JPH10265604A - Production of extruded styrene resin foam and foam produced thereby - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a process for producing an extruded styrene resin foam excellent in environmental adaptability, productivity, and physical properties and a foam produced thereby. SOLUTION: This process comprises thermally melting a styrene resin, injecting a blowing agent into the melt under a high pressure to convert it into a flowable gel, cooling the gel to a temp. suitable for extrusion foaming, and foaming it by extruding it through a die into a low-pressure zone. The blowing agent injected contains ethyl chloride in a concn. higher than 60 wt.% but not higher than 95 wt.% and a hydrocarbon (pref. a 3-6C aliph. hydrocarbon) in a concn. of 5 wt.% or higher but lower than 40 wt.%. A foam produced by the process is also provided.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a method for producing an extruded styrene resin foam and a produced foam.
More specifically, the present invention relates to a method for producing an extruded styrene-based resin foam having excellent environmental compatibility and productivity, and excellent foam properties, and a produced foam.

[0002]

2. Description of the Related Art As a method for obtaining a styrene-based resin foam, a styrene-based resin is plasticized by an extruder or the like, and a volatile organic blowing agent is injected and mixed with the plasticized resin. A method for continuously producing a styrene-based resin foam by cooling the mixture to a temperature suitable for the above and extruding the mixture into a low-pressure region is disclosed in, for example, JP-B-31-5393.
And Japanese Patent Publication No. 42-19195.

In this known technique, a chlorine atom-containing halogenated carbon (hereinafter abbreviated as CFC), which has low toxicity and is nonflammable and chemically stable, has been used as a foaming agent.
It has been pointed out that the ozone layer may be destroyed, and a method using a chlorine atom-containing halogenated hydrocarbon (hereinafter abbreviated as HCFC) in which a chlorine atom is partially hydrogenated has been adopted for the purpose of improvement. For example, it is disclosed in Japanese Patent Publication No. 41-672 and Japanese Patent Publication No. 57-7175. However, more suitable foaming agents are being studied from the viewpoint of further protecting the global environment.

[0004] From such a viewpoint, it has been proposed to use carbon dioxide or hydrocarbons containing no chlorine atom and fluorine atom in the molecule as a blowing agent. For example, the use of carbon dioxide as a blowing agent is disclosed in
068 and JP-A-3-81346, and the use of hydrocarbon as a blowing agent is disclosed in JP-A-58-74.
729 and JP-A-7-165969.

However, in producing a styrenic resin foam using an inorganic gas such as carbon dioxide as a blowing agent, it is difficult to uniformly disperse the inorganic gas in the styrenic resin. Often unable to get a body. As a remedy, it is conceivable to use a mixture with other blowing agents, but if you want to obtain a good foam,
The composition ratio of the inorganic gas in the blowing agent tends to be extremely low, and the characteristics of using the inorganic gas as the blowing agent cannot be fully utilized.

In producing a styrenic resin foam using a hydrocarbon as a foaming agent, the hydrocarbon itself is inexpensive in terms of cost, but because of its flammability, it is often contained in the foam. When hydrocarbons remain, the heat resistance of the foam itself decreases, and therefore the foam must be stored for a long time until the residual amount is appropriately reduced, resulting in a decrease in productivity. A solution is desired.

On the other hand, as a foaming agent, it contributes to the production of a styrene-based resin foam, and itself has a very high permeability to a styrene-based resin, so that methyl chloride which hardly remains in the foam is removed. JP-A-47-9
No. 593, JP-A-52-17574 and JP-A-52-94366. According to these known methods, it is further stated that methyl chloride has a high plasticizing performance of a styrene resin and can be produced by lowering the extrusion pressure. However, the recommendations of the Japan Society for Occupational Health in 1992 specify the allowable concentration of methyl chloride in the environment, especially in the working environment, and care and measures are required for its handling. It is preferable to go.

[0008]

SUMMARY OF THE INVENTION The object of the present invention is to produce a styrene resin extruded foam which can be suitably used as a heat insulating material and the like. An object of the present invention is to provide a method for producing a styrene-based resin extruded foam having excellent foam properties and a produced foam.

[0009]

Means for Solving the Problems As a result of earnest research for solving the above-mentioned problems, the present inventor has found that a styrenic resin is heated and melted, a blowing agent is injected into the styrenic resin under high pressure conditions, Gel and without, cooled to a temperature suitable for extrusion foaming,
In a method for producing a styrene-based resin extruded foam in which the fluid gel is extruded and foamed through a die to a low pressure region, by using a foaming agent containing a specific amount of ethyl chloride and a hydrocarbon, it is excellent in environmental compatibility and productivity, and Found that it is possible to obtain a styrene resin extruded foam having excellent foam properties,
The present invention has been completed.

That is, according to the present invention, (1) a styrenic resin is heated and melted, a foaming agent is poured into the styrenic resin under a high pressure condition, a fluid gel is formed, and the styrenic resin is cooled to a temperature suitable for extrusion foaming. In a method for producing an extruded styrenic resin foam in which a fluid gel is extruded and foamed through a die to a low-pressure region, the blowing agent mainly contains ethyl chloride in an amount of more than 60% by weight and 95% by weight or less based on the total amount of the blowing agent. The present invention relates to a method for producing an extruded styrenic resin foam, comprising less than 40% by weight and not less than 5% by weight of hydrogen.

Further, the present invention provides (2) a foaming agent containing more than 60% by weight and less than 85% by weight of ethyl chloride, less than 40% by weight of hydrocarbon and less than 15% by weight, based on the total amount of the blowing agent.
The present invention relates to the method for producing an extruded styrene-based resin foam according to the above (1), wherein the foamed material contains at least 1% by weight.

Further, the present invention provides (3) that the blowing agent mainly contains ethyl chloride in an amount of more than 60% by weight and 75% by weight or less and a hydrocarbon of less than 40% by weight and 25% by weight or more based on the total amount of the blowing agent. The present invention relates to a method for producing an extruded styrene resin foam according to the above (2).

Further, in the present invention, (4) the styrene resin extrusion according to the above (1), (2) or (3), wherein the hydrocarbon is an aliphatic hydrocarbon having 3 to 6 carbon atoms. The present invention relates to a method for producing a foam.

Further, the present invention relates to (5) the method for producing a styrene resin extruded foam according to the above (4), wherein the hydrocarbon is an aliphatic hydrocarbon having 3 to 4 carbon atoms.

The present invention further relates to (6) an extruded styrene resin foam produced by the method according to any one of the above (1) to (5).

[0016]

DETAILED DESCRIPTION OF THE INVENTION The styrene resin used in the present invention includes styrene monomers such as styrene, methyl styrene, ethyl styrene, isopropyl styrene, dimethyl styrene, bromo styrene, chloro styrene, vinyl toluene and vinyl xylene. Or a copolymer composed of a combination of two or more of these, or one or more of these styrene monomers and divinylbenzene, butadiene, acrylic acid, methacrylic acid, methyl acrylate, methyl methacrylate And copolymers of one or more monomers such as acrylonitrile, maleic anhydride, and itaconic anhydride. Acrylic acid, methacrylic acid, methyl acrylate, methyl methacrylate, maleic anhydride, itaconic anhydride, and the like can be used to such an extent that the physical properties such as the compressive strength of the manufactured extruded styrene resin foam are not reduced. Further, these are not copolymerized, and may be a homopolymer or a copolymer of the styrene-based monomer and a blend of a homopolymer or a copolymer of the other monomer, Diene rubber reinforced polystyrene or acrylic rubber reinforced polystyrene can also be blended.

In the present invention, among these styrene resins, a polystyrene resin can be particularly preferably used.

In the present invention, ethyl chloride and a hydrocarbon are mainly used in combination as the blowing agent.

Ethyl chloride has a much higher allowable concentration according to the recommendations of the Japan Society for Occupational Health, and has a lower burden on the environment, especially on the occupational environment and hygiene in production, as compared with conventionally used methyl chloride. Compared with methyl, it has higher permeability to styrene-based resin and can shorten the storage curing period of the foam, which is preferable in terms of productivity.

The blowing agent of the present invention is based on the total amount of the blowing agent.
More than 60% by weight and 95% by weight of ethyl chloride
Hereinafter, it contains less than 40% by weight and 5% by weight or more of hydrocarbon. When ethyl chloride exceeds 95% by weight of the total amount of the foaming agent, the internal pressure of the foam cells cannot be maintained, and the appearance characteristics of the extruded styrene resin foam tend to deteriorate. Also 60
If it is less than 10% by weight, the extrusion temperature cannot be lowered to a sufficient temperature. On the other hand, when the hydrocarbon content is 40% by weight or more, the extruded styrene resin foam having a high expansion ratio tends to have poor flame retardancy. If it is less than 5% by weight, the dimensional stability of the foam is impaired. In order to obtain a suitable extruded styrenic resin foam, it is preferable to mainly use ethyl chloride for 6 hours.
A blowing agent containing more than 0% by weight and not more than 85% by weight and containing less than 40% by weight and not less than 15% by weight of hydrocarbon is used.
More preferably, a blowing agent containing more than 60% by weight and 75% by weight or less of ethyl chloride and less than 40% by weight and 25% or more of hydrocarbons is mainly used.

The hydrocarbon used in the present invention includes methane, ethane, propane, n-butane, i-butane, and n-butane.
Pentane, i-pentane, 2,2-dimethylpropane,
Aliphatic hydrocarbons such as hexane and cyclohexane can be used. Preferably propane, n-butane, i
-Aliphatic hydrocarbons having 3 to 6 carbon atoms, such as butane, n-pentane, i-pentane, 2,2-dimethylpropane and hexane. More preferably, propane, n-
It is an aliphatic hydrocarbon having 3 to 4 carbon atoms such as butane and i-butane. These hydrocarbons can be used alone or in combination of two or more.

The amount of the foaming agent in the present invention relative to the styrene-based resin varies depending on the set value of the expansion ratio and the like. Usually, the total amount of ethyl chloride and hydrocarbon is 100 parts by weight of the styrene-based resin. The amount is about 5 to 20 parts by weight, preferably about 7 to 17 parts by weight, and more preferably about 9 to 15 parts by weight. When the amount of the foaming agent is less than the above range, the foaming ratio is low and the resin foam is lightweight,
It is difficult to exhibit properties such as heat insulation. On the other hand, if the amount exceeds the above range, defects such as voids may occur in the foam due to an excessive amount of the foaming agent.

In the present invention, other foaming agents may be added, if necessary, as long as the effects of the present invention are not impaired.
For example, it can be added in an amount of 10 parts by weight or less based on 100 parts by weight of the styrene resin. Such foaming agents include, for example, 1,1-difluoroethane, 1,2
-Difluoroethane, 1,1,1-trifluoroethane, 1,1,2-trifluoroethane, 1,1,1,2
Fluorinated hydrocarbons such as tetrafluoroethane, 1,1,2,2-tetrafluoroethane, 1,1,1,2,2-pentafluoroethane, difluoromethane, trifluoromethane, carbon dioxide, nitrogen, water, Argon, inorganic gases such as helium, dimethyl ether, diethyl ether, isopropyl ether, n-butyl ether, diisoamyl ether, furan, furfural, 2-methylfuran, tetrahydrofuran, ethers such as tetrahydropyran, dimethyl carbonate, diethyl carbonate, Carbonic esters such as dipropyl carbonate, methyl formate, ethyl formate, propyl formate, butyl formate, amyl formate, methyl propionate, ethyl propionate, etc. Carboxylic acid esters, methanol,
Ethanol, propyl alcohol, i-propyl alcohol, butyl alcohol, i-butyl alcohol, t-
Alcohols such as butyl alcohol, dimethyl ketone, methyl ethyl ketone, diethyl ketone, methyl n-
Propyl ketone, methyl n-butyl ketone, methyl i-
Butyl ketone, methyl n-amyl ketone, methyl n-hexyl ketone, ethyl n-propyl ketone, ethyl n-
Ketones such as butyl ketone can be used. These can be used alone or in combination of two or more.

The extruded styrenic resin foam of the present invention is prepared by heating and melting a styrenic resin, injecting a foaming agent into the styrenic resin under high pressure conditions, forming a fluid gel, and cooling to a temperature suitable for extrusion foaming. Then, the fluidized gel is extruded and foamed through a die into a low pressure region to form an extruded styrene resin foam.

The heating temperature, melting time, and melting means for heating and melting the styrene resin are not particularly limited. The heating temperature may be equal to or higher than the temperature at which the styrene resin is melted, usually about 150 to 250 ° C.
Since the melting time varies depending on the extrusion amount per unit time, melting means, etc., it cannot be determined unconditionally,
The time required for uniform dispersion and mixing is selected. Also,
The melting means is not particularly limited as long as it is used for ordinary extrusion foaming such as a screw type extruder.

The pressure at which the foaming agent is injected is not particularly limited, and may be any pressure as long as it is higher than the internal pressure of the extruder to be injected into the extruder.

Further, in the present invention, silica, talc, calcium silicate, wollastonite, kaolin, clay, mica, zinc oxide, titanium oxide, fatty acid metal salts such as calcium stearate and barium stearate,
Additives such as a flame retardant such as hexabromocyclododecane and an antioxidant such as a polymer type hindered phenol compound can be added. These can be blended by appropriately adjusting the blending amount as needed.

[0028]

Next, the method for producing an extruded styrene resin foam of the present invention will be described in more detail with reference to Examples.
The present invention is not limited to only such embodiments.
Unless otherwise specified, "parts" indicates parts by weight and "%" indicates% by weight.

Examples 1-4 Polystyrene resin (manufactured by Nippon Steel Chemical Co., Ltd., trade name: Estyrene G-17, melt index (MI): 3.
1) To 100 parts, 0.1 part of talc as a nucleating agent and 3.0 parts of hexabromocyclododecane as a flame retardant were added, and the mixture was heated and kneaded at 200 ° C. in an extruder.
After the foaming agent having the composition shown in Table 1 was injected into the mixture at the injection amount shown in Table 1, it was fed to a cooling and mixing machine, and the mixture was supplied to a cooling and mixing machine.
The mixture was cooled to 0 ° C. and extruded and foamed through a slit having openings of 1.8 mm and a molding die whose flow path surface was coated with a fluororesin to obtain a plate-like styrene resin foam.

The properties of the obtained foam include expansion ratio,
The foam closed cell ratio, average cell size, heat insulation, flammability, appearance, and productivity were examined according to the following methods. Table 2 shows the results.

A) Expansion ratio: Assuming that the density of the polystyrene resin is 1.05 (g / cm ³ ), the following expression: expansion ratio (times) = 1.05 / density of foam (g / c)
m ³ ). In addition, the density of the foam was calculated from the weight of the foam and the volume obtained by the submersion method.

B) Foam closed cell ratio: A multipycnometer (trade name, manufactured by Yuasa Ionics Co., Ltd.)
It was measured according to STM D-2856.

(C) Average cell size: Scanning electron microscope (S-450, manufactured by Hitachi, Ltd.) on the longitudinal section of the extruded foam.
Take a photograph of the vertical section of the foam by magnifying it by 30 times, copy the photograph taken with a dry copier, and in the obtained copy, paint the air bubbles with black ink and perform primary processing. The primary-processed image was processed by an image processing apparatus (PIAS-II, manufactured by Pierce Co., Ltd.) to determine the average bubble size.

D) Heat insulation: Measured according to JIS A 9511. ：: Thermal conductivity is 0.034 Kcal / mhr ° C. or less ×: Thermal conductivity exceeds 0.034 Kcal / mhr ° C.

E) Flammability: ：: Flame extinction time of 3 seconds or less ×: Flame extinction time of more than 3 seconds

F) Criteria for evaluation of foam appearance ○: The foam has very good appearance with no unfoamed resin blocks and voids in the cross section and no wrinkles or protrusions on the surface. Δ: A foam having a good appearance in which a small amount of unfoamed resin mass and voids are present in the cross section, or wrinkles or protrusions are present on the surface. ×: A foam having a poor appearance in which an unfoamed resin mass and voids are present in the cross section and wrinkles and protrusions are present on the surface.

G) Productivity evaluation The productivity was determined by using the initial permeation rate of the blowing agent gas obtained by the following method as an index. First, the measurement of the initial permeation rate was performed using a polystyrene resin (manufactured by Nippon Steel Chemical Co., Ltd., trade name:
Estyrene G-17, melt index (MI):
The film (thickness: 50 μm) of 3.1) was fixed to a gas permeation amount measuring device (manufactured by LISSY, GPM-200), and the gas permeating the film was subjected to gas chromatography (Hitachi, Ltd.) Using 663-30)
The permeation amount was measured by the same pressure (1 atm) method. Then FIC
The initial permeation rate of the blowing agent gas was determined using K's first and second laws and Henry's law. The evaluation was performed as follows, and shows that the higher the magnification, the shorter the storage curing period of the foam, and the higher the productivity. ：: The permeation speed of the blowing agent gas to the permeation speed of air is 2
0 or more Δ: Permeation rate of blowing agent gas to permeation rate of air is 8
× or more and less than 20 times ×: Permeation speed of blowing agent gas to permeation speed of air is 8
Less than double

Comparative Examples 1 to 3 Extruded styrene resin foams were obtained in the same manner as in Example 1 except that the composition ratio of the blowing agent was changed.

Table 2 shows the physical properties and productivity of the obtained foam.
Shown in

Comparative Example 4 Except that methyl chloride and propane were used as blowing agents,
An extruded styrene resin foam was obtained in the same manner as in Example 1.

Table 2 shows the physical properties and productivity of the obtained foam.
Shown in

[0042]

[Table 1]

[0043]

[Table 2]

From the results shown in Table 2, it can be seen that the foams obtained in Examples 1 to 4 have an appropriate foam density, excellent foam properties, and excellent productivity. I understand.

[0045]

According to the present invention, an extruded styrene resin foam which is excellent in environmental compatibility and productivity, has an appropriate foam density, and is excellent in foam properties such as heat insulation and combustion properties. Can be obtained.

Claims (6)

[Claims] 1. A styrenic resin is heated and melted, a foaming agent is injected into the styrenic resin under high-pressure conditions to form a fluidized gel, and cooled to a temperature suitable for extrusion foaming. In the method for producing an extruded styrenic resin foam which is extruded and foamed in the region of (1), the blowing agent mainly contains ethyl chloride in an amount of more than 60% by weight and 95% by weight or less and hydrocarbons of less than 40% by weight based on the total amount of the blowing agent. And a method for producing an extruded styrene-based resin foam containing at least 5% by weight. 2. The blowing agent is mainly composed of ethyl chloride in an amount of more than 60% by weight and not more than 85% by weight, based on the total amount of the blowing agent.
The method for producing an extruded styrene-based resin foam according to claim 1, comprising less than 40% by weight and not less than 15% by weight of a hydrocarbon. 3. The blowing agent comprises ethyl chloride in an amount of more than 60% by weight and not more than 75% by weight, based on the total amount of the blowing agent.
3. The method for producing an extruded styrene resin foam according to claim 2, wherein the composition contains less than 40% by weight and at least 25% by weight of a hydrocarbon. 4. The method for producing an extruded styrene resin foam according to claim 1, wherein the hydrocarbon is an aliphatic hydrocarbon having 3 to 6 carbon atoms. 5. The method for producing an extruded styrene resin foam according to claim 4, wherein the hydrocarbon is an aliphatic hydrocarbon having 3 to 4 carbon atoms. 6. An extruded styrene resin foam produced by the method according to claim 1.