JP3531922B2 - Method for producing molded article of expanded aliphatic polyester resin particles - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing expanded polyester 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 insulating property and moldability are mainly used for packaging containers, cushioning materials and the like. Since it is difficult to dispose of existing plastic waste, there is a possibility of polluting the natural environment, which has become a major social problem. For this reason, biodegradable plastics that are decomposed in the natural environment have been studied, and up to now, some of aliphatic polyesters and alloys of starch and polyvinyl alcohol have been commercialized. However, most of these biodegradable resin foams are extruded foams,
There are few foamed particle molded products. The expanded particle molded body can be molded into a desired shape and is lightweight.
A biodegradable expanded particle molded product having advantages such as buffering property and heat insulating property and having practical utility has been desired.

A method is known from JP-A-6-248106, in which a method of obtaining a molded product by making a pre-expanded particle by adding a foaming agent to an aliphatic polyester particle and then heat-molding this in a mold is known. However, according to this method, when the pre-expanded particles are molded in a mold, a foamed molded product can be obtained, but the molding shrinkage ratio is large and it is not practical.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for producing a foamed product of aliphatic polyester resin foamed particles which is biodegradable and has a small molding shrinkage.

[0005]

The present inventors have completed the present invention as a result of intensive studies to solve the above problems. That is, according to the present invention, a foamed aliphatic polyester resin foamed particle is characterized in that it has biodegradability and a foamed aliphatic polyester resin foamed particle having a gel fraction of at least 5% is heat-molded. A manufacturing method is provided.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION Expanded aliphatic polyester resin particles having a gel fraction of at least 5% (hereinafter also simply referred to as expanded particles) used as a molding material in the present invention have biodegradability. By foaming the crosslinked resin particles obtained by crosslinking the non-crosslinked aliphatic polyester-based resin particles (hereinafter also simply referred to as non-crosslinked resin particles) prepared by using the non-crosslinked aliphatic polyester-based resin having the base resin Manufactured. The non-crosslinked aliphatic polyester resin used as the base resin has a main chain containing a biodegradable aliphatic ester as a main component. The content of the aliphatic ester in the main chain is at least 60 mol%, preferably 80 to 100 mol%, more preferably 9 mol%.
It is a ratio of 0 to 100 mol%.

The aliphatic polyester resins include hydroxy acid polycondensates, lactone ring-opening polymers, and polycondensates of glycol components and dicarboxylic acid components. Examples of the hydroxy acid polycondensate include a polycondensate of hydroxybutyric acid, a ring-opening polymer of a lactone such as polycaprolactone, and a polycondensate of a glycol component and a dicarboxylic acid component. Butylene succinate and the like can be mentioned. In addition, the base resin also includes those obtained by increasing the molecular weight of the polymer through a linking agent, those obtained by blending a plurality of polymers, and carbonic acid diester 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. Examples include aryl carbonates such as carbonate, bis (chlorophenyl) carbonate, and m-cresyl carbonate. As the base resin,
In particular, it is preferable to use, as the base resin, a polycondensate of one or more glycol components having 4 or less carbon atoms and one or more aliphatic dicarboxylic acid components having 4 or less carbon atoms. . Other resins or rubber components can be mixed with the base resin as long as the object and effect of the present invention are not impaired.

The above-mentioned base resin has a melt viscosity of preferably 1 × 10 ² to 1 × 10 ⁵ Pa · s, more preferably 5 at a temperature of 190 ° C. and a shear rate of 100 sec ^−1.
× 10 ^{2 to} 5 × 10 ³ Pa · s. Its melt viscosity is 1
If it is less than × 10 ² Pa · s, the viscosity will be too low, and the closed cell content of the obtained expanded particles will be low, making it difficult to obtain a foamed molded product. On the other hand, if the melt viscosity exceeds 1 × 10 ⁵ Pa · s, the viscosity is too high, so that bubbles cannot grow when molding the foamed particles, and it is difficult to obtain a practical foamed molded product.

The melt viscosity under the conditions of a temperature of 190 ° C. and a shear rate of 100 sec ^-1 in this specification is obtained as follows. As a melt viscosity measuring device, a Revast 2100 manufactured by Cheast Co., Ltd. is used, and a molten material of a base resin is discharged from a tip nozzle attached to the device to a resin temperature of 1
It was measured by extruding under a condition of 90 ° C. and a shear rate of 100 sec ⁻¹ . In this case, the hole diameter D of the nozzle was 1.0 mm, and the ratio L / D between the nozzle length L and the nozzle hole diameter D was 10.

In order to preferably produce the expanded beads used in the present invention, first, base resin particles are prepared. These particles can be produced by a conventionally known method, for example, after melt-kneading a base resin with an extruder, extruding into a strand shape, cooling,
It can be obtained by cutting into a suitable length or by cutting the strand into a suitable length and then cooling. The weight of each base resin particle is 0.05 to 10 mg, preferably 1 to 4 mg. When the weight of the particles exceeds the above range, it becomes difficult to uniformly crosslink the inside thereof, and when the weight of the particles is less than the above range, it becomes difficult to produce the resin particles.

The base resin may be colored by adding a coloring pigment or dye such as black, gray or brown. By using colored resin particles obtained from a colored base resin, colored expanded particles and a molded product can be obtained. Further, an inorganic substance such as talc, calcium carbonate, borax, zinc borate, aluminum hydroxide or the like can be added to the base resin in advance as a cell regulator. When an additive such as a coloring pigment, a dye or an inorganic substance is added 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 taken into consideration in consideration of dispersibility and the like. It is preferable to make it and knead it with the base resin. The addition amount of the coloring pigment and the dye varies depending on the coloring color, but it is usually preferably 0.001 to 5 parts by weight with respect to 100 parts by weight of the base resin. By adding an inorganic substance to the base resin, the effect of improving the expansion ratio can be obtained.

Next, the base resin particles are crosslinked. Crosslinking of the base resin particles in this case can be carried out by dispersing the base resin particles together with the dispersion medium in a closed container, adding a crosslinking agent and, if necessary, a crosslinking aid, and heating. Any dispersion medium may be used as long as it does not dissolve the base resin particles. Examples of such substances include water, ethylene glycol, methanol, ethanol and the like, but water is usually used. When the base resin particles are dispersed in a dispersion medium and heated, a fusion preventing agent can be used to prevent the resin particles from being fused to each other. As the anti-fusing agent, any of an inorganic type and an organic type can be used as long as it does not dissolve in the dispersion medium and does not melt by heating, but an inorganic type is generally preferable. As the inorganic anti-fusing agent, powders of kaolin, talc, mica, aluminum oxide, titanium oxide, aluminum hydroxide and the like are suitable. Further, as the dispersion aid, anionic surfactants such as sodium dodecylbenzenesulfonate and sodium oleate can be preferably used. The anti-fusing agent preferably has an average particle size of 0.001 to 100 μm, and particularly preferably 0.001 to 30 μm. The amount of the anti-fusing agent added is usually 0.
01 to 10 parts by weight is preferable. Further, it is preferable to add the surfactant in an amount of usually 0.001 to 5 parts by weight with respect to 100 parts by weight of the resin particles.

As the cross-linking agent, conventionally known organic peroxides, for example, diacyl peroxides such as lauroyl peroxide, stearoyl peroxide and benzoyl peroxide, bis (4-t-butylcyclohexyl) peroxydicarbonate, Peroxydicarbonate such as diisopropyl peroxydicarbonate,
Any of peroxyesters such as t-butyl peroxyisobutyrate can be used. In the case of the present invention,
In particular, it is preferable to use a material having a temperature that gives a half-life of 1 hour lower than the melting point of the base resin. 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 becomes high and the heating time becomes long, so that the base resin may be hydrolyzed. It is not preferable because it exists.

In connection with the use of the organic peroxide, it is preferable to use a compound having at least 2 unsaturated bonds, preferably 2 to 3 unsaturated bonds, as a crosslinking aid. The unsaturated bond in this case includes a triple bond as well as a double bond. Examples of the crosslinking aid include ethylene glycol diacrylate, polyethylene glycol diacrylate, trimethylolpropane triacrylate, tetramethylolmethane triacrylate, tetramethylolmethane tetraacrylate, ethylene glycol dimethacrylate, trimethylolpropane trimethacrylate, and allyl methacrylate. Acrylate-based or methacrylate-based compounds; allyl esters of cyanuric acid or isocyanuric acid such as triallyl cyanurate, triallyl isocyanurate; trimellitic acid triallyl ester, trimesic acid triallyl ester, pyromellitic acid triallyl ester, benzophenone Tetracarboxylic acid triallyl ester, diallyl oxalate, diallyl succinate, diadipic acid Allyl esters of carboxylic acids such as Le; N- phenylmaleimide, N, N'-m- phenylene maleimide compound of bismaleimide; 1,2
Polymers having a double bond such as polybutadiene; and compounds having two or more triple bonds such as diprobagyl phthalate, diprobagyl isophthalate, triprobagyl trimesinate, diprobagyl itaconate, diprobagyl maleate, and the like. When the organic peroxide and the divinyl compound are combined, the combination of benzoyl peroxide and divinylbenzene is particularly preferable.

The proportion of the organic peroxide used as the crosslinking agent is 0.01 to 10 per 100 parts by weight of the base resin particles.
The ratio is parts by weight, preferably 0.1 to 5 parts by weight. In addition, the ratio of the unsaturated compound used as the crosslinking aid is
The amount 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 in the presence of a cross-linking agent in the dispersion medium and cross-linked, the heating temperature is difficult to uniquely determine depending on the type of the base resin, but generally, The temperature is about 60 ° C. lower than the melting point of the base resin particles or higher. For example, the base resin particles are a polyester (mp: 1) composed of a 1,4-butanediol component and a succinic acid component.
13 ° C), the heating temperature is 50 to 140 ° C, preferably 90 to 120 ° C. If necessary, the step of impregnating the organic peroxide can be adopted at a temperature lower than the heating temperature. The base resin particles are crosslinked by heating in the presence of a crosslinking agent in the dispersion medium. In the crosslinked resin particles, the gel fraction is at least 5
%, Preferably 30 to 80%, more preferably 4
It is 0 to 70%. When the gel fraction is lower than the above range, the molding shrinkage becomes large when a foamed molded product is formed using the foamed particles (pre-expanded particles) obtained from the crosslinked resin particles, and the foam molding has practical utility. You can't get a body. On the other hand, when the gel fraction is higher than the above range, the secondary foamability and fusion property of the pre-expanded particles may be deteriorated, and it may not be possible to obtain a high-quality foamed molded product. The gel fraction of the crosslinked resin particles can be adjusted by the crosslinking conditions and the like when the base resin particles are crosslinked in the dispersion medium in the presence of the crosslinking agent.

The gel fraction referred to in the specification is measured as follows. In a 150 ml flask, about 1 g of crosslinked resin particles, expanded particles or expanded particles molded product and 100 m
After adding 1 l of chloroform and heating under reflux for 8 hours under atmospheric pressure, the obtained heat-treated product is filtered using a suction filter having a 200-mesh wire net. The obtained filtered product on the wire net is dried in an oven at 80 ° C. under a vacuum condition of 760 torr for 8 hours. The dried product weight W ₁ obtained at this time is measured. This weight W ₁ of crosslinked resin particles W ₂
The gel ratio is defined as the weight ratio (W ₁ / W ₂ × 100%) to

In the above description, the method of crosslinking the base resin particles with the organic peroxide has been described, but the crosslinking is not limited to the crosslinking with the organic peroxide, and other known methods such as, for example, It can be carried out using an electron beam crosslinking method, a silane crosslinking method, or the like.

Next, in order to obtain expanded particles, the crosslinked resin particles obtained as described above are used to expand the particles. As a method for foaming the crosslinked resin particles in this case, the crosslinked resin particles are dispersed in a dispersion medium in the presence of a foaming agent in a closed container, and the contents are heated to soften the crosslinked resin particles to form the particles. Impregnate the inside with a foaming agent,
Next, open one end of the container, and while maintaining the pressure inside the container at a pressure equal to or higher than the vapor pressure of the foaming agent, simultaneously release the particles and the dispersion medium into an atmosphere at a pressure lower than that in the container (usually under atmospheric pressure) to foam. The foaming method can be preferably adopted.
In addition, as another method, after obtaining a foamable particle by impregnating a cross-linking resin particle with a foaming agent in a closed container, the method is taken out from the closed container, and the resin particle is heated and softened to foam, in advance. It is also possible to use a method in which a decomposable foaming agent is kneaded into resin particles and the resin particles are heated above the decomposition temperature of the foaming agent to foam. The expanded beads thus obtained have a crosslinked structure with the same gel fraction as the crosslinked resin particles.

The foaming agent used for obtaining the expanded beads is a conventionally known one, for example, propane, butane, hexane, cyclobutane, cyclohexane, trichlorofluoromethane, dichlorodifluoromethane, chlorofluoromethane, trifluoromethane, 1,2,2,2-tetrafluoromethane, 1-chloro-1,1-difluoroethane, 1,1-difluoroethane, 1-chloro-1,2,
Volatile foaming agents such as 2,2-tetrafluoroethane and inorganic gas-based foaming agents such as nitrogen, carbon dioxide, argon, and air are used. Among them, inexpensive inorganic gas-based foams that do not destroy the ozone layer. Agents are preferred, especially nitrogen, carbon dioxide or air.

In the foaming method, the amount of the foaming agent (excluding nitrogen and air) used is 2 to 50 parts by weight per 100 parts by weight of the crosslinked resin particles, and when nitrogen or air is used as the foaming agent, The usage is 20-60kgf
It may be press-fitted into the closed container so that the pressure range is / cm ² G. The amount of these foaming agents used is appropriately selected from the relationship between the desired bulk density of the expanded particles and the expansion temperature. Further, the heating temperature of the gelled resin particles may be a temperature suitable for impregnating the foaming agent into the particles, and the softening temperature of the crosslinked resin particles is adopted. The bulk density of the expanded beads obtained as described above is usually 0.015 to 0.6 g /
cm ³ , and the average bubble diameter is usually 0.05 to 0.
It is 5 mm. The expanded particles expand and expand by heating, and the expansion ratio thereof varies depending on the heating temperature, the content of the foaming agent, etc., but is generally 2 to 90 times, preferably 1
Expands 0 to 60 times. The expanded particles of the present invention can be used as pre-expanded particles for an expanded molded article by utilizing such characteristics. In addition to the above-described method for producing expanded particles, there is also a method in which a heat-decomposable foaming agent is present in the resin particles in advance and the expanded particles are obtained by heating the resin particles above the decomposition temperature of the expanding agent. . Also,
In the crosslinking step, after the production of non-crosslinked expanded particles, the expanded particles are crosslinked by an electron beam crosslinking method, a silane crosslinking method or the like to adjust the gel fraction to at least 5%, preferably 30 to 80%, more preferably 40 to 70%. The same effect as that obtained from the crosslinked resin particles can be expected.

In order to produce a foamed-particle molded product in the present invention, foamed aliphatic polyester resin particles having a biodegradability and a gel fraction of at least 5% are put in a mold,
Heat molding. By this heat molding, the foamed particles are fused with each other to give an integrated foamed molded body. In this case, a commonly used mold is used. Further, steam heating is usually used as the heating means, and the heating temperature may be a temperature at which the surface of the expanded beads melts.
The expanded particle molded article thus obtained has the same gel fraction as the expanded particles.

The shape of the expanded particle molded article according to the present invention is not particularly limited, and the shape may be various shapes such as a container shape, a plate shape, a cylinder shape, a column shape, a sheet shape, and a block shape. it can. The expanded particle molded article according to the present invention has a very small molding shrinkage, and the molding shrinkage is 10%.
It is preferably 5% or less. The shrinkage ratio of the foamed particle molded body is such that the gel fraction of the foamed particles is 5% or more, especially 30%.
In the above cases, a small value is shown, and in the case of such a gel fraction, since the expanded particles are excellent in heat fusion property and biodegradability, compressive strength, bending strength, tensile strength It is possible to obtain a biodegradable expanded particle molded article having excellent mechanical strength such as.

[0023]

EXAMPLES Next, the present invention will be described in more detail by way of examples.

Examples 1 to 3 Aliphatic polyester resin (Bionole # 1003) containing 1,4-butanediol and succinic acid as main components (manufactured by Showa Highpolymer Co., Ltd., melting point 113 ° C., MFR (190 ° C.) 8 g
/ 10 min, melt viscosity of 100 sec ^-1 shear rate 95
0 Pa · s) 0.2 parts by weight of aluminum hydroxide per 100 parts by weight of dry blend is melt-kneaded by an extruder and extruded into a strand, and then the strand is cut to have a diameter of 1.3 mm, Length 1.3 mm,
About 2 mg of non-crosslinked resin particles were obtained. Next, 100 parts by weight of the non-crosslinked resin particles, 300 parts by weight of water, 1.5 parts by weight of kaolin, 0.02 parts by weight of sodium dodecylbenzenesulfonate, Niper FF (benzoyl peroxide 50% purity product: NOF Corporation) 2 parts by weight of DVB-570 (divinylbenzene purity 57% product:
Nippon Steel Chemical Co., Ltd.) was charged into a 5 liter autoclave and heated to 105 ° C. with stirring, and at the same temperature, 6
After holding for 0 minutes, it was cooled to 30 ° C. to obtain crosslinked resin particles. The gel fraction of the obtained crosslinked resin particles was as shown in Table 1. Next, 100 parts by weight of crosslinked resin particles and 3 parts of water
00 parts by weight, kaolin 1 part by weight, and sodium dodecylbenzenesulfonate 0.02 parts by weight were charged into a 5 liter autoclave and heated to the softening temperature (foaming temperature) of the gelled resin particles, and the carbon dioxide gas pressure in the autoclave was adjusted to the surface. The pressure was increased up to the pressure shown in FIG. Then, one end of the autoclave was opened, and nitrogen gas was introduced into the autoclave to release the contents under atmospheric pressure while maintaining the pressure inside the autoclave to foam the crosslinked resin particles. Table 1 shows the bulk density and average cell diameter of the expanded beads. Then, the obtained expanded particles are dried and aged at 60 ° C. for 24 hours,
It was filled in a mold of 208 × 208 × 25 mm and heated at the steam pressure shown in Table 1 to be molded. The obtained molded body was aged at 60 ° C. under atmospheric pressure for 24 hours. The bulk density, shrinkage rate and biodegradability of the obtained expanded particle molded article were evaluated, and the results are shown in Table 1.

Comparative Examples 1 and 2 100 parts by weight of the non-crosslinked resin particles shown in Example 1 and 30 parts of water
0 parts by weight, 1.5 parts by weight of kaolin, and 0.02 parts by weight of sodium dodecylbenzenesulfonate were charged into a 5 liter autoclave, heated to a foaming temperature, and carbon dioxide gas was injected until the internal pressure of the autoclave was as shown in Table 1. Invaded. Then, one end of the autoclave was opened while introducing nitrogen gas into the autoclave, and the contents were discharged under atmospheric pressure to foam the resin particles. Table 1 shows the bulk density and average cell diameter of the expanded beads. Next, the obtained expanded particles are dried and aged at 60 ° C. for 24 hours to obtain 208 × 208 × 25 m.
It was filled in a mold of m and heated at the steam pressure shown in Table 1 to be molded. The obtained molded body was aged at 60 ° C. under atmospheric pressure for 24 hours. Table 1 shows the properties of the obtained expanded bead molded product.

Example 4 Aliphatic polyester resin (Bionole # 1001) having a MFR different from that shown in Example 1 containing 1,4-butanediol and succinic acid as main components (manufactured by Showa High Polymer Co., Ltd.,
Melting point 113 ° C., MFR (190 ° C.) 1.8 g / 10 mi
n, shear rate 100 sec ^-1 melt viscosity 1950 Pa
The experiment was performed in the same manner as in Example 1 except that (s) was used and the crosslinking conditions shown in Table 1 were adopted. Table 1 shows the properties of the expanded beads and the molded product obtained in this case.

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

[Equation 1] R: Mold shrinkage A: Length in the surface direction after curing at 60 ° C. for 24 hours immediately after molding B: Length in the surface direction of the mold corresponding to A. Also, the above-mentioned Examples and Comparative Examples. The biodegradability of the molded article was evaluated by the time required for reducing the weight by 50% by placing the molded article in water at 24 ° C in the presence of microorganisms, measuring the time-dependent change in the weight loss of the molded article.

Since the expanded particle molded articles of Examples 1 to 4 of the present invention have a gel fraction of 5% or more, all of them have a shrinkage rate of 5% or less, are highly practical, and are biodegradable. As for the property, the number of days for which 50% by weight reduction is 38 days or less is also good. On the other hand, the foamed particle molded products of Comparative Examples 1 and 2 each had a shrinkage ratio of more than 10% and were unsuitable as molded products. Further, in the expanded beads of Comparative Example, the expansion ratio of the bulk ratio when obtaining the expanded particles was high, and it was difficult to control the expansion ratio during the production of the expanded particles.

[0029]

[Table 1] * In Examples 1 to 4, the gel fraction of the expanded particles and the molded product was the same as the gel fraction of the crosslinked resin particles.

[0030]

INDUSTRIAL APPLICABILITY According to the present invention, it is possible to industrially advantageously produce a foamed particle molding of an aliphatic polyester resin having biodegradability and excellent in practical use. According to the method of the present invention, it is possible to obtain a foamed particle molded product which has a small heat shrinkage when heat-molded and has a good fusion property between foamed particles. The expanded particle molded product of the present invention is excellent in dimensional stability, heat resistance, cushioning property and mechanical strength, and is suitably used as a cushioning material, packaging material and the like, and since it has biodegradability, Its industrial significance is great, such as the ease of disposal.

─────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-4-23840 (JP, A) JP-A-6-248106 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) C08J 9/232

Claims (5)

(57) [Claims] 1. A method for producing a molded product of expanded aliphatic polyester resin particles, which comprises heat-molding expanded polyester resin resin particles having biodegradability and a gel fraction of at least 5%. 2. The expanded aliphatic polyester resin particles according to claim 1, wherein the base resin of the expanded expanded polyester polyester resin particles having biodegradability contains at least 60 mol% of an aliphatic ester component. Method for manufacturing molded body. 3. The method for producing a foamed aliphatic polyester resin particle according to claim 1 or 2, wherein the gel fraction of the expanded aliphatic polyester resin particle is 30 to 80%. 4. The foamed product of aliphatic polyester resin foam particles according to claim 1, 2 or 3, wherein the expanded density of the aliphatic polyester resin resin particles is 0.015 to 0.6 g / cm ^3. Method. 5. The average bubble diameter of the aliphatic polyester resin foamed particles is 0.05 to 0.5 mm.
5. The method for producing an expanded product of aliphatic polyester-based resin particles according to any one of 1.