JPH04307227A - Method for replacing residual foaming agent gas in olefinic resin foamed plate with inorganic gas - Google Patents

Abstract

PURPOSE:To replace the foaming agent gas remaining in an olefinic resin foamed plate with inorg. gas such as air within a short time by eliminating conventional inferior efficiency such that a product is kept for a long period of time up to delivery from the aspect of safety, especially, in a case using a combustible foaming agent until the foaming agent gas is replaced with air because the foaming agent gas remaining in the olefinic resin foamed plate is not simply replaced with air even when said plate is allowed to stand under atmospheric pressure for a month or more. CONSTITUTION:Small holes 2 are bored in at least the single surface of a foamed plate 3 by a needle roll 2 having needles 1 on the peripheral surface thereof and the foamed plate 3 is subsequently pressed and compressed by pinch rolls 5,6 to replace the foaming agent gas remaining in the foamed plate 3 with inorg. gas such as air.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for replacing residual blowing agent gas in an olefin resin foam board with an inorganic gas.

0002

[Prior Art and Problems to be Solved by the Invention] Olefin resin foams such as polyethylene foam and polypropylene foam have excellent cushioning properties and heat insulation properties, and are widely used as various cushioning materials, packaging materials, heat insulation materials, etc. has been done. The method for producing olefin resin foams is to melt and knead the raw resin and foaming agent in an extruder, then melt and knead the raw material resin and foaming agent in an extruder to produce long sheet-like or plate-like products. An extrusion foaming method is used in which foaming is performed by extrusion under low pressure from within an extruder.

The foaming agent gas used for foaming is contained in the sheet-like or plate-like foam obtained by the above-mentioned extrusion foaming method.
Propane, butane, pentane, hexane, cyclopentane,
When a flammable blowing agent such as cyclohexane is used, the blowing agent gas remaining in the foam board is subject to static electricity until the remaining blowing agent gas in the foam is replaced with non-flammable gas such as air. There is a risk of ignition due to sparks, etc., and manufacturers are currently unable to ship products to ensure safety until the residual blowing agent gas in the foam is replaced with air, etc.

In the case of thin-walled sheet-like foams, the blowing agent gas remaining in the foam can be replaced with air in a relatively short period of time simply by leaving the foam under atmospheric pressure after manufacture. However, in the case of thick foam boards, the residual blowing agent gas cannot be easily replaced with air, and it may take one to three months to completely replace it by leaving it under atmospheric pressure. There was a problem in that it required several months or more.

[0005] The present invention has been made in view of the above points.
A method for replacing the remaining blowing agent gas in an olefin resin foam board with an inorganic gas that can replace the remaining blowing agent gas in an olefin resin foam board with a nonflammable inorganic gas such as air in a very short time. The purpose is to provide.

[0006]

[Means for Solving the Problems] That is, the method of replacing the residual blowing agent gas in an olefin resin foam board with an inorganic gas according to the present invention involves forming small holes on at least one side of the olefin resin foam board, and then Pressure is applied to the plate in the thickness direction, and the compression ratio is 30.
% or more, and the foaming agent gas remaining in the foam board is replaced with an inorganic gas. In the present invention, it is also possible to employ a method in which small holes are formed in at least one side of the foam board and at the same time the foam board is compressed to a compression ratio of 30% or more. In addition, the small holes should have a depth of 1/4 or more of the thickness of the foam board, and should be 0.3
It is preferable that holes having a diameter of ~5 mm are bored in the foam board at intervals of 3 to 50 mm.

In the present invention, the olefin resin which is the base resin of the foamed board includes polyethylene such as high density polyethylene, medium density polyethylene, low density polyethylene, linear low density polyethylene, linear very low density polyethylene, and polypropylene. , polybutene, ethylene-propylene block copolymer, ethylene-propylene random copolymer, ethylene-butene random copolymer, ethylene-
Examples include butene-propylene random copolymers. These resins can be mixed and used as appropriate. If it is about 40% by weight or less, for example, polystyrene, high impact polystyrene, styrene-maleic anhydride copolymer, styrene-methacrylic acid copolymer, styrene-acrylonitrile copolymer, styrene-butadiene-acrylonitrile copolymer, Resins other than olefin resins such as styrene-butadiene rubber can also be mixed.

The method of the present invention is mainly applied to foams in which the gas of a volatile blowing agent remains, and is particularly suitable for application when the volatile blowing agent is flammable. Also, the plate thickness is 1
It is particularly suitable for treating foam boards with a diameter of 0 to 100 mm. Commonly used flammable blowing agents include, for example, propane, n-butane, i-butane, pentane, hexane, heptane, cyclohexane, cyclopentane, and the like.

In order to form small holes in a foam board in the method of the present invention, a needle roll 2 or the like having a plurality of needles 1 on its circumferential surface as shown in FIG. 1 can be used. The depth of the small holes 4 formed in the olefin resin foam board 3 by the needle 1 is preferably 1/3 or more of the thickness of the foam board 3, and the small holes 4 may penetrate through the foam board 3. Further, as shown in FIG. 1, small holes 4 that do not penetrate the foam board 3 can be provided on both the front and back sides of the foam board 3. In this case, the small holes 4 may be provided at corresponding positions on both the front and back surfaces, or may be provided at non-corresponding positions. The diameter of the small holes 4 is set to 0.3 in order not to reduce the heat insulation properties of the foam board 3 and to perform the continuous and efficient drilling operation of the small holes 4.
~5 mm is preferred, and 0.5 ~ 2 mm is particularly preferred. Further, the needles 1 are preferably provided on the circumferential surface of the needle roll 2 at intervals of 3 to 50 mm, particularly at intervals of 10 to 20 mm.

The foam board 3 with small holes 4 is compressed in the thickness direction by pinch rolls 5 and 6 so that the compression ratio is 30% or more, but in particular, it is compressed to a compression ratio of 50 to 80%. It is preferable to do so. After compressing the foam board 3, it is preferable to release the pressing force. Since the olefin resin foam has excellent elasticity and restoring properties, the thickness of the compressed foam board 3 returns to its original thickness when the pressure is released. Foam board 3
The preferred range of time for compressing by applying pressure varies depending on the expansion ratio of the foam board 3, the type of base resin, the type of foaming agent, the compression rate, etc. Generally, when compressing with the pinch rolls 5 and 6, it is preferable to transfer and compress the foam board 3 at a speed of 5 to 30 mm/sec. Also, instead of the pinch rolls 5 and 6, compression can be performed by applying pressure with a press device. In this case, it is preferable to release the pressure after compressing for about 0.5 to 2 minutes, but with the pinch rolls. Compressing under pressure is preferable because the blowing agent gas can be efficiently replaced in a very short period of time. These series of treatments are usually performed under atmospheric pressure, so that the blowing agent gas in the foam board is replaced with air, but the treatments may also be performed in an atmosphere of an inorganic gas other than air. Examples of inorganic gases other than air include carbon dioxide, nitrogen, oxygen, argon, and neon, but it is preferable to use carbon dioxide or nitrogen, which are inexpensive.

Further, in the present invention, as shown in FIG. 2, the needle 1 has a plurality of needles 1 on the circumferential surface, and is configured to be able to make small holes in the surface of the foam board 3 and to compress the foam board 3. It is also possible to adopt a method in which the foam board 3 is compressed at the same time as the small holes 4 are bored in the foam board 3 using needle pinch rolls 7 and 8 .

In the present invention, the compression rate α (%) is defined as the thickness of the foam board 3 before compression is D1, and the thickness after compression is D2.
When , it is the value shown by the following formula 1.

[0013]

[Math 1] α = (D1 - D2) ÷ D1 × 100

0
014]

[Examples] The present invention will be explained in more detail below with reference to Examples.

Example 1 Low density polyethylene 20% by weight, high density polyethylene 6
After adding 13 parts by weight of isobutane to 100 parts by weight of a polyethylene mixed resin consisting of 0% by weight and 20% by weight of polystyrene, the mixture was melt-kneaded in an extruder and then extruded from the extruder to obtain a foam board with a thickness of 30 mm. . Small holes with a hole diameter of 0.9 mm and a depth of 10 mm were bored at 10 mm intervals on both sides of this foam board using a needle roll. Next, this foam board was compressed to a compression ratio of 50% using a press device, and the pressure was released after 60 seconds. This foam board was heated at a room temperature of 23℃ and a relative humidity of 50%.
Placed in a constant temperature and humidity room, 1 day later, 4 days later, 1 week later, 1
A gas detector (
Measured using a GX-85 model (manufactured by Riken Keiki Co., Ltd.). To measure the amount of residual isobutane, make a non-penetrating cut at any point on the foam board, and immediately after making the cut, insert the measurement tube of the gas detector into this cut so that its tip is located approximately in the center of the foam board, and measure the amount of residual isobutane at the peak time. ○...Gas was not detected. △...Gas remains, but it is below the explosion limit. ×...Gas within the explosive limit remains. It was evaluated as The measurement was performed five times, and the worst evaluation among the five measurements is shown in Table 1.

Example 2 The same process as in Example 1 was carried out, except that pinch rolls were used instead of the press machine, and the foam board with small holes was compressed by passing between the pinch rolls at a speed of 10 mm/sec. went. The results are shown in Table 1.

Example 3 The same process as in Example 2 was carried out except that the compression ratio was 67%. The results are shown in Table 1.

Example 4 The same process as in Example 2 was carried out except that the depth of the small hole was 20 mm. The results are shown in Table 1.

Example 5 The same process as in Example 2 was carried out except that small holes were drilled through the foam board. The results are shown in Table 1.

Example 6 The same process as in Example 2 was carried out except that small holes were made only on one side of the foam board. The results are shown in Table 1.

Example 7 The same process as in Example 2 was carried out except that the compression ratio was 83%. The results are shown in Table 1.

Example 8 The same process as in Example 3 was carried out, except that a needle pinch roll was used to punch small holes in the foam board and at the same time compress it. The results are shown in Table 1.

Example 9 A pinch roll with needles was used for only one pinch roll, small holes were made only on one side of the foam board, and the compression rate was 50%.
The same treatment as in Example 8 was carried out except for the following. Table 1 shows the results.
Shown below.

Example 10 The same process as in Example 2 was carried out except that the compression ratio was 37%. The results are shown in Table 1.

Comparative Example 1 A foam board similar to that used in Example 1 was placed in a constant temperature and humidity chamber similar to Example 1 without making small holes or compressing it, and the amount of residual isobutane in the foam board was reduced. Changes over time were measured in the same manner as in Example 1. The results are shown in Table 1.

Comparative Example 2 A foam board similar to that of Example 1 was made with similar small holes, and then placed in a constant temperature and humidity chamber without being compressed. It was measured in the same manner. The results are shown in Table 1.

Comparative Example 3 The same process as in Example 2 was carried out except that a foam board without small holes was used. The results are shown in Table 1.

Comparative Example 4 The same process as in Example 2 was carried out except that the compression ratio was 20%. The results are shown in Table 1.

[0029]

[Table 1]

[0030]

[Effects of the Invention] According to the method of the present invention, the blowing agent gas remaining in the olefin resin foam board can be replaced with air etc. in a short period of time. If small holes with a diameter of 0.3 to 5 mm are formed at intervals of 3 to 50 mm, the residual blowing agent gas can be replaced more effectively. In the method of the present invention, when a combustible blowing agent is used as the blowing agent, the time required to reduce the amount of residual blowing agent gas in the foam board to below the explosion limit may be as short as one week or less; The processing time can be significantly shortened compared to the conventional method, which replaces the residual gas with air or the like by simply leaving the gas under the air. In addition, when pinch rolls are used to compress the foam board, especially if small holes are made on both sides of the foam board, it takes an extremely short period of about 4 days for the amount of residual blowing agent gas to drop below the explosive limit. It is possible to perform very efficient processing.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram illustrating an example of the method of the invention.

FIG. 2 is a diagram illustrating another embodiment of the invention.

[Explanation of symbols]

3 Olefin resin foam board 4 Small hole 5, 6 Pinch roll 7, 8 Pinch roll with needles

Claims (5)

[Claims] Claim 1: After making small holes on at least one side of an olefin resin foam board, the foam board is pressurized in the thickness direction to compress the foam board to a compression ratio of 30% or more, thereby producing a foam board. A method for replacing residual blowing agent gas in an olefin resin foam board with an inorganic gas, the method comprising replacing the blowing agent gas remaining therein with an inorganic gas. 2. The olefin resin foam according to claim 1, wherein small holes are formed on at least one side of the olefin resin foam board, and at the same time, the foam board is compressed to a compression ratio of 30% or more. A method for replacing residual blowing agent gas in a board with an inorganic gas. 3. The olefin resin foam board according to claim 1 or 2, wherein the small holes formed in the foam board have a depth of 1/4 or more of the thickness of the foam board and a diameter of 0.3 to 5 mm. Method for replacing residual blowing agent gas with inorganic gas. 4. The method for replacing residual blowing agent gas in an olefin resin foam board with an inorganic gas according to any one of claims 1 to 3, wherein the foam board is compressed by applying pressure with pinch rolls. 5. The method for replacing residual blowing agent gas in an olefin resin foam board with an inorganic gas according to any one of claims 1 to 4, wherein small holes are bored at intervals of 3 to 50 mm.