JPH03114723A - Extrusion molding method of thermoplastic resin - Google Patents

Abstract

PURPOSE:To improve heat resistance and chemical resistance, by a method wherein a filmy or sheetlike matter obtained by extruding thermoplastic resin at a specific temperature is cooled by introducing the same into a slit through which cooling water is circulated in the direction of a flow of the cooling water and the same is cooled. CONSTITUTION:Thermoplastic resin is extruded so that a surface temperature directly after extrusion becomes higher by 5-60 deg.C than the melting point of the resin and a filmy or sheetlike matter is molded. Then the filmy or sheetlike matter is cooled by introducing the same into a slit through which cooling water is circulated in the same direction with that of a flow of the cooling water. A styrene polymer having syndiotactic structure is suitable for thermoplastic resin. Then a temperature lower than the glass transition temperature of the foregoing thermoplastic resin by 5 deg.C or less is suitable as the temperature of the cooling water. The obtained film or sheet is useful as various packaging materials or industrial materials.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to an extrusion molding method for thermoplastic resins, and in particular to an extrusion molding method suitable for molding styrenic polymers, particularly styrenic polymers having a syndiotactic structure. Regarding the method.

[Prior art and problems to be solved by the invention] In general, thermoplastic resins such as styrenic polymers, especially polystyrene, are produced by radical polymerization, and are used as films or sheets for food packaging, miscellaneous goods packaging, or industrial packaging. Widely used in materials fields, etc. However, products obtained from polystyrene having an acute stereoregular structure have drawbacks such as poor heat resistance, poor chemical resistance, and poor mechanical strength, and therefore their field of use has been limited.

On the other hand, the group of the present inventors, as a result of intensive research to eliminate the above-mentioned drawbacks, recently developed a styrenic polymer having a syndiotactic structure (Japanese Patent Application Laid-Open No. 61-1999).
04818 specification).

However, this styrenic polymer with a syndiotactic structure has a characteristic of having a crystalline structure, so it has to be extruded at a higher temperature than the styrenic polymer used for boat fishing, and there is a risk of decomposition and deterioration. Therefore, when extruding a styrenic polymer with such a syndiotactic structure (hereinafter sometimes abbreviated as SPS), special consideration must be given to cooling conditions, equipment used, etc. There were various problems such as.

In addition, the method proposed in JP-A No. 61-259809 allows an extruded product with excellent properties to be obtained by rapidly cooling after extrusion molding, but the specific method up to 9 conditions, etc. There was no specific description and it was not practical. Also, although the melting temperature of SPS is described here, it is a film.

There is no mention of the surface temperature, which is important when manufacturing strip-shaped members such as sheets, that is, the surface temperature that is lowest during molding and has an important effect on the appearance of the manufactured product, and it is necessary to develop a more practical method. This had become an issue.

Therefore, in order to solve the above problems, the present inventors examined various practical conditions using specific manufacturing equipment, and conducted extensive research to develop an efficient extrusion molding method.

As a result, it has been found that the above-mentioned disadvantages can be overcome by extruding thermoplastic resins such as SPS under specific temperature conditions and by employing a specific cooling method. The present invention was completed based on this knowledge.

[Means for Solving the Problems] That is, in extrusion molding a thermoplastic resin into a film or sheet, the present invention provides a method for extruding the thermoplastic resin so that the surface temperature immediately after extrusion is 5 to 60°C below the melting point of the resin. It is characterized by extruding to a high temperature, then introducing the extruded thermoplastic resin in the form of a film or sheet into a slit through which cooling water flows in the same direction as the flow direction of the cooling water to cool it. The present invention provides a method for extrusion molding a thermoplastic resin.

Although various thermoplastic resins can be used in the present invention, styrene polymers, particularly styrene photopolymers having a syndiotactic structure, are suitable as molding materials. The syndiotactic structure in a styrenic polymer having this syndiotactic structure means that the stereochemical structure is a syndiotactic structure, that is, a phenyl group or a substituted side chain with respect to the main chain formed from carbon-carbon bonds. It has a three-dimensional structure in which phenyl groups are alternately located in opposite directions, and its toughness is determined by nuclear magnetic resonance method (13CNMR method) using carbon isotopes. ``Toughness measured by the C-N'MR method is the proportion of consecutive constituent units,
For example, a styrenic polymer having a syndiotactic structure as used in the present invention can be represented by a diand, a triat, a triat, and a pentad in the case of two, but the styrenic polymer having a syndiotactic structure as used in the present invention is usually a semi-diand. Polystyrene, poly(alkyl styrene), poly(halogenated styrene), poly(alkoxy styrene), poly(vinyl benzoate), hydrogenated polymers thereof, mixtures thereof, or copolymers having these as main components. Note that poly(alkylstyrene) here includes poly(methylstyrene), poly(ethylstyrene), poly(isopropylstyrene), poly(tert-butylstyrene) poly(
Examples of poly(halogenated styrene) include poly(chlorostyrene), poly(bromostyrene), poly(fluorostyrene), and the like.

In addition, as poly(halogenated alkylstyrene),
Examples of poly(alkoxystyrene) such as poly(chloromethylstyrene) include poly(methoxystyrene) and poly(ethoxystyrene). Furthermore, as comonomer components of copolymers containing these structural units, in addition to the above-mentioned styrene polymer monomers, olefin monomers such as ethylene, propylene, butene, hexene, and octene, diene monomers such as butadiene isoprene, and cyclic olefins can be used. Examples include polar vinyl monomers such as monomers, cyclic diene monomers, methyl methacrylate, maleic anhydride, and acrylonitrile.

Among these, particularly preferred styrenic polymers include polystyrene, poly(alkylstyrene), poly(halogenated styrene), hydrogenated polystyrene, and copolymers containing structural units thereof.

A styrenic polymer having such a syndiotactic structure can be produced by using a titanium compound and a condensation product of water and trialkylaluminum as a catalyst, for example, in an inert hydrocarbon solvent or in the absence of a solvent. (monomer corresponding to the above-mentioned styrenic polymer) (Japanese Patent Laid-Open No. 62-18770
Publication No. 8). Further, poly(halogenated alkyl styrene) can be obtained by the method described in JP-A-1-46912, and hydrogenated polymers thereof can be obtained by the method described in JP-A-1-178,505.

This styrenic polymer has no particular restriction on the molecular weight, but has a weight average molecular weight of 100,000 or more, preferably 300,000 or more. Further, there is no restriction on the width or narrowness of the molecular weight distribution, and various types can be used. Furthermore, this styrenic polymer has
Commonly used thermoplastic resins, rubbers, inorganic fillers, antioxidants, plasticizers, compatibilizers, colorants, etc. can be added.

The method of the present invention involves extrusion molding thermoplastic resins including styrenic polymers such as SPS into films or sheets.

As for the extruder, T-die, etc. used at this time, commonly used ones can be used as they are. During extrusion molding, the surface temperature of the molten resin immediately after extrusion is set to a temperature 5 to 60°C higher than the melting point (Tm) of the resin, that is, ((
The extrusion temperature and extrusion speed are set so that Tm+5°C) to (Tm+60°C)). If the surface temperature is less than (Tm+5°C), poor appearance may occur due to melt fracture during extrusion. Also, the surface temperature is (Tm+
If the temperature exceeds 60°C, the resin may decompose and deteriorate, which is not preferable.

In the present invention, a molded product (film-like or sheet-like product) extruded in the above temperature range is cooled by introducing it into a slit through which cooling water is flowing (water passing) in the same direction as the cooling water flow direction. do. At this time, if the flow direction of the cooling water and the direction in which the molded product is introduced are opposite to each other, vertical streaks will occur on the surface of the molded product due to uneven cooling, which will cause a poor appearance. Furthermore, if the cooling water is stationary, crater-like scars may occur on the surface of the molded product due to boiling of the cooling water. The temperature of the cooling water is
It can be set appropriately depending on the type of resin, the thickness of the molded product, the extrusion speed, etc., but the glass transition temperature (Tg) of the resin
), that is, (Tg-5°C) or less.

If the cooling water temperature exceeds (Tg-5°C), it is not preferable because the molded product may break in the winding or take-off line after cooling.

For example, when extruding SPS with Tm of 270°C and Tg of 100°C into a film or sheet, the surface temperature immediately after extrusion should be 275 to 330°C, and preferably the cooling water temperature should be 95°C or lower. It is possible to produce molded products with excellent properties and appearance.

As the water cooling method, various known methods such as the method described in JP-A-58-173621 can be used, and commonly used water cooling devices and take-off devices can be used.

〔Example〕

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

Reference example (Production of styrenic polymer) To a reaction vessel, add toluene 2i as a solvent, 5 mmol of tetraethoxytitanium as a catalyst component, and 500 mmol of methylaluminoxane as an aluminum atom, add styrene 151 to it at 50°C, A time polymerization reaction was performed.

After the reaction was completed, the product was washed with a hydrochloric acid-methanol mixture to decompose and remove the catalyst component. Then, it was dried to obtain 2.5 kg of a styrenic 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, analysis using 1,2-dichlorohenzene as a solvent (-NMR measurement revealed that 143
．． Absorption was observed at 35 ppm, and syndiotacticity in racemic pentad was calculated from the peak area.
was 96%. To the polystyrene thus obtained, 0.00% of each of bis(2<4-di-butylphenyl)pentaerythritol diphosphite and tetrakis[methylene(35-dibutylphenyl)pentaerythritol diphosphite]methane were added as antioxidants. They were mixed in 1 part by weight and extruded into pellets using a twin-screw extruder with a diameter of 40 mm.

The melting point of the obtained styrene polymer (sps) is 27
0° C., and the glass transition temperature was i o ”c.

Example 1 The SPS obtained in the above reference example was heated at 120 to 150°C for 2 to 5
After drying for an hour, a single screw extruder (L/D=26) with a diameter of 30 was used as an extruder, and the extrusion rate was 6.9 kg/hour.
The temperature distribution of the extruder is set to 290℃ near the input port and 30℃ in the middle part.
0°C tip part 310°C T die part 310°C, wall thickness 0.
A 5 mm sheet was extruded. At this time, the temperature of the sheet immediately after extrusion was measured using a non-contact thermometer (high-sensitivity infrared thermometer).
When measured using a Thermo Tracer 6-TO8A-3) manufactured by Sanei Sokki ■, the temperature was 302°C (Tm+32''C).

Met.

Next, the extruded sheet was cooled by introducing it into a slit through which cooling water at 90°C (Tg-10°C) was passed in the same direction as the flow of the cooling water.

Table 1 shows the surface condition, winding properties, and presence/absence of decomposition and deterioration of the obtained sheets.

Examples 2 to 4 and Comparative Examples 1 to 5 Examples 2 to 5 except that the surface temperature immediately after extrusion, the cooling water temperature, the cooling water flow direction, and the sheet introduction direction were as shown in Table 1, respectively. A sheet was extrusion molded in the same manner as in 1. Table 1 shows the surface condition, winding property, and presence or absence of decomposition deterioration of the obtained sheet.

(The following is a blank space) 14 [Effects of the invention] As described above, according to the method of the present invention, heat resistance and chemical resistance 2
Synthetic resin films or sheets with excellent mechanical strength and good surface conditions can be produced efficiently and at low cost.

Films and sheets produced in this way can be effectively used as packaging materials for various products including foods, or as various industrial materials.

and others

Claims (3)

[Claims] (1) When extrusion molding a thermoplastic resin into a film or sheet, the thermoplastic resin is extruded so that the surface temperature immediately after extrusion is 5 to 60°C higher than the melting point of the resin, and then extruded. 1. A method for extrusion molding a thermoplastic resin, which comprises introducing a thermoplastic resin in the form of a film or sheet into a slit through which cooling water is passed, in the same direction as the flow direction of the cooling water, and cooling it. (2) The method for extrusion molding a thermoplastic resin according to claim 1, wherein the temperature of the cooling water is 5° C. lower than the glass transition temperature of the thermoplastic resin. (3) The method for extrusion molding a thermoplastic resin according to claim 1, wherein the thermoplastic resin is a styrenic polymer having a syndiotactic structure.