JP2554834B2 - Styrenic resin stretched hollow molded article and method for producing the same - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a styrene resin stretched hollow molded article and a method for producing the same, and more specifically to heat resistance, solvent resistance, chemical resistance, hot water resistance, mechanical strength, elastic modulus, dimensional stability or The present invention relates to a styrene resin stretched hollow molded article which is excellent in transparency and can be used for various purposes, and an efficient production method thereof.

[0002]

2. Description of the Related Art
As a transparent plastic hollow container, polyethylene terephthalate, vinyl chloride, or the like has been used and has been used as a substitute for a glass container. However, the containers using these materials have insufficient heat resistance and cannot be filled with a boiling sterilized filling liquid at a high temperature, and therefore improvements have been demanded. On the other hand, when a conventional polystyrene having a high glass transition temperature was stretched to form a hollow container, the transparency was maintained but it was brittle and could not be put to practical use. The present inventors have paid attention to the fact that the conventional styrene-based polymer cannot exert a sufficient stretching effect in this manner, and have conducted diligent research to improve this and produce a stretched hollow molded article having excellent various physical properties. Layered.

[0003]

In the process, a styrene polymer having a high syndiotacticity, which was previously developed by the group of the present inventors (Japanese Patent Laid-Open No. 62-10481).
No. 8) is used as a raw material, and this is heated and melted, then rapidly cooled and then heated and stretched, or immediately after heat-melted and stretched at a temperature below the melting point, oriented crystallization not observed in atactic polystyrene is induced. It has been found that a stretched hollow molded article having excellent physical properties can be obtained. The present invention has been completed based on such findings.

That is, the present invention mainly has a syndiotactic structure and has a weight average molecular weight of at least 1.
A styrene-based resin stretched hollow molded article obtained by subjecting a styrene-based polymer of 0,000 to a uniaxial direction of a draw ratio of 2 times or more or a biaxial direction of a draw ratio of 1.5 times or more. . Further, the present invention, by stretching the above styrene-based polymer at the above-mentioned stretching ratio, or by heating and melting the above-mentioned styrene-based polymer, and then quenching and then stretching at the above-mentioned stretching ratio. Alternatively, the present invention also provides a method for producing a styrene-based resin stretched hollow molded article by performing a stretching treatment immediately below the melting point after heating and melting.

The material of the stretched hollow molded article of the present invention is a styrene polymer mainly having a syndiotactic structure and having a weight average molecular weight of at least 100,000. The syndiotactic structure has a stereochemical structure mainly a syndiotactic structure, that is, a stereo structure in which a phenyl group or a substituted phenyl group, which is a side chain with respect to a main chain formed from carbon-carbon bonds, is alternately located in opposite directions. It has a structure, 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 mainly having a syndiotactic structure referred to in the invention is usually 75% or more, preferably 85% in terms of diads.
Or more, or 30 for pentad (racemic pentad)
%, Preferably 50% or more of syndiotacticity polystyrene, poly (alkylstyrene), poly (halogenated styrene), poly (alkoxystyrene), poly (vinyl benzoic acid ester) and mixtures thereof, or these A copolymer containing as a main component is referred to. A styrene-based polymer having low syndiotacticity cannot be expected to have a sufficient stretching effect even if it is stretched. Here, as the poly (alkylstyrene), there are poly (methylstyrene), poly (ethylstyrene), poly (isopropylstyrene), poly (tertiarybutylstyrene), etc., and as the poly (halogenated styrene), Examples include poly (chlorostyrene), poly (bromostyrene), and poly (fluorostyrene).
Examples of poly (alkoxystyrene) include poly (methoxystyrene) and poly (ethoxystyrene). Of these, particularly preferable styrene polymers include polystyrene, poly (p-methylstyrene), poly (m-methylstyrene), poly (p-tertiarybutylstyrene), poly (p-chlorostyrene), poly ( m-
Examples thereof include chlorostyrene), poly (p-fluorostyrene), and a copolymer of styrene and p-methylstyrene.

The styrene-based polymer used in the present invention must have a weight average molecular weight of 100,000 or more, and particularly preferably 150,000 or more. Further, the molecular weight distribution is not limited in width and width, and various kinds can be applied. Here, if the weight average molecular weight is less than 100,000, it is difficult to perform a stretching operation such as breaking during stretching and sufficient stretching cannot be performed, and a stretched hollow molded article having sufficient mechanical strength and heat resistance can be obtained. Can not.

Such a styrenic polymer mainly having a syndiotactic structure is prepared, 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 the solvent. It can be produced by polymerizing a styrene-based monomer (a monomer corresponding to the styrene-based polymer) (JP-A-62-187708).

In the present invention, the above-mentioned styrene-based polymer mainly having a syndiotactic structure is used as a material for the stretched hollow molded article, but if necessary, another polymer (for example, a styrene-based polymer having an atactic structure) is used. Coalescing,
Isotactic styrenic polymers or low molecular weight syndiotactic styrenic polymers, etc., or polymers other than styrenic polymers), metal powders, inorganic fine powders such as talc and mica, glass fibers, etc. An inorganic fiber, an antistatic agent, a lubricant, an antifogging agent, a heat stabilizer, a dye, and a pigment may be used in an appropriate amount. These other polymers, fine inorganic powders, and inorganic fibers are usually used in an amount of 0.
The amount is appropriately mixed in the range of 0005 to 10 parts by weight, preferably 0.01 to 5 parts by weight.

In the present invention, the above-mentioned styrene-based polymer or a mixture of the other components in appropriate amounts is used as a molding material, which is usually first molded by injection molding, extrusion molding or the like, and a preform for stretching. And In this molding,
It is general that the above-mentioned molding material that is heated and melted is molded into a predetermined shape by various molding machines, but the molding material may be molded in a softened state without being heated and melted. Here, the melting temperature of the molding material varies depending on the melting point of the styrenic polymer to be used or a mixture of the styrene polymer and others, but it is preferably above the melting point and below the decomposition point. For example, in the case of polystyrene used in the present invention, it is 270 to 350 ° C., preferably 280.
Melt at ℃ -330 ℃. If the melting temperature is too high, problems such as decomposition of the molding material may occur, which is not preferable. The thickness of the preform molded here may be arbitrarily selected, but is generally 5 mm or less, preferably 4 mm.
It may be appropriately set in the range of mm to 20 μm. 5m thick
If it exceeds m, crystallization inside will proceed and stretching will become difficult. The crystallinity of the preform is 25% or less, preferably 15% or less, more preferably 10% or less.

When it is desired to manufacture a preform having a crystallinity as low as possible, particularly when forming a preform having a large wall thickness, it is effective to rapidly cool the above-mentioned heat-melted forming material during forming. Is. Here, in quenching, the cooling temperature is 10 ° C. or more lower than the glass transition temperature of the styrene-based polymer or a mixture thereof with another,
The temperature is preferably 20 ° C. or lower, and more preferably 30.
It may be set at a temperature lower than ℃. For example, when the styrene polymer is polystyrene, the cooling temperature is set to 80 ° C or lower, preferably 70 ° C or lower, and more preferably 60 ° C or lower. The cooling rate is 200 to 3 ° C / sec, preferably 200 to 5 ° C / sec. If the cooling temperature is too high or the cooling rate is too slow, slow cooling will occur,
Partial crystallization occurs and sufficient stretching becomes difficult.

When the preform is stretched, it is heated at a glass transition temperature of the preform to a melting point of 10 ° C. or lower, preferably at a temperature of 100 ° C. higher than the glass transition temperature to a low crystallization temperature. , Uniaxially or biaxially stretched. Here, the stretching speed is preferably 100 to 500,000% / min. In the case of uniaxial stretching, it is twice or more in the stretching direction,
It should preferably be stretched at a stretch ratio of 3 to 10 times.
In the case of biaxial stretching, it should be stretched in each stretching direction (biaxial direction) at a stretch ratio of 1.5 times or more, preferably 2.5 to 8 times. If the stretching ratio is too small, the mechanical properties, heat resistance, and transparency of the resulting stretched and molded hollow container will not be sufficiently improved. In the case of the biaxial stretching described above, the stretching may be performed simultaneously in the machine direction and the transverse direction, but may be sequentially performed in any order.

Further, in the present invention, particularly when biaxial stretching is carried out, the above-mentioned forming material is not used as a preformed body,
A biaxially stretched molded product can also be obtained by direct stretch blow molding. In the case of this stretch blow molding, it is necessary to raise the melting temperature by 20 ° C. or more above the melting point.
It is effective in preventing melt fracture, rough skin, etc., but if it is too high, decomposition proceeds during molding, so a decomposition point or lower is preferable. For example, when the styrene polymer is polystyrene, the temperature is preferably 280 to 330 ° C. Here, in the case of inflation molding, a stretching treatment is performed immediately after melting, and the stretching temperature is 5 to 150 ° C. lower than the melting point, preferably 10 to 100 ° C. lower. In stretch blow molding, the preform before stretching may be either hot parison or cold parison. Further, in the inflation molding or stretch blow molding, if the blow-up ratio is reduced, uniaxial stretching is possible.

By carrying out uniaxial stretching or biaxial stretching according to the present invention, a stretched hollow container having excellent heat resistance, transparency, solvent resistance, chemical resistance and mechanical properties can be obtained. Further, this stretched hollow molded article may be further heat-treated at a temperature of 120 to 280 ° C. The heating time is usually 1 second to 100 hours, preferably 5 seconds to 10 hours. This heat treatment is more effective if the stretched hollow molded body is heated in a tensioned state. This heat treatment further improves the heat resistance and dimensional stability of the stretched hollow molded body.

[0014]

EXAMPLES Next, the present invention will be described in more detail with reference to Examples and Comparative Examples. The physical properties of the obtained film were measured as follows. Tensile strength and tensile modulus are JI
According to SC-2318. The heat distortion temperature is 10 ° C / min using TMA (Thermal Mechanical Analyzer),
The temperature at the time of 2% deformation was set under the condition of 100 g / mm ² . Reference Example 1 (Production of polystyrene having syndiotactic structure) To a reaction vessel, 2 liters of toluene as a solvent, 5 mmol of tetraethoxytitanium as a catalyst component and 500 mmol of methylaluminoxane as an aluminum atom were added, and styrene 15 was added thereto at 50 ° C. L was added and the polymerization reaction was carried out for 4 hours. After the reaction was completed, the product was washed 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 is 800,
It was 000. From ¹³ C-NMR analysis (solvent: 1,2-dichlorobenzene), absorption was observed at 145.35 ppm due to the syndiotactic structure,
The syndiotacticity in the racemic pentad calculated from the peak area was 96%.

Reference Example 2 (Production of Polystyrene Having Syndiotactic Structure) In a reaction vessel, 2 liters of toluene as a solvent, 1 mmol of cyclopentadienyl titanium trichloride as a catalyst component, and 0.6 mol of methylaluminoxane as an aluminum atom were used. In addition, styrene 3.6 at 20 ° C
1 liter was added and a polymerization reaction was carried out for 1 hour. After the reaction was completed, the product was washed with a hydrochloric acid-methanol mixed solution to decompose and remove the catalyst component. Then, it was dried to obtain 330 g 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. This extraction residue has a weight average molecular weight of 290,000 and a number average molecular weight of 158,000.
And the melting point was 270 ° C. Also, this polymer
^{From 13} C-NMR analysis, absorption was observed at 145.35 ppm due to the syndiotactic structure, and the syndiotacticity in the racemic pentad calculated from the peak area was 96%.

Reference Example 3 (Production of Styrene Copolymer Having Syndiotactic Structure) In Reference Example 1, styrene 3.6 was used as a raw material monomer.
The same procedure as in Reference Example 1 was carried out except that copolymerization was carried out using 1 liter and 0.4 liter of p-methylstyrene. The weight average molecular weight of the obtained copolymer was 310000. The copolymer had a syndiotactic structure according to ¹³ C-NMR analysis and contained 12 mol% of p-methylstyrene unit.

Reference Example 4 (Production of polystyrene having syndiotactic structure) In a reaction vessel having an internal volume of 1 liter, toluene 5 was used as a solvent.
0 ml and 0.075 mmol of tetraethoxy titanate as a catalyst component and 7.5 mmol of methylaluminoxane as an aluminum atom were added, and 225 ml of styrene was added thereto at 40 ° C., and hydrogen was further adjusted to a partial pressure of 5 kg / cm ^2. Supply up to 1.5
The polymerization reaction was carried out for a time. After the reaction was completed, the product was treated with hydrochloric acid-
The catalyst component was decomposed and removed by washing with a mixed solution of methanol.
Then, it is dried to give a styrene polymer (polystyrene) 15
g was obtained. The weight average molecular weight of the obtained polymer was 16,000.
0, the number average molecular weight was 3,000. Also, from the analysis by ¹³ C-NMR of this polymer, absorption was observed at 145.35 ppm due to the syndiotactic structure, and the syndiotacticity in the racemic pentad calculated from the peak area was 98%. It was

Example 1 In addition to the polystyrene obtained in Reference Example 1 above, bis (2,4-di-t-butylphenyl) pentaerythritol diphosphite and tetrakis [methylene (3,5-di) were used as antioxidants. Each of 0.7 parts by weight and 0.1 part by weight of methane was mixed and extruded with a twin-screw extruder having a diameter of 40 mm to form pellets. The obtained pellets were preformed by using an injection molding machine (outer diameter of 28 mm, total length of 150 m
m, thickness 2.0 mm, basis weight 35 g) was molded. This preform (crystallinity 5%) was drawn using a stretch blow molding machine.
It was heated at 130 ° C. for 50 seconds with an infrared heater and biaxially stretch-blown with nitrogen gas having a blowing pressure of 25 kg / cm ² to obtain a hollow molded body having a volume of 1 liter. Table 1 shows the physical properties of the obtained molded product.

Example 2 The same procedure as in Example 1 was carried out using the styrene polymer obtained in Reference Example 2 above. The physical properties of the obtained container are shown in Table 1.

Example 3 Pelletization was carried out in the same manner as in Example 1, and the obtained pellets were used to obtain a stretched bottle using an injection stretch blow molding machine.
The crystallinity of the injection preform at this time was 5%,
Stretch blow molding was performed sequentially at × 3 times at 120 ° C. Table 1 shows the physical properties of the obtained molded product.

Comparative Example 1 An attempt was made to form a hollow molded article using the material of Reference Example 4 in the same manner as in Example 1, but the preformed article was brittle and stretch blow molding could not be performed.

Comparative Example 2 Atactic polystyrene (HH30 manufactured by Idemitsu Petrochemical Co., Ltd.)
E (Mw = 240,000)) was used to obtain a hollow container in the same manner as in Example 1. The physical properties of the obtained container are shown in Table 1.

Comparative Example 3 Direct blow molding was performed using the material of Reference Example 3. The physical properties of the obtained container are shown in Table 1.

[0024]

[Table 1]

[0025]

[Table 2]

[0026]

According to the present invention, a styrene polymer having a high syndiotacticity is used as a raw material and the haze is 30% or less. Therefore, the contents can be sufficiently seen through when it is used as a container. It is possible to obtain a transparent hollow molded article that is transparent and has the heat resistance, solvent resistance, chemical resistance, and hot water resistance of the material as well as excellent electrical insulation. Therefore, the hollow molded article of the present invention can be widely and effectively used as a food packaging material (bottle etc.).

Claims (4)

(57) [Claims] 1. A styrenic polymer mainly having a syndiotactic structure and having a weight average molecular weight of at least 100,000 is stretched uniaxially at least twice or biaxially at least 1.5 times. A styrene resin stretched hollow molded article that is stretched at a magnification. 2. The stretched hollow styrene resin molded article according to claim 1, which has heat resistance and transparency with a haze of 30% or less. 3. A styrenic polymer mainly having a syndiotactic structure and having a weight average molecular weight of at least 100,000 is uniaxially stretched by a factor of 2 or more or biaxially by a factor of 1.5 or more. A method for producing a styrene-based resin stretched hollow molded article, which comprises stretching at a draw ratio. 4. A styrenic polymer mainly having a syndiotactic structure and having a weight average molecular weight of at least 100,000 is melted by heating and then rapidly cooled, and then uniaxially at least twice or biaxially. 1.5 each
A method for producing a styrene-based resin stretched hollow molded article, which comprises performing a stretching treatment at a stretch ratio of 2 times or more.