JP3731529B2 - Biodegradable resin cross-linked foam and production method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for producing a continuous sheet-like biodegradable resin crosslinked foam.
[0002]
[Prior art]
Conventionally, resin foams such as polyolefin resin foams and polyurethane resin foams have been widely used industrially because they are excellent in lightness, heat insulation, moldability, buffering properties, and the like. However, although these resin foams are lightweight, they are bulky when discarded and difficult to reuse. In particular, in the case of a crosslinked resin foam obtained by crosslinking a resin, there is a drawback that recycling is virtually impossible. In addition, these resin foams remain in the ground semi-permanently even if they are buried in the soil, contaminating the global environment by securing garbage disposal sites by incineration or landfill, etc., and rarely damage the natural landscape. There wasn't.
[0003]
For this reason, biodegradable resins that are decomposed by microorganisms and the like in the natural environment have been researched and developed and commercialized as films and fibers. Also, an extruded foam of a biodegradable resin has been developed. For example, a foam using an aliphatic polyester resin as a biodegradable resin is known. However, aliphatic polyester resins are difficult to increase in molecular weight due to side reactions such as hydrolysis with water generated during polycondensation, so that sufficient melt viscosity to retain bubbles during extrusion foaming cannot be obtained, and good bubbles It was difficult to obtain a foam having a state and a surface state. As a method for solving this problem, for example, JP-A-11-279711 proposes a foamed resin using a lactone resin.
[0004]
[Problems to be solved by the invention]
However, since the lactone resin also collapses at the time of crosslinking, it is difficult to obtain a melt viscosity for sufficiently retaining bubbles during foaming, and it is difficult to obtain a foam having a good surface form. Furthermore, in order to obtain a foam having a high degree of cross-linking, there is a drawback in that radiation treatment must be performed with very high energy.
[0005]
An object of this invention is to provide the manufacturing method of the continuous sheet-like biodegradable resin crosslinked foaming body which can be bridge | crosslinked with low energy and has a favorable surface form in view of the background of this prior art.
[0006]
[Means for Solving the Problems]
The present invention adopts the following means as a result of sincerity studies in order to solve such problems. That is, the present invention
(1) A step of forming a resin composition containing a biodegradable resin containing 50% by weight or more of a lactone resin, a thermally decomposable foaming agent, and a crosslinking aid into a sheet to obtain a continuous sheet-like biodegradable resin, the continuous A step of obtaining a crosslinked continuous sheet-like biodegradable resin by irradiating the sheet-like biodegradable resin with ionizing radiation to cross-link it, and further decomposing the crosslinked continuous sheet-like biodegradable resin into the decomposition temperature of the thermally decomposable foaming agent. It is a manufacturing method of the continuous sheet-like biodegradable resin crosslinked foam characterized by including the process heat-processed at the above temperature and making it a continuous sheet-like biodegradable resin crosslinked foam.
[0007]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, preferred embodiments of the present invention will be specifically described.
[0008]
Examples of the lactone resin used in the present invention include ε-caprolactone, β-propiolactone, γ-butyrolactone, δ-valerolactone, enanthlactone, 4-methylcaprolactone, 2,2,4-trimethylcaprolactone, 3, Examples thereof include homopolymers or copolymers of various methylated lactones such as 3,5-trimethylcaprolactone, and mixtures thereof.
[0009]
As the biodegradable resin used in the present invention, 100% of a lactone resin may be used, or a biodegradable resin other than the lactone resin may be included. Examples of the biodegradable resin other than the lactone resin used in the present invention include, for example, polylactic acid, polyethylene succinate, polybutylene succinate, polybutylene succinate adipate, polybutylene succinate carbonate and the like as a synthetic polymer. Examples include aliphatic polyesters, cellulose acetate, cellulose butyrate, cellulose propionate, cellulose nitrate, cellulose sulfate, cellulose acetate butyrate, and biodegradable cellulose esters such as cellulose nitrate acetate. Examples of synthetic polymers include polypeptides such as polyglutamic acid, polyaspartic acid, and polyleucine, and polyvinyl alcohol. Examples of the natural polymer include raw starch such as corn starch, wheat starch, and rice starch as starch, processed starch such as acetate esterified starch, methyl etherified starch, and amylose. Further, natural polymers such as natural linear polyester resins such as cellulose, carrageenan, chitin / chitosan, and polyhydroxybutyrate / valerate can be exemplified. Moreover, the copolymer of the component which comprises these biodegradable resin may be sufficient. These biodegradable resins may be used alone or in combination of two kinds.
[0010]
The biodegradable resin other than the lactone resin is preferably at least selected from aliphatic polyester, biodegradable cellulose ester, polypeptide, polyvinyl alcohol, starch, cellulose, chitin / chitosan and natural linear polyester-based resin. One kind is used.
[0011]
Of the lactone resin in biodegradable resin used in the present invention, it is important that at 5 0 wt% or more, good Mashiku is 60 wt% or more.
[0012]
In the present invention, the proportion of the biodegradable resin to the total resin component in the resin composition is not particularly limited, at least 50% by weight, and, Ruhodo more biodegradable resin amount, the degradation rate becomes faster, also The deformability after decomposition is improved. There is no particular limitation as a resin component other than such biodegradable resins, 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, etc. can be added.
[0013]
The thermal decomposition type foaming agent used in the present invention is not particularly limited as long as it has a thermal decomposition temperature. For example, azodicarbonamide, benzenesulfonyl hydrazide, dinitrosopentamethylenetetramine, toluenesulfonylhydrazide, azobisiso Examples include butyronitrile and barium azodicarboxylate. These may be used alone or in combination, and are preferably used in a proportion of 1 to 50 parts by weight, more preferably 4 to 25 parts by weight, relative to 100 parts by weight of the resin composition. If the amount of the pyrolytic foaming agent added is too small, the foamability of the resin composition will decrease, and if it is too large, the strength and heat resistance of the resulting foam will tend to decrease.
[0014]
The crosslinking aid used in the present invention is not particularly limited, but conventionally known polyfunctional monomers such as 1,6-hexanediol dimethacrylate, ethylene glycol diacrylate, ethylene glycol dimethacrylate, trimethylolpropane trimethacrylate, tetra Acrylate or methacrylate compounds such as methylol methane triacrylate, 1,9-nonanediol dimethacrylate, 1,10-decanediol dimethacrylate; trimellitic acid triallyl ester, pyromellitic acid triallyl ester, oxalic acid diallyl, etc. Allyl esters of carboxylic acids; cyanuric acids such as triallyl cyanurate and triallyl isocyanurate or allyl esters of isocyanuric acid; N-phenylmaleimide, N, N′-m-pheny Maleimide compounds such as lenbismaleimide; compounds having two or more triple bonds such as dipropargyl phthalate and dipropargyl maleate; polyfunctional monomers such as divinylbenzene can be used for ease of handling and biodegradability In view of the above, ester-based polyfunctional monomers such as 1,6-hexanediol dimethacrylate are preferably used.
[0015]
These polyfunctional monomers can be used alone or in combination of two or more.
[0016]
If the addition amount of these polyfunctional monomers is too small, it is difficult to obtain a good crosslinked foam, and if it is too much, the moldability of the obtained foam tends to be lowered. The amount is preferably 0.5 to 10 parts by weight, more preferably 1 to 6 parts by weight.
[0017]
In the resin composition used for this invention, you may add additive components other than a thermal decomposition type foaming agent and a crosslinking adjuvant in the range which does not inhibit the effect of this invention. For example, as additives, crosslinking agents, antioxidants, lubricants, heat stabilizers, pigments, flame retardants, antistatic agents, nucleating agents, plasticizers, antibacterial agents, biodegradation accelerators, light stabilizers, UV absorbers, blocking Inhibitors, fillers, deodorizers, thickeners, foaming aids, cell stabilizers, metal damage inhibitors and the like may be added alone or in combination of two or more.
[0018]
In the present invention, the method for crosslinking the resin composition is not particularly limited, and examples thereof include a method of irradiating a predetermined dose of ionizing radiation, crosslinking with a peroxide, and silane crosslinking.
[0019]
Examples of the ionizing radiation include α rays, β rays, γ rays, and electron beams. The irradiation dose of ionizing radiation varies depending on the type and amount of the crosslinking aid, the target degree of crosslinking, and the like, but is usually 1 to 500 kGy, preferably 5 to 300 kGy. If the irradiation dose is too small, a sufficient melt viscosity cannot be obtained to hold the bubbles during foam molding, and if it is too large, the moldability of the resulting foam is lowered.
[0020]
In the present invention, foaming is usually performed by heating the crosslinked resin composition to a temperature equal to or higher than the thermal decomposition temperature of the pyrolytic foaming agent.
[0021]
The expansion ratio of the 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.
[0022]
The gel fraction of the foam of the present invention is preferably 3% or more. When the gel fraction is less than 3%, the secondary processability of the obtained foam tends to decrease.
[0023]
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 biodegradable resin-crosslinked foam is precisely weighed, 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.
Gel fraction (%) = {weight of insoluble matter (mg) / weight of weighed biodegradable resin crosslinked foam (mg)} × 100
Next, the preferable manufacturing method of the biodegradable resin crosslinked foam of this invention is demonstrated.
[0024]
Method for producing a continuous sheet-like biodegradable resin crosslinked foam of the present invention, a resin composition comprising a biodegradable resin containing a lactone resin 50 wt% or more and a thermally decomposable foaming agent and crosslinking aid, sheet-like molded to obtain a continuous sheet-like biodegradable resins to process the ionizing radiation and by cross-linking irradiated in continuous sheet form biodegradable resin to obtain a cross-linking continuous sheet-like biodegradable resins, further the a crosslinked continuous sheet-like biodegradable resin is characterized in that it comprises the step of a thermal decomposition type foaming agent heat-producing continuous sheet at the decomposition temperature or more of the decomposable resin crosslinked foam. Specifically, the following manufacturing method etc. are mentioned, for example.
[0025]
Kneading a resin composition containing a biodegradable resin containing 50% by weight or more of a lactone resin, a thermal decomposable foaming agent, and a crosslinking aid into a single screw extruder, twin screw extruder, Banbury mixer, kneader mixer, mixing roll, etc. Using an apparatus, the mixture is uniformly melt-kneaded at a temperature equal to or lower than the decomposition temperature of the pyrolytic foaming agent, and formed into a sheet shape . These resin compositions may be mechanically mixed with a mixer or the like as necessary before melt-kneading. The melt kneading temperature at this time is preferably a temperature lower by 10 ° C. or more than the decomposition start temperature of the foaming agent. If the kneading temperature is too high, the pyrolytic foaming agent is decomposed during kneading, and a good foam cannot be obtained.
[0026]
Then, the ionizing radiation in a continuous sheet form biodegradable resin obtained by a predetermined dose irradiated to cross-linking, to obtain a cross-linking continuous sheet-like biodegradable resins.
[0027]
Next, this crosslinked continuous sheet-like biodegradable resin is foamed by heat treatment at a temperature equal to or higher than the decomposition temperature of the pyrolytic foaming agent. The heat treatment for foam molding may be performed by a conventionally known method, for example, in a vertical or horizontal hot-air foaming furnace or a chemical bath such as a molten salt.
[0028]
【Example】
EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited to this.
[0029]
Example 1
Prepare 100 kg of polycaprolactone "TONE" (UCC Co.) as biodegradable resin, 7.5 kg of azodicarbonamide as foaming agent, and 5 kg of 1,6-hexanediol dimethacrylate as crosslinking aid. The mixture was mixed at a low speed of 200 to 400 rpm for about 3 minutes, then at a high speed of 800 to 1000 rpm and mixed for 3 minutes to obtain a foaming resin composition. This foaming resin composition was introduced into an extruder equipped with a vent heated to a temperature at which the foaming agent was not decomposed, specifically 120 ° C., extruded from a T-die, and molded into a crosslinked foamed sheet having a thickness of 1.5 mm. The sheet was irradiated with an 80 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, and wound up as a continuous sheet-like crosslinked foam.
The foam thus obtained had a thickness of 3.0 mm, a gel fraction of 40%, a foaming magnification of 12 times, a good surface form, and a beautiful appearance. When this material was buried in soil, after 1 year, the strength dropped to a non-practical strength and a degradation change was observed.
[0030]
Comparative Example 1
A foam was prepared using the same method as in Example 1 except that no crosslinking aid was used. The foam thus obtained had a thickness of 1.5 mm, a gel fraction of 2.5%, a foaming ratio of 1.8 times, and an irregular surface shape, and had a very poor appearance. Moreover, since the gas generated at the time of foaming cannot be sufficiently retained, the foamed state did not become a uniform foam.
[0031]
【The invention's effect】
ADVANTAGE OF THE INVENTION According to this invention, the biodegradable resin crosslinked foam with a favorable surface form can be provided, and the utility is large.

Claims (1)

 A step of forming a resin composition containing a biodegradable resin containing 50% by weight or more of a lactone resin, a thermal decomposable foaming agent and a crosslinking aid into a sheet to obtain a continuous sheet-like biodegradable resin, A step of obtaining a crosslinked continuous sheet-like biodegradable resin by irradiating the degradable resin with ionizing radiation to crosslink, and further, the temperature of the crosslinked continuous sheet-like biodegradable resin above the decomposition temperature of the thermally decomposable foaming agent. The manufacturing method of the continuous sheet-like biodegradable resin crosslinked foam characterized by including the process of heat-processing with a continuous sheet-like biodegradable resin crosslinked foam.