JPS58173631A - Preparation of foamed product of hard thermoplastic resin - Google Patents

Abstract

PURPOSE:To improve the flexibility, sound insulation and heat insulating capacity, etc. of a foamed product of hard thermoplastic resin by such an arrangement wherein a resin for forming a foamed product of hard thermoplastic resin is caused to foam in a gas of which gas permeability is larger than air, or in a liquid containing such a gas under specific conditions, and after that the foamed product is caused to shrink. CONSTITUTION:A plate of hard thermoplastic resin, sheetlike foaming substance, or a resin for foamed product is heated and caused to foam in a gas of which gas permeability is larger than air, or in a liquid containing such a gas up to more than 1.4 times larger than initial foaming volume and less than 15kg/m<3> of volume density. Next, the foamed resin is caused to shrink into a volume less than 60% of its foaming volume and then it is cured in a drying chamber at a temperature higher than 40 deg.C and lower than the softening temperature of the resin and then caused to expand more than 1.4 times larger the foamed volume at the time of shrinkage and a foamed product of which density is 3-17kg/m<3> is thus obtained. This foamed product has many creases, each of which has one end in a boundary area to be generated by more than 3 adjoining air bubbles and extends in the direction of the central part of an air bubble membrane.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a plate-like or sheet-like foam or foam molded product made of a hard thermoplastic resin that has ultra-low density, high flexibility, high sound insulation performance, and high heat insulation performance. (hereinafter collectively referred to as foam).

Traditionally, rigid thermoplastic foams have been used due to their low thermal conductivity,
Due to its characteristics such as low water absorption, light weight, and workability, it is widely used as a heat insulating material for buildings such as general residences. However, because it is less flexible, for example, in order to fill between the studs of a building, it is necessary to cut it in advance to match the stud spacing.
It is necessary to fix it with special metal fittings, and in reality it cannot absorb variations in the spacing between the studs, resulting in extremely poor workability and an airtight insulation structure cannot be obtained. Furthermore, if an attempt is made to fill the material airtight, a great deal of force is required due to its hardness, resulting in the destruction of the bubbles. Furthermore, the foam also breaks, making it impossible to obtain an airtight heat-insulating structure.

On the other hand, as buildings such as residences have become taller in recent years, sound shielding properties between upper and lower floors have come to be required, especially in buildings such as apartment complexes. Recently, in order to solve this problem,
This method, called the floating floor construction method, involves placing inorganic fiberboard on the base material and pouring concrete mortar on top of it with a waterproof layer in between. This utilizes the flexibility of inorganic fiberboard to reduce solid-borne sound between the upper and lower floors and improve sound insulation. Even in this application, conventional rigid thermoplastic resin foams cannot provide sufficient sound insulation due to their rigidity.

Recently, in order to solve these problems mentioned above, there are foams obtained by mechanically softening low-density polystyrene foam, but in this case, the density is 20'KP.
If it is less than /m3, the resin film constituting the bubbles will be destroyed due to mechanical flexibility, resulting in a so-called communication phenomenon. Furthermore, even if the relatively thick surface layer of the foam suppresses the destruction of the bubbles and maintains the apparent closed cell ratio as seen from the water absorption rate using a general measurement method, the inside of the foam The foam is composed of a thinner film than the surface layer, and is far inferior in terms of maintaining thermal performance.In general, the closed cell ratio according to the measurement method used in the present invention is 50.
% or more is difficult to use as a heat insulating material.

Furthermore, when it is mechanically softened, the foam as a whole is softened, and when viewed microscopically, there are parts of the foam that have been softened and parts that have not. The physical properties become non-uniform in the thickness direction or in the planar direction of the foam.

On the other hand, foamable particles containing a foaming agent are foamed in several batches and then foamed in a mold to form a plate or molded product that is used as a heat insulating material, a cushioning material, or a sound insulating material. There is. However, in foams like this one, in which the particles themselves are made to have a low density (highly foamed) by increasing the number of times they are foamed, the particles themselves become large, making it difficult to airtightly fill them when molded, and the fusion between the particles increases. This results in a weak foam. In addition, in order to strengthen the fusion bond, it is necessary to perform compression filling and compression molding when making a molded product, and the foam made in this way has the presence of wrinkles as defined in the present invention. However, there is a limit to how low the density can be made, and the density of a foam that can withstand practical use is only 17:9/m3 or higher.

However, in the market, there has been a strong demand for many years to obtain a rigid thermoplastic resin foam that is low in density, highly flexible, has heat insulating properties, and has sound insulating properties.

The present invention was achieved as a result of research in view of the current situation, and combines the permeability of various gases to resin, the temperature dependence of permeability, and softening temperature to create an ultra-low density and flexible resin. The present invention has led to the invention of a method for obtaining a foam having the heat insulating properties of a hard thermoplastic resin, which has excellent sound insulation properties due to the presence of wrinkles in the cellular membrane as used in the present invention.

That is, the present invention provides initial foaming in a gas having a higher gas permeability than air for a plate-like or sheet-like foamed body or a foam molded body of a hard thermoplastic resin, or in a liquid in which the gas is present. 1.4 times or more body volume and bulk density 1
It is heated and foamed to 5Ky/m3 or less, then shrunk to 60% or less of the volume of the heated foam, and further aged in a drying room where the ambient temperature (T) is 40'C≦(T)≦the softening temperature of the resin. , expanded to 1.4 times or more the volume of the shrinkable special foam, and the density (D) is 3 Ky/m3≦(D)≦17 Ky/m
3. In the cell structure, the cell membrane has one end at the boundary where at least six cells are formed adjacent to each other, has many wrinkles extending toward the center of the cell membrane, and has a closed cell ratio of 50% or more, and is plate-shaped. Alternatively, it is a method for producing a foam, which is characterized in that a sheet-like foam or a foam molded product is obtained.

The contents of the present invention will be explained in detail with reference to the history and drawings.

In the present invention, industrially, the foaming in the first stage is
It is preferable to do it in stages. For this purpose, it is desirable to select a foam as a starting material of 200 Ky, 7 m3 or less, and if it is 100 K, Sl 7 m3 or less, it is possible to obtain a foam with higher efficiency and better quality. It is.

Next, in the present invention, it is necessary to heat and foam the rigid thermoplastic resin foam in a gas having a higher gas permeability than air and/or a liquid containing the gas. In gases that have lower permeability than air for the resin, or in liquids containing such gases, the foam density will not decrease even if heated for a long time, and in some cases, the foam density will not decrease even if heated for a long time. Existing air and foaming agent may escape back and cause shrinkage.For example, Figure 1 shows heating temperature of 9.
F- with different permeability to styrene, unified at 5℃
11 (Freon-11), air, He1 water vapor, and hot water (with water vapor) as a liquid in the presence of gas, 6
In a heated atmosphere of
The width, length, and thickness are 400 mm, 700 mm, and 15 mm, respectively.
Figure 2 is a graph of final foam density when heating +nm polystyrene extruded foam board. According to this graph, H
It can be seen that in the case of e, steam, and hot water, the density of the foam decreased, but in air and F-11, the density of the foam increased.

Furthermore, even if the foam is filled with a gas having a lower permeability than the air under pressure inside the initial foam, if the permeability is higher than that gas,
In addition, the foam may be heated in an atmosphere of a gas (for example, air) having a permeability lower than that of air; in this case, the foam expands at a slow rate. However, at the stage of once shrinking after heating and foaming, the amount of shrinkage is so small that it cannot reach the foam obtained by the method of the present invention. This is because at the time of contraction, only gas having a permeability lower than that of air exists in the foam, so that the amount of contraction can only be equal to or less than the expansion of the gas in the foam due to heating.

From the above, it can be seen that the method of the present invention requires heating and foaming the resin constituting the foam in a gas having a higher permeability than air and/or in a liquid containing the gas. Gases with higher permeability than air vary somewhat depending on the type of resin, but generally water vapor, H
e XCO2, cH3cρ, cH2cQ2. ,”2H5
There are C1 etc. Liquids in which these nofi bodies exist include, for example, warm water, alcohol, glycerin, etc.
Among these, the heating medium is preferably water vapor or a hot water (containing water vapor) atmosphere.

Next, it is necessary to heat and foam the foam in the above-mentioned atmosphere to a bulk density of 15 to 51/m3 or less and at least 1.4 times the initial foam volume. (Methods for measuring foam volume and bulk density when heated and foamed are described separately.) The reason for this is that density 1
If it exceeds 5Ky/m3, no matter how much you increase the foaming ratio relative to the initial density, even if the density is still 15Kp/m3 or less, if it is less than 1.4 times the initial foam volume,
That is, when the increase rate in volume is less than 40%, the presence of wrinkles as defined in the present invention is hardly obtained.

Next, after performing the above heat treatment, it is necessary to shrink the volume to 60 times or less of the volume at the time of heating and foaming. The reason for this is that after the heat-foaming treatment described above, if the volume once shrunk exceeds 60% of the volume of the foam at the time of heat-foaming, that is, if the amount of shrinkage is kept small, wrinkles may form in the bubble membrane. Or, even if it is possible, the wrinkles will not be uniform throughout the foam,
This is because it is not possible to obtain a foam having the desired physical properties. However, at present, as mentioned above, the method of achieving low density is to heat and foam expandable particles containing a foaming agent in several batches, and then further heat and foam them in a mold so that there is almost no dimensional change after foaming. Since the foam is foamed to form a plate-like body or a molded body, the foam has almost no wrinkles as defined in the present invention. In order to further clarify the above contents, Fig. 2 shows a photograph of the cell structure of the foam obtained by the method of the present invention) and the heating in the particle state in several times (six times) to prevent shrinkage. A photograph (b) of the cell structure of the foam obtained by foaming is shown. The product of the present invention shown in (a) is
There are a number of wrinkles that have one end at the boundary where at least three bubbles occur adjacent to each other and extend toward the center of the bubble membrane, but the comparative product shown in (b) does not have the wrinkles defined in the present invention. I know it doesn't exist.

Furthermore, in the method of the present invention, the once-shrinked foam is dried in a drying room where the ambient temperature (T) is 40°C≦(T)≦the softening temperature of the resin, preferably at a humidity of 30°C or less. It is necessary to mature the foam preferably for at least 24 hours in a drying room with a humidity of 10% or less to expand it to at least 1.4 times the volume of the shrinkable foam.

The reason for this is that if the atmospheric temperature (T) for recovery is less than 400C, as shown in FIG. 3, it will take a long time for recovery, which is industrially disadvantageous. This is true - for example, in the fourth
This is clear from the gas permeation curve of air against polystyrene shown in the figure. In other words, this means that the amount of air permeated through polystyrene increases at 40c'C, and the recovery speed becomes faster. On the other hand, if heated to a temperature higher than the softening temperature of the resin, the resin itself will melt at the same time as recovery, making it impossible to form a foam. In addition, if the humidity is high, it is difficult for the moisture in the shrunk foam to be replaced with air, and when the foam is removed from the heated atmosphere after the recovery operation, it will shrink again, resulting in a dimensionally stable foam. becomes difficult to obtain. Furthermore, the aging time is determined by the temperature and the density of the foam to be obtained;
/m3, preferably aged for 24 hours or more. In addition, unless the foam is expanded to 1.4 times or more the volume of the shrinkable special foam, a flexible foam cannot be obtained, the amount of volume recovery will be small, and the density cannot be lowered. This is because the properties of our foam, so-called sound insulation, will no longer be effectively affected.

The recovery atmosphere described above is an example of a dry air atmosphere, but it can also be used with inorganic gases such as carbon dioxide, helium, hydrogen, or a mixture of organic gas and air depending on the purpose. .

Further, in the method of the present invention, it is more preferable to provide an auxiliary plate so that the product shape of the foam can be well maintained during heat foaming, shrinkage, and aging.

In addition, when giving directionality to the physical properties of the foam, the width, length,
It is also possible to suppress foaming in one direction or two directions in each direction of the thickness by placing it in a mold frame, and to allow free foaming only in the remaining two directions or one direction.

As mentioned above, the foam obtained by the method of the present invention is a novel foam that has not been seen before, and if necessary, it can be made into a composite with a plastic board, plastic film, wood board, inorganic material, cloth, etc. Even when used as a material, it is effective because it can provide excellent strength, heat insulation, and sound insulation.

The hard thermoplastic resin used in the present invention refers to styrene, methylstyrene, ethylstyrene, chlorostyrene, or alkenyl aromatic compounds such as those mentioned above, and other easily polymerizable olefin compounds such as maleic anhydride, acrylic acid, Copolymers with methacrylic acid etc., so-called styrene polymers such as rubber reinforcing polymers, acrylic polymers such as acrylonitrile, methyl methacrylate, acrylonitrile-butadiene-styrene copolymers, polycarbonate, polyphenylene oxide, hard vinyl chloride It is a polymer or a mixture of the above polymers. A hard thermoplastic resin foam is a foam obtained by extrusion foaming, in-mold foaming, or free foaming of the above polymer or a mixture thereof using a chemical foaming agent, a physical foaming agent, a mixture thereof, or the like.

Particularly preferably, the styrenic polymer is melt-kneaded with a physical foaming agent, a chemical foaming agent, or a mixture thereof in an extruder, and extruded through a T-die or an annular die.
So-called extruded foam is good. It also includes foamed products in which expandable particles are foamed and fused in a mold to form a plate-like object or other molded object, but in this case, the fusion between the particles is somewhat poor, and it is not possible to extrude or foam the particles in the form of a sheet. The heat insulation properties are somewhat inferior to those obtained using foamed materials. Further, the shape of the hard thermoplastic resin foam used in the method of the present invention is not particularly limited, but plate-like, prismatic, and sheet-like shapes are effective, and those with a thickness of 50111111 mm or less are suitable for the final foam. This is particularly effective in maintaining dimensional accuracy. Further, the foam may contain general nucleating agents, lubricants, colorants, ultraviolet absorbers, antistatic agents, etc., as necessary.

The methods for measuring the foam density, closed cell ratio, and softening temperature of the resin used in the present invention are based on the following methods.

○Initial, shrinkage, and final foam densities: JIS-A-9
511 0 Volume when heated and foamed: As shown in Fig. 5, two or more holes 2 are made on each side and the top of the foaming machine 1, and the foam is poured from each side of the foaming machine before and during foaming. Measure the dimensions up to 6 on scale 6, and calculate the increase in foam volume and the volume when heated and foamed. .

O closed cell ratio: Measured according to the measurement method of ASTM-D-2856 (including the value of the open cell layer on the sample surface layer). Each surface layer of the sample was cut by 1' and 721 degrees of thickness in the thickness direction of that surface, and measured again. This operation was repeated n times and expressed as the average value of the n times. The higher the number of times, the better, but there is a limit depending on the size of the original sample, so at least n≧3.

0 Softening temperature of resin: ASTM-D-1525 Example
Comparative Example 1 Using polystyrene with a resin softening temperature of 106°C as a raw material
Density 54 KLI/m, 3, Weight 142.8 fi',
The width, length, and thickness are each 400mm, 700n+, 1
A 5 mm extruded polystyrene foam plate was heated and foamed in an atmosphere of 100°C steam, '100°C hot water, and IC130C air for 15 to 120 minutes, and the foam volume and density of each sample at that time were calculated. According to this, regardless of the heating time, when foaming is done by heating in an air atmosphere, the foaming density actually increases.

However, when foamed in a hot water or steam atmosphere, the volume at the time of foaming is 2.8 to 10.0 times the initial foam volume, with a strength of 1
tfr):12. I Ky/m3~3.4 K51
7 m, 'A, and it is cooled in the atmosphere to 60% ~ 3
[After shrinking to 1%, dry it in an air open at 70 °C until there is almost no change in volume, take it out,
As a result of measuring the physical properties, the density was 15.5 to 5.4 KP/m3
When the structure of the bubble film was observed using an electron microscope, many wrinkles as defined in the present invention were uniformly observed. Also, the closed cell ratio is 5
It was 5% or more.

Example/Comparative Example 2 Similar to Example/Comparative Example 1, a foam with a density of 21 to 9/rn3 (weight 88.29-) was used, the heating medium was limited to steam, and the heating and foaming conditions (temperature, time) were changed. , the foaming ratio and density were changed to change the foam volume from 1.2 to 5.0 times and the density from 1735 to 4.2 to 51/m2. According to this, the foaming ratio is less than 1.4 times and/or the density is 15 to 9.
If the size exceeds 7 m3, it is difficult to shrink it by 60% or more, and when it is shrunk by external force, the closed cell ratio becomes less than 50%, or the wrinkles referred to in the present invention are not uniformly present. However, the foaming ratio is 1.4 times or more and the density is 1.
5. Shrink the foam of 51/m3 or less in the same manner as in Example 1,
In both cases, the foam density was 17 to 9/m.
3 or less, and the closed cell ratio was all 50 or more, and when the cell structure was observed using an electron microscope, many wrinkles as defined in the present invention were uniformly observed.

Example/Comparative Example 6 Among the foams obtained in the same manner as Example/Comparative Example 2,
Density when foaming: 8.5 to 97m3, foam volume magnification: 2.47
The foam was cooled in the air and shrunk to -H47cm.
Aging was performed at five levels: 0°C, 105°C, and 110°C. As a result, there was a difference in aging time between 40°C and 105°C, but the final recovered foams all had a density of 17Ky.
/m3 or less, there were many wrinkles as defined in the present invention, and the closed cell ratio was all 50 cm or more. Compared to this, 30℃
No change in volume was observed with the foam that was left at 110°C for 15 days.On the other hand, with the foam that was heated to 110°C, the resin melted before the foam expanded, and the desired foam could not be obtained. .

[Brief explanation of the drawing]

Figure 1 is a graph showing an example of density reduction due to different types of heating medium, Figure 2 (a) is an enlarged photograph showing the cell structure of the foam obtained by the method of the present invention, and (b) is a comparative product. FIG. 3 is a graph showing the recovery state of the aging temperature (sold separately), and FIG. 4 is a graph showing an example of the temperature dependence of direct air permeation through a polystyrene membrane. Applicant Asahi Dow Co., Ltd. Agent Yutaka 1) Yoshio No. 1 - Heating time (minutes) 1-ku Fig. 3 Kensei-no-ma [Seal Fig. 4 Temperature [0C] Fig. 5 Procedural amendment (method) ) % formula % 1. Indication of the case Japanese Patent Application No. 57-55985 2. Name of the invention Method for manufacturing rigid thermoplastic resin foam 6. Person making the amendment Relationship to the case Patent applicant Yurakucho, Chiyoda-ku, Tokyo 1-1-2 (046) Asahi Dow Co., Ltd. Representative Rei Yumikura -4, Agent Room 204, Sanshin Pill, 1-4-1 Yurakucho, Chiyoda-ku, Tokyo Telephone 501-21386, " 7-1 Contents of amendment to column Z of "Brief explanation of drawings" 7-1 The column of "Brief explanation of drawings" of the specification will be amended as follows. (1) "Enlarged photograph showing bubble structure" on page 18, line 12 of the specification tube is corrected to "electron micrograph showing bubble structure." (2) In the same line 13, r(b) is an enlarged photograph showing the bubble structure of the comparison product.'' is corrected to ``Figure 2(b) is an electron micrograph showing the bubble structure of the comparison product.'' (3) In the 16th line, "-This is a graph showing an example." was changed to "-A graph showing an example. FIG. 5 is a schematic perspective view for explaining the method of measuring the volume at the time of heating start." correct.

Claims (1)

[Claims] 1) 1 of the initial foam volume in a gas that has a higher gas permeability than air for the resin of a rigid thermoplastic resin plate or sheet foam or foam molded product, or in a liquid in which the gas exists. .4 times or more and bulk density 15Kp/m3
The following heating and foaming is performed, and then 60% of the volume of the heated foam is
Further, the ambient temperature (T) is 40℃≦(
T) ≦ softening temperature of the resin, aged in a drying chamber, expanded to 1.4 times or more the volume of the shrinkable special foam, and the density (D) was 3.
Ky 7m: l≦(D)≦17 and 5′/m3, in the cell structure, at least three bubbles have one end at the boundary area where they are adjacent to each other, and have numerous wrinkles extending toward the central portion of the cell membrane. 1. A method for producing a foam, which is characterized by obtaining a plate-like or sheet-like foam, or a foam molded product, which has a closed cell ratio of 50% or more.