JP3747592B2 - Lactic acid polymer molded product and method for producing the same - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a heat-resistant polylactic acid polymer composition having good moldability.
[0002]
[Prior art]
In recent years, from the viewpoint of protecting the natural environment, biodegradable polymers that can be decomposed in the natural environment and molded products thereof have been demanded, and research on natural degradable resins such as aliphatic polyesters has been actively conducted. In particular, a lactic acid-based polymer has a sufficiently high melting point of 170 to 180 ° C. and is excellent in transparency, and therefore is highly expected as a packaging material or a molded product utilizing the transparency.
[0003]
However, a container made by injection molding of a lactic acid-based polymer is excellent in rigidity, but has low heat resistance or both heat resistance and impact resistance. For example, hot water or a microwave oven may be used in a packaging container. It is not possible and the application is limited.
[0004]
In order to have heat resistance, it was necessary to cool the mold for a long time during the molding process, or to anneal the molded product after molding to highly crystallize. However, a long cooling process at the time of molding is not practical, and crystallization tends to be insufficient, and post-crystallization by annealing has a defect that the molded product tends to be deformed in the process of crystallizing.
[0005]
As a method for increasing the crystallization speed, in order to promote the crystallization of PET, Japanese Patent Application Laid-Open No. 60-86156 added a wholly aromatic polyester fine powder mainly composed of terephthalic acid and resorcin as a crystal nucleating agent. As it is described, a method of adding a nucleating agent for promoting crystallization is known.
[0006]
On the other hand, as an example of adding such an additive to a polymer having biodegradability, JP-A-5-70669, JP-A-4-504473, USP5180765, JP-A-6-504799, JP-A-4-220456 is cited. Japanese Patent Application Laid-Open No. 5-70696 discloses that the average particle size of a biodegradable plastic such as poly-3-hydroxybutyrate / poly-3-hydroxyvalerate copolymer, polycaprolactone or polylactic acid is used as a material for a plastic container. It is disclosed that calcium carbonate having a diameter of 20 microns or less and hydrous magnesium silicate (talc) are mixed by 10 to 40% by weight. However, this technique promotes the decomposition of the biodegradable plastic after disposal by adding a large amount of an inorganic filler, and does not improve the heat resistance by crystallizing the polymer. Japanese Patent Publication No. 4-504731 (WO 90/01521) discloses properties of hardness, strength and temperature resistance by adding fillers of inorganic compounds such as silica and kaolinite to lactide thermoplastics. In this example, 5% by weight of calcium lactate as a nucleating agent was blended with a L, DL-lactide copolymer as a nucleating agent for 5 minutes using a heating roll at 170 ° C., and the sheet was rigid. It is described that it is strong and cloudy and the crystallinity is increased.
[0007]
Japanese Patent Publication No. 6-504799 discloses lactate and benzoate as nucleating agents. In this example, 1% calcium lactate is blended in a polylactide copolymer and the residence time is 2 minutes. Although the injection molding was carried out with a mold kept at about 85 ° C. over time, crystallization was insufficient, so that an example of annealing at about 110 to 135 ° C. in the mold is described.
[0008]
Japanese Patent Laid-Open No. 8-193165 discloses injection molding using talc, silica, calcium lactate, etc. as a nucleating agent in a lactic acid-based polymer. Since it is brittle, it is impossible to obtain a molded product that can withstand practical use. Therefore, such a lactic acid-based polymer has a low crystallization rate even if it is used for general injection molding, blow molding and compression molding using ordinary talc, silica, etc., and the molded product obtained has a practical heat resistance. It is described that there is a restriction in application because it is low at 100 ° C. or lower and impact resistance is not strong. JP-A-4-220456 discloses that polyglycolic acid and its derivatives are added to poly L-lactide as a nucleating agent to increase the crystallization speed, thereby shortening the injection molding cycle time, and excellent It has been described as having mechanical properties. As an example of injection molding, the crystallization temperature without a nucleating agent is 22.6% when the cooling time is 60 seconds, and 45.5% when the nucleating agent is added.
[0009]
However, according to Japanese Patent Laid-Open No. 8-193165, when the injection molding was actually attempted without adding a nucleating agent to the lactic acid-based polymer, the mold temperature as described in Japanese Patent Laid-Open No. 4-220456 was reduced. It is described that molding could not be performed under the condition of Tg point or higher.
[0010]
[Problems to be solved by the invention]
An object of the present invention is to obtain a molded article having excellent heat resistance and impact resistance, which is made of a lactic acid polymer, for the above problems.
[0011]
[Means for Solving the Problems]
As a result of intensive studies, the present inventors have found that the above object can be achieved by using wax as a crystal nucleus and a crystallization accelerator, and the present invention has been completed.
[0012]
That is, the present invention comprises 0.01 to 1.0 parts by weight of wax in 100 parts by weight of lactic acid-based polymer, and storage modulus (E) in a test on temperature dependence of dynamic viscoelasticity (JIS-K-7198B method). ′) A composition and molded product having a minimum value of 10 ⁷ Pa or higher at 100 ° C. or lower, and 100 parts by weight of a lactic acid polymer are mixed and melted with 0.01 to 1.0 part by weight of wax to 85 to 125 ° C. It fills the mold of the molding machine set to, and molds while crystallizing, and is a method for producing a heat-resistant lactic acid-based polymer.
[0013]
In the present invention, the lactic acid-based polymer includes a polylactic acid homopolymer, a lactic acid copolymer, and a blend polymer.
[0014]
The weight average molecular weight of the lactic acid polymer is generally 5 to 500,000. In addition, the constituent molar ratio L / D of the L-lactic acid unit and D-lactic acid unit in the lactic acid-based polymer may be 100/0 to 0/100, but L lactic acid or D may be used to obtain a high melting point. In order to obtain 75 mol% or more of any unit of lactic acid and a higher melting point, it is preferable to contain 90 mol or more of either unit of L lactic acid or D lactic acid.
[0015]
The lactic acid copolymer is obtained by copolymerizing a lactic acid monomer or other component copolymerizable with lactide. Examples of such other components include dicarboxylic acids having two or more ester bond-forming functional groups, polyhydric alcohols, hydroxycarboxylic acids, lactones, etc., and various polyesters and various polyethers composed of these various components. And various polycarbonates.
[0016]
Examples of the dicarboxylic acid include succinic acid, adipic acid, azelaic acid, sebacic acid, terephthalic acid, and isophthalic acid.
[0017]
Examples of polyhydric alcohols include aromatic polyhydric alcohols such as those obtained by addition reaction of bisphenol with ethylene oxide, ethylene glycol, propylene glycol, butanediol, hexanediol, octanediol, glycerin, sorbitan, trimethylolpropane, neo Examples include aliphatic polyhydric alcohols such as pentyl glycol, ether glycols such as diethylene glycol, triethylene glycol, polyethylene glycol, and polypropylene glycol. Examples of the hydroxycarboxylic acid include glycolic acid, hydroxybutylcarboxylic acid, and others described in JP-A-6-184417.
[0018]
Examples of the lactone include glycolide, ε-caprolactone glycolide, ε-caprolactone, β-propiolactone, δ-butyrolactone, β- or γ-butyrolactone, pivalolactone, δ-valerolactone, and the like.
[0019]
The lactic acid-based polymer is synthesized by a conventionally known method. That is, a direct dehydration condensation from a lactic acid monomer or a lactic acid cyclic dimer as described in JP-A-7-33861, JP-A-59-96123, Polymer Proceedings Proceedings Vol. 44, pages 3198-3199 It can be synthesized by ring-opening polymerization of lactide.
[0020]
When performing direct dehydration condensation, any lactic acid of L-lactic acid, D-lactic acid, DL-lactic acid, or a mixture thereof may be used. Also, in the case of performing ring-opening polymerization, any lactide of L-lactide, D-lactide, DL-lactide, or a mixture thereof may be used.
The synthesis, purification and polymerization operations of lactide are described, for example, in US Pat. No. 4,057,537, published European Patent Application No. 261572, Polymer Bulletin, 14, 491-495 (1985) and Makromol Chem., 187, 1611-1628 ( 1986) and the like.
[0021]
The catalyst used in this polymerization reaction is not particularly limited, but a known lactic acid polymerization catalyst can be used. For example, tin compounds such as tin lactate, tin tartrate, dicaprylate, dilaurate, dipalmitate, tin distearate, dioleate, α-tin naphthoate, β-naphthoate, and octylate Zinc powder, zinc halide, zinc oxide, organic zinc compounds; titanium compounds such as tetrapropyl titanate; zirconium compounds such as zirconium isopropoxide; antimony compounds such as antimony trioxide; Examples thereof include bismuth compounds such as bismuth (III) oxide; aluminum compounds such as aluminum oxide and aluminum isopropoxide.
Among these, a catalyst made of tin or a tin compound is particularly preferable from the viewpoint of activity. The amount of these catalysts used is, for example, about 0.001 to 5% by weight based on lactide when ring-opening polymerization is performed.
[0022]
The polymerization reaction can be usually performed at a temperature of 100 to 220 ° C. in the presence of the catalyst, although it varies depending on the catalyst type. It is also preferable to perform two-stage polymerization as described in JP-A-7-247345.
[0023]
In the present invention, the wax includes natural wax and synthetic wax. Natural wax is preferable from the viewpoint of biodegradability, but is not particularly limited. Naturally obtained waxes include animal waxes, plant waxes, mineral waxes and petroleum waxes (from the Polymer Dictionary). Animal waxes are derived from insects or mammals. Commercially, beeswax and wool wax (unrefined lanolin) are important. Plant waxes are obtained from leaves, trunks or fruits. Candelilla wax, carnauba wax, rice wax and the like are important plant waxes. Candelilla wax and carnauba wax are obtained from candelilla grass and carnauba leaves, respectively. Rice wax is a rice bran oil that protects brown rice, which has been decolorized and refined, and includes those that are hydrogenated by post-processing. These main components are fatty acid (wax acid) and higher alcohol esters, and fatty acids include palmitic acid, stearic acid, pehenic acid, lignoceric acid, serotic acid, dotriacontanoic acid, etc. Examples of the alcohol component include ceryl alcohol, isoceryl alcohol, and myricyl alcohol. In addition, unsaponifiable matter mainly composed of myricyl alcohol, seryl alcohol, isoceryl alcohol and the like and some free acid, steric acid, squalene, phospholipid and the like may be contained.
[0024]
The wax used in the present invention is not particularly limited. For example, M-80, M-90, M-100, M-200, M-301, M-301A, M-307, etc. (all ( Etc.), and the type and grade can be arbitrarily selected according to the purpose of use.
[0025]
The addition amount of the wax in the present invention is preferably 0.01 to 1.0 part by weight with respect to 100 parts by weight of the lactic acid polymer. If the amount is less than 0.01 part by weight, the effect of addition may be insufficient. If the amount exceeds 1.0 part by weight, the lactic acid polymer will become cloudy, which is not preferable.
[0026]
In order to crystallize a lactic acid-based polymer composition, there are a method of annealing a molded product at a crystallization temperature, and a method of setting a molding die to a crystallization temperature when molding the composition and holding it for a certain time.
[0027]
When molding the composition of the present invention, the mold temperature of the injection molding, blow molding and compression molding machine is set in the range from the crystallization start temperature to the end temperature in the DSC method. Thus, the crystallization is completed in the mold, whereby a lactic acid polymer composition having excellent heat resistance and impact resistance can be obtained. Since the setting of the mold temperature varies depending on the type of lactic acid polymer composition to be molded, the crystallization temperature is measured in advance by the DSC method, and the temperature is set within the range from the crystallization start temperature to the end temperature. If it is this temperature range, it can crystallize easily and also a molded article with a high dimensional accuracy can be obtained. Outside this range, crystallization slows down and the solidification time during molding becomes longer, which is not suitable for practical use.
[0028]
The method for blending the lactic acid polymer with the wax is not particularly limited, and can be performed by a conventionally known method. For example, kneading may be performed using a mill roll, a Banbury mixer, a super mixer, a single-screw or twin-screw extruder, and the like. This mixing and kneading is usually performed at a temperature of about 120 to 220 ° C.
[0029]
Furthermore, in the lactic acid-based polymer composition of the present invention, conventionally known plasticizers, antioxidants, heat stabilizers, light stabilizers, ultraviolet absorbers, pigments, colorants, various fillers, antistatic agents, if necessary. Various additives such as agents, mold release agents, fragrances, lubricants, flame retardants, foaming agents, fillers, antibacterial / antifungal agents, and other nucleating agents may be blended.
[0030]
In the present invention, the heat resistance index is determined by measuring the dynamic storage elastic modulus (E ′) in a test on the temperature dependence of dynamic viscoelasticity (JIS K 7198B method), and dynamic storage at a temperature of 100 ° C. or less. The condition was that the minimum value of the elastic modulus (E ′) was 10 ⁷ Pa or more. The dynamic storage elastic modulus (E ′) in the JIS K 7198B method physically represents the rigidity (hardness, softness) of the composition or molded product, and is dynamically stored at a temperature of 100 ° C. or less. When the minimum value of the elastic modulus (E ′) is 10 ⁷ Pa or less, deformation easily occurs during actual use.
[0031]
The production method of the lactic acid-based polymer composition and molded product of the present invention can be applied to moldings such as injection molding, vacuum molding, and compression molding similar to general plastics, so various molded products such as rods, bottles, and containers can be easily used. Can be obtained.
[0032]
In the present invention and the following examples, the weight average molecular weight (Mw) of the polymer is a polystyrene equivalent value by GPC analysis, and the dynamic storage elastic modulus is measured by a test on the temperature dependence of dynamic viscoelasticity (JIS K 7198B method). ). The crystallization temperature was measured by a scanning differential calorimeter (DSC) at a heating rate of 10 ° C./min. Measured with
[0033]
【Example】
Example 1
Dry blend of 0.2 parts by weight of rice wax ("M-90" manufactured by Celarica Noda) with 100 parts by weight of polylactic acid ("Lacty" manufactured by Shimadzu Corporation, Mw = 180,000, hereinafter PLA1) Then, it was melt-mixed for 4 minutes on average in a 200 ° C. twin-screw kneading extruder, extruded into a strand form from a die, cooled with water, and cut to obtain a chip C1 of a lactic acid-based polymer composition containing rice wax.
As a result of measuring DSC of the obtained chip C1, the crystallization peak temperature was 105 ° C., the crystallization start temperature was 85 ° C., the crystallization end temperature was 130 ° C., and the crystallization heat amount was 25 J / g.
The chip C1 was vacuum-dried at 80 ° C. to make it completely dry, then the mold temperature was kept at 25 ° C., and a business card plate (1 mmt) was obtained by injection molding.
[0034]
The obtained 1 mm thick business card large plate was cut into a strip of 10 mm × 50 mm, and the dynamic storage elastic modulus was measured in a test on the temperature dependence of dynamic viscoelasticity (JIS K 7187B method).
[0035]
(Example 2)
The chip C1 obtained in Example 1 was vacuum-dried at 80 ° C. to make it completely dry, and then the mold temperature was kept at 100 ° C. to obtain a business card large plate (1 mmt) by injection molding. The obtained 1 mm thick business card large plate was cut into a strip of 10 mm × 50 mm, and the dynamic storage elastic modulus was measured in a test on the temperature dependence of dynamic viscoelasticity (JIS K 7187B method).
[0036]
(Comparative Example 1)
PLA1 used in Example 1 was vacuum-dried at 80 ° C. to make it completely dry, then the mold temperature was kept at 25 ° C., and a business card large plate (1 mmt) was obtained by injection molding.
The obtained 1 mm thick business card large plate was cut into a strip of 10 mm × 50 mm, and the dynamic storage elastic modulus was measured in a test on the temperature dependence of dynamic viscoelasticity (JIS K 7187B method).
[0037]
(Comparative Example 2)
As a result of measuring DSC of PLA1 used in Example 1, the crystallization peak temperature was 130 ° C., the crystallization start temperature was 80 ° C., the crystallization end temperature was 140 ° C., and the crystallization heat amount was 5.8 J / g. .
PLA1 was vacuum-dried at 80 ° C. to make it completely dry, and then the mold temperature was kept at 100 ° C. to obtain a large business card plate (1 mmt) by injection molding.
The obtained 1 mm thick business card large plate was cut into a strip of 10 mm × 50 mm, and the dynamic storage elastic modulus was measured in a test on the temperature dependence of dynamic viscoelasticity (JIS K 7187B method).
[0038]
The measurement result of the dynamic storage elastic modulus is shown in FIG. From this result, it can be seen that the elastic modulus of Example 1 rapidly increases in the temperature range of 80 ° C. or higher, and clearly crystallizes faster than the comparative example, and the elastic modulus is also improved. In addition, it can be seen from the results of Example 2 that by crystallizing in the mold, the drop in the elastic modulus near 80 ° C. can be reduced and the heat resistance of the molded product can be increased.
[0039]
【The invention's effect】
By blending the lactic acid polymer with wax, the crystallization rate of the lactic acid polymer can be increased and the elastic modulus can be improved. Furthermore, a molded product having excellent heat resistance can be obtained by crystallizing the composition in a mold.
[Brief description of the drawings]
FIG. 1 is a graph showing measurement results of dynamic storage elastic modulus.

Claims (7)

  When a composition containing 0.01 to 1.0 part by weight of a plant-based wax in 100 parts by weight of a lactic acid-based polymer is molded, a range from the crystallization start temperature to the crystallization end temperature in a scanning differential calorimeter (DSC) Lactic acid-based polymer molded product obtained by holding in. When a composition containing 0.01 to 1.0 part by weight of a plant-based wax in 100 parts by weight of a lactic acid-based polymer is molded, a range from the crystallization start temperature to the crystallization end temperature in a scanning differential calorimeter (DSC) The minimum value at 100 ° C. or lower of the storage elastic modulus (E ′) in the test on the temperature dependence of dynamic viscoelasticity (JIS-K-7198B method) obtained by holding at 10 ⁷ Pa or higher. A lactic acid polymer molded product.   The lactic acid polymer molded article according to claim 1 or 2, wherein the plant wax is rice wax.   Gold of a molding machine in which 0.01 to 1.0 part by weight of wax is mixed and melted with 100 parts by weight of a lactic acid polymer, and the temperature is set in the range of the crystallization start temperature to the end temperature in a scanning differential calorimeter (DSC). A method for producing a lactic acid-based polymer molded article, which comprises filling a mold and molding while crystallizing.   The method for producing a lactic acid polymer molded article according to claim 4, wherein the wax is a vegetable wax.   6. The method for producing a lactic acid polymer molded article according to claim 5, wherein the plant wax is rice wax.   The molded product obtained by the manufacturing method of the lactic acid-type polymer molded product as described in any one of Claims 4-6.

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