JPH0212740B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Field of Application) The present invention relates to a method for producing a thermoplastic resin foam.

BACKGROUND OF THE INVENTION Thermoplastic foams can be made in a variety of ways. Among these, the extrusion method is the most widely used. This is because the extrusion method requires low equipment costs and can produce foam continuously and efficiently.

The main equipment required to carry out the extrusion method is an extruder, a die, and a take-off machine. others,
When foaming a foam at a high magnification to obtain a low-density product, a molding channel is used to prevent the resin from foaming and causing undesirable deformation immediately after leaving the die. This molding passage is attached to the tip of the cap. The molding passage is tunnel-shaped, and is open only in the direction in which the resin travels, and is closed all around the resin, or in the case of a plate-shaped passage, the sides in the width direction are open. Open structures were often used.

When making a foam by extrusion, a thermoplastic resin containing a foaming agent is heated and softened in an extruder, and the softened resin is fed into a die and molded into the desired cross-sectional shape. It is pushed out from the mouthpiece.
The extruded resin may be allowed to foam as it is in the air, but when the molding passage is attached closely to the die, the resin will foam in the molding passage, increase its volume, and change its cross-sectional shape. It is regulated and becomes the desired shape. During this time, the resin is cooled, but
After leaving the molding channel, the resin is further cooled. The thus cooled resin is then taken off by a take-off machine to form a foam.

Molding the resin extruded from the die through the molding channel as described above has the advantage of providing a foam with a desired shape, but has the serious drawback of creating scratches on the surface of the foam. . That is, since the resin advances in contact with the wall surface of the molding passage, the surface of the foam body is rubbed against the wall surface of the passageway, and as a result, cracks and shark skin are generated in the foam body. Therefore, in this method,
It has been almost difficult to obtain a foam with a surface smooth enough to withstand practical use. Moreover, even if the above-mentioned molding is possible under very limited conditions such as the shape of the molded article, the type of resin, the expansion ratio, etc., the molding itself is impossible in most cases. That is, the resistance in the molding passage usually causes clogging and the foam deforms and breaks.

In order to improve the above-mentioned points, attempts have been made to make the walls of the molding passages slippery. One attempt was made to coat the wall surface of the molding passage with a fluororesin. When coated with fluororesin, the walls of the molding channel become slippery, making it possible to mold in many conditions, or the cracks on the foam surface are somewhat reduced, and the surface is certainly improved. be done. However, it was not possible to completely eliminate cracks and shark skin and create a smooth surface. For this reason, some products are made by peeling the skin. Also,
In such attempts, since the fluororesin is easily abraded, the effect of coating with the fluororesin disappears as production time passes, and therefore, it is not possible to stably produce a high-quality foam for a long period of time. Moreover, the coefficient of dynamic friction on the surface of fluororesin is
This increases as the speed increases, so if the extrusion speed of the foam is increased, the foam becomes less slippery, which intensifies the above-mentioned drawbacks, and therefore cannot be extruded efficiently.

As another extrusion foaming method, attempts have been made to inject lubricating oil onto the wall surface of the resin passage within the die to make the resin easier to slide on the wall surface. For example, Japanese Patent Application Laid-open No. 58-1531 and Japanese Patent Publication No. 58-37145,
describes such techniques. Both of these conventional examples aim to improve the slippage of the resin in an unfoamed state until it passes through the outlet of the mouth mold, but do not teach that the resin in a foamed state can improve its slippage. do not have. In any case, the liquid processing agents used here include, for example, mineral oils and fats,
These include vegetable or animal fats and oils, water-soluble silicone oil, triethanolamine, wax, and glycerin. However, when such a liquid treatment agent is used, the surface of the molded article is stained by the treatment agent, and cleaning the surface is rather time-consuming. In addition, some of the processing agents were expensive, so it could not be said that they were economical.

(Means for Solving the Problem) The inventor focused on the fact that fluororesin has water repellency, and constructed the wall surface of the molding passage with fluororesin, and also poured water on it as a lubricant. I came up with this. Therefore, an attempt was made to coat the wall surface of the molding channel with a fluororesin and to inject water as a lubricant between the wall surface and the foamable resin within the die. As a result, it was confirmed that the friction between the foamable resin and the fluororesin was reduced, the foamable resin slid through the molding path, the wear and tear of the fluororesin was reduced, and the surface of the foam became smooth. This invention was completed based on such confirmation.

In this invention, a heated and softened foamable thermoplastic resin is sent from an extruder into a die, extruded into a molding passage that is in close contact with the die, and the resin is foamed in the molding passage to form a molded product. In this method, the wall surface of the molding channel in contact with the die is made of a non-hydrophilic organic material, and the non-hydrophilic organic material is one on which water forms a contact angle of 70 degrees or more. The present invention relates to a method for producing a thermoplastic resin foam, which comprises extruding a foamable resin while forcing water into a space between a wall surface of the mouthpiece and the resin within the mouthpiece.

(Example) An example of implementing the method of the present invention will be explained with reference to the drawings as follows. FIG. 1 is a partially cutaway longitudinal sectional view of an apparatus in an embodiment of the method of the present invention. FIG. 2 is a partially cut away longitudinal sectional view of an apparatus in another embodiment of the method of the invention.
FIG. 3 is a sectional view taken along the - line in FIG. 2.

In FIG. 1, 1 is an extruder, 2 is a breaker plate, 3 is a die plate, 4 is a die, 5 is a molding passage, 6 is a coating layer of non-hydrophilic organic material, 7 is a water extrusion port, and 8 is a The shape-retaining core body, 9 is a cutting tool.

In this invention, a foamable thermoplastic resin that has been softened by heating is extruded from an extruder 1 through a breaker plate 2 and a die plate 3 into a die 4. The resin squeezed into the mouthpiece 4 is
It is extruded into the molding passage 5 which is in close contact with the molding passage 5, and is foamed in the molding passage 5 to form a molded body. The wall surface of the molding passage 5 in contact with the resin is formed with a coating layer 6 of a non-hydrophilic organic material. Further, a water extrusion port 7 is provided in the mouthpiece 4, and water is press-fitted between the wall surface of the mouthpiece 4 and the resin. The resin, whose surface has been coated with water in the die, is extruded into the molding passage 5, foams within the molding passage 5, and slides on the surface of the non-hydrophilic organic material coating layer 6 while being lubricated. The material moves to form a cylindrical foam. Thereafter, the cylinder is shaped using a shape-retaining core 8 and cut into pieces using a cutting tool 9 to form a foamed flat plate.

To put it simply, the non-hydrophilic organic material covering the wall surface of the molding passageway 5 in contact with the resin is an organic material that has water repellency. The degree of water repellency is expressed by the contact angle formed by water droplets when water is dropped on the surface of the organic material. The coating layer 6 of non-hydrophilic organic material used in this invention is:
A material on which water forms a contact angle of 70 degrees or more is used. The following may be considered as such materials:

Examples of solid polymers include fluororesins such as tetrafluoroethylene resin (PTFE), tetrafluoroethylene/hexafluoropropylene copolymer, and trifluorochloride ethylene resin. Also polydimethylsiloxane, polymethylphenylsiloxane, polymethylhydrodienesiloxane and their polyethers,
There are silicone resins such as modified silicone such as epoxy and aminocarboxy. Also 6 nylon, 6.6
There are polyamide resins such as nylon. There are also polyolefin resins such as polyethylene, polypropylene, and poly-1,4-methylpentene.

As for how to use the above-mentioned material, in addition to using it as a covering, it is also possible to create a molded passage itself by using it alone or in a composite with porous metal or the like.

Further, various waxes, greases, oils, etc. can also be used. Examples include higher fatty acids such as stearic acid, palmitic acid, and oleic acid, and their fatty acid esters, fatty acid amides, and metal soaps. There are also paraffin wax and wood wax. There are also synthetic polymer waxes or oils such as low polymerization degree polyethylene, polypropylene, silicone, and fluororesin. There are also industrial products such as mold release agents for plastic molding, various waxes, and greases. There are also mineral oils, synthetic oils, asphalt, tarcas, etc. There are also animal and vegetable fats and oils (for example, wool wax, beef tallow, hydrogenated beef tallow oil, fish oil, pine tar, etc.). Also, alkylpyridinium halides, pyridinium salts, alkylethylene ureas,
Compounds include alkyl ketene dimers, stearate chromium chloride, and carbamide.

Among these, some create a solid film when heated or evaporated with a solvent, while others create a viscous film that is difficult to remove. There are also liquid film types, but these are not unusable. Even if it is in liquid form, it is said that through repeated application and heating, it will be impregnated onto the metal surface and form a thin film. This is known from experience in the plastic molding industry when it comes to silicone oil and wax-based mold release agents. Moreover, many of the above-mentioned materials can be used by impregnating a porous body. At this time, if it is liquid, it can be replenished from behind constantly or intermittently.

Among the various non-hydrophilic organic materials mentioned above, solid polymers are preferred, and among them,
Fluorine resins and silicone resins are particularly preferred.

A water outlet 7 is provided in the mouthpiece 4.
Since the die 4 shown in FIG. 1 is for extruding a resin formed into a tube, the die wall surfaces in contact with the resin include a cylindrical surface of the outer mold and a cylindrical surface of the inner mold. An extrusion port 7 is provided on each of its two cylindrical surfaces. The position where the extrusion port 7 is provided is before the tip of the die 4, that is, before the resin passage gap is narrowed at the tip of the die 4. Alternatively, it may be located extremely close to the mouthpiece entrance. Moreover, although it is desirable that the extrusion ports 7 extend all the way in the circumferential direction, they may be scattered at equal intervals in the circumferential direction.

FIG. 1 shows an example in which the extrusion ports 7 on the outer mold are scattered in the circumferential direction, and the extrusion ports 7 on the inner mold are provided continuously in the circumferential direction. In detail,
Water is press-fitted onto the outer mold through a plurality of pipes 71, and each of the press-fitted water passes through a passage 72.
It is extruded from extrusion ports 7 which are scattered. The extrusion port 7 is
A sintered body of metal powder is fitted to allow water to pass through but not resin. The squeezed water is
At first, they are only scattered here and there, but they soon spread over the resin surface, producing a result similar to that of continuous extrusion ports 7.

On the inner mold, as described above, water is forced out through the extrusion ports 7 of the powder metal sintered holes provided continuously in the circumferential direction. Specifically, water is press-injected into the inner mold through one pipe 73, and the injected water forms an annular passage 74 within the inner mold, and the extrusion port 7 of the annular powder metal sintered body connected to the annular passage 74. It is forced out towards the resin passage.

Although FIG. 1 shows an example in which the extrusion ports 7 on the outer mold and the extrusion ports 7 on the inner mold have different structures, these extrusion ports 7 may have the same structure. Alternatively, the extrusion ports 7 of the outer mold may be continuous in the circumferential direction, and the extrusion ports 7 of the inner mold may be scattered.

The cap 4 and the molding passage 5 are in close contact. Close contact does not mean that the opposing surfaces are brought into close contact. As shown in FIG. 1, it is desirable that only the portions forming the resin passages be in close contact with each other, and gaps 10 be formed in the remaining portions.

Here, lubrication usually includes (A) solid lubrication, (B) boundary lubrication (for low-speed sliding), and (C) liquid lubrication (for high-speed sliding).
There is. In the examples of the present invention, if the injected water is extremely small and is adsorbed on the resin surface, it is considered to be close to (A) solid lubrication. Even in such a situation, it shows great effects,
This is confirmed by an experiment to measure the coefficient of friction in the atmosphere with varying atmospheric humidity. Also, if the amount of water injected is a little large, it is considered that the lubricated state as shown in (B) and (C) is achieved, but good results can also be obtained in this case. In other words, when water is brought into the lubricating state of (B) and (C), its performance is usually very inferior to that of lubricating oil, but when it is combined with the coating layer 6 of water-repellent material, a significant improvement is achieved. This is because

As described above, when the foamable resin leaves the mouthpiece 4, its surface in contact with the wall surface of the mouthpiece is covered with a thin layer of water.

The foamable resin covered with a thin layer of water exits the die 4 and enters the molding channel 5, where it foams. When foaming begins, the resin increases in volume and therefore changes shape. However, in the present invention, since foaming is performed within the molding passage 5, the resin is prevented from being undesirably deformed. Therefore, the resin comes into close contact with the wall surface of the molding passage 5 and advances while rubbing the wall surface.

In the method of this invention, the foamable resin is
When proceeding, the resin surface is covered with a thin layer of water. On the other hand, the wall surface of the molding passage 5 is formed of a coating layer 6 of a non-hydrophilic organic material, and the non-hydrophilic organic material is so non-hydrophilic that water forms a contact angle of 70 degrees or more on it. It is highly hydrophilic. Therefore, the foamable resin progresses smoothly on the surface of the non-hydrophilic organic material because friction is alleviated by the lubricating action of water. Therefore, the surface of the foam becomes smooth, and no cracks or rough texture occur. In this way, a good foam can be obtained.

FIGS. 2 and 3 show the case where the foam is extruded in the form of a flat plate. The cap 4 is provided with a resin passage that spreads out in a flat plate shape. Water extrusion ports 7 are provided at various places on the wall of the mouthpiece. The extrusion ports 7 are connected to independent pipes 71, respectively.

In the embodiments shown in FIGS. 2 and 3, the foamable resin is rapidly expanded in the width direction within the base 4 to form a flat shape. An extrusion port 7 is provided in this flat shape. To be more specific, the extrusion port 7 is provided as a large number of holes at a position closer to the extruder 1 than the extrusion end of the die 4 when viewed in the resin flow direction. Furthermore, when viewed in the width direction of the flattened resin, the extrusion ports 7 are lined up with equal gaps in the width direction. Note that the extrusion port 7 is not limited to this position; for example, it may be located only on both side surfaces where poor flow is likely to occur, or at the inlet of the mouthpiece 4 (immediately after the breaker plate 2).
It may be.

The wall surface of the molding passage 5 in contact with the foam is coated with, for example, silicone resin. The silicone resin is not applied to all the walls, but is applied only to the base 4 side. Specifically, in the molding passage 5, the resin passage rapidly expands in the thickness direction on the side of the die 4, and thereafter continues with almost the same thickness without changing the size in the thickness direction. The silicone resin 61 mainly covers the portion where the resin passage rapidly increases in thickness on the side of the base 4, and only covers a portion of the same thickness on the side of the base 4.

In the embodiment shown in FIGS. 2 and 3, as soon as the foamable resin enters the cap 4, it rapidly expands in the width direction to form a flat plate, and water is applied to both the front and back surfaces of the resin. It enters the molding passage 5 with the entire surface covered with water. In the molding passage 5, the resin foams, swells, and rapidly increases in thickness, and progresses while sliding on the surface of the silicone resin 61, and then progresses while sliding on the wall surface not covered with silicone resin. During that time, it is shaped into a foam board. The foam board is taken off by a taking-off device 11.

According to the method of the invention, a heated and softened foamable thermoplastic resin is sent from an extruder into a die, and is extruded into a molding passage in close contact with the die.
Since the resin is foamed in the molding passage to form a molded object, the shape of the foamable resin is regulated by the molding passage when it expands and changes its volume, so it can be shaped exactly as desired. A molded body can be obtained. In addition, since the wall surface of the molding channel in contact with the die is coated with a non-hydrophilic organic material, the foamable resin can be molded while sliding on the surface of the non-hydrophilic organic material. Therefore, it is slippery and hard to get damaged. In addition, the non-hydrophilic organic material used is one on which water forms a contact angle of 70 degrees or more, and water is not forced into the mouth between the mouth wall and the resin. Therefore, the foamable resin slides on the non-hydrophilic organic material using water as a lubricant, and therefore there is less friction on the wall surface of the molding passage 5, forming a smooth surface and improving the surface quality. form a foam. Moreover, the above friction can cause the resin to advance at a high speed. Furthermore, due to the lubricating effect of water, there is less wear and tear on the non-hydrophilic organic material, and therefore molding can be carried out continuously for a long period of time. Furthermore, since water is used as a lubricant, no post-treatment is required to remove it. The method of the invention provides these benefits.

Next, the details associated with the method of this invention will be explained. First, most thermoplastic resins can be used as long as they can be foamed. Suitable examples include polystyrene, polyethylene, polypropylene, polyvinyl chloride, and the like. In addition, acrylic resins, carbonate resins, amide resins, etc. can be used.

Some resins include resins that easily absorb water, such as polyamide and polyvinyl alcohol,
Some resins, such as polyethylene terephthalate, are easily decomposed by water, but by locating the water extrusion port close to the tip of the mouthpiece, shortening the contact time with water, and reducing the amount of press-in, this can be done without much problem. You can.

Various foaming agents can also be used. Broadly speaking, any of aliphatic hydrocarbons, halogenated aliphatic hydrocarbons, inert gases, and solid compounds that generate gas upon decomposition can be used. Ethane, propane, butane, pentane, etc. can be used as the aliphatic hydrocarbon, methyl chloride, ethyl chloride, monochlorodifluoromethane, dichlorodifluoromethane, etc. can be used as the halogenated aliphatic hydrocarbon, and as an inert gas, Carbon dioxide, nitrogen, etc. can be used, and solid compounds that generate gas include dinitrosopentamethylenetetramine, azodicarbonamide, barium carboxylate, and the like. These can be used alone or in combination. The amount used is within the range of 0.5-100 parts by weight per 100 parts by weight of the resin.

Further, it is desirable to add a cell nucleating agent to the resin. By adding a bubble nucleating agent, fine bubbles can be uniformly generated. As the bubble nucleating agent, finely powdered talc, silica, sodium bicarbonate, etc. are suitable. In addition, colorants, antistatic agents, stabilizers, plasticizers, etc. used in ordinary extrusion foaming can be added to the resin.

Water is used as the lubricant, but other substances can also be dissolved in the water and used as an aqueous solution. For example, in order to extrude water evenly from multiple extrusion ports, a suitable thickener such as ethylene glycol, glycerin, carboxymethyl cellulose, or polyvinyl alcohol can be added as a water thickener to increase the boiling point of the water. Salts and polyhydric alcohols can be added to increase the A surfactant can also be added to evenly disperse water. In addition, antistatic agents, coloring agents, adhesives, etc. can be added, and other effects can be added at the same time.

It is desirable that the water be dispersed as evenly as possible over the entire surface of the resin. For this purpose, a large number of extrusion ports 7
In the case where the extrusion port 7 is provided separately, it is desirable to provide a water pressure regulating valve or distributor in each pipe connected to the extrusion port 7. Further, when the extrusion ports 7 are provided continuously, it is desirable to provide a water storage portion extending over the entire extrusion port 7. In order to prevent the molten resin from flowing back from the extrusion port 7,
The extrusion port 7 is made into a slit with an extremely narrow gap,
Alternatively, it is desirable to use a thin nozzle, a thin porous material, or a check valve near the extrusion port 7.

Next, the method of the present invention will be explained in further detail with reference to examples.

Example 1 In Fig. 1, the inner diameter of the cylinder of extruder 1 is 65 mm.
mm, using a single screw with a length to diameter ratio of L/D = 30, and a diameter of approximately
A cylindrical cap 4 having an annular outlet with a resin passage cross-sectional area narrowed to 100 mm and a gap of 0.7 mm was connected. In addition, the maximum resin passage gap on the outlet side of the cap 4 is 8 mm.
A molding passage 5 having a passage outlet diameter (distance from center to center of the gap) of 130 mm was connected. The extruder 1 used was one equipped with an injection port for supplying the liquid foaming agent from the middle of the barrel. The water extrusion port 7 was constructed using a one-piece powder metal sintered body having an extremely large number of pores. Both inner and outer pipes 7
Separate pumps were used to send water through 1 and 73. The covering layer 6 was formed by baking a polytetrachlorethylene (PTPE) coating.

In the above configuration, low density polyethylene HE-
30 (manufactured by Mitsubishi Yuka Co., Ltd. MI=0.3) 100 parts by weight, talc 1.0 parts by weight, stearic acid monoglyceride
A kneaded product containing 1.0 part by weight of blowing agent butane and 18 parts by weight of butane as a blowing agent was prepared at a rate of about 40 kg/hour and was pumped into the nozzle 4. The temperature of the kneaded material at this time was 120 degrees. Water was injected into the cap 4 from the inside and outside at a rate of about 100 c.c./hr. The press-fit pressure at this time is approximately 90
This kneaded material, which had a weight of Kg/cm ² , was extruded into the molding passage 5 and simultaneously foam-molded, and then extruded to the outside. The cylindrical foam supported by the core 8 was taken up while being cut open with a knife 9, and wound up into a roll.

The resulting foam, after being stabilized for two weeks, had a width of 450 mm, a thickness of 7.9 mm, a foaming ratio of 33 times, and a beautiful surface with no cracks, pockmarks, or shark skin (scale pattern). Ta. For comparison, the sample in which water injection was stopped had severe cracks, pockmarks, and shark skin on the surface, and was therefore easily broken and had low mechanical strength such as tensile strength and tearing. Incidentally, the tensile strength of this example is 3.5/2.1 (length/width) Kg/ ^cm2 ,
The weight of the comparative example above was 2.1/0.8 (length/width) Kg/cm ² .

Example 2 Extruder 1 of Example 1 was used. The cap 4 used had an annular outlet with a diameter of about 100 mm and a resin passage cross-sectional area narrowed to a gap of 0.35 mm. The molding passage 5 used had a maximum resin passage interval of 4 mm, a cone shape with a spread angle of 60 degrees, and a passage exit diameter (distance from center to center of the interval) of 160 mm. The structure of the water extrusion port 7 is the same as that in FIG.
It was constructed using a divided ring-shaped powder metal sintered body. I also connected a mini pump to each of them to pressurize water. The coating layer 6 was formed by baking a PTFE coating with a thickness of about 40 μm.

In the above configuration, polypropylene MH-8
(Mitsubishi Yuka Co., Ltd. MI = 0.3) 100 parts by weight, 1.0 parts by weight of talc as a foaming nucleating agent, and 20 parts by weight of butane as a blowing agent were used at a rate of 30 kg per hour. A foam sheet was manufactured using the same procedure. The total amount of water supplied to mouthpiece 4 is 200.
cc/Hr, and the press-in pressure was approximately 120 Kg/cm ² .

The resulting foam sheet had a thickness of 4.0 mm, a width of 550 mm, and a foaming magnification of 45 times, and had a beautiful surface with no cracks, pockmarks, or shark skin (scale pattern). For comparison, when the water injection was stopped, a scratch pattern appeared on the surface.

Note that when the above production was carried out without water injection, the appearance deteriorated even more significantly after about 2 tons of production. When the molding passage 5 was observed, it was found that the PTFE coat (approximately 40 μm thick) on the die side was worn out.

On the other hand, with the water injection method, the same
Even after producing approximately 8 tons of PTFE coated products, no deterioration in quality was observed, and there was virtually no visible wear of the coating.

Example 3 Extruder 1 of Example 1 was used. The cap 4 shown in FIGS. 2 and 3 was used, having a length (width) of 200 mm and a linear outlet with a narrowed resin passage cross-sectional area of 0.5 mm. As shown in the figure, eight extrusion ports 7 were provided on each of the upper and lower surfaces. The molding passage 5 attached to the mouthpiece 4 has sufficient width in the width direction for molding, has no side restrictions, and is restricted only to the top and bottom surfaces, with a maximum gap of 4 mm and a length in the machine direction of 80 mm.
It was from. Of that 80mm, it is close to base 4.
The 40mm section is made of PTFE block, and the remaining 40mm is made of iron, both of which can be water cooled from the back.

In the above configuration, 100 parts by weight of modified polyphenylene ether resin Noryl #731 (product of Engineering Plastics Co., Ltd.), 1 part by weight of talc as a foaming nucleating agent, and 3 parts by weight of butane as a foaming agent were added at a rate of 40 kg/hour. The foam was extruded and collected in the form of a flat plate. The amount of water injected was approximately 300c.c./Hr.

The resulting foam had a width of 290 mm, a thickness of 4 mm, a foaming ratio of 3.2 times, and a very smooth surface.
By the way, in this state, without water injection, extrusion molding was not possible, and although I was able to reduce the extrusion rate to 15 kg/hr and finally succeeded in molding, the surface of this board was rough. It was warm.

Example 4 An extruder 1 with a cylinder inner diameter of 120 mm and a blowing agent injection port in the middle of the cylinder was used. The cap 4 is
A fan die with a length (width) of 300 mm and a linear outlet with a narrowed resin passage cross-sectional area of 2.5 mm gap (thickness) was used. In the middle of this van dai, in a situation similar to that shown in Figure 3, there were
Thirty-two sintered metal extrusion ports 7 were provided. Each extrusion port 7 was equipped with a system in which water could be evenly pumped from one pump via a distributor. The molding passage 5 attached to the cap 4 has a shape as shown in Fig. 3, and is designed to regulate the top, bottom, and both sides (maximum thickness 80 mm, maximum width 600 mm), and to form a thick plate by foam molding. be. The inner surface of passageway 5 was coated with PTFE and nickel electroplating (technology by Murakami Industries Co., Ltd.).

In the above configuration, polystyrene (polymerization degree Pu
= 1500) 100 parts by weight, 0.5 parts by weight of talc as a foaming nucleating agent, 10 parts by weight of methyl chloride as a foaming agent,
Similarly, 3 parts by weight of dichloromethane was extruded and foamed at a rate of 110 kg/hour, and the continuously extruded foamed plates were picked up while the speed of the sandwiching conveyor was slowed down slightly and the brakes were applied. Summer. The amount of water injected was approximately 400c.c./Hr.

The resulting foam had a width of 630 mm, a thickness of 90 mm, and a foaming ratio of 35 times, had a smooth surface with no cracks, and was well formed on both sides, and did not require peeling. By the way, in the case where the water injection was stopped, there were numerous cracks about 8 mm deep, and traces of the cracks remained even deeper, so it was necessary to peel off the skin by 20 to 30 mm from the top and bottom sides. Moreover, the shapes of both sides were also very irregular.

Example 5 An extruder 1 was used, which had a cylinder inner diameter of 40 mm, a single screw with L/D=28, and was equipped with a blowing agent injection port in the middle of the cylinder. The diameter of base 4 is 20
The exit gap of the cylindrical resin passageway is narrowed down to 3mm, and the diameter of the part of the passageway near the extruder 1 is 10mm, and there are four extrusion ports 7 with check valves on the circumference of this part. has been established. The molding passage 5 attached to this mouthpiece 4 was for rod molding, and had a maximum inner diameter of 30 mm and a total length of 70 mm. This inner wall surface was coated with silicone resin 61.

The above configuration is the same as Example 2 except that the amount of blowing agent butane is 15 parts by weight, and 4.8 kg/hour
Foam molding was carried out at a ratio of The amount of water injected is
It was approximately 30-50c.c./Hr.

The resulting foam was a smoothly molded rod with an outer diameter of 32 mm and a foaming ratio of 36 times. Incidentally, those in which water injection was stopped had severe unevenness and a poor appearance.

Example 6 The apparatus of Example 5 was used. However, the molding passage 5
The inner surface of the tube was used as is, and silicone oil was applied immediately before extrusion molding.

Extrusion molding was carried out in the same manner as in Example 5. The resulting foam was also molded well.

Note that when the water injection was stopped, the appearance immediately deteriorated, and soon (within a few minutes) a state of molding failure occurred. Therefore, by injecting silicone oil from the water inlet and applying it to the inner wall surface of the passage 5, and then switching to water injection, the original state can be restored, and it will remain in good condition for a long time (at least 1 hour). I was able to drive. There was almost no stickiness or dirt on the product.

Example 7 The extruder 1 used in Example 5 was used. Base 4
had the same shape and structure as Example 5, only the outlet nozzle dimension was changed to 4.2 mm in diameter. The molding passage 5 had a maximum inner diameter of 20 mm and a total length of 70 mm, and was designed for cylindrical rod molding. The coating layer 6 is made of a material obtained by impregnating a sintered metal porous body with higher fatty acid zinc (a metal soap mainly composed of zinc stearate) as a water-repellent material. did.

The above structure was the same as in Example 2 except that the amount of the blowing agent butane was 5 parts by weight, and foam molding was carried out in substantially the same manner as in Example 5.

The obtained foam was a smoothly molded rod with an outer diameter of 20 mm and a foaming ratio of 37 times. It was also not contaminated with lubricants that caused it to feel "sticky".

[Brief explanation of drawings]

FIG. 1 is a partially cut away longitudinal sectional view of an apparatus in one embodiment of the method of the present invention. FIG. 2 is a partially cut away longitudinal sectional view of an apparatus in another embodiment of the method of the present invention. Figure 3 shows - in Figure 2.
FIG. In the figure, 1 is an extruder, 2 is a breaker plate, 3 is a die plate, 4 is a die, 5 is a molding passage, 6 is a coating layer of non-hydrophilic polymer, 7 is a water extrusion port, and 8 is an enlarged 9 is a cutting tool, 10 is a gap, and 11 is a take-off device.

Claims (1)

[Claims] 1. A foamable thermoplastic resin that has been heated and softened is sent from an extruder into a die, extruded into a molding passage in close contact with the die, and the resin is foamed in the molding passage. In this method, the wall surface of the molding channel in contact with the die is made of a non-hydrophilic organic material, and water forms a contact angle of 70 degrees or more on the non-hydrophilic organic material. using things,
A method for producing a thermoplastic resin foam, the method comprising extruding a foamable resin while pressurizing water between a mouthpiece wall surface and a resin in a mouthpiece. 2. The method for producing a thermoplastic resin foam according to claim 1, characterized in that the non-hydrophilic organic material is a non-hydrophilic polymer.