阅读说明：本技术 低皮膜pvc树脂的制备方法 (Preparation method of low-film PVC (polyvinyl chloride) resin ) 是由 张学明 王晶 张新华 孔秀丽 贾小波 肖恩琳 裴小静 *** *** 张强 许永 于 2018-07-16 设计创作，主要内容包括：本发明涉及一种低皮膜PVC树脂的制备方法,属于聚氯乙烯树脂制备技术领域。本发明所述的低皮膜PVC树脂的制备方法,是采用悬浮聚合方法进行初步聚合,当聚合转化率达到10％-20％时,再加入氯乙烯单体,继续聚合反应,待聚合釜压力降为0.3MPa时加入终止剂终止聚合,最后通过后处理,得到低皮膜PVC树脂。本发明设计科学合理,简单易行,聚合反应平稳易行,制得的树脂性能稳定,树脂皮膜覆盖率低,多数树脂颗粒皮膜呈局部或全部裸露状态,利于工业化生产。(The invention relates to a preparation method of low-leather-membrane PVC resin, belonging to the technical field of preparation of PVC resin. The preparation method of the low-film PVC resin adopts a suspension polymerization method to carry out primary polymerization, when the polymerization conversion rate reaches 10-20%, vinyl chloride monomer is added, polymerization reaction is continued, a terminator is added to terminate polymerization when the pressure of a polymerization kettle is reduced to 0.3MPa, and finally, the low-film PVC resin is obtained through post-treatment. The invention has scientific and reasonable design, simple and easy operation, stable and easy polymerization reaction, stable performance of the prepared resin, low coverage rate of resin involucra, partial or complete exposure of most resin particle involucra, and is beneficial to industrial production.)

1. A preparation method of low-film PVC resin is characterized by comprising the following steps: performing primary polymerization by adopting a suspension polymerization method, adding vinyl chloride monomer when the polymerization conversion rate reaches 10-20%, continuing polymerization reaction, adding a terminator when the pressure of a polymerization kettle is reduced to 0.3MPa to terminate polymerization, and finally performing post-treatment to obtain the low-film PVC resin.

2. The method for producing a low-film PVC resin according to claim 1, wherein: during initial polymerization, the following raw materials in parts by weight are added:

3. the method for producing a low-film PVC resin according to claim 1, wherein: during the initial polymerization, the polyethylene monomer is added when the vacuum degree is less than or equal to 0.1 MPa.

4. The method for producing a low-film PVC resin according to claim 1, wherein: during the initial polymerization, the temperature is 50-70 ℃, and the polymerization pressure is controlled at 0.90-1.10 MPa.

5. The method for producing a low-film PVC resin according to claim 1, wherein: and when the polymerization conversion rate reaches 10-20%, adding 5-30 parts by mass of vinyl chloride monomer.

6. The method for producing a low-film PVC resin according to claim 1, wherein: the initiator is a plurality of azodiisoheptonitrile, bis-2-ethylhexyl peroxydicarbonate, dibutyl peroxydicarbonate, tert-amyl peroxypivalate or tert-butyl peroxyneodecanoate.

7. The method for producing a low-film PVC resin according to claim 1, wherein: the dispersant is a cellulose ether and polyvinyl alcohol two-component dispersion system, a cellulose ether and two-component polyvinyl alcohol composite ternary dispersion system, or a composite polyvinyl alcohol dispersion system of two or more than two.

8. The method for producing a low-film PVC resin according to claim 1, wherein: the terminator is one or more of bisphenol A, thiosemicarbazone acetonide or diethylhydroxylamine.

9. The method for producing a low-film PVC resin according to claim 1, wherein: the amount of the terminator is 0.001 to 0.300 parts by mass.

10. The method for producing a low-film PVC resin according to claim 1, wherein: the post-treatment comprises the working procedures of air stripping, centrifugation and drying.

Technical Field

The invention relates to a preparation method of low-leather-membrane PVC resin, belonging to the technical field of preparation of PVC resin.

Background

The production method for manufacturing PVC resin with loose structure and low involucra by using a chloroethylene suspension method mainly controls the granulation process of the resin PVC by adjusting a dispersing agent, using a functional auxiliary agent and matching with the change of stirring power.

For example, the U.S. has proposed several patents for the production of skinless or skinless cellular PVC resins, U.S. Pat. No. 4, 4,711,908, U.S. Pat. No. 3, 4,775,701, 4,775,702, U.S. Pat. No. 4,742,085, etc., which are used in suspension polymerization systems for vinyl chloride, using specific dispersions consisting essentially of: (a) an unneutralized ion-sensitive dispersant capable of thickening an aqueous medium as a primary dispersant; (b) polyvinyl alcohol of a certain degree of alcoholysis; when the VCM conversion is between 1 and 5%, a sufficient amount of an ionic compound is added to desorb the major amount of the ion-sensitive primary dispersant from the surface of the VCM beads in the dispersion to produce a skinless or skinnless, high porosity PVC resin. The technology adopts the special dispersant, has complex operation, is difficult to control the granulation process, and is easy to generate the conditions of coarse materials, shaft sticking and the like.

Japanese Kokai No. 57,14607 discloses that the dispersion agent is added in portions to reduce the coating of PVC resin, and the cellulose dispersion agent is added at a conversion rate of 5-40%, so that the produced resin is easy to melt, and has very good absorption of the plasticizer and less fish eyes. However, the method is not easy to control the particle size of the resin, easy to produce coarse materials, and not strong in industrial operability.

Chinese patent CN1927898A discloses a composite dispersion system composed of PVA and HPMC with low alcoholysis degree and low viscosity, a method for preparing high-porosity resin by suspension polymerization of vinyl chloride with a porosity regulator as an auxiliary agent, but the exposed part of the surface membrane of the resin is less, the internal pores are less and the distribution is not uniform.

Patent CN101717459A discloses a method for preparing polyvinyl chloride resin with reduced skin and increased porosity, which comprises the following steps: (1) adding a polyvinyl alcohol with high alcoholysis degree, a polyvinyl alcohol with medium alcoholysis degree, other auxiliary agents and vinyl chloride monomer before polymerization, and starting polymerization at a certain stirring power; (2) when the polymerization conversion rate is 12-20%, adding polyvinyl alcohol with low alcoholysis degree to improve the stirring power; (3) when the polymerization conversion rate is 30-45%, adding a certain amount of polyvinyl alcohol with low alcoholysis degree again, and changing the stirring power until the polymerization is finished. The resin produced by the method has the advantages of generally large particle size, easy coarse material generation and complex operation.

Patent CN102453176A discloses a preparation method of polyvinyl chloride resin with high porosity and low film coverage rate, which adopts suspension polymerization. The method is characterized in that water, vinyl chloride monomer, a composite dispersion system, a porosity regulator, a chain transfer agent, a pH buffering agent and an initiator are added into a polymerization kettle, and polymerization reaction is carried out at 50-75 ℃ in the polymerization kettle with a stirring device under the pressure of 0.90-1.20MPa, wherein the composite dispersion system is a mixture of two partially alcoholyzed polyvinyl alcohol and hydroxypropyl methyl cellulose. The polyvinyl chloride resin prepared by the method disclosed by the invention has the advantages of high porosity, few fish eyes, low film coverage rate, regular particle form, centralized resin particle size distribution, easiness in removing residual monomers and still higher film coverage rate.

Patent CN101466743 discloses a method for preparing a vinyl chloride-based polymer by a suspension method, and the invention provides a method for preparing a vinyl chloride polymer having excellent processability and high bulk density by adding vinyl chloride monomer step by step in the polymerization process by the suspension method. Patent CN101466743 mainly aims at improving the bulk density of PVC resin and the processability of the resin.

Disclosure of Invention

The invention aims to provide a preparation method of low-film PVC resin, which has scientific and reasonable design, is simple and feasible, has stable and easy polymerization reaction, stable performance of the prepared resin, low coverage rate of the resin film, and partial or complete exposure of most resin particle films, and is beneficial to industrial production.

The preparation method of the low-film PVC resin adopts a suspension polymerization method to carry out primary polymerization, when the polymerization conversion rate reaches 10% -20%, vinyl chloride monomer is added, polymerization reaction is continued, when the polymerization conversion rate reaches about 80% when the pressure of a polymerization kettle is reduced to a process control point, namely the pressure of the polymerization kettle is reduced to 0.3MPa, a terminator is added to terminate polymerization, and finally, post-treatment is carried out to obtain the low-film PVC resin.

The process control point is that when the polymerization conversion rate reaches about 80 percent, namely the pressure of the polymerization kettle is reduced to 0.3MPa, the terminating agent is added to terminate the polymerization.

During preliminary polymerization, cleaning and washing a polymerization kettle, coating an anti-sticking kettle agent, and adding the following raw materials in parts by weight:

130-150 parts of deionized water

0.001 to 0.120% of an initiator

0.005 to 0.100% of a dispersion system,

and (3) vacuumizing until the vacuum degree is less than or equal to 0.1MPa, and adding 100 parts by mass of polyethylene monomer.

And (3) cold stirring for 5-15 minutes, then heating to 50-70 ℃, and starting polymerization, wherein the polymerization pressure is controlled to be 0.90-1.10 MPa.

And when the polymerization conversion rate reaches 10-20%, adding 5-30 parts by mass of vinyl chloride monomer, preferably 10-20 parts by mass.

And adding 0.001-0.300 parts by mass of a terminator after the pressure of the polymerization kettle is reduced to a process control point.

And continuously stirring for 10-20 minutes, recovering the monomer, discharging slurry, and carrying out gas stripping and drying at 80-110 ℃ for 1-2 hours to obtain the PVC resin with low involucra.

The initiator is generally chosen so that it has a half-life of preferably 2 to 3 hours at the polymerization temperature. The single initiator is difficult to simultaneously meet the comprehensive requirements of the reaction system, a composite initiator system with high, medium and low activity can be used, azo initiators and peroxide initiators can be selected, and a plurality of azo initiators and peroxide initiators are preferably selected from azodiisoheptonitrile, bis-2-ethylhexyl peroxydicarbonate, dibutyl peroxydicarbonate, tert-amyl peroxypivalate or tert-butyl peroxyneodecanoate.

The using amount of the initiator is preferably 0.020-0.050 parts by mass.

The dispersant is a cellulose ether and polyvinyl alcohol binary dispersion system, a cellulose ether and two polyvinyl alcohol composite ternary dispersion system, or two or more composite polyvinyl alcohol dispersion systems, preferably a ternary dispersion system.

The amount of the dispersing agent is preferably 0.040-0.080 parts by mass.

The cellulose ether dispersant is one of methylcellulose, hydroxyethyl cellulose, hydroxypropyl cellulose or hydroxypropyl methylcellulose, preferably hydroxypropyl methylcellulose with strong dispersibility, such as Methocel E50, Metalose60SH-50, etc.

The polyvinyl alcohol dispersant at least comprises a main dispersant with alcoholysis degree of 70-90% and viscosity of 5-10cps at 20 ℃ of 4% aqueous solution or an auxiliary dispersant with alcoholysis degree of 30-50% and viscosity of 3-5cps at 20 ℃ of 4% aqueous solution, such as KURARARAY POVAL-10, KURARAY POVAL LM-20, etc.

The terminating agent can terminate the polymerization reaction of vinyl chloride and improve the whiteness of the resin. Preferably one or more of bisphenol a, thiosemicarbazone acetonide or diethylhydroxylamine. More preferably diethylhydroxylamine.

The invention is carried out according to the suspension polymerization method steps of vinyl chloride in the earlier stage, the polymerization kettle is cleaned and washed clean, the anti-sticking agent is coated, water, vinyl chloride monomer, composite disperse system and initiator are added into the polymerization reaction kettle with a stirring device, when the polymerization conversion rate reaches 10-20%, after the 'skeleton' of the resin particles is formed, a certain amount of vinyl chloride monomer is added again, the 'surplus' dispersing agent in the polymerization system is absorbed on the surface of the vinyl chloride monomer to form new liquid drops, the polymerization reaction is continued, after the pressure of the polymerization kettle is reduced to a process control point, the terminating agent is added to terminate the polymerization, and the PVC resin product with lower involucra coverage rate is obtained through the working procedures of gas stripping, centrifugation, drying and the like.

The invention has the following beneficial effects:

the invention has scientific and reasonable design, is simple and feasible, has stable and easy polymerization reaction, stable performance of the prepared resin, low coverage rate of resin films, partial or complete exposed state of most resin particle films, easy chloridization modification, high absorption rate of the plasticizer and high dissolution speed in the solvent, can be used in the fields of adhesives, coatings, chloridization modified products and the like, and is beneficial to industrial production.

Drawings

FIG. 1 is a comparative example 1 resin particle surface morphology;

FIG. 2 is a comparative example 4 resin particle surface morphology;

FIG. 3 is a comparative example 5 resin particle surface morphology;

FIG. 4 is the surface topography of the resin particle of example 1;

FIG. 5 is the surface topography of the resin particle of example 2;

FIG. 6 is the surface topography of the resin particles of example 3;

FIG. 7 shows the surface morphology of the resin particles of example 4.

Detailed Description

The present invention is further illustrated by the following examples, which are not intended to limit the practice of the invention.

Comparative example 1

The polymerization vessel was cleaned and rinsed, coated with the anti-sticking agent "Italian yellow" (NOXOL WSW), and the amount of the formula (parts by mass):

vacuumizing until the vacuum degree is 0.01MPa, and adding:

vinyl Chloride Monomer (VCM)100

The mixture was stirred for 10 minutes, then heated to the reaction temperature, and polymerization was started. And (3) controlling polymerization process parameters: the polymerization temperature is 58.0 +/-0.5 ℃; the feeding coefficient is 75 percent; the stirring speed is 180 r/min; the polymerization pressure drop was 0.3 MPa. Adding a terminating agent after the pressure of the polymerization kettle is reduced to 0.01 MPa:

diethylhydroxylamine 0.030

And continuously stirring for 10 minutes, recovering the monomer, discharging slurry, and carrying out gas stripping and boiling drying for 2 hours at 100 ℃ to obtain the PVC resin.

Comparative example 2

The polymerization was carried out in the same manner as in comparative example 1, except that the amount of vinyl chloride monomer added was 120 parts by mass.

Comparative example 3

The polymerization was carried out in the same manner as in comparative example 1 except that 35 parts by mass of the monomer was added to the polymerization reactor when the polymerization conversion rate reached 10% to 20%.

Comparative example 4

The polymerization was carried out in the same manner as in comparative example 1 except that 20 parts by mass of the monomer was charged into the polymerization reactor when the polymerization conversion rate reached 30% to 40%.

Comparative example 5

The polymerization was carried out in the same manner as in comparative example 1 except that 10 parts by mass of the monomer was added to the polymerization reactor when the polymerization conversion rate reached 30% to 40%, and 10 parts by mass of the monomer was added to the polymerization reactor when the polymerization conversion rate reached 60% to 70%.