JPS6127230A - Manufacture of thermoplastic resin foamed plate - Google Patents

Abstract

PURPOSE:To prevent the opposite sides of a foamed plate from cracking even when the foamed plate is drawn at a high speed in an extrusion foaming step, by ejecting a lubricant under pressure from passage wall surfaces at the opposite sides of the width of the plate when a resin is spread to the maximum point of the width of a mouth piece. CONSTITUTION:In the production of a foamed plate by extruding a foaming agent-containing thermoplastic in a solftened state from a passage having an opening with a width 20-1,000 times as large as the height that is open in the extruding end surface of a mouth piece, a lubricant is forcibly fed from ports 8 formed in a passage wall surface at the opposite sides of the width of the mouth piece so that the lubricant may be forced between the wall surface and the resin thereby allowing the lubricant in the form of a thin film to adhere to the resin surfaces at the opposite sides and the resin is extruded from the mouth piece. The extrudate having the lubricant adhered is immediately introduced in a mold 6 where it is foamed and all the surfaces of the planar extrudate are allowed to be in contact with the inner walls of the mold to shape and cool the extrudate. The foamed plate that has been cooled is take up by a take-up, and is foamed in a mold at a higher foaming rate.

Description

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

Thermoplastic foam board can be made by a variety of methods. Of these, extrusion is the most widely used method. This is because the extrusion method has low equipment costs and can produce foam boards continuously and efficiently.The main equipment required to carry out the extrusion method is an extruder , a cap, and a withdrawal machine. The die used is one in which the extrusion end face is opened with a passage having a long and narrow cross section, the width being ten times or more the thickness.

In practice, such a die is attached to the tip of the extruder. Further, in the extruder, the resin containing a foaming agent is softened, and the softened resin is supplied to the passage in the die, extruded from the passage having an elongated cross section, and foamed.

The resin containing the foaming agent can be extruded from the passage in the die and foamed at the same time. Zero foaming can also be carried out in the atmosphere as it is. However, since resins containing a foaming agent change shape as a result of foaming, they are often foamed in a mold called a mold to avoid undesirable deformation.

Many molds were used that had a shape that completely surrounded the resin.

(Background of the invention) When making a foamed board by extrusion, a high magnification, e.g.
In order to obtain a board that is foamed more than 0 times, it is necessary to stretch the resin board that has been extruded and foamed as described above in the extrusion direction using a take-up machine. Therefore, the resin board cannot be taken off at a high speed. Needed. However, when a foamed resin board is taken at a high speed, cracks appear on both sides of the resin board that extend in the width direction from the edges. It will be severed. Therefore, there was a need for a foam board that could be quickly removed without causing cracks on both sides of the foam board.

The inventor discovered that if a lubricant is applied to both sides of the foam board within the die, cracks will not occur on both sides of the foam board even if the foam board is taken off at high speed during the extrusion foaming process. This invention was made based on such knowledge.

(Prior art) A search of prior art documents reveals that when extruding a thermoplastic resin that does not contain a blowing agent, it has already been described that a lubricant is press-fitted around the resin passing through the die to smooth the extrusion. ing. It is described, for example, in Japanese Patent Publication No. 35-6879 and Japanese Patent Publication No. 39-10745. However, these descriptions are directed to non-foamed resins, and moreover, it is necessary to form a lubricant all around the resin. This is because if the lubricant is not distributed throughout the circumference, the resin in the die will slip unevenly, making it impossible to obtain a good molded product. However, as in the case of this invention, the entire surface of the foam board is
In particular, it is not easy to spread lubricant over both sides of the wide front and back surfaces.However, in this invention, the resin is extruded in the form of a foamed plate, and the lubricant is applied only to both sides of the extruded plate. The operation is easy, as it only needs to be press-fitted, and it is also completely new and surprising.

(Prolonged means for solving the problem) This invention is characterized in that the extrusion end surface of the die contains a foaming agent and is in a softened state through a passageway which is opened in an elongated cross section whose width is 20 to 1000 times the thickness. When extruding thermoplastic resin to make a foam board, when the resin is stretched to its maximum width in the die, lubricant is extruded from the passage walls at both widthwise ends, and at least at both widthwise ends. A thin film of lubricant is applied to the resin surface, extruded from the die, and the extruded product is immediately placed in a mold and foamed.
The present invention relates to a method for producing a thermoplastic resin foam board, which comprises bringing the inner wall surface of a mold into contact with at least both the front and back surfaces of a plate-shaped extrudate, cooling it while adjusting the shape, and then taking it off with a take-off machine.

An example of implementation of the method of the present invention will be described below with reference to the drawings. FIG. 1 is a partially cut-away horizontal sectional view of an apparatus for carrying out the method of the invention, and FIG. 2 is a partially cut-away vertical sectional view of the same apparatus. More specifically, FIG. 1 is a sectional view taken along line 1--1 in FIG. 2, and FIG. 2 is a sectional view taken along line T' in FIG.

In Figures 1 and 2, 1 is an extruder, 2 is a breaker plate, 3 is a goo plate, 4 is a 7-and-die, 5 is a flat die, 6 is a mold, 7 is a check valve, and 8 is a lubricant. This is an extrusion hole.

The method of this invention is carried out as follows using the apparatus shown in FIGS. 1 and 2. First, the thermoplastic resin is softened in the extruder 1, and a blowing agent is added thereto.
It is advanced toward the breaker plate 2 by the screw. A cap is attached to the tip of the player plate 2. The breaker plate 2 serves to apply back pressure to the extruder 1, prevent cross-contamination of the resin, remove foreign matter, and regulate the flow of the resin.

The die is a general term for a die plate 3, an under die 4, and a flat die 5. 7. The under-die 4 is a part that gradually deforms the circular cross-sectional resin coming from the extruder to make the cross-sectional shape rectangular.

At this time, the width to thickness ratio at the exit is 5 to 100 to 1.
within the range of The flat die 5 has an elongated cross section on the extrusion end surface of the flat die 5, which is the part where the resin coming from the fan die 4 is squeezed toward the extrusion end surface, especially in the thickness direction, and extruded while applying back pressure. The resin passage 9 is open. The opening of the resin passage 9 is 1+1i
1 v ItE box V has a relationship of 20 to 1000 times.

A check valve 7 is provided inside the cap, and a lubricant pressout hole 8 opens toward the resin passage beyond the check valve 7.

In terms of the circumferential direction of the resin passage, the opening positions of the extrusion holes 8 are only at both ends in the width direction.
In terms of the traveling direction of the resin passage, the opening position is the part where the cross-sectional shape becomes flat and widens in the width direction, from the tip of the fan die 4 to the flat die 5.
This is within the range of the latter half of . If this range is shown in the drawing, it is the range between lines a and b in FIG.

A mold 6 is attached to the tip of the cap. The mold 6 is
It is in close contact with the flat die 5, and a resin passage having substantially the same size as the resin passage 9 is provided in a portion in close contact with the flat die 5. However, the resin passage within the mold 6 rapidly widens both in the radial direction and in the thickness direction as it moves away from the flat die 5, and it widens particularly markedly in the thickness direction.

The method of this invention is carried out as follows using the apparatus described above. The softened resin containing the foaming agent is transferred to the extruder 1.
The cross section is gradually flattened from a circular state to an elongated cross section within the mouthpiece. That is, the die plate 3 has a circular cross section, but the fan die 4 gradually increases the width and decreases the thickness, and the flat die 5 has a slit-like cross section.

At this time, the lubricant is press-fitted through the press-out holes 8 provided in the passage wall at both ends of the mouth in the width direction, interposed between the wall surface and the resin, and is applied at least to the resin surface located at both ends of the mouth in the width direction. A thin film of lubricant is applied and the resin is extruded from the mouthpiece. Furthermore, the extrudate to which the lubricant has adhered is immediately put into a mold and foamed, and the entire circumferential surface of the plate-shaped extrudate is brought into contact with the inner wall surface of the mold to adjust its shape and cooled. In this way, the cooled foam board is taken up by a take-up machine at a high speed, and is foamed at a high magnification within the mold.

Various types of lubricants can be used. Water, silicone oil, polyethylene glycol, polybutene, paraffins, oils, etc. can be used. However, since the lubricant must not swell or dissolve the resin, it is necessary to select an appropriate lubricant from among the above-mentioned lubricants depending on the specific resin used. Generally speaking, the lubricant needs to be liquid under the temperature and pressure of the die during extrusion molding, and most lubricants can be used as long as they do not dissolve or swell the resin. It is particularly noteworthy that water can be used as a lubricant.

A small amount of lubricant is sufficient. Although this is an estimate, it is thought that it is sufficient to form a thin film of several microns to several hundred microns on the resin surface. Experimental results show that the amount of lubricant required depends on the viscosity of the lubricant, and the higher the viscosity of the lubricant, the lower the amount used. In general, if too much lubricant is used, the resin will slip too much in the mold, making it difficult to adjust the shape of the resin, or the lubricant will accumulate locally on both sides, creating depressions or holes. Therefore, excessive usage must be avoided.

To press out the lubricant, a plunger pump, gear pump, diaphragm pump, etc. may be used. However, the mold 6 is not limited to such a structure. For example, the mold 6 may be open at both ends in the width direction. In other words, the mold 6 may have a structure in which only two plates are provided vertically facing each other. That is, the mold 6 may have an inner wall surface that contacts at least both the front and back surfaces of the plate-shaped extrudate.

(Effects of the Invention) According to the method of the invention, in a state where the resin is flattened in the mouthpiece and extended to almost the maximum width in the width direction, the lubricant is forced out from the passage wall surfaces at both ends in the width direction, and at least the width Since a thin film of lubricant is applied to the resin surfaces located at both ends in the direction and the resin is extruded from the die, the resin is extruded from the die with both sides in the width direction covered with the lubricant. Therefore, both sides of the resin are smoothly extruded from the die. In other words, when trying to extrude a flat sheet with the conventional method, it was harder to extrude both sides in the width direction than the center, and small cracks were likely to occur, but the method of this invention eliminates such problems. There is no. In addition, it was difficult to apply lubricant evenly on both the flat front and back surfaces, but with the method of this invention, lubricant is deliberately not applied to both the front and back surfaces, so uneven extrusion on these surfaces can be avoided. does not occur either. As described above, according to the method of the present invention, wide objects can be extruded easily and smoothly.

The resin extruded from the die in this way is immediately put into a mold. In the forming WI mold, the resin is foamed and deformed, but since the inner wall surface of the mold is in contact with both the front and back surfaces of the plate-shaped resin, undesirable deformation is prevented. Further, since the resin is cooled within the mold, the resin exits the mold as a plate-shaped foam having a desired shape. thus,
A desired resin foam board can be obtained.

In addition, in the method of this invention, since the lubricant is applied, both ends in the width direction can be extruded smoothly, and even if the take-up speed is increased, no cracks will occur on both sides of the extrudate.
Therefore, a high-quality resin plate foamed to a high magnification can be easily and efficiently produced.

In this respect, the effect of the method of this invention is remarkable.

Next, further 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, polytetrapyrene, and polyvinyl chloride.As a foaming agent, , various substances can be used @ Mainly divided into aliphatic hydrocarbons, hetetragenated hydrocarbons,
Either an inert gas or a solid compound that decomposes to generate a gas can be used.

As aliphatic hydrocarbons, ethane, propane, butane, pentane, etc. can be used, and as halogenated hydrocarbons, methyl chloride, ethyl chloride, monochrome pt2 difluoromethane,
Dicrocydifluorop-methane and the like can be used, carbon dioxide, nitrogen, etc. can be used as the inert gas, and as the solid compound that generates gas, something like azocabonamide can be used. These can be used alone or in combination.

In this invention, the lubricant is forced out from the passage wall surfaces at both ends in the width direction within the mouthpiece. At that time, the number of lubricant injection holes was 4! J
As shown in FIG. 2, the holes 8 may be small and do not need to be so long as to cover the entire length in the thickness direction of the passage wall surface. This is thought to be because the extruded lubricant spreads in the thickness direction. Considering that the lubricant spreads in the thickness direction, the lubricant may spread further from the side surfaces in the width direction, and may even cover portions on both sides of the front and back surfaces. However, it is thought that it is impossible for it to spread to the entire front and back surfaces. In any case, it is considered to be effective because the lubricant covers both side parts where resin flow is poor.

The wall surface of the mold 6 that comes into contact with the resin is usually coated with a fluororesin to improve the slippage of the resin. In the method of this invention as well, it is desirable to use a mold coated with a fluororesin in this manner.

In addition, as a special embodiment of this invention, molded IJi6
The resin can be foamed to a higher degree within the mold by reducing the pressure inside the mold. Foaming under reduced pressure has already been proposed by the present inventor and applicant, and is disclosed in Japanese Patent Application Laid-Open No. 59-412.
It is made publicly known by Japanese Patent No. 36. When foaming to a high degree under reduced pressure in this way, it is necessary to increase the take-off speed, but according to the method of this invention, even if the take-off speed is increased, the foam board will not crack and the foam plate will remain in good condition. A high magnification foam board is obtained.

(Examples) Next, Examples and Comparative Examples will be described to further specifically explain this invention and clarify the advantages of this invention. In the following, parts simply mean parts by weight.

Example 1 As the resin, 100 parts of polystyrene (average degree of polymerization 1
460, melt index 411/10 minutes) mixed with 1 part talc (bubble regulator) and 2 parts flame retardant, and this mixture was fed to a tandem extruder with 65 feed φ-90 m- did.

Of these, #10B41I of 65am- is provided with a press-in hole for a blowing agent, and the resin is uniformly mixed and melted in an extruder in which 8 parts of butane (a blowing agent) is press-fitted to 100 parts of polystyrene. The lubricant was sent into the mouthpiece as shown in FIGS. 1 and 2. Inside the mouthpiece, lubricant extrusion holes 8 were bored, one on each side. The extrusion hole 8 has a diameter of 2 m and a length of 5 fl, and a check valve 7 is screwed into the back of the hole.
was connected to the plunger pump through piping.

In addition, the resin passage at the tip of the cap has a thickness of Zwtrs.
It was said to be 100m wide.

The resin melted in the extruder was cooled to 115° C. before entering the die, and was formed into a flat plate within the die.

At this time, water is used as a lubricant inside the mouthpiece through one pressout hole 8.
From, 1002 per hour at a pressure of 42Kg/aIII
At this time, the amount of resin extruded was 65 kg per hour.

In this way, the foamable resin formed into a plate is coated with a thin film of water on both sides, extruded from the die, and immediately introduced into the mold 6, where it is foamed and cooled to form a foam board. This foam board is taken out by a taking machine.
It was collected at a rate of 4m1.

The resulting foam board has a width of 254 m and an average thickness of 50.2 m.
+w, the R value (difference between the maximum value and the minimum value) was 0.5 bait, the thickness was uniform, and there were no cracks on both sides, making it a good foam board. In addition, this foam board has an apparent density of 35
．． It was highly foamed with OKtt/rrl.

Comparative Example 1 Example 1 except that water was not used as a lubricant.
A foam board was obtained in exactly the same manner.

The obtained foam board had a width of about 258 fi, an average thickness of about 50.5 mm, a large R value of 43 III+, and was thick in the center and thin on both sides. Also, the apparent density is 35
．． Although it was well foamed at 2 kg/-, there were cracks on both sides and it could not be said to be a good foamed board.

Example 2 The procedure was carried out in exactly the same manner as in Example 1, except that silicone oil (KF-96, manufactured by Shin-Etsu Chemical Co., Ltd.) was used instead of water, and the output amount was 20 cc per hour. carried out. As a result, a foamed board with a width of 251 m, an average thickness of 49.8 m, a small R value of 0.3, and a uniform thickness in the width direction could be obtained. In addition, there were almost no cracks on both sides 〇Example 3 A new resin temperature regulator was added to the die plate F of the same extruder as in Example 1, and a die and mold different from those used in Example 1 were added. has been added. The resin passage at the tip of this cap has a thickness of 3wm and a width of 300mm.

The mold had a structure that covered the entire surface of the resin in the circumferential direction, and the outlet dimensions were 50 g in thickness and 550 fl in width. Furthermore, the resin passage surface of this mold was coated with fluororesin.

Inside the nozzle, lubricant press-out holes were bored, one on each side, at the same positions as the nozzle used in Example 1. Further, the pressure hole had a diameter of 2 mm and a length of 5 mm, and a check valve was screwed into the depth of the hole, and the check valve was connected to the plunger pump through piping.

The mold has an inner dimension of 300w5, 1000fl, and a length of 6.
A pressure reducing device consisting of a rectangular cylinder of m is connected airtightly,
A sealing device disclosed in Japanese Patent Application Laid-Open No. 59-41236 was attached to the outlet side.

The same resin mixture used in Example 1 was fed to the extruder. Furthermore, 8.2 parts of butane was press-fitted into 100 parts of polystyrene. The resin that was uniformly mixed and melted in the extruder was cooled to 117° C. before entering the die and was formed into a flat plate in the die. At this time, water is released as a lubricant in the mouth from both extrusion holes at a pressure of 35Kf/cd.
It was extruded at a rate of 150 y/hr per extrusion hole. At this time, the amount of resin extruded was 120 kg/hr.

In this way, the foamable resin extruded from the die was foamed in the mold to form a foam board, which was immediately introduced into the pressure reducing device, and the foam board coming out of the sealing device was taken up by a take-up device. At this time, the pressure inside the decompression device is 210 rx
mHg (absolute pressure) and take-up speed were 2.0 m and 7 minutes.

The obtained foam board has a width of 660 m and an average thickness of 59.0 m.
It is machined, has an R value of 1.1, and has a uniform thickness.
The foam board was in good condition with almost no cracks on both sides. This foam board can be peeled to make a plate with a thickness of 5011 and a width of 610 fl, and its apparent density is 19.5.
It was highly foamed with a weight of 1 kg/m.

Comparative Example 2 Continuing from Example 3, the test was continued with the lubricant pumping stopped, but the cracks on both sides were so lonely that they could not be removed, so the pressure in the decompression device was reduced to 460 ml. absolute pressure) and had to reduce the take-up speed to 1.6 m/min.

The resulting foam board has cracks on both sides and has a width of 650 mm.
The cod had a large average thickness of 645 m and an R value of 6.2, with a thick center and thinner sides.

This foam board has a thickness of 50m when stripped.

A plate with a width of 550 m and an apparent density of 24.4 Ky/m could only be obtained.

[Brief explanation of drawings]

4 and 2 are sectional views of essential parts showing one embodiment of the method of the present invention. In the figure, 1 is an extrusion type, 2 is a breaker plate, and 3 is a breaker plate.
is a die plate, 4 is a fan die, 5 is a flat die,
6 is a mold, 7 is a check valve, 8 is a lubricant press-out hole, and 9 is a resin passage at the opening end of the mouthpiece. Patent Applicant: Sekisui Plastics Co., Ltd. Procedural Amendment July 10, 1985 1, Indication of the Case 1982 Patent Application No. 14871 2, Name of the Invention Method of Manufacturing Thermoplastic Resin Foam Board Relationship to the Case Patent Applicant 5 deletes the word "water" from column 6 of the detailed description of the invention in the specification subject to amendment, content of amendment fil, page 10, line 4 of the specification. (2) On page 10, lines 14 and 15, it is noteworthy that water is a lubricant. ” will be deleted. (3) On page 17, line 17, the word "water" is replaced with "polyethylene glycol (manufactured by Sanyo Chemical Co., Ltd., molecular weight 40
0) Correct it as J. (4) On the last line of page 17, the text rl 00J is corrected to "75". (5) On page 18, line 8, the word "water" is corrected to "polyethylene glycol." (6) On page 18, line 6, it says r2.4mJ. ．． Correct it to 6mJ. (7) On page 18, line 8, the text "r254J" is corrected to "r250J". (8) On page 18, line 9, it says r50.2J, r47. Correct it to IJ. (9) On page 18, line 15, the word ``water'' is corrected to ``polyethylene glycol.'' +101 On page 18, line 17 of the same page, correct r258J to 254J. (11) On the last line of page 18, the text "r50.5J" is corrected to "r46.5J". 02 On page 19, line '6, the word "water" is corrected to "polyethylene glycol." From page 19, line 15 to page 21, line 17 of the same document, there is a statement that ``The product was highly foamed using the same extruder as in Example 1.'' [In Example 1, It was carried out in exactly the same manner as in Example 1, except that polybutene (Nisseki Kagaku LV-50) was used instead of polyethylene glycol, and the extrusion rate was 500 C per hour. As a result, the width is 249
5W, average thickness of 49.5H, R value as small as 0.2 fl, and a uniform thickness in the width direction could be obtained. Moreover, there were hardly any cracks on either side. ” Sumi corrected. (141, from the bottom line of page 21 to line 11 of page 22, -
``Comparative Example 2... only results were obtained.'' Delete. that's all

Claims (1)

[Claims] In order to make a foam board by extruding a softened thermoplastic resin containing a foaming agent through a passageway that is open in the extrusion end face of the die and has a long and narrow cross section whose width is 20 to 1000 times the thickness, the inside of the die is When the resin is stretched to its maximum width in the width direction, the lubricant is forced out from the passage wall surfaces at both ends in the width direction, and the lubricant is deposited in a thin film on the resin surfaces located at both ends in the width direction. The resin is extruded from the die, the extrudate is immediately put into a mold and foamed, the inner wall surface of the mold is brought into contact with at least both the front and back sides of the plate-like extrudate, the shape is adjusted and cooled, and then the extrudate is taken off by a take-off machine. A method for producing a thermoplastic resin foam board, characterized by: