JPH10279725A - Heat-resistant foam resin particles and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide heat-resistant foaming resin particles that can form a uniform and good cell structure immediately after production in no need for any cell-forming agent (a foam regulator) or without aging treatment, moreover causes no shrinkage and realizes a high expansion ratio and provide the production process therefor as for prefoamed heat-resistant foaming resin particles. SOLUTION: In heat-resistant foaming resin particles comprising 100 pts.wt. of a heat-resistant resin composed of 60-90 pts.wt. of a styrene resin and 40-10 pts.wt. of a polyphenylene ether resin and 3-20 pts.wt., per 100 pts.wt. of said heat-resistant resin, of a foaming agent, the water content is kept <=0.03 wt.% in the resin particles. The moisture content in the resin particles can be reduced by drying the resin particles at -10 deg.C-+30 deg.C, preferably by placing the resin particles under vacuum or by allowing a dried gas to pass through the mass of the resin particles at a certain flow rate or by storing the resin particles together with a desiccating agent and separating them from each other later.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to expandable resin particles having high heat resistance and comprising a blend or copolymer of a polyphenylene ether resin and a styrene resin, and a method for producing the resin particles. More specifically, the present invention
Regarding the expanded resin particles formed in the pre-expansion process, even without adding a cell-forming agent, and without performing the aging treatment, it is possible to form uniform and favorable cells immediately after the production,
In addition, the present invention relates to heat-resistant foamed resin particles that do not shrink and can obtain a high expansion ratio, and also relates to a method for producing heat-resistant foamed resin particles having such excellent characteristics.

[0002]

2. Description of the Related Art In general, expandable styrene resin particles are
The resin particles are obtained by impregnating a granular styrene-based polymer with a foaming agent (butane, pentane, or the like), and then are processed into a foam molded article (styrene foam product) through a foaming treatment including preliminary foaming. The foamed product finally produced is used for a wide range of uses such as packing materials for home appliances, building boards and heat insulating blocks, heat insulating containers such as fish boxes, and instant food cups. In recent years, styrene-based foam molded articles have also been used as buried blocks in civil engineering works such as roads. As described above, foamed molded products have a wide variety of uses.However, foamed molded products are used in applications such as heat insulation or heat insulating materials that cover steam pipes or hot water pipes, and heat insulation materials that are installed in attics. It is required to have high heat resistance of 80 to 120 ° C. Also, components for these applications must be able to withstand long-term use even under such high temperature conditions.

[0003] However, conventional styrofoam products may significantly shrink in size during long-term use in the above-mentioned applications, and may not be able to maintain the heat insulating and heat retaining effects as they were at the beginning. It has been required to improve heat resistance. Therefore, several attempts have been made to improve the heat resistance of foam molded articles. Among them, as one promising attempt, JP-B-56-43054 and JP-B-56-43054 have been proposed.
As described in Japanese Patent No. 43055, a method of using a blend or copolymer of a polyphenylene ether-based resin and a styrene-based resin instead of a styrene-based resin as a base resin of a foam molded article has been proposed. .

[0004]

The cells of the individual expanded particles obtained by pre-expanding the above-mentioned base resin (a blend or copolymer of a polyphenylene ether-based resin and a styrene-based resin) impregnated with a foaming agent. The structure (cell size) depends on various quality characteristics of the foam molded product, especially heat resistance,
It is a very important factor (parameter) that determines the properties of heat insulation, hardness, surface gloss, and appearance (appearance) of the cut surface. The actual value of this cell size is mainly determined during the prefoaming process. In this case, it is desired that the cut surface of the pre-expanded particles has a cell size in the range of 10 μm to 200 μm. However, according to a simple manufacturing procedure (that is, without any special processing), a blowing agent is impregnated into the above-mentioned base resin (a blend or copolymer of a polyphenylene ether resin and a styrene resin) and then pre-foamed. Is performed, the obtained individual expanded particles have a cell size exceeding 200 μm, have an extremely coarse and uneven cell structure, and
The disadvantage is that the foamed particles shrink significantly after production.

For this reason, conventionally, resin particles impregnated with a foaming agent have been used, for example, in JP-B-7-116316,
In particular, as shown in the description of the examples in the specification, 1
Stored in a refrigerator at 5 ° C. for 72 hours,
An aging treatment has been usually performed to make the cell structure of the obtained pre-expanded particles finer and more uniform. However, even after such aging treatment,
When the resin particles are stored in a place where the outside air temperature is high, the cell size of the obtained pre-expanded particles becomes coarse and non-uniform as in the case where there is no aging treatment. Therefore, in the hot season (summer season), it is necessary to pay close attention to the temperature at the time of storage, such as storing the resin particles impregnated with the blowing agent in a low-temperature warehouse or the like.

Therefore, with the aim of shortening the aging period and the like, for example, as shown in Japanese Patent Application Laid-Open No. H8-100078,
Powder of inorganic substance such as talc is used as cell forming agent (bubble regulator)
A method has also been proposed in which the cell size of the obtained resin particles is optimized by adding as a component.
However, this method also requires a 5-day ripening period (column 5, line 49 to column 6, line 1 in the above publication).
reference).

The present invention has been made based on this background, and a first object of the present invention is to provide a pre-expanded heat-resistant foamed resin particle (a blend or copolymer of a polyphenylene ether resin and a styrene resin). The resin cell obtained by impregnating the base resin with a foaming agent) without adding a special cell-forming agent (bubble regulator) and without aging treatment. That is, the heat-resistant foamed resin particles can form a cell having a size of 10 to 200 μm), do not shrink, and can obtain a high expansion ratio. Heat resistance is improved,
Heat resistant foamed resin particles are heated to a high temperature (typically 35 ° C to 50 ° C).
(C), the heat-resistant foamed resin particles whose cell structure uniformity, cell dimensions and the like do not substantially change even when left unattended. Another object of the present invention is to provide a method for producing heat-resistant foamed resin particles capable of easily producing heat-resistant foamed resin particles having such characteristics and advantages.

[0008]

Means for Solving the Problems The present inventors have conducted intensive studies on the mechanism by which the cell structure is formed during the expansion process of the heat-resistant foamed resin particles. Was found to be closely related to the amount of water contained in the resin, and as a result of further study, it was found that the heat-resistant resin (60 to 90 parts by weight of styrene resin and 40 to 10 parts by weight of polyphenylene ether resin) Blend) heat-resistant foamed resin particles containing 3 to 20 parts by weight of a foaming agent based on 100 parts by weight,
When the moisture content inside the heat-resistant foamed resin particles is adjusted to 0.03% by weight or less by performing an appropriate drying treatment, a cell forming agent (cell regulator) is added to the pre-foamed particles obtained therefrom. A uniform and good cell structure (10-200 μm) without any aging treatment
Cell size), the pre-expanded particles do not shrink, a high expansion ratio is obtained, and the obtained pre-expanded particles are heated to a high temperature (a temperature of 35 ° C. to 50 ° C.). , And found that the uniformity of the cell structure and the size of each cell did not substantially change,
Here, the present invention has been completed.

Accordingly, the present invention clearly provides a heat-resistant resin comprising 60 to 90 parts by weight of a styrene resin and 40 to 10 parts by weight of a polyphenylene ether resin, and 3 to 100 parts by weight of the heat-resistant resin. 20
The present invention relates to heat-resistant foamed resin particles characterized in that, in the heat-resistant foamed resin particles containing parts by weight of a foaming agent, the amount of water contained inside the resin particles is 0.03% by weight or less. The present invention also provides the heat-resistant foamed resin particles as described above, wherein the heat-resistant resin has a physical property such that the extrapolated glass transition onset temperature Tig is 105 to 140 ° C. in a DSC curve drawn by differential scanning calorimetry according to JIS K7121. The present invention relates to heat-resistant foamed resin particles having the above characteristics. Further, a more preferred embodiment of the present invention is that the cross-sectional cells of the pre-expanded particles obtained by foaming the heat-resistant foamed resin particles to a bulk magnification of 30 times with steam at 100 ° C. have a size of 10 μm to 200 μm. The invention relates to the above-mentioned heat-resistant foamed resin particles. The invention also relates to a method for producing the heat-resistant foamed resin particles according to the invention. That is, the present invention relates to 60 to 90 parts by weight of a styrene resin and 40 to 1 part of a polyphenylene ether resin.
A heat-resistant foamed resin particle containing 0 parts by weight and 3 to 20 parts by weight of a foaming agent based on 100 parts by weight of the heat-resistant resin is dried in a temperature range of -10 ° C to + 30 ° C. Accordingly, the present invention relates to a method for producing heat-resistant foamed resin particles, characterized in that the amount of water contained in the resin particles is adjusted to 0.03% by weight or less. This manufacturing method includes three more specific embodiments.
That is, as a first aspect, the present invention is characterized in that the moisture content contained in the resin particles is adjusted to 0.03% by weight or less by placing the heat-resistant foamed resin particles under reduced pressure. As a second embodiment of the above-mentioned method for producing heat-resistant foamed resin particles, a gas having a humidity of 0 to 50% is contained in a group of heat-resistant foamed resin particles in an amount of 0.1 to 10% per kg of the resin particles.
The method for producing heat-resistant foamed resin particles described above, wherein the amount of water contained in the resin particles is adjusted to 0.03% by weight or less by passing the resin particles at a flow rate of L / min. As a third embodiment, by storing the heat-resistant foamed resin particles together with a desiccant, the amount of water contained in the resin particles is adjusted to 0.03% by weight or less, and then the resin particles and the desiccant are mixed. The present invention also relates to the above-mentioned methods for producing heat-resistant foamed resin particles, which are characterized in that they are separated.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The heat-resistant foamed resin particles of the present invention are:
Add a foaming agent to the base resin (heat-resistant resin)
It is a resin particle containing by weight. The heat-resistant resin is composed of 60 to 90 parts by weight of a styrene resin and 40 to 10 parts by weight of a polyphenylene ether resin. The resin particles of the present invention have a water content of 0.0
It is characterized in that it is not more than 3% by weight.

The heat-resistant foamed resin particles generally contain 0.1 to 1.0% by weight of water as a whole during the production process, that is, the process of impregnating the base resin with a foaming agent in a suspension system. Further, the heat-resistant foamed resin particles are generally subjected to forced dehydration / drying treatment using, for example, a centrifuge and a rotary dryer or a fluidized-bed dryer, following the impregnation treatment with the foaming agent. This drying treatment is to remove moisture adhering to the surface of the heat-resistant foamed resin particles from the surface by spraying hot air for a short time. The contained water cannot be sufficiently removed.
On the other hand, the heat-resistant foamed resin particles according to the present invention reduce the amount of water contained inside the particles to 0.03% by weight or less.
More preferably, it is reduced to 0.01% by weight or less, which is clearly different from conventional heat-resistant foamed resin particles from which the moisture on the particle surface has been removed. When the heat-resistant foamed resin particles have an internal moisture content of more than 0.03% by weight, not only does the period required for the aging treatment of the resin particles become longer, but also particularly at high temperatures of 35 ° C to 45 ° C. For example, when left standing for several days, the cell size of the obtained pre-expanded particles becomes coarser and more uneven.
In addition, the pre-expanded particles are liable to shrink and cannot have a high expansion ratio. The amount of water contained in the heat-resistant foamed resin particles is generally determined by first washing the heat-resistant foamed resin particles with methanol for removal of water adhering to the surface, and then air-drying after suction filtration. Thereafter, the measurement is carried out by a procedure of quantification according to the method of Karl Fischer.

Conventionally, the heat-resistant foamed resin particles are usually subjected to a drying treatment using the above-mentioned drier,
The blending agent (eg, a lubricant) is mixed and then packaged, typically by sealing in hundreds of kilograms into a drum or sealing in hundreds of kilograms into a flexible container pack. That is, in the packing form of the heat-resistant foamed resin particles, the water contained in the resin particles is transferred to the surface of the particles and maintained in a state in which it is difficult to diffuse into the outside air. Therefore, the treatment for reducing the internal water content of the heat-resistant foamed resin particles according to the present invention, after the resin particles are dried,
It would be more desirable to do this in the process of packing.

Next, a description will be given of a treatment method for reducing the internal water content of the heat-resistant foamed resin particles. In order to reduce the amount of water contained in the heat-resistant foamed resin particles to 0.03% by weight or less, generally, the temperature of the heat-resistant foamed resin particles manufactured according to a conventional method is from -10 ° C to + 30 ° C. An appropriate drying treatment (the treatment in the following embodiment) may be performed in a temperature range of 0 ° C, more preferably in a temperature range of 0 ° C to + 25 ° C. When the drying treatment is performed at a low temperature of less than −10 ° C., the transfer of moisture from the inside to the surface of the heat-resistant foamed resin particles and the diffusion of moisture from the surface of the resin particles to the atmosphere become slow, and the resin becomes slow. Such a treatment is not preferable in terms of productivity (production efficiency) because the time required for removing water contained in the particles becomes very long. On the other hand, when the drying treatment is performed at a high temperature exceeding + 30 ° C., the escape of the foaming agent during the treatment becomes frequent and intense, and the foaming power of the heat-resistant foamed resin particles is considerably reduced. This causes a new problem of product quality that causes the occurrence. On the other hand, when the drying treatment is performed in a temperature range of −10 ° C. to + 30 ° C., the moisture contained in the heat-resistant foamed resin particles is efficiently removed, and the foaming power is reduced due to dissipation of the foaming agent. The problem does not arise. Accordingly, the present invention comprises a heat-resistant resin comprising 60 to 90 parts by weight of a styrene resin and 40 to 10 parts by weight of a polyphenylene ether resin, and 3 to 20 parts by weight of a foaming agent based on 100 parts by weight of the heat-resistant resin. The heat-resistant foamed resin particles to be dried in a temperature range of -10 ° C to + 30 ° C,
The subject of the present invention is a method for producing a heat-resistant foamed resin particle, characterized in that the amount of water contained in the resin particle is adjusted to 0.03% by weight or less.

Although a specific method for performing the above-mentioned drying treatment according to the present invention is basically arbitrary, a more preferable drying treatment method is a method of placing heat-resistant foamed resin particles under reduced pressure. A method of passing a dried gas through a group of heat-resistant foamed resin particles at a constant flow rate, and a method of storing the heat-resistant foamed resin particles together with a desiccant and then separating the resin particles from the desiccant. . The first way is
This is a method in which heat-resistant foamed resin particles are placed in a container capable of being depressurized, air in the container is removed using a vacuum pump or the like, and the resin particles are kept under reduced pressure, that is, a vacuum drying method.
In this method, if the inside of the container in which the resin particles are charged by degassing is constantly maintained at a vacuum of 10 mmHg or less during the drying process, the water inside the resin particles can be more efficiently removed. Therefore, the present invention is characterized in that the heat resistant foamed resin particles are placed under reduced pressure to adjust the amount of water contained inside the resin particles to 0.03% by weight or less. The method for producing expanded resin particles
Subject.

The second method is, more specifically, a method in which the humidity is zero.
-25% gas, more preferably a gas conditioned to a humidity of 0-10%, is introduced into the group of heat-resistant foamed resin particles at a flow rate of 0.1 to 10 L / min per kg of the resin particles.
More preferably, the flow rate is 1 to 5 L / min. Gases that can be used in this method include N ₂ , air, A
r, etc., but use of dry air is more convenient from an economic point of view. However, if a gas having a humidity of more than 25% is used, the effect of reducing the amount of water contained in the heat-resistant foamed resin particles cannot be sufficiently obtained, and thus the use of such a gas is not appropriate. Further, when the flow rate of the gas passing through the group of heat-resistant foamed resin particles is set to a small flow rate of less than 0.1 L / min per 1 kg of the same resin particles, the internal moisture of the heat-resistant foamed resin particles is reduced from the particle surface to the atmosphere. However, such a small flow rate is not preferable in terms of production efficiency, because the time required for removing the internal moisture becomes very long because the heat is released slowly. On the other hand, even if the gas flow rate is set to a flow rate exceeding 10 L / min per 1 kg of the heat-resistant foamed resin particles, the rate at which the internal moisture of the resin particles is removed does not increase any more. Higher flow rates are not economical and are not preferred. On the other hand, when the flow rate of the gas passing through the group of the heat-resistant foamed resin particles is set to a flow rate of 0.1 to 10 L / min per 1 kg of the resin particles, the moisture contained in the resin particles can be efficiently removed. Well removed. Therefore, the present invention provides a method for controlling the humidity
By passing 50% to 50% of the gas through the population of heat-resistant foamed resin particles at a flow rate of 0.1 to 10 L / min per kg of the resin particles, the amount of water contained in the resin particles is reduced to 0.1%.
The subject of the present invention is also a method for producing the heat-resistant foamed resin particles of the present invention, which is adjusted to not more than 03% by weight.

The final method is to add a desiccant, more preferably a granular desiccant (particularly silica gel) having a particle size different from that of the heat-resistant foamed resin particles, in the heat-resistant foamed resin particles, for example, in an amount of 10 g to 100 g per 1 kg of the resin particles. Mix about
Then, the heat-resistant foamed resin particles are stored together with the desiccant for a period until the amount of water contained in the resin particles is adjusted to 0.03% by weight or less, for example, for 10 to 24 hours, and thereafter, This is a method of separating the heat-resistant foamed resin particles and the granular desiccant. Since the granular desiccant (silica gel) is a drug having a significantly larger particle size than the heat-resistant foamed resin particles, it can be easily separated by sieving. In addition, the granular desiccant separated and collected can be reused by reprocessing. In addition, since silica gel has the highest water adsorption efficiency at a low temperature of about 4 ° C., the above method is a preferable method in a cold winter season. Therefore, the present invention adjusts the amount of water contained inside the resin particles to 0.03% by weight or less by storing the heat-resistant foamed resin particles together with a desiccant,
Thereafter, the method for producing a heat-resistant foamed resin particle of the present invention, comprising separating the resin particles and the desiccant,
Subject.

As described above, the heat-resistant foamed resin particles according to the present invention have an internal water content adjusted to 0.03% by weight or less by a drying treatment at a certain temperature range. The natural amount of the heat-resistant foamed resin particles can be gently reduced to 0.03% by weight or less by long-term natural storage or storage. Drying at a high temperature exceeding 30 ° C. (for example, oven drying at 45 ° C.) can also reduce the amount of water contained in the heat-resistant foamed resin particles to 0.03% by weight or less. But,
In the case of heat-resistant foamed resin particles that have been left for a long period of time and stored, the amount of foaming agent that has escaped gradually increases during storage,
The foaming power gradually decreases, which is not preferable. Further, storage at 45 ° C. adversely affects the cell structure of the pre-expanded particles, resulting in a very non-uniform one. In the case of heat-resistant foamed resin particles rapidly dried at a temperature higher than 30 ° C., the escape of the foaming agent becomes remarkable. As a result, the expansion ratio decreases and the cell structure of the pre-expanded particles becomes coarse as a whole. Is not preferred. Therefore, these heat-resistant foamed resin particles are excluded from the scope of the present invention.

Further, the heat-resistant foamed resin particles of the present invention can be specified also from the characteristics of physical properties. The present inventor performed a heat flow rate differential scanning calorimetry (heat flow rate DSC) of the heat-resistant foamed resin particles and examined various glass transition behavior thereof. The present inventors have found that the present invention exhibits different characteristics as compared with the case of (i), that is, the fact that the extrapolated glass transition onset temperature Tig is considerably higher, and here, the present invention has been specified also in terms of physical properties. That is, the present invention relates to a heat-resistant foamed resin particle having an internal water content of 0.03% by weight or less (a resin blend of a heat-resistant resin, i.e., 60 to 90 parts by weight of a styrene resin and 40 to 10 parts by weight of a polyphenylene ether resin). Resin particles containing 3 to 20% by weight of a foaming agent), and the DSC curve drawn by differential scanning calorimetry according to JIS K7121 for the heat-resistant resin has an extrapolated glass transition onset temperature Tig of 105 to 140 ° C. The present invention relates to heat-resistant foamed resin particles. The above differential scanning calorimetry is a method of measuring the temperature difference between the test piece and the reference substance as a function of the temperature while changing the temperature of the test piece and the reference substance according to an adjusted program. About 5 heat-resistant resins according to the invention
To about 10 mg, and the test piece was heated in a differential scanning calorimeter at, for example, a heating rate of 10 ° C./min.
The temperature difference (ΔT) is measured while increasing the temperature to ° C. or more. Extrapolated glass transition onset temperature Tig
Is a parameter derived from a differential scanning calorimetry curve (DSC curve, vertical axis: ΔT, horizontal axis: temperature) drawn by the above measurement, and a straight line obtained by extending a low-temperature base line of the DSC curve to a high-temperature side. , The temperature at the intersection with the tangent drawn at the point where the slope of the curve of the step change portion of the glass transition becomes maximum. In the case of conventional expandable styrene resin particles, the extrapolated glass transition start temperature Tig is around 102 ° C., whereas in the case of the heat-resistant expanded resin particles of the present invention, the extrapolated glass transition start temperature is It is characterized in that higher values of 105 to 140 ° C. are measured for Tig.

Further, the heat-resistant foamed resin particles of the present invention are characterized by the cell structure of the pre-expanded particles obtained therefrom.
It can also be specified. The present inventors foamed the heat-resistant foamed resin particles with steam at 100 ° C. so as to have a bulk magnification of 30 times. Has a size of 10 μm to 200 μm in diameter, and here, the present invention has been specified also from the form of the pre-expanded particles. Therefore, the present invention provides a heat-resistant foamed resin particle having a bulk ratio of 30
The cross-sectional cell of the pre-expanded particles obtained by double expansion has a diameter of 10
The present invention also relates to the above-mentioned heat-resistant foamed resin particles, which have a size of from μm to 200 μm in diameter. In addition, the present invention provides other compositions, physical properties, characteristics, etc., except for the ratio of the two resin components of the heat-resistant resin and the internal moisture content of the heat-resistant foamed resin particles, for example, various additions of the heat-resistant foamed resin particles. There is no particular limitation on the types of the agent components and the amounts thereof. In addition, the present invention is not particularly limited with respect to the entire production process of the heat-resistant foamed resin particles except for the method of removing the internal moisture of the heat-resistant foamed resin particles.

The styrenic resin in the present invention is not limited to a homopolymer of a styrenic monomer, but may be a copolymer with another monomer (a styrenic monomer in a proportion of 50% or more). Made from Styrene monomers, in addition to styrene alone, α-methyl styrene, ethyl styrene,
Substituted styrenes such as p-chlorostyrene are included. The other monomer of the copolymer includes (meth) acrylates such as methyl methacrylate, methyl acrylate, butyl methacrylate, and butyl acrylate;
Examples include vinyl monomers such as acrylonitrile, vinyl toluene, and vinyl carbazole. These may be used alone or in combination of two or more. Accordingly, the styrene resin used in the present invention includes, in addition to polystyrene, poly-substituted styrene such as poly-α-methylstyrene and poly-p-chlorostyrene, as well as styrene and substituted styrene (for example, α-methylstyrene). Polymer,
Alternatively, a copolymer of styrene and a vinyl-based monomer (eg, acrylonitrile) may be used. More preferred are polystyrene, polystyrene-butadiene copolymer, polystyrene-maleic anhydride copolymer, polystyrene-acrylonitrile copolymer, and styrene graft copolymer.

The styrenic resin is generally produced by suspension polymerization of a styrenic monomer or the like in an aqueous medium. This suspension polymerization is carried out in a suspension system containing a radical initiator, a dispersant and a dispersing aid. As the radical initiator, polymerization initiators used in general radical polymerization, for example, benzoyl peroxide, butyl perbenzoate, t
Organic peroxides such as -butylperoxybenzoate; and azo compounds such as azobisisobutyronitrile. Examples of the dispersant include poorly water-soluble inorganic salts such as tricalcium phosphate, magnesium phosphate, and hydroxyapatite, and organic polymers such as polyvinyl alcohol, polyvinylpyrrolidone, and methylcellulose. Further, as a dispersing aid used in combination with a dispersant, anionic surfactants such as dodecylphenyl oxide disulfonate, sodium dodecylbenzenesulfonate, sodium α-olefin sulfonate, polyoxyethylene alkyl ether, polyoxyethylene Nonionic surfactants such as ethylene octyl phenol ether are exemplified.

The polyphenylene ether resin in the present invention is represented by the following formula I:

Embedded image (Wherein R ₁ and R ₂ independently represent an alkyl group having 1 to 4 carbon atoms or a halogen atom,
Represents the degree of polymerization. ), A specific example of which is poly (2,6).
-Dimethylphenylene-1,4-ether), poly (2,6-diethylphenylene-1,4-ether),
Poly (2,6-dichlorophenylene-1,4-ether), poly (2-methyl-6-ethylphenylene-1,
4-ether), poly (2-chloro-6-methylphenylene-1,4-ether), poly (2-methyl-6-isopropylphenylene-1,4-ether), poly (2,6-di-n) -Propylphenylene-1,4-ether), poly (2-bromo-6-methylphenylene)
1,4-ether), poly (2-chloro-6-bromophenylene-1,4-ether), poly (2-chloro-6)
-Ethylphenylene-1,4-ether) and the like. The polymerization degree n may be 10 to 5000, and is 500
If it exceeds 0, it is difficult to obtain a uniform heat-resistant foam, and 10
If it is less than 30, it is difficult to obtain a foam having the desired heat resistance.

The heat-resistant resin is a resin blend of the above styrene resin and polyphenylene ether resin,
Further, a coloring agent, a flame retardant, a heat stabilizer, a lubricant and the like can be added in an appropriate amount as needed. Concerning the compounding ratio of the styrene resin and the polyphenylene ether resin, in the present invention, it is composed of 60 to 90 parts by weight of the styrene resin and 40 to 10 parts by weight of the polyphenylene ether resin, and more preferably 70 to 90 parts by weight of the styrene resin. And 30 to 10 parts by weight of a polyphenylene ether-based resin. If the styrene-based resin exceeds 90 parts by weight (that is, if the polyphenylene ether-based resin is less than 10 parts by weight), the effect of the blend of the polyphenylene ether-based resin is substantially reduced, and the heat-resistant foamed resin particles have an expected value. When the styrene resin is less than 60 parts by weight (that is, when the polyphenylene ether resin exceeds 40 parts by weight), the heat dissipation of the blowing agent from the heat-resistant foamed resin particles is insufficient. Dispersion is rapid and intense, and a sufficiently high expansion ratio cannot be obtained.

The heat-resistant foamed resin particles are formed by impregnating the above-mentioned heat-resistant resin with a foaming agent. More specifically, the heat-resistant resin particles (in the form of granules, pellets, or spheres) are formed into an aqueous solution. It is made by dispersing in a suspension, followed by pressing the blowing agent into the suspension and heating appropriately. As the foaming agent, for example, propane, butane, n-
Aliphatic hydrocarbons such as pentane, isopentane and hexane, or halogenated hydrocarbons such as methyl chloride and freon are used. These foaming agents may be used alone or in combination of two or more. However, when removing moisture contained in the heat-resistant foamed resin particles, from the viewpoint that the escape of the foaming agent is less,
As the blowing agent, butane or pentane is more preferred, and pentane is most preferred. The heat-resistant foamed resin particles of the present invention contain the foaming agent in an amount of 3 to 20% by weight, more preferably 4 to 15% by weight, and still more preferably 5 to 1% by weight.
0% by weight.

The heat-resistant foamed resin particles of the present invention may contain, in addition to the above, other additives, such as a foaming aid, a plasticizer, and a flame retardant, if desired, in such an amount that the heat resistance is not impaired. can do. Suitable foaming aids include solvents such as toluene, xylene, cyclohexane and the like.
Suitable plasticizers include DOP, DOA, DB
P, coconut oil, palm oil and the like. Further, suitable flame retardants include hexabromocyclododecane, tetrabromobisphenol A, pentabromomonochlorocyclohexane and the like. The present invention has the advantage that the addition of a conventionally used cell-forming agent is not required, but the addition of such a cell-forming agent does not matter at all. Suitable cell formers include, for example, inorganic material powders such as talc. Further, as the dispersant used in the aqueous suspension system at the time of impregnation of the blowing agent, for example, tricalcium phosphate, magnesium phosphate, poorly water-soluble inorganic salts such as hydroxyapatite, or polyvinyl alcohol, polyvinylpyrrolidone, Organic polymers such as methyl cellulose are exemplified.
Examples of the dispersing aid used in combination with the dispersing agent include anionic surfactants such as dodecylphenyl oxide disulfonate, sodium dodecylbenzene sulfonate, sodium α-olefin sulfonate, polyoxyethylene alkyl ether, and polyoxyethylene. Nonionic surfactants such as ethylene octyl phenol ether are exemplified.

Thus, the heat-resistant foamed resin particles according to the present invention, that is, subjected to the drying treatment according to the method of the present invention, are pre-expanded to an arbitrary apparent specific gravity, if necessary, and then are pre-expanded according to a conventional method. Is filled in a molding die such as a mold, and is heated and foamed using steam, whereby the pre-expanded particles are fused to each other to produce a foam molded article having a desired shape (dimension).

[0027]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The embodiments of the present invention will be described below, including the best mode.

-Production of heat-resistant foamed resin particles- 75 parts by weight of a polystyrene resin as a main raw material, 25 parts by weight of a polyphenylene ether resin, and other additives are put together into an extruder, which is melted by heating and melted. Following kneading with a screw, the mixture was extruded in the form of a strand, and then the strand was cut and pelletized in a rotary pelletizer. 1500 g of the obtained heat-resistant resin pellets were placed in a 5 L autoclave, and 2500 g of ion-exchanged water, 15 g of tricalcium phosphate and 0.15 g of sodium alkylbenzenesulfonate were further charged into the autoclave. 150 g of n-pentane as a blowing agent,
7.5 g of toluene as a foaming aid and 7.5 g of DOP (dioctyl phthalate) as a plasticizer were injected. Next, the temperature of the aqueous suspension in the autoclave was raised to 130 ° C., and the state was maintained for 6 hours, thereby impregnating the pellets of the heat-resistant resin with the foaming agent. After this treatment, the aqueous suspension was cooled to room temperature, and the resulting heat-resistant foamed resin particles were taken out of the autoclave. Then, using a centrifuge,
The obtained heat-resistant foamed resin particles are centrifuged, and then, using a dryer, the dewatered heat-resistant foamed resin particles are dried with hot air to forcibly remove water present on the surfaces of the heat-resistant foamed resin particles. Removed. Thereafter, the obtained heat-resistant foamed resin particles having a particle size of 1.0 to 1.2 mm are subjected to the following treatment.

-Removal of moisture contained in heat-resistant foamed resin particles-Treatment 1 Heat-resistant foamed resin particles having a particle size of 1.0 to 1.2 mm are put in a vacuum dryer, and By placing the heat-resistant foamed resin particles under a reduced pressure of 5 mmHg or less at 25 ° C., the particles were vacuum-dried for different times. Treatment 2 For comparison, 0.1 g of talc was used as a cell-forming agent during extrusion.
Heat resistant foamed resin particles were produced according to the above process except that 3 parts by weight were added in advance. This allows
Heat-resistant foamed resin particles having a particle size of 1.0 to 1.2 mm that had not been subjected to a drying treatment were obtained. Treatment 3 First, a vinyl chloride tube having a diameter of about 5 cm and a net attached to the bottom is prepared, and heat-resistant foamed resin particles having a particle size of 1.0 to 1.2 mm are filled in the tube. Next, using a compressor, air with different humidity is introduced from the lower part of the vinyl chloride pipe, and is passed through the filled heat-resistant foamed resin particles at different flow rates to dry the heat-resistant foamed resin particles. Processing was performed. The outside air temperature was between 20 and 25 ° C. Treatment 4 Granular silica gel (6 mesh) is added to heat-resistant expanded resin particles 5
Of the heat-resistant foamed resin particles together with the silica gel, whereby the drying process of the resin particles is performed by the amount of silica gel, the storage temperature and the drying (storage). ) Performed at different times. Thereafter, the mixture was classified by sieving to separate heat-resistant foamed resin particles having a particle size of 1.0 to 1.2 mm, and used silica gel was recovered. The recovered silica gel was subjected to heat treatment at 150 ° C. for reuse.

-Quantification of the amount of moisture contained in the heat-resistant foamed resin particles- The amount of moisture contained in the heat-resistant foamed resin particles before and after the drying treatment in each Example was determined according to the following procedure. . First, in order to remove moisture adhering to the particle surface, a predetermined amount of the heat-resistant foamed resin particles are treated with methanol, and then the particles are suction-filtered using a suction filter. N ₂ may be blown into the population of heat-resistant foamed resin particles for 3 minutes at room temperature to dry only the surface of the particles. The condition of the air drying is a condition under which the water inside the particles does not evaporate. Thereafter, the internal moisture content of the air-dried heat-resistant foamed resin particles was measured using a Karl Fischer moisture meter (MKC-210, manufactured by Kyoto Electronics Industry Co., Ltd.) according to the following procedure. About 1 g of the sample was precisely weighed, and the
Heat at 0 ° C. for 15 minutes and weigh the amount of moisture generated during that time.

-Measurement of the amount of the foaming agent contained in the heat-resistant foamed resin particles- The heat-resistant foamed resin particles are dissolved in a solvent such as toluene, and then foamed in the solution using a gas chromatography apparatus. The amount of agent was quantified.

-Aging and storage of heat-resistant foamed resin particles at high temperature-Particle size after drying (removal of internal moisture)
20 ° C. for heat-resistant foamed resin particles of 0 to 1.2 mm
And / or storage at 45 ° C. for different times.

-Preparation of Pre-expanded Particles and Evaluation of Cell Structure- The heat-resistant expanded resin particles were treated with steam at 100.degree.
Foaming was performed 0 times to obtain pre-foamed particles. Then, the cut surface of the obtained pre-expanded particles was observed with an electron microscope, the uniformity of the cells was evaluated, and the cut surface was photographed to determine the average cell size of the pre-expanded particles. Further, such preliminary foaming was performed for 10 minutes, and the foaming ratio of the foamed particles obtained at that time was also determined.

-Heat flux differential scanning calorimetry (DSC)-Differential scanning calorimetry (DSC) of the base resin of the heat-resistant foamed resin particles subjected to the treatments 1 to 4, ie, the heat-resistant resin, is performed in accordance with JIS K7121. And
The extrapolated glass transition onset temperature Tig was determined from the DSC curve drawn by the measurement. Differential scanning calorimetry (DSC)
More specifically, 5 to 10 mg of a heat-resistant resin sample was sampled, and the test piece was heated at a heating rate of 10 ° C./min in a differential scanning calorimeter while raising the temperature to 230 ° C. The measurement was performed by a method of automatically recording the measured temperature difference ΔT on the chart paper of the calorimeter. The above differential scanning calorimeter automatically calculated the extrapolated glass transition start temperature Tig from the differential scanning calorimetry (DSC) curve drawn by the measurement. In other words, the device used for this measurement is a tangent drawn at the point where the slope of the curve at the step change portion of the glass transition becomes the maximum, with the straight line extending from the low temperature side baseline of the DSC curve to the high temperature side. And the temperature at that intersection is determined as the extrapolated glass transition onset temperature T
It has the performance of displaying ig on chart paper.

The results of the heat-resistant foamed resin particles subjected to the treatments 1 to 4 are shown in the following tables and figures.
Tables 1 and 2 summarize the results for the heat-resistant foamed resin particles that were dried according to the treatment 1. The water content inside the particles, the amount of the foaming agent and the cell size of the pre-expanded particles,
This shows the relationship with the uniformity of the cell. From Table 2, it can be seen that in Example 1 (1-1 to 1-3) and Example 2 (2-1 to 2-3), heat-resistant expanded resin particles having an internal water content of more than 0.03% by weight were obtained. In this case, it is understood that a certain period of time is required until aging is completed, and that the cells of the pre-expanded particles become coarse when stored at a high temperature of 45 ° C. On the other hand, in Example 3 (3-1 to 3-2) and Example 4 (4-1 to 4-2),
In other words, in the case of the heat-resistant foamed resin particles having an internal water content of 0.03% by weight or less, the time for aging is not required, and even if this is stored at a high temperature of 45 ° C., the pre-expanded particles are not used. Cell does not become coarse.

Table 3 summarizes the results for the heat-resistant foamed resin particles obtained according to the treatment 2, and shows the relationship between the water content inside the particles, the amount of the foaming agent, the cell size of the pre-expanded particles, and the uniformity of the cells. Indicates a relationship. From Table 3, in Example 5 (5-1 to 5-3), the stability of the cell structure by the addition of the cell-forming agent (talc) was ascertained in Table 2 when the cell-forming agent (talc) was not added. Although it is slightly improved as compared with Example 1 (1-1 to 1-3), the improvement effect is smaller than when the internal water content of the heat-resistant foamed resin particles is reduced to 0.03% by weight or less. It can be seen that they are extremely small. Also,
It was confirmed that storage at 45 ° C. made the cells of the pre-expanded particles coarse and non-uniform.

Table 4 summarizes the results of the heat-resistant foamed resin particles dried according to the treatment 3. The moisture content inside the particles, the amount of the foaming agent, the humidity, the flow rate and the ventilation time of the air to be ventilated are shown. Shows the relationship. From Table 4, when the humidity of the ventilated air exceeds 50%,
On the other hand, when the flow rate of the ventilated air is 0.1 L / min or less, the drying treatment of the heat-resistant foamed resin particles becomes slow, and it takes an extremely long time to reduce the internal water content of the particles to 0.03% by weight or less. It can be seen that time is required and the efficiency becomes very poor. On the other hand, even if the flow rate of the ventilated air exceeds 10 L / min, the time of the drying treatment for removing the internal moisture of the heat-resistant foamed resin particles is no longer reduced so much.

Table 5 summarizes the results of the heat-resistant foamed resin particles dried in accordance with the treatment 4. The water content, the amount of the foaming agent, the amount of the desiccant (silica gel), the temperature and the drying Shows the relationship with time. As shown in Table 5, when the heat-resistant foamed resin particles are stored together with a required amount of a desiccant (silica gel), the internal water content of the particles can be adjusted to 0.03% by weight or less.
It can be seen that the effect of reducing the internal water content can be sufficiently exerted even at a low temperature such as ℃.

FIGS. 1 and 2 show a part of a DSC curve drawn by heat flux differential scanning calorimetry on the heat-resistant foamed resin particles of the dried example. FIG. 1 shows a DSC curve for a sample in which the heat-resistant resin was composed of 75 parts by weight of a polystyrene resin and 25 parts by weight of a polyphenylene ether resin.
ig was 116.9 ° C. FIG. 2 shows a DSC curve for a sample in which the heat-resistant resin was composed of 85 parts by weight of a polystyrene resin and 15 parts by weight of a polyphenylene ether resin, and the extrapolated glass transition onset temperature Tig was 108.3 ° C. Is shown.
Then, not only in these examples, but also in the heat-resistant foamed resin particles of the examples, the result that the extrapolated glass transition start temperature Tig was 105 ° C. or more was obtained. On the other hand, in the case of conventional expandable polystyrene resin particles,
The extrapolated glass transition onset temperature Tig of the base resin is generally about 102 ° C. Therefore, it was confirmed that the heat-resistant foamed resin particles of the examples had one characteristic in terms of the physical properties.

[0040]

As described above, according to the present invention,
Regarding the pre-expanded heat-resistant foamed resin particles, a uniform and favorable cell structure can be formed immediately after production without adding a cell-forming agent (cell regulator) or aging treatment. In addition, the pre-expanded particles hardly shrink with time, and an effect that a high expansion ratio can be obtained can be obtained. Furthermore, according to the present invention, the heat resistance over time of the cell structure is improved, and the heat-resistant foamed resin particles are heated at 35 ° C.
Even when the pre-expanded particles are left at a high temperature such as 50 ° C., the uniformity of the cells of the pre-expanded particles can be maintained, and the cell dimensions are not substantially changed. Further, according to the method of the present invention, there is obtained an effect that heat-resistant foamed resin particles having such characteristics and advantages can be easily produced.

[Brief description of the drawings]

FIG. 1 shows heat-resistant foamed resin particles (polystyrene resin 75 parts by weight, polyphenylene ether resin 2) according to an embodiment of the present invention.
5 shows a DSC curve drawn by differential scanning calorimetry for the base resin (5 parts by weight).

FIG. 2 shows a DSC curve drawn by differential scanning calorimetry on a base resin of heat-resistant foamed resin particles (85 parts by weight of a polystyrene resin and 15 parts by weight of a polyphenylene ether resin) of another example.

Claims (7)

[Claims] 1. A heat resistant resin comprising 60 to 90 parts by weight of a styrene resin and 40 to 10 parts by weight of a polyphenylene ether resin, and 3 to 20 parts by weight of a foaming agent based on 100 parts by weight of the heat resistant resin. Heat-resistant foamed resin particles, wherein the amount of water contained in the resin particles is 0.03% by weight or less. 2. A DSC curve drawn by differential scanning calorimetry according to JIS K7121 for a heat-resistant resin,
The heat-resistant foamed resin particles according to claim 1, wherein the extrapolated glass transition onset temperature Tig is 105 to 140 ° C. 3. The cross-sectional cell of the pre-expanded particles obtained by foaming the heat-resistant foamed resin particles at a bulk magnification of 30 times with steam at 100 ° C. has a diameter of 10 μm to 200 μm. Item 2. Heat-resistant foamed resin particles according to Item 1. 4. A heat-resistant resin comprising 60 to 90 parts by weight of a styrene resin and 40 to 10 parts by weight of a polyphenylene ether resin, and 3 to 20 parts by weight of a foaming agent based on 100 parts by weight of the heat-resistant resin. The heat-resistant foamed resin particles are dried in a temperature range of -10 ° C. to + 30 ° C. to adjust the amount of water contained in the resin particles to 0.03% by weight or less. Method for producing porous foamed resin particles. 5. The heat-resistant foam according to claim 4, wherein the amount of water contained in the resin particles is adjusted to 0.03% by weight or less by placing the heat-resistant foamed resin particles under reduced pressure. Method for producing porous foamed resin particles. 6. A gas having a humidity of 0 to 50% in a mass of the heat-resistant foamed resin particles in an amount of 0.1 to 10 per kg of the resin particles.
The method for producing heat-resistant foamed resin particles according to claim 4, wherein the amount of water contained in the resin particles is adjusted to 0.03% by weight or less by passing the resin particles at a flow rate of L / min. 7. The heat-resistant foamed resin particles are stored together with a desiccant to adjust the amount of water contained in the resin particles to 0.03% by weight or less, and thereafter, the resin particles and the desiccant are mixed. The method for producing heat-resistant foamed resin particles according to claim 4, wherein the particles are separated.