JPH0649335B2 - Container manufacturing method - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for producing a container, and more specifically, to efficiently produce a container having various physical properties using a styrene polymer having a syndiotactic structure as a raw material. Regarding the method.

[Problems to be Solved by Prior Art and Invention]

Generally, a styrene polymer, particularly polystyrene produced by radical polymerization is used, and is widely used as a film or sheet in food packaging, miscellaneous goods packaging, industrial materials, and the like. However, the products obtained from polystyrene having an atactic structure of stereoregularity have the drawbacks of poor heat resistance, chemical resistance, and mechanical strength, so that their fields of use have been limited.

Further, in the case of producing a container by thermoforming, for example, in JP-A-51-57767, the container is produced by intermittently operating and thermoforming using an extruder and a plate-shaped mold. Although a device has been proposed, no attention has been paid to the temperature of a strip-shaped member such as a sheet to be extruded, and the device lacks effectiveness and specificity.

Further, Japanese Patent Laid-Open No. 55-13526 proposes a method of transferring and thermoforming a sheet by using an extruder and a temperature control conveyor. In this method, the transfer of the temperature control conveyor surface onto the sheet is performed. However, there is a drawback in that the optical characteristics of the sheet and finally the container are limited.

By the way, the group of the present inventor has conducted research to solve the above-mentioned drawbacks and succeeded in developing a styrene-based polymer having a syndiotactic structure (Japanese Patent Laid-Open No. 62-104818). .

However, this styrene-based polymer having a syndiotactic structure has to be extruded at a temperature higher than that of a general styrene-based polymer because of its characteristic of having a crystal structure, and thus the produced film or sheet. There are various problems such as a large drawdown at the time of thermoforming a belt-shaped member such as, and a defective molding phenomenon occurs.

Therefore, in order to solve the above-mentioned problems, the present inventor has conducted various studies on various practical conditions for a specific manufacturing apparatus, and has conducted earnest studies to develop an efficient thermoforming method.

As a result, it has been found that a styrene-based polymer having a syndiotactic structure can be extruded with a T-die, held in a certain temperature range, and thermoformed to produce a container having excellent physical properties. . The present invention has been completed based on such findings.

[Means for Solving the Problems]

That is, according to the present invention, a styrene-based polymer having a syndiotactic structure is extrusion-molded with a T-die and then kept in a temperature range of not less than the glass transition temperature of the styrene-based polymer and not more than 59 ° C. higher than the melting point thereof. The present invention provides a method for producing a container characterized by thermoforming.

In the method of the present invention, a styrene polymer having a syndiotactic structure is suitable as a molding material. The syndiotactic structure in the styrene-based polymer having this syndiotactic structure means that the stereochemical structure is a syndiotactic structure, that is, a phenyl group which is a side chain to the main chain formed from a carbon-carbon bond or a substitution It has a steric structure in which phenyl groups are alternately located in opposite directions, and its tacticity is quantified by a nuclear magnetic resonance method ( ¹³ C-NMR method) using isotope carbon. ¹³ C-NM
The tacticity measured by the R method can be indicated by the abundance ratio of a plurality of continuous structural units, for example, diad in the case of 2, triad in the case of 3, and pentad in the case of 5. The styrene-based polymer having a syndiotactic structure referred to in the invention is usually 75% or more, preferably 85% or more in racemic dyad, or 30% or more, preferably 50% or more in racemic pentad. City-containing polystyrene, poly (alkyl styrene), poly (halogenated styrene), poly (alkoxy styrene), poly (vinyl benzoate), hydrogenated polymers of these and mixtures thereof, or containing these as the main components This refers to a copolymer. As the poly (alkylstyrene),
There are poly (methylstyrene), poly (ethylstyrene), poly (isopropylstyrene), poly (tertiarybutylstyrene), poly (phenylstyrene), poly (vinylnaphthalene), poly (vinylstyrene), etc. Examples of the modified styrene) include poly (chlorostyrene), poly (bromostyrene) and poly (fluorostyrene). Further, as poly (halogenated alkyl styrene),
Examples of poly (alkoxystyrene) such as (chloromethylstyrene) include poly (methoxystyrene) and poly (ethoxystyrene). Further, as the comonomer component of the copolymer containing these structural units, in addition to the above-mentioned styrene-based polymer monomers, olefin monomers such as ethylene, propylene, butene, hexene, and octene, diene monomers such as butadiene and isoprene, and cyclic compounds. Examples thereof include polar vinyl monomers such as olefin monomers, cyclic diene monomers, methyl methacrylate, maleic anhydride and acrylonitrile.

Among these, particularly preferable styrene-based polymers include polystyrene, poly (alkylstyrene), and poly (alkylstyrene).
(Halogenated styrene), hydrogenated polystyrene and copolymers containing these structural units.

A styrene-based polymer having such a syndiotactic structure can be obtained, for example, by using a titanium compound and a condensation product of water and a trialkylaluminum as a catalyst in an inert hydrocarbon solvent or in the absence of a solvent to form a styrene-based monomer. It can be produced by polymerizing a polymer (a monomer corresponding to the above styrene-based polymer) (JP-A-62-18770).
No. 8). Also, poly (halogenated alkyl styrene)
Can be obtained by the method described in JP-A-1-46912, and these hydrogenated polymers can be obtained by the method described in JP-A-1-178505.

The styrene polymer is not particularly limited in molecular weight, but has a weight average molecular weight of 100,000 or more, preferably 30
It is more than 0,000. Further, the molecular weight distribution is not limited in width and width, and various kinds can be applied.

In the method of the present invention, the styrene-based polymer having a syndiotactic structure (hereinafter sometimes referred to as SPS) is further used, in addition to the commonly used amorphous thermoplastic resin, rubber, inorganic filler, Antioxidants, plasticizers, compatibilizers, colorants and the like can be added.

In the method of the present invention, first, the SPS is extruded with a T die. Here, for example, when SPS is extrusion-molded in a single layer, the surface temperature of the molten resin immediately after extrusion is determined by the resin (SPS)
The temperature is 1 ° C higher than the melting point (Tm) (Tm + 1 ° C) or higher, preferably (Tm + 5 ° C) to (Tm + 59 ° C). When a multilayer strip member such as a multilayer sheet or film containing at least one layer of SPS is extrusion-molded, coextrusion, according to the extrusion temperature of the thermoplastic resin to be combined,
Multi-layer die or a combination of co-extrusion and multi-layer die is used.
In the present invention, the extruded product may have a multi-layer structure, but in this case, it is preferable that at least one layer of SPS is included as described above. For this multilayer structure, the thermoplastic resin to be combined with the SPS should be selected according to the purpose of the container to be manufactured. For example, when it is desired to provide a gas barrier property to the container to be manufactured, the SPS layer / adhesive layer (A
D) layer / ethylene-vinyl alcohol copolymer (EVO
H) layer / AD layer / SPS layer, SPS layer / AD layer / polyvinylidene chloride (PVDC) layer / AD layer / SPS layer, SP
There are combinations such as S layer / AD layer / PVDC layer / AD layer / thermoplastic resin layer. In the case of a container that shields odor,
SPS layer / polyethylene terephthalate (PET) layer,
There are combinations of SPS / polycarbonate (PC) layers and the like. The layer ratio changes according to various situations,
Generally, it is defined in the range of SPS layer / thermoplastic resin = 1 to 50, preferably 1 to 30.

Next, in the method of the present invention, after the above-mentioned extrusion molding, an extruded product (usually a sheet or film-like product) is treated with the SP.
59 or more from the glass transition temperature (Tg) of S and the melting point (Tm)
It is necessary to keep the temperature within a temperature range higher than the temperature [Tg to (Tm + 59 [deg.] C.)]. Here, if the holding temperature is lower than Tg, sufficient mold reproducibility cannot be obtained. Further, when thermoforming is performed through a certain line, a belt-shaped member such as a sheet or film is destroyed in the line. On the other hand, (Tm + 59 ° C)
If it exceeds, the SPS will decompose and deteriorate during extrusion.

In the method of the present invention, an extruded product as described above is prepared from Tg to (T
m + 59 ° C) and thermoforming. There are various thermoforming methods, which may be appropriately selected. For example, a molding drum is installed directly below the T die to perform molding.

After extruding with a T-die, it is molded through a certain line using a flat mold.

After extruding with a T-die, it is molded with a molding drum through a certain line.

There are methods such as. Of these, the method is most preferable because it has no effect of drawdown.

〔Example〕

Next, the present invention will be described in more detail with reference to Examples and Comparative Examples.

Reference Example (Production of Styrene Polymer) Toluene 2 as a solvent, 5 mmol of tetraethoxytitanium as a catalyst component and 500 mmol of methylaluminoxane as an aluminum atom were added to a reaction vessel, and styrene 15 was added thereto at 50 ° C. The polymerization reaction was carried out for a time.

After completion of the reaction, the product was cleaned with a hydrochloric acid-methanol mixed solution to decompose and remove the catalyst component. Then, it was dried to obtain 2.5 kg of a styrene polymer (polystyrene). Next, this polymer was subjected to Soxhlet extraction using methyl ethyl ketone as a solvent to obtain an extraction residue of 95% by weight. The weight average molecular weight of this product was 800,000. In addition, from the analysis by ¹³ C-NMR measurement using 1,2-dichlorobenzene as a solvent,
Absorption was observed at 143.35 ppm due to the syndiotactic structure, and the syndiotacticity in racemic pentad calculated from the peak area was 96%. The polystyrene thus obtained was added with bis (2,4-di-butylphenyl) pentaerythritol diphosphite and tetrakis [methylene (3,5-di-butyl-hydroxyhydrocinnamate)] methane as antioxidants. 0.1 part by weight of each was mixed and extruded by a twin-screw extruder having a diameter of 40 mm to form pellets.

The obtained styrene polymer (SPS) has a melting temperature (Tm) of 270 ° C and a glass transition temperature (Tg) of 100 ° C.
Met.

Example 1 The SPS obtained in the above reference example was subjected to 2 at 120 to 150 ° C.
After drying for 5 hours, a single-screw extruder having a diameter of 40 mm was used as an extruder, and the temperature distribution of the extruder was 290 ° C. near the charging port.
A drum with a die of 500 mm in drum diameter and 340 mm in width is placed directly below the T-die, with the middle part 300 ° C., the tip part 310 ° C., and the T-die part 310 ° C., and the belt-shaped member extruded from the T-die is wound around the drum. Was vacuumed and thermoformed in a certain section. Then, punching was performed through a fixed line to obtain a container. The conditions at this time are as follows.

(Mold shape) Diameter: 50 mm x 100 mm, Height: 30 mm (Number of molds) Row direction: 13, Width direction: 3, Total 39 pieces (Molding temperature) Immediately after extrusion: 307 ° C (Tm + 37 ° C) Immediately before molding: 275 ° C (Tm + 5 ° C) The temperature of the strip-shaped member immediately after extrusion and immediately before molding is measured by a non-contact type thermometer [high-sensitivity infrared thermometer (thermotracer 6
-T08A: manufactured by Sanei Sokki Co., Ltd.].

The results are shown in the table.

Example 2 The same operation as in Example 1 was carried out except that a mold having a flat shape was used and the temperature immediately before molding was 110 ° C. (Tg + 10 ° C.). The results are shown in the table.

Example 3 The same operation as in Example 1 was performed, except that SPS and PET were used together as the resin used (SPS layer / PET layer = 5/1). The results are shown in the table.

Comparative Example 1 In Example 2, the temperature immediately before molding was 90 ° C. (Tg-1
The same operation as in Example 2 was performed, except that the temperature was 0 ° C.). The results are shown in the table.

Comparative Example 2 In Example 2, atactic polystyrene was used as the resin, and the temperature immediately before molding was 120 ° C. (Tg + 2).
The same operation as in Example 2 was performed, except that the temperature was 0 ° C.). The results are shown in the table.

Comparative Example 3 In Example 1, atactic polystyrene was used as the resin, and the temperature immediately before molding was 200 ° C. (Tg + 1).
The same operation as in Example 1 was performed except that the temperature was set to 00 ° C. The results are shown in the table.

Comparative Example 4 The same operation as in Example 2 was performed except that extrusion and thermoforming were performed on separate lines and hot-plate forming was performed.
The results are shown in the table.

[Effects of the Invention] As described above, according to the method of the present invention, a container excellent in heat resistance, chemical resistance, and mechanical strength can be manufactured with good energy efficiency and at low cost.

The container manufactured in this way is effectively used as a packaging material for various products including foods or various industrial materials.

Claims (2)

[Claims] 1. A styrene-based polymer having a syndiotactic structure is extrusion-molded with a T-die and then maintained in a temperature range of not less than the glass transition temperature of the styrene-based polymer and not more than 59 ° C. higher than its melting point. A method of manufacturing a container, characterized by thermoforming. 2. A resin containing a styrene-based polymer having a syndiotactic structure is extrusion-molded with a T-die, and then a multilayer strip-shaped member containing at least one layer of the styrene-based polymer is obtained, A method for producing a container, which comprises performing thermoforming while maintaining a temperature range of a glass transition temperature of the united body and a temperature higher than a melting point by 59 ° C. or less.