JP3592819B2 - Antistatic polylactic acid film and sheet - Google Patents

Description

（実施例４〜９）
次に、同様の方法で、表２に示す量の各種非イオン系帯電防止剤を添加し、キャストフィルムを得た。これらの評価結果を表２に示す。
【００４９】
【表２】

（比較例４〜９）
続いて、同様の方法で、表３に示す量の各種アニオン系およびカチオン系帯電防止剤を添加し、キャストフィルムを得た。これらの評価結果を表２に示す。
【００５０】
【表３】

表１に示すように、本発明に含まれる非イオン系帯電防止剤を０．１〜１０重量部含有すると、表面抵抗率が５×１０^１３以下であり、かつ、重量平均分子量保持率が５０％以上である。また表２に示すように、（１）に含まれる化合物群を使用した実施例４〜６、（２）に含まれる化合物群を使用した実施例７、（３）に含まれる化合物群を使用した実施例８および９は、表面抵抗率が５×１０^１３以下であり、かつ、重量平均分子量保持率が５０％以上である。
【００５１】
一方、（１）〜（３）の化合物群に含まれない、アニオン系、カチオン系の帯電防止剤を使用した比較例４〜９は表面抵抗率が５×１０^１３を超え、あるいは、重量平均分子量保持率が５０％未満である。
【００５２】
【発明の効果】
以上の結果で明らかなように、本発明の生分解性フィルムおよびシートは溶融押出時の熱安定性が良好で実用上の帯電防止性を有する。[0001]
The present invention relates to biodegradable films and sheets having antistatic properties.
[0002]
[Prior art]
In recent years, due to an increase in environmental problems, when a plastic product is discarded in the natural environment, it is required to decompose and disappear over time, and finally have no adverse effect on the natural environment.
[0003]
Conventional plastics are stable in the natural environment for a long period of time and have a low bulk density, which has led to problems such as shortening the life of waste landfills and impairing the natural landscape and the living environment of wild animals and plants. It had been.
[0004]
Therefore, biodegradable plastic materials are attracting attention today. It is known that biodegradable plastics gradually decompose and decompose in soil or water due to hydrolysis or biodegradation, and eventually become harmless decomposition products due to the action of microorganisms.
[0005]
Examples of biodegradable plastics that have begun to be put into practical use include aliphatic polyesters, modified PVAs, cellulose ester compounds, modified starches, and blends thereof. Each of these biodegradable plastics has its own unique characteristics, and it is conceivable to develop applications corresponding to these. Among them, polylactic acid-based polymers, one of aliphatic polyesters, are other biodegradable plastics. Compared with, it has excellent transparency, rigidity, heat resistance, workability, etc., and is used for transparent films and sheets in which rigid polyvinyl chloride (PVC), polystyrene, polyethylene terephthalate (PET) has been used. It is about to be rolled out.
[0006]
However, films and sheets made from a polylactic acid-based polymer, as seen in general-purpose plastics such as PVC, are easily charged due to friction and the like due to their large specific resistance, and have the following defects. I was
[0007]
Shocked when touched. Spark discharge may cause a fire. The workability and handleability during use are reduced due to rebound and sticking between films or other objects. Adhesion of dust impairs aesthetics and hygiene and lowers product value.
[0008]
In general-purpose plastic films and sheets, an improved technique of kneading an antistatic agent or applying it to the surface in an extrusion step has been widely adopted in order to solve such a problem.
[0009]
[Problems to be solved by the present invention]
However, a polylactic acid-based polymer has significantly lower thermal stability in an extruder than a general-purpose plastic, and tends to cause a decrease in molecular weight. Usually, the addition of an antistatic agent further promotes a decrease in molecular weight, and thus causes a decrease in production stability and a decrease or variation in product quality including mechanical properties. For this reason, kneading of the antistatic agent in the extrusion step was substantially difficult.
[0010]
Antistatic agents are broadly classified into cationic, anionic, zwitterionic and nonionic types, and are properly used depending on the processing method and application. In general-purpose plastic film and sheet applications, the most commonly used are anionics having a good balance between effectiveness and economy, and typically include 1) fatty acid salts, 2) higher alcohol sulfates, and 3). Liquid fatty oil sulfates, 4) aliphatic amine and aliphatic amide sulfates, 5) aliphatic alcohol phosphate esters, 6) dibasic fatty acid ester salts, 7) fatty acid amide sulfonates, 8) alkyl Arylsulfonic acid salts, 9) formalin-condensed naphthalenesulfonic acid salts, and the like.
[0011]
In addition, examples of cationic systems which are weak to heat and high in cost but have high antistatic properties include 1) aliphatic amine salts, 2) quaternary ammonium salts, and 3) alkylpyridinium salts. Furthermore, zwitterionic systems which have slightly improved heat resistance, which is a weak point of anionic systems, include 1) imidazoline derivatives, 2) ammonium carboxylate, 3) ammonium sulfate, 4) ammonium phosphate, 5 ) Ammonium sulfonates and the like.
[0012]
These ionic antistatic agent, a general-purpose plastic films and sheets applications have been very broad and heavy use, the polylactic acid of the present invention can not be suitably used. Because, although the antistatic effect aimed obtained, for although kneaded it, in polylactic acid extruder, cause significant thermal decomposition, because cause molecular weight reduction. A decrease in molecular weight leads to a decrease in product stability such as a decrease in production stability, mechanical properties and heat resistance, as well as a decrease in appearance such as occurrence of uneven flow, which is extremely undesirable in practical use.
[0013]
The method of applying an antistatic agent to the surface of a film or sheet has the following problems. Coating equipment is required, and the number of steps is increased, thereby increasing the production cost. Since the liquid antistatic agent scatters around, maintenance of the working environment is complicated. Quality problems such as stickiness, blooming, interference fringes, and blocking are likely to occur.
[0014]
As described above, it has been difficult to impart antistatic properties to polylactic acid-based films and sheets that are biodegradable materials.
[0015]
[Means for Solving the Problems]
The present inventors have made intensive studies in view of such a current situation, and as a result, completed the present invention.
[0016]
The main idea of the present invention, the feature that the following compounds (1) to which at least one nonionic antistatic agent selected from (3) containing 0.1 to 10 parts by weight to 100 parts by weight of polylactic acid it is antistatic polylactic Sanfu Irumu and sheets.
[0017]
(1) a polyhydric alcohol and / or its fatty acid ester (2) polyethylene glycol and / or its fatty acid esters such as ethylene glycol, diethylene glycol triethylene glycol, glycerin, trimethylolpropane penta El slit sorbitan (3) Luxury Polyethylene glycol adduct of alcohol / polyhydric alcohol / alkylphenol or polypropylene glycol adduct
BEST MODE FOR CARRYING OUT THE INVENTION
The polylactic acid used in the present invention, forming the shape processability, the film and the purpose of adjusting the physical properties of the sheet, plasticizers, lubricants, inorganic fillers, ultraviolet absorbers, light stabilizers, antifungal, pigments, fluorescent agents It is also possible to add additives and modifiers such as these.
[0019]
Examples of the lactic acid include L-lactic acid and D-lactic acid .
[0020]
As these polymerization methods, any of known methods such as condensation polymerization and ring-opening polymerization can be employed.Moreover, a small amount of a chain extender for the purpose of increasing the molecular weight, for example, a diisocyanate compound, A diepoxy compound, an acid anhydride, an acid chloride or the like may be used. The weight average molecular weight of the polymer is preferably in the range of 50,000 to 1,000,000. If the weight average molecular weight is below the range, practical properties are hardly exhibited. On the other hand, if it exceeds, the melt viscosity becomes too high and the moldability is poor. Further, in order to improve the thermal stability, it is preferable that the amount of the residual monomer or the catalyst is small.
[0021]
Such polylactic acid, in the present invention, the melt extruded from die using an extruder, formed into films and sheets. As a special case, if it passes through a molten state, pellet press molding or calendar molding may be used.
[0022]
At the time of extrusion of polylactic acid, to prevent thermal decomposition in the extruder (hydrolysis), it is desirable to sufficiently dry beforehand raw materials.
[0023]
When obtaining a film, a flat or cylindrical material melt-extruded from a T-die, I-die, round die, etc., is quenched by a cooling cast roll, water, compressed air, etc. The film is uniaxially or biaxially stretched by a method such as a tubular method. Further, a so-called inflation method, in which melt extrusion is performed from a round die and air is blown into a cylindrical material that is still in a molten state to reduce the thickness, can also be preferably used.
[0024]
Furthermore, if the film stretching and heat fixing techniques disclosed in Japanese Patent Application Laid-Open No. 5-508819 and Japanese Patent Application Laid-Open No. 6-23836 are used, excellent transparency, mechanical strength, rigidity, thermal dimensional stability, and the like are obtained. A polylactic acid-based film can be obtained. The thickness of the film is determined in the range of 10 to 250 μm depending on the application.
[0025]
The most preferable method for obtaining a sheet is a method in which the sheet is extruded into a flat shape using a T-die and rapidly cooled by a metal cast roll equipped with a temperature control device. If necessary, the sheet is nipped with a cast roll and another metal roll. By doing so, a polylactic acid-based sheet having extremely excellent transparency and smoothness can be obtained. The thickness of the sheet is generally determined in the range of 250 μm to 1 mm depending on the application.
[0026]
As the extruder to be used, any known form such as a single-screw, co-direction twin-screw, and different-direction twin-screw extruder can be used. The most common method is to preliminarily pelletize a raw material containing a predetermined additive using a co-axial twin-screw extruder having a high kneading effect, and then supply the pellet to a film / sheet extruder. An agent or the like may be directly mixed with the raw materials at the time of extruding the film / sheet.
[0027]
Set temperature of the extruder is suitably determined by chemical composition and molecular weight of polylactic acid is preferably in the range of 170 to 230 ° C.. At 170 ° C. or lower, the homopolymer having a melting point of 175 ° C. does not melt, and at 230 ° C. or higher, thermal decomposition becomes remarkable.
[0028]
In the present invention, when forming the film and sheet by melt-extruding a polylactic acid, adding a predetermined amount of a specific antistatic agent into polylactic acid, kneading them during molding.
[0029]
Minimizing thermal decomposition of the polylactic acid, to produce a practical film sheet, the most important point of the present invention employs a nonionic antistatic agent shown in the following (1) to (3) That is.
[0030]
(1) a polyhydric alcohol and / or its fatty acid ester (2) polyethylene glycol and / or its fatty acid esters such as ethylene glycol, diethylene glycol triethylene glycol, glycerin, trimethylolpropane penta El slit sorbitan (3) Luxury polyethylene glycol adduct of an alcohol-polyhydric alcohol alkyl phenol or polyhydric alcohol polypropylene glycol adduct (1), it is, can be used it is, in order to increase compatibility against the polylactic acid, a fatty acid It is more preferable to make the fatty acid ester by an esterification reaction. Fatty acids are not particularly limited, but include saturated fatty acids such as lauric acid (C12), palmitic acid (C16), stearic acid (C18), and behenic acid (C22); Unsaturated fatty acids and the like are advantageously used in terms of cost. Also, mixed fatty acids derived from natural products such as coconut oil fatty acid, soybean oil fatty acid, tallow fatty acid, and sardine oil fatty acid can be used.
[0031]
When the polyhydric alcohol is esterified with these fatty acids, it is preferable that at least one hydroxyl group remains per molecular structural unit of the polyhydric alcohol. When all hydroxyl groups are esterified, the antistatic effect is not sufficiently exhibited, particularly in the case of ethylene glycol and glycerin.
[0032]
In addition, when sorbit is esterified, it is simultaneously dehydrated in the molecule to form sorbitan, and thus the obtained compound is a sorbitan ester.
[0033]
Fatty acid esters of polyhydric alcohols are also produced by a transesterification reaction. In the case of a well-known monoglyceride, it can be obtained by adding glycerin to animal and vegetable fats and oils and heating it together with a catalyst.
[0034]
The polyethylene glycol of (2) preferably has a repeating unit of ethylene oxide of 4 to 1,000. Polyethylene glycol can be used as it is as an antistatic agent, but it is not always necessary to leave a terminal hydroxyl group in the case of esterification with a fatty acid for the purpose of further increasing the compatibility.
[0035]
The higher alcohol of (3) is not particularly limited as long as it has 6 or more carbon atoms. Typical examples of industrially easily available nonyl alcohol, decyl alcohol, lauryl alcohol, myristyl alcohol, cetyl alcohol, Primary alcohols such as stearyl alcohol and oleyl alcohol can be mentioned. Mixtures such as sperm alcohol and jojoba alcohol, and reduced alcohols such as tallow alcohol and coconut alcohol can also be used.
[0036]
Examples of the polyhydric alcohol include glycerin, trimethylolpropane, pentaer slit, sorbit, and sucrose. Examples of the alkylphenol include nonylphenol, dodecylphenol, octylphenol, octylcresol and the like.
[0037]
In the compound (3), these higher alcohols / polyhydric alcohols / alkylphenols and polyethylene glycol or polypropylene glycol form an adduct, and the reaction may be carried out in two ways. That is, the dehydration etherification reaction of both, and the addition reaction of the latter monomer, ie, ethylene oxide and propylene oxide, to the former. Industrially, an addition reaction of ethylene oxide and propylene oxide is more preferably used. The number of moles of ethylene oxide and propylene oxide to be added is determined in the range of 1 to 100, preferably 1 to 20.
[0038]
It is desirable that the antistatic agent be sufficiently dried in advance. Insufficient drying undesirably induces thermal decomposition of the polylactic acid.
[0039]
In the present invention, by selecting one or more of the antistatic agents described above, with respect to polylactic acid 1 00 parts by weight, blending 0.1-10 parts by weight. If the ratio is below the range, the antistatic effect is not sufficiently exhibited. Specifically, when the surface resistivity of the polylactic acid film and sheet, which is 10 ¹⁴ units, is 5 × 10 ¹³ or less, even if static electricity is generated in the film and sheet in the process, the charge is quickly diffused.
[0040]
On the other hand, if it exceeds, thermal decomposition occurs, causing a decrease in viscosity and poor compatibility. For this reason, extrusion becomes difficult, resulting in poor appearance of the film / sheet and poor sheeting. Specifically, it is necessary that the weight average molecular weight retention when heated at 190 ° C. for 30 minutes in a nitrogen atmosphere is 50% or more. If it is less than 50%, poor appearance and poor sheeting are caused during melt extrusion.
[0041]
【Example】
Examples are shown below, but the present invention is not limited by these. The measurement values shown in the examples were calculated by measuring under the following conditions.
[0042]
Further, polylactic acid subjected to extrusion, dried 4 hours at drier 140 ° C. was circulated dehumidified air having a dew point of -45 ° C., it was stored in moisture-proof containers until immediately before extrusion. The antistatic agent was vacuum dried at 48 ° C. for 6 hours and stored in a desiccator until immediately before extrusion.
[0043]
(1) Weight average molecular weight A gel permeation chromatography HLC-8120GPC manufactured by Tosoh Corporation was equipped with GPC-800CP of Shimadzu Corporation's Shim-Pack series, and the solvent was chloroform and the solution concentration was 0.2 wt /. The measurement was carried out at a vol% of 200 µl of the solution, the solvent flow rate was 1.0 ml / min, and the solvent temperature was 40 ° C, and the weight average molecular weight was calculated in terms of polystyrene. The weight average molecular weights of the standard polystyrene used are 2,000,000, 670000, 110,000, 35,000, 10,000, 4000, and 600.
[0044]
(2) Thermal stability (weight average molecular weight retention)
After dissolving 2 g of the polylactic acid-based polymer whose weight average molecular weight was measured and a predetermined amount of an antistatic agent in 500 ml of chloroform, and sufficiently stirring, the chloroform was volatilized by an evaporator, followed by vacuum drying at 60 ° C. for 6 hours. The obtained coarse powder was ground in a mortar to obtain a white powder. This white powder was placed in a 50 cc test tube, purged with a large excess of nitrogen, stoppered, heated with a 190 ° C. heat block for 30 minutes, and the weight-average molecular weight was measured again. The weight average molecular weight retention as an index of stability was calculated. The unit is%.
[0045]
Weight average molecular weight retention (%) = {(weight average molecular weight before heating) / (weight average molecular weight after heating)} × 100
(3) Surface resistivity After the film-shaped test piece was allowed to stand at 23 ° C. and 50% RH for 90 hours, using a surface resistivity measurement device manufactured by ADVANTEST, under the same atmosphere, in accordance with JIS K-6911, The electrode treatment was carried out by a vapor deposition method, with a main electrode diameter of 5 cm, a gap between the main electrode and the counter electrode of 1 cm, an applied voltage of 500 V, and an applied time of 60 seconds. The unit is Ω.
[0046]
(Examples 1 to 3 / Comparative Examples 1 to 3)
Poly L-lactic acid having a weight average molecular weight of 223000 (Lacty 1012 manufactured by Shimadzu Corporation) was extruded with a T-die at a set temperature of 210 ° C. using a 40 mmφ single screw extruder, and rapidly cooled with a cast roll to obtain a cast film having a thickness of 100 μm. Was.
[0047]
In the same manner, glycerin monostearate was added in an amount shown in Table 1 to 100 parts by weight of the same raw material to obtain a cast film. Table 1 shows the evaluation results.
[0048]
[Table 1]

(Examples 4 to 9)
Next, in the same manner, various nonionic antistatic agents in the amounts shown in Table 2 were added to obtain cast films. Table 2 shows the evaluation results.
[0049]
[Table 2]

(Comparative Examples 4 to 9)
Subsequently, in the same manner, various anionic and cationic antistatic agents in the amounts shown in Table 3 were added to obtain cast films. Table 2 shows the evaluation results.
[0050]
[Table 3]

As shown in Table 1, when the nonionic antistatic agent contained in the present invention is contained in an amount of 0.1 to 10 parts by weight, the surface resistivity is 5 × 10 ¹³ or less and the weight average molecular weight retention is 50%. % Or more. In addition, as shown in Table 2, Examples 4 to 6 using the compound group included in (1), Example 7 using the compound group included in (2), and the compound group included in (3) were used. In Examples 8 and 9, the surface resistivity was 5 × 10 ¹³ or less, and the weight average molecular weight retention was 50% or more.
[0051]
On the other hand, in Comparative Examples 4 to 9 using anionic or cationic antistatic agents not included in the compound group of (1) to (3), the surface resistivity exceeded 5 × 10 ¹³ or the weight average. The molecular weight retention is less than 50%.
[0052]
【The invention's effect】
As is apparent from the above results, the biodegradable film and sheet of the present invention have good thermal stability during melt extrusion and have practical antistatic properties.

Claims (2)

An antistatic polylactic acid film comprising 100 parts by weight of polylactic acid and 0.1 to 10 parts by weight of at least one nonionic antistatic agent selected from the following compound groups (1) to (3). .
(1) Polyhydric alcohols such as ethylene glycol, diethylene glycol, triethylene glycol, glycerin, trimethylolpropane, pentaerlit, sorbite and / or fatty acid esters thereof (2) Polyethylene glycol and / or fatty acid esters thereof (3) higher alcohols・ Polyhydric alcohol / alkylphenol adduct of polyethylene glycol or polypropylene glycol An antistatic polylactic acid sheet comprising 100 parts by weight of polylactic acid and 0.1 to 10 parts by weight of at least one nonionic antistatic agent selected from the following compound groups (1) to (3). .
  (1) Polyhydric alcohols such as ethylene glycol, diethylene glycol, triethylene glycol, glycerin, trimethylolpropane, pentael slit, and sorbite and / or fatty acid esters thereof
  (2) polyethylene glycol and / or fatty acid ester thereof
  (3) Polyethylene glycol adduct of higher alcohol / polyhydric alcohol / alkylphenol or polypropylene glycol adduct