JP4066683B2 - Foamable resin composition and cross-linked foam thereof - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a foamable resin composition that can be recycled and a crosslinked foamed product thereof.
[0002]
[Prior art]
Conventionally, polyolefin resin foams have been widely used because they are excellent in lightness, heat insulation, moldability, buffering properties, and the like. However, although the polyolefin resin foam is light, it is bulky when discarded and difficult to reuse. In particular, in the case of a cross-linked foam obtained by cross-linking a resin, even if an attempt is made to recycle the foam and its volume-reduced product, it cannot be remelted or has a high melt viscosity, so it is difficult to reuse it as a raw material. There is a drawback that recycling is virtually impossible.
[0003]
As a countermeasure against such problems of the polyolefin resin foam, a foam using a biodegradable resin that is decomposed by microorganisms or the like has been researched and developed as one alternative material. However, most of these biodegradable resin foams are so-called extruded foams that are foamed during extrusion molding. Although these extruded foams do not have a cross-linked structure, they can be recycled. However, they are poor in moldability at high temperatures and are limited in use.
[0004]
In this way, there was no idea to recycle the crosslinked foam and its volume-reduced material and use it as a raw material for the crosslinked foam.
[0005]
[Problems to be solved by the invention]
In view of the background of the prior art, the present invention is to recycle a crosslinked foam and to provide a crosslinked foam having a beautiful appearance and excellent moldability at high temperatures. More specifically, the present invention relates to a biodegradable resin crosslinked foam produced once and a volume-reduced product thereof, in which a crosslinked structure is introduced into the foam and the biodegradable resin constituting the volume-reduced product. In addition, the present invention has been completed by finding that it can be recycled as a raw material for biodegradable resin-crosslinked foams.
[0006]
[Means for Solving the Problems]
The present invention employs the following means in order to solve such problems. That is, the foamable resin composition of the present invention is Gel fraction less than 85% At least one selected from a biodegradable resin-crosslinked foam comprising polybutylene succinate and / or polybutylene succinate / adipate and a reduced volume thereof, , Pyrolytic foaming agent , A biodegradable resin comprising polybutylene succinate and / or polybutylene succinate / adipate and , Crosslinking aid The It is a blended foamable resin composition. In addition, the foam of the present invention is characterized in that the foamable resin composition is foamed after crosslinking.
[0007]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, preferred embodiments of the present invention will be specifically described.
[0008]
The biodegradable resin crosslinked foam and its volume-reduced product used in the present invention are characterized in that a crosslinked structure is introduced into the biodegradable resin constituting the foam and the volume-reduced product. . A method for introducing a crosslinked structure into the biodegradable resin is not particularly limited, and a conventionally known method may be used. For example, a method of irradiating a predetermined dose of ionizing radiation such as β-rays or electron beams, an organic peroxide Examples of the crosslinking method include a method of crosslinking using a silane compound and a method of crosslinking using a silane compound. Moreover, even if it is difficult to introduce a crosslinked structure with the biodegradable resin alone, the crosslinked structure can be introduced by using the crosslinking method in combination with the above method. As described above, the crosslinked structure in the biodegradable resin crosslinked foam used in the present invention and the volume-reduced product thereof is crosslinked by a silane compound or a crosslinking aid when the biodegradable resin itself is crosslinked. It is defined as a crosslinked structure.
[0009]
The gel fraction indicating the degree of crosslinking of the biodegradable resin crosslinked foam and its volume-reduced product used in the present invention is preferably 85% or less, and more preferably 75% or less. If the degree of cross-linking of the biodegradable resin cross-linked foam and its volume-reduced product exceeds 85%, the melt viscosity is too high, which makes it difficult to reuse.
[0010]
In addition, the gel fraction as used in the field of this invention is the value computed with the following method. That is, about 50 mg of the foam is precisely weighed and immersed in 25 ml of tetralin at 130 ° C. for 3 hours, filtered through a 200 mesh stainless steel wire mesh, and the wire mesh insoluble matter is vacuum dried. Next, the weight of this insoluble matter was precisely weighed, and the gel fraction was calculated as a percentage according to the following formula.
[0011]
Gel fraction (%) = {weight of insoluble matter (mg) / weight of weighed foam (mg)} × 100
Note that the gel fraction can be calculated for the reduced volume by the same measurement method.
[0012]
Although the resin composition of this invention contains at least 1 sort (s) chosen from the biodegradable resin crosslinked foam and its volume reduction thing, the shape is not specifically limited. The biodegradable resin crosslinked foam and its volume-reduced product are preferably finely cut. The size of the cutting is not particularly limited, but one side is preferably 0.1 mm. A chip shape of about 1 mm to 50 mm, more preferably 1 mm to 30 mm is preferable.
[0013]
As the biodegradable resin used in the present invention, and the biodegradable resin constituting the volume-reduced product thereof, Aliphatic polyesters such as polybutylene succinate, polybutylene succinate / adipate, Can be used. In addition, / of the above-mentioned symbol means copolymerization.
[0014]
The biodegradable resin crosslinked foam used in the present invention is produced by the following method. For example, after forming a foamable sheet using a resin composition comprising a biodegradable resin, a thermal decomposable foaming agent, and a crosslinking aid, the foamable sheet is irradiated with ionizing radiation, and the resin composition is applied to the resin composition. This is achieved by introducing a cross-linked structure and then heating to a temperature equal to or higher than the decomposition temperature of the foaming agent to cause foaming. Preferred specific examples thereof are shown below.
[0015]
In the present invention, the biodegradable resin can be mixed with the foaming agent and the crosslinking aid by a conventionally known mixing method. For example, mixing with a Henschel mixer, mixing with a Banbury mixer, mixing with a mixing roll, mixing with a kneading extruder, a method of immersing a biodegradable resin in a solution in which a foaming agent or a crosslinking accelerator is dissolved, etc. used. In addition, since the biodegradable resin used by this invention is easy to receive a hydrolysis under a heating, it is preferable to reduce a moisture content to 0.1 weight% or less previously with a vacuum dryer.
[0016]
Next, the mixture is preferably formed into a sheet using a single-screw extruder with a vacuum vent, a twin-screw extruder, a tandem extruder, or the like. In the case of producing a continuous sheet-like foam, it is preferably formed into a sheet by extrusion molding at a temperature lower than the decomposition temperature of the foaming agent. The melt kneading temperature during extrusion is preferably 10 ° C. or more lower than the decomposition start temperature of the foaming agent. At this time, the thickness of the sheet is preferably 0.1 mm to 50 mm. If the thickness of the sheet is less than 0.1 mm, there will be a lot of gas escape from the sheet surface during foam molding, making it difficult to form a uniform foam, and if it exceeds 50 mm, the sheet will have too high rigidity, and winding properties during continuous production, etc. May cause trouble.
[0017]
Next, crosslinking of the foamable sheet-like material described above is performed by irradiating ionizing radiation. Examples of the ionizing radiation include an electron beam from an electron beam accelerator, α from CO60 and other radioisotopes, β, γ rays, especially an electron beam from an electron beam accelerator is preferable. When a crosslinking aid is used, the irradiation amount varies depending on the type and amount of addition and the target crosslinking rate, but preferably 1 It is -300 kGy, More preferably, it is the range of 5-100 kGy.
[0018]
Thereafter, the cross-linked sheet is heat-treated at a temperature equal to or higher than the decomposition temperature of the foaming agent and foamed. For the heat treatment for foam molding, a conventionally known method may be used. For example, the heat treatment may be performed in a vertical and horizontal hot-air foaming furnace or a chemical bath foaming furnace. When using a resin that easily undergoes hydrolysis, such as aliphatic polyester, as the biodegradable resin, it is better to foam in the vertical and horizontal hot-air foaming furnaces than in the chemical bath. A foam is obtained. Further, if foaming is preheated as necessary and the resin is softened, a stable foam can be obtained with a small amount of heat.
[0019]
In the present invention, the volume of the biodegradable resin crosslinked foam can be reduced by the following method. Examples thereof include a method of defoaming and reducing the volume by compressing the foam with a mixing roll or the like, a method of extruding and reducing the volume of the foam from an extruder, and a method of reducing the volume by dissolving in a solvent. When the volume is reduced by extrusion from an extruder, a small amount of alcohol such as butanediol or ethylene glycol, an aqueous solution of sodium hydroxide, an aqueous solution of potassium hydroxide, hydrochloric acid, sulfuric acid or the like, an aqueous alkaline solution, water, etc. Since it plays the role of a plasticizer, it can be preferably used. In particular, when the biodegradable resin constituting the biodegradable resin crosslinked foam is a polyester resin, the addition of a solvent as described above causes the resin to be hydrolyzed to lower the molecular weight, thereby improving the fluidity. In addition to easier reuse, productivity can be improved, so that it can be preferably used.
[0020]
The resin composition of the present invention may be one obtained by adding a biodegradable resin to at least one selected from the above-described biodegradable resin crosslinked foam and its reduced volume, A foamable resin composition comprising a thermally decomposable foaming agent and at least one selected from a biodegradable resin crosslinked foam and a reduced volume thereof, or a biodegradable resin and a foamable resin composition, A foamable resin composition containing at least one selected from crosslinking aids, After cross-linking It can be preferably added in order to improve the moldability and surface properties at high temperatures of a crosslinked foam (hereinafter referred to as “recycled foam”) characterized by being foamed. The biodegradable resin is preferably the same resin as the biodegradable resin crosslinked foam and the volume-reduced product described above in terms of compatibility, but is not limited thereto. It is not a thing. As the biodegradable resin, the biodegradable resin listed above can be used as the biodegradable resin constituting the above-described biodegradable resin crosslinked foam and its reduced volume. Other biodegradable resins can be used, for example, cellulose esters such as cellulose acetate having biodegradability, cellulose butyrate, cellulose propionate, cellulose nitrate, cellulose sulfate, cellulose acetate butyrate, and cellulose nitrate acetate. Synthetic polymers of polypeptides such as polyglutamic acid, polyaspartic acid, polyleucine and / or natural polymers such as starch, raw starch such as corn starch, wheat starch, rice starch, acetate esterification Biodegradable trees such as starch, methyl etherified starch, processed starch such as amylose And it may be mixed within a range not to impair the melting characteristics of the resin composition of the present invention. In addition, these biodegradable resins constituting the resin composition of the present invention may be used alone or in combination of two or more.
[0021]
Moreover, you may use resin components other than biodegradable resin, if it is in the range which does not impair the biodegradability which is one of the effects of this invention. Resin components other than biodegradable resins are not particularly limited. For example, ultra-low density polyethylene, low density polyethylene, linear low density polyethylene, medium density polyethylene, high density polyethylene, ultra high molecular weight polyethylene, polypropylene, ethylene- Propylene rubber, polyvinyl acetate, polybutene and the like may be added. Naturally, components other than the above-described biodegradable resin may be contained in the biodegradable resin crosslinked foam and its reduced volume. However, in order not to impair the biodegradability which is one of the effects of the present invention, the ratio of the resin component other than the biodegradable resin to the total resin component in the resin composition is preferably 50% by weight or less, More preferably, it is 25% by weight or less.
[0022]
The foaming agent used in the present invention is a compound that is a liquid or solid compound at room temperature and decomposes or vaporizes when heated above the melting point of the biodegradable resin, as long as it does not substantially interfere with sheeting or crosslinking reaction. Although a thing can be used, the thing of the range whose decomposition temperature is 120 degreeC-270 degreeC among them is a thermal decomposition type foaming agent is preferable. Specific examples thereof include azo compounds such as azodicarbonamide and azodicarboxylic acid metal salts, hydrazine derivatives such as hydrazodicarbonamide, 4,4′-oxybis (benzenesulfonylhydrazide), and toluenesulfonylhydrazide, N, N Examples thereof include nitroso compounds such as' -dinitrosopentamethylenetetramine, semicarbazide compounds such as toluenesulfonyl semicarbazide, and bicarbonates such as sodium bicarbonate.
[0023]
In order to adjust the decomposition temperature of the foaming agent, for example, zinc oxide, zinc stearate,
Those containing a decomposition temperature adjusting agent such as urea can also be preferably used.
[0024]
In addition, these foaming agents are preferably used in the resin composition in the range of 0.1 to 40% by weight, and the mixing amount can be arbitrarily changed depending on each kind and foaming ratio.
[0025]
Examples of the crosslinking aid used in the present invention include divinylbenzene, diallylbenzene, divinylnaphthalene, divinylphenyl, divinylcarbazole, divinylpyridine, and their nucleus-substituted compounds and related homologues, ethylene glycol diacrylate, butylene glycol diacrylate. , Trifunctional glycolic acid compounds such as triethylene glycol diacrylate, 1,6-hexanediol diacrylate, tetramethylolmethane tetraacrylate, ethylene glycol dimethacrylate, butylene glycol dimethacrylate, triethylene glycol dimethacrylate, tetraethylene glycol Dimethacrylate, 1,6-hexanediol dimethacrylate, 1,9-nonanediol dimethacrylate, 1,10-decanediol Polyfunctional methacrylic acid compounds such as methacrylate, trimethylolpropane trimethacrylate, tetramethylolmethane tetramethacrylate, aliphatic and aromatic polycarboxylic acids such as divinyl phthalate, diallyl phthalate, diallyl malate, bisacryloyloxyethyl terephthalate Polyvinyl ethers and polyallyl ethers of aliphatic and aromatic polyhydric alcohols such as polyvinyl ester, polyallyl ester, polyacryloyloxyalkyl ester, polymethacryloyloxyalkyl ester, diethylene glycol divinyl ether, hydroquinone divinyl ether, bisphenol A diallyl ether, Cyanuric acid such as allyl cyanurate, triallyl isocyanurate, or isocyanuric acid ants Has two or more triple bonds such as ester, triallyl phosphate, trisacryloxyethyl phosphate, maleimide compounds such as N-phenylmaleimide, N, N′-m-phenylenebismaleimide, dipropargyl phthalate, dipropargyl maleate, etc. Polyfunctional monomers such as compounds can be used.
[0026]
Among them, a polyfunctional methacrylic acid compound is preferable from the viewpoints of easy handling and crosslinking reactivity, and particularly from the viewpoint of crosslinking reactivity, production applicability, etc., ethylene glycol dimethacrylate, 1,6-hexanediol dimethacrylate, Trimethylolpropane trimethacrylate is more preferable, and 1,6-hexanediol dimethacrylate can be particularly preferably used.
[0027]
The crosslinking aid may be used if necessary. When used, the amount of the crosslinking aid added is preferably 10% by weight or less, more preferably 6% by weight or less in the resin composition. If the addition amount of the crosslinking aid exceeds 10% by weight, the effect of addition is saturated, and this merely leads to an increase in cost, which is not preferable. These crosslinking aids are also useful for plasticization during extrusion molding.
[0028]
In addition, you may add additive components other than a foaming agent and a crosslinking adjuvant in the range which does not inhibit the effect of this invention in the resin composition used for this invention. For example, antioxidants, lubricants, heat stabilizers, pigments, flame retardants, antistatic agents, nucleating agents, plasticizers, antibacterial agents, biodegradation accelerators, foaming agent decomposition accelerators, light stabilizers, UV absorbers as additives An agent, an anti-blocking agent, a filler, a deodorant, a thickener, a foaming aid, a cell stabilizer, a metal harm preventing agent, etc. may be used alone or in combination of two or more.
[0029]
The form of the regenerated foam of the present invention is not particularly limited, but is preferably a sheet. By making it into a sheet form, not only the productivity is excellent, but also the biodegradation rate can be increased. The thickness of the recycled foam sheet is preferably 0.1 mm to 100 mm. These sheets can be easily processed to a desired thickness by once subjected to foaming and then subjected to secondary processing such as slicing and fusion processing.
[0030]
The expansion ratio of the regenerated foam of the present invention is preferably 1.5 to 50 times. If the expansion ratio is less than 1.5 times, the lightness and flexibility tend to decrease, and if the expansion ratio exceeds 50 times, the mechanical properties and moldability tend to decrease.
[0031]
The gel fraction indicating the degree of crosslinking of the regenerated foam of the present invention is preferably 10% or more. When the gel fraction is less than 10%, the secondary processability of the obtained regenerated foam tends to decrease.
[0032]
Next, the foamable resin composition of the present invention and the method for producing a crosslinked foam will be described.
[0033]
The cross-linked foam of the present invention is a foamable resin composition comprising at least one selected from a biodegradable resin cross-linked foam and a reduced volume thereof, and a thermally decomposable foaming agent, or the foamable resin. After forming a foamable sheet using a foamable resin composition containing at least one selected from a biodegradable resin and a crosslinking aid in the composition, the foamable sheet is irradiated with ionizing radiation, This is achieved by introducing a cross-linked structure into the resin composition and then heating to a temperature higher than the decomposition temperature of the foaming agent to cause foaming. Preferred specific examples thereof are shown below.
[0034]
In the present invention, the volume of the biodegradable resin crosslinked foam can be reduced by the following method. Examples thereof include a method of defoaming and reducing the volume by compressing the foam with a mixing roll or the like, a method of extruding and reducing the volume of the foam from an extruder, and a method of reducing the volume by dissolving in a solvent. When the volume is reduced by extrusion from an extruder, a small amount of alcohol such as butanediol or ethylene glycol, an aqueous solution of sodium hydroxide, an aqueous solution of potassium hydroxide, hydrochloric acid, sulfuric acid or the like, an aqueous alkaline solution, water, etc. Since it plays the role of a plasticizer, it can be preferably used. In particular, when the biodegradable resin constituting the biodegradable resin crosslinked foam is a polyester resin, the addition of a solvent as described above causes the resin to be hydrolyzed to lower the molecular weight, thereby improving the fluidity. In addition to easier reuse, productivity can be improved, so that it can be preferably used.
[0035]
In the present invention, at least one selected from the biodegradable resin cross-linked foam and its volume-reduced product, the thermally decomposable foaming agent, the biodegradable resin, the cross-linking aid and the like are mixed by a conventionally known mixing method. It can be carried out. For example, mixing with a Henschel mixer, mixing with a Banbury mixer, mixing with a mixing roll, mixing with a kneading extruder, biodegradable resin cross-linked foam and / or its volume-reducing product and biodegradation in a solution in which a foaming agent and a crosslinking accelerator are dissolved There is a method of immersing the functional resin, and it is used alone or in combination. In addition, since the biodegradable resin used by this invention is easy to receive a hydrolysis under a heating, it is preferable to reduce a moisture content to 0.1 weight% or less previously with a vacuum dryer.
[0036]
Next, the mixture is preferably formed into a sheet using a single-screw extruder with a vacuum vent, a twin-screw extruder, a tandem extruder, or the like. In the case of producing a continuous sheet-like foam, it is preferably formed into a sheet by extrusion molding at a temperature lower than the decomposition temperature of the foaming agent. When the biodegradable resin-crosslinked foam is reused without reducing its volume, it is not suitable for mixing with a mixer or the like because of its low density, and it is preferable to directly feed it into an extruder or the like. On the other hand, when the biodegradable resin crosslinked foam is reduced in volume and reused, it can be uniformly mixed even if it is mixed with a mixer or the like, or can be directly fed into an extruder. Also, using a tandem extruder, at least one selected from the biodegradable resin crosslinked foam and its reduced volume is melt kneaded in the first stage extruder, and this is used as the second stage extruder. A method of feeding and adding a biodegradable resin, a foaming agent, or the like to form a sheet can also be preferably used. The melt kneading temperature during extrusion is preferably 10 ° C. or more lower than the decomposition start temperature of the foaming agent. At this time, the thickness of the sheet is preferably 0.1 mm to 50 mm. If the thickness of the sheet is less than 0.1 mm, there will be a lot of gas escape from the sheet surface during foam molding, making it difficult to form a uniform foam, and if it exceeds 50 mm, the sheet will have too high rigidity, and winding properties during continuous production will be May cause trouble.
[0037]
Next, crosslinking of the foamable sheet-like material described above is performed by irradiating ionizing radiation. Examples of the ionizing radiation include an electron beam from an electron beam accelerator, α from CO60 and other radioisotopes, β, γ rays, especially electron beams from electron beam accelerators are preferred, and the irradiation amount varies depending on the type and addition amount of the crosslinking aid used, and the desired crosslinking ratio, but preferably 1 to The range is 300 kGy, more preferably 5 to 100 kGy.
[0038]
Thereafter, the cross-linked sheet is heat-treated at a temperature equal to or higher than the decomposition temperature of the foaming agent and foamed. For the heat treatment for foam molding, a conventionally known method may be used. For example, the heat treatment may be performed in a vertical and horizontal hot-air foaming furnace or a chemical bath foaming furnace. When using a resin that is prone to hydrolysis, such as aliphatic polyester, as the biodegradable resin, foaming in a vertical and horizontal hot-air foaming furnace provides a better surface condition than foaming in a chemical bath. A foam is obtained. Further, if foaming is preheated as necessary and the resin is softened, a stable foam can be obtained with a small amount of heat.
[0039]
【Example】
Hereinafter, the present invention will be described in more detail with reference to examples.
[0040]
The tensile elongation of the foam was measured in accordance with JIS K6767. In measuring at high temperature, the test piece was heated for 5 minutes in a hot air oven set at a predetermined temperature and then measured.
[0041]
Reference example 1
As biodegradable resin, polybutylene succinate / adipate “Bionore” # 3001 (manufactured by Showa Polymer Co., Ltd.) 100 kg previously dried in a vacuum dryer at 50 ° C. for 5 hours, azodicarbonamide 5.8 kg as a foaming agent 3 kg of 1,6-hexanediol dimethacrylate as a crosslinking aid and 0.5 kg of Irganox 1010 as a stabilizer were put into a Henschel mixer under a nitrogen atmosphere and mixed for 6 minutes to obtain a foaming resin. A mixture was made. This foaming resin mixture is introduced into a vented twin-screw extruder heated to a temperature at which the foaming agent does not decompose, specifically 150 ° C., extruded from a T-die, and a foamable sheet having a thickness of 1.5 mm and a width of 400 mm is obtained. Obtained.
[0042]
Thereafter, the sheet is irradiated with a 25 kGy electron beam and crosslinked, and then continuously introduced into a vertical hot-air foaming apparatus, heated and foamed at 230 ° C. for 3 to 4 minutes to form a continuous sheet-like crosslinked foam having a product width of 800 mm Rolled up as a body. At this time, both ends of the foam were cut as about 80 mm trimmings and wound up separately.
[0043]
The foam thus obtained had a thickness of 3.0 mm, a gel fraction of 57%, and an expansion ratio of 15 times. When the elongation at 80 ° C. of the obtained foam was measured, it was 580%, which was superior to the moldability at high temperatures.
[0044]
Edge trimming generated during the production of the crosslinked foam was continuously introduced several times into a mixing roll having a clearance of 0.5 mm to obtain a sheet having a thickness of about 1 mm. This sheet was applied to a cutting machine to obtain a reduced volume chip having a side of approximately 7 mm.
[0045]
The reduced-volume chip 100 kg was introduced into a twin-screw extruder equipped with a vacuum vent heated to 130 ° C. having a kneading disk at the screw tip, and extruded from a T-die to obtain a sheet having a thickness of about 2 mm. At this time, 5 kg of butenediol was continuously added to 100 kg of the reduced volume chip using a liquid addition pump. Next, the obtained sheet was put on a cutting machine to obtain a reduced volume chip having a side of about 7 mm.
[0046]
Reference example 2
30 kg of polyethylene resin (melt index at 190 ° C. of 5.2), 70 kg of polypropylene resin (melt index at 230 ° C. of 2.0) of random copolymerization of 3.5% ethylene and azodicarbonamide 6 as a blowing agent 1 kg, 3 kg of divinylbenzene as a crosslinking aid, 0.5 kg of Irganox 1010 as a stabilizer, and 0.5 kg of Irganox PS802FL were introduced into a twin-screw extruder with a vent heated to 175, and Reference Example 1 The same operation was performed to obtain a foamable sheet having a thickness of 1.5 mm and a width of 400 mm.
[0047]
This was irradiated with an electron beam of 50 kGy, the same operation as in Reference Example 1 was performed, and the product was wound up as a continuous sheet-like crosslinked foam having a product width of 800 mm. At this time, both ends of the foam were cut as about 80 mm trimmings and wound up separately.
[0048]
The foam thus obtained had a thickness of 3.2 mm, a gel fraction of 38%, and an expansion ratio of 15 times. When the elongation at 80 ° C. of the obtained foam was measured, it was 600% or more, which was excellent in molding processability at high temperatures.
[0049]
Trimming of the edge that occurs during the production of the crosslinked foam was performed in the same manner as in Reference Example 1 to obtain a volume-reducing chip having a thickness of about 1 mm and a side of about 7 mm.
[0050]
The volume reduction tip was introduced into the twin screw extruder as in Reference Example 1, and the same operation as in Reference Example 1 was performed to obtain a volume reduction tip. However, the melt viscosity was too high, and the extrusion was pushed out of the extruder. I couldn't.
[0051]
Example 1
25 kg of the volume-reduced chip obtained in Reference Example 1 and “Bionore” # 3001 (Showa High Polymer Co., Ltd.), a polybutylene succinate / adipate that was previously dried in a vacuum dryer at 50 ° C. for 5 hours as a biodegradable resin. 100 kg, 12 kg of azodicarbonamide as a foaming agent, 3 kg of 1,6-hexanediol dimethacrylate as a crosslinking aid, and 0.5 kg of Irganox 1010 as a stabilizer, and these are placed in a Henschel mixer under an N2 atmosphere. The mixture was added and mixed for 6 minutes to prepare a foaming resin mixture. This foaming resin mixture was introduced into a vented twin-screw extruder heated to a temperature at which the foaming agent was not decomposed, specifically 150 ° C., and extruded from a T-die to obtain a foamable sheet having a thickness of 1.5 mm.
[0052]
Thereafter, the sheet is irradiated with a 25 kGy electron beam and crosslinked, and then continuously introduced into a vertical hot air foaming apparatus, heated and foamed at 230 ° C. for 3 to 4 minutes to be wound as a continuous sheet-like crosslinked regenerated foam. I took it.
[0053]
The foam thus obtained had a thickness of 3.0 mm, a gel fraction of 47%, a foaming ratio of 23 times, no unevenness in the width direction, a good surface form, and a beautiful appearance. When the elongation at 80 ° C. of the foam was measured, it was 480%, which was superior to the moldability at high temperatures.
[0054]
Comparative Example 1
25 kg volume-reduced chip obtained in Reference Example 2, 30 kg of polyethylene resin (melt index at 190 ° C. of 5.2), polypropylene resin with 3.5% random copolymerization of ethylene (melt index at 230 ° C. 2.0) 70 kg, 12 kg of azodicarbonamide as a foaming agent, 3 kg of divinylbenzene as a crosslinking aid, and 0.5 kg of Irganox 1010 as a stabilizer were introduced into a twin screw extruder with a vent heated to 175. The same operation as in Example 1 was performed to obtain a foamable sheet having a thickness of 1.3 to 1.7 mm. Since the reduced volume of the cross-linked foam was not completely melted in the sheet, the sheet was not uniformly molded, and the thickness unevenness in the width direction of the sheet was large.
[0055]
The sheet was irradiated with a 50 kGy electron beam and crosslinked, and then continuously introduced into a vertical hot-air foaming apparatus and heated and foamed at 230 ° C. for 3 to 4 minutes. However, the sheet was cut in the foaming furnace. In a stable state, it could not be wound up as a continuous sheet-like crosslinked regenerated foam.
[0056]
Although the thickness of the obtained foam is small, the thickness of the foam is 2.5 mm to 3.2 mm, the expansion ratio is 15 times to 25 times, and the degree of crosslinking is 33% to 40%. Yes, the surface was uneven, and the appearance was very bad. When the elongation at 80 ° C. of the foam was measured, there was a large variation of 70% to 400%, and the molding processability at high temperatures was poor.
[0057]
【The invention's effect】
According to the present invention, it is possible to provide a biodegradable resin crosslinked foam which can be recycled.

Claims (2)

At least one selected from polybutylene succinate and / or polybutylene succinate / adipate biodegradable resin cross-linked foam having a gel fraction of 85% or less and a reduced volume thereof ,
Pyrolytic foaming agent ,
Polybutylene succinate and / or biodegradable resin made of polybutylene succinate / adipate and,
Foamable resin composition which is characterized in that a crosslinking aid. At least one selected from polybutylene succinate and / or polybutylene succinate / adipate biodegradable resin cross-linked foam having a gel fraction of 85% or less and a reduced volume thereof ,
Pyrolytic foaming agent ,
A biodegradable resin comprising polybutylene succinate and / or polybutylene succinate / adipate , and
A foamable resin composition containing a crosslinking aid,
A cross-linked foam obtained by foaming after cross-linking.