JPH1134174A - Production of anisotropic styrenic resin foam - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the deformation or crack of a foam and to reduce a treatment time and the number of processes by providing a large number of voids in a styrenic resin foam and subsequently compressing the foam. SOLUTION: A large number of voids with a cross-sectional area of 0.5-10 mm<2> are provided in a styrenic resin foam with a density of 7-50 kg/m<3> and, subsequently, the foam is compressed so that the thickness thereof becomes 90-10% of the initial thickness thereof, and, during a compression process, the compressed surface is pref. sucked under reduced pressure. Further, a foam wherein a thickness in the compression direction before compression is 3 cm or more and a vol. is 4000 cm<3> or more is pref. The number of voids is pref. 2-400 per 100 cm<2> from an aspect of physical characteristics in consideration with the thickness, total vol. density and objective compression degree of the foam. Compression is usually performed by placing the foam between two rigid members such as parallel metals to narrow the interval between the rigid members by oil pressure and a compression speed is pref. 20-100 cm/m and the holding time thereafter is pref. 1 sec-20 min.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to an anisotropic styrene-based resin foam which exhibits substantially different mechanical and physical properties depending on the measurement direction by compressing a substantially isotropic styrene-based foam. Related to manufacturing method.

[0002]

2. Description of the Related Art Polymer foams are used in many fields because of their excellent heat insulating properties, shock absorption properties, bending stiffness per unit weight, etc., which are composed of many foams. Typical foams are expanded polystyrene (EPS), expanded polyethylene (EPE), expanded polypropylene (EPP), expanded polyurethane (EPU), and the like. EPS, which is one of the styrene-based resin foams, has the same density and high rigidity as EPE and soft EPU, but has low flexibility, and hardly recovers from deformation and strain due to load. EPE, soft EPU is E
Compared with PS, it is superior in flexibility and restoring property of deformation.
Poor in rigidity.

[0003] It is known that flexibility is imparted by applying a compressive force to a closed-cell hard foam sheet (GB Patent 911,995, US Patent 3,159,7).
00 specification). Japanese Patent Application Laid-Open No. 7-148761 discloses that a well-known and commonly used foamed plate is subjected to post-processing by compression to obtain a 10M
A method for producing a foamed plate having a dynamic rigidity of N / m ³ or less, comprising an apparent specific gravity of 17 to 30 kg /
The foam board body m ^3, the compression until the original 60% to 90% maximum compression strain rate of increasing the compression set ratio, wherein the repeating at least once the process is shown However, there remain problems such as the number of steps of the compression processing being as many as 5 to 10 times and the thickness of the plate being limited. Japanese Patent Application Laid-Open No. 56-51337 discloses a method for obtaining a highly elastic foamed styrene resin by placing a foam of a styrene resin in a mold and compressing the foam so that the compression strain is 25 to 50%. Are listed. This method also requires a plurality of compression operations to reach a predetermined compression ratio. If the compression operation is not performed a plurality of times, the foam may be deformed or cracked.

On the other hand, Japanese Patent Application Laid-Open No. Hei 2-299321 proposes a method in which a foamed thermoplastic resin article having a closed cell structure is placed in a decompression chamber, exposed to reduced pressure and then compressed. (1) A high-strength decompression chamber for accommodating bulky foam and enduring decompression is required.
The number of steps of the decompression treatment increases, and the treatment time may become longer as a whole. (3) The foam taken out from the decompression chamber into the atmospheric pressure changes its decompression state with the passage of time, which causes a problem in quality stability in relation to the next step. (4) As the foam becomes larger, the surface area relatively decreases, so that it takes a long time for the decompression treatment to reach inside, and as a result, the productivity is reduced. As described above, in the known methods, there is a contradictory relationship between the product quality such as deformation and cracking of the foam and the processing time and man-hour.

[0005] The volume of the foam is reduced while the foam formed by the compression is deformed. At this time, the pressure inside the cells increases, and the gas tries to permeate and escape outward, but must pass through the myriad of cell walls before reaching the outside of the foam. For this reason, when the speed of the compression process is higher than the speed of the gas escape, the pressure inside the foam increases abnormally, and the pressure remaining after the compression force is released deforms the foam, and sometimes the foam is deformed. Or cracks. This tendency is likely to occur when the gas inside the cells has a long distance to permeate and escape to the outside of the foam having a small pressure. In other words, this tendency is greater as the foam is thicker and has a larger area.

When this phenomenon is observed in more detail, when the foam is subjected to a compressive load, the foam in the load-receiving portion is deformed, and the pressure of the cells constituting the foam is increased. The pressure difference becomes the driving force, and the gas permeates / dissipates outside the foam. However, in actuality, the permeation / dissipation occurs first from the bubbles in contact with the outside of the foam through the cell wall.
The pressure of the bubble is reduced, and a pressure difference is generated between the bubble and the bubble next to the bubble, which becomes a driving force, and propagates inside such that transmission / dissipation occurs through the bubble wall. . It is presumed that the biggest factor in changing the physical properties of the rigid foam is that the cells have a flat structure in cross section. According to the experiments and observations of the present inventors, the flattening of the bubbles does not occur simultaneously with all the bubbles of the foam subjected to the compression load, but occurs from a portion in contact with the outside or a low pressure space. The aforementioned transmission / dissipation hypothesis was confirmed.

[0007]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned problems of processing time and man-hours in the production process of anisotropic foams, and provides anisotropic foams of excellent quality from styrene-based foams. A method for producing a styrene resin foam is provided. Claim 1 provides a basic concept of a method for producing an anisotropic styrenic resin foam. Claim 2 provides a method for producing an anisotropic styrenic resin foam without deformation, cracking, and the like. Claim 3 provides an efficient method for producing an anisotropic styrenic resin foam without deformation or cracking. Claim 4 provides a short time method for producing an anisotropic foam. Claim 5 provides a production method that is effective in productivity and quality.

[0008]

SUMMARY OF THE INVENTION The present invention relates to a method for producing an anisotropic styrene resin foam in which a plurality of pores are provided in a styrene resin foam and the foam is then compressed. In the present invention, a styrene resin foam having a density of 7 to 50 kg / m ³ is provided with a plurality of pores having a cross-sectional area of 0.5 to 10 mm ² , and then has a thickness of 60 to 5% of the initial thickness of the foam. It is preferable to compress so that the thickness after the compression is 90 to 10% of the initial thickness. In the present invention, it is preferable that the compressed surface is suctioned under reduced pressure during the compression step.

In the present invention, the thickness of the styrene foam before compression is 3 cm or more in the compression direction and the volume is 4000 c.
It is preferably a foam of m ³ or more. In the present invention, the compression ratio at the time of compression processing ((dimension before compression processing−dimension after compression processing) / dimension before compression processing) × 100% is calculated as 70%.
% Is preferable.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A styrene-based resin foam refers to a foam of styrene polymer, a copolymer of styrene as a main component with other monomers, or a polymer of styrene resin as a main component other than styrene. Also refers to a foam of a mixture of Other monomer components include monomers copolymerizable with styrene, such as butadiene, acrylonitrile, acrylates, divinylbenzene, brominated styrene, and maleic acid. Examples of the polymer that can be a mixture with the styrene resin include a homopolymer or a copolymer of the above-mentioned monomer copolymerizable with styrene, polyethylene, and polyphenylene oxide (PPO).

As a method of forming a styrene-based resin into a foam, an extruder is used to extrude and foam simultaneously with extruding. A foamed resin is heated, and then the foamed granules are put into a mold and heated again to mold. However, the present invention preferably employs the latter method of foam molding from granular material. Although there is no particular restriction on the form of the foam, what is particularly effective in the present invention is that the size (thickness) in the compression direction and the volume in one processing are large. Such a thing deforms,
This is because quality problems such as cracks are likely to occur, while productivity is low. The thickness of the concrete in the compression direction of the foam before compression is the total volume in 3cm or preferably from 4000 cm ³ or more.

The density of the foam used is 7 to 50.
kg / m ³ is preferred. If it is less than 7 kg / m ³ , the shape of the foam tends to be unstable, while 50 kg / m 3
^If it exceeds ³ , its characteristics tend to be smaller than foams such as rubber and elastomer which have elasticity in material.

The pores are provided so as to reach the inside of the foam and one end of the pores communicates with the outside. Although there is no particular restriction such as the angle in the depth direction of the pores, it is usually provided so as to communicate with one or both sides perpendicularly to the compression surface. There are no restrictions on the shape of the pores. The function of the pores is to provide an escape path for the gas inside the foam with increased pressure, and its effect is to alleviate the increase in internal pressure when the volume of the foam is reduced in the compression step. Usually, a cone having a circular cross section is used from the viewpoint of workability. Since the pores are the passages of the gas that escapes through the bubble wall, even small ones are effective. However, in terms of processing efficiency, the cross-sectional area is preferably 0.5 mm ² or more. On the other hand, preferably 10 mm ² or less because influence such as mechanical properties of the foam too large.

The surface on which the pores are provided is mainly a compression surface, but may be additionally provided on a surface perpendicular to the compression surface. There is no restriction on the direction or angle of the pores, but a direction perpendicular to the foam surface is preferred for processing.

The number of pores depends on the thickness, total volume, density,
Although it is necessary to take into account the desired degree of compression and the like, in order to effectively carry out the present invention, the range is preferably about 2 to 400 per 100 cm ^{2 in} terms of physical characteristics. It is effective to reduce the peripheral portion of the compression surface and increase the central portion.

There is no particular limitation on the method of forming the pores. For example, when the target foam is ready, there is a method of piercing with a needle or a conical jig. In the case of producing a foam by heat molding with a method such as, for example, there is a method in which a wire is provided in a mold, and after molding is completed, these are pulled out.

The amount of compression treatment is selected in consideration of the physical properties of the target foam product. In general, the compression ratio increases as the compression processing amount increases, but it is affected by the density of the foam, the cell structure, the compression speed, the compression holding time, and the like. In order to obtain a compression ratio of 30% or more at which the effect of the present invention is greatly exhibited, the thickness is preferably in the range of 60 to 5% of the initial thickness of the foam.

The compression is usually performed by placing a foam between two parallel rigid bodies such as metal (hereinafter referred to as a compression platen) and reducing the distance between the rigid bodies by means of hydraulic pressure or the like. The speed and the holding time of the compression platen when reaching a predetermined compression amount are determined in consideration of the speed at which gas permeates / dissipates from the foam cells. In the present invention, the compression speed is preferably 20 to 100 cm / min, and the holding time is preferably 1 second to 20 minutes. The surface of the compression plate in contact with the foam is required to be substantially flat so as not to impair the properties and appearance of the product.
There may be a surface rougher than 00 mesh or a shallow groove on the grid. This is to make it easier for gas that has escaped from the pores to escape.

By performing the treatment while maintaining the compression surface at a reduced pressure, there is an effect of promoting the outflow of gas from the pores.
At this time, the compression surface is made of a porous material or a metal plate having pores. At this time, the opening degree of the board is set to be larger than that of the pores provided in the foam. Decompression degree is 200
The pressure is preferably not less than mmHg, and the capacity of the vacuum pump is determined in consideration of the volume of the foam.

[0020]

Next, the present invention will be described in more detail by way of examples, but the present invention is not limited to these examples.

[Examples 1 to 4] The average particle diameter before foaming was 0.1.
8 mm expanded polystyrene (EPS: Hi-Beads SSB manufactured by Hitachi Chemical Co., Ltd.) was subjected to pressurized prefoaming in the same manner as ordinary EPS, and after aging, was molded by a fusion molding method. After fully drying the expanded polystyrene (commonly known as EPS block), avoiding the peripheral part, it is 30 cm long, 30 cm wide and 18 cm thick.
Five test pieces having a size of m and a volume of 16200 cm ³ were cut out and the respective densities were measured. Of these, three specimens had 2.
121 pores were drilled in the thickness direction with a cone having a sectional area of 3.14 mm ² (diameter of 2 mm) at intervals of 5 cm.

For the compression processing, a hydraulic compression device with a mold clamping force of 20 tons that operates so as to reduce the distance between the boards when ascending and open the boards when descending. 350m compression
m / min.

In this experiment, the amount of compression means the percentage of the thickness before processing with respect to the inter-panel distance at the end of the compression stroke previously set in the apparatus. The holding time refers to the time that the compression platen is held at that position when the compression platen reaches the set distance between the plates. The compression ratio is a percentage of the thickness of the foam test piece 24 hours after the end of the compression process to the original thickness. The deformed one also uses the size of the central part. The amount of deformation is 4
The difference between the average thickness of the middle part and the thickness of the center part of the piece was divided by the average of the thickness of the four pieces, multiplied by 100, and subtracted by 100. In the experiments of Examples 2 and 3, a hole having a cross-sectional area of 3.46 mm ² (2.1 mm in diameter) was formed on the compression surface by 2.5 c.
Using two double-structure boards provided at intervals of m
It was connected to a vacuum pump with an evacuation capacity of m ³ / min.

Table 1 shows the processing conditions and results of Examples 1-4 and Comparative Examples 1-2. In Example 1, a foam having 121 pores was treated at a compression rate of 90% and the holding time was set to 10 minutes. The resulting compression rate was 60.9% and the deformation was 1.5%. there were. In Example 2, compression was performed to 90% without depressurization using only pores, and held for 5 minutes. The compression ratio was 45.3% and the deformation ratio was 2.8%. Example 3 was performed by adding a decompression operation to Example 1, and as a result, the compression ratio was 47.7% and the amount of deformation was 2.1%. Example 4 is the same experiment as Example 2 except that the holding time was changed from 5 minutes to 3 minutes, and the result was a compression ratio of 39.3% and a deformation amount of 1.4%.

[0025]

[Table 1]

[Comparative Examples 1 and 2] On the other hand, Comparative Example 1 was performed in the same manner as in Example 1 except that the pores were not provided and under the same processing conditions as in the prior art. 5
%, On the other hand, the deformation was 9.1%, and the bulge at the center was large, which was a problem as a plate-shaped member. Comparative Example 2 was performed in the same manner as in Examples 2 and 3 except that the holding time was 5 minutes, which is half of that of Comparative Example, but the compression ratio was as low as 40.1%.
The deformation was 7.8%, which was 3 to 4 times larger than Examples 2 and 3.

The compression ratio of Example 4 and Comparative Example 2 was 39.3%.
And 40.1%, which are almost the same and have the same density of 18.5 kg / m ³ , but with the addition of ordinary EPS of the same density and 11.1 kg / m ³ of EPS before compression processing, there are four types. Was prepared and the thermal conductivity and the compression set according to JIS K6767 were measured for comparison. Table 2 shows the results. From this, it can be seen that the compression treatment reduces (improves) the untreated foam and the ordinary foam having the same density in both the thermal conductivity and the compression set, and the method according to the present invention in comparison with the treatment according to the comparative example. It was confirmed that the characteristics did not change at all.

[Examples 5 to 9] [Comparative Examples 3 to 7] Table 3 shows the method of the present invention and the known method for 1 second, 1 minute, 3 minutes, 5 minutes and 10 minutes.
The results of comparing the compression ratio and the deformation ratio by changing the minutes and the holding time are shown. The method of the present invention has 121 pores and a decompression degree of 62.
The compression was performed at 0 mmHg, and the compression speed was 35 cm / min in both the examples of the present invention and the comparative examples. From these results, it was clarified that, in each of the experiments, the examples of the present invention had higher compression ratios than the comparative examples having the same holding time, while the deformation ratio was small and excellent.

[0029]

[Table 2]

[0030]

[Table 3]

[0031]

According to the method of the first aspect, an anisotropic styrene resin foam can be produced. According to the method of the second aspect, it is possible to easily produce an anisotropic styrene resin foam having a high compression ratio and a small deformation. According to the method of the third aspect, the anisotropic styrenic resin foam can be produced by compressing in a shorter time. According to the method of claim 4, the effect of the above method can be produced more reliably. According to the method of the fifth aspect, the effect of the above method can be particularly increased to manufacture.

Claims (5)

[Claims] 1. A method for producing an anisotropic styrene resin foam, comprising providing a plurality of pores in a styrene resin foam and then compressing the foam. 2. A styrene resin foam having a density of 7 to 50 kg / m ³ is provided with a plurality of pores having a cross-sectional area of 0.5 to 10 mm ² , and then has a thickness of 60 to 5% of the initial thickness of the foam. And the thickness after compression is 90 to 1 with respect to the initial thickness.
The method for producing an anisotropic styrene resin foam according to claim 1, wherein the foam is compressed to 0%. 3. The method for producing an anisotropic styrene resin foam according to claim 1, wherein the compressed surface is suctioned under reduced pressure during the compression step. 4. A process for producing anisotropic styrene resin foam of claim 1, wherein the thickness of the compressive direction the volume in 3cm or more and 4000 cm ³ or more styrenic foam before compression. 5. A compression ratio at the time of compression processing ((dimension before compression processing−dimension after compression processing) / dimension before compression processing) × 100
5. The method for producing an anisotropic styrene resin foam according to claim 1, wherein the% is 70% or more.