JP2005097590A - Polyoxalate composition and molded product obtained therefrom - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a polyoxalate composition improved in mechanical strengths without reducing biodegradationvelocity, and a molded product therefrom. <P>SOLUTION: The polyoxalate composition comprises 100 pts.wt. polyoxalate expressed by the following formula and a polylactic acid in ≥1 pt.wt. to <100 pts.wt. The molded product is produced from the polyoxalate composition. In the formula, R may contain a branched structure or an alicyclic structure and expresses a 3-12C alkylene in the main chain; n expresses a positive integer expressing the degree of polymerization. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a polyoxalate composition having a high biodegradability rate and high mechanical strength, and a molded product obtained therefrom.

  Synthetic resins such as polyolefin are used in large quantities in a wide variety of articles ranging from industrial materials to household goods. However, since these synthetic resins are developed for the purpose of high performance and long-term stability, they are not decomposed after being released to the natural world and keep their original form indefinitely. For this reason, various used articles are collected as garbage and disposed of by incineration or landfill. However, in reality, there are a large amount of scattered garbage, and adverse effects on natural ecosystems have been pointed out.

  From such a situation, since the biodegradable polymer that is decomposed into carbon dioxide and water by microorganisms in the soil or water does not remain in the environment, it is possible to reduce the environmental problems as described above. Has attracted attention. As one of the biodegradable polymers, Patent Document 1 discloses that polyoxalate has excellent biodegradability. However, it is difficult to say that polyoxalate has sufficient mechanical strength to be used as a practical plastic, and in particular, improvement in rigidity such as elastic modulus has been desired.

JP 2002-145691 A

  Conventionally, no method has been known for improving the mechanical strength of polyoxalate without degrading its biodegradability. An object of the present invention is to provide a polyoxalate composition with improved mechanical strength and a molded product obtained therefrom without reducing the biodegradability rate.

  As a result of intensive investigations to solve the above problems, the present inventors have blended polyoxalate with a certain amount of polylactic acid, thereby reducing the mechanical properties of polyoxalate without reducing the biodegradability rate. The inventors have found that the strength can be improved and have completed the present invention.

  That is, the present invention is (1) a polyoxalate composition comprising 1 part by weight or more and less than 100 parts by weight of polylactic acid with respect to 100 parts by weight of a polyoxalate represented by the following formula. In the formula, R represents an alkylene group having 3 to 12 carbon atoms in the main chain, which may contain a branched structure or an alicyclic structure, and n is a positive integer representing the degree of polymerization.

Moreover, the preferable aspect of this invention is (2) The said polyoxalate composition whose number average molecular weights of polyoxalate are 20000-100,000 and whose number average molecular weight of polylactic acid is 20000-500000, (3) Polyoxa Any of the above polyoxalate compositions wherein the number average molecular weight of the rate is 20000-70000 and the number average molecular weight of the polylactic acid is 20000-500000, (4) any of the above, wherein the polyoxalate is polycyclohexylenedimethylene oxalate The polyoxalate composition.
Furthermore, the present invention also resides in (5) a molded product obtained from any one of the polyoxalate compositions.

  The present invention provides a polyoxalate composition having improved mechanical strength (ie, having a high biodegradability rate and high mechanical strength) without reducing the biodegradability rate, and a molded product obtained therefrom. can do. This polyoxalate composition can be used in a wide range of applications where biodegradable plastics are conventionally used, such as films or sheets, various molded articles, and textile products.

Hereinafter, the present invention will be described in more detail.
The polyoxalate used in the present invention can be represented by the above formula. Although the molecular weight is not particularly limited, as will be described later, it is difficult to obtain a uniform composition when the melt viscosity of the two is greatly different at the time of melt kneading with polylactic acid, so it is selected in relation to the molecular weight of polylactic acid. Generally speaking, the number average molecular weight (Mn) of the polyoxalate is preferably 20000 to 100000, more preferably 20000 to 70000, and particularly preferably 25000 to 70000. That is, in the polyoxalate used in the present invention, the repeating unit is —O—R—O—CO—CO—, and the number average molecular weight is preferably 20000 to 100000, more preferably 20000 to 70000, and particularly preferably 25000. 70000 ones. In the above formula, “n” is a positive integer representing the degree of polymerization and is a numerical value satisfying the number average molecular weight. Moreover, it is preferable that the weight average molecular weight (Mw) of polyoxalate is the range of 30000-200000, and the molecular weight distribution prescribed | regulated by ratio (Mw / Mn) of a weight average molecular weight (Mw) and a number average molecular weight (Mn). 1-5 are preferable.

  The aliphatic diol unit of the polyoxalate is defined by the alkylene group R in the above formula. If the carbon chain of the alkylene group R is too short, the polyoxalate will be hard and brittle. If the carbon chain of the alkylene group R is too long, the polyoxalate becomes hydrophobic and the biodegradability is lowered, which is not preferable. Accordingly, the alkylene group R of the above formula is preferably one having 3 to 12 carbon atoms in the main chain. The alkylene group R may have an even or odd number of carbon atoms in the main chain, and is not limited to a straight chain structure but may include a branched structure or an alicyclic structure.

  As the aliphatic diol unit source, an aliphatic diol having 3 to 12 carbon atoms in the main chain of the alkylene group R is used. Examples of such aliphatic diols include 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,7-heptanediol, 1,8- Octanediol, 1,9-nonanediol, 1,10-decanediol, 1,11-undecanediol, 1,12-dodecanediol, neopentyl glycol, trans (or cis) -1,4-cyclohexanedimethanol, 2 , 4-Diethyl-1,5-pentanediol, 3-methyl-1,5-pentanediol, 2-ethyl-2-butyl-1,3-propanediol, 2,2,4-trimethyl-1,3- Examples include propanediol, 2,2-diethyl-1,3-propanediol, 2-ethyl-1,3-hexanediol, and the like. . Two or more of these aliphatic diols may be contained in the polyoxalate. Of the aliphatic diols, 1,4-cyclohexanedimethanol is most preferable because it provides a polyoxalate having a melting point close to that of polylactic acid.

  The aliphatic diol may contain a part of a polyhydric alcohol compound (excluding the aliphatic diol) as necessary. A long chain branched structure can also be introduced into the molecular chain of polyoxalate by introducing a polyhydric alcohol compound. Examples of such polyhydric alcohol compounds include glycerol and 1,2,6-hexanetriol. However, the use ratio of the polyhydric alcohol compound is preferably 30 mol% or less, more preferably 10 mol% or less of the aliphatic diol. Too much polyhydric alcohol compound is not preferable because it may cause gelation during polymerization of the polyoxalate or during melt processing of the composition of the present invention.

  Furthermore, the aliphatic diol may partially contain an aromatic diol as desired, for example, to increase the heat resistance of the polyoxalate. Examples of such aromatic diols include bisphenol A, p-xylylene glycol, and hydroquinone. However, the proportion of aromatic diol used is less than 50 mol% of the aliphatic diol. Too much aromatic diol is not preferable because the biodegradability of the polyoxalate may be deteriorated.

  Examples of the oxalic acid source of polyoxalate include dialkyl oxalate (dimethyl oxalate, diethyl oxalate, dibutyl oxalate, etc.), diaryl oxalate (diphenyl oxalate, di-p-tolyl oxalate, etc.), oxalic acid, and the like. Among them, dialkyl oxalate and diaryl oxalate are preferable.

  Furthermore, the oxalic acid source may contain a part of an aromatic dicarboxylic acid diester such as dimethyl terephthalate or a carbonic acid ester such as diphenyl carbonate as desired to increase the heat resistance of the polyoxalate. However, the proportion of these esters used is less than 50 mol% of the oxalic acid source, and if too large, the biodegradability of the polyoxalate may be deteriorated, which is not preferable.

  Moreover, in order to improve the compatibility with polylactic acid, it is also possible to introduce a polylactic acid segment into the molecular chain of the polyoxalate of the present invention. The amount is 50 mol% or less of the whole polyoxalate. Furthermore, what mixed the oxalate-lactic acid copolymer in the polyoxalate can also be used.

  Polyoxalate can be produced from an oxalic acid source and an aliphatic diol by a generally well-known polycondensation reaction (preferably melt polymerization). For example, it can be produced by charging a reactor with an oxalic acid source and an aliphatic diol together with a catalyst and performing polycondensation under suitable polymerization conditions. As the catalyst, compounds such as P, Ti, Ge, Zn, Fe, Sn, Mn, Co, Zr, V, Ir, La, Ce, Li, Ca, and Hf are preferable. In particular, organic titanium compounds and organotin compounds are preferable. For example, titanium alkoxide (titanium tetrabutoxide, titanium tetraisopropoxide, etc.), distanoxane compound (1-hydroxy-3-isothiocyanate-1,1,3,3-tetra) Butyl distanoxane, etc.), tin acetate, dibutyltin dilaurate, butyltin hydroxide hydrate and the like are preferred because of their high activity. In the polycondensation reaction, a heat-resistant agent may be added if necessary to prevent thermal degradation.

  In the polycondensation reaction, when dialkyl oxalate is used as the oxalic acid source, in order to increase the molecular weight of polyoxalate, dialkyl oxalate is used excessively with respect to the aliphatic diol, and the water concentration ( It is necessary to control (weight basis) to less than 2000 ppm. That is, the ratio of use of dialkyl oxalate and aliphatic diol (feeding molar ratio) is 0.5 ≦ OL / OX <1, where OX is the number of moles of dialkyl oxalate and OL is the number of moles of aliphatic diol. The range is preferably 0.6 ≦ OL / OX <1, more preferably 0.7 ≦ OL / OX <1, and particularly preferably 0.8 ≦ OL / OX <1. The water concentration in the reaction raw material is controlled to less than 2000 ppm, preferably 10 to 2000 ppm.

  On the other hand, when diaryl oxalate is used as the oxalic acid source, it is preferable to use an aliphatic diol in an amount of 0.95 to 1.05 times mol with respect to the diaryl oxalate, and the water concentration (weight basis) in the reaction raw material is It is necessary to control to less than 1000 ppm. The reaction raw material contains a catalyst in addition to dialkyl oxalate or diaryl oxalate and aliphatic diol, and dialkyl oxalate and diaryl oxalate may contain them (aromatic carboxylic acid ester, carbonate ester ), Aliphatic diols may also be included (polyhydric alcohol compounds, aromatic diols).

  The polylactic acid used in the present invention may be a polylactic acid having a sufficiently high molecular weight that exhibits practical strength, and is most commonly produced from L-lactic acid and its cyclic dimer lactide. Possible commercial products can be used. There are a ring-opening polymerization method, a direct polymerization method and the like as a method for producing polylactic acid, and any method may be used. In addition, the number average molecular weight (Mn) of polylactic acid becomes like this. Preferably it is 20000-500000, More preferably, it is 50000-200000.

  In addition, as polylactic acid, those in which a polyoxalate segment is introduced in the molecular chain at 50 mol% or less of the polylactic acid in order to enhance the compatibility with polyoxalate can be used. A mixture of lactic acid and a lactic acid-oxalate copolymer can also be used.

  In the polyoxalate composition of the present invention, 1 part by weight or more and less than 100 parts by weight, preferably 3 parts by weight or more and 90 parts by weight or less, more preferably 5 parts by weight, with respect to 100 parts by weight of the polyoxalate. Part to 85 parts by weight. If the content of polylactic acid is less than 1 part by weight, the effect of improving the mechanical strength is not sufficient, and conversely if it is 100 parts by weight or more, the biodegradability rate is remarkably lowered.

In addition to polyoxalate and polylactic acid, other components (additives, other polymers, etc.) may be blended alone or in combination with the polyoxalate composition as necessary. Additives that can be added include hydrolysis inhibitors, crystal nucleating agents, pigments, dyes, heat-resistant agents, anti-coloring agents, antioxidants, weathering agents, lubricants, antistatic agents, foaming agents, stabilizers, and fillers (talc , Clay, montmorillonite, mica, zeolite, zonotlite, calcium carbonate, carbon black, silica powder, alumina powder, titanium oxide powder, etc.), reinforcing materials (glass fiber, carbon fiber, silica fiber, cellulose fiber, etc.), flame retardant, plastic Agents, waterproofing agents (wax, silicone oil, higher alcohol, lanolin, etc.) and the like, and can be added within a range that does not impair the object of the present invention.

  Moreover, natural or synthetic polymer is mentioned as another polymer. Examples of natural polymers include starch, cellulose acetate, cellulose acetate propionate, chitosan, alginic acid, and natural rubber. Synthetic polymers include polycaprolactone or a copolymer thereof, polyglycolic acid, and polysuccinic acid. Ester, succinic acid / adipic acid copolyester, succinic acid / terephthalic acid copolyester, poly (3-hydroxybutanoic acid), (3-hydroxybutanoic acid / 4-hydroxybutanoic acid) copolymer, polyvinyl alcohol, polyethylene, polyethylene terephthalate -Polybutylene terephthalate, polyvinyl acetate, polyvinyl chloride, polystyrene, polyglutamic acid ester, polyester rubber, polyamide rubber, styrene-butadiene-styrene block copolymer (SBS), hydrogenated SBS, etc. , And the like beam or an elastomer.

The polyoxalate composition of the present invention is produced by mixing the above-mentioned polyoxalate and polylactic acid in the above-mentioned proportions (also blending the above-mentioned other components as necessary) by a known method. For example, it can be dry blended using a solid mixer such as a tumbler, but the most common method is a continuous kneading apparatus such as a single screw extruder, a twin screw extruder, a twin screw rotor kneader, or an open roll. These are kneaded and melt kneaded using a batch kneader such as a kneader or Banbury mixer, and there are no particular restrictions on the kneading method and conditions. In addition, a solution blend method using a solvent may be used.

Moreover, the polyoxalate composition of the present invention can be formed into a molded product such as a film or sheet, various molded products, and textile products by various molding methods.
The film or sheet can be obtained by a known method such as an extrusion method (T-die method, inflation method, etc.), a press method, a calendar roll method. The resulting film or sheet can be stretched (uniaxially stretched or biaxially stretched), and a laminate with other polymer, metal, paper or the like can also be produced.

  Examples of the various molded products include injection molded products, hollow molded products, thermoformed products (vacuum molded products, compressed air molded products, etc.), foam molded products, and press molded products. Examples of the fiber product include monofilaments, multifilaments, chops, and nonwoven fabrics, and other processed products such as ropes, nets, felts, and woven fabrics.

  The molded product obtained from the polyoxalate composition of the present invention can be used in a wide variety of known applications. Applications of films or sheets include agricultural materials (multi-films for agriculture and horticulture, seed tape, pesticide bags, etc.), food waste bags (compostable garbage bags, garbage bags, etc.), office supplies (paper resource recovery) Coated paper, printed laminate, card cover, window frame envelope, printing paper cover film, etc.), general packaging applications (paper diaper pack sheet, laundry bag, foam sheet, shrinkage film for miscellaneous goods, retort food pack, food packaging film) , Wrap film, etc.), shopping bags, disposable gloves and the like.

  Various molded products can be used for food (food trays, food containers, food or beverage bottles, fresh food boxes, tableware, etc.), daily goods (cosmetics containers, detergent containers, shampoo containers, toiletries, etc.), Agricultural / horticultural relations (nurturing materials, pots, planters, etc.), office supplies, sports / leisure supplies, medical equipment, electrical / electronic parts, computer / information equipment parts, automotive parts, etc.

  In addition, the use of textile products includes various nets (fish nets, insect nets, etc.), various ropes (agricultural ropes, tree ropes, etc.), various threads (fishing lines, sutures, etc.), various non-woven products (paper diapers, Sanitary and hygiene products), filters, clothes, and the like.

  Next, the present invention will be specifically described with reference to examples and comparative examples. However, measurement of physical properties of polyoxalate, production of polyoxalate composition, molding, and evaluation of physical properties were performed as follows.

1. Molecular weight measurement of polyoxalate: The number average molecular weight (Mn) was measured by gel permeation chromatography (GPC). The measurement conditions are shown below.
・ Model used: Tosoh HLC-8020
Column: Shodex K-80M (2 pieces)
・ Solvent: Chloroform ・ Sample concentration: 0.3 mg / ml
-Column temperature: 38 ° C
Standard sample: Polystyrene

2. Melting point of polyoxalate: The melting point was defined as the endothermic peak temperature in the second heating step in differential scanning calorimetry (DSC). The measurement conditions are shown below.
-Model used: Perkin Elmer DSC-7
・ First temperature rising process: −100 ° C. to melting point or higher (set by sample), temperature rising rate 10 ° C./min, holding 5 minutes ・ First temperature lowering process: melting point or higher (set by sample) to −100 ° C., temperature falling rate 10 ° C./min, holding 5 minutes, second temperature raising process: from −100 ° C. to melting point or higher (set by sample), temperature rising rate 10 ° C./min

3. Preparation of polyoxalate composition: A predetermined amount of polyoxalate was put into a kneader-type batch kneader set at 200 ° C. for plasticization, and then a predetermined amount of polylactic acid was added and melt-kneaded. The operation was performed in nitrogen.

4). Sheet forming of polyoxalate composition: A compression molding machine manufactured by Shintan Metal Industry Co., Ltd. was used. The melt-kneaded material cut into pellets with a plastic cutter was preheated at 200 ° C. for 3 minutes, pressurized at 2.9 MPa for 3 minutes, and then rapidly cooled to 20 ° C. to produce a press sheet having a thickness of about 190 microns. .

5). Tensile properties of molded sheet of polyoxalate composition: Young's modulus was measured under the following conditions using a dumbbell-shaped test piece punched out from the press sheet.
・ Model used: Orientec Tensilon ・ Sample used: JIS No. 2 tensile specimen ・ Tensile speed: 100 mm / min ・ Measurement temperature: 23 ° C.
・ Measurement humidity: 50% RH

6). Biodegradability in compost of polyoxalate composition molded sheet: Cut out a small piece of about 1 cm x 2 cm from the press sheet, put it in a polyethylene net, and mix it with compost containing plant crushed material and chicken manure. The entire net was buried. And this compost was left still for a predetermined time, circulating water saturated air from the compost lower part with a 58 degreeC thermostat. After a predetermined time, the entire net was taken out and the biodegradability was evaluated from the appearance and the weight residual ratio (%) by weight measurement. The calculation was based on the following formula.
Weight residual ratio (%) = W / W ₀ × 100
(W represents the small piece weight (mg) after the burying process, and W ₀ represents the small piece weight (mg) before the burying process.)

7). Biodegradability of polyoxalate composition molded sheet in outdoor soil: A small piece having a size of about 1 cm × 2 cm is cut out from the press sheet and placed in a polyethylene net, and the net is 5 cm deep in the outdoor field soil. Buried. After leaving as it is for a predetermined time, the whole net was taken out, and the biodegradability was evaluated by the appearance and weight residual ratio (%) by weight measurement in the same manner as described above.

[Reference Example 1]
A 1 L separable flask was charged with 180.02 g of cyclohexyne dimethanol, 302.39 g of diphenyl oxalate, and 26.1 mg of butyltin hydroxide hydrate (the water concentration in the reaction raw material was 20 ppm), and under normal pressure. The temperature was raised to 160 ° C. over 1 hour, and the temperature was further raised to 190 ° C. and reacted for 1 hour. Next, after reducing the pressure to 13.3 KPa (100 mmHg) in 1 hour, the temperature was raised to 210 ° C. and the pressure was reduced to 133 Pa (1 mmHg) and the reaction was performed for 1 hour. The obtained polycyclohexylene dimethylene oxalate had a Mn of 45900 and a melting point of 174 ° C. The reaction was performed under a nitrogen atmosphere.

[Example 1]
A polyoxalate composition comprising 100 parts by weight of the polycyclohexylenedimethylene oxalate and 11 parts by weight of polylactic acid (Lacia H-100PL; manufactured by Mitsui Chemicals) having a Mn of 90000 and a melting point of 167 ° C. was prepared and formed into a sheet. The physical property evaluation results of this molded sheet are shown in Table 1. However, the biodegradability is shown in Table 1 during composting and Table 2 in outdoor soil.

[Examples 2 to 4]
The same procedure as in Example 1 was conducted except that the blending ratio of polycyclohexylenedimethylene oxalate and polylactic acid was changed as shown in Tables 1 and 2. The results are shown in Tables 1 and 2.

[Comparative Example 1]
The same procedure as in Example 1 was performed except that only polycyclohexylenedimethylene oxalate was used. The results are shown in Table 1.

[Reference Example 2]
In a 5 L internal pressure vessel equipped with a stirrer, thermometer, pressure gauge, nitrogen gas inlet, pressure relief outlet, and polymer outlet, dimethyl oxalate 2025.0 g (17.148 mol), cyclohexanedimethanol 2312 0.0 g (16.032 mol), 3.6 g of butyltin hydroxide oxide hydrate (0.100 mol% of dimethyl oxalate DMO) and 21.6 g of heat-resistant irgaphos 168 (manufactured by Ciba Specialty Chemicals) (5000 ppm of raw material) ) And the inside was replaced with nitrogen. Next, a polycondensation reaction was performed as follows. The water concentration in dimethyl oxalate was 478 ppm, and the water concentration in cyclohexanedimethanol was 200 ppm.

(I) Pre-polycondensation step: The temperature in the pressure vessel was raised from room temperature to 100 ° C. over 1.25 hours. After confirming that the melt was uniform, the reaction was carried out while raising the temperature to 150 ° C. over 2 hours. The amount of distilled methanol in the process of raising the temperature was 394.5 g. Subsequently, it was made to react further, heating up to 190 degreeC over 2 hours. The total methanol distillate amount was 434.5 g.

(II) Post-polycondensation step: Depressurization was started while maintaining the temperature in the pressure vessel at 190 ° C., the pressure was reduced to 300 mmHg (39.9 kPa) in 0.75 hours, and 100 mmHg (13.3 kPa) in 1 hour. The reaction was performed under reduced pressure. During this time, the total amount of methanol distilled was 484.5 g. Next, the temperature in the pressure vessel is increased to 207 ° C. over 1.5 hours, and gradually decreased to 5 mmHg (665 Pa) after 1.25 hours while gradually reducing the pressure, and further to 0.8 mmHg (106 Pa) after 4 hours. The reaction was carried out. Thereafter, the stirring was stopped, and the melted contents were drawn out from the polymer outlet through a string, cooled with water, and pelletized. The obtained polycyclohexylenedimethylene oxalate (2430 g) had a Mn of 35100 and a melting point of 174 ° C.

  Next, using a twin screw extruder, at 190 ° C., 1 wt% of hydrolysis inhibitor Carbodilite LA-1 (Nisshinbo), 0.1 wt% of HMV-8CA (Nisshinbo), The heat-resistant agent Irgafos 168 was mixed at 0.32% by weight, and the antioxidant Irganox 1010 (manufactured by Ciba Specialty Chemicals) was mixed at 0.25% by weight. All blending ratios are ratios to pellets.

[Examples 5 to 8]
Using the polyoxalate pellets obtained in Reference Example 2 and the polylactic acid pellets, a polyoxalate composition was prepared at a ratio shown in Table 2 and formed into a sheet. However, the preparation of the polyoxalate composition and the sheet molding of the polyoxalate composition were performed by changing the temperature to 190 ° C. Table 2 shows the physical property evaluation results of each sheet. However, biodegradability was evaluated in compost.

[Comparative Example 2]
The same procedure as in Example 2 was performed, except that polycyclohexylene dimethylene oxalate was not used and only polylactic acid was used. The results are shown in Table 2.

The polyoxalate composition of the present invention can be used in a wide range of applications in which biodegradable plastics are used, such as films or sheets, various molded articles, and textile products.

Claims (5)

A polyoxalate composition comprising 1 part by weight or more and less than 100 parts by weight of polylactic acid based on 100 parts by weight of a polyoxalate represented by the following formula.

(In the formula, R represents an alkylene group having 3 to 12 carbon atoms in the main chain, which may contain a branched structure or an alicyclic structure, and n is a positive integer representing the degree of polymerization.)   The polyoxalate composition according to claim 1, wherein the number average molecular weight of the polyoxalate is 20,000 to 100,000, and the number average molecular weight of the polylactic acid is 20,000 to 500,000.   The polyoxalate composition according to claim 1, wherein the number average molecular weight of the polyoxalate is 20,000 to 70,000 and the number average molecular weight of the polylactic acid is 20,000 to 500,000. The polyoxalate composition according to claim 1, wherein the polyoxalate is polycyclohexylenedimethylene oxalate. A molded product obtained from the polyoxalate composition according to claim 1.