JPH05339416A - Production of expansion-molded flame-retardant styrene resin article - Google Patents

Abstract

PURPOSE:To provide a foamed styrene resin article having flame-retardancy and high dimensional stability and free from ignition danger even immediately after the expansion molding. CONSTITUTION:A flame-retardant is attached to the surface of styrene resin particles and an inorganic gas is pressed into the particles to obtain foamable particles. When the foamable particle contains more than specific amount of the inorganic gas, the particle is heated to a specific temperature by contacting with steam, the expanded particles are put into a mold and steam is blown into the mold to heat the particles at a specific temperature and obtain an expansion molded article.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a flame-retardant styrene resin foam molding. Flame-retardant styrenic resin foam moldings are required, for example, for civil engineering, to lay a styrene resin foam plate on soft ground to make stable roads on which trucks can run, and for construction. It is also required to make building wall materials, floor materials, ceiling materials, etc., and is also required for packaging.

[0002]

2. Description of the Related Art It has already been practiced to use a foamed plate made of styrene resin for civil engineering and lay it on soft ground to form a road surface. Moreover, it has already been performed to use a foamed board made of styrene resin for construction and to attach it to a wall, a ceiling, a floor and the like.

However, when a foamed molded article made of a styrene resin is used for these purposes, the styrene resin is liable to burn easily. Therefore, in order to improve this drawback, a styrene resin was blended with a flame retardant. As the flame retardant, halogenated alicyclic hydrocarbons or halogenated alkylallyl ethers have been used, and particularly brominated halogens have been often used.

In order to make the styrene resin foam difficult to burn by using the above flame retardant, it was first attempted to uniformly disperse the flame retardant in the styrene resin. For this reason, a flame retardant was added to a styrene monomer to polymerize styrene in the presence of the flame retardant, or a flame retardant was compounded in the process of impregnating a styrene resin with a foaming agent. However, the flame retardant has caused various drawbacks in producing a foam, such as inhibiting the polymerization of styrene and lowering the softening point of the styrene resin.

Therefore, it has been proposed to use a flame retardant in combination with another auxiliary agent to reduce the amount of flame retardant used. This is described in Japanese Patent Publication No. 62-11016. According to this publication, when the above-mentioned flame retardant is applied to the surface of the expandable styrenic resin particles and the flameproof synergist is impregnated into the resin particles, the flame retardant can be reduced and a flame retardant effect can be expected. Is said. As the flame retardant synergist, it is said that an unstable compound having C—C, O—O or N═N bond, such as dicumyl peroxide, can be used.

However, even when the above-mentioned flame retardant is used, an organic compound has been exclusively used as a foaming agent for foaming a styrene resin. That is, as the blowing agent, aliphatic hydrocarbons such as propane, butane, and pentane, alicyclic hydrocarbons such as cyclohexane, and halogenated aliphatic hydrocarbons such as methyl chloride and methylene chloride are used exclusively. Came.

However, it has been known that an inorganic gas is used as the foaming agent. For example, nitrogen, carbon dioxide,
The use of air or the like as a blowing agent was also described in the literature. However, it is difficult to impregnate such an inorganic gas into a styrene resin, and even if it is impregnated into the resin, it is difficult to foam the styrene resin at a high magnification. Not used.

As described above, since the organic compound has been exclusively used as the foaming agent for foaming the styrene resin, the styrene foam thus obtained has the foaming agent remaining therein. Became. For this reason, in a foam made using a halogenated aliphatic hydrocarbon, the halogenated aliphatic hydrocarbon is volatilized during use, which adversely affects the human body or the environment. In addition, foams made from aliphatic hydrocarbons or alicyclic hydrocarbons have become a risk of ignition.

Therefore, it was decided to store these foams in the factory for about one week after production, confirm that the oxygen index defined by JIS K7201 was less than 26, and then ship them. .. In addition, these foams also contract during use to gradually volatilize the foaming agent, thus creating gaps between the spread foams when used for civil engineering, for example. Exudes soft soil,
It also had the drawback of invalidating the spread of foam.

[0010]

The present invention is intended to provide a styrene resin foam which does not have the above-mentioned drawbacks. That is, the present invention provides a styrene-based resin foam which has no risk of ignition immediately after production, has no adverse effect on human body and environment, and has no dimensional stability during use and has good dimensional stability. It is the one we are trying to provide.

[0011]

The present inventor has found that an inorganic gas, which is considered to be not very effective as a foaming agent, can foam a styrene resin at a high magnification depending on the method of use. That is, the inventor of the present invention contacts the particles of the styrene resin under pressure with an inorganic gas in a gas state to make the expandable particles contain 0.05 mol or more of the inorganic gas per 1 kg of the resin, and immediately form the expandable particles with steam. It was found that when the particles are heated and once expanded, they become expanded at a high magnification. Further, this inventor, after leaving the foamed particles thus obtained once in the atmosphere, follow the conventional method of filling the foamed particles in a perforated mold and foaming again by steam contact, It has been found that a foamed styrene resin foamed molded product can be obtained here.

Furthermore, the present inventor first coated the styrene resin particles with a known flame retardant, and then impregnated the inorganic gas as described above, whereby the organic compound was used as a foaming agent. In contrast, it was found that a small amount of flame retardant, such as 0.5-2 parts by weight with respect to 100 parts by weight of the resin, produces a sufficient non-combustible effect. The present invention has been completed based on such knowledge.

According to the present invention, 0.5-2 parts by weight of a flame retardant is adhered to the surface of 100 parts by weight of styrene resin particles, and then an inorganic gas is brought into contact with it under pressure in a gaseous state, Foamable particles containing 0.05 mol or more of an inorganic gas per 1 kg of resin were prepared and immediately contacted with steam to obtain 10-40 from the Vicat softening point of the styrene resin.
After foaming the resin particles at a temperature as high as ℃ and leaving the expanded particles thus obtained in the atmosphere, they are filled in a molding die and steam is blown into the die again to foam at the above temperature. The gist of the present invention is to provide a method for producing a flame-retardant styrene resin foamed molded product, which comprises foaming particles to obtain a molded product.

The resin used in the present invention is a styrene resin. The styrene-based resin includes a homopolymer of a styrene-based monomer and a copolymer of a styrene-based monomer. The styrene-based monomer contains styrene, methylstyrene, and divinylbenzene. The styrene copolymer includes a copolymer of styrene and acrylonitrile, acrylic acid ester, methacrylic acid ester, ethylene and propylene. Of these, polystyrene is particularly suitable. The styrene resin is used in the form of particles, and the size of the particles is 0.3 mm to 3.0 m.
It is preferably m, and more preferably 0.5-2.0 mm.

In the present invention, various known flame retardants can be used. It is a brominated alicyclic compound, a brominated aromatic compound, a brominated phenylallyl ether, a brominated aromatic polymer, a brominated phenyl acrylate ester, a brominated phenyl methacrylate ester, and the like. For example, hexabromocyclododecane, tetrabromocyclooctane, tribromophenylallyl ether, pentabromophenylallyl ether, tetrabromobisphenol A bisallyl ether, tetrabromobisphenol A bisbromopropyl ether and the like can be used.

When the above flame retardant is solid, it is preferable to use it as fine powder as possible. This is because the fine powder is easy to uniformly adhere to the styrene resin particles. As the fine powder, fine powder of 149 micron passing through a standard screen defined by JIS is desirable. In order to ensure that the flame retardant adheres to the resin particles, it is preferable that a liquid flame retardant having an appropriate viscosity is first coated and then a powdery flame retardant is adhered.
Further, it is preferable that the flame retardant having a relatively low melting point is heated and adhered in a molten state.

The flame retardant may be mixed with other auxiliaries and attached to the resin particles. With other auxiliaries, a coalescence preventing agent for particles when forming expanded particles, a lubricant that facilitates filling the expanded particles into the mold, a fusion promoter during molding, a molding cooling time shortening agent, An antistatic agent, a coloring agent, etc. Specifically, talc, calcium carbonate, colloidal silica, alumina, ethylene bis-stearamide, higher fatty acid, higher fatty acid amide, higher aliphatic alcohol, edible oil, fat, higher fatty acid monoglyceride, paraffin wax, polyethylene wax, stearic acid. A flame retardant can be mixed with zinc or the like and attached to the resin particles.

In order to attach the flame retardant to the styrene resin particles, the flame retardant and the resin particles may be put in a mixer and mixed. A ribbon blender, a tumbler, a Reedige mixer, a Nauter mixer, a super mixer, etc. can be used as a mixer.

In the present invention, it is not necessary to use the flame retardant in a large amount. Usually 0.5 for styrene resin
It is -2.0% by weight, preferably 0.8-1.5% by weight.

Further, in the present invention, it is possible to use the flame retardant synergist as taught by JP-B-62-1016 together with the flame retardant. The flameproof synergist is a compound having an unstable O—O, C—C, N═N bond in the molecule. The compound is, for example, dicumyl peroxide, 1,1-diphenylbicyclohexyl, azodiisobutyromitril and the like. This flameproof synergist may be mixed with the above flame retardant to be adhered to the resin particles, or may be kneaded into the resin particles in advance. The flameproof synergist is preferably used in an amount of 0.1 to 0.5% by weight based on the styrene resin.

In the present invention, the styrene resin particles to which the flame retardant is attached contain the inorganic gas. Air, nitrogen, and carbon dioxide can be used as the inorganic gas. In order to contain the inorganic gas, the particles are placed in a pressure-resistant container capable of being sealed, and the inorganic gas is pressed into the container to bring the inorganic gas into direct contact with the resin particles. At this time, it is preferable that the resin particles are in a stationary state in the container, and the inorganic gas is introduced from the bottom of the container and simultaneously extracted from the top and circulated.

When the styrenic resin particles are impregnated with the inorganic gas, it is desirable to set the temperature within the range where the resin particles do not soften and do not coalesce, that is, the relaxation temperature. This temperature is at least 10 ° C. lower than the Vicat softening point of the styrene resin. The specific temperature depends on the composition of the styrene resin and the type of inorganic gas used. Generally speaking from the relationship between the gas impregnation amount and the pressure vessel,
The contact temperature is desirably low, preferably 40 ° C. or lower. However, if the temperature is 0 ° C or lower, energy consumption is industrially large, which is not preferable. In terms of gas impregnation rate, it is desirable that the temperature is high, but since the content of the gas contained in the particles is small, the temperature is not so high. For industrially stable foaming to a relatively high ratio, the temperature is 5-40 ° C for carbon dioxide and 0-30 ° C for nitrogen or air.

When the styrenic resin particles contain an inorganic gas, the pressure applied to the inorganic gas is changed according to the pressure of the inorganic gas used. When carbon dioxide is used as the inorganic gas, it is 15 kg / cm ² or more, preferably 20-50.
It is set to kg / cm ² . In the case of using nitrogen or air as inorganic gases, a 30kg / cm ² or more pressure, preferably 45-90kg / cm ^2. The time for inclusion is determined on the basis that the resin particles contain the inorganic gas required for foaming. 0.1 kg / kg of resin.
The time required to contain 05-0.5 mol of inorganic gas is 1-
It takes 3 hours, but it takes a longer time to contain 0.5 to 4.0 mol of the inorganic gas per 1 kg of the resin in order to obtain the particles expanded at a high expansion ratio.

In the present invention, it is necessary that the styrene resin particles contain a certain amount of the inorganic gas. The specified amount is 0.0% of inorganic gas per 1 kg of resin.
It means 5 mol or more.

The fact that the content of the inorganic gas is 0.05 mol or more per 1 kg of the resin is confirmed by the heating weight loss method as follows. After being impregnated with the inorganic gas, the pressure in the pressure-resistant container was removed, and a part of the expandable resin particles was immediately weighed, and then 80
After heating for 3 hours in a constant temperature bath at ℃ to dissipate all the inorganic gas, it is slowly cooled and weighed again to confirm the impregnated amount. For example, in the case of carbon dioxide, carbon dioxide content (mol) / resin (k
g) = Weight immediately after taking out (g) -Weight after heating (g) / Molecular weight 44 × 1000 (g) / Weight after heating (g).

The expandable particles containing a predetermined amount of inorganic gas are taken out of the closed container and immediately heated to be expanded. For this purpose, it is preferable to introduce resin particles into a preheated foaming machine at the same time as depressurization or to directly send the resin particles from a pressurized state to a prefoaming machine for foaming. In any case, it is necessary to foam while the resin particles contain 0.05 mol or more of inorganic gas per 1 kg of resin, and it is possible to foam within 30 minutes after depressurization, especially within 2 minutes. preferable.

As described above, in order to foam the expandable particles immediately after they have been formed, the container to be foamed is previously heated to a suitable foaming temperature or foamed in a pressurized gas heated to the proper foaming temperature. It is preferable to transfer the functional particles. A pressurized gas of about 0.5 to 2.0 kg / cm ² G is sufficient.

In order to expand the expandable particles containing the inorganic gas, it is necessary to heat the particles. Steam is used for this heating, and the steam is brought into direct contact with the resin particles.
As the water vapor at this time, it is preferable to use water vapor having a dew point of 60 to 100 ° C. or a mixed gas of water vapor and air. Among them, it is preferable to use water vapor having a dew point of 70-100 ° C or a mixed gas of water vapor and air. This water vapor causes the expandable particles to have a value of 1 above the Vicat softening point of the resin.
0-40 ° C higher temperature, more preferably 15-35
Heat to a temperature higher by ℃ to foam. Thus expanded particles, ie pre-expanded particles, are obtained. Foaming time is 10
It is as short as -180 seconds, usually 20-90 seconds.

The above-mentioned expanded particles are left in the atmosphere. There is no particular limitation on the time for leaving it, but it is determined on the basis that the air in the atmosphere supplements that the inside of the bubbles generated by foaming cools after foaming and becomes depressurized, and returns to normal pressure. The time is about 3 hours. Instead of leaving it in the air, it may be left in an atmosphere of carbon dioxide or nitrogen.

The foamed particles left in the atmosphere are then filled in a molding die. The mold for molding is the same mold that has been used so far to form a foamed molded product from expanded particles of a styrene resin. The mold has a structure in which a mold cavity having the shape of the molded body to be obtained, a large number of small holes are formed on the mold cavity surface, and a vacant chamber for introducing steam is provided outside. is there. The small holes allow the passage of gas,
It is a small hole that does not allow passage of softened resin.
The degree of filling is such that the expanded particles fill the mold cavity.

After the foamed particles are thus filled in the mold, steam is blown into the mold to foam the expanded particles. At this time, steam is brought into direct contact with the expanded beads so that the expanded beads are separated from the Vicat softening point of the styrene resin by 10-4.
Try to heat to a temperature as high as 0 ° C. Then, the heated expanded particles further expand and expand in the mold cavity. At the same time, the air present in the mold cavity and the gas volatilized from the foamed particles escape from the mold through the small holes. In this way, the expanded particles push the gas in the mold cavity out of the mold, and the adjacent particles are fused to each other to form an expanded molded body. Then, the molded body is cooled and taken out from the mold. In this way, a styrene resin foam molding is obtained.
The molding time for this is 10-180 seconds, usually 15-6.
0 seconds.

Although the present invention is characterized in that an inorganic gas is used as the foaming agent, it does not prevent the use of an organic foaming agent in a small amount. For example, propane,
It does not prevent the use of butane or the like in an amount of 0.5 mol or less per kg of the resin.

[0033]

According to the method of the present invention, since the flame retardant is adhered to the surface of the styrene resin particles and then the inorganic gas is brought into contact with the styrene resin particles to form the expandable particles, the foaming agent is the inorganic gas. In addition, since it is possible to make the foam flame-retardant just by using a small amount of flame retardant, and because the foam can be made flame-retardant just by attaching the flame retardant to the resin particles,
It is easy to make the foam flame retardant. Also, resin 1
Inorganic gas was contained in an amount of 0.05 mol or more with respect to kg, and then steam was brought into contact therewith to foam the resin particles at a temperature higher by 10 to 40 ° C. than the Vicat softening point of the resin. Is relatively well foamed and is therefore sufficient for civil engineering or packaging foam moldings. Further, after leaving the foamed particles in the atmosphere, the foamed particles are filled in a molding die, and steam is blown into the mold to foam the particles at a temperature higher by 10-40 ° C. than the Vicat softening point of the resin. Since it is a molded body, the obtained foamed molded body has a sufficient expansion ratio to be used as a foamed molded body for civil engineering construction or packaging. Moreover, since the inorganic gas is used as the foaming agent, the inorganic gas does not remain in the foam molded body, and therefore the foam does not ignite or shrink. Therefore, there is provided a flame-retardant styrene resin foam molded article which has no fire hazard, has no adverse effect on human body and environment, and can be shipped and used immediately after manufacturing. Will be possible.

Next, the advantages of the method of the present invention will be clarified by giving Examples and Comparative Examples.

[0035]

Example 1 Polystyrene having a Vicat softening point of 95 ° C. was used as the resin, and carbon dioxide was used as the inorganic gas. 150 g of polystyrene particles having a particle size of 0.7 to 1.0 mm were put in a super mixer, and 1.8 g of hexabromocyclododecane as a flame retardant and 0.3 g of azodiisobutyronitrile as a flame retardant auxiliary were added. Stir to coat the surface. Next, 0.2 g of calcium carbonate was added and stirred to adhere to the surface.

The particles thus obtained were placed in a pressure-resistant container having a volume of 300 ml and sealed, and carbon dioxide gas was held therein at 20 ° C. and 20 atm for 3 hours to inject carbon dioxide into the particles. Then, the pressure was removed, and the resin particles were immediately taken out from the pressure resistant container to obtain expandable particles. When the content of carbon dioxide in the expandable particles was examined by a heating weight loss method, the expandable particles contained 1.5 mol of carbon dioxide per 1 kg of the resin.

After taking out the expandable particles from the pressure-resistant container, steam was brought into contact with the particles within 1-2 minutes.
The particles were expanded at 6 ° C. to give expanded particles. At the time of this foaming, the expandable particles contained 1.1 mol of carbon dioxide with respect to 1 kg of the resin when the content of carbon dioxide was measured by the heating weight loss method. The expanded particles were left in the atmosphere for 3 hours.

Then, the foamed particles are 400 m in length.
It is filled in a molding die having a mold cavity of m × width 300 mm × thickness 20 mm, and steam is blown into the mold to obtain 1
It was expanded again at a temperature of 26 ° C. to obtain a foamed molded product having a foaming ratio of 60 times.

The foamed molded product had good quality because the foamed particles were well fused. With respect to this foamed molded product, the oxygen index showing the flame retardancy was measured according to the regulations of JIS K 7201. The oxygen index was 26.8 immediately after the production, and the condition of sufficient flame retardancy was satisfied. Further, when the contraction after 360 days was examined, the contraction rate was only 0.3%. Therefore, it was confirmed that it can be sufficiently used as a styrene-based foamed molded product for civil engineering and construction.

[0040]

[Embodiment 2] This embodiment was carried out in the same manner as the embodiment 1, except for the differences. As the flame retardant, 0.9 parts by weight of bisallyl ether of tetrabromobisphenol was used, and the impregnation temperature of carbon dioxide was 30%.
The expandable particles containing 1.0 mol of carbon dioxide with respect to 1 kg of resin were obtained.

Within 2 minutes after removing the expandable particles from the pressure-resistant container, the particles were added to 0.8 kg / kg of resin.
When it contained mol carbon dioxide, it was contacted with steam at 124 ° C. to form expanded particles.

Then, the foamed particles were filled in the molding die used in Example 1, and steam at 124 ° C. was blown into the die to obtain a foamed molding having a foaming ratio of 50 times.

The foamed molded article had good quality because the foamed particles were well fused, and had an oxygen index of 28.5.
However, the flame retardancy was sufficient. In addition, it was confirmed that the shrinkage ratio after lapse of 360 days was 0.25%, and there was almost no shrinkage.

[0044]

[Embodiment 3] This embodiment was carried out in the same manner as the embodiment 1, but only the different points will be explained as follows. As a flame retardant, tetrabromocyclooctaene 1.
0 parts by weight and nitrogen gas as a foaming agent are used.
The particles were impregnated for 12 hours at 35 ° C. under a pressure of 35 kg / cm ² G to obtain expandable particles containing 0.1 mol of nitrogen gas per 1 kg of the resin.

Within 2 minutes after taking out the expandable particles from the pressure-resistant container, the particles were added to 0.0 kg / kg of resin.
When it contained 7 mol of nitrogen gas, it was brought into contact with steam at 135 ° C. for foaming.

Then, the foamed particles are filled in a molding die, and steam at 135 ° C. is blown into the die,
A foamed molded product having an expansion ratio of about 5 times was obtained.

The foamed molded article had good quality because the foamed particles were well fused. Its oxygen index was 27.8, and it showed sufficient flame retardancy, and the shrinkage ratio after the lapse of 360 days was 0.05%, which showed almost no shrinkage.

[0048]

Example 4 This example was carried out in the same manner as in Example 1. The following is a description of only the differences of this embodiment from the first embodiment. 2.0 parts by weight of tribromophenyl allyl ether was used as a flame retardant, carbon dioxide was used as a foaming agent, and the mixture was maintained at 20 ° C. under a pressure of 45 kg / cm ² G for 4 hours to give 3.0 kg per 1 kg of resin. Effervescent particles containing moles of carbon dioxide were obtained.

Within 2 minutes after taking out the expandable particles from the pressure-resistant container, when the expandable particles contained 2.4 mol of carbon dioxide with respect to 1 kg of the resin, steam of 107 ° C. was added thereto. Contact was made to foam.

Then, the expanded particles were filled in a molding die, and steam at 107 ° C. was blown into the molding die to obtain a foamed molded article having an expansion ratio of 61 times.

The foamed molded product had good quality because the foamed particles were well fused. Its oxygen index was 27.8, and it had sufficient flame retardancy. 360
The shrinkage ratio after the lapse of days was 0.35%, and there was almost no shrinkage.

[0052]

[Embodiment 5] This embodiment was carried out in the same manner as the embodiment 1, but the different points are explained as follows. 1.0 parts by weight of pentabromophenyl allyl ether was used as a flame retardant, carbon dioxide was used as a foaming agent, and at 83 ° C.
It was kept under a pressure of 25 kg / cm ² G for 3 hours to obtain expandable particles containing 0.65 mol of carbon dioxide per 1 kg of the resin.

Within 2 minutes after removing the expandable particles from the pressure-resistant container, when the expandable particles contained 0.5 mol of carbon dioxide with respect to 1 kg of the resin, the dew point was 70 ° C and the temperature was 130 ° C. The steam-containing air at the temperature of was contacted to foam.

Thereafter, the expanded particles were filled in a molding die, and steam at 130 ° C. was blown into the molding die to obtain a foamed molded article having a foaming ratio of 30 times.

In this foamed molded product, the foamed particles were well fused and of good quality. The oxygen index of this molded product was 27.0, and the shrinkage ratio after 360 days was 0.
It was 2%, and the flame retardancy and dimensional stability were good.

[0056]

[Sixth Embodiment] This embodiment was carried out in the same manner as the first embodiment, but the different points are as follows. 1.0 parts by weight of bisdibromopropyl ether of tetrabromobisphenol was used as a flame retardant, air was used as a foaming agent, and the mixture was kept at 10 ° C. under a pressure of 40 kg / cm ² G for 12 hours to give 0 kg / kg of resin. Effervescent particles containing 0.25 mol of air were obtained.

Within 2 minutes after taking out the expandable particles from the pressure-resistant container, when the expandable particles contained 0.2 mol of air per 1 kg of the resin, steam at 106 ° C. was brought into contact with the expandable particles. , The particles were foamed.

Then, the expanded particles were filled in a molding die, and steam at 108 ° C. was blown into the molding die to obtain a foamed molded article having an expansion ratio of 15 times.

In this foamed molded product, the foamed particles were well fused and of good quality. The oxygen index of this molded product was 26.3, and the shrinkage ratio after 360 days was 0.
It was 1% and the flame retardancy and dimensional stability were good.

[0060]

[Embodiment 7] This embodiment was carried out in the same manner as Embodiment 1, but only the differences will be described as follows. As the resin, a copolymer of maleic anhydride and styrene having a Vicat softening point of 110 ° C. is used, as a flame retardant, 1.5 parts by weight of bisallyl ether of tetrabromobisphenol is used, and as a blowing agent, carbon dioxide. Was maintained at 20 ° C. under a pressure of 30 kg / cm ² G for 3 hours to obtain expandable particles containing 2.2 mol of carbon dioxide with respect to 1 kg of the resin.

Within 2 minutes after taking out the expandable particles from the pressure-resistant container, the expandable particles were found to be 1.
When it contains 9 moles of carbon dioxide, it contains 135 ℃
Was contacted with water vapor to foam the particles.

Thereafter, the expanded particles were filled in a molding die, and steam at 134 ° C. was blown into the molding die to obtain a foamed molded article having an expansion ratio of 45 times.

In this foamed molded product, the expanded particles were well fused and of good quality. The oxygen index of this molded product was 26.0, and the shrinkage ratio after 360 days was 0.
It was 2%, and the flame retardancy and dimensional stability were good.

[0064]

COMPARATIVE EXAMPLE 1 This comparative example was carried out in the same manner as in Example 3 until the expandable particles were obtained, but the resulting expandable particles were left for a long time, so that the content of the inorganic gas was small, and the results were sufficient. This is an example in which foaming did not occur.

The nitrogen gas-containing expandable particles obtained in Example 3 were taken out of the pressure vessel and allowed to stand in the air for about 1 hour, and the particles contained 0.03 mol of nitrogen gas per 1 kg of the resin. At this time, as in Example 3, steam of 135 ° C. was brought into contact therewith to foam.

Thereafter, the foamed particles were filled in a molding die in the same manner as in Example 3, and an attempt was made to blow steam at 135 ° C. into the molding die to form a foamed molded body, but it was about doubled. Only foaming occurred, and a good molded product could not be obtained due to insufficient foaming.

[0067]

COMPARATIVE EXAMPLE 2 This comparative example was carried out in the same manner as in Example 2, except that the temperature of steam was changed. The details are as follows.

The expandable particles obtained in Example 2 were used, and when the particles contained 0.8 mol of carbon dioxide with respect to 1 kg of resin, steam at 142 ° C. was brought into contact with the expanded particles to obtain expanded particles. ..

Then, the foamed particles were filled in the molding die used in Example 1, and steam at 125 ° C. was blown into the die to obtain a foamed molded article having an expansion ratio of 60 times.

This foamed molded product was not good. The reason is that when the temperature of the steam when the foamed particles are 142 ° C is 40 ° C from the Vicat softening point 95 ° C of the resin.
This is because the foamed particles contracted because of the high temperature.

[0071]

COMPARATIVE EXAMPLE 3 This comparative example was carried out in the same manner as in Example 2, except that the temperature of water vapor was changed. The details are as follows.

In this comparative example, the expandable particles obtained in Example 2 were used in the same manner as in Comparative Example 2, and steam was brought into contact with the expandable particles for foaming. Specifically, the expandable particles have a temperature of 100 ° C.
The water vapor was contacted with the water vapor to give foamed particles, which were placed in a molding die and the temperature of the water vapor blown into the metal mold was 125 ° C.

As a result, the obtained foamed molded product foamed 30 times, but was not good. The reason is that the temperature of the steam at the time of forming the expanded particles is 100 ° C. is too low,
This is because foaming was not sufficient. That is, this is because the condition that the temperature of steam of 100 ° C. when forming foamed particles is 10 ° C. or more higher than the Vicat softening point of 95 ° C. of the resin is not satisfied.

[0074]

COMPARATIVE EXAMPLE 4 This comparative example was carried out in the same manner as in Example 2, except that the temperature of steam was changed. The details are as follows.

In this comparative example, as in Comparative Examples 2 and 3, the expandable particles obtained in Example 2 were used and these were foamed with steam. Specifically, the temperature of the steam when foaming the expandable particles was 125 ° C., and the temperature of the steam blown into the molding die was 100 ° C.

As a result, the foamed molded product obtained was foamed about 60 times, but was not satisfactory because of poor fusion bonding. The reason is that the temperature of the steam blown into the mold is 1
The temperature is 00 ° C, which is 5 ° C higher than the Vicat softening point of the resin,
This is because the condition that the temperature is higher by 10 ° C or more does not meet the condition that the temperature is higher by 10 ° C.

[0077]

COMPARATIVE EXAMPLE 5 This comparative example was carried out in the same manner as in Example 2, except that the temperature of steam was changed. The details are as follows.

In this comparative example, the expandable particles obtained in Example 2 were used as in Comparative Examples 2, 3 and 4. The temperature of the steam when foaming this was changed, the temperature of the steam when forming the expanded particles was 125 ° C, and the temperature of the steam when forming the molded body was 142 ° C.

As a result, the foamed molded product obtained was foamed about 60 times, but it was not satisfactory because the shrinkage upon molding was large. The reason is that the temperature of water vapor at the time of forming a molded body is 142 ° C., which is 47 ° C. higher than the Vicat softening point 95 ° C. of the resin, and therefore it must be below the Vicat softening point plus 40 ° C. Because I have not done it.

[0080]

Comparative Example 6 This comparative example was carried out in the same manner as in Example 3, except that the amount of flame retardant used was reduced. The details are as follows.

In this comparative example, tetrabromocyclooctane was used as the flame retardant as in Example 3, but the amount was reduced to 0.3 parts by weight, and otherwise nitrogen was used in the same manner as in Example 3. Gas was impregnated to obtain expandable particles containing 0.1 mol of nitrogen gas with respect to 1 Kg of resin.

The expandable particles were 0.0 per 1 Kg of resin.
When 5 mol of nitrogen gas was contained, steam of 135 ° C. was contacted to form expanded particles in the same manner as in Example 3, and further steam of 135 ° C. was contacted in the molding die to obtain a foaming ratio of about A 5-fold foam molded product was obtained.

In this foamed molded product, the expanded particles were well fused and of good quality, but the oxygen index was 19.0 and the flame retardancy was poor.

[0084]

COMPARATIVE EXAMPLE 7 This comparative example was carried out in the same manner as in Example 3 and thus in Comparative Example 6 except that the amount of flame retardant used was increased. The details are as follows.

In this comparative example, as in Example 3 and Comparative Example 6, tetrabromocyclooctane was used as the flame retardant, but the amount was increased to 2.5 parts by weight,
Except for this, the expandable particles were obtained in the same manner as in Example 3 and Comparative Example 6, and the expandable particles were further expanded to have an expansion ratio of about 5.
A double foam molding was obtained.

This expanded molded article was not satisfactory because the expanded particles were not well fused.

[0087]

Comparative Example 8 This comparative example is an example using an aliphatic hydrocarbon that has been used up to now as a foaming agent. The details are as follows.

The Vicat softening point used in Example 1 was 9
A mixture of 1.6 parts by weight of tetrabromocyclooctane as a flame retardant and 0.3 parts by weight of dicumyl peroxide as a flame retardant was added to 100 parts by weight of polystyrene particles at 5 ° C., and a 5-liter autoclave equipped with a rotary stirrer was added. To 2.0 liters of water, polystyrene 2.0 kg, magnesium pyrophosphate 6 g, sodium dodecylbenzene sulfonate 0.3 g, flame retardant 32 g (1.6 parts by weight), dicumyl peroxide 6 g (0.3 parts by weight). Put, stir and disperse, close the autoclave, press fit 140 g of butane,
Impregnation is carried out at 110 ° C. for 18 hours at 18 atmospheres, cooled to 40 ° C., opened, washed, dehydrated and dried to give 2.6 g of calcium carbonate.
Was surface-coated with a super mixer to obtain flame-retardant expandable polystyrene particles. When this was aged for 2 days at 20 ° C., the expandable particles were
It contained 1.0 mol of butane.

After leaving the expandable particles for a while, when the particles contained 0.85 mol of butane with respect to 1 Kg of resin, they were foamed by contacting with steam at 100 ° C. This was left as particles for a while, then put in the molding die used in Example 1, steam of 117 ° C. was blown into the die to heat the particles,
A foamed molded product which was foamed about 50 times was obtained.

The foamed molded product was of good quality because the particles were well fused to each other. However, its oxygen index was 25.0, and the flame retardancy was insufficient despite the large amount of flame retardant used. In particular, since the foamed molded article immediately after molding contained 0.4 mol of butane per 1 kg of resin, the butane content should be reduced to 0.25 mol or less per 1 kg of resin in order to improve the oxygen index to 26 or more. Had to let. For this purpose, it was necessary to keep the molded body at around 60 ° C. for 24 hours or more.

[0091]

Comparative Example 9 This Comparative Example was carried out in the same manner as Comparative Example 8 except that pentane was used instead of butane as the blowing agent. The details are as follows.

The pentane was kept at 110 ° C. and 7.5 atm for 5 hours to obtain pentane-containing expandable particles. The expandable particles contained 0.85 mol of pentane per 1 kg of the resin.

After the above expandable particles were allowed to stand for a while, when the particles contained 0.75 mol of pentane per 1 kg of resin, steam was contacted with 100 ° C. to expand the particles, and the expanded particles were formed. After that, leave this for a while,
Then, this was put into the molding die used in Example 1, and steam at 117 ° C. was blown into the die to heat the particles, thereby obtaining a foamed molded product which was foamed about 50 times.

This foamed molded product had good quality, but its oxygen index was 25.0, and its flame retardancy was insufficient despite the large amount of flame retardant used. In particular, the foamed product immediately after molding has 0.45 per 1 kg of resin.
Since it contained moles of pentane, it had an oxygen index of 26
In order to improve the above, it was necessary to reduce the pentane content to 0.25 mol or less. For this purpose, it was necessary to keep the molded body at about 60 ° C. for 24 hours or more.

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Claims (2)

[Claims] 1. 0.5 to 2 parts by weight of a flame retardant is adhered to the surface of 100 parts by weight of styrene resin particles, and an inorganic gas is brought into contact with the surface of the styrene resin particles under pressure to give a resin 1k.
An expandable particle containing 0.05 mol or more of an inorganic gas relative to g was prepared, and steam was immediately brought into contact with the expanded particle to foam the resin particle at a temperature higher by 10 to 40 ° C. than the Vicat softening point of the styrene resin. After leaving the foamed particles thus obtained in the atmosphere, they are filled in a molding die,
A method for producing a flame-retardant styrene resin foam molded article, which comprises blowing water vapor into a mold to foam the expanded beads at the above temperature to obtain a molded article. 2. The flame-retardant styrenic resin according to claim 1, characterized in that after forming the expandable particles, steam is contacted with the expandable particles within 30 minutes to form expanded particles. Method for producing foamed molded article.