JP3387255B2 - Antistatic polylactic acid and its molded product - Google Patents

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to an antistatic polylactic acid and a molded product thereof.

[0002]

BACKGROUND OF THE INVENTION Polymers that are biodegradable or that decompose in the natural environment have attracted attention from the standpoint of environmental protection. In particular, polylactic acid, which is made from agricultural products, is advantageous in terms of resources,
Further, it is most expected because it has excellent melt moldability and heat resistance. However, since unmodified polylactic acid has high crystallinity and low water absorption, it is easily charged by rubbing or peeling, and causes various electrostatic troubles. Therefore, polylactic acid excellent in antistatic property is required.

Conventionally, it is well known that a synthetic resin such as polyamide or polyester is mixed with a polyether, especially polyethylene glycol or a modified product thereof to give an antistatic property (hereinafter referred to as antistatic property).

[0004]

However, when polyethylene glycol is mixed with polylactic acid, the polyethylene glycol is mixed in a relatively large particle form because of its small affinity, and in order to obtain sufficient antistatic property. It is necessary to mix a considerably large amount, and there arises a problem that the transparency and gloss of the molded product are impaired.

Therefore, the present invention provides an improved new polylactic acid composition capable of suppressing the deterioration of the transparency and gloss of a molded product and obtaining an excellent antistatic property with a relatively small mixing ratio. With the goal.

[0006]

The above object of the present invention comprises a block copolymer of a polyalkylene ether and an aliphatic polyester other than polylactic acid in a polymer (A) containing lactic acid as a main component. Antistatic agent (B), weight ratio (A /
B) It is achieved by mixing in the range of 99.7 / 0.3 to 50/50.

Here, the polymer whose main component is lactic acid is
Polylactic acid homopolymers such as poly (L-lactic acid), poly (D-lactic acid), and poly (L / D-lactic acid), and copolymerized poly (lactic acid) obtained by copolymerizing a polymerization raw material capable of forming an ester bond therewith, and a component derived from lactic acid in a polymer. Means 50% by weight or more.

Polyalkylene ether (polyalkylene oxide) is electrically conductive due to an ether bond, but polyethylene glycol, polypropylene glycol and their copolymers are excellent in antistatic property as an antistatic agent, especially polyethylene. Glycol and its modified products have the best antistatic property.

The feature of the composition of the present invention is that a block copolymer of an aliphatic polyester and a polyalkylene ether is used as the antistatic agent (B). The block copolymer may be one in which the aliphatic polyester segment (R) and the polyalkylene ether segment (E) are bonded to each other in the type R · E in a ratio of 2: 1 or 1: 2. E
It may be combined with a type such as R, E, R, E, or a large number of segments (blocks) such as R, E, R, E, R, E may be combined. Further, a third component may be inserted between them as a joint, and a secondary component other than these may be added. However, the main components (50% by weight or more) are polyalkylene ether and aliphatic polyester.

Here, the aliphatic polyester is other than polylactic acid, and is a polymer of hydroxyalkylcarboxylic acid such as glycolic acid or hydroxybutylenecarboxylic acid, ε.
-A polymer containing aliphatic lactones such as caprolactone and butyrolactone, and a polymer of an aliphatic diol and an aliphatic dicarboxylic acid as a main component (50% or more). As a secondary component, for example, an aromatic component or It may contain a small amount (50% or less) of an ether compound. As the aliphatic diol, diols having 2 to 20 carbon atoms such as ethylene glycol, butanediol, octanediol, decanediol and dodecanediol are preferably used. As the aliphatic dicarboxylic acid, dicarboxylic acids having 4 to 20 carbon atoms such as succinic acid, adipic acid, sebacic acid, decanedicarboxylic acid and dodecanedicarboxylic acid are preferably used. Among the aliphatic polyesters obtained from these diols and dicarboxylic acids, those obtained from diols having 2 to 10 carbon atoms and dicarboxylic acids such as polyethylene succinate, polyethylene adipate, polyethylene sebacate, polybutylene succinate, polybutylene Adipate, polybutylene sebacate, polyhexane succinate, polyhexane adipate, polyhexane sebacate, and the like have high affinity with polylactic acid and are preferable as a component of the antistatic agent (B) of the present invention, and have 2 to 2 carbon atoms. Most preferably, it comprises 6 components.

Similarly, polyglycolic acid, polyhydroxybutyrate, poly ε-caprolactone and the like, the polyhydroxycarboxylic acid or polylactone having 2 to 10 carbon atoms, particularly 2 to 6 carbon atoms in the constitutional unit can also be used as the antistatic agent of the present invention (B). Is particularly preferable as the component (1). Similarly, the number of carbon atoms in the constitutional unit is 2 to 1.
0, especially 2 to 6 hydroxycarboxylic acids, lactones,
A copolymerized aliphatic polyester (containing oligomer) using two or more kinds of diol and dicarboxylic acid is also particularly preferable as a constituent component of the antistatic agent (B) of the present invention.

The function of the aliphatic polyester segment in the antistatic agent (B) is to enhance the affinity between the antistatic agent (B) and polylactic acid (A) which is the matrix (matrix) polymer. The higher the affinity of the two, the more finely the antistatic agent is dispersed in the base polymer, and a molded product excellent in antistatic property, transparency, gloss and the like can be obtained. However, when the amount of the aliphatic polyester segment in the antistatic agent is too large, the polyether segment decreases and the antistatic property becomes poor. Therefore, the weight fraction of the polyalkylene ether component in the antistatic agent (B) is
50 to 97% is preferable, and 70 to 95% is particularly preferable. That is, the weight fraction of the aliphatic polyester component in the antistatic agent (B) is preferably 3 to 50%, particularly preferably 5 to 30%.

The molecular weight of the antistatic agent (B) is not particularly limited, but it is preferable that it is somewhat large, for example, a molecular weight of 1,000.
Above all, particularly preferably 3,000 or more, more preferably 5,000 or more, and 10,000 to 200,000 is most widely used.

Production of the antistatic agent (B) used in the present invention is relatively easy. For example, if one end is blocked and polyethylene glycol having a hydroxyl group at one end is mixed with the polymerization raw material of the aliphatic polyester and reacted (copolymerized), RE
Type block copolymer is obtained, and polyethylene glycol having hydroxyl groups at both ends is copolymerized with an aliphatic polyester to obtain R / E / R type, E / R / E type, E / R / E / R type.
You can get various types such as molds. Similarly, polyethylene glycol having a hydroxyl group at the terminal of the molecule and aliphatic polyester having a hydroxyl group at the terminal are reacted with a difunctional compound such as dicarboxylic acid, dicarboxylic acid anhydride, dicarboxylic acid chloride, or diisocyanate to link the two. You can Further, an alkylene oxide, for example, ethylene oxide, may be added to an aliphatic polyester having a hydroxyl group at the end to carry out addition polymerization to form a polyethylene glycol chain to obtain a block copolymer. In these reactions, it is relatively easy to control the molecular weight of the polyalkylene ether block and the molecular weight of the aliphatic polyester block. For example, if 80 parts of polyethylene glycol having a molecular weight of 8,000 and 20 parts of an aliphatic polyester raw material are completely and uniformly reacted (polymerized), polyethylene glycol having a molecular weight of 8,000 and an aliphatic polyester (oligomer) having a molecular weight of about 1,000 or less are bonded. It should be possible to obtain various types of block copolymers. Actually, as an average value, considerable variation occurs, and a mixture of various compounds is obtained, but the main component of the mixture is a block copolymer of polyethylene glycol and an aliphatic polyester, Can be used as it is as an antistatic agent.

Functional groups such as a hydroxyl group and a carboxyl group at the molecular end of the antistatic agent may be used as they are, but it is more preferable to react with a monofunctional compound to block and stabilize the same. The higher the electric conductivity of the antistatic agent (B), the better. Generally, polyethylene glycol has a volume resistivity of about 1 × 10 ⁹ ohm · cm (measured at 25 ° C., 40% RH, and direct current of 1 kV or less), and is 1 × 1 when copolymerized with an aliphatic polyester.
It increases to about 0 ¹⁰ ohm · cm. However, a compound which is easily ionized, such as sodium alkylbenzene sulfonate, is mixed to about 2 to 20% to obtain a volume resistivity of 1 ×.
It can be about 10 ^{8 to 9} ohm · cm or less, which is suitable for the purpose of the present invention. The volume resistivity of the composition and molded product of the present invention is 1 × 10 ¹² ohm · cm or less, and particularly 1 × 10 ¹¹
Ohms / cm or less is preferable. Antistatic agents such as hindered phenols, various stabilizers, ionizing compounds, ultraviolet absorbers and other additives can be added to the antistatic agent (B) as secondary additives.

The mixing of the antistatic agent (B) with the base polymer (A) is optional such as mechanical stirring, application of a static mixer, and combination of both. The mixing is generally performed after the polymerization of the base polymer (A). When added in the polymerization raw material or during the polymerization step, they may react with each other to cause copolymerization, and the antistatic property may be lost or lowered. The excellent antistatic property requires that the antistatic agent is independently present in the form of fine particles, fine fibers, network structure, thin layer, etc. dispersed in the matrix polymer. When the polyalkylene ether block is incorporated into the matrix polymer molecule by copolymerization, it is necessary to use a considerably large amount of polyalkylene ether, which leads to deterioration of physical properties and is not preferable.

Mixing by mechanical stirring can be carried out by using various stirrers, screw extruders, twin-screw kneaders, kneaders, gear pumps and the like. On the other hand, when static mixing is performed by repeating flow division and joining (composite) using a static mixer, the antistatic agent (B) has a continuous structure such as a thin layer or fine fiber in the base polymer (A). It can be finely dispersed. As examples of static mixers, the present inventors have proposed Japanese Patent Publications Nos. 47-15526, 47-15527 and 47-
15528 and 47-15533, and those disclosed in JP-A-47-34166. It is also possible to use mechanical stirring and a static mixer together. For example, after multi-layer mixing with a static mixer and metering and feeding with a gear pump, the antistatic agent is mechanically agitated in the pump portion, and the antistatic agent is dispersed into fine particles. Of course, the antistatic property of the continuous structure is much better than that of the granular (discontinuous) structure.
With a mixing ratio of the antistatic agent of 1/10, the same antistatic property is often obtained.

The mixing ratio of the antistatic agent (B) in the composition of the present invention varies depending on the conductivity of the antistatic agent, the composition of the antistatic agent and the volume resistivity, but in most cases 0.3 to 50% by weight, especially 0.5-3
A range of 0% is preferred. As described above, when the antistatic agent is dispersed / mixed in a continuous structure such as fibrous, reticulated, or thin film, it has excellent electrical conductivity and a relatively small mixing ratio, for example, 0.
An excellent antistatic property is obtained at 3 to 10%, especially 0.5 to 5%. On the other hand, when the antistatic agent is dispersed and mixed in a discontinuous structure such as a particle shape, an elongated particle shape, or a needle shape, a relatively large amount of the antistatic agent is required, for example, 3 to 50%, particularly 5 to 30%. % Mixing is preferred. In a mixed structure of discontinuous and continuous, for example, a structure in which granular and fibrous are mixed, an intermediate mixing ratio between the two is suitable.

In addition to the polymer (A) containing lactic acid as a main component and the antistatic agent (B), other components may be secondarily added to the composition of the present invention. Examples of secondary additives include stabilizers, antioxidants, ultraviolet absorbers, pigments, colorants, various inorganic particles, various fillers, water repellents, hydrophilic agents, mold release agents, plasticizers, physiologically active substances. , Antiseptics, antibacterial agents, foaming agents and the like.

[0020]

The aliphatic polyester segment in the antistatic agent (B) enhances the affinity between the antistatic agent (B) and polylactic acid (A) which is the matrix (matrix) polymer. The higher the affinity of the two, the more finely the antistatic agent is dispersed in the base polymer, and a molded product excellent in antistatic property, transparency, gloss and the like can be obtained.

[0021]

EXAMPLES In the following examples, parts and% are shown by weight ratio and weight fraction unless otherwise specified. The molecular weight of the polymer containing lactic acid as the main component is GP of 0.1% chloroform solution of the sample.
In the C analysis, of the dispersion of the high molecular weight substance except the molecular weight of 500 or less,
It is a weight average value.

[Example 1] 90 parts of polyethylene glycol having a molecular weight of 8,000 and hydroxyl groups at both ends and 15 parts of bishydroxyethyl adipate to 50 parts of antimony trioxide.
After mixing 0 ppm and 0.1% of Ciba-Geigy Irganox, the mixture was reacted in nitrogen at 240 ° C. under normal pressure for 2 hours, then gradually depressurized to reach 0.5 Torr after 1 hour, and the reaction was continued for further 4 hours to obtain polyethylene glycol. And polyethylene adipate block copolymer (copolymerization ratio approx. 100/1
2) Antistatic agent AS1 with a molecular weight of about 40,000 (volume resistivity 5 x
10 ⁹ ohm · cm) was obtained.

Biaxial continuous mixing in which 0.03% tin octylate and 0.1% titanium oxide particles (crystal nucleating agent) having a diameter of 0.05 μm are mixed with L-lactide having an optical purity of 99% or more, and two screws mesh with each other. Using a liquid feeder, continuously react in nitrogen atmosphere at 180 ° C for an average of 30 minutes, and then add 0.1% tin octylate, stirring screw groups that mesh with each other and elliptical (2-flight type) stirring with each other Using a twin-screw kneader consisting of a group of elements, polymerization was carried out at 190 ° C. for 17 minutes, and 7% of the antistatic agent AS1 that was melted and had a water content of 5 ppm or less was added to the polymerization system and mixed, After mixing through a cylinder having a static mixer 60 element incorporated by Kenix Co., Ltd., the mixture was extruded from a die, cooled with water, solidified and cut to obtain a chip C1.

The chip C1 was heated in nitrogen at 120 ° C. for 12 hours and further heat-treated (solid phase polymerization) at 160 ° C. for 48 hours to obtain a chip C2. The average molecular weight of Chip C2 is 16,100,
The amount of residual monomer (lactide) was 0.2%.

Chip C2 was melted with a screw extruder at 200 ° C., spun out from an orifice with a hole diameter of 0.2 mm and a temperature of 195 ° C., cooled in air, and oiled to 800 m / mi.
It is wound at a speed of n, then drawn 3.7 times at a drawing temperature of 80 ° C, and heat-treated at 120 ° C under tension to obtain a fineness of 75 denier / 2.
A 4-filament stretched yarn Y1 was obtained.

In the same manner as the drawn yarn Y1, except that the antistatic agent AS
The drawn yarn obtained without adding 1 is designated as Y2.

A tube knit K1 was obtained from the drawn yarn Y1 using a small circular knitting machine having a cylinder diameter of 80 mm. Knit K1 to JI
Washed 3 times with household detergent and household electric washing machine according to S L 1094-1988, rinsed thoroughly in a stream of water, then dried with hot air dryer at 80 ° C. for 2 hours, then 25
After standing in a thermostatic chamber at 33 ° C and RH for 24 hours, its triboelectric charging property was measured.

The measurement of triboelectric charge was developed by the present inventors,
It is stipulated in JIS L 1094-1988 as a reference method "measuring method of frictional electrification discharge curve".
vol.40, No.4, p181-188 (1987) and Japanese Patent Publication No. 62-11303. That is, the washed sample is cut into a length of 12 cm and a width of 12 cm,
Attached to a metal plate with a hole of 7 cm in diameter, wash, dry, and humidity-adjusted woolen fabric as a friction cloth on a wooden table,
After rubbing 10 times manually, it is moved away from the table and moved in front of the potential detector, and the friction electrification voltage and its decay curve are recorded by a recorder.

The triboelectric charge of Knit K2 obtained using the drawn yarn Y2 was measured in the same manner as Knit K1. For comparison, polyethylene glycol having a molecular weight of 50,000 was mixed as an antistatic agent in an amount of 7%, and the chargeability of a knitted fabric K3 obtained in the same manner as the knitted fabric K1 was measured. Table 1 shows the electrification voltage of the knitted fabrics K1, K2 and K3 immediately after rubbing and the electrification voltage after 1 minute of friction. As shown in Table 1, the knitted fabric K1 according to the present invention had a lower absolute value of the charged voltage (especially after 1 minute) and was excellent in antistatic property as compared with Comparative Examples K2 and K3.

[0030]

[Table 1] Example 2 Polylactic acid and poly (lactic acid) obtained by melt-copolymerizing 15 parts of polybutylene adipate having a molecular weight of about 20,000 and hydroxyl groups at both ends and 85 parts of L-lactide having an optical purity of 99% or more at 180 ° C. for 45 minutes. A block copolymer of butylene adipate is referred to as polymer P3. The molecular weight of polymer P3 is 16
At 3,000, this was melt spun in a screw extruder at a temperature of 200 ° C. Antistatic agent AS2 melted and dehydrated separately during spinning
Was mixed at 0.7% in a spinneret equipped with a static mixer and spun. Antistatic agent AS2 was obtained by mixing 15% of sodium dodecylbenzenesulfonate with AS1 of Example 1 to reduce the volume resistivity to 1 × 10 ⁸ . The static mixer is disclosed by the present inventors in Japanese Examined Patent Publication No. 57-20842, and has 12 mixing elements connected in series. The antistatic agent mixed in multiple layers (thin layers) by the static mixer is divided by the final filter immediately before the orifice, dispersed in multiple points in the cross section of the fiber, and substantially continuous in the longitudinal direction. It becomes a fibrous (linear) form. (A similar product can be obtained by using 10 to 12 mixing elements in series of a static mixer manufactured by Kenix, USA). The spun fiber was used as the drawn yarn Y1 and the knit K of Example 1.
In the same manner as in No. 1, the triboelectric chargeability of the knitted fabric K4 stretched, heat-treated, knitted, washed, dried, and conditioned was measured, and the results shown in Table 2 were obtained. As shown in Table 2, by mixing the ionizing compound into the antistatic agent and mixing the antistatic agent into the base polymer in the form of continuous fine fibers, it is possible to mix the antistatic agent in a very small amount. , High antistatic property can be obtained. Regarding the gloss and transparency of the knit, the knits K1 and K4 according to the present invention were excellent, and the antistatic knit K3 of Comparative Example was inferior in gloss and transparency.
(This difference is even greater for films and thick molded products).

[Table 2]

[0031]

INDUSTRIAL APPLICABILITY According to the present invention, various molded products excellent in antistatic property, gloss and transparency can be easily obtained. For example, fiber,
Knit, woven, non-woven, paper, steel, net, rope, film,
Examples include sheets, plates, rods, various containers, tubes, various parts, and other various molded products. With the antistatic composition according to the present invention, various molded articles are damaged by electrification, that is, dirt, contamination by adhesion of bacteria, skirts, pants, underwear and other fluffiness, ignition of flammable materials due to spark discharge, explosion, electronic discharge by spark discharge. Malfunctions and failures of equipment can be reduced or prevented, and excellent fibers, films, and molded products with high gloss and transparency can be obtained. Further, the antistatic agent of the present invention (B)
Has a small elastic modulus and is excellent in impact absorption, so that the composition and the molded product of the present invention have improved flexibility and impact resistance as secondary effects.

Claims (3)

(57) [Claims] 1. A polymer (A) containing lactic acid as a main component,
An antistatic agent (B) comprising a block copolymer of a polyalkylene ether and an aliphatic polyester other than polylactic acid,
An antistatic polylactic acid composition, which is mixed in a weight ratio (A / B) of 99.7 / 0.3 to 50/50. 2. The composition according to claim 1, wherein the polyalkylene ether is at least one selected from the group consisting of polyethylene glycol, polypropylene glycol and copolymers thereof. 3. A fiber, a knitted fabric, a woven fabric, a non-woven fabric, a paper, a felt, a net, which comprises the composition according to claim 1.
Rope, film, sheet, board, rod, tube, container,
Various parts or other molded products.