KR100582657B1 - Method for preparing thermoplastic styrene/acrylonitrile copolymer - Google Patents

Abstract

In the present invention, in preparing a nitrile copolymer having a content of unsaturated nitrile compound monomer in the copolymer of 10-20% by weight and an aromatic vinyl compound monomer in a range of 80-90% by weight, the suspension polymerization method in water, 0.10-0.30 parts by weight of a t-dodecyl mercaptan (TDM) molecular weight regulator and 0.3-0.8 in one suitable polymerization initiator having a temperature of 90 to 110 ° C. having a 10-hour half-life of 0.1 to 0.8 parts by weight relative to 100% by weight of the total monomers By using a TCP (Calcium Phosphate Tribasic) suspension dispersion stabilizer in parts by weight of the present invention relates to a method for producing a thermoplastic nitrile copolymer characterized in that the amount of the residual monomer is 1% by weight or less. Nitrile copolymers, in particular acrylonitrile copolymers prepared according to the present invention have a broad compositional distribution in addition to excellent transparency, thermal stability and mechanical properties, so the function as a compatibilizer in ABS alloys is expected. Of course, when the mixed processing with the styrene-based resin (blend) due to the excellent fluidity provides an effect of improving the workability according to the flowability of the resin.

Unsaturated nitrile compounds, aromatic vinyl compounds, water suspension polymerization

Description

Manufacturing method of thermoplastic nitrile copolymer {METHOD FOR PREPARING THERMOPLASTIC STYRENE / ACRYLONITRILE COPOLYMER}             

The present invention relates to a method for preparing a copolymer of an unsaturated nitrile compound and an aromatic vinyl compound. In particular, the content of residual monomers can be reduced even though the content of the unsaturated nitrile compound is low while maximizing the polymerization rate by using an appropriate initiator by the water suspension polymerization method. The present invention relates to a method for producing a miniaturized thermoplastic nitrile copolymer.

Copolymers containing unsaturated nitrile components, in particular acrylonitrile copolymers, are widely used commercially due to their excellent transparency, thermal stability and mechanical properties. Among these copolymers, styrene-acrylonitrile copolymers containing a low proportion of acrylonitrile have a broad compositional distribution in addition to the above characteristics, and thus are expected to function as a compatibilizer in ABS alloys. . In addition, due to its excellent fluidity, it is expected to greatly contribute to the improvement of workability due to the fluidity of the resin (blend) when mixed with styrene resin. However, the problem is how to reduce the monomer remaining in the copolymer when prepared for such use. In particular, the remaining styrene monomer is expected to be toxic to the human body as an environmental hormone, so it is necessary to reduce the residual amount to the minimum possible.

Suspension, emulsification, and bulk polymerization methods that are commercially available can be used for the preparation of these copolymers, but suspension polymerization methods that are inexpensive in manufacturing cost and easy to control and separate are generally used. In order to reduce the proportion of the unsaturated nitrile compound and maximize the reaction yield in the polymerization, the polymerization initiator and suspension necessary to prepare a copolymer having the desired unsaturated nitrile compound content in consideration of the different reactivity of the aromatic vinyl compound monomer and the unsaturated nitrile compound monomer. A stabilizer should be prescribed.

However, when a copolymer of an unsaturated nitrile compound and an aromatic vinyl compound is conventionally prepared by an underwater suspension polymerization method, the time point at which the polymerization is terminated due to an azotropic composition difference caused by the difference in reactivity between the unsaturated nitrile compound and the aromatic vinyl compound is used. The residual monomer content of the aromatic vinyl compound, which may cause environmental problems, remains as high as about 5 to 20% by weight based on the total monomers used.

As a method of reducing the amount of such high residual monomers, a method of removing residual monomers by stripping or recovery is known. However, this method allows the removal of some unreacted monomers, but some of them remain in the polymer in an uneven composition, which adversely affects the final mechanical properties and makes it impossible to obtain a polymer of the desired quality. This happens.

Another method is to minimize the content of residual monomer by maximizing the polymerization rate by mixing two kinds of initiators. However, when this method is used, it is difficult to have a uniform reproducibility of the polymers due to the use of two kinds of initiators, and a problem in that the interpretation of the polymerization reactivity is difficult.

The present invention is to overcome the problems of the prior art as described above, in the polymerization reaction of the saturated nitrile compound and the aromatic vinyl compound using one appropriate initiator and the polymerization in order to obtain the optimum polymerization reactivity of the early and late at this time Thermoplastic nitrile copolymers that optimize time-temperature control and maximize suspension suspension dispersibility, while minimizing the residual monomer content increased with low unsaturated nitrile compounds while maintaining excellent inherent mechanical and thermal properties. It is to provide a manufacturing method.

That is, the present invention is to prepare a nitrile-based copolymer having a content of unsaturated nitrile compound monomer in the copolymer of 10-20% by weight and an aromatic vinyl compound monomer in the range of 80-90% by weight by the suspension polymerization method in water. 0.10-0.30 parts by weight of a t-dodecyl mercaptan (TDM) molecular weight regulator and 0.3 to one appropriate polymerization initiator having a temperature of 90 to 110 ° C. having a 10-hour half-life of 0.1 to 0.8 parts by weight relative to 100% by weight of the total monomers. It is to provide a method for producing a thermoplastic nitrile copolymer characterized in that the amount of the residual monomer is 1% by weight or less by using -0.8 parts by weight of TCP (Calcium Phosphate Tribasic) suspension dispersion stabilizer.

In the present invention, a copolymer of an unsaturated nitrile compound and an aromatic vinyl compound is prepared by an underwater suspension method, according to the difference in reactivity between an unsaturated nitrile monomer and an aromatic vinyl compound monomer. A method for producing a thermoplastic nitrile copolymer, characterized in that it consists of a "secondary copolymerization process" which is a process for minimizing residual monomers. The unsaturated nitrile compound-aromatic vinyl compound copolymer prepared according to the present invention is an unsaturated nitrile compound. The content of the monomer component is 10-20% by weight and the content of the aromatic vinyl compound monomer component is 80-90% by weight. Preferably, the content of the unsaturated nitrile compound monomer component is in the range of 10-15% by weight and the content of the aromatic vinyl compound monomer component is in the range of 85-90% by weight. If the content of the unsaturated nitrile compound monomer component is less than 10% by weight, the chemical resistance and mechanical properties of the copolymer cannot be expected. If the content of the unsaturated nitrile compound monomer component is more than 20% by weight, the object becomes separate from the object of the present invention.

Production of Copolymer in the Present Invention The unsaturated nitrile compound monomer in the raw material monomer may be one of acrylonitrile, methacrylonitrile, or the like, or a mixture thereof, and the aromatic vinyl compound monomer may be styrene, α-methyl styrene, or p-methyl. It is recommended that it is one of styrene, t-butyl styrene, halogenated styrene, or the like or a mixture thereof.

The polymerization initiator used in the present invention is a temperature having a half-life of 10 hours is 90 ~ 110 ℃ to lead the initiation reaction in the primary copolymerization process and the secondary copolymerization process. Specifically, 1,1-bis (t-butylperoxy) cyclohexane (10 hours half-life 91 ° C), t-butyl peroxymaleic acid (10 hours half-life 96 ° C), t-butyl peroxyacetate (10 hours half-life) 102 ° C.) or t-butyl peroxy benzoate (10 hours half life 105 ° C.) may be used. Such a polymerization initiator can be added to the reaction system at once or continuously.

The content of the polymerization initiator used in the present invention will vary depending on the polymerization conditions such as the polymerization start temperature and the composition ratio of the monomer as a whole. Preferably, it is preferably used in the range of 0.1-0.8 parts by weight based on the total monomers. Is in the range of 0.3-0.6 parts by weight.

The suspending agents used in the copolymerization reaction are conventional inorganic suspending agents, cellulose derivatives, polyvinyl alcohols and the like, and a small amount of oil-soluble or water-soluble surfactant can be used together as a suspending aid as necessary. The preferred amount of suspending agent is 0.005-1.5 parts by weight based on the total monomers used, and less than 0.005 parts by weight results in poor suspension stability, resulting in non-uniform particle size distribution and excessively aggregated mass. In addition, if it is 1.5 parts by weight or more, the particles are fine, which increases the time of the post-treatment process and greatly reduces productivity.

At this time, the stability of the suspension dispersion system is very important in addition to the content of the dispersant, the stirring speed is very important, and the stability of the dispersion system is increased until the end of the reaction by increasing the speed in the secondary polymerization process by 10-20% than the stirring speed in the first polymerization process. I can keep it. Most preferably in the present system is to use a suspension dispersion stabilizer and, as a preferred example, 0.3 to 0.8 parts by weight of Calcium Phosphate Tribasic (TCP). When the use range of the suspension dispersion stabilizer is out of the range, it is not easy to provide dispersion stability.

The amount of water used as the reaction medium is preferably in the range of 50 to 500 parts by weight based on the total amount of monomers. If it is less than 50 parts by weight, it is difficult to disperse and remove the dispersing characteristics and heat of reaction, and if it is more than 500 parts by weight, it will adversely affect the dispersion state and require more dispersing agent. Deterioration of the dispersed state and a decrease in the content of the nitrile component in the final copolymer, the molecular weight is also reduced.

The polymerization method of the thermoplastic nitrile copolymer in the present invention is not significantly different from the usual in-water suspension polymerization method. However, due to the different reactivity of unsaturated nitrile monomers and aromatic vinyl monomers, the appropriate use of the above-mentioned initiators and the selection of an optimal time-temperature profile can continue the reaction of the system as the polymerization time elapses. This is necessary.

In the present invention, it is preferable to use a molecular weight modifier in an amount of 0.1 to 0.3 parts by weight based on the total monomers, but a preferable example is to use TDM, and it is selected and used within the above range according to the molecular weight distribution target described later.

The unsaturated nitrile compound-aromatic vinyl compound copolymer prepared in the present invention has a ratio Mw / Mn of the weight average molecular weight Mw and the number average molecular weight Mn of 2 or less, preferably 1.8 or less, and 0.50-0.60, preferably 0.55 or less. It is necessary to have an intrinsic viscosity. The ratio Mw / Mn is typically used as a measure of the degree of molecular weight distribution. When the value is 2 or more, the unsaturated nitrile compound-aromatic vinyl compound copolymer has poor mechanical and thermal properties compared to the increased fluidity, and thus the final resin also exhibits poor mechanical and physical properties. In general, wider molecular weight distribution tends to deteriorate physical properties such as impact resistance of the copolymer. In addition, when the intrinsic viscosity is 0.50 or less, it may not have the mechanical properties aimed in this study, and when it is 0.60 or more, the mechanical properties become worse.

The weight average molecular weight Mw and the number average molecular weight Mn were measured by calculating the elution curve obtained by gel permeation chromatography (GPC) for standard polystyrene, and the intrinsic viscosity was DMF to dissolve the unsaturated nitrile-aromatic vinyl compound copolymer and It is the value measured with the Ubbelohde viscometer at ° C. The unsaturated nitrile compound-aromatic vinyl compound copolymer produced in the present invention needs to satisfy the above conditions such as Mw / Mn and intrinsic viscosity.

The present invention will be described below with reference to Examples, but the scope of the present invention is not limited thereto. In the examples all "parts" are based on weight.

Example 1

13 parts of acrylonitrile and 87 parts of styrene were added to a stainless steel high pressure reactor equipped with an internal 300L baffle plate, a stirring device, and a heating jacket. 0.47 parts of TPC (Calcium Phosphate Tribasic) was used as an important suspension dispersion stabilizer for suspension polymerization, and 0.40 parts of t-butyl peroxymaleic acid was used as a polymerization initiator. In addition, 0.3 parts of TDM (t-Dodecyl Mercaptane) was used for molecular weight control, and 110 parts of ion-exchanged water was used as a dispersion medium. The reaction mixture was stirred constantly at a speed of 350rpm and the temperature control of the reaction mixture during the polymerization reaction was maintained for 4 hours with the initial temperature rise to 90 ℃ (primary copolymerization process). After the second temperature was raised to 110 ℃ and reacted for 4 hours as the "first copolymerization process" (secondary copolymerization process). On the other hand, since the stirring speed was increased to 400 rpm from 110 ° C., the dispersion stability was prevented from decreasing due to the increase in the polymerization conversion rate.

The physical properties of the powder obtained by washing, dehydrating and drying the reaction mixture after the polymerization reaction are shown in Table 1 below.

Example 2

A styrene-acrylonitrile copolymer was prepared in the same manner as in Example 1 except for changing 11 parts of acrylonitrile and 89 parts of styrene.

Example 3

Except that the molecular weight modifier was changed from 0.3 parts to 0.15 parts was prepared in the same manner as in Example 1.

Comparative Example 1

It was prepared in the same manner as in Example 1 except that 0.3 part of benzoyl peroxide was used as a polymerization initiator.

Comparative Example 2

A polymerization initiator was prepared in the same manner as in Example 1, except that 0.3 part of 1,1-bi (t-butylperoxy) 3,3,5-trimethyl cyclohexane was used.

The physical property evaluation results for the resins obtained in Examples 1-3 and Comparative Examples 1-2 are shown in Table 1 below.

division Polymer Properties Building properties System stability Residual SM Residual AN R-TVM Viscosity (η _SP / C) Mw Mn PDI MI Example 1 0.8 0 1.0 0.50 137K 74K 1.85 13.8 stability Example 2 0.7 0 0.9 0.62 190 K 96K 1.98 15.5 stability Example 3 0.9 0 1.1 0.69 200 K 105 K 1.90 11.7 stability Comparative Example 1 18.0 0.5 19.7 0.42 130 K 57 K 2.26 14.5 unrest Comparative Example 2 19.8 0 20.7 0.45 138 K 65 K 2.12 13.5 unrest

※ How to measure physical properties

1) Residual SM, AN, R-TVM: Gas Chromatograph (wt%)

2) Viscosity: dissolved in N, N-dimethyl formamide and measured by Ubelode viscometer at 25 ℃

3) Molecular weight (Mw, Mn, PDI): Calculated based on standard polystyrene polymer from G.P.C elution curve

4) MI: evaluated according to ASTM D-1238 (g / 10min).

As described above, according to the present invention, minimizing the content of the residual monomer by using one titration initiator makes the copolymer manufacturing process environmentally friendly and reduces the content of the unsaturated nitrile compound, thereby reducing the transparency of the conventional unsaturated nitrile compound copolymer. In addition to thermal stability and mechanical properties, it can contribute to the improvement of workability when mixing and processing with general styrene resins, and can be expected to be used as a compatibilizer.

Claims (4)

In preparing a nitrile copolymer having an unsaturated nitrile compound monomer content in the copolymer of 10-20% by weight and an aromatic vinyl compound monomer content of 80-90% by weight by the suspension polymerization method, the total monomers 100 1,1-bis (t-butylperoxy) cyclohexane, t-butyl peroxymaleic acid, t-butyl peroxyacetate having a temperature of 90 to 110 ° C. having a 10-hour half-life of 0.1-0.8 parts by weight based on the weight% And 0.10-0.30 wt% of t-dodecyl mercaptan (TDM) molecular weight modifier and 0.3-0.8 wt% of TCP (Calcium Phosphate Tribasic) in one suitable polymerization initiator selected from the group consisting of t-butyl peroxy benzoate. A method for producing a thermoplastic nitrile copolymer, characterized in that the amount of the residual monomer is 1% by weight or less by using a suspension dispersion stabilizer. delete The method for producing a thermoplastic nitrile copolymer according to claim 1, wherein the polymerization initiator is t-butyl peroxymaleic acid. The thermoplastic nitrile copolymer according to claim 1, wherein the obtained thermoplastic nitrile copolymer has a ratio Mw / Mn of a weight average molecular weight Mw and a number average molecular weight Mn of 2 or less and an intrinsic viscosity of 0.50 to 0.60. Manufacturing method.