JP2001342207A - Vessel made of styrenic resin - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a vessel excellent in printing properties such as stripping resistance of a printed surface, blur resistance of a printing ink and the like and excellent in rigidity at high temperatures in the vessel comprising a styrenic resin. SOLUTION: This vessel made of a styrene-based resin is produced by using the styrenic resin obtained by anion polymerization and containing <1000 ppm of the total amounts of monomers and oligomers.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a styrene resin container having excellent printability and high-temperature rigidity.

[0002]

2. Description of the Related Art Styrene resins represented by polystyrene are excellent in transparency, moldability, dimensional stability, and rigidity. Therefore, they are processed into a sheet or film, and the sheet is formed by vacuum forming, air pressure forming, or the like. Molded and widely used for beverage cups, food trays, food containers and the like, and films as they are for packaging materials and the like. Further, styrene resins are widely used in dessert containers such as pudding and jelly, lactic acid bacteria beverage containers, ice cream containers, food trays, and the like by injection molding or injection blow molding.

As the styrene resin used in these styrene resin containers, a styrene resin produced by a bulk radical polymerization method is usually used. Styrene resins produced by the bulk radical polymerization method are generally used because they have few impurities such as additives and are inexpensive. However, it is well known that when a styrene-based resin is produced by using the above-mentioned bulk radical polymerization, oligomers are generally produced and styrene-based monomers are also likely to remain.

[0004] For example, Encyclopedia of Chemical Techn
ology, Kirk-Othmer, Third Edition, JohnWily & Sons, 21
According to Vol. 817, thermal polymerization at 100 ° C. or higher involves by-products of oligomers such as styrene dimer and styrene trimer, and the amount thereof is about 1 wt%. Specific oligomer components include 1-phenyl-4-
(1′-phenylethyl) tetralin, 1,2-diphenylcyclobutane, 2,4-diphenyl-1-butene,
It is said that 2,4,6-triphenyl-1-hexene and the like are present.

[0005] In the bulk polymerization process, polymerization is usually carried out at 80 to 180 ° C, and then most of the contained solvent and unreacted monomer is subjected to a devolatilization treatment in a recovery step. The recovered solvent, unreacted monomers, and the like are recycled, but some monomers, oligomers such as dimers and trimers are hardly volatilized, and some remain in the product resin. As a result of analyzing the styrene-based resin thus produced, it was found that impurities, residues and by-products during the polymerization were included from the raw materials. Specifically, styrene, α-methylstyrene, n-propylstyrene, n-propylbenzene, iso-propylbenzene, 1,3-diphenyl-1-butene, 1,2-diphenylcyclobutane, 1-phenyltetraline, 2,
It has been found that 4,6-triphenyl-1-hexene, 1,3,5-triphenylbenzene, 1-phenyl-4- (1′-phenylethyl) tetralin and the like are contained in such a styrene resin.

Further, the styrene-based resin obtained by the radical polymerization method is newly added due to the irregularity of the styrene-based monomer chain, the devolatilization step in the production of the styrene-based resin and the heat history and shear stress in the processing. There is also a problem that oligomers such as monomers, dimers and trimers are generated. Such monomers and oligomers in the styrenic resin have an unfavorable effect on the performance of products such as containers.

For example, in terms of the performance of the final product, the rigidity of the product is lowered, which is not preferable. Especially at high temperature,
This is an especially important performance when a high-temperature thing is put into the contents of a food container or the like. Furthermore, the monomers and oligomers in the styrene resin penetrate from the inside of the molded product to the surface,
There is a problem that the printed surface of the molded product is peeled or bleeds.

[0008]

That is, the present invention provides:
An object of the present invention is to provide a styrene resin container excellent in rigidity of a molded article and printability on the surface of the molded article.

[0009]

According to the present invention, there is provided a styrene-based resin obtained by anionic polymerization using an organolithium initiator and having a total amount of monomers, dimers and trimers of less than 1000 ppm. The present invention provides a system resin container. Further, the present invention relates to a method wherein the total amount of monomers, dimers and trimers obtained by anionic polymerization using an organolithium initiator is 1%.
The present invention provides a styrene-based resin container characterized by comprising 10 to 99 parts by weight of a styrene-based resin having less than 000 ppm and 90 to 1 part by weight of another thermoplastic resin. Further, the present invention provides the styrene resin container, wherein the thermoplastic resin is a styrene resin.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail.
For the styrene resin container of the present invention, a monomer obtained by anionic polymerization using an organolithium initiator, a monomer,
A styrene-based resin having a total amount of a dimer and a trimer of less than 1000 ppm refers to, for example, Japanese Patent Application No. 2000-134.
No. 353, Japanese Patent Application No. 2000-134354, Japanese Patent Application No. 200
0-134359, Japanese Patent Application No. 2000-134356,
Japanese Patent Application No. 2000-134357, Japanese Patent Application No. 2000-139
No. 656, Japanese Patent Application No. 2000-139657 and the like are used. That is, the styrene-based resin obtained by the above-described anion polymerization is obtained by anion-polymerizing a styrene-based monomer with an organolithium initiator which is an anion polymerization initiator.

Specific examples of the organolithium initiator include n-butyllithium, sec-butyllithium and t-butyllithium.
-Butyllithium, methyllithium, ethyllithium,
Benzyl lithium, 1,6-dilithiohexane, and the like. These may be used alone or as a mixture of two or more. Preferred examples include n-butyllithium, sec-butyllithium, and t-butyllithium. These organic lithium initiators include hydrocarbon solvents, for example, aliphatic hydrocarbon solvents such as hexane, cyclohexane, pentane and heptane, aromatic hydrocarbon solvents such as benzene, toluene, ethylbenzene and xylene, tetrahydrofuran and dityl. ether,
It can be used by dissolving it in ethers such as dimethyl ether.

The amount of the organolithium initiator used depends on the molecular weight of the polymer to be obtained. That is, the molecular weight of the polymer is basically determined by the monomer amount and the composition ratio of the organolithium initiator. The amount of organolithium used per 100 g of monomer ranges from 0.05 to 10 mmol. Preferably it is in the range from 0.1 to 5 mmol, particularly preferably from 0.2 to 1 mmol.

There are various styrene monomers usable for the styrene resin used in the styrene resin container of the present invention.
Methylstyrene, m-methylstyrene, o-methylstyrene, 2,4-dimethylstyrene, 2,5-dimethylstyrene, 3,4-dimethylstyrene, 3,5-dimethylstyrene, p-ethylstyrene, m-ethylstyrene ,
and alkylstyrenes such as o-ethylstyrene. These styrene monomers may be used alone or in combination of two or more. The most preferred styrene monomer includes styrene.

In addition to the styrenic monomers described above,
Anionic copolymerizable monomers can be used together. Examples of copolymerizable monomers include aromatic monovinyl compounds such as α-methylstyrene, vinyltoluene, vinylethylbenzene, and vinylxylene;
Examples thereof include conjugated diene compounds such as butadiene and isoprene, and methyl methacrylates. These copolymer monomers may be useful in improving or adjusting the heat resistance, softening temperature, impact strength, rigidity, processability, etc. of the resin.

The industrial raw materials or the commercially available styrene monomers contain the corresponding acetylenes (phenylacetylene in the case of styrene). When phenylacetylene is polymerized with n-butyllithium using styrene as a monomer, it deactivates n-butyllithium,
And / or acts as a chain transfer agent, reducing the efficiency of the n-butyllithium used and / or producing a low molecular weight polymer. In order to obtain the styrenic resin of the present invention, the content of the phenylacetylene-based compound is preferably less than 200 ppm based on the styrenic monomer. More preferably less than 150 ppm, most preferably less than 100 ppm. When a styrene-based monomer containing 200 ppm or more of phenylacetylenes is used, the above-mentioned problems become apparent, low molecular components and the like in the product increase, and thermal stability during molding and the like is impaired.

The process for producing the styrene resin obtained by anionic polymerization used in the styrene resin container of the present invention is not particularly limited. Generally, it is carried out by the following process. For example, a complete batch polymerization method in which the entire amount of the monomer and the initiator is charged into the reaction tank and then polymerization, a semi-batch polymerization method in which the reaction tank is charged with part or all of the initiator, and then polymerization is performed while the monomer is additionally charged, and complete stirring. The raw material system (monomer and initiator) is continuously charged into the reaction tank in the state, and the same amount of the production system (polymer solution) is taken out while continuously stirring, or the reaction raw material system is started from one end of the tubular reaction tank. , And the product system is taken out from the other end. A continuous polymerization method of plug flow, or a series connection process thereof is conceivable.

In the production of the styrene resin used in the styrene resin container of the present invention, the styrene resin can be preferably produced by a combined process in which a continuous polymerization tank with complete stirring and a continuous polymerization tank with plug flow are connected. In the continuous polymerization process with complete stirring, the molecular weight distribution of the obtained polymer is broadened, and the remaining monomer can be efficiently converted in the continuous polymerization process in the next plug flow. Broadening the molecular weight distribution helps to improve the processability of the resin, and complete conversion of the monomer can eliminate low molecular weight components derived from the monomer mixed into the resin.

The production of the styrenic polymer obtained by anionic polymerization for use in the styrenic resin container of the present invention may be a bulk polymerization without solvent or a solution polymerization. Solution polymerization is preferred in order to facilitate stirring and heat removal. That is, the styrene monomer is a hydrocarbon solvent, for example, hexane, cyclohexane, aliphatic hydrocarbon solvents such as heptane, benzene,
Polymerization is carried out by dissolving in an aromatic hydrocarbon solvent such as toluene, ethylbenzene and xylene. Preferred solvents are cyclohexane, toluene, ethylbenzene and xylene, most preferably ethylbenzene and toluene.

The amounts of the styrene monomer and the hydrocarbon solvent are preferably 80 to 10 parts by weight for the styrene monomer and 20 to 90 parts by weight for the hydrocarbon solvent. More preferably, the styrene monomer is 60 to 10 parts by weight, and the hydrocarbon solvent is 40 to 90 parts by weight. If the styrene monomer exceeds 80 parts by weight, the viscosity of the polymerization solution increases,
Extremely large power is required for stirring and transfer, and if the polymerization temperature is increased to lower the viscosity, the reaction rate becomes very fast and heat removal becomes difficult, or the polymerization is stopped by heat deactivation. If the amount is less than 10 parts by weight, a large amount of thermal energy is required for the recovery of the solvent, so that the heat history in the recovery step becomes excessive and the thermal decomposition of the resin is promoted.

In the production of the styrene resin obtained by anionic polymerization used in the styrene resin container of the present invention, the polymerization temperature is preferably in the range of 0 to 130 ° C. More preferably 10 to 120 ° C, particularly preferably 20 to 11 ° C.
It is in the range of 0 ° C. When the polymerization temperature is extremely low, the reaction rate is reduced, and the method is not practical. On the other hand, if the polymerization temperature is extremely high, the reaction rate is lowered due to decomposition of the initiator, which is not preferable. If the temperature is higher than 110 ° C., the polymer may be colored, which is not preferable depending on the application.

In the production of a styrene-based resin obtained by anionic polymerization for use in the styrene-based resin container of the present invention, the solution viscosity during polymerization generally is extremely high, depending on the monomer concentration of the raw material system. For this reason, it is often difficult to remove the heat of polymerization by a jacket attached to a normal polymerization tank. A known method can be used as a method for increasing the heat removal capability of the equipment. For example, a method in which a heat removal coil is stretched in a reaction tank, an external circulation jacket is provided separately from a polymerization tank jacket, or a reflux condenser is provided can be preferably used.

The pressure in the polymerization tank needs to be sufficient to keep the system in a liquid tank. When a reflux condenser is used for removing the reaction heat, a reduced pressure can be used if necessary. In the production of the styrene resin obtained by anionic polymerization used in the styrene resin container of the present invention, a carbon-lithium bond remains at the polymer terminal after the polymerization. If this is left as it is, it may be subjected to air oxidation or the like at the finishing stage or the like, which may cause a decrease in stability or coloring of the obtained styrene resin. After polymerization, it is preferable to stabilize the active terminal of the polymer, that is, the carbon-lithium bond.

For example, the addition of compounds having an oxygen-hydrogen bond such as water, alcohols, phenols, and carboxylic acids, epoxy compounds, ester compounds, ketone compounds, carboxylic acid anhydrides, and compounds having a carbon-halogen bond have similar effects. Can be expected. The amount of these additives used is carbon-
The equivalent is preferably about 10 to 10 equivalents for lithium bonding. If it is too much, it is not only disadvantageous in terms of cost, but also there are many cases where mixing of the remaining additives becomes an obstacle.

In the production of the styrenic resin obtained by anionic polymerization used in the styrenic resin container of the present invention, a coupling reaction is carried out with a polyfunctional compound utilizing a carbon-lithium bond to increase the polymer molecular weight. The chains can also be branched. The polyfunctional compound used for such a coupling reaction can be selected from known compounds. Examples of the polyfunctional compound include a polyhalogen compound, a polyepoxy compound, a mono- or polycarboxylic acid ester, a polyketone compound, a mono- or polycarboxylic anhydride, and the like. Specific examples include silicon tetrachloride, di (trichlorosilyl) ethane, 1,3,5-tribromobenzene, epoxidized soybean oil, tetraglycidyl 1,3-bisaminomethylcyclohexane, dimethyl oxalate, and tri-merellitic acid. 2
-Ethylhexyl, pyromellitic dianhydride, diethyl carbonate and the like.

In the production of the styrene resin obtained by anionic polymerization used in the styrene resin container of the present invention, an alkali component derived from organic lithium, for example, lithium oxide or lithium hydroxide is neutralized and stabilized by adding an acidic compound. You can also. Examples of such acidic compounds include carbon dioxide, boric acid, various carboxylic acid compounds, and the like. By these additions, the coloring resistance can be particularly improved in some cases. In the production of a styrene resin obtained by anionic polymerization, which is used in the styrene resin container of the present invention, lithium metal derived from an organic lithium initiator remaining in the styrene resin is removed (deashed) by a known method. Is also possible. In particular, lithium metal is 10 per styrene resin obtained by anionic polymerization.
If an amount exceeding 00 ppm remains, it is preferable to remove it.

The styrene resin obtained by anionic polymerization used in the styrene resin container of the present invention is a known stabilizer for improving its thermal or mechanical stability, antioxidant property, weather resistance and light resistance. Can be added. For example, JP-A-7-292188 discloses that addition of a 2,4,6-trisubstituted phenol is advantageous as a method for stabilizing polystyrene.
Preferred examples of the 2,4,6-trisubstituted phenol include 2,2
6-di-t-butyl-4-methylphenol, triethylene glycol-bis- [3- (3-t-butyl-5-
Methyl-4-hydroxyphenyl) propionate],
Pentaerythritol tetrakis [3- (3,5-di-t-
Butyl-4-hydroxyphenyl) propionate],

Octadecyl-3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate,
3,5-trimethyl-2,4,6-tris (3,5-di-t-butyl-4-hydroxybenzyl) benzene, n
-Octadecyl 3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate, 2-tert-butyl-6
-(3-t-butyl-2-hydroxy-5-methylbenzyl) -4-methylphenyl acrylate, 2 [1-
(2-hydroxy-3,5-di-t-pentylphenyl)]-4,6-di-t-pentylphenyl acrylate,

Tetrakis [methylene 3- (3,5-di-
t-butyl-4-hydroxyphenyl) propionate] methane, 3,9bis [2- {3- (t-butyl-4)
-Hydroxy-5-methylphenyl) propynyloxy {-1,1-dimethylethyl] -2,4,8,10-
Tetraoxa [5,5] undecane, 1,3,5-tris (3 ′, 5′-di-tert-butyl-4′-hydroxybenzyl) -s-triazine-2,4,6 (1H, 2H,
3H) -trione, 1,1,4-tris (2-methyl-
4-hydroxy-5-t-butylphenyl) butane,
4,4'-butylidenebis (3-methyl-6-t-butylphenol) and the like.

These stabilizers can be mixed after the recovery of the polymer. However, it is preferable to add the stabilizer at the stage of the solution after the polymerization because mixing is easy and deterioration in the solvent recovery step can be suppressed. Used in the styrene-based resin container of the present invention, in the production of a styrene-based resin obtained by anionic polymerization, the polymerization solution obtained, after the polymerization is completed, to recover unreacted monomers and solvents, is volatilized and removed from the polymer. . Known methods can be used for volatilization.
As the volatilization removing device, for example, a method of flashing in a vacuum tank and a method of extrusion evaporation can be preferably used. Generally, the temperature is 18 ° C, depending on the volatility of the solvent.
Volatile components such as a solvent and residual monomers are volatilized and removed at 0 to 260 ° C. and a degree of vacuum of 100 Pa to 50 kPa. It is also effective to connect the devolatilizers in series and arrange them in two stages. A method of adding water between the first and second stages to increase the volatility of the second-stage monomer can also be used.

The total amount of monomers, oligomers and trimers contained in the styrene resin obtained by anionic polymerization using an organolithium initiator used in the styrene resin container of the present invention must be less than 1000 ppm. Preferably less than 500 ppm, more preferably 2 ppm
Less than 00 ppm. If the content of the low molecular weight component is high, the effects intended by the present invention cannot be sufficiently achieved. Quantification of monomers, dimers and trimers in the styrene-based resin obtained by the above-mentioned anionic polymerization can be performed using gas chromatography. Here, the dimer is the total amount of 1,2-diphenylcyclobutane and 2,4-diphenyl-1-butene, and the trimer is 1-phenyl-4- (1′-phenylethyl) tetralin,
Determined as the total amount of 4,6-triphenyl-1-hexene.

The styrene resin obtained by the above anionic polymerization generally has a weight average molecular weight of 100,000 to 50.
000, preferably from 150,000 to
400,000, particularly preferably 200,000 to 35
It is in the range of 0000. In addition, the molecular weight distribution (Mw / Mn) of the styrene resin obtained by the above-described anionic polymerization, which is represented by the ratio of the weight average molecular weight to the number average molecular weight, is generally 1.2 to 10, preferably 1.5 to 5, particularly preferably 1.5 to 5, Preferably it is in the range of 2-4.

The styrenic resin obtained by the above-mentioned anionic polymerization may further contain, if necessary, various additives usually used, for example, stabilizers, dyes, pigments, fillers, lubricants,
A release agent, a plasticizer, an antistatic agent, an antioxidant and the like can be added. The styrene-based resin container of the present invention is obtained by anionic polymerization using an organolithium initiator,
Total amount of monomer, dimer and trimer is 1000p
A thermoplastic resin containing 90 to 1 part by weight based on 10 to 99 parts by weight of a styrene resin having a particle diameter of less than pm is also included. Preferably, the styrene-based resin having a total amount of the monomer, dimer and trimer of less than 1000 ppm obtained by anionic polymerization using an organolithium initiator is 20 to 99 parts by weight, and the other thermoplastic resin is 8 to 99 parts by weight.
0 to 1 part by weight.

More preferably, the styrene resin having a total amount of the monomer, dimer and trimer of less than 1000 ppm obtained by anionic polymerization using an organolithium initiator is used in an amount of 30 to 99 parts by weight, and other thermoplastic resin. The resin is 70 to 1 part by weight. When the total amount of the monomer, dimer and trimer obtained by anionic polymerization using an organolithium initiator is less than 1000 ppm and the styrene-based resin is less than 10 parts by weight, the effects intended by the present invention cannot be sufficiently achieved. .

As the thermoplastic resin, general-purpose polystyrene obtained by radical polymerization, high-impact polystyrene, styrene-butadiene block copolymer and its hydrogenated product,
Preferred examples include styrene-isoprene block copolymers and hydrogenated products thereof, ethylene-styrene copolymers, and styrene resins such as ABS and AS. These thermoplastic resins may be used alone or as a blend of two or more. The method for processing or producing the styrene resin container of the present invention is not particularly limited. It can be obtained by a conventionally known method. For example, a pelletized styrene resin is processed into an unstretched extruded sheet by an extruder, or is sequentially processed into a biaxially stretched sheet by a T-die method, and further processed by vacuum forming, pressure forming, plug assist forming, etc. The container can be molded.

The structure of the styrene resin sheet is not particularly limited. However, generally the thickness is 0.1-5m
m, preferably 0.2-4 mm, particularly preferably 0.3
範 囲 3.0 mm. Further, the styrene resin sheet may have a structure in which the styrene resin sheet is laminated on a base material made of a thermoplastic resin, if necessary. The substrate made of the thermoplastic resin may be a multilayer film including an adhesive layer and the like. Lamination on a substrate made of a thermoplastic resin is useful not only for improving appearance and printability but also for improving physical properties such as surface scratch resistance and rigidity. Examples of the thermoplastic resin used for the substrate made of a thermoplastic resin include a styrene-based resin and an olefin-based resin.

Specific examples of the styrene resin include general-purpose polystyrene, impact-resistant polystyrene, styrene-butadiene block copolymer and its hydrogenated product, styrene-isoprene block copolymer and its hydrogenated product obtained by radical polymerization. , Ethylene-styrene copolymer, ABS,
AS and the like. Specific examples of the olefin-based resin include polypropylene, polyethylene, and a copolymer of ethylene and an α-olefin. Above all, impact-resistant polystyrene is particularly preferably used because of its excellent impact strength and easy lamination. These substrates can also be foamed layers, which enhances heat insulation.

On the other hand, various containers may be formed from a styrene resin by a method such as extrusion molding, direct blow molding, injection blow molding, stretch blow molding, multilayer blow molding, or injection molding. Hereinafter, the present invention will be described specifically with reference to Examples, but the present invention is not limited thereto.

The determination of the styrene monomer, dimer and trimer in the resin was performed using gas chromatography. Here, the dimer is a total amount of 1,2-diphenylcyclobutane and 2,4-diphenyl-1-butene,
The trimer was determined as the total amount of 1-phenyl-4- (1'-phenylethyl) tetralin and 2,4,6-triphenyl-1-hexene. Further, the weight average molecular weight (Mw) and the molecular weight distribution (Mw / Mn) of the polymer in the resin
Was determined by GPC in terms of polystyrene.

[0039]

Reference Example 1 Production of Anionic Polymerized Styrene-Based Resin (A1) A reflux condenser having a heat transfer area of 0.2 m ³ was mounted on the upper part of a 12-L capacity complete mixing type reactor equipped with a stirrer and equipped with a jacket. A reactor was used. Further, a 4 L piston flow reactor (L / D = 3.5) equipped with a stirrer was arranged in series downstream of the first reactor to form a second reactor. The insides of the first and second reactors were degassed under reduced pressure, and the inside of the tank was set to a nitrogen atmosphere.

Deaerated styrene from which a polymerization inhibitor (tertiary butyl catechol) and water had been removed in advance (phenylacetylene in the styrene was 31 ppm) was added in 50 parts.
50 parts by weight of degassed and purified ethylbenzene as a polymerization solvent were mixed in a mixing tank. In the first reactor and the second reactor, the temperature of the reaction vessel was set at 80 ° C. A mixed solution of styrene monomer and ethylbenzene was fed from the blending tank at a flow rate of 8 L / h. The amount held in the tank of the first reactor was controlled at 8 L. The pressure in the first reactor was reduced, the pressure was maintained at 15 kPa, and ethylbenzene was refluxed to maintain the polymerization temperature at 80 ° C. n-Butyl lithium was fed to the first reactor in an amount corresponding to 0.9 mmol per 100 g of styrene monomer. The average residence time in the first reactor under these conditions is 60 minutes.

The reaction liquid flowing out of the first reactor was successively introduced into the second reactor and passed through a piston flow.
The conversion from monomer to polymer at the point of exit from the first reactor was 98.5% on average, and the conversion after passing through the second reactor was 99.99% or more. The resulting polymer solution was deactivated by adding 10 times equivalent of methanol to the amount of lithium. Thereafter, 0.05 g of an antioxidant was added to the polymer solution per 100 g of the polymer, and volatile components were removed by a reduced pressure flushing tank and a vented extruder to form a pellet.

The thus obtained styrene resin polymer had a weight average molecular weight (Mw) of 215,000 and a molecular weight distribution (Mw / Mn) of 2.2. The monomer in the styrene resin was 9 ppm, and the oligomer (dimer and trimer) was 90 ppm.

[0043]

Reference Example 2 Production of Radical Polymerized Styrene Resin (B1) A 12-L capacity complete mixing reactor equipped with a stirrer and equipped with a jacket was used as the first reactor. Furthermore, a 4 L piston flow reactor equipped with a stirrer (L / D =
3.5) was arranged in series downstream of the first reactor to form a second reactor. The insides of the first and second reactors were degassed under reduced pressure, and the inside of the tank was set to a nitrogen atmosphere.

Degassed styrene from which a polymerization inhibitor (tertiary butyl catechol) and water were removed in advance (phenylacetylene in the styrene was 31 ppm) was 90 parts.
10 parts by weight of degassed and purified ethylbenzene as a polymerization solvent were mixed in a mixing tank. The temperature of the reaction vessel of the first reactor was 140 ° C. and the temperature of the second reactor was 180 ° C.
Set to ° C.

A mixture of styrene monomer and ethylbenzene is fed from the mixing tank at a flow rate of 1.3 L / h,
Thermal radical polymerization was performed. The amount held in the tank of the first reactor was controlled at 8 L. The reaction liquid flowing out of the first reactor was subsequently introduced into the second reactor and passed through a piston flow. Thereafter, 0.05 g of an antioxidant per 100 g of the polymer was added to the polymer solution, and then the volatile component was removed by performing a heat treatment at 240 ° C. in a reduced-pressure flushing tank.

The weight average molecular weight (Mw) of the styrene resin polymer thus obtained was 208,000, and the molecular weight distribution (Mw / Mn) was 3.3. The monomer content in the styrene resin was 330 ppm, and the oligomer content (dimer and trimer) was 6500 ppm.

[0047]

Reference Example 3 Production of Impact-Resistant Polystyrene (B2) The inside of a 6-L capacity 3-tank reactor equipped with a stirrer and equipped with a jacket was degassed under reduced pressure, and the inside of the tank was changed to a nitrogen atmosphere. In advance, 80 parts by weight of degassed styrene from which a polymerization inhibitor (tertiary butyl catechol) and water were removed, and 15 parts by weight of degassed and purified ethylbenzene as a polymerization solvent were mixed with polybutadiene (Asahi Kasei Kogyo Co., Ltd., Diene 55).
A) 5 parts by weight were mixed and dissolved in a mixing tank. Further, 0.03 parts by weight of 1,1-di-tert-butylperoxy-3,3,5-trimethylcyclohexane was added to 100 parts by weight of the above mixture.

The reaction tanks of the first reactor were heated at 115 ° C. and 12 ° C., respectively.
The temperature was controlled at 5 ° C and 135 ° C. A mixture of styrene monomer, ethylbenzene and a rubbery polymer was added to the mixture tank.
Feeding was performed at a flow rate of L / h to perform radical polymerization. After adding 0.05 g of an antioxidant per 100 g of the polymer to the reaction solution flowing out of the first reactor, a volatile component was removed by heat treatment at 240 ° C. in a reduced pressure flushing tank to form pellets. The proportion of polybutadiene in the obtained rubber-modified styrenic polymer was 6.5% by weight.
Met. The dispersed phase had a weight average particle size of 1.7 μm as determined from a transmission electron micrograph.

[0049]

Examples 1 to 5 and Comparative Examples 1 and 2 As the styrene resin and the styrene-butadiene block copolymer obtained in the above Reference Examples 1 to 3, B3 (Asaflex 815, manufactured by Asahi Chemical Industry Co., Ltd.) And B4 (Taphrene 125, manufactured by Asahi Kasei Kogyo Co., Ltd.) were blended at the ratio shown in Table 1 and melt-kneaded by an extruder to obtain styrene resin pellets. Next, these styrene resin pellets were obtained with a T-die extruder to obtain a stretched sheet having a thickness of 0.27 mm and a length and width of three times.
The stretched sheet thus obtained was molded into a beverage cup having an inner volume of 200 ml at a mold temperature of 60 ° C. and a hot plate temperature of 120 ° C. using a hot plate press forming machine.

Using the styrene resin pellets described above, injection blow molding was performed at a resin temperature of 200 ° C. and a mold temperature of 60 ° C. to form a beverage container having a draw ratio (area ratio) of 3 times and an inner volume of 50 ml. . The following evaluation was performed using the obtained beverage cup and beverage container. Table 1 shows the evaluation results.

(1) Printability-1 The obtained beverage cup and the side wall of the beverage container were 2 cm × 4 cm.
The printing ink for styrene resin is silk screen printed, dried at 90 ° C. for 2 hours, and
After standing at 24 ° C for 24 hours, adhere the cellophane tape closely,
By peeling the tape, the state of peeling of the printed surface was observed and evaluated. ；: No peeling of the printed surface was observed at all. Δ: Slight peeling of the printed surface was observed. X: The peeling of the printing surface was remarkably recognized.

(2) Printability-2 A printing ink for styrene resin was solid-printed on the center of the side wall of the obtained beverage cup and beverage container using a printing machine for continuous printing, and the continuous printability was evaluated. ：: No bleeding of the ink was observed. C: Slight bleeding of the ink was observed. X: Ink bleeding was remarkably observed.

(3) Rigidity upon heating The obtained beverage cup and beverage container were cut into 1 cm × 2 cm and immersed in boiling water for 1 minute. The sheet softened and was deformed by internal stress. The rigidity of the styrene resin sheet during heating was evaluated based on the deformed state. ：: Surface roughness is conspicuous, but size deformation is small,
Slight shrinkage was observed. ×: The surface roughness was remarkable with the size deformation, and remarkable shrinkage was observed.

[0054]

[Table 1] (In the table, among the evaluation results of the examples, the upper row shows the evaluation results of the sheet molded article, and the lower row shows the evaluation results of the injection blow molded article.)

[0055]

The styrenic resin container of the present invention is excellent in printability in that it has excellent peeling resistance on the printed surface, enables clear printing without ink bleeding, and also has excellent rigidity at high temperatures.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) C08L 101/00 B65D 1/00 A F term (Reference) 3E033 BA22 BB01 CA07 CA20 FA02 FA03 FA04 4J002 BC031 BC032 BC041 BC062 BC091 BN142 BN152 BP012 EA046 GG00 4J015 DA02

Claims (3)

[Claims] 1. A styrene-based resin container comprising a styrene-based resin obtained by anionic polymerization using an organolithium initiator and having a total amount of monomers, dimers and trimers of less than 1000 ppm. 2. A styrenic resin obtained by anionic polymerization using an organolithium initiator and having a total amount of monomers, dimers and trimers of less than 1000 ppm is 1
A styrene-based resin container comprising 0 to 99 parts by weight and 90 to 1 part by weight of another thermoplastic resin. 3. The styrene resin container according to claim 2, wherein the thermoplastic resin is a styrene resin.