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Process of synthesizing heat resistant copolymer

A synthesis method and a technology for copolymers, which are applied in the synthesis field of heat-resistant copolymers, can solve the problems of high free radical generation rate, increased temperature, and reduced emulsification activity of emulsifiers, and achieve low residual monomer content and improved copolymerization conversion. The effect of improving the conversion rate and copolymerization conversion rate

Inactive Publication Date: 2007-08-22
LILAI CHEM YIXING
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

The disadvantage of this emulsion polymerization is: after adding monomers to copolymerize, under the action of stirring, the monomers will form beads, and the beads will not only absorb the emulsifier from the water phase, but also take the emulsifier from the latex particles, even It will absorb and dissolve part of the latex particles in the monomer beads, reduce the stability of the emulsion system, easily produce gels, and even lead to demulsification, which will make the Trommsdorff effect more serious and difficult to control
Secondly, the sugar-containing ferric pyrophosphate redox initiator is a water-soluble initiator with the presence of iron ions, which not only has a great influence on the pH of the system during the initiation process, but also reduces the emulsifying activity of the emulsifier, resulting in a decrease in system stability. Not only aggravate the Trommsdorff effect, cause gel precipitation, reduce the conversion rate, but also cause the molecular weight of the copolymer to decrease and the molecular weight distribution to widen, and the product performance will decline; and the ferrous ions will be continuously consumed to generate ferric ions (free radicals) The reaction formula is ROOH+Fe 2+ →OH - +RO+Fe 3+ ), so it is necessary to add quite a lot of ferrous salts, excessive ferrous salts will cause iron ions to remain in the polymer, which will affect the aging resistance of the copolymer; and the concentration of ferrous ions in the initial stage of the reaction is high, and the free radical generation rate is high , which increases the difficulty of controlling the polymerization reaction, resulting in a sharp rise in temperature and violent polymerization; in the later stage of the reaction, due to the depletion of ferrous ions, the rate of free radical formation is extremely low, which will cause the polymerization reaction to stop prematurely, resulting in a reaction Incomplete, the conversion rate is low, the conversion rate is only 85-95%, the amount of residual monomer is high, reaching about 2000PPm, and the high residual monomer will cause the heat resistance temperature of the copolymer to drop, and the copolymer Vicat (VICAT) temperature It is only about 120°C, which will increase the trouble of subsequent processing
[0004] In addition, the heat-resistant copolymer produced by the existing technology has a low melt index, generally about 1g / 10min, which is difficult to process and is not suitable for use in PVC products with low processing temperature

Method used

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Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0018] Example 1: 10 parts of α-methylstyrene, 20 parts of acrylonitrile and 1.2 parts of sodium lauryl sulfate (emulsifier), and 50 parts of deionized water are added to the pre-emulsification tank, and the temperature of the kettle is kept at 30 Stir at -35°C for 25-30 minutes to form a pre-emulsion for later use;

[0019] 65 parts of α-methylstyrene, 5 parts of acrylonitrile, 0.6 parts of sodium lauryl sulfate and 1.8 parts of sodium dodecylbenzenesulfonate (emulsifier), 0.14 parts of azobisisobutyronitrile, 130 parts Put deionized water into the polymerization kettle, keep the temperature of the kettle at 30-35°C, stir for 25-30 minutes, raise the temperature to 65°C and polymerize for 1 hour, keep the temperature of the kettle at 65-70°C, and put the prepared pre-emulsion Continuously add to the polymerization kettle, finish adding within 4-5 hours, continue to polymerize for 1 hour, measure the solid content ≥ 36%, and end the reaction; heat up to 80-85°C, vacuumize to r...

Embodiment 2

[0020] Embodiment 2: as embodiment 1, add 0.45 parts of tertiary dodecyl mercaptans when emulsifying before polymerization, all the other are with embodiment 1. The melt index of the obtained resin powder was 6.2g / 10min.

Embodiment 3

[0021] Embodiment 3: 25 parts of α-methylstyrene, 20 parts of acrylonitrile and 1.6 parts of sodium lauryl sulfate (emulsifier), and 70 parts of deionized water are added in the pre-emulsification tank, and the temperature of the kettle is kept at 30 Stir at -35°C for 25-30 minutes to form a pre-emulsion for later use;

[0022] 45 parts of α-methylstyrene, 10 parts of acrylonitrile, 0.6 parts of sodium lauryl sulfate and 1.4 parts of sodium dodecylbenzenesulfonate (emulsifier), 0.14 parts of azobisisoheptanonitrile, 0.45 parts Tertiary dodecyl mercaptan, 110 parts of deionized water into the polymerization kettle, keep the temperature of the kettle at 30-35°C, stir for 25-30 minutes, raise the temperature to 65°C and polymerize for 1 hour, keep the temperature of the kettle at 65-70°C During this period, the prepared pre-emulsion solution is continuously added to the polymerization kettle, and the addition is completed within 5-6 hours, and the polymerization is continued for ...

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Abstract

The improved emulsion polymerization process of preparing heat resistant alpha-methylstyrene-acrylonitrile copolymer features that 30-50 wt% of the monomers, emulsion and initiator are pre-emulsified; and the rest monomers, emulsion and initiator are emulsified, heated to 65-70 deg.c and polymerized while adding the pre-emulsion until to obtain solid content higher than 36 %, where, the initiator is oil soluble azo diisobutyronitrile or azo diisoheptonitrile. The present invention has stable emulsion system, complete and homogeneous copolymerization, copolymerizing conversion rate as high as 98 %, low residual monomer rate, high Vicat temperature and other advantages.

Description

technical field [0001] The invention relates to a synthesis method of a heat-resistant copolymer, in particular to the improvement of a method for preparing a heat-resistant copolymer of α-methylstyrene and acrylonitrile by emulsion polymerization for heat-resistant modification of plastics. Background technique [0002] The copolymer of α-methylstyrene (α-MS) monomer and acrylonitrile (AN) monomer is a heat-resistant modifier for general plastics (such as PE, PP, PVC, PS, ABS). One kind of copolymerization method of this heat-resistant copolymer is emulsion polymerization, that is, the amphibian water-soluble α-MS monomer and AN monomer are mixed and emulsified in the emulsion, and then the temperature is raised to polymerize under the action of an initiator. This emulsion copolymerization reaction is a violent exothermic reaction, and the unavoidable Trommsdorff effect (gel effect) will occur. If the heat is not dissipated in time, it is easy to produce violent polymerizat...

Claims

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Application Information

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IPC IPC(8): C08F212/10C08F2/38
Inventor 郑志强李家旭
Owner LILAI CHEM YIXING
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