JP2001288294A - Method for producing expanded polyester resin particles - Google Patents

Abstract

(57) [Problem] To obtain a molded article of expanded polyester resin particles having a relatively low density, a molding shrinkage ratio is relatively small,
Provided is a method for producing foamed particles which is a raw material for obtaining a foamed molded article having good curing recovery properties. SOLUTION: In a closed container, a polyester resin particle containing an aliphatic ester bond in the main chain in an amount of 60 mol% or more in a dispersion medium is heated together with an organic peroxide or together with an organic peroxide and an unsaturated compound. A step of cross-linking the particles, a step of impregnating the resin particles with a foaming agent, and a step of releasing the resin particles impregnated with the foaming agent under low pressure from the closed container to foam the resin particles. .00
In the method for producing expanded polyester-based resin particles of 8 to 0.04 g / cm ³ , the temperature at which a half-life period of one hour is given as at least a part of the organic peroxide is from the Vicat softening temperature of the resin to −25 ° C. to the Vicat softening. A method for producing expanded polyester resin particles, comprising using an organic peroxide having a temperature of + 10 ° C.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for producing expanded polyester resin particles having biodegradability and excellent practicality.

[0002]

2. Description of the Related Art In recent years, plastic foams having characteristics such as light weight, elasticity, cushioning property, heat insulation property, moldability and the like have been mainly used for packaging containers, cushioning materials and the like. Due to the difficulty in treating plastic waste, the possibility of polluting the natural environment is increasing, and this has become a major social problem. For this purpose, biodegradable plastics that are decomposed in the natural environment have been studied, and some aliphatic polyesters and alloys of starch and polyvinyl alcohol have been commercialized. However, most of these biodegradable resin foams are extruded foams, and there are few foamed molded articles. The foamed particles can be molded into a desired shape by putting them into a mold, and have advantages such as light weight, cushioning properties, and heat insulating properties. Was desired.

[0003] After foaming resin particles by impregnating aliphatic polyester particles with propane and pentane as a blowing agent, the particles are heated with steam to obtain pre-expanded particles, which are then heated and molded in a mold. A method for obtaining a molded article is disclosed in Japanese Patent Application Laid-Open No. 6-248106 (Japanese Patent No.
As described above, when the pre-expanded particles are molded in a mold, an expanded molded article can be obtained, but the molding shrinkage is large and lacks practicality. Also,
The present inventors have succeeded in obtaining a molded article having a small molding shrinkage by forming a molded article having a gel fraction of at least 5% as described in JP-A-10-324766. However, when trying to obtain a relatively low-density foamed particle molded article having a bulk density of 0.04 g / cm ³ or less, the cured recovery property of the foamed particle molded article is poor, the curing time is lengthened, and the temperature of the atmosphere is adjusted. If it is not performed accurately, there is a problem that the heat shrinkage of the molded body becomes 10% or more.

[0004]

The object of the present invention is to provide a molded article of a polyester resin foamed particle having a relatively low density, in order to obtain a foamed molded article having a relatively small molding shrinkage and a good curing recovery property. An object of the present invention is to provide a method for producing expanded particles as a raw material.

[0005]

Means for Solving the Problems The present inventors have made intensive studies to solve the above-mentioned problems, and as a result, have completed the present invention. That is, according to the present invention, 60 mol% of an aliphatic ester bond is contained in the main chain in a dispersion medium in a closed container.
Heating the polyester resin particles containing the above with an organic peroxide or with an organic peroxide and an unsaturated compound to crosslink the resin particles, impregnating the resin particles with a blowing agent, and impregnating the blowing agent The method for producing foamed polyester resin particles having a bulk density of 0.008 to 0.04 g / cm ³ , comprising the step of foaming the resin particles by releasing the resin particles under a low pressure from the closed container, As at least a part of the oxide, a polyester resin expanded particle characterized by using an organic peroxide having a temperature that gives a one-hour half-life of 1 hour to the Vicat softening temperature of the resin −25 ° C. to 10 ° C. A manufacturing method is provided. The temperature at which the organic peroxide gives a one-hour half-life in the present specification means that the organic peroxide is decomposed under a certain temperature condition, and the active oxygen amount of the organic peroxide becomes half of the whole. This refers to the temperature at which the time required to reach 1 hour. The half-life was measured by adjusting the concentration of the organic peroxide to 0.1 mol / l using benzene as a solvent to prepare an organic peroxide solution, and adding the organic peroxide solution to a glass. Put in a tube, replace with nitrogen and seal,
Further, a method is employed in which the organic peroxide solution is immersed in a thermostat set at a constant temperature and thermally decomposed.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION Foamed polyester resin particles having biodegradability (hereinafter, also referred to simply as foamed particles) obtained by the present invention are resins prepared using a polyester resin having biodegradability as a base resin. Manufactured by expanding particles. The polyester resin used as the base resin in the present invention is, for example, an aliphatic polyester resin, a condensed polyester resin of an aromatic dicarboxylic acid, an aliphatic dicarboxylic acid and a fatty acid diol as shown in JP-A-10-505620, and the like. At least 60 mol%, preferably 80 to 100 mol%, more preferably 90 to 100 mol% of a biodegradable aliphatic ester in the main chain.
It is contained in the ratio of mol%.

The aliphatic polyester resin includes a hydroxy acid polycondensate, a lactone ring-opening polymer, a polycondensate of a glycol component and a dicarboxylic acid component, and the like. Examples of the hydroxy acid polycondensate include polycondensates of hydroxybutyric acid, and examples of the ring-opening polymer of lactone include polycaprolactone. Examples of the polycondensate of a glycol component and a dicarboxylic acid component include 1 A polycondensate of 1,4-butanediol and succinic acid and / or adipic acid as a main component (branching by adding a branching agent such as a trifunctional or tetrafunctional polyhydric alcohol component as a third component thereto) And the like). The base resin used in the present invention also includes those obtained by increasing the molecular weight of the above-mentioned polymer via a linking agent, those obtained by blending a plurality of polymers, and dicarbonate copolymers. Examples of the linking agent include diisocyanates such as 2,4-tolylene diisocyanate, diphenylmethane diisocyanate, 1,5-naphthylene diisocyanate, xylylene diisocyanate, hydrogenated xylylene diisocyanate, hexamethylene diisocyanate, and isophorone diisocyanate; diphenyl carbonate, ditolyl And aryl carbonates such as carbonate, bis (chlorophenyl) carbonate and m-cresyl carbonate. In the present invention, in particular, a polycondensate of one or two or more glycol components having 4 or less carbon atoms and one or two or more aliphatic dicarboxylic acid components having 4 or less carbon atoms is used as the base resin. It is preferably used. In addition, other resins or rubber components can be mixed with the base resin as long as the object and effects of the present invention are not impaired.

In order to preferably produce the expanded particles of the present invention, first, base resin particles are prepared. The particles can be produced by a conventionally known method.For example, after the base resin is melt-kneaded in an extruder, extruded into strands, cooled, and then cut into appropriate lengths or the strands are appropriately lengthened. And then cooling it. The weight of each base resin particle is 0.05 to 10 mg, preferably 1 to 8 mg. If the particle weight exceeds the above range, it becomes difficult to impregnate the organic peroxide, unsaturated compound or blowing agent into the inside thereof, which adversely affects the production of expanded particles. On the other hand, if it is smaller than the above range, the production of the resin particles becomes difficult. When the base resin has hygroscopicity, it is preferable to dry the base resin in advance. For example, the moisture content is adjusted using a dehumidifying hopper dryer. The water content of the base resin before being put into the extruder is 10
It is preferably at most 00 ppm. If the water content of the base resin exceeds 1000 ppm, air bubbles may be mixed into the base resin particles for foaming, or the MFR of the base resin may become extremely large when melt-kneaded by an extruder.
The extrusion temperature conditions are preferably set so that the MFR of the base resin does not become extremely large. Further, the extrusion can be carried out while removing water with a vacuum pump using a vented extruder. . In addition, as a suitable method for making the water content 1000 ppm or less,
A method in which the base resin is dried for 3 hours or more under a temperature condition of a Vicat softening temperature of −20 ° C. or less and a Vicat softening temperature of −50 ° C. or more. The storage of the resin particles until the crosslinking step and the foaming step is preferably performed under the conditions of 5 to 25 ° C. and a relative humidity of 50% or less, and the resin particles are used in the crosslinking step and the foaming step as soon as possible. It is preferable to prevent hydrolysis of the resin particles. The Vicat softening temperature in the present specification is a value obtained by a test load A method in a test according to JIS K7206 under a heating rate condition of 50 ° C./hr. The material resin is compression-molded at 180 ° C. for 5 minutes, and then quenched to use a test piece having a thickness of 3 mm.

The base resin may be colored by adding, for example, a coloring pigment or dye such as black, gray, brown, or green. If colored resin particles obtained from a colored base resin are used, colored foamed particles and molded articles can be obtained. Examples of the coloring agent include organic and inorganic pigments and dyes. As such pigments and dyes, various conventionally known pigments and dyes can be used.
In addition, an inorganic substance such as talc, calcium carbonate, borax, zinc borate, and aluminum hydroxide can be added to the base resin in advance as a cell regulator. When adding an additive such as a coloring pigment, a dye or an inorganic substance to the base resin, the additive can be kneaded into the base resin as it is, but usually, a master batch of the additive is used in consideration of dispersibility and the like. It is preferable to make it and knead it with the base resin. The amount of the coloring pigment or dye added depends on the color of the coloring, but it is usually preferably 0.001 to 5 parts by weight based on 100 parts by weight of the base resin. By adding an inorganic substance to the base resin, an effect of improving the expansion ratio can be obtained. On the other hand, assuming that the foam molded article is discarded after use, it is not preferable to add the pigment and the cell regulator at a high concentration.

In the present invention, the base resin particles are
This is crosslinked. Crosslinking of the base resin particles in this case,
It can be carried out by dispersing the base resin particles in a dispersion medium in a closed container, adding a crosslinking agent and, if necessary, a crosslinking aid having an unsaturated bond, and heating. Any dispersion medium may be used as long as it does not dissolve the base resin particles. Such things include, for example,
Water, ethylene glycol, methanol, ethanol and the like can be mentioned, but usually water is used. When the base resin particles are dispersed in a dispersion medium and heated, an anti-fusing agent can be used to prevent the resin particles from fusing to each other. As the anti-fusing agent, any inorganic or organic one can be used as long as it does not dissolve in the dispersion medium and does not melt by heating. In general, an inorganic one is preferable. As the inorganic anti-fusing agent, powders of tricalcium phosphate, kaolin, talc, mica, aluminum oxide, titanium oxide, aluminum hydroxide and the like are suitable.
Further, as a dispersing aid, an anionic surfactant such as sodium dodecylbenzenesulfonate and sodium oleate can be suitably used. In the anti-fusing agent, the average particle size is preferably from 0.001 to 100 μm, particularly preferably from 0.001 to 30 μm. Usually, the addition amount of the anti-fusing agent is preferably 0.01 to 10 parts by weight based on 100 parts by weight of the base resin particles. The surfactant is usually added in an amount of 0.001 to 100 parts by weight of the resin particles.
It is preferable to add up to 5 parts by weight.

Examples of the crosslinking agent include conventionally known organic peroxides, for example, diacyl peroxides such as lauroyl peroxide, stearoyl peroxide and benzoyl peroxide, and bis (4-t-butylcyclohexyl) peroxydicarbonate. And peroxydicarbonates such as diisopropylpropyl peroxydicarbonate, and peroxyesters such as t-butylperoxyisobutyrate. In the case of the present invention, the temperature at which a half-life of 1 hour is particularly given to the substrate Vicat softening temperature of resin
It is preferable to use one having a temperature of 25 ° C. to Vicat softening temperature + 10 ° C. When an organic peroxide having a decomposition temperature that is too high is used, when the base resin particles are heated in water, the heating temperature increases and the heating time also increases, so that the base resin may be hydrolyzed. Is not preferred. In addition, even if an organic peroxide having a decomposition temperature that is too low is used, crosslinking is difficult to proceed, so that the productivity of expanded particles is poor,
The hydrolysis of the base resin may also proceed. In the present invention, a crosslinking agent having the following benzoyl peroxide structure, such as benzoyl peroxide, is particularly desirable.

Embedded image R is a hydrogen atom, a methyl group or an ethyl group. The organic peroxide used as a cross-linking agent in the present invention has a temperature at which at least a part thereof has a half-life of 1 hour, as described above, the Vicat softening temperature of the base resin. A temperature in the range of not less than 25 ° C lower than the temperature and not more than 10 ° C higher than the Vicat softening temperature [(T-25) ° C to (T + 10) ° C,
T: Vicat softening temperature of base resin], preferably (T-
25) It contains an organic peroxide at a temperature of from (C) to (T-5) C. The proportion of this specific organic peroxide is 50 to 100%, preferably 70 to 100%, of all the organic peroxides.

In the present invention, in connection with the use of the organic peroxide, it is preferable to use an unsaturated compound having at least one unsaturated bond in the molecule as a crosslinking aid for increasing the amount of chloroform insoluble. The unsaturated bond in this case includes a triple bond in addition to a double bond. A divinyl compound such as divinylbenzene;
Acrylic acid, methacrylic acid; acrylates such as methyl acrylate and ethyl acrylate; methacrylates such as methyl methacrylate and ethyl methacrylate; styrene; vinyl acetate; ethylene glycol diacrylate, polyethylene glycol diacrylate, trimethylol bromide Pan triacrylate, tetramethylol methane triacrylate, tetramethylol methane tetraacrylate, ethylene glycol dimethacrylate,
Acrylic or methacrylate compounds such as trimethylolpropane trimethacrylate and allyl methacrylate; allyl esters of cyanuric acid or isocyanuric acid such as triallyl cyanurate and triallyl isocyanurate; triallyl trimellitate, triallyl trimesate Ester, pyromellitic acid triallyl ester, benzophenone tetracarboxylic acid triallyl ester, diallyl oxalate, succulent diallyl,
Allyl esters of carboxylic acids such as diallyl adipate;
Maleimide compounds such as N-phenylmaleimide and N, N'-m-phenylenebismaleimide; polymers having a double bond such as 1,2-polybutadiene; diprobagil phthalate, diprovagyl isophthalate, tribuvagyl trimesate, diprovagyl itaconate And diprovagyl maleate. In the present invention, a combination of an organic peroxide and a divinyl compound or a methacrylate, particularly a combination of benzoyl peroxide and divinylbenzene or methyl methacrylate is preferred.

The ratio of the organic peroxide used as the crosslinking agent is 0.01 to 10 per 100 parts by weight of the base resin particles.
Parts by weight, preferably 0.1 to 5 parts by weight. In addition, the proportion of the unsaturated compound used as a crosslinking aid,
The ratio is 0.001 to 10 parts by weight, preferably 0.01 to 2 parts by weight, per 100 parts by weight of the base resin particles. When the base resin particles are heated and crosslinked in a dispersion medium in the presence of a crosslinking agent, the heating temperature (hereinafter, also referred to as the crosslinking temperature)
Although it is difficult to determine uniquely according to the type of the base resin, etc., it is generally a temperature not lower than the temperature at which the one-hour half-life of the organic peroxide is given, and the upper limit is the base resin. Is 10 ° C. higher than the Vicat softening temperature of The base resin particles are cross-linked by heating in the presence of a cross-linking agent in the dispersion medium. However, performing the heating for a long time promotes the hydrolysis of the base resin and also lowers the productivity. Therefore, the crosslinking time for heating within the above crosslinking temperature range is less than 90 minutes, more preferably 60 to 80. Minutes. Further, in the present invention, it is preferable to adopt an impregnation step of impregnating the resin particles with an organic peroxide or an organic peroxide and an unsaturated compound at a temperature lower than the crosslinking temperature prior to the crosslinking step. The impregnation step is preferably performed at a temperature not higher than the temperature at which one hour half-life of the organic peroxide is given, and the impregnation time varies depending on the weight of the resin particles.
0 minutes, preferably 10 to 90 minutes. Further, for example,
Polyester whose base resin particles are composed of a 1,4-butanediol component and a succinic acid component (Vicat softening temperature: 10
9 [deg.] C.), when the organic peroxide is benzoyl peroxide, the impregnating step is performed at a temperature of not less than 60 [deg.] C. and not more than -8 [deg.] C. which gives a one hour half-life of the organic peroxide.
It is preferable to include a step of impregnating the resin particles with an organic peroxide or the like for minutes. Also in the impregnation step, holding for a long time is not preferable because the impregnation property is improved, but the hydrolysis of the base resin may proceed. In addition, if the impregnation time is short, the gel fraction inside the expanded particles will be low. When the base resin particles are reacted with a crosslinking agent and, if necessary, a crosslinking aid in a closed container, it is preferable to lower the oxygen concentration in the upper gas phase space in the closed container. The preferred oxygen concentration is 5% by volume or less, more preferably 0.5% by volume or less. As a method of lowering the oxygen concentration, a method of purging with an inorganic gas, for example, a nitrogen gas, an argon gas, water vapor, or the like can be given. Further, as a dispersion medium to be used, the dissolved oxygen concentration is 9.5 mg / l or less, and further 8.5.
It is preferred to be less than mg / l.

Next, in the present invention, the resin particles are foamed. In this case, the method of foaming the resin particles is to disperse the resin particles in a dispersion medium in the presence of a foaming agent in a closed container, and heat the contents to soften the resin particles and expand the resin particles. Impregnating agent, then open one end of the container, and simultaneously hold the particles and the dispersion medium in the container at a pressure equal to or higher than the vapor pressure of the foaming agent, in an atmosphere at a lower pressure than in the container (usually under atmospheric pressure). A foaming method in which the foam is released to form a foam is preferably used. In the present invention, the resin particles cross-linked in the above-mentioned cross-linking step are foamed in a foaming step. In this case, a crosslinking agent and, if necessary, a crosslinking aid are added, and the resin particles are impregnated with a crosslinking agent or the like and heated to a crosslinking temperature to terminate the crosslinking reaction. A method of impregnating a foaming agent and foaming as described above, a crosslinking agent, a crosslinking aid is added at the same time as the addition of a foaming agent, and the resin particles are impregnated with a crosslinking agent, a foaming agent, etc., and crosslinked. After the crosslinking reaction is completed by heating to a temperature, foaming is performed as described above, or a crosslinking agent, if necessary, a crosslinking aid is added, and the resin particles are impregnated with a crosslinking agent or the like, and then heated to a crosslinking temperature. In addition, a foaming agent is added at the same time as heating, and a crosslinking reaction and impregnation of the foaming agent are performed simultaneously, and after the completion of the crosslinking reaction, a method of foaming as described above can be employed. The cross-linking step (including the step of impregnating a cross-linking agent, etc.) and the step of impregnating the blowing agent are simultaneously performed in parallel, thereby improving the productivity by shortening the production cycle and suppressing the hydrolysis of the base resin. effective. And, in the above three crosslinking and foaming steps,
The latter method is that the crosslinking reaction proceeds stably,
This is a preferable method because the manufacturing cycle is shortened. The resin particles are impregnated with a crosslinking agent, a crosslinking aid or a foaming agent at a certain crosslinking agent impregnation temperature and at a certain foaming agent impregnation temperature for several minutes to several tens of minutes (crosslinking agent or crosslinking aid). Is preferably 5 to 55 minutes, and the impregnation holding time of the foaming agent is preferably 10 to 80 minutes.) The time from the start of the dispersion of the resin particles in the dispersion medium to the end of the foaming step is preferably 200 minutes or less. Furthermore, the Vicat softening temperature of the base resin is -40 to + 5 ° C.
It is preferable that the time of the lower state is 150 minutes or less. In the step of foaming the resin, the step of obtaining foamed particles while releasing the resin particles together with the dispersion medium from the closed container is preferably 30 minutes or less. It is preferable that these factors relating to time are controlled strictly so as to perform crosslinking and foaming on a relatively large scale such as a batch type reactor of 1 m ³ or more.

As the physical blowing agent used for obtaining the expanded particles, conventionally known physical blowing agents, for example, propane, butane, hexane, cyclobutane, cyclohexane, trichlorofluoromethane, dichlorodifluoromethane, chlorofluoromethane, trifluoromethane, 1,1,1,2-tetrafluoroethane, 1-chloro-1,1-difluoroethane, 1,1-difluoroethane, 1-chloro-1,2,2
A volatile foaming agent such as 2,2-tetrafluoroethane or an inorganic gas-based foaming agent such as nitrogen, carbon dioxide, argon, or air is used. Agents are preferred, especially nitrogen, carbon dioxide and air.

In the above foaming method, the physical foaming agent
(Excluding nitrogen and air) used amount is 100 weight resin particles
2 to 50 parts by weight per part by weight, evolving nitrogen or air
When used as a foaming agent, the amount used is 20-60 kg
f / cm^TwoPress-fit into a sealed container so that the pressure is in the range of G
do it. The amount of these foaming agents depends on the desired foaming
It is appropriately selected from the relationship between the bulk density of the particles and the foaming temperature.
Further, the heating temperature of the resin particles is determined by including the blowing agent in the particles.
Any temperature that is suitable for immersion can be used.
Vicat softening temperature ± 20 ° C is employed. Good foaming temperature
The preferred range is the Vicat softening temperature of the base resin −30 ° C.
Cutting softening temperature + 30 ° C, more preferably Vicat softening
-30 ° C to Vicat softening temperature + 20 ° C. Special
The foaming temperature should be lower than the Vicat softening temperature of the base resin -10 ° C
To prevent blocking of foam particles, independent
It is possible to obtain effects such as a reduction in the bubble rate. Departure
In the light, the range of the bulk density of the expanded particles is 0.008 to
0.04g / cm ^ThreeAnd preferably 0.008 to
0.025g / cm^ThreeIt is. For example, foam particle bulk density
Is 0.025 g / cm^ThreeA place to produce the following expanded particles
First, the bulk density is 0.03-0.12 g / cm^Three, Preferred
0.03 to 0.07 g / cm^ThreePre-expanded particles
After performing multi-stage foaming such as two-stage foaming,
0.025g / cm^ThreeClosed cells than you get
It is preferable from the viewpoint that foamed particles having a high ratio can be obtained. In addition,
Bulk density Bd (g / cm) of expanded particles in the present invention^Three)
Is stored in an empty measuring cylinder at 23 ° C and 50% relative humidity.
500 or more foams left for 24 hours under pressure
Volume V indicated by the graduated cylinder scale when particles are loaded
(Cm^Three) Total of expanded particles put in measuring cylinder
It was obtained by dividing the weight W (g) (Bd = W
/ V).

In the multistage foaming method of the present invention, foamed particles having a bulk density of 0.03 to 0.12 g / cm ³ , preferably 0.03 to 0.07 g / cm ³ are added to air,
An inorganic gas such as nitrogen or carbon dioxide, or an organic gas such as an aliphatic hydrocarbon such as butane, propane, or pentane, or a halogenated hydrocarbon is injected into each bubble in the foamed particles. ７7 kg / cm ² G), and a method of further expanding and foaming with a heating medium such as steam in a closed container. Of these, inexpensive air and inorganic gases such as carbon dioxide are preferably used as the internal pressure imparting gas. By this method, the expanded particles have a bulk density of 0.1.
008 to 0.04 g / cm ³ , preferably 0.008 to 0.04 g / cm ³
It is foamed to 0.025 g / cm ³ . When heating the foamed particles to which the internal pressure has been applied, steam is usually used as a heating medium to be used, but heating can also be performed by a heating medium in which compressed air and steam are mixed. By using such a mixed medium, there is an effect that the melting of the cell membrane of the expanded particles can be prevented, and a decrease in the closed cell ratio due to multistage expansion can be prevented. Further, after introducing the expanded particles subjected to the internal pressure into a closed container, by introducing a heating medium, the expansion ratio of the expanded particles is improved,
In particular, after reducing the pressure in the sealed container or by introducing the heating medium while reducing the pressure, a further improvement in the magnification can be obtained. The temperature of the heating medium in the case of multi-stage foaming is from the Vicat softening temperature of the base resin −30 ° C. to the Vicat conversion temperature −5
° C, preferably from Vicat softening temperature -25 ° C to Vicat softening temperature -10 ° C. If the temperature is higher than this value, the closed cell ratio of the foamed particles may be reduced, or the foamed particles may be fused together in the closed container when the foamed particles are obtained. The expanded particles of the present invention have a gel fraction (N) of the expanded particles.
Is at least 20%, preferably at least 30%, more preferably at least 40%. Incidentally, the upper limit of N is approximately 80%. The gel fraction of the foamed particles can be adjusted by the crosslinking conditions and the like when crosslinking the base resin particles in the dispersion medium in the presence of the crosslinking agent. Even in expanded particles,
It is preferable to avoid storage under conditions that promote hydrolysis, such as under high temperature and high humidity. The gel fraction is measured as follows. In a 150 ml flask, about 1 g of the foamed particles or the foamed particle molded product and 100 ml of chloroform were put, and the mixture was heated and refluxed at atmospheric pressure for 10 hours. And filtration. The obtained filtered product on the wire mesh is dried in an oven at 80 ° C. under a condition of 30 to 40 torr for 8 hours. The weight W1 of the dried product obtained at this time is measured. The weight ratio (W1 / W2 × 100%) of the weight W1 to the crosslinked resin particles W2 is defined as a gel fraction.

To produce a foamed molded article using the foamed particles of the present invention, the foamed particles are placed in a mold and heated. Due to this heating, the foamed particles fuse with each other to give an integrated foam molded article. In this case, a conventional mold is used. Also, as the heating means,
Usually, steam heating is used, and the heating temperature may be a temperature at which the surface of the foamed particles is melted. Further, in the same manner as in the pretreatment of the foamed particles when performing multistage foaming on the foamed particles to be filled in the mold, the moldability and the recoverability are improved by applying an internal pressure in advance with an inorganic gas such as air or the like in advance. . Usually 0-2
An internal pressure is applied within the range of kgf / cm ² G.

The shape of the foamed particle molded product according to the present invention is not particularly limited, and the shape may be, for example, various shapes such as a container shape, a plate shape, a cylindrical shape, a column shape, a sheet shape, and a block shape. it can.

[0020]

Next, the present invention will be described in more detail with reference to examples.

Example 1 Aliphatic polyester resin (Bionore # 1001) containing 1,4-butanediol and succinic acid as main components (manufactured by Showa Polymer Co., Ltd., melting point 112 ° C., Vicat softening temperature 109)
C., MFR (190.degree. C.) 1.5 g / 10 min) was dried with a hopper drier to a water content of 300 ppm, and a phthalocyanine green pigment was melt-kneaded with an extruder and immediately after being extruded into a strand. Quenched through a water bath. Then, this strand was cut to obtain resin particles of about 1.7 mm in diameter, about 1.9 mm in length, and about 5 mg per piece. The phthalocyanine green pigment was added as a master batch, and the added amount was 20%.
ppm was added. The resin particles obtained by the above method were stored under the conditions of a relative humidity of 50% and a temperature of 23 ° C. Next, 100 parts by weight of the resin particles, 300 parts of water
Parts by weight, aluminum oxide 0.5 parts by weight, sodium dodecylbenzenesulfone brewed sodium 0.004 parts by weight, Niper FF (benzoyl peroxide purity 50% product: NOF Corporation)
1.5 parts by weight of DVB-570 (57% divinylbenzene purity: manufactured by Nippon Steel Chemical Co., Ltd.)
A 1 liter autoclave was charged, and nitrogen gas was introduced for 5 minutes to remove oxygen in the autoclave. Then, with stirring, the temperature was raised to 75 ° C. at a rate of 1.7 ° C./min and maintained at the same temperature for 20 minutes, and then heated to 105 ° C. at a rate of 1.7 ° C./min. The gas was injected until the autoclave pressure reached 40 kgf / cm ² G, and the mixture was held at the same temperature for 45 minutes to impregnate the resin particles with a foaming agent while performing a crosslinking reaction. Is cooled at a temperature lowering rate of 1.7 ° C./min., And one end of the autoclave is opened at the same temperature for 5 minutes and further at the same temperature for 5 minutes, and nitrogen gas is introduced into the autoclave to maintain the pressure inside the autoclave. While the contents were released under atmospheric pressure, the crosslinked resin particles were foamed. The obtained foamed particles were stored under the conditions of a relative humidity of 50% and a temperature of 23 ° C. Next, the obtained foamed particles were pressurized with air in a closed container to give an internal pressure (1) as shown in Table 2. afterwards,
After filling the closed container with the foamed particles, the pressure in the container was reduced to the pressure shown in Table 2, and the container was heated with a medium in which steam and compressed air were mixed to obtain expanded foamed particles. The obtained foamed particles were stored under the conditions of a relative humidity of 50% and a temperature of 23 ° C. Table 2 shows the bulk density of the expanded particles. Fill the obtained foamed particles in a closed container,
After pressurizing with air to give the internal pressure shown in Table 2, 250
The mold was filled in a mold having a size of 300 mm x 60 mm, and was heated and formed with steam at the temperature shown in Table 2. The obtained molded body was cured at 40 ° C. under atmospheric pressure for 15 hours, and then left at normal temperature and normal pressure for 24 hours. Table 2 shows the density and shrinkage of the obtained foamed molded article.
Shown in

Example 2 The cross-linking aid was methyl methacrylate (Kanto Chemical Co., Ltd .: purity: 99% or more), and the amount added was 0.1 part by weight.
Expanded particles were obtained in the same manner as in Example 1 except that the temperature conditions were as shown in Table 1. Subsequently, expanded particles were further expanded and foamed under the conditions shown in Table 2 in the same manner as in Example 1. Next, it was molded in the same manner as in Example 1. The obtained molded body was cured at 40 ° C. under atmospheric pressure for 15 hours, and then cured at normal temperature and normal pressure for 24 hours.
Left for hours. Table 2 shows the density and shrinkage ratio of the obtained foamed molded article.

Example 3 Expanded particles were obtained in the same manner as in Example 2 except that the temperature conditions were as shown in Table 1. Subsequently, expanded particles were further expanded and foamed under the conditions shown in Table 2 in the same manner as in Example 1. Next, it was molded in the same manner as in Example 1. The obtained molded body was cured at 40 ° C. under atmospheric pressure for 15 hours, and then cured at normal temperature and normal pressure for 24 hours.
Left for hours. Table 2 shows the density and shrinkage ratio of the obtained foamed molded article.

Example 4 The weight per resin particle was about 3 mg, and the temperature was increased to 1.7 ° C./min up to the temperature shown in the cross-linking and foaming agent impregnation holding conditions without performing the impregnation and holding of the peroxide and the auxiliary agent. The foamed particles were obtained in the same manner as in Example 2 except that the resin particles were impregnated with a peroxide and an auxiliary by raising the temperature. Next, molding was performed in the same manner as in Example 1. The obtained molded body is 1
After curing for 5 hours, it was left at normal temperature and normal pressure for 24 hours.

COMPARATIVE EXAMPLE 1 The crosslinking agent was perloyl TCP (bis (4-tert-butylcyclohexyl) peroxydicarbonate, purity 90%):
Expanded particles were obtained in the same manner as in Example 1 except that 1.38 parts by weight (manufactured by Nippon Oil & Fats Co., Ltd.) was used, and the conditions for crosslinking and impregnating the foaming agent were as shown in Table 1. Then, as in Example 1, Table 2
The expanded particles were further expanded and foamed under the following conditions. Next, it was molded in the same manner as in Example 1. The obtained molded body was cured at 40 ° C. under atmospheric pressure for 15 hours, and then left at normal temperature and normal pressure for 24 hours. Density of the obtained foamed particle molded body,
Table 2 shows the shrinkage.

Comparative Example 2 Expanded particles were obtained in the same manner as in Comparative Example 1 except that the crosslinking agent was 1.26 parts by weight of Perloyl L (lauroyl peroxide purity: 98%, manufactured by NOF Corporation). Subsequently, expanded particles were further expanded and foamed under the conditions shown in Table 2 in the same manner as in Example 1. Next, it was molded in the same manner as in Example 1. The obtained molded body was cured at 40 ° C. under atmospheric pressure for 15 hours, and then left at normal temperature and normal pressure for 24 hours. Table 2 shows the density and shrinkage ratio of the obtained foamed molded article.

Comparative Example 3 The crosslinking agent was Parkmill D (dicumyl peroxide purity 9).
Expanded particles were obtained in the same manner as in Comparative Example 1 except that 0.86 parts by weight (8%: manufactured by NOF Corporation) was used. Subsequently, expanded particles were further expanded and foamed under the conditions shown in Table 2 in the same manner as in Example 1. Next, it was molded in the same manner as in Example 1.
The obtained molded body was cured at 40 ° C. under atmospheric pressure for 15 hours, and then left at normal temperature and normal pressure for 24 hours. Table 2 shows the density and shrinkage ratio of the obtained foamed molded article.

The shrinkage ratios of the compacts in the above Examples and Comparative Examples were calculated as follows, and the larger of the vertical and horizontal shrinkage ratios in the plane direction was adopted.

(Equation 1) R: Shrinkage rate of molded body A: Immediately after molding, after curing under conditions of normal pressure, 40 ° C. and 15 hours, vertical or horizontal length in the plane direction at normal temperature and normal pressure B: In the plane direction of the mold with respect to A length

[0029]

[Table 1]

[0030]

[Table 2]

[0031]

According to the present invention, there are provided foamed polyester resin particles and foamed molded articles having biodegradability and excellent practicality. According to the foamed particles obtained by the production method of the present invention, since the heat-shrinkage rate of the foamed molded article obtained by filling the inside of the mold and then heat-molding is small and the curing recovery property is good, the low-density foamed particle molding is performed. The body is obtained. The foamed particle molded article of the present invention is excellent in dimensional stability, heat resistance, mechanical strength such as cushioning and compression creep, and appearance. Due to such characteristics, it is suitably used as a buffer material, a packaging material, various containers, and the like, and has a great deal of industrial significance, such as being biodegradable so that subsequent disposal is easy.

[Brief description of the drawings]

FIG. 1 is a time-temperature chart of Example 1.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Toshio 282-1 Togami-cho, Utsunomiya-shi, Tochigi Prefecture 103 B-term, F-term (reference) 3E066 AA01 BA01 CA01 DA01 KA08 MA01 3E086 AB01 AD06 AD22 BA16 BB37 BB84 BB90 DA08 4F070 AA47 AB23 AC16 AC56 AE08 AE12 GA05 GB02 GB04 4F074 AA65 AB04 BA32 BA33 BB02 BB04 BB28 CA34 CA39 CC04X CC06X CC32X CC32Y CC34Y CC46 DA02 DA33 DA34

Claims (4)

[Claims] 1. A polyester resin particle containing at least 60 mol% of an aliphatic ester bond in a main chain of a dispersion medium in a closed container in an airtight container, heated together with an organic peroxide or with an organic peroxide and an unsaturated compound. A step of cross-linking the resin particles, a step of impregnating the resin particles with a foaming agent, and a step of releasing the resin particles impregnated with the foaming agent under low pressure from the closed container to foam the resin particles, 0.00
In the method for producing expanded polyester-based resin particles of 8 to 0.04 g / cm ³ , the temperature at which a half-life period of one hour is given as at least a part of the organic peroxide is from the Vicat softening temperature of the resin to −25 ° C. to the Vicat softening. A method for producing expanded polyester resin particles, comprising using an organic peroxide having a temperature of + 10 ° C. 2. The method according to claim 1, wherein the polyester resin particles are 1,4-
Resin particles mainly composed of a polycondensate of a glycol component consisting of butanediol and a carboxylic acid component consisting of succinic acid and / or adipic acid, and having at least a part of the organic peroxide for one hour and a half life Gives a temperature of 85
The method for producing expanded polyester resin particles according to claim 1, wherein an organic peroxide having a temperature of from 115 to 115 ° C is used. 3. Prior to the step of crosslinking, an organic peroxide or an organic peroxide and an unsaturated compound are added to the resin particles at 60 ° C. or more for one hour and a half life of the organic peroxide. 3. The method for producing expanded polyester resin particles according to claim 2, further comprising a step of impregnating at a temperature within a range of -8C or lower for 10 to 70 minutes. 4. The method for producing expanded polyester resin particles according to claim 2, wherein the organic peroxide has a benzoyl peroxide structure.