JP2003165808A - Method for producing polystyrene having wide molecular weight distribution by continuous anionic polymerization - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing a polystyrene having a wide molecular weight distribution by continuous anionic polymerization. <P>SOLUTION: This method for producing a polystyrene for a food package having 1.1-20 molecular weight distribution and 10,000-1,000,000 number-average molecular weight of the product by a anionic polymerization performs a reaction by adding 0.01-1 M polymerization initiator into 100 M styrene monomer, using hydrocarbon as a polymerization medium by the same weight or less than the weight of the used styrene monomer. The polystyrene is used for the production of a container for a cup noodle, disposable cup or common tray. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to the use of a small amount of a reaction solvent and a method for producing high-purity polystyrene for food packaging materials by a continuous anionic solution polymerization method, and a cupmen container, a disposable cup and a general tray. Related to polystyrene.

[0002]

2. Description of the Related Art Generally, most polystyrene resins used in cupmen containers, disposable dishes and the like are obtained by radical polymerization of styrene, and at this time, various side reactions are likely to occur and endothermic hormones Styrene dimers and styrene trimers, which are classified as suspected substances, will be produced (FR Mayo, J. Am. Chem. Soc. 9).
0, 1968, p1289). Therefore, when polystyrene containing a substance suspected of being an endocrine disrupter is used for food packaging such as cupmen containers, there is a risk of causing a problem of elution of endocrine disrupters into food contents.

As is well known, in Japan, styrene dimers and trimers are classified as substances suspected to be endocrine disrupters, but the World Fund for Nature also defines styrene dimers and trimers as endocrine disruptors, namely endocrine disruptors. . It is general theory that these environmental hormones are harmful due to the ecological abnormalities that are actually occurring and the results of animal experiments.

In WO 00/15678, the problem of environmental hormone elution was solved by anionic polymerization. However, since this method is a batch polymerization, it is a low-viscosity polymerization in which a large amount of reaction solvent should be used to control the heat of polymerization reaction, and thus the produced linear polystyrene has a narrow molecular weight distribution.

Generally, in the production of polystyrene polymer by a batch type low viscosity anionic polymerization method in which a large amount of solvent is used,
Polymers with a narrow molecular weight distribution (close to monodisperse) are obtained, but such polymers have poor processability due to high processing temperature and low melt index, etc. It was difficult to secure the physical properties.

Further, since the batch type polymerization has extremely low productivity, it is difficult to obtain commercial scale productivity, and a lot of energy is consumed to remove the reaction solvent.

US Pat. No. 5,39,39 discloses a continuous polystyrene production method which solves the problems of batch polymerization.
1,655, U.S. Pat. No. 4,883,846 and U.S. Pat. No. 4,748,222 are known, but these methods also require a large amount of solvent-at least a larger amount of reaction solvent than styrene monomer-low viscosity. It is an anionic polymerization method. Since these patents have adopted a continuous polymerization method, they have high productivity as compared with the batch method and can produce a polymer having a wide molecular weight distribution,
Not optimal productivity and molecular weight distribution.

As another prior art method for producing continuous polystyrene, US Pat. No. 5,902,865 and US Pat. No. 4,016,348 disclose tube loop reactors for controlling heat of reaction and mixing of polymer. Has been done.

[0009]

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and it suppresses the production of polymerization by-products such as styrene dimer and trimer, and has a high productivity and is well known. It is an object of the present invention to provide a novel method for producing polystyrene, which is advanced from the ionic polymerization method and in which it is easy to remove the heat of polymerization generated from the polymerization system by controlling the polymerization rate.

Another object of the present invention is to provide a novel method by which polystyrene having a relatively wide molecular weight distribution and suitable for food packaging can be produced.

[0011]

The above-mentioned object of the present invention is achieved by polymerizing the viscosity of the polymerization system to a certain level or more. That is, the method of the present invention, the fact that increasing the viscosity of the polymerization system can restrict the flow (activity) of the produced polymer, the polymer polystyrene produced thereby is used for food packaging materials. It is based on the discovery of the fact that it has suitable molecular weights and molecular weight distributions, and that such polymerization processes are easy to control the heat of the polymerization reaction due to the slow polymerization rate.

Specifically, the present invention has a molecular weight distribution of 1.1.
To 20 and a number average molecular weight of 10,000 to 1,000
A method for continuously producing a polystyrene for food packaging material having a viscosity of 10,000 by a high-viscosity anionic polymerization method,
Polymerization initiator 0.01 per 100 M of styrene monomer
It can be summarized as a method for producing polystyrene in which the amount of hydrocarbon used as the polymerization solvent does not exceed the weight of the styrene monomer charged, though ˜1 M is charged into the polymerization system to react.

That is, the method of the present invention suppresses the formation of styrene dimers and trimers as polymerization side reaction substances, and has a molecular weight distribution of 1.1 to 20 suitable for use as polystyrene for food packaging materials. , The number average molecular weight is 10,
Polymerization is carried out by a continuous anionic polymerization method to obtain 000 to 1,000,000 polystyrene on a commercial production scale, but the amount of styrene monomer, polymerization initiator and hydrocarbon solvent added to the polymerization system is The characteristic is that the polymerization was performed under a high viscosity by appropriately adjusting.

According to the experiments conducted by the present inventors, it was confirmed that the polymerization solvent charged should not exceed the amount of styrene monomer charged. Therefore, the high viscosity used in the claims of the present application is analyzed when the amount of the polymerization solvent added to the polymerization system is not more than the amount of the styrene monomer added.

The method of the present invention is distinguished from the known invention relating to the low-viscosity polystyrene polymerization method in Korean Patent Publication No. 2000-19517 in that it is a high-viscosity polymerization method.
From the viewpoint of polydisperse, that is, the method for producing polystyrene polymer for food packaging having a wide molecular weight distribution, it is a high molecular weight polymer that is close to monodisperse and is used only locally for standard samples of analytical instruments. Patent Publication No. 92
-808 is also distinguished. Here, the polystyrene having a wide molecular weight distribution refers to a polystyrene having a wide molecular weight distribution with a molecular weight distribution of 1.1 or more, and has the advantage that a low molecular weight polymer functions as a plasticizer to improve physical properties and processability. Have.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail below.
In the method according to the present invention, a hydrocarbon solvent, a styrene monomer, and a polymerization initiator are charged into a continuous reactor at the same time by a high-viscosity continuous anionic polymerization method to perform polymerization, and the number average molecular weight is 10,000 to 1, To produce a polystyrene polymer having a degree of molecular weight distribution of 1.1 to 20. In the high-viscosity polymerization, the fluidity of the active polymer is inferior, a broad molecular weight distribution and a slow polymerization rate are obtained, and as a result, heat control of the polymerization reaction is facilitated, which is as described above.

The reaction solvent used in the method of the present invention includes:
Non-polar or polar hydrocarbon compounds are included. For example,
Cyclohexane, benzene, n-hexane, n-heptane, toluene, ethylbenzene, xylene, tetrahydrofuran, diethyl ether or a mixture thereof can be used. Also, the amount of these reaction solvents used is required to be less than or equal to the amount of styrene monomer charged into the polymerization system.

The initiators used in the present invention are C1 to C6.
Up to aliphatic or aromatic substituted compounds such as n-butyllithium, sec-butyllithium, ter
T-butyllithium, methyllithium, ethyllithium, phenyllithium, or a mixture thereof can be used, and the amount used is the amount of the charged monomer 100.
An amount corresponding to 0.01 to 1 M per mol is continuously added.

As the monomer, it is possible to use all kinds of styrene-substituted compounds capable of undergoing anionic solution polymerization, such as styrene, alphamethylstyrene, bromostyrene, or a mixture thereof.

The polymerization is carried out under normal anionic polymerization conditions, but 10 to 160 with air and moisture removed.
℃ temperature range, more preferably 30 ~ 150 ℃
Done in.

In the method of the present invention, a coupling agent may be used after the polymerization reaction to obtain a spherical polymer.
Coupling agents that can be used include halogens, isocyanates, esters, anhydrides, lactones, aldehydes, epoxides, ketones, and the like, and of course, a mixture thereof can also be used. The amount of the coupling agent used is 0.01 to 5 parts by weight based on the weight of the charged monomers.

Polymerization is terminated by the addition of a terminator. Usable reaction terminators may be methanol, ethanol, isopropanol, water or a mixture thereof, and carbon dioxide may be used at the same time to effectively remove the lithium compound. The amount of carbon dioxide used is generally greater than or equal to the number of moles of initiator used.

[0023]

EXAMPLES Examples of the present invention will be described below, but the present invention is not limited thereto. Example 1 High purity nitrogen was charged in a continuous reactor in which two 6 liter jacketed stainless steel reactors were connected in series, 50 ml of ethylbenzene, 50 ml of styrene, and 0.05 M of n-butyllithium per minute. Solution 1
Polymerization was carried out by adding 0 ml in a continuous manner. The temperature of the first reactor is maintained at 110 ° C and the temperature of the second reactor is 100 ° C.
Hold at ° C. The polystyrene produced had a number average molecular weight of 120,000 and a prepolymer solution with a molecular weight distribution of 2.3. Carbon dioxide and water were added to the prepolymer solution to terminate the reaction, and the melt index of the product was 10 g / 10 min (measured by ASTM D-1238).

Example 2 High-purity nitrogen was charged in a continuous reactor in which two 6-liter jacketed stainless steel reactors were connected in series, 50 ml of ethylbenzene, 50 ml of styrene, and n-butyllithium per minute. 0.05M solution 1
Polymerization was carried out by continuously charging 5 ml. The temperature of the first reactor keeps 100 ℃, the temperature of the second reactor is 90 ℃
Held. The polystyrene thus produced had a number average molecular weight of 78,000 and a linear prepolymer solution having a molecular weight distribution of 2.23 was obtained. Carbon dioxide and water were added to the prepolymer solution to terminate the reaction, and the melt index of the product was 17 g / 10 min (measured by ASTM D-1238).

Example 3 50 ml of ethylbenzene, 50 ml of styrene, and 10 ml of 0.2 M solution of n-butyllithium were continuously charged into the 6-liter continuous reactor of Example 1 for polymerization. The temperature of the first reactor was maintained at 110 ° C and the temperature of the second reactor was maintained at 100 ° C. The polystyrene produced had a number average molecular weight of 35,000 and a prepolymer solution having a molecular weight distribution of 2.2 was produced. A 0.05 M solution of silicon tetrachloride corresponding to the equivalent ratio was added to this solution as a coupling agent and reacted for 20 minutes, and then the molecular weight distribution was 2.75 and the melt index was 6 g / 10 minutes (ASTM D- 1238) to obtain the final polymer in which the linear and radial forms were mixed. The number average molecular weight of the polymer was 118,000.

Comparative Example 1 60 ml of ethylbenzene, 30 ml of styrene, and 15 ml of a 0.05 M solution of n-butyllithium were continuously charged into the 6-liter continuous reactor of Example 1 for polymerization. The temperature of the first reactor was maintained at 100 ° C and the temperature of the second reactor was maintained at 90 ° C. The number average molecular weight of the polymerized polystyrene was 75,000, and a prepolymer solution having a molecular weight distribution of 1.5 was prepared. By adding carbon dioxide and water to the prepolymer solution to terminate the reaction, a melt index of 14 g / 10 min (AST
The final polymer (measured by MD-1238) was obtained. The polystyrene produced by this comparative example had a relatively narrow molecular weight distribution compared to the examples, and a relatively large amount of solvent was consumed to remove the heat of polymerization.

Comparative Example 2 600 g of ethylbenzene was added to a 2 liter batch reactor.
300 g of styrene monomer was added, 4 mol of butyllithium was added at 20 ° C., and polymerization was carried out for 40 minutes. The polymer produced after the polymerization had a molecular weight distribution of 1.03 and a melt index of 6 g / 10 min (ASTM
D-1238) to obtain a final polymer having a number average molecular weight of 91,000. This comparative example also had a narrower molecular weight distribution than the polystyrene produced in the example, and a large amount of reaction solvent was consumed to remove the heat of the polymerization reaction.

[0028]

EFFECTS OF THE INVENTION According to the method of the present invention described above, polystyrene can be produced on a commercial production scale, and styrene dimer and styrene trimer suspected of being endocrine disruptors due to a polymerization side reaction are not eluted, and of course, processing A polystyrene polymer having excellent properties is obtained.

Further, using the high-purity polystyrene produced by the above-mentioned method as a raw material, a cup-men container, a disposable cup, a general tray and the like can be produced through thermoforming, foaming or other injection molding.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Somune ▲ Gen ▼             Republic of Korea 305-720 Daejeon City Yuseong District New             Seongdong Obayashi Apartment 102-103 (72) Inventor ▲ Choi ▼ Grand Order             Republic of Korea 305-720 Daejeon City Yuseong District New             Seongdong Obayashi Apartment 101-1107 (72) Inventor Kim Bell             Republic of Korea 305-729 Daejeon City Yuseong District Old             Mindong ▲ Blue ▼ Sphere Apartment 110-             601 (72) Inventor Ken Ken Hayashi             305-330 South Korea Satoshi Yuseong District, Daejeon             Ashdong Hyundai Apartment 711-1601 (72) The inventors             Republic of Korea 305-707 Daejeon City Yuseong District New             Seongdong Hanseong Apartment 102-206 F term (reference) 3E033 AA08 AA10 BA22 BB04 CA20                       FA01 FA02                 4J015 DA02 DA33

Claims (4)

[Claims] 1. A molecular weight distribution of 1.1 to 20 and a number average molecular weight of the product of 10,000 to 1,000,000.
0 is a method for continuously producing polystyrene for food packaging materials by a high-viscosity anionic polymerization method, in which 0.01 to 1 M of a polymerization initiator is added to 100 M of a styrene monomer to react with the polymerization system, A method for producing polystyrene for food packaging materials by a high-viscosity anionic polymerization method, characterized in that the amount of hydrocarbon used in the polymerization solvent is not more than the weight of the added styrene monomer. 2. The polymerization initiator is n-butyllithium,
sec-butyllithium, tert-butyllithium,
The method for producing polystyrene for food packaging materials by the high-viscosity anionic polymerization method according to claim 1, which is one or a mixture of two or more selected from the group including methyllithium, ethyllithium, and phenyllithium. 3. A halogen compound for a styrene monomer,
To add 0.01 to 5 parts by weight of a mixture of one or more selected from the group including isocyanates, esters, anhydrides, lactones, aldehydes, epoxides and ketones as a coupling agent. The method for producing polystyrene for food packaging materials according to claim 1. 4. The method according to claim 1, which is used for manufacturing cupmen containers, disposable cups and general trays.
A polystyrene polymer produced by the method according to any one of 1.