JP2953295B2 - Extruded product made of polystyrene resin composition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an extruded product comprising a polystyrene resin composition. More specifically, the present invention has a high melt tension, excellent fluidity,
The present invention relates to an extruded product made of a polystyrene resin composition which does not cause unevenness in thickness during extrusion and does not cause wrinkling of a sheet, has little neck-in during high-speed extrusion, has excellent processing productivity, and has excellent impact strength. .

[0002]

2. Description of the Related Art It is widely practiced to extrude polystyrene into extruded products such as films and sheets. However, polystyrene has a problem that the melt tension is low, neck-in occurs during extrusion, uneven thickness and wrinkles are generated, and the impact strength of the obtained molded article is low. By the way, there is known a method of increasing the melt tension by increasing the molecular weight of polystyrene to increase the impact strength of a molded article. However, according to this method, there is a problem that fluidity is reduced and productivity during extrusion molding is reduced.

[0003]

In such a situation,
The problem to be solved by the present invention is to have a high melt tension, excellent fluidity, no thickness unevenness and sheet wrinkling during extrusion processing, few neck-in during high-speed extrusion pull-out, and an improvement in processing productivity. An object of the present invention is to provide an extruded product made of a polystyrene resin composition having excellent impact strength.

[0004]

That is, the present invention provides a polystyrene resin composition containing, as a polymer component, 50 to 100% by weight of a polystyrene copolymer satisfying the following conditions (A) to (F). The present invention relates to an extruded body comprising: (A): A compound having a plurality of vinyl groups is 100 to 10
(B): The weight average molecular weight is 200,000 to 2,000,000 (C): In the molecular weight distribution, the ratio of 100,000 or less is 20 to 30% by weight, and the molecular weight is 1,000,000 or more. (D): the number of branch points in the Z average molecular weight is 1 to 20 (E): the insoluble matter in the methyl ethyl ketone / methanol mixed solvent is 5% by weight or less ( F): Methanol soluble content is 5% by weight or less

[0005] The polystyrene copolymer of the present invention contains a styrene compound and a compound having a plurality of vinyl groups as constituent monomer.

[0006] As styrene compounds, styrene, α
Α-substituted alkylstyrene such as -methylstyrene, p
Nucleus-substituted alkylstyrenes such as -methylstyrene;

Compounds having a plurality of vinyl groups include:
Examples thereof include divinylbenzene and ethylene glycol dimethacrylate. The content of the compound having a plurality of vinyl groups is 100 to 1000 ppm by weight, preferably 100 to 700 ppm by weight. If the content is too small, it is difficult to obtain the number of branch points in the Z-average molecular weight of the present invention, while if the content is too large, it is difficult to obtain the methyl ethyl ketone / methanol mixed solvent insolubles of the present invention.

In the polystyrene copolymer of the present invention, in addition to the styrene compound and the compound having a plurality of vinyl groups, a compound copolymerizable with the styrene compound, for example, acrylonitrile, methacrylonitrile, methacryl Acid, vinyl monomers such as ester derivatives such as methyl methacrylate, furthermore, maleic anhydride,
It may contain maleimide, nucleus-substituted maleimide and the like.

The polystyrene copolymer of the present invention has a weight average molecular weight of 200,000 to 2,000,000, preferably 200,000 to 1,000,000.
Million, more preferably 300,000 to 1,000,000. When the molecular weight is too small, the melt tension is inferior and the impact strength of the molded article is inferior. On the other hand, when the molecular weight is excessive, the fluidity is poor.

In the polystyrene copolymer of the present invention, the proportion of a molecular weight of 100,000 or less in the molecular weight distribution is 20 to 30% by weight, and the proportion of a molecular weight of 1,000,000 or more is 1 to 30% by weight, preferably 5 to 20% by weight. belongs to. Molecular weight 1
If the ratio is less than 100,000, the fluidity is inferior. On the other hand, if the ratio is excessive, the melt tension is inferior and the appearance of the molded article is inferior. On the other hand, when the ratio of the molecular weight of 1,000,000 or more is too small, the melt tension is poor, and the appearance of the molded article is poor. On the other hand, if the ratio is excessive, the fluidity is poor.

The polystyrene copolymer of the present invention has a number of branch points of 1 to 20, preferably 2 in the Z average molecular weight.
~ 15. When the number of the branch points is too small, the fluidity is poor. On the other hand, when the number of the branch points is too large, the fluidity is poor and the appearance of the molded article is poor. Here, the number of branch points in the Z-average molecular weight refers to the number of branch points included in a molecular chain representing a high molecular weight component considered to reduce the fluidity of a polystyrene resin composition having a certain molecular weight distribution. This is a corresponding concept and is required in the following method.
That is, the number of branch points in the weight average molecular weight and the Z average molecular weight is determined by a viscosity-GPC method using gel permeation chromatography (GPC) equipped with a differential refractometer and a viscometer as a detector. For details, see The Rubber Association of Japan, Vol. 45, No. 2,
It is described on pages 105-118 (1972). The number of branch points (Bn (M)) at the molecular weight M is determined by the following equation.

[IV (M) / IV _L (M)] ^2/3 =
[(1 + Bn (M) / 7) ^1/2 + 4/9 · Bn (M)]
^-1/2 where IV (M) and IV _L (M) are viscosity-GP
It is the intrinsic viscosity at the molecular weight M of the linear polystyrene as the sample and the standard sample measured by the method C.

The polystyrene-based copolymer of the present invention has a methyl ethyl ketone / methanol mixed solvent insoluble content of 5% by weight or less, preferably 3% by weight or less. When the insoluble content is excessive, the fluidity is inferior, and when it is intentionally molded, the appearance of the molded article is inferior. The insoluble matter in the methyl ethyl ketone / methanol mixed solvent is measured by the following method. That is, 0.5 g of the resin composition was mixed with a mixed solvent of methyl ethyl ketone / methanol (10/1 volume mixing ratio).
Dissolve in 0 ml with stirring at room temperature for 2 hours. This solution is filtered, and the insoluble matter separated by the filter paper is dried and precisely weighed. The weight ratio of the resin composition component obtained by such an operation to the initially used resin composition is defined as the insoluble content.

The polystyrene copolymer of the present invention has a methanol-soluble content of 5% by weight or less, preferably 3% by weight.
These are: When the amount of the soluble component is excessive, the melt tension is inferior. The methanol-soluble matter is measured by the following method.
That is, about 1 g of the resin composition is dissolved in 10 ml of methyl ethyl ketone at room temperature, and reprecipitated by adding 300 ml of methanol. The solid content is collected by filtration, dried, and precisely weighed. The weight ratio of the resin composition component reduced by the above operation to the initially used resin composition is defined as a methanol-soluble component.

As a polymerization method for the polystyrene copolymer of the present invention, a batch suspension polymerization method or a continuous bulk polymerization method can be used. Either a thermal polymerization method or a polymerization method using an initiator can be used, and various radical polymerization initiators can be used as the polymerization initiator. As the polymerization tank, a complete mixing type stirring polymerization tank, a plug flow type full (vertical or horizontal) polymerization tank, a static mixing tube type polymerization tank, or a combination of these polymerization tanks can be used.

The polystyrene-based copolymer of the present invention can be optimally produced by the following method in producing a continuous bulk polymerization process. That is, upon polymerizing a compound having a plurality of vinyl groups and a styrene-based compound or a compound having a plurality of vinyl groups, a styrene-based compound and a compound copolymerizable with the styrene-based compound, a styrene-based compound and a styrene-based compound are used. 100 to 1000 ppm by weight, preferably 100 to 70
0 ppm by weight of a compound having a plurality of vinyl groups is uniformly mixed in advance, and the mixture is continuously supplied to a polymerization tank. At a polymerization temperature of 140 to 200 ° C., the final conversion is 60% by weight or more, preferably The polymerization mixture is polymerized to 70% by weight or more, and the polymerization mixture is heated at 200 to 280 ° C.
Lead to a preheater at 20-270 ° C, then 200-280
C., preferably at 220-270 ° C., through a vacuum degassing tank,
The unreacted monomer is recovered to obtain a target polystyrene copolymer.

If the amount of the compound containing a plurality of vinyl groups is too small, it is difficult to obtain the degree of branching in the Z-average molecular weight of the present invention, so that the balance between fluidity and melt tension is lacking. On the other hand, if the amount of the compound is too large, it is difficult to obtain an insoluble portion of the methyl ethyl ketone / methanol mixed solvent of the present invention, so that the fluidity is poor. In addition, when partially polymerizing only the styrene-based compound first and then adding and polymerizing a compound containing a plurality of vinyl groups, only the compound containing a plurality of vinyl groups was highly polymerized. A three-dimensional crosslinked portion is generated, and the amount of insolubles in the methyl ethyl ketone / methanol mixed solvent becomes excessive. Further, when the polymerization is terminated while the above conversion is insufficient, unreacted vinyl groups remain in the polymer, a sufficient branched structure cannot be obtained, and the obtained resin composition has fluidity. May be inferior.

The polymerization must be carried out in a temperature range from 140 to 200 ° C. If the polymerization temperature is too low, a gel is generated, and the amount of the insoluble matter in the methyl ethyl ketone / methanol mixed solvent becomes excessive, which causes a trouble that the polymerization tank and piping are blocked. On the other hand, when the polymerization temperature is too high, the melt tension of the obtained copolymer becomes insufficient.

The polystyrene resin composition of the present invention comprises 50 parts of the above polystyrene copolymer as a polymer component.
To 100% by weight, preferably 60 to 100% by weight. If the content is too small, the above object of the present invention cannot be sufficiently achieved. In addition, as a polymer component other than the polystyrene-based copolymer of the present invention in the polystyrene-based resin composition, a styrene content of 10 to 90 w
It is preferred to use t%, preferably 20-80 wt% styrene-butadiene copolymer or styrene-grafted polybutadiene.

The polystyrene resin composition of the present invention comprises:
In addition to the above polymer components, if necessary, lubricants, antistatic agents, antioxidants, heat stabilizers, ultraviolet absorbers, pigments,
It is obtained by adding a dye or the like. Further, within the range not impairing the effects of the present invention, plasticizers such as mineral oil,
A polystyrene-based resin composition other than the present invention or a recycled polystyrene-based resin may be used.

The method of extruding the polystyrene resin composition of the present invention into an extruded product is not particularly limited. For example, a method of extruding from a T-die after melting with an extruder, an extruder After extruding into a sheet, biaxial stretching may be performed by a tenter method or an inflation method.

The extruded product of the present invention is suitably used for forming a packaging container or the like by a vacuum forming method or a pressure forming method due to its excellent balance of melt tension and fluidity, and has excellent processing productivity. .

[0023]

The present invention will be described below by way of examples. In addition, among the measurement evaluation methods, the items other than the items described above were implemented as follows.

(1) MI (fluidity): JIS K721
0 was performed. In addition, temperature 200 ° C, load 5k
gf. (2) Melt tension (melt tension): Using a melt tension tester type II manufactured by Toyo Seiki Seisakusho, resin temperature 200 ° C., extrusion speed 20 mm / min, winding speed 13c
It was measured at m / sec. (3) Content of compound having a plurality of vinyl groups: Determined by pyrolysis gas chromatography. The thermal decomposition conditions were as follows: 0.5 mg of the sample was 600 ° C. for 10 seconds. (4) Sheet appearance: Measured visually. A sample without wrinkles or ripples was evaluated as ○, and a sample with wrinkles or ripples and having no gloss was evaluated as ×. (5) Sheet thickness and sheet thickness unevenness: The sheet thickness was measured every 5 cm in the width direction of the formed sheet, and the average value was defined as the sheet thickness. In addition, half of the difference between the maximum value and the minimum value of the measured thickness was divided by the sheet thickness, and the value expressed as a percentage was defined as the thickness unevenness. (6) Crack generation energy (impact strength): The impact strength of the obtained sheet was measured using a falling weight impact tester manufactured by Toyo Seiki Seisaku-sho.

Examples 1-2 and Comparative Examples 1-5 Polystyrene-based copolymers (PS-1-4) PS-1: 90% by weight of styrene, 10w of ethylbenzene
A solution prepared by adding 250 wtppm to styrene of divinylbenzene (purity: 55% by weight, manufactured by Tokyo Kasei Kogyo Co., Ltd.), which is a compound containing two or more vinyl groups, to a solution of t% was added to a continuous bulk polymerization reactor. Supply continuously, 1
Polymerization was performed at 50 ° C. until the final addition rate reached 80 wt%, and the polymerization mixture was passed through a 240 ° C. vacuum degassing tank to recover unreacted monomers, thereby obtaining a polystyrene-based copolymer.

PS-2: Divinylbenzene is used in an amount of 1200 w
The same operation was performed as in PS-1 except that tppm was added. PS-3: Except not using divinylbenzene, PS
-1 was performed. PS-4: Performed in the same manner as PS-3 except that the polymerization temperature was changed to 130 ° C.

Using the above polystyrene-based copolymer, according to the composition shown in Table 2, V65 manufactured by Tanabe Plastic Machinery Co., Ltd.
-1000 using a sheet extruder, resin temperature 240
1.degree. C., screw rotation speed 30 rpm, T-die lip clearance 1.0 mm, lip width 900 mm, first roll temperature 90.degree. C., second roll temperature 60.degree.
A sheet of about 0.3 mm was formed at 75 m / min. The results are shown in Table 2.

The following can be understood from the results. Examples 1 and 2 satisfying the conditions of the present invention show excellent results in all evaluation items. On the other hand, the ratio of the molecular weight of 1,000,000 or more is excessive, the number of branch points in the Z average molecular weight is excessive, the content of the compound having a plurality of vinyl groups is excessive, and Comparative Example 1 using an excessive amount of the polystyrene-based resin composition (PS-2) could not be molded. Comparative Examples 2 and 3 using a polystyrene-based resin composition (PS-3) having no branch point in the Z-average molecular weight and containing no compound having a plurality of vinyl groups.
The sheet has a large thickness unevenness and a narrow sheet width, that is, necking has occurred, and the sheet has poor appearance and impact strength. Furthermore, a comparison using a polystyrene-based resin composition having no branch point in the Z-average molecular weight and containing no compound having a plurality of vinyl groups and having a higher weight-average molecular weight (PS-4) In Examples 4 and 5, the extruded resin pressure was high and the discharge amount was small, that is, the productivity was poor. Table 1 shows that PS-3 has a low melt tension and PS-4 has a low fluidity.

[0029]

Table 1: Polystyrene copolymer PS-1 PS-2 PS----------------------------- 3 PS-4 DVB content wt ppm * 1 300 1500 0 0 Weight average molecular weight 10 ⁴ 35 99 25 35 Molecular weight 100,000 or less wt% 24 5 27 22 Molecular weight 1,000,000 or more wt% 9 40 0.6 4 Branch point * 2 4 30 0 0 MEK / MeOH insolubles wt% * 3 0 30 0 0 MeOH solubles wt% * 4 0.9 1.2 1.2 1.0 MI (g / 10min) 3.0 Unmeasurable 3.0 1.4 Melt tension (g) 24 Unavailable 10 19 −−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−

[0030]

Table 2------------------------------------------------------------------------------------------------ 3 4 5 Blend PS copolymer Type PS-1 PS-1 PS-2 PS-3 PS-3 PS-4 PS-4 Amount wt 100 80 100 100 80 100 80 SB copolymer * 5 wt 0 20 0 0 20 0 20 Antioxidant * 6 wt 0.1 0.1 0.1 0.1 0.1 0.1 0.1 Sheet properties and workability Extruded resin pressure kg / cm ² 40 50 40 50 70 80 Sheet thickness mm 0.32 0.32 Composition 0.28 0.30 0.28 0.29 Sheet thickness unevenness% 5 5 10 10 5 5 Sheet width cm 75 75 Non 70 70 70 70 Discharge rate kg / hr 35 35 Function 30 31 29 30 Sheet appearance ○ ○ × × ○ ○ Crack generation energy J 0.05 0.08 0.03 0.06 0.05 0.08 −−− −−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−

* 1 DVB content: content of divinylbenzene * 2 Number of branch points: number of branch points in Z average molecular weight * 3 MEK / MeOH insoluble matter: methyl ethyl ketone /
Methanol mixed solvent insolubles * 4 MeOH solubles: methanol solubles * 5 SB copolymer: K resin KR-05 (Styrene-butadiene copolymer manufactured by Philips; styrene content 75 wt%) * 6 Antioxidant: Sumilizer GS (Sumitomo Chemical Industries, Ltd.)

[0032]

As described above, according to the present invention, the present invention has a high melt tension, excellent fluidity, does not cause uneven thickness and sheet wrinkles during extrusion processing, and has little neck-in during high-speed extrusion pulling. An extruded product made of a polystyrene resin composition having excellent processing productivity and excellent impact strength could be provided.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-63-179956 (JP, A) JP-A-49-25043 (JP, A) JP-A-6-49339 (JP, A) (58) Field (Int.Cl. ⁶ , DB name) B29C 47/00 C08L 25/04 C08L 25/10 C08L 51/04

Claims (4)

(57) [Claims] 1. The polymer component (A)
50 polystyrene copolymers satisfying the condition (F)
An extruded product comprising a polystyrene-based resin composition containing about 100% by weight. (A): A compound having a plurality of vinyl groups is 100 to 10
(B): The weight average molecular weight is 200,000 to 2,000,000 (C): In the molecular weight distribution, the ratio of 100,000 or less is 20 to 30% by weight, and the molecular weight is 1,000,000 or more. (D): the number of branch points in the Z average molecular weight is 1 to 20 (E): the insoluble matter in the methyl ethyl ketone / methanol mixed solvent is 5% by weight or less ( F): Methanol soluble content is 5% by weight or less (B) a weight average molecular weight of 200,000 to 100
The extruded body according to claim 1, wherein the number is 10,000. 3. The extruded product according to claim 1, wherein (D) the number of branch points in the Z average molecular weight is 2 to 15. 4. The extruded product according to claim 1, wherein the polymer component other than the polystyrene-based copolymer is a styrene-butadiene copolymer or a styrene-grafted polybutadiene.