JP7405516B2 - Expandable chlorinated vinyl chloride resin particles, expanded particles thereof, and chlorinated vinyl chloride resin foam molded articles using the same - Google Patents

Description

The present invention relates to expandable chlorinated vinyl chloride resin particles, expanded particles thereof, and chlorinated vinyl chloride resin foam molded articles using these particles.

Resin foams have light weight, heat insulating properties, cushioning properties, etc., and have been widely used as heat insulating materials for houses, etc., and heat insulating materials for piping, etc. Among them, styrenic resin foam molded products obtained using expandable styrenic resin particles containing a blowing agent have a high degree of freedom in shape, and can be formed into simple shapes such as board shapes obtained by extrusion foaming method etc. It is widely used as a heat insulating material that can be applied to areas of the body that are difficult to install. Styrenic resin is easily flammable, but a flame retardant is added to the styrene resin foam molding to ensure a certain degree of flame retardant performance. However, due to recent fire accidents at construction sites and fires in high-rise condominiums, there is a growing demand for higher flame retardant performance in insulation materials for buildings than ever before.

Examples of foams with excellent flame retardancy include resin foam moldings using a vinyl chloride resin or chlorinated vinyl chloride resin as a base resin, which have excellent flame retardance.
For example, Patent Document 1 describes a resin foam molded article formed by foam-molding a resin composition whose main components are a chlorinated vinyl chloride resin, an acrylic resin, and/or a styrene resin.
Furthermore, Patent Document 2 describes a method for producing an extruded foam molded article by blending an acrylic resin and/or a styrene resin into a polymer mixture consisting of a vinyl chloride polymer and a chlorinated vinyl chloride polymer. Are listed.
Furthermore, Patent Document 3 describes 100 parts by weight of a chlorinated vinyl chloride resin alone or a mixture with vinyl chloride resin having an average chlorine content of 60 to 72% by weight, a specific metal compound, a stabilizer, and a methacrylic acid ester. A foaming chlorinated vinyl chloride resin composition comprising a resin and a decomposable organic blowing agent is disclosed.

The foams described in Patent Documents 1 and 2 have flame retardant performance, high closed cell ratio, and high expansion ratio. The foam described in Patent Document 3 has a very low expansion ratio of 2 to 4 times. Incidentally, since the techniques disclosed in Patent Documents 1 to 3 are all extrusion foaming techniques, they are foam molded articles with a simple shape, and problems remain in terms of the degree of freedom of shape.

On the other hand, the following invention has been proposed as a foam molded product formed by foam molding expandable particles, which has a completely different foaming process from that of an extruded foam.
Patent Document 4 describes pre-expanded chlorinated vinyl chloride resin particles containing a foaming agent and a solvent that is compatible with the chlorinated vinyl chloride resin. The base resin is chlorinated vinyl chloride resin, which has better flame retardant performance than vinyl chloride resin, so it is a foam molded product with excellent flame retardant performance, but it uses a foaming agent with a high global warming coefficient and an organic solvent. Since large amounts of carbon dioxide are used, there are environmental and cost issues.

As mentioned above, foamed molded products based on vinyl chloride resins or chlorinated vinyl chloride resins that have excellent flame retardancy have existed for a long time, but they have good flame retardancy, light weight, shapeability, and environmental compatibility. There is room for improvement in terms of performance and cost.

Japanese Unexamined Patent Publication No. 59-49243 Japanese Unexamined Patent Publication No. 59-33334 Japanese Patent Application Publication No. 11-269295 Japanese Unexamined Patent Publication No. 2-182735

Therefore, an object of the present invention is to provide expandable chlorinated vinyl chloride resin particles that can provide a chlorinated vinyl chloride resin foam molded article that has excellent flame retardancy and has both a high expansion ratio and a high closed cell ratio. It's about doing.

As a result of intensive studies to solve the above-mentioned problems, the inventors of the present application have found that expandable resin particles manufactured by combining a chlorinated vinyl chloride resin and an acrylic resin are lightweight and have closed-cell cells. The present inventors have discovered that it is possible to provide a chlorinated vinyl chloride resin foam molded article with an excellent yield, and have completed the present invention.

That is, the present invention
[1] Expandable chlorinated vinyl chloride resin particles containing the following (A) to (C):
(A) Chlorinated vinyl chloride resin,
(B) acrylic resin, and
(C) a foaming agent;
[2] The expandable chlorinated vinyl chloride resin according to [1], wherein the (B) acrylic resin is contained in 1 to 50 parts by weight based on 100 parts by weight of the (A) chlorinated vinyl chloride resin. particle,
[3] The expandable chlorinated vinyl chloride resin particles according to [1] or [2], wherein the chlorine content of the (A) chlorinated vinyl chloride resin is 60% by weight or more and 75% by weight or less;
[4] The expandable chlorinated vinyl chloride resin particles according to any one of [1] to [3], wherein the average degree of polymerization of the chlorinated vinyl chloride resin (A) is 400 or more and 1500 or less;
[5] The expandable chlorinated vinyl chloride resin according to any one of [1] to [4], wherein the (B) acrylic resin has a weight average molecular weight higher than the weight average molecular weight of the (A) chlorinated vinyl chloride resin. particle,
[6] The expandable chlorinated vinyl chloride resin particles according to any one of [1] to [5], wherein the blowing agent (C) is a physical blowing agent;
[7] The expandable chlorinated vinyl chloride resin particles according to [6], wherein the blowing agent (C) contains a saturated hydrocarbon having 4 to 6 carbon atoms;
[8] The expandable chlorinated vinyl chloride resin particles according to [7], wherein at least one of the saturated hydrocarbons having 4 to 6 carbon atoms is pentane;
[9] The expandable chlorinated vinyl chloride resin particles according to any one of [1] to [8], wherein the blowing agent (C) contains a ketone;
[10] The foaming chlorination according to any one of [1] to [9], wherein the foaming agent (C) is contained in an amount of 1 to 40% by weight based on 100% by weight of the foaming chlorinated vinyl chloride resin particles. vinyl chloride resin particles,
[11] The expandable chlorinated vinyl chloride resin particles according to any one of [1] to [10], containing chlorinated polyethylene;
[12] The expandable chlorinated vinyl chloride resin particles according to any one of [1] to [11], wherein the expandable chlorinated vinyl chloride resin particles have a true density of 1200 kg/m ³ or more.
[13] The expandable chlorinated vinyl chloride resin particles according to any one of [1] to [12], wherein the expandable chlorinated vinyl chloride resin particles have a true density of 1300 kg/m ³ or more.
[14] Method for producing expandable chlorinated vinyl chloride resin particles, including the following steps (I) to (III):
(I) Step of producing a melt-kneaded product containing a chlorinated vinyl chloride resin, an acrylic resin, and a blowing agent (II) The melt-kneaded product is passed through a die having small holes into pressurized circulating water. Extrusion step (III) cutting the melt-kneaded product immediately after extrusion, and cooling and solidifying it with pressurized circulating water;
[15] Pre-foamed from the expandable chlorinated vinyl chloride resin particles according to any one of [1] to [13] or the expandable chlorinated vinyl chloride resin particles obtained in [14] Chlorinated vinyl chloride resin foam particles,
[16] The expanded chlorinated vinyl chloride resin particles according to [15], which have a closed cell ratio of 70% or more,
[17] A chlorinated vinyl chloride resin foam molded article formed by foam molding the chlorinated vinyl chloride resin foam particles according to any one of [15] or [16],
[18] The chlorinated vinyl chloride resin foam molded article according to [17], which has a closed cell ratio of 70% or more,
[19] A method for producing a chlorinated vinyl chloride resin foam molded article, comprising a step of molding the chlorinated vinyl chloride resin foam particles according to any one of [15] or [16],
Regarding.

According to the expandable chlorinated vinyl chloride resin particles of the present invention, a chlorinated vinyl chloride resin foam having excellent flame retardant performance and a high expansion ratio and a high closed cell ratio can be obtained.

It is a graph showing the relationship between the input amount of expandable particles and the true density of expanded particles when the expandable particles are pre-foamed in Example 6 of the present invention. It is a graph showing the relationship between the true density and the closed cell ratio of foamed particles when the expandable particles are pre-foamed in Example 6 of the present invention.

(Chlorinated vinyl chloride resin)
In the present invention, by using a chlorinated vinyl chloride resin, it is possible to obtain a foamed molded article that has both excellent flame retardant performance and light weight.

The chlorinated vinyl chloride resin used in the present invention is usually produced by using vinyl chloride resin as a raw material, supplying chlorine while dispersing the vinyl chloride resin in an aqueous medium, and then irradiating it with a mercury lamp. Manufactured by chlorination, or chlorination in an aqueous medium such as heating chlorination, or chlorination of vinyl chloride resin in an air layer, such as chlorination under irradiation with a mercury lamp. be done.

As the chlorinated vinyl chloride resin, chlorinated vinyl chloride resins are used. Vinyl chloride resins to be chlorinated include vinyl chloride homopolymers and other copolymerizable monomers with vinyl chloride, such as ethylene, propylene, vinyl acetate, allyl chloride, allyl glycidyl ether, and acrylic acid. Examples include copolymers with esters, vinyl ethers, etc.

The average degree of polymerization of the vinyl chloride resin before chlorination of the raw material is not particularly limited, but the lower limit is preferably 300 or more, more preferably 400 or more. On the other hand, the upper limit is preferably 3000 or less, more preferably 1500 or less. When the average degree of polymerization is within the above range, a high expansion ratio tends to be obtained. The average degree of polymerization of the chlorinated vinyl chloride resin is substantially the average degree of polymerization of the vinyl chloride resin before chlorination. The average degree of polymerization is measured according to JIS K6720-2.

The weight average molecular weight of the chlorinated vinyl chloride is not particularly limited, but is preferably in the range of 30,000 or more and 400,000 or less. When the weight average molecular weight is within the above range, a high expansion ratio tends to be obtained. The weight average molecular weight is evaluated by gel permeation chromatography based on polystyrene equivalent molecular weight.

The chlorine content of the chlorinated vinyl chloride resin is preferably in the range of 60% by weight or more and 75% by weight or less from the viewpoint of ensuring foamability. More preferably, it is 64% by weight or more and 70% by weight or less. The higher the chlorine content, the higher the expansion ratio tends to be obtained, but on the other hand, if the chlorine content is too high, the processability tends to be significantly impaired due to an increase in melt viscosity. The chlorine content of the chlorinated vinyl chloride resin and the vinyl chloride resin is measured in accordance with JIS K7385 B method.

(acrylic resin)
In the present invention, by using an acrylic resin in combination with a chlorinated vinyl chloride resin, it is possible to obtain expanded particles and foamed molded articles having a high expansion ratio and a high closed cell ratio. This effect is particularly outstanding in pre-foaming and foam molding under air or steam heating conditions.

Specific examples of acrylic resins include polymethyl methacrylate obtained by polymerizing methyl methacrylate, methyl methacrylate, and methacrylic acid alkyl esters in which the alkyl group has 2 to 8 carbon atoms, such as n-butyl methacrylate. , a copolymer of an acrylic acid alkyl ester with an alkyl group having 1 to 8 carbon atoms such as ethyl acrylate, and at least one monomer copolymerizable with these such as butylene, substituted styrene, acrylonitrile, etc. can give. It is preferable to use an acrylic resin whose weight average molecular weight is higher than the weight average molecular weight of the chlorinated vinyl chloride resin used, since this facilitates ensuring a high expansion ratio and a high closed cell ratio. Note that the weight average molecular weight of the acrylic resin is evaluated by gel permeation chromatography based on the molecular weight in terms of polystyrene. As the acrylic resin, for example, Kane Ace PA-40 manufactured by Kaneka Co., Ltd. can be used.

The content of the acrylic resin is not particularly limited as long as it does not impair the effects of the present invention, but it is preferably 1 to 50 parts by weight, and 5 to 50 parts by weight based on 100 parts by weight of the chlorinated vinyl chloride resin. Parts by weight are more preferred, and more than 8 parts by weight and even more preferably 30 parts by weight or less. When the amount is 1 part by weight or more, it becomes easy to obtain expanded particles and/or foamed molded products having a high expansion ratio and a high closed cell ratio, and when it is 50 parts by weight or less, expanded particles and/or foamed products with excellent flame retardant performance can be obtained. A foam molded article can be obtained.

(foaming agent)
The blowing agent used in the present invention is not particularly limited, but examples include the following blowing agents. For example, hydrocarbons such as normal butane, isobutane, normal pentane, isopentane, neopentane, cyclopentane, normal hexane, or cyclohexane, dimethyl ether, diethyl ether, methyl ethyl ether, isopropyl ether, n-butyl ether, diisopropyl ether, furan, furfural, 2 - Ethers such as methylfuran, tetrahydrofuran, tetrahydropyran, dimethyl ketone, methyl ethyl ketone, diethyl ketone, methyl n-propyl ketone, methyl-n-butyl ketone, methyl-i-butyl ketone, methyl-n-hexyl ketone, ethyl-n-propyl Ketones such as ethyl-n-butyl ketone, saturated alcohols having 1 to 4 carbon atoms such as methanol, ethanol, propyl alcohol, i-propyl alcohol, butyl alcohol, i-butyl alcohol, t-butyl alcohol, formic acid methyl ester, Carboxylic acid esters such as formic acid ethyl ester, formic acid propyl ester, formic acid butyl ester, formic acid amyl ester, propionic acid methyl ester, propionic acid ethyl ester, alkyl halides such as methyl chloride, ethyl chloride, trans-1,3,3, 3-tetrafluoropropene (trans-HFO-1234e), cis-1,3,3,3-tetrafluoropropene (cis-HFO-1234ze), 2,3,3,3-tetrafluoropropene (trans-HFO- 1234yf), trans-1-chloro-3,3,3-trifluoropropene (trans-HCFO-1233zd), cis-1-chloro-3,3,3-trifluoropropene (cis-HCFO-1233zd), etc. Physical blowing agents such as hydrofluoroolefins or chlorinated hydrofluoroolefins, inorganic blowing agents such as water, carbon dioxide, and nitrogen, and chemical blowing agents such as azo compounds and tetrazole can be used. These other blowing agents may be used alone or in combination of two or more.

As the blowing agent, it is preferable to use a physical blowing agent, and among them, a saturated hydrocarbon having 4 to 6 carbon atoms is more preferable. As the saturated hydrocarbon having 4 to 6 carbon atoms, at least pentane is preferably contained from the viewpoint of solubility and retention of the blowing agent in the resin.

It is preferable to include a ketone as a blowing agent from the viewpoint of improving the solubility of the blowing agent. For example, by using a ketone together with the saturated hydrocarbon having 4 to 6 carbon atoms, the solubility of the saturated hydrocarbon having 4 to 6 carbon atoms in the resin can be further improved.

The content of the blowing agent in the expandable chlorinated vinyl chloride resin particles of the present invention is preferably 1 to 40% by weight based on 100% by weight of the expandable chlorinated vinyl chloride resin particles. By controlling the content of the blowing agent within the predetermined range, it is possible to easily obtain expanded particles and foamed molded articles having a high expansion ratio and a high closed cell ratio. A more preferable range is 5 to 20% by weight.

(Other additives)
Flame retardants, stabilizers, processing aids, lubricants, nucleating agents, foaming aids, antistatic agents, radiant heat transfer inhibitors, solvents, and pigments/dyes, as necessary, to the extent that the effects of the present invention are not impaired. It may also contain colorants such as.

As the flame retardant, known flame retardants can be used, such as brominated flame retardants, phosphorus flame retardants, ammonium polyphosphate, intumescent flame retardants such as melamine cyanurate, aluminum hydroxide, hydroxide, etc. Examples include hydroxide compounds such as magnesium, flame retardant aids such as antimony oxide, and zinc oxide.

As the stabilizer, those conventionally used for vinyl chloride resins can be used. Examples include tin-based stabilizers, antioxidants such as phenol-based compounds, phosphorus-based compounds, and amine-based compounds, epoxy-based stabilizers, and zeolites. The amount of each stabilizer used is not particularly limited as long as it does not impair the effects of the present invention, but it is preferably 10 parts by weight or less per 100 parts by weight of the chlorinated vinyl chloride resin.

Examples of processing aids include copolymers having aromatic vinyl monomers and unsaturated nitrile monomers as structural units, such as styrene-acrylonitrile copolymers, and methyl methacrylate-butadiene-styrene polymers. Examples include impact modifiers, chlorinated polyethylene, and the like. Among these, it is preferable to contain chlorinated polyethylene from the viewpoint of improving the fluidity of the chlorinated vinyl chloride resin and improving the moldability. The amount of chlorinated polyethylene used is not particularly limited as long as it does not impair the effects of the present invention, but it is preferably 1 to 30 parts by weight per 100 parts by weight of the chlorinated vinyl chloride resin. Note that the chlorine content of chlorinated polyethylene is measured in accordance with JIS K7385 B method.

Examples of the lubricant include waxes such as ester wax and polyethylene wax, and fatty acid metal salts such as calcium stearate and zinc stearate.

Nucleating agents include inorganic compounds such as silica, calcium silicate, wollastonite, kaolin, clay, mica, zinc oxide, calcium carbonate, sodium hydrogen carbonate, zeolite, or talc.

Examples of the radiation heat transfer inhibitor include substances that have the property of reflecting, scattering, or absorbing light in the near-infrared or infrared region, such as graphite, graphene, carbon black, expanded graphite, and titanium oxide.

Other thermoplastic resins or thermosetting resins may be used in combination with the chlorinated vinyl chloride resin to the extent that the effects of the present invention are not impaired. From the viewpoint of flame retardant performance, vinyl chloride resin is preferred. Examples of the vinyl chloride resin include vinyl chloride homopolymers and other monomers copolymerizable with vinyl chloride, such as ethylene, propylene, vinyl acetate, allyl chloride, allyl glycidyl ether, acrylic ester, vinyl ether, etc. Examples include copolymers with The average degree of polymerization of the vinyl chloride resin is not particularly limited, but is preferably 300 or more and 7000 or less.

When using other resins in combination, the amount of the other resins is not particularly limited as long as it does not impair the effects of the present invention, but it is 0 to 99 parts by weight based on 100 parts by weight of the chlorinated vinyl chloride resin. preferable.

The shape of the expandable chlorinated vinyl chloride resin particles of the present invention is not particularly limited as long as the particles have a shape that allows for pre-foaming and foam molding of expandable resin particles as described below, but general granules can be used. (For example, rounded small particles such as spherical, substantially spherical, convex lens, spindle, etc.) as well as rod-shaped (cylindrical), plate-shaped, and flat particles are included. In addition, the particle weight of the expandable chlorinated vinyl chloride resin particles of the present invention is 0.5 from the viewpoint of ensuring the filling property of the foamed particles into the molding die and the moldability such as the surface beauty of the foamed molded product. The amount is preferably 10 mg/grain.

The expandable chlorinated vinyl chloride resin particles of the present invention have a true density of 1200 kg/1,200 kg/cm from the viewpoint of reducing the escape rate of the blowing agent from the expandable chlorinated vinyl chloride resin particles or further improving the expansion ratio. It is preferably at least 1300 kg/m ³ , more preferably at least 1300 kg/m ³ . The true density here can be determined by the measurement method described below.

(Method for producing expandable chlorinated vinyl chloride resin particles)
The expandable chlorinated vinyl chloride resin particles of the present invention can be obtained by known manufacturing methods, and examples thereof include the following two manufacturing methods.

The first method for producing expandable chlorinated vinyl chloride resin particles (hereinafter sometimes referred to as the "first production method") includes (A) chlorinated vinyl chloride resin, and (B) acrylic resin. The chlorinated vinyl chloride resin particles are obtained by heat-melting and mixing the resin and other additives as necessary in a known kneading machine such as an extruder, roll processing machine, or Banbury mixer, followed by granulation. There is a manufacturing method for obtaining expandable chlorinated vinyl chloride resin particles by impregnating the particles with a blowing agent in an autoclave.

The second method for producing expandable chlorinated vinyl chloride resin particles (hereinafter sometimes referred to as the "second production method") includes (A) chlorinated vinyl chloride resin, and (B) acrylic. The system resin and other additives as necessary are supplied to an extruder and melt-kneaded, and the blowing agent is dissolved and dispersed in the melt-kneaded material by the extruder or dispersion equipment after the extruder. A molten kneaded material of a chlorinated vinyl chloride resin composition containing a blowing agent is extruded into a cutter chamber filled with pressurized circulating water through an attached die having many small holes, and immediately after extrusion, a rotating cutter comes into contact with the die. In this production method, the melt-kneaded material is cut by cutting the melt-kneaded material, and is cooled and solidified by pressurized circulating water to obtain expandable chlorinated vinyl chloride resin particles.

According to the second production method, the degree to which the effects of the present invention are expressed tends to be improved, and the expandable chlorinated vinyl chloride-based particles can provide expanded chlorinated vinyl chloride particles having an excellent expansion ratio and closed cell ratio. Resin particles are obtained.

In addition, common to the first and second manufacturing methods, it is preferable that the chlorinated vinyl chloride resin and the vinyl chloride resin used in combination as necessary be sufficiently gelled. If gelation is not carried out sufficiently, the dissipation rate of the blowing agent from the resin particles may increase when formed into expandable resin particles, making it difficult for the blowing agent to contribute to foaming, resulting in high It may be difficult to obtain expanded particles and foamed molded articles having a high expansion ratio or a high closed cell ratio.

Regarding the resin temperature during resin melt kneading (mixing), the temperature should be 160°C or higher and 250°C or higher, as this may affect the decomposition of the chlorinated vinyl chloride resin, the vinyl chloride resin used together if necessary, and additives. The temperature is preferably lower than 160°C and more preferably 160°C or higher and lower than 240°C. If the resin temperature exceeds 250°C, there is a risk of decomposition of the chlorinated vinyl chloride resin, the vinyl chloride resin and additives used together if necessary, and as a result, the deterioration of the expandable chlorinated vinyl chloride resin particles may be induced. , which may lead to a decrease in foaming performance.

(Each condition of granulation process)
The conditions for the step of granulating chlorinated vinyl chloride resin particles in the first and second methods for producing expandable chlorinated vinyl chloride resin particles will be described.

In the embodiment in which the melt-kneaded product is extruded from a die, the die is not particularly limited, but for example, one having small holes with a diameter of preferably 0.3 mm to 2.0 mm, more preferably 0.4 mm to 1.5 mm is used. Can be mentioned.

Regarding an embodiment in which a sheet-like melt-kneaded material is obtained using a roll processing machine, etc., an example is in which the obtained sheet is cooled and then granulated into sheet-like chlorinated vinyl chloride resin particles using cutting equipment such as a cutter or shredder. can be mentioned. The thickness of the sheet-like chlorinated vinyl chloride resin particles at this time can be adjusted by adjusting the clearance of a roll processing machine serving as kneading equipment or by further pressing the obtained sheet.

In the second method for producing expandable chlorinated vinyl chloride resin particles, the temperature of the molten resin immediately before extrusion from the die is Tg + 20°C, where Tg is the glass transition temperature of the resin without a blowing agent. It is preferably Tg+30°C to Tg+110°C, and even more preferably Tg+40°C to Tg+90°C. In addition, as for the chlorinated vinyl chloride resin, the glass transition temperature increases as the chlorine content increases, so it is preferable to adjust the temperature appropriately according to the chlorine content of the chlorinated vinyl chloride resin to be used. If the temperature is Tg + 20°C or higher, the viscosity of the extruded molten resin will be low, pore clogging will be less likely to occur, and the pore opening ratio will not actually decrease, so the resulting expandable chlorinated vinyl chloride resin particles will be It is possible to avoid a situation where the shape becomes distorted or irregular. On the other hand, if the temperature is below Tg+110°C, the extruded molten resin will solidify easily and will be difficult to wrap around the rotary cutter, allowing stable cutting.

The cutting device for cutting the molten resin extruded into the circulating pressurized cooling water in the second method for producing expandable chlorinated vinyl chloride resin particles is not particularly limited, but for example, a rotating cutter that comes into contact with a die can be used to cut the molten resin. An example of this is a device in which the water is pulverized into spherules, and then transferred to a centrifugal dehydrator for dehydration and consolidation without foaming in pressurized circulating cooling water.

The conditions of the pressurized circulating cooling water should be adjusted depending on the resin, additives, foaming agent, and content used, but the foaming of the molten resin extruded from the die is suppressed, and the cutter can cut stably. Conditions are favorable. Specifically, the temperature condition of the pressurized circulating cooling water is preferably 40°C to 99°C, more preferably 60 to 90°C. The pressure conditions are preferably adjusted so that the expansion ratio of the resulting expandable chlorinated vinyl chloride resin particles is 1.0 to 1.2 times. The expansion ratio of the expandable chlorinated vinyl chloride resin particles is calculated by dividing the true density (kg/m ³ ) of the base resin by the true density (kg/m ³ ) of the expandable chlorinated vinyl chloride resin particles. refers to a value. Although it depends on the type of blowing agent used, the pressure conditions are preferably 0.6 to 2.0 MPa, more preferably 0.7 to 1.7 MPa, and still more preferably 0.8 to 1.5 MPa.

In the method for producing expandable chlorinated vinyl chloride resin particles of the present invention, conditions for impregnating the first expandable chlorinated vinyl chloride resin particles with a blowing agent may be the same as those commonly used. , may be set appropriately.

(Chlorinated vinyl chloride resin foam particles and manufacturing method thereof)
The expandable chlorinated vinyl chloride resin particles of the present invention are pre-foamed to a size of 2 to 110 times using a heating medium such as heated air or water vapor to form expanded chlorinated vinyl chloride resin particles, and then formed into a foamed molded product. can be used.

The steam that can be used may be saturated steam or superheated steam.

The heating temperature during foaming should be appropriately adjusted depending on the glass transition temperature and melting point of the resin, as well as the content of the foaming agent, but is preferably 90°C or higher, more preferably 100°C or higher. On the other hand, the temperature is preferably 150°C or lower, more preferably 130°C or lower, from the viewpoint of suppressing variations in expansion ratio among foamed particles and preventing shrinkage of foamed particles.

Here, the differences between the technique of obtaining a foam by the extrusion foaming method described in Patent Documents 1, 2, and 3 and the technique of obtaining a foam from expandable resin particles of the present invention will be explained in detail.

The extrusion foaming method is a technology in which the foaming agent dissolved and dispersed in the resin is expanded by releasing pressure from a high pressure state to a low pressure state while the resin is molten, and a foam is obtained. is generally carried out. On the other hand, in the method of obtaining foamed particles from foamable resin particles as in the present invention, as mentioned above, the foamable resin particles are foamed by heating them using a heating medium such as air or water vapor, and the extrusion foaming method is used. The time required for foaming tends to be extremely long. If the blowing agent dissipates from the expandable resin particles or foamed particles during the foaming process, the pressure inside the foamed particle cells will decrease and the foaming power will be greatly impaired. It is assumed that this is an issue that should be given more attention.

(B) Acrylic resin tends to have better gas permeability than (A) chlorinated vinyl chloride resin, so when (B) acrylic resin is combined with (A) chlorinated vinyl chloride resin, Since there is a possibility that the blowing agent dissipates significantly during foaming, it is difficult to think that the effects of Patent Documents 1, 2, and 3 are necessarily suitable for the foaming process of expandable particles and, furthermore, for high expansion of expandable particles.

On the other hand, the present inventors focused on using air or water vapor as a heating medium in the foaming process of expandable particles, and as a result of intensive technical studies, surprisingly, (B) acrylic resin It has been found that combining (A) chlorinated vinyl chloride resin is suitable for improving the foamability of (A) chlorinated vinyl chloride resin.

The mechanism of improved foaming properties as deduced by the present inventors will be described below. (B) Acrylic resin has excellent gas permeability, although the dissipation rate of the blowing agent contained in the expandable particles may increase when combined with (B) acrylic resin and (A) chlorinated vinyl chloride resin. It is presumed that due to the effect of the resin, air or water vapor as a heating medium enters the foamed particles during the foaming process of the expandable particles, contributing to the pressure balance within the foamed particle cells and achieving a high expansion ratio. be done. The mechanism of action of causing gas not contained in the resin to contribute to foaming cannot be easily inferred from the extrusion foaming techniques described in Patent Documents 1, 2, and 3.

In addition, in order to obtain a foam from foamable resin particles as in the present invention, air or steam is used as a heating medium to raise the temperature of the foamable resin particles from a low temperature to a high temperature as described above, and the foamed resin particles are heated to a glass state. Since foaming is carried out during the process of changing from a rubber state to a rubber state, it is assumed that the resin viscosity at the time of foaming does not necessarily match the extrusion foaming method in which foaming is performed in a completely molten rubber state. From the above points of view, it is difficult even for those skilled in the art to easily guess whether the extrusion foaming technique is applicable to foaming expandable resin particles.

(Chlorinated vinyl chloride resin foam molded product and its manufacturing method)
The obtained chlorinated vinyl chloride resin foam particles are molded (for example, in-mold molding) using a conventionally known molding machine, for example, with water vapor to produce a chlorinated vinyl chloride resin foam molded article. Depending on the shape of the mold used, it is possible to obtain complex-shaped molded products or block-shaped molded products.

(Average cell diameter)
The chlorinated vinyl chloride resin foam particles and the chlorinated vinyl chloride resin foam molded articles according to the present invention preferably have an average cell diameter of 70 to 1000 μm, more preferably 90 to 500 μm, and still more preferably 100 to 400 μm. . By having an average cell diameter within the above-mentioned range, a chlorinated vinyl chloride resin foam molded product having higher heat insulation properties can be obtained. When the average cell diameter is 70 μm or more, it tends to be easy to increase the expansion ratio, and when it is 1000 μm or less, it is possible to avoid an increase in thermal conductivity, that is, a deterioration in heat insulation performance. The average cell diameter here is determined by the measurement method described below.

(closed cell ratio)
The chlorinated vinyl chloride resin foam particles and the chlorinated vinyl chloride resin foam molded articles according to the present invention preferably have a closed cell ratio of 70% or more, more preferably 80% or more, and still more preferably 90% or more. . When the closed cell ratio is within the above range, the foamed particles are likely to undergo secondary foaming during molding, the moldability of the foamed particles is improved, and the surface properties of the resulting foamed molded product are improved. play. Further, by having the closed cell ratio within the above-mentioned range, the compressive strength and other strengths of the foamed molded product tend to be increased.

(Applications of foam molded products)
A foam molded article formed using the expandable chlorinated vinyl chloride resin particles of the present invention has a high expansion ratio and a high closed cell ratio, and has excellent flame retardant performance. Therefore, it is suitable for various uses such as building insulation materials, ceiling materials, core materials for metal sandwich panels, food container boxes, cold storage boxes, cushioning materials, agricultural and fishery boxes, bathroom insulation materials, and hot water storage tank insulation materials. be.

One embodiment of the present invention is not limited to each of the embodiments described above, and various changes can be made within the scope of the claims, and technical means disclosed in different embodiments may be combined as appropriate. The obtained embodiment is also included in the technical scope of one embodiment of the present invention.

Hereinafter, one embodiment of the present invention will be specifically described based on Examples and Comparative Examples, but the present invention is not limited thereto.
Note that the measurement methods and evaluation methods in the following Examples and Comparative Examples are as follows.

(Measurement of the amount of blowing agent contained in expandable chlorinated vinyl chloride resin particles)
The weight W ₁ (g) of the expandable chlorinated vinyl chloride resin particles was measured, heated in an oven at 150°C for 30 minutes, then cooled at room temperature in a desiccator for 30 minutes, and the weight W ₂ (g) was measured. The difference in weight before and after heating (W ₁ −W ₂ ) was defined as the blowing agent content in the expandable chlorinated vinyl chloride resin particles.
Foaming agent content (wt%) = (W ₁ - W ₂ )/W ₁ ×100

(Measurement of particle weight of chlorinated vinyl chloride resin particles and expandable chlorinated vinyl chloride resin particles)
Using an electronic balance that can measure up to 0.01 mg, the weight of 100 randomly sampled chlorinated vinyl chloride resin particles and expandable chlorinated vinyl chloride resin particles was measured, and the particle weight was calculated using the following formula. .
Particle weight (mg) = [Weight of 100 particles (mg)]/100

(True density of expandable chlorinated vinyl chloride resin particles)
Submerge expandable chlorinated vinyl chloride resin particles with a weight W (kg) into a graduated cylinder containing ethanol, calculate the volume V (m ³ ) from the rise in the liquid level in the graduated cylinder (submersion method), and calculate the following: It was calculated using the formula.
True density of expandable chlorinated vinyl chloride resin particles = W/V (kg/m ³ )

(Evaluation of foamability of foamable chlorinated vinyl chloride resin particles)
Evaluation of the minimum true density of expanded particles was carried out under the following three heating atmospheres.

<Foaming evaluation under heated air atmosphere>
Expandable chlorinated vinyl chloride resin particles were placed in an oven heated to 130°C (forced convection constant temperature dryer SOFW-600, manufactured by As One Co., Ltd.), and the heating time was varied in a heated air atmosphere at a temperature of 130°C. Foaming was performed to obtain foamed particles for each heating time. The heating time was changed at 30 second intervals such as 30 seconds, 60 seconds, and 90 seconds after the oven was put in the oven, and heating was continued until shrinkage of the foamed particles (increase in the true density of the foamed particles) due to excessive heating was confirmed. The true density of the foamed particles obtained for each heating time was measured, and the lowest density among them was taken as the minimum true density of the chlorinated vinyl chloride resin foamed particles.

<Foaming evaluation under superheated steam atmosphere>
The foamable chlorinated vinyl chloride resin particles were placed in a water oven (Healsio AX-CA300-B, manufactured by SHARP Corporation) heated to 120°C, and the heating time was varied to cause foaming in a superheated steam atmosphere at 120°C. Expanded particles were obtained for each heating time. The heating time was changed at 30 second intervals such as 30 seconds, 60 seconds, and 90 seconds after the water oven was placed, and heating was continued until shrinkage of the expanded particles (increase in the true density of the expanded particles) due to excessive heating was confirmed. The true density of the foamed particles obtained for each heating time was measured, and the lowest density among them was taken as the minimum true density of the chlorinated vinyl chloride resin foamed particles.

<Foaming evaluation under water vapor atmosphere>
The expandable chlorinated vinyl chloride resin particles were put into a pre-foaming machine (manufactured by Daikai Kogyo Co., Ltd.), 0.2 MPa of water vapor was introduced into the pre-foaming machine, and the temperature inside the pre-foaming machine was 90 to 120°C. , to obtain foamed particles. The amount of foamable chlorinated vinyl chloride resin particles charged into a pre-foaming machine was foamed under the conditions of 1500 g, 1000 g, 750 g, 600 g, 500 g, and 400 g, and the true density of the expanded particles for each input amount was measured. The lowest true density among them was defined as the minimum true density of the expanded chlorinated vinyl chloride resin particles. The input amount was reduced until shrinkage of the foamed particles (increase in the true density of the foamed particles) was confirmed.

The true density of the foamed particles is determined by submerging the foamed particles with a weight W (kg) into a graduated cylinder containing ethanol, and calculating the volume V (m ³ ) from the rise in the liquid level of the graduated cylinder (submersion method). It was calculated using the following formula.
True density of expanded particles = W/V (kg/m ³ )

(Measurement of closed cell ratio of chlorinated vinyl chloride resin foam particles and chlorinated vinyl chloride foam molded product)
Test pieces of expanded particles and foamed molded products were measured using an air pycnometer (air comparison hydrometer model 1000 manufactured by Tokyo Science Co., Ltd.) in accordance with the method described in ASTM D2856 to determine the volume of the test piece Vc (cm ³ ). ) was measured. Next, the same test piece after measurement is submerged in a graduated cylinder containing ethanol, the volume Va (cm ³ ) is determined from the rise in the liquid level in the graduated cylinder (submersion method), and the closed cell ratio (%) is calculated according to the following formula. was calculated.
Closed cell ratio (%) = (Vc/Va) x 100

(Measurement of average cell diameter of chlorinated vinyl chloride resin foam particles and chlorinated vinyl chloride foam molded product)
The centers of the chlorinated vinyl chloride resin foam particles and the chlorinated vinyl chloride foam molded articles were cut with a razor, and the cross sections were observed with an optical microscope. The number of cells existing within a 1000 μm x 1000 μm square area of the cross section was measured, and the value measured using the following formula (area average diameter) was defined as the average cell diameter. The average cell diameter of five samples of each sample was measured, and the average was taken as the standard average cell diameter.
Average cell diameter (μm) = 2×[1000 μm×1000 μm/(number of cells×π)] ^1/2 .

(Density measurement of foam molded product)
The vertical dimension X (mm), the lateral dimension Y (mm), and the thickness dimension Z (mm) of the foam molded product were measured with a caliper, and the weight W (g) of the foam molded product was measured with an electronic balance, and the following formula was obtained. I asked for it from
Density of foam molded product (kg/m ³ ) = W / (X×Y×Z)×10 ⁶

(Surface properties of foam molded product)
The surface properties of the obtained foamed molded products were evaluated using the following criteria.
◎: There are almost no gaps between the foam particles on the surface of the molded product. ○: Some gaps between the foam particles on the surface of the molded product are observed. △; There are considerable gaps between the foam particles on the surface of the molded product.

The raw materials used in Examples and Comparative Examples are shown below.
(Chlorinated vinyl chloride resin)
(A-1) Chlorinated vinyl chloride resin [manufactured by Kaneka Corporation, H716S, average degree of polymerization 600, chlorine content 67.6% by weight]
(vinyl chloride resin)
(A-2) Vinyl chloride resin [manufactured by Kaneka Corporation, average degree of polymerization 600, chlorine content 56.8% by weight]
(acrylic resin)
(B) Acrylic resin [manufactured by Kaneka Corporation, Kane Ace PA-40]
(foaming agent)
(C-1) Normal pentane [manufactured by Fuji Film Wako Pure Chemical Industries, Ltd.]
(C-2) Acetone [manufactured by Fuji Film Wako Pure Chemical Industries, Ltd.]

(Example 1)
[Preparation of chlorinated vinyl chloride resin particles]
For 100 parts by weight of chlorinated vinyl chloride resin (A-1), 5 parts by weight of acrylic resin (B), further 5 parts by weight of butyltin mercapto stabilizer, 3 parts by weight of lubricant (ester wax, polyethylene wax), 5 parts by weight of chlorinated polyethylene having a chlorine content of 35% by weight was added, and the mixture was hand blended to obtain a uniform mixture.
This blend was kneaded for 5 minutes at 195° C. using an 8-inch roll, and the resulting sheet-like composition was cut with a cutter to obtain chlorinated vinyl chloride resin particles having a particle weight of 6 mg.

[Preparation of expandable chlorinated vinyl chloride resin particles]
For 100 parts by weight of the obtained chlorinated vinyl chloride resin particles, 100 parts by weight of the blowing agent (C-1) was placed in a pressure-resistant container with a volume of 100 cc, sealed, and then heated in an oil bath at 120°C for 4 hours. The mixture was heated, the pressure container was cooled, and the expandable chlorinated vinyl chloride resin particles were taken out from the pressure container. The foaming agent content of the expandable chlorinated vinyl chloride particles was 12% by weight, and the true density was 1290 kg/m ³ .

[Preparation of expanded chlorinated vinyl chloride resin particles]
After storing the obtained expandable chlorinated vinyl chloride resin particles at 10°C for 7 days, foaming evaluation was carried out using the above-mentioned <Foaming evaluation under heated air atmosphere>. As a result, the minimum true density of the expanded particles was 52 kg/m ³ , and the closed cell ratio of the expanded particles at that time was 100%.

(Example 2)
In [Preparation of chlorinated vinyl chloride resin particles] in Example 1, the same operation as in Example 1 was performed except that the acrylic resin (B) was changed to 13 parts by weight to obtain expanded particles. The results are shown in Table 1.

(Example 3)
In [Preparation of chlorinated vinyl chloride resin particles] in Example 1, the same operation as in Example 1 was performed except that the acrylic resin (B) was changed to 20 parts by weight to obtain expanded particles. The results are shown in Table 1.

(Example 4)
In [Preparation of expanded chlorinated vinyl chloride resin particles] in Example 1, the same operation as in Example 1 was performed except that the acrylic resin (B) was changed to 30 parts by weight to obtain expanded particles. The results are shown in Table 1.

(Comparative example 1)
In [Preparation of chlorinated vinyl chloride resin particles] in Example 1, the same operation as in Example 1 was performed except that acrylic resin (B) was not added to obtain expanded particles. The results are shown in Table 1.

(Comparative example 2)
Except that in [Preparation of chlorinated vinyl chloride resin particles] in Example 1, 100 parts by weight of vinyl chloride resin (A-2) was used instead of 100 parts by weight of chlorinated vinyl chloride resin (A-1). The same operation as in Example 2 was carried out, but no foaming occurred and no foamed particles were obtained. The results are shown in Table 1.

(Example 5)
[Preparation of chlorinated vinyl chloride resin particles]
For 100 parts by weight of chlorinated vinyl chloride resin (A-1), 13 parts by weight of acrylic resin (B), further 5 parts by weight of butyltin mercapto stabilizer, 3 parts by weight of lubricant (ester wax, polyethylene wax), 5 parts by weight of chlorinated polyethylene with a chlorine content of 35% by weight was added, and this mixture was blended to obtain a uniform mixture, which was then passed through a co-intermeshing twin-screw extruder to obtain pellets having the above blending ratio.
The obtained pellets were melt-kneaded in a φ26 mm co-intermeshing twin-screw extruder at a discharge rate of 8 kg/hr, and strands were passed through a die equipped with 13 small holes with a diameter of 1.7 mm attached to the tip of the extruder. After cooling and solidifying in a water tank, the mixture was cut with a strand cutter to obtain chlorinated vinyl chloride resin particles. The particle weight of the obtained vinyl chloride resin particles was 6 mg.

[Preparation of expandable chlorinated vinyl chloride resin particles]
Into a 6 L autoclave equipped with a stirring device, 100 parts by weight of a blowing agent (C-1) was charged to 100 parts by weight of the obtained chlorinated vinyl chloride resin particles, and the autoclave was sealed. Thereafter, it was heated to 120° C. over 1 hour and 30 minutes, and then kept as it was for 24 hours.
Next, the resin particles were cooled to room temperature, and the resin particles impregnated with the foaming agent were taken out from the autoclave to obtain expandable chlorinated vinyl chloride resin particles. The foaming agent content of the expandable chlorinated vinyl chloride particles was 12% by weight, and the true density was 1280 kg/m ³ .

[Preparation of expanded chlorinated vinyl chloride resin particles]
(Evaluation of foaming under heated air atmosphere)
After storing the obtained expandable chlorinated vinyl chloride resin particles at 10°C for 7 days, foaming evaluation was carried out using the above-mentioned <Foaming evaluation under heated air atmosphere>. As a result, the minimum true density of the expanded particles was 48 kg/m ³ , and the closed cell ratio of the expanded particles at that time was 95%.

(Evaluation of foaming under superheated steam atmosphere)
After storing the obtained expandable chlorinated vinyl chloride resin particles at 10°C for 7 days, foaming evaluation was performed using the above-mentioned <Foaming evaluation under superheated steam atmosphere>. As a result, the minimum true density of the expanded particles was , 43 kg/m ³ , and the closed cell ratio of the expanded particles at that time was 86%.

(Preparation of foamed particles for molding in a steam atmosphere)
After storing the obtained expandable chlorinated vinyl chloride resin particles at 10°C for 7 days, 1500 g of expandable chlorinated vinyl chloride resin particles were put into a pre-foaming machine (manufactured by Daikai Kogyo Co., Ltd.) and the pressure was increased to 0.2 MPa. of water vapor was introduced into a pre-foaming machine and foamed at a temperature of 110° C. inside the pre-foaming machine to obtain expanded particles having a true density of 93 kg/m ³ , a closed cell ratio of 96%, and an average cell diameter of 320 μm.

[Preparation of chlorinated vinyl chloride resin foam molded product]
The foamed particles with a true density of 93 kg/m ³ obtained in the above steam atmosphere were filled into an in-mold mold of 400 mm long x 400 mm wide x 25 mm thick attached to a styrofoam molding machine, and the pressure was 0.12 MPa. After introducing water vapor to cause foaming in the mold, the mold was cooled by spraying water for 20 seconds. After holding the chlorinated vinyl chloride resin foam molding in the mold until the pressure of the chlorinated vinyl chloride resin foam molding pressing against the mold reaches 0.05 MPa (gauge pressure), the chlorinated vinyl chloride resin foaming The molded product was taken out to obtain a rectangular parallelepiped-shaped chlorinated vinyl chloride resin foam molded product. The density of the molded body was 62 kg/m ³ , the closed cell ratio was 87%, the surface property of the molded body was Δ, and the average cell diameter was 360 μm. The results and evaluation results are shown in Table 2.

(Example 6)
[Preparation of expandable chlorinated vinyl chloride resin particles]
For 100 parts by weight of chlorinated vinyl chloride resin (A-1), 13 parts by weight of acrylic resin (B), further 5 parts by weight of butyltin mercapto stabilizer, 3 parts by weight of lubricant (ester wax, polyethylene wax), After adding 5 parts by weight of chlorinated polyethylene with a chlorine content of 35% by weight and blending this mixture to obtain a uniform mixture, the mixture was melt-kneaded in a co-intermeshing twin-screw extruder to form pellets with the above blending ratio. Obtained.
The obtained pellets were melt-kneaded in a φ40 mm co-intermeshing twin-screw extruder at a feed rate of 40 kg/hr.
From the middle of the twin-screw extruder, 9 parts by weight of normal pentane (C-1) and 4 parts by weight of acetone (C-2) were injected into 100 parts by weight of the resin composition. After that, the resin passes through a continuation pipe attached to the tip of the twin-screw extruder, a single-screw extruder, a gear pump, and a diverter valve, and is cooled to a resin temperature of 170°C. It was extruded into pressurized circulating water at a temperature of 70°C and 1.3 MPa at a discharge rate of 45 kg/hr from a die having 30 small holes of .5 mm and set at 230°C. The extruded molten resin was cut into small particles using a rotating cutter in contact with a die, and transferred to a centrifugal dehydrator to obtain expandable chlorinated vinyl chloride resin particles having a particle weight of 6 mg. The foaming agent content of the expandable chlorinated vinyl chloride particles was 10% by weight, and the true density was 1330 kg/m ³ .

[Preparation of expanded chlorinated vinyl chloride resin particles]
(Evaluation of foaming under steam heating atmosphere)
After storing the obtained expandable chlorinated vinyl chloride resin particles at 10°C for 7 days, the expandable chlorinated vinyl chloride resin particles were put into a pre-expanding machine (manufactured by Daikai Kogyo Co., Ltd.) and Foaming evaluation under atmosphere> As a result, foamed particles were obtained with a minimum true density of 49 kg/m ³ , a closed cell ratio of 78%, and an average cell diameter of 400 μm. FIG. 1 shows the relationship between the input amount of expandable chlorinated vinyl chloride resin particles and the true density of the expanded particles, and FIG. 2 shows the relationship between the true density of the expanded particles and the closed cell ratio.

(Preparation of foamed particles for molding in a steam atmosphere)
After storing the obtained expandable chlorinated vinyl chloride resin particles at 10°C for 7 days, 1500 g of expandable chlorinated vinyl chloride resin particles were put into a pre-foaming machine (manufactured by Daikai Kogyo Co., Ltd.) and the pressure was increased to 0.2 MPa. of water vapor was introduced into a pre-foaming machine and foamed at a temperature inside the pre-foaming machine of 110°C to obtain expanded particles having a true density of 110 kg/m ³ , a closed cell ratio of 97%, and an average cell diameter of 350 μm.

[Preparation of chlorinated vinyl chloride resin foam molded product]
The foamed particles with a true density of 110 kg/m ³ obtained in the above water vapor atmosphere are filled into an in-mold forming mold attached to a foamed polystyrene molding machine, and 0.12 MPa of water vapor is introduced to cause in-mold foaming. After that, the mold was cooled by spraying water for 20 seconds. After holding the chlorinated vinyl chloride resin foam molding in the mold until the pressure of the chlorinated vinyl chloride resin foam molding pressing against the mold reaches 0.05 MPa (gauge pressure), the chlorinated vinyl chloride resin foaming The molded product was taken out to obtain a rectangular parallelepiped-shaped chlorinated vinyl chloride resin foam molded product. The density of the molded product was 75 kg/m ³ , the closed cell ratio was 91%, the average cell diameter was 400 μm, and the surface property of the molded product was ◎. The results and evaluation results are shown in Table 3.

Claims (16)

Contains the following (A) to (C),
(A) Chlorinated vinyl chloride resin,
(B) acrylic resin, and
(C) a foaming agent ;
1 to 50 parts by weight of the (B) acrylic resin is contained relative to 100 parts by weight of the (A) chlorinated vinyl chloride resin,
The chlorine content of the (A) chlorinated vinyl chloride resin is 60% by weight or more and 75% by weight or less,
Expandable chlorinated vinyl chloride resin particles for in-mold molding, wherein the blowing agent (C) is contained in an amount of 1 to 40% by weight based on 100% by weight of the expandable chlorinated vinyl chloride resin particles. The expandable chlorinated vinyl chloride resin particles according to claim 1 , wherein the average degree of polymerization of the (A) chlorinated vinyl chloride resin is 400 or more and 1,500 or less. The expandable chlorinated vinyl chloride resin particles according to claim 1 or 2 , wherein the acrylic resin (B) has a weight average molecular weight higher than the weight average molecular weight of the chlorinated vinyl chloride resin (A). The expandable chlorinated vinyl chloride resin particles according to any one of claims 1 to 3 , wherein the blowing agent (C) is a physical blowing agent. The expandable chlorinated vinyl chloride resin particles according to claim 4 , wherein the blowing agent (C) contains a saturated hydrocarbon having 4 to 6 carbon atoms. The expandable chlorinated vinyl chloride resin particles according to claim 5 , wherein at least one of the saturated hydrocarbons having 4 to 6 carbon atoms is pentane. The expandable chlorinated vinyl chloride resin particles according to any one of claims 1 to 6 , wherein the blowing agent (C) contains a ketone. The expandable chlorinated vinyl chloride resin particles according to any one of claims 1 to 7 , containing chlorinated polyethylene. The expandable chlorinated vinyl chloride resin particles according to any one of claims 1 to 8 , wherein the expandable chlorinated vinyl chloride resin particles have a true density of 1200 kg/m ³ or more. The expandable chlorinated vinyl chloride resin particles according to any one of claims 1 to 9 , wherein the expandable chlorinated vinyl chloride resin particles have a true density of 1300 kg/m ³ or more. Including the following steps (I) to (III),
(I) Step of producing a melt-kneaded product containing a chlorinated vinyl chloride resin, an acrylic resin, and a blowing agent (II) The melt-kneaded product is passed through a die having small holes into pressurized circulating water. Extrusion step (III) cutting the melt-kneaded product immediately after extrusion, and cooling and solidifying it with pressurized circulating water ;
The acrylic resin is contained in 1 to 50 parts by weight per 100 parts by weight of the chlorinated vinyl chloride resin,
The chlorine content of the chlorinated vinyl chloride resin is 60% by weight or more and 75% by weight or less,
A method for producing expandable chlorinated vinyl chloride resin particles for in-mold molding, wherein the blowing agent is contained in an amount of 1 to 40% by weight based on 100% by weight of the expandable chlorinated vinyl chloride resin particles. Chlorinated vinyl chloride resin particles obtained by pre-foaming the expandable chlorinated vinyl chloride resin particles according to any one of claims 1 to 10 or the expandable chlorinated vinyl chloride resin particles obtained in claim 11 . Resin foam particles. The expanded chlorinated vinyl chloride resin particles according to claim 12 , having a closed cell ratio of 70% or more. A chlorinated vinyl chloride resin foam molded article obtained by foam molding the chlorinated vinyl chloride resin foam particles according to claim 12 or 13 . The chlorinated vinyl chloride resin foam molded article according to claim 14 , having a closed cell ratio of 70% or more. A method for producing a chlorinated vinyl chloride resin foam molded article, comprising the step of molding the chlorinated vinyl chloride resin foam particles according to claim 12 or 13 .