JPH05338052A - Manufacture of polyolefin foam body and apparatus for foaming polyolefin - Google Patents

Abstract

PURPOSE:To provide a manufacture of a polyolefin foam body and an apparatus therefor for obtaining a final foam body having the properties of excellent surface smoothness, enriched compression stress, and low permanent distortion by efficiently performing cooling and heating without spoiling advantages of a two-stage foaming method with a high manufacturing yield. CONSTITUTION:A polyolefin foaming apparatus (secondary foaming apparatus) comprises a cooling mold 1 and a pair of heating plates 2, 2 that are disposed above and below the cooling mold 1 and has heating medium flow path 21 therein, and the cooling mold 1 is equipped with a side mold frame 11 provided with coolant flow paths 121 therein and a pair of flat plates 12a, 12b that are arranged to secure the side mold frame 11 from its upper and lower sides and thus form a non-sealed inner space corresponding to the conflgurational dimensions of a final foam body in association with the side mold frame 11, and have coolant paths 121 therein. A final foam body is manufactured by secondarily foaming an intermediate foam body obtained by firstly foaming it in use of this apparatus.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a polyolefin foam and a foaming apparatus for processing an intermediate foam to produce a final foam. More specifically, in a second foaming step of two-stage foaming. The present invention relates to a method for producing a polyolefin foam which is uniformly and efficiently heated and cooled, is excellent in moldability and surface smoothness, is rich in compressive stress, and has a relatively small permanent set, and an apparatus therefor.

[0002]

2. Description of the Related Art A method for producing a polyolefin block foam is to fill a mold with a mixture of a polyolefin resin, a cross-linking agent and a foaming agent, and completely decompose the cross-linking agent and the foaming agent under pressure and heat. Then, by depressurizing the mixture, the mixture is expanded at a time to a desired density (hereinafter, referred to as one-stage foaming), or Japanese Patent Publication No. 2-42649.
As disclosed in Japanese Unexamined Patent Publication (Kokai), etc., the mixture is filled in a primary mold and heated under pressure to decompose 15 to 60% of the foaming agent to cause primary expansion. A method of heating by pressure to decompose the residual foaming agent and subjecting it to secondary expansion to obtain a foam having a desired density (hereinafter referred to as two-stage foaming).
It has been known.

However, in order to obtain a high foam by the above-mentioned first-stage foaming, in order to expand the final foam at a desired density at a time,
There has been a problem that the final foam obtained is deformed, or the foam is cracked when taken out from the mold, resulting in a very low commercialization rate. Therefore, the two-stage foaming was developed in order to improve the reduction in the production yield of the above-mentioned one-stage foaming. In the two-stage foaming, a product having a predetermined expansion ratio is not expanded and expanded at a time, but expanded and expanded in two stages, thereby eliminating a factor such as cracking which lowers a product yield.

[0004]

However, even in such a two-stage foaming method, the surface smoothness of the final foam was not sufficient. As a countermeasure against this, JP-A-61-2664
As described in Japanese Patent Publication No. 41, No. 41, the final foam after the second foaming process is taken out at the time of heating, and a cooling plate (in the expression of Japanese Patent Laid-Open No. 61-266441, a heating plate is used in the cooling process as the third process). However, when viewed from the temperature of the foam,
Its function is a cooling plate. ), Cool down,
It is necessary to add new steps such as smoothing the surface of the foam. When a new process is added in this way, there is an unavoidable decrease in productivity due to an increase in equipment costs, complication of processes and the like. In addition, JP-A 61-266
When the foam is taken out during heating as described in Japanese Patent No. 441, there is a problem that the foam itself is soft, the foam is deformed during the taking-out work, cracks occur on the surface, and the product yield is lowered. It was

The most reliable solution to the above drawbacks is to cool the foam that has undergone the final foaming in the second foaming step without removing it from the mold. However, the heating method described in Japanese Examined Patent Publication No. 2-42649, that is, by directly inserting the intermediate foam into a mold in which a flow path is provided in a hot plate and circulating a heat medium in the flow path With the method of heating the mold, it was difficult to cool the mold. Even if a refrigerant is allowed to flow into this heat medium passage to cool it, it is usually very difficult to switch from a heat medium such as steam in a high-pressure state to a refrigerant such as water, and vice versa. There is a defect that it takes a considerable amount of time to lower the temperature and to re-rise the temperature for heating the next intermediate foam, and the energy loss increases.

The present invention solves the above-mentioned problems, and efficiently cools and heats without deteriorating the advantages of the two-stage foaming method, which has an excellent production yield, and has a good moldability and surface. It is an object of the present invention to provide a method for producing a polyolefin foam, which provides a final foam excellent in smoothness, rich in compressive stress, and small in permanent set, a foaming apparatus therefor, and the like.

[0007]

[Means for Solving the Problems] That is, in the method for producing a polyolefin foam of the first aspect of the present invention, a mold is filled with a foamable composition containing a polyolefin, a cross-linking agent and a foaming agent, and heated under pressure. After decomposing a part of the foaming agent to induce foaming, the first step of depressurizing at high temperature heat and taking out from the mold to produce an intermediate foam, and then the intermediate foaming obtained in the first step The body is provided with a lateral formwork (11) having a refrigerant flow passage therein, and the lateral formwork is fixed from above and below to form an unsealed space corresponding to the shape and dimensions of the final foam together with the sidework form. Cooling molding die (1) comprising a pair of flat plates (12) arranged so as to form and having a refrigerant channel inside
The pair of heating plates (2) disposed above and below the cooling mold are heated by injecting a heat medium into the flow passages provided in each of the heating plates, and the cooling molding is performed. By heating the intermediate foam under atmospheric pressure through a working mold, the rest of the foaming agent is decomposed to induce foaming, and then the cooling medium flow of the flat plate of the cooling molding mold and the side molds. The second step of manufacturing the final foam by cooling the outer peripheral surface of the foam uniformly by injecting a refrigerant into the passage.

In the present invention, the term "polyolefin" refers to, for example, polyethylene, ethylene-propylene copolymer, ethylene-butene copolymer, ethylene-, which are produced by the high pressure method, medium pressure method or low pressure method which are usually commercially available.
Vinyl acetate copolymer, copolymer of ethylene and acrylic acid ester of methyl, ethyl, propyl or butyl (content of this ester; within 45 mol%), or chlorine content up to 60% by weight of chlorine And the like, or a mixture of two or more kinds thereof, or a mixture of these with isotactic polypropylene or atactic polypropylene.

The "crosslinking agent" referred to in the present invention has a decomposition temperature of at least the flow initiation temperature of the polyolefin in the above-mentioned polyolefin, and is decomposed by heating to generate free radicals to cause intermolecular formation. It refers to an organic peroxide that is a radical generator that causes cross-linking. For example, dicumyl peroxide, 2,5-dimethyl-2,5-bis-tert-butylperoxyhexane, 1,3-bis-tert-peroxy-isopropylbenzene and the like. The "foaming agent" referred to in the present invention
The term "having a decomposition temperature not lower than the flow initiation temperature of the above polyolefin" means, for example, azodicarbonamide, dinitrosopentamethylenetetramine and the like.

In the present invention, in order to control the foaming state, compounds containing urea as a main component, metal oxides such as zinc oxide and lead oxide, lower or higher fatty acids or metal salts of lower or higher fatty acids, etc. A foaming aid or the like can be added. Further, in order to improve the physical properties, carbon black, zinc white, titanium oxide and other commonly used compounding agents may be added.

In the method for producing a polyolefin foam of the present invention, the decomposition rate of the foaming agent at the time of primary foaming in the first step is not particularly limited, but as in the second invention, in the first step, 50 kg / m of the mold is used. By heating in a pressurized state of cm ² or more, the foaming agent is decomposed so as to have a decomposition rate satisfying the following formula to induce foaming, depressurized at high temperature and taken out from the mold to produce an intermediate foamed product. Is preferred. Decomposition rate of foaming agent in the first step (%) = (9 to 12) × (100 / final expansion ratio) By doing in this way, 250 to 450 μm
A product having a relatively large cell diameter of m and an open cell ratio of 5 to 20%, rich in compressive stress, and small in permanent compression strain can be obtained.

In the above, the pressure in the first step is 50 k
If it is less than g / cm ² , the foaming agent decomposition rate of the present invention is such that the foam will be expanded up to about 10 times, and the foam will leak from the primary mold during foaming expansion, and It is not preferable because it causes deformation, which further lowers the productization rate. In the two-stage foaming method, in general, "innumerable nuclear bubbles formed by thermal decomposition of a partial blowing agent under primary high pressure are grown into 70 to 90 μm fine cells during decompression expansion, and further secondary secondary This fine cell is expanded by pressure expansion to 10
Grow uniformly to an average bubble size of 0 to 150 μm. "
Due to the cell formation mechanism, the resulting foam becomes a uniform and fine closed cell, and such a foam generally has poor compression hardness and relatively large permanent set. There is.

On the other hand, in the second aspect of the present invention, the decomposition rate of the foaming agent in the primary foaming step is set to a decomposition rate satisfying the above equation, whereby the foaming agent is formed during decomposition of the foaming agent in the first foaming step. The number density of the nuclear bubbles becomes high, and the interval between the nuclear bubbles, that is, the bubble wall can be made thin. The bubble wall formed in this way and the explosive expansion caused during depressurization combine,
In the process of growing the fine cells at the time of explosive expansion, it is possible to partially induce the bubble wall destruction. As a result, the fine cells aggregate, the cell size increases and the strands of the destroyed bubble wall fuse to the remaining bubble wall, which reinforces the bubble wall and is rich in compressive stress, and has a relatively small permanent set. It becomes possible to provide a foam. For example, when the final expansion ratio is 15 times, the decomposition rate is 60 to 8
If it is less than 60%, the average bubble diameter becomes too small and the compressive stress becomes poor, while if it exceeds 80%,
The primary and secondary foams will be deformed and cracked.

As a means for adjusting the decomposition amount of the foaming agent, there is a method of adjusting the addition amount of a foaming auxiliary agent such as a metal oxide, but the simplest and surest method is the primary foaming. There is a method in which the heating temperature is set to a relatively low temperature of about 130 to 170 ° C. and the heating time is controlled. Further, the heating temperature in the secondary foaming is important to completely decompose and foam the foaming agent, and is preferably set in a range that does not adversely affect the polyolefin, and is usually about 160 to 190 ° C. The heating time is usually about 20 to 60 minutes.

The polyolefin foaming apparatus of the third invention is
It is for processing an intermediate foam to produce a final foam, and includes a cooling mold (1) and a pair of cooling medium molds disposed above and below the cooling mold and having a heat medium channel inside. The cooling mold (1) includes a heating plate (2), and the cooling mold (1) is a lateral mold in which a refrigerant channel is provided, and the lateral mold is fixed from above and below. A pair of flat plates (12) which are arranged together with the frame (11) so as to form an unsealed internal space corresponding to the shape and size of the final foam and which has a refrigerant channel inside.
And are provided.

In the polyolefin foaming apparatus of the present invention, the shape of the cavity of the primary foaming mold and the unsealed internal space formed by the side mold of the cooling mold and the pair of flat plates is not particularly limited, As in the fourth aspect of the invention, the cavity in the primary foaming mold and the unsealed internal space formed by the side mold and the pair of flat plates of the cooling molding mold are both substantially similar to the final foam. Yes, and the internal space of the cooling mold has a vertical, horizontal and height dimensions, respectively, with respect to the respective dimensions immediately after foaming of the foam that has been finally foamed in the cooling mold. It is preferable that the size is reduced by 1 to 10%. In this case, the term “vertical, horizontal and height” is used to mean a substantially similar shape when viewed three-dimensionally in the case of a three-dimensional shape that is not clearly defined. The term "non-sealed internal space" as used in the present invention refers to a structure in which, when the intermediate foam expands secondarily in the space, the air remaining in the space can be removed to the outside by the expansion pressure of the foam. Means, usually,
It is common to provide one or two small holes on each side for allowing the internal space and the external atmosphere to communicate with each other on the side surface of the side mold part.

By making the shape of the cavity of the primary foaming mold and the internal space of the cooling molding mold or the like substantially similar to the shape of the final foam, the three-dimensional expansion of the foam can be induced as uniformly as possible. .. With this, it is possible to prevent unevenness and dimensional error due to shrinkage unevenness on the surface of the final foam due to aging shrinkage. In particular, by reducing the size of the internal space of the cooling molding die by 1 to 10%, the foamed and expanded final foam is uniformly and uniformly pressed against the wall surface of the internal space by its self-expanding force. Thus, the molding can be performed according to the shape of the internal space, and the variation in the final product shape is reduced. In addition, heat transfer efficiency in heating and cooling is also improved.

When the size of the internal space is less than 1%, the pressing force of the foam on the inner wall surface of the internal space due to the self-expansion force of the foam becomes insufficient and the side surface of the foam becomes uneven. And the corners are not formed, it becomes difficult to mold the secondary mold and the heating efficiency and cooling efficiency also deteriorate. On the other hand, when it is made smaller than 10%, even if the foam shrinks due to subsequent cooling, the outer dimension of the foam is still considerably larger than the inner dimension of the space, and it is difficult to remove the foam from the cooling mold. Or when the cooling mold is opened, the center part of the foam rises, causing deformation and cracking.

Further, the contact surfaces of the pair of flat plates of the cooling mold with the final foam can be smooth surfaces having fine irregularities as in the fifth aspect of the invention.
The smoothness (Rmax) of this smooth surface is usually 3 to 1
It is about 00 μm. As a result, the foam can be expanded without applying excessive resistance during expansion, and a foam in a very good molded state can be obtained, and the foam can be easily taken out. Further, unlike the conventional case, it is not necessary to coat the metal nitrate aqueous solution or the like in order to improve the sliding property of the foam in the mold, and thus the cleaning of the foam is not required, which leads to a great labor saving. still,
As a method for obtaining the smoothness of the foam contact surface, JIS
It is desirable to perform a satin finish of 4S to 20S according to the standard B0601 or a Teflon coating process.

Further, in the polyolefin foaming apparatus of the present invention, as in the sixth aspect of the present invention, the cooling molding mold is detachably attached to the heating plate, and the side mold of the mold and the pair of flat plates are provided. Are preferably separable. The flat plate itself can be easily separated from the heating plate and the side mold even if the smoothness of the surface is impaired due to long-term use, so it is suitable for replacement and reworking. This is because those corresponding to the above can be appropriately replaced and used.

[0021]

In the present invention, the intermediate foam obtained in the first step is
A side mold with a coolant channel inside, and a side mold that is fixed from above and below to form an unsealed space corresponding to the shape and dimensions of the final foam together with the side mold. Which is placed in a cooling molding die composed of a pair of flat plates each having a cooling medium flow path therein, and heat is applied to the flow paths provided in a pair of heating plates arranged above and below the cooling molding die. By injecting a medium, the intermediate foam is heated under normal pressure through a cooling mold to decompose the rest of the foaming agent, and thereafter,
Refrigerant is injected into the flat plate of the cooling mold and the coolant channels of the side frame. Therefore, the outer peripheral surface of the foam can be uniformly and efficiently heated and cooled.

Since the foamed body after the final foaming is continuously cooled and molded without taking it out of the mold, a new cooling step is added to improve the surface smoothness of the foamed body. You don't even have to. Further, while cooling the refrigerant by flowing it through a cooling medium passage in the cooling molding die, a heating medium passage is provided in a heating plate sandwiching the cooling molding die, and the heating medium is circulated and heated. Therefore, switching from heating to cooling or cooling to heating can be smoothly performed, and the time required to reach a predetermined heating temperature or cooling temperature can be shortened, and production efficiency can be improved.

Further, in the method of heating the foam through the flat plate of the cooling mold as in the present invention, the heat transfer efficiency may be poor, but as in the second invention, the primary foaming is performed. In the process, about 1/3 or more of the foaming agent is decomposed, and the residual foaming agent is decomposed in the second step. In other words, the second step is mainly a molding and cooling step. The decrease in heat transfer efficiency is not a serious problem. On the contrary, by heating through a flat plate, the thermal conductivity of the metal hot plate is extremely high, so the temperature difference between the heat medium flow path near the hot plate and other parts can be relaxed, so uniform heating is possible. It has the advantage of enabling In addition, by setting the foaming decomposition rate in the first step within a predetermined appropriate range, a foam having a relatively large cell diameter of 250 to 450 μm and an open cell ratio of 5 to 20% is obtained. It is possible to obtain a product which is rich in and has a small permanent compression set.

[0024]

EXAMPLES The present invention will be specifically described below with reference to examples. (1) Configuration of Polyolefin Foaming Device (Secondary Mold) FIG. 1 shows an embodiment of the polyolefin foaming device according to the present invention, in which a foam molding part includes a cooling molding mold 1, a heating plate 2, Composed of. The cooling mold 1 includes a pair of side molds 11a and 11b and a pair of flat plates 12a and 12b.
And consists of. The flat plates 12a and 12b are side molds 11a,
11b is fixed from above and below with bolts 4 and 4 to form an unsealed internal space 3. The internal space 3 is substantially similar to the final foam, and the vertical, horizontal, and height dimensions forming the internal space 3 of the cooling mold 1 are substantially similar to the final foam 1. The intermediate foam obtained in the subsequent foaming type is set to have a size reduced by 1 to 10% with respect to the respective sizes of the foamed product finally foamed immediately after foaming. A coolant channel 111 is formed in the side mold 11. The flat plate 12a, 12b is also provided with a refrigerant flow channel 121.

Reference numeral 5 indicates a bolt for fixing the cooling mold 1 to the upper and lower heating plates 2 and 2. The lateral formwork 11 is shown in FIG.
As described above, the upper mold frame 11a and the lower mold frame 11b are divided into two, and when any one of the heating plates 2 and 2 moves upward or downward, the cooling molding mold 1 is opened, and the foam after cooling and foaming is completed. It can be taken out. Flat plates 12a, 12
As shown in FIG. 2 (an explanatory view in which one upper flat plate is omitted), b has a structure in which a middle plate 122 having a meandering through hole 121 is sandwiched between normal plate members 123 from both sides. The through hole 121 is finally the refrigerant flow channel 121.
(Fig. 1). Incidentally, as shown by the reference numeral 12a, the tubular bodies 1211a and 1211b may be inserted and reinforced in the refrigerant flow channel 121.

The heating plate 2 is composed of a thick metal plate, and a heating medium passage 21 is provided inside the heating plate 2 so that it can be heated by the injected heating medium. Here, as shown in FIG. 3, the heating plate 2 includes a metallic box-shaped body 22 and a tubular body 24 inside the box-shaped body 23 that is brazed to the bottom plate 23 to form a flow path of the heat medium. , Can be provided. Since the tubular body 24 is brazed to the metal bottom plate 23a, the heat conduction is excellent, and the box-shaped body is filled with air, which is a poor heat conductor, so that heat loss is reduced. As shown in FIG. 3, ribs 25 may be provided in the box-shaped body for reinforcement. Further, a heat insulating material (for example, foam ceramic or the like) may be filled and arranged in the metal box-shaped body.

(2) Production of Polyolefin Foam Example 1 100 parts by weight of polyethylene having a melt index of 1.0 (hereinafter referred to as "part"), 5 parts of azodicarbonamide,
A composition containing 2 parts of dicumyl peroxide and 0.5 part of zinc oxide was kneaded on a roll having a surface temperature of 100 ° C. to obtain a mixture. 6 kg of this mixture was added to the primary mold (410 mm ×
(410 mm × 40 mm), heated under pressure of 70 kg / cm ² , and heated at 160 ° C. for 30 minutes, then depressurized at high temperature to expand and expand about 10 times.
mm × 880 mm × 86 mm) was obtained. This intermediate foam in a high temperature state is sandwiched between a pair of heating plates 2 as shown in FIG. 1 for a cooling molding die 1 (internal space dimension: 1000 mm × 1).
000 mm × 100 mm), and heating was performed through the cooling mold 1 for 30 minutes using the heating plate 2 which was maintained at 165 ° C. by passing steam through the heat medium flow passage 21.

The flat plates 12a and 12b attached to the upper and lower sides of the cooling mold 1 are contacted with the foam by Teflon coating, and the inner wall surface of the mold has a lubricant such as a metal nitrate aqueous solution. Has not been sprayed at all. After the heating was completed, the steam being supplied to the heating plate 2 was stopped, and at the same time, the cooling water at room temperature was circulated through the coolant channels 111 and 121 of the cooling mold 1. In this case, the heating medium passage 21 of the heating plate 2
The heat medium inside is as it is, but it can be removed by compressed air or the like.

As a result, the side mold 11 of the cooling mold 1 is formed.
After about 3 minutes, the temperature of the portion was lowered to around 50 ° C, and after 30 minutes, the temperature of the outer peripheral portion of the foam was lowered to 90 ° C. at this point,
Simultaneously with taking out the final foam, the cooling water was stopped, and the steam was circulated to the heating plate 2 again. In this case, the refrigerant in the refrigerant channels 111 and 121 is removed by compressed air or the like, but it can be left as it is. It took about 18 minutes for the heating plate 2 to reach 165 ° C. again. Therefore, the time required for cooling start → cooling completion → cooling mold temperature rise again was only 48 minutes. Further, it was easy to remove the final foam from the mold. The final foam obtained is
The density is 0.06 g / cc, the expansion ratio is about 15 times, the length and width are 995 to 1000 mm, and the thickness is 98 to 10.
It was approximately 1 mm and was almost the same as the shape of the internal space 3 of the cooling mold 1, and the outer peripheral surface thereof was excellent in smoothness and was extremely beautiful.

Comparative Example 1 An intermediate foam obtained by the same method as in Example 1 was used as a secondary mold 6 (internal space size: 1000 mm × 100) shown in FIG.
0 mm × 100 mm), and the steam is conducted to the heat medium flow paths 611 and 621 of the metal plates 61 and 62 forming the upper and lower surfaces of the mold to maintain the metal plate at 165 ° C. Heated for 30 minutes. An aqueous solution of a metal nitrate salt is previously sprayed as a lubricant on the contact surface of the metal plate with the foam so that the foam expansion can be smoothly performed.

After the heating is completed, the steam supplied to the metal plates 61 and 62 is stopped, and the cooling medium pipes are connected to the heat medium flow passages 611 and 621 of the metal plates by switching the pipes. Cooling water was supplied to 621. Heat medium channel 61
It took 10 minutes to reduce the pressure of the steam remaining in 1,621 and to circulate the cooling water. Furthermore, it took 40 minutes for the mold frame temperature to drop to around 50 ° C. After about 60 minutes, the outer peripheral portion of the foam body was cooled to 90 ° C. At this time, the final foam body was taken out, cooling water was stopped, and the piping was switched to steam again to change the heat medium flow path 6
Steam was supplied to 11,621. However, due to the occurrence of the water hammering phenomenon, the steam pressure had to be gradually increased. It took about 40 minutes to bring the metal plate to 165 ° C. again. The obtained foam had excellent dimensions, shape, and outer peripheral surface state as in Example 1, but it took 100 minutes to start cooling, complete cooling, and reheat. It took twice as long as 1.

Examples 2-3 and Comparative Examples 2-3 Predetermined amounts of the same admixture as in Example 1 (shown in Table 1) were used.
Processing was performed under the same conditions as in Example 1 using a primary mold having predetermined mold dimensions shown in Table 1. Further, secondary foaming and cooling molding were performed under the same conditions and equipment as in Example 1. The size of the secondary mold is shown in Table 1. The results are shown in Table 1. In Table 1, the foam dimension [C] immediately after the completion of the secondary foaming is the foam immediately after the completion of the secondary foaming. It is a value obtained by measuring the dimensions at each of three places and expressing the average value. In addition, the variation in the final foam size is expressed by the difference between the maximum, minimum, and vertical dimensions of the foam after cooling is completed. Numerical values marked with * in Table 1 are out of the range of the second invention.

According to the above results, as shown in Table 1,
In Comparative Examples 2 and 3 in which the secondary mold reduction ratio was inappropriate, the dimensional variation of the final foam was large. Further, in Comparative Example 3, a crack having a length of 200 mm and a depth of 10 mm was generated on the upper surface of the foam, and the final foam was difficult to remove from the mold.
I had to take it out forcibly. On the other hand, in Examples 1 and 2, the above-mentioned problems did not occur (there were variations, but very few), and the results were good.

[0034]

[Table 1]

Examples 4 to 5 and Comparative Examples 4 to 6 In Example 1, the heating time for primary foaming was variously changed to change the decomposition rate of the foaming agent in the primary foaming step. Table 2 shows these conditions. 100 foams were made for each processing condition, and the product yield and physical properties at that time were investigated. The results are shown in Table 2. Here, the numerical values marked with * in Table 2 are out of the scope of the present invention. Also,
In the same table, the columns "Foam leak in the primary mold" and "Primary, 2"
The unit of the numbers in the "Following foam deformation and cracking" column is a number. The average cell diameter is measured by measuring the diameter of 100 cells in each foam and showing the average value. The 25% compressive stress was measured by the method of JIS K6767. When the value obtained by such measurement is large, the compressive stress is large, and the compressive stress is rich. The open cell ratio is measured by the air pycnometer method (ASTM D28
56). Further, the measurement of the 25% compression set was performed according to JIS K6767.

[0036]

[Table 2]

According to the results shown in Table 2, in Comparative Example 4, the primary decomposition rate was as small as 50%, so that although the foam did not leak or deform, the average cell diameter was too small (not desired). , 25% compressive stress is small, open cell ratio is low, and 25% compression set is large. In Comparative Examples 5 and 6,
Although the physical properties of the final foam were satisfactory, the foam leaked and deformed in all cases. On the other hand, in Examples 4 and 5, there were no such defects, and excellent performance products could be efficiently manufactured. The present invention is not limited to the specific examples described above, and various modifications may be made within the scope of the present invention depending on the purpose and application. That is, in the above embodiment, one pair of heating plates and one cooling molding die are set, but the heating plate and the cooling molding die are sequentially laminated, and the heating plate is further laminated and fixed on the other end. That is, one heating plate and one cooling molding die are set as one set, and a plurality of these are sequentially combined and heating plates are arranged at both ends, so that a plurality of intermediate foams can be simultaneously heated and cooled. be able to. This fixing method is not particularly limited, and for example, each member may be fixed by bolts as in the above-described embodiment, or a plurality of heating plates may be fixed at the same time by stays, long fixing bolts or the like. Further, the side molds may be made of one piece instead of a pair, or may be three or more. Furthermore, the cross-sectional shape, size, and number of the refrigerant passages provided in the side mold and the flat plate are not particularly limited, and the number of inlets and outlets thereof can be variously selected. Further, the flat plate structure is not limited to the sandwich type, and may be a thick one plate-shaped body having a refrigerant channel inside.

[0038]

As described above, according to the manufacturing method and the foaming apparatus of the present invention, the upper and lower heating plates and the cooling molding die are individually combined, so that cooling and heating can be shared respectively. Therefore, heating and cooling can be efficiently performed. Moreover, since the internal space formed by the cooling mold corresponds to the shape and size of the final foam, a product having excellent moldability and surface smoothness can be obtained. Furthermore, since the foaming agent decomposition rate in the first step can be kept within a certain range and a foam having a relatively large cell diameter and an appropriate open cell rate can be obtained, it is rich in compressive stress and permanent set. Fewer final foams can be obtained.

[Brief description of drawings]

FIG. 1 is an explanatory cross-sectional view showing a foam molding part of a manufacturing apparatus for a polyolefin foam according to the present invention.

FIG. 2 is a schematic explanatory view of a flat plate having a coolant channel in FIG.

FIG. 3 is a schematic explanatory diagram of a heating plate having a heat medium passage.

FIG. 4 is an explanatory sectional view showing a conventional secondary foaming device.

[Explanation of symbols]

1; Cooling mold, 11; Side mold, 11a; Upper mold,
11b; Lower formwork, 111; Refrigerant flow path, 12a, 12b;
Flat plate, 121; refrigerant channel, 1211; tubular body, 122;
Middle plate, 123; plate-shaped body, 2; heating plate, 21; heat medium flow path,
22; metal box-like body, 23; bottom plate, 24; tubular body, 2
5; rib, 3; internal space, 4; bolt, 5; bolt,
6; Secondary mold.

Claims (6)

[Claims] 1. A mold is filled with a foaming composition containing a polyolefin, a cross-linking agent and a foaming agent, and heated under pressure to decompose a part of the foaming agent to induce foaming, and then at high temperature heat. The first step of depressurizing and taking out from the mold to produce an intermediate foam, and thereafter, the intermediate foam obtained in the first step is used as a side mold (11) having a refrigerant channel inside. , A pair of flat plates which are fixed so that the side molds are fixed from above and below so as to form an unsealed space corresponding to the shape and dimension of the final foam together with the side molds, and which have a refrigerant flow passage therein. (12), and a pair of heating plates (2) arranged above and below the cooling molding die (1) are placed in the cooling mold (1). It is heated by injecting a heating medium, and the intermediate foam is heated under normal pressure through the cooling mold. With, to induce the foaming by decomposing the remaining portion of the foaming agent, then by injecting a refrigerant into the refrigerant channels of the flat plate of the cooling mold and the side mold, the outer peripheral surface of the foam A second step of uniformly cooling to produce the final foam;
A method for producing a polyolefin foam, comprising: 2. In the first foaming of the first step, the mold is 5
The foaming agent is heated under a pressure of 0 kg / cm ² or more to decompose the foaming agent so as to have a decomposition rate satisfying the following formula to induce foaming, depressurize at high temperature and taken out from the mold to obtain the intermediate foaming. The method for producing a polyolefin foam according to claim 1, wherein the body is produced. Decomposition rate of foaming agent in the first step (%) = (9 to 12) × (10
0 / final expansion ratio) 3. A cooling molding die (1) comprising: a cooling molding die (1); and a pair of heating plates (2) arranged above and below the cooling molding die and having a heat medium flow passage therein. The working mold (1) was prepared by fixing a side mold having a refrigerant flow path inside and the side mold from above and below, together with the side mold (11) in conformity with the shape and size of the final foam. A pair of flat plates (12) arranged so as to form a non-hermetic internal space and having a refrigerant channel therein, and processing an intermediate foam to produce a final foam. Polyolefin foaming equipment. 4. An unsealed internal space formed by the side molds of the cold-molding mold and the pair of flat plates has a shape substantially similar to that of the final foam, and the cold-molding mold has a shape similar to that of the final foam. Foaming of a foamed product obtained by finally foaming an intermediate foamed product obtained by a primary foaming mold having a cavity having a shape similar to that of the final foamed product in all of the longitudinal, lateral and height dimensions forming the internal space. The polyolefin foaming apparatus according to claim 3, wherein the polyolefin foaming device has a size reduced by 1 to 10% with respect to the respective sizes immediately after. 5. The polyolefin foaming apparatus according to claim 3 or 4, wherein a contact surface of the pair of flat plates of the cooling molding die with the final foam is a smooth surface having fine irregularities. 6. The cooling molding die is detachably attached to the heating plate, and the side mold of the cooling molding die and the pair of flat plates are separable from each other. The polyolefin foaming device according to 3 to 5.