JPH07323474A - Molded object composed of styrenic resin composition - Google Patents

Abstract

PURPOSE:To provide a molded object composed of a styrenic resin compsn. excellent in impact strength while holding transparency and flowability to a satisfiable level. CONSTITUTION:A molded object is composed of a styrenic resin compsn. containing a component (A) and a component (B) and contains a part where stretching magnification is 1.05-20 times at least at one place. The component (A) is composed of 99.000-99.998wt.% of a styrenic resin with a wt. average mol. wt. of 100000-2000000 and the component (B) is composed of 1.000-0.002wt.% of fine particles wherein a refractive index is 1.5-2.0, an average particle size is 0.1-20mum and glass transition temp. is not present within a temp. range of -130-90 deg.C.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a molded product made of a styrene resin composition. More specifically, the present invention relates to a molded product made of a styrene-based resin composition having excellent impact strength while maintaining transparency and fluidity at satisfactory levels.

[0002]

2. Description of the Related Art Styrenic resins are widely used for molding because they are rigid, have excellent dimensional stability, and are inexpensive. Since the resin alone is inferior in impact resistance, it is generally used as a rubber-modified styrenic resin by blending an elastomer in applications requiring higher impact strength. However, blending an elastomer has a drawback that the excellent properties inherent to the styrene resin such as rigidity and transparency are lost.

Inflation drawing of styrene resin,
Stretched products such as stretched films and sheets can be stretched by tenter stretching, roll stretching, etc. -Blow molding or stretch blow molding to form a blow molded body is widely performed. In particular, it is widely used in the packaging field such as packaging materials and containers. Recently, it has been required to reduce the weight of stretch-molded products, vacuum / pneumatic molded products, and blow-molded products, and in order to meet the demand, thinning of molded products is being promoted. However, there is a problem that the impact strength of the molded product is reduced because the molded product is thin. By the way, a method of increasing the impact strength of a molded article by increasing the molecular weight of polystyrene is known. However, according to this method, there is a problem that the fluidity is lowered, the productivity at the time of stretching is lowered, and the productivity of the extrusion process of the vacuum / compressed blank is reduced. Further, during injection / blow molding, there was a problem that a short shot occurred at the injection molding stage because the fluidity decreased. Further, there is known a method of increasing the processing temperature in order to increase productivity and prevent short shots, but this method has a problem that impact strength of a molded product and other physical properties are deteriorated.

[0004]

In such a situation,
The problem to be solved by the present invention is to provide a molded product made of a styrene resin composition having excellent impact strength while maintaining transparency and fluidity at satisfactory levels.

[0005]

That is, the present invention comprises a styrene resin composition containing the following component (A) and the following component (B), and has a draw ratio of 1.05 to 20 times at least at one position. The present invention provides a molded product including a part that is (A) Styrenic resin having a weight average molecular weight of 100,000 to 2,000,000 99.000 to 99.998% by weight (B) A refractive index of 1.5 to 2.0 and an average particle size of 0.
1 to 20 μm and glass transition temperature of −130 to 90
Fine particles not existing at ℃ 1.000 to 0.002% by weight

The present invention will be described in detail below. The styrene resin used in the present invention has a weight average molecular weight of 100,000 to 2,000,000, preferably 250,000 to 500,000.
When the molecular weight is too small, impact strength is poor, while when the molecular weight is too large, fluidity is poor. As a monomer constituting the styrene resin, styrene, α-substituted alkylstyrene such as α-methylstyrene, nuclear-substituted alkylstyrene such as p-methylstyrene, and a copolymer with a styrene compound together with the styrene compound. Possible compounds, for example vinyl monomers such as acrylonitrile, methacrylonitrile, methacrylic acid, ester derivatives such as methyl methacrylate, maleic anhydride, maleimide,
Examples include nuclear-substituted maleimide.

Examples of the styrene resin of the present invention include binary copolymers such as polystyrene (PS), styrene-acrylonitrile copolymer (AS resin), styrene-methyl methacrylate copolymer (MS resin) or terpolymer. It can be selected from the original copolymers.

The styrene resin composition and the molded product of the present invention have a refractive index of 1.5 to 2.0, preferably 1.55.
The average particle size is 1.65, the average particle size is 0.1 to 20 μm, preferably 0.1 to 5 μm, more preferably 1 to 4 μm, and the glass transition temperature is 0.002 to 0.002. % By weight to 1% by weight, preferably 0.
The content is from 01% by weight to 0.1% by weight. Preferred specific examples of such fine particles include calcium phosphate, barium sulfate, talc, polystyrene crosslinked beads, divinylbenzene crosslinked beads and the like which satisfy the above conditions.

If the range of the refractive index of the fine particles is too small or too large than 1.5 to 2.0, the molded product becomes cloudy and the appearance and transparency are poor. If the average particle size of the fine particles is too large or the content ratio is too small, it is difficult to obtain sufficient impact strength, and if the content ratio of the fine particles is too large, the surface roughness of the molded product becomes conspicuous, and the appearance and transparency are poor. Inferior. The refractive index of the fine particles is measured, for example, by the following method. That is, it is a method of dispersing fine particles in a solution of known refractive index, sandwiching them with a slide glass, observing with a polarizing microscope, and comparing with the refractive index of the approximate solution. For details, see the book “How to use a polarizing microscope”. (Kenya Hamano, Gihodo)
It is described in. The average particle size of the fine particles is measured, for example, by a method called a sedimentation method or a centrifugation method. A typical measurement method is a method in which particles are dispersed in an appropriate medium and the change in particle concentration when light is transmitted is measured, and for details, see, for example, the book “Powder Properties Chart” ( Powder Engineering Study Group, edited by Japan Powder Industry Association, published by Industrial Technology Center, 1975). Also,
The average particle size of the fine particles can also be measured by the following method. That is, a method of taking a transmission electron microscope photograph of an ultrathin section of an extruded body and measuring the particle diameter of the fine particles in the photograph, and the average particle size is calculated by the following formula. Average particle size = Σn _i D _i ² / Σn _i D _i where n _i is the number of particles having a particle size D _i .

The glass transition temperature of the fine particles is -130 to 90.
Whether or not it exists at ℃ can be determined by differential scanning calorimetry (DSC), for example, by measuring the differential heat in the range of -130 to 90 ℃ with a PERKIN ELMER (manufactured by Perkin Elmer) model 7700 DSC. it can. The details are described in, for example, the book "New Experimental Chemistry Course 2 (3. Thermal Analysis and Measurement)" (edited by The Chemical Society of Japan, published by Maruzen, 1984, pp. 87-122).

The styrene resin composition used in the present invention is
Weight average molecular weight is 100,000 to 300,000, styrene content is 40 to 90% by weight, and butadiene content is 10 to 6
It may contain 0% by weight of styrene-butadiene block copolymer. The blending amount of the styrene-butadiene block copolymer is 0 to 50 parts by weight, preferably 20 to 40 parts by weight, based on 100 parts by weight of the styrene resin.

The styrene resin composition used in the present invention is
It can be manufactured by the following method. A method in which the styrene compound, the compound copolymerizable with the styrene compound, and the fine particles defined in the present invention are uniformly mixed in advance, and the styrene-butadiene block copolymer is further uniformly mixed in advance, and the mixed solution is polymerized. Or a method of adding the fine particles defined in the present invention to a polymerization solution of a styrene compound, or a method of adding the fine particles defined in the present invention to a melt of a styrene polymer. As the polymerization method, a batch suspension polymerization method or a continuous bulk polymerization method can be used, and either a thermal polymerization method or a polymerization method using an initiator can be used. Various radical polymerization initiators can be used as the polymerization initiator. For the resin obtained by the polymerization, if necessary, a lubricant, an antistatic agent, an antioxidant, a heat stabilizer, an ultraviolet absorber, a pigment,
A dye or the like may be added and used, and a plasticizer such as mineral oil may be used as long as the effect of the present invention is not impaired.

In the styrene resin composition used in the present invention, the styrene resin and the fine particles, or the styrene resin, the fine particles and the styrene-butadiene block copolymer are mixed in a specific ratio, and melt-kneaded in an extruder. May be manufactured.

The molded article of the present invention has a draw ratio of 1.05 to 20 times, preferably 1.5 to 10 at least at one location.
It includes a doubled portion. The draw ratio is 1.0
If it is less than 5 times or more than 20 times, sufficient impact strength cannot be obtained. Further, the stretching is preferably biaxial stretching. The stretch ratio of the molded product is calculated by the following formula. Stretching ratio = (stretching degree in x direction) x (stretching degree in y direction) In addition, the stretching ratio is the thickness before stretching processing, vacuum / pressure molding and blow molding, and stretching processing, vacuum / pressure molding and blowing. It can also be obtained as a value divided by the thickness after molding. Examples of the molded article of the present invention include a vacuum / pressure molded article, an injection / blow molded article, a stretch blow molded article, an inflation stretched molded article, a tenter stretched molded article, or a roll stretched molded article.

The method for stretching the styrene resin composition used in the present invention to obtain a stretched molded article is not particularly limited, but for example, it is extruded into a sheet or film from an extruder and then stretched by a tenter method. Examples of the method include a method of stretching by an inflation stretching method or a roll stretching method, a method of stretching a press or an injection-molded article by a table-top stretching machine, and the like. The styrene resin composition used in the present invention is vacuum / compressed and molded into a vacuum / compressed molded body, but it is not particularly limited. For example, it is melted by an extruder and then extruded from a T-die. A method of forming the obtained extruded sheet raw material into a vacuum / compressed air molded body by using a vacuum / compressed air molding machine can be mentioned. The method of blow molding the styrene resin composition used in the present invention to form a blow molded body is not particularly limited, but for example, a mold having a blow device is attached to an injection molding machine, and molten resin is placed in the mold. After injection, there may be mentioned a method of blowing air into the mold to obtain a blow-molded body. The molded product of the present invention may be one that contains at least 50% by weight of the styrene resin composition.

The stretch-molded article of the present invention is obtained by thoroughly mixing the styrene resin composition to which fine particles have not been added during polymerization or extrusion melt kneading with the fine particles specified in the present invention before stretching and then stretching. It can also be obtained by a processing method. In addition, the vacuum / pneumatic molded article of the present invention is polymerized,
Alternatively, a styrene resin composition to which fine particles are not added at the time of extrusion melt kneading, and the fine particles specified in the present invention are well mixed before being extrusion-molded, and an extruded sheet extruded into a sheet is used to obtain a vacuum. -It can also be obtained by a method of pressure forming. Further, the blow-molded article of the present invention is a mixture of a styrene resin composition to which fine particles have not been added at the time of polymerization or extrusion melt kneading, and the fine particles specified in the present invention, which are well mixed before blow molding, and then blow molded. It is also possible to obtain it.

[0017]

EXAMPLES The present invention will be described below with reference to examples, but the present invention is not limited to the examples. Among the evaluation methods, items other than those described above were carried out as follows. (1) MI (fluidity): Performed in accordance with JIS K7210. The temperature was 200 ° C. and the load was 5 kgf. (2) Transparency (total light transmittance, haze) It was measured according to JIS K7105 using a sample obtained by cutting the obtained molded body into 40 × 40 × 2 mmt. (3) Impact strength (cracking energy): Using a falling weight impact tester manufactured by Toyo Seiki Seisaku-sho, the impact strength of the obtained molded body was measured.

Example 1 Weight average molecular weight of 3 obtained by continuous bulk polymerization method
0.1 weight of fine particles of barium sulfate having a refractive index of 1.64, an average particle size of 2.5 μm, and a glass transition temperature of −130 to 90 ° C. in a polystyrene resin composition in the form of pellets of 0,000. %, And mixed well, then V65-1000 manufactured by Tanabe Plastic Machinery Co., Ltd.
Using a sheet extruder, resin temperature 240 ° C., screw rotation speed 30 rpm, T-die lip clearance 1.
5 mm, lip width 900 mm, first roll temperature 90 ° C.,
Second roll temperature 60 ° C, take-up speed 0.7m / min
Then, a sheet having a thickness of about 1.0 mm was formed. The central portion of the obtained sheet was cut into 100 × 100 cm, and using a TF-1-16-VP type vacuum / compressed air molding machine manufactured by Nakakura Kyokusho Co., Ltd., a heating heater temperature of 150 ° C. and a heating time of 2
Vacuum molding was performed for 0 seconds, a vacuum time of 15 seconds, and a cooling time of 15 seconds to obtain a vacuum molded body shown in FIG. Further, the shaded surface of FIG. 1 was cut out and evaluated for transparency and impact strength.
The thickness of the surface indicated by the diagonal lines in FIG. 1 was 0.46 mm, and the draw ratio was 2.2 times. The results are shown in Table 1.

Example 2 A styrene-butadiene block copolymer containing 77% by weight of styrene and 23% by weight of 1,3-butadiene in the styrene resin composition of Example 1 and having a weight average molecular weight of 173,000. (SBS) 20% by weight, 40mmφ
Vacuum molding was carried out in the same manner as in Example 1 except that re-granulation was carried out at 210 ° C. in the extruder to obtain the vacuum molded body shown in FIG. Further, the hatched surface in FIG. 1 was cut out and evaluated in the same manner as in Example 1. The thickness of the hatched surface in FIG. 1 was 0.47 mm, and the draw ratio was 2.1 times. The results are shown in Table 1.

Example 3 Weight average molecular weight of 3 obtained by continuous bulk polymerization method
0.1% by weight of fine particles of barium sulfate having a refractive index of 1.64, an average particle size of 2.5 μm, and a glass transition temperature not existing at −130 to 90 ° C. were added to a pellet-shaped polystyrene resin of 0,000. Add and 2 with 40mmφ extruder
It was re-granulated at 10 ° C. Furthermore, using a press molding machine manufactured by Shinto Metal Industry Co., Ltd., a heating temperature of 200 ° C. and a heating time of 5
Minute, pressurizing pressure 50 kg / cm ² , pressurizing time 5 minutes, 1
A flat plate of 50 × 150 × 1.9 mm was press-molded. This press-molded flat plate was cut out at a center portion of 90 × 90 mm using a tabletop biaxial stretching machine manufactured by Toyo Seiki Co., Ltd.
Heating temperature 145 ° C., heating time 3 minutes, x-direction stretching degree 2 times,
A biaxially stretched sheet molding was obtained at a stretching ratio of 2 times in the y direction and a stretching speed of 5 m / min. The obtained biaxially stretched sheet had a thickness of 0.45 mm and a stretching ratio of 4.2 times. The results are shown in Table 1.

Example 4 The procedure of Example 3 was repeated except that the degree of biaxial stretching was 2.5 times in the x direction and 2.5 times in the y direction. The obtained biaxially stretched sheet had a thickness of 0.30 mm and a stretching ratio of 6.3 times. The results are shown in Table 1.

Example 5 The procedure of Example 3 was repeated except that the degree of biaxial stretching was 3 times in the x direction and 3 times in the y direction. The obtained biaxially stretched sheet had a thickness of 0.24 mm and a stretching ratio of 7.
It was 9 times. The results are shown in Table 1.

Comparative Example 1 Example 1 except that fine particles of barium sulfate were not used.
I went the same way. The thickness of the hatched surface in FIG. 1 is 0.46.
mm, and the draw ratio was 2.2 times. The results are shown in Table 2.
Shown in.

Comparative Example 2 Example 2 except that fine particles of barium sulfate were not used.
I went the same way. The thickness of the hatched surface in FIG. 1 is 0.5 m
m, and the draw ratio was 2 times. The results are shown in Table 2.

Comparative Example 3 Example 3 except that fine particles of barium sulfate were not used.
I went the same way. The thickness of the obtained biaxially stretched sheet,
It was 0.45 mm and the draw ratio was 4.2 times. The results are shown in Table 2.

Comparative Example 4 Example 4 was repeated except that fine particles of barium sulfate were not used.
I went the same way. The thickness of the obtained biaxially stretched sheet,
It was 0.30 mm and the draw ratio was 6.3 times. The results are shown in Table 2.

Comparative Example 5 Example 5 was repeated, except that fine particles of barium sulfate were not used.
I went the same way. The thickness of the obtained biaxially stretched sheet,
It was 0.24 mm and the draw ratio was 7.9 times. The results are shown in Table 2.

The following can be seen from the results. Examples 1 to 5 satisfying the conditions of the present invention show excellent results in all evaluation items. On the other hand, Comparative Examples 1 to 5, which do not contain the fine particles defined by the present invention, are inferior in impact strength (the term of crack generation energy).

[0029]

[Table 1] ─────────────────────────────────── Actual Examples 1 2 3 4 5 ─── ──────────────────────────────── Weight average molecular weight 10 ⁴ 30 30 30 30 30 SBS wt% 0 20 0 0 0 Fine particle Refractive index 1.64 1.64 1.64 1.64 1.64 Average particle size ^{* 1} μm 2.5 2.5 2.5 2.5 2.5 Glass transition temperature ℃ * 2 * 2 * 2 * 2 * 2 Content ratio wt% 0.1 0.1 0.1 0.1 0.1 Stretching ratio 2.2 2.1 4.2 6.3 7.9 (Evaluation Results] MI g / 10min 2.4 2.6 2.4 2.4 2.4 Transparency Total light transmittance% 90.0 90.0 90.0 90.0 90.0 Haze% 1.0 5.0 1.0 1.6 0.9 Impact strength Cracking energy J 0.223 0.224 0.119 0.467 0.241 ─────────── ─────────────────────────

[0030]

[Table 2] ─────────────────────────────────── Comparative Examples 1 2 3 4 5 5 ─── ──────────────────────────────── Weight average molecular weight 10 ⁴ 30 30 30 30 30 SBS wt% 0 20 0 0 0 Fine particle Refractive index − − − − − Average particle size ^{* 1} μm − − − − − Glass transition temperature ℃ − − − − − Content ratio wt% 0 0 0 0 0 Stretching ratio 2.2 2.0 4.2 6.3 7.9 [Evaluation result] MI g / 10min 2.4 2.6 2.4 2.4 2.4 Transparency Total light transmittance% 90.0 90.0 90.0 90.0 90.0 Haze% 0.8 4.0 0.7 0.6 0.9 Impact strength Cracking energy J 0.026 0.133 0.034 0.042 0.100 ──────────────── ────────────────────

* 1: The average particle size was measured using an ultracentrifugal automatic particle size distribution analyzer CAPA-700 (dispersion medium: 60% glycerin aqueous solution) manufactured by Horiba Ltd. * 2: Glass transition temperature does not exist below -130 to 90 ° C.

[0032]

As described above, according to the present invention, it is possible to provide a molded article made of a styrene resin composition having excellent impact strength while maintaining transparency and fluidity at satisfactory levels.

[Brief description of drawings]

FIG. 1 is a schematic view showing a vacuum formed body obtained in an example.

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Claims (4)

[Claims] 1. A molded product comprising a styrene-based resin composition containing the following component (A) and the following component (B), and including at least one portion having a stretch ratio of 1.05 to 20 times. (A) Styrenic resin having a weight average molecular weight of 100,000 to 2,000,000 99.000 to 99.998% by weight (B) A refractive index of 1.5 to 2.0 and an average particle size of 0.
1 to 20 μm and glass transition temperature of −130 to 90
Fine particles not existing at ℃ 1.000 to 0.002% by weight 2. The fine particles have a refractive index of 1.5 to 2.0.
The molded article according to claim 1, which is calcium phosphate, barium sulfate, talc, polystyrene crosslinked beads or divinylbenzene crosslinked beads having an average particle size of 0.1 to 20 µm. 3. The styrene resin composition has a weight average molecular weight of 100,000 to 300,000 and a styrene content of 40 to
90 wt%, butadiene content 10-60 wt%
The molded product according to claim 1 or 2, which is a styrene-based resin composition containing the styrene-butadiene block copolymer. 4. The molded article is a vacuum / pneumatic molded article, an injection / blow molded article, a stretch blow molded article, an inflation stretched molded article, a tenter stretched molded article, or a roll stretched molded article. The molded article according to.