JP2003012844A - Polyolefin foamed material and production method thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polyolefin foamed material wherein a molecular chain does not decompose too much but suitably decomposes to a biodegradable degree in a kneading step and the like. SOLUTION: The polyolefin foamed material is obtained by foaming a resin composition, composed mainly of a resin having a biodegradable component containing a polyolefin, starch and an aromatic ketone, an antioxidant, a crosslinking agent and a foaming agent, wherein a mass ratio of the resin to the antioxidant is 1:(0.02-0.5). The antioxidant is preferably a phenolic antioxidant. The polyolefin foamed material is produced by filling the resin composition in a metallic mold, heating and pressurizing to be foamed and cured. Otherwise, the polyolefin foamed material may be produced by filling the resin composition in the metallic mold, heating and pressurizing to be primarily expanded, and thereafter to be foamed and cured.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a polyolefin foam and a method for producing the same, and more specifically, in a kneading step or the like, decomposition of molecular chains does not proceed excessively and is appropriately decomposed to such a degree that biodegradation is possible. And a method for producing the same.

[0002]

2. Description of the Related Art Conventionally, a polyolefin foam has been widely used as a packing material, an impact resistant material, a heat insulating material and the like, and is properly used depending on its physical properties. These polyolefin foams are generally disposed of in an incinerator at the time of disposal. However, in recent years, due to environmental problems such as air pollution due to incineration, a disposal method other than incineration has been demanded.

Therefore, as a resin foam having biodegradability, Japanese Patent Laid-Open Nos. 2000-143862 and 2000 are known.
No. 169612 is disclosed. These resin foams are obtained by foaming a composition containing starch, an aromatic ketone, a polyolefin resin, a foaming agent and a cross-linking agent. A resin or the like is biodegraded by being oxidatively decomposed and reduced in molecular weight to a stage where it can be biodegraded by a microorganism or the like.

[0004]

However, in the production of the above resin foam, in the kneading step (step of kneading each raw material component to obtain the resin composition), heating is performed while being exposed to the outside air, and If the heat treatment is applied, the action of the oxidation accelerator becomes large due to this heat, the decomposition of the resin proceeds excessively, the degree of entanglement between molecular chains decreases, and the viscosity of the resin decreases. On the other hand, if the kneading is not carried out sufficiently, the respective raw material components are not evenly dispersed. In this way, inconvenience arises in kneading workability. Further, even in the case of the secondary expansion in the case of the two-stage foaming, since the resin is heated while being exposed to the outside air, the decomposition of the resin may similarly proceed.

The present invention solves the above problems, and in the kneading step or the like, the decomposition of the molecular chain does not proceed excessively, and the polyolefin foam is appropriately decomposed to the extent that it can be biodegraded, and a method for producing the same. The purpose is to provide.

[0006]

The present inventor has found that a polyolefin foam obtained by foaming a resin composition containing a polyolefin, a resin containing a biodegradable component containing starch and an aromatic ketone, and an antioxidant. In, by blending the resin and the antioxidant in a specific mass ratio, in the kneading step or the like, the decomposition of the molecular chain does not proceed excessively, and the polyolefin foam appropriately decomposed to the extent that it can be biodegraded. Focusing on the fact that it can be obtained, the present invention has been completed.

The polyolefin foam according to claim 1 is
Polyolefin, a resin containing a biodegradable component containing starch and aromatic ketone, an antioxidant, a cross-linking agent, and a foaming agent as main components, and the resin and the antioxidant have a mass ratio of 1:
It is characterized in that the resin composition of (0.02 to 0.5) is foamed.

Examples of the above-mentioned "polyolefin" include polyethylene, poly-1,2-butadiene, ethylene-propylene copolymer, ethylene-butene copolymer and ethylene produced by a commercially available high pressure method, medium pressure method or low pressure method. -Vinyl acetate copolymer, copolymer of ethylene and acrylic acid ester of methyl, ethyl, propyl, or butyl (content of this ester; 45 mol% or less), or chlorine content of each of them is 60% by mass. And the like, or a mixture thereof with polypropylene having an atactic structure or an isotactic structure. These may be used alone or 2
You may mix and use 1 or more types.

The above-mentioned "resin" contains the above-mentioned "biodegradable component" including the above-mentioned "starch" and the above-mentioned "aromatic ketone". This is a so-called masterbatch containing a large amount of components. This biodegradable component also has the function of decomposing the polyolefin by oxidation, lowers the molecular weight of the polyolefin, and facilitates biodegradation.

The resin that serves as the base of the above masterbatch includes ethylene-vinyl acetate copolymer, ethylene-vinyl alcohol copolymer, ethylene-acrylic acid copolymer, ethylene-methyl acrylate copolymer, ethylene-
Examples thereof include butyl acrylate copolymer, ethylene-methacrylic acid copolymer, polyvinyl alcohol, ethylene-vinyl alcohol-carbon monoxide terpolymer, polymethylmethacrylate and polyethylene oxide.

As the starch, (1) corn starch, potato starch, sweet potato starch, wheat starch,
Cassava starch, sago starch, tabioca starch, rice starch, bean starch, kudzu starch, bracken starch, lotus starch, and starch starch, etc.,
(2) Physically modified starch such as α-starch, fractionated amylose and heat-treated starch, (3) Hydrolyzed dextrin, enzymatically modified starch such as enzymatically decomposed dextrin and amylose, (4) Acid-treated starch, hypochlorous acid starch And chemically degraded starch such as dialdehyde starch, (5) esterified starch, etherified starch,
Examples include chemically modified starch derivatives such as cationized starch and crosslinked starch. These starches may be used alone or in combination of two or more. The content of starch is preferably 5 to 29 parts by mass (more preferably 10 to 15 parts by mass) when the resin (resin serving as the masterbatch base) is 100 parts by mass.

Aromatic ketones interact with the following peroxides and the oxidation of oxidizable components,
Further, it facilitates the biodegradation of polyolefin by heat or light. Examples of aromatic ketones include benzophenone, anthraquinone and anthrone, acetylbenzophenone,
Examples thereof include derivatives such as 4-octylbenzophenone. Among them, as described in claim 4, benzophenone is preferable because biodegradation always occurs at a constant rate without distinction between individuals. These may be used alone or in combination of two or more. The content of the aromatic ketone is preferably 10 to 50 parts by mass (more preferably 15 to 30 parts by mass) when 100 parts by mass of the resin (resin serving as the base of the masterbatch) is used.

Further, the biodegradable component preferably contains an oxidizable component, a transition metal component, and the like. As the oxidizable component, unsaturated fatty acids, fatty acid esters, natural fats and the like are used, for example, corn oil,
Examples include olive oil, rapeseed oil, soybean oil and sunflower oil. It may also be an unsaturated substance such as natural rubber or synthetic rubber. Examples of the transition metal component include iron hydroxystearate, iron stearate, copper stearate and vanadium stearate. Each of these components may be used alone or in combination of two or more.

The total content of starch, aromatic ketone, oxidizable component and transition metal component is 10 to 70 parts by mass when the resin (resin which is the base of the masterbatch) is 100 parts by mass. (More preferably 20 to 60 parts by mass, further preferably 30 to 50 parts by mass). If this content is less than 10 parts by mass, it is not recognized that biodegradation has substantially occurred, and the effects of the above-mentioned added components such as starch may not be sufficiently obtained. On the other hand, 7
If it exceeds 0 parts by mass, biodegradation may proceed excessively and a sufficient product life may not be obtained.

The above-mentioned "antioxidant" is not particularly limited as long as it can control the oxidation of the polyolefin by heat, but as described in claim 2, it is preferably a phenolic antioxidant. As an antioxidant,
2,6-di-tert-butyl-4-ethylphenol, stearyl-β- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate, 2,2 ′
-Methylenebis (4-methyl-6-tert-butylphenol), 4,4'thiobis (3-methyl-6-te
rt-butylphenol), 1,1,3-tris (2-
Methyl-4-hydroxy-5-tert-butylphenyl) butane, tetrakis- [methylene-3- (3 ′,
5′-di-tert-butyl-4′-hydroxyphenyl) propionate] methane (trade name “Irganox 1010”, manufactured by Ciba-Geigy) and the like. In particular, according to claim 3, tetrakis- [methylene-
3- (3 ′, 5′-di-tert-butyl-4′-hydroxyphenyl) propionate] methane is preferred. These may be used alone or in combination of two or more.

The content of these antioxidants is 0.4 to 10 parts by mass (more preferably 0.8 to 9 parts by mass, still more preferably 2 to 100 parts by mass) when the total amount of the resin components is 100 parts by mass. It is preferably 8 parts by mass). When the content of the antioxidant is less than 0.4 parts by mass, the action of the oxidation accelerator becomes large, the decomposition of the resin proceeds excessively, the degree of entanglement between molecular chains decreases, and the viscosity of the resin increases. Has fallen,
Workability during kneading may be poor. On the other hand, when the amount exceeds 10 parts by mass, the action of the antioxidant exceeds the action of the oxidation accelerator, and biodegradation may not occur when the foamed molded product is used.

Furthermore, the mass ratio of the resin containing the biodegradable component and the antioxidant (resin: antioxidant) is 1: (0.
02-0.5), preferably 1: (0.04-
0.45), more preferably 1: (0.1-0.4). When the mass ratio of the antioxidant to the resin is less than 0.02, the antioxidant effect cannot be sufficiently obtained, and the molecular chain of the resin is excessively decomposed in the kneading step or the like,
It is not preferable because the workability during kneading is poor. On the other hand, if the mass ratio exceeds 0.5, the antioxidant action is excessively exerted, and sufficient biodegradability cannot be obtained, which is not preferable.

Examples of the above-mentioned "crosslinking agent" include dicumyl peroxide (for example, manufactured by NOF CORPORATION, trade name "Parkmill D"), 1,1-di-tert-butylperoxy-3,3,5-. Trimethylcyclohexane, 1,3-
Di-tert-butylperoxy-isopropylbenzene, 2,5-dimethyl-2,5-di-tert-butylperoxyhexane (for example, NOF CORPORATION, trade name "Perhexa 25B"), n-butyl- 4,4-di-tert-butylperoxyvalerate (for example, manufactured by NOF CORPORATION, trade name “Perhexa V”) and the like can be mentioned. These may be used alone or in combination of two or more.

The content of these cross-linking agents is 0.2 to 2 parts by mass (more preferably 0.3 to 1.5 parts by mass, and further preferably 0 when the total amount of the resin components is 100 parts by mass). 0.5 to 1.2 parts by mass) is preferable. If the content of the cross-linking agent is less than 0.5 parts by mass, the cross-linking may not proceed sufficiently and the viscosity of the resin necessary for foaming may not be obtained. On the other hand, if it exceeds 2 parts by mass, crosslinking may proceed excessively and the resin may be hardened more than necessary.

The above-mentioned "foaming agent" may be any as long as it has a decomposition temperature above the flow initiation temperature of the resin, such as azodicarbonamide, barium azodicarboxylate, dinitrosopentamethylenetetramine, trinitrotrimethyltriamine, P. , P'-oxybisbenzenesulfonyl hydrazide, sodium citrate, sodium hydrogencarbonate and the like. These may be used alone or in combination of two or more.

The content of the foaming agent is 10 in total of the resin components.
When it is 0 parts by mass, it is preferably 2 to 30 parts by mass (more preferably 4 to 25 parts by mass). If this content is less than 2 parts by mass, the foaming may not proceed sufficiently and the desired foam may not be obtained. On the other hand, when the amount exceeds 30 parts by mass, the foaming proceeds so much that it is difficult to obtain a proper foamed state, and the desired foam may not be obtained.

A method for producing a polyolefin foam according to a fifth aspect is characterized in that the resin composition is filled in a mold and heated and pressed to foam and cure. A method for producing a polyolefin foam according to claim 6, which is a method for producing the polyolefin foam, comprising:
It is characterized in that it is filled in a mold, heated and pressurized to undergo primary expansion to form a primary foam, and then the primary foam is further foamed and cured. In the above “resin composition”,
The above description can be applied as it is.

The mold and other manufacturing equipment used may be those conventionally used in the manufacture of resin foams, and the pressure, temperature, etc. may vary depending on the type of resin, foaming agent, organic peroxide, etc. It can be appropriately set by the following. Further, in order to control the foaming state of the foam, a compound containing urea as a main component, a metal oxide such as zinc oxide or lead oxide, a lower or higher fatty acid such as hexanoic acid or stearic acid, or a metal salt thereof or the like is used. Foaming aids can be added.
Further, for the purpose of improving physical properties, carbon black, zinc white, titanium oxide, and other additives usually used by being blended with the raw material of the main foam, for example, colorants, ultraviolet absorbers, flame retardants, crosslinking aids. Agents and the like can also be used.

[0024]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in more detail below with reference to Examples and Comparative Examples. (1) Preparation of Polyolefin Foam (Examples 1 to 5 and Comparative Examples 1 and 2) Mixtures obtained by mixing the components shown below in the proportions shown in Table 1 were prepared.
After kneading with a kneader at a temperature of 110 ° C. for 20 minutes and then with a biaxial mixing roll at a temperature of 100 ° C. for 20 minutes to prepare a resin composition, the resin composition was filled in a mold heated to 150 ° C. and 10 MPa. It was heated under the pressure of 40 minutes for foaming to obtain a polyolefin foam of 650 mm length × 1300 mm width × 60 mm thickness. The expansion ratios of Examples 1 to 5 and Comparative Examples 1 and 2 were all 13 times.

Details of the components used in Examples and Comparative Examples are shown below. (A) Polyolefin; polyethylene, manufactured by Tosoh Corporation, trade name "PETROSEN 186" (b) Masterbatch containing biodegradable components; manufactured by Novon Japan Co., trade name "Degranobon NBK31"
0 "(base resin: linear low-density polyethylene) (c) antioxidant; manufactured by Ciba Geigy, trade name" Irganox 1010 "(d) cross-linking agent; dicumyl peroxide (e) foaming agent; azodicarbonamide Manufactured by Eiwa Chemical Co., Ltd.
Product name "AC # 3" (f) Foaming aid; Zinc white; Zinc stearate (g) Urea-based foaming aid; Eiwa Chemical Co., Ltd., trade name "Cellpaste 101"

[0026]

[Table 1]

(2) Evaluation of polyolefin foam kneading workability In the production of each polyolefin foam of the above (1),
The workability during the kneading work was evaluated by kneading with a twin-screw mixing roll, and the kneaded product was easily released from the roll and kneaded smoothly. The results are shown in Table 2. In addition, in the evaluation result, "good" means that the kneading work is performed as usual, there is no adhesion to the roll, and "somewhat difficult"
Indicates that adhesion to the roll was observed, but there was no hindrance to the kneading work, and "difficult" indicates that the adhesion to the roll was severe and the kneader was stopped and cleaned.

Degradability (aging resistance) Each of the polyolefin foams produced in the above (1) was
Put it in a constant temperature bath at 0 ° C and the tensile strength of each foam will be 1 of the initial value.
The decomposition time to 0% or less was measured to evaluate the decomposability of the foam. The results are shown in Table 3.

Biodegradability in Soil Each of the polyolefin foams produced in the above (1) was buried in sunny soil, and the time until biodegradation was visually measured to obtain the foam in soil. Was evaluated for biodegradability. The results are shown in Table 4.

[0030]

[Table 2]

[0031]

[Table 3]

[0032]

[Table 4]

According to Table 2, the mass ratio of the masterbatch (resin containing the biodegradable component) and the antioxidant is 1:
(0.025 to 0.5) The workability during the kneading operation during the production of the polyolefin foams of Examples 1 to 5 is "good" (Examples 2 to 5) or "somewhat difficult" (Example 1). )Met. On the other hand, this mass ratio is 1: 0.5
The workability during the kneading work during the production of the foam of Comparative Example 2 of No. 5 was “good”, but the mass ratio was 1:
In Comparative Example 1 of 0.015, the viscosity of the resin composition at the time of producing the foam was low, and the kneading workability was poor and "difficult".

According to Table 3, the decomposition time of the polyolefin foams of Examples 1 to 5 in which the mass ratio of the masterbatch and the antioxidant is 1: (0.025 to 0.5) is 48 to.
It is 240 hours and seems to have sufficient biodegradability.
On the other hand, the decomposition time of the foam of Comparative Example 1 in which the mass ratio was 1: 0.015 was 48 hours, but the decomposition time in Comparative Example 2 in which the mass ratio was 1: 0.55 was Thirty
It took 0 hours and a long time.

According to Table 4, the biodegradation of the polyolefin foams of Examples 1 to 5 in which the mass ratio of the masterbatch and the antioxidant is 1: (0.025 to 0.5) in soil. The time was 12 to 28 months, and sufficient biodegradability could be confirmed. On the other hand, the biodegradation time of the foam of Comparative Example 1 whose mass ratio was 1: 0.015 was 12 months,
The biodegradation time in Comparative Example 2 in which the mass ratio was 1: 0.55 required a long time of 30 months.

According to the present invention, in the kneading step and the like,
It is possible to provide a polyolefin foam in which decomposition of a molecular chain does not proceed excessively and which is appropriately decomposed to the extent of being biodegradable, and a method for producing the same.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) C08L 3/02 ZBP C08L 3/02 ZBP 23/00 23/00 // B29K 23:00 B29K 23:00 105 : 04 105: 04 F-term (reference) 4F074 AA03 AA16 AD07 AD12 AG04 BA13 BB02 CA24 CA30 CC03Y CC04Y CC07Y CC62 DA24 DA32 DA33 4F204 AA01 AA03 AB02 AB03 AB06 AB20 AG20 FA01 FA18 FB01 BB01 BB0105041 BB1 BB01 AC042 BB131 BB151 BB241 EE036 EE056 EJ027 EJ037 EJ047 EJ067 EK038 EK068 EV077 FD077 FD148 FD192 FD196 FD329

Claims (6)

[Claims] 1. A polyolefin, a resin containing a biodegradable component containing starch and an aromatic ketone, an antioxidant, a cross-linking agent and a foaming agent as main components, and the mass ratio of the resin to the antioxidant is 1. A polyolefin foam, which is obtained by foaming a resin composition of 1: (0.02-0.5). 2. The polyolefin foam according to claim 1, wherein the antioxidant is a phenolic antioxidant. 3. The phenolic antioxidant is tetrakis- [methylene-3- (3 ′, 5′-di-tert-
Butyl-4'-hydroxyphenyl) propionate]
The polyolefin foam according to claim 2, which is methane. 4. The polyolefin foam according to claim 1, wherein the aromatic ketone is benzophenone. 5. The method for producing a polyolefin foam according to claim 1, wherein the resin composition is filled in a mold and heated and pressed to foam and cure. A method for producing a polyolefin foam, which comprises: 6. The method for producing a polyolefin foam according to claim 1, wherein a mold is filled with the resin composition, and the resin composition is heated and pressurized to perform primary expansion. A method for producing a polyolefin foam, which is characterized in that the primary foam is further foamed and cured.