JP2006057052A - Plastically deformable resin composition at normal temperature and molded article by using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a resin composition capable of plastically deforming at a normal temperature and being produced by a simple device at a low cost, having an equivalent good form-maintaining capacity and durability for repeated bends as compared with those of conventional molded articles, and especially decomposed by microorganisms in a state of being left in a natural environment after its use, thereby reducing its load to environment, and its molded article. <P>SOLUTION: This plastically deformable resin composition at a normal temperature is obtained by containing (A) a polylactic acid-based resin, and (B) a thermoplastic resin having ≥200% tensile elongation at break and biodegradability, and having (90:10)-(35:65) ratio of A:B. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a room temperature plastically deformable resin composition that provides a molded body having both plastic deformability and repeated bending durability required for horticultural use and bundling of elongated wires, and a molded body using the same (preferably A strip-shaped or linear molded body).

In recent years, it has been referred to as a binding material or binding material that can be easily folded and fixed by human hands for planting, planting gardens for fruit and vegetable tying, packaging food, and binding other electric wires. Bands and linear bodies are often used.
This type of plastically deformable elongated strip that is widely used as a binding material or binding material of this type can be easily folded and twisted with fingers, and in addition, after bending and twisting, external force is applied. The plastic deformation property and the shape retaining property that do not return to the original shape even when it does not work, and the durability that can withstand repeated bending for repeated use are required.

Conventionally, metals such as wire are mainly used as materials that can be plastically deformed at room temperature. On the other hand, resin moldings called plastics are mostly thermoplastic resin moldings that are plastically deformed by applying heat and pressure, and many of them have excellent elastic recovery at room temperature, and are usually deformed by external stress. Even after removing external stress, it is difficult to maintain its form.
For this reason, ordinary binding materials, binding materials, and the like are used in which a metal wire such as soft copper or aluminum is used as a core material and the surface thereof is covered with a resin material such as PVC or polyethylene.
In addition, a special treatment such as a thermoplastic resin, for example, a special polyethylene having a plastic deformation property obtained by subjecting special polyethylene to thermal stretching at a specific magnification (see Patent Document 1) is coated with the resin. Are provided.

However, molded products in which these surfaces are coated with a halogen-containing resin such as PVC using a metal as the core material may be toxic gas or corrosive depending on the combustion conditions when they are subjected to combustion treatment as a disposal method after use. Gas may be generated. Even if it is coated with a non-halogen resin such as polyethylene, it is improperly treated after use and will remain semi-permanently if left in the natural environment due to illegal dumping. It is expected that it is not preferable for environmental conservation. The remaining of the molded product due to illegal dumping is the same even when the core material is made of the above-mentioned special polyethylene having plastic deformability.
JP 2004-183001 A

  The present invention has been made to solve the above-described problems, and the object of the present invention is to enable mass production at a low cost with a simple apparatus and to maintain a good shape equivalent to that of a conventional molded body. An object of the present invention is to provide a resin composition capable of being plastically deformed at room temperature and its molded product, preferably a strip-shaped or linear molded product, having the ability and durability against repeated bending. In addition, by using a biodegradable resin as a resin for providing them, the molded body is decomposed by microorganisms and the like even if it is left in the natural environment after use, and the burden on the environment can be reduced. .

In order to solve the above problems, the present invention includes (1) a polylactic acid-based resin (A) and a biodegradable thermoplastic resin (B) having a tensile elongation at break of 200% or more. A room temperature plastically deformable resin composition having a ratio of 90:10 to 35:65 is provided. Preferably, (2) the polylactic acid-based resin (A) is a homopolymer having L-lactic acid or D-lactic acid as a structural unit, and (3) a thermoplastic resin (B) ) Is an aliphatic polyester resin or an aliphatic-aromatic polyester.
(4) A room-temperature plastically deformable resin molded product molded using the resin composition according to (1) to (3), (5) The molded product according to (4) is an elongated strip or wire. A normal temperature plastically deformable resin molded body of (6) a width of 3 mm, a length of 15 mm, and a thickness of 0.5 mm, and a return angle after being bent by 180 degrees is 60 degrees or less, and a tensile strength at break is 20 MPa or more. The room-temperature plastically deformable resin molded product according to (4) or (5) is provided.

By using the resin composition of the present invention, it is possible to obtain a molded product having excellent plastic deformation properties and bending durability by a general molding method. In addition, since the resin constituting the product is biodegradable, it is also beneficial in terms of environmental protection.

The normal temperature plastically deformable resin composition referred to in the present invention means a resin composition that can be plastically deformed in a normal temperature range (0 ° C. to 30 ° C.) that is a normal human life.
Plastic deformation refers to deformation that occurs when a force is applied to a solid substance from the outside, but does not return to its original shape for a long time even when the force is removed, and when it returns to its original shape, it is called elastic deformation. The normal temperature plastic deformability of the present invention means that at least in the form of a tape, a film (band shape) or a thread (linear shape), the return angle after 10 minutes when bent at 180 ° C. is 60 degrees or less.

Examples of the polylactic acid-based resin (A) used in the resin composition of the present invention include homopolymers whose structural units are L-lactic acid or D-lactic acid, copolymers thereof, and α-hydroxycarboxylic acids. It may be a copolymer with other hydroxycarboxylic acid units or an aliphatic diol / aliphatic carboxylic acid and a copolymer.
The resulting polylactic acid has a D-lactic acid unit of about 10% or less and an L-lactic acid unit of about 90% or more, or an L-lactic acid unit of 10% or less and a D-lactic acid unit of 90% or more, and an optical purity. About 80% or more crystalline polylactic acid and amorphous polylactic acid having D-lactic acid units of 10% to 90%, L-lactic acid units of 10% to 90%, and optical purity of less than about 80% However, any polylactic acid may be used in the present invention, and crystalline polylactic acid is preferably used when used for a product requiring further heat resistance.
Specific examples of the polylactic acid-based resin include “LACTY” manufactured by Shimadzu Corporation and “Lacia” manufactured by Mitsui Chemicals.
The weight average molecular weight (hereinafter referred to as Mw) of the polylactic acid-based resin is preferably in the range of 50,000 to 400,000, more preferably 100,000 to 250,000. If the Mw is less than 50,000, the molding processability is inferior and practical physical properties are difficult to obtain. On the other hand, when it exceeds 400,000, the melt viscosity is too high and the molding processability is poor.

  The thermoplastic resin (B) used in the present invention is preferably a biodegradable thermoplastic resin other than polylactic acid resin, and has a physical property with a tensile elongation at break of 200% or more. More preferably, a resin having an elongation at break of 300% or more, more preferably 500% to 900% is used. When the elongation at break is too small, the durability of repeated bending of a molded article made of the resulting resin composition is inferior. The tensile elongation at break can be measured by, for example, a measuring method based on JIS K7161 (JIS No. 3 dumbbell test piece, tensile speed 200 mm / min).

  Examples of the resin (B) include (B1) an aliphatic-aromatic polyester-based resin, (B2) an aliphatic polyester synthesized based on an aliphatic dicarboxylic acid and an aliphatic diol, and (B3) a hydroxycarboxylic acid. Examples include terpolymers of aliphatic dicarboxylic acids and aliphatic diols, with (B1) and (B2) being particularly preferred.

  As the (B1) aliphatic-aromatic polyester resin used in the present invention, for example, a polyester obtained by copolymerization of an aliphatic dicarboxylic acid and an aromatic dicarboxylic acid with an aliphatic diol can be used. The aliphatic dicarboxylic acid, aromatic dicarboxylic acid, and aliphatic diol are not particularly limited, and examples of the aliphatic dicarboxylic acid include succinic acid, maleic acid, glutaric acid, adipic acid, suberic acid, sebacic acid, and dodecane. Examples of the aromatic dicarboxylic acid include phthalic acid, terephthalic acid, isophthalic acid, and naphthalenedicarboxylic acid. Examples of the aliphatic diol include ethylene glycol, propylene glycol, 1,3-butylene glycol, and 1,4. -Butylene glycol, neopentyl glycol, diethylene glycol, dipropylene glycol, 1,4-butanediol, 1,4-cyclohexanedimethanol and the like can be used.

Preferred combinations of aliphatic dicarboxylic acid, aromatic dicarboxylic acid and aliphatic diol include succinic acid / terephthalic acid / butanediol, succinic acid / terephthalic acid / ethylene glycol, succinic acid / isophthalic acid / butanediol, and succinic acid / isophthalic acid. Examples include combinations of acid / ethylene glycol, adipic acid / terephthalic acid / butanediol, adipic acid / terephthalic acid / ethylene glycol, adipic acid / isophthalic acid / butanediol, adipic acid / isophthalic acid / ethylene glycol, and the like.
The copolymerization ratio of aliphatic dicarboxylic acid / aromatic dicarboxylic acid is preferably about 1 / 0.02 to 1/5, and more preferably about 1 / 0.05 to 1/2 in terms of molar ratio.
Specific examples of such aliphatic-aromatic polyester resins include “ECOFLEX” manufactured by BASF, “EASTAR BIO” manufactured by EASTMAN CHEMICAL, “BIOMAXS” manufactured by DuPONT, and the like.

The aliphatic polyester (B2) is a polyester synthesized by combining aliphatic dicarboxylic acid and aliphatic diol as main components and various other aliphatic hydroxycarboxylic acids and the like, and has biodegradability. . Specific examples include polyethylene succinate, polybutylene succinate, polybutylene succinate, polybutylene succinate adipate, polyhexamethylene succinate, polyethylene adipate, polybutylene adipate, and the like.
Specific examples include “Bionore” manufactured by Showa Polymer Co., Ltd., “GS Pla” manufactured by Mitsubishi Chemical Corporation, and the like.
Moreover, the modified aliphatic polyester which co-condensed terephthalic acid, carbonate, etc. may be sufficient.

The room temperature plastically deformable resin composition of the present invention comprises the above (A) resin and (B) resin, and the (weight) ratio A: B is 90:10 to 35:65. Particularly preferably, a resin composition having A: B in the range of 85:15 to 55:45, that is, a polylactic acid resin (A) as a main component is preferable because of high tensile breaking strength and plastic deformability.
The resin composition of the present invention includes various heat stabilizers, antioxidants, ultraviolet absorbers, light stabilizers, nucleating agents, pigments, lubricants, as long as necessary, in addition to the above components, as long as necessary performance is not impaired. An antistatic agent, a flame retardant aid, a filler, a plasticizer, a crosslinking agent, a crosslinking aid and the like can be blended.
However, since the addition of the plasticizer tends to inhibit the room temperature plastic deformability of the present invention, it is preferable to use a resin composition in which a substantial amount of the plasticizer is not added.
Preferably, the total amount of the resin (A) and the resin (B) is 80% by weight or more, preferably 85% by weight or more of the entire resin composition.

  There is no restriction | limiting regarding the manufacturing method of the resin composition of this invention. By melting and mixing the components in an arbitrary order or simultaneously, a composition in which the components are uniformly distributed can be obtained. In addition, a well-known means is mentioned as a means to melt-mix. For example, a continuous kneader such as a single screw extruder or a twin screw extruder, or a batch kneader such as a mill roll, a Banbury mixer, or a pressure kneader can be preferably used. The melt mixing temperature is preferably 160 ° C to 230 ° C.

The room temperature plastically deformable resin composition of the present invention can be used as a molded body by any molding method. Examples of the shape of the molded body include a band shape, a linear shape, a plate shape, a rod shape, and the like, and particularly preferably when used as a strip shape or a linear shape, the plastic deformability and the repetitive characteristics can be effectively used. .
The normal temperature plastic deformability of the present invention means that at least in the form of a tape, a film (band shape) or a thread (linear shape), the return angle after 10 minutes when bent at 180 ° C. is 60 degrees or less.

  The room temperature plastic deformable resin molded product obtained in the present invention is used for applications that require conventional metal wire replacement and shape retention, such as packaging binders, fruit vegetable binders, wire binders, and food products. It can be used in a wide range of applications such as binding materials for clothes, hanger materials for clothes, core materials for clothes, color core materials for Y-shirts, edge members for hats, and core materials for dolls.

  Since the room temperature plastically deformable resin composition of the present invention is excellent in mechanical properties and workability, a desired molded product can be easily obtained. Further, the obtained molded product has mechanical properties that can sufficiently withstand the requirements and appropriate flexibility without deteriorating workability. In addition, since it has biodegradability, it can be decomposed without generating harmful substances that cause environmental load even when left in the natural environment after use, and is useful for environmental conservation.

Hereinafter, the present invention will be described in detail with reference to examples and comparative examples. However, the present invention is not limited to these.
<Raw Materials> Table 1 shows the raw materials used. The tensile breaking elongation is a value obtained according to JIS K7161.
<Sample preparation> Various raw materials weighed in accordance with the blending ratios in Tables 2 and 3 were charged into a 20 L Henschel mixer (rotation speed: 100 revolutions, agitation time: 3 minutes), stirred, and the mixture was mixed in the same direction twin screw extruder ( After inserting into a 30 mm diameter, L / D = 30, rotation speed 200 rpm, set temperature 200 ° C. and melt-kneading, the strand-shaped resin was cooled and cut to obtain pellets having a uniform composition.
<Preparation of Test Sample> Using a 20 mm single screw extruder equipped with a die having a die with a width of 20 mm and a thickness of 0.5 mm, the obtained resin composition was extruded at a molding temperature of 200 ° C. and then cooled at 25 ° C. As a result, a tape-shaped molded product having a width of 15 mm and a thickness of 0.5 mm was obtained.
Bending test piece: A tape-shaped molded body obtained by the above-described extrusion molding was cut into a strip-shaped molded body having a width of 3 mm to obtain a folding test piece.
<Various test methods>
Bending test: A test was carried out using the bending test piece described above. In the test method, the left end and the center of a horizontally placed test piece are fixed, the right end of the test piece is bent 180 degrees in the forward direction until it contacts the left end of the test piece, then returned to the original position, and then 180 degrees in the reverse direction. Bent. The number of times of the test was set to 10 times in total with one folding in the forward and reverse directions, and the speed was 1 time / second.
Shape retention confirmation test: Using the above-mentioned bending test piece, after bending 180 degrees in the forward direction by the same method as the bending test, the external force was removed, and the return angle after 10 minutes was measured.
Tensile test: A tensile test was performed on the test piece after the bending test at a tensile speed of 200 mm / min.
<Evaluation criteria> Repeated bending endurance test: In the repeated bending endurance test, those in which brittle fracture was not confirmed were accepted, and then a tensile test was performed.
Shape retainability: In the shape retainability confirmation test, those having a return angle of 60 degrees or less were regarded as acceptable.
Tensile test: A sample having a tensile strength at break of 20 MPa or more was regarded as acceptable.

<Result>
As described above, according to the resin composition comprising the specific resin combination of the present invention, it is possible to obtain a molded article that can be plastically deformed at room temperature and has excellent repeated bending durability and tensile strength.

Claims (6)

Room temperature plastic deformation, comprising a polylactic acid resin (A) and a biodegradable thermoplastic resin (B) having a tensile elongation at break of 200% or more and a ratio of A: B of 90:10 to 35:65 Resin composition. The resin composition according to claim 1, wherein the polylactic acid resin (A) is a homopolymer having L-lactic acid or D-lactic acid as a structural unit. 2. The resin composition according to claim 1, wherein the thermoplastic resin (B) is an aliphatic polyester resin or an aliphatic-aromatic polyester. A room-temperature plastically deformable resin molded product molded using the resin composition according to claim 1. A room-temperature plastically deformable resin molded product, wherein the molded product according to claim 4 is in the form of an elongated strip or wire. 6. A room temperature plastically deformable resin molded article according to claim 4 or 5, wherein when the test piece is 3 mm wide, 15 mm thick and 0.5 mm thick, the return angle after bending 180 degrees is 60 degrees or less, and the tensile strength at break is 20 MPa or more. body.