JP2002097340A - Rubber-modified polystyrene resin excellent in blow molding property - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a rubber-modified polystyrene resin for blow molding excellent in extrusion characteristic for parison formation, processability which is characteristic to blow molding such as draw down resistance and uniformity of wall thickness. SOLUTION: In this rubber-modified polystyrene resin excellent in blow molding, weight average molecular weight Mw of a matrix is 20,000 to 35,000 and a ratio Mw/Mn of the weight average molecular weight to number average molecular weight is >=3.0 and median diameter D of a rubber-like elastomer particles containing as disperse particles is 2.0 to 8.0 and when gel content is defined as GC, the relationship of formula I: ln(GC)+0.348×D>=4.37 is satisfied.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a rubber-modified polystyrene resin suitable for blow molding. More specifically, the present invention provides extrusion properties for parison formation,
The present invention relates to a rubber-modified polystyrene resin for blow molding, which is excellent in workability such as draw-down resistance and the like, which is unique to blow molding, and excellent in thickness uniformity.

[0002]

2. Description of the Related Art Blow molding is the most general molding method capable of molding a hollow molded article, and is particularly widely used as a method for producing a container made of a thermoplastic resin. Among them, polyethylene terephthalate (PET), polyvinyl chloride (PVC), polyethylene (PE), polypropylene (P
Blow-molded articles made of P) are widely used as containers for beverages, foods, toiletries, chemicals, and the like.

[0003] In recent years, since the era when blow molding was the mainstream as a method for molding a container having a simple shape, the molding method has changed from a molding method for molding a large-sized, functional part having a complicated shape with the progress of molding technology. Typical large blow molded products include automobile parts such as bumpers, gas tanks, and air spoilers, double-walled containers, and housing panels such as ceiling materials for unit baths. In addition, blow molding is advantageous in that the investment in the mold is cheaper than injection molding, and the mold processing is easy.

[0004] Materials used for blow molding are required to have stable parison formation and holding ability (drawdown resistance) in order to perform stable continuous molding. Drawdown is a phenomenon in which, during or after the formation of a parison, the parison is unable to withstand its own weight, is stretched, and becomes thin or uneven. Materials with good drawdown resistance are less likely to cause uneven wall thickness, have a longer parison holding time, and are excellent in stable molding. For example, there is ultra-high molecular weight high-density polyethylene and the like, but polyolefin-based materials have a high molding shrinkage, and it is difficult to express dimensional accuracy to a high degree. On the other hand, rubber-modified styrene resins represented by ABS resins and rubber-modified polystyrene resins have the advantages of relatively low molding shrinkage, excellent dimensional accuracy, and excellent balance between rigidity and impact strength. Although there is an ABS resin having excellent drawdown resistance, development of a rubber-modified polystyrene resin which is less expensive and has excellent blow moldability is desired.

[0005] As a means for improving the drawdown resistance of a rubber-modified polystyrene resin, simply increasing the molecular weight makes extrusion difficult, and melt fracture occurs during parison extrusion. Further, Japanese Patent Application Laid-Open No. 10-130443 proposes a blow molded product using a styrene-based resin having a non-linearity of elongational viscosity at 160 ° C. of a certain value or more. Then, drawdown property cannot be improved sufficiently.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to provide a rubber for blow molding which is excellent in extrusion characteristics for forming a parison, workability peculiar to blow molding such as drawdown resistance, and uniformity of wall thickness. A modified polystyrene resin is provided.

[0007]

Means for Solving the Problems As a result of extensive studies, the present inventors have found that, in a rubber-modified polystyrene resin, the median diameter and gel content of rubber-like elastic material-dispersed particles greatly contribute to drawdown resistance. It was discovered that the blow molding material shown below solves all of the above problems,
The present invention has been reached. That is, the weight average molecular weight Mw of the matrix is 200,000 to 350,000, the ratio Mw / Mn of the weight average molecular weight to the number average molecular weight is 3.0 or more, and the rubber-like elastic particles contained as dispersed particles have a medium weight Blow moldability having a diameter D (μm) of 2.0 to 8.0 and a gel content of GC (wt%), which satisfies the relationship of formula (1) ln (GC) + 0.348 × D ≧ 4.37 It is a rubber-modified polystyrene resin with excellent properties. Hereinafter, the present invention will be described in detail.

[0008] The weight average molecular weight Mw, number average molecular weight Mn and Z average molecular weight Mz of the rubber-modified polystyrene resin in the present invention can be determined by GPC. The weight-average molecular weight Mw of the matrix of the rubber-modified polystyrene resin in the present invention is from 200,000 to 350,000, and the ratio Mw / Mn of the weight-average molecular weight to the number-average molecular weight is 3.0 or more. Molecular weight Mw is 25-3
100,000, the ratio of the weight average molecular weight to the number average molecular weight, Mw / M
n is 3.5 or more, and the ratio Mz / Mw of the Z average molecular weight to the weight average molecular weight is 2.1 or more. If the weight average molecular weight Mw of the matrix is less than 20, the drawdown resistance is inferior. On the other hand, when the weight average molecular weight Mw of the matrix exceeds 350,000, stable extrusion of the parison becomes difficult, and melt fracture occurs. In the present invention, the weight average molecular weight Mw, number average molecular weight Mn and Z average molecular weight Mz are HLC- manufactured by Tosoh Corporation.
The measurement was performed under the following conditions using a type 802A gel permeation chromatography (GPC). (A) Column: Tosoh Corporation column (b) Mobile phase: tetrahydrofuran (c) Sample concentration: 0.3% by mass (d) Measurement temperature: 38 ° C (e) Detector: differential refractometer

In the present invention, the intermediate system D (μm) of the rubber-like elastic material-dispersed particles of the rubber-modified polystyrene resin may be within a range satisfying the expression (1). This is not preferred because the properties deteriorate. on the other hand,
If the median diameter D exceeds 8.0 μm, phase inversion during polymerization becomes unstable and there is a risk of gelation, so that production becomes difficult.
The median diameter D (μm) of the rubber-like elastic material-dispersed particles of the rubber-modified polystyrene resin is determined by dissolving the rubber-modified polystyrene resin in dimethylformamide, and measuring the particle size using a laser diffraction particle size distribution analyzer (Coulter laser diffraction particle analyzer LS-230). The median diameter D (μ) of the present invention is defined as the median particle diameter of the volume-based particle size distribution curve obtained by measurement according to
m).

[0010] The gel component GC (wt%) of the rubber-modified polystyrene resin in the present invention may be in the range satisfying the formula (1), but is preferably 10 wt% or more from the viewpoint of impact resistance. The gel component GC (wt%) of the rubber-modified polystyrene resin can be measured by the following method. That is, 35 ml of toluene
Then, 1 g of a rubber-modified polystyrene resin is dissolved and centrifuged (10000 rpm × 30 minutes) to separate insoluble components. Discard the supernatant and dry the insoluble matter with a dryer (90 ° C
× 3 hours) and then dried in a vacuum dryer (120 ° C ×
1 hour), and let the weight after drying be a. GC (wt%) is determined by (a / 1.0) × 100.

[0011] The method for producing the rubber-modified polystyrene resin in the present invention is not particularly limited, and known methods such as bulk polymerization, bulk / suspension polymerization, and solution polymerization can be employed. However, it may be a batch type. For example, in the case of bulk polymerization, a styrene monomer solution of a rubber-like elastic body or a solution obtained by adding ethylbenzene, toluene, or the like as a diluent thereto is preliminarily polymerized to a predetermined polymerization rate by heating under stirring, Further, a method of performing bulk polymerization up to a predetermined polymerization rate, removing unreacted monomers and diluent under heating and reduced pressure conditions, and completing the polymerization may be mentioned. In the case of the bulk / suspension polymerization method, bulk polymerization is performed to a predetermined polymerization rate by heating the styrene monomer solution of the rubber-like elastic body with stirring, and the polymerization solution is dissolved in water containing a suspending agent. And the suspension polymerization is carried out to complete the polymerization. In the polymerization, additives such as a chain transfer agent, a polymerization initiator, a plasticizer, and an antioxidant can be appropriately used as needed.

The rubbery elastic material used in the rubber-modified polystyrene resin of the present invention includes, for example, polybutadiene, styrene-butadiene random copolymer, styrene-butadiene block copolymer and the like.

The gel content G of the rubber-modified polystyrene resin of the present invention
The molecular weights of C and the matrix are as follows: the ratio of the rubber-like elastic material to the styrene monomer used, the composition of the rubber-like elastic material, the solution viscosity,
It can be adjusted by the method of using the chain transfer agent and / or the polymerization initiator, the polymerization temperature, and the like, but can also be adjusted by blending two or more types of rubber-modified polystyrene resins, or a polystyrene resin that is not rubber-modified. . There is no limitation on the blending method, and a method of mixing rubber-modified polystyrene resin pellets and non-rubber-modified polystyrene resin pellets and re-granulating with an extruder, or a method of mixing rubber-modified polystyrene resin pellets and rubber There is a method in which a mixture of unmodified polystyrene resin pellets is directly introduced into a blow molding machine and blow molded.

The particle size of the rubber-like elastic material-dispersed particles of the rubber-modified polystyrene resin in the present invention may be, for example, the composition of the rubber-like elastic material used, the solution viscosity, the concentration of the styrene monomer solution of the rubber-like elastic material, It can be adjusted by the stirring speed during the prepolymerization, the method of using the chain transfer agent and / or the polymerization initiator, and the like.

The rubber-modified polystyrene resin of the present invention may contain additives such as an antioxidant, a heat stabilizer, an ultraviolet absorber, an antistatic agent, a lubricant, a pigment, a colorant, a mineral oil and a silicone oil, if necessary. May be added.

[0016] The rubber-modified polystyrene resin of the present invention comprises
In particular, it is excellent in extrusion characteristics at the time of forming a parison in large blow molding, processability such as drawdown resistance, and uniformity of wall thickness. The large blow molding refers to a parison having a weight of about 5 kg or more and a long side of the blow molded article in the parison extrusion direction of about 80 cm or more.

[0017]

The embodiments of the present invention will be described below with reference to examples and comparative examples. However, the present invention is not limited at all by these examples.

First, the evaluation method will be described. (1) Drawdown property The resin is plasticized at a temperature of 175 ° C. with a 120 mmφ single screw extruder, and the resin is stored in an accumulator (a set temperature of 175 ° C.) having a volume of 15 liters, and an extrusion rate of 0.9 kg / sec.
At a die / core diameter ratio of 35
9.5k of molten resin (parison) from 0mmφ die
g When extruding, the time from the completion of the parison extrusion to the time when the parison reaches 3 m was measured. The longer this time is, the better the drawdown resistance is. In addition, the total length of the parison at the completion of the parison extrusion was defined as the parison length.

(2) Uniformity of wall thickness The resin is plasticized at a temperature of 175 ° C. with a 120 mmφ single screw extruder, and the resin is stored in an accumulator (a set temperature of 175 ° C.) having a capacity of 15 liters, and an extruding amount is 0.9 kg. / Sec
At a die / core diameter ratio of 35
Extrude molten resin (parison) from a 0 mmφ die,
A rectangular parallelepiped blow-molded product of length × width × height = 1200 × 800 × 50 mm was obtained. The obtained molded article is cut, and the center thickness (upper thickness) at a position 100 mm from the upper part of the molded article and the central part thickness (lower thickness) at a position 100 mm from the lower part of the molded article are measured. Ratio = (lower wall thickness) /
(Upper wall thickness) was calculated. A: Ratio is less than 1.2. ：: The ratio is 1.2 or more and less than 1.6. Δ: The ratio is 1.6 or more and less than 2.0. ×: The ratio is 2.
0 or more. Was evaluated in four steps.

(3) Izod impact strength Izod impact strength was evaluated by a method according to JIS K7110.

Example 1 Low-cis polybutadiene rubber 8.0 as a rubber-like elastic body
80.5% by weight of styrene monomer, 10.0
A raw material solution was prepared by dissolving in a mixed solution of ethylbenzene of 1.5% by weight, mineral oil of 1.5% by weight, a polymerization initiator of 0.01% by weight, and a chain transfer agent of 0.02% by weight. An autoclave with a stirrer having a capacity of 18 liters and a volume 42 connected in series at the subsequent stage of the autoclave were prepared.
The reactor was continuously fed at 7.2 liters per hour to a liter tube reactor. The number of stirrings in the autoclave was adjusted to 90 rpm and the reaction temperature to 128 ° C, and the reaction temperature in the tubular reactor was adjusted so that a temperature gradient of 100 to 170 ° C was formed in the flow direction of the reaction solution. The monomer conversion at the outlet of the autoclave was 26% by weight, and the monomer conversion at the outlet of the tubular reactor was 90% by weight. The reaction solution exiting the tubular reactor is heated to 220 ° C. by a heat exchanger, and then has a degree of vacuum of 10 ton.
After being guided to a devolatilization tank adjusted to rr to remove volatile components such as unreacted monomers and solvents, the mixture was taken out of the devolatilization tank with a gear pump, made into a strand through a die plate, cooled with water, and pelletized to obtain a rubber-modified polystyrene resin.

The obtained rubber-modified polystyrene resin had a number average molecular weight Mn of 80,000 and a weight average molecular weight Mw of 24.2.
Blended with a rubber-unmodified polystyrene resin having a Z-average molecular weight Mz of 500000 at a ratio of 70/30,
Re-granulation was performed with an extruder to obtain a rubber-modified polystyrene resin of Example 1. Table 1 shows the physical properties and the evaluation results.

Example 2 A rubber-modified polystyrene resin was obtained under the same manufacturing conditions as in Example 1. The obtained rubber-modified polystyrene resin was subjected to a number average molecular weight Mn of 80,000 and a weight average molecular weight Mw.
Was blended with a non-rubber-modified polystyrene resin having a molecular weight of 242,000 and a Z-average molecular weight Mz of 500000 at a ratio of 50/50, and re-granulated with an extruder to obtain the rubber-modified polystyrene resin of Example 2. Obtained. Table 1 shows the physical properties and the evaluation results.

Example 3 A rubber-modified polystyrene resin of Example 3 was obtained under the same conditions as in Example 1 except that the number of stirring in the autoclave was changed to 150 rpm. Table 1 shows the physical properties and the evaluation results.

Example 4 Production was performed under the same production conditions as in Example 1 to obtain a rubber-modified polystyrene resin. The obtained rubber-modified polystyrene resin was subjected to a number average molecular weight Mn of 82,000 and a weight average molecular weight Mw.
Was blended with a non-rubber-modified polystyrene resin having a Z-molecular weight of 387,000 and a Z-average molecular weight Mz of 79,980 at a ratio of 50/50, followed by re-granulation with an extruder to obtain the rubber-modified polystyrene resin of Example 4. Obtained. Table 1 shows the physical properties and the evaluation results.

Example 5 Production was carried out under the same conditions as in Example 1 to obtain a rubber-modified polystyrene resin. The obtained rubber-modified polystyrene resin is
Number average molecular weight Mn is 71,000 and weight average molecular weight Mw is 3
It was blended with a non-rubber-modified polystyrene resin having a molecular weight of 11,000 and a Z-average molecular weight Mz of 7680,000 at a ratio of 40/60, and re-granulated with an extruder to obtain a rubber-modified polystyrene resin of Example 5. Was. Table 1 shows the physical properties and the evaluation results.

Comparative Example 1 A rubber-modified polystyrene resin of Comparative Example 1 was obtained under the same conditions as in Example 1 except that 0.05% by weight of a chain transfer agent was added at the inlet of the tubular reactor. Table 2 shows the physical properties and evaluation results.

Comparative Example 2 A rubber-modified polystyrene resin was obtained under the same manufacturing conditions as in Example 1. The obtained rubber-modified polystyrene resin was subjected to a number average molecular weight Mn of 1570,000 and a weight average molecular weight M
The rubber-modified polystyrene resin of Comparative Example 2 was blended with a non-rubber-modified polystyrene resin having a w of 570,000 and a Z-average molecular weight Mz of 9,690,000 at a ratio of 50/50, followed by re-granulation by an extruder. I got Table 2 shows the physical properties and evaluation results.

Comparative Example 3 A rubber-modified polystyrene resin of Comparative Example 3 was obtained under the same conditions as in Example 1 except that the number of stirring in the autoclave was changed to 220 rpm. Table 2 shows the physical properties and evaluation results.

Comparative Example 4 A rubber-modified polystyrene resin was obtained under the same conditions as in Example 1 except that the number of stirring in the autoclave was changed to 220 rpm. The obtained rubber-modified polystyrene resin was subjected to a number average molecular weight Mn of 82,000 and a weight average molecular weight Mw of 3
87,000 and a Z-average molecular weight Mz of 7,980,000 were blended with a non-rubber-modified polystyrene resin at a ratio of 60/40, and re-granulated with an extruder to obtain a rubber-modified polystyrene resin of Comparative Example 4. Was. Table 2 shows the physical properties and evaluation results.

Comparative Example 5 A rubber-modified polystyrene resin was obtained under the same conditions as in Example 1 except that the number of stirring in the autoclave was changed to 150 rpm. The obtained rubber-modified polystyrene resin was converted into a number average molecular weight Mn of 80,000 and a weight average molecular weight Mw of 2
Blend in a ratio of 60/40 with a non-rubber-modified polystyrene resin having 42,000 and a Z-average molecular weight Mz of 50,000,000 and re-granulating by an extruder to obtain a rubber-modified polystyrene resin of Comparative Example 5. Was. Table 2 shows the physical properties and evaluation results.

[0032]

[Table 1]

[0033]

[Table 2]

[0034]

The rubber-modified polystyrene resin of the present invention comprises:
The parison can be formed stably, the drawdown resistance is good, and the thickness of the molded product is excellent in uniformity. On the other hand, in Comparative Example 1, although the left side of Formula (1) exceeded 4.37, the weight average molecular weight Mw of the matrix was 2
Since it is less than 100,000, drawdown occurs significantly during parison extrusion. In Comparative Example 2, the left side of Expression (1) was 4.3.
Weight average molecular weight M of the matrix, although exceeding 7.
Since w exceeded 350,000, melt fracture occurred during parison extrusion, and stable parison formation was impossible. In Comparative Example 3, the weight average molecular weight Mw of the matrix was in the range of 200,000 to 350,000, and the median diameter D (μm) of the rubber-like elastic material dispersed particles was in the range of 2.0 to 8.0 μm. Since the left side of the equation (1) is less than 4.37, the drawdown resistance and the uniformity of the thickness are inferior. In Comparative Example 4, the weight average molecular weight Mw of the matrix was 25 to 30.
And the ratio M between the weight average molecular weight and the number average molecular weight M
w / Mn is 3.5 or more, the ratio Mz / Mw of the Z average molecular weight to the weight average molecular weight is 2.1 or more, and the median diameter D (μm) of the rubber-like elastic material dispersed particles is 2.0 ~ 8.0 μm
However, since the left side of the equation (1) is less than 4.37, the drawdown resistance and the uniformity of the thickness are inferior. In Comparative Example 5, the weight average molecular weight Mw of the matrix was 2
Although the median diameter D (μm) of the rubber-like elastic material-dispersed particles is in the range of 2.0 to 8.0 μm, the left side of the formula (1) is less than 4.37. Therefore, the drawdown resistance and the uniformity of the wall thickness are poor.

Continued on the front page F term (reference) 3E033 BA22 BB01 CA20 FA03 4F071 AA10 AA12 AA12X AA22 AA22X AA75X AA76X AA81 AD06 AH05 BB06 BC04 4F208 AA13A AA13J AM32 LA01 LG01 4J002 AC00X AC03X AC03X BC01 BC02 BC01

Claims (3)

[Claims] 1. A matrix having a weight average molecular weight Mw of 20
~ 350,000, ratio Mw of the weight average molecular weight to the number average molecular weight
/ Mn is 3.0 or more, and the median diameter D (μm) of rubber-like elastic particles contained as dispersed particles is 2.0 to
A rubber-modified polystyrene resin having an excellent blow moldability that satisfies the relationship of In (GC) + 0.348 × D ≧ 4.37, where 8.0 is the gel content and GC (wt%) is the gel content. 2. The weight average molecular weight Mw of the matrix is 25.
３０300,000, the ratio Mw between the weight average molecular weight and the number average molecular weight
2. The rubber-modified polystyrene resin according to claim 1, wherein / Mn is 3.5 or more, and a ratio Mz / Mw of the Z average molecular weight to the weight average molecular weight is 2.1 or more. 3. A blow-molded product comprising the rubber-modified polystyrene resin according to claim 1.