JPS58215328A - Manufacture of stylene based resin foamed body - Google Patents

Abstract

PURPOSE:To achieve an even foaming of a stylene based reson foamable body with a large thickness by heat foaming of a stylene based resin foamable body bringing steam into contact with the surface thereof when it is at a high temperature thereinside while the surface thereof below the thermal deformation temperature. CONSTITUTION:A molten stylene based resin which is blended with a foaming agent such as aliphatic hydrocarbon and aliphatic hydrocarbon halide with a boiling point lower than the thermal deformation temperature of the stylene based resin is extruded to a low pressure area from an extruder and foamed to obtain a foamed body. When the foamed body is at a high temperature thereinside which the surface thereof is below the thermal deformation temperature, the surface of the foamed body heated to foam above the thermal deformation temperature in contact with steam to obtain a stylene based resin foamed body. The steam to contact the foamed body is preferably 80-120 deg.C and the contact time normally 1-10min.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a styrenic resin foam.

According to the extrusion molding method, a molded body can be manufactured continuously and efficiently, so the extrusion molding method is preferable in order to produce a foamed body having a constant cross-sectional shape. When making a thin, wide foam such as a sheet using styrene resin, a good foam can be produced by extrusion molding. However, when the thickness of the foamed sheet becomes large, for example, 10 sheets or more, and becomes so-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 become noticeable, making it difficult to foam the surface portion and the interior uniformly. Therefore, it was necessary to devise a method suitable for uniformly foaming thick products using extrusion molding.

Therefore, the inventor conducted various experiments in order to devise a method for uniformly foaming a thick styrene foam. At that time, this inventor foamed the thick foam that came out of the press machine in the air, cooled it from the surface, solidified only the surface part, and put on a skin, while the inside was still hot. When it is in a state where soft foaming power remains,
Steam was brought into contact with the surface of the skin to heat it from the surface. As a result, it was found that by doing this, as the skin on the surface of the foam foams, the interior of the foam also foams again due to the residual foaming force, and in the cross section, both the surface and the interior become foamed in the same way. This invention was made based on such knowledge.

In this invention, molten styrene resin containing a blowing agent is discharged from an extruder to a low pressure region, and is foamed to form a foam, in which the inside of the foam is at a high temperature and the surface area is below the heat distortion temperature. The present invention relates to a method for producing a styrenic resin foam, which is characterized in that the surface of the foam is brought into contact with water vapor in a state in which the surface of the foam is heated to a temperature equal to or higher than a rhombus temperature to cause foaming.

It is already known that when a styrenic resin foam is heated again, the foam undergoes secondary foaming and the expansion ratio increases. In this case, it was determined that a certain amount of time must be allowed between the initial foaming, or primary foaming, and the subsequent foaming, or secondary foaming. For example, it was necessary to leave it alone for at least one star night. This means that when foaming beads made of styrene resin are placed in a perforated mold and water vapor is blown into the mold to form a foamed product, from the time the beads are firstly foamed to the time when they are secondarily foamed.
This is clear from the fact that it was usually necessary to leave it for several days. In other words, it has conventionally been thought that if secondary foaming is performed subsequent to secondary foaming, the effect of secondary foaming is not sufficient.

In the method of this invention, secondary foaming and secondary foaming are carried out in the process of extrusion foaming, so according to conventional wisdom, the effect of secondary foaming is not sufficient, and therefore it is wasteful. it was thought. However, contrary to common sense, if steam is used after extrusion foaming and secondary foaming is performed by bringing the steam into direct contact with the foam, the secondary foaming effect will appear and the foaming will be uniform. It is. This is completely surprising.

In the conventional method, when performing extrusion foaming, after foaming, the foam is shaped and continued to cool to form a molded product.
In the method of the present invention, the material is foamed in the air, shaped, and completely cooled as usual, but the cooling is not continued until the molded product is obtained, but the cooling is temporarily stopped midway. The point of termination is when only the surface portion of the foam is below the heat distortion temperature. In other words, when the inside of the foam is at kudzu temperature, the foaming power is maintained, and only the surface is cold, cooling is stopped and the foam is heated from the surface instead. Steam is used for heating, and the steam is brought into direct contact with the foam. This point differs from the conventional method.

In the conventional method of cooling the foam, the surface of the foam expands to a low magnification and the inside expands to a low magnification. Therefore, the obtained molded article had a hard skin on its surface. However, as mentioned above, if cooling is stopped midway and the product is brought into contact with water vapor and heated again, the surface portion will foam again, and the residual foaming force inside will also be released, resulting in uniform foaming throughout. .

As mentioned above, if cooling, which is carried out in the post-extrusion process, is stopped midway through and instead heats and causes secondary foaming by contacting with water vapor, the resulting molded product will simply be uniformly foamed. Instead, it will be even better in many ways. For example, the foam will be a high-density foam as a whole, have good dimensional stability, and will be non-directional. Among these, in terms of high magnification, the expansion magnification increases by up to 50% due to secondary foaming, and the thermal insulation properties are also improved accordingly. In addition, in terms of dimensional stability, this molded product does not expand or contract significantly even if it is exposed to slightly higher temperatures. Furthermore, in terms of directionality, in the conventional method, the foam was stretched or compressed in the extrusion direction in order to take off the foaming material at a constant speed during extrusion. More specifically, if the expansion caused by foaming is removed too early, the foam will be stretched in the extrusion direction, making it easy to tear along the extrusion direction.On the other hand, if the foam is removed too late, the foam will was compressed and softened in the extrusion direction, and in any case, it was inevitable that the molded product would have directionality. However, in the method of this invention, the surface is further heated when the inside still has foaming power after foaming has finished, so both the inside and the surface foam freely and the directionality is reduced or lost. becomes. Therefore, the product according to the present invention has excellent quality.

The foam can be cooled by natural cooling, but a preferred method is to bring a cooling fluid into contact with the mold or the foam. Air or water can be used as the cooling fluid.

The point at which the surface portion of the foam has cooled below the heat distortion temperature while the interior is still at high temperature can be approximately estimated as the foam is continuously extruded from the extruder. That is, the extruded foam is gradually cooled from the surface, and since the foam itself is a heat insulating material, cooling progresses very slowly into the interior.

Therefore, the interior of the foam remains hotter than the surface portions for a significant period of time. Therefore, when it comes out of the mold, a skin forms on the surface, and the outer dimensions are approximately determined, we stop cooling and switch to heating. However, if you do not know the relationship between the cooling of the skin and the internal temperature, it is possible to cut the expanding foam at certain points and observe its cross section, and select the point at which the interior expands due to residual foaming power before switching to heating. can.

In method 2 of this invention, if switching from cooling to heating is performed when the foam has cooled too much, there will be almost no secondary foaming, or there will be little foaming in the center of the resulting foam. This will generate a middle layer of .

On the other hand, if the foam is cooled in the absence of light, the effect of secondary foaming will not be sufficiently achieved. Therefore, at the time of switching,
The cooled surface portion and the interior portion that maintains residual foaming power at high temperatures must coexist in an appropriate ratio. More preferably, the suitable condition is when the thickness of the surface portion cooled below the heat distortion temperature is within a range of approximately 1/50 to 1/2 of the thickness from the center to the surface of the foam. This is when it is within the range of 1/20 to 1/5.

Steam is used to heat the foam. It is preferable to use water vapor at 80°C to 120°C.

The water vapor brings it directly into contact with the surface of the foam.

The contact time is appropriately determined in consideration of the temperature of the water vapor, the size of the foam, etc., and based on the criterion that the surface of the foam reaches a temperature equal to or higher than the heat deformation temperature and foams appropriately. The time is usually about 1 minute to 10 minutes.

During heating with steam and immediately after warping, the foam must be maintained in a state in which it can expand while it expands and increases in volume. At the same time, it is necessary to avoid undesirable deformations of the foam. For this purpose, the foam is loosely sandwiched between Teflon-coated plate surfaces, or a large number of rolls are arranged in parallel to support the foam from at least the top and bottom. When carrying out continuously, the intervals between plates or rolls are gradually widened from the entrance to the exit.
Allow the foam to expand as it spreads. During its passage between the plates or rolls, the foam is thus brought into contact with water vapor and heated from the surface. Further, during heating, the heating area may be divided into one tank, and the foam may be continuously fed into the tank and passed through the tank to perform 71I'l heating.

The foamed material whose surface portion is subjected to secondary foaming by heating from the surface j is then cooled and is made into a product as it is or by being cut. The product thus obtained has a uniform surface area similar to that of the internal area. It is characterized by being finely foamed, with no difference in expansion ratio, that is, no difference in density, between the surface portion and the inside. In addition, as mentioned above, it is foamed at a high magnification, has no directionality, and has other characteristics such as little dimensional change due to temperature fluctuations. Therefore, the product produced by the method of this invention is good as a foam, and the board produced by this method is particularly suitable for use as a heat insulating material in the ceiling of a house, the roof of a general building, or the outer wall.

The styrenic resin used in the method of this invention is not limited to homopolymers of styrene monomers, but also includes copolymers. In addition to styrene, styrenic monomers include methylstyrene and ethylstyrene. Further, the copolymer includes a copolymer containing 50 mol% or more of a styrene monomer. Examples of the monomer to be copolymerized include methacrylic acid, methacrylic acid, acrylonitrile, maleic anhydride, and the like. Among them, preferred resins are polystyrene, styrene-acrylonitrile copolymer, and styrene-maleic anhydride copolymer.

The blowing agent used in the method of this invention is an aliphatic hydrocarbon or a halogenated aliphatic hydrocarbon having a boiling point lower than the heat distortion temperature of the styrenic resin. Examples of aliphatic hydrocarbons are saturated aliphatic hydrocarbons such as propane, butane, pentane, hexane, and unsaturated aliphatic hydrocarbons such as propylene, butene. Examples of halogenated aliphatic hydrocarbons include methyl chloride, methylene chloride, dichlorodifluoromethane, and the like.

These materials can be used alone or in combination of two or more.

The foaming agent may be added to the resin before the resin is supplied to the extruder or during the extruder. The extruder may be a -screw or a twin-screw extruder.

Although the method of this invention is particularly effective when producing foams with large walls, it can also be applied to the production of foams with small walls. Here, the term "large-walled foam" refers to a foam with a thickness of 10 fi or more.

Next, specific examples of the method of this invention will be described with reference to Examples.

In the following, parts simply mean parts by weight.

Example Using polystyrene as the resin, 100 parts of polystyrene was mixed with 0.5 part of finely powdered talc (bubble control agent), and this mixture was fed to an extruder at a ratio of 60 to 9 parts for 1 hour. The blowing agent was injected into the resin. As a foaming agent,
Using a mixture of 3 parts of dichlorodifluoromethane and 7 parts of methyl chloride, add 11 parts of this mixture to each resin.
It was press-fitted at a rate of 0g.

The cap has an opening with a thickness of 2.5 M and a width of 501 Eg at the tip, and holes with a diameter of 10 mm are made above and below the opening, and while cooling the surface by passing water at 60°C, resin is poured through this opening at a temperature of 110°C. Extruded. A molding tool was attached closely to the tip of the cap to prevent the resin from deforming.

As a forming tool, the inlet dimensions are substantially equal to the opening of the cap, and the outlet dimensions are 82111 in thickness, 130 m in width, and 3 in length.
10 mm and provided with a resin passageway that gradually expanded from the inlet to the outlet.

The resin passage wall of the molding tool was coated with fluororesin.

Water at 60°C was circulated within the molding tool.

The foam that came out of the molding tool was highly foamed. This foam was cooled by blowing air at 20°C. Cooling was performed from the end of the molding tool to a point 1005. At this time,
The foam had a surface temperature of 35°C and a center temperature of 75°C. A steam house with a length of 5 m is placed ahead of this, and Q and l are placed inside the tank.
The foam was heated by blowing out /g/c+d of steam (95°C).

When the physical properties of the molded product thus obtained were measured, as shown in the Examples column of the following table, the density became uniform throughout, the expansion ratio increased, and the density became smaller.
Furthermore, it was observed that the directionality of compressive strength was reduced. Moreover, the resulting molded product had a slightly flexible μ.

For comparison purposes, the physical properties of molded articles obtained by direct cooling without using a steam bath in the operations of the above examples are listed in the column of comparative examples. In the case of the comparative example, the density difference in the thickness direction of the molded product is large, and the difference in the compressive strength direction is also large.

Sara K. After leaving the molded product of the comparative example at room temperature for one week,
It was heated for 2 minutes in a steam bath at 95℃, but the density was lower than 3.
0.5, middle part 30.1, and lower part 81.4, and almost no secondary foaming occurred.

Table Physical properties of molded product *1 Peel off the skin of a 200 m long molded product by approximately 5 m each on the top, bottom, left and right sides, divide the remaining foam into three parts in the thickness direction, and calculate the density % of the top, middle, and bottom (Q). It was measured.

*2 Cut out a 50m square test piece from the molded product, and measure it in the extrusion direction (MD), width direction (TD), and thickness direction (VD).
) from three directions, h compressive strength 'Q is measured, and M
The respective ratios were determined so that DXTDXVD=1.

Patent applicant Sekisui Plastics Co., Ltd. --- Agent: Patent attorney Masami Sakai -

Claims (1)

[Claims] Molten styrene resin containing a foaming agent is extruded from an extruder to a low pressure region, and is foamed to form a foam. When the inside of the foam is at a high temperature and the surface is below the heat distortion temperature, the foam surface is A method for producing a styrene resin foam, which comprises bringing the foam into contact with water vapor and heating the surface to a temperature higher than the heat distortion temperature to cause foaming.