JP2001233990A - Plasticizer for thermoplastic resin composition and thermoplastic resin composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide suitable plasticizers which are through to be most efficient for broadening the use of thermoplastic resins and, simultaneously, various types of thermoplastic resin compositions added with the plasticizers. SOLUTION: The plasticizers for thermoplastic resins (excluding each resin of vinyl chloride based and cellulose acetate based resins) comprise a citric ester compound represented by formula [I] (wherein R1 is a hydrogen atom or an aliphatic acyl group; and R2 is an alkyl group).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a thermoplastic resin comprising a specific citrate compound (excluding vinyl chloride-based and cellulose acetate-based resins. Hereinafter, vinyl chloride-based resin is referred to as PVC, and cellulose acetate-based resin is referred to as CA). And a thermoplastic resin composition obtained by adding the plasticizer to the thermoplastic resin.
More specifically, it has good kneading workability for thermoplastic resins other than PVC and CA, maintains the mechanical, thermal, and other physical properties of the resin in a well-balanced manner, and has a problem that all resins requiring a plasticizer have. A plasticizer comprising a citrate compound having a specific chemical structural formula, which hardly causes bleed-out of the plasticizer, which is a plasticizer suitable for the thermoplastic resin, particularly for a styrene resin, and The present invention relates to a thermoplastic resin composition to which a plasticizer is added, excluding PVC and CA, and more particularly to a thermoplastic resin composition in which the thermoplastic resin is a styrene resin.

[0002]

2. Description of the Related Art Plastics are generally lightweight, have high strength, are excellent in solvent resistance, and are easy to mold and process as compared with metals and woods. It is used in materials, automotive materials, and various other fields, and is consumed in large quantities. On the other hand, as a method of processing the plastic, various means such as vacuum forming, blow molding, and inflation molding can be used according to the intended use. Looking at the plastic material from the perspective of its application,
In the case of film applications, polyethylene and polypropylene are mainly suitable, and in the case of sheets and containers, polystyrene and polypropylene are usually suitable, and various types are used depending on the application. These choices are made mainly in consideration of resin physical properties, resin price, moldability, etc.

[0003] Usually, the choice of the type of plastic is made according to its use, as described above, and the criteria for selection depend on the known properties of the plastic. However, these known properties are not fixed and can be changed by modifying the molecular structure of the plastic, especially the steric structure, modification by a chemical reaction, modification by the addition of other resins or additives, and the like. In some cases, it greatly contributes to expanding the use of plastics.

[0004] In particular, the effect of using a plasticizer as an additive is great, and the use of various plastics is expanding. However, there is a case where only a limited plasticizer can be used for a specific plastic, or a case where a suitable plasticizer does not yet exist, and the technology for modifying a plastic by using a plasticizer is not yet satisfactory. Absent. For example, for polystyrene, its tensile modulus is 2 × 10 ⁴
If it can be reduced to about 2.5 × 10 ⁴ Kgf / cm ² to a low value of 6 × 10 ³ Kgf / cm ² or less, it can be used for thin polystyrene film as well as rigid objects such as current containers and bottles. It is expected that the film can be expanded, and a multi-film for agriculture and a bag for garbage can be formed. In this case, as a means for adjusting the tensile modulus, there is a method of adjusting the molecular weight or the branched chain, etc., but fine adjustment by the adjusting method is difficult and requires a lot of work, and the adjustable range is also large. Because of its narrowness, it is not always a suitable means for adjusting the above-mentioned various characteristics.

[0005]

SUMMARY OF THE INVENTION The present invention focuses on thermoplastic resins other than vinyl chloride resins and cellulose acetate resins, and it is most efficient to provide a suitable plasticizer to expand the range of use thereof. In particular, it was considered to be particularly beneficial to provide a plasticizer for styrenic resins for which there was no suitable plasticizer, and the provision of the plasticizer, and at the same time, the addition of the plasticizer was considered. Another object is to provide the above-mentioned various thermoplastic resin compositions.

[0006]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to solve the above-mentioned problems, and as a result, when a specific citrate compound was blended with a thermoplastic resin such as polystyrene, the thermoplastic resin was removed. Can be an excellent plasticizer,
It is possible to solve various problems at the time of kneading operation which occur when a conventionally known plasticizer is added to these thermoplastic resins, kneading, occurrence of bleed-out after molding, remarkable deterioration phenomenon of the basic physical properties of the thermoplastic resin and the like. They have found that they can do this and have completed the present invention. The gist of the present invention is as follows.

That is, the first invention relates to a plasticizer for a thermoplastic resin (excluding vinyl chloride-based and cellulose acetate-based resins) comprising a citrate ester compound represented by the following general formula [I].

[0008]

Embedded image Wherein, R ¹ is hydrogen atom or an aliphatic acyl group, R ²
Is an alkyl group. ]

The second invention relates to a plasticizer for a thermoplastic resin comprising the citrate compound of the first invention, wherein R ¹ is an aliphatic acyl group having 1 to 5 carbon atoms. The third invention is the first invention, wherein R ² is an alkyl group having 1 to 4 carbon atoms.
Or, it relates to a plasticizer for a thermoplastic resin comprising the citrate ester compound of the second invention. The fourth invention relates to a plasticizer for a thermoplastic resin comprising the citrate ester compound of the first invention, wherein R ¹ is a hydrogen atom and R ² is a methyl group or an ethyl group. The fifth invention relates to a plasticizer for a thermoplastic resin comprising the citrate ester compound of the first invention, wherein R ¹ is an acetyl group and R ² is a methyl group or an ethyl group. A sixth invention relates to a plasticizer for a thermoplastic resin comprising the citrate compound of any one of the first to fifth inventions, wherein the thermoplastic resin is a styrene-based resin. The seventh invention relates to a thermoplastic resin composition obtained by adding 5-200 parts by weight of a citrate ester compound represented by the general formula [I] to 100 parts by weight of a thermoplastic resin. The eighth invention relates to the thermoplastic resin composition according to the seventh invention, wherein the thermoplastic resin is a styrene resin.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION (Thermoplastic resin excluding PVC and CA) The thermoplastic resin excluding PVC and CA (hereinafter abbreviated as "thermoplastic resin" unless otherwise specified) is particularly limited. However, widely used thermoplastic resins can be used. For example, styrene resins such as general-purpose polystyrene, impact-resistant polystyrene, AS resin and ABS resin, olefin resins such as polyethylene, ethylene-vinyl acetate copolymer, polypropylene and ethylene-propylene copolymer, polyethylene terephthalate, and polybutylene Ester resins such as terephthalate,
Nylon 46, Nylon 6, Nylon 66, Nylon 1
Polyamide resins such as 1, nylon 12, etc. can be used, and styrene resins are particularly preferred.

(Citrate ester compound) In the citrate ester compound represented by the general formula [I], which is a plasticizer for a thermoplastic resin according to the present invention and is a component of the resin composition, R ¹ is A hydrogen atom or an aliphatic acyl group, and the aliphatic acyl group is not particularly limited, but is preferably an acyl group having 1 to 12 carbon atoms;
Particularly preferred is an acyl group having 1 to 5 carbon atoms. Specifically, groups such as acetyl, propionyl, butyryl, valeryl, palmitoyl, and oleyl can be exemplified.

R ² in the formula is an alkyl group,
The alkyl group is not particularly limited, and may be linear or branched. Incidentally, an alkyl group having 1 to 24 carbon atoms is preferable, and an alkyl group having 1 to 4 carbon atoms is particularly preferable. Specific examples include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a sec-butyl group, and a t-butyl group.

The thermoplastic resin according to the present invention is blended with
Represented by the general formula [I]
Particularly preferred acid ester compounds include R
¹Is an aliphatic acyl group having 1 to 5 carbon atoms, R^TwoBut charcoal
An alkyl group having a prime number of 1 to 4, R¹Is a hydrogen atom
Yes, R^TwoIs a methyl group or an ethyl group, and R ¹
Is an acetyl group;^TwoIs a methyl group or an ethyl group
Things.

Next, an example of the method for producing the citrate compound represented by the general formula [I] according to the present invention will be outlined. (Preparation of the Citrate Ester Compound Where R ¹ is a Hydrogen Atom) Among the citrate ester compounds represented by the general formula [I] according to the present invention, those in which R ¹ is a hydrogen atom can be prepared by a known method. It can be manufactured by applying. As a method known here, for example, a method for producing phthalyl glycolate from a phthalic acid half ester and an α-halogenated acetic acid alkyl ester described in British Patent No. 931781 can be mentioned. Specifically, an alkyl α-monohalogenated acetate, for example, monochloroacetic acid, which is an alkyl ester corresponding to R ² , based on 1 mol of trisodium citrate, tripotassium citrate or citric acid, preferably trisodium citrate Methyl, ethyl monochloroacetate and the like are reacted in a stoichiometric amount or more, preferably 1 to 10 mol, more preferably 2 to 5 mol. If water is present in the reaction system, the yield of the target compound is reduced. Therefore, it is preferable to use an anhydrous or anhydrous product as possible. Reactively, a chain or cyclic aliphatic tertiary amine such as trimethylamine, triethylamine, tri-n-propylamine, triisopropylamine, tri-n-butylamine, and dimethylcyclohexylamine can be used as a catalyst, and among them, triethylamine is preferable. The amount of the catalyst used is 0.1 to 1 mol of the citric acid raw material.
The amount is preferably from 01 to 1.0 mol, more preferably from 0.2 to 0.5 mol. Regarding the reaction temperature and time, 60 to 1
The reaction is preferably performed at 50 ° C. for 1 to 24 hours. Although the use of a reaction solvent is not always necessary, toluene, benzene, xylene, methyl ethyl ketone and the like can be used as necessary. After the reaction, for example, by-products and a catalyst are removed by adding water, the oil layer is washed with water, and then separated from unreacted starting compounds by distillation to isolate the target compound.

[0015] (production method the citric acid ester compound R ¹ is an aliphatic acyl group) R ¹ is an aliphatic acyl group, citric acid ester compound of the present invention where R ² is alkyl group, said R It can be produced using a citrate compound in which ¹ is a hydrogen atom. That is, with respect to 1 mol of the citrate compound in which R ¹ is a hydrogen atom,
An acyl halide corresponding to the desired aliphatic acyl group, for example, formyl chloride, acetyl chloride and the like are reacted in 1 to 10 mol. As the catalyst, it is preferable to use 0.1 to 2.0 mol of basic pyridine or the like per 1 mol of the citrate compound. The reaction may be solvent-free, and the reaction temperature and time are preferably from 80 to 100 ° C for 1 to 5 hours. After the reaction, water and an organic solvent insoluble in water are added to the reaction mixture,
For example, toluene is added to dissolve the target substance in an organic solvent,
After separating the aqueous layer and the organic solvent layer and washing the organic solvent layer with water,
The target substance can be isolated by a conventional method such as distillation.

The amount of the citrate compound added to the thermoplastic resin in the plasticizer according to the present invention is selected from the range of 5 to 200 parts by weight based on 100 parts by weight of the thermoplastic resin. A thermoplastic resin composition is obtained.
However, the amount of the citrate compound is usually more preferably 20 to 100 parts by weight from the viewpoints of moldability and other processability of the composition, mechanical properties of the molded article, and the like. In addition,
When the amount of the citrate compound is less than 5 parts by weight, the function as a plasticizer is hardly observed, and when it exceeds 200 parts by weight, no change is observed in the function as a plasticizer, and an unnecessary amount of It will be added.

When the thermoplastic resin composition according to the present invention is obtained by adding the citric acid ester compound to the thermoplastic resin, the method of kneading the two is not particularly limited, and the thermoplastic resin is usually used. Means used for general kneading can be used as they are. For example, various methods such as kneading at a melting temperature using an extruder (single or twin screw), a kneader, a Banbury mixer, a roll, or the like, or kneading by dissolving with a suitable solvent in combination can be applied. .

The thermoplastic resin composition according to the present invention may contain other additives, such as an antioxidant, if necessary, as in the case of the conventionally known ordinary molding resin composition. Various stabilizers such as ultraviolet absorbers, dyes, pigments, fillers, lubricants, antistatic agents, flame retardants and the like may be added alone or in combination of two or more.

[0019]

Next, the present invention will be described in detail with reference to examples, but the present invention is not limited by the contents of these examples. In the following examples, first, the citrate compound according to the present invention, which is a specific method for producing the compound used in the examples, will be described. The result of confirmation that the compound belongs to. Next, melt kneading characteristics when the obtained citrate compound was added to and blended with polystyrene (hereinafter sometimes referred to as PS), which is a typical example of a thermoplastic resin, was examined. Various characteristics (basic physical properties and bleed-out characteristics) were measured for a test piece molded using the product. First, these measurement and evaluation methods will be described.

(Melting Kneading Property) The melting kneading property was evaluated using a small melt kneading apparatus (“Laboplast Mill” manufactured by Toyo Seiki Co., Ltd.) using the citrate ester compound according to the present invention. About 50 g of each of the compounds represented by the formulas [II] and [III] obtained by the production method described in A test for melt kneading was performed. Cellulose acetate used for dissolution kneading was dried at 80 ° C. for 10 hours or more in advance. As the test items for examining the melt-kneading properties, emphasis is placed on workability in the case of scale-up manufacturing, the degree of torque application (qualitatively small, medium, and large) and the generation of odor (qualitatively Extremely low, low, medium, high), fuming (same as odor), liquid leakage status (displayed with or without), colored state (displayed with observed color), kneadability (qualitatively, Tests and evaluations were made by listing six items (shown in order of goodness, indicated by ○, Δ, ×). The “liquid leakage” in the above evaluation items
The term “phenomenon” refers to a phenomenon in which a kneaded substance or a decomposed substance exudes from a joint of “Laboplast Mill” manufactured by Toyo Seiki Co., Ltd. which is an assembly-type kneading apparatus. The melt-kneading conditions for the above evaluation test are as follows. Kneading temperature: 220 ° C Kneading time: 10 min Screw rotation speed: 50 rpm Sample amount: 50 g

(Basic Physical Properties) As a test piece for evaluating the basic physical properties of the thermoplastic resin composition according to the present invention, a mixture having the same composition as the mixture used for the evaluation of the melt-kneading property was used. What was dried for more than an hour was kneaded with a twin-screw kneading extruder, pelletized, and molded by injection molding. Pellets at 80 ° C before injection molding
Dried for 0 hours or more. The test piece was 23 ° C x 50.
% RH was used for the test after conditioning for 24 hours in a constant temperature and humidity chamber. Next, basic physical property evaluation items and measurement criteria are shown below. Tensile test: According to JIS K7113. No. 1 dumbbell piece used. Bending test: According to JIS K7203. Izod impact test: According to JIS K7110. Notch is a mold notch.

(Bleed-out characteristics) The melt-kneaded product having a plasticizing effect in the melt-kneading property evaluation test using the small-sized melt-kneading apparatus was subjected to a test for the bleed-out characteristics (time-lapse transferability) of a plasticizer. This test was conducted to check the presence or absence of bleed-out, and was conducted by observing the weight retention (unit:%) and appearance. As the test piece for the bleed-out test, a color plate (90
mm × 50 mm × thickness 1 mm, 2 mm, 3 mm). Bleed-out characteristics test at 80 ° C
Hot air treatment for 24 hours in a hot air dryer
C., 90% RH Under the two kinds of test conditions in which the temperature and humidity were controlled in a constant temperature and humidity chamber for 24 hours, both the weight retention and the appearance observation were examined for the former treated test piece, and the latter treatment was performed. For the test piece, only the appearance was observed. The observation results were displayed in the following three types. (a) No change: No change is observed in all points such as sample dimensions and surface condition. (b) Softening: The sample is softened and its shape is slightly changed, but no dimensional shrinkage change has occurred. (c) Shrinkage: A change in shrinkage in the dimensions of the sample is observed due to the precipitation of the plasticizer. Poor dimensional stability.

(Example 1) Trisethoxycarbonylmethyl citrate, which is obtained as a plasticizer by the following production method and represented by the following structural formula [II] (wherein R ¹ in the general formula [I] is a hydrogen atom, R ² is an ethyl group) and commercially available polystyrene (manufactured by Daicel Chemical Industries, Ltd., GPP
S) 100 parts by weight, 10 parts by weight, 20 parts by weight, and 40 parts by weight, respectively, were blended to obtain three types of mixtures, and the mixtures were kneaded using the small melt kneading apparatus (Laboplast mill). did. The evaluation results of the kneading workability at that time are shown in Table 1 (1), and those with good kneading properties were pelletized using a twin-screw extruder with the same formulation, and evaluated for basic physical properties using an injection molding machine. And a sample for bleed-out property evaluation was molded. Table 2 (1) shows the evaluation results of the basic physical properties using these samples, and Table 3 (1) shows the evaluation results of the bleed-out property.

[0024]

Embedded image

Next, a method for producing the compound represented by the above formula [II] and results of confirming the obtained compound will be described. Attach a stirrer, a thermometer, and a condenser to the four-necked flask, and add anhydrous anhydrous sodium citrate 774.4.
g (3.0 mol), triethylamine 26.5 g (0.
26 mol), 1323 g of ethyl monochloroacetate (10.
8 mol) and heated to 120 ° C. while stirring,
Stirring was continued at 120 ° C. for 7 hours. After the reaction, the mixture was cooled to 80 ° C., and 1500 g of water was added to remove by-product sodium chloride. The oil layer was washed three more times with 500 g of water,
After recovering ethyl monochloroacetate by vacuum distillation at 0 ° C. and 45 mmHg, steam distillation was performed at 100 ° C. and 40 mmHg for 1 hour to obtain 1284 g of a product. The specific gravity of the product was 1.280, and the purity measurement result by gel permeation chromatography (GPC: HLC-8020, manufactured by Tosoh Corporation) was 88.0%. ¹³ C-NMR
Based on the measurement results, an assignment was made. From the chart, a peak of 73.306 ppm of a quaternary carbon (citrate skeleton) and a peak of a methylene group bonded to the quaternary carbon (4
2.591 ppm), a peak of a carbonyl group bonded thereto (167.090 ppm), a peak of a methylene group bonded thereto (61.593 ppm), and a peak of a methyl group bonded thereto (14.152 ppm) were confirmed. The peak of the carbonyl group bonded to the quaternary carbon (1
72.402 ppm), the peak of the methylene group bonded thereto (61.894 ppm), the peak of the carbonyl group bonded thereto (167.485 ppm), and the peak of the methylene group bonded thereto (14.152 ppm) can also be confirmed. It was determined that the structure of the citrate compound was represented by the above structural formula [II]. In addition,
In order to make it easier to understand the position of each of the peaks described above, the structural formula [II] is given a code as described below, and also shows the relationship between the code and each peak value. In addition, C = O stretching of 1747.4 cm ⁻¹ obtained from the result of FT-IR measurement, 349
6.7 cm ^-1 O-H stretch, 2870-2990 cm ^-1
The nearby C—H stretch also suggests that the results of the above compounds are correct.

[0026]

Embedded image

(Example 2) Trisethoxycarbonylmethyl acetylcitrate obtained by the following production method as a plasticizer and represented by the following structural formula [III] (wherein R ¹ in the general formula [I] is an acetyl group, , R ² is an ethyl group) and commercially available polystyrene (same as in Example 1) 1
The three types of mixtures were obtained by mixing 10 parts by weight, 20 parts by weight, and 40 parts by weight with respect to 00 parts by weight, respectively, and the mixtures were kneaded using the small melt kneading apparatus (Laboplast mill). Table 1 shows the kneading workability evaluation results at that time.
For (1), and for those with good kneading properties,
Pellets were formed using a screw extruder, and samples for evaluating basic physical properties and for evaluating bleed-out property were formed using an injection molding machine. Table 2 (1) shows the evaluation results of the basic physical properties using these samples, and Table 3 (1) shows the evaluation results of the bleed-out property.

[0028]

Embedded image

Next, a method for producing the compound represented by the above formula [III] and results of confirming the obtained compound will be described. A stirrer, a thermometer, and a condenser were attached to a four-necked flask, and citrate ester 1 synthesized in Example 1 was used.
50 g (0.333 mol), pyridine 27.7 g (0.
345 mol) and cooled to 10 ° C. while stirring. Acetyl chloride 27.1 g (0.345 mol)
Was added over 30 minutes while cooling from the additional funnel. Thereafter, the reaction temperature was gradually raised, and the reaction was carried out at 80 ° C. for 2 hours. After the reaction, 200 g of toluene and 200 g of water were added,
By-product pyridine hydrochloride was removed. 100 more oil layers
g of water were washed three times to obtain 356 g of a toluene solution of the product. After toluene was recovered by vacuum distillation at 100 ° C. and 45 mmHg, steam distillation was performed at 110 ° C. and 30 mmHg for 30 minutes to obtain 147 g of a product. The specific gravity of the product was 1.264, and as a result of measurement by gel permeation chromatography (same as in Example 1), the purity was 87.
8%. ^An assignment was performed based on the measurement results of ¹³ C-NMR. 73.245 ppm of 4 from the chart
Peak of a quaternary carbon (citrate skeleton), a peak of a methylene group bonded to the quaternary carbon (42.530 ppm), and a peak of a carbonyl group bonded thereto (169.002 pp
m), a peak of a methylene group bonded thereto through oxygen (61.044 ppm), a peak of a carbonyl group bonded thereto (167.030 ppm), and a peak of a methyl group bonded thereto (14.092 ppm) were confirmed.
Also, the peak of the carbonyl group bonded to the quaternary carbon (17
2.341 ppm), a peak of a methylene group bonded thereto via oxygen (61.742 ppm), a peak of a carbonyl group bonded thereto (167.424 ppm), and a peak of a methylene group bonded thereto via oxygen (61.
530 ppm) and the peak of the methyl group attached thereto (1
4.092 ppm). The carbonyl peak of the acetyl group bonded to the quaternary carbon (169.670)
ppm) and the peak of the methyl group (20.860 ppm)
Was confirmed, and from the above results, it was concluded that the structure of the citrate compound was represented by the above structural formula [III]. In addition, in order to make it easier to understand the position related to each peak described above, a code is given to the structural formula [III] as described below, and a relationship between the code and each peak value is also shown. Also, FT-
C = 1747.4 cm ⁻¹ obtained from the result of IR measurement
The O stretching and the CH stretching around 2870-2990 cm ^-1 also suggest that the confirmation results of the above compound are correct.

[0030]

Embedded image

Comparative Example 1 A commercially available polystyrene (same as in Example 1) was molded into an evaluation sample of basic physical properties and an evaluation sample of bleed-out property using an injection molding machine. Table 2 shows the evaluation results of the basic physical properties using these samples.
Table 2 shows the results of the bleed-out evaluation.

Comparative Example 2 10 parts by weight, 20 parts by weight, and 40 parts by weight of dibutyl phthalate (DBP) as a phthalic acid plasticizer were added to 100 parts by weight of a commercially available polystyrene resin (the same as in Example 1). Parts of the mixture were mixed to obtain three kinds of mixtures, and the mixtures were kneaded using the same small melt-kneading apparatus (Laboplast mill) used in the examples. Table 1 (2) shows the evaluation results of the kneading workability at that time.
Further, those having good kneading properties were pelletized using a twin-screw extruder with the same formulation, and then samples for evaluation of basic physical properties and bleed-out property were molded using an injection molding machine. Table 2 shows the evaluation results of the basic physical properties using these samples.
Table (2) shows the results of the bleed-out evaluation in (2).

(Comparative Example 3) 10 parts by weight and 20 parts by weight of tricresyl phosphate (TCP) as a phosphate plasticizer were added to 100 parts by weight of a commercially available polystyrene resin (the same as in Example 1). And 40 parts by weight, to obtain three types of mixtures, and the mixtures were kneaded using the same small melt-kneading apparatus (Laboplast mill) used in the examples. Table 1 shows the kneading workability evaluation results at that time.
In (2), those having good kneading properties were pelletized using a twin-screw extruder with the same formulation, and then samples for evaluation of basic physical properties and bleed-out property were formed using an injection molding machine. Table 2 shows the physical property evaluation results using these samples.
Table 2 shows the results of the bleed-out evaluation.

[0034]

[Table 1]

[0035]

[Table 2]

[0036]

[Table 3]

[0037]

[Table 4]

[0038]

[Table 5]

[0039]

[Table 6]

[0040]

The citrate compound represented by the general formula [I] is useful as a plasticizer for a thermoplastic resin, especially a styrene resin, and produces a resin composition mixed with the thermoplastic resin. In this case as well, it was found that various problems associated with the conventional plasticizer addition can be almost eliminated.

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Claims (8)

[Claims] 1. A plasticizer for a thermoplastic resin (excluding vinyl chloride-based and cellulose acetate-based resins) comprising a citrate compound represented by the following general formula [I]. Embedded image Wherein, R ¹ is hydrogen atom or an aliphatic acyl group, R ²
Is an alkyl group. ] 2. A plasticizer for a thermoplastic resin comprising the citrate ester compound according to claim 1, wherein R ¹ is an aliphatic acyl group having 1 to 5 carbon atoms. 3. A plasticizer for a thermoplastic resin comprising the citrate compound according to claim 1, wherein R ² is an alkyl group having 1 to 4 carbon atoms. 4. The plasticizer for a thermoplastic resin comprising a citrate compound according to claim ¹ , wherein R ¹ is a hydrogen atom and R ² is a methyl group or an ethyl group. 5. The plasticizer for a thermoplastic resin comprising a citrate compound according to claim 1, wherein R ¹ is an acetyl group and R ² is a methyl group or an ethyl group. 6. A plasticizer for a thermoplastic resin comprising a citrate compound according to claim 1, wherein the thermoplastic resin is a styrene resin. 7. A citrate ester compound represented by the general formula [I] is added in an amount of 5 to 20 parts by weight per 100 parts by weight of the thermoplastic resin.
A thermoplastic resin composition obtained by adding 0 parts by weight. 8. The thermoplastic resin composition according to claim 7, wherein the thermoplastic resin is a styrene resin.