JPH1149885A - Polystyrene resin foam and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain the subject foamed product not using a foaming agent disrupting the ozonosphere, capable of exhibiting a high foaming ratio and a low density, capable of exhibiting excellent flame retardation facilitation, excellent heat insulation, etc., useful for building materials, etc., by extruding and foaming a resin with a specific foaming agent. SOLUTION: A polystyrene resin is mixed with (B) a foaming agent comprising (B1 ) propane, butane or their mixture and (B2 ) 1,1-difluoroethane (concretely a mixture comprising 95-20 wt.% of the component B1 and 5-80 wt.% of the component B2 ) e.g. in an A:B weight ratio of 100:(5-12) and subsequently extruded and foamed. The foamed product may have e.g. a 10-150 mm thick plate-like form having a density of 0.02-0.04 g/cm<3> , a heat conductivity of 0.02-0.029 kcal/ m.hr after two month, and satisfying flammability regulated by JIS A9511 in the presence of a flame retardant.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a polystyrene resin foam and a method for producing the same. More specifically, the present invention relates to a thick low-density polystyrene resin foam produced by extrusion foaming using an environmentally friendly foaming agent having a low global warming coefficient and not destroying the ozone layer, and a method for producing the same.

[0002]

2. Description of the Related Art At present, foaming agents used in plate-like polystyrene resin foams include, for example, hydrocarbons such as butane and propane, and 1,1-monochloro-1,1-difluoroethane (F-142b). Are known. F
Since -142b has low thermal conductivity, low flammability, and remains in the foam for a long time, -142b is preferably used for a plate-like styrene resin foam.

[0003] However, since F-142b destroys the ozone layer, the total amount was regulated since 1996 in the previous Montreal resolution at the United Nations Environment Conference, and 2020
In the year it was decided to abolish its use. Therefore,
There is a need to develop a foaming agent that replaces F-142b. Therefore, as an alternative to F-142b, 1,1,1,2
-Tetrafluoroethane (F-134a) is being considered. F-134a is considered to be particularly promising for low thermal conductivity foams from the viewpoints of foaming properties, the rate of remaining in air bubbles over time, cost, and the like. However, F-134a
Has a low ozone depletion potential, but a warming potential of 420
(When the carbon dioxide gas is set to 1), which is extremely high, it is not preferable to use it on environmental issues. It could be subject to regulation in the future. Therefore, further study of a foaming agent was required. Therefore, as a blowing agent having an ozone depletion potential of 0 and a low warming potential, 1,1-difluoroethane (F-1)
52a) can be considered.

[0004]

The warming potential of this F-152a is 47, which is about 1/10 of that of F-134a, and is considered to be an effective blowing agent when only warming is considered. However, since the foaming agent of F-152a alone has poor compatibility with the polystyrene resin when foaming is performed, it has been difficult to obtain a low-density foam. Also,
In addition to fluorinated hydrocarbons, it is conceivable to use hydrocarbons such as propane and butane as blowing agents. However, when foaming is performed using only these hydrocarbons, the residual gas in the bubbles must be increased in order to obtain a foam having low thermal conductivity. Then, since the contents of propane and butane increase, there is a danger of ignition and it is considered difficult.

Further, JP-A-7-165970 describes a blowing agent comprising F-152a and methyl chloride, but this methyl chloride has a problem that it has a bad influence on work hygiene and safety. there were.

[0006]

Accordingly, by mixing propane, butane or a mixture thereof having a high vapor pressure with 1,1-difluoroethane (hereinafter referred to as F-152a), polystyrene having a low density can be stably formed. The present inventors have surprisingly found that a resin foam can be produced.

Thus, according to the present invention, a polystyrene resin is mixed with propane, butane or a mixture thereof with 1,1,1.
-A polystyrene-based resin foam characterized by comprising a polystyrene-based resin foam obtained by extrusion-foaming using a foaming agent comprising difluoroethane.

Further, according to the present invention, a polystyrene resin is mixed with propane, butane or a mixture thereof with 1,1-
A method for producing a polystyrene resin foam is provided, wherein a polystyrene resin foam is produced by mixing a foaming agent comprising difluoroethane and extruding and foaming the mixture.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION One of the features of the present invention is that it contains propane, butane or a mixture thereof and F-152a as a foaming agent. Because F-152
As a result of studying on a, F-152a has zero ozone depletion potential (ODP) and low warming potential and thermal conductivity.
And propane, butane, or a mixture thereof to provide low thermal conductivity, low density and JIS
This is because it has been found that a foam that can satisfy the flammability specified in A9511 can be obtained.

The polystyrene resins usable in the present invention include styrene, methylstyrene, ethylstyrene,
Homopolymers of styrene monomers such as isopropylstyrene, dimethylstyrene, chlorostyrene, bromostyrene, vinyltoluene, and vinylxylene, or acrylonitrile, methacrylonitrile, acrylic acid, methacrylic acid, and acrylic acid esters (for example, methyl, ethyl And methacrylic acid esters (eg, esters with methyl, ethyl and the like), and copolymers with vinyl monomers such as maleic anhydride and butadiene. Specifically, polystyrene resin, styrene-maleic anhydride copolymer, styrene-acrylic acid copolymer, styrene-
Acrylic acid ester copolymer, impact-resistant styrene resin (HIPS), styrene-acrylonitrile copolymer,
An acrylonitrile-butadiene-styrene terpolymer is exemplified.

The above foaming agent is usually mixed in an amount of 5 to 12 parts by weight with respect to 100 parts by weight of the polystyrene resin in order to reduce the density. Further, it is preferable that propane, butane or a mixture thereof is mixed at a ratio of 95 to 20% by weight, and F-152a is mixed at a ratio of 5 to 80% by weight. When propane, butane or a mixture thereof is used at this ratio, a foam having low density, low thermal conductivity, and flammability specified in JIS A9511 can be obtained. In addition, butane may be n-butane, isobutane, or a mixture thereof. In this mixture, propane or butane contains 95
If the amount is more than 80% by weight, a low-density foam cannot be obtained. The mixing ratio of propane, butane or a mixture thereof and F-152a is 70 to 30% by weight.
And 30 to 70% by weight are more preferable. When a mixture of propane and butane is used here, the mixture may be in any ratio as long as the total amount of both is within the above range.

Incidentally, a foaming agent comprising another organic gas may be added as long as the effect of the foaming agent according to the present invention is not impaired. Methane, ethane, heptane, etc. are mentioned as a foaming agent consisting of another organic gas. Further, for example, a small amount of an inorganic gas such as a carbon dioxide gas, a nitrogen gas, an oxygen gas, and water vapor may be contained as long as the effect of the blowing agent according to the present invention is not hindered.

Further, as a plasticizer, ethers such as dimethyl ether, ethyl methyl ether and ethyl ether may be mixed within 5% by weight of the resin. These plasticizers also have a function as a foaming agent. Furthermore, SM
An antistatic agent such as G (stearic acid monoglyceride) may be added.

Next, a polystyrene resin and a foaming agent are mixed. The mixing method is not particularly limited, and any known screw extruder or the like can be used. Further, for example, a method of mixing at a temperature of 180 to 300 ° C. using a pin mixer, a dalmage, a cavity transfer mixer, or the like provided in the resin passage is exemplified. It is preferable that the mixing is sufficiently performed. If mixing is not sufficient, the foaming agent may cause internal foaming and voids may occur.

The mixed resin and foaming agent are extruded from a die provided at the tip of the extruder to form a polystyrene resin foam. Here, the pressure per hour (die pressure) at the tip of the die during extrusion is 30 to 70 kg /.
cm ² is preferred. The polystyrene resin foam obtained by the above method is 0.020 to 0.040 g.
/ Cm ³ is preferred. Density 0.0
If less than 20 g / cm ³ , it is difficult to manufacture.

Furthermore, the polystyrene resin foam of the present invention has a thickness of 0.1 to 1.0 mm (more preferably, 0.2 to 1.0 mm).
(6 mm). If the average bubble diameter is smaller than 0.1 mm, the thermal conductivity increases and the density does not decrease, which is not preferable. When the average bubble diameter is larger than 1.0 mm, the thermal conductivity increases, which is not preferable.

Further, the polystyrene resin foam of the present invention has a thermal conductivity of 0.020-0.
029 kcal / m · hour · ° C. When the thermal conductivity is greater than 0.029 kcal / m · hr · ° C,
It is not preferable for use of a heat insulating material. Here, the thermal conductivity two months after the production was measured according to JIS A1412. That is, the foamed body 2 months after the production was subjected to the thickness 2
A test piece having a size of 5 mm and a length × width = 200 mm × 200 mm is used. The heat flow passing through the test piece is measured using a two-plate heat flow meter, and the temperature difference of the test piece at that time is measured.
The value obtained from the obtained heat flow rate and temperature difference is defined as the thermal conductivity specified in the present invention. Note that the inventors of the present invention
It has been found that the thermal conductivity after a lapse of months has become substantially constant.

Further, a polystyrene-based resin foam can be used in JI
It is preferable to satisfy the flammability specified in SA9511. If this flammability cannot be achieved as it is, it may be achieved by adding a flame retardant. Specifically, a relatively small amount of a flame retardant such as hexabromocyclododecane and tetrabromobisphenol A is added as 1 to 3% by weight, and the residual gas amounts after two months of production of propane and butane are reduced by 3 respectively. It can be achieved by adjusting the content to 0.5% by weight or less and 2.0% by weight or less. Note that F-1
The residual gas amount after two months of production of 52a is 2 to 6% by weight.
It is preferred that

The method of measuring flammability specified in JIS A9511 is briefly described below. First, five test pieces having a thickness of about 10 mm, a length of about 200 mm, and a width of about 25 mm are prepared. Each test piece is fixed, and a flame is applied from one end of the test piece to an arbitrary point at a constant speed. After reaching an arbitrary point, the flame is removed, the time from the moment until the flame disappears is measured, and the average value of the time of the five test pieces is taken. This average value indicates flammability. Satisfying the flammability specified in JISA 9511 means that the average value is within 3 seconds.

In addition, the polystyrene resin foam is 10
It can be manufactured as a plate-like foam having a thickness of 150 to 150 mm (more preferably 25 to 100 mm). Thickness 10
If the thickness is smaller than mm, the density cannot be reduced. If the thickness is more than 150 mm, manufacturing becomes difficult. The polystyrene-based resin foam obtained by the present invention has low density, excellent flammability and excellent heat insulation properties, and is used for heat insulation outside a roof, for tatami, for walls, for dirt, for roofs, and for foundations. It can be suitably used as a heat insulating material when building a building.

[0021]

The present invention will be described in more detail with reference to the following examples. In the examples, “parts” means parts by weight.

Example 1 100 parts of polystyrene (Stylon 680 manufactured by Asahi Kasei Corporation) was used as a polystyrene resin, 0.5 parts of talc powder was added as a foam nucleating agent, and 0.06 parts of monoglyceride stearate (SMG) was used as an antistatic agent. Then, 3.0 parts of hexabromocyclododecane (HBCD) was added as a flame retardant, and the mixture was supplied to an extruder. The extruder used was a tandem type. This mixture was melt-kneaded in an extruder, and butane (70% normal, iso-3
0%) / F-152a = 70/30 (% by weight)
Part was press-fitted. As shown in FIG. 1 (FIG. 1 (a) shows a schematic side view of a cut-out portion, and FIG. 1 (b) shows a schematic cross-sectional view) in a cylinder serving as a molten resin passage after kneading with a screw after gas injection. A pin mixer 1 in which eight pins 2 are provided in a row in the circumferential direction and 52 rows in the longitudinal direction.
The foaming agent and the polystyrene resin were thoroughly kneaded at rpm and a mixing pressure of 180 kg / cm ² , and then cooled to a foaming-suitable resin temperature of 135 ° C. by a second extruder. These mixtures were applied to a slit-shaped die (lip: W = 50 mm, t = 1.2 mm) attached to the extruder tip for 4 hours / hour.
Extruded at 0 kg. The extruded foam was molded by passing it through a molding tool in which two plates closely attached to the tip of a die face each other, and cooling at the same time as shaping.

Thus, the width is 191 mm and the thickness is 29.5 m.
m was obtained. The obtained foam had a density of 0.0311 g / cm ³ , a flammability measurement result specified in JIS A9511 of 2.9 seconds, and an average cell diameter of 0.30 mm. The residual gas amount in the foam after two months of aging was 1.9% by weight of butane and F-152a.
It was 1.2% by weight. Further, the thermal conductivity after two months of aging was 0.0236 kcal / m · hour · ° C.

Example 2 Using the same compounding, extruder, and die as in Example 1, butane / F-152a = 50/50 (% by weight) as a foaming agent was used as 7.2.
Part was press-fitted to foam. As a result, a plate-like foam having a width of 187 mm and a thickness of 30 mm was obtained. The resulting foam is
The density is 0.0307 g / cm ³ and JIS A95
The measurement result of the flammability specified in No. 11 was 2.3 seconds, and the average bubble diameter was 0.32 mm. The residual gas amount in the foam after two months of aging was 1.6% by weight of butane and F-15.
2a was 1.8% by weight. Further, the thermal conductivity after two months of aging was 0.0223 kcal / m · hour · ° C.

Example 3 Using the same compounding, extruder, and die as in Example 1, butane / F-152a = 30/70 (% by weight) as a foaming agent was used.
Part was press-fitted to foam. Thus, a plate-like foam having a width of 186 mm and a thickness of 33 mm was obtained. The resulting foam is
The density is 0.0291 g / cm ³ and JIS A95
The measurement result of the flammability specified in No. 11 was 1.9 seconds, and the average bubble diameter was 0.33 mm. The residual gas amount in the foam after two months of aging was 1.3% by weight of butane, F-15
2a was 2.6% by weight. Further, the thermal conductivity over a period of two months was 0.0228 kcal / m · hour · ° C.

Example 4 Propane / F-152a = 50/50 (% by weight) was used as a blowing agent in the same formulation, extruder, and die as in Example 1.
Four parts were press-fitted and foamed. Thus, a plate-like foam having a width of 194 mm and a thickness of 28 mm was obtained. The obtained foam has a density of 0.0320 g / cm ³ and is JIS A
The measurement result of the flammability specified in 9511 was 1.1 seconds, and the average bubble diameter was 0.23 mm. In addition, aging 2
The amount of residual gas in the foam for one month is 1.2% by weight of butane, F
-152a was 1.7% by weight. Further, the thermal conductivity after two months of aging was 0.0245 kcal / m · hour · ° C.

Comparative Example 1 Using the same compounding, extruder, and die as in Example 1, only 4.0 parts of F-152a was injected as a foaming agent and foamed. The density of the obtained foam was 0.045 g / cm ³ , and a low-density foam could not be obtained.

[0028]

The polystyrene resin foam of the present invention is
It is characterized by comprising a polystyrene-based resin foam obtained by extrusion-foaming a polystyrene-based resin using a foaming agent comprising propane, butane or a mixture thereof and F-152a.

Therefore, it is possible to form a polystyrene-based resin foam of the same quality as those foaming agents without using a conventional blowing agent containing a fluorinated hydrocarbon that destroys the ozone layer. Further, the present invention uses a foaming agent comprising propane, butane or a mixture thereof and F-152a, and this foaming agent has relatively good compatibility with a polystyrene-based resin, and by using an extruder, A low-density and thick polystyrene resin foam that has been foamed at a high magnification can be manufactured.

Furthermore, in the flammability test, the polystyrene resin foam of the present invention is suitable for applications such as building materials only by reducing the residual gas amount of propane and / or butane and adding a small amount of a flame retardant. Flammability can be imparted. In addition, the polystyrene resin foam of the present invention can reduce the thermal conductivity after two months by 0.029 by reducing the cell diameter and increasing the residual gas amount of F-152a.
Since it can be set to kcal / m · hour or less, it can also be used for applications requiring heat insulating properties.

F-152a is an environmentally friendly blowing agent having a low global warming potential. Furthermore, the present invention is a foam excellent in hygiene and safety and a method for producing the same, since it is not necessary to mix conventionally used methyl chloride and ethyl chloride.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view of a pin mixer used in an example and a schematic side view of a cutout portion.

[Explanation of symbols]

 1 pin mixer 2 pins

Claims (6)

[Claims] 1. A polystyrene resin foam obtained by extrusion foaming a polystyrene resin using a foaming agent comprising propane, butane or a mixture thereof and 1,1-difluoroethane. Polystyrene resin foam. 2. The polystyrene-based resin foam is 0.02
Foam according to claim 1 is the density of 0~0.040g / cm ^3. 3. A foam according to claim 1, wherein the foaming agent comprises 95 to 20% by weight of propane, butane or a mixture thereof, and 5 to 80% by weight of 1,1-difluoroethane. 4. The method according to claim 1, wherein the polystyrene resin foam is 10 to 1
A plate-like foam having a thickness of 50 mm.
3. Any one of the foams. 5. A polystyrene-based resin foam comprising 0.02
The foam according to any one of claims 1 to 4, having a thermal conductivity of 2 months after aging of 0 to 0.029 kcal / m · hour and satisfying the flammability specified in JIS A9511 in the presence of a flame retardant. 6. A polystyrene resin foam is produced by mixing a polystyrene resin with a blowing agent comprising propane, butane or a mixture thereof and 1,1-difluoroethane and subjecting the mixture to extrusion foaming. A method for producing a polystyrene resin foam.