JPH0547577B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention relates to a method for manufacturing a flame-retardant styrene resin plate-like foam. (Prior Art) Generally, flame-retardant resin is made by mixing a flame retardant with a synthetic resin. Various types of flame retardants are known, but they can be broadly classified into inorganic compounds and organic compounds. Antimony oxide, phosphate, etc. are used as inorganic compounds, and various halogen compounds are used as organic compounds. If the styrene resin is flame retardant and used as a non-foaming material, there is no particular difficulty. If it is non-foamed,
This is because it is sufficient to simply mix the flame retardant with the styrene resin. However, when trying to make a foam from flame-retardant styrene resin, it is not as easy to clean up as when it is made from non-foamed material. This is because the flame retardant may inhibit the foamability of the resin. For this reason, it is necessary to specially select and use flame retardants and to give special consideration to the method of use. Conventionally, aliphatic hydrocarbons such as propane and butane have often been used as blowing agents for styrenic resins. Since aliphatic hydrocarbons generally have poor reactivity, as long as they are used, the relationship between the blowing agent and the flame retardant does not pose much of a problem. However, since aliphatic hydrocarbons are easily flammable, there is a risk of fire when they are used, and it is also difficult to control the bubbles themselves, so the method using aliphatic hydrocarbons cannot be said to be superior. Therefore, halogenated aliphatic hydrocarbons have come to be used as blowing agents instead of aliphatic hydrocarbons. However, among the halogenated aliphatic hydrocarbons that are used to safely obtain good foams, perchlorofluorocarbons (e.g. dichlorodifluoromethane, trichloromonofluoromethane) are in the stratosphere and harmful ultraviolet-B ( Its use is regulated because it is known to absorb light in the wavelength range of 290 to 320 nm, preventing it from reaching the earth's surface and destroying the ozone layer, which maintains atmospheric temperature. Therefore, the present inventor attempted to obtain a plate-shaped polystyrene foam for general molding using monochlorodifluoromethane (hereinafter abbreviated as F22) as a blowing agent in place of perchlorofluorocarbons. A plate-shaped foam with good strength was obtained. However, for polystyrene
Due to the large dissipation of F22, the molded product's thermal insulation properties were not suitable for use as a heat insulating material. Therefore, as a result of investigating various styrene-based resins with low F22 dissipation properties, it was found that using a copolymer of styrene and acrylonitrile is effective. On the other hand, the present inventor used hexabromocyclododecane and 2,2'-bis-(4-allyloxy-
We found that 3,5-dibromophenyl)-propane and/or 2,4,6-tribromophenyl allyl ether are suitable and proposed an extrusion method. This method is described in Japanese Patent Publication No. 60-29743. The present inventor combined the above two methods, used F22 and methyl chloride as the blowing agent, used a copolymer of styrene and acrylonitrile as the styrene resin, and added the above mixed flame retardant to this. An attempt was made to create a foam with good flammability and high heat insulation properties. However, this method could only produce a colored, easily flammable foam. (Problems to be Solved by the Invention) The present inventor has improved the above-mentioned drawbacks, and has used a mixture of F22, which has a low ozone depleting ability, and other halogenated hydrocarbons as a blowing agent, and used it as a styrenic resin.
A copolymer of styrene and acrylonitrile with low F22 dissipation property is used, and a mixture of a multi-membered cyclic compound containing a halogen element and an aromatic compound is used as a flame retardant to achieve flame retardancy and heat insulation properties. To provide a method for producing a flame-retardant styrene resin plate-like foam. (Means for Solving the Problem) That is, the present invention uses a copolymer of styrene and acrylonitrile as the styrene resin, and uses 1.6 to 0.2 moles of monochlorodifluoromethane and 0.2 to 0.2 moles of monochlorodifluoromethane per 1 kg of the styrene resin as a blowing agent. A mixture of 2.0 mol of halogenated aliphatic hydrocarbons is used at 5 to 20 wt% based on the styrenic resin, and hexabromocyclododecane and pentabromotoluene are used as flame retardants at a weight ratio of 1:0.1.
This is a method for producing a flame-retardant styrene-based resin plate-like foam, characterized in that a mixture of the present invention and the styrene-based resin at a ratio of 0.5 to 10 wt% is used in a ratio of 1:1 to 1:1. The present invention will be described in more detail. The styrenic resin used in the method of the present invention is a copolymer of styrene and acrylonitrile. Moreover, this styrene-based resin may also include a blend obtained by mixing this copolymer with other resins (for example, polyethylene, synthetic rubber, etc.). However, the blend contains 50wt% styrene.
or more. As the blowing agent, a mixture of 1.6 to 0.2 mol of monochlorodifluoromethane (F22) and 0.2 to 2.0 mol of other halogenated aliphatic hydrocarbons is used per 1 kg of styrenic resin as described above.
The reason is that if the amount of F22 added is 1.6 mol or more per 1 kg of styrene resin, molding will be defective, and if it is less than 0.2 mol, the insulation properties will be poor. Further, if the amount of other halogenated aliphatic hydrocarbons is 0.2 mol or less, foaming cannot be achieved at a high rate, and if it is 1.6 mol or more, the heat insulation properties are poor. Other halogenated aliphatic hydrocarbons used include methyl chloride, methylene chloride, ethyl chloride, dichloromonofluoromethane (F21), monochlorodifluoroethane (F142b), difluoroethane (F152a), etc.
Furthermore, the amount of dichlorodifluoromethane (F12) that is said to have a large ozone-depleting ability is regulated, but it can be mixed in any proportion with the mixture of F22 and other halogenated aliphatic hydrocarbons. . The mixing ratio of F22 and other halogenated aliphatic hydrocarbons and/or F12 is appropriately determined depending on the properties of the intended foam. Generally, these mixed blowing agents are added in an amount of 5 to 20% by weight based on the resin. The reason is that it is not possible to foam at a high magnification with less than 5wt%;
If it exceeds 20wt%, the blowing agent will bump from the resin,
This is because it becomes difficult to foam uniformly and finely. These mixed blowing agents may be added to the resin separately, or may be mixed and added before being added to the resin.
Further, the additive may be added in the extruder, or may be added to the resin before being put into the extruder. In this invention, a mixture of hexabromocyclododecane and pentabromotoluene is used as a flame retardant in a weight ratio of 1:0.1 to 1:1. If the amount of toluene is less than 0.1, extrusion stability will deteriorate if added in an amount sufficient to exhibit flame retardancy, and if 1 part of hexabromocyclododecane is added to 1 part of pentabromotoluene or more, the melting temperature of pentabromotoluene is high, so styrene-based This is because it is not uniformly dispersed in the resin. The amount of these flame retardants added is 0.5 to 10 wt% based on the styrene resin. This is because the effect of flame retardant is not fully demonstrated below 0.5wt%, and conversely, below 10wt%
This is because, if the amount exceeds that amount, not only will the effect of the increase not be apparent, but also the extrusion stability and foamability will deteriorate. Further, among the flame retardants used, pentabromotoluene has a high melting temperature and therefore has poor compatibility with styrenic resins. Therefore, it is desirable to use highly soluble methyl chloride, ethyl chloride, methylene chloride, etc. in the mixed blowing agent used. The order in which the blowing agent and flame retardant are added to the styrenic resin is not particularly limited. However, a preferred method is to dry blend the flame retardant with the styrenic resin, place this mixture in an extruder, and press the blowing agent into the extruder. In addition, in the method of the present invention, in addition to foaming agents and flame retardants, stabilizers, bubble control agents such as talc, pigments,
Colorants such as dyes and surfactants such as nonionic surfactants can be added. Among the stabilizers used here, a particularly preferred one is phosphite, and this compound has the effect of stabilizing flame retardants as well as monochlorodifluoromethane (F22) used as a blowing agent. This is an effective stabilizing function. (Function) According to the method of the present invention, since a mixture of F22 and other halogenated aliphatic hydrocarbons is used as the blowing agent, there is a greater risk of the blowing agent causing a fire than when the blowing agent is an aliphatic hydrocarbon. Furthermore, there is less risk of ozone depletion than when the blowing agent is perchlorofluorocarbons, and by appropriately selecting the mixing ratio of F22 and other hydrogen halides, it is possible to It is possible to generate large bubbles and freely expand the foam to a high expansion ratio, and it is possible to obtain a good, large foam with no internal cavities. In addition, since a copolymer of styrene and acrylonitrile was used as the styrene resin, this F22
It is possible to prevent the dissipation of heat and improve heat insulation, and also to obtain a molded product with a smooth surface and strong strength. Furthermore, since a mixture of hexabromocyclododecane and pentabromotoluene is used as a heat retardant, it dissolves well and uniformly in the styrene and acrylonitrile copolymer, and also has high flame retardancy because it does not deteriorate the resin. A styrenic resin plate-like foam can be obtained. EXAMPLES The method of the present invention will be specifically explained below with reference to Examples and Comparative Examples. Hereinafter, parts simply refer to parts by weight. Example 1 0.7 part of finely powdered talc as a bubble regulator, 0.24 part of trisnonyl phenyl phosphorite as a stabilizer, and dibutyltin malate polymer to 100 parts of a copolymer of styrene and acrylonitrile (Nippon Steel Chemical Estyrene AS-61) Add 0.1 parts of hexabromocyclododecane (HBCD) and pentabromotoluene (PBT) as flame retardants.
The mixture containing 0.2 part of the mixture was supplied at a rate of about 15 kg/h to an extruder with a 40 mm diameter and a 50 mm diameter extruder connected to each other. A mixture of 5.3 parts of monochlorodifluoromethane (F22) as a blowing agent and 5.3 parts of methyl chloride (MC) as another halogenated aliphatic hydrocarbon was used, and the mixture was injected into the resin from near the tip of an extruder with a diameter of 40 mm. did. As a base, the tip has a thickness of 0.6
A rectangular resin outlet with a width of 60 mm and a length of 5 mm is used, and the tip of the cap has an inlet dimension substantially equal to the resin outlet dimension and an outlet dimension of 12 mm in thickness.
A molding tool was used in which the wall of the resin passage was coated with fluororesin, and the resin passage had a length of 50 mm, which was 120 mm wide and gently expanded from near the inlet toward the outlet. The resin fed to the extruder with a diameter of 40 mm is 220
The resin was heated to ℃, melted, and kneaded, then the resin temperature was adjusted to about 140℃ using an extruder with a diameter of 50 mm, and the resin was supplied to the die.
The resin discharged from the nozzle foams greatly and has a thickness of 20 mm.
~22mm, extrusion stability with width 175~200mm,
The moldability was also good. The results are shown in Table 1.

[Table] Examples 2 to 4 The same composition as in Example 1 was used except for those shown in Table 1 as the flame retardant and blowing agent, and Example 1
A foam was produced by extrusion foaming using the same extruder and operating conditions. The resulting foam had good extrusion stability and moldability. The properties of the foam obtained are shown in Table 1. Comparative Examples 1-2 Foams were produced in the same manner as in Example 1 using the blending ratios shown in Table 1. The properties of the foam obtained are shown in Table 1. As is clear from this table,
Even if the amount of flame retardant was the same as in the example, when only one kind was used, the appearance, extrusion stability, and bubble size were good, but the flame retardance was lower than in the example. It's inferior. Comparative Examples 3-4 Foams were produced in the same manner as in Example 1 using the blending ratios shown in Table 1. The properties of the foam obtained are shown in Table 1. These foams had poor extrusion stability and the molded products were also severely colored. Furthermore, the bulk density was approximately 28 Kg/m ³ immediately after extrusion due to deterioration of the flame retardant, but the molded product immediately shrank and its surface was rough. Also, these did not self-lyse. Comparative Example 5 The same as Example 1 except that a styrene-maleic anhydride copolymer (Sekisui Plastics Dylarc #332) was used as the styrene resin. The extruded molded product had a density of 38 Kg/m ³ and no coloration was observed, but the surface was not smooth and did not self-extinguish. Comparative Example 6 This was the same as in Example 1 except that polystyrene (Nippon Steel Chemical Estyrene G-10) was used as the styrene resin. The extruded molded product had a density of 38Kg/ ^m3 , good moldability, and excellent flame retardancy of n=2.3.
There was a large amount of F22 dissipated from the molded product, and the heat insulation properties were not as expected. Next, Table 2 shows the measurement results of the amount of F22 dissipated and the thermal conductivity of the molded product (over 1 month over time) based on the differences in styrene resins.

[Table] In the table, the amount of dissipation (wt%) is determined by gas chromatography and is included in the molded product immediately after extrusion.
The amount of F22 and the amount of F22 contained in the molded product after aging were quantified, and the calculation was made from the difference between them. (Effects of the Invention) As already detailed, according to the present invention, a mixture of monochlorodifluoroethane and other halogenated aliphatic hydrocarbons is used as the blowing agent, and a copolymer of styrene and acrylonitrile is used as the styrene light resin. , it is possible to obtain a smooth and strong foam with a high expansion ratio that is uniform and fine, and a plate-shaped foam with high heat insulation properties can be obtained because the copolymer of styrene and acrylonitrile prevents F22 from escaping. . Furthermore, since a mixture of hexabromocyclododecane and pentabromotoluene was used as a flame retardant, sufficient flame retardancy could be obtained without deteriorating the copolymer of styrene and acrylonitrile. In this way, a plate-shaped foam with good flame retardancy can be easily obtained.

Claims (1)

[Claims] 1 A copolymer of styrene and acrylonitrile is used as the styrene resin, and a mixture of 1.6 to 0.2 moles of monochlorodifluoromethane and 0.2 to 2.0 moles of halogenated aliphatic hydrocarbon is added as a blowing agent to 1 kg of the styrene resin. 5 to 20 wt% based on the resin, and 0.5 wt% of a mixture of hexabromocyclododecane and pentabromotoluene as flame retardants at a weight ratio of 1:0.1 to 1:1 based on the styrene resin. A method for producing a flame-retardant styrene-based resin plate-like foam, characterized by using at least 10 wt%.