JP2015071749A - Styrene-based resin composition and method for producing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a styrene-based resin composition combining usefulness of a styrenic resin with that of a polylactic acid without impairing the usefulness of them.SOLUTION: There is provided the styrene-based resin composition containing a styrene-methacrylic acid copolymer (A), a polylactic acid (B), and an epoxidized oil (C). There is also provided a method for producing styrene-based resin composition including (1) a step of melt mixing polylactic acid (B) and epoxidized oil (C), (2) after step (1), a step of adding styrene-methacrylic acid copolymer (A) and further melt mixing the same, and (3) after step (2), further adding polylactic acid (B) and styrene-methacrylic acid copolymer (A) and melt mixing them.

Description

  The present invention relates to a styrene resin composition containing a styrene-methacrylic acid copolymer, polylactic acid, and epoxidized oil.

  In recent years, it has been recognized by general consumers that the use of plastic products containing various biodegradable polymers is preferable from the viewpoint of environmental protection and that the use of plant-derived raw materials is preferable from the viewpoint of saving petroleum resources. Therefore, attempts to use biodegradable polymers and plant-derived polymers as raw materials have been widely conducted for industrial products.

  In particular, polylactic acid is a plant-derived and biodegradable polymer, and among the biodegradable polymers, it is practically superior because it has a relatively high melting point, toughness, transparency, and chemical resistance. Recognized as a polymer.

  On the other hand, the styrene resin is excellent in moldability and practical physical properties such as rigidity. Therefore, studies have been made to make use of the characteristics of these resins. For example, studies have been made on blending a styrene resin and polylactic acid to ensure fluidity and improve mechanical properties (see, for example, Patent Document 1). However, the compatibility between styrene-based resins and polylactic acid is very poor, and it is difficult to design products that take advantage of the physical properties required by the market and the characteristics of each resin by simply blending and melting and mixing.

JP 2008-50426 A

  In view of the above circumstances, the problem to be solved by the present invention is to provide a styrenic resin composition using these in combination without impairing the usefulness of the styrenic resin and polylactic acid.

  As a result of intensive research to solve the above problems, the present inventors have solved dispersibility failure by containing a styrene resin, polylactic acid, and epoxidized oil, and have moldability, strength, heat resistance and The present inventors have found that a styrenic resin composition having excellent oil resistance and the like can be provided, and have completed the present invention.

  That is, the present invention provides a styrene-based resin composition and a production method characterized by containing a styrene-methacrylic acid copolymer, polylactic acid, and epoxidized oil.

  The styrenic resin composition of the present invention has good moldability, mechanical strength, oil resistance, and the like. Moreover, it can reduce an environmental load by mix | blending a plant-derived resin, and can also be used for various general purpose molded objects, and is preferable from a viewpoint of environmental protection.

The present invention is described in detail below.
The styrene-methacrylic acid copolymer (A) used in the present invention is a copolymer of a styrene monomer and methacrylic acid, and the copolymerization type may be block or random. From the viewpoint of dispersibility (compatibility) with polylactic acid (B) described later, the content ratio derived from the methacrylic acid component is preferably 2 to 20% by mass, and more preferably 5 to 15% by mass. . Examples of styrenic monomers include styrene and derivatives thereof; for example, styrene, methyl styrene, dimethyl styrene, trimethyl styrene, ethyl styrene, diethyl styrene, triethyl styrene, propyl styrene, butyl styrene, hexyl styrene, heptyl styrene, octyl styrene, and other alkyl styrenes. , Halogenated styrene such as fluorostyrene, chlorostyrene, bromostyrene, dibromostyrene, and iodostyrene, and further nitrostyrene, acetylstyrene, methoxystyrene, and the like. These may be used alone or in combination of two or more. Among these, it is preferable to use a styrene monomer from the viewpoint of excellent versatility.

  The fluidity of the styrene-methacrylic acid copolymer (A) used in the present invention is 1 to 20 g / 10 min. It is preferable to be in the range of (230 ° C., 37.3 N).

  The polylactic acid (B) used in the present invention is obtained by, for example, saccharifying starch obtained from corn, potatoes, etc., further obtaining lactic acid by lactic acid bacteria, and then cyclizing the lactic acid to form lactide. Generally available polylactic acid (B) obtained by ring polymerization can be used. Also, polylactic acid obtained by synthesizing lactide from petroleum and ring-opening polymerization thereof, or polylactic acid obtained by obtaining lactic acid from petroleum and directly dehydrating and condensing it may be used.

  The lactic acid constituting the polylactic acid can also be used by mixing L-lactic acid and D-lactic acid. However, from the viewpoint of excellent heat resistance of the molded product when the resulting composition is used as a molded product, L -It is preferable that it consists of any one isomer of lactic acid or D-lactic acid. Specifically, the D isomer content rate (ratio of D-lactic acid to the total mass of lactic acid used as a raw material) is 3.0%. The following are preferred.

  Furthermore, other components may be copolymerized with polylactic acid (B) in addition to D-lactic acid and L-lactic acid, which are main constituent monomers. Examples of other copolymer components include ethylene glycol, propylene glycol, butanediol, oxalic acid, adipic acid, and sebacic acid. Such a copolymer component is preferably contained in an amount of generally 0 to 30 mol%, more preferably 0 to 10 mol%, in all monomer components.

  The molecular weight and molecular weight distribution of polylactic acid (B) are not particularly limited as long as it can be substantially molded, but the weight average molecular weight is preferably 10,000 to 400,000, more preferably 40,000 to 200,000. It is a range.

  Although the oil component used for the epoxy modification of the epoxidized oil (C) is not particularly limited, it is naturally derived from the viewpoint that the composition obtained in the present invention can be suitably used as a food packaging material. It is preferably an oil component, and examples include animal oils such as beef tallow, pork tallow and fish, and vegetable oils.

  Vegetable oil is mainly composed of fatty acid triglyceride, which is a triester (triglyceride) between fatty acid and glycerin, and unsaturated fatty acid (carbon--) such as oleic acid, linolenic acid and linoleic acid A fatty acid having a carbon double bond in the main chain). This carbon-carbon bond can generally be easily epoxidized using a peracid (percarboxylic acid) or other peroxy compound.

  Examples of vegetable oils include dry oils such as dehydrated castor oil, tung oil, linseed oil, sunflower oil, rosehip oil, coconut oil, and semi-dry oils such as soybean oil, rapeseed oil, safflower oil, cottonseed oil, sesame oil, and corn oil. It is done. Among these, linseed oil or soybean oil is preferable. That is, the epoxidized vegetable oil is preferably epoxidized linseed oil obtained by epoxy-modifying linseed oil or epoxidized soybean oil obtained by epoxy-modifying soybean oil. Linseed oil and soybean oil are highly stable as starting materials, and also have a relatively large number of carbon-carbon double bonds in the structure.

  As the epoxidized oil, commercially available ones can be used as they are. For example, as epoxidized soybean oil, “ADEKA SIZER O-130P” manufactured by ADEKA Corporation, “New Sizer 510R” manufactured by NOF Corporation, Kapo Co., Ltd. “Capox S-6”, DIC Corporation “Epocizer W-100-EL”, etc., ADEKA Co., Ltd. “Adeka Sizer O-180A” as an epoxidized linseed oil, NOF Corporation “New Sizer” 512 "," Eposizer W-109 "manufactured by DIC Corporation, and the like.

  Regarding kneading of styrene-methacrylic acid copolymer (A), polylactic acid (B) and epoxidized oil (C), epoxidized oil is added to dried styrene-methacrylic acid copolymer (A) and polylactic acid (B). After dry blending (C), it can be adjusted using an extruder.

  Further, as means for improving dispersibility and physical properties, those containing a compound (D) obtained by reacting a styrene-methacrylic acid copolymer (A), a polylactic acid (B) and an epoxidized oil (C) are more preferable.

  The following method (process) is mentioned as a method of obtaining the said compound (D).

Step (1): Dry polylactic acid (B) [non-terminal-modified (carboxyl group remaining)] and epoxidized oil (C) are dry-blended and polylactic acid (B) in a melt kneader. The carboxylic group of the epoxidized oil (C) is reacted with the carboxyl group.
Step (2): The dry styrene-methacrylic acid copolymer (A) is dry blended into the reaction mixture obtained in the step (1), and the epoxy remaining in the reaction mixture obtained in the step (1) The group is reacted with the carboxyl group of the styrene-methacrylic acid copolymer (A).

  As a condition for obtaining the compound (D), the molar ratio of the polylactic acid (B) and the epoxidized oil (C) can be expressed by the carboxyl group in the polylactic acid (B) / the epoxy group in the epoxidized oil (C). The ratio is preferably 1 / 1.1-1 / 20. This is because if the amount of carboxy group is large, the epoxy group to be reacted in the next step is insufficient, and if the amount of carboxy is small, it is difficult to obtain the compound (D) efficiently. In addition, each mole number was calculated | required using the molecular weight of each substance, the addition amount, the carboxy group number of polylactic acid, and the epoxy group number in 1 molecule of epoxidized oil.

  As a condition for suitably obtaining the compound (D), the theoretical residual epoxy group when the total amount of carboxy groups in the polylactic acid (B) reacts with the epoxy group in the epoxidized oil (C) in the step (1). It is preferable to use it so that the number of moles of the carboxy group in the styrene-methacrylic acid copolymer (A) is in the range of 0.1 to 150 times the number of moles. If it is this range, the reaction efficiency with the number-of-moles of the carboxyl group of a styrene methacrylic acid copolymer (A) and an epoxy group can be improved, intermolecular bridge | crosslinking can be suppressed and gelatinization can be prevented. In addition, about the mole number, about the styrene-methacrylic acid copolymer (A), it calculated | required from the addition amount, the methacrylic acid ratio in a styrene-methacrylic acid copolymer, and the molecular weight of a styrene-methacrylic acid copolymer. The number of moles of the theoretical residual epoxy group in step (1) is obtained by subtracting the total number of carboxy groups of polylactic acid from the total number of epoxy groups of the epoxidized oil added in step (1).

  The mass ratio when the compound (D), the styrene methacrylic acid copolymer (A), and the polylactic acid (B) are added and melt-kneaded is styrene methacrylic acid copolymer with respect to the theoretical mass of the compound (D). The combined (A) is preferably 0.5 to 5.0 times and the polylactic acid (B) is preferably 0.5 to 2.0 times. If the ratio of the compound (D) with respect to the total mass is within this range, the dispersibility is improved and the mechanical properties of the obtained molded article are good.

  The mixing order of the resins is not particularly limited. For example, the styrene-methacrylic acid copolymer (A), the polylactic acid (B), the epoxidized oil (C), and the compound (D) are isolated and then dry blended. And a master batch in which a styrene-methacrylic acid copolymer (A) and an isolated compound (D), a polylactic acid (B) and an isolated compound (D) are melt-kneaded. Then, this master batch and the styrene-methacrylic acid copolymer (A) or polylactic acid (B) may be melt-kneaded. A method of adding the styrene-methacrylic acid copolymer (A) or the polylactic acid (B) in a state containing unreacted components without removing the compound (D) from the melt-kneader.

  In addition, if necessary, a method of melt-kneading other additives at the same time, or preparing a master batch in which styrene-methacrylic acid copolymer (A) or polylactic acid (B) and other additives are previously melt-kneaded Alternatively, a method of melt-kneading the master batch, the styrene-methacrylic acid copolymer (A) and the polylactic acid (B) may be used.

  Moreover, it is preferable that the temperature at the time of melt-kneading each component is in the range of 180 ° C. to 260 ° C. From the viewpoint of efficiently producing the compound (D) in the process, and deterioration of the polylactic acid (B) due to heat. From the viewpoint of prevention and from the viewpoint of kneadability of the polylactic acid (B) and the styrene-methacrylic acid copolymer (A), the temperature at which each component is melt-kneaded is more preferably in the range of 190 ° C to 240 ° C.

  Further, in the present invention, the styrene-methacrylic acid copolymer (A), polylactic acid (B), epoxidized oil (C) and compound (D) are used in the above-mentioned blending proportions, but other than that as required. These resins and various additives may be used in combination to form a styrene resin composition.

  Examples of the various additives include an antistatic agent, an antioxidant, an ultraviolet absorber, a lubricant, an antiblocking agent, and a heat stabilizer.

  The obtained styrene-based resin composition has particularly improved compatibility between the styrene-methacrylic acid copolymer (A) and the polylactic acid (B), and has excellent moldability. It is good. Therefore, it is possible to use molding methods such as injection molding, sheet extrusion molding, foam molding, vacuum molding, and blow molding. Moreover, it can use for various uses. Specifically, it can be suitably used for parts for electric / electronic devices, automobile parts, packaging applications, daily commodities, and the like.

  EXAMPLES Hereinafter, although an Example is given and this invention is further demonstrated, this invention is not limited to these Examples at all. Unless otherwise indicated, both parts and% are based on mass.

  The raw materials, intermediate raw materials, and physical properties of the obtained styrene resin composition were measured and evaluated by the following methods.

(1) Molecular weight measurement (styrene methacrylic acid copolymer, polylactic acid)
Using a high-speed GPC HLC-8220 (manufactured by Tosoh Corporation) and a column (TSK-GELGMHXL × 2), a solution prepared by dissolving 5 mg of a sample in 10 g of THF was injected into the apparatus (200 μL), and a flow rate: 1 ml / min (THF ), Thermostat temperature: 40 ° C., measured with an RI detector.

(2) Dispersion state (compatibility) observation The sample was cut out and the cross section was produced with an ultramicrotome, and confirmed with an optical microscope. Good dispersibility was indicated by ◯, substantially good dispersibility by Δ, and poor dispersibility by x.

(3) Bending test A measurement sample (shape: width 10 mm, thickness: 2.0 mm) was measured with a bending tester (Instron). (Conditions: Span ratio: 40 mm, speed: 2.0 mm / min) Less than 75 MPa was evaluated as x, 75 MPa or more and less than 80 MPa was evaluated as Δ, and 80 MPa or more was evaluated as ◯.

(4) Oil resistance Using a hot plate press (230 ° C.), a styrenic resin composition is used to produce a sheet having a thickness of 100 μm, cut into a 100 × 20 mm strip, wound around a paper tube having a diameter of 90 mm, and edible oil ( White F-2 (manufactured by Fuji Seiki Co., Ltd.) was applied and allowed to stand in a thermostatic device at 60 ° C., and the crack condition after 1 hour was confirmed. The case with cracks was rated as x, the case with some cracks as Δ, and the case without change as ○.

  As the styrene-methacrylic acid copolymer (A), styrene / methacrylic acid = 90/10 (mass%), weight average molecular weight (Mw): 320,000, fluidity: 2.5 g / 10 min. (230 ° C., 37.3 N) was used.

  As polylactic acid (B), fluidity 10 g / 10 min (190 ° C., 21.2 N), D-form: 1.4 mol%, weight average molecular weight: 180,000, terminal unmodified (carboxy group remaining) raw material is used. did.

  As the epoxidized oil (C), “Eposizer W-100-EL” (molecular weight: 933) manufactured by DIC Corporation as epoxidized soybean oil, and “Eposizer W-109” (molecular weight: manufactured by DIC Corporation) as epoxidized linseed oil. 975) was used.

Reference Example 1 (Synthesis of Compound D-1)
Step (1): Laboplast mill [Mixer (R-60) (Toyo Seiki), all of which are the same for Laboplast Mill), dried polylactic acid: 50 g, Eposizer W-100-EL: 0.1 g was added. (Mole ratio of carboxyl group / epoxy group = 1 / 1.15), and melt-kneaded at 210 ° C for 30 minutes.

  Step (2): The reaction mixture obtained in Step (1): 0.212 g and the styrene methacrylic acid copolymer: 50 g were added to the lab plast mill (the number of moles of theoretical residual epoxy groups in step (1) / styrene methacrylic acid). The number of moles of carboxy groups in the acid copolymer was 1 / 85.7), and melt kneaded at 210 ° C. for 30 minutes to obtain a mixture containing compound D-1.

Reference Example 2 (Synthesis of Compound D-2)
Step (1): Polylactic acid dried in a lab plast mill: 50 g, Eposizer W-100-EL: 0.3 g was added (carboxyl group / epoxy group molar ratio = 1 / 3.46), 210 ° C., Melted and kneaded for 30 minutes.

  Step (2): The reaction mixture obtained in Step (1): 0.212 g and the styrene methacrylic acid copolymer: 50 g were added to the lab plast mill (the number of moles of theoretical residual epoxy groups in step (1) / styrene methacrylic acid). The number of moles of carboxy group in the acid copolymer was 1 / 5.4), 210 ° C., melt-kneaded for 30 minutes to obtain a mixture containing compound D-2.

Reference Example 3 (Synthesis of Compound D-3)
Step (1): Laboplast mill-dried polylactic acid: 50 g, Eposizer W-109: 0.15 g was added (carboxyl group / epoxy group molar ratio = 1 / 3.32), and melted at 210 ° C. for 30 minutes. Kneaded.

  Step (2): The reaction mixture obtained in Step (1): 0.53 g and styrene methacrylic acid copolymer: 50 g were added to Laboplast mill (the theoretical residual number of moles of epoxy groups in Step (1) / styrene methacrylate). The number of moles of carboxy group of the acid copolymer = 1 / 2.3), 210 ° C., melt-kneaded for 30 minutes to obtain a mixture containing compound D-3.

Reference Example 4 (Synthesis of Compound D-4)
Step (1): Polylactic acid dried to Laboplast Mill: 50 g, Eposizer W-109: 0.45 g was added (carboxyl group / epoxy group molar ratio = 1 / 9.97), 210 ° C., 30 minutes Melted and kneaded.

  Step (2): The reaction mixture obtained in Step (1): 0.53 g and styrene methacrylic acid copolymer: 50 g were added to Laboplast mill (the theoretical residual number of moles of epoxy groups in Step (1) / styrene methacrylate). The number of moles of carboxy group of the acid copolymer was 1 / 0.6), and melt-kneaded at 210 ° C. for 30 minutes to obtain a mixture containing compound D-4.

Example 1
Styrene methacrylic acid copolymer (A): 35 g, polylactic acid (B): 15 g, epoxidized soybean oil: 0.1 g are dry blended and kneaded at 230 ° C. for 15 minutes using a lab plast mill. A system resin composition was obtained.

Example 2
Styrene methacrylic acid copolymer (A): 15 g, polylactic acid (B): 15 g, 15 g of a mixture containing the compound (D-1) obtained in Reference Example 1 was dry-blended and used at 230 ° C. for 10 The mixture was kneaded to obtain a styrene resin composition.

Example 3
Styrene methacrylic acid copolymer (A): 27 g, polylactic acid (B): 9 g, 9 g of the mixture containing the compound (D-1) obtained in Reference Example 1 was dry-blended, and 230 using a lab plast mill. Kneading at 10 ° C. for 10 minutes gave a styrene resin composition.

Example 4
Styrene methacrylic acid copolymer (A): 15 g, polylactic acid (B): 15 g, a mixture containing the compound (D-2) obtained in Reference Example 2: 15 g is dry-blended and 230 using a lab plast mill. Kneading at 10 ° C. for 10 minutes gave a styrene resin composition.

Example 5
Styrene methacrylic acid copolymer (A): 27 g, polylactic acid (B): 9 g, a mixture containing the compound (D-2) obtained in Reference Example 2: 9 g was dry-blended and 230 using a lab plast mill. Kneading at 10 ° C. for 10 minutes gave a styrene resin composition.

Example 6
Styrene methacrylic acid copolymer (A): 15 g, polylactic acid (B): 15 g, a mixture containing 15 g of the compound (D-3) obtained in Reference Example 3 is dry-blended and 230 using a lab plast mill. Kneading at 10 ° C. for 10 minutes gave a styrene resin composition.

Example 7
Styrene methacrylic acid copolymer (A): 27 g, polylactic acid (B): 9 g, and a mixture containing 9 g of the compound (D-3) obtained in Reference Example 3 were dry-blended and 230 using a lab plast mill. Kneading at 10 ° C. for 10 minutes gave a styrene resin composition.

Example 8
Styrene methacrylic acid copolymer (A): 15 g, polylactic acid (B): 15 g, a mixture containing 15 g of the compound (D-4) obtained in Reference Example 4 was dry blended, and 230 using a lab plast mill. Kneading at 10 ° C. for 10 minutes gave a styrene resin composition.

Example 9
Styrene methacrylic acid copolymer (A): 27 g, polylactic acid (B): 9 g, a mixture containing the compound (D-4) obtained in Reference Example 4: 9 g was dry blended, and 230 using a lab plast mill. Kneading at 10 ° C. for 10 minutes gave a styrene resin composition.

Comparative Example 1
35 g of styrene methacrylic acid copolymer (A) and 15 g of polylactic acid (B) were dry blended and kneaded at 230 ° C. for 10 minutes using a lab plast mill to obtain a styrene resin composition.

Comparative Example 2
16.6 g of styrene methacrylic acid copolymer (A) and 33.4 g of polylactic acid (B) were dry blended and kneaded at 230 ° C. for 10 minutes using a lab plast mill to obtain a styrene resin composition. .

Comparative Example 3
The styrene-methacrylic acid copolymer (A) was evaluated in the same manner as the resin composition.

  The evaluation results are shown in Tables 1-3.

Claims (9)

A styrene-based resin composition comprising a styrene-methacrylic acid copolymer (A), polylactic acid (B), and epoxidized oil (C). The styrenic resin composition according to claim 1, wherein the epoxidized oil (C) is epoxidized soybean oil or epoxidized linseed oil. The styrene-based resin composition according to claim 1 or 2, comprising a compound (D) obtained by reacting a styrene-methacrylic acid copolymer (A), a polylactic acid (B), and an epoxidized oil (C). The compound (D) reacts with a styrene-methacrylic acid copolymer (A) after reacting a carboxy group in the polylactic acid (B) with a part of the epoxy group in the epoxidized oil (C). The styrenic resin composition according to claim 3, which is a block copolymer obtained by reacting the remaining epoxy group and the carboxy group in the styrene methacrylic acid copolymer (A) in addition to the system. (1) Melting and kneading polylactic acid (B) and epoxidized oil (C),
(2) After the step (1), a step of adding a styrene-methacrylic acid copolymer (A) and further melt-kneading,
(3) A method for producing a styrene-based resin composition, which further comprises a step of adding and melt-kneading polylactic acid (B) and a styrene-methacrylic acid copolymer (A) after the step (2). The molar ratio in which the proportion of polylactic acid (B) and epoxidized oil (C) used in step (1) is represented by the carboxy group in polylactic acid (B) / the epoxy group in epoxidized oil (C). The method for producing a styrenic resin composition according to claim 5, wherein the range is from 1 / 1.1 to 1/20. The use ratio of the styrene-methacrylic acid copolymer (A) in the step (2) is that in the step (1), the total amount of carboxy groups in the polylactic acid (B) reacts with the epoxy groups in the epoxidized oil (C). 6. The styrene methacrylic acid copolymer (A) is used so that the number of moles of carboxy groups in the styrene-methacrylic acid copolymer (A) is in the range of 0.1 to 150 times the number of moles of theoretical residual epoxy groups. Or the manufacturing method of the styrene-type resin composition of 6. The use ratio of the polylactic acid (B) in the step (3) is in the range of 0.5 to 2.0 times the theoretical mass after the step (2). The manufacturing method of the styrene resin composition of description. The use ratio of the styrene-methacrylic acid copolymer (A) in the step (3) is in the range of 0.5 to 5.0 times the theoretical mass after the step (2). The manufacturing method of the styrene-type resin composition of any one.