JPH07116316B2 - Method for producing heat resistant foam - Google Patents

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a method for producing a heat resistant foam. More specifically, it relates to a method for producing a high-quality synthetic resin foam having heat resistance.

[0002]

2. Description of the Related Art Conventionally, it is widely known that a method for producing a foamed molded product by foaming a polystyrene resin, and that the molded product is used as a heat insulating material or heat insulating material for pipes and the like. ing. Recently, in the field of automobiles, there is a demand for weight reduction of a vehicle body for the purpose of energy saving. As one means for reducing the weight, various foams are used according to the characteristics of the parts. Among them, the high density foam is used as a structural member in the field of automobile interior materials.

In these fields, a heat resistance of 80 to 120 ° C. is required, although it varies depending on the part. Further, since these parts are used for a long time of 3 to 10 years, they are required to have durability, particularly dimensional stability. Since a polystyrene foam has a problem in heat resistance, a polyphenylene ether resin-modified polystyrene foam has been proposed.

Of these, in JP-A-52-101267 and JP-A-52-101268, molding processability is maintained when forming a foamed product based on a mixed composition of a polystyrene resin and a polyphenylene ether resin. Therefore, the amount of gas in the pre-expanded particles is required to be 3% by weight or more, and the amount of gas in the foam is required to be 3% by weight or less in order to improve the heat resistance of the product. Specifically, the base resin will not be able to be foamed and molded even if a foaming agent having a large plasticizing effect is used unless it is added in an amount far exceeding 3% by weight. , A foaming agent having a faster vaporization rate than the base resin, for example, a vaporization rate such that after the primary foaming (primary foaming treatment), the content of the content of the foaming agent can be 3% by weight or less. With a fast foaming agent, sufficient foaming cannot be achieved. In addition, even if these are to be adjusted by the conditions (temperature, pressure) at the time of foam molding, there is a limit naturally, and in any case, the content of the foaming agent is 3% by weight in the primary treatment.
It is said that the following foam cannot be obtained.

[0005]

Means for Solving the Problems As a result of various investigations by the present inventors, the content of the volatile foaming agent in the base resin particles was 3 parts by weight or less and 0.8 parts by weight or more of the expandable resin particles were obtained. It was found that the obtained foam was excellent in both heat resistance and stability. That is, in the present invention, the base resin particles composed of 90 to 10 parts by weight of the polystyrene resin and 10 to 90 parts by weight of the polyphenylene ether resin have a boiling point of 90 ° C. or less at normal pressure under pressure in an aqueous medium. A volatile foaming agent is impregnated to obtain expandable resin particles having a content of the volatile foaming agent in the base resin particles of 3 parts by weight or less and 0.8 parts by weight or more, and heating the expandable resin particles. Bulk density 0.
A method for producing a heat-resistant foam, comprising obtaining pre-expanded particles in an amount of 05 to 0.35 g / cm ³ and then filling the pre-expanded particles in a molding die to heat and foam to obtain an expanded molded article. provide.

The polystyrene resin in the present invention includes, for example, polystyrene, polystyrene-butadiene copolymer, polystyrene-maleic anhydride copolymer, polystyrene-acrylonitrile copolymer, styrene graft copolymer and the like. The polyphenylene ether resin referred to in the present invention is represented by the following formula I

[0007]

[Chemical 1]

(Here, R ₁ and R ₂ represent an alkyl group having 1 to 4 carbon atoms or a halogen atom, and n represents the degree of polymerization.), Which is a polyphenylene ether resin. Is poly (2,6-dimethylphenylene-1,4-ether), poly (2,6-diethylphenylene-1,4-ether), poly (2,6-
Dichlorophenylene-1,4-ether), poly (2-
Methyl-6-ethylphenylene-1,4-ether),
Poly (2-chloro-6-methylphenylene-1,4-ether), Poly (2-methyl-6-isopropylphenylene-1,4-ether), Poly (2,6-di-n-propylphenylene-1) , 4-ether), poly (2-bromo-6, methylphenylene-1,4-ether), poly (2-chloro-6-bromophenylene-1,4-ether), poly (2-chloro-6-). Ethylphenylene-
1,4-ether) and the like. The degree of polymerization n is 10
If it exceeds 5,000, it is difficult to obtain a uniform foam, and if it is less than 10, it is difficult to obtain a foam having the desired heat resistance.

In addition, if necessary, the resin may be mixed with an appropriate amount of a colorant, a flame retardant, a nucleating agent, a heat stabilizer, a lubricant and the like. The ratio of the polystyrene resin and the polyphenylene ether resin in the base resin particles of the present invention is 90 to 10 parts by weight of the polystyrene resin and the polyphenylene ether resin 1.
0 to 90 parts by weight, preferably 90 to 30 parts by weight of polystyrene resin and polyphenylene ether resin 10
˜70 parts by weight.

If the polystyrene-based resin exceeds 90 parts by weight, the heat resistance is insufficient, and if the polyphenylene ether resin is less than 10 parts by weight, it is difficult to obtain a heat-resistant foam. As the shape of the base resin particles, bead-shaped, pellet-shaped, spherical, irregular-shaped pulverized products having a size of about 0.2 to 2 mm can be suitably applied.

The volatile blowing agent referred to in the present invention means an aliphatic hydrocarbon having a boiling point of 90 ° C. or less at atmospheric pressure, and examples thereof include propane, n-butane, iso-butane, n-pentane, iso-pentane and neopentane. , Cyclopentane, cyclohexane and the like. These volatile foaming agents can be used alone or as a mixture of 2 to 3 kinds. Further, a small amount of an organic solvent such as styrene, toluene and ethylbenzene may be used together.

In the method of the present invention, since the volatile foaming agent is impregnated, it can be carried out in a closed container according to a conventional method. One of them is a so-called wet method in which a suspension system such as water is used in an aqueous medium. The other is the use of the so-called dry method, which is carried out under substantially anhydrous conditions. However, it has been found that the dry method cannot achieve the predetermined purpose.

As a dispersant when a suspension system of an aqueous medium is used, a water-insoluble inorganic substance such as magnesium pyrophosphate or magnesium oxide is preferably used, and a known surfactant can also be used in combination. . The impregnation temperature of the volatile foaming agent is in the range of 40 ° C. or higher and 60 ° C. or lower of the glass transition temperature (measured by a differential scanning calorimeter) Tg of the base resin particles, preferably 25 ° C. or higher and 40 ° C. or lower of Tg. When the impregnation temperature is 40 ° C. or less of Tg, it takes a long time to uniformly impregnate the foaming agent to the central portion of the base resin particles, which is not economical. Also, if the Tg is 60 ° C. or higher, the interparticle bonding of the base resin particles is likely to occur in the impregnation step, which is inconvenient. The impregnation time is about 8-15 hours.

The timing of adding the volatile foaming agent is appropriately adjusted depending on the amount and type of the volatile foaming agent used, a combination thereof, and the like. That is, in the manufacturing process of the base resin particles, any of a taking-out process, a dehydration / drying process, or a process of blending an anti-bonding agent, a lubricant, an antistatic agent, a flame retardant at the time of pre-foaming may be performed. Furthermore, the temperature at the time of adding the volatile foaming agent may be after the step reaches the impregnation temperature, or after the impregnation, it may reach the impregnation temperature.

The content of the volatile foaming agent in the base resin particles is 3 parts by weight or less and 0.8 parts by weight or more, preferably 2.5 parts by weight or less and 1.5 parts by weight or more. If the mixing ratio exceeds 3 parts by weight, the heat resistance of the product deteriorates, and if it is 0.8 parts by weight or less, sufficient foamability cannot be obtained. After producing the expandable resin particles, the expandable resin particles are heated and expanded to have a bulk density of 0.05 to 0.35 g / cm ³ , preferably 0.10 to 10.
0.35 g / cm ³ pre-expanded particles are obtained.

The pre-expanded particles thus produced are filled in a mold and heated and foamed to prepare a foamed molded product. In order to further increase the vaporization rate of the volatile foaming agent in this foaming treatment step, it is effective to set the treatment temperature to a temperature not lower than Tg of the base resin particles, and further to a high temperature not lower than 20 ° C and not higher than 50 ° C. Target. If the Tg is 20 ° C. or less, the foaming is not sufficiently performed and the volatile foaming agent cannot be rapidly reduced. Further, if the temperature is 50 ° C. or higher, uniform foaming cannot be performed.

[0017]

EXAMPLES Example 1 Polystyrene-modified polyphenylene ether resin (polyphenylene ether content of about 5 in a 5 lit autoclave).
0 parts by weight, Tg; about 145 ° C.) 1600 g, water 25
00 g and magnesium oxide (32 g) were added, and n-butane (80 g) was press-fitted and impregnated while stirring in a sealed state.
After that, the temperature was raised to 120 ° C. and maintained at this temperature for 15 hours. The pressure at that time was 14 kg / cm ² . Then, it was cooled to 30 ° C. and taken out. After washing, dehydrating, and drying the bead-shaped base resin particles, the beads are placed in a closed container,
It was kept and aged for 72 hours at a temperature of a cool box (15 ° C.) to obtain expandable resin particles. The content of n-butane in the bead-shaped base resin particles was 2.5 parts by weight. The bead-shaped expandable resin particles were put into a pressure foaming machine and steam pressure was adjusted to 3.0.
When heated at kg / cm ² for 120 seconds, the bulk density was 0.083 g / cm ³ . The bulk density of the pre-expanded particles was adjusted to 0.167 g / cm ³ (steam pressure 2.0
(pressure foaming at kg / cm ² ), leave for 24 hours and age, then mold with an automatic molding machine under heating conditions of steam pressure 4.0 kg / cm ² for 75 seconds, bulk density 0.167 g / cm ³ 40
0 m / m (width) x 300 m / m (length) x 15 m / m
A foamed molded product having a dimension of (height) was obtained.

Example 2 In the same manner as above, a polystyrene-modified polyphenylene ether resin (polyphenylene ether) was placed in a 5-lit autoclave.
Tell content about 50 parts by weight, Tg; about 145 ° C.) 160
0 g, 2800 g of water, 12.4 g of metathesis magnesium pyrophosphate and 0.4 g of sodium dodecylbenzene sulfonate were added, and then n-
96 g of butane was pressed in and impregnated. After that, the temperature was raised to 110 ° C. and maintained at this temperature for 10 hours. The pressure at that time was 12.5 kg / cm ² . Similar to the above, the bead-shaped base resin particles are washed, dehydrated and dried, and at the same time, 7
It was kept for 2 hours and aged to obtain expandable resin particles. The content of n-butane in the bead-shaped base resin particles was 2.7 parts by weight. The bead-like expandable resin particles were put into a pressure foaming machine and heated at a steam pressure of 3.0 kg / cm ² for 120 seconds to find that the bulk density was 0.0714 g / cm ³ . The bulk density of the pre-expanded particles was adjusted to 0.167 g / cm ³ , and the mixture was allowed to stand for 24 hours (pressure foaming at a steam pressure of 2.0 kg / cm ² ) and after aging, a steam pressure of 4.0 kg / cm with an automatic molding machine. Molded under heating conditions of ² and 75 seconds, and a bulk density of 0.167 g / cm ³ and 400 m / m (width) x 3
A foamed molded product of 00 m / m (length) × 15 m / m (height) was obtained.

Comparative Example 1 1600 g of polystyrene-modified polyphenylene ether resin (polyphenylene ether content: about 50 parts by weight, Tg: about 145 ° C.) was placed in a 5 lit autoclave in the same manner as above.
And 2800 cc of water, 12.4 g of metathesis magnesium pyrophosphate and 0.4 g of sodium dodecylbenzene sulfonate were added, and then n-
112 g of butane and 48 g of n-pentane were pressed in and impregnated. After that, the temperature was raised to 140 ° C. and maintained at this temperature for 10 hours. The pressure at that time was 18.5 kg / cm ² .

The bead-shaped base resin particles are washed, dehydrated and dried in the same manner as above, and similarly held and aged for 72 hours,
Expandable resin particles were used. The content of n-butane in the bead-shaped base resin particles was 3.5 parts by weight, the amount of n-pentane was 1.3 parts by weight, and the total amount of the nonvolatile foaming agents was 4.8 parts by weight. . The bead-like expandable resin particles were put into a pressure foaming machine, and steam pressure was set to 120 kg at 3.0 kg / cm ² .
When heated for a second, the bulk density was 0.036 g / cm ³ . The bulk density of the pre-expanded particles is 0.167 g / cm ³
Was adjusted to (pressurized foam with steam pressure 1.2kg / cm ^2), after aging for 24 hours, they were molded under the heating conditions of the steam pressure of 4.0 kg / cm ² in an automatic molding machine for 30 seconds and a bulk density Is 0.167 g / cm ³ and 400 m / m
A foam molded product having a width of 300 m / m and a length of 15 m / m was obtained.

Next, the foamability, heat resistance and long-term stability of Examples 1 and 2 and Comparative Example were evaluated. Table 1 shows the pressure during foaming under pressure and foamability, and Table 2 shows the content of the non-volatile foaming agent in the molded product. As can be seen from Table 2, in the present invention, the content of the non-volatile foaming agent is 3 parts by weight or less, and the heat resistance is good.

[0022]

[Table 1]

[0023]

[Table 2]

Then, as the evaluation of heat resistance, changes in dimensions during heating durability and changes in the appearance of molding were evaluated. The results are shown in Tables 3, 4, and 5, and it can be seen that the product of the present invention has extremely good dimensional stability during heating durability and has an excellent appearance.

[0025]

[Table 3]

[0026]

[Table 4]

[0027]

[Table 5]

Furthermore, long-term dimensional stability is obtained immediately after molding,
It was carried out until 180 days. Tables 6 and 7 show the actually measured values and the dimensional change divided by the original size at that time. As can be seen from this table, the product of the present invention has excellent dimensional stability in the long term.

[0029]

[Table 6]

[0030]

[Table 7]

Example 3 Expandable resin particles were obtained in the same manner as in Example 1 except that 48 g of n-butane was press-fitted. This was placed in a pressure foaming machine and heated at a steam pressure of 5.0 kg / cm ² for 240 seconds, whereby pre-expanded particles foamed to a bulk density of 0.111 g / cm ³ could be obtained. The expandable resin particles having such foaming performance were adjusted to have a bulk density of 0.333 g / cm ³ and pre-expanded, and then the pre-expanded particles were steamed at a pressure of 6.0 k.
When it was heated for 90 seconds at g / cm ² and foam-molded in the mold,
A good foam molded product was obtained.

[0032]

EFFECTS OF THE INVENTION Thus, the obtained foamed molded article is molded as compared with the conventional product, although the content of the volatile foaming agent in the base resin particles is as small as 3 parts by weight or less and 1 part by weight or more. The product has excellent heat resistance and long-term stability. The foam molding is
Glass transition temperature of base resin -20 ° C. 2
It has excellent heat resistance that does not substantially cause expansion deformation when left for 4 hours.

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Claims (1)

[Claims] 1. A volatile foaming agent having a base resin particle consisting of 90 to 10 parts by weight of a polystyrene resin and 10 to 90 parts by weight of a polyphenylene ether resin in an aqueous medium under pressure and having a boiling point of 90 ° C. or less at normal pressure. And the content of the volatile foaming agent in the base resin particles is 3 parts by weight or less 0.8
More than parts by weight of expandable resin particles are obtained, the expandable resin particles are heated to obtain pre-expanded particles having a bulk density of 0.05 to 0.35 g / cm ³ , and then the pre-expanded particles are filled in a molding die. A method for producing a heat resistant foam, which comprises heating and foaming to obtain a foamed molded article.