight ratio of 1:10, and heat to 80°C to dissolve to obtain a stearic acid aqueous solution; 2) Add the stearic acid aqueous solution to the MBS latex at a weight ratio of 1:5 and stir evenly; Wherein, the terminator is a 4% by mass N,N-diethylhydroxylamine solution; The polymerization method of the PVC resin of this embodiment comprises the following steps: Take vinyl chloride as the monomer, in the presence of desalted water, dispersant and initiator emulsion, stir and mix at room temperature for 15 minutes, then raise the kettle temperature to 58.0℃ to start the reaction, when the pressure drop in the kettle reaches 0.20MPa, add terminator into the kettle, then add modified MBS emulsion, continue stirring for 20 minutes, centrifuge dehydrate, dry and sieve the polymer material obtained by the reaction to obtain PVC resin powder.

[0032] Example 2 The PVC resin of this embodiment is made from the following raw materials in parts by weight: 60 parts of vinyl chloride, 180 parts of desalted water, 0.07 parts of dispersant, 0.06 parts of initiator emulsion, 7 parts of terminator and 2 parts of modified MBS emulsion; Wherein, the dispersant, initiator emulsion, modified MBS emulsion, and terminator components are the same as those in Example 1; The polymerization method of the PVC resin of this embodiment comprises the following steps: Take vinyl chloride as the monomer, in the presence of desalted water, dispersant and initiator emulsion, stir and mix at room temperature for 15 minutes, then raise the kettle temperature to 58.0℃ to start the reaction, when the pressure drop in the kettle reaches 0.10MPa, add terminator into the kettle, then add modified MBS emulsion, continue stirring for 20 minutes, centrifuge dehydrate, dry and sieve the polymer material obtained to obtain PVC resin powder.

[0033] Example 3 The PVC resin of this embodiment is made from the following raw materials in parts by weight: 65 parts of vinyl chloride, 190 parts of desalted water, 0.06 parts of dispersant, 0.07 parts of initiator emulsion, 9 parts of terminator and 4 parts of modified MBS emulsion; The dispersant is a compound of high alcoholysis degree polyvinyl alcohol and low alcoholysis degree polyvinyl alcohol in a weight ratio of 1:2; high alcoholysis degree polyvinyl alcohol is polyvinyl alcohol with a polymerization degree of 1500 and an alcoholysis degree of 90%; low alcoholysis degree polyvinyl alcohol is polyvinyl alcohol with a polymerization degree of 500 and an alcoholysis degree of 30%; The initiator emulsion is a uniform emulsion in which the emulsifier, initiator and deionized water are homogenized to form an initiator content of 40%, wherein the weight ratio of the emulsifier to the initiator is 1:2; the emulsifier is polyvinyl alcohol with a polymerization degree of 1500 and an alcoholysis degree of 90%; the initiator is a mixture of TAPP and EHP in a weight ratio of 1:1; The preparation method of the modified MBS emulsion comprises the following steps: 1) Mix stearic acid and water in a weight ratio of 1:10, and heat to 70°C to dissolve to obtain a stearic acid aqueous solution; 2) Add stearic acid aqueous solution to MBS latex at a weight ratio of 1:4 and stir evenly; Wherein, the terminator is a 5% by mass N,N-diethylhydroxylamine solution; The polymerization method of the PVC resin of this embodiment comprises the following steps: Take vinyl chloride as the monomer, in the presence of desalted water, dispersant and initiator emulsion, stir and mix at room temperature for 20 minutes, then raise the kettle temperature to 60°C to start the reaction, when the pressure drop in the kettle reaches 0.30MPa, add terminator into the kettle, then add modified MBS emulsion, continue stirring for 20 minutes, centrifuge dehydrate, dry and sieve the polymer material obtained by the reaction to obtain PVC resin powder.

[0034] Example 4 The PVC resin of this embodiment is made from the following raw materials in parts by weight: 55 parts of vinyl chloride, 170 parts of desalted water, 0.11 parts of dispersant, 0.05 parts of initiator emulsion, 6 parts of terminator and 2 parts of modified MBS emulsion; The dispersant is a compound of high alcoholysis degree polyvinyl alcohol and low alcoholysis degree polyvinyl alcohol in a weight ratio of 1:2; high alcoholysis degree polyvinyl alcohol is polyvinyl alcohol with a polymerization degree of 2000 and an alcoholysis degree of 70%; low alcoholysis degree polyvinyl alcohol is polyvinyl alcohol with a polymerization degree of 200 and an alcoholysis degree of 30%; The initiator emulsion is a uniform emulsion in which the emulsifier, initiator and deionized water are homogenized to form an initiator content of 20% by mass, wherein the weight ratio of the emulsifier to the initiator is 1:2; the emulsifier is polyvinyl alcohol with a polymerization degree of 2000 and a degree of alcoholysis of 70%; and the initiator is a mixture of TAPP and EHP in a weight ratio of 1:1.

[0035] The preparation method of the modified MBS emulsion comprises the following steps: 1) Mix stearic acid and water in a weight ratio of 1:5, and heat to 90° C. to dissolve to obtain a stearic acid aqueous solution; 2) Add stearic acid aqueous solution to MBS latex at a weight ratio of 1:3 and stir evenly; Wherein, the terminator is a 4% by mass N,N-diethylhydroxylamine solution; The polymerization method of the PVC resin of this embodiment comprises the following steps: Take vinyl chloride as the monomer, in the presence of desalted water, dispersant and initiator emulsion, stir and mix at room temperature for 10 minutes, then raise the kettle temperature to 57°C to start the reaction, when the pressure drop in the kettle reaches -0.30MPa, add terminator into the kettle, then add modified MBS emulsion, continue stirring for 25 minutes, and subject the polymer material obtained by the reaction to centrifugal dehydration, drying and sieving operations to obtain PVC resin powder.

[0036] Example 5 The PVC resin of this embodiment is made from the following raw materials in parts by weight: 90 parts of vinyl chloride, 240 parts of desalted water, 0.15 parts of dispersant, 0.04 parts of initiator emulsion, 10 parts of terminator and 5 parts of modified MBS emulsion; The dispersant is a compound of high alcoholysis degree polyvinyl alcohol and low alcoholysis degree polyvinyl alcohol in a weight ratio of 1:5; high alcoholysis degree polyvinyl alcohol is polyvinyl alcohol with a polymerization degree of 800 and an alcoholysis degree of 90%; low alcoholysis degree polyvinyl alcohol is polyvinyl alcohol with a polymerization degree of 200 and an alcoholysis degree of 30%; The initiator emulsion is a uniform emulsion in which the emulsifier, initiator and deionized water are homogenized to form an initiator content of 40%, wherein the weight ratio of the emulsifier to the initiator is 1:5; the emulsifier is polyvinyl alcohol with a polymerization degree of 800 and an alcoholysis degree of 90%; the initiator is a mixture of TAPP and EHP in a weight ratio of 2:1; The preparation method of the modified MBS emulsion comprises the following steps: 1) Mix stearic acid and water in a weight ratio of 1:10, and heat to 70-90°C to dissolve to obtain a stearic acid aqueous solution; 2) Add stearic acid aqueous solution to MBS latex at a weight ratio of 1:4 and stir evenly; Wherein, the terminator is a 2% by mass N,N-diethylhydroxylamine solution; The polymerization method of the PVC resin in this embodiment is the same as that in Example 1.

[0037] Example 6 The PVC resin of this embodiment is made from the following raw materials in parts by weight: 40 parts of vinyl chloride, 125 parts of desalted water, 0.05 parts of dispersant, 0.10 parts of initiator emulsion, 5 parts of terminator and 1 part of modified MBS emulsion; The dispersant is a compound of high alcoholysis degree polyvinyl alcohol and low alcoholysis degree polyvinyl alcohol in a weight ratio of 1:1; high alcoholysis degree polyvinyl alcohol is polyvinyl alcohol with a polymerization degree of 1000 and an alcoholysis degree of 80%; low alcoholysis degree polyvinyl alcohol is polyvinyl alcohol with a polymerization degree of 500 and an alcoholysis degree of 45%; The initiator emulsion is a uniform emulsion in which the emulsifier, initiator and deionized water are homogenized to form an initiator content of 5%, wherein the weight ratio of the emulsifier to the initiator is 1:1; the emulsifier is polyvinyl alcohol with a polymerization degree of 1000 and an alcoholysis degree of 80%; the initiator is a mixture of TAPP and EHP at a weight ratio of 1.5:1; The preparation method of the modified MBS emulsion comprises the following steps: 1) Mix stearic acid and water in a weight ratio of 1:15, and heat to 70-90°C to dissolve to obtain a stearic acid aqueous solution; 2) Add stearic acid aqueous solution to MBS latex at a weight ratio of 1:5 and stir evenly; Wherein, the terminator is a 5% by mass N,N-diethylhydroxylamine solution; The polymerization method of the PVC resin in this embodiment is the same as that in Example 1.

[0038] Comparative Example 1 The preparation method of this comparative example is the same as that of Example 1, except that the modified MBS emulsion is different. No stearic acid is added during the preparation of the modified MBS emulsion of this comparative example.

[0039] The step 1) of the method for preparing the modified MBS emulsion is deleted, the stearic acid aqueous solution in the step 2) is replaced with water of equal mass, and in the step 2) the following is adopted: water is added to the MBS latex and stirred evenly.

[0040] Comparative Example 2 The preparation method of this comparative example is the same as that of Example 1, except that no modified MBS emulsion is added in the polymerization method for preparing the PVC resin to obtain the PVC resin.

[0041] Comparative Example 3 The preparation method of this comparative example is the same as that of Example 1, except that: in the preparation method of the modified MBS emulsion, step 2) adds the stearic acid aqueous solution to the MBS latex at a weight ratio of 1:1 and stirs evenly.

[0042] Comparative Example 4 The preparation method of this comparative example is the same as that of Example 1, except that: in the preparation method of the modified MBS emulsion, step 2) adds the stearic acid aqueous solution to the MBS latex at a weight ratio of 1:7, and stirs evenly.

[0043] Performance Testing The PVC resin obtained in the embodiment and the comparative example was tested, and the test methods were as follows: Test 1: Whiteness: Tested in accordance with GB2913-1982.

[0044] Test 2: Aging whiteness (160℃, 10min): Tested in accordance with GB / T15595-2008.

[0045] Test 3: 60℃ Congo red heat stability time: tested in accordance with GB / T8815-2008.

[0046] Test 4: The high temperature condition of the PVC resin odor classification test is also determined to be 90° C. Referring to the standard SMC30156-2007 Car Interior Material Odor Test, this standard is used to judge the odor classification of rubber and plastic materials, where the classification criteria are shown in Table 1, and the odor grades of PVC resins at different temperatures in the examples and comparative examples are shown in Table 2.

[0047] Table 1 Odor classification criteria . Table 2 Odor levels of PVC resins at different temperatures in Examples and Comparative Examples .

[0048] Table 3 Quantitative results of PVC resin materials of Example 1 and Comparative Example (mg·L -1 ) .

[0049] Table 4 Test results of PVC resin in embodiments and comparative examples .

[0050] It can be seen from Tables 1-4 that the modified MBS emulsions in Comparative Examples 1-4 are different, namely, no stearic acid is added, no modified MBS emulsion is added, too much stearic acid aqueous solution, and too little stearic acid aqueous solution. The deodorization effect of Comparative Example 1-2 is obviously not as good as that of the embodiments. In Comparative Examples 3-4, the amount of stearic acid aqueous solution is too large, and the solution causes the MBS latex to demulsify and precipitate, which is not conducive to uniform mixing with PVC during the subsequent polymerization reaction; the amount of stearic acid aqueous solution is too small, and the corresponding deodorization effect cannot be achieved. It proves that the addition of modified MBS emulsion in the polymerization reaction of the present invention can indeed play the role of deodorizing PVC resin and reducing the odor level.

[0051] As can be seen from Tables 1-2, the odor level of the PVC resin of the present invention is level 1 at 23°C, level 2 at 60°C, and level 2.5-3 at 90°C, and it can still maintain low odor in a hot environment. As can be seen from Table 3, the total volatiles in Example 1 are significantly less than those in the comparative example.

[0052] It can be seen from Table 4 that the PVC resin of the present invention has high whiteness and good aging resistance, the whiteness of the PVC resin can reach 97.6-98.5%, and the aging whiteness of the PVC resin (160°C, 10min) can reach 88.0-90.7%. In addition, the PVC resin of the present invention has good thermal stability, and the 160°C Congo red thermal stability time is 4.61-5.10min.

[0053] The above is only a preferred embodiment of the present invention, and does not limit the present invention in other forms. Any technician familiar with the profession may use the above disclosed technical content to change or modify it into an equivalent embodiment with equivalent changes. However, any simple modification, equivalent change and modification made to the above embodiment according to the technical essence of the present invention without departing from the technical solution of the present invention still belongs to the protection scope of the technical solution of the present invention.

Claims

1. A PVC resin, characterized in that: The invention is prepared from the following raw materials in parts by weight: 40-90 parts of vinyl chloride, 125-240 parts of desalted water, 0.05-0.15 parts of dispersant, 0.04-0.10 parts of initiator emulsion, 5-10 parts of terminator and 1-5 parts of modified MBS emulsion.

2. A PVC resin according to claim 1, characterized in that: The invention is prepared from the following raw materials in parts by weight: 55-65 parts of vinyl chloride, 170-190 parts of desalted water, 0.06-0.11 parts of dispersant, 0.05-0.07 parts of initiator emulsion, 6-9 parts of terminator and 2-4 parts of modified MBS emulsion.

3. A PVC resin according to claim 1, characterized in that: The terminator is a 2-5% by mass N,N-diethylhydroxylamine solution.

4. A PVC resin according to claim 1, characterized in that: The dispersant is a compound of high alcoholysis degree polyvinyl alcohol and low alcoholysis degree polyvinyl alcohol in a weight ratio of 1:1-5; the high alcoholysis degree polyvinyl alcohol is a polyvinyl alcohol with a polymerization degree of 800-2000 and an alcoholysis degree of 70-90%; the low alcoholysis degree polyvinyl alcohol is a polyvinyl alcohol with a polymerization degree of 200-500 and an alcoholysis degree of 30-55%.

5. A PVC resin according to claim 1, characterized in that: The initiator emulsion is a uniform emulsion obtained by homogenizing an emulsifier, an initiator and deionized water into an initiator mass content of 5-40%, wherein the weight ratio of the emulsifier to the initiator is 1:1-5.

6. A PVC resin according to claim 5, characterized in that: The emulsifier is polyvinyl alcohol with a polymerization degree of 800-2000 and an alcoholysis degree of 70-90%; the initiator is a mixture of tert-amyl peroxypivalate and di(2-ethylhexyl) peroxydicarbonate in a weight ratio of 1-2:

1.

7. A PVC resin according to claim 1, characterized in that: The preparation method of the modified MBS emulsion comprises the following steps: 1) Mix stearic acid and water, and heat to 70-90°C to dissolve to obtain a stearic acid aqueous solution; 2) Add stearic acid aqueous solution into MBS latex and stir evenly.

8. A PVC resin according to claim 7, characterized in that: Step 1) The weight ratio of stearic acid to water is 1:5-15; Step 2) The weight ratio of stearic acid aqueous solution to MBS latex is 1:3-5.

9. A method for polymerizing a PVC resin according to any one of claims 1 to 8, characterized in that: The steps include: Take vinyl chloride as the monomer, in the presence of desalted water, dispersant and initiator emulsion, stir and mix at room temperature for 10-20 minutes, then raise the kettle temperature to 57-60°C to start the reaction, when the pressure drop in the kettle reaches 0.10-0.30MPa, add terminator into the kettle, then add modified MBS emulsion, continue stirring for 20-30 minutes, centrifuge, dehydrate, dry and sieve the polymer material obtained by the reaction to obtain PVC resin powder.

10. The use of a PVC resin according to any one of claims 1 to 8, characterized in that: Application in the field of medical plastic products.