JP2008120953A - Extruded foam of polystyrenic resin and method for producing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an extruded foam of a polystyrenic resin excellent in heat insulating performance and a method for producing the same, reducing the amount of use of a blowing agent giving influence on the environment and raising formation ratio of small cells in the foam in which large and small cells are present, by effectively using water and carbon dioxide, which is friendly to the environment, as blowing agents. <P>SOLUTION: The invention relates to the extruded foam of a polystyrenic resin formed by press-fitting the blowing agent into a heat melted polystyrenic resin and then extrusion foaming, wherein the extruded foam of the polystyrenic resin comprises 0.05-10 pts.wt. of polyvinylpyrrolidone per 100 pts.wt. of the polystyrenic resin, and preferably 0.2-4 pts.wt. of water as the blowing agent is used per 100 pts.wt. of the polystyrenic resin. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a polystyrene resin extruded foam and a method for producing the same. More specifically, the present invention relates to a plate-like polystyrene-based resin extruded foam that is excellent in environmental compatibility and heat insulation, has appropriate strength properties, and is particularly useful as a heat insulating material, and a method for producing the same.

  As a method for obtaining a styrene resin foam, a styrene resin is plasticized with an extruder or the like, a foaming agent is injected and mixed therein, and the mixture is further cooled to a temperature suitable for obtaining a good foam. A method of continuously producing a styrene resin foam by extruding into a low pressure region is known. And since the obtained polystyrene resin foam has excellent heat insulation performance, it can be used as a building material in heat insulation materials for houses, etc., and as industrial material use in refrigeration / cooling vehicle loading platforms, vending machines, etc. It is used as a structural member that has both heat insulation properties. Since this contributes to energy saving, it has become an effective product for preventing global warming.

  For this polystyrene-based resin extruded foam, a production method using an evaporating foaming agent has become the mainstream. The evaporating foaming agent used here does not only become foaming energy, but also exhibits a plasticizing function in the extrusion system, and also functions to adjust the bubble size and control the bubble growth rate in the foaming process. By being contained in the foam of the manufactured foam, the performance of the foam, particularly the thermal conductivity that governs the heat insulation, is greatly affected. Therefore, the selection of such an evaporating foaming agent has always been a main research subject in the development of extrusion foaming technology.

  Conventionally, as foaming agents used in synthetic resin extrusion foams, poorly permeable foaming agents that govern the performance of foams after foaming, plasticizing in the extruder, foaming energy and bubble growth rate control, etc. A combination with an easily permeable foaming agent that affects the surface is often used. As a typical example, in the group of hardly permeable foaming agents, chlorofluorinated hydrocarbons (HFC) such as 1-difluoro-1-chloroethane (hereinafter abbreviated as HCFC142b) as examples of chlorofluorinated hydrocarbons (HCFC) are used. Examples include 1,1,1,2-tetrafluoroethane (hereinafter abbreviated as HFC134a), and examples of hydrocarbons include propane, normal butane, and isobutane. Examples of the easily permeable foaming agent include methyl chloride and ethyl chloride, which are examples of halogenated hydrocarbons.

  However, in recent years, environmental problems such as ozone layer destruction, global warming, and the effects of chemical substances on the atmosphere and water quality have been highlighted, and it is desirable to use foaming agents that are environmentally friendly. In particular, do not use blowing agents such as chlorofluorocarbons, halogenated hydrocarbons, and saturated hydrocarbons if possible, or reduce the amount used as much as possible, and have high thermal insulation performance using clean blowing agents such as water and inorganic gases. Development of synthetic resin extruded foam is desired.

Until now, the use of water, which is considered as a representative example of the cleanest blowing agent, as a blowing agent has been studied for a long time. For example, a method of press-fitting water into an extruder has already been attempted (Patent Document 1), but is impossible to achieve (industrialization is impossible) due to the difficulty in dispersing water in a synthetic resin. It is in full condition.
Also disclosed is a method in which water is uniformly dispersed in a synthetic resin to improve the foam structure of the foam and improve the heat insulation performance (Patent Documents 2, 3, and 4).

  In the above method, HCFC142b, which is Freon, is used as an example of the hardly permeable foaming agent, and methyl chloride is used as an example of the easily permeable foaming agent. Water is used together with inorganic powder and water-absorbing polymer substance having many hydroxyl groups on the surface in order to obtain a bubble structure mainly consisting of bubbles having a bubble diameter of 0.25 mm or less and bubbles having a bubble diameter of 0.4 to 1 mm. It has been.

  However, since water is not compatible with the synthetic resin, even when such a method is adopted, the amount of addition is limited, and if the amount of addition is too large, water becomes difficult to be uniformly dispersed in the synthetic resin. Phenomena such as the generation of pores in the foam may occur. Although sodium polyacrylate was used as the water-absorbing polymer substance, it was poorly dispersed in the molten resin, or in an environment where the pH of the molten resin containing water was acidic or alkaline due to other additives, For example, when carbon dioxide and water are used in combination with the foaming agent, it becomes acidic, so the water absorption ability decreases, and even when a small amount of water is added, the dispersion of water deteriorates, causing the phenomenon of pores in the foam. It was. Thus, it has been desired to use water more effectively as a part of the foaming agent than just improving the cell structure.

  On the other hand, Patent Document 4 discloses a silicate powder using magnesium silicate as a representative example as a water absorbing medium. Here, the contents to be used in combination with water are described in the case of obtaining a bubble structure in which two kinds of large bubbles and small bubbles coexist in a limited gas type and gas ratio. As described above, what is shown in this International Publication is the content of the limited gas types and the gas ratio under the constraint conditions, and the technology has not been completed under a wide range of conditions. Furthermore, when a large amount of magnesium silicate exemplified in this publication is added, it tends to be difficult to maintain closed cells. In addition, there is a tendency that inconveniences such as poor foam molding due to extreme cell miniaturization tend to occur. For this reason, in addition to having to limit the amount of magnesium silicate used, there is a problem that the amount of water added is also restricted from the viewpoint of dispersibility in the extrusion system, and improvement thereof is desired. It was.

  In Patent Document 5, it is said that water can be used by means of using a low molecular weight polymer in a method of making a styrene resin extruded foam using a mixed foaming agent of water and carbon dioxide. If the product is used, the heat resistance of the resulting foam will deteriorate, and if it is attempted to obtain a high molten resin pressure in the die to satisfy the solubility of carbon dioxide in the resin, extrusion molding will not be possible. If it is attempted to obtain a foam having a large thickness in order to be stable or to reduce the opening of the slit die, it is difficult to obtain a foam having excellent heat insulating properties because bubbles are hardly formed into a spherical shape. In addition, it is said that the use of a hydrophilic polymer or hydrophilic copolymer gives water solubility, and a foam having a unimodal cell size distribution can be obtained. However, there is no specific example, and a polystyrene system having excellent heat insulation performance. No proposal has been made for a resin extruded foam.

  Moreover, in patent document 6, although it has succeeded in increasing the usage-amount of water by using bentonite as a water absorption medium, as a foaming agent component, Freon-type foaming agent, alkyl chloride, saturated hydrocarbon, etc. The ratio of the organic evaporative foaming agent component is large, and it has not yet been achieved to obtain a foam having light weight and excellent heat insulation properties mainly composed of water and an inorganic foaming agent. In addition, when a large amount of bentonite is used to increase water absorption, there is a problem that bentonite accumulates and adheres to the molding die to deteriorate the moldability, and the surface property and heat insulating property of the foam deteriorate over time. However, there was a problem that was not suitable for long-term continuous production. Further, when environmentally friendly carbon dioxide is used as a foaming agent, there is a problem that it is difficult to obtain a foam having large and small bubbles.

In this way, the use of foaming agents that have an impact on the environment is reduced, and foams with excellent heat insulation using foaming agents mainly composed of inorganic foaming agents such as water and carbon dioxide, which are environmentally friendly and inexpensive. The proposal of the solution for building was awaited.
JP 58-176226 JP-A-3-109445 JP-A-3-273034 WO99 / 54390 Special table flat 8-502786 JP2001-200087

  The present invention has been made in view of the prior art, and does not use, for example, HCFC, HFC, or methyl chloride, which has an effect on the environment such as ozone layer destruction and global warming, and further, foaming agents such as propane and butane. The purpose of the present invention is to provide a foam having excellent heat insulation performance by reducing the amount of use of water or by using environmentally friendly water and, depending on the case, inorganic gas as a foaming agent.

  As a result of intensive studies to solve the above-mentioned problems, the present inventor has added water as a foaming agent by adding polyvinylpyrrolidone as a substance for uniformly dispersing incompatible water in a polystyrene resin. It was found that a foam with good heat insulation can be obtained even when an inorganic foaming agent such as carbon dioxide is used in combination, and the present invention has been completed. Even if polyvinylpyrrolidone is added in a large amount, it has a feature that it can secure closed cells and does not cause molding defects due to extreme cell miniaturization. In addition, the amount of water added can be increased, so that the expansion ratio can be improved. it can. In addition, HCFC, HFC, and methyl chloride, which have been used in the past, are not used, and even when using organic evaporation type blowing agents such as propane and butane, closed cells can be secured even when carbon dioxide is used. It has the feature that molding defects do not occur due to cell miniaturization. Then, mainly bubbles having a bubble diameter of 0.2 mm or less (hereinafter sometimes referred to as small bubbles) and bubbles having a bubble diameter of 0.25 to 1 mm (hereinafter sometimes referred to as large bubbles) are passed through the cell membrane. It is easy to obtain a foam having a cell structure dispersed in a sea-island shape. Moreover, it is possible to increase the occupied area ratio of small bubbles per cross-sectional area of the foam, and the heat insulation performance of the obtained foam can be further improved. Furthermore, the range of production conditions for stably obtaining a foam in which the large and small bubbles coexist can be greatly expanded. On the other hand, by using alcohol such as methanol or ethanol in combination with the foaming agent, it has been found that it is possible to obtain a lightweight foam with a uniform cell structure in which the distribution of large and small bubbles is not separated, leading to the present invention. It was.

  That is, the present invention provides a polystyrene resin extruded foam obtained by press-fitting a foaming agent into a heat-melted polystyrene resin and extrusion-foaming it. Polyvinylpyrrolidone is 0.05 to 100 parts by weight of polystyrene resin. It is a polystyrene resin extruded foam containing 10 parts by weight, and the amount of water used as a foaming agent is preferably 0.2 to 4 parts by weight with respect to 100 parts by weight of the polystyrene resin.

The density of the polystyrene resin extruded foam is preferably 15 to 50 kg / m ³ .

  The bubbles constituting the polystyrene resin extruded foam are mainly composed of bubbles having a bubble diameter of 0.2 mm or less and bubbles having a bubble diameter of 0.25 to 1 mm, and these bubbles are dispersed in a sea-island shape through the cell membrane, Bubbles having a bubble diameter of 0.2 mm or less can have an occupied area ratio of 10 to 90% per foam cross-sectional area. The bubbles constituting the extruded polystyrene resin foam are uniform, and the average cell diameter is preferably 1 mm or less.

 Moreover, it is preferable that the polystyrene-type resin extrusion foam of this invention is a plate-shaped object which has thickness 10-150 mm.

 Furthermore, 0.05 to 0.3 parts by weight of at least one selected from smectite, zeolite, and silica can be used with respect to 100 parts by weight of the polystyrene-based resin.

  On the other hand, in the production method of the present invention, 0.05 to 10 parts by weight of polyvinylpyrrolidone is added to 100 parts by weight of a polystyrene resin, and after heat-melting and kneading, 0.2 to 4 parts by weight of water is injected as a blowing agent. A method for producing a polystyrene-based resin extruded foam, which is obtained by extrusion foaming to obtain a foam mainly composed of bubbles having a bubble diameter of 0.2 mm or less and bubbles having a bubble diameter of 0.25 to 1 mm. It is preferable to use 50 to 100% of a foaming agent containing water and carbon dioxide as the total number of moles of the foaming agent, and as the other foaming agent, dimethyl ether and one type having 3 to 5 carbon atoms as necessary. The above saturated hydrocarbons or nitrogen can be used.

In addition, 0 to 0.3 part of a solid inorganic substance can be used with respect to 100 parts by weight of the polystyrene-based resin.
A more preferred method is that 0.05 to 10 parts by weight of polyvinylpyrrolidone is added to 100 parts by weight of polystyrene resin, and after heating and melt-kneading, a foaming agent is injected and extruded and foamed to obtain a foam having uniform cells. In the method for producing a polystyrene resin foam characterized in that it includes water, carbon dioxide gas, and alcohol as the foaming agent to be used, and carbon dioxide gas, nitrogen, dimethyl ether, and carbon as other foaming agents as necessary. It is a manufacturing method of the polystyrene-type resin extrusion foam characterized by using together the foaming agent chosen from 1 or more types of saturated hydrocarbons whose number is 3-5.

  Thus, according to the styrene-based resin extruded foam according to the present invention and the production method thereof, environmentally friendly water and, depending on the case, an inorganic gas is used as a foaming agent, which is highly foamed and has excellent heat insulation performance. A foam can be obtained. Furthermore, a thick foam having a large and small cell structure and excellent heat insulating performance can be obtained.

  The styrenic resin used in the present invention is not particularly limited, and includes a styrene homopolymer obtained only from a styrene monomer, a styrene monomer and a monomer copolymerizable with styrene, or a derivative thereof. The obtained random copolymer, block copolymer or graft copolymer, modified polystyrene such as brominated polystyrene and rubber-reinforced polystyrene are used. These may be used alone or in admixture of two or more.

  Monomers that can be copolymerized with styrene include methylstyrene, dimethylstyrene, ethylstyrene, diethylstyrene, isopropylstyrene, styrene derivatives such as bromostyrene, dibromostyrene, and tribromostyrene, and polyfunctional vinyl compounds such as divinylbenzene. , (Meth) acrylic compounds such as acrylic acid, methacrylic acid, methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, acrylonitrile, diene compounds such as butadiene or derivatives thereof, maleic anhydride, itaconic anhydride And unsaturated carboxylic acid anhydrides. These are used alone or in admixture of two or more. When obtaining a foam having a large and small cell structure, a styrene homopolymer is preferred.

  Polyvinylpyrrolidone used in the present invention is a substance also called poly (1-vinyl-2-pyrrolidone), poly (1-vinyl-2-pyrrolidinone), poly (1-ethenyl-2-pyrrolidone), or popidone. . Polyvinylpyrrolidone that can be used has a weight average molecular weight of 50,000 to 2,000,000, more preferably 500,000 to 1,500,000. In addition, the K value, which is the relative viscosity value of Fikentscher at 25 ° C. measured with an Ubbelohde capillary viscometer, is 20 to 110, preferably 80 to 100. Polyvinylpyrrolidone is characterized by high compatibility with resins, good dispersibility, and excellent acid and alkali resistance, so it uses not only conventional foaming agents but also carbon dioxide and water. In some cases, water can be stably dispersed even when the foamable molten resin in the extruder becomes an acidic environment. Similarly, when flame retardants and other additives that change pH are added, water can be stably used as a foaming agent, and in this case, a wide range of conditions can be used without reducing the amount of water added. Water can be used as an effective blowing agent. In addition, since it has high thermal stability, it can be used without problems even when subjected to heating in an extruder or shearing. For example, water-soluble polymers such as polyvinyl alcohol, polyamide, and carboxymethyl cellulose have a problem that they cannot be recycled because they are inferior in thermal stability. It is also a substance that does not have any particular environmental impact problems. And since it is a water-soluble polymer, unlike a mineral-type water absorbing substance, the nucleation action at the time of foaming is small, and it is especially useful when using an inorganic foaming agent.

  The effect of the polyvinyl pyrrolidone used here is considered to be that water incompatible with the polystyrene resin is absorbed to form a gel and can be uniformly dispersed in the polystyrene resin in the gel state. The blending amount of polyvinyl pyrrolidone is preferably adjusted to 0.05 to 10 parts by weight, preferably 0.1 to 2 parts by weight with respect to 100 parts by weight of the polystyrene resin. If the blending amount is less than 0.05 parts by weight, the amount of water absorbed by polyvinylpyrrolidone is insufficient with respect to the amount of water injected, and pores due to non-dispersion of water are generated in the extruder, which tends to cause a defective molded body. On the other hand, when the amount exceeds 10 parts by weight, bubble unevenness tends to occur. Furthermore, it tends to be difficult to maintain closed cells. Therefore, it becomes easy to produce deterioration and variation of the heat insulation performance of a foam. The mixing ratio of water / polyvinylpyrrolidone is 0.02 to 20, preferably 0.1 to 10, and more preferably 0.1 to 1 by weight.

  In the polystyrene resin extruded foam of the present invention, 0.05 to 10 parts by weight of polyvinylpyrrolidone is added to 100 parts by weight of the polystyrene resin, and after heat-melt kneading, 0.2 to 4 parts by weight of water, or 0.2 of water is added. It is obtained by press-fitting -4 parts by weight and a foaming agent other than water, followed by extrusion foaming in a low pressure region.

  In a combination of water and a foaming agent other than water, when the ratio of water to the foaming agent other than water is small, when the foaming agent other than water and water does not form an azeotrope, and when the amount of nucleating agent is small Produces a foam having a characteristic bubble structure in which small bubbles having a bubble diameter of 0.2 mm or less and large bubbles having a bubble diameter of 0.25 to 1 mm are dispersed in a sea-island shape through a cell membrane.

  A foam having such a large and small cell structure is excellent in heat insulation performance and mechanical bending characteristics. The heat insulation performance of the foam having the large and small cell structure is excellent because the heat flow moving through the uniform cell structure in the conventional foam having the uniform cell structure is less than the cell diameter 0 in the present foam. It is estimated that this is because it is divided by small bubbles having a fine bubble diameter of 0.2 mm or less existing around large bubbles of 25 to 1 mm. In addition, regarding the bending strength and bending deflection, the stress applied to the cell membrane is dispersed by, for example, fine bubbles having a bubble diameter of 0.2 mm or less present in a sea island shape, and thus it is estimated that suitable bending characteristics are exhibited. .

  In the present invention, when aiming at a foam excellent in heat insulation having a bubble structure composed of large and small bubbles, small bubbles having a bubble diameter of 0.2 mm or less seem to have an occupied area ratio of 10 to 90% per foam cross-sectional area. To. The occupied area ratio of the small bubbles is preferably 20 to 90%, more preferably 30 to 80%, and most preferably 40 to 70% per cross-sectional area of the foam. If the above range is exceeded, it tends to be impossible to obtain a lightweight foam.

In the present invention, depending on the required performance, either a conventional foam having a uniform cell structure or a foam having a large and small cell structure can be produced.
Further, as the water-absorbing medium used in the present invention, as a substance that gives an auxiliary effect to the polyvinyl pyrrolidone described above, for example, sodium polyacrylate as another water-soluble polymer, inorganic powder having many hydroxyl groups on its surface, such as Nippon Aerosil AEROSIL (average particle size: 12 × 10 ⁻³ μm) such as Smectite such as bentonite and hectorite, or zeolite may be mixed. Bentonite can be obtained, for example, as Bentonite Hotaka, Wenger Bright 11, etc. from Hojun Co., Ltd. Hectorite can be obtained, for example, as Laponite from Rockwood and as synthetic smectite from Corp Chemical. Zeolite can be obtained as, for example, ZEOSTAR NA-100P manufactured by Nippon Chemical Industry Co., Ltd., natural zeolite SP # 2300 manufactured by Nitto Flour Industry Co., Ltd., or the like. Such water-soluble polymers, smectites, zeolites, silicas and the like can also be used as a mixture.

  The amount of water-absorbing medium other than polyvinylpyrrolidone is preferably adjusted to be 0 to 0.3 parts by weight, particularly 0 to 0.5 parts by weight, with respect to 100 parts by weight of the polystyrene resin. When the blending amount exceeds the above range, non-dispersion of the water-absorbing polymer compound occurs in the extruder, resulting in bubble unevenness, or bentonite adheres to the mold and stable continuous production over a long period of time. It becomes impossible. When carbon dioxide is used as the foaming agent, the amount of water added is 0 for other water-soluble polymers other than polyvinylpyrrolidone because molding becomes difficult due to finer bubbles or an acidified environment. About 5 parts is the limit.

  There is no limitation in particular as water used for this invention, For example, a pure water etc. can be used. In addition, as foaming agents other than water used together with water in the present invention, inorganic gases such as carbon dioxide, nitrogen, argon, helium, methanol, ethanol, propyl alcohol, i-propyl alcohol, butyl alcohol, i-butyl alcohol, Examples thereof include alcohols exemplified by t-butyl alcohol, ethers such as dimethyl ether, diethyl ether and methyl ethyl ether, saturated hydrocarbons having 3 to 6 carbon atoms, halogenated hydrocarbons such as methyl chloride and ethyl chloride.

  The foaming agent other than water or water and water may be added by means such as press-fitting at the same time after heat-melting the polystyrene-based resin and the additive, or may be separately press-fitted or added. It is not limited by the method of press-fitting or adding. Alternatively, polyvinyl pyrrolidone may be dissolved in water, pressed together with water, and added.

  The pressure when the water or the foaming agent other than water and water is press-fitted into the heated melt-kneaded product is not particularly limited as long as it can be press-fitted at a pressure larger than the internal pressure of the extruder.

  The foam of the present invention is obtained by adjusting a predetermined amount of the polystyrene-based resin and the additive, heating and kneading, and then press-fitting or adding water or a foaming agent other than water and water to perform extrusion foaming.

  There is no particular limitation on the heating temperature, melt kneading time and melt kneading means when the polystyrene resin and additive are heated and melt kneaded, and the heating temperature may be usually 160 to 250 ° C. Since it depends on the amount of extrusion per unit time, melt kneading means, etc., it cannot be determined in general, but usually the time required for uniform dispersion of the polystyrene resin and additives is determined, and the melt kneading means For example, a screw type extruder may be used, but there is no particular limitation as long as it is used for normal extrusion foaming.

  In addition, in this invention, you may mix | blend a nucleating agent with a polystyrene resin as needed. Examples of the nucleating agent include nucleating agents used in known extrusion foaming. Typical examples of such nucleating agents include solid inorganic substances such as talc powder and calcium carbonate powder, and these nucleating agents can be used alone or in admixture of two or more. The particle size of such a nucleating agent is usually 3 to 100 μm, preferably 5 to 20 μm. The nucleating agent is mainly used for adjusting the foam diameter of the obtained foam to be 0.3 to 1 mm, and the blending amount of the nucleating agent is 100 parts by weight of polystyrene resin. It is preferable to adjust it to 0 to 2 parts by weight, particularly 0 to 0.3 parts by weight. When such a blending amount exceeds the above range, it becomes difficult to achieve the target density although the cell size is small.

  However, in order to obtain a foam composed mainly of bubbles having a bubble diameter of 0.2 mm or less and bubbles having a bubble diameter of 0.25 to 1 mm, the nucleating agent described above is used. Is preferable, and in particular, when the foaming agent contains carbon dioxide, a smaller amount is more preferable. At that time, barium stearate or the like having a nucleating action smaller than that of talc can be used for adjusting the bubble diameter. Moreover, what reduced the nucleation effect | action of the additive by surface treatments, such as a silane type | system | group, an aluminum type coupling agent, and a higher fatty acid process, can also be used.

  In the present invention, in addition to the bentonite, the water-absorbing polymer compound, the nucleating agent, the inorganic powder having many hydroxyl groups on the surface, a flame retardant such as hexacyclobromododecane, a polymer-type hindered phenol compound Antioxidants such as barium stearate, magnesium stearate, olefinic resin waxes and other commonly used additives such as colorants and the like can be blended by appropriately adjusting the blending amount.

  As for the foam molding method, a plate-shaped foam having a large cross-sectional area is obtained by using a molding die and a molding roll installed in close contact with or in contact with the slit die. A general method of molding can be used. In addition, the cell diameter of the foam having a uniform cell structure is not particularly limited, but in order to give preferable heat insulation, mechanical strength, and workability, it is possible to adjust the cell diameter to 1.0 mm or less, especially 0.4 mm or less. preferable.

The thickness of the foam of the present invention is not particularly limited. In particular, in order to give preferable heat insulating properties, bending strength and bending deflection, a thick plate like a normal plate is preferable to a thin plate such as a sheet, usually 10 to 150 mm, preferably 20 to 100 mm. Further, the density of the foam of the present invention is preferably 15 to 50 kg / m ³ and more preferably 25 to 40 kg / m ³ in order to give light weight and excellent heat insulation and bending strength.

Next, although the polystyrene-type resin extrusion foam of this invention and its manufacturing method are demonstrated still in detail based on an Example, this invention is not limited only to this Example. As physical properties of the obtained foam, foam density, foam appearance, foam thermal conductivity, and small bubble occupation area ratio were examined according to the following methods.
(1) Foam density It calculated | required by following Formula.
Foam density = foam weight / foam volume (2) Foam appearance When the foam is visually observed, the skin is smooth, and there are no voids and other giant bubbles and bubble irregularities, ○, the skin is not smooth, The case where there were giant bubbles such as voids and bubble irregularities was evaluated as x.
(3) Thermal conductivity of foam was measured according to JIS A 9511.
(4) Small bubble occupied area ratio The occupied area ratio per cross-sectional area of a foam having a bubble diameter of 0.2 mm or less was determined as follows. Here, a bubble having a bubble diameter of 0.2 mm or less is a bubble having an equivalent circle diameter of 0.2 mm or less.
a) Magnify 30 times with a scanning electron microscope (manufactured by Hitachi, Ltd., product number: S-450) and photograph a longitudinal section of the foam.
b) An OHP sheet is placed on the photograph taken, and a portion corresponding to a bubble having a diameter in the thickness direction larger than 6.0 mm (corresponding to a bubble having an actual dimension larger than 0.2 mm) is black ink. Fill in and copy (primary processing).
c) The primary processed image is taken into an image processing apparatus (Pierce Co., Ltd., product number: PIAS-II), and a dark color portion and a light color portion, that is, a portion painted with black ink are identified.
d) Of the dark portion, a portion corresponding to the area of a circle having a diameter of 6.0 mm or less, that is, a portion having a long diameter in the thickness direction but only having an area of a circle having a diameter of 6.0 mm or less. Is lightened to correct the dark portion.
e) Using the “area ratio” in the image analysis calculation function, the area ratio of the bubble diameter of 6.0 mm or less (light color portion divided by shading) in the entire image is obtained by the following equation.
Small bubble occupation area ratio (%) = (1−area of dark color portion / area of entire image) × 100
(Example 1)
Polyvinylpyrrolidone (manufactured by Nippon Shokubai Co., Ltd., K-90) is 0 with respect to 100 parts by weight of polystyrene resin (manufactured by PS Japan Co., Ltd., trade name: G-9401, melt index (MI): 2.5). .1 part by weight, without using a nucleating agent, add 2.5 parts by weight of hexabromocyclododecane as a flame retardant and 0.1 part by weight of calcium stearate as a lubricant, and knead by heating to 200 ° C. in an extruder . While kneading, 0.8 parts by weight of water and 3 parts by weight of carbon dioxide, 2 parts by weight of dimethyl ether, which is an organic evaporation type foaming agent, and 2 parts of isobutane as the other foaming agents were injected and kneaded. It cooled and extrusion-foamed through the molding die by which the opening interval of the slit was 4 mm, and the flow-path surface was coated with the fluororesin, and the plate-shaped styrene resin foam of thickness 90-100mm was obtained.

(Examples 2 to 5)
A foam was obtained in the same manner as in Example 1 except that the addition amount of polyvinylpyrrolidone and the amount of foaming agent were changed as shown in Table 1. The results are also shown in Table 1.

(Comparative Examples 1 and 2)
A foam was obtained in the same manner as in Example 1 except that polyvinylpyrrolidone was not added as the water-absorbing agent and the water-absorbing agent shown in Table 1 was changed.

(Comparative Examples 3 and 4)
A foam was obtained in the same manner as in Example 1 except that the water absorbing agent and the foaming agent shown in Table 1 were used. The results are also shown in Table 1.

  When the water-absorbing agent of Comparative Examples 1 and 2 was used, pores were generated, the foam appearance was poor, the generation of small bubbles was small, and the foam was inferior in heat insulation. In Comparative Examples 3 and 4, the foam appearance was excellent, but since the amount of water + carbon dioxide was small, a large amount of isobutane was required. On the other hand, the foam of Examples 1-5 was able to obtain the foam excellent in heat insulation, mainly using the environmentally friendly foaming agent.

(Examples 6 and 7)
1 part by weight of polyvinylpyrrolidone K-90 is used as the water-absorbing agent, 2.5 parts by weight of water and 3 parts by weight of carbon dioxide are used as the foaming agent, and 0.1 parts by weight of calcium stearate and 0.1 parts by weight of PE wax are used as the lubricant, respectively. Used to foam. The results are shown in Table 1.
In both cases, while using only an environmentally friendly foaming agent, it was possible to obtain a foam that was lightweight and excellent in heat insulation.

(Example 8)
Foaming was carried out in the same manner as in Example 7, except that 10 parts by weight of polyvinylpyrrolidone K-90 was added to the water-absorbing agent and 0.05 parts by weight of talc was added as the nucleating agent. The results are shown in Table 1.

(Comparative Examples 5 and 6)
Only Examples 6 and 7 and the water-absorbing agent were changed as shown in Table 1 and foamed. The results are shown in Table 1.

  In the water absorbing agent of the comparative example, the added water could not be sufficiently dispersed, pores were generated in the foam, the appearance of the foam was inferior, and the heat insulation was inferior. As in Comparative Example 6, 0.01 parts by weight of polyvinylpyrrolidone was insufficient in water absorption, but no pores were observed when 10 parts by weight were used as in Example 8.

Example 9
Use 0.3 parts by weight of polyvinylpyrrolidone K-90 as a water-absorbing agent, 0.8 parts by weight of water as a foaming agent, 3 parts by weight of carbon dioxide, 2 parts by weight of dimethyl ether, and 0.1 parts by weight of PE wax as a lubricant. It was. The results are shown in Table 1.

(Example 10)
Foaming was carried out using 1 part by weight of polyvinylpyrrolidone K-90 as a water absorbing agent, 2.5 parts by weight of water as a foaming agent, 2.5 parts by weight of dimethyl ether, and 0.1 part by weight of PE wax as a lubricant. The results are shown in Table 1.

  The appearance of the foam obtained under the conditions where no butane was used was good, and the foam was lightweight and excellent in heat insulation.

(Comparative Example 7)
Foaming was carried out in the same manner as in Example 7 except that 6 parts by weight of water and 3 parts by weight of carbon dioxide were used as the foaming agent. The results are shown in Table 1. The appearance of the foam obtained by using 6 parts by weight of water was poor.

  The following is an example relating to a method of obtaining a lightweight foam by using an environmentally friendly foaming agent, in which the bubbles constituting the polystyrene-based resin extruded foam are uniform without being divided into large bubbles and small bubbles. .

(Example 11)
1 part by weight of polyvinylpyrrolidone K-90 is used as the water-absorbing agent, 1 part by weight of water is used as the foaming agent, 4 parts by weight of carbon dioxide, 1.5 parts by weight of ethanol and 3 parts by weight of dimethyl ether are used. Foaming was performed using 0.1 parts by weight of PE wax as a lubricant and a lubricant. The results are shown in Table 2.

The density of the foam using a blowing agent that does not use butane was as light as 26 kg / m ³ .

(Examples 12 and 13)
Except that the water-absorbing agent was changed as shown in Table 2, foaming was performed in the same manner as in Example 11 to obtain a foam having a light weight and excellent appearance as in Example 11.

(Comparative Examples 8 to 10)
Except for changing the water-absorbing agent as shown in Table 2, foaming was carried out in the same manner as in Example 11, but in Comparative Examples 8 and 10, the appearance of the foam was poor due to the occurrence of pores, and the foam density was also low. It was as heavy as 35 kg / m ³ or more. In Comparative Example 9, there was no problem with the appearance of the foam, but the foam density was slightly high.

Claims (12)

  In a polystyrene resin extruded foam obtained by press-fitting a foaming agent into a heat-melted polystyrene resin and extrusion foaming, 0.05 to 10 parts by weight of polyvinylpyrrolidone is contained with respect to 100 parts by weight of the polystyrene resin. Polystyrene resin extruded foam.   The polystyrene resin extruded foam according to claim 1, wherein the amount of water used as a foaming agent is 0.2 to 4 parts by weight with respect to 100 parts by weight of the polystyrene resin. The polystyrene resin extruded foam according to claim 1 or 2, wherein the density of the polystyrene resin extruded foam is 15 to 50 kg / m ³ .   The bubbles constituting the polystyrene resin extruded foam are mainly composed of bubbles having a bubble diameter of 0.2 mm or less and bubbles having a bubble diameter of 0.25 to 1 mm, and these bubbles are dispersed in a sea-island shape through the cell membrane, The polystyrene-based resin extruded foam according to any one of claims 1 to 3, wherein bubbles having a bubble diameter of 0.2 mm or less have an occupied area ratio of 10 to 90% per foam cross-sectional area.   The polystyrene resin extruded foam according to any one of claims 1 to 3, wherein the bubbles constituting the polystyrene resin extruded foam are uniform, and the average cell diameter is 1 mm or less.   The polystyrene resin extruded foam according to any one of claims 1 to 5, wherein the polystyrene resin extruded foam is a plate having a thickness of 10 to 150 mm.   Furthermore, 0.05-0.3 weight part of at least 1 sort (s) selected from a smectite, a zeolite, and a silica is used with respect to 100 weight part of polystyrene-type resin, The polystyrene type of any one of Claims 1-6. Resin extruded foam.   0.05 to 10 parts by weight of polyvinyl pyrrolidone is added to 100 parts by weight of a polystyrene-based resin, and after heat-melting and kneading, 0.2 to 4 parts by weight of water as a foaming agent is injected and extruded and foamed. A method for producing a polystyrene-based resin extruded foam, comprising obtaining a foam composed of bubbles of 2 mm or less and bubbles having a bubble diameter of 0.25 to 1 mm.  The manufacturing method of the polystyrene-type resin extrusion foam of Claim 8 which uses 50-100% of foaming agents containing water and a carbon dioxide gas as a foaming agent with respect to the total number of moles of a foaming agent.  The method for producing a polystyrene-based resin extruded foam according to claim 8 or 9, wherein dimethyl ether, one or more saturated hydrocarbons having 3 to 5 carbon atoms, or nitrogen is used as the foaming agent as necessary.   Furthermore, the manufacturing method of the polystyrene-type resin extrusion foam of Claim 9 or 10 which uses 0-0.3 parts of solid inorganic substances with respect to 100 weight part of polystyrene-type resins.   0.05 to 10 parts by weight of polyvinyl pyrrolidone is added to 100 parts by weight of polystyrene resin, and after heating and melt-kneading, a foaming agent is press-fitted and extruded to obtain a foam having uniform cells. In the method for producing a polystyrene resin foam, water, carbon dioxide gas and alcohol are used as a foaming agent to be used. Carbon foam, nitrogen, dimethyl ether, and carbon number of 3 to 5 are used as other foaming agents as necessary. A method for producing a polystyrene resin extruded foam, wherein a foaming agent selected from one or more saturated hydrocarbons is used in combination.