JPS6124976B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a thick styrene resin foam board. In particular, the present invention relates to a method for manufacturing a styrene resin foam board that is thick, foams uniformly and finely both on the surface and inside, and exhibits little dimensional change due to fluctuations in outside temperature.

The most efficient way to make a foamed board with a constant cross-sectional shape is to extrude it using an extruder. Using styrene resin,
When making thin, wide foam boards called sheets, extrusion molding is definitely the best method.
However, when the thickness of the foam sheet increases to about 10 mm or more, which is what is called a plate, it becomes difficult to make it by extrusion molding. This is because, as the thickness increases, local density differences in the foam board become noticeable, making it difficult to uniformly foam the surface portion and the inside.

When extrusion molding a plate, the influence of the blowing agent is also significant. For foaming styrene resins, aliphatic hydrocarbons such as propane, butane, pentane, and hexane are said to be suitable as blowing agents, and halogenated aliphatic hydrocarbons such as methyl chloride, methylene chloride, and trichlorofluoromethane It is said that it can also be used as a blowing agent. Among these blowing agents, there are few documents describing which blowing agent is particularly suitable for extrusion molding of thick plates, but JP-A-52-17573 describes this and It is suggested that methane should be mixed with dichlorodifluoromethane, propane, propylene or butane.

That is, JP-A-52-17573 discloses that 2 to 15 parts by weight of trichlorofluoromethane, dichlorodifluoromethane, propane, propylene, and butane selected from dichlorodifluoromethane, propane, propylene, and butane are used as blowing agents for 100 parts by weight of styrene resin. It is recommended to use a mixture of 3 to 18 parts by weight of one or more blowing agents, and that the total amount of the blowing agent does not exceed 3 moles per kg of styrenic resin. However, this bulletin
As a result of using such a foaming agent, what kind of foaming ratio was obtained, what was the dimensional change on heating, and whether the surface and inside of the foam were foamed uniformly? It does not say what.

Therefore, the inventor attempted an experiment according to the disclosure of Japanese Patent Application Laid-Open No. 17573/1983. As a result, it was found that when carried out according to this disclosure, the foam board could not be foamed uniformly on the surface portion and inside. It has also been found that this foam board has the disadvantage that its dimensions vary greatly due to changes in the surrounding air temperature. Furthermore, it has been found that among the blowing agents disclosed herein, mixtures of trichlorofluoromethane and propane or propylene do not give good results as blowing agents.

After that, as a result of repeated experiments, this inventor used a mixture of trichlorofluoromethane and dichlorodifluoromethane or butane in a specific ratio as a blowing agent, mixed it with styrene resin, and performed extrusion molding. I learned that it is possible to obtain a foam board that is well foamed and has a large thickness. However, it was found that this foamed board had a tendency to have a high density on the surface and a low density on the inside, and therefore was not a foamed board in which both the inside and the surface were uniformly foamed. However, once this foam board has been cooled, when it is heated again from the surface to a temperature higher than the thermal deformation temperature of the resin, the surface foams further, and for the first time, both the surface and the inside become uniformly foamed, resulting in a uniform foam thickness. It was confirmed that the board could be obtained. Moreover, it was found that the foam board shows little dimensional change even when the surrounding temperature rises and falls. This invention was made based on such confirmation.

It is already known that a sheet that has been foamed to some extent can be heated to a high degree of foaming. However, this is only done when the sheet has a small wall thickness, and foaming by heating from the surface of a foam body such as a thick board has not yet been done. This is because it was thought that it would be difficult to apply heat to the inside of a thick foamed plate, and therefore it would be difficult to foam uniformly.

This invention provides a method for producing a styrenic resin foam by supplying a styrene resin and a blowing agent to an extruder, heating and kneading them, and extruding them. Mix fluoromethane and 1.0 to 0.3 moles of butane or dichlorodifluoromethane or a mixture thereof, extrude the kneaded mixture of resin and blowing agent to obtain a foam board with a thickness of 10 mm or more, and then coat the surface of the foam board. A thick styrene material that is made of foam by once lowering the temperature to below the heat distortion temperature of the resin, then heating it from the surface again after leaving it as it is, and heating the surface to a temperature 5 to 70 degrees Celsius higher than the heat distortion temperature. The present invention relates to a method of manufacturing a resin foam board.

The blowing agents used in the method of this invention are trichlorofluoromethane (hereinafter abbreviated as F11) and butane (hereinafter abbreviated as B).
or dichlorodifluoromethane (hereinafter referred to as F12)
It is a mixture of Moreover, the mixed blowing agent has a mixing ratio of 0.3 to 1.5 mol of F11 and 1.0 to 0.3 mol of B.
Or it is limited to a ratio of F12. moreover,
A mixture in the above proportions is required to be used for 1 kg of styrenic resin. These limitations were established based on the results of experiments conducted by this inventor, and if the conditions were not within these limitations, it would be difficult to extrude styrene resin in a thick state to make a good foam. That's because you can't. Here, B or F12 includes the case where a mixture of B and F12 is used.

The resin used in the method of this invention is not limited to homopolymers of styrenic monomers, but also includes copolymers. Styrenic monomers include methylstyrene and ethylstyrene in addition to styrene. In addition, the copolymer contains 50% of the styrenic monomer.
Contains more than mol%. Contains a copolymer. Examples of the copolymerization partner monomer include methyl methacrylate, acrylonitrile, maleic anhydride, and the like. Among them, suitable resins include polystyrene, styrene-acrylonitrile copolymer,
and a styrene-maleic anhydride copolymer.

The foaming agent may be added to the resin before the resin is supplied to the extruder, or within the extruder. The extruder may be a single screw or a twin screw extruder. A nozzle is attached to the tip of the extruder, and the nozzle has a slit opening extending in a straight line at the tip. Then, the foaming agent-containing resin is extruded from this slit. The width of the slit is selected in consideration of the expansion ratio of the resin passing through the slit so that the thickness will be 10 mm or more after foaming.

During or immediately after extrusion, the resin is cooled from the surface. What is conveyed when cooling during extrusion is
Cooling the resin at the tip within the die, and cooling immediately after extrusion means cooling the resin from the surface immediately after it exits the die. In order to prevent the extruded resin from undesirably deforming during foaming, it is desirable to provide a molding channel in the resin passageway. When providing a molding passage, it is desirable to simultaneously cool the molding passage so that the resin on the surface is cooled while the resin passes through the passage. Further, it is desirable that the molding passage gradually become wider and thicker as it advances, depending on the degree of foaming of the resin.

The resin that has come out of the die and has become a foam board is cooled once, regardless of whether it passes through the molding path or not.
Cooling is performed at least until the surface becomes below the thermal deformation temperature of the resin. As a result, the surface is at least hardened, and the extruded plate appears to be in a state where foaming has stopped. The extruded plate is cooled to the inside,
Although it is desirable that the material be cured, the interior may still be at a temperature above the heat deformation temperature and be in a state where it is about to foam.

A foam board whose surface has a temperature below the thermal deformation temperature of the resin has fine bubbles on the surface, and the bubbles are evenly distributed. However, when this foam board is cut and a cross section is viewed, there is a slight difference in density between the surface portion and the inside of the board. Specifically, the surface portion contains relatively fine bubbles and is foamed to a low magnification, resulting in a high density, while the interior portion contains relatively coarse bubbles, and is foamed to a high magnification, resulting in a low density. To give an example, if you divide a 20mm thick plate into a surface part 5mm from the surface and the rest of the inside,
The surface density is 5 to 50% higher than the internal density.
% higher density, even in narrow cases 10 to 30%
is increasing in density.

The tendency for foam boards made by extrusion to have a high-density surface area and a low-density interior becomes more pronounced as the thickness of the foam board increases;
In addition, this is generally more likely to occur with smaller densities than with larger densities.More specifically, when trying to obtain highly foamed products with a thickness of 10 mm or more, especially 20 mm or more, and an attractiveness of 40 Kg/ ^m3 or less, This tendency is noticeable.

In the method of the invention, the extruded foam board is heated from the surface, either after cooling from the surface or subsequently after cooling to the inside, or in a separate step. This heating is carried out until at least the surface of the foam board reaches a temperature 5 to 70° C. higher than its heat distortion temperature. Of course, the inside of the foam board may also be heated. Then, at least the surface portion is further foamed. In this way, the surface area approaches the lower density of the interior, and the board becomes a homogeneous foam as a whole. During this heating, the inside of the foam board does not foam as much as the surface area.

When heating the foam board, the purpose is to foam the surface portion, so care must be taken to place the foam board in an expandable state. Further, during this heating, it is desirable to avoid causing unnecessary deformation of the foam board. For this purpose, it is better to support the foam board from at least the top and bottom by sandwiching it loosely between Teflon-coated board surfaces, or by arranging a large number of rolls in parallel. When carrying out continuously, it is desirable to gradually widen the interval from the inlet to the outlet so that the foam board can expand as the interval between the rolls widens. It is thus desirable that the foam board be heated from the surface during its passage between the rolls. Heating can be done by various methods such as circulating heated air, blowing in steam, and irradiating with infrared rays. This heating is desirably carried out by dividing the heating area into one tank and continuously feeding the foam board into the tank and passing it through the tank.

The plate, which is heated from the surface to further foam the surface portion, is then cooled and used as it is or cut into a product. Cooling is done by air or by water. The foam board thus obtained is
Needless to say, when viewed from the surface, it is foamed uniformly and finely, and furthermore, it foams in the same way on the surface and inside, and there is no difference in expansion ratio, that is, density. In addition, the foamed board thus obtained has the advantage that dimensional changes due to temperature fluctuations are small even in places where the temperature changes. This advantage is particularly remarkable as an effect brought about by heating after foaming. Therefore, the foam board thus obtained is particularly useful for use as a heat insulator for ceilings of ordinary houses, rooftops or outer walls of reinforced buildings, etc.

In the method of this invention, various auxiliary agents such as colorants, bubble regulators, flame retardants, and lubricants can be added to the resin. The bubble control agent is, for example, finely powdered talc, and serves to make the bubbles uniform and fine. Further, the flame retardant is a compound containing, for example, phosphorus or a halogen element, and imparts flame retardancy to the resin. A lubricant is a compound that improves the slippage of heated resin, such as zinc stearate. Addition of these auxiliaries can facilitate extrusion operations and improve the properties of the foam board.

Next, a specific example of the method of this invention will be described with reference to Examples. In the examples, parts simply mean parts by weight.

Example: Using polystyrene (Denka Styrol GP-1, manufactured by Denki Kagaku Co., Ltd.) as the resin, polystyrene 100
0.5 parts of finely powdered talc (bubble control agent) and 3 parts of a brominated flame retardant (FG3200, manufactured by Teijin Kasei) were blended and supplied to an extruder. A blowing agent was injected into the resin midway through the extruder. As the blowing agent, a mixture of 0.63 mol of trichlorofluoromethane and 0.57 mol of dichlorodifluoromethane was used per 1 kg of resin.

Adjust the resin temperature to approximately 110℃ in the extruder nozzle,
I pushed it out of the mouthpiece. As a base, the tip has a thickness of 2
mm, with a slit of 100 mm width used. A molding tool was attached closely to the tip of the cap. As a forming tool, the inlet dimensions are substantially equal to the above-mentioned slit of the cap, and the outlet dimensions are 35 mm thick and 200 mm wide.
mm, with a total length of 50 mm, and a resin passageway that gradually expanded from the inlet to the outlet was used. Furthermore, the inner surface of this resin passage was coated with fluororesin. Oil at 90°C was circulated through the molding tool. In this way, the resin coming out of the cap is guided to the molding tool,
By passing through this, an extruded foam board with a thickness of 50 mm and a width of 245 mm was obtained.

This extruded foam board had an average density of 0.042 g/cc, had a high density on the surface and a low density on the inside, and the surface cells were finer than the internal cells. This foam board was cut to a length of 200 mm, left at room temperature for a day, then loosely sandwiched between two Teflon-coated iron plates, placed in an oven at 80°C for 24 hours to foam, and then cooled. A secondary foam board was obtained. The secondary foam board expanded to a thickness of 57 mm, a width of 325 mm, and a length of 225 mm, with an average density of 0.027 g/cc. The secondary foam board was foamed uniformly both on the surface and inside. The secondary foam board was then heated above the softening point of the resin, but the dimensional change was slight.

For comparison, the above primary foam was
When we heated the product that had been left for a week above the softening point of the resin, the dimensional change caused by heating was very large.

Comparative examples are described below, and the amount of blowing agent in each comparative example was set so that the resin could be expanded to the maximum extent using the blowing agent, and an extruded foam board with the lowest density could be obtained. I chose. Also,
The resin temperature was slightly changed in conjunction with the change in the type of blowing agent, but the degree of change was small.
It can be seen that they are almost the same.

Comparative Example 1 An extruded foam board was obtained in substantially the same manner as in the above example except that 1.31 mol of trichlorofluoromethane was used per 1 kg of resin as a blowing agent.

This extruded foam board has an average thickness of 52mm, width of 210mm,
The density was 0.044 g/cc, but the center part in the width direction was 49 mm thick, and both ends were 53 mm thick, so the center part in the width direction was concave and did not form a regular foam board, and the surface was rough with bubbles and the inside was The cells were fine and had a high-density core inside. This extruded foam board was cut into a length of 200 mm and subjected to secondary foaming in exactly the same manner as in the example to obtain a secondary foam board. The secondary foam board has a thickness of 56 mm, a width of 300 mm, a length of 260 mm, and an average density of 0.027.
g/cc, but the surface shrank and the interior contained a high-density core, making it unusable as a foam board.

Comparative Example 2 A foam with a thickness of 47 mm and a width of 260 mm was prepared in the same manner as in the above example, except that 0.91 mol of dichlorodifluoromethane was used per 1 kg of resin as a blowing agent.
An extruded foam board was obtained.

This extruded foam board had an average density of 0.039 g/cc, but the skin was torn and there were cavities inside, so it could not be used as a foam board. This extruded foam board was subjected to secondary foaming in exactly the same manner as in the above example to obtain a secondary foam board. The thickness of the secondary foam board is 52
mm, width 310mm, length 230mm, average density 0.030g/cc
However, the outer skin was torn, the interior contained cavities, and it was deformed and had a poor appearance, so it could not be used as a foam board.

Comparative Example 3 An extruded foam board was obtained in substantially the same manner as in the above example, except that 1.65 mol of butane was used per 1 kg of resin as a blowing agent.

This extruded foam board has a thickness of 50mm, a width of 260mm, and a density of
The density was 0.037 g/cc, and the density was almost uniform, but the epidermis was broken in some places and air bubbles were opened. This extruded foam board was subjected to secondary foaming in exactly the same manner as in the above example to obtain a secondary foam board. The secondary foam board has a thickness of 56mm, a width of 300mm, a length of 220mm, and an average density.
It was 0.029g/cc, but the epidermis was severely torn.
Furthermore, due to the residual butane gas, self-extinguishing properties were poor and the material could not be used as a foam board.

Claims (1)

[Claims] 1. In a method of producing a styrene resin foam by supplying a styrene resin and a blowing agent to an extruder, heating, kneading, and extruding, 0.3 to 1.5 moles of trichlorofluoro are added as the blowing agent to 1 kg of styrene resin. Mixing methane and 1.0 to 0.3 moles of butane or dichlorodifluoromethane or a mixture thereof, extruding a kneaded mixture of resin and blowing agent, and cooling the resin surface during or immediately after extrusion,
Obtain a foam board with a thickness of 10 mm or more, and once the surface of the foam board is below the heat distortion temperature of the resin, continue or leave it as it is, and then heat it again from the surface to make the surface 5 to 70°C higher than the heat distortion temperature. to temperature,
A method for manufacturing a thick styrene resin foam board, which is characterized by foaming.