JPH0382518A - Manufacture of high foamed molding of polystyrene resin - Google Patents

Abstract

PURPOSE:To enable the highly foamed molding with large thickness to be economically produced by a method in which when a foamed molding is produced, while the polystyrene resin whose melt flow rate-value is specified, is used, the amount of the foamable molten kneaded material discharged from a die orifice is specified. CONSTITUTION:Polystyrene resin and foaming material are fusion-kneaded under pressure, and after foamable molten kneaded material has been prepared, the molten kneaded material is extruded in the accumulator kept at the temperature and pressure where the molten kneaded material is not foamed, and then when the foamed formed object is produced by discharging intermittently said kneaded material by the pressure of a movable ram from the die orifice provided on the tip of the accumulator, the resin having the value of melt flow rate of 1-30g/10min is used as polystyrene resin, and simultaneously the amount of the foamable molten kneaded material to be discharged per one time from the die orifice is made to be 60g or more per 1cm<2> of the cross sectional area of the orifice per one second.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field) The present invention relates to a method for producing a highly foamed polystyrene resin molded article.

(Prior art and its problems) Bead foam molding method and extrusion foam molding method are generally used as methods for manufacturing polystyrene resin foams.

The bead foam molding method is a method in which foamed beads made of raw resin particles are placed in a mold, heated by flowing heated steam, and fused together while performing secondary foaming. According to this method, it is possible to obtain a highly foamed molded product, but the resulting highly foamed molded product has the disadvantage of large shrinkage after molding, and when trying to obtain a thick foamed product, heating steam The disadvantage is that the flow within the mold becomes non-uniform, the whole cannot be heated to a uniform temperature, and the fusion of the foamed beads becomes incomplete. Another problem is that the compressive strength of the resulting foamed molded product is smaller than that of an extruded foamed molded product.

On the other hand, the extrusion foam molding method is a method in which a single foamable melt-kneaded material is continuously extruded and foamed from an extrusion device.

Although this method has the advantage of being able to continuously produce foamed molded products, it has the disadvantage that it is difficult to obtain highly foamed molded products and thick foamed molded products. If an attempt is made to obtain a thick, highly foamed molded product using this method, it is necessary to use very large machinery and equipment, resulting in high costs and extremely poor economic efficiency.

(Problem of the Invention) An object of the present invention is to solve the above-mentioned problems seen in the prior art and to provide a method that can economically produce a thick, highly foamed molded article.

(Means for Solving the Problems) The present inventors have conducted extensive research to solve the above problems, and as a result, have completed the present invention.

That is, according to the present invention, a polystyrene resin and a blowing agent are melt-kneaded under pressure to form a foamable melt-kneaded product, and then the melt-kneaded product is placed in an accumulator maintained at a temperature and pressure that do not cause a foaming effect. When the polystyrene resin is extruded into the accumulator, and then intermittently discharged from the die orifice provided at the tip of the accumulator by the pressure of a movable ram to produce a foamed molded product, the melt flow rate value of the polystyrene resin is 1 to 30 g/10 minutes, and the amount of foamable melt-kneaded material discharged from the die orifice per time is 60 g or more per second with an orifice cross-sectional area of 1 d. A method for producing a highly foamed resin molded article is provided.

The polystyrene resin used in the present invention includes homopolymers or copolymers of styrene monomers, copolymers of styrene monomers and other monomers, and the like. Examples of the styrene monomer include styrene, α-methylstyrene, chlorostyrene, dichlorostyrene, dimethylstyrene, t-butylstyrene, vinyltoluene, and the like. Examples of monomers other than styrene include divinylbenzene, maleic anhydride, acrylic acid, methyl methacrylate, acrylonitrile, butadiene, and the like. The content of the styrene monomer component in the polystyrene resin is 50 mol 2 or more, preferably 70 mol 2 or more.

Melt flow rate value (MFR) of polystyrene resin used in the present invention (JIS K 7210, measurement conditions: 2
00° C., 5 kg) is usually in the range of 1-30 g/10 min, preferably 10 to 25 g/10 min. If the melt flow rate value of the styrenic resin is too high, the foamability will deteriorate and it will be difficult to obtain a foam with excellent cell conditions and surface conditions.

As the foaming agent used in the present invention, a solvent-based foaming agent is used. Examples of such substances include conventionally known ones, such as cycloaliphatic hydrocarbons such as cyclobutane and cyclopentane, aliphatic hydrocarbons such as propane, butane, pentane, hexane, and heptane, methyl chloride, and ethyl chloride. , dichlorodifluoromethane, 1,2-dichloro-1,1,2,2-tetrafluoroethane, 1.1
-dichloro-2,2,2-trifluoroethane, 1,2
, 2.2-tetrafluoroethane, 1-chloro-1,1
-Difluoroethane, 1-chloro-1,2,2,2-tetrafluoroethane, chlorodifluoromethane, and other halogenated hydrocarbons. These materials can be used alone or in the form of a mixture.

Next, the present invention will be explained with reference to the drawings.

FIG. 1 shows a system diagram of an apparatus for carrying out the present invention.

In FIG. 1, numeral 1 denotes a melt mixing device, which is usually a screw type extruder. The raw polystyrene resin is supplied from the hopper 7 to the melt-mixing device 1, and the blowing agent is forced into the melt-kneading device 1 from the blowing agent introduction pipe 8, where it is uniformly melt-kneaded.

The amount of the blowing agent used is 2 to 50 parts by weight, preferably 5 to 20 parts by weight, based on 100 parts by weight of the polystyrene resin. In this melt-mixing process, various auxiliary additive components can be added, such as inorganic substances such as talc and silica as bubble regulators, or chemical foams that decompose at the temperature inside the melt-mixer 1 to generate gas. or an acid-alkali combination that reacts at the internal temperature of the device to generate carbon dioxide, such as citric acid and sodium bicarbonate, or an alkali salt of citric acid and sodium bicarbonate. The conditions for this melting cross-wire process are: temperature =
95-250℃, preferably 100-180℃, pressure crab 10-200kg/aJG, preferably 30-look
g/a&G.

Next, a predetermined amount of the foamable melt-kneaded material containing the polystyrene resin and foaming agent obtained above is filled into a discharge device 2 equipped with a die 24 through a conduit 3, and once foamed and melt-kneaded therein. After the material is maintained at a temperature and pressure condition that does not cause foaming, it is intermittently discharged from here through the orifice of the die 4 to a low pressure zone such as atmospheric pressure to cause foaming. In this case, as the discharge device 2, one having a cylindrical accumulator 6 having a die 4 at the tip and a reciprocating discharge ram 5 inside can be used. That is, the melted and kneaded material from the melt mixing device 1 is press-fitted into the accumulator through the communication hole provided in the accumulator, and the pressure at that time causes the ram 5 to move back within the accumulator by a predetermined distance, and the accumulator is filled with a predetermined distance. A fixed amount of foamable melt-kneaded material is filled. After this filling operation is completed, the gate that had closed the die is opened, and the ram is advanced by a separately provided hydraulic device via a piston rod installed between the ram and the hydraulic device. , the foamable melt-kneaded material held in the accumulator is discharged to an external low-pressure zone through a die orifice. After this discharge is completed, the gate is closed, the pressure of the hydraulic device is reduced, and the pressing force of the ram is reduced to a predetermined pressure, thereby filling the accumulator with the foamable melt-kneaded material again as described above. In this way, the foamable melt-kneaded material is intermittently discharged from the accumulator. The pressure at which the foamable melt-kneaded material is charged into the accumulator is within a range that does not cause foaming, and is adjusted by the pressing force applied to the ram.

The specific equipment system equipped with the melt-kneading device 1 and the melt-kneaded material discharge bag @ 2 is described in Japanese Patent Publication No. 57-5013.
Details are given in Publication No. 17.

The temperature at which the foamable melt-kneaded material is once filled and held in the foamable melt-kneaded material discharge device 2 is above the Vicat softening point of the raw material polystyrene resin and below the Vicat softening point +40°C, and the pressure is 10°C. ~200 kg/aJ, preferably 30-100 kg/al.

As described above, the foamable melt-kneaded material is intermittently discharged from the orifice of the die 4, and the foam F is obtained.
In the present invention, the amount of foamable melt-kneaded material discharged per one time from the orifice of the die 4 is determined by the orifice cross-sectional area l.
a&and 60g or more, preferably 120~ per second
Specified at 600g. By this regulation, it is possible to efficiently obtain a thick foam molded product with a high expansion ratio and excellent internal cell state and surface state.

In the present invention, the foamable melt-kneaded material discharged from the die orifice rapidly foams at the same time as it is discharged, and the obtained foam is taken up by a belt conveyor or the like and cooled. The foamable melt-kneaded product is preferably cooled after completing foaming by maintaining the foaming atmosphere temperature at 40 to 80°C using hot air or the like.The foaming atmosphere temperature is maintained at 40 to 80°C and melt-kneaded. By foaming the product, cooling of the skin of the foam can be suppressed and foaming can be further promoted.

The shape of the die orifice used in the present invention is arbitrary and can be circular or square. Further, the die orifice may or may not have an internal land, but a larger and thicker foamed molded product can be obtained by using an orifice without an internal land.

(Effects of the Invention) According to the present invention, it is possible to efficiently produce a highly foamed, thick (large cross-sectional area) polystyrene resin foam molded product with good cell conditions and surface conditions. According to the present invention, a thick foam molded article having a diameter or thickness of 15 mm or more can be easily obtained. Further, according to the present invention, a foam with a high expansion ratio of 30 times (density 0.035 g/aj) to 80 times (density 0.013 g/cd) can be easily obtained, and the foam The strength is superior to that of foam produced by bead foaming.

The foam molded article of the present invention also has excellent machinability and cuttability. Therefore, the foam molded article of the present invention can be easily molded into a desired size and shape by cutting or machining.

Furthermore, in the present invention, a small-scale device is used, and since the discharge amount during foam molding is large, the manufacturing cost of the foam molded product is also low.

The thick foam molded article of the present invention is suitable as a civil engineering material for ground improvement, which is currently attracting attention.

(Example) Next, the present invention will be explained in more detail with reference to Examples.

Note that the structures of dice A, dice B, and dice C used below are as follows.

Dice A...Diameter 2 without land with the structure shown in Figure 2
5mm round dice. However, a=150+*m.

b=25++n, C=30.5mm, d=90mm,
e=110am.

Dice B: Diameter 3 without land with the structure shown in Fig. 2
0mm round die 6 However, a = 150mm.

b=30i+m, C=30.5mm, d=90mI1
．． e=110-Otori.

Dice C: A round die with a diameter of 30 mm and a land having the structure shown in FIG. However, a=150m+a+b=30
mm, C=30.5mm, d=90mm, e:11
0m+a.

Example 1 Density 1.05g/aI? , melt flow rate value (MF
R) 100.02 parts by weight of 0.02 parts by weight of talc as a bubble regulator added to 100 parts by weight of 20g 710-minute polystyrene, and 3 parts by weight of dichlorodifluoromethane.
After melt-kneading 15 parts by weight of a blowing agent consisting of a mixture of 2 parts by weight of 2 parts by weight and 70 parts by weight of methyl chloride at a temperature of 145°C using a screw type extruder with a discharge capacity of 15 kg/hr, the foamable melt-kneaded product was The temperature was adjusted to 110°C (Vicat softening point (91'C) + 19°C) and once extruded into an accumulator.

Next, the foamable melt-kneaded material extruded and filled into the accumulator was passed through the orifice of a die with an opening cross-sectional area of 4.9 d, and 391 g per 1 second with an orifice area of 1 d.
The mixture was instantaneously discharged under atmospheric pressure at a rate of 100 mL to cause foaming, and the foamed molded product was taken up by a belt conveyor.

The round rod-shaped foam thus obtained has a foaming ratio of 5
3 times, foam density: 0.020g/aj, foam diameter:
It showed 21.7 cm. Furthermore, the foam had a very good cell condition, with very fine cells, and the surface condition of the foam was also good, with a glossy surface and a taut skin.

Example 2 An experiment was conducted in the same manner as in Example 1, except that polystyrene having a melt flow rate of 10 g/10 minutes was used as the raw material polystyrene.

The obtained round rod-shaped foam had an expansion ratio of 53 times and a density of 0.
．． 018 g/aJ, diameter: 19.9 cm, and the cell condition and surface condition of the foam were both very excellent as in Example 1.

Example 3 In Example 1, as raw material polystyrene.

The experiment was conducted in the same manner except that polystyrene having a melt flow rate value of 30 g/10 minutes was used.

The obtained round rod-shaped foam has a foaming ratio of 51 times and a density of 0.
．． 021g/ad, diameter: 17.9c++. Further, the cell condition of the foam was slightly inferior to that of Example 1, and the cell diameter was slightly larger than that of Example 1.

The surface condition of the foam was also slightly inferior to that of Example 1,
Although there was some tension on the surface, there was no shine.

Example 4 An experiment was conducted in the same manner as in Example 1, except that polystyrene having a melt flow rate of 2 g/10 minutes was used as the raw material polystyrene.

The obtained round rod-shaped foam had an expansion ratio of 53 times and a density of 0.
．． 020g/aJ, diameter: 21.7aa. Furthermore, the state of the cells in the foam was slightly less uniform than that in Example 1.

Example 5 An experiment was conducted in the same manner as in Example 1 except that 15 parts by weight of a mixture of butane and methyl chloride (mixing weight ratio = 3:1) was used as the blowing agent.

The obtained round rod-shaped foam has an expansion ratio of 57 times and a density of 0.
．． 018 g/aJ and a diameter of 22.0 cm. Also,
The bubble state and surface state were also good as in Example 1.

Example 6 An experiment was conducted in the same manner as in Example 1 except that methyl chloride was used as one blowing agent.

The obtained round rod-shaped foam had an expansion ratio of 53 times and a density of 0.
．． 020 g/alf, diameter: 21.3 cm. In addition, the bubble state and surface state were also good as in Example 1.

Example 7 In Example 1, 16.6 parts by weight of a mixture of butane and methyl chloride (mixed weight ratio = L: 8) was used as one blowing agent, and the amount of foamable melt-kneaded material discharged from the die was varied. The experiment was conducted in the same manner except for the following. The properties of the obtained round rod-shaped foam are shown in Table 1 in relation to the discharge amount from the accumulator.

The evaluation criteria for the cell state and surface state of the foam shown in Table 1 are as follows.

(Bubble condition) O...Very fine 0...Fine Δ...Slightly fine ×...Rough (Surface condition) O...Shiny, the epidermis is tense △...Gloss Table 1 Example 8 In Example 5, die B was used, and the foaming agent was 15.4 ml. The experiment was conducted in the same manner except that parts by weight were used.

The obtained round rod-shaped foam has a foaming ratio of 55 times and a density of 0.
．． 019 g/aJ and a diameter of 24.9 cm, and both the bubble state and the surface state were as good as in Example 5.

Example 9 An experiment was carried out in the same manner as in Example 5, except that Dice C was used, and 0.06 parts by weight of talc and 18.6 parts by weight of a blowing agent were used.

The obtained round rod-shaped foam has an expansion ratio of 55 times and a density of Q.
, 019 g/aJ, diameter: 21.2 cm.

Moreover, both the bubble state and the surface state were as good as in Example 5.

[Brief explanation of drawings]

FIG. 1 shows a system diagram of an apparatus for foam-molding polystyrene resin. 2 and 3 show cross-sectional structural diagrams of the die, and the second
The figure shows a round die without a land, and Figure 3 shows a round die with a land. DESCRIPTION OF SYMBOLS 1... Melt kneading device, 2... Discharge device, 4... Dice, 5... Ram. 6...Accumulator. F... Foamed molded product.

Claims (1)

[Claims] (1) A polystyrene resin and a blowing agent are melt-kneaded under pressure to form a foamable melt-kneaded product, and then the melt-kneaded product is extruded into an accumulator maintained at a temperature and pressure that do not cause a foaming effect; Thereafter, when producing a foamed molded product by intermittently discharging the foam from a die orifice provided at the tip of the accumulator under the pressure of a movable ram,
The polystyrene resin has a melt flow rate of 1.
~30 g/10 minutes, and the discharge amount of the foamable melt-kneaded material from the die orifice per 1 cm^2 and 60 g per second.
A method for producing a highly foamed polystyrene resin molded article, which is characterized by the above steps.