CN113388055B - Low-polymerization-degree polyvinyl chloride special resin - Google Patents

Low-polymerization-degree polyvinyl chloride special resin Download PDF

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CN113388055B
CN113388055B CN202110716421.4A CN202110716421A CN113388055B CN 113388055 B CN113388055 B CN 113388055B CN 202110716421 A CN202110716421 A CN 202110716421A CN 113388055 B CN113388055 B CN 113388055B
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polymerization
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initiator
polyvinyl chloride
pvc
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CN113388055A (en
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宋晓玲
郭成军
汪海位
孙中常
韩忠良
邹磊
王多荣
马宝琪
刘培锋
郭伟杰
赵雁升
潘鑫德
赵保强
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Tianwei Chemical Co ltd
Xinjiang Tianye Group Co Ltd
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Tianwei Chemical Co ltd
Xinjiang Tianye Group Co Ltd
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    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
    • C08F114/00—Homopolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by a halogen
    • C08F114/02—Monomers containing chlorine
    • C08F114/04—Monomers containing two carbon atoms
    • C08F114/06—Vinyl chloride
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
    • C08F2/00—Processes of polymerisation
    • C08F2/34—Polymerisation in gaseous state
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
    • C08F2/00—Processes of polymerisation
    • C08F2/36—Polymerisation in solid state
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
    • C08F2/00—Processes of polymerisation
    • C08F2/44—Polymerisation in the presence of compounding ingredients, e.g. plasticisers, dyestuffs, fillers
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
    • C08F4/00—Polymerisation catalysts
    • C08F4/28—Oxygen or compounds releasing free oxygen
    • C08F4/32—Organic compounds
    • C08F4/38—Mixtures of peroxy-compounds

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  • Health & Medical Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Medicinal Chemistry (AREA)
  • Polymers & Plastics (AREA)
  • Organic Chemistry (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Addition Polymer Or Copolymer, Post-Treatments, Or Chemical Modifications (AREA)
  • Polymerisation Methods In General (AREA)

Abstract

The invention relates to a low-polymerization-degree polyvinyl chloride special resin which is mainly prepared from the following raw materials: 100 parts of vinyl chloride monomer, 115-130 parts of deionized water, 0.005-0.02 part of neutralizer, 0.04-0.068 part of dispersant A, 0.017-0.036 part of dispersant B, 0.014-0.034 part of surfactant, 0.014-0.026 part of initiator A and 0.012-0.02 part of initiator B. The PVC resin with the average polymerization degree of 650-850 obtained by the invention has higher internal porosity and uniform porosity, increases the diffusion capacity of the special resin to small molecular substances, and can be widely applied to the production process of the special PVC resin for chlorination by a gas-solid phase method.

Description

Low-polymerization-degree special resin for polyvinyl chloride
Technical Field
The invention relates to the technical field of polymer chemical industry, in particular to a low-polymerization-degree polyvinyl chloride special resin.
Background
Chlorinated polyvinyl chloride (CPVC) is obtained by further chlorinating polyvinyl chloride (PVC) and is a novel high-molecular elastomer material between rubber and plastics. After the PVC resin is chlorinated, the irregularity of molecular bonds is increased, the polarity is enhanced, the solubility of the resin is increased, and the chemical stability is improved, so that the heat resistance, the corrosion resistance of acid, alkali, salt, an oxidant and the like of the material are improved, compared with PVC, the heat resistance, the corrosion resistance, the flame-retardant self-extinguishing property, the mechanical property and the like of CPVC are greatly improved, and the CPVC resin is widely applied to the fields of building materials, electrical, chemical engineering, metallurgy, medicine, coatings and the like.
At present, the quality of domestic CPVC resin has a large difference from that of imported resin, and one reason for the difference is that high-quality special PVC resin for chlorination is lacked in China. The development of PVC resin suitable for chlorination is a development requirement of CPVC industry and a development direction of PVC manufacturing enterprises.
The diffusion speed of chlorine molecules in PVC resin particles is an important factor for determining the chlorination reaction rate and the product quality. The diffusion of chlorine molecules in PVC resin particles can be divided into three stages from outside to inside, namely stage 1, the chlorine molecules enter the pores in the particles from the thin layer or the rupture part of the membrane of the PVC resin particles; stage 2, chlorine molecules entering the interior of the granules continuously diffuse to the deep part of the granules along the unobstructed pores in the granules and contact the surfaces of primary particles and primary particle aggregates surrounding the pores; and 3, diffusing chlorine molecules on the inner surface of the PVC resin particles into the primary particles and the aggregates. The diffusion process of chlorine gas into PVC granules puts 3 requirements on the structural characteristics of PVC resin special for chlorination: firstly, the surface of the resin particles has no or few skins, which is beneficial to the diffusion of chlorine molecules to the interior; secondly, the resin particles have uniform pores and small average particle size; the more uniform the pore distribution, the smaller the average diameter, the larger the specific surface area within the particle and the smaller the average depth to which chlorine gas needs to diffuse into the primary particles in stage 3; because the consumption speed of chlorine gas in the primary particles is greater than the diffusion supplement speed, the reduction of the diffusion depth is beneficial to uniform chlorination; thirdly, the primary particles and the aggregates have loose structures, the more loose the structures are, the faster the diffusion speed of chlorine molecules is, and the smaller the concentration gradient of the chlorine in the primary particles is.
Chinese patent CN112029137A discloses a preparation method of special PVC resin for chlorination, which comprises the following steps: adding the wet material of the water-containing PVC resin centrifuged by the PVC polymerization production system into a closed container with stirring, adding the functional organic solvent, uniformly stirring and mixing, and performing microwave heating and drying on the uniformly mixed primary material to obtain the special PVC resin for chlorination. The PVC resin wet material particles obtained by the aqueous phase polymerization method contain a large amount of water, water is changed into water vapor during microwave heating, the structure around the PVC resin particles is pressed to be closed at the initial stage of the water vapor, the constraint of the PVC resin particles and the external involucra of the particles is broken at the later stage, the PVC resin particles and the external involucra of the particles escape quickly, the special chlorination resin with loose particle structure, high plasticizer oil absorption rate and large specific surface area is obtained, the production requirement of the CPVC resin can be met, and the chlorination reaction is more favorably carried out.
Chinese patent CN112029138A discloses a preparation method of polyvinyl chloride resin special for chlorination, which comprises the following steps: adding the centrifuged wet water-containing PVC resin material obtained in the PVC polymerization production system into a stirred closed container, adding a functional organic solvent, uniformly stirring and mixing, freezing, and performing microwave heating and drying on the frozen low-temperature primary material to obtain the special PVC resin for chlorination. The inside of PVC resin wet material granule that aqueous phase polymerization method obtained contains a large amount of moisture, water becomes ice to the inside aperture inflation effect of PVC resin granule when freezing, ice sublimates to vapor when microwave heating, the initial stage oppression PVC resin granule structure around closes, later stage breaks through the constraint of PVC resin granule and the outside involucra of granule, the rapid escape, it is loose to obtain the granular structure, the plasticizer oil absorption rate is high, the big special resin of chlorination of specific surface area, can satisfy the production needs of CPVC resin, more do benefit to going on of chlorination.
The above patent introduces the technology of expanding aperture by moisture expansion in frozen pores of wet material cake, or adopting the technology of rapidly gasifying and expanding aperture by microwave heating of wet material cake, or adopting the technology of combining frozen and frozen expanded aperture and rapidly gasifying and expanding aperture by microwave heating, the technology expands the aperture of original PVC resin particles, but the size and volume of the original aperture are improved, but the problems of porosity abundance and uniformity are not solved fundamentally.
The industrial production method of the CPVC resin mainly comprises three methods: the method comprises a solvent method, a water phase method and a gas-solid phase method, wherein the gas-solid phase method is a cleaner and more efficient method. According to the chlorinated polyvinyl chloride process produced by the gas-solid phase method, gas-phase chlorine molecules enter through internal pore channels of particles to perform grafting reaction with PVC molecular chains, the grafting rate and the grafting uniformity are directly influenced by the abundance of pores and the uniformity of the pores, meanwhile, the reaction heat is removed by circularly vulcanized chlorine, polyvinyl chloride resin is produced by the suspension method process, the particle morphology of the polyvinyl chloride resin can be changed macroscopically remarkably by regulating the stirring speed of a polymerization kettle and the type and the using amount of a dispersing agent, the particle size distribution and the shape roundness are regulated, the internal pore structure is better improved, but the regulation of a deep micro-nano structure of the resin is not easy to complete, the PVC resin produced by the prior art has low specificity in the production and application of chlorinated polyvinyl chloride, and particularly, the process is adopted, the heat removal is difficult, and the thermal stability of the chlorinated polyvinyl chloride resin is poor.
The production temperature of the polyvinyl chloride resin with low polymerization degree is high, the thermal motion of molecules is violent, the growth rate of a polyvinyl chloride molecular chain is high, the initiation rate is reduced by controlling the quantity of free radicals required by chain initiation, generally, the concentration of the free radicals decomposed by the initial initiator is high by a process of adding the initiator at one time, the reaction rate is too high, the precipitation is too fast to form compact particles, the porosity of PVC particles is reduced, the apparent density of the PVC particles is improved, and the vulcanization of materials and the diffusion of chlorine in the process are influenced.
Disclosure of Invention
In order to solve the technical problems, the invention provides the special low-polymerization-degree polyvinyl chloride resin, which meets the chlorination process of a gas-solid phase method, reduces the degree of covering the surface of the special resin with a film, reduces the degree of bonding of sub-particle structures inside and outside particles, and improves the abundance and uniformity of gaps among micro-nano structures inside the particles, so that chlorine can be effectively diffused into PVC particles to perform grafting reaction in the process, and meanwhile, the reaction heat is favorably removed by outward diffusion through abundant micro-pore structures.
The technical scheme adopted by the invention for solving the technical problems is as follows: the low-polymerization-degree polyvinyl chloride special resin is mainly prepared from the following raw materials in parts by mass: 100 parts of vinyl chloride monomer, 115-130 parts of deionized water, 0.005-0.02 part of neutralizer, 0.04-0.068 part of dispersant A, 0.017-0.036 part of dispersant B, 0.014-0.034 part of surfactant, 0.014-0.026 part of initiator A and 0.012-0.02 part of initiator B.
In the low-polymerization-degree polyvinyl chloride special resin, the dispersant A is a polyvinyl alcohol dry base with alcoholysis degree of 65-75%; the dispersant B is hydroxypropyl methyl cellulose dry base; the surfactant is polyvinyl alcohol dry base with alcoholysis degree of 35-50% and block distribution; the initiator A is peroxide 3, 5-trimethyl hexanoyl dry radical; the initiator B is cumyl peroxyneodecanoate dry basis; the neutralizing agent is 3% -5% carbonate solution.
The polyvinyl alcohol with low alcoholysis degree block distribution is selected 35% -50%, more acetyl groups and less hydroxyl groups are distributed on a molecular chain segment of PVA, the acetyl groups are good in lipophilicity and can quickly adsorb the surface of a monomer liquid drop and even be dissolved in the monomer, the existence of the hydroxyl groups has lipophobicity, if the polyvinyl chloride with low alcoholysis degree can be dissolved in the monomer liquid drop, the oleophobic hydroxyl groups in the liquid drop can continuously form separation in the liquid drop, the cohesion among the polymerized bodies is weakened in the polymer forming process, and the internal pore volume of PVC particles is adjusted.
In vinyl chloride polymerization, the type and amount of the initiator have very important influences on the polymerization reaction rate, the reaction process control and the product quality of the finally synthesized polyvinyl chloride resin. The initiator has high activity, fast reaction rate, low activity and relatively slow reaction. The selection and the dosage of the initiator have certain relation with whether the equipment can remove the reaction heat in time and reasonably control the reaction process. In production, a high-low activity matching and composite initiator combination is often selected to control the vinyl chloride polymerization process. The special resin for chloroethylene by the gas-solid phase method is cumyl peroxyneodecanoate and tert-butyl peroxyneodecanoate, and the two initiators are compounded to be suitable for the industrial production of low-polymerization-degree resin and also accord with the production process method provided by the application.
The low-polymerization-degree polyvinyl chloride special resin is prepared by sequentially adding cold deionized water, hot deionized water, a neutralizer, a dispersant A, a surfactant, a dispersant B, an initiator A and a vinyl chloride monomer into a polymerization kettle, and uniformly mixing the materials; continuously and constantly heating the materials in the polymerization kettle by using a polymerization kettle jacket and a hot circulating water system, and activating the materials in the polymerization kettle; the temperature of materials in the polymerization kettle reaches the reaction temperature of 62-68 ℃, the jacket hot water is switched to the circulating cooling water, the reaction temperature of the polymerization kettle is controlled, the reaction lasts for 60-90 min, and the initiator B is continuously supplemented to the set formula amount; discharging, stripping and drying the PVC slurry to obtain the PVC resin with the average polymerization degree of 650-850.
The vinyl chloride monomer added into the polymerization kettle comprises recycled vinyl chloride monomer and fresh vinyl chloride monomer.
The cold deionized water and the hot deionized water of the low-polymerization-degree polyvinyl chloride special resin are proportionally adjusted to have material temperature controlled at 32-36 ℃; the neutralizing agent is used for adjusting the pH value of the material to 6.5-8.0.
In the material activation process of the low-polymerization-degree polyvinyl chloride special resin, the temperature of circulating water is controlled to be 80-85 ℃, and the continuous constant heating rate is 0.5-2.0 ℃/min. Vinyl chloride polymerization is a free radical chain polymerization. The extent of free radical formation controls the rate of strand initiation. After chain initiation, vinyl chloride chain growth occurs. After the free radicals of the PVC chain grow to a certain extent, precipitation tends to occur. After continued growth into the original particles, precipitation is easily re-occurring. The reaction is difficult or even impossible to initiate at very low temperature growth rates. At too fast a temperature growth rate, the rate of initiator decomposition into free radicals increases and the rate of molecular collision chain growth also increases. When a large number of primary particles are formed simultaneously, the system becomes extremely viscous and unstable. When the rapid sedimentation is carried out, the adhesive is easy to adhere to form a whole body to close the pore channel. By controlling the heating rate, the materials are slowly and stably activated, the initial reaction rate is properly adjusted, the formation rate of original particles is controlled, and the polyvinyl chloride resin is slowly precipitated. When the primary particles form primary particle cores, the primary particles continue to grow into primary particles, and the primary particles grow up and are flocculated into agglomerates again. In order to avoid the concentration of the formation stage of the micro-nano structure, the chain initiation and chain growth rate is regulated and controlled through low-temperature activation treatment in an unstable period, the bonding of original particles is reduced, and the aggregation degree of primary particles is reduced, so that the aim of regulating and controlling the micro-nano structure of PVC resin particles is fulfilled.
The initiator A is added at one time in the feeding process of a polymerization kettle of the special low-polymerization-degree polyvinyl chloride resin, the initiator B is replenished in the middle of polymerization, the replenishing flow rate of the initiator B is controlled by a flow-limiting orifice plate to be 80-120kg/h, the initiator B is mixed with water injected in the middle of polymerization, and the temperature of the water injected in the middle of polymerization is controlled to be 7-10 ℃. In the polymerization reaction process, in a certain area, the activity of the initiator is high, or the local concentration of the initiator is too high, the polymerization reaction rate of vinyl chloride can cause uneven conditions, more 'fish eyes' are easily formed in the initial reaction stage, or compact particles are formed, so that the pore structure of a resin product is poor, and the resin product is not easily used in the chlorination process. If the initiator can be continuously dripped, the concentration of the initiator in a polymerization system, the concentration of free radicals and the reaction rate are uniformly and stably controlled, so that the reaction is stable.
The polymerization temperature of the special low-polymerization-degree polyvinyl chloride resin is controlled within 62-65 ℃, so that a polyvinyl chloride product with the average polymerization degree of 800 +/-50 is obtained; the polymerization temperature is controlled within the range of 65-68 ℃, and the polyvinyl chloride product with the average polymerization degree of 700 +/-50 is obtained.
The fluctuation deviation of the reaction temperature of the polymerization kettle is controlled within plus or minus 0.5 ℃ in the polymerization reaction control process of the special low-polymerization-degree polyvinyl chloride resin.
The discharging, steam stripping and drying processes of the PVC slurry of the low-polymerization-degree polyvinyl chloride special resin are as follows: after 4.5-6h of polymerization reaction, when the reaction pressure of a polymerization kettle is reduced to-0.05 MPa to-0.07 MPa, adding a terminator into the polymerization kettle after the polymerization reaction is finished, discharging PVC slurry, recovering unreacted vinyl chloride monomer, removing PVC and residual monomer in water from the PVC slurry through steam stripping, removing mother liquor in the slurry, and drying a material cake to obtain a finished product PVC resin with the average polymerization degree of 650-850; the specific surface area of the PVC resin is 2-5m 2 /g。
The percentages referred to in the invention are mass percentages.
Compared with the prior art, the PVC resin with the average polymerization degree of 650-850, which is obtained by the invention, has higher internal porosity and uniform porosity, increases the diffusibility of the special resin to small molecular substances, and can be widely applied to the production process of the special PVC resin for chlorination by a gas-solid phase method.
Part of initiator is added in a decrement way at one time when the materials are fed, the initiator with low concentration and high activity is continuously replenished in the middle and later stages of the reaction, and the rate of the free radical initiation reaction is adjusted; by selecting a surfactant with a block distribution structure, a protection structure is formed inside and outside a vinyl chloride monomer liquid drop by a special group possessed by the surfactant, so that the sub-particle structure adhesion degree inside and outside particles is reduced; the growth process of the PVC from the primary particles to the aggregates is adjusted by controlling the chemical reaction kinetics, so that the aggregation density of primary particles is reduced, the strength of flocculated primary particles is improved, the adhesion degree of the flocculated primary particles during forming the aggregates is reduced, and more uniform pores are formed among micro-nano structures such as PVC aggregates.
The invention overcomes the defects that the traditional process adds the initiator with medium and low activity into the reaction kettle at one time, the effective concentration of the initiator decomposed into free radicals is high after the activation, the initial initiation rate is too high, and the internal reaction is causedThe original particle structure is precipitated and coalesced too fast, the internal porosity is lower and inhomogeneous shortcoming, intervene in the PVC particle synthesis stage, macroscopically regulate and control the particle structure form with dispersant and stirring, microscopically control the micro-nano structure and deposit polymerization rate regulation micro-nano structure, the two go on in step, the quantity of dispersant in the suspension polymerization has been reduced, reduce PVC resin and form the involucra structure, the abundance in general suspension method production PVC resin pore and the not enough problem of degree of consistency have been overcome, the diffusibility of special resin to the micromolecule material has been increased, when chlorination grafting reaction, be convenient for chlorine to getting into the inside deep diffusion of granule, carry out chlorination reaction to the granule deep layer. In the production of low-polymerization-degree resin by high-temperature polymerization, the low-concentration high-activity initiator is used for replacing the high-concentration low-activity initiator, so that the reaction acceleration out of control caused by the treatment after the initiator residue is polymerized is reduced, and the BET specific surface area of the PVC resin prepared by the invention can reach 2-5m 2 The BET specific surface area of the PVC resin produced by the original process is 0.4-0.8m 2 (ii) in terms of/g. The invention can be widely applied to the production process of the special polyvinyl chloride paste resin for chlorination by a gas-solid phase method.
Detailed Description
Example 1: the low-polymerization-degree polyvinyl chloride special resin is mainly prepared from the following raw materials in parts by weight: 100 parts of vinyl chloride monomer, 115 parts of deionized water, 0.005 part of neutralizer, 0.04 part of dispersant A, 0.017 part of dispersant B, 0.014 part of surfactant, 0.014 part of initiator A and 0.012 part of initiator B.
Example 2: the low-polymerization-degree polyvinyl chloride special resin is mainly prepared from the following raw materials in parts by mass: 100 parts of vinyl chloride monomer, 130 parts of deionized water, 0.02 part of neutralizer, 0.068 part of dispersant A, 0.036 part of dispersant B, 0.034 part of surfactant, 0.026 part of initiator A and 0.02 part of initiator B.
Example 3: the low-polymerization-degree polyvinyl chloride special resin is mainly prepared from the following raw materials in parts by mass: 100 parts of vinyl chloride monomer, 120 parts of deionized water, 0.01 part of neutralizer, 0.05 part of dispersant A, 0.025 part of dispersant B, 0.024 part of surfactant, 0.020 part of initiator A and 0.015 part of initiator B.
Example 4: an anti-adhesion agent spraying method for low-polymerization-degree polyvinyl chloride special resin comprises the steps of firstly spraying an anti-adhesion agent on the inner wall of a polymerization kettle, completely discharging residual liquid of the spraying kettle after spraying is finished, starting the polymerization kettle to stir, sequentially adding 120 parts of deionized water, 0.005 part of neutralizing agent, 0.06 part of dispersing agent A, 0.030 part of surfactant, 0.030 part of dispersing agent B, 0.014 part of initiator A and 100 parts of vinyl chloride monomer into the polymerization kettle, wherein the deionized water comprises cold deionized water and hot deionized water, the temperature of the materials is adjusted to 35 ℃ according to a ratio by the cold deionized water and the hot deionized water, the pH value of the materials is adjusted to 7.5 by the neutralizing agent, then uniformly mixing the materials in the polymerization kettle, and utilizing a jacket of the polymerization kettle and a hot circulating water system to adjust the water inflow of the jacket of the polymerization kettle by DCS control, and continuously keeping a constant heating rate of 1.2 ℃/min, heating the materials in the polymerization kettle, and activating the materials in the polymerization kettle. When the temperature of the materials in the polymerization kettle reaches 64 ℃, the hot water of the jacket is switched to the cooling water of 7 ℃ for circulation, the fluctuation deviation of the reaction temperature of the polymerization kettle is controlled to be +/-0.5 ℃, the reaction is carried out for 60min, and 0.5 percent of the initiator B is continuously supplemented to the set formula amount. After reacting for 6 hours, when the reaction pressure drop of the polymerization kettle reaches-0.005 MPa, adding a terminator into the polymerization kettle after the polymerization reaction is finished, discharging the material to a discharge chute to recover unreacted vinyl chloride monomer, removing PVC and residual monomer in water from the slurry through a stripping tower, then feeding the slurry into a centrifuge to remove mother liquor in the slurry, and drying the cake to obtain a finished product through a cyclone drying device to obtain the special resin with the average polymerization degree of 800 +/-50.
Example 5: the low-polymerization-degree polyvinyl chloride special resin is mainly prepared from the following raw materials in parts by mass: 25t of vinyl chloride monomer (including recycled vinyl chloride monomer and fresh vinyl chloride monomer), 30t of deionized water (including cold deionized water and hot deionized water), 3kg of a polyvinyl alcohol dry basis with a degree of alcoholysis of 65%, 4.5 kg of a hydroxypropyl methylcellulose dry basis, 6kg of a polyvinyl alcohol dry basis with a degree of alcoholysis of 50%, 3.6 kg of a 3, 5-trimethylhexanoyl peroxide dry basis, and 3.0 kg of a cumyl peroxyneodecanoate dry basis.
Another embodiment is different in that the dispersant A is polyvinyl alcohol with 65% -75% alcoholysis degree on a dry basis; the dispersant B is hydroxypropyl methyl cellulose dry base; the surfactant is polyvinyl alcohol dry base with alcoholysis degree of 35-50% and block distribution; the initiator A is peroxide 3, 5-trimethyl hexanoyl dry radical; the initiator B is cumyl peroxyneodecanoate dry basis; the neutralizing agent is 3% -5% carbonate solution.
The difference of another embodiment is that the material temperature of the cold deionized water and the hot deionized water is adjusted to be 32 ℃ according to the proportion; the neutralizing agent adjusts the pH value of the material to 8.0.
The difference of another embodiment is that the material temperature of the cold deionized water and the hot deionized water is adjusted to be 36 ℃ according to the proportion; the neutralizing agent adjusts the pH value of the material to 6.5.
The difference of another embodiment is that in the material activation process, the temperature of the circulating water is controlled at 80, and the constant heating rate is kept at 0.5 ℃/min.
The difference of another embodiment is that the temperature of the circulating water is controlled at 82 ℃ in the material activation process, and the constant heating rate is 1.2 ℃/min.
Another example differs in that the temperature of the circulating water is controlled at 85 ℃ during the activation of the material, with a constant rate of temperature rise of 2.0 ℃/min.
The difference of another embodiment is that the initiator A is added in one time in the feeding process of the polymerization kettle, the initiator B is replenished in the middle of polymerization, the replenishing flow of the initiator B is controlled by a flow-limiting orifice plate to be 80kg/h, the initiator B is mixed with water injected in the middle, and the temperature of the water injected in the middle is controlled to be 7 ℃.
The difference of another embodiment is that the initiator A is added at one time in the feeding process of the polymerization kettle, the initiator B is replenished in the middle of polymerization, the replenishing flow rate of the initiator B is controlled by a flow-limiting orifice plate to be 120kg/h, the initiator B is mixed with water injected in the middle, and the temperature of the water injected in the middle is controlled to be 10 ℃.
The difference of another embodiment is that the polymerization temperature is controlled within 62 ℃ to obtain a polyvinyl chloride product with the average polymerization degree of 800 +/-50; the polymerization temperature is controlled within 66 ℃, and the polyvinyl chloride product with the average polymerization degree of 700 +/-50 is obtained.
The other embodiment is different in that the polymerization temperature is controlled within 64 ℃ to obtain a polyvinyl chloride product with the average polymerization degree of 800 +/-50; the polymerization temperature is controlled within 68 ℃, and the polyvinyl chloride product with the average polymerization degree of 700 +/-50 is obtained.
The difference of another embodiment is that the discharging, steam stripping and drying processes of the PVC sizing agent are as follows: after 4.5 of polymerization reaction, when the reaction pressure of the polymerization kettle is reduced to-0.05 MPa, adding a terminator into the polymerization kettle after the polymerization reaction is finished, discharging PVC slurry, recovering unreacted vinyl chloride monomer, removing PVC and residual monomer in water from the PVC slurry through steam stripping, removing mother liquor in the slurry, and drying a material cake to obtain a finished product PVC resin with the average polymerization degree of 650-850; the specific surface area of the PVC resin is 2 m 2 /g。
The difference of another embodiment is that the discharging, steam stripping and drying processes of the PVC sizing agent are as follows: after the polymerization reaction is carried out for 6 hours, when the reaction pressure of a polymerization kettle is reduced to-0.07 MPa, adding a terminator into the polymerization kettle after the polymerization reaction is finished, discharging PVC slurry, recovering unreacted vinyl chloride monomer, removing PVC and residual monomer in water from the PVC slurry through steam stripping, removing mother liquor from the slurry, and drying a material cake to obtain a finished product PVC resin with the average polymerization degree of 650-850; the specific surface area of the PVC resin is 5m 2 /g。
The difference of another embodiment is that the discharging, steam stripping and drying processes of the PVC sizing agent are as follows: after 5 hours of polymerization reaction, when the reaction pressure of a polymerization kettle is reduced to-0.06 MPa, adding a terminator into the polymerization kettle after the polymerization reaction is finished, discharging PVC slurry, recovering unreacted vinyl chloride monomer, removing PVC and residual monomer in water from the PVC slurry through steam stripping, removing mother liquor in the slurry, and drying a material cake to obtain a finished product PVC resin with the average polymerization degree of 650-850; the specific surface area of the PVC resin is 4 m 2 /g。

Claims (8)

1. A special low-polymerization-degree polyvinyl chloride resin for gas-solid phase chlorination is characterized by being mainly prepared from the following raw materials in parts by mass: 100 parts of vinyl chloride monomer, 115-130 parts of deionized water, 0.005-0.02 part of neutralizer, 0.04-0.068 part of dispersant A, 0.017-0.036 part of dispersant B, 0.014-0.034 part of surfactant, 0.014-0.026 part of initiator A and 0.012-0.02 part of initiator B; the preparation method comprises the following steps: sequentially adding cold deionized water, hot deionized water, a neutralizer, a dispersant A, a surfactant, a dispersant B, an initiator A and a vinyl chloride monomer into a polymerization kettle, and uniformly mixing the materials; continuously and constantly heating the materials in the polymerization kettle by using a polymerization kettle jacket and a hot circulating water system, and activating the materials in the polymerization kettle; the temperature of materials in the polymerization kettle reaches the reaction temperature of 62-68 ℃, the jacket hot water is switched to circulating cooling water, the reaction temperature of the polymerization kettle is controlled, the reaction lasts for 60-90 min, and the initiator B is continuously supplemented to the set formula amount; discharging, stripping and drying the PVC slurry to obtain PVC resin with the average polymerization degree of 650-850; the initiator A is added at one time in the feeding process of the polymerization kettle, and the initiator B is added in the middle of polymerization; the initiator A is peroxide 3, 5-trimethyl hexanoyl dry radical; the initiator B is cumyl peroxyneodecanoate dry basis.
2. The low-polymerization-degree polyvinyl chloride resin special for gas-solid phase chlorination according to claim 1, wherein the dispersant A is a polyvinyl alcohol dry basis with alcoholysis degree of 65-75%; the dispersant B is hydroxypropyl methyl cellulose dry base; the surfactant is polyvinyl alcohol dry base with alcoholysis degree of 35-50% and distributed by blocks; the neutralizer is 3-5% carbonate solution.
3. The low-polymerization-degree polyvinyl chloride resin special for gas-solid phase chlorination according to claim 2, wherein the vinyl chloride monomer added to the polymerization kettle comprises recycled vinyl chloride monomer and fresh vinyl chloride monomer.
4. The low-polymerization-degree polyvinyl chloride resin special for gas-solid phase chlorination according to claim 3, wherein: the cold deionized water and the hot deionized water are proportionally adjusted to the material temperature of 32-36 ℃; the neutralizing agent is used for adjusting the pH value of the material to 6.5-8.0.
5. The low-polymerization-degree polyvinyl chloride resin special for gas-solid phase chlorination according to claim 4, wherein: in the process of material activation, the temperature of circulating water is controlled to be 80-85 ℃, and the continuous constant heating rate is 0.5 ℃/min-2.0 ℃/min.
6. The low-polymerization-degree polyvinyl chloride resin special for gas-solid phase chlorination according to claim 1, wherein: in the feeding process of the polymerization kettle, the initiator B adopts a flow-limiting orifice plate to control the replenishment flow rate to be 80-120kg/h and is mixed with water injected midway at the temperature of 7-10 ℃.
7. The low-polymerization-degree polyvinyl chloride resin special for gas-solid phase chlorination according to any one of claims 4 to 6, wherein: the polymerization temperature is controlled within the range of 62-65 ℃, and a polyvinyl chloride product with the average polymerization degree of 800 +/-50 is obtained; the polymerization temperature is controlled within the range of 65-68 ℃, and the polyvinyl chloride product with the average polymerization degree of 700 +/-50 is obtained.
8. The low-polymerization-degree polyvinyl chloride resin special for gas-solid phase chlorination according to claim 7, wherein: discharging, stripping and drying processes of the PVC slurry: after 4.5-6h of polymerization reaction, when the reaction pressure of a polymerization kettle is reduced to-0.05 MPa to-0.07 MPa, adding a terminator into the polymerization kettle after the polymerization reaction is finished, discharging PVC slurry, recovering unreacted vinyl chloride monomer, removing PVC and residual monomer in water from the PVC slurry through steam stripping, removing mother liquor in the slurry, and drying a material cake to obtain a finished product PVC resin with the average polymerization degree of 650-850; the specific surface area of the PVC resin is 2-5m 2 /g。
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BR8402292A (en) * 1983-06-23 1985-04-02 Occidental Chem Co POLYMERIZATION PROCESS AND PRODUCT IN SUSPENSION OF POLYVINYL CHLORIDE
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