JP4519510B2 - Stretch molding of aliphatic polyester resin composition - Google Patents

Description

  The present invention relates to a resin composition containing an aliphatic polyester such as polyglycolic acid as a main component, in particular, a composition with adjusted hydrolysis resistance and a stretched molded product thereof.

  Aliphatic polyesters such as polyglycolic acid and polylactic acid have been attracting attention as biodegradable polymer materials that have a low environmental impact because they are decomposed by microorganisms or enzymes existing in nature such as soil and sea. In addition, since aliphatic polyester has biodegradable absorbability, it is also used as a medical polymer material such as surgical sutures and artificial skin.

  Among aliphatic polyesters, polyglycolic acid is excellent in gas barrier properties such as oxygen gas barrier properties, carbon dioxide gas barrier properties, and water vapor barrier properties, and is excellent in heat resistance and mechanical strength. Or, it is being used in combination with other resin materials.

  However, aliphatic polyesters containing polyglycolic acid are generally hydrolyzable, and there is a problem that barrier properties and strength are reduced with the hydrolysis.

On the other hand, according to the study by the present inventors, when the degree of orientation is increased by subjecting the aliphatic polyester to uniaxial or biaxial stretching such as 4 times or more in each direction, It has been found that water resistance can be improved in addition to barrier properties and strength (Patent Document 1). However, it has also been found that at lower draw ratios, the improvement in water resistance is insufficient.
Specification of International Application PCT / JP03 / 12089

  However, considering application development as a packaging material, the draw ratio may not be high, and if a stretched product with high water resistance and high orientation can be obtained at a low draw ratio, it will not be exceeded.

Accordingly, an object of the present invention is generally to obtain a stretch-molded product of an aliphatic polyester resin composition having improved water resistance.

A more specific object of the present invention, stretching of the relatively low draw ratio in the aliphatic polyester resin composition improved and highly oriented and water resistance improvement is obtained in the characteristic of the barrier properties and the like can be obtained a There is to get.

The stretched molded product of the present invention has been developed in order to achieve the above-mentioned object, and is composed of an aliphatic polyester resin composition obtained by blending a trifunctional epoxy compound with an aliphatic polyester resin, and is at least in one direction. This is a stretched molded product having a main dispersion peak temperature of 67 ° C. or higher by dynamic viscoelasticity measurement .

The stretched molded product of the present invention is obtained by stretching the above aliphatic polyester resin composition uniaxially or biaxially.

  The reason why the aliphatic polyester resin composition of the present invention provides a stretched product having high water resistance and high degree of orientation at a low stretch ratio is not necessarily clear, but the three epoxy groups of the epoxy compound are the same as those of the aliphatic polyester resin. It is conceivable that the carboxyl group terminal is bonded and blocked to improve the water resistance, and the generated high-dimensional three-dimensional rope-like structure improves the stretching orientation effect at a low magnification.

  The aliphatic polyester resin constituting the aliphatic polyester resin composition of the present invention is glycolic acid and glycolic acid containing glycolide (GL), which is a bimolecular cyclic ester of glycolic acid, ethylene oxalate (that is, 1,4). -Dioxane-2,3-dione), lactides, lactones (for example, β-propiolactone, β-butyrolactone, pivalolactone, γ-butyrolactone, δ-valerolactone, β-methyl-δ-valerolactone, ε- Cyclic monomers such as caprolactone, carbonates (such as trimethylene carbonate), ethers (such as 1,3-dioxane), ether esters (such as dioxanone), amides (such as ε-caprolactam); lactic acid, 3 -Hydroxypropanoic acid, 4-hydroxybutanoic acid, 6-hydride Hydroxycarboxylic acid such as roxicaproic acid or alkyl ester thereof; substantially aliphatic diols such as ethylene glycol and 1,4-butanediol and aliphatic carboxylic acids such as succinic acid and adipic acid or alkyl esters thereof In addition, an equimolar mixture; a homo- or copolymer of aliphatic ester monomers such as Of these, hydroxycarboxylic acid homopolymers or copolymers are preferable from the viewpoint of heat resistance, and polyglycolic acid resins containing glycolic acid homopolymers or copolymers having excellent heat resistance, gas barrier properties, and mechanical strength are particularly preferably used. It is done.

More specifically, the polyglycolic acid resin used in the present invention is a homopolymer or copolymer containing a repeating unit (glycolic acid unit) represented by the formula — (— O—CH ₂ —C (O) —) —. It is a coalescence. The content ratio of the repeating unit represented by the above formula in the polyglycolic acid resin is 60% by weight or more, preferably 70% by weight or more, more preferably 80% by weight or more, and the upper limit is 100% by weight. When there is too little content rate of the repeating unit represented by the said Formula, gas barrier property and heat resistance will fall.

  In addition to the glycolic acid unit represented by the above formula, the polyglycolic acid resin can contain a polymerization unit of a comonomer copolymerizable with glycolic acid to obtain a glycolic acid copolymer.

  As the comonomer, monomers other than glycolic acid, particularly α-hydroxycarboxylic acid, particularly lactic acid (or lactide thereof) are preferably used among the monomers constituting the aliphatic polyester resin.

The glycolic acid (co) polymer used in the present invention has a melt viscosity of 100 to 10,000 Pa · s, more preferably 300 to 8,000 Pa · s, measured at a temperature of 240 ° C. and a shear rate of 100 sec ^−1. s, particularly preferably in the range of 400 to 5,000 Pa · s.

  According to the present invention, triglycidyl isocyanurate is particularly preferably used as the trifunctional epoxy compound in which the trifunctional epoxy compound is blended with the aliphatic polyester resin containing the polyglycolic acid resin described above.

  In order to give the aliphatic polyester resin composition of the present invention, it is preferable to blend 0.1 to 10 parts by weight of a trifunctional epoxy compound with respect to 100 parts by weight of the aliphatic polyester resin. If the amount is less than 0.1 parts by weight, the blending effect is poor, and if it exceeds 10 parts by weight, the melt viscosity increases and molding becomes difficult. Addition of 0.1 to 5 parts by weight is preferable in order to give a composition with good moldability.

  In blending the trifunctional epoxy compound into the aliphatic polyester resin, it is preferable to melt and knead both using an extruder. Thereby, the bond structure by reaction of the carboxy terminal of aliphatic polyester resin and the epoxy group of an epoxy compound is formed. In particular, it is preferable to melt and knead at a temperature of 200 to 300 ° C. using a twin screw extruder.

  In addition to the trifunctional epoxy compound, the aliphatic polyester resin composition of the present invention includes, for example, a phosphate ester having a pentaerythritol skeleton structure of 0.003 to 1 part by weight per 100 parts by weight of the aliphatic polyester resin. It is also preferable to add a heat stabilizer such as alkyl phosphate ester and other additives. These additives are also preferably melt kneaded with the aliphatic polyester resin together with the epoxy compound using an extruder.

  A stretch-molded product can be obtained by subjecting a single layer of the aliphatic polyester resin composition of the present invention or a laminate with another thermoplastic resin layer to strong stretching under appropriate conditions.

  Other thermoplastic resins include, for example, polyolefin resins, thermoplastic polyester resins, polystyrene resins, chlorine-containing resins, polyamide resins, polycarbonate resins, cyclic olefin resins, polyurethane resins, polyvinylidene chloride resins, ethylene Examples include vinyl alcohol copolymer (EVOH) and aliphatic polyester resin.

  In the laminate, an adhesive resin layer can be interposed between the respective layers for the purpose of increasing the delamination strength. The adhesive resin (also simply referred to as “adhesive”) is preferably one that can be extruded and exhibits good adhesion to each resin layer.

  Examples of the adhesive resin include maleic anhydride-modified polyolefin resin (Modic S525 manufactured by Mitsubishi Plastics), glycidyl group-containing ethylene copolymer (Lex Pearl RA3150 manufactured by Nippon Petrochemical Co., Ltd., Bond Fast 2C, E, B manufactured by Sumitomo Chemical Co., Ltd.) , Thermoplastic polyurethane (Kuraray 1950L), polyamide ionomer (Mitsui DuPont AM7926), polyacrylimide resin (Rohm and Haas XHTA), Mitsui Chemicals Admer NF550 [acid-modified linear low Density polyethylene, MFR = 6.2 g / 10 min (temperature 190 ° C., load 2160 g load)], Mitsubishi Chemical Corporation Modic S525, and the like.

  The aliphatic polyester-based resin composition of the present invention is stretched uniaxially or biaxially to increase the degree of orientation, thereby improving properties such as gas barrier properties, mechanical properties, and water resistance. In stretching, proper setting of conditions is important. The stretching temperature is preferably less than 80 ° C, and more preferably 45 to 65 ° C. The aliphatic polyester resin composition of the present invention is characterized by high water resistance and high orientation, particularly at a low draw ratio. Accordingly, the draw ratio is preferably 2 to 4.5 times and more preferably 2 to 3 times in each direction of uniaxial (vertical) or biaxial (vertical / horizontal).

  After the above stretching treatment, it is preferable to hold the stretched molded product at 100 to 200 ° C. for 10 seconds to 20 minutes and perform heat treatment from the viewpoint of further improvement of the dimensional stability, heat resistance, gas barrier property, etc. of the molded product. .

  As a result of the above stretch molding, the aliphatic polyester resin stretch molded product of the present invention has a peak temperature of main dispersion by dynamic viscoelasticity measurement in at least one direction (that is, at least one of the longitudinal direction and the transverse direction during stretching). It becomes 67 ° C or higher. In addition, the degree of crystal orientation by wide-angle X-ray diffraction measurement in at least one direction is 85% or more.

  The above-obtained stretched molded product of the aliphatic polyester resin monolayer or other thermoplastic resin is co-extruded by using another thermoplastic resin layer and an adhesive as necessary. Alternatively, it can be laminated. The stretched molded article of the aliphatic polyester resin of the present invention includes such a molded article having a laminated form.

  The stretch-molded product of the aliphatic polyester resin of the present invention takes the form of a film or sheet, a blow-molded container or bottle, a tray or cup or lid by sheet molding, a bag-shaped container, or a tubular packaging material as an overall shape. obtain. The film or sheet is usually further processed and formed into a cup, tray, bag-like container or the like.

  Therefore, the primary molded body obtained by laminating the above-mentioned aliphatic polyester resin with a single layer or other thermoplastic resin can take the form of a flat sheet by extrusion or injection, or a parison or preform, and this can be treated with a tenter. Alternatively, the stretching is realized in the process of blow molding or vacuum molding.

  Specific examples of application of the stretch-molded product of the present invention include various forms in which a gas barrier resin is replaced with an aliphatic polyester resin in a multilayer bottle or package containing a layer made of a gas barrier resin such as EVOH. Can be taken.

  Hereinafter, the present invention will be specifically described with reference to Examples and Comparative Examples. The measuring method of physical properties etc. is as follows.

(1) Main dispersion peak temperature by dynamic viscoelasticity measurement After leaving a sample in an atmosphere of 23 ° C. and 50% RH (relative humidity) for 24 hours, a dynamic viscoelasticity measuring device “RSA II” manufactured by Rheometrics Co., Ltd. The temperature was raised from 30 ° C. to 100 ° C. at a rate of temperature increase of 2 ° C./min at a measurement frequency of 10 Hz, and the loss tangent tan δ was measured at each temperature. The temperature at which the temperature dispersion curve shows a maximum was defined as the main dispersion peak temperature (° C.).

(2) Degree of crystal orientation measured by wide-angle X-ray diffraction Sample film surface is aligned with the stretching direction of the sample film, stacked so as to have a width of 1 mm, a length of 20 mm, and a thickness of 3 mm, and fixed with a cyanoacrylate adhesive X-rays were incident in parallel (Edge direction) and photographed with an imaging plate. As the X-ray generator, “Rotaflex RU-200B” manufactured by Rigaku Corporation was used, and CuKα rays passed through a Ni filter at 40 kV-200 mA were used as an X-ray source. Using “BAS-SR 127” manufactured by Fuji Film Co., Ltd. as an imaging plate, exposure was performed with a distance between the sample and the imaging plate of 60 mm and an exposure time of 20 minutes. The diffraction image was read using “R-AXIS DS3” manufactured by Rigaku Corporation, and a diffraction azimuth (β angle) intensity distribution curve from the polyglycolic acid crystal (110) plane was prepared. From this β-angle intensity distribution curve, two points on the equator line (according to the method for measuring the degree of orientation described in page 81 of the third edition of the X-ray handbook issued by Rigaku Corporation (issued June 30, 1985)) From the total value W ₉₀ + W ₂₇₀ (degrees) of the full width at half maximum Wi (degrees) for β angles of 90 ° and 270 °, the degree of orientation (%) was determined by the following formula:
[Equation 1]
Degree of orientation [(360− (W ₉₀ + W ₂₇₀ )) / 360] × 100

(3) Oxygen gas barrier property maintenance time The sample film is allowed to stand in a high temperature and humidity chamber with a temperature of 60 ° C. and a relative humidity of 100% RH. 20 ”was measured under the conditions of a temperature of 23 ° C. and a relative humidity of 80%, and the time during which the measured oxygen permeability coefficient was maintained at 1 × 10 ⁻¹³ cm ³ · cm ² · sec · cmHg or less was expressed as“ oxygen ”. The maintenance time of gas barrier property ”.

Example 1
Polyglycolic acid (added 0.1 parts by weight of heat stabilizer (Adeka Stub AX-71 manufactured by Asahi Denka Kogyo Co., Ltd.) to a homopolymer having a melt viscosity of 1200 Pa · sec measured at a temperature of 270 ° C. and a shear rate of 120 sec-1 ) 0.25 parts by weight of triglycidyl isocyanurate (“TEPIC” manufactured by Nissan Chemical Industries, Ltd.) was added to 100 parts by weight, and the mixture was melted, kneaded and pelletized by a twin screw extruder. The pellets were melted from an extruder at a temperature of 220 ° C. to 270 ° C., and a sheet having a thickness of 100 μm was prepared by a T-die method, and the obtained sheet was heated to a temperature using a biaxial stretching machine manufactured by Toyo Seiki Co., Ltd. After preheating at 60 ° C. for 20 to 30 seconds, the film was simultaneously biaxially stretched at a stretching speed of 7 m / min and a stretching ratio of 3 times in each of the longitudinal and transverse directions, followed by heat treatment at 120 ° C. for 1 minute. To obtain a stretched film having a thickness of 10μm.

(Example 2)
A stretched film having a thickness of 6 μm was obtained in the same manner as in Example 1 except that the longitudinal and transverse stretching ratios were changed to 4 times and simultaneous biaxial stretching was performed.

(Comparative Example 1)
Without adding triglycidyl isocyanurate, only polyglycolic acid was pelletized, sheeted and biaxially stretched in the same manner as in Example 1 to obtain a stretched film having a thickness of 10 μm.

(Comparative Example 2)
Without adding triglycidyl isocyanurate, only polyglycolic acid was pelletized, sheeted and biaxially stretched in the same manner as in Example 2 to obtain a stretched film having a thickness of 6 μm.

(Comparative Example 3)
The sheet before stretching in Example 1 was directly used as a sample film.

(Comparative Example 4)
The sheet before stretching in Comparative Example 1 was directly used as a sample film.

About each film obtained by the said Example and comparative example, the crystal orientation degree (%) by wide-angle X-ray diffraction, the main dispersion peak temperature by dynamic viscoelasticity measurement, and the maintenance time of oxygen gas barrier property were measured. The results are shown in Table 1 below.

  Comparing Example 1 and Comparative Example 1, it can be seen that Example 1 has a higher degree of crystal orientation, main dispersion peak temperature, and time for maintaining the oxygen gas barrier property. On the other hand, when Example 2 and Comparative Example 2 are compared, there is no significant change in these characteristic values. From the results shown in Table 1, the aliphatic polyester resin composition obtained by adding the trifunctional epoxy compound according to the present invention has a low stretch ratio, a high degree of orientation, and a high hydrolysis resistance. I know that I give things.

Claims (4)

A stretch-molded product comprising an aliphatic polyester resin composition obtained by blending a trifunctional epoxy compound with an aliphatic polyester resin, and having a main dispersion peak temperature of 67 ° C. or higher by dynamic viscoelasticity measurement in at least one direction . The stretched molded product according to claim 1, wherein the aliphatic polyester resin is a polyglycolic acid resin. The stretch-molded product according to claim 1 or 2, wherein the trifunctional epoxy compound is triglycidyl isocyanurate. The stretch-molded product according to any one of claims 1 to 3 , wherein the degree of crystal orientation by wide-angle X-ray measurement in at least one direction is 85% or more.